A nanoscale DNA force spectrometer capable of applying tension and compression on biomolecules.

Single molecule force spectroscopy is a powerful approach to probe the structure, conformational changes, and kinetic properties of biological and synthetic macromolecules. However, common approaches to apply forces to biomolecules require expensive and cumbersome equipment and relatively large probes such as beads or cantilevers, which limits their use for many environments and makes integrating with other methods challenging. Furthermore, existing methods have key limitations such as an inability to apply compressive forces on single molecules. We report a nanoscale DNA force spectrometer (nDFS), which is based on a DNA origami hinge with tunable mechanical and dynamic properties. The angular free energy landscape of the nDFS can be engineered across a wide range through substitution of less than 5% of the strand components. We further incorporate a removable strut that enables reversible toggling of the nDFS between open and closed states to allow for actuated application of tensile and compressive forces. We demonstrate the ability to apply compressive forces by inducing a large bend in a 249bp DNA molecule, and tensile forces by inducing DNA unwrapping of a nucleosome sample. These results establish a versatile tool for force spectroscopy and robust methods for designing nanoscale mechanical devices with tunable force application.

North American Practice-Based Recommendations for Transjugular Intrahepatic Portosystemic Shunts in Portal Hypertension.

Complications of portal hypertension, including ascites, gastrointestinal bleeding, hepatic hydrothorax, and hepatic encephalopathy, are associated with significant morbidity and mortality. Despite few high-quality randomized controlled trials to guide therapeutic decisions, transjugular intrahepatic portosystemic shunt (TIPS) creation has emerged as a crucial therapeutic option to treat complications of portal hypertension. In North America, the decision to perform TIPS involves gastroenterologists, hepatologists, and interventional radiologists, but TIPS creation is performed by interventional radiologists. This is in contrast to other parts of the world where TIPS creation is performed primarily by hepatologists. Thus, the successful use of TIPS in North America is dependent on a multidisciplinary approach and technical expertise, so as to optimize outcomes. Recently, new procedural techniques, TIPS stent technology, and indications for TIPS have emerged. As a result, practices and outcomes vary greatly across institutions and significant knowledge gaps exist. In this consensus statement, the Advancing Liver Therapeutic Approaches group critically reviews the application of TIPS in the management of portal hypertension. Advancing Liver Therapeutic Approaches convened a multidisciplinary group of North American experts from hepatology, interventional radiology, transplant surgery, nephrology, cardiology, pulmonology, and hematology to critically review existing literature and develop practice-based recommendations for the use of TIPS in patients with any cause of portal hypertension in terms of candidate selection, procedural best practices and, post-TIPS management; and to develop areas of consensus for TIPS indications and the prevention of complications. Finally, future research directions are identified related to TIPS for the management of portal hypertension.

Final Two-Year Outcomes for the Sentry Bioconvertible Inferior Vena Cava Filter in Patients Requiring Temporary Protection from Pulmonary Embolism.

PURPOSE: To report final 2-year outcomes with the Sentry bioconvertible inferior vena cava (IVC) filter in patients requiring temporary protection against pulmonary embolism (PE). MATERIALS AND METHODS: In a prospective multicenter trial, the Sentry filter was implanted in 129 patients with documented deep vein thrombosis (DVT) and/or PE (67.5%) or who were at temporary risk of developing DVT/PE (32.6%). Patients were monitored and bioconversion status ascertained by radiography, computed tomography (CT), and CT venography through 2 years. RESULTS: The composite primary 6-month endpoint of clinical success was achieved in 97.4% (111/114) of patients. The rate of new symptomatic PE was 0% (n = 126) through 1 year and 2.4% (n = 85) through the second year of follow-up, with 2 new nonfatal cases at 581 and 624 days that were adjudicated as not related to the procedure or device. Two patients (1.6%) developed symptomatic caval thrombosis during the first month and underwent successful interventions without recurrence. No other filter-related symptomatic complications occurred through 2 years. There was no filter tilting, migration, embolization, fracture, or caval perforation and no filter-related deaths through 2 years. Filter bioconversion was successful for 95.7% (110/115) of patients at 6 months, 96.4% (106/110) of patients at 12 months, and 96.5% (82/85) of patients at 24 months. Through 24 months of follow-up, there was no evidence of late-stage IVC obstruction or thrombosis after filter bioconversion or of thrombogenicity associated with retracted filter arms. CONCLUSIONS: The Sentry IVC filter provided safe and effective protection against PE, with a high rate of intended bioconversion and a low rate of device-related complications, through 2 years of follow-up.

Quantitative Modeling of Nucleosome Unwrapping from Both Ends.

In eukaryotic cells, DNA is packaged into chromatin where nucleosomes are the basic packaging unit. Important cellular processes including gene expression, DNA replication, and DNA repair require nucleosomal DNA to be unwrapped so that functional proteins can access their target sites, which otherwise are sterically occluded. A key question in this process is what the unwrapped conformations individual nucleosomes adopt within chromatin are. Here, we develop a concurrent nucleosome unwrapping model to address this question. We hypothesize that for a given end-to-end distance of the nucleosomal DNA, the nucleosomal DNA stochastically unwraps from the histone core from both ends independently and that this combination of unwrapping from both sides results in a significant increase in the average distance between the DNA extending from both sides of the nucleosomes. We test our model on recently published experiments using a DNA origami nanocaliper that quantifies nucleosome unwrapping and achieve good agreement between experiment and model prediction. We then investigate the DNA origami caliper distribution when attached to a hexasome (a nucleosome lacking an H2A/H2B dimer). A significant shift in the caliper angle distribution caused by the asymmetric structural features of the hexasome seen experimentally is consistent with the model. Our modeling approach may be more broadly useful to the interpretation of other studies of nucleosome dynamics, chromatin dynamics, and regulatory processes involving nucleosome unwrapping, as well as more generally to optimization of future DNA origami designs to probe mechanical properties of biomolecules.

One-Year Analysis of the Prospective Multicenter SENTRY Clinical Trial: Safety and Effectiveness of the Novate Sentry Bioconvertible Inferior Vena Cava Filter.

PURPOSE: To prospectively assess the Sentry bioconvertible inferior vena cava (IVC) filter in patients requiring temporary protection against pulmonary embolism (PE). MATERIALS AND METHODS: At 23 sites, 129 patients with documented deep vein thrombosis (DVT) or PE, or at temporary risk of developing DVT or PE, unable to use anticoagulation were enrolled. The primary end point was clinical success, including successful filter deployment, freedom from new symptomatic PE through 60 days before filter bioconversion, and 6-month freedom from filter-related complications. Patients were monitored by means of radiography, computerized tomography (CT), and CT venography to assess filtering configuration through 60 days, filter bioconversion, and incidence of PE and filter-related complications through 12 months. RESULTS: Clinical success was achieved in 111 of 114 evaluable patients (97.4%, 95% confidence interval [CI] 92.5%-99.1%). The rate of freedom from new symptomatic PE through 60 days was 100% (n = 129, 95% CI 97.1%-100.0%), and there were no cases of PE through 12 months for either therapeutic or prophylactic indications. Two patients (1.6%) developed symptomatic caval thrombosis during the first month; neither experienced recurrence after successful interventions. There was no filter tilting, migration, embolization, fracture, or caval perforation by the filter, and no filter-related death through 12 months. Filter bioconversion was successful for 95.7% (110/115) at 6 months and for 96.4% (106/110) at 12 months. CONCLUSIONS: The Sentry IVC filter provided safe and effective protection against PE, with a high rate of intended bioconversion and a low rate of device-related complications, through 12 months of imaging-intense follow-up.

Laparoscopic Nephrectomy: Initial Case Report.

A tumor-bearing right kidney was completely excised from an 85-year-old woman using a laparoscopic approach. A newly devised method for intra-abdominal organ entrapment and a recently developed laparoscopic tissue morcellator made it possible to deliver the 190 gm. kidney through an 11 mm. incision.

Allosteric Wip1 phosphatase inhibition through flap-subdomain interaction.

Although therapeutic interventions of signal-transduction cascades with targeted kinase inhibitors are a well-established strategy, drug-discovery efforts to identify targeted phosphatase inhibitors have proven challenging. Herein we report a series of allosteric, small-molecule inhibitors of wild-type p53-induced phosphatase (Wip1), an oncogenic phosphatase common to multiple cancers. Compound binding to Wip1 is dependent on a 'flap' subdomain located near the Wip1 catalytic site that renders Wip1 structurally divergent from other members of the protein phosphatase 2C (PP2C) family and that thereby confers selectivity for Wip1 over other phosphatases. Treatment of tumor cells with the inhibitor GSK2830371 increases phosphorylation of Wip1 substrates and causes growth inhibition in both hematopoietic tumor cell lines and Wip1-amplified breast tumor cells harboring wild-type TP53. Oral administration of Wip1 inhibitors in mice results in expected pharmacodynamic effects and causes inhibition of lymphoma xenograft growth. To our knowledge, GSK2830371 is the first orally active, allosteric inhibitor of Wip1 phosphatase.

Technically Successful Geniculate Artery Embolization Does Not Equate Clinical Success for Treatment of Recurrent Knee Hemarthrosis after Knee Surgery.

PURPOSE: To evaluate technical details, clinical outcomes, and complications in patients undergoing geniculate artery embolization for treatment of spontaneous hemarthrosis after knee surgery. MATERIALS AND METHODS: During 2009-2014, 10 consecutive patients (seven women; mean age, 57.4 y) underwent geniculate artery embolization at a single tertiary care center. All patients except one had hemarthrosis after total knee replacement (TKR). One patient presented with hemarthrosis after cartilage surgery. Two patients in the TKR group had a history of TKR revisions before the embolization. Embolization was performed with polyvinyl alcohol particles (range, 300-700 µm). In one patient requiring repeat embolization, N-butyl cyanoacrylate/ethiodized oil was used. The endpoint for embolization was stasis in the target artery and elimination of the hyperemic blush. RESULTS: In 10 patients, 14 embolizations were performed with 100% technical success. Hemarthrosis resolved in six patients. Four patients required repeat embolization for recurrent hemarthrosis, which subsequently resolved in two of four patients. Three of the four patients who required repeat embolization had serious comorbidities, either blood dyscrasias or therapeutic anticoagulation. There were two minor skin complications that resolved with conservative management. The average length of follow-up after embolization was 545 days (range, 50-1,655 d). One patient was lost to follow-up. CONCLUSIONS: Geniculate artery embolization is a safe, minimally invasive treatment option for spontaneous and refractory knee hemarthrosis after knee surgery with 100% technical success. However, limited clinical success and higher repeat embolization rates were noted in patients with serious comorbidities.

US-Guided, Direct Puncture Retrograde Thoracic Duct Access, Lymphangiography, and Embolization: Feasibility and Efficacy.

PURPOSE: To describe technical details, success rate, and advantages of direct puncture of the thoracic duct (TD) under direct ultrasound (US) guidance at venous insertion in the left neck. MATERIALS AND METHODS: All patients who underwent attempted thoracic duct embolization (TDE) via US-guided retrograde TD access in the left neck were retrospectively reviewed. Indications for lymphangiography were iatrogenic chyle leak, pulmonary lymphangiectasia, and plastic bronchitis. Ten patients with mean age 41.4 years (range, 21 d to 72 y) underwent US-guided TD access via the left neck. Technical details, procedural times, and clinical outcomes were evaluated. TD access time was defined as time from start of procedure to successful access of TD, and total procedural time was defined from start of procedure until TDE. RESULTS: All attempts at TD access via the neck were successful. Technical and clinical success of TDE was 60%. There were no complications. Mean TD access time was 17 minutes (range, 2-47 min), and mean total procedure time was 49 minutes (range, 25-69 min). Mean follow-up time was 5.4 months (range, 3-10 months). CONCLUSIONS: TDE via US-guided access in the left neck is technically feasible and safe with a potential decrease in procedure time and elimination of oil-based contrast material.

Older age is associated with increased early mortality after transjugular intrahepatic portosystemic shunt.

INTRODUCTION & AIM: The role of age as a predictor of mortality after transjugular intra hepatic portosystemic shunt (TIPS) is controversial. Age has been found to be an important predictor of post-TIPS mortality in some, but not all, studies and is not a component of the MELD score. The purpose of this study was to compare the 90-day survival of subjects with cirrhosis age ≥ 70 years with younger subjects undergoing TIPS. MATERIAL AND METHODS: A database of adult with cirrhosis undergoing TIPS from 2003-2011 was analyzed. The primary endpoint was survival 90-days post-TIPS. Survival was analyzed by the Kaplan-Meier method and proportional hazard modeling. RESULTS: 539 subjects met study criteria. 474 (88%) were between the ages of 24-69 and 65 (12%) were age 70-89 years. The groups were similar with respect to the indication for TIPS, mean MELD score and distribution of MELD score. Survival 90-days post-TIPS was 60% in the older cohort compared with 85% in the younger cohort (p < 0.001). Proportional hazards modeling controlled for comorbidities identified age ≥ 70 and MELD score as predictors of early post-TIPS survival. The hazard ratio associated with age increased monotonically, became significant at age ≥ 70 years (HR 3.22; 95% CI 1.81-5.74; p < 0.001) and exceeded the effect of MELD on survival. CONCLUSIONS: Age ≥ 70 was associated with reduced survival within 90 days following TIPS. The findings from this study indicate that age is a relevant consideration in assessing the early mortality risk of TIPS.

Ras-GRF2 mediates long-term potentiation, survival, and response to an enriched environment of newborn neurons in the hippocampus.

Hippocampal adult neurogenesis contributes to key functions of the dentate gyrus (DG), including contextual discrimination. This is due, at least in part, to the unique form of plasticity that new neurons display at a specific stage of their development when compared with the surrounding principal neurons. In addition, the contribution that newborn neurons make to dentate function can be enhanced by an increase in their numbers induced by a stimulating environment. However, signaling mechanisms that regulate these properties of newborn neurons are poorly understood. Here, we show that Ras-GRF2 (GRF2), a calcium-regulated exchange factor that can activate Ras and Rac GTPases, contributes to both of these properties of newborn neurons. Using Ras-GRF2 knockout mice and wild-type mice stereotactically injected with retrovirus containing shRNA against the exchange factor, we demonstrate that GRF2 promotes the survival of newborn neurons of the DG at approximately 1-2 weeks after their birth. GRF2 also controls the distinct form of long-term potentiation that is characteristic of new neurons of the hippocampus through its effector Erk MAP kinase. Moreover, the enhancement of neuron survival that occurs after mice are exposed to an enriched environment also involves GRF2 function. Consistent with these observations, GRF2 knockout mice display defective contextual discrimination. Overall, these findings indicate that GRF2 regulates both the basal level and environmentally induced increase of newborn neuron survival, as well as in the induction of a distinct form of synaptic plasticity of newborn neurons that contributes to distinct features of hippocampus-derived learning and memory.

Age-dependent role for Ras-GRF1 in the late stages of adult neurogenesis in the dentate gyrus.

The dentate gyrus of the hippocampus plays a pivotal role in pattern separation, a process required for the behavioral task of contextual discrimination. One unique feature of the dentate gyrus that contributes to pattern separation is adult neurogenesis, where newly born neurons play a distinct role in neuronal circuitry. Moreover,the function of neurogenesis in this brain region differs in adolescent and adult mice. The signaling mechanisms that differentially regulate the distinct steps of adult neurogenesis in adolescence and adulthood remain poorly understood. We used mice lacking RASGRF1(GRF1), a calcium-dependent exchange factor that regulates synaptic plasticity and participates in contextual discrimination performed by mice, to test whether GRF1 plays a role in adult neurogenesis.We show Grf1 knockout mice begin to display a defect in neurogenesis at the onset of adulthood (~2 months of age), when wild-type mice first acquire the ability to distinguish between closely related contexts. At this age, young hippocampal neurons in Grf1 knockout mice display severely reduced dendritic arborization. By 3 months of age, new neuron survival is also impaired. BrdU labeling of new neurons in 2-month-old Grf1 knockout mice shows they begin to display reduced survival between 2 and 3 weeks after birth, just as new neurons begin to develop complex dendritic morphology and transition into using glutamatergic excitatory input. Interestingly, GRF1 expression appears in new neurons at the developmental stage when GRF1 loss begins to effect neuronal function. In addition, we induced a similar loss of new hippocampal neurons by knocking down expression of GRF1 solely in new neurons by injecting retrovirus that express shRNA against GRF1 into the dentate gyrus. Together, these findings show that GRF1 expressed in new neurons promotes late stages of adult neurogenesis. Overall our findings show GRF1 to be an age-dependent regulator of adult hippocampal neurogenesis, which contributes to ability of mice to distinguish closely related contexts.

Endovascular treatment of superior mesenteric artery pseudoaneurysms using covered stents in six patients.

OBJECTIVE: The objective of our study was to evaluate our experience with the use of endovascular treatments for superior mesenteric artery (SMA) pseudoaneurysms using covered stents. MATERIALS AND METHODS: Between 2002 and 2011, six patients (mean age, 41.7 years; range, 23-65 years) with SMA pseudoaneurysms were treated percutaneously with the placement of covered stents at our institution. The causes of SMA pseudoaneurysms were penetrating trauma (n = 2), blunt trauma (n = 1), and previous surgical procedures (n = 3). The mean diameter of the SMA pseudoaneurysms was 16 mm (range, 4-24 mm). Technical success and clinical success were retrospectively analyzed. RESULTS: Immediate technical success, defined as exclusion of the pseudoaneurysm and lack of active extravasation, was achieved in all six patients. Secondary balloon angioplasty was needed in one patient with residual narrowing. There was a small dissection of the proximal SMA necessitating placement of a second bare stent across the dissection. A second covered stent (Fluency stent, 8 mm) was placed in the same patient because of recurrent bleeding due to a type II endoleak 5 days after the first covered stent had been placed. This patient had no subsequent episodes of bleeding or bowel ischemia. Follow-up CT in the remaining five patients (mean, 21 months; range, 1-58 months) confirmed stent patency and preserved distal arterial flow to the bowel without episodes of bleeding or bowel ischemia during follow-up (mean, 27 months; range, 11-58 months). CONCLUSION: Percutaneous endovascular treatment using a covered stent may be a safe and feasible tool for SMA pseudoaneurysms.

Successful Percutaneous Ultrasonic Lithotripsy of Gallstones.

Background: Acute calculous cholecystitis is the obstruction of the cystic duct by a gallstone that leads to inflammation of the gallbladder necessitating cholecystectomy. Case Series: We present the cases of 2 patients with acute calculous cholecystitis who were deemed ineligible candidates for cholecystectomy because of their complicating medical histories. Both patients initially underwent cholecystostomy and drain placement with interventional radiology for management of acute calculous cholecystitis. Their large gallstones remained refractory to attempts at removal by electrohydraulic lithotripsy via the cholecystostomy access. The patients' gallstones were successfully removed via percutaneous ultrasonic lithotripsy during a collaborative procedure with interventional radiology and urology. Conclusion: An interdisciplinary approach using percutaneous cholecystolithotomy with rigid ultrasonic lithotripsy is an effective method for removing challenging gallstones in patients for whom traditional approaches fail.

Ultrasound as a tool for preoperative planning, monitoring, and interventions in dialysis arteriovenous access.

OBJECTIVE: The rising prevalence of end-stage renal disease has resulted in increasing focus on delivery of vascular access care for hemodialysis. Duplex Doppler ultrasound, with its unique ability to reliably evaluate both structural and functional aspects of the peripheral vessels, is the preferred imaging modality for access planning and follow-up. CONCLUSION: This article will review how ultrasound is currently used to evaluate patients pre-, intra-, and postoperatively for vascular access.

Management of iatrogenic bile duct injuries: role of the interventional radiologist.

Bile duct injuries are infrequent but potentially devastating complications of biliary tract surgery and have become more common since the introduction of laparoscopic cholecystectomy. The successful management of these injuries depends on the injury type, the timing of its recognition, the presence of complicating factors, the condition of the patient, and the availability of an experienced hepatobiliary surgeon. Bile duct injuries may lead to bile leakage, intraabdominal abscesses, cholangitis, and secondary biliary cirrhosis due to chronic strictures. Imaging is vital for the initial diagnosis of bile duct injury, assessment of its extent, and guidance of its treatment. Imaging options include cholescintigraphy, ultrasonography, computed tomography, magnetic resonance cholangiopancreatography, endoscopic retrograde cholangiopancreatography, percutaneous transhepatic cholangiography, and fluoroscopy with a contrast medium injected via a surgically or percutaneously placed biliary drainage catheter. Depending on the type of injury, management may include endoscopic, percutaneous, and open surgical interventions. Percutaneous intervention is performed for biloma and abscess drainage, transhepatic biliary drainage, U-tube placement, dilation of bile duct strictures and stent placement to maintain ductal patency, and management of complications from previous percutaneous interventions. Endoscopic and percutaneous interventional procedures may be performed for definitive treatment or as adjuncts to definitive surgical repair. In patients who are eligible for surgery, surgical biliary tract reconstruction is the best treatment option for most major bile duct injuries. When reconstruction is performed by an experienced hepatobiliary surgeon, an excellent long-term outcome can be achieved, particularly if percutaneous interventions are performed as needed preoperatively to optimize the patient's condition and postoperatively to manage complications.

Impact of General Anesthesia on the Right Atrial Pressure During Transjugular Intrahepatic Portosystemic Shunt Creation: A Propensity Score Match Analysis.

PURPOSE: To evaluate the effect of general anesthesia on right atrial (RA) pressure measurements during transjugular intrahepatic portosystemic shunt (TIPS) placement using propensity score match analysis. MATERIALS: A single-institution database was used to identify 664 patients who underwent TIPS creation under either conscious sedation (CS) or general anesthesia (GA) between 2009 and 2018. A propensity-matched cohort was created using logistic regression of sedation method on demographics, liver disease status, and indications. Paired analyses were performed using mixed models for RA pressure and Cox proportional hazards model with robust standard errors for mortality. RESULTS: Of the 664 patients, 270 patients were matched based on similar characteristics (135 for GA and 135 for CS). Indications for TIPS creation included intractable ascites (n = 170, 63%), hepatic hydrothorax (n = 30, 11%), variceal bleeding (n = 43, 16%), and other (n = 27, 10%). Pre-TIPS RA pressure was greater in the matched GA group as compared to CS group by a mean of 4.2 mmHg (p < 0.0001). Similarly, post-TIPS RA pressure was greater in the matched GA group as compared to CS group by a mean of 3.3 mmHg (p < 0.0001). Pre- and post-procedure RA pressure was found to have no association with post-procedure mortality (0.8891, HR 1.077; p 0.917, HR 0.997; respectively). CONCLUSIONS: Utilization of GA during TIPS creation raises the intra-procedural RA pressure compared to CS. However, this elevated intra-procedural RA pressure does not appear to be predictive of mortality post-TIPS creation.