High arterial compliance in cirrhosis is related to low adrenaline and elevated circulating calcitonin gene related peptide but not to activated vasoconstrictor systems.
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BACKGROUND AND AIMS: Static and dynamic functions of the wall of large arteries are largely unknown in cirrhosis in vivo. The present study was undertaken to determine arterial compliance (COMP(art)) in relation to vasodilator and vasoconstrictor systems in patients with cirrhosis. In addition, vasoactivity was manipulated by inhalation of oxygen. STUDY POPULATION AND METHODS: In 20 patients with alcoholic cirrhosis and 12 controls we determined COMP(art) (stroke volume relative to pulse pressure), cardiac output, plasma volume, systemic vascular resistance, central circulation time, plasma catecholamines, renin activity, endothelin-1, and calcitonin gene related peptide (CGRP) at baseline and during oxygen inhalation. RESULTS: COMP(art) was significantly increased in cirrhotic patients compared with controls (1.32 v 1.06 ml/mm Hg; p< 0.05) and inversely related to plasma adrenaline levels (r=-0.53; p<0.02) but positively related to circulating levels of CGRP (r=0.58; p<0.01). No significant relation was found for plasma noradrenaline, renin activity, or endothelin-1. COMP(art) was positively related to plasma volume (r=0.50; p<0.02) and inversely to systemic vascular resistance (r=-0.69; p<0.001) and central circulation time (r=-0.49; p<0.02). During oxygen inhalation, COMP(art) decreased (-13%; p<0.005) and systemic vascular resistance increased (+10%; p<0.001) towards normal values without significant changes in mean arterial pressure. Plasma adrenaline (-16%; p<0.01) decreased and the relation to COMP(art) disappeared. The relation of COMP(art) to CGRP and circulatory variables remained unchanged. CONCLUSION: Elevated arterial compliance in cirrhosis is related to low adrenaline, high CGRP, and systemic hyperdynamics but not to indicators of the activated vasoconstrictor systems (noradrenaline, renin, endothelin-1). Thus the altered static and dynamic characteristics of the wall of large arteries are intimately associated with circulatory and vasodilatory derangement in cirrhosis but biomanipulation indicates that the changes are, at least in part, reversible during isobaric conditions. (+info)
H. pylori and transient lower esophageal sphincter relaxations induced by gastric distension in healthy humans.
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The role of Helicobacter pylori infection in the control of lower esophageal sphincter (LES) motility, especially the occurrence of transient LES relaxations (TLESRs), was studied in eight H. pylori-positive and eight H. pylori-negative healthy subjects. During endoscopy, biopsy specimens were taken from the cardia, fundus, and antrum for determinations of H. pylori status, gastritis, and proinflammatory cytokine mucosal concentrations. LES motility was monitored during three different 30-min periods: baseline, gastric distension (barostat), and gastric distension with CCK infusion. Gastric distension significantly increased the TLESR rate, whereas CCK increased the rate of distension-induced TLESRs further and reduced resting LES pressure without significant differences between infected and noninfected subjects. H. pylori status did not influence resting LES pressure or gastric compliance. Cytokine mucosal concentrations were increased in infected patients, but no correlation was found with the TLESR rate, which was also independent of inflammation at the cardia, fundus, and antrum. These results suggest that H. pylori-associated inflammation does not affect the motor events involved in the pathogenesis of gastroesophageal reflux. (+info)
Viscoelastic properties of the human colon.
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Our objectives were to characterize colonic viscoelastic properties of the human descending colon by assessing pressure-volume (P-V) relationships during barostatic balloon distension. In 16 healthy subjects, a balloon was inflated to 44 mmHg and then deflated to 0 mmHg in 4-mmHg steps at 10, 30, and 60 ml/min, allowing volume fluctuations to stabilize at each pressure increment. Thereafter, these "quasi-static" P-V curves were compared with "dynamic" distensions to 300 ml, at 1 and 10 ml/s, before and after intravenous atropine in another five subjects. During quasi-static curves, balloon volume stabilized at each pressure increment. Quasi-static P-V curves were reproducible within individuals and approximated to a power exponential function and revealed hysteresis, indicative of viscoelasticity. Body mass index influenced quasi-static P-V curves during inflation but not during deflation. The colon was less compliant during dynamic distensions at 10 ml/s than during quasi-static distensions. Atropine increased quasi-static compliance and attenuated differences between quasi-static and rapid distensions. We conclude that colonic viscoelastic properties can be assessed by quasi-static P-V curves. Rapid colonic distension activated neural reflexes, thereby reducing colonic compliance compared with quasi-static distensions. (+info)
Decreased carotid artery distensibility as a sign of early atherosclerosis in viscose rayon workers.
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Carbon disulphide (CS(2)) is known to accelerate atherosclerosis and to increase the risk for cardiovascular diseases. To assess the effect of CS(2) on the functional (distensibility and compliance) and the structural (intima media thickness) properties of the common carotid artery, and blood pressure and lipid metabolism parameters, a cross-sectional study on 85 workers from a viscose rayon factory and 37 controls was carried out. Exposure to CS(2) was assessed by personal monitoring and was well below the threshold limit value-time weighted average. Carotid arterial wall properties were determined using a non-invasive ultrasound wall movement detector system. No significant effect of CS(2) on blood pressure, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol or triglycerides was found. Among the vascular parameters studied, only distensibility was significantly lower and heart rate was significantly higher in exposed subjects compared with the controls. In conclusion, occupational exposure to CS(2) may cause early alterations in arterial elastic properties in young individuals, and even before lipid and clinical findings have occurred, important functional changes in the vessel wall are present. (+info)
Cardiac nitric oxide production due to angiotensin-converting enzyme inhibition decreases beta-adrenergic myocardial contractility in patients with dilated cardiomyopathy.
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OBJECTIVES: This study tested the hypothesis that angiotensin-converting enzyme (ACE) inhibitors attenuate beta-adrenergic contractility in patients with idiopathic dilated cardiomyopathy (DCM) through nitric oxide (NO) myocardial signaling. BACKGROUND: The ACE inhibitors increase bradykinin, an agonist of NO synthase (NOS). Nitric oxide inhibits beta-adrenergic myocardial contractility in patients with heart failure. METHODS: The study patients were given the angiotensin-1 (AT-1) receptor antagonist losartan for one week. The hemodynamic responses to intravenous dobutamine were determined before and during intracoronary infusion of enalaprilat (0.2 mg/min) with and without the NOS inhibitor N(G)-monomethyl-L-arginine (L-NMMA, 5 mg/min). RESULTS: In patients with DCM (n = 8), dobutamine increased the peak rate of rise of left ventricular pressure (+dP/dt) by 49 +/- 8% (p < 0.001) and ventricular elastance (Ecs) by 53 +/- 16% (p < 0.03). Co-infusion with enalaprilat decreased +dP/dt to 26 +/- 12% and Ecs to -2 +/- 17% above baseline (p < 0.05), and this anti-adrenergic effect was reversed by L-NMMA co-infusion (p < 0.05 vs. enalaprilat). In addition, intracoronary enalaprilat reduced left ventricular end-diastolic pressure (LVEDP), but not left ventricular end-diastolic volume, consistent with increased left ventricular distensibility. Infusion with L-NMMA before enalaprilat in patients with DCM (n = 5) prevented the reduction in +dP/dt, Ecs and LVEDP. In patients with normal left ventricular function (n = 5), enalaprilat did not inhibit contractility or reduce LVEDP during dobutamine infusion. CONCLUSIONS: Enalaprilat attenuates beta-adrenergic contractility and enhances left ventricular distensibility in patients with DCM, but not in subjects with normal left ventricular function. This response is NO modulated and occurs in the presence of angiotensin receptor blockade. These findings may have important clinical and pharmacologic implications for the use of ACE inhibitors, AT-1 receptor antagonists and their combination in the treatment of heart failure. (+info)
Material properties of Thera-Band Tubing.
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BACKGROUND AND PURPOSE: Thera-Band Tubing has been used in rehabilitation to provide resistance for exercise and splinting. However, the forces required to stretch the tubing have not been thoroughly quantified. Therefore, the therapist cannot assess, with certainty, how much force is applied when using a given length and type of Thera-Band Tubing. The purpose of this study was to quantify the material properties of Thera-Band Tubing. METHODS: Force versus percentage of strain for all types of Thera-Band Tubing was measured during elongation in a mechanical testing machine. RESULTS: The material is very compliant and displays nonlinear behavior in the initial stretching phase and linear behavior after 50% elongation. DISCUSSION AND CONCLUSION: From the data obtained in this project, plots that can provide the therapist with information about the forces needed for exercises with Thera-Band Tubing were generated. These data should allow therapists to make better choices about which size of tubing to use for each patient. (+info)
Aerobic exercise training does not modify large-artery compliance in isolated systolic hypertension.
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The present study characterized large-artery properties in patients with isolated systolic hypertension (ISH) and determined the efficacy of exercise training in modifying these properties. Twenty patients (10 male and 10 female) with stage I ISH and 20 age- and gender-matched control subjects were recruited, and large-artery properties were assessed noninvasively. Ten ISH patients (5 male and 5 female) were enrolled in a randomized crossover study comparing 8 weeks of moderate intensity cycling with 8 weeks of sedentary activity. Brachial and carotid systolic, diastolic, mean, and pulse pressures were higher in the ISH group than in the control group. Systemic arterial compliance (0.43+/-0.04 versus 0.29+/-0.02 arbitrary compliance units for the control versus ISH groups, respectively; P=0.01) was lower, and carotid-to-femoral pulse-wave velocity (9.67+/-0.36 versus 11.43+/-0.51 m. s(-1) for the control versus ISH groups, respectively; P=0.007), input impedance (2.39+/-0.19 versus 3.27+/-0.34 mm Hg. s. cm(-1) for the control versus ISH groups, respectively; P=0.04), and characteristic impedance (1.67+/-0.17 versus 2.34+/-0.27 mm Hg. s. cm(-1) for the control versus ISH groups, respectively; P=0.05) were higher in the ISH group than in the control group. Training increased maximal oxygen consumption by 13+/-5% (P=0.04) and maximum workload by 8+/-4% (P=0.05); however, there was no effect on arterial mechanical properties, blood lipids, or left ventricular mass or function. These results suggest that the large-artery stiffening associated with ISH is resistant to modification through short-term aerobic training. (+info)
Time course of forearm arterial compliance changes during reactive hyperemia.
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Ultrasonic studies have shown that arterial compliance increases after prolonged ischemia. The objective of the present study was to develop an alternative plethysmographic method to investigate compliance, exploring validity and clinical applicability. Forearm pulse volume (FPV) and blood pressure (BP) were used to establish the FPV-BP relationship. Forearm arterial compliance (FAC) was measured, and the area under the FAC-BP curve (FAC(AUC)) was determined. The time course curve of compliance changes during reactive hyperemia was obtained by continuous measurements of FAC(AUC) for 20 s before and for 300 s after arterial occlusion. This technique allows us to effectively assess compliance changes during reactive hyperemia. Furthermore, the selected measurement protocol indicated the necessity for continuous measurements to detect "true" maximal FAC(AUC) changes. On multivariate analysis, preischemic FAC(AUC) was mainly affected by sex, peak FAC(AUC) was affected by sex and systolic BP, percent changes were affected by plasma high-density and low-density lipoprotein cholesterol, peak time was affected by age and body mass index, and descent time was affected by plasma triglyceride levels. The proposed technique is highly sensitive and well comparable with the generally accepted echotracking system. It may thus be considered as an alternative tool to detect and monitor compliance changes induced by arterial occlusion. (+info)