1. Exchangeable sodium (NaE), plasma electrolytes and arterial pressure were measured in 121 normal subjects and 91 patients with untreated essential hypertension (diastolic greater than 100 mmHg), 21 of whom had low-renin hypertension. Plasma concentrations of renin, angiotensin II and aldosterone were measured in all hypertensive patients, total body sodium, total body potassium and exchangeable potassium (KE) in some patients. 2. Mean NaE was not different in normal and hypertensive subjects provided the two groups were matched for leanness index. In the subgroup of young hypertensive patients aged 35 years or less mean NaE was below normal. NaE was not related to arterial pressure in normal subjects but in hypertensive patients there were positive and significant correlations of arterial pressure with NaE and with total body sodium. 3. NaE and total body sodium increased with age in hypertensive but not in normal subjects. Partial regression analysis suggested that the correlation of NaE with arterial pressure was not explained by an influence of age. 4. Mean NaE was not increased and mean KE was not decreased in patients with low-renin hypertension. 5. Plasma potassium concentration, KE and total body potassium correlated inversely and significantly with blood pressure in hypertensive patients. These correlations were more marked in young than in old patients. 6. Multiple regression analysis showed that the combination of NaE and plasma potassium concentration 'explained' more of the variation of systolic blood pressure in hypertensive patients than it did in normal subjects. Plasma potassium concentration 'explained' more of the variation in young hypertensives and NaE 'explained' more in older patients. 7. Our findings suggest than changes of plasma and body potassium are important in the earlier stages of essential hypertension and that changes of body sodium become important later.
1. Blood pressure, left ventricular mass and platelet cytosolic free calcium concentrations were measured in 23 patients with untreated primary hyperparathyroidism, 30 normotensive control subjects and 23 control subjects matched for age, sex and blood pressure. In 12 patients measurements were repeated after parathyroidectomy. 2. Patients with primary hyperparathyroidism had significantly elevated blood pressures (139 +/- 6/86 +/- 3 mmHg, mean +/- SEM) compared with control subjects (125 +/- 2/78 +/- 1 mmHg), but high values persisted after hypercalcaemia was corrected. 3. Despite chronic extracellular hypercalcaemia, intracellular free calcium levels were lower in patients with hyperparathyroidism than in controls matched for age, sex and blood pressure (median concentrations 81.5 nmol/l vs 93 nmol/l, 95% confidence interval 0.1 to 20.1; P less than 0.05) and values tended to increase after parathyroidectomy. 4. Left ventricular mass index was increased in the primary hyperparathyroid group as compared with control subjects matched for age, sex and blood pressure (123 g/m2 vs 100 g/m2, 95% confidence interval -36.1 to -3.1; P = 0.03). Parathyroidectomy resulted in a small reduction of the left ventricular mass index (123.5 g/m2 vs 104 g/m2, 95% confidence interval 46.5 to 2.5; P = 0.1) but no change in blood pressure. 5. Hypertension and left ventricular hypertrophy in primary hyperparathyroidism are associated with relatively low levels of free calcium in platelets.
SUMMARY We made separate measurements of angiotensin II (A II) and of its immunoreactire metabolites (2-8 heptapeptide, 3-8 bexapeptide, and 4-8 pentapeptide) in arterial and venous plasma from subjects with widely different plasma levels of the peptides. A II and its three metabolites were extracted from blood, separated by paper chromatography, and measured by radioimmunoassay using an A II antisemm which had a 100% cross-reaction with each metabolite. In contrast to results of previous studies, A II was found to predominate in both arterial (60-100%) and venous (55-100%) blood. The biologically active 2-8 beptapeptide metabolite accounted for only 10% of the activity in arterial plasma. Radioimmunoassay of venous plasma extracts using an A II antisemm which had a low cross-reaction with the 3-8 hexapeptide and the 4-8 pentapeptide confirmed the results obtained using the antisemm which had a 100% cross-reaction with the metabolites. We conclude that radioimmunoassay methods for measuring A II in venous blood may be more accurate and relevant than has previously been recognized. The small difference between A II concentrations in arterial and venous plasma suggests further that there may be significant conversion of angiotensin I (A I) to A II in the limb vasculature.THE PRESSOR octapeptide, angiotensin II (A II), coexists in blood with its major metabolites, the C-terminal 2-8 heptapeptide, 3-8 hexapeptide, and 4-8 pentapeptide. Compared to A II, the heptapeptide has only weak pressor activity in the rat, whereas the remaining metabolites have none.1 ' * In contrast, the heptapeptide is equally as potent as A II in stimulating aldosterone secretion in the sheep' and in the conscious rat,'1 and more potent as a stimulus to aldosterone biosynthesis in vitro using rabbit capsular adrenal tissue. 5 The aldosterone-stimulating properties of the remaining metabolites are weak.*-* Antisera raised against A II usually cross-react with the C-terminal heptapeptide and hexapeptide metabolites'-' and sometimes also with the pentapeptide metabolite.' Radioimmunoassays of A II thus measure not only A II but also these immunoreactive metabolites. A II can be separated from metabolites by chromatography of blood extracts before immunoassay. Cain et al.*"" used this approach and found that A II comprised 85% of the immunoreactive material in human arterial blood, but only 28% of that in venous blood. In venous blood, they found the major immunoreactive substance to be the hexapeptide, although the concentrations of hepta-and pentapeptides were not determined.Our present paper describes a method for determining the relative proportions of A II and the three major peptide metabolites in arterial and venous blood, and the results obtained in a group of subjects with a wide range of circulating levels of renin and A II. Further, because the analogue of A II, l-Asp(NH,)-5-Val-angiotensin II, often used in investigations of the renin-angiotensin system, is degraded, in plasma at least, by a different enzyme from that which catalyze...
This research investigated the effect of musical tempo on the rhythmical interpretation of six temporal patterns of varying rhythmic complexity. For each pattern, listeners tapped at regular intervals in synchrony with what they perceived to be the most natural placement of beats. Consistent with previous research, the perceived time interval (period) of successive beats was at a lower metrical level at slow tempos than at fast tempos. Tempo effects were dependent on musical experience, with musically trained participants demonstrating a stronger tendency to perceive a different relative beat period with changes in tempo, than were musically untrained participants. Musically untrained participants tended to select the same relative beat period, independent of tempo. The predictions of three models permit the observed differences to be interpreted in terms of the relative use of positive and negative evidence in assigning beats to a rhythmic pattern. This explanation offers an alternative to preferred tempo hypotheses.
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