Apparent Depletion Research Articles

Bioaccumulation and sub-lethal physiological effects of metal mixtures on mussel, Mytilus edulis: Continuous exposure to a binary mixture of mercury and cadmium

In the natural ecosystem, aquatic organisms are exposed to a cocktail of chemicals that may result in toxicological responses differing from those of individual chemicals. In the present study, mussels were exposed using a semi-static and triplicated design to either control (no added metal), 50 µg l−1 (Hg alone), 50 µg l−1 (Cd alone), or 50 µg l−1 Hg plus 50 µg l−1 Cd (Hg + Cd) mixture for 14 days. Tissues were collected on days 0, 2, 4, 8, and 14 for metal analysis and sub-lethal responses using a suite of assays. Tissue metal concentrations were not significantly different in the single metal (Hg or Cd) compared to the Hg plus Cd mixture treatment for all tissues, apart from the gill of the Cd alone treatment. At the end of the experiment, the gill Cd concentration was significantly increased in the Hg plus Cd mixture compared to the Cd alone treatment, suggesting the influence of Hg on Cd uptake. The percentage increases of the Hg plus Cd mixture compared to the arithmetic sum of the individual metals were ( %): 20.2, 9.3, 25.1, 23.8, 10.7, and 12.4 for adductor muscle, digestive gland, gill, gonad, remaining soft tissue, and haemolymph, respectively. There were no observed treatment effects on total haemocyte count, haemolymph protein, or glucose concentration in the cell-free haemolymph. Neither was there any treatment effect on osmotic pressure, ions in the tissues, or in the cell-free haemolymph. At the end of the experiment, Hg-mediated oxidative damage, as an increase of thiobarbituric reactive substances (TBARS) and apparent depletion of total glutathione. This was observed in the gill and digestive gland of the Hg alone and Hg plus Cd mixture. Histopathology examination showed similar pathology in the Hg alone and the Hg plus Cd treatment. In conclusion, despite some oxidative stress and pathology during metal exposure, the accumulation of metals and effects on mussel health were similar between single exposures and a mixture of Hg plus Cd. In terms of risk assessment, regulations for the individual metals should suffice to protect against the mixture of Hg plus Cd, at least for adult M. edulis in full-strength seawater.

Energetic processing of thioacetamide in cryogenic matrices.

There is an ongoing debate on the apparent depletion of sulfur in the interstellar medium (ISM) compared to its universal abundance; therefore, the investigation of sulfurous compounds at low temperatures is of utmost importance. This work aims to study thioacetamide, H3C-C(=S)-NH2, in low-temperature inert Ar and para-H2 matrices by IR spectroscopy. The samples have been exposed to various sources of irradiation, such as Lyman-α or laser UV photons as well as energetic electrons. Using different host materials enabled assessing the matrix's impact on precursor decomposition. The response of the molecule to different types of irradiation has also been evaluated. The existence of three main decomposition channels were deduced: formation of (i) CH3, CH4, and HNCS; (ii) H2S and H2C=C=NH; and (iii) NH3 and H2C=C=S. The H3C-CN and H3C-NC isomers of H2C=C=NH could also be identified. Secondary products such as HNC and HCN were also detected in the quantum solid para-H2 in contrast to the more rigid Ar matrix. The listed decomposition products have been observed in the ISM, with the exception of H2C=C=NH and H3C-NC. The results point to the potential sensitivity of the precursor molecule to energetic radiation in space environments. Finally, the findings of this work will serve as a foundation for future irradiation experiments using the astrochemically more relevant pure thioacetamide ice.

Antimicrobial efficacy of magnetite nanoparticles against Aeromonas sobria challenge in African catfish: Biochemical, protein profile, and immuno-antioxidant indices

Recently, researchers in aquaculture become interested in green synthesized nanomaterials as a superior alternative to current conventional methodologies. The present work shows that Moringa oleifera synthesized magnetite nanoparticles (MS-Fe3O4NPs) might offer a possible substitute for common antibiotics to treat Aeromonas sobria infection in African catfish (Clarias gariepinus). MS-Fe3O4NPs demonstrated an in vitro antibacterial potential (21 mm inhibition zone) against A. sobria. The fish (n = 120; average body weight: 90 ± 3.5 g) were randomized into four groups (control, MS-Fe3O4NPs, A. sobria, and MS-Fe3O4NPs + A. sobria), where 1.2 mg/L of MS-Fe3O4NPs was used as bath treatment for seven-days. A. sobria infection caused substantial elevations in malondialdehyde, tumor necrosis factor-alpha, stress indices, and hepato-renal biomarkers as well as a lower survival rate. Moreover, an apparent depletion in the level of antioxidants, the protein profile, and immune indicators were the consequences of A. sobria infection. Surprisingly, treatment of A. sobria-infected fish with MS-Fe3O4NPs recovered these parameters. Hence, MS-Fe3O4NPs as a water additive show promise as an antibacterial treatment against A. sobria in fish.

RNA polymerase II depletion from the inactive X chromosome territory is not mediated by physical compartmentalization.

Subnuclear compartmentalization has been proposed to play an important role in gene regulation by segregating active and inactive parts of the genome in distinct physical and biochemical environments. During X chromosome inactivation (XCI), the noncoding Xist RNA coats the X chromosome, triggers gene silencing and forms a dense body of heterochromatin from which the transcription machinery appears to be excluded. Phase separation has been proposed to be involved in XCI, and might explain the exclusion of the transcription machinery by preventing its diffusion into the Xist-coated territory. Here, using quantitative fluorescence microscopy and single-particle tracking, we show that RNA polymerase II (RNAPII) freely accesses the Xist territory during the initiation of XCI. Instead, the apparent depletion of RNAPII is due to the loss of its chromatin stably bound fraction. These findings indicate that initial exclusion of RNAPII from the inactive X reflects the absence of actively transcribing RNAPII, rather than a consequence of putative physical compartmentalization of the inactive X heterochromatin domain.

Seasonal Dynamics of Primary Production in the Southeastern Bering Sea Assessed Using Continuous Temporal and Vertical Dissolved Oxygen and Chlorophyll‐a Measurements

AbstractThe Bering Sea and other high‐latitude systems are experiencing unprecedented changes related to climate warming and the consequent loss of sea ice. Understanding how such changes influence primary production is a pressing question. Here, we quantify primary production rates in the southeastern Bering Sea over 4 years (2016–2019) at daily to weekly time resolution. A moored high‐resolution Profiling Crawler was used in combination with in situ sampling to collect physical and biological data in the ocean's upper 50 m. We used dissolved oxygen (O2) data to estimate gross and net primary production (NPP), and chlorophyll‐a (Chl‐a), temperature, and irradiance data to model NPP rates. We then assessed seasonal variation in phytoplankton production rates, phytoplankton community growth rates () and explored to what extent summer phytoplankton community growth rates may be influenced by nitrogen limitation. Our analyses revealed that the majority of gross primary production (GPP) and net community production occurs in association with the spring phytoplankton bloom. After the bloom, the water column generally experienced low GPP and net biological carbon consumption. Phytoplankton growth rates were commonly suppressed in late summer due to apparent nitrogen depletion. Using high temporal resolution vertically resolved measurements of O2 and Chl‐a, our analyses provides important insight into how biogeochemical cycles, phytoplankton community growth rates, and carbon available for export vary seasonally in the southeastern Bering Sea.

Neural network for determining an asteroid mineral composition from reflectance spectra

Context.Chemical and mineral compositions of asteroids reflect the formation and history of our Solar System. This knowledge is also important for planetary defence and in-space resource utilisation. In the next years, space missions will generate extensive spectral datasets from asteroids or planets with spectra that will need to be processed in real time.Aims.We aim to develop a fast and robust neural-network-based method for deriving the mineral modal and chemical compositions of silicate materials from their visible and near-infrared spectra. The method should be able to process raw spectra without significant pre-processing.Methods.We designed a convolutional neural network with two hidden layers for the analysis of the spectra, and trained it using labelled reflectance spectra. For the training, we used a dataset that consisted of reflectance spectra of real silicate samples stored in the RELAB and C-Tape databases, namely olivine, orthopyroxene, clinopyroxene, their mixtures, and olivine-pyroxene-rich meteorites.Results.We used the model on two datasets. First, we evaluated the model reliability on a test dataset where we compared the model classification with known compositional reference values. The individual classification results are mostly within 10 percentage-point intervals around the correct values. Second, we classified the reflectance spectra of S-complex (Q-type and V-type, also including A-type) asteroids with known Bus–DeMeo taxonomy classes. The predicted mineral chemical composition of S-type and Q-type asteroids agree with the chemical composition of ordinary chondrites. The modal abundances of V-type and A-type asteroids show a dominant contribution of orthopyroxene and olivine, respectively. Additionally, our predictions of the mineral modal composition of S-type and Q-type asteroids show an apparent depletion of olivine related to the attenuation of its diagnostic absorptions with space weathering. This trend is consistent with previous results of the slower pyroxene response to space weathering relative to olivine.Conclusions.The neural network trained with real silicate samples and their mixtures is applicable for a quantitative mineral evaluation of spectra of asteroids that are rich in dry silicates. The modal abundances and mineral chemistry of common silicates (olivine and pyroxene) can be derived with an accuracy better than 10 percentage points. The classification is fast and has a relatively small computer-memory footprint. Therefore, our code is suitable for processing large spectral datasets in real time.

Abundant ammonium hydrosulphide embedded in cometary dust grains

ABSTRACT Ammonium hydrosulphide has long since been postulated to exist at least in certain layers of the giant planets. Its radiation products may be the reason for the red colour seen on Jupiter. Several ammonium salts, the products of NH3, and an acid have previously been detected at comet 67P/Churyumov-Gerasimenko. The acid H2S is the fifth most abundant molecule in the coma of 67P followed by NH3. In order to look for the salt NH4+SH−, we analysed in situ measurements from the Rosetta/ROSINA Double Focusing Mass Spectrometer during the Rosetta mission. NH3 and H2S appear to be independent of each other when sublimating directly from the nucleus. However, we observe a strong correlation between the two species during dust impacts, clearly pointing to the salt. We find that NH4+SH− is by far the most abundant salt, more abundant in the dust impacts than even water. We also find all previously detected ammonium salts and for the first time ammonium fluoride. The amount of ammonia and acids balance each other, confirming that ammonia is mostly in the form of salt embedded into dust grains. Allotropes S2 and S3 are strongly enhanced in the impacts, while H2S2 and its fragment HS2 are not detected, which is most probably the result of radiolysis of NH4+SH−. This makes a prestellar origin of the salt likely. Our findings may explain the apparent depletion of nitrogen in comets and maybe help to solve the riddle of the missing sulphur in star-forming regions.

Mechanisms of density dependence in juvenile salmonids: prey depletion, interference competition, or energy expenditure?

AbstractDensity dependence is a strong regulator of animal populations, operating primarily through intraspecific competition for a limiting resource. Because food is generally limited in natural environments, it is typically assumed that increasing animal density leads to reduced individual fitness through food depletion or monopolization. However, recent work demonstrates that density dependence can occur without apparent food depletion, or with virtually unlimited resources, suggesting that other mechanisms must also be important. Alternatively, density‐dependent regulation could be achieved through increasing energy costs rather than decreasing food abundance. The relative importance of these two processes (food depletion and energy costs) and their underlying mechanisms remains unclear. Here, we manipulated the density of juvenile stream‐dwelling brook trout (Salvelinus fontinalis) in three neighboring populations over two consecutive summers to relate food availability and consumption to density‐dependent growth, survival, and their trade‐off. Despite strong patterns of density dependence and evidence of food limitation, increasing fish density did not lead to detectable prey depletion in the environment. Instead, behavioral observations suggested that increasing densities resulted in higher energetic costs, primarily via increasing interference competition and the use of less suitable foraging microhabitats. These results highlight that animal populations may be regulated by density dependence without necessarily impacting prey communities.

Two contrasting Neoarchean metavolcanic rock suites in eastern Hebei and their geodynamic implications for the northern North China Craton

The late Archean was a crucial transition period for global geodynamics. Metavolcanic rocks, as one of the predominant components of Archean cratons, are key to deciphering the geodynamic regimes of early Earth crust-mantle interactions. Neoarchean supracrustal rocks in the central K-rich granitoid belt of the eastern Hebei-western Liaoning Province, northern North China Craton, may be subdivided into a lower metavolcanic sequence and an upper metavolcanic-sedimentary sequence by an angular unconformity.The lower sequence metavolcanic rocks consist primarily of 2558–2536 Ma amphibolite to granulite facies metamorphosed basaltic-andesitic rocks and high- and low-MgO dacitic rocks. The basaltic-andesitic samples display calc-alkaline affinity, high MgO contents, low (Nb/La)N and moderate (Hf/Sm)N values and were most likely derived from partial melting of mantle materials metasomatized by subducted slab- and sediment-derived melts and fluids. The high-MgO dacitic samples are characterized by strongly fractionated rare earth element (REE) patterns and relatively high MgO contents, which resemble typical high-SiO2 adakites. The magmatic precursors originated from subducted oceanic slabs and sediments. The samples with low-MgO dacite compositions have the highest SiO2 and lowest MgO contents, and the magmatic precursors were generated by partial melting of metamorphosed high-K mafic rocks and sedimentary rocks in the lower crustal level.The upper sequence metavolcanic rocks chiefly comprise greenschist to amphibolite facies metamorphosed tholeiites, tholeiitic to transitional basalts, calc-alkaline basalts, andesites, and dacites with magmatic crystallization ages of 2522–2511 Ma. The tholeiite samples are characterized by left-declined REE patterns and high (Nb/La)N and chondrite-like (Hf/Sm)N values resembling typical N-MORBs and were formed by partial melting of a depleted mantle source. The tholeiitic to transitional basalt samples resemble back-arc basin basalts and display weakly right-declined REE patterns, mildly negative Nb and Ti anomalies, and low (Nb/La)N and chondrite-like (Hf/Sm)N values. Their magmatic precursors were derived from partial melting of a slightly fluid- and melt-metasomatized depleted mantle source. The calc-alkaline basalt and andesite samples exhibit fractionated REE patterns and apparent Nb, Ta, and Ti depletions and originated from a strongly fluid- and melt-metasomatized depleted mantle source. The dacite samples show the highest SiO2 and lowest MgO contents in the upper sequence metavolcanic rocks and were derived from partial melting of lower crustal metasedimentary rocks. Systematic petrological, geochemical, and petrogenetic studies indicate that a mature continental arc setting and a back-arc basin setting may account for the formation of the lower and upper sequence metavolcanic rocks, respectively. Three stages of deformation can be identified in the K-rich granitoid belt, including 2525–2505 Ma extensional deformation in a back-arc basin setting (D1), ca. 2500 Ma top-to-the-NEE-SSE thrusting in a collisional orogenic setting (D2) and 2500–1800 Ma nearly N-S-oriented strike-slip shearing (D3), with D2 deformation accompanied by the synchronous occurrence of paired high-pressure and high-temperature medium-pressure granulite facies metamorphism. Integrating the petrogenesis, spatiotemporal relationships, deformational and metamorphic features of the Archean lithological assemblages, we consider that the late Neoarchean K-rich granitoid belt was formed in an active continental margin setting with a southeastward subduction polarity and experienced multi-stage trench retreats and a subsequent collision between the arc and continent.

A material balance based practical analysis method to improve the dynamic reserve evaluation reliability of ultra-deep gas reservoirs with ultra-high pressure

Ultra-deep major gas fields are typically characterized by high and ultra-high pressure, tight matrix and developed fractures, so the reserve estimation is of higher uncertainty. In order to accurately estimate the reserves of this type of gas reservoir, this paper analyzed the correlation between the effective rock compressibility and the cumulative effective rock compressibility based on the material balance equation of high and ultra-high pressure gas reservoirs, and accordingly selected the material balance based analysis method suitable for the reserves estimation of high and ultra-high pressure gas reservoirs. Then, the starting calculation conditions of reserve estimation were determined using the non-linear regression method. In addition, a semi-logarithmic type curve matching method was established for the cases where the starting conditions could not be met. Finally, this method was applied to calculate the reserves of three ultra-high pressure gas fields (reservoirs) to verify its reliability. And the following research results were obtained. First, the cumulative effective compressibility of gas reservoir in the material balance equation of high and ultra-high pressure gas reservoir is a key parameter influencing its reserves, and it is the function of original formation pressure and current average formation pressure, but its numerical value can be hardly obtained by core experiments. Second, it is recommended to adopt the nonlinear regression method without compressibility to estimate the reserves of high and ultra-high pressure gas reservoirs. Third, the calculation starting point of reserves by the nonlinear regression method (the starting point of dimensionless apparent formation pressure-cumulative gas production curve deviating from the straight line relationship) cannot be theoretically calculated. The calculation starting point for different dimensionless linear coefficients (ωD) obtained from the statistical results by the graphic method corresponds to the dimensionless apparent pressure depletion degree of 0.06–0.38, and that obtained based on the data statistics of the example gas reservoir falls within this interval. Fourth, when the starting conditions are not satisfied, the semi-logarithmic type curve matching method can be used for reserve estimation. The ratio of the reserves to the apparent geological reserves G/Gapp is a function of ωD.The higher the ωD, the lower the G/Gapp. Fifth, for the high and ultra-high pressure gas reservoirs in the production test stage, the test production time shall be extended as long as possible to improve the reliability of reserve estimation. And for those in the middle and late stages of development, it is necessary to prepare the comprehensive treatment measures on the basis of reserves so as to improve the development effects of gas reservoirs continuously.

The Biological Effect of Different Doses of Gold Nanoparticles on the Liver of Female Rats: A Histological and Immunohistochemical Study

Background: Gold nanoparticles [GNPs] are significant scientific achievements which are effectively employed in medicine. However, in vivo biological impact of these particles should be assessed to investigate their safety on human health.Aim: Study of the biological effect of different gold nanoparticles doses on the liver of adult female rats exploring the novel mechanisms of gold nanoparticles induced liver damage.Materials and Methods: Forty adult female rats were separated into one control group [Group I] and two GNPs-treated groups [Group II; 40μg/kg and Group III; 400μg/kg]. Specimens of the liver were taken to be processed for the light and electron microscopy in addition to immunohistochemical staining technique for the p53 protein, tumor necrosis factor alpha [TNF-α] and B-cell lymphoma 2 [Bcl-2].Results: Administration of gold nanoparticles to adult female rats caused various histological deterioration in the liver depending on the dose. Hepatocytes showed vacuolated cytoplasm and pyknotic nuclei. Dilation and congestion of the central veins, blood sinusoids, hepatic artery and portal vein were seen. Disrupted endothelial layer was observed in some central veins. An apparent increase in kupffer cells and mononuclear cellular infiltration were observed. The immunohistochemical results demonstrated a significant increase in p53 and TNF-α and a decrease in Bcl-2 immunoreactions. Ultrastructurally, swollen or damaged mitochondria, dilated rough endoplasmic reticulum [RER] and apparent glycogen depletion were observed in the hepatocytes.Conclusion: Gold nanoparticles induced various dose dependent histological deterioration, inflammation and apoptosis in the liver of adult female rats. So, it should be given cautiously to females to avoid liver damage.

Isotopic ‘Altitude’ and ‘Continental’ Effects in Modern Precipitation across the Adriatic–Pannonian Region

It is generally observed that precipitation is gradually depleted in 18O and 2H isotopes as elevation increases (‘altitude’ effect) or when moving inland from seacoasts (‘continental’ effect); the regionally accurate estimation of these large-scale effects is important in isotope hydrological or paleoclimatological applications. Nevertheless, seasonal and spatial differences should be considered. Stable isotope composition of monthly precipitation fallen between January 2016 and December 2018 was studied for selected stations situated along an elevation transect and a continental transect in order to assess the isotopic ‘altitude’ and ‘continental’ effects in modern precipitation across the Adriatic–Pannonian region. Isotopic characteristics argue that the main driver of the apparent vertical depletion of precipitation in heavy stable isotopes is different in summer (raindrop evaporation) and winter (condensation), although, there is no significant difference in the resulting ‘altitude’ effect. Specifically, an ‘altitude’ effect of −1.2‰/km for δ18O and −7.9‰/km for δ2H can be used in modern precipitation across the Adriatic–Pannonian region. Isotopic characteristics of monthly precipitation showed seasonally different patterns and suggest different isotope hydrometeorological regimes along the continental transect. While no significant decrease was found in δ18O data moving inland from the Adriatic from May to August of the year, a clear decreasing trend was found in precipitation fallen during the colder season of the year (October to March) up to a break at ~400 km inland from the Adriatic coast. The estimated mean isotopic ‘continental’ effect for the colder season precipitation is −2.4‰/100 km in δ18O and −20‰/100 km in δ2H. A prevailing influence of the Mediterranean moisture in the colder season is detected up to this breakpoint, while the break in the δ18O data probably reflects the mixture of moisture sources with different isotopic characteristics. A sharp drop in the d-excess (>3‰) at the break in precipitation δ18O trend likely indicates a sudden switch from the Mediterranean moisture domain to additional (mainly Atlantic) influence, while a gradual change in the d-excess values might suggest a gradual increase of the non-Mediterranean moisture contribution along the transect.

H- and Dissociation in Ultra-hot Jupiters: A Retrieval Case Study of WASP-18b

Abstract Atmospheres of a number of ultra-hot Jupiters (UHJs) with temperatures ≳2000 K have been observed recently. Many of these planets show largely featureless thermal spectra in the near-infrared observed with the HST WFC3 spectrograph (1.1–1.7 μm) even though this spectral range contains strong H2O opacity. Recent works have proposed the possibility of H- opacity masking the H2O feature and/or thermal dissociation of H2O causing its apparent depletion at the high temperatures of UHJs. In this work, we test these hypotheses using observations of the exoplanet WASP-18b as a case study. We report detailed atmospheric retrievals of the planet using the HyDRA retrieval code, extended to include the effects of H- opacity and thermal dissociation. We report constraints on the H2O, CO, and H- abundances as well as the pressure–temperature profile of the dayside atmosphere for retrievals with and without H-/dissociation for each data set. We find that the H2O and H- abundances are relatively unconstrained given the featureless WFC3 spectra. We do not conclusively detect H- in the planet, contrary to previous studies that used equilibrium models to infer its presence. The constraint on the CO abundance depends on the combination of WFC3 and Spitzer data, ranging from solar to super-solar CO values. We additionally see signs of a thermal inversion from two of the data sets. Our study demonstrates the potential of atmospheric retrievals of UHJs, including the effects of H- and thermal dissociation of molecules.

Ultraviolet photolysis of H2S and its implications for SH radical production in the interstellar medium

Hydrogen sulfide radicals in the ground state, SH(X), and hydrogen disulfide molecules, H2S, are both detected in the interstellar medium, but the returned SH(X)/H2S abundance ratios imply a depletion of the former relative to that predicted by current models (which assume that photon absorption by H2S at energies below the ionization limit results in H + SH photoproducts). Here we report that translational spectroscopy measurements of the H atoms and S(1D) atoms formed by photolysis of jet-cooled H2S molecules at many wavelengths in the range 122 ≤ λ ≤155 nm offer a rationale for this apparent depletion; the quantum yield for forming SH(X) products, Γ, decreases from unity (at the longest excitation wavelengths) to zero at short wavelengths. Convoluting the wavelength dependences of Γ, the H2S parent absorption and the interstellar radiation field implies that only ~26% of photoexcitation events result in SH(X) products. The findings suggest a need to revise the relevant astrochemical models.

Atmospheric Aridity and Apparent Soil Moisture Drought in European Forest During Heat Waves

AbstractLand‐atmosphere feedbacks, in particular the response of land evaporation to vapor pressure deficit (VPD) or the dryness of the air, remain poorly understood. Here we investigate the VPD response by analysis of a large database of eddy covariance flux observations and simulations using a conceptual model of the atmospheric boundary layer. Data analysis reveals that under high VPD and corresponding high temperatures, forest in particular reduces evaporation and emits more sensible heat. In contrast, grass increases evaporation and emits less sensible heat. Simulations show that this VPD feedback can induce significant temperature increases over forest of up to 2 K during heat wave conditions. It is inferred from the simulations that the effect of the VPD feedback corresponds to an apparent soil moisture depletion of more than 50%. This suggests that previous studies may have incorrectly attributed the effects of atmospheric aridity on temperature to soil dryness.

Lack of detectable neoantigen depletion signals in the untreated cancer genome.

Somatic mutations can result in the formation of neoantigens, immunogenic peptides that are presented on the tumor cell surface via HLA molecules. These mutations are expected to be under negative selection pressure, but the extent of the resulting neoantigen depletion remains unclear. Based on HLA affinity predictions, we annotated the human genome for its translatability to HLA binding peptides and screened for reduced single nucleotide substitution rates in large genomic datasets from untreated cancers. Apparent neoantigen depletion signals became negligible when considering trinucleotide-based mutational signatures, either due to lack of power or efficient immune evasion mechanisms active early during tumor evolution.

No Evidence for Hematopoietic Stem Cell Self-Renewal in-Vivo Following Inflammatory Challenge

Elevated levels of inflammation have been previously linked to both inherited and acquired bone marrow failure (BMF) syndromes, as well as to normal aging, suggesting a role in the etiology of these conditions. One potential explanation for this phenomenon is that repeated inflammation can promote the suppression of hematopoietic stem cell (HSC) function.We have previously demonstrated that interferon-α can accelerate HSC attrition by driving HSCs out of quiescence, leading to the development of BMF in a mouse model of Fanconi anemia (Walter et al. Nature, 2015). To more broadly address the impact of repetitive inflammatory challenge on HSC regeneration, we challenged C57BL6 wild type (WT) mice with polyinosinic:polycytidylic acid (pI:C), a TLR3 agonist that mimics viral infection. Injection with 1-3 rounds of pI:C (8 injections per round) in WT mice had no sustained impact on hematopoiesis, since peripheral blood (PB) and bone marrow (BM) counts were within normal ranges at 5 weeks (5wk) post-treatment. However, in vitro analysis of the clonal proliferation potential of 411 individual sorted long-term (LT)-HSCs revealed a 2-fold reduction (p<0.0001) in the total number of progeny produced per HSC. Additionally, cell fate tracking experiments showed accelerated entry into first division and differentiation following treatment. In line with this data, competitive repopulation assays demonstrated a progressive depletion of functional HSC numbers, with an approximate 2-fold decrease in multi-lineage competitive repopulating activity with each additional round of inflammatory challenge (p<0.01). In order to assess in vivo recovery of HSCs following inflammatory challenge, competitive and limiting dilution transplantation assays were used to quantify HSC frequencies using BM harvested from mice at 5, 10 or 20wk after 3 rounds of pI:C treatment. In both assays we observed a sustained ~18 fold decrease in functional HSCs, with no evidence of recovery within the 20wk window. To exclude microenvironment effects on HSC function, we performed reverse transplantation experiments in which pI.C challenged WT mice were injected with saturating doses of LT-HSCs from non-treated WT donors, in the absence of additional irradiation conditioning. We observed a durable suppression of endogenous HSCs that was sufficient to facilitate robust engraftment of donor LT-HSCs up to 20wk post-treatment. We next used the inducible transgenic Scl-tTA;H2B-GFP mouse model (Wilson et al., Cell, 2008) in order to prospectively segregate quiescent label retaining LT-HSCs (LRCs) from LT-HSCs that proliferate in vivo in response to pI:C (nonLRCs). Following a single round of pI:C challenge, label retention was reduced as a result of LT-HSC proliferation (Table 1). Importantly, the clonal proliferative potential of individual LRCs was preserved upon pI:C challenge while that of nonLRCs was more than halved. This suggests that LT-HSCs fail to undergo self-renewal divisions in vivo under these conditions but rather are functionally compromised in line with increasing proliferative history. We hypothesized that this apparent progressive irreversible depletion of functional HSCs may eventually lead to compromised hematopoiesis. We therefore assessed the hematologic parameters of aged mice that had been exposed to repetitive pI:C treatment in early to mid-life. While these mice had normal PB counts at 5wk post-treatment, upon reaching 2 years of age, treated mice demonstrated mild PB cytopenias, BM hypocellularity and a relative expansion of BM adipocytes (Table 2). Taken together, our data contradict the canonical view that HSCs demonstrate extensive self-regenerative capacity following injury. Rather, in the context of inflammatory challenge, HSCs are progressively and irreversibly depleted as they are driven out of their quiescent state. These findings have broad implications regarding the role of inflammation in the suppression of hematopoiesis that are likely relevant to BMF and also normal aging. Disclosures Lipka: InfectoPharm GmbH: Employment. Frenette:Pfizer: Consultancy; Cygnal Therapeutics: Equity Ownership; Ironwood Pharmaceuticals: Research Funding; Albert Einstein College of Medicine, Inc: Patents & Royalties.

Was the Sun a Slow Rotator? Sodium and Potassium Constraints from the Lunar Regolith

Abstract While the Earth and Moon are generally similar in composition, a notable difference between the two is the apparent depletion in moderately volatile elements in lunar samples. This is often attributed to the formation process of the Moon, and it demonstrates the importance of these elements as evolutionary tracers. Here we show that paleo space weather may have driven the loss of a significant portion of moderate volatiles, such as sodium and potassium, from the surface of the Moon. The remaining sodium and potassium in the regolith is dependent on the primordial rotation state of the Sun. Notably, given the joint constraints shown in the observed degree of depletion of sodium and potassium in lunar samples and the evolution of activity of solar analogs over time, the Sun is highly likely to have been a slow rotator. Because the young Sun’s activity was important in affecting the evolution of planetary surfaces, atmospheres, and habitability in the early Solar System, this is an important constraint on the solar activity environment at that time. Finally, as solar activity was strongest in the first billion years of the Solar System, when the Moon was most heavily bombarded by impactors, evolution of the Sun’s activity may also be recorded in lunar crust and would be an important well-preserved and relatively accessible record of past Solar System processes.

Concentrations, variations and distribution of molybdenum (Mo) in catchment outlet sediments of China: Conclusions from the China geochemical baselines project

The concentrations, variations and distribution of molybdenum (Mo) in catchment outlet sediments from China were studied in this contribution based on the results of recently-finished, continental-scale, China Geochemical Baselines (CGB) project. The data from CGB were combined with other published data-sets with the purpose of understanding the spatial distribution of Mo in China and, in addition, relating the observed geochemical features to natural and/or anthropogenic processes. This geochemical mapping with a density of ca. 3000 km2 per site involves catchment sediments in two horizons at each site: a top sample (TOS) at a depth of 0–25 cm and a bottom sample (BOS) at a depth greater than 100 cm. In total, 3382 TOS and 3380 BOS samples were collected. The analytical results show that the concentrations of Mo in the catchment outlet sediments of China range from 0.07 to 57.86 μg/g for the TOS and 0.09–32.43 μg/g for the BOS. The median and mean values of the TOS data are 0.73 and 1.01 μg/g respectively, and those of the BOS data are 0.71 and 0.94 μg/g. The variations of both the TOS and BOS are high at this continental scale. The Mo concentrations vary greatly from one geological and/or geographic unit to another. For instance, from the Cathaysia Block with the TOS and BOS median values of 1.22 and 1.46 μg/g to the North China craton with those of approximately 0.61 and 0.58 μg/g. Various processes govern the spatial distribution of Mo in the catchment sediments of China but regional-scale natural sources (e.g. lithologies) predominate. Sedimentary sandstones and carbonate rocks, alluvium in plain terrain and aeolian materials (e.g. loess) account for the extensive low concentrations (<0.5 μg/g) at such regions as the Songpan-Ganzi orogen and Songliao Basin; whereas shales, basalts and granitoids like granodiorite, plagiogranite and granite porphyry are taken to be responsible for the high concentrations (>1.2 μg/g) in the Yangtze and Cathaysia blocks. Simultaneously, some local mineralized areas can be also identified at this scale because the sampled sites just happened to fall on sediments derived from mineralized rocks or anthropogenic addition by mining activities. Furthermore, the TOS share the similar patterns with the BOS indicating relatively stable inheritance and no apparent extensive secondary enrichment or depletion in the catchment sediments of China. The CGB demonstrates that a series of baseline levels of Mo are needed at different regions and scales and ultra-low density mapping can still deliver robust geochemical patterns.

Exploring circumstellar effects on the lithium and calcium abundances in massive Galactic O-rich AGB stars

Context. We previously explored the circumstellar effects on Rb and Zr abundances in a sample (21) of massive Galactic O-rich asymptotic giant branch (AGB) stars. Here we are interested in clarifying the role of the extended atmosphere in the case of Li and Ca. Li is an important indicator of hot bottom burning while the total Ca abundances in these stars could be affected by neutron captures. Aims. We report new Li and Ca abundances in a larger sample (30) of massive Galactic O-rich AGB stars by using more-realistic extended model atmospheres. Li abundances had previously studied with hydrostatic models, while the Ca abundances have been determined here for the first time. Methods. We used a modified version of the spectral synthesis code Turbospectrum and consider the presence of a gaseous circumstellar envelope and radial wind in the modelling of the spectra of these massive AGB stars. The Li and Ca abundances were obtained from the 6708 Å Li I and 6463 Å Ca I resonance lines, respectively. In addition, we studied the sensitivity of the pseudo-dynamical models to variations of the stellar and wind parameters. Results. The Li abundances derived with the pseudo-dynamical models are very similar to those obtained from hydrostatic models (the average difference is 0.18 dex, σ2 = 0.02), with no difference for Ca. This indicates that the Li and Ca content in these stars is only slightly affected by the presence of a circumstellar envelope. We also found that the Li I and Ca I line profiles are not very sensitive to variations of the model wind parameters. Conclusions. The new Li abundances confirm the Li-rich (and super Li-rich, in some cases) nature of the sample stars, supporting the activation of hot bottom burning in massive Galactic AGB stars. This is in good agreement with the theoretical predictions for solar metallicity AGB models from ATON, Monash, and NuGrid/MESA but is at odds with the FRUITY database, which predicts no hot bottom burning leading to the production of Li. Most (20) sample stars display nearly solar (within the estimated errors and considering possible non-local thermodynamic equilibrium effects) Ca abundances that are consistent with the available s-process nucleosynthesis models for solar metallicity massive AGB stars, which predict overproduction of 46Ca relatively to the other Ca isotope and the creation of the radioactive isotope 41Ca (half life of 0.1 Myr) but no change in the total Ca abundance. A minority (five) of the sample stars seem to show a significant Ca depletion (by up to 1.0 dex). Possible explanations are offered to explain their apparent and unexpected Ca depletion.