MEDICAL JOURNAL CENTER

Optical Methods to observe all kind of microbes in all living area around our life

noreply@blogger.com (MEDICAL TIPS) — Wed, 4 Jan 2012 00:05:00 -0800

1. The Light Microscope

The resolving power of the light microscope under ideal conditions is about half the wavelength of the light being used. (Resolving power is the distance that must separate two point sources of light if they are to be seen as two distinct images.) With yellow light of a wavelength of 0.4 m, the smallest separable diameters are thus about 0.2 m, ie, one-third the width of a typical prokaryotic cell. The useful magnification of a microscope is the magnification that makes visible the smallest resolvable particles. Several types of light microscopes are commonly used in microbiology:

2. Bright-Field Microscope

The bright-field microscope is most commonly used in microbiology courses and consists of two series of lenses (objective and ocular lens), which function together to resolve the image. These microscopes generally employ a 100-power objective lens with a 10-power ocular lens, thus magnifying the specimen 1000 times. Particles 0.2 m in diameter are therefore magnified to about 0.2 mm and so become clearly visible. Further magnification would give no greater resolution of detail and would reduce the visible area (field).

With this microscope, specimens are rendered visible because of the differences in contrast between them and the surrounding medium. Many bacteria are difficult to see well because of their lack of contrast with the surrounding medium. Dyes (stains) can be used to stain cells or their organelles and increase their contrast so that they can be more easily seen in the bright-field microscope.

3. Phase Contrast Microscope

The phase contrast microscope was developed to improve contrast differences between cells and the surrounding medium, making it possible to see living cells without staining them; with bright-field microscopes, killed and stained preparations must be used. The phase contrast microscope takes advantage of the fact that light waves passing through transparent objects, such as cells, emerge in different phases depending on the properties of the materials through which they pass. This effect is amplified by a special ring in the objective lens of a phase contrast microscope, leading to the formation of a dark image on a light background.

4. Dark-Field Microscope

The dark-field microscope is a light microscope in which the lighting system has been modified to reach the specimen from the sides only. This is accomplished through the use of a special condenser that both blocks direct light rays and deflects light off a mirror on the side of the condenser at an oblique angle. This creates a "dark field" that contrasts against the highlighted edge of the specimens and results when the oblique rays are reflected from the edge of the specimen upward into the objective of the microscope. Resolution by dark-field microscopy is quite high. Thus, this technique has been particularly useful for observing organisms such as Treponema pallidum, a spirochete which is less than 0.2 m in diameter and therefore cannot be observed with a bright-field or phase contrast microscope.

5. Fluorescence Microscope

The fluorescence microscope is used to visualize specimens that fluoresce, which is the ability to absorb short wavelengths of light (ultraviolet) and give off light at a longer wavelength (visible). Some organisms fluoresce naturally because of the presence within the cells of naturally fluorescent substances such as chlorophyll. Those that do not naturally fluoresce may be stained with a group of fluorescent dyes called fluorochromes. Fluorescense microscopy is widely used in clinical diagnostic microbiology. For example, the fluorochrome auramine O, which glows yellow when exposed to ultraviolet light, is strongly absorbed by Mycobacterium tuberculosis, the bacterium that causes tuberculosis. When the dye is applied to a specimen suspected of containing M tuberculosis and exposed to ultraviolet light, the bacterium can be detected by the appearance of bright yellow organisms against a dark background.

The principal use of fluorescence microscopy is a diagnostic technique called the fluorescent-antibody (FA) technique or immunofluorescence. In this technique, specific antibodies (eg, antibodies to Legionella pneumophila) are chemically labeled with a fluorochrome such as fluorescein isothiocyanate (FITC). These fluorescent antibodies are then added to a microscope slide containing a clinical specimen. If the specimen contains L pneumophila, the fluorescent antibodies will bind to antigens on the surface of the bacterium, causing it to fluoresce when exposed to ultraviolet light.

Differential Interference Contrast (DIC) Microscope

Differential interference contrast microscopes employ a polarizer to produce polarized light. The polarized light beam passes through a prism that generates two distinct beams; these beams pass through the specimen and enter the objective lens where they are recombined into a single beam. Because of slight differences in refractive index of the substances each beam passed through, the combined beams are not totally in phase but instead create an interference effect, which intensifies subtle differences in cell structure. Structures such as spores, vacuoles, and granules appear three dimensional. DIC microscopy is particularly useful for observing unstained cells because of its ability to generate images that reveal internal cell structures that are less apparent by bright-field techniques.

6.The Electron Microscope

The high resolving power of the electron microscope has enabled scientists to observe the detailed structures of prokaryotic and eukaryotic cells. The superior resolution of the electron microscope is due to the fact that electrons have a much shorter wavelength than the photons of white light.

There are two types of electron microscopes in general use: the transmission electron microscope (TEM), which has many features in common with the light microscope, and the scanning electron microscope (SEM). The TEM was the first to be developed and employs a beam of electrons projected from an electron gun and directed or focused by an electromagnetic condenser lens onto a thin specimen. As the electrons strike the specimen, they are differentially scattered by the number and mass of atoms in the specimen; some electrons pass through the specimen and are gathered and focused by an electromagnetic objective lens, which presents an image of the specimen to the projector lens system for further enlargement. The image is visualized by allowing it to impinge on a screen that fluoresces when struck with the electrons. The image can be recorded on photographic film. TEM can resolve particles 0.001 m apart. Viruses, with diameters of 0.01–0.2 m, can be easily resolved.

The SEM generally has a lower resolving power than the TEM; however, it is particularly useful for providing three-dimensional images of the surface of microscopic objects. Electrons are focused by means of lenses into a very fine point. The interaction of electrons with the specimen results in the release of different forms of radiation (eg, secondary electrons) from the surface of the material, which can be captured by an appropriate detector, amplified, and then imaged on a television screen.

An important technique in electron microscopy is the use of "shadowing." This involves depositing a thin layer of heavy metal (such as platinum) on the specimen by placing it in the path of a beam of metal ions in a vacuum. The beam is directed at a low angle to the specimen, so that it acquires a "shadow" in the form of an uncoated area on the other side. When an electron beam is then passed through the coated preparation in the electron microscope and a positive print is made from the "negative" image, a three-dimensional effect is achieved (eg, see Figure 2–22).Confocal Scanning Laser Microscope

The confocal scanning laser microscope (CSLM) couples a laser light source to a light microscope. In confocal scanning laser microscopy, a laser beam is bounced off a mirror that directs the beam through a scanning device. Then the laser beam is directed through a pinhole that precisely adjusts the plane of focus of the beam to a given vertical layer within the specimen. By precisely illuminating only a single plane of the specimen, illumination intensity drops off rapidly above and below the plane of focus, and stray light from other planes of focus are minimized. Thus, in a relatively thick specimen, various layers can be observed by adjusting the plane of focus of the laser beam.

Cells are often stained with fluorescent dyes to make them more visible. Alternatively, false color images can be generated by adjusting the microscope in such a way as to make different layers take on different colors. The CSLM is equipped with computer software to assemble digital images for subsequent image processing. Thus, images obtained from different layers can be stored and then digitally overlaid to reconstruct a three-dimensional image of the entire specimen.(Jawetz, Melnick, & Adelberg's Medical Microbiology, 24th Edition by Vishal )

What’s bacteria that cause many kind of diseases???

noreply@blogger.com (MEDICAL TIPS) — Sun, 1 Jan 2012 04:59:00 -0800

Bacteria are the smallest (0.1 to 10 _m) living cells. They have a cytoplasmic membrane

surrounded by a cell wall; a unique interwoven polymer called peptidoglycan makes the wall rigid. The simple prokaryotic cell plan includes no mitochondria, lysosomes, endoplasmic reticulum, or other organelles. In fact, most bacteria are about the size of mitochondria.Their cytoplasm contains only ribosomes and a single, double-stranded DNA chromosome. Bacteria have no nucleus, but all the chemical elements of nucleic acid and protein synthesis are present. Although their nutritional requirements vary greatly, most bacteria are free-living, if given an appropriate energy source. Tiny metabolic factories, they divide by binary fission and can be grown in artificial culture, often in less than a day. The Archaebacteria differ radically from other bacteria in structure and metabolic processes; they live in environments humans consider hostile (eg, hot springs, high salt areas) but are not associated with disease.

What’s Viruse that cause many kind of diseases???

noreply@blogger.com (MEDICAL TIPS) — Thu, 29 Dec 2011 04:56:00 -0800

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Viruses are strict intracellular parasites of other living cells, not only of mammalian and

plant cells, but also of simple unicellular organisms, including bacteria (the bacteriophages). Viruses are simple forms of replicating, biologically active particles that carry genetic information in either DNA or RNA molecules, but never both. Most mature viruses have a protein coat over their nucleic acid and sometimes a lipid surface membrane derived from the cell they infect. Because viruses lack the protein-synthesizing enzymes and structural apparatus necessary for their own replication, they bear essentially no resemblance to a true eukaryotic or prokaryotic cell. Viruses replicate by using their own genes to direct the metabolic activities of the cell they infect to bring about the synthesis and reassembly of their component parts. A cell infected with a single viral particle may thus yield many thousands of viral particles, which can be assembled almost simultaneously under the direction of the viral nucleic acid. With many viruses, cell death and infection of other cells by the newly formed viruses result. Sometimes, viral reproduction and cell reproduction proceed.

WHAT’S MICROBIOLOGY IN MEDICAL SCIENCE ????

noreply@blogger.com (MEDICAL TIPS) — Tue, 27 Dec 2011 02:37:00 -0800

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Microbiology is a science defined by smallness. Its creation was made possible by the invention of the microscope (Gr. micro, small _ skop, to look, see), which allowed visualization

of structures too small to see with the naked eye. This definition of microbiology as the study of microscopic living forms still holds if one can accept that some organisms can live only in other cells (eg, all viruses, some bacteria) and others have macroscopic forms (eg, fungal molds, parasitic worms). Microorganisms are responsible for much of the breakdown and natural recycling of organic material in the environment. Some synthesize nitrogen-containing compounds that contribute to the nutrition of living things that lack this ability; others (oceanic algae) contribute to the atmosphere by producing oxygen through photosynthesis. Because

microorganisms have an astounding range of metabolic and energy-yielding abilities,some can exist under conditions that are lethal to other life forms. For example, some bacteria can oxidize inorganic compounds such as sulfur and ammonium ions to generate energy, and some can survive and multiply in hot springs at temperatures above 75°C. Some microbial species have adapted to a symbiotic relationship with higher forms of life. For example, bacteria that can fix atmospheric nitrogen colonize root systems oflegumes and of a few trees such as alders and provide the plants with their nitrogenrequirements. When these plants die or are plowed under, the fertility of the soil is enhanced by nitrogenous compounds originally derived from the metabolism of the bacteria.

Ruminants can use grasses as their prime source of nutrition, because the abundant flora of anaerobic bacteria in the rumen break down cellulose and other plant compounds to usablecarbohydrates and amino acids and synthesize essential nutrients including some amino acids and vitamins. These few examples illustrate the protean nature of microbial life and their essential place in our ecosystem. The major classes of microorganisms in terms of ascending size and complexity are viruses, bacteria, fungi, and parasites. Parasites exist as single or multicellular structures with the same eukaryotic cell plan of our own cells. Fungi are also eukaryotic but have a rigid external wall that makes them seem more like plants than animals. Bacteria also have a cell wall, but their cell plan is prokaryotic and lacks the organelles of eukaryotic cells. Viruses have a genome and some structural elements but must take over the machinery of another living cell (eukaryotic or prokaryotic) in order to replicate.

noreply@blogger.com (MEDICAL TIPS) — Tue, 6 Dec 2011 16:52:00 -0800

the top 10 serious diseases causes of death in the world

World	Deaths in millions	% of deaths
Ischaemic heart disease	7.25	12.8%
Stroke and other cerebrovascular disease	6.15	10.8%
Lower respiratory infections	3.46	6.1%
Chronic obstructive pulmonary disease	3.28	5.8%
Diarrhoeal diseases	2.46	4.3%
HIV/AIDS	1.78	3.1%
Trachea, bronchus, lung cancers	1.39	2.4%
Tuberculosis	1.34	2.4%
Diabetes mellitus	1.26	2.2%
Road traffic accidents	1.21	2.1%

noreply@blogger.com (MEDICAL TIPS) — Sun, 4 Dec 2011 04:47:00 -0800

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KANKER SERVIKS

noreply@blogger.com (MEDICAL TIPS) — Fri, 2 Dec 2011 22:30:00 -0800

Kanker serviks merupakan pertumbuhan dari suatu kelompok sel yang tidak normal pada serviks (leher rahim) yang bersifat ganas dan invasif.Faktor etiologik paling penting pada timbulnya kanker serviks ialah infeksi Human Papillomavirus (HPV). HPV adalah virus DNA yang menimbulkan proliferasi pada permukaan epidermal dan mukosa, yang mengarahkan ke keadaan Cervical Intraepithelial Neoplasia (CIN) kemudian berlanjut menjadi kanker. HPV ditemukan pada 85-90 % lesi prakanker dan neoplasma invasif, dan secara lebih spesifik terdapat beberapa tipe HPV yang berisiko tinggi yaitu tipe 16, 18, 31, 33, 35, 39, 45, 52, 56, 58, dan 59. Selain infeksi HPV, ada faktor – faktor lain yang berpengaruh terhadap proses pembentukan kanker serviks. Faktor lain yang mempengaruhi kanker serviks seperti merokok, sistem imunitas yang menurun, infeksi chlamydia, pil kontrasepsi, usia pada saat kehamilan pertama, faktor ekonomi (kemiskinan), dan riwayat keluarga yang menderita kanker serviks.

Patogenesis kanker serviks diawali dengan adanya infeksi oleh HPV melalui skin-to-skin contact ketika berhubungan seksual. Infeksi HPV terbatas pada basal sel dari sel epitel pipih berlapis yang merupakan jaringan khusus tempat HPV dapat bereplikasi. Virus HPV tidak dapat menempel pada jaringan hidup tetapi dapat menyerang jaringan epitel melalui mikro abrasi atau trauma epitelial lain yang mampu memaparkan membran dasarnya. Proses infeksi memakan waktu 12-24 jam untuk inisiasi transkripsi. Infeksi dan replikasi dari human papilloma virus (HPV) terdapat di sel epitel serviks. Serviks normal memiliki zona transformasi yang ditandai dengan perubahan dari epitel kolumnar menjadi epitel skuamousa. HPV kemungkinan menginfeksi bagian ini dan mengekspresikan viral genes E1, E2, E4, E5, E6, dan E7 pada lapisan basal akibat proses penggadaan diri secara episomal.

Basal sel yang terinfeksi akan menunjukkan tanda disrupsi sel sebagai hasil dari infeksi virus dan melanjutkan proliferasi dan bermigrasi ke permukaan sel epitel, dimana sel skuamous yang sekarang mengekspresikan gen HPV L1 dan L2. Partikel virus infektif akan terbentuk dan tertanam ke lumen vagina. Infeksi HPV bisa berubah menjadi HPV-induced mild dysplasia, Stadium akhir Cervical Intraepithelial neoplasia (CIN3) dan dapat menjadi kanker serviks yang bersifat invasif, saat membran dasar pecah dan sel kanker bermetastasis.Pada sel epitel yang bertransformasi, gen HPV diintegrasi ke kromosom host dengan mengekspresikan protein onkogenik E6 dan E7. Protein E6 akan menempel dan menginaktivasi protein supresor p53, sedangkan protein HPV E7 mampu berikatan dengan pRb menghasilkan terbebasnya host transcriptional factor E2F dari kompleks pRb/E2F. E2F menghasilkan banyak gen yang penting untuk mitosis, akan memulai siklus sel, dan menyebabkan hiperproliferasi. Kombinasi antara protein HPV E6 dan E7 yang berisiko tinggi tersebut mampu menyebabkan instabilitas genetik dan perkembangan lesi kanker ke tingkat yang lebih mematikan.

Selanjutya, karsinoma invasif serviks terbentuk di zona transformasi dan berkisar dari fokus mikroskopik invasi stroma. Kemudian, kanker serviks menyebar secara luas masuk ke dalam jaringan paraservikal. Pertumbuhan yang berlangsung mengakibatkan lesi yang dapat dilihat dan terlibat lebih progresif pada jaringan jaringan servikal. Pada tahap lebih lanjut, karsinoma servikal invasif dapat menginvasi dan meluas ke dinding vagina, ligamentum kardinale, dan rongga endometrium, kelenjar getah bening dan pembuluh darah. Hal ini mengakibatkan metastasis ke bagian tubuh yang lebih jauh, dan sebagian besar penyebab kematian pada penderita.