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PubMed1996

Amyloid probes based on Congo Red distinguish between fibrils comprising different peptides.

BACKGROUND: Amyloid plaques, which characterize degenerating tissue in Alzheimer's disease (brain) and type II diabetes (pancreas), were first visualized by staining with the dye Congo Red (CR). The ability of CR to recognize amyloid fibrils comprising diverse proteins suggests that the binding site includes an unidentified structural feature common to all amyloid fibrils. We set out to design and synthesize analogs of CR that could distinguish between fibrils comprising different peptides. RESULTS: Relative affinities of several CR analogs for two model amyloid fibrils were measured and compared to that of CR. Amyloid fibrils comprising peptides based on the critical carboxyl terminus of the Alzheimer's disease amyloid protein beta1-42 (beta34-42) and the critical region of the type II diabetes pancreatic amyloid protein, IAPP (IAPP20-29) were tested. The ratio of affinities of each individual CR analog for the two amyloid fibrils varied considerably. Complexation of certain metal ions (Cu(II), Zn(II), Ni(II), Cd(II)) by a CR analog did not abolish its affinity for amyloid but changed the affinity ratio significantly. CONCLUSIONS: This study demonstrates that small organic and organometallic molecules are capable of detecting differences in amyloid fibril structure and/or amyloid protein sequence. Molecules of this type could have utility as neuropathological probes or imaging agents, since they are much easier to prepare and functionalize than antibodies and are specific for the fibrillar form of the amyloid proteins.

Amino Acid Sequence↗
PubMed1992

Gonadal effects of fetal exposure to the azo dye congo red in mice: infertility in female but not male offspring.

The present study describes the relationship between gonadal agenesis and fertility in male and female mice exposed in utero to the diazo dye Congo red (CR). Maternal CR treatment inhibited testicular and ovarian function in the offspring after oral administration of 1 or 0.5 g/kg/day on Gestational Days 8-12. The testes of male offspring from CR-exposed dams were small in size and contained hypospermatogenic seminiferous tubules. However, despite the fact that testis weight was reduced by more than 70% in some males, they displayed normal levels of fertility when mated to untreated females for over 10 months. In contrast, female offspring from CR-exposed dams produced only about half as many litters and pups as the control pairs did under long-term mating conditions. Histological examination of the ovaries revealed that subfertility was correlated with ovarian atrophy. Females lacking maturing follicles were considerably less productive (1.3 litters and 11.5 pups) than treated females with histologically normal ovaries (7.1 litters and 78.1 pups). In summary, prenatal exposure to the dye CR affects the gonads of both male and female offspring, but only the female offspring display reduced fertility.

Animals↗
PubMed2002

Determination of sodium 3,4-diaminonaphthalene-1-sulfonate, a Congo Red derivative, in plasma and brain of hamsters by high-performance liquid chromatography after solid-phase extraction and ultraviolet absorbance.

In the search for compounds with similar or greater activity than Congo Red (CR) in protecting normal prion protein from being converted into the pathological form, we have synthesized various compounds which derive from CR. One of these is the sodium 3,4-diaminonaphthalene-1-sulfonate (RCA) which has an activity similar to CR in preliminary experiments. This study describes a method to determine RCA in plasma and in brain tissue by high-performance liquid chromatography (HPLC), using a solid-phase extraction and UV detection. RCA is an amphoteric molecule difficult to separate from biological matrices. Extraction was achieved by solid-phase extraction (ENV+ columns) together with the use of a counter ion. The resulting solid-phase extraction is efficient and rapid. RCA was separated on a Symmetry C18 250 x 4.6 mm I.D. 5 lm column at 1 ml/min using a 50 mM NaSO4 in 5 mM tetra-n-butylammoniumiodide (TEBA) in water-methanol (82:18, v/v) mobile phase. Retention times of RCA and I.S. were 21 and 24 min. The UV detector was set at 210 nm. The limit of quantitation was 0.5 microg/ml. The method has intra-assay and inter-assay accuracies higher than 95%, coefficients of variation ranging between 2.8 and 8.6%, and recovery rates between 74.3 and 80.1% in plasma and in brain tissue. A linear response to quantities of RCA from 0.5 to 100 microg/ml or 10 microg/g in plasma or brain was obtained. The present method allows the study of the pharmacokinetics of RCA in plasma after i.p. administration, and the distribution of the compound into the brain at the peak time.

Animals↗
PubMed2000

Polarization confocal microscopy and congo red fluorescence: a simple and rapid method to determine the mean cellulose fibril orientation in plants.

The mean or net preferential orientation of cellulose fibrils in plant cell walls is detected with polarization confocal laser scanning microscopy using the fluorescence dichroism of Congo Red. Single cells, arrays of cells in a tissue, or the epidermis of whole organs can be assayed in vivo. Aerial parts require an extra pectinase treatment because of the cuticle, which is impermeable to aqueous solutions. Peeling off the epidermis can be an elegant alternative, especially for leaves. With this method the net preferential fibril orientation can be related to the symmetry axis of the cell in quantitative terms. Data issuing from this approach are useful in current research on plant biomechanics.

Cell Wall↗
PubMed1998

Interpretation of postvagotomy endoscopic Congo red test results in relation to ulcer recurrence 5 to 12 years after operation.

BACKGROUND: The aim of the present study was to estimate, after vagotomy, the location and extension of residual vagal innervation of the gastric corpus mucosa by using the endoscopic Congo red test (ECRT) and its relation to recurrent ulcer (RU), as well as the results of quantitative gastric acid tests: basal acid output (BAO), maximal acid output (MAO), and nocturnal acid output (NAO). METHODS: A total of 271 consecutive vagotomized duodenal ulcer (DU) patients were studied 5 to 12 years (mean 8 years) after the operation. In all cases gastroscopy and ECRT were performed simultaneously. ECRT was considered positive if a red to black-blue (pH <3.0) color change of the gastric corpus mucosa occurred within the first 3 minutes, and the cases were classified as having small extension (SE), ie, one or more areas with a diameter of 1 to 30 mm, or large extension (LE), ie, 20% or more of the gastric corpus showing residual vagal innervation. No red to black-blue changes (pH >3.0) were attributed to negative ECRT. BAO, MAO, and NAO were determined preoperatively and postoperatively in 108 cases out of 271 and correspond with ECRT results. RESULTS: Recurrent ulcer occurred in 18 out of 135 ECRT-positive and in 1 out of 136 ECRT-negative cases. RU occurred 5 times more frequently in LE than SE cases (P <0.05). The postoperative mean values of BAO, MAO, and NAO were significantly higher in ECRT-positive than in ECRT-negative cases (P <0.001), and higher in LE than in SE cases (P <0.01; for NAO, P >0.05). CONCLUSION: ECRT is a practical and reliable method in the evaluation of postvagotomy DU patients: Negative ECRT practically includes recurrent ulcer risk; positive ECRT of large extension is related to fivefold higher recurrent ulcer risk compared with ECRT of small extension; and ECRT reflects BAO, MAO, and NAO results and can be used instead of them as a less time-consuming procedure, which is more convenient for the patient.

Adult↗
PubMedDate not supplied

A model for structure-dependent binding of Congo red to Alzheimer beta-amyloid fibrils.

The cytotoxic A beta fibril is a logical candidate for the entity causing the initiating damage to neurons in Alzheimer's disease and Down's syndrome. We have derived a model of binding for the dye molecule, Congo red (CR), to a beta-sheet structure of beta-amyloid (1-42). This model is based on the crystal coordinates of CR binding to porcine insulin fibrils from Turnell and Finch. Intact insulin is composed of protein dimers and X-ray diffraction studies show that CR intercalates between two insulin monomers at an interface formed by a pair of antiparallel beta-strands. The intercalation of CR has disrupted the four main-chain hydrogen bonds between the two beta-strands, but they are still tethered with each other through new hydrogen bonds with the CR nitrogen atoms. The CR molecule has been aligned along the homologous stretch of amino acids in Alzheimer beta peptide (two molecules in antiparallel distorted or pseudo beta-sheet conformation) using the crystal coordinates from the Turnell-Finch paper to arrive at a putative structure for CR binding to Alzheimer's amyloid fibrils.

Algorithms↗
PubMed1986

Symptomatic ectopic gastric epithelium of the cervical esophagus. Demonstration of acid production with Congo red.

Four patients were found with patches of gastric fundal type epithelium just distal to the cricopharyngeus, separated from the gastroesophageal junction by 15-20 cm of normal squamous epithelium. Three of the four had symptoms of dysphagia localized to the area of the esophagus containing the epithelium. Congo red dye (a pH indicator) applied to the mucosa during endoscopy revealed acid production by the mucosa after stimulation with pentagastrin. Interestingly, the patients' symptoms decreased during treatment with cimetidine only to return on cessation of therapy.

Adult↗
PubMed1986

Detection and quantitation of cellulase by Congo red staining of substrates in a cup-plate diffusion assay.

A simple, inexpensive, and sensitive cellulase assay which allows simultaneous enzyme quantitation for many samples has been developed. Radial diffusion of enzyme into substrate incorporated in an agar gel produces zones of hydrolysis which can be visualized by staining undegraded substrate with Congo red dye. Comparisons were made between this and other commonly used cellulase assays based on accuracy, sensitivity, and ease of use.

Azure Stains↗
PubMedDate not supplied

Congo red effect on cyst viability and cell wall structure of encysting. Entamoeba invadens.

BACKGROUND: The cell wall of Entamoeba invadens cysts is composed of chitin microfibrils as the main structural component. It has been demonstrated in yeast that the chitin cell wall assembly is altered by dyes such as Congo red (CR) and Calcofluor. METHODS: The purpose of this work was to study the cell wall assembly under the effect of CR dye on encysting E. invadens by means of light and electron microscopy, after the amebas were subjected to the effect of 100-2,000 micrograms CR/mL. Experiments were performed either in BI-S-33 or in mLG media. RESULTS: Trophozoite growth was not inhibited by 100-1,000 micrograms/mL CR after 8 days of incubation in BI-S-33 medium. However, low levels of growth were observed with 2,000 micrograms/mL of dye. No significant differences in morphologically viable (hyaline) cyst production occurred after 24-48 h, when 100 micrograms CR/mL was used, while the highest concentration of CR (2,000 micrograms/mL) resulted in a significant decrease of hyaline cyst yield; dead cysts prevailed in cultures, particularly at 72 h of CR treatment. Differentiation of amebas incubated in the presence of 500-2,000 micrograms/mL CR produced abnormal chitin deposits, rendering irregularly thick or double cell walls, as shown by transmission and scanning electron microscopy. Cyst cultures obtained under 100 micrograms/mL CR produced as many trophozoites as did the control when they were incubated in BI-S-33, but only low numbers of trophozoites were found in culture cysts obtained under higher CR doses. CONCLUSION: Our results suggest that CR affects E. invadens encystment, alters the cell wall formation, and also affects the cyst viability.

Animals↗
PubMed1986

Molecular cloning of a genetic determinant for Congo red binding ability which is essential for the virulence of Shigella flexneri.

A DNA sequence of about 1.0 kilobase (kb) derived from a 230-kb (140-megadalton) plasmid in a fully virulent Shigella flexneri 2a strain, YSH6000, was cloned into Escherichia coli K-12 by selecting for the ability to bind Congo red (Pcr+ phenotype). It was mapped and localized within the SalI restriction fragment F on the plasmid. This clone converted an S. flexneri strain which is avirulent as a result of a small deletion in the plasmid to full virulence but did not convert those without the 230-kb plasmid or with a plasmid bearing a more extensive deletion. This indicates that there are more than two virulence determinants on the plasmid. Thus, this sequence contains a genetic determinant which is essential but not sufficient for full virulence and expression of the Pcr+ phenotype in S. flexneri but is essential and sufficient for expression of the Pcr+ phenotype in E. coli K-12. We noted that there exist some other regions on the 230-kb plasmid which express the Pcr+ phenotype in E. coli K-12. Although these regions express the Pcr+ phenotype less markedly than the region cloned in the present study, they do hybridize with it.

Chromosome Deletion↗
PubMed1982

Heterotopic gastric mucosa in the duodenum - reaction to Congo red under fiberscopic observation.

A 64-year-old woman had gastric heterotopic of the duodenal bulb without any specific complaints. The lesion with irregular excrescence was diagnosed by means of target biopsies through endoscopy, and 3 years later, no noteworthy changes were observed in the endoscopic findings of the lesion, and it was also proved by an endoscopic Congo red test that the excrescence had a function of acid output. This is the second report of congenital heterotopic gastric mucosa of the duodenum which was confirmed not only by histological, but also functional examination.

Child↗
PubMed1998

The anti-prion activity of Congo red. Putative mechanism.

PrPSc, an abnormal conformational isoform of the normal prion protein, PrPC, is the only known component of the prion, a proteinacious agent that causes fatal neurodegenerative disorders in humans and other animals. The hallmark properties of PrPSc are its insolubility in nondenaturing detergents and its resistance to digestion by proteases. Anions such as Congo red (CR) have been shown to reduce the accumulation of PrPSc in a neuroblastoma cell line permanently infected with prions as well as to delay disease onset in rodents when administrated prophylactically. The mechanism by which such anti-prion agents operate is unknown. We show here that in vitro incubation with CR renders native PrPSc resistant to denaturation by boiling SDS. This resulted from PrPSc conformation, since neither the properties of PrPC nor those of predenatured PrPSc were changed by the addition of CR. CR-PrPSc could only be denatured by the addition of acidic 3 M guanidine thiocyanate. Since in vitro conversion experiments have suggested that partial denaturation may be required for PrPSc to serve as template in the PrPC --> PrPSc conversion, we propose that CR inhibits prion propagation by overstabilizing the conformation of PrPSc molecules.

Animals↗
PubMed2005

Removal of congo red from aqueous solution by bagasse fly ash and activated carbon: kinetic study and equilibrium isotherm analyses.

Present investigation deals with the utilisation of bagasse fly ash (BFA) (generated as a waste material from bagasse fired boilers) and the use of activated carbons-commercial grade (ACC) and laboratory grade (ACL), as adsorbents for the removal of congo red (CR) from aqueous solutions. Batch studies were conducted to evaluate the adsorption capacity of BFA, ACC and ACL and the effects of initial pH (pH(0)), contact time and initial dye concentration on adsorption. The pH(0) of the dye solution strongly affected the chemistry of both the dye molecules and BFA in an aqueous solution. The effective pH(0) was 7.0 for adsorption on BFA. Kinetic studies showed that the adsorption of CR on all the adsorbents was a gradual process. Equilibrium reached in about 4h contact time. Optimum BFA, ACC and ACL dosages were found to be 1, 20 and 2 g l(-1), respectively. CR uptake by the adsorbents followed pseudo-second-order kinetics. Equilibrium isotherms for the adsorption of CR on BFA, ACC and ACL were analysed by the Freundlich, Langmuir, Redlich-Peterson, and Temkin isotherm equations. Error analysis showed that the R-P isotherm best-fits the CR adsorption isotherm data on all adsorbents. The Freundlich isotherm also shows comparable fit. Thermodynamics showed that the adsorption of CR on BFA was most favourable in comparison to activated carbons.

Adsorption↗
PubMed2001

The adsorption of Congo red and vacuum pump oil by rice hull ash.

Rice hull ash (RHA) of large surface area was obtained by acid wash and then calcination at 600 degrees C for 4 h. The white ash was then mixed with kaolin and starch to make pellet adsorbents with reasonable strength to be utilized in a packed column. Both ash and pellet samples showed good adsorption capacities toward the organic substances in wastewater. Furthermore, the surface nature of the white ash and pellet adsorbent could be modified through either hydration or esterification reactions. Corresponding changes in silanol concentrations were successfully correlated to changes in adsorption capacity toward either Congo red or vacuum pump oil molecules.

Adsorption↗
PubMed1993

Long-term results of highly selective vagotomy in the treatment of duodenal ulcer patients using the intra-operative endoscopic congo red test to identify the parietal cell antrum-corpus borderline.

A total of 151 patients with uncomplicated duodenal ulcers were treated with highly selective vagotomy. The patients were subsequently observed prospectively for a period of 3-17 years. The recurrence rate for the whole group reached 4.6%. The parietal cell antrum-corpus borderline for denervation was marked using the intra-operative endoscopic Congo Red Test. The test was useful for the classification of patients into the group (own method) and for the identification of patients with "acid antrum". Between 1974-1980, Highly selective vagotomy was performed in 93 patients in some of whom single clusters of parietal cells were diagnosed in the prepyloric region (acid antrum, type A). The recurrence rate in this group reached 7.5%. In a group of 58 patients operated on after 1980 from which "acid antrum" cases were eliminated, no recurrences have so far been observed. Additionally, the results of early and late complications and the results of patient self-estimation using to Visick's scale are discussed.

Adolescent↗