Medical Applications of Tissues

Question 1

7 steps of tissue preparation

Answer 1

1. Fixation
2. Dehydration
3. Clearing
4. Embedding
5. Sectioning
6. Mounting
7. Staining

Question 2

Fixation

Answer 2

Formalin Glutaraldehyde
Function–Preservation of normal tissue architecture after death. Fixatives coagulate or precipitate proteins. This renders the structures resistant to further processing.

Question 3

Dehydration

Answer 3

Chemical used-50-100% of ethanol

Purpose of step-to remove the H2O for the tissue specimen and replace it with alcohol

Question 4

Clearing

Answer 4

Xylene

Prepares the tissue for the embedding medium

Question 5

Embedding

Answer 5

Paraffin

Tissus is infiltrated with paraffin so that it is hard enough to section

Question 6

Sectioning

Answer 6

Tissue is cut into thin sections with a microtome

Question 7

Mounting

Answer 7

Cut paraffin section is placed on a glass microscope slide

Question 8

Staining

Answer 8

Various chemicals used

To impact contrast to tissue structures so that they may be distinguished upon microscopic observation

Question 9

Acid dyes

Answer 9

Chemicals with a net negative charge

Question 10

Basic dyes

Answer 10

chemicals with net positive charge

Question 11

Acidophilic

Answer 11

cellular or tissue structures that possess a net positive charge and hence have an affinity for the negative acid dye.

Question 12

Basophilic

Answer 12

– cellular or tissue structures that possess a net negative charge and hence have an affinity for the positive basic dye.

Question 13

Metachromasia

Answer 13

a phenonmenon in which a given stain imparts different colors to the tissue

Question 14

Hematoxylin and eosin (H & E)

Answer 14

Structure Affinity
   a.H – RNA, DNA, ribosomes, and rER
   b. E – secretory vesicles, sER, lysosomes, mitochondria, and type I collagen
Colors imparted	
   a. H – blue
   b. E – pink 
-used for coagulative necrosis

Question 15

Feulgen reaction

Answer 15

Structure Affinity
   a. DNA
Color imparted
   a. Magenta (purplish-pink)
--can be used to demonstrate nuclear changes in cancer

Question 16

Mallory triple

Answer 16

Strcture affinity
   a. Nuclei, muscle, collagen, hyaline cartilage
Color imparted
   a. Nuclei – red 
   b. Muscle – red to orange
   c. Collagen – blue 
   d. Hyaline cartilage – blue 
--can be used to highlight fibrosis

Question 17

PAS reaction

Answer 17

Carbohydrates
Magenta
–can be used in to thickened basement membranes in kidney disease, glycogen storage diseases and in alpha1-antitrypsin deficiency in liver cells (hepatocytes)

Question 18

Osmic acid

Answer 18

Lipids

Black

Question 19

Verhoeff

Answer 19

Elastic fibers
Black
–elastic fibers (Marfan syndrome)

Question 20

Silver methods

Answer 20

Intermediate filaments of nerve cells, glial cells, and reticular fibers
Black

Question 21

Trypan blue

Answer 21

Macrophages

Blue

Question 22

Prussian Blue

Answer 22

Hemosiderin (ferric iron)
Blue
–used to demonstrate excessive iron accumulation in hemochromatosis

Question 23

Nissl

Answer 23

Ribosomes

Blue

Question 24

Iron hematoxylin

Answer 24

Nuclear elements, chromosomes, mitochondria, centrioles, and muscle striation
Dark blue to black

Question 25

Congo red

Answer 25

to identify extracellular deposits of amyloid

Question 26

Immunocytochemistry

Answer 26

A. Technique that uses an antibody tagged with a marker (e.g., fluorescent molecule) directed to a specific antigen (e.g., a protein associated with the cell or tissue).

i. Direct method is less sensitive as fewer antibodies bind to the antigens
ii. Indirect method is more sensitive as more antibodies bind thus amplifying the signal.

Question 27

Direct method of immunocytochemistry

Answer 27

less sensitive as fewer antibodies bind to the antigens

Question 28

Indirect method of immunocytochemistry

Answer 28

is more sensitive as more antibodies bind thus amplifying the signal.

Question 29

Clinical utility of immunocytochemistry

Answer 29

i. Categorization of tumor origin
a. Cytokeratins and epithelial cells
b. Kaposi sarcoma – D2-40 and lymphatic endothelium
ii. Breast cancer
a. Estrogen receptors
b. HER2/neu (aka ERB B2) is a member of the epidermal growth factor receptor family and is overexpressed in some types of breast cancers as well as some adenocarcinomas
c. Carcinoembryonic antigen in breast and intestinal cancers

Question 30

In situ hybridization

Answer 30

A. Instead of antibodies, this technique uses complementary nucleic acid probes to specifically identify a nuclei acid sequence of interest
B. Can be used to identify a cell infected with a virus (e.g., human papillomavirus type 2) or specific genes on a chromosome (e.g., BRCA1 or BRCA2 genes). The human papillomavirus is a causative agent in cervical and anal cancers and genital warts (e.g., condyloma).
C. Of clinical utility to detect amplification of genes (e.g., Myc genes, HER2/neu). Gene amplification may produce multiple extrachromosomally copies of double minute chromosomes or by another mechanism, amplified genes are interpolated into a region of a chromosome.