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Improving sensitivity of amyloid detection by Congo red stain by using polarizing microscope and avoiding pitfalls.

ABSTRACT: Systemic amyloidosis is a devastating group of disorders for which there is no current cure. The treatment goal is to reduce the burden of amyloidogenic protein precursors. The treatment is only effective if applied early in the disease process before significant and irreversible end organ damage has taken place. 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. Here we describe improved sensitivity of identifying Congophilic materials in histologic sections using a metallurgical polarized microscope specifically constructed for polarized microscopy. The microscope is equipped with strain-free optics, matching polarizers, dis-integrated compensators, and a circular mobile stage. Compared to a standard clinical microscope, this setup significantly improves sensitivity of identifying amyloid material in Congo red-stained slides. We also describe the deleterious effect of plastic coverslip which can interfere with the ability to examine the slides under polarized light. We present a series of 10 different patients who had cardiac, brain, and salivary gland biopsies that were either equivocal or deemed negative using a standard clinical microscope but were positive using the equipment described above. These samples were confirmed to be positive by other methods including electron microscopy. We conclude that use of the correct equipment is needed before ruling out amyloidosis in tissue sections.

SUBMITTER: El-Meanawy A

PROVIDER: S-EPMC6567537 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Improving sensitivity of amyloid detection by Congo red stain by using polarizing microscope and avoiding pitfalls.

El-Meanawy Ashraf A Mueller Christopher C Iczkowski Kenneth A KA

Diagnostic pathology 20190614 1

Systemic amyloidosis is a devastating group of disorders for which there is no current cure. The treatment goal is to reduce the burden of amyloidogenic protein precursors. The treatment is only effective if applied early in the disease process before significant and irreversible end organ damage has taken place. 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 ...[more]

PMID: 31200733

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Project description:Inhibition of fungal growth by Congo Red (CR) has been known for a long time and claimed to be associated to a specific binding to fibrillar chains of β-1,3-glucans which blocks cell wall polysaccharide synthesis. It has also been suggested that the effect of CR could be pleiotropic, especially because of its oxido-reductive properties. One way to elucidate the mechanism of action of CR is to identify transcription factors (TF) which regulate the response to CR and interrogate their regulon. The analysis of TF mutants with differential sensitivity to CR would be also a way to identify new regulatory pathways involved in cell wall biosynthesis. During the investigation of the sensitivity to CR of a TF mutant library, several mutants either sensitive or resistant to CR were analysed . The morphology of the conidial germination was affected differently by CR in the parental strain and TF mutants. Abnormal distorted swollen conidia called Quasimodo cells were seen in presence of the CR. The size of the Quasimodo cells in the resistant mutants are bigger and adsorb more CR than the germinating conidia of the sensitive or parental strain. This is associated to a difference in permeability of the mutants. The clearing of the drug from the medium by the resistant strain was mainly responsible for the survival and later growth of some of resting conidia of these mutants which did not adsorb intracellularly the drug whereas in the sensitive mutants all conidia adsorbed the drug and were consequently killed. Although there are some modifications of the composition of the cell wall, a transcriptomic analysis of the mutant showed that CR affected many different pathways, including iron and calcium metabolism. Accordingly, the susceptibility to other cell wall drugs of the sensitive and the resistant TF mutants varied with the mutants and not always in connexion with their sensitivity to CR. Interestingly, a new paradoxical effect of the CR was discovered in the resistant mutant since the growth of one of them could be stimulated after recovering from the CR stress.

Dataset Information

Improving sensitivity of amyloid detection by Congo red stain by using polarizing microscope and avoiding pitfalls.

Publications

Improving sensitivity of amyloid detection by Congo red stain by using polarizing microscope and avoiding pitfalls.

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