OBJECTIVE:Bisphosphonate-related osteonecrosis of the jaw is a common complication with defective wound healing of oral mucosa and frequently occurs in patients receiving zoledronic acid (ZA). The aim of this in vitro study was to investigate whether ZA has a cytotoxic effect at clinically relevant concentrations on epithelial cells when calcium conditions are altered. METHODS:HaCaT human keratinocyte cells were treated with ZA in the presence of various concentrations of calcium. The concentrations of ZA included submicromolar ones, which are comparable with those found in the plasma of patients. Cell viability and apoptosis were assessed using MTT assay and annexin V flow cytometry. RESULTS:Under standard culture conditions, cell growth was inhibited at 1 μM of ZA or above, but was unaffected by lower concentrations. However, when calcium concentrations were moderately increased, cell viability was decreased and apoptosis was induced at 0.2-0.3 μM of ZA. Moreover, a 50% reduction in serum in the hypercalcemic medium resulted in a significant decrease in cell viability at a much lower concentration (0.05 μM). CONCLUSION:These results suggest that clinically relevant concentrations of ZA, which alone have little effects, can be toxic to the epithelial cells depending on the conditions of extracellular calcium.

Divalent ytterbium was found in great amounts in calcium carbonate polymorphs (calcite and aragonite) and calcium fluoride, and the Yb2+/Yb3+ ratios in these materials increased with increasing saturation states of the respective starting solutions.

We measured XAFS spectra of trace amount of ytterbium (Yb) incorporated in calcite, a stable phase of calcium carbonate. Calcium carbonate was precipitated from a mixed solution of CaCl2 aq and NaHCO3 aq with a given amount ofYbCl3. Concentrations ofYb were 5 mol kg−1 in the starting solutions andYb/Ca molar ratio in the precipitated calcium carbonate was 1.2 × 10−3. Ytterbium LIII-edge XAFS spectra were collected in the fluorescence mode at the beamline BL-12C of the KEK-PF. Analysis of the XAFS results indicated, (1) Approximately 15% Yb ion existed as divalent ions in the calcite. (2) Yb3+, major Yb species in the calcite, is located at the Ca2+ site in the calcite. The local structure around Yb3+ is significantly different from that of Ca2+. The coordination number of Ca2+ in the crystal structure of calcite is 6 and Ca-O distance is 2.36 Å. In contrast, the nearestYb-O coordination forYb-doped calcite is split into two shells, the nearest 4 oxygen atoms and the second nearest 2 oxygen atoms, and their Yb-O distances are 2.24 Å and 2.77 Å, respectively. It was shown that localized structural relaxation occurred around Yb3+ which has smaller ionic radius than Ca2+.

We measured XAFS spectra of trace amount of ytterbium (Yb) incorporated in calcite, a stable phase of calcium carbonate. Calcium carbonate was precipitated from a mixed solution of CaCl2 aq and NaHCO3 aq with a given amount of YbCl3. Concentrations of Yb were 5 μmol kg−1 in the starting solutions and Yb/Ca molar ratio in the precipitated calcium carbonate was 1.2 × 10−3. Ytterbium LIII-edge XAFS spectra were collected in the fluorescence mode at the beamline BL-12C of the KEK-PF. Analysis of the XAFS results indicated, (1) Approximately 15% Yb ion existed as divalent ions in the calcite. (2) Yb3+, major Yb species in the calcite, is located at the Ca2+ site in the calcite. The local structure around Yb3+ is significantly different from that of Ca2+. The coordination number of Ca2+ in the crystal structure of calcite is 6 and Ca–O distance is 2.36 Å. In contrast, the nearest Yb–O coordination for Yb-doped calcite is split into two shells, the nearest 4 oxygen atoms and the second nearest 2 oxygen atoms, and their Yb–O distances are 2.24 Å and 2.77 Å, respectively. It was shown that localized structural relaxation occurred around Yb3+ which has smaller ionic radius than Ca2+.

Rare earth element (REE) concentrations in the carbonate lattice of four species of coral have been analyzed and compared with the dissolved REE in ambient seawaters. The corals were from two areas of different salinity, marine (34–34.5) and bay (33–34). The measurement of REE in coral was carried out with inductively coupled plasma mass spectrometry (ICP-MS) after meticulous washing of coral samples, digestion with acetic acid and preconcentration of REE. The concentrations of REE in the two ambient seawaters were quite different, being ten-times higher in the bay area and enriched in light REE. However, the average distribution coefficients (D’s) were almost identical in the two areas. Substantial distribution coefficient differences were observed among the four coral species and the magnitude of inter-species variation in D was also species-dependent. Theoretical calculations imply that pH variation could cause variations in D large enough to account for the small differences between the two areas.

Introduction Aeolian dust (Kosa) is transported from the arid or semi-arid region in East Asia to Japan during spring. A large particle of aeolian dust (>1 μm) mainly consists of mineral aerosol. Most elements originate in mineral aerosol. Some elements such as Cu, Zn, and Pb are rich in a small particle (< 1 μm). A small particle consists mainly of carbon aerosol, which is released by a vehicle, plant and heating system. We have studied chemical characteristics of aeolian dust during the transportation from China to Japan [1, 2]. The purpose of this study is to examine the variation of XANES spectra with change in the particle size and those during aeolian dust transport from China to Japan.

Impurity effects of trace lanthanum ion (La3+) on the dissolution and growth of calcium carbonate were studied with in situ observation techniques. Dissolution kinetics of two polymorphs of calcium carbonate, calcite and vaterite, were investigated by monitoring the pH in the solution with laser-induced fluorescence spectroscopy using a pH-sensitive reagent, seminaphthorhodafluors. No effect on dissolution of vaterite was observed with the spectroscopic observations, whereas calcite dissolution was significantly inhibited by lanthanum ion with concentrations higher than 1 μM. Crystal growth and dissolution processes of calcite under the lanthanum-doped condition were observed by means of atomic force microscopy. Step propagations during crystal growth and dissolution of calcite were inhibited by trace lanthanum ion (5 μM). An insoluble thin layer of lanthanum carbonate deposited on the step site of the calcite surface could be a possible cause of the inhibitions observed both for dissolution and growth.

Atsuyuki OHTA, Hiroshi TSUNO, Hiroyuki KAGI*, Yoshio, TAKAHASHI, Masaharu, NOMURA, Iwao KAWABE Geological Survey of Japan, AIST, Tsukuba, Ibaraki 305-8567, Japan 2 Institute for Environmental Management Technology, AIST, Tsukuba, 305-8569, Japan The University of Tokyo, Tokyo 113-0033, Japan Hiroshima University, Hiroshima 739-8526, Japan Institute of Materials Structure Science, KEK, Ibaraki 305-0801, Japan Naogya University, Aichi 464-8567, Japan

XANES spectra showed the occurrence of divalent ytterbium in the synthetic calcite (CaCO3). Approximately 15% ytterbium ion existed as divalent in calcite, although ytterbium ion was trivalent in the starting solutions.

A significant inhibiting effect was observed on the dissolution of calcite by addition of 5 μM lanthanum ion to the solution, whereas no inhibition was observed both for aragonite and vaterite under the same conditions. In situ AFM (atomic force microscopy) images suggested that micro-precipitates depositing at the step site of calcite inhibited the dissolution in the lanthanum-doped solution. The solubility-calculation for the given solution was consistent with lanthanum carbonate being the micro-precipitate.

The formation of calcium carbonate from a Supersaturated solution doped with trace lanthanum was studied at various temperatures. At a temperature of around 50degreesC, more than 80% of calcium carbonate precipitated from 5 mumol kg(-1) LaCl3, 15 mmol kg(-1) CaCl2-NaHCO3 solution was vaterite while from a lanthanum-free solution carbonate precipitated exclusively as calcite.

The effect of lanthanum ion on the crystallization of calcium carbonate was investigated using CaCl2-NaHCO3 solutions. A sampling vessel enabling us to sample a small aliquot of a solution at any time almost under a closed condition was invented for the experiments. The abundance of the crystallographic polymorphs in the precipitate was determined by powder X-ray diffraction. The formation of calcium carbonate from lanthanum-doped solutions can be featured by three stages: a spontaneous and rapid precipitation of vaterite, a transitive static stage and a delayed formation of calcite. Almost all lanthanum (> 95%) in the solution system (dissolved + suspended solid phases) was proved to be incorporated in the initially formed vaterite, and lanthanum in the vaterite seemed to be immobilized throughout the experiment. The presence of lanthanum in the starting solution (10(-4) of calcium in more) stabilized the initial vaterite crystal, preserved it much longer than one month and increased the solubility of CaCO3 to the level of vaterite. It is suggested that the lanthanum ion prohibited either the transformation initially formed vaterite to calcite or the overgrowth of calcite.