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Title: Apoptosis in unloading-induced muscle atrophy and the effect of electrical stimulation in preventing muscle atrophy
Authors: Guo, BS
Zhu, TY
Zhang, BT
Yeung, SS 
Wan, Q
Yeung, EW 
Keywords: Apoptosis
Muscle atrophy
Issue Date: 2008
Publisher: 科學出版社
Source: 生理学报 (Acta physiologica sinica), Oct. 2008, v. 60, suppl. 1, 594 How to cite?
Journal: 生理学报 (Acta physiologica sinica) 
Abstract: Apoptotic cell death is a highly regulated process which plays a crucial role in many biological events; this process has been implicated in muscle atrophy.This study aims to examine the mitochondria-associated apoptotic response in unloading-induced muscle atrophy and to examine whether electrical stimulation can attenuate apoptosis and prevent muscle atrophy.Male Balb/c mice(n=6)were hindlimb unloaded via tail suspension for 14 d.One hindlimb of the mice serves as control(HU)and the contralateral limb was given electrical stimulation(ES)at a stimulation frequency of 20 Hz and pulse duration of 0.2 ms for 2×3 h/day.Following 14 d HU,the soleus(SOL) and extensor digitorum longus(EDL)muscles were dissected for in vitro evaluation including maximal isometric force(P_o),mean cross-sectional area of fibre(mCSA_f),force-frequency and force-length relationship.The degree of apoptosis was assessed by the TUNEL index and immunohistochemical staining for detecting the expressions of pro-apoptotic mitochondrial proteins Bax,AIF,cytochrome C and caspase-3 were performed.The P_o and mCSA_f of the SOL in the HU limb was reduced by 48%and 44%compared to that of the age-matched ambulatory mice(P<0.001).ES treatment led to an improvement in P_o and mCSA_f by 48%and 20%respectively.HU also caused a leftward shift of the force-frequency and length-tension relation in the SOL muscle.There was no obvious change of these parameters in the EDL muscles.The TUNEL index in the HU limb increased to 2.41 times while in the HU+ES treated limb,this apoptotic index averaged 0.49 times(P<0.01).In the HU limb,the immunostaining of Bax, AIF,cytochrome C and caspase-3 was increased by 129%,127%,76%,and 89%respectively compared to that of the ambulatory mice;ES decreased the percentage of Bax(16.8%,P<0.05)and AIF(27.8%,P<0.05)positive fibres when compared with the HU limb.Our results showed that mitochondria-associated apoptotic signaling is upregulated in unloading-induced muscle atrophy.Electrical stimulation attenuated the loss of muscle mass and contractile activity,and possibly reduced mitochondria-associated apoptosis.
Description: The Beijing Joint Conference of Physiological Sciences, Beijing, China, 19-22 October 2008
ISSN: 0371-0874
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