American Society for Gastrointestinal Endoscopy-European Society of Gastrointestinal Endoscopy guideline on primary endoscopic bariatric and metabolic therapies for adults with obesity

This joint ASGE-ESGE guideline provides an evidence-based summary and recommendations regarding the role of endoscopic bariatric and metabolic therapies (EBMTs) in the management of obesity. The document was developed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) framework. It evaluates the efficacy and safety of EBMT devices and procedures that currently have CE mark or FDA-clearance/approval, or that had been approved within five years of document development. The guideline suggests the use of EBMTs plus lifestyle modification in patients with a BMI of ≥ 30 kg/m2, or with a BMI of 27.0-29.9 kg/m2 with at least 1 obesity-related comorbidity. Furthermore, it suggests the utilization of intragastric balloons and devices for endoscopic gastric remodeling (EGR) in conjunction with lifestyle modification for this patient population.

American Society for Gastrointestinal Endoscopy-European Society of Gastrointestinal Endoscopy guideline on primary endoscopic bariatric and metabolic therapies for adults with obesity

This joint ASGE-ESGE guideline provides an evidence-based summary and recommendations regarding the role of endoscopic bariatric and metabolic therapies (EBMTs) in the management of obesity. The document was developed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) framework. It evaluates the efficacy and safety of EBMT devices and procedures that currently have CE mark or FDA-clearance/approval, or that had been approved within five years of document development. The guideline suggests the use of EBMTs plus lifestyle modification in patients with a BMI of ≥30 kg/m2, or with a BMI of 27.0-29.9 kg/m2 with at least 1 obesity-related comorbidity. Furthermore, it suggests the utilization of intragastric balloons and devices for endoscopic gastric remodeling (EGR) in conjunction with lifestyle modification for this patient population.

Endoscopic Ultrasound Predicts Risk of Occult Intra-Abdominal Metastases in Localized Gastric Cancer: A Validation Study

Background

In gastric cancer (GC) patients without imaging evidence of distant metastasis, diagnostic staging laparoscopy (DSL) is recommended to detect radiographically occult peritoneal metastasis (M1). DSL carries a risk for morbidity and its cost-effectiveness is unclear. Use of endoscopic ultrasound (EUS) to improve patient selection for DSL has been proposed but not validated. We aimed to validate an EUS-based risk classification system predicting risk for M1 disease.

Methods

We retrospectively identified all GC patients without positron emission tomography (PET)/computed tomography (CT) evidence of distant metastasis who underwent staging EUS followed by DSL between 2010 and 2020. T1-2, N0 disease was EUS "low-risk"; T3-4 and/or N+ disease was "high-risk".

Results

A total of 68 patients met inclusion criteria. DSL identified radiographically occult M1 disease in 17 patients (25%). Most patients had EUS T3 tumors (n = 59, 87%) and 48 (71%) patients were node-positive (N+). Five (7%) patients were classified EUS "low-risk" and 63 (93%) were classified "high-risk". Of 63 "high-risk" patients, 17 (27%) had M1 disease. The ability of "low-risk" EUS to predict M0 disease at laparoscopy was 100% and DSL would have been avoided in five patients (7%). This stratification algorithm showed a sensitivity of 100% (95% confidence interval (CI): 80.5-100%) and a specificity of 9.8% (95% CI: 3.3-21.4%).

Conclusions

Use of an EUS-based risk classification system in GC patients without imaging evidence of metastasis helps identify a subset of patients at low-risk for laparoscopic M1 disease who may avoid DSL and proceed directly to neoadjuvant chemotherapy or resection with curative intent. Larger, prospective studies are needed to validate these findings.

Endoscopic sleeve gastroplasty for treatment of class 1 and 2 obesity (MERIT): a prospective, multicentre, randomised trial

BACKGROUND

Endoscopic sleeve gastroplasty (ESG) is an endolumenal, organ-sparing therapy for obesity, with wide global adoption. We aimed to explore the efficacy and safety of ESG with lifestyle modifications compared with lifestyle modifications alone.

METHODS

We conducted a randomised clinical trial at nine US centres, enrolling individuals aged 21-65 years with class 1 or class 2 obesity and who agreed to comply with lifelong dietary restrictions. Participants were randomly assigned (1:1·5; with stratified permuted blocks) to ESG with lifestyle modifications (ESG group) or lifestyle modifications alone (control group), with potential retightening or crossover to ESG, respectively, at 52 weeks. Lifestyle modifications included a low-calorie diet and physical activity. Participants in the primary ESG group were followed up for 104 weeks. The primary endpoint at 52 weeks was the percentage of excess weight loss (EWL), with excess weight being that over the ideal weight for a BMI of 25 kg/m². Secondary endpoints included change in metabolic comorbidities between the groups. We used multiple imputed intention-to-treat analyses with mixed-effects models. Our analyses were done on a per-protocol basis and a modified intention-to-treat basis. The safety population was defined as all participants who underwent ESG (both primary and crossover ESG) up to 52 weeks.

FINDINGS

Between Dec 20, 2017, and June 14, 2019, 209 participants were randomly assigned to ESG (n=85) or to control (n=124). At 52 weeks, the primary endpoint of mean percentage of EWL was 49·2% (SD 32·0) for the ESG group and 3·2% (18·6) for the control group (p<0·0001). Mean percentage of total bodyweight loss was 13·6% (8·0) for the ESG group and 0·8% (5·0) for the control group (p<0·0001), and 59 (77%) of 77 participants in the ESG group reached 25% or more of EWL at 52 weeks compared with 13 (12%) of 110 in the control group (p<0·0001). At 52 weeks, 41 (80%) of 51 participants in the ESG group had an improvement in one or more metabolic comorbidities, whereas six (12%) worsened, compared with the control group in which 28 (45%) of 62 participants had similar improvement, whereas 31 (50%) worsened. At 104 weeks, 41 (68%) of 60 participants in the ESG group maintained 25% or more of EWL. ESG-related serious adverse events occurred in three (2%) of 131 participants, without mortality or need for intensive care or surgery.

INTERPRETATION

ESG is a safe intervention that resulted in significant weight loss, maintained at 104 weeks, with important improvements in metabolic comorbidities. ESG should be considered as a synergistic weight loss intervention for patients with class 1 or class 2 obesity. This trial is registered with ClinicalTrials.gov, NCT03406975.

FUNDING

Apollo Endosurgery, Mayo Clinic.

Safety and efficacy of a novel resection system for direct endoscopic necrosectomy of walled-off pancreas necrosis: a prospective, international, multicenter trial

BACKGROUND AND AIMS

Direct endoscopic necrosectomy (DEN) of walled-off pancreatic necrosis (WOPN) lacks dedicated instruments and requires repetitive and cumbersome procedures. This study evaluated the safety and efficacy of a new powered endoscopic debridement (PED) system designed to simultaneously resect and remove solid debris within WOPN.

METHODS

This was a single-arm, prospective, multicenter, international device trial conducted from November 2018 to August 2019 at 10 sites. Patients with WOPN ≥6 cm and ≤22 cm and with >30% solid debris were enrolled. The primary endpoint was safety through 21 days after the last DEN procedure. Efficacy outcomes included clearance of necrosis, procedural time, adequacy of debridement, number of procedures until resolution, hospital stay duration, and quality of life.

RESULTS

Thirty patients (mean age, 55 years; 60% men) underwent DEN with no device-related adverse events. Of 30 patients, 15 (50%) achieved complete debridement in 1 session and 20 (67%) achieved complete debridement within 2 or fewer sessions. A median of 1.5 interventions (range, 1-7) were required. Median hospital stay was 10 days (interquartile range, 22). There was an overall reduction of 91% in percent necrosis within WOPN from baseline to follow-up and 85% in collection volume. Baseline WOPN volume was positively correlated with the total number of interventions (ρ = .363, P = .049).

CONCLUSIONS

The new PED system seems to be a safe and effective treatment tool for WOPN, resulting in fewer interventions and lower hospital duration when compared with published data on using conventional instruments. Randomized controlled trials comparing the PED system with conventional DEN are needed. (Clinical trial registration number: NCT03694210.).

A Novel Flocked Swab Protocol Proves to Be an Effective Method for Culturing Elevator-Containing Endoscopes

BACKGROUND

The challenging disinfection process for the elevator mechanism on duodenoscopes and linear echoendoscopes has been identified as a source of clinically significant bacterial transmission. Despite increased awareness, there continues to be a lack of definitive guidelines for bacterial culturing protocols for elevator-containing endoscopes.

AIMS

To compare two different prospective bacterial surveillance protocols for duodenoscopes and linear echoendoscopes with regard to accuracy, efficiency, and cost.

METHODS

Consecutive duodenoscopes and linear echoendoscopes used at a single tertiary care center were reprocessed following hospital and manufacturer guidelines, dried using an automatic endoscope-drying machine, and hung overnight in an upright position. Following reprocessing, culture samples were sequentially obtained from each endoscope using two methods, first, the brush protocol followed immediately by the swab protocol.

RESULTS

A total of 532 primary cultures were collected from 17 duodenoscopes and eight linear echoendoscopes. Of these, 266 cultures gathered using the brush protocol were negative, while 266 cultures gathered using the swab protocol resulted in three positive cultures (1.1%). Positive cultures showed Enterobacter cloacae and Klebsiella pneumoniae from one duodenoscope and two linear echoendoscopes. Yearly, the brush protocol amounts to approximately 520 nursing hours, and the swab protocol takes an estimated 42 nursing hours. Annually, the swab protocol could save over $26,500 and 478 nursing hours.

CONCLUSIONS

The proposed swab protocol was superior to the brush protocol when evaluating the presence of residual bacteria on elevator-containing endoscopes following reprocessing and saves cost and nursing hours.

Endoscopic submucosal dissection for colorectal lesions: outcomes from a United States experience

BACKGROUND AND STUDY AIMS

Endoscopic submucosal dissection (ESD) is commonly used in Asia for resection of large non-pedunculated colorectal polyps (LNPCPs) and early (T1) colorectal cancers. It allows for en bloc removal and is often curative. We describe outcomes of colorectal ESD from a United States (US) academic medical center and compare this to international experiences.

METHODS

Retrospective review was performed of colonic lesions referred to the University of Chicago Medical Center for ESD from 2012 to 2020. Clinical and procedural data were collected.

RESULTS

The study included 78 lesions with mean size of 29.7 mm (range 10-100 mm). The overall en bloc resection rate was 73.1% (n = 57). Between the first and second half of the study, it improved from 61.5 to 84.6% (p = 0.02). Histology showed adenocarcinoma in fifteen lesions (19.2%). Of all neoplastic lesions (n = 68), resection with negative margins (R0) was achieved in 54 cases (79.4%). Adverse events occurred in 9 cases (11.5%), but most (n = 6, 66.7%) were successfully treated endoscopically. Follow-up endoscopy was performed in 46 patients (59.0%) at a mean interval of 6.8 months (SD ± 5.0 months) with two case of recurrent lesion (4.3%).

CONCLUSIONS

This study shows successful colorectal ESD outcomes at a US tertiary center. The en bloc resection rate was lower than other cohorts, but a learning curve was demonstrated. The R0 resection, lesion recurrence, and adverse event rates were similar to other non-Asian experiences, but not as favorable as in Asia [Fuccio et al. in Gastrointest Endosc 86:74-86.e17, 2017]. Increased ESD training in the US can help optimize utilization and outcomes.

Adjustable intragastric balloon for treatment of obesity: a multicentre, open-label, randomised clinical trial

BACKGROUND

Intragastric balloons are anatomy-preserving, minimally invasive obesity therapies. Enhanced tolerance and durability could help broaden clinical adoption. We investigated the safety and efficacy of an adjustable intragastric balloon (aIGB) in adults with obesity.

METHODS

In this prospective, multicentre, open-label, randomised clinical trial done at seven US sites, adults aged 22-65 years with obesity were randomly assigned (2:1) to aIGB with lifestyle intervention or lifestyle intervention alone (control) for 32 weeks. Balloon volume could be increased to facilitate weight loss or decreased for tolerability. Coprimary endpoints included mean percentage total bodyweight loss and responder rate (≥5% total bodyweight loss) at 32 weeks. We used a multiple imputed intention-to-treat population analysis. This study was registered with ClinicalTrials.gov, NCT02812160.

FINDINGS

Between Aug 9, 2016, and Dec 7, 2018, we randomly assigned 288 patients to aIGB (n=187 [65%]) or control (n=101 [35%]) groups. Mean total bodyweight loss at 32 weeks was 15·0% (95% CI 13·9-16·1) in the aIGB group versus 3·3% (2·0-4·6) in the control group (p<0·0001). Clinical response was observed in 171 (92%) patients in the aIGB group. Adjustments to the aIGB occurred in 145 (80%) patients for weight loss plateau or intolerance. Upward volume adjustment facilitated an additional mean 5·2% (4·5-5·8) total bodyweight loss. Downward volume adjustment allowed 21 (75%) patients in the aIGB group to complete the full duration of therapy. Intolerance caused early removal of the device in 31 (17%) patients. No micronutrient deficiencies were observed in the aIGB cohort. Device-related serious adverse events were observed in seven (4%) patients, without any deaths.

INTERPRETATION

When aIGB was combined with lifestyle modification, significant weight loss was achieved and maintained for 6 months following removal. Balloon volume adjustability permitted individualised therapy, maximising weight loss and tolerance.

FUNDING

Spatz Medical.

Histologic changes caused by injection of a novel submucosal lifting agent for endoscopic resection in GI lesions

BACKGROUND AND AIMS

ORISE Gel is a recently introduced, U.S. Food and Drug Administration-approved submucosal lifting agent used in endoscopic resection of GI lesions. Histologically evident gel deposits in resected specimens may pose a potential diagnostic pitfall. To aid in recognition of this procedure-related artifact, we report the largest histologic series of ORISE Gel in endoscopic and surgical resection specimens to date.

METHODS

Fifty-eight EMR/endoscopic submucosal dissection (ESD) specimens with ORISE Gel injection and 5 interval surgical resection specimens with previous ORISE Gel injection were included. Patient demographics and endoscopy reports were obtained. Histologic slides from all cases were reviewed. Histochemical stains were performed on select cases.

RESULTS

Fifty-one EMR and 7 ESD specimens were identified. In 51 of 58 (88%) endoscopic resection specimens, amorphous, pale blue-gray, finely granular material was evident in the submucosa, as well as focally within the mucosa in 4 cases. Most cases showed homogeneous near-complete filling of the submucosa with this material, whereas a few demonstrated areas of condensation and retraction. Mucicarmine and periodic acid-Schiff stains were negative for mucin. Interval surgical resection specimens revealed extensive deposition of dense, eosinophilic material with associated multinucleated giant cells in the submucosa in all cases, with transmural extension in 3 cases.

CONCLUSION

ORISE Gel injection during endoscopic resection of GI lesions results in deposition of amorphous, blue-gray material seen in histologic sections, whereas interval surgical resection specimens demonstrate dense, eosinophilic material with an associated giant cell reaction. Awareness of these artifacts will help avoid misinterpretation of their presence as pathologic findings.

Endoscopic resection is more effective than biopsy or EUS to detect residual rectal neuroendocrine tumor

Background and study aims  Rectal neuroendocrine tumors (NETs) are often discovered incidentally and may be misidentified as adenomatous polyps. This can result in a partial resection at the index procedure, and lesions are often referred for staging or evaluation for residual disease at the resection site. The aim of this study was to identify the ideal method to confirm complete excision of small rectal NETs. Patients and methods  Data from patients with a previously resected rectal NET referred for follow-up endoscopy or endoscopic ultrasound (EUS) were retrospectively reviewed. Univariate analysis was performed on categorical data using the Chi-squared test. Results  Forty-nine patients with rectal NETs were identified by pathology specimens. Of those, 39 underwent follow-up endoscopy or EUS and were included. Baseline characteristics included gender (71 % F, 29 % M), age (57.2 ± 13.4 yrs) lesion size (7.3 ± 4.2 mm) and location. The prior resection site was identified in 37/39 patients who underwent tissue sampling. Residual NET was found histologically in 14/37 lesions. All residual disease was found during salvage endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD) and 43 % had a normal-appearing scar. Every patient undergoing EUS had an unremarkable exam. Initial cold biopsy polypectomy ( P  = 0.006), visible lesions ( P  = 0.001) and EMR/ESD of the prior resection site ( P  = 0.01) correlated with residual NET. Conclusions  Localized rectal NETs may be incompletely removed with standard polypectomy. If an advanced resection is not performed initially, repeat endoscopy with salvage EMR or ESD of the scar should be considered. For small rectal NETs, biopsy may miss residual disease when there is no visible lesion and EUS appears to have no benefit.

Revisional endoscopic sleeve gastroplasty of laparoscopic sleeve gastrectomy: an international, multicenter study

BACKGROUND AND AIMS

Laparoscopic sleeve gastrectomy (LSG) facilitates significant and durable weight loss; however, weight recidivism and need for revisional surgery occur in a subset of patients. Reduction of a dilated LSG using the revisional endoscopic sleeve gastroplasty (R-ESG) approach is an appealing and minimally invasive alternative to surgical revision that is congruent with obesity as a chronic relapsing disease model. In this study, we examine the safety and efficacy of the technique in a large multicenter international cohort.

METHODS

Prospectively collected data from 9 centers for 82 consecutive adults who underwent R-ESG for weight regain after LSG using the OverStitch device (Apollo Endosurgery, Austin, Tex, USA) from March 2014 to November 2019 were reviewed. Total body weight loss (TBWL) and adverse events were reported up to 12 months. Univariable logistic regression was used to identify predictors of response at 12 months.

RESULTS

Eighty-two adults (92.7% female) experienced 27.9 ± 20.7 kg weight regain from post-LSG nadir weight, prompting R-ESG (mean age, 42.8 ± 10.4 years) at a mean weight of 128.2 ± 57.5 kg. Mean R-ESG procedure duration was 48.3 ± 20.5 minutes, and the median number of sutures used was 4 (interquartile range, 3-4). After R-ESG, TBWL (follow-up %) was 6.6% ± 3.2% at 1 month (81.7%), 10.6% ± 4.4% at 3 months (74.4%), 13.2% ± 10.1% at 6 months (63.4%), and 15.7% ± 7.6% at 12 months (51.2%). In a per-protocol analysis, ≥10% TBWL was achieved by 37 of 51 patients (72.5%) at 6 months and 34 of 42 patients (81.0%) at 12 months; ≥15% TBWL was achieved by 20 of 46 patients (43.5%) at 6 months and 22 of 42 patients (52.4%) at 12 months. Only 1 moderate adverse event occurred in the form of a narrowed gastroesophageal junction, which resolved after a single endoscopic dilation.

CONCLUSIONS

R-ESG is a safe and effective means of facilitating weight loss for weight recidivism after LSG, with sustained results at 1 year. R-ESG should be considered before pursuing more-invasive surgical revisional options.

Endoscopic ultrasound acquired portal venous circulating tumor cells predict progression free survival and overall survival in patients with pancreaticobiliary cancers

BACKGROUND AND AIMS

Despite recent advances, patients with pancreaticobiliary cancers have a poor prognosis. We previously demonstrated the efficacy of endoscopic ultrasound (EUS) guided acquisition of portal vein (PV) blood for enumeration of circulating tumor cells (CTCs). The aim of this study was to assess PV-CTCs as potential biomarkers for the assessment of progression-free (PFS) and overall survival (OS) in patients with pancreaticobiliary cancers.

METHODS

17 patients with biopsy-proven pancreaticobiliary malignancy were enrolled. CTCs were enumerated from both peripheral and PV blood. All patients were followed until death. PFS and OS were evaluated with the log-rank test and summarized with the use of Kaplan-Meier methods. Unadjusted and adjusted Cox-proportional hazards models were fitted to study the relationship between PV-CTCs and PFS and OS.

RESULTS

After 3.5 years of follow-up, all patients had expired. PV-CTCs were detected in all patients (median PV-CTCs 62.0/7.5 mL (interquartile range [IQR] 17-132). The mean PFS in patients with PV-CTCs <185/7.5 mL was significantly longer than patients with PV-CTCs ≥185/7.5 mL (43.3 weeks vs. 12.8 weeks, log-rank p = 0.002). The mean OS in patients with PV-CTCs <185/7.5 mL was significantly longer than patients with PV-CTCs ≥185/7.5 mL (75.8 weeks vs. 29.5 weeks, log-rank p = 0.021). In an adjusted Cox-proportional hazards model, PV-CTCs were significant predictors of both PFS and OS (HR 1.004, p = 0.037; HR 1.004, p = 0.044 respectively).

CONCLUSION

In this pilot and feasibility study, EUS-acquired PV-CTCs predicted PFS and OS. Our findings suggest that PV-CTCs can help provide important prognostic data for both providers and patients.

EUS-Guided Portal Venous Sampling of Circulating Tumor Cells

PURPOSE OF REVIEW

Although liquid biopsies hold significant promise in the management of patients with cancer, peripheral blood analyses remain dependent on the degree of tumor burden with prohibitively low yields until the cancer is widely metastatic. Multiple lines of evidence support a dynamic, spatiotemporal localization of circulating tumor cells (CTCs) supporting specific targeting of vascular compartments, such as the portal vein. This review discusses the literature evaluating the possibility of portal venous blood as a new, potentially higher yield liquid biopsy and the current devices and techniques for endoscopic ultrasound (EUS)-guided portal venous sampling for CTC detection.

RECENT FINDINGS

Two recent studies in pancreatic cancer have demonstrated that portal venous blood can be safely sampled via EUS and consistently yields significantly higher CTC counts compared with matched peripheral blood. EUS-acquired samples can be used for molecular testing, clinical prognostication, and drug sensitivity analyses. Portal venous CTCs are identified in higher quantity relative to peripheral blood and can be safely obtained via EUS. Further studies are required to demonstrate the clinical utility of EUS-guided portal venous tumor material enrichment and analysis; however, obtaining EUS-guided "liquid biopsies" appears to merit significant consideration for procedural adoption.

Partially Covered Versus Uncovered Self-Expandable Metal Stents: Coating Nor Diameter Affect Clinical Outcomes

INTRODUCTION

Jaundice is a common initial presentation of malignant biliary stricture. In patients with life expectancies that are greater than 3 months, self-expanding metal stents (SEMS) offer a larger diameter stent with longer patency and fewer complications compared to plastic stents. There have been conflicting results in the published literature as to efficacy and safety between the various SEMS types and diameters. We compared stent coating (PCSEMS vs USEMS) and diameter on clinical outcomes regarding management of malignant biliary obstruction.

METHODS

A retrospective cohort study was conducted using a database of consecutive patients who underwent an ERCP with biliary SEMS placement (only 8 and 10 mm) between 2009 and 2017.

RESULTS

In total, 278 patients who had SEMS at ERCP for malignant biliary obstruction were included (213 PCSEMS vs 65 USEMS). The groups were demographically evenly matched. Clinical success rates and patency duration were not statistically significant between PCSEMS and USEMS (98.1% vs 95.5%, P = 0.36, and 302.5 vs 225.5 days, P = 0.72, respectively). Adverse event rates were similar between both PCSEMS and USEMS with regard to overall adverse events. Stent diameter did not have an impact on overall clinical success (98.9% vs 95.3%, P = 0.11) or patency duration (239 days vs 336 days, P = 0.51).

CONCLUSIONS

Our comparison of PCSEMS versus USEMS and 8 mm versus 10 mm showed no difference in clinical efficacy or adverse events between the two SEMS coatings and diameter, illustrating that coating and size do not matter in regard to stent choice, despite prior suggestive data.

Increased Yield of Human Tissue-Type Plasminogen Activator Obtained by Means of Recombinant DNA Technology

Extra copies of the human tissue-type plasminogen activator (t-PA) gene were introduced into the Bowes melanoma cell line. We obtained a recombinant cell line (TRBM6) which secretes approximately ten-fold more t-PA than the parent cell line. The identity of the plasminogen activator made by the new cell line was confirmed by sizing on sodium dodecyl sulphate polyacrylamide gels and by specific quenching using anti-t-PA antibody. We estimate that the recombinant line produces t-PA at a rate of approximately 3 pg/cell/24 hr and that t-PA accumulates in the harvest medium at a rate of approximately 4000 International t-PA Units/ml/24 hr.

Dissection-enabled scaffold-assisted resection (DeSCAR): a novel technique for resection of residual or non-lifting GI neoplasia of the colon (with video)

BACKGROUND AND AIMS

As a result of previous manipulation or submucosal invasion, GI lesions referred for EMR frequently have flat areas of visible tissue that cannot be snared. Current methods for treating residual tissue may lead to incomplete eradication or not allow complete tissue sampling for histologic evaluation. Our aim is to describe dissection-enabled scaffold-assisted resection (DeSCAR), a new technique combining circumferential ESD with EMR for removal of superficial non-lifting or residual "islands" with suspected submucosal involvement/fibrosis.

METHODS

From 2015 to 2017, lesions referred for EMR were retrospectively reviewed. Cases were identified where lifting and/or snaring of the lesion was incomplete and the DeSCAR technique was undertaken. Cases were reviewed for location, previous manipulation, rates of successful hybrid resection, and adverse events.

RESULTS

Twenty-nine lesions underwent DeSCAR because of non-lifting or residual "islands" of tissue. Fifty-two percent of the patients were male and 48% were female; average age was 66 years (standard deviation ±9.9 years). Lesions were located in the cecum (n = 10), right side of the colon (n = 12), left side of the colon (n = 4), and rectum (n = 3). Average size was 31 mm (standard deviation ±20.6 mm). Previous manipulation had occurred in 28 of 29 cases (83% biopsy, 34% resection attempt, 52% tattoo). The technical success rate for resection of non-lifting lesions was 100%. There was one episode of delayed bleeding but no other adverse events.

CONCLUSIONS

DeSCAR is a feasible and safe alternative to argon plasma coagulation and avulsion for the endoscopic management of non-lifting or residual GI lesions, providing en bloc resection of tissue for histologic review. Further studies are needed to demonstrate long-term eradication and for comparison with other methods.

EUS-guided portal vein sampling

EUS provides real-time images of the intramural gastrointestinal tract and adjacent structures that otherwise would not be visible. Given the anatomic proximity to the bowel, accurate identification of the major abdominal vasculature, such as the portal vein, serves as a useful landmark tool for identifying anatomy and staging of malignancies. Recently, increased reports have centered on the utility of EUS-guided vascular access of the portal vein for diagnostic and therapeutic interventions. Pilot and feasibility studies in human patients utilizing EUS-guided portal vein access for circulating tumor cell enumeration and portal pressure gradient monitoring suggest that sampling the portal vein under EUS guidance is safe and effective. This review discusses the rationale and technical aspects of EUS-guided portal vein sampling for diagnostic purposes in gastrointestinal cancer. Understanding the technical aspects of EUS-guided portal vein sampling will be critical to standardizing the procedure, developing new vascular access technologies, and increasing the safety profile.

Risk of infection transmission in curvilinear array echoendoscopes: results of a prospective reprocessing and culture registry

BACKGROUND AND AIMS

The complex design of the elevator mechanism in duodenoscopes has been recognized as a challenge for disinfection and recently implicated as a potential source of persistent bacterial contamination. Curvilinear array (CLA) echoendoscopes also have an elevator mechanism; however, there are no recommendations or data regarding the risk of persistent bacterial contamination of echoendoscopes. Here we hoped to determine the yield of microbial growth with routine bacterial surveillance cultures of reprocessed CLA echoendoscopes.

METHODS

Beginning in February 2015 to February 2016, CLA echoendoscopes at a single tertiary care center underwent prospective bacterial surveillance cultures after reprocessing. Any growth of gram-negative bacilli was considered to be critical. Echoendoscopes with a positive result underwent quarantine followed by repeat disinfection and culture.

RESULTS

During the study period, 540 cultures were obtained; 521 (96.5%) were primary cultures obtained from 18 CLA echoendoscopes. Twenty-two primary cultures (4.2%) were positive for gram-negative bacilli after high-level disinfection reprocessing. Eleven different bacteria were isolated: Klebsiella pneumoniae, Citrobacter freundii, Escherichia coli, Pseudomonas aeruginosa, Klebsiella oxytoca, Sphingomonas paucimobilis, Acinetobacter baumanii, Enterobacter cloacae, Hafnia alvei, Pseudomonas putida, and Stenotrophomonas maltophilia. Antibiotic sensitivity data on 19 of 24 bacteria (79.2%) isolated from positive primary cultures revealed no documented cases of carbapenem-resistant enterobacteriaceae, cephalosporin-resistant-Klebsiella, or multidrug-resistant Acinetobacter. There have been no documented cases of patient-to-patient transmission.

CONCLUSIONS

After following standard high-level disinfection and reprocessing, CLA echoendoscopes can remain culture positive for high-concern organisms. Recommendations regarding infection risk should take into consideration elevator-containing echoendoscopes in addition to duodenoscopes to ensure patient safety and endoscope reprocessing efficacy.

Endoscopic Ultrasound (EUS)-Guided Pancreatic Duct Drainage: The Basics of When and How to Perform EUS-Guided Pancreatic Duct Interventions

Despite the advances in endoscopy, endoscopic ultrasound-guided pancreatic duct drainage (EUS-PDD) remains a technically challenging procedure. Technical success rates are greater than 70%; however, the average rate of adverse events is nearly 20%, which increases to 55% when stent migration is included. Until recently, a significant difficulty with this technique was the absence of dedicated devices. Proper patient selection is of utmost importance, and EUS-PDD should be reserved for patients who have failed endoscopic retrograde pancreatography. Furthermore, EUS-PDD must be performed by experienced endoscopists who are familiar with the technique. The most common indications include chronic pancreatitis induced strictures and stones, disconnected pancreatic ducts, inaccessible ampulla, and post-surgical altered anatomy. This manuscript will review the accessories used, techniques employed, and published literature reporting outcomes as well as adverse events regarding EUS-PDD.

New Scopes, New Accessories, New Stents for Interventional Endoscopic Ultrasound

Technological advances have rapidly expanded the therapeutic potential of endoscopic ultrasound (EUS). Innovations in stent technology; directed adjunctive therapy for pancreatic tumors, including radiofrequency ablation and fiducial marker placement; advanced imaging modalities, including needle-based confocal laser endomicroscopy; and new echoendoscopes, such as the forward-viewing linear echoendoscope, are emerging as safe and effective tools and devices for providing a broad range of treatments and therapies previously not thought possible. In this review, we summarize and discuss the new echoendoscopes, accessories, and stents for interventional EUS and highlight the recent literature on technical and therapeutic efficacy. The therapeutic role and indications for EUS are rapidly evolving well beyond its current limits as new EUS-specific designed tools are designed, and ultimately, should help achieve the goal of improving patient outcomes.

Acquisition of Portal Venous Circulating Tumor Cells From Patients With Pancreaticobiliary Cancers by Endoscopic Ultrasound

BACKGROUND & AIMS

Tumor cells circulate in low numbers in peripheral blood; their detection is used predominantly in metastatic disease. We evaluated the feasibility and safety of sampling portal venous blood via endoscopic ultrasound (EUS) to count portal venous circulating tumor cells (CTCs), compared with paired peripheral CTCs, in patients with pancreaticobiliary cancers (PBCs).

METHODS

In a single-center cohort study, we evaluated 18 patients with suspected PBCs. Under EUS guidance, a 19-gauge EUS fine needle was advanced transhepatically into the portal vein and as many as four 7.5-mL aliquots of blood were aspirated. Paired peripheral blood samples were obtained. Epithelial-derived CTCs were sorted magnetically based on expression of epithelial cell adhesion molecules; only those with a proper morphology and found to be CD45 negative and positive for cytokeratins 8, 18, and/or 19 and 4',6-diamidino-2-phenylindole were considered to be CTCs. For 5 samples, CTCs also were isolated by flow cytometry and based on CD45 depletion. ImageStream was used to determine the relative protein levels of P16, SMAD4, and P53. DNA was extracted from CTCs for sequencing of select KRAS codons.

RESULTS

There were no complications from portal vein blood acquisition. We detected CTCs in portal vein samples from all 18 patients (100%) vs peripheral blood samples from only 4 patients (22.2%). Patients with confirmed PBCs had a mean of 118.4 ± 36.8 CTCs/7.5 mL portal vein blood, compared with a mean of 0.8 ± 0.4 CTCs/7.5 mL peripheral blood (P < .01). The 9 patients with nonmetastatic, resectable, or borderline-resectable PBCs had a mean of 83.2 CTCs/7.5 mL portal vein blood (median, 62.0 CTCs/7.5 mL portal vein blood). In a selected patient, portal vein CTCs were found to carry the same mutations as those detected in a metastatic lymph node and expressed similar levels of P16, SMAD4, and P53 proteins.

CONCLUSIONS

It is feasible and safe to collect portal venous blood from patients undergoing EUS. We identified CTCs in all portal vein blood samples from patients with PBCs, but less than 25% of peripheral blood samples. Portal vein CTCs can be used for molecular characterization of PBCs and share features of metastatic tissue. This technique might be used to study the pathogenesis and progression of PBCs, as well as a diagnostic or prognostic tool to stratify risk of cancer recurrence or developing metastases.

The emerging role of miRNAs in inflammatory bowel disease: a review

Inflammatory bowel disease (IBD), comprised of ulcerative colitis and Crohn's disease, is believed to develop as a result of a deregulated inflammatory response to environmental factors in genetically susceptible individuals. Despite advances in understanding the genetic risks of IBD, associated single nucleotide polymorphisms have low penetrance, monozygotic twin studies suggest a low concordance rate, and increasing worldwide IBD incidence leave gaps in our understanding of IBD heritability and highlight the importance of environmental influences. Operating at the interface between environment and heritable molecular and cellular phenotypes, microRNAs (miRNAs) are a class of endogenous, small noncoding RNAs that regulate gene expression. Studies to date have identified unique miRNA expression profile signatures in IBD and preliminary functional analyses associate these deregulated miRNAs to canonical pathways associated with IBD pathogenesis. In this review, we summarize and discuss the miRNA expression signatures associated with IBD in tissue and peripheral blood, highlight miRNAs with potential future clinical applications as diagnostic and therapeutic targets, and provide an outlook on how to develop miRNA based therapies.

The potential for medical therapy to reduce the risk of colorectal cancer and optimize surveillance in inflammatory bowel disease

It has been proposed that effective disease control through abrogation of inflammation in IBD may also reduce CRC risk in these individual patients. This article summarizes the potential for medical therapy to reduce the risk of CRC via primary and secondary prevention, and offers practical ways in which a goal of mucosal improvement or healing may be incorporated into clinical practice.

Expectations of iPad use in an internal medicine residency program: is it worth the "hype"?

Background

While early reports highlight the benefits of tablet computing in hospitals, introducing any new technology can result in inflated expectations.

Objective

The aim of the study is to compare anticipated expectations of Apple iPad use and perceptions after deployment among residents.

Methods

115 internal medicine residents received Apple iPads in October 2010. Residents completed matched surveys on anticipated usage and perceptions after distribution 1 month prior and 4 months after deployment.

Results

In total, 99% (114/115) of residents responded. Prior to deployment, most residents believed that the iPad would improve patient care and efficiency on the wards; however, fewer residents “strongly agreed” after deployment (34% vs 15% for patient care, P<.001; 41% vs 24% for efficiency, P=.005). Residents with higher expectations were more likely to report using the iPad for placing orders post call and during admission (71% vs 44% post call, P=.01, and 16% vs 0% admission, P=.04). Previous Apple iOS product owners were also more likely to use the iPad in key areas. Overall, 84% of residents thought the iPad was a good investment for the residency program, and over half of residents (58%) reported that patients commented on the iPad in a positive way.

Conclusions

While the use of tablets such as the iPad by residents is generally well received, high initial expectations highlight the danger of implementing new technologies. Education on the realistic expectations of iPad benefits may be warranted.

Gain-of-function mutant p53 upregulates CXC chemokines and enhances cell migration

The role of dominant transforming p53 in carcinogenesis is poorly understood. Our previous data suggested that aberrant p53 proteins can enhance tumorigenesis and metastasis. Here, we examined potential mechanisms through which gain-of-function (GOF) p53 proteins can induce motility. Cells expressing GOF p53 -R175H, -R273H and -D281G showed enhanced migration, which was reversed by RNA interference (RNAi) or transactivation-deficient mutants. In cells with engineered or endogenous p53 mutants, enhanced migration was reduced by downregulation of nuclear factor-kappaB2, a GOF p53 target. We found that GOF p53 proteins upregulate CXC-chemokine expression, the inflammatory mediators that contribute to multiple aspects of tumorigenesis. Elevated expression of CXCL5, CXCL8 and CXCL12 was found in cells expressing oncogenic p53. Transcription was elevated as CXCL5 and CXCL8 promoter activity was higher in cells expressing GOF p53, whereas wild-type p53 repressed promoter activity. Chromatin immunoprecipitation assays revealed enhanced presence of acetylated histone H3 on the CXCL5 promoter in H1299/R273H cells, in agreement with increased transcriptional activity of the promoter, whereas RNAi-mediated repression of CXCL5 inhibited cell migration. Consistent with this, knockdown of the endogenous mutant p53 in lung cancer or melanoma cells reduced CXCL5 expression and cell migration. Furthermore, short hairpin RNA knockdown of mutant p53 in MDA-MB-231 cells reduced expression of a number of key targets, including several chemokines and other inflammatory mediators. Finally, CXCL5 expression was also elevated in lung tumor samples containing GOF p53, indicating relevance to human cancer. The data suggest a mechanistic link between GOF p53 proteins and chemokines in enhanced cell motility.

Acute hypoxia occludes hTREK-1 modulation: re-evaluation of the potential role of tandem P domain K+ channels in central neuroprotection

The human tandem P domain K+ channel hTREK-1 (KCNK2) is distributed widely through the CNS. Here, whole-cell patch clamp recordings were employed to investigate the effects of hypoxia on hTREK-1 channels stably expressed in human embryonic kidney cells. Acute hypoxia caused a rapid and reversible inhibition of whole-cell K+ current amplitudes; this was PO2 dependent with a maximal inhibition achieved at 60 mmHg and below. In accordance with previous studies, hTREK-1 current amplitudes were enhanced by arachidonic acid. This effect was concentration dependent, with maximal enhancement observed at a concentration of 10 microM. Membrane deformation by the crenator trinitrophenol (to mimic cell swelling) or the cup former chlorpromazine (to mimic cell shrinkage) caused robust activation and inhibition of currents, respectively. However, current augmentation by either arachidonic acid or trinitrophenol was completely prevented during hypoxia; conversely, hypoxia blunted the inhibitory action of chlorpromazine. The abilities of arachidonic acid to augment currents and of hypoxia to completely abrogate this effect were also observed in cell-attached patches. Our data indicate that hypoxia interacts with hTREK-1, and occludes its modulation by arachidonic acid and membrane deformation. These findings also suggest that the potential neuroprotective role of TREK channels, which has recently been proposed, requires reconsideration since hTREK-1 activation is unlikely when ambient PO2 is below 60 mmHg - a situation which normally pertains in the CNS even during systemic normoxia.

Recombinant hTASK1 is an O(2)-sensitive K(+) channel

Hypoxic inhibition of background K(+) channels is crucial to O(2) sensing by chemoreceptor tissues, but direct demonstration of O(2) sensitivity by any member of this K(+) channel family is lacking. HEK293 cells were transfected with a pcDNA3.1-hTASK1 construct; expression of hTASK1 was verified using RT-PCR and immunocytochemistry. Whole-cell K(+) currents of cells stably expressing hTASK-1 were, as anticipated, extremely sensitive to extracellular pH, within the physiological range (IC(50) approximately 7.0). All cells expressing this signature pH sensitivity were acutely modulated by pO(2); reduction of pO(2) from 150 to <40 mmHg (at pH 7.4) caused rapid and reversible suppression of pH-sensitive K(+) currents. Furthermore, these two regulatory signals clearly acted at the same channel, since the magnitude of the O(2)-sensitive current was dependent on the extracellular pH. These data represent the first direct verification that hTASK1 is O(2)-sensitive and reinforce the idea that this K(+) channel is key to O(2) sensing in chemoreceptors.

The neuroprotective agent sipatrigine (BW619C89) potently inhibits the human tandem pore-domain K(+) channels TREK-1 and TRAAK

We have cloned and functionally expressed the human orthologue of the mouse TRAAK gene. When cDNA for hTRAAK is expressed in either Xenopus oocytes or HEK293 cells it forms a K(+)-selective conductance and hyperpolarises the resting membrane potential. Quantitative mRNA expression analysis using Taqman revealed that hTRAAK mRNA is predominantly present in the central nervous system where it exhibits a regionally diverse pattern of expression. Like the related channel TREK-1, the activity of TRAAK was potentiated by arachidonic acid. The neuroprotective agent sipatrigine (10 microM) inhibited both hTREK-1 (73.3+/-4.4%) and hTRAAK (45.1+/-11.2%) in a reversible, voltage-independent manner. Inhibition of both channels was dose-dependent and for TREK-1 occurred with an IC(50) of 4 microM. The related compound lamotrigine, which is a better anticonvulsant but weaker neuroprotective agent than sipatrigine, was a far less effective antagonist of both channels, producing <10% inhibition at a concentration of 10 microM.

Distribution analysis of human two pore domain potassium channels in tissues of the central nervous system and periphery

Potassium channels are amongst the most heterogeneous class of ion channels known and are responsible for mediating a diverse range of biological functions. The most recently described family of K+ channels, the 'two pore-domain family', contain four membrane spanning domains and two pore-forming domains, suggesting that two channel subunits associate to form a functional K+ pore. Several sub-families of the two pore domain potassium channel family have been described, including the weakly inward rectifying K+ channel (TWIK), the acid-sensitive K+ channel (TASK), the TWIK-related K+ channel (TREK) and the TWIK-related arachidonic acid stimulated K+ channel (TRAAK). However, comparison of the mRNA expression of these channels has been difficult due to the differences in methods used and the species studied. In the present study, we used a single technique, TaqMan semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), to investigate the mRNA distribution of all currently known two pore potassium channels in human central nervous system (CNS) and peripheral tissues. TWIK-1 and the TWIK-1-like channel KCNK7 were predominantly expressed in the CNS, in contrast to TWIK-2 which was preferentially expressed in peripheral tissues such as pancreas, stomach, spleen and uterus. TASK-1 was expressed in the CNS and some peripheral tissues, whereas TASK-2 was exclusively expressed in the periphery except for mRNA expression observed in dorsal root ganglion and spinal cord. In addition, mRNA expression of the recently identified TASK-3, was almost completely exclusive to cerebellum with little or no mRNA detected in any other tissues. TREK-1 and TRAAK mRNA expression was predominantly CNS specific in contrast to the closely related TREK-2, which was expressed in both CNS and peripheral tissues. Studying the mRNA expression profiles of known two pore domain K+ channels will aid in the understanding of the biological roles of these channels. Furthermore, identification of common areas of expression may help identify which channels, if any, associate to form heteromeric K+ channel complexes.

Cloning, localisation and functional expression of a novel human, cerebellum specific, two pore domain potassium channel

We have isolated, by degenerate PCR, a complementary DNA encoding a novel two pore domain potassium channel. This is the 7th functional member of the human tandem pore domain potassium channel family to be reported. It has an open reading frame of 1.125 kb and encodes a 374 amino acid protein which shows 62% identity to the human TASK-1 gene: identity to other human members of the family is 31-35% at the amino acid level. We believe this gene to be human TASK-3, the ortholog of the recently reported rat TASK-3 gene: amino acid identity between the two is 74%. 'Taqman' mRNA analysis demonstrated a very specific tissue distribution pattern, showing human TASK-3 mRNA to be localised largely in the cerebellum, in contrast rat TASK-3 was reported to be widely distributed. We have shown by radiation hybrid mapping that human TASK-3 can be assigned to chromosome 8q24.3. Human TASK-3 was demonstrated to endow Xenopus oocytes with a negative resting membrane potential through the presence of a large K(+) selective conductance. TASK-3 is inhibited by extracellular acidosis with a mid-point of inhibition around pH 6. 5, supporting the predictions from the sequence data that this is a third human TASK (TWIK-related acid sensitive K(+) channel) gene.

Cloning, localisation and functional expression of the human orthologue of the TREK-1 potassium channel

We have cloned human TREK-1, one of the newly emerging mammalian family of 2-P domain potassium channels. The channel has 411 amino acids with a 41-amino-acid extension at the C-terminus when compared with the cloned mouse TREK-1 channel. Expression of hTREK-1 produced a substantial hyperpolarising shift in resting membrane potential accompanied by the induction of large, outwardly rectifying, non-inactivating currents which were potassium selective. Pharmacologically, hTREK-1-mediated currents were only blocked to a limited extent by classic potassium channel blockers or open channel pore blockers known to potently inhibit other channels. The channel was reversibly potentiated by arachidonic acid. CNS distribution of hTREK-1 is widespread with higher levels being observed in caudate, putamen, amygdala, thalamus and spinal cord. Only low levels of expression were seen in the majority of peripheral regions. Thus, hTREK-1, although functionally and pharmacologically similar to mouse TREK-1, appears to have a more CNS-specific distribution.

The putative 116 kDa osteoclast specific vacuolar proton pump subunit has ubiquitous tissue distribution

The pharmacological profile of the osteoclast proton pump has been demonstrated to be unique and to be the most active of all acid transport systems thus far studied. The recently reported putative 116 kDa osteoclast specific vacuolar proton pump subunit could possibly explain the unique nature of this proton pump. Here, we demonstrate however, that the osteoclast 116 kDa subunit is not osteoclast specific but has ubiquitous expression in human tissue.

Agonist potency at the cloned human beta-3 adrenoceptor depends on receptor expression level and nature of assay

The cloned human beta-3 adrenoceptor was expressed in Chinese hamster ovary cells at three different levels (130, 400 and 3000 fmol/mg). The potency and intrinsic activity of a range of agonists in functional assays with these cell lines rose as a function of increasing receptor density. Operational analysis of concentration-response data allowed calculation of functional affinity and efficacy of agonists at the human beta-3 adrenoceptor. The data highlighted the low efficacy of BRL 37344 ¿(RR,SS)-(+/-)-4-[(2-(2-(3-chlorophenyl)-2-hydroxyethyl)amino)-propyl] phenoxyacetate¿ for the human beta-3 adrenoceptor, which may explain its lower potency at the human receptor despite its higher affinity relative to isoprenaline. The potency of catecholamines at the human beta-3 adrenoceptor was found to be 1 to 2 orders of magnitude higher when determined in an intact cell cAMP accumulation assay compared with a membrane-based adenylyl cyclase activation assay. The reason for this enhanced sensitivity is not clear, but the result is that the potency of the natural agonist noradrenaline in the intact cell is considerably higher than predicted either from its ligand binding affinity, or from its potency in membrane-based assays. Much smaller enhancements in sensitivity were observed for compounds of the aryloxypropanolamine class such as CGP 12177 [(+/-)-4-(3-t-butylamino-2-hydroxypropoxy)benzimidazol-2-one], with the result that the rank order of potency of such agonists at the beta-3 adrenoceptor was altered. In particular, CGP 12177 exhibited high relative potency in the cyclase assay, but low relative potency in intact cell assays. These findings highlight the importance of selecting appropriate expression levels and appropriate assay methodology when cloned receptors are used to characterize agonists.

Molecular cloning and analysis of one member of a polymorphic family of GACA-hybridising DNA repeats in tomato

Simple sequence repeat oligonucleotides were used to probe the tomato genome for elements displaying variability amongst commercial cultivars. The oligonucleotide (GACA)4 was found to be particularly informative on genotype screening blots, hybridising to a highly polymorphic family of elements, and was used to clone one such member from a lambda library. The GACA-hybridisation was localised to a 1.3-kbHinfI fragment within the original 15-kb lambda insert. This 1,349-bp subclone (pT-GACA-2:1.3) was used to probe 27 Californian processing varieties and found to be capable of distinguishing all from each other, thus demonstrating its utility as a genetic fingerprinting probe for cultivar identification. Hybridisation occurred to approximately 10 major high molecular weight (> 4-kb) bands, most of which segregated independently in F2 populations, as well as a large number of less clearly resolvable smaller fragments. Sequence analysis of the cloned element reveals that it is almost entirely composed of GACA or GATA repeats. These tetranucleotides are organised into distinct repetitive domains, consisting either of tandem arrays of each tetranucleotide or interspersions of GACA and GATA to form dodecanucleotides that are then further repeated. The boundaries between domains contain sufficient departures from the concensus repeat to allow construction of unique polymerase chain reaction (PCR) primers. Amplification from two such contiguous regions identifies length variation in both, thus yielding a genotype screen appropriate for high-throughput applications, such as assessment of purity in F1 hybrid seed lots.

Deletion of residues K296-G302 from the slowly-cleared tissue-type plasminogen activator t-PA del (G) leads to partial loss of plasminogen activating activity

Plasmids encoding tissue-type plasminogen activators lacking residues K296-G302 were constructed and were expressed in a Hela cell transient expression system. Conditioned media from the cultures were tested in a number of systems designed to detect function or antigen. Functional assays comprised the chromogenic substrate S2288 and three plasminogen activation assays. All t-PA variants were active in all assays but to varying degrees. The results are consistent with the conclusion that deletion of residues K296-G302 from the slowly-cleared t-PA mutant t-PA del(G) adversely affects the plasminogen activating ability of the molecule without altering the integrity of the active site. This is in contrast to the situation in native t-PA where the same mutation has little overall effect on activity.

The use of bovine fibrin-streptokinase films for the determination of recombinant human plasminogen

Plasminogen is a key component of the haemostatic system in man and the plasma-derived protein molecule has been actively investigated. Within the last few years cDNA and the gene encoding plasminogen have been cloned and the protein has been expressed in a number of eukaryotic or prokaryotic systems. Yields of expressed plasminogen are frequently low. Currently available assays for plasminogen generally rely on the determination of antigen or utilize tripeptide substrates for measuring functional activity, and they have certain limitations. Assays employing relevant protein substrates offer an alternative way to measure function and overcome the drawbacks associated with the other tests. The use of fibrin films for the assay of low levels of recombinant plasminogen has not been described fully before. The two fibrin film-based assays described in this paper are significant additions to the array of assays available for plasminogen molecules.

A recombinant, chimeric enzyme with a novel mechanism of action leading to greater potency and selectivity than tissue-type plasminogen activator

BACKGROUND

Early intervention with thrombolytic agents has been shown unequivocally to reduce mortality after acute myocardial infarction. Presently used agents have disadvantages such as short half-life, immunogenicity, hypotension, and bleeding complications. Therefore, there is a need to develop improved thrombolytic drugs with novel mechanisms of action leading to improved properties.

METHODS AND RESULTS

Hybrid plasminogen/tissue-type plasminogen activator (t-PA) complementary DNA was constructed and expressed in Chinese hamster ovary cells. The chimeric protein, comprising the fibrin-binding domains of plasminogen covalently linked to the catalytic domain of t-PA, was purified and evaluated in vitro and in vivo. The hybrid was inhibited rapidly in human and animal plasmas. The mediator of this rapid inhibition was shown to be alpha 2-antiplasmin. The active center of the hybrid could be protected by reversible active center acylation with a novel inverse acylating agent, 4'-amidinophenyl-4-chloroanthranilic acid (AP-CLAN). An acylated (CLAN-) hybrid was cleared from the bloodstream of guinea pigs at 0.35 +/- 0.02 ml/min.kg-1 compared with a clearance rate of 36 +/- 4 ml/min.kg-1 for t-PA. The CLAN-plasminogen/t-PA hybrid was evaluated in a quantitative, "humanized" guinea pig pulmonary embolism model and shown to be approximately threefold more potent when given by bolus than an infusion of t-PA. Furthermore, the acylated hybrid was more fibrin selective than t-PA as determined by the relation between clot lysis and fibrinogen degradation.

CONCLUSIONS

An acylated, recombinant plasminogen/t-PA hybrid has sufficiently slow clearance to be administered by bolus and is more potent and fibrin selective than t-PA in vivo.

Developments in the meiotic analysis of hybrids. II. Amended models for tetraploids

Amended models of meiotic behaviour in tetraploid species' hybrids have been constructed which better reflect the theory and assumptions about chromosome pairing necessary to conduct such analyses. In particular they correct problems concerning the distribution of chiasmata among and within chromosome configurations inherent in the earlier models of Kimber & Alonso (1981). In general these analyses give similar interpretations to the earlier models but in some cases call the previous conclusions into question.

Developments in the meiotic analysis of hybrids. I. Review of theory and optimization in triploids

The theory, construction and optimization of a model of chromosome pairing in triploid hybrids are re-examined and the model reconstructed. A new approach to optimization is described that removes a bias in the estimation of x, the measure of relative affinity, by weighting the observed and calculated meiotic figure frequencies by the number of chromosomes in each figure type. The amended analysis is compared with its antecedent and with other models.