Données nouvelles sur les mammifères et les nummulites de l'éocène supérieur subalpin (synclinaux du Charbon et d'entrevernes,Bauges, Savoie et Haute-Savoie)

Vertebrate remains and nummulites have been investigated from the Late Eocene—Early Oligocene transgressive sequence of the «Chaînes subalpines south of the lake Annecy. The sedimentary environments range from fluvio-lacustrine shales and conglomerates at the base to hemipelagic Globigerina shales at the top. The fluvio-lacustrine white marls contain mammals of the upper, probably terminal Ludian, with affinities to the assemblage of Saint-Capraise. The brackish Cerithium beds have furnished charophytes of the Bembridge zone. The nummulite limestones are not dated precisely, but isolated, probably redeposited nummulites from the base of the Globigerina shales are of terminal Eocene or basal Oligocene age. The Globigerina shales themselves belong to the Oligocene.     

APE1 overexpression in XRCC1-deficient cells complements the defective repair of oxidative single strand breaks but increases genomic instability

XRCC1 protein is essential for mammalian viability and is required for the efficient repair of single strand breaks (SSBs) and damaged bases in DNA. XRCC1-deficient cells are genetically unstable and sensitive to DNA damaging agents. XRCC1 has no known enzymatic activity and is thought to act as a scaffold protein for both SSB and base excision repair activities. To further define the defects leading to genetic instability in XRCC1-deficient cells, we overexpressed the AP endonuclease APE1, shown previously to interact with and be stimulated by XRCC1. Here, we report that the overexpression of APE1 can compensate for the impaired capability of XRCC1-deficient cells to repair SSBs induced by oxidative DNA damage, both in vivo and in whole-cell extracts. We show that, for this kind of damage, the repair of blocked DNA ends is rate limiting and can be performed by APE1. Conversely, APE1 overproduction resulted in a 3-fold increase in the sensitivity of XRCC1-deficient cells to an alkylating agent, most probably due to the accumulation of SSBs. Finally, the overproduction of APE1 results in increases of 40% in the frequency of micronuclei and 33% in sister chromatid exchanges of XRCC1⁻ cells. These data suggest that the spontaneous generation of AP sites could be at the origin of the SSBs responsible for the spontaneous genetic instability characteristic of XRCC1-deficient cells.     

The Podospora rmp1 gene implicated in nucleus-mitochondria cross-talk encodes an essential protein whose subcellular location is developmentally regulated

It has been previously reported that, at the time of death, the Podospora anserina AS1-4 mutant strains accumulate specific deleted forms of the mitochondrial genome and that their life spans depend on two natural alleles (variants) of the rmp1 gene: AS1-4 rmp1-2 strains exhibit life spans strikingly longer than those of AS1-4 rmp1-1. Here, we show that rmp1 is an essential gene. In silico analyses of eight rmp1 natural alleles present in Podospora isolates and of the putative homologs of this orphan gene in other filamentous fungi suggest that rmp1 evolves rapidly. The RMP1 protein is localized in the mitochondrial and/or the cytosolic compartment, depending on cell type and developmental stage. Strains producing RMP1 without its mitochondrial targeting peptide are viable but exhibit vegetative and sexual defects.     

Characterization of a cardiac-specific enhancer, which directs {alpha}-cardiac actin gene transcription in the mouse adult heart

Expression of the mouse alpha-cardiac actin gene in skeletal and cardiac muscle is regulated by enhancers lying 5' to the proximal promoter. Here we report the characterization of a cardiac-specific enhancer located within -2.354/-1.36 kbp of the gene, which is active in cardiocytes but not in C2 skeletal muscle cells. In vivo it directs reporter gene expression to the adult heart, where the proximal promoter alone is inactive. An 85-bp region within the enhancer is highly conserved between human and mouse and contains a central AT-rich site, which is essential for enhancer activity. This site binds myocyte enhancer factor (MEF)2 factors, principally MEF2D and MEF2A in cardiocyte nuclear extracts. These results are discussed in the context of MEF2 activity and of the regulation of the alpha-cardiac actin locus.     

Five labdane diterpenoids from the seeds of Aframomum zambesiacum

Five labdane diterpenoids, (3-5), zambesiacolactone A (7) and zambesiacolactone B (8), were isolated from the seeds of Aframomum zambesiacum (Baker) K. Schum., along with five known labdanes and a linear sesquiterpene, nerolidol. Their structures were elucidated by spectroscopic analysis. Their antiplasmodial activity was evaluated in vitro against Plasmodium falciparum. Compound 3 was the most active with an IC(50) value of 4.97 microM.     

Micropropagation of ‘Durondeau’ pear in modified-gelled medium

Summary The influence of partial substitution of agar by galactomannans (GMs) in culture media was studied in pear (Pyrus communis L. cv. ‘Durondeau’) micropropagation. GMs. extracted from seeds of Cassia fastuosa (cassia) or Cyamopsis tetragonolobus (guar gum, a commercial GM), were mixed in equal proportions with agar to a final concentration of 0.3% (w/v) for each type of gelling agent. The production of multiple shoots and the formation of roots from shoots were compared with the control solidified with agar alone at a concentration of 0.6% (w/v). In the media solidified with the mixtures of agar/guar and agar/cassia GMs, an, increase of 32 and 17%, respectively, was obtained in the number of regenerated shoots. The modified media promoted a higher number of roots and increased the rooting percentage. A maximum of 91% rooting was obtained in the medium solidified with the agar/cassia GM and containing 9.80 μM indole-3-butyric acid. Less callus formation at the base of the shoot was also observed on this medium. The improved in vitro performance of shoot formation and rooting, combined with a significantly lower cost, suggests a potential use of agar/GM gels in plant tissue culture.     

Aggregation of some water-soluble derivatives of chitin in aqueous solutions: Role of the degree of acetylation and effect of hydrogen bond breaker

By dynamic light scattering in combination with fluorescence spectroscopy and TEM it was shown that aggregation in aqueous solutions is inherent not only to chitosan, but also to two other water-soluble derivatives of chitin: O-carboxymethylchitin and di-N,N-carboxymethylchitosan. Aggregation is observed even for the samples without N-acetyl-d-glucosamine units, which remain upon incomplete chemical modification of chitin, indicating that specific interactions between residual chitin repeat units cannot be the main reason for the aggregation. At the same time, 7 M urea weakens the aggregation, thus testifying that hydrogen bonding and/or hydrophobic interactions are partially responsible for this phenomenon. The incomplete disruption of aggregates in 7 M urea may arise from crystallization of junction zones between different macromolecules, which makes some hydrogen bonds inaccessible for urea or too stable for breaking by this agent.