The technique of tissue engineering is developing for the restoration of lost tissues. This new technique requires cells that fabricate tissue. Mesenchymal stem cells in bone marrow have been used as the cell source for this technique; however, dental pulp cells have recently been shown to possess stem-cell-like properties. We earlier demonstrated that dental pulp cells proliferate and produce an extracellular matrix that subsequently becomes mineralized in vitro. We now report that such dental pulp cells (first to eighth passage) produced bone instead of dentin when those cells were implanted into subcutaneous sites in immunocompromised mice with HA/TCP powder as their carrier. This evidence shows that dental pulp cells are the common progenitors of odontoblasts and osteoblasts, or dental pulp cells are mesenchymal stem cells themselves. It is expected that dental pulp cells can be a useful candidate cell source for tissue engineering, and contain the potential of new therapeutic approaches for the restoration of damaged or diseased tissue.

SYNOPSISRadical copolymerization of dialkyl fumarates (DRF) with various vinyl monomers was carried out in benzene at 60°C. The monomer reactivity ratios, r1 and r2, were determined from the comonomer-copolymer composition curves. The relative reactivity of DRFs with various ester substituents toward a polystyryl radical was revealed to depend on both steric and polar effects of the ester groups. It has also been clarified that a-substituents of the polymer radical have a significant role in addition of DRF, from the comparison of the monomer reactivity ratios determined in copolymerizations with monosubstituted and 1,ldisubstituted ethylenes. The absolute cross-propagation rate constants were also evaluated and discussed. 0 1992 John Wiley & Sons, Inc. Keywords: radical copolymerization dialkyl fumarate substituent effect monomer reactivity ratio steric effect polar effect

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SUMMARY Surface modified poly(ethy1ene terephthalate) (PET) films with 2-(methacryloyloxy)ethylphosphorylcholine (MPC) and 2-(glucosy1oxy)ethyl methacrylate (GEMA) moieties, PMPC-g-PET and PGEMAg-PET, were prepared by graft copolymerization using an Ar plasma-post polymerization technique. The degrees of polymerization of the grafts PMPC and PGEMA were p,, = 30 and p,, = 40, respectively. The contact angle of the modified PET film decreased from 6' = 68 O (the original PET film) to 6' = 26 O for PMPCg-PET and to 6' = 43 O for PGEMA-g-PET. The modified PET films adsorb less serum proteins than the original PET film. Egg yolk lecithin did not adsorb on PGEMA-g-PET but adsorbed on PMPC-g-PET. PMPC-g-PET showed activity for the inhibition of fibrin formation and no adhesion of mouse fibroblasts (L-929).

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