For the successful establishment of secondary tumours, blood-borne metastatic tumour cells must adhere and spread on the vascular endothelium before they can migrate through it to form secondary growths in the tissue beneath. In this study an in vitro assay was developed to study the behavourial interactions between B16F10 cells and Bovine aortic endothelial cells. It was hypothesized that molecules synthesized by the endothelial cells may be involved in the mediation of the adhesion, spreading and migration events and hence that such molecules may possibly be involved in the process of haematogenic metastasis. Endothelial derived extracts were obtained from the cell surface and from conditioned medium. The extracts were tested for their adhesion promoting abilities in a quick dot blot adhesion assay. To verify that these molecules promoted adhesion, antibodies were raised against the extracts. Partial characterisation of the molecules was achieved using SDS-PAGE and immunoprobing. The extracts were also tested for their spreading and migration promoting properties. An attempt was made to block the adhesion, spreading and migration events using antibodies directed against components of the extracts. Clearly, if endothelial-derived molecules are involved in metastasis, then preventing the mediation of adhesion, spreading and migration may ultimately have relevance in the clinical situation.

The investigation into the mechanisms by which compounds such as butyrate induce differentiation in HT-29 cells, is lacking. The colonic carcinoma cell line, HT-29, undergoes differentiation induction in the presence of butyrate and acetoacetate. The Caco-2 cell line spontaneously differentiates on contact inhibition. In this study, a signal transduction pathway involving ATP, cAMP, Ca2+ and the transcriptional factor CREB was investigated following suggestions that the energy state of the cell and diffferentiation are linked. The activity of the MAP kinase cascade, including possible crosstalk that may exist between these pathways was determined. The HT-29 cells were exposed to 5 mM acetoacetate, butyrate, DMSO and propionate. The results of this differentiation induction were compared to Caco-2 and HeLa cells, which are cervical carcinoma cells. It was found that ATP levels are decreased on differentiation induction in HT-29 cells, which, in turn affected the cAMP concentrations. Theoretically, the inducers do not have any effect on PDE 4 activity, and may facilitate the interaction between cAMP and PKA. Influx of Ca2+ into the cells was inhibited to a degree by the inducers, which was possibly overcome by crosstalk between the cAMP and Ca2+ pathways. CREB activation, lineage-specific gene expression, ERK activity and c-myc expression were all dependent on both the inducers used and the cell-type. PKA played a major role in CREB activation in acetoacetate- and butyrate -induced HT-29, Caco-2 and HeLa cells, while a2+/Calmodulin-dependent kinases I/IV may have a secondary role. Alkaline phosphatase expression in HeLa cells was independent of CREB. Evidence that crosstalk between the MAP kinase cascade and the REBactivation pathways exist, was illustrated by increased CREB activation on ERK inhibition in acetoacetate- and butyrate-induced HT-29 and HeLa cells. Also, the role that ERK played in the cells differed with inducer and cell-type. The dependence of cmyc expression on c-jun and c-fos, appeared to be differentiation induction- and celltype specific. Results from this study indicate the potential use of acetoacetate and butyrate as anti-cancer compounds.

The effects of stalk cell differentiation inducing factor (DIF) on stalk cell induction from vegetative cells and prestalk cells of Dictyostelium discoideum were investigated. It was found that the major DIF component DIF-1 is a poor inducer of stalk cell formation from prestalk cells, but a minor component, DIF-2 is a more important inducer for the conversion of prestalk to stalk cells. Evidence is presented that DIF-2 synergizes the activity of the other DIF components for prestalk to stalk cell conversion. In contrast DIF-5 inhibits the activity of DIF-1 and DIF-3/4. A model is proposed to explain those results. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

A leukemia Differentiation Factor (DF), that induced differentiation of rat leukemia MIA C51 cells, was isolated from endotoxin-stimulated rat lung conditioned media.

In this study, ADP-ribosylation reactions in the murine myelomonocytic cell line WEHI-3BD+ were investigated.

No description available.

published_or_final_version / Medicine / Master / Master of Philosophy

This study elucidates the temporal expression and regulation of transglutaminase (TGase) and ornithine decarboxylase (ODCase) during cell proliferation and differentiation. In synchronized CHO cells, there were two peaks of TGase activity expressed in G₁ and a smaller peak of activity in mid S phase. ODCase exhibited a single peak of expression in mid G₁ which was inhibited by the administration of both cycloheximide and actinomycin D. In contrast, the increase in TGase activity was not inhibited at any time measured by administration of either cycloheximide or actinomycin D to these cells. TGase activity in CHO cells was not affected by the addition of analogs of cyclic AMP, whereas ODCase activity was increased at all times measured. Retinol administration increased TGase activity 1 hr after release in CHO cells and the activity remained elevated for 4 hr. Retinol administration resulted in the inhibition of ODCase expression in these cells. The administration of α-melanocyte-stimulating hormone (MSH) to mouse melanoma cells resulted in a biphasic increase of TGase activity and a single peak of ODCase activity within 7 hr. In melanoma cells, addition of cycloheximide abolished the first peak of TGase activity but not the second peak. Actinomycin D did not inhibit either peak of TGase expression. The administration of both cycloheximide and actinomycin D inhibited ODCase activity after MSH stimulation. Analogs of cyclic AMP, when added to log phase mouse melanoma cells, increased ODCase but not TGase activity at all points measured. In these cells, retinoic acid plus MSH markedly enhanced the activity of the initial TGase peak compared to MSH alone. ODCase expression was attenuated with retinoic acid plus MSH. Dexamethasone (DEX) induced the first peak of TGase activity but not the second peak seen with MSH administration alone. Administration of DEX resulted in a peak expression of ODCase activity approximately 30% of that seen with MSH alone. In general, chelation of extracellular calcium with EGTA totally blocked ODCase expression with MSH, retinoic acid or DEX. Partial or total ablation of TGase expression was seen with addition of MSH or retinoic acid, but very little inhibition of this enzyme was evident when EGTA was added with DEX or DEX plus MSH. Addition of calcium after all CA⁺⁺-blocks restored the expression of both enzymes.

No description available.

No description available.