Base de dados : MEDLINE
Pesquisa : E05.318.740.996 [Categoria DeCS]
Referências encontradas : 13152 [refinar]
Mostrando: 1 .. 10   no formato [Detalhado]

página 1 de 1316 ir para página                         

  1 / 13152 MEDLINE  
              next record last record
seleciona
para imprimir
Fotocópia
Texto completo
[PMID]:29207942
[Au] Autor:Sasson DA; Ryan JF
[Ad] Endereço:Whitney Laboratory for Marine Bioscience, University of Florida, 9505 Ocean Shore Blvd, St. Augustine, FL, USA.
[Ti] Título:A reconstruction of sexual modes throughout animal evolution.
[So] Source:BMC Evol Biol;17(1):242, 2017 Dec 06.
[Is] ISSN:1471-2148
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:BACKGROUND: Although most extant animals have separate sexes, simultaneous hermaphrodites can be found in lineages throughout the animal kingdom. However, the sexual modes of key ancestral nodes including the last common ancestor (LCA) of all animals remain unclear. Without these data, it is difficult to infer the reproductive-state transitions that occurred early in animal evolution, and thus a broad understanding of the evolution of animal reproduction remains elusive. In this study, we use a composite phylogeny from four previously published studies, two alternative topologies (ctenophores or sponges as sister to the rest of animals), and multiple phylogenetic approaches to conduct the most extensive analysis to date of the evolution of animal sexual modes. RESULTS: Our analyses clarify the sexual mode of many ancestral animal nodes and allow for sound inferences of modal transitions that have occurred in animal history. Our results also indicate that the transition from separate sexes to hermaphroditism has been more common in animal history than the reverse. CONCLUSIONS: These results provide the most complete view of the evolution of animal sexual modes to date and provide a framework for future inquiries into the correlation of these transitions with genes, behaviors, and physiology. These results also suggest that mutations promoting hermaphroditism have historically been more likely to invade gonochoristic populations than vice versa.
[Mh] Termos MeSH primário: Evolução Biológica
Comportamento Sexual Animal
[Mh] Termos MeSH secundário: Animais
Filogenia
Reprodutibilidade dos Testes
Reprodução
Processos Estocásticos
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1803
[Cu] Atualização por classe:180309
[Lr] Data última revisão:
180309
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:171207
[St] Status:MEDLINE
[do] DOI:10.1186/s12862-017-1071-3


  2 / 13152 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
[PMID]:29339817
[Au] Autor:Crandall JW; Oudah M; Tennom; Ishowo-Oloko F; Abdallah S; Bonnefon JF; Cebrian M; Shariff A; Goodrich MA; Rahwan I
[Ad] Endereço:Computer Science Department, Brigham Young University, 3361 TMCB, Provo, UT, 84602, USA. crandall@cs.byu.edu.
[Ti] Título:Cooperating with machines.
[So] Source:Nat Commun;9(1):233, 2018 01 16.
[Is] ISSN:2041-1723
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:Since Alan Turing envisioned artificial intelligence, technical progress has often been measured by the ability to defeat humans in zero-sum encounters (e.g., Chess, Poker, or Go). Less attention has been given to scenarios in which human-machine cooperation is beneficial but non-trivial, such as scenarios in which human and machine preferences are neither fully aligned nor fully in conflict. Cooperation does not require sheer computational power, but instead is facilitated by intuition, cultural norms, emotions, signals, and pre-evolved dispositions. Here, we develop an algorithm that combines a state-of-the-art reinforcement-learning algorithm with mechanisms for signaling. We show that this algorithm can cooperate with people and other algorithms at levels that rival human cooperation in a variety of two-player repeated stochastic games. These results indicate that general human-machine cooperation is achievable using a non-trivial, but ultimately simple, set of algorithmic mechanisms.
[Mh] Termos MeSH primário: Inteligência Artificial
Comportamento Cooperativo
[Mh] Termos MeSH secundário: Algoritmos
Comunicação
Seres Humanos
Processos Estocásticos
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Em] Mês de entrada:1803
[Cu] Atualização por classe:180305
[Lr] Data última revisão:
180305
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:180118
[St] Status:MEDLINE
[do] DOI:10.1038/s41467-017-02597-8


  3 / 13152 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
[PMID]:28747400
[Au] Autor:Gupta A; Milias-Argeitis A; Khammash M
[Ad] Endereço:Department of Biosystems Science and Engineering, ETH Zurich, Mattenstrasse 26, 4058 Basel, Switzerland.
[Ti] Título:Dynamic disorder in simple enzymatic reactions induces stochastic amplification of substrate.
[So] Source:J R Soc Interface;14(132), 2017 Jul.
[Is] ISSN:1742-5662
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:A growing amount of evidence over the last two decades points to the fact that many enzymes exhibit fluctuations in their catalytic activity, which are associated with conformational changes on a broad range of timescales. The experimental study of this phenomenon, termed dynamic disorder, has become possible thanks to advances in single-molecule enzymology measurement techniques, through which the catalytic activity of individual enzyme molecules can be tracked in time. The biological role and importance of these fluctuations in a system with a small number of enzymes, such as a living cell, have only recently started being explored. In this work, we examine a simple stochastic reaction system consisting of an inflowing substrate and an enzyme with a randomly fluctuating catalytic reaction rate that converts the substrate into an outflowing product. To describe analytically the effect of rate fluctuations on the average substrate abundance at steady state, we derive an explicit formula that connects the relative speed of enzymatic fluctuations with the mean substrate level. Under fairly general modelling assumptions, we demonstrate that the relative speed of rate fluctuations can have a dramatic effect on the mean substrate, and lead to large positive deviations from predictions based on the assumption of deterministic enzyme activity. Our results also establish an interesting connection between the amplification effect and the mixing properties of the Markov process describing the enzymatic activity fluctuations, which can be used to easily predict the fluctuation speed above which such deviations become negligible. As the techniques of single-molecule enzymology continuously evolve, it may soon be possible to study the stochastic phenomena due to enzymatic activity fluctuations within living cells. Our work can be used to formulate experimentally testable hypotheses regarding the nature and magnitude of these fluctuations, as well as their phenotypic consequences.
[Mh] Termos MeSH primário: Enzimas/metabolismo
Modelos Biológicos
[Mh] Termos MeSH secundário: Simulação por Computador
Enzimas/química
Cinética
Conformação Proteica
Processos Estocásticos
Especificidade por Substrato
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Enzymes)
[Em] Mês de entrada:1802
[Cu] Atualização por classe:180228
[Lr] Data última revisão:
180228
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170728
[St] Status:MEDLINE


  4 / 13152 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
[PMID]:29360863
[Au] Autor:Laufenberg JS; Clark JD; Chandler RB
[Ad] Endereço:Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, Tennessee, United States of America.
[Ti] Título:Estimating population extinction thresholds with categorical classification trees for Louisiana black bears.
[So] Source:PLoS One;13(1):e0191435, 2018.
[Is] ISSN:1932-6203
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Monitoring vulnerable species is critical for their conservation. Thresholds or tipping points are commonly used to indicate when populations become vulnerable to extinction and to trigger changes in conservation actions. However, quantitative methods to determine such thresholds have not been well explored. The Louisiana black bear (Ursus americanus luteolus) was removed from the list of threatened and endangered species under the U.S. Endangered Species Act in 2016 and our objectives were to determine the most appropriate parameters and thresholds for monitoring and management action. Capture mark recapture (CMR) data from 2006 to 2012 were used to estimate population parameters and variances. We used stochastic population simulations and conditional classification trees to identify demographic rates for monitoring that would be most indicative of heighted extinction risk. We then identified thresholds that would be reliable predictors of population viability. Conditional classification trees indicated that annual apparent survival rates for adult females averaged over 5 years ([Formula: see text]) was the best predictor of population persistence. Specifically, population persistence was estimated to be ≥95% over 100 years when [Formula: see text], suggesting that this statistic can be used as threshold to trigger management intervention. Our evaluation produced monitoring protocols that reliably predicted population persistence and was cost-effective. We conclude that population projections and conditional classification trees can be valuable tools for identifying extinction thresholds used in monitoring programs.
[Mh] Termos MeSH primário: Extinção Biológica
Ursidae
[Mh] Termos MeSH secundário: Animais
Simulação por Computador
Conservação dos Recursos Naturais
Monitorização de Parâmetros Ecológicos/estatística & dados numéricos
Espécies em Perigo de Extinção
Feminino
Louisiana
Masculino
Modelos Biológicos
Modelos Estatísticos
Dinâmica Populacional/estatística & dados numéricos
Processos Estocásticos
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Em] Mês de entrada:1802
[Cu] Atualização por classe:180227
[Lr] Data última revisão:
180227
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:180124
[St] Status:MEDLINE
[do] DOI:10.1371/journal.pone.0191435


  5 / 13152 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
[PMID]:27775393
[Au] Autor:Gonzalez-Navarrete M
[Ad] Endereço:Institute of Mathematics and Statistics, Universidade de São Paulo, Rua do Matao, 1010, CEP 05508-090, Sao Paulo, Brazil. email: manuelg@ime.usp.br.
[Ti] Título:Type-dependent stochastic Ising model describing the dynamics of a non-symmetric feedback module.
[So] Source:Math Biosci Eng;13(5):981-998, 2016 10 01.
[Is] ISSN:1551-0018
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:We study an alternative approach to model the dynamical behaviors of biological feedback loop, that is, a type-dependent spin system, this class of stochastic models was introduced by Fernández et. al [13], and are useful since take account to inherent variability of gene expression. We analyze a non-symmetric feedback module being an extension for the repressilator, the first synthetic biological oscillator, invented by Elowitz and Leibler [7]. We consider a mean-field dynamics for a type-dependent Ising model, and then study the empirical-magnetization vector representing concentration of molecules. We apply a convergence result from stochastic jump processes to deterministic trajectories and present a bifurcation analysis for the associated dynamical system. We show that non-symmetric module under study can exhibit very rich behaviours, including the empirical oscillations described by repressilator.
[Mh] Termos MeSH primário: Expressão Gênica/fisiologia
Modelos Biológicos
[Mh] Termos MeSH secundário: Retroalimentação Fisiológica
Processos Estocásticos
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Em] Mês de entrada:1712
[Cu] Atualização por classe:180228
[Lr] Data última revisão:
180228
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:161025
[St] Status:MEDLINE
[do] DOI:10.3934/mbe.2016026


  6 / 13152 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
[PMID]:29377891
[Au] Autor:Hadjichrysanthou C; Ower AK; de Wolf F; Anderson RM; Alzheimer's Disease Neuroimaging Initiative
[Ad] Endereço:Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, United Kingdom.
[Ti] Título:The development of a stochastic mathematical model of Alzheimer's disease to help improve the design of clinical trials of potential treatments.
[So] Source:PLoS One;13(1):e0190615, 2018.
[Is] ISSN:1932-6203
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Alzheimer's disease (AD) is a neurodegenerative disorder characterised by a slow progressive deterioration of cognitive capacity. Drugs are urgently needed for the treatment of AD and unfortunately almost all clinical trials of AD drug candidates have failed or been discontinued to date. Mathematical, computational and statistical tools can be employed in the construction of clinical trial simulators to assist in the improvement of trial design and enhance the chances of success of potential new therapies. Based on the analysis of a set of clinical data provided by the Alzheimer's Disease Neuroimaging Initiative (ADNI) we developed a simple stochastic mathematical model to simulate the development and progression of Alzheimer's in a longitudinal cohort study. We show how this modelling framework could be used to assess the effect and the chances of success of hypothetical treatments that are administered at different stages and delay disease development. We demonstrate that the detection of the true efficacy of an AD treatment can be very challenging, even if the treatment is highly effective. An important reason behind the inability to detect signals of efficacy in a clinical trial in this therapy area could be the high between- and within-individual variability in the measurement of diagnostic markers and endpoints, which consequently results in the misdiagnosis of an individual's disease state.
[Mh] Termos MeSH primário: Doença de Alzheimer/diagnóstico
Biometria/métodos
Técnicas de Apoio para a Decisão
[Mh] Termos MeSH secundário: Biomarcadores
Estudos de Coortes
Erros de Diagnóstico
Progressão da Doença
Seres Humanos
Estudos Longitudinais
Computação Matemática
Modelos Teóricos
Probabilidade
Projetos de Pesquisa
Processos Estocásticos
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Biomarkers)
[Em] Mês de entrada:1802
[Cu] Atualização por classe:180226
[Lr] Data última revisão:
180226
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:180130
[St] Status:MEDLINE
[do] DOI:10.1371/journal.pone.0190615


  7 / 13152 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
[PMID]:29351322
[Au] Autor:Datta S; Seed B
[Ad] Endereço:Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, United States of America.
[Ti] Título:Influence of multiplicative stochastic variation on translational elongation rates.
[So] Source:PLoS One;13(1):e0191152, 2018.
[Is] ISSN:1932-6203
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Experimental data indicate that stochastic effects exerted at the level of translation contribute substantially to the variation in abundance of proteins expressed at moderate to high levels. This study analyzes the theoretical consequences of fluctuations in residue-specific elongation rates during translation. A simple analytical framework shows that rate variation during elongation gives rise to protein production rates that consist of sums of products of random variables. Simulations show that because the contribution to total variation of products of random variables greatly exceeds that of sums of random variables, the overall distribution exhibits approximately log-normal behavior. Empirical fits of the data can be satisfied by either sums of log-normal distributions, or sums of log-normal and log-logistic distributions. Elongation rate stochastic variation offers an accounting for a major component of biological variation. The analysis provided here highlights a probability distribution that is a natural extension of the Poisson and has broad applicability to many types of multiplicative noise processes.
[Mh] Termos MeSH primário: Modelos Teóricos
Biossíntese de Proteínas
Processos Estocásticos
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1802
[Cu] Atualização por classe:180221
[Lr] Data última revisão:
180221
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:180120
[St] Status:MEDLINE
[do] DOI:10.1371/journal.pone.0191152


  8 / 13152 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
[PMID]:29346392
[Au] Autor:Duarte K; Monnez JM; Albuisson E
[Ad] Endereço:Université de Lorraine, Institut Elie Cartan de Lorraine, UMR 7502, Vandoeuvre-lès-Nancy, F-54506, France.
[Ti] Título:Sequential linear regression with online standardized data.
[So] Source:PLoS One;13(1):e0191186, 2018.
[Is] ISSN:1932-6203
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:The present study addresses the problem of sequential least square multidimensional linear regression, particularly in the case of a data stream, using a stochastic approximation process. To avoid the phenomenon of numerical explosion which can be encountered and to reduce the computing time in order to take into account a maximum of arriving data, we propose using a process with online standardized data instead of raw data and the use of several observations per step or all observations until the current step. Herein, we define and study the almost sure convergence of three processes with online standardized data: a classical process with a variable step-size and use of a varying number of observations per step, an averaged process with a constant step-size and use of a varying number of observations per step, and a process with a variable or constant step-size and use of all observations until the current step. Their convergence is obtained under more general assumptions than classical ones. These processes are compared to classical processes on 11 datasets for a fixed total number of observations used and thereafter for a fixed processing time. Analyses indicate that the third-defined process typically yields the best results.
[Mh] Termos MeSH primário: Modelos Lineares
[Mh] Termos MeSH secundário: Algoritmos
Interpretação Estatística de Dados
Processos Estocásticos
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Em] Mês de entrada:1802
[Cu] Atualização por classe:180220
[Lr] Data última revisão:
180220
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:180119
[St] Status:MEDLINE
[do] DOI:10.1371/journal.pone.0191186


  9 / 13152 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
[PMID]:28455349
[Au] Autor:Chen KY; Srinivasan T; Tung KL; Belmonte JM; Wang L; Murthy PKL; Choi J; Rakhilin N; King S; Varanko AK; Witherspoon M; Nishimura N; Glazier JA; Lipkin SM; Bu P; Shen X
[Ad] Endereço:School of Electrical and Computer Engineering, Cornell University, Ithaca, NY, USA.
[Ti] Título:A Notch positive feedback in the intestinal stem cell niche is essential for stem cell self-renewal.
[So] Source:Mol Syst Biol;13(4):927, 2017 Apr 28.
[Is] ISSN:1744-4292
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:The intestinal epithelium is the fastest regenerative tissue in the body, fueled by fast-cycling stem cells. The number and identity of these dividing and migrating stem cells are maintained by a mosaic pattern at the base of the crypt. How the underlying regulatory scheme manages this dynamic stem cell niche is not entirely clear. We stimulated intestinal organoids with Notch ligands and inhibitors and discovered that intestinal stem cells employ a positive feedback mechanism via direct Notch binding to the second intron of the Notch1 gene. Inactivation of the positive feedback by CRISPR/Cas9 mutation of the binding sequence alters the mosaic stem cell niche pattern and hinders regeneration in organoids. Dynamical system analysis and agent-based multiscale stochastic modeling suggest that the positive feedback enhances the robustness of Notch-mediated niche patterning. This study highlights the importance of feedback mechanisms in spatiotemporal control of the stem cell niche.
[Mh] Termos MeSH primário: Retroalimentação Fisiológica
Intestinos/citologia
Receptor Notch1/genética
Receptores Acoplados a Proteínas-G/metabolismo
[Mh] Termos MeSH secundário: Animais
Sítios de Ligação
Autorrenovação Celular
Seres Humanos
Intestinos/metabolismo
Camundongos
Mutação
Organoides/metabolismo
Receptor Notch1/química
Transdução de Sinais
Nicho de Células-Tronco
Processos Estocásticos
Biologia de Sistemas/métodos
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (LGR5 protein, human); 0 (NOTCH1 protein, human); 0 (Receptor, Notch1); 0 (Receptors, G-Protein-Coupled)
[Em] Mês de entrada:1802
[Cu] Atualização por classe:180213
[Lr] Data última revisão:
180213
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170430
[St] Status:MEDLINE
[do] DOI:10.15252/msb.20167324


  10 / 13152 MEDLINE  
              first record previous record
seleciona
para imprimir
Fotocópia
Texto completo
[PMID]:29370187
[Au] Autor:Ainsworth CH; Paris CB; Perlin N; Dornberger LN; Patterson WF; Chancellor E; Murawski S; Hollander D; Daly K; Romero IC; Coleman F; Perryman H
[Ad] Endereço:University of South Florida College of Marine Science, St. Petersburg, FL, United States of America.
[Ti] Título:Impacts of the Deepwater Horizon oil spill evaluated using an end-to-end ecosystem model.
[So] Source:PLoS One;13(1):e0190840, 2018.
[Is] ISSN:1932-6203
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:We use a spatially explicit biogeochemical end-to-end ecosystem model, Atlantis, to simulate impacts from the Deepwater Horizon oil spill and subsequent recovery of fish guilds. Dose-response relationships with expected oil concentrations were utilized to estimate the impact on fish growth and mortality rates. We also examine the effects of fisheries closures and impacts on recruitment. We validate predictions of the model by comparing population trends and age structure before and after the oil spill with fisheries independent data. The model suggests that recruitment effects and fishery closures had little influence on biomass dynamics. However, at the assumed level of oil concentrations and toxicity, impacts on fish mortality and growth rates were large and commensurate with observations. Sensitivity analysis suggests the biomass of large reef fish decreased by 25% to 50% in areas most affected by the spill, and biomass of large demersal fish decreased even more, by 40% to 70%. Impacts on reef and demersal forage caused starvation mortality in predators and increased reliance on pelagic forage. Impacts on the food web translated effects of the spill far away from the oiled area. Effects on age structure suggest possible delayed impacts on fishery yields. Recovery of high-turnover populations generally is predicted to occur within 10 years, but some slower-growing populations may take 30+ years to fully recover.
[Mh] Termos MeSH primário: Ecossistema
Peixes
Modelos Biológicos
Poluição por Petróleo/efeitos adversos
[Mh] Termos MeSH secundário: Animais
Biomassa
Meio Ambiente
Pesqueiros
Cadeia Alimentar
Golfo do México
Modelos Estatísticos
Petróleo/análise
Petróleo/toxicidade
Poluição por Petróleo/análise
Dinâmica Populacional/tendências
Especificidade da Espécie
Processos Estocásticos
Fatores de Tempo
Poluentes Químicos da Água/análise
Poluentes Químicos da Água/toxicidade
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Petroleum); 0 (Water Pollutants, Chemical)
[Em] Mês de entrada:1802
[Cu] Atualização por classe:180213
[Lr] Data última revisão:
180213
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:180126
[St] Status:MEDLINE
[do] DOI:10.1371/journal.pone.0190840



página 1 de 1316 ir para página                         
   


Refinar a pesquisa
  Base de dados : MEDLINE Formulário avançado   

    Pesquisar no campo  
1  
2
3
 
           



Search engine: iAH v2.6 powered by WWWISIS

BIREME/OPAS/OMS - Centro Latino-Americano e do Caribe de Informação em Ciências da Saúde