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Biomedical subjects

C E Davis

Publications and source records attributed to C E Davis.

At least 19 recordsLinked to original sources
PubMed1992

Effect of enalapril on mortality and the development of heart failure in asymptomatic patients with reduced left ventricular ejection fractions.

BACKGROUND: It is not known whether the treatment of patients with asymptomatic left ventricular dysfunction reduces mortality and morbidity. We studied the effect of an angiotensin-converting--enzyme inhibitor, enalapril, on total mortality and mortality from cardiovascular causes, the development of heart failure, and hospitalization for heart failure among patients with ejection fractions of 0.35 or less who were not receiving drug treatment for heart failure. METHODS: Patients were randomly assigned to receive either placebo (n = 2117) or enalapril (n = 2111) at doses of 2.5 to 20 mg per day in a double-blind trial. Follow-up averaged 37.4 months. RESULTS: There were 334 deaths in the placebo group, as compared with 313 in the enalapril group (reduction in risk, 8 percent by the log-rank test; 95 percent confidence interval, -8 percent [an increase of 8 percent] to 21 percent; P = 0.30). The reduction in mortality from cardiovascular causes was larger but was not statistically significant (298 deaths in the placebo group vs. 265 in the enalapril group; risk reduction, 12 percent; 95 percent confidence interval, -3 to 26 percent; P = 0.12). When we combined patients in whom heart failure developed and those who died, the total number of deaths and cases of heart failure was lower in the enalapril group than in the placebo group (630 vs. 818; risk reduction, 29 percent; 95 percent confidence interval, 21 to 36 percent; P less than 0.001). In addition, fewer patients given enalapril died or were hospitalized for heart failure (434 in the enalapril group; vs. 518 in the placebo group; risk reduction, 20 percent; 95 percent confidence interval, 9 to 30 percent; P less than 0.001). CONCLUSIONS: The angiotensin-converting--enzyme inhibitor enalapril significantly reduced the incidence of heart failure and the rate of related hospitalizations, as compared with the rates in the group given placebo, among patients with asymptomatic left ventricular dysfunction. There was also a trend toward fewer deaths due to cardiovascular causes among the patients who received enalapril.

Blood Pressure↗
PubMed1992

The relation of high density lipoprotein cholesterol and its subfractions to apolipoprotein A-I and fasting triglycerides: the role of environmental factors. The Atherosclerosis Risk in Communities (ARIC) Study.

Cross-sectional analysis of four general representative populations of middle-aged adults in the United States in 1986-1989 provides estimates of the close relation of high density lipoprotein cholesterol (HDL cholesterol) to its major structural apolipoprotein (apolipoprotein A-I) and to fasting plasma triglyceride levels. HDL cholesterol differences of approximately 0.4 mg were associated with 1-mg differences in apolipoprotein A-I; differences of 20% in HDL cholesterol (reductions) were associated with triglyceride doublings. Variation in apolipoprotein A-I and triglyceride concentration together accounted for 66% of the population variance in HDL cholesterol. The uniformity of this pattern in the four race-sex groups studied suggests an important role of triglyceride-cholesterol transfer as a determinant of HDL cholesterol. The fundamental relations observed among HDL cholesterol, apolipoprotein A-I, and triglycerides were unaltered by levels of factors under personal volition. The volitional factors appeared to influence HDL cholesterol indirectly: Obesity and physical activity were affected primarily through their associations with triglycerides, and alcohol use and smoking through associations with apolipoprotein A-I. The association of alcohol use with elevated HDL cholesterol was attenuated in persons with greater body mass.

Aged↗
PubMed1992

Body mass index and body girths as predictors of mortality in black and white men.

Anthropometric measurements collected from black and white men in the 1960 (n = 946) and 1963 (n = 456) examinations of the Charleston Heart Study cohort (Charleston County, South Carolina) were examined as predictors of all cause and coronary heart disease mortality. Anthropometric measurements included body mass index, chest girth (at the third intercostal space), abdominal girth (at the umbilicus) and midarm circumference. Vital status of 98 percent of the cohort was determined through 1988. Body mass index was not associated with mortality in the white men; however, it was predictive of all cause and coronary heart disease mortality in the black men. Analyses conducted separately in the lower and upper range of body mass index in black men showed the adjusted relative hazard at the 50th versus the 10th percentile of body mass index was 0.54 for all cause mortality, but was not significant for coronary heart disease mortality; whereas the adjusted relative hazard for the 90th relative to the 50th percentile was 1.7 for coronary heart disease deaths, but not significant for deaths from all causes. The circumference measurements were not predictive of all cause or coronary heart disease mortality in the white men. In the black men, the adjusted relative hazard ratios for all cause mortality for the 85th relative to the 15th percentiles were 0.22 for midarm circumference and 2.0 for abdominal circumference.

Age Factors↗
PubMed1992

Association of coagulation factors and inhibitors with carotid artery atherosclerosis. Early results of the Atherosclerosis Risk in Communities (ARIC) Study.

Several population studies have shown that plasma levels of fibrinogen and factor VII are significantly associated with ischemic cardiovascular events. However, there is little information regarding the association of hemostatic factors with early atherosclerosis. To evaluate this, we compared the plasma concentrations of several coagulation proteins (fibrinogen, factor VII, factor VIII, von Willebrand factor, protein C, and antithrombin III) between 385 case patients, defined by high-resolution B-mode ultrasonography as having carotid arterial wall thickening, and 385 age-, race-, and sex-matched control subjects. These case patients and control subjects were selected from participants in a prospective population investigation, the Atherosclerosis Risk in Communities (ARIC) Study, who were examined between May 1987 and May 1989. Plasma fibrinogen, factor VII, protein C, and antithrombin III levels were significantly higher in case patients than in control subjects (P < 0.05). Factor VIII and von Willebrand factor were not different. These findings were supported by quartile distribution and univariate analysis. However, only fibrinogen remained significantly associated with carotid atherosclerosis on multivariate analysis taking other atherosclerosis risk factors into consideration. A one standard deviation increase in fibrinogen (67 mg/dL) was associated with a 1.6-fold increase in the odds of carotid atherosclerosis univariately (P < 0.001) and with a 1.3-fold increase in the odds multivariately (P = 0.010). Further analysis revealed that the association of fibrinogen with carotid atherosclerosis was somewhat stronger in cigarette smokers than in nonsmokers. This early case-control analysis of the ARIC Study demonstrates a significant association between plasma fibrinogen concentration and early atherosclerosis in the carotid arteries. In the context of published findings from population studies, our results indicate that plasma fibrinogen concentrations may be a useful marker for identifying individuals at high risk of developing arterial thrombotic disorders.

Antithrombin III↗
PubMed1992

Relations between hemostasis variables and cardiovascular risk factors in middle-aged adults. Atherosclerosis Risk in Communities (ARIC) Study Investigators.

The relations between hemostatic variables and cardiovascular risk factors were examined in a biracial population sample of middle-aged adults. Fibrinogen, factor VII, factor VIII, von Willebrand factor, protein C, and antithrombin III levels varied considerably by age, sex, and race. Hemostatic variables also were associated with several life-style and biochemical risk factors. For the most part, higher levels of the risk factors were associated with higher levels of the hemostatic variables. The findings point to potential confounders that warrant consideration in cardiovascular disease studies, and/or mechanisms by which cardiovascular risk is conferred. They also suggest that modification of the cardiovascular risk factors may have the potential to alter the risk of thrombosis.

Antithrombin III↗
PubMed1992

Antihypertensive treatment and US trends in stroke mortality, 1962 to 1980.

OBJECTIVES: This study examines the association between increases in antihypertensive pharmacotherapy and declines in stroke mortality among 96 US groups stratified by race, sex, age, metropolitan status, and region from 1962 to 1980. METHODS: Data on the prevalence of controlled hypertension and socioeconomic profiles were obtained from three successive national health surveys. Stroke mortality rates were calculated using data from the National Center for Health Statistics and the Bureau of the Census. The association between controlled hypertension trends and stroke mortality declines was assessed with weighted regression. RESULTS: Prior to 1972, there was no association between trends in controlled hypertension and stroke mortality declines (beta = 0.04, P = .69). After 1972, groups with larger increases in controlled hypertension experienced slower rates of decline in stroke mortality (beta = 0.16, P = .003). Faster rates of decline were modestly but consistently related to improvements in socioeconomic indicators only for the post-1972 period. CONCLUSIONS: These results do not support the hypothesis that increased antihypertensive pharmacotherapy has been the primary determinant of recent declines in stroke mortality. Additional studies should address the association between declining stroke mortality and trends in socioeconomic resources, dietary patterns, and cigarette smoking.

Black or African American↗
PubMed1992

Basic epidemiology of tuberculosis in Peru: a prevalence study of tuberculin sensitivity in a Pueblo joven.

Tuberculosis continues to cause significant morbidity and mortality in developing nations. As a first step in defining the magnitude of the problem in Peru, we determined the prevalence of tuberculin sensitivity in an age-stratified, community-based population on the outskirts of Lima in December 1990. The overall prevalence of 10 mm or more induration in 368 individuals was 34%. When stratified by age, the prevalence was 12% in the 0-1-year-old group, 18% in the 2-4-year-old group, 24% in the 5-14-year-old group, 60% in the 15-24-year-old group, and 68% in the > or = 25-year-old group. Vaccination with bacillus Calmette-Guerin (87% of the study population) caused significant increases in weak (5-9 mm) reactions to purified protein derivative, but did not cause strong (10 mm or more) reactions. The prevalence of tuberculous infection in this population is higher than that previously reported in Peru and in most other high-risk populations. Unfortunately, the current political and economic situation in Peru makes it difficult to implement public health measures to prevent infection and progression of infection to disease.

Adolescent↗
PubMed1992

Distributions of hemostatic variables in blacks and whites: population reference values from the Atherosclerosis Risk in Communities (ARIC) Study.

The Atherosclerosis Risk in Communities Study measured hemostatic variables in nearly 16,000 men and women, aged 45 to 64 years, from four US communities. This report, based on the first 12,681 participants, presents distributions of fibrinogen concentration, factor VII activity, factor VIII activity, von Willebrand factor antigen, protein C antigen, antithrombin III activity, and activated partial thromboplastin time. Many of the hemostatic variables differed between blacks and whites, and by sex and age. For example, compared to whites, blacks had higher mean values of fibrinogen, factor VIII, von Willebrand factor, and antithrombin III, and lower mean values of protein C. Some seasonal fluctuations in hemostatic variables were noted; most notably, mean values of factor VII were lowest and protein C were highest in subjects examined in the summer compared to those examined during the other seasons. These results provide population-based reference values on blacks and whites for those interested in the relation of hemostasis to disease.

Arteriosclerosis↗
PubMed1992

Body mass index and body girths as predictors of mortality in black and white women.

BACKGROUND: The high prevalence of obesity in black women has been hypothesized to contribute to higher rates of coronary heart disease and total mortality. Investigators have recently refined the study of obesity by differentiating anatomic patterns of the physical location of adipose tissue on the body. We examined fat patterning as a predictor of mortality in black women. METHODS: Body mass index (BMI) and body girths were examined as predictors of all-cause and coronary heart disease mortality during 25 to 28 years of follow-up in black and white women in the Charleston Heart Study. RESULTS: The BMI was associated with all-cause and coronary heart disease mortality in white, but not black, women. After controlling for differences in BMI, the risk of all-cause mortality was greater in white women with larger chest and abdominal girths, while midarm girths were inversely associated with mortality. The hazard at the 85th percentile relative to the 15th percentile of abdomen/midarm ratio was 1.44 in models that included BMI, education, and smoking as covariates. In black women, the girths were not predictive of either all-cause or coronary heart disease mortality. CONCLUSIONS: The failure of BMI and fat patterning to predict mortality in black women challenges previously held assumptions regarding the role of overweight in the higher mortality experienced by black women.

Adult↗
PubMed1991

Population correlates of plasma fibrinogen and factor VII, putative cardiovascular risk factors.

Recent prospective investigations have reported that higher plasma fibrinogen concentrations and higher factor VII coagulant activity are associated with greater risk of cardiovascular disease. To discover what characteristics may influence fibrinogen and factor VII, we analyzed data from the Atherosclerosis Risk in Communities Study obtained from over 12,000 men and women, aged 45-64 years, from four communities in December 1986 to June 1989. Fibrinogen was higher in blacks than whites and in women than men; in general, it increased with age, smoking, body size, diabetes, fasting serum insulin, LDL cholesterol, lipoprotein(a), leukocyte count, and menopause, and it decreased with ethanol intake, physical activity, HDL cholesterol, and female hormone use. Factor VII was higher in women than men and, in women, increased with age; in both sexes, it increased with body size, triglycerides, LDL cholesterol, and HDL cholesterol, and it decreased with ethanol intake. These findings indicate that elevations in fibrinogen and factor VII may be modifiable through appropriate lifestyle changes.

Body Constitution↗
PubMed1991

Myosin isoform transitions and physiological properties of regenerated and re-innervated soleus muscles of the rat.

Soleus muscles in young female rats were destroyed by the local injection of the crude venom of the Australian tiger snake, Notechis scutatus and allowed to regenerate. The regenerated muscles consisted almost exclusively of type I muscle fibres, and histograms of fibre cross-sectional area were unimodal. In contrast the normal contralateral muscles consisted of a mixture of type I and IIa fibres, and histograms of fibre cross-sectional area were bimodal. There was no change in the ability of the regenerated muscles to generate tension in response to indirect stimulation, and muscle fibre number and motor unit index were similar to controls. The regenerated muscles often contained split muscle fibres, but if re-innervation of the regenerated muscles was delayed, splitting did not occur. The principal features of the regenerated muscles (fibre type homogeneity, unimodal histograms of muscle fibre area, normal numbers of muscle fibres and normal motor unit index) were reproduced in soleus muscles that were simply denervated by nerve crush and allowed to re-innervate. We conclude that the phenotypic homogeneity of the regenerated muscles is a consequence of the temporary disconnection of muscle from nerve, rather than of the cycle of degeneration/regeneration, and suggest that this disconnection results in the reprogramming of the soleus motor neurones.

Animals↗
PubMed1991

Expression and deletion analysis of the Trypanosoma brucei rhodesiense cysteine protease in Escherichia coli.

Trypanosoma brucei, the cause of African sleeping sickness, differentiates in the mammalian bloodstream from a long, slender trypanosome into a short, stumpy trypanosome. This event is necessary for infection of the tsetse fly and maintenance of the life cycle. We have previously shown that the stumpy form contains 10- to 15-fold-greater cysteine protease activity than either the slender form or the insect midgut procyclic, and we have isolated a cDNA encoding the protease. In order to determine whether the cDNA encodes the developmentally regulated cysteine protease, we have purified the protease from trypanosomes and have made a polyclonal antiserum against it. The trypanosomal protease gene was then expressed in Escherichia coli with three different methionines within the pre- and propeptides acting as initiation sites. In each case, a protein was synthesized that was recognized by an antiserum specific for the developmentally regulated trypanosomal cysteine protease. The protein synthesized from the more upstream initiation site within the propeptide was proteolytically active. The recombinant protease and the trypanosomal enzyme were identical with respect to peptide substrates and protease inhibitors. The protein remained active when synthesized in a truncated form lacking the nine consecutive prolines and carboxy-terminus extension, indicating that the terminal 108 amino acids are not necessary for proteolytic activity.

Amino Acid Sequence↗
PubMed1990

A single cholesterol measurement underestimates the risk of coronary heart disease. An empirical example from the Lipid Research Clinics Mortality Follow-up Study.

In prospective epidemiologic studies of coronary heart disease, a single measurement of cholesterol is made to assess its relationship to the risk of coronary disease. Statistical theory states that if this measurement is subject to within-individual variability, the strength of the relationship will be underestimated. This is empirically shown for the example of plasma cholesterol. For the Lipid Research Clinics Follow-up Study population (comprising 2170 white men over 30 years of age), the age-adjusted coronary heart disease mortality regression coefficient increases from .453 to .496 if the average of two cholesterol measurements is used instead of a single measurement. Since the correlation between the two repeated cholesterol measurements is .815, an increase in the regression coefficient up to .556 would be expected if the true cholesterol values were available. Thus, epidemiologic studies have substantially underestimated the strength of the relationship between cholesterol levels and the risk of coronary disease by calculating the relationship on the basis of a single cholesterol determination.

Adult↗
PubMed1990

The assessment of muscle fibre loss after the injection of the venom of Notechis scutatus (Australian tiger snake).

We have used the W.H.O. International Reference Venom from the Australian tiger snake, Notechis scutatus, to study possible methods for the assessment of local myonecrosis caused by this venom. We made subcutaneous injections of various doses (0.25-20.0 micrograms) of venom into the antero-lateral aspect of the rat hind limb. The soleus muscle was removed after 24 hr and muscle fibre loss calculated from photo-montages of histological sections. Muscle tissue which had been either frozen or wax-embedded was preferable to resin-embedded tissue for making muscle fibre counts. There was a dose-dependent relationship between muscle fibre loss and the amount of venom inoculated. One microgramme of crude venom caused the loss of 50% of muscle fibres from the soleus muscle. This dose of venom neutralized by 1.5 microliters of the W.H.O. International Standard Antivenom for Notechis scutatus. Muscle wet weight increased following the inoculation of venom, to reach a peak of 42% at a dose of 0.5 microgram. There was no correlation between fibre loss and increase in wet weight. Biochemical analysis of both the venom-damaged muscle and the plasma showed that there was a strong linear correlation (r = 0.95) between loss of muscle aspartate aminotransferase and muscle fibre loss. There was a non-linear relationship between muscle fibre loss and the increase of plasma aspartate aminotransferase (EC 2.6.1.1). There was no correlation between either the loss of muscle creatine kinase or the increase of plasma creatine kinase and muscle fibre loss. We conclude that direct measurements are required to calculate muscle fibre loss with precision, but that the loss of muscle aspartate aminotransferase AST and its release into the plasma may also be important criteria to be used when studying local necrosis.

Animals↗
PubMed1990

Empirical Bayes estimates of subgroup effects in clinical trials.

At the completion of a clinical trial it is often desirable to compare the treatments within subgroups of patients. The results of the subgroup analysis are usually reported for the subgroups within which sizable treatment differences are found. This practice can lead to an overestimate of the difference between treatments within the subgroups reported. One way of adjusting for this bias is to use empirical Bayes methods which shrink the extreme estimates toward the overall measure of treatment difference. Both point and interval estimates can be obtained. The computations are illustrated with an example using subgroup data from the Lipid Research Clinics Coronary Primary Prevention Trial.

Bayes Theorem↗