Monotropein alleviates acute pulmonary embolism in rats by inhibiting the NF-κB pathway.

OBJECTIVE: This study examines the therapeutic potential of monotropein (Mon) in a rat model of acute pulmonary embolism (APE), aiming to elucidate its mechanistic role and provide new insights for APE treatment. METHODS: Thirty Sprague Dawley (SD) rats were randomly assigned to five groups (n = 6 per group): sham, Mon (40 mg/kg), APE, APE + 20 mg/kg Mon, and APE + 40 mg/kg Mon. APE was induced via autologous thrombus infusion in all groups except sham and Mon-only groups. We assessed blood gas parameters, lung wet/dry weight (W/D) ratio, and oxidative stress markers. Additionally, excised lung tissues underwent evaluation for serum inflammatory factors via ELISA, apoptotic cells via TUNEL assay, and protein expression via Western blot. RESULTS: Compared to the sham group, APE-induced rats exhibited significantly elevated blood oxygen levels and increased pro-inflammatory factors, including interleukin (IL)-1ß, IL-6, tumor necrosis factor (TNF)-α, and IL-8. Mon treatment effectively mitigated these APE-induced changes, reducing blood oxygen concentration and downregulating IL-1ß and TNF-α levels. Furthermore, Mon demonstrated anti-apoptotic effects by decreasing cleaved caspase-3 and Bax protein levels while upregulating Bcl-2 expression. Mon also suppressed nuclear factor-κB (NF-κB) activation by inhibiting the phosphorylation levels of p65/RelA and IκBα proteins, while the total protein level of IκBα was increased with Mon treatment. CONCLUSION: Mon effectively ameliorated lung tissue injury in APE rats by inhibiting apoptosis, attenuating inflammatory responses, and alleviating oxidative stress. These beneficial effects appear to be mediated through modulation of the NF-κB pathway, suggesting Mon as a promising therapeutic candidate for APE treatment.

Interaction of transcription factors Islet2 and Nr2f1b to control vascular patterning during zebrafish development.

Many regulators controlling arterial identity are well described; however, transcription factors that promote vein identity and vascular patterning have remained largely unknown. We previously identified the transcription factors Islet2 (Isl2) and Nr2f1b required for specification of the vein and tip cell identity mediated by notch pathway in zebrafish. However, the interaction between Isl2 and Nr2f1b is not known. In this study, we report that Nr2f2 plays minor roles on vein and intersegmental vessels (ISV) growth and dissect the genetic interactions among the three transcription factors Isl2, Nr2f1b, and Nr2f2 using a combinatorial knockdown strategy. The double knockdown of isl2/nr2f1b, isl2/nr2f2, and nr2f1b/nr2f2 showed the enhanced defects in vasculature including less completed ISV, reduced veins, and ISV cells. We further tested the genetic relationship among these three transcription factors. We found isl2 can regulate the expression of nr2f1b and nr2f2, suggesting a model where Isl2 functions upstream of Nr2f1b and Nr2f2. We hypothsized that Isl2 and Nr2f1b can function together through cis-regulatory binding motifs. In-vitro luciferase assay results, we showed that Isl2 and Nr2f1b can cooperatively enhance gene expression. Moreover, co-immunoprecipitation results indicated that Isl2 and Nr2f1b interact physically. Together, we showed that the interaction of the Nr2f1b and Nr2f2 transcription factors in combination with the Islet2 play coordinated roles in the vascular development of zebrafish.

Coral-Derived Natural Marine Compound GB9 Impairs Vascular Development in Zebrafish.

Blood vessels in vertebrates are established and genetically controlled in an evolutionarily-conserved manner during embryogenesis. Disruption of vascular growth by chemical compounds or environmental hormones may cause developmental defects. This study analyzed the vascular impacts of marine compound GB9 in zebrafish. GB9 was isolated from the marine soft coral Capnella imbricata and had shown anti-neuroinflammatory and anti-nociceptive activities. However, the role of GB9 on vascular development has not been reported. We first tested the survival rate of embryos under exogenous 5, 7.5, 10, and 15 µM GB9 added to the medium and determined a sub-lethal dosage of 10 µM GB9 for further assay. Using transgenic Tg(fli:eGFP) fish to examine vascular development, we found that GB9 treatment impaired intersegmental vessel (ISV) growth and caudal vein plexus (CVP) patterning at 25 hours post-fertilization (hpf) and 30 hpf. GB9 exposure caused pericardial edema and impaired circulation at 48-52 hpf, which are common secondary effects of vascular defects and suggest the effects of GB9 on vascular development. Apoptic cell death analysis showed that vascular defects were not caused by cell death, but were likely due to the inhibition of migration and/or proliferation by examining ISV cell numbers. To test the molecular mechanisms of vascular defects in GB9-treated embryos, we examined the expression of vascular markers and found the decreased expression of vascular specific markers ephrinb2, flk, mrc1, and stabilin. In addition, we examined whether GB9 treatment impairs vascular growth due to an imbalance of redox homeostasis. We found an enhanced effect of vascular defects during GB9 and H2O2 co-treatment. Moreover, exogenous N-acetyl-cysteine (NAC) treatment rescued the vascular defects in GB9 treated embryos. Our results showed that GB9 exposure causes vascular defects likely mediated by the imbalance of redox homeostasis.

The clinical significance of preoperative serum triglyceride, high-density lipoprotein, and low-density lipoprotein levels in lung squamous cell carcinoma.

To evaluate the prognostic role of the preoperative plasma lipid profile, including triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) in patients with lung squamous cell carcinoma (LUSC) who underwent complete resection. Clinical data, including preoperative plasma profile levels, were retrospectively collected and reviewed in 300 patients with LUSC who underwent radical lung resection between 2016 and 2017. The overall survival (OS) and disease-free survival (DFS) were assessed by the Kaplan-Meier method and the Cox proportional hazards regression model. TG ≤ 1.35, HDL-C ≤ 1.17, and LDL-C ≤ 2.32 were deemed as independent preoperative risk factors for OS, and HDL-C ≤ 1.17 was an independent preoperative risk factor for DFS. In the multivariate analyses involving OS and DFS, a decreased HDL-C level was significantly associated with worse OS (HR, 0.546; 95% CI, 0.380-0.784, P = 0.001) and DFS (HR, 0.644; 95% CI, 0.422-0.981, P = 0.041). Additionally, an increased TG (HR, 0.546; 95% CI, 0.366-0.814, P = 0.003) or LDL-C (HR, 0.652; 95% CI, 0.456-0.933, P = 0.019) level was significantly associated with better OS. In patients with LUSC, decreased levels of HDL-C may predict worse outcomes for both DFS and OS, while increased TG or LDL-C levels may predict better OS.

Anoxic/oxic treatment without biomass recycle.

The Anoxic/Oxic (A/O) process involves recirculating mixed liquor between its A and O tanks so that nitrate produced in the O tank can be used to for denitrification with influent COD in the A tank. Because biomass is recirculated along with nitrate, A/O operation leads to similar microbial communities in the A and O tanks, which may decrease the rates of denitrification and nitrification in each tank. Here, bench-scale experiments simulated this aspect of the A/O process by exchanging biomass between an anoxic flask and an oxic cylinder at exchange ratios of 0%, 20%, 30%, and 50%. Nitrification and denitrification rates were only 40% and 19% for 50% biomass exchange of that for no biomass exchange. Phylogenetic analysis documented that the microbial communities became much more similar with biomass exchange, and the finding was consistent with community composition in a full-scale A/O process in a municipal wastewater treatment plant. A two-stage vertical baffled bioreactor (VBBR) realized efficient total­nitrogen removal in recirculation without biomass exchange. Average removals of COD and TN were respectively 6% and 22% higher for the two-stage VBBR than the conventional A/O process, but its hydraulic retention time (HRT) was 55% to 70% of the volume of a conventional A/O process treating the same influent wastewater. The VBBR was more efficient because its anoxic biofilm was enriched in denitrifying bacteria, while its oxic biofilm was enriched in nitrifying bacteria. For example, the phylum Chloroflexi was greater in the An-VBBR, while the phylum Proteobacteria was greater in the Ox-VBBR.

In vivo monitoring of carbonic anhydrase expression during the growth of larval zebrafish: a new environment-sensitive fluorophore for responsive turn-on fluorescence.

This study monitors the dynamic progress of a newly developed background-free, target responsive strategy; 2,3-dihydroquinolin-4-imine (DQI) that can instantly respond to environmental changes with fluorescence enhancement, revealing a comprehensive platform for in vivo fluorescence bioimaging of mebrane-bound carbonic anhydrase II in HeLa cells and its expression during the growth of larval zebrafish.

Ionizing radiation-induced bystander mutagenesis and adaptation: quantitative and temporal aspects.

This work explores several quantitative aspects of radiation-induced bystander mutagenesis in WTK1 human lymphoblast cells. Gamma-irradiation of cells was used to generate conditioned medium containing bystander signals, and that medium was transferred onto naïve recipient cells. Kinetic studies revealed that it required up to 1h to generate sufficient signal to induce the maximal level of mutations at the thymidine kinase locus in the bystander cells receiving the conditioned medium. Furthermore, it required at least 1h of exposure to the signal in the bystander cells to induce mutations. Bystander signal was fairly stable in the medium, requiring 12-24h to diminish. Medium that contained bystander signal was rendered ineffective by a 4-fold dilution; in contrast a greater than 20-fold decrease in the cell number irradiated to generate a bystander signal was needed to eliminate bystander-induced mutagenesis. This suggested some sort of feedback inhibition by bystander signal that prevented the signaling cells from releasing more signal. Finally, an ionizing radiation-induced adaptive response was shown to be effective in reducing bystander mutagenesis; in addition, low levels of exposure to bystander signal in the transferred medium induced adaptation that was effective in reducing mutations induced by subsequent gamma-ray exposures.

Deficiencies of double-strand break repair factors and effects on mutagenesis in directly gamma-irradiated and medium-mediated bystander human lymphoblastoid cells.

Using RNA interference techniques to knock down key proteins in two major double-strand break (DSB) repair pathways (DNA-PKcs for nonhomologous end joining, NHEJ, and Rad54 for homologous recombination, HR), we investigated the influence of DSB repair factors on radiation mutagenesis at the autosomal thymidine kinase (TK) locus both in directly irradiated cells and in unirradiated bystander cells. We also examined the role of p53 (TP53) in these processes by using cells of three human lymphoblastoid cell lines from the same donor but with differing p53 status (TK6 is p53 wild-type, NH32 is p53 null, and WTK1 is p53 mutant). Our results indicated that p53 status did not affect either the production of radiation bystander mutagenic signals or the response to these signals. In directly irradiated cells, knockdown of DNA-PKcs led to an increased mutant fraction in WTK1 cells and decreased mutant fractions in TK6 and NH32 cells. In contrast, knockdown of DNA-PKcs led to increased mutagenesis in bystander cells regardless of p53 status. In directly irradiated cells, knockdown of Rad54 led to increased induced mutant fractions in WTK1 and NH32 cells, but the knockdown did not affect mutagenesis in p53 wild-type TK6 cells. In all cell lines, Rad54 knockdown had no effect on the magnitude of bystander mutagenesis. Studies with extracellular catalase confirmed the involvement of H2O2 in bystander signaling. Our results demonstrate that DSB repair factors have different roles in mediating mutagenesis in irradiated and bystander cells.

Partial deficiency of DNA-PKcs increases ionizing radiation-induced mutagenesis and telomere instability in human cells.

The correct repair of DNA double-strand breaks (DSBs) is essential to maintaining the integrity of the genome. Misrepair of DSBs is detrimental to cells and organisms, leading to gene mutation, chromosomal aberration, and cancer development. Nonhomologous end-joining (NHEJ) is one of the principal rejoining processes in most higher eukaryotic cells. NHEJ is facilitated by DNA-dependent protein kinase (DNA-PK), which is composed of a catalytic subunit, DNA-PKcs, and the heterodimeric DNA binding regulatory complex Ku70/86. Null mutation of DNA-PKcs leads to immunodeficiency, chromosomal aberration, gene mutation, telomeric end-capping failure, and cancer predisposition in animals and cells. However, it is unknown whether partial deficiency of DNA-PKcs as might occur in a fraction of the population (e.g., heterozygotes), influences cellular function. Using small interfering RNA (siRNA) transfection, we established partial deficiency of DNA-PKcs in human cells, ranging from 4 to 85% of control levels. Our results reveal for the first time, that partial deficiency of DNA-PKcs leads to increased ionizing radiation (IR)-induced mutagenesis, cell killing, and telomere dysfunction. Radiation mutagenesis was increased inversely with DNA-PKcs protein level, with the most pronounced effect being observed in cells with protein levels below 50% of controls. A small but statistically significant increase in IR-induced cell killing was observed as DNA-PKcs levels decreased, over the entire range of protein levels. Frequencies of IR-induced telomere-DSB fusion was increased at levels of DNA-PKcs as low as approximately 50%, similar to what would be expected in heterozygous individuals. Taken together, our results suggest that even partial deficiency of DNA repair proteins may represent a considerable risk to genomic stability.

The effects of NBS1 knockdown by small interfering RNA on the ionizing radiation-induced apoptosis in human lymphoblastoid cells with different p53 status.

Mutations of NBS1 are responsible for the human hereditary disease Nijmegen breakage syndrome (NBS), which is characterized by an extremely high cancer rate. In this study, we investigated the influence of NBS1 on ionizing radiation (IR) induced apoptosis. Using small interfering RNA (siRNA) transfection, we knocked down NBS1 protein in three closely related human lymphoblastoid cell lines differing in p53 status: TK6 with a wild-type p53, NH32 with a null mutation of p53, and WTK1 with a mutant p53. We found that up to 48h after 5Gy IR, all three lines showed an obvious induction of apoptosis regardless of the p53 status. The magnitude of apoptosis induction was TK6>NH32>WTK1. This suggested that although p53 is an important modulator of IR-induced apoptosis, other p53-independent apoptosis pathway also exists. Moreover, NBS1 knockdown led to reduction of IR-induced apoptosis in all three lines and both NBS1/ATM/p53/BAX and NBS1/ATM/CHK2/E2F1 apoptosis pathways were partially inactivated. Our results suggest that NBS1 plays an important role in IR-induced apoptosis via both p53-dependent and p53-independent mechanisms. The impaired apoptosis response to DNA damage in NBS1 deficient cells might be one of the important mechanisms of cancer predisposition in NBS patients.

NBS1 knockdown by small interfering RNA increases ionizing radiation mutagenesis and telomere association in human cells.

Hypomorphic mutations which lead to decreased function of the NBS1 gene are responsible for Nijmegen breakage syndrome, a rare autosomal recessive hereditary disorder that imparts an increased predisposition to development of malignancy. The NBS1 protein is a component of the MRE11/RAD50/NBS1 complex that plays a critical role in cellular responses to DNA damage and the maintenance of chromosomal integrity. Using small interfering RNA transfection, we have knocked down NBS1 protein levels and analyzed relevant phenotypes in two closely related human lymphoblastoid cell lines with different p53 status, namely wild-type TK6 and mutated WTK1. Both TK6 and WTK1 cells showed an increased level of ionizing radiation-induced mutation at the TK and HPRT loci, impaired phosphorylation of H2AX (gamma-H2AX), and impaired activation of the cell cycle checkpoint regulating kinase, Chk2. In TK6 cells, ionizing radiation-induced accumulation of p53/p21 and apoptosis were reduced. There was a differential response to ionizing radiation-induced cell killing between TK6 and WTK1 cells after NBS1 knockdown; TK6 cells were more resistant to killing, whereas WTK1 cells were more sensitive. NBS1 deficiency also resulted in a significant increase in telomere association that was independent of radiation exposure and p53 status. Our results provide the first experimental evidence that NBS1 deficiency in human cells leads to hypermutability and telomere associations, phenotypes that may contribute to the cancer predisposition seen among patients with this disease.

Association of serum cystatin C levels with mortality in patients with acute type A aortic dissection.

Increased serum cystatin C levels are related to the prognosis of cardiovascular diseases. This study aims to investigate the effect of admission serum cystatin C levels on short- and long-term mortality in patients with acute type A aortic dissection (ATAAD). From 2010 to 2014, 136 consecutive patients with ATAAD were enrolled and followed up. Clinical data and laboratory assays including were measured. During a median follow-up of 198.7 days, the short-term mortality (30-days) was 20.6%, whereas the long-term death rate was 10.2%. We identified that the expression of cystatin C and high-sensitivity C-reactive protein (hs-CRP) in the dying patients was higher than in the surviving patients (P < 0.01). Hs-CRP (HR = 1.41, 95% CI: 1.03-2.59, P = 0.037) was an independent risk factor of short-term death determined by univariate and multivariate Cox analyses. No impact of cystatin C was observed on the short-term mortality. For long-term mortality, cystatin C (HR = 1.49, 95% CI: 1.10-7.36, P = 0.013) was identified as an independent predictor at above the cut-off value ≥ 1.10 mg/L. ROC analysis showed the AUC values of cystatin C and hs-CRP were 0.772 (95% CI, 0.692-0.839) and 0.640 (95% CI, 0.574-0.739), respectively, in the prediction of long-term death. The combined AUC value of cystatin C and hs-CRP was 0.883 (95% CI, 0.826-0.935; P < 0.01). Taken together, high cystatin C levels (≥ 1.10 mg/L) on admission are independently associated with the long-term mortality in patients with ATAAD.

The role of NBS1 in DNA double strand break repair, telomere stability, and cell cycle checkpoint control.

The genomes of eukaryotic cells are under continuous assault by environmental agents and endogenous metabolic byproducts. Damage induced in DNA usually leads to a cascade of cellular events, the DNA damage response. Failure of the DNA damage response can lead to development of malignancy by reducing the efficiency and fidelity of DNA repair. The NBS1 protein is a component of the MRE11/RAD50/NBS1 complex (MRN) that plays a critical role in the cellular response to DNA damage and the maintenance of chromosomal integrity. Mutations in the NBS1 gene are responsible for Nijmegen breakage syndrome (NBS), a hereditary disorder that imparts an increased predisposition to development of malignancy. The phenotypic characteristics of cells isolated from NBS patients point to a deficiency in the repair of DNA double strand breaks. Here, we review the current knowledge of the role of NBS1 in the DNA damage response. Emphasis is placed on the role of NBS1 in the DNA double strand repair, modulation of the DNA damage sensing and signaling, cell cycle checkpoint control and maintenance of telomere stability.

The role of NBS1 in the modulation of PIKK family proteins ATM and ATR in the cellular response to DNA damage.

Ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR) kinases have been considered the primary activators of the cellular response to DNA damage. They belong to the protein kinase family, phosphoinositide 3-kinase-related kinase (PIKKs). In human beings, deficiency of these kinases leads to hereditary diseases, namely ataxia telangiectasia (AT) with ATM deficiency and ATR-Seckel with ATR deficiency. NBS1, a component of MRE11/RAD50/NBS1 (MRN) complex, is another important player in DNA damage response (DDR). Mutations of NBS1 are responsible for Nijmegen breakage syndrome (NBS), a human hereditary disease with the characteristics that almost encompassed those of AT and ATR-Seckel. NBS1 has been conventionally thought to be a downstream substrate of ATM and ATR in DDR; however, recent studies suggest that NBS1/MRN functions upstream of both ATM and ATR by recruiting them to the proximity of DNA damage sites and activating their functions. In this mini-review, we would emphasize the requirement of NBS1 as an upstream mediator for the modulation of PIKK family proteins ATM and ATR.

Regulatory roles of tankyrase 1 at telomeres and in DNA repair: suppression of T-SCE and stabilization of DNA-PKcs.

Intrigued by the dynamics of the seemingly contradictory yet integrated cellular responses to the requisites of preserving telomere integrity while also efficiently repairing damaged DNA, we investigated roles of the telomere associated poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) tankyrase 1 in both telomere function and the DNA damage response following exposure to ionizing radiation. Tankyrase 1 siRNA knockdown in human cells significantly elevated recombination specifically within telomeres, a phenotype with the potential of accelerating cellular senescence. Additionally, depletion of tankyrase 1 resulted in concomitant and rapid reduction of the nonhomologous end-joining protein DNA-PKcs, while Ku86 and ATM protein levels remained unchanged; DNA-PKcs mRNA levels were also unaffected. We found that the requirement of tankyrase 1 for DNA-PKcs protein stability reflects the necessity of its PARP enzymatic activity. We also demonstrated that depletion of tankyrase 1 resulted in proteasome-mediated DNA-PKcs degradation, explaining the associated defective damage response observed; i.e., increased sensitivity to ionizing radiation-induced cell killing, mutagenesis, chromosome aberration and telomere fusion. We provide the first evidence for regulation of DNA-PKcs by tankyrase 1 PARP activity and taken together, identify roles of tankyrase 1 with implications not only for DNA repair and telomere biology, but also for cancer and aging.

High level glucose increases mutagenesis in human lymphoblastoid cells.

Epidemiological data have suggested an increased cancer rates in diabetic patients, for which the underlying mechanism is poorly understood. We studied whether high level of glucose (HG) treatment that mimic the hyperglycemic condition in diabetes mellitus is mutagenic. Mutagenesis studies were carried out at both hypoxanthine phosphoribosyltransferase (hprt) and thymidine kinase (tk) loci. Role of p53 in HG-induced mutagenesis was also investigated by using human lymphoblastoid cell lines derived from same donor but differs in p53 statuses; TK6 has wild-type p53, NH32 has null p53, and WTK1 has mutant p53 (ile237). In addition, we studied the influence of antioxidant treatment on HG-induced mutagenesis. Mutation fractions at both loci increased significantly in all three lines at 21 and 28 days after HG treatments. At tk locus, the increase of a class of mutants with normal growth rate is mainly responsible for the overall increased mutant fraction. Compared to TK6 cells, both NH32 and WTK1 cells showed an early onset of mutagenesis. Treatment of cells with antioxidant N-acetyl-L-cysteine partially reduced HG induced mutagenesis. This study is the first to indicate that HG is able to induce gene mutation which may be one of the important mechanisms of diabetes-associated carcinogenesis.

Wild-type p53 reduces radiation hypermutability in p53-mutated human lymphoblast cells.

Many studies have shown that an alteration of p53 affects various cellular responses to DNA damage after treatment with ionizing radiation. The human lymphoblast cell WTK1, which contains a mutant p53 (ile237), is 10-fold hypermutable at the thymidine kinase (tk) locus compared with TK6 cells, which are from the same donor but contain wild-type p53. These results implied that the specific p53 mutation found in WTK1 may actively contribute to mutagenesis in a gain of function manner. To further investigate this, the present experiments involved transfecting WTK1 cells with a wild-type p53 vector; this restored p53 activity in WTK1 cells, as evidenced by radiation-induced expression of p21. We compared radiosensitivity, as measured both by clonogenic survival and the induction of apoptosis, as well as mutant fractions (MFs) at the tk locus. WTK1 cells expressing wild-type p53 were more sensitive to gamma-ray-induced toxicity as measured by either clonogenic survival or apoptosis. The mutation assays revealed that both the spontaneous and gamma-ray-induced MFs were significantly decreased in WTK1 cells expressing wild-type p53; the MFs were similar to those observed in p53-null NH32 cells, also derived from the same donor. These results indicate that wild-type p53 can reduce the apparent gain-of-function hypermutable effects of a particular p53 gene mutation and thereby help maintain genomic stability.

Off-bypass implantation of a self-expandable valved stent between inferior vena cava and right atrium.

A glutaraldehyde preserved valved bovine jugular xenograft mounted in a nitinol 'Z' stent, expandable from 7 to 28 mm of internal diameter, was evaluated in vitro (column of water developing a pressure of 45 mmHg and a mock loop including a pulsatile pump) and in vivo in five adult pigs with intra-vascular ultrasound to measure the inferior vena cava diameter via a retroperitoneal access. Through a stent-graft delivery system (24 French) the self expandable valved stent was implanted off-bypass in the inferior vena cava, between hepatic veins and cavo-atrial junction, with flow and pressure gradient recording. The mean length of the valved stent was 22.80+/-1.06 mm, the mean internal diameter 20.97+/-0.5 mm and the mean external diameter 26.67+/-0.9 mm. The valve leaking under pressure was 32.5+/-12.3 ml/min. The mean pressure gradient recorded across the self expandable valved stent implanted in the inferior vena cava was 1.0+/-0.5 mmHg (range 0-2 mmHg). Intra-vascular ultrasound showed partial opening and closing of the valve (mean area reduction from 148.5 to 81.5 mm2), with almost complete occlusion only during deep breaths. The in vitro and in vivo experiments confirmed the feasibility of potential application of the self-expandable valved stent implanted off-bypass in the inferior vena cava for late conversion of failing total cavo-pulmonary connection; intra-vascular ultrasound allows for adequate implantation and evaluation.