Zenker's fixative is a rapid-acting
fixative for animal tissues. It is employed to prepare specimens of
animal
Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
or
vegetable
Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is applied to plants collectively to refer to all edible plant matter, including the flowers, fruits, stems, ...
tissues for microscopic study. It provides excellent fixation of nuclear
chromatin
Chromatin is a complex of DNA and protein found in eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important roles in r ...
,
connective tissue fibers and some
cytoplasmic features, but does not preserve delicate cytoplasmic
organelles such as
mitochondria. Helly's fixative is preferable for traditional dye staining of mitochondria. Zenker's fixative permeabilises the plasma, but not the nuclear membrane. It can therefore be used to selectively stain mitotic cells (where the nuclear membrane has dissolved) with antibodies against chromatin
Zenker's fixative contains
mercuric chloride
Mercury(II) chloride (or mercury bichloride, mercury dichloride), historically also known as sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2. It is white crystalline solid and is a ...
("corrosive sublimate"),
potassium dichromate
Potassium dichromate, , is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is acutely and chronically harmful to health ...
,
sodium sulfate,
water
Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
, and
acetic acid. Fixatives containing mercuric chloride or potassium dichromate are toxic, making disposal as
hazardous waste costly. Mercuric chloride can be replaced with the same weight of less toxic
zinc chloride
Zinc chloride is the name of inorganic chemical compounds with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. This salt is hygroscopic and e ...
, but the resulting "zinc-Zenker" may not give the same quality of fixation as the original mixture.
This fixative is named after Konrad Zenker, a German histologist, who died in 1894 (Baker 1958).
Stock solution
Zenker is usually made with 50g of
mercuric chloride
Mercury(II) chloride (or mercury bichloride, mercury dichloride), historically also known as sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2. It is white crystalline solid and is a ...
, 25g of
potassium dichromate
Potassium dichromate, , is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is acutely and chronically harmful to health ...
, 10g of
sodium sulfate (decahydrate) and distilled water to complete 1000 ml.
Before use, 5 ml glacial
acetic acid is added to 100 ml of the solution. Both the stock solution and the complete Zenker fixative are stable for many years.
Helly's fixative
If the glacial acetic acid is replaced by 5 ml of
formalin
Formaldehyde ( , ) ( systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section F ...
(37–40%
formaldehyde
Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...
), the resulting solution is Helly's fixative, also sometimes called "formol-Zenker". Helly is stable for only a few hours because the formaldehyde and dichromate components react, producing
formic acid and chromium(III)
ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
s; the orange solution becomes greenish.
See also
*
Fixation (histology)
In the fields of histology, pathology, and cell biology, fixation is the preservation of biological tissues from decay due to autolysis or putrefaction. It terminates any ongoing biochemical reactions and may also increase the treated tissues' mec ...
*
Dorland's Medical Dictionary
''Dorland's'' is the brand name of a family of medical reference works (including dictionaries, spellers and word books, and spell-check software) in various media spanning printed books, CD-ROMs, and online content. The flagship products are ''Do ...
References
* Barszcz CA (1976) Use of zinc chloride in Zenker-type fixatives. Histo-Logic 6: 8
* Baker JR (1958) Principles of Biological Microtechnique. London: Methuen, p. 344.
* Gabe M (1976) Histological Techniques (Transl. E. Blakith and A. Kavoor). Paris: Masson.
* Kiernan JA (2008) Histological and Histochemical Methods. 4th ed. Bloxham, UK: Scion. p. 40–41.
* Lillie RD & Fullmer HM (1976) Histopathologic Technic and Practical Histochemistry. 4th ed. New York: McGraw-Hill. p. 54–57.
www.whonamedit.com
Histology
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