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At least 811 records · Page 45Linked to original sources
PubMed1999

Morphological adaptation of the cardiovascular system in fetal rats during late gestation.

The aim of this study was to evaluate morphological changes of the cardiovascular system in fetal rats during late gestation. We used the rapid whole-body freezing technique for rats of day 17 through 21 of gestation. The right and left ventricular volumes increased markedly and significantly during this period by about 11- and 24-fold, respectively. Although the right ventricular volume was 108% larger with statistical significance than the left ventricular volume on day 17, they were almost equal after day 19. The length of the primum septum of the atrium significantly increased by 92% within 4 days, but the opening distance of foramen ovale significantly decreased by 14%. The ratio of the inner diameter (the sum of right and left pulmonary arteries to ductus arteriosus) significantly increased from 0.72+/-0.03 on day 17 to 1.17+/-0.07 on day 21. There was also a significant increase in the ratio of the inner diameters of the ascending to descending aorta. These observations suggest that the reduction of the opening distance of foramen ovale reflect the growth of pulmonary arteries.

Adaptation, Physiological↗
PubMed1996

Does corticosteroid metabolism in target organs affect the cardiovascular system?

The target organ metabolism of corticosteroids has been measured with biochemical and immunohistochemical techniques. Attention was focused on the key enzyme system 11 beta-hydroxysteroid oxidoreductase (11 beta-HSOR, EC 1.1.1.146). Several organs of rats, including kidney, colon, testis, pancreas, liver, lung and heart, express oxidative, as well as reductive activity, albeit with different ratios. The specific co-substrate preference in different organs points to the presence of isoforms of the enzyme, which can be inhibited by steroid compounds. In kidney tubules longitudinal heterogeneity of the enzyme distribution pattern has been reported. Inhibition of 11 beta-HSOR in transporting epithelia such as those of kidney and colon by liquorice, glycyrrhetinic acid and others leads to aldosterone-like effects of glucocorticosteroids. The mechanism of this effect is breakdown of the specific 11 beta-HSOR barrier for glucocorticosteroids which subsequently bind to mineralocorticosteroid receptors. Other possible mechanisms of interaction of the corticosteroid metabolism and the cardiovascular system are discussed.

Adrenal Cortex Hormones↗
PubMed1998

P2 receptor subtypes in the cardiovascular system.

Extracellular nucleotides have been implicated in a number of physiological functions. Nucleotides act on cell-surface receptors known as P2 receptors, of which several subtypes have been cloned. Both ATP and ADP are stored in platelets and are released upon platelet activation. Furthermore, nucleotides are also released from damaged or broken cells. Thus during vascular injury nucleotides play an important role in haemostasis through activation of platelets, modulation of vascular tone, recruitment of neutrophils and monocytes to the site of injury, and facilitation of adhesion of leucocytes to the endothelium. Nucleotides also moderate these functions by generating nitric oxide and prostaglandin I2 through activation of endothelial cells, and by activating different receptor subtypes on vascular smooth muscle cells. In the heart, P2 receptors regulate contractility through modulation of L-type Ca2+ channels, although the molecular mechanisms involved are still under investigation. Classical pharmacological studies have identified several P2 receptor subtypes in the cardiovascular system. Molecular pharmacological studies have clarified the nature of some of these receptors, but have complicated the picture with others. In platelets, the classical P2T receptor has now been resolved into three P2 receptor subtypes: the P2Y1, P2X1 and P2TAC receptors (the last of these, which is coupled to the inhibition of adenylate cyclase, is yet to be cloned). In peripheral blood leucocytes, endothelial cells, vascular smooth muscle cells and cardiomyocytes, the effects of classical P2X, P2Y and P2U receptors have been found to be mediated by more than one P2 receptor subtype. However, the exact functions of these multiple receptor subtypes remain to be understood, as P2-receptor-selective agonists and antagonists are still under development.

Adenosine Diphosphate↗
PubMed2004

Evaluation of the teaching strategy of cardiovascular system in a problem-based curriculum: student perception.

It is generally acknowledged that an integrated approach to teaching cardiovascular system (CVS) is clinically relevant. However, very little attention has been paid with respect to student perception of teaching CVS in an integrated problem-based curriculum. A questionnaire on the feedback and perception of medical students (n = 60) to their learning experience of CVS exposed early in the problem-based integrated curriculum at the Arabian Gulf University (AGU) was used. The average percentage scores of positive student responses to items related to knowledge was 62.7%, to integration was 87.3%, and to skills was 77.1%. A significant positive correlation was observed among skills and knowledge (r = 0.408, P = 0.002), skills and integration (r = 0.506, P < 0.000), and integration and knowledge (r = 0.294, P = 0.028). The lowest individual percentage score related to knowledge items was given to the role of resource sessions in understanding difficult concepts (32.7%). Interestingly, 90.7% of the students were aware of the presence of gaps in their knowledge. On the other hand, 92.7% of students expressed their satisfaction with the study experience of CVS in the integrated problem-based approach. These results indicate that students overall achieved satisfactory learning outcome during the study of CVS in the problem-based integrated curriculum at AGU. The study also points out issues where improvement and fine tuning of the educational system can take place.

Education, Medical↗
PubMed2006

Quantitative evaluation of interrelations between spontaneous low-frequency oscillations in cerebral hemodynamics and systemic cardiovascular dynamics.

A common issue in blood-related brain-function measurements, such as optical topography, is that the observed signals are usually corrupted with strong noise that is primarily spontaneous low-frequency oscillations (LFOs) in cerebral hemodynamics, which are difficult to separate from the signals due to functional brain activity because of their common spectral range. We discuss the analysis of information transfer between LFOs around 0.1 Hz in the hemoglobin concentration change (HbCC) in the cerebral cortex, the heart rate (HR), and the mean arterial blood pressure (ABP) to understand the origin of spontaneous LFOs in cerebral hemodynamics. As measures of information transfer, we used transfer entropy (TE) for two-variable system analysis and introduced intrinsic transfer entropy for further analysis of three-variable systems by extending the original TE. Data for analysis were obtained from simultaneous measurements with optical topography and infrared finger plethysmography under rest conditions. The analysis revealed that the LFOs in oxy HbCC, a parameter of cerebral hemodynamics, mainly stem from HR, but its contribution is only about 20%. In addition, the intrinsic contribution of ABP is about 5% and the common contribution of HR and ABP is about 10%. From these, HR and ABP cannot account for more than the half the information carried with variable oxy HbCC, which suggests the origin of LFOs in cerebral hemodynamics may lie in the regulation of regional cerebral blood flow change and energetic metabolism rather than due to the systemic regulation of the cardiovascular system.

Aged↗
PubMed1971

Comparison of the effects of isoprenaline, orciprenaline, salbutamol and isoetharine on the cardiovascular system of anaesthetized dogs.

1. The intravenous injection of isoprenaline, orciprenaline, salbutamol and isoetharine increased heart rate in anaesthetized dogs. Log dose-response curves obtained with a series of doses of salbutamol and isoetharine were flatter than those for isoprenaline and orciprenaline. The order of activity of the drugs in increasing heart rate was isoprenaline, orciprenaline, and salbutamol=isoetharine.2. The injection into the external iliac artery of isoprenaline, orciprenaline, salbutamol and isoetharine produced dose dependent increases in femoral blood flow. Log dose-response curves for all drugs were parallel. The order of activity of the drugs was isoprenaline, salbutamol=isoetharine and orciprenaline.3. Salbutamol and isoetharine were less active than orciprenaline in increasing heart rate but more active in increasing femoral blood flow.4. These observations indicate that salbutamol and isoetharine have a greater effect on beta(2) than on beta(1)-adrenoceptors in the cardiovascular system.

Amino Alcohols↗
PubMedDate not supplied

Effects of some catecholamines on the cat cardiovascular system: interactions with adrenoceptor antagonists.

The effects of intravenous infusions of norepinephrine, epinephrine, isoproterenol, N-t-butylnorepinephrine, oxymethyleneisoproterenol, and RO363 on heart rate, mean arterial blood pressure, cardiac output, total peripheral resistance, and stroke volume were evaluated in chloralose-anaesthetized cats before and after phentolamine, propranolol, atenolol, and butoxamine. Pressor responses to both norepinephrine and epinephrine largely resulted from alpha-receptor-mediated increases in total peripheral resistance. Vasomotor reversal was noted with both drugs in the presence of alpha-receptor blockade. Dilator responses to norepinephrine were abolished by the beta 1-receptor selective antagonist atenolol, as were those to the beta 1-receptor selective agonists oxymethyleneisoproterenol and RO363. Dilator responses to epinephrine were abolished by the beta 2-receptor selective antagonist butoxamine, as were those to N-t-butylnorepinephrine (beta 2-selective) and isoproterenol (nonselective). These results indicate that in addition to beta 2-receptors, beta 1-receptors subserving vasodilatation occur in the cat vasculature. Atenolol displayed agonist-dependent inhibition of the cardiac responses. Responses to noradrenaline, RO363, and oxymethyleneisoproterenol were blocked to a greater extent than were those to epinephrine, N-t-butylnorepinephrine, and isoproterenol. Butoxamine did not display any marked agonist-dependent inhibition of cardiac responses. Nevertheless, the results are in accord with previous suggestions that cardiostimulant beta 2-receptors exist in the cat heart. Interpretation of the actions of catecholamines may be complicated by mixed beta-adrenoceptor populations in the cat cardiovascular system.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

L-arginine and cardiovascular system.

L-arginine is a basic endogenous amino acid. Its significant metabolic role as the product of ammonia detoxification, the urea cycle metabolite, the precursor of proteins, ornithine, urea and creatinine, and the amino acid involved in the formation of active enzyme centers was very well established. The current interest in this amino acid refers mainly to its close relation with an important signal molecule nitric oxide (NO). Literature review demonstrates that L-arginine, the only substrate of the NO production, affects cardiovascular system (blood vessels and heart). The majority of experimental and clinical studies clearly show a beneficial effect of L-arginine on endothelium in conditions associated with its hypofunction and thus with reduced NO synthesis. Some clinical studies involving healthy volunteers or patients suffering from hypertension and diabetes indicate that it may also regulate vascular hemostasis. Moreover, experiments performed on animals and in vitro data also suggest that L-arginine may have a complex antiaggregatory, anticoagulatory and profibrinolytic effect. Therefore, a novel therapeutic potential of L-arginine should be taken into consideration.

Animals↗
PubMed1980

Effects of delta-9-tetrahydrocannabinol on the cardiovascular system, and pressor and behavioral responses to brain stimulation in rats.

Effects of delta-9-tetrahydrocannabinol (delta 9-THC) on the cardiovascular system, and pressor and behavioral responses to brain stimulation were investigated in rats. In urethane-anesthetized rats, intravenous administration of delta 9-THC (1, 2 and 5 mg/kg) produced a significant and transient dose-related rise but no fall in blood pressure. delta 9-THC at these doses also produced marked reduction in heart rate which was antagonized by atropine (0.5 mg/kg i.v.) or bilateral vagotomy. In freely moving rats with chronically implanted electrodes and arterial cannula implants, intraperitoneal administration of delta 9-THC (4, 6 and 8 mg/kg) induced a rise in blood pressure and marked bradycardia. Abnormal behavior such as catalepsy, walking backwards and pivoting was also observed. delta 9-THC failed to inhibit the pressor responses to electrical stimulation of the posterior hypothalamus and midbrain reticular formation, whereas the drug suppressed the behavioral responses to stimulation of both regions. It is concluded that the cardiovascular effects seen with delta 9-THC injection are mainly the result of alteration of the efferent vagal activity by acting on the central nervous system and a more potent influence is exerted on the behavioral changes than on autonomic responses to brain stimulation.

Anesthesia↗
PubMed1988

Fundamentals of laser light interaction with human tissue, especially in the cardiovascular system.

The absorption of single photons in the molecules of biological tissue can induce various reactions. For the most medical laser applications the transformation from radiation energy into heat is relevant. The laser beam is used for coagulation or vaporization of tissue. The changes in tissue, which are created by light of different wavelengths depends on the thermal and optical properties (absorption and scatting) of tissue but also on the parameters of irradiation. As an example measurements from human skin are discussed. In the cardiovascular system laser light must have a clearly defined effect. Atherosclerotic plaques of different consistence have to be vaporized without damage of the vessel walls. From different reasons the usual medical CW-lasers, Argon-laser, CO2-laser and Nd:YAG-laser, are not optimal for direct ablation of arterial occlusions. In order to mimize reocclusion the walls of the channels have to be completely smooth and free of coagulation necrosis. This can be obtained by short laser pulses. Selection of a light wavelength, which is stronger absorbed in atherosclerotic plaques than in vessel walls and additional selective staining are two ways to reduce the risk of damaging the vessel walls.

Cardiovascular Diseases↗
PubMed2001

Effects of exercise training on baroreflex control of the cardiovascular system.

Dynamic exercise training has been recommended as an antihypertensive therapy and as a way to modify the effects of many cardiovascular risk factors (Arakawa, 1993; Arroll and Beaglehole, 1992; Kelly and McClellan, 1994: see references 1-3 in the paper). However, the mechanisms underlying the blood-pressure lowering effect of chronic exercise are still poorly understood. It has been suggested that a decrease in sympathetic tone is one of the major effects elicited by chronic exercise on the cardiovascular system. The importance of the sympathetic component is confirmed in this review, since it was found that in spontaneously hypertensive rats (SHR) a marked decrease in sympathetic activity occurred after exercise training. Moreover, our findings suggest that this effect is mediated by improving the depressed baroreceptor function, which is, in part, responsible for the attenuation of the baroreflex sensitivity observed in the sedentary SHR (Krieger et al., 1998, 1999; see references 4 and 5 in the paper).

Animals↗