Leishmanicidal activity of combretastatin analogues and heteroanalogues.

We have investigated the in vitro leishmanicidal activity of representative members from series II-V of combretastatin analogues and heteroanalogues. Most of them exhibited different degrees of activity against various strains of Leishmania spp. The diaryl(heteroaryl)ethane system or the more complex fused heterocyclic stilbenoids, constitute useful skeletal bases to support some kind of antiparasitic activity. Particularly, the incorporation of 2-furyl substituents led to potent antileishmanial compounds, which have been selected for in vivo testing on murine models.     

Role of disturbance in maintaining a savanna-like pattern in Mediterranean Retama sphaerocarpa shrubland

Abstract. Can the interaction of episodic and chronic disturbances explain the maintenance of savanna-like patterns? We explored the morphological and spatial patterns of the leguminous shrub Retama sphaerocarpa in a Mediterranean environment in relation to disturbance. Various morphological variables of R. sphaerocarpa shrubland were found to be determined by a combination of two types of disturbance: (1) mechanical cutting: an episodic, heavy, short-term disturbance of anthropogenic origin for management purposes, and (2) herbivore activity primarily by rabbits: generally a chronic, more lenient, long-term disturbance. The intensities of these two types of disturbance were not correlated. Mechanical cutting effects on R. sphaerocarpa shrubland morphology predominated quantitatively over herbivore effects. Herbivores generally produced open shrubland with fewer, more scattered, thicker branched, larger R. sphaerocarpa shrubs. In contrast, intense sprouting after cutting produced a higher density of smaller R. sphaerocarpa shrubs with denser aerial biomass. However, heavy herbivory in abnormally dry periods produced some effects similar to those of mechanical cutting. The size of R. sphaerocarpa shrubs was positively related to seed production. Thus, the means of propagation depended upon the type of disturbance: episodic disturbances resulted in intense sprouting, whereas chronic herbivore activity resulted in the formation of thick branches that produced a large number of seeds. The combination of these two disturbances determine, in part, space occupancy patterns of dominant woody species in this Mediterranean landscape and similar savanna-type ecosystems. Investigations of environmental constraints on vegetation distribution and abundance should take into account the historical role of herbivores in shaping present systems.     

A minimal continuous model for simulating growth and development of plant root systems

Aims: This paper proposes a general and minimal continuous model of root growth that aggregates architectural and developmental information and that can be used at different spatial scales. Methods: The model is described by advection, diffusion and reaction operators, which are related to growth processes such as primary growth, branching, mortality and root death. Output variable is the number of root tips per unit volume of soil. Operator splitting techniques are used to fit, solve and analyze the model with regards to ontogeny. The modeling approach is illustrated on a 2D case study concerning a part of Eucalyptus root system. Results: Operator splitting is helpful to fit the model. Basic knowledge on root architecture and development allows decreasing the number of unknown parameters and defining ontogenic phases on which specific calibrations must be carried out. Simulation results reproduce quantitatively the dynamic evolution of root density distribution with a good accuracy. Conclusion: The proposed root growth model is based on a continuous formalism that can be easily coupled with other physical models, e.g. nutrient and water transfer. The equations are generic and allow simulating different root architectures and growth strategies. They can be efficiently solved using adapted numerical methods.     

Spatio-temporal expression of MMP-2, MMP-9 and tissue kallikrein in uteroplacental units of the pregnant guinea-pig (Cavia porcellus)

Background  

In humans trophoblast invasion and vascular remodeling are critical to determine the fate of pregnancy. Since guinea-pigs share with women an extensive migration of the trophoblasts through the decidua and uterine arteries, and a haemomonochorial placenta, this species was used to evaluate the spatio-temporal expression of three enzymes that have been associated to trophoblast invasion, MMP-2, MMP-9 and tissue kallikrein (K1).     

Non-Invasive Detection of Early Retinal Neuronal Degeneration by Ultrahigh Resolution Optical Coherence Tomography

Optical coherence tomography (OCT) has revolutionises the diagnosis of retinal disease based on the detection of microscopic rather than subcellular changes in retinal anatomy. However, currently the technique is limited to the detection of microscopic rather than subcellular changes in retinal anatomy. However, coherence based imaging is extremely sensitive to both changes in optical contrast and cellular events at the micrometer scale, and can generate subtle changes in the spectral content of the OCT image. Here we test the hypothesis that OCT image speckle (image texture) contains information regarding otherwise unresolvable features such as organelle changes arising in the early stages of neuronal degeneration. Using ultrahigh resolution (UHR) OCT imaging at 800 nm (spectral width 140 nm) we developed a robust method of OCT image analyses, based on spatial wavelet and texture-based parameterisation of the image speckle pattern. For the first time we show that this approach allows the non-invasive detection and quantification of early apoptotic changes in neurons within 30 min of neuronal trauma sufficient to result in apoptosis. We show a positive correlation between immunofluorescent labelling of mitochondria (a potential source of changes in cellular optical contrast) with changes in the texture of the OCT images of cultured neurons. Moreover, similar changes in optical contrast were also seen in the retinal ganglion cell- inner plexiform layer in retinal explants following optic nerve transection. The optical clarity of the explants was maintained throughout in the absence of histologically detectable change. Our data suggest that UHR OCT can be used for the non-invasive quantitative assessment of neuronal health, with a particular application to the assessment of early retinal disease.     

Tree,sex and size: Ecological determinants of male vs. female fecundity in three Fagus sylvatica stands

Interindividual variation in fecundities has major consequences on population evolutionary potential, through genetic drift and selection. Using two spatially explicit mating models that analyse the genotypes of seeds and seedlings, we investigated the variation of male and female fecundities within and among three European beech (Fagus sylvatica) stands situated along an altitudinal gradient. Female and male individual fecundity distributions were both skewed in this monoecious species, and we found a higher variance in female as compared to male fecundities. Both female and male fecundities increased with tree size and decreased with density and competition in the neighbourhood, the details of these effects suggesting sex‐specific strategies to deal with the impact of limited resource on fecundity. The studied populations were functionally male‐biased. Among‐individual variations in functional gender were not driven by tree size but by density and competition in the neighbourhood. Femaleness decreased under limited resource availability, an expected consequence of the higher cost of female reproduction. Considering the variation of gene flow and genetic drift across elevation, our results suggest that the adaptive potential could be enhanced by low genetic drift at low elevation, and by high pollen‐mediated gene flow at high elevation. Finally, this study predicts a more efficient response to selection for traits related to male vs. female fitness, for a given selection intensity.     

Enhanced Liposomal Vaccine Formulation and Performance: Simple Physicochemical and Immunological Approaches

The Dtxd (Diphtheria toxoid) was the first antigen encapsulated within liposomes, their adjuvant properties were discovered (their capacity to enhance the vaccine immunogenicity). The point here is not to propose a new method to prepare this lipossomal vaccine. The central idea is to give new dresses for old vaccines by using classical and well-established liposome preparation method changing only the encapsulation pH and the immunization protocol.

The most appropriate method of Dtxd encapsulation within liposome was based on lipid film hydration in 100 mM citrate buffer, pH 4.0. This was accompanied by changes on protein hydrophobicity, observed by CD and fluorescence spectroscopies. Whenever the Dtxd exposed its hydrophobic residues at pH 4.0, it interacted better with the lipossomal (observed by electrophoretic mobility) film than when its hydrophobic residues were buried (pH 9.0). The Dtxd partition coefficient in Triton-X114 and the acrylamide fluorescence quenching were also pH dependent. Both were bigger at pH 4.0 than at pH 9.0. The relationship protein structure and lipid interaction was pH dependent and now it can be easily maximized to enhance encapsulation of antigens in vaccine development.

Mice were primed with formulations containing 5 μg of Dtxd within liposomes prepared in pH 4.0 or 7.0 or 9.0. The boosters were done 38 or 138 days after the first immunization. The IgM produced by immediate response of all lipossomal formulations were higher than the control (free protein). The response patterns and the immune maturity were measured by IgG₁ and IgG_2a titrations. The IgG₁ titers produced by both formulations at pH 4.0 and 7.0 were at least 2² higher than those produced by mice injected lipossomal formulation at pH 9.0. When the boosters were done, 138 days after priming the mice produced a IgG_2a titer of 2⁹ and the group that received the booster 30 days after priming produced a titer of 2⁵. The strongest antibody production was the neutralizing antibody (2⁴⁵ higher than the control) produced by those mice injected with lipossomal formulation at pH 4.0 with the booster done 138 days after priming. The simple change on lipossomal pH formulation and timing of the booster enhanced both antibody production and selectivity.     

Extended phylogeny of Aquilegia: the biogeographical and ecological patterns of two simultaneous but contrasting radiations

Studies of the North American columbines (Aquilegia, Ranunculaceae) have supported the view that adaptive radiations in animal-pollinated plants proceed through pollinator specialisation and floral differentiation. However, although the diversity of pollinators and floral morphology is much lower in Europe and Asia than in North America, the number of columbine species is similar in the three continents. This supports the hypothesis that habitat and pollinator specialisation have contributed differently to the radiation of columbines in different continents. To establish the basic background to test this hypothesis, we expanded the molecular phylogeny of the genus to include a representative set of species from each continent. Our results suggest that the diversity of the genus is the result of two independent events of radiation, one involving Asiatic and North American species and the other involving Asiatic and European species. The ancestors of both lineages probably occupied the mountains of south-central Siberia. North American and European columbines are monophyletic within their respective lineages. The genus originated between 6.18 and 6.57 million years (Myr) ago, with the main pulses of diversification starting around 3 Myr ago both in Europe (1.25–3.96 Myr ago) and North America (1.42–5.01 Myr ago). The type of habitat occupied shifted more often in the Euroasiatic lineage, while pollination vectors shifted more often in the Asiatic-North American lineage. Moreover, while allopatric speciation predominated in the European lineage, sympatric speciation acted in the North American one. In conclusion, the radiation of columbines in Europe and North America involved similar rates of diversification and took place simultaneously and independently. However, the ecological drivers of radiation were different: geographic isolation and shifts in habitat use were more important in Europe while reproductive isolation linked to shifts in pollinator specialisation additionally acted in North America.     

Scoring docking models with evolutionary information

We have developed methods for the extraction of evolutionary information from multiple sequence alignments for use in the study of the evolution of protein interaction networks and in the prediction of protein interaction. For Rounds 3, 4, and 5 of the CAPRI experiment, we used scores derived from the analysis of multiple sequence alignments to submit predictions for 7 of the 12 targets. Our docking models were generated with Hex and GRAMM, but all our predictions were selected using methods based on multiple sequence alignments and on the available experimental evidence. With this approach, we were able to predict acceptable level models for 4 of the targets, and for a fifth target, we located the residues involved in the binding surface. Here we detail our successes and highlight several of the limitations and problems that we faced while dealing with particular docking cases.