bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time-course and relationship of the early changes in renal sodium excretion and aldosterone secretion during dietary sodium restriction in normal man
Authors: Carmichael D. J. S. , Sutters M. S. , Unwin R. J. , Gordon D. , Few J. , James V. H. T. , Wadsworth J. , Peart W. S. 
Published: August 2015

1. The fall in renal sodium excretion after dietary sodium restriction is prompt and reproducible. The importance of increased aldosterone secretion during the early phase (within 48 h) of this response is unclear. Using two indirect measures of aldosterone secretion (in urine and saliva), we have tried to relate changes in excretion and concentration of this hormone to renal sodium excretion during the abrupt transition from a normal (approximately 150 mmol/day) or high (260 mmol/day) to a low (5–25 mmol/day) sodium intake in 11 and seven male volunteers, respectively.
2. All subjects showed reduced renal sodium excretion within 36 h of dietary restriction, but the times at which increases in renal aldosterone excretion, saliva aldosterone concentration and plasma renin activity became statistically significant varied widely (8–72 h, 2.5–&gt;62.5 h and 38 h for renal aldosterone secretion, saliva aldosterone concentration and plasma renin activity, respectively). Circadian fluctuations in saliva aldosterone concentration were apparent and increased in amplitude during sodium restriction.
3. Urine flow rate tended to increase on the first day of sodium restriction and this reached statistical significance in the group initially on a high sodium intake (64.0 ± 8.8 to 84.3 ± 11.2 ml/h, P &lt;0.01); although the pattern of urine flow did correlate with plasma arginine vasopressin concentration (r = −0.49, P &lt;0.01), there was no significant decrease in mean plasma arginine vasopressin concentration [1.15 (0.92–1.44) to 0.90 (0.72–1.12) pmol/l, P = 0.08; geometric mean and 95% confidence limits]. Renal arginine vasopressin excretion fell significantly after the change from a normal or high to a low sodium diet [2.70 (2.38–8.69) to 2.19 (1.72–4.00) and 3.80 (2.92–5.01) to 2.50 (1.26–2.35) pmol/h, respectively, P &lt;0.05]; in four subjects assayed, plasma atrial natriuretic peptide concentration also fell significantly [20.1 (16.3–24.9)to 13.1 (10.6–16.2) pmol/l, P &lt;0.05].
4. We conclude that after acute dietary sodium withdrawal: (1) unless enhanced renal sensitivity to aldosterone develops rapidly, increased secretion alone is unlikely to account for the initial decline in renal sodium excretion; (2) decreased atrial natriuretic peptide secretion may have a permissive role in ‘low-sodium’ adaptation; (3) the early ‘low-sodium’ diuresis is probably vasopressin-dependent and is an important mechanism in the preservation of normal plasma osmolality.
Capillary Hypertension and Abnormal Pressure Dynamics in Patients with Essential Hypertension
Authors: Williams S. A. , Boolell M. , MacGregor G. A. , Smaje L. H. , Wasserman S. M. , Tooke J. E. 
Published: August 2015

1. Pressure was measured within 28 capillaries of the nailfolds of nine patients with essential hypertension and in 33 capillaries of nine age- and sex-matched normotensive control subjects, using direct micropuncture, a dynamic servo-nulling system and computerized analysis.
2. Average pressure at the apex of the capillary was found to be elevated in the patients with hypertension (21.1 ± 4.9 mmHg compared with 13.0 ± 2.0 mmHg in the control subjects; mean ± SD, P &lt; 0.01). If the two groups were combined, there was an overall correlation between average capillary pressure and mean blood pressure (r = 0.68, P &lt; 0.01, n = 18), but within each group separately there was no significant relation between these parameters.
3. There were also abnormalities in the waveforms of pulsations in capillary pressure in the group with hypertension, with an increased attenuation of high-frequency harmonics. Pulses appeared to be conducted more rapidly along the vascular tree in the patients with hypertension.
4. The elevation of capillary pressure in essential hypertension demonstrated in this study is in agreement with indirect evidence of capillary hyperfiltration provided by other studies which showed a reduced plasma volume and increased transcapillary escape rate of plasma proteins.
5. The finding of elevated capillary pressure demands the inclusion of the postcapillary segment (and possibly vascular density) in the resistance equation in essential hypertension.
Impaired Natriuretic Response to Atrial Natriuretic Peptide in the Isolated Kidney of Rats with Experimental Cirrhosis
Authors: Panos Marios Z. , Gove Christopher , Firth John D. , Raine Anthony E. G. , Ledingham John G. G. , Westaby David , Williams Roger 
Published: August 2015

1. Sodium retention in cirrhosis may be partly attributable to resistance to a putative circulating natriuretic factor. In cirrhosis, plasma concentrations of atrial natriuretic peptide are often increased in the presence of sodium retention.
2. In order to determine whether the kidney of cirrhotic animals may be insensitive to atrial natriuretic peptide, isolated perfused kidneys from six cirrhotic and five control rats were exposed to increasing concentrations of atrial natriuretic peptide. Cirrhosis had been induced by carbon tetrachloride administration.
3. Excretion in vivo of a 2 mmol sodium load, administered by gavage, was impaired in cirrhotic animals for up to 4 h as compared with control animals (4.2 ± 1.9 vs34.9± 13.4% P &lt; 0.05).
4. During perfusion at 110 mmHg in the absence of atrial natriuretic peptide, sodium excretion by isolated kidneys of cirrhotic animals tended to be lower than in control animals, but the difference was not significant (4.93 ± 1.01 vs 8.41 ± 1.48 μmol min−1 g−1 kidney weight, P = 0.09). There was a smaller increase in urinary sodium excretion by the kidneys of cirrhotic rats compared with control rats in the presence of atrial natriuretic peptide at 10, 50 and 200 pmol/l (respectively: 0.06 ± 0.08 vs 1.29 ± 0.35 μmol min−1 g−1 kidney weight, P &lt; 0.02; 0.49 ± 0.08 vs 1.82 ± 0.42 μmol min−1 g−1 kidney weight, P &lt; 0.03; 1.42 ± 0.16 vs 3.23 ± 0.73 μmol min−1 g−1 kidney weight, P &lt; 0.05), but not at 1000 pmol/l.
5. In this animal model of cirrhosis, renal resistance to the natriuretic action of atrial natriuretic peptide at physiological and pathophysiological concentrations may contribute to sodium retention.
Comparison of Dye-Dilution and Plethysmographic Blood Flow Measurements: An Evaluation of the Influence of Invasive Techniques on Blood Flow and on Arterial and Femoral Venous Substrate Variables in Man
Authors: Jorfeldt Lennart , Rutberg Hans 
Published: August 2015

1. In eight healthy volunteers we compared leg blood flow, as determined in a calf segment by strain-gauge plethysmography, with the flow measured by a constant-rate infusion of Indocyanine Green dye into the femoral artery. The representativeness of the calf segment was evaluated by complementary measurements with additional strain gauges attached around the proximal and distal crural and the distal thigh segments (n = 6). Furthermore, we investigated the influence of the catheterization procedure and a simulated vascular puncture, as well as repeated venous occlusions, on blood flow and on arterial and femoral venous substrate concentrations and blood gases (n = 8).
2. The leg blood flow measured by dye dilution was 0.31 ± 0.03 litre/min (mean ± sem). The blood flow in the calf segments was 14.8 ± 1.6 ml min−1 litre−1 and no difference between the legs was observed. Extended to the whole leg the plethysmographic blood flow was 0.17 ± 0.01 litre/min and thus lower (43 ± 7%, P &lt; 0.001) than the flow determined by the indicator-dilution method. Blood flow in the legs was not influenced by catheterization or sham punctures of the vessels or by repeated venous occlusions.
3. The concentrations of glucose, lactate and glycerol, as well as blood gas variables, in arterial and femoral venous blood did not change during the study or decreased so slightly (pH and lactate) that the arteriovenous difference was not influenced.
4. We conclude that the blood flow of the total leg cannot be satisfactorily estimated from strain-gauge plethysmography of a single calf segment. Strain-gauge plethysmography can therefore not be recommended for quantitative studies of substrate turnover in the leg tissues applying the Fick principle. Catheterization of the femoral vessels, or manipulations close to them with a thin cannula or repeated venous occlusions, has no significant effect on leg blood flow and substrate exchange.
Simplifying the Lithium-Marker Technique Used to Assess the Dietary Intake of Discretionary Sodium in Population Studies
Authors: Leclercq C. , Avalle V. , Ranaldi L. , Toti E. , Ferro-Luzzi A. 
Published: August 2015

1. Lithium has been used by Sanchez-Castillo et al. (Clin. Sci. 1987; 72, 81–6) for tracking sodium in order to monitor the domestic use of salt. The present study was designed to simplify the original protocol, which is too cumbersome for epidemiological studies.
2. A preliminary study conducted on nine volunteers showed that sharp modifications of lithium intake are detected within 24 h in urinary excretion. The average intake over a 5-day period could be predicted by the mean excretion of the last 3 days. Lithium recovery established from 1 baseline day and 3 plateau days was 95 ± 6% (mean ± sd), not significantly different from the recovery obtained by the integrated excretion curve over 12 days.
3. A simplified protocol was therefore developed, reducing to 4 the 12 days of urine collection originally required.
4. This simplified protocol was tested on five households (14 adults and five children). All domestic salt was substituted with lithium-tagged salt. Urine samples were collected on 1 baseline day and on 3 plateau days. The lithium/sodium ratio of all urine collections (both complete and incomplete) could be used to estimate the proportion of discretionary sodium. In our sample it was about 29% of total sodium intake.
5. The simplified protocol can thus be proposed for population studies.
Impaired Nutritive Skeletal Muscle Blood Flow in Patients with Chronic Renal Failure
Authors: Bradley John R. , Anderson Janice R. , Evans David B. , Cowley Alan J. 
Published: August 2015

1. The possibility that abnormalities of skeletal muscle may limit the exercise tolerance of patients with chronic renal failure was investigated in patients undergoing regular haemodialysis.
2. Blood flow to the calf, a vascular bed consisting predominantly of skeletal muscle, was measured in six patients before and after exercise and compared with values obtained from 12 control subjects.
3. The patients were limited on exertion and had an abnormal response of calf blood flow to bicycle exercise. Resting calf blood flow was similar in patients and control subjects, but the mean increase in calf blood flow in response to submaximal exercise was 0.55 (sem 0.12) ml min−-1 100 ml−-1 in the patients and 1.43 (sem 0.17) ml min−-1 100 ml−-1 in the control subjects. The increase after symptom-limited maximal exercise was 1.50 (sem 0.80) ml min−-1 100 ml−-1 in the patients and 4.20 (sem 0.40) ml min−-1 100 ml−-1 in the control subjects.
4. Skeletal muscle biopsies from eight haemodialysis patients were studied by histochemistry and electron microscopy.
5. Oxidative enzyme activity was increased and there were large subsarcolemmal aggregates of structurally normal mitochondria. Necrotic capillaries were observed as empty basement membrane tubes containing fragments of degenerating endothelium.
6. The changes were compatible with a response to a chronic reduction in skeletal muscle blood flow.
Diurnal and Postural Variations in Plasma Atrial Natriuretic Factor, Plasma Guanosine 3′:5′-Cyclic Monophosphate and Sodium Excretion
Authors: Bell Gordon M. , Atlas Steven A. , Pecker Mark , Sealey Jean E. , James Gary , Laragh John H. 
Published: August 2015

1. We studied diurnal patterns of plasma atrial natriuretic factor, plasma guanosine 3′:5′-cyclic monophosphate and urinary sodium excretion in normal subjects after 3 days on a 200 mmol of sodium/60 mmol of potassium diet. On the fourth day blood samples and urine were collected every 3 h.
2. Two studies were performed. In study 1, normal subjects (n = 8) were recumbent for 23 h from 09.00 hours to 08.00 hours the next day. In study 2, normal subjects (n = 10) were permitted to ambulate from 09.00 hours to 23.00 hours and then were recumbent until 08.00 hours the next day.
3. In study 1, assumption of the recumbent posture was associated with increases in plasma atrial natriuretic factor (P &lt; 0.01), plasma guanosine 3′:5′-cyclic monophosphate (P &lt; 0.05) and urinary sodium excretion (P &lt; 0.05).
4. In contrast, in study 2 there were no significant changes in plasma atrial natriuretic factor during the day; instead, plasma atrial natriuretic factor increased overnight, reaching a peak at 24.00 hours after 1 h of recumbency (P &lt; 0.01). A smaller rise in plasma guanosine 3′:5′-cyclic monophosphate (P &lt; 0.05) occurred; urinary sodium excretion decreased markedly (P &lt; 0.01) and there was no change in creatinine clearance.
5. In both studies, recumbency was associated with an initial drop, followed by a rise, in packed cell volume.
6. These data demonstrate that assumption of the supine position induces a rise in plasma atrial natriuretic factor and accounts for most of the observed variation. This is associated with natriuresis during the day, but it does not reverse the pattern of antinatriuresis that occurs at night. Instead, changes in plasma atrial natriuretic factor appear to reflect and, in turn, influence changes in intravascular volume.
Platelet-Activating Factor Mediates Glycerol-Induced Acute Renal Failure in Rats
Authors: López-Farré Antonio , Gómez-Garre Dulcenombre , Bernabeu Fernando , Cajal Santiago Ramón Y , Perez-Rodrigo Paloma , Braquet Pierre , López-Novoa José Miguel 
Published: August 2015

1. We have studied the effect of inhibiting the interaction of platelet-activating factor with its receptor by using two structurally different antagonists BN-52021 (1 mg/kg, intraperitoneally) and alprazolam (1 and 5 mg/kg, intraperitoneally) on the evolution of glomerular filtration and renal blood flow, in the experimental model of acute renal failure induced by the intramuscular injection of glycerol in rats.
2. We have also measured arteriovenous differences in platelet-activating factor concentration, as well as platelet-activating factor content in glomeruli from rats with glycerol-induced acute renal failure.
3. After glycerol injection, untreated rats showed a marked reduction in inulin clearance which reached 77% in the first 30 min. The reduction was only 27% in the rats treated with BN-52021 and 38% in the rats treated with alprazolam (5 mg/kg), with statistically significant differences between treated and untreated groups.
4. Clearance of p-aminohippuric acid was also improved with BN-52021 or alprazolam treatment.
5. This protective effect of BN-52021 was observed in a more prolonged follow-up (3 days).
6. Glomeruli from rats with acute renal failure, treated or untreated with BN-52021, showed similar amounts of platelet-activating factor, whereas it was undetectable in glomeruli from normal rats. Furthermore, rats with glycerol-induced acute renal failure released greater amounts of platelet-activating factor.
7. These results provide evidence of a role for platelet-activating factor in the genesis of this model of experimental acute renal failure.
Skeletal Muscle Metabolism in Heart Failure: A 31P Nuclear Magnetic Resonance Spectroscopy Study of Leg Muscle
Authors: Arnolda Leonard , Conway Michael , Dolecki Michael , Sharif Hasanat , Rajagopalan Bheeshma , Ledingham John G. G. , Sleight Peter , Radda George K. 
Published: August 2015

1. The gastrocnemius muscle of seven patients with mild to moderate chronic heart failure and of five healthy control subjects was studied using 31P nuclear magnetic resonance spectroscopy. Spectra were collected at rest and during an incremental, symptom-limited, exercise protocol. Blood flow was measured in the same study during brief interruptions to exercise.
2. The phosphocreatine/(phosphocreatine plus inorganic phosphate) ratio was lower in patients with heart failure than in control subjects at an exercise rate of 1.5 W, although intracellular pH and blood flow were similar.
3. The cytosolic free adenosine 5′-diphosphate concentration was markedly increased in patients with heart failure exercising at 1.5 W compared with control subjects exercising at the same workload.
4. Although the maximum workload achieved by patients with heart failure was less than half of that reached by control subjects, the pH and the phospho-creatine/(phosphocreatine plus inorganic phosphate) ratio were lower in patients with heart failure at maximal load. Blood flow was less at maximal exercise in patients with heart failure than in control subjects in keeping with the reduced work load.
5. The phosphocreatine depletion induced in the gastrocnemius muscle by exercise was more severe than previously described in the forearm of patients with heart failure.
6. Metabolic abnormalities in skeletal muscle may contribute to exercise intolerance in heart failure, particularly during submaximal exercise.
Mucosal Peptide Hydrolase and Brush-Border Marker Enzyme Activities in Three Regions of the Small Intestine of Rats with Experimental Uraemia
Authors: Haines D. J. , Swan C. H. J. , Green J. R. B. , Woodley J. F. 
Published: August 2015

1. The activities of nine peptide hydrolases and three non-peptidase brush-border marker enzymes have been quantified in crude homogenates prepared from the proximal, mid and distal regions of small-intestinal mucosa for sham-operated (n = 9) and uraemic (n = 14) rats. Abnormalities in enzyme activities were observed in all regions studied in the uraemic group, although no reduction in food intake occurred.
2. The proximal region of the small intestine from uraemic rats showed a general fall in enzyme activities associated with the brush-border. This fall was combined with a decline in mucosal protein content. In contrast, the mid and distal regions showed increased activity against the dipeptide tyrosyl-glycine.
3. It is proposed that the fall in brush-border enzyme activities in the proximal small intestine of uraemic rats is a response to the increased water intake associated with this, and presumably other, rat models of uraemia. The increased enzyme activity against tyrosyl-glycine found in the mid and distal regions of the small intestine of uraemic rats may be caused by an increased small-intestinal transit rate, but could be an attempt to maximize tyrosine absorption in response to decreased plasma tyrosine levels.
4. This study casts doubt on specific activities being the most useful units of enzyme activity, when measured in crude homogenates prepared from the proximal small intestine of uraemic rats. It also demonstrates that enzyme activities measured at a single site in the small intestine of uraemic rats may not be representative of the enzymatic changes occurring in the small-intestinal mucosa as a whole.
Alterations of Platelet Membrane Microviscosity in Essential Hypertension
Authors: Sang Kim-Hanh Le Quan , Montenay-Garestier Thérèse , Devynck Marie-Aude 
Published: August 2015

1. The metabolism of blood platelets, taken as an accessible model of excitable cells, has been reported to be altered in hypertension. Most of the identified alterations concern the functions of various plasma membrane constituents.
2. A possible modification of membrane microviscosity was investigated by 1,6-diphenyl-1,3,5-hexatriene and 1-[4-(trimethylamino)phenyl]-6-phenyl-1,3,5-hexatriene fluorescence depolarization. In order to determine whether or not the membrane structures probed by these indicators were related to platelet physiological functions, the cytosolic free Ca2+ concentration was determined in parallel.
3. At physiological temperature, the fluorescence anisotropy of 1-[4-(trimethylamino)phenyl]-6-phenyl-1,3,5-hexatriene was decreased in untreated hypertensive patients (0.276 ± 0.002 versus 0.288 ± 0.002, n = 23 and 22, P &lt; 0.001), indicating a lowered microviscosity at the lipid-water interface of cell membrane. It correlated inversely with blood pressure (P &lt; 0.001) and cytosolic free Ca2+ concentration (P &lt; 0.030). On the contrary, 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy was observed to vary with sex but not with blood pressure.
4. These results suggest that structural membrane modifications may participate in the various functional abnormalities observed in platelets from hypertensive patients.
Cardiac and Whole-Body [3H]Noradrenaline Kinetics during Adrenaline Infusion in Man
Authors: McCance Alastair J. , Forfar J. Colin 
Published: August 2015

1. To investigate the possible role of adrenaline as a modulator of noradrenaline release from the sympathetic nervous system, the responses of cardiac and whole-body noradrenaline kinetics to intravenous infusions of adrenaline (30 ng min−1 kg−1) and matching saline placebo were determined at rest and during supine bicycle exercise in 16 patients undergoing cardiac catheterization, in whom β-adrenoceptor antagonists had been discontinued for 72 h.
2. At rest and compared with placebo, infusion of adrenaline was associated with a small increase in arterial plasma noradrenaline from 211 ± 129 pg/ml to 245 ± 29 pg/ml (P &lt; 0.05). Increases in whole-body noradrenaline spillover to arterial plasma were larger (from 282 ± 40 ng min−1 m−2 to 358 ± 41 ng min−1 m−2, P &lt; 0.01) and there was a trend towards an increase in whole-body noradrenaline clearance. Cardiac noradrenaline clearance was modestly increased during adrenaline infusion, but cardiac noradrenaline spillover was not altered despite increases in heart rate and coronary sinus plasma flow. Adrenaline infusion was associated with symptomatic myocardial ischaemia in four of 14 patients with coronary heart disease.
3. Supine bicycle exercise was associated with significant increases in peripheral noradrenaline concentrations and in cardiac and whole-body noradrenaline spillover. The increases on exercise were not significantly different for these variables during saline and adrenaline infusions.
4. Infusion of adrenaline to produce ‘physiological’ increases in plasma adrenaline concentration was associated with an increase in total noradrenaline release, as assessed by whole-body noradrenaline spillover to plasma. This is consistent with the hypothesis that adrenaline may modulate noradrenaline release by acting upon pre-junctional β-adrenoceptors, but could also be explained by reflexogenic responses to the haemodynamic effects of adrenaline.