First in a series of papers entitled "Physical and Chemical Properties of Amyloid Fibers." 673 'l'i II: .11)1 uN '.1, 0,-11 IsTod-ti EM IsTRY AN Ii (2 YTOCII EMISTRt' ('opvrigtit i 1965 by 'lb 11 istis-liemiciut Society, Inc.

This study evaluated a rapid biomineralization phenomenon exhibited by an osteoblastic cell line, UMR 106-01 BSP, when treated with either organic phosphates [beta-glycerophosphate (beta-GP), Ser-P, or Thr-P], inorganic phosphate (P(i)), or calcium. In a dose-dependent manner, these agents (2-10 mM) stimulated confluent cultures to deposit mineral in the cell layer (ED50 of approximately 4.6 mM for beta-GP (30 +/- 2 nmol Ca2+/microgram DNA) and approximately 3.8 mM (29 +/- 2 nmol Ca2+/microgram DNA) for P(i)) with a plateau in mineral formation by 20 h (ET50 approximately 12-15 h). beta-GP or P(i) treatment yielded mineral crystals having an x-ray diffraction pattern similar to normal human bone. Alizarin red-S histology demonstrated calcium mineral deposition in the extracellular matrix and what appeared to be intracellular paranuclear staining. Electron microscopy revealed small, needle-like crystals associated with fibrillar, extracellular matrix deposits and intracellular spherical structures. Mineral formation was inhibited by levamisole (ED50 approximately 250 microM), pyrophosphate (ED50 approximately 1-10 microM), actinomycin C1 (500 ng/ml), cycloheximide (50 micrograms/ml), or brefeldin A (1 microgram/ml). These results indicate that UMR 106-01 BSP cells form a bio-apatitic mineralized matrix upon addition of supplemental phosphate. This process involves alkaline phosphatase activity, ongoing RNA and protein synthesis, as well as Golgi-mediated processing and secretion.

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Setting reactions and compressive strengths of a self-hardening calcium phosphate cement (CPC) were investigated. The CPC consists of tetracalcium phosphate (TTCP) and anhydrous dicalcium phosphate (DCPA). The cement specimens were prepared by mixing 0.7 g of the powder (TTCP 72.9 wt% + DCPA 27.1 wt%) with 0.175 mL of the liquid (25 mmol/L H3PO4 and 1.32 mmol/L sodium fluoride). The specimens were removed from the molds at pre-determined time intervals after being mixed, and their compressive strengths were measured. Immediately afterward, the fractured specimens were rapidly frozen in ethanol (-80 degrees C), lyophilized, and examined by powder x-ray diffraction and scanning electron microscopy (SEM). The results showed that (1) hydroxyapatite was the only reaction product; (2) the reaction was nearly completed within four h, during which both the reaction product and compressive strength increased linearly with time, resulting in a strong correlation between the two; and (3) fully set CPC consisted primarily of small rod-like crystals and some platy crystals.

A thermodynamic analysis of the precipitation of amorphous calcium phosphate (ACP) and its transformation to crystalline apatite had been made. A nearly constant ion product, over a wide variety of conditions, was obtained for a tricalcium phosphate (TCP)-like phase suggesting that the molecular unit which governs the solubility of ACP may be similar in composition to TCP. The introduction of 10% acid phosphate into the formula for the TCP ion product improves the fit of experimental data and results in an invariant ion product. The stability of ACP in solution was found to be dependent upon its thermodynamic instability with respect to an octacalcium phosphate (OCP)-like phase. The dependence of the induction period for the amorphous to crystalline transformation upon the pH and the Ca/P ratio of the solution is best explained by the assumption that an OCP-like phase is initially nucleated on the surfaces of the ACP particles. The events that occur in the immediate post-transition period suggest the hydrolysis of this OCP-like material to an apatitic phase.

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Amorphous calcium phosphate (ACP), a postulated precursor in the formation of biological hydroxyapatite, has been evaluated as a filler phase in bioactive polymeric composites that utilize dental monomers to form the matrix phase on polymerization. In addition to excellent biocompatibility, these composites provided sustained release of calcium and phosphate ions into simulated saliva milieus. In an effort to enhance the physicochemical and mechanical properties and extend the utility of remineralizing ACP composites to a greater variety of dental applications, we have focused on: a) hybridizing ACP by introducing silica and/or zirconia, b) assessing the efficacy of potential coupling agents, c) investigating the effects of chemical structure and compositional variation of the resin matrices on the mechanical strength and ion-releasing properties of the composites, and d) improving the intrinsic adhesiveness of composites by using bifunctional monomers with an affinity for tooth structure in resin formulations. Si- and Zr-modified ACPs along with several monomer systems are found useful in formulating composites with improved mechanical and remineralizing properties. Structure-property studies have proven helpful in advancing our understanding of the remineralizing behavior of these bioactive composites. It is expected that this knowledge base will direct future research and lead to clinically valuable products, especially therapeutic materials appropriate for the healing or even regeneration of defective teeth and bone structures.

The term "amyboid" refers to a pathologic proteinaceous substance (24, 38) deposited cxtraceblubarly in tissue and most commonly identified by light microscopy as a homogeneous eosinophilic material which stains with alkaline Congo red (7, 65). These deposits may be restricted to a single tissue Infrared spectroscopy: Samples were prepared for infrared spectroscopy as films cast onto thin silver chloride discs from either distilled water or (in the case of the V1 fragments) 50% formic acid solution and dried at 35#{176}C in vacuo. Amyboid fibrils were also