Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “DENERVATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,135 records · Page 63Linked to original sources
PubMed1980

Chronic sympathetic denervation increases muscarinic cholinoceptor binding in the rat submaxillary gland.

Superior cervical ganglionectomy was found to produce a large decrease in the cocaine-sensitive accumulation of 3H-noradrenaline in the rat submaxillary gland, indicating an effective sympathetic denervation. Six weeks after unilateral denervation the muscarinic cholinoceptor binding of 3H-QNB was increased by over 50% compared to the contralateral, innervated gland. There were no differences in the Kd values between the innervated and denervated glands. These results suggest that changes in muscarinic cholinoceptor density might be in part responsible for the postsynaptic supersensitivity to cholinoceptor agonists observed after chronic sympathetic denervation.

Animals↗
PubMed1978

Course of denervation atrophy in type I and type II fibres of rat extensor digitorum longus muscle.

In the denervated extensor digitorum longus muscle of the rat type I and type II muscle fibres were differentiated histochemically and their course of atrophy was studied. Until 42 days after denervation type I and type II fibres could be identified by means of the myofibrillar ATPase reaction. Up to that time an exclusive atrophy of type II fibres was found. Type I fibres, the smallest of the normal muscle, did not change their diameters and therefore represented the largest fibres 42 days after denervation. Type II fibres of the "white" muscle portion, in which the larger IIB fibres are predominant, showed a higher rate of atrophy than those of the "red" muscle portion, in which the smaller IIA fibres are predominant: by 42 days the diameters of all type II fibres had gone down to equal values. Combined with a further progress of atrophy at later stages, there was a dedifferentiation of the histochemical properties, and the type I fibres exhibited atrophy as well. 120 days after denervation all muscle fibres were found to be highly atrophied.

Adenosine Triphosphatases↗
PubMed1975

Changes of ribosomal capacity for protein synthesis, contraction and histochemical properties of muscle after implantation of fast nerve into denervated and into self-reinnervated slow soleus muscle of the rat.

The ribosomal capacity for protein synthesis in the fast extensor digitorum longus muscle of the rat is markedly higher than in the slow soleus muscle. Implantation of the "fast" peroneal nerve into the denervated or into the self-reinnervated soleus muscle results in transformation (increase) of capacity of isolated ribosomes for protein synthesis into that of the fast muscle type. The degree of transformation is higher after implantation into the self-reinnervated than into the denervated soleus muscle. A high degree of recovery of weight and tetanic tension output is recorded after the "fast" nerve implantation. The effect of transformation with respect to contraction properties is considerably more marked in the case of heteroinnervation of the denervated muscle and persists even after 5 months of heteroinnervation. Transformation of the histochemical muscle fibre pattern is also more pronounced after heteroinnervation of the denervated than self-reinnervated soleus muscle; the muscle acquires the fibre pattern of the fast extensor digitorum longus muscle. The acquisition of the reciprocal pattern of oxidative and glycolytic enzymes suggests that the activation of protein synthesis induced by the foreign "fast" nerve supply is coupled with the operation of specific RNA species.

Animals↗
PubMed1986

Effects of skin temperature on cold defense after cutaneous denervation of the trunk.

In intact goats the core temperature threshold below which heat production increases with falling core temperature, is inversely related to the temperature of the water bath in which they stand and is therefore assumed to be indicative of the central integration of signals from skin and core temperature receptors. The present study shows that a difference in core temperature thresholds for bath temperatures of 35 degrees C and 40 degrees C persisted after denervation of about two-thirds of the skin of the trunk and limbs. Also, for a given combination of skin and core temperatures, heat production was as great or greater after cutaneous denervation as before. It is concluded that, following denervation of the trunk and upper limbs, intact temperature receptors in the non-denervated skin of the legs and tail, and/or also in tissues between the skin and core, provide important and significant inputs to the temperature regulating system. But these inputs cannot explain fully the thermoregulatory responses observed unless it is assumed that the thermosensitivity of these tissues increased.

Acclimatization↗
PubMed1988

Prepontine knife cut-induced hyperthermia in the rat. Effect of chemical sympathectomy and surgical denervation of brown adipose tissue.

The effect of brown adipose tissue (BAT) denervation on the prepontine knife cut-induced hyperthermia was studied. The knife cut has earlier been shown to induce a steady state hyperthermia of 3 to 4 degrees C, as a result of marked activation of the BAT. Before the lesion, the interscapular BAT (IBAT) temperature was lower than the colonic temperature, but the temperature gradient reversed a few minutes after the lesion and the fractional blood flow increased 12-fold. Bilateral sectioning of the 5 nerves supplying IBAT did not modify either the magnitude or the kinetics of the IBAT hyperthermic response. The IBAT fractional blood flow, which was 15 times higher in denervated than in intact tissue before the lesion, scarcely increased following the lesion despite the sharp increase in the tissue's metabolic activity. Chemical sympathectomy with 6-hydroxydopamine suppressed the hyperthermic response. Propranolol or hexamethonium injected i.v. during the steady state hyperthermia resulted in a rapid drop in IBAT temperature and in a reversal of the gradient between IBAT and colonic temperature both in denervated and in intact IBAT. Injection of desipramine, an inhibitor of noradrenaline reuptake, resulted in itself in an increase of temperature in both intact and denervated tissue, which is circumstantial evidence for the presence of a functional residual innervation in the latter.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue, Brown↗
PubMed1987

Effects of selective cutaneous denervation on hypothalamic thermosensitivity in rats.

The effect of altering input from cutaneous thermoreceptors of the face and trunk on the relationship between hypothalamic temperature (Thy) and heat production (HP) was studied in three rats. The signal from cutaneous receptors was altered in two ways: by altering skin temperature (Tsk) and by sectioning nerves supplying cutaneous receptors. It was found that when Tsk was lowered in normal rats Thy threshold for thermoregulatory HP was elevated, but the slope of the relationship between Thy and HP was not significantly altered. After the spinal nerves serving the trunk skin were sectioned, the slope was reduced and the threshold was elevated markedly at both test ambient temperatures (Ta), but Ta had essentially the same effect on the Thy vs. HP relationship after cutaneous denervation as before. Clearly, eliminating input from trunk cutaneous thermoreceptors has a different effect than does lowering or raising Tsk, but thermoregulation is being achieved by the same basic mechanism before and after cutaneous denervation. After the cranial nerves supplying the skin of the face were also sectioned, there was a further elevation in the Thy threshold for HP at Ta = 25 degrees C but no change at Ta = 15 degrees C. It is concluded that cutaneous denervation does not substantially interfere with the rat's ability to regulate its body temperature, and that the reduced Thy sensitivity and increased Thy threshold exhibited after cutaneous denervation is the result of input from intact warm- and cold-thermoreceptors located in the core and in tissues intermediate to core and skin.

Animals↗
PubMed1986

Supersensitivity of the renal tubule to catecholamines in the chronically denervated canine kidney.

Experiments were performed on anesthetized dogs to study whether or not renal tubules of the chronically denervated kidney show supersensitivity toward circulating catecholamines. In one kidney the influence of plasma catecholamines was inhibited by intrarenal administration of the alpha adrenergic receptor blocker phenoxybenzamine (POB, 2 micrograms/min), and renal parameters of the infused kidney were compared to those of the contralateral noninfused organ. Before POB infusion urine flow (V), urinary sodium and potassium excretion (UNa V, UKV) as well as clearance of inulin and PAH (GFR, CPAH) were similar in infused and contralateral kidneys in all groups studied. In dogs (n = 8) with two innervated kidneys POB infusion elevated V and UNa V by 53 +/- 13% and 102 +/- 34% (p less than 0.05). In dogs (n = 8) with acute bilateral renal denervation POB administration failed to alter any of the measured parameters. In contrast, V and UNaV from chronically denervated kidneys (n = 7) were increased after POB infusion by 40 +/- 9% and 103 +/- 34% (p less than 0.05). Glomerular filtration rate, CPAH and UKV were not changed by alpha adrenoceptor blockade in any of the groups. In an additional group of animals (n = 8) acute unilateral renal denervation increased V and UNaV to a significantly higher extent (by 282 +/- 85% and 330 +/- 106%) than POB administration did in the innervated kidney and elevated UKV (44 +/- 10%), too.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

Inhibition of cell division and the development of denervation hypersensitivity in skeletal muscle.

1. It was found that in 3 day denervated soleus and EDL muscles nuclear division takes place. This can be stopped by administration of either 5-fluoro-uracil or vincristine. 2. The increased sensitivity to acetylcholine following denervation developed at a time when rapid cell division takes place. Both 5-fluoro-uracil and vincristine prevent the development of denervation hypersensitivity both in soleus and EDL muscles. 3. Muscle injury causes some cell division locally, but some phagocytic cells that infiltrate the damaged muscle appear to be blood-borne as their appearance within the muscle is not entirely prevented by either 5-fluoro-uracil or vincristine. Correspondingly the development of increased sensitivity that follows muscle injury is only partly prevented by administration of cytotoxic drugs. 4. It is suggested that the presence of dividing cells is causally related to the development of denervation hypersensitivity.

Acetylcholine↗
PubMed1985

Influence of direct low frequency stimulation on contractile properties of denervated fast-twitch rabbit muscle.

A continuous electrical 8 Hz impulse pattern imposed directly via implanted electrodes on denervated fast twitch muscle induced changes in its contractile characteristics. Compared with non-stimulated denervated muscle, stimulated muscle showed slowing of contraction time and improved fatigue resistance. The reaction for succinic dehydrogenase was more intense in the denervated stimulated muscle, indicating an increased capacity of oxidative enzymes. The rate of atrophy was not influenced by stimulation. The 8 Hz frequency pattern is the mediator for these changes in the characteristics of denervated muscles. It demonstrates a comparable effect on innervated muscle. The contralateral normal innervated muscle was also influenced by the electrical stimulation. Contraction time as well as twitch tension were increased. This finding is important when using the normal muscle as intraindividual control.

Animals↗
PubMed1981

Desensitization in denervated mouse muscles.

In denervated mouse soleus (DSOL) muscle preparations washed in Na methanesulfonate solutions containing 30 mmol X 1(-1) K+, bath-applied ACh (55 mumol X 1(-1) ) caused the resting potential to decrease from about -36 to -3.2 mV within 2-4 s; the potential remained stable or became slightly more negative when ACh was applied for 1- 2 min. Two components of the membrane current change (ACh current) were found in DSOL when using a point voltage clamp, an initial current component declining to 1/2 the initial amplitude in 11-15 s (desensitization) and a steady late current comprising 16-47% of the maximum ACh current. Membrane conductance (in microseconds X cm-2) was 0.35 in the absence of ACh, 20.3 at the peak of the initial current, and 1.57 during late current. The late current saturated at 0.55 to 5.5 mumol X 1(-1) ACh, whereas the initial current required 55 or more mumol X 1(-1) ACh to saturate. The null (reversal) potential was 6-13 mV more positive for the late current than for the initial current. The late current was masked when Na+ was replaced by Tris+, sucrose, or K+. An initial and a late current could also be distinguished in non-denervated endplates. The late current was more sensitive to ACh than the initial current, but the null potential was more negative than that for the initial current in endplates. In denervated membrane, the half time of desensitization was increased when Mg2+ was replaced by Ca2+ but the changes were on the average less than 15% the control values. It was concluded that desensitizing and non-desensitizing receptors may exist in extrajunctional membranes of denervated muscles and in endplates, the two being attached to different ionic channels.

Animals↗
PubMed1979

The fine structure of denervated and reinnervated muscle spindles: morphometric study of intrafusal muscle fibers.

The fine structure of normal, denervated, and reinnervated muscle spindles in lower lumbrical muscles of rats was studied morphometrically at time intervals ranging from 3-14 months. In control spindles, the mean transverse area of mitochondria was estimated to be more than twice as large in nuclear chain than in typical nuclear bag fibers. Following denervation, there was a severe decrease of the mean number and transverse area of mitochondria, and a moderate, but statistically significant decrease of the mean transverse area of intrafusal muscle fibers (IMFs) despite an increase of the number of IMFs. At 12-14 months of reinnervation, changes of the transverse areas of IMFs were statistically insignificant, but the mean values for the mitochondria were incompletely restored. At 4 x 3 months, after fourfold repeated crush injuries to the nerve, most of the values estimated (transverse area of mitochondria; number, shape, and transverse area of IMFs and nuclei) tended to approach those in denervated rather than in reinnervated IMFs. The differences of the reactions of intra- and extrafusal muscle fibers following complete motor and sensory denervation appeared to be in accordance with their normal dimensional dissimilarities.

Animals↗
PubMed1986

Effects of short-term denervation on avian muscle spindle structure.

The role of the nerve in maintaining the ultrastructural integrity of avian muscle spindles was investigated by denervating the pigeon's extensor digitorum communis for periods of 10, 19, and 28 days. The equatorial region of control intrafusal fibers had a reduced density of myofilaments. Sensory endings contained mitochondria and structures resembling synaptic vesicles, and were associated with satellite cells. In the polar region, fibers had a high concentration of myofilaments; small motor endings, unlike sensory endings, lay outside of the fiber's basal lamina. The outer capsule consisted of thin, tightly layered cells which gradually became reduced in number distal to the equatorial region. In both equatorial and polar regions the capsule became more disrupted with longer denervation periods, and lysosomes and phagocytes became more abundant. The equatorial region of denervated fibers contained many myofibrils and some had peripherally-located nuclei, unlike the controls; sensory terminals were absent. The polar region of some fibers had disorganized myofilaments and others had a reduced myofilament density. Fiber diameters increased significantly in both regions. Thus, denervated intrafusal fibers lost some characteristics which distinguish them from extrafusal fibers.

Animals↗
PubMed1985

Effects of denervation, immobilization and cachexia on fibre size in the anterior tibial muscle of the rat.

The effects of denervation, immobilization and cachexia on the size of the various histochemical fibre types were studied in the anterior tibial muscle of male Wistar rats aged 60-100 days. Denervation was induced by unilateral sectioning of the sciatic nerve, immobilization by a plaster cast on one hindlimb and cachexia by restriction of food intake. In the anterior tibial muscle of the normal rat, three fibre types can be identified by myofibrillar ATPase stain after alkaline preincubation. These fibres were called dark (D-fibres), intermediate (I-fibres) and light fibres (L-fibres), respectively. The I-fibres correspond to the fast-twitch type 2 fibres and the L-fibres to the slow-twitch type 1 fibres. The D-fibres have intermediate characteristics, but they probably belong to the type 2 group. The three fibre types reacted differently to denervation, immobilization and cachexia. Denervation caused progressive atrophy of the D- and I-fibres and almost no change of the L-fibres. Immobilization caused minor reduction in size of the D- and I-fibres during the first days and no change thereafter, whereas the L-fibres showed transitory hypertrophy. Cachexia, on the other hand, resulted in progressive atrophy of all three fibre types but a predominant affection of the D- and I-fibres. The different susceptibilities of the various fibre types suggest different mechanisms for atrophy of muscle in these three conditions.

Adenosine Triphosphatases↗
PubMed1985

Fibre-type specificity and effect of thyroid hormone on glucose 6-phosphate dehydrogenase activity in normal and denervated skeletal muscles of the rat.

Glucose-6-phosphate dehydrogenase activity increases following denervation of rat skeletal muscle. The specificity of this effect to muscle fibre type was studied. Basal activity of the dehydrogenase was higher in soleus, a muscle composed predominantly of type I fibres, than in extensor digitorum longus, a muscle composed predominantly of type IIa and b fibres. The enzymatic activity of the soleus was also greater than that of the red (RQ) and white (WQ) portions of quadriceps muscle (predominantly type IIa and type IIb fibres, respectively). Following denervation, glucose-6-phosphate dehydrogenase increased in extensor digitorum longus and RQ, but not in WQ or the soleus. Following chronic treatment of rats with 3,3',5-triiodothyronine, which converts type I muscle fibres to type II, the dehydrogenase activity increased in both denervated soleus and extensor digitorum longus. It is concluded that the effect of denervation on glucose-6-phosphate dehydrogenase activity is selective for type IIa (fast oxidative-glycolytic) muscle fibres.

Animals↗
PubMed1992

Calbindin D-28k-immunoreactivity in rat muscle spindles during postnatal maturation and after denervation.

Calbindin D-28k-immunoreactivity has been demonstrated in some of the intrafusal muscle fibres and in the capsule of adult rat muscle spindles. In this study, the immunocytochemical localization of calbindin D-28k in the muscle spindles of triceps surae muscle was studied during postnatal maturation and after denervation. In young rats calbindin D-28k-immunoreactivity was seen in a few intrafusal fibres, first at the age of 4 days. At the 7th day, three calbindin D-28k-immunoreactive fibres and one unlabelled fibre were seen in most muscle spindles, as in adult rats. The spindle capsule and perineurial sheath of nerves were first seen to exhibit calbindin D-28k immunoreactivity at the age of 14 days, and thereafter the localization of calbinding D-28k-like immunoreactivity was similar to that in adult rats. After denervation, calbindin D-28k-immunoreactivity remained in intrafusal muscle fibres and the spindle capsule for a long period. After two months of denervation, calbindin D-28k immunoreactivity could still be seen in the spindle capsule, but the intrafusal fibres were not labelled. The innervation is known to have trophic effects on the intrafusal fibres. The present findings suggest that the expression of calbindin D-28k-immunoreactivity in maturating muscle spindles may be induced by the developing innervation. The decrease of calbindin D-28k-immunoreactivity in intrafusal fibres after denervation may be due to the loss of trophic factors released by the nerves.

Animals↗
PubMed1987

Clenbuterol, a beta agonist, induces growth in innervated and denervated rat soleus muscle via apparently different mechanisms.

Dietary administration of the anabolic agent, clenbuterol, has already been shown to inhibit or reverse denervation-induced atrophy in rat soleus muscles. We now show that the ameliorative effects of clenbuterol in denervated rat muscles are due principally to a large increase in protein synthesis. This results from both an increase in protein synthetic capacity and a normalised translational efficiency. The responses of innervated and denervated muscles are therefore fundamentally different, the changes in denervated muscles being reminiscent of the classical pleiotypic response of cells to growth factors.

Animals↗
PubMed1993

Differential expression of tenascin after denervation, damage or paralysis of mouse soleus muscle.

The expression of the extracellular matrix molecule tenascin was studied by immunocytochemistry and Western blotting in soleus muscles of adult mice after nerve damage (denervation), muscle injury (induced by enforced running or freezing) and functional block of synaptic transmission (botulinum toxin). Enhanced expression of tenascin in the extracellular spaces around focally damaged muscle fibres was found already 10 h after onset of running on a motor-driven treadmill which causes muscle injury in soleus muscle. Tenascin expression reached a peak at 2-3 days post-exercise, after which it declined gradually and became undetectable by two weeks after injury. Similarly, cryo-damage of soleus muscles in situ led to upregulation of tenascin. Chronic muscle denervation after sciatic nerve transection caused a persistent (studied up to 31 days) expression of tenascin at denervated endplates and in intramuscular nerve branches but not in other tissue compartments. Local application of botulinum toxin Type A, which results in muscle inactivity but not in tissue degeneration, however, did not induce tenascin expression 12 h to 12 days post-injection. Expression of tenascin after denervation and muscle damage, but its absence after paralysis, were verified by SDS-PAGE and Western blot analysis. Independent of the type of injury (muscle, nerve or both) the known major isoforms of mouse tenascin, as judged by M(r) comparison, were re-expressed, with no preponderance of individual M(r) forms. These results show that tenascin expression in adult muscles is induced by both axon and muscle fibre damage but not by muscle inactivity. In contrast, NCAM, in accordance with previous observations, showed enhanced expression both as a result of inactivity and in association with tissue repair.

Animals↗
PubMed1987

Intramembrane particles and terminal responses following denervation of frog muscle spindles.

The sizes and population density of intramembrane particles in the non-myelinated sensory nerve terminals of frog muscle spindles were studied in comparison with changes in the responses to spindles to stretch 1-28 days after denervation. The sciatic nerve in the right leg was cut at the dorsal part of the hip joint. Spindle receptors in the left leg were used as controls. Muscle spindles were isolated from semitendinosus and iliofibularis muscles. The mean density of particles, which occurred mainly on the protoplasmic (P) face, declined rapidly to 60% of the control values 2 days after denervation, 30% after 4 days and to less than 10% after 7 days. The mean diameter of particles changed from 8.0 +/- 1.5 nm in the control to 12.8 +/- 2.5 nm 7 days after denervation. No significant difference between the results for the trunks (greater than 2 micron in diameter) and the branches (less than 0.5 micron) of the non-myelinated axons was observed. The peak rate of afferent discharges during a ramp-and-hold stretch survived up to 4 days after denervation, whereas the static component disappeared after 3 days. It is suggested that the decline to less than 20% of the control density of particles removes the mechanosensitivity of the sensory endings.

Animals↗