Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Catherine B. Kirn-Safran, Dept. of Biological Sciences. Includes bibliographical references.

Thesis (M. Med. Sc.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 75-86).

There is a growing recognition that conservation programs using hatchery-reared fish should strive to produce individuals that represent phenotypes present in natural environments. Size variability within cohorts, mediated through inter-individual differences in growth rates, provides one avenue by which phenotype can be studied. High growth rates are generally equated with greater fitness. However, there is evidence that fish with slower relative growth and smaller sizes continue to persist within populations. This thesis aimed to better understand the causes and potential implications of variable sizes and growth rates on the potential recruitment of hatchery-reared Lake Sturgeon, Acipenser fulvescens. Studies were developed to 1) determine the mechanisms behind these observed variations and 2) assess the behavioural and physiological consequences of being either a fast- or slow-grower (i.e., large or small). Laboratory studies concluded that external factors, most notably the presence of conspecifics during feeding events, influenced size variability more than inherent predispositions towards faster or slower growth. Examination of size-dependent versus size-independent feeding interactions further confirmed that variability does not appear to be the result of underlying fixed behaviours. The consequence of slower growth rates and smaller sizes did not lead to higher mortality or reduced body condition during a low temperature challenge. Recapture rates and downstream movements following stocking events of both young-of-the-year (YOY) and yearling Lake Sturgeon in the Winnipeg River, Manitoba could not be correlated to inter-individual differences in size. Although initial study on the cause of growth and size divergence may lead one to conclude that slow-growing (i.e., small) Lake Sturgeon represent a substandard phenotype, subsequent studies could not point to inferior performance of these individuals when compared to faster-growing (i.e., large) individuals of the same age. As such, the practice of size-selection for relatively faster-growing and larger individuals in future Lake Sturgeon enhancement programs is discouraged, at least until there are more conclusive findings to suggest otherwise. Future studies should continue to look at recruitment in relation to growth rate and size among naturally produced Lake Sturgeon juveniles in order to put the results of this research into context.

The ability of traits to adapt in response to change is one of the most fundamental aspects of evolution. Optimality models used to predict adaptation frequently make simplifying assumptions about the ability of traits to evolve freely within simple tradeoffs. However, we frequently have little understanding of genomic mechanisms underlying phenotypic evolution. Genetic constraints clearly limit phenotypic change, but the extent to which they do so is unclear. I will explore molecular and phenotypic responses to genomic and environmental perturbations through experimental evolution in T7 bacteriophage. First, I studied evolutionary robustness of the lysis time phenotype when lysin gene lysozyme was deleted. This deletion profoundly delayed lysis and thus decreased fitness. Evolved phages recovered much of the lost fitness and mostly restored lysis timing. The recovery was mediated by changes in a tail fiber gene (gene 16) with muralytic activity that is generally used in genome entry. Next, I extended the work on lysozyme to observe the effect of increasing constraint on evolutionary recovery. The effects of various combinations of deletions of lysozyme, 17.5 (which plays a role in lysis) and 16 suggested that another gene played a role similar to 17.5 in lysis. The phage defective in both lysozyme and 16 did not lyse hosts thoroughly even after long periods of infection, suggesting that these were the only effective lysin genes. Adaptation of this phage on cells expressing the essential gp16 constrained the primary adaptive pathway of recovery from lysozyme deletion. A mutually exclusive alternative pathway involving a variety of different genes evolved. The line recovered the ability to lyse normal hosts, by a mechanism involving multiple mutations. Finally, I tested the ability of T7 to adapt to an optimum lysis time. Based on empirical results from other phages, mature phage virions accumulate linearly inside the cell over time. This assumption underlies a model suggesting that availability of hosts determines optimal lysis time. While adaptation to different host densities caused the expected qualitative evolutionary changes, adaptation to conditions expected to select for slow lysis did not lead to the quantitative optimum. This is probably due to nonlinear virion accumulation.

No description available.

No description available.

Variability between individuals in pain and analgesia phenotypes is often observed in both clinical and experimental settings. The source of this variability has long been attributed to the interplay of environmental and genetic factors, but we have only recently begun identifying these determinants. Experiments comparing isogenic strains of mice have suggested that different pain tests may share a genetic basis; likewise, analgesic magnitude induced by disparate drug classes may be influenced by a common set of genes. / We have presently used a quantitative trait locus mapping strategy to search for genes responsible for variability in analgesic response to five analgesic drugs (the opioids morphine and U50,488, and the non-opioid drugs clonidine, epibatidine, and WIN55,212-2). We first used a B6129PF2 intercross population to map sensitivity to clonidine, morphine, and WIN55,212-2 to a 30 cM region on distal Chromosome 1. In silico and congenic strain mapping techniques allowed us to refine this linkage, as well as generalize it to four of the five drugs and seven mouse strains. Kcnj9 (GIRK3) was identified as a likely candidate gene underlying response to multiple analgesic modalities. We showed that this gene is differentially expressed between C57BL/6 and 129P3 strains in the periaqueductal gray. We also determined that Kcnj9 null mutant mice exhibit attenuated analgesic responses. / We previously mapped nociceptive response to the formalin test to two loci on Chr. 9 and 10 using an AB6F2 cross. Using in silico mapping, we identified several haplotypes near the Atp1b3 gene on Chr. 9 (a subunit of the sodium-potassium pump) that correlated highly with early phase formalin response. We then showed that pharmacological antagonism of the sodium-potassium channel eliminates the strain difference observed between A and C57BL/6 mice, supporting a role for this gene in determining response to formalin. Positional cloning of the Chr. 10 locus, employing recombinant and congenic strains, allowed us to refine the location of the locus to a <3 cM interval. A small number of genes in this region were identified as differentially expressed by microarray analysis, providing a short list of candidate genes for follow-up investigation.

No description available.

Clinical transplantation continues to rely on the use of non-specific immunosuppressive therapy, which reduces the incidence of graft rejection but also carries with it undesirable side effects such as infection and malignancy. A preferable option would be to induce operational graft tolerance without the need for such non-specific therapy, for example by harnessing natural mechanisms. In recent years there has been much progress in the characterisation of CD4⁺ cells that possess suppressive or regulatory properties in experimental systems; particular attention has been focussed upon CD4⁺ cells expressing CD25, the α subunit of the IL-2 receptor, which have been shown to possess regulatory capacity both in vitro and in vivo in autoimmune disease and transplantation models. The aim of this study was to examine the potential role of CD4⁺CD25⁺ regulatory T cells (Treg) in the induction phase of tolerance in a transplantation model. Pre-treatment of mice with fully allogeneic blood administered under the cover of anti-CD4 antibody is shown to lead to the generation of CD4⁺CD25⁺ cells capable of preventing the rejection of donor type, but not third party, skin allografts mediated by CD4⁺CD45RB^high cells in secondary recipients. In addition to their suppressive properties in vivo, these CD4⁺CD25⁺ cells also display the ability to regulate the proliferation of target T cell populations in vitro. Generation of CD4⁺CD25⁺ Treg by the pre-treatment protocol is not reliant upon an intrathymic selection process nor upon the expansion of a pre-existing CD4⁺CD25⁺ Treg population, but can occur through the conversion of peripheral CD4⁺CD25^- cells to a regulatory phenotype. Although the regulatory function of the CD4⁺CD25⁺ cells generated by pre-treatment is donor strain-specific in vivo, this specificity can be overcome by activating the cells before their regulatory capacity is tested. Moreover, CD4⁺CD25⁺ cells generated by pre-treatment with a non-cellular protein antigen completely unrelated to the graft can also regulate skin allograft rejection provided that these Treg are first activated. It is hoped that the principles defined by these findings identify a strategy that may be applicable in clinical transplantation and in the therapy of autoimmune disease.

Previous studies of association of ABO phenotypes with gonorrhoea have shown contradictory results. Despite the interdependencies, none have examined the combined effect of ABO, Lewis and Secretor phenotypes. Furthermore, none have used genotyping to confirm phenotyping. This study is ground-breaking in this regard, and illustrates how such an association study should be performed. STUDY DESIGNS AND METHODS: The study examined 175 individuals who tested positive for gonorrhoea, and 211 individuals who tested negative for gonorrhoea. Strain typing was not performed. The following blood grouping methods were performed on the study participants: ABO phenotyping Lewis phenotyping, and genotyping of selected samples Secretor genotyping Chi-square and p values were used to examine whether or not there is an association of ABO, Lewis and Secretor blood group related molecules with gonorrhoea infection. RESULTS: Neither random statistical analysis of data sets, nor statistical analysis of data sets arranged by blood group, yielded a statistically significant association of ABO, Lewis and Secretor phenotypes and genotypes with Neisseria gonorrhoeae that could not be refuted when the data was disaggregated for ethnicity. The study did show a statistically significant difference in the incidence of the partial secretor phenotype (26.7%) in the gonorrhoea positive population and the incidence of the partial secretor phenotype (15.4%) in the gonorrhoea negative population, when all ethnic groups were analysed together. However, when the data was disaggregated for ethnicity, the p values were no longer statistically significant. CONCLUSION: There is no association of ABO, Lewis and Secretor phenotypes and genotypes with Neisseria gonorrhoeae. Nevertheless, this study still has merit, because, to the author's knowledge, it is the first time a study of these human blood groups with a disease has been performed correctly.