Analysis Tools
mortality/aging
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• mice exhibit a lifespan about 8 weeks shorter than controls
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behavior/neurological
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• mice show a reduction in motor function at 12 and 24, but not 3 or 6, months of age on the rotarod
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• mice show reduced muscle strength at 12 and 24, but not 3 or 6, months of age in the forelimb grip test
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muscle
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• tibialis anterior and gastrocnemius muscle masses are reduced at 12 and 24, but not 3 or 6, months of age
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• tibialis anterior and gastrocnemius muscle masses are reduced at 12 and 24, but not 3 or 6, months of age
• the myofiber cross-sectional area of GA muscle is reduced at 12 and 24, but not 3, months of age
• mice at 12 and 24, but not 3, months of age display shifts in cross-sectional area distribution with a higher frequency of small fibers, indicating muscle atrophy
• however, mice show no obvious alternation of muscle fiber type distribution
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• the compound muscle action potential (CMAP) amplitude ratios of the 10th to first trace at 5-, 20-, or 40-Hz stimulations of the sciatic nerve of TA muscle are reduced, indicating a more pronounced decrement in the CMAP
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• mice show reduced muscle strength at 12 and 24, but not 3 or 6, months of age in the forelimb grip test and twitch and tetanic force tests of hindlimb muscle upon electrical stimulation
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nervous system
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• the ratio of post-versus-pre-synaptic membrane length of synaptic contacts is reduced in NMJs at 12 months of age, indicating impaired organization and complexity of the postsynaptic membrane
• the size and density of junctional folds in the postsynaptic membrane of synaptic contacts is reduced
• terminal Schwann cells exhibit enhanced penetration of their processes into the synaptic clefts, and the synaptic cleft width is increased
• however, densities of mitochondria and synaptic vesicles in the presynaptic motor nerve terminals are normal
• no differences in NMJ morphology are seen at E18.5
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• mice show acceleration of age-related degeneration of neuromuscular junctions (NMJs) as early as 6 months of age, showing increases in the rates of axonal swelling and nerve sprouting at 6, 12, and 24, but not 3, months of age, increases in the rate of denervation at 12 and 24, but not 3 or 6, months of age, reductions in the areas of acetylcholine receptor (AChR) clusters and presynaptic motor nerve terminals at 6, 12, and 24, but not 3 months of age, and in the cover ratios of presynaptic motor never terminals to postsynaptic AChR clusters at NMJs at 12 months of age, but not other ages, and nearly significant difference at 24 months
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• the compound muscle action potential (CMAP) amplitude ratios of the 10th to first trace at 5-, 20-, or 40-Hz stimulations of the sciatic nerve of TA muscle are reduced, indicating a more pronounced decrement in the CMAP
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