Recently we developed a new microwave spectroscopy technique in the frequency range up to 40 GHz, and measured the static dielectric constant and the dielectric relaxation time for supercritical water. In the present work we report the dielectric properties of heavy water at temperatures and pressures up to 770 K and 59 MPa, respectively. The static dielectric constant of D2O as well as H2O are well described by the Uematsu–Franck formula when the number density instead of the mass density is used as the input parameter. The dielectric relaxation time decreases rapidly with increasing temperature in liquid H2O and D2O and jumps to a large value at the liquid–gas transition. The relaxation time of D2O is longer than that of H2O in the liquid state, and the difference becomes smaller with decreasing density in the gaseous state. For both H2O and D2O the most relevant parameter determining the relaxation time is the temperature at high densities or at low temperatures, and it is the density at low densities or at high temperatures. Based upon the observation that the dielectric relaxation time becomes fairly long in the dilute limit, we have concluded that the dielectric relaxation in the gaseous state is governed by the binary collision of water molecules and explained the relaxation time quantitatively by the collision time. We have extended the interpretation of the dielectric relaxation to the liquid state by taking into account the contribution of bound water molecules that are incorporated in the hydrogen-bond network. Anomalous relaxation at low temperatures is also discussed.
Microwave spectroscopy that can be applied to study the dielectric relaxation of various fluids under high temperature and pressure has been developed in the frequency range up to 40 GHz. By utilizing this new technique, the dielectric relaxation of water has been measured in the temperature and pressure range up to 750 °C and 120 MPa, which corresponds to a density range between 0.05 and 1 g/cm3. The static dielectric constant ε(0) is deduced from the time required for a microwave signal to travel through the sample by means of the time domain analysis, and is in good agreement with the literature. The dielectric relaxation time τ is obtained by fitting the experimentally observed microwave transmission rate to the value calculated using the S-matrices on the assumption that the dielectric constant obeys the Debye relaxation. The results of τ at ambient pressure agree very well with previous data. Below about 350 °C, τ rapidly decreases with increasing temperature nearly independent of pressure, while above about 350 °C, τ changes little with temperature and increases rapidly with decreasing density. It is concluded that the most relevant parameter determining τ is the temperature at lower temperatures or higher densities, and it is the density d at higher temperatures or lower densities. A possible change in the nature of hydrogen bonding is suggested to explain the observed temperature and density dependence of τ.
S100A8 and S100A9 (S100 proteins) are regulators of immune cells of myeloid origin. Whereas S100 proteins are found at high concentrations in such cells, their immunologic roles remain unclear. We focused on cluster of differentiation 68 (CD68). The aim of this study is to investigate whether CD68 binds to extracellular S100A8 and/or S100A9 and subsequently participates in the regulation of the cells' immune functions. ELISA and affinity chromatography showed that both recombinant rat S100A8 (r-S100A8) and r-S100A9 bound to r-CD68, but not to r-CD14. Flow cytometry clearly showed evidences supporting above the 2 results. As analyzed by flow cytometry, a less amount of r-S100A8 or r-S100A9 bound to the macrophages treated with some deglycosylation enzymes. In an in vitro assay, the expression levels of S100A8 and S100A9 were significantly suppressed after the macrophages had been treated with an anti-CD68 antibody (ED1). As stimulated macrophages with r-S100A9, the expression of IL-1β mRNA in macrophages, which were treated with anti-TLR4 or -RAGE antibodies, was significantly suppressed. r-S100A8 up-regulated IL-6 and IL-10 mRNAs, while r-S100A9 did TNF-α and IL-6 mRNAs, although these regulations were not statistically significant. Small interfering CD68 also significantly suppressed activation of macrophages through an autocrine pathway by r-S100A8 or r-S100A9. In macrophages stimulated with LPS, fluorescent immunologic staining showed that most CD68 colocalized with S100A8 or S100A9 and that the levels of all 3 molecules were markedly increased. In conclusion, CD68 on macrophages binds to S100A8 and S100A9 and thereby, plays a role in the regulation of the cells' immune functions.
Background The clinical significance of human S100A8/A9 (h-S100A8/A9) in patients with inflammatory bowel disease (IBD) is poorly understood. Objective To clarify whether serum S100A8/A9 is a sensitive biomarker for IBD. Methods Serum specimens from outpatients with IBD (n = 101) and healthy volunteers (HVs) (n = 101) were used in this study. Enzyme-linked immunosorbent assays for h-S100A8/A9 and inflammatory cytokines were performed using these specimens. Further, correlation analysis was performed to investigate the significance of h-S100A8/A9 fluctuation in patients with IBD. Results The average of serum h-S100A8/A9 concentration in outpatients with IBD was significantly higher than that in HVs. The concentration of h-S100A8/A9 in patients with IBD was barely correlated with that of CRP and inflammatory cytokines. Despite that finding, the serum level of h-S100A8/A9 in patients with ulcerative colitis (UC) was correlated with the severity of IBD, compared with other inflammatory proteins. Conclusion Serum h-S100A8/A9 is superior to CRP as a sensitive biomarker for IBD.
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