Skeletal Muscle Perfusion Research Articles

Malleability of the system in overcoming limitations: functional elements.

Three different views can be found in the literature concerning the classical question in exercise physiology: what limits maximal oxygen uptake in man? Some authors believe that the limitation is the maximal rate of oxygen delivery by the cardiovascular system. Others argue that oxygen uptake is limited by the capillary bed or metabolic capacity of skeletal muscle, and the third line of thought is that no single factor can be found to be directly limiting as all links in the oxygen transport are so closely matched. The stand taken in this paper is that the skeletal muscle of man can be excluded as a limiting factor for maximal oxygen uptake in whole body exercise. It can be shown, by direct measurements, that in sedentary and in trained man maximal perfusion and oxygen utilization of skeletal muscle is so high that if all muscles in the body were engaged in intense exercise, the cardiac pump function would have to be 2-3 fold larger than it is. What happens in whole body exercise is that each muscle group receives only a fraction of the blood it can accommodate. The primary role for a larger capillary network observed in trained muscles is to keep or extend mean transit time. Elevated mitochondrial enzyme activities affect the metabolic response (i.e. lipid oxidation is elevated in trained muscles). However, these adaptations are not necessary for increasing the maximal oxygen uptake of man, as the capacity of the heart is limiting. Improved training techniques (which induce even larger improvements in cardiac pump function) may reveal that pulmonary diffusion capacity is the limiting factor.

Geometric accommodation between the dimensions of erythrocytes and the calibre of heart and muscle capillaries in the rat.

The finer and more closely arrayed the capillaries are, the more efficiently oxygen will be transported to tissue because the same blood volume has greater contact area with the tissue and the diffusion distance for the oxygen is minimized. If these principles are actually governing microvascular structure, then the finest capillaries will be the narrowest channels which circulating erythrocytes can transit. Ascertaining the existence of this geometric limit requires quantitative data of demonstrated reliability on erythrocyte geometry and on capillary diameters. The study was done on Wistar rats. Constant flow perfusion of skeletal and cardiac muscle by a modified Batson's compound for anatomical casting made available rigid three-dimensional replicas of the microvasculature which shrank less than 1% when the tissue was digested with potassium hydroxide. Measurements of individual capillaries were made on high contrast scanning electron micrographs of the casts. Measurements on individual rat erythrocytes were done on photomicrographs of cells on edge. Reliability of these data was tested in three ways. First, repeatability of the tracing of the cell outline was tested by processing a duplicate set of photomicrographs. Secondly, correlations of the various parameters were found. Thirdly, results from other techniques of measuring erythrocytes were examined for areas of agreement and also for causes of possible error for areas in dispute. Because of known variability in erythrocyte sizes and shapes between species and between individuals within a species, we compared the data on erythrocyte geometry and capillary diameters for samples taken from the same individual rat. The data revealed a very positive indication that the lowest range of capillary diameters were at the limits of deformation of the circulating erythrocytes. Ninety-five per cent of the erythrocytes sampled could pass through a channel 2.9 micron in diameter. A small number of the capillaries measured were narrower than this limit. The data on erythrocytes and capillaries were compared for six rats. The limiting diameter for passage of erythrocytes was remarkably uniform for all six animals.

Role of Insulin in the Regulation of Protein Synthesis

Recent research has established an anabolic role for insulin in the regulation of protein turnover, and in some instances identified specific reactions as the site of hormone action. Two major control mechanisms have been implicated, one in muscle tissue and one in liver. The major advances in recent years have included vastly greater knowledge of the chemical reactions in the pathway of protein synthesis; new methods for accurate measurements of synthetic rates; procedures for in vitro perfusion of liver, heart, and skeletal muscle; methods for measurement of intermediates in the synthetic pathway; methods for quantifying the synthesis of individual proteins; and techniques for measuring messenger RNA levels for specific proteins. Future work is dependent on further definition and characterization of the individual components of the synthetic pathway

The detrimental effects of prolonged hypothermia and rewarming in the dog.

The authors had previously observed a deleterious cerebrovascular effect of prolonged hypothermia in primates and cats. In this study they examined the systemic as well as cerebral hemodynamic and metabolic effects of 24 hours of hypothermia in the dog. With decreases in temperature to 29 C, cardiac output (Q) and whole-body oxygen consumption (VO2) initially decreased 52 and 42 per cent, respectively. Thereafter, despite a stable temperature, both Q and VO2 continued to decrease, and at 24 hours values were 7 and 28 per cent of control, respectively, Cerebral blood flow (CBF) and cerebral oxygen consumption responded similarly. At 24 hours inhomogeneous perfusion of both brain and skeletal muscle was observed. With rewarming, cardiovascular collapse with severe tissue hypoxia and acidosis developed; CBF became grossly inadequate, resulting in depletion of brain energy stores.

The influence of blood flow and arterial blood pressure during cardiopulmonary bypass on deltoid muscle gas tensions and body temperature after bypass.

The results of this study demonstrate that skeletal muscle perfusion during bypass requires high flows and mean arterial pressures and that use of vasopressors during bypass impairs skeletal muscle blood flow. Our findings also indicate that skeletal muscle perfusion during bypass decreases metabolic acidosis after operation and prevents decreases in body temperature and poor skeletal muscle blood flow in the post-bypass and early postoperative periods. Our results suggest that perfusing to maintain normal Pmo2 during extracorporeal circulation is superior to more conventional techniques of conducting bypass.

Arterial pressure and deltoid muscle gas tensions during cardiopulmonary bypass in man

The results of this study demonstrate that standard techniques of conducting cardiopulmonary bypass produce low muscle oxygen and high muscle carbon dioxide tensions and, thus, little perfusion of skeletal muscle. Our findings also show that PmO2 and PmCO2 do not return to pre-bypass levels until the mean arterial blood pressure exceeds 12 kPa (90 torr) during bypass and that utilization of vasopressor drugs during bypass maintains the pressure; but at the expense of muscle blood flow. The data indicate that both high mean blood pressure and high flow are necessary during bypass to ensure skeletal muscle perfusion and suggest, when combined with preliminary animal findings, that this type of bypass perfusion may prove to be superior to standard techniques in hastening recovery after cardio-pulmonary bypass.

Interaction between the hypothalamic defence reaction and cardiac ventricular receptor reflexes.

The interference with regard to the cardiovascular and gastric motility responses which follows stimulation of the hypothalamic defence area (D.A.) and a simultaneous afferent input from cardiac ventricular receptors was analysed in chloralose-anesthetized cats. In spinalized animals with only the vagal efferent innervation of autonomic effectors from supraspinal structures intact, a D.A. stimulation increased the heart rate to the same level irrespective whether the cardiac receptor afferents were stimulated or not. This suggests that the vagal component of the reflex bradycardia of cardiac receptor origin was completely suppressed by the D.A. stimulation. The reflex gastric relaxation to cardiac receptor activation, mediated via vagal efferent non-adrenergic fibres, was similarly completely blocked by D.A. stimulation. In contrast, the reflex inhibition of the sympathetic outflow to the heart and vessels from cardiac receptors was still effective during a D.A. stimulation, a phenomenon which seems compatible with a simple summation of excitatory D.A. and inhibitory cardiac receptor influences on the sympathetic neurons. The modifying influence from ventricular receptors on D.A. responses closely resembles that exerted by the arterial baroreceptors. The two reflex mechanisms thus work in concert and synergistically with the hypothalamic influences to produce maximal cardiac output and skeletal muscle perfusion without undue increases of pressure load on the pump during a defence reaction.

The influence of varying oxygen tensions in inspired gas on 133Xenon muscle clearance and fatigue levels during sustained and dynamic conctractions.

Isometric and isotonic endurance levels of both elbow flexors and knee extensors were tested during inspired gas mixtures of ca. 10%, 21% or 100% oxygen in nitrogen. The four work loads were set a 25, 50, 60 and 70% of maximal volitional isometric strength (IS). The isotonic exercise routine was carried out using weight lifting techniques of 20 repetitions per min from 75 degrees to 105 degrees of elbow flexion and knee extensions respectively. Prior to, during, and after the endurance experiments 133Xe clearance was monitored by light weight scintillation counters. A depot of 0.1 to 0.2 ml of isotonic saline containing 50 to 150 muCi of the isotope was used as an intramuscular tracer. The exercise clearance values varied inversely to the test load during isometric exercise. Isotonic exercise for both elbow flexors and knee extensors showed increasing clearance values up to 60% IS. Above this level a decrease in total clearance was recorded. Oxygen tension had no statistical effect on the clearance values. However, the relatively large scatter of the 133Xe clearance method, and an inhomogenous perfusion of skeletal muscle may have masked any anticipated effect of the various O2 tensions. Variations due to the raised intramuscular pressure appeared to be much more dominant than the hypothezised variation due to the 3 set oxygen tensions.

Alterations in Rubidium-86 Extraction in Normal Mouse Tissues after Irradiation: An Estimate of Long-Term Blood Flow Changes in Kidney, Lung, Liver, Skin and Muscle

Using the method of ${}^{86}\text{rubidium}$ extraction as developed by Sapirstein, we have studied the uptake of this isotope to measure changes in perfusion of normal mouse kidney, lung, liver, skin, and skeletal muscle after regional single doses of 240 kV X-rays estimated to be at or near the level of normal tissue tolerance for viscera. In the kidney, the extraction of isotope declines soon after irradiation and becomes significantly decreased from age controls by 2 months after 1100, 1500, or 1900 rads. This decrease in86 Rb extraction appears dose-dependent, continues to decline for at least 1 yr, and preceded histologic fibrosis by several months. The uptake of86 Rb in irradiated lung decreased significantly between 3 and 4 months after which it gradually returned to normal levels. No significant change in86 Rb extraction was seen in liver, skin or muscle after doses up to 1500 rads. Details of this isotopic technique and possible implications of perfusion changes in normal tissues for clinical ra...

An implantable glass electrode used for pH measurement in working skeletal muscle.

ArticleAn implantable glass electrode used for pH measurement in working skeletal muscle.G Gebert, and S M FriedmanG Gebert, and S M FriedmanPublished Online:01 Jan 1973https://doi.org/10.1152/jappl.1973.34.1.122MoreSectionsPDF (470 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByAnaerobic MetabolismCauses of differences in exercise-induced changes of base excess and blood lactate7 November 2006 | European Journal of Applied Physiology, Vol. 99, No. 2Effects of changes in pH on the afferent impulse activity of isolated cat muscle spindlesBrain Research, Vol. 1043, No. 1-2Regulation and Modulation of pH in the BrainMITCHELL CHESLER1 October 2003 | Physiological Reviews, Vol. 83, No. 4Control of skeletal muscle perfusion at the onset of dynamic exerciseMedicine & Science in Sports & Exercise, Vol. 31, No. 7Relationship of peak exercise capacity with indexes of peripheral muscle vasodilationMedicine &amp Science in Sports &amp Exercise, Vol. 28, No. 1031P-Nuclear magnetic resonance spectroscopy study of the time course of energy metabolism during exercise and recoveryEuropean Journal of Applied Physiology and Occupational Physiology, Vol. 66, No. 6Changes in intracellular pH during repeated exerciseEuropean Journal of Applied Physiology and Occupational Physiology, Vol. 67, No. 3The regulation and modulation of pH in the nervous systemProgress in Neurobiology, Vol. 34, No. 5Changes in extracellular pH during electrical stimulation of isolated rat vagus nerveNeuroscience Letters, Vol. 64, No. 2Continuous monitoring of tissue pH with a fiberoptic conjunctival sensorAnnals of Emergency Medicine, Vol. 14, No. 9The relevance of tumour pH to the treatment of malignant diseaseRadiotherapy and Oncology, Vol. 2, No. 4Differential serotonin responses in the skeletal muscle microcirculationLife Sciences, Vol. 34, No. 12Effects of pH onin vitro gallbladder responses to cholecystokinin octapeptideDigestive Diseases and Sciences, Vol. 27, No. 7Tumour pH in human mammary carcinomaEuropean Journal of Cancer and Clinical Oncology, Vol. 18, No. 5Alkalinization of phosphorylase kinase-deficient muscle during tetanic contractionBioscience Reports, Vol. 1, No. 2The Use of ISMs in Working Skeletal Muscles and Venous Effluent BloodExtracellular K+ concentration and K+ Balance of the gastrocnemius muscle of the dog during exercisePfl�gers Archiv European Journal of Physiology, Vol. 387, No. 3Modification of α-adrenergic responses of small arteries by altered PCO2 and pHEuropean Journal of Pharmacology, Vol. 57, No. 4On-line, computer-controlled potentiometric analysis system1 May 2002 | Analytical Chemistry, Vol. 48, No. 2Glass microelectrode probes for routine pH measurements1 May 2002 | Analytical Chemistry, Vol. 48, No. 2The interstitial pH of the working gastrocnemius muscle of the dogPfl�gers Archiv European Journal of Physiology, Vol. 367, No. 2Reversible metal/salt interfaces and the relation of second kind and all-solid-state membrane electrodes1 May 2002 | Analytical Chemistry, Vol. 46, No. 14Ion selective electrodes, potentiometry, and potentiometric titrations1 May 2002 | Analytical Chemistry, Vol. 46, No. 5 More from this issue > Volume 34Issue 1January 1973Pages 122-4 https://doi.org/10.1152/jappl.1973.34.1.122PubMed4697369History Published online 1 January 1973 Published in print 1 January 1973 Metrics

Systemic haemodynamic changes due to pulmonary embolization in rabbits as influenced by trimethaphancamsylate.

The effect of trimethaphancamsylate (Arfonad, Roche) on the transformation of systemic circulation occurring as a result of pulmonary embolization was examined in a group of rabbits with pulmonary embolization caused by x-ray contrast blood clots. This group was compared with a control group and with a group of rabbits with pulmonary embolization after the application of Arfonad. Pulmonary embolization results in systemic arterial hypotension, decrease of total systemic resistance, and decrease of perfusion in kidneys, splanchnic organs, and in lungs and skin, whereas the perfusion of myocardium and skeletal muscle is retained. Arfonad abolished this vasoconstriction; nevertheless it also decreased cardiac output, probably due to the reduced venous return, and aggravated the systemic hypotension. This effect of Arfonad indicated that the transformation of circulation in pulmonary embolization was of reflex origin.

Effect of prolonged infusion of angiotensin II on ionic composition of the arterial wall.

ARTICLESEffect of prolonged infusion of angiotensin II on ionic composition of the arterial wallMF Villamil, P Nachev, and CR KleemanMF Villamil, P Nachev, and CR KleemanPublished Online:01 May 1970https://doi.org/10.1152/ajplegacy.1970.218.5.1281MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByChronic inhibition of angiotensin converting enzyme decreases Ca2+-dependent tone of aorta in hypertensive rats.Hypertension, Vol. 13, No. 6_pt_1Southwestern Internal Medicine Conference: The Multifacetted Role of Angiotensin Converting Enzyme Inhibitors in Congestive Heart FailureThe American Journal of the Medical Sciences, Vol. 296, No. 4Dependence of enhanced maximal exercise performance on increased peak skeletal muscle perfusion during long-term captopril therapy in heart failureJournal of the American College of Cardiology, Vol. 10, No. 4Potentiating Effects of Angiotensin II on Norepinephrine-Induced Vasoconstriction in Isolated and Perfused Dog Mesenteric ArteriesJapanese Journal of Pharmacology, Vol. 42, No. 1Calcium Blockade as a Therapeutic Principle in Arterial Hypertension: Clinical aspects and experimental studies on isolated vessels from spontaneously hypertensive rats and normotensive man.13 March 2009 | Acta Pharmacologica et Toxicologica, Vol. 49Content and Fluxes of Electrolytes1 January 2011Electrophysiological study of the action of angiotensin II on the rat myometrium.Circulation Research, Vol. 45, No. 2Increased resistance and impaired maximal vasodilation in normotensive vascular beds of rats with coarctation hypertension.Hypertension, Vol. 1, No. 2PROCEEDINGS OF THE British Pharmacological Society19 July 2012 | British Journal of Pharmacology, Vol. 59, No. 3Effect of Saluretic Therapy on Muscle Content of Water and Electrolytes in Relation to Hemodynamic Variables24 April 2009 | Acta Medica Scandinavica, Vol. 202, No. 1-6Cell permeability, sodium transport, and the hypertensive process in the rat.Circulation Research, Vol. 39, No. 3Effect of angiotensin II on short-circuit current in amphibian membranesBiochemical Pharmacology, Vol. 25, No. 1Lithium Substitution and the Distribution of Sodium in the Rat Tail ArteryCirculation Research, Vol. 34, No. 2Angiotensin on Vascular Smooth MuscleHYPERTENSION AND SECONDARY HYPERALDOSTERONISM ASSOCIATED WITH A RENIN-SECRETING RENAL JUXTAGLOMERULAR-CELL TUMOURThe Lancet, Vol. 302, No. 7840Angiotensin I as a dipsogen: Efficacy in brain independent of conversion to angiotensin IIPharmacology Biochemistry and Behavior, Vol. 1, No. 4Iso-renin, electrolytes and catecholamines in dog brain: Possible interrelationshipLife Sciences, Vol. 12, No. 1Water and electrolyte composition of the medulla oblongata of normal and hypertensive ratsLife Sciences, Vol. 12, No. 1Calcium Dependence of Vascular Smooth Muscle from Normotensive and Hypertensive RatsAn Intrinsic Renin-Angiotensin System in the BrainMineralocorticoidsyndromeRenin in heart muscle and arterial tissueHypothalamic Inputs: Methods, and Five ExamplesAngiotensin-Forming Enzyme in Brain TissueScience, Vol. 173, No. 3991 More from this issue > Volume 218Issue 5May 1970Pages 1281-1286 Copyright & PermissionsCopyright © 1970 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1970.218.5.1281PubMed4314565History Published online 1 May 1970 Published in print 1 May 1970 Metrics

Action of oxygen and potassium on vascular resistance of dog skeletal muscle.

Action of oxygen and potassium on vascular resistance of dog skeletal muscle.

Local xenon 133 clearance from the quadriceps muscle during exercise in man.

Local xenon 133 clearance from the quadriceps muscle during exercise in man.

Venous Pressure in the Saphenous Vein at the Ankle in Man during Exercise and Changes in Posture

<i>Venous Pressure in the Saphenous Vein at the Ankle in Man during Exercise and Changes in Posture</i>