3. • In fields of
,
and
fixation is a chemical
process by which biological tissues are
preserved from decay,thereby preventing
from
• Fixation terminates ongoing biochemical
reactions
• It also increase the mechanical strenght or
stability of treated tissues.
4. •
•
•
•
•
•
•
Which are to be fixed are following
Proteins
Lipids
Carbohydrates
Biogenic amines
Nucleic acids
Water and lipid soluble substances
5. • Crosslinking fixatives act by creating covalent chemical
bonds between proteins in tissue.
• Most commonly used fixative in histology is the crosslinking
fixative formaldehyde (also named formalin).
• Formaldehyde is the most commonly used fixative for amino
acid histochemistry.
• Another popular aldehyde for fixation is glutaraldehyde.
• Glutaraldehyde fix proteins very rapidly.
• Glutaraldehyde may not penetrate thicker tissue
specimens as effectively as formaldehyde.
• Glutaraldehyde may offer a more rigid or tightly linked
fixation.
6. • In order to demonstrate lipids,frozen sections
are commonly used.
used to preserve
phospholipids.
• For preservation of lipids in cryostat sections
fixative should contain
• For this purpose we use the
• Fixation is over 3 days at room temperature.
7.
8. • Alcoholic fixatives are used for glycogen
fixation.
are
• Fixatives for ultrasturctural preservation of
dextrans and glycogen is
•
•
•
•
•
It is used by making stock solutions of
Formaldehyde
Glutaraldehyde
Osmium tetraoxide
Lead citrate
9. • Biogenic amines can be demonstrated in
tissues using a variety of techniques.
•
In this reaction potassium dichromateformaldehyde is used.
Formaldehyde fixation of the adrenal medulla
produced fluorescence of cells which
contained biogenic amines
or carnoy
fixed paraffin section
For histamines
• Primary biogenic amines are well preserved
by
10. • Fixatives choosen for nucleic acids must depend upon
subsequent methods which are to be employed in
analysis of tissue.
–based fixatives (used but mostly
avoided)
– (most widely used)
• It is to be used then the hydrolysis time varies with the
fixative.
11. • For accurate demonstration of water soluble
substances,non-aqueous fixatives are used.
For example, Urates in gout
is a satisfactory fixative
For steriods.
