Fixation, Decalcification, Dehydration, Clearing

Question 1

Amount of fixing fluid should be:

Answer 1

10-20 times the volume of the specimen

Question 2

Nuclear fixatives usually contain ____ as their primary component due to its affinity for nuclear chromatin.

Answer 2

Glacial acetic acid

Question 3

Added as a preservative to formaldehyde; prevents decomposition to formic acid

Answer 3

Methanol

Question 4

Concentrations solutions must never be neutralized since this might precipitate violent explosions.

Answer 4

Formaldehyde

Question 5

Dark brown artifact pigment granules from unbuffered formalin can be removed by:

Answer 5

Picric acid

Question 6

Mercuric chloride pigment may be removed by:

Answer 6

Iodine-sodium thiosulfate sequence

Question 7

Fixatives that give the best results with metachromatic staining

Answer 7

Mercurial

Question 8

Highly explosive when dry

Answer 8

Picric acid

Question 9

Demonstrates Rickettsiae and other bacteria

Answer 9

Orth’s fluid

Question 10

Recommended for fixation of embryos

Answer 10

Bouin’s solution

Question 11

Used in fixing brain tissues for diagnosis of rabies

Answer 11

Acetone

Question 12

Considered the most rapid fixative; fixes and dehydrates at the same time

Answer 12

Carnoy’s fluid

Question 13

Chemical reactions are rapid at ___C.

Answer 13

60-65

Question 14

Thickness of section for light microscopy

Answer 14

2 cm^2

Question 15

Brain is suspended whole in ____ for 2-3 weeks to ensure hardening prior to sectioning.

Answer 15

10% buffered formalin

Question 16

Recommended osmolality for fixation

Answer 16

400-500 mOsm

Question 17

Fixation inn buffered formalin is carried out for ___ hours.

Answer 17

2-6

Question 18

Fixatives diffuse into tissue at the rate of ___ per hour and slows down as its goes deeper into the tissue.

Answer 18

1 mm

Question 19

If the fixative is osmium tetroxide, it should be ___ times the tissue volume.

Answer 19

5-10

Question 20

TRUE or FALSE: Fibrous organs take longer than small or loosely textured tissues.

Answer 20

True

Question 21

Microanatomical vs Cytologic: fixatives that preserve specific parts and particular microscopic elements of the cell

Answer 21

Cytologic

Question 22

Why must cytoplasmic fixatives not contain glacial acetic acid?

Answer 22

It destroys mitochondria and Golgi bodies

Question 23

pH required for nuclear fixatives

Answer 23

<4.6

Question 24

Removes chromates, formalin, osmic acid

Answer 24

Tap water

Question 25

Removes picric acid

Answer 25

50-70% alcohol/ethanol or lithium carbonate

Question 26

Removes excess mercuric fixative

Answer 26

Alcoholic iodine (Dezenkerization)

Question 27

Form of secondary fixation whereby primarily fixed tissue is placed in a 2.5-3% potassium dichromate for 24 hours

Answer 27

Post-chromatization

Question 28

Most reliable method of determining the extent of decalcification due to its ability to detect even the smallest focus of calcium

Answer 28

Radiological method

Question 29

Recommended ratio of fluid to tissue volume for decalcification

Answer 29

20:1

Question 30

Ideal time for decalcifying tissue

Answer 30

24-48 hours

Question 31

After decalcification, acid must be removed by ___ changes of 70-90% ethanol.

Answer 31

3

Question 32

Decalcifying agent and tissue softener at the same time

Answer 32

Perenyi's fluid

Question 33

Decal agent recommended for teeth and small bone pieces

Answer 33

Von Ebner's fluid

Question 34

Ammonium form of polystyrene resin that hastens decalcification by removing calcium ions from formic acid

Answer 34

Ion exchange resin

Question 35

Whatever dehydrating agent is used, the amount in each stage should be:

Answer 35

>10x the tissue volume

Question 36

Toxic dehydrating agent, primarily employed or blood and tissue films and for smear preparations

Answer 36

Methyl alcohol

Question 37

Most rapid and most commonly used clearing agent in histology laboratories

Answer 37

Xylene

Question 38

Most probably cause when clearing agent turns milky as soon as the tissue is placed in it

Answer 38

Incomplete dehydration

Question 39

Dehydrating agent recommended for routine dehydration of tissues

Answer 39

Ethanol

Question 40

Method of dioxane dehydration which uses pure dioxane and paraffin

Answer 40

Graupner's

Question 41

Method of dioxane dehydration where tissues are wrapped in a gauze and submerged in dioxane with calcium oxide

Answer 41

Weiseberg's

Question 42

TRUE or FALSE: Dioxane is a dehydrating but not a clearing agent.

Answer 42

False

Question 43

Dehydrating agent that is combustible at 110-120F

Answer 43

Cellosolve

Question 44

A blue discoloration of ____ crystals will indicate full saturation of dehydrating fluid with water.

Answer 44

Copper sulfate

Question 45

Clearing agent should be miscible with ____ and ____.

Answer 45

Alcohol; paraffin wax

Question 46

Amount of clearing agent should be ____ times the tissue volume.

Answer 46

>10

Question 47

Clearing agent used as a substitute for xylene or benzene

Answer 47

Toluene

Question 48

Clearing agent recommended for CNS tissues and cytological studies; turns milky upon prolonged storage

Answer 48

Cedarwood oil

Question 49

Clearing agent recommended for clearing embryos, insects, and delicate specimens

Answer 49

Aniline oil