Masakatsu Tamechika

Inflammatory and Anti-inflammatory Cytokines Regulate the Recovery from Sublethal X Irradiation in Rat Thymus

Abstract Mizutani, N., Fujikura, Y., Wang, Y-H., Tamechika, M., Tokuda, N., Sawada, T. and Fukumoto, T. Inflammatory and Anti-inflammatory Cytokines Regulate the Recovery from Sublethal X Irradiation in Rat Thymus. Radiat. Res. 157, 281 – 289 (2002). We investigated the regeneration of rat thymus after sublethal X irradiation (6 Gy). The number of thymocytes was much lower on day 3 after irradiation, and many apoptotic cells were observed. However, by day 5, there had been a rapid proliferation of thymocytes. Since cytokines are considered to be important regulatory factors in postirradiation recovery, we performed in vivo cytokine assays using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and found serial changes in the cytokine message. The messenger RNA (mRNA) expression of the pro-inflammatory cytokines interleukin 1 beta (Il1b), Il6 and tumor necrosis factor alpha (Tnf) was higher than normal on day 3, lower on day 5, and higher again on day 7. In particular, Tnf was completely absent on day 5 and was expressed again on day 7. Of the anti-inflammatory cytokines Il4, transforming growth factor beta (Tgfb) and Il10, only the Il10 message changed substantially. Il10 expression was very high on day 5 but was completely absent on day 7. Thus the Tnf and Il10 messages were expressed alternately. The changes in the distribution of macrophages detected by the immunohistochemical analysis may be related to the changes in the cytokines. Analysis of cytokine messages in the regenerating thymus in vivo may provide new insights into potential therapies for radiation-induced damage.

A novel trigger for cholesterol-dependent smooth muscle contraction mediated by the sphingosylphosphorylcholine-Rho-kinase pathway in the rat basilar artery: a mechanistic role for lipid rafts.

Hyperlipidemia is a risk factor for abnormal cerebrovascular events. Rafts are cholesterol-enriched membrane microdomains that influence signal transduction. We previously showed that Rho-kinase-mediated Ca2+ sensitization of vascular smooth muscle (VSM) induced by sphingosylphosphorylcholine (SPC) has a pivotal role in cerebral vasospasm. The goals of the study were to show SPC-Rho-kinase-mediated VSM contraction in vivo and to link this effect to cholesterol and rafts. The SPC-induced VSM contraction measured using a cranial window model was reversed by Y-27632, a Rho-kinase inhibitor, in rats fed a control diet. The extent of SPC-induced contraction correlated with serum total cholesterol. Total cholesterol levels in the internal carotid artery (ICA) were significantly higher in rats fed a cholesterol diet compared with a control diet or a β-cyclodextrin diet, which depletes VSM cholesterol. Western blotting and real-time PCR revealed increases in flotillin-1, a raft marker, and flotillin-1 mRNA in the ICA in rats fed a cholesterol diet, but not in rats fed the β-cyclodextrin diet. Depletion of cholesterol decreased rafts in VSM cells, and prevention of an increase in cholesterol by β-cyclodextrin inhibited SPC-induced contraction in a cranial window model. These results indicate that cholesterol potentiates SPC-Rho-kinase-mediated contractions of importance in cerebral vasospasm and are compatible with a role for rafts in this process.

Distribution of the surface antigen HAM-4 and cytoskeleton during reformation of bile-canalicular structures in rat primary cultured hepatocytes

The distribution of rat bile-canalicular surface antigen (HAM-4 antigen) and cytoskeletal elements (microtubules, actin filaments, and cytokeratin filaments) was examined during the reformation of bile-canalicular structures (BC-structures) in primary cultures of dissociated hepatocytes obtained following collagenase perfusion. HAM-4 antigen, which initially dispersed after cell dissociation, became focused into regions of cell-to-cell contact even before formation of BC-structures. Typical bile-canalicular microvilli also appeared in these regions before the intercellular spaces were completely closed. Finally, after in vitro reformation of BC, HAM-4 antigen was localized specifically at the BC-surface. The process of BC-reformation and the intracellular organization of actin and cytokeratin filaments were not significantly affected by microtubule inhibitors (nocodazole, colcemid, and colchicine). However, the localization of HAM-4 antigen molecules at the surface of BC was disrupted by these inhibitors, suggesting that the distribution of HAM-4 antigen, which represents a marker for the reconstruction of surface polarity, is dependent on microtubule function.

Induced Absorption in X-ray-Irradiated CdS-Doped Glass

Optical transmission spectra have been measured in X-ray-irradiated CdS-doped glass as functions of X-ray dose at 0.5–100 Gy and effective X-ray energy at 10–65 keV. Induced absorption is observed in the X-ray-irradiated glass with a dose higher than about 0.5 Gy, and it increases linearly with a dose of up to 80 Gy. The induced absorption decreases with decreasing effective X-ray energy. Thermal stability was also studied. The origin of the induced absorption was discussed.

CdS-Doped Glass as Dosimetric Material with Electron Spin Resonance

Electron spin resonance (ESR) spectra have been measured in X-ray-irradiated CdS-doped glass as functions of X-ray dose and effective X-ray energy. The intensity of the ESR signal is proportional to X-ray dose up to 40 Gy. CdS-doped glass is more sensitive than a commercial alanine dosimeter. The intensity of the ESR signal decreases with decreasing effective X-ray energy for energies lower than 33 keV. Thermal stability was also studied. The ESR signal is relatively stable at room temperature.

Thermoluminescence of X-Ray-Irradiated CdS-Doped Glass

Thermoluminescence has been observed in X-ray-irradiated CdS-doped glass. The intensity of thermoluminescence is proportional to the X-ray dose up to 10 Gy. The intensity of thermoluminescence for Asahi Y-44 is approximately 0.5% of that of phosphor for a commercial radiation dosimeter: MSO-S (Mg2SiO4:Tb). Photofading of Y-44 is markedly lower than that for MSO-S.

Electron Spin Resonance of X-ray-Irradiated CdS-Doped Glass before Heat Treatment

The electron spin resonance (ESR) spectrum has been measured in X-ray-irradiated CdS-doped glass before heat treatment to examine the possibility of using such glass as a dosimetric material. No ESR signal is observed before X-ray irradiation, but it was observed after X-ray irradiation. The intensity of the ESR signal of the glass before heat treatment is higher than that after heat treatment. The thermal stability of the ESR signal of the former glass is slightly better than that of the latter. Therefore, the glass before heat treatment has better properties than that after heat treatment.