A 51-year-old man with a history of an abdominoperineal resection of the rectum and colostomy for rectal cancer underwent chemotherapy for multiple liver metastases.Twenty -two courses of the folinic acid, 5-fluorouracil(5-FU)and oxaliplatin(FOLFOX4)/bevacizumab(BEV)regimen and 39 courses of 5-FU/Leucovorin/BEV were administered.Progressive splenomegaly and stomal varices were observed during the course of chemotherapy.The patient was admitted due to excessive bleeding after colostomy.Angiography revealed bleeding stomal varices secondary to portal hypertension.Splenectomy was performed with subsequent reduction in the size of the stomal varices and no rebleeding was observed.Oxaliplatin -based chemotherapy could lead to hepatic sinusoidal dilation and induce splenomegaly and varix formation secondary to portal hypertension.Our experience with this case suggests that careful attention should be paid to stomal varices in colostomy patients receiving oxaliplatin-based chemotherapy.
A 33-year-old man was transported to our hospital following a traffic accident. He was found to have hemopneumothorax, multiple rib fractures and lung injury by computed tomography(CT). Despite thoracic drainage and fluid resuscitation, he became hemodynamically unstable. At 2 hours after arrival, CT revealed worsening in hemothorax. Emergency angiography of intercostal arteries showed signs ofhemorrhage from intercostal arteries, and embolization of the 3?6th intercostal arteries was performed. After transcatheter arterial embolization(TAE), his vital signs got stable and he was discharged without significant complication.
The early endosome acts as a sorting station for internalized molecules destined for recycling or degradation. While recycled molecules are sorted and delivered to tubular endosomes, residual compartments containing molecules to be degraded undergo "maturation" before final degradation in the lysosome. This maturation involves acidification, microtubule-dependent motility, and perinuclear localization. It is currently unknown how sorting and the processes of maturation cooperate with each other. Here, we show that fission of a tubular endosome triggers the maturation of the residual endosome, leading to degradation. Use of the dynamin inhibitor dynasore to block tubular endosome fission inhibited acidification, endosomal motility along microtubules, perinuclear localization, and degradation. However, tubular endosome fission was not affected by inhibiting endosomal acidification or by depolymerizing the microtubules. These results demonstrate that the fission of recycling tubules is the first important step in endosomal maturation and degradation in the lysosome. We believe this to be the first evidence of a cascade from sorting to degradation.
Early endosomes (EEs) are known to be a sorting station for internalized molecules destined for degradation, recycling, or other intracellular organelles. Segregation is an essential step in such sorting, but the molecular mechanism of this process remains to be elucidated. Here, we show that actin is required for efficient recycling and endosomal maturation by producing a motile force. Perturbation of actin dynamics by drugs induced a few enlarged EEs containing several degradative vacuoles and also interfered with their transporting ability. Actin repolymerization induced by washout of the drug caused the vacuoles to dissociate and individually translocate toward the perinuclear region. We further elucidated that cortactin, an actin-nucleating factor, was required for transporting contents from within EEs. Actin filaments regulated by cortactin may provide a motile force for efficient sorting within early endosomes. These data suggest that actin filaments coordinate with microtubules to mediate segregation in EEs.
The GTPase dynamin, a key player in endocytic membrane fission, interacts with numerous proteins that regulate actin dynamics and generate/sense membrane curvature. To determine the functional relationship between these proteins and dynamin, we have analyzed endocytic intermediates that accumulate in cells that lack dynamin (derived from dynamin 1 and 2 double conditional knockout mice). In these cells, actin-nucleating proteins, actin, and BAR domain proteins accumulate at the base of arrested endocytic clathrin-coated pits, where they support the growth of dynamic long tubular necks. These results, which we show reflect the sequence of events in wild-type cells, demonstrate a concerted action of these proteins prior to, and independent of, dynamin and emphasize similarities between clathrin-mediated endocytosis in yeast and higher eukaryotes. Our data also demonstrate that the relationship between dynamin and actin is intimately connected to dynamins endocytic role and that dynamin terminates a powerful actin- and BAR protein-dependent tubulating activity.
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