Low-intensity pulsed ultrasound (LIPUS) has been proved to promote the proliferation of myoblast C2C12. However, whether LIPUS can effectively prevent muscle atrophy has not been clarified, and if so, what is the possible mechanism. The aim of this study is to evaluate the effects of LIPUS on muscle atrophy in hindlimb unloading rats, and explore the mechanisms. The rats were randomly divided into four groups: normal control group (NC), hindlimb unloading group (UL), hindlimb unloading plus 30 mW/cm2 LIPUS irradiation group (UL + 30 mW/cm2), hindlimb unloading plus 80 mW/cm2 LIPUS irradiation group (UL + 80 mW/cm2). The tails of rats in hindlimb unloading group were suspended for 28 days. The rats in the LIPUS treated group were simultaneously irradiated with LIPUS on gastrocnemius muscle in both lower legs at the sound intensity of 30 mW/cm2 or 80 mW/cm2 for 20 min/d for 28 days. C2C12 cells were exposed to LIPUS at 30 or 80 mW/cm2 for 5 days. The results showed that LIPUS significantly promoted the proliferation and differentiation of myoblast C2C12, and prevented the decrease of cross-sectional area of muscle fiber and gastrocnemius mass in hindlimb unloading rats. LIPUS also significantly down regulated the expression of MSTN and its receptors ActRIIB, and up-regulated the expression of Akt and mTOR in gastrocnemius muscle of hindlimb unloading rats. In addition, three metabolic pathways (phenylalanine, tyrosine and tryptophan biosynthesis; alanine, aspartate and glutamate metabolism; glycine, serine and threonine metabolism) were selected as important metabolic pathways for hindlimb unloading effect. However, LIPUS promoted the stability of alanine, aspartate and glutamate metabolism pathway. These results suggest that the key mechanism of LIPUS in preventing muscle atrophy induced by hindlimb unloading may be related to promoting protein synthesis through MSTN/Akt/mTOR signaling pathway and stabilizing alanine, aspartate and glutamate metabolism.
Low-intensity pulsed ultrasound (LIPUS) has been proved to promote the proliferation of myoblast C2C12. However, whether LIPUS can effectively prevent muscle atrophy has not been clarified, and if so, what is the possible mechanism. Myostatin (MSTN) is a negtive regulator of skeletal muscle, and inhibition of its expression has a positive effect on the growth and development of skeletal muscle.The aim of this study is to evaluate the effects of LIPUS on muscle atrophyin hind limb unloading rats, and explored the mechanisms. The rats were randomly divided into four groups: normal control group (NC), hind limb unloading group (UL), hind limb unloading plus 30 mW/cm2 irradiation group (UL + 30 mW/cm2), hind limb suspension plus 80 mW/cm2 irradiation group (UL + 80 mW/cm2). The rats were suspended or/and treated with LIPUS for 20 min/d for 28 days. C2C12 cells were exposed to LIPUS at 30 or 80 mW/cm2 for 5 days. After 28 days, LIPUS significantly prevented the decrease of cross-sectional area of muscle fiber and promoted the quality of gastrocnemius muscle. In addition, LIPUS significantly inhibited the content of MSTN in the serum and gastrocnemius muscle of hind limb rats, and its receptor, and promoted myoblast C2C12 proliferation, promoted the stability of alanine, aspartate and glutamate metabolism pathway. These results suggest that the key mechanism of LIPUS in preventing muscle atrophy induced by hind limb unloading may be through inhibiting MSTN and stabilizing alanine, aspartate and glutamate metabolism.
A recent theory provides a unified cross-linguistic analysis of the interpretations that are assigned to expressions for disjunction, Negative Polarity Items, Free Choice Items, and the non-interrogative uses of wh-phrases in languages such as Mandarin Chinese. If this approach is on the right track, children should be expected to demonstrate similar patterns in the acquisition of these linguistic expressions. Previous research has found that, by age four, children have acquired the knowledge that both the existential indefinite renhe “any” and wh-words in Mandarin Chinese are interpreted as Negative Polarity Items when they are bound by downward entailing operators, but the same expressions are interpreted as Free Choice Items (with a conjunctive interpretation) when they are bound by deontic modals (Mandarin keyi) or by the Mandarin adverbial quantifier dou “all”. The present study extends this line of research to the Mandarin disjunction word huozhe. A Truth Value Judgment Task was used to investigate the possibility that disjunction phrases that are bound by the adverbial quantifier dou generate a conjunctive interpretation in the grammars of Mandarin-speaking 4-year-old children. The findings confirmed this prediction. We discuss the implications of the findings for linguistic theory and for language learnability.
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