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A lysochrome is a soluble dye used for histochemical staining of lipids, which include triglycerides, fatty acids, and lipoproteins. Lysochromes such as Sudan IV dissolve in the lipid and show up as colored regions. The dye does not stick to any other substrates, so a quantification or qualification of lipid presence can be obtained.
Sudan stain test is often used to determine the level of fecal fat to diagnose steatorrhea. A small sample is dissolved in water or saline, glacial acetic acid is added to hydrolyze the insoluble salts of fatty acids , a few drops of alcoholic solution of Sudan III are added, the sample is spread on a microscopic slide, and heated twice to boil.
Main staining types when using hematoxylin and eosin (H&E). A Basophil granulocyte stains dark purple upon H&E staining. Basophilic is a technical term used by pathologists. It describes the appearance of cells, tissues and cellular structures as seen through the microscope after a histological section has been stained with a basic dye.
For example, ethyl formate or orthoformate reacts with two equivalents of phenylhydrazine to yield 1,5-diphenylformazan, under acidic conditions. Under basic conditions, ethyl nitrate reacts at the methylene position to yield 3-methyl-1,5-diphenylformazan, which can also be obtained from the reaction of phenylazoethane with isoamyl nitrite .
Oil Red O is one of the dyes used for Sudan staining. Similar dyes include Sudan III, Sudan IV, and Sudan Black B. The staining has to be performed on fresh samples, as alcohol fixation removes most lipids. Oil Red O largely replaced Sudan III and Sudan IV, as it provides much deeper red color and the stains are therefore much easier to see.
Sudan III is a dye used for Sudan staining. Similar dyes include Oil Red O, Sudan IV, and Sudan Black B. They are used for staining of triglycerides in frozen sections, and some protein bound lipids and lipoproteins on paraffin sections. It has the appearance of reddish brown crystals and a maximum absorption at 507(304) nm. [6]
Nile red (also known as Nile blue oxazone) is a lipophilic stain. Nile red stains intracellular lipid droplets yellow. In most polar solvents, Nile red will not fluoresce; however, when in a lipid-rich environment, it can be intensely fluorescent, with varying colors from deep red (for polar membrane lipid) to strong yellow-gold emission (for neutral lipid in intracellular storages).
It is a non-fluorescent, relatively thermostable lysochrome (fat-soluble dye) diazo dye used for staining of neutral triglycerides and lipids on frozen sections and some lipoproteins on paraffin sections. It has the appearance of a dark brown to black powder with maximum absorption at 596–605 nm and melting point 120–124 °C.