(Uncorrected OCR) ABSTRACT Abstract of thesis entitled 'Chondroitin sulphate proteoglycans produced by astrocytes modulate neuron adhesion and neurite outgrowth' submitted by HO Yeung for the degree of Master of Philosophy at the University of Hong Kong in 2000 Several types of proteoglycans were known to be associated with the glial boundary during CNS development and glial scar following CNS injury. The aim of this study is to investigate the role of astroglial proteoglycans, particularly chondroitin sulfate proteoglycans (CSPGs), in modulating neuron adhesion and neurite growth. Neonatal rat cerebral cortical astrocytes as well as an astrocyte cell line DI TNCI were studied for the expression of CSPGs and their effects on neuron adhesion and neurite outgrowth. Immunocytochemical staining with CS-56, a monoclonal antibody against epitopes in the CS moiety of CSPGs, demonstrated the localization of CSPGs on both primary astrocytes and DI TNCI cell line. Immunostaining with anti-neurocan (a neuronal CSPG originally thought) showed pericellular and intracellular distribution in confluent cultures of primary astrocytes but only intracellular distribution in the DI TNCI cells, both being positive for glial fibrillary acidic protein (GFAP). Neurocan was also found deposited by primary astrocytes on the culture substratum. Western blots of the conditioned medium of primary astrocytes indicated a distinct 220 kDa neurocan core protein band. Five immunoreactive bands were also found on Western blots detected with stub-sensitve antibody against C-6-S-PG. Furthermore, RT-PCR analysis indicated the expression of neurocan mRNA in the primary astrocytes. Cortical neural cells (from E18 rats) selectively attached and extended neurites on the primary astrocytes but not on the non-cellular, neurocan immuoreactive gaps left by the astrocytes nor on the DI TNCI cells. Neuronal distribution on astrocytes remained similar even after digestion with chondroitinase or neutralization with antibody, CS-56 or antineurocan. Neurite length on the chondroitinase ABC (20mU/ml) treated astrocytes was however increased. Taken together, these in vitro observations suggest that apart from neurons, astrocytes are another cellular source of brain-specific CSPG, neurocan. They also suggest that CS components expressed on the surface of astrocytes are supportive of neuronal attachment and survival but limiting towards neurite extension. Evidence is also provided for the selective development of embryonic neurons directly on astrocytes and not on neurocan immunoreactive non-cellular routes traversed by astrocytes. 11 / abstract / toc / Biochemistry / Master / Master of Philosophy

No description available.

Morphine is one of the most commonly prescribed medications for the relief of prolonged pain. Both basic science and clinical studies indicate that females require 2-3 times more morphine than males to achieve the same analgesic effect. To date, the mechanisms underlying sex differences in opiate responsiveness are unknown. Recent studies suggest that glial cells are potent modulators of morphine-based analgesia, and in particular, decrease the analgesic effect of opiates. Therefore, we tested the hypothesis that the sexually dimorphic effects of morphine were due to sex differences in glial cell activity. Our studies focused on the midbrain periaqueductal gray (PAG) as this region of the brain is critical for the analgesic effects of morphine. Adult male and female Sprague Dawley rats (250g- 400g) were procured from Charles River Laboratories, and were allowed 7 days to acclimate to the new facility. On the day of the experiment, animals received a subcutaneous injection of morphine (5mg/kg) or were handled in a similar manner. Thirty or 60 minutes after injections or handling, animals were perfused with a 4% paraformaldehyde and 2.5% acrolein tissue fixative solution. Brains were removed and stored in 20% sucrose until ready for sectioning. Brains were sectioned at 25mm using a freezing microtome, and immunohistochemical localization of markers for astrocyte glial cell activity was performed. Antibodies to glial fibrillary acidic protein (GFAP) were used to label activated astrocytes. If our hypothesis is correct, then females will have significantly greater density of the astrocyte cell activity marker GFAP as compared with males. Sex differences in PAG glial cell activity may provide the biological bases for the sexually dimorphic effect of morphine. This research may lead to better treatment for females experiencing prolonged chronic or neuropathic pain.

Introduction: Around a quarter of patients with spinal cord injury develop post traumatic syringomyelia (PTS), causing progressive neurological deficits. Current surgical treatment is unsatisfactory. Endogenous stem cell therapy, aiming at replacing lost tissue and repairing damaged ones by endogenous progenitors, may offer hope. Investigation into the reaction of endogenous progenitors in PTS may extend our knowledge about stem cell biology and help to develop a new treatment option for PTS. Endogenous stem cells were found to differentiate into astrocytes. Reactive astrocytes and gliosis are shown to have an important role in spinal cord injury, such as protecting neurons, limiting inflammation and regulating local environment to suit progenitors. We hypothesize that reactive astrocytes may play an important protective and potential therapeutic roles in PTS. The aim of this thesis is to study proliferation, differentition and location of endogenous progenitors and their roles in PTS. Materials and methods: Excitotoxic injury model of PTS was performed in adult Wistar rats. Proliferating cells were marked by either exogenous mitotic marker bromodeoxyuridine or endogenous mitotic marker Ki67.lmmunofluorescence techniques targeting mitotic markers were used to trace the proliferating cells. Immunofluorescent double staining techniques were used to phenotype the proliferating cells. Results: A large number of endogenous progenitors appear in PTS from 24 hours to at least 8 weeks post injury (PI). They proliferate much faster in PTS than in the control animals. Although less endogenous progenitors are observed after 4 weeks PI, their number is still much higher than that in the control animals. Immediately after injury, progenitors exist mainly in the white matter, but the majority of them shift their position closer to the lesion within 2 days. In the chronic stage, the majority of stem cells are located in and around the lesion site. Endogenous progenitors differentiate into astrocytes but not oligodendrocytes or neurons within 8 weeks. Astrocytes respond to injury by upgrading GFAP (1 day PI), becoming hypertrophic (7 days PI) and forming glial scar (2 weeks PI) in PTS. The development of a glial scar corresponds with the stage of cyst stability or reduction in size. Conclusions: Endogenous progenitors exist in PTS and they respond to injury by proliferating and shifting their position towards the lesion. These studies are important in understanding the endogenous stem cell response to PTS and lay the groundwork for future studies examining stem cell therapy for the condition. Endogenous progenitors in the PTS model differentiate into astrocytes, which help to form the glial scar lining the syrinx. Reactive gliosis may play an important role to seclude the injury site from healthy tissue, prevent a cascading wave of uncontrolled tissue damage and restrict the syrinx enlargement.

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2006. / Härtill 3 uppsatser.

Thesis (Ph. D.)--University of Washington, 1991. / Vita. Includes bibliographical references (leaves [106]-116).

Thesis (Ph. D.)--Virginia Commonwealth University, 2008. / Prepared for: Dept. of Biochemistry and Molecular Biology. Bibliography: leaves 157-174. Also available online via the Internet.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 93-112).

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 98-115). Also available in electronic version. Access restricted to campus users.

Thesis (M. Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 92-107).