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To examine the effect of the arginine-vasopressin fragment, [pGlu4,Cyt6]AVP(4–9) (AVP4–9), on group II metabotropic glutamate receptor (mGluR2/3) agonist and antagonist induced impairment of passive avoidance (PA) task performance, AVP4–9 or phorbol 12-myristate 13-acetate (PMA) was administered in the presence of mGluR2/3-related drugs that induced the impairment of the step-through-type PA task performance. The PA task performance was evaluated in terms of the latency (the time that elapsed prior to entry into the dark compartment) at 24 h after the electrical stimulation. The subcutaneous injection of AVP4–9 at 1 μg/kg had the greatest facilitative effect on the performance, and the facilitative effect of AVP4–9 was inhibited by NPC-15437, a specific protein kinase C (PKC) inhibitor. The injection of AVP4–9 ameliorated PA task performance impairment induced by DCG-IV, an mGluR2/3 agonist. Intracisternal injection of PMA, a PKC activator, also ameliorated the DCG-IV-induced impairment. High doses of AVP4–9 exacerbated the PA task performance impairment induced by LY341495 (an mGluR2/3 antagonist), and PMA injection (1 μg) also exacerbated the impairment induced by the antagonist. These results suggest that an increase in the activity of the PKC-signaling pathway may not always facilitate PA task performance; therefore, AVP4–9 can either enhance or inhibit memory performance in mice. Keywords:: memory, [pGlu4,Cyt6]AVP(4–9), protein kinase C

We examined the effect of the acetylcholinesterase (ACHE) inhibitor, donepezil hydrocloride (DONP), on group II metabotropic glutamate (mGlu) receptor agonist- or antagonist-induced amnesia in the step-through passive avoidance task in male mice. DCG-IV, a group II mGlu receptor agonist, at dose of 50 ng and LY341495, a group II mGlu receptor antagonist, at dose of 300 ng, significantly attenuated the latency on the step-through task. The subcutaneous injection of DONP at dose of 1 mg/kg 1 hour before passive avoidance performance ameliorated the amnesia induced by DCG-IV and LY341495, whereas donepezil alone did not affect task latency. The results suggest that activation of group II mGlu receptors and disinhibition of the cAMP/PKA signaling pathway (caused by group II mGlu receptor antagonist) have a negative action on step-through passive avoidance memory performance, and that group II mGlu receptors and ACh interact to modulate learning and memory function.

Fullerene is known to effectively produce mainly singlet oxygen by absorbing light energy, and therefore may be useful as a virucidal photosensitizer. This study was designed to investigate the virucidal activity of a water-soluble fullerene derivative, which is conjugated with methoxy polyethylene glycol amine to enhance its water solubility. Vesicular stomatitis virus (VSV) was inactivated upon illumination with this water-soluble fullerene, in a concentration- or dose-dependent manner. The titer of VSV was reduced by5log 10 in the presence of 10 mg/ml (400 microM) fullerene derivative with 120 J/cm2 white light irradiation. VSV inactivation was inhibited by oxygen removal or by the addition of sodium azide, a known singlet oxygen scavenger. The substitution of H2O by D2O, which is known to prolong the lifetime of singlet oxygen, promoted the virucidal activity. These results indicate that singlet oxygen may play a major role in VSV photoinactivation by the water-soluble fullerene derivative. The concentration needed for virus inactivation is higher than that of other sensitizers such as methylene blue.

In the CNS, reactive oxygen species (ROS) have been implicated in a wide range of degenerative processes including amyotrophic lateral sclerosis, ischemia-reperfusion injury, Alzheimer disease, Parkinson disease and aging. However, the exact mechanism is unknown, and there is little information on possible roles of ROS in cell injury and the process on recovery of astrocytes, the most abundant glial cells in the brain. We examined hydrogen peroxide (H2O2)-induced DNA fragmentation and thymidine incorporation into cultured astrocytes as an indicator of the process of recovery from astrocytic DNA injury. Astrocytes were isolated from cerebral cortices of 0-day-old rats and treated with 1 mM dibutyryl cyclic AMP for 4 days. H2O2 of 100 microM stimulated thymidine incorporation into astrocytes. Caffeine, ryanodine, cyclic ADP-ribose (endogenous ryanodine receptor agonist) and beta-NAD+ (precursor of cyclic ADP-ribose) suppressed partially the stimulatory effect of H2O2. Ruthenium red (ryanodine receptor antagonist) facilitated further the stimulatory effect of H2O2. The facilitated effect of ruthenium red on H2O2-induced thymidine incorporation was suppressed by caffeine, ryanodine, cyclic ADP-ribose and beta-NAD+. H2O2-induced DNA fragmentation and astrocytic death were suppressed by ruthenium red. These findings suggest that the process of recovery from astrocytic DNA injury by H2O2 may be regulated by Ca2+ efflux from ryanodine-sensitive intracellular Ca2+ stores.

The alloreactive cytotoxic T lymphocytes (CTL) were generated by coculturing peripheral blood mononuclear cells (PBMC) with allogeneic Sa cells (an Epstein-Barr virus [EBV]-transformed B-cell line). The CTL did not proliferate in response to UV-B-irradiated Sa cells unless exogenous interleukin-2 (IL-2) was present, although they could kill the UV-B-irradiated Sa cells. The results indicate that UV-B-irradiated Sa cells do not provide sufficient signals for the proliferation of the CTL while they can be recognized by CTL and induce high-affinity IL-2 receptor (IL-2R) expression on them. The alloreactive CTL could be rendered anergic by previous exposure to UV-B-irradiated Sa cells. The alloreactive CTL previously stimulated with UV-B-irradiated Sa cells failed to proliferate in response to nontreated Sa cells. Proliferation of the anergic CTL could not be restored by Sa cells and exogenous IL-2 but by the combination of phorbol 12-myristate 13-acetate (PMA) and calcium ionophore (A23187). The anergic CTL showed a considerably low cytotoxic activity against Sa target cells. The expression of TCR on the anergic CTL was downregulated while expression of high-affinity IL- 2R was upregulated. Their CD28 and CD8 expression were unchanged. In addition, the proliferative response and cytotoxicity of the anergic CTL to Sa cells could be restored after the cells had been rested for 7 days to allow reexpression of TCR. These results suggest that downregulation of T-cell receptor (TCR) and impairment in the post-IL- 2/IL-2R signaling pathway are relevant to the clonal anergy induced in the alloreactive CTL by stimulation of UV-B-irradiated Sa cells.

The effects of a novel vasopressin fragment analog NC-1900 (pGlu-Asn-Ser-Pro-Arg-Gly-NH2 acetate) were studied on learning and/or memory impairment in passive avoidance task and on cell damage of cultured cerebro-cortical neurocytes induced by glutamic acid. A small dose of NC-1900 (1 ng/kg, s.c.) ameliorated impairments of learning and/or memory induced by intracisternal injection of 467.6 micrograms of 10 microliters glutamic acid. NC-1900 also ameliorated the impairments induced by intracisternal NMDA, AMPA-antagonist CNQX and by metabotropic receptor (mGluR1) agonist 3,5-dihydroxyphenylglycine but not by kainate agonist domoic acid nor MK-801 in mice. NC-1900 (100 pM, 1nM) ameliorated the cell damage of cultured rat cerebro-cortical neurocytes induced by 100 and 1000 microM of glutamic acid. These results suggest that NC-1900 may serve as a remedies in various patients with certain brain disorders induced by excess glutamic acid.

6-β-Methoxypropionyl-3-methyllumazine and 6-β-methoxypropionyl-1,3-dimethyllumazine, and 6-β-hydroxypropionyl-3-methyllumazine have been newly isolated from the swimming polychaete, Odontosyllis undecimdonta.

The study of chemical forms and physiological mobility of elements found in plants is always essential to establishing the roles of elements in plant life. Such information in combination with the results of growth experiments will lead to more. reliable conclusions on the physiological functions of elements.

As seen in the previous paper1) the use of HF-etching method has added much information to the mode of silicon deposition in rice tissues. The results obtained cover a wide range from root to husk. However, the importance of silicon deposition in epidermis in relation to the resistance of plants to diseases or insect pests makes it desirable to continue further studies of the mode of silicon deposition in outer region of epidermis. The study of microstructure of epidermis in connection with silicon deposition will provide valuable information to the mechanism of resistance rice plant to blast disease, because penetration of the rice leaf by piricularia oryzae is ordinarily through the cuticle rather than via the stomata. It will be of importance also to the study of a possible role of silicon in water economy of rice plant as already suggested by the present authors.

In spite of tremendous efforts by many plant physiologists, it still remains unsolved whether or not silicon is essential to higher plants. It is, however, generally accepted that some plant species markedly respond to silicon under some conditions and accordingly silicon is often described as a beneficial element.

As seen in the previous paper1) the use of HF-etching method has added much information to the mode of silicon deposition in rice tissues. The results obtained cover a wide range from root to husk. However, the importance of silicon deposition in epidermis in relation to the resistance of plants to diseases or insect pests makes it desirable to continue further studies of the mode of silicon deposition in outer region of epidermis. The study of microstructure of epidermis in connection with silicon deposition will provide valuable information to the mechanism of resistance rice plant to blast disease, because penetration of the rice leaf by piricularia oryzae is ordinarily through the cuticle rather than via the stomata. It will be of importance also to the study of a possible role of silicon in water economy of rice plant as already suggested by the present authors.