Carsons Histotechnology verified to pass 2023/2024 passed

Carsons Mordant . substance’s or metals that act as a link between dye and tissue A mordant is a metal with a valency of at least two. The two commonest metals used in histotechnology are aluminum and ferric iron, both with valencies of three. The attachment of mordant to dyes is by means of a covalent and a coordinate bond. Fixative additive fixation- stabilizes proteins by denaturing proteins (chemical, heat) and combines with fixative molecule becoming insoluble non additive fixative (alcohol, acetone)-denatured proteins dissociate bound water molecules but molecules do not combine prevents decay, purification and autolysis enhances staining w exception of masking antigenic sites but retrievable using antigen retrieval techniques makes tissue firmer for grossing protein stabilizing of fixatives renders enzymes inactive as result of protein stabilizing action/denaturing tissues rich in enzymes more susceptible to autolysis ie brain, pancreas, liver Amino NH2 and Hydroxyl -COOH groups at pH 7 formaldehyde adds on tissue proteins primarily at the amino group with eventual formation of a methylene bridge Coagulant fixative fixatives that form a gel which is difficult for subsequent reagents to penetrate Non coagulative fixative permeable meshwork of protein strands Factors affecting fixation temperature, size, volume ratio (15-20x) , time (6-24 hrs esp. Her2), penetration, tissue storage (formalin indefinitely, immunos affected), pH (7.2-7,4 EM, 4-9 for light), osmolality, Immediate vs delayed fixation improper fixation of lung tissue Well fixed lung poor vs well fixed tumor IF or enzyme profile no fixative/frozen chrommafin grannules found in cells of adrenal gland must be fixed in ortho solution Kidney bx for IF Micheles Nuclear bubbling nuclei often show coalescence of the chromatin into strands with intervening clear spaces. Introduced in the deparaffinization step on formalin-fixed tissue, because the nuclei are only delicately fixed What 2 chemicals will fix lipids so they are not lost during processing osmium tetroxide and chromic acid 100% Formalin 30-40% formaldehyde solution in water 10% formalin (or 3.7-4% formaldehyde) 1 part stock and 9 parts water