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Biomedical subjects

H Fraser

Publications and source records attributed to H Fraser.

At least 55 records · Page 3Linked to original sources
PubMed1997

The prevalence of hypertension in seven populations of west African origin.

OBJECTIVES: This study was undertaken to describe the distribution of blood pressures, hypertension prevalence, and associated risk factors among seven populations of West African origin. METHODS: The rates of hypertension in West Africa (Nigeria and Cameroon), the Caribbean (Jamaica, St. Lucia, Barbados), and the United States (metropolitan Chicago, Illinois) were compared on the basis of a highly standardized collaborative protocol. After researchers were given central training in survey methods, population-based samples of 800 to 2500 adults over the age of 25 were examined in seven sites, yielding a total sample of 10014. RESULTS: A consistent gradient of hypertension prevalence was observed, rising from 16% in West Africa to 26% in the Caribbean and 33% in the United States. Mean blood pressures were similar among persons aged 25 to 34, while the increase in hypertension prevalence with age was twice as steep in the United States as in Africa. Environmental factors, most notably obesity and the intake of sodium and potassium, varied consistently with disease prevalence across regions. CONCLUSION: The findings demonstrate the determining role of social conditions in the evolution of hypertension risk in these populations.

Adult↗
PubMed1997

Prevalence of NIDDM among populations of the African diaspora.

OBJECTIVE: Rates of non-insulin-dependent diabetes mellitus have risen sharply in recent years among blacks in the U.S. and the U.K. Increases in risk have likewise been observed in the island nations of the Caribbean and in urban West Africa. To date, however, no systematic comparison of the geographic variation of NIDDM among black populations has been undertaken. RESEARCH DESIGN AND METHODS: In the course of an international collaborative study on cardiovascular disease, we used a standardized protocol to determine the rates of NIDDM and associated risk factors in populations of the African diaspora. Representative samples were drawn from sites in Nigeria, St. Lucia, Barbados, Jamaica, the United States, and the United Kingdom. A total of 4,823 individuals aged 25-74 years were recruited, all sites combined. RESULTS: In sharp contrast to a prevalence of 2% in Nigeria, age-adjusted prevalences of self-reported NIDDM were 9% in the Caribbean and 11% in the U.S. and the U.K. Mean BMI ranged from 22 kg/m2 among men in West Africa to 31 kg/m2 in women in the U.S. Disease prevalence across sites was essentially collinear with obesity, pointing to site differences in the balance between energy intake and expenditure as the primary determinant of differential NIDDM risk among these populations. CONCLUSIONS: In ethnic groups sharing a common genetic ancestry, these comparative data demonstrate the determining influence of changes in living conditions on the population risk of NIDDM.

Adult↗
PubMed1996

Observations on the transmission of scrapie in experiments using embryo transfer.

This investigation studied the maternal transmission of scrapie in sheep by using embryo transfer to examine the viability of highly susceptible offspring derived from scrapie-affected and uninfected donors. The study also examined the effect of washing the embryos. Scrapie occurred in both washed and unwashed embryo-derived Sip sAsA progeny from both groups of donor ewes. As a result, the earlier observation that scrapie might pass via the unwashed embryo to develop as disease in adult sheep has to be reassessed. Several other implications of the work are considered, including the possibility that natural scrapie is not purely a genetic disease.

Alleles↗
PubMed1996

Obesity in the Caribbean.

People of African origin who live in the Caribbean share a common genetic heritage but live in socioeconomic environments that diverge widely. A cross-cultural study of males and females from Jamaica, St. Lucia and Barbados investigated the prevalence of hypertension and its environmental determinants. Standardized measurement techniques allowed comparable measurements of weight, height, waist and hip circumferences, and blood pressure. The population values for body mass index (BMI), per cent overweight (males BMI > or = 27.8 kg/m2; females BMI > or = 27.3 kg/m2) and per cent obese (males BMI > or = 31.1 kg/m2; females BMI > or = 32.3 kg/m2) are presented. Prevalence of hypertension is based on the age-adjusted total population. The gradient in per capita gross national product in Jamaica, St. Lucia and Barbados parallels the gradient in the proportions of population in those countries who are obese. BMI explained 26% of the variance in blood pressure in females and 13% in males. Obesity is a significant problem in the Caribbean, as it is in many other developing countries, and it is associated with a high prevalence of hypertension, particularly in women.

Body Composition↗
PubMed1996

Obesity in peoples of the African diaspora.

People of African descent in the Caribbean and the USA originated from the Bight of Benin in West Africa. Although these populations share a common genetic heritage, they now live under different socioeconomical conditions. Assuming genetic similarity, a cross-cultural examination of these peoples in West Africa, the Caribbean and the USA may attenuate the effect of genetic factors and allow the assessment of environmental contributions to a biological outcome. We carried out an epidemiological survey to determine the prevalence of hypertension and the contribution of risk factors to the variation in blood pressure. We measured the height, weight, waist and hip circumferences, and blood pressure of adults in Nigeria, Cameroon, Jamaica, St. Lucia, Barbados and the USA. In urban populations there was a trend towards increasing weight, height, body mass index, and proportions of those overweight and obese going from West Africa to the USA, with the Caribbean being intermediate. The prevalence of hypertension lay on a similar gradient. Given a common genetic susceptibility, urbanization and western acculturation are therefore associated with increasing hypertension and obesity.

Adult↗
PubMed1996

Standardization of blood pressure measurement in an international comparative study.

In the context of a collaborative study on the epidemiology of hypertension in populations of West African origin procedures for standardization of the measurement of blood pressure were evaluated. Comparisons of mean levels of blood pressure, which in large part determine prevalence rates, are highly sensitive to differences in technique. While rotating a single field team may be the ideal approach to multisite studies, it is not practical in international collaborative research. Appropriate techniques to standardize multiple teams over a long period of time have not been well developed, however. In the present study 8981 individuals were examined in eight sites in six countries with the standard mercury sphygmomanometer. An evaluation of the effectiveness of central training, site visits, monitoring of digit preference, and the use of an electronic device for internal standardization is described. In all but one of the sites reliability was high and comparable to the observers at the Coordinating Center. Digit preference for the entire set of measurements was limited (frequency of terminal zero = 23.5% for systolic and 28.9% for diastolic readings) and could be shown to have virtually no effect on prevalence rates or correlation estimates. Mean differences among observers within a given site and between sites were small (+/- 0-5 mmHg). While logistically complex, these methods can provide the basis for standardization in international comparative blood pressure surveys.

Adult↗
PubMed1996

Scrapie infection can be established readily through skin scarification in immunocompetent but not immunodeficient mice.

Scarification of the skin is a possible route of entry for scrapie infectivity in sheep, and for Creutzfeldt-Jakob disease agent in humans within the context of occupational exposure to infected brain in the autopsy room or laboratory. The effectiveness of skin scarification routes as portals of entry for infectivity had not previously been tested experimentally but this study has shown that these are efficient routes for establishing infection in mice using the 139A and ME7 strains of scrapie agent. Scarification had much the same efficiency as inoculation by the intraperitoneal, intravenous or perivenous routes but was not effective in immunocompromised (SCID) mice. It was concluded that replication of infectivity within the lymphoreticular system, which is precluded in SCID mice, is a necessary prerequisite for the development of infection in the central nervous system following inoculation via scarification.

Animals↗
PubMed1996

Replication of scrapie in spleens of SCID mice follows reconstitution with wild-type mouse bone marrow.

SCID mice are resistant to intraperitoneal infection with 10(3) and 10(4) intracerebral ID50 units of ME7 scrapie agent whereas they develop disease after intracerebral challenge. However, higher doses introduced, by intraperitoneal or subcutaneous routes, produce disease. Immunocompetent mice of the same strain (CB20) developed scrapie following either intracerebral or intraperitoneal infection. Bioassay of spleens from SCID mice infected with 10(-1) dilutions of ME7 scrapie by intraperitoneal, intracerebral or abdominal subcutaneous injection showed traces or low levels of infectivity in spleen. However, subcutaneous injection beneath the skin of the neck failed to infect the spleen. CB20 bone marrow reconstitution of SCID mice resulted in the regeneration of a normal lymphoid architecture in the spleen. Spleens from these reconstituted mice, infected intracerebrally with a 10(-1) dilution of ME7 contained high levels of infectivity. These results suggest that the ability to replicate scrapie agent in spleen or lymphoid tissue depends on the restoration of normal lymphoid structure and in particular the presence of differentiated follicular dendritic cells. The possibility that SCID mice can select minor strains of scrapie which are normally unrecognized in cloned ME7 is discussed.

Animals↗
PubMed1996

Mouse inoculation studies reveal no transmissible agent in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) resembles the spongiform encephalopathies in its dual pattern of inherited and sporadic cases, its uniform prevalence in different populations, its late onset (suggestive of a long incubation period) and its pathological picture of neuronal degeneration without inflammation. There is a well-established protocol for primary transmission of scrapie and related diseases to mice. Using this, we inoculated four longlived, inbred, mouse strains with cord material fresh-frozen within three hours of death, from a case of ALS or a control case. No motor neuron loss, gliosis or tract demyelination was found in the experimental group. Fifty per cent of each group were observed for more than 600 days. Two types of lesions were found in these animals at death: widespread foci of white matter vacuolation and bilateral thalamic mineral deposits. They were present in the control group at the same incidence and severity as in the experimental group and were thus considered to represent an age-related change. Attention is drawn to them because they have been claimed as significant when found in a transgenic model of spongiform encephalopathy. The results of our carefully-controlled experiment suggest that it is unlikely that ALS is caused by a scrapie-like agent capable of transmission to mice.

Amyotrophic Lateral Sclerosis↗
PubMed1996

A comparative study of hypertension prevalence, awareness, treatment and control rates in St Lucia, Jamaica and Barbados.

BACKGROUND: Cardiovascular diseases represent the most common cause of death in the English-speaking Caribbean, and hypertension represents the most important predisposing condition. However, direct between-country comparative studies in the Caribbean have not previously been undertaken. OBJECTIVE: To obtain estimates of hypertension prevalence, awareness, treatment and control in three countries in the Caribbean. DESIGN: Population-based samples of adults aged 25-74 years in St Lucia, Barbados and Jamaica were surveyed regarding their cardiovascular health and their blood pressures were measured using a highly standardized protocol. A reference site was available from a collaborative study among blacks in metropolitan Chicago, Illinois, USA. RESULTS: At the 160/95 mmHg threshold, age-adjusted hypertension prevalence estimates for Jamaica, St Lucia and Barbados were 17.5, 18.3 and 21.5%, respectively, and 24.7, 26.9 and 27.9%, respectively, at the 140/90 mmHg threshold. The corresponding estimate for the Chicago site at the 140/90 mmHg threshold was 33.2%. The gradient in prevalence resembled the gradient in body mass index (25.7 kg/m2 in Jamaica to 29.3 kg/m2 in the USA). At the 160/95 mmHg threshold, the proportion of all hypertensives who were aware of their disease, pharmacologically treated and controlled was highest in Barbados (90, 85 and 72%, respectively) and lowest in St Lucia (74, 59 and 35%, respectively). Men, particularly those aged less than 55 years, were less likely to have their hypertension treated and controlled. CONCLUSIONS: Compared with estimates from earlier independent surveys, considerable progress has been made in hypertension detection and control in these countries, which should lead to sizable reductions in the burden of cardiovascular disease.

Adult↗
PubMed1996

Web interface for the Heart Disease Program.

The task of making a large complex diagnostic program available to a broad audience of physicians has become more feasible with the ubiquitous accessibility of the client-server architecture of the World Wide Web. This paper describes the design and implementation of a Web interface for the Heart Disease Program (HDP). The client-server architecture imposes a number of requirements on the program. The graphical capabilities of the Web enable a number of enhancements to the program but also cause some limitations. Our initial experience with physicians using the HDP through the Web interface has been positive and we are now conducting an evaluation of the HDP using this form of access.

Computer Communication Networks↗
PubMed1995

Detection of apoptosis in murine scrapie.

In order to determine whether apoptosis contributes to the neuronal loss in scrapie, in situ end labeling was applied on brains of mice showing clinical signs of the disease. Positively labeled, apoptotic neurons were observed in the cerebellum, cerebral cortex and hippocampus, areas known to show characteristic scrapie-related vacuolation, and were absent in the brains of control mice. We conclude that apoptosis plays a role in the neuronal loss that occurs in scrapie. The importance of apoptosis as a predominant cell death mechanism in scrapie, however, remains to be determined.

Animals↗
PubMed1995

Distribution of anthropometric variables and the prevalence of obesity in populations of west African origin: the International Collaborative Study on Hypertension in Blacks (ICSHIB).

A survey of the prevalence of hypertension and associated risk factors including obesity was carried out among persons of West African heritage currently living in societies at different stages of social, economic and technological development. We present here the distribution of several anthropometric variables and the prevalence of obesity in these populations. Using a standard protocol with centralized training of field staff, 7,439 men and women aged 24 to 75 from six multinational sites were recruited and examined. Although men were taller, women were more obese across sites. Body mass index (BMI) and consequently the prevalence of overweight and obesity increased with westernization from rural African subsistence farming communities to suburban Chicago. Average BMI increased with age until about age 54, and then began to decline or at least level off. The mean BMI for African-American men and women was 27.1kg/m2 and 30.8kg/m2, respectively. Men displayed high levels of centripetal fatness, measured as the waist-to-hip ratio (WHR), compared to the women across site. Based on the US Department of Agriculture guidelines, 22.6% and 56.9% of the African-American men and women had elevated WHR. Although account must be taken of the important contribution of an individual's genetic background, this multinational study of persons with similar heritage clearly shows the potent impact of current environmental factors on the distribution and level of obesity.

Adult↗