Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0042961 (volvulus)
 4,305 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The viability of adult Onchocerca volvulus and the effect of 12 known anthelmintic compounds on the parasites have been evaluated in an in vitro culture system. Three different parameters, a colorimetric assay, using NADH-dependent reduction of a tetrazolium salt to dark blue formazan by living adult worms, motility indices of male worms and lactate excretion of female worms were used to determine worm viability. The experiments showed that over a short term period of six days the viability of the worms did not decline significantly. The use of males isolated by dissection of whole nodules for the evaluation of drug effects in vitro is preferable to collagenase isolated worms. Mel W, milbemycin a and d, ivermectin, levamisole, CGP 6140 and, to a lesser extent, suramin immobilized male worms or significantly reduced the motility indices at a concentration of 10 microM. The tetrazolium reduction by male worms was not affected by levamisole, whereas the other active compounds demonstrated significant inhibitory effects. Diethylcarbamazine, mebendazole, flubendazole, metrifonate and CGP 20376 had no significant effect on male viability. Comparable activity was seen with the intact female worms isolated by collagenase digestion. Mel W, the milbemycins and ivermectin significantly inhibited tetrazolium reduction, whereas suramin and the other compounds had only slight or no inhibitory effects on female O. volvulus. Although one still has to aim at an improvement of the culture conditions, the in vitro test system using adult O. volvulus provides a basis for further research on potential antifilarial compounds.
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PMID:In vitro assessment of the activity of anthelmintic compounds on adults of Onchocerca volvulus. 237 12

A simple three-step colorimetric assay based on the tetrazolium salt MTT (3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) has been developed for quantifying filarial viability. Living (but not dead) filariae take up MTT and rapidly reduce it to formazan, so staining themselves dark blue. This colour change which is easily seen provides a rapid qualitative test for filarial viability. Quantitative data can be obtained by solubilizing formazan out of the worm with DMSO and measuring the absorbance of the resulting solution at 510 nm. To date the technique has been demonstrated in several species of filariae including Onchocerca volvulus. MTT reduction is thought to be selective for NADH-dependent dehydrogenase activity in viable worms. The reaction occurs readily in all developmental stages of Dipetalonema viteae including fragments of filarial tissue. Enzyme activity in viable intact D. viteae appears to be primarily associated with the hypodermis/muscle cells, with minimal formazan formation in the gut and reproductive tracts. The application of this MTT assay as a parameter for quantifying in vitro drugs effects is described. Assay procedures have been developed and optimized with D. viteae and Brugia pahangi for the assessment of effects of macrofilariae and microfilarial release, and the activity of a range of antifilarial standards reported. Several potential applications of the technique to studies on filarial biology are discussed.
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PMID:Colorimetric quantitation of filarial viability. 270 65

Lactate dehydrogenase and malate dehydrogenases were partially purified and characterized from adult O. volvulus. The molecular weight of lactate dehydrogenase was determined to be 130 000, those of malate dehydrogenase I and II to be 120 000 and 65 000, respectively. The activities of both malate dehydrogenases and of the lactate dehydrogenase were strongly inhibited by suramin. The inhibition constants were determined to be in the range of 2 microM to 5 microM. The type of inhibition was found to be competitive with respect to the coenzyme NADH and to be non-competitive to the substrates. It is suggested that the mode of action of suramin in the therapy of Onchocerciasis might depend on the blokkade of reoxidation of NADH produced within the glycolytic pathway.
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PMID:Onchocerca volvulus: effect of suramin on lactate dehydrogenase and malate dehydrogenase. 737 52

Glutathione metabolism represents a potential target for anti-parasite drug design. The central role of glutathione reductase (GR) in maintenance of the thiol redox state and in anti-oxidative defence has to be evaluated in more detail in order to establish the essential function of this enzyme for the survival of the filarial parasite Onchocerca volvulus. The O. volvulus GR (OvGR) gene was cloned and sequenced. The gene is composed of 13 exons and 12 introns and spans 4065 bp. The first intron is located within the 5'-untranslated region of the gene, 16 nucleotides upstream of the translation initiation codon. Southern-blot analysis and structural characterization of the genomic sequence indicate that OvGR is encoded by a single-copy gene. Isolation of various cDNA clones revealed a polymorphism of polyadenylation initiation with no consensus polyadenylation sites in any of the cDNAs analysed. The entire cDNA is 1977 bp long and carries the nematode-specific spliced leader sequence SL1 at its 5' end, 236 nucleotides upstream of the first in-frame methionine. The cDNA codes for a polypeptide of 462 amino acids with 53.5% sequence identity with human GR (HsGR). A total of 18 out of 19 residues contributing to glutathione binding are identical in OvGR and HsGR. However, one of the arginine residues (Arg-224 in HsGR) involved in discrimination between NADPH and NADH in all known GRs is substituted by tryptophan (Trp-207 in OvGR). The coding region of OvGR was expressed in Escherichia coli as a histidine-fusion protein, and it was established that the parasite protein still favours the binding of NADPH (Km 10.9 microM) over NADH (Km 108 microM). The histidine-fusion protein has a subunit size of 54 kDa and is active as a homodimer of 110 kDa.
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PMID:Molecular characterization and expression of Onchocerca volvulus glutathione reductase. 927 Oct 84