From the Cover: Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites

Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight ¹⁵N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C–O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C–O bonding environments and nanoglobular organics with dominant aromatic and C–N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid.Primitive extraterrestrial materials, including unmetamorphosed carbonaceous chondrites, chondritic porous interplanetary dust particles (CP-IDPs), carbonaceous Antarctic micrometeorites, and material from comet 81P/Wild 2, contain isotopically anomalous carbonaceous matter typically enriched in D and/or ¹⁵N compared with the Earth and bulk meteorites (1–11). This carbonaceous matter occurs as diffuse material but also in the form of sub-µm– to µm-sized grains that are extremely enriched in D and/or ¹⁵N and therefore stand out in isotopic maps as so-called “hot spots.” These hot spots represent good candidates to study ancient organic compounds that may have served as precursors for the prebiotic history of the early Earth. In many, but not all, cases, the isotopic hot spots occur as so-called “nanoglobules,” which are observed as hollow or compact carbonaceous sub-µm spheres in a wide range of primitive extraterrestrial samples (e.g., refs. 11–16). The most widely accepted theory for the origins of the anomalies invokes exothermic ion–molecule isotope exchange reactions at very low temperatures (<25 K) in cold interstellar clouds or the outer reaches of the nascent solar nebula (e.g., refs. 6, 7, 17, and 18). A second possible mechanism for the observed ¹⁵N enrichments is N₂ self-shielding, in which optical depth effects lead to isotope-selective photodissociation (19–22), but the applicability of the N₂ self-shielding model to the observed ¹⁵N anomalies is still uncertain.Correlated isotopic and structural information on these organic grains is sparse. Secondary ion mass spectrometry (SIMS) at high spatial resolution [∼100 nm can be achieved by Cameca NanoSIMS instruments (23)] in combination with transmission electron microscopy (TEM) allows the analysis of both isotopic composition and electronic bonding configuration on a sub-µm scale. These investigations are important to understand the origins and evolution of complex organic compounds in ancient meteoritic materials that contributed to the organic inventory of early Earth. Such combined studies have so far been performed, e.g., on organic grains in the Tagish Lake meteorite (15, 24), IDPs (5, 13, 25), comet 81P/Wild 2 material (9, 10), insoluble organic matter (IOM) extracted from meteorites (11, 26), and matrix regions in Renazzo-type (CR) and Ivuna-type (CI) chondrites (27–29) all applying only standard TEM techniques. Recently, synchrotron X-ray absorption near-edge structure (XANES) analyses have been performed on these organic grains before further TEM investigations (e.g., refs. 10, 11, 26, and 30). These analyses can reveal the bonding configuration of organic grains with high energy resolution (∼0.1 eV) and relatively high spatial resolution (∼20 nm) (9).Functionality studies of IOM, IDPs, and comet 81P/Wild 2 material (e.g., refs. 2, 3, 5, 9–13, 16, 25, 26, 30, and 31) as well as combined isotope functionality studies (5, 11, 24, 26, 32) show that meteoritic IOM as well as cometary organics from IDPs and Wild 2 are relatively similar in their dominant functional group characteristics. The meteoritic IOM component can be quite complex but is in general characterized by three main bonding environments, i.e., aromatic C=C, aromatic ketone or aldehyde bonding, and carboxyl bonding (Table S1) (ref. 9 and references therein). The two latter bands can be assigned to the existence of C–O bonding environments. The IOM-like functionality represents a common reservoir from which other, chemically more complex or more polymerized organic compounds may have evolved. Models on the molecular structure of IOM from the CM carbonaceous chondrite Murchison agree well with this overall functional group chemistry, where small aromatic units are interconnected by aliphatic, oxygenated, and N-containing chains (33). A further component has been identified among organic grains, usually best preserved in nanoglobules (11, 12, 15, 16). The organic functionality of nanoglobules is in general also IOM-like but often more aromatic with stronger absorption at 285 eV. Some nanoglobules may derive from circumstellar settings as highly primitive polycyclic aromatic hydrocarbons (PAHs) (34) or form late on the parent bodies by aqueous alteration reactions. Cody et al. (35) have recently suggested that the bulk of IOM found in chondrites can be synthesized from soluble formaldehyde (H₂CO) moieties which evolve into more complex, aromatic units upon progressive polymerization by aqueous alteration on the parent body. This model was further supported by experimental work (36), but the role of anomalous nitrogen in these fluid scenarios has not been demonstrated yet on true samples. Furthermore, the resulting evolution of pristine organic matter with respect to electronic bonding configuration and chemical constitution in these synthesis models is still poorly constrained.We present here an alternative way to investigate these organic grains with superior spatial resolution, via the Nion UltraSTEM 100 analytical aberration-corrected scanning TEM (STEM) operated at a low acceleration voltage of 60 kV. The flexibility offered by this type of microscope is ideal for investigating organic grains. The instrument can be operated in so-called “gentle STEM” conditions (37) below the knock-on damage threshold for carbon [<∼80kV (38)], while retaining a much higher spatial resolution than X-ray techniques. Moreover, the probe current and electron dose can be tailored to minimize ionization damage (39). The microscope operates with a cold field emission electron source achieving an energy spread of only ∼0.3 eV without a monochromator. This energy resolution is only marginally worse than synchrotron XANES while still maintaining a very high spatial resolution (∼0.1 nm at 60 kV). We used the UltraSTEM to observe and analyze eight isotopically anomalous organic grains identified by NanoSIMS ion imaging within four different primitive extraterrestrial samples: two CR2 chondrites, Northwest Africa (NWA) 852 and the Antarctic Graves Nunataks (GRA) 95229, and two IDPs. Both IDPs in this study are from the L2036 collector (cluster 20, AK 5 and 6, IDP AK5, and IDP AK6) (Table S2 and Materials and Methods). The STEM data provide combined morphological and structural details of isotopically anomalous organic grains with electronic bonding configuration analyses by electron energy loss spectroscopy (EELS). Our results provide the first direct observational evidence to our knowledge for an alteration scenario of anomalous organics on the CR parent body and how the two organic components described above can be linked by transformation reactions.     

In 6- to 8-year-old children,cardiorespiratory fitness moderates the relationship between severity of life events and health-related quality of life

Purpose

In children, the pathways by which physical activity and fitness are associated with physical and psychological wellbeing are still not fully understood. The present study examines for the first time in young children whether high levels of cardiorespiratory fitness and physical activity moderate the relationship between severity of life events and health-related quality of life.

Methods

Three hundred and seventy-eight children (188 girls, 190 boys, M _age = 7.27 years) participated in this cross-sectional study. Parental education, gender, age, severity of life events, health-related quality of life and physical activity were assessed via parental questionnaires. Cardiorespiratory fitness was assessed with the 20 m shuttle run test. Hierarchical regression analyses were used to test whether physical activity and fitness interacted with critical life events to explain health-related quality of life.

Results

When exposed to critical life events, children with higher fitness levels experienced higher levels of psychological wellbeing, relative to their less fit peers. On the other hand, children with higher fitness levels experienced higher physical wellbeing and more positive friendship relationships when severity of life events was low. A similar moderation effect was found for physical activity with overall quality of life as outcome.

Conclusions

Recent stressful experiences alone were not sufficient to explain negative health outcomes in young children. Children with low cardiorespiratory fitness levels experienced lower psychological wellbeing when they were exposed to critical life events. More research is needed to find out whether similar findings emerge with objective physical activity measurements and when critical life events are assessed over longer periods of time.

     

Defective B cell tolerance in adenosine deaminase deficiency is corrected by gene therapy

Adenosine deaminase (ADA) gene defects are among the most common causes of SCID. Restoration of purine metabolism and immune functions can be achieved by enzyme replacement therapy, or more effectively by bone marrow transplant or HSC gene therapy (HSC-GT). However, autoimmune complications and autoantibody production, including anti-nuclear antibodies (ANAs), frequently occur in ADA-SCID patients after treatment. To assess whether ADA deficiency affects the establishment of B cell tolerance, we tested the reactivity of recombinant antibodies isolated from single B cells of ADA-SCID patients before and after HSC-GT. We found that before HSC-GT, new emigrant/transitional and mature naive B cells from ADA-SCID patients contained more autoreactive and ANA-expressing clones, indicative of defective central and peripheral B cell tolerance checkpoints. We further observed impaired B cell receptor (BCR) and TLR functions in B cells after ADA inhibition, which may underlie the defects in B cell tolerance. Strikingly, after HSC-GT, ADA-SCID patients displayed quasi-normal early B cell tolerance checkpoints, as evidenced by restored removal of developing autoreactive and ANA-expressing B cells. Hence, ADA plays an essential role in controlling autoreactive B cell counterselection by regulating BCR and TLR functions.     

Activated memory B cells may function as antigen‐presenting cells in the joints of children with juvenile idiopathic arthritis

Objective

B cells impact the perpetuation of chronic inflammatory or autoimmune diseases in multiple ways. A role of B cells as antigen‐presenting cells (APCs) in the pathogenesis of chronic arthritis in humans has been suggested; however, as of yet the presence of such B cells at the site of inflammation has not been demonstrated. This study was undertaken to investigate whether synovial B cells in patients with juvenile idiopathic arthritis (JIA) might display features of APCs.

Methods

The frequency, phenotype, and immunoglobulin repertoire of synovial B cells were studied by flow cytometry and single‐cell polymerase chain reaction (PCR). Cytokine expression by B cells was analyzed by real‐time PCR, and interaction between B cells and T cells was investigated in a mixed lymphocyte culture.

Results

CD27+IgD− and CD27−IgD− B cells accumulated in the joints of JIA patients and displayed an activated phenotype. Both B cell subsets expressed hypermutated and class‐switched immunoglobulins, indicators of memory B cells. The accumulating memory B cells expressed the costimulatory molecules CD80/CD86 and showed a higher capacity to activate allogeneic T cells and prime a Th1 phenotype than their peripheral blood counterparts.

Conclusion

Activated immunoglobulin class–switched CD27− and CD27+ memory B cells, indicating a phenotype of APCs with expression of costimulatory molecules, accumulate in the joints of patients with JIA and might be involved in the amplification of pathogenic T cell activation. These findings provide evidence that B cells play an antibody‐independent immunopathologic role in human chronic inflammatory arthritis of childhood.

     

Polarity and intracellular compartmentalization of Drosophila neurons

Background

The choice of a stem cell to divide symmetrically or asymmetrically has profound consequences for development and disease. Unregulated symmetric division promotes tumor formation, whereas inappropriate asymmetric division affects organ morphogenesis. Despite its importance, little is known about how spindle positioning is regulated. In some tissues cell fate appears to dictate the type of cell division, whereas in other tissues it is thought that stochastic variation in spindle position dictates subsequent sibling cell fate.

Results

Here we investigate the relationship between neural progenitor identity and spindle positioning in the Drosophila optic lobe. We use molecular markers and live imaging to show that there are two populations of progenitors in the optic lobe: symmetrically dividing neuroepithelial cells and asymmetrically dividing neuroblasts. We use genetically marked single cell clones to show that neuroepithelial cells give rise to neuroblasts. To determine if a change in spindle orientation can trigger a neuroepithelial to neuroblast transition, we force neuroepithelial cells to divide along their apical/basal axis by misexpressing Inscuteable. We find that this does not induce neuroblasts, nor does it promote premature neuronal differentiation.

Conclusion

We show that symmetrically dividing neuroepithelial cells give rise to asymmetrically dividing neuroblasts in the optic lobe, and that regulation of spindle orientation and division symmetry is a consequence of cell type specification, rather than a mechanism for generating cell type diversity.     

RO4938581, a novel cognitive enhancer acting at GABAA α5 subunit-containing receptors

Rationale

GABA_A α5 subunit-containing receptors are primarily expressed in the hippocampus and their role in learning and memory has been demonstrated recently by both genetic and pharmacological approaches.

Objectives

The objective of the study is to evaluate the cognitive effects of a novel GABA_A α5 receptor inverse agonist, RO4938581 in rats and monkeys.

Materials and methods

The in vitro profile was determined using radioligand binding and electrophysiological assays for the GABA_A α1, α2, α3, and α5 receptors. Long-term potentiation (LTP) was performed in mouse hippocampal slices. Cognitive effects were assessed in rats in the delayed match to position (DMTP) task and the Morris water maze. In monkeys, the object retrieval task was used. Pro-convulsant and anxiogenic potentials were evaluated in mice and rats. In vivo receptor occupancy was determined using [³H]-RO0154513.

Results

RO4938581 is a potent inverse agonist at the GABA_A α5 receptor, with both binding and functional selectivity, enhancing hippocampal LTP. RO4938581 reversed scopolamine-induced working memory impairment in the DMTP task (0.3–1 mg/kg p.o.) and diazepam-induced spatial learning impairment (1–10 mg/kg p.o.). RO4938581 improved executive function in monkeys (3-10 mg/kg p.o.). Importantly, RO4938581 showed no anxiogenic and pro-convulsive potential. RO4938581 dose-dependently bound to GABA_A α5 receptors and approximately 30% receptor occupancy was sufficient to produce enhanced cognition in the rat.

Conclusions

The data further support the potential of GABA_A α5 receptors as a target for cognition-enhancing drugs. The dual binding and functional selectivity offers an ideal profile for cognition-enhancing effects without the unwanted side effects associated with activity at other GABA_A receptor subtypes.     

Sediment-contact fish embryo toxicity assay with Danio rerio to assess particle-bound pollutants in the Tietê River Basin (São Paulo, Brazil)

The Tietê River and its tributary Pinheiros River receive a highly complex organic and inorganic pollutants load from sanitary sewage and industrial sources, as well as agricultural and agroindustrial activities. The aim of the present study was to evaluate the embryotoxic and teratogenic effects of sediments from selected locations in the Tietê River Basin by means of the sediment contact embryo toxicity assay with Danio rerio, in order to provide a comprehensive and realistic insight into the bioavailable hazard potential of these sediment samples. Lethal and sub-lethal effects were recorded, and high embryo toxicity could be found in the samples not only in the vicinity of the megacity São Paulo (Billings reservoir and Pinheiros River samples), but also downstream (in the reservoirs Barra Bonita, Promissão and Três Irmãos). Results confirm that most toxicity is due to the discharges of the metropolitan area of São Paulo. However, they also indicate additional sources of pollutants along the river course, probably from industrial, agricultural and agroindustrial residues, which contribute to the degradation of each area. The sediment contact fish embryo test showed to be powerful tool to detect embryo toxicity in sediments, not only by being a sensitive method, but also for taking into account bioavailability. This test provides an ecological highly realistic and relevant exposure scenario, and should therefore be added in ecotoxicological sediment quality assessments.