Structure and properties of poly(phenylacetylene)s were investigated. The poly(phenylacetylene)s were obtained in the polymerization at 30°b y WCle or M0CI5 in several solvents (C6He, CCI4, CHCI3, and CH2CI2). Molecular weights of the polymers were 5500-12000. The polymers produced by WCle in polar solvents showed high softening points (~226°), a small absorption at 870 cm-1 in ir spectrum, and an emission at 430 nm by excitation at 250 nm; these were correlated with high content of trans structure. On the other hand, the polymers formed by M0CI5 in nonpolar solvents showed low softening points (~215°), a large absorption at 870 cm-1, and an emission at 360 nm, which were attributed to high content of cis structure. The numbers of unpaired spin of the polymers were in a range of 1016-1017 spin g_1, and the electric conductivities were 10"18-10"15 ohm"1 cm"1.

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Induction of hematopoietic chimerism and subsequent donor-specific immune tolerance via bone marrow transplantation is an ideal approach for islet transplantation to treat type-1 diabetes. We examined the potential of mesenchymal stem cells (MSCs) in the induction of chimerism and islet allograft tolerance without the incidence of graft-versus-host disease (GVHD). Streptozotocin-diabetic rats received a conditioning regimen consisting of antilymphocyte serum and 5 Gy total body irradiation, followed by an intraportal co-infusion of allogeneic MSCs, bone marrow cells (BMCs) and islets. Although all the recipients rejected the islets initially, half of them developed stable mixed chimerism and donor-specific immune tolerance, shown by the engraftment of donor skin and second-set islet transplants and acute rejection of a third-party skin. The engraftment of the primary islet allografts with stable chimerism was achieved by the addition of a 2-week peritransplant administration of 15-deoxyspergualin (DSG). Without MSCs, none of the recipients treated with DSG developed chimerism or reversal of diabetes. GVHD was not observed in any of the recipients infused with MSCs (0/15), whereas it occurred in 4/11 recipients without MSCs. These results indicate a potential use of MSCs for induction of hematopoietic chimerism and subsequent immune tolerance in clinical islet transplantation.

The apparent diffusivities (Da) for cesium and tritium in compacted sodium bentonite saturated with distilled water were measured at ambient temperature. The dry density of the bentonite had a significant effect on Da for cesium, which decreased with increasing the dry density in the range of 0.2 to 2.0 Mg/m 3 . Α batch-Äi/ for cesium measured using a high solution/bentonite ratio is not applicable to predict Da(Cs) with a model based on linear sorption, because the ionic strength of pore water in the compacted bentonite is probably higher than the value of the solution for the batch sorption test in the existing experimental condition.

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