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

The methods used for the assessment of adult Onchocerca volvulus by histology are described. Based on the results of several studies, mainly in Liberia and Burkina Faso, the morphology of the adult filariae in histological sections is represented as far as it is relevant for the evaluation. Especially are described the morphological alterations due to old age of the worms, to chronic hyperreactivity of the human host (sowda) and effects of the macrofilaricidal suramin and of microfilaricidal drugs. Quantitative results are reported on untreated adult O. volvulus from various countries, the changes of the worm population during 12 years of vector control in Burkina Faso and the effects of suramin, diethylcarbamazine, metrifonate, and ivermectin. The data from the histological examinations are compared with those gained from the examination of worms isolated by the collagenase technique in the same studies.
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PMID:Histological examination of adult Onchocerca volvulus and comparison with the collagenase technique. 285 93

The collagenase technique developed more than twelve years ago has successfully been applied to isolate living and intact O. volvulus from excised onchocercomata for various biological, morphological, biochemical, immunological and in vitro studies. The experience gained with this technique and its modifications is critically reviewed giving practical advice for the selection, preservation and treatment of nodules for different purposes, especially for the evaluation of antifilarial drug effects. The composition of the worm load, the morphology of adult worms found in untreated patients, signs of degeneration and ageing of worms are described to show the broad morphological spectrum of the worm population in endemic areas to avoid false conclusions in drug trials. When these parameters are carefully considered, the collagenase technique provides a reliable method for examination of onchocercomata. An immediate answer can be obtained concerning the viability of the parasite. The qualitative and quantitative assessment of reproduction (embryogram) can give further valuable information on any changes in the reproductive dynamics and provide a sensitive indicator of any disturbances in the adult worms which may explain the early or late reinvasion of microfilariae into the skin after treatment with microfilaricidal drugs.
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PMID:The collagenase technique: how to isolate and examine adult Onchocerca volvulus for the evaluation of drug effects. 285 94

Instructions are provided for selection of nodules, isolation of female Onchocerca volvulus and shipping to obtain suitable, intact and live worms for drug-screening and metabolic studies in vitro as well as material for isolation of enzymes, receptors, antigens etc.
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PMID:Preparation and shipping of Onchocerca volvulus material. 285 95

Observations were made on the spontaneous motility in vitro of entire adult worms and segments of Onchocerca volvulus, Brugia pahangi and Acanthocheilonema viteae. Segment motility was recorded in a mechano-transducer apparatus and responses of worm tissues to anthelmintics and other pharmacological agents were compared. Entire adult female O. volvulus showed varied patterns of motor activity, ranging from continuous low level whole body motion to periodic spasmodic contractions interspersed between intervals of quiescence lasting from a few to 30 seconds. The same range characterized movements of 1.5-4 cm segments cut from worms liberated from collagenase digested nodules. However, fresh segments dissected directly from surgical specimens were completely inactive due to the paralyzing effect of xylocaine, used as local anesthetic. This effect wore off in 2-5 hours in vitro, and recovered segments behaved in the same way as those from enzymatically liberated worms. Segments of B. pahangi and A. viteae also showed motor activity patterns which reflected those of whole adults. Segments of O. volvulus behaved reproducibly, whether examined in the field in endemic areas, or after transport of nodules or freed worms to Michigan from Guatemala or Sudan. Segments of all worms were unresponsive to most anthelmintics, but O. volvulus was susceptible to paralysis by CGP 6140, levamisole, pyrantel and carbachol at concentrations of ten to a thousand times lower than those required to produce any influence on B. pahangi. Segments of A. viteae more closely resembled O. volvulus in their dose responses to these drugs, although CGP 6140 was without effect.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:In vitro motility of isolated adults and segments of Onchocerca volvulus, Brugia pahangi and Acanthocheilonema viteae. 285 96

A range of culture conditions were examined to optimize parasite maintenance. Using male worms in a cell-free system, good results were obtained with medium NCTC 135 + 10% inactivated calf serum (IFCS) in an atmosphere of 95% N2/5% CO2 (median survival time 45 days). Survival was increased to 6-7 months using medium MEM + 10% IFCS + LLCMK2 (monkey kidney) feeder cells in a gas phase of 5% CO2 in air. Worms exposed to collagenase solution (5 mg/ml) were subsequently less motile and survived shorter periods compared to unexposed controls. The drug responses of worms (in vitro) were examined using 13 antiparasitic compounds. Ivermectin and CGP 6140 were among the most active, with the majority of drugs significantly affecting motility levels at a concentration of 5 x 10(-5) M or less. This system may provide useful information on the intrinsic activity of new compounds. A technique was developed for the successful cryopreservation of males in liquid nitrogen using ethanediol as a cryoprotectant in a 2-step incubation procedure, thereby enabling the long-term storage and transportation of worms. In conclusion, the common bovine parasite O. gutturosa provides a practical alternative for research in the absence of O. volvulus.
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PMID:The development of a laboratory model for onchocerciasis using Onchocerca gutturosa: in vitro culture, collagenase effects, drug studies and cryopreservation. 285 98

In an attempt to describe the changing population dynamics of Onchocerca volvulus during a period of vector control, nodulectomies were undertaken in 256 patients from ten villages in the Onchocerciasis Control Programme (OCP) and in 74 patients from two villages in an area with ongoing transmission. A total of 1198 nodules were excised and 4350 adult worms were isolated and examined for viability and productivity. In the OCP villages, the worm population is ageing and dying without replacement by new generations of parasites and various findings signal a breakdown of the worm population after about 12 years interruption of transmission. The sexual activity of the worms was significantly reduced. A Productivity Index was developed to measure the microfilariae production at the nodule level. The reduction in this index for the OCP villages correlates closely with the decline over the control period in the community microfilarial loads in the skin. The results show that it is not only the longevity of the parasite which will determine the duration of vector control, but that the reduced productivity of the ageing parasite population is of equal importance.
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PMID:Population dynamics of Onchocerca volvulus after 7 to 8 years of vector control in West Africa. 289 34

Phosphoenolpyruvate carboxykinase, a rate-limiting enzyme at the branchpoint of phosphoenolpyruvate (PEP), was demonstrated in Onchocerca volvulus and O. gibsoni. The activity of PEP-carboxykinase from both filarial worms depends absolutely on the presence of divalent cations; in addition to Mg2+ the enzyme activity was strongly activated by Mn2+. The Michaelis constants for PEP, GDP and KHCO3 of the PEP-carboxykinase from O. volvulus were determined to be 0.16 mM, 0.15 mM and 20 mM, respectively; those of the enzyme from O. gibsoni were 0.16 mM, 0.13 mM and 12 mM. Quinolinate was found to be a potent inhibitor of the enzyme from both filarial worms. The inhibition constants were determined to be 11 microM and 15 microM for the enzyme from O. volvulus and O. gibsoni. It is suggested that the activity of PEP-carboxykinase, the initial enzyme of the alternate route from PEP to succinate, may be regulated by ATP-levels. The inhibition constants for ATP were determined to be 0.26 mM and 0.13 mM for the enzyme from O. volvulus and O. gibsoni.
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PMID:Phosphoenolpyruvate carboxykinase from Onchocerca volvulus and O. gibsoni. 295 41

The presence of 5'-nucleotidase was demonstrated in Onchocerca volvulus and Dirofilaria immitis; the bulk of activity was found in the particulate fraction. The enzyme of filarial worms exhibited a broad pH-optimum between 6.4 and 8.0 and substrate specificity for nucleotides compared to glucose-6-phosphate and p-nitrophenyl phosphate. The apparent Km-values for AMP were found to be 0.15 mM and 0.22 mM for the enzyme from O. volvulus and D. immitis, respectively. The activity of 5'-nucleotidase from both filarial worms was effectively inhibited by the filaricidal compound CGP 8065, a dithiocarbamate-derivative of amoscanate, whereas the 5'-nucleotidase from rat liver was not affected. The parasite-specific inhibition by CGP 8065 was found to be reversible and to be competitive with respect to the substrate AMP. The inhibition constants were calculated to be 24 microM and 8 microM for the enzyme from O. volvulus and D. immitis, respectively.
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PMID:Parasite-specific inhibition of 5'-nucleotidase from Onchocerca volvulus and Dirofilaria immitis by the amoscanate-derivative CGP 8065. 299 82

Very young, middle-aged and old macrofilariae of Onchocerca volvulus were isolated alive or intact from onchocercomata using the collagenase digestion technique and studied by transmission electron microscopy. The body wall and the internal organs showed a well preserved morphology and no differences were detected compared with worms which had not been in contact with collagenase solution.
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PMID:The fine structure of adult Onchocerca volvulus recovered by collagenase digestion. 300 15

The composition of proteins and antigens of female Onchocerca volvulus from one focus of transmission was studied by SDS-PAGE and immunoblotting. Worms that had been exposed to collagenase digestion of onchocercomata for different periods of time and parasites of different age and status of reproduction were tested. Some O. volvulus antigens were found to be sensible to prolonged digestion (molecular weights: 18 KD, 21 KD, 24 KD) but the majority of the antigens was stable up to 64 hours of incubation at 34 degrees C. The composition of proteins and antigens varied with the age and the status of reproduction of the worms. Slight differences between individual filariae were found, even when worms of comparable age and status of reproduction were tested that had been exposed to nodule digestion for comparable time.
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PMID:Studies on the protein and antigen composition of individual female Onchocerca volvulus after collagenase digestion. 300 80


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