The importance of diazotrophic cyanobacteria as primary producers during Cretaceous Oceanic Anoxic Event 2

In Livello Bonarelli black shale deposited during Cretaceous Oceanic Anoxic Event 2 (OAE-2, ca.&nbsp;94 Ma), nitrogen isotopic compositions of bulk sediments are mostly in a narrow range from &ndash;2.7 to &ndash;0.7&permil;. We also determined molecular distribution and nitrogen isotopic compositions of geoporphyrins extracted from the black shale. The nitrogen isotopic compositions of C₃₂ Ni deoxophylloerythroetioporphyrin (DPEP) and total Ni porphyrins are &ndash;3.5 and &ndash;3.3&permil;, respectively, leading us to the estimation that the mean nitrogen isotopic composition of photoautotrophic cells were around +1&permil; during the formation of Bonarelli black shale. This value is suggestive of N₂-fixation, a dominant process for these photoautotrophs when assimilating nitrogen. Furthermore, Ni-chelated C₃₂ DPEP, derived mainly from chlorophyll <i>a</i> had the highest concentration. Based on this evidence, we conclude that diazotrophic cyanobacteria were major primary producers during that time. Cyanobacteria may be key photoautotrophs during the formation of black shale type sediments intermittently observed throughout the later half of the Earth&apos;s history, and hence may have played a crucial role in the evolution of geochemical cycles even in the later half of the Earth&apos;s history

An importance of diazotrophic cyanobacteria as a primary producer during Cretaceous Oceanic Anoxic Event 2

International audienceIn Livello Bonarelli black shale deposited during Cretaceous Oceanic Anoxic Event 2 (OAE-2, ca. 94 Ma), nitrogen isotopic compositions of bulk sediments are in a narrow range from ?2.7 to ?0.7. We also determined molecular distribution and nitrogen isotopic compositions of geoporphyrins extracted from the black shale. The nitrogen isotopic compositions of C32 Ni deoxophylloerythroetioporphyrin (DPEP) and total Ni porphyrins are ?3.5 and ?3.3, respectively, leading us to the estimation that the mean nitrogen isotopic composition of photoautotrophic cell was around +1 during the formation of Bonarelli black shale. This value is suggestive of N2-fixation a dominant process for these photoautotrophs when assimilating nitrogen. Furthermore, Ni-chelated C32 DPEP, derived mainly from chlorophyll a was the highest concentration. Based on these evidence, we conclude that diazotrophic cyanobacteria were major primary producers during that time. The cyanobacteria may be key photoautotrophs during the formation of black shale type sediments intermittently observed throughout the later half of the Earth's history, and hence may have played a crucial role in the evolution of geochemical cycles

Reconstruction of the biogeochemistry and ecology of photoautotrophs based on the nitrogen and carbon isotopic compositions of vanadyl porphyrins from Miocene siliceous sediments

We determined both the nitrogen and carbon isotopic compositions of various vanadyl alkylporphyrins isolated from siliceous marine sediments of the Onnagawa Formation (middle Miocene, northeastern Japan) to investigate the biogeochemistry and ecology of photoautotrophs living in the paleo-ocean. The distinctive isotopic signals support the interpretations of previous works that the origin of 17-nor-deoxophylloerythroetioporphyrin (DPEP) is chlorophylls-&lt;i&gt;c&lt;/i&gt;&lt;sub&gt;1-3&lt;/sub&gt;, whereas 8-nor-DPEP may have originated from chlorophylls-&lt;i&gt;a&lt;/i&gt;&lt;sub&gt;2&lt;/sub&gt; or &lt;i&gt;b&lt;/i&gt;&lt;sub&gt;2&lt;/sub&gt; or bacteriochlorophyll-&lt;i&gt;a&lt;/i&gt;. Although DPEP and cycloheptanoDPEP are presumably derived from common precursory pigments, their isotopic compositions differed in the present study, suggesting that the latter represents a specific population within the photoautotrophic community. The average &amp;delta;&lt;sup&gt;15&lt;/sup&gt;N value for the entire photoautotrophic community is estimated to be &amp;ndash;2 to +1&amp;permil; from the &amp;delta;&lt;sup&gt;15&lt;/sup&gt;N values of DPEP (&amp;ndash;6.9 to &amp;ndash;3.6&amp;permil;; &lt;i&gt;n&lt;/i&gt;=7), considering that the empirical isotopic relationships that the tetrapyrrole nuclei of chloropigments are depleted in &lt;sup&gt;15&lt;/sup&gt;N by ~4.8&amp;permil; and enriched in &lt;sup&gt;13&lt;/sup&gt;C by ~1.8&amp;permil; relative to the whole cells. This finding suggests that nitrogen utilized in the primary production was supplied mainly through N&lt;sub&gt;2&lt;/sub&gt;-fixation by diazotrophic cyanobacteria. Based on the &amp;delta;&lt;sup&gt;13&lt;/sup&gt;C values of DPEP (&amp;ndash;17.9 to &amp;ndash;15.6&amp;permil;; &lt;i&gt;n&lt;/i&gt;=7), we estimated isotopic fractionation associated with photosynthetic carbon fixation to be 8&amp;ndash;14&amp;permil;. This range suggests the importance of &amp;beta;-carboxylation and/or active transport of the carbon substrate, indicating in turn the substantial contribution of diazotrophic cyanobacteria to primary production. Based on the &amp;delta;&lt;sup&gt;15&lt;/sup&gt;N values of 17-nor-DPEP (&amp;ndash;7.4 to &amp;ndash;2.4&amp;permil; &lt;i&gt;n&lt;/i&gt;=7), the &amp;delta;&lt;sup&gt;15&lt;/sup&gt;N range of chlorophylls-&lt;i&gt;c&lt;/i&gt;-producing algae was estimated to be &amp;ndash;3 to +3&amp;permil;. This relative depletion in sup&gt;15&lt;/sup&gt;N suggests that these algae mainly utilized nitrogen regenerated from diazotrophic cyanobacteria. Given that diatoms are likely to have constituted the chlorophylls-&lt;i&gt;c&lt;/i&gt;-producing algae within the biogenic-silica-rich Onnagawa Formation, cyanobacteria-hosting diatoms may have been important contributors to primary production

Frog α- and β-Ryanodine Receptors Provide Distinct Intracellular Ca2+ Signals in a Myogenic Cell Line

Background In frog skeletal muscle, two ryanodine receptor (RyR) isoforms, α-RyR and β-RyR, are expressed in nearly equal amounts. However, the roles and significance of the two isoforms in excitation-contraction (E-C) coupling remains to be elucidated. Methodology/Principal Findings In this study, we expressed either or both α-RyR and β-RyR in 1B5 RyR-deficient myotubes using the herpes simplex virus 1 helper-free amplicon system. Immunological characterizations revealed that α-RyR and β-RyR are appropriately expressed and targeted at the junctions in 1B5 myotubes. In Ca2+ imaging studies, each isoform exhibited caffeine-induced Ca2+ transients, an indicative of Ca2+-induced Ca2+ release (CICR). However, the fashion of Ca2+ release events was fundamentally different: α-RyR mediated graded and sustained Ca2+ release observed uniformly throughout the cytoplasm, whereas β-RyR supported all-or-none type regenerative Ca2+ oscillations and waves. α-RyR but not β-RyR exhibited Ca2+ transients triggered by membrane depolarization with high [K+]o that were nifedipine-sensitive, indicating that only α-RyR mediates depolarization-induced Ca2+ release. Myotubes co-expressing α-RyR and β-RyR demonstrated high [K+]o-induced Ca2+ transients which were indistinguishable from those with myotubes expressing α-RyR alone. Furthermore, procaine did not affect the peak height of high [K+]o-induced Ca2+ transients, suggesting minor amplification of Ca2+ release by β-RyR via CICR in 1B5 myotubes. Conclusions/Significance These findings suggest that α-RyR and β-RyR provide distinct intracellular Ca2+ signals in a myogenic cell line. These distinct properties may also occur in frog skeletal muscle and will be important for E-C coupling

Parallel finite element method utilizing the mode splitting and sigma coordinate for shallow water flows

Abstract Parallel ®nite element method for the analysis of quasi-three dimensional shallow water¯ow is presented. The mode splitting technique and the sigma coordinate (generalized coordinate) are employed to use parallel computers effectively. Parallel implementation of the unstructured grid-based formulation is carried out on the Hitachi parallel-super computer SR2201. The tidal¯ow of Tokyo Bay is simulated for a numerical example. The speed-up ratio and the ef®ciency of the parallelization are investigated. The present method is shown to be a useful and powerful tool for the large scale computation of shallow water¯ows. Introduction The shallow water¯ow analysis is usefully applied to thē ows in oceans, lakes and rivers. A number of numerical methods for the shallow water¯ow based on the two dimensional model have been presented in the past. The present authors have been presented a parallel ®nite element method to solve the large scale computations of shallow water¯ows, such as the storm surges and tidal ows, using the ®ne mesh which represents the geography accurately This paper presents a parallel ®nite element modeling utilizing the mode-splitting and sigma coordinate for the quasi-three dimensional shallow water analysis. The three dimensional¯ow ®eld is divided into two ®elds; the horizontal¯ow ®eld and the vertical¯ow ®eld. The quasi-three dimensional¯ow analysis can be achieved by solving both ®eld mutually. The ®nite element method is employed for the horizontal¯ow ®eld and the ®nite difference method is employed for the vertical distribution of¯ow ®eld. Parallel implementation of the unstructured-grid-based formulations are carried out on the Hitachi parallel-super computer SR2201. The effect of parallelization on the ef®ciency of the computations are examined. Governing equations The shallow water equations can be obtained from the conservation of momentum and mass, assuming a hydrostatic pressure distribution

Reconstruction of the past compound-specific N and C isotopic analyses of sedimentary porphyrins

Porphyrins are thought to have derived from biomoleculessuch as chlorophylls and heme, among which eoxophylloerythroetioporphyrins(DPEP) and its analogues arestructurally related to chloropigments. These compounds thuspreserve stable isotopic compositions of N and C ofphototrophs of the past environment. We have developedmethods for precise determinations of N and C isotopiccompositions of individual sedimentary porphyrins andmaleimides, which include isolation and purification ofindividual alkylporphyrins and porphyrin acids by dual-stepHPLC preparation (Kashiyama et al., 2007a). We haveanalyzed various alkylporphyrins and porphyrin acids fromorganic-rich Miocene sediments of the paleo-Japan Sea(Onnagawa Formation) as well as Cretaceous black shales(Livello Selli and Livello Bonarelli, Italy) deposited in thewestern Tethys during the Ocean Anoxic Events (OAEs). TheN isotopic composition of DPEP, which should have derivedin chlorophylls in general, ranged from -6.9 to -3.6‰ (n=7) inthe Miocene shale and -6.6 to -3.9‰ (n=5) in the OAE blackshales, indicating that the N2 fixation was a major process forN assimilation hence the dominance of diazotrophiccyanobacteria in primary production in these paleo-oceans.Furthermore, DPEP were relatively enriched in 13C in bothenvironments (-17.9 to -15.6‰ in the Miocene shale and -20.5to -17.9‰ in the OAE black shales), which suggests relativelysmall carbon isotopic fractionation during photosynthesis andsupports significant contribution of cyanobacteria-derivedchloropigments. We also determined isotopic compositions ofsource-specific porphyrins such as 17-nor-DPEP (derivedfrom chlorophyll-c), 8-nor-DPEP (possibly derived fromdivinylchlorophylls; Kashiyama et al., 2007b) as well asDPEP with extended alkyl side chains and their equivalentsamong porphyrin acids (derived from bacteriochlorophyll c, d,and e; analyzed as maleimides). The latter two porphyrins hadvariable and rather unique isotopic compositions compared toDPEP. Such an approach should allow reconstruction ofcommunity structures of phototrophs and associatedbiogeochemical processes associated with the photosynthesisin the past oceans.abstractの

Late-Time Radio and Millimeter Observations of Superluminous Supernovae and Long Gamma Ray Bursts: Implications for Obscured Star Formation, Central Engines, and Fast Radio Bursts

We present the largest and deepest late-time radio and millimeter survey to date of superluminous supernovae (SLSNe) and long duration gamma-ray bursts (LGRBs) to search for associated non-thermal synchrotron emission. Using the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA), we observed 43 sources at 6 and 100 GHz on a timescale of $\sim 1 - 19$ yr post-explosion. We do not detect radio/mm emission from any of the sources, with the exception of a 6 GHz detection of PTF10hgi (Eftekhari et al. 2019), as well as the detection of 6 GHz emission near the location of the SLSN PTF12dam, which we associate with its host galaxy. We use our data to place constraints on central engine emission due to magnetar wind nebulae and off-axis relativistic jets. We also explore non-relativistic emission from the SN ejecta, and place constraints on obscured star formation in the host galaxies. In addition, we conduct a search for fast radio bursts (FRBs) from some of the sources using VLA Phased-Array observations; no FRBs are detected to a limit of $16$ mJy ($7\sigma$; 10 ms duration) in about 40 min on source per event. A comparison to theoretical models suggests that continued radio monitoring may lead to detections of persistent radio emission on timescales of $\gtrsim {\rm decade}$.Comment: 30 pages; 12 figures; accepted to Ap

Variations in Mre11/Rad50/Nbs1 status and DNA damage-induced S-phase arrest in the cell lines of the NCI60 panel

<p>Abstract</p> <p>Background</p> <p>The Mre11/Rad50/Nbs1 (MRN) complex is a regulator of cell cycle checkpoints and DNA repair. Defects in MRN can lead to defective S-phase arrest when cells are damaged. Such defects may elicit sensitivity to selected drugs providing a chemical synthetic lethal interaction that could be used to target therapy to tumors with these defects. The goal of this study was to identify these defects in the NCI60 panel of cell lines and identify compounds that might elicit selective cytotoxicity.</p> <p>Methods</p> <p>We screened the NCI60 panel in search of cell lines that express low levels of MRN proteins, or that fail to arrest in S-phase in response to the topisomerase I inhibitor SN38. The NCI COMPARE program was used to discover compounds that preferentially target cells with these phenotypes.</p> <p>Results</p> <p>HCT116 cells were initially identified as defective in MRN and S phase arrest. Transfection with Mre11 also elevated Rad50 and Nbs1, and rescued the defective S-phase arrest. Cells of the NCI60 panel exhibited a large range of protein expression but a strong correlation existed between Mre11, Rad50 and Nbs1 consistent with complex formation determining protein stability. Mre11 mRNA correlated best with protein level suggesting it was the primary determinant of the overall level of the complex. Three other cell lines failed to arrest in response to SN38, two of which also had low MRN. However, other cell lines with low MRN still arrested suggesting low MRN does not predict an inability to arrest. Many compounds, including a family of benzothiazoles, correlated with the failure to arrest in S phase. The activity of benzothiazoles has been attributed to metabolic activation and DNA alkylation, but we note several cell lines in which sensitivity does not correlate with metabolism. We propose that the checkpoint defect imposes an additional mechanism of sensitivity on cells.</p> <p>Conclusions</p> <p>We have identified cells with possible defects in the MRN complex and S phase arrest, and a series of compounds that may preferentially target S phase-defective cells. We discuss limitations of the COMPARE program when attempting to identify compounds that selectively inhibit only a few cell lines.</p