Environmental DNA reveals a mismatch between diversity facets of Amazonian fishes in response to contrasting geographical,environmental and anthropogenic effects

Freshwater ecosystems are among the most endangered ecosystem in the world. Understanding how human activities affect these ecosystems requires disentangling and quantifying the contribution of the factors driving community assembly. While it has been largely studied in temperate freshwaters, tropical ecosystems remain challenging to study due to the high species richness and the lack of knowledge on species distribution. Here, the use of eDNA-based fish inventories combined to a community-level modelling approach allowed depicting of assembly rules and quantifying the relative contribution of geographic, environmental and anthropic factors to fish assembly. We then used the model predictions to map spatial biodiversity and assess the representativity of sites surveyed in French Guiana within the EU Water Framework Directive (WFD) and highlighted areas that should host unique freshwater fish assemblages. We demonstrated a mismatch between the taxonomic and functional diversity. Taxonomic assemblages between but also within basins were mainly the results of dispersal limitation resulting from basin isolation and natural river barriers. Contrastingly, functional assemblages were ruled by environmental and anthropic factors. The regional mapping of fish diversity indicated that the sites surveyed within the EU WFD had a better representativity of the regional functional diversity than taxonomic diversity. Importantly, we also showed that the assemblages expected to be the most altered by anthropic factors were the most poorly represented in terms of functional diversity in the surveyed sites. The predictions of unique functional and taxonomic assemblages could, therefore, guide the establishment of new survey sites to increase fish diversity representativity and improve this monitoring program.     

A rapid assay for chloroplast-encoded triazine resistance in higher plants

We have designed a simple and rapid assay for chloroplast-based triazine resistance in higher plants using PCR amplification of thepsbA gene coupled toMaeI digestion of the amplified product to distinguish triazine resistant from sensitive biotypes. Our assay is universal and avoids the need of lengthy procedures of previously published assays, which either required spraying of seedlings in a controlled environment, quantification of chlorophyll fluorescence of leaf discs after incubation in triazine solution, DNA sequencing of thepsbA gene, or Southern-blot analysis. Our diagnostic system is qualitative, reliable, fast and simple. More than 100 seedlings taken directly from the field can be analyzed in one day. This system has a direct application towards a more rational use of herbicides in production fields. It also represents a valuable tool to monitor spreading of resistant biotypes through time and space and can serve as a model system applicable to other gene monitoring needs.     

Casearia Essential Oil: An Updated Review on the Chemistry and Pharmacological Activities

Casearia species are found in the America, Africa, Asia, and Australia and present pharmacological activities, besides their traditional uses. Here, we reviewed the chemical composition, content, pharmacological activities, and toxicity of the essential oils (EOs) from Casearia species. The EO physical parameters and leaf botanical characteristics were also described. The bioactivities of the EOs from the leaves and their components include cytotoxicity, anti-inflammatory, antiulcer, antimicrobial, antidiabetic, antioxidant, antifungal, and antiviral activities. The main components associated with these activities are the α-zingiberene, (E)-caryophyllene, germacrene D, bicyclogermacrene, spathulenol, α-humulene, β-acoradiene, and δ-cadinene. Data on the toxicity of these EOs are scarce in the literature. Casearia sylvestris Sw. is the most studied species, presenting more significant pharmacological potential. The chemical variability of EOs components was also investigated for this species. Caseria EOs have relevant pharmacological potential and must be further investigated and exploited.     

Possible interference of fertilization in the natural recovery of a declining sugar maple stand in southern Quebec

A five year study was conducted in a 100–120 year old even-aged sugar maple stand in southern Quebec (46°07N 73° 56W; 305 m altitude) to explore the effect of different fertilization formulations aimed at 1) correcting the most common nutrient deficiencies observed in declining maple stands (K and Mg), 2) decreasing soil acidity, and 3) simulating enrichment with atmospheric N. Seven fertilizer mixtures were applied in the spring of 1987: 400 kg ha^-1 of K₂SO₄, CaCO₃, CaMg(CO₃)₂, (NH₄)₂SO₄, complete fertilizer (Maplegro) and 800 kg ha^-1 of an equal mixture of K₂SO₄+CaCO₃ or K₂SO₄+CaMg(CO₃)₂. The site was divided into twenty-four 25×25 m plots and treatments including control were replicated three times. Leaves and soils (organic and mineral) were sampled in 1987, 1988 and 1991. Trees were cored at 1.2 m to measure their response in diameter growth. The application of K₂SO₄+CaMg(CO₃)₂ was the only treatment that significantly increased (+13%) the average growth rate over the five year period after fertilization. The application of (NH₄)₂SO₄, Maplegro, CaMg(CO₃)₂ and K₂SO₄ reduced growth relative to the control for the five year period by 29, 24, 20 and 12 %, respectively. Positive and negative effects on growth can be explained mainly in terms of changes in leaf K. Both the application of Maplegro and (NH₄)₂SO₄ increased soil P availability. Overall, the rate of growth showed a cubic pattern of change over the 5 year period with peaks in 1988 and 1991. Trees in control plots went from a limiting foliar status of Ca and Mg, and surplus N in 1987 to a surplus of Ca and Mg, and lower N concentration in 1991. Our results suggest that nutrient deficiencies observed at our site were associated with a disturbance of the biogeochemical cycle of nutrients rather than soil nutrient depletion.Abbreviations BS base saturation - CEC cation exchange capacity - DRIS diagnosis and recommendation integrated system     

Spatio-temporal distribution of the microphytobenthic biomass in intertidal flats of Tagus Estuary (Portugal)

A study on spatio-temporal distribution of microphytobhethos in intertidal zones of Tagus Estuary was carried out from 1990 to 1992. Near Lisbon, Portugal, Tagus Estuary is a shallow mesotidal estuary, covering an area of 320 km². The intertidal area ranges from 20 to 40% off the total area and it is constituted mainly by mudflats. Intertidal flats are richly populated by microalgae, diatoms being the most important and ubiquitos group.Spatial variation of microphytobethos was studied in spring 1990, 21 different sites were sampled. Microphytobenthos biomass was evaluated as chlorophyll a content of the surface centimeter, ranging from 10 to 240 mg m^–2. A Principal Component Analysis showed that 62% of the total variability found in intertidal flats of Tagus estuary could be attributed to two major factors: sediment type and tidal height. A hierarchical grouping defined 3 major groups of similar stations, each one representing a different strata of the ecosystem.One station from each group was chosen for the study of the temporal variation. A sampling, rogram took place from April 1991 to April 1992, with fortnightly sampling, the Chl a ranged from 20–300 mg m^–2. No clear seasonal variation was found, and our results indicated that tidal height of sampledsite played an essential role in temporal biomass evolution, thus upper littoral sites were influenced by climatic parameters, whereas in lower sites action of tides mainly controlled microphytic biomass.

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Résumé Une étude sur l'hétérogénéité spatio-temporelle du microphytobenthos dans les sédiments intertidaux de l'Estuaire du Tage a été accompli de 1990 á 1992.L'Estuaire du Tage, prés de Lisbonne (Portugal) est un estuaire peu profond, mesotidal, avec une aire total de 320 km². L'aire intertidale est comprise entre 20 et 40% du total, et constituéé surtout par des vasiéres. Ces slikkes sont peuplées par une communauté assez riche de microalgues, ou les diatomées sont les plus abundantes.La variation spatialle du microphytobenthos était évalué au Printemps 1990, ou 21 différentes stations étaient échantillonnées. La biomasse était évalué par la concentration enchlorophylle a du premier centimétre de sédiment, qui a varié de 10 á 240 mg Chl a m^–2. Une Analyse en Composants Principales a montré que 62% de la variabilité de la biomasse était lié á deux facteurs: le sédiment et l'hauteur vis-á-vis la marée. Une classification hiérarchique des stations par similitude a établi 3 groupes principaux, représantantles différents strates de écecosytéme.Une station de chaque groupement a été choisie pour l'étude de la variation temporelle, qui s'est deroulé d'avril 1991 á avril 1992, avec des prélévements deux fois par mois. Les valeurs de Chl a obtenus vont de 20 á 300 mg m^–2. Les variations saisonniéres observées ne sont pas claires: nos résultats indiquent que l'hauteur de la station (m) joue un rôle essentiel dans l'évolution temporel de la biomasse, c'est á dire, la biomasse microalgal des sites du supra-littoral est influencié par les paramétres climatiques, tandis que dans l'infra-littoral c'est l'action des marées le facteur principal.

     

Hyperbolic Modeling of Starburst Dendrimers

Starburst dendrimers are highly branched oligomers. A rigid dendritic hydrocarbon, C₁₁₃₄H₁₁₄₆, has recently been synthesized. It consists of 94 phenylacetylene units displayed in a self-similar two-dimensional skeleton isomorphous to the three-coordinated Bethe lattice. The three-dimensional representation of phenylacetylene dendrimer shows a globular architecture with large voids and niches in its interior, characteristic of hyperbolic surfaces. This work investigates the geometrical scaling behavior of this starburst dendrimer using the symmetry properties of a Bethe lattice embedded in the hyperbolic plane. The results for C₁₁₃₄H₁₁₄₆ provide its density profile and an upper bound for its macromolecular size. This revised version was published online in June 2006 with corrections to the Cover Date.     

Modeling Lanthanide Complexes: Towards the Theoretical Design of Light Conversion Molecular Devices

Theoretical techniques have been developed and/or improved to predict the molecular structure of lanthanide complexes which were used to calculate their electronic properties, in particular, their electronic spectra and energy levels necessary to calculate the rates of energy transfer from the ligands to the metal ion. The molecular structure has been obtained by the SMLC/AM1 (Sparkle Model for the Calculation of Lanthanide Complexes – Austin Model 1) model where the lanthanide ion is simulated by a sparkle implemented into the AM1 Hamiltonian used to perform a HF-SCF (Hartree-Fock Self-Consistent Field) calculation. The previous implementation of the SMLC/AM1 model (sparkle/1) involving only two parameters has been generalized to be consistent with the AM1 Hamiltonian and the new model (sparkle/2) significantly improved the prediction of molecular structures of Eu(III) complexes. For the electronic spectra and energy level calculations of the lanthanide complexes the model replaces the metal ion by a point charge with the ligands held in their positions as determined by the SMLC/AM1 model, and uses a INDO/S-CI (intermediate neglect of differential overlap/spectroscopic-configuration interaction) model. A preliminary study of the solvent effects on the absorption spectra of the free ligand is also presented. For the ligand-lanthanide ion energy transfer Fermi's golden rule is used with the multipolar and exchange mechanisms being implemented and tested for several complexes. These theoretical techniques have been applied to several complexes yielding very good results when compared to experimental data as well as predictions for the molecular and electronic structures and the relative contributions of the mechanisms for the energy transfer rates. This revised version was published online in June 2006 with corrections to the Cover Date.     

The beta chorionic gonadotropin-beta luteinizing gene cluster maps to human chromosome 19

Summary We used a cloned human cDNA probe homologous to the placenta chorionic gonadotropin subunit (CGB) and to the pituitary luteinizing hormone subunit (LHB) and Southern blotting techniques to analyse DNA from a series of rodent x human somatic cell hybrids for the presence of specific gonadotropin subunit related sequences. Our results provide evidence for the assignment and linkage of the eight genes (or pseudogenes) coding for the subunit of these glycoprotein hormones to chromosome 19. Moreover, we observed a strict concordance between the permissivity of mouse x man hybrid cells to enteroviruses (which is linked to the presence of specific cell receptors encoded by human chromosome 19) and the presence of CGB and LHB related sequences, thus confirming the localization of the structural genes for the subunits on chromosome 19.This work was supported in part by INSERM grants CRL 81 1041 and by MRC grant MT 4860     

Photochemical reaction of 9-cis-retro-γ-rhodopsin at low temperatures

9-cis-Retro-γ;rhodopsin (λ_max = 420 nm) was prepared from 9-cis-retro-γ-retinal and cattle opsin. After cooling to liquid nitrogen temperature (77 K), the pigment was irradiated with light at 380 nm. The spectrum shifted to the longer wavelengths, owing to formation of a batho product. This fact indicates that the conjugated double bond system from C-5 to C-8 of the chromophoric retinal in rhodopsin was not necessary for formation of bathorhodopsin. Reirradiation of the batho product with light at wavelengths longer than 520 nm yielded a mixture composed of presumably 9- or 11-cis forms of retro-γ-rhodopsin. These three isomers are interconvertible by light at liquid nitrogen temperature. Thus the retro-γ-rhodopsin system is similar in photochemical reaction at 77 K to cattle rhodopsin system. Each system has its own batho product. Based on these results, it was infered that the formation of bathorhodopsin is due to photoisomerization of the chromophoric retinal of rhodopsin and is not due to translocation of a proton on the ring or on the side chain from C-6 to C-8 of the chromophoric retinal to the Schiff-base nitrogen.