Ligand-specific changes in conformational flexibility mediate long-range allostery in the lac repressor.

Biological regulation ubiquitously depends on protein allostery, but the regulatory mechanisms are incompletely understood, especially in proteins that undergo ligand-induced allostery with few structural changes. Here we used hydrogen-deuterium exchange with mass spectrometry (HDX/MS) to map allosteric effects in a paradigm ligand-responsive transcription factor, the lac repressor (LacI), in different functional states (apo, or bound to inducer, anti-inducer, and/or DNA). Although X-ray crystal structures of the LacI core domain in these states are nearly indistinguishable, HDX/MS experiments reveal widespread differences in flexibility. We integrate these results with modeling of protein-ligand-solvent interactions to propose a revised model for allostery in LacI, where ligand binding allosterically shifts the conformational ensemble as a result of distinct changes in the rigidity of secondary structures in the different states. Our model provides a mechanistic basis for the altered function of distal mutations. More generally, our approach provides a platform for characterizing and engineering protein allostery.

Clinical Course and Treatment Implications of Combination Immune Checkpoint Inhibitor-Mediated Hepatitis: A Multicentre Cohort.

BACKGROUND: Immune-related adverse events can occur after treatment with immune checkpoint inhibitors (ICI), limiting treatment persistence. We aimed to evaluate the clinical course of ICI-mediated hepatitis (IMH) associated with combination ipilimumab and nivolumab treatment. METHODS: A retrospective cohort study including consecutive patients with metastatic melanoma treated with ipilimumab and nivolumab between 2013 and 2018 was conducted at two tertiary care centres. IMH was defined by the Common Terminology Criteria for Adverse Events (CTCAE). We determined the proportion of patients developing IMH, and compared the duration, treatment patterns and outcomes, stratified by hepatitis severity. Kaplan-Meier survival analysis was used to evaluate time to hepatitis resolution, and a linear mixed-effects model was used to compare longitudinal outcomes by treatment. RESULTS: A total of 63 patients were included. Thirty-two patients (51%) developed IMH (34% Grade 1-2, 66% Grade 3-4), at a median of 34 days (IQR 20 to 43.5 days) after the first dose. Baseline FIB4 index ≥1.45 was associated with IMH (OR 3.71 [95% CI: 1.03 to 13.38], P = 0.04). Ninety-four per cent (30/32) of patients had liver enzyme normalization after a median duration of 43 days (IQR 26 to 70 days). Corticosteroid use was not associated with faster IMH resolution or less ICI discontinuation. A total of 24 patients died during the study; no deaths were attributable to hepatitis-related complications. Fifty-three per cent (17/32) of patients resumed anti-PD-1 monotherapy and three patients developed IMH recurrence. CONCLUSIONS: Approximately half of the patients treated with combination ipilimumab and nivolumab developed IMH in this cohort. However, most patients experienced uncomplicated IMH resolution.

Phlebosclerotic Colitis - An Enigma Among Ischemic Colitis.

Phlebosclerotic Colitis is a rare, potentially life-threatening condition of unclear etio-pathogenesis seen almost exclusively in Asians and people of Asian descent. The condition predominantly affects the right hemicolon and imaging plays a crucial role in its diagnosis. Here we report the only second documented case of phlebosclerotic colitis in North America in a 60-year-old Canadian resident of Vietnamese descent with a history of consuming herbal medication (sanshishi) in soup for 2-3 decades.

Clinical Impact of Portal Vein Thrombosis Prior to Liver Transplantation: A Retrospective Cohort Study

ABSTRACT Introduction. To identify the impact of portal vein thrombosis (PVT) and associated medical and surgical factors on outcomes post liver transplant (LT). Material and methods. Two analyses were performed. Analysis One: cohort study of 505 consecutive patients who underwent LT (Alberta) between 01/2002-12/2012. PVT was identified in 61 (14%) patients. Analysis Two: cohort study of 144 consecutive PVT patients from two sites (Alberta and London) during the same period. Cox multivariable survival analysis was used to identify independent associations with post-LT mortality. Results. In Analysis One (Alberta), PVT was not associated with post-LT mortality (log rank p = 0.99). On adjusted analysis, complete/occlusive PVT was associated with increased mortality (Hazard Ratio (HR) 8.4, p < 0.001). In Analysis Two (Alberta and London), complete/occlusive PVT was associated with increased mortality only on unadjusted analysis (HR 3.7, p = 0.02). On adjusted analysis, Hepatitis C (HR 2.1, p = 0.03) and post-LT portal vein re-occlusion (HR 3.2, p = 0.01) were independently associated with increased mortality. Conclusion: Well-selected LT patients who had PVT prior to LT had similar post-LT outcomes to non-PVT LT recipients. Subgroups of PVT patients who did worse post-LT (complete/occlusive thrombosis pre-LT, Hepatitis C or post-LT portal vein re-occlusion) warrant closer evaluation in listing and management post-LT.

Clinical Impact of Portal Vein Thrombosis Prior to Liver Transplantation: A Retrospective Cohort Study.

INTRODUCTION: To identify the impact of portal vein thrombosis (PVT) and associated medical and surgical factors on outcomes post liver transplant (LT). MATERIAL AND METHODS: Two analyses were performed. Analysis One: cohort study of 505 consecutive patients who underwent LT (Alberta) between 01/2002-12/2012. PVT was identified in 61 (14%) patients. Analysis Two: cohort study of 144 consecutive PVT patients from two sites (Alberta and London) during the same period. Cox multivariable survival analysis was used to identify independent associations with post-LT mortality. RESULTS: In Analysis One (Alberta), PVT was not associated with post-LT mortality (log rank p = 0.99). On adjusted analysis, complete/occlusive PVT was associated with increased mortality (Hazard Ratio (HR) 8.4, p &lt; 0.001). In Analysis Two (Alberta and London), complete/occlusive PVT was associated with increased mortality only on unadjusted analysis (HR 3.7, p = 0.02). On adjusted analysis, Hepatitis C (HR 2.1, p = 0.03) and post-LT portal vein re-occlusion (HR 3.2, p = 0.01) were independently associated with increased mortality. CONCLUSION: Well-selected LT patients who had PVT prior to LT had similar post-LT outcomes to non-PVT LT recipients. Subgroups of PVT patients who did worse post-LT (complete/occlusive thrombosis pre-LT, Hepatitis C or post-LT portal vein re-occlusion) warrant closer evaluation in listing and management post-LT.

Computed Tomography Measurement of Hepatic Steatosis: Prevalence of Hepatic Steatosis in a Canadian Population.

Background/Aims. Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease that can progress to cirrhosis and hepatocellular carcinoma. This retrospective chart review investigated the incidence of hepatic steatosis in London, Ontario, Canada. Methods. A retrospective chart review was performed on emergency room (ER) patients undergoing nonscheduled computed tomography (CT) imaging over a six-month period in London, Ontario. CT images and reports were examined to determine presence of steatosis. Analyses of the electronic chart for a period of six months following the CT and communication with the patients' family doctors were used to determine if there was follow-up. Waist circumference, subcutaneous fat depth, and abdominal fat volumes were calculated. Results. 48/450 patients meeting inclusion criteria were identified by radiology as having steatosis, with 34/40 (85%) family physicians unaware of the finding. 24.7% (100/405) of patients met standard CT criteria for steatosis, 40 of which were reported by the radiologist. Waist circumference, subcutaneous adipose tissue depth, subcutaneous adipose tissue volume, and visceral adipose tissue volume were significantly associated with steatosis. Conclusions. The hepatic steatosis prevalence we report is the first reported in a Canadian population. Early identification of steatosis will become more important as new pharmacologic therapies arise.

Submucosal tunneling and endoscopic resection of submucosal tumors at the esophagogastric junction.

AIM: To evaluate the safety and efficacy of submucosal tunneling and endoscopic resection (STER) for treating submucosal tumors (SMTs). METHODS: Between August 2012 and October 2013, 21 patients with SMTs originating from the muscularis propria (MP) layer at the esophagogastric junction were treated by STER of their tumors. Key steps of the procedure include: (1) mucosal incision: a 2-cm longitudinal mucosal incision was made 5 cm proximal to the tumor; (2) submucosal tunneling: a submucosal tunnel was created 5 cm proximal to and 1 to 2 cm distal to the tumor; (3) tumor resection: the SMT was resected under direct endoscopic viewing; (4) hemostasis: while finishing the tumor resection, careful hemostasis of the MP defect and the tunnel was performed; and (5) mucosal closure: the mucosal incision site was closed by using hemostatic clips. During the operation, equipment used included a cap-fitted endoscope, an insulated-tip knife, a hook knife, hemostatic forceps, an injection needle, a snare, an endoclip, and a high-frequency generator. Carbon dioxide (CO2) insufflation was achieved by using a CO2 insufflator. RESULTS: The median age of the patients was 46.2 years (range, 35-59 years), and the majority were male (18 male vs 3 female). Complete resection rate was 100% (21/21). Eighteen lesions were resected en bloc. Mean tumor size was 23 mm (range, 10-40 mm), and mean procedure time was 62.9 min (range, 45-90 min). Pathological diagnosis of these tumors included leiomyoma (15 out of 21) and gastrointestinal stromal tumor (6 out of 21). Full-thickness MP resection was performed in 9 of 21 patients (42.9%), with mediastinal and subcutaneous emphysema occurring in all nine. At the completion of the procedure, all patients received closure of the incision with hemoclips. One patient required percutaneous drainage. The remaining 20 patients required no further endoscopic or surgical intervention. There were no incidents of massive or delayed bleeding. The median follow-up period after the procedure was 6 mo (range, 2-14 mo). During follow-up, no patients were found to have residual or recurrent tumor or esophageal stricture. CONCLUSION: STER is safe, effective and feasible, which provides accurate histopathologic evaluation and curative treatment for SMTs originating from the MP layer at the esophagogastric junction.

Comparing outcomes of donation after cardiac death versus donation after brain death in liver transplant recipients with hepatitis C: a systematic review and meta-analysis.

BACKGROUND: Liver transplantation (LT) using organs donated after cardiac death (DCD) is increasing due, in large part, to a shortage of organs. The outcome of using DCD organs in recipients with hepatits C virus (HCV) infection remains unclear due to the limited experience and number of publications addressing this issue. OBJECTIVE: To evaluate the clinical outcomes of DCD versus donation after brain death (DBD) in HCV-positive patients undergoing LT. METHODS: Studies comparing DCD versus DBD LT in HCV-positive patients were identified based on systematic searches of seven electronic databases and multiple sources of gray literature. RESULTS: The search identified 58 citations, including three studies, with 324 patients meeting eligibility criteria. The use of DCD livers was associated with a significantly higher risk of primary nonfunction (RR 5.49 [95% CI 1.53 to 19.64]; P=0.009; I2=0%), while not associated with a significantly different patient survival (RR 0.89 [95% CI 0.37 to 2.11]; P=0.79; I2=51%), graft survival (RR 0.40 [95% CI 0.14 to 1.11]; P=0.08; I2=34%), rate of recurrence of severe HCV infection (RR 2.74 [95% CI 0.36 to 20.92]; P=0.33; I2=84%), retransplantation or liver disease-related death (RR 1.79 [95% CI 0.66 to 4.84]; P=0.25; I2=44%), and biliary complications. CONCLUSIONS: While the literature and quality of studies assessing DCD versus DBD grafts are limited, there was significantly more primary nonfunction and a trend toward decreased graft survival, but no significant difference in biliary complications or recipient mortality rates between DCD and DBD LT in patients with HCV infection. There is insufficient literature on the topic to draw any definitive conclusions.

Increased duration of dual pegylated interferon and ribavirin therapy for genotype 1 hepatitis C post-liver transplantation increases sustained virologic response: a retrospective review.

BACKGROUND/AIM: In patients with advanced post-transplant hepatitis C virus (HCV) recurrence, antiviral treatment (AVT) with interferon and ribavirin is indicated to prevent graft failure. The aim of this study was to determine and report Canadian data with respect to the safety, efficacy, and spontaneous virologic response (SVR) predictors of AVT among transplanted patients with HCV recurrence. PATIENTS AND METHODS: A retrospective chart review was performed on patients transplanted in London, Ontario and Edmonton, Alberta from 2002 to 2012 who were treated for HCV. Demographic, medical, and treatment information was collected and analyzed. RESULTS: A total of 85 patients with HCV received pegylated interferon with ribavirin post-liver transplantation and 28 of the 65 patients (43%) with genotype 1 achieved SVR. Of the patients having genotype 1 HCV who achieved SVR, there was a significantly lower stage of fibrosis (1.37 ± 0.88 vs. 1.89 ± 0.96; P = 0.03), increased ribavirin dose (total daily dose 1057 ± 230 vs. 856 ± 399 mg; P = 0.02), increased rapid virologic response (RVR) (6/27 vs. 0/31; P = 0.05), increased early virologic response (EVR) (28/28 vs. 18/35; P = 0.006), and longer duration of therapy (54.7 ± 13.4 weeks vs. 40.2 ± 18.7; P = 0.001). A logistic regression model using gender, age, RVR, EVR, anemia, duration of therapy, viral load, years' post-transplant, and type of organ (donation after cardiac death vs. donation after brain death) significantly predicted SVR (P < 0.001), with duration of therapy having a significant odds ratio of 1.078 (P = 0.007). CONCLUSIONS: This study identified factors that predict SVR in HCV-positive patients who received dual therapy post-transplantation. Extending therapy from 48 weeks to 72 weeks of dual therapy is associated with increased SVR rates. Future studies examining the role of extended therapy are needed to confirm these findings, since the current study is a retrospective one.

A case of tinea incognito.

Tinea incognito is a dermatophyte infection of the skin that presents atypically because it has previously been treated with imunnosuppresive medication. Herein we present a case of a middle-aged man who was initially clinically diagnosed to have plaque-type psoriasis on his arms. Over the course of two months of topical hydrocortisone and calciptriol treatment as well as phototherapy, the rash worsened. At the time of presentation to hospital the patient had a pruritic, widespread, sloughing, erythematous rash with areas of eschar. A punch biopsy skin confirmed dermatophyte fungal infection of the skin. Fungal culture was positive for Trichophyton Rubrum and the eruption resolved with systemic anti-fungal therapy. Patient specific risk factors for atypical presentation included poor hygiene and hepatatic disease.

Sleep disruption secondary to overnight call shifts is associated with irritable bowel syndrome in residents: a cross-sectional study.

OBJECTIVES: Sleep disruption has been associated with irritable bowel syndrome (IBS). We hypothesized that residents with greater sleep disruption secondary to intermittent overnight call shifts would have a higher prevalence of IBS. METHODS: Postgraduate residents completed a Web-based survey including demographic data, frequency and characteristics of call shifts, the Rome III questionnaire, and the IBS-quality of life measure. RESULTS: For every hour of sleep deprivation while on call vs. off call, the odds ratio for an increased likelihood of IBS was 1.32, after adjustment for age and gender. The mean number of calls per block, sleep deprivation while on call, and specialty program vs. family practice each predicted the severity of IBS. CONCLUSIONS: Sleep disruption secondary to overnight call in residents was associated with an increased prevalence of IBS.

A cross-sectional study of the association between overnight call and irritable bowel syndrome in medical students.

BACKGROUND: Shift work has been associated with irritable bowel syndrome (IBS), which includes gastrointestinal symptoms such as abdominal pain, constipation and diarrhea. Overnight call shifts also lead to a disruption of the endogenous circadian rhythm. HYPOTHESIS: Medical students who perform intermittent overnight call shifts will demonstrate a higher prevalence of IBS symptoms when compared with medical students who perform no overnight call shifts. METHODS: First- and second-year (preclinical) medical students have no overnight call requirements, whereas third- and fourth-year medical (clerkship) students do have overnight call requirements. All medical students at the Schulich School of Medicine and Dentistry (London, Ontario) were invited to complete an anonymous, web-based survey or an identical paper copy that included demographic data, the Rome III questionnaire and the IBS-Quality of Life measure (IBS-QOL). The prevalence of IBS symptoms and quality of life secondary to those symptoms were determined. RESULTS: Data were available for 247 medical students (110 preclinical students, 118 clerkship students and 19 excluded surveys). There was no significant difference in the presence of IBS between preclinical and clerkship students (21 of 110 [19.1%] versus 26 of 118 [22.0%]; P=0.58). The were no significant differences in mean (± SD) IBS-QOL score of those with IBS between preclinical (43.5±8.3) and clerkship students (45.7±13.8) (P=0.53). CONCLUSIONS: Participation in overnight call was not associated with the development of IBS or a lower quality of life secondary to IBS in medical students.

Engaging medical staff in clinical governance: introducing new technologies and clinical practice into public hospitals.

INTRODUCTION: To enhance patient care, medical staff at major tertiary teaching hospitals are encouraged to innovate through introducing new technologies and clinical practices. However, such introduction must be safe, efficient, effective and appropriate for patients and the organisation, and actively lead by engage medical staff. METHOD: This study outlines the development, implementation and evaluation of a framework for introducing new technologies and clinical practice to a major tertiary health service. Evaluation includes survey of medical Heads of Units (HOUs) for framework's effectiveness, and comparison of level of medical staff engagement against a best-practice model. RESULTS: Over 2-year period: 19 applications, 7 approved. Successful external funding of $1.993 million achieved. Survey of HOUs in June 2009: response rate 59% (25 of 42 HOUs), with 11 of 25 respondents utilised the committee. Of those 14 of 25 who had not utilised the committee, low awareness of the committee's existence (2 respondents). Most elements of the best-practice model for engaging medical staff were achieved. Recommendations include improvements to committee process and raising profile with medical staff. DISCUSSION: This study demonstrates an effective and successful clinical governance process for introducing new technologies and clinical practice into a major tertiary teaching hospital, supported by moderate levels of medical staff engagement.