Capillarization and vascular endothelial growth factor expression in hypertrophying anterior latissimus dorsi muscle of the Japanese quail.

Hypertrophy may increase the diffusion distances from capillaries to the interior of the muscle fibers. We hypothesized that capillary proliferation occurs during hypertrophy, which is accompanied by an up-regulation of vascular endothelial growth factor (VEGF). Hypertrophy of the left anterior latissimus dorsi muscle of Japanese quail (2-3 months old) was induced by 1-4 week stretch-overload. Capillarization was analyzed in cross-sections stained for ATPase. VEGF expression was determined with RT-PCR. Initially, hypertrophy was not accompanied by increases in fiber cross-sectional area (FCSA), but after 1 week the average FCSA did increase. The capillary to fiber ratio was decreased after 1 week, but returned to control values in subsequent weeks. This indicates that capillary proliferation occurred, because this model is characterized by extensive fiber proliferation. The absence of any significant change in VEGF mRNA levels indicates that increased levels of VEGF mRNA are not crucial for capillary proliferation during muscle hypertrophy

Apoptosis and Id2 expression in diaphragm and soleus muscle from the emphysematous hamster.

Contains fulltext : 52053.pdf (publisher's version ) (Closed access)During chronic obstructive pulmonary disease (COPD) diaphragm and peripheral muscle weakness occur. Muscle remodeling and wasting may be a result of apoptosis and changes in muscle-specific transcription factors, such as MyoD, altering muscle-specific gene transcription and muscle regenerative capacity. To investigate this, we instilled under ketamine/xylazine anesthesia porcine elastase in the lungs of hamsters to induce emphysema. The emphysematous hamster is an accepted model for COPD. In the diaphragm and peripheral muscles we assessed the occurrence of apoptosis, and in the diaphragm and soleus also the expression of MyoD and inhibitor of differentiation protein 2 (Id2). There was no significant muscle atrophy in emphysematous hamsters. The mRNA levels of TNF-alpha and markers of apoptosis were significantly elevated in the diaphragm and soleus muscles during emphysema. This was accompanied by an increased presence of nucleosomes in the cytosol. Caspase 3 activity and the DNA-binding activity of the p65 subunit of NF-kappaB, however, were unaltered in all muscles. The protein expression of MyoD and Id2 were decreased and increased in the diaphragm and the soleus muscle, respectively. Thus, despite the absence of muscle atrophy in emphysematous hamsters, there was evidence of increased TNF-alpha expression, apoptosis, and altered muscle-specific transcriptional regulation as reflected by decreased MyoD and elevated Id2 levels at least in the soleus and diaphragm muscle. These alterations may impair the regenerative capacity of skeletal muscles and ultimately contribute to muscle wasting

Can Aerobic Training Improve Muscle Strength and Power in Older Men?

This study examined the effect of aerobic training on leg strength, power, and muscle mass in previously sedentary, healthy older men (70-80 yr). Training consisted of 30-45 min of cycle ergometry at 50-70... maximal oxygen consumption (VO2max), 3 times weekly for 16 wk, then 4 wk detraining, or assignment to a nontraining control group (n...12 both groups). Training increased leg strength, leg power, upper leg muscle mass, and VO2max above pretraining values (21..., 12..., 4..., and 15..., respectively; p....05). However, all gains were lost after detraining, except for some gain in VO2max. This suggests that cycle ergometry is sufficient stimulus to improve neuromuscular function in older men, but gains are quickly lost with detraining. For the older population cycle ergometry provides the means to not only increase aerobic fitness but also increase leg strength and power and upper leg muscle mass. However, during periods of inactivity neuromuscular gains are quickly lost