Ostracodes limniques de la Formation d'Irbzer, Crétacé terminal du Moyen-Atlas, Maroc : taxonomie, biostratigraphie, paléoécologie, paléobiogéographie

An association of limnic ostracodes has been discovered in the upper part of the Irbzer Formation, of Maastrichtian age, in the Moroccan Middle-Atlas. A new species is described, Gomphocythere achloujensis nov. sp. Paracandona occitanica, which is very common in terminal Cretaceous non-marine deposits of southern Europe (France, Spain), is found for the first time on the south Tethyan margin.     

Wingless secretion requires endosome-to-Golgi retrieval of Wntless/Evi/Sprinter by the retromer complex

The glycolipoproteins of the Wnt family raise interesting trafficking issues, especially with respect to spreading within tissues. Recently, the retromer complex has been suggested to participate in packaging Wnts into long-range transport vehicles. Our analysis of a Drosophila mutant in Vps35 show that, instead, the retromer complex is required for efficient progression of Wingless (a Drosophila Wnt) through the secretory pathway. Indeed expression of senseless, a short-range target gene, is lost in Vps35-deficient imaginal discs. In contrast, Vps35 is not required for Hedgehog secretion, suggesting specificity. Overexpression of Wntless, a transmembrane protein known to be specifically required for Wingless secretion overcomes the secretion block of Vps35-mutant cells. Furthermore, biochemical evidence confirms that Wntless engages with the retromer complex. We propose that Wntless accompanies Wingless to the plasma membrane where the two proteins dissociate. Following dissociation from Wingless, Wntless is internalized and returns to the Golgi apparatus in a retromer-dependent manner. Without the retromer-dependent recycling route, Wingless secretion is impaired and, as electron microscopy suggests, Wntless is diverted to a degradative compartment.     

Toxoplasma gondii exploits UHRF1 and induces host cell cycle arrest at G2 to enable its proliferation

Toxoplasma gondii is an obligate intracellular parasite that causes severe disease in humans. It is able to infect all nucleated mammalian cells leading to lifelong persistence of the parasite in the host. Here, we studied the effect of T. gondii infection on host cell proliferation and explored the molecular mechanisms involved in host cell cycle progression. We found that T. gondii induced G1/S transition in host cells in the presence of UHRF1, followed by G2 arrest after cyclin B1 downregulation which is probably the major cause of the arrest. Other molecules at the G2/M checkpoint including p53, p21 and Cdk1 were normally regulated. Interestingly, while parasite proliferation was normal in cells that were in the G2 phase, it was suppressed in G1-arrested cells induced by UHRF1-siRNA, indicating the importance of the G2 phase via UHRF1-induced G1/S transition for T. gondii growth.     

Sugar beet leaves as new source of hydroperoxide lyase in a bioprocess producing green-note aldehydes

Hydroperoxide lyase activity was found in sugar beet leaves. Its optimum pH and temperature were, respectively, 6.7 and 22°C. Under these conditions, conversion of linolenic acid 13-hydroperoxide to cis-3-hexenal with a maximum yield of 80% was reached after only 2 min. The stability of cis-3-hexenal was improved by acidifying the reaction medium. Based on these studies, a bioprocess producing green-note aldehydes in a laboratory-scale was achieved. The authors Holy N. Rabetafika and Cédric Gigot contributed equally.     

The role of atmospheric dispersion models and ecosystem sensitivity in the determination of characterisation factors for acidifying and eutrophying emissions in LCIA

Background, aim and scope  The methodological choices and framework to assess environmental impacts in life cycle assessment are still under discussion. Despite intensive developments worldwide, few attempts have been made hitherto to systematically present the role of different factors of characterisation models in life cycle impact assessment (LCIA). The aim of this study is to show how European average and country-dependent characterisation factors for acidifying and eutrophying emissions differ when using (a) acidifying and eutrophying potentials alone, (b) depositions from an atmospheric dispersion model or (c) critical loads in conjunction with those depositions. Furthermore, in the latter case, the contributions of emissions, an atmospheric transport model and critical loads to changes in characterisation factors of NO₂ are studied. In addition, the new characterisation factors based on the accumulated exceedance (AE) method are presented using updated emissions, a new atmospheric transport model and the latest critical loads. Materials and methods  In this study, characterisation factors for acidifying and eutrophying emissions are calculated by three different methods. In the ‘no fate’ (NF) methods, acidifying and eutrophying potentials alone are considered as characterisation factors. In the ‘only above terrestrial environment’ (OT) approach, characterisation factors are based on the deposition of the acidifying or eutrophying substances to terrestrial land surfaces. The third method is the so-called AE method in which critical loads are used in conjunction with depositions. The results of the methods are compared both at the European and the country level using weighted mean, weighted standard deviation, minimum and maximum values. To illustrate the sensitivity of the AE method, changes in European emissions, employed atmospheric dispersion model and the critical loads database are conducted step-by-step, and the differences between the results are analysed. Results and discussion  For European average characterisation factors, the three characterisation methods of acidification produce results in which the contributions of NH₃, NO₂ and SO₂ to the acidification indicator do not differ much within each method when 1 kg of each acidifying substance is emitted. However, the NF methods cannot describe any spatial aspects of environmental problems. Both OT and AE methods show that the spatial aspects play an important role in the characterisation factors. The AE method results in greater differentiations between country-dependent characterisation factors than does the OT method. In addition, the results of the AE and OT methods differ from each other for individual countries. A major shortcoming of the OT approach is that it does not consider the sensitivity of the ecosystems onto which the pollutants are deposited, whereas the AE approach does. In the case of the AE method, a new atmospheric dispersion model, new information on emissions and critical loads have a different influence on the characterisation factors, depending on the country. The results of statistics show that the change in the atmospheric dispersion model has a greatest influence on the results, since ecosystem-specific depositions are taken into account for the first time. Conclusions and recommendations  The simple NF methods can be used in a first approximation to assess the impacts of acidification and terrestrial eutrophication in cases where we do not know where the emissions occur. The OT approach is a more advanced method compared with the NF method, but its capability to describe spatial aspects is limited. The AE factors are truly impact-oriented characterisation factors and the information used here represents the current best knowledge about the assessment practice of acidification and terrestrial eutrophication in Europe. The key message of this study is that there is no shortcut to achieving advanced characterisation of acidification and terrestrial eutrophication: an advanced methodology cannot develop without atmospheric dispersion models and information on ecosystem sensitivity.     

Targeting DNA with triplex-forming oligonucleotides to modify gene sequence

Molecules that interact with DNA in a sequence-specific manner are attractive tools for manipulating gene sequence and expression. For example, triplex-forming oligonucleotides (TFOs), which bind to oligopyrimidine.oligopurine sequences via Hoogsteen hydrogen bonds, have been used to inhibit gene expression at the DNA level as well as to induce targeted mutagenesis in model systems. Recent advances in using oligonucleotides and analogs to target DNA in a sequence-specific manner will be discussed. In particular, chemical modification of TFOs has been used to improve binding to chromosomal target sequences in living cells. Various oligonucleotide analogs have also been found to expand the range of sequences amenable to manipulation, including so-called "Zorro" locked nucleic acids (LNAs) and pseudo-complementary peptide nucleic acids (pcPNAs). Finally, we will examine the potential of TFOs for directing targeted gene sequence modification and propose that synthetic nucleases, based on conjugation of sequence-specific DNA ligands to DNA damaging molecules, are a promising alternative to protein-based endonucleases for targeted gene sequence modification.     

Sequence-specific DNA cleavage mediated by bipyridine polyamide conjugates

The design of molecules that damage a selected DNA sequence provides a formidable opportunity for basic and applied biology. For example, such molecules offer new prospects for controlled manipulation of the genome. The conjugation of DNA-code reading molecules such as polyamides to reagents that induce DNA damages provides an approach to reach this goal. In this work, we showed that a bipyridine conjugate of polyamides was able to induce sequence-specific DNA breaks in cells. We synthesized compounds based on two polyamide parts linked to bipyridine at different positions. Bipyridine conjugates of polyamides were found to have a high affinity for the DNA target and one of them produced a specific and high-yield cleavage in vitro and in cultured cells. The bipyridine conjugate studied here, also presents cell penetrating properties since it is active when directly added to cell culture medium. Harnessing DNA damaging molecules such as bipyridine to predetermined genomic sites, as achieved here, provides an attractive strategy for targeted genome modification and DNA repair studies.     

Lipase-catalysed hydrolysis of short-chain substrates in solution and in emulsion: a kinetic study

We have studied the enzymatic hydrolysis of solutions and emulsions of vinyl propionate, vinyl butyrate and tripropionin by lipases of various origin and specificity. Kinetic studies of the hydrolysis of short-chain substrates by microbial triacylglycerol lipases from Rhizopus oryzae, Mucor miehei, Candida rugosa, Candida antarctica A and by (phospho)lipase from guinea-pig pancreas show that these lipolytic enzymes follow the Michaelis–Menten model. Surprisingly, the activity against solutions of tripropionin and vinyl esters ranges from 70% to 90% of that determined against emulsions. In contrast, a non-hyperbolic (sigmoidal) dependence of enzyme activity on ester concentration is found with human pancreatic lipase, triacylglycerol lipase from Humicola lanuginosa (Thermomyces lanuginosa) and partial acylglycerol lipase from Penicillium camembertii and the same substrates. In all cases, no abrupt jump in activity (interfacial activation) is observed at substrate concentration corresponding to the solubility limit of the esters. Maximal lipolytic activity is always obtained in the presence of emulsified ester. Despite progress in the understanding of structure–function of lipases, interpretation of the mode of action of lipases active against solutions of short-chain substrates remains difficult. Actually, it is not known whether these enzymes, which possess a lid structure, are in open or/and closed conformation in the bulk phase and whether the opening of the lid that gives access to the catalytic triad is triggered by interaction of the enzyme molecule with monomeric substrates or/and multimolecular aggregates (micelles) both present in the bulk phase. From the comparison of the behaviour of lipases used in this study which, in some cases, follow the Michaelis–Menten model and, in others, deviate from classical kinetics, it appears that the activity of classical lipases against soluble short-chain vinyl esters and tripropionin depends not only on specific interaction with single substrate molecules at the catalytic site of the enzyme but also on physico-chemical parameters related to the state of association of the substrate dispersed in the aqueous phase. It is assumed that the interaction of lipase with soluble multimolecular aggregates of tripropionin or short-chain vinyl esters or the formation of enzyme–substrate mixed micelles with ester bound to lipase, might represent a crucial step that triggers the structural transition to the open enzyme conformation by displacement of the lid.     

Uncoupling protein 3 gene is associated with body composition changes with training in HERITAGE study.

The uncoupling protein 3 (UCP3) is a mitochondrial membrane transporter mainly expressed in skeletal muscle that we have shown to be associated with obesity. We have analyzed UCP3 polymorphisms, Val102Ile, Tyr210Tyr, and a new microsatellite GAIVS6 located in the sixth intron, among 276 black and 503 white subjects from the HERITAGE Family Study. Linkage and association studies were undertaken with body composition variables measured in a sedentary state (baseline) and after 20 wk of endurance training (changes). Allele and genotype frequencies were found to be significantly different between whites and blacks. Suggestive linkages (0.009 < or = P < or = 0.033) with Tyr210Tyr were found in blacks and whites for baseline body mass index, fat mass, or leptin level and with GAIVS6 in whites for changes in fat mass and percent body fat. Associations were also found in whites between GAIVS6 and changes in the sum of eight skinfold thicknesses (P = 0.0006), with a borderline result for body mass index (P = 0.06). We concluded that UCP3 could be involved in body composition changes after regular exercise.