Biomedical subjects

T Kusama

Publications and source records attributed to T Kusama.

At least 37 records · Page 2Linked to original sources

PubMed2000

Activation of protein kinase C induces internalization of the GABA(C) receptors expressed in Xenopus oocytes.

In a previous study, we showed that the protein kinase C (PKC) activator 4beta-phorbol 12-myristate 13-acetate (PMA) inhibited the gamma-aminobutyric acid (GABA)-gated currents in Xenopus oocytes expressing human rho1 GABA(C) receptors. To investigate whether the inhibition of currents was due to a decrease in efficacy or in the potency of rho1 GABA(C) receptor, concentration-response curves for GABA were compared before and after PMA treatment. The EC50 concentrations of GABA obtained during the maximally inhibited period were not statistically different from the concentrations obtained before PMA treatment (1.74 +/- 0.33 and 1.45 +/- 0.28 microM, respectively). These results indicate that the inhibition depends on a change in number or conductance of active receptor channels, but not on a change in affinity for GABA. To allow histochemical detection of rho1 GABA(C) receptors, we constructed a receptor tagged at the C-terminal position with human c-myc epitope. Electrophysiologically, the tagged receptors showed almost the same sensitivities for GABA and PMA as those of wild-type rho1 GABA(C) receptors. Immunohistochemistry with anti-myc antibody detected a dense concentration of tagged receptors at the surface area of Xenopus oocytes. Transient exposure to PMA reduced the density of immunofluorescence at the surface area and increased it in the subsurface area. These results suggest that the stimulation of protein kinase C leads to internalization of rho1 GABA(C) receptors expressed in Xenopus oocytes.

Animals↗

PubMed2000

[Study on evaluation method of patient dose in diagnostic radiology required for introducing the guidance level: investigation of entrance surface dose of patient using direct measurement by TLD].

Using direct measurement, we investigated entrance surface doses of patients for routine radiographs in attempt to develop evaluation methods of patient dose in order to establish the guidance level in Japan. To date, patient doses have been evaluated by calculations based on radiographic conditions, or model experiments using phantoms. Their patient doses are then evaluated based on several assumptions. Direct measurement of patient dose is difficult to perform in many patients due to its time requirement, level of expertise required and difficulty in providing an explanation of the procedure to the patient. However, such direct measurement is essential since it incorporates all aspects of radiography from the radiographic equipment used, to the actual conditions of each patient without assumption. In this study, we examined the (1) need for introducing the guidance level, (2) controversial points in the calculation method for patient dose evaluation, (3) evaluation accuracy required for introducing the guidance level, and (4) necessity for a standardized method.

Guidelines as Topic↗

PubMed1999

Detection and localization of Mip-3alpha/LARC/Exodus, a macrophage proinflammatory chemokine, and its CCR6 receptor in human pancreatic cancer.

Macrophage Proinflammatory Human Chemokine-3alpha (Mip-3alpha/LARC/Exodus) belongs to a large family of chemotactic cytokines, which participate in directing inflammatory cell migration and in modulating angiogenesis. Mip-3alpha signals through a recently identified G-protein linked 7-transmembrane receptor, CCR6. In this study, we have characterized the expression of Mip-3alpha and CCR6 in 12 normal and 16 cancerous human pancreatic tissues and in 4 cultured pancreatic cancer cell lines, and assessed the effects of Mip-3alpha on growth and invasion of these cell lines. Pancreatic cancer tissues markedly overexpressed Mip-3alpha in comparison with normal pancreatic samples. By in situ hybridization Mip-3alpha and CCR6 mRNA moieties were present in cancer cells within the tumors. In addition, Mip-3alpha was abundant in the macrophages infiltrating the tumor mass. Mip-3alpha and its receptor CCR6 were expressed in all 4 tested pancreatic cancer cell lines. Mip-3alpha stimulated the growth of one cell line, enhanced the migration of another cell line, and was without effect in the other 2 cell lines. Together, our findings suggest that Mip-3alpha has the potential to act via autocrine and paracrine mechanisms to contribute to the pathobiology of human pancreatic cancer.

Adolescent↗

PubMed1999

Antigen-induced elevation of immunoreactive endothelin-1 (ET-1) levels in ovalbumin-sensitized guinea pig airway tissue.

Changes in the immunoreactive ET-1 levels during the anaphylactic reaction of airway tissue from ovalbumin-sensitized guinea pigs were investigated. ET-1-immunoreactivity (ET-IR) was detected in the epithelial and smooth muscle layers of tracheal sections from normal guinea pigs and it was enhanced slightly by phosphoramidon (1 microM) treatment. The ET-IR level of the epithelial layer of ovalbumin-treated tissue from actively sensitized animals was slightly higher than that from normal animals, but it was enhanced markedly by phosphoramidon (1 microM) treatment. Furthermore, the mean ET-IR level of homogenates of antigen-treated tracheal tissues from sensitized guinea pigs (22.8 +/- 1.55 fmol mg-1 protein, n = 5) was significantly higher than the corresponding normal level (12.3 +/- 1.21 fmol mg-1 protein, n = 5). These results suggest that increased epithelial airway ET-1 levels contribute to the anaphylactic reaction of guinea pig airways.

Anaphylaxis↗

PubMed1999

Stimulatory and inhibitory properties of aminoglycoside antibiotics at N-methyl-D-aspartate receptors.

The effects of aminoglycoside antibiotics on N-methyl-D-aspartate (NMDA) receptors were studied using voltage-clamp recording of recombinant NMDA receptors expressed in Xenopus oocytes. A number of aminoglycosides were found to potentiate macroscopic currents at heteromeric NR1A/NR2B receptors, but not at NR1A/NR2A, NR1A/NR2C, NR1A/NR2D, or NR1B/NR2B receptors. The degree of potentiation had a rank order neomycin B > paromomycin > gentamicin C > geneticin > kanamycin A > streptomycin. Potentiation was not seen with kasugamycin and spectinomycin. The degree of stimulation paralleled the number of the amino groups in the aminoglycosides. The stimulatory effects of aminoglycosides were more pronounced at subsaturating concentrations of glycine and at acidic pH, similar to the stimulatory effects of spermine. We measured the effects of aminoglycosides at mutant NMDA receptors to determine which amino acid residues in NMDA receptor subunits are involved in stimulation. Mutations that reduced or abolished spermine stimulation also reduced stimulation by aminoglycosides. Several aminoglycosides produced a weak voltage-dependent block of NMDA receptors, but the degree of inhibition did not appear to correlate with the number of amino groups in the molecule. The results suggest that aminoglycosides having more than three amino groups have stimulatory effects that are mediated through the spermine-binding site on NMDA receptors.

Aminoglycosides↗

PubMed1998

Consensus phosphorylation sites of human GABA(c)/GABArho receptors are not critical for inhibition by protein kinase C activation.

The mechanism of inhibition of human GABA(C)/GABArho receptors by protein kinase C (PKC) activation was investigated in Xenopus oocytes. Phorbol 12-myristate 13 acetate (PMA), a potent PKC activator, at 25 nM inhibited the currents through GABArho2 receptors, which have one consensus phosphorylation site by PKC in the predicted intracellular loops. The time-courses and amplitudes of inhibition were not significantly different from those occurring through GABArho1 receptors, which have six such sites. The inhibitory effect of PMA was also observed after removing each consensus phosphorylation site in both GABArho1 and rho2 receptors by site-directed mutagenesis. These results suggest that phosphorylation of consensus sites in the intracellular loops is not involved in the inhibition of human GABA(C)/GABArho receptors by PKC activation.

Animals↗

PubMed1998

Monte Carlo simulation of DNA strand-break induction in supercoiled plasmid pBR322 DNA from indirect effects.

We present a new Monte Carlo simulation code system (DBREAK) of the detailed events that occur when ionizing radiation interacts with water and DNA molecules. The model treats the initial energy deposition by radiation, the formation of chemically active species, subsequent diffusion-controlled chemical reactions, and induction of DNA strand breaks. DBREAK assumes one-hit single-strand break (SSB) and two-hit double-strand break (DSB) mechanisms. A high-resolution model of plasmid DNA structure has been introduced. The calculated results are compared with the results of previously performed experiments of the same type. Under aerobic conditions, 89.4% of the DNA damage was attributed to OH-radical and 10.5% and 0.1% to eaq- and H, respectively. We also compared the differences between liquid-water track structure and gas-phase-water track structure. The calculated yield of SSBs by liquid-water track structure exceeded that of gas-phase-water track structure by a factor of 1.2.

Aerobiosis↗

PubMed1997

Inhibitory activity of a naturally occurring heterocyclic beta-substituted alanine, beta-(isoxazolin-5-on-4-yl)-L-alanine, on the L-glutamate/L-aspartate transporter (GLAST) expressed in Xenopus oocytes.

Excitatory amino acid (EAA) transporters are of physiological importance in the regulation of the extracellular concentration of excitatory amino acids and the neuroexcitation in CNS. Among four identified transporters, the Na+-dependent high-affinity L-glutamate/L-aspartate transporter (GLAST) is highly expressed in glial cells. Here, we report a naturally occurring inhibitor of GLAST, derived from bovine retina, using the Xenopus oocyte expression system. Beta-(isoxazolin-5-on-4-yl)-L-alanine (TAN), an antifungal antibiotic, inhibited [14C]L-glutamate (L-Glu) transport into GLAST-expressing oocytes. TAN also served as a substrate for this transporter in voltage-clamp experiments measuring the current coupled to the EAA transport. The maximum current of TAN itself was approximately 1/3 of that of L-glutamate, and its apparent affinity was almost the same as L-Glu. In combination with L-Glu, TAN antagonized L-glutamate transport. In radioisotope experiments, the inhibitory potency of this compound against [14C]L-Glu uptake into oocytes was approximately 1/6 of that of L-(-)-threo-3-hydroxyaspartate (THA). The glucoside of TAN (TANG), occurring in seedlings of the garden pea, the lentil and some Lathyrus species, did not show any electrophysiological activity nor was it transported into oocytes. It is proposed that TAN is a novel type antagonist of natural origin on GLAST. By affecting such transport system, naturally occurring compounds may affect the regulation of the extracellular level of endogenous EAA.

ATP-Binding Cassette Transporters↗

PubMed1997

Increased endothelial cell retraction and tumor cell invasion by soluble factors derived from pancreatic cancer cells.

BACKGROUND: Tumor cells induce endothelial cell retraction before invasion. In pancreatic cancer cells, the factors affecting endothelial cell retraction are not well-understood. METHODS: The activities of the endothelial cell retraction in conditioned media (CM) derived from three human pancreatic cancer cell lines, PSN-1, MiaPaca-2, and Capan-1, were measured for the amount of intercellular junctional transport of FITC dextran through an endothelial cell monolayer in a transwell cell culture system. RESULTS: The CM derived from the three pancreatic cancer cells induced endothelial cell retraction. The endothelial cell retraction activity in the CM from PSN-1 cells was significantly higher than those from MiaPaca-2 and Capan-1 cells. The CM from PSN-1 cells enhanced both the adhesion and the invasion of MiaPaca-2 and Capan-1 cells. The factors with endothelial cell retraction activity in the CM from PSN-1 cells were characterized as heat-stable, trypsin-sensitive glycoproteins ranging from 10,000 to 50,000 in molecular weight, and were found both in heparin-bound and unbound fractions. CONCLUSIONS: PSN-1 cells produced and secreted at least two factors inducing the endothelial cell retraction. The factors could play an important role in the establishment of invasion and metastasis of PSN-1 cells.

Cell Adhesion↗

PubMed1997

Monte Carlo simulation of physicochemical processes of liquid water radiolysis. The effects of dissolved oxygen and OH scavenger.

The paper describes developments of the physicochemical part of a computer code system that estimates DNA strand break induction on plasmid pBR322 DNA. In order to test the reliability of the model, we evaluated the dielectric function and the time-dependent yield of chemical species in the presence of OH radical scavenger or dissolved oxygen. Results agree with measurements on the radiolysis of liquid water. When a hybrid model of a liquid inelastic cross-section and a vapour elastic cross-section is used, energy deposition by vibrational excitations is estimated to be approximately 11% of total energy deposition.

Free Radical Scavengers↗

PubMed1997

Synergistic actions of pentobarbital and dihydropyridine Ca2+ antagonists on guinea pig isolated thoracic aorta.

In order to elucidate the mechanism(s) behind the interactions between barbiturates and Ca2+ antagonists, the effects of pentobarbital combined with three structurally diverse types of Ca2+ antagonist on CaCl2-induced contractile responses of the guinea pig thoracic aorta in Ca(2+)-free and 40 mM K+ medium and the effects of pentobarbital on Ca2+ antagonist binding to guinea pig aortic membranes were investigated. The dihydropyridine derivatives isradipine (10(-10)-10(-8) M) and nifedipine (10(-10)-10(-8) M) inhibited CaCl2-induced contractions concentration-dependently. Treatment with both pentobarbital (10(-4) M) and dihydropyridine Ca2+ antagonists (10(-9) M) shifted the CaCl2 concentration-response curves to the right significantly compared with those after treatment with the Ca2+ antagonists and pentobarbital alone. However, no synergistic effects of pentobarbital (10(-4) M) with other types of Ca2+ antagonist (verapamil (10(-7) M) and diltiazem (10(-6) M)) were observed. The binding of [3H]isradipine (2 x 10(-9) M) to guinea pig aortic membranes was increased significantly by simultaneous pentobarbital treatment, but no such effect was observed with [3H]verapamil (10(-8) M) or [3H]diltiazem (2 x 10(-8) M). These findings suggest that the synergistic contractile effects of pentobarbital and dihydropyridines were, in part, due to enhancement of dihydropyridine binding to guinea pig aortic membranes (L-type Ca2+ channels) by pentobarbital and that the interactions between pentobarbital and Ca2+ antagonists may be structurally specific.

Animals↗

PubMed1997

Inhibition of tumor necrosis factor alpha-induced vascular endothelial permeability by gadolinium chloride.

Tumor necrosis factor-alpha (TNF alpha) is an important mediator of endotoxic and septic shock. We previously reported that the survival rate in a rat sepsis model was improved by the administration of gadolinium chloride (GdCl3), whereas the level of TNF alpha in the blood was not affected. In the present study, we examined the effect of GdCl3 on endothelial permeability in vitro. Endothelial permeability was monitored by measuring the amount of fluorescein isothiocyanate-labeled dextran (FITC-Dx) passing through the calf pulmonary arterial endothelial (CPAE) cell monolayer. The incubation of the CPAE cell monolayer with TNF alpha (10-500 JUR/ml for 6-24 h) caused a dose- and time-dependent increase in the permeation of FITC-Dx passing through the monolayer. Whereas the integrity of the monolayer was not affected after preincubation with GdCl3 at concentrations from 10(-7) to 10(-4) M, the increased endothelial permeability induced by TNF alpha was inhibited by a pretreatment of the CPAE cell monolayer with GdCl3 in a dose-dependent manner. Our results suggest that GdCl3 has a protective effect on the endothelial cell monolayer exposed to TNF alpha.

Animals↗

PubMed1997

Chromosome aberrations in bone marrow cells of C3H/He mice at an early stage after whole-body irradiation.

Murine acute myeloid leukemia is characterized by chromosome 2 aberrations, and genesis of the marker chromosome 2 by radiation is suspected to be an initiating event of radiation leukemogenesis. A detailed analysis of the type and frequency of chromosome 2 aberrations in murine bone marrow cells at an early stage after irradiation is provided here. A total of 40 male C3H/He mice was exposed to 137Cs gamma-ray at a dose of 1, 2 or 3 Gy, and sacrificed 24 hours after irradiation. Metaphase samples prepared from bone marrow cells were Q-banded for karyotyping or painted with DNA probes specific to chromosome 2. In 5 mice analyzed by karyotyping, one mouse showed high frequency of the marker aberrations as well as other chromosome 2 aberrations. Chromosome painting analysis for the rest of the mice also detected 3 animals showing significantly high frequencies of chromosome 2 aberrations. Dose-dependence of the frequencies was observed even among those mice that tended to be sensitive. The results indicated that there was a subgroup of mice carrying hypersensitive chromosome 2. The subgroup could be leukemia-sensitive if radiation-induced chromosome aberrations are responsible for an early change in myeloid leukemogenesis.

Animals↗

PubMed1997

The embryonic and fetal effects in ICR mice irradiated in the various stages of the preimplantation period.

Pregnant ICR mice were irradiated with 0.1-2.5 Gy 137Cs gamma rays at a dose rate of 0.2 Gy/min at 2, 48, 72 or 96 h postconception. In the mice irradiated during these stages of preimplantation, embryonic/fetal mortalities, incidence of external gross malformations, fetal body weight and sex ratio were observed at day 18 of gestation. There were significant increases in death in the preimplantation period compared to control levels after exposure to at least 0.25 Gy at 2 and 72 h postconception and 0.5 Gy at 96 h postconception. In contrast, a dose of 1.5 Gy was required at 48 h postconception. The frequency of embryonic death was analyzed using a logistic regression for comparing among stages. These analyses demonstrated that the regression slopes were significantly positive for groups in all stages and increased with decreasing time after conception. Furthermore, the regression analyses suggested that the most sensitive stage for preimplantation death and embryonic death was 2 h postconception, when embryos consisted of one cell. Many types of external gross malformations, such as exencephaly, cleft palate and anophthalmia, were observed even in the mice irradiated with 0.1 Gy at 2, 72 and 96 h postconception. In the same manner as embryonic mortality, the regression analyses suggested that the susceptibility of the mice irradiated at 2, 72 and 96 h postconception during preimplantation to external malformations was higher than that of the mice irradiated at 8 or 11 days of gestation, which is the period of organogenesis, and that the most sensitive stage for external malformations was 2 h postconception. However, no malformations were observed in the mice irradiated at 48 h postconception when the embryos were precompacted with four to eight cells.

Abnormalities, Radiation-Induced↗

PubMed1995

GABA rho1 receptor: inhibition by protein kinase C activators.

The effects of protein kinase C (PKC) activators on gamma-aminoburyric acid (GABA) rho 1 receptor function were studied in rho 1 -expressing Xenopus oocytes. The PKC activator phorbol 12-myristate 13-acetate (PMA) but not the inactive analog phorbol 12-mono-myristate inhibited the GABA-gated chloride currents. Mezerein, a non-phorbol ester type PKC activator, also inhibited the rho 1 responses, but 8-chlorophenylthio-cyclic AMP, a protein kinase A activator, had no effect. The effect of PMA was significantly reduced by a PKC inhibitor, staurosporine. These results suggest that GABA rho 1 receptor function can be regulated by PKC-mediated phosphorylation events.

Alkaloids↗

PubMed1995

Enhancement of in vitro tumor-cell transcellular migration by tumor-cell-secreted endothelial-cell-retraction factor.

To investigate the factors affecting endothelial-cell retraction, we have studied the interaction of tumor cells with endothelial cells in 2 human pancreatic cancer cell lines, PSN-1 and MiaPaca-2. The extent of endothelial-cell retraction measured by the amount of intercellular junctional transport of FITC-dextran through an endothelial monolayer was increased by the addition of a conditioned medium (CM) from both cell lines, while CM from PSN-1 cells was 2 to 3 times more potent than that from MiaPaca-2 cells. After the treatment of endothelial monolayer with CM of PSN-1 cells, the ability of both PSN-1 cells and MiaPaca cells to adhere to or invade the monolayer increased. The addition of CM from PSN-1 cells did not affect the growth rate of either the endothelial or the tumor cells. The activity in the CM was heat-stable and bound to heparin-Sepharose, but was inactivated when treated by 0.5% trypsin. Protease inhibitors did not influence the activity. Pre-treatment of PSN-1 cells by an inhibitor of protein synthesis, cycloheximide, or of protein processing, benzyl-N-acetyl-alpha-D-galactosaminide, reduced endothelial-cell-retraction activity in the CM. The active substance in the CM fractionated in the molecular-weight range of 10,000 to 50,000. These results suggest that PSN-1 cells produce and secrete (a) soluble factor(s) that can induce endothelial-cell retraction, thus facilitating tumor-cell invasion.

Animals↗

PubMed1995

Occupational exposure in pediatric cardiac catheterization.

Radiation doses to staff involved with pediatric cardiac catheterization were measured using thermoluminescent dosimeters in 18 procedures. The average doses to the lens and thyroid, and the effective dose per procedure to the main operating physicians was 88, 180, and 8 microSv, respectively; to assistant physicians, 23, 51, and 2 microSv; and to technicians, 23, 27, and 2 microSv. In some procedures, the dose to the technician's hand approached 1,500 microSv. The doses received by physicians were proportional to cineangiographic time but with no correlation with integrated currents. The number of procedures which may be performed in a year by individual staff members was estimated to be 430 and 2,780 procedures for physicians and assistants, respectively. It was suggested that the front of the neck is an adequate position for the dosimeter to measure doses during pediatric catheterization.

Adolescent↗

PubMed1995

Strand break formation in plasmid DNA irradiated in aqueous solution: effect of medium temperature and hydroxyl radical scavenger concentration.

Plasmid pBR322 DNA (4363 base pairs) in aerobic aqueous solution was irradiated with 60Co gamma-radiation. The change of diffusion coefficients (D) of chemical species, rate constants (k) of radical-DNA interaction and solubilities of O2 in water cannot be ignored when a temperature varies more than a few tens of centigrade. It is important to examine the variation of the yields of DNA strand breaks as a function of temperature in order to analyze the mechanisms of DNA strand breaks from the chemical point of view. Hence, we observed the change of the yield of strand breaks with temperatures between -20 and 42 degrees C by agarose gel electrophoresis. We also observed the change of the yield of strand breaks with the concentration of OH scavenger (Tris) from 1 mmol dm-3 to 100 mmol dm-3 and summarized it with previous experiments. This summarization indicated that the order of the lifetime of OH radical in cellular environment is several nanosecond. This value is consistent with the measurement of the lifetime of 8.7 nanosecond for OH radical in mammalian cell (Roots, R. and Okada, S. (1975) Radiat. Res. 64, 306-320).

Culture Media↗