Sunday, December 2, 2018

Preparing Microscope Slides For Studies In Schools

By Kenneth Collins


Slides for university students are usually prepared in the histology lab. Students in medical sciences are often trained to know what a tissue is when placed on a slide. The essence is for them to be able to identify anomalies or deviations from the standard ones. However, before they can start taking any of the required lectures, the lab technologists must take the tissues through some histology techniques to prepare microscope slides.

There are different kinds of microscopes the students can use in the lab. The ones to be used should depend on what they will be asked to identify as well as the conditions in the laboratory. They include the electron, light, phase contrast, fluoresce, confocal microscopes.

Components of a light microscope include lamp, diaphragm, tube, eyepiece lens, objective lens, and knobs. The adjustment knobs are of three types and they are used to change the clarity of the slide in view. They are fine knob, coarse knob, and condenser height.

After the microscopes have been made available, the next step would be tissue processing. This involves different steps such as fixation, dehydration, clearing, wax impregnation, embedding, sectioning, clearing, staining, and mounting. Each of these steps has its own chemicals and their compositions must be applied strictly to avoid any distortion from what the slides should be after preparation.

When a cell dies, the first thing that must be done is the fixation. Fixation is the process taken to prevent putrefaction. The method involves soaking the tissue in chemicals known as fixatives and they include salt, Bouin's fluid, and buffered formalin. Apart from the use of chemicals, the tissue can be heated or kept inside a refrigerator. The ratio of the volumes of fixatives to the tissue should be 3:1. It is important to use more fixatives so that the tissue can be well covered.

Fixation usually introduces water that must be removed through the process called dehydration. Since alcohol and water are miscible, alcohol can be used in the process. The concentration of alcohol used should vary from low to high and in an ascending order. It is good to do it with 50%, 50%, 75%, 75%, 98%, and 98% alcohol concentrations one after the other. This is necessary to remove all bubbles and to prevent the possibility of shrinking.

After dehydrating the tissue, the alcohol has to be removed and this can be done by the process called clearing. It can be done with clearing agents such as xylene, benzene, toluene, and chloroform. Afterward, impregnate with wax to remove xylene. Apart from removing the xylene, waxing makes cutting easy and the quality of the cuts to be strong.

The slides that will be viewed should not contain wax. Thus, it should be removed by the process of rehydration. Rehydration is done with alcohol in descending grades; that is from absolute to 50 percent. Water can be reintroduced since the tissue must be brought back to water. Staining is the final process in the technique and the stains used depends on the tissue and what should be identified. They include Periodic Acid Schiff, Sudan black, Van Gieson and Osmium tetroxide.




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