Biomedical subjects

Y Kumashiro

Publications and source records attributed to Y Kumashiro.

6 recordsLinked to original sources

PubMed2003

Raman scattering study of water clusters around polyrotaxane and pseudopolyrotaxane supramolecular assemblies.

We have measured Raman spectra of collective O-H stretching vibration of water clusters in polyrotaxane and pseudopolyrotaxane aqueous solutions and the aqueous solutions of their constituent molecules. The intensities of the collective bands of water clusters in the polyrotaxane and pseudopolyrotaxane solutions were approximately equal to that of their solvents. On the other hand, those in the solutions of linear polymeric chains and cyclic molecules were smaller. These results indicate that the water molecules in the solvents cannot approach to interact with the hydrophobic parts of the constituent molecules sterically when the constituent molecules form the inclusion complexes. Thus, the polyrotaxane and pseudopolyrotaxane molecules are observed as inert in terms of molecular interaction with water, although the constituent molecules have hydrophobic parts in their structure.

Cyclodextrins↗

PubMed2002

Hand-assisted laparoscopic hepatic resection.

Thanks to recent advances, performance of liver resection is now possible using laparoscopic procedures. However, still there are some difficulties to overcome. The hand-assisted method lends safety and reliability to the laparoscopic procedure. A 54-year-old man diagnosed with hepatocellular carcinoma (HCC) was referred for hepatectomy. Angiography with computed tomography (CT) scans revealed a 2-cm hepatocellular carcinoma (HCC) at segment V, close to the gallbladder. A hand-assisted laparoscopic hepatic resection was performed. Four 10-mm trocars, one for wall lifting and three for working, were placed in the upper abdomen. A small incision was added at the right side of umbilicus, and the operator's left hand was inserted through it. A microwave tissue coagulator and laparoscopic ultrasonic dissector were used for liver resection. Total operation time was 162 min; blood loss was 20 g. The postoperative course was uneventful, and the postoperative hospital stay was 7 days. We thus demonstrated that laparoscopic liver resection is safer and easier when the hand of the operator can be inserted into the abdomen. The small incision does not greatly diminish the benefits that accrue from minimally invasive laparoscopic surgery. The hand-assisted procedure allows better access to the tumor. In addition, hand assistance restores the sense of touch to the operator and is an effective means of controlling sudden and unexpected bleeding.

Angiography↗

PubMed2001

Modulatory factors on temperature-synchronized degradation of dextran grafted with thermoresponsive polymers and their hydrogels.

Several types of dextran grafted with poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide [dextran-g-poly(NIPAAm-co-DMAAm)] with different graft lengths and numbers were synthesized in a preciously controlled fashion, and their enzymatic degradation was examined by viscosity measurement and gel permeation chromatography as a function of temperature. Degradation of dextran-g-poly(NIPAAm-co-DMAAm)s decreased with increasing the graft length below their lower critical solution temperatures (LCSTs). Above the LCST, enzymatic degradation was independent of the graft length. A larger amount of the graft chain with increasing the graft length rather than the graft number was effective to modulate the temperature-synchronized degradation. Hydrogels were prepared by cross-linking the graft copolymers using 1,6-hexamethylenediamine. While all the hydrogels have water content of about 93-96% in a wide range of temperatures, their degradation behaviors show a significant dependence on a temperature change. Such a unique property is closely related to the structure of graft copolymers such as graft lengths. Consequently, introducing thermoresponsive grafts with longer length to dextran and its hydrogels is suggested to be an important factor for modulating enzymatic degradation of dextran in synchronization with temperature.

Biocompatible Materials↗

PubMedDate not supplied

Beneficial effect of tetrahydrobiopterin on the survival of rats exposed to hepatic ischemia-reperfusion injury.

INTRODUCTION: The protective role of nitric oxide (NO) against hepatic ischemia-reperfusion (I/R) injury remains controversial. In this study we investigated the effect of tetrahydrobiopterin (BH4) on the survival of rats exposed to an hepatic I/R injury. METHODS: The rats were subjected to 100 minutes of 70% hepatic ischemia 30 minutes after administration of BH4 or saline. A specific inducible NO synthase (iNOS) blocker, 1400W, was used to evaluate endogenous iNOS. NOS protein measured the histological appearance of the liver by Western blotting, and survival was evaluated after reperfusion. RESULTS: The 1-week survival rate was 60% among the BH4 group and 10% for the saline group. The serum ALT and bilirubin values in the BH4 group were significantly lower than the saline group. Histological examination of the liver revealed only a small necrotic area in the BH4 group as opposed to massive necrosis and cell infiltration in the saline group. Injection of 1400W significantly decreased the prolongation of survival produced by BH4. CONCLUSIONS: BH4 significantly improved the survival rate, the histological findings, and the liver function, thereby reducing liver failure. Western blotting showed a higher level of iNOS protein in the BH4 group than the saline group, 1400W suppressed this effect of BH4. Taken together, these observations suggest that NO derived from reactions driven by BH4-induced iNOS exerts a protective effect against reperfusion injury.

Animals↗

PubMedDate not supplied

Teratoma formation and hepatocyte differentiation in mouse liver transplanted with mouse embryonic stem cell-derived embryoid bodies.

We previously reported that mouse embryonic stem (ES) cells are capable of differentiating into hepatocytes in cultured embryoid bodies (EBs) and that hepatocytes generate in the recipient liver injected with cultured day-9 EB cells via spleen without the formation of a teratoma. Because ES cells frequently form teratomas in recipient mice, we investigated incidence of teratoma formation when day-9 EBs derived from ES cells were transplanted directly into the subcapsule of mouse liver. In contrast to injection of day-9 EB cells through the portal vein via the spleen, direct subcapsular injection of cultured day-9 EB cells into liver, and even of cultured day-15 EBs, resulted in an high incidence of teratoma in the liver. In teratomas of livers injected directly with day-15 EBs, hepatocytes were detected singly and in clusters. These results imply that undifferentiated cells capable of developing into teratomas exist in cultured EBs, and even in cultured day-15 EBs containing differentiated hepatocytes.

Animals↗

PubMedDate not supplied

Isolation of hepatocyte-like cells from mouse embryoid body cells.

We previously reported that embryoid body (EB) cells derived from embryonic stem (ES) cells are capable of differentiating into functional hepatocyte-like cells both in vitro and in vivo. Because transplantation of EB-derived cells into the liver via the spleen resulted in a low incidence of teratoma formation, purification of hepatocyte-like cells is required to prevent teratoma formation. The aim of this study was to purify hepatocyte-like cells from cultured EBs. For the isolation of hepatocyte-like cells, EBs cultured for 15 days were treated with trypsin-EDTA. The disaggregated cells were plated on a gelatin-coated dish as a monolayer. These cells were separated by Percoll gradient centrifugation, enriched by magnetic cell sorting, and purified by FACS. The purified hepatocyte-like cells in monolayer cultures were positive for immunostaining for albumin and expressed albumin mRNA, but not Oct3/4 mRNA. Transplantation of the purified hepatocyte-like cells derived from mouse ES cells might be an effective treatment for liver failure.

Animals↗