The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have greater transposon density (25–50%) than euchromatic reference regions (3–11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% vs. 11–27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density and types of transposons affect the degree of local heterochromatin formation. F element genes have lower estimated DNA melting temperatures than D element genes, potentially facilitating transcription through heterochromatin. Most F element genes (~90%) have remained on that element, but the F element has smaller syntenic blocks than genome averages (3.4–3.6 vs. 8.4–8.8 genes per block), indicating greater rates of inversion despite lower rates of recombination. Overall, the F element has maintained characteristics that are distinct from other autosomes in the Drosophila lineage, illuminating the constraints imposed by a heterochromatic milieu.

Background & Aims Barrett’s esophagus (BE) with low-grade dysplasia (LGD) can progress to high-grade dysplasia (HGD) and esophageal adenocarcinoma (EAC). Radiofrequency ablation (RFA) has been shown to be an effective treatment for LGD in clinical trials but its effectiveness in clinical practice is unclear. We compared the rate of progression of LGD following RFA to that with endoscopic surveillance alone in routine clinical practice. Methods We performed a retrospective study of patients who either underwent RFA (n=45) or surveillance endoscopy (n=125) for LGD, confirmed by at least 1 expert pathologist, from October 1992 through December 2013 at 3 medical centers in the US. Cox regression analysis was used to assess the association between progression and RFA. Results Data were collected over median follow-up periods of 889 days (inter-quartile range, 264–1623 days) after RFA and 848 days (inter-quartile range, 322–2355 days) after surveillance endoscopy (P=.32). The annual rates of progression to HGD or EAC was 6.6% in the surveillance group and 0.77% in the RFA group. The risk of progression to HGD or EAC was significantly lower among patients who underwent RFA than those who underwent surveillance (adjusted hazard ratio, 0.06; 95% confidence interval, 0.008–0.48). Conclusions Among patients with BE and confirmed LGD, rates of progression to a combined endpoint of HGD and EAC were lower among those treated with RFA than among untreated patients. Although selection bias cannot be excluded, these findings provide additional evidence for the use of endoscopic ablation therapy for LGD.

Background and study aims Per-oral endoscopic myotomy (POEM) is associated with a short-term clinical response of 82 % to 100 % in treatment of patients with achalasia. Data are limited on the long-term durability of the clinical response in these patients. The aim of this study was to determine the long-term outcomes of patients undergoing POEM for management of achalasia. Methods This was a retrospective multicenter cohort study of consecutive patients who underwent POEM for management of achalasia. Patients had a minimum of 4 years follow-up. Clinical response was defined by an Eckardt score ≤ 3. Results A total of 146 patients were included from 11 academic medical centers. Mean (± SD) age was 49.8 (± 16) years and 79 (54 %) were female. The most common type of achalasia was type II, seen in 70 (47.9 %) patients, followed by type I seen in 41 (28.1 %) patients. Prior treatments included: pneumatic dilation in 29 (19.9 %), botulinum toxin injection in 13 (8.9 %) and Heller myotomy in seven patients (4.8 %). Eight adverse events occurred (6 mucosotomies, 2 pneumothorax) in eight patients (5.5 %). Median follow-up duration was 55 months (IQR 49.9–60.6). Clinical response was observed in 139 (95.2 %) patients at follow-up of ≥ 48 months. Symptomatic reflux after POEM was seen in 45 (32.1 %) patients, while 35.3 % of patients were using daily PPI at 48 months post POEM. Reflux esophagitis was noted in 16.8 % of patients who underwent endoscopy. Conclusion POEM is a durable and safe procedure with an acceptably low adverse event rate and an excellent long-term clinical response.

Background & Aims Esophageal anastomotic strictures often require repeat dilation to relieve dysphagia. Little is known about factors that affect their remediation. We investigated long-term success and rates of recurrence or refractoriness following dilation, and factors associated with refractory stenosis. Methods We performed a retrospective study of 74 patients with an anastomotic stricture that had been dilated over a 5-year period (564 dilations; median follow-up period, 8 months). A stricture was refractory if luminal patency could not be maintained after ≥5 dilation sessions over 10 weeks. Results Of the 74 patients, 93% had initial relief of dysphagia. The stricture recurred in 43% of patients, and 69% were considered refractory. Removal of sutures/staples protruding into the lumen did not accelerate time to initial patency (median 37 days; interquartile range [IQR], 20–82 days) or lengthen the dysphagia-free interval (37.4 days; IQR 8–41 weeks), compared to patients who did not undergo removal (initial patency, median 55 days; IQR, 14–109 days; P=.66 and median dysphagia-free interval, 21.7 days; IQR, 9–64 weeks; P=.8). Use of fluoroscopy during dilation (odds ratio=8.92; 95% confidence interval, 1.98–40.14) was positively associated with development of refractory strictures, whereas neoadjuvant chemotherapy (odds ratio=0.28; 95% confidence interval, 0.07–0.97) was inversely associated. Female sex and distal location of strictures increased risk of refractoriness as effect modifiers in multivariate analysis. Conclusions Endoscopic dilation is highly successful in achieving luminal remediation, yet anastomotic strictures are often refractory and frequently recur. Removal of sutures/staples within the lumen does not help achieve patency. Need for fluoroscopic guidance indicates a high likelihood of refractoriness to dilation, whereas prior neoadjuvant chemotherapy indicates a lower risk.

Background Radiation therapy for head, neck, and esophageal cancer can result in esophageal strictures that may be difficult to manage. Radiation-induced esophageal strictures often require repeat dilation to obtain relief of dysphagia. This study aimed to determine the long-term clinical success and rates of recurrent and refractory stenosis in patients with radiation-induced strictures undergoing dilation. Methods Retrospective cohort study of patients with radiation-induced strictures who underwent endoscopic dilation by a single provider from October 2007– October 2012. Outcomes measured included long-term clinical efficacy, interval between sessions, number of dilations, and proportion of radiation strictures that were recurrent or refractory. Risk factors for refractory strictures were assessed. Results 63 patients underwent 303 dilations. All presented with a stricture > 30 days after last radiation session. Clinical success to target diameter was achieved in 52 patients (83%). A mean of 3.3 (+/− 2.6) dilations over a median period of 4 weeks was needed to achieve initial patency. Recurrence occurred in 17 (33%) at a median of 22 weeks. Twenty-seven strictures (43%) were refractory to dilation therapy. Fluoroscopy during dilation (OR, 22.88; 95% CI, 3.19 – 164.07), severe esophageal stenosis (lumen <9 mm) (OR, 10.51; 95% CI, 1.94 – 56.88), and proximal location with prior malignancy extrinsic to the lumen (OR, 6.96; 95% CI, 1.33 – 36.29) were independent predictors of refractory strictures in multivariate analysis. Conclusions 1. Radiation-induced strictures have a delayed onset (>30 days) from time of radiation injury. 2. Endoscopic dilation can achieve medium-term luminal remediation but the strictures have a high long-term recurrence rate of up to 33%. 3. Remediation of radiation strictures following laryngectomy can be achieved but require frequent dilations. 4. Clinical and procedural predictors may identify patients at high risk of refractory strictures. 5. The optimal strategy in highly selected refractory patients is not clear.