Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.4.1 (myosin ATPase)
 1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Isometric twitch and tetanic contractile properties and velocity of unloaded shortening (V0) of whole avian posterior latissimus dorsi muscle (PLD) were examined between embryonic day 15 and the first 2 wk after hatching. The time to peak twitch force, time to half-relaxation of the twitch response, and time to half-peak tetanic force all change significantly during the final week in ovo but do not change during the first 2 wk ex ovo. Comparisons with previously published reports by others indicate that the twitch half-relaxation time at hatching is approximately the same as that of the adult PLD. The velocity of unloaded shortening increases 2.3-fold during the period studied. It has previously been shown by other that the velocity of shortening is well correlated with a muscle's myosin ATPase activity. Therefore, the observed changes in V0 suggest that the myosin ATPase activity of the avian PLD increases between embryonic day 15 and the first 2 wk posthatching, and this change could account, at least in part, for some of the changes in the isometric properties that were measured.
Am J Physiol 1982 Sep
PMID:Isometric contractile properties and velocity of shortening during avian myogenesis. 621 93

Myocardial preservation during open heart surgery in children was studied using biopsies of the right ventricle taken at the beginning and end of a bypass with a Tru-Cut biopsy needle. Three assessments were used: (1) semi-quantitative cytochemical grading of Baker's acid haematein reaction, and the distribution of succinate dehydrogenase and myosin ATPase; (2) microdensitometry of the succinate dehydrogenase activity; and (3) quantitative birefringence measurements to assess the response of the myocardial fibres to ATP and calcium. For each assessment, the values at the beginning and end of the bypass were compared. In a series of 42 children, two died in low cardiac output and three others required substantial inotropic support. No patient showed deterioration in the overall cytochemical assessment. Two patients showed deterioration in birefringence, one died and one had low cardiac output. The remaining three patients who had post-operative problems had low birefringence values at the beginning of bypass. Thirty-two patients were used for the microdensitometric assays, one died and three required substantial inotropic support. Succinate dehydrogenase activity decreased significantly during bypass in only two patients. One of these died and the other required substantial inotropic support.
Histochem J 1982 Sep
PMID:Cellular chemical indices of right ventricular protection in children. 621 86

Experimental right ventricular pressure-overload hypertrophy in small mammals is associated with early muscle dysfunction, even before the onset of overt pump failure. Experimental results are quite heterogeneous regarding muscle function of the pressure hypertrophied left ventricle. Muscle dysfunction of the right or left ventricle, when found, may be causally related to alterations of myosin ATPase activity and isozyme type. However, the effect of a gradual pressure overload, analogous to that which occurs in human aortic stenosis, on myocardial contractile function and myosin ATPase activity has not been studied in a large animal whose normal myosin isozyme pattern resembles that of man. We therefore studied pump performance, myocardial contractile function, and myosin ATPase activity and isozyme pattern in pigs with severe, gradually applied left ventricular pressure overload. Thirteen weeks after supravalvular aortic banding, 10 pigs grew more than 7-fold in body weight and were found to have an aortic stenosis area of 0.5 +/- 0.1 cm2 with a gradient of 93 +/- 12 mm Hg. Compared with nine control animals, the banded animals had a 67% increase in left ventricular mass relative to body weight without overt pump failure as measured by cardiac index and pulmonary artery wedge pressure. Left ventricular ejection performance, measured as shortening fraction, was maintained except in three animals with extreme hypertrophy, in which depressed ejection performance may have been due to an afterload mismatch, myocardial dysfunction, or both. Myocardial contractile function, determined from the end-systolic stress-diameter relationship, was normal except in two pigs in which ejection performance was depressed and left ventricular mass was more than doubled. Only the slow V3 isozyme of myosin ATPase was found in both normal and hypertrophied pig myocardium, and the ATPase activity was normal in pigs with all degrees of hypertrophy. Thus, in a large animal model of severe, gradual left ventricular pressure overload, in which myosin isozyme pattern remains apparently unaltered, moderate hypertrophy can be associated with normal myosin ATPase activity and contractile function that is normal by current methods of evaluation.
Circ Res 1983 Sep
PMID:Contractile function, myosin ATPase activity and isozymes in the hypertrophied pig left ventricle after a chronic progressive pressure overload. 622 6

Muscle fibre composition and capillarity were evaluated in frozen sections stained for myosin ATPase of the soleus and the white area of the medial head of the gastrocnemius of rats made hyperthyroid by injections of triiodothyronine (300-400 micrograms/kg body weight, every other day) for 2, 3 and 4 weeks. O2 consumption of homogenates of these muscles in the presence of excess inorganic phosphate (Pi) and ADP with pyruvate and malate as substrates was also measured. Increased oxidative capacity was observed in the soleus homogenates of hyperthyroid animals after 2 weeks of treatment while no changes were observed in the oxidative capacity of the homogenates of the white area of the medial head of the gastrocnemius, even after 4 weeks of treatment. Hyperthyroid animals showed a greater capillarity than controls in both muscles. In the soleus this was evident after 2 weeks of treatment while in the white area of the medial head of the gastrocnemius, it was evident only after 4 weeks of treatment. Fibre composition was affected in the soleus after 4 weeks of treatment. In control animals two fibre types were present in the soleus: slow-twitch oxidative fibres (s.o. or type I fibres) with a high ATPase activity after acid pre-incubation and fast-twitch glycolytic oxidative fibres (f.o.g. or type IIa fibres) with a low ATPase activity after acid pre-incubation. In the soleus of the hyperthyroid animals, a third fibre type with intermediate ATPase activity after acid pre-incubation was also present. This most probably represents a change in the type of myosin being synthesized by some fibres. No changes in fibre composition were observed in the white area of medial head of the gastrocnemius which was made up of only fast-twitch glycolytic fibres (f.g. or type IIb fibres). The changes in oxidative capacity and capillarity in the soleus preceded and did not seem to be related to the changes in the type of myosin being synthesized. The increased capillarity found in the white area of the medial head of the gastrocnemius of the hyperthyroid animals, in the absence of an increase in the oxidative capacity, indicates that the latter is not the only factor that determines capillarity in skeletal muscle.
J Physiol 1983 Sep
PMID:The effect of hyperthyroidism on capillarity and oxidative capacity in rat soleus and gastrocnemius muscles. 622 77

Luciani's ipsilaterally acting 'trophic' cerebellar influence on striated muscle was reinvestigated in hemidecerebellate preparations of varying extent. Cats with hindlimb postural asymmetries for 4 or more days after the lesion developed a bilateral reduction of maximum tetanic tension and increased twitch/tetanus ratios of soleus. In addition, soleus on the side of the lesion lost force and weight, showed decreased twitch contraction and half-relaxation times, elevated myosin ATPase activity in part of its fibres, occasional fibre necrosis and a few snake coils. Protracted postural asymmetry occurred only if complete hemicerebellectomy included ablation of the lateral vestibular nucleus and extended for at least 3.0 mm across the midline into the contralateral vermal and intermediate cortex, especially of Larsell's lobuli IV and V. Most simply, the cerebellar effect on muscle is explained as the result of altered motoneuronal activation patterns. Comparison of the experimental soleus changes with Holmes's clinical findings in cases of cerebellar injury suggests that muscle itself participates in experimental and human cerebellar asthenia.
Brain 1983 Sep
PMID:Motor activity and muscle properties in the hemidecerebellate cat. 622 71

The effects of different thyroid states on some histochemical and biochemical properties of fast-twitch muscle were studied using rat extensor digitorum longus (EDL) muscle. This muscle was found to be much less responsive to thyroidal influence than the slow-twitch soleus muscle. In EDL muscles of hypothyroid rats, fast leads to slow conversions were observed in fibre type composition, myosin ATPase activity and light chain pattern, and in the subunit composition of lactate dehydrogenase, while the only significant slow leads to fast conversion observed in thyrotoxicosis was a decrease in the proportion of slow-oxidative fibres. Denervation of the hypothyroid muscle produced the highest degree of fast leads to slow transformation. These findings support the view that denervation and dysthyreosis alter gene expression in muscle by independent mechanisms.
J Muscle Res Cell Motil 1981 Sep
PMID:The effects of thyroid status on some properties of rat fast-twitch muscle. 645 58

This paper reports the following data with regard to the BBWT cardiovascular system: 1) Arterial Blood pressure progressively increases from 1 to 12 month of age, accompanied by marked left ventricular hypertrophy; 2) The myosin ATPase activity is enhanced about three times; 3) No differences in myosin light chain pattern is observed; 4) The peptide pattern obtained after chymotryptic digestion of the myosin molecule shows that some peptides, which are not evident or barely discernible, in 1 month old animal, are present in the adult one. These findings are surprising because it is well known that the ATPase activity decreases with age and hypertrophy. It is possible that other factors, as the levels of circulating cathecolamines or the thyroid hormones, are involved in the control of myosin synthesis and consequently in its ATPase activity.
Boll Soc Ital Biol Sper 1981 Sep 15
PMID:Changes in ventricular myosin properties during broad breasted white turkey (BBWT) development. 645 20

Skeletal limb muscles of the dog could generally be differentiated into three fibre types according to myosin adenosine triphosphatase (ATPase) (pH 9.4) and succinic dehydrogenase activities. However, because this was not always possible, for comparative purposes only, division into low myosin ATPase (slow twitch) type I and high myosin ATPase (fast twitch) type II fibres was used. The percentage of these fibre types in m deltoideus, m triceps brachii caput longum, m vastus lateralis, m gluteus medius, m biceps femoris and m semitendinosus was examined in the greyhound, crossbred and foxhound. In all muscles the greyhound had a significantly higher percentage of fibres with high myosin ATPase activity at pH 9.4 than the other breeds, with almost 100 per cent in most muscles examined. The activities of nine enzymes and glycogen concentration were determined in m gluteus medius and m semitendinosus of the greyhound and crossbred. Significantly higher levels of creatine kinase, aldolase, alanine aminotransferase and citrate synthase and significantly lower activities of 3-hydroxyacyl coenzyme A dehydrogenase and hexokinase were found in both muscles of the greyhound. The implications of these findings are discussed.
Res Vet Sci 1981 Sep
PMID:Skeletal muscle fibre composition in the dog and its relationship to athletic ability. 645 29

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.
Exp Neurol 1983 Sep
PMID:Central core degeneration after tenotomy in soleus muscles of hyperthyroid rats. 688 81

Immunocytochemical characteristics of myosin have been demonstrated directly in normal and cross-reinnervated skeletal muscle fibers whose physiological properties have been defined. Fibers belonging to individual motor units were identified by the glycogen-depletion method, which permits correlation of cytochemical and physiological data on the same fibers. The normal flexor digitorum longus (FDL) of the cat is composed primarily of fast-twitch motor units having muscle fibers with high myosin ATPase activity. These fibers reacted with antibodies specific for the two light chains characteristic of fast myosin, but not with antibodies against slow myosin. Two categories of fast fibers, corresponding to two physiological motor unit types (FF and FR), differed in their immunochemical response, from which it can be concluded that their myosins are distinctive. The soleus (SOL) consists almost entirely of slow-twitch motor units having muscle fibers with low myosin ATPase activity. These fibers reacted with antibodies against slow myosin, but not with antibodies specific for fast myosin. When the FDL muscle was cross-reinnervated by the SOL nerve, twitch contraction times were slowed about twofold, and motor units resembled SOL units in a number of physiological properties. The corresponding muscle fibers had low ATPase activity, and they reacted with antibodies against slow myosin only. The myosin of individual cross-reinnervated FDL muscle units was therefore transformed, apparently completely, to a slow type. In contrast, cross-reinnervation of the SOL muscle by FDL motoneurons did not effect a complete converse transformation. Although cross-reinnervated SOL motor units had faster than normal twitch contraction times (about twofold), other physiological properties characteristic of type S motor units were unchanged. Despite the change in contraction times, cross-reinnervated SOL muscle fibers exhibited no change in ATPase activity. They also continued to react with antibodies against slow myosin, but in contrast to the normal SOL, they now showed a positive response to an antibody specific for one of the light chains of fast myosin. The myosins of both fast and slow muscles were thus converted by cross-reinnervation, but in the SOL, the newly synthesized myosin was not equivalent to that normally present in either the FDL or SOL. This suggests that, in the SOL, alteration of the nerve supply and the associated dynamic activity pattern are not sufficient to completely respecify the type of myosin expressed.
J Cell Biol 1983 Sep
PMID:Myosin isozymes in normal and cross-reinnervated cat skeletal muscle fibers. 688 17


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