bluuebunny/crossref_metadata_2025_split huggingface dataset:
31P nuclear magnetic resonance measurement of free erythrocyte magnesium concentration in man and its relation to blood pressure
Authors: Woods K. L. , Walmsley D. , Heagerty A. M. , Turner D. L. , Lian Lu-Yun 
Published: August 2015

1. 31P n.m.r. spectroscopy was used to measure the dissociation constant of MgATP under simulated intracellular conditions and to measure erythrocyte free magnesium concentration.
2. In a group of 40 subjects, the relationship between erythrocyte free magnesium and blood pressure, age and sex was examined by univariate and multivariate regression analysis.
3. A weak positive association was found between erythrocyte free magnesium and mean blood pressure. This association was lost in a multivariate regression analysis including both age and sex.
4. No significant relationship was found between erythrocyte free magnesium and age, sex, family history of hypertension or use of the combined oral contraceptive pill in the sample studied.
Biochemical studies of N-methyltransferase in human and guinea-pig lung: no apparent role in the pathogenesis of asthma
Authors: Henderson G. D. , Ruffin R. E. , Alpers J. H. , Crockett A. J. , Schembri D. A. , Latimer K. M. 
Published: August 2015

1. N-Methyltransferase activity was measured in surgical specimens of human lung using phenylethanolamine as substrate. Thirty-three male and seven female patients, age range 19–78 (median 62.5) years were studied. The activity in lung homogenates was 0.59 × 10−6 units/mg of protein (sem 0.03, n = 40), with a range of 0.16–1.16 × 10−6 units/mg of protein. There was no difference (P = 0.97) in activity between males and females.
2. Non-specific N-methyltransferase activity was estimated in 17 of the surgical specimens using β-phenylethylamine as substrate. This activity was 38.9% (sem 5.3) of that with phenylethanolamine. Comparative studies with rabbit lung, which has a well-characterized non-specific N-methyltransferase, showed significant differences in substrate specificity between the two species.
3. The apparent Km and Vmax for phenylethanolamine in seven human lung homogenates was 22.0 (sem 4.6). mmol/l and 1.82 × 10−6 units/mg of protein (sem 0.36). The noradrenaline N-methyltransferase (NMT; EC 2.1.1.28) inhibitors SKF 64139-A and LY 134046 did not inhibit this activity up to a concentration of 100 μmol/l. This activity was inhibited 51.4% (sem 8.6, n = 6) by 100 μmol/l S-adenosyl-l-homocysteine. Immunohistochemistry did not reveal immunoreactive NMT in human lung sections.
4. Comparative studies with guinea-pig lung homogenates demonstrated non-specific N-methyltransferase activity in this species which is similar to the human lung. Using an ovalbumin-sensitized guinea-pig model of allergic bronchoconstriction, there was no difference (P = 0.24) between control (2.74 × 10−6 units/mg of protein, sem 0.25, n = 5) and sensitized (2.24 × 10−6 units/mg of protein, sem 0.27, n = 9) guinea pigs.
5. These results show that human lung has significant N-methylating activity. This is not NMT but a nonspecific N-methyltransferase. There was no difference (P = 0.34) in activity between asthmatic and non-asthmatic lung. The animal model did not reveal a relationship between this activity and the development of allergic bronchoconstriction.
Pathogenesis of abnormal acid–base balance in the young spontaneously hypertensive rat
Authors: Lucas Philip A. , Lacour Bernard , Comte Lydie , Drüeke Tilman 
Published: August 2015

1. We have previously reported reduced blood pH and plasma bicarbonate in young Okamoto–Aoki spontaneously hypertensive rats (SHR) compared with normotensive Wistar–Kyoto rats (WKY). Acid loading with 1.5% (w/v) NH4Cl as the sole drinking fluid produced identical falls in blood pH, the difference remaining significant.
2. The ability of SHR to excrete acid and alkaline loads was compared with that of WKY under metabolic cage conditions. The effects of such manipulations on urinary sodium, potassium, calcium and phosphate excretion were also determined.
3. No difference was found in the ability to excrete an acid load or to reduce urine pH. Neither total urinary ammonium ion nor titratable acid differed significantly between the strains under either baseline or acid-loading conditions.
4. Baseline urinary bicarbonate excretion was not significantly different between strains but intraperitoneal administration of NaHCO3 at 2.0 mmol/kg body weight resulted in enhanced excretion in the SHR (SHR vs WKY: 625.2±71.5 vs 381.8±40.6 μmol 24h−1 kg−1 body weight, P &lt; 0.01, mean±sem).
5. No difference in urinary sodium or potassium excretion was observed between SHR and WKY, but basal calcium and phosphate excretion were reduced in SHR (P &lt; 0.05).
6. Increased urinary bicarbonate excretion in the presence of significantly reduced plasma bicarbonate suggests reduced tubular reabsorption of bicarbonate, which may contribute to the mild metabolic acidosis in young SHR.
Atrial natriuretic peptide inhibits osmolality-induced arginine vasopressin release in man
Authors: Allen M. J. , Ang V. T. Y. , Bennett E. D. , Jenkins J. S. 
Published: August 2015

1. Eight normal volunteers were infused with 5% saline (5 g of NaCl/100 ml) at a rate of 0.06 ml min−1 kg−1 for 120 min to increase plasma osmolality and plasma arginine vasopressin. Human atrial natriuretic peptide (α-hANP; 100 μg) or placebo was given in random order in a double-bind cross-over design for the last 20 min of the saline infusion.
2. Compared with the placebo infusion, atrial natriuretic peptide (ANP) produced a 43% greater sodium excretion and a 34% greater urinary volume in the subsequent hour.
3. Mean plasma immunoreactive ANP did not increase in response to changes in osmolality and rose to a peak of 118 pg/ml during the α-hANP infusion. α-hANP produced significant suppression of mean plasma arginine vasopressin over the 60 min after the infusions.
4. We conclude that ANP is not released in response to increased osmolality in vivo, and that it inhibits osmolality-induced arginine vasopressin release in man.
Fluid homoeostasis during prolonged low-intensity walking on consecutive days
Authors: Leiper J. B. , McCormick K. , Robertson J. D. , Whiting P. H. , Maughan R. J. 
Published: August 2015

1. The effect on fluid homoeostasis of walking 37 km on each of 4 consecutive relatively cool days was studied in six male subjects. The daily exercise intensity was consistent and was equivalent to 17(1)% [mean (se)] of maximum oxygen uptake for these subjects.
2. The diet during the study consisted of a mainly carbohydrate breakfast, consumed immediately before each day‘s exercise, and unrestricted access to a normal mixed diet after completion of each day's exercise. Water was allowed ad libitum during the walk. Food and fluid intake were recorded.
3. Body weight remained constant over the 4-day walk. The difference between total daily fluid intake and the corresponding 24 h urine output was 1684 (250) ml, 1621 (522) ml, 1107 (252) ml and 1406 (208) ml, respectively, on each of the 4 exercise days.
4. There was a calculated increase of 21.3(6.6)% in plasma volume over the 4-day walk; the largest daily change [11.3(2.9)%] occurred during the walk on day 1. The increase in plasma volume was maintained for at least 4 days after completion of the walk.
5. From day 2, serum sodium concentration tended to increase during the exercise period and fell to the pre-exercise concentration during the overnight rest periods. The concentration of the other measured serum constituents remained relatively constant, and serum osmolality did not alter over the study period.
Effects of hyperinsulinaemia on the cardiovascular responses to graded hypovolaemia in normal and diabetic subjects
Authors: Scott A. R. , Bennett T. , MacDonald I. A. 
Published: August 2015

1. Two experiments were carried out. The first with five normal male subjects was placebo controlled and single blind, each subject being studied on two occasions. Lower body subatmospheric pressure (LBSP) was used to assess the cardiovascular effects of graded hypovolaemia before and during either a hyperinsulinaemic, euglycaemic clamp or a placebo clamp using 0.9% (w/v) NaCl only.
2. During hyperinsulinaemia, resting systolic blood pressure rose and was accompanied by forearm vasodilatation. Forearm blood flow (FABF) and heart rate (HR) were higher at each level of LBSP during than before hyperinsulinaemia. In addition, hyperinsulinaemia was accompanied by a small increase in noradrenaline, but packed cell volume did not change.
3. In the second experiment, the effects of a hyperinsulinaemic euglycaemic clamp on the cardiovascular responses to LBSP were assessed in seven diabetic subjects with peripheral and autonomic neuropathy.
4. In contrast to the normal subjects, there was a slight fall in systolic blood pressure during the clamp but no effect was noted on HR or FABF. Mean arterial blood pressure was lower at each level of LBSP during hyperinsulinaemia compared with the pre-elamp period. Packed cell volume fell during the clamp and plasma noradrenaline rose. In one of the diabetic subjects, a precipitous fall in blood pressure occurred during hyperinsulinaemia when LBSP of 10 mmHg (1.3 kPa) was applied, this manoeuvre having been well tolerated before the clamp.
5. The mode of action of hyperinsulinaemia is not clear, but there was, however, no evidence that a fall in plasma volume had occurred.
Effect of a meal containing protein on lithium clearance and plasma immunoreactive atrial natriuretic peptide in man
Authors: Solomon L. R. , Atherton J. C. , Bobinski H. , Cottam S. L. , Gray C. , Green R. , Watts H. J. 
Published: August 2015

1. The effect of meals with a high and low protein content and of the fasting state on renal function and plasma atrial natriuretic peptide was studied in water-loaded normal volunteers.
2. Creatinine clearance increased after the high protein meal, but did not change after the low protein meal or while fasting. Observations of similar increases in urine sodium and potassium excretion and a transient decrease in urine flow after both meals suggest that the protein content of the meal is not an important contributory factor in these responses to feeding.
3. Absolute delivery of sodium and water out of the proximal tubules (assessed by the lithium clearance method) was higher after both meals than while fasting; fractional lithium clearance was higher after the low protein meal than the high protein meal and while fasting. Absolute reabsorption from proximal tubules was increased after only the high protein meal.
4. A transient decrease in the fraction of water delivered to distal nephron segments that appeared in the urine (fractional distal water excretion) was observed after both meals. Fractional distal sodium excretion and absolute distal sodium and water reabsorption increased after both meals.
5. Since plasma atrial natriuretic peptide either decreased (high protein meal) or remained unchanged (low protein meal and fasting), it is unlikely that this hormone is involved in the hyperfiltration after the high protein meal and the natriuresis after both high and low protein meals.
Age-related changes in factor VII activation in healthy women
Authors: Scarabin P. Y. , Van Dreden P. , Bonithon-Kop C. , Orssaud G. , Bara L. , Conard J. , Samama M. 
Published: August 2015

1. To investigate the age-related changes in factor VII activation in healthy women, a regular factor VII clotting assay (factor VIIc) was carried out simultaneously with a new enzyme immunoassay for the quantification of antigen factor VII (factor VIIag).
2. Both factor VIIc and factor VIIag levels were positively correlated with age (r = 0.79 and r = 0.62, respectively, n = 25, P &lt; 0.001). The rise with age in factor VIIc was steeper than in factor VIlag and the ratio of factor VIIc to factor VIlag (an indicator of the activity state of factor VII) increased with age (r = 0.42, P &lt; 0.05).
3. The results show that an increased conversion of native single-chain factor VII to the fully active double-chain form is associated with advancing age in women.
4. This finding is consistent with a possible role of activated factor VII in the pathogenesis of thromboocclusive vascular disease in women.
Acute effect of smoking on rebreathing carbon monoxide, breath-hold carbon monoxide and alveolar oxygen
Authors: Kirkham Andrew J. T. , Guyatt Andrew R. , Cumming Gordon 
Published: August 2015

1. The rise (‘boost’) in carboxyhaemoglobin (HbCO) on smoking has been studied with alveolar carbon monoxide measurements before and after smoking a cigarette. We re-examined this in 28 subjects with HbCO values compared with rebreathing carbon monoxide [FAco(Rb)] and breath-hold alveolar carbon monoxide and oxygen concentrations, obtained after a 20 s breath-hold [FAco(Bh)] and FAo2(Bh), respectively]. Tests were done in the order FAco(Bh) and FAo2(Bh), FAco(Rb), FAco(Bh) and FAo2(Bh) before and after smoking a single cigarette, with HbCO being measured 1 min before and after smoking.
2. The changes were expressed as the relative boost:
For HbCO the average value was 23.7%, but the FAco(Rb) boost was only 9.8%. The first post-smoking FAco(Bh) boost was 3.9% (5.0 min after smoking), rising to 8.5% 9.4 min later.
3. The FAo2(Bh) values fell from a mean of 15.4% before smoking to 14.3% (5.0 min after smoking) then recovered to 15.4% 9.4 min later, suggesting a transient effect on pulmonary gas exchange. Correction of the first post-smoke FAco(Bh) data for this effect increased the relative boost to 11.5%. Routine FAo2(Bh) measurements may be useful in further smoking studies.
4. We conclude that none of the alveolar sampling techniques gives a reliable measurement of the acute HbCO changes associated with smoking.
Effect of intravenous infusion of adrenaline on the cardiovascular responses to distal body subatmospheric pressure in man
Authors: Fellows I. W. , MacDonald I. A. , Bennett T. , O'Donoghue D. P. 
Published: August 2015

1. On two separate occasions, at least 1 week apart, seven young healthy male subjects received intravenous infusions of either adrenaline [0.27 nmol (50 ng) min−1 kg−1] or saline (154 mmol/l NaCl), plus ascorbic acid (5.68 mmol/l), over 30 min.
2. On each occasion, the subjects were exposed to distal body subatmospheric pressure (DBSP), 0 to 50 mmHg (0 to 6.65 kPa) in 10 mmHg (1.33 kPa) steps, before infusion, during the final 15 min of the infusion, and at 15 min and 30 min after the cessation of the infusion.
3. Venous adrenaline concentrations of 2.85 ±0.22 nmol/l were achieved during the adrenaline infusion, compared with 0.49 ± 0.07 nmol/l during the saline infusion (P &lt; 0.001). At 15 min and at 30 min after cessation of the adrenaline infusion, venous adrenaline concentrations had fallen to levels similar to those achieved after the cessation of the saline infusion.
4. Heart rate rose significantly from 58 ±4 beats/min to 67 ±4 beats/min during the adrenaline infusion (P &lt; 0.05), but there was no further significant change in response to 50 mmHg (6.65 kPa) DBSP. At 30 min after the cessation of the adrenaline infusion, heart rate rose from 60 ± 4 beats/min to 78 ± 7 beats/min in response to 50 mmHg DBSP. This increase was significantly greater than that observed before the adrenaline infusion [58 ± 4 beats/min to 69 ±7 beats/min during 50 mmHg (6.65 kPa) DBSP; P &lt; 0.01].
5. During the infusion of adrenaline, systolic arterial blood pressure rose and diastolic arterial blood pressure fell, but the blood pressure responses to DBSP were unaffected.
6. Forearm blood flow increased significantly during adrenaline infusion but there was no significant difference in the fall in forearm blood flow during DBSP compared with the values before infusion. At 15 min after the cessation of the adrenaline infusion, forearm vascular resistance rose proportionately more in response to DBSP than it had before the adrenaline infusion (P &lt; 0.05).
7. These results are consistent with adrenaline-mediated facilitation of sympathetic neuronal release of noradrenaline in the heart and in the forearm vascular bed.
Effect of low dose infusion of atrial natriuretic peptide on renal function in man
Authors: Solomon L. R. , Atherton J. C. , Bobinski H. , Hillier V. , Green R. 
Published: August 2015

1. The effects of the infusion of a low dose (2 pmol min−1 kg−1 for 3 h) of human atrial natriuretic peptide (hANP) were studied in seven healthy volunteers undergoing a water diuresis. Lithium clearance was used to monitor proximal tubular function.
2. hANP increased urine flow rate, sodium, calcium and magnesium excretion without significant changes in potassium and phosphate excretion, heart rate or blood pressure.
3. hANP caused a small change in fractional lithium clearance, and larger changes in distal nephron handling of sodium and water.
4. Plasma renin activity tended to decrease during the infusion of hANP, while plasma aldosterone concentration decreased during and increased after stopping the infusion of hANP.
5. The data suggest that hANP inhibits the reabsorption of sodium and water by an action on distal segments of the nephron and perhaps the proximal tubule. Inhibition of renin and aldosterone secretion may contribute to the natriuresis.
Urinary guanosine 3′: 5′-cyclic monophosphate but not tissue kallikrein follows the plasma atrial natriuretic factor response to acute volume expansion with saline
Authors: Lewis Helen M. , Wilkins M. R. , Selwyn Brenda M. , Yelland Ursula J. , Griffith Megan E. , Bhoola K. D. 
Published: August 2015

1. The relationship between plasma immunoreactive atrial natriuretic factor (Ir-ANF) and the urinary excretion of sodium, guanosine 3′:5′-cyclic monophosphate (cyclic GMP) and of tissue kallikrein was examined in seven healthy female volunteers.
2. Each volunteer attended on two occasions, a control and a saline infusion day. On the infusion day saline (2 litres, 0.9% NaCl) was administered over 60 min. Measurements of plasma Ir-ANF and urinary excretion of sodium, cyclic GMP and of tissue kallikrein were made at 30 min intervals during the infusion and for 3 h after the infusion.
3. Mean (± sem) urinary sodium excretion increased from a basal value (time 0) of 102 ±15 μmol/min to 222 ± 47 μmol/min 60–90 min from the start of the infusion and thereafter remained significantly elevated (P &lt; 0.01) above sodium excretion on the control day.
4. In response to saline infusion there was a transient rise in mean (± sem) plasma Ir-ANF from 6.7 ± 0.8 pmol/l to a peak of 22.5 ±3.7 pmol/l at 75 min, falling to 12.7 ± 1.9 pmol/l at 135 min. The peak plasma Ir-ANF level on the infusion day was significantly elevated (P &lt; 0.05) above the time-matched measurement on the control day.
5. Similarly, there was a transient rise in mean (± sem) urinary cyclic GMP excretion on the infusion day from 30.9 ±4.4 fmol/min to 64.6 ± 11.4 fmol/min during the 60–90 min collection period, returning to 43.7 ± 14.5 fmol/min at 210–240 min. Cyclic GMP excretion on the infusion day was significantly elevated (P &lt; 0.05) above the time-matched measurement on the control day during the period 60–180 min.
6. Serum and urinary tissue kallikrein on the infusion day did not differ significantly from time-matched measurements on the control day.
7. Thus urinary cycle GMP but not tissue kallikrein follows the plasma Ir-ANF response to acute volume expansion with saline, and may be a useful marker of the activity of this peptide.
Effect of potassium supplementation on blood pressure and vasodilator mechanisms in spontaneously hypertensive rats
Authors: Barden Anne , Beilin Lawrence J. , Vandongen Robert 
Published: August 2015

1. Supplementation with 1% (w/v) KCl solution significantly attenuated the blood pressure rise with age normally observed in spontaneously hypertensive rats, resulting in a difference in blood pressure of 18 mmHg after 5 weeks.
2. Urinary 6-keto-prostaglandin F1α (the stable hydrolysis product of prostacyclin) and kallikrein excretion were significantly elevated in rats receiving potassium.
3. No difference was observed in sodium excretion during the initial days of potassium supplementation; however, the potassium-supplemented animals excreted relatively more sodium over the 5 week period.
4. Plasma renin activity was significantly reduced in those animals receiving potassium after 5 weeks.
5. It is proposed that a combination of increased systemic and/or renal prostacyclin and kallikrein synthesis may, in combination with reduced renin activity, contribute to the attenuation of blood pressure in potassium-supplemented spontaneously hypertensive rats.
Changes in calcium metabolic indices during long-term treatment of patients with essential hypertension
Authors: Hvarfner Andreas , Bergström Reinhold , Lithell Hans , Mörlin Claes , Wide Leif , Ljunghall Sverker 
Published: August 2015

1. Disturbances of calcium metabolism, mimicking mild, compensated secondary hyperparathyroidism, accompany essential hypertension, but it is not known whether these alterations are primary or only secondary to the elevated blood pressure.
2. Indices of systemic calcium metabolism were followed prospectively during 6 months' treatment with either propranolol, bendroflumethiazide or verapamil in 35 patients with essential hypertension. Multivariate statistical methods were employed to study the effects of blood pressure reduction upon the metabolic indices with adjustment for the effects of the different antihypertensive agents.
3. Propranolol treatment increased the plasma ionized calcium and serum phosphate concentrations, and reduced the serum levels of parathyroid hormone, free fatty acids and glycerol. Neither the total nor the total albumin-modified serum calcium concentration was significantly affected. Thus, presumably the decrease in free fatty acids reduced the calcium complex and the calcium binding to albumin, and consequently increased the plasma ionized calcium, thereby suppressing the secretion of parathyroid hormone.
4. Bendroflumethiazide caused a reduction of the fasting renal calcium excretion to half the pretreatment level, but produced no other significant changes in the various indices of calcium metabolism.
5. During verapamil treatment, the fasting renal excretion of calcium and magnesium increased, whereas the free fatty acids and glycerol concentrations in serum were reduced. These two changes presumably balanced each other, as the plasma ionized calcium and serum parathyroid hormone concentrations were not significantly altered.
6. There were no consistent relationships between the decrease in blood pressure and the changes in the metabolic indices, either in the total sample or within any subgroup. These findings indicate that disturbances of calcium metabolism in essential hypertension are primary to, and not induced by, the elevated blood pressure per se.