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PubMed1986

Absence of the alpha and gamma subunits of 7S nerve growth factor in denervated rodent iris: immunocytochemical studies.

Immunocytochemical studies were performed to determine if denervated rodent iris produces nerve growth factor (NGF) in a form chemically similar to that of the 7S NGF complex in mouse submandibular glands. Antisera to the alpha, beta, and gamma subunits of 7S NGF were raised in rabbits and characterized on immunoblots of SDS-containing polyacrylamide gels. Antisera were applied to stretch preparations of rat and mouse irides that were cultured for periods of 2 to 6 days or sympathetically denervated by superior cervical ganglionectomy and left in situ 4 days. Antibody binding was visualized by indirect immunofluorescence. In control studies done on plastic sections of mouse submandibular glands, antisera co-localized the three subunits of 7S NGF within secretory granules of granular tubule cells. In denervated rat iris, beta NGF immunoreactivity was evident in a cellular plexus that resembled in distribution and morphology nerve fibers in the normal iris, in agreement with a previous study (R.A. Rush (1984). Nature (London) 312, 364-367). Identical staining patterns were observed in mouse iris. In neither rat or mouse, however, did the nerve-like processes stain with antibodies suggests that the NGF-like protein in denervated rodent iris is not synthesized as part of the 7S NGF complex. Iris also did not react with antibodies to epidermal growth factor, a protein co-localized with NGF in mouse submandibular glands and in guinea pig prostate.

Animals↗
PubMed1991

Expression of Ca2(+)-ATPase isoforms in denervated, regenerating, and dystrophic chicken skeletal muscle.

The expression of fast and slow isoforms of the sarcoplasmic reticulum Ca2(+)-ATPase was studied in denervated, regenerating, and dystrophic fast and slow avian skeletal muscles. We found that both fast and slow Ca2(+)-ATPase isoforms were expressed in most myofibers following denervation of adult fast-twitch muscle, but only the slow Ca2(+)-ATPase isoform was found in slow-tonic muscle which had been denervated. Regenerating myotubes in normally innervated and previously denervated adult fast-twitch or slow-tonic muscle expressed both Ca2(+)-ATPase isoforms. Expression of the slow Ca2(+)-ATPase isoform was found to persist in dystrophic fast-twitch muscle, long after it had disappeared from normal fast-twitch muscle. However, the fast Ca2(+)-ATPase isoform disappeared from slow-tonic muscle similarly in normal and dystrophic birds. These results demonstrate that the appearance of myosin heavy chain isoforms characteristic of developing muscle is correlated with similar changes in the expression of sarcoplasmic reticulum Ca2(+)-ATPases.

Animals↗
PubMed1976

Influence of chloride and sodium pump activity on carbachol- and acetylaholine-induced depolarizations in denervated rat diphragm.

The effect was measured of low chloride medium and ouabain on carbachol- and acetylcholine-induced depolarizations in denervated rat diaphragm. Membrane potentials were measured in rat diaphragm muscle fibers 10-14 days after denervation. Depolarizations induced by carbachol and acetycholine were increased when the extracellular chloride concentration was diminished from 110 to 40 or 10 mM. Sodium pump inhibition by ouabain (10(-4) M) dramatically enhanced the carbachol depolarizations. In 40 mM Cl- solutions, dose-response relations were determineed with ACh in the absence of presence of dTc. For ACh a pD2 value of 5.2 was found; the pA2 value for dTC appeared to be about 6.4. Therefore, the binding properties of the post-denervational receptors do not appear to be influenced by the chloride gradient. It was concluded that drug-induced depolarizations of the denervated rat diaphragm are short-circuited by chloride ions and counteracted by sodium pumping.

Acetylcholine↗
PubMed1979

Denervation supersensitivity to noradrenaline in the guinea-pig vas deferens in vivo: absence of the postjunctional component.

The effects of denervation and cocaine on the responsiveness of the guinea-pig vas deferens to noradrenaline (NA) were studied. The magnitude of the denervation supersensitivity differed in vivo and in vitro. Cocaine-induced supersensitivity to NA was similar in vivo and in vitro. Only denervation increased the maximum response in experiments in vitro. It is suggested that in the guinea-pig vas deferens the postjunctional component of denervation supersensitivity to NA could result from the experimental conditions involving the isolation procedure.

Animals↗
PubMed1992

Type-specific changes in fiber morphometry following denervation of canine extraocular muscle.

To investigate the changes that occur in extraocular muscle morphometry following denervation, 12 beagles were subjected to intracranial section of the left oculomotor nerve. The inferior and medial rectus muscles were removed from both orbits of four dogs killed at each 4-week postoperative interval. Fiber diameters and fiber-type ratios of denervated muscles were compared with those from paired muscles in the normal orbit. We found significant, persistent atrophy of the singly innervated fibers in both the global and orbital layers of denervated extraocular muscle. The multiinnervated fibers were predominantly spared from denervation atrophy. We also found a significant increase in the proportion of multiinnervated fibers in the orbital layer only. These results suggest a relative neurotrophic independence of multiinnervated fibers in extraocular muscle.

Animals↗
PubMed1983

Trophic action of nerve extract on denervated skeletal muscle in vivo: dose dependency, species specificity, and timing of treatment.

Atrophy in a denervated muscle results from the disuse caused by paralysis of the muscle, and from the loss of special neurotrophic substances. Proteins extracted from rats' sciatic nerves have been shown to prevent the nondisuse atrophy of denervated rats' extensor digitorum longus (EDL) muscles when administered by intramuscular injection. The present investigation elicited more information about this neurotrophic phenomenon. Extract of liver failed to affect the rate of atrophy of denervated EDL muscles. Injection of various doses of extract of rats' or sheep's sciatic nerves indicated that the action of the extract was dose-dependent but not species-specific. Muscles denervated for 14 days and injected with extract on all 14 days or only on the first or last 7 days all exhibited significantly less atrophy than those that were not injected.

Animals↗
PubMed1986

Effects of actinomycin D on contractile properties of denervated rat skeletal muscle.

We studied the mechanical and electrical properties in the extensor digitorum longus muscle of Wistar rats in vitro 4 days after denervation. In a group of animals, actinomycin D was injected intravenously at the time of denervation. The prolongation of contraction and relaxation time, and the increase in twitch tension observed in denervated muscles were prevented by the drug. Other denervatory changes such as the elimination of cooling potentiation, posttetanic potentiation, staircase phenomenon, and shortening of caffeine contracture were also inhibited or partially reverted by actinomycin D. In addition, some electrical denervatory changes such as the decrease of resting membrane potential and slowing of maximum rate of fall of the action potential were partially abolished by actinomycin D. These results support the hypothesis that a new synthesis of proteins is related to denervation changes.

Animals↗
PubMed1987

Effects of denervation on calpain and calpastatin in hamster skeletal muscles.

Three leg muscles (soleus, extensor digitorum longus, and plantaris) of adult male golden Syrian hamsters were denervated by bilateral transecting of the sciatic nerve. Eighteen days after denervation, wet weights, amounts of soluble protein, and activities of wide-specificity calpain II, intermediate filament protein-specific calpain I, and calpastatin were measured by protein determination and enzyme and immunological assays. In comparison with control (nondenervated) muscles and depending on the specific muscle and protein, the activities of the calpains increased 1.3 to 1.9 times the control values, whereas the calpastatin decreased to one-half and one-third of control values. The muscle which showed the greatest increase in both calpain activities and the largest decrease in calpastatin activity was the plantaris (a fast-twitch, oxidative glycolytic muscle). The extensor digitorum longus (fast-twitch glycolytic) showed increases in calpain II activity similar to those in the plantaris, but smaller changes in calpain I and calpastatin. The soleus (slow-twitch, oxidative) showed the smallest changes in calpain II and calpastatin activities, although an increase in the calpain I activity was seen after denervation. These results suggest a possible relationship between the presence of fast-twitch, oxidative glycolytic fibers in a muscle and increased potential for intracellular proteolysis following denervation.

Animals↗
PubMed1988

Reinnervation of long-term denervated rat muscle freely grafted into an innervated limb.

This experiment was designed to test the hypothesis that in the presence of regenerating nerve fibers long-term denervated skeletal muscle does not become reinnervated. This hypothesis was tested in rats by the transplantation of 22-month denervated extensor digitorum longus (EDL) muscles into the sites of EDL muscles in the contralateral, normally innervated legs. Two months after transplantation, the muscles contracted when stimulated via the motor nerve, and based on silver-acetylcholinesterase staining, all grafts possessed innervated motor end plates. Compared to values for control EDL muscles in old rats, the maximum force developed by standard free grafts in old rats was 19% and that of long-term denervated grafts was 7%. For standard free grafts, nerve stimulation produced a maximum force that was 81% of that produced by direct stimulation, and for control EDL muscles in young and old rats, the values were 96 and 90%, respectively. These results show that after long-term denervation rat muscles are capable of becoming functionally reinnervated, even though by the time of reinnervation the animals have attained an advanced age of 26 months.

Animals↗
PubMed1992

Effect of complete cardiac denervation on atrial natriuretic factor release in baboons.

We investigated the influence of cardiac innervation on atrial natriuretic factor (ANF) release in baboons. For this purpose, plasma ANF levels were measured in control conditions and in response to head-down (-45 degrees) and head-up tilt (+45 degrees) in six anesthetized baboons before and after complete cardiac denervation obtained by orthotopic autotransplantation of the heart. Cardiac denervation did not modify baseline plasma ANF levels (60.4 +/- 17 pg/ml before and 63.1 +/- 16 pg/ml after heart autotransplantation). In contrast the significant ANF responses to changes in central venous pressure (CVP) induced by postural maneuvers (-45 degrees, + 16.2 +/- 4 pg/ml; +45 degrees, -18.5 +/- 4 pg/ml) were markedly altered after cardiac denervation (-45 degrees, +5.8 +/- 2 pg/ml; +45 degrees, -7.6 +/- 1 pg/ml). The changes in CVP and systemic blood pressure evoked by the postural challenges were comparable before and after cardiac denervation. These results demonstrate that cardiac nerves play a role in the control of ANF release.

Animals↗
PubMed1986

An ultrastructural study of the segmental uptake of horseradish peroxidase in the endplate region of denervated skeletal muscle fibres.

The segmental uptake of horseradish peroxidase (HRP) in the endplate region of denervated skeletal muscle fibres has been studied ultrastructurally using a method for selecting single muscle fibres with high segmental peroxidase staining from denervated mouse tibialis anterior muscle. Segments containing large peroxidase positive phagosomes could already be seen 10-15 min after i.v. injection of HRP. Such segments were still present 24 h after HRP injection. The localization of phagosomes, deep in the fibres rather than immediately under the sarcolemma, suggests that the uptake occurs from t-tubuli. Vivid proliferation of t-tubuli, consisting of vesiculation, enlargement and encircling of cytoplasmic components, was also observed. The HRP accumulates in phagosomes of varying size and shape. Similar membrane-limited bodies without or with very weak peroxidase staining were also observed. The peroxidase-positive phagosomes participate in autophagic processes as suggested by their content of undegraded cellular material. Golgi profiles, which occurred deep in the muscle fibres, and enlarged components of the sarcoplasmic reticulum were frequently encountered in the segments. Myofibrillar degeneration occurs in the segments and progresses with time after denervation. The described segments may be related to the increased membrane turnover in denervated muscle fibres and/or they may be related to processes aimed at establishing new synaptic contacts.

Animals↗
PubMed1992

Effect of partial denervation on motor units in the ageing rat medial gastrocnemius.

The ageing neuromuscular system is thought to undergo a continual process of reorganization as motoneurones are lost and surviving motor nerves reinnervate neighbouring denervated muscle fibres. However, the extent to which collateral reinnervation is able to compensate for neural deficits in the ageing individual is unknown. The ability of the senescent motoneurone to increase the size of its peripheral field was therefore investigated following transection of the right L5 ventral root in male Sprague Dawley rats aged 775 +/- 50 days. This procedure resulted in an extensive partial denervation of the right medial gastrocnemius muscle. After a recovery period of between 28 and 31 days the isometric contractile properties of surviving motor units were compared to control motor units from both the contralateral muscle and a group of unoperated control animals aged 791 +/- 39 days. Motor unit force was found to be unchanged after partial denervation and the absence of any alteration in motor unit size was confirmed by histological analysis. However, the time course of the isometric twitch was significantly longer for both fast and slow motor unit types and the conduction velocity of motoneurones innervating fast units was decreased following partial denervation. These results demonstrate that senescent motor nerves are unable to substantially increase the size of their peripheral fields by extensive collateral reinnervation.

Aging↗
PubMed1990

Effect of denervation of the phrenic nerve on the action of calcitonin gene-related peptide in rat diaphragm.

The effect of denervation on Calcitonin gene-related peptide (CGRP)-induced enhancement of the twitch contraction of skeletal muscle was studied. In rat diaphragm denervated 2 weeks previously, the basal twitch contraction induced by transmural stimulation was about twice that in control muscle, and the basal adenylate cyclase activity and cyclic AMP (cAMP) contents of the tissue were increased. This denervation did not affect the dose-dependent beta -adrenergic stimulation of twitch contraction, but abolished the CGRP-induced enhancement of twitch contraction. The latter phenomenon seems to be caused in part by decrease in CGRP-induced accumulation of cAMP over the basal level, because of increase in the basal cAMP level after denervation. The involvement of another inhibitory second messenger system coupled with CGRP receptors is discussed.

Adenylyl Cyclases↗
PubMed1985

Reflex effects on breathing of laryngeal denervation, negative pressure and SO2 in upper airways.

Respiratory reflex effects of laryngeal denervation, negative pressure and SO2 in upper airways were studied in anesthetized rabbits. Inspiratory efforts with nasal occlusion had longer duration (TIo) and smaller diaphragm activity (Adi) than with tracheal occlusion. After section of superior laryngeal nerves (SLN) these differences disappeared: values with tracheal occlusion became similar to those with nasal occlusion before denervation. This suggests that laryngeal pressure receptors, firing at zero pressure and decreasing their discharge with negative pressures, increase central inspiratory activity. After SO2 TIo, both with tracheal and nasal occlusion, increased even after laryngeal denervation, provided SO2 flowed through nasal pathway. Hence, nose and/or rhinopharynx contain receptors affected by SO2. After laryngeal denervation and SO2 TIo was shorter with nasal than with tracheal occlusion, despite equal Adi. This, combined with the above findings, suggests two groups of pressure receptors in nose and/or rhinopharynx with opposite effects on inspiratory off-switch: one unaffected and the other probably blocked by SO2. During nose breathing section of SLN produced only a slight decrease in mean inspiratory flow.

Animals↗
PubMed1986

Effects of denervation and direct electrical stimulation upon the post-hatching differentiation of posterior latissimus dorsi muscle in chicken.

The influences of denervation and of direct electrical stimulation of denervated muscle upon the post-hatching differentiation of fibre types in the fast avian muscle posterior latissimus dorsi have been investigated. Denervation inhibits the normal decrease in number of muscle fibres exhibiting acid-stable myofibrillar ATPase activity and leads to weak oxidative activity in all the fibres. Direct stimulation at a low rhythm of denervated muscle induces the normal decrease of fibres exhibiting acid-stable myofibrillar ATPase but does not allow the occurrence of normal oxidative activity pattern. The results emphasize the role of muscular activity upon the differentiation of fibre types in a developing muscle.

Adenosine Triphosphatases↗
PubMed1994

Trophic effect of ciliary neurotrophic factor on denervated skeletal muscle.

The actions and receptor for ciliary neurotrophic factor (CNTF) are largely restricted to cells of the nervous system, although one of the CNTF receptor components, CNTFR alpha, is expressed by skeletal muscle. Here we show that the other CNTF receptor components, LIFR beta and gp130, are also expressed by skeletal muscle and that expression of all three CNTF receptor components is greatly increased in denervated muscle. In vivo, administration of CNTF activates these receptors on skeletal muscle by inducing receptor phosphorylation and immediate-early gene responses. Furthermore, CNTF reduces the denervation-induced atrophy of muscle and attenuates the reduced twitch and tetanic tensions that result from muscle denervation. Our findings reveal that, in addition to its known neurotrophic actions, CNTF exerts myotrophic effects by attenuating the morphological and functional changes associated with denervation of rat skeletal muscle.

Animals↗
PubMed1984

Calcium binding capacity and calcium sensitive protein content in denervated frog muscles.

Total and ionic calcium content, calcium binding capacity of sarcoplasmic proteins and calcium insensitive proteins were examined in atrophying leg muscles of frog after 1-5 months period of denervation. Different muscles showed different levels of atrophy and the total calcium content varied with reference to the type of muscle. Ionic calcium levels doubled in the gastrocnemius muscle after three months denervation. Calcium binding capacity of proteins and calcium insensitive proteins decreased rapidly up to four months after denervation in the gastrocnemius muscle. However no significant changes in the levels of calcium binding capacity and calcium insensitive proteins were found with reference to the type of muscle. Since total calcium content remains constant and wet muscle mass (expressed as atrophy) decreased markedly, an apparent increase in calcium concentration occurs in each muscle on denervation.

Animals↗
PubMed1993

Rapid and transient alterations in transglutaminase activity in rat superior cervical ganglia following denervation or axotomy.

The activity of transglutaminase (TG), a Ca(2+)-dependent enzyme contributing to cross-linkage formation of intracellular polypeptide chains decreased rapidly to ca. 25% of control level in superior cervical ganglia (SCG) within 0.5 h following denervation. The reduced level was maintained for at least 24 h. By contrast, following axotomy, ganglionic TG activity increased by ca. 50% within 1 h, maintained the increase to 4 h, and returned to control level by 24 h. When SCG were transferred to aerobic in vitro incubation conditions 3 h following denervation, the addition of the protein kinase C (PKC) inhibitor, trifluoperazine (TFP, 10 micrograms/ml), to the medium partially reversed the denervation-induced reduction in ganglionic TG activity. Addition of a PKC activator, 12-O-tetradecanoylphorbol 13-acetate (TPA, 1 microM), had no effect on the TG activity. These findings suggest that the pathway resulting in the rapid, denervation-induced inhibition of TG activity may involve the transsynaptic activation of PKC. When SCG were placed in vitro 3 h following axotomy, addition of nerve growth factor (NGF, 0.25 micrograms/ml) to the medium reversed approximately one-half of the axotomy-induced increase in TG activity. Thus, following axotomy, the reduction in delivery to the SCG of NGF, which can be transported retrogradely within the axon and is indispensable for morphological and functional survival of sympathetic neurons, may trigger the transient, axotomy-induced TG activation in the SCG.

Animals↗