Boston University

About: Boston University is a education organization based out in Boston, Massachusetts, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 48688 authors who have published 119622 publications receiving 6276020 citations. The organization is also known as: BU & Boston U.

Adverse Events Associated with Testosterone Administration

Abstract: Background Testosterone supplementation has been shown to increase muscle mass and strength in healthy older men. The safety and efficacy of testosterone treatment in older men who have limitations in mobility have not been studied. Methods Community-dwelling men, 65 years of age or older, with limitations in mobility and a total serum testosterone level of 100 to 350 ng per deciliter (3.5 to 12.1 nmol per liter) or a free serum testosterone level of less than 50 pg per milliliter (173 pmol per liter) were randomly assigned to receive placebo gel or testosterone gel, to be applied daily for 6 months. Adverse events were categorized with the use of the Medical Dictionary for Regulatory Activities classification. The data and safety monitoring board recommended that the trial be discontinued early because there was a significantly higher rate of adverse cardiovascular events in the testosterone group than in the placebo group. Results A total of 209 men (mean age, 74 years) were enrolled at the time the trial was terminated. At baseline, there was a high prevalence of hypertension, diabetes, hyperlipidemia, and obesity among the participants. During the course of the study, the testosterone group had higher rates of cardiac, respiratory, and dermatologic events than did the placebo group. A total of 23 subjects in the testosterone group, as compared with 5 in the placebo group, had cardiovascular-related adverse events. The relative risk of a cardiovascular-related adverse event remained constant throughout the 6-month treatment period. As compared with the placebo group, the testosterone group had significantly greater improvements in leg-press and chest-press strength and in stair climbing while carrying a load. Conclusions In this population of older men with limitations in mobility and a high prevalence of chronic disease, the application of a testosterone gel was associated with an increased risk of cardiovascular adverse events. The small size of the trial and the unique population prevent broader inferences from being made about the safety of testosterone therapy. (ClinicalTrials.gov number, NCT00240981.)

Strain-Induced Pseudo–Magnetic Fields Greater Than 300 Tesla in Graphene Nanobubbles

Abstract: Recent theoretical proposals suggest that strain can be used to engineer graphene electronic states through the creation of a pseudo-magnetic field. This effect is unique to graphene because of its massless Dirac fermion-like band structure and particular lattice symmetry (C3v). Here, we present experimental spectroscopic measurements by scanning tunneling microscopy of highly strained nanobubbles that form when graphene is grown on a platinum (111) surface. The nanobubbles exhibit Landau levels that form in the presence of strain-induced pseudo-magnetic fields greater than 300 tesla. This demonstration of enormous pseudo-magnetic fields opens the door to both the study of charge carriers in previously inaccessible high magnetic field regimes and deliberate mechanical control over electronic structure in graphene or so-called "strain engineering."

Overall C as a measure of discrimination in survival analysis: model specific population value and confidence interval estimation

Abstract: The assessment of the discrimination ability of a survival analysis model is a problem of considerable theoretical interest and important practical applications. This issue is, however, more complex than evaluating the performance of a linear or logistic regression. Several different measures have been proposed in the biostatistical literature. In this paper we investigate the properties of the overall C index introduced by Harrell as a natural extension of the ROC curve area to survival analysis. We develop the overall C index as a parameter describing the performance of a given model applied to the population under consideration and discuss the statistic used as its sample estimate. We discover a relationship between the overall C and the modified Kendall's tau and construct a confidence interval for our measure based on the asymptotic normality of its estimate. Then we investigate via simulations the length and coverage probability of this interval. Finally, we present a real life example evaluating the performance of a Framingham Heart Study model.

Blood Pressure as a Cardiovascular Risk Factor: Prevention and Treatment

Abstract: Objective. —To examine the prevalence, incidence, predisposing factors for hypertension, its hazards as an ingredient of the cardiovascular risk profile, and the implications of this information for prevention and treatment. Methods. —Prospective longitudinal analysis of 36-year follow-up data from the Framingham Study of the relation of antecedent blood pressure to occurrence of subsequent cardiovascular morbidity and mortality depending on the metabolically linked burden of associated risk factors. Results. —Hypertension is one of the most prevalent and powerful contributors to cardiovascular diseases, the leading cause of death in the United States. There is, on average, a 20 mm Hg systolic and 10 mm Hg diastolic increment increase in blood pressure from age 30 to 65 years. Isolated systolic hypertension is the dominant variety. There is no evidence of a decline in the prevalence of hypertension over 4 decades despite improvements in its detection and treatment. Hypertension contributes to all of the major atherosclerotic cardiovascular disease outcomes increasing risk, on average, 2- to 3-fold. Coronary disease, the most lethal and common sequela, deserves highest priority. Hypertension clusters with dyslipidemia, insulin resistance, glucose intolerance, and obesity, occurring in isolation in less than 20%. The hazard depends on the number of these associated metabolically linked risk factors present. Coexistent overt cardiovascular disease also influences the hazard and choice of therapy. Conclusion. —The absence of a decline in the prevalence of hypertension indicates an urgent need for primary prevention by weight control, exercise, and reduced salt and alcohol intake. The urgency and choice of therapy of existing hypertension should be based on the multivariate cardiovascular risk profile that more appropriately targets hypertensive persons for treatment and prevention of cardiovascular sequelae. ( JAMA . 1996;275:1571-1576)

Obesity and Systemic Oxidative Stress. Clinical Correlates of Oxidative Stress in The Framingham Study

Abstract: Objective— To determine the clinical conditions associated with systemic oxidative stress in a community-based cohort. Information regarding cardiovascular risk factors associated with systemic oxidative stress has largely been derived from highly selected samples with advanced stages of vascular disease. Thus, it has been difficult to evaluate the relative contribution of each cardiovascular risk factor to systemic oxidative stress and to determine whether such risk factors act independently and are applicable to the general population. Methods and Results— We examined 2828 subjects from the Framingham Heart Study and measured urinary creatinine–indexed levels of 8-epi-PGF2α as a marker of systemic oxidative stress. Age- and sex-adjusted multivariable regression models were used to assess clinical correlates of oxidative stress. In age- and sex-adjusted models, increased urinary creatinine–indexed 8-epi-PGF2α levels were positively associated with female sex, hypertension treatment, smoking, diabetes, blood glucose, body mass index, and a history of cardiovascular disease. In contrast, age and total cholesterol were negatively correlated with urinary creatinine–indexed 8-epi-PGF2α levels. After adjustment for several covariates, decreasing age and total/HDL cholesterol ratio, sex, smoking, body mass index, blood glucose, and cardiovascular disease remained associated with urinary 8-epi-PGF2α levels. Conclusions— Smoking, diabetes, and body mass index were highly associated with systemic oxidative stress as determined by creatinine-indexed urinary 8-epi-PGF2α levels. The effect of body mass index was minimally affected by blood glucose, and diabetes and may suggest an important role of oxidative stress in the deleterious impact of obesity on cardiovascular disease.