Reproductive Flexibility: Genetic Variation, Genetic Costs and Long-Term Evolution in a Collembola

In a variable yet predictable world, organisms may use environmental cues to make adaptive adjustments to their phenotype. Such phenotypic flexibility is expected commonly to evolve in life history traits, which are closely tied to Darwinian fitness. Yet adaptive life history flexibility remains poorly documented. Here we introduce the collembolan Folsomia candida, a soil-dweller, parthenogenetic (all-female) microarthropod, as a model organism to study the phenotypic expression, genetic variation, fitness consequences and long-term evolution of life history flexibility. We demonstrate that collembola have a remarkable adaptive ability for adjusting their reproductive phenotype: when transferred from harsh to good conditions (in terms of food ration and crowding), a mother can fine-tune the number and the size of her eggs from one clutch to the next. The comparative analysis of eleven clonal populations of worldwide origins reveals (i) genetic variation in mean egg size under both good and bad conditions; (ii) no genetic variation in egg size flexibility, consistent with convergent evolution to a common physiological limit; (iii) genetic variation of both mean reproductive investment and reproductive investment flexibility, associated with a reversal of the genetic correlation between egg size and clutch size between environmental conditions ; (iv) a negative genetic correlation between reproductive investment flexibility and adult lifespan. Phylogenetic reconstruction shows that two life history strategies, called HIFLEX and LOFLEX, evolved early in evolutionary history. HIFLEX includes six of our 11 clones, and is characterized by large mean egg size and reproductive investment, high reproductive investment flexibility, and low adult survival. LOFLEX (the other five clones) has small mean egg size and low reproductive investment, low reproductive investment flexibility, and high adult survival. The divergence of HIFLEX and LOFLEX could represent different adaptations to environments differing in mean quality and variability, or indicate that a genetic polymorphism of reproductive investment reaction norms has evolved under a physiological tradeoff between reproductive investment flexibility and adult lifespan.     

Initiation and duration of breastfeeding in obstetrical hospitals of Aix-Chambery (France)]

Our objectives were to estimate duration of breastfeeding and to identify factors associated with initiation and weaning. METHODS: A prospective study was carried out among 353 mothers delivering in three obstetric hospitals at Aix-Chambery (Savoie, France). Breastfeeding was considered as survival data with censored observations. Univariate and multivariate analyses were performed. RESULTS: Breastfeeding was initiated by 70.8% (66.1-75.5) (exclusive breastfeeding = 39.9% and complementary breastfeeding = 30.9%). Respectively, 58.1% (52.9-63.3) and 12.2% (8.3-16.1) were continuing some breastfeeding at one and six months. The median duration of breastfeeding was 13 weeks (11.6-14.4). Shorter duration was associated with contact beyond one hour from birth (adjusted Hazard Ratio [aHR] = 1.25 [1.03-1.52] and with contact beyond eight hours aHR = 1.78 [1.66-1.92]), pacifier use (aHR = 1.72 [1.19-2.47]), breastfeeding at fixed hours (aHR = 1.78 [1.29-2.45]), and decision to breastfeed during pregnancy or the postpartum period (aHR = 1.70 [1.45-2.00]). CONCLUSION: Breastfeeding initiation and duration were higher in maternity hospitals of Chambéry than estimations measured in the 1998 French perinatal survey and in other ad hoc surveys. Identified factors should be used in order to plan future programs designed to increase duration of breastfeeding.     

Contrôle de l’équilibre et port unilatéral d’une orthèse rigide de cheville. Partie I : effets sur des sujets sains évalués debout en unipédie

In order to assess the effects induced by wearing a rigid ankle orthosis, 14 healthy adults, without traumatic previous injuries at this level, were tested in a one-legged postural task. The subjects stood upright on a force platform and were required to remain still, eyes open. Ten trials lasting 32 s were recorded in a random order in two conditions: with a rigid orthosis model worn at the ankle level of the supporting leg (Thuasne, Ligastrap Immo^®) and with an elastic stocking. Balance strategies have been quantified by studying the centre of pressure (CP) trajectories, that is, the successive positions of the resultant reaction forces, and processed through a frequency analysis. The results indicate that slight decreases occur for the CP displacements intervening along the medio-lateral axis whereas statistically significant trends were found for those intervening along the anteroposterior one. This finding a priori suggests that wearing a rigid orthosis affects one-legged standing in healthy individuals but mainly along an axis not usually weakened by sprained ankles.     

Acute and chronic pain in hemophilia

The present study compared acute vs. chronic pain in hemophiliac subjects who suffer both types of pain. Characteristics of the acute pain produced by a hemorrhage into a joint and the chronic arthritic pain that results from repeated bleeding episodes were assessed with the McGill Pain Questionnaire and a visual analogue pain intensity scale. The results showed a high degree of similarity in the sensory, affective and evaluative properties of the two types of pain. The main difference between the acute and chronic pains was one of overall intensity, with the acute pain generally being described as more intense. A comparison of the arthritic pain in hemophilia with the pain of other arthritic disorders revealed no major differences. Sources of inter-individual variability were also explored and the results showed that the pain scores in hemophiliac subjects were largely unrelated to demographic and pain history variables. However, significant differences were observed in the way French- and English-speaking subjects described and rated their pain. Irrespective of the origin of their pain, French-speaking subjects characteristically rated their pain as more intense and more affectively laden than the English group. These results demonstrate that ethnocultural factors associated with language affiliation may contribute to inter-individual variation in pain perception.     

Transferrin microheterogeneity in rats treated chronically with ethanol

The microheterogeneity of rat serum transferrin was analyzed by isoelectric focusing and immunofixation from Wistar rats chronically treated with ethanol either by inhalation (4 weeks) or by a liquid diet (6 weeks) and from pair-fed controls. In spite of the length of ethanol exposure, a daily ethanol intake of 13-18 g/kg b.wt. and BAC levels of 1.0-4.1 g/l, no transferrin abnormality similar to that found in human alcoholics was observed. It is apparent that these two common animal models for chronic high ethanol consumption are not suitable for experimental studies of ethanol-associated effects on transferrin.