Similarities in Skeletal Muscle Strength and Exercise Capacity Between Renal Transplant and Hemodialysis Patients

Exercise intolerance is common in hemodialysis (HD) and renal transplant (RTx) patients. Aim of the study was to assess to what extent exercise capacity and skeletal muscle strength of RTx patients differ from HD patients and healthy controls and to elucidate potential determinants of exercise capacity in RTx patients. Exercise capacity, muscle strength, lean body mass (LBM) and physical activity level (PAL) were measured by cycle-ergometry, isokinetic dynamometry, DEXA and Baecke Questionnaire, respectively, in 35 RTx, 16 HD and 21 controls. VO2peak and muscle strength of the RTx patients were significantly lower compared to controls (p<0.01), but not different compared to HD patients. In RTx patients, strength (p<0.001), PAL (p=0.001) and age (p=0.045) were significant predictors of VO2peak. Muscle strength was related to LBM (p=0.001) and age (p=0.001), whereas gender (p<0.001) and renal function (p=0.01) turned out to be significant predictors of LBM. No effects of corticosteroids were observed. Exercise capacity and muscle strength seem equally reduced in RTx and HD patients compared to controls. In RTx patients, muscle strength and PAL are highly related to exercise capacity. Renal function appears to be a significant predictor of LBM, and through the LBM, of muscle strength and exercise capacity.     

丹参改善骨骼肌缺血再灌注损伤的超微结构观察

目的:通过透射电镜观察骨骼肌缺血再灌注损伤过程的病理生理变化探讨丹参的干预作用及机制。方法:采用90只清洁级雄性SD大鼠,6只作为健康对照组,84只行左侧提睾肌主滋养动脉夹闭造模,在缺血2.5 h时,丹参组腹腔注射丹参(42只),对照组注射等剂量的生理盐水(42只),两组分别设缺血再灌注10、20、30、40、50、60、90 min观测点(每个观测点6只)。观测结束后,迅速切取提睾肌,放入电镜固定液。电镜下进行组织形态学观察。结果:健康对照组正常情况下,组成肌原纤维的粗、细2种肌丝沿其长轴排列,每条肌原纤维上均可见明暗相间的带,肌浆内见有较多糖原颗粒及少量内质网、线粒体等细胞器,肌浆网纵向分布于肌原纤维周围,线粒体膜及嵴清晰可见,基质着色深,无肿胀、空泡形成等改变,在肌丝之间分布有较多糖原颗粒;骨骼肌缺血再灌注后10、20、30、40、50、60、90 min的2组各观测点,其病理变化较相似,肌丝模糊、凌乱,部分溶解、消失,甚至完全消失,肌浆网不同程度扩张,线粒体变大变圆,基质变淡,嵴变短变少甚至消失,部分线粒体极度肿胀,呈空泡状。丹参组,其病理变化大体相似,肌纤维均有不同程度恢复。结论:骨骼肌缺血再灌注损伤导致线粒体极度肿胀,肌纤维紊乱。丹参能有效地消除线粒体的水肿,恢复肌纤维,减轻骨骼肌缺血再灌注损伤。     

心脏营养素-1治疗失神经骨骼肌萎缩过程中对正常肌肉组织的影响

目的 探讨应用心脏营养素-1(cardiotrophin-1,CT-1)治疗失神经骨骼肌萎缩的有效剂量和安全剂量,观察不同剂量的CT-1对正常骨骼肌、心肌和血管平滑肌的副作用.方法 取Swiss小鼠80只,随机分成8组,每组分别于胫神经切断术后连续腹腔注射重组小鼠CT-1(rmCT-1)40、60、80、100、120、140、160μg·kg-1·d-1,剩余1组腹腔注射等体积CT-1溶媒,28d后称量失神经侧腓肠肌、正常侧腓肠肌和心脏的湿重;测量胸主动脉平滑肌厚度;检测正常腓肠肌中α-actin和MHC Ⅱa以及心肌中β-MHC的表达、胸主动脉血管平滑肌细胞中α-actin的含量.结果 采用腹腔注射给药,当CT-1用量达到60μg·kg-1·d-1时,开始对失神经骨骼肌产生营养作用,并呈剂量依赖性增强,当给药剂量超过100 μg·kg-1·d-1后,出现对正常骨骼肌、心肌和血管平滑肌的影响.给药剂量达到120μg·kg-1·d-1时,开始促进心肌β-MHCmRNA的表达,增加正常心脏的湿重.当给药剂量达到140μg·kg-1·d-1时,开始促进正常骨骼肌α-actin和MHC Ⅱ amRNA的表达,以及骨骼肌湿重的增加,同时提高了主动脉血管平滑肌α-actin的含量,增加了血管平滑肌的厚度.结论 腹腔注射CT-1防治失神经骨骼肌萎缩的有效剂量为60 μg·kg-1·d-1,最高安全剂量为100 μg·kg-1·d-1.当给药剂量达到120 μg·kg-1·d-1时,开始出现心肌肥厚,当给药剂量达到140 μg·kg-1·d-1时,可导致正常骨骼肌的肥大和血管平滑肌的增厚.     

甘露醇和低温对兔骨骼肌缺血再灌流损伤的保护作用

通过兔后肢缺血模型，观察了甘露醇和低温对骨骼肌缺血再灌流损伤的保护作用。结果：甘露醇和低温可以不同程度地降低再灌流后患肢静脉回流血中细胞内酶（ＣＰＫ、ＬＤＨ、ＡＳＴ）的活性和脂质过氧化反应终末代谢产物丙二醛（ＭＤＡ）的含量，减轻骨骼肌细胞超微结构的破坏。两者单独应用效果不明显（Ｐ＞０．０５），联合应用效果非常明显（Ｐ＜０．０１）。提示自由基介导的脂质过氧化反应参与骨骼肌缺血再灌流损伤，甘露醇和低温对其具有协同保护作用。     

Local and central sympathetic reflex control of blood flow in skeletal muscle and subcutaneous tissue in normal man

Summary. The effect of age and sex on relative changes in blood flow and vascular resistance in skeletal muscle and subcutaneous tissue during postural changes and during local increase in transmural pressure was studied in 33 healthy subjects. The intra-individual variation was studied in five subjects. Blood flow was measured by the local ¹³³Xenon wash-out method. No relation to age or sex was seen in the centrally elicited sympathetic vasoconstrictor responses in subcutaneous tissue and skeletal muscle and in the locally elicited vasoconstriction in subcutaneous tissue. A small, but statistically significant, correlation to sex and age was found in the local sympathetic vasoconstrictor response in skeletal muscle. The age correlation was caused only by an attenuated response in the young subjects below 40 years of age and may be fortuitous. The intra-individual variation was acceptably small. Based on the present results, a reduction in blood flow in skeletal muscle and subcutaneous tissue during centrally or locally elicited sympathetic vasoconstriction of 10% or less should be considered abnormal. The local ¹³³Xenon wash-out method is of value in examining patients suspected of dysfunction in the sympathetic part of the autonomic nervous system.     

Synovial haemangioma of the knee: a frequently misdiagnosed lesion

Objective The objective of this study was to assess the contribution of magnetic resonance (MR) imaging in the diagnosis and surgical planning of five cases of synovial haemangioma of the knee.Patients and Methods The clinical, radiological and arthroscopic features of five pathologically proven synovial haemangiomas of the knee were retrospectively reviewed.Results A diagnostic delay, on average of 8 years, had occurred in four of the cases. Plain films were unremarkable, except for one case with arthropathy mimicking haemophilia, Arteriography, performed in three patients, was normal in one. CT, performed in three patients, showed the lesion, but the extent of the latter was better demonstrated with MR imaging. Synovial haemangiomas had a high signal intensity on T2-weighted images, without any extensive mass effect. Fibrofatty septa within the lesion were observed in three cases and muscular and/or fatty invasion in two. Arthroscopy allowed diagnosis of the lesion in two cases, but showed only non-specific synovitis in another two.Conclusion This study emphasizes the valuable contribution of MR imaging in the diagnosis and surgical planning of synovial haemangiomas.     

2022年欧洲临床营养与代谢学会和欧洲肥胖研究学会《肌肉减少性肥胖的定义和诊断标准共识》解读及启示

近年来,欧洲临床营养与代谢学会（ESPEN）和欧洲肥胖研究学会（EASO）的专家组成员对肌肉减少性肥胖（SO）的相关研究进行了系统地评价。2022年2月,ESPEN和EASO共同发布了《肌肉减少性肥胖的定义和诊断标准共识》,该共识对SO的定义和诊断进行了详细的阐述,旨在就SO的定义和诊断达成共识,为研究人员和临床工作者提供参考依据,以推进SO预防和治疗的发展。本文主要对《肌肉减少性肥胖的定义和诊断标准共识》中SO的定义,诊断流程包括筛查、诊断和分期标准,拟采用的方法和相关的参数等主要内容进行梳理和解读,旨在为国内医务工作者提供更多参考。     

Plateau potentials evoked by climbing-fibre stimulation are restricted to the Purkinje cell dendrites of the cat

The present study investigated the duration of afterdepolarizations in Purkinje cell somata following climbing-fibre activation. Intracellular recordings revealed that, in cells with membrane potentials more negative than -50 mV and with normal spike-generating capabilities, climbing-fibre activation resulted in somatic responses with short afterdepolarizations. As the cell deteriorated and the resting membrane potential became more positive, the duration and form of the climbing-fibre response resembled the plateau potentials recorded from proximal dendrites. The absence of plateau potentials in undamaged Purkinje cell somata was confirmed by extracellular recording of test spike amplitudes following evoked climbing-fibre responses.     

Calcium transport and ATPase activity in mitochondria and fragments of sarcoplasmic reticulum of the heart and muscles of rabbits with hypercholesteremia

Keeping rabbits on a high-cholesterol diet (1 g/kg) for 3–7 months led to an increase in cholesterol concentration in the mitochondrial membranes and fragments of the sarcoplasmic reticulum (SPR) of the myocardium and skeletal muscles. Saturation of the membranes with cholesterol led to a decrease in efficiency of the Ca-pump of the SPR, as reflected in lowering of the Ca/ATP ratio and an increase in the outflow of Ca⁺⁺ from the SPR. Under these conditions the rate of accumulation of Ca⁺⁺ was higher in SPR than in the mitochondria. Activity of mitochondrial Mg⁺⁺-activated 2,4-DNP-ATPase was reduced in hypercholesteremia.Laboratory of Molecular Pathology and Biochemistry, Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. M. Chernukh.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 89, No. 3, pp. 292–294, March, 1980.     

Role of nitric oxide in skeletal muscle: synthesis,distribution and functional importance

Over the last two decades, nitric oxide (NO) has been established as a novel mediator of biological processes, ranging from vascular control to long-term memory, from tissue inflammation to penile erection. This paper reviews recent research which shows that NO and its derivatives also are synthesized within skeletal muscle and that NO derivatives influence various aspects of muscle function. Individual muscle fibres express one or both of the constitutive NO synthase (NOS) isoforms. Type I (neuronal) NOS is localized to the sarcolemma of fast fibres; type III (endothelial) NOS is associated with mitochondria. Isolated skeletal muscle produces NO at low rates under resting conditions and at higher rates during repetitive contraction. NO appears to mediate cell–cell interactions in muscle, including vasodilation and inhibition of leucocyte adhesion. NO also acts directly on muscle fibres to alter cell function. Muscle metabolism appears to be NO-sensitive at several sites, including glucose uptake, glycolysis, mitochondrial oxygen consumption and creatine kinase activity. NO also modulates muscle contraction, inhibiting force output by altering excitation–contraction coupling. The mechanisms of NO action are likely to include direct effects on redox-sensitive regulatory proteins, interaction with endogenous reactive oxygen species, and activation of second messengers such as cyclic guanosine monophosphate (cGMP). In conclusion, research published over the past few years makes it clear that skeletal muscle produces NO and that endogenous NO modulates muscle function. Much remains to be learned, however, about the physiological importance of NO actions and about their underlying mechanisms.