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Biomedical subjects

S Bennett

Publications and source records attributed to S Bennett.

At least 109 records · Page 6Linked to original sources
PubMed1996

Geographical perspectives on bednet use and malaria transmission in The Gambia, West Africa.

Insecticide-impregnated bednets are now widely accepted as an important tool in reducing malaria-related deaths in children in Africa. Defining the circumstances in which net treatment programmes are likely to be effective is essential to a rational development of this control strategy. In The Gambia a National Impregnated Bednet Programme was introduced into the primary health care system in 1992. Prior to its introduction baseline epidemiological and entomological studies were conducted throughout the country. These studies showed that in areas where mosquito biting nuisance was high, people protected themselves with bednets and that where mosquito densities (and therefore bednet usage) was low malaria prevalence rates were relatively high. Since the national programme is designed to assist only those people who already own a bednet (by providing the insecticide) an understanding of the factors which determine bednet ownership is needed to help evaluate the programme's effectiveness and provide guidelines for increasing bednet usage. Village scale bednet usage rates and malaria prevalence rates obtained from the baseline survey were correlated with certain geographical variables: dominant ethnic group, area, habitat, distance from the River Gambia and distance from the 'bluffline' (the interface between the sandstone soils and alluvial soils which border the river system). In a multiple regression analysis, bednet usage was independently associated with area (P < 0.001), ethnic group (P = 0.010), habitat (P = 0.006) and distance from the river (P = 0.013). A negative association of bednet usage with malaria prevalence persisted after allowing for the other variables. Malaria prevalence was not independently associated with area, ethnic group, habitat or distance from the river. Our analysis showed that the impregnated bednet programme is likely to be most effective in villages which are sited near to or on the alluvial soils in the middle and lower river zones. These villages, which were originally settled for easy access to the river (for transport) and its swampy margins (for rice production) are within the flight distance of mosquitoes that have their breeding sites on the poorly drained alluvial soils. Variation in malaria prevalence rates (after bednet usage has been taken into account) may be related to factors such as poverty and access to health care, and/or to localized differences in the ecology of The Gambia, which determine the duration and intensity of transmission. If the National Bednet Programme is to be effective throughout The Gambia it is vital to develop promotional activities which will encourage bednet usage in areas where nuisance biting by mosquitoes is low.

Animals↗
PubMed1996

Initial biocompatibility studies of a novel degradable polymeric bone substitute that hardens in situ.

Clinical management of osseous defects often requires bone grafts. The standard for treatment is autogenous bone harvested from sites such as either the iliac crest or the outer table of the calvaria. In addition to the problem of donor site morbidity and the limited supply of graft material, there is the additional operating time associated with harvesting procedures. A synthetic, bone graft substitute that can match the clinical performance of autogenous bone could alleviate these deficiencies. Therefore, a polymeric bone substitute was developed that consists of a four-armed star polymer of poly(dioxanone-co-glycolide) endcapped at each termini with a biocompatible lysine-based diisocyanate crosslinker. The polymer can be mixed with inorganic fillers such as either hydroxyapatite or tricalcium phosphate to form either injectable or moldable putty. The addition of a catalyst (for example, diethylaminoethanol and water) to the polymer produces a crosslinking reaction causing the combination to harden. This reaction is nontoxic, normo-thermic and can be performed in situ. During the course of the polymerization, carbon dioxide is liberated, producing an interconnected porous network within the implant, suitable for bone ingrowth. This paper will describe a preliminary biocompatibility assay of the bone substitute.

Animals↗
PubMed1996

Both in vitro and in vivo irradiation are associated with induction of macrophage-derived fibroblast growth factors.

Fibrosis in the lung directly underlying the field of irradiation is an almost universal long term sequelae of thoracic irradiation. It is assumed to represent the consequence of direct damage to local tissues and/or vascular endothelium by ionizing radiation. This view, however, is not in keeping with our current understanding of fibrotic processes, which suggest that growth factors for fibroblasts (including platelet-derived growth factor (PDGF), insulin-like growth factor I (IGF-I)) and cytokines stimulating collagen synthesis (notably transforming growth factor-beta) are largely responsible for this process. Since a major source of these factors is the macrophage, present in large numbers within the lung, it appeared possible that radiation-induced fibrosis might be mediated by similar mechanisms. Therefore, a study was designed to determine, first, whether in vitro irradiation of mononuclear phagocytes could induce the release of growth factors for fibroblasts. Second, we wished to ascertain whether these same growth factors might also be secreted by bronchoalveolar cells from humans who had undergone in vivo thoracic irradiation. The results of this study indicate that irradiation of a number of different types of mononuclear phagocytes resulted in the dose-dependent synthesis and release of several growth factors for fibroblasts, including PDGF, tumour factor-alpha (TNF-alpha) and IGF-I. Further, cells obtained by bronchoalveolar lavage from patients undergoing thoracic radiation spontaneously released PDGF following irradiation. These findings strongly support the contention that synthesis and release of macrophage-derived growth factors for fibroblasts (particularly PDGF and IGF-I) occur after thoracic irradiation and play a significant role in the pathogenesis of irradiation-induced pulmonary fibrosis in humans.

Breast Neoplasms↗
PubMed1996

Implementing a nationwide insecticide-impregnated bednet programme in The Gambia.

Earlier studies in The Gambia suggested that the use of impregnated bednets might prove to be a useful malaria control strategy. Based on the results of these studies, in 1992 the Government of The Gambia was encouraged to initiate a National Impregnated Bednet Programme (NIBP) as part of the National Malaria Control Programme Strategy. This paper describes the implementation process/procedure of the NIBP. Evaluation results showed that, overall, 83% of the bednets surveyed has been impregnated, and 77% of children under the age of five years and 78% of women of childbearing age were reported to be sleeping under impregnated bednets.

Adolescent↗
PubMed1996

Socioeconomic inequalities in coronary heart disease and stroke mortality among Australian men, 1979-1993.

BACKGROUND: During the 1970s in Australia, mortality from coronary heart disease (CHD) and stroke was higher among lower socioeconomic groups and inequalities were widening. This analysis examines subsequent trends in socioeconomic inequalities, with reference to socioeconomic patterns in major cardiovascular risk factors. METHODS: Socioeconomic status was defined by occupation. Age-standardized mortality rates were calculated for men aged 25-64, using death registration data and labour force estimates for 1979-1993. Risk factor data were taken from three cross-sectional population surveys conducted in 1980, 1983 and 1989. RESULTS: Men in manual occupations were at least 35 percent more likely to die from CHD than men in professional occupations and 60 percent more likely to die from stroke. Their 5-year population risk of a coronary event was 30 percent higher. Since 1979, both groups experienced reductions in coronary risk and mortality. CONCLUSIONS: Socioeconomic inequalities in CHD mortality continued to widen during the early 1980s, stabilized thereafter and persisted into the 1990s. Decreases in blood pressure and smoking prevalence contributed most to declines in coronary risk and to socioeconomic differentials.

Adult↗
PubMed1996

The effect of a monoclonal antibody to tumor necrosis factor on survival from childhood cerebral malaria.

Tumor necrosis factor (TNF) is thought to play a key role in the pathogenesis of cerebral malaria. A double-blind, placebo-controlled trial of an anti-TNF monoclonal antibody (B-C7) comprised 610 Gambian children with cerebral malaria, with mortality and residual neurologic sequelae as primary study end points. Sixty (19.9%) of 302 children who received B-C7 died compared with 64 (20.8%) of 308 children who received placebo (adjusted odds ratio [OR], 0.90; 95% confidence interval [CI], 0.57-1.42). Residual neurologic sequelae were detected in 15 (6.8%) of 221 survivors from the B-C7 group and in 5 (2.2%) of 225 survivors of the placebo group (adjusted OR, 3.35; 95% CI, 1.08-10.4). The monoclonal antibody used in this study did not improve survival in cerebral malaria and was associated with a significant increase in neurologic sequelae. A possible explanation of the latter observation is that the antibody acts to retain TNF within the circulation and thereby prolongs its effects on vascular endothelium.

Antibodies, Monoclonal↗
PubMed1996

Chloroquine resistance of Plasmodium falciparum malaria in Ethiopia and Eritrea.

We report on the first 2 years of operation of a new strategy for treatment for P. falciparum malaria patients who were not cured by a standard course of chloroquine. Any such patient who returned to a malaria treatment and detection post within 2 weeks was treated daily under supervision with chloroquine. Patients whose parasitaemia had not decreased below 25% of the initial level by day 3 or cleared completely by day 7 were given sulphadoxine/pyrimethamine (Fansidar). Of 39824 patients treated initially with chloroquine, 4% returned to the malaria post within 2 weeks of treatment; 87% of these were chloroquine resistant and treated with Fansidar and 28% of the returning patients were RIII resistant. Resistance was associated with geographical area, initial parasite density and age. Earlier studies had shown resistance to be confined to border areas, but we found that it was highest in the centre of the region, notably in the lowlands of the Shewa and Arsi provinces, and lowest in the west. Although imported cases have been held responsible for the development of resistance in border areas, other factors are likely to be important in the middle of the region. The implications of these findings for a treatment policy of P. falciparum malaria in the region are discussed.

Adolescent↗
PubMed1995

Efficacy trial of malaria vaccine SPf66 in Gambian infants.

SPf66 malaria vaccine is a synthetic protein with aminoacid sequences derived from pre-erythrocytic and asexual blood-stage proteins of Plasmodium falciparum. SPf66 was found to have a 31% protective efficacy in an area of intensive malaria transmission in Tanzanian children, 1-5 years old. We report a randomised, double-blind, placebo-controlled trial of SPf66 against clinical P falciparum malaria in Gambian infants. 630 children, aged 6-11 months at time of the first dose, received three doses of SPf66 or injected polio vaccine (IPV). Morbidity was monitored during the following rainy season by means of active and passive case detection. Cross-sectional surveys were carried out at the beginning and at the end of the rainy season. An episode of clinical malaria was defined as fever (> or = 37.5 degrees C) and a parasite density of 6000/microL or more. Analysis of efficacy was done on 547 children (316 SPf66/231 IPV). No differences in mortality or in health centre admissions were found between the two groups of children. 347 clinical episodes of malaria were detected during the three and a half months of surveillance. SPf66 vaccine was associated with a protective efficacy against the first or only clinical episode of 8% (95% CI -18 to 29, p = 0.50) and against the overall incidence of clinical episodes of malaria of 3% (95% CI -24 to 24, p = 0.81). No significant differences in parasite rates or in any other index of malaria were found between the two groups of children. The findings of this study differ from previous reports on SPf66 efficacy from South America and from Tanzania. In The Gambia, protection against clinical attacks of malaria during the rainy season after immunisation in children 6-11 months old at time of the first dose was not achieved.

Animals↗
PubMed1995

Mortality and morbidity from malaria in Gambian children after introduction of an impregnated bednet programme.

After the success of a controlled trial of insecticide-treated bednets in lowering child mortality, The Gambia initiated a National Insecticide Impregnated Bednet Programme (NIBP) in 1992 with the objective of introducing this form of malaria control into all large villages in The Gambia. Five areas (population 115,895) were chosen as sentinel sites for evaluation of the NIBP. During the first year of intervention a 25% reduction was achieved in all-cause mortality in children 1-9 years old living in treated villages (rate ratio 0.75 [95% CI 0.57-0.98], p = 0.04). If one area where the programme was ineffective was excluded, the reduction was 38% (0.62 [0.46-0.83), p = 0.001). A decrease in rates of parasitaemia and high-density parasitaemia, an increase in mean packed-cell volume (rate ratio 0.75 [95% CI 0.59-0.98], p = 0.04) and an improvement in the nutritional status of children living in treated villages were also detected. In a country such as The Gambia, where nets were widely used and which has a good primary health care system, it is possible to achieve insecticide-treatment of bednets at a national level with a significant reduction in child mortality; but at a cost which the country cannot afford.

Bedding and Linens↗
PubMed1995

Priorities in global measles control: report of an outbreak in N'Djamena, Chad.

In N'Djamena, capital of Chad, measles vaccination coverage of 12-23-month-old children fell from 61% in 1990 to 15% in 1993. A community survey of measles after an outbreak in 1993 showed that among children < 5 years of age, the mean monthly attack rate was 37 per 1,000 (95% CI, 32-43) and the mean case fatality rate was 7.4%. Measles incidence was highest (77/1,000/month) in children aged 9-11 months and fell among children > 3 years of age. Incidence rates were high (56/1,000/month) among 6-8-month-old children, but only 3 deaths occurred in this age group. Measles vaccine efficacy, estimated by comparing attack rates in unvaccinated and vaccinated children, was 71% (95% CI, 59-80%). Extrapolation of the results to the city population indicated that an estimated 19,000 cases and > 1,000 measles-associated deaths occurred in 1993. This preventable morbidity and mortality, in a city where coverage was formerly among the highest in Africa, shows the need for sustained global commitment to preventive health care.

Age Distribution↗
PubMed1995

Entomological evaluation of the Gambia's National Impregnated Bednet Programme.

Entomological studies were conducted in paired study villages in three of the five study areas used for the epidemiological assessment of the Gambia's National Impregnated Bednet Programme. Baseline data collected in 1991 were compared with post-intervention data from 1992, when one of each village pair (from areas II, III and V) was included in the treatment programme in which villagers' nets were dipped in permethrin. In a longitudinal study, indoor-resting densities of Anopheles gambiae s.l. in the treated villages were significantly reduced, when compared with their paired untreated village, in areas II (t = 3.32, 13 degrees of freedom, P = 0.006) and III (t = 3.71, 13 degrees of freedom, P = 0.003). However, this was not associated with higher outdoor-biting rates in the evenings in the treated villages than in the controls. The reduction in vector population was most evident in area II, where the treated village was relatively isolated and 74% of the population slept under a treated net. Anopheles gambiae s.l. were also collected during two fortnightly periods in area V, where the sporozoite rates in 1991 had been relatively high (7.65% and 6.07%). There was no significant decrease in the sporozoite rate in the treated village in area V in 1992, despite the fact that this village was over 5 km from its nearest neighbouring village. However, the proportion of villagers sleeping under a treated net in this village was < 50%. No clear evidence for an epidemiologically significant 'mass killing effect', resulting from the village-wide use of treated nets, emerges in this or any other study undertaken in The Gambia. However, such an effect is indicated by results from Salikene, where the village mosquito population was relatively isolated and where the majority of the population slept under a treated net. This situation is unlikely to be repeated in most Gambian villages in the primary-health-care scheme, since treated and untreated villages are generally interspersed and the mosquito populations move freely between them. We must therefore conclude that, on a national scale, the nets provide an exceptionally high level of personal rather than community protection. The mechanisms underlying the personal protection are, however, still unclear.

Animals↗
PubMed1995

The manipulation of vision during the powerlift squat: exploring the boundaries of the specificity of learning hypothesis.

The available information for controlling a multidegree-of-freedom sport action was manipulated in 2 experiments. In the first, 10 intermediate lifters were participants; for the second, 8 skilled and 8 less skilled lifters were observed. Three single repetitions of a powerlift squat were performed under 3 vision conditions (i.e., full, ambient, no vision). The less skilled and intermediate lifters' technical performance decreased significantly with the removal of visual information. There was no detrimental effect in the skilled group. Despite the differing information constraints, skilled lifters exhibited a high level of positioning accuracy and timing consistency across conditions. These data fail to support the theoretical predictions of the specificity of learning hypothesis. The differences between the task constraints in this study and those in manual aiming investigations may represent a boundary to the current propositions of the specificity of learning hypothesis.

Adult↗
PubMed1995

Genetic regulation of fever in Plasmodium falciparum malaria in Gambian twin children.

The role of genetic factors in determining the clinical response of children to Plasmodium falciparum infection is not fully understood. A longitudinal survey of malaria morbidity in a cohort of 258 pairs of twin children was conducted in a rural area of Gambia to assess the extent to which genetic factors determine the host's susceptibility and clinical response to infection. The marginal correlation (which measures the excess probability of both twins being affected above that expected assuming independence) for malaria was higher in dizygous (DZ) than in monozygous (MZ) twin pairs, indicating that infection per se is largely determined by environmental factors. Once infected however, both members of an MZ pair were more likely to develop fever than were twins of a DZ pair, suggesting that genetic factors influence the presentation of clinical disease.

Child↗
PubMed1995

Evidence against a potential endoplasmic reticulum transmembrane domain of 27K zein expressed in Xenopus oocytes.

During the cellular protein targeting process, zeins (maize storage proteins) are retained in the endoplasmic reticulum (ER) where they accumulate into protein bodies. There are circumstantial and preliminary data indicating that the 27K zein, a class of zein proteins, may span the ER membrane. This potential transmembrane domain is considered very significant with regard to the mechanism of ER retention for zeins. The potential transmembrane domain may permit the 27K zein to remain in the ER and to serve as an anchor for other classes of zein, thus acting as a nucleating factor for protein body formation. This study investigated the potential transmembrane feature in a heterologous system (Xenopus laevis oocyte). Following injection of synthetic 27K zein mRNA, isolated protein vesicles were subjected to proteinase K digestion, surface biotinylation and alkaline extraction. Throughout three categories of assay the possible role of the 27K zein as a transmembrane protein was consistently refuted in this study. The 27K zein polypeptide was affected by neither proteinase K digestion nor biotinylation and was released from alkali-stripped membranes. This study, therefore, concludes that the 27K zein is not a protein body nucleating factor by virtue of an ER transmembrane feature.

Animals↗