bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell Membrane Microviscosity and Ca2+-Mg2+-ATPase Activity do Not Contribute to Hypertension in the Spontaneously Hypertensive Rat Model
Authors: Norman Robert I , Achall Navtej 
Published: August 2015

1. The relationships between systolic blood pressure and altered erythrocyte Ca2+-Mg2+-ATPase activity and membrane microviscosity were assessed in membranes prepared from 20-week-old female Wistar-Kyoto normotensive and spontaneously hypertensive rats obtained from two different sources (Charles River and Harlan OLAC) and a second filial (F2) generation derived from a cross between Wistar-Kyoto rats and spontaneously hypertensive rats from one source (Charles River).
2. Spontaneously hypertensive rats from both sources had systolic blood pressures significantly higher than those of Wistar-Kyoto animals (P &lt;0.05; 151 + 4 and 110 + 3 mmHg, Charles River; 155 + 4 and 122 + 4 mmHg, Harlan OLAC). The systolic blood pressures for the F2 rat population ranged between 73 and 168 mmHg.
3. Ca2+-Mg2+-ATPase activity was measured as ATP-dependent 45Ca2+ uptake into inside-out vesicles and microviscosity assessed by the measurement of polarization anisotropy of membrane incorporated fluorescent probes including 1,6-diphenyl-1,3,5-hexatriene, trimethylamino-1,6-diphenyl-1,3,5-hexatriene and a series of anthroyloxy fatty acids.
4. Contrary to previous studies, no relationship between adult systolic blood pressure and erythrocyte Ca2+-Mg2+-ATPase activity or general or localized membrane microviscosity was indicated by the comparison of spontaneously hypertensive and Wistar-Kyoto animals or in the analysis of the F2 rat population.
5. These results suggest that Ca2+-Mg2+-ATPase activity and membrane microviscosity are causally unrelated to hypertension in these animals. On the assumption that biophysical properties of the erythrocyte membrane reflect those of smooth muscle, our results suggest that membrane alteration does not play a significant role in the pathogenesis of hypertension in the spontaneously hypertensive rat model.
Physiological Determinants of Inspiratory Effort Sensation during CO2 Rebreathing in Normal Subjects
Authors: Clague J. E. , Carter J. , Pearson M. G. , Calverley P. M. A. 
Published: August 2015

1. The physiological basis of inspiratory effort sensation remains uncertain. Previous studies have suggested that pleural pressure, rather than inspiratory muscle fatigue, is the principal determinant of inspiratory effort sensation. However, only a limited range of inspiratory flows and breathing patterns have been examined. We suspected that inspiratory effort sensation was related to the inspiratory muscle tension-time index developed whatever the breathing pattern or load, and that this might explain the additional rise in sensation seen with hypercapnia.
2. To investigate this we measured hypercapnic re-breathing responses in seven normal subjects (six males, age range 21–38 years) with and without an inspiratory resistive load of 10 cm H2O. Pleural and transdiaphragmatic pressures, mouth occlusion pressure and breathing pattern were measured. Diaphragmatic and ribcage tension-time indices were calculated from these data. Inspiratory effort sensation was recorded using a Borg scale at 30s intervals during each rebreathing run.
3. Breathing pattern and inspiratory pressure partitioning were unrelated to changes in inspiratory effort sensation during hypercapnia. Tension-time indices reached pre-fatiguing levels during both free breathing and inspiratory resistive loading.
4. Stepwise multiple regression analysis using pooled mechanical, chemical and breathing pattern variables showed that pleural pressure was more closely related to inspiratory effort sensation than was transdiaphragmatic pressure. When converted to tension-time indices, ribcage tension-time index was the major determinant of inspiratory effort sensation during loaded rebreathing, but partial pressure of CO2 was an important independent variable, whereas during unloaded rebreathing partial pressure of CO2 was the most important determinant of inspiratory effort sensation.
5. These results suggest that the pattern of inspiratory pressure partitioning and inspiratory flow rate have little influence on inspiratory effort sensation during CO2 stimulated breathing. The close association between inspiratory effort sensation and ribcage tension-time index, an index of inspiratory muscle work, suggests that inspiratory effort sensation may forewarn of potential inspiratory muscle fatigue. Changes in PaCO2 have a small independent effect on respiratory perception.
Agonist-Induced Desensitization of β-Adrenoceptors of Bovine Bronchial Epithelial Cells
Authors: NoGami M. , Romberger D. J. , Rennard S. I. , Toews M. L. 
Published: August 2015

1. Cultured bovine bronchial epithelial cells express a large number of β-adrenoceptors of the β2 subtype which are coupled to activation of adenylate cyclase and synthesis of cyclic AMP. The mechanisms involved in agonist-induced desensitization of β-adrenoceptor function in these cells were investigated.
2. Preincubation of cells with the β-adrenoceptor agonist isoprenaline induced a rapid desensitization of adenylate cyclase activity stimulated by isoprenaline (40% at 30 min) with little or no decrease in forskolin stimulation or in the number of β-adrenoceptors detected by radioligand binding, indicating that uncoupling of β-adrenoceptors from adenylate cyclase had occurred.
3. Uncoupling of β-adrenoceptors from the stimulatory guanine-nucleotide-binding protein Gs was indicated by the loss of GTP effects on agonist competition for radioligand binding. Results from subcellular fractionation by sucrose density gradient centrifugation suggest that rapid internalization or sequestration of β-adrenoceptors occurred along with the desensitization.
4. Preincubation with isoprenaline for longer times led to a marked decrease in total receptor number (85% at 18 h), indicating that receptor down-regulation also occurs. Recovery of receptors after down-regulation was prevented by cyclobeximide and by actinomycin D, suggesting that degradation of both receptor protein and receptor mRNA may be involved in down-regulation.
Haemodynamks of Recovery after Strenuous Exercise in Physically Trained Hypertensive and Normotensive Subjects
Authors: Casiglia Edoardo , Palatini Paolo , Bongiovi Stefano , Mario Luca , Colangeli Giovanna , Ginocchio Giuliana , Pessina Achille C. 
Published: August 2015

1. Central and peripheral post-exercise haemo-dynamics were studied in 18 physically trained male subjects (10 hypertensive and eight normotensive) engaging in sports activities for 3–5 h/week. After a preliminary multistage bicycle ergometric test to evaluate their maximal oxygen consumption and anaerobic threshold, they underwent prolonged exercise at anaerobic threshold in the semi-supine position at 30% grade until exhaustion (mean duration 60.0 + 16.7 min in the normotensive subjects and 61.0 + 5.7 min in the hypertensive subjects, not significant). During the recovery time, intra-arterial blood pressure, echocardiographic cardiac output and indium-gallium strain-gauge plethysmographc peripheral flow were measured, and total, forearm and leg peripheral resistances were calculated respectively from mean blood pressure/cardiac output and mean blood pressure/peripheral resistance.
2. Systolic blood pressure was decreased during the entire recovery period in comparison with the baseline values (−8.4 mmHg, −43.8 mmHg and −39.7 mmHg at the 1st, 5th and 10th min in the hypertensive subjects, P = 0.001, P = 0.0001 and P = 0.0001 respectively; −18.8, −25.5 and −24.1 mmHg in the normotensive subjects, not significant, P = 0.01 and P = 0.01, respectively) without any significant difference between the two groups, whereas the reduction in diastolic blood pressure was not statistically significant. Peripheral flow increased and peripheral resistance decreased in parallel in the forearm and the leg and showed similar trends in the hypertensive subjects and the normotensive subjects. The increase in cardiac output and left ventricular ejection fraction and the decrease in total resistance were also similar in the two groups.
3. In conclusion, after long-lasting strenuous leg exercise central and peripheral haemodynamics vary to the same degree in hypertensive and normotensive trained subjects. Peripheral haemodynamics (similar in the leg and the arm in both groups) closely reflect systemic haemodynamics. The blood pressure reduction observed in the recovery period is totally due to the fall in systemic vascular resistance, while cardiac output is increased.
Rates of Change in Peak Expiratory Flow and in Diurnal Variation in Peak Flow in Patients Recovering from Acute Severe Asthma
Authors: Packe G. E. , Freeman W. , Cayton Ruth M. 
Published: August 2015

1. The rates of change in mean peak expiratory flow and in diurnal variation in peak flow were compared in 14 patients recovering from acute severe asthma.
2. Peak expiratory flow was measured on hospital admission, and at 6-hourly intervals for the next 3 weeks.
3. Diurnal variation in peak flow was assessed by measuring the following: amplitude (the highest minus the lowest peak expiratory flow during any given 24 h period), amplitude % mean (the highest minus the lowest peak expiratory flow during any given 24 h period divided by the mean peak expiratory flow over that period) and residual amplitude (the maximum variation about the mean peak expiratory flow during any given 24 h period).
4. Plots of diurnal variation in peak flow and peak expiratory flow against time were constructed for each patient. To enable comparison of changes in peak expiratory flow and diurnal variation in peak flow the data were transformed.
5. The rate of change for mean peak expiratory flow and for the three measures of diurnal variation in peak flow was assessed by fitting an exponential function to each set of data, and calculating the slope of the exponential curve halfway through the period of observation (10.5 days).
6. Median (range) slope for peak expiratory flow was 0.055 (0-2.57). The comparable value for amplitude was −3.15 (−1.27 to −4.22) (absolute median values compared, P = 0.0029), for amplitude % mean was −1.87 (−0.18 to −5.95) (P = 0.012) and for residual amplitude was −1.43 (−0.62 to −3.09) (P = 0.033).
7. Diurnal variation in peak flow therefore takes longer to reach a stable value than does mean peak expiratory flow. We conclude that the magnitude of diurnal variation in peak flow during recovery from an acute attack of asthma is not governed exclusively by mean airway calibre.
Nitrogen Homoeostasis in man: Influence of Protein Intake on the Amplitude of Diurnal Cycling of Body Nitrogen
Authors: Price Gill M. , Halliday David , Pacy Paul J. , Quevedo Marcelo R. , Millward D. Joe 
Published: August 2015

1. The diurnal nature of nitrogen (N) homoeostasis was investigated in adults fed increasing protein intakes. N balance was estimated during a 48 h period of consecutive 12 h periods of feeding hourly meals and fasting, after 12 days of adaptation to diets containing 0.36 +0.01, 0.77 + 0.03, 1.59 +0.08 and 2.31 +0.65 g of protein day−1 kg−1. N losses were determined from measured urinary N excretion corrected for changes in the body urea pool, and estimated faecal and miscellaneous losses. [13C] Leucine and [2H5]phenylalanine balances were measured during a primed, continuous infusion of the two amino acids during the fasting and feeding phase on the second day.
2. Increasing fasting N losses were observed (47 +7, 60+6, 95+15 and 140+36 mg day−1 kg−1) on the four intakes, with corresponding increasing fed gains of 8.2+3.9, 40.2+7.1, 112+24 and 180+ 56 mg day−1 kg−1.
3. Increasing fed-state amino acid gains with increasing protein intake were observed with both [13C]leucine and [2H5]phenylalanine, whereas increasing fasting amino acid losses were confirmed with [13C]leucine.
4. The N equivalent of the leucine oxidation rate was mostly in the range of 10–50% lower than expected from the N excretion rates. This may reflect the timing of the amino acid balance measurements and non-uniform rates of gain and loss throughout the diurnal cycle.
5. We conclude on the basis of both N and amino acid balances that the amplitude of the diurnal cycling of body protein N in human adults increases with increasing dietary protein intake. Thus one component of the protein requirement for N balance reflects a demand for repletion of fasting losses which increases with increasing habitual protein intake.
Abnormal Erythrocyte and Renal Frusemide-Sensitive Sodium Transport in Idiopathic Calcium Nephrolithiasis
Authors: Baggio Bruno , Gambaro Giovanni , Marchini Francesco , Vincenti Massimo , Ceolotto Giulio , Pessina Achille C. , Semplicini Andrea 
Published: August 2015

1. Anomalous transmembrane anion transport has been observed in erythrocytes of patients with idiopathic calcium nephrolithiasis.
2. To verify whether cation transport is also abnormal, we investigated the frusemide-sensitive Na+ efflux from Na+-loaded erythrocytes and the natriuretic response to acute intravenous frusemide administration in calcium oxalate renal stone formers.
3. Frusemide administration induced a statistically significant smaller increase in the fractional excretion of Na+ in patients than in control subjects. Abnormal kinetic properties of erythrocyte Na+-K+-2Cl− co-transport were observed in approximately 60% of stone formers. The Km for Na+ of Na+-K+-2Cl− co-transport correlated with urinary Ca2+ excretion.
4. The abnormal kinetic properties of Na+-K+-2Cl− co-transport may be relevant for stone formation, hampering renal Ca2+ reabsorption in the distal nephron and determining critical physicochemical conditions for calcium/oxalate crystallization.
Albumin Excretory Rate in Normal and Hypertensive Pregnancy
Authors: Brown Mark A. , Wang Min-Xia , Buddle Megan L. , Carlton Mark A. , Cario Gregory M. , Zammit Vivienne C. , Whitworth Judith A. 
Published: August 2015

1. The purpose of this study was to determine whether the 24 h urinary albumin excretory rate was increased in the third trimester of normal pregnancy or in pregnant women with hypertension who had 24 h urinary total protein excretion within the normal range.
2. Twenty-four hour urinary creatinine and albumin excretions were determined prospectively in 26 non-pregnant and 115 pregnant women in their third trimester (40 in normal pregnancy, 38 with mild pre-eclampsia, 20 with severe pre-eclampsia, 17 with essential hypertension) in whom urinary total protein excretion was normal. Both the urinary albumin excretion rate and the urinary albumin/creatinine ratio were compared among the groups. The clearance of albumin relative to that of creatinine was also calculated in the hypertensive women and in 14 of the non-pregnant women and nine of the normal pregnant women.
3. The twenty-four hour urinary albumin excretion rate was similar in non-pregnant [8(5–10) mg/day; median (interquartile range)] and normal pregnant [7(6–10) mg/day] women. Women with essential hypertension [6(4–16) mg/day] and mild pre-eclampsia [7(4–10) mg/day] had a urinary albumin excretion rate similar to that of normal pregnant women. Women with severe pre-eclampsia had an urinary albumin excretion rate increased [13(7–32) mg/day] compared with other groups (P &lt; 0.05). The clearance of albumin relative to that of creatinine was elevated significantly only in women with severe pre-eclampsia compared with normal pregnant women (0.00054 versus 0.00012; P &lt; 0.05). Blood pressures were similar among all hypertensive groups. The upper limit of the urinary albumin excretion rate was 20 mg/day in normal pregnant women, similar to that in non-pregnant women.
4. Urinary albumin excretion is unchanged in the third trimester of normal pregnancy, but is increased in women with features of severe pre-eclampsia who have normal total urinary protein excretion. This is not fully explained by a reduction in glomerular filtration rate nor by different systemic blood pressures, and probably reflects enhanced glomerular capillary permeability, possibly with altered maximum renal tubular reabsorption capacity for albumin.
Role of Cardiorespiratory Abnormalities, Smoking and Dive Characteristics in the Manifestations of Neurological Decompression Illness
Authors: Wilmshurst Dr Peter , Davidson Craig , O'Connell Geraldine , Byrne Christopher 
Published: August 2015

1. Blind analysis of contrast echocardiograms to detect intracardiac shunts, blind analysis of lung function tests for evidence of small airways disease, smoking history and dive characteristics were examined in an attempt to explain neurological symptoms that occurred within 5 min of surfacing from unprovocative dives.
2. Pulmonary abnormalities were significantly more frequent in those divers without intracardiac shunts (50%) than in those with shunts (0%). Smoking was more common in those divers without shunts (55% versus 15%), although this just failed to reach conventional significance levels. Divers without shunts experienced cerebral rather than spinal symptoms after significantly shallower dives with lower tissue nitrogen loads. Depths of dives, tissue nitrogen loads and clinical manifestations in those divers without shunts were similar to the findings in divers who had symptoms after rapid ascents. Despite conservative dive profiles, clinical manifestations in divers with shunts resembled those observed after missed decompression stops.
3. The findings suggest that occult lung disease, and probably smoking, increase the risk of neurological symptoms, even after unprovocative dives, and the similarity of the dive profiles and clinical manifestations to cases with rapid ascents suggest that pulmonary barotrauma and arterial gas embolism are responsible. In divers with intracardiac shunts the different dive profiles and clinical manifestations imply that there is another mechanism, involving different tissue and bubble nitrogen kinetics resulting in venous gas liberation and peripheral amplification in embolized tissues, rather than paradoxical embolism per se.
Do Thiazides Reduce Intestinal Oxalate Absorption?: A Study In Vitro Using Rabbit Colon
Authors: Hatch M. , Vaziri N. D. 
Published: August 2015

1. The purpose of the present study was to examine the effects of various diuretics on intestinal oxalate transport. Transmural oxalate fluxes were measured across isolated, short-circuited tissue segments removed from rabbits and placed in Ussing chambers.
2. The net absorptive flux of oxalate across the distal colon was significantly reduced in the presence of trichlormethiazide at 10−4 mol/l. In contrast, this diuretic had no effect on oxalate transport in the other intestinal segments examined. Several of the thiazide diuretics tested had some inhibitory effect on colonic oxalate absorption, but at higher concentrations of 10−3 mol/l or 10−2 mol/l.
3. We conclude that the previously reported hypooxaluric effects of hydrochlorothiazide and chlorthalidone are most likely not the result of an exclusive or primary effect on intestinal oxalate transport. It is suggested that the reduction in colonic oxalate absorption that was observed with the thiazides probably involves the transport system responsible for oxalate efflux across the basolateral membrane of the colonocyte.
Ambulatory Blood Pressure and Left Ventricular Hypertrophy in Subjects with Untreated Obstructive Sleep Apnoea and Snoring, Compared with Matched Control Subjects, and their Response to Treatment
Authors: Davies Robert J. O. , Crosby Joy , Prothero Anthony , Stradling John R. 
Published: August 2015

1. Obstructive sleep apnoea and snoring are associated with daytime hypertension. It is uncertain whether this association is directly due to the disturbed sleeping respiration or the result of confounding variables, particularly obesity, smoking and alcohol intake.
2. Ambulatory blood pressure and echocardiographic left ventricular muscle mass were measured in 19 patients with obstructive sleep apnoea, 19 men who snore without apnoea and 38 control subjects matched for age, sex, body mass index, smoking and alcohol intake. Ambulatory blood pressure was also measured before and after treatment in 11 patients with obstructive sleep apnoea and their matched control subjects.
3. Compared with matched control subjects, untreated obstructive sleep apnoea and snoring were not associated with an increase in daytime blood pressure. A daytime elevation of either systolic or diastolic blood pressure of &gt; 3.8 mmHg due to obstructive sleep apnoea or snoring was excluded with 95% confidence in each of the study groups. Daytime blood pressure was also unchanged when obstructive sleep apnoea was treated with nasal continuous positive airway pressure. Night-time blood pressure was not significantly different in the patients with obstructive sleep apnoea or the snorers when compared with their matched control subjects. However, a fall in night-time systolic blood pressure was seen in the patients with obstructive sleep apnoea after treatment [fall in systolic blood pressure −6.3 (SD 8.2) mmHg, P &lt; 0.02].
4. Left ventricular diameter, wall thickness and calculated mass were similar in each of the study groups and their matched control groups.
5. Compared with well-matched control subjects, daytime ambulatory blood pressure is not increased in patients with obstructive sleep apnoea or snoring and these patients do not show left ventricular hypertrophy. Night-time ambulatory blood pressure may be raised by obstructive sleep apnoea since it falls with treatment.