Infiltration

Question 1

What is impregnation/infiltration in tissue processing?

Answer 1

The process of permeating tissue with a support medium, completely removing clearing medium and replacing it with a medium that fills all tissue cavities.

Question 2

What are the main types of tissue impregnation/embedding?

Answer 2

Paraffin Wax, Celloidin (Collodion), Gelatin, and Plastic

Question 3

What are the 3 ways of paraffin impregnation and embedding?

Answer 3

1) Manual Processing (hand processing)
2) Automatic Processing (e.g., Autotechnicon)
3) Vacuum Embedding

Question 4

What are the time requirements for manual paraffin processing?

Answer 4

At least 4 changes of wax at 15-minute intervals; specimen immersed in fresh melted paraffin for approximately 3 hours; recommended tissue thickness: 3mm.

Question 5

What equipment is used for automatic processing?

Answer 5

Autotechnicon Elliott Bench

Question 6

What are the main steps in automatic processing?

Answer 6

Fixation, Dehydration, Clearing (12 processing steps above the melting point)

Question 7

What is the wax bath temperature in automatic processing?

Answer 7

3°C

Question 8

What is the critical step in automatic processing?

Answer 8

Dehydration

Question 9

What is the advantage of automatic processing?

Answer 9

“Constant agitation”

Question 10

What is vacuum embedding?

Answer 10

Wax impregnation under negative atmospheric pressure inside an embedding oven

Question 11

For which types of specimens is vacuum embedding recommended?

Answer 11

Urgent biopsies; delicate tissues (lung, connective tissues, decalcified bones, eyes, spleen, CNS)

Question 12

What are the advantages of vacuum embedding?

Answer 12

Fastest results; removes air bubbles and clearing agent

Question 13

What temperature should be maintained during vacuum embedding?

Answer 13

2°C to 4°C above wax melting point

Question 14

What are the common melting points of paraffin wax?

Answer 14

45°C, 52°C, 56°C and 58°C

Question 15

Which melting point of paraffin wax is routinely used?

Answer 15

56°C

Question 16

What are the melting point ranges for paraffin at different room temperatures?

Answer 16

54°C-58°C at 20°C-24°C (Room temp)
50°C-54°C at 15°C-18°C

Question 17

What are the advantages of paraffin wax methods?

Answer 17

Simplest; most common; best embedding medium; ease in cutting; permanent paraffin blocks; good staining results

Question 18

What are the limitations of paraffin wax methods?

Answer 18

Not recommended for fatty tissue; overheated paraffin → BRITTLE SPECIMEN; inadequate impregnation → CLEARING AGENT RETENTION; prolonged impregnation → TISSUE SHRINKAGE

Question 19

What is Paraplast?

Answer 19

A mixture of highly purified paraffin and synthetic plastic with MP: 56-57°C

Question 20

What are the properties of Paraplast?

Answer 20

More elastic and resilient than paraffin wax; for large tissue blocks (e.g., bones and brain); blocks more uniform → better ribboning; prevents ice crystal artifacts; no slide deposits after staining; soluble in most clearing agents

Question 21

What is Embeddol?

Answer 21

Synthetic wax similar to Paraplast but less brittle and less compressible; MP: 56-58°C

Question 22

What variants of embedding waxes are mentioned in relation to Embeddol?

Answer 22

Bioloid (semisynthetic wax) and Tissue Mat (paraffin containing rubber, recommended for embedding EYES)

Question 23

What are the properties of Ester Wax?

Answer 23

MP: 46-48°C
harder than paraffin; insoluble in water; soluble in 95% ethyl alcohol; requires Cellosolve or xylene; procedure: 3-4 wax changes; requires heavy-duty microtome

Question 24

What are water soluble waxes and their properties?

Answer 24

Mostly polyethylene glycols; MPs: 38°C, 48°C, 45°C, 56°C; Carbowax most commonly used

Question 25

What are the advantages of water soluble wax?

Answer 25

No dehydration/clearing needed; suitable for enzyme histochemistry; easily dissolved (add soap or 10% Polyethylene Glycol 900)

Question 26

What is celloidin made of and what is it recommended for?

Answer 26

Purified form of nitrocellulose soluble in many solvents; recommended for large hollow organs (prone to collapse), hard/dense tissues (bones, teeth), large tissue sections (e.g., whole embryos), and neurological tissues (permits thicker sections)

Question 27

What are the advantages and disadvantages of celloidin?

Answer 27

Advantages: prevents tissue crumbling, good for large/hollow organs, permits thick sections (neurological tissues). Disadvantages: very slow process, difficult to cut thin sections, challenging to prepare serial sections

Question 28

For what tissues is the wet celloidin method recommended?

Answer 28

Bones, teeth, large brain sections, whole organs

Question 29

What is the procedure for wet celloidin method?

Answer 29

Tissue blocks stored in 70-80% alcohol to prevent dehydration and shrinkage; ether and alcohol: 12-24 hours; thin celloidin (2-4%): 5-7 days; medium celloidin (4-6%): 5-7 days; thick celloidin (8-12%): 3-5 days