Analysis Tools
growth/size/body
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• the anterior scalene muscle at 1 to 1.5 years of age show dystrophic changes similar to those of the diaphragm at 6 months of age
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muscle
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• from 2 weeks of age in both type 1 and 2 fibers of the extensor digitorum longus and soleus
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• regenerating fibers, with central nuclei, are most abundant around 35 to 39 days of age when they are approximately 30% of the extensor digitorum longus and 50% of the soleus
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• the anterior scalene muscle at 1 to 1.5 years of age show dystrophic changes similar to those of the diaphragm at 6 months of age
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• the extensor digitorum longus, but not the soleus, at 32 weeks of age has a greater proportion of fast-twitch-oxidative-glycolytic fibers and a smaller proportion of fast-twitch-glycolytic fibers than controls
(J:152749)
• electron microscopy shows an accumulation of small pools of non-membrane-bound glycogen from 14 days of age on in both type 1 and type 2 fibers, and membrane-bound vacuoles of variable size and form with finely granular contents are found beginning at 2 weeks of age in the type 1 fibers of the soleus but not extensor digitorum longus
(J:152892)
• at 15 days of age necrotic fibers are found, occassionally in clusters, at 20 days of age necrotic fibers are numerous as are groups of regenerating fibers with internally placed nuclei, necrotic fibers are most numerous between 30 and 60 days of age and gradually dissapear although a few scattered necrotic fibers are present at 120 and 180 days of age, and the regenerating fibers increase in size after 30 days of age and almost all of the fibers have internally placed nuclei by 60 to 120 days of age, but there is almost no fibrous tissue proliferation or adipose tissue replacement
(J:152525)
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• at 32 weeks of age in the soleus fast-twitch-oxidative-glycolytic fibers have a larger cross-sectional area than those of controls
(J:152749)
• at 32 weeks of age in the extensor digitorum longus muscle both the slow-twitch-oxidative and fast-twitch-glycolytic fibers have a larger cross-sectional area than those of controls
(J:152749)
• although the number of fibers is normal, the cross-sectional area of the fibers of the tibialis anterior is larger than normal at 3 and 6 months of age
(J:19034)
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(J:152525)
• peripherally nucleated fibers replace the normal fibers in the tibialis anterior, extensor digitorum longus, plantaris, and soleus in a progressive manner, reaching a plateau of 80-90% of fibers at 26 weeks of age
(J:19034)
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• unlike skeletal muscle, the diaphragm undergoes progressive degeneration without regeneration such that, although at 30 days of age foci of myofiber degeneration, necrosis, mineralization, and regeneration are present but not extensive, at 6 months of age the diaphragm has a wide variation in myofiber size and architecture, continued necrosis and connective tissue proliferation, and at 16 months of age the diaphragm is pale due to the extensive myofiber loss and replacement fibrosis and the remaining fibers are ensheathed in dense collagenous tissue with most having architectural aberrations
• at 16 months of age there are twice normal levels of slow myosin in the diaphragm, a decrease in isometric force generation, and a shortened fiber length
• at 1.5 years of age the diaphragm is found to have significantly reduced passive stretch capacity although overt respiratory compromise is not found in aging mutants
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• the intercostal muscles at 1 to 1.5 years of age have dystrophic changes similar to those of the diaphragm at 6 months of age
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• the cross-sectional area and wet weight of the tibialis anterior is greater than normal by 10 weeks of age
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• detectable up to 12 months of age but not at 15 months of age, at which point muscle fibers appear atrophied and extensively split
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• found with age in the soleus and plantaris
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• by 28 days of age necrosis and phagocytosis, with rounded off and swollen mitochondria in the necrotic fibers, is widespread, but is rare at 21 days of age
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• although younger homozygotes do not have fat or fibrous connective tissue in the skeletal muscles, by 270 days of age some fibrous connective tissue is found
(J:152892)
(J:152525)
• scattered foci of necrotizing fibers surrounded by cellular infiltration can be found in soleus and plantaris muscles as early as 14 days of age, and subsequently in the tibialis anterior, and lastly the extensor digitorum longus with foci of basophilic myotubes being found from 4 weeks of age on
(J:19034)
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• in skeletal muscle fibers myosin magnesium-ATPase activity is higher than normal, myosin B ATPase activity is higher than normal in low free calcium concentrations, and rapid phosphate liberation by magnesium-ATPase is lower than normal
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• satellite cell mitosis is found at 14 days of age and by 28 days increased satellite cells are found in healthy appearing fibers but frequently adjacent to necrotic fibers
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• scattered hypercontracted fibers are found by electron microscopy at 10 days of age
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• at 23 degrees hemidiaphragm preparations show lower than normal resting membrane potentials and insertion of a glass microelectrode into a single muscle fiber results in repetitive bursts of muscle action potentials in 30 to 50% of fibers, while at 37 degrees only 7.8% of muscle fibers display this electrical myotonia and the resting membrane potentials are normal
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• at 4 weeks of age the soleus muscle has decreased twitch and tetanus tension compared with controls, but this is normal by 32 weeks of age
• at 3 and 32 weeks of age the extensor digitorum longus muscle has decreased twitch and tetanus tension and faster time-to-peak twitch tension compared with controls and the maximum velocity of unloaded shortening is also decreased at 32 weeks of age
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homeostasis/metabolism
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• injection of the gastrocnemius muscle with chlorpromazine results in a less destruction of calmitine than in controls (20% versus 40%) and has less of an impact on calcium binding to calmitine
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vision/eye
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• nuclear opacity of the lens is found at 1 day of age
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• a slight anterior subcapsular opacity is seen at 4 days of age, which spreads anteriorly such that at 150 days of age there is complete anterior subcapsular opacity in addition to the nuclear opacity
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nervous system
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N |
• at 8 weeks of age miniature endplate potential frequency, the quantal content of endplate potentials, the amplitude and time course of miniature endplate currents, and the number of acetylcholine receptors at the postsynaptic membrane are all normal
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• although the nerve terminal innervation of epitronchleoanconeus muscle is normal, the terminal architecture of regenerated muscle fibers, those with central nuclei, are more complex than normal with an increase in the number of fine terminal aborizations, many of which have bouton-like swellings and, rather than the normal confluent pattern at postsynaptic regions, staining of acetylcholine receptors is found in numerous small spots corresponding to the boutons on the motor axon terminals with acetylcholinesterase staining in close association
• electron microscopy shows that neuromuscular junction postsynaptic membranes are variably simplified with a reduction in the number of secondary synaptic folds
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cellular
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• from 2 weeks of age in both type 1 and 2 fibers of the extensor digitorum longus and soleus
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• satellite cell mitosis is found at 14 days of age and by 28 days increased satellite cells are found in healthy appearing fibers but frequently adjacent to necrotic fibers
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