Acute oxidative stress is associated with cell proliferation in the mouse liver

Oxidative stress is known to produce tissue injury and to activate various signaling pathways. To investigate the molecular events linked to acute oxidative stress in mouse liver, we injected a toxic dose of paraquat. Liver necrosis was first observed, followed by histological marks of cell proliferation. Concomitantly, activation of the MAP kinase pathway and increased levels of the anti-apoptotic protein Bcl-XL were observed. Gene expression profiles revealed that the differentially expressed genes were potentially involved in cell proliferation. These data suggest that paraquat-induced acute oxidative stress triggers the activation of regeneration-related events in the liver.     

Identification of a gonadotropin-releasing hormone receptor orthologue in Caenorhabditis elegans

Background  

The Caenorhabditis elegans genome is known to code for at least 1149 G protein-coupled receptors (GPCRs), but the GPCR(s) critical to the regulation of reproduction in this nematode are not yet known. This study examined whether GPCRs orthologous to human gonadotropin-releasing hormone receptor (GnRHR) exist in C. elegans.     

N-arylsulfonyl-2-vinyltryptamines as new 5-HT6 serotonin receptor ligands

Several new 2-vinyl-Nb,Nb-dimethyltryptamines were prepared using Fischer indole synthesis followed by simple functional group transformations and evaluated on 5-HT4, 5-HT5, 5-HT6 and 5-HT7 serotonin receptors. It was found that 2-vinyl substitution conferred a potent and selective 5-HT6 binding activity to these molecules which could be enhanced by Na-arylsulfonyl substituents.     

Adipose tissue cells, lipotransfer and cancer: A challenge for scientists, oncologists and surgeons

Despite recent evidence of the cancer-promoting role of adipose tissue-derived progenitor and differentiated cells, the use of lipotransfer for tissue/organ reconstruction after surgical removal of cancer is increasing worldwide. Here we discuss in a multidisciplinary fashion the preclinical data connecting obesity, adipose cells and cancer progression, as well as the clinical data concerning safety of lipotransfer procedures in cancer patients. A roadmap towards a more rationale use of lipotransfer in oncology is urgently needed and should include preclinical studies to dissect the roles of different adipose tissue-derived cells, the evaluation of drugs currently candidate to inhibit the interaction between adipose and tumor cells, and carefully designed clinical trials to investigate the safety of lipotransfer procedures in cancer patients.     

Tryptose phosphate broth improves Rickettsia felis replication in mammalian cells

In cell culture, Rickettsia felis grows only at low temperatures (< 31 °C). Therefore, its ability to enter, survive and grow in cell lines has primarily been tested in cells derived from amphibians and arthropods, which naturally grow at low temperatures, and only infrequently in mammalian cells. We subcultured R. felis in mammalian cells for more than 10 passages using media supplemented with tryptose phosphate broth (TPB) and found that TPB is critical for optimal growth of R. felis in mammalian cells.     

Maize genetic diversity and association mapping using transposable element insertion polymorphisms

Transposable elements are the major component of the maize genome and presumably highly polymorphic yet they have not been used in population genetics and association analyses. Using the Transposon Display method, we isolated and converted into PCR-based markers 33 Miniature Inverted Repeat Transposable Elements (MITE) polymorphic insertions. These polymorphisms were genotyped on a population-based sample of 26 American landraces for a total of 322 plants. Genetic diversity was high and partitioned within and among landraces. The genetic groups identified using Bayesian clustering were in agreement with published data based on SNPs and SSRs, indicating that MITE polymorphisms reflect maize genetic history. To explore the contribution of MITEs to phenotypic variation, we undertook an association mapping approach in a panel of 367 maize lines phenotyped for 26 traits. We found a highly significant association between the marker ZmV1-9, on chromosome 1, and male flowering time. The variance explained by this association is consistent with a flowering delay of +123 degree-days. This MITE insertion is located at only 289 nucleotides from the 3′ end of a Cytochrome P450-like gene, a region that was never identified in previous association mapping or QTL surveys. Interestingly, we found (i) a non-synonymous mutation located in the exon 2 of the gene in strong linkage disequilibrium with the MITE polymorphism, and (ii) a perfect sequence homology between the MITE sequence and a maize siRNA that could therefore potentially interfere with the expression of the Cytochrome P450-like gene. Those two observations among others offer exciting perspectives to validate functionally the role of this region on phenotypic variation.     

Flavones and structurally related 4-chromenones inhibit carbonic anhydrases by a different mechanism of action compared to coumarins

An inhibition study of several carbonic anhydrase (CA, EC 4.2.1.1) isoforms with flavones and aminoflavones, compounds possessing a rather similar scaffold with the coumarins, recently discovered inhibitors of this enzyme, is reported. The natural product flavone and some of its hydroxylated derivatives did not show time-dependent inhibition of the CAs, sign that they are not hydrolyzed within the enzyme active site as the (thio)coumarins and lactones. These compounds were low micromolar inhibitors of hCA I, II, IX and XII, with K(I)s in the range of 1.88-9.07 μM. A series of substituted 2-amino-3-phenyl-4H-chromen-4-ones, incorporating chloro- and methoxy substituents in various positions of the heterocycle, were then prepared and assayed as hCA I and II inhibitors, showing activity in the micromolar range. Some of these derivatives, as well as cis+trans resveratrol, were then assayed for the inhibition of all catalytically active mammalian CA isoforms, hCA I, II, III, IV, VA, VB, VI, VII, IX, XII, XIII, XIV and mCA XV (h=human, m=murine enzyme). These derivatives inhibited these CAs in the submicromolar-low micromolar range. Flavones, although not as active as the coumarins, may be considered as interesting leads for the design of non-sulfonamide CA inhibitors.     

Long-chain acylcarnitines regulate the HERG channel

Background and purpose

In some pathological conditions carnitine concentration is high while in othersitis low.In bothcases,cardiac arrhythmiascan occur and lead to sudden cardiac death. It has been proposed that in ischaemia, acylcarnitine (acyl-CAR), but not carnitine, is involved in arrhythmiasthrough modulation of ionic currents. We studied the effects of acyl-CARs on hERG, K_IR2.1 and K_v7.1/minKchannels (channels responsible for I_KR, I_K1 and I_KS respectively).

Experimental approach

HEK293 cells stably expressing hERG, K_IR2.1 or Kv7.1/minK were studied using the patch clamp technique. Free carnitine (CAR) and acyl-CAR derivatives from medium- (C8 and C10) and long-chain (C16 and C18∶1) fatty acids were applied intra- and extracellularly at different concentrations. Forstudies onhERG, C16 and C18∶1 free fatty acid were also used.

Key results

Extracellular long-chain (LCAC), but not medium-chain, acyl-CAR,induced an increase of I_hERG amplitude associated with a dose-dependent speeding of deactivation kinetics. They had no effect on K_IR2.1 or Kv7.1/minK currents.Computer simulations of these effects wereconsistent with changes in action potential profile.

Conclusions and applications

Extracellular LCAC tonically regulates I_hERG amplitude and kineticsunder physiological conditions. This modulation maycontribute tothe changes in action potential duration thatprecede cardiac arrhythmias in ischaemia, diabetes and primary systemic carnitine deficiency.     

The microRNA pathway controls germ cell proliferation and differentiation in C. elegans

The discovery of the miRNA pathway revealed a new layer of molecular control of biological processes. To uncover new functions of this gene regulatory pathway, we undertook the characterization of the two miRNA-specific Argonaute proteins in Caenorhabditis elegans, ALG-1 and ALG-2. We first observed that the loss-of-function of alg-1 and alg-2 genes resulted in reduced progeny number. An extensive analysis of the germline of these mutants revealed a reduced mitotic region, indicating fewer proliferating germ cells. We also observed an early entry into meiosis in alg-1 and alg-2 mutant animals. We detected ALG-1 and ALG-2 protein expressions in the distal tip cell (DTC), a specialized cell located at the tip of both C. elegans gonadal arms that regulates mitosis-meiosis transition. Re-establishing the expression of alg-1 specifically in the DTC of mutant animals partially rescued the observed germline defects. Further analyses also support the implication of the miRNA pathway in gametogenesis. Interestingly, we observed that disruption of five miRNAs expressed in the DTC led to similar phenotypes. Finally, gene expression analysis of alg-1 mutant gonads suggests that the miRNA pathway is involved in the regulation of different pathways important for germline proliferation and differentiation. Collectively, our data indicate that the miRNA pathway plays a crucial role in the control of germ cell biogenesis in C. elegans.     

Phenotypic plasticity in response to mechanical stress: hydrodynamic performance and fitness of four aquatic plant species

Plastic responses of plants exposed to mechanical stress can lead to modified, performance-enhancing, morphologies, sometimes accompanied by costs to reproduction. The capacity to present short-term plastic responses to current stress, the resulting performance (expected lower mechanical forces), and the costs of such responses to reproduction were tested for four aquatic plant species. Two ramets of the same genet were submitted to running vs standing water treatment. Traits describing the morphology, hydrodynamic performance and reproduction (sexual and vegetative) were measured. For one species, plastic responses led to reduced hydrodynamic forces, without apparent costs to reproduction, indicating that the plastic response could be beneficial for plant maintenance in stressful habitats. For two species, plastic responses were not associated with variations in performance and reproduction, possibly because of the low hydrodynamic forces experienced, even for morphologies produced under standing conditions. For one species, plastic responses were associated with a sharp decrease in sexual reproduction, without variations in performance, revealing the negative impact of currents over a short time scale. Species maintenance is linked to the capacity of individuals to tolerate mechanical forces. The contrasting responses to currents may be a key element for predicting community dynamics.