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Cardiovascular Changes (cardiovascular + change)
Selected AbstractsCardiovascular changes and physiological response during nitrite exposure in rainbow troutJOURNAL OF FISH BIOLOGY, Issue 1 2001S. Aggergaard Nitrite-exposed (1 mM) rainbow trout Oncorhynchus mykiss fell into two distinct groups with regard to susceptibility and physiological response. Group 1 accumulated nitrite in plasma to a concentration of 2·9 mM within 24 h and died before 48 h. Group 2 survived for 96,144 h, and the accumulation of nitrite was slower, levelling off at a concentration c. 2·3 mM at 72 h. Methaemoglobin (metHb) formation was faster in group 1 than in group 2, but both groups had a metHb fraction c. 70% before dying. The extracellular electrolyte balance was perturbed significantly only in group 1, where plasma [Cl - ] decreased and plasma [K+] increased. Heart rate increased rapidly, more in group 1 than in group 2. The tachycardia occurred before any significant changes in metHb or [K+] had developed, suggesting that it was due to nitrite-induced vasodilation, possibly via nitric oxide generated from nitrite, that was countered by an increased cardiac pumping to re-establish blood pressure. Arterial blood pressure and pulse pressure were accordingly kept reasonably constant. Heart rate variability was significantly depressed in group 1. The ventilation rate was significantly increased after 9 h of nitrite exposure in group 1, while the ventilation in group 2 did not increase significantly before 21 h. The data reveal that nitrite has substantial influence on the cardio-respiratory function in fishes. [source] Cardiovascular changes induced by cold water immersion during hyperbaric hyperoxic exposureCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2007Alain Boussuges Summary The present study was designed to assess the cardiac changes induced by cold water immersion compared with dry conditions during a prolonged hyperbaric and hyperoxic exposure (ambient pressure between 1·6 and 3 ATA and PiO2 between 1·2 and 2·8 ATA). Ten healthy volunteers were studied during a 6 h compression in a hyperbaric chamber with immersion up to the neck in cold water while wearing wet suits. Results were compared with measurements obtained in dry conditions. Echocardiography and Doppler examinations were performed after 15 min and 5 h. Stroke volume, left atrial and left ventricular (LV) diameters remained unchanged during immersion, whereas they significantly fell during the dry session. As an index of LV contractility, percentage fractional shortening remained unchanged, in contrast to a decrease during dry experiment. Heart rate (HR) significantly decreased after 5 h, although it had not changed during the dry session. The changes in the total arterial compliance were similar during the immersed and dry sessions, with a significant decrease after 5 h. In immersed and dry conditions, cardiac output was unchanged after 15 min but decreased by almost 20% after 5 h. This decrease was related to a decrease in HR during immersion and to a decrease in stroke volume in dry conditions. The hydrostatic pressure exerted by water immersion on the systemic vessels could explain these differences. Indeed, the redistribution of blood volume towards the compliant thoracic bed may conceal a part of hypovolaemia that developed in the course of the session. [source] Muscle afferent contributions to the cardiovascular response to isometric exerciseEXPERIMENTAL PHYSIOLOGY, Issue 6 2004James P. Fisher The cardiovascular response to isometric exercise is governed by both central and peripheral mechanisms. Both metabolic and mechanical stresses on the exercising skeletal muscle produce cardiovascular change, yet it is often overlooked that the afferent signal arising from the muscle can be modified by factors other than exercise intensity. This review discusses research revealing that muscle fibre type, muscle mass and training status are important factors in modifying this peripheral feedback from the active muscles. Studies in both animals and humans have shown that the pressor response resulting from exercise of muscle with a faster contractile character and isomyosin content is greater than that from a muscle of slower contractile character. Athletic groups participating in training programmes that place a high anaerobic load on skeletal muscle groups show attenuated muscle afferent feedback. Similarly, longitudinal studies have shown that specific local muscle training also blunts the pressor response to isometric exercise. Thus it appears that training may decrease the metabolic stimulation of muscle afferents and in some instances chronic exposure to the products of anaerobic metabolism may blunt the sensitivity of the muscle metaboreflex. There may be surprising parallels between the local muscle conditions induced in athletes training for longer sprint events (e.g. 400 m) and by the low-flow conditions in, for example, the muscles of chronic heart failure patients. Whether their similar attenuations in muscle afferent feedback during exercise are due to decreased metabolite accumulation or to a desensitization of the muscle afferents is not yet known. [source] Cardiovascular effects of noradrenaline microinjected into the dorsal periaqueductal gray area of unanaesthetized ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2005Gislaine Garcia Pelosi Abstract The periaqueductal grey area (PAG) is a mesencephalic region that is involved in the modulation of cardiovascular changes associated with behavioural responses. Among the neurotransmitters present in the PAG, noradrenaline (NA) is also known to be involved in central nervous system cardiovascular regulation. In the present study we report the cardiovascular effects of the microinjection of NA into the dorsal portion of the PAG (dPAG) of unanaesthetized rats and the peripheral mechanism involved in their mediation. Injection of NA in the dPAG of unanaesthetized rats evoked a dose-dependent pressor response accompanied by bradycardia. The magnitude of the pressor responses was higher at more rostral sites in the dPAG and decreased when NA was injected into the caudal portion of the dPAG. The responses to NA were markedly reduced in urethane-anaesthetized rats. The pressor response was potentiated by i.v. pretreatment with the ganglion blocker pentolinium and blocked by i.v. pretreatment with the vasopressin antagonist dTyr(CH2)5(Me)AVP. The results suggest that activation of noradrenergic receptors within the dPAG can evoke pressor responses, which are mediated by acute vasopressin release. [source] Exposure to a hot environment can activate rostral ventrolateral medulla-projecting neurones in the hypothalamic paraventricular nucleus in conscious ratsEXPERIMENTAL PHYSIOLOGY, Issue 1 2008Joo Lee Cham A major integrative site within the brain for autonomic function is the hypothalamic paraventricular nucleus (PVN). Several studies have suggested that the PVN may be involved in the responses regulating body temperature. Hyperthermia elicits redirection of blood flow from the viscera to the periphery and involves changes in sympathetic nerve activity mediated by the central nervous system. The hypothalamic PVN includes neurones that project to the rostral ventrolateral medulla (RVLM), an important autonomic region involved in the tonic regulation of sympathetic nerve activity. This pathway could contribute to the cardiovascular changes induced by hyperthermia. The PVN has a high concentration of nitrergic neurones and it is known that nitric oxide within the brain mediates heat dissipation. Thus the aims of this study were to determine whether RVLM-projecting neurones in the PVN are activated by heat and whether those neurones are also nitrergic. The results show that, compared with control conditions, exposure of conscious rats to a hot environment of 39°C significantly increased the number of neurones containing a Fos-positive nucleus (a marker of activation) and significantly increased the number of activated RVLM-projecting neurones in the PVN. Also, although heating significantly increased the number of activated nitrergic PVN neurones, triple-labelled neurones (i.e. activated, nitrergic and RVLM projecting) in the PVN were rarely observed. The results suggest that RVLM-projecting neurones in the PVN may play a role in responses to heat exposure but these are not nitrergic. [source] Respiratory Changes in Vasovagal SyncopeJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2000ARVINDER S. KURBAAN M.D. Respiratory Changes in Vasovagal Syncope. introduction: Respiratory changes accompany the cardiovascular changes during head-up. tilt test-induced vasovagal syncope. Methods and Results: Using the 45-minute 60° head-up Westminster protocol, 29 patients were studied (mean age 53.9 ± 20.0 years; 19 females). Two groups resulted: tilt-induced vasovagal syncope positive and negative. The cardiorespiratory parameters blood pressure (BP), heart rate (HR), tidal volume, and minute volume were measured. Comparisons of the cardiorespiratory parameters were made within the positive group and negative group, and then between the two groups. There were 14 in the positive group and 15 in the negative group. Baseline measurements were normalized to 1.0. Comparing the late tilt periods between the positive and negative groups, there were differences in BP (P < 0.002), HR (P < 0.002), tidal volume (P < 0.05), and minute volume (P < 0.002). In the positive group comparing early with late intervals: BP l.11 ± 0.09 versus 0.49 ± 0.17, P < 0.0001; HR 1.18 ± 0.12 versus 0.85 ±0.35, P < 0.009; tidal volume 1.39 ± 0.34 versus 2.17 ± 1.00, P < 0.015; and minute volume 1.24 ± 0.26 versus 3.3 ± 2.03, P < 0.0025. There were no comparable cardiorespiratory changes in the negative group. Conclusion: There were significant differences in the respiratory and cardiovascular parameters measured between those who were positive and those who were negative for tilt-induced vasovagal syncope. Within the positive group, in addition to the falls in HR and BP, there were significant increases in minute volume and tidal volume during late tilt. This suggests that there may be a role for respiratory sensors in vasovagal syncope that may permit earlier and hence possibly more effective therapy for selected patients. [source] Comparison of the cardio-respiratory effects of methadone and morphine in conscious dogs,JOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 4 2009A. A. MAIANTE The effects of methadone and morphine were compared in conscious dogs. Six animals received morphine sulfate (1 mg/kg) or methadone hydrochloride (0.5 mg/kg [MET0.5] or 1.0 mg/kg [MET1.0]) intravenously (i.v.) in a randomized complete block design. Cardiopulmonary variables were recorded before (baseline), and for 120 min after drug administration. One outlier was not included in the statistical analysis for hemodynamic data. Morphine decreased heart rate (HR) compared to baseline from 30 to 120 min (,15% to ,26%), while cardiac index (CI) was reduced only at 120 min (,19%). Greater and more prolonged reductions in HR (,32% to ,46%) and in CI (,24% to ,52%) were observed after MET1.0, while intermediate reductions were recorded after MET0.5 (,19 to ,28% for HR and ,17% to ,27% for CI). The systemic vascular resistance index (SVRI) was increased after methadone; MET1.0 produced higher SVRI values than MET0.5 (maximum increases: 57% and 165% for MET0.5 and MET1.0, respectively). Compared to morphine, oxygen partial pressure (PaO2) was lower (,12% to ,13%) at 5 min of methadone (0.5 and 1.0 mg/kg), while carbon dioxide partial pressure (PaCO2) did not change significantly. It was concluded that methadone induces cardiovascular changes that are dose-related and is a more potent cardiovascular depressant agent than morphine in conscious dogs. [source] Physiological and performance effects of glycerol hyperhydration and rehydrationNUTRITION REVIEWS, Issue 12 2009Simon P Van Rosendal Studies have shown that beverages containing glycerol can enhance and maintain hydration status and may improve endurance exercise performance by attenuating adverse physiological changes associated with dehydration. Improvements to performance include increased endurance time to exhaustion by up to 24%, or a 5% increase in power or work. However, some studies have found no performance benefits during either prolonged exercise or specific skill and agility tests. In studies that have shown benefits, the improvements have been associated with thermoregulatory and cardiovascular changes. These include increased plasma volume and sweat rates, as well as reduced core temperature and ratings of perceived exertion. In a very small number of subjects, glycerol consumption has been associated with side-effects including nausea, gastrointestinal discomfort, dizziness, and headaches. In summary, while glycerol and fluid ingestion results in hyperhydration, the documented benefits to exercise performance remain inconsistent. [source] Assessment of small-dose fentanyl and sufentanil blunting the cardiovascular responses to laryngoscopy and intubation in childrenPEDIATRIC ANESTHESIA, Issue 6 2007FU SHAN XUE MD Summary Background:, The authors found no study assessing the efficacy of small-dose narcotics on the cardiovascular response from intubation in children, so they observed the effects of fentanyl 2 ,g·kg,1 and sufentanil 0.2 ,g·kg,1 on the cardiovascular changes during laryngoscopy and intubation in children. Methods:, Ninety-three children aged 3,9 years were randomized to one of three groups to receive the following treatments in a double-blind manner: normal saline (group C), fentanyl 2 ,g·kg,1 (group F) and sufentanil 0.2 ,g·kg,1 (group S) 2 min before induction. Noninvasive blood pressure (BP) and heart rate (HR) were recorded before anesthesia induction (baseline value), immediately before intubation (postinduction values), at intubation and 5 min after intubation at 1-min interval. Results:, Tracheal intubation caused significant increases in BP and HR in the three groups compared with baseline values. BP and HR at intubation and after intubation and their maximum values during observation were significantly lower in groups F and S than in group C (P < 0.05). The mean percent increases of systolic blood pressure (SBP) and HR at intubation were significantly lower in group S, 7% and 10%, than in group F, 17% and 25% (P < 0.05). The increases in SBP and HR of more than 30% of baseline values during the observation period were significantly higher in group F, 27% and 43%, than in group S, 0% and 3% (P < 0.05). Conclusions:, When used as part of anesthesia induction with propofol in children, sufentanil 0.2 ,g·kg,1 2 min before induction is more effective in attenuating the cardiovascular intubation response than fentanyl 2 ,g·kg,1. [source] Assessment of autonomic cardiovascular changes associated with recovery from anaesthesia in children: a study using spectral analysis of blood pressure and heart rate variabilityPEDIATRIC ANESTHESIA, Issue 6 2000ISABELLE CONSTANT MD PhD Recovery from anaesthesia is associated with large changes in cardiovascular autonomic activity, which are poorly documented in children. This study was undertaken to investigate the cardiovascular autonomic activity in anaesthetized and recovering children, using a noninvasive approach based on spectral analysis of heart rate (HR) and blood pressure (BP) variability. Ten children (aged 5,13 years) undergoing major surgery were studied. Continuous HR and BP were recorded using a noninvasive device during deep anaesthesia and recovery. Spectral analysis was used to determine the main oscillatory components of HR and BP signals. For each power spectrum, the frequency components were identified as follows (i): the low frequency (LF) component (0.04,0.14 Hz) both parasympathetically and sympathetically mediated for HR and corresponding to vasomotor sympathetic modulation for BP; and (ii) the high frequency (HF) component (0.2,0.6 Hz) parasympathetically mediated for HR, and reflecting mechanical influence of ventilation on cardiac output for BP. In addition, the LF : HF ratio for HR, reflecting the cardiac sympathovagal balance, was calculated. Under deep anaesthesia, HR variability and BP variability were very low and mainly due to mechanical influence of intermittent positive pressure ventilation. Conversely, the recovery period was associated with a marked increase of HR and BP overall variability. Compared to anaesthesia, spectral analysis of HR and BP revealed that the LF component of BP and HR spectra increased 40-fold during recovery; the LF : HF ratio of HR was also increased during recovery (0.1 ± 0.1 versus 1.3 ± 1.2, P=0.008). The results of this study demonstrate that the recovery period is associated with an increase of cardiovascular sympathetic drive in children after major surgery. [source] The perioperative management of children with phaeochromocytomaPEDIATRIC ANESTHESIA, Issue 5 2000H.A. Hack MB, MRCP(UK) Summary The safe anaesthetic management of a child with a phaeochromocytoma requires an understanding of the pathophysiology of the disease, together with a thorough knowledge of its pharmacology, in order to avoid or minimize the potentially harmful cardiovascular changes that may occur during anaesthesia. Although there is a considerable amount of information on the management of the adult with phaeochromocytoma, much less has been written concerning children with the disease. Children differ significantly from adults in the incidence, location, presentation and management of this condition and these differences are discussed here together with some of the more controversial issues of management. [source] Sequence of cardiovascular changes in IUGR in pregnancies with and without preeclampsiaPRENATAL DIAGNOSIS, Issue 5 2008Giancarlo Mari Abstract Objective The aim of this study was to determine the cardiovascular changes sequence in intrauterine-growth-restricted (IUGR) fetuses using Doppler ultrasound. Methods Sequential Doppler evaluations were carried out in 29 severe IUGR fetuses in pregnancies without maternal medical complications (group A) and in pregnancies complicated by preeclampsia (group B) delivered at , 32 weeks. Nine fetal vessels and two cardiac valves were studied. Results One hundred and forty three Doppler studies were performed (median: five studies; range 3,9 per patient). There were 19 fetuses in the preeclamptic group and 10 fetuses in the second group. In group A IUGR fetuses, a progressive change was observed in the parameters studied more often than in group B IUGR fetuses (P < 0.05). In six cases, an abnormal tricuspid valve (TV) followed by an abnormal mitral valve (MV) Doppler was recorded prior to the occurrence of the intrauterine-fetal demise. Conclusions Our data indicate that (1) in patients without preeclampsia a series of cardiovascular changes almost always occurs in severe IUGR fetuses; (2) the changes preceding intrauterine demise are right cardiac failure followed by left cardiac failure; (3) in patients with preeclampsia, the sequential Doppler changes are unpredictable and are seen in a few patients only. Copyright © 2008 John Wiley & Sons, Ltd. [source] Cardiovascular and thermal responses evoked from the periaqueductal grey require neuronal activity in the hypothalamusTHE JOURNAL OF PHYSIOLOGY, Issue 6 2009Rodrigo C. A. De Menezes Stimulation of neurons in the lateral/dorsolateral periaqueductal grey (l/dlPAG) produces increases in heart rate (HR) and mean arterial pressure (MAP) that are, according to traditional views, mediated through projections to medullary autonomic centres and independent of forebrain mechanisms. Recent studies in rats suggest that neurons in the l/dlPAG are downstream effectors responsible for responses evoked from the dorsomedial hypothalamus (DMH) from which similar cardiovascular changes and increase in core body temperature (Tco) can be elicited. We hypothesized that, instead, autonomic effects evoked from the l/dlPAG depend on neuronal activity in the DMH. Thus, we examined the effect of microinjection of the neuronal inhibitor muscimol into the DMH on increases in HR, MAP and Tco produced by microinjection of N -methyl- d -aspartate (NMDA) into the l/dlPAG in conscious rats. Microinjection of muscimol alone modestly decreased baseline HR and MAP but failed to alter Tco. Microinjection of NMDA into the l/dlPAG caused marked increases in all three variables, and these were virtually abolished by prior injection of muscimol into the DMH. Similar microinjection of glutamate receptor antagonists into the DMH also suppressed increases in HR and abolished increases in Tco evoked from the PAG. In contrast, microinjection of muscimol into the hypothalamic paraventricular nucleus failed to reduce changes evoked from the PAG and actually enhanced the increase in Tco. Thus, our data suggest that increases in HR, MAP and Tco evoked from the l/dlPAG require neuronal activity in the DMH, challenging traditional views of the place of the PAG in central autonomic neural circuitry. [source] Peptide YY administration into the posterior hypothalamic nucleus of the rat evokes cardiovascular changes by non-adrenergic, non-cholinergic mechanismsAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 2 2005J. R. Martin Summary 1 Microinjection of peptide YY (PYY) (0.23,2.3 nmol) into the posterior hypothalamic nucleus (PHN) of conscious rats evokes a dose-dependent pressor response and a bradycardia. 2 The increase in mean arterial pressure evoked by 2.3 nmol of PYY was not blocked by intravenous pretreatment with: (i) the nicotinic ganglionic receptor antagonist pentolinium (PENT, 10 mg kg,1) alone, or in combination with the muscarinic receptor antagonist methylatropine (MeATR, 1 mg kg,1); (ii) the ,1 -adrenoceptor antagonist prazosin (PRAZ, 0.2 mg kg,1); (iii) the V1 -vasopressin receptor antagonist [d(CH2)5Tyr(Me)]AVP (AVPX, 20 ,g kg,1); (iv) the combination of AVPX, PENT and MeATR; (v) the combination of PRAZ, AVPX, PENT, MeATR, and the ,2 -adrenoceptor antagonist yohimbine (0.3 mg kg,1); or (vi) the angiotensin II type 1 receptor antagonist ZD 7155 (1 mg kg,1). 3 Adrenal demedullation inhibited the PYY-evoked responses of drug-naïve rats, and rats pretreated with the combination of PENT, MeATR and AVPX. 4 Transection of the splanchnic nerve innervating the adrenal medullae attenuated the bradycardia, as did ZD 7155, but not the PYY-evoked pressor response. 5 Systemic pretreatment of rats with the neuropeptide Y1 receptor antagonist BIBP 3226 (1 mg kg,1) blocked the PYY-evoked cardiovascular changes, but not those evoked by microinjection of carbachol (5.5 nmol) into the PHN. 6 These results suggest that the cardiovascular changes evoked from the PHN by PYY requires the presence of the adrenal medullae, which are stimulated by: (i) a hormone to release an NPY-like substance that evokes the pressor response, and (ii) the splanchnic nerve to evoke the release of a substance that results in the bradycardia. [source] Effects of histamine receptor blockade on cardiovascular changes induced by 35 GHz radio frequency radiation heatingAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 1 2004J. R. Jauchem Summary 1 The role of histamine in heat-induced cardiovascular changes is uncertain. The purpose of this study was to examine effects of histamine H-1- and H-2-antagonism on heart rate, mean arterial blood pressure (MAP), localized body temperature changes, survival times, and lethal body temperatures that occur during the exposure of anaesthetized rats to 35 GHz radio frequency radiation (RFR). 2 Forty-eight ketamine-anaesthetized Sprague,Dawley rats were exposed, in several different treatment groups (n = 8 in each), to 35 GHz RFR at a level that resulted in significant body heating and subsequent death. During irradiation, a continuous increase in heart rate and a biphasic response in blood pressure (initial increase followed by a decrease) were observed in all groups of animals. 3 An H-1-antagonist, diphenhydramine (1 mg kg,1 body wt) and an H-2-antagonist, cimetidine (5 mg kg,1), administered after sustained RFR exposure, failed to reverse the RFR-induced hypotension. High doses of the drugs (5 and 10 mg kg,1, respectively) also did not alter the response. Post-RFR survival time was significantly decreased in the high-dose drug-treated group, compared with vehicle-treated (0.9% NaCl, 50% ethanol and 50% D5W) controls. 4 In experiments in which the two drugs were administered prior to RFR exposure, MAP in animals receiving high-dose antihistamines was significantly depressed compared with that of vehicle-treated animals during the first 35 min of RFR exposure. Antihistamine pretreatment, however, did not alter the total RFR exposure time required for death to occur. 5 In summary, pharmacological blockade of H-1 and H-2 receptors is not beneficial in anaesthetized rats made hypotensive by RFR exposure. This indicates that activation of H-1 and H-2 receptors by histamine does not occur to any significant extent and does not mediate the hypotensive response developed in this model of hyperthermia. [source] Aortic and ventricular dilation and myocardial reduction in gestation day 17 ICR mouse fetuses of diabetic mothersBIRTH DEFECTS RESEARCH, Issue 6 2007J. Claudio Gutierrez Abstract BACKGROUND: Maternal diabetes mellitus is associated with increased fetal teratogenesis, including cardiovascular defects. Information regarding cardiovascular changes in late-gestation fetal mice, related to maternal hyperglycemia, is not present in the literature. METHODS: Late-gestation fetal heart and great vessel morphology were analyzed in fetuses from control and diabetic mice. Female ICR mice were injected with streptozocin (200 mg/kg IP) prior to mating to induce diabetes (n = 8). Nonhyperglycemic females were used as controls (n = 8). At day 17 of gestation, females were euthanized and one fetus was arbitrarily selected per litter to analyze the heart and great vessels. Six additional fetuses from different litters, showing external malformations (spina bifida and/or exencephaly), were also evaluated from the diabetic group. Fetal thoraxes were processed using routine histopathologic techniques, and 7-,m transversal sections were stained with hematoxylin-eosin. Digital images of sections were made and analyzed using NIH Image J software to compare regional cardiac development. Student's t tests for means were performed to determine differences between groups (p < .05). RESULTS: Maternal hyperglycemia caused a dilation of late-gestation fetal ventricular chambers, a reduction of total ventricular myocardial area, and an increase in transversal ascending thoracic aortic area. Three of six fetuses that displayed external malformations showed an overt cardiac defect, beyond the ventricular and myocardial changes. CONCLUSIONS: Maternal hyperglycemia altered morphology of the late-gestation fetal mouse heart. Postnatal persistence or consequences of late-gestation heart chamber dilation and myocardial reduction are not yet known. Birth Defects Research (Part A) 2007. © 2007 Wiley-Liss, [source] Heat stress increases endothelium-dependent relaxations and prevents reperfusion-induced endothelial dysfunctionCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 11 2002Vincent Richard Summary 1.,Heat stress has been widely used to stimulate the expression of stress proteins and is associated with various cardiovascular changes, including anti-ischaemic effects. However, the effect of heat stress on endothelial function is less clear. 2.,Heat stress was induced in anaesthetized rats by increasing body temperature to 42°C for 15 min. Twenty-four hours later, segments of rat aorta and mesenteric and coronary arteries were mounted in organ chambers. 3.,Heat stress markedly increased relaxation to acetylcholine (ACh) in all three blood vessels studied, without affecting the response to the nitric oxide (NO) donor sydnonimine-1. 4.,Heat stress also increased aortic relaxation to histamine and the calcium ionophore A23187. 5.,In the aorta, an inhibitor of NO synthesis abolished the response to ACh in both control and heat stressed-rings, whereas a cyclo-oxygenase inhibitor had no effect. 6.,Heat stress also prevented completely the impaired response to ACh in coronary arteries isolated from rats subjected to myocardial ischaemia and reperfusion. 7.,Thus, heat stress increases the stimulated release of NO the rat aorta and mesenteric and coronary arteries and prevents reperfusion-induced injury at the level of the coronary endothelium. [source] Multiple Inert Gas Elimination Technique For Determining Ventilation/Perfusion Distributions In Rat During Normoxia, Hypoxia And HyperoxiaCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2001V Alfaro SUMMARY 1. The use of the multiple inert gas elimination technique (MIGET) in quantifying ventilation/perfusion distributions (V,A/Q,) in small animals, such as the rat, may cause results to be biased due to haemodilution produced by the large volume of liquid infused intravenously. 2. We tested two methods of administering inert gases in rats using the MIGET: (i) standard continuous intravenous administration of inert gases (method A); and (ii) a new method based on the physicochemical properties of each inert gas (method B). This method included acute simultaneous inert gas administration using three pathways: inhalation, intravenous infusion and rectal infusion. Both MIGET methods were applied to obtain data while breathing three different inspiratory fractions of oxygen (FIO2): normoxia, hypoxia and hyperoxia. 3. Inert gas levels obtained from blood or expired air samples were sufficient for chromatographic measurement, at least during a 2 h period. The V,A/Q, distributions reported using both methods were acceptable for all the physiological conditions studied; therefore, the alternative method used here may be useful in further MIGET studies in rats because haemodilution resulting from continuous intravenous infusion of less-soluble gases can be avoided. 4. Normoxic rats showed lower mean values of the V,A/Q, ratio of ventilation distribution and higher mean values of the V,A/Q, ratio of perfusion distribution with the usual method of inert gas administration (method A). These non-significant differences were observed under almost all physiological conditions studied and they could be caused by haemodilution. Nevertheless, the effect of interindividual differences cannot be discarded. An additional effect of the low haematocrit on cardiovascular changes due to low FIO2, such as pulmonary vasoconstriction or increased cardiac output, may explain the lower dispersion of perfusion distributions found in group A during hypoxia. [source] Exercise capacity and cardiovascular changes in patients with ,-thalassaemia majorCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2006Filippo Tocco Summary Despite the introduction of deferoxamine, 50% of thalassaemia major patients die before the age of 35 years predominantly from iron induced heart failure. Indeed, the assessment of myocardial performance may be of particular interest since it can reveal an early myocardial dysfunction. By using impedance cardiography and mass spectrometry, we studied the cardiac function and the oxygen extraction ratio (O2ER) of 14 thalassaemic patients and 15 control healthy subjects during an incremental cycle-ergometer test. The achieved mechanical power output and the relative O2 uptake did not reach any significant difference between groups. At the highest workload, O2ER reached significantly higher values in thalassaemic patients versus control subjects while the relationship between cardiac index (CI) and O2ER (CI/O2ER) decreased showing a lower contribution of cardiovascular system to maintain O2 uptake. Results of this study imply that CI/O2ER allows an early diagnosis of the iron induced myocardial dysfunction, whereas it is not clinically patent yet. To our knowledge, this is the first study revealing an O2ER pivotal role as compensatory mechanism to maintain a normal working capacity in subjects suffering from thalassaemia major. [source] | |||||||||||||