人参皂苷对制动所致大鼠骨骼肌萎缩的保护作用

目的探讨人参皂苷对制动所导致的萎缩骨骼肌结构及功能的影响。方法选用SD大鼠,随机分为3组,对照组(CON)、制动组(IMM)和制动加人参皂苷处理组(GIN),每组10只。制动组采用石膏固定后肢模型,人参皂苷处理组在制动基础上按50 mg/kg·d体重腹腔注射人参皂苷,同步对照组及后肢制动组每日腹腔注射同等体积的生理盐水,共3周。实验结束观察大鼠比目鱼肌重量变化;通过Western blot观察骨架蛋白dystrophin和desmin的表达变化;通过离体肌条实验观察骨骼肌收缩功能的变化。结果制动组比目鱼肌湿重显著低于对照组及人参皂苷处理组;制动组比目鱼肌dystrophin表达显著降低,desmin降解明显增强,人参皂苷处理后上述改变明显缓解;制动组比目鱼肌收缩功能显著低于对照组及人参皂苷处理组。结论人参皂苷可有效防护制动所导致的骨骼肌萎缩。     

Respiratory Muscle Overloading and Dyspnoea During Bronchoconstriction in Asthma: Protective Effects of Fenoterol

Whether, and to what extent, β₂-agonists protect against respiratory muscle overloading and breathlessness during bronchoconstriction remains to be defined in patients with asthma. In a double blind placebo-controlled study, 100 μg of fenoterol were administered to six stable asthmatics before a bronchial provocation test, performed by inhaling doubling concentrations of histamine from a Devilbiss 646 nebulizer. We recorded breathing pattern (tidal volume V_T, inspiratory time T_I, total time of the respiratory cycle T_TOT), inspiratory capacity (IC), dynamic pleural pressure swing (P_plsw), total lung resistance (R_L) and FEV₁. V_Twas expressed both in actual values and as % of IC. Changes in V_T(%IC) during histamine inhalation reflected changes in dynamic end-inspiratory lung volume (EILV). P_plswwas expressed as % of maximal (the most negative in sign) pleural pressure, obtained under control conditions during a sniff manoeuvre (P_plsn). P_plsw(%P_plsn) is an index of inspiratory muscle effort. The test ended when the concentration of histamine which caused a decrease in FEV₁of ≥40% post-saline was reached. Dyspnoea rating was scored by a modified Borg scale. At the ultimate degree of bronchoconstriction (UDB) with histamine: (i) decrease in FEV₁was similar after placebo and fenoterol, while increase in R_Lwas lower after fenoterol (P<0.005); (ii) V_T(%IC) increased less after fenoterol (P<0.027); (iii) increases in P_plsw(%P_plsn) was lower after fenoterol (P<0.001); (iv) ΔBorg (from saline) was lower (P<0.01) after fenoterol; (v) differences in ΔBorg, from placebo to fenoterol, related to concurrent changes in V_T(%IC) (r²=0.67). In conclusion, at UDB 100 μg of fenoterol produced a beneficial effect on the degree of inspiratory muscle loading and breathlessness, an effect greater than it would be expected from measuring FEV₁alone.     

Age and gender effects on submental motor-evoked potentials

It is not known whether there are age- and/or gender-related differences in magnitude of motor-evoked potentials (MEPs) of the submental muscles. Knowledge of this is important in investigations of neurophysiological aspects of swallowing. Forty healthy participants (20 males, 20 females; 20 young [21–35 years], 20 old [53–88 years]) were recruited. Surface electromyography (EMG) electrodes were placed at midline underlying the submental muscle group. Age- and gender-related differences were evaluated in two neurophysiologic measures of swallowing: MEPs stimulated by single-pulse transcranial magnetic stimulation (TMS) over the motor cortex and surface electromyography (sEMG) recorded from the same submental muscle group during non-stimulated swallows. The older participants had larger MEPs during saliva swallowing than the young participants (p = 0.04, d = 0.86). Conversely, the older participants had lower amplitude submental EMG activity during non-stimulated swallows (p = 0.045, d = 0.67). Gender had no significant effect on MEP magnitude and on submental activity during saliva swallowing. There were no effects of age or gender on MEP latencies. These findings suggest deterioration in muscle function with age in a sample of healthy adults presenting with functional swallowing. We speculate that muscular decline is partially ameliorated by increased cortical activity—i.e., increased submental MEPs—so as to preserve swallowing function in healthy older subjects. These findings emphasize the need for different reference points for evaluation of submental MEPs of different age groups.     

Innervation zone locations in 43 superficial muscles: Toward a standardization of electrode positioning

Introduction: We describe the innervation zone (IZ) location in 43 muscles to provide information for appropriate positioning of bipolar electrodes for clinical and research applications. Methods: The IZ was studied in 40 subjects (20 men and 20 women) using multichannel surface electromyography (sEMG). Signal quality was checked visually to identify motor unit action potentials and estimate muscle fiber conduction velocity. Results: Results in 33 muscles were classified as excellent or good, because it was possible to identify an area which is favorable for appropriate positioning of an electrode pair without the need to previously determine the IZ location. Conclusions: Knowledge of IZ location will increase standardization and repeatability of sEMG measures. Muscle Nerve 49 :413–421, 2014     

Assessment of muscle stiffness using a continuously scanning laser‐Doppler vibrometer

Introduction: A stand‐alone and low‐cost elastography technique has been developed using a single continuously scanning laser Doppler vibrometer. Methods: This elastography technique is used to measure the propagation velocity of surface vibrations over superficial skeletal muscles to assess muscle stiffness. Results: Systematic variations in propagation velocity depending on the contraction level and joint position of the biceps brachii were demonstrated in 10 subjects. Conclusions: This technique may assist clinicians in characterizing muscle stiffness (or tone) changes due to neuromuscular disorders. Muscle Nerve 50 : 133–135, 2014