Cardiovascular abnormalities associated with human and rodent obesity

Obesity is a major risk factor for cardiovascular disease. However, a direct link between these two states is difficult to establish, since obesity frequently occurs with other disease states such as diabetes, hypertension and atherosclerosis. Clinical studies have clearly shown that uncorrected obesity is associated with cardiac hypertrophy and compromised ventricular function. A number of rodent models of obesity have been studied in terms of cardiovascular adaptations. Cardiac function of the obese Zucker rat appears to be normal at a younger age. Only after several months is depression in cardiac function discernable. These animals are mildly hypertensive, but do not exhibit the characteristic increase in cardiac output associated with human obesity. A unique characteristic of JCR:LA-cp rat is that they develop atherosclerotic and myocardial lesions. Hearts from these animals will maintain normal function when perfused with physiological levels of calcium. At higher calcium concentrations, however, mechanical function becomes impaired. Dietary-induced obese rats exhibit many of the hemodynamic alterations associated with human obesity, but there is no evidence to-date that these animals will develop severe cardiac depression. Short-term weight reduction apparently has beneficial cardiovascular effects, but weight cycling may be harmful. Given the widespread occurrence of obesity, further studies are warranted to characterize the cardiac manifestations of this condition.     

Evaluation of humoral immune responses in cattle grazing endophyte-infected or endophyte-free fescue

Anecdotal reports suggest cattle with fescue toxicosis may not respond to vaccination and thus, experience increased incidence of Bovine Respiratory Disease Complex (BRDC) when shipped to feedlots. Fescue toxicosis causes hypoprolactemia in cattle. Hypoprolactemia decreases humoral immune responses in mice. Therefore, a study was conducted to compare the magnitude of primary and secondary humoral immune responses against specific antigens in cattle grazing endophyte-infected or endophyte-free fescue. Angus steers were blocked by weight and allocated into four groups. Two groups grazed endophyte-infected (EI) fescue and the other two groups grazed endophyte-free (EF) fescue. All steers were injected IM on d 0 and 21 with lysozyme without adjuvant and concanavalin. A (Con A) with sheep red blood cells (SRBC) in incomplete adjuvant of Freund. Steers were bled on days 0, 21 and 35 post-vaccination. Average daily gains (ADG), alkaline phosphatase (ALP) activity, cholesterol concentrations, rectal temperatures, and serum prolactin concentrations were measured to confirm fescue toxicosis in steers grazing EI fescue. Antibodies to Con A and SRBC were determined by ELISA and hemagglutination assay, respectively. The ADG were decreased for the EI group during the first month. Rectal temperature were elevated and serum prolactin concentrations were decreased in the EI group. Cholesterol and ALP concentrations also were decreased in the EI group. Primary and secondary immune responses against Con A tended to be increased and were increased against SRBC in the EI group. Antibodies against lysozyme were not induced in either group. In conclusion, cattle grazing EI fescue mounted similar humoral immune responses to vaccination, despite hypoprolactemia, as cattle grazing EF fescue. Increases in bovine respiratory disease in cattle maintained on EI fescue probably is not associated with lack of humoral immune response to vaccination protocols as a result of fescue toxicosis.     

A population study of the natural history of Wolff-Parkinson-White syndrome in Olmsted County, Minnesota, 1953-1989

BACKGROUND: Virtually all natural history studies of Wolff-Parkinson-White (WPW) syndrome have been case series and, as such, have been constrained by referral biases, skewed age and sex distributions, or brief follow-up periods. The purpose of our study was to examine the natural history, the development of arrhythmias, and the incidence of sudden death in an entire cohort of pediatric and adult WPW patients from a community-based local population. METHODS AND RESULTS: We identified 113 residents of Olmsted County, Minnesota, during the period 1953-1989 using the centralized records-linkage system provided by the Mayo Clinic and the Rochester Epidemiology Program Project. Medical records and ECGs were reviewed to confirm the diagnosis and to establish pathway location by ECG criteria. Follow-up, via record review and telephone interview, was complete in 95% of subjects through 1990. The incidence of newly diagnosed cases was approximately four per 100,000 per year. Preexcitation was not present on the initial ECG of 22% of the cohort. Approximately 50% of the population was asymptomatic at diagnosis, with 30% subsequently having symptoms related to arrhythmia at follow-up. Two sudden cardiac deaths (SCD) occurred over 1,338 patient-years of follow-up, yielding an overall SCD rate of 0.0015 (95% confidence interval, 0.0002-0.0054) per patient-year. No SCD occurred in patients asymptomatic at diagnosis. CONCLUSIONS: The incidence of sudden death in a local community-based population is low and suggests that electrophysiological testing should not be performed routinely in asymptomatic patients with WPW syndrome. Nevertheless, young, asymptomatic patients, particularly those < 40 years old, should return for medical follow-up should symptoms develop.