Stepwise and large-magnitude negative shift in δ13Ccarb preceded the main marine mass extinction of the Permian–Triassic crisis interval

Large perturbations to the global carbon cycle occurred during the Permian–Triassic boundary mass extinction, the largest extinction event of the Phanerozoic Eon (542 Ma to present). Controversy concerning the pattern and mechanism of variations in the marine carbonate carbon isotope record of the Permian–Triassic crisis interval (PTCI) and their relationship to the marine mass extinction has not been resolved to date. Herein, high-resolution carbonate carbon isotope profiles (δ¹³C_carb), accompanied by lithofacies, were generated for four sections with microbialite (Taiping, Zuodeng, Cili, and Chongyang) in South China to better constrain patterns and controls on δ¹³C_carb variation in the PTCI and to test hypotheses about the temporal relationship between perturbations to the global carbon cycle and the marine mass extinction event. All four study sections exhibit a stepwise negative shift in δ¹³C_carb during the Late Permian–Early Triassic, with the shift preceding the end-Permian crisis being larger (> 3‰) than that following it (1–2‰). The pre-crisis shifts in δ¹³C_carb are widely correlatable and, hence, represent perturbations to the global carbon cycle. The comparatively smaller shifts following the crisis demonstrate that the marine mass extinction event itself had at most limited influence on the global carbon cycle, and that both Late Permian δ¹³C_carb shifts and the mass extinction must be attributed to some other cause. Their origin cannot be uniquely determined from C-isotopic data alone but appears to be most compatible with a mechanism based on episodic volcanism in combination with collapse of terrestrial ecosystems and soil erosion.     

TMEM43-S358L mutation enhances NF-κBTGFβ signal cascade in arrhythmogenic right ventricular dysplasia/cardiomyopathy

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is a genetic cardiac muscle disease that accounts for approximately 30% sudden cardiac death in young adults. The Ser358Leu mutation of transmembrane protein 43 (TMEM43) was commonly identified in the patients of highly lethal and fully penetrant ARVD subtype, ARVD5. Here, we generated TMEM43 S358L mouse to explore the underlying mechanism. This mouse strain showed the classic pathologies of ARVD patients, including structural abnormalities and cardiac fibrofatty. TMEM43 S358L mutation led to hyper-activated nuclear factor κB (NF-κB) activation in heart tissues and primary cardiomyocyte cells. Importantly, this hyper activation of NF-κB directly drove the expression of pro-fibrotic gene, transforming growth factor beta (TGFβ1), and enhanced downstream signal, indicating that TMEM43 S358L mutation up-regulates NF-κB-TGFβ signal cascade during ARVD cardiac fibrosis. Our study partially reveals the regulatory mechanism of ARVD development.     

Genetic differentiation of Pseudoregma bambucicola population based on mtDNA COII gene

mtDNA COII gene sequences were identified and analyzed using different types of software, namely, MEGA5.0, DNAMAN, and DnaSP5.0 in four Chinese provinces, namely, Sichuan, Zhejiang, Guizhou and Shanghai. Analysis of molecular genetic variation and its genetic structure and differentiation, combined with NJ tree, MP tree analysis and analysis of molecular variance (AMOVA), at Fst = 0.0582 conclude that the genetic differentiation is low, gene flow is Nm = 8.0911, and gene exchange is sufficient. However, for the geographic populations of Pseudoregma bambucicola in the four provinces, their gene exchange is relatively weak at Nm = 0.8284, whereas the genetic differentiation is high at Fst = 0.3764. Based on the data, total nucleotide diversity between the populations is 0.00158 ± 0.00021. The results showed that the total population of Tajima’s D and Fu’s Fs results are D = ?0.885 and Fs = 0.226, respectively. The experimental numerical results showed that this total population is not significant (P > 0.10), indicating that nine different geographic populations are short-term. No expansion occurred in the internal population. This study provided a theoretical and practical basis for the comprehensive prevention and control of P. bambucicola.     

Inhibition of circular RNA CDR1as increases chemosensitivity of 5‐FU‐resistant BC cells through up‐regulating miR‐7

This study aims to explore the mechanism of Circular RNA CDR1as implicating in regulating 5‐fluorouracil (5‐FU) chemosensitivity in breast cancer (BC) by competitively inhibiting miR‐7 to regulate CCNE1. Expressions of CDR1as and miR‐7 in 5‐FU‐resistant BC cells were determined by RT‐PCR. CCK‐8, colony formation assay and flow cytometry were applied to measure half maximal inhibitory concentration (IC50), 5‐Fu chemosensitivity and cell apoptosis. Western blot was used to detect the expressions of apoptosis‐related factors. CDR1as was elevated while miR‐7 was inhibited in 5‐FU‐resistant BC cells. Cells transfected with si‐CDR1as or miR‐7 mimic had decreased IC50 and colony formation rate, increased expressions of Bax/Bcl2 and cleaved‐Caspase‐3/Caspase‐3, indicating inhibition of CDR1as and overexpression of miR‐7 enhances the chemosensitity of 5‐FU‐resistant BC cells. Targetscan software indicates a binding site of CDR1as and miR‐7 and that CCNE1 is a target gene of miR‐7. miR‐7 can gather CDR1as in BC cells and can inhibit CCNE1. In comparison to si‐CDR1as group, CCNE1 was increased and chemosensitivity to 5‐Fu was suppressed in si‐CDR1as + miR‐7 inhibitor group. When compared with miR‐7 mimic group, CDR1as + miR‐7 mimic group had increased CCNE1 and decreased chemosensitivity to 5‐Fu. Nude mouse model of BC demonstrated that the growth of xenotransplanted tumour in si‐CDR1as + miR‐7 inhibitor group was faster than that in si‐CDR1as group. The tumour growth in CDR1as + miR‐7 mimic group was faster than that in miR‐7 mimic group. CDR1as may regulate chemosensitivity of 5‐FU‐resistant BC cells by inhibiting miR‐7 to regulate CCNE1.     

蔓生百部的化学成分研究

从蔓生百部(Stemona japonica)根中分离得到13个化合物,通过波谱数据,它们鉴定为β-谷甾醇(1)、豆甾醇(2)、5,11-豆甾二烯-3β-醇(3)、苯甲酸(4)、4-甲氧基苯甲酸(5)、1,8-二羟基-3-甲基蒽醌(6)、1,8-二羟基-6-甲氧基-3-甲基蒽醌(7)、氧代狭叶百部碱(8)、百部定碱(9)、异狭叶百部碱(10)、绿原酸(11)、栀子苷(12)和藏红花素A(13).所有化合物均为首次从该植物中分离得到.     

An empirical EEG analysis in brain death diagnosis for adults

Electroencephalogram (EEG) is often used in the confirmatory test for brain death diagnosis in clinical practice. Because EEG recording and monitoring is relatively safe for the patients in deep coma, it is believed to be valuable for either reducing the risk of brain death diagnosis (while comparing other tests such as the apnea) or preventing mistaken diagnosis. The objective of this paper is to study several statistical methods for quantitative EEG analysis in order to help bedside or ambulatory monitoring or diagnosis. We apply signal processing and quantitative statistical analysis for the EEG recordings of 32 adult patients. For EEG signal processing, independent component analysis (ICA) was applied to separate the independent source components, followed by Fourier and time-frequency analysis. For quantitative EEG analysis, we apply several statistical complexity measures to the EEG signals and evaluate the differences between two groups of patients: the subjects in deep coma, and the subjects who were categorized as brain death. We report statistically significant differences of quantitative statistics with real-life EEG recordings in such a clinical study, and we also present interpretation and discussions on the preliminary experimental results.

ARHI (DIRAS3)-mediated autophagy-associated cell death enhances chemosensitivity to cisplatin in ovarian cancer cell lines and xenografts

Autophagy can sustain or kill tumor cells depending upon the context. The mechanism of autophagy-associated cell death has not been well elucidated and autophagy has enhanced or inhibited sensitivity of cancer cells to cytotoxic chemotherapy in different models. ARHI (DIRAS3), an imprinted tumor suppressor gene, is downregulated in 60% of ovarian cancers. In cell culture, re-expression of ARHI induces autophagy and ovarian cancer cell death within 72 h. In xenografts, re-expression of ARHI arrests cell growth and induces autophagy, but does not kill engrafted cancer cells. When ARHI levels are reduced after 6 weeks, dormancy is broken and xenografts grow promptly. In this study, ARHI-induced ovarian cancer cell death in culture has been found to depend upon autophagy and has been linked to G1 cell-cycle arrest, enhanced reactive oxygen species (ROS) activity, RIP1/RIP3 activation and necrosis. Re-expression of ARHI enhanced the cytotoxic effect of cisplatin in cell culture, increasing caspase-3 activation and PARP cleavage by inhibiting ERK and HER2 activity and downregulating XIAP and Bcl-2. In xenografts, treatment with cisplatin significantly slowed the outgrowth of dormant autophagic cells after reduction of ARHI, but the addition of chloroquine did not further inhibit xenograft outgrowth. Taken together, we have found that autophagy-associated cancer cell death and autophagy-enhanced sensitivity to cisplatin depend upon different mechanisms and that dormant, autophagic cancer cells are still vulnerable to cisplatin-based chemotherapy.Autophagy has a well-defined role in cellular physiology, removing senescent organelles and catabolizing long-lived proteins.^{1, 2} Under nutrient-poor conditions, the fatty acids and amino acids produced by hydrolysis of lipids and proteins in autophagolysosomes can provide energy to sustain starving cells. Prolonged autophagy is, however, associated with caspase-independent type II programmed cell death. Although the mechanism of autophagy-associated cell death has not been adequately characterized, programmed necrosis or necroptosis has been implicated in some studies.^{3, 4}Given the ability to sustain or kill cells, the role of autophagy in cancer is complex and dependent on the context of individual studies. During oncogenesis in genetically engineered mice, reduced hemizygous expression of genes required for autophagy (BECN1, Atg4, ATG5, Atg7) can accelerate spontaneous or chemically induced tumor formation,^{5, 6} suggesting that autophagy can serve as a tumor suppressor. Other observations with established cancers suggest that autophagy can sustain metabolically challenged neoplasms, particularly in settings with inadequate vascular access.^{7, 8} Autophagy has also been shown to protect cancer cells from the lethal effects of some cytotoxic drugs.^{9, 10}Our group has found that cancer cell proliferation,^{11, 12, 13} motility,¹⁴ autophagy and tumor dormancy^{15, 16} can be regulated by an imprinted tumor suppressor gene, ARHI (DIRAS3), that is downregulated in 60% of ovarian cancers by multiple mechanisms,^{17, 18} associated with shortened progression-free survival.¹⁹ Ovarian cancer cell sublines have been developed with tet-inducible expression of ARHI. In cell culture, re-expression of ARHI induces autophagy and clonogenic ovarian cancer cell death within 72 h.¹⁶ In xenografts, re-expression of ARHI arrests cell growth, inhibits angiogenesis and induces autophagy, but does not kill engrafted cancer cells. When ARHI levels are reduced after 6 weeks of induction, dormancy is broken, vascularization occurs and xenografts grow promptly. Treatment of dormant xenografts with chloroquine (CQ), a functional inhibitor of autophagy, delays tumor outgrowth, suggesting that autophagy facilitates survival of poorly vascularized, nutrient-deprived ovarian cancer cells. The relevance of this model to human disease is supported by the recent observation that small deposits of dormant ovarian cancer found on the peritoneal surface at ‘second look'' operations following initial surgery and chemotherapy exhibit autophagy and increased expression of ARHI in >80% of cases.²⁰Ovarian cancer develops in >22 000 women each year in the United States.²¹ Over the past four decades, the 5-year survival has increased from 37% to ∼50% with optimal cytoreductive surgery and combination chemotherapy using taxane- and platinum-based regimens,^{21, 22} but long-term survival and cure stand at ∼30% for all stages, due, in large part, to the persistence and recurrence of dormant, drug-resistant ovarian cancer cells. For the past two decades, standard chemotherapy for ovarian cancer has included a combination of a platinum compound and a taxane. Carboplatin and cisplatin are alkylating agents that bind covalently to DNA producing intra- and inter-strand crosslinks that, if not repaired, induce apoptosis and cell death.^{23, 24} Our previous studies suggest that ∼20% of primary ovarian cancers exhibit punctate immunohistochemical staining for LC3, a biomarker for autophagy that decorates autophagosome membranes, whereas >80% of cancers that have survived platinum-based chemotherapy exhibit punctate LC3.²⁰ Consequently, autophagy might provide one mechanism of resistance to platinum-based therapy.In this report, we have explored mechanism(s) by which ARHI induces autophagy-associated cell death and enhances cisplatin cytotoxicity. Cisplatin has been found to trigger apoptosis by inducing caspase-3 activation and PARP cleavage in ovarian cancer cells.^{25, 26} We hypothesized that autophagy-associated cell death and autophagy-enhanced sensitivity to cisplatin depend upon different mechanisms and that dormant, autophagic cancer cells might still be vulnerable to platinum-based chemotherapy.