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PubMed2001

Chronic extrinsic denervation after small bowel transplantation in rat jejunum: Effects and adaptation in nitrergic and non-nitrergic neuromuscular inhibitory mechanisms.

BACKGROUND: Extrinsic denervation of the transplanted small bowel could play a substantial role in motor dysfunction of the transplanted gut. We attempted to determine the effect of chronic extrinsic denervation on intestinal contractility. METHODS: Jejunal longitudinal muscle strips were obtained from rats 1 week and 8 weeks after (1) syngeneic small bowel transplantation, (2) ischemia/reperfusion, or (3) gut transection/reanastomosis. Nonoperated rats (naive controls) and sham-operated rats (sham controls), 1 week after celiotomy/gut manipulation, served as controls. We evaluated the effects of exogenous nitric oxide, increasing doses of cholinergic and adrenergic agonists, and electrical field stimulation (EFS) in the presence or absence of N(G)-monomethyl-l-arginine, methylene blue, tetraethylammonium, or tetrodotoxin. RESULTS: Spontaneous contractile activity (_chi +/- SEM), when compared with the naive controls (11.3 +/- 2.0 g.5 min/mg), was increased in all 4 groups at 1 week (15.9 +/- 10 to 19.4 +/- 2 g.5 min/mg; P < or =.03 each) but not at 8 weeks postoperatively. The inhibition of contractile activity by nitric oxide was increased in small bowel transplantation in naive controls at 8 weeks to 80% +/- 10% versus 50% +/- 7% (P <.02). EFS induced an inhibition of contractile activity that was tetraethylammonium- and tetrodotoxin-sensitive but N(G)-monomethyl-l-arginine- and methylene blue-insensitive; the maximal EFS-induced inhibition was increased at 1 week and 8 weeks but only in the small bowel transplantation groups to 103% +/- 5% and 95% +/- 7%, respectively, versus 72% +/- 8% in naive controls (P </=.05). CONCLUSIONS: [corrected] Increased inhibition of contractile function after small bowel transplantation lasts at least 8 weeks and is mediated by changes in the enteric neuromuscular unit caused by extrinsic denervation.

Adaptation, Physiological↗
PubMed2003

Pharmacologic denervation of frown muscles enhances baseline expression of happiness and decreases baseline expression of anger, sadness, and fear.

BACKGROUND: Individuals with intense frowning are commonly perceived as expressing negative emotions. Anger, fear, and sadness are associated with corrugator ("frown") muscle activity. OBJECTIVE: We sought to study how faces were perceived by others after denervation of frown muscles with localized botulinum toxin injections for treatment of facial frown lines. METHODS: Facial photographs were taken from volunteers before and after botulinum toxin injection. These photographs were shown to viewers who were naive to the procedure and asked to rate the expressed intensity of anger, sadness, fear, and happiness. As reference for this task we used a standard set of pictures of facial affect displaying different intensity levels for each emotion tested. RESULTS: Of 40 viewers, 39 were able to discriminate different intensity levels (0%, 25%, 50%, 75%, and 100%) of emotional affect in the control task. According to their ratings faces with denervated frown muscle activity expressed relatively less anger (-40%), fear (-49%), sadness (-10%), and more happiness (+71%). CONCLUSION: Frown muscle activity is essential for both negative and positive emotional expressions. Temporary denervation using botulinum toxin enhances the facial expression of positive emotion resulting in a shift rather than a loss of facial affect.

Anti-Dyskinesia Agents↗
PubMed1970

Effect of muscle denervation on growth of transplanted tumor in mice.

A temporary retardation of transplanted Round Cell Neuroblastoma growth in the gastrocnemius muscle of mice was observed in 20% of the animals after denervation of the muscle. The tumor cells in these denervated animals showed structural alterations and deterioration in function. These altered cells when mixed with associated denervated muscle tissue, to which was added fresh tumor, produced a higher percentage of retardation upon subsequent transplants in innervated muscle.

Animals↗
PubMed1976

Synthesis of acetylcholine receptors by cultured chick myotubes and denervated mouse extensor digitorum longus muscles.

Mono-[125I]iodo- alpha - bungarotoxin - receptor complexes extracted from chick myotube cultures as well as from adult denervated extensor digitorum longus muscles of the mouse have been banded at their buoyant density in gradients of metrizamide-deuterium oxide. When cultures or denervated adult muscles are preincubated in media containing 2H- or 13C-substituted amino acids under conditions of active receptor accumulation, the mono-[125I]iodo-alpha-bungarotoxin-receptor complexes have an increased buoyant density and band in a position of higher density in the gradient relative to a marker of mono-[131I]iodo-alpha-bungarotoxin-receptor complexes extracted from cells preincubated in normal media. It is concluded that the accumulation of receptors on the surfaces of cultured chick myotubes and on the non-synaptic surfaces of extensor digitorum longus muscles following denervation are the result of de novo synthesis.

Animals↗
PubMed1977

L-3,4-dihydroxyphenylalanine-induced hypersensitivity simulating features of denervation.

The manner in which dyskinesia and intermittency of neurological control had emerged late in the therapy of Parkinsonism with L-3,4-dihydroxyphenylalanine (levodopa) had suggested to us that this drug can imprint on the brain a chemical memory of its passage. The majority of authors ascribed these events to denervation hypersensitivity caused by the nigral and other lesions of the disease. By feeding levodopa to mice, however, we induced a state that simulated denervations hypersensitivity, including hyperreaction to single injections of levodopa and increased dopamine-stimulated adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] activity in homogenates of caudate nuclei. These phenomena were not caused by actual denervation, because the hypersensitivity declined and disappeared some weeks after the dietary levodopa was stopped.

Adenylyl Cyclases↗
PubMed1983

Demonstration of a neurotrophic factor for the maintenance of acetylcholinesterase and butyrylcholinesterase in the preganglionically denervated superior cervical ganglion of the cat.

Under sodium pentobarbital anesthesia, the superior cervical ganglia of cats were preganglionically denervated bilaterally. The following day cats were reanesthetized, the external carotid and lingual arteries were ligated bilaterally, and the right common carotid artery was infused for 24 hr with an extract prepared from cat brain, spinal cord, and sciatic nerves, with and without the incorporation of aprotinin, an inhibitor of proteases. They were sacrificed 48 hr after denervation, and the acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) and butyrylcholinesterase (acylcholine acylhydrolase, EC 3.1.1.8) contents of the superior cervical ganglia were compared with those of similarly denervated control ganglia. Both types of extract produced a significant reduction in the loss of both enzymes from the superior cervical ganglia, as did infusions of aprotinin alone. These findings demonstrate the presence of an endogenous neurotrophic factor for the maintenance of ganglionic acetylcholinesterase and butyrylcholinesterase. Its possible mechanisms of action, and those of aprotinin, are discussed.

Acetylcholinesterase↗
PubMed1983

Effects of sodium pentobarbital anesthesia and neurotrophic factor on the maintenance of acetylcholinesterase and butyrylcholinesterase in the preganglionically denervated superior cervical ganglion of the cat.

In continuation of a previously reported study, the superior cervical ganglia of cats were preganglionically denervated bilaterally under sodium pentobarbital anesthesia. The following day cats were reanesthetized and infused via the common carotid artery with an aqueous extract of cat brain, spinal cord, and sciatic nerves for periods of 24, 12, 6, and 3 hr, without ligation of the external carotid or lingual arteries as was done previously. Values for acetylcholinesterase and butyrylcholinesterase of superior cervical ganglia at 48 hr postdenervation were all considerably above those of denervated controls. However, values for cats infused with 0.9% NaCl solution and for noninfused cats in which sodium pentobarbital anesthesia was maintained during the 24- to 48-hr postdenervation period were similarly elevated, to approximately twice the values in denervated controls. Ligation of the external carotid and lingual arteries at 24 hr postdenervation was found to oppose the preservation of acetylcholinesterase and butyrylcholinesterase contents of the ganglia induced by barbiturate anesthesia. When arterially ligated cats were infused with extract for periods of 12, 6, or 3 hr, beginning 24 hr postdenervation, acetylcholinesterase contents of superior cervical ganglia were elevated significantly above those of reanesthetized, arterially ligated controls after 12 and 6 hr but not after 3 hr of infusion, at 48 hr postdenervation.

Acetylcholinesterase↗
PubMed1984

Changes in rat adrenal catecholamines and proenkephalin metabolism after denervation.

Adrenal enkephalin-containing peptides are known to increase 10- to 15-fold in the rat after surgical denervation of the gland. In this report we show that the increase is preceded by a lag of several hours, which is indicative of stimulation of protein synthesis at the transcriptional level. The major species of newly appearing enkephalin-containing peptide appears to be the intact precursor, proenkephalin. Processing of proenkephalin to smaller enkephalin-containing peptides in the denervated glands is slow and limited. The only product that accumulates in the process is a peptide of 3-4 kilodaltons that is derived from the carboxyl terminus of proenkephalin. An interesting observation was the dissociation between the effects of denervation on enkephalin-containing peptides and catecholamines. This is surprising because both are localized in the chromaffin granules of the gland.

Adrenal Glands↗
PubMed1998

The E protein CTF4 and acetylcholine receptor expression in development and denervation supersensitivity.

Motor activity blocks the extrasynaptic expression of many genes in skeletal muscle, including those encoding ion channels, receptors, and adhesion molecules. Denervation reinduces transcription throughout the multinucleated myofiber, restoring the developmental pattern of expression, especially of the genes coding for the acetylcholine receptor. A screen for trans-acting factors binding to the enhancer region of the alpha-subunit gene of the acetylcholine receptor identified CTF4, a ubiquitously expressed and alternatively spliced chicken homologue of the human E protein transcription factor HTF4/HEB. Expression of the CTF4 locus closely parallels that of myogenin and acetylcholine receptor during development and maturation of skeletal muscle, but transcription is not similarly regulated by neuronal cues. Alternative splicing within the region encoding the transactivation domain generates two CTF4 isoforms with different tissue distributions, but similar binding affinities for the acetylcholine receptor alpha-subunit enhancer and similar transcriptional potential when complexed to myogenin. Direct injection of a myogenin, but not a MyoD, antisense expression vector into denervated skeletal muscle caused a significant decrease in the transcriptional activation of a depolarization-sensitive reporter gene. Similarly, injection of a CTF4, but less so of an E12, antisense expression vector impaired the denervation response, further implicating the involvement of a myogenin/CTF4 heterodimer in the expression of AChR genes in vivo.

3T3 Cells↗
PubMed2005

Effects of renal denervation of the contralateral kidney on blood pressure and sodium and eicosanoid excretion in the chronic phase of two-kidney, one-clip renovascular hypertension in rats.

OBJECTIVE: To define the role of the renal nerves of the contralateral kidney in the maintenance of two-kidney, one-clip (2K-1C) renovascular hypertension in rats. MATERIAL AND METHODS: The contralateral kidney of 2K-1C rats was denervated 6 months after induction of hypertension and 4 weeks after nephrectomy of the clipped kidney. Blood pressure, sodium and potassium balance and eicosanoid excretion were measured. RESULTS: Denervation of the contralateral kidney induced normalization of blood pressure in post-Goldblatt hypertensive rats. This effect was not mediated by a negative sodium balance. Excretion of prostaglandin E2 and thromboxane B2 increased after denervation of the contralateral kidney in both post-Goldblatt hypertensive and post-Goldblatt normotensive rats, while urine extraction remained unaffected. CONCLUSION: Afferences from the contralateral kidney appear to participate in the maintenance of 2K-1C renovascular hypertension due to the activation of central mechanisms regulating blood pressure.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Plasminogen activator in mammalian skeletal muscle: characteristics of effect of denervation on urokinase-like and tissue activator.

Analyses were made of the fibrinolytic, plasminogen-activating system in skeletal muscle to determine if a regulating influence of the nerve could be detected on these enzymes. Young male mice underwent right sciatic neurectomy. Extracts were prepared from denervated muscle at 2-17 d after axotomy and compared with controls. Using a cascade-style biochemical assay (Rånby, M., B. Norrman, and P. Wallén, 1982, Thromb. Res., 27:743-748) we found that low levels of plasminogen activator (PA) were present in adult, innervated mouse muscle, but that denervation resulted in a marked time-dependent increase in enzyme activity. Qualitative separation showed an eightfold increase in urokinase-like PA with moderate elevation of tissue PA activity after 10 d. Fibrin zymography (Granelli-Piperno, A., and E. Reich, 1978, J. Exp. Med., 148:223-234) revealed clear zones of lysis corresponding to molecular masses of 48 kD for urokinase-like PA and 75 kD for tissue PA, consistent with the molecular masses found for these enzymes in other tissues of the mouse (Danø, K., P. A. Andreasen, J. Grøndahl-Hansen, P. Kristensen, L. S. Nielsen, and L. Skriver, 1985, Adv. Cancer Res., 44:139-266). In other studies we have shown that PA-activated plasmin readily attacks critical adhesive basement membrane molecules. The present results indicate that enzymes involved in plasminogen activation, particularly urokinase-like PA, rapidly increase after axotomy, suggesting they may have a role early in muscle denervation. Similar alterations in PA activity might underlie the elimination of polyneuronal innervation during mammalian muscle development. Certain neuromuscular diseases may also involve activation of these enzymes, resulting in degradation of basement membrane zone components and, therefore, warrant further study.

Animals↗
PubMed1987

Cell accumulation in the junctional region of denervated muscle.

If skeletal muscles are denervated, the number of mononucleated cells in the connective tissue between muscle fibers increases. Since interstitial cells might remodel extracellular matrix, and since extracellular matrix in nerve and muscle plays a direct role in reinnervation of the sites of the original neuromuscular junctions, we sought to determine whether interstitial cell accumulation differs between junctional and extrajunctional regions of denervated muscle. We found in muscles from frog and rat that the increase in interstitial cell number was severalfold (14-fold for frog, sevenfold for rat) greater in the vicinity of junctional sites than in extrajunctional regions. Characteristics of the response at the junctional sites of frog muscles are as follows. During chronic denervation, the accumulation of interstitial cells begins within 1 wk and it is maximal by 3 wk. Reinnervation 1-2 wk after nerve damage prevents the maximal accumulation. Processes of the cells form a multilayered veil around muscle fibers but make little, if any, contact with the muscle cell or its basal lamina sheath. The results of additional experiments indicate that the accumulated cells do not originate from terminal Schwann cells or from muscle satellite cells. Most likely the cells are derived from fibroblasts that normally occupy the space between muscle fibers and are known to make and degrade extracellular matrix components.

Animals↗
PubMed1987

Quantitation of an alpha subunit splicing intermediate: evidence for transcriptional activation in the control of acetylcholine receptor expression in denervated chick skeletal muscle.

We have investigated the mechanisms responsible for the increase in acetylcholine receptor subunit mRNAs during the induction of denervation supersensitivity in skeletal muscle. Using a cRNA probe specific for exon 7 (224 nucleotides; with flanking intron sequences of 105 nucleotides on the 3' end, and of 70 nucleotides on the 5' end) of the alpha subunit of the chicken muscle acetylcholine receptor gene, we were able to quantitate the concentration of mature alpha subunit mRNA and its precursor. In 3-wk-old chicks, the concentration of alpha subunit message in leg muscle was found to be 4.0 attomoles per microgram total RNA, and to increase 40-fold within 1 wk after section of the sciatic nerve. The molar ratio of precursor/mature mRNA, which was approximately 0.023 in innervated as well as denervated muscle, transiently rose to 0.047 at the beginning of the second postoperative day when mature message content increased 20-fold; the rise in precursor level preceded the increase in mature message content. These findings suggest that an accelerated rate of transcription of the message coding for the alpha subunit causes increased message content and the stimulation of receptor synthesis characteristic of denervated muscle.

Animals↗
PubMed1989

Skeletal muscle denervation activates acetylcholine receptor genes.

Transcriptional activity of acetylcholine receptor subunit genes was investigated in innervated and denervated chick skeletal muscle. The sciatic nerve of 3-d-old White Leghorn chicks was sectioned unilaterally; after various intervals, nuclei were isolated from operated and sham-operated animals, and run-on assays performed. Nuclei were incubated with 32P-UTP, and total RNA was extracted and hybridized onto filters containing an excess of subunit-specific DNA. Specific transcripts were detected by autoradiography and quantitated densitometrically. A sharp increase in transcriptional activity was observed to begin approximately 1/2 d after the operation and peak 1 d later when transcriptional rates reached approximately seven-, six-, and fivefold control levels for the alpha-, delta-, and gamma-subunit genes, respectively. The specificity of the effect was ascertained by normalization to total RNA synthesis and by the demonstration that several nonreceptor genes respond differently to denervation. These results suggest that a denervation signal reaches the genome to induce receptor expression. In addition, since the increase in mRNA levels significantly exceeds what can be accounted for by increased gene activity, posttranscriptional effects are suggested.

Animals↗
PubMed1963

CHOLINESTERASE IN DENERVATED END PLATES AND MUSCLE FIBRES.

Parallel studies were made of cholinesterase activities and localizations in denervated rat and rabbit gastrocnemius muscle. Koelle's histochemical reaction was used for demonstrating the localization of cholinesterases. Enzyme activities in whole sliced muscle were measured by electrometric titration. The Cartesian ampulla-diver technique was used for cholinesterase activity determinations in end plate regions or in small pieces of the muscle fibre itself. No changes in the activity of cholinesterases (ChE) were found in the whole denervated muscle which would account for its chemical supersensitivity. The ChE distribution pattern was changed so that the end plate region became less active in the denervated muscle than in the normal one. The decrease in ChE activity in the end plates seems to be largely compensated for by an increase of this enzyme elsewhere in the muscle. A possible connection between the spatial spread of cholinesterase activity and the enlargement of the acetylcholine-sensitive surface is discussed.

Acetylcholine↗
PubMed1972

Development of the neuromuscular junction. 3. Degeneration of motor end plates after denervation and maintenance in vitro by nerve explants.

To determine the effects of nerve explants on the integrity of motor end plates in vitro, cholinesterase activity and structure of end plates were compared in newt muscle denervated in vivo, cultured in the absence of nerve explants, and cultured in the presence of sensory ganglia. In neuromuscular junctions denervated in vivo or in vitro, the synaptic vesicles become clumped and fragmented. A few intact vesicles escape into the synaptic cleft. Axon terminals degenerate until they are left as residual bodies within the Schwann cell cytoplasm. Junctional folds on the muscle surface are reduced in height and are no longer evident once traces of axoplasm within the Schwann cell disappear. End plate cholinesterase activity is reduced as junctional folds are lost. When muscle is cultured in the presence of a sensory ganglion, the terminal axoplasm degenerates in the same manner but junctional folds persist on the muscle surface. Moderately intense cholinesterase activity remains in association with the junctional folds, so that normal motor end plates are maintained in the absence of innervation. These results show that degenerative changes in the structure of the motor end plate and loss of cholinesterase activity occurring in organ culture as a result of denervation can be retarded by nerve explants that do not directly innervate the muscle.

Animals↗
PubMed1972

Acetylcholine receptors. Distribution and extrajunctional density in rat diaphragm after denervation correlated with acetylcholine sensitivity.

Using (125)iodine-labeled alpha-bungarotoxin (alpha-BGT-(125)I) and quantitative radioautography, we have studied the time-course of the change in acetylcholine (ACh) receptor distribution and density occurring in rat diaphragm after denervation. In innervated fibers, ACh receptors are localized at the neuromuscular junction and the extrajunctional receptor density is less than five receptors per square micrometer. The extrajunctional receptor density begins to increase between 2 and 3 days after denervation and increases approximately linearly to 1695 receptors/microm(2) at 14 days, subsequently decreasing to 529 receptors/microm(2) at 45 days. We have isolated plasma membranes from rat leg muscles at various times after denervation and find that the change in concentration of ACh receptors in the membranes measured by alpha-BGT-(125)I binding and scintillation counting follows a time-course similar to the change in ACh receptor density measured radioautographically. Furthermore, we have correlated extrajunctional ACh receptor density measured by radioautography with extrajunctional ACh sensitivity measured by iontophoretic application of ACh and intracellular recording and find that the log of ACh receptor density is related to 0.53 times the log of ACh sensitivity. These results are discussed in terms of the electrophysiological experiments on the ACh receptor and the recent, more biochemical approaches to the study of ACh receptor control and function.

Acetylcholine↗
PubMed1974

Acetylcholine receptors. Revised estimates of extrajunctional receptor density in denervated rat diaphragm.

The number of extrajunctional acetylcholine receptors ((125)I-labeled alpha-bungarotoxin binding sites) per unit length of muscle fiber and the average fiber circumference were determined for rat diaphragm muscle fibers denervated 0, 2, 4, 7, 10, and 14 days. From these data receptor densities (sites per square micrometer of surface) were calculated. Values thus obtained were considerably lower than those estimated previously by autoradiography. Receptor density increased from < 6 sites/microm(2) in innervated muscle to 635 +/- 29 sites/microm(2) 14 days after denervation. The form of the relationship between receptor density and acetylcholine sensitivity and the time-course of change in receptor density after denervation are as previously reported.

Acetylcholine↗

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