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Results for “adaptive evolution”

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At least 1,315 records · Page 73Linked to original sources
PubMed2006

Characteristics of neural and humoral systems involved in the regulation of blood pressure in snakes.

Cardiovascular function is affected by many mechanisms, including the autonomic system, the kallikrein-kinin system (KKS), the renin-angiotensin system (RAS) and the endothelin system. The function of these systems seems to be fairly well preserved throughout the vertebrate scale, but evolution required several adaptations. Snakes are particularly interesting for studies related to the cardiovascular function because of their elongated shape, their wide variation in size and length, and because they had to adapt to extremely different habitats and gravitational influences. To keep the normal cardiovascular control the snakes developed anatomical and functional adaptations and interesting structural peculiarities are found in their autonomic, KKS, RAS and endothelin systems. Our laboratory has characterized some biochemical, pharmacological and physiological properties of these systems in South American snakes. This review compares the components and function of these systems in snakes and other vertebrates, and focuses on differences found in snakes, related with receptor or ligand structure and/or function in autonomic system, RAS and KKS, absence of components in KKS and the intriguing identity between a venom and a plasma component in the endothelin system.

Animals↗
PubMed2025

One thousand SARS-CoV-2 antibody structures reveal convergent binding and near-universal immune escape.

Understanding antibody recognition and adaptation to viral evolution is central to vaccine and therapeutic development. Over 1,100 SARS-CoV-2 antibody structures have been resolved, marking the largest structural biology effort for a single pathogen. We present a comprehensive analysis of this landmark dataset to investigate the principles of antibody recognition and immune escape. Human immunoglobulins and camelid single-chain antibodies dominate, collectively mapping 99% of the receptor-binding domain. Despite remarkable sequence and conformational diversity, antibodies exhibit convergence in their paratope structures, revealing evolutionary constraints in epitope selection. Analyses reveal near-universal immune escape of antibodies, including all clinical monoclonals, by advanced variants such as KP3.1.1. On average, over one-third of antibody epitope residues are mutated. These findings support pervasive immune escape, underscoring the need to effectively leverage multi-epitope-targeting strategies to achieve durable immunity. To support community accessibility, we developed an interactive web server for visualization and analysis of antibody-antigen complexes and mutational data.

SARS-CoV-2↗
PubMed2006

Are mistakes inevitable? Sex allocation specialization by workers can reduce the genetic information needed to assess queen mating frequency.

Insect workers can increase their inclusive fitness by biasing colony sex allocation towards males when their mother queen is mated to multiple males and females when she is singly mated. Workers need heritable variation in odour diversity to assess queen mating frequency. Here we present a simple one-locus two-allele model, which shows that the sex ratio specialization itself will often select against rare alleles that would provide additional information for the assessment of queen mating frequency. However, under certain rather restricted conditions, such as when sex ratios are highly female biased, and when worker reproduction is rare, sex ratio specialization can select for rare alleles. This suggests that sex allocation biasing by workers will usually reduce the very information that workers need to assess queen mating frequency. Our model is an example where an explicit treatment of underlying genetics and mechanisms of behaviour, such as information use, is necessary to fully understand the evolution of an adaptive behavioural strategy.

Alleles↗
PubMed2004

Comparative analysis of structural properties of Portunid Crab Hemocyanin.

In order to explore the hemocyanin adaptative potential and evolutive dynamics, we have analyzed the structural properties of this oxygen-carrier protein, in some species of portunid Crabs, (Brachyura, Portunida). We have compared the intra- and interspecific subunits patterns, in native and denaturant conditions, to estimate the phenetic relationships and the different stabilities of the protein.

Animals↗
PubMedDate not supplied

Incremental learning of feature space and classifier for face recognition.

We have proposed a new approach to pattern recognition in which not only a classifier but also a feature space of input variables is learned incrementally. In this paper, an extended version of Incremental Principal Component Analysis (IPCA) and Resource Allocating Network with Long-Term Memory (RAN-LTM) are effectively combined to implement this idea. Since IPCA updates a feature space incrementally by rotating the eigen-axes and increasing the dimensions, the inputs of a neural classifier must also change in their values and the number of input variables. To solve this problem, we derive an approximation of the update formula for memory items, which correspond to representative training samples stored in the long-term memory of RAN-LTM. With these memory items, RAN-LTM is efficiently reconstructed and retrained to adapt to the evolution of the feature space. This function is incorporated into our face recognition system. In the experiments, the proposed incremental learning model is evaluated over a self-compiled video clip of 24 persons. The experimental results show that the incremental learning of a feature space is very effective to enhance the generalization performance of a neural classifier in a realistic face recognition task.

Algorithms↗
PubMed2004

The Horizontal Gene Pool: an ESF workshop summary.

The European Science Foundation (ESF) funds a limited number of exploratory workshops each year that enable scientists to meet and develop plans for a program of integrated research which would benefit from a coordinated European effort. In summer 2003, the Standing Committee for Life and Environmental Sciences (LESC) sponsored such a workshop called The Horizontal Gene Pool: The Functional Role of Mobile Genetic Information--How Bacteria Perceive, Sample, and Utilize Genetic Elements in evolution and Local Adaptation. The workshop took place at St. Catherine's College, Oxford, UK. Its purpose was to identify how recent advances in the application of genomics and microbial ecology can be harnessed to determine the genetic mechanisms that underpin the biological role of the horizontal gene pool. Scientific excellence at the workshop was contributed by senior scientists and young investigators from research institutes located in nine European countries.

Bacteria↗
PubMed2005

High contents of both docosahexaenoic and arachidonic acids in milk of women consuming fish from lake Kitangiri (Tanzania): targets for infant formulae close to our ancient diet?

Current recommendations for arachidonic (AA) and docosahexaenoic (DHA) acids in infant formulae are based on milk of Western mothers. Validity may be questioned in view of the profound dietary changes in the past 100 years, as opposed to our slowly adapting genome. Hominin evolution occurred in the proximity of East-African freshwater lakes and rivers and early homo sapiens had higher intakes of AA and DHA from a predominantly lacustrine-based diet. In search of milk AA and DHA contents of our African ancestors, we investigated the milk of 29 lactating women living in Doromoni near lake Kitangiri (Tanzania). They consumed sunflower oil-fried local fish as only animal lipid sources, maize and local vegetables. AA and DHA contents of Doromoni milk may be close to that of early homo sapiens, because of the similarity of their life-long consumption of East-African lacustrine-based foods. Human milk fatty acid relationships from our historical worldwide database and the literature revealed that disparities between the Doromoni diet and the presumed ancient diet (i.e. higher carbohydrate and linoleic acid intakes) are unlikely to affect milk AA and DHA contents. Doromoni milk had high contents of AA (median 0.70 mol%), DHA (0.75) and eicosapentaenoic acid (EPA, 0.17), and low AA/DHA ratios (median 0.91; 0.55-2.61). This tracks down to consumption of fish with high AA and DHA contents, and AA/EPA ratios. We conclude that the milk AA, DHA and EPA contents of Doromoni women might provide us with clues to optimize infant formulae and perhaps the milk of Western women.

Adolescent↗
PubMed2005

Effective sizes of macroparasite populations: a conceptual model.

Effective population size (N(e)) is a crucial parameter in evolutionary biology because it controls genetic drift and the response to selection. Thus, N(e) influences evolutionary processes in parasites, such as speciation, host-race formation, local host adaptation and the evolution of drug resistance. However, N(e) is a parameter that is ignored almost completely in parasitology. Our goal is to provide a conceptual framework that facilitates future studies of the N(e) of macroparasites. The key feature of macroparasite populations is that breeders are subdivided into infrapopulations. We use a model of subdivided breeders to show how some basic demographic factors that control N(e) in all species could be estimated for macroparasites. An important conclusion is that several features of parasite life cycles probably function in concert to reduce N(e) below that expected in a single free-living population of equivalent census size.

Animals↗
PubMed2005

What do monkeys' music choices mean?

McDermott and Hauser have recently shown that although monkeys show some types of preferences for sound, preferences for music are found only in humans. This suggests that music might be a relatively recent adaptation in human evolution. Here, I focus on the research methods used by McDermott and Hauser, and consider the findings in relation to infancy research and music psychology.

Animals↗
PubMed2005

A map of the diversity of RNA3 recombinants appearing in plants infected with Cucumber mosaic virus and Tomato aspermy virus.

In order to better understand the role of recombination in creating the diversity of viral genomes that is acted on by selection, we have studied in detail the population of recombinant RNA3 molecules occurring in tobacco plants coinfected with wild-type strains of cucumber mosaic virus (CMV) and tomato aspermy virus (TAV) under conditions of minimal selection pressure. Recombinant RNA3s were observed in 9.6% of the samples. Precise homologous recombination predominated since it was observed at 28 different sites, primarily in six hot spots. Imprecise homologous recombination was observed at two sites, particularly within a GU repeat in the 5' noncoding region. Seven of the eight aberrant homologous recombination sites observed were clustered in the 3' noncoding region. These results have implications on the role of recombination in host adaptation and virus evolution. They also provide essential baseline information for understanding the potential epidemiological impact of recombination in transgenic plants expressing viral sequences.

Base Sequence↗
PubMed2005

Structure and composition of the septal nacreous layer of Nautilus macromphalus L. (Mollusca, Cephalopoda).

The nacreous layer of Mollusca is the best-known aragonitic structure and is the usual model for biomineralization. However, data are based on less than 10 species. In situ observations of the septal nacreous layer of the cephalopod Nautilus shell has revealed that the tablets are composed of acicular laths. These laths are composed of round nanograins surrounded by an organic sheet. No hole has been observed in the decalcified interlamellar membranes. A set of combined analytical data shows that the organic matrices extracted from the nacreous layer are glycoproteins. In both soluble and insoluble matrices, S amino acids are rare and the soluble organic matrices have a higher sulfated sugar content than the insoluble matrices. It is possible that the observed differences in the structure and composition of the nacreous layers of the outer wall and septa of the Nautilus shell have a dual origin: evolution and functional adaptation. However, we have no appropriate data as yet to answer this question.

Animals↗
PubMed2002

kDNA markers define two major Trypanosoma rangeli lineages in Latin-America.

Trypanosoma rangeli is a hemoflagellate parasite of man, domestic and wild animals in Central and South America. The genus Rhodnius is particularly susceptible to infection by T. rangeli and transmission by salivary inoculation has been demonstrated in 12 of 14 nominal species of naturally and experimentally infected insects. This report describes the molecular characterization of 37 strains of T. rangeli isolated from vertebrate and invertebrate hosts. Strains were analyzed by hybridization with kinetoplast DNA (kDNA) probes, polymerase chain reaction (PCR) amplification of kDNA minicircles and random amplification polymorphic DNA (RAPD). Strains isolated from Rhodnius prolixus present KP1, KP2 and KP3 minicircle amplification products but strains isolated from R. colombiensis or Panstrongylus megistus present amplification products derived only from KP2 and KP3 minicircles. The two T. rangeli groups defined as KP1(+) and KP1(-) present a high genetic divergence as they have probably been co-evolutioned with different adaptive radiated lines of the genus Rhodnius in Latin-America. The data obtained from insects with intestinal and salivary glands infections confirm that each Rhodnius species select the sub-population of T. rangeli KP1(+) or KP1(-) which is susceptible to transmit it by salivary inoculation to the vertebrate host.

Animals↗
PubMedDate not supplied

Second-order selection in bacterial evolution: selection acting on mutation and recombination rates in the course of adaptation.

The increase in genetic variability of a population can be selected during adaptation, as demonstrated by the selection of mutator alleles. The dynamics of this phenomenon, named second-order selection, can result in an improved adaptability of bacteria through regulation of all facets of mutation and recombination processes.

Adaptation, Physiological↗
PubMed2002

Mitochondrial dynamics and division in budding yeast.

Mitochondria adopt a variety of different shapes in eukaryotic cells, ranging from multiple, small compartments to elaborate tubular networks. The establishment and maintenance of different mitochondrial morphologies depends, in part, on the equilibrium between opposing fission and fusion events. Recent studies in yeast, flies, worms and mammalian cells indicate that three high-molecular-weight GTPases control mitochondrial membrane dynamics. One of these is a dynamin-related GTPase that acts on the outer mitochondrial membrane to regulate fission. Recently, genetic approaches in budding yeast have identified additional components of the fission machinery. These and other new findings suggest a common mechanism for membrane fission events that has been conserved and adapted during eukaryotic evolution.

Cell Cycle↗
PubMed2001

Segmentation of brain 3D MR images using level sets and dense registration.

This paper presents a strategy for the segmentation of brain from volumetric MR images which integrates 3D segmentation and 3D registration processes. The segmentation process is based on the level set formalism. A closed 3D surface propagates towards the desired boundaries through the iterative evolution of a 4D implicit function. In this work, the propagation relies on a robust evolution model including adaptive parameters. These depend on the input data and on statistical distribution models. The main contribution of this paper is the use of an automatic registration method to initialize the surface, as an alternative solution to manual initialization. The registration is achieved through a robust multiresolution and multigrid minimization scheme. This coupling significantly improves the quality of the method, since the segmentation is faster, more reliable and fully automatic. Quantitative and qualitative results on both synthetic and real volumetric brain MR images are presented and discussed.

Algorithms↗