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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Actomyosin was extracted from myocardial homogenates from male rats of different ages of a long-inbred Fischer rat colony maintained under controlled conditions of temperature, humidity, and light. ATPase specific activity rose to a maximum at 2 months of age; this was followed by a progressive decline by about 25% at 16 months of age. However, the extractable actomyosin remained constant during this period. This loss in actomyosin ATPase specific activity is in good agreement with previously reported decrements in both stroke index and myocardial calcium content and an increase in myocardial contraction duration in aged rats.
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PMID:Reduced myocardial actomyosin adenosine triphosphatase activity in the ageing male Fischer rat. 14 29

The effects of gram-negative endotoxin (Escherichia coli 4 mg/kg) induced myocardial failure in the pentobarbital-anesthesized dog were examined by monitoring its influence on coronary and systemic hemodynamics and correlating these results with myofibrillar ATPase activity. An identical series of studies was performed incorporating a femoral-femoral arterial-venous shunt to augment venous return. Over a five-hour period, gram-negative endotoxemia was associated with a progressive fall in arterial pressure, stroke volume, cardiac output, coronary flow, and a rise in total peripheral resistance and diastolic coronary vascular resistance. Augmenting venous return by 313 +/- 71 ml/min significantly increased cardiac output, stroke volume, and coronary flow and substantially reduced total peripheral resistance and coronary vascular resistance. Myofibrillar ATPase activity from both endocardium and epicardium was significantly depressed in the endotoxin-shocked preparations. However, with the augmentation of venous return with the A-V shunt in the endotoxin-treated animal, myofibrillar ATPase activity is normal. It appears that endotoxin causes a decrease both in venous return and in cardiac contractility by increasing total peripheral resistance, coronary vascular resistance, and impedance to left ventricular ejection. Augmenting venous return by optimizing preload and reducing afterload prevents any significant increase in total peripheral resistance, coronary vascular resistance, or impedance to left ventricular ejection. This is manifested by a rise in cardiac output, stroke volume, and coronary flow and the preservation of myocardial function. This is the first successful application of left ventricular afterload reduction in noncardiogenic shock.
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PMID:Augmented venous return: protection of the ischemic myocardium during endotoxemia. 16 74

The permissible duration of brain ischemia without sustaining damage is short. Less clear are the mechanisms accounting for the vulnerability of brain to ischemic insults. Neurochemical factors implicated include impairment of energy synthesis by mitochondria and of energy-dependent processes such as synaptic transmission, ATPase activity, membrane conductance and altered protein and lipid synthesis. To clarify the vulnerability of energy metabolism, we investigated energy availability and synthesis in our model of global cerebral ischemia. Our studies evaluated in vitro mitochondrial ATP synthesis and the in vivo quantitation of the cortical adenylate pool. Results of our investigations support a growing body of evidence showing the energy state to be relatively stable to ischemia. We conclude that an energy-dependent process of brain is primarily vulnerable to ischemia.
Stroke
PMID:Energy metabolism during brain ischemia. Stability during reversible and irreversible damage. 119 33

We conducted the present studies in intact animals to assess alterations in integrated cardiovascular function due to hypothyroidism. Rats were surgically thyroidectomized or sham operated. Most obvious among the alterations detected under resting conditions was the bradycardia present in hypothyroid animals. Cardiac output was significantly reduced by slower heart rate; however, mean arterial blood pressure and left ventricular +dP/dt were maintained. Total peripheral resistance was increased in hypothyroid animals. Functional responsiveness to hemodynamic challenges unmasked additional characteristics. Thyroidectomized animals had normal stroke index-left ventricular end diastolic pressure relationships in response to rapid volume infusion. Peak left ventricular +dP/dt response to brief aortic occlusion was attenuated in thyroidectomized animals. Hypothyroid rats failed to augment left ventricular -dP/dt in response to isoproterenol challenge. Moreover, isoproterenol failed to reduce total peripheral resistance in the hypothyroid rat. Therefore, the hemodynamic responses observed in the intact, hypothyroid animal are consistent with the presence of (a) decreased cardiac contractile protein ATPase, (b) reduced calcium uptake by cardiac sarcoplasmic reticulum and (c) altered vascular adrenergic receptors. Many cellular and subcellular defects are compensated by integrative mechanisms operating under resting conditions, while other defects are unmasked only when examined in the intact, functional cardiovascular system undergoing hemodynamic challenge.
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PMID:Cardiovascular alterations in the hypothyroid rat. 128 75

Study of functional changes in sarcoplasmic reticulum membranes of the rat skeletal muscles shows that mild hyperthermia is accompanied by the activation of Ca-transporting system function (the increase in accumulation of Ca ions and the rise of Ca(2+)-ATPase activity are observed), a passive release of this ion being unchanged. The revealed changes are regarded as reaction induced by the body temperature increase. The effectiveness of the SR Ca-pump decreases sharply under heat stroke, but the increase of Ca2+ release from SR vesicles is observed. This is considered to be one of possible factors, causing disorder of electromechanical coupling and the disturbance of the skeletal muscle contractility.
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PMID:[Transport of Ca2+ in the sarcoplasmic reticulum of skeletal muscles in hyperthermia]. 138 48

Maximum heart rates (HR) of three soricine shrews and six other small mammals were measured in response to a single supramaximal dose of isoproterenol (Iso) under urethan anesthesia. The highest HR, 1,043 +/- 66 (SD) beats/min (n = 3), was in least shrew (Sorex minutus, mean body mass 3.02 +/- 0.81 g). Maximum HRs of common shrew (Sorex araneus, 7.16 +/- 1.54 g) and water shrew (Neomys fodiens, 12.80 +/- 1.54 g) were 938 +/- 29 (n = 7) and 887 +/- 21 (n = 6), respectively. In general, maximum HRs of soricine shrews and other small wild mammals followed the common mammalian pattern, fHmax/Iso = 443 x Mb-0.14, determined by body size. The exponent for this equation is smaller than that of resting HR (-0.25) (Stahl, J. Appl. Physiol. 22: 453-460, 1967), predicting crossover at approximately 3 g body mass. However, resting HRs of small mammals were clearly lower than expected on the basis of body mass. Lowering resting HR below the common mammalian level, with concomitant increase in stroke volume, seems to be a prerequisite for small mammals to regulate cardiac output against the ceiling of maximum HR. Electrophoretic analysis showed that the myosin of shrew ventricles is different from those of rodent species. In native conditions, shrew myosin, designated V1', migrated faster than the V3 and V1 forms of rat heart. On SDS gradient gel the single heavy chain of shrew myosin migrated slower than the alpha- or beta-chains of rat ventricle. Differences in the molecular weight of light chains were also noted between small mammals. Despite the notable differences in myosin composition, myosin-ATPase activity of the shrew hearts was similar to that of mouse and rat heart. Because duration of isometric contraction was inversely related to resting and maximum HRs, it was concluded that in the small mammals rate and duration of contraction are determined mainly by the release and uptake rate of myoplasmic Ca2+ and less by myosin-ATPase activity.
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PMID:Maximum heart rate of soricine shrews: correlation with contractile properties and myosin composition. 153 6

At the molecular level, muscle contraction is the result of cyclic interaction between myosin crossbridges, which extend from the thick filament, and the thin filament, which consists mainly of actin. The energy for work done by a single crossbridge during a cycle of attachment, generation of force, shortening and detachment is believed to be coupled to the hydrolysis of one molecule of ATP. The distance the actin filament slides relative to the myosin filament in one crossbridge cycle has been estimated as 12 nm by step-length perturbation studies on single fibres from frog muscle. The 'mechanical' power stroke of the attached crossbridge can therefore be defined as 12-nm shortening with a force profile like that shown by the quick recovery of force following a length perturbation. According to this definition, power strokes cannot be repeated faster than the overall ATPase rate. Here, however, we show that the power stroke can be regenerated much faster than expected from the ATPase rate. This contradiction can be resolved if, in the shortening muscle, the free energy of ATP hydrolysis is used in several actin-myosin interactions consisting of elementary power strokes each of 5-10 nm.
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PMID:Rapid regeneration of the actin-myosin power stroke in contracting muscle. 153 50

Ca2+, Mg2+, K+, Na+ ATPase activities, and the changes in K, Na, Ca, cholesterol, its fractions and esters contents in the red blood cells of 95 patients with acute cerebral stroke were studied on day 1-3, 5-7, 19-21. Statistically significant differences were found in the enzyme activities, the levels of K, Na, Ca, cholesterol and its fractions and esters in the red blood cells of patients vs. healthy donors. These features were dependent on the nature of the stroke: reversible--irreversible, ischemic--hemorrhagic.
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PMID:[ATPase activity and erythrocyte levels of potassium, sodium, calcium and cholesterol and its fractions and esters in patients in the acute period of cerebral stroke]. 164 6

The present report describes methods and procedures which have been developed and used in the intact, anesthetized rat for cardiovascular functional evaluation. Integrative hemodynamic mechanisms are ascertained under resting conditions by measuring arterial blood pressure, cardiac output and heart rate. Stroke volume and total peripheral resistance are derived from the above measurements. In addition, left ventricular pressure is determined by direct cardiac puncture. Derived rates of left ventricular pressure development (+dP/dt) and left ventricular pressure decline (-dP/dt) provide estimates of myocardial contractility and cardiac relaxation, respectively. Hemodynamic responses to isoproterenol infusion test the functional adequacy of the beta-adrenergic receptor, adenylate cyclase, cyclic AMP system. Ventricular function curves relating stroke volume and end-diastolic pressure during rapid volume infusion provide useful indices of cardiac pump performance in the intact heart. Peak left ventricular +dP/dt in response to brief aortic occlusion provides an index of cardiac contractile performance. Cardiac cellular/subcellular mechanisms relating (a) myofibrillar ATPase with heart contractility and (b) sarcoplasmic reticulum calcium handling properties with myocardial relaxation can be assessed. Thus, the methods and procedures described represent an experimental animal preparation which should prove useful for comprehensive evaluation of cardiovascular function.
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PMID:Comprehensive evaluation of cardiovascular function in the anesthetized rat. 183 72

The separation between Cys 697 (SH1) and Cys 707 (SH2) of the heavy chain of myosin subfragment-1 was previously measured by fluorescence resonance energy transfer with a donor linked to SH1 and an acceptor to SH2. In the present study the distribution of the distances between the two thiols was recovered from frequency-domain fluorometry. In the native state and in the presence of ligands such as MgADP, pyrophosphate, orthovanadate (Vi) and actin, we found wide distributions of the separations between SH1 and SH2 (11-16 A) comparable to that found in the random-coil state (20 A). These results suggest that the SH1-SH2 segment has a high degree of conformational flexibility even in native S1. The flexibility is not much affected by the physiological state of S1. However, the ligands MgADP, Vi and MgADP + Vi decrease significantly the mean SH1-SH2 distance from 27 to 17 A with the effect of MgADP+ Vi being the most pronounced. The anisotropy decay of donor-labeled S1 is biphasic with two rotational correlation times. The long component is decreased by these ligands from 289 to 93 ns, suggesting a more compact symmetric structure of S1 in the presence of the ligands. The complex S1(MgADP)Vi has been shown to be a stable analogue of S1(MgADP)Pi, an unstable intermediate that is generated in the actomyosin ATPase cycle during muscle contraction. Since the power stroke of muscle is accompanied by release of Pi from S1(MgADP)Pi, the present results are consistent with a model in which force generation can be accompanied by transition of S1 from a highly symmetric or compact structure to a more extended structure.
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PMID:Conformational flexibility of the Cys 697-Cys 707 segment of myosin subfragment-1. Distance distributions by frequency-domain fluorometry. 187 69


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