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 ...

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 eukaryote, 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 ...

connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tissue ...

fibers and some

cytoplasmic In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. T ...

features, but does not preserve delicate cytoplasmic

organelle In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' t ...

s 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 ...

("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 healt ...

sodium sulfate Sodium sulfate (also known as sodium sulphate or sulfate of soda) is the inorganic compound with formula Na2SO4 as well as several related hydrates. All forms are white solids that are highly soluble in water. With an annual production of 6 mill ...

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

, and

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main componen ...

. 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

, 25g of

, 10g of

(decahydrate) and distilled water to complete 1000 ml. Before use, 5 ml glacial

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 ...

(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 Formic acid (), systematically named methanoic acid, is the simplest carboxylic acid, and has the chemical formula HCOOH and structure . It is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. Est ...

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 conven ...

s; the orange solution becomes greenish.

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.
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Histology {{chemistry-stub

Stock solution

Helly's fixative

See also

References