Our meta analysis of a homogeneous set of studies is the first to provide valuable LLNs for fiber CSA according to fiber type and gender .
Skeletal muscle atrophy is a major systemic impairment in chronic diseases .
Yet its determinants have been hard to identify because a clear research definition has not been agreed upon .
The reduction in muscle fiber cross-sectional area ( CSA ) is a widely acknowledged marker of muscle atrophy , but no reference values for the muscle fiber CSA at the age of the onset of chronic disease have ever been published .
Atrophy responses to muscle inactivity. I. Cellular markers of protein deficits.
The goal of this study was to use the model of spinal cord isolation ( SI ) , which blocks nearly all neuromuscular activity while leaving the motoneuron muscle-fiber connections intact , to characterize the cellular processes linked to marked muscle atrophy . Rats r and omly assigned to normal control and SI groups were studied at 0 , 2 , 4 , 8 , and 15 days after SI surgery . The slow soleus muscle atrophied by approximately 50 % , with the greatest degree of loss occurring during the first 8 days . Throughout the SI duration , muscle protein concentration was maintained at the control level , whereas myofibrillar protein concentration steadily decreased between 4 and 15 days of SI , and this was associated with a 50 % decrease in myosin heavy chain ( MHC ) normalized to total protein . Actin relative to the total protein was maintained at the control level . Marked reductions occurred in total RNA and DNA content and in total MHC and actin mRNA expressed relative to 18S ribosomal RNA . These findings suggest that two key factors contributing to the muscle atrophy in the SI model are 1 ) . a reduction in ribosomal RNA that is consistent with a reduction in protein translational capacity , and 2 ) . insufficient mRNA substrate for translating key sarcomeric proteins comprising the myofibril fraction , such as MHC and actin . In addition , the marked selective depletion of MHC protein in the muscles of SI rats suggests that this protein is more vulnerable to inactivity than actin protein . This selective MHC loss could be a major contributor for the previously reported loss in the functional integrity of SI muscles . Collectively , these data are consistent with the involvement of pretranslational and translational processes in muscle atrophy due to SI
Our meta analysis of a homogeneous set of studies is the first to provide valuable LLNs for fiber CSA according to fiber type and gender .
Skeletal muscle atrophy is a major systemic impairment in chronic diseases .
Yet its determinants have been hard to identify because a clear research definition has not been agreed upon .
The reduction in muscle fiber cross-sectional area ( CSA ) is a widely acknowledged marker of muscle atrophy , but no reference values for the muscle fiber CSA at the age of the onset of chronic disease have ever been published .