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At least 1,513 records · Page 84Linked to original sources
PubMed2005

Molecular epidemiology of human respiratory syncytial virus in Uruguay: 1985-2001--a review.

The variability of the G glycoprotein from human respiratory syncytial viruses (HRSV) (groups A and B) isolated during 17 consecutive epidemics in Montevideo, Uruguay have been analyzed. Several annual epidemics were studied, where strains from groups A and B circulated together throughout the epidemics with predominance of one of them. Usually, group A predominates, but in some epidemics group B is more frequently detected. To analyse the antigenic diversity of the strains, extracts of cells infected with different viruses of group A were tested with a panel of anti-G monoclonal antibodies (MAbs). The genetic variability of both groups was analyzed by sequencing the C-terminal third of the G protein gene. The sequences obtained together with previously published sequences were used to perform phylogenetic analyses. The data from Uruguayan isolates, together with those from the rest of the world provide information regarding worldwide strain circulation. Phylogenetic analyses of HRSV from groups A and B show a model of evolution analogous to the one proposed for influenza B viruses providing information that would be beneficial for future immunization programs and to design safe vaccines.

Amino Acid Sequence↗
PubMed2006

Recognition that causal processes change during plant invasion helps explain conflicts in evidence.

Despite intensive research, we still have no general understanding of why plant invasions occur. Many different mechanisms of plant invasions have been proposed, but studies designed to investigate them often produce inconsistent results. It remains unclear whether this unsatisfying state of affairs reflects the complexity of the real world (in which every invasion is unique) or the failure to identify the key processes driving most plant invasions. Here we argue that greater generalization is possible, but only if we recognize that the ecological and evolutionary processes enabling a species to advance into a new area change during the course of an invasion. In our view, an invasion can often usefully be subdivided into a primary phase, in which the abundance of an often preadapted species increases rapidly (typically in resource-rich, disturbed habitats), and a secondary phase, in which further spread is contingent upon plastic responses or genetic adaptation to new ecological circumstances. We present various examples to show how this partitioning of the invasion phase sensu stricto produces new hypotheses about the processes underlying plant invasions. Some of these hypotheses can be conveniently tested by investigating plant invasions along strong environmental gradients such as those that occur in mountainous regions.

Adaptation, Biological↗
PubMed2000

Diversification of the North American shrub genus Ceanothus (Rhamnaceae): conflicting phylogenies from nuclear ribosomal DNA and chloroplast DNA.

Ceanothus comprises ∼55 morphologically and ecologically diverse species of woody perennials endemic to North America. Interpretations of the natural history of Ceanothus have served as a general model of evolution for woody perennials with simple entomophilous pollination systems, but these interpretations lacked explicit phylogenetic context. We used cladistic analysis of sequences of the chloroplast-encoded matK and the internal transcribed spacers (ITS) and 5.8S coding region of nuclear ribosomal DNA (nrDNA) to reconstruct the phylogeny of Ceanothus. The nuclear and organellar phylogenies exhibited very low levels of both topological and character congruence. Subgenera Ceanothus and Cerastes are monophyletic sister taxa in both phylogenies, but both data sets suffer from a lack of resolution below the level of subgenus. Lack of taxonomic congruence between the two data sets may be a result of introgression and/or lineage sorting. The ITS tree was accepted as the better estimate of a species phylogeny for Ceanothus, on the assumption that nuclear markers are less prone to introgression. Three of five polytypic species in the ITS data set were paraphyletic, and four of six polytypic species in the matK data set were paraphyletic. This study demonstrates the degree to which matched independent data sets can produce conflicting summaries of evolutionary history.

Journal Article↗
PubMed2000

[Plea for interdisciplinary dimension in medicine. The example of consent].

A philosophical and legal analysis of consent in the patient-doctor relationship leads to operational limitations. Getting over these limits requires a transdiciplinary approach aimed at understanding the living world and modeling its evolution. This approach rests on recognition of different philosophical, legal, sociological, economical, and historical reality levels, permitting a new non-exclusive role of consent in medicine, i.e. the respect of human dignity.

Humans↗
PubMed2002

Unifying evolutionary dynamics.

Darwinian evolution is based on three fundamental principles, reproduction, mutation and selection, which describe how populations change over time and how new forms evolve out of old ones. There are numerous mathematical descriptions of the resulting evolutionary dynamics. In this paper, we show that apparently very different formulations are part of a single unified framework. At the center of this framework is the equivalence between the replicator-mutator equation and the Price equation. From these equations, we obtain as special cases adaptive dynamics, evolutionary game dynamics, the Lotka-Volterra equation of ecology and the quasispecies equation of molecular evolution.

Animals↗
PubMed2004

Heterogeneity and evolution of expectations in a model of currency crisis.

A simple model of a portfolio allocation between mature and emerging markets is specified. The representative-agent, rational expectations version of the model has an unlimited number of equilibria, providing no reason to expect that heterogeneous agents would all coordinate on one or another equilibrium. Therefore, the model is simulated with heterogeneous expectations based on ex post returns, imitation, and experimentation. Solutions produce periodic crises, as periods of excessive optimism plant the seed for their reversal, despite the fact that interest rates fall before crises, instead of rising.

Journal Article↗
PubMed2005

Crossing heterogeneous information sources for better analysis of health and social care data.

In this paper we describe a methodology that emerged during an implementation of a health-and-social-care-oriented data repository, which consists in grouping information from heterogeneous and distributed information sources. We developed this methodology by first constructing a concrete data repository, containing information about elderly patients flows in the UK's long-term care (LTC) system. In our specific case, the role of the data repository is to allow knowledge extraction about consumption and behavioural tendencies in the elderly people population within the LTC system. These tendencies can be depicted in terms of survival behaviour (modelling), cost evolution, and bed use. Other types of knowledge that can be extracted are typical patient profiles, placement policy in term of rules and criteria effectively applied and, specific features of the business process behind the long-term care provision. A well-constructed data repository can support the discovery (analysis) of hidden aspects about the way patients are placed and accepted in the LTC, and also how the allocated resources are consumed. We argue that the use of this methodology could save time in similar undertakings or in other fields than health and social care.

Humans↗
PubMed2005

Short report: Phylogenetic relationships of the anthropophilic Plasmodium falciparum malaria vectors in Africa.

Malaria kills more than one million people a year, and understanding the historical association between its most notorious causative agent, Plasmodium falciparum, and its mosquito vectors is important in fighting the disease. We present a phylogenetic analysis of a number of species within the mosquito subgenus Cellia based on a selection of mitochondrial and nuclear genes. Although some of these relationships have been estimated in other studies, generally few species were included and/or statistical support at many nodes was low. Here we include two additional species of anthropophilic P. falciparum malaria vectors and reanalyze these relationships using a Bayesian method that allows us to simultaneously incorporate different models of evolution. We report data that indicate a paraphyletic relationship between five anthropophilic African mosquito vectors. Such a relationship suggests that these species can serve as independent natural experiments for anopheline immunologic responses to regular, prolonged contact with P. falciparum.

Africa↗
PubMed2005

Parasite-host fitness trade-offs change with parasite identity: genotype-specific interactions in a plant-pathogen system.

Simultaneous effects of host and parasite in determining quantitative traits of infection have long been neglected in theoretical and experimental investigations of host-parasite coevolution with the notable exception of gene-for-gene resistance studies. A cross-infection experiment, using five lines of the plant Arabidopsis thaliana and two strains of its oomycete pathogen Hyaloperonospora parasitica, revealed that three traits traditionally considered those of the parasite (number of infected leaves, transmission success, and time until 50% transmission), differed among specific combinations of host and parasite lines, being determined by the two protagonists of the infection. However, the two parasite strains did not differ significantly for most measured phenotypic traits of the infection. Globally, transmission increased with increasing virulence among the different host-parasite combinations, as assumed by most models of evolution of virulence. Surprisingly, however, there was no general relationship between parasite and host fitness, estimated respectively as transmission and seed production. Only one of the two strains showed the expected significant negative genetic correlation between these two variables. Our results thus highlight the importance of taking into account both host and parasite genetic variation because their interaction can lead to unexpected evolutionary outcomes.

Arabidopsis↗
PubMed2006

Genetic population structure and call variation in a passerine bird, the satin bowerbird, Ptilonorhynchus violaceus.

Geographic variation in vocalizations is widespread in passerine birds, but its origins and maintenance remain unclear. One hypothesis to explain this variation is that it is associated with geographic isolation among populations and therefore should follow a vicariant pattern similar to that typically found in neutral genetic markers. Alternatively, if environmental selection strongly influences vocalizations, then genetic divergence and vocal divergence may be disassociated. This study compared genetic divergence derived from 11 microsatellite markers with a metric of phenotypic divergence derived from male bower advertisement calls. Data were obtained from 16 populations throughout the entire distribution of the satin bowerbird, an Australian wet-forest-restricted passerine. There was no relationship between call divergence and genetic divergence, similar to most other studies on birds with learned vocalizations. Genetic divergence followed a vicariant model of evolution, with the differentiation of isolated populations and isolation-by-distance among continuous populations. Previous work on Ptilonorhynchus violaceus has shown that advertisement call structure is strongly influenced by the acoustic environment of different habitats. Divergence in vocalizations among genetically related populations in different habitats indicates that satin bowerbirds match their vocalizations to the environment in which they live, despite the homogenizing influence of gene flow. In combination with convergence of vocalizations among genetically divergent populations occurring in the same habitat, this shows the overriding importance that habitat-related selection can have on the establishment and maintenance of variation in vocalizations.

Animals↗
PubMedDate not supplied

[The problem of organism integrity and its perspectives].

The organism integrity in onto- and phylogenesis is considered as an initial element of biosphere integrity and its evolution at the eukaryotic level. The Schmalhausen's concept of organism integrity is discussed in the context of his original strategy of evolutionary synthesis and his works on stabilizing selection. The perspectives of investigations on the problem of integrity and development of the principle of dynamic stability in contemporary evolutionary biology as integrating factors are discussed.

Animals↗
PubMed1991

The rise and fall of the RNA world.

It is generally believed that there was a time when life on earth was based on RNA rather than on DNA and protein. Considering the relevant evidence from geophysics, geology, paleobiology, and molecular biology, it is possible to set the time frame for the existence of RNA-based life to a 400 million year interval beginning 4.0 to 4.2 billion years ago and ending 3.6 to 3.8 billion years ago. The minimum level of biochemical complexity that existed during this time consists of those functions necessary for the establishment and maintenance of an RNA-based evolving system, namely, an RNA unwinding activity, an RNA replicase activity, and a primitive biosynthetic apparatus leading to enrichment of the local environment with activated D mononucleotides.

Biological Evolution↗