Matsui, Hideki

The induction of both long-term potentiation (LTP) and long-term depression (LTD) in the hippocampal CA1 region is triggered by the activation of N-methyl-D-aspartate (NMDA) receptors and the subsequent postsynaptic intracellular Ca2+ increase. However, how NMDA receptor activation differs between LTP and LTD induction is unclear. In the present study, we examined the eff ects of the magnitude and duration of NMDA receptor activation on the induction of LTP and LTD. Partial blockage of NMDA receptors by a low concentration of aminophosphonovaleric acid (APV)(2 μM) prevented the induction of LTP, but not LTD. In contrast, a high concentration of APV(25 μM) blocked both LTP and LTD. Tetanus stimulation-induced LTP was impaired when hippocampal slices were given the tetanus stimulation for more than 5 min. Under partial blockage of NMDA receptors, the prolonged-tetanus stimulation induced LTD but not LTP. This phenomenon was mimicked by the application of glutamate to the slices. Finally, LTD induced by prolonged activation of NMDA receptors was not aff ected by inhibition of the desensitization of α-amino-3-hydroxy-5 methylisoxazole-4-propionic acid (AMPA) receptors. These results suggest that critical diff erences exist between the induction of LTP and that of LTD in terms of both the magnitude and the duration of NMDA receptor activation. The duration of the increase in intracellular Ca2+ concentration may be critical for determining whether LTP or LTD induction occurs.

 To determine whether the predominant infiltration with memory CD4⁺T cells in joints is specific to the local immune and inflammatory response in rheumatoid arthritis (RA), the proportions of CD45RA⁺ or CD45RO⁺ cells in the CD4⁺T cell populations in three different compartments (i.e., peripheral blood, synovial fluid, and synovial tissue) from patients with RA and osteoarthritis (OA) were compared by two-color flow-cytometric analysis. In the CD4⁺T cell population of peripheral blood, the number of CD45RO⁺ cells was relatively higher than CD45RA⁺ cells in both RA and OA patients, but their percentages did not differ from those found in healthy individuals. However, the great majority of CD4⁺T cells present in synovial fluid and synovial tissue were CD45RO-positive and CD45RA-negative in both patient groups; although CD4⁺T cells infiltrating both the disease compartments were markedly greater in RA joints, their mean percentages of CD45RO⁺ cells were not significantly different from those in OA joints. These data indicate that an accumulation of CD45RO⁺ memory CD4+T cells is a generalized phenomenon during local inflammatory responses in both RA and OA joints, and may be due mainly to the propensity of these cells to preferentially transmigrate into the inflamed joint via adhesion molecules as compared with CD45RA⁺ naive CD4⁺T cells.

Two factors from normal rat liver cytoplasm inhibited the proliferation of cultured L-929 fibroblasts. One was arginase, the other was a small molecular weight inhibitor stable to trypsin and heat treatment. The small molecular weight inhibitor inhibited the protein and DNA synthesis of L-cells. Inhibition of DNA synthesis was thought to be secondary to the inhibition of protein synthesis.

Peptides and proteins in the extracellular space in the central nervous system were investigated in vivo using an intracerebral microdialysis probe. The molecular cut-off of the hollow fiber which was used for the probe was approximately 100 kDa. We examined recovery rates of several compounds in vitro. The recovery rates of proteins and peptides were between 7-28%, with the exceptions of substance P and insulin-like growth factor I. The recovery rates of monoamines and their metabolites were 22-40%. In in vivo studies, two major proteins with apparent molecular weights of 62 kDa and 12 kDa, and several minor proteins (28 kDa, 43 kDa, 52 kDa and 70 kDa) were detected by SDS-polyacrylamide gel electrophoresis in the dialysate from a probe implanted in the striatum of anesthetized rats. These results suggest that the newly developed, intracerebral microdialysis probe might be useful for investigating the dynamic changes of peptides and proteins in the central nervous system.