Associate Professor of Rehabilitation Medicine
Affiliate Scientist, Yerkes Regional Primate Research Center
Ph.D., University of Illinois, 1974
Program: Neuroscience (NS)
The neuromuscular junction is a very stable synapse that changes shape
little during the lifetime of an individual. Under a number of different
conditions, new neuritic processes are induced to grow from the synaptic
terminal at the junction. These are known as sprouts. My lab is investigating
the role played by a Scwann cell peptide, ciliary neurotrophic factor (CNTF),
in the production of motoneuron sprouts. These experiments are based
on our finding that in mice lacking the gene for CNTF, motoneuron sprouting
is not found, but that exogenous CNTF restores this ability.
Sprout at an adult neuromuscular synapse. The motor nerve
terminals at these two neuromuscular junctions are stained green by binding
of an antibody to the high molecular weight neurofilament protein.
The motor endplates on the postsynaptic muscle fibers are marked by the
binding of tetramethylrhodamine conjugated alpha bungarotoxin (red).
The synapse on the left contains a sprout.
In cut or injured peripheral nerves, the axons of motoneurons are capable
of extensive regeneration, through a process known as regenerative sprouting.
However, these regenerating axons frequently make synaptic connections
with inappropriate or multiple target muscles, and this loss of specificity
leads to poor functional recovery. We are attempting to determine
the mechanisms by which regenerating axons are stimulated to grow and the
factors involved in choosing both peripheral pathways and synaptic partners.
It is widely held that motoneurons determine the phenotypes of the
muscle fibers they innervate. This important interaction between motoneurons
and the musculoskeletal system is based on the activity of the motoneurons.
My laboratory is studying a naturally-occuring change in fiber phenotype
in the rabbit jaw muscles that is induced by androgenic hormones. We are
investigating the role of motoneuron activity in this process, how motoneurons
are influenced by these hormones, and what functional consequences they
impose.
The
effects of testosterone on contractile protein expression in the rabbit
masseter muscle. Castrated animals were given testosterone for 3
or 6 weeks and myosin heavy chain isoform content sampled after 3, 6, and
9 weeks using immunoblotting. The hormone induced a dramatic change in
isoform content that lasted well past the cessation of treatment.
Recent Publications: