University of Hamburg

About: University of Hamburg is a education organization based out in Hamburg, Germany. It is known for research contribution in the topics: Population & Laser. The organization has 45564 authors who have published 89286 publications receiving 2850161 citations. The organization is also known as: Hamburg University.

Biogeographic Evolution of Madagascar's Microendemic Biota

Abstract: The endemic species richness on Madagascar, relative to landmass area, is unparalleled in the world. Many organisms on the island have restricted geographical ranges. A comprehensive hypothesis explaining the evolution of this microendemism has yet to be developed. Using an analysis of watersheds in the context of Quaternary climatic shifts, we provide a new mechanistic model to explain the process of explosive speciation on the island. River catchments with sources at relatively low elevations were zones of isolation and hence led to the speciation of locally endemic taxa, whereas those at higher elevations were zones of retreat and dispersion and hence contain proportionately lower levels of microendemism. These results provide a framework for biogeographic and phylogeographic studies, as well as a basis for prioritizing conservation actions of the remaining natural forest habitats on the island.

Mutations in GRIN2A and GRIN2B encoding regulatory subunits of NMDA receptors cause variable neurodevelopmental phenotypes.

Abstract: N-methyl-D-aspartate (NMDA) receptors mediate excitatory neurotransmission in the mammalian brain. Two glycine-binding NR1 subunits and two glutamate-binding NR2 subunits each form highly Ca²(+)-permeable cation channels which are blocked by extracellular Mg²(+) in a voltage-dependent manner. Either GRIN2B or GRIN2A, encoding the NMDA receptor subunits NR2B and NR2A, was found to be disrupted by chromosome translocation breakpoints in individuals with mental retardation and/or epilepsy. Sequencing of GRIN2B in 468 individuals with mental retardation revealed four de novo mutations: a frameshift, a missense and two splice-site mutations. In another cohort of 127 individuals with idiopathic epilepsy and/or mental retardation, we discovered a GRIN2A nonsense mutation in a three-generation family. In a girl with early-onset epileptic encephalopathy, we identified the de novo GRIN2A mutation c.1845C>A predicting the amino acid substitution p.N615K. Analysis of NR1-NR2A(N615K) (NR2A subunit with the p.N615K alteration) receptor currents revealed a loss of the Mg²(+) block and a decrease in Ca²(+) permeability. Our findings suggest that disturbances in the neuronal electrophysiological balance during development result in variable neurological phenotypes depending on which NR2 subunit of NMDA receptors is affected.

Olaparib combined with chemotherapy for recurrent platinum-sensitive ovarian cancer: a randomised phase 2 trial

Abstract: Summary Background The poly(ADP-ribose) polymerase inhibitor olaparib has shown antitumour activity in patients with platinum-sensitive, recurrent, high-grade serous ovarian cancer with or without BRCA1 or BRCA2 mutations. The aim of this study was to assess the efficacy and tolerability of olaparib in combination with chemotherapy, followed by olaparib maintenance monotherapy, versus chemotherapy alone in patients with platinum-sensitive, recurrent, high-grade serous ovarian cancer. Methods In this randomised, open-label, phase 2 study, adult patients with platinum-sensitive, recurrent, high-grade serous ovarian cancer who had received up to three previous courses of platinum-based chemotherapy and who were progression free for at least 6 months before randomisation received either olaparib (200 mg capsules twice daily, administered orally on days 1–10 of each 21-day cycle) plus paclitaxel (175 mg/m 2 , administered intravenously on day 1) and carboplatin (area under the curve [AUC] 4 mg/mL per min, according to the Calvert formula, administered intravenously on day 1), then olaparib monotherapy (400 mg capsules twice daily, given continuously) until progression (the olaparib plus chemotherapy group), or paclitaxel (175 mg/m 2 on day 1) and carboplatin (AUC 6 mg/mL per min on day 1) then no further treatment (the chemotherapy alone group). Randomisation was done by an interactive voice response system, stratified by number of previous platinum-containing regimens received and time to disease progression after the previous platinum regimen. The primary endpoint was progression-free survival according to Response Evaluation Criteria in Solid Tumors version 1.1, analysed by intention to treat. Prespecified exploratory analyses included efficacy by BRCA mutation status, assessed retrospectively. This study is registered with ClinicalTrials.gov, number NCT01081951, and has been completed. Findings Between Feb 12 and July 30, 2010, 173 patients at 43 investigational sites in 12 countries were enrolled into the study, of whom 162 were eligible and were randomly assigned to the two treatment groups (81 to the olaparib plus chemotherapy group and 81 to the chemotherapy alone group). Of these randomised patients, 156 were treated in the combination phase (81 in the olaparib plus chemotherapy group and 75 in the chemotherapy alone group) and 121 continued to the maintenance or no further treatment phase (66 in the olaparib plus chemotherapy group and 55 in the chemotherapy alone group). BRCA mutation status was known for 107 patients (either at baseline or determined retrospectively): 41 (38%) of 107 had a BRCA mutation (20 in the olaparib plus chemotherapy group and 21 in the chemotherapy alone group). Progression-free survival was significantly longer in the olaparib plus chemotherapy group (median 12·2 months [95% CI 9·7–15·0]) than in the chemotherapy alone group (median 9·6 months [95% CI 9·1–9·7) (HR 0·51 [95% CI 0·34–0·77]; p=0·0012), especially in patients with BRCA mutations (HR 0·21 [0·08–0·55]; p=0·0015). In the combination phase, adverse events that were reported at least 10% more frequently with olaparib plus chemotherapy than with chemotherapy alone were alopecia (60 [74%] of 81 vs 44 [59%] of 75), nausea (56 [69%] vs 43 [57%]), neutropenia (40 [49%] vs 29 [39%]), diarrhoea (34 [42%] vs 20 [27%]), headache (27 [33%] vs seven [9%]), peripheral neuropathy (25 [31%] vs 14 [19%]), and dyspepsia (21 [26%] vs 9 [12%]); most were of mild-to-moderate intensity. The most common grade 3 or higher adverse events during the combination phase were neutropenia (in 35 [43%] of 81 patients in the olaparib plus chemotherapy group vs 26 [35%] of 75 in the chemotherapy alone group) and anaemia (seven [9%] vs five [7%]). Serious adverse events were reported in 12 (15%) of 81 patients in the olaparib plus chemotherapy group and 16 of 75 (21%) patients in the chemotherapy alone group. Interpretation Olaparib plus paclitaxel and carboplatin followed by maintenance monotherapy significantly improved progression-free survival versus paclitaxel plus carboplatin alone, with the greatest clinical benefit in BRCA -mutated patients, and had an acceptable and manageable tolerability profile. Funding AstraZeneca.

amoA-based consensus phylogeny of ammonia-oxidizing archaea and deep sequencing of amoA genes from soils of four different geographic regions.

Abstract: Ammonia-oxidizing archaea (AOA) play an important role in nitrification and many studies exploit their amoA genes as marker for their diversity and abundance. We present an archaeal amoA consensus phylogeny based on all publicly available sequences (status June 2010) and provide evidence for the diversification of AOA into four previously recognized clusters and one newly identified major cluster. These clusters, for which we suggest a new nomenclature, harboured 83 AOA species-level OTU (using an inferred species threshold of 85% amoA identity). 454 pyrosequencing of amoA amplicons from 16 soils sampled in Austria, Costa Rica, Greenland and Namibia revealed that only 2% of retrieved sequences had no database representative on the species-level and represented 30–37 additional species-level OTUs. With the exception of an acidic soil from which mostly amoA amplicons of the Nitrosotalea cluster were retrieved, all soils were dominated by amoA amplicons from the Nitrososphaera cluster (also called group I.1b), indicating that the previously reported AOA from the Nitrosopumilus cluster (also called group I.1a) are absent or represent minor populations in soils. AOA richness estimates on the species level ranged from 8–83 co-existing AOAs per soil. Presence/absence of amoA OTUs (97% identity level) correlated with geographic location, indicating that besides contemporary environmental conditions also dispersal limitation across different continents and/or historical environmental conditions might influence AOA biogeography in soils.