Pelvic mucocele following colostomy: CT and ultrasound findings

Up-regulation of voltage-gated sodium channels by peptides mimicking S4-S5 linkers reveals a variation of the ligand-receptor mechanism

Prokaryotic Na_V channels are tetramers and eukaryotic Na_V channels consist of a single subunit containing four domains. Each monomer/domain contains six transmembrane segments (S1-S6), S1-S4 being the voltage-sensor domain and S5-S6 the pore domain. A crystal structure of Na_VMs, a prokaryotic Na_V channel, suggests that the S4-S5 linker (S4-S5_L) interacts with the C-terminus of S6 (S6_T) to stabilize the gate in the open state. However, in several voltage-gated potassium channels, using specific S4-S5_L-mimicking peptides, we previously demonstrated that S4-S5_L/S6_T interaction stabilizes the gate in the closed state. Here, we used the same strategy on another prokaryotic Na_V channel, Na_VSp1, to test whether equivalent peptides stabilize the channel in the open or closed state. A Na_VSp1-specific S4-S5_L peptide, containing the residues supposed to interact with S6_T according to the Na_VMs structure, induced both an increase in Na_VSp1 current density and a negative shift in the activation curve, consistent with S4-S5_L stabilizing the open state. Using this approach on a human Na_V channel, hNa_V1.4, and testing 12 hNa_V1.4 S4-S5_L peptides, we identified four activating S4-S5_L peptides. These results suggest that, in eukaryotic Na_V channels, the S4-S5_L of DI, DII and DIII domains allosterically modulate the activation gate and stabilize its open state.

Carcinoembryonic antigen elevation due to bowel sequestration with mucocele formation following colonic resection

Carcinoembryonic antigen (CEA) is recommended as a serologic marker to monitor colorectal carcinoma recurrence. Elevations of CEA due to causes other than carcinoma exist and may lead to a misdiagnosis of recurrent carcinoma. We report a case of bowel sequestration with mucocele formation at the site of previous colo-colic anastomosis causing a mild elevation in CEA. The patient exhibited increasing CEA levels 6 years after resection of a sigmoid colon carcinoma with end-to-end anastomosis. Subsequently, computed tomographic and positron emission tomographic scans documented the presence of a cystic mass showing increased uptake at the anastomotic site. At exploratory laparotomy a mass lesion with mucus-filled protrusions was resected. Pathologic examination documented the presence of sequestration of a segment of the bowel wall with a mucocele and no overlying defect at the mucosal anastomotic site by demonstrating the presence of all bowel layers. After resection of the lesion, the CEA level normalized.