Tissue prep and staining Flashcards Preview

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Flashcards in Tissue prep and staining Deck (28):

what are the steps needed to prepare tissues for observation

fixing, dehydration, removal of alcohol, embedding


what does fixation prevent

further deterioration of the specimen and helps to harden the tissue prior to embedding and sectioning


what is the main downfall of fixation

it radically distorts the specimen


what is one of the most widely used fixing agents



what does formalin do

fixing agent that reacts with the amino acids of the tissue proteins and stabilizes tissue structure to prevent further deterioration


what do acid fixatives fix? don't fix?

fix: chromatin, nuclei and spindle fibers
don't fix: mitochondria and nucleoplasm


name three acid fixatives

carnoy's fluid
zenker's fluid
Bouin's fluid


what is Carnoy's fluid good for

good general fixative and is useful for preserving glycogen in animal tissues


what is Zenker's fluid good for

useful when sharp histological detail is desired, but must be washed out carefully to prevent the precipitation of black crystals


what is Bouin's fluid good for

widely used general fixative that gives cytological detail


when are basic fixatives usually used

when mitochondrial staining is desired


what is the main downfall of basic fixatives

chromatin is dissolved


what are 2 main fixatives for TEM

Glutaraldehyde: preserves proteins by cross-linking them
Osmium tetroxide: reacts with lipids and imparts electron density to cell and tissue structure


why must dehydration occur for tissue fixing and embedding?

because the tissue sample will eventually be embedded and infiltrated with a hydrophobic material (usually paraffin)


what is clearing?

consists of replacing the alcohol with an agent such as xylene or cedar oil


what are the steps of embedding

1. the tissue specimen is moved sequentially through several melted paraffin baths
2. after the final bath the specimen is placed in a mold that is then filled with melted paraffin
3. the paraffin mold is rapidly hardened by placing it in a cold water bath


steps to prepare for staining

1. paraffin must be removed from the section, which is now mounted on a microscope slide (accomplished with xylene)
2. xylene must be removed using a graded series of alcohol down to water
3. stains are then applied and the section is again dehydrated through a graded series of alcohols
4. the alcohol is removed with xylene
5. a drop of cement followed by a cover slip is applied


what is hematoxylin derived from

logwood as hematein


what can orcein and resorcin fuchsin stains be used for?

to reveal elastic material


what is silver impregnation useful for

to show reticular fibers and basement membranes


how do acid dyes bind to tissue components?

by forming electrostatic linkages with cationic groups such as the amino groups of proteins


define metachromasia

phenomenon whereby a dye changes color after reacting with a tissue component


what can histochemical techniques be used for

to study the chemistry of cells and tissues


what does the schiff reaction depend on

formation of aldehyde groups following exposure to HCL or periodic acid


what is periodic acid used for

used to cleave bonds between adjacent carbons of carbohydrates and form aldehyde groups


what is best carmine used for

dye that may be used to demonstrate glycogen deposits


what can immunocytochemical techniques be used for

to study the presence of specific tissue constituents (antigens) by using monoclonal antibodies


what are monoclonal antibodies derived from

activated B cell clones exposed to a specific antigen