The art of cobbling a running pump—Will human embryonic stem cells mend broken hearts?

The heart is one of the least regenerative organs in the body, and highly vulnerable to the increasing incidence of cardiovascular diseases in an aging world population. Cell-based approaches aimed at cardiac repair have recently caused great public excitement. But clinical trials of patients’ own skeletal myoblasts or bone marrow cells for transplantation have been disappointing. Human embryonic stem cells (hESCs) form bona fide cardiomyocytes in vitro which are readily generated in mass culture and are being tested in animal models of heart damage. The early results, while encouraging, underscore that much remains to be done. This review focuses on the many challenges that remain before hESCs-mediated repair of the human heart becomes a reality.     

Life history responses of fishes to culture

The protected environment in culture permits fishes to reduce the proportion of energy normally channelled into the costs associated with competition for food, shelter and mates, avoidance of predators and counteracting parasites and diseases. The surplus energy so released is allocated to growth and reproduction, accelerating development through increased growth rate, earlier maturation and increased relative fecundity. Cultivators manipulate the rearing environment to remove seasonal variation in availability of resources, so that the fishes grow and develop through otherwise unproductive seasons. Such environmental manipulations exaggerate the basic accelerative effects. Since maturation deflects energy from growth, farmers also manipulate the fishes nutritionally, physiologically, hormonally and genetically to postpone maturation. As environmental regulators determine sex in many fish species, environmental manipulation in culture may have unintended effects on sex ratios. Mortality in culture should be very low, but survival of fishes released from culture is rarely as high as that of wild conspecifics. Finally, while short life‐cycles and simplified population age‐structures permit high rates of production in farms, they lead to ecological instability when the fishes are cultured for support of wild populations.     

Understanding cell fate acquisition in stem-cell-derived pancreatic islets using single-cell multiome-inferred regulomes

1. Download : Download high-res image (205KB)
2. Download : Download full-size image

     

Quadrat covariance analysis and the scales of interspecific association during primary succession

Abstract. Three term covariance analysis is used to investigate interspecific association at a range of spatial scales, using both density and presence/absence data to evaluate the strength of species interactions. This procedure also investigates the relationship between the spatial patterns of species. These methods are applied to the vegetation on a series of glacial moraines near Mt. Robson, British Columbia, Canada, in order to test whether the plants of different species and their patterns become more independent and more random during succession. Another hypothesis tested is that if a species exerts a positive influence on others by increasing soil nutrients, this effect decreases with surface age. The vegetation analysed supports both these hypotheses to the extent that most species pairs have maximum covariance intensity on medium aged surfaces. The covariance-blocksize graphs derived from density data and from presence/absence data were qualitatively similar in their trends; however, the results are sufficiently different to suggest that the relationships among species can be subtle, affecting density rather than presence. The results also show that the affect of scale on species associations is more complex than simple models predict.     

Mapping of complementation groups within a Rhizobium leguminosarum CFN42 chromosomal region required for lipopolysaccharide synthesis

Summary A major genetic region specifying portions of the carbohydrate structure of Rhizobium leguminosarum CFN42 lipopolysaccharide was analyzed by Tn5 mutagenesis, constructing deletions in cloned DNA, restriction mapping, and complementation analysis. Mutations affecting lipopolysaccharide synthesis were arranged in nine complementation groups spanning 18 kb of DNA. One mutation resulted in O-polysaccharide-containing lipopolysaccharide having a slightly increased mobility in gel electrophoresis. This mutation did not affect the symbiosis with bean plants. The other mutations eliminated the 0-polysaccharide-containing lipopolysaccharide and resulted in strains defective in eliciting bean nodule development.     

Endocrine changes during diapause development in the cabbage army moth Mamestra brassicae

Many insects undergo diapause to survive adverse seasons. Although the mechanism of diapause induction is the subject of extensive study, that of diapause termination remains poorly understood. In the present study, we show the endocrine processes leading to the termination of pupal diapause in Mamestra brassicae. Diapause of this insect is terminated if the pupae are exposed to a low temperature for several weeks. During this period, the prothoracic glands (PGs) of pupae acquire the potential to secrete sufficient ecdysteroids necessary for inducing adult development. The main endocrine changes observed under the low temperature conditions are: (i) the increase in activity of the PGs in two steps; (ii) the increase in responsiveness of the glands to prothoracicotropic hormone (PTTH); and (iii) two‐step increase in PTTH gene expression in the brain. The timing of the first and second increases in PG activity roughly coincides with that of the two steps of increase in PTTH gene expression, and the timing of the increase in the responsiveness of the PGs to PTTH coincides with the second, larger increase in PTTH gene expression. The ablation of the PGs prior to cooling pupae does not affect the increase in PTTH gene expression, whereas brain removal results in a failure to increase PG activity, strongly suggesting that PTTH is the master regulator of diapause development and termination.     

On the morphology of antennular sensory and attachment organs in cypris larvae of the deep‐sea vent/seep barnacles,Ashinkailepas and Neoverruca

Barnacle cypris larvae show high morphological variation in the organs used in search of and attaching to a substratum. This variation may represent adaptation to the habitat of the species. Here, we studied SEM level morphologies of cypris antennular sensory and attachment organs in a deep‐sea vent endemic species (Neoverruca sp.) and a vent/seep inhabiting species (Ashinkailepas seepiophila). We compare them with three species from other environments. The antennular morphologies of Neoverruca sp. and A. seepiophila were similar, which is consistent with recent molecular studies showing a close relationship of the two species. The setation pattern of the antennules was very conservative among species from various environments. In contrast, striking differences were observed in the structure of the attachment organ (the third antennular segment). Neoverruca sp. and A. seepiophila had no velum or a skirt surrounding the attachment disc on the third segment, while other cirripede cyprids almost always have either of these structures. In addition, both cyprids of A. seepiophila and Neoverruca sp. had the attachment disc angled toward the substratum, whereas it faces distally in cyprids from hard bottom inhabiting barnacles. We suggest that both velum/skirt and the angle of the attachment disc play an important role, when the antennules are contacting the substratum during surface exploration. Differences in attachment organ structures may be highly adaptive, enabling cirripede species to enter new habitats during evolution. J. Morphol. 277:594–602, 2016. © 2016 Wiley Periodicals, Inc.     

The contributions of programmed developmental change and phenotypic plasticity to within-individual variation in leaf traits in Dicerandra linearifolia

Variation among modules of a single genet could provide a means of adaptation to environmental heterogeneity. Two mechanisms that can give rise to such variation are programmed developmental change and phenotypic plasticity. I quantified the relative roles of these two mechanisms in causing within-individual variation in six leaf traits of an annual plant. Under controlled temperatures, morphological, anatomical, and physiological traits of leaves produced by the same individual differed as a function of both the node at which they were produced and the temperature they experienced during development. Temperature, node, and interactions between them all contributed significantly to the pattern of within-individual variation in leaf traits, although the relative contributions of programmed developmental change and phenotypic plasticity differed for different traits. I hypothesize that these two mechanisms for generating within-individual variation in module phenotype are favored by different patterns of environmental heterogeneity; when the sequence of environments encountered by modules of a single individual is predictable, programmed developmental change may be favored, and phenotypic plasticity may be favored when the sequence of environments is irregular with respect to individual ontogeny and therefore not predictable.     

Differential lipid reserves influence host-seeking behaviour in the mosquitoes Aedes cantans and Aedes punctor

ipid reserves of bait-caught female Ae.cantans and Ae.punctor mosquitoes (Diptera: Culicidae) were significantly higher than in teneral females. Female Ae.cantans given access to 10% w/v sucrose solution post-emergence showed an ability to synthesize lipid and, after 192 h, they were willing to take a bloodmeal from a human volunteer. At this point, mean lipid reserves were not significantly different from mean lipid reserves of bait-caught females. Prior to 192 h, females would not take a bloodmeal and lipid reserves were significantly lower than in bait-caught females. Female Ae.punctor given access to 10% w/v sucrose solution post-emergence also showed an ability to synthesize lipid. Females of this species were willing to feed from a human host after only 48 h, at which point lipid content was not significantly different from that in bait-caught females. The level of lipid reserves in females coming to bait differs significantly between species: Ae.cantans has lipid reserves approximately double those of Ae.punctor . In addition, Ae.punctor is able to synthesize lipid to a level comparable with that found in bait-caught females after only 24 h, whilst it takes 192 h for Ae.cantans females to synthesize the amount of lipid found in host-seeking females, when allowed free access to sugar. Physiological differences in lipid synthesis and the level of lipid reserves required may therefore explain the differences observed between the species in the time taken to initiate host seeking.