Congo red was formerly used to dye cotton but has been superseded by dyes more resistant to light and to washing. It is still used in histology to stain tissues for microscopic examination, and to serve as an acid-base indicator, since it turns red in the presence of alkalies and blue when exposed to acids.
2.2. Preparation of Congo Red 1000 mg/L (stock solution) was prepared by dissolving 1 g of congo red in 1 Liter of distilled water. 20, 40, 70 and 100 ppm solution prepared by dilution from the stock solution.
Congo red is still the standard stain used in most histopathology laboratories to identify amyloid material in tissues. The identification of Congophilic amyloid material is challenging because of multiple interfering factors.
The cause of AL amyloidosis is usually a plasma cell dyscrasia, an acquired abnormality of the plasma cell in the bone marrow with production of an abnormal light chain protein (part of an antibody).
In AA amyloidosis, the deposited protein is serum amyloid A protein (SAA), an acute-phase protein which is normally soluble and whose plasma concentration is highest during inflammation.
| AA amyloidosis |
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| Specialty | Rheumatology |
"Congo" red was introduced in Berlin in 1885 as the first of the economically lucrative direct textile dyes. Conclusions: The Congo red stain was named "Congo" for marketing purposes by a German textile dyestuff company in 1885, reflecting geopolitical current events of that time.
The Congo Red Capsule stain is a modification of the nigrosin negative stain you may have done previously. The bacteria take up the congo red dye and the background is stained then with acid fuchsin dye.
Congo Red and Thioflavin S are the two major histological stains used to detect any form of amyloid. These dyes bind to the characteristic β-pleated sheet conformation of amyloid.
Congo Red is synthesised by coupling bis-diazotised benzidine with two molecules of napthionic acid. The blue dye so obtained is converted into its red disodium salt during its salting out with sodium chloride (Fig. Congo Red dye.
Amyloidosis refers to a variety of conditions characterized by deposits of Congo red–positive materials in tissue; these are recognized by their apple-green birefringence under polarized light. Amyloid deposits are β-pleated, non-branching fibrillar proteins of about 7.5 to 10 nm in diameter.
Congo red is an acid-base indicator dye. In free solution the colour and absorption characteristics of Congo red depend not only on the pH but are also governed by the nature of the solvent environment.
It most commonly happens when a protein made by your liver is abnormal. This protein is called transthyretin (TTR). Wild-type amyloidosis. This variety of amyloidosis occurs when the TTR protein made by the liver is normal but produces amyloid for unknown reasons.
Reticulin Stain. The reticulin stain is extensively used in the histopathology laboratory for staining liver specimens, but can also be used to identify fibrosis in bone marrow core biopsy specimens.
When a staining procedure colors the cells present in a preparation, but leaves the background colorless (appearing as white), it is called a direct stain. If a procedure colors the background, leaving the cells colorless (white) it is called an indirect or negative stain.
The kidneys are the organs most commonly affected by primary amyloidosis. Amyloid deposits damage the kidneys and make it harder for them to filter wastes and break down proteins. When the kidneys become too damaged, they may no longer be able to function well enough to maintain health, resulting in kidney failure.
In the kidney, amyloid deposits may be found in any of the parenchymal compartments, including glomeruli, tubules, interstitium and/or vessels. Glomeruli are most commonly involved, with 97% of cases in a study showing glomerular deposition [7].
Amyloids are aggregates of proteins characterised by a fibrillar morphology of 7–13 nm in diameter, a β-sheet secondary structure (known as cross-β) and ability to be stained by particular dyes, such as Congo red. In the human body, amyloids have been linked to the development of various diseases.
Other methods of detection of amyloid include fluorescent stains, e.g., thioflavin T or S, and metachromatic stains such as crystal violet. Immunofluorescence and immunoperoxidase methods are used to identify and classify amyloid proteins in tissues.
Amyloidosis has a poor prognosis, and the median survival without treatment is only 13 months. Cardiac involvement has the worst prognosis and results in death in about 6 months after onset of congestive heart failure. Only 5% of the patients with primary amyloidosis survive beyond 10 years.
Blood and urine tests may reveal an abnormal immunoglobulin protein in the body in those patients with AL Amyloidosis, but the only way to diagnose amyloidosis for certain is to take a sample of tissue for analysis under a microscope.
FIXATION: Carnoy's and absolute alcohol are recommended, 10% NBF or Bouin's.
Previously known as secondary amyloidosis, this condition is the result of another chronic infectious or inflammatory disease such as rheumatoid arthritis, Crohn's disease, or ulcerative colitis. It mostly affects your kidneys, but it can also affect your digestive tract, liver, and heart.
Giemsa stain is mainly used for staining of peripheral blood smears and specimens obtained from the bone marrow. It is used to obtain differential white blood cell counts. Giemsa stain is also used in cytogenetics to stain the chromosomes and identify chromosomal aberrations.
Thioflavin S is a homogenous mixture of compounds that results from the methylation of dehydrothiotoluidine with sulfonic acid. It is also used to stain amyloid plaques. Like thioflavin T it binds to amyloid fibrils but not monomers and gives a distinct increase in fluorescence emission.
Amyloid plaques are hard, insoluble accumulations of beta amyloid proteins that clump together between the nerve cells (neurons) in the brains of Alzheimer's disease patients.
Secondary systemic amyloidosis is a disorder in which abnormal proteins build up in tissues and organs. Clumps of the abnormal proteins are called amyloid deposits. Secondary means it occurs because of another disease or situation.
