TGF-β receptor kinase inhibitor enhances growth and integrity of embryonic stem cell–derived endothelial cells

Recent findings have shown that embryonic vascular progenitor cells are capable of differentiating into mural and endothelial cells. However, the molecular mechanisms that regulate their differentiation, proliferation, and endothelial sheet formation remain to be elucidated. Here, we show that members of the transforming growth factor (TGF)-β superfamily play important roles during differentiation of vascular progenitor cells derived from mouse embryonic stem cells (ESCs) and from 8.5–days postcoitum embryos. TGF-β and activin inhibited proliferation and sheet formation of endothelial cells. Interestingly, SB-431542, a synthetic molecule that inhibits the kinases of receptors for TGF-β and activin, facilitated proliferation and sheet formation of ESC-derived endothelial cells. Moreover, SB-431542 up-regulated the expression of claudin-5, an endothelial specific component of tight junctions. These results suggest that endogenous TGF-β/activin signals play important roles in regulating vascular growth and permeability

Ras signaling directs endothelial specification of VEGFR2+ vascular progenitor cells

Vascular endothelial growth factor receptor 2 (VEGFR2) transmits signals of crucial importance to vasculogenesis, including proliferation, migration, and differentiation of vascular progenitor cells. Embryonic stem cell–derived VEGFR2+ mesodermal cells differentiate into mural lineage in the presence of platelet derived growth factor (PDGF)–BB or serum but into endothelial lineage in response to VEGF-A. We found that inhibition of H-Ras function by a farnesyltransferase inhibitor or a knockdown technique results in selective suppression of VEGF-A–induced endothelial specification. Experiments with ex vivo whole-embryo culture as well as analysis of H-ras−/− mice also supported this conclusion. Furthermore, expression of a constitutively active H-Ras[G12V] in VEGFR2+ progenitor cells resulted in endothelial differentiation through the extracellular signal-related kinase (Erk) pathway. Both VEGF-A and PDGF-BB activated Ras in VEGFR2+ progenitor cells 5 min after treatment. However, VEGF-A, but not PDGF-BB, activated Ras 6–9 h after treatment, preceding the induction of endothelial markers. VEGF-A thus activates temporally distinct Ras–Erk signaling to direct endothelial specification of VEGFR2+ vascular progenitor cells

Early Gastric Cancer Presenting Pyloric or Prepyloric Stenosis

Out of 390 patients with early gastric cancer (EGC) who underwent gastric resection between Jan. 1968 and Jul. 1987, four patients developed pyloric stenosis and one patient developed prepyloric stenosis. Macroscopic types of EGC were II c in three cases and II c + III in two cases. Histologic types were tubular adenocarcinoma in four patients, and poorly differentiated adenocarcinoma in one patient. Cancer existed just right on or immediately adjacent to the pyloric ring in all patients; and extended transversely to the gastric axis in four patients, and longitudinally in one patient. An associated open ulcer and/or ulcer scar in the cancer lesion was seen in four patients, and submucosal fibrosis in three patients to a variety of degree, both of which were thought to be greatly attributed to pyloric or prepyloric stenosis. A duodenal ulcer was not present in any patients

Underground behavior of overwintering Tokyo daruma pond frogs in early spring

Although Tokyo daruma pond frogs (Pelophylax porosus porosus) were once commonly observed throughout paddy fields in Japan, their populations have recently declined. The mode by which frogs survive during the overwintering period is largely unknown. In this study, we observed the underground behavior of 12 free-living Tokyo daruma pond frogs that overwintered in paddy soil and a dry field by periodically excavating their overwintering positions from late March to early May. The mean overwintering depth of these frogs was similar to 19.8 cm, with 10 having migrated toward the soil surface (mean depth: similar to 8.6 cm) by late March, and finally, all 11 live frogs migrated further upward close to the soil surface. In addition, males tended to emerge earlier in spring than females. One monitored frog in the paddy soil that migrated close to the soil surface died, presumably from plowing. Aside from the 12 study frogs, several other mutilated frog corpses were found in the paddies. This species starts migrating to the soil surface during the same period when human disturbances begin, making the frogs vulnerable to these disturbances during this period. Consequently, it is necessary to facilitate the emergence of frogs to protect them from human disturbances-e.g., by temporarily filling fields with water

Interaction with Smad4 Is Indispensable for Suppression of BMP Signaling by c-Ski

c-Ski is a transcriptional corepressor that interacts strongly with Smad2, Smad3, and Smad4 but only weakly with Smad1 and Smad5. Through binding to Smad proteins, c-Ski suppresses signaling of transforming growth factor-β (TGF-β) as well as bone morphogenetic proteins (BMPs). In the present study, we found that a mutant of c-Ski, termed c-Ski (ARPG) inhibited TGF-β/activin signaling but not BMP signaling. Selectivity was confirmed in luciferase reporter assays and by determination of cellular responses in mammalian cells (BMP-induced osteoblastic differentiation of C2C12 cells and TGF-β–induced epithelial-to-mesenchymal transdifferentiation of NMuMG cells) and Xenopus embryos. The ARPG mutant recruited histone deacetylases 1 (HDAC1) to the Smad3-Smad4 complex but not to the Smad1/5-Smad4 complex. c-Ski (ARPG) was unable to interact with Smad4, and the selective loss of suppression of BMP signaling by c-Ski (ARPG) was attributed to the lack of Smad4 binding. We also found that c-Ski interacted with Smad3 or Smad4 without disrupting Smad3-Smad4 heteromer formation. c-Ski (ARPG) would be useful for selectively suppressing TGF-β/activin signaling