Efeitos da suplementação de Waxy Maize e placebo em medidas psicofisiológicas em lutadores de Jiu-Jitsu: Estudo duplo cego, crossover, placebo controlado

Introdução: O aumento do metabolismo dos carboidratos é diretamente proporcional à intensidade do exercício e o Jiu Jitsu é um bom exemplo de atividade intensa como predominância de força muscular. O objetivo desse estudo foi avaliar as respostas psicofisiológicas de lutadores de Jiu Jitsu em função da suplementação do Waxy Maize (WM) e Placebo (PL). Materiais e Métodos: Foram selecionados 18 lutadores de jiu jitsu de diferentes academias da cidade de Natal-RN, para receberem uma suplementação de WM e PL (duplo cego) previamente a uma série de combates sucessivos de cinco minutos com intervalo de um minuto entre eles, até a exaustão auto reportada. O estudo aconteceu em duas etapas como cruzamento do suplemento ofertado em cada uma delas. Foi dado uma semana de intervalo entre elas para whashout. Nas comparações intergrupos e intragrupos foi usado o teste t de Student e ANOVA respectivamente. Resultados: A PSE não apresentou diferenças significativas intergrupos, mas os valores do grupo WM foram ligeiramente mais baixos. Em ambos os grupos a glicemia periférica não aumentou significativamente 10min depois da suplementação. Não encontramos diferenças significativas nos valores de glicemia final obtidos pelo grupo WM e PL. Conclusão: A oferta de WM não foi efetiva para diminuir a PSE quando comparado com o PL, o que aponta para o fato de que os mecanismos de fadiga possam estar mais intimamente ligados aos processos de absorção e utilização do substrato do que à sua biodisponibilidade. ABSTRACTEffects of supplementation waxy maize and placebo on psychophysiological measures in fighters jiu-jitsu: Test Double Blind, Crossover, Placebo ControlledIntroduction: The increase of carbohydrate metabolism is directly proportional to the intensity of exercise and Jiu Jitsu can is a good example of intense activity as a predominance of muscle strength. The aim of this study was to evaluate psychophysiological responses Jiu Jitsu due to the supplementation of Waxy Maize (WM) and Placebo (PL). Materials and Methods: A total of 18 Jiu Jitsu different academies of Natal-RN, were selected to receive supplemental WM and PL (double blind) prior to a series of successive combats five minutes with one minute interval between them until exhaustion self-reported. The study took place in two steps as crossing offered in each supplement. It was given an interval of a week between them. Intragroup and intergroup comparisons, it was used the Student t test and ANOVA, respectively. Results: The PSE showed no significant differences between groups but the values of the WM group were slightly lower. In both groups, no significant increase in peripheral blood sugar 10 minutes after supplementation. We found no significant differences in final glucose values obtained by the WM and PL group. Conclusion: The availability of WM was not effective to decrease the PSE compared with PL, which points to the fact that the mechanisms of fatigue may be more closely linked to the processes of absorption and utilization of the substrate than to their bioavailability

General framework for estimating the ultimate precision limit in noisy quantum-enhanced metrology

The estimation of parameters characterizing dynamical processes is central to science and technology. The estimation error changes with the number N of resources employed in the experiment (which could quantify, for instance, the number of probes or the probing energy). Typically, it scales as 1/N^(1/2). Quantum strategies may improve the precision, for noiseless processes, by an extra factor 1/N^(1/2). For noisy processes, it is not known in general if and when this improvement can be achieved. Here we propose a general framework for obtaining attainable and useful lower bounds for the ultimate limit of precision in noisy systems. We apply this bound to lossy optical interferometry and atomic spectroscopy in the presence of dephasing, showing that it captures the main features of the transition from the 1/N to the 1/N^(1/2) behaviour as N increases, independently of the initial state of the probes, and even with use of adaptive feedback.Comment: Published in Nature Physics. This is the revised submitted version. The supplementary material can be found at http://www.nature.com/nphys/journal/v7/n5/extref/nphys1958-s1.pd

A carnosina diminui os efeitos da acidose muscular durante o exercício

A carnosina é um dipeptídeo composto pelos aminoácidos beta-alanina e histidina encontrado em maior parte no tecido muscular. Sua síntese ocorre através da enzima carnosina sintase tendo a beta alanina como precursor limitante. Estudos tem mostrado que o aumento nos níveis de carnosina melhora o desempenho esportivo, devido a redução da diminuição do pH intramuscular durante o exercício, proporcionando maior capacidade de tamponamento de íons de hidrogênio (H+). O objetivo da presente revisão foi analisar estudos relacionados aos efeitos da suplementação crônica de beta-alanina no desempenho esportivo nos últimos anos. A estratégia de busca foi realizada através de consulta às bases de dados PubMed e Trip database, utilizando os descritores “carnosineâ€, “beta-alanine†e “exercise†de forma combinada em artigos publicados entre janeiro de 2007 e dezembro de 2013. Foram incluídos na análise apenas artigos originais e foram excluídos artigos que avaliaram amostra não saudável, suplementação de beta-alanina associada a outras substâncias, além de teses, dissertações e trabalhos de revisão. Com base na reunião de informações acreditamos que a suplementação de beta alanina pode ser considerada uma estratégia eficaz no aumento dos níveis de carnosina, refletindo em melhoria de desempenho através de aumento do tempo de exaustão e atraso no limiar de fadiga neuromuscular, apresentando melhores efeitos em atividades de alta intensidade. ABSTRACTDoes carnosine reduce the effects of muscle acidosis during exercise?Carnosine is a dipeptide of beta-alanine and histidine amino acids, being found in most of the muscle tissue. Its synthesis occurs through carnosine synthase enzyme having the beta alanine as a limiting precursor. The most recent works have shown that increased levels of carnosine improves sports performance due to reducing of decrease in pH intramuscular during exercise, providing greater buffering capacity of hydrogen ions (H +). The aim of this review was to analyze works related to the effects of chronic beta-alanine supplementation on exercise performance recent years. The search strategy was done through consultation with PubMed and Trip Database data using the combined descriptors “carnosineâ€, “beta-alanine†and “exercise†in articles published between January 2007 and December 2013. We included in this analysis just original articles and articles that evaluated unhealthy sample, beta-alanine supplementation associated with other substances, as well as these, dissertations and reviews were excluded. Based on information meeting, we believe that beta-alanine supplementation can be considered an effective strategy in increasing carnosine levels, reflecting improved performance through increased time to exhaustion and delayed on neuromuscular fatigue threshold, presenting better effects in high intensity activities

Painel: a dívida externa dos países em desenvolvimento e o caso brasileiro

A publicação deste painel foge à tradição editorial desta revista, mas a leitura da transcrição da fita gravado nos levou a esta decisão

Allelopathy of Bracken Fern (Pteridium arachnoideum): New Evidence from Green Fronds, Litter, and Soil

The neotropical bracken fern Pteridium arachnoideum (Kaulf.) Maxon. (Dennstaedtiaceae) is described as an aggressive pioneer plant species. It invades abandoned or newly burned areas and represents a management challenge at these invaded sites. Native to the Atlantic Forest and Cerrado (Tropical Savanna) Brazilian biomes, P. arachnoideum has nevertheless become very problematic in these conservation hotspots. Despite some reports suggesting a possible role of allelopathy in this plant’s dominance, until now there has been little evidence of isolated and individually identified compounds with phytotoxic activities present in its tissues or in the surrounding environment. Thus, the aim of this study was to investigate the allelopathic potential of P. arachnoideum by isolating and identifying any secondary metabolites with phytotoxic activity in its tissues, litter, and soil. Bioguided phytochemical investigation led to the isolation and identification of the proanthocyanidin selligueain A as the major secondary compound in the green fronds and litter of this fern. It is produced by P. arachnoideum in its green fronds, remains unaltered during the senescence process, and is the major secondary compound present in litter. Selligueain A showed phytotoxic activity against the selected target species sesame (Sesamum indicum) early development. In particular, the compound inhibited root and stem growth, and root metaxylem cell size but did not affect chlorophyll content. This compound can be considered as an allelochemical because it is present in the soil under P. arachnoideum patches as one of the major compounds in the soil solution. This is the first report of the presence of selligueain A in any member of the Dennstaedtiaceae family and the first time an isolated and identified allelochemical produced by members of the Pteridium species complex has been described. This evidence of selligueain A as a putative allelochemical of P. arachnoideum reinforces the role of allelopathy in the dominance processes of this plant in the areas where it occurs

P-cadherin expression in breast cancer: a review

P-cadherin is frequently over-expressed in high-grade invasive breast carcinomas and has been reported to be an enhancer of migration and invasion of breast cancer cells, being correlated with tumour aggressiveness. In addition, expression of P-cadherin is well established as an indicator of poor prognosis in human breast cancer, which has stimulated our interest in studying its role in this setting. This review describes the most important findings on P-cadherin expression and function in normal mammary tissue and breast cancer cells, emphasizing that further research is required to elucidate the role played by this protein in human mammary tumours