Expression of myostatin RNA transcript and protein in gastrocnemius muscle of rats after sciatic nerve resection

Myostatin, a member of the transforming growth factor-beta (TGF-beta) superfamily, has been identified as an inhibitor of skeletal muscle mass. To have an insight into the expression pattern of myostatin and its potential role in skeletal muscle atrophy induced by denervation, we used an animal model of peripheral nerve resection to examine the time-dependent changes in myostatin mRNA and protein levels in the denervated gastrocnemius muscle of rats after sciatic neurectomy by the aid of quantitative real-time RT-PCR and Western blotting, respectively. We also conducted morphometric analyses to measure the wet weight ratio of the denervated muscle (the operated side/contralateral non-operated side) and the cross sectional area of muscle fibers and to observe muscle morphology. The experimental results showed that myostatin mRNA and protein levels in rat gastrocnemius muscle persistently elevated after denervation, despite a fluctuation of myostatin mRNA level at day 3 after denervation, reached their respective peaks at day 28 after denervation, and then depressed slightly until day 56 after denervation. Furthermore, a significant negative linear correlation was found between myostatin abundance and muscle atrophy degree, suggesting that myostatin might probably play an important role in denervation-induced muscle atrophy. Our present study perhaps provides a new window into myostatin regulation in association with a specific type of muscle atrophy.     

Activation of embryonic red and white muscle fibers during fictive swimming in the developing zebrafish

Sub-threshold, motoneuron-evoked synaptic activity was observed in zebrafish embryonic red (ER) and white (EW) muscle fibers paralyzed with a dose of D-tubocurarine insufficient to abolish synaptic activity to determine whether muscle activation was coordinated to produce the undulating body movements required for locomotion. Paired whole-cell recordings revealed a synaptic drive that alternated between ipsilateral and contralateral myotomes and exhibited a rostral-caudal delay in timing appropriate for swimming. Both ER and EW muscle were activated during fictive swimming. However, at the fastest fictive swimming rates, ER fibers were de-recruited, whereas they could be active in isolation of EW fibers at the slowest fictive swimming rates. Prior to hatching, fictive swimming was preceded by a lower frequency, more robust and rhythmic synaptic drive resembling the "coiling" behavior of fish embryos. The motor activity observed in paralyzed zebrafish closely resembled the swimming and coiling behaviors observed in these developing fishes. At the early developmental stages examined in this study, myotomal muscle recruitment and coordination were similar to that observed in adult fishes during swimming. Our results indicate that the patterned activation of myotomal muscle is set from the onset of development.     

氯化胆碱与制动性骨骼肌萎缩肌肉生成抑制素mRNA的表达

背景：研究发现类胆碱物质可增加乙酰胆碱的弥散及终板电流的幅度,对神经肌肉接点功能退化有一定的对抗作用。 目的：观察氯化胆碱对制动性骨骼肌萎缩的防治作用及对骨骼肌萎缩大鼠肌肉生成抑制素mRNA表达的影响。 方法：将30只雄性SD大鼠随机分为对照组、模型组和治疗组,每组10只。采用可塑性石膏固定模型组和治疗组大鼠右后肢制备肌萎缩模型。治疗组每日灌胃氯化胆碱(150 mg/kg),对照组和模型组灌胃等体积蒸馏水。4周后解剖右后肢腓肠肌,检测腓肠肌收缩张力、肌湿质量、蛋白质水平及肌肉生成抑制素mRNA的表达。 结果与结论：与对照组比较,模型组大鼠腓肠肌的收缩张力、肌湿质量、蛋白质水平均显著降低(P < 0.05或P < 0.01),肌肉生成抑制素mRNA表达显著增高(P < 0.01)。与模型组比较,治疗组大鼠腓肠肌的收缩张力、肌湿质量、蛋白质水平均显著升高(P < 0.05),肌肉生成抑制素mRNA表达显著降低(P < 0.05)。说明氯化胆碱能够显著提高制动性萎缩骨骼肌的收缩张力、肌湿质量、蛋白质水平,减少肌肉生成抑制素mRNA的表达,从而有效抑制骨骼肌制动性萎缩的发生。     

The expression of IGF-I and myostatin mRNAs in skeletal muscle of hypophysectomized and underfed rats during postnatal growth

Aim: To determine the roles of myostatin and insulin‐like growth factor‐I (IGF‐I) during postnatal growth, we examined IGF‐I and myostatin mRNA expression in the skeletal muscles of hypophysectomized and underfed rats during postnatal growth. Methods: Five‐week‐old rats were divided into four groups: freely fed control, moderately underfed, severely underfed and hypophysectomized. Four weeks later, blood and muscle samples were gathered to determine serum IGF‐I, myosin heavy chain (MHC) isoforms, IGF‐I Ea, IGF‐I Eb and myostatin mRNA. Results: The weights of soleus, plantaris and masseter muscles were decreased in underfed and hypophysectomized rats. Hypophysectomy resulted in significant increases of type I MHC at the expense of type IIx in plantaris muscle and of neonatal MHC at the expense of types IIx and IIb in masseter muscle. Serum IGF‐I was decreased by underfeeding and hypophysectomy. Plantaris muscle IGF‐I Ea mRNA in underfed and hypophysectomized rats was significantly lower than in normal controls. Plantaris muscle IGF‐I Eb mRNA in underfed rats was significantly lower than in normal controls. Masseter muscle IGF‐I Eb mRNA in severely underfed rats was significantly lower than in normal control and hypophysectomized rats. Soleus muscle myostatin mRNA in hypophysectomized rats was significantly higher than in normal and significantly underfed rats. No significant differences in plantaris and masseter muscle myostatin mRNA were observed between groups. Conclusion: Suppressed muscle growth caused by hypophysectomy and underfeeding may be attributed mainly to reduced circulating IGF‐I and partially to reduced IGF‐I mRNA, rather than to a change in myostatin.     

Effect of creatine supplementation on cardiac muscle of exercise-stressed rats

The role of creatine supplementation in altering the physiological parameters regulating cardiac muscle's functional capacity through the initiation of cardiac hypertrophy and altered contractile protein expression has not been determined. The purpose of this study was to determine the effect of creatine supplementation, with and without exercise stress, on physiological parameters regulating functional capacity through alterations in rat cardiac mass and contractile-protein expression. Thirty male Sprague-Dawley rats were subjected to 30 min of exercise stress 5 days/week for 3 weeks with 2% of total body mass attached to the tail. Animals were randomly assigned to one of four treatment groups: group 1 (Con) received (1 ml/day) sucrose water by intubation tube (n=8); group 2 (Cr) received (1 ml/day) sucrose/creatine solution (n=6); group 3 (EX) received 1 ml/day sucrose water and the exercise stimulus (n=8), and group 4 (Cr/EX) received (1 ml/day) sucrose/creatine solution and the exercise stimulus (n=8). At the conclusion of the 21-day exercise-training period, the heart was collected and weighed for determination of wet weight, total protein, total RNA, and myosin heavy chain protein expression. RNA concentration decreased significantly (13%) in the EX group, but not in the CR/EX group, indicating an interactive effect of creatine and exercise. Total RNA significantly decreased (15%) in the EX group. Protein concentration significantly increased (9%) in the exercising treatments, while total protein did not change. Cardiac myosin heavy chain expression significantly shifted towards a predominant expression of the β-isoform in the Cr/EX group [54.53% (3.42) β]. These results indicate an interaction of creatine supplementation and swimming exercise stress that potentially alters cardiac protein synthesis and demonstrates a possible mechanism through which the combination of creatine supplementation and swimming stress stimuli act to alter the physiological parameters regulating cardiac functional capacity. Electronic Publication     

Growth of medial gastrocnemius muscle and Achilles tendon in Wistar rats

Dimensions, architecture, material properties and functional characteristics of medial gastrocnemius muscles and Achilles tendons of young and old Wistar rats were compared. Dimensions associated with length of the leg segment grow isometric with it. Muscle belly transsectional dimensions, volume of muscle tissue and associated functional indices increase out of proportion either with the dimensions of the limb segment or the weight of the animal. As the properties of the contractile tissue remain the same and relative proportions of tissue components alter, changes in architecture result. These are not reflected in transsection of the tendon. Functional characteristics of the muscle tendon complex can be explained by architectural or dimensional-peculiarities emerging in the complex by growth processes of which the main is that the muscle belly of this pennated muscle grows in length mainly by increments in girth of the muscle fibers proper.     

Myostatin在小鼠腓肠肌失神经支配萎缩过程中的表达

目的:分析myostatin在腓肠肌失神经支配萎缩过程中的表达变化及其在肌萎缩过程中的作用。方法:采用坐骨神经横断术制备小鼠腓肠肌失神经支配模型,实时荧光定量PCR和Western印迹法分别检测失神经支配不同时段腓肠肌myostatin mRNA和蛋白表达水平,并对失神经前后肌肉湿重比、肌纤维横截面积进行比较。结果:失神经支配1 d时,腓肠肌myostatin mRNA迅速上升,3 d达到高峰,随后逐渐下降,而相应蛋白水平逐渐增高,7 d达到高峰继而逐渐下降,至56 d时mRNA和蛋白水平仍略高于正常水平。结论:腓肠肌失神经支配萎缩过程中myostatin的表达变化是一重要的分子事件。     

人参二醇组皂甙对游泳训练大鼠红细胞膜流动性的影响

目的:探讨人参二醇组皂甙(PDS)防治长期耐力运动引起的红细胞损伤的作用。方法:稳态荧光偏振技术测定7周大运动量递增负荷游泳训练大鼠红细胞膜流动性,邻苯三酚-氯化硝基四氮唑蓝法测定红细胞超氧化物歧化酶活性,硫代巴比妥酸比色法测定血清丙二醛(MDA),扫描电镜观察红细胞形态。结果:运动·生理盐水组大鼠红细胞膜脂荧光偏振度(polatization,P值)显著高于安静对照组,反映红细胞膜流动性低于安静对照组(P＜0.05);运动·生理盐水组的血清MDA水平显著高于安静对照组(P＜0.05),而RBC-SOD活性显著低于安静对照组;运动·PDS组P值显著低于运动·生理盐水组,红细胞膜脂流动性高于运动·生理盐水组(P＜0.05);运动·PDS组血清MDA水平显著低于运动·生理盐水组(P＜0.01),RBC-SOD活性显著高于运动·生理盐水组(P＜0.05);运动·生理盐水组的RBC计数、Hb、MCHC、Hb指数显著低于安静对照组(P＜0.05);而运动·PDS组RBC计数、Hb、MCHC、Hb指数显著高于运动·生理盐水组(P＜0.05);扫描电镜观察到运动·生理盐水组红细胞呈口形,棘形,嵴形,靶形等异常改变,而运动·PDS组红细胞形态基本正常。结论:PDS可降低运动训练后血清和红细胞脂质过氧化产物的形成,具有保护红细胞膜减少膜损伤的作用。     

The effect of exercise on the distribution of glycogen and proteins in the cardiac muscle of white rats

Summary The tetrazone method shows that in normal conditions the internal myocardial layers contain far more glycogen, SH-protein groups and proteins than do the external layers. In the inner layers, the glycogen is diffusely distributed in the from of small granules, whereas in the external layers it is found in the form of large granules. The effect of physical work is to reduce considerably the glycogen content of all parts, especially the external layers. The large glycogen granules are the first to disintegrate. There was no significant change in the protein composition of the cardiac muscle.Presented by Active Member AMN SSSR A. A. Vishnevskii Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 53, No. 1, pp. 56–59, January, 1962