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Biomedical subjects

S Kobayashi

Publications and source records attributed to S Kobayashi.

At least 19 recordsLinked to original sources
PubMed1992

Visual and infrared input to the same dendrite in the tectum opticum of the python, Python regius: electron-microscopic evidence.

In snakes with infrared receptors, the optic tectum receives input from both the visual and the infrared senses. We investigated the infrared and optic fiber terminations in the tectum with a combination of horseradish peroxidase and degeneration labeling. In addition to synapses by visual and infrared fibers onto individual neurons, we were able to observe for the first time visual and infrared synapses on one and the same dendrite.

Animals↗
PubMed1992

Developmental change in subcellular location of Bp-1 protein with an ability to interact with both identifier sequence and its brain-specific transcript, BC-1 RNA.

Identifier sequences are transcribed to generate a brain-specific BC-1 RNA present as a ribonucleoprotein particle in the dendrites and somata of neurons. This ribonucleoprotein particle contains an identifier sequence-binding protein (Bp-1 protein). We report here the purification of BC-1 RNA and demonstrate that Bp-1 protein interacts directly with the RNA. We also demonstrate an accumulation of Bp-1 protein in the nucleus of brain cells from mouse fetus and newborns that precedes the postnatal increase in BC-1 RNA. Cytoplasmic Bp-1 protein present in a complex with BC-1 RNA increases postnatally with a concomitant decrease in nuclear Bp-1 protein. These observations suggest that Bp-1 protein may play a role(s) in the synthesis and nuclear export of BC-1 RNA.

Aging↗
PubMed1992

Platelet derived growth factor induces c-fos and c-myc mRNA in rat aortic smooth muscle cells in primary culture without elevation of intracellular Ca2+ concentration.

Platelet derived growth factor (PDGF) has been shown to induce c-fos and c-myc proto-oncogenes. In the present study, we investigated the effects of genistein, a tyrosine kinase inhibitor, and NiCl2, a Ca2+ influx blocker, on PDGF-induced Ca2+ transient and on expression of c-fos and c-myc mRNA. In the presence of extracellular Ca2+, PDGF induced elevation of intracellular Ca2+ concentration ([Ca2+]i) and increases in c-fos and c-myc mRNA, as detected by reverse transcription polymerase chain reaction (RT-PCR) and Northern hybridization. PDGF-induced [Ca2+]i elevation was composed of an initial transient increase (first component) followed by steady state elevation (second component). Genistein (10 microM) blocked the 1st, but not the 2nd, component of [Ca2+]i elevation induced by PDGF. NiCl2 (1 mM) and removal of extracellular Ca2+ inhibited the 2nd, but not the 1st, component. In the presence of 10 microM genistein and 1 mM NiCl2, PDGF induced c-fos and c-myc mRNA, although the [Ca2+]i elevation could be completely blocked by these two agents. These results indicate that elevation of [Ca2+]i is not a prerequisite condition for PDGF to induce c-fos and/or c-myc mRNA in rat aortic smooth muscle cells in primary culture.

Animals↗
PubMed1992

cAMP induces up-regulation of ETA receptor mRNA and increases responsiveness to endothelin-1 of rat aortic smooth muscle cells in primary culture.

The effects of cAMP on the expression of ETA (ET-1 selective type) receptor mRNA and on the response to endothelin-1 (ET-1) were investigated in rat aortic smooth muscle cells in primary culture, using reverse transcription polymerase chain reaction (RT-PCR) and fura-2 microfluorometry of cytosolic Ca2+ concentrations ([Ca2+]i). Incubation of the smooth muscle cells with 10 microM forskolin and 10 microM 3-isobutyl-1-methyl-xanthine (IBMX) induced an increase in ETA receptor mRNA by 420% of control after 24 hours. ET-1 induced a biphasic increase in [Ca2+]i, first transient and second sustained phases. Incubation of the smooth muscle cells with forskolin and IBMX for 24 hours increased the [Ca2+]i response by 849% in the first phase and 286% in the second phase, compared with time-matched controls. From these results, we conclude that cAMP induces an up-regulation of the ETA receptor mRNA and increases responsiveness to ET-1 of rat aortic smooth muscle cells in primary culture.

1-Methyl-3-isobutylxanthine↗
PubMed1992

Arachidonic acid inhibits myosin light chain phosphatase and sensitizes smooth muscle to calcium.

Arachidonic acid (AA) increased, at constant Ca2+, the levels of force and 20-kDa myosin light chain (MLC20) phosphorylation in permeabilized smooth muscle, and slowed relaxation and MLC20 dephosphorylation. The Ca(2+)-sensitizing effect of AA was not inhibited by inhibitors of AA metabolism (indomethacin, nordihydroguaiaretic acid, or propyl gallate), of protein kinase C (pseudopeptide) or by guanosine-5'-O-(beta-thiodiphosphate) and was abolished by oxidation of AA in air. A non-metabolizable AA analog, 5,8,11,14-eicosatetraynoic acid) also had Ca(2+)-sensitizing effects. Extensive treatment with saponin abolished the Ca(2+)-sensitizing effects of phorbol 12,13-dibutyrate and guanosine-5'-O-(gamma-thiotriphosphate), but not that of AA. A purified, oligomeric MLC20 phosphatase isolated from gizzard smooth muscle was dissociated into subunits by AA, and its activity was inhibited toward heavy meromyosin but not phosphorylase. We conclude that AA may act as a messenger-promoting protein phosphorylation through direct inhibition of the form of protein phosphatase(s) that dephosphorylate MLC20 in vivo.

Animals↗
PubMed1992

The 10 S BC-1 ribonucleoprotein particle contains identifier sequence-binding proteins that interact with an array of GCAAG/CTTGC motifs between split promoter sequences for RNA polymerase III.

BC-1 RNA is a brain-specific small RNA transcript of identifier sequences present in the somas and dendrites of neurons. We recently reported that the RNA is complexed with a protein(s) to form a 10 S ribonucleoprotein particle (Kobayashi, S., Goto, S., and Anzai, K. (1991) J. Biol. Chem. 266, 4726-4730). We demonstrate here that this 10 S BC-1 ribonucleoprotein particle contains a DNA-binding protein(s) (Bp-1 protein) capable of interacting with a region between split promoter sequences for RNA polymerase III within the identifier sequences. The region has short inverted repeats: a perfect octanucleotide repeat (GCGCTTGCCTAGCAAGCGC) and an imperfect heptanucleotide repeat (GCCTAGCAAGCGCAAGGC), each of which contains a GCAAG/CTTGC motif. We also demonstrate that the binding of this protein either to the array of pentamer motifs or to BC-1 RNA is mutually exclusive. The molecular masses of photo-cross-linking adducts of Bp-1 protein to a 32P-labeled GCAAG/CTTGC motif-specific probe were estimated to be about 31 and 36 kDa, indicating that two species of Bp-1 proteins may be present in the brain.

Animals↗
PubMed1992

Epimorphin: a mesenchymal protein essential for epithelial morphogenesis.

A novel 150 kd protein expressed on the surface of mesenchymal cells of mouse embryonic tissues was identified. A monoclonal antibody to this molecule inhibited various processes of epithelial morphogenesis, such as hair follicle growth and lung epithelial tubular formation, in organ cultures of these tissues. Sequence analysis of cDNA encoding this protein revealed that it had 289 amino acids with a hydrophobic stretch at the C-terminus. NIH 3T3 cells transfected with the cDNA of this protein expressed the exogenous 150 kd protein on their surface. When lung epithelial cells were cocultured with these transfected cells, they showed normal tubular morphogenesis, but not with untransfected NIH 3T3 cells. These results indicate that this protein, termed epimorphin, plays a central role in epithelial-mesenchymal interactions.

Amino Acid Sequence↗
PubMed1992

c-myc expression is down-regulated by cell-cell and cell-extracellular matrix contacts in normal hepatocytes, but not in hepatoma cells.

Primary culture of adult rat hepatocytes resulted in marked increase of c-myc expression within a few hours. The high level of c-myc mRNA was maintained throughout culture on collagen-coated dishes, but decreased greatly with time during culture on collagen-gel or matrigel. Expression of c-myc was also down-regulated at high cell density. The decrease in its expression appeared closely related to inhibitions of DNA synthesis and cell spreading. In contrast, hepatoma H4TG cells showed a high level of c-myc expression which was not affected by culture on any extracellular matrices examined or by the cell density. These results suggest that up-regulation of expression of the c-myc gene is linked to G0 to G1 transition during cell cycle progression, which in normal hepatocytes is strictly regulated by cell-cell and cell-extracellular matrix interactions, but that this control mechanism is defective in malignant hepatic tumor cells.

Animals↗
PubMed1992

Endothelin-1 inhibits and enhances contraction of porcine coronary arterial strips with an intact endothelium.

Using front-surface fluorometry and fura-2-loaded porcine coronary arterial strips with an intact endothelium, changes in cytosolic Ca2+ concentrations ([Ca2+]i) and tension of smooth muscle were simultaneously monitored in an attempt to determine the vasoactive properties of endothelin-1 (ET-1). ET-1 in low concentrations (0.1-1nM) caused a significant transient decrease in [Ca2+]i and tension of the strips precontracted with 10(-7) M U-46619. The maximal decreases in [Ca2+]i and tension were obtained with 0.6nM ET-1. In higher concentrations (1nM-100nM), there was no reduction in [Ca2+]i or tension; the contraction induced by U-46619 was potentiated. The decreases in [Ca2+]i and tension induced by ET-1 were inhibited by the mechanical removal of the endothelium or by pretreatment with NG-nitro-L-arginine and were slightly attenuated by indomethacin. Thus, ET-1 in low concentrations can induce endothelium-dependent transient relaxations accompanied by transient reductions of [Ca2+]i in isolated porcine coronary arteries. This effect is mainly mediated by the release of endothelium-derived relaxing factor.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1992

Catecholamine histofluorescence depletion in the infarcted brain parenchyma but not in the adventitia of the occluded cerebral arteries in rats.

The effect of acute cerebral ischemia on the catecholamine-containing nerve fibers in the brain parenchyma and in the adventitia of the cerebral arteries was studied in the rat. Unilateral cerebral ischemia was produced with an intraluminal thread technique which does not damage the adventitia of cerebral arteries. One to three days after surgery the ischemic damage of the brain was consistently observed in the territory of the middle cerebral artery of the operated side. Depletion of catecholamine histofluorescence was observed in the infarcted brain parenchyma. However, in the adventitia of the middle cerebral arteries of the operated side, catecholamine histofluorescence remained intact. No detectable changes in fluorescence were observed in the brain parenchyma or adventitia of the cerebral arteries in the contralateral side. The results indicate that the perivascular catecholamine-containing nerve fibers are not impaired by the intraluminal occlusion of the cerebral artery in the early stage of ischemia.

Animals↗
PubMed1992

N.m.r. study on the formation and geometry of inclusion complexes of 6-O-(alpha-maltosyl)cyclomalto-hexaose and -heptaose with p-nitrophenol in aqueous solution.

The formation and molecular geometry of inclusion complexes of some branched cyclomaltaoses with p-nitrophenol in aqueous solution have been investigated by using high-resolution 1H-n.m.r. spectroscopy. 6-O-(alpha-Maltosyl)cyclomalto-hexaose and -heptaose were found to form 1:1 inclusion complexes with p-nitrophenol, and the dissociation constants for their complexes are quite similar to those for corresponding unbranched cyclomaltaose-p-nitrophenol complexes, indicating that formation of these inclusion complexes is not hampered by the maltosyl branch. From measurement of nuclear Overhauser enhancements, it was concluded that the maltosyl branch is not situated over the entrance of the cavity.

Carbohydrate Sequence↗
PubMed1992

Changes in cerebral energy metabolism and calcium levels in relation to delayed neuronal death after ischemia.

Using a brief transient ischemic model, we examined changes in regional tissue calcium content and energy metabolism in the hippocampus. In the CA1 region, tissue calcium ions began to increase 24 h after reperfusion, accompanied by changes in tissue pH and ATP. In the CA3 region, energy metabolism remained unchanged for 72 h after reperfusion, and the calcium pool was first noted 24 h after reperfusion, while tissue calcium ions began to increase 48 h after reperfusion. These results suggest that the neurons in the CA3 region seem to survive because of the well-preserved metabolic function to cope with excessive calcium ions.

Adenosine Triphosphate↗
PubMed1992

Reduction in the ADP release from shear-stressed red blood cells by fish oil administration.

Fish oil concentrate (5.4 g/day) was administered to 8 young male volunteers and to 7 middle-aged male volunteers for 1 week. ADP released into the supernatant of red blood cell (RBC) suspension by a shear stress of 375/sec for 3 min was measured before and after fish oil administration. Before the administration the ADP release from shear-stressed RBCs in the middle-aged group was significantly higher than in the young group. After the administration the ADP release was reduced significantly in the young group (by 46%, p less than 0.001) and nonsignificantly in the middle-aged group (by 54%, p = 0.09). If the two groups were combined, the reduction was also significant (by 50%, p less than 0.005). This reduction was significantly correlated with the improvement of RBC filterability after fish oil administration (n = 13, r = 0.62, p less than 0.05). We suggest that the reduction of the ADP release from shear-stressed RBCs is one of the mechanisms of action of eicosapentaenoic acid against thrombotic disease.

Adenosine Diphosphate↗
PubMed1992

Interleukin-11 enhances human megakaryocytopoiesis in vitro.

We investigated the effect of recombinant human interleukin-11 (rhIL-11) on human megakaryocytopoiesis. Nonadherent and T-cell-depleted human bone marrow (BM) mononuclear cells were cultured in a serum-free agar culture system. rhIL-11 alone did not stimulate the growth of human megakaryocyte colonies. However, when rhIL-11 was combined with optimal or suboptimal doses of rhIL-3, the number and size of the megakaryocyte colonies increased. The same results were obtained when highly purified BM CD34-positive cells were used as target cells. Next, we investigated the effect of rhIL-11 on the ploidy of megakaryocytes. The ploidy distribution of individual cells in megakaryocyte colonies obtained by rhIL-11 in combination with rhIL-3 was significantly shifted towards higher values. Furthermore, when highly purified CD41-positive BM cells were cultured in the presence of rhIL-11, the ploidy distribution was shifted towards higher values. This effect was not suppressed by anti-IL-6 antibody. These results suggest that rhIL-11 acts directly as a megakaryocyte potentiator and may play a role in regulating human megakaryocytopoiesis.

Antigens, CD↗
PubMed1992

A simplified approach for evaluation of hepatic drug-oxidizing activity with a simultaneous determination of caffeine and trimethadione and their demethylated metabolites in rats with a selective cytochrome P-450 inducer.

We determined the blood concentrations of caffeine (CA) and its three primary dimethylxanthine metabolites: theobromine (TB), paraxanthine (PX), and theophylline (TP), and trimethadione (TMO) and its demethylated metabolite dimethadione (DMO) after the simultaneous administration of CA (10 mg kg-1) and TMO (4 mg kg-1) to rats pretreated with phenobarbital (PB:40 and 80 mg kg-1 i.p. daily for 3 days) and 3-methylcholanthrene (MC: 10 and 20 mg kg-1 i.p. daily for 2 days). After the oral administration of CA and TMO, the PB-pretreated rats showed a significant increase in TMO metabolism, whereas the CA metabolism was greatly accelerated in rats pretreated with MC. In five pretreated groups, there were correlations which were determined 1 h after the administration of CA and TMO, between the plasma half-life (t1/2) of CA and the TB/CA, PX/CA, and TP/CA ratios. The coefficients of correlation (r) ranged from -0.881 to -0.908, and the coefficients of correlation between the CL of CA and the TB/CA, PX/CA, and TP/CA ratios ranged from 0.959 to 0.989. There were high correlations between the t1/2 of TMO and the DMO/TMO ratio at 1 h after administration with r = -0.966, and between the CL of TMO and the DMO/TMO ratio with r = 0.971. The above results suggest that one blood sampling after the simultaneous administration of CA and TMO enables prediction of the degree of each hepatic drug-oxidizing activity because the P-450 isozymes involved in metabolism of CA and TMO are different.

Animals↗
PubMed1992

Adenomatous goitre: therapeutic strategy, postoperative outcome, and study of epidermal growth factor receptor.

A total of 377 patients with histologically proven adenomatous goitre was operated on, 34 as a second operation, and assessed for postoperative outcome (including the incidence of unsuspected malignancy) and immunohistochemical localization of epidermal growth factor receptor. In primary surgery, enucleation of all the nodules was carried out. Patients requiring reoperation showed multicystic degenerate nodules involving one or both lobes. A coexistent cancer was observed in 18 patients (4.8 per cent). The immunohistochemically detected expression of epidermal growth factor receptor in adenomatous goitre was more evident in patients with multinodular lesions. Near-total lobectomy of the involved side(s) is desirable for the prevention of recurrence and complications after operation.

Adolescent↗