FIXATION Flashcards
(27 cards)
fixative of choice for many other procedures that require paraffin embedding
Buffered Formalin
immunohistochemistry and interphase Fluorescent In-Situ
Hybridization (FISH)
Buffered Formalin
added by the
manufacturer to retard the formation of higher polymers that eventually fall out
of solution as paraformaldehyde.
10% methanol,
Prolonged fixation
Loss of natural color of tissues [bleaching of the
specimen]
- Dispersal of fat into fluid
- Dissolution or loss of glycogen and urate crystals
may happen
RNA DNA TEMPERATURE FOR B.F
RNA: 45°C
DNA: 65°C
disadv of b.f
Allergic rhinitis, and excessive lacrimation
10% FORMAL SALINE FIXATION TIME
12-24 hours
application of 10% Formal Saline
MPLC
MICROANTOMICAL FIXATIVE
- CNS tissues
- General post-mortem tissues for
histochemical examination [post-mortem
analysis] - Preservation of lipids, especially
phospholipids
10% Formal-Saline Formula
40% formaldehyde: 100 ml
Distilled water: 900 ml
Sodium dihydrogen phosphate monohydrate: 4 gm
Disodium hydrogen phosphate anhydrous 6.5 gm
ph of fomal saline
6.8
ph of buffered formalin
7.0
ph of neutral buffered formalin
7.4
adv of nbf
PIPES
1. It prevents precipitation of acid formalin pigments on postmortem
tissue.
2. It is the best fixative for tissues containing iron pigments and for
elastic fibers which do not stain well after Susa, Zenker’s or
chromate fixation.
3. It requires no post-treatment after fixation and goes directly into 80%
alcohol for processing.
Positivity of mucin to PAS is reduced
nbf
Reactivity of myelin to Weigert’s iron hematoxylin stain is reduced
nbf
inert towards lipids, especially neutral fats and phospholipids
nbf
dadv of nbf
MIM
1. It is longer to prepare; hence, is time-consuming.
2. Positivity of mucin to PAS is reduced.
3. It may produce gradual loss in basophilic staining of cells.
4. Reactivity of myelin to Weigert’s iron hematoxylin stain is reduced.
5. It is inert towards lipids, especially neutral fats and phospholipids.
alternatives to mercuric chloride
formulations
Zinc formalin (unbuffered)
Formol-Corrosive (Formol-Sublimate)
formula
Sat. Aq. Mercuric chloride 90 ml.
Formaldehyde 40% 10 ml.
fixation time of formol corrosive
3 – 24 hours
adv of f.c
SSWL
polymerized form of formaldehyde, usually obtained
as a fine white powder, which depolymerizes back to formalin when heated.
Paraformaldehyde
composition of karnovsky
4% paraformaldehyde + 1% glutaraldehyde in 0.1M of p.b
For samples for light microscopy in resin embedding
and sectioning and Electron microscopy
KARNOVSKY’S FIXATIVE
