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Biomedical subjects

J Z Miller

Publications and source records attributed to J Z Miller.

At least 37 records · Page 2Linked to original sources
PubMed1988

Dietary sodium restriction as adjunctive treatment of hypertension.

To examine the effect of modest dietary sodium ion restriction in treated hypertensive individuals, we studied 114 hypertensive patients undergoing individualized dietary counseling with a research dietitian to achieve reduction in dietary sodium ion intake. A significant reduction in mean sodium ion intake was achieved after the first of three lessons and was maintained for 30 weeks with no change in potassium ion intake. Significant falls in blood pressure and body weight were observed with no significant correlations noted between the two variables, implying independence of these effects. Individuals compliant with the dietary sodium ion restriction goal (urinary excretion, less than or equal to 80 mmol/d [less than or equal to 80 mEq/24 h]) were more likely to have a reduction in number of medications than those not reaching that goal. Ninety-eight of the 114 patients completed the entire 30 weeks. Patients who dropped out tended to have lower diastolic blood pressures and required fewer medications for blood pressure control than those who completed the 30 weeks. For these reasons, patients in the former group may have been less highly motivated to complete the study. These observations suggest that modest dietary sodium ion restriction is feasible in treated hypertensive patients and that adherence to such a regimen may permit blood pressure control with fewer medications.

Adult↗
PubMed1988

Nutrient intake and blood pressure: families of adult identical twins.

To investigate the relationship of dietary intake to blood pressure, 198 adults and 53 children who were members of 92 nuclear families completed a 3-day diet diary prior to an outpatient clinic examination for cardiovascular disease risk factors. Nutrient intake was significantly related to age and anthropometric variables in adults. Sodium and potassium intake were related to blood pressure in adults, but this relationship was no longer significant after adjustment for caloric intake. The diet and blood pressure relationships in children were less clear. Multiple linear regression techniques using age, anthropometric variables, and nutrient intake demonstrated that in adults age and skinfold were the principal determinants of blood pressure, but in children age and saturated fat intake were most likely to enter the equations. In comparisons of normotensive and hypertensive adults, there were no differences in the dietary intakes of these electrolytes. The results of this investigation underscore the complex interaction of nutrient intake with body size and age. Investigators who focus only on a few nutrients and fail to account for other sources of variation can be misled.

Adult↗
PubMed1988

Blood pressure response to dietary sodium restriction in healthy normotensive children.

To examine the effect of dietary sodium restriction on blood pressure, 149 healthy, normotensive children (64 males, 85 females) participated in a study designed to lower Na intake and maintain Na excretion at less than or equal to 75 mmol/d or half usual intake for 12 wk. Na excretion was decreased during the study period in both males (112.9 +/- 6.3 vs 53.4 +/- 3.6 mmol, p less than 0.001) and females (91.1 +/- 3.2 vs 41.1 +/- 1.9 mmol, p less than 0.001). Changes in systolic blood pressure were not significant in either sex but females showed a decrease (p less than 0.05) in diastolic and mean arterial blood pressures. Because blood pressure in children is correlated with age and body size, multiple linear regression was used to adjust blood pressure levels for age and weight. These analyses yielded small but significant decreases in systolic, diastolic, and mean arterial pressure measurements. The blood pressure response was heterogeneous but this variable response could not be attributed to varying degrees of compliance within families. These results suggest that compliance with modest Na restriction does not consistently lower blood pressure in normotensive children.

Blood Pressure↗
PubMed1988

Calcium absorption from calcium carbonate and a new form of calcium (CCM) in healthy male and female adolescents.

Calcium absorption from two Ca salts was investigated in a crossover design using stable isotopic tracers in 12 healthy adolescents (6 males, 6 females). A Ca supplement in the form of Ca carbonate or Ca citric and malic acids (CCM) was ingested with a standardized breakfast and the order of administration was randomized. The oral supplement contained 250 mg elemental Ca, 21.8 mg of which was highly enriched 44Ca tracer. Thirty minutes later subjects received 3.6 mg 42Ca tracer intravenously. The molar concentrations of 42Ca and 44Ca tracers in a urine sample obtained 24 h after tracer administration were quantified by fast-atom-bombardment mass spectrometry and used to determine fractional absorption of the Ca from the supplement. Ca in the form of CCM had an increased fractional absorption (p less than 0.03) relative to Ca carbonate in healthy adolescents (36.2 vs 26.4%). This increase was not related to body size, sex, or indices of Ca metabolism.

Administration, Oral↗
PubMed1988

Genetic influences on the response to dietary salt reduction, acute salt loading, or salt depletion in humans.

The effect of heredity on blood pressure is established. However, not all genetically predisposed individuals develop an elevated blood pressure. Thus, an environmental factor may also be required for expression of this genetic predisposition. To elucidate this effect further, as well as to examine the relationship between inherited factors and the influence of salt intake, we conducted acute and chronic investigations in normal subjects. We present evidence that renal function, the renin-angiotensin-aldosterone system, and sympathetic nervous system are all influenced by genetic variance. We found that the blood pressure response to both acute changes in volume and changes in salt intake is normally distributed, supporting the notion of salt sensitivity and resistance of blood pressure. We identified phenotypes of haptoglobin as possibly useful indicators of salt sensitivity and resistance. We documented a parent-offspring resemblance in blood pressure and also a maternal-offspring resemblance in the change in blood pressure with salt reduction. We present evidence that suggests that salt-sensitive persons exhibit differences in renin-aldosterone relationships and natriuretic responses consistent with volume expansion compared to salt-resistant individuals. Finally, we identified a potential role for altered adrenoreceptors in the development of salt sensitivity. Our observations speak to the inherited nature of salt sensitivity and resistance of blood pressure. They may have mechanistic implications as well.

Diet, Sodium-Restricted↗
PubMed1987

Blood pressure and metabolic effects of calcium supplementation in normotensive white and black men.

A randomized, double-blind, placebo-controlled trial was conducted to examine the effect of calcium supplementation on blood pressure in normotensive black (n = 21) and white (n = 54) men, aged 19 to 52 years. After a four-week baseline period of weekly blood pressure measurement, subjects were randomly assigned within racial groups to either a treatment (calcium, 1500 mg/d) or placebo group for a 12-week period. During the experimental period, multiple blood pressure measurements were taken every two weeks in both the seated and supine positions, using a random baseline sphygmomanometer. A repeated-measures analysis of covariance yielded a modest but significantly lower seated mean arterial pressure in the treatment group compared with the control group, but no differences between the races. Results were similar for supine blood pressure. Calcium supplementation, in comparison with placebo, resulted in lower mean arterial pressure in normotensive white and black men during a 12-week period. The overall blood pressure-lowering effect was not correlated with the response of serum levels of total and ionized calcium, total inorganic phosphorus, or parathyroid hormone, or overnight urinary electrolyte values.

Adult↗
PubMed1987

Influence of genetic variance on sodium sensitivity of blood pressure.

To examine the effect of genetic variance on blood pressure, sodium homeostasis, and its regulatory determinants, we studied 37 pairs of monozygotic twins and 18 pairs of dizygotic twins under conditions of volume expansion and contraction. We found that, in addition to blood pressure and body size, sodium excretion in response to provocative maneuvers, glomerular filtration rate, the renin-angiotensin system, and the sympathetic nervous system are influenced by genetic variance. To elucidate the interaction of genetic factors and an environmental influence, namely, salt intake, we restricted dietary sodium in 44 families of twin children. In addition to a modest decrease in blood pressure, we found heterogeneous responses in blood pressure indicative of sodium sensitivity and resistance which were normally distributed. Strong parent-offspring resemblances were found in baseline blood pressures which persisted when adjustments were made for age and weight. Further, mother-offspring resemblances were observed in the change in blood pressure with sodium restriction. We conclude that the control of sodium homeostasis is heritable and that the change in blood pressure with sodium restriction is familial as well. These data speak to the interaction between the genetic susceptibility to hypertension and environmental influences which may result in its expression.

Adolescent↗
PubMed1987

Effects of age on renal sodium homeostasis and its relevance to sodium sensitivity.

Age-related changes in blood pressure, renal function, and sodium homeostasis suggest that sodium sensitivity of blood pressure may also be influenced by age. Blood pressure was measured in 378 normal volunteers and 198 patients with essential hypertension after an intravenous infusion of normal saline and after sodium and volume depletion. Those whose mean arterial blood pressure decreased more than 10 mm Hg after sodium and volume depletion were considered sodium-sensitive, whereas those with a decrease of less than 5 mm Hg were considered sodium resistant. The normal and hypertensive subjects were divided into groups of those above and those below 40 years of age. The blood pressure responses of both older and younger groups were normally distributed, indicating that blood pressure could either decrease or increase following volume depletion. Older hypertensive and normotensive subjects are more likely to be sodium sensitive. They usually have lower renin values than do younger subjects, but substantial heterogeneity is found. Age and renin status do not reliably predict sodium sensitivity. Volume contraction and dietary sodium restriction are more likely to decrease blood pressure in older than in younger subjects, but regimens must be tailored individually.

Adolescent↗
PubMed1987

Heterogeneity of blood pressure response to dietary sodium restriction in normotensive adults.

To investigate the effect of dietary sodium restriction on blood pressure in healthy, normotensive adults, 82 individuals (36 men, 46 women) participated in a study of restricted sodium intake (less than or equal to 75 mEq/day) for a period of 12 weeks. For the entire population there was a small but significant (p less than 0.01) decrease in mean arterial pressure during sodium restriction. The change in blood pressure was significantly correlated with age (r = 0.23, p less than 0.05). Division of the population at age 40, showed that the older individuals were more likely to have a decreased blood pressure during sodium restriction, while as a group younger adults showed no change. The individual blood pressure responses were heterogeneous with increases in pressure observed in some subjects. These results suggest that "sodium sensitivity" of blood pressure may be more evident with increasing age. Further, sodium restriction in all normotensive adults may not be innocuous.

Adult↗
PubMed1987

Familial resemblance in the blood pressure response to sodium restriction.

Familial resemblance in the blood pressure response to sodium restriction in normotensive persons was investigated. Forty-four families of identical twin children participated in a sodium restriction (less than or equal to 75 meq/day) protocol for a period of 12 weeks. Subjects were residents of central Indiana, and the study was conducted over a three-year period. Parent-offspring and sibling-sibling resemblances for actual blood pressure were not different under conditions of ad lib sodium intake versus sodium restriction. Mother-offspring resemblance in blood pressure change with sodium restriction was significant for systolic (p less than 0.001), diastolic (p less than 0.05), and mean arterial (p less than 0.05) pressures. Sibling-sibling and twin-twin resemblances were also highly significant for the change in all three blood pressures. Father-offspring resemblances were marginal (p less than 0.10). This study is, to the author's knowledge, the first to demonstrate significant familial resemblances in blood pressure change with sodium restriction in normotensive persons.

Adolescent↗
PubMed1987

Blood pressure response to potassium supplementation in normotensive adults and children.

To investigate the effect on blood pressure of a modest increase in dietary potassium intake, 38 healthy, free-living families were enrolled in a study involving 4 weeks of potassium supplementation. This was preceded by collection of five baseline measurements of blood pressure and urinary electrolyte excretion and followed by a 4-week recovery period. Although there was a significant increase in urinary potassium excretion during supplementation in both adults and children (p less than 0.001), there were no significant changes in systolic, diastolic, or mean arterial blood pressure. Height and weight increased significantly in children (p less than 0.001), and weight increased in adults (p less than 0.01) over the course of the study. Multivariate analysis of variance of blood pressure controlling for these confounding variables failed to reveal any effect of the potassium supplementation on blood pressure. These results suggest that increasing intake of dietary potassium alone in a healthy, free-living normotensive population is unlikely to have a discernible effect on blood pressure.

Adolescent↗
PubMed1987

Association of haptoglobin with sodium sensitivity and resistance of blood pressure.

Sodium sensitivity and resistance of blood pressure were examined in 117 normotensive and 85 hypertensive subjects by means of a protocol using rapid extracellular fluid volume expansion with intravenously administered saline (2 L over 4 hours) followed by a day of low dietary sodium intake (10 mEq) and volume contraction induced by a diuretic (furosemide, 120 mg orally). Genetic markers were also examined. Both hypertensive and normotensive subjects with haptoglobin 1-1 phenotype were significantly more (p less than 0.05) likely to be sodium-sensitive than were those with 2-1 or 2-2 phenotypes, and subjects with 2-2 phenotypes were more apt to be sodium-resistant. A second population was examined in which both adults and children with haptoglobin 1-1 phenotype were found to have significantly (p less than 0.05) higher casual systolic and diastolic blood pressures. These two studies independently confirm a relationship between haptoglobin phenotypes and blood pressure and suggest an environmental factor (sodium) as well.

Adolescent↗
PubMed1986

Aldosterone excretion rates in children and adults during sleep.

The present study undertook to examine aldosterone excretion during sleep as an integrated measurement of aldosterone production. A 24-hour urine collection was divided into awake and sleep fractions. Urinary aldosterone and electrolyte excretion were measured in 26 healthy children (mean age, 8.9 +/- 1.9 [SD] years) and 28 adults (mean age, 29.9 +/- 9.5 years). Aldosterone excretion in children was 5.6 +/- 3.9 (SD) micrograms/g creatinine during the awake period, which was significantly different from the 3.9 +/- 4.1 micrograms/g creatinine value recorded during sleep (p less than 0.002). In adults, awake aldosterone excretion was significantly greater than that during sleep; 4.9 +/- 2.7 versus 3.2 +/- 1.6 micrograms/g creatinine (p less than 0.001). Sleep aldosterone excretion values were highly correlated with the corresponding 24-hour aldosterone excretion values (r = 0.85, p less than 0.001) in children and in adults (r = 0.64, p less than 0.001). Sleep aldosterone excretion was correlated with 24-hour potassium excretion (p less than 0.02) only in children. Sleep aldosterone excretion correlated with neither sleep nor 24-hour sodium excretion in children or adults. Sleep electrolyte excretion rates were highly correlated with 24-hour excretion rates in both children and adults. Dexamethasone, 1 mg, administered the night before to suppress the normally high morning levels of endogenous adrenocorticotropic hormone, had no discernible effect on sleep aldosterone excretion. These results indicate that measurement of aldosterone excretion in an easily collected sleep urine sample provides a reliable index of aldosterone production in children and adults.

Adrenocorticotropic Hormone↗
PubMed1986

Definitions and characteristics of sodium sensitivity and blood pressure resistance.

Sensitivity and resistance to the effects of sodium were evaluated in normotensive and hypertensive humans by two approaches. Blood pressure was measured after an intravenous infusion of 2 L of normal (0.9%) saline and after sodium and volume depletion induced by a low sodium diet and furosemide administration in 378 normal volunteers and 198 subjects with essential hypertension. Those in whom mean arterial blood pressure decreased by at least 10 mm Hg after sodium and volume depletion were considered sodium-sensitive, and those with a decrease of 5 mm Hg or less (including an increase in pressure) were considered sodium-resistant. The second study utilized the blood pressure response to modest dietary sodium restriction in 74 normotensive subjects to identify sodium sensitivity and resistance. In both studies the responses were heterogeneous. In the first study significantly more hypertensive subjects were sodium-sensitive, as compared with those in the normotensive group (p less than 0.001). Plasma renin activity (low, normal, or high) did not predict sodium responses. In both groups sodium-sensitive individuals were significantly older (p less than 0.001) and had lower baseline renin values than sodium-resistant subjects. Factors related to the change in mean arterial blood pressure after sodium and volume depletion included baseline pressure (r = -0.54, p less than 0.001) and age (r = -0.16, p = 0.002 in the normotensive group; r = -0.28, p less than 0.001 in the hypertensive group). The response to dietary sodium restriction was also correlated with baseline pressure (r = 0.61, p less than 0.001) and the initial urinary sodium excretion (r = 0.27, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Blood pressure response to sodium restriction and potassium supplementation in healthy normotensive children.

To examine the effects of dietary sodium on blood pressure 149 healthy, normotensive children (64 males, 85 females) participated in a study to restrict sodium intake to 60 mEq/day or half of the usual intake for 3 months. Sodium excretion was significantly decreased during the study period (100.6 +/- 3.4 mEq vs 46.5 +/- 2.0 mEq, P less than .001). As a group there was no significant change in systolic and a small decrease in diastolic blood pressure (54.2 +/- 0.8 mmHg vs 53.0 +/- 0.7 mmHg, p less than .03, one tailed). Adjustment of blood pressure for weight and age and analysis of residuals yielded significant decreases in both mean arterial (p less than .05) and diastolic blood pressure (p less than .05). In the potassium supplement study, comparison of supplementation to post-supplement periods in 31 children (13 male, 18 female) showed a significantly lower (p less than .05) systolic blood pressure during supplementation (101.3 +/- 2.1 mmHg vs 103.3 +/- 20 mmHg). Analyses of diastolic pressures, sodium excretion and weight were not significant. These studies show heterogeneity in the blood pressure response to sodium restriction and suggest that sodium restriction and potassium supplementation have different effects on blood pressure in children.

Adolescent↗
PubMed1985

The efficacy of quantitative and qualitative chloride titrators in the estimation of human salt intake.

We evaluated the utility of chloride titrator sticks for facilitating the assessment of dietary salt intake, in a systematic series of clinical trials. These inexpensive devices were applied daily to 24-h or nocturnal urine specimens, thereby avoiding the inter- and intra-subject variability in salt excretion which confounds the use of occasional 24-h urine collections. Chloride and sodium concentrations in urine were highly correlated (r greater than 0.92) in either nocturnal, diurnal, or 24-h collections. The quantitative chloride titrator estimates and measured chloride concentrations were highly correlated as well (r greater than 0.99). The qualitative chloride titrator was graded on a simple scale, and was successfully employed by outpatients attempting to limit their salt intake. Commonly used antihypertensive medications did not interfere with the determinations. Additional chloride intake, such as supplemental potassium chloride, interfered with estimates of salt ingestion, but if the daily amount of potassium chloride supplement was constant, adjustments in interpretation could be made. Renal insufficiency introduced a systematic over-estimation of salt intake by the qualitative chloride tirator, but only at high salt intakes. Relative estimates of salt intake in subjects with renal failure were still possible. We conclude that chloride titrators can facilitate the management of patients who require a prescribed salt intake.

Adult↗