To re-establish neuronal circuits lost after CNS injury, transplanted neurons must be able to extend axons toward their appropriate targets. Such growth is highly restricted within the adult CNS attributable to the expression of inhibitory molecules and general lack of guidance cues to direct axon growth. This environment typically induces random patterns of growth and aberrant innervation, if growth occurs at all. To target the growth of axons from neuronal transplants, we are using viral vectors to create guidance pathways before neuronal transplantation. In this study, we transplanted postnatal rat dorsal root ganglia neurons into the corpus callosum of adult rats. Replication-incompetent adenoviruses encoding growth or guidance factors were injected along the desired pathway 1 week before cell transplantation, allowing time for sufficient protein expression by host glial cells. With expression of nerve growth factor (NGF) and basic fibroblast growth factor, sensory axons were able to grow along the corpus callosum, across the midline, and toward an NGF-expressing target in either the contralateral striatum or cortex: a distance of 7-8 mm including a 90°turn from white matter into gray matter. Furthermore, expression of semaphorin 3A slightly dorsal and lateral to the turning point increased the number of axons turning into the striatal target. These results show that judicious expression of neuron-specific chemoattractant and chemorepellant molecules using viral vectors can support and target axon growth from neuronal transplants in the adult CNS.

Scavenger receptor class B type I (SR-BI) delivers cholesterol ester from HDL to cells via a selective uptake mechanism, whereby lipid is transferred from the core of the particle without concomitant degradation of the protein moiety. The precise metabolic fate of HDL particles after selective lipid uptake is not known. To characterize SR-BImediated HDL processing in vivo, we expressed high levels of this receptor in livers of apoA-I Ϫ / Ϫ mice by adenoviral vector gene transfer, and then injected the mice with a bolus of human HDL 2 traced with 125 I-dilactitol tyramine. HDL recovered from apoA-I Ϫ / Ϫ mice over-expressing SR-BI was significantly smaller than HDL recovered from control mice as measured by non-denaturing gel electrophoresis. When injected into C57BL/6 mice, these HDL "remnants" were rapidly converted to HDL 2 -sized lipoprotein particles, and were cleared from the plasma at a rate similar to HDL 2 . In assays in cultured cells, HDL remnants did not stimulate ATP-binding cassette transporter A1-dependent cholesterol efflux. When mixed with mouse plasma ex vivo, HDL remnants rapidly converted to larger HDL particles. These studies identify a previously ill-defined pathway in HDL metabolism, whereby SR-BI generates small, dense HDL particles that are rapidly remodeled in plasma. This remodeling pathway may represent a process that is important in determining the rate of apoA-I catabolism and HDL-mediated reverse cholesterol transport. Numerous epidemiological studies have indicated that HDL cholesterol (HDL-C) and apoA-I concentrations are inversely correlated to the risk for coronary heart disease. Consequently, much effort has been focused on the factors that regulate plasma HDL and apoA-I levels. Metabolic studies in humans have shown that variations in HDL-C and apoA-I concentrations are primarily associated with differences in the rate of apoA-I catabolism rather than apoA-I production (1-5). Many of the factors known to influence apoA-I catabolic rate have a major effect on the lipid composition of the HDL particle. For example, the accumulation of cholesterol ester (CE) in HDL (brought about in humans by a deficiency in CETP) is associated with delayed apoA-I catabolism (6). Conversely, LCAT deficiency, which results in a depletion of HDL CE, is associated with accelerated apoA-I catabolism (7). Accumulating evidence suggests that the kidney cortex is an important site for degrading lipid-poor apoA-I, perhaps through glomerular filtration followed by degradation in the proximal tubule. Cubilin, an endocytic receptor that is expressed on the apical surfaces of kidney proximal tubule cells, has been implicated in renal uptake of lipid-poor HDL (8, 9).Scavenger receptor class B type I (SR-BI) is an HDL receptor that mediates selective lipid uptake from receptor-bound HDL. During this process, CE is transferred from the core of the HDL particle to cells without the concomitant degradation of HDL apolipoproteins. Despite the fact that SR-BI mediates only CE uptake, liver-specific SR-BI o...

Different experimental and clinical strategies have been used to promote survival of transplanted embryonic ventral mesencephalic (VM) neurons. However, few studies have focused on the long-distance growth of dopaminergic axons from VM transplants. The aim of this study is to identify some of the growth and guidance factors that support directed long-distance growth of dopaminergic axons from VM transplants. Lentivirus encoding either glial cell line-derived neurotrophic factor (GDNF) or netrin-1, or a combination of lenti-GDNF with either lenti-GDNF family receptor α1 (GFRα-1) or lenti-netrin-1 was injected to form a gradient along the corpus callosum. Two weeks later, a piece of embryonic day 14 VM tissue was transplanted into the corpus callosum adjacent to the low end of the gradient. Results showed that tyrosine hydroxylase (TH+) axons grew a very short distance from the VM transplants in control groups, with few axons reaching the midline. In GDNF or Netrin-1 expressing groups, more TH+ axons grew out of transplants and reached the midline. Pathways co-expressing GDNF with either GFRα-1 or netrin-1 showed significantly increased axonal outgrowth. Interestingly, only the GDNF/netrin-1 combination resulted in the majority of axons reaching the distal target (80%), whereas along the GDNF/GFRα-1 pathway only 20% of the axons leaving the transplant reached the distal target. This technique of long-distance axon guidance may prove to be a useful strategy in reconstructing damaged neuronal circuits, such as the nigrostriatal pathway in Parkinson’s disease.

In the Empress Leilia butterfly, Asterocampa leilia, as in many insects, males have larger eyes than females. We explore the morphological causes and consequences of this dimorphism in eye size by comparing the corneal surface area, facet numbers, and patterns of variation in facet dimensions in males and females. We report that, with body size (measured by forewing length) controlled, male eyes are consistently larger than female eyes, and that, although males and females do not differ significantly in the number of facets per eye, males have significantly larger facets. Also, males have disproportiontely larger facets both frontally and dorsally. As a result of these sexual differences in eye structure, males are expected to have a larger and more acute visual field than females which could be advantageous in the context of this species' mate searching tactic.

Our previous studies showed that axonal outgrowth from dorsal root ganglia (DRG) transplants in the adult rat brain could be directed toward a specific target location using a preformed growthsupportive pathway. This pathway induced axon growth within the corpus callosum across the midline to the opposite hemisphere. In this study, we examined whether such pathways would also support axon growth either through or around a lesion of the corpus callosum. Pathways expressing GFP, NGF, or FGF2/NGF were set up by multiple injections of adenovirus along the corpus callosum. Each pathway included the transplantation site in the left corpus callosum, 2.8 mm away from the midline, and a target site in the right corpus callosum, 2.5 mm from the midline. At the same time, a 1 mm lesion was made through the corpus callosum at the midline in an anteroposterior direction. A group of control animals received lesions and Ad-NGF injections only at the transplant and target sites, without a bridging pathway. DRG cell suspensions from postnatal day 1 or 2 rats were injected at the transplantation site three to four days later. Two weeks after transplantation, brain sections were stained using an anti-CGRP antibody. The CGRP-positive axons were counted at 0.5 mm and 1.5 mm from the lesion site in both hemispheres. Few axons grew past the lesion in animals with control pathways, but there was robust axon growth across the lesion site in the FGF2/NGF and NGFexpressing pathways. This study indicated that preformed NGF and combination guidance pathways support more axon growth past a lesion in the adult mammalian brain.