Search PubMed⌕ Search

Biomedical subjects

J A Metz

Publications and source records attributed to J A Metz.

At least 37 records · Page 2Linked to original sources
PubMed1998

Comprehensive nutrition plan improves cardiovascular risk factors in essential hypertension.

Increased arterial pressure is known to be influenced by a variety of nutrients. Compliance with dietary recommendations for risk reduction is often limited by the complexity of their implementation. In addition, how improvements in total diet, rather than single nutrients, influence concomitant cardiovascular risk factors has not been thoroughly explored. We assessed the effects of a nutritionally complete prepared meal program, the Campbell's Center for Nutrition and Wellness plan (CCNW), compared with dietary therapy in which participants received a structured nutritional assessment and prescription and selected their own foods, in 101 women and men with mild-to-moderate hypertension. Outcome measures included blood pressure (BP), lipids and lipoproteins, glucose, glycosylated hemoglobin (HbA1c), insulin, homocysteine, nutrient intake, compliance, and quality of life. Both dietary interventions significantly lowered BP (P < .0001), while simultaneously improving the overall cardiovascular risk profile. Significantly greater benefits were observed with the CCNW plan as compared with the participant selected diet in cholesterol and LDL levels (both P < .0001), LDL:HDL (P < .001), HbA1c (P < .05), homocysteine (P < .001), total nutrient intake (P < .0001), compliance (P < .0001), and quality of life (P < .001). This study demonstrates that improving the total diet to include the full array of recommended dietary guidelines, rather than focusing on single nutrients, has significant benefits for the cardiovascular risk profile of hypertensive persons beyond BP control. Compared with typical dietary therapy, the comprehensive CCNW meal plan has significantly greater effects on multiple cardiovascular risk factors while yielding greater compliance and improved quality of life.

Adult↗
PubMed1997

Nutritional management of cardiovascular risk factors. A randomized clinical trial.

BACKGROUND: Adherence to dietary recommendations for disease management is often hindered by the complexity of incorporating them into the daily diet. Nutrition and cardiovascular scientists and food technologists collaborated to develop a prepared meal plan that meets national dietary guidelines for cardiovascular risk reduction. OBJECTIVE: To assess the clinical effects of this plan, which incorporates all National Academy of Sciences National Research Council recommended dietary allowances for vitamins, minerals, and macronutrients, compared with a patient-selected American Heart Association Step I and Step II diet plan. METHODS: This multicenter, randomized, parallel-intervention trial was conducted at 10 medical centers in the United States and Canada and involved 560 men and women with hypertension, dyslipidemia, or diabetes. Following calculation of prescriptions to meet individual nutritional requirements based on the Harris-Benedict equation, participants were randomized to the Campbell's Center for Nutrition and Wellness (CCNW) plan, which is composed of prepackaged breakfast, lunch, and dinner meals provided to participants, or a nutritionist-guided American Heart Association Step I and Step II diet, in which participants self-selected foods to meet their nutrition prescription for 10 weeks. MAIN OUTCOME MEASURES: Blood pressure (BP); lipid, glucose, glycosylated hemoglobin (HbA1c), and insulin levels; body weight; dietary intake; and quality of life. RESULTS: Patients' BP, lipid levels, carbohydrate metabolism, weight, and quality of life (P < or = .001 for all findings except low-density lipoprotein-high-density lipoprotein ratio, P = .25) all improved on both nutrition plans. Mean differences (+/-SD) between baseline and treatment clinical values for the CCNW and the self-selected diet groups (between-group P values), respectively, were as follows: systolic BP, -6.4 +/- 9.2 mm Hg and -4.6 +/- 9.0 mm Hg (P = .02); diastolic BP, -4.2 +/- 5.7 mm Hg and -3.0 +/- 5.1 mm Hg (P = .006); cholesterol, -0.32 +/- 0.58 mmol/L and -0.27 +/- 0.56 mmol/L (-12.4 +/- 22.5 mg/dL and -10.4 +/- 21.9 mg/dL) (P = .30); glucose, -0.65 +/- 1.88 mmol/L and -0.75 +/- 2.03 mmol/L (-11.7 +/- 34.0 mg/dL and -13.5 +/- 36.6 mg/dL) (P = .10); and HbA1c, -0.4% +/- 0.8% and -0.3% +/- 0.7% (P = .66). Weight loss with the CCNW and self-selected plans, respectively, was as follows: men, -4.5 +/- 3.6 kg and -3.5 +/- 3.3 kg; and women, -4.8 +/- 3.0 kg and -2.8 +/- 2.8 kg. Quality of life was significantly improved for daily and work activities (P < .05) and nutritional health perceptions (P < .05) with the CCNW plan relative to the self-selected group. Overall nutrient intake and compliance were both significantly (P < .001) better with the CCNW plan. CONCLUSIONS: Nutritionally balanced meals that meet the recommendations of national health organizations improved multiple risk factors for patients with cardiovascular disease. The CCNW plan resulted in greater clinical benefits, nutritional completeness, and compliance than the self-selected diet. The CCNW is a comprehensive nutrition plan, convenient for both prescription and practice, and appears viable for effecting favorable dietary changes in patients at high risk for cardiovascular disease.

Adult↗
PubMed1997

Vessel tearing at the edge of intracoronary stents detected with intravascular ultrasound imaging.

Stent deployment strategies have changed significantly in the past 2 yr, with "high-pressure" balloon inflations postdilatation being performed in the large majority of cases. There is currently little information about the effects of high pressure on the geometry of stent expansion and on the adjacent areas of the vessel wall. Intravascular ultrasound (IVUS) imaging is well-suited to investigate these issues, since it provides information not only about stent expansion and apposition but also about adjacent vessel-wall morphology at transition points such as the articulation site of the stent and the the stent borders. We report on the results of a cohort of 30 consecutive stent cases which were systematically examined by IVUS following high-pressure inflation. All deployments were deemed successful by angiographic inspection. However, in 6 cases, intimal disruptions or "edge tears" were noted at the stent borders by IVUS. In 5 cases, edge tears were seen to occur at the distal border, whereas in one case edge tears were seen at both the proximal and distal edges of the stent. No angiographic and sonographic parameters were different except percent plaque area at the stent margins, which was significantly higher (53 +/- 11%) in the lesions with edge tears, compared to 40 +/- 10% plaque area in the group without evidence of pocket flaps (P = 0.007). This experience suggests that intimal disruptions or "edge tears" are a relatively common occurrence following high-pressure stent deployment, and may be related to the extent of marginal dissections.

Angioplasty, Balloon↗
PubMed1997

Intravascular ultrasound: basic interpretation.

IVUS provides a new gold standard for visualization and measurement of coronary artery disease. Morphologic and morphometric observations by IVUS are in general considerably more detailed and accurate than those obtained by angiography. IVUS has led to new insights into the pathophysiology of coronary plaque accumulation with respect to adaptive vessel responses (remodeling) and their exhaustion (de-remodeling, shrinkage). Further technologic refinements need to focus on issues such as improvement in resolution and miniaturization of IVUS catheters to enhance the applicability of this imaging technique.

Animals↗
PubMed1997

Dietary compliance and cardiovascular risk reduction with a prepared meal plan compared with a self-selected diet.

Noncompliance with therapeutic diets remains a major obstacle to achieving improvements in cardiovascular disease (CVD) morbidity and mortality. This study compared dietary compliance and CVD risk factor response to two dietary interventions designed to treat hypertension, dyslipidemia, and diabetes mellitus. In a multicenter trial, 560 adults were randomly assigned to either a self-selected, mixed-food plan (n = 277), or a nutrient-fortified prepared meal plan (n = 283); each was designed to provide 15-20% of energy from fat, 55-60% from carbohydrate, and 15-20% from protein. Nutrient intake was estimated from 3-d food records collected biweekly throughout the 10-wk intervention. Compliance was determined by evaluating the participants' ability to meet specific criteria for energy intake [+/-420 kJ (100 kcal) from the midpoint of the prescribed energy range], fat intake (< 20%, < 25%, or < 30% of energy from total fat), and the National Cholesterol Education Program/American Heart Association Step 1 and 2 diet recommendations. Compliance with energy, fat, and Step 1 and 2 criteria was better in participants who followed the prepared meal plan than in those who followed the self-selected diet (P < 0.0001). Compliant participants in both groups achieved greater reductions in body weight, systolic and diastolic blood pressure, and total and low-density-lipoprotein cholesterol than noncompliant participants (P < 0.05). In general, better endpoint responses were observed with lower fat intakes regardless of group assignment. The prepared meal plan is a simple and effective strategy for meeting the many nutrient recommendations for CVD risk reduction and improving dietary compliance and CVD endpoints.

Adult↗
PubMed1993

The saturating contact rate in marriage- and epidemic models.

In this note we show how to derive, by a mechanistic argument, an expression for the saturating contact rate of individual contacts in a population that mixes randomly. The main assumption is that the individual interaction times are typically short as compared to the time-scale of changes in, for example, individual-type, but that the interactions yet make up a considerable fraction of the time-budget of an individual. In special cases an explicit formula for the contact rate is obtained. The result is applied to mathematical epidemiology and marriage models.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Contributions of dietary calcium and physical activity to primary prevention of osteoporosis in females.

In the United States and many Western nations, increasing prevalence of osteoporotic fracture is contributing to the health care system burden, and costs and needs for medical services are predicted to increase significantly by the beginning of the 21st century. Recent reports investigating developmental changes in skeletal mass of adolescent girls and young women under different experimental or ecological conditions support the contention that modification of environmental factors, especially dietary calcium and physical activity, can favorably modulate bone mass and bone density compared to controls. The peripubertal period, starting as early as 10 years of age, seems to be most responsive to modification of environmental/lifestyle factors, whereas potential gains of bone mass during late adolescence and early adulthood, although smaller, may be more readily achieved through improved dietary calcium intakes and regular exercise programs. Scientific evidence in support of these beneficial effects on bone is presented as part of the rationale for prevention of osteoporotic fractures. Also discussed is the need for a national policy to prevent osteoporosis through primary prevention strategies focused at young girls prior to puberty. The goal would be for every prepubertal girl, over the next decade, to achieve peak bone mass (and density) of the spine, hips and other bones by age 20, i.e., early adulthood. A second target group for national policy should be women in their 20s. Attainment of the goal to gain 3-5% additional bone mass during this decade would prolong the time before the fracture threshold range (low bone mass) is reached in the postmenopausal decades.

Adolescent↗
PubMed1993

Intakes of calcium, phosphorus, and protein, and physical-activity level are related to radial bone mass in young adult women.

A cross-sectional study of 38 24-28-y-old Caucasian women was undertaken to identify associations between dietary factors, physical activity (PA), and radial bone measurements during the third decade. Measurements included radial bone mineral content (BMC) and bone density (BD), nutrient intakes, and PA patterns. PA and calcium intake were positively associated by multiple linear-regression analysis whereas protein and phosphorus were negatively associated with radial bone measurements (P < 0.05). Lean body mass was positively associated with mid BMC only (P = 0.0203). No significant effect of age on BD or BMC was observed. We conclude that in this sample of 24-28-y-old women BD and BMC did not differ by age, and behaviors that had a positive impact on radial bone measurements included at least moderate PA and adequate dietary calcium intake, whereas adverse dietary practices for BD included intakes of protein and phosphorus greater than recommended amounts.

Adult↗
PubMed1991

Models on butterfly protandry: virgin females are at risk to die.

Current models on protandry in butterflies assume that females are mated instantaneously upon eclosion. However, for most butterfly species this assumption is not realistic. In this paper a model is formulated in which the mating rate depends on both male and female density. Given the female presence curve, protandry is an evolutionarily stable strategy (ESS) for males. The evolutionarily stable amount of protandry decreases with increasing death rate and decreasing encounter rate. Given the male presence curve, protandry also is an ESS for females. However, male and female ESS are not identical; moreover, in the present model a simultaneous ESS does not exist. Protandry critically depends on the assumption that females mate only once, whereas males are capable of multiple mating. If females too are capable of multiple mating, absence of protandry is the ESS for males as well as females. The model predicts that protandry depends on population density: protandry should be more pronounced in populations with high density than in populations with low density. Protandry also depends on sex ratio. It becomes more pronounced when the proportion of males among emerging adults increases.

Animals↗
PubMed1990

On the definition and the computation of the basic reproduction ratio R0 in models for infectious diseases in heterogeneous populations.

The expected number of secondary cases produced by a typical infected individual during its entire period of infectiousness in a completely susceptible population is mathematically defined as the dominant eigenvalue of a positive linear operator. It is shown that in certain special cases one can easily compute or estimate this eigenvalue. Several examples involving various structuring variables like age, sexual disposition and activity are presented.

Age Factors↗
PubMed1990

Bone mineral density in spontaneous hypertension: differential effects of dietary calcium and sodium.

Dietary calcium and sodium have been postulated to modify both bone mineral status and blood pressure regulation in humans and animals. The spontaneously hypertensive rat (SHR) manifests several defects in calcium metabolism that may contribute to its hypertension. Blood pressure and bone mineral status were measured in SHR and normotensive Wistar-Kyoto rats (WKY) as a marker of whole animal calcium metabolism. In addition, the effect of alterations in dietary calcium and sodium on bone status were examined. At 6 weeks of age, seven male SHR and seven male WKY were placed on a control diet. At the same age, 28 SHR and 28 WKY were randomized to four diets containing either 2.0% or 0.1% calcium and 1.0% or 0.25% sodium. Four markers of bone mineral status were analyzed: bone density measured by direct photon absorptiometry, and total bone calcium, phosphorus, and magnesium content measured by atomic absorption spectrophotometry. The SHR exhibited significantly lower levels (p less than 0.001) of bone density and bone magnesium content than the WKY, whereas bone phosphorus and calcium did not differ between the two strains. The 2.0% calcium diets resulted in increased bone density and bone calcium content, and lower bone magnesium in both strains. The 1.0% sodium diets were associated with decreased bone density in the SHR, but not in the WKY. These findings identify another indicator of disturbed calcium metabolism in the SHR that may be related to impaired renal calcium handling. They are consistent with previously reported reductions in renal calcium reabsorption and decreased intestinal calcium transport in older SHR.

Animals↗
PubMed1989

Dietary calcium alters blood pressure in neonatal spontaneously hypertensive rats.

Dietary alterations in young genetically hypertensive rats have been shown to have a substantial impact on subsequent blood pressure (BP) development. In the present study, spontaneously hypertensive rat (SHR) pups fostered at birth to high calcium (2%) SHR dams developed significantly lower mean arterial pressures by 28 days of age than pups fostered to low calcium (0.1%) dams (93.7 v 107.7 mm Hg, P less than .01). To determine whether BP differences were due to milk ingestion or to late lactational solid diet consumption, a second experiment was performed. Pups were fostered at birth to medium calcium (1.0%) dams and weaned at 21 days to one of three calcium diets. Blood pressures were determined at 28 days after birth. Pups weaned to the high diet at 21 days had lower pressures at 28 days than pups weaned to the low diet (94.2 v 108.3, P less than .01), suggesting that the pressure variations in the first experiment were due primarily to solid food consumption by the pups late in the suckling period. This rapid BP alteration suggests that neonatal SHR have an enhanced susceptibility to the pressure effects of dietary calcium.

Aging↗
PubMed1989

Dietary calcium alters blood pressure reactivity in spontaneously hypertensive rats.

Plasma catecholamines and blood pressure reactivity were investigated in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats maintained on three levels of dietary calcium: low (0.1%), intermediate (1.0%), or high (2.0%). In the SHR, restricted dietary calcium resulted in elevations of mean arterial pressure that were most pronounced during handling and restraint stress (p less than 0.05). There was no difference between SHR on intermediate and high calcium diets and no dietary effects in the WKY rats. Resting and stressed levels of circulating catecholamines did not differ across diet conditions in either strain. The SHR on low calcium diets had significantly larger pressor responses to infused norepinephrine (p less than 0.05). There were no differences between the rats on intermediate and high calcium diets. The results indicate that differences observed in blood pressure reactivity across diets in this study may have been a consequence of altered postsynaptic sensitivity rather than an increase in norepinephrine release.

Animals↗
PubMed1988

Modification of total body fat in spontaneously hypertensive rats and Wistar-Kyoto rats by dietary calcium and sodium.

Studies have indicated that spontaneously hypertensive rats (SHRs) consuming diets high in calcium (Ca2+) and sodium (Na+) weigh less compared to SHRs consuming diets lower in Ca2+ and Na+ while consuming similar amounts of food. Based on calcium's known effects on lipid metabolism, it was important to determine if manipulations of dietary Ca2+ and Na+ would modify total body fat in the SHR. Fifteen SHRs and 17 Wistar Kyoto rats (WKY) were randomized at 4 weeks of age to three diets varying in Ca2+ and Na+: 2% Ca2+/1.0% Na+, 1% Ca2+/0.45% Na+, and 0.1% Ca2+/0.25% Na+. At 15 weeks of age, blood pressure, body weight, and body composition were determined. Significant differences in body weight, blood pressure, and total body fat were observed between diet groups in both strains. Dietary Ca2+ and Na+ induced favorable changes in total body fat content in both the SHR and WKY.

Adipose Tissue↗
PubMed1987

Genetic variability in response to dietary calcium.

Supplemental dietary calcium has been shown to reduce blood pressure in spontaneously hypertensive rats while restricted calcium diets cause an elevation in blood pressure. This latter nutrient effect has been enhanced by modest sodium restriction and is associated with a reduction in serum ionized calcium concentration. To determine whether alterations of dietary calcium and sodium have a similar influence on blood pressure in genetically normotensive rats, Fisher 344, Wistar Furth, and ACI rats were fed either a low (0.1%) calcium, low (0.25%) sodium diet or normal (1.0%) calcium, normal sodium (0.45%) diet from 4 weeks of age through 29 weeks of age. Indirect measurements of systolic blood pressure showed that only the Fisher 344 rats consistently responded to the low calcium/low sodium diets with an elevation of blood pressure. There was considerable variation in serum electrolytes across strains in the normal diets but all three strains experienced a reduction in ionized calcium and an elevation in phosphorus and magnesium on the restricted diets. In the Fisher 344 rats there were significant (p less than .05) inverse correlations among systolic blood pressure and serum ionized and total calcium concentrations and positive correlations among systolic blood pressure, phosphorus, and magnesium. There was no significant correlation between serum electrolytes and blood pressure in the other two strains. The data indicate that there is genetic variability in the blood pressure response to alterations in dietary calcium and sodium. The pattern of change in serum electrolytes across strains suggests that diet-induced alterations of serum electrolytes, specifically calcium, are not necessarily predictive of a pressor response. It would appear that some other calcium-sensitive physiological process involved in blood pressure regulation must respond differentially to calcium availability across strains.

Animals↗