Active oxygen radicals induce peroxidase activity in rice blade tissues.

The relationship between active oxygen radicals and peroxidase induction on disease resistance in rice blades was investigated. Nitric oxide was produced in the whole blade stimulated by blast fungus elicitor. The induction of peroxidase activity was detected in active oxygen radical-treated rice blades 1 hour after treatment and thereafter. These results suggest that active oxygen radicals produced by stimulation with the elicitor could trigger peroxidase induction.

Effects of ionic valency of interacting metal elements in ion uptake by carrot (Daucas carota cv. U.S. harumakigosun).

Interaction of elements in the course of element uptake by carrot (Daucas carota cv. U.S. harumakigosun) exerted by the addition of elements, such as Rb, Zn, and Al, was investigated. For the purpose of precise evaluation of uptake behavior, the simultaneous determination of absorption of Na, Be, Sr, Mn, Co, Zn, Ce, Pm, and Gd was conducted by the multitracer technique. For root uptakes, Al exhibited its influence on the uptake of essential elements and on the uptake of toxic or unbeneficial ones, presumably as a result of the large electric valency that caused cell membrane disintegrity. On the other hand, Zn as a divalent cation only affected the uptake of essential and beneficial elements. Rubidium, which is a monovalent cation, did not exhibit any effect on the uptake of other ions. Concerning shoot uptakes, inhibition by Zn and Al, but not by Rb, was observed for the uptake of Sr, Mn, Co, and Zn. From the present investigation, it is suggested that there exists an interaction between added ions and the elements taken into plants and that the degree of interaction increases in the increasing order of ionic valency: M+ (Rb), M2+ (Zn), and M3+ (Al).

A survey of trace elements in pteridophytes.

Concentration of 11 trace elements (Ca, Sc, Cr, Fe, Co, Zn, Rb, Cs, Ba, La, and Ce) in 96 pteridophytes (fern and fern ally species) was determined by instrumental neutron activation analysis to evaluate a concentration range for each element and also to find species characteristic in the uptake of trace elements. Asplenium trichomanes was found to accumulate Sc, Cr, and Co to the highest concentrations among 96 pteridophytes. The highest concentration of Ca and Zn was observed for Asplenium obscurum. The other Pteridophytes exhibited only one element whose concentration was the highest. A positive correlation was found between the concentrations of Fe and Sc, and also between the concentrations of Cr and Co. The remarkable accumulation of lanthanides (La and Ce) was observed mainly in diversifying genera (Polystichum and Dryopteris in Dryopteridaceae, Diplazium in Woodsiaceae, and Asplenium in Aspleniaceae).

Difference in signal transduction for IL-10 and IFN-gamma production in a CD8+ T cell clone.

CD8+ T cell clones produced both interleukin 10 (IL-10) and interferon-gamma (IFN-gamma) when these cells were stimulated with a T-cell-specific mitogen, concanavalin A (Con A). One of these CD8+ T cell clones, 13G2, secreted IFN-gamma at similar levels with calcium ionophore, A23187, as well as by Con A, but IL-10 production by A23187 was less than by Con A. On the other hand, N6,O2-dibutyryl cAMP enhanced the production of IL-10 but not IFN-gamma when the low doses of Con A or A23187 coexisted. In a T cell clone, the production of these two cytokines required different signal transductions. These results indicate that a T cell clone can produce diverse cytokines depending on the surrounding condition.

Autoreactive CD8+ T cell clones producing immune suppressive lymphokines IL-10 and interferon-gamma.

Highly purified CD8+ T cells were stimulated repeatedly by syngeneic irradiated spleen cells. From separate cloning experiments, we succeeded in isolating two CD8+ clones, 4B4 and D2, which proliferated in response to autologous antigen-presenting cells (APC) completely in the absence of fetal calf serum. A T cell proliferation assay, using congenic strain of mice, indicates that both autoreactive clones were restricted to self-Db molecules. Our study is the first report of establishing murine autoreactive CD8+ clones restricted to self MHC class I molecules. To assess the immune suppressive activity of each autoreactive clone, we measured the production of IL-10 and interferon-gamma, which have specific immune suppressive activity toward type 1 helper T cell (Th1) proliferation and IgE synthesis, respectively. In response to autologous APC, both D2 and 4B4 produced considerable amounts of interferon-gamma and a low but significant level of IL-10. Each supernatant of D2 and 4B4 significantly suppressed IgE synthesis. These results strongly suggest the existence of CD8+ autoreactive T cells with immune suppressive activity.

Anti-IL-10 antibody enhances the proliferation of CD8+ T cell clones: autoregulatory role of murine IL-10 in CD8+ T cells.

All CD8+ T cell clones used in this study secreted IL-10, and their proliferation was inhibited by exogenous IL-10. This study addresses the question of whether IL-10 produced by responding T cell clones would inhibit proliferation of the secreting T cells themselves. Anti-IL-10 antibodies enhanced the proliferative response of the CD8+ T cell clones, the enhancing effect appearing in the late period of proliferation. However, the proliferation of both CD4+ Th1 and Th2 clones was not affected by anti-IL-10 throughout the culture. In addition to that of the cloned T cells, the proliferative response of a primary culture of CD8+ T cells was enhanced by the anti-IL-10 antibody. This is the first report on a lymphokine which has an autoregulatory role in inhibiting T cell proliferation.

Activation via TCR or IL-2 receptor of a CD8+ suppressor T cell clone: effect on IL-10 production and on proliferation of the suppressor T cell.

In a previous study, we established CD8+ suppressor T cell (Ts) clone 13G2 which produced the suppressive lymphokine, interleukin-10 (IL-10). In this study, we examined what physiological activator could induce both production of IL-10 from 13G2 and the proliferation of 13G2. Both the antigenic stimulation mimicked by the anti-CD3 antibody and the T cell growth factor interleukin-2 (IL-2) induced IL-10 production from the 13G2 clone equally well. 13G2 cells proliferated remarkably with IL-2 stimulation, while anti-CD3 only slightly induced proliferation of the clone. 13G2 cells also produced IL-10 in the presence of hydroxyurea which blocked transit of cells from G1 to S phase. However, cycloheximide blocked the production of IL-10 from the Ts clone. The study demonstrates that both the anti-CD3 antibody and IL-2 induced IL-10 synthesis of the Ts clone equally well, and the proliferative response of Ts cells was induced more by IL-2 than by anti-CD3. IL-2 proved to be a good stimulator for Ts cells to produce suppressive lymphokine and to multiply their population.

A suppressive lymphokine derived from Ts clone 13G2 is IL-10.

CD8+ suppressor T cell (Ts) clone 13G2 produced a soluble suppressive lymphokine, termed the T-cell growth inhibitory factor (TGIF), which suppressed the proliferation of type 1 helper T-cell (Th1) clone 3D20 cells. The specific activity of TGIF was concentrated approximately 66,000-fold (3.7 x 10(6) U/mg of protein) by sequential chromatography from the culture supernatant of 13G2 cells. The suppressive activity of the highly purified TGIF toward the proliferation of Th1 cells was neutralized by the anti-IL-10 monoclonal antibody, and was replaced by IL-10. We detected the IL-10 molecule in the highly purified TGIF by using immunoblotting with the anti-IL-10 antibody. A PCR study showed that mRNA of IL-10 was expressed in the 13G2 cells. From these results, we conclude that TGIF produced from CD8+ T-cell clone 13G2 was IL-10. The suppressive activity of the whole supernatant was also completely blocked by the anti-IL-10 antibody, suggesting that IL-10 could play an important role in immune suppression by Ts cells.

CD8+ suppressor T cell clone capable of inhibiting the antigen- and anti-T cell receptor-induced proliferation of Th clones without cytolytic activity.

A CD8+ Ts clone 13G2 was established from lymph node cells of bovine alpha s1-casein-primed C57BL/6 mice by in vitro antigenic stimulation followed by maintenance with IL-2-containing medium. The clone suppressed the Ag-induced proliferative responses of CD4+ Th cell clones without detectable cytotoxicity for both APC and responding T cells. The clone was able to suppress the in vitro proliferative response and antibody formation of Ag-primed lymph node cells. The suppression was Ag-nonspecific and not restricted to the MHC. The clone was able to suppress the proliferation of Th clones induced by an immobilized anti-TCR antibody in which APC was absent. The clone was, however, unable to suppress the proliferation of Th clones induced by anti-CD3 or IL-2. Thus, the mechanism of suppression by 13G2 was found to be due to a direct action on Th by inhibiting a consequence of signal transduction initiated through the TCR.

Baseband frequency response measurement system for optical components.

Knowledge of the baseband frequency responses of optical components is prerequisite to the design of optical fiber transmission systems. The sweep-frequency method is effective for obtaining frequency responses because of its large SNR. However, the use of GaAs lasers as optical signal sources involves several problems such as resonances below 1 GHz and spectrum broadening. In order to overcome these problems, a single transverse mode GaAs laser called a buried heterostructure GaAs laser was employed as an optical signal source in the sweep-frequency measurement system. This measurement system has a wideband flat sweep-frequency range of 0.5-1300 MHz as well as a wide dynamic range of more than 60 dB at optical levels.