PAS REACTION Meaning and
Definition
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The term "PAS reaction" refers to the periodic acid-Schiff reaction, which is a histochemical staining technique used in biology and histology to detect the presence of carbohydrates, particularly polysaccharides and glycoproteins, within tissues. This reaction is named after the two key components used in the staining process.
Periodic acid (HIO4) is a strong oxidizing agent that cleaves the individual sugar molecules present in the carbohydrates. This step generates aldehyde groupings in the sugar molecules. The Schiff reagent, usually fuchsin-sulfurous acid, is then applied, which forms a purple-pink color complex when it reacts with the aldehyde groups. This complex can be observed under a microscope and indicates the presence of carbohydrates.
The PAS reaction has widespread application in histopathology, as it allows researchers and pathologists to identify and distinguish specific tissue components, such as the basement membrane of epithelial tissues, mucus secretions, goblet cells, glycogen, and certain tumors that express glycoproteins.
The PAS reaction is particularly advantageous as it provides a permanent and reliable stain that is resistant to fading over time. It can be used alongside other staining techniques to obtain comprehensive information about the composition and structure of tissues. Moreover, the PAS reaction can be modified and combined with other staining methods to investigate specific cell types or antigens.
Common Misspellings for PAS REACTION
Etymology of PAS REACTION
The term "PAS reaction" is an abbreviation for "Periodic Acid-Schiff reaction". Its etymology can be traced to the names of two scientists who contributed to its development.
The first part, "periodic acid", refers to the chemical reagent used in the reaction. Periodic acid (HIO₄) was discovered by French chemist Jean-Baptiste Boussingault in 1829 and named by Swedish chemist Jöns Jacob Berzelius in 1831. It is called "periodic acid" because it is derived from the mineral permanganate, which is also known as "manganese dioxide". This mineral was initially named "periodate of potash" due to its similarity to the compound iodate of potash.
The second part, "Schiff reaction", honors the German chemist Hugo Schiff.
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