Electrochemical analysis of the performance of carbon supported Pd nanoparticles for direct formic acid fuel cells: from gold supported electrodes to catalyst-coated membranes

In this work carbon supported Pd nanoparticles were prepared and used as electrocatalysts for formic acid electrooxidation fuel cells. The influence of some relevant parameters such as the nominal Pt loading, the Nafion/total solids ratio as well as the Pd loading towards formic acid electrooxidation was evaluated using gold supported catalytic layer electrodes which were prepared using a similar methodology to that employed in the preparation of conventional catalyst coated membranes (CCM). The results obtained show that, for constant Pd loading, the nominal Pd loading and the Nafion percentage on the catalytic layer do not play an important role on the resulting electrocatalytic properties. The main parameter affecting the electrocatalytic activity of the electrodes seems to be the Pd loading, although the resulting activity is not directly proportional to the increased Pd loading. Thus, whereas the Pd loading is multiplied by a factor of 10, the activity is only twice which evidences an important decrease in the Pd utilization. In fact, the results obtained suggest the active layer is the outer one being clearly independent of the catalytic layer thickness. Finally, catalyst coated membranes with Pd catalyst loadings of 0.1, 0.5 and 1.2 mg cm-2 were also tested in a breathing direct formic acid fuel cell.

Implicating the mechanisms of ADP-ribosylation factor activation in the resistance of invasive breast cancer cells to EGFR tyrosine kinase inhibitors

ADP-ribosylation factor-1 (ARF1) est une petite GTPase principalement connue pour son rôle dans la formation de vésicules au niveau de l’appareil de Golgi. Récemment, dans des cellules de cancer du sein, nous avons démontré qu’ARF1 est aussi un médiateur important de la signalisation du récepteur du facteur de croissance épidermique (EGFR) contrôlant la prolifération, la migration et l'invasion cellulaire. Cependant, le mécanisme par lequel l’EGFR active la GTPase ainsi que le rôle de cette dernière dans la régulation de la fonction du récepteur demeure inconnue. Dans cette thèse, nous avions comme objectifs de définir le mécanisme d'activation de ARF1 dans les cellules de cancer du sein hautement invasif et démontrer que l’activation de cette isoforme de ARF joue un rôle essentiel dans la résistance de ces cellules aux inhibiteurs de l'EGFR. Nos études démontrent que les protéines d’adaptatrices Grb2 et p66Shc jouent un rôle important dans l'activation de ARF1. Alors que Grb2 favorise le recrutement d’ARF1 à l'EGFR ainsi que l'activation de cette petite GTPase, p66Shc inhibe le recrutement du complexe Grb2-ARF1 au récepteur et donc contribue à limiter l’activation d’ARF1. De plus, nous démontrons que ARF1 favorise la résistance aux inhibiteurs des tyrosines kinases dans les cellules de cancer du sein hautement invasif. En effet, une diminution de l’expression de ARF1 a augmenté la sensibilité descellules aux inhibiteurs de l'EGFR. Nous montrons également que de hauts niveaux de ARF1 contribuent à la résistance des cellules à ces médicaments en améliorant la survie et les signaux prolifératifs à travers ERK1/2, Src et AKT, tout en bloquant les voies apoptotiques (p38MAPK et JNK). Enfin, nous mettons en évidence le rôle de la protéine ARF1 dans l’apoptose en réponse aux traitements des inhibiteurs de l’EGFR. Nos résultats indiquent que la dépletion d’ARF1 promeut la mort cellulaire induite par gefitinib, en augmentant l'expression de facteurs pro-apoptotiques (p66shc, Bax), en altérant le potentiel de la membrane mitochondriale et la libération du cytochrome C. Ensemble, nos résultats délimitent un nouveau mécanisme d'activation de ARF1 dans les cellules du cancer du sein hautement invasif et impliquent l’activité d’ARF1 comme un médiateur important de la résistance aux inhibiteurs EGFR.

Investigating the thymopoiesis stimulating property of interleukin-21 in aging mice

La vaccination est largement utilisée pour la génération de lymphocytes T spécifiques contre les tumeurs. Malheureusement, cette stratégie n'est pas adaptée aux personnes âgées car leur thymus régresse avec l'âge conduisant ainsi à une baisse dans la production de cellules T et à l'accumulation de cellules immunitaires âgées ayant des défauts liés à leurs stimulations. Comme il a été démontré auparavant que L’IL-21 est capable d’induire des fonctions thymiques, nous avons émis l’hypothèse que l’injection d’IL-21 à des souris âgées stimulera la thymopoïèse. Nos résultats montrent que l’administration de l’IL-21 augmente le nombre absolu de thymocytes chez les souris âgées et augmente la migration de ces cellules vers la périphérie ou ils contribuent à la diversité du TCR. De plus les cellules T en périphérie expriment un niveau plus élevé de miR181-a, et par conséquent moins de phosphatase comme SHP2, DUSP5/6 qui inhibent le TCR. En vaccinant des souris âgées avec le peptide Trp2, les souris traitées avec l’IL-21 montrent un retard dans la croissance des cellules B16 tumorales. Cette étude montre que l’IL-21 pourrait être utilisé comme stratégie pour le rétablissement du systeme immunitaire chez les personnes âgées.

Endothelial Progenitor Cells in Breast Cancer

Editorial

Non-Viral Gene Therapy to Cells of the bovine Intervertebral Disc

Background. Low back pain is an increasing global health problem, which is associated with intervertebral disc (IVD) damage and degeneration. Major changes occur in the nucleus pulposus (NP), with the degradation of the extracellular matrix (ECM).1 Further studies showed that growth factors from transforming growth factor β (TGFβ) and bone morphogenic proteins (BMP) family may induce chondrogenic differentiation of mesenchymal stem cells (MSC).2 Focusing on non-viral gene therapies and their possible translation into the clinics, we investigated if GDF6 (syn. BMP13 or CDMP2) can induce regeneration of degraded NP. We hypothesized that IVD transfected with plasmid over-expressing GDF6 also up-regulates other NP- and chondrogenic cell markers and enhances ECM deposition. Methods. Bovine nucleus pulposus (bNPC) and annulus fibrosus cells (bAFC) were harvested from bovine coccygeal IVD. Primary cells were then electroporized with plasmid GDF6 (Origene, vector RG211366) by optimizing parameters using the Neon Transfection system (Life Technologies, Basel). After transfection, cells were cultured in 2D monolayer or 3D alginate beads for 7, 14 or 21 days. Transfection efficiency of pGDF6 was analyzed by immunohistochemistry and fluorescent microscopy. Cell phenotype was quantified by real-time RT-PCR. To test a non-viral gene therapy applied directly to 3D whole organ culture, coccygeal bovine IVDs were harvested as previously described. Bovine IVDs were transfected by injection of plasmid GDF6 into the center. Electroporation was performed with ECM830 Square Wave Electroporation System (Harvard Apparatus, MA) using 2-needle array electrode or tweezertrodes. 72 h after tranfection discs were fixed and cryosectioned and analyzed by immunofluorescence against GDF6. Results. RT-PCR and immunohistochemistry confirmed up-regulation of GFP and GDF6 in the primary bNPC/bAFC culture. The GFP-tagged GDF6 protein, however, was not visible, possibly due to failure of dimer formation as a result of fusion structure. Organ IVD culture transfection revealed GDF6 positive staining in the center of the disc using 2-needle array electrode. Results from tweezertrodes did not show any GDF6 positive cells. Conclusion. Non-viral transfection is an appealing approach for gene therapy as it fulfills the translational safety aspects of transiency and lacks the toxic effects of viral transduction. We identified novel parameters to successfully transfect primary bovine IVD cells. For transfection of whole IVD explants electroporation parameters need to be further optimized. Acknowledgements. This project was funded by the Lindenhof Foundation (Funds “Research & Teaching”) Project no. 13-02-F. The imaging part of this study was performed with the facility of the Microscopy Imaging Center (MIC), University of Bern. References. Roughly PJ (2004): Spine (Phila), 29:2691-2699 Clarke LE, McConell JC, Sherratt MJ, Derby B, Richardson SM, Hoyland JA (2014), Arthritis Research & Therapy, 16:R67

Age, pollen and spores of ODP Site 175-1082

The present-day condition of bipolar glaciation characterized by rapid and large climate fluctuations began at the end of the Pliocene with the intensification of the Northern Hemisphere continental glaciations. The global cooling steps of the late Pliocene have been documented in numerous studies of Ocean Drilling Program (ODP) sites from the Northern Hemisphere. However, the interactions between oceans and between land and ocean during these cooling steps are poorly known. In particular, data from the Southern Hemisphere are lacking. Therefore I investigated the pollen of ODP Site 1082 in the southeast Atlantic Ocean in order to obtain a high-resolution record of vegetation change in Namibia between 3.4 and 1.8 Ma. Four phases of vegetation development are inferred that are connected to global climate change. (1) Before 3 Ma, extensive, rather open grass-rich savannahs with mopane trees existed in Namibia, but the extension of desert and semidesert vegetation was still restricted. (2) Increase of winter rainfall dependent Renosterveld-like vegetation occurred between 3.1 and 2.2 Ma connected to strong advection of polar waters along the Namibian coast and a northward shift of the Polar Front Zone in the Southern Ocean. (3) Climatically induced fluctuations became stronger between 2.7 and 2.2 Ma and semiarid areas extended during glacial periods probably as the result of an increased pole-equator thermal gradient and consequently globally enhanced atmospheric circulation. (4) Aridification and climatic variability further increased after 2.2 Ma, when the Polar Front Zone migrated southward and the influence of Atlantic moisture brought by the westerlies to southern Africa declined. It is concluded that the positions of the frontal systems in the Southern Ocean which determine the locations of the high-pressure cells over the South Atlantic and the southern Indian Ocean have a strong influence on the climate of southern Africa in contrast to the climate of northwest and central Africa, which is dominated by the Saharan low-pressure cell.

Bubble load measurement in the pulp zone of industrial flotation machines - a new device for determining the froth recovery of attached particles

A new device has been developed to directly measure the bubble loading of particle-bubble aggregates in industrial flotation machines, both mechanical flotation cells as well as flotation column cells. The bubble loading of aggregates allows for in-depth analysis of the operating performance of a flotation machine in terms of both pulp/collection zone and froth zone performance. This paper presents the methodology along with an example showing the excellent reproducibility of the device and an analysis of different operating conditions of the device itself. (C) 2004 Elsevier B.V All rights reserved.

Functional memory CD8+ T cells can be generated in vivo without evident T help

Synthetic cytotoxic T cell (CTL) epitope peptides provide an effective and safe means of vaccination against cancers and viruses, as these peptides can induce specific CD8+ effector T cells in vivo. However, the effector CD8+ T cells induced by the minimal CTL epitope peptides do not last past about 3 weeks after the induction and no functional memory CD8+ T cells are generated. It is held that simultaneous induction of CD4+ T cells by incorporating peptides containing T-helper epitopes in the vaccine at the time of primary vaccination are necessary for the induction of long-lived functional memory CD8+ T cells. We now report that, surprisingly, incorporation of medium length (>20 AA) peptides devoid of detectable T-helper epitopes in a minimal CTL epitope-based vaccine can also induce long-lasting! functional rumour antigen specific memory CD8+ T cells that are capable of promoting protection against tumour challenge. This observation may have implications for the formulation of therapeutic anti-cancer and anti-virus peptide vaccines where a strong induction of CD4 T help would be undesirable. (C) 2004 Elsevier Ltd. All rights reserved.

Germ cells enter meiosis in a rostro-caudal wave during development of the mouse ovary

Germ cells in the mouse embryo remain undifferentiated until about 13.5 days post-coitum (dpc), when male germ cells enter mitotic arrest and female germ cells enter meiosis. The molecular signals and transcriptional control mechanisms governing the differential fate of germ cells in males and females remain largely unknown. In order to gain insights into the behavior of germ cells around this period and into likely mechanisms controlling entry into meiosis, we have studied by wholemount in situ hybridization the expression pattern of two germ cell-specific markers, Oct4 and Sycp3, during mouse fetal gonad development. We observed a dynamic wave of expression of both genes in developing ovaries, with Oct4 expression being extinguished in a rostro-caudal wave and Sycp3 being upregulated in a corresponding wave, during the period 13.5-15.5 dpc. These results indicate that entry into meiosis proceeds in a rostro-caudal progression, in turn suggesting that somatically derived signals may contribute to the control of germ cell entry into meiosis in developing ovaries. (C) 2004 Wiley-Liss, Inc.

Identifying the molecular phenotype of renal progenitor cells

Although many of the molecular interactions in kidney development are now well understood, the molecules involved in the specification of the metanephric mesenchyme from surrounding intermediate mesoderm and, hence, the formation of the renal progenitor population are poorly characterized. In this study, cDNA microarrays were used to identify genes enriched in the murine embryonic day 10.5 (E10.5) uninduced metanephric mesenchyme, the renal progenitor population, in comparison with more rostral derivatives of the intermediate mesoderm. Microarray data were analyzed using R statistical software to determine accurately genes differentially expressed between these populations. Microarray outliers were biologically verified, and the spatial expression pattern of these genes at E10.5 and subsequent stages of early kidney development was determined by RNA in situ hybridization. This approach identified 21 genes preferentially expressed by the E10.5 metanephric mesenchyme, including Ewing sarcoma homolog, 14-3-3 theta, retinoic acid receptor-alpha, stearoyl-CoA desaturase 2, CD24, and cadherin-11, that may be important in formation of renal progenitor cells. Cell surface proteins such as CD24 and cadherin-11 that were strongly and specifically expressed in the uninduced metanephric mesenchyme and mark the renal progenitor population may prove useful in the purification of renal progenitor cells by FACS. These findings may assist in the isolation and characterization of potential renal stem cells for use in cellular therapies for kidney disease.

Functional maturation of isolated neural progenitor cells from the adult rat hippocampus

Although neural progenitor cells (NPCs) may provide a source of new neurons to alleviate neural trauma, little is known about their electrical properties as they differentiate. We have previously shown that single NPCs from the adult rat hippocampus can be cloned in the presence of heparan sulphate chains purified from the hippocampus, and that these cells can be pushed into a proliferative phenotype with the mitogen FGF2 [Chipperfield, H., Bedi, K.S., Cool, S.M. & Nurcombe, V. (2002) Int. J. Dev. Biol., 46, 661-670]. In this study, the active and passive electrical properties of both undifferentiated and differentiated adult hippocampal NPCs, from 0 to 12 days in vitro as single-cell preparations, were investigated. Sparsely plated, undifferentiated NPCs had a resting membrane potential of approximate to -90 mV and were electrically inexcitable. In > 70%, ATP and benzoylbenzoyl-ATP evoked an inward current and membrane depolarization, whereas acetylcholine, noradrenaline, glutamate and GABA had no detectable effect. In Fura-2-loaded undifferentiated NPCs, ATP and benzoylbenzoyl-ATP evoked a transient increase in the intracellular free Ca2+ concentration, which was dependent on extracellular Ca2+ and was inhibited reversibly by pyridoxalphosphate-6-azophenyl-2'-4'-disulphonic acid (PPADS), a P2 receptor antagonist. After differentiation, NPC-derived neurons became electrically excitable, expressing voltage-dependent TTX-sensitive Na+ channels, low- and high-voltage-activated Ca2+ channels and delayed-rectifier K+ channels. Differentiated cells also possessed functional glutamate, GABA, glycine and purinergic (P2X) receptors. Appearance of voltage-dependent and ligand-gated ion channels appears to be an important early step in the differentiation of NPCs.

Modelling of entrainment in industrial flotation cells: the effect of solids suspension

Solids concentration and particle size distribution gradually change in the vertical dimension of industrial flotation cells, subject primarily to the flotation cell size and design and the cell operating conditions. As entrainment is a two-step process and involves only the suspended solids in the top pulp region near the pulp-froth interface, the solids suspension characteristics have a significant impact on the overall entrainment. In this paper, a classification function is proposed to describe the state of solids suspension in flotation cells, similar to the definition of degree of entrainment for classification in the froth phase found in the literature. A mathematical model for solids suspension is also developed, in which the classification function is expressed as an exponential function of the particle size. Experimental data collected from three different Outokumpu tank flotation cells in three different concentrators are well fitted by the proposed exponential model. Under the prevailing experimental conditions, it was found that the solids content in the top region was relatively independent of cell operating conditions such as froth height and air rate but dependent on the cell size. Moreover, the results obtained from the total solids tend to be similar to those from a particular gangue mineral and hence may be applied to all minerals in entrainment calculation. (C) 2004 Elsevier Ltd. All rights reserved.

Alterations in the phenotype of neocortical pyramidal cells in the Dyrk1A+/- mouse

The gene encoding the dual-specificity tyrosine-regulated kinase DYRK1A maps to the chromosomal segment HSA21q22.2, which lies within the Down syndrome critical region. The reduction in brain size and behavioral defects observed in mice lacking one copy of the murine homologue Dyrk1A (Dyrk1A+/-) support the idea that this kinase may be involved in monosomy 21 associated mental retardation. However, the structural basis of these behavioral defects remains unclear. In the present work, we have analyzed the microstructure of cortical circuitry in the Dyrk1A+/- mouse and control littermates by intracellular injection of Lucifer Yellow in fixed cortical tissue. We found that labeled pyramidal cells were considerably smaller, less branched and less spinous in the cortex of Dyrk1A+/- mice than in control littermates. These results suggest that Dyrk1A influences the size and complexity of pyramidal cells, and thus their capability to integrate information. (c) 2005 Elsevier Inc. All rights reserved.

Selective transport of attached particles across the pulp-froth interface

A technique for determining the recovery of attached particles across the froth phase in flotation that relies on measuring the rate at which bubble-particle aggregates enter the froth is used to investigate the selectivity of attached particles across the froth phase. Combining these measurements with those of other techniques for determining the froth recovery of attached particles provides an insight into the different sub-processes of particle rejection in the froth phase. The results of experiments conducted in a 3 m(3) Outokumpu tank cell show that the detachment of particles from aggregates in the froth phase occurs largely at the pulp-froth interface. In particular it is shown that the pulp-froth interface selectively detaches particles from aggregates according to their physical attributes. (C) 2005 Elsevier Ltd. All rights reserved.

Modelling of entrainment in industrial flotation cells: Water recovery and degree of entrainment

Entrainment in flotation can be considered as a two-step process, including the transfer of the suspended solids in the top of the pulp region just below the pulp-froth interface to the froth phase and the transfer of the entrained particles in the froth phase to the concentrate. Both steps have a strong classification characteristic. The degree of entrainment describes the classification effect of the drainage process in the froth phase. This paper briefly reviews two existing models of degree of entrainment. Experimental data were collected from an Outokumpu 3 m(3) tank cell in the Xstrata Mt. Isa Mines copper concentrator. The data are fitted to the models and the effect of cell operating conditions including air rate and froth height on the degree of entrainment is examined on a size-by-size basis. It is found that there is a strong correlation between the entrainment and the water recovery, which is close to lineal. for the fines. The degree of entrainment decreases with increase in particle size. Within the normal range of cell operating conditions, few particles coarser than 50 mu m are recovered by entrainment. In general, the degree of entrainment increases with increase in the ail rate and decreases with increase in the froth height. Air rate and froth height strongly interact with each other and affect the entrainment process mainly via changes in the froth retention time, the froth structure and froth properties. As a result, other mechanisms such as entrapment may become important in recovering the coarse entrained particles. (c) 2005 Elsevier Ltd. All rights reserved.