Search PubMed⌕ Search

Biomedical subjects

S Bennett

Publications and source records attributed to S Bennett.

At least 163 records · Page 9Linked to original sources
PubMed1992

An investigation of some risk factors for severe leptospirosis on Barbados.

Between November 1979 and the end of December 1986 (7.17 years), 248 cases of leptospirosis were confirmed among hospital patients on Barbados (mean 35 per year; range 25-57). Considering the 235 who were greater than or equal to 15 years of age, the annual incidence of leptospirosis was 19.2/100,000 population (14.0 for all age groups). There were 173 males and 62 females, and for cases aged 15-34 leptospirosis was 9.6 times more common in men than women. Among men, incidence increased fairly steadily with age, and an even steadier increase was apparent in women up to age 64, with some decline in later years. The incidence of disease was much higher among agricultural than other workers and the non-employed. Highest case numbers were recorded in the parishes of St Michael (65 or 28%) and Christ Church (36 or 15%), though the incidence was lowest in these two parishes (13.1/100,000 and 17.4/100,000, respectively). The highest incidence rates were in St Andrew and St Joseph (50.2 and 36.1/100,000, respectively). The incidence in areas with rainfall greater than or equal to 1600 mm (32.6/100,000) was nearly twice that in areas with rainfall less than 1600 mm (17.3/100,000). There is a clear link between cases of severe disease and recent rainfall. Using 134 patients greater than or equal to 15 years of age with fever due to other illnesses as controls, a higher proportion of cases than controls came from rural areas. The risk of contracting leptospirosis was increased for all categories of manual workers relative to the group at lowest risk (non-manual indoor workers). Sugar-cane workers were five times more likely to contract leptospirosis than were non-manual indoor workers, while those whose families minded livestock were 2.5 times more likely, and those with rodents in their garden/yard were 1.8 times more likely to do so. Other risk factors examined did not show significant associations with the disease. Despite increasing mechanization and the use of more protective clothing, agricultural workers are still at high risk from leptospirosis. The annual range of cases is likely to stay much as it is in the foreseeable future.

Adolescent↗
PubMed1991

Common west African HLA antigens are associated with protection from severe malaria.

A large case-control study of malaria in West African children shows that a human leucocyte class I antigen (HLA-Bw53) and an HLA class II haplotype (DRB1*1302-DQB1*0501), common in West Africans but rare in other racial groups, are independently associated with protection from severe malaria. In this population they account for as great a reduction in disease incidence as the sickle-cell haemoglobin variant. These data support the hypothesis that the extraordinary polymorphism of major histocompatibility complex genes has evolved primarily through natural selection by infectious pathogens.

Animals↗
PubMed1991

Immune response to soluble exoantigens of Plasmodium falciparum may contribute to both pathogenesis and protection in clinical malaria: evidence from a longitudinal, prospective study of semi-immune African children.

Some soluble exoantigens of Plasmodium have lipopolysaccharide (LPS)-like properties and are believed to contribute to the pathogenesis of acute malaria. We have studied cellular and humoral immune responses to several purified exoantigens of Plasmodium falciparum in a cohort of children and compared these responses with their subsequent susceptibility to malaria infection and clinical disease. We found no evidence that either lymphoproliferative or interferon-gamma (IFN-gamma) responses to these antigens were associated with protective immunity. On the contrary, children whose cells produced IFN-gamma after in vitro activation with one of the soluble antigens (Ag7) were more likely to experience clinical manifestations of malaria infection (fever and malaise) than were children whose cells did not produce IFN-gamma. It is possible that exoantigen-induced IFN-gamma may exacerbate the LPS-like effects of these antigens. However, serum antibodies to another antigen (Ag2) were more prevalent in children with asymptomatic infections or low parasitemia than in children with fever and higher parasitemia (confirmed clinical malaria), suggesting that these antibodies may contribute to the development of protective immunity.

Animals↗
PubMed1991

Absence of epidemicity of severe leptospirosis in Barbados.

The possibility of micro-epidemics of severe leptospirosis occurring on the island of Barbados was investigated by examining the space-time clustering of the disease in 212 laboratory-confirmed cases admitted to Queen Elizabeth Hospital, Bridgetown, over a 7-year period. A series of 109 patients with symptoms compatible with leptospirosis but shown to be otherwise by laboratory examination were also examined for comparison. No significant space-time clustering was found among the leptospirosis cases, indicating no evidence for micro-epidemics. By comparison, statistically significant clustering was apparent among the smaller non-leptospirosis series. Possible explanations for the absence of observed micro-epidemics of leptospirosis are discussed.

Barbados↗
PubMed1991

Age-dependent effects of sodium nitroprusside and dopamine in lambs.

Vasodilators and cardiotonic agents are frequently used in hypoxemic newborn infants with persistent pulmonary hypertension. We studied the effects of sodium nitroprusside and dopamine on hypoxia-induced pulmonary hypertension in seven newborn (0-3 d) and seven young (10-14 d) lambs under chloralose anesthesia. Pulmonary blood flow, pulmonary arterial pressure, systemic arterial pressure, and left atrial pressure were measured during the experimental states of hypoxia, hypoxia plus nitroprusside, and hypoxia plus both nitroprusside and dopamine. Pulmonary and systemic arterial pressure and cardiac output all decreased significantly when hypoxemic newborn lambs were given nitroprusside; in contrast, when hypoxemic young lambs were given nitroprusside, cardiac output did not change, whereas both pulmonary and systemic arterial pressure decreased significantly. Calculated pulmonary vascular resistance was unchanged in the newborn lambs but fell in the young lambs, implying that active pulmonary vasodilation by nitroprusside occurred only in the latter group. Systemic vascular resistance was not significantly affected by nitroprusside in either group. The addition of dopamine resulted in qualitatively similar changes in both groups of lambs, with increased pulmonary blood flow and no significant change in pulmonary or systemic arterial pressures. Maturation in vascular smooth muscle responsiveness to nitrovasodilators may explain the age-related differences that we found in lambs, and could also account for the variable clinical responses to vasodilators observed in hypoxemic human infants.

Age Factors↗
PubMed1991

A simplified general method for cluster-sample surveys of health in developing countries.

General guidelines are presented for the use of cluster-sample surveys for health surveys in developing countries. The emphasis is on methods which can be used by practitioners with little statistical expertise and no background in sampling. A simple self-weighting design is used, based on that used by the World Health Organization's Expanded Programme on Immunization (EPI). Topics covered include sample design, methods of random selection of areas and households, sample-size calculation and the estimation of proportions, ratios and means with standard errors appropriate to the design. Extensions are discussed, including stratification and multiple stages of selection. Particular attention is paid to allowing for the structure of the survey in estimating sample size, using the design effect and the rate of homogeneity. Guidance is given on possible values for these parameters. A spreadsheet is included for the calculation of standard errors.

Child↗
PubMed1991

Is childhood sexual abuse really increasing in prevalence? An analysis of the evidence.

One controversy regarding childhood sexual abuse is whether the increased rate of reported cases reflects a true increase in prevalence. In this report, data obtained in the 1970s and 1980s were compared with those of the 1940s. Using predetermined criteria for quality of information, commonality of definitions of childhood sexual abuse, and research design, the authors reviewed the Kinsey report published in 1953 and 19 prevalence studies reported in the last 10 years. Interrater reliability was .97 for each paper. In spite of differences in study designs and populations surveyed, where definitions of childhood sexual abuse were similar, the more recent studies with the strongest methodology reported prevalence figures similar to those of Kinsey in the 1940s, ie, 10% to 12% of girls younger than 14 years of age. Thus it would appear that increased reporting is due to changes in legislation and social climate rather than a true increase in prevalence. The absence of an increase in prevalence of childhood sexual abuse should not deter those interested in pursuing solid research in prevention and treatment because any childhood sexual abuse is too much.

Adolescent↗
PubMed1990

Cellular and humoral immune responses to Plasmodium falciparum gametocyte antigens in malaria-immune individuals. Limited response to the 48/45-kilodalton surface antigen does not appear to be due to MHC restriction.

We have examined immune responses to a cultured Plasmodium falciparum gametocyte lysate and to an affinity-purified preparation of the 48/45-kDa gamete surface Ag in a group of 30 malaria immune individuals and in 24 Europeans with no previous exposure to malaria. Cellular responses were assessed in vitro by lymphoproliferation and production of IFN-gamma; antigamete antibodies were detected by immunofluorescence, Western blotting, and competitive ELISA. Cells from all the malaria immune donors responded to the gametocyte lysate in both assays while cells from nonimmune donors gave only weak proliferative responses. Antigamete antibodies were detected in the serum of all the immune donors but not in serum from nonimmunes. Nonimmune donors were completely unresponsive to the purified 48/45-kDa surface Ag while cells from 40% of immune donors responded by either proliferation or IFN-gamma production. Only 3 of 30 immune donors had detectable antibodies to the 48/45-kDa Ag. Class II HLA type was determined for 27 of the immune donors but no relationship between HLA-DR or -DQ and responsiveness to the 48/45-kDa Ag was discerned. The possible reasons for limited recognition of this gamete surface Ag are discussed.

Animals↗
PubMed1990

Persistence of leptospiral agglutinins in Trinidadian survey subjects.

Participants in a survey for leptospiral agglutinating antibodies undertaken in Trinidad, West Indies, in 1977-78, were further monitored for up to 5-and-a-half years. 52 individuals with a titre greater than or equal to 1:400 were matched for age, sex and occupation with seronegative subjects. They were re-bled twice (on average 2.38 and 4.84 years later), and changes of titre were noted. At the first follow-up, 78% of negative controls remained negative, and 22%, showed titre changes. Among the seropositive subjects, 47% showed a fall in titre, 38% showed no change, and in 15% the titre rose. New exposure rates between the original and first follow-up samples were 96/1,000 survey population per year in the controls, and 68/1,000 for the subjects with titres greater than or equal to 1:400. Between the first and second follow-up, 47% of the seropositive subjects lost titre, 40% showed no change, and 13% showed a rise in titre. These data demonstrate that although antibody titres may be maintained for a few years at the same level, or show a loss as is usually expected, about 8.3% of individuals in Trinidad may be infected/reinfected per year. The infection/reinfection rate is an important factor in the epidemiology of leptospirosis.

Adolescent↗
PubMed1990

The comparison of trends in perinatal mortality in small areas.

Year to year changes in perinatal mortality rates for small populations are difficult to interpret. Because local rates are based on small numbers of events, they are subject to apparently large fluctuations. A technique for analysing trends in mortality, for detecting changes in trends and comparing variations in trends between areas is described. It is illustrated by an analysis of perinatal mortality rates for Area Health Authorities in the West Midlands Region of England from 1974-1981, but the same techniques could be used to analyse trends at other times and in other places.

Birth Rate↗
PubMed1990

Surgical techniques of oocyte collection and embryo transfer.

In the decade since the birth of the first child conceived as a result of in vitro fertilization and embryo transfer much has been achieved in the field of assisted conception. Although in vitro fertilization (IVF) was successful first for the treatment of tubal disease, the indications for its use have now widened to include unexplained infertility, oligozoospermia, endometriosis and infertility due to immunological disorders. Gamete intrafallopian transfer (GIFT) and zygote intrafallopian transfer (ZIFT) are now used commonly for the treatment of couples where the woman has patent fallopian tubes. The huge increase in the demand for therapy using these techniques of assisted conception places considerable strain on the finances available for health care, and has led some to question the wisdom of such use of limited resources. To reduce the cost of treatment, and because repeated IVF-ET attempts may be necessary before achieving pregnancy, the initial laparoscopic approach for oocyte recovery has been largely replaced by ultrasound-guided techniques. Non-surgical embryo transfer techniques have changed little since originally described. However, where the tubes are patent, one-cell zygotes or cleavage stage embryos may be transferred into the fallopian tube (ZIFT and tubal embryo stage transfer respectively). On the other hand if the tubes are blocked, surgical embryo transfer (SET) may be performed. Most recently, some success has been achieved following the transfer of embryos into the fallopian tube by the technique of retrograde fallopian tube catheterisation.

Biopsy, Needle↗