CYTOCHEMISTRY and HISTOENZYMOLOGY

1. 1 CYTOCHEMISTRY and HISTOENZYMOLOGY

2. 2 CYTOCHEMISTRY It is based on the affinity of some substances for the chemical structures inside the cell that we want to localize Could be a chemical or immunologic reaction The result is a colored, insoluble compound that can be visualized on light microscopy

3. 3 THE BASIC REQUIREMENTS For the analyzed substance Must not diffuse from the original site The fixative used should preserve the structure and prevent degradation of the reactive groups Ex . The fixatives used to study lipids should not contain lipid solvents The reaction product should be Insoluble � to prevent diffusion Colored � so that it can be studied on light microscopy The method � should be specific for the studied substance

4. 4 In some reactions the intensity of the reaction product color is proportionate with the concentration of the studied substance The concentration can be determined by spectrophotometry using a spectrophotometer

5. 5 POLYSACCHARIDES Mono- and oligosaccharides are very soluble and can�t be demonstrated by cytochemistry Polysaccharides can be found free � glycogen, glycosaminoglycans combined with proteins � glycoconjugates : glycoproteins, glycolipids, proteoglycans

6. 6 PAS REACTION PAS � periodic acid Schiff Demonstrate the presence of glycogen, glycosaminoglycans, glycoproteins, glycolipids Based on the oxidative action of periodic acid on the glycol groups of the glucose residues, which will be transformed on aldehyde groups The aldehyde groups will react with Schiff reagent - purple precipitate

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