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Biomedical subjects

J Z Miller

Publications and source records attributed to J Z Miller.

At least 55 records · Page 3Linked to original sources
PubMed1984

Genetic, familial and racial influences on blood pressure control systems in man.

This paper reviews investigations by the Indiana University Medical Centre Hypertension Research Centre into genetic influences on blood pressure control systems in man. Our studies have used the families of adult identical twins to partition the relationships of age, sex and body size to the genetic contribution to blood pressure variability. These studies provide little evidence for environmental influence on the familial aggregation of blood pressure and suggest that at least 63% of the variability is due to genetic factors. Studies on the renin-angiotensin-aldosterone system and on the kidney's ability to excrete sodium were also undertaken in identical and fraternal twins, as well as in black and white subjects, and provided unequivocal evidence of genetic control. Studies in first degree relatives of patients with essential hypertension have demonstrated higher plasma renin levels and a decreased ability to excrete a sodium load when compared to first degree relatives of normotensive subjects. Blacks in the U.S.A. have a decreased ability to excrete a sodium load and a greater rise in blood pressure with sodium loading than do whites. We suggest that the heritability of blood pressure is directly related to a genetic influence on the level of renin and that this increase in renin level results in subtle increases in angiotensin II. These chronic elevations of angiotensin II directly increase blood pressure and decrease the kidney's ability to excrete sodium by either a direct renal effect or indirectly by stimulating aldosterone-dependent sodium retention.

Adult↗
PubMed1984

Influence of home monitoring on compliance with a reduced sodium intake diet.

To test the utility of a qualitative chloride titrator strip in facilitating compliance with a reduced sodium intake diet, we enrolled 32 patients into a randomized crossover trial comprising two study periods of four weeks each. The study periods were begun after the patients had undergone extensive instruction in the diet and the use of the strip. A high degree of correlation between the patient's and the laboratory's interpretation of the strip result was identified in 29 of the subjects. Ability to use the strip was not related to level of education. A total of 12 patients achieved compliance with the diet when using the strips. Of these, nine were able to achieve compliance without the strips. Ten patients (30%) had significantly lower sodium intake when using the strips than when they did not use them. We conclude that the use of the chloride titrator strip can be mastered by most patients and, in conjunction with dietary counseling, can facilitate compliance with a reduced sodium intake diet.

Adult↗
PubMed1984

Estimation of dietary sodium intake in children.

To examine the utility of nocturnal urine collections in the estimation of dietary sodium intake in children, 29 families who agreed to lower their dietary sodium intake to less than 65 mEq/d were studied. A total of 58 adults and 95 children collected urine specimens weekly or biweekly before and after being instructed in a dietary sodium restriction regimen. Urine collections were fractionated into a diurnal and nocturnal portion. Sodium was measured directly, and estimated by measuring chloride excretion with a chloride titrator stick. Nocturnal chloride and 24-hour sodium excretion were highly correlated in adults (r = .75), and slightly less so (r = .56) in children. The slopes of the relationships were not different. Discriminant analysis showed that two or more chloride estimates permitted classification of both adults and children into the low sodium intake category with 100% accuracy, and into the normal sodium intake category with 75% accuracy. It was concluded that nocturnal chloride estimates are as useful in estimating compliance to a reduced sodium intake in children as in adults.

Adolescent↗
PubMed1983

Sodium sensitivity in normotensive human subjects.

Compelling evidence implicates a high sodium intake in the development and maintenance of arterial hypertension. However, dietary sodium restriction reduces blood pressure in only a fraction of hypertensive patients. Studies in normotensive persons suggest that blacks and older persons excrete a sodium load less efficiently than persons of the same sex and race who are also matched for body weight and body surface area. Blacks show a greater natriuresis and decrease in blood pressure in response to volume contraction with furosemide administration than whites. These observations are consistent with an intrinsic renal abnormality in blacks and older persons, resulting in modest volume expansion. Such changes may contribute to sodium sensitivity and promote the development and maintenance of hypertension in persons with a high sodium intake.

Adult↗
PubMed1981

Twin-family studies of perceptual speed ability. II. Parameter estimation.

Offspring of monozygotic (MZ) twins form half-ships that permit a direct test of maternal effects and differentiate several sources of between-family environmental variance. Combined with conventional twin data, these genetic half-sibships provide a unique data set for estimating sources of variation in quantitative traits. To illustrate, genetic and environmental parameters were estimated for Identical Pictures Test data obtained from children of MZ twin parents and an (approximate) age-matched cohort of like-sex twins. Analyses of variance of the data, standardized for age and sex, yield 12 mean squares to which gene-environment models were fit. Maximum-likelihood estimation revealed a complete absence of maternal influences and shared environmental effects; a simple two-parameter model, assuming random mating and attributing variation in test scores to additive genes and within-family environment, adequately accounts for the familial data.

Adolescent↗
PubMed1981

Genetic aspects of the blood pressure control system.

Utilization of several genetic models (twins, families of monozygotic twins, characterized hypertensives and normotensive first-degree-relatives of essential hypertensives) has permitted us to probe for evidence of genetic mediation of several components of the blood pressure control system in humans. These studies have identified evidence for genetic mediation of systolic blood pressure in a cross-sectional study of normotensive subjects covering a wide age span. Further, this effect was independent of body size. The twin model, studied under conditions of sodium loading and sodium and volume depletion, demonstrated a genetic component in the response of plasma renin activity, aldosterone, norepinephrine and renal sodium excretion to these maneuvers. Among hypertensive subjects and unexpected abnormality in the distribution of a specific MNS blood group pattern was seen in renal vascular hypertensives. This may provide a new genetic marker for identifying individuals at increased risk to develop this abnormality.

Blood Pressure↗
PubMed1980

Genetic influences on plasma and urinary norepinephrine after volume expansion and contraction in normal men.

Heritable influences on venous plasma norepinephrine (PNe) and urinary norepinephrine (UNe) values were examined in normotensive monozygotic and dizygotic twins during volume expansion and contraction. The presence of genetic variance was tested by calculating the within-pair estimate of genetic variance. Significant genetic variance was found to influence PNe during recumbency before and after a 4-h iv infusion of 2 liters saline. Similarly, heritable influences on UNe excretion were observed in a 10-h urine collection after the sodium load. Heritable influences on PNe or UNe were not observed after postural stimulation or volume contraction. The data suggest that sympathetic nervous system activity is influenced by heritable factors which may contribute to the development of hypertension in some individuals.

Female↗
PubMed1979

Glomerular filtration rate and electrolyte handling in response to sodium loading and depletion. A twin study.

Possible genetic influences on glomerular filtration rate and electrolyte excretion were investigated in 55 (37 monozygotic, 18 dizygotic) young adult white twin pairs. Subjects were studied during a five-day hospitalization involving sodium loading and sodium depletion. No evidence of genetic variability was found in the control levels of serum or urine sodium and potassium. Following a saline infusion it was possible to detect genetic influence in electrolyte handling. Creatinine clearance, used as a measure of glomerular filtration rate, did not appear to be genetically mediated. The results indicate that genetic factors are important in sodium handling in normal individuals and that this is independent of glomerular filtration rate.

Adolescent↗
PubMed1979

Aggregation of blood pressure in the families of identical twins.

The multiple relationships which exist within families of adult monozygotic (MZ) twins permit evaluation of genetic and environmental variance and provide a direct test of maternal effects. Systolic blood pressure (SBP) was measured in 610 members of the families of 76 MZ twin pairs. Age and sex effects on BP were removed via a Z-transformation. Correlations for SBP were .72 for MZ twins and .23 for full siblings. Regression of offspring on single parent was .26. The husband-wife correlation was significant, but it was no higher than the resemblance of a twin to the spouse of his co-twin. Comparisons of maternal and paternal half-siblings provide no evidence of maternal influences on SBP. To evaluate whether familial resemblance of BP is mediated by body size, the original systolic pressures were adjusted by stepwise multiple regression of age, sex, height, weight and skinfold thickness. Adjusting BP for effects of body size reduced regression of offspring on mid-parent from .40 to .23. The authors conclude that familial aggregation of systolic pressure reflects additive genetic variance mediated, in part, by body size and augmented by social homogamy arising from non-random mating.

Blood Pressure↗
PubMed1979

Effects of sodium loading and depletion in normotensive first-degree relatives of essential hypertensives.

To examine potential mechanisms responsible for the greater prevalence of hypertension among relatives of hypertensives than among relatives of normotensives, we subjected 43 normotensive first-degree relatives of known essential hypertensives and 43 age-, race-, and sex-matched normal subjects with no family history of hypertension to sodium loading and depletion. The data show that the relatives had higher blood pressures than did controls. They also had higher PRA values before and after a 2 L intravenous saline infusion over 4 hr. In addition, the relatives excreted less (p less than 0.05) sodium on the day of the infusion than did the controls. PA values and UNe excretion in the two groups did not differ. In the relatives, age correlated with systolic and diastolic blood pressure. Age correlated inversely with the 24 h urine sodium excretion on the sodium loading day. These correlations were not observed in controls. Normotensive first-degree relatives of hypertensives differ from relatives of nonhypertensives in that they have higher PRA values and a blunted natriuretic response to a saline load. These features may predispose them to the development of hypertension.

Adult↗