Methods of preparation of samples for optical and electron microscopy of films
The microfilming method generally includes four categories: sectioning method, overall sealing method, coating method and pressing method.
①Slice method. Optical microscope slice thickness between 2 to 25 microns, general plant and animal materials, the slice is about 10 microns thick is appropriate. Sectioning method varies according to the different embedding agents. Commonly used are paraffin sectioning method, cotton glue sectioning method, frozen sectioning method, and glycol methacrylate method (referred to as GMA method). The paraffin sectioning method includes the steps of fixation, embedding, sectioning, staining, dehydration and sealing. The key is to embed the biomaterial in paraffin wax, and use paraffin wax as a support to cut the biomaterial immersed in the wax block into ideal thin slices. The operation process is as follows: fixation → water washing → step-by-step from low to high concentration alcohol dehydration → xylene transparency → wax immersion → embedding → sectioning → patching → xylene dewaxing → step-by-step from high to low concentration alcohol treatment, and finally transitioning to water → staining → step-by-step from low to high concentration alcohol dehydration → xylene transparency → sealing with resin adhesive. The basic steps involved are the same in all kinds of film-making techniques.
② Integral sealing method. Used for single cells, tiny organisms or dispersed organs of the whole mounted film method. This method also requires various steps of fixation, staining, dehydration, transparency and sealing. This method is used for the preparation of the mouthparts of lacewings and insects.
Smear method. A method of preparation in which an easily dispersed biological specimen is coated on a slide. Blood smear is an example.
④Pressing method. The natural, easily dispersed tissues or easily dispersed tissues after treatment, such as animal spermatocytes, root tip cells, etc. on the slide, plus a coverslip, and then forcefully crush the tissues, so that the cells or intracellular structures spread into a layer of filming methods. The press method is often used to observe chromosomes, usually stained with magenta acetate, lichen red and carbolic acid red.
