SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Native glycogen was prepared from intact and 12 and 36 h denervated white and red rat muscles, ultracentrifuged on a sucrose density gradient (3) and the fractions stained by the iodine method (4). An increase of the optical density of the fractions showing a relatively high density was observed, which may be related to the well known changes of muscle glycogen levels after denervation.
Whole gastrocnemius muscles of rabbits, preliminarily denervated, were grafted. At the moment of grafting (60 days after the operation) the muscles were in the state of deep atrophy attended by distrophic changes. The autotransplantated muscles took at the site of grafting, their further reorganization provided progressive development of the muscle tissue within the transplant, its growth, and formation of definitive muscle fibers with nerve terminals. After a definite time some degenerative changes were observed in the transplant muscle tissue; as a result the muscle tissue was substituted by connective tissue. These data support the statement founded before on feasible free grafting of preliminary denervated whole muscles. However, deep denervation atrophy seems to influence the remote results of the transplantation.
Rats were denervated in one hind limb and injected with 2,4-dichlorophenoxyacetic acid (2,4-D). Isotonic tetanic contractions of the muscles treated with 2,4-D after more than 10 days of denervation revealed prolonged relaxation times similar to those of the intact side and characteristic of clinical myotonia. No myotonic discharges were observed in the muscles denervated for more than 10 days and treated with 2,4-D. The increase in threshold for action potential generation secondary to denervation is suggested as the factor limiting the initiation of the repetitive discharges.
To test the hypothesis that human muscular dystrophies may be secondary to denervation, the responses in vitro of muscle in human malignant hyperpyrexia to electrical and pharmacological stimuli have been compared with those of the denervated mouse soleus muscle. The results suggest that the muscle abnormality in malignant hyperpyrexia is different from that produced by denervation. This must cast doubt on the concept that other human muscular dystrophies are secondary to denervation.
Denervated frog sartorius muscles showed an approximately 2--3 fold increase of cyclic GMP in their end-plate rich regions which did not appear up to 5 weeks after denervation in the normally end-plate-free pelvic region. No increase in cyclic AMP was seen in these preparations. The results suggest that the increase of cyclic GMP is related to processes specific to the region in which end plates are normally present.
Intact soleus and extensor digitorum longus muscles in the rat were freely grafted to the contralateral leg after either no preliminary treatment or 14 days prior denervation. Normal muscle grafts during the first week were characterized by a central zone of degenerating original muscle fibers (disappearing by 7-9 days) and a peripheral zone, containing regenerating muscle as well as small numbers of surviving original muscle fibers. A radial gradient of regeneration was establihed, with more mature muscle at the periphery and less mature muscle toward the center. Denervated grafts were characterized by rapid degeneration (within 2-3 days) of original muscle fibers in the central area, rapid appearance of regenerating muscle fibers (e.g. cross striations by 5 days) with uniform levels of differentiation throughout the graft and larger numbers of surviving original muscle fibers at the periphery. During the first week, stages of muscle differentiation in denervated grafts were attained 1-2 days earlier than comparable stages in normal grafts. Later stages of muscle differentiation were similar in both types of grafts. Histochemical studies revealed a loss of enzyme activity (phosphorylase, ATPase and SDH) in the center of early (2-4-day) normal and denervated grafts. Denervated grafts, however, possessed a thicker peripheral rim of enzymatically active surviving muscle fibers than normal grafts. In both types of grafts the old muscle fibers in the center were replaced by enzymatically active regenerating muscle fibers which stained uniformaly (ATPase) until 30 days. By 60 days a mixed fiber pattern had developed. Muscle spindles were found within the grafts.
Single motor unit firing rates were measured from the first dorsal interosseous muscle (FDI) of normal subjects and patients with partial denervation of that muscle. Motor unit discharges were recorded at various levels of voluntary, stationary, isometric contraction of the FDI. The mean increase in firing rate associated with an increased muscle tension of 100 gm was significantly greater in severely weak muscle. However, when an "adjustment" was made for the degree of weakness, reduced firing rate responses were observed which correlated with the degree of muscle weakness.
Ca2+ATPase activity and light chains of myosin, fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, in developing, adult and denervated fast, slow and cardiac muscles of the rat, guinea-pig, cat, rabbit and chick were studied. It has been shown that in normal adult muscles the electrophoretic pattern of light chains of myosin reflects the myosin ATPase activity only when muscles from the same animal species are compared. In homologous muscles from adult animals differing in size, the size-dependent difference in myosin ATPase activity is not revealed in the electrophoretic pattern. Both in developing and in denervated muscle, changes in myosin ATPase activity are either connected with changes in the pattern of light chains of myosin or this pattern does not change. This relation is different in fast and slow muscles and also differs in chick and rabbit muscles. There are several possibilities of explaining the relation between ATPase activity of myosin and the pattern of light chains of myosin. The observation that myosin from the soleus muscle of 1-month-old rabbit contains light chains corresponding to both fast and slow type of myosin, indicates that the change in myosin ATPase activity during development is due to changes in the ratio between the fast and slow type of myosin.
Denervated frog's semitendinosus muscles were studied. Fibrillation potentials generate propagated spikes which are conducted at a rate similar to that calculated for innervated muscles. The twitch tension per unit area was similar in denervated and innervated single fibres; the average value corresponded with values reported in the literature for fibres stimulated at 125/sec. Manganese ions (1-3 mM), selectively inhibit fibrillation potentials and have no appreciable effect upon evoked spikes. Mn2+ also inhibits (40-50%) the twitch responses and abolishes the resting tension of muscle fibres. The latter effects were observed in denervated as well as in innervated preparations when the fibres studied belonged to fasicles located at the site of entrance of the nerve. Disruption of the transverse tubular system by glycerol treatment does not interfere with the generation of fibrillation potentials, although the effects on twitching are similar to those reported in the literature. A possible mechanism is proposed to explain the generation of fibrillation potentials in frog denervated muscles.
Explore the source record for details and available documents.
Glycogen levels in the extensor digitorum longus of the rat undergo different changes after cutting the sciatic nerve compared with the destruction of the lumbosacral spinal cord. The differences most probably are due to early changes of the endocrine (adrenal and pancreatic) function after the latter type of denervation.
After preliminary conditioning depolarizations, single muscle fibers of the frog were tested for ability to contract in response to depolarization by 100 mM K+ Ringer solution. Denervated fibers (6-42 days) lose their ability to produce a 100 mM K+ contracture more rapidly than do control fibers. This decrease in 100 mM K+ contracture size (inactivation) is dependent on length of exposure to and magnitude of the conditioning depolarization and on the calcium concentration in the external medium. At 0.4 mM Ca++, the inactivation is 3 times faster than at 1.5 mM Ca++. The rate of contracture loss is not correlated with fiber diameter or the number of days after failure of neuromuscular transmission, and the preliminary conditioning depolarizations do not affect the rate of terminal relaxation from the 100 mM K+ contractures.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
1. Motoneurones provide trophic control of some of the functional characteristics of skeletal muscle fibres. This study has been designed to test whether the adenylate cyclase: cyclic AMP system may offer one potential mechanism for the mediation of neurotrophic regulation. 2. The concentration of cyclic AMP was measured at various intervals after muscle denervation. Muscle cyclic AMP concentration increases for the first 2 days after nerve section. It reaches a maximum value at 48 h and subsequently returns to the control value at 7 days. 3. Cyclic AMP concentration is unchanged by muscle disuse for the first 3 days following limb immobilization. Four days after immobilization, however, cyclic AMP increases in both the disused and contralateral control muscles. This phenomenon has been tentatively ascribed to some aspect of the inflammatory response. 4. Changing the level of nerve section, and therefore the length of the residual nerve stump, changes the temporal pattern of the increase in muscle cyclic AMP concentration. 5. Reinnervation of a denervated muscle produces a decrease in muscle cyclic AMP concentration. 6. It is concluded from the results that some aspect of nerve function provides trophic regulation of the muscle adenylate cyclase: cyclic AMP system. The mechanisms by which this regulation may be applied are considered in the Discussion.
This study of reinnervation of the larynx results from the research for a functional method of treatment for laryngeal paralysis of peripheral origin. The physiological reality of reinnervation of a denervated muscle by a nerve other than that anatomically destined for it, or "neurotisation", is now an established fact. This experimental study in 12 dogs consisted of neurotisation of a posterior crico-thyroid muscle, denervated by section of the recurrent laryngeal nerve, by implantation of a graft of sub-hyoid muscle with a nerve pedicle. Only one positive result at six months was seen. 8 failures could be explained by the absence of ventilatory difficulty necessary for the sub-hyoid muscles to be brought into action, and the other 3 failures two months after the operation by muscular fibrosis of the graft before neurotisation could occur. Physiology and the experience of other teams justify the continuation of this study.
Motor nerves to soleus muscles of rats were kept anesthetized for up to 7 days by applying solutions of lidocaine base or marcaine HCl. The anesthetic solutions were delivered from a subcutaneously located ALZA-minipump and reached the nerves through silastic cuffs. The ACh supersensitivity of muscles inactivated by nerve anesthesia for 3--7 days was comparable to that of muscles denervated for the same length of time. gm/gk (the ratio of total membrane conductance to the membrane K conductance) decreased from a normal value of 5--10 to less than two in 6--7 days, in anesthetic-inactivated and denervated muscles. The results were variable after 3 days of anesthesia. gm/gk of muscles which were tenotomized for 3 weeks was unchanged. The voltage-current curve for muscles kept in a solution containing 50 mM K propionate, which is steep at +50 mV, was less steep in denervated and anesthetic-inactivated, but not in tenotomized muscles, although atrophy was marked in all non-normal muscles.