B cells have unique machinery to make up a large pool of antibody repertoire. After V(D)J recombination in early B cell development, the rearranged immunoglobulin genes are further diversified by somatic hypermutation (SHM), gene conversion (GC) and class switch recombination (CSR). Acitvation induced cytidine deaminase (AID) is a key initiating factor for SHM, GC and CSR. A majority of research data supports the model that AID modifies Ig genes at the DNA level by deaminating cytosines to uracils. The mutagenic activity of AID is largely restricted to Ig genes to avoid genomic instability in general. The specificity cannot be attributed to the primary sequence of the Ig genes since unrelated DNA is mutated by AID in the context of Ig genes. A clue to this problem is that AID function is dependent on transcription. Since not all transcribed genes are mutated by AID, there must be something special about the transcription of Ig genes, and the reasoning has prompted extensive analysis of Ig promoters and enhancers. We addressed this question in chicken B cell line DT40. We identified a 2.4-kilobase regulatory region which is important for AID function both within and outside of Ig locus. This regulatory region contains binding sites for multiple transcription factors. Mutation of these binding sites impairs AID mediated gene conversion. In addition, ablation of NF-κB family member, c-Rel and p50, reduces the AID targeting function of this regulatory region. Since the implicated transcription factors have been reported to associate with histone acetylases, the regulatory region may function by facilitating the access of AID to target DNA. To test this hypothesis, we used the I-SceI endonuclease and dam methylase as probes for chromatin structure. We found that the regulatory region does not increase chromatin accessibility to these probes. In fact, the regulatory region appears to interfere with the cleavage of target DNA by I-SceI. Another possible role of the regulatory region could be direct recruitment of AID to Ig genes. To test this hypothesis, we utilized Dam identification method. Surprisingly, we found that the regulatory region facilitates AID targeting to the Igλ locus. / text

Despite over seven decades of speciation research and 25 years of phylogeographic studies, a comprehensive understanding of mechanisms that generate biological species remains elusive. In temperate zones, the pervasiveness of range fragmentation and subsequent range expansions suggests that secondary contact between diverging lineages may be important in the evolution of species. Thus, such contact zones provide compelling opportunities to investigate evolutionary processes, particularly the roles of geographical isolation in initiating, and indirect selection against hybrids in completing (reinforcement), the evolution of reproductive isolation and speciation. The spring peeper (Pseudacris crucifer) has six well-supported mitochondrial lineages many of which are now in secondary contact. Here I investigate the evolutionary consequences of secondary contact of two such lineages (Eastern and Interior) in Southwestern Ontario using genetic, morphological, acoustical, experimental, and behavioural evidence to show accentuated divergence of the mate recognition system in sympatry. Mitochondrial and microsatellite data distinguish these two lineages but also show ongoing hybridization. Bayesian assignment tests and cline analysis imply asymmetrical introgression of Eastern lineage nuclear markers into Interior populations. Male calls are divergent between Eastern and Interior allopatric populations and show asymmetrical reproductive character displacement in sympatry. Female preference of pure lineage individuals is also exaggerated in sympatry, with hybrids showing intermediate traits and preference. I suggest that these patterns are most consistent with secondary reinforcement. I assessed levels of post-zygotic isolation between the Eastern and Interior lineages using a laboratory hybridization experiment. Hybrid tadpoles showed equal to or greater fitness than their pure lineage counterparts, but this may be countered through competition. More deformities and developmental anomalies in hybrid tadpoles further suggest post-zygotic isolation. Despite evidence for pre-mating isolation between the two lineages, isolation appears incomplete (i.e. hybridization is ongoing). I hypothesize that potentially less attractive hybrids may circumvent female choice by adopting satellite behaviour. Although mating tactics are related to body size, genetic status may play a role. I show that pure Eastern males almost always engage in calling, while hybrids adopt a satellite tactic. An absence of assortative mating, despite evidence of female preference, suggests successful satellite interception possibly facilitating introgression. / Thesis (Ph.D, Biology) -- Queen's University, 2013-03-04 16:01:33.892

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

The need to develop tourism and diversify as well as redirect the Nigerian economy away from crude oil as the sole foreign exchange earner is overwhelming for several reasons. Not only does tourism hold huge capacity to forge effective backward and forward linkages with the rest of the economy, it has proved to be a significant foreign exchange earner and a major source of employment and income in many developing countries. Given Nigeria’s many tourist attractions, tourism has the potential to attract huge internal capital investment as well as foreign direct investments necessary to enhance tourist infrastructure provisions and services. This is particularly so in rural areas given that most tourist attractions in Nigeria are rural based, and where tourism development can become a catalyst for rural development particularly where tourism is developed within the tenets of sustainable development. Presently, Nigeria’s tourism industry is rudimentary, undeveloped, and suffers from chronic shortages of infrastructure as well as supporting and enhancing institutions. In particular, the lack of awareness and appreciation for landscaping in particular, and the environment in general, has compounded the problems of tourism development in Nigeria. This research is motivated by the desire to understand the structure, conduct, and performance of the tourism sector in Nigeria and emphasise, amongst other factors, the significant role landscaping could play in the desire for sustainable tourism in Nigeria. In conducting the research, a mixed methods research approach was employed using the sequential strategy of quantitative survey; followed by a qualitative data gathering method using interviews. These were conducted among tourism stakeholders within two geopolitical zones in Nigeria, namely, the North-central and the South-west. This approach was informed by the pragmatic philosophy adopted by the researcher, which allows the triangulation of methods in order to come up with a more comprehensive and complementary results on the focus of this research. Data obtained were critically analysed using the Statistical Packages for Social Sciences (SPSSx) and Nvivo8 software. The research identified setbacks which have prevented sustainable tourism development in Nigeria. Also is the need for the beautification of the attractions through landscaping as well as the provision of tourism infrastructures. The implication of the findings is that if landscaping is not made the centre of tourism policy, tourism is likely to fall short of expectation. A conceptual framework for the way forward was suggested based on the outcome of the analyses and two regression models developed and presented the roles landscaping could play in sustainable tourism and in Nigeria economic diversification. If implemented, the suggestions should provide a solid basis for redressing the current pitfalls in Nigeria’s tourism landscape.

By using the data on Indian firms on the BSE 500 Index during the period 2005-2006, we find that family ownership affects group affiliated firms more positively than standalone firms. Group affiliated firms underperform initially as compared to standalone firms but after certain threshold of family ownership their performance becomes better than standalone firms. Within diversified Indian Business Group, family ownership affects highly diversified affiliates positively. Effect of family excess vote holdings and involvement of family management is found to be insignificant. We also find that block holders affect firm value negatively. Our results are in contrast with the existing literature of diversification and family ownership on developed market especially, US and UK. Some of our results are consistent with those of Khanna and Palepu (2000). This paper supports most of the findings of Khanna and Palepu based on more complete and reliable data set. In addition, it shows that the superior performance of highly diversified groups is related to greater family ownership. In the second essay, we examined the issues related to market reaction on IT outsourcing announcement and firm characteristics which induce firms to outsource. We find that IT outsourcing has a strong positive effect on stock prices of announcing firms, especially for longer event windows. We also find that the higher the pre-announcement inefficiency of a firm (as evidenced by lower asset turnover ratios, higher operating cost to sales, and higher cost of good sales to sales), the greater the positive price reaction to the outsourcing announcements. We also find that firms with higher information asymmetry problems (firms in the service industry) elicit a higher positive market reaction at the time of outsource announcement. Finally, firms that are likely to outsource are cost inefficient, and/or are cash needy.

In chapter 1, I provide evidence against the claim in the conventional literature on corporate diversification discount that the diversification effect is homogeneous across the industries. I argue that the responsiveness of consumer demand to the changing economic conditions or the product demand sensitivity is an important characteristic of the industries that should be considered to have a more complete understanding of the issue of underperformance of diversified firms compared to single-segment firms. Differentiating industries based on the measure of product demand sensitivity, I show that the diversification effects are not to be homogeneous across the industries. Much of the value destroying effect from the diversification gets reduced when industry experiences any shock or increase in the sensitivity of demand. It implies a better shock observing capacity of diversified firms and a source of premium that conglomerates can enjoy due to their diversified operations during the periods of the increase of sensitivity of product demand. Our result is robust to difference specification and difference measure of sensitivity. In chapter 2, I include organizational forms as industrial and global diversification, and geographic dispersion in the empirical framework to find out which types of diversification do matter for the cost of bank loans. I find that firms which are only globally diversified, neither industrially diversified nor geographically dispersed, experience higher cost of bank loans. The other types of firms incurring higher cost of bank debt are the firms which are only geographically dispersed, and the firms which are diversified in all three ways with the combination of geographic, global, and industrial diversification. Examining the effects of organizational forms on the non-price loan terms, I observe that covenant restrictions are generally higher for the combination of diversified firms which are either both geographically dispersed and industrially diversified, or geographically dispersed and globally diversified.

This thesis analyzes the interdependence of stock markets in the Czech Republic, Hungary, Germany and the U.S. between 1994 and 2010. Its aim is to prove or disprove the hypothesis that the correlation of stock markets is growing. Furthermore, it aims to determine whether the benefits of international diversification are important in the 21st century. The first part defines the basic terms related to this issue. The next section describes the historical development of stock markets and major stock indexes. The following is the longest chapter, which deals with the dependence of equity markets. The degree of dependence between markets is measured by correlation coefficients. In order to calculate the correlation coefficients 3 methods were used: 12-month, 24-month moving window and the exponential weighting. It was confirmed that correlation increases in periods of high market volatility and if the equity markets go up. Correlation decreases in periods of low market volatility and if the stock markets go down. There is a long-term increasing trend in the correlation development. The last chapter describes the recent study of P. Christoffersen, V. Errunza, K. Jacobs, and X. Jin, which also deals with this issue. Although the authors used more complex mathematical and statistical methods, their conclusions are similar. At the end of this chapter there is a study dealing with the benefits of international diversification in 2005 and 2009. Its conclusion is that the benefits of international diversification are disappearing.

This paper investigates the long-term diversification opportunities that exists for global investors among the BRICS nations. It analyzes how risk-averse investors can allocate funds between the countries in order to maximize the expected return in relation to the overall risk. It utilizes an empirical cointegration approach in tandem with modern portfolio theory during the time period 1999-2019. The empirical results of cointegration that is found supports the suggestion that the BRICS markets have a stable risk-premium between each other and that they all share similar systematic risk factors. The results further support the construction of a portfolio solely compromising of stocks from four out of the five BRICS markets, since then they do not share any long-run co-movements with each other. Moreover, the markets of Brazil, India, China and South Africa are strong candidates for reducing portfolio risk without sacrificing the adjusted portfolio return. The results also indicate several causal relationships between the nations, with China as the main driving force. This suggest that shocks in the Chinese market will spread and effect the rest of the BRICS markets, either directly or through one of the other markets. This is important knowledge for global policy-makers since China could be affected by markets outside the co-operation and subsequently transfer it to the rest of the BRICS markets. Since the countries accounts approximately 25 % of the global GDP, policy-makers must act with great care before implementing economic policies against China, since the consequences can have a much larger and wider effect than they anticipate.

As angiospermas são um dos grupos mais diversos de organismos, e grande parte dessa diversidade deve-se às muitas formas florais existentes. Devido a isso, determinar os padrões de variação floral e os fatores históricos e ecológicos que levaram à evolução desta alta diversidade floral é essencial para entender os processos que dirigem a diversificação das angiospermas. A tribo Bignonieae (Bignoniaceae) representa um excelente modelo para o estudo de diversificação floral na região Neotropical, por ser o clado mais diverso de lianas neotropicais e apresentar uma altíssima diversidade floral. Nesta tese, utilizei a tribo Bignonieae para caracterizar: (i) o padrão de evolução de caracteres florais discretos e morfologias florais, assim como possíveis associações entre as morfologias florais e grupos de polinizadores, (ii) o sinal filogenético e as taxas de evolução de caracteres florais contínuos, (iii) o padrão e a magnitude de integração fenotípica entre caracteres florais contínuos ao longo da filogenia do grupo e (iv) a influência da filogenia, da morfologia floral e de fatores abióticos para a co-ocorrência de espécies e a estrutura de comunidades de Bignonieae. Os resultados indicam grande labilidade na evolução de caracteres discretos e morfologias florais, contrapondo o sinal filogenético encontrado para os 16 caracteres contínuos avaliados. O sinal filogenético, entretanto, difere entre caracteres de cálice-corola e estame-estigma. As taxas de evolução também variam entre caracteres, indicando a ação de diferentes pressões seletivas ou resposta diferencial à seleção em diferentes partes da flor. Os padrões de integração fenotípica se mantêm constantes ao longo da história evolutiva de Bignonieae, apesar da evolução homoplástica da magnitude das correlações entre caracteres. Essa aparente complexidade evolutiva, sugerida pela presença de padrões diferentes em diferentes tipos de caracteres, não se repete na estrutura ecológica das comunidades, já que nem a morfologia floral e nem a filogenia influenciam a co-ocorrência entre espécies. Por outro lado, há evidente especialização das espécies a fatores abióticos, sugerindo um papel crítico de filtro ambiental na estrutura das comunidades de Bignonieae. Esse resultado contraria a hipótese de que saturação causada por competição por polinizadores seria o fator determinante da estrutura interna de comunidades de Bignonieae. / Flowering plants represent one of the most diverse groups of organisms in the Planet. A large portion of this diversity results from the multitude of floral forms encountered nowadays. To understand the patterns of floral variation and of the historical and ecological factors that led to the evolution of such diversity in floral forms are critical for a better understanding of the processes that led to the diversification of angiosperms. The tribe Bignonieae (Bignoniaceae) is the most diverse clade of Neotropical lianas and represents an excellent model for the study of floral evolution due to the high diversity of floral forms of this group. In this Ph.D. thesis, I aimed to characterize: (i) the pattern of evolution of discrete floral traits and floral morphologies in Bignonieae, as well the potential associations between floral morphologies and pollinators; (ii) the phylogenetic signal and the rates of evolution of continuous floral traits; (iii) the pattern and the magnitude of phenotypic integration among floral traits across the phylogenetic history of the group; and, (iv) the influence of phylogeny, floral morphology and abiotic factors for the patterns of species co-occurrence and the structure of communities of Bignonieae in the Neotropics. The results indicate high lability in the evolution of discrete floral traits and floral forms, contrasting the significant phylogenetic signal encountered in all 16 continuous floral traits examined. However, the phylogenetic signal differs between traits of different floral whorls. The rates of evolution also varied among different characters, suggesting the action of different selective pressures or differential responses to selection in different floral parts. Overall, the patterns of phenotypic integration were constant during the history of Bignonieae, despite the homoplastic evolution of the magnitude of correlation among characters. This apparent evolutionary complexity, leading to different patterns in different traits, is not reflected in the ecological structure of communities, given that nor floral morphology or phylogeny influence species co-occurrence. On the other hand, species specialization to abiotic factors was encountered, suggesting that environmental filtering played a key role in the structure of communities of Bignonieae. The results reject the hypothesis that saturation caused by competition for pollinators would be the main factor determining the intra-community structure of Bignonieae.