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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Maintenance of low coronary flow (1 ml/min) during 40 or 70 min of anoxia maintained function and prevented Ca2+ overload during reoxygenation in isolated rat hearts. In comparison, recovery from 40 min of global ischemia resulted in only 20% of preischemic function and an increase in end-diastolic pressure (LVEDP) to 39 mmHg. Reperfusion Ca2+ uptake rose from 0.6 to 10.2 mumol/g dry tissue. Intracellular Na+ (Nai+) increased from 13 to 61 mumol/g dry tissue after 40 min of global ischemia, but was unchanged in hearts with low flow anoxia. When glucose and pyruvate were omitted from buffer used for anoxic perfusion, recovery was only 15% of preanoxic values, LVEDP rose to 32 mmHg, and reperfusion Ca2+ uptake was 7.2 mumol/g dry. In addition, Nai+ increased (47.4 mumol/g dry tissue) and ATP was depleted (1.0 mumol/g dry tissue) in the absence of substrate. In anoxic hearts supplied substrate, Nai+ stayed low (12 mumol/g dry tissue) and ATP was preserved (11.6 mumol/g dry tissue). Addition of ouabain (100 or 200 microM) and provision of zero-K+ buffer increased Nai+ and resulted in impaired functional recovery, increased LVEDP, and greater reperfusion Ca2+ uptake. These interventions also decreased energy availability in anoxic hearts. To distinguish between effects of Na+ accumulation and ATP depletion, monensin, a Na+ ionophore, was added during low flow anoxia. Monensin increased Nai+, decreased functional recovery and increased reperfusion Ca2+ uptake in a dose-dependent manner (1-10 microM) without changing ATP content. These results suggested that reduction of Nai+ accumulation by maintenance of Na+, K+ pump activity was the major mechanism of the beneficial effects of low coronary flow on reperfusion injury.
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PMID:Na+ accumulation increases Ca2+ overload and impairs function in anoxic rat heart. 215 54

About 22% of persons who suffer from acute paralytic poliomyelitis 20 to 30 years ago and were fully rehabilitated with maximal functional recovery began to experience new symptoms termed "Post-polio Sequelae" (PPS). These include unaccustomed fatigue, weakness in muscles previously affected or apparently unaffected, new joint pains, respiratory difficulties and intolerance to cold. Predictors for PPS are development of acute attack of paralytic polio before 10 years of age, involvement of all four limbs and having needed a ventilator during acute stage. The functional decompensation in PPS is presumed to be due to loss of normal neurones by aging and by metabolic fatigue of stressed neurones over passing years. Joint deformities due to muscular imbalance are also responsible for some of the symptoms. Treatment consists of reassurance and use of assistive devices and assistive exercises. The extent of problem of PPS is not known in India.
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PMID:New dimensions to poliomyelitis. 227 68

Unloading the rat hindlimb results in a decrease in mass, especially in those muscles that normally have a load-bearing function. The present study was designed to evaluate the effect of intermittent periods of weight support in ameliorating this atrophic response. Adult male Sprague-Dawley rats were assigned to either a control (CON), a hindlimb suspended (HS), or a hindlimb suspended plus intermittent weight support (HS-WS) group. HS-WS rats were walked slowly on a treadmill at 0.2 m/s and a 19% incline for 10 min, every 6 h. After 7 d, the in situ mechanical properties of the soleus (Sol) and medial gastrocnemius (MG) were studied. Body weights of HS and HS-WS rats were 9 and 13% lower than CON. The SOl weight relative to body weight was 21 and 9% lower in HS and HS-WS than CON. Maximum tetanic tension relative to muscle mass was significantly lower in HS than CON, whereas HS-WS had values similar to CON. The MG weight relative to body weight was significantly lower in both suspended groups. The maximum tetanic tension relative to muscle weight was significantly elevated in HS-WS compared to CON, suggesting that weight support may have preferentially maintained the contractile protein component of the muscle. Contraction times were 25% faster (p less than 0.05) in the Sol and unchanged in teh MG of HS rats. For each muscle, the fatigue properties were similar in all groups. These data indicate that a low-force, short-duration exercise regime results in a significant functional recovery in the "slow" Sol, whereas the "fast" MG is less affected.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Influence of 7 days of hindlimb suspension and intermittent weight support on rat muscle mechanical properties. 231 73

The muscle fibers in freely grafted skeletal muscles degenerate and are replaced by new fibers which develop within the graft. Myogenesis in regenerating muscle recapitulates, to a large extent, developmental myogenesis and may depend on similar modulating influences. In addition to the generation of new fibers, functional recovery of free muscle grafts also requires reinnervation and revascularization of the new fibers. Recovery of function should be improved by enhancing either myogenesis or reinnervation and revascularization. We have used two procedures, shown previously to stimulate peripheral nerve regeneration, to improve the morphologic and functional recovery of free, orthotopic grafts of rat extensor digitorum longus muscle. Each of the procedures was effective, but had potentially different sites of action. The first procedure, the condition/test paradigm, presumably increases the rate and extent of graft reinnervation. The second procedure, continuous infusion of the adenylate cyclase activator forskolin during the first 21 days after grafting, may influence both myogenesis and nerve regeneration. Each procedure increased regenerating muscle fiber size and functional capacity, and forskolin also significantly increased capillary density and fatigue resistance.
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PMID:Recovery of free muscle grafts in rat: improvement is associated with an increase in cyclic adenosine monophosphate concentration or use of the condition/test paradigm. 244 98

The purpose of this study was to document the recovery of isometric contractile function following tourniquet ischemia. Male Wistar rats (N = 27) were subjected to unilateral hindlimb tourniquet ischemia of 0 hr (control, N = 6), 1 hr (N = 5), 2 hr (N = 5), 3 hr (N = 5) and 4 hr (N = 3). Following a 2-week recovery period, isometric force measurements were made from both gastrocnemii of each rat with the contralateral limb acting as the control side. Each muscle was analyzed for maximal twitch (Pt, N/g), maximal rate of rise of twitch tension (DP/dt, N/sec), time to peak tension (TPT, msec), half relaxation time (RT 1/2, msec), maximal tetanus (P0, N/g, at 100 Hz), and fatigue (Burke Fatigue Protocol). Pt, P0, and DP/dt were significantly different from control values (P less than 0.05) for all hours of tourniquet ischemia. A strong negative correlation (P less than 0.001) was found for twitch (R = -0.84), tetanus (R = -0.78), and maximal rate of force development (R = -0.83) with respect to increasing hours of ischemia. The recovery of isometric twitch and tetanic function following tourniquet ischemia is inversely related to the ischemic interval. This study quantified the relationship between muscle ischemia and recovery of function following a 2-week interval and stresses the functional physiological changes which occur in skeletal muscle following tourniquet ischemia.
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PMID:Isometric contractile function recovery following tourniquet ischemia. 277 Feb 93

Isometric contractile function was studied after recovery in free, vascularized muscle transfer subjected to graded periods of intraoperative ischemia. Fifteen dogs had orthotopic replantation of their left gracilis muscles, with intraoperative ischemia times grouped as 0 (n = 3), 1 to 2 (n = 3), 2 to 3 (n = 4), or 3 to 4 (n = 5) hours. After recovery (mean 61.8 weeks), isometric twitch and tetanic tension and fatigue measurements were made in the replants and in the contralateral, control gracilis. On the average, replants were found to produce significantly less twitch (0.32 +/- 0.13 versus 0.49 +/- 0.24 N/g) and 75 Hz tetanic tension (2.2 +/- 0.9 versus 3.4 +/- 0.5 N/g) than controls. However, in several individual replants, 100% of control maximal tetanic tension was observed. Intraoperative ischemia time of up to 4 hours was not correlated with functional return. It is concluded that (1) full recovery is possible after free muscle transfer; (2) intraoperative ischemia, if less than 4 hours long, is not the primary determinant of functional recovery; and (3) factors besides intraoperative ischemia must be operative in producing the variability in recovery seen in this setting.
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PMID:The effect of intraoperative ischemia on the recovery of contractile function after free muscle transfer. 335 Dec 55

Persons with good recovery of function following their initial poliomyelitis are now, more than 30 years later, experiencing new weakness, fatigue, and muscle pain. The likelihood of muscle overuse being the cause of this late functional loss was investigated by dynamic electromyography (EMG) and foot-switch stride analysis in 34 symptomatic patients. Manual testing grouped the muscles, with strong (S) encompassing Grades Good (G) and Normal (N) while weak (W) included Fair plus (F+) to zero (0). After testing quadriceps and calf strength, the patients fell into one of four classes: strong quadriceps and calf (SQ/SC), strong quadriceps and weak calf (SQ/WC), weak quadriceps and strong calf (WQ/SC), or combined weak quadriceps and calf (WQ/WC). Quantified EMG (normalized by the manual muscle test EMG) defined the mean duration and intensity of the quadriceps, soleus, lower gluteus maximus, and long head of the biceps femoris during walking. Overuse was defined as values greater than the laboratory normal (mean + 1 SD). Each muscle exhibited instances of overuse, normalcy, and sparing. The biceps femoris was the only muscle with dominant overuse (82%). Quadriceps overuse was next in frequency (53%). Soleus activity infrequently exceeded normal function (34%), but this still represented more than twice the intensity and duration of the other muscles. Gluteus maximus action was also seldom excessive (34%). The patients averaged two muscles with excessive use during walking. Gait velocity of the SQ/SC strong group was highest (71% of normal) while the three categories that included weak muscles had walking speeds in the range of 50% of normal. The finding of muscle overuse during a single free-speed walking test that does not attain normal velocity supports the concept of muscle overuse being the cause of the patient's dysfunction.
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PMID:The postpolio syndrome. An overuse phenomenon. 340 20

The sciatic nerve was crushed in 5-6-day-old rats and the time course of recovery and changes in physiological and morphological properties of reinnervated fast and slow muscles was compared. The maximal tetanic tension developed by the reinnervated muscles was recorded at different times from about 18 days of age, when functional recovery was first seen, until 2 months. The maximal indirectly elicited tetanic tension of the reinnervated slow soleus muscle gradually increased from 55% of normal at 18 days to 75% of normal at 2 months. In contrast, the tension of the reinnervated fast muscle extensor digitorum longus (e.d.l.) fell sharply from 70% of normal at 18 days to 40% at 21 days and remained at that level till the end of the study. The total number of muscle fibres in control, reinnervated and denervated e.d.l. muscles was counted. At 18 days the number of fibres in the reinnervated e.d.l. was similar to normal but by 1 month it had fallen to one-third. This decrease did not take place in permanently denervated muscles until at least 35 days. Loss of fibres in the reinnervated soleus was small. During the early stages of reinnervation the contraction and relaxation of the fast muscles was very prolonged. By 1 month the time taken to reach peak twitch tension had decreased to normal values but the relaxation was still slower and remained so for several months. The study of fatigue resistance showed that at 18 days the reinnervated fast muscles were as fatigable as normal muscles from animals of the same age. The fatigability of normal muscles increased with age to adult levels, but the reinnervated muscles became more fatigue resistant and remained so. Our findings suggest that fast muscles become selectively impaired after nerve injury at 6 days because they lose a large number of fibres after reinnervation.
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PMID:Different pattern of recovery of fast and slow muscles following nerve injury in the rat. 673 99

Volleyball players commonly complain of pain in the hypothenar area. Fatigue fracture of the pisiform bone is suggested as a cause of this sport incapacity. The diagnostic importance of oblique and axial X-ray views of the Wrist is demonstrated. Early treatment by immobilization for 6 weeks usually results in complete functional recovery.
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PMID:Possible fatigue fracture of the pisiform bone in volleyball players. 706

1. The sciatic nerve was crushed in 5-6-day-old rats and the recovery of function of slow and fast muscles was studied. The first signs of recovery of function were seen 10-12 days after the operation. 2. Maximal tetanic tension developed by the reinnervated muscles was recorded and taken as an indication of their recovery. Two months after nerve crush, slow soleus muscles developed only slightly less tension than the control unoperated soleus muscles. The reinnervated fast muscles tibialis anterior (t.a.) and extensor digitorum longus (e.d.l.) developed only about 50% of the tension of the unoperated controls. 3. The fast muscles never recovered, remaining weaker and smaller throughout the animals' life. 4. The number of muscle fibres in the reinnervated fast muscles was substantially reduced and their fibre composition altered in that they contained mainly muscle fibres with high levels of oxidative enzymes. 5. The reinnervated fast muscles became much more fatigue resistant than the unoperated controls. 6. The possibility that these changes are due to motoneurone death was examined. The motoneurones innervating the fast muscles were labelled by retrograde transport of HRP. No significant reduction in the number of motoneurones innervating the operated muscles was found. 7. These results show that nerve injury during early post-natal life causes permanent changes in fast muscles that are not caused by motoneurone death.
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PMID:Recovery of slow and fast muscles following nerve injury during early post-natal development in the rat. 715 15


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