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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

cDNA clone banks have been constructed in a plasmid vector (pJSC73) using mRNA isolated from adult worms and eggs of Schistosoma mansoni. These clone banks have been screened by message selection (hybrid release translation) and clones containing fragments of genes encoding schistosome antigens have been identified by immunoprecipitation of the corresponding mRNA in vitro translation product. Over 50 clones encoding schistosome antigens have been identified including those of the 100 000, 86 000, 28 000, and 27 000 molecular weight surface antigen precursors.
Mol Biochem Parasitol 1986 Jan
PMID:Identification by message selection of cDNA clones encoding antigens of Schistosoma mansoni. 375 8

We describe a glass fiber filter binding assay for the levamisole receptor, a putative acetylcholine receptor of the nematode Caenorhabditis elegans, and we show that receptor detected in vitro binds both levamisole derivatives and cholinergic agonists with the pharmacological specificity expected of the physiologically functional nematode receptor. The receptor is detected by the binding of tritiated meta-aminolevamisole ([3H]MAL, 27 Ci/mmol). In extracts of the wild-type nematode, there is a saturable, high affinity binding activity for [3H]MAL (Kd approximately 5-10 nM). Well fed wild-type worms contain as much as 3 fmol of high affinity binding activity per mg of extract protein (0.14 pmol/g of wet weight of worms) and dauer larvae, a special juvenile stage, contain as much as 15 fmol of activity per mg of protein. Specific binding activity per mg of protein is highest in larval stages and decreases severalfold in the adult worm. The rates of formation and dissociation of the [3H]MAL-receptor complex are relatively slow (dissociation half-life, 17 min), in agreement with physiological studies of levamisole on Ascaris muscle strips. Levamisole derivatives and cholinergic agonists have the same relative potencies in inhibiting [3H]MAL binding as they do in causing nematode muscle contraction. Vertebrate cholinergic antagonists do not inhibit [3H]MAL binding, but several antagonists (mecamylamine, alpha-bungarotoxin, and cobra venom) potentiate the binding of [3H]MAL and can be used to demonstrate more clearly the presence of a second, lower affinity binding activity whose ligand-binding affinity is also potentiated by these agents. Both high and low affinity wild-type binding components are missing in the extremely levamisole-resistant mutant unc-74(x19).
Mol Pharmacol 1987 Feb
PMID:The levamisole receptor, a cholinergic receptor of the nematode Caenorhabditis elegans. 380 94

When Schistosoma mansoni cercariae penetrate the skin of the mammalian host they rapidly pass from fresh water to a high salt physiologic environment and transform into schistosomula. Following this transition, the parasites migrate from the skin to the lungs during which time they change from being highly susceptible to immune attack to being refractory, as measured by in vitro cytotoxicity assays. In this study, in vivo or in vitro schistosomula of different ages were examined for developmentally linked changes in membrane function which might correlate with the attainment of the resistant state. In particular, alterations in the distribution of tetraphenylphosphonium (TPP+), a synthetic lipophilic cation which shows a potential dependent partition across membranes, were followed. Three-hour-old schistosomula, which are greater than 75% susceptible to antibody-dependent complement-mediated attack or lymphokine-activated macrophage-mediated cytotoxicity, acquired TPP+ at a similar rate and steady state level to 5-day-old lung worms, which were completely resistant to both these effector mechanisms. The addition of ouabain, a Na+/K+-ATPase inhibitor, caused a 50% decrease in both the rate and steady state of TPP+ uptake by 3 h parasites but had little effect on these parameters in lung worms. Valinomycin, a K+-ionophore, completely inhibited TPP+ influx in both stages. The characteristics of TPP+ efflux from 3-h and 5-day-old parasites preloaded with the cation were found to be dissimilar. Whereas 30% of acquired TPP+ was lost from lung worms within 2 h, only 10% of acquired cation was released from 3-h schistosomula during the same period.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Biochem Parasitol 1986 Dec
PMID:Kinetic correlation of the acquisition of resistance to immune attack in schistosomula of Schistosoma mansoni with a developmental change in membrane potential. 380 46

The 31P NMR spectrum of the adult tapeworm, Hymenolepis diminuta, at 37 degrees C during perfusion with physiological saline was composed of 10 peaks. Based on chemical shifts and analysis of worm extracts, the phosphorus components included glucose-6-phosphate, fructose-6-phosphate, phosphorylcholine, glycerophosphoryl choline and -ethanolamine, nucleotide monophosphate-diphosphate and -triphosphate, nicotinamide adenine dinucleotide and uridine diphosphate glucose. The mean level of nucleotide triphosphate was 0.86 nmol (mg fresh weight)-1 and the nucleotide triphosphate/-diphosphate ratio 3.9. Based on the nucleotide triphosphate level, worms were viable for at least 3 h and the intracellular pH was maintained constant at approximately 6.7. Short-term exposure to mebendazole perfused at 11 or 27 microM solubilized in physiological saline containing 0.5% Tween 80 or 0.1% dimethyl sulphoxide had little effect on the nucleotide triphosphate level. Some cytological changes, however, were evident following perfusion of mebendazole. In contrast, exposure to 2,4-dinitrophenol caused a rapid decline in nucleotide triphosphate level. It was concluded that mebendazole does not exert its primary effect on oxidative phosphorylation.
Mol Biochem Parasitol 1987 Jan 02
PMID:In vivo 31P NMR spectrum of Hymenolepis diminuta and its change on short-term exposure to mebendazole. 380 50

DNA was introduced into the germ line of the nematode Caenorhabditis elegans by microinjection. Approximately 10% of the injected worms gave rise to transformed progeny. Upon injection, supercoiled molecules formed a high-molecular-weight array predominantly composed of tandem repeats of the injected sequence. Injected linear molecules formed both tandem and inverted repeats as if they had ligated to each other. No worm DNA sequences were required in the injected plasmid for the formation of these high-molecular-weight arrays. Surprisingly, these high-molecular-weight arrays were extrachromosomal and heritable. On average 50% of the progeny of a transformed hermaphrodite still carried the exogenous sequences. In situ hybridization experiments demonstrated that approximately half of the transformed animals carried foreign DNA in all of their cells; the remainder were mosaic animals in which some cells contained the exogenous sequences while others carried no detectable foreign DNA. The presence of mosaic and nonmosaic nematodes in transformed populations may permit detailed analysis of the expression and function of C. elegans genes.
Mol Cell Biol 1985 Dec
PMID:Extrachromosomal DNA transformation of Caenorhabditis elegans. 383 45

From the above discussion it is quite obvious that the bioenergetics in helminths are different in many ways from those found in higher organisms. All adult helminths appear to be able to consume oxygen when it is available but none of them can use it to drive the pathways of complete substrate degradation, like typical aerobic organisms, as a major strategy for energy generation. These properties hold also true for those worms residing in a highly aerobic environment, such as the blood stream or the muscle and lung tissues. Although in a number of recent studies oxygen was found to play apparently a greater role in the bioenergetics of adult helminths than originally thought, energy-generating mechanisms in adult worms seem to place greater emphasis on fermentations and anaerobic electron transport processes. These exhibit relatively low energy conservation efficiencies and result in the formation of a variety of organic end products, most of which must be excreted. The obvious correlation between the type of bioenergetic strategy operative in a particular helminth species and its environmental conditions is not well understood. The increased capacity to generate chemical energy and key metabolites of helminths possessing multiple fermentations and anaerobic respirations may give the organism greater versatility and metabolic flexibility to respond to the environmental changes observed in its corresponding habitat. Other helminths, such as schistosomes and filariids, which have continuous access to a fairly constant nutrient supply, were found to depend primarily on the more inefficiently functioning and primitive strategy of glycolysis for energy production. The reason for the occurrence in helminths of limited oxidative capacities is not completely clear. It may be assumed that the variety of alternative anaerobic pathways have evolved in response to the lack of a circulatory system and/or to the specific, often peculiar, environmental conditions prevailing in most parasitic habitats. An alternative idea put forward by Barrett [8] is that helminth metabolism represents a form of biochemical economy. Most endoparasites have an abundant supply of food and swim as if in a land of Cockain, obviously without any need to extract a maximum amount of chemical energy from the nutrients they take up. On the other hand, the fact that free-living and other larval or juvenile stages of helminths often have a typical aerobic bioenergetic pattern is a clear indication that the DNA of these organisms carries the genetic message for all the enzymes involved in complete substrate degradation.(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Biochem Parasitol 1985 Oct
PMID:The strategies of energy conservation in helminths. 390 98

Brugia malayi microfilariae and gravid adult females were examined to determine whether chitin (poly beta(1----4)-linked N-acetylglucosamine) is a structural component of the microfilarial sheath. Two lectins which are specific for beta(1----4)-linked oligomers of N-acetylglucosamine bind to the sheaths of living microfilariae. Diflubenzuron, a potent inhibitor of chitin synthesis in insects and crustaceans, causes gravid female worms to shed progeny microfilariae with truncated sheaths. A chitin-like fraction (hot alkali-insoluble and chitinase-sensitive) can be isolated from gravid female (but not male) worms. This fraction can be metabolically labelled with radioactive glucosamine, but such labelling is inhibited by diflubenzuron. These data suggest that chitin synthesis is critical to microfilarial sheath morphogenesis in this parasitic nematode.
Mol Biochem Parasitol 1985 Oct
PMID:Chitin synthesis and sheath morphogenesis in Brugia malayi microfilariae. 393 52

Metabolic pathways leading to lipid biosynthesis in four different developmental stages of Schistosoma mansoni were explored and quantified by incubation in the presence of labeled precursors in a chemically defined medium. At the schistosomulum stage and in male, female, or paired worms, glycerol and oleate incorporation into neutral lipids, mainly in the form of triacylglycerols, was greater than into phospholipids, whereas in 11-and 15-day-old worms, synthesis mainly led to phospholipids. Incorporation into phospholipids was recovered largely in phosphatidylcholine, and distribution into other phospholipids depended on the developmental stage. Incorporation of choline and ethanolamine into their respective phospholipids represented up to 15% of the parasitic phospholipid content. The formation of phosphatidylcholine by phosphatidylethanolamine methylation occurred mainly in the immature parasitic stages. Inositol incorporation was also measurable, whereas [14C]serine incorporation was low or undetectable. Addition of 1-palmitoyl-2-[14C]oleyl phosphatidylcholine revealed a very high uptake of this phospholipid by the immature stages but further metabolism was not detectable. In contrast, adult S. mansoni were completely unable to take up or absorb this exogenous phospholipid. The most striking aspect of this study was the relatively high metabolic activity in 11-day-old worms and the lower but sustained activity on day 15 and at the schistosomulum stage. By comparison, biosynthetic activity in adult S. mansoni, on which research studies have been focused until now, was very low. We also discuss the participation of lipid metabolism in the constant renewal of the membrane complex which is essential to parasitism by S. mansoni.
Mol Biochem Parasitol 1985 Nov
PMID:Renewal of the membrane complex of Schistosoma mansoni is closely associated with lipid metabolism. 393 36

A mild surface-labeling procedure was applied to various developmental stages of Schistosoma mansoni. An 18 kDa protein was preferentially labeled in freshly transformed schistosomula. The labeled protein was equally present on skin-penetrated and mechanically prepared schistosomula and it disappeared upon digestion of intact parasites with proteolytic enzymes. The 18 kDa protein could be specifically precipitated with an antiserum raised against 3-h schistosomula. Six-day lung forms also presented a single major labeled protein component, but the apparent molecular weight of this protein in acrylamide gels was higher than 18 000. Fourteen-day-old and adult schistosomes showed only weak labeling distributed in several bands. The radioactivity pattern of adult worms (but not of schistosomula) could also be obtained by incubating fresh parasites in a medium which had previously been used to label schistosomes and to which a 100 000-fold excess of 127I over 125I had been added. Post-labeling incubation of parasites was found to be essential for the detection of stable surface proteins.
Mol Biochem Parasitol 1986 Jan
PMID:A surface-labeled 18 kilodalton antigen in Schistosoma mansoni. 396 50

A technique employing Sephadex G25 gel filtration has been developed for the rapid isolation and purification of live microfilariae of Onchocerca volvulus from subcutaneous nodules and skin samples. Microfilariae, adult worms and L3 larvae have been surface radiolabelled using the Iodogen technique. Two proteins have been characterised on the surface of uterine microfilariae: these have apparent molecular weights of 14,800 and 15,000. A MW 15,000 protein was the only molecule labelled on the surface of skin microfilariae. Ten proteins were labelled on adult male worms: these have molecular weights of 15,000, 17,500, 20,000, 22,000, 24,000, 29,000, 32,000, 37,000, 42,000, and 50,000. Some, if not all, of these proteins were also identified on female worms. Seven proteins were labelled on the surface of L3 larvae: these have molecular weights of 17,500, 48,000, 50,000, 52,000, 54,000, 57,000, and 105,000. Three of the adult surface proteins were precipitated by selected human infection serum: these are the MW 17,500, 32,000 and 42,000 molecules. The microfilarial surface proteins were not precipitated by human infection serum. The antiserum used in these experiments was shown by Western blot analysis to contain high levels of antibody with specificity for microfilarial and adult antigens. Indirect immunofluorescent assays showed these sera to contain antibody which bound to the surface of adult worms and eggs but not microfilariae. The possibility that skin microfilariae absorb host serum albumin was investigated: Western blot analysis and surface immunofluorescence assays using a specific anti-human albumin serum gave negative results. Fluorescent lectin binding studies revealed the presence of stage-specific carbohydrate moieties exposed on the surface of adult worms and eggs. Microfilariae do not have surface carbohydrate determinants.
Mol Biochem Parasitol 1986 Mar
PMID:Surface components of Onchocerca volvulus. 396 55


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