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Biomedical subjects

R W Snow

Publications and source records attributed to R W Snow.

At least 109 records · Page 6Linked to original sources
PubMed1988

Comparison of two strategies for control of malaria within a primary health care programme in the Gambia.

Two drug strategies for the control of malaria in children aged 3-59 months have been compared in a rural area of The Gambia--treatment of presumptive episodes of clinical malaria with chloroquine by village health workers, and treatment combined with fortnightly chemoprophylaxis with 'Maloprim' (pyrimethamine/dapsone) which was also given by village health workers. Treatment alone did not have any significant effect on mortality or morbidity from malaria. In contrast, treatment and chemoprophylaxis reduced overall mortality in children aged 1-4 years, mortality from probable malaria, and episodes of fever associated with malaria parasitaemia. A high level of compliance with chemoprophylaxis was obtained and no harmful consequences of chemoprophylaxis were observed.

Antimalarials↗
PubMed1988

Permethrin-treated bed nets (mosquito nets) prevent malaria in Gambian children.

The incidence of clinical attacks of malaria was significantly less in Gambian children aged 1-9 years who slept in villages where all the bed nets (mosquito nets) were treated with permethrin than in children who slept in control villages with placebo-treated nets. Significant differences in changes in spleen size and in packed cell volume were also observed between the 2 groups during the course of a rainy season. No side effect was noted. Treatment of bed nets with insecticide is a form of malaria control that is well suited to community participation and can readily be incorporated into primary health care programmes. Insecticide-treated nets may be more effective in areas of seasonal or low intensity transmission than in areas with heavy perennial challenge.

Animals↗
PubMed1988

Immunity to malaria in young Gambian children after a two-year period of chemoprophylaxis.

A cohort of 48 Gambian children was protected against malaria by fortnightly administration of Maloprim (pyrimethamine and dapsone) for 2 years between their 3 and 5 birthdays. A matched cohort of 47 children received placebo. During the year following the termination of prophylaxis there was no increase in the frequency of clinical attacks of malaria in the protected children compared with the control children. Antibody levels to circumsporozoite protein were measured by a radioimmunoassay and that to blood-stage antigens by a variety of techniques including an ELISA to whole blood-stage Plasmodium falciparum antigen, immunofluorescent assays (IFAT) to acetone fixed, glutaraldehyde fixed and unfixed parasites, a merozoite inhibition test and an opsonizing assay. Antibody levels were, in general, lower in protected than in control children and several differences between the two groups were statistically significant. When antibody levels were measured by ELISA and IFAT at the end of the following rainy season, when malaria transmission was intense, those in protected children had increased to comparable levels to those found in control children. Our findings suggest that chemoprophylaxis given for 2 years lowers malaria antibody levels but that it does not interfere with the development of protective immunity.

Animals↗
PubMed1988

A trial of bed nets (mosquito nets) as a malaria control strategy in a rural area of The Gambia, West Africa.

An intervention trial was undertaken in a rural area of The Gambia to assess the impact on malaria morbidity of the use of bed nets. Bed nets were allocated at random among a group of 16 Fula hamlets, where they were previously rarely used. The incidence of febrile episodes with associated malaria parasitaemias throughout the rainy season and the prevalence of splenomegaly and parasitaemia at the end of the rainy season were determined in 233 children aged 1-9 years who slept under bed nets and in 163 children who did not. Bed nets were used correctly by the children in the study cohort, but direct observations showed that a significant number of children left their nets for a period during the night. There was no significant difference in the incidence of clinical attacks of malaria or in any other malariometric measurement between the 2 groups. Thus, bed nets were not effective in reducing malaria morbidity in this group of children. The apparent protection from bed nets demonstrated in previous retrospective surveys may have been due to an increased number of infective bites being received by exposed individuals sleeping close to users of bed nets.

Child↗
PubMed1988

T cell reactivity of defined peptides from a major Plasmodium falciparum vaccine candidate: the Pf155/RESA antigen.

Several immunodominant B-cell epitopes of the P. falciparum antigen blood stage Pf155/RESA, a major vaccine candidate antigen, are located in the molecular regions containing amino acid repeats. We started to map Pf155/RESA for T cell reactive epitopes. For this purpose, short synthetic peptides corresponding to the 3'- and 5' repeat regions of the molecule as well as to non-repeated sequences outside these regions were prepared. T cells from P. falciparum primed donors from two highly endemic areas of Africa were tested for their responsiveness to the peptides by thymidine incorporation and/or interferon gamma (IFN-gamma) release. There was a considerable variation in the response to the different peptides. However, the strongest and most frequent responses were seen with a few peptides from the 3'- and 5'-repeat regions. Thus, the immunodominant B cell epitope regions of Pf155/RESA, contain several T cell epitopes. Since the repeat regions are known to be conserved in different P. falciparum strains, the T cell epitopes reported here may be suitable constituents of a P. falciparum subunit vaccine.

Animals↗
PubMed1988

Sociodemographic characteristics and drinking locations of convicted drunken drivers.

The present study utilizes multiple regression analysis to identify relationships between 13 sociodemographic characteristics and the frequency of drinking in seven different types of drinking places among convicted drunken drivers (N = 6,183). The results indicate that different sociodemographic subgroups of drinking drivers tend to drink in different types of places. Younger respondents were more likely than older respondents to report frequent drinking in away-from-home locations such as friends' homes, bars, parties, cars, and parking lots. The males were more likely than the females to report frequent drinking in cars and parking lots, and unmarried respondents drink at parties and in bars more frequently than married respondents. Education, race, and the frequency of worship service attendance are also found to be important predictors of drinking locations.

Adult↗
PubMed1987

Presynaptic and postsynaptic effects of histamine and histamine agonists in the superior cervical ganglion of the rat.

Extracellular and intracellular recording techniques were used to study the effects of histamine and the histamine agonists [impromidine (IMP) and 2-thiazolylethylamine (2-TH)] on synaptic transmission in the superior cervical ganglion of the rat in vitro. At the concentrations employed (up to 10(-5) M) these compounds did not produce detectable effects on the electrical properties of the postsynaptic neurons. Histamine produced a dose-dependent reduction in the amplitude of the extracellularly-recorded presynaptic and postsynaptic compound action potential. The H2 receptor agonist impromidine reduced only the postganglionic compound action potential. Cimetidine, a specific H2 receptor antagonist, produced parallel shifts in the log dose-response curves for impromidine. Impromidine also reduced the average size of the evoked excitatory postsynaptic potential. The reduction of the mean amplitude of the excitatory postsynaptic potential was due to a decrease in the amount of acetylcholine (ACh) liberated by each preganglionic volley (mean quantal content, m) and a diminution in quantal size. The H1 receptor agonist, 2-TH produced a dose-dependent increase in the presynaptic and postsynaptic compound action potential and in m. The increase in m was not associated with changes in quantal size. The H1 antagonists, pyrilamine and promethazine, did not prevent facilitation of ganglionic transmission induced by 2-TH. It is concluded that histamine H1 and H2 receptors exist on preganglionic axons, or terminals in sympathetic ganglia of the rat. Activation of H1 receptors facilitates release of ACh whereas H2 receptor activation results in depressed release.

Action Potentials↗
PubMed1987

A trial of permethrin-treated bed nets in the prevention of malaria in Gambian children.

A trial was undertaken in a rural area of The Gambia to investigate the impact of permethrin-treated bed nets on malaria. Two groups of children, matched for age, sex, and malaria exposure, were followed through the rainy season of 1985 for illness and febrile episodes. One group of 205 children slept under permethrin-treated bed nets (0.5 g/m2); 184 children who slept under placebo-treated nets formed the control group. At the end of the rains the children were examined for splenomegaly and blood samples were taken for determination of packed cell volume (PCV) and parasitaemia. Permethrin treatment of bed nets was well accepted and was without side-effects. Children who slept under treated nets had significantly fewer episodes of clinical malaria than control children. However, at the end of the rains there was no significant difference in the prevalence of splenomegaly or parasitaemia or in the mean PCV between the groups. It is suggested that permethrin treatment of nets may have a greater effect on the duration of probing by mosquitoes for a blood meal than on the number of bites received.

Animals↗
PubMed1987

Use of a DNA hybridization assay for the detection of Plasmodium falciparum in field trials.

A DNA probe consisting of 21 base pair repeats obtained from a Tanzanian isolate of Plasmodium falciparum, cloned in pBR322 and labeled with 32P by nick translation was used to detect malaria parasitemia in samples obtained during a malaria survey undertaken in The Gambia. In an initial trial the hybridization assay had a specificity for P. falciparum of 100% and a sensitivity of 68%. False negative results were obtained only on samples with low parasitemia. Assay of red cells collected during an earlier malaria survey which had been stored for 1 year at -20 degrees C gave a higher level of sensitivity (85%), suggesting a beneficial effect from freezing and thawing. This was confirmed by examining in the same assay red cells processed immediately after collection and after 2 weeks of storage at -20 degrees C. Freezing and thawing gave a 21% increase in positivity, and a sensitivity of 100% was achieved with the frozen samples. Quantitation of autoradiographs by visual inspection and by scintillation counting gave a reasonable correlation with parasite counts. The DNA hybridization assay has considerable promise as an epidemiological tool.

Animals↗
PubMed1986

Evidence for neuronal interactions by electrical field effects in the CA3 and dentate regions of rat hippocampal slices.

During population spikes in slices of rat hippocampus, transmembrane differential recordings (intracellular minus extracellular) revealed electrical field-effect depolarizations in CA3 pyramidal and dentate granule neurons. The field-effect depolarizations were not seen in single-ended recordings, and were consistently shown to increase neuronal excitability. Therefore, as previously shown for the CA1 area, large population spikes from CA3 pyramidal and dentate granule cells are associated with transmembrane depolarizations that increase neuronal excitability.

Animals↗