IMAGES

Fiber type classification in the rat diaphragm muscle. Muscle fibers can be classified as type I, IIa, IIx or IIb, using either histochemical stains for myofibrillar ATPase (top panels) or using immunocytochemistry with antibodies specific to different myosin heavy chain isoforms.

Satellite cell activation in diaphragm muscle fibers. Events such as muscle fiber injury may trigger mitotic activation of normally quiescent myonuclei (satellite cells). These satellite cells may fuse with other myonuclei and promote protein synthesis, inducing muscle hypertrophy. Satellite cells may migrate to other fibers, leading to MHC co-expression. New fibers may also be formed via satellite cell activation.

Effect of denervation of myosin heavy chain isoform expression in rat diaphragm muscle. Following denervation, co-expression of MHC isoforms is increased. Muscle fibers predominantly co-express the slow and 2A isoforms. Co-expression is observed along a significant length of the muscle fiber, and may be mediated via satellite cell activation.

3-Color confocal image of axons and neuromuscular junctions on phenotype identified muscle fibers of the adult rat diaphragm. Axons and presynaptic nerve terminals are shown in red, motor endplates in green, and type II (fast-twitch) muscle fibers in blue.

Effect of cervical spinal cord injury on the neuromuscular junction. Junctions on type II (fast-twitch) fibers are selectively enlarged.

Effect of aging on the neuromuscular junction. Junctions on type II(fast-twitch) fibers show enlargement and profuse terminal sprouting.

Effect of cervical spinal cord injury and phrenic nerve blockade on neuromuscular transmission in the rat diaphragm.

Phrenic motoneurons in the adult rat, retrogradely labelled using choleratoxin.