Neuromuscular dysfunction in the mutant superoxide dismutase mouse model of amyotrophic lateral sclerosis.

To better understand the interaction between motor neuron dysfunction and denervation in amyotrophic lateral sclerosis (ALS), we have evaluated motor neuron number and the retrograde uptake and transport of fluorogold by motor neurons in mice overexpressing mutant superoxide dismutase (mSOD), and wild-type controls. N-CAM immunoreactivity and protein kinase expression were determined in skeletal muscle during denervation. We found that in severely affected mSOD mice, motor neuron loss is moderate (approximate 40% reduction), whereas retrograde uptake/transport as assessed using fluorogold is profoundly impaired (approximately 90% reduction).

Age-related differences in the des IGF-I-mediated activation of Akt-1 and p70 S6K in mouse skeletal muscle.

The ability of des IGF-I to activate Akt-1 and p70 S6K in skeletal muscle with or without acute endurance exercise was examined in young and old mice. Mice were sacrificed 12 h after a moderate intensity treadmill run following an interperitoneal injection of des-IGF-I or saline. Blood and skeletal muscle were collected and IGF-I receptor, Akt-1 and p70 S6K protein contents and their phosphorylation status were determined.

Effects of aging on hepatic IGF-I signaling.

Little is known regarding hepatic insulin-like growth factor-1 IGF-I signaling with aging despite the observation that other tissues demonstrate resistance to IGF-I with aging and declines in liver mass accompany aging. Our aim was to determine if the IGF-I-induced signaling process changes with aging. Young (5 months) and old (24 months) C57BL/6 mice hepatic tissues and blood samples were taken 20 min after an intraperitoneal injection of desIGF-I.