Periodic acid-Schiff
Encyclopedia
Periodic acid-Schiff is a staining method used to detect glycogen
and other polysaccharides in tissues. The reaction of periodic acid
oxidizes the diol functional groups in glucose
and other sugars, creating aldehyde
s that react with the Schiff reagent to give a purple-magenta color. A suitable basic stain is often used as a counterstain
.
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PAS staining is mainly used for staining structures containing a high proportion of carbohydrate
macromolecules (glycogen
, glycoprotein
, proteoglycan
s), typically found in e.g. connective tissue
s, mucus
, the glycocalyx
, and basal lamina
e.
PAS staining can be used to assist in the diagnosis of several medical conditions:
Presence of glycogen can be confirmed on a section of tissue by using diastase
to digest the glycogen from a section, then comparing a diastase digested PAS section with a normal PAS section. The diastase negative slide will show a magenta staining where glycogen is present within a section of tissue. The slide that has been treated with diastase will lack any positive PAS staining in those locations on the slide
PAS staining is also used for staining cellulose
. One example would be looking for implanted medical devices composed of nonoxidized cellulose.
If the PAS stain will be performed on tissue, the recommended fixative
is 10% neutral-buffered formalin
or Bouin solution
. For blood smears
, the recommended fixative is methanol
. Glutaraldehyde
is not recommended because free aldehyde groups may be available to react with the Schiff reagent, which may result in false positive staining.
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...
and other polysaccharides in tissues. The reaction of periodic acid
Periodic acid
Periodic acid, or iodic acid is an oxoacid of iodine having chemical formula HIO4 or H5IO6.In dilute aqueous solution, periodic acid exists as discrete hydronium and metaperiodate ions. When more concentrated, orthoperiodic acid, H5IO6, is formed; this dissociates into hydronium and...
oxidizes the diol functional groups in glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
and other sugars, creating aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
s that react with the Schiff reagent to give a purple-magenta color. A suitable basic stain is often used as a counterstain
Counterstain
A counterstain is a stain with color contrasting to the principal stain, making the stained structure more easily visible.An example is the malachite green counterstain to the fuchsine stain in the Gimenez staining technique....
.
Uses
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
macromolecules (glycogen
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...
, glycoprotein
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
, proteoglycan
Proteoglycan
Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan chain. The point of attachment is a Ser residue to which the glycosaminoglycan is joined through a tetrasaccharide bridge...
s), typically found in e.g. connective tissue
Connective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...
s, mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
, the glycocalyx
Glycocalyx
Glycocalyx is a general term referring to extracellular polymeric material produced by some bacteria, epithelia and other cells. The slime on the outside of a fish is considered a glycocalyx. The term was initially applied to the polysaccharide matrix excreted by epithelial cells forming a...
, and basal lamina
Basal lamina
The basal lamina is a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits. It is often confused with the basement membrane, and sometimes used inconsistently in the literature, see below....
e.
PAS staining can be used to assist in the diagnosis of several medical conditions:
- Glycogen storage diseaseGlycogen storage diseaseGlycogen storage disease is the result of defects in the processing of glycogen synthesis or breakdown within muscles, liver, and other cell types. GSD has two classes of cause: genetic and acquired. Genetic GSD is caused by any inborn error of metabolism involved in these processes...
(versus other storage disorders) - Paget's diseasePaget's diseaseSir James Paget, a surgeon and pathologist, described several diseases, including:* Paget's disease of bone * Paget's disease of the breast* Paget-Schroetter disease* Extramammary Paget's disease...
- Alveolar soft part sarcomaAlveolar soft part sarcomaAlveolar soft part sarcoma, abbreviated ASPS, is a very rare type of soft tissue sarcoma, that grows slowly and whose cell of origin is unknown.It arises mainly in children and young adults...
- staining macrophages in Whipple's diseaseWhipple's diseaseWhipple's disease is a rare, systemic infectious disease caused by the bacterium Tropheryma whipplei. First described by George Hoyt Whipple in 1907 and commonly considered a gastrointestinal disorder, Whipple's disease primarily causes malabsorption but may affect any part of the body including...
- It can be used to diagnose α1-antitrypsin deficiencyAlpha 1-antitrypsin deficiencyAlpha 1-antitrypsin deficiency is an autosomal recessive genetic disorder caused by defective production of alpha 1-antitrypsin , leading to decreased A1AT activity in the blood and lungs, and deposition of excessive abnormal A1AT protein in liver cells...
if periportal liver hepatocytes stain positive. - aggregates of PAS positive lymphocytes are present in epidermis in Mycosis fungoidesMycosis fungoides-External links:* * *...
and Sezary syndrome, called Pautrier microabscesses. - erythroleukemiaErythroleukemiaAcute erythroid leukemia is a rare form of acute myeloid leukemia where the myeloproliferation is of erythroblastic precursors.It is defined at type "M6" under the FAB classification.-Types:...
, a leukemia of immature red blood cells. These cells stain a bright fuchsia. - Pulmonary alveolar proteinosisPulmonary alveolar proteinosisPulmonary alveolar proteinosis is a rare lung disease in which abnormal accumulation of surfactant occurs within the alveoli, interfering with gas exchange. PAP can occur in a primary form or secondarily in the settings of malignancy , pulmonary infection, or environmental exposure to dusts or...
- Fungal infection, the cell walls of fungi stain magenta. This only works on living fungi; in contrast, Grocott's methenamine silver stain(GMS) will stain both living and dead fungal organisms.
Presence of glycogen can be confirmed on a section of tissue by using diastase
PAS diastase
PAS diastase is a histological stain often used by pathologists as an ancillary study in making a diagnosis on paraffin-embedded tissue samples. Diastase is an enzyme that breaks down glycogen and PAS is a stain that typically gives a magenta color in the presence of glycogen. When the two are used...
to digest the glycogen from a section, then comparing a diastase digested PAS section with a normal PAS section. The diastase negative slide will show a magenta staining where glycogen is present within a section of tissue. The slide that has been treated with diastase will lack any positive PAS staining in those locations on the slide
PAS staining is also used for staining cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
. One example would be looking for implanted medical devices composed of nonoxidized cellulose.
If the PAS stain will be performed on tissue, the recommended fixative
Fixation (histology)
In the fields of histology, pathology, and cell biology, fixation is a chemical process by which biological tissues are preserved from decay, thereby preventing autolysis or putrefaction...
is 10% neutral-buffered formalin
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
or Bouin solution
Bouin Solution
Bouin solution is a compound fixative used in histology. It is composed of picric acid, acetic acid and formaldehyde in an aqueous solution. It is especially good for gastrointestinal tract biopsies because this fixative allows crisper and better nuclear staining than 10% neutral-buffered formalin...
. For blood smears
Blood film
A blood film or peripheral blood smear is a thin layer of blood smeared on a microscope slide and then stained in such a way to allow the various blood cells to be examined microscopically...
, the recommended fixative is methanol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
. Glutaraldehyde
Glutaraldehyde
Glutaraldehyde is an organic compound with the formula CH22. A pungent colorless oily liquid, glutaraldehyde is used to disinfect medical and dental equipment...
is not recommended because free aldehyde groups may be available to react with the Schiff reagent, which may result in false positive staining.
See also
- PAS diastasePAS diastasePAS diastase is a histological stain often used by pathologists as an ancillary study in making a diagnosis on paraffin-embedded tissue samples. Diastase is an enzyme that breaks down glycogen and PAS is a stain that typically gives a magenta color in the presence of glycogen. When the two are used...
- Methyl violetMethyl violetMethyl violet is a family of organic compounds that are mainly used as dyes. Depending on the amount of attached methyl groups, the color of the dye can be altered. Its main use is as a purple dye for textiles and to give deep violet colors in paint and ink...
- Prussian bluePrussian bluePrussian blue is a dark blue pigment with the idealized formula Fe718. Another name for the color Prussian blue is Berlin blue or, in painting, Parisian blue. Turnbull's blue is the same substance but is made from different reagents....
- Egyptian BlueEgyptian BlueEgyptian blue is chemically known as calcium copper silicate . It is a pigment used by Egyptians for thousands of years. It is considered to be the first synthetic pigment. The pigment was known to the Romans by the name caeruleum...
- Methyl blueMethyl blueMethyl blue, also known as Cotton blue, Helvetia blue, Acid blue 93, or C.I. 42780, is a chemical compound with the molecular formula C37H27N3Na2O9S3. It is used as a stain in histology. Methyl blue stains collagen blue in tissue sections. It is soluble in water and slightly soluble in ethanol...
- Methylene blueMethylene blueMethylene blue is a heterocyclic aromatic chemical compound with the molecular formula C16H18N3SCl. It has many uses in a range of different fields, such as biology and chemistry. At room temperature it appears as a solid, odorless, dark green powder, that yields a blue solution when dissolved in...
- New methylene blueNew methylene blueNew methylene blue is an organic staining agent used in diagnostic cytopathology and histopathology, typically for staining immature red blood cells. It is closely related to methylene blue, an older stain already in wide use....
- Han PurpleHan PurpleHan purple and Han blue are synthetic barium copper silicate pigments that were developed in China at least 2,000 years ago....
- Potassium ferrocyanidePotassium ferrocyanidePotassium ferrocyanide is the inorganic compound with formula K4[Fe6]•3H2O. It is the potassium salt of the coordination complex [Fe6]4-. This salt forms lemon-yellow monoclinic crystals.-Synthesis:...
- Potassium ferricyanidePotassium ferricyanidePotassium ferricyanide is the chemical compound with the formula K3[Fe6]. This bright red salt contains the octahedrally coordinated [Fe6]3− ion. It is soluble in water and its solution shows some green-yellow fluorescence.-Preparation:...
- Gentian violet
- EosinEosinEosin is a fluorescent red dye resulting from the action of bromine on fluorescein. It can be used to stain cytoplasm, collagen and muscle fibers for examination under the microscope. Structures that stain readily with eosin are termed eosinophilic....
- FluoresceinFluoresceinFluorescein is a synthetic organic compound available as a dark orange/red powder soluble in water and alcohol. It is widely used as a fluorescent tracer for many applications....
- CarboxyfluoresceinCarboxyfluoresceinCarboxyfluorescein refers to two fluorescent dyes with an excitation and emission of 492/517 nm, respectively. They are commonly used as a tracer agents. The dyes are membrane-impermeant and can be loaded into cells by microinjection or scrape loading. It can be incorporated into liposomes,...
- Fluorescein isothiocyanateFluorescein isothiocyanateFluorescein isothiocyanate is a derivative of fluorescein used in wide-ranging applications including flow cytometry. FITC is the original fluorescein molecule functionalized with an isothiocyanate reactive group , replacing a hydrogen atom on the bottom ring of the structure...
(FITC) - Fluorescein amiditeFluorescein amiditeFluorescein amidite, abbreviated as FAM , is an important synthetic equivalent of fluorescein dye used in oligonucleotide synthesis and molecular biology...
(FAM) - ErythrosineErythrosineErythrosine, also known as Red No. 3, is an organoiodine compound, specifically a derivative of fluorone. It is cherry-pink synthetic, primarily used for food coloring. It is the disodium salt of 2,4,5,7-tetraiodofluorescein...
- Rose BengalRose bengalRose Bengal is a stain. Its sodium salt is commonly used in eye drops to stain damaged conjunctival and corneal cells and thereby identify damage to the eye...
- DyLight FluorDyLight FluorThe DyLight Fluor family of fluorescent dyes are produced by Dyomics in collaboration with Thermo Fisher Scientific. DyLight dyes are typically used in biotechnology and research applications as biomolecule, cell and tissue labels for fluorescence microscopy, cell biology or molecular...
, a product line of fluorescent dyes - Fluorescein diacetate hydrolysisFluorescein diacetate hydrolysisFluorescein diacetate hydrolysis assays can be used to measure enzyme activity produced by microbes in a sample. A bright yellow glow is produced and is strongest when enzymatic activity is greatest...
, a biochemistry laboratory test - Laser dyeLaser dyeLaser dyes are very large organic molecules with molecular weights of a few hundred mu. When one of these organic molecules is dissolved in a suitable liquid solvent it can be used as gain medium in a dye laser. Laser dye solutions absorb at shorter wavelengths end emit at longer wavelengths...
s