Dancing between the devil and deep blue sea: the stabilizing effect of enemy-free and victimless sinks

Theoretical and empirical studies have shown that enemy–victim interactions in spatially homogenous environments can exhibit diverging oscillations which result in the extinction of one or both species. For enemy–victim models with overlapping generations, we investigate the dynamical implications of spatial heterogeneity created by enemy-free sinks or victimless sinks. An enemy-free sink is a behavioral, physiological or ecological state that reduces or eliminates the victim's vulnerability to the enemy but cannot sustain the victim population. For victims that move in an ideal-free manner, we prove that the inclusion of an enemy-free sink shifts the population dynamics from diverging oscillations to stable oscillations. During these stable oscillations, the victim disperses in an oscillatory manner between the enemy-free sink and the enemy-occupied patch. Enemy-free sinks with lower mortality rates exhibit oscillations with smaller amplitudes and longer periods. A victimless sink, on the other hand, is a behavioral, physiological or ecological state in which the enemy has limited (or no) access to its victims. For enemies that move in an ideal-free manner, we prove that victimless sinks also stabilize diverging oscillations. Simulations suggest that suboptimal behavior due to information gathering or learning limitations amplify oscillations for systems with enemy-free sinks and dampen oscillations for systems with victimless sinks. These results illustrate that the coupling of a sink created by unstable enemy–victim interactions and a sink created by unsuitable environmental conditions can result in population persistence at the landscape level.     

"Personal best times in an olympic distance triathlon and a marathon predict an ironman race time for recreational female triathletes"

"The aim of this study was to investigate whether the characteristics of anthropometry, training or previous performance were related to an Ironman race time in recreational female Ironman triathletes. These characteristics were correlated to an Ironman race time for 53 recreational female triathletes in order to determine the predictor variables, and so be able to predict an Ironman race time for future novice triathletes. In the bi-variate analysis, no anthropometric characteristic was related to race time. The weekly cycling kilometers (r = -0.35) and hours (r = -0.32), as well as the personal best time in an Olympic distance triathlon (r = 0.49) and in a marathon (r = 0.74) were related to an Ironman race time (< 0.05). Stepwise multiple regressions showed that both the personal best time in an Olympic distance triathlon ( P = 0.0453) and in a marathon (P = 0.0030) were the best predictors for the Ironman race time (n = 28, r2 = 0.53). The race time in an Ironman triathlon might be partially predicted by the following equation (r2 = 0.53, n = 28): Race time (min) = 186.3 + 1.595 × (personal best time in an Olympic distance triathlon, min) + 1.318 × (personal best time in a marathon, min) for recreational female Ironman triathletes."     

Incrimination of Anopheles (Anopheles) intermedius Peryassú, An. (Nyssorhynchus) nuneztovari Gabaldón, An. (Nys.) oswaldoi Peryassú as natural vectors of Plasmodium falciparum in French Guiana

Anopheles darlingi Root is the major vector of human malaria in the Neotropics and has been considered to be the sole malaria vector in French Guiana. The presence of other potential vectors suggests that malaria may be transmitted by other species under certain conditions. From 2006-2011, all anopheline specimens collected from 11 localities were assayed to determine if the Plasmodium circumsporozoite protein was present. In addition to An. darlingi, we found Anopheles oswaldoi, Anopheles intermedius and Anopheles nuneztovari specimens that were infected with Plasmodium sp. Further investigations on the behaviour and ecology of An. oswaldoi, An. intermedius and An. nuneztovari are necessary to determine their role in malaria transmission in French Guiana.     

Linkage disequilibrium between GABRB3 gene and nonsyndromic familial cleft lip with or without cleft palate

The malformation of nonsyndromic cleft lip with or without cleft palate (CL/P) is a common congenital disease that affects approximately 1/1000 newborns in Caucasian populations. Genetic studies indicate that CL/P has the characteristics of a complex genetic trait. Linkage analysis and mouse-model knockout studies have suggested several candidate genes mapping in different chromosome regions for CL/P malformation. On these grounds, we have investigated, by linkage disequilibrium (LD) and parametric and nonparametric linkage analyses, five different candidate genes, including those for the beta3 subunit of the gamma-aminobutyric acid receptor (GABRB3), glutamic acid decarboxylase 1 (GAD1), retinoic acid receptor alpha (RARA), transforming growth factor beta3 (TGFB3), and msh ( Drosophila) homeobox homolog 1 (MSX1). Interestingly, a significant LD between GABRB3 and CL/P was obtained ( P-value=0.008 in the allele-wise analysis for multiallelic markers), suggesting that the GABRB3 gene is involved in this congenital disease. This new finding in humans is in agreement with previously reported data obtained with the murine model. Indeed, mouse studies indicate a role for gamma-aminobutyric acid (GABA) and its receptor in normal palate development. Exclusion of the GAD1 gene, which encodes the GABA-producing enzyme, in CL/P pathogenesis was obtained in our study. Moreover, we were unable to confirm the involvement of the MSX1 gene in nonsyndromic CL/P. Modest evidence of LD between marker alleles and CL/P was found at the RARA and TGFB3 loci suggesting a minor role for these genes in our family set of nonsyndromic CL/P.     

Regulation of protein synthesis by estradiol-17beta in cultured hepatocytes

Estradiol-17beta added to cultured chick embryo hepatocytes induced the appearance in the medium of a phosphoprotein, identified as phosvitin on the basis of: (i) its behaviour on ionic exchange columns; (ii) its SDS-acrylamide gel electrophoretic mobility; (iii) its amino acid composition. The hormone treatment was also followed by a decreased synthesis of other proteins secreted by the hepatocytes.     

Relation between hyaluronan and sulphated glycosaminoglycan synthesis and degradation in cultured embryonic fibroblasts. Effect of concanavalin A and ammonium chloride administration.

In order to evaluate the relationship between glycosaminoglycan (GAG) synthesis and degradation, the effect of NH4Cl, which inhibits lysosomal degradation, on GAG production was analysed in vitro in concanavalin A (Con A) stimulated fibroblasts from 7 and 14-day-old chick embryos. 35SO4 incorporation into total proteoglycan (PG), 3H incorporation into individual GAG classes, beta-N-acetyl-D-glucosaminidase and beta-D-glucuronidase activity were determined. The results indicate a correlation between Con A and NH4Cl effects: NH4Cl induced a reduction principally in the GAG classes most stimulated by Con A. Thus HA and DS are much more stimulated by Con A and inhibited by NH4Cl than are CS and HS.     

Axially chiral Ni(II) complexes of α‐amino acids: Separation of enantiomers and kinetics of racemization

Herein we present design, synthesis, chiral HPLC resolution, and kinetics of racemization of axially chiral Ni(II) complexes of glycine and di‐(benzyl)glycine Schiff bases. We found that while the ortho‐fluoro derivatives are configurationally unstable, the pure enantiomers of corresponding axially chiral ortho‐chloro‐containing complexes can be isolated by preparative HPLC and show exceptional configurational stability (t_1/2 from 4 to 216 centuries) at ambient conditions. Synthetic implications of this discovery for the development of new generation of axially chiral auxiliaries, useful for general asymmetric synthesis of α‐amino acids, are discussed.     

Aedes aegypti survival and dengue transmission patterns in French Guiana.

Field survival of Aedes aegypti females is a key parameter for estimating the dengue transmission potential of a mosquito population. The objectives of this study were to explore the dynamics of these survival rates at different times of the year in French Guiana and to analyze the results from the perspective of dengue patterns. The mosquitoes were captured, marked, released, and recaptured during four consecutive days in six houses every month, for three to 24 months, from January 1997 to December 1998. Laboratory experiments showed no effects on female survival but some effect on the survival of males. Females' daily survival in the field varied from 0.525 to 1 but was mostly between 0.8 and 0.95 during the entire year, with a mean value of 0.913. The field survival of Ae. aegypti females in French Guiana was thus in agreement with the likely transmission of dengue and the dengue endemic patterns throughout the year. On the other hand, heavy rainfalls during this time were less favorable to Ae. aegypti survival, which may explain part of the El Ni?o effect on dengue epidemics in French Guiana. The methods and results on Ae. aegypti survival will be implemented in a global dengue surveillance network in French Guiana.     

Neuromuscular fatigue differs with biofeedback type when performing a submaximal contraction.

The aim of the study was to examine alterations in contractile and neural processes in response to an isometric fatiguing contraction performed with EMG feedback (constant-EMG task) when exerting 40% of maximal voluntary contraction (MVC) torque with the knee extensor muscles. A task with a torque feedback (constant-torque task) set at a similar intensity served as a reference task. Thirteen men (26+/-5 yr) attended two experimental sessions that were randomized across days. Endurance time was greater for the constant-EMG task compared with the constant-torque task (230+/-156 s vs. 101+/-32s, P<0.01). Average EMG activity for the knee extensor muscles increased from 33.5+/-4.5% to 54.7+/-21.7% MVC EMG during the constant-torque task (P<0.001), whereas the torque exerted during the constant-EMG task decreased from 42.8+/-3.0% to 17.9+/-5.6% MVC torque (P<0.001). Comparable reductions in knee extensors MVC (-15.7+/-8.7% for the constant-torque task vs. -17.5+/-9.8% for the constant-EMG task, P>0.05) and voluntary activation level were observed at exhaustion. In contrast, excitation-contraction coupling process, assessed with an electrically evoked twitch and doublet, was altered significantly more at the end of the constant-EMG task despite the absence of M-wave changes for both tasks. Present results suggest that prolonged contractions using EMG biofeedback should be used cautiously in rehabilitation programs.