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Biomedical subjects

S Nakamura

Publications and source records attributed to S Nakamura.

At least 19 recordsLinked to original sources
PubMed1992

Regional accumulation of amyloid beta/A4 protein precursor in the gerbil brain following transient cerebral ischemia.

Alterations of beta/A4 amyloid protein precursor (APP) were investigated immunohistochemically in the gerbil brain after transient global ischemia and subsequent reperfusion. Marked accumulation of this protein peaking at 24 h occurred in the neurons of the CA3 and paramedian region of the hippocampus as well as layers III, V and VI of the cerebral cortex. On the contrary, the accumulation was not observed in the neurons of the CA1 region. These results indicate that distribution of APP is altered depending on tissue viabilities after cerebral ischemia.

Amyloid beta-Protein Precursor↗
PubMed1992

Tactile and taste sensory maturation of the frog larvae tongue.

The maturation process of organs in the oral cavity of the larvae of bullfrogs, Rana catesbeiana, corresponding to the larval stages XVIII to XXV distinguished by Taylor and Kallros Anat. Rec., 94 (1946) 7-25, were investigated. In this study, these larval stages were divided by the width of the mouth slit into A1, A2, B and C stages. The A1 and A2 stages corresponded to larval stages XVIII-XIX and XX, respectively. The B and C stages corresponded to stages XXI and XXII-XXV, respectively. In stage A1, mechanical and chemical stimulation of the tongue rudiment, in most larvae, failed to elicit afferent discharges in glossopharyngeal nerves. However, in a small number of larvae, obvious afferent discharges of these nerves were generated. In stage A2, glossopharyngeal nerves in most larvae began responding to the same stimulations. The amplitude increased with decreasing duration of afferent discharges, resembling those of the adult. In stage B, the first glossopharyngeal-hypoglossal nerve reflex (G-H reflex) was elicited by mechanical stimulation of the tongue. In stage C, the G-H reflex was also induced by chemical stimulation and the latency of the G-H reflex elicited by mechanical stimulation decreased. In this stage, expansion and extension of the tongue increased. Therefore, the natural function of this reflex for the intake of food may follow this stage.

Animals↗
PubMed1992

Transmitter-like 3,4-dihydroxyphenylalanine is tonically released by nicotine in striata of conscious rats.

Microdialysis and high performance liquid chromatography with an electrochemical detector were applied to compare the characteristics of nicotine-evoked release of endogenous 3,4-dihydroxyphenylalanine (DOPA) from striata of conscious rats and those of the release of dopamine (DA). Dialysates were collected every 20 min 3-8 h after the start of perfusion. Nicotine was perfused for 20 min through a probe. (+/-)-Nicotine (100-300 microM) constantly and repeatedly released DOPA and DA over a similar time course in a dose-dependent manner. The ratio of the DOPA and DA release evoked was approximately 1:3. The (+/-)-nicotine (200 microM)-induced DOPA release was mecamylamine (500 microM)-sensitive, tetrodotoxin (100 nM)-sensitive and Ca2+ (removal plus 12.5 mM Mg2+ addition)-dependent. The (+)-isomer produced no DOPA release. These characteristics of DOPA release were almost the same as those of DA release. Furthermore, mecamylamine alone inhibited the basal release of DOPA but not of DA. Nicotine released stereoselectively endogenous DOPA via nicotinic acetylcholine receptors from striata of freely moving rats in a manner similar to transmitter DA. These acetylcholine receptors function tonically for the release of DOPA. These findings are further support for our proposal that DOPA is an endogenous neuroactive substance.

Animals↗
PubMed1992

Detection of bcl-2 protein and bcl-2 messenger RNA in normal and neoplastic lymphoid tissues by immunohistochemistry and in situ hybridization.

bcl-2 protein has been detected in surgical specimens and cultured permanent cell lines of non-Hodgkin's lymphomas and leukemias using enzyme immunohistochemistry and immunofluorescence with anti-bcl-2 monoclonal antibodies. Of 40 surgical specimens, bcl-2 protein was expressed in 50% of B-cell and 41% of T-cell lymphomas, both with and without the bcl-2 gene rearrangement. In investigations of 38 hematopoietic cell lines, bcl-2 protein was detected not only in lymphoid cell lines but also in myeloid cell lines. In situ hybridization and immunohistochemical analysis of reactive lymph nodes showed that lymphocytes in mantle zones and paracortical areas expressed bcl-2 protein consistent with the messenger RNA distribution and that germinal center cells showed abundant bcl-2 transcript, despite the absence of detectable bcl-2 protein. These results suggest that bcl-2 protein is broadly expressed in various hematopoietic neoplasms not restricted in t(14; 18) lymphomas and that germinal center cells may be involved in some arrest of bcl-2 protein expression at the posttranscriptional level.

Blotting, Northern↗
PubMed1992

Active metabolism of arachidonic acid by Kaposi sarcoma cells cultured from lung biopsies (KS-3); identification by HPLC and MS/MS of the predominant metabolite secreted as the 11,12-epoxy-eicosatrienoic acid.

The development of long-term culture of AIDS-KS cells has allowed us to investigate further a possible vascular origin of Kaposi sarcoma. Taking into account the relative specificity of arachidonic acid (AA) metabolism according to cell type, the AA 'cascade' was analyzed in cultured KS-3 cells established from lung biopsies and compared to human umbilical venous endothelial (H-UVE) cells and human myometrial smooth muscle (H-MSM) cells, under basal conditions and after stimulation with vasoactive agents such as histamine or thrombin. Considering strictly the 'prostaglandin' profile given by RIAs, the metabolism of AA was closer, whilst not identical, to H-UVE than to H-MSM cells. However, evaluation of all the eicosanoids released from [3H]AA labeled KS-3 cells revealed that the predominant metabolite was not prostacyclin (PGI2), as suggested from PG RIAs, but an epoxy-eicosatrienoic acid (EET), identified as the 11, 12 isomer by HPLC and MS/MS. The synthesis of this EET is probably cytochrome P-450 monooxygenase dependent. Its potential role in the development of the KS tumor cells is under investigation.

8,11,14-Eicosatrienoic Acid↗
PubMed1992

Activation of mitogen-activated protein kinase and its activator by ras in intact cells and in a cell-free system.

Mitogen-activated protein (MAP) kinase is a serine/threonine kinase whose function is thought to be essential for the transduction of mitogenic signals. MAP kinase is activated by phosphorylation induced by a variety of extracellular stimuli, and its direct upstream activator has been identified. Using amphibian and mammalian systems, we show here that ras can activate MAP kinase and its activator. Injection of v-Ha-ras p21 into Xenopus immature oocytes activated both MAP kinase and maturation-promoting factor (MPF) activities. The activation of MAP kinase preceded that of MPF, demonstrating that ras activates MAP kinase in an MPF-independent pathway. Moreover, we found that the MAP kinase activator is also activated in ras-injected oocytes. Activation of MAP kinase and its activator occurred also when the v-Ki-ras gene was conditionally induced in rat fibroblastic 3Y1 cells. Furthermore, we observed that ras activated MAP kinase and its activator in a cell-free system prepared from Xenopus oocytes. Using an antibody against the Xenopus 45-kDa MAP kinase activator, we demonstrated that the 45-kDa activator molecule was activated by ras. These findings suggest that the MAP kinase activator/MAP kinase system may be the downstream components of ras signal transduction pathways.

Animals↗
PubMed1992

Retinoic acid ambivalently regulates the expression of MyoD1 in the myogenic cells in the limb buds of the early developmental stages.

The expression of MyoD1 in myogenic cells located in the muscle prospective region of the limb bud at stage 20-22 was highly sensitive to retinoic acid. Unlike RAR-beta, the expression of MyoD1 mRNA in the muscle precursor cells was significantly increased by retinoic acid at lower concentrations (0.1-10 nM), but inhibited by it at higher concentrations (0.1-1 microM). The ambivalent modulation of MyoD1 expression suggested that MyoD1 expression is regulated by not only the retinoic acid receptor and its response element, but also by other factors. Retinoic acid may be involved in the differentiation of the myogenic cells during early development.

Animals↗
PubMed1992

Distributions of heat shock protein (HSP) 70 and heat shock cognate protein (HSC) 70 mRNAs after transient focal ischemia in rat brain.

The distribution of heat shock protein (HSP) 70 and heat shock cognate protein (HSC) 70 mRNA after 30 min of middle cerebral artery (MCA) occlusion was investigated in rat brain by in situ hybridization using cloned cDNA probes selective for the mRNAs. While HSP70 mRNA was hardly present at caudate and dorsal hippocampal levels of the sham brain this mRNA was greatly induced in cells of the MCA territory 1 h after reperfusion. Although the maximum amount of induced HSP70 mRNA in the caudate was much smaller than that in the cortex the maximum induction in the caudate (3 h) preceded that in the cortex (8 h). In contrast to the case of HSP70 mRNA, HSC70 mRNA was present in most cells of the sham brain, and was especially dense in hippocampal CA3 cells. Further induction of HSC70 mRNA was observed after reperfusion in the same cell populations, as in the case of HSP70 mRNA. HSC70 mRNA levels were significantly reduced in the caudate at 8 h when small amounts of HSP70 mRNA were still elevated. In the ipsilateral granule cells of the dentate gyrus and hippocampal CA3 cells a slight but significant induction of HSC70 mRNA was observed from 1 h to 1 day, while obvious induction of HSP70 mRNA never occurred. All the induced signals of HSP70 and HSC70 mRNA were diminished or returned to the sham level by 7 days, except for HSC70 mRNA in the caudate. These results are the first observations of the distribution of HSP70 and HSC70 mRNA after transient focal ischemia of rat brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

High-performance liquid chromatographic determination of pamaquine, primaquine and carboxy primaquine in calf plasma using electrochemical detection.

A high-performance liquid chromatographic method with electrochemical detection is described for quantification of pamaquine, primaquine and carboxy primaquine in calf plasma. After the proteins had been precipitated with acetonitrile, the drugs were separated on a 5-microns C18-modified polymer gel column with an isocratic mobile phase. The detection limit was 0.01 microgram/ml in plasma for all three compounds. The applicability of the method in pharmacokinetic studies was demonstrated by determining the plasma concentrations of the three substances in calves administered a single dose of pamaquine or primaquine.

Aminoquinolines↗
PubMed1992

Apoptotic cell death of primed CD45RO+ T lymphocytes in Epstein-Barr virus-induced infectious mononucleosis.

The expansion of activated T cells, characterized by the expression of CD45RO as well as HLA-DR antigens, is a central feature in acute infectious mononucleosis (IM) induced by primary infection of Epstein-Barr virus (EBV). However, the fate of these activated T cells in this disease is not clearly understood. We found that, on simple culture, a large proportion of T cells isolated from acute IM patients died rapidly, but only a few T cells from normal individuals did. Morphologic observations and DNA fragmentation analysis showed that the loss of viability of IM T cells after incubation was mediated by apoptosis. IM T cells undergoing apoptosis resided exclusively in the CD45RO+ populations of both CD4+ and CD8+ T cells, most of which were shown to coexpress apoptosis-related Fas antigen. Some cytokines such as interleukin-2 (IL-2), IL-5, and IL-6 could rescue IM T cells from apoptotic cell death. The results seemed to imply that most of primed (CD45RO+) T cells in acute IM might be subject to apoptotic cell death, possibly when leaving from the local sites actively producing certain soluble factors required for their survival. Our studies suggest the programmed cell death of peripheral mature T cells as a mechanism of antigen-driven selection.

Antigens, CD↗
PubMed1992

R1-20, a novel monoclonal antibody reacting with a molecule distinct from integrin family, induces homotypic cell aggregation.

R1-20, a novel mAb reacting with a cell surface Ag on normal human lymphocytes and leukemic cell lines, was shown to induce homotypic cell aggregation in leukemic cell lines. This phenomenon was specific to mAb R1-20 because antibodies recognizing CD2, CD7, CD28, and HLA-ABC failed to exhibit homotypic cell aggregation. Induction of aggregation by mAb R1-20 occurred at 37 degrees C, but not at 4 degrees C and required cytoskeletal integrity. Sodium azide, a metabolic inhibitor, had no effect on the aggregation. Distinct from lymphocyte function-associated Ag-1/intercellular adhesion molecule-1 interaction in which divalent cations are essential elements, R1-20-mediated aggregation was not abolished with EDTA treatment. The R1-20 Ag was determined as a molecule of M(r) 100 to 110 kDa in immunoprecipitation and immunoblotting methods, under both reducing and nonreducing conditions. The molecular composition is quite different from that of any known integrin molecule. The R1-20 Ag was expressed on resting and activated T Lymphocytes as well as on normal B lymphocytes. Monocytes and granulocytes had no detectable R1-20 Ag. Among the leukemia-derived cell lines we used, mAb R1-20 reacted with 18 of 32 T cell lines, 2 of 20 B cell lines, 2 of 3 non-T-non-B cell lines, 2 of 7 myelomonocytic cell lines, and 2 of 3 nonlymphoid-nonmyeloid cell lines. All EBV-transformed B cell lines examined (10 cell lines) were R1-20+. The spectrum of reactivity among the cell lines tested was different from that of known antiadhesion antibodies tested. All these findings indicate that the Ag recognized by mAb R1-20 may represent a new type of cell adhesion molecule.

Antibodies, Monoclonal↗
PubMed1992

Inhibition of Ca(2+)-dependent catecholamine release by myosin light chain kinase inhibitor, wortmannin, in adrenal chromaffin cells.

To elucidate the possible involvement of myosin light chain kinase (MLCK) in the mechanism of exocytosis, we studied effects of MLCK inhibitor, wortmannin, on the secretory function of bovine adrenal chromaffin cells. Preincubation of chromaffin cells with wortmannin inhibited both acetylcholine- and high K(+)-evoked catecholamine (CA) release. The IC50 for high K(+)-evoked CA release was 1 microM. When the cells were permeabilized with digitonin after wortmannin preincubation, Ca(2+)-dependent exocytosis was inhibited in a dose-dependent manner (IC50, 1 microM). These findings suggest the implication of MLCK in the Ca(2+)-triggered process in the machinery of exocytosis.

Acetylcholine↗
PubMed1992

Specific inhibition of NGF receptor tyrosine kinase activity by K-252a.

An involvement of protein tyrosine kinase in the transduction of the signals initiated by nerve growth factor (NGF) was investigated. A tyrosine kinase inhibitor, herbimycin, inhibited neurite outgrowth of rat pheochromocytoma PC12 cells induced by NGF but not that by dibutyryl-cAMP. Herbimycin and genistein blocked NGF-dependent activation of ras p21 whose essential function in neuronal differentiation has been reported. These observations suggested that tyrosine kinase activity is involved in the signaling pathways. K-252a, by contrast, inhibited NGF-induced but not EGF-dependent activation of ras p21. Tyrosine kinase activity of gp140trk, a constituent of NGF receptor, is activated by NGF for much a longer period compared to the activation of EGF receptor autokinase activity by EGF. We further demonstrated that autophosphorylation of gp140trk is selectively inhibited by K-252a.

Adrenal Gland Neoplasms↗
PubMed1992

Evidence for L-dopa systems responsible for cardiovascular control in the nucleus tractus solitarii of the rat.

Microinjections of L-DOPA (10-100 ng) into the medial area of the nucleus tractus solitarii (NTS) led to dose-dependent decreases in arterial blood pressure and heart rate in rats treated with i.p. 3-hydroxybenzylhydrazine, a central inhibitor of DOPA decarboxylase, or similarly with intraventricular 6-hydroxydopamine. D-DOPA, dopamine or noradrenaline (100 ng) produced no effect. L-DOPA methyl ester (1 microgram), a competitive antagonist for L-DOPA, microinjected into NTS, blocked the depressor and bradycardic responses to L-DOPA. High K+ (40 mM) released endogenous DOPA in a Ca(2+)-dependent manner from slices of the rat dorsomedial medulla including NTS. These results support the hypothesis that there exist systems of L-DOPA itself responsible for cardiovascular regulation in NTS of rats. This regulatory action of L-DOPA seems to be postsynaptic in nature.

Animals↗
PubMed1992

Evaluation of the expression of the cationic peptide gene in various types of leukocytes.

To understand the regulation of the production of antimicrobial cationic peptide (CP) in leukocytes, expression of the CP gene was evaluated in various types of leukocytes using guinea pig neutrophils, monocytes, macrophages, eosinophils, lymphocytes and bone marrow cells. Acid-urea PAGE and SDS-PAGE/immunoblot analyses showed that CP was present in neutrophils and bone marrow cells, but not in other leukocytes. Northern blot and transcription run-off analyses revealed that only bone marrow cells expressed CP mRNA and transcribed the CP gene. Interestingly, in situ hybridization analysis using bone marrow cells demonstrated that CP mRNA was expressed in the neutrophil precursor cells, such as promyelocytes and myelocytes, but was not detected in the mature neutrophils and other bone marrow cells. Moreover, immunocytochemical study indicated that CP was present in the neutrophil precursor cells and the mature neutrophils in the bone marrow. Thus, the CP gene appears to be expressed during a limited period of neutrophil maturation, and CP is likely synthesized by the neutrophil precursor cells in the bone marrow.

Animals↗
PubMed1992

A phenotypic and genotypic study of three node-based, low-grade peripheral T-cell lymphomas: angioimmunoblastic lymphoma, T-zone lymphoma, and lymphoepithelioid lymphoma.

Phenotypic and genotypic findings were correlated and compared for 35 specimens taken from 34 patients with three specific types of low-grade peripheral T-cell lymphoma: lymphoepithelioid (LeL), angioimmunoblastic (AILD), and T-zone (TzL) lymphoma. Frozen sections were stained by the double immunoenzymatic method using a combination of the monoclonal antibody Ki-67 for proliferating nuclei and those against lymphocyte surface antigens. Data were correlated by observing clonal rearrangements in the genes of the T-cell receptor beta chain (TCR beta). Of the 35 specimens studied, 32 (91%) were of predominantly CD4+ helper cell proliferation, and 21 (60%) showed the TCR beta gene rearrangement. There were 15 cases of AILD and TzL with predominantly helper cell proliferation, which contained a minimum of 21% CD4+Ki-67+ cells based on the total number of cells present in the specimen. Of these, 13 (87%) showed TCR beta rearrangement. In eight cases, containing a maximum of 20% CD4+Ki-67+ cells, only one (13%) showed any rearrangement. In addition, TCR beta rearrangement was observed in five of the nine cases of LeL, including two cases with only 12% CD4+Ki-67+ cells. For each of the three types, the proportion of CD4+ cells among the Ki-67+ population showed a relatively good correlation with the clonal TCR beta gene rearrangement. Moreover, there was a significant difference (P less than 0.05) in survival curves between groups with and without TCR beta rearrangement, although no obvious plateau was seen. These results suggest that the paucity of tumor cells in these lesions may account for the absence of a detectable band of rearrangements in some patients with one of these three specific types of low-grade peripheral T-cell lymphoma.

Antigens, CD↗