Changes In Cardiac Muscle Research Articles

Ethanol-induced electrophysiological alterations in canine cardiac Purkinje fibers.

THANOL HAS BEEN FOUND to have a d pressant effect on the mammalian heart. Studies (1-4) using a variety of experimental conditions and subject ypes have shown increased left ventricular end-diastolic pressure and heart diameter and decreased stroke output and contractile force. The relative contributions of ethanol's various actions to cardiac tissue depression are unclear, but electrophysiological alterations appear to be a significant factor. Ethanol-induced lectrophysiological changes in cardiac muscle have been related to depressed contractility (5, 0). In addition to causing myocardial depression, ethanol has been shown to affect intracardiac onduction and to possess possible arrhythmogenic properties. Gimeno et al. (5) observed ethanolinduced dysrhythmias, a shortened action-potential duration (,•,])) and increased conduction i rat atrial tissue. In frog and cat ventricular muscle, ethanol has been shown to shorten the a•,]) and

Age related changes in cardiac muscle of rats: S. Mohan and E. Radha. Department of Zoology, Bangalore University, Bangalore-560 001, India

Age related changes in cardiac muscle of rats: S. Mohan and E. Radha. Department of Zoology, Bangalore University, Bangalore-560 001, India

Simultaneous heat and fluorescence changes in cardiac muscle at high rates of energy expenditure: Effects of caffeine and isoprenaline

The relationship between the fluorescence-time integral and heat production was investigated in isolated rabbit papillary muscles at room temperature. Four treatments were used: (1) control; (2) 10⁻³ m caffeine; (3) 5×10⁻³m caffeine; (4) 5×10⁻³ m caffeine +2×10⁻⁷m isoprenaline. The first two treatments were associated with low rates of energy expenditure for a given rate of stimulation whereas high rates of energy turnover occurred with the last two treatments. The enthalpy versus load relationship was studied in each treatment as a means for obtaining plots of fluorescence-time integral versus active heat production. All the plots showed high correlations between the two parameters but the linearity of the relationship broke down at high rates of energy expenditure, associated with treatments (3) and (4), as complexities arose in the fluorescence waveforms. No significant changes in resting heat production were induced by any of the drug treatments. Although the mechanical work output was much higher in treatments (3) and (4), the associated extra-active heat production was sufficient to cause a marked drop in mechanical efficiency. Possible biochemical mechanisms underlying the results are discussed.

Heat and fluorescence changes in cardiac muscle: Effects of substrate and calcium

A combined myothermic and fluorescent investigation into the effects of substrate and calcium ions on the contractility of paired rabbit papillary muscles has shown that, (i) as shown in earlier studies pyruvate, when substituted for glucose, increases contractility, increases the levels of fluorescence and resting heat production and speeds the kinetics of fluorescent transients and the time cours of heat production, (ii) reducing the extracellular calcium level from 2.5m m to 1.25m m, decreases contractility without altering the resting fluorescence level and without changing the kinetics of fluorescent transients or the time course of active heat production. Neither treatment (substrate or calcium) altered the isometric heat coefficient. Evidence is presented showing that the fluorescence-time integral is linearly related to the energy expended in a cardiac contraction.

Cardiovascular function in potassium-depleted dogs

Chronic potassium depletion in the dog is associated with multiple cardiovascular alterations. The rate of automaticity of the S-A node appears diminished and its response to a chronotropic stimulus is impaired. The reduced peripheral resistance causes a decline in the characteristic hypertensive response to pentobarbital anesthesia. Cardiac function is not impaired, in the absence of arrhythmias, and contractility seems enhanced since potassium depletion produces a significant increase in the mean systolic ejection rate, a rise in LV dp dt , and a higher LVSW and a trend to increased LVMW at similar levels of LVEDP. These hemodynamic alterations are not associated with light microscopic changes in cardiac muscle.

Functional changes of cardiac muscle in adaptation to two types of chronic hypoxia.

ARTICLESFunctional changes of cardiac muscle in adaptation to two types of chronic hypoxiaJ. Souhrada, B. Mrzena, O. Poupa, and R. W. BullardJ. Souhrada, B. Mrzena, O. Poupa, and R. W. BullardPublished Online:01 Feb 1971https://doi.org/10.1152/jappl.1971.30.2.214MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByLactate dehydrogenase and pyruvate kinase in rat heart during sideropenic anemiaBiochimica et Biophysica Acta (BBA) - Enzymology, Vol. 334, No. 1 More from this issue > Volume 30Issue 2February 1971Pages 214-218 Copyright & PermissionsCopyright © 1971 the American Physiological Societyhttps://doi.org/10.1152/jappl.1971.30.2.214PubMed5539886History Published online 1 February 1971 Published in print 1 February 1971 Metrics

Excitation and synaptic transmission.

The main properties of nerve and muscle cells to be considered in this section are the differences in potential and in ion contents between the interior of the cell and its normal environment, and excitability. The most widely accepted model used to explain these properties is that of a mem­ brane of limited permeability separating the internal and external phases, in which the potential, ion gradients, and excitability are ascribed to the properties of the membrane. An alternative model in which the potential and ion gradients are ascribed to the properties of the protoplasm (195, 196, 201) will not be considered here. Among the membrane hypotheses, that of Hodgkin & Huxley (157) , originally proposed for the squid giant axon, has been frequently used to account for findings in other excitable tissues. In this hypothesis Na+, K+, and CIcurrents are considered to be independent both at rest and during activity, and the membrane is considered to behave as though the indi­ vidual ionic elements were connected in parallel (127, 2 12 , 221 , 309). If appropriate values be given to the several parameters included in Hodgkin & Huxley's empirical formulation, it is possible to picture and to account for striking differences in behavior among excitable tissues. Some recent examples are the accounts of potential changes in cardiac muscle (28, 229), in the lobster giant axon (70), and in crustacean muscle (see below) . However, data have been obtained in the last few years which, accord­ ing to the investigators, cannot be fitted to the above hypothesis. The prob­ lem has been discussed here in preceding reviews (124, 268) , and some new findings will be mentioned below. Prominent in the interpretations of many of these findings is the suggestion that fixed charges are present within the membrane, as in the model analyzed by Teorell (284) . Active transport.-A comprehensive review of the current status of the problem of active transport of ions across nerve and muscle membranes was given by Edelman (98) . Investigations of the mechanisms involved have been somewhat limited in the past by the difficulty of obtaining cell mem­ brane material. A method has now been described for isolating this material which offers hope of circumventing this difficulty (213).

The acute oral toxicity of phenacetin

Phenacetin given orally in doses of 1 and 2 g per kilogram body weight produced vomiting in cats and dogs. Further toxicity studies were confined to albino rats in which the oral LD 50 ± S.E. was found to be 1.65 ± 0.35 g per kilogram body weight. Clinical signs of intoxication were lethargy, hyporeflexia, ataxia, exophthalmos, dacryorrhea, sialorrhea, bradycardia, hypopnea, hypothermia, anorexia, adipsia, oliguria or anuria, and death due to respiratory failure in marked hypothermia at 22.8 ± 17.7 (mean ± S.D.) hours. Survivors had diarrhea and dark-colored urine. At autopsy there were found a fulminating gastroenteritis, hepatitis, pancreatitis, nephritis, pulmonary edema, capillary and venous congestion of the mesentery, heart, thymus gland, ovaries, lymph nodes, and spleen, and evidence of minor toxic changes in cardiac muscle, skeletal muscle, and the adrenal glands.

The effect of sulfonamide administration on cardiac function in the dog

The effect of various sulfonamide drugs on the electrocardiogram was studied in thirty-nine dogs. Sulfonamide administration had no effect upon the cardiac muscle and conducting system which could be demonstrated by the electrocardiogram in thirty-two dogs (82 per cent of the number studied), even though eleven of these dogs showed conduction defects before treatment. Electrocardiographic abnormalities consisting of slight S-T segment deviation and change in direction of T wave occurred in seven dogs during medication and indicated some myocardial involvement. These changes were transient and disappeared after drug administration was stopped in all except three cases. The possibility that these electrocardiographic changes were the result of morphologic changes in cardiac muscle caused by sulfonamide sensitization is discussed.

Tonus changes in cardiac muscle and their significance for the initiation of impulses: Bozler, E.: Am. J. Physiol. 139: 477, 1943

Tonus changes in cardiac muscle and their significance for the initiation of impulses: Bozler, E.: Am. J. Physiol. 139: 477, 1943

TONUS CHANGES IN CARDIAC MUSCLE AND THEIR SIGNIFICANCE FOR THE INITIATION OF IMPULSES

ArticleTONUS CHANGES IN CARDIAC MUSCLE AND THEIR SIGNIFICANCE FOR THE INITIATION OF IMPULSESEmil BozlerEmil BozlerFrom the Department of Physiology, Ohio State UniversityPublished Online:01 Jul 1943https://doi.org/10.1152/ajplegacy.1943.139.3.477MoreSectionsPDF (674 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Download PDF FiguresReferencesRelatedInformation Cited BySynergism of coupled subsarcolemmal Ca2+ clocks and sarcolemmal voltage clocks confers robust and flexible pacemaker function in a novel pacemaker cell modelVictor A. Maltsev and Edward G. Lakatta1 March 2009 | American Journal of Physiology-Heart and Circulatory Physiology, Vol. 296, No. 3 More from this issue > Volume 139Issue 3July 1943Pages 477-480 Copyright & PermissionsCopyright © 1943 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1943.139.3.477History Received 25 March 1943 Published online 1 July 1943 Published in print 1 July 1943 Metrics