A practical study of the air chamber model of the cardiovascular system.
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Cardiovascular System↗
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[The state of the cardiovascular system in children with Botkin's disease].
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Cardiovascular System↗
[Passive raising of the body to the vertical at different angular speeds; behavior of cardiovascular system].
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Cardiovascular System↗
Bradykinin and related peptides in central control of the cardiovascular system.
The evidence for a brain kallikrein-kinin system and for the possible role for kinins in brain control of the cardiovascular system are reviewed. All components of the kallikrein-kinin system are present in brain and kinins have a variety of cardiovascular actions of central origin following peripheral, intracerebroventricular or brain parenchymal administration. How components of the brain kallikrein-kinin system are regulated or even whether they function as a system remains to be established. However, bradykinin does fulfill several of the criteria necessary for establishing a substance as a neurotransmitter and these are discussed.
Animals↗
Periconceptional nutrition programs development of the cardiovascular system in the fetal sheep.
It has been proposed that fetal adaptations to intrauterine nutrient deprivation permanently reprogram the cardiovascular system. We investigated the impact of restricted periconceptional nutrition and/or restricted gestational nutrition on fetal arterial blood pressure (BP), heart rate, rate pressure product, and the fetal BP responses to ANG II and the angiotensin-converting enzyme inhibitor captopril during late gestation. Restricted periconceptional nutrition resulted in an increase in fetal mean arterial BP between 115 and 125 days gestation (restricted 41.5 +/- 2.8 mmHg, n = 12; control 38.5 +/- 1.5 mmHg, n = 13) and between 135 and 147 days gestation (restricted 50.5 +/- 2.2 mmHg, n = 8; control 42.5 +/- 1.9 mmHg, n = 10) as well as an increase in the rate pressure product in twin, but not singleton, fetuses between 115 and 147 days gestation. Mean BP and fetal plasma ACTH were also positively correlated in twin, but not singleton, fetuses. This is the first demonstration that maternal undernutrition during the periconceptional period results in an increase in fetal arterial BP. This increase occurs concomitantly with an increase in fetal ACTH but is not dependent on activation of the fetal renin-angiotensin system.
Adrenocorticotropic Hormone↗
Effects of isoflurane on cardiovascular system and sympathovagal balance in New Zealand white rabbits.
We investigated the effects of isoflurane on the rabbit cardiovascular system at several end-tidal concentrations. Furthermore, because isoflurane has been reported to produce tachycardia while reducing sympathetic nervous activity and baroreflex function, we evaluated whether the chronotropic effects of isoflurane could be due to a vagal withdrawal. ECG, mean arterial pressure (MAP), and heart rate (HR) were obtained in rabbits the conscious, unsedated state and during isoflurane anesthesia by telemetric device. Measurements of pH, oxygen, carbon dioxide, plasma catecholamines, baroreflex sensitivity, and spectral analysis of HR variability were made in nonanesthetized and anesthetized animals. Isoflurane caused an increase in HR at 0.5, 1, and 1.5 minimum alveolar concentration (MAC) and a decrease in systolic and diastolic blood pressure (SBP, DBP) and MAP at 1 and 1.5 MAC. Biochemical analysis showed that isoflurane-mediated cardiovascular effects were not accompanied by any significant changes in plasma norepinephrine (NE) and epinephrine (Epi) levels. Neither were any significant differences in plasma catecholamine levels noted between anesthetized and awake animals. The analysis of spectral components of HR variability and baroreflex function indicated that isoflurane induced a marked reduction in the low- and high-frequency spectral power of HR variability and in baroreflex sensitivity. Tachycardia under isoflurane was suppressed dose dependently by the administration of clonidine or atenolol and was not influenced by bilateral vagotomy. Collectively, our results indicate that cardiovascular effects induced by isoflurane in smaller animals such as rabbits are similar to those observed in humans and other animal species. We showed that isoflurane-induced tachycardia is mainly the result of vagal withdrawal rather than a baroreflex response, even though a marginal role of baroreflex in heart response to higher concentrations of isoflurane cannot be excluded.
Anesthetics, Inhalation↗
Recent progress in angiotensin II type 2 receptor research in the cardiovascular system.
Angiotensin II (Ang II) plays an important role in regulating cardiovascular hemodynamics and structure. Multiple lines of evidence have suggested the existence of Ang II receptor subtypes, and at least 2 distinct receptor subtypes have been defined on the basis of their differential pharmacological and biochemical properties and designated as type 1 (AT1) and type 2 (AT2) receptors. To date, most of the known effects of Ang II in adult tissues are attributable to the AT1 receptor. Recent cloning of the AT2 receptor contributes to reveal its physiological functions, but many functions of the AT2 receptor are still an enigma. AT1 and AT2 receptors belong to the 7-transmembrane, G protein-coupled receptor family. However, accumulating evidence demonstrates that the function and signaling mechanisms of these receptor subtypes are quite different, and these receptors may exert opposite effects in terms of cell growth and blood pressure regulation. We will review the role of the AT2 receptor in the cardiovascular system and the molecular and cellular mechanisms of AT2 receptor action.
Adult↗
[Effects of oral hypoglycemic agents, gliclazide and tolbutamide, on the cardiovascular system (author's transl)].
Recent clinical studies have suggested an association of tolbutamide (TB) therapy with an increased incidence of cardiovascular deaths. In this study, the effects of a newly synthetized hypoglycemic agent, gliclazide (GC), on the cardiovascular system were investigated, and compared with those of TB. Results are as follows: GC was found to be about ten times as active as TB in decreasing blood glucose in rabbits. GC and TB produced a dose-dependent increase in blood pressure and little change in heart rate in rats and rabbits. In driven left rat and rabbit atria, these agents produced a positive inotropic effect. The positive inotropic effects of these drugs were not altered by pretreatment with propranolol, or theophylline. These agents produced little change in the rate in spontaneous beating rat, rabbit and guinea pig atria. Higher doses produced a slightly negative chronotropic response. Neither agent potentiated the intropic effects of isoproterenol on the rabbit and guinea pig left atria. In isolated perfused working rabbit hearts, these compounds produced a slight decrease in coronary flow. It is concluded that GC and TB possess positive inotropic effects on isolated atria, and these effects are not mediated either through adrenergic mechanisms or the cyclic AMP system.
Animals↗
Medical evaluation of the cardiovascular system.
The approach to pre-purchase evaluation of the equine cardiovascular system is discussed with emphasis on cardiac auscultation and on the terminology that should be used when reporting clinical findings. Innocent cardiac murmurs and arrhythmias are contrasted with those that should be considered as reliable signs of cardiovascular disease. Ultrasonography and electrocardiography are recommended to establish baseline values for future reference, to support opinions rendered by the examining veterinarians, or to provide for diagnosis and treatment.
Animals↗
Normal and pathological distribution of nitric oxide in the cardiovascular system.
Using microsensors, it is possible to quantify the amount and concentration of nitric oxide (NO) release throughout the cardiovascular system in veins, arteries and the heart. Under normal physiological conditions a well defined distribution of NO is maintained. This concentration depends++ on the laminar, turbulent, or pulsatile flow rate of blood. Significantly reduced production of NO is observed in the pathogenesis of cardiovascular disorders like hypertension, atherosclerosis and diabetes. This is due to increased generation of superoxide by a dysfunctional endothelium and the rapid formation of peroxynitrite followed by formation of peroxynitrite followed by the formation of highly reactive OH and NO2 radicals and NO2+. Elevated concentration or improved mass transport of L-arginine and (6)-5,6,7,8-tetrahydrobiopterin can be applied to increase/decrease NO/superoxide release by the dysfunctional endothelium.
Animals↗
Pharmacology of gap junctions in the cardiovascular system.
Gap junction channels provide the basis for intercellular communication and play an important physiological role in the cardiovascular system for maintenance of the normal cardiac rhythm, regulation of vascular tone, endothelial function and myoendothelial interaction as well as for metabolic interchange between the cells. Thus, pharmacological influence on these channels might help to elucidate their role in physiology and pathophysiology and might reveal new therapeutic approaches. The gap junction conductance between two cells is defined by the number of channels, the single channel conductance and the mean open and closed time. In principle, it is possible pharmacologically to induce closing of the channels, to change preferred single channel conductance, to open channels (or to keep them open), and to regulate the expression, synthesis, assembly and degradation of the channels thereby controlling the number of channels. This review describes the various substances affecting these parameters and outlines the possible pharmacological use of such drugs.
Animals↗
Time-related changes of the cardiovascular system during maintenance anesthesia with sevoflurane and isoflurane in horses.
To clarify time-related changes in equine cardiovascular system during maintenance anesthesia (180 min, 1.2 minimum alveolar concentration) with sevoflurane (Sev-group) compared to isoflurane (Iso-group) as the basis for clinical use of Sev, horses were examined for the heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), systemic vascular resistance (SVR) and pre-ejection period (PEP)/ejection time (ET) that is an index of the cardiac contractility. The HR was almost 30 beats/min in both groups without significant temporal change. MAP was significantly elevated with time but there was no significant difference between the groups. In the Sev-group, CI remained unchanged but the significant increase of CI with time was observed in the Iso-group. In the Sev-group SVR was significantly higher than that of the Iso-group and increased with time. No significant difference of PEP/ET was seen between the groups, but PEP/ET lowered with time in the Iso-group in association with prolonged ET. The results indicated that the time-dependent elevation of MAP in the Sev-group reflected increased SVR without increase of CI and that it reflected increased CI resulting from increased stroke volume in the Iso-group in association with lowered PEP/ET, that is, increased cardiac contractility.
Anesthesia, Inhalation↗
Acute effects of exercise on the cardiovascular system.
Exercise presents a major stress to the circulatory system. This article reviews the physiologic effects of acute exercise on the healthy cardiovascular system and contrasts them with the altered effects seen in selected cardiac conditions. The following topics are covered: oxygen production and utilization, isometric versus dynamic exercise, responses to dynamic exercise, and selected clinical applications. The major focus is on the acute effects of dynamic exercise.
Body Temperature Regulation↗
The effects of pergolide on the cardiovascular system of 40 patients with Parkinson's disease.
The effect of pergolide, a semisynthetic ergot alkaloid, on the cardiovascular system of 40 patients with Parkinson's disease (PD) was evaluated. The mean daily dose of pergolide was 2.4 mg (range, 0.1 to 10 mg). The mean duration of follow-up was 6 months (range, 2 weeks to 20 months). The 40 patients were selected only on the basis of severe PD. All 13 patients in the first part of the study underwent 1 to 5 days of Holter monitoring before starting pergolide. Monitoring was then carried out for an additional period of between 2 and 10 weeks while the patients were on pergolide. Seven of the 13 patients manifested repetitive ventricular rhythms. These were isolated and unassociated with increases in premature ventricular contractions. The dose at which the RVRs occurred was a function of the presence or absence of heart disease. The changes occurred below 3 mg/day in patients with heart disease and above 3 mg/day in patients without heart disease. Pergolide was discontinued in three of the patients with heart disease. It was concluded that pergolide may, in the diseased heart, predispose to RVRs. In the second part of the study, Holter monitoring was carried out only at the discretion of the cardiologist, and five patients were so monitored. None of these patients was rejected from the study. Only one patient (with heart disease) of the 27 patients in the second part of the study experienced an arrhythmia. This consisted of an increase in PVCs on 4 mg/day of pergolide. Pergolide was discontinued. Eight of the 40 patients in these early dose-ranging studies experienced orthostasis, two with syncope, immediately on addition of pergolide (0.1 to 0.4 mg) to levodopa. The orthostasis could be eliminated in all but two patients by reducing or discontinuing levodopa.
Adult↗
Estrogen modifies stress response of catecholamine biosynthetic enzyme genes and cardiovascular system in ovariectomized female rats.
Estrogen is likely involved in the gender specific differences in coping with stress. Activation of catecholamine (CA) biosynthetic enzyme gene expression in central and peripheral CA systems plays a key role in response to stress and in regulation of the cardiovascular system. Here we examined whether estradiol can modulate response of hypothalamic-pituitary-adrenal axis (HPA), gene expression of enzymes related to CA biosynthesis in several noradrenergic locations, tetrahydrobiopterin (BH4) concentration and blood pressure (BP) in response to immobilization stress (IMO) of ovariectomized female rats. Rats were injected with 25 mug/kg estradiol benzoate (EB) or sesame oil once daily for 16 days and subsequently exposed to two hours of IMO. The IMO triggered elevation in plasma ACTH was lessened in EB-pretreated animals. However, estradiol did not alter the IMO-elicited rise of tyrosine hydroxylase mRNA levels in adrenal medulla (AM) and in the nucleus of solitary track (NTS) compared with controls. The response of GTP cyclohydrolase I (GTPCH) mRNA in AM to IMO was also similar in both groups. Several responses to IMO in EB-treated rats were reversed. Instead of IMO-elicited elevation in dopamine beta-hydroxylase mRNA levels in the locus coeruleus, GTPCH mRNA and BH4 levels in the NTS, they were reduced by IMO. In a parallel experiment, BP was monitored during restraint stress. The elevation of BP in response to single or repeated restraint stress was sustained during 2 h in controls and reduced after 70 min stress in EB treated rats. One month after withdrawal of EB treatment, the BP response to restraint was similar to that of rats which never received EB. The results demonstrate that estrogen can modulate responses to stress affecting HPA axis, CA biosynthesis, in central and peripheral noradrenergic systems, and BP.
Adrenal Medulla↗
[Effects of 2-(4-benzyl-piperidino)-1-(4-hydroxyphenyl)-1-propanol (ifenprodil) on the cardiovascular system in vivo].
Effects of ifenprodil (2-(4-benzyl-piperidino)-1-(4-hydroxyphenyl)-1-propanol) tartrate on the cardiovascular system were studied in mongrel dogs anesthetized with pentobarbital sodium and with alpha-chloralose and in rabbits. Ifenprodil (12.5 to 5,000 mug/kg i.v.) lowered systemic blood pressure in a dose-dependent manner in association with increased heart rate and augmented myocardial contractile force in dogs. Fall in blood pressure and tachycardia caused by ifenprodil were inhibited by pretreatment with phenoxybenzamine (5 mg/kg). The pressor responses to adrenaline and bilateral carotid occlusion were moderately reduced by pretreatment with ifenprodil (5 mg/kg), while the response to noradrenaline was attenuated only slightly. Ifenprodil (less than 1 mg/kg i.v.) decreased the total peripheral resistance and resistances of common carotid, internal carotid, vertebral, coronary, superior mesenteric, renal and femoral vascular beds in dogs. Ifenprodil increased the vertebral and femoral blood flow consistently (93.6 and 174.0%, respectively) but decreased the renal blood flow. Intra-arterial injection of ifenprodil (0.01 to 5 mug/kg) produced a dose-dependent increase in blood flow of vascular beds tested. The femoral and vertebral arterial blood flows were in particular consistently increased. Increases in the vertebral and femoral blood flows following i.v. and i.a. injections of ifenprodil were only slightly attenuated by pretreatment with phenoxybenzamine. Intravenous injections of ifenprodil (12.5 to 5,000 mug/kg) produced tachycardia in conscious rabbits but caused bradycardia after pretreatment with reserpine. From these results it was revealed that ifenprodil causes a fall in systemic blood pressure and an increase in the blood flow particularly in vertebral and femoral vasculatures following the vasodilating action directly on vascular smooth muscle. Blocking action of alpha-adrenoceptors in vessels was also demonstrated.
Animals↗
Short-term autonomic nervous control of the cardiovascular system: a system theoretic approach.
A non-linear model of the human cardiovascular regulation system (CVS) has been developed, with the aim of studying the short-term regulation process by the autonomic nervous system (ANS). This restricts the time interval under study to range from fractions of seconds to about 30 seconds. As a consequence, the only feedback mechanism taken into account is the baroreceptors loop. Our main guideline has been first to try to capture the main features of the system that have been observed and reported in the relevant publications in physiology--main non-linearities in the elementary components of the system, intrinsic periodicities--while keeping to a minimum the number of model parameters, with the question of identifiability from real data in mind. Also, we have tried to retain as much physiological significance to these parameters as possible, for forthcoming diagnosis purposes, while using non invasive measurements only. At the present time, no venous return has been taken into account but should be included later on. The long term objective of this research is to develop tools for helping in medical diagnosis. This may go through the detection of defaults in this closed loop system, within the framework of control systems theory, hereby using all the known concepts from that field, that have been much used for engineering systems (mechanical, electrical etc...): these include signal processing techniques as well as control algorithms or identification and detection methods.
Autonomic Nervous System↗
Heart rate variability biofeedback as a method for assessing baroreflex function: a preliminary study of resonance in the cardiovascular system.
This study describes the use of a biofeedback method for the noninvasive study of baroreflex mechanisms. Five previously untrained healthy male participants learned to control oscillations in heart rate using biofeedback training to modify their heart rate variability at specific frequencies. They were instructed to match computer-generated sinusoidal oscillations with oscillations in heart rate at seven frequencies within the range of 0.01-0.14 Hz. All participants successfully produced high-amplitude target-frequency oscillations in both heart rate and blood pressure. Stable and predictable transfer functions between heart rate and blood pressure were obtained in all participants. The highest oscillation amplitudes were produced in the range of 0.055-0.11 Hz for heart rate and 0.02-0.055 Hz for blood pressure. Transfer functions were calculated among sinusoidal oscillations in the target stimuli, heart rate, blood pressure, and respiration for frequencies at which subjects received training. High and low target-frequency oscillation amplitudes at specific frequencies could be explained by resonance among various oscillatory processes in the cardiovascular system. The exact resonant frequencies differed among individuals. Changes in heart rate oscillations could not be completely explained by changes in breathing. The biofeedback method also allowed us to quantity characteristics of inertia, delay, and speed sensitivity in baroreflex system. We discuss the implications of these findings for using heart rate variability biofeedback as an aid in diagnosing various autonomic and cardiovascular system disorders and as a method for treating these disorders.
Adult↗