A forward genetic screen to identify hydrogenase-deficient mutants in the unicellular green alga Chlamydomonas reinhardtii

The ability of the unicellular green alga Chlamydomonas reinhardtii to evolve molecular hydrogen (H2) is due to the presence of oxygen-sensitive Fe-hydrogenases (HydA1/2), expressed in anoxic conditions that drive the photosynthetic electron flow to reduce protons into H2. In order to identify new players involved in H2 photoproduction in Chlamydomonas, an insertion mutant library was generated using cassettes conferring resistance to hygromycin or paromomycin. Hydrogenase activity is physiologically relevant during a transition from dark anoxia to light. In dark anoxic conditions, the cellular redox poise is high and the photosynthetic electron transport chain is fully reduced. Upon illumination, hydrogenase activity allows the reoxidation of photosynthetic intersystem electron carriers until oxic conditions and carbon fixation ability are restored. We thus designed an in vivo fluorescence imaging screen based on the different kinetics of photosynthesis induction between wild type and hydrogenase-deficient mutants [1]. At this stage, three putative hydrogenase mutants have been identified on 10,000 transformants. Molecular characterization of the insertion site of the resistance cassette by TAIL-PCR and genetic analyses of the linkage between the antibiotic resistance and the fluorescence phenotype showed that one mutant was untagged with the resistance while two tagged mutants were deficient for the HydG assembly factor

3D modelling of long-term sulfide corrosion of copper canisters in a spent nuclear fuel repository

Copper canisters are a central component in the safety of the Finnish spent fuel repository concept (KBS-3), where the main corrodent potentially affecting the canister integrity is sulfide. In this study, a 3D numerical model is developed to assess the evolution of sulfide fluxes and the spatially resolved canister corrosion depths for the Finnish spent nuclear fuel repository concept. The backfilled tunnel and the disposal hole are implemented using repository geometries, with sulfide being produced at their interface with the rock (excavation damaged zone) by sulfate reducing bacteria (SRB). Recent experimental findings regarding the microbial sulfate reduction process as well as the scavenging of sulfide via iron (oxy)hydroxides are incorporated in the reactive transport model. Long-term simulations are performed, predicting a heterogeneous corrosion of the canister with a max. corrosion depth of 1.3 mm at the bottom corner after one million years. The evolution of sulfide fluxes shows two main phases, depending on the source of sulfate: first sulfate is supplied by the dissolution of gypsum from the bentonite barriers, followed by a steady, low-level supply from the groundwater. Sensitivity cases demonstrate that both the organic carbon and Fe(III) oxide contents in the bentonite are critical to the corrosion evolution, by being the main electron donor for SRB activities and the major sulfide scavenger in the bentonite, respectively. The backfilled tunnel contributes little to the flux of corrosive sulfide to the canister due to the attenuation by Fe(III)-oxides/hydroxides but induces a notable flux of sulfate into the disposal hole

Dramatically Increased Rearrangement and Peripheral Representation of Vβ14 Driven by the 3′Dβ1 Recombination Signal Sequence

AbstractV(D)J recombination is targeted by short recombination signal (RS) sequences that are relatively conserved but exhibit natural sequence variations. To evaluate the potential of RS sequence variations to determine the primary and peripheral TCRβ repertoire, we generated mice containing specific replacement of the endogenous Vβ14 RS with the 3′Dβ1 RS (Vβ14/3′DβRS). These mice exhibited a dramatic increase in Vβ14+ thymocyte numbers at the expense of thymocytes expressing other Vβs. In addition, the percentage of peripheral Vβ14+ αβ T lymphocytes was similarly increased. Strikingly, this altered Vβ repertoire resulted predominantly from a higher relative level of primary Vβ14/3′DβRS rearrangement to DβJβ complexes, despite the ability of the 3′Dβ1 RS to break B12/23 restriction and allow direct rearrangement of Vβ14/3′DβRS to Jβ segments

Neonatal sex reversal of the brain and the urinary excretion of sex dependent proteins (SDP) in the rat

In contrast to females adult male rats excrete a variety of low molecular weight sex dependent urinary proteins (SDP). Electrophoretic separation of these proteins yields at least 8 protein bands which are arranged in typical patterns. The present study was performed to investigate the effert of sexual differentiation, which can be influenced by neonatal hormone treatment, on production and excretion of the individual SDP-bands (I - VIII). Two major groups of rats were studied: one group was neonatally treated with testosterone propionate (TP, females) or cyproterone acetate (males). Another group of rats with or without neonatal TP-treatment were gonadectomized in adulthood and subsequently implanted with TP. The results demonstrated that SDP excretion is mainly related to the circulating plasma testosterone levels. The sexual differentiation of the brain, however, influences the quantity of SDP excreted which is especially evident for bands I and II. Neonatal cyproterone had influence on these two bands only. The results demonstrate that the hormonal mechanisms regulating tho excretion of SDP varies in respect to the different protein bands. The functional role of sexual brain differentiation on the excretion of SDP and the detailed mechanisms by which the brain may control this extcretion remain to be determined

Embryonic Lethality in Mice Homozygous for a Targeted Disruption of the N-myc Gene

The N-myc gene encodes a putative transcription factor that is thought to function in the regulation of gene expression during cell differentiation and/or growth. To examine the role of N-myc during development, we have used targeted mutagenesis in embryonic stem cells to produce a mouse line that carries an N-myc null allele. Mice homozygous for the mutation died between 10.5 and 12.5 days of gestation. Histological analysis of mutant embryos revealed that organs and tissues expected at these stages of development were present. However, multiple defects were observed, primarily in tissues and organs that normally express N-myc. In particular, mutant hearts were underdeveloped, often retaining the S-shape more typical of 9-day-old embryos. In addition, cranial and spinal ganglia were reduced in size and/or cellularity. Most of the noted defects were more consistent with a role of N-myc in proliferation of precursor populations than with a block in differentiation per se, at least at these early stages. These results demonstrate that N-myc plays an essential role during development and clearly confirm that N-myc has a physiological function that is distinct from that of the other myc-family genes

The Basel-Gasfabrik research project: Addressing complex topics by an integrative approach

The late La Tène period site of Basel-Gasfabrik has been under investigation for more than a century. During that time, the unfortified settlement with its two cemeteries has yielded huge amounts of everyday and exceptional objects and features. Beginning in the mid-1970s, samples were systematically collected for scientific analyses during ongoing excavations, thus producing ideal preconditions for interdisciplinary research. In 2011-2014, the international research project “Approaching the living via the dead: human remains from the Late La Tène site Basel-Gasfabrik and their cultural-historical interpretations” addressed the multifarious ways in which the Iron Age community handled their deceased. The intense collaboration involved researchers from the Archäologische Bodenforschung Basel-Stadt and the universities of Basel (CH), Mainz and Freiburg i.Br. (D) and spanned eight disciplines: archaeology, archeoanthropology, archaeobotany, archaeozoology, geoarchaeology, biogeochemistry, molecular genetics and statistics. Research topics and theoretical frameworks were developed jointly as well as procedures to combine the disciplinary results in multistage processes in order to generate integrative syntheses of novel insights. The challenges and specific research potentials of the integrative approach may serve as a positive example for future interdisciplinary research project

No increased injury incidence in the German Bundesliga after the SARS-CoV-2 virus lockdown

Introduction The coronavirus lockdown in 2020 resulted in a worldwide suspension of professional sports. The first major professional football league to restart after the lockdown was the German Bundesliga. This study investigates whether the injury incidence increased after the restart of the season with only 9 days of regular preparation time and without any friendly matches in comparison to three control periods. Materials and methods In a prospective cohort study, injury analysis (at least 1 day of absence from official football matches or training sessions) of the German Bundesliga registry was standardised according to Hägglund et al. (Br J Sports Med 39:340–346, 2005) and Fuller et al. (Clin J Sports Med 16:97–106, 2006) for data collection and to previous publications for the validated use of media sources for injury registration. The study period after the lockdown in May and June of the 2019–2020 season was compared to three control periods: the period directly before the lockdown, the beginning of the 2019–2020 season and the 2018–2019 season final. Results The nine match days after the restart of the 2019–2020 season showed an overall injury incidence of 4.9 per 1000 h football. This rate was significantly lower than that of the previous season final (9 last match days, overall injury incidence: 6.9 per 1000 h football; p  0.05) or the winter break (8 match days; incidence: 5.6/1000 h, p > 0.05). Conclusion The period after the unexpected break in the 2019–2020 season due to the coronavirus lockdown and the rapid return to competition showed no increase in the injury rate compared to the pre-lockdown period and a lower injury rate than in the previous season final. The unintentional mid-season rest with its potential for physical recovery and individual fitness training seems to have had a positive effect on injury occurrence

Ancient DNA from European Early Neolithic Farmers Reveals Their Near Eastern Affinities

The first farmers from Central Europe reveal a genetic affinity to modern-day populations from the Near East and Anatolia, which suggests a significant demographic input from this area during the early Neolithic