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Primary Locus (primary + locus)
Selected AbstractsEVOLUTION OF DOMINANCE UNDER FREQUENCY-DEPENDENT INTRASPECIFIC COMPETITION IN AN ASSORTATIVELY MATING POPULATIONEVOLUTION, Issue 2 2010Stephan Peischl We study the evolution of higher levels of dominance as a response to negative frequency-dependent selection. In contrast to previous studies, we focus on the effect of assortative mating on the evolution of dominance under frequency-dependent intraspecific competition. We analyze a two-locus two-allele model, in which the primary locus has a major effect on a quantitative trait that is under a mixture of frequency-independent stabilizing selection, density-dependent selection, and frequency-dependent selection caused by intraspecific competition for a continuum of resources. The second (modifier) locus determines the degree of dominance at the trait level. Additionally, the population mates assortatively with respect to similarities in the ecological trait. Our analysis shows that the parameter region in which dominance can be established decreases if small levels of assortment are introduced. In addition, the degree of dominance that can be established also decreases. In contrast, if assortment is intermediate, sexual selection for extreme types can be established, which leads to evolution of higher levels of dominance than under random mating. For modifiers with large effects, intermediate levels of assortative mating are most favorable for the evolution of dominance. For large modifiers, the speed of fixation can even be higher for intermediate levels of assortative mating than for random mating. [source] Neuroprotective effects of bcl-2 overexpression in hippocampal cultures: interactions with pathways of oxidative damageJOURNAL OF NEUROCHEMISTRY, Issue 4 2002Sarah Howard Abstract Overexpression of bcl-2protects neurons from numerous necrotic insults, both in vitro and in vivo. While the bulk of such protection is thought to arise from Bcl-2 blocking cytochrome c release from mitochondria, thereby blocking apoptosis, the protein can target other steps in apoptosis, and can protect against necrotic cell death as well. There is evidence that these additional actions may be antioxidant in nature, in that Bcl-2 has been reported to protect against generators of reactive oxygen species (ROS), to increase antioxidant defenses and to decrease levels of ROS and of oxidative damage. Despite this, there are also reports arguing against either the occurrence, or the importance of these antioxidant actions. We have examined these issues in neuron-enriched primary hippocampal cultures, with overexpression of bcl-2 driven by a herpes simplex virus amplicon: (i) Bcl-2 protected strongly against glutamate, whose toxicity is at least partially ROS-dependent. Such protection involved reduction in mitochondrially derived superoxide. Despite that, Bcl-2 had no effect on levels of lipid peroxidation, which is thought to be the primary locus of glutamate-induced oxidative damage; (ii) Bcl-2 was also mildly protective against the pro-oxidant adriamycin. However, it did so without reducing levels of superoxide, hydrogen peroxide or lipid peroxidation; (iii) Bcl-2 protected against permanent anoxia, an insult likely to involve little to no ROS generation. These findings suggest that Bcl-2 can have antioxidant actions that may nonetheless not be central to its protective effects, can protect against an ROS generator without targeting steps specific to oxidative biochemistry, and can protect in the absence of ROS generation. Thus, the antioxidant actions of Bcl-2 are neither necessary nor sufficient to explain its protective actions against these insults in hippocampal neurons. [source] On the Tasks of a Population Commission: A 1971 Statement by Donald RumsfeldPOPULATION AND DEVELOPMENT REVIEW, Issue 3 2003Article first published online: 20 APR 200 In its most familiar form, analytic assessment of the impact of demographic change on human affairs is the product of a decentralized cottage industry: individual scholars collecting information, thinking about its meaning, testing hypotheses, and publishing their findings. Guidance through the power of the purse and through institutional design that creates and sustains cooperating groups of researchers can impose some order and coherence on such spontaneous activity. But the sum total of the result may lack balance and leave important aspects of relevant issues inadequately explored. Even when research findings are picked up by the media and reach a broader public, the haphazardness of that process helps further to explain why the salience of population change to human welfare and its importance in public policymaking are poorly understood. The syndrome is not unique to the field of population, but the typically long time-lags with which aggregate population change affects economic and social phenomena make it particularly difficult for the topic to claim public attention. A time-tested, if less than fool-proof remedy is the periodic effort to orchestrate a systematic and thorough examination of the causes, consequences, and policy implications of demographic processes. Because the most potent frame for policymaking is the state, the logical primary locus for such stocktaking is at the country level. The Commission on Population Growth and the American Future was a uniquely ambitious enterprise of this sort. The Commission was established by the US Congress in 1970 as a result of a presidential initiative. Along with the work of two earlier British Royal Commissions on population, this US effort, mutatis mutandis, can serve as a model for in-depth examinations conducted at the national level anywhere. Chaired by John D. Rockefeller 3rd, the Commission submitted its final report to President Richard M. Nixon in March 1972. The background studies to the report were published in seven hefty volumes; an index to these volumes was published in 1975. Reproduced below is a statement to the Commission delivered on April 14, 1971 by Donald Rumsfeld, then Counsellor to President Nixon and in charge of the Office of Economic Opportunity. (Currently, Mr. Rumsfeld serves as US Secretary of Defense.) The brief statement articulates with great clarity the objectives of the Commission and the considerations that prompted them. The text originally appeared in Vol. 7 (pp. 1-3) of the Commission's background reports, which contains the statements at public hearings conducted by the Commission. National efforts toward comprehensive scientific reviews of population issues have their analogs at the international level. Especially notable on that score were the preparatory studies presented at the 1954 Rome and 1965 Belgrade world population conferences. The world population conferences that took place in Bucharest in 1974, in Mexico City in 1984, and in Cairo in 1994 were intergovernmental and political rather than scientific and technical meetings, but they also generated a fair amount of prior research. The year 2004 will break the decadal sequence of large-scale international meetings on population, and apart from the quadrennial congresses of the IUSSP, which showcase the voluntary research offerings of its members, none is being planned for the coming years. A partial substitute will be meetings organized by the UN's regional economic and social commissions. The first of these took place in 2002 for the Asia-Pacific region; the meetings for the other regions will be held in 2003-04. The analytic and technical contribution of these meetings, however, is expected to be at best modest. National efforts of the type carried out 30 years ago by the Commission on Population Growth and the American Future would be all the more salutary. [source] Benchmark tipping and the role of the swap market in price discoveryTHE JOURNAL OF FUTURES MARKETS, Issue 10 2007Russell PoskittArticle first published online: 14 AUG 200 The author uses a high-frequency data set to investigate the roles of the sterling swap and futures markets in price discovery at the short-end of the sterling yield curve. Information flows between the futures and swap markets are found to be largely contemporaneous. Causal information flows are bidirectional, although the futures market dominates the information flow over the very short term. Thus, the futures market remains the primary locus of price discovery despite the increased use of swaps as a pricing benchmark and hedging instrument in recent years. © 2007 Wiley Periodicals, Inc. Jrl Fut Mark 27:981,1001, 2007 [source] Identifying Modifier Loci in Existing Genome Scan DataANNALS OF HUMAN GENETICS, Issue 5 2008E. W. Daw Summary In many genetic disorders in which a primary disease-causing locus has been identified, evidence exists for additional trait variation due to genetic factors. These findings have led to studies seeking secondary ,modifier' loci. Identification of modifier loci provides insight into disease mechanisms and may provide additional screening and treatment targets. We believe that modifier loci can be identified by re-analysis of genome screen data while controlling for primary locus effects. To test this hypothesis, we simulated multiple replicates of typical genome screening data on to two real family structures from a study of hypertrophic cardiomyopathy. With this marker data, we simulated two trait models with characteristics similar to one measure of hypertrophic cardiomyopathy. Both trait models included 3 genes. In the first, the trait was influenced by a primary gene, a secondary ,modifier' gene, and a third very small effect gene. In the second, we modeled an interaction between the first two genes. We examined power and false positive rates to map the secondary locus while controlling for the effect of the primary locus with two types of analyses. First, we examined Monte Carlo Markov chain (MCMC) simultaneous segregation and linkage analysis as implemented in Loki, for which we calculated two scoring statistics. Second, we calculated LOD scores using an individual-specific liability class based on the quantitative trait value. We found that both methods produced scores that are significant on a genome-wide level in some replicates. We conclude that mapping of modifier loci in existing samples is possible with these methods. [source] | ||||||||||