Mark Willard

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We report here certain properties of three polypeptides that are rapidly transported in greatly increased amounts during the regeneration of toad optic nerves. All three of these growth-associated polypeptides (GAPs) are associated with a membrane(s) with a buoyant density similar to the plasma membrane. Since none of these GAPs are solubilized(More)
In an effort to understand the regulation of the transition of a mature neuron to the growth, or regenerating, state we have analyzed the composition of the axonally transported proteins in the retinal ganglion cells of the toad Bufo marinus after inducing axon regeneration by crushing the optic nerve. At increasing intervals after axotomy, we labeled the(More)
In an effort to determine whether the "growth state" and the "mature state" of a neuron are differentiated by different programs of gene expression, we have compared the rapidly transported (group I) proteins in growing and nongrowing axons in rabbits. We observed two polypeptides (GAP-23 and GAP-43) which were of particular interest because of their(More)
We analyzed the subcellular distributions of proteins that are transported down the axons of rabbit retinal ganglion cells and compared these distributions to those of enzyme markers for endoplasmic reticulum, plasma membrane, and mitochondria. The proteins of each of five previously identified transport groups were uniquely distributed through the(More)
Using a method of gradient gel electrophoresis coupled with autoradiography, we have analyzed the polypeptide composition of the proteins being transported down the axons of the projecting neurons of the rabbit retina. This analysis reveals: (1) the molecular weight distribution of 43 transported polypeptides; (2) the existence of at least four components(More)
Clinical interventions that accelerate conversion of cholesterol to bile acids reduce circulating low density lipoprotein (LDL) cholesterol concentrations. The initial and rate-limiting step in the bile acid biosynthetic pathway is catalyzed by hepatic cholesterol 7 alpha-hydroxylase. To examine the effects of transient primary overexpression of this enzyme(More)
Two polypeptides (M1 and M2) which co-sediment with F-actin in an ATP-reversible way have been detected in extracts of tissue from the rabbit visual system. Both polypeptides resemble skeletal muscle myosin in their ATP-sensitive co-sedimentation with actin, while they resemble the heavy chain of myosin and the lighter polypeptide of erythrocyte spectrin in(More)
This study was undertaken to determine the effect of transient overexpression of hepatic cholesterol 7alpha-hydroxylase on low density lipoprotein (LDL) cholesterol transport in mice lacking LDL receptors (LDL receptor-/-). Primary overexpression of hepatic 7alpha-hydroxylase in LDL receptor-/- mice was accompanied by a dose-dependent decrease in the rate(More)
Hepatic 7alpha-hydroxylase activity appears to be regulated at the transcriptional level by the quantity of bile salts fluxing through the enterohepatic circulation. Whether bile salts directly suppress 7alpha-hydroxylase expression at the level of the hepatocyte or do so indirectly by promoting the release or absorption of an intestinal factor has not been(More)