Immunohistochemical staining of cells in the brain of a patient with acquired immune deficiency syndrome (AIDS) with a monoclonal antibody to visna virus

Summary Isaxonine is reported to have a favourable effect on nerve regeneration. The histological and histochemical changes were compared in the gastrocnemius muscles of 20 rats, in which the left sciatic nerve was frozen-crushed for 10 s at the level of the buttock. The animals received a daily dose of intraperitoneal isaxonine and ten others the solvent only. After 8 weeks small type grouping was seen in rats receiving solvent only and large type grouping in rats treated with isaxonine. After 10 weeks a checkerboard pattern of the fibre types was observed in the muscles of animals receiving solvent only but fibre type grouping was present in those treated with isaxonine. This experiment indicates that isaxonine prevents synaptic remodelling by suppression of the redundant nerve endings from additional axons, which have regenerated more slowly, in making contact with motor endplates.     

Effects of isaxonine on skeletal muscle reinnervation in the rat: an electrophysiologic evaluation

Electrophysiologic detection of the first signs of gastrocnemius muscle reinnervation shows that after a single localized freezing of the rat sciatic nerve, isaxonine does not significantly increase the rate of axonal regeneration. However, this drug does significantly enhance axonal sprouting, as it induces an increase of 50% in the number of muscle fibers with multiple innervation 10-30 days after freezing. After 30 days, the proportion of multiinnervated fibers decreases in both the control and isaxonine-treated rats, and the differences between them gradually disappear.     

Development and inhibition of the target phenomenon in tenotomized rat muscle

Summary The sequence of development of the target phenomenon in tenotomized gastrocnemius muscle was studied: the presence of target fibres was preceded by the occurrence of contraction bands and of moth eaten appearance of the fibres. This phenomenon was far more pronounced and occurred earlier in type II than in type I fibres.This target phenomenon and the contraction artefacts could be inhibited in the tenotomized muscles by simultaneous neurotomy or immobilization of the muscle with a plaster cast. Delayed denervation inhibited also the target phenomenon, if performed less than 5 days after the tenotomy. These series of experiments seem to indicate that the target phenomenon occurs in more irritable muscle fibres and that muscular activity is needed for its development.     

经皮电刺激大鼠骨骼肌失神经肌萎缩时成肌调节因子基因的表达

背景：在去神经早期大鼠骨骼肌成肌调节因子(MyoD)表达明显上调,有明显延缓骨骼肌肌萎缩的作用。临床实验证实电刺激是治疗失神经肌萎缩的有效方法。尚未有实验证实电刺激对失神经肌萎缩MyoD表达的影响。 目的：验证电刺激对大鼠骨骼肌MyoD基因表达的影响。 设计、时间及地点：随机对照动物实验,于2008-07/11在山西医科大学动物实验中心完成。 材料：健康的SD大鼠36只,雌雄不限。随机分成3组,即空白对照组、去神经组、电刺激组,每组12只。 方法：空白对照组不做任何处理;去神经组和电刺激组大鼠制作右侧坐骨神经离断,腓肠肌失神经支配模型。用电刺激对电刺激组进行刺激,1次/d,30 min/次。分别于去神经第2,7,14,28天,处死大鼠,取小腿的腓肠肌肉标本。 主要观察指标：用反转录聚合酶链式反应技术检测MyoD mRNA的表达变化,免疫组织化学检测MyoD蛋白表达的变化。 结果：在去神经支配后第2,7,14,28天,去神经组和电刺激组标本中MyoDmRNA和蛋白含量表达上调,与空白对照组比较差异有显著性意义(P < 0.05),电刺激组表达高于去神经组(P < 0.05)。 结论：通过电刺激可以上调大鼠腓肠肌失神经模型MyoD的表达,说明电刺激是延缓骨骼失神经肌萎缩的有效方法。     

The influence of skeletal muscle reinnervation on experimentally induced myotonia

Earlier studies have shown that prior denervation of muscle prevents myotonia induced by 2,4-dichlorophenoxy acetic acid (2,4-D) both in vivo and in vitro. This work studied the effect of reinnervation on 2,4-D myotonia. Twenty Sprague-Dawley rats were injected with 2,4-D at specific intervals following unilateral sciatic nerve crushing; the gastrocnemius muscle on both sides was studied electromyographically to assess myotonia and to document denervation and reinnervation. All the rats gradually became amyotonic following denervation; myotonia reappeared during reinnervation. Myotonic discharges were no longer detectable 1 week after nerve crushing, but returned completely within 3 weeks. Blocking axoplasmic transport with colchicine had essentially the same effect on myotonia. A reciprocal temporal relationship was noted between the occurrence of fibrillations and myotonic discharges. These findings substantiate the view that innervation is essential to maintain the muscle membrane in a state that will support myotonic discharges.     

Morphological differences in skeletal muscle atrophy of rats with motor nerve and/or sensory nerve injury

Skeletal muscle atrophy occurs after denervation. The present study dissected the rat left ventral root and dorsal root at L4-6 or the sciatic nerve to establish a model of simple motor nerve injury, sensory nerve injury or mixed nerve injury. Results showed that with prolonged denervation time, rats with simple motor nerve injury, sensory nerve injury or mixed nerve injury exhibited abnormal behavior, reduced wet weight of the left gastrocnemius muscle, decreased diameter and cross-sectional area and altered ultrastructure of muscle cells, as well as decreased cross-sectional area and increased gray scale of the gastrocnemius muscle motor end plate. Moreover, at the same time point, the pathological changes were most severe in mixed nerve injury, followed by simple motor nerve injury, and the changes in simple sensory nerve injury were the mildest. These findings indicate that normal skeletal muscle morphology is maintained by intact innervation. Motor nerve injury resulted in larger damage to skeletal muscle and more severe atrophy than sensory nerve injury. Thus, reconstruction of motor nerves should be considered first in the clinical treatment of skeletal muscle atrophy caused by denervation.     

Electrophysiologic assessment of sciatic nerve regeneration in the rat: surrounding limb muscles feature strongly in recordings from the gastrocnemius muscle

Striking inconsistencies between the results of morphometric and electrophysiologic examinations of the regenerating nerve were observed in a previous study featuring the bridging of a 14 mm gap in the rat sciatic nerve. To shed light on this dichotomy, seven further rats were subjected to permanent sciatic nerve transection and assessed electrophysiologically, histologically and by retrograde axonal tracing at various postoperative intervals (1 h to 8 weeks). The results of the histological examinations and retrograde tracing revealed that in spite of the fact that compound muscle action potentials could be recorded in the gastrocnemius muscle, no reinnervation of the gastrocnemius muscle, either physiological or aberrant, had actually taken place. Furthermore, it was established that the electrical activity recorded in the gastrocnemius muscle after stimulation of the proximal or distal stump is generated by surrounding hind limb muscles unaffected by denervation. These are stimulated either directly, or indirectly due to spreading of the impulse. It is therefore strongly recommended that caution should be exercised when interpreting recordings from the gastrocnemius muscle after stimulation of a regenerating sciatic nerve in laboratory rodents.     

Neurotrophic factors improve muscle reinnervation from embryonic neurons

Motoneurons die in diseases like amyotrophic lateral sclerosis and after spinal cord trauma, inducing muscle denervation. We tested whether transplantation of embryonic cells with neurotrophic factors into peripheral nerve of adult rats improves muscle reinnervation and motor unit function more than cells alone. One week after sciatic nerve section, embryonic ventral spinal cord cells were transplanted into the tibial nerve with or without glial cell line-derived neurotrophic factor, hepatocyte growth factor, and insulin-like growth factor-1. These cells represented the only neuron source for muscle reinnervation. Ten weeks after transplantation, all medial gastrocnemius muscles contracted in response to electrical stimulation of cell transplants with factors. Only 80% of muscles responded with cells alone. Factors and cells resulted in survival of more motoneurons and reinnervation of more muscle fibers for a given axon (motor unit) number. Greater reinnervation from embryonic cells may enhance muscle excitation by patterned electrical stimulation.     

Biometrical and histochemical comparison between extra- and intra-fusal muscle fibres in denervated and re-innervated rat muscle

Summary Biometrical and histochemical changes in extra- and intrafusal muscle fibres were determined in twenty adult rats during denervation and re-innervation. The right sciatic nerve was severed and at regular intervals the denervated gastrocnemius, soleus and peroneal muscles were examined and compared with the corresponding muscles of the non denervated limb.Although the extra- and intra-fusal muscle fibres show the same histochemical changes, the atrophy of the intra-fusal muscle fibres is insignificant compared with the atrophy of the extra-fusal muscle fibres in the denervation phase. This could be explained by the small size of the intra-fusal fibres and the increased fluid resorption of the spindle.In the re-innervation phase the same histochemical changes occur in both types of muscle fibres.     

Perlecan and synaptophysin changes in denervated skeletal muscle

The present study observed sciatic nerve and gastrocnemius muscle changes in denervated rats using morphology methods,and assessed expression of perlecan,an extracellular matrix com-ponent,which is located at the skeletal muscle cell surface as acetylcholine esterase,as well as synaptophysin,a synaptic marker.Results showed degeneration and inflammation following transection of the sciatic nerve.In addition,the sciatic nerve-dominated skeletal muscle degen-erated with mild inflammation,indicating that skeletal muscle atrophy primarily contributed to denervation-induced nutritional disturbances.With prolonged injury time(1-4 weeks post-injury),perlecan expression gradually decreased and reached the lowest level at 4 weeks,but synap-tophysin expression remained unchanged after denervation.Results suggested that perlecan expression was more sensitive to denervation and reflected regional extracellular matrix changes following denervation.     

Influence of stretch on the target phenomenon in the tenotomized and immobilized gastrocnemius muscle of the rat

The influence of traction on the target phenomenon was analysed in the tenotomized gastrocnemius muscle of Wistar rats. Target fibres were constantly observed at the medial side of the heads of the non-immobilized and tenotomized gastrocnemius muscles used as control. In the muscles fixed in flexion, no target fibres could be detected, while in the muscles fixed in hyperextension some target fibres were seen. The latter were less numerous than those present in the non-immobilized muscles. This experiment proves the importance of stretch mechanisms in the pathogenesis of the target phenomenon.     

Brain-Derived Neurotrophic Factor mRNA Levels Are Up-Regulated in Hindlimb Skeletal Muscle of Diabetic Rats: Effect of Denervation

In a previous study the levels of brain-derived neurotrophic factor (BDNF) mRNA were shown to be elevated in skeletal muscle of the diabetic rat compared with age-matched control animals. It was proposed that diabetes-induced changes in nerve function may initiate changes in nerve/muscle contact akin to those following denervation of target skeletal muscle. In this study hindlimb skeletal muscles were denervated by sciatic nerve crush or transection and the effect on BDNF mRNA levels in control and diabetic rats was observed using Northern blotting. Contralateral to the side of nerve injury, the levels of BDNF mRNA in soleus muscle of diabetic rats were higher than in controls (three- to sevenfold), as has been seen previously in diabetic rats without any axotomy. Sciatic nerve crush or transection, of 1 week or of 3 weeks duration, lowered the levels of BDNF mRNA by 50% in ipsilateral soleus muscle of diabetic rats. BDNF mRNA levels in contralateral gastrocnemius muscle were not similarly raised in diabetic rats compared with controls and nerve injury had no effect. In control animals, ipsilaterally, the BDNF mRNA levels of soleus muscle were raised approximately twofold at 1 week and were lowered by approximately 50% at 3 weeks following nerve injury. Neurotrophin-3 mRNA levels were reduced approximately 50% in soleus muscle of diabetic rats compared with control rats, and nerve injury had no significant effect. The specific up-regulation of BDNF mRNA in soleus muscle of diabetic rats is discussed in terms of a proposed diabetes-induced ischemia within hindlimb skeletal muscle, with a protective role for BDNF in muscle and/or nerve being introduced.     

The target phenomenon in rat muscle following tenotomy and neurotomy

Summary Target fibers were checked at regular intervals in two groups of rat gastrocnemius muscle namely after tenotomy and neurotomy. The highest amount of target fibres was observed during the first week. following tenotomy and around the seventh week, when the muscle became again functional by spontaneous union of the tendon. The target phenomenon was restricted to the type II fibres. It appeared also in the early stage of re-innervation, 5 weeks following neurotomy and remained present subsequently in a transitional zone between denervated and re-innervated muscle fibres and was restricted to the type I muscle fibres. The target phenomenon was not the only histochemical alteration observed following tenotomy and neurotomy. This experimental study allowed to determinate more precisely the causal factors of the target phenomenon.     

Magnetic resonance imaging of mouse skeletal muscle to measure denervation atrophy

We assessed the potential of different MRI measures to detect and quantify skeletal muscle changes with denervation in two mouse models of denervation/neurogenic atrophy. Acute complete denervation and chronic partial denervation were examined in calf muscles after sciatic nerve axotomy and in transgenic SOD1^G93A mice, respectively. Serial T₂, diffusion tensor, and high resolution anatomical images were acquired, and compared to behavioral, histological, and electrophysiological data. Increase in muscle T₂ signal was first detected after sciatic nerve axotomy. Progressive muscle atrophy could be monitored with MRI-based volume measurements, which correlated strongly with postmortem muscle mass measurements. Significant increase in muscle fractional anisotropy and decreases in secondary and tertiary eigenvalues obtained from diffusion tensor imaging (DTI) were observed after denervation. In SOD1^G93A animals, muscle denervation was detected by elevated muscle T₂ and atrophy in the medial gastrocnemius at 10 weeks. Changes in T₂ and muscle volume were first observed in medial gastrocnemius and later in other calf muscles. Alterations in secondary and tertiary eigenvalues obtained from DTI were first observed in tibialis anterior and medial gastrocnemius muscles at age 12 weeks. We propose that MRI of skeletal muscle is a sensitive surrogate outcome measure of denervation atrophy in animal models of neuromuscular disorders, with potential applicability in preclinical therapeutic screening studies in rodents.     

Inhibition of the target phenomenon in tenotomized rabbit muscle by medullary lesions

Summary Target fibres were demonstrated in the gastrocnemius muscles following section of the Achilles tendon of two rabbits. In five other animals with tenotomized gastrocnemius muscles, a subarachnoid phenol block of the lumbar and sacral spinal cord was performed. Large and small medullary lesions inhibited the occurrence of target fibres in the tenotomized muscle, the smallest one being neurolysis of the dorsal roots. This final experiment suggests that the target phenomenon is the morphological expression of an increased stretche sensitivity of the tenotomized muscle.     

Sensory nerves impair sympathetic reinnervation and recovery of smooth muscle function.

Neuronal populations projecting to a common target may compete for neurotrophic substances. To determine if competition impairs target reinnervation, we examined the effect of capsaicin-induced sensory denervation on sympathetic nerve ingrowth to the sympathectomized rat superior tarsal smooth muscle. In tarsal muscles with intact sympathetic innervation, capsaicin injection on Day 2 reduced numbers of perimuscular CGRP-ir sensory nerves by 68% at 3-4 months; however, it did not alter dopamine-beta-hydroxylase-ir nerve density, response to nerve stimulation, or tarsal muscle adrenoceptor-mediated contraction. Tarsal muscles denervated by ipsilateral superior cervical ganglionectomy on Postnatal Day 4 were partially reinnervated by fibers from the contralateral ganglion, as noted in previous studies. Sensory denervation by capsaicin improved sympathetic reinnervation, as evidenced by a 174% increase in numbers of DBH-ir nerves and a 62% increase in neurally mediated smooth muscle contraction evoked by electrical stimulation of the contralateral pathway relative to reinnervated muscles of vehicle-injected rats; smooth muscle function was also influenced, as indicated by a decrease toward normal in adrenoceptor sensitivity. Tarsal muscles denervated at 30 days were not reinnervated in either vehicle-injected or capsaicin-treated rats, indicating that sensory denervation does not extend the developmental window during which contralateral reinnervation can occur. Both the vehicle-injected and capsaicin-treated preparations with sustained juvenile sympathectomy showed sensory hyperinnervation as adults; thus, a chronic reduction in competition from sympathetics is a sufficiently powerful stimulus to overcome the decreased nerve density induced by neonatal capsaicin treatment. We conclude that sensory nerves limit the extent of sympathetic reinnervation and functional recovery that can occur following neonatal sympathetic denervation.     

Recovery of muscle after different periods of denervation and treatments

Three aspects of reinnervation and recovery of skeletal muscle following various periods of denervation were investigated: (1) the effect of duration of denervation; (2) the effect of hyperthyroidism on recovery; and (3) whether the muscle or the nerve limits recovery. The rat medial gastrocnemius (MG) nerve was cut and then resutured after 0, 3, 7, 21, or 56 days. In a second group of animals, the MG muscle was denervated and, in addition, the animal received triiodothyronine (T₃) supplementation during reinnervation. The third group of animals had the denervated MG muscle reinnervated by a larger number of newly transected foreign axons. The force produced by the reinnervated muscle depends on the period that the muscle was denervated. Recovery was impaired when the period of denervation exceeded 7 days. T₃ treatment did not benefit the return of force production, nor did providing the muscle with a larger number of newly transected axons.     

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

Summary 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.     

Morphological properties of experimentally produced target fibres in tenotomized rat gastrocnemius muscle

Summary The gastrocnemius muscles of 3 groups of 10 rats, sacrified 5, 7, and 12 days respectively, following tenotomy, were submitted to different types of fixation, fixative and embedding.The occurrence of target fibres is shown not to be an artefact due to the histological procedures. Further examination demonstrates that the target phenomenon occurs in the shortest fibres on the medial side of both heads of the gastrocnemius muscle and that is consists mainly of a disarrangement of the contractile elements of the muscle fibres. This study argues that this phenomenon represents some kind of myotonic state of a pathological muscle.     

Effects of vitamin E and electrical stimulation on the denervated rat gastrocnemius muscle malondialdehyde and glutathione levels

Effects of vitamin E treatment and local electrical stimulation on progression of atrophy in the denervated rat gastrocnemius muscle were studied. Denervation was performed by right leg sciatic nerve axotomy. Electrical stimulation (3-10 mA ms(-1), 10 min per day for 7 days) was applied to the right gastrocnemius muscle starting from day 1 of denervation. The muscle samples were assayed for malondialdehyde (MDA) and glutathione levels, as well as the histological appearance after 8 days of denervation. MDA levels were markedly increased following denervation. However, electrical stimulation, vitamin E treatment (30 mg kg(-1), i.m., everyday for 7 days), and combination of electrical stimulation and vitamin E treatment markedly reduced MDA levels. Glutathione levels were significantly decreased in the denervation group. Electrical stimulation, vitamin E treatment, and electrical stimulation plus vitamin E treatment prevented these reductions in glutathione levels. In the vitamin E treatment group, glutathione levels were markedly higher than in the control group. These results indicate that electrical stimulation and vitamin E treatment alone, or in combination, were able to prevent the effects of denervation on muscle atrophy.