胞内游离钙离子浓度增加抑制大鼠离体比目鱼肌肌梭传入放电（英文）

目的探讨大鼠离体比目鱼肌胞内游离钙离子浓度增加对肌梭传入放电的影响。方法 12只大鼠随机分为3组,2.0ion组、5.0ion组、二甲基亚砜(dimethyl sulfoxide,DMSO)组。分离大鼠比目鱼肌单一肌梭,2.0ion组、5.0ion组分别给予2和5μmol/L钙离子导入剂伊吾诺霉素(ionomycin)孵育,采用激光扫描共聚焦显微镜观察肌梭内游离钙离子浓度的改变。采用空气隔绝法记录大鼠比目鱼肌单一肌梭传入放电活动,观察3组肌梭传入放电活动的变化。结果伊吾诺霉素(2和5μmol/L)能显著增加大鼠比目鱼肌梭內肌静息钙的含量,且呈浓度依赖性(P0.01)。DMSO对大鼠比目鱼肌单一肌梭传入放电活动无明显影响。2和5μmol/L伊吾诺霉素可明显抑制比目鱼肌单一肌梭传入放电(P0.05)。5μmol/L伊吾诺霉素可延长单一肌梭传入放电周期间隔(P0.05),在此基础上给予50mg/L氯化琥珀酰胆碱(Sch)诱发肌梭传入发电,可见肌梭传入放电无明显改变。结论大鼠比目鱼肌梭內肌游离钙离子浓度的增加可抑制肌梭传入放电。     

100 Hz正弦波振动对悬吊大鼠比目鱼肌肌梭传入放电的影响

目的探讨100 Hz正弦波振动对尾部悬吊大鼠比目鱼肌肌梭传入放电的影响.方法采用尾部悬吊大鼠模型模拟失重,用振动仪实施100 Hz正弦波刺激,利用从背根分离神经细束并记录比目鱼肌肌梭传入放电的方法,7 d后观察大鼠比目鱼肌肌梭传入放电的变化.结果 1)吊尾7 d后,大鼠比目鱼肌肌梭的传入放电与对照组相比明显减低(P<0.05).2)吊尾加100 Hz正弦波振动7 d后,与单纯吊尾组相比肌梭的传入放电明显增多(P<0.05). 结论 100 Hz正弦波振动可选择性兴奋肌梭,使悬吊大鼠比目鱼肌肌梭的传入放电明显增多.     

三磷酸腺苷二钠盐增强大鼠比目鱼肌肌梭传入放电活动

目的:探讨三磷酸腺苷二钠盐对大鼠肌梭传入放电的影响。方法:采用分离神经细束在体记录肌梭传入放电的方法,分别注射三种浓度(1 mg.kg-1、2 mg.kg-1、3 mg.kg-1)的三磷酸腺苷二钠盐,观察大鼠比目鱼肌肌梭传入放电活动的变化。结果:注射三种浓度三磷酸腺苷二钠盐后,肌梭传入放电峰值分别增至38.71 Hz、92.56 Hz、148.25 Hz,放电持续时间分别延长至20.47 min、30.65min、51.36 min。结论:三磷酸腺苷二钠盐可明显增加大鼠肌梭传入放电频率,且呈剂量依赖关系。     

冬虫夏草提取液增强大鼠肌梭传入放电频率

目的:探讨冬虫夏草(CS)提取液对大鼠比目鱼肌肌梭传入放电的影响。方法:雌性SD大鼠20只,麻醉后行气管插管术和颈外静脉插管术,在比目鱼肌神经上分离神经细束,记录肌梭的传入放电,观察CS对放电的影响。结果:分别注射50 mg.kg-1、100 mg.kg-1、150 mg.kg-1CS提取液后,肌梭传入放电峰值频率均明显增加,且随着药物浓度升高,放电频率明显增加,放电持续时间明显延长。结论:CS提取液明显增加大鼠肌梭的传入放电频率,且与剂量呈依赖关系。     

尾部悬吊对大鼠比目鱼肌肌梭电生理特性的影响

目的 观察模拟失重不同时期大鼠离体比目鱼肌肌梭电生理特性的改变。方法 采用大鼠尾悬吊法建立模拟失重模型。雌性大鼠随机分为模拟失重7d,14d组以及对照组。采用电生理学方法,观察模拟失重不同时期离体比目鱼肌肌梭的自发放电及对动-静式(ramp-and—hold)牵拉反应特性的改变。结果 模拟失重7d组大鼠肌梭自发放电频率明显降低,对动-静式牵拉反应性下降。14d组变化更为显著。结论 模拟失重可致肌梭的电生理特性发生明显的改变,并随模拟失重时间延长而加重。     

肌梭调节运动性通气增强反应的机理研究

在63只麻醉、制动、断双侧迷走神经、人工呼吸的家兔,观察了股动脉注射琥珀胆碱(Sch)诱发肌梭传入对延髓呼吸相关神经元自发放电的影响.结果发现股动脉注射Sch对延髓吸气神经元的作用以兴奋为主(37/56),对呼气神经元的作用以抑制为主(10/17),而对非呼吸性神经元这种兴奋与抑制反应则不明显;Seh对吸气神经元的兴奋作用,一般在给药后1～2min即可达高峰,而对呼气神经元的抑制作用则发生较晚,一般在给药后2～3min达高峰;肌注布比卡因破坏肌梭后可明显降低Sch对延髓呼吸相关神经元的影响.结果提示,股动脉注射Sch诱发的肌梭传入可通过延髓呼吸中枢参与对运动性通气增强反应的调节.     

肌梭传入在运动性通气增强反应中的作用

在63只麻醉、制动、断双侧迷走神经、人工呼吸的家兔中,以膈神经传出放电作为呼吸效应的客观指标,用琥珀胆碱(Sch)选择性地兴奋肌梭,观察了肌梭传入在运动性通气增强反应中的作用.结果表明股动脉注射Sch后有23例(占36.51%)产生吸气延长效应,表现为吸气时程(Ti)延长(P＜0.05),呼气时程(Te)有缩短趋势,但差异无显著性,Ti/Te比值增加(P＜0.05),肺通气量加大;17例(占26.98%)呈抑呼增频效应,表现为Te缩短,Ti变化不明显.Ti/Te比值增加,呼吸频率(RF)加快,最终也导致肺通气量加大.肌注布比卡因破坏肌梭后,同剂量的Sch则使上述呼吸易化效应明显减弱.提示肌梭传入活动在运动性通气增强反应中具有重的作用.     

高频正弦波振动对尾吊大鼠比目鱼肌H反射变化的改善作用

目的 本研究旨在进一步观察尾吊大鼠与肌梭兴奋性传入有关的α运动神经元的兴奋性的变化,并探讨高频正弦波振动比目鱼肌能否对这种兴奋性的变化产生影响.方法 用大鼠尾部悬吊法建立模拟失重模型.对比目鱼肌施加机械正弦波振动(100 Hz,0.3 mm).电刺激坐骨神经,同时记录比目鱼肌肌电图.结果 尾吊和高频正弦波振动均不影响H反射幅值在刺激强度增加时的变化趋势.尾吊14d后,大鼠最大运动反应(Mmax)和Hmax与Mmax之比(Hmax/Mmax)明显减小,而在尾吊期间给予高频振动后二者没有显著性差异.结论 模拟失重状态下肌梭的传入冲动减少可引起大鼠脊髓运动神经元兴奋性降低.高频正弦波振动比目鱼肌可以提高模拟失重条件下脊髓仅运动神经元的兴奋性.     

三种活血类中药对蟾蜍离体单一肌梭传入放电的影响

目的对几种常用的活血类药物进行筛选，以寻找能兴奋肌梭，使肌梭传入放电增加的活血类药物，从而为预防和治疗失重性肌萎缩提供新思路。方法利用蟾蜍缝匠肌分离制备单一肌梭标本，使用空气隔绝法记录离体单一肌梭的传入放电，比较几种活血类药物对肌梭传入放电的影响。结果川芎嗪能显著兴奋肌梭，并呈现出良好的量效依赖关系。红花与丹参注射液则均无这种作用。结论川芎嗪是已知具有扩张血管、促进微循环的药物，其对肌梭的兴奋作用，使其有可能成为缓解失重性肌萎缩的候选药物。     

高频振动对尾部悬吊大鼠比目鱼肌梭内、外肌纤维肌球蛋白重链表达的影响

目的 观察高频正统波振动对尾部悬吊大鼠比目鱼肌（SOL）梭内、外肌纤维MHC表达的影响。方法 采用大鼠尾部悬吊法建立模拟失重模型,高频正弦波振动大鼠比目鱼肌。用免疫组织化学技术,观察大鼠比目鱼肌（SOL）梭内、外肌纤维MHC表达变化。结果 尾部悬吊7d后大鼠比目鱼肌梭内、外肌纤维中快缩型MHC的表达均有所增加,而在另尾期间给予高频正弦波振动比目鱼肌后梭内、外肌快缩型MHC表达没有明显变化。结论 高频正弦波振动尾部悬吊大鼠比目鱼肌梭内、外肌纤维MHC表型转化有明显的对抗作用。     

To stretch or not to stretch: the role of stretching in injury prevention and performance

Stretching is commonly practiced before sports participation; however, effects on subsequent performance and injury prevention are not well understood. There is an abundance of literature demonstrating that a single bout of stretching acutely impairs muscle strength, with a lesser effect on power. The extent to which these effects are apparent when stretching is combined with other aspects of a pre‐participation warm‐up, such as practice drills and low intensity dynamic exercises, is not known. With respect to the effect of pre‐participation stretching on injury prevention a limited number of studies of varying quality have shown mixed results. A general consensus is that stretching in addition to warm‐up does not affect the incidence of overuse injuries. There is evidence that pre‐participation stretching reduces the incidence of muscle strains but there is clearly a need for further work. Future prospective randomized studies should use stretching interventions that are effective at decreasing passive resistance to stretch and assess effects on subsequent injury incidence in sports with a high prevalence of muscle strains.     

The magnitude of intramuscular deoxygenation during exercise is an unreliable measure to diagnose the cause of leg pain

We measured intramuscular oxygenation in the anterior tibial muscle of 176 patients with exercise‐induced leg pain by noninvasive near‐infrared spectroscopy before, during, and after an exercise test that elicited the symptoms. Clinical investigation was performed after each test. Intramuscular pressure was measured in patients with nonconclusive findings. Chronic anterior compartment syndrome (CACS) was diagnosed in 47 patients, and other causes for the leg pain were diagnosed in 129 patients by clinical means. The mean level of oxygenation decreased to 33 ± 19% in patients with CACS and to 34 ± 19% in patients without CACS compared with baseline level (100%) at rest before exercise. The level of oxygenation was below 20% during the exercise test in 12 of 47 (26%) patients with CACS and in 30 of 129 (23%) patients without CACS. The time required for reoxygenation after the cessation of exercise was 61 ± 34 s in patients with CACS and 46 ± 20 s in patients without CACS (P < 0.05). We conclude that the magnitude of intramuscular deoxygenation during exercise is an unreliable measure to diagnose CACS. However, the time for reoxygenation returning to baseline level following an exercise test is a valuable adjunct in diagnosing CACS.     

The association between muscular power from childhood to adulthood and adult measures of glucose homeostasis

This study aimed to assess whether the longitudinal association between childhood muscular fitness and adult measures of glucose homeostasis persist despite changes in muscular fitness across the life course. This prospective longitudinal study included 586 participants who had their muscular power (standing long jump distance), cardiorespiratory fitness (CRF), and waist circumference measured as children (aged 9, 12, 15 years) and again 20 years later as adults. In adulthood, these participants also provided a fasting blood sample which was tested for glucose and insulin. Glucose homeostasis measures including insulin resistance (HOMA2‐IR) and beta cell function (HOMA2‐β) were estimated. Child and adult muscular power levels were separated into thirds, and tracking groups (persistently low, decreasing, persistently moderate, increasing, and persistently high) were created. Sex‐stratified multivariable linear regression models were used to examine the association between muscular power tracking groups and adult measures of glucose homeostasis. Compared with males with persistently high muscular power, males with increasing and persistently low muscular power had higher fasting insulin (increasing: β = 1.12 mU/L, P = .04; persistently low: β = 2.12 mU/L, P = .001) and HOMA2‐β (increasing: β = 8.50%, P = .03; persistently low: β = 11.27%, P = .01) independent of CRF and males with persistently low muscular power had greater fasting insulin (β = 1.22 mU/L, P = .02) and HOMA2‐IR (β = 0.14, P = .02) independent of waist circumference. Non‐significant associations were present for females. For males, maintaining persistently high muscular power between childhood and adulthood could lead to a healthier adult glucose homeostasis profile.     

长期模拟失重大鼠心肌收缩性能的改变

应用在体及离体实验对一批悬吊90d大鼠的心肌收缩性能进行了观察。在体实验结果表明：悬吊组大鼠左室舒张本压及主动脉血压与对照组无显著性差别（P＞0．05）；但悬吊组大鼠左心室内压峰值较对照组降低16％（P＜0．01），左心室内压最大上升速率与最大下降速率也分别较对照组减慢28％（P＜0．05）与21％（P＜0．05）。对同一批大鼠的离体乳头肌，又用等长收缩灌流技术观察了力学特性变化。结果是：反映心肌收缩强度的指标，如最大发展张力（DT），在两组间无显著差别；反映心肌收缩速度的指标，如最大张力发展速率对DT的校正值，悬吊组较对照组降低了17．2％（P＜0．05）；反映收缩时程的指标，如悬吊组的至峰张力收缩时间与至峰张力发展速率收缩时间分别较对照组延长了12．7％（P＜0．01）和22．2％（P＜0．05）；反映心肌舒张的时程指标，如张力下降一半时间与至峰张力下降速率舒张时间分别较对照组延长183％（P＜0．01）与20．3％（P＜0．01）。以上结果表明，长期模拟失重大鼠心肌收缩性能明显降低，并主要表现为心肌收缩速率减慢和收缩与舒张时程延长。     

后肢去负荷对大鼠比目鱼肌肌梭神经末梢的影响

目的观察后肢去负荷对大鼠比目鱼肌肌梭神经末梢形态的影响。方法采用大鼠尾部悬吊法建立后肢去负荷动物模型，按体重配对原则随机将大鼠分为5组，即后肢去负荷7d组、14d组、21d组、28d组和正常同步对照组。分离单一肌梭，采用快速的银染方法，光镜下对肌梭的形态及其神经末梢进行观察并拍照。结果正常对照组大鼠比目鱼肌肌梭形态完整，包囊光滑，边缘清晰，赤道部和两极部神经末梢清晰完整，梭内肌横纹亦清晰可见；后肢去负荷7d后肌梭神经末梢与对照组相比未见明显异常；后肢去负荷14d后肌梭赤道部神经纤维淡染，末梢出现轻微的溶解，断裂；后肢去负荷21d后肌梭内神经末梢密度明显减少，肌梭赤道部神经纤维断裂，溶解；后肢去负荷28d后肌梭神经末梢呈严重的退行性改变，出现断裂，迂曲。结论后肢去负荷可引起肌梭赤道部与极部神经末梢的退行性改变，且随去负荷时间的延长而加重。     

Changes of functional status and volume of triceps brachii measured by magnetic resonance imaging after maximal resistance training

Purpose

To evaluate the effect of 6‐week self‐perceived maximal resistance training on muscle volume utilizing magnetic resonance imaging and maximal, average, and endurance strength of the elbow extensors and to assess the relationship between muscle strength and volume before and after the training.

Materials and Methods

This was a prospective blinded study. A total of 15 healthy untrained men, aged 22.5 ± 3.7 years (mean ± SD), were engaged in elbow extensor training using isoacceleration dynamometry for 6 weeks with a frequency of five sessions per week (five sets of 10 maximal voluntary contractions, 1‐minute rest period between each set). Prior to and after the training, cross‐sectional magnetic resonance images of the upper arm were obtained and muscle volumes were calculated using the truncated cone formula.

Results

Average, maximal, and endurance strength of the upper arm extensors increased significantly by 43%, 15%, and 56%, respectively. The volume of triceps brachii increased in both arms (P < 0.05): right from 456.9 ± 113.8 cm³ to 475.8 ± 100.9 cm³ and left from 444.3 ± 121.9 cm³ to 468.4 ± 110.4 cm³, or 5%. Maximal and average strength correlated significantly with muscle volume before and after the training.

Conclusion

A specific 6‐week resistance training protocol resulted in muscle strength improvement, together with increase in triceps brachii muscle volume, as demonstrated by volumetric imaging. J. Magn. Reson. Imaging 2009;29:671–676. © 2009 Wiley‐Liss, Inc.     

Strenuous resistance exercise effects on magnetic resonance diffusion parameters and muscle–tendon function in human skeletal muscle

Purpose:

To assess the effects of strenuous exercise on magnetic resonance diffusion parameters and muscle–tendon complex function in skeletal muscle.

Materials and Methods:

Six men performed ankle plantar flexion exercises with eccentric contraction. The fractional anisotropy (FA), λ₁, λ₂, λ₃, mean diffusivity (MD), and T₂ values in the triceps surae muscles were measured by magnetic resonance diffusion tensor and spin‐echo imaging. Passive torque of plantar flexors, maximal voluntary isometric plantar flexion torques (MVIP), and Achilles tendon stiffness during MVIP were measured by combined ultrasonography and dynamometry. Plasma creatine kinase and muscle soreness were also assessed. These parameters were measured before and 1–8 days postexercise.

Results:

The medial gastrocnemius exhibited significantly decreased FA 2–5 days after, increased λ₂ 3 days after, and increased λ₃ 2 and 3 days after exercise. This muscle also showed significantly increased MD and T₂ values 3 days postexercise. MVIP significantly decreased 2 and 3 days postexercise, while passive torque significantly increased 2 days postexercise. Creatine kinase and muscle soreness increased 3–5 days and 1–5 days postexercise, respectively.

Conclusion:

Exercise‐induced muscle damage manifested as significant changes in muscle diffusion parameters with muscle–tendon complex dysfunction and delayed‐onset muscle soreness. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Differential muscle hypertrophy and edema responses between high‐load and low‐load exercise with blood flow restriction

We sought to determine whether early increases in cross‐sectional area (CSA) of different muscles composing the quadriceps with low‐load resistance training with blood flow restriction (LL‐BFR) were mainly driven by muscle hypertrophy or by edema‐induced swelling. We also compared these changes to those promoted by high‐load resistance training (HL‐RT). In a randomized within‐subject design, fifteen healthy, untrained men were submitted to magnetic resonance imaging (MRI) for CSA and edema‐induced muscle swelling assessment (fast spin echo inversion recovery, FSE‐STIR). MRI was performed in LL‐BFR and HL‐RT at baseline (W0) and after 3 weeks (W3), with a further measure after 6 weeks (W6) for HL‐RT. Participants were also assessed at these time points for indirect muscle damage markers (range of motion, ROM; muscle soreness, SOR). CSA significantly increased for all the quadriceps muscles, for both LL‐BFR and HL‐RT at W3 (all P < .05) compared to W0. However, FSE‐STIR was elevated at W3 for all the quadriceps muscles only for HL‐RT (all P < .0001), not LL‐BFR (all P > .05). Significant increases and decreases were shown in SOR and ROM, respectively, for HL‐RT in W3 compared to W0 (both P < .05), while these changes were mitigated at W6 compared to W0 (both P > .05). No significant changes in SOR or ROM were demonstrated for LL‐BFR across the study. Early increases in CSA with LL‐BFR seem to occur without the presence of muscle edema, whereas initial gains obtained by HL‐RT were influenced by muscle edema, in addition to muscle hypertrophy.     

运动诱导的大鼠腓肠肌细胞凋亡与肌纤维类型百分构成关系的研究

目的:探讨运动诱导的骨骼肌细胞凋亡和肌纤维类型百分构成的关系。方法:30只成年雄性SD大鼠随机分为安静对照组(不运动)、中等强度运动组(18m/min,100min)和大强度运动组(28m/min,20min),每组10只。安静组和运动组大鼠分别于安静状态和运动后即刻处死,取后肢腓肠肌内侧头,分别以原位末端标记法(TUNEL)测试细胞凋亡,ATP酶染色法鉴定Ⅰ型和Ⅱ型骨骼肌纤维,SDS-PAGE凝胶电泳分离肌凝蛋白重链(MHC),MHCⅠ、MHCⅡa、MHCⅡb和MHCⅡx。结果:(1)安静对照组大鼠腓肠肌内侧头仅检测到少量TUNEL阳染细胞核;中等强度运动组有散在的TUNEL阳染细胞核,凋亡指数为19.01±6.61;大强度运动组也检测到TUNEL阳染细胞核,凋亡指数为11.51±4.33%。(2)中等强度运动组细胞凋亡指数与Ⅱ型肌纤维面积百分比的相关系数r为0.776(P<0.05);大强度运动组细胞凋亡指数与Ⅱ型肌纤维面积百分比的相关系数r为0.737(P<0.05)。(3)中等强度运动组细胞凋亡指数与MHCⅡa亚型百分比呈高度正相关(r=0.787,P<0.05);与MHCⅡb亚型百分比呈低度负相关(r=-0.334,P<0.05);大强度运动组的结果与中等强度组基本一致。结论:运动量是影响骨骼肌细胞凋亡率的关键因素之一,肌细胞凋亡率在一定程度上随运动量的增加而升高,并且Ⅱ型肌纤维(快肌纤维)百分比高的骨骼肌在大强度和中等强度跑台运动中更易发生细胞凋亡。