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Biomedical subjects

S Sasakawa

Publications and source records attributed to S Sasakawa.

At least 19 recordsLinked to original sources
PubMed1993

Na+/H+ exchange activity induced by thrombin is not inhibited by protein kinase inhibitors, staurosporine, K-252a, H-7 and sphingosine, in human platelets.

In human platelets stimulated with thrombin (40 mU/ml), Na+/H+ exchange activity [the ethylisopropylamiloride (EIPA)-sensitive increase of cytoplasmic pH (pHc)] and protein kinase C (PKC) activity [phosphorylation of 47 kDa protein (P47), a substrate for PKC] were determined in the presence of protein kinase inhibitors, staurosporine (0.05-1 microM), K-252a (0.5-10 microM), H-7 (100 microM) and sphingosine (20-40 microM). Staurosporine and K-252a completely blocked PKC activity. H-7 and sphingosine reduced the P47 phosphorylation to 64% and 35%, respectively. On the contrary, the thrombin-induced pHc increase was not inhibited by staurosporine, K-252a or H-7. Sphingosine elevated the resting pHc by 0.26-0.42 independently of the Na+/H+ exchanger and inhibited the thrombin-induced pHc increase. However, after the resting pHc elevated by sphingosine had been reduced to the initial level by adding sodium propionate, the thrombin-induced pHc increase was observed again. These results suggested that sphingosine inhibited the thrombin-induced pHc increase by elevating the resting pHc. Thus, we concluded that the Na+/H+ exchanger was activated by thrombin through a pathway independent of PKC.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Changes of platelet functions by extracellular sodium ion.

Effects of extracellular Na+ on platelet responses were examined. Cytoplasmic pH decreased by stimulation with thrombin, TPA and AA in Na(+)-containing buffer as well as in Na(+)-free buffer. Thrombin-induced aggregation and serotonin release were higher in Na(+)-containing buffer, but TPA- and A23187-induced responses exhibited lower values. Thrombin-stimulated platelet in Na(+)-free buffer started to aggregate by the addition of NaCl. Inhibition of thrombin-induced aggregation by indomethacin was apparently weaker than that by removal of Na+. These results suggest that the changes of platelet responses by removal of Na+ is due to the effect of Na+ ion itself, not by the inhibition of Na+/H+ exchanger, and that Na+ affects on mechanisms other than arachidonic acid mobilization.

Amiloride↗
PubMed1990

De novo protein synthesis is essential to human interferon gamma gene expression by the stimulation with polyI:polyC.

Transcription of human interferon (IFN) gamma gene is induced in human peripheral lymphocyte nylon-nonadherent cells (NNA cells) by double strand RNA poly I:poly C [(1985) J. Interferon Res. 5, 77-84]. In this report, the necessity of de novo protein synthesis in an early stage of IFN gamma gene expression is described. For induction of IFN gamma gene expression, only initial 4 h treatment of poly I:poly C to NNA cells is sufficient. Addition of inhibitor of protein synthesis, cycloheximide (CHX), at an early stage of induction periods (0-4 h) inhibits the IFN gamma induction by poly I:poly C. Cell free translation assay using RNAs isolated from NNA cells which are induced by poly I:poly C in the presence of CHX reveals that in these RNAs, IFN gamma mRNA does not exist. These results demonstrate that CHX inhibits de novo synthesis of a certain protein (or proteins) and for lack of the protein(s), IFN gamma mRNA cannot be transcribed. The evidence is also described in this report which suggests that the essential protein(s) might be that (those) involved in protein kinase C (pkC) activation.

Cycloheximide↗
PubMed1990

Mechanisms of blood coagulation induced by latex particles and the roles of blood cells.

Latex particles with highly negative or positive charges shortened the clotting time of whole blood and platelet-rich plasma and activated platelet factor 3. Platelet-poor plasma was clotted by the particles with a highly negative charge, but not by those with a positive charge, except hydrophobic particles. Blood coagulation by positively-charged particles was attributed to platelet activation. An enhancement of blood coagulation was also observed in the presence of erythrocytes, leucocytes, their cell membranes or negatively charged phospholipids, and phosphatidylserine instead of platelets. Hydrophilic and low-charged particles suppressed blood coagulation.

Biocompatible Materials↗
PubMed1989

Cytoplasmic pH dependency of Na+/H+ exchange in human platelets activated with thrombin, arachidonic acid, A23187 and TPA.

The cytoplasmic pH (pHc) of human platelets was lowered to 6.8-7.2 by treatment with various doses of nigericin (K+/H+ ionophore), then these platelets were stimulated with thrombin, arachidonic acid (AA), A23187 or 12-o-tetradecanoylphorbol-13-acetate (TPA), to monitor the pHc changes using a pH-sensitive fluorescent dye, BCECF. The pHc increased with the stimulation in an amiloride-sensitive manner only when the resting-pHc was lower than a certain value (pHc 6.99 for thrombin-stimulation, 6.95 for AA, 7.04 for A23187 and 6.95 for TPA, n = 3). At a higher resting-pHc, the pHc decreased. Similar observations were found using platelets acid-loaded by Na-acetate treatment. These results suggest that stimulation-induced activation of the Na+/H+ exchanger depends on cytoplasmic H+ concentration, and it can function properly only when the resting-pHc is lower than about pHc 7.

Arachidonic Acid↗
PubMed1989

The roles of protein kinase C and cyclic nucleotide dependent kinase in signal transduction in human interferon gamma induction by poly I:poly C.

The signal transduction mechanisms involved in interferon (IFN) gamma induction in human peripheral mononuclear lymphocyte nylon-nonadherent cells (NNA cells) by stimulation with poly(I):poly(C) are investigated. Significant enhancement of IFN gamma production by poly(I):poly(C) is observed in the presence of the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA, a protein kinase C (PKC) activator). Our study shows that in NNA cells, poly(I):poly(C) with or without TPA causes prolonged activation of cytosolic PKC of NNA cells for at least 120 min. The level of activation of PKC is quite remarkable in the case of the combined stimulation by poly(I):poly(C) and TPA as compared to poly(I):poly(C) alone. This demonstrates that prolonged activation of cytosolic PKC for at least 120 min is essential for high levels of production of IFN gamma. Moreover, inhibition experiments using the PKC inhibitor H-7 and cAMP-dependent protein kinase inhibitor H-8 suggest that the mechanism of signal transduction with regard to PKC is involved in stimulation of IFN gamma production in NNA cells by poly(I):poly(C) in the presence of TPA and that along with PKC, cAMP-dependent protein kinase is probably involved in induction of IFN gamma by stimulation with poly(I):poly(C) alone.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

Effect of cytoplasmic pH on platelet activation by arachidonic acid.

The effects of cytoplasmic acidification by nigericin, monovalent cation ionophore, on platelet activation induced by arachidonic acid (AA) were examined. AA-induced aggregation and TXB2 formation were inhibited with decreasing cytoplasmic pH (pHc). Although TXA2 receptor agonists (STA2, U-46619)-induced aggregation of some platelet samples were suppressed by nigericin, the suppression did not correspond to the acidification of pHc. Aggregation initiated by collagen was inhibited by nigericin. The inhibition, however, was not observed in platelets treated by aspirin. These results suggest that the inhibition of AA-induced aggregation by cytoplasmic acidification is due to inhibition of the metabolism of AA to TXA2.

Anti-Bacterial Agents↗
PubMed1989

Platelet aggregation induced by latex particles. I. Effects of size, surface potential and hydrophobicity of particles.

Latex particles induced platelet aggregation associated with the release of ATP from the platelets. The smaller the diameter of particles having the same surface structure, the greater numbers or greater total surface area of particles were required for both reactions. The higher hydrophobic and higher negatively charged particles, having a diameter of about 0.3 micron, induced platelet aggregation most easily. Hydrophilic particles without high negative surface potential activated platelets only a little. Particle-induced platelet aggregation is not only caused by colloidal electronic force and hydrophobic interaction between platelets and latex particles but also by factors concerning cell activation.

Adenosine Triphosphate↗
PubMed1989

Leukocyte-poor platelet concentrates at the bedside by filtration through Sepacell-PL.

We developed a new filter, 'Sepacell-PL', consisting of a blood administration set for the preparation of leukocyte-poor platelet concentrates at the patient's bedside. This filter is packed with 1.8 microns polyester fibers coated with a new polymer, and has a volume of 14 ml. Sepacell-PL removed more than 99% of the leukocytes while approximately 93% of platelets were recovered from 10 units of platelet concentrates which contained 5 x 10(8) leukocytes and 3 x 10(11) platelets. The functions of pre- and postfiltrated platelets were unchanged. The filtration procedure is very simple, without priming with saline to remove air and wet the filter. Moreover, platelet concentrates can be passed through the filter at a flow rate of 4 ml/min, or at a higher flow rate of 54 ml/min by gravity.

Blood Transfusion↗
PubMed1989

Multiple enzymes related to differentiation of lymphocyte subpopulations in man.

We studied the relation of various enzymes to subpopulations of lymphocytes in man. T cell-rich fractions were separated with a nylon column from mononuclear cells in the buffy coat. Comparing the enzymatic profiles of the two fractions, we found that the difference between the two groups came from the dominancy of B cells and/or macrophages in the former fraction, and from that of T cells in the latter. The enzymes characterizing T cells included N-Ac-beta-D-glucosaminidase (GlcNAc-ase), prolyl endopeptidase (Post-Pro-Enz), and dipeptidyl aminopeptidase IV (DAP-IV), whereas those characterizing B cells and/or macrophages include poly(ADP-ribose) synthetase, leucine aminopeptidase (Leu-AP), AP-B, cathepsin B, sialidase, and AP-A. Inhibitors of these enzymes may lead to modification of the function of T and B cells.

B-Lymphocytes↗
PubMed1988

Effects of changes in intracellular pH induced by platelet storage and treatment with monovalent cation ionophores on platelet functions.

The intracellular pH of platelets was measured by the fluorescent dye technique using 9-aminoacridine and BCECF-AM. Although platelet cytoplasmic pH determined by BCECF remained constant, the intracellular pH, determined by 9-aminoacridine, decreased during storage then increased when the stored platelets were incubated with fresh plasma, which led to the restoration of platelet functions. Since the average pH of cytoplasm and cell organelles is detected by 9-aminoacridine and only the cytoplasmic pH is detected by BCECF, the results suggested that changes of the organelle pH affected the platelet functions. Aggregability was measured using thrombin, ADP, collagen, A23187, arachidonic acid (AA), TPA and ristocetin, after the intracellular pH had been altered by treating the platelets with ionophores (monensin and nigericin) or after the membrane potential had been depolarized by treating with a buffer containing a high concentration of potassium ion. The depolarization increased platelet sensitivity only to three of the agonists, ADP, collagen and a low concentration of AA, while the increase of organelle pH and/or cytoplasmic pH enhanced the sensitivity to six of the above agonists, excluding ristocetin. Decrease of cytoplasmic pH reduced the sensitivity of the platelets to a low concentration of AA, but enhanced the sensitivity to thrombin and TPA. The results indicated that membrane potential, organelle pH and cytoplasmic pH influenced platelet functions via different mechanisms.

Aminacrine↗
PubMed1988

Effects of taxol and colchicine on platelet membrane properties.

The effects of the assembly-disassembly of microtubule on the membrane lipid fluidity, the fragmental motion of sulfhydryl groups of membrane proteins, and the functions of shape change and hypotonic shock response (shrinkage ratio) in human platelets were studied. We have employed electron spin resonance (ESR) utilizing spin labels for bilayer lipids or membrane proteins and microtubule reactive reagents to change microtubule assembly. Both, taxol, a microtubule stabilizing agent, and colchicine, a microtubule disrupting agent, did not affect the platelet membrane lipid fluidity detected by 5- or 16-doxylstearate. On the other hand, the mobility of sulfhydryl groups detected by 4-maleimide-tempo increased by taxol treatment and decreased by colchicine. Moreover, the temperature sensitivity of platelets below 20 degrees C decreased by taxol treatment, but unchanged by colchicine treatment. This behavior was similar to the shape change ability or the shrinkage ratio of platelets pre-treated with taxol, in which microtubule disassembly was inhibited due to taxol binding to microtubule. Therefore, it is confirmed that the assembly-disassembly state of microtubule which may control the ability of platelets to change shape, influences the mobility of sulfhydryl groups in platelet membrane proteins and its temperature sensitivity.

Adult↗
PubMed1988

Effects of autoclave sterilization on the physical properties of storage bags and granulocyte function.

Autoclave sterilization altered the leaching of plasticizer, CO2 gas permeability, surface area and the surface wettability of bag films. These changes affected granulocyte cell counts and functions during storage. Four types of polyvinyl chloride bags, with di-(2-ethylhexyl)phthalate (DEHP) or tri-(2-ethylhexyl)trimellitate (TOTM) as plasticizer, with or without treatment by glow discharge (H2), were sterilized with ethylene oxide (EO) or autoclaving (AC). The greatest amounts of plasticizer leached from DEHP-EO bags. TOTM plasticizer did not leach into plasma. CO2 gas permeability was greater with TOTM than DEHP. AC sterilization decreased the surface area of bags. Wettability of film surfaces was greatest with H2-TOTM-EO. After storage in these bags for 24 and 48 h at 22 degrees C, the granulocyte cell counts and functions were greatest in H2-TOTM-EO bags with the nonleaching plasticizer, higher CO2 gas permeability and higher wettable surface due to glow-discharge treatment. The H2-TOTM-EO bag was useful as a granulocyte storage container.

Benzoates↗
PubMed1987

Membrane potential of stored platelets and its effect on platelet functions.

Relationships among intracellular Ca2+ level, membrane potential in resting state and platelet functions were examined. Membrane potential of platelets was increased (hyperpolarized) during storage and decreased (depolarized) by 37 degrees C incubation with plasma after storage. The degree of depolarization was greater in fresh plasma than in stored plasma. Changes of platelet functions were reverse with the membrane potential change. Aggregation induced by ADP or collagen was enhanced by depolarization with increasing extracellular [K+]. Shrinkage ratio (hypotonic shock response) of stored platelet which were hyperpolarizing, exhibited optimal value when the membrane potential was slightly depolarized. Intracellular [Ca2+] was not affected by the extracellular [K+]. These results suggest that platelet sensitivity is controlled by the membrane potential in resting state.

Blood Platelets↗
PubMed1987

Effects of plasticizers and plastic bags on granulocyte function during storage.

The influence of the plasticizers, di-(2-ethylhexyl)phthalate (DEHP) and tri-(2-ethylhexyl)trimellitate (TOTM), on granulocyte function was examined. Polyvinyl chloride (PVC) bags with DEHP (DEHP-PVC) leaked DEHP into plasma, but TOTM did not dissolve in plasma under the same conditions. Glow discharge treatment inhibited the leakage of DEHP from DEHP-PVC bags. Depending on the amount of DEHP added into granulocyte suspension, chemotaxis and bactericidal activity decreased, but cell counts and phagocytosis were not affected. During storage for 24 h at 22 degrees C, granulocyte function decreased greatly in DEHP-PVC, but was well maintained in the bags which did not leak plasticizers, TOTM-PVC and glow-discharged DEHP-PVC.

Benzoates↗