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Query: UMLS:C0042961 (volvulus)
 4,305 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The in vitro killing of Onchocerca volvulus infective third stage larvae (L3) by components of their human hosts' defence mechanisms is not well documented, as no suitable assay exists. Motility is inappropriate as a criterion of larval viability because of the unsteady winding movements of L3. In the present study, a metabolic parameter for larval viability, the uptake of [3H]2-deoxy-D-glucose, was evaluated. To demonstrate the reproducibility and validity of this test, the oxygen radical hydrogen peroxide (H2O2) was applied to viable L3 and the death of L3 demonstrated by a 90% reduction in glucose uptake. The incorporation of glucose by the filarial larvae was also determined after in vitro exposure to lysates of the putative effector cells, i.e. eosinophilic and neutrophilic granulocytes and monocytes. Effector-cell-derived components led to a 30-80% dose-dependent decrease in deoxy-glucose uptake, with a half-maximal effect at about 500 micrograms ml-1. These experiments demonstrate, for the first time, the deleterious impact of effector cell constituents on the metabolic activity of O. volvulus L3. The assay could be used to evaluate the effect of distinct natural or recombinant effector molecules on the viability of O. volvulus infective larvae and to investigate the effect of parasite molecules which interfere with effector mechanisms.
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PMID:Inhibition of carbohydrate uptake of Onchocerca volvulus infective larvae (L3) by effector cell constituents. 132 84

Use was made of seven FITC labelled lectins as tools to investigate the surface of Onchocerca lienalis larvae as they develop through to the infective third-stage in a natural vector, Simulium ornatum. The lectins were derived from Canavalia ensiformis (Con A), Lens culinaris (lentil), Triticum vulgaris (wheat germ), Arachis hypogaea (peanut), Helix pomatia, Phaseolus vulgaris (kidney bean) and Tetragonolobus purpureus (asparagus pea). Between 70 and 100 living parasites were examined for each developmental stage; i.e. skin microfilariae, late first-stages, second-stages, preinfective third-stages and infective third-stages isolated from the mouth parts of the flies. None of the lectins used bound to the surface of the microfilariae. However, progressive binding to the cuticle of the first- and second-stages was observed using Con. A, lentil lectin and wheat germ agglutinin (WGA). Following moulting to the third-stage, binding of these three lectins declined. Furthermore, as these lectins decreased, peanut and Helix pomatia lectins progressively increased in their binding, despite the fact that they showed little or no binding to the first- and second-stages; stages at which Con A, lentil and WGA were at their maximum. Asparagus pea and kidney bean lectins failed completely to bind to any of the larvae examined. Carbohydrate inhibition tests showed that the lectin was indeed binding specifically to glycoconjugates on the parasite surface. WGA binding was not inhibited by prior incubation with N-acetyl-D-glucosamine, even at high concentrations, but neuraminic acid did completely inhibit its binding. Judging from the patterns of binding on the nematodes themselves, the carbohydrates may not be vector in origin, but derive from the worms. The lectin specificities indicate that initially mannose/glucose type derivatives are present on the surface. Following moulting to the third-stage these are progressively replaced, or overlaid with galactosamine type derivatives, also present on the infective third-stage as it enters the bovine host. The availability of these surface glycoconjugates to attack mediated by natural insect lectins may be of importance in the parasite regulatory mechanisms of the blackfly. Variability in these surface carbohydrates, and in the response to them could well be a contributing factor in the cytospecific variation in S. damnosum susceptibility to geographical variants of O. volvulus.
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PMID:Surface carbohydrate changes on Onchocerca lienalis larvae as they develop from microfilariae to the infective third-stage in Simulium ornatum. 314 48

The lectin-binding properties of microfilariae of Onchocerca volvulus, O. lienalis, Brugia pahangi, Wuchereria bancrofti, Dirofilaria immitis, and Monanema (= Ackertia) marmotae share a number of characteristics. Carbohydrates specific for lectins are associated with the egg shell or sheath. N-acetyl-D-glucosamine is the predominant carbohydrate associated with the ensheathed forms with lesser quantities of D-galactose and/or alpha-lactose and D-galactosamine. The density of these carbohydrates on the sheath surface diminishes as the larvae undergo normal growth and development. Similar carbohydrates are not found on the cuticle as exsheathed microfilariae show virtually no ability to bind lectins.
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PMID:Microfilarial surface carbohydrates as a function of developmental stage and ensheathment status in six species of filariids. 341 56

Embryonic stages of various Onchocerca species have been used to stimulate resistance in CBA mice to challenge injections with the microfilariae of Onchocerca lienalis. Comparable levels of resistance to challenge (29-37% reductions) were conferred by living, freeze-killed, or sonicated organisms administered with Freunds' Complete Adjuvant (FCA). Antigens extracted in saline, or with the detergent sodium deoxycholate, were also protective. Adjuvants enhanced the protective effect, particularly FCA (78% reduction), Freunds' Incomplete Adjuvant (74% reduction), aluminum hydroxide (70% reduction) and Bordetella pertussis (70% reduction). Detergent extracts prepared from intact embryos with n-octyl glucoside also stimulated significant levels of protection against microfilarial challenge when given with FCA (37-45% reductions). Levels of resistance induced by immunizations with intact organisms were greatest following subcutaneous (s.c.) injection over the neck or by intramuscular inoculation. Soluble extracts were also particially effective given by s.c. inguinal or intraperitoneal injection. A time-interval of greater than 3 weeks between the completion of immunization and challenge was required for the expression of immunity. Cross-protection against challenge with O. lienalis microfilariae was also afforded to mice by immunization with intact embryos or detergent extracts of Onchocerca gutturosa (45 and 34% reductions), Onchocerca gibsoni (66 and 47% reductions) or Onchocerca volvulus (58 and 41% reductions). It is concluded that the embryonic stages of both human and animal parasites provide a source of cross-protective antigens of value in studies on resistance to Onchocerca microfilariae in experimental hosts.
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PMID:Resistance to Onchocerca lienalis microfilariae in mice conferred by egg antigens of homologous and heterologous Onchocerca species. 361 90

The key point in perioperative management of a patient with congenital nephrogenic diabetes insipidus is fluid and electrolytes management. Since the urine of these patients consists mainly of solute free water, replacement fluids should be fluids which provide free water. A 2-year-old girl with congenital nephrogenic diabetes insipidus was scheduled for dental extraction. Her daily fluid intake was 10 liter. She had a history of recurrent fever, polyuria and polydipsia since 2 months of age. Her previous perioperative course for gastric volvulus at another hospital was complicated with postoperative hyponatremia and convulsion. A venous line was secured the day before surgery and 5% dextrose in water was infused at a rate of 12 ml.kg-1.hr-1. Intraoperative infusion was mainly with 5% dextrose in water combined with maintenance fluid. Five hours after surgery oral intake was started. Her intraoperative electrolytes levels were low (Na 133 mEq.l-1, K 2.8 mEq.l-1), but otherwise her perioperative course was uneventful.
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PMID:[Perioperative management of a child with congenital nephrogenic diabetes insipidus]. 1129 43

Onchocerca volvulus is a human pathogenic filarial parasite which, like other parasitic nematodes, is capable of surviving in an immunologically competent host by employing a variety of immune evasion strategies and defense mechanisms including the detoxification and repair mechanisms of the glutathione S-transferases (GSTs). In this study we analyzed the glycosylation pattern and the immunological properties of extracellular O. volvulus GST1a and -1b (OvGST1a and -1b). The enzymes differ in only 10 amino acids, and both are glycoproteins that have cleavable signal peptides and unusual N-terminal extensions. These characteristics have not been described for other GSTs so far. Mass spectrometry analyses indicate that both enzymes carry high-mannose type oligosaccharides on at least four glycosylation sites. Glycosylation sites 1 to 3 of OvGST1a (OvGST1b sites 2 to 4) are occupied by truncated N-glycans (Man(2)GlcNAc2 to Man(5)GlcNAc(2)), and N glycosylation site 4 of OvGST1a (OvGST1b site 5) carries Man(5)GlcNAc2 to Man(9)GlcNAc(2). To analyze the capacity of these secretory GSTs to stimulate host immune responses, we studied the antibody responses of onchocerciasis patients against the native affinity-purified OvGST1a and -1b. By enzyme-linked immunosorbent assay we showed that OvGST1a and -1b are immunodominant antigens, with less than 7% nonresponder patients. A direct comparison of the antibody responses to the glycosylated and deglycosylated forms demonstrates the high immunogenicity of the N-glycans. Analyses of the antibody responses to the unusual N-terminal extension show an enhanced recognition of this portion by patients as opposed to recognition of the recombinant protein without extension.
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PMID:Structural analysis and antibody response to the extracellular glutathione S-transferases from Onchocerca volvulus. 1170 53

The biosynthesis in vitro of phosphorylcholine oligosaccharides in Caenorhabditis elegans has been investigated. Here we show that extracts of C. elegans' microsomes transfer phosphorylcholine from L-alpha-dipalmitoyl phosphatidylcholine to hybrid and complex type N-linked oligosaccharides containing mannose residues disubstituted with N-acetylglucosamine. The reaction products are consistent with structures reported for C. elegans as well those found in the filarial nematodes Acanthocheilonema viteae, Onchocerca volvulus, and Brugia malayi, strongly supporting the concept that the phosphorylcholine oligosaccharide biosynthetic enzymes are conserved in this group of organisms. Because it is thought that phosphorylcholine substitution of oligosaccharides modulates host immune response in filarial infections, this in vitro system may help in gaining an understanding of the basis for this response.
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PMID:Biosynthesis in vitro of Caenorhabditis elegans phosphorylcholine oligosaccharides. 1499 96