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PubMed2003

Aromatic amine degradation in a UASB/CSTR sequential system treating Congo Red dye.

In this study an anaerobic (upflow anaerobic sludge blanket reactor)/aerobic (completely stirred tank reactor) sequential system was used to treat a synthetic wastewater with minerals and co-substrate together with 100-4000 mg L(-1) of Congo Red dye (Direct red 28) (CR), which is a banned azo dye in Turkey. The effect of hydraulic retention time (HRT) on the decolorization and the COD removal efficiency was investigated at constant 100 mg L(-1) Congo Red concentration. 77% of COD and 95% of color was removed at a HRT of 0.486 days and a maximum organic loading rate of 6.656 kg COD m(-3) day(-1) in the anaerobic/aerobic stage. In the continuous operations, 88% of COD, 99% of color and 91% of total aromatic amine (TAA) were removed at a HRT of 3.60 days and at a CR concentration of 4000 mg L(-1). This corresponds to an organic loading rate of 1.81 kg COD m(-3) day(-1), and a CR dye loading rate of 46.37 g dye m(-3) h(-1), respectively, in the whole system. The TAA produced under anaerobic conditions was ultimately removed in the aerobic stage, resulting in very low aromatic amine recoveries (5-18%) in the last one. Therefore the aerobic effluents exhibited higher IC50 and specific methanogenic activities (SMA) compared to anaerobic and dye containing samples, indicating the reduced toxicity.

Amines↗
PubMed1995

Chronic atrophic fundic gastritis diagnosed by a modified Congo red test.

BACKGROUND AND STUDY AIMS: Chronic atrophic fundic gastritis (CAFG) is associated with several diseases, such as gastric cancer, gastric ulcer, pernicious anemia, and bacterial overgrowth. In spite of recent technical improvements, the gastroscopic diagnosis of CAFG remains uncertain. Congo red chromogastroscopy is capable of visualizing acid-producing normal fundic mucosa, but has hitherto not been suitable for routine use. The aim of our study was to establish a reliable endoscopic technique with which to diagnose CAFG. PATIENTS AND METHODS: This prospective study comprises 124 consecutive patients (71 women, 53 min) with a mean age of 65 years (range 36-92). Macroscopic evaluation of the gastric fundic mucosa in routine endoscopy using video techniques was compared with evaluation by means of a modified endoscopic Congo red test (MCRT). In routine gastroscopy, CAFG was recognized by the thin, friable mucosa, with a marked visible vascular pattern and fold atrophy. With MCRT, the diagnosis of CAFG was made within five minutes' observation when no red-to-blue color shift in the fundic mucosa could be induced by 0.2 mu g/kg intravenous pentagastrin. The results were then compared with the histological examination of biopsies from the fundic mucosa. RESULTS: CAFG was confirmed by histology in 40 of 124 cases. The diagnostic sensitivity of MCRT was 1.0 (40/40), with a positive predictive value of 0.90, whereas the values for macroscopic gastroscopic evaluation were 0.25 (10/40) and 0.50, respectively. CONCLUSIONS: We conclude that MCRT is a sensitive, fast, and cost-effective method of identifying patients with CAFG, and well suited for use in routine gastroscopy.

Adolescent↗
PubMed1991

[Effects of NIK-228 on gastric acid secretion in rats using the congo red sprayed method].

We have reported the antiulcer activities of a new compound that we named NIK-228 (3-hydroxy-methyl-2-methylimidazo [2, 1-b] benzothiazole). In the present report, we studied the antisecretory effects of NIK-228 on basal and stimulated gastric acid secretion using the Congo red sprayed method. Male Wistar rats (200 to 250 g) were used after 24 hr of fasting (without water). NIK-228, atropine and cimetidine were administered orally or intravenously 1 hr before operation for Congo red spraying. NIK-228 (100 mg/kg, p.o.), atropine (5 mg/kg p.o.) and cimetidine (100 mg/kg, p.o.) all inhibited basal gastric acid secretion. Oral administration of NIK-228 and atropine inhibited gastrin, 2-deoxy-D-glucose (2-DG) and bethanechol-induced acid secretion, but didn't inhibit histamine-induced acid secretion. Cimetidine inhibited all of histamine, gastrin, 2-DG and bethanechol-induced acid secretion. In vagotomized rats, oral and intravenous administration of atropine both inhibited bethanechol-induced acid secretion, but NIK-228 was not inhibited. These results suggested that antisecretory effects of NIK-228 were caused by the central vagal systems.

Animals↗
PubMed2004

Growth, Congo Red agar colony morphotypes and antibiotic susceptibility testing of Mycobacterium avium subspecies paratuberculosis.

OBJECTIVE: Mycobacterium avium subspecies (subsp.) paratuberculosis (MAP) is the causative agent of Johne's disease in ruminants and has been associated with Crohn's disease in humans. We sought to test growth rates and susceptibilities of various strains of MAP in two available growth media. DESIGN: Paired comparison design. METHODS: Using the BACTEC macrobroth radiometric growth system and Congo Red-staining agar media, we determined inherent differences in growth characteristics of three bovine and two human strains of MAP and compared susceptibility results obtained in each growth system. RESULTS: Significant differences were observed in growth rate as well as mycobactin J dependence between strains and between a laboratory-adapted isolate of the same strain in the macrobroth system. Similarly, colonial morphology and Congo Red staining on agar media were observed. Two strains, one human and one bovine, demonstrated a 100% rough transparent colony with white coloration on Congo Red agar, while one bovine isolate exclusively grew as a smooth opaque colony with red coloration on Congo Red agar. The remaining strains exhibited mixtures of these two colonial morphotypes on agar media. Comparative susceptibility results between the BACTEC radiometric macrobroth method and the agar proportionality method showed good correlation for most antibiotics/inhibitors tested. However, erratic or poor growth in the macrobroth system prevented minimal inhibitory concentration determinations for two bovine strains by this method. CONCLUSION: This study demonstrates the variability in the colonial morphology of MAP on Congo Red agar as well as the correlation of antibiotic susceptibility results between the BACTEC macro broth method and the agar proportionality method. This study also emphasizes the need for the development of improved, standardized culture and susceptibility test methods for MAP.

Agar↗
PubMed2005

Determination of nucleic acids at nanogram level using resonance light scattering technique with Congo Red.

Based on the enhancement of the resonance light scattering (RLS) of Congo Red (CR) by nucleic acid, a new quantitative method for nucleic acid is developed. In the Tris-HCl buffer (pH 10.5), the weak light scattering of CR is greatly enhanced by addition of nucleic acid and CTMAB, the maximum peak is at 560 nm and the enhanced intensity of RLS is in proportion to the concentration of nucleic acid. The linear range is 1.0 x 10(-9) to 1.0 x 10(-6) g ml(-1), 7.5 x 10(-8) to 1.0 x 10(-6) g ml(-1) and 7.5 x 10(-8) to 2.5 x 10(-6) g ml(-1) for herring sperm DNA, calf thymus DNA and yeast RNA, and the detection limits are 0.019, 0.89 and 1.2 ng ml(-1) (S/N = 3), respectively. Actual biological samples were satisfactorily determined.

Animals↗
PubMed1989

Congo red staining on 1 micron de-plasticized sections for detection of lesions in Alzheimer's disease and related disorders.

Neuritic plaques (NPs), neurofibrillary tangles (NFTs) and congophilic angiopathy (CA), the three characteristic lesions in Alzheimer's disease, are easily detected in paraffin sections using light microscopy and specific staining methods including Congo red and Thioflavin S. Identification of these lesions in plastic thick sections (1 micron) is more tedious and relies essentially on morphological criteria. This causes investigators to subsequently analyze large numbers of thin sections under the electron microscope. Since many researchers use electron microscopy for various aspects of Alzheimer's disease and related research, it would be advantageous to have a rapid method enabling the investigator to quickly and reliably identify in thick sections the characteristic NPs, NFTs and/or CA, which can then be used for further analysis at the ultrastructural level. In this context, the present study describes a dependable technique for identifying NPs, NFTs and/or CA in Alzheimer's disease and related disorders and involves Congo red staining on one micron sections after plastic removal.

Aged↗
PubMed1979

Amyloid-like green birefringence in cytoskeletal 10 nm filaments after staining with Congo red.

The commonly accepted markers for amyliod are a fibrillar ultrastructure and congophilia combined with green birefringence when viewed under polarized light. Although a number of cells have been implicated in amyloid formation the detailed events leading to accumulation of amyloid are still unknown. Previous studies have suggested that amyloid shares antigenic properties with cytoskeletal intermediate (10 nm) filaments and connective tissue microfibrils. In the present study we show that such filaments present in fibroblasts and lymphoid cells have an affinity for Congo red, exhibit the typical green birefringence and are ultrastructurally indistinguishable from amyloid fibrils. Intermediate filaments of cultured fibroblasts depleted of nutrient medium retained the Congo red birefringent property and typical ultrastructure despite cell damage. Our observations suggest that amyloid deposits may form locally through abnormal accumulation of bundles of cytoskeletal intermediate filaments under conditions characterized by increased cell proliferation and death.

Amyloid↗
PubMed1994

Beta-amyloid neurotoxicity requires fibril formation and is inhibited by congo red.

beta-Amyloid (beta A) is normally produced as a nontoxic soluble peptide. In Alzheimer disease, beta A aggregates and accumulates in the brain as inert diffuse plaques or compact plaques associated with neurodegenerative changes. To determine the relationship of neurotoxicity to the physical state of beta A, we created (i) nonamyloidogenic amorphous aggregates of beta A [amorphous beta A (Am-beta A)] analogous to diffuse plaques and (ii) amyloidogenic fibrils of beta A [fibrillar beta A (Fib-beta A)] analogous to compact plaques. In primary rat hippocampal culture, Fib-beta A was neurotoxic, whereas Am-beta A was not toxic. Fib-beta A caused significant loss of synapses in viable neurons, while Am-beta A had no effect on synapse number. The amyloid fibril-binding dye Congo red inhibited Fib-beta A neurotoxicity by inhibiting fibril formation or by binding to preformed fibrils. Congo red also inhibited the pancreatic islet cell toxicity of diabetes-associated amylin, another type of amyloid fibril. These results indicate that beta A neurotoxicity requires fibril formation. These findings and our previous demonstration that amylin fibrils are toxic suggest that a common cytopathic effect of amyloid fibrils may contribute to the pathogenesis of Alzheimer disease and other amyloidoses.

Amyloid↗
PubMed1978

A simple manganous chloride and Congo red disc method for differentiating Neisseria gonorrhoeae from Neisseria meningitidis.

Manganous chloride and Congo red incorporated into blotting paper discs have been used to differentiate gonococci from meningococci. The new technique is simple and reliable; the materials for the test are inexpensive. The method will increase the efficiency of distinguishing between the pathogenic Neisseria in any clinical bacteriology laboratory and especially in those in the tropical areas.

Bacteriological Techniques↗
PubMed1982

Haematological and biochemical characteristics of Heteropneustes fossilis under the stress of Congo Red (diphenyl disazo binaphthionic acid).

The effects of the sublethal concentration (0.012%) of Congo Red on Heteropneustes fossilis were studied after 30 days exposure. The RBC count haemoglobin (Hb)% and PCV decreased significantly. The total WBC count, MCV, MCH, and MCHC showed a significant increase. Serum calcium, serum cholesterol and blood urea nitrogen (BUN) were significantly elevated, whereas serum phosphorus was significantly reduced. The activities of serum alkaline phosphatase (AlPase), acid phosphatase (AcPase). RNase, GOT, GPT and amylase were also significantly elevated. The possible reasons for these changes are discussed.

Animals↗
PubMed2000

Opposite effects of dextran sulfate 500, the polyene antibiotic MS-8209, and Congo red on accumulation of the protease-resistant isoform of PrP in the spleens of mice inoculated intraperitoneally with the scrapie agent.

The mode and the site of action of the major antiscrapie drugs have been studied by investigating their effects on the abnormal protease-resistant isoform of PrP (PrPres) and on its accumulation in mouse spleen. Day-by-day PrPres accumulation in the spleen and in other peripheral organs was first monitored to describe the early steps of scrapie pathogenesis. Three phases were identified: the detection of scrapie inoculum on the day of scrapie infection, a clearance phase, and then the peripheral accumulation of PrPres. In a second step, the effects of the polyene antibiotic MS-8209, the polyanion dextran sulfate 500 (DS500), and Congo red were assessed on these phases, after the drugs were coincubated with scrapie inoculum. Highly different mechanisms and sites of action were apparent. MS-8209 had a weak effect on the accumulation of PrPres in spleen, suggesting another site of intervention for this drug. DS500 delayed the beginning of the clearance phase but then blocked PrPres synthesis for a long period of time, probably because of its immunological effects on the spleen. Surprisingly, Congo red suppressed the clearance phase of scrapie inoculum and then increased transiently accumulation of PrPres in spleen. We showed in vitro that this effect was related to a direct enhancement of the protease resistance of PrPres by the drug.

Amphotericin B↗
PubMed1998

Oligomerization of endogenous and synthetic amyloid beta-protein at nanomolar levels in cell culture and stabilization of monomer by Congo red.

Amyloid beta-proteins (A beta) are proteolytic fragments of the beta-amyloid precursor protein (beta APP) that are secreted by mammalian cells throughout life but also accumulate progressively as insoluble cerebral aggregates in Alzheimer's disease (AD). Because mounting evidence indicates that A beta aggregation and deposition are early, critical features of AD leading to neurotoxicity, many studies of A beta aggregation have been conducted using synthetic peptides under generally nonphysiological conditions and concentrations. We recently described the oligomerization of A beta peptides secreted by beta APP-expressing cells at low nanomolar (20-30 ng/mL) levels into sodium dodecyl sulfate- (SDS-) stable oligomers of 6-16 kDa. Here, we extensively characterize this in vitro system and show that the amyloid binding dye, Congo red, acts to markedly decrease oligomer/monomer ratios by stabilizing the 4 kDa A beta monomers (ID50 approximately equal to 3.4 microM). Addition of radioiodinated synthetic A beta 1-40 to the cultures or to their conditioned media at physiological concentrations (0.25-2.5 nM) reveals that it undergoes progressive aggregation into SDS-stable oligomers of 6-25 kDa during brief (approximately 4 h) incubation at 37 degrees C, and this is inhibitable by Congo red. The level of A beta oligomers can be quantitated in the Chinese hamster ovary (CHO) conditioned medium by size-exclusion chromatography as well as by SDS-polyacrylamide gel electrophoresis (PAGE), and comparison of these two methods suggests that aggregation of A beta into higher molecular weight polymers that are not detectable by SDS-PAGE occurs in the cultures. We conclude that both endogenous and synthetic A beta can assemble into stable oligomers at physiological concentrations in cell culture, providing a manipulable system for studying the mechanism of early A beta aggregation and identifying inhibitors thereof under biologically relevant conditions.

Amyloid beta-Peptides↗
PubMed2002

Anaerobic reduction of a sulfonated azo dye, Congo Red, by sulfate-reducing bacteria.

The capacity for anaerobic decolorization of a sulfonated azo dye, Congo Red, by a strain of a sulfate-reducing bacterium was evaluated. After optimizing the growth rate of the bacteria on a simple carbon source and terminal electron acceptor pair, lactate and sulfate, respectively, the effect of the dye concentration on their growth rate was analyzed. The decolorization rate was affected by the dye concentration in the growth medium. The azo-bond cleavage mechanism of reductive decolorization with the formation of benzidine was consistent with the results, as this metabolite was identified by high-performance liquid chromatography. Several fractions of the culture medium, including lysed cell extracts, were examined for the capacity to reduce the azo dye. This reduction capacity was found in the culture medium in which the cells had previously grown. The results showed that the mechanism of reductive decolorization of this sulfonated azo dye was extracellular and nonenzymatic, consistent with the production of sulfide anion by the microorganisms while growing on lactate and sulfate. The sulfide anions were the cause of the reduction leading to the disappearance of color in the medium. To increase the rate of decolorization, the presence of ferrous ion was also necessary together with the lactate and sulfate substrates.

Azo Compounds↗
PubMed2003

Congo red populates partially unfolded states of an amyloidogenic protein to enhance aggregation and amyloid fibril formation.

Congo red (CR) has been reported to inhibit or enhance amyloid fibril formation by several proteins. To gain insight into the mechanism(s) for these apparently paradoxical effects, we studied as a model amyloidogenic protein, a dimeric immunoglobulin light chain variable domain. With a range of molar ratios of CR, i.e. r = [CR]/[protein dimer], we investigated the aggregation kinetics, conformation, hydrogen-deuterium exchange, and thermal stability of the protein. In addition, we used isothermal titration calorimetry to characterize the thermodynamics of CR binding to the protein. During incubation at 37 degrees C or during thermal scanning, with CR at r = 0.3, 1.3, and 4.8, protein aggregation was greatly accelerated compared with that measured in the absence of the dye. In contrast, with CR at r = 8.8, protein unfolding was favored over aggregation. The aggregates formed with CR at r = 0 or 0.3 were typical amyloid fibrils, but mixtures of amyloid fibrils and amorphous aggregates were formed at r = 1.3 and 4.8. CR decreased the apparent thermal unfolding temperature of the protein. Furthermore, CR perturbed the tertiary structure of the protein without significantly altering its secondary structure. Consistent with this result, CR also increased the rate of hydrogen-deuterium exchange by the protein. Isothermal titration calorimetry showed that CR binding to the protein was enthalpically driven, indicating that binding was mainly the result of electrostatic interactions. Overall, these results demonstrate that at low concentrations, CR binding to the protein favors a structurally perturbed, aggregation-competent species, resulting in acceleration of fibril formation. At high CR concentration, protein unfolding is favored over aggregation, and fibril formation is inhibited. Because low concentrations of CR can promote amyloid fibril formation, the therapeutic utility of this compound or its analogs to inhibit amyloidoses is questionable.

Amyloid↗
PubMed2006

The effect of ionic strength on the UV-vis spectrum of congo red in aqueous solution.

The major peak near 498 nm in the ultraviolet-visible spectrum of congo red in aqueous solution shifts toward the blue while the molar absorptivity of this peak decreases predictably with increasing ionic strength. The shift was observed for solutions in which ionic strength was varied from 0.0 to 1.8M using the uni-univalent ionic compounds, NaCl, NaClO(4), KNO(3) and KBr separately. A plot of the log of the absorbance at the peak versus ionic strength was linear as well as a plot of the log of the wavelength of the major peak (shifted from 498 nm) versus the ionic strength. The slopes of each of these plots were somewhat different depending on the ionic compound.

Bromides↗
PubMed1984

Morphological anomalies induced by Congo red in Aspergillus niger.

Aspergillus niger germ tubes were exposed for 6 h to 0.15 mg/ml of Congo red, a stain which prevents chitin microfibril assembly. The most evident alterations, detected under ultraviolet light and by transmission and scanning electron microscopy, concerned the hyphal tips which burst or, most frequently, expanded into bulges. In the latter structures, new hyphal tips appeared which, after giving rise to more or less developed hyphae, were themselves converted into new bulges. Therefore, segments derived from isotropic and polarized growth alternated in the organisms exposed to the dye. An interpretation of these abnormalities is advanced based upon the assumption that the maintainance of a regular gradient of wall viscosity in the hyphal extension zone depends primarily on the capability of glycan chains to form crystalline aggregates of increasing complexity.

Aspergillus niger↗