bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of prior ventilatory experience on the estimation of breathlessness during exercise
Authors: Wilson Rachel C. , Jones P. W. 
Published: August 2015

1. The intensity of breathlessness was measured during exercise in nine normal subjects using a modified Borg scale to examine the effect of prior experience of breathlessness on subsequent estimates of breathlessness.
2. Each subject performed four exercise tests, each of which consisted of two identical runs of workload incrementation (run 1 and run 2). An inspiratory resistive load of 3.8 cmH2O s−1 l−1 was applied during the appropriate run of the exercise test to examine the effect of (a) prior experience of ‘loaded’ breathing on breathlessness estimation during ‘unloaded’ breathing, and (b) prior experience of ‘unloaded’ breathing on breathlessness estimation during ‘loaded’ breathing. Run 1 was the conditioning run; run 2 was the run in which the effect of conditioning was measured.
3. There was a good correlation between breathlessness and minute ventilation during both unloaded’ breathing (median r = 0.93) and ‘loaded’ breathing (median r = 0.95).
4. The slope of the Borg score/minute ventilation relationship was greater during ‘loaded’ breathing than during ‘unloaded’ breathing (P &lt; 0.01). There was no difference in mean Borg score between ‘unloaded’ and ‘loaded’ breathing.
5. After a period of ‘loaded’ breathing during run 1, estimated breathlessness was significantly reduced during ensuing ‘unloaded’ breathing in run 2 (P &lt; 0.01) compared with the exercise test in which ‘unloaded’ breathing was experienced throughout both run 1 and run 2.
6. After a period of ‘unloaded’ breathing in run 1, estimated breathlessness was significantly increased during ensuing ‘loaded’ breathing in run 2 (P &lt; 0.01) compared with the exercise test in which the inspiratory load had already been experienced in run 1.
7. Changes in the pattern of breathing (inspiratory time, expiratory time, total breath duration, inspiration time/total breath duration ratio and tidal volume) were not consistent with the changes in breathlessness.
8. We suggest that perception of breathlessness may be influenced by a subject's immediate prior experience of an altered relationship between breathlessness and ventilation.
Free fatty acids stimulate mucin hypersecretion by rabbit gall-bladder epithelium in vitro
Authors: Mingrone G. , Greco A. V. , Mastromattei E. Arcieri 
Published: August 2015

1. Mucin, a high-molecular-weight glycoprotein secreted by the gall-bladder and biliary duct epithelium, is a well-known nucleation-prompting factor in experimental and human gall-stone disease.
2. Free fatty acids when incubated in vitro (micellar suspension with 1 mmol/l Tween 40) with rabbit gallbladders can promote abundant mucus secretion.
3. The hexosamine content of rabbit gall-bladder walls, measured by gas-liquid chromatography, was significantly higher in gall-bladders incubated with fatty acids than in control tissues.
4. The biochemical data were supported by ultra-structural findings showing numerous droplets with a translucent content in the perinuclear cytoplasm. Exocytosis was also seen in treated gall-bladders, confirming the secretory nature of the vesicles.
5. These results suggest that free fatty acids, which appear in high amounts when bile lecithins are hydrolysed by phospholipase, play an active role in the gall-stone formation.
Broadband ultrasound attenuation in the os calcis: relationship to bone mineral at other skeletal sites
Authors: McCloskey E. V. , Murray S. A. , Miller C. , Charlesworth D. , Tindale W. , O'Doherty D. P. , Bickerstaff D. R. , Hamdy N. A. T. , Kanis J. A. 
Published: August 2015

1. We have examined the relationship between broadband ultrasound attenuation in the os calcis and measurements of bone mineral in the distal forearm and lumbar spine of normal and postmenopausal osteoporotic women.
2. Values of broadband ultrasound attenuation in postmenopausal women with vertebral osteoporotic fractures were significantly lower (35%) than in normal pre-and peri-menopausal women (55.4 ± 3.8 and 79.6 ± 0.8 dB/MHz, respectively).
3. Broadband ultrasound attenuation correlated significantly with bone mineral content measured in the distal forearm by single-photon absorptiometry (r = 0.77, P &lt; 0.0001) and with bone mineral content (r = 0.66, P &lt; 0.0001) and bone mineral density (r = 0.72, P &lt; 0.0001) measured in the lumbar spine by dual-photon absorptiometry.
4. Although significant, these correlations are not sufficiently close to be predictive. However, the accuracy of broadband ultrasound attenuation in discriminating between normal subjects and patients with vertebral fracture compared very favourably with direct measurements in the spine by dual-photon absorptiometry.
5. Broadband ultrasound attenuation, but not the other measurements, correlated significantly with age in the osteoporotic patients (r = 0.50, P &lt; 0.05).
6. These findings may reflect the partial dependence of broadband ultrasound attenuation on the intrinsic trabecular architecture of cancellous bone, the disruption of which contributes to an increase in fracture risk.
A sensitive radioimmunoassay measuring endothelin-like immunoreactivity in human plasma: Comparison of levels in patients with essential hypertension and normotensive control subjects
Authors: Davenport Anthony P. , Ashby Michael J. , Easton Patricia , Ella Sarah , Bedford Joy , Dickerson Claire , Nunez Derek J. , Capper Stephen J. , Brown Morris J. 
Published: August 2015

1. A radioimmunoassay has been developed for measuring endothelin-like immunoreactivity in human plasma using an antibody raised against endothelin-1 which also cross-reacts with big endothelin-1 and endothelin-2 but not endothelin-3.
2. The sensitivity of the assay was 1 fmol/tube with inter- and intra-assay coefficients of variation of 13% and 9%, respectively. Cross-reactivity with endothelin-3 and non-endothelin peptides was less than 1%.
3. Endothelin-like immunoreactivity was present in the plasma of hypertensive patients (n = 25) at a concentration of 5.7 ± 0.5 pmol/l (mean ± sem), which was not significantly different from that of age-matched control subjects (5. ± 10.5 pmol/l). At these levels, endothelin-1 is unlikely to function as a circulating hormone.
4. Within the normotensive group, the concentration of endothelin-like immunoreactivity in plasma was positively correlated with mean arterial blood pressure, but in hypertensive patients it showed a significant negative correlation.
Effects of glucose on nitrogen balance during high nitrogen intake in malnourished patients
Authors: Forse R. Armor , Elwyn David H. , Askanazi Jeffrey , Iles Mary , Schwarz Yvonne , Kinney John M. 
Published: August 2015

1. The effects of increasing glucose intake on nitrogen balance, energy expenditure and fuel utilization were measured in 12 malnourished adult patients receiving parenteral nutrition with constant, very high nitrogen intake (500 mg of N/kg), high (105 kJ/kg) or low (30 kJ/kg) glucose intake and constant fat intake (7 kJ/kg). Each patient received each diet for 8-day periods in random order.
2. Energy balance and nitrogen balance were determined daily. Blood samples, taken at admission, during 5% (w/v) dextrose (D-glucose) infusion and at the end of days 7 and 8 of each diet, were analysed for urea, glucose, lactate, triacylglycerols, fatty acids, glycerol, 3-hydroxybutyrate, insulin and glucagon.
3. The effect of increasing glucose intake was to increase nitrogen balance by 0.60 ± 0.25 (sem) mg/kJ. At zero energy balance, nitrogen balance was 48 mg day−1 kg−1. This confirms findings of previous studies: that the effects of glucose on nitrogen balance are greater at high than at low nitrogen intakes, and that, in malnourished patients, unlike in normal adults, markedly positive nitrogen balance can be achieved at zero or negative energy balances.
4. Changes in nitrogen balance were due almost entirely to changes in urea excretion.
5. The high nitrogen intake markedly increased plasma insulin and glucagon concentrations and reduced glycerol, fatty acid and 3-hydroxybutyrate concentrations, independent of any glucose effect. Glucagon concentrations were significantly decreased by added glucose intake, an effect not previously seen at low nitrogen intakes. At this high nitrogen intake, the effects of added glucose appear to be mediated by both insulin and glucagon.
6. Unlike the effects at low nitrogen intakes, added glucose caused no increase in energy expenditure (thermogenesis) or creatinine excretion, and almost no increase in glycogen stores.
A non-invasive method of measuring concentrations of rubidium in rat skeletal muscle in vivo by 87Rb nuclear magnetic resonance spectroscopy: implications for the measurement of cation transport activity in vivo
Authors: Syme P. D. , Dixon R. M. , Allis J. L. , Aronson J. K. , Grahame-Smith D. G. , Radda G. K. 
Published: August 2015

1. We have used n.m.r. spectroscopy to measure rubidium concentrations in the skeletal muscle of live intact rats. Using a 1.9 T superconducting magnet and an ear-phone coil tuned to both protons (1H) and rubidium (87Rb), it was possible to make measurements of both tissue rubidium content and water content, and from these measurements to obtain the rubidium concentration.
2. The n.m.r. estimate of rubidium concentration in muscle in vivo was found to be a constant 31% (sem 4%) of that estimated by flame atomic absorption spectroscopy in an extract of excised muscle. This is close to the predicted theoretical n.m.r. visibility of 33%. The visibility was constant for muscle rubidium concentrations ranging between 10 and 34 mmol/l.
3. Rubidium concentration measurement by this method is unaffected by variations in sample geometry, sample volume, tissue conductivity, coil tuning and amplifier gain.
4. By using this method to measure changes in tissue rubidium concentration with time in the same animal, it should now be possible to assess the activity of ion transport systems, such as sodium- and potassium-activated adenosine triphosphatase in vivo, by measuring the rates of change of tissue rubidium concentrations during the administration of rubidium salts.
5. This method could also be used to measure the absolute concentration of any n.m.r.-visible nucleus and could be applied to man.
Is hydrochlorothiazide-induced hypocalciuria due to inhibition of prostaglandin E2 synthesis?
Authors: Caló Lorenzo , Cantaro Salvatore , Marchini Francesco , Giannini Sandro , Castrignano Rocco , Gambaro Giovanni , Antonello Augusto , Baggio Bruno , D'Angelo Angela , Williams Hibbard , Borsatti Arturo 
Published: August 2015

1. Since prostaglandin E2 could play a role in idiopathic hypercalciuria, and considering the well-established hypocalciuric action of hydrochlorothiazide, we have evaluated the effect of 15 days' treatment with hydrochlorothiazide in 10 hypercalciuric male stone-formers on urinary Ca2+ and prostaglandin E2, as well as on plasma bicyclo-prostaglandin E2, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D and parathyroid hormone.
2. In addition to lowering urinary Ca2+ (P &lt;0.001), hydrochlorothiazide also promoted a significant fall in urinary prostaglandin E2 (P &lt;0.001), plasma bicyclo-prostaglandin E2 (P &lt;0.001) and 1,25-dihydroxyvitamin D (P &lt;0.01), and an increase in plasma parathyroid hormone (P &lt;0.025), whereas plasma 25-hydroxyvitamin D was unchanged.
3. A positive correlation between urinary Ca2+ and prostaglandin E2 was present before (P &lt;0.00005), but not after, hydrochlorothiazide. Plasma bicyclo-prostaglandin E2 and plasma 1,25-dihydroxyvitamin D were positively correlated both before (P &lt;0.005) and after (P &lt;0.005) hydrochlorothiazide, as was also the percentage change in each induced by the drug (P &lt;0.05). Furthermore, the changes in plasma 25-hydroxyvitamin D and plasma 1,25-dihydroxyvitamin D after hydrochlorothiazide were negatively correlated (P &lt;0.05).
4. It is suggested that a block of prostaglandin E2 synthesis plays a role in the effect of hydrochlorothiazide on Ca2+ metabolism, most probably through an inhibition of 1α-hydroxylase activity.
Synthesis and secretion of atrial natriuretic factor during chronic hypoxia: A study in the conscious instrumented rat
Authors: Raffestin Bernadette , Adnot Serge , Mercadier Jean Jacques , Levame Micheline , Duc Philippe , Braquet Pierre , Viossat Isabelle , Chabrier Pierre Etienne 
Published: August 2015

1. To investigate the mechanisms leading to enhanced synthesis and release of atrial natriuretic factor during chronic hypoxia, we measured immunoreactive plasma atrial natriuretic factor, blood gases, packed cell volume, pulmonary artery pressure and systemic artery pressure in male Sprague–Dawley rats exposed to 1, 2 or 3 weeks of normobaric hypoxia. Rats were implanted with pulmonary and carotid artery catheters and studied conscious, 23 h after return to hypoxia.
2. The concentration of atrial natriuretic factor messenger RNA was measured in the right and left ventricular free walls of rats exposed to 3 weeks of hypoxia and in normoxic control rats.
3. There was a trend for plasma atrial natriuretic factor to increase with the duration of exposure to hypoxia but only the 3-week hypoxic rats had a significantly higher level (1080 ± 193 pg/ml) than the normoxic control rats (318 ± 46 pg/ml, P &lt;0.05, mean ± sem). When all the data from normoxic and hypoxic rats were considered together, plasma atrial natriuretic factor was positively correlated with packed cell volume (r = 0.66, P &lt;0.001), pulmonary artery pressure (r = 0.68, P &lt;0.002), and the index of right ventricular hypertrophy (r = 0.54, P &lt;0.01), but after analysis of partial correlation, packed cell volume was the only independent contributing factor to the variance in the level of plasma atrial natriuretic factor (r2 = 0.24).
4. Three weeks exposure to hypoxia produced a 3.4-and a 2.9-fold increase in atrial natriuretic factor messenger RNA concentration in the right and left ventricles, respectively, suggesting that the increase in pulmonary artery pressure and the resulting right ventricular hypertrophy may not be the only trigger for the increase in atrial natriuretic factor synthesis and that both ventricles may contribute to the increase in plasma atrial natriuretic factor.
Rapid Communication: Response of the Human Brain to a Hypercapnic Acid Load in Vivo
Authors: Cadoux-Hudson T. A. D. , Rajagopalan B. , Ledingham J. G. G. , Radda G. K. 
Published: August 2015

1. The aim of this investigation was to measure the change in intracellular pH of human brain in vivo in response to hypercapnia.
2. Five healthy male subjects inspired air for 20 min and then 5% CO2/95% O2 for 30 min, of which the first 10 min was used to achieve a steady-state end-tidal CO2 measurement.
3. 31P nuclear magnetic resonance spectroscopy was used to measure intracellular pH while breathing air and during hypercapnia. Simultaneous localization between superficial and deep brain was achieved by using the phase-modulated rotating frame imaging technique. One subject volunteered to breath air for a further phase-modulated rotating frame imaging study while recovering from hypercapnia.
4. End-tidal CO2 increased when breathing 5% CO2/95% O2 (on air, 5.57 ± 0.21%; on 5% CO2/95% O2, 6.41 ± 0.16%; rise = +0.84 ± 0.09%; means ± sem) causing a reduction in brain intracellular pH, which was more pronounced in deep brain (5 cm = mainly white matter, from 7.02 ± 0.006 pH units to 6.96 ± 0.001 pH units, mean ± sem) than in superficial brain (2 cm = mainly grey matter, from 7.02 ± 0.006 pH units to 7.00 ± 0.006 pH units, mean ± sem).
5. The white matter responded to hypercapnia with a greater fall in intracellular pH than the grey matter. This could either be due to differences in blood flow between grey and white matter in response to hypercapnia or to differences in intracellular pH regulation/buffering between these two tissues.
Effects of Chronic Administration of an Angiotensin-Converting Enzyme Inhibitor on Angiotensin-Converting Enzyme Activity in the Pars Recta of Rabbits
Authors: Praddaude Françoise , Tran-Van Tuan , Marchetti Jeannine , Girolami Jean-Pierre , Ader Jean-Louis 
Published: August 2015

1. To determine whether chronic angiotensin-converting enzyme inhibition induces a decrease in proximal tubular angiotensin-converting enzyme activity, urine and blood samples were collected in conscious New Zealand rabbits before and after 16 days administration in drinking water of low doses of captopril (2.6 ± 0.6 mg 24 h−1 kg−1), high doses of captopril (7.6 ± 0.9 mg 24 h−1 kg−1) or no captopril (controls). The kidneys were then removed and angiotensin-converting enzyme activity was determined in isolated pars recta of microdissected nephrons as pmol of tritiated hippurylglycylglycine substrate hydrolysed min−1 of incubation and mm−1 of tubule.
2. Both low and high doses of captopril significantly decreased plasma angiotensin-converting enzyme activity and increased plasma renin activity, thus indicating an effective inhibition of circulating angiotensin-converting enzyme. Both low and high doses of captopril also significantly decreased mean arterial pressure and increased water intake and urine flow rate. Neither dose modified creatinine clearance and absolute and fractional sodium excretion.
3. None of the doses altered urinary kallikrein excretion. Urinary excretion of kinins was increased by 98.7% compared with control rabbits by the high dose of captopril (402 ± 152 vs 251 ± 104 ng/24 h, P &lt; 0.01) but was unchanged by the low dose of captopril.
4. Angiotensin-converting enzyme activity in the pars recta was lower in rabbits given the high dose of captopril than in control rabbits (17.6 ± 7.2 vs 37.3 ± 9.0 pmol min−1 mm−1, P &lt; 0.01) but was not decreased in rabbits given the low dose of captopril (40.4 ± 5.0 pmol min−1 mm−1).
5. Our results indicate that only high doses of captopril are able to inhibit tubular angiotensin-converting enzyme activity in rabbit kidneys. Changes in arterial pressure and water handling are not related to tubular angiotensin-converting enzyme inhibition. The increase in urinary kinins with no change in kallikrein excretion could be the result of a reduction in proximal kininase activity induced by the higher dose.
Direct Vascular Effects in the Rat of the Vehicles Used for the Intravenous and Oral Administration of Cyclosporin A
Authors: Amorena C. , Castro A. , Müller A. , Villamil M. F. 
Published: August 2015

1. The contraction and relaxation responses to the polyoxyethylated vehicles currently used for the intravenous and oral administration of cyclosporin A in allograft recipients were studied in isolated rat aorta. The results were compared with those obtained with commercially available cyclosporin A for intravenous administration.
2. None of these compounds affected resting tension, noradrenaline-induced contraction or endothelium-independent relaxation produced by sodium nitroprusside or bumetanide. However, they all reversed the relaxation induced by acetylcholine, carbamylcholine or adenosine 5′-triphosphate, by a factor of approximately 66%.
3. This reversal of relaxation was unaffected by indomethacin and did not require the presence of cyclosporin A in the vehicles, and was completely abolished by l-arginine (3 × 10−-5 mol/l).
4. It is concluded that vehicles used for commercial preparations of cyclosporin A interfere with the synthesis of endothelium-derived relaxing factor at an early stage during which l-arginine is made available for enzymatic degradation.
Physiological Levels of Plasma Non-Esterified Fatty Acids Impair Forearm Glucose Uptake in Normal Man
Authors: Walker M. , Fulcher G. R. , Catalano C. , Petranyi G. , Orskov H. , Alberti K. G. M. M. 
Published: August 2015

1. The purpose of the present study was to maintain physiological plasma non-esterified fatty acid levels and to (i) examine their effect on skeletal muscle insulin-stimulated glucose uptake and metabolite exchange using the forearm technique, and (ii) evaluate their effect on whole-body glucose uptake and fuel oxidation.
2. Intralipid (10%) and heparin (Lipid) or saline (Control) was administered to eight healthy male subjects on separate occasions for 210 min. Insulin, glucagon and somatostatin were administered from 60 to 210 min in each study and euglycaemia was maintained.
3. Plasma non-esterified fatty acid levels plateaued at 420 ±50 μmol/l with the Lipid infusion but were completely suppressed during the Control clamp. Forearm non-esterified fatty acid uptake increased with the Lipid infusion (+ 50±10 nmol min−1 100 ml−1 of forearm) and was accompanied by a significant decrease in forearm glucose uptake (+ 3.23 ± 0.25 versus + 3.65 ± 0.35 μmol min−1 100 ml−1 of forearm, Lipid and Control, respectively; P &lt; 0.05) and alanine release (–84±12 versus −113 ± 15 nmol min−1 100 ml−1 of forearm, Lipid and Control, respectively; P &lt; 0.05).
4. Whole-body glucose uptake showed a comparable decrease with the Lipid infusion (6.36 ±0.81 versus 6.85±0.66 mg min−1 kg−1; P &lt; 0.05) and was accompanied by an increase in lipid oxidation (0.33 ±0.08 versus 0.16 ±0.05 mg min−1 kg−1; P &lt; 0.02) and a decrease in glucose oxidation (2.93 ±0.23 versus 3.30±0.20 mg min−1 kg−1; P &lt; 0.05).
5. We conclude that the maintenance of physiological plasma non-esterified fatty acid levels is associated with a decrease in forearm and whole-body insulin-stimulated glucose uptake. The changes in substrate oxidation and forearm alanine exchange provide support for the operation of the glucose—fatty acid cycle.
Errors Inherent in the Primed Infusion Method for the Measurement of the Rate of Glucose Appearance in Man when Uptake is not Forced by Glucose or Insulin Infusion
Authors: Heath D. F. 
Published: August 2015

1. My aim was to investigate, by mathematical simulation, the errors inherent in the measurement by the primed infusion method of the rate of appearance of glucose in man when turnover was as low or lower than in overnight-fasted normal subjects (control subjects). The simulations were based on published data for means and variances of turnover rates and concentrations in non-diabetic subjects and diabetic patients.
2. Systematic errors (bias) were shown to be considerable whether or not the Steele equation was used, unless run-times were longer than is customary. Errors were greater the lower the turnover rate, and were greatest in patients with diabetes, owing to insulin resistance. Studies of, for example, control subjects, age, obesity, exercise, sepsis and injury, are, however, all likely to be affected.
3. Estimates of variance, within-group means, between-group differences and slopes of rate—concentration relationships were all biased. Entirely spurious results appeared statistically significant.
4. When the Steele equation was not used, run-times had to exceed 3 h in control subjects and 10 h in some diabetic patients to reduce bias to acceptable levels. The nature of the bias depended on how the priming dose/infusion rate ratio was chosen. Each choice implies a particular hypothesis about the values of the rate of appearance of glucose, their variance, and how they are related to concentration. The bias was always such as to favour that hypothesis.
5. When the Steele equation was used, the accessible glucose space (pool fraction × distribution volume) had to be correct to 20–30 ml to avoid unacceptable bias in some patients in runs 4 h long. The space is not known this accurately. Theoretically, in the near-steady metabolic states considered, the pool fraction should be near 1.00, i.e. the accessible space should be near the glucose distribution volume of 200–300 mg/kg. There is some confirmatory experimental evidence.
6. Large random errors from variance of specific (radio)activity measurements when the Steele equation is used can be reduced by a suitable choice of protocols.
7. The propagation of errors is too complex to permit correction of results. It is essential to choose protocols that can be shown to give results that are acceptably bias-free. Ways of doing this are discussed.