Earth's biosphere witnessed the first major extinction event in the Phanerozoic during the Cambrian Age 4, with a genera loss up to ∼45%. The traditional view suggested that marine anoxia was the ...main cause of the biotic crisis, yet recent geochemical investigations yielded highly debated opinions on marine redox states during the Cambrian Age 4. Herein, we supplement new geochemical evidence for expanded marine euxinia at the extinction intervals on the Yangtze Platform, South China. Most importantly, modern‐level sedimentary δ98Mo (∼+2.34‰) records were most parsimoniously explained by transitory expansion of continental margin euxinia and concomitant intensification of sedimentary Mo sequestration via Fe‒Mn shuttles in the global ocean. The results clarify global marine redox conditions during the Cambrian Age 4, and lend firm support to a causal link between expanded marine euxinia and the extinction event.
Plain Language Summary
Marine life experienced the first major mass extinction during the Cambrian Age 4 (∼509–514 Ma) right after the Cambrian explosion, with a genera loss up to ∼45%. The mass extinction was traditionally attributed to expanded marine anoxia in the global ocean based on lithological changes, but geochemical evidence for this scenario is still lacking. Molybdenum (Mo) isotopes can be used to track global marine redox states in ancient oceans. Herein, new Mo isotope data revealed transitory expansion of sulfidic waterbodies on in the global ocean at the major mass extinction intervals. Sulfidic waters enriched in H2S are lethal for marine animals. Therefore, expanded sulfidic waterbodies in the global ocean could have served as a major driver for the mass extinction event.
Key Points
Dynamic marine Mo cycling via Fe‒Mn shuttles during the Cambrian Age 4 is revealed
Robust Mo isotope evidence for expanded continental margin euxinia in the global ocean during mass extinction
Firm support to a causal link between expanded marine euxinia and the extinction event
Subducted sediments have been suggested to be a possible cause for local Mg isotopic variation in the overall homogeneous mantle based on anomalous Mg isotopic compositions detected in some ...mantle-derived rocks. Here we examine the Mg isotopic systematics of 77 bulk marine sediment samples from ten DSDP and ODP drill sites adjacent to the world's major subduction zones to assess their potential to cause mantle heterogeneity. In contrast to the limited mantle range (δ26Mg=−0.25±0.07‰), δ26Mg of these sediments varies widely from −1.34‰ to +0.46‰, which is similar to values measured in continental sediments and appears to be linked to sediment lithology. Calcareous oozes are generally isotopically lighter than seawater; however, the presence of detrital impurities can shift their δ26Mg to higher values. In comparison to calcareous oozes, Mg-rich aluminosilicate sediments typically have higher δ26Mg values, although they may be either isotopically heavier or lighter than the mantle. Detrital sediments are the dominant sediment type and display large variation (−0.90‰ to +0.18‰) that reflects provenance heterogeneity and textural/mineralogical sorting. Sediments derived from juvenile terranes have δ26Mg similar to mantle values while those derived from mature, and thus more strongly weathered sources, often have higher δ26Mg values. On the other hand, turbidites may have lower δ26Mg values if containing isotopically light dolomite and/or garnet. In addition, clay-size fractions in turbidites commonly have higher δ26Mg than the associated sands. Hydrogenetic clays have a relatively high and uniform δ26Mg value of +0.02±0.14‰ (2SD, n=14), suggesting preferential uptake of heavy Mg isotopes during authigenic clay formation while hydrothermal clays have highly variable δ26Mg values (−0.57‰ to +0.46‰) that likely reflect variable exchange with seawater/hydrothermal fluids. Overall, considerable variations exist in both regional Mg mass flux and the weighted δ26Mg average of sedimentary sections subducting at different trenches. The flux-weighted δ26Mg of −0.336‰ is estimated for Global Subducting Sediments (GLOSS-II), which is isotopically lighter than the mantle average because of the presence of thick turbidite sequences with relatively low δ26Mg values and local carbonate enrichment in a few trenches near the equator. Therefore, it appears that subducting marine sediments are a source of heterogeneous δ26Mg values in the mantle, and they may be manifested locally in volcanic rocks that form in regions having a high flux of sediment melts to the mantle.
•Subducting marine sediments from ten drill sites display large Mg isotopic variation from −1.34‰ to +0.46‰.•Magnesium isotopic variations among different sediment groups reflect differing fractionation mechanisms.•The estimated average δ26Mg for GLOSS-II (−0.336‰) is lower than the mantle average.•Both Mg mass flux and average δ26Mg value of subducting sediment columns vary significantly from arc to arc.•Subducting sediments are a source of Mg isotopic heterogeneity in the mantle.
Enhanced continental phosphorus input into the ocean has been suggested as a potential trigger for the transient oxygenation events during the mid‐Proterozoic; however, the response of phosphorus ...cycling to these marine oxygenations remains unclear. Here, we report the changes in phosphorus cycling associated with a ∼1.7 Ga transient oxygenation. Abundant authigenic aluminum phosphate–sulfate mineral svanbergite (SrAl3(PO4) (SO4) (OH)6; 8.02 ± 4.92 wt%) is identified within the ∼1.7 Ga Yunmengshan ironstones from the Xiong'er Basin, North China and other contemporaneous basins. This observation provides new evidence to support the suggestion that early diagenetic aluminum phosphate‐sulfate minerals could have represented a critical sink of marine phosphorus during the Proterozoic. We suggest that atmospheric oxygenation and concomitant changes in porewater redox chemistry may have enhanced the formation of early diagenetic phosphates, leading to a negative feedback on the oceanic phosphorus reservoir and atmospheric oxygen levels.
Plain Language Summary
It becomes increasingly clear that multiple transient oxygenation events likely punctuated the low background oxygen world during the mid‐Proterozoic. This may imply that a negative feedback could have inhibited a secular rise in atmospheric oxygen, though the deoxygenation mechanisms remain unclear. Phosphorus (P) availability regulated primary production and therefore controlled the atmospheric oxygen levels during this time, and oxygenation would in turn affect phosphorus cycling. Here we investigate the P cycling during a ca. 1.7 Ga transient oxygenation using mineralogical and geochemical methods. The results show an enhanced phosphorus burial during this transient oxygenation. The elevated phosphorus and sulfate inputs from the enhanced continental weathering and oxygenation may have promoted the formation of aluminum phosphate‐sulfate minerals. This, in turn, reduced the bio‐availability of phosphorus in the marine environment, ultimately limiting marine productivity and leading to a negative feedback on the oxygenation event. This study highlights that phosphorus cycling pathway, which was previously overlooked, may have played a role in the deoxygenation during the intermittent oxygenation events in the mid‐Proterozoic.
Key Points
Abundant phosphorus and sulfur precipitation as authigenic svanbergite is associated with the ∼1.7 Ga transient oxygenation
The oxygenation resulted in suboxic and acidic porewater conditions rich in P‐ and sulfate, facilitating the authigenesis of svanbergite
The enhanced P and S burial as svanbergite represents a significant but overlooked negative feedback during the transient oxygenation
To investigate the behavior of Mg isotopes during low-temperature alteration of oceanic crust and to further understand its role in the global Mg cycle, we measured the Mg isotopic compositions ...(25Mg/24Mg and 26Mg/24Mg) of a set of samples of altered oceanic crust (AOC) recovered from the Ocean Drilling Program Hole 801C, the reference site for old crust (∼170 Ma) subducting in the Pacific. The measured δ26Mg values range from −1.70‰ to 0.21‰, deviating from that of pristine oceanic basalts (−0.25 ± 0.07‰). Composite samples of volcanoclastic breccia that have experienced relatively intense alteration have larger variation in δ26Mg values (−1.01‰ to 0.15‰) than composite samples of massive basaltic flows (−0.53‰ to −0.04‰), indicating significant Mg isotope fractionation during low-temperature alteration of the oceanic crust. Moreover, the upper off-axis basement has on average lower δ26Mg values (−1.70‰ to −0.04‰) than the lower on-axis basement (−0.16‰ to 0.21‰). These findings, combined with the co-variations between MgO content and FeO∗/CaO ratio and between δ26Mg and FeO∗/CaO ratio, suggest that formation of Mg-bearing minerals (i.e., saponite and calcite) during low-temperature alteration of the oceanic crust accounts for the highly variable δ26Mg of AOC. Early formation of saponite under anoxic condition preferentially takes up heavy Mg isotopes and accounts for Mg enrichment and relatively high δ26Mg in the on-axis basement. Subsequent precipitation of carbonates results in the dilution of Mg and relatively low δ26Mg in the off-axis basement. In addition, accumulation of carbonate-rich interflow sediments in the upper basement may contribute further to the low δ26Mg. A weighted average δ26Mg value of 0.00 ± 0.09‰ is estimated for the AOC at Site 801, implying that low-temperature alteration of oceanic crust drives the ocean to a lighter Mg isotopic composition, and thus requires additional carbonate precipitation to maintain a steady-state Mg isotopic composition of seawater. A mass balance calculation suggests that the Mg output flux due to low-temperature alteration of the oceanic crust equals ∼12% of the annual Mg riverine input, indicating that AOC is a significant sink of Mg in seawater. Our study further highlights that recycling of AOC with highly variable δ26Mg along with overlying marine sediments into the mantle through subduction may generate Mg isotopic heterogeneity in the mantle at small scales.
Stem cells are biological cells that can self-renew and can differentiate into multiple cell lineages. Stem cell-based therapy is emerging as a promising alternative therapeutic option for various ...disorders. Mesenchymal stem cells (MSCs) are multipotent adult stem cells that are isolated from various tissues and can be used as an alternative to embryonic stem cells. Stem cells from the apical papilla (SCAPs) are a novel population of MSCs residing in the apical papilla of immature permanent teeth. SCAPs present the characteristics of expression of MSCs markers, self-renewal, proliferation, migration, differentiation, and immunosuppression, which support the application of SCAPs in stem cell-based therapy, including the immunotherapy and the regeneration of dental tissues, bone, neural, and vascular tissues. In view of these properties and therapeutic potential, SCAPs can be considered as promising candidates for stem cell-based therapy. Thus the aim of our review was to summarize the current knowledge of SCAPs considering isolation, characterization, and multilineage differentiation. The prospects for their use in stem cell-based therapy were also discussed.
Few reports exist regarding the expression and function of Wilms' tumor 1-associated protein (WTAP) in colorectal cancer (CRC), and the evidence is controversial. Our analysis explored the expression ...of WTAP in CRC tissue, and analyzed its clinical and prognostic significance. WTAP expression was significantly higher in CRC tissue than in colorectal adenoma and normal colorectal tissue. WTAP was highest in left colon tumor samples and negatively associated with tumor differentiation, as well as depth of tumor invasion. In multiple logistic regression analysis, independent predictors of WTAP expression in CRC included tumor in the left colon (odds ratio = 2.634; 95% confidence interval: 1.129-6.142; P = 0.025) and poorly differentiated tissue (0.072; 0.014-0.367; P = 0.002). No clear relationship was observed between CRC patient prognosis and WTAP expression. We suggest that WTAP expression is upregulated in CRC, highly expressed in left colon cancer and negatively correlated with tumor differentiation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We have prepared a large volume of pure, concentrated and homogeneous magnesium standard solution (GSB-Mg) to be used as a secondary reference standard by the magnesium isotope community. This new ...standard solution can also be used for quality assurance, including the development and validation of analytical procedures, preparation and test of analytical methods, quality control and training of analysts. The
δ
26
Mg values relative to DSM3, measured by multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), are −2.038 ± 0.027‰ (
n
= 45, Lab 1), −2.024 ± 0.055‰ (
n
= 7, Lab 2), −2.078 ± 0.081‰ (
n
= 6, Lab 3), −2.037 ± 0.015‰ (
n
= 8, Lab 4), and −2.067 ± 0.039‰ (
n
= 12, Lab 5). The
δ
26
Mg and
δ
25
Mg values for the GSB-Mg standard solution are −2.049‰ and −1.056‰, with a combined expanded (
k
= 2) uncertainty of 0.049‰ and 0.028‰, respectively. These values show higher similarity to Mg isotopic compositions of carbonates and marine sediments compared to those of the mantle and crustal rocks, making the GSB-Mg solution a great reference material for Mg isotopic analysis of carbonates and marine sediments.
We have prepared a large volume of pure, concentrated and homogeneous magnesium standard solution (GSB-Mg) to be used as a secondary reference standard by the magnesium isotope community.
The piRNA machinery is known for its role in mediating epigenetic silencing of transposons. Recent studies suggest that this function also involves piRNA-guided cleavage of transposon-derived ...transcripts. As many piRNAs also appear to have the capacity to target diverse mRNAs, this raises the intriguing possibility that piRNAs may act extensively as siRNAs to degrade specific mRNAs. To directly test this hypothesis, we compared mouse PIWI （MI- WI）-associated piRNAs with experimentally identified cleaved mRNA fragments from mouse testes, and observed cleavage sites that predominantly occur at position 10 from the 5＇ end of putative targeting piRNAs. We also noted strong biases for U and A residues at nucleotide positions 1 and 10, respectively, in both piRNAs and mRNA frag- ments, features that resemble the pattern of piRNA amplification by the ＇ping-pong＇ cycle. Through mapping of MIWI-RNA interactions by CLIP-seq and gene expression profiling, we found that many potential piRNA-targeted mRNAs directly interact with MIWI and show elevated expression levels in the testes of Miwi catalytic mutant mice. Reporter-based assays further revealed the importance of base pairing between piRNAs and mRNA targets and the requirement for both the slicer activity and piRNA-loading ability of MIWI in piRNA-mediated target repression. Importantly, we demonstrated that proper turnover of certain key piRNA targets is essential for sperm formation. Together, these findings reveal the siRNA-like function of the piRNA machinery in mouse testes and its central requirement for male germ cell development and maturation.
Magnesium isotopic compositions are reported for twenty‐four international geological reference materials including igneous, metamorphic and sedimentary rocks, as well as phlogopite and serpentine ...minerals. The long‐term reproducibility of Mg isotopic determination, based on 4‐year analyses of olivine and seawater samples, was ≤ 0.07‰ (2s) for δ26Mg and ≤ 0.05‰ (2s) for δ25Mg. Accuracy was tested by analysis of synthetic reference materials down to the quoted long‐term reproducibility. This comprehensive dataset, plus seawater data produced in the same laboratory, serves as a reference for quality assurance and inter‐laboratory comparison of high‐precision Mg isotopic data.
Les compositions isotopiques du magnésium sont fournies pour vingt‐quatre matériaux géologiques de référence internationaux, comprenant des roches ignées, métamorphiques et sédimentaires, ainsi qu'une phlogopite et des serpentines. La reproductibilité à long terme de la détermination isotopique du Mg, basée des analyses sur quatre ans d’échantillons d'olivine et d'eau de mer, était ≤ 0.07% (2s) pour δ26Mg et ≤ 0.05% (2s) pour δ25Mg. La précision a été testée par l'analyse de matériaux de référence synthétiques jusqu’à la reproductibilité à long terme indiquée. Cette base de données complète, ainsi que des données d'eau de mer produites dans le même laboratoire, servent de référence pour l'assurance qualité et la comparaison inter‐laboratoires de haute précision des données isotopiques du Mg.
It is unclear as to whether Wilms' tumor 1-associated protein (WTAP) promotes or suppresses breast cancer. This immunohistochemistry analysis explored levels of WTAP expression in 347 cases of breast ...cancer and analyzed the relationship between WTAP expression and the clinicopathological characteristics and prognosis of breast cancer patients. The rate of high WTAP expression was significantly higher in breast cancer tissue than in adjacent normal breast tissue (37.5% vs 0.0%; P < 0.001). WTAP expression was positively associated with tumor size and grade, and negatively associated with axillary lymph node metastasis, estrogen and progesterone receptor status. Rates of high WTAP expression were 66.1% in triple-negative breast cancer (TNBC) tissue and 31.3% in non-TNBC tissue. In multiple logistic regression analysis, independent predictors of WTAP expression in breast cancer included larger tumor size (odds ratio = 1.907; 95% confidence interval: 1.185-3.067; P = 0.008), lymph node metastasis (0.597; 0.373-0.956; P = 0.032) and TNBC status (3.735; 2.056-6.784; P < 0.001). No clear relationship was observed between patient prognosis and WTAP expression. We suggest that WTAP expression is upregulated in breast cancer and appears to both promote tumor growth and inhibit lymph node metastasis.
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