bluuebunny/crossref_metadata_2025 huggingface dataset:
Biophysical effects of pore mutations of ROMK1
Authors: BHANDARI Sunil , HUNTER Malcolm
Published: August 2015

Potassium channels are ubiquitous, being present in all living organisms. These proteins share common structural elements, which confer common functional features. In general, all K+ channels have a high selectivity for K+, and are blocked by cations of similar dimensions, such as Cs+ and Ba2+. Mutations in the pore region tend to lead to either the total loss of function or K+ selectivity. We have made mutations to one of the most highly conserved residues of the pore, glycine-143, of the inward rectifier ROMK1 (Kir1.1), and examined the resulting channel properties in the Xenopus oocyte expression system with a two-electrode voltage clamp. Mutations G143A and G143R resulted in failure to express functional channels. Co-injection of wild-type ROMK1 cRNA with these mutants led to rescue of channel function, which was different from wild-type ROMK1. In both mutants, the sensitivity to Ba2+ and Cs+ was increased, the rate of onset of block by Ba2+ was enhanced, and the selectivity to potassium was reduced. Whereas the crystallographic evidence shows that cations bind to the carbonyl backbone of the pore-lining residues, the present results indicate that the side chains of these amino acids, which face away from the pore lining, also affect permeation.
Diagnosing coeliac disease by rectal gluten challenge: aprospective study based on immunopathology, computerized image analysisand logistic regression analysis
Authors: ENSARI Arzu , MARSH Michael N. , MORGAN Shethah , LOBLEY Robert , UNSWORTH D. J. , KOUNALI Daphne , CROWE Peter T. , PAISLEY Jane , MORIARTY Kieran J. , LOWRY John
Published: August 2015

The purpose of this study was to evaluate the use of rectal gluten challenge in the diagnosis of coeliac disease. A total of 103 patients with features suggestive of this diagnosis were prospectively enrolled into the study; a diagnosis of coeliac disease was based on strictly defined criteria used in judging the proximal jejunal biopsy. On that basis, 45 out of the 103 patients were deemed to have coeliac disease. A slurry of gluten powder in physiological saline was introduced into the rectum, and biopsies taken before and at 2 h or 4 h after the challenge were examined immunohistochemically by computerized image analysis. Cell counts were analysed by logistic regression, and the best equations were obtained for each challenge group. The 2 h challenge yielded diagnostic sensitivity and specificity of 69.6% and 78.6% respectively. The 4 h challenge provided sensitivity and specificity of 100% and 100% respectively. These results were compared with other clinical diagnostic predictors, including anti-endomysial antibodies, which yielded diagnostic sensitivity and specificity of 70% and 98% respectively. It is concluded that a 4 h rectal challenge is a highly sensitive means of identifying gluten-sensitized individuals, and would be of particular value in cases showing negative antibody screening or equivocal biopsy appearances.
Post-load glucose measurements in oral glucose tolerance tests correlate well with 1,5-anhydroglucitol, an indicator of overall glycaemic state, in subjects with impaired glucose tolerance
Authors: YAMANOUCHI Toshikazu , INOUE Tae , OGATA Eri , KASHIWABARA Akiko , OGATA Nobuyuki , SEKINO Nori , YOSHIMURA Tomoe , ICHIYANAGI Kaoru , KAWASAKI Takahiro
Published: August 2015

Using both cross-sectional and longitudinal methods, we investigated the relationship between post-load serum glucose concentration in a 75 g oral glucose tolerance test (OGTT) and overall glycaemic state in subjects with impaired glucose tolerance (IGT). Glycaemic state was assessed by measuring glycated haemoglobin (HbA1c) and the serum concentration of 1,5-anhydroglucitol (1,5-AG). In the cross-sectional study, the concentration of 1,5-AG, while remaining within a normal range, was reduced to a degree proportional to the post-load glycaemic level. Although the correlation between HbA1c and post-load plasma glucose was relatively weak (r = 0.281, P < 0.001), a significant inverse correlation (r =-0.824, P < 0.0001) was found between 1,5-AG and mean post-load plasma glucose concentration in 211 subjects with IGT. Fasting plasma glucose (r =-0.539, P < 0.0001) and 2 h plasma glucose (r =-0.621, P < 0.0001) were correlated with 1,5-AG less strongly than was post-load glycaemia. Both 1,5-AG and HbA1c were correlated weakly but significantly with the fasting insulin concentration. In the longitudinal study we measured 1,5-AG and mean post-load plasma glucose with an OGTT once yearly for 10 years in 15 subjects with IGT. Strong inverse correlations were seen between 1,5-AG and mean post-load plasma glucose in each subject (range of r values among subjects of -0.584 to -0.978). These findings suggest a close relationship between post-load plasma glucose concentration measured by OGTT and overall glycaemic state in subjects with IGT.
Peripheral vascular and nerve function associated with lower limb amputation in people with and without diabetes
Authors: CARRINGTON Anne L. , ABBOTT Caroline A. , GRIFFITHS Joan , JACKSON Nicky , JOHNSON Sylvia R. , KULKARNI Jai , VAN ROSS Ernest R. E. , BOULTON Andrew J. M.
Published: August 2015

Multiple factors, including peripheral vascular disease and neuropathy, contribute to the development and perpetuation of complications of the lower extremities in diabetes. The main aim of the present study was to assess the peripheral vascular and nerve status of diabetic and non-diabetic subjects that had undergone lower limb amputation. Various non-invasive tests of peripheral vascular and nerve function were carried out on subjects who had undergone unilateral lower limb amputation and were now attending a Rehabilitation Centre. The control group (n = 23), the diabetic amputee group (n = 64) and the non-diabetic amputee group (n = 32) were age-matched. Only the diabetic amputee group had evidence of medial arterial calcification. Transcutaneous oxygen levels were significantly lower in the diabetic amputee group (median 43 mmHg; interquartile range 33–49 mmHg) than in the control (59; 56–74 mmHg) and non-diabetic amputee (57; 43–65 mmHg) groups (control compared with diabetic amputee group, P < 0.001; diabetic amputee compared with non-diabetic amputee group, P < 0.01). The same trend was found for carbon dioxide levels in the skin [mmHg: diabetic amputees, 25 (21–37); controls, 38 (32–42); non-diabetic amputee, 34 (31–39)] (control compared with diabetic amputee, P < 0.01; diabetic amputee compared with non-diabetic amputee, P < 0.05). Vibration and pressure perception measurements (which assess Aβ nerve fibre function) showed that both the diabetic amputee and non-diabetic amputee subjects had significantly greater impairment than the controls. However, measures of Aα and C nerve fibre function were abnormal only in the diabetic amputee group. Thus the peripheral vascular and nerve functions of age-matched diabetic and non-diabetic subjects having undergone lower limb amputation show specific differences, with non-diabetic amputees exhibiting signs of neuropathy. This indicates that factors characteristic of diabetes (such as hyperglycaemia and non-enzymic glycation) are associated with calcification, lower oxygen and carbon dioxide levels in the skin, and abnormal Aα and C nerve fibre function.
Interactions between nitric oxide and renal nerves in the excretion of a saline load in obese Zucker rats
Authors: WONGMEKIAT Orawan , JOHNS Edward J.
Published: August 2015

The present study investigated the potential role of nitric oxide (NO) and its interaction with renal sympathetic nerves in modulating the excretory responses to an acute saline volume expansion (VE), of 10% of body weight, in the innervated and denervated kidneys of both lean and obese Zucker rats. This was done using the NO synthase inhibitors NG-nitro-l-arginine methyl ester (l-NAME), 7-nitroindazole and aminoguanidine. In lean rats, cumulative urinary sodium excretion (cuUNaV) after 40 min of VE in the innervated kidney was enhanced by 48% in l-NAME-treated rats compared with that in untreated rats, but this was not the case for the denervated kidney. VE in untreated obese rats raised cuUNaV to a lesser extent than in the untreated lean rats, by 36% and 46% in the denervated and innervated kidneys respectively (both P < 0.001). l-NAME treatment of obese rats increased cuUNaV after VE compared with that in untreated obese rats, by 48% in the denervated kidney and by 136% in the innervated kidney (both P < 0.001). The magnitude of cuUNaV after VE in both kidneys of 7-nitroindazole-treated obese rats was not different from that in untreated obese rats. However, cuUNaV was raised (P < 0.01) by 56% in the innervated, but not the denervated, kidney of aminoguanidine-treated obese rats. These data show that NO is partially involved in mediating the reflex renal responses to VE in Zucker rat strains. NO, possibly generated by endothelial NO synthase, exerts its effects in obese rats through a renal-nerve-independent mechanism, while the effect of NO generated by inducible NO synthase requires intact renal innervation.
Acid production and base balance in patients on chronic haemodialysis
Authors: MIONI R. , GROPUZZO M. , MESSA M. , BOSCUTTI G. , D'ANGELO A. , CRUCIATTI A. , MIONI G.
Published: August 2015

Acid generation and elimination processes were compared with total base (bicarbonate plus metabolizable anions) turnover in 18 anuric patients undergoing post-dilutional haemofiltration. The study was conducted during the second haemodialysis session of the week by means of a whole-body base balance technique. The results showed that the mean rates of base loss and base gain during dialysis did not differ (i.e. the dialysis base balance approximated to zero). The concurrent mean rate of intestinal base absorption was 66±26 mmol/2 days, as calculated from the whole-body balance of the various inorganic cation and anion differences in a metabolic steady state. This level of intestinal base absorption would be capable of neutralizing the 59±21 mmol of H+ ions/2 days that is contributed by sulphuric acid, which is the most important endogenous acid produced in anuric patients. In spite of the fact that intestinal base supply was adequate to neutralize endogenous acid production completely, our patients presented with pre-dialysis non-carbonic acidosis. The depression of plasma bicarbonate levels could not, however, be explained by increased concentrations of the anion gap and organic acids, which were within normal limits both before and after dialysis. We suggest as an alternative hypothesis that this pre-dialysis acidosis may represent an isotonic dilution acidosis that is induced by the ingestion of base-free tap water in order for plasma tonicity to be protected from the accumulation of impermeant dietary solutes, which takes place during the interdialysis period in anuric patients.
Heart rate response to hypoxic exercise: role of dopamine D2-receptors and effect of oxygen supplementation
Authors: LUNDBY Carsten , MØLLER Peter , KANSTRUP Inge-Lis , OLSEN Niels Vidiendal
Published: August 2015

This study examined the effects of dopamine D2-receptor blockade on the early decrease in maximal heart rate at high altitude (4559m). We also attempted to clarify the time-dependent component of this reduction and the extent to which it is reversed by oxygen breathing. Twelve subjects performed two consecutive maximal exercise tests, without and with oxygen supplementation respectively, at sea level and after 1, 3 and 5 days at altitude. On each study day, domperidone (30mg; n = 6) or no medication (n = 6) was given 1h before the first exercise session. Compared with sea level, hypoxia progressively decreased the maximal heart rate from day 1 and onwards; also, hypoxia by itself increased plasma noradrenaline levels after maximal exercise. Domperidone further increased maximal noradrenaline concentrations, but had no effect on maximal heart rate. On each study day at altitude, oxygen breathing completely reversed the decrease in maximal heart rate to values not different from those at sea level. In conclusion, dopamine D2-receptor blockade with domperidone demonstrates that hypoxic exercise in humans activates D2-receptors, resulting in a decrease in circulating levels of noradrenaline. However, dopamine D2-receptors are not involved in the hypoxia-induced decrease in the maximal heart rate. These data suggest that receptor uncoupling, and not down-regulation, of cardiac adrenoreceptors, is responsible for the early decrease in heart rate at maximal hypoxic exercise.
Intermittent hypoxic training: implications for lipid peroxidation induced by acute normoxic exercise in active men
Authors: BAILEY Damian M. , DAVIES Bruce , YOUNG Ian S.
Published: August 2015

Oxidant generation during regular physical exercise training may influence the adaptive responses that have been shown to confer protection against oxidative stress induced by subsequent acute exercise. To examine this, we randomly assigned 32 males to either a normoxic (n = 14) or a hypoxic (n = 18) group. During the acute phase, subjects in the hypoxic group performed two maximal cycling tests in a randomized double-blind fashion: one under conditions of normoxia and the other under hypoxic conditions (inspired fraction of O2 = 0.21 and 0.16 respectively). During the intermittent phase, the normoxic and hypoxic groups each trained for 4 weeks at the same relative exercise intensity, under conditions of normoxia and hypoxia respectively. During acute exercise under hypoxic conditions, the venous concentrations of lipid hydroperoxides and malondialdehyde were increased, despite a comparatively lower maximal oxygen uptake (o2max) (P < 0.05 compared with normoxia). The increases in lipid hydroperoxides and malondialdehyde were correlated with the exercise-induced decrease in arterial haemoglobin oxygen saturation (r =-0.61 and r =-0.50 respectively; P < 0.05), but not with o2max. Intermittent hypoxic training attenuated the increases in lipid hydroperoxides and malondialdehyde induced by acute normoxic exercise more effectively than did normoxic training, due to a selective mobilization of α-tocopherol (P < 0.05). The latter was related to enhanced exercise-induced mobilization/oxidation of blood lipids due to a selective increase in o2max (P < 0.05 compared with normoxic group). We conclude that lipid peroxidation induced by acute exercise (1) increases during hypoxia; (2) is not regulated exclusively by a mass action effect of o2; and (3) is selectively attenuated by regular hypoxic training. Oxidative stress may thus be considered as a biological prerequisite for adaptation to physical stress in humans.
Randomized controlled trial of home-based exercise training to evaluate cardiac functional gains
Authors: MARSHALL Paul , AL-TIMMAN Jawad , RILEY Rhona , WRIGHT Jay , WILLIAMS Simon , HAINSWORTH Roger , TAN Lip-Bun
Published: August 2015

There is evidence that multiple benefits can be obtained through exercise training that leads to increases in peak oxygen consumption (O2). It is unclear whether significant improvements can also be achieved through unsupervised low-budget home-based training regimes, especially in terms of cardiac functional gains. A randomized cross-over trial was conducted to investigate the effects of a home-based unsupervised exercise training programme of moderate intensity on aerobic capacity, cardiac reserve and peak cardiac power output in healthy middle-aged volunteers. Nine subjects with no known cardiovascular diseases performed symptom-limited treadmill cardiopulmonary exercise tests after an 8-week period of exercise training, and results were compared with those obtained after a similar ‘non-exercising’ control period. Cardiac output was measured non-invasively during exercise tests using the CO2-rebreathing method. With exercise training, resting heart rate decreased significantly from 88.3±3.4 to 78.7±3.2beatsċmin-1 (P < 0.05), heart rate at a submaximal workload (O2 = 1.5litresċmin-1) decreased from 125.5±2.4 to 115.5±1.6beatsċmin-1, and peak O2 increased by 9% from 2.62±0.19 to 2.85±0.18litresċmin-1 (P < 0.01). Baseline cardiac power output was 1.11±0.05W, and this remained unchanged with training. Peak cardiac power output increased by 16% from 4.1±0.3 to 4.7±0.3W (P < 0.001), and cardiac reserve increased by 21% (P < 0.01). A major contribution to these increases was from the 11% increase in stroke volume, from 100.1±5.3 to 111.2±6.2ml (P < 0.001). All subjects reported more positive perceptions of their health (P < 0.05), fitness (P < 0.01) and levels of activity (P < 0.01) after the training period. These results show that motivated subjects undergoing low-budget unsupervised home-based exercise training of moderate intensity can derive benefit in terms of symptoms, aerobic capacity and cardiac functional reserve.
17β-Hydroxysteroid dehydrogenase type 2 expression and enzyme activity in the human gastrointestinal tract
Authors: SANO Toshikazu , HIRASAWA Gen , TAKEYAMA Junji , DARNEL Andrew D. , SUZUKI Takashi , MORIYA Takuya , KATO Katuaki , SEKINE Hitoshi , OHARA Syuichi , SHIMOSEGAWA Tooru , NAKAMURA Junji , YOSHIHAMA Makoto , HARADA Nobuhiro , SASANO Hironobu
Published: August 2015

The 17β-hydroxysteroid dehydrogenases (17βHSDs) play an important role in the regulation of intracellular levels of biologically active sex steroid hormones in various human tissues. To date, eight distinctive 17βHSD enzymes have been cloned and characterized in humans. Among these isoenzymes, 17βHSD type 2 (17βHSD2) catalyses the conversion of testosterone into androstenedione and/or oestradiol into oestrone in various tissues, and it has thus been suggested to be involved in the biological inactivation of these sex steroids. The human gastrointestinal tract and liver are considered as the principle sites of inactivation and metabolism of various forms of orally administered sex steroids. We therefore examined 17βHSD2 expression and activity in human adult non-pathological gastrointestinal tract in order to clarify further the biological significance of this enzyme. A total of 80 specimens (40 from males and 40 from females) of normal oesophageal, stomach, duodenal, ileal, colonic and rectal tissues were examined for immunohistochemistry. Altogether, 17 tissue specimens were used for enzyme assay, and eight for RNA analysis. 17βHSD2 activity was detected in the stomach, duodenum, ileum, colon and rectum. 17βHSD2 mRNA was most abundant in the small intestine. 17βHSD2 immunoreactivity was localized almost exclusively to the absorptive epithelium, which may be involved in the inactivation of excessive endogenous and exogenous active sex steroids. Results from the present study thus suggest that the human gastrointestinal tract is an important sex steroid metabolizing organ in humans.
Glucan phosphate potentiates endotoxin-induced interferon-γ expression in immunocompetent mice, but attenuates induction of endotoxin tolerance
Authors: SHERWOOD Edward R. , VARMA Tushar K. , FRAM Ricki Y. , LIN Cheng Y. , KOUTROUVELIS Aristides P. , TOLIVER-KINSKY Tracy E.
Published: August 2015

Glucan phosphate has been shown to enhance antimicrobial immunity in a variety of experimental models. However, the mechanisms by which glucans enhance resistance to infection remain largely unknown. Interferon-γ (IFN-γ) is a key regulator of both innate and acquired immunity. Suppression of IFN-γ production is a prominent feature of the altered immune response that follows major trauma or sepsis. The present studies were designed to determine the effect of glucan phosphate on IFN-γ expression in normal mice and endotoxin [lipopolysaccharide (LPS)]-tolerant mice. The model of LPS tolerance was used because it results in patterns of cytokine expression similar to those commonly observed following severe trauma or sepsis. Glucan treatment potentiated LPS-induced IFN-γ expression in control mice. The induction of LPS tolerance resulted in marked suppression of LPS-induced IFN-γ production. However, co-administration of glucan with LPS, during the tolerance induction phase, attenuated the LPS-tolerant response. Interleukin-12 (IL-12) and IL-18 are important mediators of LPS-induced IFN-γ production. LPS-induced IL-12 p40 mRNA expression was increased in the spleens of glucan-treated mice compared with controls. Induction of LPS tolerance caused marked suppression of IL-12 production, a response that was attenuated by glucan treatment. IL-18 was constitutively expressed in both control and LPS-tolerant mice, and LPS-induced serum levels of IL-18 were increased in mice treated with glucan. T cells isolated from glucan-treated mice exhibited increased IFN-γ expression in response to IL-12 and IL-18, as well as increased expression of the IL-12 and IL-18 receptors. The ability of glucan to potentiate IFN-γ expression in control mice provides a potential mechanism by which glucan enhances antimicrobial immunity. The ability of glucan to attenuate suppressed IFN-γ expression in LPS-tolerant mice denotes its potential benefit for the treatment of trauma and sepsis-induced immunosuppression.
Effects of angiotensin II (AT1) receptor blockade on cardiac vagal control in heart failure
Authors: VAILE J. C. , CHOWDHARY S. , OSMAN F. , ROSS H. F. , FLETCHER J. , LITTLER W. A. , COOTE J. H. , TOWNEND J. N.
Published: August 2015

The objective of the present study was to determine the autonomic effects of angiotensin II (AT1) receptor blocker therapy in heart failure. In a randomized double-blind cross-over study, we compared the effects of candesartan and placebo on baroreflex sensitivity and on heart rate variability at rest, during stress and during 24h monitoring. Acute effects were assessed 4h after oral candesartan (8mg) and chronic effects after 4 weeks of treatment (dose titrated to 16mg daily). The study group comprised 21 patients with heart failure [mean (S.E.M.) ejection fraction 33% (1%)], in the absence of angiotensin-converting enzyme (ACE) inhibitor therapy. We found that acute candesartan was not different from placebo in its effects on blood pressure or mean RR interval. Chronic candesartan significantly reduced blood pressure [placebo, 137 (3)/82 (3)mmHg; candesartan, 121 (4)/75 (2)mmHg; P<0.001; values are mean (S.E.M.)], but had no effect on mean RR interval [placebo, 857 (25)ms; candesartan, 857 (21)ms]. Compared with placebo there were no significant effects of acute or chronic candesartan on heart rate variability in the time domain and no consistent effects in the frequency domain. Baroreflex sensitivity assessed by the phenylephrine bolus method was significantly increased after chronic candesartan [placebo, 3.5 (0.5)ms/mmHg; candesartan, 4.8 (0.7)ms/mmHg; P<0.05], although there were no changes in cross-spectral baroreflex sensitivity. Thus, in contrast with previous results with ACE inhibitors, angiotensin II receptor blockade in heart failure did not increase heart rate variability, and there was no consistent effect on baroreflex sensitivity.
The effect of glutamate infusion on cardiac performance is independent of changes in metabolism in patients undergoing routine coronary artery bypass surgery
Authors: LANGENBERG Chris J. , PIETERSEN Henk G. , GESKES Gijs , WAGENMAKERS Anton J.M. , DE LANGE Simon , SCHOUTEN Hubert J. , SOETERS Peter B.
Published: August 2015

In a double-blind randomized placebo-controlled study, the effects of intravenous glutamate infusion on myocardial haemodynamics and metabolism were studied in 22 patients undergoing routine coronary artery bypass graft (CABG) surgery. Immediately after aortic cross-clamp release, an intravenous infusion of a solution of glutamate (125mmolċl-1) at a rate of 1.5mlċh-1ċkg-1 was given over 1h to 11 patients (G group). The other 11 patients received a placebo infusion (0.9% NaCl) (P group). Haemodynamic functions and rates of exchange of glucose, non-esterified fatty acids and lactic acid over the heart were measured before sternotomy (T1), 40min after cross-clamp release (T2) and 4h after cross-clamp release (T3). At T2, decreases were seen in comparison with T1 in systemic vascular resistance index, and increases were seen in cardiac index and coronary sinus flow. All of these changes were greater in the G group than in the P group (P < 0.05). Myocardial glutamate consumption increased 2-fold after glutamate administration. No significant changes were observed in the myocardial utilization of glucose, lactate or non-esterified fatty acids between the P and the G groups at T1, T2 or T3. These data show that an intravenous glutamate infusion after routine CABG surgery significantly improved cardiac haemodynamic performance without direct effects on cardiac substrate metabolism. This suggests that a reduction of the afterload via a peripheral vasodilatory effect is the main mechanism leading to the observed changes in haemodynamics. Earlier claims that patients with post-operative cardiac failure show metabolic benefits from the glutamate infusion do not seem to apply to patients undergoing routine CABG surgery.
Lymphocyte protein synthesis is increased with the progression of HIV-associated disease to AIDS
Authors: CASO Giuseppe , GARLICK Peter J. , GELATO Marie C. , MCNURLAN Margaret A.
Published: August 2015

HIV infection has been shown to affect lymphocyte function and to reduce lymphocyte responsiveness in vitro to mitogenic stimulation, but little is known about lymphocyte metabolism in vivo and how it is affected during the course of the disease. This study investigated the metabolic activity of lymphocytes in vivo through the progression of HIV-associated disease. Lymphocyte protein synthesis was measured with l-[2H5]phenylalanine (45mg/kg body weight) in healthy volunteers (n = 7), in patients who were HIV-positive (n = 7) but asymptomatic, and in patients with AIDS (n = 8). The rates of lymphocyte protein synthesis [expressed as a percentage of lymphocyte protein, i.e. fractional synthesis rate (FSR)] were not altered in HIV-positive patients compared with healthy controls (7.9±1.28% and 9.1±0.53%/day respectively), but were significantly elevated in AIDS patients (14.0±1.16%/day; P < 0.05). The serum concentration of the cytokine tumour necrosis factor-α (TNF-α) increased with the progression of the disease, and TNF-α levels were significantly higher in AIDS patients (6.81±0.88ng/l) than in healthy controls (3.09±0.27ng/l; P < 0.05). Lymphocyte protein FSR was positively correlated with serum TNF-α concentration (r = 0.55, P = 0.009) and negatively correlated with CD4+ lymphocyte count (r =-0.70, P = 0.004). The elevation of lymphocyte protein synthesis in AIDS patients suggests a higher rate of turnover of lymphocytes. This may be associated with a generalized activation of the immune system, which is also reflected by the elevated serum TNF-α concentration in the late stages of HIV-associated disease.
Flow-mediated dilatation following wrist and upper arm occlusion in humans: the contribution of nitric oxide
Authors: DOSHI Sagar N. , NAKA Katerina K. , PAYNE Nicola , JONES Christopher J.H. , ASHTON Moira , LEWIS Malcolm J. , GOODFELLOW Jonathan
Published: August 2015

Flow-mediated dilatation (FMD) of the brachial artery assessed by high-resolution ultrasound is widely used to measure endothelial function. However, the technique is not standardized, with different groups using occlusion of either the wrist or the upper arm to induce increased blood flow. The validity of the test as a marker of endothelial function rests on the assumption that the dilatation observed is endothelium-dependent and mediated by nitric oxide (NO). We sought to compare the NO component of brachial artery dilatation observed following wrist or upper arm occlusion. Dilatation was assessed before and during intra-arterial infusion of the NO synthase inhibitor NG-monomethyl-l-arginine (l-NMMA) following occlusion of (i) the wrist (distal to ultrasound probe) and (ii) the upper arm (proximal to ultrasound probe) for 5min in ten healthy males. Dilatation was significantly greater after upper arm occlusion (upper arm, 11.62±3.17%; wrist, 7.25±2.49%; P = 0.003). During l-NMMA infusion, dilatation after wrist occlusion was abolished (from 7.25±2.49% to 0.16±2.24%; P < 0.001), whereas dilatation after upper arm occlusion was only partially attenuated (from 11.62±3.17% to 7.51±2.34%; P = 0.006). The peak flow stimulus was similar after wrist and upper arm occlusion. We conclude that dilatation following upper arm occlusion is greater than that observed after wrist occlusion, despite a similar peak flow stimulus. l-NMMA infusion revealed that FMD following wrist occlusion is mediated exclusively by NO, while dilatation following upper arm occlusion comprises a substantial component not mediated by NO, most probably related to tissue ischaemia around the brachial artery. FMD following wrist occlusion may be a more valid marker of endothelial function than dilatation following upper arm occlusion.
Endothelial dysfunction is an independent factor responsible for vasospastic angina
Authors: TERAGAWA Hiroki , KATO Masaya , KUROKAWA Junichi , YAMAGATA Togo , MATSUURA Hideo , CHAYAMA Kazuaki
Published: August 2015

In order to evaluate peripheral endothelial function in patients with vasospastic angina (VSA), we measured flow-mediated dilation (FMD) of the brachial artery in patients with VSA and compared it with FMD in patients without VSA. Endothelial dysfunction is considered one of the mechanisms underlying VSA. However, its exact role remains to be clarified. The study included 30 patients with positive spasm-provocational test results without evidence of significant coronary stenosis (VSA group) and 30 patients with negative spasm-provocational test results without evidence of significant coronary stenosis (control group). In each patient, brachial artery diameter responses to hyperemic flow and glyceryl trinitrate spray were measured using high-resolution ultrasound. The carotid intima-media thickness was also measured as a marker of systemic atherosclerosis. FMD was lower in the VSA group (4.8±0.5%) compared with the control group (9.4±0.7%, P < 0.0001). In the VSA group, FMD was not affected by coronary risk factors or the presence of atherosclerotic changes on coronary angiography. Glyceryl trinitrate-induced dilation did not differ between the two groups. The intima-media thickness was comparable between the VSA (0.85±0.04mm) and control groups (0.81±0.05mm). These findings indicated that peripheral endothelial function is impaired only in the VSA group, whereas the atherosclerotic changes were similar in the two groups. We conclude that endothelial dysfunction may be an independent factor responsible for the development of VSA.
Comparison of two spatially resolved near-infrared photometers in the detection of tissue oxygen saturation: poor reliability at very low oxygen saturation
Authors: KOMIYAMA Takashi , QUARESIMA Valentina , SHIGEMATSU Hiroshi , FERRARI Marco
Published: August 2015

Two spatially resolved oximeters, NIRO-300 and OM-200, were compared with regard to the measurement of oxygen saturation values in two forearm muscle groups at rest and during arterial occlusion in nine healthy volunteers. There was a significant correlation between the muscle oxygen saturation values obtained at rest using the two oximeters (n = 33, r2 = 0.43, P < 0.0001), whereas these values were significantly different during arterial occlusion. Thus, although there was good agreement between muscle oxygen saturation values measured using the two oximeters, the operating range of the tissue oximeters should be recognized and indicated.
Endothelin-1 plus oxidized low-density lipoprotein, but neither alone, increase human monocyte adhesion to endothelial cells
Authors: LANGENFELD M.R. , NAKHLA S. , DEATH A.K. , JESSUP W. , CELERMAJER D.S.
Published: August 2015

Endothelin-1 is a potent vasoconstrictor and mitogenic peptide that is implicated in the atherosclerosis of apolipoprotein E-deficient mice and may promote atherogenesis in humans. We hypothesized that endothelin-1 might promote the adhesion of monocytes to endothelial cells, a key early event in atherosclerosis. We investigated the adhesion of primary human monocytes (isolated by elutriation) to human umbilical vein endothelial cell cultures after incubation with endothelin-1 (0.1 and 0.01nM; approximately physiological concentrations), copper-oxidized low-density lipoprotein (LDL) (0.1mg/ml) and a combination of the two. After a 4h incubation with 0.1 or 0.01nM endothelin-1 combined with oxidized LDL, adhesion was increased to 120±4% (P < 0.001 compared with control) and 118±4% (P < 0.002) respectively, whereas neither substance alone increased adhesion (92-104% of control values; not significant). Neither endothelin receptor A blockade nor co-incubation with anti-fibronectin antibody inhibited the pro-adhesive effects of endothelin-1 plus oxidized LDL (115±7% and 115±3% of control compared with 120±4% respectively; not significant). Endothelial cell expression of intercellular adhesion molecule-1, vascular adhesion molecule-1 and E-selectin were unchanged throughout the experiment. Therefore physiological concentrations of endothelin-1 and oxidized LDL may act synergistically to increase the adhesion of human monocytes to endothelial cells, contributing in part to the observed pro-atherogenic effects of endothelin-1.
Sex steroids and insulin resistance
Authors: LIVINGSTONE Callum , COLLISON Mary
Published: August 2015

There is extensive experimental evidence that sex steroids and insulin interact in their actions on tissues. At physiological levels, testosterone and oestradiol are thought to be involved in maintaining normal insulin sensitivity. However, outside this ‘physiological window’ these steroids may promote insulin resistance. Considerable research has been carried out on polycystic ovarian syndrome, a common disorder associated with excessive androgen production and insulin resistance. Hyperinsulinaemia in patients with this condition is believed to stimulate ovarian androgen production, and there is also evidence that androgens act directly on peripheral tissues to promote insulin resistance. There is the potential for a vicious circle to develop with increasing androgen production and insulin resistance. The molecular basis of this insulin resistance has been reported to involve reduced insulin receptor autophosphorylation, reduced expression and translocation of insulin-responsive glucose transporters and defects of the insulin signalling pathway distal to the insulin receptor. These defects await full characterization. Insulin-sensitizing agents can reverse many of the effects of insulin resistance and may have a future place in the treatment of polycystic ovarian syndrome and other conditions associated with steroid-induced insulin resistance. Recognition and treatment of sex steroid-associated insulin resistance at an early stage in patients may reduce their risk of developing Type II (non-insulin-dependent) diabetes mellitus, hypertension and dyslipidaemia, and so may improve fertility and reduce cardiovascular risk. Here we review the interplay between sex steroids and insulin resistance, and consider the implications this has for clinical conditions.
Vascular endothelial growth factor and its receptor, Flt-1, in the plasma of patients with coronary or peripheral atherosclerosis, or Type II diabetes
Authors: BLANN Andrew D. , BELGORE Funmi M. , McCOLLUM Charles N. , SILVERMAN Stanley , LIP Peck Lin , LIP Gregory Y.H.
Published: August 2015

Since atherosclerosis is characterized by endothelial damage, re-growth seems likely to be occurring in order to repair or replace injured cells. Angiogenic vascular endothelial growth factor (VEGF), a likely mediator of these events, acts on the endothelium via a specific receptor, Flt-1. We hypothesized that patients with different manifestations of atherosclerosis, and others with diabetes, would have altered plasma levels of VEGF and Flt-1 compared with healthy individuals. Accordingly, 70 patients with peripheral artery disease (PAD), 70 patients with coronary artery disease (CAD), and 70 age- and sex-matched healthy controls were recruited. We also recruited 14 patients with diabetes asymptomatic for atherosclerosis, 14 patients with diabetes and atherosclerosis, and 14 age- and sex-matched controls. VEGF and soluble Flt-1 (sFlt-1) were measured by ELISA. In the main study of PAD and CAD, VEGF was raised in both patient groups (P < 0.05) compared with the controls, but was not different between the patient groups. sFlt-1 was lower in patients with PAD (P < 0.05), but not in those with CAD, compared with the controls. VEGF was raised in the patients with diabetes plus atherosclerosis (P < 0.05), but not in the group with diabetes alone; levels of sFlt-1 were unaltered in both diabetes groups. Our data point to changes in plasma levels of VEGF and its receptor sFlt-1 in diabetes and atherosclerosis that may have relevance for therapy and angiogenesis in these conditions.
Effect of glycyrrhetinic acid on 11β-hydroxysteroid dehydrogenase activity in normotensive and hypertensive subjects
Authors: VAN UUM Stan H.M. , WALKER Brian R. , HERMUS Ad R.M.M. , SWEEP C.G.J. (Fred) , SMITS Paul , DE LEEUW Peter W. , LENDERS Jacques W.M.
Published: August 2015

The 11β-hydroxysteroid dehydrogenase (11β-HSD) isoenzymes catalyse the interconversion of cortisol and cortisone. Type 1 11β-HSD mainly converts cortisone into active cortisol. Type 2 11β-HSD inactivates cortisol in mineralocorticoid target tissues, and its activity can be inhibited by glycyrrhetinic acid (GA). Inactivation of cortisol to cortisone is impaired in a subgroup of patients with primary hypertension. To study where this defect is located, we measured cortisol and cortisone concentrations in arterial plasma, in saliva and across the forearm at baseline and after administration of GA in normotensive and hypertensive subjects. GA (500mg) or placebo was administered orally to 20 normotensive subjects in a placebo-controlled double-blind fashion. Further, we compared the effect of GA in 20 patients with primary hypertension with that in 20 normotensive subjects. Cortisol and cortisone were measured in plasma from the brachial artery and vein and in saliva. Samples were obtained at 0, 90 and 150min. Forearm blood flow (FBF) was measured simultaneously. Forearm production of corticosteroid hormones was assessed by multiplying the arteriovenous difference in corticosteroid concentration by FBF. The cortisol/cortisone ratio in arterial plasma remained at baseline levels after placebo (4.9±1.2; mean±S.D.), while after GA the ratio increased similarly in normotensive subjects (12.3±3.4) and in hypertensive patients (12.2±3.7). A similar effect of GA on the salivary cortisol/cortisone ratio was found. In both normotensive subjects and hypertensive patients no forearm production of cortisol or cortisone could be demonstrated, either at baseline or after administration of GA. Thus, both before and after GA administration, we did not find any difference in systemic and salivary 11β-HSD type 2 activity between subjects with primary hypertension and normotensive controls. Further, both at baseline and after GA administration we were not able to demonstrate net inactivation or re-activation of cortisol and cortisone by the 11β-HSD isoenzymes in the forearm in either normotensive or primary hypertensive subjects.
QT-interval variability and autonomic control in hypertensive subjects with left ventricular hypertrophy
Authors: PICCIRILLO Gianfranco , GERMANÒ Giuseppe , QUAGLIONE Raffaele , NOCCO Marialuce , LINTAS Filippo , LIONETTI Marco , MOISÈ Antonio , RAGAZZO Maddalena , MARIGLIANO Vincenzo , CACCIAFESTA Mauro
Published: August 2015

Left ventricular hypertrophy is a risk factor for sudden death. Malignant ventricular arrhythmias originate from altered cardiac repolarization. Ample data have described spatial abnormalities in cardiac repolarization [QT interval (QT) dispersion] in subjects with hypertension; more data are needed on temporal changes. This study was designed to assess the QT variability index (QTVI), the slope between QT and the RR interval (QT-RRslope) and spectral QT variability in subjects with arterial hypertension. The results were compared with those from a population at high risk of sudden death, i.e. patients with hypertrophic cardiomyopathy (HCM) who had received an implantable cardioverter/defibrillator (ICD), and those from normotensive control subjects. A total of 44 hypertensive subjects, six patients with HCM and an ICD and 33 control subjects underwent simultaneous short-term recording (256 beats) of QT, RR and systolic blood pressure variability, in the supine position, during controlled breathing. QTVI and spectral components of QT variability in the hypertensive group were significantly higher than in normotensive control subjects (P < 0.001), but significantly lower than in patients with HCM and an ICD (P < 0.001). The severity of left ventricular hypertrophy correlated significantly with QTVI and the ratio of low-frequency (LF) to high-frequency (HF) power obtained from the RR variability spectra (RRLF/HF, slope = 0.24, P < 0.05; QTVI, slope = 4.06, P < 0.0001; intercept, slope = 2.40, P < 0.05; χ2 = 38.8; P < 0.0001). The QT-RR slope was significantly higher only in patients with HCM and an ICD (P < 0.001). In conclusion, the increased QTVI and the correlation of this index with left ventricular hypertrophy indicates that hypertension increases temporal cardiac repolarization abnormalities. At the level of the cardiac sinus node, this alteration is associated with increased sympathetic and reduced vagal modulation. As already noted in patients with HCM, the increased QTVI could be a factor responsible for triggering malignant ventricular arrhythmias in subjects with hypertension.
Delayed cardioprotective effects of exercise in dogs are aminoguanidine sensitive: possible involvement of nitric oxide
Authors: BABAI László , SZIGETI Zsolt , PARRATT James R. , VÉGH Ágnes
Published: August 2015

Dogs were subjected to exercise on a treadmill, using a protocol in which the speed and slope were increased every 3min, and which elevated both heart rate (to a mean of 198±14beatsċmin-1) and mean arterial blood pressure (to 150±4mmHg). Then, 24 or 48h later, the dogs were anaesthetized with a mixture of α-chloralose and urethane and subjected to a 25min occlusion of the left anterior descending coronary artery. The control dogs (instrumented but not exercised) were subjected to the same procedure. In some dogs the nitric oxide synthase inhibitor aminoguanidine (50mgċkg-1; intravenous) was administered 30min before occlusion. Baroreflex sensitivity (BRS) was determined by the rapid bolus injection of phenylephrine 60min before, and again 3min after, the onset of occlusion. Exercise markedly reduced the consequences of coronary artery occlusion 24h (but not 48h) later, without modifying myocardial tissue blood flow. In the exercised dogs there were reductions in arrhythmia severity [ventricular fibrillation (VF) during occlusion, 0%; survival from the combined ischaemia/reperfusion insult, 70%] compared with controls (VF during occlusion, 36%; survival, 9%). BRS was preserved during occlusion in the exercised dogs (before occlusion, 1.60±0.54msċmmHg-1; 3min after occlusion, 1.37±0.4msċmmHg-1), but not in controls (before occlusion, 1.28±0.29msċmmHg-1; 3min after occlusion, 0.45±0.12msċmmHg-1; P < 0.05), and other ischaemic changes (inhomogeneity of electrical activation and changes in the ST-segment, recorded over the ischaemic region) were also less marked in the exercised dogs. Exercise-induced cardioprotection was abolished by aminoguanidine (VF during occlusion, 25%; survival, 0%). The results show that even a single period of exercise affords delayed protection against ischaemia/reperfusion-induced VF and other ischaemic changes. Since this protection is abolished by aminoguanidine, and since (inducible) NO synthase activity was elevated 3-fold in left ventricular samples 24h after exercise, we suggest that this protection is mediated by nitric oxide.
Garlic attenuates nitric oxide production in rat cardiac myocytes through inhibition of inducible nitric oxide synthase and the arginine transporter CAT-2 (cationic amino acid transporter-2)
Authors: SCHWARTZ Idit F. , HERSHKOVITZ Rami , IAINA Adrian , GNESSIN Ehud , WOLLMAN Yoram , CHERNICHOWSKI Tamara , BLUM Miriam , LEVO Yoram , SCHWARTZ Doron
Published: August 2015

It is now accepted that allicin, the main biologically active compound in garlic, exhibits antioxidant activity. The present study was designed to test the hypothesis that the antioxidant activity of garlic can be partially attributed to the inhibition of nitric oxide (NO) production by cytokine-induced NO synthase (iNOS). Cardiac myocytes cultured from neonatal Wistar rats were stimulated by lipopolysaccharide (LPS) and incubated for 24h with various concentrations of allicin. This resulted in marked inhibition of nitrite production. Interestingly, a low concentration of allicin (10μM) was significantly more potent in abrogating the effect of LPS on nitrite production than a higher concentration (40μM). Allicin decreased steady-state iNOS mRNA levels, and this effect was maximal when a lower concentration was used (10μM compared with 40μM). In order to explore additional effects of allicin on NO generation that might counteract the effect on iNOS, we assessed the effects of higher allicin concentrations on arginine transport. Allicin inhibited the uptake of 1mM extracellular arginine in a concentration-dependent manner. The expression of the two arginine transporters that are expressed in cardiac myocytes [CAT-1 (cationic amino acid transporter-1) and CAT-2] was studied using reverse transcription-PCR. A concentration of 200μM allicin abolished the expression of CAT-2 mRNA, 100μM significantly attenuated it, whereas 50μM had no effect. Allicin had no effect on steady-state CAT-1 mRNA levels. Our results suggest that allicin inhibits iNOS activity through two different mechanisms: at lower concentrations it decreases iNOS mRNA levels, whereas at higher concentrations it inhibits arginine transport through down-regulation of CAT-2 mRNA.
Carbohydrate ingestion, with transient endogenous insulinaemia, produces both sympathetic activation and vasodilatation in normal humans
Authors: SCOTT Eleanor M. , GREENWOOD John P. , VACCA Giovanni , STOKER John B. , GILBEY Stephen G. , MARY David A.S.G.
Published: August 2015

It has been shown that sustained insulin infusion causes an increase in sympathetic vasoconstrictor discharge but, despite this, also causes peripheral vasodilatation. The present study was designed to determine in healthy subjects the effect of ingestion of a carbohydrate meal, with its attendant physiological insulinaemia, on vascular resistance in and sympathetic vasoconstrictor discharge to the same vascular bed, and the relationship between these parameters. Fifteen healthy subjects were studied for 2h following ingestion of a carbohydrate meal. Calf vascular resistance was measured by venous occlusion plethysmography, and muscle sympathetic nerve activity was assessed by peroneal microneurography. Five of the subjects also ingested water on a separate occasion, as a control. Following the carbohydrate meal, the serum insulin concentration increased to 588±72pmol/l. This was associated with a 47% increase in skeletal muscle blood flow (P < 0.001), a 39% fall in vascular resistance (P < 0.001) and a 57% increase in sympathetic activity (P < 0.001). There was a significant correlation between the increase in insulin and the changes in blood flow, vascular resistance and sympathetic activity. In conclusion, we have shown that ingestion of a carbohydrate meal, with its attendant physiological insulinaemia, was associated with overriding skeletal muscle vasodilatation, despite an increase in sympathetic vasoconstrictor discharge to the same vascular bed. These mechanisms may be important in ensuring optimal glucose uptake and maintenance of blood pressure postprandially.