Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Subjects tried to maintain 15%, 30% and 50% maximum voluntary contraction (MVC) of their handgrip for 60 sec and 70% MVC for 30 sec. When the subjects watched the tension record, they could maintain the contraction for the required time. However, without visual cues (uncued), the tests resulted in a tension decline. Ae-alpha t described the tension decline in the 15% tests, Be-beta t the 70% test, while the form in the 30% and 50% tests was Ae-alpha t + Be-beta t. In all cases alpha and/or beta were found to be dependent on the starting tension. The electrical activity obtained from surface electromyograms did not increase during the uncued tests which would be expected if muscle fatigue were involved in the tension decline. Instead the electrical activity was directly proportional to the decline in tension suggesting that the fall in tension was not due entirely to muscle fatigue. 15% MVC uncued tests in which fatigue is known not to be a factor also showed a tension decline. Precooling the hand in an attempt to alter sensory input produced no systematic change from the original uncued tests, indicating that sensory information from the hand was probably not a major factor in the tension decline. It is suggested that during the uncued tests the fast component of the tension decline may be related to a sensory adaptation involving the Golgi tendon organs. The slow component is due to forearm muscle fatigue which is related to the ischemia produced during the isometric contractions.
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PMID:Tension decline during isometric contractions without visual cues. 115 32

Contractile and morphological properties of the rabbit tibialis anterior muscle were measured 48 hours following a two-hour ischaemic episode. Ischaemia was induced using a specially-designed pneumatic tourniquet placed on the rabbit thigh. Maximum tetanic tension of muscle subjected to ischaemia (381 +/- 77 g) was only about 30% of the tension generated by control muscles (1,212 +/- 67 g). The rate of rise of tetanic tension of muscles subjected to ischaemia (15.9 +/- 3 g/ms) was only 33% of control values (44.5 +/- 5.9 g/ms). Muscle fatigue index increased significantly from 0.22 +/- 0.7 in control muscles to 0.55 +/- 0.09 in ischaemic muscles suggesting that muscles subjected to ischaemia had a greater endurance capacity than control muscles. Morphologically, focal necrotic regions and inflammatory cells were observed in ischaemic muscle fibers. Taken together, these data are consistent with selective damage to the fast glycolytic muscle fibers within the ischaemic tibialis anterior muscles. Thus, ischaemia results in overall decreased muscle speed, strength and fatigability.
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PMID:Decreased muscle speed, strength and fatigability following two hours of tourniquet-induced ischaemia. 141 39

Recent evidence indicates that muscle ischemia and activation of the muscle chemoreflex are the principal stimuli to sympathetic nerve activity (SNA) during isometric exercise. We postulated that physical training would decrease muscle chemoreflex stimulation during isometric exercise and thereby attenuate the SNA response to exercise. We investigated the effects of 6 wk of unilateral handgrip endurance training on the responses to isometric handgrip (IHG: 33% of maximal voluntary contraction maintained for 2 min). In eight normal subjects the right arm underwent exercise training and the left arm sham training. We measured muscle SNA (peroneal nerve), heart rate, and blood pressure during IHG before vs. after endurance training (right arm) and sham training (left arm). Maximum work to fatigue (an index of training efficacy) was increased by 1,146% in the endurance-trained arm and by only 40% in the sham-trained arm. During isometric exercise of the right arm, SNA increased by 111 +/- 27% (SE) before training and by only 38 +/- 9% after training (P less than 0.05). Endurance training did not significantly affect the heart rate and blood pressure responses to IHG. We also measured the SNA response to 2 min of forearm ischemia after IHG in five subjects. Endurance training also attenuated the SNA response to postexercise forearm ischemia (P = 0.057). Sham training did not significantly affect the SNA responses to IHG or forearm ischemia. We conclude that endurance training decreases muscle chemoreflex stimulation during isometric exercise and thereby attenuates the sympathetic nerve response to IHG.
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PMID:Forearm endurance training attenuates sympathetic nerve response to isometric handgrip in normal humans. 156 57

beta-Blockers are known to suppress exercise-induced ischemia but give rise to such problems as fatigue or dyspnea on effort and also bradycardia. In a series of double-blind, placebo-controlled studies of celiprolol (a cardioselective beta 1-blocker with beta 2-agonist and vasodilatory properties) in patients with hypertension and angina and in normal volunteers, it was found that celiprolol did not produce bradycardia when given in combination with verapamil. Celiprolol did reduce exercise-induced ischemia, but there was no reduction in cardiac output at rest or on exercise compared with placebo. Compared with atenolol, celiprolol produced less dyspnea and fatigue at submaximal levels of exercise. It is concluded that celiprolol possesses certain differences, compared with conventional beta-blockers, that may be of direct clinical benefit.
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PMID:Angina, ischemia, and effort tolerance with vasodilating beta-blockers. 167 26

Celiprolol is a third generation beta blocking drug with intrinsic vasodilator effect. We evaluated the effect of this drug at a fixed dose of 400 mg daily in 20 patients with coronary artery disease and stable angina having 2 to 40 episodes of pain a week. All patients had positive exercise stress test with greater than 1 mm ST depression. Compared to the 1 month baseline placebo phase, patients after 3 months of treatment with celiprolol had less episodes of angina (2.4 vs 7.2 a week, p less than 0.001), higher angina threshold (667 vs 337 sec, p less than 0.025), higher ischemia threshold (614 vs 401 sec, p less than 0.001) and were able to perform more work (3937 vs 2403 kgm/min. p less than 0.01). 9 patients had no pain during exercise. A decrease in blood pressure, heart rate and double product was evident in the stress tests of the active phase. Adverse effects included headache (4 patients), sweating (1) and fatigue (1) not requiring modification of drug dose. No adverse effects were seen in 13 patients. Thus, celiprolol is effective to decrease angina during daily life and increase exercise tolerance in patients with chronic stable angina pectoris.
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PMID:[Celiprolol in the treatment of chronic stable angina]. 168 95

This review addresses current understanding of oxygen radical mechanisms as they relate to the brain during ischemia and reperfusion. The mechanism for radical production remains speculative in large part because of the difficulty of measuring radical species in vivo. Breakdown of lipid membranes during ischemia leads to accumulation of free fatty acids. Decreased energy stores during ischemia result in the accumulation of adenine nucleotides. During reperfusion, metabolism of free fatty acids via the cyclooxygenase pathway and metabolism of adenine nucleotides via the xanthine oxidase pathway are the most likely sources of oxygen radicals. Although leukocytes have been found to accumulate in some models of ischemia and reperfusion, their mechanistic role remains in question. Therapeutic strategies aimed at decreasing brain injury have included administration of radical scavengers at the time of reperfusion. Efficacy of traditional oxygen radical scavengers such as superoxide dismutase and catalase may be limited by their inability to cross the blood-brain barrier. Lipid-soluble antioxidants appear more efficacious because of their ability to cross the blood-brain barrier and because of their presence in membrane structures where peroxidative reactions can be halted.
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PMID:Oxygen radical mechanisms of brain injury following ischemia and reperfusion. 175 40

The diagnostic potentialities of bicycle ergometry (BEM) and treadmill test were comparatively analysed in 57 males aged 37-64 years who were examined to detect coronary heart disease. In 34 cases, the results of BEM and treadmill test were consistent, of them 13 were positive, 15, negative, 3 intermediate, and 3 inadequate. With positive results, the treadmill test was more reliable than BEM in revealing the criteria for ischemia from statistically significantly more pronounced ST-segment depression at a lower threshold heart rate. Inconsistency of the BEM and treadmill test results was found in 23 cases. In 14 of 18 patients who had indefinite BEM results, the treadmill test allowed one to make a definite conclusive diagnosis, showing 6 positive and 8 negative results. This is accounted for by lower cases when the treadmill test was discontinued due to a hypertensive reaction of blood pressure or fatigue. The study indicated that the treadmill test was more sensitive and better tolerated than BEM.
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PMID:[Comparing the informative value of bicycle ergometry and treadmill tests in the evaluation of the coronary reserve]. 180 56

The prognosis of coronary patients in terms of the mortality of coronary heart disease shows a positive relation to the severity of clinical and functional diagnostic parameters. Thus exercise therapy should be monitored by criteria that take ischemia, the myocardial situation and rhythm disorders into account. These criteria should be reliable and should be easy to determine as well as to apply. For pragmatic reasons the non-invasive evaluation of findings and the diagnostic symptom-limited ergometer test are especially significant for dosage and monitoring of exercise therapy. Monitored exercise therapy is here understood to mean individually adjusted exercising by patients, and training thus has to be based on diagnostic findings. First existing complaints have to be analyzed and such findings as size of infarction in the ECG, heart volume in the X-ray, size and function of the left ventricle by echography, etc. checked. Afterwards maximum physical work capacity on a multistage bicycle ergometer test is measured with respect to the following termination criteria: a) subjective reports by the patient during exercise (e.g. onset and severity of angina pectoris, dyspnea and/or fatigue of the leg muscles) and b) objective criteria such as significant ischemic ST-depression, exercise-hypertension, age-related submaximal heart rate and significant rhythm disorders. An inverse correlation is found between measured maximum symptom-limited physical performance and the frequency of cardiac termination criteria; a comparable inverse correlation exists with heart volume: max. O2 pulse.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Can the training of coronary patients be monitored by readily measurable parameters?]. 191 21

Impaired diastolic function of the hypertrophied and stiffened left ventricle is a characteristic feature of hypertrophic cardiomyopathy (Figure 1). Altered left ventricular filling dynamics and reduced left ventricular distensibility or increased left ventricular diastolic chamber stiffness are associated with reduced left ventricular stroke volume, increased left ventricular filling pressures and compressive effects on the coronary microcirculation. These factors contribute importantly to the clinical presentation of many patients, including symptoms of fatigue, dyspnea and angina pectoris. Reduced distensibility results both from factors determining the passive elastic properties of the ventricular chamber (including severity of hypertrophy, fibrosis and cellular disarray) and from factors influencing the rate and extent of active left ventricular relaxation (Figure 2). The factors contributing to impaired relaxation in hypertrophic cardiomyopathy are mediated via either inactivation dependent or load-dependent mechanisms. In laboratory animals, compromise of myocardial inactivation results in a persistent increase in intracellular calcium concentration and in prolonged interaction of the contractile proteins. Additionally, there is evidence for an increased number of active receptors for calcium antagonists and, lastly, for myocardial ischemia (Figure 3). Load-dependent mechanisms include diminished wall tension at the opening of the mitral valve, changes in afterload, contractility and coronary flow. Other factors are nonuniform and asynchronous regional ventricular function due to differing increases in thickness of the ventricular walls and ischemia (Figure 4). Calcium channel blockers exert a favorable influence on left ventricular relaxation and filling (Figure 5); verapamil and diltiazem are preferable to nifedipine. Verapamil increases left ventricular stroke volume without an increase in the end-diastolic pressure (Figure 6), reduces regional asynchrony if present, and leads to a more homogeneous regional diastolic filling (Figure 4).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Left ventricular diastolic function in hypertrophic cardiomyopathy. 202 81

We have studied contractile property and fatigue rates of skeletal muscle ventricle (SMV) constructed using the latissimus dorsi muscles of 11 dogs. The role of early interruption of collateral blood supply in the prevention of muscle ischemia and SMV fatigue was evaluated. Systolic function of SMV was measured in a hydraulic test system; afterload was set at 70 mmHg and preload 15 or 25 mmHg. Control SMV (GI: N = 7), which was fashioned immediately after interruption of collateral blood supply, generated an initial SMV pressure of 222 +/- 50 mmHg and stroke volume of 15 +/- 7 ml/beat with muscle stimulation at a burst-frequency of 50 Hz, but could sustain flow for only 3.5 +/- 0.8 minutes. SMV subjected to a vascular delay (Group II: N = 4) demonstrated improvement of fatigue rates; duration of flow 32.4 +/- 14.0 and sufficient contractile property (initial SMV pressure 182 +/- 17 mmHg, stroke volume 1- +/- 2 ml/beat). Thermography surface temperature mapping revealed remarkable improvement of blood distribution in GII muscles. Flow rates of thoracodorsal artery were significantly greater in GII muscles compared to those in GI muscles (15.0 +/- 3.7 ml/min/LD 100 g, 10.1 +/- 3.1 ml/min/LD 100 g, p less than 0.05, respectively). Despite significant improvement of functional durability in GII muscles, the ratio of oxygen consumption to lactate output was not different between 2 groups. These results suggest that early interruption of collateral blood supply can minimize muscle ischemia, resulting in diminishing fatigue of latissimus dorsi muscles without changes in skeletal muscle metabolism.
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PMID:[Experimental study on potential for cardiac assist by latissimus dorsi myograft--an importance of muscle ischemia]. 205 Oct 84


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