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Biomedical subjects

R S Bray

Publications and source records attributed to R S Bray.

14 recordsLinked to original sources
PubMed1979

Falciparum malaria and pregnancy.

During pregnancy an increase occurs in the prevalence and density of Plasmodium falciparum malaria. The increase relative to non-pregnant women remains fairly constant with age though there is an over-all decrease in prevalence and density in both groups with age. The increase is at a height relatively early in pregnancy and declines after mid-term. At the height of the malaria season in The Gambia less antimalarial antibody appears in cord bloods than in the early dry season when transmission is lower. Infants show an increase in malaria prevalence and density in the early dry season as compared to the mid-wet season while the remainder of the population shows a decrease.

Adult↗
PubMed1979

Direct Coombs antiglobulin reactions in Gambian children with Plasmodium falciparum malaria. I. Incidence and class specificity.

Gambian children with past or present Plasmodium falciparum malaria were investigated for the incidence of Coombs positivity using monospecific antisera. Approximately 50% were positive and the most frequent form of erythrocyte sensitization was with C3d. Other specificities, EIgG, EIgGC3d and EIgGC4bC3d were less common. Erthyrocytes were never found sensitized with IgA or IgM. There was no correlation between a positive test and age, tribal status or level of parasitaemia at presentation, although a positive test was often found in association with anaemia. Sensitized erythrocytes were present in the circulation for a period of up to 6 weeks following initial observation. The mechanism of erythrocyte sensitization is not known, but the results suggest a Type III complex-mediated hypersensitivity involving parasite antigen-antibody complexes. It is likely that these reactions contribute to the pathogenesis of the anaemia in falciparum malaria.

Anemia↗
PubMed1977

The epidemiology of infection with Entamoeba histolytica in the Gambia, West Africa.

A country-wide stool survey of The Gambia showed the prevalence of Entamoeba histolytica cysts to range from 13.7% up-country in the dry season to 52.3% near the coast. A longitudinal survey showed a near 100% infection rate over one year and a sharp rise in prevalence as the rains commence with an equally sharp fall as the rains progress. Specific antibody levels are elevated and reasonably constant through the year. Carriers generally show no specific lymphocyte reactivity to amoebic antigen but consistently parasite-negative individuals tended to show elevated lymphocyte reactivity. Attempts to discover the presence of cysts in the environment of villages by cultivation of specimens of water, soil, food, flies and washing from clothes and hands generally failed though E. histolytica was recovered once from a well.

Amebiasis↗
PubMed1977

Cellular immune responses to amoebic liver abcess in the guinea-pig.

Guinea-pigs infected in the liver with the Biswas strain of Entamoeba histolytica showed no dermal hypersensitivity but showed positive lymphocyte transformation and macrophage-migration inhibition. The time sequence showed an activated response at 4 days after infection, a full response at 8 days when the liver abscesses were resolving and a waning response at 12 days when the abscesses had healed.

Animals↗
PubMed1975

A strain of Plasmodium vivax characterized by prolonged incubation: morphological and biological characteristics.

Numerous strains of P. vivax, distinguishable chiefly by their biological characteristics, are known to exist. Two main varieties are recognized: the so-called temperate and tropical strains. The most extreme example of the former-designated by Nikolaev as P. vivax hibernans-constantly exhibited an extremely long incubation period. The strain is no longer in existence and no type material has been preserved. In its place, a North Korean strain with a generally long incubation period has been studied and compared with the well-known tropical Madagascar strain, which frequently but not constantly has a short incubation period. The data presented here concern the behaviour of various strains from the USSR and the morphological characteristics of the North Korean and Madagascar strains. Splenectomized chimpanzees were used as the host of these parasites, particularly in regard to exoerythrocytic schizogony. Attempts were also made, by late biopsies of the liver of the apes, to elucidate the prolonged latency of the North Korean strain. Although there was no evidence of specifically dormant forms, it is probable that certain sporozoites fail to develop in the normal time and that they are reactivated by an unknown factor a year or more after inoculation.

Animals↗