Properties of slow- and fast-twitch muscle fibres in a mouse model of amyotrophic lateral sclerosis.

This investigation was undertaken to determine if there are altered histological, pathological and contractile properties in presymptomatic or endstage diseased muscle fibres from representative slow-twitch and fast-twitch muscles of SOD1 G93A mice in comparison to wildtype mice. In presymptomatic SOD1 G93A mice, there was no detectable peripheral dysfunction, providing evidence that muscle pathology is secondary to motor neuronal dysfunction. At disease endstage however, single muscle fibre contractile analysis demonstrated that fast-twitch muscle fibres and neuromuscular junctions are preferentially affected by amyotrophic lateral sclerosis-induced denervation, being unable to produce the same levels of force when activated by calcium as muscle fibres from their age-matched controls.

Isolation and culture of motor neurons from the newborn mouse spinal cord.

A protocol for the isolation and culture of motor neurons from postnatal day 1 mouse spinal cord is described. After 72 h in culture, phase contrast microscopy reveals healthy cells with motor neuronal morphology and extensive neuritic processes. These neurons express the 75-kDa low-affinity neurotrophin receptor (p75NTR) and choline acetyltransferase (ChAT), both proteins are specifically expressed by neonatal and embryonic motor neurons in vivo.