Axonally transported proteoglycans were characterized in terms of their structure, subcellular localization, and possible functions during goldfish optic nerve regeneration. This study confirmed previous findings, that regeneration is correlated with an increase in the $\sp{35}$SO$\sb4$-radioactive labeling of the heparan sulfate and chondroitin sulfate glycosaminoglycan components of proteoglycans. Further, regenerating optic axons appear to transport proportionally more chondroitin sulfate than heparan sulfate, in contrast to intact axons, which favor heparan sulfate. The major change in glycosaminoglycan transport was seen at 21-28 days regeneration, a time of active axon growth and re-formation of synapses. Structural features of chondroitin sulfate, including molecular size, negative charge density, and sulfation site (carbon-4 of N-acetylgalactosamine), and the size of heparan sulfate do not change significantly during regeneration. In contrast, the heparan sulfate isolated from regenerating optic axons appears to have a lower negative charge density and altered sulfation pattern, indicating reduced sulfation. / The distribution of axonally transported proteoglycans among the soluble and membranous compartments of optic axons does not dramatically change with regeneration. However, increased proteoglycan radioactivity was found in each compartment, with the greatest increase in soluble locations. The in vivo findings suggest that the functions of axonally transported proteoglycans during goldfish optic nerve regeneration require increased amounts of chondroitin sulfate proteoglycans of types already present in the intact system, and heparan sulfate proteoglycans with an altered sulfation pattern. / Goldfish retinal explant cultures were used to observe the effects of different proteoglycan-perturbing treatments on retinal axon growth in vitro. Inhibition of proteoglycan synthesis and addition of a high concentration of heparan sulfate to the culture medium of explants reduced axon growth on a poly- scL-lysine substratum, while proteoglycan synthesis inhibition did not alter axon growth on poly- scL-lysine + laminin. This suggests that axonal proteoglycans facilitate outgrowth on poly- scL-lysine, while proteoglycan-laminin interactions are not necessary for regenerative outgrowth. Soluble chondroitin 4-sulfate stimulated axon growth on both substrata. Results support the hypothesis that proteoglycans participate in regenerative retinal axon outgrowth in the goldfish optic system. / Source: Dissertation Abstracts International, Volume: 55-04, Section: B, page: 1314. / Major Professor: John S. Elam. / Thesis (Ph.D.)--The Florida State University, 1994.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_77156 |
| Contributors | Challacombe, Jean Faust., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 205 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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