Exploring the mechanism of neural-function reconstruction by reinnervated nerves in targeted muscles

A lack of myoelectric sources after limb amputation is a critical challenge in the control of multifunctional motorized prostheses. To reconstruct myoelectric sources physiologically related to lost limbs, a newly proposed neural-function construc- tion method, targeted muscle reinnervation （TMR）, appears promising. Recent advances in the TMR technique suggest that TMR could provide additional motor command information for the control of multifimctional myoelectric prostheses. However, little is known about the nature of the physiological functional recovery of the reinnervated muscles. More understanding of the under- lying mechanism of TMR could help us fine tune the technique to maximize its capability to achieve a much higher performance in the control of multifunctional prostheses. In this study, rats were used as an animal model for TMR surgery involving transferring a median nerve into the pectoralis major, which served as the target muscle. Intramuscular myoelectric signals reconstructed following TMR were recorded by implanted wire electrodes and analyzed to explore the nature of the neural-fimction recon- struction achieved by reinnervation of targeted muscles. Our results showed that the active myoelectric signal reconstructed in the targeted muscle was acquired one week after TMR surgery, and its amplitude gradually became stronger over time. These pre- liminary results from rats may serve as a basis for exploring the mechanism of neural-function reconstruction by the TMR tech- nique in human subjects.     

Caenorhabditis elegans as a Model System for Duchenne Muscular Dystrophy

The nematode worm Caenorhabditis elegans has been used extensively to enhance our understanding of the human neuromuscular disorder Duchenne Muscular Dystrophy (DMD). With new arising clinically relevant models, technologies and treatments, there is a need to reconcile the literature and collate the key findings associated with this model.     

Classification of wooden breast myopathy in chicken pectoralis major by a standardised method and association with conventional quality assessments

Wooden breast (WB) abnormalities of broilers compromise the quality of fresh and processed meat. Yet, no standardised classification method for evaluating WB currently exists. We here provide a novel classification method to determine the severity of WB by palpation. Data were evaluated by one‐way anova . The classification method proved robust and reliable to classify broiler filets into three distinct categories (no, moderate and severe WB). This was supported by histological findings, demonstrating less muscle tissue in WB‐affected samples. Moreover, moisture content, resistance to compression, mobile water fraction, drip loss and cooking loss, as well as intramuscular and surface pH also increased with WB. Using the classification method, we demonstrated that severe WB increased the diversity of the endogenous microflora and promoted growth of Enterobacteriaceae. In conclusion, the presented classification method correlates with known meat quality traits and will be a valuable tool for future studies on WB.     

Chronic Ouabain Prevents Na,K-ATPase Dysfunction and Targets AMPK and IL-6 in Disused Rat Soleus Muscle

Sustained sarcolemma depolarization due to loss of the Na,K-ATPase function is characteristic for skeletal muscle motor dysfunction. Ouabain, a specific ligand of the Na,K-ATPase, has a circulating endogenous analogue. We hypothesized that the Na,K-ATPase targeted by the elevated level of circulating ouabain modulates skeletal muscle electrogenesis and prevents its disuse-induced disturbances. Isolated soleus muscles from rats intraperitoneally injected with ouabain alone or subsequently exposed to muscle disuse by 6-h hindlimb suspension (HS) were studied. Conventional electrophysiology, Western blotting, and confocal microscopy with cytochemistry were used. Acutely applied 10 nM ouabain hyperpolarized the membrane. However, a single injection of ouabain (1 µg/kg) prior HS was unable to prevent the HS-induced membrane depolarization. Chronic administration of ouabain for four days did not change the α1 and α2 Na,K-ATPase protein content, however it partially prevented the HS-induced loss of the Na,K-ATPase electrogenic activity and sarcolemma depolarization. These changes were associated with increased phosphorylation levels of AMP-activated protein kinase (AMPK), its substrate acetyl-CoA carboxylase and p70 protein, accompanied with increased mRNA expression of interleikin-6 (IL-6) and IL-6 receptor. Considering the role of AMPK in regulation of the Na,K-ATPase, we suggest an IL-6/AMPK contribution to prevent the effects of chronic ouabain under skeletal muscle disuse.     

Stepping behavior and muscle activity of dairy cattle standing on concrete or rubber flooring for 1 or 3 hours

The type of flooring in dairy cattle systems influences cows' health and welfare. Although concrete is common, the use of more compressible flooring, such as rubber, is increasing. Cows prefer to stand and walk on rubber surfaces than on concrete; however, it is largely unknown how walking and standing for longer periods of time influence muscle activity and fatigue. Therefore, we used measures of behavior and muscle activity to investigate the potential benefits of providing a rubber flooring surface to dairy cattle. Sixteen lactating Holstein cows were forced to stand on either concrete or rubber flooring for 1 or 3 h in a 2 × 2 crossover design. Surface electromyograms (SEMG) and skin surface temperature were used to evaluate muscle activity, fatigue, and movement of muscle activity between the hind legs. Activity of 2 muscles, the bicep femoris and middle gluteal, was assessed during both static contractions, when cows transferred weight to each hind leg, before and after 1 and 3 h of standing, and dynamic contractions, associated with steps and with shifts in weight without steps. In addition, we evaluated stepping rate, time between each step, feeding behavior, skin surface temperature, and latency to lie down after standing. Standing duration influenced both the behavior and muscle activity of cows. Stepping rate increased with standing time for cows on both flooring types. Static muscle activity parameters of the bicep femoris muscle were higher after 3 h of standing for cows standing on both flooring types (2.3 and 3.6% increases in median amplitude and median power frequency, respectively) compared with the change after 1 h and compared with baseline values before the standing treatment. Flooring type influenced the behavior and muscle activity of the cows, particularly during the first hour of exposure; cows standing on rubber had a higher stepping rate, shorter interval between steps, and higher number of SEMG shifts (muscle activity shifts with or without visible steps) than cows on concrete. There was no difference in skin surface temperature, feeding behavior, or latency to lie down between the treatments. The results show that standing on a rubber flooring caused a different initial behavioral response compared with standing on concrete; however, possible reasons for these changes are unclear. Standing for 3 h resulted in an increase in stepping rate and in some muscle activity parameters; however, the results regarding muscle fatigue in relation to flooring type are inconclusive.     

Insight into the mechanism of the quality improvement of porcine after ultrasound-assisted immersion freezing

The influences of ultrasound-assisted immersion freezing (UIF) at different power density levels (15, 30, 45 W L⁻¹) on the quality characteristics of porcine M. longissimus lumborum were evaluated. The results showed that UIF was effective in inhibiting juice loss, enhancing tenderness along with colour stability of porcine, especially at UIF of 30 W L⁻¹ (UIF-30). This improvement induced by UIF was attributed to the rapid freezing rate, the reduction of freezable water content, the formation of tiny and even ice crystals and the maintenance of muscle fibre integrity. This study indicated UIF with appropriate density (UIF-30) and was beneficial to improve the quality of pork muscle to the greatest extent.     

基于转录组学的养殖密度影响斑节对虾品质的分子机制

采用高通量转录组测序和实时定量聚合酶链式反应（quantitative real time polymerase chain reaction，qRT-PCR）技术，在分子水平揭示养殖密度对斑节对虾肌肉品质形成的影响机制。选取养殖密度100 尾/m2、300 尾/m2的斑节对虾为实验材料，进行转录组测序和qRT-PCR验证。结果表明：所有样本Q20和Q30的最小值均大于90%，测序数据均满足生物信息学分析的要求；不同密度养殖条件下，斑节对虾的差异表达基因为778 个；将差异基因序列与7个数据库进行比对，得到不同密度养殖的斑节对虾中与肌肉品质相关的差异基因分布在胶原蛋白代谢、蛋白水解、蛋白转运、细胞蛋白代谢、细胞骨架组织、肌肉连接及葡萄糖代谢途径；qRT-PCR验证结果与转录组测序结果一致。