epithelial tissue

connective tissue

muscle tissue

nervous tissue

nerve

cycle

immunity

endocrine

Feel

Digestion

breathe

Urology

reproduction

paraffin sectioning

cryosection

Refers to the method of making slices without steps such as embedding and slicing.

Smear: directly apply blood, semen, isolated cells, exfoliated cells, etc. on a glass slide

Spreading: tear the mesentery and subcutaneous tissue into thin slices and lay them directly on the glass slide

Grinding: Mechanically grind hard tissues and organs such as teeth and bones into thin slices and attach them to a glass slide.

Sample preparation: 1 mm × 1 mm × 1 mm tissue is fixed with glutaraldehyde or osmic acid, embedded in resin, and made into 50~100 nm ultrathin sections using an ultramicrotome, mounted on a copper grid, and covered with lead and uranium. After the heavy metal salt is electron stained, it is observed under an electron microscope.

Any part that is electron-stained and bound by heavy metal salts has a darker image and is said to have high electron density. On the contrary, if the image is brighter, it is said that the electron density is low.

The staining method that combines the detected structure with heavy metal salts is called positive staining. The staining method when the heavy metal salt does not bind to the structure to be examined but binds to the area around the structure to be examined is called negative staining.

It is shown that polysaccharides and proteoglycans are commonly used in periodic acid-Schiff reaction, referred to as PAS reaction.

Principle: The periodic acid oxidation reaction can oxidize the ethylene glycol group of the sugar molecule to form a glyoxal group. The latter is combined with the colorless basic fuchsin in the Schiff reagent to form a purple-red reaction at the site where the original sugar molecule exists. The product forms a precipitate, indirectly showing the status of intracellular sugar substances.

In order to prevent organic solvents from dissolving it, frozen sections are often used.

Sudan black, Oil Red O, Nile Blue and other lipid-soluble dyes can be used for dyeing; Osmic acid fixation and dyeing can also be used. Fatty acid or choline treatment can reduce osmic acid to OsO₂, making the lipids appear black.

The basic principle is to use an enzyme to hydrolyze and oxidize its corresponding substrate. When the reactant produced by the enzyme reacts with the capture agent, a colored product can be formed. The intensity of the color of the final product is often used to indicate the strength of the enzyme activity.

Fulgen reaction reveals DNA Principle: The bond between deoxyribose and purine in DNA is opened after treatment with dilute hydrochloric acid. After forming an aldehyde group, it reacts with the basic fuchsin in Schiff reagent to make the DNA purple-red.

Methyl green-pyronine (pyro red) reaction Can make DNA appear blue-green and RNA appear red at the same time