Pulsation waves along the Ciona heart tube reverse by bimodal rhythms expressed by a remote pair of pacemakers.

The heart of ascidians (marine invertebrate chordates) has a tubular structure, and heartbeats propagate from one end to the other. The direction of pulsation waves intermittently reverses in the heart of ascidians and their relatives; however, the underlying mechanisms remain unclear. We herein performed a series of experiments to characterize the pacemaker systems in isolated hearts and their fragments, and applied a mathematical model to examine the conditions leading to heart reversals. The isolated heart of Ciona robusta autonomously generated pulsation waves at ∼20 to 25 beats min-1 with reversals at ∼1 to 10 min intervals. Experimental bisections of isolated hearts revealed that independent pacemakers resided on each side and also that their beating frequencies periodically changed as they expressed bimodal rhythms, which comprised an ∼1.25 to 5.5 min acceleration/deceleration cycle of a beating rate of between 0 and 25 beats min-1. Only fragments including 5% or shorter terminal regions of the heart tube maintained autonomous pulsation rhythms, whereas other regions did not. Our mathematical model, based on FitzHugh-Nagumo equations applied to a one-dimensional alignment of cells, demonstrated that the difference between frequencies expressed by the two independent terminal pacemakers determined the direction of propagated waves. Changes in the statuses of terminal pacemakers between the excitatory and oscillatory modes as well as in their endogenous oscillation frequencies were sufficient to lead to heart reversals. These results suggest that the directions of pulsation waves in the Ciona heart reverse according to the changing rhythms independently expressed by remotely coupled terminal pacemakers.

An auxin signaling network translates low-sugar-state input into compensated cell enlargement in the fugu5 cotyledon.

In plants, the effective mobilization of seed nutrient reserves is crucial during germination and for seedling establishment. The Arabidopsis H+-PPase-loss-of-function fugu5 mutants exhibit a reduced number of cells in the cotyledons. This leads to enhanced post-mitotic cell expansion, also known as compensated cell enlargement (CCE). While decreased cell numbers have been ascribed to reduced gluconeogenesis from triacylglycerol, the molecular mechanisms underlying CCE remain ill-known. Given the role of indole 3-butyric acid (IBA) in cotyledon development, and because CCE in fugu5 is specifically and completely cancelled by ech2, which shows defective IBA-to-indoleacetic acid (IAA) conversion, IBA has emerged as a potential regulator of CCE. Here, to further illuminate the regulatory role of IBA in CCE, we used a series of high-order mutants that harbored a specific defect in IBA-to-IAA conversion, IBA efflux, IAA signaling, or vacuolar type H+-ATPase (V-ATPase) activity and analyzed the genetic interaction with fugu5-1. We found that while CCE in fugu5 was promoted by IBA, defects in IBA-to-IAA conversion, IAA response, or the V-ATPase activity alone cancelled CCE. Consistently, endogenous IAA in fugu5 reached a level 2.2-fold higher than the WT in 1-week-old seedlings. Finally, the above findings were validated in icl-2, mls-2, pck1-2 and ibr10 mutants, in which CCE was triggered by low sugar contents. This provides a scenario in which following seed germination, the low-sugar-state triggers IAA synthesis, leading to CCE through the activation of the V-ATPase. These findings illustrate how fine-tuning cell and organ size regulation depend on interplays between metabolism and IAA levels in plants.

[Multimodal therapy improved carcinoid syndrome secondary to liver metastases of an atypical lung carcinoid tumor:a case report].

A 69-year-old male presented for an annual medical examination, and his chest X-ray showed an abnormal shadow. He presented to our hospital, and was diagnosed with typical carcinoid tumor of the lung by bronchoscopy. We recommended surgery, however the patient did not agree to the operation. One year later, two masses were detected in the liver. Ultrasound guided biopsy revealed that they were metastases from the atypical carcinoid tumor of the lung. We recommended chemotherapy, but he refused. Six months later, he was admitted to our hospital for symptoms of flushing, fever, watery diarrhea, and palpitations. We diagnosed this combination of symptoms as carcinoid syndrome, and started the administration of a long acting release (LAR) octreotide. The patient's symptoms improved, but did not resolve completely. We then performed a hepatic artery embolization for the liver metastases, and the symptoms resolved. However, viable lesions of the liver metastases slowly grew and caused a carcinoid crisis. By increasing the dosage of octreotide up to a continuous intravenous infusion of 1500µg/day, as well as LAR 30mg/4weeks, the patient recovered from the crisis. Hepatic artery embolization was performed shortly afterward. Because it was difficult to control the carcinoid syndrome by hepatic artery embolization alone, he underwent a resection of the liver metastases. After the hepatic resection, he has had no recurrence of carcinoid syndrome while still being treated with octreotide LAR.

Efficacy of 6-mm diameter fully covered self-expandable metallic stents in preoperative biliary drainage for pancreatic ductal adenocarcinoma.

Objectives: Plastic stents (PS) used for preoperative biliary drainage (PBD) of pancreatic ductal adenocarcinomas (PDAC) tend to be associated with a high incidence of recurrent biliary obstruction (RBO). Although 10-mm diameter fully covered self-expanding metallic stents (FCSEMS) have come into use, vigilance is still required to prevent complications, such as cholecystitis and surgical site infection. The present study examined the efficacy and safety of the 6-mm diameter FCSEMS for PBD. Methods: The present retrospective study compared the incidence of complications associated with the use of 6-mm FCSEMS and PS. The inclusion criteria were a diagnosis of PDAC and preoperative endoscopic biliary tract drainage performed at our institution between April 2012 and June 2019. Results: Of the 51 patients enrolled, 25 and 26 patients received a PS and a 6-mm FCSEMS, respectively. The RBO incidence was significantly lower in the 6-mm FCSEMS group (7.7%) than in the PS group (40.0%) (p = 0.009), and time to RBO was significantly longer in the 6-mm FCSEMS group (HR = 6.008, p = 0.021). The patency rate at three months after stent placement was significantly higher in the latter group (83.5% vs. 45.3%, p = 0.009, Log-rank test). The groups did not differ significantly in terms of complications associated with PBD, such as cholecystitis and surgical site infection. Conclusion: The present findings suggested that the 6-mm FCSEMS may be an effective drainage device for use in PBD in PDAC treatment.