兼受快肌和慢肌两种神经支配的大白鼠比目鱼肌纤维的组织化学类型和收缩特性

大白鼠比目鱼肌(SOL)在其原来神经被夹断暂时处于去神经状态期间,可以从预先埋置好的伸趾长肌(EDL)神经得到外加的神经支配。在这样的肌肉中有一部分肌纤维兼受快肌和慢肌两种神经支配。我们检查了这种肌纤维的组织化学类型和收缩特性。主要结果是:SOL 肌纤维,在原有神经支配之外加上了 EDL 神经的支配,保持原来慢肌型的肌原纤维 ATP_(ase)组织化学特性不变。在历时长短很不同(夹 SOL 神经后20至120天,有一例是402天)的实验,这个结果都是一样。另一方面,有外加 EDL 神经支配的 SOL 肌纤维收缩加快,虽然改变的程度不大。考虑到影响肌肉收缩速度的因素不限于肌原纤维 ATP_(ase)的活力,而所用组织化学方法在反映 ATP_(ase)活力变化方面又有其局限性,上述两方面的结果并不矛盾。尽管一根肌纤维上有由两种不同神经支配形成的两个完全分开的终板,但整根纤维从一端到另一端的组织化学染色是均一的,看不出两个终板各自周围的染色有何差别。虽然这观察倾向于支持肌原纤维 ATP_(ase)类型为肌肉活动所决定的假说,每种神经支配对收缩系统是否还有其特殊营养性影响的问题尚未解决,还需要用更精细的检测肌纤维类型的方法作进一步的研究。     

肌卫星细胞在失重肌萎缩中的可塑性变化及机制

肌卫星细胞在骨骼肌生长发育和出生后骨骼肌损伤修复中起着重要的作用,但是有关肌萎缩中肌卫星细胞的可塑性变化、作用及其机制尚不清楚.本研究采用小鼠尾悬吊模拟失重效应诱导失重肌萎缩,动态分析了失重肌萎缩发生过程中不同类型肌纤维的肌卫星细胞数量和增殖、分化潜能可塑性的改变,发现在失重肌萎缩过程中,处于安静状态的肌卫星细胞显著增多、激活增殖的肌卫星细胞显著减少,而具有成肌分化潜能的肌卫星细胞有持续减少趋势.此外,在失重肌萎缩比目鱼肌单根肌纤维移出的体外培养中,证明了失重肌萎缩肌纤维肌卫星细胞可塑性降低的特征性变化.进一步,通过对比分析Smad3基因敲除及其同窝野生型小鼠,在失重肌萎缩中肌卫星细胞可塑性的差异性变化,揭示了Smad3在调控失重肌萎缩肌卫星细胞可塑性变化中的关键作用.     

运动调控昼夜节律在抗肌萎缩中的作用

随着全球老龄化进程加剧,老年人口剧增,伴随着工作和生活方式的改变,导致体育锻炼减少与生活作息不规律等问题愈发严重。这样的结果显著增加了骨骼肌萎缩的发病率,降低了老年和慢性疾病人群机体健康,影响其生活质量。与此同时,饮食不均衡和运动量降低以及激素水平波动等进一步加剧骨骼肌萎缩的发生,其病理机制主要为慢性炎症加重、线粒体功能障碍、自噬功能状态低下、细胞凋亡增加、肌卫星细胞功能受损以及昼夜节律紊乱等。其中,随着昼夜节律相关研究的深入,骨骼肌作为机体最大的外周生物钟,可通过调控昼夜节律核心基因BMAL1以及CLOCK基因,对骨骼肌纤维结构、线粒体功能、肌肉质量等产生影响。运动锻炼作为改善骨骼肌质量的重要干预策略,还可激活昼夜节律信号通路,调控其相位,进而改善肌肉再生、提高肌肉力量,发挥延缓肌萎缩作用。为此,本文从昼夜节律的角度去阐述其与肌萎缩发生以及潜在运动干预的分子机制,以期为肌萎缩的预防、治疗及康复提供新的靶向思路。     

去负荷小鼠比目鱼肌收缩特性和纤维类型转化

目的:探讨去负荷后小鼠比目鱼肌的收缩特性与骨骼肌纤维类型转化之间的关系。方法:采用离体肌肉灌流技术和电刺激方法,在小鼠后肢去负荷28 d引起骨骼肌萎缩后,观察比目鱼肌单收缩、强直收缩能力和肌疲劳指标等收缩特性的改变,同时利用组织免疫荧光染色和实时定量聚合酶链式反应(real-time PCR)等技术检测去负荷后比目鱼肌快慢肌纤维组成和纤维类型转化的变化。结果:去负荷28 d后,小鼠比目鱼肌单收缩力、强直收缩能力和疲劳指数(fatigue index)均有显著性下降,同时伴有快肌纤维亚型的增加和慢肌纤维亚型的减少。结论:去负荷28 d后小鼠比目鱼肌收缩特性的改变和快慢肌纤维类型的转化有关。     

鸡前、后背阔肌去神经后对辣根过氧化物酶(HRP)的胞纳作用

本文报道了用辣根过氧化物酶(HRP)作为大分子标记物,以组织化学和生物化学方法观察了鸡前后背阔肌在去神经后的胞纳现象。结果表明,在去神经后发生肥大的前背阔肌和去神经后发生萎缩的后背阔肌同样都出现胞纳的明显增加。组织化学所观察的结果表明,浸泡在含 HRP 的任氏液中的有完整神经支配的前、后背阔肌只有极少数的肌纤维摄取 HRP,而在去神经的前、后背阔肌中则有不少的肌纤维内部出现 HRP 染色反应。这种反应在有的纤维表现为弥散性染色,有的表现为浓的 HRP 反应颗粒。生物化学的结果显示,去神经后的前、后背阔肌中 HRP 的相对含量分别比有神经支配的对照肌肉明显地增多54%和87%,我们在鸡前背阔肌用组织化学和生物化学所得的实验结果与 Thesleff 等人提出的关于肌肉萎缩机制的假设显然不符。本工作证实了肌肉的胞纳作用的增加并不一定最终导致肌纤维的变性和萎缩。     

哺乳动物不活动化肌纤维的动作电位

用河豚毒素(TTX)慢性阻断大鼠坐骨神经的冲动传导,使后肢不活动,经过不同时间(最长7d)后离体观察了快肌伸趾长肌(EDL)和慢肌比目鱼肌(SOL)肌纤维终板区的诱发动作电位。我们发现在不活动期间动作电位超射和上升速率逐步下降,并从第4天起部分肌纤维能在含有1×10~(-7)g/ml TTX的溶液中被诱发产生动作电位(称抗TTX动作电位),待至第7天时全部SOL肌纤维和90％的EDL肌纤维都能被诱发出抗TTX动作电位。与去神经肌纤维相比,不仅抗TTX动作电位出现较晚,并且其超射和上升速率较低。在去掉TTX阻断使肌肉恢复活动后,动作电位超射和上升速率渐趋恢复,抗TTX动作电位逐渐消失。无论是动作电位的恢复还是抗TTX动作电位的消失,EDL肌纤维均快于SOL肌纤维。本文还讨论了不活动化使肌纤维动作电位变化以及快、慢肌差别的可能原因。     

DMD的ATP酶组织化学研究

目的观察DMD(Duchenne muscular dystrophy)患者病变肌肉的酶组织化学病理改变,加深对其发病机制和预后的认识.方法对5例Duchenne型肌营养不良症患者进行肌肉活检,标本经处理,分别在HE染色、改良Gomori三色染色以及ATP酶染色(pH9.4和pH4.3)下进行观察,研究病变肌肉酶组织化学的病变特征及其意义.结果在DMD组织中肌纤维大小不等,肌纤维圆形化,炎性细胞浸润,并可见到不透光纤维.在再生肌纤维中可见到IIc型纤维.结论 DMD病变组织中纤维坏死显著,伴有不同程度的再生,故临床症状严重,病程短,预后较差.     

老年人肌少症发生机制

因年龄增长所致骨骼肌质量减少及功能衰退称为肌少症,其特点是随着年龄的增加,肌纤维的质量、力量、肌耐力、代谢能力下降,而脂肪、结缔组织增多。肌少症的本质是肌纤维数量与横截面积下降及蛋白质净降解,与炎症加剧、氧化应激损伤、线粒体功能障碍、细胞自噬异常和肌肉质量调控因子失调等因素密切相关。本文系统阐述了肌少症发生的分子机制,加深人们对肌少症的理解与认识,为肌少症的预防与治疗提供潜在靶点。     

肌肉萎缩与氧化应激

肌肉是机体具有收缩性的组织,它的主要功能是通过力量产生引起机体各部位的运动.肌肉萎缩是肌肉质量和力量丧失,肌肉活动功能减退的一种反应,在许多生理和病理情况下都可以出现.肌肉萎缩时不仅表现为肌肉结构形态的变化,如肌肉的重量和体积减少,肌纤维类型改变,最主要是肌肉蛋白质水解作用增强、合成减少.氧化应激是机体氧化产物超过机体抗氧化防御能力一种应激状态,可以导致细胞、组织和器官的损伤.大量证据表明,氧化应激参与肌肉萎缩的致病过程.探讨氧化应激在肌肉萎缩中的作用,对了解肌肉萎缩的致病机制有重要作用.本文对氧化应激和肌肉萎缩的关系,氧化应激参与肌肉萎缩时的蛋白质水解途径,以及连接氧化应激和肌肉萎缩的两个重要细胞信号转导通路做一简要综述.     

低氧暴露诱导肌萎缩发生的机制探讨

高海拔地区常伴随着诸多不利环境因素,使初上高原者处于应激状态,对机体代谢系统产生一系列不良影响,其中之一就是诱发骨骼肌萎缩。肌萎缩是一种肌肉功能减退的反应,表现为肌纤维横截面积减小,肌纤维类型转变和肌肉力量、耐力下降。高原环境造成的肌萎缩与低氧环境密切相关。高原训练是竞技体育中一种提高氧运输能力、心脏供血能力及最大摄氧量的有效训练方式,但此过程中造成的骨骼肌质量丢失会影响运动员力量和耐力的发挥,不利于运动表现;同时,随着高原旅游和低氧减肥的兴起,世居平原大众进入高原后发生的肌量丢失和肌力下降也会影响其健康状态。低氧暴露所诱发的肌萎缩程度由低氧浓度和暴露时长所决定,是一个多器官、多组织参与的整体调控骨骼肌蛋白代谢失衡的过程,且在不同类型的肌纤维中表现不同。但目前关于低氧暴露导致肌萎缩的机制还不完全清楚。因此,本文将就该问题相关研究进展进行综述,以期进一步阐明低氧诱导肌萎缩的生物学机制,从而利用低氧刺激更好地提高运动成绩和服务大众健康。     

Axonal degeneration of peripheral facial nerve in a patient with progressive hemifacial atrophy.

We report a case of a 23-year-old woman with progressive hemifacial atrophy. She showed an atrophic change on the left side of her face for 8 years. A skin biopsy obtained from the lesion revealed the fibrotic changes in the deep dermis and adipose tissue with infiltrations of lymphocytes and plasma cells. She underwent the augmentation using a deepithelialized anteromedial thigh flap with endoscopic assistance. A specimen of the peripheral facial nerve taken from the region adjacent to the skin lesion during the operation showed atrophy of neurofibers with vacuole degeneration. On an electron microscopic examination, a high degree of degeneration of myelinated and unmyelinated axons was observed. These findings may provide direct evidence that atrophic changes of nerve fibers are closely related with the pathology of this disease.     

Cell types required to efficiently innervate human muscle cells in vitro

Previous studies carried out in our laboratory have shown that myofibers formed by fusion of muscle satellite cells from donors with spinal muscular atrophy (SMA) type I or II undergo a characteristic degeneration 1.5-3 weeks after innervation with rat embryonic spinal cord explants. The only cells responsible for degeneration of innervated cocultures are SMA muscle satellite cells. In order to study the kinetics of nerve and muscle cell degeneration in nerve-muscle cocultures implicating SMA muscle cells, we attempted to simplify the nervous component of the coculture and identify the nerve cell types necessary for a successful innervation. We demonstrate here that motoneurons alone were unable to innervate myotubes. However, when three cell types (motoneurons, sensory neurons, and Schwann cells) were added onto a reconstituted muscular component consisting of cloned muscle satellite cells and cloned muscular fibroblasts, myotubes contracted, indicating that functional neuromuscular junctions were formed. We concluded that the three cell types were required for a successful innervation. Moreover, we studied the effects of culture medium conditioned by different combinations of nerve cells on innervation; we observed that physical contacts among sensory neurons, motoneurons, and myotubes are required for a successful innervation; in contrast Schwann cells can be replaced by a Schwann-cell-conditioned medium, indicating that these cells produce a putative soluble "innervation-promoting factor." Obviously such a reconstituted system does not reflect the in vivo situation but it allows the formation of functional motor synapses and could therefore allow us to elucidate neuromuscular disease pathogenesis, especially that of spinal muscular atrophy.     

Degeneration and regeneration in denervated tonic and phasic skeletal muscle: Morphology and acid phosphatase cytochemistry

Following denervation, ultrastructural alterations were observed in the tonic, anterior (ALD) and phasic posterior (PLD) latissimus dorsi muscles of the chicken. In the ALD muscle these changes were characteristic of both degeneration and regeneration, while in the PLD muscle, the changes were characteristic only of degeneration. Acid phosphatase positive structures, which included dense bodies in the ALD and PLD as well as T-tubules in the PLD, were observed intact with no evidence of release of enzyme into the sarcoplasm. No evidence of an increase in the number of autophagic vacuoles was found. The morphological evidence presented in this communication does not support the hypothesis that lysosomes are involved in denervation atrophy through autophagy of muscle cell constituents.     

Potentialities of temporal bone computed tomography in the study of the facial nerve and in the diagnosis of peripheral pareses of thr 7th pair of cranial nerves

Computed tomography (CT) was used to examine 200 patients (400 temporal bones) aged 3 to 74 years who had no signs of facial nerve lesion and 28 patients who had clinical manifestations of peripheral paresis of the facial nerve of varying genesis. Multipositional CT of the temporal bone is the most informative mode of visualization of the fallopian canal which is embodied on tomographic scans in 100% of cases irrespective of the age of a patient. CT data indicate that the formation of the facial nerve canal brings to completion by the age of 6 years. The following causes of n. facialis paresis were identified: facial neuroma; sarcoma of the temporal bone sarcoma; dehiscence of the canal wall in otitis media acuta; destruction of the tympanic wall of the canal in otitis nedia chronica, fractures of the temporal bone, anomalies of the fallopian canal in temporal bone malformations; stenosis of the canal in fibrous dysplasia. The detected alterations of the n. facialis canal permits further policy of management of a patient to be defined.     

Effects of safranal,a constituent of saffron,and vitamin E on nerve functions and histopathology following crush injury of sciatic nerve in rats

Safranal is one of the major components of saffron and has many biological effects such as antioxidant property. The present study investigated the effects of safranal on sciatic nerve function after induction of crush injury. We also used of vitamin E as a reference potent antioxidant agent.In anesthetized rats, right sciatic nerve was crushed using a small haemostatic forceps. Functional recovery was assessed using sciatic functional index (SFI). Acetone spray and von Frey filament tests were used for neuropathic pain assay. Histopathological changes including severities of Wallerian degeneration of sciatic nerve and gastrocnemius muscle atrophy were investigated by light microscopy. Blood levels of malodialdehyde (MDA) were also measured.The SFI values were accelerated, cold and mechanical allodynia were suppressed, the severities of Wallerian degeneration and muscular atrophy were improved, and the increased MDA level was reversed with 10 consecutive days intraperitoneal injections of 0.2 and 0.8 mg/kg of safranal and 100 mg/kg of vitamin E.It is concluded that safranal and vitamin E produced same improving effects on crushed-injured sciatic nerve functions. Inhibition of oxidative stress pathway may be involved in improving effects of safranal and vitamin E on functions and histopathology of an injured peripheral nerve.     

An HRP study of the central connections of the facial nerve in the mallard (Anas platyrhynchos L.)

The location of several facialis innervated muscles has been determined by injecting individual muscles with horseradish peroxidase. The depressors of the lower jaw are represented in the dorsal facial motor nucleus and the tongue retractor muscles in the intermediate facial motor nucleus. HRP was also directly applied to the rostral and caudal branch of the facial nerve. The afferent connections are described including two small projections to the principal sensory nucleus and n. interpolaris which were not found in birds before.     

Comparative proteomic profile of rat sciatic nerve and gastrocnemius muscle tissues in ageing by 2‐D DIGE

Ageing induces a progressive morphological change and functional decline in muscles and in nerves. Light and electron microscopy, 2‐D DIGE and MS, were applied to profile the qualitative and quantitative differences in the proteome and morphology of rat gastrocnemius muscle and sciatic nerve, in healthy 22‐month‐old rats. At muscle level, morphological changes are associated to fibre atrophy accompanied by myofibrillar loss and degeneration, disappearance of sarcomeres and sarcoplasmic reticulum dilatation, internal migration of nuclei, longitudinal fibre splitting, increment of subsarcolemmal mitochondria aggregates and increment of lipofuscin granules. Sciatic nerve shows myelin abnormalities like enfoldings, invaginations, onion bulbs, breakdowns and side axonal atrophy. Proteomic analysis identified changes correlated to morphological abnormalities in metabolic, contractile and cytoskeletal proteins, deregulation of iron homeostasis, change of Ca²⁺ balance and stress response proteins, accompanied by a deregulation of myelin membrane adhesion protein and proteins regulating the neuronal caliber. By comparing proteomic results from the two tissues, 16 protein isoforms showed the same up and down regulation trend suggesting that there are changes implying a general process which may act as a signal event of degeneration. Only β enolase and tropomyosin 1α were differentially expressed in the tissues.     

Neurovascular free-muscle transfer for the treatment of established facial paralysis following ablative surgery in the parotid region

Neurovascular free-muscle transfer for facial reanimation was performed as a secondary reconstructive procedure for 45 patients with facial paralysis resulting from ablative surgery in the parotid region. This intervention differs from neurovascular free-muscle transfer for treatment of established facial paralysis resulting from conditions such as congenital dysfunction, unresolved Bell palsy, Hunt syndrome, or intracranial morbidity, with difficulties including selection of recipient vessels and nerves, and requirements for soft-tissue augmentation. This article describes the authors' operative procedure for neurovascular free-muscle transfer after ablative surgery in the parotid region. Gracilis muscle (n = 24) or latissimus dorsi muscle (n = 21) was used for transfer. With gracilis transfer, recipient vessels comprised the superficial temporal vessels in 12 patients and the facial vessels in 12. For latissimus dorsi transfer, recipient vessels comprised the facial vessels in 16 patients and the superior thyroid artery and superior thyroid or internal jugular vein in four. Facial vessels on the contralateral side were used with interpositional graft of radial vessels in the remaining patient with latissimus dorsi transfer. Cross-face nerve grafting was performed before muscle transfer in 22 patients undergoing gracilis transfer. In the remaining two gracilis patients, the ipsilateral facial nerve stump was used as the primary recipient nerve. Dermal fat flap overlying the gracilis muscle was used for cheek augmentation in one patient. In the other 23 patients, only the gracilis muscle was used. With latissimus dorsi transfer, the ipsilateral facial nerve stump was used as the recipient nerve in three patients, and a cross-face nerve graft was selected as the recipient nerve in six. The contralateral facial nerve was selected as the recipient nerve in 12 patients, and a thoracodorsal nerve from the latissimus dorsi muscle segment was crossed through the upper lip to the primary recipient branches. A soft-tissue flap was transferred simultaneously with the latissimus muscle segment in three patients. Contraction of grafted muscle was not observed in two patients with gracilis transfer and in three patients with latissimus dorsi transfer. In one patient with gracilis transfer and one patient with latissimus dorsi transfer, acquired muscle contraction was excessive, resulting in unnatural smile animation. The recipient nerves for both of these patients were the ipsilateral facial nerve stumps, which were dissected by opening the facial nerve canal in the mastoid process. From the standpoint of operative technique, the one-stage transfer for latissimus dorsi muscle appears superior. Namely, a combined soft-tissue flap can provide sufficient augmentation for depression of the parotid region following wide resection. A long vascular stalk of thoracodorsal vessels is also useful for anastomosis, with recipient vessels available after extensive ablation and neck dissection.     

Transplantation and transposition of skeletal muscles into the faces of monkeys

Restoration of normal facial movement after long-term facial paralysis with muscle atrophy has not yet been achieved reliably by either free grafts, in which fibers degenerate and regenerate, or by grafts made with microneurovascular repair, in which most fibers survive. Our purpose was to compare the structural and functional properties of free muscle grafts and continuously perfused muscle flaps transplanted into the faces of monkeys. In adult monkeys, the facial muscles were replaced by either a free graft of a donor muscle from the lower limb or a denervated flap of ipsilateral temporalis muscle. Each graft or flap was reinnervated with the preserved buccal branch of the facial nerve. The control muscles, grafts, and flaps were examined 90 days later for gross appearance, contractile properties, and fiber areas. Compared with muscle flaps, free grafts showed greater adaptability to the new location and innervation and a closer approximation to the structural and functional properties of the original facial musculature.     

Acetylcholinesterase activity in nerve endings of tails of Rana japonica and R. catesbeiana during metamorphosis

Summary In anuran tadpole tails, the myelinated motor nerve fibers branch in the myoseptum to innervate both red and white muscle fibers at, or near, their ends. There are no significant ultrastructural differences between the nerve endings of the two types of muscle fibers.Intense acetylcholinesterase reaction product was observed in synaptic clefts and junctional folds, as well as in transverse tubules. As metamorphosis proceeded, the junctional folds of the nerve endings disappeared, however, acetylcholinesterase reaction product was still observed in the synaptic clefts. As muscle fibers began to degenerate, nerve endings began to separate from them. However, after nerve endings were completely separated from the surfaces, degenerated muscle fibers, synaptic and cored vesicles were still well preserved although no acetylcholinesterase reaction product was found. It seems clear that the mechanism of the muscle degeneration in the tadpole tail during metamorphosis is not the result of the degeneration of its nerve endings.