Ecological correlates and evolutionary divergence in the skull of turtles: a geometric morphometric assessment

Resource use and phylogeny are often correlated with morphological variation. Moreover, because biological shapes are often complex and evolve depending on several internal constraints, they must be assessed using integrative methods. We analyzed the morphological variation of the turtle skull in the context of an adaptive radiation. Our focus are turtles of the superfamily Testudinoidea, which are remarkably diverse, both in number of species and in ecology. In this study, we depict morphological variation in the turtle skull in three dimensions with respect to diet, phylogeny, and habitat using modern geometric morphometrics. Our study revealed that morphological specialization was related to both diet and habitat. Morphological variation is decomposed in regard of both resource use (habitat and diet) and phylogeny. Feeding mode depending on environment was suggested as a key factor determining morphological evolution and diversification of turtle skulls. Diet (especially durophagy) leads to parallel morphologies in different clades. Phylogeny seemed to constrain only localized features of the skull and remained of minor influence, because overall morphotypes, closely correlated with ecological factors, occurred in both clades. In conclusion, the adaptive radiation of the Testudinoidea is revealed to demonstrate a clear relationship between the skull shape and life style.     

Preparation and in vivo evaluation of PEGylated spherulite formulations

Spherulites are multilamellar vesicles obtained by shearing a lamellar phase of lipids and surfactants. They consist of concentric bilayers of amphiphiles alternating with layers of aqueous medium in which hydrophilic drugs can be sequestered with high yield. To be useful for drug targeting applications, spherulites should be small and long circulating. The objectives of this work were threefold. First, the spherulite size was optimized to obtain a mean diameter of less than 300 nm. Second, the vesicle composition was adjusted to minimize in vitro leakage of internal content. Third, the spherulites were coated with 1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine-N-[methoxy poly(ethylene glycol)] (DSPE-PEG) to impart them with a long half-life. Then, the PEGylated spherulites (Phospholipon 90G/Solutol HS15/cholesterol/DSPE-PEG 2000 or 5000) were loaded with 1-beta-d-arabinofuranosylcytosine (ara-C) and injected intravenously to rats. They were compared to uncoated spherulites and to an ara-C solution. The surface-modified vesicles exhibited long circulation times with areas under the blood concentration vs. time curve exceeding by 3.1- to 6.9-fold that of uncoated spherulites. Similarly, blood levels of ara-C encapsulated in PEGylated vesicles were higher than those of the controls, but they did not parallel the carrier pharmacokinetics. Two hours post-injection, most of the drug was cleared from the systemic circulation, reflecting rapid leakage of ara-C from the vesicles.     

Phosphorylation at tyrosine-524 influences nuclear accumulation of HSP72 with heat stress

Nuclear accumulation of heat shock protein (HSP) 72 occurs after cardiac ischemia. This nuclear accumulation of HSP72 with stress occurs in other tissues and species. We postulated that nuclear accumulation of HSP72 was important for the protective effect of HSP72 and that phosphorylation of a single tyrosine (Y(524)) regulated nuclear accumulation of HSP72. Western blots of immunoprecipitated HSP72 from Cos-1 cells demonstrated that tyrosine becomes phosphorylated after heat shock. Treatment with the tyrosine kinase inhibitor geldanamycin blocked nuclear accumulation of HSP72 with heat shock. Two epitope-tagged constructs were made: M17 converting Y(524) to aspartic acid (pseudophosphorylation) and M18 converting Y(524) to phenylalanine. When transfected into Cos-1 cells, M17 accumulates more rapidly and M18 less rapidly than wild-type (WT) HSP72 in the nucleus following heat shock. Cells expressing M18 had less viability after heat shock at 43.5 degrees C than other constructs. After heat shock at 45 degrees C, cells expressing M17 had superior survival compared with WT and M18. These data suggest that phosphorylation at Y(524) facilitates nuclear accumulation of HSP72 following heat stress, and substitution of aspartic acid at Y(524) enhances resistance to heat-shock injury.     

Localization of heat shock proteins in clinical Actinobacillus actinomycetemcomitans strains and their effects on epithelial cell proliferation

Actinobacillus actinomycetemcomitans is an important pathogen in periodontitis. In the present study we localized the GroEL- and DnaK-like heat shock proteins (Hsp) in subcellular fractions of 12 A. actinomycetemcomitans strains of various clinical origin and compared their effects on periodontal epithelial cell proliferation and viability. In all strains, GroEL-like protein was found in the membrane, cytoplasm, and periplasm, whereas DnaK-like protein was present in the cytoplasm and periplasm. No correlation was observed between the Hsp expression and the serotype or origin of A. actinomycetemcomitans strains. The bacterial membrane fractions that expressed the GroEL-like protein moderately or strongly induced epithelial cell proliferation more strongly than strains that expressed the protein weakly. The results suggest that GroEL-like Hsp may play a role in the virulence of A. actinomycetemcomitans by increasing epithelial proliferation.     

Tackling the population genetics of clonal and partially clonal organisms

Many clonal organisms experience occasional events of sexual recombination, with profound consequences for their population dynamics and evolutionary trajectories. With the recent development of polymorphic genetic markers and new statistical methods, we now have an unprecedented ability to detect recombination in organisms that are thought to reproduce strictly, or essentially asexually. However, it is not always obvious which methodology to apply. Consequently, biologists might decide how to analyse their data without clear guidelines. Here, we discuss the available methods, focusing on those best suited when working with limited genetic information, such as a few genetic markers or DNA sequences. We conclude by commenting on the prospects offered by some recent conceptual advances and the access to high throughput technologies in an increasing number of model organisms.     

Interleukin-9 stimulates the production of interleukin-5 in CD4+ T cells

We recently showed that interleukin-9 (IL-9), a Th2 cytokine, promotes IL-5-mediated rejection of allografts in mice. This observation led us to investigate the functional link between IL-9 and IL-5 production during alloreactive T cell responses in vitro and in vivo. Firstly, we found that IL-9 was produced by alloreactive Th2 cells, and IL-9 mRNA was detected in skin allograft during Th2-type rejection. We then established that IL-5 production was impaired in alloreactive Th2 cells isolated from IL-9-deficient mice and that optimal IL-5 production after allogeneic stimulation requires a functional IL-9 receptor (IL-9R) on the responding cells. Finally, the production of IL-5 by anti-CD3-stimulated CD4+ T cells was abolished by neutralization of IL-9. Despite the fact that IL-9 promotes IL-5 production by alloreactive T cells, IL-9-deficient recipients of skin allografts still developed eosinophilic graft infiltrates and neither IL-9 nor IL-9R deficiency modified Th2-type allograft rejection.