Histology Lecture 3: Tissue Prep and Staining

Question 1

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

Answer 1

fixing

Question 2

one of the most widely used fixatives

Answer 2

Formalin

Question 3

fix chromatin, nucleoli, and spindle fibers but not mitochondria or nucleoplasm.

Answer 3

acid fixatives

Question 4

a mixture of alcohol, chloroform, and glacial acetic
acid. It is a good general fixative and is useful for preserving glycogen in animal tissues and looking at glycogen storage related disorders.

Answer 4

Carnoy’s Fluid

Question 5

contains potassium dichromate, mercuric chloride, and
glacial acetic acid. It is useful when sharp histological detail is desired, but must be washed out carefully to prevent the precipitation of black crystals.

Answer 5

Zenker’s Fluid

Question 6

contains picric aid, formalin, and glacial acetic acid. It is a
widely used general fixative that gives good cytological detail. It requires a prolonged and careful washing cycle because picric acid is yellow and your specimen will be yellow if you do not wash it well.

Answer 6

Bouin’s Fluid

Question 7

can be used to fix tissues where mitochondrial staining is

desired. In this fixing procedure, chromatin is dissolved.

Answer 7

basic fixatives

Question 8

contains potassium dichromate, ammonium dichromate, copper sulfate, and distilled water. It requires a long fixing time (2 days) and washing under running water.

Answer 8

Zirkle-Erliki fixative

Question 9

consists of placing the tissue in successively increasing

strengths of ethanol until all the water is removed

Answer 9

Dehydration

Question 10

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

Answer 10

Dehydration

Question 11

consists of replacing the alcohol with an agent such as xylene or cedar oil because parrafin is not miscible with alcohol

Answer 11

Clearing

Question 12

The tissue specimen is moved sequentially through several (usually three) melted paraffin baths where the paraffin displaces the clearing fluid (xylene). After the final bath the specimen is placed in a mold that is then filled with melted paraffin. The paraffin mold is rapidly hardened by placing it in a cold water bath. What is this process called?

Answer 12

Embedding

Question 13

typically done on a rotary microtome which utilizes a very
sharp blade over which the paraffin block is raised and lowered after being advanced a fixed distance per cycle. Can also be done using a sharp razor and a tubular holder in which the specimen is tightly held

Answer 13

Sectioning

Question 14

behaves like a basic dye and stains the acidic components of a cell (like nuclei) dark purple due to the properties of the mordant that is used to help it bind to the tissues

Answer 14

Hematoxylin

Question 15

An acid dye. Stains most of the cytoplasmic components and much of the extracellular material yellowish/pinkish

Answer 15

Eosin

Question 16

fat-soluble stains used to demonstrate lipids are in this class of dye

Answer 16

Sudans

Question 17

useful to show reticular fibers and basement membrane

Answer 17

silver impregnation

Question 18

can be used specifically to reveal elastic material

Answer 18

Orcein and resorcin fuchsin stains

Question 19

Any tissue component that reacts with a basic dye (or with hematoxylin) is said to be this.

Answer 19

basophilic

Question 20

React with the anionic groups of tissue components such as phosphate groups, sulfate groups, and carboxyl groups. The exact nature of binding depends on the pH. At a high pH all three groups are available for binding with the dye.

Answer 20

Basic Dyes

Question 21

bind to tissue components by forming electrostatic
linkages with cationic groups such as the amino groups of proteins. Different types of acid dyes have slightly different properties and can be used in sequence to give different results

Answer 21

Acidic Dyes

Question 22

Any tissue component that reacts with an acid dye is said to be

Answer 22

acidophilic

Question 23

This term refers to a phenomenon whereby a dye changes color after reacting with a tissue component

Answer 23

metachromasia

Question 24

Used to demonstrate the presence of iron in tissues. Incubate tissues in a mixture of potassium ferrocyanide and HCl. Results are an insoluble blue precipitate of ferric
ferrocyanide

Answer 24

Perls’ Reaction

Question 25

soluble in the reagents that are used in the normal processing of tissues for histological examination, thus the use of frozen sections gives best results.

Answer 25

lipids

Question 26

depends on the formation of aldehyde groups following exposure to HCl or periodic acid

Answer 26

schiff reagent reaction

Question 27

A colorless fuchsin; reacts with the aldehyde groups and forms a deep pinkish color.

Answer 27

Schiff reagent

Question 28

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

Answer 28

Periodic acid-Schiff reaction (PAS)

Question 29

Useful for staining carbohydrates

Answer 29

Period acid-Schiff reaction (PAS)

Question 30

converts carbohydrates to aldehyde groups

Answer 30

Periodic Acid

Question 31

a dye that may also be used to demonstrate glycogen deposits

Answer 31

Best Carmine

Question 32

stain RNA-rich organelles

Answer 32

basic dyes

Question 33

derived from activated B cell clones exposed to a specific antigen and are specific to a single epitope

Answer 33

monoclonal antibodies

Question 34

In this variation, the marker is attached to a second antibody which is specific to the antibody used to locate the antigen of interest; typically anti-IgG antibodies

Answer 34

Indirect Labeling