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Histopath Readings - Chapter 6(Midterms) > Part 2 > Flashcards

Part 2 Flashcards

1
Q

Tissue blocks should be in what size?

A

Small (1 to 2mm^2 for EM and 2cm^2 for LM)

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2
Q

T/F: Large solid tissue, such as uterus, should be opened or sliced thinly to improve penetration of fixatives

A

TRUE

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3
Q

Contents that can inhibit the penetration of fixative, as well as damage tissue during sectioning, and therefore must be removed before fixation.

A

Fecal matter and stomach contents

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4
Q

Brain is usually suspended whole in

A

10% buffered formalin for 2-3 weeks to ensure fixation and some hardening prior to sectioning

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5
Q

T/F: The brain must be fixed before “grossing” or sectioning.

A

TRUE

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6
Q

Fixative that penetrate the best and worst

A

Best = Formalin and alcohol
Worst = Glutaraldehyde

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7
Q

To maintain an adequate fixation time of

A

4-6 hours

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8
Q

Recommended size of tissue

A

2cm^2 and no more than 4mm thick

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9
Q

The best results are usually obtained using

A

Slightly hypertonic solutions (400-450mOsm; isotonic solutions are 340 mOsm)

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10
Q

Commonly added to osmium tetroxide fixatives for electron microscopy.

A

Sucrose

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11
Q

Normally used as a 10% solution

A

Formalin

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12
Q

The presence of a buffer causes

A

Polymerization of the aldehyde, with consequent decrease in its effective concentration

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13
Q

Found to be an ideal concentration for immuno-electron microscopy

A

Low concentration of glutaraldehyde (0.25%)

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14
Q

Primary fixation in buffered formalin is usually carried out for

A

2-6 hours during the day when the specimen is obtained

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15
Q

Most of the formalin can be washed out after fixation for

A

24 hours

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16
Q

Prolonged fixation may cause

A

Shrinkage and hardening of tissue, and may severely inhibit enzyme activity and immunological reactions,

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17
Q

Remedy to restore the activity of some enzymes

A

Washing of tissue

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18
Q

For electron microscopy, it is recommended that diced tissues be fixed for

A

3 hours then placed in a holding buffer

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19
Q

Artefacts will be introduced by drying, so if the tissue is left out in the open, it should be kept moist with

A

saline

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20
Q

May act as mordants or accentuators to promote and hasten staining, or they may inhibit certain dyes in favor of another

A

Formaldehyde intensifies while osmium tetroxide inhibits

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21
Q

T/F: Fixatives increase the optical differentiation of cells and tissue components thereby rendering them more readily visible during examination.

A

TRUE

22
Q

Characteristics of a GOOD Fixatives (9)

A
  • It must be cheap.
  • It must be stable.
  • It must be safe to handle.
  • It must kill the cell quickly thereby producing minimum distortion of cell constituents.
  • It must inhibit bacterial decomposition and autolysis.
  • It must produce minimum shrinkage of tissue.
  • It must permit rapid and even penetration of tissues.
  • It must harden tissues thereby making the cutting of sections easier.
  • It must be isotonic, causing minimal physical and chemical alteration of the cells and their constituents
  • It must make cellular components insoluble to hypotonic solutions and render them insensitive to subsequent processing.
  • It must permit the subsequent application of many staining procedures to facilitate easier and more profitable examination.
23
Q

Protein-denaturing agents.

A

Alcohol based fixatives

24
Q

Act by forming insoluble metallic precipitates like mercuric chloride and picric acid

A

Metallic Fixatives

25
Q

Are made up of only one component substance

A

Simple fixatives

26
Q

Examples of simple fixatives

A

Aldehydes, Metallic fixatives, Picric acid, Acetic acid, Acetone, Alcohol, Osmium teteroxide

27
Q

Those that are made up of two or more fixatives which have been added together to obtain the optimal combined effect of their individual actions upon the cells and tissue constituents

A

Compound fixatives

28
Q

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

A

Microanatomical fixatives (10% formol saline, neutral buffered formalin, Heindenhain’s Susa, Formol sublimate, Zenker’s, Zenker-formol, Bouin’s, Brasil’s)

29
Q

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

A

Cytological fixatives

30
Q

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

A

Nuclear fixatives (Flemming’s, Carnoy’s, Bouin’s Newcomer’s, HS)

31
Q

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

A

Mercuric chloride

32
Q

Are those that preserve cytoplasmic structures in particular. They must never contain glacial acetic acid which destroys mitochondria and Golgi bodies of the cytoplasm. They have a pH of more than 4.6.

A

Cytoplasmic Fixatives

33
Q

Example of Cytoplasmic Fixatives

A

Flemming’s fluid without acetic acid
Kelly’s fluid
Formalin with “post-chroming”
Regaud ‘s fluid (Muller ‘s fluid)
Orth ‘s fluid

34
Q

For RNA, give the best quantitative results using frozen tissues as the standard.

A

Ethanol and acetone

35
Q

Are those that preserve the chemical constituents of cells and tissues.

A

Histochemical fixatives

36
Q

Examples of histochemical fixatives

A

10% formol saline
Absolute ethyl alcohol
Acetone
Newcomer’s fluid

37
Q

It is the process of placing an already fixed tissue in a second fixative in order:
- To facilitate and improve the demonstration of particular substances.
- To make special staining techniques possible (with secondary fixative acting as a mordant).
- To ensure further and complete hardening and preservation of tissue

A

Secondary fixation

38
Q

It is a form of secondary fixation whereby a primarily fixed tissue is placed in aqueous solution of 2.5-3% potassium dichromate for 24 hours to act as mordant for better staining effects and to aid in cytologic preservation of tissues.

A

Post-Chromatization

39
Q

It is the process of removing excess fixative from the tissue after fixation in order to improve staining and remove artefacts from the tissues. Several solutions may be used.

A

Washing out

40
Q

Used to remove excess chromates, formalin and osmic acid

A

Tap water

41
Q

Used to wash out excess amount of picric acid (Bouin’s solution)

A

50-70% alcohol

42
Q

Used to remove excessive mercuric fixatives

A

Alcoholic Iodine

43
Q

PLS READ GENERAL PRECAUTIONS IN HANDLING AND FIXATION OF SPECIMENS

A

Read mo ha :>

44
Q

May lead to formation of ice crystal artifacts

A

Frozen sections

45
Q

T/F: The position or shape that is desired for sectioning should be maintained
BEFORE fixation

A

TRUE

46
Q

Give the cause: Failure to arrest early autolysis of cells

A

Failure to fix immediately
Insufficient fixative

47
Q

Give the cause: Removal of substances soluble in fixing agent

A

Wrong choice of fixative

48
Q

Give the cause: Presence of artefact pigments on tissue sections

A

Incomplete washing of fixative

49
Q

Give the cause: Tissues are soft and feather-like in consistency

A

Incomplete fixation

50
Q

Give the cause: Loss or inactivation of enzymes needed for study

A

Wrong choice of fixatives

51
Q

Give the cause: Shrinkage and swelling of cells and tissue structure

A

Overfixation

52
Q

Give the cause: Tissue blocks are brittle and hard

A

Prolonged fixation

Histopath Readings - Chapter 6(Midterms) (3 decks)

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