Skeletal muscle differentiation, maturation, and regeneration are regulated by interactions between signaling pathways activated by hormones and growth factors, and intrinsic genetic programs controlled by myogenic transcription factors, including members of the MyoD and myocyte enhancer factor 2 (MEF2) families. Insulin-like growth factors (IGFs) play key roles in muscle development in the emb...

We applied K-means cluster analysis to test the hypothesis that muscle-specific factors known to modulate protein synthesis and satellite cell activity would be differentially expressed during progressive resistance training (PRT, 16 wk) in 66 human subjects experiencing extreme, modest, and failed myofiber hypertrophy. Muscle mRNA expression of IGF-I isoform Ea (IGF-IEa), mechanogrowth factor ...

Insulin resistance in skeletal muscle is an early event in the development of diabetes, with obesity being one of the major contributing factors. In vitro, conditioned medium (CM) from differentiated human adipocytes impairs insulin signaling in human skeletal muscle cells, but it is not known whether insulin resistance is reversible and which mechanisms may underlie this process. CM induced in...

Muscle wasting is a critical feature of patients afflicted by acquired immune deficiency syndrome (AIDS), cancer, or chronic inflammatory diseases. In a mouse model of muscle wasting, TNF-alpha induces oxidative stress and nitric oxide synthase-2 (NOS2) and decreases myogenin, Jun-D, and creatinine kinase muscle isoform (CKM) expression. Here, we studied 12 patients with muscle wasting due to c...

The current-producing cells of the electric organ, i.e., electrocytes, in Sternopygus macrurus derive from skeletal muscle fibers. Mature electrocytes are not contractile, but they do retain some muscle proteins, are multinucleated, and receive cholinergic innervation. Electrocytes express the myogenic regulatory factors (MRFs) MyoD, myogenin, Myf5 and MRF4 despite their incomplete muscle pheno...

BACKGROUND Although muscle dysfunction caused by unfamiliar lengthening contraction is one of most important issues in sports medicine, there is little known about the molecular events on regeneration process. The purpose of this study was to investigate the temporal and spatial expression patterns of myogenin, myoD, pax7, and myostatin after acute lengthening contraction (LC)-induced injury in...

During the development of skeletal muscle, myoblasts withdraw from the cell cycle and differentiate into myotubes. The insulin-like growth factors IGF-I and IGF-II, through their cognate tyrosine kinase receptor (IGF-I receptor), are known to play a role in this process. After withdrawal of myoblasts from the cell cycle, IGF-I promotes muscle differentiation by inducing the expression or activi...

A unique pattern of expression of the four muscle regulatory factor (MRF) proteins was found to distinguish early somitic from embryonic, fetal and newborn limb myogenic cells in vitro. Expression of the myosin heavy chain (MHC), MyoD, myogenin, Myf-5, and MRF4 proteins was examined by immunocytochemistry in cultures of four distinct types of mouse myogenic cells: somitic (E8.5), embryonic (E11...

The spatio-temporal expression patterns of mRNA transcripts coding for acetylcholine receptor (AChR) subunits and myogenic factors were measured in denervated rat soleus muscle and in soleus muscle chronically paralyzed for up to 12 d by conduction block of the sciatic nerve by tetrodotoxin (TTX). In denervated muscle the AChR alpha-, beta-, gamma-, and delta-subunit mRNAs were elevated with hi...