Showing papers by "Susumu Kobayashi published in 2004"

Remote asymmetric induction with vinylketene silyl n,o-acetal.

Abstract: A highly regio- and diastereoselective TiCl4-mediated vinylogous Mukaiyama aldol reaction using the chiral vinylketene silyl N,O-acetal has been developed. The present vinylogous Mukaiyama aldol reaction provides a unique and effective means of controlling remote asymmetric induction. The methyl group at the alpha-position is important in achieving a high level of stereoselectivity. From a synthetic point of view, this methodology can provide a one-step construction of delta-hydroxy-alpha,gamma-dimethyl-alpha,beta-unsaturated carbonyl unit that is seen in many natural polyketide products.

New beauveriolides produced by amino acid-supplemented fermentation of Beauveria sp. FO-6979.

Abstract: Five new beauveriolides were isolated from the acetone extracts of Beauveria sp. FO-6979 mycelia fermented in amino acid-supplemented media. The structures were elucidated by spectroscopic studies including NMR experiments and chemical degradation. All the beauveriolides are cyclodepsipeptides consisting of one 3-hydroxy-4-methyl fatty acid, two L-amino acids and one D-amino acid in common. Beauveriolide VII with the structure of cyclo-[3-hydroxy-4-methyloctanoyl-L-phenylalanyl-L-alanyl-D-valyl] inhibited lipid droplet formation and cholesteryl ester synthesis in macrophages, but the other beauveriolides showed only slight or almost no effect on lipid droplet formation.

Sphere-filled organ model for virtual surgery system

Abstract: We have been developing a virtual surgery system that is capable of simulating surgical maneuvers on elastic organs. In order to perform such maneuvers, we have created a deformable organ model using a sphere-filled method instead of the finite element method. This model is suited for real-time simulation and quantitative deformation. Furthermore, we have equipped this model with a sense of touch and a sense of force by connecting it to a force feedback device. However, in the initial stage the model became problematic when faced with complicated incisions. Therefore, we modified this model by developing an algorithm for organ deformation that performs various, complicated incisions while taking into account the effect of gravity. As a result, the sphere-filled model allowed our system to respond to various incisions that deform the organ. Thus, various physical manipulations that involve pressing, pinching, or incising an organ's surface can be performed. Furthermore, the deformation of the internal organ structures and changes in organ vasculature can be observed via the internal spheres' behavior.

Attenuation by cyclic phosphatidic acid of peritoneal metastasis of azoxymethane-induced intestinal cancers in Wistar rats.

Abstract: The effect of cyclic phosphatidic acid, a unique analogue of lysophosphatidic acid, on the induction of bombesin-enhanced peritoneal metastases from intestinal adenocarcinomas induced by azoxymethane was investigated in male Wistar rats. Rats were given 10 weekly injections of azoxymethane (7.4 mg/kg body weight, s.c.) and of bombesin (40 μg/kg body weight, s.c.) every other day from the start of the experiment, and from week 16, they received injections of cyclic phosphatidic acid (3 or 6 mg/kg body weight, s.c.) every other day until the end of the experiment in week 45. Cyclic phosphatidic acid at both dosages significantly decreased the incidence of bombesin-enhanced cancer metastases to the peritoneum but had little or no effect on the location, histologic type, depth of involvement or infiltrating growth patterns of the tumors. Cyclic phosphatidic acid at either dose decreased significantly the incidence of lymphatic vessel invasion of adenocarcinomas and the activity of RhoA protein in the tumors, both of which were enhanced by bombesin. Our findings indicate that cyclic phosphatidic acid inhibits cancer metastasis through inhibition of RhoA protein activation. © 2004 Wiley-Liss, Inc.

Multiseptate gallbladder: diagnostic value of MR cholangiography and ultrasonography.

Abstract: Multiseptate gallbladder is a rare congenital malformation. We present a case that emphasizes the importance of ultrasonography and magnetic resonance imaging. Ultrasound examination of the abdomen showed multiple linear internal echoes consistent with multiple septa crossing the entire gallbladder lumen, creating a honeycomb appearance. Magnetic resonance cholangiopancreatography showed a grapelike cluster of the whole gallbladder.

New Beauveriolides Produced by Amino Acid‐Supplemented Fermentation of Beauveria sp. FO‐6979

Abstract: Five new beauveriolides were isolated from the acetone extracts of Beauveria sp. FO-6979 mycelia fermented in amino acid-supplemented media. The structures were elucidated by spectroscopic studies including NMR experiments and chemical degradation. All the beauveriolides are cyclodepsipeptides consisting of one 3-hydroxy-4-methyl fatty acid, two L-amino acids and one D-amino acid in common. Beauveriolide VII with the structure of cyclo-[3-hydroxy-4-methyloctanoyl-L-phenylalanyl-L-alanyl-D-valyl] inhibited lipid droplet formation and cholesteryl ester synthesis in macrophages, but the other beauveriolides showed only slight or almost no effect on lipid droplet formation.

Effect of the anastomosis-site after Billroth I gastrectomy on the motility of the remnant stomach.

Abstract: Background/aims Gastric emptying, in healthy individuals, is a highly regulated process, and plasma cholecystokinin plays a major role in its feedback regulation. However, the hormonal regulation of postprandial gastric emptying of the remnant stomach after distal gastrectomy with Billroth I reconstruction procedure has not been well described. The aim of this study is to characterize the gastroduodenal motility and gastric emptying of the two anastomosis-methods after Billroth I gastrectomy, while assessing the effect of cholecystokinin on the motility of the remnant stomach. Methodology Two types of anastomosis (end-to-end, side (posterior wall)-to-end) after Billroth I gastrectomy were measured with strain gauge force transducers, and evaluated as to gastroduodenal motility, gastric emptying, gastrointestinal hormones (cholecystokinin, gastrin), and blood glucose associated with food administration. Results Remnant stomachs with side-to-end anastomosis showed superior motility as compared to those with end-to-end anastomosis. Plasma cholecystokinin was higher in the end-to-end anastomosis group. No differences as to gastric emptying, levels of plasma gastrin, or blood glucose were observed between the two groups. Conclusions Plasma cholecystokinin may explain the difference in motility index between the two groups.

Molecular Design of Cholesterols as Inhibitors of DNA Polymerase α

Abstract: The triterpenoid structure is a promising motif for the molecular design of DNA polymerase inhibitors.1 In this study, 2-(cholesteryloxy)acetic acid (3), 2-(cholestanyl)acetic acid (7), and 2-(stigmasteryl)acetic acid (11) were found to selectively affect only DNA polymerase α (pol.α). The presence of a carboxyl group at position 28 appears to be essential for the inhibition of the pol.α activity. With pol.α, these compounds acted by competing with the template-primer DNA and noncompetitively with the substrate.

A Convergent Total Synthesis of Epolactaene: An Application of the Bridgehead Oxiranyl Anion Strategy.

Abstract: The generation and reaction of a lactone-derived oxiranyl anion is described. The aldol-type reaction of the epoxylactone and aldehydes was accomplished by a two-step procedure via the trimethylsilyl epoxylactone. The application of this methodology to the total synthesis of (+)-epolactaene and its analogs is described.