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The biocompatibility of various magnetic materials used in dentistry to secure prostheses was assessed. In vitro cell cultures were performed on coated and uncoated covered and uncovered rare earth magnets. These studies were completed by essays of the lactic dehydrogenase used as an indicator of membrane damage. The various analyses indicate that the magnets in common clinical use are not significantly cytotoxic.

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Somites from 9H. H. chick embryos and PC12 cells were co-cultivated in synthetic medium containing N.G.F., which induces the transformation of PC12 cells into neuron-like cells. During the first two days of culture, PC12 cells retained the spherical shape and tended to cluster. Somitic mesoderm cells exhibited a fibroblastic aspect. By the third day, PC12 cells extended long processes resembling nerve fibres which surrounded and penetrated the mesodermic explants. On the 10th day of culture, contractions, limited at first to a few cells were perceptible. Later, the contractions involved large cellular masses. Microscopic observations at 10 days revealed the presence of an increasing number of fusiform mononucleated cells. Later, long and narrow multinucleated elements appeared. Such elements never developed from cultures of only somites. Immunohistochemical observations revealed a desmin positivity in both mononucleated and multinucleated elements characterizing them as myogenic cells that are formed in and because of the presence of PC12 cells which were transformed by N.G.F. into nerve cells. After 10 days of culture, PC12 cells positive to antiserum antidesmin were noted. Desmin positivity of PC12 cells leads to the conclusion that newly-formed muscle cells exert an induction on Pheocromocytoma cells which, as derivatives of the neural crest, have a greater multipotentiality.

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The Authors expose their observations about the fibroblasts adhesion to materials used as implants in orthopaedic surgery; the first part of the experiment uses normal culture conditions. In the second part the materials have been pre-coated with Fibronectin (FN), a glycoprotein involved in cell-to-substratum adhesion Fibroblasts adhesion increases about 30-40% with pre-coated materials. This observation is important for comprehension of adhesion mechanisms in a multidisciplinary approach to biocompatibility of implant materials.

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The time and modalities of degradation of the muscles acetylcholine receptor have been studied by several investigator, both in vivo and in vitro and under normal and pathological condition. The metod employed in this study for assessment of possible changes in the degradation to age involves the valutation of several parameters. These are explained and discussed. The preliminary results show the turnover of the receptor for junction acetylcholine, which is known to be considerably accellerated in conditions such denervation and myastenia, is slowed down during senescence.

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The authors expose their results about the biological compatibility of Bioglass (BG), using a new experimental model; this model implicates the use of Fibronectin (FN), a glycoprotein involved in cellular adhesion. The term Bioglass indicates a family of glasses (of possible use as implants) with the formation of a stable calcium-phosphate film on their surface when in contact with an aqueous environment. Two types of BG, B5 and B6, have been incubated with FN; the first binds three times B6 the FN. The results are discussed considering other preliminary results.

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The Authors expose their experience about a new model for testing the biocompatibility of materials of possible use as implants in surgery. This model uses a glycoprotein, Fibronectin (FN) involved in cellular adhesion; FN was purified from human plasma by affinity chromatography on denatured collagen; the protein obtained by this procedure is about 95% pure. The best value of FN binding was found to be on bioglass B5 whereas in the case of Titanium Alloy and B6 an intermediate value was measured. Results may be discussed considering other preliminary results about cell adhesion.

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Five independent hybrids producing monoclonal antibodies to human plasma fibronectin have been obtained by fusing P3/X63-Ag8 myeloma cells with immune mouse splenocytes. The specificity of these monoclonal antibodies (MABs) for fibronectin was demonstrated by three independent tests: binding to the purified soluble molecule, immunofluorescence staining of insoluble extracellular matrices produced by endothelial cells in vitro, immunostaining of fibronectin tryptic peptides after separation on SDS-PAGE and transfer to nitrocellulose sheets. Two antibodies (MAB 29 and 52) recognized selectively human fibronectin while the others (MAB 5, 30 and 59) reacted also with plasma fibronectin from calf, hamster and chicken. Four distinct epitopes were recognized by the MABs studied. MAB 5, 30, 52 and 59 reacted with distinct antigenic sites, while MAB 29 and 52 bind to the same site. Antigenic fragments were identified by immunostaining of fibronectin tryptic peptides. MAB 5 reacted with a collagen binding fragment with a molecular weight of 120 K. In addition, each of the MAB 29, 30, 52 and 59 reacted with peptides with a molecular weight of 40 K that bind to gelatin. Since these antibodies do not inhibit fibronectin-collagen interaction, it is concluded that their corresponding epitopes are clustered in a region close, but not coincident, to the collagen binding site of fibronectin.

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