Environment and Scheduling Effects on Sprint and Middle Distance Running Performances

Purpose

Achievement of athletes’ performances is related to several factors including physiological, environmental and institutional cycles where physical characteristics are involved. The objective of this study is to analyse the performance achieved in professional sprint and middle-distance running events (100 m to 1500 m) depending on the organization of the annual calendar of track events and their environmental conditions.

Methods

From 2002 to 2008, all performances of the Top 50 international athletes in the 100 m to 1500 m races (men and women) are collected. The historical series of world records and the 10 best annual performances in these events, amounted to a total of 26,544 performances, are also included in the study.

Results

Two periods with a higher frequency of peak performances are observed. The first peak occurs around the 27.15^th ±0.21 week (first week of July) and the second peak around 34.75^th ±0.14 week (fourth week of August). The second peak tends to be the time of major international competitions (Olympic Games, World Championships, and European Championships) and could be characterized as an institutional moment. The first one, however, corresponds to an environmental optimum as measured by the narrowing of the temperature range at the highest performance around 23.25±3.26°C.

Conclusions

This is the first study to demonstrate that there are two performance peaks at a specific time of year (27th and 34th weeks) in sprint and middle distance. Both institutional and ecophysiological aspects contribute to performance in the 100 m to 1500 m best performances and define the contours of human possibilities. Sport institutions may take this into account in order to provide ideal conditions to improve the next records.     

Analyse multiparamétrique de la composition minérale des pollens d'une population de Bactris gasipaes (Arecaceae)

Bactris gasipaes Kunth is important both economically and as a food resource in several countries of tropical Africa. The profitability of cultivation can be increased by genetic amelioration of natural morphotypes. We observed that pollen characteristics influence the morphological and physiological features of the fruits. This prompted us to undertake a study based upon ten morphotypes from the Yurimaguas (Peru). We here complete the morphological and ultrastructural investigation of pollen, previously started by one of us, with an analysis of the elements with respect to the importance of the role they play in relation to pollen function. A determination of the 8 major elements, which corresponds to a precise analysis of the exine, was performed by micro-X-Ray diffraction analysis using an electron probe coupled with a scanning electron microscope. At the same time, the determination of calcium, magnesium and twelve oligo-elements by inductive coupled plasma spectrometry (ICP) provided a complete mineral analysis of the pollen. A comparison of the element patterns of the morphotypes, obtained by both was carried out through a number of numerical data reduction techniques (Factor analysis and clustering). This led us to suggest two classifications: (1) that of pollen based upon mineral elements (2) that of mineral elements based upon pollen and further to look for possible multiple correlations between elements and pollens.

From the results obtained the following conclusions may be drawn: (1) the sequence of elements in descending order of concentration in the exine is an indication of the functional integrity of pollen and depends upon conservation and storage; (2) further, this sequence is a good fertility criterion; (3) variations in oligo-element concentrations in one cultivar allows infraspecific groups to be distinguished. This multiparametric approach also allow the location of an unknown pollen sample of Bactris gasipaes in the population under investigation.

Bactris gasipaes Kunth, ressource économique et alimentaire importante pour plusieurs pays d'Amérique tropicale, fait actuellement l'étude de recherches intensives. La rentabilité de sa culture pourra être augmentée par l'amélioration génétique des morphotypes naturels. Les caractéristiques du pollen ayant montré leur influence sur les caractères morphologiques et physiologiques des fruits, nous avons entrepris une étude sur la base de dix morphotypes originaires de Yurimaguas, au Pérou. Nous avons compléte l'étude morphologique et ultra-structurale du pollen, réalisée précédemment par l'un de nous, par une analyse des éléments minéraux qu'il contient en raison de l'importance qu'ils revêtent dans les différentes fonctions du pollen. Ainsi, la teneur en huit éléments minéraux majeurs, qui correspond à une analyse ponctuelle de l'exine, a été déterminée par micro-analyse X par sonde électronique couplée au microscope à balayage. De même, le dosage du calcium, du magnésium et de douze oligoéléments, effectué par spectométrie à plasma à couplage inductif (ICP), correspond à l'analyse minérale globale du pollen. L'étude comparative des profils en éléments minéraux des différents morphotypes, obtenue par chacune de ces deux méthodes d'analyse, a été réalisée par différentes techniques d'analyse mathématique de réduction de données multidimensionnelles (analyse factorielle et classifications automatiques). Nous avons ainsi pu proposer une double classification: (1) celle des pollens sur la base des éléments minéraux, (2) celle des éléments minéraux sur la base des pollens, puis rechercher les corrélations multiples éléments minéraux/pollens. Les résultats obtenus ont montré: (1) que la séquence des éléments minéraux dans l'ordre de concentration décroissante dans l'exine est caractéristique de l'intégrité fonctionnelle du pollen et dépend de ses conditions de conservation et de stockage, (2) que çette même séquence constitue un bon marqueur de la fertilité de pollen, (3) que la variabilité entre les concentrations en oligoéléments observée entre les différents cultivars permet la constitution d'un marqueur chimiotaxonomique satisfaisant pour discriminer sur la base du pollen les groupes d'individus au sein même de l'espèce végétale considérée. Cette approche multiparamétrique offre également la possibilité de positionner a priori un nouvel échantillon de pollen de Bactris par rapport à la population initiale étudiée.     

Redundant Regulation of Cdk1 Tyrosine Dephosphorylation in Saccharomyces cerevisiae

Cdk1 activity drives both mitotic entry and the metaphase-to-anaphase transition in all eukaryotes. The kinase Wee1 and the phosphatase Cdc25 regulate the mitotic activity of Cdk1 by the reversible phosphorylation of a conserved tyrosine residue. Mutation of cdc25 in Schizosaccharomyces pombe blocks Cdk1 dephosphorylation and causes cell cycle arrest. In contrast, deletion of MIH1, the cdc25 homolog in Saccharomyces cerevisiae, is viable. Although Cdk1-Y19 phosphorylation is elevated during mitosis in mih1∆ cells, Cdk1 is dephosphorylated as cells progress into G₁, suggesting that additional phosphatases regulate Cdk1 dephosphorylation. Here we show that the phosphatase Ptp1 also regulates Cdk1 dephosphorylation in vivo and can directly dephosphorylate Cdk1 in vitro. Using a novel in vivo phosphatase assay, we also show that PP2A bound to Rts1, the budding yeast B56-regulatory subunit, regulates dephosphorylation of Cdk1 independently of a function regulating Swe1, Mih1, or Ptp1, suggesting that PP2A^Rts1 either directly dephosphorylates Cdk1-Y19 or regulates an unidentified phosphatase.     

A Wee1 checkpoint inhibits anaphase onset

Cdk1 drives both mitotic entry and the metaphase-to-anaphase transition. Past work has shown that Wee1 inhibition of Cdk1 blocks mitotic entry. Here we show that the budding yeast Wee1 kinase, Swe1, also restrains the metaphase-to-anaphase transition by preventing Cdk1 phosphorylation and activation of the mitotic form of the anaphase-promoting complex/cyclosome (APC^Cdc20). Deletion of SWE1 or its opposing phosphatase MIH1 (the budding yeast cdc25⁺) altered the timing of anaphase onset, and activation of the Swe1-dependent morphogenesis checkpoint or overexpression of Swe1 blocked cells in metaphase with reduced APC activity in vivo and in vitro. The morphogenesis checkpoint also depended on Cdc55, a regulatory subunit of protein phosphatase 2A (PP2A). cdc55Δ checkpoint defects were rescued by mutating 12 Cdk1 phosphorylation sites on the APC, demonstrating that the APC is a target of this checkpoint. These data suggest a model in which stepwise activation of Cdk1 and inhibition of PP2A^Cdc55 triggers anaphase onset.     

Hemizygous Le-Cre Transgenic Mice Have Severe Eye Abnormalities on Some Genetic Backgrounds in the Absence of LoxP Sites

Eye phenotypes were investigated in Le-Cre^Tg/−; Pax6^fl/+ mice, which were expected to show tissue-specific reduction of Pax6 in surface ectoderm derivatives. To provide a better comparison with our previous studies of Pax6^+/− eye phenotypes, hemizygous Le-Cre^Tg/− and heterozygous Pax6^fl/+mice were crossed onto the CBA/Ca genetic background. After the Le-Cre transgene had been backcrossed to CBA/Ca for seven generations, significant eye abnormalities occurred in some hemizygous Le-Cre^Tg/−; Pax6^+/+ controls (without a floxed Pax6^fl allele) as well as experimental Le-Cre^Tg/−; Pax6^fl/+ mice. However, no abnormalities were seen in Le-Cre^−/−; Pax6^fl/+ or Le-Cre^−/−; Pax6^+/+ controls (without the Le-Cre transgene). The severity and frequency of the eye abnormalities in Le-Cre^Tg/−; Pax6^+/+ control mice diminished after backcrossing Le-Cre^Tg/− mice to the original FVB/N strain for two generations, showing that the effect was reversible. This genetic background effect suggests that the eye abnormalities are a consequence of an interaction between the Le-Cre transgene and alleles of unknown modifier genes present in certain genetic backgrounds. The abnormalities were also ameliorated by introducing additional Pax6 gene copies on a CBA/Ca background, suggesting involvement of Pax6 depletion in Le-Cre^Tg/−; Pax6^+/+ mice rather than direct action of Cre recombinase on cryptic pseudo-loxP sites. One possibility is that expression of Cre recombinase from the Pax6-Le regulatory sequences in the Le-Cre transgene depletes cofactors required for endogenous Pax6 gene expression. Our observation that eye abnormalities can occur in hemizygous Le-Cre^Tg/−; Pax6^+/+ mice, in the absence of a floxed allele, demonstrates the importance of including all the relevant genetic controls in Cre-loxP experiments.     

Dynamical compensation in physiological circuits

Biological systems can maintain constant steady‐state output despite variation in biochemical parameters, a property known as exact adaptation. Exact adaptation is achieved using integral feedback, an engineering strategy that ensures that the output of a system robustly tracks its desired value. However, it is unclear how physiological circuits also keep their output dynamics precise—including the amplitude and response time to a changing input. Such robustness is crucial for endocrine and neuronal homeostatic circuits because they need to provide a precise dynamic response in the face of wide variation in the physiological parameters of their target tissues; how such circuits compensate their dynamics for unavoidable natural fluctuations in parameters is unknown. Here, we present a design principle that provides the desired robustness, which we call dynamical compensation (DC). We present a class of circuits that show DC by means of a nonlinear feedback loop in which the regulated variable controls the functional mass of the controlling endocrine or neuronal tissue. This mechanism applies to the control of blood glucose by insulin and explains several experimental observations on insulin resistance. We provide evidence that this mechanism may also explain compensation and organ size control in other physiological circuits.     

An okadaic acid-sensitive phosphatase negatively controls the cyclin degradation pathway in amphibian eggs.

Inhibition of okadaic acid-sensitive phosphatases released the cyclin degradation pathway from its inhibited state in extracts prepared from unfertilized Xenopus eggs arrested at the second meiotic metaphase. It also switched on cyclin protease activity in a permanent fashion in interphase extracts prepared from activated eggs. Even after cdc2 kinase inactivation, microinjection of okadaic acid-treated interphase extracts pushed G2-arrested recipient oocytes into the M phase, suggesting that the phosphatase inhibitor stabilizes the activity of an unidentified factor which shares in common with cdc2 kinase the maturation-promoting factor activity.     

Enzyme-resistant CCK analogs with high affinities for central receptors

Based on the results of the in vitro metabolism of CCK8 by various peptidases, we have synthesized three CCK analogs: Boc-Tyr(SO3H)-Nle-Gly-Trp-(N- Me)Nle-Asp-Phe-NH2 (compound I), Boc-Tyr(SO3H)-gNle-mGly-Trp-Nle-Asp-Phe-Nh2 (compound II), Boc-Tyr(SO3H)-gNle-mGly-Trp-(N-Me)Nle-Asp-Phe-NH2 (compound III). In in vitro enzymatic degradation studies, these compounds showed a high stability toward either enkephalinase or the enzymes present in crude rat brain membranes preparations. Moreover, in binding studies on guinea pig tissues, these CCK-related peptides were characterized by high apparent affinities for brain CCK receptors and by a broader range of affinities for pancreatic CCK receptors. This broad range of affinities was reflected by their pharmacological potencies in the guinea pig pancreatic amylase release and ileum contraction assays. These enzyme-resistant CCK analogs provide therefore valuable tools to investigate the pharmacology of CCK.     

Bronchiolectasis-a complication of artificial ventilation.

Pulmonary barotrauma associated with artificial ventilation is recognised clinically as pneumothorax, pneumo-mediastinum, or subcutaneous emphysema. Eleven patients who died in the intensive therapy unit after artificial ventilation were found at necropsy to have pronounced bronchiolectasis, which was associated with a greatly increased physiological dead space during life. The condition was best predicted by the maximum level of positive end expiratory pressure and the duration of application of positive end expiratory pressure. The clinical course of the lesion in survivors is not known. Further detailed studies are needed, but it is suggested that high levels of positive end expiratory pressure should be used with caution.