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71.
Nitrification and nitrifying bacteria in the lower Seine River and estuary (France) 总被引:10,自引:0,他引:10
The Achères wastewater treatment plant, located just downstream of Paris, discharges its effluents into the lower Seine River. The effluents contain large numbers of heterotrophic bacteria, organic matter, and ammonium and are a source of nitrifying bacteria. As a result, degradation of organic matter by heterotrophic bacteria and subsequent oxygen depletion occur immediately downstream of the effluent outlet, whereas nitrifying bacteria apparently need to build up a significant biomass before ammonium oxidation significantly depletes the oxygen. We quantified the potential total nitrifying activity and the potential activities of the ammonia- and nitrite-oxidizing communities along the Seine River. In the summer, the maximum nitrifying activity occurs in the upper freshwater estuary, approximately 200 km downstream of Achères. The quantities of nitrifying bacteria, based on amoA gene copy numbers, and of Nitrobacter organisms, based on 16S rRNA gene copy numbers, were correlated with the potential nitrifying activities. The species composition of ammonia-oxidizing bacteria was investigated at two sites: the Triel station just downstream from Achères (km 84) and the Seine freshwater estuary at the Duclair station (km 278). By means of PCR primers targeting the amoA gene, a gene library was created. Phylogenetic analysis revealed that the majority of the analyzed clones at both sites were affiliated with the genus NITROSOMONAS: The Nitrosomonas oligotropha- and Nitrosomonas urea-related clones represented nearly 81% of the community of ammonia-oxidizing bacteria at Triel and 60% at Duclair. Two other ammonia-oxidizing clusters of the beta subclass of the Proteobacteria, i.e., Nitrosomonas europaea- and Nitrosospira-like bacteria, were found in smaller numbers. The major change in the ammonia-oxidizing community between the two stations along the Seine River-upper estuary continuum was the replacement of the N. oligotropha- and N. urea-related bacteria by the Nitrosospira-affiliated bacteria. Although the diversities of the ammonia oxidizers appear to be similar for the two sites, only half of the restriction patterns are common to both sites, which could be explained by the differences in ammonium concentrations, which are much lower in the upper estuary than in the river at the effluent outlet. These results imply a significant immigration and/or selection of the ammonia-oxidizing bacterial population along the continuum of the Seine River from Paris to the estuary. 相似文献
72.
Orlando L Leonard JA Thenot A Laudet V Guerin C Hänni C 《Molecular phylogenetics and evolution》2003,28(3):485-499
With ancient DNA technology, DNA sequences have been added to the list of characters available to infer the phyletic position of extinct species in evolutionary trees. We have sequenced the entire 12S rRNA and partial cytochrome b (cyt b) genes of one 60-70,000-year-old sample, and partial 12S rRNA and cyt b sequences of two 40-45,000-year-old samples of the extinct woolly rhinoceros (Coelodonta antiquitatis). Based on these two mitochondrial markers, phylogenetic analyses show that C. antiquitatis is most closely related to one of the three extant Asian rhinoceros species, Dicerorhinus sumatrensis. Calculations based on a molecular clock suggest that the lineage leading to C. antiquitatis and D. sumatrensis diverged in the Oligocene, 21-26 MYA. Both results agree with morphological models deduced from palaeontological data. Nuclear inserts of mitochondrial DNA were identified in the ancient specimens. These data should encourage the use of nuclear DNA in future ancient DNA studies. It also further establishes that the degraded nature of ancient DNA does not completely protect ancient DNA studies based on mitochondrial data from the problems associated with nuclear inserts. 相似文献
73.
Marcade M Bourdin J Loiseau N Peillon H Rayer A Drouin D Schweighoffer F Désiré L 《Journal of neurochemistry》2008,106(1):392-404
Pharmacological modulation of the GABAA receptor has gained increasing attention as a potential treatment for central processes affected in Alzheimer disease (AD), including neuronal survival and cognition. The proteolytic cleavage of the amyloid precursor protein (APP) through the α-secretase pathway decreases in AD, concurrent with cognitive impairment. This APP cleavage occurs within the β-amyloid peptide (Aβ) sequence, precluding formation of amyloidogenic peptides and leading to the release of the soluble N-terminal APP fragment (sAPPα) which is neurotrophic and procognitive. In this study, we show that at nanomolar-low micromolar concentrations, etazolate, a selective GABAA receptor modulator, stimulates sAPPα production in rat cortical neurons and in guinea pig brains. Etazolate (20 nM–2 μM) dose-dependently protected rat cortical neurons against Aβ-induced toxicity. The neuroprotective effects of etazolate were fully blocked by GABAA receptor antagonists indicating that this neuroprotection was due to GABAA receptor signalling. Baclofen, a GABAB receptor agonist failed to inhibit the Aβ-induced neuronal death. Furthermore, both pharmacological α-secretase pathway inhibition and sAPPα immunoneutralization approaches prevented etazolate neuroprotection against Aβ, indicating that etazolate exerts its neuroprotective effect via sAPPα induction. Our findings therefore indicate a relationship between GABAA receptor signalling, the α-secretase pathway and neuroprotection, documenting a new therapeutic approach for AD treatment. 相似文献
74.
Le Questel JY Graton J Cerón-Carrasco JP Jacquemin D Planchat A Thany SH 《Bioorganic & medicinal chemistry》2011,19(24):7623-7634
Structural features and hydrogen-bond interactions of dinotefuran (DIN), imidacoloprid (IMI) and acetamiprid (ACE) have been investigated experimentally through analyses of new crystal structures and observations in structural databases, as well as by Density Functional Theory quantum chemical calculations. Several conformations are observed experimentally in the solid state, highlighting the large flexibility of these compounds. This feature is confirmed by the theoretical calculations in the gas phase, the numerous and different energetic minima of the three neonicotinoids being located within a 10kJ/mol range. Comparisons of the observed and simulated data sheds light on the hydrogen-bond (HB) strength of the functional group at the tip of the electronegative fragment of each pharmacophore (NO(2) for DIN and IMI and CN for ACE). This effect originates in the 'push-pull' nature of these fragments and the related extensive electron delocalization. Molecular electrostatic potential calculations provide a ranking of the two fragments of the three neonicotinoid in terms of HB strength. Thus, the NO(2) group of DIN is the strongest HB acceptor of the electronegative fragment, closely followed by the cyano group of ACE. These two groups are significantly more potent than the NO(2) group of IMI. With respect to the other fragments of the three neonicotinoids, the nitrogen atom of the pyridine of IMI and ACE are stronger HB acceptors than the oxygen atom of the furanyl moiety of DIN. Finally, compared to electrophysiological studies obtained from cockroach synaptic and extrasynaptic receptors, DIN appears more effective than IMI and ACE because it strongly increases dose-dependently the ganglionic depolarisation and the currents amplitudes. These data suggest that DIN, IMI and ACE belong to two subgroups which act differently as agonists of insect nicotinic receptors. 相似文献
75.
76.
Reduced sexual dichromatism,mutual ornamentation,and individual quality in the monogamous Zenaida dove Zenaida aurita 下载免费PDF全文
Aurélie Quinard Frank Cézilly Sébastien Motreuil Jean‐Marc Rossi Clotilde Biard 《Journal of avian biology》2017,48(4):489-501
Although variation in plumage coloration is known to occur both between and within sexes, its study remains limited to a few bird families. The Zenaida dove Zenaida aurita is a socially monogamous tropical columbid bird species, characterized by an overall cinnamon‐brownish plumage and structural colorations on the head and neck. The species has been described as sexually dichromatic for plumage, although color differences between males and females are not obvious in the field. We investigated variation in the presumably melanin‐based color of the crown, mantle, breast, and belly, in the iridescent dark‐blue streaks on the head, and in the symmetric iridescent patches on the neck, over the whole spectrum visible to birds. Further, unlike most previous studies, we assessed covariation between plumage color and phenotypic traits in both males and females in relation to the putative signaling function of ornaments. Zenaida doves appeared to be slightly sexually dichromatic for the hue of pigment‐based colored areas, with males being on average more reddish than females. However, this difference was not discernible when considering the avian visual system. Conversely, although the reflectance spectra of iridescent plumage did not significantly differ between sexes in brightness, chroma or spectral position of the peaks, color discrimination analyses showed that individuals should be able to perceive between‐ or within‐sex differences in the color of the iridescent patch. In addition, several color parameters of brown and iridescent feathers were significantly related to territorial status, body condition, wing chord, and, albeit weakly, to individual multilocus heterozygosity. Overall, our results thus suggest that plumage color might be a reliable signal of quality in individuals of both sexes in this species. Further studies are needed to test the potential implication of plumage coloration in mate choice and mating patterns in the Zenaida dove. 相似文献
77.
The contrasting effects of short‐ and long‐term habitat drainage on the population dynamics of freshwater turtles in a human‐dominated landscape 下载免费PDF全文
Zoey Owen‐Jones Pauline Priol Stephanie Thienpont Marc Cheylan Gabrielle Sauret Christophe Coïc Aurélien Besnard 《Freshwater Biology》2016,61(1):121-132
78.
Nathalie Gallay Aurélien Rizk Seungkirl Ahn Jihee Kim Jonathan D Violin Laurence Dupuy Christophe Gauthier Vincent Piketty Pascale Crépieux Anne Poupon Frédérique Clément François Fages Robert J Lefkowitz Eric Reiter 《Molecular systems biology》2012,8(1)
Seven‐transmembrane receptors (7TMRs) are involved in nearly all aspects of chemical communications and represent major drug targets. 7TMRs transmit their signals not only via heterotrimeric G proteins but also through β‐arrestins, whose recruitment to the activated receptor is regulated by G protein‐coupled receptor kinases (GRKs). In this paper, we combined experimental approaches with computational modeling to decipher the molecular mechanisms as well as the hidden dynamics governing extracellular signal‐regulated kinase (ERK) activation by the angiotensin II type 1A receptor (AT1AR) in human embryonic kidney (HEK)293 cells. We built an abstracted ordinary differential equations (ODE)‐based model that captured the available knowledge and experimental data. We inferred the unknown parameters by simultaneously fitting experimental data generated in both control and perturbed conditions. We demonstrate that, in addition to its well‐established function in the desensitization of G‐protein activation, GRK2 exerts a strong negative effect on β‐arrestin‐dependent signaling through its competition with GRK5 and 6 for receptor phosphorylation. Importantly, we experimentally confirmed the validity of this novel GRK2‐dependent mechanism in both primary vascular smooth muscle cells naturally expressing the AT1AR, and HEK293 cells expressing other 7TMRs. 相似文献
79.
Albert Darque Aurélien Dumètre Sébastien Hutter Gilles Casano Maxime Robin Christophe Pannecouque Nadine Azas 《Bioorganic & medicinal chemistry letters》2009,19(20):5962-5964
We have synthesized quinolinones with potential antiparasitic and anti-HIV activities by an original two-step method involving microwave irradiation and have evaluated their activities against Plasmodium falciparum, Leishmania donovani, Trichomonas vaginalis, and HIV. None of the tested compounds had been previously described using this method of synthesis. One of the compounds had interesting antiparasitic and anti-HIV activity, which could be improved by substitution with different radicals. 相似文献
80.
Nicolas Feau Aurélien Lauron-Moreau Dominique Piou Benoît Marçais Cyril Dutech Marie-Laure Desprez-Loustau 《Fungal Ecology》2012,5(2):154-162
Recent molecular studies have shown that four genetic lineages, probably cryptic species, cause oak powdery mildew in Europe. We tested the hypothesis of niche differentiation between the two most frequent species (Erysiphe alphitoides and Erysiphe quercicola), by determining their relative prevalences at various times during the growing season. E. quercicola was strictly associated with the flag-shoot symptom in a 2-yr sampling campaign of 35 natural oak seedling populations. Additional sampling during Aug.–Sep. in the same stands showed that E. alphitoides predominated in most (70 %) cases. Time-course monitoring of powdery mildew in two natural regenerating oak populations confirmed the inverse patterns of relative abundance for these two species in early and late season. The coexistence of these two closely related species may be due to the use of different strategies, resulting from a trade-off between overwintering (flag-shoots vs. chasmothecia) and late-season performance. 相似文献