nervous system
• myelinated nerve fibers in the soleus and medial gastrocnemius are decreased by 12-13% compared to wild-type
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• the interosseous nerve is present at E16.5 but absent after birth
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• golgi tendon organ numbers are decreased in the soleus (by 77%), medial gastrocnemius (by 64%), and extensor hallucis longus (by 26%)
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• in some cases the soleus lacks golgi tendon organs
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• spindle density is increased in dorsal and to a lesser extent in ventral crural muscles
• at P20-22, average spindle number is increased by 57% in the soleus, by 80% in the medial gastrocnemius, and by 26% in the extensor hallucis longus
• however, spindle numbers are decreased in proximal hindlimb muscles with dorsal muscles more severely affected than ventral muscles resulting in an overall decrease in spindle density in the hindlimbs
• about 69% of spindles contain fewer than the normal 4 intrafusal fibers and these spindles also have a shorter capsule and smaller periaxial fluid space
• the missing intrafusal fibers are generally the later forming chain fibers
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• the proprioceptive branch of the soleus muscle nerve has 12% fewer myelinated fibers, innervates more spindles and fewer golgi tendon organs, and contains more group Ia afferents and fewer group Ib afferents
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• absent from the crus at E16.5 - E18.5 and P0 - P1
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• fewer dorsal root ganglion neurons and axonal projections express calbindin 2
(J:75311)
• about a 14% and 23% decrease in neuron numbers are seen in the L4 and L3 dorsal root ganglia, respectively
(J:75311)
• a 25% and 32% decrease in myelinated nerve fiber numbers are seen in the L4 and L3 dorsal root ganglia, respectively
(J:75311)
• only 0.2% of 9400 neuron profiles show calbindin 2 expression compared to 5.6% of 700 neuron profiles in wild-type mice
(J:107207)
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• both L3 and L4 ventral spinal roots contain fewer small caliber motor axons (19% of the myelinated axon population) compared to wild-type mice (38% of the myelinated axon population)
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muscle
• golgi tendon organ numbers are decreased in the soleus (by 77%), medial gastrocnemius (by 64%), and extensor hallucis longus (by 26%)
|
• in some cases the soleus lacks golgi tendon organs
|
• spindle density is increased in dorsal and to a lesser extent in ventral crural muscles
• at P20-22, average spindle number is increased by 57% in the soleus, by 80% in the medial gastrocnemius, and by 26% in the extensor hallucis longus
• however, spindle numbers are decreased in proximal hindlimb muscles with dorsal muscles more severely affected than ventral muscles resulting in an overall decrease in spindle density in the hindlimbs
• about 69% of spindles contain fewer than the normal 4 intrafusal fibers and these spindles also have a shorter capsule and smaller periaxial fluid space
• the missing intrafusal fibers are generally the later forming chain fibers
|