Cerebral oxygenation during the Richalet hypoxia sensitivity test and cycling time-trial performance in severe hypoxia.

BACKGROUND: The Richalet hypoxia sensitivity test (RT), which quantifies the cardiorespiratory response to acute hypoxia during exercise at an intensity corresponding to a heart rate of ~130 bpm in normoxia, can predict susceptibility of altitude sickness. Its ability to predict exercise performance in hypoxia is unknown. OBJECTIVES: Investigate: (1) whether cerebral blood flow (CBF) and cerebral tissue oxygenation (O2Hb; oxygenated hemoglobin, HHb; deoxygenated hemoglobin) responses during RT predict time-trial cycling (TT) performance in severe hypoxia; (2) if subjects with blunted cardiorespiratory responses during RT show greater impairment of TT performance in severe hypoxia. STUDY DESIGN: Thirteen men [27 ± 7 years (mean ± SD), Wmax: 385 ± 30 W] were evaluated with RT and the results related to two 15 km TT, in normoxia and severe hypoxia (FIO2 = 0.11). RESULTS: During RT, mean middle cerebral artery blood velocity (MCAv: index of CBF) was unaltered with hypoxia at rest (p > 0.05), while it was increased during normoxic (+22 ± 12 %, p < 0.05) and hypoxic exercise (+33 ± 17 %, p < 0.05). Resting hypoxia lowered cerebral O2Hb by 2.2 ± 1.2 μmol (p < 0.05 vs. resting normoxia); hypoxic exercise further lowered it to -7.6 ± 3.1 μmol below baseline (p < 0.05). Cerebral HHb, increased by 3.5 ± 1.8 μmol in resting hypoxia (p < 0.05), and further to 8.5 ± 2.9 μmol in hypoxic exercise (p < 0.05). Changes in CBF and cerebral tissue oxygenation during RT did not correlate with TT performance loss (R = 0.4, p > 0.05 and R = 0.5, p > 0.05, respectively), while tissue oxygenation and SaO2 changes during TT did (R = -0.76, p < 0.05). Significant correlations were observed between SaO2, MCAv and HHb during RT (R = -0.77, -0.76 and 0.84 respectively, p < 0.05 in all cases). CONCLUSIONS: CBF and cerebral tissue oxygenation changes during RT do not predict performance impairment in hypoxia. Since the changes in SaO2 and brain HHb during the TT correlated with performance impairment, the hypothesis that brain oxygenation plays a limiting role for global exercise in conditions of severe hypoxia remains to be tested further.

Test-retest repeatability of the pupil light response to blue and red light stimuli in normal human eyes using a novel pupillometer.

In this study, we evaluated the repeatability of pupil responses to colored light stimuli in healthy subjects using a prototype chromatic pupillometer. One eye of 10 healthy subjects was tested twice in the same day using monochromatic light exposure at two selected wavelengths (660 and 470 nm, intensity 300 cd/m(2)) presented continuously for 20 s. Pupil responses were recorded in real-time before, during, and after light exposure. Maximal contraction amplitude and sustained contraction amplitude were calculated. In addition, we quantified the summed pupil response during continuous light stimulation as the total area between a reference line representing baseline pupil size and the line representing actual pupil size over 20 s (area under the curve). There was no significant difference in the repeated measure compared to the first test for any of the pupil response parameters. In conclusion, we have developed a novel prototype of color pupillometer which demonstrates good repeatability in evoking and recording the pupillary response to a bright blue and red light stimulus.

Cardiorespiratory and Cardiac Autonomic Responses to 30-15 Intermittent Fitness Test in Team Sport Players

Buchheit, M, Al Haddad, H, Millet GP, Lepretre, PM, Newton, M, and Ahmaidi, S. Cardiorespiratory and cardiac autonomic responses to 30-15 Intermittent Fitness Test in team sport players. J Strength Cond Res 23(1): xxx-xxx, 2009-The 30-15 Intermittent Fitness Test (30-15IFT) is an attractive alternative to classic continuous incremental field tests for defining a reference velocity for interval training prescription in team sport athletes. The aim of the present study was to compare cardiorespiratory and autonomic responses to 30-15IFT with those observed during a standard continuous test (CT). In 20 team sport players (20.9 +/- 2.2 years), cardiopulmonary parameters were measured during exercise and for 10 minutes after both tests. Final running velocity, peak lactate ([La]peak), and rating of perceived exertion (RPE) were also measured. Parasympathetic function was assessed during the postexercise recovery phase via heart rate (HR) recovery time constant (HRRtau) and HR variability (HRV) vagal-related indices. At exhaustion, no difference was observed in peak oxygen uptake (&OV0312;o2peak), respiratory exchange ratio, HR, or RPE between 30-15IFT and CT. In contrast, 30-15IFT led to significantly higher minute ventilation, [La]peak, and final velocity than CT (p < 0.05 for all parameters). All maximal cardiorespiratory variables observed during both tests were moderately to well correlated (e.g., r = 0.76, p = 0.001 for &OV0312;o2peak). Regarding ventilatory thresholds (VThs), all cardiorespiratory measurements were similar and well correlated between the 2 tests. Parasympathetic function was lower after 30-15IFT than after CT, as indicated by significantly longer HHRtau (81.9 +/- 18.2 vs. 60.5 +/- 19.5 for 30-15IFT and CT, respectively, p < 0.001) and lower HRV vagal-related indices (i.e., the root mean square of successive R-R intervals differences [rMSSD]: 4.1 +/- 2.4 and 7.0 +/- 4.9 milliseconds, p < 0.05). In conclusion, the 30-15IFT is accurate for assessing VThs and &OV0312;o2peak, but it alters postexercise parasympathetic function more than a continuous incremental protocol.

Théorie bayesienne de la décision statistique et mesure de la radioactivité

L'objet de ce travail est l'évaluation de l'activité de radionucléides présents à l'état de traces, par exemple dans l'environnement. Lorsque les mesures sont de courte durée, ou si les sources sont peu actives, l'analyse statistique standard ne donne plus une estimation fiable de l'activité et de son incertitude. L'introduction du concept bayesien d'a priori permet de modéliser l'information à disposition de l'observateur avant qu'il effectue la mesure. Cette information conduit à une estimation plus cohérente des grandeurs physiques recherchées. Le cadre de la théorie est tout d'abord présenté, définissant les concepts d'état, d'observation et de décision. La mesure physique est traduite par un modèle statistique qui est une probabilité de transition des états vers les observations. L'information de Fisher et celle de Shannon-Kullback sont introduites dans le but d'obtenir les a priori nécessaires au théorème de Bayes. Les modèles propres à la mesure de la radioactivité sont ensuite traités. Si l'on peut considérer l'activité comme constante, le modèle est celui de Poisson et conduit à des a priori de type gamma. Pour les grandes activités, ces deux lois se rapprochent des gaussiennes et l'on retrouve l'analyse statistique classique. Lorsque la décroissance du nombre de noyaux n'est plus négligeable, ou lors de l'évaluation de certains temps d'attente, d'autres modèles sont développés. Quelques applications sont présentées ensuite, notamment une définition cohérente des intervalles de confiance et l'estimation de l'activité de radionucléides à schéma complexe par spectrométrie gamma, où l'obtention de tout un spectre permet une analyse multidimensionnelle. Le paradigme bayesien conduit à une répartition complète et globale pour l'état du système physique mesuré. L'observateur obtient ainsi la meilleure estimation possible de l'état basée sur son modèle d'expérience et l'information préalable en sa possession.

Phylogenetic study of the Grimmia Hedw. (Grimmiales, Bryopsida) based on a combination of morphological and molecular characters

Résumé Les mousses sont la plus ancienne lignée de plantes terrestres et leur longue évolution a été accompagnée par des tendances à la simplification des caractères morphologiques. Ce phénomène a quelque peu compliqué les reconstructions phylogénétiques basées sur la morphologie. Les analyses génétiques ont permis de donner de nouvelles informations dans le cadre des analyses phylogénétiques et une réévaluation de certains caractères morphologiques. La plupart des études combinant les données morphologiques et moléculaires ne concernent que des niveaux systématiques élevés comme l'ordre ou la famille et très peu considèrent le niveau du genre. La présente étude tend à tester les relations phylogénétiques du genre Grimmia à l'aide d'une combinaison de caractères morphologiques et moléculaires. Les 40 espèces de Grimmia utilisées dans la première partie de cette étude représentent la majorité des espèces trouvées en Eurasie, un des centres de diversification du genre. Lors de l'analyse morphologique, 52 caractères morphologiques/anatomiques (33 du gamétophyte et 19 du sporophyte) ont été numérisés. Malgré le peu de support statistique des arbres, la topologie des arbres est stable. Les Grimmia, comme décrit précédemment, sont paraphylétiques. Trois clades, correspondant respectivement aux sous-genres Rhabdogrimmia Limpr, Litoneuron I.Hagen et Gasterogrimmia Schimp. sont présents, tandis que le restant des taxons appartenant aux Grimmia forment un groupe non-résolu et indistinct des autres Grimmiaceae. Les séquences chloroplastiques trnL-trnF et rps4 combinés à la morphologie ont été ensuite utilisés pour reconstruire la phylogénie des Grimmia. Les arbres obtenus soutiennent la monophylie des Grimmiaceae tandis que les Grimmia, sont paraphylétiques. Deux clades principaux correspondant aux "Rhabdogrimmia" et aux "Grimmia" se détachent. Seules les espèces de "Rhabdogrimmia" produisent des gemmules foliaires (reproduction asexuée). Dans une étude considèrant 91 séquences trrIL-trnF les espèces appartenant aux "Rhabdogrimrnia" (reproduction asexuée essentiellement) ont des variabilités intraspécifique très faible et interspécifique relativement élevée tandis que les "Grimmia" possèdent la tendance inverse (plus de reproduction sexuée). Summary The mosses are a very old land plant lineage and their long evolutionary history has been accompanied by a trend of morphological character simplifications. This phenomenon has somewhat complicated morphological based phylogenetic reconstructions. Genetic analyses have provided new insights for phylogenetic studies, and have allowed morphological data to be re¬evaluated. Most of the studies combining morphological and molecular data have concerned the higher systematic levels of order and family and only have few considered the genus. The present study aims to test the phylogenetic relationships of the genus Grimmia using a combination of morphological and molecular characters. The 40 chosen Grimmia species represent the majority of those found in Eurasia, one diversification centers of the genus. For the morphological analysis, 52 morphological/anatomical characters (33 gametophyte and 19 sporophyte characters) were numerized. Although the internal statistical support was relatively low, the tree topologies were stable. Grimmia as currently defined was found to be paraphyletic. Three subclades, corresponding to the subgenera Rhabdogrimmia Limpr., Litoneuron I.Hagen, and Gasterogrimmia Schimp. were observed in the trees, while the reminder of the Grimmia species formed an unresolved group indistinct from other Grimmiaceae. Chloroplast (trnL-trnF and rps4) DNA sequences combined with morphology were used to reconstruct the phylogeny of Grimmia. The resulting trees supported the monophyly of Grimmiaceae and that the genus Grimmia, as currently defined, as paraphyletic. Two main clades were resolved corresponding to "Rhabdogrimmia" and "Grimmia". The species belonging to "Rhabdogrimmia" produce foliar-gemmae (asexual reproduction). In a study using 91 sequences of trnL-trnF,"Rhabdogrimmia" species (mainly asexual reproduction) have very low intraspecific variability and high interspecific variability whereas the "Grimmia" species possess the inverse tendency.

Use of a pre-sidedress soil nitrate test (PSNT) to determine nitrogen fertilizer requirements for irrigated corn

In the present study, a 2-year N rate response experiment was conducted in different fields to monitor NO3-N soil profiles, N accumulation by the crop and final crop performance, in order to assess if soil NO3-N at pre-sidedressing (Pre-Sidedress Soil Nitrate Test, PSNT) is a reliable indicator for soil N availability for corn in the irrigated area served by canal d’Urgell (Lleida, Spain), and if the test can be used to separate responsive fields from non-responsive fields to sidedress N fertilizer applications. Preliminary soil N availability (N sidedress fertilizer rate + PSNT) critical levels to identify fields that need supplementary N fertilizer applications were established at ca. 300 and 210 kg NO3-N·ha–1, for PSNTrooting–zone and PSNT0–30 cm, respectively (for a yield goal of 14 t grain·ha–1).