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[1] We statistically examine changes in the composition of two different ion species, proton and oxygen ions, in the near-Earth plasma sheet (X = À16 R E $ À6 R E ) during substorm-associated dipolarization. We use 10 years of energetic (9-212 keV/e) ion data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particles and ion composition (EPIC) instrument on board the Geotail spacecraft. The results are as follows: (1) Although the percentage increase in the energy density of O + ions before and after a dipolarization exceeds that of H + ions in the low-energy range (9-36 keV/e), this property is not evident in the high-energy range (56-212 keV/e); (2) the energy spectrum of H + and that of O + become harder after dipolarization in almost all events; and (3) in some events the energy spectrum of O + becomes harder than that of H + as reported by previous studies, and, importantly, in other events, the spectrum of H + becomes harder than that of O + . In order to investigate what mechanism causes these observational results, we focus on magnetic field fluctuations during dipolarization. It is found that the increase of the spectrum slope is positively correlated with the power of waves whose frequencies are close to the gyrofrequency of H + or O + , respectively (the correlation coefficient is 0.48 for H + and 0.68 for O + ). In conclusion, ions are nonadiabatically accelerated by the electric field induced by the magnetic field fluctuations whose frequencies are close to their gyrofrequencies.

Abstract. The prevalence of hypovitaminosis D has been recently reevaluated, and diabetes is considered as a risk factor for osteoporosis. We studied the association of the prevalence of hypovitaminosis D with the clinical features of diabetes. We conducted the observational study in 581 Japanese patients with type 2 diabetes mellitus and 51 normal subjects, and analyzed the relationship between serum 25-hydroxyvitamin D (25-OHD) concentration and the clinical features associated with type 2 diabetes. Mean serum 25-OHD concentration in type 2 diabetes patients was 17.0 ± 7.1 ng/ml (Mean ± SD) in winter, and was not statistically different from normal population (17.5 ± 3.6 ng/ml). The prevalence of hypovitaminosis D (<20 ng/ml) was 70.6%. Serum concentrations of 25-OHD were associated with HbA1c (P = 0.013), age (P = 0.070) and serum albumin (P<0.001), but were not related to BMI or the duration of diabetes. The levels of 25-OHD were significantly lower in the population with apparent microvascular complications, although serum creatinine levels were below 2.0 mg/dl. Serum 25-OHD concentrations in the group treated with insulin (15.4 ± 6.5 ng/ml) was lower than those in the patients treated with diet alone (20.8 ± 7.6 ng/ml) and with oral hypoglycemic agents (17.3 ± 7.0 ng/ml). Furthermore, the highest incidence of osteoporotic fracture and/or back deformity was observed in insulin-treated patients with hypovitaminosis D. In conclusion, these results suggest that microvascular complications and insulin treatment in type 2 diabetes patients are associated with the co-existence of hypovitaminosis D, and that hypovitaminosis D in insulin-treated patients is possibly related to the risk of osteoporotic fracture.

Pi handling by osteogenic cells is important for bone mineralization. The role of Pi transport in BMP-2-induced matrix calcification was studied. BMP-2 enhances Pit-1 Pi transporters in osteogenic cells. Experimental analysis suggest that this response is required for bone matrix calcification.Introduction: Bone morphogenetic proteins (BMPs) are produced by osteogenic cells and play an important role in bone formation. Inorganic phosphate (Pi) is a fundamental constituent of hydroxyapatite, and its transport by osteogenic cells is an important function for primary calcification of the bone matrix. In this study, we investigated the role of Pi transport in BMP-2-induced matrix mineralization. Materials and Methods: Confluent MC3T3-E1 osteoblast-like cells were exposed to BMP-2 for various time periods. Pi and alanine transport was determined using radiolabeled substrate, Pit-1 and Pit-2 expression by Northern blot analysis, cell differentiation by alkaline phosphatase activity, matrix mineralization by alizarin red staining, and the characteristics of mineral deposited in the matrix by transmission electron microscopy, electron diffraction analysis, and Fourier transformed infrared resolution (FTIR). Results: BMP-2 time-and dose-dependently stimulated Na-dependent Pi transport in MC3T3-E1 cells by increasing the V max of the transport system. This effect was preceded by an increase in mRNA encoding Pit-1 but not Pit-2. BMP-2 also dose-dependently enhanced extracellular matrix mineralization, an effect blunted by either phosphonoformic acid or expression of antisense Pit-1. Enhanced Pi transport and matrix mineralization induced by BMP-2 were blunted by a specific inhibitor of the c-Jun-N-terminal kinase (JNK) pathway. Conclusions: Results presented in this study indicate that, in addition to its well-known effect on several markers of the differentiation of osteoblastic cells, BMP-2 also stimulates Pi transport activity through a selective increase in expression of type III Pi transporters Pit-1. In MC3T3-E1 cells, this effect is mediated by the JNK pathway and plays an essential role in bone matrix calcification induced by BMP-2.

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