Bt. Himes et al., GRAFTS OF FETAL CENTRAL-NERVOUS-SYSTEM TISSUE RESCUE AXOTOMIZED CLARKE NUCLEUS NEURONS IN ADULT AND NEONATAL OPERATES, Journal of comparative neurology, 339(1), 1994, pp. 117-131
Many conditions are thought to contribute to neuron death after axotom
y, including immaturity of the cell at the time of injury, inability t
o reestablish or maintain target contact, and dependence on trophic fa
ctors produced by targets. Exogenous application of neurotrophic facto
rs and transplants of peripheral nerve and embryonic central nervous s
ystem (CNS) tissue temporarily rescue axotomized CNS neurons, but perm
anent rescue may require transplants that are normal targets of the in
jured neurons. We examined the requirements for survival of axotomized
Clarke's nucleus (CN) neurons. Two months after hemisection of the sp
inal cord at the T8 segment, there was an ipsilateral 30% loss of neur
ons at the Ll segment in adult operates and a 40% loss in neonates. Tr
ansplants of embryonic spinal cord, cerebellum, and neocortex inserted
into the T8 segment at the time of hemisection prevented virtually al
l of the cell death in both adults and neonates, but transplants of em
bryonic striatum were ineffective. None of the grafts prevented the so
mal atrophy of CN neurons caused by axotomy. Retrograde transport of f
luoro-gold from the cerebellum demonstrated that 33% of all CN neurons
at Ll project to the cerebellum, 50% of these died following a T8 hem
isection, but all these projection neurons were rescued by a transplan
t of embryonic spinal cord. These results suggest that the rescue of a
xotomized CN neurons is relatively specific for the normal target area
s of these neurons, but this specificity is not absolute and may depen
d on the distribution and synthesis of particular neurotrophic agents.
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