Heterogametic sex chromosomes have evolved independently in various lineages of vertebrates. Such sex chromosome pairs often contain nonrecombining regions, with one of the chromosomes harboring a master sex-determining (SD) gene. It is hypothesized that these sex chromosomes evolved from a pair of autosomes that diverged after acquiring the SD gene. By linkage and association mapping of the SD locus in fugu (Takifugu rubripes), we show that a SNP (C/G) in the anti-Müllerian hormone receptor type II (Amhr2) gene is the only polymorphism associated with phenotypic sex. This SNP changes an amino acid (His/Asp384) in the kinase domain. While females are homozygous (His/His384), males are heterozygous. Sex in fugu is most likely determined by a combination of the two alleles of Amhr2. Consistent with this model, the medaka hotei mutant carrying a substitution in the kinase domain of Amhr2 causes a female phenotype. The association of the Amhr2 SNP with phenotypic sex is conserved in two other species of Takifugu but not in Tetraodon. The fugu SD locus shows no sign of recombination suppression between X and Y chromosomes. Thus, fugu sex chromosomes represent an unusual example of proto–sex chromosomes. Such undifferentiated X-Y chromosomes may be more common in vertebrates than previously thought.

Background and study aim This study aimed to assess the safety and feasibility of endoscopic submucosal dissection (ESD) using a scissors‐type knife with prophylactic closure using over‐the‐scope clip (OTSC) for superficial non‐ampullary duodenal epithelial tumors (SNADETs). Patients and methods Consecutive patients who underwent ESD for SNADETs >10 mm between January 2009 and July 2019 were retrospectively enrolled. We performed ESD using either a needle‐type knife (Flush Knife‐ESD) or a scissors‐type knife (Clutch Cutter‐ESD). Mucosal defects were prophylactically closed using three methods: conventional clip, laparoscopic closure, or OTSC. Results A total of 84 lesions were resected using the Flush Knife‐ESD and the Clutch Cutter‐ESD (37 and 47 patients, respectively), and conventional clip, laparoscopic closure, and OTSC for mucosal defect closure after ESD were applied in 13, 13, and 56 lesions, respectively. The R0 resection rate was significantly higher in the Clutch Cutter‐ESD than that in the Flush Knife‐ESD (97.9% vs 83.8%, respectively, P = 0.040). The intraoperative perforation rate was significantly lower in the Clutch Cutter‐ESD than in the Flush Knife‐ESD (0% vs 13.5%, respectively, P = 0.014). Complete closure rates of conventional clip, laparoscopic closure, and OTSC were 76.9%, 92.3%, and 98.2%, respectively (P = 0.021); and delayed perforation rates were 15.4%, 7.7%, and 1.8%, respectively (P = 0.092). Conclusions Endoscopic submucosal dissection using a scissors‐type knife with prophylactic OTSC closure is safe and feasible for the low‐invasive treatment of SNADETs.

Highlights d A trans-species SNP in a steroidogenic Hsd17b1 determines sex in genus Seriola d The Z-linked allele of HSD17B1 attenuates E1 to E2 conversion activity d The data support a long-standing hypothesis on steroidinduced sex determination

The tiger pufferfish (fugu), Takifugu rubripes, is a model fish that has had its genome entirely sequenced. By performing genomewide linkage analyses, we show that the sex of fugu is determined by a single chromosomal region on linkage group 19 in an XX-XY system.

Endoscopic diagnosis of Helicobacter pylori (H. pylori) infection, the most common cause of gastric cancer, is very important to clarify high-risk patients of gastric cancer for reducing morbidity and mortality of gastric cancer. Recently, the Kyoto classification of gastritis was developed based on the endoscopic characteristics of H. pylori infection-associated gastritis for clarifying H. pylori infection status and evaluating risk factors of gastric cancer. Recently, magnifying endoscopy with narrow-band imaging (NBI) has reported benefits of the accuracy and reproducibility of endoscopic diagnosis for H. pylori-related premalignant lesions. In addition to NBI, various types of image-enhanced endoscopies (IEEs) are available including autofluorescence imaging, blue laser imaging, and linked color imaging. This review focuses on understanding the clinical applications and the corresponding evidences shown to improve the diagnosis of gastritis based on Kyoto classification using currently available advanced technologies of IEEs.

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A molecular phylogenetic analysis of luxA gene sequences of light organ symbionts of the fish Acropoma japonicum (Acropomatidae) and Siphamia versicolor (Apogonidae) revealed that the sequences were related to those of Photobacterium leiognathi ssp. mandapamensis, which is not known to occur as a light organ symbiont among bioluminescent P. leiognathi clades. The presence of another lux gene element, luxF, coding for nonfluorescent protein, provided additional support for the identity of the light organ symbionts of the fish. Cladogenesis of the light organ symbiont P. leiognathi may be influenced by the radiation of host fishes.

<b><i>Background/Aims:</i></b> The purpose of this study was to evaluate the safety and efficacy of gastric endoscopic submucosal dissection (ESD) using the Clutch Cutter (CC), a scissor-type knife, compared with those of procedures using conventional devices. <b><i>Methods:</i></b> This single-center retrospective study evaluated 237 patients with early gastric cancer: 83 who underwent ESD using the CC group and 154 who underwent ESD using the insulated-tip knife 2 (IT2 group). Clinicopathological features and technical outcomes were compared between the 2 groups using a propensity score-matched analysis. <b><i>Results:</i></b> In 61 pairs of matched patients, there was no significant difference in R0 resection, perforation, or postoperative bleeding between the CC and IT2 groups. Comparisons between the 2 groups showed similar treatment outcomes for an expert endoscopist. Nevertheless, there were significant differences between the 2 groups for nonexperts in terms of self-completion (61.7 and 24.5%, respectively, <i>p</i> &#x3c; 0.001), mean procedure times (45 and 61 min, respectively, <i>p</i> = 0.002), and mean numbers of intraoperative bleeding points and bleeding points requiring hemostatic forceps (3 and 0 vs. 8 and 3, respectively, <i>p</i> &#x3c; 0.001). <b><i>Conclusion:</i></b> Better self-completion rates and shorter procedure times were noted for gastric ESD using the CC by nonexperts than for that using IT2, probably due to hemostatic efficacy.