Periodic acid–Schiff–diastase (PAS-D, PAS diastase) stain is a
periodic acid–Schiff (PAS) stain used in combination with
diastase A diastase (; from Greek διάστασις, "separation") is any one of a group of enzymes that catalyses the breakdown of starch into maltose. Alpha amylase degrades starch to a mixture of the disaccharide maltose; the trisaccharide maltotriose, ...
, an enzyme that breaks down
glycogen. PAS-D is a
stain often used by
pathologists
A list of people notable in the field of pathology.
A
* John Abercrombie, Scottish physician, neuropathologist and philosopher.
* Maude Abbott (1869–1940), Canadian pathologist, one of the earliest women graduated in medicine, expert in co ...
as an ancillary study in making a
histologic
Histology,
also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vis ...
diagnosis on
paraffin Paraffin may refer to:
Substances
* Paraffin wax, a white or colorless soft solid that is used as a lubricant and for other applications
* Liquid paraffin (drug), a very highly refined mineral oil used in cosmetics and for medical purposes
* Alkan ...
-embedded tissue specimens. PAS stain typically gives a
magenta
Magenta () is a color that is variously defined as pinkish- purplish- red, reddish-purplish-pink or mauvish-crimson. On color wheels of the RGB (additive) and CMY (subtractive) color models, it is located exactly midway between red and blu ...
color in the presence of glycogen. When PAS and diastase are used together, a light pink color replaces the deep magenta. Differences in the intensities of the two stains (PAS and PAS-D) can be attributed to different glycogen concentrations and can be used to semiquantify glycogen in samples. In practice, the tissue is deparaffinized, the diastase incubates, and then the PAS stain is applied.
An example of PAS-D in use is in showing
gastric
The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...
/
duodenal
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine ...
metaplasia
Metaplasia ( gr, "change in form") is the transformation of one differentiated cell type to another differentiated cell type. The change from one type of cell to another may be part of a normal maturation process, or caused by some sort of abno ...
in duodenal
adenomas. PAS diastase stain is also used to identify alpha-1 antitrypsin globules in
hepatocytes
A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass.
These cells are involved in:
* Protein synthesis
* Protein storage
* Transformation of carbohydrates
* Synthesis of cholesterol, ...
, which is a characteristic finding of
alpha-1 antitrypsin deficiency
Alpha-1 antitrypsin deficiency (A1AD or AATD) is a genetic disorder that may result in lung disease or liver disease. Onset of lung problems is typically between 20 and 50 years of age. This may result in shortness of breath, wheezing, or an inc ...
.
PAS diastase stain is also used in diagnosing
Whipple’s disease, as the foamy
macrophages
Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer ce ...
that infiltrate the
lamina propria of the small intestine in this disease possess PAS-positive, diastase-resistant inclusions.
Additional images
Image:Histoplasma pas-d small.jpg, Histoplasma. PAS diastase stain.
Image:Histoplasma in granuloma pas-d.jpg, Histoplasma in a granuloma. PAS diastase stain.
See also
*
Periodic acid-Schiff stain
Periodicity or periodic may refer to:
Mathematics
* Bott periodicity theorem, addresses Bott periodicity: a modulo-8 recurrence relation in the homotopy groups of classical groups
* Periodic function, a function whose output contains values tha ...
*
Diastase A diastase (; from Greek διάστασις, "separation") is any one of a group of enzymes that catalyses the breakdown of starch into maltose. Alpha amylase degrades starch to a mixture of the disaccharide maltose; the trisaccharide maltotriose, ...
References
{{reflist
External links
PAS Diastase Protocol
Staining