Biogeochemical control on the temporal variability of trace element concentrations in the Oubangui river (Central African Republic)

Dissolved Ba, Cd, Co, Mn, Mo, Ni, Rb, Sb, Sr, U and V were measured in the Oubangui river (Central African Republic) during a complete flood period. The dissolved concentrations vary by factors ranging from 1.4 to 8.2 as a function of river discharge : Sr, Ba, Rb and Mo concentrations decrease with rising stage ; Ni, U, Sb, Cd, V and Mn concentrations increase with rising stage. These distributions are explained by a mixing of quick flow, mostly surface runoff with delayed flow, mostly groundwater. The dual origin of stream waters is demonstrated by the major element ratios, which are close to a silicate end-member during the high-flow period and trend towards a carbonate end-member during the low-flow period. Moreover, geological heterogeneities in the Oubangui basin may play a role in the variation of concentrations observed at the basin outlet. The previously indicated presence of a subsurface carbonate sequence in the lower part of the basin is confirmed. Cd, V, Mn and Co show peak concentrations during decreasing stage. We suggest that biological processes such as release from phytoplanktonic material and dissolution of oxides or carbonate phases may explain this maximum. (Résumé d'auteur

Seasonal variability in concentration, composition, age, and fluxes of particulate organic carbon exchanged between the floodplain and Amazon river

International audienceThe composition, sources, and age of particulate organic matter were determined in an Amazonian river-floodplain system during rising, high, falling, and low water periods over 7 yr (1999-2006), and a mass balance for total organic carbon (dissolved and particulate) was estimated. The Curuai floodplain, composed of several temporally interconnected lakes, is permanently connected to the Amazon River via channels. Organic matter (OM) is imported to the floodplain from the Amazon River mainly during the rising water period and produced in the floodplain and exported to the river during high and falling water periods. No significant exchanges occurred during low water periods. The OM produced in the floodplain is characterized by low C/N ratios and by high chlorophyll a concentrations (Chl-a). The δ13C signature has a seasonal trend, with more negative δ13C values during the high water period than other periods. Δ14C results indicate that the bulk OM present in floodplain lakes is predominantly post-bomb (i.e., post-1950). Particulate organic carbon (POC) and dissolved organic carbon (DOC) fluxes exported by the Curuai floodplain represent 1.3% and 0.1%, respectively, of the POC and DOC annual fluxes in the mainstem Amazon River at Óbidos but may reach up to 3.3% and 0.8% during falling water. Based on Δ14C, δ13C, Chl-a, and elemental analysis of the particulate organic matter, we demonstrate that floodplain lakes have intense phytoplankton and macrophyte primary production, which is partly exported to the main river channel. Floodplains are thus a significant source of modern and labile organic carbon to the river mainstem, where it can be rapidly degraded and recycled back to the atmosphere

Haemophagocytic Syndrome in a 19-Year-Old Male with Plasmodium falciparum Malaria

Objectives: Infectious agents triggering haemophagocytic lymphohistiocytosis (HLH) primarily involve the herpes virus group. We report a case of HLH precipitated by Plasmodium falciparum. Materials and methods: Clinical and laboratory findings in a patient presenting with fever were collected. After confirmation of acute malaria, anti-malarial treatment was administered. Results: Despite initial favourable evolution, the patient developed fever again together with a worsening of the haematological parameters and increased ferritin levels. A bone marrow biopsy confirmed the diagnosis of HLH. Conclusion: This case illustrates that HLH should be considered in the differential diagnosis of acute malaria in patients with persisting fever and pancytopenia

Subtype-specific differentiation of cardiac pacemaker cell clusters from human induced pluripotent stem cells

Background: Human induced pluripotent stem cells (hiPSC) harbor the potential to differentiate into diverse cardiac cell types. Previous experimental efforts were primarily directed at the generation of hiPSC-derived cells with ventricular cardiomyocyte characteristics. Aiming at a straightforward approach for pacemaker cell modeling and replacement, we sought to selectively differentiate cells with nodal-type properties. Methods: hiPSC were differentiated into spontaneously beating clusters by co-culturing with visceral endoderm-like cells in a serum-free medium. Subsequent culturing in a specified fetal bovine serum (FBS)-enriched cell medium produced a pacemaker-type phenotype that was studied in detail using quantitative real-time polymerase chain reaction (qRT-PCR), immunocytochemistry, and patch-clamp electrophysiology. Further investigations comprised pharmacological stimulations and co-culturing with neonatal cardiomyocytes. Results: hiPSC co-cultured in a serum-free medium with the visceral endoderm-like cell line END-2 produced spontaneously beating clusters after 10–12 days of culture. The pacemaker-specific genes HCN4, TBX3, and TBX18 were abundantly expressed at this early developmental stage, while levels of sarcomeric gene products remained low. We observed that working-type cardiomyogenic differentiation can be suppressed by transfer of early clusters into a FBS-enriched cell medium immediately after beating onset. After 6 weeks under these conditions, sinoatrial node (SAN) hallmark genes remained at high levels, while working-type myocardial transcripts (NKX2.5, TBX5) were low. Clusters were characterized by regular activity and robust beating rates (70–90 beats/min) and were triggered by spontaneous Ca2+ transients recapitulating calcium clock properties of genuine pacemaker cells. They were responsive to adrenergic/cholinergic stimulation and able to pace neonatal rat ventricular myocytes in co-culture experiments. Action potential (AP) measurements of cells individualized from clusters exhibited nodal-type (63.4%) and atrial-type (36.6%) AP morphologies, while ventricular AP configurations were not observed. Conclusion: We provide a novel culture media-based, transgene-free approach for targeted generation of hiPSC-derived pacemaker-type cells that grow in clusters and offer the potential for disease modeling, drug testing, and individualized cell-based replacement therapy of the SAN

Inhibition of Histone Deacetylases Induces K+ Channel Remodeling and Action Potential Prolongation in HL-1 Atrial Cardiomyocytes

Background/Aims: Cardiac arrhythmias are triggered by environmental stimuli that may modulate expression of cardiac ion channels. Underlying epigenetic regulation of cardiac electrophysiology remains incompletely understood. Histone deacetylases (HDACs) control gene expression and cardiac integrity. We hypothesized that class I/II HDACs transcriptionally regulate ion channel expression and determine action potential duration (APD) in cardiac myocytes. Methods: Global class I/II HDAC inhibition was achieved by administration of trichostatin A (TSA). HDAC-mediated effects on K+ channel expression and electrophysiological function were evaluated in murine atrial cardiomyocytes (HL-1 cells) using real-time PCR, Western blot, and patch clamp analyses. Electrical tachypacing was employed to recapitulate arrhythmia-related effects on ion channel remodeling in the absence and presence of HDAC inhibition. Results: Global HDAC inhibition increased histone acetylation and prolonged APD90 in atrial cardiomyocytes compared to untreated control cells. Transcript levels of voltage-gated or inwardly rectifying K+ channels Kcnq1, Kcnj3 and Kcnj5 were significantly reduced, whereas Kcnk2, Kcnj2 and Kcnd3 mRNAs were upregulated. Ion channel remodeling was similarly observed at protein level. Short-term tachypacing did not induce significant transcriptional K+ channel remodeling. Conclusion: The present findings link class I/II HDAC activity to regulation of ion channel expression and action potential duration in atrial cardiomyocytes. Clinical implications for HDAC-based antiarrhythmic therapy and cardiac safety of HDAC inhibitors require further investigation

Risk and prognostic significance of tuberculosis in patients from The TREAT Asia HIV Observational Database

10.1186/1471-2334-9-46BMC Infectious Diseases94

Renal replacement therapy in acute kidney injury: controversy and consensus

Renal replacement therapies (RRTs) represent a cornerstone in the management of severe acute kidney injury. This area of intensive care and nephrology has undergone significant improvement and evolution in recent years. Continuous RRTs have been a major focus of new technological and treatment strategies. RRT is being used increasingly in the intensive care unit, not only for renal indications but also for other organ-supportive strategies. Several aspects related to RRT are now well established, but others remain controversial. In this review, we review the available RRT modalities, covering technical and clinical aspects. We discuss several controversial issues, provide some practical recommendations, and where possible suggest a research agenda for the future

Harmful Elements in Estuarine and Coastal Systems

Estuaries and coastal zones are dynamic transitional systems which provide many economic and ecological benefits to humans, but also are an ideal habitat for other organisms as well. These areas are becoming contaminated by various anthropogenic activities due to a quick economic growth and urbanization. This chapter explores the sources, chemical speciation, sediment accumulation and removal mechanisms of the harmful elements in estuarine and coastal seawaters. It also describes the effects of toxic elements on aquatic flora and fauna. Finally, the toxic element pollution of the Venice Lagoon, a transitional water body located in the northeastern part of Italy, is discussed as a case study, by presenting the procedures adopted to measure the extent of the pollution, the impacts on organisms and the restoration activities