电针结合有氧运动对自然衰老大鼠骨骼肌IGF-I/Akt通路的作用

目的:探索低频电针结合有氧运动对增龄性骨骼肌萎缩的效应,以及IGF-I/Akt及其下游蛋白质合成相关通路信号蛋白的影响。方法:以自然衰老SD大鼠为研究对象,将6月龄雄性SD大鼠32只,体重400～450 g,饲养至大鼠12月龄,根据体重随机分为4组。对照组(YC,只抓取、固定、放回,不做其他干预),电针组(YA,电针干预),运动组(YE,运动干预),电针+运动组(YEA,电针结合运动干预),自SD大鼠12月龄开始持续干预至18月龄,实验结束时观察各组自然衰老大鼠:骨骼肌湿重/体重比;光学显微镜下比目鱼肌HE染色形态;Real-time qPCR法检测骨骼肌中IGF-I mRNA的表达水平;Western印迹法测定的大鼠腓肠肌中AKT、mTOR、p70S6K和p-p70S6K相关蛋白表达情况。结果:与YC组相比,YA组、YEA组皆明显增加18月龄大鼠腓肠肌湿重/体重比(P0.05);YEA组能明显增加比目鱼肌湿重/体重比,高于YC组和YA组(P0.05)。与YC组相比,各个干预组大鼠的腓肠肌IGF-I mRNA表达水平皆有上升趋势,其中YEA组IGF-I mRNA表达增加更为明显(P=0.051)。与YC组相比,电针组(YA)p-Akt,p-mTOR表达升高(P0.05),电针+运动组(YEA)p-Akt,p-mTOR,p-p70S6K表达也显示出升高趋势(P0.05)。结论:电针结合有氧运动可延缓18月龄自然衰老大鼠增龄性骨骼肌萎缩,其分子机制可能与通过激活IGF-I/Akt通路,促进蛋白合成有关。     

Stretch activation and myogenic oscillation of isolated contractile structures of heart muscle

Summary Glycerinated or freeze-dryed fibre bundles of heart muscles (papillary and trabecular muscles of rabbit or guinea pig) show in ATP-salt solution with about 10^–6M Ca²⁺ an active, delayed tension increment after quick or sinusoidal stretching. The active tension increase is completely different from the passive tension increment caused by stretching of the elastic structures of the muscle; this well known length dependence of tension is also in phase with the length changes (or the tension-phase preceeds the length-phase in visco-elastic bodies). On the other hand, the active tension increase is delayed with respect to the length change; this can be observed very well after rectangular changes in length. The delayed activation of the contractile bonds at stretch and the delayed deactivation at shortening induce the muscle-during sinusoidal length changes in a characteristic frequency range-to produce power output. The frequency range corresponds to the heart beat frequency of the living muscle. Temperature rise and inorganic phosphate accelerate, Mg-ions and ADP retard the contraction speed. Ca-ions influence only the amount of the isometric tension, but not the contractile velocity.Supported by the Deutsche Forschungsgemeinschaft (Grant RU 154/3).     

Voltage clamp of a small muscle membrane area by means of a circular sucrose gap arrangement

Summary A new method is described which permits the measurement of membrane currents of thick muscle fibres (diameter 300 m or more) ofAstacus fluviatilis orBalanus balanus under voltage clamp conditions.The potential difference across a small patch of membrane (60–100 m in diameter) is controlled by connecting a voltage source across it with two external electrodes. One of them is connected to the fluid bathing the muscle fibre. The other, tubular one is in touch with the test area. The current flowing through the electrodes represents the sum of the membrane current flowing across the test area and the leak current flowing in the external fluid between the electrodes. In the first version of the method the leak current is limited by a circular sucrose gap around the test area. In the second, more elaborate method, the leak current is eliminated by a system of two concentric sucrose rings with a guard ring electrode between them. This method permits in addition the measurement of full sized action potentials in the test area.This work has been briefly reported in Cs. fysiol.17, 48 (1968).     

A convenient method for repeated intracellular recording of action potentials from the same muscle fibre without membrane damage

Summary Repeated intracellular recording of end-plate and action potentials from the same muscle fibre is often impossible because the membrane is damaged by the microelectrode when the muscle twitches. Membrane damage can be avoided by rolling and simultaneously stretching the muscle around a polyethylene rod; the amount of stretch necessary is about 50% of the “in-situ” length. Supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 38 “Membranforschung”, Bad Godesberg. Established Investigator of the Consejo Nacional de Investigaciones Científicas y Tecnicas, Argentina     

Practice improves even the simplest movements

Summary Three subjects practiced accurate, fast elbow flexions of 54° to a 3° wide target. Movements of 36°, 54° and 72° were then tested. Comparison over the three distances showed that the normally monotonic relationship between movement distance and movement time is alterable by specific training. Subjects learn to go faster over the practiced distance by refining their neural commands to the muscles. The benefits of practice only partially transfer to other distances. We conclude that many of the relationships seen among movement variables in simple tasks are plastic in nature and affected by prior experience.     

Lysosomal and energy enzyme activities in hypertrophied rat soleus muscle after denervation

Muscle hypertrophy was induced in the soleus muscle of young rats by tenotomy of the gastrocnemius and plantaris muscles. Three and 7 days afterwards the sciatic nerve was sectioned. The loss of weight of muscles subjected to this combined procedure three days after denervation was 30–40%. Lysosomal enzyme activities (acid phosphatase, -glucosidase, -galactosidase and N-acetyl--d-glucosaminidase) and energy enzyme activities (lactate dehydrogenase, LDH, triose-3-phosphate dehydrogenase, TPDH,d-hexokinase, HK and citrate synthase, CS) were determined 3 days after denervation, 3, 7 and 10 days after hypertrophy had been induced and 3 days after denervation of hypertrophying muscles on day 3 and 7. Normal non-operated rats of corresponding body wieght served as controls and their enzyme activities were estimated on the same day. In the course of muscle hypertrophy, the 4 lysosomal enzyme activities increased progressively. Although 3 days' denervation of control muscles did not alter lysomal enzyme activities, denervation of hypertrophying muscles greatly enhanced the activity of these enzymes. Enzymes of energy metabolism were affected to a lesser degree. The results suggest that denervation of hypertrophying muscles causes more extreme changes in muscle weight and lysosomal enzyme activities than denervation alone. The possible implications of this finding are discussed in relation to the rapid atrophy.     

中枢、神经—肌肉接头、肌肉疲劳的实验模型及其应用研究

目的：建立研究中枢、神经－肌肉接头和肌肉疲劳动物模型,为各种因素对运动性疲劳的影响及机制的研究,提供一种新的实验方法。方法：用铂金电极刺激蟾蜍脊髓,保护电极刺激坐骨神经干,直刺电极刺激腓肠肌,用MS302实验系统记录坐骨神经干的动作电位和腓肠肌的收缩曲线。观察丹参和生脉注射液对上述疲劳的影响。结果：中枢出现疲劳时间最短;神经－肌肉接头次之;肌肉出现疲劳时间最长。丹参和生脉注射液使中枢、神经－肌肉接头和肌肉出现疲劳时间都相应延长。结论：运动性疲劳首先发生在中枢,其次是神经－肌肉接头,最后是肌肉疲劳,丹参和生脉具有抗疲劳的作用。     

鸟苷素对结肠平滑肌运动的影响

目的 :研究鸟苷素在结肠运动中的作用。方法 :建立束缚应激诱发排便异常大鼠动物模型 ,应用放射配基法测定结肠组织及血浆中鸟苷素含量。结果 :束缚应激刺激可诱发大鼠排便异常且无结肠粘膜病理组织学改变 ,可用于模拟人肠易激综合征。束缚应激大鼠血浆及结肠组织中鸟苷素的含量增加。结论 :鸟苷素是调节肠道水及电解质的分泌 ,加强结肠平滑肌的运动的重要物质 ,是肠易激综合征腹泻产生的重要机制之一。