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Y Ohya

Publications and source records attributed to Y Ohya.

178 records · Page 10Linked to original sources
PubMed1986

Calcium-sensitive cls4 mutant of Saccharomyces cerevisiae with a defect in bud formation.

A calcium-sensitive cls4 mutant of Saccharomyces cerevisiae ceased dividing in the presence of 100 mM CaCl2, producing large, round, unbudded cells. Since its DNA replication and nuclear division still continued after interruption of normal budding, the cls4 mutant had a defect in bud formation in Ca2+-rich medium. Its calcium content and calcium uptake activity were the same as those of the wild-type strain, suggesting that the primary defect of the mutation was not in a Ca2+ transport system. Genetic analysis showed that the cls4 mutation did not complement the cdc24-1 mutation, which is known to be a temperature-sensitive mutation affecting bud formation and localized cell surface growth at a restrictive temperature. Moreover, cls4 was tightly linked to cdc24, and a yeast 3.4-kilobase-pair DNA fragment carrying both the CLS4 and CDC24 genes was obtained. These results suggest that the cls4 mutation is allelic to the cdc24 mutation. Thus, Ca2+ ion seems to control bud formation and bud-localized cell surface growth.

Biological Transport↗
PubMed1986

Membrane currents recorded from a fragment of rabbit intestinal smooth muscle cell.

Properties of ionic currents in smooth muscle membranes of the longitudinal muscle layer of the rabbit ileum were investigated using the single electrode voltage clamp method. In the present experiments, this method was applicable only to the smooth muscle ball (fragment) and not for the dispersed whole cell, because of incompleteness of the voltage clamping. A voltage step elicited a transient inward current followed by an outward current. This outward current was partly inhibited by Mn2+ or nisoldipine or by a reduction in the extracellular [Ca2+] ([Ca2+]o). Tetraethylammonium (TEA) reduced the delayed outward current in a dose-dependent manner, but 50 mM TEA did not produce a complete block of a residual current. When the pipette contained K+-free (Cs+ with TEA+) solution, the residual outward current was abolished. The inward current was elicited at -30 mV (holding potential of -60 mV) and reached the maximal value at +10 mV; the polarity was reversed at +60 mV. This inward current depended on the [Ca2+]o and was blocked by Mn2+ or nisoldipine. Ba2+ also permeated the membrane, and the inward current evoked by Ba2+ was also blocked by Mn2+ or nisoldipine. Reduction of [Na+]o in a solution containing 2.4 mM Ca2+ neither modified the current-voltage relation nor the decay of the inward current, but when [Ca2+]o was reduced to below 1 microM, Na+ permeated the membrane and was blocked by nisoldipine. In conclusion, ionic currents were recordable from the fragmented ball of the longitudinal muscle of rabbit ileum. There were at least two K+ currents as the outward current (Ca2+-dependent K+ and delayed K+ currents) and a Ca2+ current as the inward current. The property of the Ca2+ channel was similar to that observed with other preparations.

Animals↗
PubMed1986

Microvascular actions of platelet-activating factor on rat gastric mucosa and submucosa.

Intravenous infusion of platelet-activating factor (PAF or AGEPC) induces extensive acute hemorrhagic damage in the ra gastric mucosa. The effects of PAF have now been investigated on several microcirculatory parameters in the rat gastric mucosa. Infusion of PAF (25-100 ng X kg-1 X min-1 iv) dose-dependently reduced systemic arterial blood pressure and mucosal blood flow, as determined by hydrogen gas clearance. Microscopic observation likewise indicated a dose-dependent slowing of mucosal capillary blood flow, as determined by red blood cell velocity after PAF infusion with stasis of flow at the highest dose. These actions were not the consequence of vasoconstriction, since there was no significant change in arteriolar and venular vessel diameter in the submucosa during PAF infusion, although a dose-related slowing and stasis of blood flow was observed. There was no capillary leakage of plasma protein in the gastric mucosa during PAF infusion, as determined by a fluorescence marker (FITC-BSA) technique. The precursor and breakdown product, lyso-PAF (200 ng X kg-1 X min-1) had no significant action on any of these microcirculatory parameters. These observations support the suggestion that microvascular changes leading to stasis may contribute to the ulcerogenic actions of PAF.

Animals↗
PubMed1986

An analysis of polyclonal B cell activation in Sjögren's syndrome. Characterization of B cell lines spontaneously established from the peripheral blood.

We intended to analyze the mechanism of polyclonal B cell activation in patients with Sjögren's syndrome (SS). Peripheral blood mononuclear cells (PBMC) were grown in bulk cultures without stimulation. Four cell lines (SS-1, SS-7, SS-10, SS-14) were successfully established from SS patients but none from normal controls. All of the cell lines were B cell origin possessing B1, B4 and HLA-DR antigens on their surfaces and were positive for EB virus associated nuclear antigens (EBNA). Both SS-7 and SS-10 spontaneously produced IgM whereas SS-1 and SS-14 IgG. All the cell lines except SS-7 expressed receptors for B cell stimulatory factors (BSF). Culture supernatants of these cell lines contained multiple biological activities including those for IL-1, IL-2, IL-3 and BCGF. These data suggest that B cells are polyclonally activated in vivo presumably by EB virus in SS and these activated B cells might perturb immunoregulatory system by producing multiple lymphokines.

B-Lymphocytes↗
PubMed1985

Prostaglandin cytoprotection: role of microcirculatory changes.

Both the fluorescent in vivo microscopic study and the hydrogen-gas-clearance study revealed complete absence of blood flow in the areas of gross ethanol damage. PG pretreatment prevented this cessation of flow. However, the hydrogen-gas-clearance study demonstrated that PG administered in a cytoprotective dose did not increase blood flow. It maintained blood flow by some other mechanism. The final in vivo microscopic studies demonstrated a marked leak of albumin from microvessels and slowing and then cessation of flow very shortly after topical ethanol application. This suggests that an increase in blood viscosity due to plasma leak may be the mechanism of the ethanol-induced flow stasis. PG prevented this leak. PG cytoprotection, by preventing this permeability change, maintains mucosal blood flow and may thus protect the mucosa against the deeper and more severe ethanol injury.

16,16-Dimethylprostaglandin E2↗
PubMed1985

Potentiation of histamine-induced microvascular permeability by prostaglandin E2 in rat mesentery.

The effect of prostaglandin E2 and histamine and their interaction on microvascular permeability in the rat mesentery was examined using fluorescent in vivo microscopy. Leak of a fluorescein-albumin conjugate from microvessels was determined 3 min after the topical application of prostaglandin E2 and/or histamine. The size of the leak (micron 2) was quantitated using a grid over the face of the videomonitor. To determine the role of endogenous prostaglandin, some rats were pretreated with 10 mg kg-1 indomethacin intravenously. All studies were performed coded. Dose-response studies performed with either prostaglandin E2 or histamine alone revealed that each agent increased microvascular permeability in a dose-related fashion. On a molar basis, prostaglandin E2 was more potent than histamine in this regard. When a low dose of prostaglandin E2 was administered together with a low or intermediate dose of histamine, the size of the resulting leak was significantly greater than the sum of the size of leak produced by each agent given separately. When rats were pretreated with 10 mg kg-1 indomethacin intravenously to inhibit prostaglandin synthesis, the histamine dose response was shifted to the right. From these experiments, we conclude that: In the rat mesentery, both topical prostaglandin E2 and histamine increase microvascular permeability to macromolecules in a dose-related fashion. Prostaglandin E2 is significantly more potent than histamine in this regard. Both exogenous and endogenous prostaglandin potentiate histamine's effect on microvascular permeability.

Animals↗
PubMed1984

Genetic study of the role of calcium ions in the cell division cycle of Saccharomyces cerevisiae: a calcium-dependent mutant and its trifluoperazine-dependent pseudorevertants.

A cal1-1 mutant of the yeast Saccharomyces cerevisiae showing Ca2+-dependent growth was isolated. Its growth continued exponentially in Ca2+-rich medium, but stopped in Ca2+-poor medium at 37 degrees C. Mg2+ ions could not replace Ca2+ ions. In Ca2+-poor medium, the mutant cells stopped growing homogeneously at the stage of cell division cycle with a tiny bud. The nucleus in these arrested cells was in the G2 stage, judging from observation after nuclear staining and determination of the DNA content. Trifluoperazine-dependent pseudorevertants, which could grow in the presence of 20 microM to 80 microM trifluoperazine in Ca2+-poor medium at 37 degrees C, were obtained from this cal1-1 mutant. The suppressor mutation, tfr1, itself conferred trifluoperazine resistance. Other calmodulin inhibitors structurally unrelated to trifluoperazine had similar effects to trifluoperazine on these pseudorevertants. These results suggest that Ca2+ ions and a calmodulin play important roles in the yeast cell division cycle at the stage of bud growth and nuclear division.

Calcium↗
PubMedDate not supplied

Whole-cell voltage clamp and intracellular perfusion technique on single smooth muscle cells.

Using freshly isolated single smooth muscle cells prepared by collagenase treatment, membrane currents were recorded by whole-cell voltage clamp. Intracellular constituents were modified by using an intracellular perfusion technique, i.e., pipette solutions were continuously exchanged from control to test solutions during current recording. In smooth muscle cells, intracellular application of ATP, but not cyclic AMP, enhanced the amplitude of Ca2+ currents and prevented current run-down. In addition, with this stabilization of Ca2+ current recording by ATP, introduction of various chemicals into the cell using the intracellular perfusion technique is useful for investigations of regulation of ion channels in smooth muscle cells.

Adenosine Triphosphate↗
PubMedDate not supplied

Scleral fibroblasts of the chick embryo differentiate into chondrocytes in soft-agar culture.

Scleral fibroblasts, perichondrial cells of the scleral layer of the 12-day chick embryo, always manifest a fibroblastic morphology in monolayer culture. In soft-agar culture, these cells produce two types of colonies. One type of colony, F-type, consists of adherent fibroblastic cells, and the other, C-type, is composed of scattered round chondrocytic cells. Cells of the C-type colony are surrounded by a halo of extracellular matrix, positive with Alcian blue and with an antibody to cartilage-specific proteoglycan. When a single fibroblast clone in monolayer, derived from a single scleral fibroblast, is subcultured into soft agar, the cells give rise to both C-type and F-type colonies. Further, it was found that cells constituting F-type colonies eventually separate and become spherical, and the F-type colony converts to a C-type colony (C-type conversion). In regard to the C-type convertibility, the primary fibroblast clones were divided into four categories, early time differentiating, middle-time differentiating, late-time differentiating and nondifferentiating. This suggests that the scleral perichondrial layer of the 12-day chick embryo is composed of a variety of cells with different chondrogenic potentialities maintained in each individual cell.

Agar↗
PubMedDate not supplied

Yeast calmodulin: structural and functional elements essential for the cell cycle.

The budding yeast Saccharomyces cerevisiae is a suitable organism for studying calmodulin function in cell proliferation. Genetic studies in yeast demonstrate that vertebrate calmodulin can functionally replace yeast calmodulin. In addition, expression of half of the yeast calmodulin molecule is found to be sufficient for cell growth. Characterization of conditional-lethal mutants of yeast calmodulin as well as the intracellular distribution of calmodulin have suggested that at least two cell cycle steps require calmodulin function. One is nuclear division and the other is the maintenance of cell polarity. A current focus is to understand which kinds of target proteins are involved in mediating the essential functions of yeast calmodulin in these processes. Thus far, three yeast enzymes whose activity is regulated by calmodulin have been identified.

Calmodulin↗
PubMedDate not supplied

Nonketotic hyperglycinemia: treatment with NMDA antagonist and consideration of neuropathogenesis.

Patients with neonatal-onset nonketotic hyperglycinemia have high-glycine content in cerebrospinal fluid (CSF) which is believed to be a cause of intractable neurologic manifestations. The glycine receptor was believed to be inhibitory in the central nervous system; however, a newly discovered glycine receptor is of the excitatory N-methyl-D-aspartate (NMDA) receptor type, which cannot be antagonized by strychnine. The NMDA receptor antagonist, ketamine, was administered to a patient with nonketotic hyperglycinemia; he demonstrated some improvement in hyperirritability, voluntary movement, and electroencephalographic findings. Strychnine therapy had been administered before this trial of NMDA antagonist, but without improvement. The respiratory condition improved with the reduction of the CSF glycine level after withdrawal of sodium valproate. Our findings indicate that high-glycine content in CSF may affect the brain in different ways via NMDA and classic glycine receptors.

Brain↗
PubMedDate not supplied

Release behaviour of 5-fluorouracil from chitosan-gel microspheres immobilizing 5-fluorouracil derivative coated with polysaccharides and their cell specific recognition.

In order to provide a device releasing drugs in a controlled manner and having targetability to specific organs or cells, chitosan-gel microspheres, CMS, crosslinked with glutaraldehyde, immobilizing 1-[N-(5-aminopentyl) carbamoyl]-5-fluorouracil, 1, coated with anionic polysaccharides, such as 6-O-carboxymethyl-N-acetyl-alpha-1,4-polygalactosamine (CM-NAPGA), 6-O-carboxymethyl-chitin, alginic acid and heparin, by polyelectrolyte complex membrane formation were prepared. When chitosan was crosslinked with glutaraldehyde, 1 was simultaneously immobilized into CMS by Schiff's base formation. Average diameter of CMS obtained was estimated to be about 0.5-1.0 micron by SEM observation. In physiological saline media, only free 5-FU was released from the CMS but 1 and any 5-FU derivative was not. Release rate of 5-FU from the CMS was reduced by coating with polyelectrolyte complex membrane of cationic chitosan and anionic polysaccharides. CMS coated with CM-NAPGA showed a lectin-mediated specific aggregation phenomenon by addition of Abrus precatorius agglutinin. Moreover, the CMS immobilizing 1 coated with CM-NAPGA showed higher growth-inhibitory effect against SK-Hep-1 (human hepatoma) cells in vitro than the CMS coated with other polysaccharides.

Carcinoma, Hepatocellular↗