Hi Shireen,
You mentioned that the museum specimens you saw were STORED in 70%
isopropyl alcohol. That is a good long-term STORAGE solution for
most types of specimens, including those for museum display, for
eventual dissection, and for histological studies, but NOT for
materials intended for DNA or other molucular studies. However,
long-term storage and initial preservation (or fixation as we call it
in histological circles) are two different matters. Tissues for DNA
work are best preserved by direct immersion in strong, 95% to 100%,
ethanol (ethyl alcohol), and best stored in the same medium.
However, this kind of tissue fixation, like most types of fixation,
is a trade-off. In this case you gain DNA stability at the expense
of cellular detail and general tissue morphology. If histological
study is the intended purpose, then formalin, or any of several other
aqueous fixative agents, should normally be used. These compounds
form molecular cross-links between protein molecules, and produce
other submicroscopic effects which stabilize tissue components at the
microscopic level. Alcohol, while it stabilizes DNA very well, also
rapidly extracts water from the tissue, causing cells to shrink and
become misshapen. It also dissolves various substances out of the
cells, which would be stabilized by a good fixative; and it hardens
tissues excessively. However, once the tissue is properly fixed in
something like formalin, it can then be transferred to 70% alcohol,
safely stored without cellular damage, and later used for
histological studies.
If electron microscopy is intended, then neither alcohol nor formalin
is suitable, and other fixatives, such as glutaraldehyde, must be
used. So, there is no general preservative that is suitable for all
purposes, and you have to know up front what the tissue will be used
for, in order to preserve it properly.
There are any number of biological supply houses which sell
dissecting instruments and supplies.
A few are:
PGC Scientifics
9161 Indistrial Ct.
Gaithersburg, MD 20877
301-840-1111; 800-424-3300
Fisher Scientific
(offices in Atlanta, Cincinnati, Chicago, Dallas, Denver, Houston,
Los Angeles, New York, Orlando, Philadelphia, Pittsburgh, Puerto
Rico, San Francisco, St. Louis)
Main Headquarters:
711 Forbes Ave.
Pittsburgh, PA 15219-4785
412-562-8300
Cole-Parmer Instrument Company
625 East Bunker Court
Vernon Hills, IL 60061-1844
800-323-4340
Baxter Diagnostics, Inc.
Scientific Products Division
(offices in Atlanta, Boston, Charlotte, Chicago, Cincinnati,
Columbus, Dallas, Denver, Detroit, Honolulu, Houston, Indianapolis,
Kansas City, Los Angeles, Minneapolis, New Orleans, New York, Ocala,
Phoenix, Pittsburgh, Puerto Rico, St. Louis, Salt Lake City, San
Francisco, Seattle, Washington DC)
Main Offices:
1430 Waukegan Road
McGaw Park, IL 60085-6787
800-234-5227
A. Daigger & Co.
199 Carpenter Ave.
Wheeling, IL 60090
800-621-7193
Connecticut Valley Biological
82 Valley Road
P.O. Box 326
Southampton, MA 01073
(413) 527-4030
This last-listed place is a smaller company, and has a lot of very
inexpensive student-grade instruments.
Regards,
Paul M.
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