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Biomedical subjects

P C Zemel

Publications and source records attributed to P C Zemel.

16 recordsLinked to original sources
PubMed1993

Carotid plaque associations among hypertensive patients.

OBJECTIVE: To assess the relationship between cardiovascular risk factors and carotid plaque. DESIGN: Hypertensive patients were screened for randomization into the Multicenter Isradipine Diuretic Atherosclerosis Study, a trial intended to determine if blood pressure control by isradipine as compared with hydrochlorothiazide will blunt the progression of carotid plaque (intima plus media thickness, 1.3 to 3.5 mm) in patients with serum cholesterol levels of less than 6.85 mmol/L (265 mg/dL) without insulin-dependent diabetes mellitus or estrogen therapy. Demographics of those who underwent B-mode ultrasound evaluations at common, bifurcation, and internal carotid artery sites to detect plaque were assessed from a southern and a northern site. SETTING: Participants were from ambulatory outpatient clinics associated with medical schools. PATIENTS: The initial screening included 1823 hypertensive volunteer patients who were between 40 and 83 years of age who had a diastolic pressure of 90 to 114 mm Hg (or < 90 mm Hg with treatment). OUTCOME MEASURES: Complete data were collected on the variables of age, cholesterol, cigarette smoking, race, gender, and the presence of carotid plaque in 1126 patients. RESULTS: All variables were significantly associated with carotid plaque (intima plus media thickness, > or = 1.3 mm). The adjusted percentage with plaque was 66.4% +/- 3.4% for blacks and 70.1% +/- 2.3% for whites at the southern site and 42.7% +/- 4.5% for blacks and 61.3% +/- 3.2% for whites at the northern site. The rate of plaque was 75.8% among cigarette smokers, despite a mildly elevated cholesterol level. CONCLUSIONS: Although these 1126 cases do not constitute a random sample of patients, these data suggest that there may be regional differences in racial tendencies toward plaque among blacks.

Aged↗
PubMed1991

Calcium metabolism and dietary calcium in salt sensitive hypertension.

Evidence has accumulated over the past decade that suggests a relationship between low calcium intake, abnormalities in cation metabolism and hypertension in certain segments of the essential hypertension population. This evidence has been developed from epidemiological data, calcium intervention trials and observations related to biochemical alterations suggestive of a calcium deficiency in certain patients with hypertension and in animal models of essential hypertension. It is becoming increasingly evident that salt sensitive individuals are especially likely to be characterized by abnormalities of calcium metabolism and blood pressure responses to dietary calcium. In this review the role of calcium in the regulation of blood pressure is examined with an emphasis on epidemiological, biochemical, hemodynamic and dietary intervention data in the salt sensitive hypertensive patient.

Blood Pressure↗
PubMed1990

Relation between lipids and atherosclerosis: epidemiologic evidence and clinical implications.

Coronary artery disease (CAD) is the leading cause of death in most developed countries. Therefore, elucidation of risk factors and associated mechanisms for CAD has been a high priority. Data from the Framingham Heart Study and other large-scale epidemiologic studies have identified major risk factors associated with CAD, demonstrating the adverse effects of increased total and low-density lipoprotein cholesterol levels and the protective effect of high-density lipoprotein cholesterol. Other more recent investigations, including the Lipid Research Clinics Trial and the Helsinki Heart Study, have shown that lowering total cholesterol and raising high-density lipoprotein cholesterol significantly reduce the risk for CAD. Because hypertension is also a significant risk factor for CAD, the assumption has been that blood pressure reduction should offer significant benefits in terms of CAD risk. However, despite their antihypertensive efficacy, diuretics and beta blockers have failed to significantly reduce CAD morbidity or mortality. The adverse effects of these antihypertensive agents on lipid profiles, glucose metabolism and other metabolic parameters may account for their disappointing performance in reducing CAD morbidity and mortality. As a result, newer agents such as angiotensin-converting enzyme inhibitors and calcium antagonists that appear to be free of such adverse effects have garnered considerable attention for their potential to reduce CAD risk.

Cholesterol, Dietary↗
PubMed1990

Altered platelet calcium metabolism as an early predictor of increased peripheral vascular resistance and preeclampsia in urban black women.

BACKGROUND: Although preeclampsia is an important and relatively common medical problem, its pathophysiology remains unresolved and the search for a biochemical marker that precedes the hemodynamic abnormalities of preeclampsia continues. We designed a study to investigate the hemodynamic changes that characterize preeclampsia and to evaluate the metabolism of platelet intracellular calcium as a possible predictor of the development of preeclampsia. METHODS: Hemodynamic measurements and spectrofluorometric determinations of the levels of intracellular calcium in platelets in the basal state and after stimulation with an agonist were performed in 48 nulliparous black women during each trimester of pregnancy. The data on the 14 women (29 percent) in whom preeclampsia developed were then compared with the data on the other 34, who served as normotensive controls. RESULTS: There was no significant difference between the two groups in the basal levels of intracellular calcium at any time. In contrast, the levels measured after arginine vasopressin was administered during the first trimester indicated an exaggerated response in the group with preeclampsia as compared with the control group (1494 +/- 388 [+/- SEM] percent vs. 545 +/- 55 percent of base line; P less than 0.0002), which was sustained through the second and third trimesters. All but three of the women with preeclampsia had responses higher than the highest response among the controls. Platelet intracellular calcium responses to arginine vasopressin during the first trimester were a sensitive predictor of the subsequent development of preeclampsia (P less than 0.00009). Although vascular resistance was similar in the two groups during the first trimester, it subsequently decreased in the control group (P less than 0.02) but not in the group with preeclampsia. CONCLUSIONS: Our findings indicate that preeclampsia is characterized by the absence of the normal pregnancy-related decrease in vascular resistance, which is preceded in most instances by an exaggerated response of platelet intracellular calcium to arginine vasopressin early in pregnancy. We therefore propose that an increase in the sensitivity of platelet calcium to arginine vasopressin can be used as an early predictor of subsequent preeclampsia.

Adolescent↗
PubMed1990

Metabolic and hemodynamic effects of magnesium supplementation in patients with essential hypertension.

The effect of magnesium supplementation on blood pressure, erythrocyte cation metabolism, and serum lipids was evaluated in 13 patients with mild hypertension. After randomization and a 3-wk placebo run-in period, seven patients received 40 mmol Mg aspartate (20 mmol elemental Mg twice daily) and six received placebo for 3 mo. In comparison with placebo treatment, magnesium aspartate therapy had no effect on blood pressure, lipid concentrations, or erythrocyte cation metabolism. These results demonstrate that in magnesium-repleted hypertensive subjects, magnesium supplementation does not affect blood pressure or lipids probably because magnesium has no effect on cellular cation metabolism in magnesium-replete individuals.

Adult↗
PubMed1990

Effects of normal pregnancy on cellular cation metabolism and peripheral vascular resistance.

Normal pregnancy is associated with a poorly understood loss of vascular responsiveness to the pressor effects of infused angiotensin II. Since cellular cation metabolism appears to be a critical determinant of basal vascular tone and vascular reactivity, we have evaluated platelet ionized calcium, erythrocyte sodium, calcium and magnesium levels, and erythrocyte Ca-ATPase and Na/K ATPase activity in 15 normal black pregnant women (37.5 +/- 0.6 weeks gestation) and 10 normal age-matched nonpregnant black women. Plasma levels of factors potentially affecting vascular reactivity (endoxin, renin activity (PRA), and atrial natriuretic peptide (ANP] were measured by RIA and peripheral vascular resistance by biolectrical impedance. Peripheral vascular resistance was almost twice as high (P less than .003) in the normal group as in the pregnant women. Intracellular calcium concentrations were not significantly different in erythrocytes or platelets of the two groups. Although erythrocyte membrane Ca-ATPase was similar, Na/K ATPase activity was significantly higher in the pregnant subjects than in the nonpregnant controls, and intracellular sodium was lower. All three measured plasma factors, ANP, endoxin and PRA, were significantly elevated in the pregnant women. Our results suggest that the decrease in peripheral vascular resistance seen in normal pregnancy is probably not the result of alterations in cellular cation concentrations and/or cell membrane pump activity. However, the significant correlation between vascular reactivity and circulating ANP indicates this potent vasodilator may play a role in the observed decrease in peripheral vascular resistance associated with pregnancy.

Adult↗
PubMed1990

Dietary calcium induces regression of left ventricular hypertrophy in hypertensive non-insulin-dependent diabetic blacks.

Recent data from this laboratory indicate that dietary calcium supplementation causes reduced intracellular calcium in type II diabetic hypertensives. Consequently, we have assessed the effects of calcium supplementation on forearm blood flow (FBF) and vascular resistance (FVR) and left ventricular mass (LVM) in seven type II diabetic hypertensive black men with left ventricular hypertrophy (LVH) maintained off antihypertensive treatment for four weeks and then supplemented with 600 mg calcium per day for three months. A comparable group of black diabetic hypertensive patients treated with atenolol (50 mg) served as controls. LVM was determined by M-mode echocardiography and FBF and FVR by electrical impedance plethysmography at the end of the four week baseline and the 12 week supplementation periods. Calcium supplementation resulted in a decrease (P less than .05) in mean arterial pressure (from 121 +/- 4 to 114 +/- 3 mm Hg) which was accompanied by an 18% increase in FBF and a 20% reduction in FVR (P less than .05). LVM decreased from 289 +/- 22 at baseline to 240 +/- 22 g at the end of the supplementation period (P less than .02) and there was a significant correlation between changes in FBF and LVM (r = 0.82). Left ventricular end diastolic dimension decreased by 11% (P less than .05). These data indicate that calcium supplementation sufficient to normalize dietary calcium in black hypertensive diabetic men significantly reduces vascular resistance and causes partial regression of LVH.

Black People↗
PubMed1990

Increased sodium-lithium countertransport in black non-insulin-dependent diabetic hypertensives.

Black hypertensive diabetics have been shown to exhibit elevated intracellular calcium which may stimulate Na/H antiport. Since Na/Li countertransport appears to be a functional mode of Na/H antiport, we measured erythrocyte Na/Li countertransport in nondiabetic normotensive and hypertensive blacks and whites and hypertensive non-insulin-dependent diabetic blacks. Na/Li countertransport was significantly lower in the blacks than in the whites (0.170 +/- 0.017 v 0.230 +/- 0.017 mmol/L/h, P less than .02), but there was no significant difference between the black hypertensives and normotensives. In contrast, black hypertensive diabetics exhibited a significant increase in Na/Li countertransport compared to normotensive and hypertensive nondiabetic blacks (0.252 +/- 0.032 v 0.170 +/- 0.017, P less than .02. Thus, these data indicate that the activity of this antiporter is elevated in black diabetics, possibly further contributing to the development of hypertension in this population.

Adult↗
PubMed1989

Erythrocyte cation metabolism in preeclampsia.

To determine if there are abnormalities in cellular cation regulation in pregnancy-induced hypertension, erythrocyte intracellular levels of calcium, magnesium, sodium, and potassium and circulating parathyroid hormone and "endoxin" were examined in 13 women with pregnancy-induced hypertension and 34 control subjects matched for gestational age (greater than or equal to 35 weeks). Both endoxin and parathyroid hormone levels were higher in patients with pregnancy-induced hypertension than in control subjects (endoxin, 294 +/- 34 vs. 210 +/- 19 pg/ml, p less than 0.05; parathyroid hormone, 0.65 +/- 0.05 vs. 0.60 +/- 0.03 ng/ml); the increase was significant only for endoxin. Intracellular calcium was higher in the patients with pregnancy-induced hypertension (0.033 +/- 0.010 vs. 0.015 +/- 0.001 mEq/L, p less than 0.05, in the patients with pregnancy-induced hypertension and control patients, respectively) but intracellular sodium, potassium, and magnesium levels were not different. This intracellular calcium elevation may be caused directly by the increase in parathyroid hormone or indirectly by the observed elevation in endoxin. Our data indicate that the observed effect is specific because no changes in intracellular sodium, potassium, or magnesium levels were found.

Black People↗
PubMed1989

Calcium and hypertension.

A possible relationship between dietary calcium intake and blood pressure has been the focus of considerable recent observational and experimental research. To provide a current perspective, we have reviewed and summarized the epidemiologic data, evidence suggesting abnormalities in calcium metabolism in human hypertension, studies evaluating calcium supplementation in various hypertension populations, and data that may help elucidate possible blood pressure-lowering mechanisms of calcium supplementation. An important relationship between "calcium metabolism" and "salt-sensitivity" is emerging and appears to be providing insights into potential mechanisms that account for the antihypertensive properties of dietary calcium in certain individuals. More experimental work needs to be performed to further define the individuals with hypertension who demonstrate a blood pressure-lowering response to dietary calcium supplementation.

Animals↗
PubMed1988

Altered cation transport in non-insulin-dependent diabetic hypertension: effects of dietary calcium.

Erythrocyte cation transport and intracellular calcium in 15 black type II diabetic hypertensives were compared with 11 otherwise similar non-diabetic hypertensives and 16 normal black adults. The diabetic hypertensives were then randomized into either a placebo group or a calcium-supplemented (600 mg/day) group and studied again after 4 weeks. Na+,K+-ATPase activity was significantly lower in both groups of hypertensives than in the normotensives. In contrast, Ca-ATPase activity was similar among the non-diabetic hypertensive and normotensives but was markedly (approximately 60%) suppressed in the diabetics, while intracellular calcium was proportionally elevated. Calcium supplements significantly increased Ca-ATPase activity and reduced intracellular calcium and blood pressure compared with the placebo group. We conclude that type II diabetes is characterized by a defect in Ca-ATPase which may be responsible for increases in intracellular calcium and vascular resistance and which is partially corrected by dietary calcium supplementation.

Calcium↗
PubMed1982

Master standard data quantity food production code.

The Master Standard Data (MSD) Quantity Food Production Code was applied to production of roast entrées in a hospital food service. Ten stopwatch time studies were used to measure actual production times for roast entrées in the operation. Comparison showed that median production times by stopwatch exceeded MSD-predicted time by 27 min. Analysis of 13 macro elements in the hospital food service operation showed wide variability in production times because of differences in performance of individual employees and/or fluctuations in product demand. Further study of these variables, in the facility where the research was conducted, may isolate contributing factors.

Cooking↗
PubMed1982

Determining labor production time for roast entrées in hospital food services.

The Master Standard Data (MSD) Quantity Food Production Code was used to simulate entrée production in a hospital food service for 100 through 400 portions of roast entrée at intervals of 25 portions. Increases in labor time occurred at 125, 225, and 325 portions and were due to increased handling of containers and pans by employees. Production schedules, based on the MSD Quantity Food Production Code, may be developed and implemented in facilities where managers have identified standards for labor production time.

Food Service, Hospital↗
PubMed1978

Master standard data quantity food production code. Macro elements for synthesizing production labor time.

Preparation procedures of standardized quantity formulas were analyzed for similarities and differences in production activities, and three entrée classifications were developed, based on these activities. Two formulas from each classification were selected, preparation procedures were divided into elements of production, and the MSD Quantity Food Production Code was applied. Macro elements not included in the existing Code were simulated, coded, assigned associated Time Measurement Units, and added to the MSD Quantity Food Production Code. Repeated occurrence of similar elements within production methods indicated that macro elements could be synthesized for use within one or more entrée classifications. Basic elements were grouped, simulated, and macro elements were derived. Macro elements were applied in the simulated production of 100 portions of each entrée formula. Total production time for each formula and average production time for each entrée classification were calculated. Application of macro elements indicated that this method of predetermining production time was feasible and could be adapted by quantity foodservice managers as a decision technique used to evaluate menu mix, production personnel schedules, and allocation of equipment usage. These macro elements could serve as a basis for further development and refinement of other macro elements which could be applied to a variety of menu item formulas.

Animals↗
PubMed1978

Food production relationships between entrée combinations and forecasted demand.

Macro elements and values for associated Time Measurement Units were applied to three classifications of entrées to synthesize production time for 100, 300, and 500 portions. Average handling and process time for each classification and time per portion were calculated. Data revealed that roast and single-item entrées required greater average handling time than combination entrées, because more individual handling of portions was required as forecasted demand increased. Process time for combination and single-item entrées increased as forecasted demand increased. The time for the single-item classification doubled for 300 and 500 portions, because oven capacity was exceeded. Production time data were applied to six combinations (menu mixes) and quantity levels of entrée classifications to determine production feasibility in a simulated foodservice system. Production problems were encountered in five of the six menu mixes because of system constraints. This study indicated that total production time estimates would be useful to foodservice managers when planning a menu mix, scheduling production personnel, and forecasting labor costs.

Food Handling↗