No abstract

All mice treated with 3-methylcholanthrene (MC) suffered with tumor 114 days after treatment. However, 40% dietary restriction caused a great inhibition of tumor incidence. In order to understand the mechanisms by which dietary restriction decreased the occurrence of tumor in mice, we investigated the correlation between tumor incidence and host T cell immune responses. At 114 days after MC administration, the mice were sacrificed and their T cell immune responses were assessed. Flow cytometry studies demonstrated that dietary restriction caused a marked increase of the proportion of Thy 1.2+, L3T4+ T cells in MC-treated diet-restricted mice. Consistent with this result, T cell responses against concanavalin A and interleukin-2 were also potentiated in spleen cells obtained from MC-treated diet-restricted mice, while spleen cells obtained from MC-treated unrestricted mice showed decreased T cell responses because of their tumor burden. Such potentiation of T cell functions by dietary restriction was also observed at earlier stages of MC-induced tumorigenesis. During the course of carcinogenesis, spleen cells obtained from diet-restricted mice showed decreased natural killer activity in vivo. However, in vitro induction of cytotoxic T cells was markedly augmented in MC-treated diet-restricted mice compared with unrestricted mice. These results strongly suggest that the increase of host T cell immune responses might be one of the major causes for the reduction of tumor occurrence by dietary restriction.

LiF/CaF2/LiBaF3 eutectic scintillators were grown by the m-PD method. In the solidified eutectic the phases were uniformly distributed in the transverse direction and slightly aligned along the growth direction. For the Eudoped samples, the expected emission peak observed at 420 nm was ascribed to Eu 2+ 5d-4f transition from Eu:CaF2 under X-ray excitation. The Li concentration in the LiF/CaF2/LiBaF3 eutectic is around 67.9 mol%. This is the advantage for neutron detection because 6 Li has high neutron capture cross-section. Due to the expected high sensitivity, the grown eutectic scintillator is promising candidate for application in neutron imaging such as nondestructive inspection, etc. In our presentation, relation between chemical composition of starting materials, growth rate and volume ratio of eutectic will be discussed. Furthermore, other scintillation properties will be reported.

Ce and Ca co-doped LiGdF4-LiF eutectics were grown and their directionally solidified eutectic (DSE) system has been investigated. In these eutectics, apart from the expected 305 nm emission of the regular Ce3+, 310 nm emission of the Gd3+ and Ce3+-perturbed emission around 320-380 nm was observed. Ce3+-perturbed emission at 340 nm shows the intrinsic decay time of about 27 ns. In photoluminescence mechanism the observed decay time shortening of the regular Ce3+ and Gd3+ centers point to the energy transfer in the sequence the regular Ce3+→ (Gd3+)n→ the perturbed Ce3+ sites.

Mice fed a 40% restricted diet until 1 year of age showed a 35% drop in body weight and markedly lower weights in the central lymphoid organs such as spleen and thymus than those of unrestricted mice. In contrast, the percentage of splenic Thy 1.2⁺ T cells was dramatically increased by dietary restriction. Splenic Ly 1⁺ T cells were also increased in the restricted mice. Spleen cells of the restricted mice revealed significantly higher responses not only in macrophage (MP)-dependent responses such as concanavalin A response and mixed-lymphocyte reaction but also in MP-independent T cell responses to recombinant interleukin 2 even at 1 year of age. These results strongly suggest that dietary restriction causes an enrichment of Thy 1.2⁺ T cells in spleen and augments the functions of T cells in mice.