Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (M.S.)--Montana State University--Bozeman, 2005. / Title from PDF t.p. (viewed on June 10, 2006). Chairperson, Graduate Committee: Thomas McMahon. Includes bibliographical references (p. 52-62).

Let G be a nontrivial connected, edge-colored graph. An edge-cut R of G is called a rainbow cut if no two edges in R are colored the same. An edge-coloring of G is a rainbow disconnection coloring if for every two distinct vertices u and v of G, there exists a rainbow cut in G, where u and v belong to different components of G − R. We introduce and study the rainbow disconnection number rd(G) of G, which is defined as the minimum number of colors required of a rainbow disconnection coloring of G. It is shown that the rainbow disconnection number of a nontrivial connected graph G equals the maximum rainbow disconnection number among the blocks of G. It is also shown that for a nontrivial connected graph G of order n, rd(G) = n−1 if and only if G contains at least two vertices of degree n − 1. The rainbow disconnection numbers of all grids Pm Pn are determined. Furthermore, it is shown for integers k and n with 1 ≤ k ≤ n − 1 that the minimum size of a connected graph of order n having rainbow disconnection number k is n + k − 2. Other results and a conjecture are also presented.

Understanding that disease is a limiting factor to the aquaculture industry together with the knowledge that drugs and chemotherapeutics can cause newly resistant bacterial strains, has driven attention to finding new prophylactic measures to control diseases that include vaccination and the use of “functional feeds” to modulate the fish immune system. The supplementation of immunostimulants into fish diets is already widely used in aquaculture. However, searching for new and effective substances is one of the targets of many fish feed suppliers, including EWOS Ltd. who have co-funded the work presented in this study. There are a number of immunostimulant molecules used at present. Some bacterial components such as LPS are used to enrich fish diets and have been described to improve the natural immune defences. In contrast, peptidoglycan (PG), another ubiquitous component of the bacterial cell wall, has so far received less attention and is therefore investigated in this present study. Its ability to stimulate innate immunity is assessed using antimicrobial peptides (AMPs) as molecular markers, which are known to be involved in the early response against a broad range of pathogens. To date, AMPs in fish are not well characterised and in most cases the mechanisms of pathogen killing as well as the pathways inducing their expression still remain to be elucidated. Initially the cloning and characterisation of three novel trout β-defensin genes (omDB-2, omDB-3, omBD-4) was performed, and the molecules compared to the previously reported omDB-1. Each β-defensin gene was fully cloned and preliminary expression work in vivo and in vitro revealed the ability of these genes to be induced by bacteria and viruses. Analysis of the gene organization found that all three new genes contained three exons divided by two introns. Constitutive expression of these genes was detected by real time PCR ofmucosal and systemic tissues from healthy fish, with omDB-3 and omDB-4 showing the highest expression levels. Following bacterial challenge in vivo, the defensin genes were induced at the three mucosal sites examined (skin, gill, gut), with levels of omDB-2 and omDB-3 increased some 16-fold in gut and gill respectively. Using polyinosinic polycytosinic RNA (polyI:C) as a viral mimic, all of the four trout -defensin genes were induced in head kidney primary leucocyte cultures at 4h post-stimulation, with omDB-1 and omDB-3 showing particularly high expression. To determine the -defensin spectrum of activity against 10 strains of Gram negative and Gram positive bacteria, transfected RTG-2 cell lines over expressing GFP and the target genes omDB-1, omDB-3 and omDB-4 -defensins were produced and their supernatants used. Results showed highest bioactivity against Gram negative bacteria, in particular the supernatant from omDB-1 transfected cells showed the widest range of activity towards the majority of selected bacteria. In addition immune relevant genes (Toll-like receptors, genes involved in the anti-inflammatory response and in the apoptosis process) were screened in normal cell lines stimulated with the supernatant of omDB-1, as well as in the RTG-2 cells transfected with the three different defensins. Results showed for all the cell lines, a clear link with the viral recognition receptors TLR 3 and TLR 9, which supported the poly I:C data reported in Chapter 2 and by the induction in omDB-1 and omDB-3 transfected cell lines of the IFN- gene known to be involved in the antiviral response. Trout β-defensins also up-regulated MHC II and the CCR6 receptor. To determine the effects of fish diets enriched with different concentrations of PG, three in vivo feeding trial experiments in rainbow trout were carried out. Effectiveness of the diets was assessed using gene expression of selected AMPs, including β-defensins, cathelicidins and liver expressed antimicrobial peptide molecules. Fish fed with diets containing either 10 mg/Kg or 50 mg/Kg of PG respectively, showed the highest up-regulation of AMPs at 14 days of feeding. Data showed omDB-2 in the gut as the most inducible gene in agreement with the results obtained in the first experiment and omDB-3 was the fastest to respond in skin and gill. In addition, after ceasation of feeding the enriched diet, modulation of AMP expression was still detectable 28 days later, although a lower degree of induction was found in such fish relative to those maintained on the enriched diet. A final PG feeding trial was combined with a Yersinia ruckeri bacterial challenge which used two PG supplemented diets containing 10 mg/Kg and 50 mg/Kg of immunostimulant, and a commercial β-glucan supplemented diet (as a positive control), and fed to trout for 7 and 14 days before intraperitoneal injection challenge of the fish. Only a delay in the mortality rate was found in fish fed for 14 days with the 10 mg/Kg diet, with no clear protection from any of the functional feeds assessed. Finally, at least 500 bp of the regulatory 5’ end flanking region of two defensin (omDB-1 and omDB-2) and two liver expressed (hepcidin and LEAP-2A) genes were cloned and sequenced. In addition, the promoter sequence already known for the cathelicidin-1 gene was used in this study. Bioinformatic tools were used to search for putative transcription factor binding sites, and revealed the presence in all promoters of regulatory elements which could enhance or inhibit the expression of these genes, in response to different stimuli.

No description available.

Graduation date: 1998

Temperature influences the incidence of chemically induced cancer in fish, with warmer temperatures being associated with higher cancer incidence. The mechanisms of temperature-modulated chemical carcinogenesis in fish, however, have not been described in detail. Therefore, one primary objective of this study was increased understanding of how temperature-modulated genotoxicity of 7,12- dimethylbenz(a)anthracene (DMBA) corresponded with tumor response. The second entails the potential of temperature to modulate cancer promotion. Rainbow trout (Oncorhyncus mykiss) (2 g) were acclimated at 10, 14 or 18��C for one month and then exposed to 1.0 ppm DMBA in their water for 20 hr. Exposures were at respective acclimation temperatures or 10 and 18��C acclimated fish were shifted to 14��C for DMBA exposures. Adduction of [��H]DMBA to hepatic DNA 21 days after exposure was higher in 10��C than 18��C fish exposed at their respective acclimation temperatures. However, in fish shifted to 14��C, the concentration of hepatic [��H]DMBA DNA adducts was similar in 10��C and 18��C acclimated fish at that time. Temperature effects on tumor incidence were assessed 9 months after DMBA waterborne exposures. Incidence of stomach, liver and swim-bladder cancer increased with rearing temperature. Differences in tumor incidence were less marked in fish reared at the same temperature (14��C). Retrospective analyses of livers from a tumor study initiated with aflatoxin B1 (AFB1) was conducted with antibodies to endogenous proliferating nuclear antigen (PCNA). Proliferating cells were scored by counting labeled nuclei in 5 random 10x fields using an image analysis program (BIOQUANT SYSTEM IV). There was no significant increase in numbers of PCNA labeled hepatocytes with temperature. The influence of acclimation temperature on plasma mitogens that stimulate cell division was assessed in cultured Chinook salmon embryo cells (CHSE-214). Plasma from rainbow trout (120-150 g) acclimated to either 10 or 18��C for at least four weeks stimulated in vitro proliferation of CHSE-214 cells to the same extent. This study demonstrated that chemically induced tumors in fish were modulated by temperature not only through genotoxin disposition and formation but also through persistence of DNA adducts. It also discounted the role of mitogenesis in temperature-modulated chemical carcinogenesis. / Graduation date: 1996

Thesis (Ph. D.)--University of Washington, 1985. / Vita. Bibliography: leaves [144]-152.

No description available.

Graduation date: 1991