bluuebunny/crossref_metadata_2025 huggingface dataset:
Platelet Membrane Microviscosity in Sabra Rats with Early Salt Hypertension
Authors: Sang Kim Hanh Le Quan , Kunes Jaroslav , Zicha Josef , Lacour Bernard , Ben-Ishay Drori , Devynck Marie-Aude
Published: August 2015

1. To investigate the possibility that arterial hypertension is associated with changes in the physicochemical properties of cell membranes, we have studied the effects of dietary salt loading on platelet membrane microviscosity in hypertension-prone and -resistant Sabra rats.

2. Sixteen hypertension-prone and 14 hypertension-resistant Sabra rats were submitted to either a low-salt (0.25% NaCl) or a high-salt (4% NaCl) diet for 3–4 weeks. Platelet membrane anisotropy was determined, in the presence and absence of extracellular Na+, using two fluorescent probes, diphenylhexatriene and trimethylamino-diphenylhexatriene, inserted in different areas of the cell membranes.

3. A decrease in diphenylhexatriene anisotropy was demonstrated when platelets of hypertension-prone (but not hypertension-resistant) Sabra rats were suspended in a Na+-free medium. This alteration in membrane dynamic properties is localized within the hydrophobic core of the platelet membranes and is independent of salt intake. It reflects an abnormal fluidizing effect of extracellular Na+ removal.

4. Platelets of hypertension-prone and hypertension-resistant Sabra rats did not differ significantly in trimethylamino-diphenylhexatriene fluorescence anisotropy, irrespective of the incubation media used. Extracellular Na+ removal caused an increase in trimethylamino-diphenylhexatriene fluorescence anisotropy in all groups, the change being greatest in salt-loaded rats.

5. This study indicates that platelet membrane microviscosity is specifically altered in the hypertension-prone Sabra rat irrespective of salt intake. This raises the question of the relation of this inherited defect with the susceptibility of this strain to dietary salt loading.
Plasma Levels of 5-Hydroxytryptamine during Sympathetic Stimulation and in Raynaud's Phenomenon
Authors: Coffman Jay D. , Cohen Richard A.
Published: August 2015

1. The involvement of plasma 5-hydroxytryptamine in normal subjects during sympathetic stimulation and in patients with Raynaud's phenomenon was studied.

2. Arterial and venous plasma levels of 5-hydroxytryptamine were measured in normal subjects in a warm room, during reflex sympathetic stimulation by body cooling and during intra-arterial infusions of tyramine. Normal subjects (n = 19) had significantly higher levels of 5-hydroxytryptamine in venous plasma [mean 1.42 (SEM 0.23) ng/ml] than in arterial plasma [0.67 (0.12) ng/ml; P < 0.01]. Body cooling (n = 10) or tyramine infusion (n = 8) did not increase venous levels of 5-hydroxytryptamine despite significant decreases in blood flow and increases in vascular resistance.

3. Venous plasma levels of 5-hydroxytryptamine were also determined in patients with primary Raynaud's phenomenon (n = 12) or secondary Raynaud's phenomenon due to scleroderma (n = 11). Patients with primary or secondary Raynaud's phenomenon did not have significantly higher venous plasma levels of 5-hydroxytryptamine than normal subjects, even during vasospastic attacks (n = 3).

4. It is concluded that either 5-hydroxytryptamine is not involved in sympathetic nerve vasoconstriction or in Raynaud's phenomenon, or 5-hydroxytryptamine released in the microcirculation is largely taken up or metabolized by endothelial cells or platelets.
Effects of Nitric Oxide Inhibition on the Renal Papillary Blood Flow Response to Saline-Induced Volume Expansion in the Rat
Authors: Atucha Noemí M. , Ramírez Ana , Quesada Tomás , García-Estañ Joaquán
Published: August 2015

1. Evidence indicates that nitric oxide (NO) exerts a paracrine influence in the renal medulla. Increases in papillary blood flow are thought to be an important determinant of the renal response to extracellular volume expansion. Therefore, in the present study, we have evaluated the role of NO in mediating papillary blood flow (laser-Doppler flowmetry) and excretory responses to volume expansion with isotonic saline (3% body weight, 15 min).

2. Infusion of the NO synthesis inhibitor Nω-nitro-l-arginine methyl ester (10 μg min−1 kg−1), significantly attentuated the renal diuretic and natriuretic responses to volume expansion as well as the renal hydrostatic interstitial pressure increase induced by this manoeuvre. The percentages of the water and sodium excreted in 1 h by the Nω-nitro-l-arginine methyl ester-pretreated animals were 36% and 40% of the load, whereas those of the control animals were 44% and 65%, respectively.

3. In similar experiments performed in the exposed papilla of Munich Wistar rats, the same dose of Nω-nitro-l-arginine methyl ester reduced basal papillary blood flow and blunted the elevation in papillary blood flow induced by volume expansion (6% versus 16% in the control animals).

4. These results indicate that the inhibition of NO synthesis blunts the renal excretory and papillary responses to volume expansion, suggesting that NO modulates these responses through changes in papillary blood flow and renal interstitial hydrostatic pressure.
Non-Respiratory Components of Heart Rate Variability in Heart Transplant Recipients: Evidence of Autonomic Reinnervation?
Authors: Bernardi Luciano , Valle Felice , Leuzzi Stefano , Rinaldi Mauro , Marchesi Eugenia , Falcone Colomba , Martinelli Luigi , Viganó Mario , Finardi Giorgio , Radaelli Alberto
Published: August 2015

1. Although the high-frequency fluctuations in R—R interval (respiratory sinus arrhythmia) observed in heart transplant recipients are not a reliable marker of reinnervation because of a previously shown direct mechanical effect of breathing, the presence of a non-respiration-related low-frequency oscillation reflects rhythms generated outside the heart, and thus could be neurally mediated.

2. To evaluate the presence of reinnervation, the spontaneous variability in R—R interval was investigated, supine and after passive tilting, in 23 heart transplant recipients (age 43 years, range 23–64 years) and in 25 normotensive control subjects by autoregressive spectral analysis of low- and high-frequency spontaneous fluctuations in R—R interval and respiration. The response of R—R interval to amyl nitrite inhalation was also evaluated in five heart transplant recipients and eight control subjects.

3. Detectable low-frequency oscillations, unrelated to respiration, were present in 13/23 heart transplant recipients, particularly in those who were transplanted at least 20 months earlier (11/14). The natural logarithm of the power of low-frequency fluctuations was markedly lower than in control subjects (0.75 ± 0.21 versus 5.62 ± 0.20 ms2, P < 0.001). The low-frequency but not the high-frequency fluctuations correlated with time since transplantation (r = 0.44, P < 0.05). The subjects with low-frequency fluctuations showed a sudden decrease in R—R interval with amyl nitrite linearly related to the decrease in mean blood pressure (r ≧ 0.94). The slopes obtained in these heart transplant recipients were comparable (although of lower values) with those obtained in control subjects. The subjects with no low-frequency fluctuations showed no change in R—R interval despite a similar reduction in blood pressure.

4. Twenty months after transplantation signs of functional (reflex) reinnervation can be found in most heart transplant recipients.
Impaired Erythropoietin Responsiveness in Anaemic Rheumatoid Arthritis Patients: Potential Relation to Immune Mechanisms
Authors: Stockenhuber Felix , Keil Michaela , Wurnig Christian , Kurz Robert W. , Gottsauner-Wolf Michael , Balcke Peter
Published: August 2015

1. Serum levels of erythropoietin and the immune parameters tumour necrosis factor-α, soluble interleukin-2 receptor, interleukin-2, interleukin-6 and interferon-γ were measured in patients with rheumatoid arthritis.

2. Out of 69 patients, 44 had anaemia with serum haemoglobin concentrations of 10.8 (SD 1.2) g/dl. In these patients erythropoietin levels were significantly higher than in non-anaemic patients [51.97 (SD 23.9) versus 26.06 (SD 11.9) m-units/ml; P < 0.0001; control patients: 18.1 (SD 13.8) m-units/ml]. Mean soluble interleukin-2 receptor activity was elevated in all patients with rheumatoid arthritis [1324 (SD 715) units/ml; control patients: 480 (SD 75) units/ml; P < 0.001] and was significantly higher in the anaemic group than in the non-anaemic group [1562 (SD 662) versus 696 (SD 402) units/ml; P < 0.0001]. The serum activity of soluble interleukin-2 receptor showed an inverse correlation with haemoglobin (r = 0.79; P < 0.0001) and a positive correlation with erythropoietin (r = 0.70, P < 0.0001).

3. Elevated serum tumour necrosis factor-α levels were found in 19 anaemic patients [20.6 (SD 9.1) pg/ml]. Concentrations of tumour necrosis factor-α in serum showed an inverse correlation with haemoglobin (r = 0.57, P < 0.001) and a positive correlation with erythropoietin (r = 0.46, P < 0.05). Interleukin-6 was detected in seven anaemic patients [21 (SD 14) pg/ml] and interleukin-2 activity in three anaemic patients (12, 16 and 14 units/ml, respectively). Interferon-γ was not detected in any of the patients investigated.

4. The present study supports the concept that in patients with rheumatoid arthritis the responsiveness to erythropoietin is impaired. Immune mechanisms may be operative and point to a pivotal role for tumour necrosis factor-α.
Association of Cerebrospinal Fluid Deficiency of 5-Methyltetrahydrofolate, but Not S-Adenosylmethionine, with Reduced Concentrations of the Acid Metabolites of 5-Hydroxytryptamine and Dopamine
Authors: Surtees Robert , Heales Simon , Bowron ANN
Published: August 2015

1. Folate deficiency, or inborn errors of folate metabolism, cause reduced turnover of 5-hydroxytryptamine (serotonin), and perhaps dopamine, in the central nervous system. The mechanism by which this occurs are not known. One possibility is that this is mediated by deficiency of the methyl-donor S-adenosylmethionine.

2. To test this in humans, we have measured cerebrospinal fluid concentrations of 5-hydroxyindoleacetic acid and homovanillic acid, metabolites of 5-hydroxytryptamine and dopamine, respectively, in children with inborn errors of the methyl-transfer pathway. These children are naturally deficient in 5-methyltetrahydrofolate, S-adenosylmethionine or both before treatment, and replete with S-adenosylmethionine, but not necessarily with 5-methyltetrahydrofolate, during treatment.

3. Children with subnormal cerebrospinal fluid concentrations of 5-methyltetrahydrofolate had significantly reduced concentrations of 5-hydroxyindoleacetic acid and homovanillic acid. Children with subnormal cerebrospinal fluid concentrations of S-adenosylmethionine did not have significantly reduced concentrations of these metabolites.

4. We conclude that the mechanism by which deficiency of 5-methyltetrahydrofolate causes reduced 5-hydroxytryptamine and dopamine turnover is unlikely to be mediated by S-adenosylmethionine.
Reduced Cytosolic Free Sodium Concentration in Vascular Smooth Muscle Cells from Spontaneously Hypertensive Rats
Authors: Tepel Martin , Holthues JAN , Neusser Marcus , Golinski Petra , Zhu Zhiming , Mehring Norbert , Zidek Walter
Published: August 2015

1. Cytosolic free sodium concentration and sodium transport systems were measured in intact cultured vascular smooth muscle cells from spontaneously hypertensive rats of the Münster strain and from normotensive Wistar—Kyoto rats using the sodium-sensitive fluorescent dye sodium-binding benzofuran isophthalate.

2. Resting cytosolic free sodium concentration was significantly lower in vascular smooth muscle cells from spontaneously hypertensive rats than from Wistar-Kyoto rats (10.2 ± 1.5 mmol/l, n = 26, versus 19.4 ± 2.5 mmol/l, n = 20, P < 0.01).

3. Inhibition of Na+, K+-ATPase by ouabain caused a dose-dependent increase in cytosolic free sodium concentration in spontaneously hypertensive rats and Wistar—Kyoto rats.

4. Activation of Na+-Ca2+ exchange by ionomycin increased cytosolic free sodium concentration in both strains. However, the ionomycin-induced increase in cytosolic free sodium concentrations was significantly higher in vascular smooth muscle cells from spontaneously hypertensive rats than from Wistar—Kyoto rats (220 ± 35% of the resting cytosolic free sodium concentration versus 148 ± 27%; P < 0.05). The ionomycin-induced increase in cytosolic free sodium concentration was prevented in the absence of external sodium or by inhibition of Na+-Ca2+ exchange by NiCl2.

5. Activation of Na+-H+ exchange by intracellular acidification of vascular smooth muscle cells with propionic acid increased cytosolic free sodium concentration in each strain (19.6 ± 5.7 versus 16.3 ± 3.2 mmol/l).

6. It is concluded that concepts concerning the role of cytosolic free sodium concentration in the pathogenesis of primary hypertension need to be reinvestigated. However, the conclusions from results obtained in cultured vascular smooth muscle cells are limited with respect to conditions in vivo.
Effects of the Neutral Endopeptidase Inhibitor, SCH 42495, on the Cardiovascular Remodelling Secondary to Chronic Hypoxia in Rats
Authors: Thompson J. S. , Sheedy W. , Morice A. H.
Published: August 2015

1. We have investigated the effects of inhibition of neutral endopeptidase on the cardiovascular remodelling secondary to chronic hypoxia in rats using a novel neutral endopeptidase inhibitor, SCH 42495.

2. Rats were divided into four groups, two of which were maintained in a normobaric, hypoxic chamber (10% O2) and two in room air. Animals received either neutral endopeptidase inhibitor, SCH 42495 (30 mg/kg), or aqueous methyl cellulose vehicle (0.4%) twice daily by oral gavage.

3. At 1, 3, 7, 10 and 14 days, animals (n = 4 per group for days 1, 3, 7 and 14, and n =8 for day 10) were killed. Hearts were dissected and weighed for determination of ventricular ratios, lungs were perfused with formol saline for histological examination of the pulmonary vasculature, and blood was collected for measurement of plasma atrial natriuretic peptide level.

4. Treatment with SCH 42495 caused a significant reduction in the pulmonary vascular remodelling and ventricular hypertrophy in hypoxic rats after 10 days. Plasma atrial natriuretic peptide levels were significantly elevated in both SCH 42495-treated and control hypoxic animals (n = 8) after 10 days when compared with the normoxic groups. However, there was no difference in plasma ANP levels between SCH 42495-treated and control chronic hypoxic groups at day 10.

5. Treatment with SCH 42495 leads to a decrease in cardiovascular remodelling secondary to chronic hypoxia in rats. A local action of atrial natriuretic peptide within the pulmonary vasculature may be responsible for this effect. Modulation of atrial natriuretic peptide may have therapeutic potential in the management of conditions characterized by pulmonary hypertension and pulmonary vascular remodelling.
Physiological and Symptomatic Responses to Postural Change in Non-Diabetic Subjects during Hypoglycaemia
Authors: Maggs D. G. , Macdonald I. A.
Published: August 2015

1. Insulin-induced hypoglycaemia is characterized by an autonomic disturbance which produces some of the symptoms of hypoglycaemia. How an additional autonomic stress like postural change may alter physiological responses and symptoms of hypoglycaemia is not known. In 10 healthy male subjects (mean age 24 years) we observed physiological and symptomatic responses to postural change during acute (20 min) and prolonged (60 min) hyperinsulinaemic (60 m-units min−1 m−2) hypoglycaemia (2.5 mmol/l) and euglycaemia (4.5 mmol/l), and placebo control (saline).

2. In all studies standing increased plasma catecholamines (adrenaline, P < 0.001; noradrenaline, P < 0.0001), blood pressure (P < 0.0001) and heart rate (P < 0.0001). Catecholamine responses to standing were augmented by acute hypoglycaemia (adrenaline, P < 0.005; noradrenaline, P < 0.01), but less so by prolonged hypoglycaemia (adrenaline, P < 0.05; noradrenaline, P < 0.05). Supine heart rate was higher before standing during prolonged hypoglycaemia (P < 0.05), but did not increase as much on standing when compared with acute hypoglycaemia and prolonged euglycaemia.

3. During acute hypoglycaemia, autonomic symptoms increased on standing, but during prolonged hypoglycaemia, in the presence of generally higher symptom scores, standing had no effect. Autonomic symptoms, with the exception of hunger, tended to decrease with time (P < 0.05) during prolonged hypoglycaemia.

4. To conclude, posture does modify the catecholamine and symptomatic responses to hypoglycaemia, but this effect is dependent on the duration of hypoglycaemia. Hypoglycaemia and hyperinsulinaemia had little or no effect on the cardiovascular responses to changing posture.
Interactions of Body Fat and Muscle Mass with Substrate Concentrations and Fasting Insulin Levels in Adults with Growth Hormone Deficiency
Authors: Salomon F. , Cuneo R. C. , Umpleby A. M. , Sönksen P. H.
Published: August 2015

1. Adults with growth hormone deficiency have an abnormal body composition. Alterations in body composition are closely related to substrate concentrations and insulin action. The lack of growth hormone has been associated with increased insulin sensitivity.

2. We investigated the correlations of body composition with fasting insulin levels and substrate concentrations in 24 adults with growth hormone deficiency over a wide range of adiposity (body mass index 18.8-42.3 kg/m2).

3. Lean body mass was measured by total body potassium, computer tomography of the thigh and urinary creatinine excretion. Muscle fibre distribution was evaluated from vastus lateralis biopsies. Fat mass was assessed by skinfold thickness measurements, computer tomography of the thigh, and waist and hip girth.

4. Fasting plasma insulin level increased with fat mass (r = 0.67, P = 0.0004) and with waist girth (r = 0.76, P = 0.0001). Fasting plasma insulin level increased with fasting plasma glucose level (r = 0.53, P = 0.01). Fasting plasma glucose level in turn was positively correlated with lean body mass (r = 0.49, P = 0.01) and with total thigh muscle area (r = 0.54, P = 0.01). There was no correlation between lean body mass and fat mass (r = 0.17, not significant) nor between muscle fibre types and fat mass or fat distribution. Fasting plasma insulin level showed no correlation with any measurement of lean body mass or muscle fibre type.

5. These data demonstrate that the presence of obesity is associated with hyperinsulinaemia as the result of insulin resistance in adults with growth hormone deficiency, which could contribute to the increased cardiovascular mortality in adults with growth hormone deficiency.
Hypertension and Cardiac Hypertrophy in Growth Hormone-Deficient Rats
Authors: Harrap Stephen B. , Datodi Shari R. , Crapper Emma K. , Bach Leon A.
Published: August 2015

1. Growth hormone may influence cardiac growth during post-natal maturation or in response to hypertension, and the growth-hormone deficient dwarf rat model offers an opportunity to study this question.

2. We compared the blood pressure and heart weight of dwarf rats and Fischer (F344) control rats in early adulthood, after two hypertensive stimuli: unilateral renal ischaemia (two-kidney, one-clip) or the administration of deoxycorticosterone acetate and saline drinking fluid.

3. In untreated animals at 13 weeks of age the body weight of dwarf rats was significantly less than that of F344 rats, but the mean arterial pressure was similar. Although the hearts of dwarf rats were smaller than those of F344 rats, the heart weight/body weight ratio was significantly greater in dwarf rats.

4. Both dwarf and F344 rats developed similar hypertensive mean arterial pressures 5 weeks after left renal artery clipping or treatment with deoxycorticosterone acetate salt. The heart weights of hypertensive dwarf and F344 rats were equivalent, indicating a proportionally greater increase in cardiac size in dwarf rats for the same rise in blood pressure.

5. The plasma insulin-like growth factor-I level was markedly lower in dwarf than in F344 rats, and hypertension did not have any significant effects on these levels.

6. These findings indicate that the developmental increase in blood pressure and heart size in growing animals and the adaptive cardiac hypertrophy accompanying hypertension are not affected by growth hormone deficiency.
Effects of Phosphoramidon and Pepstatin a on the Secretion of Endothelin-I and Big Endothelin-I by Human Umbilical Vein Endothelial Cells: Measurement by Two-Site Enzyme-Linked Immunosorbent Assays
Authors: Plumpton C. , Kalinka S. , Martin R. C. , Horton J. K. , Davenport A. P.
Published: August 2015

1. Two-site enzyme-linked immunosorbent assays have been developed for the rapid, sensitive and non-isotopic measurement of endothelin-1 and big endothelin-1. The sensitivities of detection were 0.5 and 0.3 fmol/well, with ED50 values of 13 and 12 fmol/well for the endothelin-1 and big endothelin-1 assays, respectively. Each assay is highly selective for its corresponding antigen. The ET-1 assay showed no detectable cross-reactivity with ET-1-(1-20), indicating that the assay only recognizes the 21-amino acid biologically active peptide.

2. The two assays were used to measure the effects of two classes of protease inhibitor on the basal release of enothelin-1 and big endothelin-1 from cultured first-passage human umbilical vein endothelial cells.

3. The secretion of both peptides was time-dependent over 12 h. The metalloprotease inhibitor phosphoramidon (1 × 10−4 mol/l) significantly reduced the amount of endothelin-1 secreted into the medium (P < 0.05), with a concomitant increase in the secreted levels of big endothelin-1 (P < 0.01). The aspartyl protease inhibitor, pepstatin A, also caused a significant decrease in the secretion of endothelin (P < 0.05). However, unlike phosphoramidon, there was no increase in the levels of big ET-1 compared with the controls. At these concentrations, neither inhibitor affected the viability of the cells as indicated by Trypan Blue exclusion.

4. The two assays permit the direct measurement of endothelin-1 and its precursor, and will be of use in the elucidation of the putative human endothelin-converting enzyme(s). In addition to a phosphoramidon-sensitive enzyme, the results also suggest the existence of a pepstatin A-sensitive enzyme in human endothelial cells. Furthermore, pepstatin A also appears to limit the generation of big endothelin-1. Thus pepstatin A-sensitive enzymes may be better targets for inhibitors to reduce the harmful vasoconstrictive effects of endothelin-1 in cardiovascular diseases.
Effect of Progestogens and Oestrogens on the Contractile Response of Rat Detrusor Muscle to Electrical Field Stimulation
Authors: Elliott Ruth A. , Castleden C. M.
Published: August 2015

1. The effect of oestradiol and progesterone pre-treatment on the contractile response of isolated rat detrusor muscle to electrical field stimulation was investigated. The response to direct administration of 2 μmol/l progesterone and 2 μmol/l diethylstilboestrol in the organ bath was also examined.

2. Virgin female Wistar rats were injected sub-cutaneously with oestradiol benzoate (150 μg/kg) for 3 days followed by 1 day of progesterone (160 μg/kg). This cycle was repeated once. Control rats received no injections.

3. In controls, progesterone significantly reduced the maximum contractile response of rat detrusor muscle in vitro by 12% (P < 0.01). The EF50 was significantly increased compared with control. When 2 μmol/l diethylstilboestrol, was added, the maximum contractile response was significantly reduced by 42% (P < 0.01) and the frequency-response curve showed a further increase in EF50.

4. Progesterone had no effect on the atropine-resistant component of electrical field stimulation, but progesterone and diethylstilboestrol reduced the atropine-resistant response by 16% (P < 0.01).

5. Detrusor muscle from pretreated rats showed a non-significant increase in maximum contractile response compared with untreated controls. The addition of 2 μmol/l progesterone to the bath chamber had no effect on this response, but the further addition of 2 μmol/l diethylstilboestrol reduced the maximum contraction.

6. Pretreatment with oestradiol and progesterone had no effect on the atropine- or tetrodotoxin-sensitive response to electrical field stimulation.

7. In conclusion, the direct effect of progesterone and diethylstilboestrol inhibited the contractile response of detrusor muscle to electrical field stimulation and the effects of each summated. Atropine blocked this effect of progesterone, but not that of diethylstilboestrol. Pretreatment with progesterone and oestradiol had no significant effect on rat detrusor contractile response. Since treatment with oestradiol alone has been shown to have a significant inhibitory action on contractile response, the addition of progesterone would appear to alter this effect of oestradiol.
Stable Strontium Absorption as a Measure of Intestinal Calcium Absorption: Comparison with the Double-Radiotracer Calcium Absorption Test
Authors: Blumsohn Aubrey , Morris Brian , Eastell Richard
Published: August 2015

1. Stable strontium (Sr) has been proposed as an alternative to calcium (Ca) isotopes for the measurement of intestinal Ca absorption. The aim of this study was to compare the time course and fractional absorption of Ca and Sr, when both are measured using dual-tracer techniques.

2. 45Ca and Sr absorption tests were carried out on consecutive days in patients with osteoporosis (n = 10) or chronic renal failure (n = 7). Both tests were repeated in four patients with chronic renal failure after treatment with calcitriol (1 μg daily for 10 days).

3. The time course of Ca absorption was determined using the 85Sr (intravenous)/45Ca (oral) dual-tracer technique, and the time course of Sr absorption using 85Sr (intravenous)/stable Sr (oral). Oral tracers were administered on consecutive days with a test meal containing 5.3 mmol of Ca and 2.5 mmol of either stable Sr or Ca carrier. The fractional absorption of 45Ca and Sr at 6 h (FA360) and the absorption rate as a function of time were calculated by deconvolution.

4. The mean FA360 for Sr (20.2%) was lower than the mean FA360 for 45Ca (37.8%, P < 0.001, paired t-test), but the time course of Sr absorption was similar to that of Ca. There was a significant correlation between the FA360 for 45Ca and Sr, although the relationship was improved by including a quadratic term (R2 = 0.89, P < 0.001, significance of quadratic term, P < 0.05). After 1,25-dihydroxyvitamin D treatment, the FA360 of stable Sr increased 4.29-fold, whereas the FA360 of 45Ca increased only 2.4-fold.

5. Although the fractional absorption of Sr determined by dual-tracer deconvolution was the best predictor of FA360 for 45Ca, little was lost by confining the analysis to a single serum Sr measurement taken 3 h or more after oral administration.

6. We conclude that Sr absorption is qualitatively similar to that of Ca, although absorption of Sr is much lower than that of Ca. Furthermore, the relationship does not appear to be linear. Stable Sr may be useful in place of Ca isotopes in the routine clinical evaluation of Ca absorption.
Effects of Angiotensin II and Aldosterone on Diastolic Function In Vivo in Normal Man
Authors: Clarkson P. B. M. , Wheeldon N. M. , MacLeod C. , Tennent M. , MacDonald T. M.
Published: August 2015

1. Doppler echocardiographic indices of diastolic function and systemic haemodynamics were studied in response to infusions of angiotensin II (1, 2, 5 and 10 ng min−1 kg−1), D-aldosterone (2, 4, 10 and 20 ng min−1 kg−1) and placebo [0.9% (w/v) NaCl] in ten normal male subjects.

2. Dose-related increases in systolic and diastolic blood pressure were observed with angiotensin II infusion at rates of 2 ng min−1 kg−1 and above, whereas no changes in blood pressure occurred with D-aldosterone. No changes in aortic stroke distance or heart rate were seen with either angiotensin II or aldosterone infusion.

3. Compared with placebo, angiotensin II infusion produced a dose-related prolongation of the isovolumic relaxation time [mean and 95% confidence intervals 12.0 (8.2–15.8) ms, P < 0.001] at 10 ng min−1 kg−1, and a significant reduction in the ratio between early and late transmitral flow velocity integrals at 2 ng min−1 kg−1, [−0.84 (−1.63 to −0.05), P < 0.05] and 5 ng min−1 kg−1 [−0.76 (−1.47 to −0.05), P < 0.05]. No changes in Doppler echocardiographic indices of diastolic function were observed with D-aldosterone infusion.

4. These data suggest that angiotension II, even at a sub-pressor concentration, produces an impairment of left ventricular diastolic filling, which occurs independently of its effect on aldosterone release.
Recovery of 13C in Breath from Infused NaH13CO3 Increases During Euglycaemic Hyperinsulinaemia
Authors: Reaich D. , Graham K. A. , Cooper B. G. , Scrimgeour C. M. , Goodship T. H. J.
Published: August 2015

1. The effect of euglycaemic hyperinsulinaemia on the recovery of 13C in expired CO2 has been assessed in six normal subjects. Each was studied on three occasions: once with a 6 h primed constant infusion of NaH13CO3 combined with a euglycaemic hyperinsulinaemic clamp for the last 3 h (study 1), once with a 6h primed constant infusion of NaH13CO3 alone (study 2) and once with a 6 h infusion of normal saline combined with a hyperinsulinaemic clamp for the last 3 h (study 3). Measurements of 13C enrichment of expired CO2 were made in the third and sixth hour of each infusion.

2. There was no significant increase in enrichment during study 3 (3 h 0.00047 ± 0.00016 versus 6 h 0.00069 ± 0.00028 atom per cent excess) with potato-starch-derived D-glucose used to maintain eugly-caemia. 13C recovery increased in the sixth hour of both study 1 and 2 (study 1: 3 h 74.4 ± 2.0 versus 6 h 85.5 ± 2.6%, P < 0.01; study 2: 3 h 72.1 ± 2.4 versus 6 h 81.7 ± 1.4%, P < 0.01). There was no significant difference in recovery between studies 1 and 2.

3. These results suggest that increased recovery during a sequential euglycaemic clamp is predominantly time-dependent. Studies which use this technique to examine the effect of insulin on substrate oxidation should take this into account.
Restoration by Corticosteroids of the Hyperaldosteronism in Hyponatraemic Rats with Panhypopituitarism
Authors: Decaux G. , Crenier L. , Namias B. , Gervy C. , Soupart A.
Published: August 2015

1. In the syndrome of inappropriate secretion of antidiuretic hormone, hyponatraemia is associated with a normal bicarbonate concentration despite dilution. This normal bicarbonate concentration is related to the development of a hyperaldosteronism, which is attributed to a direct stimulation of the zona glomerulosa by the hyponatraemic state. Some workers have suggested that, to develop this hyperaldosteronism requires the presence of a pituitary factor. To determine whether the pituitary gland plays a role in this hyponatraemia-induced hyperaldosteronism, water intoxication was performed for 24 h in normal and in panhypopituitaric rats.

2. In normal rats, hyponatraemia (108 mmol/l), induced by the administration of 1-desamino-8-D-arginine vasopressin and 2.5% D-glucose-0.45% NaCl by gavage (15% body weight) was associated with a mild increase in bicarbonate concentration, and blood acid-base equilibrium showed a mixed metabolic and respiratory alkalosis (pH 7.57, partial pressure of CO2 29 mmHg, base excess + 5.5 mmol/l), and aldosterone concentration was increased 3-fold as compared with the control value. When hyponatraemia (110 mmol/l) was induced in a similar manner in panhypopituitaric rats, we observed a very low aldosterone concentration (< 50 pg/ml) and a compensated respiratory alkalosis (pH 7.45, partial pressure of CO2 30 mmHg, base excess −2.6 mmol/l). The restoration of a hyperaldosteronaemic state in this group of rats was related essentially to corticosteroid intake.

3. These data suggest that corticosteroids play a critical role in the development of hyponatraemia-related hyperaldosteronism, a phenomenon not necessarily dependent on a pituitary factor.
Fatty Acid Synthesis by Rat Liver after Chronic Ethanol Feeding with a Low-Fat Diet
Authors: Simpson K. J. , Venkatesan S. , Peters T. J.
Published: August 2015

1. Chronic alcohol feeding with a low-fat diet (4.4% total calories) produced a two- to three-fold increase in hepatic triacylglycerol and esterified cholesterol compared with pair-fed low-fat diet controls. Plasma lipids were similar in both groups.

2. Hepatic fatty acid synthesis rates measured in vivo with 3H2O were significantly lower in the alcohol-fed animals than in controls. Activities of hepatic fatty acid synthase (EC 2.3.1.85) and acetyl-CoA carboxylase (EC 6.4.1.2) were reduced in the alcohol-fed rats.

3. These results indicate that enhanced hepatic fatty acid synthesis does not occur in rats fed alcohol and a low-fat diet for 4 weeks, and is thus not implicated in the pathogenesis of alcohol-induced fatty liver.
Model for Whole Body Production of Tumour Necrosis Factor-α in Experimental Endotoxaemia in Healthy Subjects
Authors: Koopmans R. , Hoek F. J. , van Deventer S. J. H. , van der Poll T.
Published: August 2015

1. Tumour necrosis factor-α is considered an important mediator in the pathophysiology of several diseases. Although much information is available about the serum concentrations of this cytokine in these illnesses, little is known about the production of tumour necrosis factor-α in disease in vivo.

2. In the present study we aimed to estimate the extent and the kinetics of whole body tumour necrosis factor-α synthesis in experimental endotoxaemia in six healthy humans. For this purpose we first examined the pharmacokinetic behaviour of an intravenously injected bolus of recombinant human tumour necrosis factor-α (50 μg/m2) in another group of six normal subjects. We then calculated the total amount of tumour necrosis factor-α produced after intravenous injection of endotoxin (2 ng/kg) as the product of the systemic clearance of recombinant human tumour necrosis factor-α (9.5 ± 5.0 ml min−1 kg−1) and the area under the tumour necrosis factor-α concentration-time curves in the endotoxaemic subjects.

3. Recombinant human tumour necrosis factor-α showed evident two-compartment kinetics with an initial rapid disappearance (t1/2 5.1 ± 2.2 min) and a terminal slower elimination (t1/2 49 ± 5 min). Tumour necrosis factor-α synthesis after endotoxin varied markedly between individuals, ranging from 11.8 to 114.1 μg (52.7 ± 34.7 μg). The changes in time of the serum concentrations of tumour necrosis factor-α after administration of endotoxin could be accurately described with an adapted two-compartment open model that incorporated both rapid tumour necrosis factor-α production (74% of the total amount) and slow tumour necrosis factor-α production (26%).

4. Our results suggest that, in endotoxaemia, circulating tumour necrosis factor-α originates from two different sources, one in rapid and one in slow equilibrium with the circulation. We propose that the pharmacokinetic characteristics of intravenous recombinant human tumour necrosis factor-α may be used to estimate the production of rumour necrosis factor-α in clinical disease.
Ammonium Chloride Inhibits Pyruvate Oxidation in Rat Liver Mitochondria: A Possible Cause of Fatty Liver in Reye's Syndrome and Urea Cycle Defects
Authors: Maddaiah Vaddanahally T. , Kumbar Uday
Published: August 2015

1. Earlier studies with liver slices showed that inhibition by NH+4 of the oxidation of palmitate to CO2 was greater than total oxidation, whereas salicylate exerted a stronger inhibitory effect on the latter. We have now investigated the effects of NH4Cl and salicylate on ADP-induced O2 consumption by mitochondria (State 3 rate) respiring on pyruvate, and oxidation of [1-14C]- and [2-14C]-pyruvate to14CO2.

2. The rate of State 3 respiration was inhibited and plateaued at 45% with 10 mmol/l NH4Cl.

3. Oxidation of [1-14C]pyruvate was not significantly affected by either NH4Cl or salicylate. Oxidation of [2-14C]pyruvate was strongly inhibited and plateaued at 70% with 1 mmol/1 NH4Cl (IC50 = 0.125 mmol/1). ADP (1 mmol/l) increased the rate of decarboxylation of [2-14C] pyruvate but the extent of NH4Cl inhibition was not affected. Salicylate had a slight activating effect in the absence or presence of NH4Cl.

4. These results indicate that NH4Cl inhibits the oxidative metabolism of acetyl-CoA in the tricarboxylic acid cycle. Therefore, inhibition of fatty acid oxidation to acetyl-CoA as well as its further oxidative metabolism occurring under hyperammonaemia (>0.1 mmol-1.49 mmol/l in Reye's syndrome patients) may be one of the causes of fatty acidaemia.

5. The cumulative inhibitory effects of NH+4 and fatty acyl derivatives on mitochondrial oxidative metabolism and production of ATP, as well as the uncoupling effects of salicylate, may contribute to some of the pathophysiology observed in patients with Reye's syndrome, and enzyme defects of the urea cycle.
Renal Impairment Associated with the Pre-Operative Administration of Recombinant Interleukin-2
Authors: Deehan D. J. , Heys S. D. , Broom J. , Eremin O. , Whiting P. H.
Published: August 2015

1. The T-cell-derived cytokine interleukin-2 may be used to reverse the immune suppression associated with major surgery. However, both major surgical procedures and recombinant interleukin-2 therapy are known to induce renal dysfunction.

2. Eighteen patients were randomized to receive either recombinant interleukin-2 (18 × 106 i.u./day) or placebo, given subcutaneously for 3 days before undergoing curative colorectal cancer surgery. Indices of renal function were determined pre-operatively and for 21 days after surgery.

3. Pre-operative recombinant interleukin-2 was found to significantly increase, compared with placebo controls, N-acetyl-β-D-glucosaminidase [peak levels 28 (SEM 2) versus 11 (SEM 3) i.u./mmol of Cr] and γ-glutamyltransferase [peak levels 5.3 (SEM 0.6) versus 2.4 (SEM 0.2) i.u./mmol/l] and decrease urinary fractional excretion of sodium [peak difference 0.32 (SEM 0.06) versus 0.76 (SEM 0.08)] (all P < 0.05). Significantly increased urinary excretions of creatinine, N-acetyl-β-D-glucosaminidase and γ-glutamyltransferase were also identified after surgery. All variables returned to pretreatment limits by the seventh day post-operatively, except N-acetyl-β-D-glucosaminidase, which was still significantly elevated 21 days after surgery. No differences in the serum concentrations of sodium, creatinine or urea were observed before or after surgery in either group.

4. Recombinant interleukin-2, when given in the preoperative period, was associated with significant renal dysfunction. However, routine monitoring of serum indices (i.e. sodium, urea, creatinine and albumin) failed to detect such renal damage. These results suggest that, with the use of recombinant interleukin-2 to enhance natural cytotoxicity in the peri-operative period, such therapy may potentiate the renal impairment occurring after surgery.
Glomerular Filtration Rate and Segmental Tubular Function in the Early Phase after Transplantation/Uninephrectomy in Recipients and Their Living-Related Kidney Donors
Authors: Kamper Anne-Lise , Holstein-Rathlou Niels-Henrik , Strandgaard Svend , Leyssac Paul Peter , Munck Ole
Published: August 2015

1. Glomerular filtration rate and sequential tubular function were investigated in 18 adult renal transplant recipients and in their matched, adult living-related kidney donors before and 5 days after transplantation/uninephrectomy. At day 54, 13 donors and 11 recipients were re-investigated. Sixteen of these constituted eight matched pairs. This reduction in the study population was caused by the application of two withdrawal criteria.

2. In the recipients glomerular filtration rate was unchanged at day 5 and had increased to 61 ml/min at day 54 (P < 0.05). In the donors glomerular filtration rate had increased to 59 ml/min by day 5 (P < 0.01) and was unchanged at day 54.

3. In the recipients lithium clearance was unchanged at day 5 and had increased to 23 ml/min at day 54 (P < 0.01). In the donors the lithium clearance had increased by day 5 (P < 0.01).

4. In the recipients the absolute proximal fluid reabsorption rate was about 36 ml/min throughout the study period. In the donors the absolute proximal fluid reabsorption rate had increased to 42 ml/min by day 5 (P < 0.05) and increased further to 44 ml/min by day 54 (P < 0.01).

5. In the recipients sodium clearance increased from 0.54 ml/min to 2.10 ml/min at day 54 (P < 0.01). In the donors it increased from 0.64 ml/min to 0.99 ml/min at day 54 (P < 0.05).

6. Donor-recipient comparison showed that at day 54 there was no significant difference with regard to glomerular filtration rate, lithium clearance, absolute and fractional proximal fluid reabsorption rate and absolute distal sodium reabsorption rate. The sodium clearance was higher and the fractional distal sodium reabsorption rate was lower in the recipients.

7. In conclusion, the difference in function between donors and recipients at day 5 can probably be explained by the damaging effect of many inevitable factors on the graft. Fifty-four days after transplantation the function of the graft could not be distinguished from that of the remaining kidney. This suggests that the ideal homograft possesses a normal potential for compensatory hypertrophy once the effects of the initial post-operative ischaemia and toxic factors have subsided.
Lack of Importance in Humans of the Slow Component of the Response of Force to an Increase in Cardiac Muscle Length
Authors: Noble Mark I. M. , Drake-Holland Angela J.
Published: August 2015

1. An increase in length in isolated animal muscles causes an immediate increase in contractile force, which is followed by a slower further progressive increase: the slow component. However, the pressure-volume concept, used in characterizing left ventricular function, is dependent on a constant relationship between pressure and volume.

2. We therefore examined the possible occurrence of the slow inotropic component of the response to cardiac muscle stretch in man at cardiac catheterization.

3. Human subjects undergoing left heart catheterization for clinical indications were studied. The development of the slow component was studied by measurement of rate of rise in left ventricular developed pressure and the time course after an increase in end-diastolic volume.

4. No evidence for any slow component was elicited.

5. It is concluded that the slow component of force (or pressure) increase after an increase in cardiac muscle length (or volume) does not have a role in the human heart in situ.
Plasma Kinins Increase after Angiotensin-Converting Enzyme Inhibition in Human Subjects
Authors: Pellacani Andrea , Brunner Hans R. , Nussberger Jürg
Published: August 2015

1. In patients treated with angiotensin-converting enzyme inhibitors, kinin-related effects have been postulated repeatedly, but information on changes in plasma kinin levels in these patients is sparse. Difficulties in the measurement of plasma kinins account for this, at least in part.

2. The main purpose of the present study was to investigate, in normal human subjects, the effect of the angiotensin-converting enzyme inhibitor quinapril on plasma kinins.

3. High-affinity antisera (Kd <10−11 mol/l) of C-terminal specificity were raised in rabbits for radioimmunoassay of immunoreactive kinins activating the bradykinin B2-receptor, and three different liquid-and solid-phase extraction methods for plasma kinins were evaluated. Ethanol and subsequent petroleum ether extraction of 5–40 fmol of bradykinin added to plasma yielded recoveries of 39 ± 16% (mean ± SD); normal kinin levels in human plasma were 18.6 ± 3.3 pmol/l (mean ± SEM). Solid-phase extraction on urea-equilibrated phenylsilylsilica produced recoveries of 89 ± 5% and normal values of 36.4 ± 18 pmol/l. Finally, with an assay based on ethanol extraction alone, recoveries of 100 ± 16% and normal values of 16.8 ± 5.8 pmol/l were obtained, with a detection limit of 1.5 fmol/ml of plasma. Blanks were below the detection limit. Serial dilution of plasma extracts (n = 4) provided linear kinin concentrations (r = 0.99). For two different plasma pools, coefficients of variation for within-assay precision were 16.7% and 21.7%, respectively. Between-assay coefficients of variation were 12.8% and 17.4%.

4. After an oral quinapril dose of 20 mg, we found, in nine healthy men, an increase in plasma kinin levels from 16.1 ± 1.9 pmol/1 (mean ± SEM) to 22.4 ± 2.8, 23.9 ± 23, 29.1 ± 4.7 (P < 0.05) and 203 ± 4.2 pmol/1 at 2, 4, 8 and 24 h after drug intake, respectively.

5. Thus, in normal subjects treated with angiotensin-converting enzyme inhibitor plasma levels of B2-receptor stimulating kinins increase.
Reflex Sympathetic Dystrophy: Result of Autonomic Denervation?
Authors: Kurvers H. A. J. M. , Jacobs M. J. H. M. , Beuk R. J. , Van den Wildenberg F. A. J. M. , Kitslaar P. J. E. H. M. , Slaaf D. W. , Reneman R. S.
Published: August 2015

1. To investigate the nature of sympathetic dysfunction in the pathogenesis of reflex sympathetic dystrophy, the microcirculatory vasoconstrictive responses to dependency were investigated in the skin of the hand of 76 reflex sympathetic dystrophy patients with unilateral disease by means of laser Doppler flowmetry (in perfusion units) and capillary microscopy. The patients were divided into three stages according to their perception of skin temperature (stage I in the case of a stationary warmth sensation, stage II in the case of an intermittent warmth and cold sensation, and stage III in the case of a stationary cold sensation). The vasoconstrictive responses were induced by lowering of the affected hand.

2. As compared to controls, the mainly sympathetically mediated vasoconstrictive response at thermoregulatory level of the skin microcirculation, as measured by laser Doppler flowmetry, was attenuated at stage I (1.82 versus 1.41, P < 0.05), stage II (1.82 versus 1.09, P < 0.0001) and stage III (1.82 versus 1.14, P < 0.01), suggesting the involvement of sympathetic denervation at all stages of the reflex sympathetic dystrophy syndrome. This sympathetic denervation may also account for the observed increase in thermoregulatory skin blood flow at stage I as compared to controls (152 versus 81, P < 0.01).

3. Since sympathetic denervation has been reported to cause increased sensitivity of vascular structures to catecholamines, the decrease in thermoregulatory skin blood flow at stages II (54 versus 81, P < 0.05) and III (31 versus 81, P < 0.05), both as compared to controls, may result from hypersensitivity to catecholamines of skin microvessels.

4. The sympathetically independent vasoconstrictive response at the nutritive level of skin microcirculation, as measured by capillary microscopy, was impaired only at stage III as compared to controls (1.04 versus 2.06, P < 0.05). This divergence in microvascular reactivity upon dependency of the nutritive and thermoregulatory subsystems also supports the hypothesis of sympathetic dysfunction.

5. The disturbed vasoconstrictive responses to dependency may give rise to raised capillary pressures, contributing to the formation of oedema.

6. These findings suggest that sympathetic denervation and consequent hypersensitivity to catecholamines play an important role in the pathophysiology of reflex sympathetic dystrophy.