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Biomedical subjects

R S Cooper

Publications and source records attributed to R S Cooper.

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

Relationship between birth weight and awake blood pressure in children and adolescents in absence of intrauterine growth retardation.

This study was designed to examine the relationship between birth weight (BW) and ambulatory blood pressure in children and adolescents, born at term in absence of intrauterine growth retardation. Twenty-four hour ambulatory blood pressure monitoring (ABPM) was performed on 332 children (150 boys), aged from 6 to 16 years. Subjects were stratified by BW tertiles and age. ABPM was performed using SpaceLabs 90207 monitor during a regular school day. Blood pressure (BP) was measured every 20 min from 06:00 to 24:00, and thereafter every 30 min. Means of systolic BP (SBP) and diastolic BP (DBP) during 24 h, daytime (08:00 to 22:00), and nighttime (24:00 to 06:00) were calculated. Systolic and diastolic load was estimated as the percentage of measurements above the age- and sex-specific 95th percentile during the 24 h. BW was inversely related to daytime (SBP (P = .04) and SBP load (P = .04) when controlled for sex, current height, ponderal index (weight/height3), and age. The predictive values of daytime SBP throughout the pediatric age group in the two extreme tertiles of BW (lowest, 2.500 to 3.200 kg; and highest, 3.501 to 4.820 kg) were obtained from regression equations including SBP during activity period or SBP load and age. Children who had lower BW tended to have higher daytime SBP or SBP load at any age although this difference was not statistically significant. These differences became more evident as the subjects got older. BW is a determinant of daytime SBP even in the absence of intrauterine growth retardation. The influence of BW seems to increase with age.

Adolescent↗
PubMed1996

Is hypertension more severe among U.S. blacks, or is severe hypertension more common?

It is frequently stated that the risk of sequelae from hypertension at a given level of severity is higher among blacks than whites, although little empirical evidence supports that supposition. In this work we examined the basis for accepting the existence of a black: white differential in hypertension outcomes in a representative biracial sample of the U.S. population followed in the First National Health and Nutrition Examination Survey (NHANES-1) Epidemiologic Follow-up Study. As well recognized, the risk associated with increasing blood pressure is not dichotomous but varies across the entire distribution in a curvilinear fashion. The rightward skew of the blood pressure distribution with increasing mean levels affects comparisons between populations, since the change in shape results in a change in the mix of case severity. These considerations can influence estimates of the relative population-attributable risk from hypertension, considered as a dichotomous classification in blacks and whites. Although the relative risk of death associated with a systolic blood pressure of > or = 140 mmHg in this study was higher for blacks than for whites (1.7 and 1.5, respectively), with all-cause mortality as the outcome, the logistic coefficient for systolic blood pressure was not significantly different among white as compared with black men (beta = 0.016 vs. 0.010; p = 0.320 for race interaction term) and was slightly greater among white vs. black women (beta = 0.013 vs. 0.010; P = 0.05). After strata-specific blood pressure adjustment, the principal determinant of increased population risk for both black men and women was the higher prevalence of hypertension, not differential severity. The population-attributable risk for hypertension was at least two times higher among blacks because of the higher prevalence among them; moreover, the increased prevalence accounted for 10% of the interethnic difference in mortality. Data from this study indicate that hypertension was not more severe among individual blacks, simply more common in the population.

Adult↗
PubMed1996

Intracellular cations and hypertension in blacks.

Considerable attention has been focused in recent years on the role of intracellular ions in the pathophysiology of hypertension in African Americans. Following the identification of marked differences in red cell sodium content and sodium-lithium counter-transport between blacks and whites, the hypothesis emerged that cation metabolism at the cellular level might account for part of the ethnic difference in susceptibility to hypertension. Unfortunately, findings in the red cell have not significantly increased our understanding of the physiologic pathways and may prove to be anomalous. Interest has recently shifted to calcium metabolism, because of its greater physiologic relevance, and a new series of questions are being defined. With the development of fluoroprobes to measure sodium and calcium simultaneously, wider application of pharmacologic agonists and the use of single cell techniques have provided a new direction for this field. Whether the ethnic contrasts observed for sodium in the red cell can be reproduced in platelets remains to be seen. It may be that the earlier red cell differences were epiphenomena, unrelated to the control of blood pressure, and that the more closely one approaches basic physiologic mechanisms, the greater the cross-ethnic group similarity. Rather than drawing attention to unusual phenotypic characteristics, the study of hypertension in blacks may be more instructive for the insight it provides into the basic physiology of this disorder, common to all ethnic groups.

Antiporters↗
PubMed1996

Obesity and hypertension prevalence in populations of African origin. The Investigators of the International Collaborative Study on Hypertension in Blacks.

Obesity has been shown to be associated with hypertension in Africa, the Caribbean, and the United States, but there has not previously been an opportunity to compare the magnitude of this relation and estimate the contribution of obesity to hypertension risk across these populations. The International Collaborative Study on Hypertension in Blacks (ICSHIB) used age-stratified sampling and a standardized protocol to measure blood pressure and hypertension risk factors. We analyzed data on 9,102 men and women, age 25-74 years, from seven sites. We studied hypertension (140/90 mmHg or medication) in relation to body mass index (BMI) and sex-specific BMI cut-points designating "overweight" and "obesity." The prevalence of these conditions ranged from 6% to 63% for overweight, from 1% to 36% for obesity, and from 12% to 35% for hypertension. Adjusted relative risks were similar in most sites, ranging from 1.3 to 2.3 for both cut-points. We found that 6-29% of hypertension in each population was attributable to overweight and 0-16% to obesity. Comparing rural Africa with the United States, 43% of the difference in hypertension prevalence for women was attributable to overweight, and 22% for men, whereas respective values for obesity were 14% and 11%. These results indicate that the association between adiposity and hypertension is roughly constant across a range of environments, with little evidence for variation in susceptibility to effects of overweight in these groups.

Adult↗
PubMed1996

The mortality risk associated with hypertension: preliminary results of a prospective study in rural Nigeria.

The contribution of hypertension to adult mortality in Africa has not been well studied. Although cross-sectional surveys have provided data on the prevalence of this condition, the relative risk of death associated with hypertension has not been defined. In the face of high levels of competing mortality from infectious disease among the general population, and the virtual absence of atherosclerotic precursors, estimates of risk derived from industrialised countries may not be generalisable to this setting. We conducted a 2-year prospective study among 1344 mean and women in a rural community in south-western Nigeria. The prevalence of hypertension (140/90 mm Hg) at baseline was 9.3%. In the observational phase, 3.0% of the survey participants died each year. Among the 74 decedents, hypertension was nearly twice as common as among those who survived (14.9% vs 8.4%). In multivariate analysis the risk of death increased over 60% for a 20 mm Hg increase in diastolic blood pressure. The population attributable risk, or the reduction in mortality that would have been observed if hypertension were not present in this community, was estimated as 7%. These findings document an identifiable impact of hypertension on all-cause mortality in rural Africa and demonstrate that programs to evaluate potential treatment options are needed.

Adult↗
PubMed1996

Questions on adult mortality.

The technique of verbal autopsy is being used to investigate the causes of adult deaths in part of Ibadan, Nigeria. The problems encountered in the first year of the study and the measures taken to overcome them are described below.

Adolescent↗
PubMed1995

Regulation of c-jun mRNA expression by hydroxyurea in human K562 cells during erythroid differentiation.

Hydroxyurea (HU) is an antitumor agent which also induces hemoglobinization during erythroid differentiation. In addition, HU stimulates the synthesis of fetal hemoglobin in sickle cell anemia patients. To further understand its mechanism of action, we investigated the effects of HU on regulation of c-jun expression prior to the onset of erythroid differentiation of K562 cells. HU induced a dose-dependent stimulation of c-jun synthesis. The levels of c-jun mRNA was elevated 4 to 7.5-fold by HU within 2 h. This was followed by a gradual decline to the basal level by 24 h. Both nuclear run-on and actinomycin D pulse experiments strongly indicate that HU regulates c-jun mRNA expression by increasing the rate of synthesis as well as stabilizing the c-jun mRNA. In addition, the level of jun protein was elevated by 2 to 5-fold within 4 h in HU treated cells. Furthermore, concentrations of HU below 250 microM slightly increased the 5X AP-1/CAT activity. These results strongly suggest that HU induces both transcriptional and post-transcription regulation of c-jun during erythroid differentiation.

Cell Differentiation↗
PubMed1995

Left ventricular hypertrophy has a greater impact on survival in women than in men.

BACKGROUND: Echocardiographically determined left ventricular hypertrophy (LVH) has a well-demonstrated association with cardiovascular morbidity and mortality. However, whether or not there is a sex differential in the impact of LVH on mortality has never been systematically explored. METHODS AND RESULTS: This study enrolled 436 consecutive black patients (163 men and 273 women) free of angiographic coronary artery disease from a hospital registry. LVH (left ventricular [LV] mass/body surface area > or = 117 g/m2 in men and > or = 104 g/m2 in women) was present in 84 men (52%) and 119 women (44%). During a mean of 5 years' follow-up (range, 0 to 9), 49 patients (26 men and 23 women) died. The mortality rate was 5.40 per 100 patient-years in men with LVH and 2.58 in men without LVH (crude relative risk [RR] = 2.09) and 3.21 and 0.66, respectively, in women (RR = 4.87). In Cox regression analysis, adjusting for age, hypertension, and ejection fraction, the RR of total death for LVH versus non-LVH was 2.0 (95% confidence interval [CI], 0.8 to 5.0) in men and 14.3 (95% CI, 1.6 to 11.7) in women. For cardiac death, RR was 1.3 (95% CI, 0.4 to 3.7) and 7.5 (95% CI, 1.6 to 33.8) in men and women, respectively. Analyses using LV mass indexed by height or height with the use of different LVH cut points, comparing patients in the highest sex-specific tertile of mass index to those in the lower two tertiles, and the use of LV mass indexes as continuous variables similarly demonstrated a greater increase in risk of either fatal end point among women than men. CONCLUSIONS: These findings indicate a sex difference in the contribution of LV mass and hypertrophy to mortality in the absence of coronary artery disease.

Adult↗
PubMed1995

Interleukin-13 induces rapid tyrosine phosphorylation and activation of Raf-1 kinase in human monocytic progenitor cell line U937.

IL-13 is a pleiotropic cytokine produced by Th0, Th1-like, and CD8 T cells in response to antigen stimulation. Its biological effects include suppression of cytotoxic activity of monocytes/macrophages and suppression of pro-inflammatory cytokine production. However, the mechanism of IL-13 remains unknown. In this study we investigated the effects of rhIL-13 on tyrosine phosphorylation in U937 monocytic progenitor cells by immunoblotting and immunocomplex kinase assays. We demonstrate that rhIL-13 stimulates dose-dependent tyrosine phosphorylation of several proteins of Mr. 93, 80, 74, 49.5, 42, 30, 22 and 18 kDa within 30 sec. The effect of IL-13 was blocked by the tyrosine kinase inhibitor erbstatin. Furthermore, IL-13 induces tyrosine phosphorylation and rapid activation of raf-1 kinase. These findings provide the first evidence that the mechanism of IL-13 involves rapid tryrosine phosphorylation and activation of raf-1 serine/threonine kinase.

Blotting, Western↗
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↗
PubMed1995

Absence of black-white differences in sodium and calcium in platelets.

Consistent differences in sodium transport in red blood cells are observed in blacks compared to whites and have been the basis for speculation regarding physiologic differences in the vascular bed as well. The theoretical link between these metabolic markers and the risk of hypertension generally assumes a secondary effect on calcium. Calcium metabolism in red cells is difficult to study, however, so this proposition has never been tested directly. Given the growing importance of platelets in this area of research, and the availability of sensitive laboratory methods, we carried out a systematic examination of calcium and sodium homeostasis in this cell line among black and white normotensive subjects. No differences were noted in resting cytosolic calcium, mobilizable stores, agonist-induced response, or sodium-calcium exchange. In addition, resting sodium was not different between groups, nor was the increase in sodium induced by ouabain. A correlation of 0.3 was observed between blood pressure and both resting and stimulated cytosolic calcium (P < .05). Red cells may be atypical for studies of calcium and sodium homeostasis, and their relevance for interethnic studies of causal pathways in hypertension should be reconsidered.

Adult↗
PubMed1995

Racial/ethnic differences in health care utilization of cardiovascular procedures: a review of the evidence.

Studies based on a variety of primary data sets have consistently demonstrated that African Americans are about half as likely as whites to receive interventional therapy for coronary artery disease. Neither disease severity per se nor access to hospitals performing these procedures accounts for this finding. Likewise, available measures of income and ability to pay, including insurance status, do not explain the differences. Subtle personal factors, including physician bias and the willingness of patients to accept referral for surgery, may be important but have not as yet been measured. These findings present a challenge to the presumed equality in access to health care within the United States medical system. A new generation of health services research studies will be required to provide definitive reasons for this important disparity in treatment.

Black or African American↗