This study evaluated the in vivo influence of a poly-(2-Acrylamido-2-methylpropane sulfonic acid)/poly-(N,N'-dimetyl acrylamide) (PAMPS/PDMAAm) double-network (DN) hydrogel on counterface cartilage in rabbit knee joints and its ex vivo friction properties on normal cartilage. In the first experiment, the DN gel was implanted in a surgically created defect in the femoral trochlea of rabbit knee joints and the left knee was used as the control. Evaluations using a confocal laser scanning microscopy demonstrated that the DN gel did not affect the surface microstructure (surface roughness, the number of small pits) of the counterface cartilage in vivo at 4 and 12 weeks. The histology also showed that the DN gel hadno pathological damage on the cartilage matrices and cells at 4 weeks. However, two of the five DN gel-implanted knees showed mild irregularity on the counterface cartilage surface at 12 weeks. In the second experiment, the friction property between the normal and the artificial cartilage was determined using a joint simulator apparatus. The ex vivo mean friction coefficient of the DN gel to normal cartilage was 0.029, while that of the normal-to-normal cartilage articulation was 0.188. The coefficient of the DN gel-to-normal cartilage articulation was significantly lower than that of the normal-to-normal cartilage articulation (p < 0.0001). This study suggested that the PAMPS/PDMAAm DN gel has very low friction coefficient on normal cartilage and has no significant detrimental effects on counterface cartilage in vivo, and can be a promising material to develop the artificial cartilage.

The results of the present study suggest that delayed fracture healing in MIF KO was mainly attributable to a delay in osteoid mineralization.

Phase relationship in the [(K1/2Bi1/2)1- y (Na1/2Bi1/2) y ](Ti1- x B x )O3 system with B=Zr, Fe1/2Nb1/2, Zn1/3Nb2/3 or Mg1/3Nb2/3 has been investigated by dielectric measurement and X-ray diffractometry. All of the bi-binary systems were solid-soluble throughout the entire composition range. With increasing y and x, ferroelectric Curie point decreased and the ε-T curve became flat. Composition dependence of the transition temperature was examined by varying x or y. Phase diagrams were mostly determined at room temperature on square diagrams except for a restricted area in the vicinity of (Na1/2B1/2)ZrO3, which involved a tetragonally distorted phase and could not be accounted for. The ferroelectric tetragonal phase was confined within a narrow range of x<0.1 and the rhombohedral phase was dominant in all of the systems studied here.

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