Southern ocean carbon and heat impact on climate.

The Southern Ocean greatly contributes to the regulation of the global climate by controlling important heat and carbon exchanges between the atmosphere and the ocean. Rates of climate change on decadal timescales are therefore impacted by oceanic processes taking place in the Southern Ocean, yet too little is known about these processes. Limitations come both from the lack of observations in this extreme environment and its inherent sensitivity to intermittent processes at scales that are not well captured in current Earth system models. The Southern Ocean Carbon and Heat Impact on Climate programme was launched to address this knowledge gap, with the overall objective to understand and quantify variability of heat and carbon budgets in the Southern Ocean through an investigation of the key physical processes controlling exchanges between the atmosphere, ocean and sea ice using a combination of observational and modelling approaches. Here, we provide a brief overview of the programme, as well as a summary of some of the scientific progress achieved during its first half. Advances range from new evidence of the importance of specific processes in Southern Ocean ventilation rate (e.g. storm-induced turbulence, sea-ice meltwater fronts, wind-induced gyre circulation, dense shelf water formation and abyssal mixing) to refined descriptions of the physical changes currently ongoing in the Southern Ocean and of their link with global climate. This article is part of a discussion meeting issue 'Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities'.

The biotechnological potential of microbial communities from Antarctic soils and sediments: Application to low temperature biogenic methane production.

Anaerobic digestion (AD) is an attractive bioprocess for waste treatment and energy recovery through methane-rich biogas production. Under temperate to cold climate, the implementation of AD for low-organic load wastewater treatment has been limited to date, due to the energetic and economic cost of maintaining optimal mesophilic temperature. Hence, we aim at (i) exploring the biotechnological potential of a microbial inoculum from Antarctic soils and sediments to run AD at low temperatures; and (ii) evaluating the effect of temperature over a psychrophilic-mesophilic range on both methane production rates and microbial community composition. Methane production stimulated by acetate amendment was detected from 5 to 37 °C, with a maximum at 25 °C, corresponding to the highest relative abundance of methanogenic archaea (c. 21.4% of the total community). From 5 to 25 °C, the predominant methanogen was Methanosaeta, while it shifted to Methanocorpusculum at 30 °C. Compared with an industrial mesophilic sludge, the relative methane production rate at 5 °C (compared to the maximum) was 40% greater in the Antarctic inoculum. Microbial communities from permanently cold Antarctic sediments efficiently produce methane at low temperatures revealing a biotechnological potential for the treatment of low-organic load residues in cold regions.

Diel Rhythm Does Not Shape the Vertical Distribution of Bacterial and Archaeal 16S rRNA Transcript Diversity in Intertidal Sediments: a Mesocosm Study.

In intertidal sediments, circadian oscillations (i.e., tidal and diel rhythms) and/or depth may affect prokaryotic activity. However, it is difficult to distinguish the effect of each single force on active community changes in these natural and complex intertidal ecosystems. Therefore, we developed a tidal mesocosm to control the tidal rhythm and test whether diel fluctuation or sediment depth influence active prokaryotes in the top 10 cm of sediment. Day- and nighttime emersions were compared as they are expected to display contrasting conditions through microphytobenthic activity in five different sediment layers. A multiple factor analysis revealed that bacterial and archaeal 16S ribosomal RNA (rRNA) transcript diversity assessed by pyrosequencing was similar between day and night emersions. Potentially active benthic Bacteria were highly diverse and influenced by chlorophyll a and phosphate concentrations. While in oxic and suboxic sediments, Thaumarchaeota Marine Group I (MGI) was the most active archaeal phylum, suggesting the importance of the nitrogen cycle in muddy sediments, in anoxic sediments, the mysterious archaeal C3 group dominated the community. This work highlighted that active prokaryotes organize themselves vertically within sediments independently of diel fluctuations suggesting adaptation to physicochemical-specific conditions associated with sediment depth.

Medicinal Mascarene Aloes: An audit of their phytotherapeutic potential.

A phytochemical and biological investigation of the endemic Mascarene Aloes (Aloe spp.), including A. tormentorii (Marais) L.E.Newton & G.D.Rowley, A. purpurea Lam, A. macra Haw., A. lomatophylloides Balf.f and A. vera (synonym A. barbadensis Mill.), which are used in the traditional folk medicine of the Mascarene Islands, was initiated. Methanolic extracts of the Aloes under study were analysed using high resolution LC-UV-MS/MS and compounds belonging to the class of anthraquinones, anthrones, chromones and flavone C-glycosides were detected. The Mascarene Aloes could be distinguished from A. vera by the absence of 2″-O-feruloylaloesin and 7-O-methylaloeresin. GC-MS analysis of monosaccharides revealed the presence of arabinose, fucose, xylose, mannose and galactose in all the Mascarene Aloes and in A. vera. The crude extracts of all Aloes analysed displayed antimicrobial activity against Bacillus cereus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Only extracts of A. macra were active against P. aeruginosa and Klebsiella pneumoniae, while none of the Aloe extracts inhibited Propionibacterium acnes. A. macra displayed anti-tyrosinase activity, exhibiting 50% inhibition at 0.95mg/mL, and extracts of A. purpurea (Mauritius) and A. vera displayed activity in a wound healing-scratch assay. In vitro cytotoxicity screening of crude methanolic extracts of the Aloes, using the MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) showed that only A. purpurea (Réunion) elicited a modest toxic effect against HL60 cells, with a percentage toxicity of 8.2% (A. purpurea-Réunion) and none of the Aloe extracts elicited a toxic effect against MRC 5 fibroblast cells at a concentration of 0.1mg/mL. Mascarene Aloe species possess noteworthy pharmacological attributes associated with their rich phytochemical profiles.

Abyssal ocean overturning shaped by seafloor distribution.

The abyssal ocean is broadly characterized by northward flow of the densest waters and southward flow of less-dense waters above them. Understanding what controls the strength and structure of these interhemispheric flows-referred to as the abyssal overturning circulation-is key to quantifying the ocean's ability to store carbon and heat on timescales exceeding a century. Here we show that, north of 32° S, the depth distribution of the seafloor compels dense southern-origin waters to flow northward below a depth of about 4 kilometres and to return southward predominantly at depths greater than 2.5 kilometres. Unless ventilated from the north, the overlying mid-depths (1 to 2.5 kilometres deep) host comparatively weak mean meridional flow. Backed by analysis of historical radiocarbon measurements, the findings imply that the geometry of the Pacific, Indian and Atlantic basins places a major external constraint on the overturning structure.

Dynamic mechanical properties of a biomimetic hydroxyapatite/polyamide 6,9 nanocomposite.

A biomimetic composite of nanohydroxyapatite (nHap) and semicrystalline polyamide 6,9 (PA 6,9) was synthesized by thermally induced phase separation. The nHap powder was dispersed in a polymer matrix with a low ratio ranging 1-10 wt %. The mean size of the nHap, determined by scanning electron microscopy (SEM) was approximately 100-200 nm (length), 40-60 nm (width). Physicochemical analyses were performed in order to characterize the PA 6,9 and nHap separately on the one hand, and the PA 6,9/nHap composites on the other hand. Differential scanning calorimetry (DSC) and dynamic mechanical analyses (DMA) have pointed out an optimization of the composite physical properties as a function of nHap content till a limit value of 5 wt %. Above this value, the mechanical properties decreased. Four main parameters have been found to influence the composite physical properties improvement: the fillers content, the physical structure of the polymeric matrix, the particles dispersion and the physical interaction strength between organic and inorganic phases. The dynamic mechanical properties of this biomimetic nanocomposite were compared with human cortical bone.

[How to calculate the completeness of ascertainment of a morbidity register? Example of the Isere childhood handicap register in Grenoble, France]. / Comment calculer l'exhaustivité d'un registre de morbidité? L'exemple du registre des handicaps de l'enfant et observatoire périnatal de l'Isère.

BACKGROUND: It should no longer be necessary to demonstrate the importance of knowing the completeness of ascertainment for a morbidity register, particularly with respect to the interpretation of prevalence rates and their trends, but also when using register data for etiological studies. METHOD: The study covered 9 generations of children born between 1980 and 1988. All of these children lived in the Isère department in SouthEast France, and each of them had at least one major deficiency, according to the inclusion criteria laid down by the RHEOP ("Registre des Handicaps de l'Enfant et Observatoire Périnatal", in French, or Childhood Handicap Register and Perinatal Observatory). These children were recruited from four different data sources. The completeness of ascertainment of the register was estimated first by means of the capturerecapture method, based on two sources that were shown to be independent by the Wittes method. Following this, loglinear models were used. The advantage of this was the absence of restrictions involved in adhering to the necessary validity conditions before applying the capture-recapture method, and the possibility of introducing heterogeneity variables, such as the number of deficiencies per child, for example. RESULTS: The applied capturerecapture method, with two main sources that have been found to be independent, gives an overall completeness of ascertainment of 86% CI(95%)[8291], with a variation of between 76% CI(95%)[6787] and 97% CI(95%)[93100] when the number of deficiencies per child is taken into account. After application of the loglinear models, the results obtained are very close to those obtained with the capture-recapture method, both in the case of estimation of the overall completeness of ascertainment and in the case of the completeness of ascertainment that is estimated according to the number of deficiencies variable. The similarity of the results obtained by the two methods appears to support our empirical study, but is only possible because of the validity of certain conditions (the interactions of the order of three were not significant) which can only be verified using statistical tests in the linear log models. CONCLUSION: If the application conditions of the capture-recapture method are carefully adhered to, it becomes possible, without the help of software, to produce a correct estimate of the number of missing cases. Nevertheless, it would be unreasonable to continue using this method alone since log linear models have been found to be independent of these validity conditions.

Differential effects of forskolin and 1,9-dideoxy-forskolin on nicotinic receptor- and K+-induced responses in chromaffin cells.

The diterpene forskolin inhibits nicotine-evoked chromaffin cell Ca2+ influx, scinderin redistribution, F-actin disassembly and catecholamine secretion in a concentration-dependent (10-50 microM) fashion. On the other hand, forskolin showed weak inhibitory effects when the same responses were elicited by K+-induced depolarization. Similar concentrations of 1,9-dideoxy-forskolin, a forskolin analog which does not activate adenylate cyclase, blocked very effectively the responses evoked by either of the two stimuli. Patch-clamp (whole-cell configuration) studies demonstrated that both diterpenes blocked fast and reversibly peak and total chromaffin cell nicotinic acetylcholine receptor currents, effects not mediated through adenylate cyclase activation. Moreover, both forskolin and 1,9-dideoxy-forskolin exhibited Ca2+ channel blocking properties. However, 1,9-dideoxy-forskolin was more potent than forskolin as a Ca2+ channel blocker. Furthermore, 1,9-dideoxy-forskolin was also more potent than forskolin as a nicotinic acetylcholine receptor and Ca2+ channel blocker and it was more potent as a nicotinic acetylcholine receptor blocker than Ca2+ channel blocker. The results showed powerful cAMP-independent effects of the diterpenes and suggest caution in interpretation of cAMP effects on chromaffin cells when its cellular levels are modified by forskolin.

Control of SHB gene expression by protein phosphorylation.

To increase our understanding of the role of the Src homology 2 (SH2) domain-containing protein Shb in the mitogenic signal transduction, Shb mRNA contents were determined in the fibroblast-like NIH3T3 cells and the insulin producing beta TC-1 cells under various conditions. In NIH3T3 cells, the serine/ threonine phosphatase inhibitor okadaic acid and the tyrosine kinase inhibitor genistein increased Shb mRNA contents, the protein kinase C activating phorbol ester 12-O-tetradecanoyl 13-acetate (TPA) decreased the Shb mRNA content, whereas the tyrosine kinase inhibitor tyrphostin 25 and the mitogen platelet-derived growth factor (PDGF-BB) had no effect. In beta TC-1 cells, okadaic acid and genistein increased the Shb mRNA content, whereas tyrphostin 25 and serum were without effect. Okadaic acid and genistein decreased the rates of beta TC-1 cell DNA synthesis. It is concluded that expression of the SHB gene is under a complex mode of regulation involving at least three different protein kinases. As a consequence of this, it is likely that SHB gene expression is significantly modulated by conditions of specific activation of certain pathways, whereas its expression appears little influenced by serum and a mitogen.

Molecular interactions of the Src homology 2 domain protein Shb with phosphotyrosine residues, tyrosine kinase receptors and Src homology 3 domain proteins.

The molecular interactions of the Src homology 2 (SH2) domain and the N-terminal proline-rich sequence motifs (pro-1 to pro-5) of the SH2 protein Shb with other components were presently characterised. Using a degenerate phosphopeptide library the preferred binding site for the Shb SH2 domain was determined to pTyr-Thr/Val/Ile-X-Leu at positions +1 to +3 relative the phosphotyrosine residue. Experiments with competing peptides and platelet-derived growth factor (PDGF) beta-receptor mutants with Y to F substitutions in autophosphorylation sites revealed multiple binding sites for the Shb SH2 domain in the receptor. The Shb SH2 domain also binds to in vitro phosphorylated fibroblast growth factor receptor-1 (FGFR-1) mainly through position Y776. The receptor experiments suggest that other residues besides the +1 to +3 positions may also be of significance for Shb binding. The pro-4/pro-5 motif of Shb binds in vitro particularly well to the Src, p85 alpha PI3-kinase and Eps8 SH3 domains expressed as GST fusion proteins. However, the GST-SH3 domain fusion proteins tested bind in vitro to peptides corresponding to the pro-1 to pro-5 motifs of Shb with low affinity and selectivity, suggesting that sequences outside the core proline motif may also be important for Shb-SH3 domain interactions. In vivo association between Shb-SH3 domain proteins v-Src and Eps8 was detected by coimmunoprecipitation. PDGF treatment did not affect the association between Eps8 and Shb. The data suggest that Shb is an adaptor protein linking SH3 domain proteins to tyrosine kinases or other tyrosine phosphorylated proteins.

HIT cells secrete ß-cell mitogenic factors.

We studied the growth characteristics of the insulin-producing HIT cells. Although successful in many cell lines such as ßTC1, growth arrest could not be obtained with HIT cells left for 3 days without serum. Cytofluorometric analysis showed that about 24% of the cells continuously exposed to serum peaked in the S phase. A similar proportion was found for cells cultured for 1 or 2 days in serum-free medium. A treatment with suramin, disrupting the binding of ligands from their receptors, was associated with a rapid and transient increase in c-fos and c-jun gene expression after suramin removal, in the absence of serum. In addition, HIT cells secrete mitogenic factors, different from IGF-I or IGF-II, acting on insulin-secreting ßTC1 cells and on BP-A31 fibroblasts. Chromatography of the medium conditioned by the HIT cells on gel filtration gave two major mitogenic fractions, of hydrodynamic characteristics 33 000 and 3000-10 000. The activity was heat stable and bound to heparin. Comparative studies of the self-regulatory HIT cells, with the ßTC1 cells requiring external growth factors, should contribute significantly to our understanding of the regulation of ß cell growth.

Shb is a ubiquitously expressed Src homology 2 protein.

To identify serum-inducible genes in the insulin-producing cell line beta TC-1, a library subtraction screening procedure was performed on serum-deprived (G0) and serum-restimulated (G1) insulin-producing beta TC-1 cells. A cDNA containing a motif with strong homology to Src homology 2 (SH2) domains was found using this procedure and called Shb. The Shb cDNA contains two methionine codons in its N-terminus and thus may code for two proteins of 67 and 56 kDa, each with one SH2 domain in its C-terminus. No other structural similarity to proteins with catalytic activity could be detected, suggesting that Shb is a so called adaptor. Shb contains the proline-rich sequence PPPGPGR between the two proposed initiator methionines which resembles a sequence for binding to Src homology 3 (SH3) domains. A second proline-rich sequence was detected after the second methionine codon. The Shb cDNA hybridized to a similar or identical mRNA of 3.1 kb expressed in mouse brain, liver, kidney, heart, NIH3T3 fibroblasts and beta TC-1 cells. Western blot analysis of the same tissues using an antiserum directed against a synthetic peptide corresponding to a part of the SH2 domain of Shb, revealed reactivity with two proteins of 56 and 67 kDa. In addition, a third reactive component of 40 kDa was detected in most tissues. Transfection and transient expression of the Shb cDNA in COS-1 cells yielded increased expression of the 67, 56 and 40 kDa proteins. Transfection and stable expression of the Shb cDNA in pig aortic endothelial cells showed increased expression primarily of the 67 kDa protein. A fusion protein consisting of the SH2 domain of Shb linked to glutathione S-transferase showed increased binding to glycoproteins of cells stimulated with platelet-derived growth factor (PDGF-BB). Furthermore, the autophosphorylated PDGF beta-receptor but not the autophosphorylated epidermal growth factor (EGF) receptor bound specifically to immobilized fusion protein. It is concluded that Shb is a novel SH2-containing protein with proline-rich domains and therefore probably involved in the signal-transduction of some ligand-activated tyrosine kinase receptors.

Logistic regression model to estimate the risk of unbalanced offspring in reciprocal translocations.

The aim of this study was to estimate the risk of viable unbalanced offspring for a parental carrier of reciprocal translocation. On a large computerized database of reciprocal translocations we used logistic regression to model this risk. The status of the progeny is the outcome variable. Explanatory covariates are cytogenetic characteristics of the translocation, age and sex of the parental carrier, and potential viability of the gametes. The results obtained by the logistic model demonstrate the important role of certain variables such as the sex of the parental carrier and the R band length of the translocated segments. Within the group of lower risk (risk of viable unbalanced offspring less than 5%), 97% of the individuals are correctly classified with this model. For this group, the choice prenatal diagnosis can be best discussed by considering both the risk for viable unbalanced offspring and the risk of induced abortion following prenatal diagnosis.

Modulation of growth-related gene expression and growth inhibition by cyclic adenosine 3',5'-monophosphate-elevating agents in the insulin-producing cell line beta TC1.

We studied the involvement of the cAMP pathway in the regulation of beta TC1 cell growth with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) and the activator of adenylate cyclase forskolin. We examined the effect of the increase in cAMP content on the serum-induced resumption of the cell cycle of quiescent cells. IBMX and forskolin both inhibited the mitogenic effect of serum in a concentration-dependent manner. Intracellular cAMP levels were, respectively, enhanced 3.0- and 8.6-fold by IBMX (0.5 mM) and forskolin (20 microM) within 1 h. IBMX and forskolin were also inducers of insulin release, indicating that the growth-arrested beta TC1 cells have retained the essential characteristics of the normal differentiated beta-cells. The effects of IBMX and forskolin were correlated with a modulation of cell cycle-related gene expression. IBMX induced expression of the c-fos gene, which was further enhanced by the simultaneous addition of serum, whereas forskolin alone elicited maximal induction of this gene. Interestingly, c-jun expression was only enhanced with forskolin. We also studied the effects of IBMX and forskolin on the expression of the simian virus-40 T-antigen controlled by the rat insulin II promoter in beta TC1 cells. IBMX and forskolin inhibited the serum-induced accumulation of simian virus-40 T-antigen mRNA in quiescent as well as exponentially growing beta TC1 cells.

Cell cycle and gene expression in the insulin producing pancreatic cell line beta TC1.

The pancreatic cell line beta TC1, established from insulinomas of transgenic mice carrying a hybrid insulin-promoted large T antigen gene, has retained several characteristics of normal cells, including the insulin content and inducibility of insulin secreting by glucose. We show here that the growth of beta TC1 cells is arrested in low serum-concentration medium. Cells exposed for three days to 0.25% fetal calf serum ceased to incorporate [3H]thymidine but were still able to resume the cell division cycle upon addition of serum. In this cell line, we have determined by cytofluorometry the cell cycle kinetic parameters to be of 21 h, 10 h 30 min and 12 h for the G1, S and G2/M phases, respectively. Quiescent beta TC1 cells constitutively expressed the protooncogene c-jun that codes for the transcriptional factor AP1, as well as cdc2, another cell cycle-related gene. A large transient increase in the expression of the c-fos gene was obtained rapidly, 30 min after addition of serum and a similar increase in c-jun expression after one hour. Expression of the cdc2 gene was also enhanced to a lesser extent. The same effects were also observed in the presence of cycloheximide, thus proving that the expression of these three genes is directly stimulated by serum growth factors. Consequently, quiescent beta TC1 cells provide a good model for studying the short- and long-term effects of growth factors on Beta-cell proliferation.