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Biomedical subjects

P B Morris

Publications and source records attributed to P B Morris.

13 recordsLinked to original sources
PubMed1994

Gender differences in left ventricular functional response to aortic valve replacement.

BACKGROUND: To characterize gender differences in recovery of ventricular function and survival after aortic valve replacement (AVR), baseline characteristics related to outcome were analyzed in 1012 consecutive patients (329 women and 683 men) undergoing AVR in 1983 through 1990. METHODS AND RESULTS: Seventy-seven percent of patients had aortic stenosis (AS), 11% insufficiency (AI), and 12% mixed AS/AI; 42% underwent concomitant coronary artery bypass. Women as a group had a greater mean age (P < .0001), had AS more frequently than AI or AS/AI (P < .01), had coronary disease less frequently (P < .01), and had a higher preoperative left ventricular ejection fraction (EF) (P < .0001), although preoperative New York Heart Association (NYHA) functional class was similar (P = NS) compared with men. Male sex (P < .0001), advanced age (P < .0003), AI rather than AS (P < .01), and greater extent of coronary disease (P < .04) were independently associated with lower preoperative EF. Women with coronary disease were as likely as men (P = NS) to undergo concomitant coronary bypass, and completeness of revascularization did not differ (P = NS) by gender. Observed survival probabilities after AVR (expressed as 30-day/5-year) were .97/.81 overall, .94/.77 for women, and .98/.83 for men (P < .02). Cox model analysis showed advanced age, decreased preoperative EF, greater extent of coronary disease, requirement for annular enlargement, smaller prosthetic valve size, and advanced NYHA class (all P < .04) but neither female sex nor smaller body surface area (both P = NS) as multivariate risk factors for overall mortality. In 664 patients (66%), postoperative EF was measured a mean 1.4 years after AVR. In patients with preoperative EF < or = 45% (n = 167), the change in EF after AVR was greater (P < .02) in women (from 33 +/- 8% to 48 +/- 15%, P < .001) than in men (from 32 +/- 9% to 42 +/- 15%, P < .001). By multivariate regression analysis, female sex (P < .02) and lesser extent of coronary disease (P < .05) were independent predictors of early improvement in EF. Improvement in EF conveyed an independent subsequent survival benefit to both women (P < .03) and men (P < .001), and the magnitude of benefit did not differ (P = .4) between the two groups. CONCLUSIONS: These data suggest that gender-related factors importantly influence the adaptive and recovery response of the left ventricle to pressure and volume overload. However, gender differences in LV adaptation do not influence survival after AVR.

Aged↗
PubMed1991

Influence of diabetes and mammary artery grafting on survival after coronary bypass.

The effect of diabetes on survival after coronary bypass surgery is uncertain. Also, although the overall clinical benefits of internal mammary artery (IMA) grafting are well established, the survival benefit attributable to IMA grafting in diabetics is not well characterized. To determine the influence of diabetes and IMA grafting on survival after bypass surgery in the current surgical era, characteristics related to subsequent outcome were analyzed in 5,654 consecutive patients undergoing surgery in the decade of the 1980s. The 1,132 diabetic patients (20%) had more extensive coronary disease, had more left ventricular dysfunction, were older, were more frequently female, received a greater number of grafts (mean, 3.5 versus 3.1), and received more IMA grafts (67% versus 58%) than the 4,522 nondiabetic patients (all p less than 0.001). Overall 5-year survival probability was 0.91 in nondiabetic and 0.80 in diabetic patients (p less than 0.0001). Nondiabetic survival exceeded diabetic survival even in high-risk subgroups such as ejection fraction less than or equal to 0.40 (0.80 versus 0.66, p less than 0.02), age greater than or equal to 65 years (0.85 versus 0.73, p less than 0.0003), and, urgent surgery (0.89 versus 0.76, p less than 0.0001). By multivariate analysis, impairment of left ventricular function, advanced age, failure to use an IMA graft, diabetes, female sex, urgent surgery, number of diseased vessels, and mitral insufficiency were incremental risk factors for cardiac mortality (all p less than 0.006). Failure to use an IMA graft and diabetes were equally strong predictors of outcome. Use of an IMA graft conveyed an independent survival benefit to both nondiabetic (p less than 0.0001) and diabetic (p less than 0.02) patients. The magnitude of the survival benefit attributable to IMA grafting in the two groups did not differ (p = 0.4). Diabetes is an important risk factor for late cardiac mortality after bypass surgery and should be included in analyses of the efficacy of therapies for coronary artery disease. IMA grafting conveys a similar benefit to diabetic and nondiabetic patients but does not negate the adverse effect of diabetes on survival.

Age Factors↗
PubMed1989

Angiogenic potency of nucleotide metabolites: potential role in ischemia-induced vascular growth.

Hypoxia and ischemia are potent stimuli to vascular growth. The mechanisms by which vascular growth is induced are unknown. During ischemia, such as that which occurs in the heart, purine and pyridine nucleotides are degraded and their metabolites accumulate. At least two of these metabolites, adenosine and nicotinamide, have previously been demonstrated to induce vascular growth. The goal of this study was to determine whether other purine and pyridine metabolites have the potential to stimulate angiogenesis in vivo, to determine the relative angiogenic potency of these metabolites, and to determine if their angiogenic effects is mediated through a direct effect on endothelial cell proliferation. Purine metabolites (adenosine, inosine, hypoxanthine, xanthine, guanosine, uric acid), the pyridine metabolite nicotinamide, and chemical derivatives of nicotinamide, were tested at various concentrations for their ability to stimulate angiogenesis in the chick choriollantoic membrane assay. Although none of the purine metabolites were effective in promoting the angiogenic response, nicotinamide as well as several derivatives of nicotinamide induced an angiogenic response in a dose-dependent manner. Nicotinamide was then evaluated to determine if its angiogenic effect is a result of a direct effect on capillary endothelial cell proliferation. In concentrations of 100 microM to 1 mM nicotinamide was not demonstrated to be mitogenic for bovine capillary endothelial cells. These results demonstrate that pyridine nucleotides are indirect angiogenic agents that do not exert a primary effect on endothelial cell proliferation. The results of this study suggest that increases in vascular growth induced by ischemia and hypoxia might be mediated, at least in part, by pyridine metabolites released from ischemic tissues.

Animals↗
PubMed1988

Comparison of high- and low-intensity exercise training early after acute myocardial infarction.

The effects of the intensity of exercise training on cardiorespiratory variables were investigated in a consecutive series of men with recent (median 8 weeks) acute myocardial infarction. Forty-five patients were randomly assigned either to a high- (65 to 75% maximum oxygen consumption rate [VO2max]) or to a low-intensity (less than 45% VO2max) exercise group. Patients engaged in medically supervised aerobic training 3 sessions a week for 12 weeks. With training, mean VO2max significantly increased by 11% (2.09 to 2.31 liters/min) within the high group and by 14% (1.93 to 2.21 liters/min) within the low group. Differences between groups were not statistically significant. Both groups also had comparable changes in heart rate, blood pressure and double-product at submaximal and maximal workloads. Analysis of blood lipids revealed that both groups experienced a significant increase in high density lipoprotein cholesterol. There were no significant changes in total serum cholesterol or triglycerides. These findings suggest that within an unselected population of patients after acute myocardial infarction referred for cardiac rehabilitation, low- and high-intensity exercise training produces relatively similar changes in cardiorespiratory variables during the initial 3 months of exercise training.

Adult↗
PubMed1988

Tumor-promoting phorbol esters induce angiogenesis in vivo.

It has been hypothesized that tumor growth is dependent on the concomitant growth of its vascular supply, and thus agents that stimulate angiogenesis may help support tumor growth. Phorbol esters are potent tumor promoters that induce a variety of biochemical effects in cells, including activation of protein kinase C. The specific mechanisms responsible for tumor promotion by phorbol esters are unknown. The objective of this study was to determine whether the tumor-promoting phorbol esters can induce vascular growth. Phorbol esters were tested for their ability to stimulate angiogenesis in vivo using the chick chorioallantoic membrane and rabbit cornea assays. The active tumor promoters 12-O-tetradecanoyl phorbol-13-acetate and phorbol 12,13-didecanoate, which activate protein kinase C, were found to stimulate angiogenesis in a dose-dependent manner. In contrast, 4 alpha-phorbol 12,13-didecanoate, which is inactive as a tumor promoter and does not activate protein kinase C, did not stimulate angiogenesis. Phorbol esters may be indirect angiogenic factors, since no mitogenic effect on bovine capillary endothelial cells in culture could be detected. The results demonstrate that the tumor-promoting activity of phorbol esters may, in part, be secondary to stimulation of neovascularization to support tumor growth and suggest a role for the activation of protein kinase C in this process.

Allantois↗
PubMedDate not supplied

An accurate temperature controller for linear accelerators.

Linear accelerators use water cooling systems to ensure that certain components operate at specific temperatures. The water cooling system used on a Siemens Mevatron 77 has been found by us to be inadequate for our purposes for three major reasons. First, the controller is not able to regulate the machine temperature accurately when the beam is on for more than 10 min. Second, there is a high risk of failure at our site due to a high level of impurities in the utility water, and finally, changes in the temperature of the utility water necessitate adjustments to the temperature controller. A microprocessor-based temperature controller has been designed and built for use with a Mevatron 77. The three areas of concern mentioned have been eliminated by the use of the new controller.

Humans↗
PubMedDate not supplied

A dynamic quality control phantom for radionuclide cardiology.

A three-dimensional dynamic cardiac phantom suitable for quality control of equilibrium gated nuclear cardiographic procedures is described. Its flexible microprocessor based design provides an absolute standard for ejection fraction determination, ventricular volume quantitation, and physiologically gated single photon emission computed tomography. The cost of the phantom is comparable to that of commercially available phantoms suitable for ejection fraction quality control alone.

Heart↗