Coloring (histology)
The biological coloring of Tissu is often necessary for the identification.
Colorings under the photonic microscope
Topographic colorings
A dye is an aqueous solution which can change electrically and which can color a substance or a whole of substances in a stable way.
Constituted of a chromophoric grouping (color) and of a grouping auxochrome (ionized grouping): permanent fixing on acid or basic groupings of the cellular components (with a given pH)
Characteristics: - nonspecific of a type of molecule - an overall picture gives of fabric: inform about the distribution, the architecture and the structure of the cells - results from the combined action of an acid dye (éosine) and of a basic dye (hémalun, methylene blue)
The acid substances of the cell are coloured by a basic dye, the basic substances of the cell by an acid dye.
This coloring colors a type of load. One can see the morphology of the cell (form), the position of the core and his form. Thus, one can determine the number of the cellular types in fabric and the structure of this fabric (cells stuck or not).
Histochemical colorings
Reactions redox acting on macromolecules, inform about the chemical constitution of the cell. Examples: APS (acid periodical-Schiff) Feulgen (DNA) Brachet (DNA and/or ARN)
Types of fabric revealed by coloring
Acid dyes
The acid dyes have a good affinity with the alkaline substances, they highlight fabrics acidophiles .
-
éosine (Red)
- Picric acid (Yellow)
- Green rapid
- Orange G
- acid Fuchsine (red)
- érythrosine
Basic dyes
They highlight fabrics acid, known as basophilic .
Silver coloring
Certain fabrics fix the money. One speaks about structures argentaffines or structures argyrophiles .
Coloring with Chromium salts
One thus highlights the fabrics chromaffines , like the adrenal medulla.
Various methods of coloring
Several methods of coloring were developed to reveal certain structures. Here are some indexed in a table:
Coloring used in microbiology
Even it is not a question itself directly of histological colorings, these methods aim at distinguishing between several cellular types. They use also the same types of dyes:
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the Coloring of Gram, to determine types of cells Procaryotic S;
- the Coloration of Ziehl-Neelsen reveals the mycobacteries.