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PubMed1996

Induction of dystrophin-associated proteins together with nicotinic acetylcholine receptors by denervation in the absence of dystrophin in skeletal muscles of mdx mice.

We purified the nicotinic acetylcholine receptor from digitonin-solubilized rabbit skeletal muscle by affinity chromatography and detected many proteins linked to AChR, including dystrophin, adhalin, beta-dystroglycan, utrophin, rapsyn, and actin. To determine whether or not AChR links to dystrophin-associated proteins (DAPs) without dystrophin, we studied the effects of denervation on AChR and DAPs in the skeletal muscle of a mdx mouse. Following surgical denervation, the levels of adhalin and beta-dystroglycan dramatically increased at the extrajunctional sarcolemma with AChR, suggesting that their association is independent of dystrophin. Furthermore, the diffuse extrajunctional appearance of adhalin, beta-dystroglycan, and AChR was observed after pharmacological denervation through the subcutaneous administration of succinylcholine. Since the depletion of DAPs and the subsequent disruption of sarcolemmal linkage are believed to be a primary cause of muscle cell necrosis in dystrophinopathies, pharmacological denervation may have some beneficial effect on these diseases.

Amino Acid Sequence↗
PubMed1995

High endocytotic activity occurs periodically in the endplate region of denervated mouse striated muscle fibers.

High endocytotic activity after denervation of skeletal muscle occurs in a proportion of muscle fibers (both slow and fast fiber types) in the endplate region. The present study was performed in order to examine if a periodicity in the endocytotic activity could explain why the process is not observed in all fibers at a given time. Three markers, horseradish peroxidase (HRP), rhodamine B isothiocyanate-labeled dextran, and fluorescein isothiocyanate-labeled dextran were used to demonstrate endocytotic activity of muscle fibers of the denervated mouse hemidiaphragm in vivo. Acetylcholine esterase staining was used in conjunction with HRP uptake to determine the proportion of denervated muscle fibers with endocytotic activity in the endplate region at any one time. The results show that 25-50% of the muscle fibers display high endocytotic activity in the endplate region at a given time 10 days after denervation. The existence of a periodicity in this endocytotic activity is suggested by results obtained using two different endocytotic markers administered at time intervals of 0-7 days. We conclude that loss of contact with the innervating motorneuron induces a high endocytotic activity which occurs periodically in the perisynaptic region of skeletal muscle fibers.

Animals↗
PubMed1998

Regional difference in epidermal thinning after skin denervation.

Denervation of skin has a profound influence on epidermis; epidermal thinning was a consistent finding in rats. However, it is not clear whether the degree of epidermal thinning was similar in the region receiving the same innervation. In mice, how early epidermal nerves were degenerated after nerve injury remained unknown. To address these issues, we transected the sciatic nerve in mice and compared the changes of epidermal thickness in different areas of the hind foot skin. Epidermal nerves degenerated within 48 h after nerve transection, similar to what was observed in rats. Seven days after nerve transection, there was differential thinning of epidermis. The interpad area, in the center of the sciatic nerve-innervated region, exhibited the most profound degree of epidermal thinning (34.6 +/- 3.1 vs 47.8 +/- 2.4 microns, P < 0.01). The heel area, in the periphery of the sciatic nerve-innervated zone, did not show significant thinning of epidermis after denervation (37.3 +/- 4.8 vs 41.5 +/- 5.1 microns, P > 0.05). The degree of epidermal thinning after denervation in the pad area was the intermediate one: with 98.8 +/- 4.8 vs 120.1 +/- 7.3 microns, P < 0.02, in the rete pegs, and 51.1 +/- 4.1 vs 62.1 +/- 6.0 microns, P < 0.02, in the dermal papilla. The differential thinning was obvious when the thickness of the denervated epidermis was normalized to that of the control epidermis with the ratios of 0.73 +/- 0.03 in the interpad area, 0.83 +/- 0.04 in the rete peg, 0.85 +/- 0.05 in the dermal papilla, and 0.92 +/- 0.05 in the heel. Epidermal thinning was reversed by reinnervation of the epidermis after sciatic nerve crush (41.5 +/- 1.5 vs 45.0 +/- 2.0 microns in the interpad area, P > 0.05). These findings suggest that sensory nerves exhibit trophic influences on the epidermis presumably through the effects of diffusible factors.

Animals↗
PubMed1999

C-Fos in enteric nerves after extrinsic denervation of guinea pig ileum.

BACKGROUND: Gastrointestinal function is controlled partly by an interaction between extrinsic (sympathetic, parasympathetic, sensory) and intrinsic (enteric) nerves. However, normal gut function occurs in the absence of extrinsic innervation as enteric nerves adapt to the loss of extrinsic nerves from the gut wall. Expression of the proto-oncogene product, c-Fos, is a signal for activity-dependent changes in gene expression and immunocytochemical detection of c-Fos is used as a marker for changes in neuronal activity. The purpose of this study was to determine if enteric neurons in guinea pig ileum respond to loss of extrinsic innervation by expressing c-Fos protein. MATERIALS AND METHODS: Fos protein was localized using immunohistochemical methods and an antiserum raised against synthetic Fos. Segments of ileum were extrinsically denervated by crushing the mesenteric nerves in anesthetized animals or by treating animals with 6-hydroxydopamine (6-OH-DA) or capsaicin to destroy sympathetic and extrinsic sensory nerves, respectively. RESULTS: One week after surgical extrinsic denervation of loops of ileum, 12 +/- 1 nuclei/submucosal ganglion and 114 +/- 6 nuclei/myenteric ganglion contained Fos immunoreactivity (ir). These values were greater (P < 0.05) than those from unoperated segments from the same animals (4 +/- 1 Fos-ir nuclei/submucosal ganglion and 13 +/- 4 Fos-ir nuclei/myenteric ganglion) or from sham-operated segments. Significantly more nuclei contained Fos-ir at 4, 7, 10, and 24 weeks after denervation. Finally, capsaicin or 6-OH-DA treatment increased the number of Fos-ir nuclei in enteric ganglia. CONCLUSIONS: These data suggest that Fos expression may be part of the adaptation of enteric nerves to extrinsic denervation.

Animals↗
PubMed1999

Intrinsic myenteric denervation: a new model to increase the intestinal absorptive surface in short-bowel syndrome.

INTRODUCTION: Short-bowel syndrome (SBS) is caused by resection of massive portions of the small intestine and is characterized by symptoms related to malabsorption, of which severe weight loss is the most apparent. Surgical treatments for SBS are not yet satisfactory. In rats, the myenteric denervation by benzalkonium chloride (BAC) leads to development of megaileum with visceral dilatation and mucosal hyperplasia and increases the intestinal transit time. Such operation in the remaining intestinal segment after massive small bowel resection could increase the duration of contact between luminal nutrients and ileal mucosal epithelium, and furthermore, it could increase the superficial area of the mucosa. Thus, our aim in this study was to evaluate the epithelial morphology and body weight changes of animals after intrinsic ileal denervation associated with extensive small intestine resection. MATERIAL AND METHODS: Wistar rats were submitted to resection of 80% of small intestinal length (Group R). Another group (B) of animals also received topical serosal application of BAC 0.3%. Control animals were submitted to simulated surgery (Group C). Animals were weighed weekly and sacrificed after 90 days. Intestinal walls were collected for histological procedure and morphometry. RESULTS: At the end of the experimental period all groups showed weight increase, which was reduced in the R group (P < 0.01). Interestingly, the denervated Group B showed a marked increase in weight, similar to the control animals. Morphometric analysis of the mucosal layer area showed a major increase in mucosal surface area, mainly in Group B. CONCLUSIONS: Our results showed that the ileal intrinsic denervation associated with massive intestinal resection induced an increase in the superficial absorptive area and was able to improve the postsurgical conditions for the animals, with accentuated weight increase. This procedure may be a useful model for further studies related to the role of the enteric nervous system on intestinal adaptations after extensive resections and may provide a new approach for the surgical treatment of short-bowel syndrome.

Animals↗
PubMed2001

Range of motion physiotherapy reduces the force deficit in antagonists to denervated rat muscles.

BACKGROUND: We used a rat hindlimb model of tibial nerve transection to determine if a loss of mechanical function exists in innervated antagonists compared with denervated muscles. We tested two hypotheses: (1) denervation of the rat ankle plantar flexors results in decreased force production of the ankle dorsiflexors, and (2) daily passive ankle range of motion (ROM) physiotherapy prevents or reduces the force deficit. METHODS: Adult Lewis rats were assigned to one of three groups: (1) a sham (S) group, in which the tibial nerve was exposed but not transected; (2) a no rehabilitation (NR) group, in which a 2-cm segment of tibial nerve was excised at midthigh to denervate the ankle plantar flexors; or (3) a rehabilitation (R) group, in which a 2-cm segment of tibial nerve was excised and the animals were subjected to ankle passive ROM physiotherapy for two 5-min sessions each day. After 14 days, maximum isometric tetanic force (F(0)) and specific force (sF(0)) were measured in the extensor digitorum longus (EDL) muscle, an ankle dorsiflexor. RESULTS: Compared with those from animals in the S group, EDL muscles from animals in the NR group demonstrated a 22% decrease in both F(0) and sF(0). In the EDL from animals in the R group, daily passive ROM physiotherapy diminished the deficit in F(0) but not in sF(0). CONCLUSIONS: These data support the hypotheses that nerve injuries result in impaired mechanical function in the innervated antagonists to denervated muscles and that passive ROM physiotherapy can improve force production in these muscles.

Animals↗
PubMed1990

Effects of selective cardiac denervation on collateral blood flow after coronary artery occlusion in conscious dogs.

The extent to which cardiac nerves regulate responses to myocardial ischemia remains controversial. Our data in conscious dogs indicate that neither selective posterior left ventricular (LV) wall denervation nor selective ventricular denervation, leaving the atria intact, modifies the effects of coronary artery occlusion (for 24 h) on regional myocardial function and infarct size as compared to normally innervated dogs. Since hemodynamic changes were similar among the three groups after coronary artery occlusion, it is possible to speculate that responses of collateral blood flow to the ischemic zone were also not modified by chronic selective cardiac denervation. To address this, individual samples were selected and included in either the infarcted (TTC negative) or salvaged (TTC positive) group. The infarcted and salvaged samples were paired according to blood flow levels of 0.1-0.2, 0.2-0.3, or 0.3-0.4 ml/min/g at either 5 min, 1 h, 3 h, or 6 h after coronary artery occlusion. The results demonstrated similar patterns of myocardial blood flow in tissue samples within the area at risk after coronary artery occlusion in the animals, regardless of whether the ischemic zone was innervated or denervated. While blood flow rose in ischemic tissue that ultimately was salvaged, and tended not to rise over the 24 h monitoring period in tissue samples that became necrotic, no differences could be discerned on the basis of intact or absent innervation of the ischemic zone. Thus, chronic absence of cardiac nerves does not affect regulation of ischemic zone blood flow following coronary artery occlusion in conscious dogs.

Animals↗
PubMed1993

Denervated chicken breast muscle displays discoordinate regulation and differential patterns of expression of alpha f and beta tropomyosin genes.

The expression of the alpha fast (alpha f) and beta tropomyosin (TM) genes has been analysed with muscle-specific and common cDNA probes after unilateral nerve section of the pectoralis major muscle (PM) in 4-week-old chickens. The following were observed in denervated muscles. (1) The beta TM mRNA, which was repressed during development, reaccumulates in a biphasic curve with the increase in the beta TM protein lagging behind the changes in its mRNA. Accordingly, no beta TM is seen in products translated in vitro from total and polyA+ RNA obtained 1 week after denervation. No such translation block is seen with RNA obtained from control or muscles denervated for 6 weeks. (2) No changes in the alpha fTM mRNA and corresponding protein are observed. (3) RNA processing of the two genes is not changed. (4) In the contralateral muscles, transitory increases in alpha f and beta TM mRNAs are observed while the corresponding proteins remain unchanged. Our data suggest that muscle fibres display early and long-term responses to the loss of neural input which might result from a combination of changes produced by regenerative processes and reprogramming of existing fibres. Moreover, in contrast to normal development, no reciprocal changes of alpha f and beta TM expression are seen in denervated muscles.

Animals↗
PubMed1996

Increased expression of dystrophin, beta-dystroglycan and adhalin in denervated rat muscles.

To evaluate a potential regulatory role of the nerve, the distribution and expression of dystrophin, of beta-dystroglycan (43DAG) and adhalin (50DAG), two of the dystrophin-associated proteins and utrophin (dystrophin related protein or DRP) were studied in rat muscles after 2 weeks of denervation. We found that dystrophin, beta-dystroglycan and adhalin were overexpressed in denervated muscle, whereas utrophin did not increase and was found only in the post-synaptic membrane. The study of the distribution of dystrophin in the sarcolemma of single muscle fibres indicates that the molecular organization of dystrophin was maintained after denervation. Dystrophin in addition of forming a scaffold around the fibre was found around the clusters of AChR that reappeared in the extra-synaptic membrane after denervation. Also beta-dystroglycan colocalises at these clusters. These results suggest that the increase in dystrophin, beta-dystroglycan and adhalin is correlated with the reappearance of AChRs in the extra synaptic membrane.

Animals↗
PubMed1982

Survival of Pacinian corpuscles after denervation in adult rats.

The ultrastructure of Pacinian corpuscles located on the crural interosseous membrane was studied in adult rats 6h to 10 months after transection of the right sciatic nerve. Axon terminals degenerated one day after transection and were engulfed and resorbed by cells of the inner core within one week. The axial space left after removal of the axonal debris was closed by the lamellae of the inner core. The main structural features of the inner core and capsule remained preserved after denervation throughout the period of study. The denervated inner cores, however, became atrophic 10 months after neurotomy, their mean diameter being reduced by 17.5% compared with that of contralateral control corpuscles. The number of capsular lamellae was unaltered, and perineurial pathways of the peripheral nerve stump remained preserved. Schwann cells proliferated and formed Büngner bands during the first month after denervation, but retracted their processes and became atrophic at later stages after neurotomy. Survival of Pacinian corpuscles after long-term denervation in adult rats is in contrast to their rapid degeneration within several days after nerve section in neonates.

Animals↗
PubMed1985

Nerve fiber production by intraocular adrenal medullary grafts: stimulation by nerve growth factor or sympathetic denervation of the host iris.

This study evaluates the production of adrenergic nerve fibers by adrenal medullary tissue of the adult rat grafted to the anterior chamber of the eye of adult recipients. The chromaffin grafts attach to and become vascularized by the host iris. They decrease in size intraocularly during the first 3 weeks. This decrease is somewhat counteracted by sympathetic denervation of the host iris, and better counteracted by sympathetic denervation and addition of nerve growth factor (NGF, given at grafting and 1 and 2 weeks after grafting). Outgrowth of adrenergic nerve fibers from the grafts into the host iris was studied in wholemount preparations by use of the Falck-Hillarp technique 3 weeks after grafting. The innervated area of the host iris was approximately doubled in the chronically sympathectomized group and doubled again in the chronically sympathectomized NGF-supplemented group. Chronic sympathetic denervation had no effect on density of outgrowing nerves, whereas addition of NGF more than doubled nerve density. Since sympathetic denervation causes a slight elevation of NGF activity in the iris, the present experiments are taken as evidence that the level of NGF in the iris regulates formation of nerve fibers by adrenal medullary tissue grafts from adult rats.

Adrenal Medulla↗
PubMed1975

Evidence for myoblastic potential of satellite cells in denervated muscle.

The failure of denervated muscle to undergo effective regeneration, despite reported increases in the number of muscle satellite cells, warranted an investigation of the viability and myoblastic capacity of these cells present in denervated muscle. Four types of satellite cells present in muscle denervated for three weeks are described, based on their ultrastructure and relationship to their principal fiber. The increased number of ribosomes, including helically arranged polysomes; the number of Golgi complexes; the presence of microtubules; the branching subsarcolemmal tubular system; and the appearance of regularly arranged 96 A microfilaments with diffuse electron dense areas are structural features of satellite cells that are similar to those of developing myoblasts in growing and regenerating muscle. The electron microscopic observations suggest that "activated" satellite cells do have myoblastic potential. Possible explanations for the ultimate failure of denervated muscle to regenerate include: 1) the inability of the muscle to produce satellite cells rapidly enough to keep pace with muscle degeneration; 2) a cytotoxic effect produced by the degenerating muscle fiber on the satellite cell; and 3) the inability of satellite cells to form stable, mature multinucleated fibers in the absence of the trophic effect of the nerve.

Animals↗
PubMed1992

Modifications in myotendinous junction structure following denervation.

Changes in the structure of myotendinous junctions in response to peripheral nerve lesions are examined by transmission electron microscopy and morphometric analysis. Modifications in the folding of the plasma membrane at myotendinous junctions relative to the cross-sectional area of myofibrils terminating at the membrane are evaluated quantitatively using a morphometric analysis in which the muscle cell processes at the myotendinous junction are modeled as circular paraboloids. Denervated frog semitendinosus muscles were analyzed at 2, 4 and 8 weeks following denervation and compared to innervated, contralateral controls. No significant differences were found in relative folding of junctional plasma membranes between any two data sets, although myofibril diameter decreased over time following denervation. This shows that junctional plasma membrane and associated junctional structures, such as basement membrane, are removed from the myotendinous junction at a rate similar to that of myofibril thinning, thereby keeping constant the ratio between junction area and myofibril cross-sectional area. Electron microscopic observations indicate that 4 weeks post-denervation is the most active stage of junction remodeling of the time points sampled.

Animals↗
PubMed1975

Duchenne muscular dystrophy and poliomyelitis. A study of dystrophic-denervated muscle.

A systematic study of dystrophy-denervation in human muscle showed minimal morphometabolic differences between dystrophic and dystrophic-denervated muscle. The only certain conclusion is that denervation influences the rhythm of evolution of the dystrophy without impressing any of the few characteristics considered at present as peculiar to denervation.

Child↗
PubMed1979

Microangiographic studies of denervated, reinnervated and hypertrophic muscles of rats.

The behavior of the capillaries of denervated, reinnervated and hypertrophic muscle of rats was investigated with aid of microangiography. The vessels of the denervated muscle ran irregular, formed spirals and their parallel position to the muscle fibers was completely lost. The appearance of vessels after 3 and 6 weeks in the reinnervated muscle was similar to that observed after denervation. The pattern of vessels became more normal 3 months after the operation. The hypertrophic exercised muscles had an irregular course but with less tendency to spiral formation than atropic muscles. Their caliber was enlarged. The results showed that in denervated, reinnervated and hypertrophic muscle similar changes in capillary vessels develop. The vessels lose their parallel position to the muscle fibers and have a tendency to spiralization. The changes probably contributed to impairment of the circulation.

Angiography↗
PubMed1975

[Representative enzymes of energy supplying metabolism in the normal and denervated human brachial biceps, deltoid and anterior tibial muscles (author's transl)].

Representative enzyme activities of energy supplying metabolism were measured in muscle specimens of brachial biceps, deltoid or anterior tibial muscle of patients with affections of the peripheral nerves. Simultaneously performed measurements of the same enzyme activities in the contralateral normal muscles served as a control. 5 patients suffered from a lesion of the brachial plexus, 7 patients had a paralysis of the axillary nerve, and 8 patients had a peroneal paralysis. In all denervated muscles no electrophysiological signs of reinnervation were present. The activities of glycogen phosphorylase, triosephosphate dehydrogenase, lactate dehydrogenase and alpha-glycerophosphate dehydrogenase were found to be highest in the normal brachial biceps muscle. Lower activities were measured in the normal deltoid and anterior tibial muscle. The oxidative enzymes, 3-hydroxyacyl-CoA dehydrogenase and citrate synthase as well as hexokinase, showed no significant difference from the levels of the control. It is suggested that a probable factor determining the differences of the enzyme activities of glycogenolysis, glycolysis and alpha-glycerophosphate oxidation between brachial biceps, deltoid and anterior tibial muscle, might be the pattern of impulse activity in the motor nerves of these muscles. The enzyme activities of glycogen phosphorylase, triosephosphate dehydrogenase, lactate dehydrogenase and alpha-glycerophosphate dehydrogenase, decreased rapidly during the first 2 months after denervation in the brachial biceps, deltoid and anterior tibial muscle, whereas the decrease was slight during the following months. The activities of the oxidative enzymes (3-hydroxyacyl-CoA dehydrogenase and citrate synthase) showed no significant change after denervation. The metabolic difference of glycogenolysis, glycolysis and alpha-glycerophosphate oxidation between the three muscles was no longer maintained. The possible causes of the deeply decreased enzyme activities of glycogenolysis, glycolysis and alpha-glycerophosphate oxidation, as well as the causes of the unchanged oxidative enzyme activities and of the increased hexokinase activity after denervation in the human brachial biceps, deltoid and anterior tibial muscle, are discussed.

Adolescent↗
PubMed1994

Effect of small bowel transplantation, denervation and ischaemia on rat intestinal microflora.

The effects of denervation and warm ischaemia on quantitative and qualitative changes in small intestinal microflora following rat heterotopic small-bowel isotransplantation were assessed. Animals with Thiry-Vella fistula, but without transplants, acted as controls. Thirty and 40-fold increases in bacterial colony counts were seen in the isografts compared to controls at 2 and 7 days, respectively (P < 0.05). Aerobic faecal organisms predominated at 2 and 7 days, but an overgrowth of Flavobacterium meningosepticum occurred at 28 days in the transplanted and host bowels. The effect of warm ischaemia on intestinal microflora was assessed by the application of a microvascular clamp to the superior mesenteric artery for 90 min. The effect of denervation was assessed following microsurgical division of all nervous tissue around the superior mesenteric artery. After 7 days, lengths of jejunum and ileum were removed and intraluminal microflora assessed. The number of bacterial colonies isolated from the ileum in the warm ischaemia group was six times greater than the number in the control group, whereas no significant changes were seen in the upper bowel. In contrast, denervation led to a slight, but consistent, decrease in colony counts. These findings suggest that the increase in bacterial numbers in an isografted small bowel primarily results from warm ischaemia rather than from mesenteric denervation, and that physical aspects of the procedure may affect the development of sepsis following small-bowel transplantation.

Animals↗
PubMed1983

The effect of cardiac denervation and beta-blockade on control of cardiac output in exercising dogs.

Normal and cardiac denervated dogs, with an electromagnetic aortic flowprobe implanted at least 14 days before the experiments, ran at different speeds on a 25% graded treadmill. The experiments were carried out before and after blockade of betareceptors in the heart by PO administration of 125 mg X kg-1 practolol per day. Changes in stroke volume, heart rate, and cardiac output were measured. After beta-adrenergic blockade, only two of the seven dogs with denervated hearts were prepared to run at a limited number of speeds. Time constants of the cardiac output changes at the onset of exercise were significantly different (P less than 0.001) for the normal (11.5 +/- 0.7 s, mean +/- SEM) and the denervated dogs (29.5 +/- 1.1 s), but in normal dogs did not change with practolol (11.8 +/- 0.8 s). The steady state relationship between cardiac output (CO) and work per unit time performed on the treadmill (P) was for normal dogs: CO = 156 + 1.55P, for normal dogs after practolol treatment: CO = 156 + 0.43P (slope significantly different, P less than 0.05), and for dogs with denervated hearts: CO = 121 + 2.06P (not significantly different from normal dogs). It was concluded that changes in the venous or arterial system alone are not sufficient to increase cardiac output appreciably during exercise. The magnitude of the cardiac output increase depends more on the presence of intact beta-receptors than on the presence of intact cardiac nerves.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗