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Several Generations (several + generation)
Selected AbstractsGenetic pattern of the recent recovery of European otters in southern FranceECOGRAPHY, Issue 2 2008Xavier Janssens We investigated how landscape affects the population genetic structure and the dispersal of the elusive European otter Lutra lutra in a contemporary colonization context, over several generations and at the level of hydrographic basins. Our study area included 10 basins located in the Cévennes National Park (CNP), at the southern front of the natural otter recovery in France. Each basin comprised 50 to 300 km of permanent rivers that were surveyed for otter presence from 1991 to 2005. Faecal samples collected in 2004 and 2005 in this area were genotyped at 9 microsatellite loci, resulting in the identification of 70 genetically distinct individuals. Bayesian clustering methods were used to infer genetic structure of the populations and to compare recent gene flow to the observed colonization. At the regional level, we identified 2 distinct genetic clusters (NE and SW; FST=0.102) partially separated by ridges, suggesting that the CNP was recolonized by 2 genetically distinct otter populations. At the basin level, the genetic distance between groups of individuals in different basins was positively correlated to the mean slope separating these basins. The probable origins and directions of individual movements (i.e. migration between clusters and basin colonization inside clusters) were inferred from assignment tests. This approach shows that steep and dry lands can stop, impede or divert the dispersal of a mobile carnivore such as the otter. [source] Connectivity, non-random extinction and ecosystem function in experimental metacommunitiesECOLOGY LETTERS, Issue 5 2010Philip Staddon Ecology Letters (2010) 13: 543,552 Abstract The spatial insurance hypothesis indicates that connectivity is an important attribute of natural ecosystems that sustains both biodiversity and ecosystem function. We tested the hypothesis by measuring the impact of manipulating connectivity in experimental metacommunties of a natural and diverse microecosystem. Isolation led to the extinction of large-bodied apex predators, subsequently followed by increases in prey species abundance. This trophic cascade was associated with significantly altered carbon and nitrogen fluxes in fragmented treatments. The ecosystem impacts were characteristic of a function debt because they persisted for several generations after the initial loss of connectivity. Local extinctions and disruption of ecosystem processes were mitigated, and even reversed, by the presence of corridors in the connected metacommunities, although these beneficial effects were unexpectedly delayed. We hypothesized that corridors maintained grazer movement between fragments, which enhanced microbial activity, and decomposition in comparison to isolated fragments. Our results indicate that knowledge of habitat connectivity and spatial processes is essential to understand the magnitude and timing of ecosystem perturbation in fragmented landscapes. [source] Genetic variability in a population of arbuscular mycorrhizal fungi causes variation in plant growthECOLOGY LETTERS, Issue 2 2006Alexander M. Koch Abstract Different species of arbuscular mycorrhizal fungi (AMF) alter plant growth and affect plant coexistence and diversity. Effects of within-AMF species or within-population variation on plant growth have received less attention. High genetic variation exists within AMF populations. However, it is unknown whether genetic variation contributes to differences in plant growth. In our study, a population of AMF was cultivated under identical conditions for several generations prior to the experiments thus avoiding environmental maternal effects. We show that genetically different Glomus intraradices isolates from one AMF population significantly alter plant growth in an axenic system and in greenhouse experiments. Isolates increased or reduced plant growth meaning that plants potentially receive benefits or are subject to costs by forming associations with different individuals in the AMF population. This shows that genetic variability in AMF populations could affect host-plant fitness and should be considered in future research to understand these important soil organisms. [source] Techniques for continuous rearing and assessing host preference of a multivoltine leaf-mining moth, Acrocercops transecta (Lepidoptera: Gracillariidae)ENTOMOLOGICAL SCIENCE, Issue 3 2005Issei OHSHIMA Abstract Techniques for rearing the leaf-mining moth Acrocercops transecta successively over several generations are described. Based on continuous rearing, some life historical parameters in A. transecta were determined. Because of its short generation time, successive rearing makes the moth suitable for mating experiments and a model organism to elucidate the mechanism of host-associated speciation. [source] MINIMAL SELFING, FEW CLONES, AND NO AMONG-HOST GENETIC STRUCTURE IN A HERMAPHRODITIC PARASITE WITH ASEXUAL LARVAL PROPAGATIONEVOLUTION, Issue 3 2006Charles D. Criscione Abstract Little is known about actual mating systems in natural populations of parasites or about what constitutes the limits of a parasite deme. These parameters are interesting because they affect levels of genetic diversity, opportunities for local adaptation, and other evolutionary processes. We expect that transmission dynamics and the distribution of parasites among hosts should have a large effect on mating systems and demic structure, but currently we have mostly speculation and very few data. For example, infrapopulations (all the parasites in a single host) should behave as demes if parasite offspring are transmitted as a clump from host to host over several generations. However, if offspring are well mixed, then the parasite component population (all the parasites among a host population) would function as the deme. Similarly, low mean intensities or a high proportion of worms in single infections should increase the selfing rate. For species having an asexual amplification stage, transmission between intermediate and definitive (final) hosts will control the variance in clonal reproductive success, which in turn could have a large influence on effective sizes and rates of inbreeding. We examined demic structure, selfing rates, and the variance in clonal reproductive success in natural populations of Plagioporus shawi, a hermaphroditic trematode that parasitizes salmon. Overall levels of genetic diversity were very high. An a posteriori inference of population structure overwhelmingly supports the component population as the deme, rather than individual infrapopulations. Only a single pair of 597 adult individuals was identified as clones. Thus, the variance in clonal reproductive success was almost zero. Despite being hermaphroditic, P. shawi appears to be almost entirely outcrossing. Genetic estimates of selfing (<5%) were in accordance with the proportion of parasites from single infections. Thus, it appears that individual flukes outcross whenever possible and only resort to selfing when alone. Finally, our data support the hypothesis that aquatic transmission and the use of several intermediate hosts promotes high genetic diversity and well-mixed infrapopulations. [source] THE EVOLUTION OF GENETIC CANALIZATION UNDER FLUCTUATING SELECTIONEVOLUTION, Issue 1 2000Tadeusz J. Kawecki Abstract., If the direction of selection changes from generation to generation, the ability to respond to selection is maladaptive: the response to selection in one generation leads to reduced fitness in the next. Because the response is determined by the amount of genetic variance expressed at the phenotypic level, rapidly fluctuating selection should favor modifier genes that reduce the phenotypic effect of alleles segregating at structural loci underlying the trait. Such reduction in phenotypic expression of genetic variation has been named "genetic canalization." I support this argument with a series of two- and multilocus models with alternating linear selection and Gaussian selection with fluctuating optimum. A canalizing modifier gene affects the fitness of its carriers in three ways: (1) it reduces the phenotypic consequences of genetic response to previous selection; (2) it reduces the genetic response to selection, which is manifested as linkage disequilibrium between the modifier and structural loci; and (3) it reduces the phenotypic variance. The first two effects reduce fitness under directional selection sustained for several generations, but improve fitness when the direction of selection has just been reversed. The net effect tends to favor a canalizing modifier under rapidly fluctuating selection regimes (period of eight generations or less). The third effect improves fitness of the modifier allele if the fitness function is convex and reduces it if the function is concave. Under fluctuating Gaussian selection, the population is more likely to experience the concave portion of the fitness function when selection is stronger. Therefore, only weak to moderately strong fluctuating Gaussian selection favors genetic canalization. This paper considerably broadens the conditions that favor genetic canalization, which so far has only been postulated to evolve under long-term stabilizing selection. [source] Reproductive interference determines persistence and exclusion in species interactionsJOURNAL OF ANIMAL ECOLOGY, Issue 5 2009Shigeki Kishi Summary 1.,Reproductive interference is a negative interspecific sexual interaction that adversely affects the fitness of males and females during reproductive process. Theoretical studies suggest that because reproductive interference is characterized by positive frequency dependence it is far more likely to cause species exclusion than the density dependence of resource competition. However, the respective contributions of resource competition and reproductive interference to species exclusion, which have been frequently observed in many competition studies, remain unclear. 2.,We show that reproductive interference is a far more critical cause of species exclusion than resource competition in the competition between Callosobruchus bean weevil species. In competition experiments over several generations, we manipulated the initial relative abundance of the adzuki bean beetle, Callosobruchus chinensis, and the southern cowpea beetle, Callosobruchus maculatus. When the initial adult ratio of C. chinensis : C. maculatus were 6 : 2 and 4 : 4, C. chinensis excluded C. maculatus. However, when C. maculatus was four times more abundant than C. chinensis at the start, we observed the opposite outcome. 3.,A behavioural experiment using adults of the two species revealed asymmetric reproductive interference. The fecundity and longevity of C. maculatus females, but not those of C. chinensis females, decreased when the females were kept with heterospecific males. Fecundities of females of both species decreased as the number of heterospecific males increased. In contrast, resource competition at the larval stage resulted in higher survival of C. maculatus than of C. chinensis. 4.,These results suggest that the positive frequency-dependent effect of reproductive interference resulted in species exclusion, depending on the initial population ratio of the two species, and the asymmetry of the interference resulted in C. chinensis being dominant in this study, as in previous studies. Classical competition studies should be reviewed in light of this evidence for reproductive interference. [source] A silver spoon for a golden future: long-term effects of natal origin on fitness prospects of oystercatchers (Haematopus ostralegus)JOURNAL OF ANIMAL ECOLOGY, Issue 2 2006MARTIJN VAN DE POL Summary 1Long-term effects of conditions during early development on fitness are important for life history evolution and population ecology. Using multistrata mark,recapture models on 20 years of data, we quantified the relation between rearing conditions and lifetime fitness in a long-lived shorebird, the oystercatcher (Haematopus ostralegus). We addressed specifically the relative contribution of short- and long-term effects of rearing conditions to overall fitness consequences. 2Rearing conditions were defined by differences in natal habitat quality, in which there is a clear dichotomy in our study population. In the first year of life, fledglings from high-quality natal origin had a 1·3 times higher juvenile survival. Later in life (age 3,11), individuals of high-quality natal origin had a 1·6 times higher adult prebreeder survival. The most striking effect of natal habitat quality was that birds that were reared on high-quality territories had a higher probability of settling in high-quality habitat (44% vs. 6%). Lifetime reproductive success of individuals born in high-quality habitat was 2·2 times higher than that of individuals born in low-quality habitat. This difference increased further when fitness was calculated over several generations, due to a correlation between the quality of rearing conditions of parents and their offspring. 3Long-term effects of early conditions contributed more to overall fitness differences as short-term consequences, contrary to common conceptions on this issue. 4This study illustrates that investigating only short-term effects of early conditions can lead to the large underestimation of fitness consequences. We discuss how long-term consequences of early conditions may affect settlement decisions and source,sink population interactions. [source] Moving to suburbia: ontogenetic and evolutionary consequences of life on predator-free islandsJOURNAL OF BIOGEOGRAPHY, Issue 5-6 2002Daniel T. Blumstein Aim Many species find themselves isolated from the predators with which they evolved. This situation commonly occurs with island biota, and is similar to moving from the dangerous inner-city to the suburbs. Economic thinking tells us that we should expect costly antipredator behaviour to be lost if it is no longer beneficial. The loss of antipredator behaviour has important consequences for those seeking to translocate or reintroduce individuals from predator-free islands back to the predator-rich mainland, but we have neither a detailed understanding of the mechanisms of loss nor information on the time course of relaxed selection. Some antipredator behaviours are experience-dependent: experience with predators is required for their proper performance. In these cases, antipredator behaviour is lost after only a single generation of isolation, but it should be able to be regained following exposure to predators. Other behaviours may be more `hard-wired'. The evolutionary loss of antipredator behaviour may occur over as few as several generations, but behaviours may also persist for many thousands of years of predator-free living. Location Australia and New Zealand. Methods I discuss the results of a series of studies designed to document the mechanisms and time course of relaxed selection for antipredator behaviour in macropodid marsupials. Controlled studies of visual, acoustic and olfactory predator recognition, as well as field studies of antipredator vigilance focused on several species of kangaroos and wallabies. Results Visual predator recognition may be retained following 9500 years of relaxed selection, but olfactory and acoustic predator recognition may have to be learned. Insular populations allow humans to approach closer before fleeing than mainland animals. Insular species may retain `group size effects' , the ability to seek safety in numbers , when they are exposed to any predators. Main conclusions I suggest that the presence of any predators may be an important factor in maintaining functional antipredator behaviour. Managers should pay particular attention as to the source and evolutionary history of their population when planning translocations or reintroductions. [source] Telomerase reverse transcriptase haploinsufficiency and telomere length in individuals with 5p, syndromeAGING CELL, Issue 5 2007Hong-Yan Du Summary Telomerase, which maintains the ends of chromosomes, consists of two core components, the telomerase reverse transcriptase (TERT) and the telomerase RNA (TERC). Haploinsufficiency for TERC or TERT leads to progressive telomere shortening and autosomal dominant dyskeratosis congenita (DC). The clinical manifestations of autosomal dominant DC are thought to occur when telomeres become critically short, but the rate of telomere shortening in this condition is unknown. Here, we investigated the consequences of de novo TERT gene deletions in a large cohort of individuals with 5p, syndrome. The study group included 41 individuals in which the chromosome deletion resulted in loss of one copy of the TERT gene at 5p15.33. Telomere length in peripheral blood cells from these individuals, although within the normal range, was on average shorter than in normal controls. The shortening was more significant in older individuals suggesting an accelerated age-dependent shortening. In contrast, individuals with autosomal dominant DC due to an inherited TERC gene deletion had very short telomeres, and the telomeres were equally short regardless of the age. Although some individuals with 5p, syndrome showed clinical features that were reminiscent of autosomal dominant DC, these features did not correlate with telomere length, suggesting that these were not caused by critically short telomeres. We conclude that a TERT gene deletion leads to slightly shorter telomeres within one generation. However, our results suggest that several generations of TERT haploinsufficiency are needed to produce the very short telomeres seen in patients with DC. [source] PATERNAL LEAKAGE OF MITOCHONDRIAL DNA IN A FUCUS (PHAEOPHYCEAE) HYBRID ZONE,JOURNAL OF PHYCOLOGY, Issue 3 2009Galice Hoarau Eukaryotic mitochondria are mostly uniparentally (maternally) inherited, although mtDNA heteroplasmy has been reported in all major lineages. Heteroplasmy, the presence of more than one mitochondrial genome in an individual, can arise from recombination, point mutations, or by occasional transmission of the paternal mtDNA (=paternal leakage). Here, we report the first evidence of mtDNA paternal leakage in brown algae. In Denmark, where Fucus serratus L. and Fucus evanescens C. Agardh have hybridized for years, we found eight introgressed individuals that possessed the very distinct haplotypes of each parental species. The finding of heteroplasmy in individuals resulting from several generations of backcrosses suggests that paternal leakage occurred in earlier generations and has persisted through several meiotic bottlenecks. [source] Christian Bodies: Dialectics of Sickness and Salvation Among the Maisin of Papua New GuineaJOURNAL OF RELIGIOUS HISTORY, Issue 3 2003John Barker This article examines the impact of a Charismatic youth fellowship movement among the Maisin people of Oro Province, Papua New Guinea, in the late 1990s. Drawing upon ethnographic and archival sources, I show that the response conforms to a pattern repeated periodically over a century of regional religious movements focused upon eradicating sorcery and promoting health. Over several generations, Maisin have experienced and interpreted Christianity in ways that at once confirm a basic belief in sorcery while prodding the faithful towards increasingly individualistic notions of morality and, thus, new collectivist responses to misfortunes like life-threatening illnesses. Thus, while the main intent of religious movements among the Maisin has remained remarkably consistent, the underlying conception of the links between morality, sickness, and healing has shifted markedly over the years. The article thus demonstrates that Christianity in this Melanesian community has had both conservative and transformational effects upon everyday conceptions of morality, sickness, healing, and redemption. More generally, the article advocates moving the study of religious change in longer contacted regions of Melanesia from a dualistic model that opposes Western and indigenous cultures to one that examines the complex historical development of vernacular Christianity. [source] Asian and Pacific Islander women scientists and engineers: A narrative exploration of model minority, gender, and racial stereotypesJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 4 2002Pauline W.U. Chinn This qualitative study uses narrative methodology to understand what becoming a scientist or engineer entails for women stereotyped as "model minorities." Interviews with four Chinese and Japanese women focused on the social contexts in which science is encountered in classrooms, families, and community. Interpretation was guided by theories that individuals construct personal narratives mediated by cultural symbolic systems to make meaning of experiences. Narratives revealed that Confucian cultural scripts shaped gender expectations even in families several generations in America. Regardless of parents' level of education, country of birth, and number of children, educational expectations, and resources were lower for daughters. Parents expected daughters to be compliant, feminine, and educated enough to be marriageable. Findings suggest K,12 gender equity science practices encouraged development of the women's interests and abilities but did not affect parental beliefs. The author's 1999 study of Hawaiians/Pacific Islander and Filipina female engineers is included in implications for teacher education programs sensitive to gender, culture, ethnicity, and language. © 2002 Wiley Periodicals Inc. J Res Sci Teach 39: 302,323, 2002 [source] Damped oscillations in the adaptive response of the iron homeostasis network of E. coliMOLECULAR MICROBIOLOGY, Issue 2 2010Amnon Amir Summary Living organisms often have to adapt to sudden environmental changes and reach homeostasis. To achieve adaptation, cells deploy motifs such as feedback in their genetic networks, endowing the cellular response with desirable properties. We studied the iron homeostasis network of E. coli, which employs feedback loops to regulate iron usage and uptake, while maintaining intracellular iron at non-toxic levels. Using fluorescence reporters for iron-dependent promoters in bulk and microfluidics-based, single-cell experiments, we show that E. coli cells exhibit damped oscillations in gene expression, following sudden reductions in external iron levels. The oscillations, lasting for several generations, are independent of position along the cell cycle. Experiments with mutants in network components demonstrate the involvement of iron uptake in the oscillations. Our findings suggest that the response is driven by intracellular iron oscillations large enough to induce nearly full network activation/deactivation. We propose a mathematical model based on a negative feedback loop closed by rapid iron uptake, and including iron usage and storage, which captures the main features of the observed behaviour. Taken together, our results shed light on the control of iron metabolism in bacteria and suggest that the oscillations represent a compromise between the requirements of stability and speed of response. [source] A heritage of ambiguity: The historical substrate of vernacular multiculturalism in Yucatán, MexicoAMERICAN ETHNOLOGIST, Issue 2 2009FERNANDO ARMSTRONG-FUMERO ABSTRACT Forms of official multiculturalism that many recent scholars have characterized as a reflection of post,Cold War social movements and emergent forms of neoliberal governmentality can be experienced locally in ways that reflect a greater degree of continuity with older institutions and styles of politics. In Yucatán, ambiguities in the meaning of officially sanctioned categories such as "Maya" and "indigenous" have persisted even as local people and representatives of the state collaborate in the consolidation of official cultural institutions. The collective experience of several generations of Maya speakers in negotiating this ambiguous discursive space creates strong parallels between contemporary multiculturalism and older indigenist policies. [Maya, Mexico, Yucatán, multiculturalism, indigenous policy, ambiguity] [source] Low birth weight of contemporary African Americans: An intergenerational effect of slavery?AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 1 2009Grazyna Jasienska The average birth weight in the contemporary African-American population is about 250 g lower than the average birth weight of European Americans. Differences in genetic and socioeconomic factors present between these two groups can explain only part of birth weight variation. I propose a hypothesis that the low birth weight of contemporary African Americans not only results from the difference in present exposure to lifestyle factors known to affect fetal development but also from conditions experienced during the period of slavery. Slaves had poor nutritional status during all stages of life because of the inadequate dietary intake accompanied by high energetic costs of physical work and infectious diseases. The concept of "fetal programming" suggests that physiology and metabolism including growth and fat accumulation of the developing fetus, and, thus its birth weight, depend on intergenerational signal of environmental quality passed through generations of matrilinear ancestors. I suggest that several generations that have passed since the abolition of slavery in the United States (1865) has not been enough to obliterate the impact of slavery on the current biological and health condition of the African-American population. Am. J. Hum. Biol., 2009. © 2008 Wiley-Liss, Inc. [source] Development of dominant nuclear male-sterile lines with a blue seed marker in durum and common wheatPLANT BREEDING, Issue 1 2001N. Tian Abstract In order to develop genie male-sterile lines with a blue seed marker, male-sterile plants, controlled by a dominant nuclear gene Ms2, were used as female parents against a 4E disomic addition line ,Xiaoyan Lanli'(2n= 44, AABBDD+4EII) as the male parent to produce monosomic addition lines with blue seed. Male-sterile plants from the monosomic addition lines were pollinated with durum wheat for several generations and in 1989 a male-sterile line with the blue grain gene and the male-sterile gene Ms2 on the same additional chromosome was detected and named line 89-2343. Using this line, the blue seed marker was successfully added to a short male-sterile line containing Ms2 and Rht10. The segregation ratios of male sterility and seed colour as well as the chromosome figurations of different plants indicated that the blue grain genes, Ms2 and Rht10 were located on the same additional chromosome. Cytological analysis showed that the blue marker male-sterile lines in durum wheat and common wheat were monosomic with an additional chromosome 4E. The inheritance ratio for blue seed male-sterile plants and white seed male-fertile plants was 19.7% and 80.3%, respectively, in common wheat. The potential for using blue marker sterile lines in population improvement and hybrid production is discussed. [source] Martin K. Starr: A Visionary Proponent for System Integration, Modular Production, and Catastrophe AvoidancePRODUCTION AND OPERATIONS MANAGEMENT, Issue 1 2007Sushil Gupta Martin K. Starr facilitated the creation of an identity for production and operations management (POM) as an academic discipline. This paper aims to summarize Starr's substantial contributions to scholarly inquiry on system integration and interfunctional coordination, modular production, and catastrophe avoidance. Even after four decades, we describe how his legacy in these areas continues to define several major drivers of operations and supply chain management research and practice. Starr has influenced several generations of students, professors, and executives with his writings, teaching, and leadership roles in the POM community that include 32 years on the faculty of the Columbia School of Business, 15 years as Editor-in-Chief of Management Science, and presidency of the Production and Operations Management Society. [source] Brief communication: Evaluating grandmother effectsAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2009Kristen Hawkes Abstract Women who have outlived child-bearing have long been described as postreproductive. But contributions they make to the survival or fertility of their descendants enhance the reproduction of their genes. Consequently, natural selection affects this characteristic stage of human life history. Grandmother effects can be measured in data sets that include births and deaths over several generations, but unmeasured covariates complicate the task. Here we focus on two complications: cohort shifts in mortality and fertility, and maternal age at death. We use the Utah Population Database to show that longevity of grandmothers may be associated with fewer grandchildren, as reported by Madrigal and Melendez-Obando (Am J Phys Anthropol 136 (2008) 223,229) for a Costa Rican sample, even when grandmother effects are actually positive. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source] Parental failure in captive cotton-top tamarins (Saguinus Oedipus)AMERICAN JOURNAL OF PRIMATOLOGY, Issue 3 2001Massimo Bardi Abstract Several New World monkey species experience high rates of infant mortality in captivity, and parental failure in the form of infant neglect and abuse is often regarded as one of the leading causes of this problem. We explored a large archival database to assess environmental, familial, and biological variables identified as significant for parental success in previous studies of captive tamarins, through several generations and across several dozen pedigrees. Using a stepwise multiple regression analysis we developed a model including the fewest variables able to identify statistically significant predictors of infant outcome. We found that seven independent variables could predict infant outcome in the colony. The most important appeared to be the presence of helpers with whom parents could share infant carrying. Mother's experience and litter size were two other variables that contributed to a significant extent to explaining parental failure. Moreover, the model showed that there is a measurable contribution to infant outcome due to the health status of both parents. Finally, we found a distinct role for mothers and fathers, and that parental failure follows different patterns for abuse and rejection. Am. J. Primatol. 54:159,169, 2001. © 2001 Wiley-Liss, Inc. [source] A Likelihood-Based Trait-Model-Free Approach for Linkage Detection of Binary TraitBIOMETRICS, Issue 1 2010S. Basu Summary Trait-model-free (or "allele-sharing") approach to linkage analysis is a popular tool in genetic mapping of complex traits, because of the absence of explicit assumptions about the underlying mode of inheritance of the trait. The likelihood framework introduced by Kong and Cox (1997,,American Journal of Human Genetics,61, 1179,1188) allows calculation of accurate p-values and LOD scores to test for linkage between a genomic region and a trait. Their method relies on the specification of a model for the trait-dependent segregation of marker alleles at a genomic region linked to the trait. Here we propose a new such model that is motivated by the desire to extract as much information as possible from extended pedigrees containing data from individuals related over several generations. However, our model is also applicable to smaller pedigrees, and has some attractive features compared with existing models (Kong and Cox, 1997), including the fact that it incorporates information on both affected and unaffected individuals. We illustrate the proposed model on simulated and real data, and compare its performance with the existing approach (Kong and Cox, 1997). The proposed approach is implemented in the program lm_ibdtests within the framework of MORGAN 2.8 (http://www.stat.washington.edu/thompson/Genepi/MORGAN/Morgan.shtml). [source] Environmental risk factors and allergic bronchial asthmaCLINICAL & EXPERIMENTAL ALLERGY, Issue 9 2005G. D'Amato Summary The prevalence of allergic respiratory diseases such as bronchial asthma has increased in recent years, especially in industrialized countries. A change in the genetic predisposition is an unlikely cause of the increase in allergic diseases because genetic changes in a population require several generations. Consequently, this increase may be explained by changes in environmental factors, including indoor and outdoor air pollution. Over the past two decades, there has been increasing interest in studies of air pollution and its effects on human health. Although the role played by outdoor pollutants in allergic sensitization of the airways has yet to be clarified, a body of evidence suggests that urbanization, with its high levels of vehicle emissions, and a westernized lifestyle are linked to the rising frequency of respiratory allergic diseases observed in most industrialized countries, and there is considerable evidence that asthmatic persons are at increased risk of developing asthma exacerbations with exposure to ozone, nitrogen dioxide, sulphur dioxide and inhalable particulate matter. However, it is not easy to evaluate the impact of air pollution on the timing of asthma exacerbations and on the prevalence of asthma in general. As concentrations of airborne allergens and air pollutants are frequently increased contemporaneously, an enhanced IgE-mediated response to aeroallergens and enhanced airway inflammation could account for the increasing frequency of allergic respiratory allergy and bronchial asthma. Pollinosis is frequently used to study the interrelationship between air pollution and respiratory allergy. Climatic factors (temperature, wind speed, humidity, thunderstorms, etc) can affect both components (biological and chemical) of this interaction. By attaching to the surface of pollen grains and of plant-derived particles of paucimicronic size, pollutants could modify not only the morphology of these antigen-carrying agents but also their allergenic potential. In addition, by inducing airway inflammation, which increases airway permeability, pollutants overcome the mucosal barrier and could be able to ,prime' allergen-induced responses. There are also observations that a thunderstorm occurring during pollen season can induce severe asthma attacks in pollinosis patients. After rupture by thunderstorm, pollen grains may release part of their cytoplasmic content, including inhalable, allergen-carrying paucimicronic particles. [source] Explaining Color Term Typology With an Evolutionary ModelCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 1 2007Mike Dowman An expression-induction model was used to simulate the evolution of basic color terms to test Berlin and Kay's (1969) hypothesis that the typological patterns observed in basic color term systems are produced by a process of cultural evolution under the influence of biases resulting from the special properties of universal focal colors. Ten agents were simulated, each of which could learn color term denotations by generalizing from examples using Bayesian inference, and for which universal focal red, yellow, green, and blue were especially salient, but unevenly spaced in the perceptual color space. Conversations between these agents, in which agents would learn from one another, were simulated over several generations, and the languages emerging at the end of each simulation were investigated. The proportion of color terms of each type correlated closely with the equivalent frequencies found in the World Color Survey, and most of the emergent languages could be placed on one of the evolutionary trajectories proposed by Kay and Maffi (1999). The simulation therefore demonstrates how typological patterns can emerge as a result of learning biases acting over a period of time. [source] | ||||||||||||||||