No description available.

No description available.

In an investigation of intergeneric and interspecific relationships within the Asteraceae-Anthemideae, chromosome numbers were determined in 98 taxa (species, subspecies or varieties) from 27 genera, and chromosome morphology was also studied in many cases. The chromosome numbers of Mania tibetica, Anthemis chrysantha, A. melanoloma, Artemisia argentea, Handelia trichophylla, Lasiospermum bipinnatum, and Lepidolopha filifolia (all 2n=18) and of L. karatavica (2n=36-38) and Achillea depressa (2n=54) had not been reported previously. Wild tetraploid (2n=36) populations of Chamomilla recutita were found for the first time. Further cytological studies including a detailed analysis of meiosis were made in 12 species from the genera Anacyclus, Anthemis, Chrysanthemum and Piatricaria; aneuploidy was studied in Anthemis cotula, M. maritime and Matricaria perforate, the occurrence and meiotic behaviour of B chromosome was studied in Matricaria maritime, and a series of high polyploidm (from 5x to 8x) were studied in M. perforate. Nineteen different artificial intercytotype, interspecific and intergeneric F1 hybrid combinations within and between the genera Anthemis, Chamaemelum and Matricaria were obtained. Eleven of these had not been previously reported or studied. Meiotic chromosome behaviour was studied in these hybrids. Morphological studies of the hybrids and their parents were also made, including SEM studies of the achenes that revealed some new and distinctive micromorphological features in Anthemis.

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No description available.

No description available.

Heparan sulphate proteoglycans (HSPGs) are cell surface molecules that act as co- . receptors for a number of important signalling ligands such as the fibroblast growth factors (FGFs). The Sulf-l enzyme was recently identified by Dhoot et aL, (2001) as a modifier of HSPG structure. Specifically, Sulf-l removes sulphate groups from the 6-0 position of the glycosaminoglycan chains which decorate the HSPG core. In doing so, Sulf-l affects the ability of HSPGs to bind to both signalling ligands and receptors. Previous studies have shown that Sulf-l can inhibit F'GF signalling (Wang et aI., 2004). This thesis advances previous work by providing a complete expression analysis of the Su/f-l gene in the early Xenopus tropicalis embryo. It shows that XtSulf-l acts as an endogenous FGF inhibitor, and shows for the first time that it also acts as an endogenous BMP inhibitor. This work reveals that XtSu/f-1 .is an essential regulator of cell signalling events in the early Xenopus embryo.

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Xenopus embryos have long been used as a developmental model organism, their potential as an in vivo model for single cell migration has yet to be fully explored. The PhD study presented used two cell types, macrophage and melanophores. Xenopus melanophores were assayed in a chemical genetic screen to identify novel small molecule compounds effecting their migration. With respect to macrophage migration, a set of three identified XMMPs showed expression in the migrating macrophages their functional role was unknown. The function of three Xenopus MMPs was characterised. by loss-of-function. Analysis of each XMMP shows that they are all functional. The MMPs were shown to act synergistically when knocked down with each other. Localisation of the XMMPs in an embryonic wound healing model was also characterised. The highest model organism used in chemical genetic studies to date is the developing zebrafish embryo. Xenopus embryos offer a higher evolutionary model and an alternative to zebrafish embryos. Xenopus embryos were characterised as a potential developmental chemical genetic model. This proof of principle study assayed penetrance, efficacy, genetic variation and throughput. From these studies, a large-scale screen was undertaken to identify novel compounds modulating melanophore migration. Compounds effecting a number of other areas of embryonic development were identified including pigmentation, edema formation, eye development, general morphology and melanophore morphology were also identified. One compound (NCI 84093) has a striking pigment phenotype, causing a vertical banding pattern and effecting only one pigment stripe. The mode of action of NCI 84093 was further characterised. Application of the compound disrupts the formation of the dorsal pigment stripe at an early stage in development, before migration is normally observed. By molecular, biochemical and computational analysis NCI 84093 was discovered to have the pharmacological properties of a matrix metalloproteinase (MMP) inhibitor. A set of novel small molecule compounds effecting melanophore migration was identified and the mode of action of one of the compounds characterised. The set of three macrophage expressed XMMPs are shown to be functional, evidence suggests they act in combination. The application of NCI 84093 and the loss-of-function of an XMMP (XMMP-14) previously identified as being expressed by the migrating melanophores were used to characterise the migration routes of embryonic melanophores.

No description available.