骨关节病患者肌纤维萎缩类型及其与日常活动的相关性

背景:骨关节病患者因制动等原因可出现严重的肌纤维萎缩,但目前对这类肌纤维萎缩的微观分类及其与日常活动的研究较少。目的:观察骨关节病患者肌肉萎缩类型以及其与日常活动的相关性。方法:纳入24例老年女性骨关节病患者,应用功能独立性评定量表对患者习惯性的日常运动进行了评价,在进行关节置换过程中对患者肌纤维进行了测定并通过活检进行组织病理学侧量。同时选取同期因骨折需要进行修复的4例女性患者为对照组。观察患者的肌纤维(Ⅰ型、ⅡA型和ⅡB型)发生萎缩类型和比率变化。结果与结论:骨关节病患者根据发生萎缩的肌纤维类型不同,分为1型、2B型何1+2AB型。Ⅰ型的肌纤维肌横截面积明显小于ⅡA型和ⅡB型肌纤维(P<0.05)。大部分骨关节病患者在得病过程中仅发生同一种肌纤维类型的萎缩,而非所有的肌纤维均出现萎缩。功能独立性评定量表评分从1+2AB型,2B型和1型逐渐减少(P<0.05)。结果证实,肌肉萎缩1+2AB型对骨关节病患者日常活动影响最大,而单纯的2B型影响最小。     

骨关节病患者肌纤维萎缩类型及其与日常活动的相关性

背景：骨关节病患者因制动等原因可出现严重的肌纤维萎缩,但目前对这类肌纤维萎缩的微观分类及其与日常活动的研究较少。目的：观察骨关节病患者肌肉萎缩类型以及其与日常活动的相关性。方法：纳入24例老年女性骨关节病患者,应用功能独立性评定量表对患者习惯性的日常运动进行了评价,在进行关节置换过程中对患者肌纤维进行了测定并通过活检进行组织病理学侧量。同时选取同期因骨折需要进行修复的4例女性患者为对照组。观察患者的肌纤维（Ⅰ型、ⅡA型和ⅡB型）发生萎缩类型和比率变化。结果与结论：骨关节病患者根据发生萎缩的肌纤维类型不同,分为1型、2B型何1＋2AB型。Ⅰ型的肌纤维肌横截面积明显小于ⅡA型和ⅡB型肌纤维（P〈0.05）。大部分骨关节病患者在得病过程中仅发生同一种肌纤维类型的萎缩,而非所有的肌纤维均出现萎缩。功能独立性评定量表评分从1＋2AB型,2B型和1型逐渐减少（P〈0.05）。结果证实,肌肉萎缩1＋2AB型对骨关节病患者日常活动影响最大,而单纯的2B型影响最小。     

Strenuous exercise-induced alterations of muscle fiber cross-sectional area and fiber-type distribution in steroid myopathy rats

OBJECTIVE: To investigate the effect of exercise intensity on the muscle histopathology in steroid myopathy rats. DESIGN: Eight-week-old male Wistar rats (n=40) were divided into four groups: a control group (n=4), steroid-only group (n=12), moderate exercise + steroid group (n=12), and a high-intensity exercise + steroid group (n=12). Five weeks after triamcinolone injection, the soleus muscle (SOL) and extensor digitorum longus muscle (EDL) were removed and stained for adenosine triphosphatase (ATPase). The muscle fiber area and fiber type distribution of each fiber type were measured. RESULTS: In the high-intensity exercise group, the type I fibers in the SOL and the type IIb fibers in the EDL showed significant atrophy. In the fiber distribution of the SOL, type I fibers decreased in the steroid-only group and high-intensity exercise group as compared with the control, whereas there was a significant increase in the moderate exercise group vs. the steroid-only group. In the EDL, type I fibers were significantly greater in the moderate- and high-intensity exercise groups, whereas type IIb fibers significantly decreased in the moderate-exercise group as compared with the steroid-only group. CONCLUSIONS: In rats with steroid myopathy, high-intensity exercise caused changes such as muscle atrophy. The fiber type distribution of the SOL changed from type II fibers to type I fibers in the moderate exercise group. Intensive exercise, however, resulted in transformation from type I to type II in the fiber type distribution. For the EDL, no significant fiber type changes were observed with high-intensity exercise when compared with moderate exercise.     

Effects of short duration static stretching on the denervated and reinnervated soleus muscle morphology in the rat

OBJECTIVE: To investigate the effect of short duration static stretching of denervated and reinnervated muscle using a histochemical study on the soleus muscle of the rat. DESIGN: Prospective randomized trial. SETTING: University medical school in Japan. ANIMALS: Fifty-four 8-week-old female Wistar rats with a mean weight +/- standard deviation of 185.8+/-9.9g. INTERVENTIONS: After a cold injury was applied to the rat right sciatic nerve, the bilateral soleus muscles were maximally stretched in the dorsiflex posture of the ankle joints for 40 minutes a day, 6 times a week (group S). Rats were compared with nonstretched rats (group D) for up to 4 weeks.Main outcome measures Muscle fiber cross-sectional areas, muscle fiber types, and sciatic nerve morphology. RESULTS: No apparent difference in the morphologic changes of the sciatic nerve was found between groups D and S. The mean fiber size progressively declined to a minimum 2 weeks after the injury and reversed in the following weeks. At weeks 1 and 2, the mean type I fiber size in group S was significantly larger than in group D (P<.05). The number ratio of the type II to total fibers increased until 3 weeks in group D, whereas the ratio in group S was increased at 2 weeks, and successively decreased. CONCLUSIONS: The mechanical stimuli of static stretching could prevent atrophy of the type I fibers in the denervated muscle and affect the reinnervated muscle fiber-type composition.     

Effects of controlled mechanical ventilation on respiratory muscle contractile properties in rabbits

OBJECTIVE: We examined in rabbits the effects of more than 48 h of mechanical ventilation on the contractile properties and fiber type adaptations of the respiratory muscles. DESIGN AND SETTING: Experimental prospective study in a university laboratory. ANIMALS AND INTERVENTIONS: Nineteen rabbits were randomly allocated to two groups: control (n=10) or mechanically ventilated (MV; n=9) for 51+/-3 h. MEASUREMENTS AND RESULTS: Respiratory muscles contractile properties were analyzed before and after a fatigue protocol using in vivo isometric 1-s tetanic contraction characteristics in both muscles: peak tetanic force, contraction time, relaxation time, and total contraction time. Both muscle fiber type proportions, diameter, and cross-sectional areas were measured using ATPase staining. The MV rabbits showed significant weight loss in both muscles, accompanied by a reduced peak tetanic force (9.96+/-3.2 vs. 7.44+/-2.2 N for diaphragm of control and MV animals respectively), fatigue resistance index, and increased relaxation time (57.5+/-8.7 vs. 85.8+/-9.4 ms for diaphragm of control and MV animals) and contraction time. These impairments in the MV group worsened after the fatigue runs. Both muscle showed a significant atrophy of type IIa and IIb fibers but a stability in type I fibers cross-sectional area. CONCLUSIONS: Mechanical ventilation in rabbits produces alterations in contractile properties of the diaphragm and 5th external intercostal muscle, increases both muscles fatigue, and promotes atrophy of type II fibers.     

The effects of non-weight bearing on skeletal muscle in older rats: an interrupted bout versus an uninterrupted bout

Age-related changes in skeletal muscle, in combination with bed rest, may result in a poorer rehabilitation potential for an elderly patient. The purpose of this study was to determine the effects of non-weight bearing (hind limb unweighting [HU]) on the soleus and extensor digitorum longus (EDL) in older rats. Two non-weight bearing conditions were used: an uninterrupted bout of HU and an interrupted bout of HU. Twenty-one rats were randomly placed into 1 of 3 groups: control, interrupted HU (2 phases of 7 days of HU, separated by a 4-day weight-bearing phase) and an uninterrupted HU (18 uninterrupted days of HU). Following non-weight bearing, the soleus and EDL muscles were removed. Fiber type identification was performed by myofibrillar ATPase and cross-sectional area was determined. The findings suggest that any period of non-weight bearing leads to a decrease in muscle wet weight (19%-45%). Both type I and type II fibers of the soleus showed atrophy (decrease in cross-sectional area, 35%-44%) with an uninterrupted bout of non-weight bearing. Only the type II fibers of the soleus showed recovery with an interrupted bout of weight bearing. In the EDL, type II fibers were more affected by an uninterrupted bout of non-weight bearing (15% decrease in fiber size) compared to the type I fibers. EDL type II fibers showed more atrophy with interrupted bouts of non-weight bearing than with a single bout (a 40% compared to a 15% decrease). This study shows that initial weight bearing after an episode of non-weight bearing may be damaging to type II fibers of the EDL.     

Clenbuterol in the prevention of muscle atrophy: a study of hindlimb-unweighted rats.

OBJECTIVE: To determine whether the administration of clenbuterol, a beta2-adrenergic agonist, prevents loss of muscle mass during a period of imposed inactivity. DESIGN: Randomized trial. SETTING: Basic laboratory research. ANIMALS: Thirty Fischer 344 Brown Norway F1 Hybrid rats, 12 and 30 months of age. INTERVENTIONS: The rats were randomly assigned to a control group, or to 1 of 2 experimental groups: hindlimb unweighted for 2 weeks (HU-2), or hindlimb unweighted with daily injections of clenbuterol for 2 weeks (HU-2Cl). MAIN OUTCOME MEASURES: Muscle mass weighed in milligrams and single fiber cross-sectional area histochemically evaluated. RESULTS: In both age groups, the HU-2 animals had greater muscle atrophy (decrease in muscle mass) in the soleus muscle than the extensor digitorum longus (EDL) muscle. In the HU-2Cl groups, the decline in muscle mass of both the soleus and EDL muscles was attenuated by about 4% to 20%. In the HU-2 group, single fiber cross-sectional area decreased for both fiber types (type I, 20%-40%; type II, 37%-50%) in both age groups. Clenbuterol retarded the inactivity-induced decline in single fiber cross-sectional area by 12% to 50%. In the EDL muscles of the HU-2Cl group, we found hypertrophy in both fiber types in the 30-month-old animals and in type I fibers in the 12-month-old animals. CONCLUSIONS: Clenbuterol attenuated the decrease in muscle mass and single fiber cross-sectional area in both age groups. By preventing the loss of muscle mass, clenbuterol administered early in rehabilitation may benefit severely debilitated patients imposed by inactivity. The attenuated muscle atrophy found with clenbuterol in the present study provides cellular evidence for the reported change in muscle strength after its administration after knee surgery. Thus, the administration of clenbuterol may lead to a more rapid rate of rehabilitation.     

Study of skeletal muscle glycogenolysis and glycolysis in chronic steroid myopathy, non-steroid histochemical type-2 fiber atrophy, and denervation

OBJECTIVE: Muscle biopsies from chronic steroid (glucocorticoid) myopathy, non-steroid histochemical type-2 fiber atrophy, and muscle denervation patients were studied to determine if their glycogen contents, or enzymes involved in glycogenolysis and glycolysis might be related to their fiber atrophy. DESIGN AND METHODS: Fast frozen muscle biopsies from the above patients and from patients later judged by histochemistry to be normal were assayed enzymatically for glycogen content, for enzymes involved in glycogenolysis, and for 6 of the enzymes involved in glycolysis. RESULTS AND CONCLUSION: All three groups of patients had glycogen content, but only the chronic steroid myopathy muscle had statistically less glycogen content than did normal human muscle. All 3 groups had statistically low mean values compared to normal muscles for glycogen phosphorylase activity. This suggests that the biosynthesis and phosphorolysis of glycogen are not involved in muscle fiber atrophy, and glucocorticoid administration does not activate muscle glycogen biosynthesis. Histochemical type-2 fiber atrophy muscles were low compared to normal muscles in three glycogenolysis enzyme activities plus four glycolysis enzyme activities. Muscles from denervation patients were low compared to normal muscles in three glycogenolysis enzyme activities plus five glycolysis enzyme activities. This suggests that muscle denervation may lower the rate of glycolysis enough to fail to provide sufficient pyruvate for mitochondrial ATP biosynthesis, resulting in insufficient protein biosynthesis in both fiber types.     

Type II fiber activation with electrical stimulation: a preliminary report

Electrical stimulation to augment or maintain muscle performance has been well documented. The purpose of this preliminary report is to present the results of a single-case study conducted to determine the order of activation of skeletal muscle fibers as a result of electrical stimulation. The subject's quadriceps femoris muscles were electrically stimulated at 80% of maximal isometric torque. Pre-stimulation and immediate post-stimulation muscle biopsy samples were obtained, and a modification of the glucogen-depletion method was used to determine activation of muscle fibers. The pre-stimulation muscle biopsy sample demonstrated uniform periodic acid-Schiff (PAS)-positive staining in all fiber types, whereas the post-stimulation muscle biopsy sample showed glycogen depletion of type II muscle fibers. The most PAS-negative muscle fibers were type IIa skeletal muscle fibers. The results of this single-case study provide evidence that electrical stimulation, as described, selectively activates type II skeletal muscle fibers. The implication of this finding is that, in many chronic diseases, type II fibers are selectively and preferentially affected. Electrical stimulation may be a clinically viable technique to use in patients with type II fiber involvement.     

Reflexes evoked by group II afferent fibers from muscle spindles.

The purpose of this paper is to review research on the reflex action of group II afferent fibers originating in the muscle spindle. Although the reflex actions of the Ia afferent fibers from muscle spindles are well defined, the reflex action of the group II afferent fibers is not clearly understood. Experiments on animals whose spinal cord had been transected gave rise to the idea that group II afferent fibers facilitate flexor muscles and inhibit extensor muscles regardless of the origin of the fibers. This concept has been accepted by neurophysiologists and has even been incorporated into therapeutic exercise procedures by physical therapists. However, accumulating evidence is presented that challenges this classical concept. Physical therapists, when trying to incorporate the reflexes evoked by the group II afferent fibers into treatment, must become better aware of the complex reflex actions of which these fibers are capable.     

Motor unit number estimation in the assessment of performance and function in motor neuron disease

Motor unit number estimation (MUNE) is a unique electrophysiologic test used to estimate the number of surviving motor units in a muscle or group of muscles. It is used most frequently to monitor lower motor neuron loss in amyotrophic lateral sclerosis and spinal muscle atrophy. Of particular interest is its use as an endpoint measure in clinical trials for these diseases. This article describes the principles of MUNE and the factors that need to be considered, and reviews several techniques that have been used in clinical trials and in monitoring progression. It then reviews experience with MUNE in clinical trials for amyotrophic lateral sclerosis and spinal muscle atrophy and discusses how MUNE correlates with measures of function.     

成人型脊髓性肌萎缩─附1例临床及病理报告

成人型脊髓性肌萎缩，是一组较少见、以下级运动神经元变性的疾病。发病年龄较晚，多在３０岁以后，为性连隐性遗传，主要表现为近端肌萎缩伴球麻痹。可见广泛的束震颤，无锥体束征及感觉障碍。病理上病变仅在脊髓前角及脑干运动神经核，故认为是不同于肌萎缩侧索硬化的一组独立的疾病。现将我院经尸检确诊的１例报告如下，并结合文献进行简单地讨论。     

Muscle fiber composition in patients with traumatic cord lesion.

Muscle fiber composition and oxidative and glycolytic enzymatic activity have been studied with complete traumatic transection of the spinal cord and spastic paralysis of the lower extremities. Muscle sample were taken by means of needle biopsy from the vastus lateralis, gastrocnemius, and soleus muscles. Biopsies were also taken for comparison from the deltoid muscle. Fibers staining darkly for alkaline stable myofibrillar ATP-ase (type II) dominated or were the only fibers identified in the paralysed muscles. The deltoid muscles of the same patients had a rather even mixture of type I and II fibers. Staining pattern was reversed after acid preincubation (pH 4.3). Mean diameters in the paralysed muscles were reduced for both fiber types. All fibers stained relatively weakly for NADH-diaphorase. Succinyldehydrogenase activity was low and phosphofructokinase activity usually moderately reduced. The findings imply that neuronal influence on the muscular fibers had led to a change in the staining characteristics of the muscle fibers. Such a change migh indicate altered contractile characteristics, though the detailed nature of the observed findings in still unclear.     

肉毒毒素A作用下肌细胞形态的变化规律研究

目的探讨肉毒毒素A(BTX-A)作用下肌细胞形态的变化规律。方法 90只成年雄性SD大鼠通过随机数字表随机分为实验组和对照组,每组45只,分别注射BTX-A与生理盐水,每组通过随机数字表法又分为9个时间组,每时间组5只大鼠,按观察时间的不同(注射后30分钟、6小时、1天、3天、1周、2周、4周、6周和8周),采用线粒体酶组织化学染色的方法动态观察局部注射BTX-A后大鼠胸舌骨肌纤维直径变化。结果注`射BTX-A后30分钟,肌纤维直径开始变小,萎缩于2~4周内接近高峰,大多数肌纤维的这种萎缩状态会持续到8周以后;从第4周起,点状区域的肌纤维直径有恢复的趋势,而且这些肌纤维的酶活性也比其它肌纤维高;注射BTX-A后白肌纤维受影响最早而且明显,恢复亦最慢,红肌纤维受影响迟而恢复快。结论注射BTX-A后,大鼠胸舌骨肌的线粒体酶活性受到抑制,能量代谢出现障碍,肌纤维随之发生去神经性萎缩;但随着神经发芽和新轴突生成,BTX-A导致的骨骼肌能量代谢障碍及萎缩也逐渐恢复。     

Increased proportion of megafibers in chronically painful muscles

Trapezius myalgia - chronic pain from the upper trapezius muscle - is frequent in female employees in monotonous stressful jobs, potentially due to chronic overload of type I muscle fibers. In this study, we investigated the intra-individual distribution of trapezius muscle fiber size, and hypothesized that females with myalgia compared with matched healthy controls have a higher percentage of grossly hypertrophied type I fibers with poor capillarization. Forty-two female office workers with trapezius myalgia (MYA) and 20 healthy matched controls (CON) participated in the study. Standard histochemical methods were used to determine fiber size, fiber type, and capillarization. Type I megafiber were defined as at least twice the size of the median type I fiber size of each individual. The main finding was that MYA had a significantly higher proportion of type I megafibers than CON, in spite of no significant difference in overall type I fiber size. In MYA and CON type I megafibers were located in 46% and 11% of the females, respectively. Capillarization of the overall type I fiber pool was not different between CON and MYA, but was significantly lower in type I megafibers of both groups. The percentage of megafibers was positively related to age and weekly working hours, indicating an effect of long-term exposure. In conclusion, this study shows that trapezius myalgia is associated with a significantly higher percentage of grossly hypertrophied type I muscle fibers with poor capillarization - type I megafibers.     

低频电刺激对坐骨神经损伤大鼠不同类型骨骼肌萎缩及内源性胰岛素样生长因子1表达的影响

背景：低频电刺激可以缓解骨骼肌的萎缩,但对肌纤维类型的影响尚不清楚,同时内源性胰岛素样生长因子1在萎缩后的肌纤维中的表达与电刺激的关系尚无公识。目的：观察低频电刺激对坐骨神经损伤大鼠不同类型骨骼肌纤维萎缩情况及内源性胰岛素样生长因子1表达的影响。方法：将健康雄性SD大鼠随机分为3组,切断模型组和电刺激组大鼠左侧坐骨神经制备失神经支配模型,适应5d后,对电刺激组大鼠损伤侧腓肠肌施以2Hz的电刺激,2次/d,每次持续20min,正常组和模型组常规饲养。30d后,取大鼠腓肠肌腹部,检测其肌纤维直径和数量;免疫组织化学法检测肌组织中胰岛素样生长因子1的水平。结果与结论：失神经支配后,大鼠腓肠肌Ⅰ、Ⅱ型肌纤维直径减小,Ⅰ型肌纤维数比例增大。与模型组比较,电刺激组大鼠腓肠肌Ⅰ、Ⅱ型肌纤维直径有所增大,尤以Ⅰ型肌纤维直径增大更明显（P〈0.05）。同时,电刺激组大鼠腓肠肌中胰岛素样生长因子1的表达也明显高于模型组（P〈0.05）。提示,2Hz的电刺激可促进胰岛素样生长因子1的表达,减轻Ⅰ型肌纤维的萎缩。     

低频电刺激对坐骨神经损伤大鼠不同类型骨骼肌萎缩及内源性胰岛素样生长因子1表达的影响

背景:低频电刺激可以缓解骨骼肌的萎缩,但对肌纤维类型的影响尚不清楚,同时内源性胰岛素样生长因子1在萎缩后的肌纤维中的表达与电刺激的关系尚无公识。目的:观察低频电刺激对坐骨神经损伤大鼠不同类型骨骼肌纤维萎缩情况及内源性胰岛素样生长因子1表达的影响。方法:将健康雄性SD大鼠随机分为3组,切断模型组和电刺激组大鼠左侧坐骨神经制备失神经支配模型,适应5d后,对电刺激组大鼠损伤侧腓肠肌施以2Hz的电刺激,2次/d,每次持续20min,正常组和模型组常规饲养。30d后,取大鼠腓肠肌腹部,检测其肌纤维直径和数量;免疫组织化学法检测肌组织中胰岛素样生长因子1的水平。结果与结论:失神经支配后,大鼠腓肠肌Ⅰ、Ⅱ型肌纤维直径减小,Ⅰ型肌纤维数比例增大。与模型组比较,电刺激组大鼠腓肠肌Ⅰ、Ⅱ型肌纤维直径有所增大,尤以Ⅰ型肌纤维直径增大更明显(P<0.05)。同时,电刺激组大鼠腓肠肌中胰岛素样生长因子1的表达也明显高于模型组(P<0.05)。提示,2Hz的电刺激可促进胰岛素样生长因子1的表达,减轻Ⅰ型肌纤维的萎缩。     

The effects of therapeutic electric stimulation on acute muscle atrophy in rats after spinal cord injury.

OBJECTIVE: To evaluate the effects of electric stimulation in preventing acute muscle atrophy after spinal cord transection in rats. DESIGN: A randomized experimental design. SETTING: Animal facilities for experimental medicine. ANIMALS: Fifty-six adult male Wistar rats assigned to control, low-frequency, and high-frequency groups. INTERVENTIONS: The rats were implanted with a percutaneous intramuscular electrode in the vicinity of the peroneal nerve; then the spinal cord was transected in a T9 level. The stimulation frequency was low (20Hz) or high (100Hz). The stimulation cycle was 4 seconds of stimulation every 8 seconds. MAIN OUTCOME MEASUREMENTS: The lesser fiber diameters from type 1, 2A, and 2B muscle fibers were measured. In another assessment, maximal contraction force was measured. The muscle force produced at 20 and 100Hz was expressed as increasing values in tetanic force. RESULTS: Comparison between nonstimulated and stimulated tibialis anterior muscles found that atrophy of type 1 fibers (p < .01) and type 2B fibers (p < .05) at both stimulated levels and of type 2A fibers at 100-Hz level (p < .05) was prevented by therapeutic electric stimulation (TES). There were significant differences in the size of muscle fiber diameter between nonstimulated and stimulated muscles at 100Hz in type 2A and, markedly, in type 2B. The increasing value of muscle force was significantly greater at 100Hz than at 20Hz (p < .05). No significant histologic differences were observed between high- and low-frequency stimulated fibers of any of the 3 muscle types. CONCLUSIONS: Acute atrophy of muscle fibers was more effectively prevented by high-frequency stimulation (100Hz) than by no stimulation or low-frequency stimulation (20Hz). The increasing value of muscle force was significantly greater at high-frequency than low-frequency stimulation, suggesting that the clinical application of high-frequency stimulation in acute spinal cord injury should be studied.