Fixation Lec

Question 1

fixatives employed prevent autolysis by

Answer 1

inactivating lysosomal enzymes

Question 2

allows the tissue to be more properly oriented in the cassette in
preparation for paraffin embedding and microtomy

Answer 2

fixation

Question 3

results from tissue digestion by intracellular enzymes that are released
when organelle membranes rupture

Answer 3

autolysis

Question 4

brought about by microorganisms which may already be present in the specimen

Answer 4

Bacterial decomposition or putrefaction

Question 5

During processing, however,
the specimen may shrink and lose ______ of its volume

Answer 5

20% -30%

Question 6

Leaving the tissue in ____ (a hypotonic solution)
will cause the cell to ______

Answer 6

water, swell

Question 7

Leaving the tissue in _____ (hypertonic solution) will cause
the cell to ______.

Answer 7

strong salt, shrink

Question 8

rarely used on tissue specimens, its application being confined to
smears of microorganisms

Answer 8

heat fixation

Question 9

regarded as a form of heat fixation, is now widely practiced in routine laboratories

Answer 9

microwave fixation

Question 10

usually in the form of freeze drying, has some applications in
histochemistry but is not usually applied to diagnostic tissue specimens

Answer 10

cryopreservation

Question 11

usually achieved by immersing the specimen in the fixative solution

Answer 11

chemical fixation (immersion fixation)

Question 12

in the case of small animals or some whole organs such as a lung, by perfusing or injecting the vascular system with
fixative

Answer 12

chemical fixation (perfusion fixation)

Question 13

can be used to vapor-fix freeze-dried tissues

Answer 13

paraformaldehyde and osmium tetroxide

Question 14

• chemical constituent of the fixative is taken in and becomes part of the tissue
• cross-links or
  molecular complexes and giving stability to the protein

Answer 14

additive fixation

Question 15

fixing agent is not incorporated
into the tissue, but alters the tissue composition and stabilizes the tissue

Answer 15

non-additive fixation

Question 16

Specimens should be transferred to fixative quickly______ as deterioration will commence with the loss of blood supply.

Answer 16

(<1 hour) after
surgery

Question 17

Fixative to tissue ratio

Answer 17

10-20:1

Question 18

also enhance fixation of
the specimen

Answer 18

agitation

Question 19

The most common error in histotechnology

Answer 19

insufficient ratio of tissue volume to fixative volume

Question 20

Fixation is best carried out close to
_____ (indicate range)

Answer 20

neutral pH, in the range of 6-8

Question 21

Acidity favors formation of
______ that appears as black, polarizable deposits in
tissue

Answer 21

formalin-heme pigment

Question 22

Commercial formalin is buffered with ____ at a pH of ___

Answer 22

phosphate, 7

Question 23

common/regular tissue processor temperature

Answer 23

40C

Question 24

Temperature for electron microscopy

Answer 24

0-4C

Question 25

temperature for mast cell

Answer 25

room temp

Question 26

to slow down decomposition if the tissue needs to be photographed and cannot be fixed immediately

Answer 26

refrigeration

Question 27

_____ continues to undergo mitosis (growth) up to ___ minutes after death when refrigerated

Answer 27

bone marrow, 30

Question 28

do not react with fixatives to any extent at room temperatures

Answer 28

nucleic acids

Question 29

temp for rapid fixation

Answer 29

60 C

Question 30

tissue block size for electron microscopy

Answer 30

1 to 2 mm2

Question 31

tissue block size for light microscopy

Answer 31

2cm2

Question 32

thinness of tissue block for light microscopy

Answer 32

no more than 0.4 cm

Question 33

brain is fixed (suspended whole) in ____

Answer 33

10% buffered formalin for 2-3 weeks

Question 34

A commonly quoted rate of penetration for aldehyde fixative is

Answer 34

2-3mm/hr

Question 35

solid material/ tissue (e,g, liver) longest dimension is ____

Answer 35

not more than 10-15mm

Question 36

commonly added to osmium tetroxide fixatives for electron microscopy

Answer 36

sucrose

Question 37

ideal concentration of glutaraldehyde for immuno-electron microscopy

Answer 37

0.25%

Question 38

routine conc. of glutaraldehyde

Answer 38

3%

Question 39

For electron microscopy, it is recommended that ____ tissues be fixed for___ hours and then placed in a holding buffer.

Answer 39

diced, 3

Question 40

four major groups of fixatives

Answer 40

aldehydes oxidizing agents alcohol based fixatives metallic group

Question 41

type of fixative that act by cross-linking proteins

Answer 41

aldehyde and oxidizing agents

Question 42

type of fixative that are protein-denaturing agents

Answer 42

alcohol based

Question 43

type of fixative that act by forming insoluble metallic precipitates like mercuric chloride and picric acid

Answer 43

metallic fixatives

Question 44

fixatives according to composition

Answer 44

simple fixative compound fixative

Question 45

fixative according to action

Answer 45

microanatomical cytological

Question 46

fixative that permit the general microscopic study of tissue structures without altering the structural pattern and normal intercellular relationship of the tissues in question

Answer 46

microanatomical fixatives

Question 47

fixatives that preserve specific parts and particular microscopic elements of the cell itself

Answer 47

cytological fixatives

Question 48

- preserve the nuclear structures (e.g., chromosomes) in particular - usually contain glacial acetic acid as their primary component due to its affinity for nuclear chromatin. - have a pH of 4.6 or less.

Answer 48

nuclear fixatives

Question 49

has been found to react with viruses, and causes the loss of their infective power

Answer 49

mercuric chloride