Soft-tissue response to injectable calcium phosphate cements.

Item does not contain fulltextIn this study, the soft tissue reaction to two newly developed injectable calcium phosphate bone cements (cement D and W) was evaluated after implantation in the back of goats. For one of the cements (cement D) the tissue reaction was also investigated after varying the concentration of accelerator Na(2)HPO(4) in the cement liquid (resulting in cement D1 and D2). Eight healthy mature female Saanen goats were used. The cement was applied 10min after mixing while it was still moldable and plastic. The material was given a standardized cylindrical shape. Thirty-two implants of each cement formulation were inserted and left in place for 1, 2, 4, and 8weeks. At the end of the study, eight specimens of each material and healing period were available for further analysis. Two specimens were used for X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) and six specimens were used for light microscopical evaluation. XRD and FTIR showed that the cements did set as microcrystalline carbonate apatite with the disappearance of monetite from the cements during implantation. Histological analysis showed that after 8weeks of implantation around all materials a thin soft-tissue capsule was formed (thickness ranging from 5 to 15 cell layers) with almost complete absence of inflammatory cells. Only in some specimens a slightly higher inflammatory reaction was observed. This was due to cement surface defects and a zone of dispersed particles near the cement-soft tissue interface. There was almost no resorption of the material after 8 weeks of implantation. In a few 4 and 8weeks samples, small areas of calcification were found in the fibrous capsule surrounding the implants. On the basis of our observations, we conclude that the tested cements were biocompatible and can be used next to soft tissue

Abscisic-acid and the induction of desiccation tolerance in the extremely xerophilic liverwort Exormotheca holstii

HELLWEGE EM, Dietz K-J, VOLK OH, HARTUNG W. Abscisic-acid and the induction of desiccation tolerance in the extremely xerophilic liverwort Exormotheca holstii. Planta. 1994;194(4):525-531.Abscisic acid (ABA) induces formation of a set of proteins in the xerophilic liverwort Exormotheca holstii. Some of them have immunological properties similar to the dehydrins of desiccated corn embryos and the desiccation-related proteins of Craterosrigma plantagineum. The fluctuations of endogenous ABA during cycles of desiccation and rehydration seem to be sufficiently high to indicate a role for ABA as a stress hormone and thereby as an endogenous inductor of stress-related protein synthesis. Desiccation tolerance disappears when thalli are cultivated for a longer period under well-watered conditions; such thalli are not able to increase stress-dependent ABA biosynthesis sufficiently, or to form the desiccation-related proteins unless they are treated with external ABA. The rehydrated thalli cannot recover from a rapid water loss, while ABA-treated, non-hardened thalli regain their photosynthetic activity within two hours