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

A reexamination of the question of specificity of reinnervation of fast and slow muscle was undertaken using the original "self" nerve supply to the fast lateral gastrocnemius (LG) and slow soleus muscles in the rat hindlimb. This paradigm takes advantage of the unusual situation of a common nerve branch, which supplies both a fast and slow muscle, and of the opportunity to keep the reinnervating nerve in its normal position. In addition it provides a test of the effects of cross-reinnervation among muscles of the same functional group. The properties of soleus and LG muscles and of individual muscle units were characterized in normal rats and in rats 4-14 mo after cutting the lateral gastrocnemius-soleus (LGS) nerve and suture of the proximal stump to the dorsal surface of the LG muscle. Individual muscle units were functionally isolated by stimulation of single motor axons to LG or soleus muscle contained in teased filaments in the L4 and L5 ventral roots. Motor units were classified as fast contracting fatiguable (FF), fast contracting fatigue resistant (FR), and slow (S) on the basis of criteria described in the cat by Burke et al. and applied to rat muscle units by Gillespie et al. Muscle fibers were classified as fast glycolytic (FG), fast oxidative glycolytic (FOG), and slow oxidative (SO) on the basis of histochemical staining for myosin ATPase, nicotinamide-adenine dinucleotide diaphorase (NADH-D), and alpha-glycerophosphate (alpha-GPD). Reinnervated muscles developed less force and weighed less in accordance with having fewer than normal motor units and having lost denervated muscle fibers. Normal LG contained a small proportion of S-type motor units (9%), whereas the majority (80%) of control soleus units were S type. After reinnervation, each muscle contained similar proportions of fast and slow motor units with S-type units constituting 30% of units in both muscles. When compared with the normal motor-unit sample, there was no significant change in average twitch and tetanic force in reinnervated muscles for each type of motor unit. However, the range within each type was greater, and there was considerable overlap between types. Twitch contraction time was inversely correlated with force in normal and reinnervated muscles as shown previously in self- and cross-reinnervated LGS in the cat. Changes in proportions of motor units in reinnervated LG were accompanied by corresponding changes in histochemical muscle types. This contrasted with reinnervated soleus in which the proportion of muscle fiber types was not significantly changed from normal despite significant change in motor-unit proportions.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Motor units and histochemistry in rat lateral gastrocnemius and soleus muscles: evidence for dissociation of physiological and histochemical properties after reinnervation. 295 72

The effects of 28 days of hindlimb suspension (HS) and HS plus 10 daily forceful lengthening contractions on rat soleus muscle fibers were studied. Compared with age-matched controls (CON), soleus wet weights of suspended rats were significantly decreased (approximately 49%). In HS rats, the light adenosinetriphosphatase (ATPase) fibers (staining lightly for myosin ATPase, pH = 8.8) atrophied more than the dark ATPase fibers (staining darkly for myosin ATPase, pH = 8.8). Single-fiber alpha-glycerophosphate dehydrogenase (GPD) and succinate dehydrogenase (SDH) activities and the proportion of dark ATPase fibers were higher in HS than CON rats. Daily forceful lengthening contractions did not prevent the suspension-induced changes. These results considered in conjunction with a collaborative study on the mechanical properties of HS rats (Roy et al., accompanying paper) suggest a shift in the contractile potential of the muscle following HS without a deficit in SDH, a metabolic property commonly associated with resistance to fatigue. The results support the view that soleus muscle fibers can change from a slow-twitch oxidative to a fast-twitch oxidative-glycolytic profile, but rarely to a fast-twitch glycolytic one, and that SDH and GPD activity per volume of tissue can be maintained or increased even when there are severe losses of contractile proteins.
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PMID:Size and metabolic properties of single muscle fibers in rat soleus after hindlimb suspension. 295 34

The atrophy produced by endocrine disorders is primarily due to alterations in protein and carbohydrate metabolism. Type II muscle fibers are more severely affected than are Type I fibers. Steroid myopathy and the myopathy associated with excess ACTH have a typical pattern of proximal weakness affecting the legs more than the arms. Steroid myopathy is usually not apparent until other signs of glucocorticoid excess are present. Treatments of steroid myopathy are as follows: Lower the dose of steroid, use a nonfluorinated glucocorticoid, and exercise or physical therapy. Adrenal insufficiency produces generalized weakness, muscle cramping, and fatigue in 50 per cent of patients. Some patients also develop hyperkalemic paralysis. The treatment is hormone replacement. Thyrotoxicosis produces myopathy caused by net protein catabolism, accelerated basal metabolic rate and impaired carbohydrate metabolism. Shortening of contraction time may result from accelerated myosin ATPase activity and enhanced calcium uptake by the sarcoplasmic reticulum. Depolarization of the muscle fiber and impaired Na-K activity in muscle may predispose to thyrotoxic periodic paralysis. Neuromuscular presynaptic impairment may account for the worsening of myasthenia gravis by thyrotoxicosis. In hypothyroidism, impaired energy metabolism may limit force generation. Slow contraction and relaxation reflect reduction in myosin ATPase activity and impaired calcium uptake by the sarcoplasmic reticulum. Treatment for thyroid-associated muscle disorders is restoration of a euthyroid state. Muscle weakness associated with hypopituitarism is due to loss of thyroid and adrenal cortical hormones. Children require growth hormone for muscle development. T3 and growth hormone synergize to maintain normal protein synthesis. Primary and secondary hyperparathyroidism and osteomalacia are often associated with proximal weakness and fatigability. The myopathy improves with restoration of normal PTH levels and vitamin D replacement. Hypoparathyroidism and pseudohypothyroidism are associated with tetany. Tetany is worsened by alkalosis and is treated by calcium and magnesium replacement.
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PMID:Endocrine myopathies. 306 2

Contractile and histochemical properties of the triceps surae were compared in 16 males and 4 females aged 20 to 49 years. Surface electrical stimulation was used to determine twitch, tetanic and fatigue parameters. From these tests, twitch tension (Pt), time to peak tension (TPT), half relaxation time (1/2 RT), tetanic tensions at 10, 20 and 50 Hz and an index of fatigue (FI) were calculated. A maximal voluntary contraction (MVC) was also performed. Muscle samples from the belly of the lateral gastrocnemius were obtained using the needle biopsy technique. The samples were treated histochemically for myosin ATPase and NADH-tetrazolium reductase in order to classify the fibres as either Type I, slow twitch (ST) or Type II, fast twitch (FT) and to determine fibre areas. Correlations were performed between the grouped male and female contractile and histochemical variables. The results demonstrated significant positive relationships demonstrated significant positive relationships between percentage of ST fibres (%ST) and TPT (r = 0.49), and %ST and the ratio of tetanic forces at 10 Hz to 50 Hz (Po10/Po50) (r = 0.55). No significant relationships were obtained for Pt, 1/2 RT, MVC or FI with any histochemical parameter. The results suggest that fibre type distribution determined using myosin ATPase is related to electrically stimulated isometric contractile speeds and not to voluntary force generation (MVC) or electrically induced fatigue.
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PMID:Comparison of the histochemical and contractile properties of human triceps surae. 320 63

To study the relation between the response of respiratory muscle to inspiratory loads and glycogen content, we subjected unanesthetized sheep to moderate and severe inspiratory flow resistive (IFR) loads. Only severe IFR loads eventually led to a decrease in transdiaphragmatic pressure (Pdi) and a concomitant rise in PaCO2. Respiratory and nonrespiratory skeletal muscle samples were obtained at necropsy. Glycogen content was determined biochemically in muscle homogenates. Frozen sections were stained with periodic acid-Schiff (PAS) for glycogen and fibers were typed using myosin ATPase stain. Fibers were categorized as full, intermediate, or devoid of glycogen by a subjective scoring system of PAS staining intensity. We found that glycogen content decreased in the costal and crural diaphragm and in the intercostal muscles as the duration of moderate IFR loaded breathing was increased. With severe loads glycogen content decreased significantly, reaching about 40 and 22% of control levels in the costal and crural diaphragm, respectively (P less than 0.01). In addition, with severe IFR loads, a statistically significant proportion of both type I and type II muscle fibers was depleted of glycogen when compared with that of controls (P less than 0.05), but more type II fibers were depleted than type I fibers (50 vs 23%). These data indicate that in sheep subjected to IFR loads: (1) glycogen content in the respiratory muscles decreases as the severity and duration of loaded breathing increases and (2) respiratory muscle fatigue occurs at a time when considerable glycogen is still present in type I fibers in the diaphragm.
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PMID:Respiratory muscle response to load and glycogen content in type I and II fibers. 339 Dec 57

The contractile, histochemical, morphological and electrophysiological properties of two rat laryngeal muscles, the cricothyroid and posterior cricoarytenoid, have been measured. Both muscles act during respiration to maintain upper airway patency and an even distribution of air in the lungs. The cricothyroid and posterior cricoarytenoid are fast-twitch muscles, having contraction times of 3.4 and 7.2 ms respectively, high myosin ATPase activity, abundant sarcoplasmic reticulum (with average volumes of 9% and 15%, respectively, of the fibre volume) and T-system membrane (with average areas of 0.4 and 0.5 micron 2 micron -3 of fibre). The large areas of T-tubule membrane are reflected in the average specific membrane capacities of 6.5 muF cm-2 to 10.5 muF cm-2, which are high considering the small diameter of the fibres (20-30 micron). Of the two muscles, the posterior cricoarytenoid has the faster contraction time and the more abundant sarcoplasmic reticulum content. In addition, the posterior cricoarytenoid is less resistant to fatigue and demonstrates lower succinic dehydrogenase activity. The fatigability of this muscle, coupled with its general lack of functional reserve, suggest that its failure may contribute to upper airway obstruction during respiratory distress.
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PMID:The contractile properties, histochemistry, ultrastructure and electrophysiology of the cricothyroid and posterior cricoarytenoid muscles in the rat. 621 35

Lizard skeletal muscle fiber types were investigated in the iliofibularis (IF) muscle of the desert iguana (Dipsosaurus dorsalis). Three fiber types were identified based on histochemical staining for myosin ATPase (mATPase), succinic dehydrogenase (SDH), and alphaglycerophosphate dehydrogenase (alphaGPDH) activity. The pale region of the IF contains exclusively fast-twitch-glycolytic (FG) fibers, which stain dark for mATPase and alphaGPDH, light SDH. The red region of the IF contains fast-twitch-oxidative-glycolytic (FOG) fibers, which stain dark for all three enzymes, and tonic fibers, which stain light for mATPase, dark for SDH, and moderate for alphaGPDH. Enzymatic activities of myofibrillar ATPase, citrate synthase, and alphaGPDH confirm these histochemical interpretations. Lizard FG and FOG fibers possess twitch contraction times and resistance to fatigue comparable to analogous fibers in mammals, but are one-half as oxidative and several times as glycolytic as analogous fibers in rats. Lizard tonic fibers demonstrate the acetylcholine sensitivity common to other vertebrate tonic fibers.
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PMID:Histochemical, enzymatic, and contractile properties of skeletal muscle fibers in the lizard Dipsosaurus dorsalis. 645 26

This review describes muscle fiber types based on their histochemical, ultrastructural, biochemical, and physiologic properties. Reportedly the speed of muscle fiber contraction is directly proportional to relative myosin ATPase activity (at pH 9.4) while fatigability relates to relative oxidative capacity. Type I fibers have low ATPase activity (at pH 9.4), are slow twitch, have high oxidative and low glycolytic capacity, and are relatively resistant to fatigue. Type IIA fibers have high myosin ATPase activity (pH 9.4), are fast twitch, have high oxidative and glycolytic capacity, and are relatively resistant to fatigue. Type IIB fibers have high myosin ATPase activity (pH 9.4), are fast twitch, have low oxidative and high glycolytic capacity, and fatigue rapidly.
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PMID:Muscle fiber types. 646 27

Tenotomy of the rat soleus muscle is followed by a central degeneration of slow, fatigue-resistant muscle fibers. Previous experiments showed that fast, fatigable fibers of the gastrocnemius when transformed to slow, fatigue-resistant fibers by cross-reinnervation also develop lesions after tenotomy. The experiments described in this communication were carried out to discover whether the susceptibility of fibers to lesions was determined by their fiber type or the nature of their innervation. Rats were rendered hyperthyroid by the administration of sodium 3,3',5-triiodo-L-thyronine (T3) for 7 to 10 weeks. Tenotomy of the soleus muscles was then carried out and the experimental and contralateral muscles were removed and stained for myosin ATPase activity after a further 2 weeks. The hyperthyroid state of each animal was confirmed by the assay of succinate dehydrogenase activity of liver and the contralateral muscle. After acid preincubation, whole muscle fiber type counts of contralateral muscles showed a statistically significant change from a predominantly acid-stable population of fibers to acid-labile fibers. In addition, many fibers of intermediate staining properties were seen. When the experimental muscles were examined, all three varieties of fiber showed central degeneration. The nature of the fiber type change induced by T3 and the role that innervation might play in this is discussed. It was concluded that the susceptibility of fibers to the lesions that follow tenotomy is dependent on the nature of their innervation rather than their fiber type.
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PMID:Central core degeneration after tenotomy in soleus muscles of hyperthyroid rats. 688 81

1. Contractile and fatigue-resistance characteristics, temperature sensitivity (10-37 degrees C) of contraction, and histochemical fibre types were determined for two of the extraocular muscles, the superior rectus and levator palpebrae superioris (levator), of the rabbit. 2. The levator displayed similar contractile characteristics (time to peak, half-relaxation time of twitch response, and twitch-tetanus force ratio) to mammalian fast-twitch limb muscle at room temperature (20 degrees C). However, normalized twitch and tetanic force levels were significantly less than those found in limb muscle. The superior rectus displayed the characteristics of even faster contraction than the levator at 20 degrees C, but generated lower maximum force levels than the levator. 3. The twitch response of the superior rectus showed a biphasic relaxation phase. This response was not due to non-twitch (tonic) fibres present in the superior rectus as it was unaffected by propranolol application during muscle stimulation. 4. The superior rectus and levator displayed significantly less fatigue in the tetanic force response than fast-twitch limb muscles did in response to a fatiguing electrical stimulation protocol. The levator was significantly more fatigue resistant than the superior rectus. 5. The force responses of both extraocular muscles displayed a similar dependence on temperature (10-37 degrees C) to limb skeletal muscles. 6. The superior rectus and levator exhibited a high proportion of fast-twitch muscle fibres (type II) as shown by myosin ATPase staining. Succinate dehydrogenase activity indicated that these muscles showed a high oxidative capacity, with a staining intensity typical of type I or type II A fibres of limb muscles. 7. The results emphasize the morphological and functional complexity of mammalian extraocular muscles. The combination of very fast contractile properties with high oxidative capacity make these muscles well suited to their role in eye/eyelid movement.
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PMID:Contractile properties and temperature sensitivity of the extraocular muscles, the levator and superior rectus, of the rabbit. 802 38


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