Mating timing,dispersal and local adaptation in patchy environments

Dispersal is a life‐history trait that can evolve under various known selective pressures as identified by a multitude of theoretical and empirical studies. Yet only few of them are considering the succession of mating and dispersal. The sequence of these events influences gene flow and consequently affects the dynamics and evolution of populations. We use individual‐based simulations to investigate the evolution of the timing of dispersal and mating, i.e. mating before or after dispersal. We assume a discrete insect metapopulation in a heterogeneous environment, where populations may adapt to local conditions and only females are allowed to disperse. We run the model assuming different levels of species habitat tolerance, carrying capacity, and temporal environmental variability. Our results show that in species with narrow habitat tolerance, low to moderate dispersal evolves in combination with mating after dispersal (post‐dispersal mating). With such a strategy dispersing females benefit from mating with a resident male, as their offspring will be better adapted to the local habitat conditions. On the contrary, in species with wide habitat tolerance higher dispersal rates in combination with pre‐dispersal mating evolves. In this case individuals are adapted to the ‘average’ habitat where pre‐dispersal mating conveys the benefit of carrying relatives’ genes into a new population. With high dispersal rates and large population size, local adaptation and kin structure both vanish and the temporal sequence of dispersal and mating may become a (nearly) neutral trait.     

Cardiac tissue engineering using perfusion bioreactor systems

This protocol describes tissue engineering of synchronously contractile cardiac constructs by culturing cardiac cell populations on porous scaffolds (in some cases with an array of channels) and bioreactors with perfusion of culture medium (in some cases supplemented with an oxygen carrier). The overall approach is 'biomimetic' in nature as it tends to provide in vivo-like oxygen supply to cultured cells and thereby overcome inherent limitations of diffusional transport in conventional culture systems. In order to mimic the capillary network, cells are cultured on channeled elastomer scaffolds that are perfused with culture medium that can contain oxygen carriers. The overall protocol takes 2-4 weeks, including assembly of the perfusion systems, preparation of scaffolds, cell seeding and cultivation, and on-line and end-point assessment methods. This model is well suited for a wide range of cardiac tissue engineering applications, including the use of human stem cells, and high-fidelity models for biological research.     

Swimming performance and energetics as a function of temperature in killifish Fundulus heteroclitus

Populations of the common killifish Fundulus heteroclitus are found along a latitudinal temperature gradient in habitats with high thermal variability. The objectives of this study were to assess the effects of temperature and population of origin on killifish swimming performance (assessed as critical swimming speed, U(crit)). Acclimated fish from northern and southern killifish populations demonstrated a wide zone (from 7 degrees to 33 degrees C) over which U(crit) showed little change with temperature, with performance declining significantly only at lower temperatures. Although we observed significant differences in swimming performance between a northern and a southern population of killifish in one experiment, with northern fish having an approximately 1.5-fold-greater U(crit) than southern fish across all acclimation temperatures, we were unable to replicate this finding in other populations or collection years, and performance was consistently high across all populations and at both low (7 degrees C) and high (23 degrees C) acclimation temperatures. The poor swimming performance of southern killifish from a single collection year was correlated with low muscle [glycogen] rather than with other indicators of fuel stores or body condition. Killifish acclimated to 18 degrees C and acutely challenged at temperatures of 5 degrees , 18 degrees , 25 degrees , or 34 degrees C showed modest thermal sensitivity of U(crit) between 18 degrees and 34 degrees C, with performance declining substantially at 5 degrees C. Thus, much of the zone of relative thermal insensitivity of swimming performance is intrinsic in this species rather than acquired as a result of acclimation. These data suggest that killifish are broadly tolerant of changing temperatures, whether acute or chronic, and demonstrate little evidence of local adaptation in endurance swimming performance in populations from different thermal habitats.     

Telomerase in T lymphocytes: use it and lose it?

The enzyme telomerase counteracts telomere loss in proliferating cells and extends their capacity for replication. The importance of telomerase is highlighted by the award of the 2006 Albert Lasker Prize for Basic Medical Research for its discovery. Malignant cells subvert telomerase induction to their advantage, and up-regulation of this enzyme confers these populations with unlimited proliferative potential with obvious detrimental consequences. However this enzyme is also essential for the lifelong maintenance of normal cell populations that have a high rate of turnover. Thymic involution in early adulthood dictates that memory T cell populations have to be maintained by continuous proliferation. This highlights the inherent paradox that telomerase down-regulation in T cells may protect against malignancy yet also lead to replicative exhaustion of repeatedly activated memory T cells. In this article, we review the data on telomerase regulation in T lymphocytes and the implications this has for the maintenance of T cell memory.     

Anthropogenic pressure explains variations in the biodiversity of pond communities along environmental gradients: a case study in south-eastern Serbia

Hydrobiologia - Identifying the evolutionary and developmental bases of adaptive phenotypes is of central interest in evolutionary biology. Cichlid fishes have been a useful research model due to...     

Effects of different dietary regimes alone or in combination with standardized Aronia melanocarpa extract supplementation on lipid and fatty acids profiles in rats

This study investigated different dietary strategies, high-fat (HFd), or standard diet (Sd) alone or in combination with standardized Aronia melanocarpa extract (SAE), as a polyphenol-rich diet, and their effects on lipids and fatty acids (FA) in rats with metabolic syndrome (MetS). Wistar albino rats were randomly divided into two groups: healthy and rats with MetS, and then depending on dietary patterns on six groups: healthy rats fed with Sd, healthy rats fed with Sd and SAE, rats with MetS fed with HFd, rats with MetS fed with HFd and SAE, rats with MetS fed with Sd, and rats with MetS fed with Sd and SAE. 4 weeks later, after an overnight fast (12–14 h), blood for determination of total cholesterol (TC), triglycerides (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), index of lipid peroxidation (measured as TBARS), and FA was collected. Increased FA and lipid concentration found in MetS rats were reduced when changing dietary habits from HFd to Sd with or without SAE consumption. Consumption of SAE slightly affects the FA profiles, mostly palmitoleic acid in healthy rats and PUFA in MetS?+?HFd rats. Nevertheless, in a high-fat diet, SAE supplementation significantly decreases n-6/n-3 ratio, thereby decreasing systemic inflammation. Further researches are warranted to confirm these effects in humans.