Andrew S. Nett

Comparison of dot chromosome sequences from D. melanogaster and D. virilis reveals an enrichment of DNA transposon sequences in heterochromatic domains

BackgroundChromosome four of Drosophila melanogaster, known as the dot chromosome, is largely heterochromatic, as shown by immunofluorescent staining with antibodies to heterochromatin protein 1 (HP1) and histone H3K9me. In contrast, the absence of HP1 and H3K9me from the dot chromosome in D. virilis suggests that this region is euchromatic. D. virilis diverged from D. melanogaster 40 to 60 million years ago.ResultsHere we describe finished sequencing and analysis of 11 fosmids hybridizing to the dot chromosome of D. virilis (372,650 base-pairs) and seven fosmids from major euchromatic chromosome arms (273,110 base-pairs). Most genes from the dot chromosome of D. melanogaster remain on the dot chromosome in D. virilis, but many inversions have occurred. The dot chromosomes of both species are similar to the major chromosome arms in gene density and coding density, but the dot chromosome genes of both species have larger introns. The D. virilis dot chromosome fosmids have a high repeat density (22.8%), similar to homologous regions of D. melanogaster (26.5%). There are, however, major differences in the representation of repetitive elements. Remnants of DNA transposons make up only 6.3% of the D. virilis dot chromosome fosmids, but 18.4% of the homologous regions from D. melanogaster; DINE-1 and 1360 elements are particularly enriched in D. melanogaster. Euchromatic domains on the major chromosomes in both species have very few DNA transposons (less than 0.4 %).ConclusionCombining these results with recent findings about RNAi, we suggest that specific repetitive elements, as well as density, play a role in determining higher-order chromatin packaging.

Quality Bowel Preparation for Surveillance Colonoscopy in Patients with Inflammatory Bowel Disease Is a Must

Colonoscopy is routinely performed in patients with inflammatory bowel disease (IBD) for surveillance of dysplasia. Thorough bowel preparation is necessary to facilitate lesion detection. Patients with IBD do not have poorer bowel preparation outcomes but may have decreased preparation tolerance affecting adherence to surveillance protocols. A low-fiber prepreparation diet may improve preparation tolerance without affecting preparation quality. The standard preparation regimen should consist of split-dose administration of a polyethylene glycol-based purgative. Low-volume, hyperosmolar purgatives may be considered in patients with previous preparation intolerance, heightened anxiety, stenotic disease, or dysmotility. Appropriate patient education is critical to enhance preparation quality.

Pancreatic Fluid Collections and Leaks

Abstract Pancreatic fluid collections (PFCs) and leaks develop due to main or secondary pancreatic ductal disruption caused by acute or chronic pancreatitis, trauma, or pancreatic surgery. PFCs include acute fluid collections, acute necrotic collections, pseudocysts, and walled-off necrosis. Most nonnecrotic PFCs resolve spontaneously without need for drainage. Fluid collections that have become infected, or those that cause persistent symptoms, warrant drainage. Drainage of PFCs has historically been performed by open surgical approaches, but less invasive interventions have displaced open surgery over time. Whereas appropriate management of PFCs entails a multidisciplinary approach involving interventional endoscopy, interventional radiology, and minimally invasive surgery, endoscopic therapy of PFCs and pancreatic leaks has become a predominant initial therapeutic modality.

Multicenter evaluation of the clinical utility of laparoscopy-assisted ERCP in patients with Roux-en-Y gastric bypass

BACKGROUND AND AIMS The obesity epidemic has led to increased use of Roux-en-Y gastric bypass (RYGB). These patients have an increased incidence of pancreaticobiliary diseases, yet standard ERCP is not possible because of surgically altered gastroduodenal anatomy. Laparoscopy-assisted ERCP (LA-ERCP) has been proposed as an option, but supporting data are derived from single-center small case series. Therefore, we conducted a large multicenter study to evaluate the feasibility, safety, and outcomes of LA-ERCP. METHODS This is a retrospective cohort study of adult patients with RYGB who underwent LA-ERCP in 34 centers. Data on demographics, indications, procedure success, and adverse events were collected. Procedure success was defined when all the following were achieved: reaching the papilla, cannulating the desired duct, and providing endoscopic therapy as clinically indicated. RESULTS A total of 579 patients (median age, 51; 84% women) were included. Indication for LA-ERCP was biliary in 89%, pancreatic in 8%, and both in 3%. Procedure success was achieved in 98%. Median total procedure time was 152 minutes (interquartile range [IQR], 109-210), with a median ERCP time of 40 minutes (IQR, 28-56). Median hospital stay was 2 days (IQR, 1-3). Adverse events were 18% (laparoscopy related, 10%; ERCP related, 7%; both, 1%) with the clear majority (92%) classified as mild/moderate, whereas 8% were severe and 1 death occurred. CONCLUSIONS Our large multicenter study indicates that LA-ERCP in patients with RYGB is feasible with a high procedure success rate comparable with that of standard ERCP in patients with normal anatomy. The ERCP-related adverse events rate is comparable with conventional ERCP, but the overall adverse event rate was higher because of the added laparoscopy-related events.