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This dissertation, Ultrastructural and Stereological Investigation of the Effects of Hexamethylene Bisacetamide on Human Colon Carcinoma LoVo Cells in Vitro by 劉汝這, Yue-huen, Thomas, Lau, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract Abstract of thesis entitled Ultrastructural and Stereological Investigation of the Effects of Hexamethylene Bisacetamide on a Human Colon Carcinoma LoVo Cells In Vitro submitted by Thomas Yue-Huen LAU for the degree of Master of Philosophy at The University of Hong Kong, Hong Kong, S.A.R., P.R. China in May, 2000. Hexamethylene bisacetamide (HMBA), a synthetic cytodifferentiation agent, has shown induction effects on murine erythroleukemic cell lines (MELC) to terminal differentiation. Little is known about the biological effect of HMBA on solid tumours including their metastatic counterparts to distant organs. The aim of the present study was to determine the effects of HMBA on the morphology of a metastatic human colon carcinoma cell line (LoVo) using electron microscopy and stereological method. Using cell culture techniques, 2mM and 4mM of HMBA were administered to the LoVo cells for a period of 7 days and then for another 3 days with fresh culture medium without HMBA. LoVo cells in the control flasks were not exposed to HMBA. Cell numbers were estimated on days 0, 1, 3, 5, 7 and 10 using MTT assay and haemocytometry. Viable cells were processed for light and electron microscopy. The biological effects of HMBA exerted on the LoVo cells were time and concentration dependent manner. Progressive growth iinhibition of the LoVo cells was obtained by 2mM and 4mM HMBA treatment during the first 7 days of culture. Cell viability showed that the inhibitory effect of 4mM HMBA on LoVo cell growth was more potent than 2mM HMBA when compared with the control group. The inhibitory effect of HMBA on LoVo cells was reversible since cell proliferation resumed in both HMBA treated groups after its withdrawal on day 7. After HMBA withdrawal, the resumption in LoVo cell proliferation was more pronounced in the 2mM HMBA- treated group than the 4mM HMBA-treated group when compared with the control group. The ultrastructural changes of the LoVo cells during the HMBA treatment period were cytoplasmic blebbing, cell membrane irregularity, heterochromatin condensation and nucleolar inconspicuity in the HMBA-treated LoVo cells. These alterations were reverted to resemble LoVo cells in the control group after HMBA withdrawal from the culture medium. However, qualitative observations of the HMBA-treated LoVo cells showed no evidence of a more differentiated cell phenotype towards terminal differentiation. There was ultrastructural evidence of induction of apoptosis in LoVo cells in both HMBA-treated cells. Stereological analysis of the HMBA treated LoVo cells showed reduction in the cytoplasmic (V ) volume and slight reduction in the CYT nuclear volume (Vv ) in the early stage of HMBA treatment period NUC (day 0 - day 3). The reduction in cell volume (V ) and nucleolar CELL volume (V ) was more pronounced in the 4mM HMBA-treated group NC iithan the 2mM HMBA-treated group. The surface area of the plasma (S ) and nuclear (S ) membranes of the HMBA treated LoVo cells CELL N were in phase with their volumetric alterations. At the later stage of the HMBA treatment period on day 7, a significant increase in V CELL and V was detected in the HMBA-treated LoVo cells without CYT significant alteration in Vv heterochromatin volume (V ) and NUC, HET euchromatin volume (V ). There was also no significant alteration in EU th

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