The genetics of adaptation in freshwater Eurasian shad (Alosa)

Studying the genetics of phenotypic convergence can yield important insights into adaptive evolution. Here, we conducted a comparative genomic study of four lineages (species and subspecies) of anadromous shad (Alosa) that have independently evolved life cycles entirely completed in freshwater. Three naturally diverged (A. fallax lacustris, A. f. killarnensis, and A. macedonica), and the fourth (A. alosa) was artificially landlocked during the last century. To conduct this analysis, we assembled and annotated a draft of the A. alosa genome and generated whole-genome sequencing for 16 anadromous and freshwater populations of shad. Widespread evidence for parallel genetic changes in freshwater populations within lineages was found. In freshwater A. alosa, which have only been diverging for tens of generations, this shows that parallel adaptive evolution can rapidly occur. However, parallel genetic changes across lineages were comparatively rare. The degree of genetic parallelism was not strongly related to the number of shared polymorphisms between lineages, thus suggesting that other factors such as divergence among ancestral populations or environmental variation may influence genetic parallelism across these lineages. These overall patterns were exemplified by genetic differentiation involving a paralog of ATPase-α1 that appears to be under selection in just two of the more distantly related lineages studied, A. f. lacustris and A. alosa. Our findings provide insights into the genetic architecture of adaptation and parallel evolution along a continuum of population divergence

Effect of heavy-intensity 'priming' exercise on oxygen uptake and muscle deoxygenation kinetics during moderate-intensity step-transitions initiated from an elevated work rate

We examined the effect of heavy-intensity ‘priming’ exercise on the rate of adjustment of pulmonary O2 uptake (τ 2p) initiated from elevated intensities. Fourteen men (separated into two groups: τ 2p≤25s [Fast] or τ 2p>25s [Slow]) completed step-transitions from 20W-to- 45%lactate threshold (LT; lower-step, LS) and 45%-to-90%LT (upper-step, US) performed (i) without; and (ii) with US preceded by heavy-intensity exercise (HUS). Breath-by-breath 2p and near-infrared spectroscopy-derived muscle deoxygenation ([HHb+Mb]) were measured. Compared to LS, τ 2p was greater (p0.05) from LS or Fast group US. In Slow, τ[HHb+Mb] increased (p<0.05) in US relative to HUS; this finding coupled with a reduced τ 2p indicates a priming-induced improvement in matching of muscle O2 delivery-to-O2 utilization during transitions from elevated intensities in those with Slow but not Fast 2p kinetics

Eficacia de la pliometría en la fatiga neuromuscular en triatlón: estudio piloto

Las transiciones en triatlón afectan al rendimiento y riesgo de lesión. El objetivo fue determinar la fatiga neuromuscular inducida por 40 km de ciclismo y la eficacia del entrenamiento pliométrico en la fatiga y rendimiento de la carrera a pie. Participaron doce triatletas, 5 realizaron un entrenamiento pliométrico y 7 continuaron su entrenamiento habitual. Se realizaron tests de salto antes y después de 40 km de ciclismo para determinar la fatiga y se registró el ritmo de 5 km de carrera. Se observaron diferencias significativas en la altura de salto (p&lt;0,05) indicando que 40 km de ciclismo inducen fatiga en la extremidad inferior. Tras el entrenamiento pliométrico se observaron mejoras significativas en el test Squat Jump posterior al ciclismo (p=0,038) y en el ritmo del primer kilómetro (p=0,015). El entrenamiento pliométrico parece ser más eficaz que el entrenamiento habitual para mejorar la fatiga neuromuscular y el ritmo del primer kilómetro

Increasing arterial blood pressure with norepinephrine does not improve microcirculatory blood flow: A prospective study

Introduction: Our goal was to assess the effects of titration of a norepinephrine infusion to increasing levels of mean arterial pressure (MAP) on sublingual microcirculation. Methods: Twenty septic shock patients were prospectively studied in two teaching intensive care units. The patients were mechanically ventilated and required norepinephrine to maintain a mean arterial pressure (MAP) of 65 mmHg. We measured systemic hemodynamics, oxygen transport and consumption (DO2 and VO2), lactate, albumin-corrected anion gap, and gastric intramucosal-arterial PCO2 difference (ΔPCO2). Sublingual microcirculation was evaluated by sidestream darkfield (SDF) imaging. After basal measurements at a MAP of 65 mmHg, norepinephrine was titrated to reach a MAP of 75 mmHg, and then to 85 mmHg. Data were analyzed using repeated measurements ANOVA and Dunnett test. Linear trends between the different variables and increasing levels of MAP were calculated. Results: Increasing doses of norepinephrine reached the target values of MAP. The cardiac index, pulmonary pressures, systemic vascular resistance, and left and right ventricular stroke work indexes increased as norepinephrine infusion was augmented. Heart rate, DO2 and VO2, lactate, albumin-corrected anion gap, and ΔPCO2 remained unchanged. There were no changes in sublingual capillary microvascular flow index (2.1 ± 0.7, 2.2 ± 0.7, 2.0 ± 0.8) and the percent of perfused capillaries (72 ± 26, 71 ± 27, 67 ± 32%) for MAP values of 65, 75, and 85 mmHg, respectively. There was, however, a trend to decreased capillary perfused density (18 ± 10,17 ± 10,14 ± 2 vessels/mm2, respectively, ANOVA P = 0.09, linear trend P = 0.045). In addition, the changes of perfused capillary density at increasing MAP were inversely correlated with the basal perfused capillary density (R2 = 0.95, P < 0.0001). Conclusions: Patients with septic shock showed severe sublingual microcirculatory alterations that failed to improve with the increases in MAP with norepinephrine. Nevertheless, there was a considerable interindividual variation. Our results suggest that the increase in MAP above 65 mmHg is not an adequate approach to improve microcirculatory perfusion and might be harmful in some patients.Facultad de Ciencias Médica

Aerobic Function and Muscle Deoxygenation Dynamics during Ramp Exercise in Children

PURPOSE:To characterise changes in deoxyhemoglobin ([HHb]) response dynamics in boys and girls during ramp incremental exercise to investigate whether the reduced peak oxygen uptake (peakV˙O2) in girls is associated with a poorer matching of muscle O2 delivery to muscle O2 utilisation, as evidenced by a more rapid increase in [HHb].METHODS:52 children (31 boys, 9.9 ± 0.6 years, 1.38 ± 0.07 m, 31.70 ± 5.78 kg) completed ramp incremental exercise on a cycle ergometer during which pulmonary gas exchange and muscle oxygenation parameters were measured.RESULTS:When muscle [HHb] was expressed against absolute work rate and V˙O2, girls had an earlier change in [HHb] as evidenced by the lower c/d parameter (Girls: 54 ± 20 W vs Boys: 67 ± 19 W, P=0.023; Girls: 0.82 ± 0.28 L·min vs. Boys: 0.95 ± 0.19 L·min, P=0.055) and plateau (Girls: 85 ± 12 W vs. Boys: 99 ± 18 W, P=0.031; Girls: 1.02 ± 0.25 L·min vs. Boys: 1.22 ± 0.28 L·min, P=0.014). However, when expressed against relative work-rate or V˙O2, there were no sex differences in [HHb] response dynamics (all P&#62;0.20). Significant correlations were observed between absolute and fat-free mass normalised peak V˙O2 and the HHb c/d and plateau parameters when expressed against absolute work-rate or V˙O2. Furthermore, when entered into a multiple regression model, the [HHb] plateau against absolute V˙O2 contributed 12% of the variance in peak V˙O2 after adjusting for fat-free mass, gas exchange threshold, and body fatness (model R =0.81, P&#60;0.001).CONCLUSION:The sex-difference in peak V˙O2 in 9-10 year old children is, in part, related to sex-specific changes in muscle O2 extraction dynamics during incremental exercise