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At least 163 records · Page 9Linked to original sources
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↗
PubMed2006

Evaluation of health, nutrition and food security programmes in a complex emergency: the case of Congo as an example of a chronic post-conflict situation.

OBJECTIVE: To describe the case of Congo as an example of the assessment and appropriateness of donor operational and sectoral strategies in a complex emergency. DESIGN AND SETTING: The paper reports the findings of an external evaluation of operations financed by the European Commission Humanitarian Office in the Democratic Republic of Congo (DRC). RESULTS: The Congolese health system is suffering from severe deterioration. What is functioning in the public health context is donor-dependent with high costs and limited coverage. Despite a relatively favourable agro-climatic situation, food shortage and famine severely affect the nutritional status of large population groups. In this context, humanitarian programmes have generally improved access to health care and the nutritional status of beneficiaries. The reduction of malnutrition in project areas is often demonstrated even though the context did not permit consolidation of these results. Malnutrition continues to claim a massive cost of lives owing to the effect of widespread food insecurity that follows a circular cause-and-effect pattern of very low food production and extreme poverty. CONCLUSIONS: The current context in DRC does not correspond yet to 'post-crisis': neither at population level with regard to indicators of poverty, malnutrition, disease and death, nor at institutional level, with regard to state support to institutions. In these situations, the international community is often called upon to replace the state as service provider. Integrated humanitarian actions should be the future of relief projects in DRC. Health, nutrition and food security components should be considered a standard public health intervention strategy representing the most sensible approach to address the needs of the affected population.

Delivery of Health Care↗
PubMed2006

The increased flexibility of CDR loops generated in antibodies by Congo red complexation favors antigen binding.

The dye Congo red and related self-assembling compounds were found to stabilize immune complexes by binding to antibodies currently engaged in complexation to antigen. In our simulations, it was shown that the site that becomes accessible for binding the supramolecular dye ligand is located in the V domain, and is normally occupied by the N-terminal polypeptide chain fragment. The binding of the ligand disrupts the beta-structure in the domain, increasing the plasticity of the antigen-binding site. The higher fluctuation of CDR-bearing loops enhances antigen binding, and allows even low-affinity antibodies to be engaged in immune complexes. Experimental observations of the enhancement effect were supported by theoretical studies using L lambda chain (4BJL-PDB identification) and the L chain from the complex of IgM-rheumatoid factor bound to the CH3 domain of the Fc fragment (1ADQ-PDB identification) as the initial structures for theoretical studies of dye-induced changes. Commercial IgM-type rheumatoid factor (human) and sheep red blood cells with coupled IgG (human) were used for experimental tests aimed to reveal the dye-enhancement effect in this system. The specificity of antigen-antibody interaction enhanced by dye binding was studied using rabbit anti-sheep red cell antibodies to agglutinate red cells of different species. Red blood cells of hoofed mammals (horse, goat) showed weak enhancement of agglutination in the presence of Congo red. Neither agglutination nor enhancement were observed in the case of human red cells. The dye-enhancement capability in the SRBC-antiSRBC system was lost after pepsin-digestion of antibodies producing (Fab)2 fragments still agglutinating red cells. Monoclonal (myeloma) IgG, L lambda chain and ovoalbumin failed to agglutinate red cells, as expected, and showed no enhancement effect. This indicates that the enhancement effect is specific.

Animals↗
PubMed2003

Decolorization of Congo Red with three-dimensional flow-by packed-bed electrodes.

The electrochemical removal of the color of the dyestuff Congo Red was investigated experimentally by using packed graphite anodes as well as packed graphite or C-304 stainless steel cathodes in an undivided reactor. The effects of the applied apparent current density, the amount of chloride ion addition, the pH value of the solution, the cathode material, the operating temperature, the volumetric flow rate and the initial concentration of Congo Red on the removal efficiencies were investigated in this study. Experimental results showed that the main pathway of color removal was by the hypochlorite generated in-situ at the anodes. Compared with the indirect oxidation, the color removal due to direct oxidation was insignificant. Cathodic oxidation by using graphite cathodes had little influence on the removal rate in an undivided electrochemical cell.

Coloring Agents↗
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↗
PubMed2002

Imaging Abeta plaques in living transgenic mice with multiphoton microscopy and methoxy-X04, a systemically administered Congo red derivative.

The identification of amyloid deposits in living Alzheimer disease (AD) patients is important for both early diagnosis and for monitoring the efficacy of newly developed anti-amyloid therapies. Methoxy-X04 is a derivative of Congo red and Chrysamine-G that contains no acid groups and is therefore smaller and much more lipophilic than Congo red or Chrysamine-G. Methoxy-X04 retains in vitro binding affinity for amyloid beta (Abeta) fibrils (Ki = 26.8 nM) very similar to that of Chrysamine-G (Ki = 25.3 nM). Methoxy-X04 is fluorescent and stains plaques, tangles, and cerebrovascular amyloid in postmortem sections of AD brain with good specificity. Using multiphoton microscopy to obtain high-resolution (1 microm) fluorescent images from the brains of living PSI/APP mice, individual plaques could be distinguished within 30 to 60 min after a single i.v. injection of 5 to 10 mg/kg methoxy-X04. A single i.p. injection of 10 mg/kg methoxy-X04 also produced high contrast images of plaques and cerebrovascular amyloid in PSI/APP mouse brain. Complementary quantitative studies using tracer doses of carbon- 11-labeled methoxy-X04 show that it enters rat brain in amounts that suggest it is a viable candidate as a positron emission tomography (PET) amyloid-imaging agent for in vivo human studies.

Alkenes↗
PubMed1994

Mother-to-child transmission of HIV-1 in Congo, central Africa. Congolese Research Group on Mother-to-Child Transmission of HIV.

OBJECTIVE: To assess the risk of mother-to-child transmission of HIV-1 in a central African population and to study maternal factors associated with perinatal transmission. DESIGN: Prospective cohort study of infants born to HIV-1-positive women and controls born to HIV-1-negative women enrolled sequentially in two prenatal clinics and one maternity hospital in Brazzaville, Congo. SUBJECTS AND METHODS: A total of 118 exposed and 208 control infants were followed from birth for at least 2 years. Assessment of infection in children and computation of transmission rate were made according to the European Economic Community/World Health Organization Ghent guidelines (1992). RESULTS: The transmission rate was 40.4% [95% confidence interval (CI), 30.7-50.1]. Maternal age, parity, history of adverse pregnancy outcome or history of decreased children were not associated with transmission. However, independently, women whose relationship with their infant's father was less than 1 year, or women who had symptoms of HIV-1 during pregnancy had an increased risk of transmission [adjusted odds ratios, 11.1 (95% CI, 2.4-50.2) and 10.3 (95% CI, 2.9-37.1), respectively]. CONCLUSION: The transmission rate observed in Congo is in the upper range of the rates reported in Africa. The uneven distribution of cofactors for perinatal transmission, such as the presence of symptoms of HIV disease during pregnancy, may explain some of the variation observed across studies.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Differentiation of phase I and variant strains of Bordetella pertussis on Congo red media.

The addition of Congo red, Trypan blue or haemin to the growth medium allowed the differentiation of phase-I and variant strains of Bordetella pertussis. Phase-I strains produced red (CR+), blue or dark brown colonies on a modified cyclodextrin solid medium containing Congo red, Trypan blue or haemin, respectively, whereas variant (Vir- and phase IV) strains grew as pale (CR-) colonies. Spontaneous CR- variants were isolated and characterised and had a phenotype like that of Vir- or phenotypically modulated, C-mode strains in that they did not produce the haemolysin, haemagglutinin(s), histamine-sensitising factor (pertussis toxin), heat-labile toxin and two major envelope polypeptides associated with phase-I strains. Two such variants had reduced virulence for mice. CR+ strains, when grown on a high nicotinic acid medium to induce modulation, gave CR- colonies. Thus the CR+ phenotype is a characteristic of phase-I B. pertussis and its expression appears to be controlled in a manner similar to that of other phase I-related factors. CR- variants of B. parapertussis and B. bronchiseptica were also deficient in these factors. Four isolates of B. avium were CR-.

Bordetella pertussis↗
PubMed2005

Presence of broadly reactive and group-specific neutralizing epitopes on newly described isolates of Crimean-Congo hemorrhagic fever virus.

Crimean-Congo hemorrhagic fever virus (CCHFV), a member of the genus Nairovirus of the family Bunyaviridae, causes severe disease in humans with high rates of mortality. The virus has a tripartite genome composed of a small (S), a medium (M) and a large (L) RNA segment; the M segment encodes the two viral glycoproteins, G(N) and G(C). Whilst relatively few full-length M segment sequences are available, it is apparent that both G(N) and G(C) may exhibit significant sequence diversity. It is unknown whether considerable antigenic differences exist between divergent CCHFV strains, or whether there are conserved neutralizing epitopes. The M segments derived from viral isolates of a human case of CCHF in South Africa (SPU 41/84), an infected tick (Hyalomma marginatum) in South Africa (SPU 128/81), a human case in Congo (UG 3010), an infected individual in Uzbekistan (U2-2-002) and an infected tick (Hyalomma asiaticum) in China (Hy13) were sequenced fully, and the glycoproteins were expressed. These novel sequences showed high variability in the N-terminal region of G(N) and more modest differences in the remainder of G(N) and in G(C). Phylogenetic analyses placed these newly identified strains in three of the four previously described M segment groups. Studies with a panel of mAbs specific to G(N) and G(C) indicated that there were significant antigenic differences between the M segment groups, although several neutralizing epitopes in both G(N) and G(C) were conserved among all strains examined. Thus, the genetic diversity exhibited by CCHFV strains results in significant antigenic differences that will need to be taken into consideration for vaccine development.

Animals↗
PubMedDate not supplied

Congo red birefringent structures in the hypothalamus in senile dementia of the Alzheimer type.

Serial cryostat sections of hypothalamus from four cases of Alzheimer-type dementia and four controls were stained with Congo red and examined for birefringence. Green birefringence and dichroism was associated with (a) neurofibrillary tangles, which were most numerous at the level of the tuberomammillary nucleus where they were found in large acetylcholinesterase-positive neurons; (b) neuropil processes within tangle fields; (c) a few plaque cores in the mammillary body; (d) spicules at the ependyma of the third ventricle, and (e) blood vessels. Birefringence (e) had different properties from (a) to (d) and was considered to be due to collagen. The ependymal spicules did not react with an antibody which recognized the tangles and neuropil processes. Each Alzheimer case had many more tangles than the control cases. Birefringence in (b)-(d) tended to be greater in the Alzheimer than in the control cases. This study confirms previous reports of large numbers of tangles in circumscribed areas of caudal hypothalamus in Alzheimer-type dementia and demonstrates that Congo red staining reveals abnormalities in hypothalamic structures (neuropil processes and ependyma) not demonstrated by other staining techniques.

Aged↗
PubMed1993

Binding of hemin and congo red by oral hemolytic spirochetes.

Colony-forming units or cells in suspension of oral anaerobic spirochetes (Treponema denticola, Treponema vincentii and Treponema socranskii) bind hemin and Congo red. Hemin or Congo red binds to a hydrophobic polypeptide receptor that is located in the outer membrane of the bacterial cells and it has a relative molecular mass of 47 kDa. These oral spirochetes also lyse sheep erythrocytes to produce beta-hemolytic zones around colony-forming units. The oral spirochetes may acquire iron for growth when they lyse erythrocytes and bind heme from which they may sequester and transport iron into the cells.

Bacterial Outer Membrane Proteins↗
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↗
PubMed1977

Detection and differentiation of iron-responsive avirulent mutants on Congo red agar.

Agar medium containing Congo red dye differentiates virulent and avirulent colonies of Shigella, Vibrio cholerae, Escherichia coli, and Neisseria meningitidis. Like virulent plague bacilli, wild-type cells of these species absorb the dye and produce red colonies. Mutants or colonial variants have been isolated that fail to absorb the dye and produce colorless colonies. These mutants exhibit reduced virulence in the chicken embryo model, but their virulence is enhanced by supplementation with iron. Of those species tested, only Neisseria gonorrhoeae isolates failed to grow in the presence of this dye. Inhibition of growth by Congo red may thus provide a simple means for differentiating gonococci from other Neisseria.

Bacteria↗
PubMed1985

Cloning the gene for Congo red binding in Shigella flexneri.

The ability to bind the dye Congo red from agar medium is associated with virulence of Shigella species. DNA sequences conferring this property have been cloned from a large, 140-kilobase plasmid of Shigella flexneri into a plasmid vector. This recombinant plasmid does not fully restore virulence to S. flexneri isolates which have lost the large plasmid. This indicates that other genes present on the 140-kilobase plasmid must also be required for virulence of S. flexneri. The cloned fragment contains a copy of the insertion sequence IS1 closely linked to the gene for Congo red binding.

Base Sequence↗
PubMed1989

A 101-kilodalton heme-binding protein associated with congo red binding and virulence of Shigella flexneri and enteroinvasive Escherichia coli strains.

The ability of Shigella flexneri to bind Congo red or hemin is associated with virulence. A 101-kilodalton (kDa) protein responsible for this phenotype (Crb+) in S. flexneri was identified by a tetramethylbenzidine staining procedure which detects heme-protein complexes in polyacrylamide gels. Labeling of cell-surface polypeptides with 125I revealed that the 101-kDa heme-binding protein is expressed on the cell surface. Expression of the protein was regulated by growth temperature and was found to be encoded by the large virulence plasmid of S. flexneri. Deletion mutants and a Tn5 insertion mutant which were negative for Congo red binding (Crb-) did not express the 101-kDa protein. Enteroinvasive Escherichia coli strains that were Crb+, and whose plasmids shared homology with the S. flexneri virulence plasmid, also expressed the 101-kDa protein. Expression of the protein in S. flexneri and enteroinvasive E. coli correlated with the presence of a 9.2-kilobase EcoRI fragment of these plasmids.

Bacterial Proteins↗
PubMed1986

Comparison of methods for isolation and titration of Crimean-Congo hemorrhagic fever virus.

The fluorescence focus assay and the plaque assay in CER cells were compared with mouse inoculation for the isolation and titration of Crimean-Congo hemorrhagic fever virus. The fluorescence focus assay and the plaque assay were of similar sensitivity, but both produced 10- to 100-fold lower titers than did mouse inoculation. For specimens from 26 Crimean-Congo hemorrhagic fever patients in South Africa, virus was isolated from 20 by mouse inoculation and from only 11 by cell culturing. Although cell cultures were less sensitive for the isolation of virus from clinical specimens, they produced diagnostic results much more rapidly.

Animals↗
PubMed1993

Congo red inhibition of scrapie agent replication.

Congo red inhibits the accumulation of protease-resistant PrP in scrapie-infected mouse neuroblastoma cells. Here we show that Congo red also inhibits the replication of scrapie infectivity in these cells. This observation is consistent with the idea that protease-resistant PrP is a vital component of the scrapie agent or that agent replication depends on the presence of protease-resistant PrP in the cell.

Animals↗