Behind The Darkness

CASPASES

2013-11-19T10:43:00.002-08:00

Introduction

Proteolytic enzymes, includes the cell's degrading machine preoteasome, caplains, and integral membrane proteases (such as γ-secretase and rhomboid); participate in several intracellular signaling processes. Caspases are one of the protein families in the body which are the only constitute a formal multistep pathway able to transmit intracellular signals by proteolysis and the name of this family is an abbreviation of cysteine-dependent aspartate-directed proteases, with a cysteine in their active site, as catalytic nucleophile, that cleave on the C-terminal side of aspartate residues.

The first discovery by Robert Horvitz and his colleagues who found that the ced-3 gene was required for the cell to die that take place during the development of the nematode, which called c.elegans. They found in 1993 that the protein, which encoded by ced-3 gene, was a cystiene protease with similar properties to the mammalian interleukiene-1-beta converting enzyme (ICE, or IL-1β), in which at this time is the only known caspase, named caspase-1. Other caspases have been discovered and numbered in the order in which they have been identified.

The human body contains cells with different life expectancies. Some (white blood cells, skin) are programmed to rapidly die and be replaced. Others (nerve cells) are programmed to survive the lifetime of the individual and are seldom replaced. There is a central role of enzymatic pathways play in the life and death of cells. When death pathways slowing down in cells that are normally programmed to die, cancer results. Conversely, when death pathways become overactive in cells that are programmed to survive, a degenerative disease occurs. So there is must be a balance between cell survival and programmed cell death (apoptosis) and that balance is managed by a family of proteases called caspases.

Some of them are essential for apoptosis (which mean the falling of leaves in Greek), others are required in the immune system for the maturation of cytokines, and also they have a role in necrosis and inflammation.

Basic properties

Nowadays there are many caspases have been discovered in many species, currently there are 11 members from human, 4 from c.elegans and 7 from Drosophila with obvious conservation in evolution.

¨ The General structure

Caspases are regulated at post-translational level, ensuring that they can be activated rapidly. They are first synthesized as inactive single chain polypeptide precursor, called zymogens or pro-caspases, in each caspase zymogen an N-terminal peptide (prodomain) is followed by sequences comprising first a large and then a small subunit [Fig. 1 and 2 ]. Pro-caspases have an intrinsic proteolytic activity. This unusual property is essential for triggering the proteolytic pathways that lead to complete their functions as in apoptosis.

Initiator caspases have a longerN-terminal prodomain (>90 amino acids) than the effector caspases, which their prodomain is very small (20-30 residues). The prodomain of the initiator caspases contain domains such as CARD or DED, which enables caspases to interact with other molecules that regulate their activation by responding to the stimuli that cause the clustering of the initiator caspases. This allowing them to be auto-activated via auto-catalytic intra-chain cleavage and then they can proceed to activate the effector caspases by intra-chain cleavage.

¨ The Specificity

Caspases recognizing at least 4 contiguous amino acids, named P4-P3-P2-P1, and cleaving after the C-terminal residue (P1), it is usually an Asp or D. Although the P1 residue was thought to be exclusively Asp, recent studies indicate that some caspases can also cleave after Glu (Hawkins et al., 2000; Srinivasula et al., 2001).

Interestingly, the preferred P3 position is invariantly Glu or E for all mammalian caspases examined (Thornberry et al., 1997). Thus the preferred specificity can be described as X-Glu-X-Asp. All caspases contain a conserved QACXG (where X is R, Q or G) pentapeptide active-site motif [Table 1].

Table 1, shows the different human caspases with their different names and with their common and different active sites.

Figure 2, Proenzyme organization of the caspases: Caspases are synthesized as proenzymes, with an N-terminal peptide or prodomain (PRO), and two subunits sometimes separated by a linker peptide (black box). Based on caspase-1 and caspase-3, active enzymes are heterotetramers of two large (~20 KDa) & and two small (~ 10 KDa) subunits. The proenzymes are cleaved at specific Asp residues (Dn, where n is the position in the protein). The numbers at the right-hand side are the numbers of amino acids in the protein.^aExact cleavage site not known.^bthe cleavage site of caspase-3 may be at Asp-9 or Asp-28. ^ccaspase-9 is cleaved preferentially at Asp-330 by caspase-3 and at Asp-315 by granzyme B. Caspase-2 cleavage sites are based on equivalent sites being present in Nedd2.FADD (in the white box) represents the domains of caspase-8 and caspase-10 that are homologous to the DED of FADD/MORT1.

¨ The Activation of caspases

Conversion of each caspase zymogen [dormant state of the enzyme] to the mature enzyme requires a minimum of 2 cleavages, one separating the prodomain from the large subunit and another is separating the large and small subunits [Fig. 3]. All of these cleavages involve Asp-X bond. This process eventually yields a heterodimeric enzyme with both fragments contributing to the formation of the catalytic machinery.

It is believed now that the functional caspase unit is a homodimer [which referred to as "homodimer of heterodimer"], with each monomer comprising a large (20KDa, named p20.) and a small (10 KDa, named p10.) subunit, according to the structural characterization of the caspase-1 which reveals the homodimeric structure. In addition to caspase-1, structural information is available for caspase-3, -7, -8 and -9. The overall architecture of them is similar and consists of 2 heterodimers composed of large and small subunits. The subunits of each heterodimer are folded into a compact cylinder that is dominated by a central six-stranded β-sheet and five α-helices that are distributed on opposing sides of the plane that is formed by the β-sheet. This so-called caspase-fold is a unique quaternary structure among proteases and has only been described for caspases [Fig. 4].

Figure 3, Schematic diagram of the mammalian caspases: except caspase-11 and 12 (mouse), caspase-13 (bovine), all listed caspases are of human origin. Their phylogenetic relationship (left) appears to correlate with their function in apoptosis or inflammation. The initiator and effector caspases are labeled in purple and red, respectively. The position of the cleavage (between the large and small subunits) is highlighted with a large arrow while additional sites of cleavage are represented by medium and small arrows.The four surface loops (L1-L4) that shape the catalytic groove are indicated. The catalytic residue Cys is shown as a red line at the beginning of loop L2.

Homodimerization [Fig. 4a] is mediated by hydrophobic interactions, with 6 β-strands (5 are parallel and one anti-parallel) from each catalytic subunit forming a single contiguous 12-stranded β-sheets. Several α-helices (six helices) and short β-strands (β_{I, II, III, IV and V}) are located on either side of the central β-sheet, giving rise to globular fold. The active sites, formed by 4 protruding loops form the scaffold, are located at 2 opposite ends of the β-sheet.

Crystallographic analysis has demonstrated that the active caspase is a tetramer composed of two such heterodimers. As first appreciated in the structure of caspase-1, this general rule is valid also for caspases, since the catalytic residue His-237 is located in the loop that connects β-strand (β3) to the "front" helix (α3), while the neighbouring strand (β1) is followed by the "back" helix (α1) (‘back’ and ‘front’ refer to the standard caspase orientation shown in [Fig. 4a]). The β1-α1 loop has one of the residues that determine the characteristic P1 specificity, Arg-179.

The entire active center of caspases, consisting of the S4-S3-S2-S1 specificity sub-sites binding P4-P3-P2-P1 residues of the substrate, respectively, is formed by a flexible loops (L1– L4, Fig. 5). Loop L1 and a portion of L2, which contains the catalytic Cys-285 residue, are a part of the large subunit, whereas L3 and L4 come from the small subunit. The activation-mediated cleavage of caspases occurs in the loop L2; liberating the C-terminus of the large (L2) and the N-terminus of the small subunits (L2^\). [Fig. 6] is an example of caspases activation by proteolysis.

Figure 4, Structure of active caspases: (a) the crystal structure of human caspase-8 exemplifies the fundamental caspase fold, and is shown bound to the tetrapeptide aldehyde inhibitor acetyl-Ile-Glu-Thr-Asp-CHO (PDB entry 1QTN), which represents the highest-resolution structure of a caspase reported to date. Note the three-layer structure of a twisted, 12-stranded β-sheet that is sandwiched by α-helices. Most of the interdomain contact area is built by the central small subunits, with additional interactions (the characteristic ‘loop bundle’) tying together the C- and N-termini of large and small subunits from neighbouring domains. The bound inhibitor is represented with a ball-and-stick model, as are dithiane diol molecules trapped in the cleft between the two monomers (termed the central cavity, for obvious reasons).

(b) Simplified topological diagram of the caspase structure, following the CATCH definition of secondary structure elements for 1QTN. An additional N-terminal α-helix of variable length (α0; not shown) is present in caspases-1, -2 and -9, and closes the ‘bottom’ of the α/β barrel. Also not depicted is an additional α-helix found solely in the long 179-loop of caspase-8. The positions of catalytic dyad residues His-237 and Cys-285 (red), along with those of the specificity-determining arginine residues (Arg-179 and Arg-341), are indicated. The location of loops that contain important functional elements is indicated in bluetext using the numbering convention designated throughout this review, along with an alternative designation.

Figure 5, The Generalized distribution of caspase catalytic center loops (L1– L4) on small and large subunits: Loops are shown in blue. Position of the activating cleavage processing is shown by arrows. Numbers represent the order of the activation cleavages. The active site Cys is shown by a red asterisk. Processing occurs in L2. The resulting large subunit portion of the L2 loop of one monomer and small subunit portion of the L2 loop of another monomer (L2^\). On the right is Schematic diagram of the substrate-binding groove: L1 and L4 constitute two parallel sides of the groove while L3 serves as the base. L2, harboring the catalytic residue Cys, is positioned at one end of the groove, poised for catalysis. L2^\ plays a critical role by stabilizing the conformation of the L2 and L4 loops.

Figure 6, Mechanism of activation for effector caspases as exemplified by caspase-7: A schematic diagram of procaspase-7 activation is shown here. The active-site loops before and after the proteolytic processing is shown in orange/cyanand magenta/green, respectively. The detailed conformational changes at the active site are depicted in the middle panel, in which the four surface loops, L1-L4, and the L2^\ loop are labeled.

Role of caspases in Apoptosis

Apoptosis is a physiological cell suicide program (one of the main types of PCD) that is critical for the development and maintenance of healthy tissues. Regulation of PCD allows the organism to control the cell number and the tissue size, and to protect itself from rogue cells that threaten homeostasis. The changed activity of numerous genes influences switching of cells to a self-destruction program. Apoptosis requires co-ordinate action and fine tuning of a set of proteins that are either regulators or executors of the process. Cancer, autoimmune diseases, immunodeficiency disease, reperfusion injury and neurodegenerative disorders are characterized by unregulated apoptosis. Modulation of the expression and activation of the key molecular components of the apoptotic process has emerged as an attractive therapeutic strategy for many diseases.

There are two distinct types of cell death, death by injury and death by suicide. Cells that are damaged by injury, such as mechanical damage or exposure to toxic chemicals, undergo a series of changes characterized by swelling of cells and their organelles, leakage of cell content and inflammation of the surrounding tissues. In other words, cells die by necrosis. In contrast, apoptosis is an organized, genetically directed process, which leads to cell death. Cells dying by apoptosis share unique morphological features, distinct from autolytic, degenerative cell changes observed during necrosis [Fig. 7].

m MORPHOLOGY OF APOPTOSIS

Morphological changes of an apoptotic cell might be easily detected under the microscope. Some of these changes can be seen even by light microscopy using specific dyes, while other can be detected only by electron microscopy. The dying cell starts to show protrusion from the plasma membrane, referred to as bleb [Fig. 8]. Staining DNA with certain dyes allows observation of the condensation of the cell nucleus, which usually starts as a condensed ring along the nuclear envelope. The condensed nucleus can disassemble into several fragments. The entire cell condenses and is re-organized into apoptotic bodies [Fig. 8], which are membrane-bound vesicles varying in size and composition, containing the entire cell content in various combinations, such as cytosolic elements, organelles or parts of condensed nuclei. Additional changes have been described by electron microscopy. Condensation or swelling of mitochondria, dilatation of endoplasmic reticulum (ER), vacuolisation of cytoplasm and loss of plasma membrane microvilli have been observed. At a certain point, apoptosis affects all compartments and organelles in a dying cell.

Apoptosis includes cellular shrinking, chromatin condensation and margination at the nuclear periphery with the eventual formation of membrane-bound apoptotic bodies that contain organelles, cytosol and nuclear fragments and are phagocytosed without triggering inflammatory processes.The necrotic cell swells, becomes leaky and finally is disrupted and releases its contents into the surrounding tissue resulting in inflammation. Modified from [Van Cruchten, 2002].

Figure 7, Schematic diagram of differences between apoptosis and necrosis: (A) Apoptosis includes cellular shrinking, chromatin condensation and margination at the nuclear periphery with the eventual formation of membrane-bound apoptotic bodies that contain organelles, cytosol and nuclear fragments and are phagocytosed without triggering inflammatory processes (B). The necrotic cell swells, becomes leaky and finally is disrupted and releases its contents into the surrounding tissue resulting in inflammation.

Figure 8, Schematic diagram of morphological changes in the cell during apoptosis.

Molecular mechanism of apoptosis

Apoptosis can be triggered by various stimuli from outside or inside the cell, as by ligation of cell surface receptors, DNA damage as a cause of defects in DNA repair mechanisms, treatment with cytotoxic drugs or irradiation, a lack of survival signals, contradictory cell cycle signaling or by developmental death signals. Death signals of such diverse origin nevertheless appear to eventually activate common cell death machinery leading to the characteristic features of apoptotic cell death [Fig. 9].The apoptosis process can be divided into at least three functionally distinct phases: initiation, effector and degradation. During the initiation phase, cells receive death-inducing signals: as lack of obligatory survival factors, shortage of metabolite supply, ligation of death-signal transmitting receptors, sub-necrotic damage by toxins, heat or irradiation.

During the effector phase, these signals are translated into metabolic reactions and the decision to die is taken. The ultimate fate of the cell is subject to regulatory events. Beyond this stage, during the degradation phase, an increase in the overall entropy, including activation of catabolic enzymes, precludes further regulatory effects. During the late phase, DNA fragmentation and massive protein degradation becomes apparent. Subsequently, fragments are encapsulated into ‘apoptotic bodies’.

Figure 9, Apoptosis may occur through 2 main signaling pathways: The intrinsic pathway may be triggered by DNA damage and other types of severe cell stress. It may involve the release of intracellular pro-apoptotic proteins that activate caspases, a network of proteases that ultimately destroy critical structural proteins in the cell and stimulate fragmentation of the chromosomal DNA, resulting in cell death. The extrinsic pathway may be triggered in response to external pro-apoptotic signals, such as endogenous Apo2L/TRAIL. Binding of this molecule to pro-apoptotic cell surface transmembrane receptors DR4 and DR5 may lead to apoptosis by initiating a signaling cascade, which results in the activation of the caspase system. The intrinsic and extrinsic apoptosis pathways converge via the activated caspases that ultimately trigger cell death.

 Caspases in apoptosis

Caspases are the family which can be classified into 3 subgroups according to their function:

I-Initiator caspases [caspase-2, -8, -9 and -10]

II-Executioner caspases [caspase-3, -6 and -7]

Both (I) and (II) have either direct or indirect role in the processing, propagation and amplification of apoptotic signals, which result in the destruction of the cellular structure.

III-Inflammatory caspases, which involved in the maturation of pro-inflammatory cytokines [caspase-1, -4, -5, -11, -12, -13 and -14]

At the molecular level, two principal pathways of apoptotic cell death have been described (Twomey and McCarthy, 2005). The pathway of apoptosis often referred to as:

A) Extrinsic apoptosis (Receptor-mediated apoptosis or type 1 apoptosis).

B) Intrinsic apoptosis (mitochondria-independent apoptosis and or type 2 apoptosis) [Fig. 10].

Many of the proteins involved utilize at least two types of sequence motifs. One motif is known as DD and the other motif as DED [The instigators include the long prodomain, DED containing caspases 8 and 10, and the CARD containing caspase-9].

Figure 10, Basic two principal pathways: the receptor and the mitochondria-mediated apoptosis.

A) Extrinsic apoptosis:

Extrinsic apoptosis signalling is mediated by the activation of so called “death receptors” which are cell surface receptors that transmit apoptotic signals after ligation with specific ligands. DRs belong to (TNFR) gene superfamily, including TNFR-1, Fas/CD95, and the TRAIL receptors DR-4 andDR-5 [Fig. 11 B and 12 and table 2]. All members of the TNFR family consist of cysteine rich extracellular sub-domains which allow them to recognize their ligands with specificity, resulting in the trimerization and activation of the respective death receptor. Subsequent signalling is mediated by the cytoplasmic part of the DR which contains a conserved sequence termed the DD. Adapter molecules like FADD or TRADD themselves possess their own DDs by which they are recruited to the DDs of the activated DR, thereby forming the so-called DISC [Fig. 12 A]. In addition to its DD, the adaptor FADD also contains a DED which through homotypic DED-DED interaction sequesters procaspase-8 to the DISC [Fig. 11 B]. The local concentration of several procaspase-8 molecules at the DISC leads to their autocatalytic activation and release of active caspase-8. Active caspase-8 then processes downstream effector caspases which subsequently cleave specific substrates resulting in cell death. The signal needs to be amplified via mitochondria-dependent apoptotic pathways. The link between the caspase signalling cascade and the mitochondria is provided by the Bcl-2 family member Bid. Bid is cleaved by caspase-8 in to its truncated form (tBid), translocates to the mitochondria where it acts in concert with the proapoptotic Bcl-2 family members Bax and Bak to induce the release of cytochrome c (Apaf-2) and other mitochondrial proapoptotic factors into the cytosol [Fig. 9, 10 and (11 A)]. Cytosolic cytochrome c is binding to monomeric Apaf-1 which then, in a dATP-dependent conformational change, oligomerizes to assemble the apoptosome, a complex of wheel-like structure with 7-fold symmetry, which triggers the activation of the initiator procaspase-9. Activated caspase-9 subsequently initiates a caspase cascade involving downstream effector caspases such as caspase-3, caspase-7, and caspase-6, ultimately resulting in cell death.

Figure 11, (A)

Table 2, Shows many different molecules and receptors involved in apoptosis.

Figure 11,(B)

B) Intrinsic apoptosis

Besides amplifying and mediating extrinsic apoptotic pathways, mitochondria also play a central role in the integration and propagation of death signals originating from inside the cell such as DNA damage, oxidative stress, starvation, as well as those induced by chemotherapeutic drugs. Most apoptosis-inducing conditions involve the disruption of normal mitochondrial inner transmembrane potential (Δψ) [Fig. 13 A] as well as the so called permeability transition (PT), a sudden increase of the inner mitochondrial membrane permeability to solutes with a molecular mass below approximately 1.5 kDa. Concomitantly, osmotic mitochondrial swelling has been observed by influx of water into the matrix with eventual rupture of the outer mitochondrial membrane, resulting in the release of proapoptotic proteins from the mitochondrial intermembrane space into the cytoplasm. Released proteins include cytochrome c, which activates the apoptosome [Fig. 14] and therefore the caspase cascade [Fig. 11 A, B and Fig. 13 A], but also other factors such as the apoptosis-inducing factor (AIF), the endonuclease (endoG), Smac/Diablo, and Htr/Omi. In addition to the release of mitochondrial factors, the dissipation of Δψ and PT also cause a loss of the biochemical homeostasis of the cell: ATP synthesis is stopped, redox molecules such as NADH, NADPH, and glutathione are oxidized, and reactive oxygen species (ROS) are increasingly generated.

 Caspases and chromatin break down

One of the hallmarks of apoptosis is the cleavage of chromosomal DNA into nucleosomal units. The caspases play an important role in this process by activating DNases, inhibiting DNA repair enzymes and breaking down structural proteins in the nucleus. The role of the caspases in the breakdown of chromatin is illustrated in [Fig. 15].

1) Inactivation of enzymes involved in DNA repair: The enzyme poly (ADP-ribose) polymerase, or PARP, is an important DNA repair enzyme and was one of the first proteins identified as a substrate for caspases. The ability of PARP to repair DNA damage is prevented following cleavage of PARP by caspase-3.

2) Breakdown of structural nuclear proteins: Lamins are intra-nuclear proteins that maintain the shape of the nucleus and mediate interactions between chromatin and the nuclear membrane. Degradation of lamins by caspase 6 results in the chromatin condensation and nuclear fragmentation.

3) Fragmentation of DNA: The fragmentation of DNA into nucleosomal units is caused by an enzyme known as CAD, or caspase activated DNase. Normally CAD exists as an inactive complex with ICAD (inhibitor of CAD). During apoptosis, ICAD is cleaved by caspases, such as caspase 3, to release CAD. Rapid fragmentation of the nuclear DNA follows.

Caspases in inflammation

In mammles, there are 5 inflammatory caspases that all have a CARD at their N-terminus. Human inflammatory caspases are clustered on chromosome 11q22 in following order from the telomere: caspase-1, caspase-5, caspase-4, and finally the gene for caspase-12 [Fig. 16].

The role of caspase-1 in the maturation of IL-1β and IL- 18 renders it a key player in response to pathogenic infection as well as in inflammatory and autoimmune disorders. IL-1β and IL-18 are key cytokines in these conditions. Although they share certain proinflammatory activities, they also have very important individual functions. For example, IL-1β but not IL-18 is anorectic, pyrogenic, results in skin rashes and urticaria, induces hepatic-acute phase proteins, up-regulates prostanoid synthesis, and is involved in inflammatory pain hypersensitivity. IL-1β is also implicated in destructive joint and bone disease, tumor angiogenesis and invasiveness, and toxicity of insulin-producing pancreatic islets β-cells, and neurons in stroke and neurodegeneration. IL-18, in contrast, was originally known for its ability to stimulate IFN-γ production and to mediate T cell polarization. Now it is known that it possesses many other functions including modulation of the heart contractile force, upregulation of adhesion molecules and NO synthesis, and regulation of energy intake and insulin sensitivity. Therefore, inhibition of caspase-1 is an attractive therapeutic strategy aimed at blocking the effects of both cytokines in inflammatory and autoimmune diseases. Although we know of many biological effects of IL-1β and IL-18, we still lack information on the exact mechanisms by which caspase-1 is activated, and by which these cytokines are matured and secreted.

Our understanding of the inflammatory caspases and their regulatory mechanisms has recently improved substantially. Multiple new players have now been identified to modulate the function of these enzymes. The discovery of the caspase-12 polymorphism and the characterization of its function in sepsis and the host response to pathogenic infection have emphasized the essential role of these caspases in innate immunity. In parallel, the identification of the NLR family and its regulation of the inflammatory caspases has provided an important step forward in our knowledge of the tight and highly specific mechanisms of activation of these enzymes.

Abbreviations

1. C.elegans: Caenorhabditis elegans, it is a type of nematodes.

2. Ced-3 gene: c.elegans death gene or Cell Death Defective-3, which is involved in the cell death.

3. CARD: caspase recruitment domains, they are interaction motifs found in a wide array in proteins, typically those involved in apoptosis and inflammation.

4. DED: death effector domain (DD is Death Domain), which is a protein domain found in procaspases and proteins that regulate caspase activation in apoptotic cascade such as FADD.

5. FADD: fas-associated with death domain protein.

6. Glu or E: Glutamic acid.

7. Asp or D: Aspartic acid.

8. X: any amino acid (aa^\).

9. MORT-1: Mediator Of Receptor-induced Toxicity-1, which is also called FADD.

10. Nedd2: Neural precursor cell Expressed Developmentally Down-regulated 2, it is a developmental regulated mouse gene that encodes a protein (mouse homologue of ICH-1, ICE and Ced-3 Homolouge-1) similar to the ced-3 gene protein and mammalian ICE. It is renamed as caspase-2 (Alnemri et al Human ICE/CED-3 protease nomenclature, 1996).

11. Cys or C: Cysteine aa^\.

12. PDB: Protein Data Bank. (http://www.rcsb.org/pdb/home/home.do)

13. P: Pocket.

14. PCD: Programmed Cell Death.

15. TNFR1: Tumor Necrosis Factor Receptor-1

16. TRAIL-R1 or 2: TNF-Related Apoptosis-Inducing Ligand Receptor-1 or -2

17. p75-NGFR: p75-Nerve Growth Factor Receptor.

18. TNF: Tumor Necrosis Factor.

19. Motif and domain appear to be used interchangeable.

20. Initiator caspases (º activator or apical or upstream or instigator caspases).

21. Effector caspases (ºExecutioner or downstream or terminator caspases).

22. DISC: Death Inducing Signaling Complex.

23. L: Ligand.

24. TRADD: TNF Receptor-Associated Death Domain.

25. TRAF2: TNF Receptor-Associated Factor-2

26. BH: Bcl-2 Homology (has 4 domains BH1, BH2, BH3 and BH4).

27. DR: Death Receptor.

28. APAF-1: Apoptotic Protease Activating Factor-1, it is a protein contains three functional regions: an N-terminal CARD domain that can bind to the zymogen form of caspase-9, a CED4like region enabling self-oligomerization, and a regulatory C-terminus with WD-40 repeats masking the CARDand CED4region. During apoptosis, cytochrome-C and dATP can relieve the inhibitory action of the WD-40 repeats and thus enable the oligomerization of APAF-1 and the subsequent recruitment and activation of caspase-9 from its zymogen form.

29. Smac: Second Mitochondria-Derived Activator of Caspases.

30. DIABLO: Direct Inhibitor of Apoptosis-Binding Protein with LOw pI.

31. NLR: Nod-Like Receptor.

Ref:

1- http://www.cryst.bbk.ac.uk/pps97/assignments/projects/jekely/caspase.htm

2- http://mupnet.com/JOCM%201(1)%209-18.pdf

3- http://en.wikipedia.org/wiki/Caspases

4- Biochem. J. (2004) 384, 201–232, Review article: the protein structures that shape caspase activity, specificity, activation and inhibition.

5- Acta Pharm. 53 (2003) 151–164, Review: Biochemistry of apoptotic cell death.

6- Oncogene (2003) 22, 8543–8567, 2003 Nature Publishing Group, A decade of caspases.

9- http://en.wikipedia.org/wiki/Apoptosis

10- http://www.erin.utoronto.ca/~w3bio380/picts/lectures/lecture3/Apoptotic%20Cells%2006%201.jpg

11- http://whyfiles.org/250alcohol_brain/images/apoptosis.jpg

12- http://physiologyonline.physiology.org/cgi/reprint/18/3/89

13- http://www.biooncology.com/bioonc/research/apoptosis/index.m

14- BioEssays 25:888–896, 2003. 2003 Wiley Periodicals, Inc. Review articles, Apoptosis—an introduction, Alfons Lawen.

15- Current science, VOL. 80, NO. 3, 10 February 2001, Review article: Apoptosis: Molecular machinery.

16- http://www.copewithcytokines.de/cope.cgi?key=Apoptosis

17- ApoReview - Introduction to Apoptosis: Page 1 of 26, this review was composed by Andreas Gewies in 2003.

19- http://mol-biol4masters.org/Apoptosis.htm

20- http://e-biolearning.com/bbs/context.asp?id=252

21- Basic Medical Sciences, St.George’s, University of London, Apoptosis by Phil Dash.

22- The journal of immunology, Copyright 2006 by The American Association of Immunologists, Inc. Brief reviews, the inflammatory caspases.

(***Note: The last update by me was in 2009. Therefore, if there any new updates, please do not hesitate to contact me.)

Cell Communication; GPCR part 1

2013-02-07T07:00:00.000-08:00

G protein-coupled receptors, often abbreviated GPCRs, are an abundant superfamily of proteins also known as seven-transmembrane domain receptors, 7TM receptors, 7 pass transmembrane receptors, heptahelical receptors, serpentine receptor, and G protein-linked receptors (GPLRs). G protein-coupled receptors are cell surface signalling proteins involved in many physiological functions and in multiple diseases.

The presence of GPCRs in the genomes of bacteria, yeast, plants, nematodes and other invertebrate groups argues in favor of a relatively early evolutionary origin of this group of molecules. The diversity of GPCRs is dictated both by the multiplicity of stimuli to which they respond, as well as by the variety of intracellular signalling pathways they activate. These include light, neurotransmitters, odorants, biogenic amines, lipids, proteins, amino acids, hormones, nucleotides, chemokines and, undoubtedly, many others. In addition, there are at least 18 different human G-alpha proteins to which GPCRs can be coupled (Hermans, 2003; Wong, 2003). These G-alpha proteins form heterotrimeric complexes with G-beta subunits, of which there are at least 5 types, and G-gamma subunits, of which there are at least 11 types (Hermans, 2003).

How do GPCRs work?

1*The first step in signal transduction is ligand (shown in Golden color in the above fig.) binding.

2*Agonist binding is followed by a change in the conformation of the receptor that may involve disruption of a strong ionic interaction between the third and sixth transmembrane helices (Ballesteros et al., 2001; Shapiro et al., 2002), which facilitates activation of the G-protein heterotrimer.

3*Depending on the type of G protein to which the receptor is coupled, a variety of downstream

signalling pathways can be activated (reviewed by Marinissen and Gutkind, 2001; Neves et al., 2002).

4*Signalling is then attenuated as following:

GPCRs become desensitized when exposed to their ligand for a prolonged period of time. There are two recognized forms of desensitization:

1) Homologous desensitization, in which the activated GPCR is downregulated

2) Heterologous desensitizationc (cross-desensitisation), wherein the activated GPCR causes downregulation of a different GPCR. The key reaction of this downregulation is the phosphorylation of the intracellular receptor domain by protein kinases.

Ligand + GPCR = conformation change to GPCR = α subunit-GTP + beta-gamma complex = α subunit-GTP activates a specific effector (such as Adenylyl cyclase, PLC, ion channel, phosphodiesteras) = production of second messengers (such as cAMP, DAG, sodium and calcium conc. changes) = physiological response by controlling cellular functions = α subunit-GTP + Regulatory of G protein signalling (RGSs) =[ α subunit-GDP + beta-gamma complex] (GPCR)

-Phosphorylation by cAMP-dependent protein kinases

Cyclic AMP-dependent protein kinases (protein Kinase A) are activated by the signal chain coming from the G protein (that was activated by the receptor) via Adenylyl cyclase and cAMP. In a feedback mechanism, these activated kinases phosphorylate the receptor. The longer the receptor remains active, the more kinases are activated, the more receptors are phosphorylated.

-Phosphorylation by GRKs

GRKs-mediated receptor phosphorylation rapidly initiates profound impairment of receptor signaling and desensitization. Activity of GRKs and subcellular targeting is tightly regulated by interaction with receptor domains, G protein subunits, lipids, anchoring proteins and calcium-sensitive proteins.

G protein:

G proteins, also known as guanine nucleotide-binding proteins, are a family of proteins involved in transmitting chemical signals originating from outside a cell into the inside of the cell. G proteins function as molecular switches. Their activity is regulated by factors that control their ability to bind to and hydrolyze Guanosine triphosphate (GTP) to Guanosine diphosphate (GDP). When they bind GTP, they are 'on', and, when they bind GDP, they are 'off'. G proteins belong to the larger group of enzymes called GTPases.

GDP GTP

There are two classes of G proteins. The first function as monomeric small GTPases while the second form and function as heterotrimeric G protein complexes. The latter class of complexes are made up of alpha (α), beta (β) and gamma (γ) subunits. In addition, the beta and gamma subunits can form a stable dimeric complex referred to as the beta-gamma complex.

Note: Small GTPases are a family of hydrolase enzymes that can bind and hydrolyze GTP. They are a form of G proteins found in the cytosol which are homologous to the alpha subunit of heterotrimeric G protein complexes, but unlike the alpha subunit of G proteins, a small GTPase can function independently as a hydrolase enzyme to bind to and hydrolyze a GTP to form GDP. The most well-known members are the Ras GTPases and hence they are sometimes called Ras superfamily GTPases.

G proteins are molecular switches that use GDP (colored purple here) to control their signaling cycle. When GDP is bound, as shown here, the G protein is inactive. To activate the protein, the GDP is replaced with GTP, the G protein will deliver its signal. G proteins come in many shapes and sizes. Most are used for cell signaling, but other types play an important role in other tasks, such as powering protein synthesis. The ones described here are termed heterotrimeric G proteins because they are composed of three different chains, denoted as alpha (tan), beta (blue), and gamma (green). The little red piece is a loop on the surface of the alpha subunit that is important in transmitting the signal.

Some Types of Gα Subunits:

#The family consists of the G protein α subunit, which acts as a weak GTPase. G protein classes are defined based on the sequence and the function of their α subunits:

Gα_s:

_{"S" stands for stimulation since it stimulates cAMP-dependent pathway via activating Adenylyl cyclase.}_{It is associated with the receptors for many hormones such as (}Adrenaline, Glucagon, LH, PTH, ACTH).

Note: Gα_sis the target of the toxin liberated by Vibrio cholerae. Therefore, Binding of cholera toxin to Gα_s keeps it turned "on". The resulting continuous high levels of cAMP causes a massive loss of salts from the cells of the intestinal epithelium. Massive amounts of water follow by osmosis causing a diarrhea that can be fatal if the salts and water are not quickly replaced.

The cAMP Dependent Pathway is used as a signal transduction pathway for many hormones including:

ADH - Promotes water retention by the kidneys (V2 Cells of Posterior Pituitary)
GHRH - Stimulates the synthesis and release of GH (Somatotroph Cells of Anterior Pituitary)
GHIH - Inhibits the synthesis and release of GH (Somatotroph Cells of Anterior Pituitary)
CRH - Stimulates the synthesis and release of ACTH (Anterior Pituitary)
ACTH - Stimulates the synthesis and release of Cortisol (zona fasiculata of adrenal cortex in kidneys)
TSH - Stimulates the synthesis and release of a majority of T4 (Thyroid Gland)
LH - Stimulates follicular maturation and ovulation in women; Stimulates testosterone production and spermatogenesis in men
FSH - Stimulates follicular development in women; Stimulates spermatogenesis in men
PTH - Increases blood calcium levels (PTH1 Receptor: Kidneys and Bone; PTH2 Receptor: Central Nervous system, Bones, Kidneys, Brain)
Calcitonin - Decreases blood calcium levels (Calcitonin Receptor: Intestines, Bones, Kidneys, Brain)
Glucagon - Stimulates glycogen breakdown (liver)
hCG - Promotes cellular differentiation; Potentially involved in apoptosis

Ref:
http://inbehindthedarkness.blogspot.com/p/ce.html

1. http://proteopedia.org/wiki/index.php/G_protein-coupled_receptor

2. http://jcs.biologists.org/content/116/24/4867.full.pdf+html

3. http://en.wikipedia.org/wiki/G_protein-coupled_receptor
4. http://www.wjgnet.com/1007-9327/12/7753.pdf
5. http://www.rcsb.org/pdb/101/motm.do?momID=58
6. http://en.wikipedia.org/wiki/G_protein
7. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellSignaling.html#Introduction

Simple charts and diagrams

2013-02-07T04:39:00.001-08:00

Simple Brain and spinal cord anatomy:

Transparent Brain: (CLARITY technique)

CLARITY transforms biological tissues into an optically transparent object which retains the original structure of the brain as well as its molecular information.

To view the video, please go through the following link:

http://link.brightcove.com/services/player/bcpid1469910597001?bckey=AQ~~,AAAArZFA_pE~,D1__qX58jeoh0JCT0LXFEJSV4ZR-CnWj&bctid=2279779824001

Ref:

1. http://www.youtube.com/watch?v=c-NMfp13Uug&feature=youtu.be&WT.i_dcsvid=6042130-MTQ2NDU2MTY1MTIS1&WT.ec_id=MARKETING

2. http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12107.html

3. http://www.nature.com/news/see-through-brains-clarify-connections-1.12768

4. http://www.hhmi.org/news/deisseroth20130410.html

Simplified Nervous system chart:

Different food experiences among population

2012-07-26T20:10:00.002-07:00

Why we differ in taste perception

Humans use several kinds of information to decide what to eat, and the combination of experience and sensory evaluation helps us to choose whether to consume a particular food. If the sight, smell, and taste of the food are acceptable, and we see others enjoying it, we finish chewing and swallow it. Several senses combine to create the idea of food flavor in the brain. For example, a raw chili pepper has a crisp texture, an odor, a bitter and sour taste, and a chemesthetic ‘burn.’ Each of these sensory modalities is associated with a particular group of receptors: at least three subtypes of somatosensory receptors (touch, pain, and temperature), about 400 human odor receptors, which respond either singly or in combination at least five types of taste receptors [bitter, sour, sweet, salty, and umami (the savory experience associated with monosodium glutamate)], and several families of other receptors tuned to the irritating chemicals in foods, especially herbs and spices (for example, Eugenol found in cloves or Allicin found in garlic). The information from all these receptors are transmitted to the brain, where it is processed and integrated. Experience is a potent modifier of chemosensory perception, and persistent exposure to an odorant is enough to change sensitivity.

The combined senses of taste, smell and the common chemical sense merge to form what we call ‘flavor.’ People show marked differences in their ability to detect many flavors. Most of the genes identified to date encode receptors responsible for detecting tastes or odorants. Although the repertoire of receptors involved in taste perception is relatively small, with 25 bitter and only a few sweet and umami receptors, the number of odorant receptors is much larger, with about 400 functional receptors and another 600 potential odorant receptors predicted to be non-functional. Despite this, to date, there are only a few cases of odorant receptor variants that encode differences in the perception of odors: receptors for androstenone (musky), isovaleric acid (cheesy), cis-3-hexen-1-ol (grassy), and the urinary metabolites of asparagus. A genome-wide study also implicates genes other than olfactory receptors for some individual differences in perception. Although there are only a small number of examples reported to date, there may be many more genetic variants in odor and taste genes yet to be discovered.

Each person lives in a unique flavor world, and part of this difference lies in our genetic composition, especially within our sensory receptors. This idea is illustrated by bitter perception and bitter receptors. The bitter receptor family, TAS2, has approximately 25 receptors, found at three locations in the human genome. We say ‘approximately’ because bitter receptors have copy number variants, and it is currently unclear at what point a recently duplicated gene should be assigned a distinct name. This conundrum is more than a mere matter of record-keeping; the bitter receptor gene copy number is a source of biological variation and may affect perception, although this prospect has not yet been demonstrated empirically.

The first demonstration that genetic variants contribute to person-to-person differences in human taste perception was for the bitter receptor TAS2R38. It has been known since 1931 that some people are insensitive to the bitter compound phenylthiocarbamide (PTC), a chemical that was synthesized by Arthur Fox for making dyes. While he was working in his laboratory, Fox accidentally tasted the compound and found it bland, yet when his benchmate also accidentally tasted the compound, he found it very bitter. This observation contributed to the formation of a hypothesis, now widely accepted, that there is a family of bitter receptors, at least one of which is sensitive to this compound, but that is inactive in some people. In 2003, this hypothesis was tested using genetic linkage analysis. Relatives such as parents and children were assessed for their ability to taste PTC and for their pattern of DNA sharing. The genomic region most often shared by relatives with similar tasting ability was near the TAS2R38 gene, but this evidence in itself was insufficient to conclude that the TAS2R38 gene was responsible for this sensory trait. Genes encoding bitter taste receptors are physically clustered on chromosomes, and nearby DNA regions tend to be inherited together, so it was not clear whether TAS2R38 or a neighboring receptor was the responsible gene. This issue was resolved later, when individual bitter receptors were introduced into cells without taste receptors. Only those cells that contained the TAS2R38 gene responded to PTC. Moreover, cells containing naturally occurring genetic variants of the TAS2R38 gene from people who could not taste PTC were also unresponsive to this bitter compound. Together, these data showed that TAS2R38 and its variants explained the inability of some people to taste PTC at concentrations at which it is readily detectable to others. The inability to taste PTC as bitter can be considered a categorical trait (either people can taste it or they cannot), and can also be considered a quantitative trait, that is, as a continuum, but with most people falling at either end.

Although the genetics of taste perception has been dominated by the study of PTC and its effects, evidence is gradually accumulating that the ability (or inability) to perceive other bitter tastes is heritable. For example, identical twins, who have identical genetics, are more similar in their perception of bitter compounds (other than PTC) than are fraternal twins, who are no more similar genetically than siblings. A variant in a cluster of bitter receptors on chromosome 12 is associated with quinine perception, and the bitterness of some high-intensity sweeteners is associated with alleles within a cluster of bitter receptors on chromosome 12. These observations suggest that individual differences in bitter perception may be common, and related to genotype.

Bitterness is a part of human life in two ways, in food and in medicine. In general, humans tend to avoid bitter foods; in a study by Mattes, nearly half of people surveyed ate no bitter foods at all. When these subjects were asked to consume a bitter solution, they diluted it with water until the bitterness could no longer be detected. Other common methods to reduce bitterness include cooking, or the addition of salt or flavors, but bitterness is not an inevitable part of life for everyone. To illustrate this point, when we asked 8 people to rate 23 vegetables for bitterness intensity, we found that some people were insensitive to even the most bitter vegetables. Of course, people who are sensitive to the bitterness of a particular vegetable or other food can avoid eating it.

Beyond the receptor

Most of the known gene variations relating to perceptual differences in taste and smell are specific to a single receptor. It may be that receptor variation affects only the perception of its ligand or it may have broader effects due to brain rewiring (in response to missing input) or to the clustering of receptor variants (LD). Thus, more characterization of human perceptual differences in conjunction with genotype studies is needed. The reduced ability to detect a single compound (such as PTC) might be associated with a reduced ability to detect structurally unrelated bitter compounds or even other taste qualities.

Food-tasting business (Getting paid to eat)

The only thing that matters here is the food. Behind a door marked "Sensory Staff Only," a dozen or so professional tasters spend their days testing ingredients that end up in thousands of products around the world. They sniff, taste, feel and spit. All day long.

Painstakingly trained, these tasters can describe the difference between a "vine-y green" and a "fresh-cut grassy green," a roasted peanut note from an over-roasted one. They are 'sensory specialists" — and an increasingly mechanized, sophisticated and complex food industry rests on their taste buds. "You get paid to eat stuff," said Chaquita Johnson-Moore, a chef-turned-sensory panelist, during a recent break from a session tasting a nutritional drink. "People can't believe there are people who do this."

Ref:

1.http://www.flavourjournal.com/content/1/1/9/abstract

2.http://www.stltoday.com/business/local/article_5fe1a780-f782-5f5f-bd6e-72b4b13f87f8.html

One-size-fits-all drug targets harmful brain inflammation in many diseases

2012-07-26T09:14:00.000-07:00

A "one-size-fits-all" new class of drugs that targets a particular type of brain inflammation is showing early promise for the treatment of Alzheimer's disease, Parkinson's disease, multiple sclerosis and traumatic brain injury.

A pre-clinical study due to be published this week in the Journal of Neuroscience shows one of the drugs stopped mice bred to have Alzheimer's from developing the full-blown disease. Northwestern has recently been issued patents to cover this new drug class and has licensed the commercial development to a biotech company that has recently completed the first human Phase 1 clinical trial for the drug.

The drugs in this class target a particular type of brain inflammation, which is a common denominator in these neurological diseases and in traumatic brain injury and stroke. This brain inflammation, also called neuroinflammation, is increasingly believed to play a major role in the progressive damage characteristic of these chronic diseases and brain injuries. By addressing brain inflammation, the new class of drugs -- represented by MW151 and MW189 -- offers an entirely different therapeutic approach to Alzheimer’s than current ones being tested to prevent the development of beta amyloid plaques in the brain. The plaques are an indicator of the disease but not a proven cause.

MW151 and MW189 work by preventing the damaging overproduction of brain proteins called proinflammatory cytokines. Scientists now believe overproduction of these proteins contributes to the development of many degenerative neurological diseases as well as to the neurological damage caused by traumatic brain injury and stroke.

Ref:

http://www.northwestern.edu/newscenter/stories/2012/07/brain-inflamation-drug.html

http://www.medicalnewstoday.com/articles/248221.php

Humor

2012-07-26T05:16:00.001-07:00

http://www.cartoonresource.com/archive/medical-health/office-visits/hpr191-th.aspx

Some Antioxidants that can cross or strength the BBB

2012-07-24T08:20:00.000-07:00

1. α-lipoic acid:

Possible beneficial effects

Lipoic acid has been the subject of numerous research studies and clinical trials:

Prevent organ dysfunction

Reduce endothelial dysfunction and improve albuminuria

Treat or prevent cardiovascular disease

Accelerate chronic wound healing

Reduce levels of ADMA in diabetic end-stage renal disease patients on hemodialysis

Management of burning mouth syndrome

Reduce iron overload

Treat metabolic syndrome

Improve or prevent age-related cognitive dysfunction

Prevent or slow the progression of Alzheimer’s Disease

Prevent erectile dysfunction (animal models but anecdotally applies to humans as well)

Prevent migraines

Treat multiple sclerosis

Treat chronic diseases associated with oxidative stress

Reduce inflammation

Inhibit advanced glycation end products (AGE)

Treat peripheral artery disease.

2. Vitamin C:

Ascorbic acid is well known for its antioxidant activity, acting as a reducing agent to reverse oxidation in liquids. When there are more free radical (reactive oxygen species, ROS) in the human body than antioxidant, the condition is called oxidative stress, and has an impact on cardiovascular disease, hypertension, chronic inflammatory diseases,diabetes as well as on critically ill patients and individuals with severe burns. Individuals experiencing oxidative stress have ascorbate blood levels lower than 45 µmol/L, compared to healthy individual who range between 61.4-80 µmol/L.

3.Astaxanthin:

The primary use for humans is as a food supplement. Research shows that, due to astaxanthin's potent antioxidant activity, it may be beneficial in cardiovascular, immune, inflammatory and neurodegenerative diseases. Some research supports the assumption that it may protect body tissues from oxidative damage.

4. Ginkgo Biloba Leaf Extract:

Out of the many conflicting research results, Ginkgo extract may have three effects on the human body: improvement in blood flow (including microcirculation in small capillaries) to most tissues and organs; protection against oxidative cell damage from free radicals; and blockage of many of the effects of platelet-activating factor (platelet aggregation, blood clotting) that have been related to the development of a number of cardiovascular, renal, respiratory and CNS disorders. Ginkgolides, especially ginkgolide B, are potent antagonists against platelet-activating factor; and thus may be useful in protection and prevention of thrombus, endotoxic shock, and from myocardial ischeamia. Ginkgo can be used for intermittent claudication.

The WHO reports that the medicinal uses of Ginkgo biloba that are supported by clinical data include treatment of the effects mild to moderate cerebrovascular insufficiency as well as the effects of peripheral arterial occlusive diseases. Cerebrovascular insufficiency, i.e., insufficient blood flow to the brain, may manifest itself as such memory deficit, disturbed concentration or headaches. Peripheral arterial occlusive diseases are those in which the blood flow to the smaller arteries are restricted and may include claudication, i.e., painful walking, and Raynaud's disease, a condition in which the extremities such as fingers, toes, nose or ears, feel numb and cold. Preliminary studies suggested that Ginkgo might be of benefit in multiple sclerosis, but clinical trials failed to show any effect on cognitive function in MS patients.

5.Grape seed extract:

Grape seed extracts are industrial derivatives from whole grape seeds that have a great concentration of vitamin E, flavonoids, linoleic acid and phenolic OPCs (oligomeric proanthocyanidins, Proanthocyanidins). The typical commercial opportunity of extracting grape seed constituents has been for chemicals known as polypehols having antioxidant activity in vitro.

Grape seed extract is sometimes suggested for the following, although evidence is slight:

Alzheimer's disease
Diabetes (improving blood sugar control)
Improving night vision
Protecting collagen and elastin in skin (anti-aging)
Treating hemorrhoids
Protecting against oxidative rancidity and bacterial pathogens

Chronic venous insufficiency

In chronic venous insufficiency, blood pools in the legs, causing pain, swelling, fatigue, and visible veins. A number of high quality studies have shown that OPCs from grape seed can reduce symptoms.

High blood pressure

Theoretically, grape seed extract might help treat hypertension or high blood pressure. Antioxidants, like the ones found in grape seed, help protect blood vessels from damage. Damaged blood vessels can lead to higher blood pressure. In several animal studies, grape seed extract substantially reduced blood pressure. But human studies are needed to see whether grape seed extract helps people with high blood pressure.

Cancer

Studies have found that grape seed extracts may prevent the growth of breast, stomach, colon, prostate, and lung cancer cells in test tubes. However, there is no clear evidence yet whether it works in humans. Antioxidants, such as those found in grape seed extract, are thought to reduce the risk of developing cancer. Grape seed extract may also help prevent damage to human liver cells caused by chemotherapy medications. Talk to your doctor or pharmacist before combining antioxidants with any chemotherapy drugs to make sure they interact safely together and that they don't interfere with effects of the chemotherapy medications.

Structures of the major flavan-3-ols identified in grape seed extract

Proanthocyanidin B-1 Dimer Proanthocyanidin C-1 Trimmer

6.Pine bark extract:

Pine bark extract is made from the bark of the maritime pine tree (Pinus pinaster), which contains naturally occurring chemicals called proanthocyanidins. The maritime pine is native to the western Mediterranean, with a range extending over Portugal, Spain, France, Italy, and Morocco. Pine bark extract is commonly sold under the brand name Pycnogenol. Pycnogenol is also the name of a group of compounds that contain proanthocyanidins taken from a number of natural sources, such as grape seeds and other plants. In addition to the Pycnogenol brand, there are several other pine bark extract supplements available, which may use different types of pine bark and have different formulations. Pine bark extract is used for its antioxidant properties.

As a member of the flavonoid family, OPCs have established free radical scavenging and antioxidant activity. Pine bark extracts have been used in France since 1950 to prevent cardiovascular disease primarily on the basis of its antioxidant functionality. More recently, pine bark extracts have garnered growing research attention because of accumulating evidence regarding its diverse clinical pharmacology. Recent studies suggest that in addition to its well-known antioxidant properties, pine bark extracts may also have lowering effects on blood pressure. The blood pressure lowering effect of pine bark extracts have physiological plausibility because of its ability to antagonize the vasoconstriction caused by epinephrine and norepinephrine through increased activity of endothelial nitric oxide synthase. Pine bark extracts have also been found to reduce blood concentrations of endothelin – the most potent endothelial-derived vasoconstrictor.

Furthermore, published preliminary data of pine bark extracts suggest a myriad of additional cardiovascular benefits, including improved glycemic control, reduced body weight, improved lipid profile, improved peripheral circulation, and blunted platelet aggregation. While these studies provide promising information, relative few were as large or as rigorous as optimal for such a widely used herbal therapy. Again, please note that the published studies to date used a variety of pine bark extracts other than the specific formulation we are researching in the Pine Bark Research Study

Ref:

Blood Brain Barrier

2012-07-24T08:11:00.002-07:00

Blood-brain barrier (BBB) is the mechanism that controls the passage of substances from the blood into the cerebrospinal fluid and, thus, into the brain and spinal cord. The BBB lets essential metabolites, such as Oxygen and glucose, pass from the blood to the brain and central nervous system (CNS) but blocks most molecules that are more massive than about 500 Daltons. This is a low mass in biomolecular terms and means that everything from hormones and neurotransmitters to viruses and bacteria are refused access to the brain by the BBB. It also means that many drugs, which would otherwise be capable of treating CNS disorders, are denied access to the very regions where they would be affective.

Key functions of the BBB are:

Protecting the brain from "foreign substances" in the blood that could injure the brain.
Shielding the brain from hormones and neurotransmitters in the rest of the body.
Maintaining a constant environment (homoestasis) for the brain.

a | The blood–brain barrier (BBB) is formed by endothelial cells at the level of the cerebral capillaries. These endothelial cells interact with perivascular elements such as basal lamina and closely associated astrocytic end-feet processes, perivascular neurons (represented by an interneuron here) and pericytes to form a functional BBB. b | Cerebral endothelial cells are unique in that they form complex tight junctions (TJ) produced by the interaction of several transmembrane proteins that effectively seal the paracellular pathway. These complex molecular junctions make the brain practically inaccessible for polar molecules, unless they are transferred by transport pathways of the BBB that regulate the microenvironment of the brain. There are also adherens junctions (AJ), which stabilize cell–cell interactions in the junctional zone. In addition, the presence of intracellular and extracellular enzymes such as monoamine oxidase (MAO), γ-glutamyl transpeptidase (γ-GT), alkaline phosphatase, peptidases, nucleotidases and several cytochrome P450 enzymes endow this dynamic interface with metabolic activity. Large molecules such as antibodies, lipoproteins, proteins and peptides can also be transferred to the central compartment by receptor-mediated transcytosis or non-specific adsorptive-mediated transcytosis. The receptors for insulin, low-density lipoprotein (LDL), iron transferrin (Tf) and leptin are all involved in transcytosis. P-gp, P-glycoprotein; MRP, multidrug resistance-associated protein family.

Discovery of the BBB:

The special properties of the BBB were first observed in the late 19th century by the German bacteriologist Paul Ehrlich. He found that when he injected coloured dyes into the blood stream they leaked out of capillaries in most regions of the body to stain the surrounding tissues; the brain, however, remained unstained. Ehrlich wrongly surmised that the brain had a low affinity for the dyes. It was his student, Edwin Goldmann, who did the other half of the experiment and realized the truth of what was going on. Goldmann injected a dye into the cerebrospinal fluid that surrounds the brain and observed that it stained the brain, but nothing else. Goldmann correctly concluded that the dyes was unable to cross the specialized walls of brain capillaries.

Anatomy of the BBB:

The key aspect of the BBB is the presence of the thin, flat cells known as Endothelial cells which form the walls of capillaries. In most the body, the Endothelial cells in the capillaries overlap at what is called junctions. These junctions are leaky enough to let a lot of different materials move through the wall of the blood vessel into the tissue and back again. These materials include normally beneficial stuff such as hormones and nutrient molecules as well as potentially harmful agents like toxins, viruses, and bacteria. Substances can get into the surrounding tissues either by leaking out of the junctions or passing straight through the Endothelial cells.

However, in the brain there is a different arrangement where the Endothelial cells joins up. The Endothelial cells meet each other at what is called TIGHT JUNCTIONS. These junctions block the passage of most things except for small molecules and are a crucial components of the BBB.

In order to traverse the walls of the brain capillaries, substances must move through the Endothelial cell membranes. Because the main constitute of cell membranes are lipids, it would seem that a molecule could only can get into the brain if it was lipid-soluble. However, many ions and small molecules that are not readily soluble is lipids do move quite readily from brain capillaries into brain tissue. A molecule like glucose, the primary source of metabolic energy for neurons and glial cells, is an obvious example. The explanation for this is the presence of specific transporters for glucose and other critical molecules and ions.

In addition to tight junctions, the "end feet" of Astrocytes (Astraglia)[ the terminal regions of astrocytic processes] surround the outside of capillary Endothelial cells.

Barriers are present at three main sites: the brain endothelium forming the blood–brain barrier (BBB) (1), the arachnoid epithelium (2) forming the middle layer of the meninges, and the choroid plexus epithelium (3), which secretes cerebrospinal fluid (CSF). At each site, the physical barrier is caused by tight junctions that reduce the permeability of the paracellular (intercellular cleft) pathway. In circumventricular organs (CVOs, not shown), which contain neurons specialized for neurosecretion and/or chemosensitivity, the endothelium is leaky. This allows tissue–blood exchange, but as these sites are separated from the rest of the brain by an external glial barrier, and from CSF by a barrier at the ependyma, CVOs do not form a leak across the BBB. Modified, with permission, from Ref.163 © (1990) Kluwer Academic.

The barrier is formed by capillary endothelial cells, surrounded by basal lamina and astrocytic perivascular endfeet. Astrocytes provide the cellular link to the neurons. The figure also shows pericytes and microglial cells. a | Brain endothelial cell features observed in cell culture. The cells express a number of transporters and receptors, some of which are shown. EAAT1–3, excitatory amino acid transporters 1–3; GLUT1, glucose transporter 1; LAT1, L-system for large neutral amino acids; Pgp, P-glycoprotein. b | Examples of bidirectional astroglial–endothelial induction necessary to establish and maintain the BBB. Some endothelial cell characteristics (receptors and transporters) are shown. 5-HT, 5-hydroxytryptamine (serotonin); ANG1, angiopoetin 1; bFGF, basic fibroblast growth factor; ET1, endothelin 1; GDNF, glial cell line-derived neurotrophic factor; LIF, leukaemia inhibitory factor; P₂Y₂, purinergic receptor; TGF, transforming growth factor-; TIE2, endothelium-specific receptor tyrosine kinase 2. Data obtained from astroglial–endothelial co-cultures and the use of conditioned medium.

Molecular composition of endothelial tight junctions

Simplified and incomplete scheme showing the molecular composition of endothelial tight junctions. Occludin and the claudins — proteins with four transmembrane domains and two extracellular loops — are the most important membranous components. The junctional adhesion molecules (JAMs) and the endothelial selective adhesion molecule (ESAM) are members of the immunoglobulin superfamily. Within the cytoplasm are many first-order adaptor proteins, including zonula occludens 1, 2 and 3 (ZO-1–3) and Ca²⁺-dependent serine protein kinase (CASK), that bind to the intramembrane proteins. Among the second-order adaptor molecules, cingulin is important, and junction-associated coiled-coil protein (JACOP) may also be present. Signalling and regulatory proteins include multi-PDZ-protein 1 (MUPP1), the partitioning defective proteins 3 and 6 (PAR3/6), MAGI-1–3 (membrane-associated guanylate kinase with inverted orientation of protein–protein interaction domains), ZO-1-associated nucleic acid-binding protein (ZONAB), afadin (AF6), and regulator of G-protein signalling 5 (RGS5). All of these adaptor and regulatory/signalling proteins control the interaction of the membranous components with the actin/vinculin-based cytoskeleton. In epithelial cells, tight and adherens junctions are strictly separated from each other, but in endothelial cells these junctions are intermingled. The most important molecule of endothelial adherens junctions is vascular endothelial cadherin (VE-cadherin). In addition, the platelet–endothelial cell adhesion molecule (PECAM) mediates homophilic adhesion. The chief linker molecules between adherens junctions and the cytoskeleton are the catenins, with desmoplakin and p120 catenin (p120^ctn) also involved. Itch, E3 ubiquitin protein ligase. Modified, with permission, from Ref. 20 © (2005) Wiley-VCH.

General Properties of the BBB

Large molecules do not pass through the BBB easily.
Low lipid (fat) soluble molecules do not penetrate into the brain. However, lipid soluble molecules, such as barbituate drugs, rapidly cross through into the brain.
Molecules that have a high electrical charge are slowed.

What can weaken BBB ?

Hypertension (high blood pressure): high blood pressure opens the BBB.
Development: the BBB is not fully formed at birth.
Hyperosmolitity: a high concentration of a substance in the blood can open the BBB.
Microwaves: exposure to microwaves can open the BBB.
Radiation: exposure to radiation can open the BBB.
Infection: exposure to infectious agents can open the BBB.
Trauma, Ischemia, Inflammation, Pressure: injury to the brain can open the BBB.

There are several areas of the brain where the BBB is weak. This allows substances to cross into the brain somewhat freely. These areas are known as "circumventricular organs". Through the circumventricular organs the brain is able to monitor the makeup of the blood. The circumventricular organs include:

* Pineal body: Secretes melatonin and neuroactive peptides. Associated with circadian rhythms.

* Neurohypophysis (posterior pituitary): Releases neurohormones like oxytocin and vasopressin into the blood.

* Area postrema: "Vomiting center": when a toxic substance enters the bloodstream it will get to the area postrema and may cause the animal to throw up. In this way, the animal protects itself by eliminating the toxic substance from its stomach before more harm can be done.

* Subfornical organ: Important for the regulation of body fluids.

* Vascular organ of the lamina terminalis: A chemosensory area that detects peptides and other molecules.

* Median eminence: Regulates anterior pituitary through release of neurohormones.

Pathophysiology:

The blood–brain barrier acts very effectively to protect the brain from many common bacterial infections. Thus, infections of the brain are very rare. However, since antibodies and antibiotics are too large to cross the blood–brain barrier, infections of the brain that do occur are often very serious and difficult to treat. However, the blood–brain barrier becomes more permeable during inflammation. This allows some antibiotics and phagocytes to move across the BBB; although, this can allow bacteria/viruses to also move across.

Astroglial–endothelial signalling under pathological conditions

Examples of astroglial–endothelial signalling in infection or inflammation, stroke or trauma, leading to opening of the blood–brain barrier (BBB) and disturbance of brain function. bradykinin, produced during inflammation in stroke or brain trauma, acts on endothelial and astroglial bradykinin B₂ receptors, leading to an increase in the concentration of intracellular Ca²⁺. In astrocytes, this can trigger the production of interleukin-6 (IL-6) through activation of nuclear factor-B (NF-B) (1). Bradykinin, substance P, 5-hydroxytryptamine (5-HT, serotonin) and histamine acting on astrocytes can lead to the formation of ATP and prostaglandins (PGs), with effects on vascular tone and endothelial permeability (2) by mechanisms that are known to involve endothelium. Lipopolysaccharide (LPS), formed in infections, leads to the release from microglia of tumour necrosis factor- (TNF), IL-1 and reactive oxygen species (including O₂^-), all of which have the ability to open the BBB (3). Astrocytes downregulate tissue plasminogen activator (tPA) production via transforming growth factor- (TGF), but there is still sufficient tPA to open the BBB, leading to an influx of tPA from the blood (4). Following disruption of the BBB involving a decrease in agrin expression, K⁺ and glutamate (Glu) from the blood can reach the brain extracellular space. Aquaporin 4 (AQP4) is upregulated on the astroglial endfeet, leading to astroglial swelling (5). ET1, endothelin 1.

Meningitis

Meningitis is an inflammation of the membranes that surround the brain and spinal cord. Meningitis is most commonly caused by infections with various pathogens, examples of which are Streptococcus pneumoniae and Haemophilus influenza. When the meninges are inflamed, the blood–brain barrier may be disrupted. This disruption may increase the penetration of various substances (including either toxins or antibiotics) into the brain. Antibiotics used to treat meningitis may aggravate the inflammatory response of the central nervous system by releasing neurotoxins from the cell walls of bacteria-like lipopolysaccharide (LPS). Depending on the causative pathogen, whether it is bacterial, fungal, or protozoan, treatment with 3rd generation or 4th generation cephalosporins or amphotericin B is usually prescribed.

De Vivo disease

De Vivo disease (also known as GLUT1 deficiency syndrome) is a rare condition caused by inadequate transportation of the sugar, glucose, across the blood–brain barrier, resulting in developmental delays and other neurological problems. Genetic defects in glucose transporter type 1 (GLUT1) appears to be the primary cause of De Vivo disease.

Pathways across the BBB:

A schematic diagram of the endothelial cells that form the blood–brain barrier (BBB) and their associations with the perivascular endfeet of astrocytes. The main routes for molecular traffic across the BBB are shown. a | Normally, the tight junctions severely restrict penetration of water-soluble compounds, including polar drugs. b | However, the large surface area of the lipid membranes of the endothelium offers an effective diffusive route for lipid-soluble agents. c | The endothelium contains transport proteins (carriers) for glucose, amino acids, purine bases, nucleosides, choline and other substances. Some transporters are energy-dependent (for example, P-glycoprotein) and act as efflux transporters. AZT, azidothymidine. d | Certain proteins, such as insulin and transferrin, are taken up by specific receptor-mediated endocytosis and transcytosis. e | Native plasma proteins such as albumin are poorly transported, but cationization can increase their uptake by adsorptive-mediated endocytosis and transcytosis. Drug delivery across the brain endothelium depends on making use of pathwaysb–e; most CNS drugs enter via route b. Modified, with permission, from Ref. 8 © (1996) Elsevier Science.

Ref:

Sepsis

2012-07-23T09:28:00.001-07:00

Sepsis is a serious medical condition caused by an overwhelming immune response to infection. Immune chemicals released into the blood to combat the infection trigger widespread inflammation, which leads to blood clots and leaky vessels. This results in impaired blood flow, which damages the body’s organs by depriving them of nutrients and oxygen. In severe cases, one or more organs fail. In the worst cases, blood pressure drops, the heart weakens and the patient spirals toward septic shock. Once this happens, multiple organs—lungs, kidneys, liver—may quickly fail and the patient can die. Sepsis is a major challenge in the intensive care unit, where it’s one of the leading causes of death. It arises unpredictably and can progress rapidly. Sepsis can be defined as the body's response to an infection. An infection is caused by micro-organisms or "germs" (usually bacteria, fungi and viruses,but bacteria are the most common culprits) invading the body, and can be limited to a particular body region (e.g., a tooth abscess) or can be widespread in the bloodstream (often called "septicemia" or "blood poisoning"). It stems from another medical condition such as an infection in the lungs, urinary tract, skin, abdomen (such as appendicitis) or other part of the body. Invasive medical procedures like the insertion of a vascular catheter can introduce bacteria into the bloodstream and bring on the condition.

Although everybody is at potential risk of developing sepsis from minor infections (e.g., flu, urinary tract infections, gastroenteritis, etc.), sepsis is most likely to develop in people who:

Are very young (e.g. premature babies) or very old
Have a weakened ("compromised") immune system, often because of treatments such as chemotherapy for cancer, steroids (e.g. cortisone) for inflammatory conditions, etc.
Have wounds or injuries, such as those from burns, a car crash, or a bullet
Have certain addictive habits, such as alcohol or drugs
Are receiving certain treatments or examinations (e.g., intravenous catheters [a small tube for dripping fluids into the vein], wound drainage, urinary catheters [a small tube inserted into the bladder]
Are more prone to develop sepsis than others because of genetic factors (or their "genes")

Patients who are admitted to the hospital with serious diseases are at the highest risk of developing sepsis because of:

Their underlying disease
Their previous use of antibiotics
The presence of drug-resistant bacteria in the hospital
The fact that they often require an intravenous tube, urinary catheter, or wound drainage

The infection leading to sepsis can be acquired outside the hospital (known as community acquired) or in the hospital (known as nosocomial). Hospital-acquired infections are generally more difficult to manage than those acquired in the community, because:

The infecting microorganism is more dangerous to the patient
The patient is often already sick
The microorganism may be resistant to common treatments due to the widespread use of antibiotics in hospitals

THE OCCURRENCE OF SEPSIS

Every year, severe sepsis strikes about 750,000 Americans. It’s been estimated that between 28 and 50 percent of these people die—far more than the number of U.S. deaths from prostate cancer, breast cancer and AIDS combined. The number of sepsis cases per year has been on the rise in the United States. This may be due to an aging population, the increased longevity of people with chronic diseases, the spread of antibiotic-resistant organisms, an upsurge in invasive procedures and broader use of immunosuppressive and chemotherapeutic agents.

Sepsis occurs in three different forms or stages, called:

# Uncomplicated sepsis

# Severe sepsis

# Septic shock

The disease progresses in some people through all three stages. Despite optimal (best or most favourable) care, some patients may not respond to treatment, and may develop multiple organ disease and eventually die.

UNCOMPLICATED SEPSIS:

Uncomplicated sepsis, such as that caused by flu and other viral infections, gastroenteritis, or dental abscesses, is very common and is experienced by millions of people each year. The majority of these people will not need hospital treatment.

2.SEVERE SEPSIS:

Severe sepsis arises when sepsis occurs in combination with problems in one or more of the vital organs, such as the heart, kidneys, lungs, or liver. Because of problems with their vital organs, people with severe sepsis are likely to be very ill and are more likely to die (in 30-35 % of cases) than those with uncomplicated sepsis.

3.SEPTIC SHOCK

Septic shock occurs when sepsis is complicated by low blood pressure that does not respond to standard treatment (fluid administration) and leads to problems in one or more of the vital organs as described above. The condition means that the body does not receive enough oxygen to properly function and drugs called vasopressors are used to raise the blood pressure. Septic shock patients are very ill and need rapid emergency admission to the hospital intensive care unit (ICU). Despite active treatment in the ICU, the death rate is around 50%.

What are the symptoms of sepsis?

Common symptoms of sepsis are fever, chills, rapid breathing and heart rate, rash, confusion and disorientation. Many of these symptoms, such as fever and difficulty breathing, mimic other conditions, making sepsis hard to diagnose in its early stages.

HOW IS SEPSIS TREATED?

The treatment of severe sepsis and septic shock may include:

Antibiotics to treat the infection
Surgery to control the source of the infection
Fluids through the intravenous or IV catheter (drip) - these fluids may sometimes include nutritional liquids if the patient cannot eat normally
Drugs to raise the blood pressure or improve the function of the heart
Organ support, such as artificial ventilation for the lungs (breathing machine), kidney support (kidney machine), etc

Despite the best possible care, some patients may not respond to treatment, and but rather develop further organ failure and die. Research into better treatment methods continues. Recent studies have shown that survival in some patients with severe sepsis can be improved with medications that alter blood clotting, reduce inflammation, or support the stress response, and by new approaches to support organ function. These treatments are not appropriate in all patients. These therapies may include:

- Activated protein C

- Steroids

- Using modest breath sizes

- Maintaining blood sugar

Ref: http://www.nigms.nih.gov/Education/factsheet_sepsis.htm

New Drug Candidate Shows Promise Against Cancer

2012-07-22T04:40:00.001-07:00

Drugs containing platinum are among the most powerful and widely used cancer drugs. However, such drugs have toxic side effects, and cancer cells can eventually become resistant to them. The Food and Drug Administration (FDA)-approved platinumbased antitumor drugs, cisplatin [cis-diamminedichloroplatinum ( II)], carboplatin [cis-diammine(1,1′-cyclobutanedicarboxylato)- platinum(II)], and oxaliplatin [(R,R)-1,2-diaminocyclohexane) oxalatoplatinum(II)], are currently among the most effective chemotherapies in clinical use for the treatment of cancers. These Pt-based anticancer agents typically form bifunctional intra- and interstrand DNA cross-links through covalent bond with purine nucleobases. These cross-links inhibit transcription and result in cell death. Platinum-based drugs are limited by side effects and poor activity in certain types of cancer resulting from acquired or intrinsic resistance. These limitations evoke a need for new platinum-based chemotherapeutics with novel mechanisms of action.

MIT chemistry professor Stephen J. Lippard, who has spent much of his career studying platinum drugs, has now identified a compound that kills cancer cells better than cisplatin, the most commonly used platinum anticancer drug. The new compound may be able to evade cancer-cell resistance to conventional platinum compounds. “I’ve long believed that there’s something special about platinum and its ability to treat cancer,” Lippard says. Using new variants, “we might have a chance of applying platinum to a broader range of cancer types, more successfully,” he says. Lippard is senior author of a paper describing the new drug candidate, known as phenanthriplatin, in the Proceedings of the National Academy of Sciences (PNAS). Lead author is postdoc Ga Young Park; other authors are graduate student Justin Wilson and postdoc Ying Song.

The unique features of pyriplatin strongly encouraged further study of monofunctional Pt(II) compounds as anticancer drug candidates. Because pyriplatin is more than 10-fold less potent than cisplatin or oxaliplatin, it was of interest to explore analogs with improved activity. We therefore devised a strategy, based on our understanding of the structure of pyriplatin on DNA in pol II, to synthesize other monofunctional platinum compounds that might act more efficaciously as anticancer drugs and to investigate how cells process the specific lesions induced by these previously untried candidates. To improve the potency and cellular uptake of monofunctional Pt(II) complexes, various N-heterocyclic ligands (Am) were substituted for pyridine and the resulting compounds were fully characterized and evaluated for biological activity. Among them, phenanthriplatin, cis-[Pt(NH3)2(phenanthridine)Cl]NO3, was identified to exhibit greater efficacy than cisplatin and oxaliplatin in established human cancer cell lines. The cellular uptake, DNA binding, and transcription-inhibition properties of phenanthriplatin were investigated to provide insight into the high potency of this compound.

Phenanthriplatin was tested against 60 types of cancer cells as part of the National Cancer Institute’s cancer-drug screening program, and it was found to be four to 40 times more potent than cisplatin, depending on the cancer type. It also showed a different pattern of activity than that of cisplatin, suggesting that it could be used to treat types of cancer against which cisplatin is ineffective. One reason for the efficacy of phenanthriplatin is that it can get into cancer cells more easily than cisplatin, Lippard says. Previous studies have shown that platinum compounds containing carbon can pass through specific channels, found in abundance on cancer cells, that allow positively charged organic compounds to enter. Another reason is the ability of phenanthriplatin to inhibit transcription, the process by which cells convert DNA to RNA in the first step of gene expression. Another advantage of phenanthriplatin is that it seems to be able to evade some of cancer cells’ defences against cisplatin. Sulfur-containing compounds found in cells, such as glutathione, can attack platinum and destroy it before it can reach and bind to DNA. However, phenanthriplatin contains a bulky three-ring attachment that appears to prevent sulfur from inactivating the platinum compounds as effectively.

Among the series of recent monofunctional, cationic platinum(II) compounds, phenanthriplatin destroys cancer cells with greater efficacy than either cisplatin or oxaliplatin. Our data indicate that the higher cytotoxicity of phenanthriplatin originates from its efficient cellular uptake and strong transcription inhibitory properties. Studies of its reactivity toward cellular components reveal efficient binding to nucleobases, typically required of an active platinum drug, but retarded reactivity toward a sulfurcontaining nucleophile, such as those associated with cellular resistance mechanisms. An important feature of phenanthriplatin is that its spectrum of activity against panels of cells does not match those of the FDA-approved platinum-based drugs. Phenanthriplatin may therefore be effective against cancer types that are typically resistant to platinum therapy.

Ref:

1. http://www.technologynetworks.com/admet/news.aspx?id=141134

2. http://www.technologynetworks.com/admet/news.aspx?id=141134

3. http://web.mit.edu/chemistry/www/news/inthenews.html

Federal Register Notice on Drugs

2012-07-17T02:33:00.000-07:00

Risk Evaluation and Mitigation Strategy (REMS)

A Risk Evaluation and Mitigation Strategy (REMS) is a strategy to manage a known or potential serious risk associated with a drug or biological product. A REMS will be required if FDA finds that a REMS is necessary to ensure that the benefits of the drug or biological product outweigh the risks of the product, and FDA notifies the sponsor. A REMS can include a Medication Guide, Patient Package Insert, a communication plan, elements to assure safe use, and an implementation system, and must include a timetable for assessment of the REMS. Some drug and biological products that previously were approved/licensed with risk minimization action plans (RiskMAPs) will now be deemed to have REMS.

The decision to approve a drug is highly dependent on the answer to the following question: “Do the benefits of the drug outweigh the risks?” Both pharmaceutical manufacturers and the Food and Drug Administration (FDA) continually evaluate the potential benefits of a drug versus its potential risks. Many factors are taken into consideration, some of which include:

Seriousness of the disease or condition to be treated
Size of the patient population
Expected benefit of the drug
Expected duration of treatment
Seriousness of the known or potential adverse events

These evaluations are performed not only prior to the approval of a new drug, but also throughout the entire life cycle of the drug. This serves as a means to continuously assess the safety and efficacy of existing drugs based on adverse event reports and results from post-marketing clinical studies.

Risk Minimization Action Plans (RiskMAPs)

After several products (e.g., Lotronex®, Rezulin®) were removed from the market because of safety concerns, the FDA came under increased scrutiny. FDA formed working groups that developed three risk management concept papers and draft guidances in May 2004. Final risk minimization guidances were issued in March 2005 to address safety monitoring and interventions:

Premarketing Risk Assessment
Development and Use of Risk Minimization Action Plans
Good Pharmacovigilance Practices and Pharmacoepidemiologic Assessment

The guidance for RiskMAPs gave manufacturers specific direction about how to address product risk-related goals with tools or interventions to mitigate the risks and ensure strict adherence to product labeling. Products considered risky by the FDA were approved only if an appropriate RiskMAP was instituted by the manufacturer.

Despite Roche’s earlier efforts to communicate the risks associated with the use of Accutane® via the S.M.A.R.T. program, which included branded and generic products, product use among women of childbearing potential continued. This led to collaboration in 2006 among Roche, generic manufacturers, and the FDA to launch a shared RiskMAP program for isotretinoin – iPLEDGE.

Other examples of products with RiskMAPs included:

Tikosyn® (dofetilide)
Tracleer® (bosentan)
Plenaxis® (abarelix)

Elements of these programs varied from the highest level of restricted distribution systems (e.g., performance-linked access systems) to educational materials to mitigate known or potential risks.

REMS

In September 2007, the Food and Drug Administration Amendments Act (FDAAA) was signed into law providing the FDA with expanded authority. Some of the new provisions gave FDA the authority to:

Require post-approval studies or clinical trials to assess a known or serious risk, or to learn more about a hypothetical serious risk,
Require that new safety information be added to the product labeling, and
Require that companies submit Risk Evaluation and Mitigation Strategies (REMS) when deemed necessary to ensure that the product’s benefits outweigh the risks

FDA may now require REMS for any NDA, ANDA, or BLA at any stage of the product lifecycle. If the FDA requires a REMS, the manufacturer has 120 days to submit a proposed REMS if it is for a marketed drug. For a new drug, the manufacturer must include the proposed REMS as part of its New Drug Application (NDA) submission. Once approved, the REMS creates enforceable obligations for the manufacturer and the FDA.

The FDA requested that 16 selected products with current RiskMAPs transition into REMS by September 2008. Because of this expanded FDA authority beyond what was previously called RiskMAP, REMS have superseded the regulatory authority of RiskMAPs, making use of the term RiskMAP obsolete.

REMS Elements

Proposed REMS may contain any of the following elements:

Medication Guide – Document written for patients highlighting important safety information about the drug; this document must be distributed by the pharmacist to every patient receiving the drug.
Communication Plan – Plan to educate healthcare professionals on the safe and appropriate use of the drug and consists of tools and materials that will be disseminated to the appropriate stakeholders.
Elements to Assure Safe Use (EASU) – These are strictly controlled systems or requirements put into place to enforce the appropriate use of a drug. Examples of EASUs include physician certification requirements in order to prescribe the drug, patient enrollment in a central registry, distribution of the drug restricted to certain specialty pharmacies, etc.
Implementation Plan – A description of how certain EASUs will be implemented.
Timetable for Submission of Assessments – The frequency of assessment of the REMS performance with regard to meeting the goal(s) and objective(s). FDA requires that assessments be conducted at 18 months, 3 years, and 7 years post-launch, at a minimum. Results of these evaluations must be reported to the FDA and will determine whether additional actions or modifications to the REMS program are required.

At this date, over 88 REMS have been approved by the FDA since the implementation of FDAAA. Final FDA guidance is anticipated by the end of 2009.

REMS Requirements

To assist manufacturers in developing REMS, the FDA has issued an outline of specific elements that should be included in the proposed document. The proposed REMS should be concise and specific and include the goal(s) along with the explicit components that will be developed to ensure that the drug will be used safely and appropriately.

The manufacturer should also describe how it intends to evaluate whether the REMS is meeting its goal(s) and objective(s) at various time points from the time of launch and beyond.

Failure to comply with FDA REMS requirements can render the company’s drug misbranded and result in substantial penalties (e.g., $250,000 to $1 MM cap per violation; $1 MM to $10 MM cap per proceeding).

Check the following link For Approved Risk Evaluation and Mitigation Strategies (REMS) :

http://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm111350.htm

Ref:

http://www.paragonrx.com/rems-hub/rems-history/

http://www.fda.gov/RegulatoryInformation/Legislation/FederalFoodDrugandCosmeticActFDCAct/SignificantAmendmentstotheFDCAct/FoodandDrugAdministrationAmendmentsActof2007/ucm095439.htm

Pre-exposer prophylaxis (PrEP)

Pre-exposure prophylaxis (PrEP) is any medical or public health procedure used before exposure to the disease causing agent, its purpose is to prevent, rather than treat or cure a disease. An example would be if a doctor gave a medication used to treat a disease to a healthy person who is not thought to have that disease, but is at risk for contracting it. More specifically, this practice is common with people who are about to travel from an area without Malaria to an area where malaria is a risk, and also it is being researched as a tool to prevent persons from contracting HIV. Pre-exposure prophylaxis can also refer to the aggressive use of vaccination, for example in an attempt to prevent Rabies in people such as laboratory workers who are high risk for being bitten by rabid animals.

http://www.prepwatch.org/

Post-exposure prophylaxis (PEP)

Post-exposure prophylaxis (PEP) is any prophylactic treatment started immediately after exposure to a pathogen (such as a disease-causing virus), in order to prevent infection by the pathogen and the development of disease. PEP is commonly and very effectively used to prevent the outbreak of Rabies after a bite by a rabid animal. The treatment consists of repeated injections of Rabies vaccine and immunoglobulin. Tetanus post-exposure consists of 2 to 3 injections of tetanus vaccine and tetanus immunoglobulin, this treatment is also used in rabies post-exposure prophylaxis.

http://www.who.int/hiv/topics/prophylaxis/en/

HIV Infection Prevention

2012-07-16T18:15:00.000-07:00

Gilead Sciences announced that the FDA has approved Truvada (Emtricitabine 200mg and Tenofovir disoproxil fumarate 300mg tablets), for pre-exposure prophylaxis (PrEP) in combination with safer sex practices, to reduce the risk of sexually acquired HIV-1 infection in adults at high risk. This approval was based on data from two large placebo-controlled trials known as the Pre-Exposure Prophylaxis Initiative (iPrEx) and Partners PrEP that found that Truvada reduced the risk of acquiring HIV infection by 42% and 75%, respectively.

As part of the approval, Gilead worked with the FDA to develop a Risk Evaluation and Mitigation Strategy (REMS) to help ensure safe use of Truvada for PrEP as part of a comprehensive prevention strategy. Gilead has developed FDA-approved materials to educate and inform healthcare providers and uninfected individuals about Truvada for PrEP.

PHARMACOLOGICAL CLASS FOR TRUVADA

Nucleoside/nucleotide analogue (reverse transcriptase inhibitors)

Emtricitabine Tenofovir disoproxil fumarate

INDICATIONS FOR TRUVADA

HIV-1 infection.

ADULT DOSE FOR TRUVADA

≥18yrs (CrCl ≥50mL/min): 1 tab once daily. Renal impairment: CrCl 30–49mL/min: 1 tab every 48 hrs; CrCl <30mL/min, hemodialysis: not recommended.

CHILDREN'S DOSING FOR TRUVADA

Not recommended for <18 years

INTERACTIONS FOR TRUVADA

Avoid concomitant drugs that contain Emtricitabine, Tenofovir, Lamivudine, or Adefovir dipivoxil. Potentiates didanosine toxicity (>60kg; reduce dose of didanosine); discontinue didanosine if toxicity develops. Monitor drugs that reduce renal function or compete for renal tubular secretion (eg, Adefovir dipivoxil, Cidofovir, Acyclovir, Valacyclovir, Ganciclovir, Valganciclovir). Avoid concomitant or recent use of nephrotoxic agents. Potentiated by Lopinavir/Ritonavir, Atazanavir; monitor for toxicity. Concomitant Atazanavir: must give with Ritonavir. Caution with triple nucleoside-only regimen (high rate of early viral non-response); monitor and consider alternative therapy. See literature for dosing of concomitant didanosine or ritonavir.

WARNINGS/PRECAUTIONS FOR TRUVADA

Suspend if lactic acidosis or hepatotoxicity occurs. Renal impairment: monitor CrCl and serum phosphorus. Women, obesity, prolonged nucleoside exposure, other risk factors for hepatic dysfunction: increased risk of toxicity.

Not for treating chronic hepatitis B; test for HBV before starting therapy and monitor patients co-infected with HIV-1 and HBV during and for several months after stopping treatment (discontinuing therapy may exacerbate HBV infection).

History or risk of fractures or osteopenia: monitor bone mineral density (BMD); consider Vit. D and calcium supplementation. Elderly.

Pregnancy (Category B).

Nursing mothers: not recommended.

These materials highlight the importance of strict adherence to the dosing regimen, emphasize that Truvada must be considered as only one part of a comprehensive prevention strategy to reduce the risk of HIV-1 infectionm, and convey that Truvada for PrEP should only be used in individuals who are confirmed HIV negative. HIV-1 screening should be repeated at least every three months while taking Truvada for PrEP.

Ref:http://www.gilead.com/

DISCLAIMER: All information on this website is for educational purposes only and is not intended to provide medical advice nor medical decision.

Sunscreen

2012-07-16T09:24:00.000-07:00

Choosing Sunscreen?

SATURDAY, July 14 (HealthDay News) -- You may know that it's important to protect your skin when you're outdoors this summer, but you need to know how to pick the correct sunscreen and how to apply it, the American Academy of Dermatology says.

"Consumers can be overwhelmed by the large number of sunscreen products available and because of that they avoid using sunscreen all together, resulting in sunburn and overexposure to the sun's ultraviolet (UV) radiation," dermatologist Dr. Henry Lim said in an AAD news release.

"Dermatologists can provide the public with the information they need to make smart choices when it comes to sun protection, which can help reduce their risk for skin cancer, and keep their skin looking healthy and youthful," he added.

The AAD says you should read the label on sunscreen products and use only those that offer:

Broad-spectrum coverage (label may say "broad spectrum," "protects against UVA/UVB" or "UVA/UVB protection").
SPF of 30 or higher.
Water resistance.

The AAD also recommends that you: re-apply sunscreen every two hours when outdoors; find shade whenever your shadow appears to be shorter than you are; wear protective clothing, including long sleeves, pants, wide-brimmed hat and sunglasses.

An AAD online survey found that many people are still confused about SPF numbers and how to use sunscreen correctly. Only 18 percent of respondents knew that a sunscreen with SPF 30 does not provide twice the protection of an SPF 15, and only 28 percent of respondents who said they sometimes or always use sunscreen reapplied sunscreen every two hours.

UV protection does not increased proportionately with a designated SPF number, Lim said. An SPF 30 screens out 97 percent of UV rays, an SPF 15 screens 93 percent of UV rays, and an SPF 2 screens 50 percent of UV rays, he explained.

Lim also noted that not applying enough sunscreen or not covering all exposed areas may result in a lower SPF than a sunscreen offers.

"For adequate protection, sunscreens are best applied 15 minutes prior to going outside, and re-applied every two hours or immediately after swimming or sweating," Lim said. "Research demonstrates that most people only apply 25 to 50 percent of the recommended amount of sunscreen, which is one ounce for the entire body or enough to fill a shot glass. The relationship between SPF and amount applied is not a linear one. For example, if only half the proper amount of SPF 15 is applied, the actual in-use SPF would be approximately 5, which is then inadequate protection."

SOURCE: American Academy of Dermatology, news release, June 14, 2012

http://www.nlm.nih.gov/medlineplus/news/fullstory_127253.html

http://www.nlm.nih.gov/medlineplus/sunexposure.html

Higgs

2012-07-14T07:06:00.004-07:00

Natural products

2012-07-12T04:38:00.000-07:00

Natural products are specific chemical compounds which are produced and secreted by living creatures. There is no mean of any human intervention in the production processes of these products. Some people may get confused purification or extraction with production. Simply because purification or extraction are processes done by humans to obtain these natural products from their sources in a concentrated form. Some natural products may undergo certain modifications to obtain specific function so that these products are called semi-synthesized. However, synthesized products are those completely designed in laboratories and research institutes. There are many types of natural products; such as Carbohydrates, Glycosides, Lipids, Proteins, Alkaloids, Volatile oils, Prostaglandins, Plants exudate and Herbal medicines.

These small molecules provide the source or inspiration for the majority of FDA-approved agents and continue to be one of the major sources of inspiration for drug discovery. In particular, these compounds are important in the treatment of life-threatening conditions. Many of these products are either official in the USP, listed in the Food Chemical Codex (FCC) or generally used in pharmacy.

CARBOHYDRATES:

It is one of the important groups of organic natural products. Carbohydrates embrace A) Aliphatic polyhydric alcohols whether primary alcohols, which are oxidized into Aldehydes [R-CHO], or secondary alcohols, which are oxidized into Ketones [R-CO-R]. Those types of Carbohydrates produce monosaccharides (simple sugars); Aldoses and Ketoses and B) condensation products which are saccharides anhydride; disaccharides trisacchardes.. and so on. Polysaccharides, on the other hand, contain many monosaccharide units joined in long linear or branched chains. Polysacchrides have 2 major biological functions: as storage form for fuel and as structural elements. The di-, tri- and up to about the decasacchrides sometimes are grouped together under the term Oligosacchrides.
The total scheme for the Aldoses and the Ketoses is shown in the following table:

Ref: Remington 1-The Science and Practice of Pharmacy (20th Ed)

For more details on Carbohydrates structures, cyclic structures and Nomenclature check the following link:

http://www.chem.qmul.ac.uk/iupac/2carb/

Official Carbohydrates:

1.Monosaccharides: Dextrose [D-glucose] and Fructose are the only monosaccharides that occur in the free state to any important extent as well as they are present in the juices of many ripe fruits.

2.Disaccharides: Lactose [milk sugar] and Sucrose [cane or beet sugar].

3.Polysaccharides: Dextrin, Collagen, Inulin, Starch, Cellulose and Rice starch.

Inulins are a group of naturally occurring polysacchrides produced by many types of plants.They belong to a class of dietary fibers. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes. Most plants that synthesize and store inulin do not store other forms of carbohydrate such as startch.

Inulin and its analog Sinistrin are used to help measure kindney function by determining the glomerular filtration rate (GFR). GFR is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman's capsule per unit time. Inulin is not secreted or reabsorbed in any appreciable amount at the nephron allowing GFR to be calculated. However, due to clinical limitations, Inulin and Sinistrin although characterised by better handling features are rarely used for this purpose and Creatinine values are the standard for determining an approximate GFR. It is also used for rehydration and remineralization following important loss of water, like diarrhea and diaphoresis. Inulin can also be used as a vaccine adjuvant.

Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch or glycogen. Dextrins are mixtures of polymers of D-glucose units linked by α-(1→4) or α-(1→6) glycosidic linkage. Cyclodextrins are produced from starch by means of enzymatic conversion. They are used in food, pharmaceutical, drug delivery, and chemical industries. Cyclodextrins are able to form host-guest complexes with hydrophobic molecules given the unique nature imparted by their structure. As a result, these molecules have found a number of applications in a wide range of fields. One example is Sugammadex, a modified γ-cyclodextrin which reverses neuromuscular blockade by binding the drug Rocuronium. Other than the above mentioned pharmaceutical applications, cyclodextrins can be employed in environmental protection: these molecules can effectively immobilise inside their rings toxic compounds, like Trichloroethane or heavy metals, or can form complexes with stable substances, like Trichlorfon (an organophosphorus insecticides) or sewage sludge, enhancing their decomposition.

4.Natural products: Other than mentioned above are Acacia, Agar, Pectin, Plantago seed and Tragancanth.

Dietary fiber:

Dietary fiber is the indigestible portion of plant foods having two main components:

soluble (prebiotic or viscous) fiber that is readily fermented in the colon into gases and physiologically active byproducts.
insoluble fiber that is metabolically inert, absorbing water as it moves through the digestive system, easing defecation.

Plant sources of fiber

Soluble fiber is found in varying quantities in all plant foods, including:

Legumes (peas, soybeans, lupins and other beans)
Oats, Rye, Chia, and Barely
Some fruits and fruit juices (including prune juice, plums, berries, bananas, and the insides of apples and pears)
Certain Vegetables such as Broccoli, Carrots, and Jerusalem artichokes.
Root tubules and root vegetables such as sweet potatoes and Onions (skins of these are sources of insoluble fiber also)
Psyllium seed husk (a mucilage soluble fiber) and flax seeds
Nuts, with Almonds being the highest in dietary fiber

Sources of insoluble fiber include:

Whole grain foods
Wheat and Corn bran
nuts and seeds
Potato skins
Hemp seed
Lignans
vegetables such as green beans, cauliflower, zucchini (courgette), celery, and nopal.
some fruits including avocado, and unripe bananas.
the skins of some fruits, including Kiwifruit and tomatoes.

Ref: http://en.wikipedia.org/wiki/Dietary_fiber

GLYCOSIDES:

Glycosides may be defined broadly as condensation products of sugars with various kinds of organic hydroxy compounds. The nonsugar portion is termed aglycone,or aglycon, or agenin. Glycosides undergo hydrolysis yielding sugar and nonsugar moieties. In general , the hydrolysis is catalysed energetically by protons ( in lab we may use dilute acids). Acid hydrolysis occurs whether the Glycosidic linkage is alpha or beta. In addition to acid hydrolysis, nature produces many enzyme to catalyse the hydrolysis. That enzymatic catalyses is quite specific. It should be noted that there are 2 enzymes , namely Emulsin of Almond kernels and Myrosin of black mustard seeds, each of which has the ability to hydrolyse a considerable number of Glycosides. The enzymes frequently occur in the same plant along with Glycosides, but usually in different cells. Glycosides that are derivatives of Rhamnose require a special enzyme known as Rhamnase for their hydrolysis.

List of common Glycosides:

Ref: Remington 1-The Science and Practice of Pharmacy (20th Ed)

Many naturally occurring compounds not usually classed among the Glycosides actually contain glycosidic linkage in their structure. For instance, Gentamycin, Amikacine, Netilmicin, Tobramycin, Novobiocin, and Streptomycin among the antibiotics, Solanine and various other alkaloids (Glucoalkaloids), and nucleosides (consist of purine or pyrimidine base linked with D-ribose or D-2-deoxyribose).

LIPIDS:

The lipids are the fat and fat-like substances that occur in plants and animals. Like the carbohydrates and proteins, the lipids constitute a very important group of organic substances from the standpoint of physiological use. The lipids may be divided into 5 classes according to their chemical structure:

Fixed oils and fat [ester of Glycerol and fatty acids] - Olive oil and Lard
Waxes [esters of high-molecular-weight, monohydric alcohols and high-molecular-weight fatty acids] - Spermaceti
Sterols [ alcohols containing the CYCLOPENTANOPHENANTHEREN, steroids, nucleus] - Cholesterol and Ergosterol
Phospholipids (phosphatides) [esters consisting of Glycerol in combination with fatty acids, phosphoric acid and certain nitrogenous compounds] - Lecithins
Glycolipids (Cerebrosides) These substances are isolated from the brain and from various other sources that, on hydrolysis, yield fatty acids, Galactose, and the nitrogenous compound Sphingosine.

Fixed oils and fats

Fixed oils and fats are mixtures of Glyceryl esters of the so-called high fatty acids [higher molecular weight aliphatic acids], especially Palmitic, Stearic, and Oleic acids.

The Heart

2012-07-03T09:23:00.000-07:00

People have been using heart as a symbol for presenting love, mercy, emotion and passion since centuries. It represents our emotion and health. We have been taught to draw ♥ when we want to tell someone we love you since childhood. The majority of children draw themselves with their parents around it with smiles in their faces under sun shine in the middle of a garden. However, some other people complain because their heart has been recently broken due to a break up or because there is a medical problem.

Heart and its blood vessels, by Leonardo da Vinci, 15th century

Ref: http://en.wikipedia.org/wiki/Heart

In fact, the real heart is not simple as we thought. It is very complex to serve our life. It pumps blood to our body all the time without a break. Can you do it? Can you work 24/7 without taking rest? It can.

This organ consists of 4 chambers; 2 of them for receiving blood and the other 2 are for pumping blood. When we draw a heart, we should consider that we draw someone's heart who is looking at us; that means both right Atrium and Ventricle are on the left and both left Atrium and Ventricle are on the right side.

Lets see how we can draw a heart so easily by this awesome video:

Ref: http://www.handwrittentutorials.com/videos.php?id=47

For donation: http://www.handwrittentutorials.com/donate.php

The real heart looks like this:

Ref: http://en.wikipedia.org/wiki/Heart

Blood circulation:
There are 2 types of blood circulation
1. Major circulation (systemic circulation): the blood is pumped from the heart to the body through Aorta and vice versa through both superior and inferior Vena Cava.
2. Minor circulation (Pulmonary circulation): the blood is pumped from the heart to the lungs through Pulmonary arteries and vice versa through Pulmonary veins.

Ref: http://en.wikipedia.org/wiki/Heart

Some important definitions:

1.Cardiac cycle: Sequence of events in 1 heartbeat. Blood is pumped through the entire cardiovascular system.

2.Systol: Contraction phase, usually refers to ventricular contraction.

3.Diastol: Relaxation phase, the atria and ventricles are filling. Lasts longer than systole.

4.Stroke volume (SV): Amount of blood ejected from either ventricle in a single contraction.

5.Starling’s Law of the Heart states that degree of cardiac muscle stretch can increase force of ejected blood. More blood filling the ventricles ↑ SV.

6.Cardiac output (CO): Amount of blood pumped through the cardiovascular system per min.

CO = SV X Heart rate (HR)

7.Depolarization: The electrical charge of a cell is altered by a shift of electrolytes on either side of the cell membrane. This change stimulates muscle fiber to contract.

8.Repolarization: Chemical pumps re-establish an internal negative charge as the cells return to their resting state.

The conduction system of the heart:

Several types of cardiac muscle fibers exist within the heart. It is often useful to classify these types broadly as either contractile or conductile.

CONTRACTILE cells are the cells of the working myocardium and constitute the bulk of the muscle cells that make up the atria and the ventricles. An action potential in any one of these cells leads to vigorous force development and/or mechanical shortening.

CONDUCTILE cells are specialized muscle cells that are involved with the initiation or propagation of action potentials rather than direct generation of force. In addition to the effects of the CNS on the heart, the heart can work on its own. The conducting system of the heart consists of cardiac muscle cells and conducting fibers (not nervous tissue) that are specialized for initiating impulses and conducting them rapidly through the heart. They initiate the normal cardiac cycle and coordinate the contractions of cardiac chambers. Both atria contract together, as do the ventricles, but atrial contraction occurs first. The conducting system provides the heart its automatic rhythmic beat. For the heart to pump efficiently and the systemic and pulmonary circulations to operate in synchrony, the events in the cardiac cycle must be coordinated.

Ref: http://en.wikipedia.org/wiki/Heart

This conduction can be summarized as the following:

From Sinoatrial node (60-100 times/minute, bpm) to Atrioventricular node (40-60 times/minute) to bundle of His to left and right bundles to Purkinje fibers (20-40 times/minute).

Ref: http://emedicine.medscape.com/article/1922987-overview#aw2aab6b3

Types of pacemakers:
SA node is the natural (main) pacemaker of the heart.
AV node, bundle of His and Purkinje fibers are the latent pacemakers.

Cardiac action potential:

Ref:http://en.wikipedia.org/wiki/Electrical_conduction_system_of_the_heart

Cardiac Pacemaker action potential:

1.At membrane potential -60 mV, Na/K channels (funny channels) open to influx Na and efflux K [GRADUAL DEPOLARIZATION].

2.When membrane action potential reaches the threshold at -40 to -45 mV, T Ca channels open (T stands for Transit = FAST)

3. L Ca channels open (L stands for Long = SLOW) for Ca influx till the action potential reaches 0 mV [SPIKE or FAST DEPOLARIZATION].

4.At this point, K channels open to facilitate K efflux.

5.That makes the cytosol increasingly negative and creates the following phase of action potential [REPOLARIZATION].

6.When repolarization is complete, K channels close and pacemaker action potential starts over.

Each depolarization of SA node sets off ONE heart beat

POLARIZED state ----DEPOLARIZATION --- REPOLARIZATION --- POLARIZED state

The effect of Autonomic nervous system on heart pacemaker

All what the Autonomic nervous system does is REGULATING the heart rate whether increases or decreases the heart rate. That means increasing or decreasing number of action potentials per particular time; the slope of gradual depolarization.

Paraympathetic nervous system DECREASES heart rate through neurotransmitter Ach (Acetycholine).

Sympathetic nervous system INCREASES heart rate through neurotransmitter NE/E (NorEpinephrine/Epinephrine)

Myocardial action potential:

Myocardial action potential occurs in atrial and ventricular myocytes, and it proceeds like the following:

1.Phase 0: RAPID DEPOLARIZATION (Na influx)

2.Phase 1: Early RAPID REPOLARIZATION (K efflux)

3.Phase 2: Plateau (Ca influx)

4.Phase 3:Final RAPID REPOLARIZATION (K efflux)

5.Phase 4: SLOW DEPOLARIZATION (K influx, Na and Ca efflux) through Na/K ATPase pump (3 Na/ 2 K)which pumps Na out of the cell and pumps K inside the cell and generating energy, Ca ATPase pump which pumps Ca out of the cell and regain concentration gradient and Na/Ca exchanger [NCX] (3 Na/1 Ca) which exchanges Na influx with Ca efflux. The previous pumps are called Electrogenic pumps.

From phase 1 to starting phase 3 is absolute REFRACTORY period (effective refractory period); the cell can not respond to any stimuli.
During phase 3 is RELATIVE refractory period; the cell respond to strong stimuli.

New Discovery On Magnetic Reconnection To Impact Future Space Missions

2012-07-01T09:30:00.001-07:00

Space is filled with plasma (a gas composed of ions and electrons, globally neutral) and is threaded by magnetic fields. These magnetic fields store energy which can be released explosively, in a process called magnetic reconnection.

This process plays a key role in numerous astrophysical phenomena: star formation, solar flares and intense aurorae, to name a few. On Earth, magnetic reconnection prevents the efficient production of electricity in controlled fusion reactors, potential sources of electricity for the future.

New Discovery On Magnetic Reconnection To Impact Future Space Missions

Centeral Nervous System ((CNS))

2008-08-14T03:28:00.000-07:00

Human body is a living biochemical laboratory composed of 4 types of tissues [epidermal, muscular, nervous and connective tissues]. CNS consists of nervous cells with various types and functions.CNS is responsible for important vital functions for human body. It is responsible for protection of the body by performing reflex action, communicating with the others, learning , recalling for past events (memory), understanding, responding to the external stimuli and so on .......
Human being is different from any other living organism by his developed CNS, which makes him capable of controlling, developing and using, as he can, all the present elements in the environment to improve his life.
This system is the most complex one in the human body and understanding how it works is a very complicated task.

CNS consists of 2 types; they are Autonomic nervous system ((ANS)), which is involuntary, and Somatic nervous system ((SNS)), which is voluntary.
SNS is controlling the movement of the skeletal muscles and ANS is controlling the RATE of movement of the body internal parts such as heart rate, GIT [Gastrointestinal tract] motility, eye pupil with different light intensities and other different organs.

CNS anatomically is divided into Medulla spinalis [Spinal cord] and Encephalon [Brain].

The division of brain is:
(1) Truncus Cerebri [Brain stem]: Mesencephalon (midbrain) and Rhombencephalon (hindbrain)
(2) Pronsecephalon: Diencephalon and Telencephalon.

#Ventricular System:
It is a structure in the brain continuous with the central canal of the spinal cord.
-There are 4 ventricles:
1-Right and Left Lateral ventricle.
2-Third Ventricle.
3-Fourth Ventricle.
-Each Ventricle contain CHOROID PLEXUS, which produce CerebroSpinal Fluid (CSF) by modification of ependymal cells.
"Ependymal cells are epithelial membrane lining the ventricular system of the brain and spinal cord and it is one of 4 types of neuroglia in the CNS"1-posterior medullary velum
2-Choroid plexus
3-Cisterna cerebellodellaris of subarachnoid cavity
4-Central canal
5-Corpora quadrigemina
6-Cerabral peduncle
7- Anterior medullary
8-Ependymal lining of ventricle
9-Cisterna pontis of subarachnoid cavity
Arrow = Flow of cerebrospinal fluid (CSF) through foramen of Magendie.

TO BE CONTINUED......

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CNS.html
http://www.thehumanbrainproject.org/

Behind The Darkness

CASPASES

Cell Communication; GPCR part 1

Some Types of Gα Subunits:

Gαs:

Simple charts and diagrams

Transparent Brain: (CLARITY technique)

Different food experiences among population

Food-tasting business (Getting paid to eat)

One-size-fits-all drug targets harmful brain inflammation in many diseases

Humor

Some Antioxidants that can cross or strength the BBB

Possible beneficial effects

Blood Brain Barrier

Cellular constituents of the blood–brain barrier

General Properties of the BBB

Meningitis

De Vivo disease

Pathways across the BBB:

Sepsis

New Drug Candidate Shows Promise Against Cancer

Federal Register Notice on Drugs

Risk Minimization Action Plans (RiskMAPs)

REMS

REMS Elements

REMS Requirements

HIV Infection Prevention

PHARMACOLOGICAL CLASS FOR TRUVADA

INDICATIONS FOR TRUVADA

ADULT DOSE FOR TRUVADA

CHILDREN'S DOSING FOR TRUVADA

INTERACTIONS FOR TRUVADA

WARNINGS/PRECAUTIONS FOR TRUVADA

Sunscreen

Choosing Sunscreen?

Higgs

Natural products

Plant sources of fiber

The Heart

New Discovery On Magnetic Reconnection To Impact Future Space Missions

Centeral Nervous System ((CNS))

Gα_s: