FIXATIVES Flashcards
pale yellow powder that dissolves in water (6% at 20C)
osmium tetroxide
uses of Osmium Tetroxide
- Fix and stain unconjugated fats (stained black)
- fixative for electron microscopy
disadvantage of osmium tetroxide
expensive; inhibits hematoxylin
most common chrome-osmium acetic acid fixative
flemming’s
excellent fixative for nuclear structures
flemming’s
for cytoplasmic structures especially mitochondria
flemming’s without acetic acid
precipitates proteins; weak decalcifying agent; has a softening effect on dense tissues
TCA fixatives
used at ice cold temperature from -5C to 4C
acetone fixatives
for diffusible enzymes such as phosphatases and lipases
acetone fixatives
for fixing brain tissues; rabies diagnosis
acetone fixatives
optimum temp for microwave technique
45-55C
fixatives for enzyme histochemistry
4% formalin or formol saline
Fixatives for EM
- Osmium tetroxide (Pallade’s, MIllonig’s, S. collidine)
- Glutaraldehyde
- Paraformaldehyde
Best Fixative for Electron Histochemistry and Electron Immunocytochemistry
Karnovsky’s, Paraformaldehyde, Glutaraldehyde
mixture of methanol and PEG, cost effective alternative to formalin
UMFIX
fixation is retarded by:
- size and thickness
- presence of mucus
- presence of fat
- presence of blood
- cold temp
fixation is enhanced by:
- thinner and small size of tissues
- agitation (reduce overall processing time by 30%)
- heat
special staining; ensure further and complete hardening and preservation
secondary fixation
also known as post mordanting
post-chromatization
liquid used for washing out
tap water, 50-70% alcohol, alcoholic iodine
removed by washing out using tap water
chromates, formalin, osmium tetroxide
removed by washing out using 50-70% alcohol
picric acid
removed by washing out using alcoholic iodine
mercury
transport medium for unfixed tissues renal, skin, oral mucosa biopsies) refrigerated
Michel’s solution
