No description available.

No description available.

No description available.

In the <i>Drosophila </i>peripheral nervous system (PNS), neuronal cell fates are specified by a hierarchy of events that are ultimately regulated at the level of transcription. The basic helix-loop helix (bHLH) protein family of transcription regulators are widely implicated throughout development. The first bHLH proteins shown to be involved in neurogenesis were those encoded by the <i>Drosophila achaete-scute</i> complex (AS-C). These are known as proneural genes because they are required during the earliest step of neurogenesis in which naive ectodermal cells are selected to become neural precursors. The AS-C govern the determination of precursors for the external sensory bristles. Another proneural gene, <i>ato</i>, is required for the precursors of the chordotonal organs, photoreceptors and some olfactory sensilla. However, these genes alone do not account for the formation of the rest of the nervous system, thus there must be other proneural candidate genes to be discovered. Furthermore, there is evidence to suggest that other bHLH factors are required throughout neurogenesis, acting in interlinked cascades at each successive level of cell differentiation. These too, have yet to be identified. In the expectation that more <i>Drosophila</i> neural bHLH genes exist, I searched for new genes on the basis of homology to <i>ato.</i> Indeed in this way I identified two new <i>ato</i>-like bHLH proteins. The molecular characterisation, expression and functional analyses of these genes are presented in this thesis. <i>amos</i> (absent MD neurons and olfactory sensilla) is a new proneural gene, required for the selection of neural precursors of larval md neurons and adult olfactory sensilla. On the other hand, <i>cato</i> (cousin of ato), ensures the proper differentiation of the sensory neurons.

No description available.

Under ultraviolet light, massive coral skeletons reveal a series of luminescent bands that can be categorised as "bright" (yellow/green) and "dull" (blue). This work elucidates the photophysical processes that are responsible for the appearance of bright and dull bands. Samples from Papua New Guinea (subject to terrestrial inundation) and Oman (not subject to terrestrial inundation) have been investigated and compared. It has been shown that luminescent banding can be recorded directly from the surface of the coral, without the need for extraction of the component luminophores. Using 3D EEM spectroscopy, the luminescence properties of the bright and dull bands have been reproducibility characterised. Using optical fibre beam delivery, spatial resolution of the banding pattern has been achieved. The variations in intensity of luminescence along the coral core have been recorded with excellent reproducibility. The bright and dull bands observed in all samples contain similar groups of luminophores. The relative intensity of luminescence from each group varies between bands and between samples from different locations. Samples from locations with no terrestrial input exhibit similar luminescence characteristics as those that are regularly inundated with terrestrial run-off. This suggests that luminescent banding is not due solely to the incorporation of terrestrial matter into the coral skeleton. Studies have suggested that the banding pattern is also related to structural variations in the skeleton. It has been established that corals exhibit phosphorescence. The difference is phosphorescence intensity between bright and dull bands is substantially greater than the difference in total luminescence intensity. Hence, phosphorescence is an important indicator of the banding pattern and may prove to be a more valuable tool than luminescence in unravelling the environmental records stored in coral skeletons.

No description available.

No description available.

In this project it has been shown that <I>Myosin heavy chain at 95F (Mhc95F)</I> and the <I>Broad-complex (BR-C) </I>are the target genes of two <I>Gal4 </I>lines which show asymmetric follicle cell expression patterns. <I>Mhc95F, </I>which encodes <I>Drosophila </I>myosin 95F, a class VI unconventional myosin, is expressed in the anterior follicle cells, including the follicle cells undergoing centripetal migration and dorsal-anterior migration. P-element mediated mutagenesis has been undertaken to create mutations in the <I>Mhc95F </I>gene. Several lines showing deletions in the chromosomal 95F region have been obtained. However, no strong evidence shows that the mutant phenotype of these lines and the <I>Mhc95F </I>gene are directly related. Additionally, targeted silencing technique has been used for the study of its function during development. Using a transformed fly line which contains the antisense <I>Mhc95F</I> gene downstream of the Gal4 binding sequences, UAS, to cross with a tissue-specific <I>Gal4</I> line, the progeny exhibit the malformed leg and unexpanded wing phenotype. Moreover, the female progeny from the cross have disrupted centripetal migration of the follicle cells, and degenerated egg chambers. These results indicate that myosin 95F is likely to be involved in cell shape change and cell migration during development. The target gene of line C726b is the <I>BR-C</I>, which encodes a family of zinc-finger transcription factors and plays a key role in metamorphosis. During stage 10b of oogenesis, <I>BR-C</I> mRNA is present in two groups of follicle cells over the lateral-dorsal-anterior ooctye. This expression domain is related to its function in dorsal appendage morphogenesis, and this is confirmed by studying the eggshell phenotype of partial "loss-of-function" <I>BR-C</I> mutants and heat-stock inducible <I>BR-C</I> transgenic fly lines. Expression of the <I>BR-C </I>in the lateral-dorsal-anterior follicle cells is specified by the Gurken/Torpedo(DER) signalling pathway along the D/V axis in a dose-dependent manner.

No description available.