muscle
• gastrocnemius and quadriceps muscles show abundant accumulations resembling nemaline bodies, with less abundance in the masseter, extensor digitorum longus and diaphragm, and none in soleus or tibialis anterior muscles
• aggregates are predominately found in MHC type IIB (fast, glycolytic) fibers
• nemaline bodies are large and irregular
• males show tubular aggregates in skeletal muscles at 9 months of age comparable to those seen in wild-type males at 18 months of age
• core-like structures are present in the oxidative fibers of tibialis anterior and masseter muscles, and occasionally in the quadriceps; core-like structures do not correspond to areas of nemaline body aggregation and are only present in a subset of fibers
• split myofibers are seen in the quadriceps and extensor digitorum longus
• large intermyofibrillar aggregates of mitochondria are seen in a subpopulation of myofibers of skeletal muscles, with variation in mitochondrial size within the aggregates
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• all myofibers containing fast MHC (type IIA, IIB, IIA, and/or IIX) fibers are smaller in the EDL
• all myofibers form the soleus muscle are smaller
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• myofiber size variation is seen in the quadriceps
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• in EDL and soleus, the oxidative fiber types (slow MHC I or fast IIA) are more abundant, while there are fewer fast twitch, glycolytic type II fibers
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• tibials anterior muscle myofibers show a 22% lower mean maximum specific force, a 28% slower mean rate of force redevelopment, and an unaffected maximum unloaded shortening velocity and normal thin filament length
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• twitch contraction times are faster in the extensor digitorum longus (EDL) muscles, however no difference in soleus muscle twitch contraction times is seen
• EDL and soleus muscles show a decrease in normalized force at low stimulation frequencies
• the EDL is more susceptible to eccentric contraction-induced muscle damage than wild-type controls when stretched from 120 to 140% of optimal muscle length during eccentric activation
• EDL muscles are stiffer, with EDL transient stretch response 20% greater than in wild-type mice response during 140% of optimal muscle length stretch
• soleus muscle show a 15% decrease in stiffness during 140% of optimal muscle length stretch
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behavior/neurological
• 6 month old females, but not males, show a deficit in muscle force in the grip strength test
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• females show decreased performance in daily distance, average speed, and maximum speed at 6 months, but not 3 months, in voluntary running wheels
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growth/size/body
• females are smaller than controls at 6 months of age
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Mouse Models of Human Disease |
DO ID | OMIM ID(s) | Ref(s) | |
nemaline myopathy 2 | DOID:0110928 |
OMIM:256030 |
J:285564 |