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Biomedical subjects

M G Taylor

Publications and source records attributed to M G Taylor.

At least 109 records · Page 6Linked to original sources
PubMed1981

Reliability of nitroxide spin probes in reporting membrane properties: a comparison of nitroxide- and deuterium-labeled steroids.

The reliability for the study of membrane properties of the steroid nitroxide spin probe, 3-doxylcholestane, was tested by comparison of analogous data for the deuterated steroid, cholesterol-3 alpha-d. Good agreement between the two probes was found for the dependence of their order parameters on variation of temperature or cholesterol concentration in egg phosphatidylcholine bilayers. This finding is contrasted with the results of a previous study of fatty acid probes where poor agreement was found for the spectral responses of nitroxide- and deuterium-labeled species. The angular dependence of the ESR spectra of nitroxide-labeled probes in oriented multibilayer films was examined to determine if the probes were oriented in a tilted fashion in the bilayer. The 3-doxylcholestane probe and a doxylstearic acid labeled at position 14 orient with their long molecular axes perpendicular to the bilayer plane. In contrast, the stearic acid probe nitroxide labeled at position 5 does not appear to orient in such a fashion. We suggest that the behavior of the latter probe reflects the difficulty of inserting a bulky nitroxide group into a highly ordered region of the bilayer rather than an inherent tilting of the phospholipid acyl chains. On the basis of the comparisons between various types of probes, some suggestions are made concerning the choice of ESR spin probe to obtain reliable information in membrane studies.

Cholesterol↗
PubMed1980

Observations on cattle schistosomiasis in the Sudan, a study in comparative medicine. I. Epizootiological observations on Schistosoma bovis in the White Nile Province.

A 2-year epizootiological study was carried out on Schistosoma bovis in cattle in an enzootic area of the Sudan. The prevalence of infection, as judged by the Pitchford fecal egg counting technique, was very high, approaching 90% in 1.5-year-old animals. There was, however, a lower prevalence in older cattle, and this trend was also seen with the fecal egg counts. This suggests that the cattle gradually acquire resistance to reinfection, particularly since there seems to be little age-related variation in the amount of water contact. Monthly incidence rates, estimated from fecal examinations of initially uninfected "tracer" calves showed a marked seasonal pattern, being much higher in the hot summer months, and snail infection rates showed a similar seasonal pattern. In addition, both the monthly incidence measurements and the snail infection rates showed that transmission was much heavier in 1976 than in 1977. Epizootics such as those recorded previously in this area presumably arise from exceptionally intense transmission years.

Animals↗
PubMed1980

Observations on cattle schistosomiasis in the Sudan, a study in comparative medicine. II. Experimental demonstration of naturally acquired resistance to Schistosoma bovis.

Epizootiological observations on Schistosoma bovis in cattle at Kosti, Sudan, showed a significant fall in age-specific prevalence and intensity with age, based on fecal egg count. To test the possibility that this is due to acquired resistance, Kosti cattle and a control group of cattle of similiar breed and age from a nonenzootic area were experimentally challenged with 70,000 S. bovis cercariae. Clinical observations showed very clearly that the Kosti cattle were able to withstand almost completely the effects of the challenge, whereas the controls developed lethal infections. Resistance was further demonstrated by clear differences between the two groups in terms of their body weights, hematological measurements, histopathological and pathophysiological responses, and worm and egg counts. The data suggested that the main basis of the resistance was a suppression of egg production by the worms from the challenge, rather than absolute prevention of their maturation. There was also evidence of a suppression of the fecundity of worms in the naturally infected Kosti cattle.

Animals↗
PubMed1980

Observations on cattle schistosomiasis in the Sudan, a study in comparative medicine. III. Field testing of an irradiated Schistosoma bovis vaccine.

Previous work has shown that cattle can acquire a strong resistance to Schistosoma bovis infection following repeated natural exposure. Partial resistance to a laboratory challenge with S. bovis has also been demonstrated in calves after immunization with an irradiated schistosomular or cercarial vaccine. The aim of the present study was to see whether this type of vaccine could protect calves under the very different conditions of natural exposure to S. bovis in the field. Thirty 6- to 9-month-old calves were each immunized with 10,000 irradiated S. bovis schistosomula by intramuscular injection and 8 weeks later were released into an enzootic area along with 30 unvaccinated animals. The calves were followed up for 10 months, during which period protection was evidenced by a lower mortality rate, a slower rate of acquisition of infection, and lower fecal egg counts in the vaccinated calves. Necropsy of the survivors showed 60--70% reductions in worm and tissue egg counts of the vaccinated calves as compared to those not vaccinated.

Animals↗
PubMed1980

Schistosoma bovis in calves: the development and clinical pathology of primary infections.

The clinico-pathological effects of Schistosoma bovis were monitored in zebu calves for a year after exposure to 100 or 200 cercariae/kg body weight and were related to the number and reproductive activities of the parasites present. The disease was characterised by diarrhoea, weight loss or poor weight gain, anaemia, serum protein changes and eosinophilia. These changes were broadly related to the level of infection and were most prominent during the two months following patency when faecal egg counts were highest. Subsequently, the condition of most animals improved. This was associated with a marked reduction in faecal egg excretion which in turn was related to worm deaths, reduced worm fecundity and egg retention in the tissues.

Animals↗
PubMed1979

Further observations on immunization of sheep against Schistosoma mansoni and S. bovis using irradiation-attenuated schistosomula of homologous and heterologous species.

This paper describes further characteristics of the immunization of sheep against schistosomes using live, irradiation schistosomula. Sheep immunized with a non-virulent strain of Schistosoma mattheei were protected against a more virulent strain of the same species for over a year. As there was no evidence that the irradiated parasites were able to persist this long, it was concluded that the vaccine had induced a sterile resistance. Heterologous vaccination, using irradiated S. mattheei schistosomula to immunize against S. bovis or irradiated S. mansoni schistosomula to immunize against S. mattheei, failed to induce any protection.

Animals↗
PubMed1979

Immunization of mice with gamma-irradiated intramuscularly injected schistosomula of Schistosoma mansoni.

The parameters involved in the induction of resistance against Schistosoma mansoni by injection of irradiated, artificially transformed schistosomula were studied in mice. Single intramuscular injections of 500 schistosomula exposed to radiation doses in the range 2.3 to 160 krad. resulted in significant protection (in the range 20 to 50% as assessed by reduced worm burdens) against a challenge infection administered at intervals from 3 to 24 weeks post-vaccination. However, schistosomula irradiated with 20 krad. consistently resulted in better protection than those exposed to either higher or lower radiation doses despite the persistence of stunted adults from the infections irradiated with 2.3 krad. Vaccination with 40 krad. schistosomula resulted in significant protection in terms of reduced worm and tissue egg burdens and increased survival following lethal challenge. Varying the number of irradiated schistosomula, the frequency and route of their administration, the site of challenge and the strain of host all failed to enhance the level of resistance. However, percutaneously applied, irradiated cercariae were found to be more effective in stimulating resistance (60%) than intramuscularly injected, irradiated schistosomula (40%).

Animals↗