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Biomedical subjects

R S Reneman

Publications and source records attributed to R S Reneman.

At least 271 records · Page 15Linked to original sources
PubMed1984

Cardiovascular and some respiratory effects of high doses of alfentanil in dogs.

The cardiovascular and some respiratory effects of alfentanil, a potent and short-acting morphinomimetic, were studied in conscious (n = 6) and anaesthetized, artificially ventilated dogs (n = 7). The compound was injected intravenously in increasing doses of 12.5, 12.5, 25, 50, 100, 200, 400 and 800 micrograms X kg-1 in the conscious dogs and of 0.16, 0.32, 0.64, 1.25, 2.5 and 5 mg X kg-1 in the anaesthetized animals. In the conscious dogs, the heart rate decreased significantly reaching a maximum decrease after the injection of 400 micrograms X kg-1 X PCO2 and arterial and venous lactate concentrations increased, while PO2, pH and base excess decreased significantly. At higher dose levels (100-400 micrograms X kg-1) short periods of convulsions were seen. The most pronounced change in the anaesthetized dogs was a significant fall in LVdP/dt max and LV dP/dt max/P, associated with a rise in left ventricular end-diastolic pressure following the injection of 5 mg X kg-1, suggesting negative inotropic properties at this high dose level. Most of the animals showed A-V dissociations which disappeared at higher doses. All animals survived. These findings indicate that alfentanil is a safe analgesic as far as the effects on the cardiovascular system are concerned. High doses are tolerated well, especially when the animals are artificially ventilated. The short periods of convulsions, seen only in the awake dogs, may have been facilitated by the low PO2 levels reached (median value: 9 kPa).

Alfentanil↗
PubMed1984

Platelet-vessel wall interactions: implication of 5-hydroxytryptamine. A review.

The evidence for an impact of platelet-derived 5-hydroxytryptamine (5-HT) on local tissue perfusion is reviewed. By interacting with 5-HT2 serotonergic receptors, 5-HT, directly or through amplification, activates platelets, endothelial and vascular smooth muscle cells producing platelet aggregation, vascular permeability increase and large vessel constriction. Pharmacodissection in experimental animals with selective serotonergic 5-HT2 receptor antagonists, e.g. ketanserin, shows that 5-HT largely contributes to the platelet-mediated increase in vascular permeability, to platelet-vessel wall interaction during hemostasis, to cardiopulmonary dysfunction provoked by thromboembolism and to the platelet-mediated inhibition of peripheral collateral circulation. Clinical results obtained with ketanserin further substantiate an involvement of platelet-derived 5-HT in the pathogenesis of impaired tissue perfusion in some cardiovascular conditions.

Animals↗
PubMed1984

Fiber shortening in the inner layers of the left ventricular wall as assessed from epicardial deformation during normoxia and ischemia.

A mathematical model of left ventricular mechanics predicts that fiber shortening in the inner layers of the left ventricular wall can be estimated (eendo, est) from the magnitude of minimal (emin, o) and maximal shortening (emax, o) of the outer surface (= epicardium) of this wall. To evaluate this prediction, eendo, est and emin, o were compared with the shortening in the inner layers approximately along the fiber direction (eendo) as measured directly, before and during one minute of coronary artery occlusion. Deformation of the epicardium and the inner layers was determined by measuring mutual motion and angulation of three needles pierced into the myocardial wall, using an electromagnetic inductive technique. The proposed linear relations of eendo, est and emin, o with eendo were found to be significant. The needles hardly influenced wall deformation since similar values of epicardial deformation were found in separate, comparable, experiments (n = 13) using a triplet of epicardial coils. So eendo, est and emin, o are useful estimates of fiber shortening in the inner layers during normoxia and ischemia, especially when the time course of events is followed in the same animal.

Animals↗
PubMed1984

Torsion of the left ventricle during the ejection phase in the intact dog.

Torsion of the left ventricle (LV) is associated with rotation of the apex with respect to the base around the long axis of the LV. A mathematical model of LV mechanics, which relates torsion to transmural distribution of fibre shortening, was evaluated with two-dimensional echocardiography in nine anaesthetised closed-chest dogs. Torsion was calculated as the difference between the angles of rotation (radians) of echo-derived transverse cross-section projections of the LV obtained at the mitral valve and low papillary level, divided by the axial distance between these projections measured in a long-axis cross-section, and multiplied by the outer radius in a mid-papillary transverse projection of the LV. A shortening to torsion ratio (STR) was defined as the ratio of inner wall shortening to torsion occurring during ejection. In a series of 11 measurements, each based on frame-to-frame analysis of 15 cardiac cycles, STR was found to be 2.31 +/- 0.23 rad-1 (mean +/- SD), whereas the mathematical model predicted a STR value of 2.4 rad-1 over a wide range of preload, afterload and contractility levels. We conclude that two-dimensional echocardiography validates the presence of torsion in the normal canine left ventricle, as predicted by the model of left ventricular mechanics.

Animals↗
PubMed1984

Accumulation of nonesterified fatty acids in ischemic canine myocardium.

In ischemic myocardium the time course of nonesterified fatty acid (NEFA) accumulation was studied in relation to changes in regional metabolism and mechanics. In open-chest dogs a coronary artery was partially occluded for 120 min. In the ischemic myocardium no increase was observed in NEFA content within 10 min, whereas changes were found in regional shortening, high-energy phosphate content, and glucose arteriologcal venous difference. During prolonged ischemia NEFA content increased, the highest values being found in the inner and middle layers after 120 min (112 and 85 nmol X g-1, respectively; control values 30); the value in the outer layers after 60 min was 93 nmol X g-1. After 120 min of ischemia, accumulation of NEFA generally occurred when myocardial blood flow was below 0.3 ml X min-1 X g-1 and ATP content was below 10 mumol X g dry wt-1. Under these circumstances the individual NEFA with the highest relative increase was arachidonic acid. The present findings indicate that the changes in mechanical function and metabolism, as observed in myocardium rendered ischemic for 10 min, are not caused by increased NEFA content and that NEFA accumulation may partly result from hydrolysis of glycerophospholipids.

Adenosine Triphosphate↗
PubMed1984

Orientation and diameter distribution of rabbit blood platelets flowing in small arterioles.

Spatial orientation of blood platelets flowing in small arterioles of the rabbit mesentery was investigated using intravital fluorescence microscopy. Only platelets were studied that could be localized objectively within a thin optical section around the median plane of the vessel. The orientation of a platelet was assessed from its microscopic image and described by an angle pair, assuming the platelet to be an ellipsoidal body and using an empirical frequency distribution for its thickness to diameter ratio. The orientation of the platelets was not random; they tended to align themselves with their equatorial planes parallel to the wall. The degree of alignment increased from the center of the vessel toward the wall. As a corollary a frequency distribution of their diameter (3.15 +/- 0.72 micron (mean +/- sd) was obtained in vivo.

Animals↗
PubMed1984

Rheological behavior of blood platelets in vivo.

Blood platelets labeled in vivo with the fluorochrome acridine red can be localized objectively within a thin optical section, using fluorescence microscopy. This allows the study of the rheological behavior of platelets in vivo as exemplified by the assessment of the concentration distribution and the orientation of platelets flowing in small arterioles of the rabbit mesentery.

Animals↗
PubMed1984

Cardiac and haemodynamic effects of intravenous administrations of flunarizine in closed-chest anaesthetized mongrel dogs.

This study was performed to evaluate the cardiac and haemodynamic effects of 1-cinnamyl-4-[bis(p-fluorophenyl)methyl]piperazine dihydrochloride (flunarizine, Sibelium ). The compound was dissolved in distilled water acidified with tartaric acid in a concentration of 2 mg/ml (pH 1.8) and administered intravenously in cumulative doses of 0.03, 0.1, 0.3, 1.0, and 3.0 mg/kg. Flunarizine induced systemic vasodilatation dose- relatedly starting with a dose of 0.1 mg/kg i.v. as indicated by the decrease in systemic vascular resistance, while this compound had no vasodilating properties in the pulmonary circulation. Flunarizine caused an increase in heart rate following the administration of the higher doses. This effect is probably reflexogenic in nature and secondary to the decrease in aortic blood pressure. As a consequence the oxygen demand of the myocardium enhanced after these high doses of flunarizine as indicated by the increase in pressure-rate product. Flunarizine did not affect the contractility and the conduction of the heart in the doses of 0.03 up to and including 1.0 mg/kg i.v., but could have some negative inotropic properties at the highest dose used. The end-tidal CO2 concentration in the expired air increased after the administration of 0.3 up to and including 3.0 mg/kg i.v. From these results, it is concluded that flunarizine has systemic vasodilating properties without any cardiac effects at doses from 0.03 up to and including 1.0 mg/kg i.v.

Animals↗
PubMed1983

Serum-myocardium gradients of non-esterified fatty acids in dog, rat and man.

In the three species under investigation (dog, rat and man) a gradient from serum to heart tissue for total non-esterified fatty acids was assessed. The ratios serum/left ventricular tissue in dogs, serum/right auricular appendage in dogs, serum/whole heart tissue in rats and serum/right auricular appendage in man were found to be 6.4, 2.5, 5.6 and 2.8, respectively. The highest gradient was found for oleic acid, whereas no significant gradient for arachidonic acid could be detected. In the dog the arterio:local venous differences of non-esterified fatty acids across the left ventricular tissue correlated better with the serum/tissue ratio of non-esterified fatty acids than with the arterial non-esterified fatty acid level. Since the correlation coefficient (0.74) was still far from excellent, more factors than the non-esterified fatty acid serum/tissue gradient are likely to be involved in determining the extent to which non-esterified fatty acids are extracted by myocardial tissue.

Animals↗
PubMed1983

Cardiac dimensions in athletes in relation to variations in their training program.

The cardiac dimensions of male long-distance runners (LDR) and cycle racers (CR) were determined echocardiographically during four different training seasons, i.e., a preparation, a competitive, a slowing-down and a resting season, and were compared with those of control subjects (CS). Left ventricular hypertrophy (LVH) was also assessed from the electrocardiogram. The maximal aerobic performance was determined on a bicycle ergometer. In the athletes, left ventricular mass was significantly greater in all seasons than the values in the CS. This difference resulted from a thicker interventricular septum and left ventricular posterior wall as well as a larger left ventricular internal diameter. The existence of LVH was confirmed by the electrocardiographic findings. No differences were observed between the four different training seasons, despite considerable changes in the training program for weeks to months. The maximal aerobic performance test in LDR showed a significantly higher workload during the competitive than during the preparation season. The CR reached significantly lower values during the resting season than during the other seasons. The results indicate that the possible adaptation of the cardiac dimensions to variations in the heaviness of the training program is relatively slow.

Adolescent↗
PubMed1983

The use of ketanserin, a 5-hydroxytryptamine receptor antagonist, for treatment of postoperative hypertension following coronary artery bypass surgery.

In patients developing hypertension following coronary artery bypass surgery (CABG) the possible role of 5-hydroxytryptamine (5-HT; serotonin) was investigated by injecting ketanserin, a specific 5-HT2-receptor antagonist. Ketanserin was administered intravenously when intraarterial systolic blood pressure (SAP) exceeded 150 mm Hg either as a 10-mg bolus (group 1, N = 15), or as a 10-mg bolus followed by infusion of 4 mg/h for either 2.5 h (group 2, N = 15) or for 1 h (group 3, N = 10). In 33 patients (82.5%), SAP and diastolic arterial pressure decreased significantly within 5 min after the 10-mg bolus. In group 1, SAP gradually increased after 30-50 min but in groups 2 and 3 SAP remained normal. The triple index (TI) decreased significantly in all groups. Heart rate decreased slightly but significantly in groups 2 and 3. Central venous and left atrial pressures did not change substantially in any of the three groups. Cardiac output increased significantly (0.51 +/- 0.158 L/min); hence, systemic vascular resistance (SVR) decreased significantly (452.1 +/- 50.57 dyn . s . cm-5--group 3). No rebound increase in SAP occurred after terminating the infusions (groups 2 and 3). These findings indicate that 5-HT plays a role in the majority of patients who develop hypertension following CABG. The decrease of SVR without reflex tachycardia is a favorable effect of ketanserin.

Coronary Artery Bypass↗
PubMed1982

Fluorescent labeling of blood platelets in vivo.

In rabbits, a clear microscopic image of individual, fluorescent blood platelets flowing in a mesenteric microvessel could be obtained over the whole cross-sectional area of the vessel, following an intravenous injection of a solution containing 5-15 mg of the fluorochrome Acridine Red. Most of the circulating platelets were labeled. Activation of the platelets by the injected dye was not seen. A fall in platelet count or hematocrit following injection did not occur. Electron microscopy revealed no gross ultrastructural changes. In vitro, the dye reduced platelet aggregation in a dose dependent way. In vivo, aggregation and adhesion of platelets as induced by laser injury or transection of an arteriole was observed in all cases, even following multiple injections of Acridine Red. Primary hemostatic plug formation times as measured in mesenteric arterioles were normal after the first and second injection of 5 mg Acridine Red, but prolonged after subsequent injections. Bleeding times as measured on the ear were prolonged following injection of 15 mg of the dye. It is concluded that this labeling procedure allows the study of the rheological behavior of the platelets in vivo. Whether this technique can also be used to study functional platelet behavior in vivo, needs further investigation.

Acridines↗