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Biomedical subjects

D B Copeman

Publications and source records attributed to D B Copeman.

At least 55 records · Page 3Linked to original sources
PubMed1988

Reproduction in female Onchocerca gibsoni.

The embryonic stages in the uteri of adult female Onchocerca gibsoni were studied to determine the reproductive potential of this worm. It was concluded that female O. gibsoni undergo cyclic phases of reproduction, each lasting about 14.5 weeks. Once insemination occurred and a cycle commenced, the rate of embryonic development was reasonably constant irrespective of the age of the worm. Mature young females had fewer embryos than older females but both contained a similar proportion (about 19%) of abnormal embryos. In comparison to the older female worms, a greater proportion of mature young females were in the early phase of a reproductive cycle and fewer were actively reproducing. This difference was considered to be due to a greater access of males to older than to recently mature females. There were marked similarities between these observations with O. gibsoni and those reported for O. volvulus, providing further evidence of the usefulness of O. gibsoni as a model for O. volvulus.

Animals↗
PubMed1988

An evaluation of implanted male Onchocerca gibsoni in mice as a screen for macrofilaricides against Onchocerca volvulus.

An in vivo drug screen for identifying new compounds with activity against Onchocerca macrofilariae was developed using male Onchocerca gibsoni implanted subcutaneously in outbred mice. There were several similarities (Mel W, CGP 20376, CGP 6140, levamisole) and two differences (suramin, furapyrimidone) between levels of drug efficacy in this model and activity against natural infections of O. gibsoni and O. volvulus. There was considerable variation in the mouse reaction. This mouse model is a potentially useful primary screen for macrofilaricidal drugs against Onchocerca.

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PubMed1987

Electron-microscopic observations on the female worms of six Onchocerca species from cattle and red deer.

The midbody regions of female worms of six Onchocerca species (O. flexuosa, O. tarsicola, O. lienalis, O. gutturosa, O. armillata, O. gibsoni) were studied by transmission electron microscopy. The cuticular layering was rather similar in all species with the ridges built up by the cortical layers and the inner cuticular striations by the median or basal layers. Differences in the epicuticular morphology were considerable. O. flexuosa and O. lienalis had a thin epicuticle without protuberances, the epicuticle of O. armillata carried small knobs, and O. tarsicola, O. gutturosa, and O. gibsoni had a thick trilaminar epicuticle with long protuberances. Extreme hypertrophy of hypodermis and reductions of somatic musculature were observed in O. flexuosa and O. gibsoni. Less extended thickenings of the hypodermis were observed in the other species. No degenerative alterations were found in the muscle cells of O. gutturosa and O. lienalis. The intestinal lumen of most of the species was in a central position, but in O. tarsicola and O. gibsoni the lumen was reduced to small clefts between the intestinal cells. In these species, numerous electron-dense, concentric granules were observed in the cytoplasm of the intestinal cells. The proportions of the various organs differed considerably from species to species, e.g., the uteri contained the embryos filed one behind the other in O. tarsicola, whereas 50 or more embryos were found beside one another in cross-sections of the uterus of O. gibsoni. The comparative study showed that O. gibsoni and O. volvulus have many derived morphological characteristics in common and that in the other species more primitive stages of development of these morphological marks can be observed.

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PubMed1987

In vitro drug screening in isolated male Onchocerca gibsoni using motility suppression.

A primary in vitro screen was developed to screen for drug activity against isolated Onchocerca gibsoni. The assay estimates variation in motility through the use of a motility meter. Of the seven compounds tested in the screen; ivermectin, CGP 6140, CGP20376, Mel W and furapyrimidone gave MI50 concentrations (the concentration at which the motility was reduced to 50% of the control value at 72 hours) below 10(-4) M, whereas suramin gave variable results depending on the varying susceptibility of individual worms and levamisole at 10(-4) M had no significant effect on the worms. The effects of these drugs were not reversible as removal of the worms into drug-free medium caused no increase in motility. Thus the reduction in motility is regarded as indicating significant metabolic damage. The results compared favourably with reported in vivo tertiary screens for activity against Onchocerca species. This is a quantitative, inexpensive and reproducible method for assessing the effectiveness of drugs against Onchocerca and could be included into the primary screens for activity against filarial worms.

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PubMed1986

Onchocerca gutturosa and Onchocerca lienalis in cattle: effect of age, sex, and origin on prevalence of onchocerciasis in subtropical and temperate regions of Florida and Georgia.

Evaluation of 845 cattle from Florida and Georgia for onchocerciasis indicated a significantly higher prevalence of infection with Onchocerca gutturosa and a significantly lower prevalence of infection with Onchocerca lienalis in the southern portion of Florida (subtropical region) than in the northern portion of Florida or in Georgia (temperature region). In all regions, prevalence of infection with O gutturosa was significantly higher than infection with O lienalis. In the temperate region, bulls were infected more often with O lienalis than were cows. Other sex-related differences in infection with either filariid was not found. Prevalence of infection with O lienalis was similar between age groups in all regions. Rates of infection with O gutturosa differed between age groups within and between subtropical and temperate regions. Examination of cervical and umbilical skin specimens for microfilariae detected an additional 6.6% of infected animals that had not been found by examination for adult worms. However, microfilariae were not found in 21.4% of animals that were positive for adult worms.

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PubMed1984

Onchocerca gibsoni: increase of circulating egg antigen with chemotherapy in bovines.

Monoclonal antibodies directed to stage-specific surface antigens of Onchocerca gibsoni eggs were used in immunoradiometric assays to detect antigens in the sera of cattle infected with O. gibsoni. Two monoclonal antibodies detected antigens, presumably of egg origin, in sera. The target antigens appeared to be carbohydrate in nature and of variable molecular weights. Significant increases in levels of circulating egg antigens were found after treatment of infected cattle with benzimidazole compounds. These drugs cause disruption of embryogenesis and accelerated loss of worm uterine contents. In contrast, administration of either macrofilaricides or microfilaricides to infected cattle did not alter pretreatment levels of circulating egg antigens. Measurement of changes in levels of circulating antigens by immunoradiometric assays with stage-specific monoclonal antibodies provides a new means of assessing the efficacy of drugs and their site of action in onchocerciasis.

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PubMed1984

Differences in the surface radioiodinated proteins of skin and uterine microfilariae of Onchocerca gibsoni.

Surface labeling studies using two populations of Onchocerca gibsoni microfilariae revealed important differences in major radioiodinated proteins. Small numbers of microfilariae harvested from the skin of cattle or the uteri of adult worms from skin nodules were purified, radioiodinated, solubilized and the proteins analysed by two dimensional gel electrophoresis and autoradiography. As reported previously, uterine microfilariae showed a complex profile of radioiodinated proteins, none of which appeared to be bovine albumin or immunoglobulin. In contrast, application of the same techniques to skin microfilariae demonstrated only one major labeled protein complex of approximate Mr 67 000. This protein complex was immunoprecipitated with an antiserum to bovine serum albumin. Surprisingly, fluorescence techniques failed to show bovine serum albumin on the surface of living microfilariae. Although the evidence is circumstantial at present, acquisition of host albumin (perhaps oriented in a particular way) may be a means whereby skin microfilariae evade immune effector mechanisms and, when living, generally fail to elicit inflammatory reactions in the skin of the host.

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PubMed1981

Identification of radioiodinated cuticular proteins and antigens of Onchocerca gibsoni microfilariae.

The filarial parasite of cattle, Onchocerca gibsoni, has been used to establish procedures of antigen identification with a view of applying these techniques to studies on human filarial parasites. Emphasis has been placed on methods suitable for use with small numbers of parasites. Microfilariae (mf) of O. gibsoni were extracted from nodular worms, purified and 125I-labeled using IODO-GEN in solid-phase. Radioactivity was shown to be confined to the cuticle of sectioned mf using the technique of electronmicroscope autoradiography. Radiolabeled mf were analysed by two-dimensional gel electrophoresis. Autoradiographs of 125I-labeled proteins of O. gibsoni mf were relatively complex, there being at least 32 proteins ranging in molecular weights from 20,000 to 120,000 and displaying considerable charge heterogeneity. Evidence was obtained that at least the major serum proteins of the host, albumin or immunoglobulin, were not absorbed on the surface of these uterine mf and detectable in the labeled surface protein patterns. Sera from infected cattle immunoprecipitated 5 labeled proteins from a Triton X-100 extract of 125I-labeled mf. Sera from either of two calves which had been given multiple injections of mf subcutaneously, and which had no detectable skin mf, recognised 6 additional proteins in this extract as well as 3 of the proteins recognised by sera from infected cattle.

Animals↗
PubMed1981

The major radioiodinated cuticular antigens of Onchocerca gibsoni microfilariae are neither species nor onchocerca specific.

The possible role of microfilarial surface (cuticular) antigens in immuno-diagnosis of human filarial infections has been assessed using microfilariae (mf) of the cattle parasite Onchocerca gibsoni. A Triton X-100 extract of 125I-labeled O. gibsoni mf was reacted with a panel of sera from humans infected with Onchocerca volvulus, Wuchereria bancrofti and Schistosoma japonicum as well as sera from uninfected controls. Results of these immunoprecipitations indicated that sera from humans infected with O. volvulus or W bancrofti contain antibody specificities recognising certain of the radioiodinated cuticular proteins of O. gibsoni mf. Two-dimensional gel analysis and subsequent autoradiography of these immunoprecipitates showed that 8 radioiodinated proteins recognised by sera from calves injected with O. gibsoni mf were also immunoprecipitated by sera from humans infected with either O. volvulus or W. bancrofti. Thus there appear to be no major radioiodinated cuticular antigens of O. gibsoni mf which are species or onchocerca specific.

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