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PubMedDate not supplied

Immunity, immunoregulation and the ecology of trichuriasis and ascariasis.

Immune responses to human roundworm (Ascaris lumbricoides) and whipworm (Trichuris trichiura) and their role in controlling worm populations are reviewed. Recent immunoepidemiological data implicate T(H)2-mediated responses in limiting A. lumbricoides and T. trichiura populations. Reinfection studies further suggest that IL-5 cytokine responses are negatively associated with adult recruitment in T. trichiura but not A. lumbricoides and may therefore be involved in negative intraspecific and interspecific interactions mediated through the host immune system. The importance of inducible immunoregulatory networks in the ecology of the host-parasite relationship is considered, with particular regard to possible manipulative strategies by the parasites. This aspect of the worms' interaction with the host immune system is both poorly known and potentially central to an understanding of parasite population dynamics and the evolutionary pressures that have shaped present-day host-parasite associations. Some possible implications of worm-mediated immunomodulation for the occurrence of bystander infectious diseases in human populations and the management of de-worming programmes are also discussed.

Adult↗
PubMed2006

Low genetic variation and no detectable population structure in aspergillus fumigatus compared to closely related Neosartorya species.

Aspergillus fumigatus is an anamorphic euascomycete mold with a ubiquitous presence worldwide. Despite intensive work to understand its success as a pathogen infecting immunosuppressed patients, the population dynamics and recent evolutionary history of A. fumigatus remain understudied. We examined patterns of genetic variation at three intergenic loci for 70 natural isolates from Europe, North America, South America, Asia, Africa, and Australia. The same loci were used to analyze within-population genetic variation for 33 isolates obtained from five geographic locations. Neither data set detected evidence of population differentiation or found any association between the genetic and geographic distances among these isolates. No evidence for genetic differentiation within the two A. fumigatus mating types was detected. The genetic diversity of A. fumigatus, contrasted with that of its close teleomorphic relatives, Neosartorya fischeri and Neosartorya spinosa, is remarkably low.

Aspergillus fumigatus↗
PubMed2006

Quantification of the retrotransposon BARE-1 reveals the dynamic nature of the barley genome.

We used quantitative real-time PCR analysis to measure the copy number of the BARE-1 retrotransposon in 5 cultivars of barley (Hordeum vulgare), as well as in samples from its wild relative, Hordeum spontaneum. Two sets of PCR primers were used to amplify regions within the long terminal repeat (LTR) and the reverse transcriptase (RT) gene of BARE-1 (GenBank accession Z17327). The LTR primers detected an average of 2.148 x 105 +/- 0.012 x 105 copies per haploid genome among barley samples, whereas the RT primers detected an average of 1.588 x 104 +/- 0.085 x 104 copies. The average ratio of LTR:RT was estimated to be 13.5:1. This finding indicates that more than 7% of the barley genome is occupied by BARE-1 elements in the form of solo LTRs and another 2.6% of the genome is occupied by the full-length element. Taken together, BARE-1 sequences represent approximately 9.6% of the barley genome among the barley plants used in this study. For the above estimation, a genome size of 5.44 x 103 Mb for H. vulgare and 5.39 x 103 Mb for H. spontaneum were assumed. Our study on quantification results of the BARE-1 for a small group of barley cultivars showed that there are significant differences among cultivars in terms of BARE-1 copy number, providing further evidence that BARE-1 is active and has a major role in shaping the barley genome as a result of breeding and selection. Quantification results also showed that most of the elements (> 90%) are present as truncated copies (solo LTRs). These results show that there is a high level of recombination leading to the formation of truncated elements and a subsequent DNA loss from the genome. Taken together, our study provides a glimpse into a dynamic micro-evolutionary process that is the by-product of genome reshuffling and directional selection in barley breeding programs.

Breeding↗
PubMed2004

Spatio-temporal dynamics of a neutralized B chromosome in the grasshopper Eyprepocnemis plorans.

Spatial and temporal patterns of frequency variation for a neutralized B chromosome in the grasshopper Eyprepocnemis plorans were analyzed along six transects in the east of Spain to explore possible factors affecting the population dynamics of this polymorphism. Three parameters were employed to quantify B frequency: prevalence, load and mean frequency. Of them, load seemed to be the less sensitive parameter, probably due to its small range of variation. Prevalence, however, shows ample variation, but the mean frequency of B chromosomes per individual is the best parameter to characterize B frequency. Only river transects revealed significant differences among populations, and the use of two geographic explicit approaches (Mantel test and distograms) revealed significant isolation by distance (IBD), especially at the Segura River mouth, presumably due to low gene flow and drift. No temporal trend was found in the Segura River transects, which is consistent with the slow changes in B frequency expected during the random walk for neutralized B chromosomes. But these transects showed a clear spatial pattern, with B1 showing lower frequency in the upper course of this river. The present results provide the first empirical evidence of IBD in the evolution of a neutralized B chromosome, and support the notion that B dynamics at this evolutionary stage is best explained by a metapopulation approach.

Animals↗
PubMed1997

Nature of pathology: the character of danger implicit in functional impairment.

OBJECTIVE: To facilitate clinical and scientific consensus in definitions of psychiatric disorders and with regard to the nature and meaning of pathology more generally. METHOD: An essay based on a review of definitional problems encountered by psychiatric epidemiologists, with examples taken from selected studies of historic importance. A remedy is suggested and illustrated by experiences with its use in the Stirling County Study. RESULTS: A concept of pathology, termed for reference as "impairment-risk," is defined as the danger that functional impairment carries for subsequent health adversities. The concept is based on the classical notions of Rudolf Virchow, the empirical orientations of Adolf Meyer's psychobiology, the functional concepts of physiology, and the dynamics implied by evolutionary biology. The ideas embedded in "impairment-risk" are beginning to be represented in official classifications of mental disorders. CONCLUSIONS: Impairment-risk has potential in the further development of psychiatric epidemiology because of the connections made possible among neuroscience, genetics, general medicine, psychology, and the more empirical of the social and behavioural sciences.

Adolescent↗
PubMed1990

Overlooked connections: policy development and implementation in state-local relations.

Increased public demand for health services, combined with fiscal and operating restraints, has led to the need for programs that will operate efficiently and effectively to achieve their objectives. Establishing such programs requires an understanding of the factors that contribute to their development and implementation. This in turn requires a greater understanding of the policy formulation and policy implementation processes. This paper uses a case study of Michigan's State/Local Cost Sharing Program to explore how policy formulation links to and influences implementation; it considers the interaction between the administrative and political processes and how they are affected by shifting power relations, constituencies, and the environment, and how in turn these affect program leadership and operating policies. The paper develops a model as a framework for monitoring the course of the program through the policy cycle and recommends that the policy process be considered as dynamic, interactive, and evolutionary. The case study approach allows for a greater understanding of the phases of the process, their interaction, and their impact on specific policy outcomes.

Community Participation↗
PubMed2003

A caudorostral wave of RALDH2 conveys anteroposterior information to the cardiac field.

Establishment of anteroposterior (AP) polarity is one of the earliest decisions in cardiogenesis and plays an important role in the coupling between heart and blood vessels. Recent research implicated retinoic acid (RA) in the communication of AP polarity to the heart. We utilized embryo culture, in situ hybridization, morphometry, fate mapping and treatment with the RA pan-antagonist BMS493 to investigate the relationship between cardiac precursors and RA signalling. We describe two phases of AP signalling by RA, reflected in RALDH2 expression. The first phase (HH4-7) is characterized by increasing proximity between sino-atrial precursors and the lateral mesoderm expressing RALDH2. In this phase, RA signalling is consistent with diffusion of the morphogen from a large field rather than a single hot spot. The second phase (HH7-8) is characterized by progressive encircling of cardiac precursors by a field of RALDH2 originating from a dynamic and evolutionary-conserved caudorostral wave pattern in the lateral mesoderm. At this phase, cardiac AP patterning by RA is consistent with localized action of RA by regulated activation of the Raldh2 gene within an embryonic domain. Systemic treatment with BMS493 altered the cardiac fate map such that ventricular precursors were found in areas normally devoid of them. Topical application of BMS493 inhibited atrial differentiation in left anterior lateral mesoderm. Identification of the caudorostral wave of RALDH2 as the endogenous source of RA establishing cardiac AP fates provides a useful model to approach the mechanisms whereby the vertebrate embryo confers axial information on its organs.

Aldehyde Oxidoreductases↗
PubMed2006

Evolving metacommunities: toward an evolutionary perspective on metacommunities.

The metacommunity framework predicts that local coexistence depends on the outcome of local species interactions and regional migration. In analogous fashion, spatial structure among populations can shape species interactions through evolutionary mechanisms. Yet, most metacommunity theories assume that populations do not evolve. Here, we evaluate how evolution shapes local species coexistence and exclusion within the multiscale and multispecies context embodied by the metacommunity framework. In general, coexistence in joint ecological-evolutionary models requires low to intermediate dispersal rates that can promote maintenance of both regional species and genetic diversity. These conditions support a set of key mechanisms that modify patterns of species coexistence including local adaptation, gene storage effects, genetic rescue effects, spatial genetic subsidies, and metacommunity evolution. Multispecies extensions indicate that correlated selection can further alter the outcome of interspecific interactions depending on the magnitude and direction of correlations and shape of fitness trade-offs. We suggest that an evolving metacommunity perspective has the potential to generate novel predictions about community structure and function by incorporating the genetic and species diversity that characterize natural communities. In adopting such a perspective, we seek to facilitate understanding about the interactions between evolutionary and metacommunity dynamics.

Biological Evolution↗
PubMed2000

Molecular evolution of the chalcone synthase multigene family in the morning glory genome.

Plant genomes appear to exploit the process of gene duplication as a primary means of acquiring biochemical and developmental flexibility. Thus, for example, most of the enzymatic components of plant secondary metabolism are encoded by small families of genes that originated through duplication over evolutionary time. The dynamics of gene family evolution are well illustrated by the genes that encode chalcone synthase (CHS), the first committed step in flavonoid biosynthesis. We review pertinent facts about CHS evolution in flowering plants with special reference to the morning glory genus, Ipomoea. Our review shows that new CHS genes are recruited recurrently in flowering plant evolution. Rates of nucleotide substitution are frequently accelerated in new duplicate genes, and there is clear evidence for repeated shifts in enzymatic function among duplicate copies of CHS genes. In addition, we present new data on expression patterns of CHS genes as a function of tissue and developmental stage in the common morning glory (I. purpurea). These data show extensive differentiation in gene expression among duplicate copies of CHS genes. We also show that a single mutation which blocks anthocyanin biosynthesis in the floral limb is correlated with a loss of expression of one of the six duplicate CHS genes present in the morning glory genome. This suggests that different duplicate copies of CHS have acquired specialized functional roles over the course of evolution. We conclude that recurrent gene duplication and subsequent differentiation is a major adaptive strategy in plant genome evolution.

Acyltransferases↗
PubMed2001

Rates of evolution on the time scale of the evolutionary process.

A generational time scale, involving change from one generation to the next, is the time scale of evolution by natural selection. Microevolutionary and macroevolutionary patterns reflect this process on longer time scales. Rates of evolution are most efficiently expressed in haldane units, H, in standard deviations per generation, indexed by the log of the time interval. Rates from replicated selection experiments and simulations have rate-interval [RI] and log rate-log interval [LRI] scaling relations enabling directional, stationary, and random time series to be distinguished. Empirical microevolutionary and macroevolutionary data exhibit stationary scaling, but point to generational rates of evolution (H0) conservatively on the order of 0.2 standard deviations per generation on the time scale of the evolutionary process. This paradox of long-term stationary scaling and short-term high rates of change can be explained by considering the shape of an heuristic time-form evolutionary lattice. Cenozoic mammals occupy a lattice that is about four orders of magnitude longer in time than it has ever been wide in form. The evolutionary process is dynamic but operates within relatively narrow morphological constraints compared to the time available for change.

Animals↗
PubMed2006

Population genetic models of male and mutual mate choice.

Examples of male mate choice are becoming increasingly common, even in polygynous species. We create a series of population genetic models to examine the evolutionary equilibria and dynamics resulting from male mate choice during polygyny, alone and in the context of mutual mate choice by both sexes. We find that unless males with a preference are able to increase their overall courtship output, male preference will be lost. This loss can be counteracted if males choose females not based on arbitrary traits, but based on a trait that indicates high fertility or viability. We also conclude that if male and female preferences and traits are all controlled by different loci, the male and female mate choice systems are decoupled; the presence of a male preference then has no influence on the equilibria or dynamics of female mate choice. If male and female traits are coupled by pleiotropy, it becomes possible for a male preference to be maintained, regardless of whether preferences between the sexes are pleiotropic or controlled by separate loci.

Animals↗
PubMed1996

Unifying plant molecular data and plants.

Located at a botanical department at an Agricultural University, our taxonomical and genetic research is mainly directed towards cultivated plants and their wild relatives. The investigations are usually under a common heading 'experimental taxonomy', and include basic systematics, cytogenetics, biodiversity, population dynamics, conservation and evolutionary questions correlating the wild species and the cultivated forms. Our point of initiation is the plants and questions/problems raised regarding these plants. Our way of approaching the problems is usually by applying different sets of data and testing them. Experimental taxonomy covers classical cytogenetics (chromosome counting and karyotyping) as well as molecular cytogenetic methods (RAPD, RFLP, in situ hybridization), and includes also chemical data on isoenzymes and anthocyanins. We have had good collaborations with other laboratories and found their expertise on the plants in question very helpful. The aim is always to unify various data on the same set of problems, in order to get a more complete understanding of the plants. At present the department is working on several, quite different plant genera, comprising herbs, aquatic plants, and trees. The methods vary, depending on the plants and the problems in question. Some of the current investigations concern the horticultural genera Lilium and Crocus, in which the main point of interest is the study of chromosome evolution using fluorescence in situ hybridization; preliminary investigations into the composition of anthocyanins in Crocus look very promising. In the tropical starch tuber crop Pachyrhizus (Fabaceae), molecular analyses of relationships between existing cultivars, landraces and wild material have been carried out. A genus which we, in cooperation with a number of other laboratories, have been working with for many years is Hordeum (Poaceae) with one cultivated species (barley) and 31 wild species. Here the main areas of investigation have been field studies and collecting, followed by a taxonomical treatment, hybridization experiments, cytogenetic analysis and isoenzyme studies. Within the field of forestry, we have used population genetics as a tool in the management of natural and domesticated populations and for conservation of genetic diversity. We have also ventured into the identification and use of DNA markers that are suited for genome mapping in Picea abies (Norway Spruce).

Cytogenetics↗
PubMed1994

Molecular evolution of serine protease and its inhibitor with special reference to domain evolution.

The evolution of serine protease and its inhibitor are discussed with special reference to domain evolution. It is now known that most proteins are composed of more than one functional domain. Because serine proteases such as urokinase and plasminogen are made of various functional domains, these proteins are typical examples of the so-called mosaic proteins. When Kringle domains in serine proteases and a Kunitz-type protease inhibitor domain in the amyloid beta precursor protein in Alzheimer's disease patients were examined by the molecular evolutionary analysis, the phylogenetic trees constructed showed that these functional domains had undergone dynamic changes in the evolutionary process. In particular, these domains are evolutionarily movable. Thus, it is concluded that various functional domains evolved independently of each other and that they have been shuffled to create the existent mosaic proteins. This conclusion leads us to the reasonable speculation that those functional domains must have been minigenes possibly at the time of primordial life or the origin of life. We call these minigenes 'ancestral minigenes'. Every effort should be made to answer the question about the minimum set of ancestral minigenes that must have existed and must have been needed for maintaining life forms. The DNA sequence database is useful for making attempts to answer such difficult but significant questions.

Alzheimer Disease↗
PubMed2006

The current and future dynamics of disease in plant communities.

Pathogens are powerful evolutionary forces shaping the structure and dynamics of both individual species and of the communities of which they are part, at a broad range of genetic, ecological, spatial, and temporal scales. At all these levels their impact varies from the subtle and little recognized through to the most obvious destruction. Today the direct role of pathogens in natural plant communities is better recognized than at previous times, although the nuances of their interactions and the cascade of ramifications that can flow through changing biotic and abiotic effects are only now gaining recognition. However, as human influence on pathogens increases--either directly through enhanced if accidental dispersal, or through anthropogenic impacts on climate--we may expect to see increasing evidence of pathogens affecting plant species, community structure, and ecosystem function.

Ecosystem↗
PubMed2003

Metapopulation-level adaptation of insect host plant preference and extinction-colonization dynamics in heterogeneous landscapes.

Species living in highly fragmented landscapes typically occur as metapopulations with frequent turnover of local populations. The turnover rate depends on population sizes and connectivities, but it may also depend on the phenotypic and genotypic composition of populations. The Glanville fritillary butterfly (Melitaea cinxia) in Finland uses two host plant species, which show variation in their relative abundances at two spatial scales: locally among individual habitat patches and regionally among networks of patches. Female butterflies in turn exhibit spatial variation in genetically determined host plant preference within and among patch networks. Emigration, immigration and establishment of new populations have all been shown to be strongly influenced by the match between the host plant composition of otherwise suitable habitat patches and the host plant preference of migrating butterflies. The evolutionary consequences of such biased migration and colonization with respect to butterfly phenotypes might differ depending on spatial configuration and plant species composition of the patches in heterogeneous patch networks. Using a spatially realistic individual-based model we show that the model-predicted evolution of host plant preference due to biased migration explains a significant amount of the observed variation in host plant use among metapopulations living in dissimilar networks. This example illustrates how the ecological extinction-colonization dynamics may be linked with the evolutionary dynamics of life history traits in metapopulations.

Adaptation, Physiological↗
PubMed2001

Phylogenetic analyses of two mitochondrial genes and one nuclear intron region illuminate European subterranean termite (Isoptera: Rhinotermitidae) gene flow, taxonomy, and introduction dynamics.

Phylogenetic analyses of multiple DNA sequences were conducted to elucidate gene flow, evolutionary patterns, taxonomy, and the dynamics of two accidental introductions: Reticulitermes lucifugus grassei into Devon, United Kingdom and R. flavipes into Europe. Two mitochondrial DNA genes totaling 1495 bp and a 380-bp ribosomal intergenic transcribed spacer were sequenced. Neighbor-joining and parsimony analyses revealed that multiple female lineages of R. lucifugus grassei were introduced into Devon possibly from southwestern France, where the species was indigenous. The taxonomic status of the European R. santonensis as a species separate from the North American R. flavipes has been questioned since it was described in 1924. Phylogenetic analyses revealed a close genetic relationship between R. flavipes from the United States and R. santonensis from France. These analyses, coupled with morphological and chemotaxonomic data, provide strong support for R. santonensis and R. flavipes being the same species. They also suggested that R. santonensis infestations likely resulted from R. flavipes being introduced into Europe.

Animals↗
PubMed2003

Strategy updating rules and strategy distributions in dynamical multiagent systems.

In the evolutionary version of the minority game, agents update their strategies (gene value p) in order to improve their performance. Motivated by the recent intriguing results obtained for prize-to-fine ratios, which are smaller than unity, we explore the system's dynamics with a strategy updating rule of the form p-->p+/-delta(p) (0<or=p<or=1). We find that the strategy distribution depends strongly on the values of the prize-to-fine ratio R, the length scale delta(p), and the type of boundary condition used. We show that these parameters determine the amplitude and the frequency of the temporal oscillations observed in the gene space. These regular oscillations are shown to be the main factors which determine the strategy distribution of the population. In addition, we find that the agents characterized by p=1/2 (a coin-tossing strategy) have the best chances of survival at asymptotically long times, regardless of the value of delta(p) and the boundary conditions used.

Journal Article↗
PubMed2005

The evolution of phenotypic polymorphism: randomized strategies versus evolutionary branching.

A population is polymorphic when its members fall into two or more categories, referred to as alternative phenotypes. There are many kinds of phenotypic polymorphisms, with specialization in reproduction, feeding, dispersal, or protection from predators. An individual's phenotype might be randomly assigned during development, genetically determined, or set by environmental cues. These three possibilities correspond to a mixed strategy of development, a genetic polymorphism, and a conditional strategy. Using the perspective of adaptive dynamics, I develop a unifying evolutionary theory of systems of determination of alternative phenotypes, focusing on the relative possibilities for random versus genetic determination. The approach is an extension of the analysis of evolutionary branching in adaptive dynamics. It compares the possibility that there will be evolutionary branching, leading to genetic polymorphism, with the possibility that a mixed strategy evolves. The comparison is based on the strength of selection for the different outcomes. An interpretation of the resulting criterion is that genetic polymorphism is favored over random determination of the phenotype if an individual's heritable genotype is an adaptively advantageous cue for development. I argue that it can be helpful to regard genetic polymorphism as a special case of phenotypic plasticity.

Adaptation, Physiological↗