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PubMed1992

Potent inhibition of scrapie-associated PrP accumulation by congo red.

Transmissible spongiform encephalopathies (prion diseases), Alzheimer's disease, and other amyloidoses result in the accumulation of certain abnormally stable proteins that are thought by many to play central roles in disease pathogenesis. Using scrapie-infected neuroblastoma cells as a model system, we found that Congo red, an amyloid-binding dye, potently inhibits the accumulation of the scrapie-associated, protease-resistant isoform of protein PrP without affecting the metabolism of the normal isoform. Growth of the cells with submicromolar concentrations of Congo red for 5 days reduced the amount of protease-resistant PrP detected in the cultures by greater than 90%. This activity of Congo red suggests that it selectively disrupts the conversion of PrP to the protease-resistant isoform or destabilizes this isoform once it is made. Potential therapeutic applications of Congo red are discussed.

Animals↗
PubMed2004

In vivo accumulation of self-assembling dye Congo red in an area marked by specific immune complexes: possible relevance to chemotherapy.

Supramolecular micellar structures have been proposed as carriers in aim-oriented drug transportation to a target marked by specific immune complexes. In this study, the self-assembling dye Congo red was used as a model supramolecular carrier and its accumulation in the target was studied in vivo. The target was created in vivo as the local specific inflammation provoked by subcutaneous injection of antigen to the ear of a previously immunized rabbit. The color caused by accumulation of Congo red after its intravenous injection was registered by pictures of the ear with suitably filtered visible light shining through it to distinguish Congo red against the background color of hemoglobin. The results confirmed the expected accumulation and retention of Congo red in the inflammation area marked by deposits of specific immune complexes. The role of albumin and its possible interference with transportation of drugs through the blood by supramolecular carriers was also subjected to preliminary examination. The results revealed that albumin collaborates rather than interferes with drug transportation; this is another factor making the use of supramolecular carriers for aim-oriented chemotherapy highly promising.

Albumins↗
PubMed2000

The conformational characteristics of Congo red, Evans blue and Trypan blue.

The structures of the closely related bis-azo dyes Evans blue, Trypan blue and Congo red, which appeared to have different self-assembly properties and correspondingly different abilities to form complexes with amyloids and some other proteins, were compared in this work. Ab initio and semi-empirical methods were used to find the optimal structures and partial charge distributions of the dyes. The optimal structures were searched using different widely used programs. The structures of Congo red and evans blue were found to be planar, except for the torsion on the central diphenyl bond connecting the two halves of the dye. Both symmetrical parts of the molecules appeared very close to planarity. However, Trypan blue exhibits non planarity on the di-azo bonds, as well as on the central bond between the symmetrical parts of the dye. In a consequence, the non planarity of this molecule is higher than in the case of its isomer, Evans blue and Congo red as well. The extra rotation around the azo bonds extorted by the close proximity of the sulfonic groups may be the direct cause of its poor self-assembling and complexation properties versus Evans blue.

Coloring Agents↗
PubMed2000

Congophilicity (Congo red affinity) of different beta2-microglobulin conformations characterized by dye affinity capillary electrophoresis.

The amyloidogenic protein beta-microglobulin was characterized by affinity capillary electrophoresis (CE). CE could separate conformational variants of beta2-microglobulin and with the amyloid-specific dye Congo red as a buffer additive it was possible to measure different Congo red-affinities of native and abnormally folded beta2-microglobulin. We find that native beta2-microglobulin has an intermediate affinity for Congo red at pH 7.3 and that binding involves electrostatic interactions. The conformational variant of beta2-microglobulin that appears in acetonitrile solutions binds Congo red more strongly. Affinity CE using Congo red as a buffer additive is a new, simple, fast, and quantitative micromethod for the characterization of soluble conformational intermediates of amyloidogenic proteins.

Coloring Agents↗
PubMed1987

Can the use of an endoscopic Congo red test decrease the incidence of incomplete proximal gastric vagotomy?

The endoscopic Congo red test allows accurate and rapid evaluation of the completeness of vagotomy and may result in a lower incidence of postoperative incomplete vagotomy. This report describes 44 patients tested during proximal gastric vagotomy. Evidence of incomplete vagotomy was found in over 95% at the conclusion of the conventional operation. Importantly, the test was a guide to further operative maneuvers which abolished the evidence of incomplete vagotomy upon subsequent testing. The endoscopic Congo red test satisfies the requirements for an ideal test for complete vagotomy: it is easily performed, does not require special equipment, and can be repeated several times if necessary to verify that desired effects have been achieved. The wider use of this test, therefore, appears justified.

Congo Red↗
PubMed1995

High-sensitivity diagnosis of AA amyloidosis using Congo red and immunohistochemistry detects missed amyloid deposits.

Biopsy diagnosis of early amyloid-A (AA) amyloidosis has often been difficult. Examination of 57 consecutive biopsy specimens from 42 patients with inflammatory pediatric diseases permitted comparison of the precision of biopsy amyloid diagnosis in six different laboratories (labs), which applied the following methods: Congo red alone (four unspecialized labs combined as Lab 1), Congo red and electron microscopy (Lab 2), or Congo red and immunohistochemistry using monoclonal antibodies (Lab 3). Lab 3 reexamined the diagnoses made by Lab 1 and Lab 2. Of the 42 patients, 17 patients with 32 biopsies were selected for this study based on the presence of amyloid in at least one biopsy. Whereas massive or no amyloid was concordantly recognized by all labs in 18 biopsies from nine patients, discordance was demonstrated in 14 biopsies from eight patients. Comparison of Labs 1-3 revealed amyloid in 12 rectal and 18 renal biopsies evaluated by Lab 3, whereas Lab 2 missed amyloid in two of 18 renal biopsies and Lab 1 missed amyloid in 11 of 12 rectal biopsies. Most amyloid was missed when only minute amounts of amyloid were present. Had our technique (Lab 3) been available at the time of biopsy, amyloid could have been diagnosed years earlier, thereby sparing the patient further biopsies and allowing initiation of earlier treatment before organ damage could occur.

Adolescent↗
PubMed1993

Proximal gastric vagotomy and anterior seromyotomy with posterior truncal vagotomy assessed by the endoscopic congo red test.

The completeness of vagotomy following proximal gastric vagotomy or anterior seromyotomy with posterior truncal vagotomy was assessed prospectively in 48 patients using the intraoperative congo red test. Pentagastrin (6 micrograms/kg) was given subcutaneously before the assessment. An endoscope was passed into the stomach and 180 ml congo red solution washed over the gastric mucosa. Continuing acid production was indicated by the appearance of a black colour (pH < 3) 2 min after introduction of the dye. A grading system was adopted where grades I and II showed little black discoloration and grades III and IV showed increasing areas of discoloration indicating that further denervation was required. All 20 patients undergoing anterior seromyotomy with posterior vagotomy were classified as grade I. Fifteen of an initial 23 patients receiving proximal gastric vagotomy were grade III or IV. Following division of either the right gastroepiploic nerve or the posterior vagal trunk, 22 patients improved to grade I (16) or II (six). In the subsequent five proximal vagotomies, modification of the dissection produced grade I results. Anterior seromyotomy with posterior truncal vagotomy gave consistently complete vagotomy. The congo red test highlighted major differences in the adequacy of vagotomy achieved using various dissection techniques during proximal gastric vagotomy. The test is a useful, reproducible and simple intraoperative method for assessing the completeness of denervation.

Adolescent↗
PubMed1981

Thionine-Feulgen Congo Red -- a new staining technique for automated cytology.

A new staining method has been developed for an automated pre-screening device for cervical smears called BioPEPR. The method is a combination of the Feulgen technique with thionine as th Schiff reagent, and congo red. Thionine and congo red have absorption maxima at 585 nm and 500 nm respectively. The staining results in cells with an orange-red cytoplasm and brownish-blue nucleus. These smears can e easily screened using a normal microscope. The BioPEPR system scans photonegatives of the smears that are made at a magnification of ten using monochromatic light of 545 nm. The staining facilitates good discrimination between background and cytoplasm and between cytoplasm and nucleus, allowing morphologic parameters such as cytoplasmic area, nuclear area and nuclear integrated darkness to be well measured.

Autoanalysis↗
PubMed1987

Endoscopic Congo red test during proximal gastric vagotomy.

Although proximal gastric vagotomy is widely performed as an elective treatment for duodenal ulcer, the incidence of recurrent ulcer is troublesome. There are several theories to explain recurrent ulcers, and important technical steps should be considered when performing proximal gastric vagotomy. The use of an intraoperative test may allow more accurate performance of the operation and more complete vagotomy of the parietal cell mass. This report describes the use of the endoscopic Congo red test in patients during proximal gastric vagotomy. The test allows rapid and accurate mapping of areas of the stomach with intact vagus and secretory nerves after operative vagotomy, and can be repeated several times if necessary to verify completion of the vagotomy. The use of universally available equipment and the potential for intraoperative and postoperative use are other attractive features of the test. Use of the endoscopic Congo red test provides physiologic evidence that vagus secretory nerve fibers traverse the right and left gastroepiploic nerves, leading us to believe that the gastroepiploic nerves should be routinely divided during proximal gastric vagotomy. In patients with recurrent duodenal ulcer requiring reoperation, the endoscopic Congo red test allows preoperative demonstration of the site of the intact vagal nerve trunks. The endoscopic Congo red test deserves further investigation and wider application during operations for chronic duodenal ulcer.

Congo Red↗
PubMed1995

Docking of congo red to the surface of crystalline cellulose using molecular mechanics.

A method for the docking of ligands to crystalline surfaces using molecular mechanics was developed and applied to study the molecular features of the adsorption of Congo Red to cellulose crystals. The docking procedure was based on a grid search exploring the surface repeat unit of the cellulose crystals using several orientations of Congo Red at each grid point. Results suggest a preferential adsorption of Congo Red onto certain faces of the cellulose crystals and that the lower energy conformers have a similar positioning and orientation with respect to the cellulose chains at the surface repeat unit.

Adsorption↗
PubMedDate not supplied

Risk evaluation of postvagotomy ulcer recurrence by using endoscopic Congo red test and gastric secretion tests.

BACKGROUND/AIMS: To evaluate the usefulness of the endoscopic Congo red test (ECRT), and to compare sensitivity and specificity of different tests in the discrimination of cases with high risk for postvagotomy recurrent ulcer (RU). METHODOLOGY: In 271 consecutive postvagotomy duodenal ulcer patients the endoscopic Congo red test (ECRT) was used 5-12 years after vagotomy. Further, 39 patients out of 271 were selected and classified into two groups: A--13 ECRT positive cases with RU, B--26 controls without RU (13 ECRT positive and 13 ECRT negative cases). Basal acid output (BAO), maximal acid output (MAO), and nocturnal acid output (NAO) were determined pre- and postoperatively, the serum pepsinogen I (S-PGI) and insulin test were estimated postoperatively. RESULTS: Positive ECRT had 95% sensitivity and 53% specificity for RU. S-PGI > 150 microg/l had 54% sensitivity and 92% specificity (in ECRT positive cases 100% specificity). The insulin test showed 83% sensitivity and 78% specificity. The respective data for the combination of BAO > 1.5 mmol/h + NAO > 30 mmol/12 h were 80% and 81%. CONCLUSION: ECRT should be a primary step in estimating postvagotomy ulcer risk. In negative ECRT cases, the development of recurrent ulcer is unlikely. Additional gastric secretion studies as S-PGI or BAO+NAO or insulin test are needed only in ECRT positive cases.

Coloring Agents↗
PubMed1995

Congo red prolongs the incubation period in scrapie-infected hamsters.

In scrapie-infected cells, Congo red inhibits both the replication of the infectious agent and accumulation of the protease-resistant form of PrP (PrP-res). In this report, we show that Congo red prolongs the incubation periods of hamsters experimentally infected with two different strains of scrapie.

Animals↗
PubMed1988

Aberrant development of Trichophyton mentagrophytes hyphae cultured in the presence of Congo red.

When Trichophyton mentagrophytes colonies were placed on a medium containing 150 micrograms/ml of Congo red, a dye which prevents chitin fibrillogenesis, their growth rate was reduced. The newly formed mycelium, examined under an ultraviolet microscope, consisted of thick, curled and branched hyphae endowed with swollen tips and subapical bulges. Short-time exposure revealed that the major sites of dye accumulation were the extension zones. Normally structured hyphae arose from aberrant mycelia when they were transferred onto a dye-free medium. The phenomena observed suggest that Congo red alters the wall properties of the extension zone, by inhibiting the gradual conversion of chitin chains, synthesized at the extreme tip, into microfibrils of increasing size and density.

Congo Red↗
PubMedDate not supplied

[Effect of Congo red on the motility of the bacterium Azospirillum brasilense].

In semiliquid laboratory media, the bacterium Azospirillum brasilense migrates with the formation of swarming rings. It is demonstrated that adsorption of the sulfonated azodye Congo Red confers on A. brasilense the ability to consistently spread in a semiliquid agar and form microcolonies. Spontaneous variants of A. brasilense with rapid swarming are described, as well as variants that swarm in the presence of Congo Red. It is assumed that at least two types of compounds are formed, which are (a) necessary for swarming and/or spreading with the formation of microcolonies and (b) capable of interacting with Congo Red.

Azospirillum brasilense↗
PubMedDate not supplied

Congo red medium to distinguish between invasive and non-invasive Escherichia coli pathogenic for poultry.

In the course of our molecular studies of virulence factors associated with invasive avian Escherichia coli infections, it was first necessary to distinguish between common E. coli and those that cause septicemia in poultry. We found a direct correlation between the ability of clinical isolates of E. coli to bind Congo red dye (CR) and their ability to cause septicemic infection in chickens. This finding was supported by bacteriological studies of 30 broiler flocks (26 sick and 4 healthy) and by virulence studies in chickens and mice. All 144 isolates of E. coli from internal tissues of diseased birds were determined to be CR-positive (red colonies). Congo-red-positive E. coli colonies were isolated from air sacs, pericardium, liver, lung, joint fluid, and heart blood of chickens with lesions of colisepticemia. In contrast, of 170 E. coli isolates from the poultry house environment and from the trachea and cloaca of healthy birds, more than half were CR-negative (white colonies). No CR-negative (white) E. coli colonies were found in internal organs from birds with typical lesions of colisepticemia. We feel that these preliminary findings suggest that the CR dye binding could be used as a phenotypic marker to distinguish between invasive and noninvasive isolates.

Animals↗
PubMed2006

Regional differences in the recovery of gastric acid secretion after Helicobacter pylori eradication: evaluations with Congo red chromoendoscopy.

BACKGROUND: Gastric-acid secretion is reduced in Helicobacter pylori-positive fundic atrophic gastritis, but it is restored by the eradication. However, changes in the distribution of acid-secreting mucosa after the eradication remain unknown. Congo red chromoendoscopy is capable of visualizing the acid-secreting fundic mucosa. OBJECTIVE: To evaluate the effect of H pylori eradication on the distribution of acid-secreting mucosa in the fundus by using Congo red chromoendoscopy. DESIGN: An assessment of the distribution of acid-secreting mucosa by the visualized images of Congo red chromoendoscopy and a histologic evaluation of biopsy specimens were performed before and 1 and 7 months after the eradication. The areas of the acid-secreting mucosa in the lesser and greater curvatures of the fundus were evaluated semiquantitatively. PATIENTS: Thirty-seven patients positive for H pylori and with fundic atrophic gastritis. RESULTS: The area of the acid-secreting mucosa increased in 27 cases (73%) by 1 month after eradication, and in 32 cases (86%) by 7 months. This expansion of the acid-secreting mucosa coincided with the improvement of inflammatory changes rather than with that of the mucosal atrophy and was more prominent on the greater curvature than on the lesser curvature. CONCLUSIONS: The acid-secreting mucosa in the fundus expanded in most cases with fundic atrophic gastritis after H pylori eradication, which could be responsible for the increase in acid secretion after the treatment. Regional differences in the recovery of local acid secretion may be associated with site-specific susceptibility to the development of gastric cancer after successful eradication.

Aged↗
PubMed2005

Alzheimer's beta-amyloid: insights into fibril formation and structure from Congo red binding.

We consider here the chemistry of Congo red (CR), its binding equilibrium to Alzheimer's beta-amyloid, and the kinetics of beta-amyloid formation. Spectroscopic UV/V is measurements for the pH- and time-dependence binding of CR to Abeta analogues are analysed by Scatchard binding and the theory of nucleation-dependent fibril formation. CR likely binds electrostatically to the imidazolium sidechains of histidine residues that are exposed at the surface of amyloid fibrils. As revealed by atomic models of the Abeta protofilament, such as the nanotube beta-helix and parallel beta-sheet, the regular arrangement of histidines likely acts as a template for the end-to-end J-aggregation of CR molecules, which produces a red shift in UV/V is absorption.

Alzheimer Disease↗
PubMed1984

Assessment of viability of Schistosoma mansoni miracidia by Congo red staining.

The viability of Schistosoma mansoni miracidia, either hatched or unhatched, has been assessed by a staining technique using Congo red, a pH-sensitive dye (pH 3-5), under the light microscope. Hatched, free-swimming miracidia and live miracidia inside egg shells were stained light blue whereas dying miracidia altered the dye color from blue to orange and eventually to red. Immature eggs containing undeveloped miracidia were not stained by Congo red. This staining technique is simple, rapid and can be used as a method to assess both the viability of S. mansoni miracidia and the hatching process.

Cilia↗