Biological microscope regarding the volume of tissue blocks
Biological microscopy So far, cold fixation, frozen ultrathin sectioning and freeze-drying are routine methods for x-ray micro-section of tissues and cells. The following are the details of this method:
Biological microscopes. For microscopes with a condenser, the condenser can be moved up and down to achieve moderate brightness. In addition, the aperture of the variable light emitting diodes can be changed to achieve moderate 9b brightness. If the light is bright, the condenser can be raised appropriately and the aperture of the variable light can be appropriately enlarged. If the light is too strong, the condenser can be lowered appropriately and the aperture of the cross-light beam can be appropriately reduced. If you still feel dazzling under this situation, you can choose an appropriate filter and place it on the bracket under the condenser. This way you can get the brightness that satisfies you. Of course, it takes a certain period of practice to gain experience in adjusting the up and down position of the condenser to achieve variable aperture size and selecting appropriate filters.
A very important issue in biological microscopy is that during the process of collecting and separating cells, after freeze-drying and resin embedding (FD), after freezing ultra-thin pellets, and after freeze-drying, the 65 element content of each part must be analyzed very carefully, and absolutely Do not damage the cells to be analyzed. Because X-ray micro-area analysis not only involves many steps, but also costs a lot. If after a long time and multiple steps, the analyzed cells are damaged cells or dead cells, it would be a pity to draw wrong conclusions. For example, cardiomyocytes isolated after collagenase treatment have two shapes, one is long rod-shaped and the other is round. The latter are dying cells that are damaged during cell isolation.
Biological Microscopy The content and distribution of electrolytes in these two types of cells are very different. Na is very high and K is very low in round cardiomyocytes, and the Ca concentration in linear branches is very high. After checking with other analysis methods, it was proved that the high Na and low K in round cells and the high ca in mitochondria were due to the damage to the cell membrane during the cell separation process. The cold fixation method of cells and tissues is often to first quench and fix them, and then store them in liquid nitrogen. Quenching and fixation are very important for the preservation effect. Living cells or fresh tissues are rich in water. When quenching, the parts of the cells or tissues that are in direct contact with the cryogen (especially when quenched with liquid nitrogen) are first frozen and fixed, thus forming a "shell", which hinders the The central part of the cells was crushed and cold-fixed. Therefore, when doing X-line micro-area analysis, it is often found that there are ice crystals in the center of larger cells. In order to prevent this from happening, a substance with a higher melting point than liquid nitrogen but a lower dryness of -806c is used as the crushed refrigerant. There are many such substances, but the easiest and cheapest one is concentrated propane (boiling point - 42.120c, melting point - 187.10c, molecular weight 44.1), and the cooling rate is also the fastest. But its disadvantage is that it is flammable.
Biological microscope can put the muscle fiber on a special frame. When the muscle fiber contraction reaches a certain phase and needs to be fixed, the nozzle is started immediately to spray liquid propane to the muscle fiber to quench and fix it. Then the muscle fibers together with the frame were taken out and put into liquid nitrogen. If blood cells or separated cells are fixed, first centrifuge at low speed to concentrate the cells, transfer the cells to a small silver tube with good thermal conductivity, place the tube in liquid propane and freeze to fix it. When fixing the rat pancreas in the Hall laboratory, first pre-cool the two steel blocks with liquid helium (or liquid nitrogen), clamp the two copper blocks with forceps, and place them before and after the pancreas to quench and fix the uterine gland. Tissues or cells can be quenched and fixed and then transferred to liquid nitrogen for long-term storage.
