Biological Regulation of Atmospheric Chemistry En Route to Planetary Oxygenation

Emerging evidence suggests that atmospheric oxygen may have varied before rising irreversibly ∼2.4 billion years ago, during the Great Oxidation Event (GOE). Significantly, however, pre-GOE atmospheric aberrations toward more reducing conditions—featuring a methane-derived organic-haze—have recently been suggested, yet their occurrence, causes, and significance remain underexplored. To examine the role of haze formation in Earth’s history, we targeted an episode of inferred haze development. Our redox-controlled (Fe-speciation) carbon- and sulfur-isotope record reveals sustained systematic stratigraphic covariance, precluding nonatmospheric explanations. Photochemical models corroborate this inference, showing Δ³⁶S/Δ³³S ratios are sensitive to the presence of haze. Exploiting existing age constraints, we estimate that organic haze developed rapidly, stabilizing within ∼0.3 ± 0.1 million years (Myr), and persisted for upward of ∼1.4 ± 0.4 Myr. Given these temporal constraints, and the elevated atmospheric CO₂ concentrations in the Archean, the sustained methane fluxes necessary for haze formation can only be reconciled with a biological source. Correlative δ¹³C₀rg and total organic carbon measurements support the interpretation that atmospheric haze was a transient response of the biosphere to increased nutrient availability, with methane fluxes controlled by the relative availability of organic carbon and sulfate. Elevated atmospheric methane concentrations during haze episodes would have expedited planetary hydrogen loss, with a single episode of haze development providing up to 2.6–18 × 10¹⁸ moles of O₂ equivalents to the Earth system. Our findings suggest the Neoarchean likely represented a unique state of the Earth system where haze development played a pivotal role in planetary oxidation, hastening the contingent biological innovations that followed

High-frequency fluctuations in redox conditions during the latest Permian mass extinction

This study was supported financially by NERC Fellowship NE/H016805/2 (to AZ), NERC Standard Grant NE/J023485/2 (to AZ and MC), NSFEAR-1455258 (to CJK). Samples were collected by RJT, who thanks G. Cuny and the Danish National Research Foundation for logistics and financial support.New high-resolution geochemical and sedimentological data from Fiskegrav, East Greenland, reveal fluctuations in marine redox conditions associated with the final disappearance of bioturbating organisms during the latest Permian mass extinction (LPME). Sedimentological observations imply a transgressive episode, and associated geochemical evidence for decreasing oxygen availability and the establishment of persistently ferruginous (Fe2 +-rich) conditions implies the shoreward migration of oxygen deficient waters. The long-term decline in dissolved oxygen (DO) availability could have been exacerbated by increasing water temperatures, reducing the solubility of oxygen and promoting thermal stratification. Mixing of the water column could have been further inhibited by freshwater influxes that could have generated salinity contrasts that reinforced thermal stratification. Enhanced runoff could also have increased the delivery of nutrients to the marine shelf, stimulating biological oxygen demand (BOD). During the transition to persistently ferruginous conditions we identify intervals of intermittent benthic meiofaunal recolonization, events that we attribute to small transient increases in DO availability. The mechanism controlling these fluctuations remains speculative, but given the possible centennial- to millennial-scale frequency of these changes, we hypothesise that the mid-latitude setting of Fiskegrav during the Late Permian was sensitive to changes in atmospheric circulation patterns, which may have influenced local precipitation and intermittently modulated some of the processes promoting anoxia.Publisher PDFPeer reviewe

Vivianite formation in methane-rich deep-sea sediments from the South China Sea

Phosphorus is often invoked as the ultimate limiting nutrient, modulating primary productivity on geological timescales. Consequently, along with nitrogen, phosphorus bioavailability exerts a fundamental control on organic carbon production, linking all the biogeochemical cycles across the Earth system. Unlike nitrogen that can be microbially fixed from an essentially infinite atmospheric reservoir, phosphorus availability is dictated by the interplay between its sources and sinks. While authigenic apatite formation has received considerable attention as the dominant sedimentary phosphorus sink, the quantitative importance of reduced iron-phosphate minerals, such as vivianite, has only recently been acknowledged, and their importance remains underexplored. Combining microscopic and spectroscopic analyses of handpicked mineral aggregates with sediment geochemical profiles, we characterize the distribution and mineralogy of iron-phosphate minerals present in methane-rich sediments recovered from the northern South China Sea. Here, we demonstrate that vivianite authigenesis is pervasive in the iron-oxide-rich sediments below the sulfate–methane transition zone (SMTZ). We hypothesize that the downward migration of the SMTZ concentrated vivianite formation below the current SMTZ. Our observations support recent findings from non-steady-state post-glacial sedimentary successions, suggesting that iron reduction below the SMTZ, probably driven by iron-mediated anaerobic oxidation of methane (Fe-AOM), is coupled to phosphorus cycling on a much greater spatial scale than previously assumed. Calculations reveal that vivianite acts as an important burial phase for both iron and phosphorus below the SMTZ, sequestering approximately half of the total reactive iron pool. By extension, sedimentary vivianite formation could serve as a mineralogical marker of Fe-AOM, signalling low-sulfate availability against methanogenic and ferruginous backdrop. Given that similar conditions were likely present throughout vast swathes of Earth's history, it is possible that Fe-AOM and vivianite authigenesis may have modulated methane and phosphorus availability on the early Earth, as well as during later periods of expanded marine oxygen deficiency. A better understanding of vivianite authigenesis, therefore, is fundamental to test long-standing hypotheses linking climate, atmospheric chemistry and the evolution of the biosphere.</p

Effect of combination glipizide GITS/metformin on fibrinolytic and metabolic parameters in poorly controlled type 2 diabetic subjects

WSTĘP. Wyniki badań epidemiologicznych wskazują, że podwyższone stężenie inhibitora aktywatora plazminogenu 1 (PAI-1) w surowicy krwi może być wskaźnikiem lub predyktorem przyspieszonego rozwoju choroby wieńcowej u chorych na cukrzycę typu 2. Celem pracy było określenie, czy poprawa wyrównania metabolicznego, niezależnie od rodzaju stosowanych leków doustnych, wpływa na stężenie PAI-1 u chorych ze znaczną hiperglikemią. MATERIAŁ I METODY. Do badania zakwalifikowano 91 chorych. Po okresie 4 tygodni, w którym pacjenci nie przyjmowali żadnych leków, chorych losowo przydzielono do grupy leczonej glipizydem GITS (w dawce maksymalnej 20 mg, n = 46) lub grupy otrzymującej metforminę (maksymalnie 2550 mg, n = 45) w monoterapii. Po okresie monoterapii wprowadzono leczenie skojarzone, dodając drugi lek do preparatu już stosowanego. U wszystkich pacjentów przed i po randomizacji oraz podczas badania oznaczono glikemię (na czczo i po posiłku), stężenie HbA1c, fruktozaminy oraz PAI-1. U części chorych zmierzono również wątrobową produkcję glukozy (HGO, hepatic glucose output) oraz oznaczono rozkład brzusznej tkanki tłuszczowej. WYNIKI. Wyrównanie glikemii na początku badania było niezadowalające (średnie stężenie HbA1c 10,4 &plusmn; 0,2% w grupie glipizydu GITS; 10,0 &plusmn; 0,2% w grupie metforminy), ale poprawiło się istotnie w obu grupach, stosujących monoterapię oraz w wyniku leczenia skojarzonego (p < 0,0001 vs. wyniki wyjściowe), co oceniono na podstawie badania tolerancji posiłku, stężenia fruktozaminy oraz HGO. Masa ciała oraz rozkład brzusznej tkanki tłuszczowej nie zmieniły się istotnie w żadnej z grup. Stężenie PAI-1 było wyjątkowo wysokie (5-10-krotnie wyższe od wartości prawidłowych) na początku badania (202 &plusmn; 12 ng/ml w grupie glipizydu GITS; 201 &plusmn; 13 ng/ml w grupie metforminy), ale istotnie obniżyło się podczas badania, w sposób porównywalny w monoterapii w obu grupach. Podczas leczenia skojarzonego stężenie to uległo dalszemu obniżeniu. WNIOSKI. W przypadkach nasilonej hiperglikemii stężenie PAI-1 jest również znacznie podwyższone. Obniżenie hiperglikemii za pomocą leku nasilającego wydzielanie insuliny, glipizydu GITS lub metforminy, stosowanych w monoterapii, w porównywalny sposób powoduje obniżenie stężenia PAI-1.INTRODUCTION. Epidemiological studies have implicated increased plasminogen-activated inhibitor 1 (PAI-1) as a marker or predictor of accelerated coronary atherosclerotic disease in type 2 diabetes. We sought to determine whether metabolic control, independent of its oral mode of implementation, affects PAI-1 in patients with marked hyperglycemia. MATERIAL AND METHODS. A total of 91 subjects were screened, subjected to a 4-week drug washout, and randomized to daily treatment with glipizide GITS (maximum 20 mg, n = 46) or metformin (maximum 2,550 mg, n = 45) as monotherapy. After monotherapy, combination therapy was initiated by adding the second agent to the regimen. Plasma glucose (fasting and postprandial), HbA1c, fructosamine, and PAI-1 were assayed before and after randomization and sequentially thereafter in all subjects; hepatic glucose output (HGO) and abdominal fat distribution were each measured in a subset of subjects. RESULTS. Glycemic control was markedly impaired at baseline (mean HbA1c 10.4 &#177; 0.2% glipizide GITS; 10.0 &#177; 0.2% metformin) but improved comparably with each agent as monotherapy and in combination (P < 0.0001 vs. baseline), as assessed with meal tolerance studies, fructosamine values, and HGO. Body weight and abdominal fat distribution did not change significantly in either group. PAI-1 concentrations were extraordinarily high (5- to 10-fold more than normal) at baseline (202 &#177; 12 ng/ml glipizide GITS; 201 &#177; 13 ng/ml metformin) but declined comparably, and significantly, after treatment with either agent as monotherapy and decreased further with combination therapy. CONCLUSIONS. When hyperglycemia is profound, increases in PAI-1 are also profound. Control of hyperglycemia with either glipizide GITS, an insulin secretagogue, or metformin as monotherapy comparably ameliorates elevated PAI-1

In memoriam mr. sc. Vesna Burić (1943. - 2002.)

The exceptionally organic-rich rocks of the 1.98 Ga Zaonega Formation deposited in the Onega Basin, NW Russia, have refined our understanding of Earth System evolution during the Paleoproterozoic rise in atmospheric oxygen. These rocks were formed in vent- or seep influenced settings contemporaneous with voluminous mafic volcanism and contain strongly 13C-depleted organic matter. Here we report new isotopic (δ34S, Δ33S, Δ36S, δ13Corg) and mineralogical, major element, total sulphur and organic carbon data for the upper part of the Zaonega Formation, which was deposited shortly after the termination of the Lomagundi-Jatuli positive carbon isotope excursion. The data were collected on a recently obtained 102 m drillcore section and show a δ13Corg shift from -38‰ to -25‰. Sedimentary sulphides have δ34S values typically between +15‰ and +25‰ reflecting closed-system sulphur isotope behaviour driven by high rates of microbial sulphate reduction, high sulphate demand, hydrothermal activity and hydrocarbon seepage. Four intervals record δ34S values that exceed +30‰. We interpret these unusually 34S-enriched sulphides to be a result of limited sulfate diffusion into pore waters due to changes in sedimentation and/or periods of basinal restriction. Additionally, there are four negative δ34S and positive Δ33S excursions that are interpreted to reflect changes in the open/closed-system behaviour of sulphate reduction or availability of reactive iron. Our findings highlight the influence of basinal processes in regulating sulphur isotope records and the need for care before interpreting such signals as reflecting global conditions

Notch Ankyrin Repeat Domain Variation Influences Leukemogenesis and Myc Transactivation

, cell-based and structural analyses to compare the abilities of activated Notch1-4 to support T cell development, induce T cell acute lymphoblastic leukemia/lymphoma (T-ALL), and maintain T-ALL cell growth and survival., a direct Notch target that has an important role in Notch-associated T-ALL.We conclude that the leukemogenic potentials of Notch receptors vary, and that this functional difference stems in part from divergence among the highly conserved ankyrin repeats, which influence the transactivation of specific target genes involved in leukemogenesis

Earth: Atmospheric Evolution of a Habitable Planet

Our present-day atmosphere is often used as an analog for potentially habitable exoplanets, but Earth's atmosphere has changed dramatically throughout its 4.5 billion year history. For example, molecular oxygen is abundant in the atmosphere today but was absent on the early Earth. Meanwhile, the physical and chemical evolution of Earth's atmosphere has also resulted in major swings in surface temperature, at times resulting in extreme glaciation or warm greenhouse climates. Despite this dynamic and occasionally dramatic history, the Earth has been persistently habitable--and, in fact, inhabited--for roughly 4 billion years. Understanding Earth's momentous changes and its enduring habitability is essential as a guide to the diversity of habitable planetary environments that may exist beyond our solar system and for ultimately recognizing spectroscopic fingerprints of life elsewhere in the Universe. Here, we review long-term trends in the composition of Earth's atmosphere as it relates to both planetary habitability and inhabitation. We focus on gases that may serve as habitability markers (CO2, N2) or biosignatures (CH4, O2), especially as related to the redox evolution of the atmosphere and the coupled evolution of Earth's climate system. We emphasize that in the search for Earth-like planets we must be mindful that the example provided by the modern atmosphere merely represents a single snapshot of Earth's long-term evolution. In exploring the many former states of our own planet, we emphasize Earth's atmospheric evolution during the Archean, Proterozoic, and Phanerozoic eons, but we conclude with a brief discussion of potential atmospheric trajectories into the distant future, many millions to billions of years from now. All of these 'Alternative Earth' scenarios provide insight to the potential diversity of Earth-like, habitable, and inhabited worlds.Comment: 34 pages, 4 figures, 4 tables. Review chapter to appear in Handbook of Exoplanet

Mo-isotopes as tracers of Cretaceous ocean anoxia

Recent observations and modelling have shown that ocean warming and stagnation, driven by global climate change, may lead to widespread ocean deoxgyenation with direct impacts on marine biogeochemistry and ecosystems