bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of four sequential methods allowing for early stopping of comparative clinical trials
Authors: SEBILLE Véronique , BELLISSANT Eric
Published: August 2015

Phase III trials aim to assess whether a new treatment has superior efficacy than a standard treatment. Sequential methods, such as the sequential probability ratio test (SPRT), the triangular test (TT) and so-called one-parameter boundaries (OPB), now allow early stopping of such trials, both in the case of efficacy (alternative hypothesis; H1) and in the case of lack of efficacy (null hypothesis; H0). We compared the statistical properties of the SPRT and the TT, and of OPB with Pocock (OPBΔ = 0.5) and O'Brien and Fleming (OPBΔ = 0) type boundaries, in the setting of one-sided comparative trials with normal response. We studied the type I error (α), power (1-β), average sample number (ASN) and 90th percentile (P90) of the number of patients required to reach a conclusion using simulations. The four tests were also compared with the corresponding single-stage design (SSD). All sequential tests display α and 1-β close to nominal values and, as compared with SSD, allow important decreases in ASN: for example, -48%, -42%, -40% and -31% under H0 and H1 for SPRT, TT, OPBΔ = 0.5 and OPBΔ = 0 respectively. For situations between H0 and H1, ASNs of all sequential tests were still smaller than the sample size required by SSD, with the TT displaying the largest decrease (-25%). The P90s of the TT and OPBΔ = 0 under H0 and H1 were smaller than the P90s of the SPRT and OPBΔ = 0.5, which were similar to the sample size required by SSD. If all sequential tests display approximately similar features, the TT is the most appealing regarding decreases in sample size, especially for situations between H0 and H1.
Relationship between the clinical features of neurological decompression illness and its causes
Authors: WILMSHURST Peter , BRYSON Philip
Published: August 2015

There is dispute as to whether paradoxical gas embolism is an important aetiological factor in neurological decompression illness, particularly when the spinal cord is affected. We performed a blind case-controlled study to determine the relationship between manifestations of neurological decompression illness and causes in 100 consecutive divers with neurological decompression illness and 123 unaffected historical control divers. The clinical effects of neurological decompression illness (including the sites of lesions and latency of onset) were correlated with the presence of right-to-left shunts, lung disease and a provocative dive profile. The prevalence and size of shunts determined by contrast echocardiography were compared in affected divers and controls. Right-to-left shunts, particularly those which were large and present without a Valsalva manoeuvre, were significantly more common in divers who had neurological decompression illness than in controls (P < 0.001). Shunts graded as large or medium in size were present in 52% of affected divers and 12.2% of controls (P < 0.001). Spinal decompression illness occurred in 26 out of 52 divers with large or medium shunts and in 12 out of 48 without (P < 0.02). The distribution of latencies of symptoms differed markedly in the 52 divers with a large or medium shunt and in the 30 divers who had lung disease or a provocative dive profile. In most cases of neurological decompression illness the cause can be determined by taking a history of the dive profile and latency of onset, and by performing investigations to detect a right-to-left shunt and lung disease. Using this information it is possible to advise divers on the risk of returning to diving and on ways of reducing the risk if diving is resumed. Most cases of spinal decompression illness are associated with a right-to-left shunt.
Induction of osteoclasts from CD14-positive human peripheral blood mononuclear cells by receptor activator of nuclear factor κB ligand (RANKL)
Authors: NICHOLSON Geoffrey C. , MALAKELLIS Mary , COLLIER Fiona M. , CAMERON Paul U. , HOLLOWAY Wayne R. , GOUGH Tamara J. , GREGORIO-KING Claudia , KIRKLAND Mark A. , MYERS Damian E.
Published: August 2015

Osteoclasts are bone-resorbing cells that are derived from haemopoietic precursors, including cells present in peripheral blood. The recent identification of RANKL [receptor activator of nuclear factor (NF)-κB ligand], a new member of the tumour necrosis factor ligand superfamily that has a key role in osteoclastogenesis, has allowed the in vitro generation of osteoclasts in the absence of cells of the stromal/osteoblast lineage. Human peripheral blood mononuclear cells (PBMC) cultured in vitro with soluble RANKL and human macrophage colony-stimulating factor form osteoclasts. However, PBMC are heterogeneous, consisting of subsets of monocytes and lymphocytes as well as other blood cells. As the CD14 marker is strongly expressed on monocytes, the putative osteoclast precursor in peripheral blood, we have selected CD14+ cells from PBMC to examine their osteoclastogenic potential and their expression of novel members of the tumour necrosis factor superfamily involved in osteoclastogenesis. Highly purified CD14+ cells demonstrated mRNA expression of receptor activator of NF-κB, but no expression of RANKL or osteoprotegerin, whereas PBMC expressed mRNAs for all three factors. CD14+ (but not CD14-) cells cultured on bone slices for 21 days with human macrophage colony-stimulating factor and soluble RANKL generated osteoclasts and showed extensive bone resorption. Similar numbers of osteoclasts were generated by 105 CD14+ cells and 106 PBMC, but there was significantly less intra-assay variability with CD14+ cells, suggesting the absence of stimulatory/inhibitory factors from these cultures. The ability of highly purified CD14+ cells to generate osteoclasts will facilitate further characterization of the phenotype of circulating osteoclast precursors and cell interactions in osteoclastogenesis.
Use of anti-(tumour necrosis factor-α) antibody or 3-deaza-adenosine as additives to promote protection by University of Wisconsin solution in ischaemia/reperfusion injury
Authors: CHIANG Chi-Huei , WU Chin-Pyng , PERNG Wann-Cherng , YAN Horng-Chin , YU Cheng-Ping
Published: August 2015

Experimental interventions that reduce ischaemia/reperfusion (I/R) lung injury can be used to improve the properties of preservation solutions. We attempted to increase the attenuation of I/R injury by University of Wisconsin solution (UW) by adding an antibody against tumour necrosis factor-α (TNF-α), to neutralize TNF-α, and/or by adding 3-deaza-adenosine (c3-Ado), to inhibit leucocyte adhesion and the biosynthesis of ICAM-1 (intercellular cell-adhesion molecule 1). We examined I/R injury using an isolated rat lung model. Six different solutions were perfused individually, followed by evaluation of I/R injury: (1) 0.9% NaCl (normal saline; NS), (2) NS+anti-TNF-α antibody, (3) UW alone, (4) UW+anti-TNF-α, (5) UW+c3-Ado and (6) UW+anti-TNF-α+c3-Ado. Haemodynamic changes, lung weight gain, capillary filtration coefficient, TNF-α levels and lung pathology were analysed in order to evaluate I/R injury. Compared with lungs perfused with NS, lungs treated with NS+anti-TNF-α showed less I/R injury. The addition of anti-TNF-α and/or c3-Ado to UW reduced I/R injury compared with unmodified UW. Among the six solutions tested, UW containing anti-TNF-α antibody reduced I/R injury to the greatest extent. We conclude that addition of anti-TNF-α antibody or c3-Ado protects against I/R lung injury when using UW. Further investigation of the improved properties of modified UWs would be beneficial with regard to lung transplantation research.
Role of protein kinase C in electrical-stimulation-induced neuronal nitric oxide release in mesenteric arteries from hypertensive rats
Authors: MARÍN Jesús , FERRER Mercedes , BALFAGÓN Gloria
Published: August 2015

This study examines the influence of hypertension on neuronal nitric oxide (NO) release and its modulation by protein kinase C (PKC). For this purpose, mesenteric segments without endothelium were obtained from Wistar–Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs), and neurogenic NO release induced by electrical field stimulation (EFS) was examined in these segments. EFS induced frequency-dependent contractions. The NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) and the sensorial neurotoxin capsaicin increased EFS-induced contractions in SHR segments, but did not affect these contractions in segments from WKY rats. In segments from SHRs, the increase in EFS-induced response by capsaicin was further increased by the combination of capsaicin and L-NAME. EFS-induced contractions in SHR arteries were unaltered by the protein synthesis inhibitor cycloheximide or by 2-amine-5,6-dihydro-6-methyl-4H-1,3-tiazine (AMT), an inhibitor of inducible NO synthase, and increased by the guanylate cyclase inhibitor Methylene Blue. In these arteries, capsaicin plus the PKC inhibitor calphostin C increased the contractions elicited by EFS; the addition of L-NAME did not affect this increase. Phorbol 12,13-dibutyrate (PDBu) did not modify the response to EFS in these arteries pretreated with capsaicin, although a combination of PDBu and L-NAME was effective. These results indicate that, in mesenteric arteries, EFS induces the release of NO from perivascular nitrergic nerves and of neuropeptides from sensory nerves, but only in hypertensive rats. The NO released is synthesized by constitutive neuronal NO synthase in a manner that is positively modulated by PKC, an enzyme that seems to be activated in hypertension.
Changes in atrial natriuretic peptide concentration and expression of its receptors after pneumonectomy in the rat
Authors: TAMURA Kohichi , TAKAMORI Shinzo , MIFUNE Hiroharu , HAYASHI Akihiro , SHIROUZU Kazuo
Published: August 2015

Atrial natriuretic peptide (ANP) is a cardiac hormone which affects endothelial cell function through a receptor-mediated process. Pneumonectomy is a common thoracic surgical procedure that can cause pulmonary oedema in the remaining lung. Few reports have investigated the aetiology of this complication. The aim of this study was to determine the changes in ANP concentration and expression of its receptors following pneumonectomy as a possible aetiology for postpneumonectomy pulmonary oedema (PPE). We compared plasma ANP concentrations, cGMP concentrations, and natriuretic peptide receptor (NPR)-A mRNA and NPR-C mRNA expression in rat lung 3 h after pneumonectomy (n = 5) or a sham operation (n = 5). The ANP concentrations in plasma and lung tissue in the pneumonectomy group were significantly higher than in the control group (749.5 versus 202.7 pgċml-1, P < 0.01; 33.1 versus 6.8 ngċg-1 wet tissue, P < 0.01 respectively). The level of ANP mRNA expression in the pneumonectomy group was significantly higher than in the control group (1.44 versus 0.41 relative ANP mRNA expression, P < 0.05). The concentration of cGMP and the level of NPR-A mRNA expression were not significantly different between the pneumonectomy and control groups. The level of NPR-C mRNA expression in the pneumonectomy group was significantly higher than in the control group (4.17 versus 2.19 relative NPR-C mRNA expression, P < 0.01). These findings suggest that changes in pulmonary ANP and NPR-C expression may contribute to the development of PPE in the remaining lung in the acute phase following pneumonectomy.
Elevation of two molecular forms of adrenomedullin in plasma and urine in patients with acute myocardial infarction treated with early coronary angioplasty
Authors: ASAKAWA Hiroshi , NISHIKIMI Toshio , SUZUKI Takeshi , HARA Suomi , TSUBOKOU Yusuke , YAGI Hiroshi , YABE Akihisa , TSUCHIYA Noriaki , HORINAKA Shigeo , KANGAWA Kenji , MATSUOKA Hiroaki
Published: August 2015

Adrenomedullin (AM) has vasodilatory, diuretic and natriuretic actions. Two molecular forms of AM circulate in human plasma: an active, mature form of AM (AM-m) and an intermediate, inactive, glycine-extended form of AM (AM-Gly). In the present study we investigated the pathophysiological significance of the two molecular forms of AM in plasma and urine in patients with acute myocardial infarction. We serially measured venous and arterial plasma levels and urinary excretion of AM-m, AM-Gly and total AM (Am-T; = AM-m+AM-Gly) over 2 weeks using our recently developed immunoradiometric assay in 26 consecutive patients with acute myocardial infarction and in age-matched normal controls, and studied the relationships between AM levels and clinical parameters. Plasma AM-m, AM-Gly and AM-T levels were increased on admission in patients with acute myocardial infarction compared with age-matched normal controls. Levels of AM-m, AM-Gly and AM-T in plasma reached a peak 24 h after the onset of symptoms. Plasma AM-m, AM-Gly and AM-T levels were significantly correlated with plasma levels of brain natriuretic peptide and pulmonary arterial pressure. Plasma AM-Gly levels in the vein were similar to those in the artery, whereas plasma AM-m levels were significantly lower in the artery than in the vein. Urinary excretion of AM-m, AM-Gly and AM-T was also increased on admission, and reached a peak at 12 h after the onset of symptoms. Urinary excretion of AM-m and AM-Gly was significantly correlated with urinary sodium excretion. The AM-m/AM-T ratio was significantly higher in the urine than in the vein or artery. AM-m levels were significantly correlated with AM-Gly levels in both the urine and plasma; however, there were no significant correlations between plasma and urinary AM levels. The results suggest that levels of both molecular forms of AM are increased in the urine as well as in the plasma in the acute phase of myocardial infarction. Since AM exerts potent cardiovascular and renal effects, increased concentrations of AM in plasma and urine in the acute phase of myocardial infarction may be involved in the defence mechanism against further elevations of peripheral and pulmonary vascular resistance and oliguria in acute myocardial infarction.
Relationships between baseline serum leptin levels and 2-year changes in body mass index, blood pressure and metabolic parameters in Japanese male adolescents and middle-aged men
Authors: HIROSE Hiroshi , SAITO Ikuo , KAWAI Toshihide , TSUJIOKA Minako , KAWABE Hiroshi , SARUTA Takao
Published: August 2015

We and others have reported that serum leptin levels are positively correlated with body mass index (BMI), blood pressure and heart rate (HR) in cross-sectional clinical studies. However, only a few longitudinal studies have focused on the relationships between leptin, BMI and blood pressure. The present study was performed to elucidate the relationships between baseline serum leptin levels and 2-year changes in BMI, blood pressure, HR and metabolic parameters in 314 Japanese male adolescents aged 16–17 years and in 225 Japanese men aged 30–63 years. Height, weight, systolic blood pressure (SBP), diastolic blood pressure (DBP), HR, fasting plasma glucose (FPG), serum lipids [total cholesterol (TC), triacylglycerols (TG), high-density-lipoprotein cholesterol (HDL-C) and low-density-lipoprotein cholesterol (LDL-C)], uric acid (UA), insulin and leptin levels were measured in the morning after an overnight fast. In the male adolescents, serum leptin levels in 1996 (log[leptin'96]) were significantly correlated with BMI, SBP, mean blood pressure and HR in 1998 (r = 0.40, 0.13, 0.11 and 0.14, respectively). The percentage change in BMI per year (ΔBMI) was negatively correlated with log[leptin'96], even after adjustment for baseline BMI (r =-0.12, P = 0.030). In men aged 30–63 years, log[leptin'96] was also positively correlated with BMI'98, SBP'98, DBP'98, FPG'98, TC'98, log[TG'98], LDL-C'98 and UA'98 (all P < 0.05), and negatively correlated with HDL-C'98, ΔBMI, ΔFPG, ΔTC and ΔLDL-C. The relationship between log[leptin'96] and ΔTC was significant, even after adjustment for initial BMI (r =-0.15, P = 0.023). These findings therefore suggest that serum leptin levels are correlated with subsequent decreases in BMI and TC in Japanese men.
Mucosal protective effects of ecabet sodium: pepsin inhibition and interaction with mucus
Authors: PEARSON J. P. , ROBERTS N. B.
Published: August 2015

Pepsin, acid and Helicobacter pylori are major factors in the pathophysiology of peptic ulcer disease and reflux oesophagitis. Ecabet sodium reduces the survival of H. pylori in the stomach and inhibits pepsin activity in the gastric juice of experimental animals. Here we have investigated the effects of ecabet sodium on some of the factors involved in the dynamics of the mucosal barrier, i.e. pepsins and mucins. This study used gastric juice obtained from 12 non-symptomatic volunteers and nine patients with reflux oesophagitis. Ecabet sodium significantly inhibited pepsin activity in human gastric juice, with a maximum inhibition of 78%. Pepsin 1, the ulcer-associated pepsin, was inhibited to the greatest extent. The ability of gastric juice to digest mucin was significantly inhibited by ecabet. As with gastric juice proteolytic activity, the inhibitory effect of ecabet on mucolysis was greater in gastric juice from patients with reflux oesophagitis than in that from controls. Ecabet sodium showed a positive interaction with gastric mucin, as assessed by an increase in viscosity. Thus ecabet sodium may reduce the aggressive potential of gastric juice towards the mucosa, which may be relevant in the treatment of reflux oesophagitis and peptic ulcer disease. In addition, it may strengthen the mucus barrier in peptic ulcer disease and gastritis.
Urocortin in the synovial tissue of patients with rheumatoid arthritis
Authors: UZUKI Miwa , SASANO Hironobu , MURAMATSU Yasunari , TOTSUNE Kazuhito , TAKAHASHI Kazuhiro , OKI Yutaka , IINO Kazumi , SAWAI Takashi
Published: August 2015

Urocortin is a newly identified member of the corticotropin-releasing factor (CRF) neuropeptide family, and is known to be involved in the modulation of the inflammatory process. We examined the expression of urocortin, CRF and their receptors (CRF receptor; CRF-R) in the synovial tissue of patients with rheumatoid arthritis (RA) in order to study the possible biological roles of urocortin. Synovial tissues/fluids were obtained from 38 patients with RA, nine patients with osteoarthritis and four with trauma. We studied the concentration of urocortin in the synovial fluid using RIA, and the expression of urocortin in synovial tissue using immunohistochemistry, mRNA in situ hybridization and reverse transcriptase–PCR (RT-PCR). In addition, we examined the immunolocalization of CRF and the expression of CRF-R1, -R2-α and -R2-β mRNAs utilizing RT-PCR in these synovial tissues. Urocortin concentrations in synovial fluid were higher in RA patients (79.8±154 pg/ml) than in control patients (12.3±4.8 pg/ml; P ≤ 0.05). Urocortin immunoreactivity and mRNA signals were both detected in synovial cells, lymphocytes, fibroblasts and macrophages. The number of urocortin-positive cells in the synovium was significantly higher in RA (73.1±32.1 cells per high-power field) than in control (18.4±10.4 cells per high-power field) patients. In addition, both urocortin immunoreactivity and mRNA signals in the synovium reached maximum levels in the active stage of RA inflammation. Moreover, the number of immunoreactive urocortin-positive cells was significantly correlated with the urocortin concentration in synovial fluid (r = 0.705; P < 0.001) and with histologically defined local inflammatory activity (r = 0.641; P < 0.001). The distribution and number of immunoreactive CRF-positive cells in synovial tissue were similar to those of urocortin-positive cells (r = 0.701; P < 0.001). Urocortin, CRF-R1 and CRF-R2-α mRNAs detected by RT-PCR were expressed in in the synovium of 10/10, 10/10 and 2/10 RA patients respectively, but CRF-R2-β was not expressed. Urocortin was actively synthesized in the synovium of RA patients. The present study suggests that urocortin may play an important role as an autocrine and/or paracrine regulator of synovial inflammation in RA.
A comparative study of the adsorption of amino acids on to calcium minerals found in renal calculi
Authors: FLEMING David E. , VAN BRONSWIJK Wilhelm , RYALL Rosemary Lyons
Published: August 2015

To assess the binding of individual amino acids to the principal calcium minerals found in human kidney stones, the adsorption of 20 amino acids on to calcium oxalate monohydrate, CaHPO4.2H2O, Ca3(PO4)2 and Ca5(PO4)3OH crystals was determined over the physiological urinary pH range (pH 5–8) in aqueous solutions. All amino acids adsorbed most strongly at pH 5, and this decreased in all cases as the pH was increased. The amino acids which adsorbed most strongly were aspartic acid, glutamic acid and γ-carboxyglutamic acid, with the last displaying the strongest affinity. All amino acids bound more avidly to calcium oxalate monohydrate than to any of the phosphate minerals. Adsorption on to CaHPO4.2H2O was generally higher than for Ca3(PO4)2 and Ca5(PO4)3OH, for which all amino acids, with the exception of γ-carboxyglutamic acid, had only a weak affinity. The binding affinity of these acids is thought to be due to their zwitterions being able to adopt conformations in which two carboxyl groups, and possibly the amino group, can interact with the mineral surface without further rotation. The strong binding affinity of di-and tri-carboxylic acids for calcium stone minerals indicates that proteins rich in these amino acids are more likely to play a functional role in stone pathogenesis than those possessing only a few such residues. These findings, as well as the preferential adsorption of the amino acids for calcium oxalate monohydrate rather than calcium phosphate minerals, have ramifications for research aimed at discovering the true role of proteins in stone formation and for potential application in the design of synthetic peptides for use in stone therapy.
Effects of indomethacin on energy metabolism in rat and human jejunal tissue in vitro
Authors: JACOB Molly , BJARNASON Ingvar , SIMPSON Robert J.
Published: August 2015

Non-steroidal anti-inflammatory drugs (NSAIDs) are known to cause enteropathy, but the mechanism by which this toxicity occurs is less well established. This paper sets out to test the hypothesis that these drugs affect oxidative phosphorylation in jejunal tissue, thereby interfering with energy metabolism and rendering the tissue vulnerable to damage. Jejunal tissue obtained from rats and humans was used for in vitro determinations of oxygen uptake, lactate production and energy charge levels in the presence of indomethacin, a commonly used NSAID. In the rat jejunal tissue, drug concentrations of 0.5mM and 2.5mM produced significant decreases in oxygen uptake (P < 0.01) and energy charge levels in the tissue (P < 0.05). There was a corresponding increase in lactate production by the tissue at these indomethacin concentrations (P < 0.05). Rat jejunum examined by electron microscopy after incubation with various concentrations of indomethacin showed ultrastructural effects of the drug on mitochondrial morphology. In human tissue, an inhibitory effect of indomethacin on oxygen uptake was seen, but the effects on lactate production and energy charge were less conclusive. These findings suggest that indomethacin affects mitochondria and thereby impairs energy metabolism in jejunal tissue.
Brain natriuretic peptide: is it a predictor of cardiomyopathy in cirrhosis?
Authors: WONG Florence , SIU Samuel , LIU Peter , BLENDIS Laurence M.
Published: August 2015

Subtle cardiac abnormalities have been described in patients with cirrhosis. Natriuretic peptide hormones have been reported to be sensitive markers of early cardiac disease. We postulate that plasma levels of N-terminal pro-atrial natriuretic peptide and brain natriuretic peptide could be used as markers of cardiac dysfunction in cirrhosis. The aim of the study was to evaluate the levels of N-terminal pro-atrial natriuretic peptide and brain natriuretic peptide and their relationship with cardiac structure and function in patients with cirrhosis. The study population comprised 36 patients with cirrhosis of mixed aetiologies, but with no cardiac symptoms; 19 of the patients had ascites and 17 did not. The subjects underwent (i) trans-thoracic two-dimensional echocardiography, and (ii) radionuclide angiography for measurements of cardiac structural parameters, diastolic and systolic function. Levels of N-terminal pro-atrial natriuretic peptide and brain natriuretic peptide were also measured. The results were compared with those from eight age- and sex-matched healthy volunteers. Compared with the controls, the baseline mean ejection fraction was increased significantly in both patient groups (P = 0.02), together with prolonged deceleration times (P = 0.03), left atrial enlargement (P = 0.03) and interventricular septal thickening (P = 0.02), findings that are compatible with diastolic dysfunction. Levels of N-terminal pro-atrial natriuretic peptide and brain natriuretic peptide were significantly higher in all patients with cirrhosis with ascites (P = 0.01 and P = 0.05 respectively), but in only some of the pre-ascitic cirrhotic patients, compared with controls. All high levels of brain natriuretic peptide were correlated significantly with septal thickness (P < 0.01), left ventricular diameter at the end of diastole (P = 0.02) and deceleration time (P < 0.01). We conclude that elevated levels of brain natriuretic peptide are related to interventricular septal thickness and the impairment of diastolic function in asymptomatic patients with cirrhosis. Levels of brain natriuretic peptide may prove to be useful as a marker for screening patients with cirrhosis for the presence of cirrhotic cardiomyopathy, and thereby identifying such patients for further investigations.
Relationship of skeletal muscle metaboreceptors in the upper and lower limbs with the respiratory control in patients with heart failure
Authors: SCOTT Adam C. , DAVIES L. Ceri , COATS Andrew J. S. , PIEPOLI Massimo
Published: August 2015

Increased activity of muscle metaboreceptors (afferents sensitive to muscle contraction that are responsible for the ventilatory responses to exercise) has been proposed in patients with chronic heart failure (CHF) to constitute a missing link between muscle metabolic abnormalities and exercise overventilation. We looked at this reflex overactivation to determine if it is systemic or limited to a single muscle region in the same human subject. This was done by comparing the metaboreflex response of ventilatory control in the lower and upper limbs in CHF patients and healthy controls. Groups of 15 stable CHF patients (63.7±2.7 years) and eight control subjects (69.8±1.8 years) performed both leg and arm metaboreflex tests. These metaboreflex tests involved two 5min episodes of bicycle or handgrip exercise: on one occasion after the exercise the subjects recovered normally, while on the other occasion tourniquet cuffs were inflated around the exercising limb to supra-systolic pressure at the onset of recovery to obtain a regional circulatory occlusion, which isolates and maintains the stimulation of the metaboreflex after exercise. The contribution of the metaboreflex to exercise ventilation was computed as the absolute increment of peak ventilation that was maintained by regional circulatory occlusion. The metaboreceptor contribution to the ventilatory response to both leg exercise (patients, 5.3±1.6litres/min; controls, 0.2±0.7litres/min) and arm exercise (patients, 3.7±1.0litres/min; controls, 0.02±0.4litres/min) was significantly higher in CHF patients (P < 0.05). A significant correlation was present between metaboreflex responses to arm and leg exercises (r = 0.4, P < 0.05). Metaboreflex responses during both types of exercise were inversely correlated with peak oxygen uptake (leg, r =-0.43, P < 0.05; arm, r =-0.633, P = 0.0009), but only the reflex during arm exercise was correlated with the E (ventilation)/co2 (CO2 production) slope (r = 0.576, P < 0.005). Thus the metaboreflex system is systemically overactive and may potentially contribute to exercise intolerance during both lower- and upper-limb efforts in CHF. This suggests a unique mechanism responsible for overactivation of this system in the skeletal muscle of heart failure patients.
Nitric oxide and renal and cardiac dysfunction in cirrhosis
Authors: GARCÍA-ESTAÑ Joaquín , ORTIZ M. Clara , LEE Samuel S.
Published: August 2015

Nitric oxide (NO) has diverse physiological and pathophysiological effects. The roles of NO in the renal and cardiac dysfunction found in cirrhosis are reviewed. In the kidneys of experimental animals with cirrhosis, several lines of evidence speak in favour of an enhanced production of NO, through the activation of both endothelial constitutive and inducible isoforms of NO synthase. In contrast with the situation in normal animals, inhibition of NO synthesis in rats with cirrhosis improves sodium and water excretion via blood pressure-dependent and -independent mechanisms, which indicates that the renal sodium and water retention of cirrhosis is related to an excess of NO production. The deleterious effect of excessive NO on the kidney may be mediated by peroxynitrite, a potent oxidant that is readily formed whenever superoxide anions and the ·NO radical are produced together. The peroxidation of arachidonic acid by peroxynitrite leads to the formation of F2a-isoprostanes, which are powerful renal vasoconstrictors. F2a-isoprostane levels are correlated with the severity of liver injury during cirrhosis. However, whether peroxynitrite or F2a-isoprostanes are the elusive mediator of the NO-induced renal alterations in cirrhosis remains to be firmly established. NO is also involved in cardiac contractility, probably in the normal heart as well as in disease conditions such as non-cirrhotic and cirrhotic cardiomyopathy. In the latter state, evidence suggests that inducible NO synthase attenuates ventricular contractility, mediated by cGMP. Another gas that transduces its signal through cGMP, carbon monoxide, is also likely to play a role in cirrhotic cardiomyopathy, but the nature of the interaction between NO and carbon monoxide in this syndrome remains unclear.
The role of inducible nitric oxide synthase in lipopolysaccharide-mediated hyporeactivity to vasoconstrictors differs among isolated rat arteries
Authors: PIEPOT H.A. , GROENEVELD A.B.J. , VAN LAMBALGEN A.A. , SIPKEMA P.
Published: August 2015

We investigated whether organ-specific differences exist in the role of inducible nitric oxide synthase (iNOS) in hyporeactivity to vasoconstrictors following 20h in vitro exposure of isolated superior mesenteric, renal, hepatic and coronary arteries from the rat to bacterial lipopolysaccharide (LPS). LPS attenuated contraction in response to depolarizing KCl in all arteries. Maximum contractile responses to noradrenaline were attenuated in superior mesenteric and hepatic arteries, and those to the thromboxane A2 analogue U46619 were attenuated in coronary arteries. LPS shifted the concentration-response curve to noradrenaline in renal arteries to the right. Removal of extracellular l-arginine improved the response to noradrenaline in superior mesenteric and renal arteries only. Addition of the iNOS inhibitor aminoguanidine resulted in full recovery of the responses to noradrenaline in superior mesenteric, renal and hepatic arteries. Contractile responses in coronary arteries did not improve after inhibition of iNOS activity. Therefore the pattern of the LPS-induced changes in vascular reactivity, as well as the contribution of iNOS to impaired vascular constriction, differed among vascular beds. These differences are likely to represent a contributory factor in the sepsis-associated redistribution of cardiac output.
Combined angiotensin-converting enzyme inhibition and adrenomedullin in an ovine model of heart failure
Authors: RADEMAKER Miriam T. , CHARLES Chris J. , COOPER Garth J.S. , COY David H. , ESPINER Eric A. , LEWIS Lynley K. , NICHOLLS M. Gary , RICHARDS A. Mark
Published: August 2015

Advances in the treatment of heart failure may require manipulation of neurohumoral responses to cardiac impairment in addition to the established strategy of angiotensin-converting enzyme (ACE) inhibition. Importantly, since new treatments are likely to be used in conjunction with ACE inhibition therapy, the effects of the combination of agents need to be assessed. Adrenomedullin (ADM) is a peptide with potent vasodilator and natriuretic actions. ADM and an ACE inhibitor (captopril) were administered for 3h both separately and together in eight sheep with heart failure. Both ADM and captopril alone reduced arterial pressure, left atrial pressure (greater with captopril) and peripheral resistance, and increased cardiac output (greater with ADM). Compared with either treatment separately, combined ADM+captopril produced directionally similar but significantly greater changes in all haemodynamic variables (particularly falls in blood pressure). ADM increased renal sodium and creatinine excretion and creatinine clearance, and maintained urine output. Captopril and ADM+captopril reduced creatinine excretion and creatinine clearance, while urine volume and sodium excretion were not significantly altered. Plasma renin activity rose with all active treatments, whereas angiotensin II levels rose during ADM, but fell during captopril and ADM+captopril. Aldosterone was reduced by all active treatments. ADM+captopril reduced plasma noradrenaline (norepinephrine). In conclusion, short-term co-treatment with ADM and an ACE inhibitor produced significantly greater decreases in ventricular filling pressures and cardiac afterload, and increases in cardiac output, compared with either treatment alone. Despite the greater falls in blood pressure (and presumably renal perfusion pressure), renal function was maintained at a level similar to that observed with captopril alone.
Effect of linsidomine on the human radial artery
Authors: REMADI J.P. , COLAS B. , MASSON H. , SLAMA M. , ANDRÉJACK M.
Published: August 2015

The response of the human radial artery to a direct NO donor, linsidomine or 3-morpholino-sydnonimine (Sin 1), in the therapeutic management of peri-operative spasm may increase the patency rates of these grafts in the short, medium and long term. Evaluation of the effects of Sin 1 on the human radial artery is of even greater interest as it has not been published previously. Ninety-six human radial artery rings were studied with two protocols. Rings were mounted in an isolated organ bath between two stainless steel metallic rods connected to stress gauges. Protocol 1 studied the vasorelaxant effect of Sin 1 and nitroglycerin (TNT). Protocol 2 studied the reactivity of the radial artery to the vasoconstrictor agents arginine vasopressin (AVP) and angiotensin II (ANG II). The vasorelaxant effect of Sin 1 on the human radial artery was comparable with that of TNT, but with no tolerance effect. After Sin 1 pre-incubation, the vasoconstrictor effect of ANG II was abolished, whereas AVP induced maximum vasoconstriction similar to that of the control (not statistically significant), but with a shift in the EC50 to higher concentrations, EC50 = 15±20nM. Sin 1 vasorelaxation of rings precontracted by ANG II was maximal, whereas after contraction by AVP, relaxation remained less than 70%; Sin 1 is a potent vasorelaxant on the human radial artery, which does not exhibit cross-tolerance with nitrates. This compound may be used pre- or post-operatively, and would undoubtedly be of benefit in the peri-operative preparation bath.
Angiotensinogen M235T gene polymorphism and recurrent restenosis after repeated percutaneous transluminal coronary angiography
Authors: HERTWIG Sabine , VÖLZKE Henry , ROBINSON Daniel M. , MOTZ Wolfgang , RETTIG Rainer
Published: August 2015

The present study was designed to prospectively test the hypothesis that gene polymorphisms of the renin-angiotensin system are associated with recurrent restenosis after repeated percutaneous transluminal coronary angioplasty. Five hundred and eleven patients after first successful angioplasty were characterized with respect to the angiotensinogen M235T, angiotensin-converting enzyme insertion/deletion and angiotensin II type 1 receptor A1166C gene polymorphisms. In 164 of these patients repeated angioplasty on a restenotic lesion was performed. After repeated angioplasty, 46 patients had recurrent restenosis as defined by a greater than 50% progression of residual stenosis. In the recurrent restenosis group there was a statistically significant higher percentage of patients receiving cholesterol-lowering drugs compared with the group of patients without recurrent restenosis. The two groups of patients did not differ with respect to procedural and angiographic parameters. There were significantly more carriers of the angiotensinogen 235T allele in the recurrent restenosis group than in the control group without recurrent restenosis. No differences between the two groups were found with respect to the other gene polymorphisms investigated. According to the results of a multifactorial analysis of variance, only the 235T allele of the angiotensinogen gene and not cholesterol drug therapy independently affected the increase of stenosis at follow-up angiography. In conclusion, the angiotensinogen 235T allele may be an independent predictor for recurrent restenosis after repeated angioplasty.
Left ventricular long-axis diastolic function is augmented in the hearts of endurance-trained compared with strength-trained athletes
Authors: VINEREANU Dragos , FLORESCU Nicolae , SCULTHORPE Nicholas , TWEDDEL Ann C. , STEPHENS Michael R. , FRASER Alan G.
Published: August 2015

In order to determine left ventricular global and regional myocardial functional reserve in endurance-trained and strength-trained athletes, and to identify predictors of exercise capacity, we studied 18 endurance-trained and 11 strength-trained athletes with left ventricular hypertrophy (172±27 and 188±39g/m2 respectively), and compared them with 14 sedentary controls. Global systolic (ejection fraction) and diastolic (transmitral flow) function, and regional longitudinal and transverse myocardial velocities [tissue Doppler echocardiography (TDE)], were measured at rest and immediately after exercise. In endurance-trained compared with strength-trained athletes, resting heart rate was lower (59±11 and 76±9beats/min respectively; P<0.001), and the increase at peak exercise was greater (+211% and +139% respectively; P<0.001). In addition, exercise duration, workload, maximal oxygen consumption and global systolic functional reserve (but not peak ejection fraction) were higher in the endurance-trained athletes, and resting global diastolic function (E/A ratio 1.62±0.40 compared with 1.18±0.23; P<0.01) (where E-wave is peak velocity of early-diastolic mitral inflow and A-wave is peak velocity of mitral inflow during atrial contraction) and long-axis diastolic velocities (ETDE/ATDE ratio 2.2±1.2 compared with 1.1±0.3; P<0.01) (where ETDE and ATDE represent peak early- and late-diastolic myocardial or tissue velocity respectively) were augmented. Systolic velocities were similar. Exercise capacity was best predicted from end-diastolic diameter index and E/A ratio at rest, and end-diastolic volume index and diastolic longitudinal velocity during exercise (r = 0.74, n = 43, P<0.001). In conclusion, endurance-trained athletes had higher left ventricular long-axis diastolic velocities, augmented global early diastolic filling, and greater chronotropic and global systolic functional reserve. Maximal oxygen consumption was determined by diastolic loading and early relaxation rather than by systolic function, suggesting that dynamic exercise training improves cardiac performance by an effect on diastolic filling.
Forearm elevation augments sympathetic activation during handgrip exercise in humans
Authors: MICHIKAMI Daisaku , KAMIYA Atsunori , FU Qi , NIIMI Yuki , IWASE Satoshi , MANO Tadaaki , SUZUMURA Akio
Published: August 2015

Although angina pectoris in patients with coronary heart disease often occurs when their forearms are in an elevated position for a prolonged period, and sympathetic activation is a major cause of this condition, little is known about the physiological effects of forearm elevation on sympathetic activity during forearm exercise. We hypothesized that forearm elevation augments sympathetic activation during the static handgrip exercise in humans. A total of 10 healthy male volunteers performed 2min of static handgrip exercise at 30% of maximal voluntary contraction followed by 2min of post-exercise muscle ischaemia (PEMI; specific activation of the muscle metaboreflex) with two forearm positions: the exercising forearm was elevated 50cm above the heart (forearm-elevated trial) or fixed at the level of the heart (heart-level trial). Muscle sympathetic nerve activity (MSNA), blood pressure and heart rate were monitored. MSNA increased during handgrip exercise in both forearm positions (P<0.001); the increase was 51% greater in the forearm-elevated trial (516±99 arbitrary units) than in the heart-level trial (346±44units; P<0.05). The increase in mean blood pressure was 8.4mmHg greater during exercise in the forearm-elevated trial (P<0.05), while changes in heart rate were similar in both forearm positions. The increase in MSNA during PEMI was 71% greater in the forearm-elevated trial (393±71 arbitrary units/min) than in the heart-level trial (229±29units/min; P<0.05). These results support the hypothesis that forearm elevation augments sympathetic activation during handgrip exercise. The excitatory effect of forearm elevation on exercising MSNA may be mediated primarily by increased activation of the muscle metaboreflex.
Membrane structural changes support the involvement of mitochondria in the bile salt-induced apoptosis of rat hepatocytes
Authors: SOLÁ Susana , BRITO Maria A. , BRITES Dora , MOURA José J.G. , RODRIGUES Cecília M.P.
Published: August 2015

The accumulation of toxic bile salts within the hepatocyte plays a key role in organ injury during liver disease. Deoxycholate (DC) and glycochenodeoxycholate (GCDC) induce apoptosis in vitro and in vivo, perhaps through direct perturbation of mitochondrial membrane structure and function. In contrast, ursodeoxycholate (UDC) and its taurine-conjugated form (TUDC) appear to be protective. We show here that hydrophobic bile salts induced apoptosis in cultured rat hepatocytes, without modulating the expression of pro-apoptotic Bax protein, and caused cytochrome c release in isolated mitochondria. Co-incubation with UDC and TUDC prevented cell death and efflux of mitochondrial factors. Using spin-labelling techniques and EPR spectroscopy analysis of isolated rat liver mitochondria, we found significant structural changes at the membrane—water surface in mitochondria exposed to hydrophobic bile salts, including modified lipid polarity and fluidity, altered protein order and increased oxidative injury. UDC, TUDC and cyclosporin A almost completely abrogated DC- and GCDC-induced membrane perturbations. We conclude that the toxicity of hydrophobic bile salts to hepatocytes is mediated by cytochrome c release, through a mechanism associated with marked direct effects on mitochondrial membrane lipid polarity and fluidity, protein order and redox status, without modulation of pro-apoptotic Bax expression. UDC and TUDC can directly suppress disruption of mitochondrial membrane structure, which may represent an important mechanism of hepatoprotection by these bile salts.
Cardiovascular effects and cardiopulmonary plasma gradients following intravenous infusion of neuropeptide Y in humans: negative dromotropic effect on atrioventricular node conduction
Authors: ULLMAN Bengt , PERNOW John , LUNDBERG Jan M. , ÅSTRÖM Hans , BERGFELDT Lennart
Published: August 2015

Neuropeptide Y (NPY) is co-released with noradrenaline from sympathetic nerves, has a strong vasoconstrictive action, and causes an attenuation of parasympathetic action in animal experiments. The plasma level of NPY is greatly elevated in patients with congestive heart failure, but the clinical relevance of this finding is unclear. Central haemodynamic effects, cardiac conduction system electrophysiology and coronary sinus blood flow were therefore studied in two sets of experiments, each carried out on seven healthy men. In the first series, NPY was given intravenously at doses of 3, 10 and 30pmolμmin-1μkg-1, and in the second it was given as a bolus injection of 90, 200 or 900pmol/kg, which resulted in plasma concentrations similar to those seen in heart failure patients. During continuous infusion of NPY, systemic blood pressure increased slightly, but myocardial perfusion, cardiac output, pulmonary arterial pressure, cardiac conduction intervals and atrioventricular (AV) node functional measures remained unchanged. In contrast, the bolus injection of NPY evoked prolongation and block (in four out of seven subjects) of AV node conduction, but did not affect haemodynamic variables, apart from a minor increase in systemic blood pressure. Impaired AV node conduction is a novel observation, which might reflect a baroreceptor-mediated vagal reflex, or–more likely–an NPY-induced direct negative dromotropic effect, caused by a reduction of the L-type calcium current as observed in vitro, or a combination of the two.
Inhibition of aquaporin-mediated CO2 diffusion and voltage-gated H+ channels by zinc does not alter rabbit lung CO2 and NO excretion
Authors: SWENSON Erik R. , DEEM Steven , KERR Mark E. , BIDANI Akhil
Published: August 2015

Aquaporins (AQs) increase cell membrane CO2 diffusivity, and it has been proposed that they may serve as transmembrane channels for CO2 and other small gas molecules. In addition, it has been hypothesized that voltage-gated H+ channels located on the apical membrane of the alveolar epithelium contribute to CO2 elimination by the lung. To test whether these membrane proteins contribute to CO2 elimination in vivo, we measured CO2 exchange in buffer- and blood-perfused rabbit lungs before and after addition of 0.5mM ZnCl2, an inhibitor of both AQ-mediated CO2 diffusion and voltage-gated H+ channels. For comparison, red cell and lung carbonic anhydrases (CAs) were inhibited by 0.1mM methazolamide. ZnCl2 had no effect on CO2 exchange when inspired CO2 was altered between 2% and 5% in 5-min intervals. Pulmonary vascular and airway resistances were not altered by ZnCl2. In contrast, methazolamide inhibited CO2 exchange by 30% in buffer-perfused lungs and by 65% in blood-perfused lungs. Exhaled NO concentrations were unaffected by ZnCl2 or by CA inhibition. Lung capillary gas exchange modelling shows that under normal resting conditions it would be necessary to reduce the alveolar–capillary membrane CO2 diffusion capacity by >90% to lower CO2 elimination by 10%. Therefore we conclude that red cell and lung AQs and voltage-gated H+ channels in the alveolar epithelium contribute minimally to normal physiological CO2 elimination.