A new methodology for precise cadmium isotope analyses of seawater

Previous studies have revealed considerable Cdisotope fractionations in seawater, which can be used tostudy the marine cycling of this micronutrient element. Thelow Cd concentrations that are commonly encountered innutrient-depleted surface seawater, however, pose a particularchallenge for precise Cd stable isotope analyses. In thisstudy, we have developed a new procedure for Cd isotopeanalyses of seawater, which is suitable for samples as largeas 20 L and Cd concentrations as low as 1 pmol/L. Theprocedure involves the use of a 111Cd–113Cd double spike,co-precipitation of Cd from seawater using Al(OH)3, andsubsequent Cd purification by column chromatography. Tosave time, seawater samples with higher Cd contents can beprocessed without co-precipitation. The Cd isotope analysesare carried out by multiple collector inductively coupledplasma mass spectrometry (MC-ICP-MS). The performanceof this technique was verified by analyzing multiplealiquots of a large seawater sample that was collected fromthe English Channel, the SAFe D1 seawater referencematerial, and several samples from the GEOTRACESAtlantic intercalibration exercise. The overall Cd yield ofthe procedure is consistently better than 85% and themethodology can routinely provide ?114/110Cd data with aprecision of about ±0.5 ? (2sd, standard deviation) when atleast 20–30 ng of natural Cd is available for analysis.However, even seawater samples with Cd contents of only1–3 ng can be analyzed with a reproducibility of about ±3to ±5 ?. A number of experiments were furthermoreconducted to verify that the isotopic results are accurate to within the quoted uncertainty

Genome-wide association study of antidepressant treatment-emergent suicidal ideation

Emergence of suicidal ideation (TESI) during treatment with antidepressants in major depression led to a black box warning. We performed a genome-wide association study to identify genetic markers, which increase the risk for this serious side effect. TESI was evaluated in depressed in-patients (N=397) and defined by an emergence of suicidal thoughts during hospitalization without suicidal thoughts at admission using the suicide item (3) of the Hamilton Depression Rating Scale. Genotype distribution of 405.383 single-nucleotide polymorphisms (SNPs) in patients with TESI (N=32/8.1%) was compared to patients without increase in suicidal ideation (N=329/82.9%) and to a subgroup never reported suicidal ideation (N=79/19.9%). Top results were analyzed in an independent sample (N=501). None variant reached genome-wide significance, the best associated SNP was rs1630535 (p-value=1.3 × 10−7). The top 79 SNPs could be analyzed in an independent sample, and 14 variants showed nominal significant association with the same risk allele in the replication sample. A discriminant analysis classifying patients using these 79 SNPs revealed a 91% probability to classify TESI vs non-TESI cases correctly in the replication sample. Although our data need to be interpreted carefully owing to the small numbers in both cohorts, they suggest that a combination of genetic markers might indeed be used to identify patients at risk for TESI.Andreas Menke, Katharina Domschke, Darina Czamara, Torsten Klengel, Johannes Hennings, Susanne Lucae, Bernhard T Baune, Volker Arolt, Bertram Müller-Myhsok, Florian Holsboer, and Elisabeth B Binde