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Background and Purpose: Environmental factors are important with respect to the rupture of cerebral aneurysms. However, the relationship between the gut microbiome, an environmental factor, and aneurysm rupture is unclear. Therefore, we compared the gut microbiome in patients with unruptured intracranial aneurysms (UIAs) and ruptured aneurysms (RAs) to identify the specific bacteria causing the rupture of cerebral aneurysms. Methods: A multicenter, prospective case-control study was conducted over one year from 2019 to 2020. The fecal samples of patients with stable UIAs and RAs immediately after onset were collected. Their gut microbiomes were analyzed using 16S rRNA sequencing. Subsequently, a phylogenetic tree was constructed, and polymerase chain reaction was performed to identify the specific species. Results: A total of 28 RAs and 33 UIAs were included in this study. There was no difference in patient characteristics between RAs and UIAs: age, sex, hypertension, dyslipidemia, diabetes status, body mass index, and smoking. No difference was observed in alpha diversity; however, beta diversity was significantly different in the unweighted UniFrac distances. At the phylum level, the relative abundance of Campylobacter in the RA group was larger than that in the UIA group. Furthermore, the gut microbiome in the RA and UIA groups exhibited significantly different taxonomies. However, Campylobacter was focused on because it is widely known as pathogenic among these bacteria. Then, a phylogenetic tree of operational taxonomic units related to Campylobacter was constructed and 4 species were identified. Polymerase chain reaction for these species identified that the abundance of the genus Campylobacter and Campylobacter ureolyticus was significantly higher in the RA group. Conclusions: The gut microbiome profile of patients with stable UIAs and RAs were significantly different. The genus Campylobacter and Campylobacter ureolyticus may be associated with the rupture of cerebral aneurysms.

We report on an extremely rare case of a giant solitary fibrous tumor (SFT) of the mesentery in a 65-year-old male who was admitted to our hospital because of lower abdominal pain and abdominal fullness. Computed tomography demonstrated a well-defined solid mass of 25 × 11 cm located in the lower abdomen, which was completely resected during surgery. Histopathologically, this lesion had a heterogeneous cell population, mainly comprising spindle cells with fibrous collagen proliferation, and various other cell populations exhibiting patternless growth. Immunohistochemically, the tumor revealed strong and diffuse staining for CD34, bcl-2, and vimentin, and a high mitotic index (seven mitoses per 10 high-power fields). We diagnosed this case as an SFT of the mesentery, which is unusual according to a PubMed search that reported only nine such cases. Our case may be the largest tumor reported to date, and only one retrieved case reported recurrence, although the lesion was exceptionally large with deep invasion. Nonetheless, the lesion in our case was larger than that in the reported case of recurrence and invasive to the ileum. Since surgery, there has been no evidence of recurrence. Hence, we propose that a large SFT and high mitotic index may present risk factors for recurrence. Therefore, long-term careful follow-up is necessary in such cases, although our case exhibited few risk factors for recurrence. A follow-up at 12 months after surgery found no indications of recurrence.

In order to study the reaction mechanism of RNase Rh from Rhizopus niveus, the rates of cleavage of four 2',3'-cyclic nucleotides by mutant enzymes of RNase Rh, H46F, H109F, E105Q, and K108L were measured. H46F is virtually inactive towards cyclic nucleotides, but H109F hydrolyzed these substrates at 0.7-4.5% of the rates of the native RNase Rh. The other mutants hydrolyzed 2',3'-cyclic nucleotides at 15-20% of the rates of the native enzyme. Relative enzymatic activities towards four cyclic nucleotides of H109F in the hydrolysis reaction (2nd step) were much higher than in the transphosphorylation reaction (the 1st step). In the presence of a 13-fold excess of uridine, H109F catalyzed the transphosphorylation reaction of 2',3'-cyclic AMP (A>p) to ApU. However, this reaction was not catalyzed by H46F mutant or native RNase Rh. These results showed that His46 is crucial to the hydrolysis reaction, and to the reversed reaction of the transphosphorylation reaction. We suggest that His46 in RNase Rh plays a major role in these reactions by acting as a base catalyst to activate water and the 5'-hydroxyl group of nucleosides, respectively.

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