Relationship between simulated weightlessness-induced muscle spindle change and muscle atrophy / 生理学报

One of the most important and urgent issues in the field of space medicine is to reveal the potential mechanism underlying the disused muscle atrophy during the weightlessness or microgravity environment. It will conduce to find out effective methods for the prevention and treatment of muscle atrophy during a long-term space flight. Increasing data show that muscle spindle discharges are significantly altered following the hindlimb unloading, suggesting a vital role in the progress of muscle atrophy. In the last decades, we have made a series of studies on changes in the morphological structure and function of muscle spindle following simulated weightlessness. This review will discuss our main results and related researches for understanding of muscle spindle activities during microgravity environment, which may provide a theoretic basis for effective prevention and treatment of muscle atrophy induced by weightlessness.

Method of isolation of intrafusal fibres of muscle spindle in soleus of rats / 生理学报

Capsule restricts the further study on muscle spindle function and the involved mechanism. The aim of this study was to establish the isolation method of intrafusal fibres from the isolated rat muscle spindle. Intrafusal fibres were harvested from muscle spindle of soleus muscle in rats using neutrase-collagenase digestion. A variety of incubation mediums have been tested to find out an appropriate medium of intrafusal fibers in vitro. Trypan blue staining was used to detect cell death, and patch clamp was used to record resting potential. The results showed that the intrafusal fibres incubated with amine acid-saline solution were almost all dead. DMEM could maintain good condition of the fibres, but excess CO2 ventilation would induce cellular swelling or even death. While Leiboviz's 15 (L-15) medium can guarantee 1-2 h of physiological condition of the intrafusal fibres. Coverslips treated with gelatin, polylysine and serum was the better interfaces for the intrafusal fibres to adhere easily, compared with regularly treated coverslip. The resting potential of intrafusal fibres was (-45.3 ± 5.1) mV, consistent with others obtained from in vivo muscle spindle from cats and frogs. These results suggest that the isolation method of the intrafusal fibres has been successfully established in the present study, providing a new approach in better understanding of muscle spindle activities and the involved mechanism.

Electrophysiological characteristics of the isolated muscle spindle in rats / 生理学报

The aim of this study was to observe the electrophysiological characteristics of the isolated rat muscle spindle. The muscle spindle was isolated from rat soleus and the afferent discharge of the isolated muscle spindle was recorded by air-gap technique. In the basic physiological salt solution, the spontaneous impulses of muscle spindle were at a lower level with irregular intervals. The mean frequency of afferents was (51.78 ± 25.63) impulses/1 000 s (n = 13). The muscle spindle afferents were significantly increased and maintained over time by the addition of certain amino acids during the observation. The number of the action potential recorded per 1 000 s was 200-1 000 [mean: (687.62 ± 312.56) impulses/1 000 s, n = 17]. In addition to the typical propagated action potential, a large number of abortive spikes were observed. The results indicate that the activities of isolated muscle spindles in rats can be well maintained by the addition of certain amino acids. The results initially establish and provide the possibility for further research conducted in isolated rat muscle spindles.

Effects of 100 Hz sinusoidal vibration on H reflex and M wave in rat soleus muscle following immobilization / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the effects of 100 Hz sinusoidal vibration on H reflex and M wave in rat soleus muscle following immobilization.</p><p><b>METHODS</b>The immobilization of rat soleus muscle was induced as a disuse muscle model, and 100 Hz sinusoidal vibration was generated by a vibrator and applied to the immobilized soleus muscle, then the changes of H reflex and M wave in muscle were observed after 14 d.</p><p><b>RESULTS</b>Compared to control, after 14 d of immobilization M(max) in soleus muscle decreased (P<0.01), stimulus threshold and S(max) increased (P<0.01); Hmax and H(max)/M(max) decreased (P<0.05, S(max) increased (P<0.05). Compared to immobilized soleus muscle, after 14 d of immobilization with 100 Hz sinusoidal vibration, the M(max) increased(P<0.01), stimulus threshold and S(Mmax) decreased (P<0.05), H(max) (P<0.01) increased and H(max)/M(max) increased (P<0.05).</p><p><b>CONCLUSION</b>100 Hz sinusoidal vibration plays a significant antagonist role against the changes in H reflex and M wave in rat soleus muscle following immobilization.</p>

Protective effect of albumin on lungs injury in traumatic/hemorrhagic shock rats / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To determine the effect of albumin administration on lung injury in traumatic/hemorrhagic shock (T/HS) rats.</p><p><b>METHODS</b>Forty-eight adult Sprague-Dawley rats were divided into three groups randomly (n=16 in each group): Group A, Group B, Group C. In Group A, rats underwent laparotomy without shock. In Group B, rats undergoing T/HS were resuscitated with their blood plus lactated Ringer's (twice the volume of shed blood). In Group C, rats undergoing T/HS were resuscitated with their shed blood plus additional 3 ml of 5% human albumin. The expression of polymorphonuclear neutrophils CD18/CD11b in jugular vein blood was evaluated. The main lung injury indexes (the activity of myeloperoxidase and lung injury score) were measured.</p><p><b>RESULTS</b>Significant differences of the expression of CD18/11b and the severity degree of lung injury were founded between the three groups. (P<0.05). The expression of CD18/CD11b and the main lung injury indexes in Group B and Group C increased significantly compared with those in Group A (P<0.05). At the same time, the expression of CD18/CD11b and the main lung injury indexes in Group C decreased dramatically, compared those in Group B (P<0.05).</p><p><b>CONCLUSIONS</b>The infusion of albumin during resuscitation period can protect lungs from injury and decrease the expression of CD18/CD11b in T/HS rats.</p>