No description available.

It is the purpose of this study to ascertain what environmental factors might cause morphological changes exhibited by certain algae, also to determine if this variation in morphology is vegetative, reproductive, or artifactual in nature, and to show what effects these changes in morpohology might have on classification of the organisms in question.

No description available.

Two strains (NCm 9897 and 9898; strains A and B respectively) of a Pseudomonas· species have been shown to display antifungal and antibacterial activity on solid media. Biochemical tests indicate that the organisms may be two distinct strains of a new species. Cell morphology was studied using scanning electron microscopy. Chemically defined media, established for the organisms, indicate non-fastidous characteristics. Four liquid media, able to elicit antibiotic production from Strain A have been developed: a chemically defined medium (antibacterial), a chemically defined medium and a complex medium (antifungal) and a chemically defined medium (antibacterial and antifungal). Nitrogen and magnesium limitation significantly increased yields. Magnesium content in a medium (without a magnesium salt component) and in whole cell samples grown in the said medium were assessed using atomic absorption spectroscopy and elemental analysis respectively. Optimization experiments for antibacterial and antifungal activity, assessed by a disc diffusion assay, increased yields, in 250 ml conical flasks by a factor of X9 and 109% respectively. A 6 litre laboratory-scale fermentor was used for larger batch cultivations . Procedures for extraction of the active compounds from the biological matrices were . developed leading to the isolation of one antibacterial compound, ABl (yellow crystalline) and three antifungal compounds, AFl, AF2 and AF3 (pale yellow and amorphous). Structure determination of ABl, involving mass spectrometry, IR/UV spectroscopy, lH-NMR and x-ray diffraction, indicated it to be 1.6 dimethyl pyrimido[5,4-e ]-1,2,4- triazine-5,7(IH,6H)-dione (Xanthothricin; Toxoflavin), a toxic metabolite previously detected in foods contaminated with Ps. cocovenenans. Selective media, developed ' for Strain A and Strain B, did not support growth of Ps. cocovenenans. Preliminary structural analysis suggests that AFl may possess a mono-substituted ring system with CHz chain and a terminal hydroxyl group; that AF2 may belong to the polyene group of antifungal antibiotics and that AF3 may be an aliphatic ketone with hydroxyl group . Agar diffusion, minimum inhibitory concentration, assays for the compounds, indicate activity to be in the ~gml range for sensitive microorganisms. Antibiotic challenge against test microorganisms suggest bacteriostatic activity for ABl, fungistatic activity for AFl and AF3 and fungicidal activity for AF2.

Desmoglein 3 (Dsg3) belongs to the desmoglein subfamily and functions as an adhesion molecule in desmosomes. Two pools of Dsg3 have been identified, detergent soluble and insoluble proteins. Recent studies show that DSG3 is upregulated in squamous cell carcinoma (SCC). However, its biological function in cancer remains poorly understood. The aim of this study was to investigate the extra-junctional functions of Dsg3, in particular its roles in signalling that regulates cell morphology and locomotion in cancer cells. This study adopted a unique cancer cell model with Dsg3 gain-of-function and has discovered two novel regulatory signal pathways that may play a crucial role in the control of cell invasion and metastasis in Dsg3 associated cancers. Firstly, Dsg3 regulates the phosphorylation of Ezrin at Thr567 in a PKCdependent manner that is crucial for its activation and regulation of actin based membrane projections and accelerated cell locomotion in SCC. Secondly, Dsg3 modulates the transcriptional activity of cJun:AP1 that is responsible for regulating a cohort of genes to confer an invasive phenotype. It is likely that these two pathways are closely linked in that the Dsg3-mediated activation of cJun:AP1 elicits PKCdependent Ezrin activation that in turn enable it to form a complex with Dsg3 at the plasma membrane to promote membrane projection and cell locomotion. Several lines of evidence support these conclusions: Dsg3 forms a complex with Ezrin at the plasma membrane and induces phosphorylation of Ezrin resulting in augmented membrane protrusions and cell migration. Dsg3 silencing inhibits junction formation concomitant with collapse of membrane protrusion. Furthermore, Dsg3 regulates the activity of cJun:AP1. Collectively, these findings provide new insight regarding Dsg3 in cancer, suggesting it acts as a key regulator of cell invasion and metastasis in SCC. Therefore, targeting Dsg3 could be a potential new strategy in the control of cancer progression and metastasis.

Legionella pneumophila is an intracellular pathogen and the etiological agent of Legionnaires’ disease, a severe atypical pneumonia. This bacterium is ubiquitous to freshwater ecosystems where it spreads in the planktonic form but is primarily found associated with protozoa. Protozoa serve as a niche for its replication because the extracellular environment often does not offer sufficient nutrients to support the growth of this bacterium. L. pneumophila is an opportunistic pathogen in humans and utilizes an arsenal of virulence factors to colonize hosts and cause Legionnaires’ disease. The transition between extracellular and intracellular milieus triggers a series of metabolic, morphological and genetic changes that define two developmental stages in this bacterium: replicative and transmissive. Relatively high concentration of nutrients triggers the replicative stage of growth, where the bacterium has the appearance of a thin, elongated rod without the presence of flagella. In addition, is characterized by active metabolism and expression of genes required for productive replication. In contrast, once nutrient levels are relatively low, L. pneumophila switches to its transmissive form. In this form, the bacterium activates a genetic program that includes the expression of many traits associated with the transmissive stage, such as coccoid cell shape, motility, pigmentation and important virulence factors. These multifaceted changes in gene expression leading the differentiation from replicative to the transmissive form, are controlled by two-component regulatory systems. Specifically, the LetAS two-component system plays a key role in the regulation of cell morphology and in the production of the pigment pyomelanin. Here we report the identification of a LetAS-regulated protein, Lpg0586 (designated as Larp1), capable of inducing changes in cell morphology and pigment production. We found that Larp1 expression was accompanied by accumulation of the RecA protein, but evaluation of recA deletion mutants indicated that RecA is not involved in cell morphology changes in L. pneumophila. The specific reason as to why RecA accumulates upon Larp1 expression remains to be elucidated. However, we show that upon synthetic HGA treatment, L. pneumophila cultures display cell elongation and increased RecA levels. Lastly, Larp1 expression restored pyomelanin production in an un-pigmented mutant and increased the transcription of important genes involved in the pyomelanin production pathway. Based on these findings, Larp1 is the first LetAS-regulated protein reported to be involved in pyomelanin production.

No description available.

A crytological and nutritional study was conducted on Vitreoscilla stercoraria, ATCC 15218, and Vitreoscilla species, ATCC 13982. Cell and trichome morphology in broth cultures and on solid media were studied.

Subcellular localization of polyoma mT was determined by immuno-fluorescence microscopy, using primary monoclonal/ polyclonal antibodies and secondary polyclonal antibodies conjugated with fluorescent dyes. Our results confirm and extend previous studies reporting the association of mT with an intracellular compartment. However, it is shown that the perinuclear compartment containing the bulk of mT expressed in MRC5 cells is both Brefeldin A resistant and distinct from the known compartments of the secretory pathway. The integrity of most subcellular compartments was not altered by mT expression. However, secondary lysosomes and late endosomes were reorganized in cells expressing mT. Early in cell transformation mT alters several members of the cytoskeletal array, with the most profound effects on actin. In cells coinfected with viruses encoding either mT or pp60csrc, the areas of subcellular localization of both proteins are largely overlapping. In addition, mT recruits She to this subcellular localization indicating that mitogenesis as well as morphological cell transformation may be regulated from this novel intracellular compartment. / Thesis / Master of Science (MS)

N^6,O^2' -Dibutyryl cyclic adenosine 3',5'-monophosphate (Bt_2cAMP) was investigated for its effects on various tissue culture cells infected with temperature-sensitive (ts) mutant, LA31 and Bratislava 77 (B77), a wild-type Rous sarcoma virus. Specifically, known parameters of transformation were investigated and a possible site of action has been tenably proposed. The drug Bt_2cAMP was found to have little effect on the transformation related properties of primary chick embryo fibroblasts (CEF) infected with either virus or normal rat kidney fibroblasts (NRK) infected with the wild-type B77-RSV. However, significant inhibition of the transforming properties in NRK infected with the ts mutant LA31 (LA31-NRK) were reported at the permissive temperature 33 degrees centigrade (33 C).