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Chemicals
used for
preservation of carcasses and samples
First
unrevised draft. Help for improvement would be appreciated
For
fixing of tissues for histology
For histological studies,
buffered
neutral formalin is a good general purpose fixative. For certain
histological
procedures, however, other fixatives may be better because they
penetrate
tissues more rapidly and may render tissues more easily stained
by certain
histological dyes. Tissues can be left in some fixatives (e.g.,
buffered
neutralized formalin) for several months; with other fixatives
(e.g., Bouin's),
tissues must be transferred to alcohol immediately after fixing.
Three
of the more widely used fixatives are described here. For more
information
on fixatives and histological methods, Nagorsen and Peterson
recommend
Luna (1968).
Formalin
(=
formaldehyde solution):
Commercially available formalin
solution
is usually a 37 % or 40 % (weight / volume) solution. It may be
best to
take this full strength solution to the field to reduce volume
and to dilute
it before use; in this case the full strength solution is
treated as 100
%, which means that for production of a 10 % solution one part
of 40 %
formalin solution must be mixed with 9 parts water. Formalin
solution is
usually acidic (pH 3 to 4.6) and tends to decalcify teeth and to
excessively
harden tissue. Therefore, it is best to buffer it to pH 7.0
(neutral) (Nagorsen,
Peterson 1980).
10 % buffered formalin
(from
Nagorsen, Peterson 1980, Munson 2000)
For 1 litre:
100 ml
formalin
(38-40 % formaldehyde)
900 ml
distilled
water
Buffer added:
Buffer
mixture for precise buffering to neutrality (pH 7.0) (Nagorsen,
Peterson
1980):
4
g of acid or monobasic sodium phosphate monohydrate (NAH2PO4H2O)
6.5
g of dibasic sodium phosphate anhydrate (NA2HPO4)
This
dry salt mixture can be prepared in advance and carried into the
field
in plastic bags.
Another
possible buffer mixture (Munson 2000):
4.5
gm sodium phosphate (monobasic)
3.6
g sodium hydroxide
Mixture
in cases when such buffer is not available:
4
g sodium chloride = table salt (Munson 2000)
or
a
quarter of a teaspoon of borax powder or household ammonia
(Nagorsen,
Peterson 1980) per litre
Bouin's
solution (from Nagorsen, Peterson 1980)
Picric acid,
saturated
aqueous solution 750 ml
(if
not stored in an aqueous solution, picric acid is highly
volatile)
37-40%
formalin
250 ml
Glacial
acetic
acid 50 ml
Alcohol-formalin-acetic
acid
solution (AFA) (from Nagorsen, Peterson 1980)
37-40%
formalin
10 ml
Alcohol, 80%
90
ml
Glacial
acetic
acid 5 ml
Formalin-sodium
acetate
solution (from Nagorsen, Peterson 1980)
37-40%
formalin
100 ml
Sodium
acetate
20 g
Tap water 900
ml
Chemicals
for other purposes
Sterile
buffered
glycerin (50%) for transporting tissues for culture when
refrigeration
is not available (from Munson, 2000):
Buffer
composed
of:
A:
21 g citric acid mixed in 1000 distilled water
B:
28.4 g anhydrous sodium phosphate in 1000 distilled water
Buffer:
mixture of 9.15 ml of A and 90.85 ml of B.
100 ml of buffer mixed with 100
ml
of glycerin.
To take the mixture into the
field,
it can then be sterilised in small tubes.
"Easy
Blood" for transporting DNA from blood cells for genetic
studies when
refrigeration is not available and for preserving refrigerated
or frozen
DNA for longer periods of time (from Munson 2002):
1.2 g Tris
HCI
3.7 g Na2
EDTA
2 g sodium
dodecyl
sulfate (SDS)
Water added
to
100 ml
In:
Loris and potto conservation database: field
methods
http://www.species.net/primates/loris. |
Last
amendment: 7 November 2002
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