Successful Removal and Replacement of a Stuck Hemodialysis Catheter via Thoracotomy: Report of Two Cases and Literature Review.

Introduction: Stuck tunneled central venous catheters (CVCs) have been increasingly reported. In rare cases, the impossibility of extracting the CVC from the central vein after regular traction is the result of rigid adhesions to the surrounding fibrin sheath. Forced traction during catheter removal can cause serious complications, including cardiac tamponade, hemothorax, and hemorrhagic shock. Knowledge and experience on how to properly manage the stuck catheter are still limited. Case Presentation: Here, we present two cases that highlight the successful removal of the stuck tunneled CVC via thoracotomy through the close collaboration of multidisciplinary specialists in the best possible way. Both patients underwent an unsuccessful attempt at thrombolytic therapy with urokinase, catheter traction under the guidance of digital subtraction angiography and intraluminal balloon dilation. And we reviewed the literature on stuck catheters in the hope of providing knowledge and effective approaches to attempted removal of stuck catheters. Conclusion: There is no standardized procedure for dealing with stuck catheters. Intraluminal percutaneous transluminal angioplasty should be considered as the first-line treatment, while open surgery represents a second option only in the event of failure. Care must be taken that forced extubation can cause patients life-threatening.

ALCAT1-mediated abnormal cardiolipin remodelling promotes mitochondrial injury in podocytes in diabetic kidney disease.

BACKGROUND: Cardiolipin (CL) plays a critical role in maintaining mitochondrial membrane integrity and overall mitochondrial homeostasis. Recent studies have suggested that mitochondrial damage resulting from abnormal cardiolipin remodelling is associated with the pathogenesis of diabetic kidney disease (DKD). Acyl-coenzyme A:lyso-cardiolipin acyltransferase-1 (ALCAT1) was confirmed to be involved in the progression of Parkinson's disease, diet-induced obesity and other ageing-related diseases by regulating pathological cardiolipin remodelling. Thus, the purpose of this investigation was to determine the role of ALCAT1-mediated CL remodelling in DKD and to explore the potential underlying mechanism. METHODS: In vivo study, the mitochondrial structure was examined by transmission electron microscopy (TEM). The colocalization of ALCAT1 and synaptopodin was evaluated by double immunolabelling. Western blotting (WB) was performed to assess ALCAT1 expression in glomeruli. Lipidomics analysis was conducted to evaluate the composition of reconstructed cardiolipins. In vitro study, the lipidomics, TEM and WB analyses were similar to those in vivo. Mitochondrial function was evaluated by measuring the mitochondrial membrane potential (MMP) and the production of ATP and ROS. RESULTS: Here, we showed that increased oxidized cardiolipin (ox-CL) and significant mitochondrial damage were accompanied by increased ALCAT1 expression in the glomeruli of patients with DKD. Similar results were found in db/db mouse kidneys and in cultured podocytes stimulated with high glucose (HG). ALCAT1 deficiency effectively prevented HG-induced ox-CL production and mitochondrial damage in podocytes. In contrast, ALCAT1 upregulation enhanced ox-CL levels and podocyte mitochondrial dysfunction. Moreover, treatment with the cardiolipin antioxidant SS-31 markedly inhibited mitochondrial dysfunction and cell injury, and SS-31 treatment partly reversed the damage mediated by ALCAT1 overexpression. We further found that ALCAT1 could mediate the key regulators of mitochondrial dynamics and mitophagy through the AMPK pathway. CONCLUSIONS: Collectively, our studies demonstrated that ALCAT1-mediated cardiolipin remodelling played a crucial role in DKD, which might provide new insights for DKD treatment. Video Abstract.

Evaluation of the reliability and validity of the health regulatory focus scale in Chinese samples.

This study sought to validate the psychometric properties of the Health Regulatory Focus Scale (HRFS), emphasizing its manifestation and association with personality traits in a Chinese context. Originally developed by Ferrer, the HRFS gauges individuals' inclinations either to avoid negative health outcomes (prevention focus) or achieve positive health outcomes (promotion focus). Our cross-sectional analysis involved a diverse sample of 652 Chinese participants, averaging 39.6 years in age (SD = 9.39). Data were analyzed using SPSS and AMOS, and both exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were employed to assess the HRFS's factor structure. Additionally, we evaluated convergent and discriminant validity, criterion-related validity, internal consistency reliability, and test-retest reliability. The CFA results (CFI = 0.985, TLI = 0.971, RMSEA = 0.059, and SRMR = 0.047), combined with McDonald's omega value (0.916) and the test-retest correlation coefficient (0.78) for the HRFS, underscore its robust construct validity and reliability. Furthermore, the promotion dimension of the HRFS exhibited significant positive correlations with all dimensions of the Chinese Adjectives Short Scale of Big-Five Factor Personality (BFFP-CAS-S). In conclusion, the HRFS's Chinese adaptation offers a reliable and valid instrument for assessing health regulatory focus.

Curcumin protects from LPS-induced activation of astrocytes via AMPK pathway.

Curcumin, a phenolic pigment, plays an inhibitory role in astrocytes activation which are involved in the pathogenesis of neurological diseases and inflammatory responses. The present study aimed to investigate the underlying regulatory mechanism behind the therapeutic effect of curcumin on the lipopolysaccharide (LPS)-activated astrocytes in vitro. Specifically, we investigated the inhibitory effect of curcumin on LPS-induced astrocyte's proliferation. Additionally, we investigated whether the adenosine-monophosphate-activated protein kinase signaling (AMPK) pathway was involved in this process. Our data demonstrated that curcumin significantly increased the level of phosphorylated AMPK protein in LPS-activated astrocytes. In addition, our data demonstrated that curcumin play an inhibitory role on the migration, autophagy, the pro-inflammatory mediators by the AMPK signaling pathway in LPS-activated astrocytes. These results could shed light on understanding of molecular mechanism for the inhibition of curcumin on migration, autophagy, and the pro-inflammatory mediators during the process of astrocyte activation, and might contribute to a promising therapeutic intervention in the neurological diseases-related astrocytes activation.

Identification of Hub Genes Correlated with the Initiation and Development in Chronic Kidney Disease via Bioinformatics Analysis.

INTRODUCTION: Chronic kidney disease (CKD) is a major public health issue worldwide, which is characterized by irreversible loss of nephron and renal function. However, the molecular mechanism of CKD remains underexplored. METHODS: This study integrated three transcriptional profile datasets to investigate the molecular mechanism of CKD. The differentially expressed genes (DEGs) between Sham control (Con) and unilateral ureteral obstruction (UUO)-operated mice were analyzed by utilizing the limma package in R. The shared DEGs were analyzed by Gene Ontology and functional enrichment. Protein-protein interactions (PPIs) were constructed by utilizing the STRING database. Hub genes were analyzed by MCODE and Cytohubba. We further validated the gene expression by using the other dataset and mouse UUO model. RESULTS: A total of 315 shared DEGs between Con and UUO samples were identified. Gene function and KEGG pathway enrichment revealed that DEGs were mainly enriched in inflammatory response, immune system process, and chemokine signaling pathway. Two modules were clustered based on PPI network analysis. Module 1 contained 13 genes related to macrophage activation, migration, and chemotaxis. Ten hub genes were identified by PPI network analysis. Subsequently, the expression levels of hub genes were validated with the other dataset. Finally, these four validated hub genes were further confirmed by our UUO mice. Three validated hub genes, Gng2, Pf4, and Ccl9, showed significant response to UUO. CONCLUSION: Our study reveals the coordination of genes during UUO and provides a promising gene panel for CKD treatment. GNG2 and PF4 were identified as potential targets for developing CKD drugs.

Overexpressing SIRT6 can Attenuate the Injury of Intracerebral Hemorrhage by Down-Regulating NF-kB.

Sirtuin-6 (SIRT6), a member of the sirtuins family of NAD ( +) dependent deacetylases, has been shown to have beneficial effects in ischemic stroke. However, the role of SIRT6 in intracerebral haemorrhage (ICH) has not reported. We observed that SIRT6 expression was down-regulated in human ICH patients and down-regulated in ICH-induced rat cortical neurons. We subsequently found that SIRT6 overexpression reduced brain tissue damage and increased neuronal survival in the ICH model of rats and hemin-induced cortical neurons. Our further study found that overexpression of SIRT6 can reduce inflammatory response by down-regulating the expression of NF-kB and thus promote the recovery of neurological function in ICH animals. In conclusion, SIRT6 can inhibit the expression of NF-kB and plays a neuroprotective role in ICH by inhibiting the NF-kB-mediated inflammatory response.SIRT6 could be a novel therapeutic target for ICH.

Anthocyanins accumulation analysis of correlated genes by metabolome and transcriptome in green and purple peppers (Capsicum annuum).

BACKGROUND: In order to clarify the the molecular mechanism of anthocyanin accumulation in green and purple fruits of pepper using metabolomics and transcriptomics,to identify different anthocyanin metabolites,and to analyze the differentially expressed genes involved in anthocyanin biosynthesis.. RESULTS: We analyzed the anthocyanin metabolome and transcriptome data of the fruits of 2 purple pepper and 1 green pepper. A total of 5 anthocyanin metabolites and 2224 differentially expressed genes were identified between the green and purple fruits of pepper. Among the 5 anthocyanin metabolites,delphin chloride was unique to purple pepper fruits,which is the mainly responsible for the purple fruit color of pepper. A total of 59 unigenes encoding 7 enzymes were identified as candidate genes involved in anthocyanin biosynthesis in pepper fruit. The six enzymes (PAL,C4H,CHI,DFR,ANS,UFGT) had higher expression levels except the F3H gene in purple compared with green fruits. In addition,seven transcription factors were also found in this study. These transcription factors may contribute to anthocyanin metabolite biosynthesis in the fruits of pepper. One of differentially expressed gene novel.2098 was founded. It was not annotated in NCBI. Though blast analysis we preliminarily considered that this gene related to MYB transcription factor and was involved in anthocyanin biosynthesis in pepper fruit. CONCLUSIONS: Overall, the results of this study provide useful information for understanding anthocyanin accumulation and the molecular mechanism of anthocyanin biosynthesis in peppers.

Sirt6-mediated Nrf2/HO-1 activation alleviates angiotensin II-induced DNA DSBs and apoptosis in podocytes.

Recent studies suggested that DNA double-strand breaks (DSBs) were associated with the pathogenesis of chronic kidney disease (CKD). The purpose of this investigation was to determine the role of Sirtuin6 (Sirt6), a histone deacetylase related to DNA damage repair, in angiotensin (Ang) II-induced DNA DSBs and the cell injury of podocytes and explore the possible mechanism. Here we showed that an increase of DNA DSBs was accompanied by a reduction in Sirt6 expression in the glomeruli of patients with hypertensive nephropathy (HN). Similar results were found in rat kidneys infused with Ang II and in cultured podocytes stimulated with Ang II. Sirt6 overexpression inhibited Ang II-induced ROS generation and DNA DSBs, and thus served as a protection against Ang II-induced apoptosis in podocytes. Moreover, Sirt6 activation enhanced Nrf2 and HO-1 gene expressions in podocytes after Ang II treatment. Furthermore, Nrf2 knockdown could partly reverse the cytoprotective effects of Sirt6 activation. In conclusion, our observations demonstrated that the Sirt6-Nrf2-HO-1 pathway played a vital role in relieving Ang II-mediated oxidative DNA damage and podocyte injury.

Transcranial direct-current stimulation protects against cerebral ischemia-reperfusion injury through regulating Cezanne-dependent signaling.

Transcranial direct-current stimulation (tDCS) is proved safe and shows therapeutic effect in cerebral ischemic stroke in clinical trials. But the underlying molecular mechanisms remain unclear. Here we show that tDCS treatment reduces the infarct volume after rat cerebral ischemia-reperfusion (I/R) injury and results in functional improvement of stroke animals. At the cellular and molecular level, tDCS suppresses I/R-induced upregulation of Cezanne in the ischemic neurons. Cezanne inhibition confers neuroprotection after rat I/R and oxygen glucose deprivation (OGD) in the cortical neuronal cultures. Inhibiting Cezanne increases the level of SIRT6 that is downregulated in the ischemic neurons. Suppressing SIRT6 blocks Cezanne inhibition-induced neuroprotective effect and overexpressing SIRT6 attenuates OGD-induced neuronal death. We further show that downregulating Cezanne reduces DNA double-strand break (DSB) through upregulation of SIRT6 in OGD-insulted neurons. Together, this study suggests that Cezanne-dependent SIRT6-DNA DSB signaling pathway may mediate the neuroprotective effect of tDCS in ischemic neurons.

Mfn2 Regulates High Glucose-Induced MAMs Dysfunction and Apoptosis in Podocytes via PERK Pathway.

The endoplasmic reticulum (ER) stress and mitochondrial dysfunction in high glucose (HG)-induced podocyte injury have been demonstrated to the progression of diabetic kidney disease (DKD). However, the pathological mechanisms remain equivocal. Mitofusin2 (Mfn2) was initially identified as a dynamin-like protein involved in fusing the outer mitochondrial membrane (OMM). More recently, Mfn2 has been reported to be located at the ER membranes that contact OMM. Mitochondria-associated ER membranes (MAMs) is the intercellular membrane subdomain, which connects the mitochondria and ER through a proteinaceous tether. Here, we observed the suppression of Mfn2 expression in the glomeruli and glomerular podocytes of patients with DKD. Streptozotocin (STZ)-induced diabetic rats exhibited abnormal mitochondrial morphology and MAMs reduction in podocytes, accompanied by decreased expression of Mfn2 and activation of all three unfolded protein response (UPR) pathways (IRE1, ATF6, and PERK). The HG-induced mitochondrial dysfunction, MAMs reduction, and increased apoptosis in vitro were accompanied by the downregulation of Mfn2 and activation of the PERK pathway. Mfn2 physically interacts with PERK, and HG promotes a decrease in Mfn2-PERK interaction. In addition, Mfn2-silenced podocytes showed mitochondrial dysfunction, MAMs reduction, activation of PERK pathway, and increased apoptosis. Conversely, all these effects of HG stimulation were alleviated significantly by Mfn2 overexpression. Furthermore, the inhibition of PERK phosphorylation protected mitochondrial functions but did not affect the expression of Mfn2 in HG-treated podocytes. Therefore, this study confirmed that Mfn2 regulates the morphology and functions of MAMs and mitochondria, and exerts anti-apoptotic effects on podocytes by inhibiting the PERK pathway. Hence, the Mfn2-PERK signaling pathway may be a new therapeutic target for preventing podocyte injury in DKD.

Sestrin­2 regulates podocyte mitochondrial dysfunction and apoptosis under high­glucose conditions via AMPK.

Diabetic kidney disease (DKD) is a severe form of microangiopathy among diabetic patients, of which podocyte injury is one of the more predominant features. There is increasing evidence to suggest that mitochondrial dysfunction is associated with podocyte injury, thus contributing to the progression of DKD. Initially identified as a p53 target protein, the endogenous antioxidant protein, sestrin­2 (sesn2), has recently attracted attention due to its potential function in various inflammatory diseases. However, the association between sesn2 and podocytes in DKD remains unclear. In the present study, to elucidate the role of sesn2 in podocyte mitochondrial dysfunction, the effects of sesn2 on the regulation of AMP­activated protein kinase (AMPK) were examined in vitro and in vivo. Abnormal mitochondria were found in rats with streptozotocin­induced diabetes, and hyperglycemia downregulated the expression of sesn2. The upregulation of sesn2 increased the level of AMPK phosphorylation, and thus ameliorated mitochondrial dysfunction under high glucose conditions (HG). On the whole, these results suggest that sesn2 is associated with mitochondrial dysfunction in podocytes under HG conditions. In addition, the decreased expression of sesn2 may be a therapeutic target for DKD.

Sirt6 attenuates hypoxia-induced tubular epithelial cell injury via targeting G2/M phase arrest.

Acute kidney injury (AKI) is a condition that has a high incidence and death rate. Unfortunately, the kidney may not recover completely after AKI, which then develops to chronic kidney disease (CKD). Therefore, it is necessary to identify potential curative targets to avoid its development to CKD. As an NAD+ -dependent deacetylase, sirtuin 6 (Sirt6) has been linked to different types of biological processes. In the present work, our group investigated the role of Sirt6 in tubular epithelial cells (TECs) under hypoxic stress. Sirt6 expression was examined in mouse kidney following ischemia/reperfusion (IR) injury and hypoxia-challenged TECs. Using Sirt6 plasmid and small interfering RNA, we also investigated how, in regard to inflammation and epithelial-to-mesenchymal transition, Sirt6 affects hypoxia-triggered injury. In addition, cell cycle was detected in hypoxia-challenged TECs. Sirt6 was downregulated in the kidney of mice with IR injury and hypoxia-challenged TECs. Consequently, Sirt6 depletion aggravated hypoxia-induced injury and G2/M phase arrest. Sirt6 overexpression attenuated hypoxia-triggered damage and G2/M phase arrest in TECs. Sirt6 prevented hypoxia-triggered TEC damage via suppressing G2/M phase arrest. Thus, Sirt6 is a possible candidate for alleviating the effects of kidney injury.

ACSL4 suppresses glioma cells proliferation via activating ferroptosis.

Acyl­CoA synthetase long­chain family member 4 (ACSL4) is a member of the long chain family of acyl­CoA synthetase proteins, which have recently been shown to serve an important role in ferroptosis. Previous studies have suggested that ferroptosis is involved in the occurrence of glioma; however, the role of ACSL4 in glioma remains unknown. In the present study, a reduction of ferroptosis in human glioma tissues and glioma cells was observed. Subsequently, it was demonstrated that the expression of ACSL4 was also downregulated in human glioma tissues and cells. A ferroptosis inhibitor and inducer were used to investigate the effects of ferroptosis on viability. The results showed that promoting ferroptosis inhibited the proliferation of glioma cells, and that the use of inducers had the reverse effect. Therefore, it was hypothesized that the reduction in ACSL4 expression may have been involved in ferroptosis and proliferation in glioma. Overexpression of ACSL4 decreased expression of glutathione peroxidase 4 and increased the levels of ferroptotic markers, including 5­hydroxyeicosatetraenoic (HETE), 12­HETE and 15­HETE. Additionally, ACSL4 overexpression resulted in an increase in lactate dehydrogenase release and a reduction in cell viability. The opposite results were observed when ACSL4 was silenced. These findings suggest that ACSL4 regulates ferroptosis and proliferation of glioma cells. To further investigate the mechanism underlying ACSL4­mediated regulation of proliferation in glioma cells, cells were treated with small interfering (si)­ACSL4 and sorafenib, a ferroptosis inducer. sorafenib attenuated the ability of siRNA­mediated silencing of ACSL4, thus improving cell viability. These results demonstrate that ACSL4 protects glioma cells and exerts anti­proliferative effects by activating a ferroptosis pathway and highlight the pivotal role of ferroptosis regulation by ACSL4 in its protective effects on glioma. Therefore, ACSL4 may serve as a novel therapeutic target for the treatment of glioma.

HIF-1α contributes to Ang II-induced inflammatory cytokine production in podocytes.

BACKGROUND: Studies have indicated that changed expression of hypoxia-inducible factor-1α (HIF-1α) in epithelial cells from the kidney could affect the renal function in chronic kidney disease (CKD). As Angiotensin II (Ang II) is a critical active effector in the renin-angiotensin system (RAS) and was proved to be closely related to the inflammatory injury. Meanwhile, researchers found that Ang II could alter the expression of HIF-1α in the kidney. However, whether HIF-1α is involved in mediating Ang II-induced inflammatory injury in podocytes is not clear. METHODS: Ang II perfusion animal model were established to assess the potential role of HIF-1α in renal injury in vivo. Ang II stimulated podocytes to observe the corresponding between HIF-1α and inflammatory factors in vitro. RESULTS: The expression of inflammatory cytokines such as MCP-1 and TNF-α was increased in the glomeruli from rats treated with Ang II infusion compared with control rats. Increased HIF-1α expression in the glomeruli was also observed in Ang II-infused rats. In vitro, Ang II upregulated the expression of HIF-1α in podocytes. Furthermore, knockdown of HIF-1α by siRNA decreased the expression of MCP-1 and TNF-α. Moreover, HIF-1α siRNA significantly diminished the Ang II-induced overexpression of HIF-1α. CONCLUSION: Collectively, our results suggest that HIF-1α participates in the inflammatory response process caused by Ang II and that downregulation of HIF-1α may be able to partially protect or reverse inflammatory injury in podocytes.

Mechanism and Treatment Related to Oxidative Stress in Neonatal Hypoxic-Ischemic Encephalopathy.

Hypoxic ischemic encephalopathy (HIE) is a type of neonatal brain injury, which occurs due to lack of supply and oxygen deprivation to the brain. It is associated with a high morbidity and mortality rate. There are several therapeutic strategies that can be used to improve outcomes in patients with HIE. These include cell therapies such as marrow mesenchymal stem cells (MSCs) and umbilical cord blood stem cells (UCBCs), which are being incorporated into the new protocols for the prevention of ischemic brain damage. The focus of this review is to discuss the mechanism of oxidative stress in HIE and summarize the current available treatments for HIE. We hope that a better understanding of the relationship between oxidative stress and HIE will provide new insights on the potential therapy of this devastating condition.

Sirt6 Suppresses High Glucose-Induced Mitochondrial Dysfunction and Apoptosis in Podocytes through AMPK Activation.

Previous studies have shown that mitochondrial dysfunction plays an important role in high- glucose(HG)-induced podocyte injury and thus contributes to the progression of diabetic nephropathy(DN). The histone deacetylase Sirtuin6 (Sirt6) has been revealed to have an essential role in the regulation of mitochondrial function in skeletal muscle and cardiomyocytes. However, its specific role in mitochondrial homeostasis in podocytes is undetermined. Here, we aimeds to explore the physiological function of Sirt6 in podocyte mitochondria and apoptosis under HG conditions and explore the possible mechanism. Herein, we observed that Sirt6-WT-1 colocalization was suppressed in the glomeruli of patients with DN. In addition, diabetic mice exhibited reduced Sirt6 expression and AMP kinase (AMPK) dephosphorylation accompanied by mitochondrial morphological abnormalities. In vitro, podocytes exposed to HG presented with mitochondrial morphological alterations and podocyte apoptosis accompanied by Sirt6 and p-AMPK downregulation. In addition, HG promoted a decrease in mitochondrial number and an increase in mitochondrial superoxide production as well as a decreased mitochondrial membrane potential. ROS production was also increased in HG-treated podocytes. Conversely, all these mitochondrial defects induced by HG were significantly alleviated by Sirt6 plasmid transfection. Sirt6 overexpression simultaneously alleviated HG-induced podocyte apoptosis and oxidative stress, as well as increased AMPK phosphorylation. Increased levels of H3K9ac and H3K56ac induced by HG were attenuated in podocytes transfected with Sirt6 plasmids. Therefore, these results elucidated that Sirt6 protects mitochondria of podocytes and exerts anti-apoptotic effects via activating AMPK pathway. The present findings provide key insights into the pivotal role of mitochondria regulation by SIRT6 in its protective effects on podocytes.

Effect of Preserving the Pituitary Stalk During Resection of Craniopharyngioma in Children on the Diabetes Insipidus and Relapse Rates and Long-Term Outcomes.

OBJECTIVE: The objective of this study was to investigate the effect of preserving an infiltrated pituitary stalk during the resection of craniopharyngioma of pituitary stalk origin on postoperative outcomes and thus provide a theoretical basis for microsurgical treatment and prognosis. METHODS: We screened the clinical data of all 103 pediatric patients with craniopharyngioma undergoing surgical treatment at our department between January 2006 and January 2013 and conducted a retrospective analysis of 82 patients with craniopharyngioma originating in the pituitary stalk. The patients were followed up from 12 months to 8 years. We analyzed the effect of preserving the pituitary stalk on the early and persistent diabetes insipidus rates, postoperative relapse rate, and mortality. RESULTS: In the total resection group (n = 67), the early and persistent diabetes insipidus rates were significantly lower in the 46 patients (68.7%) with a pituitary stalk than in those whose pituitary stalk was removed (P < 0.05); no significant difference was observed in the relapse rate between the 2 subgroups (P > 0.05). In the subtotal resection group (n = 15), a significant difference was observed in the early and persistent diabetes insipidus rates (P < 0.05), but no significant difference was observed in the relapse rate between the patients with a pituitary stalk and those whose pituitary stalk was removed (P > 0.05). CONCLUSIONS: For children with craniopharyngioma of pituitary stalk origin, preserving the pituitary stalk has a significant effect on the early and persistent diabetes insipidus rates. When intraoperative exploration showed excessive adhesion between the tumor and pituitary stalk, we opted to preserve the pituitary stalk, which significantly reduced the early and persistent postoperative diabetes insipidus rates, without significantly increasing the relapse or mortality rate.

Estimation and model selection of semiparametric multivariate survival functions under general censorship.

We study estimation and model selection of semiparametric models of multivariate survival functions for censored data, which are characterized by possibly misspecified parametric copulas and nonparametric marginal survivals. We obtain the consistency and root-n asymptotic normality of a two-step copula estimator to the pseudo-true copula parameter value according to KLIC, and provide a simple consistent estimator of its asymptotic variance, allowing for a first-step nonparametric estimation of the marginal survivals. We establish the asymptotic distribution of the penalized pseudo-likelihood ratio statistic for comparing multiple semiparametric multivariate survival functions subject to copula misspecification and general censorship. An empirical application is provided.