Re: B5 Fixative & ? substitutes
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From: | "J. A. Kiernan" <jkiernan@julian.uwo.ca> |
To: | Histonet <Histonet@pathology.swmed.edu> |
Reply-To: | |
Content-Type: | TEXT/PLAIN; charset=US-ASCII |
On Thu, 13 Jul 2000 RSRICHMOND@aol.com wrote:
> Lori Karnes in Saskatoon, Saskatchewan asks about using Surgipath's I.B.F.
> fixative as a substitute for B-5 fixative.
>
> My information may be outdated, but in 1992 Surgipath described this fixative
> as "an alcohol based tissue fixative that contains barium chloride and a very
> low percentage of formalin." The barium chloride, which is (they claimed) not
> a hazardous waste problem, was supposed to substitute for the mercury in B-5.
Mercuric chloride fixes by coagulating proteins. The coagula are
generally too small to see with light microscopy, unlike those
from other coagulants like picric acid and alcohol. Barium chloride
isn't a precipitant of proteins, so it could not substitute for
mercuric chloride in a fixative.
Barium salts are chemically similar to those of calcium, and may
help to maintain the integrity of some lipid structures. BaCl2 is
used in a mixture with formaldehyde in Saxena's silver method for
showing the Golgi apparatus. Zinc chloride (or sulphate) is a
protein precipitant that some people claim can replace mercuric
chloride (see earlier HistoNet discussions), though perhaps
not for every purpose.
Regarding toxicity, barium chloride is considered quite
poisonous. Oral LD50 in rodents around 120 mg/kg. Mercuric
chloride is about 10 times as toxic as this (Data from
MSDS sheets). The nearest oral LD50 I can find for a zinc salt
is 2460 mg/kg for zinc acetate (Merck Index). Zinc salts are
not considered dangerously poisonous. Barium chloride is a
component of several traditional injection masses for
showing blood vessels, ducts etc: it reacts with sulphate ions
to give the completely insoluble (and harmless) sulphate - the
same compound that is used in radiological examinations of
the GI tract.
John A. Kiernan,
Department of Anatomy & Cell Biology,
The University of Western Ontario,
LONDON, Canada N6A 5C1
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