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Biomedical subjects

M Hoshi

Publications and source records attributed to M Hoshi.

At least 253 records · Page 14Linked to original sources
PubMed1988

Protein-kinase-C-catalyzed phosphorylation of the microtubule-binding domain of microtubule-associated protein 2 inhibits its ability to induce tubulin polymerization.

It has previously been demonstrated that microtubule-associated protein 2 (MAP2) is a good substrate for the purified protein kinase C [Tsuyama, S., Bramblett, G. T., Huang, K.-P. & Flavin, M. (1986) J. Biol. Chem. 261, 4110-4116; Akiyama, T., Nishida, E., Ishida, J., Saji, N., Ogawara, H., Hoshi, M., Miyata, Y. & Sakai, H. (1986) J. Biol. Chem. 261, 15648-15651]. We have shown here that phosphorylation of MAP2, catalyzed by protein kinase C, reduces the ability to induce tubulin polymerization. MAP2 is divided into two domains by digestion with alpha-chymotrypsin; the microtubule-binding and the non-binding (projection) domains. The limited chymotryptic digestion following phosphorylation of MAP2 by protein kinase C has shown that both the domains of MAP2 were phosphorylated by protein kinase C, 50-60% of the incorporated phosphates being detected in the microtubule-binding domain. Polypeptide fragments, containing the microtubule-binding domain of MAP2, were purified by DEAE-cellulose column chromatography after chymotryptic digestion of MAP2. The purified microtubule-binding fragments were competent to polymerize tubulin, and served as good substrates for protein kinase C. The phosphorylation of the microtubule-binding fragments by protein kinase C reduced their ability to induce tubulin polymerization. These results suggest that the ability of MAP2 to induce tubulin polymerization is inhibited by phosphorylation of the microtubule-binding domain catalyzed by protein kinase C.

Actins↗
PubMed1988

Activation of a Ca2+-inhibitable protein kinase that phosphorylates microtubule-associated protein 2 in vitro by growth factors, phorbol esters, and serum in quiescent cultured human fibroblasts.

Treatment of quiescent human embryonic lung fibroblastic cells (TIG-3) with 10 nM epidermal growth factor (EGF) resulted in 4-6-fold activation of a protein kinase activity in cell extracts that phosphorylated microtubule-associated protein 2 (MAP2) on serine and threonine residues in vitro. The half-maximal activation of the kinase activity occurred within 5 min after EGF treatment, and the maximal level was attained at 15 min. Casein and histone were very poor substrates for this EGF-stimulated MAP2 kinase activity. The activation of the kinase activity persisted after brief dialysis. Interestingly, the EGF-stimulated MAP2 kinase activity was sensitive to micromolar concentrations of free Ca2+; it was inhibited 50% by 0.5 microM Ca2+ and almost totally inhibited by 2 microM Ca2+. The activated MAP2 kinase activity was recovered in flow-through fractions on phosphocellulose column chromatography, while kinase activities that phosphorylate 40 S ribosomal protein S6 (S6 kinase activities) were mostly retained on the column and eluted at 0.5 M NaCl. Platelet-derived growth factor, fibroblast growth factor, insulin-like growth factor-I, insulin, phorbol esters (12-O-tetradecanoylphorbol 13-acetate and phorbol 12,13-dibutyrate), and fresh fetal calf serum also induced activation of the MAP2 kinase in the quiescent TIG-3 cells. The activated MAP2 kinase activity in cells stimulated by platelet-derived growth factor, fibroblast growth factor, insulin-like growth factor-I, insulin, 12-O-tetradecanoylphorbol 13-acetate, phorbol 12,13-dibutyrate, or fetal calf serum was almost completely inhibited by 2 microM Ca2+, like the EGF-stimulated kinase. In addition, MAP2 phosphorylated by the kinase activated by different stimuli gave very similar phosphopeptide mapping patterns. These results suggest that several growth factors, phorbol esters, and serum activate a common, Ca2+-inhibitable protein kinase which is distinct from S6 kinase in quiescent human fibroblasts.

Blood↗
PubMed1988

Rapid stimulation of fluid-phase endocytosis and exocytosis by insulin, insulin-like growth factor-I, and epidermal growth factor in KB cells.

Effects of growth factors on fluid-phase endocytosis and exocytosis in human epidermoid carcinoma KB cells were examined by measuring horseradish peroxidase (HRP) as a marker. Insulin, insulin-like growth factor-I (IGF-I), and epidermal growth factor (EGF) promoted HRP accumulation. They also stimulated the efflux of the preloaded HRP from the cells. From these results it follows that these growth factors stimulate the influx as well as the efflux of HRP, because the accumulation rate is the sum of the influx rate and the efflux rate. The stimulation of both HRP accumulation and HRP efflux was rapidly induced within 2-4 min of the addition of growth factors and persisted for at least 60 min. The concentrations eliciting half-maximal stimulatory effects of insulin, IGF-I, and EGF were about 5 X 10(-7), 1 X 10(-9), and 5 X 10(-10) M, respectively. aIR-3 (anti-type I IGF receptor antibody) completely blocked the stimulation of HRP accumulation by IGF-I but very slightly inhibited the stimulation by insulin. The 528 IgG (anti-EGF receptor antibody) inhibited the stimulation of HRP accumulation by EGF. These results indicated that each of these growth factors stimulates the HRP accumulation mediated by the corresponding (homologous) growth factor receptors. The rapid stimulation of fluid-phase influx and efflux may constitute one of the common early cellular responses to growth factors.

Antibodies↗
PubMed1988

Physiological inducers of the acrosome reaction.

This article reviews recent studies on physiological inducers of the acrosome reaction in starfish. Upon encountering the jelly coat of eggs, starfish sperm undergo the acrosome reaction in response to a cooperation of three jelly components: a sulfated glycoprotein named acrosome reaction-inducing substance (ARIS), a group of steroidal saponins named Co-ARIS, and an oligopeptide presumably having an activity to increase the intracellular pH of sperm. ARIS induces the acrosome reaction in high Ca2+ or high pH sea water. In normal sea water, both ARIS and Co-ARIS are required for the induction. In addition to ARIS and Co-ARIS, a third jelly component, the oligopeptide, is necessary to mimic the full capacity of the jelly coat to induce the acrosome reaction. ARIS and Co-ARIS cooperatively increase the intracellular Ca2+ by stimulating Ca2+ channels, while the oligopeptide increases the intracellular pH by stimulating Na+/H+ exchange systems. When sperm meet the eggs, both changes are simultaneously achieved in them and thus they undergo the acrosome reaction.

Acrosome↗
PubMed1988

Soft X-ray dosimetry and RBE for survival of Chinese hamster V79 cells.

Dosimetry and biological effects of 40 and 50 keV low-energy X-rays generated by a SOFTEX Model CMBW-2 apparatus were studied. Doses were measured using a thin-window parallel-plate ionization chamber; beam quality was assessed using aluminum absorbers; exposure rates per unit current were determined according to the X-ray tube current and exposure times; and thermoluminescent (BeO chip) dosimeters were used to ascertain dose distributions in the irradiation field. The average correction factors for nonuniformity were calculated from the measured dose distributions. The means for ascertaining accurate exposures and doses using these methods are discussed. The dose-survival relationship of Chinese hamster V79 cells were assessed by irradiating them with 40 and 50 kV soft X-rays, 180 kV X-rays, and 60 Co gamma rays. Soft X-rays with three distinct effective energies were tested by changing the tube voltage kV and aluminium filter thicknesses; namely (1) 40 kV without filter, (2) 40 kV with a 0.2 mm thick aluminium filter and (3) 50 kV with a 0.7 mm thick aluminium filter. The effective energies obtained according to attenuation measurements using aluminium for these soft X-rays were 8.1, 11.7 and 18.5 kV, respectively. In this study the relative biological effectiveness (RBE) at 10 per cent survival compared with 60Co gamma rays ranged from 1.5 to 1.6. The RBE of 180 kV X-rays relative to 60Co gamma rays was 1.29. This study provided experimental data for the RBE of V79 cells in the intermediate energy range between hard and ultrasoft X-rays, data for which were previously reported by Goodhead and co-workers (1977, 1979, 1981).

Aluminum↗
PubMed1988

Melibiosylceramide as the sole ceramide dihexoside from the eggs of the sea urchin, Anthocidaris crassispina.

Melibiosylceramide (Gal alpha 1-6Glc beta 1-1Cer) was found as the sole ceramide dihexoside from the eggs of the sea urchin, Anthocidaris crassispina. Ceramide monohexoside of the eggs consisted only of glucosylceramide (Glc beta 1-1Cer). These lipids were purified by successive column chromatographies on DEAE-Sephadex A-25, silicic acid and Florisil, and identified by gas-liquid chromatography, negative-ion fast atom bombardment mass spectrometry and proton nuclear magnetic resonance spectroscopy as well as methylation analysis. Long-chain base compositions of both lipids were almost identical and comprised n-C18-phytosphingosine and small amounts of its homologs (C17-C19). Fatty acid compositions were qualitatively very similar, but the glucosylceramide contained more 2-hydroxy fatty acid than the melibiosylceramide. Although the chain length of fatty acids was distributed over a wide range, six major fatty acids, namely 22:1, 23:1, 24:1, 22h:1, 23h:1 and 24h:1, constituted more than 92% of the fatty acid content in these lipids.

Animals↗
PubMed1988

Monte Carlo calculations of doses to tiles irradiated by 60Co and 252Cf simulating atomic bomb gamma-ray fluences.

Dose calculations for tiles exposed to the Hiroshima atomic bomb radiations were undertaken. A Monte Carlo code, ABOMB, was developed which considers the characteristics of atomic bomb gamma-ray fluences and geometrical configurations. ABOMB was applied to tile dose calculations for the available photon sources with definite fluences. Its validity was tested by comparing the depth-dose curves calculated for 60Co and 252Cf beams with the equivalent experimental data obtained in the laboratory. Selection of parameters, contribution of backscattering, and computing time also were considered. Present calculations are considered to be accurate with uncertainties less than +/- 10%, and may be useful for correcting or reinforcing atomic bomb gamma-ray doses, together with tile dose measurements by thermoluminescent (TL) dosimetry.

Californium↗
PubMed1988

Restoration by xanthine of development of mouse embryos inhibited by mycophenolic acid.

Mouse embryos at the 1-cell stage were cultured in various concentrations of mycophenolic acid and xanthine. Mycophenolic acid at 10 and 2.5 micrograms/ml completely inhibited development to the morula and blastocyst stages, respectively. The addition of xanthine reversed the inhibitory effects of mycophenolic acid on the embryos but the reversal effect depended on the concentration of xanthine. Development was normal with a xanthine concentration of 25 micrograms/ml, even when an inhibitory concentration of mycophenolic acid was present. Embryo transfer experiments showed that the blastocysts formed in vitro in the presence of mycophenolic acid + xanthine could implant in foster mothers and develop normally to fetuses.

Animals↗
PubMed1988

Thermoluminescence dosimetry of gamma rays from the atomic bomb at Hiroshima using the predose technique.

Thermoluminescence dosimetry measurements of gamma rays produced by the atomic bomb in Hiroshima were made by the predose technique using eight ceramic samples collected from five buildings located at distances between 1271 and 2051 m from the hypocenter. The results of our measurements are compared to both the newer dose estimates (Dosimetry System 1986) and older dose estimates (Tentative 1965 Doses) for survivors of the Hiroshima atomic bomb. In comparison with the older estimates, our results are larger by a factor of 2.3 at 1271 m and 3.9 at 2051 m. Our results and the newer estimates for Hiroshima differ by a factor of only 1.14 +/- 0.16 on the average.

Ceramics↗
PubMed1987

Tyrosine phosphorylation by the epidermal growth factor receptor kinase induces functional alterations in microtubule-associated protein 2.

We have examined the effect of tyrosine phosphorylation of microtubule-associated protein 2 (MAP2) by the epidermal growth factor (EGF) receptor kinase on its functions. Incubation of MAP2 with the EGF receptor in the presence of ATP resulted in a great decrease in the ability of MAP2 to promote tubulin polymerization. Under a variety of conditions, the decrease in the ability correlated with the extent of phosphorylation of MAP2. Furthermore, another function of MAP2, the actin filament cross-linking activity, was also inactivated by the incubation of MAP2 with the EGF receptor and ATP. The loss of this activity also correlated well with the extent of phosphorylation. These data indicate that tyrosine phosphorylation of MAP2 by the EGF receptor kinase inactivates both the tubulin polymerizing activity and actin filament cross-linking activity of MAP2. Thus, this study has clearly shown that tyrosine phosphorylation could modify the function of a cytoskeletal protein.

Actins↗
PubMed1987

Protein kinase C phosphorylates tau and induces its functional alterations.

We found that tau, one of the major microtubule-associated proteins, is a good substrate for protein kinase C. The phosphorylation occurred mainly on serine residues and the sites phosphorylated by protein kinase C were largely different from those phosphorylated by cAMP-dependent protein kinase as analyzed by phosphopeptide mapping. The protein kinase C-mediated phosphorylation of tau reduced its abilities to promote tubulin polymerization and to cross-link actin filaments. The reduction in its abilities was in proportion to the number of phosphates incorporated into tau.

Actins↗
PubMed1987

Structures of the sugar chains of a major glycoprotein present in the egg jelly coat of a starfish, Asterias amurensis.

Sugar chains of a major glycoprotein, obtained from the egg jelly coat of a starfish (Asterias amurensis), were released quantitatively as oligosaccharides by hydrazinolysis. After N-acetylation, they were converted to radioactive oligosaccharides by reduction with NaB3H4. Analysis by paper electrophoresis revealed that all of them were neutral oligosaccharides. Upon Bio-Gel P-4 column chromatography, the radioactive oligosaccharide mixture was separated into four components. Structural study of each component by sequential glycosidase digestion in combination with 1H-NMR spectroscopy revealed that the glycoprotein contains the following oligosaccharides, in which R represents either proton, Glc alpha 1----, Glc alpha 1----3Glc alpha 1----, or Glc alpha 1----2Glc alpha 1----3Glc alpha 1----. (Formula: see text)

Acetylation↗
PubMed1987

Observation of fallout in Hiroshima caused by the reactor accident at Chernobyl.

Fallout from the reactor accident at Chernobyl has been surveyed at Hiroshima. gamma-rays from samples of aerosol, rain water and tap water were measured using low-background gamma-ray spectrometers and concentrations of activities were followed. Almost all of the nuclides detected in Europe were observed in Hiroshima. In addition to dominant volatile fission products of 131I, 132Te-132I and 103Ru, long-lived fission products 137Cs, 106Ru-106Rh, 125Sb and activities produced through the (n, gamma) process in the reactor such as 134Cs, 136Cs and 110mAg were observed in relatively high concentrations.

Accidents↗
PubMed1987

Thermoluminescence dosimetry of gamma rays from the Hiroshima atomic bomb at distances of 1.27 to 1.46 kilometers from the hypocenter.

Sixteen ornamental tile samples were collected from 1982 to 1983 from the rooftops of two buildings at Hiroshima University, Hiroshima, Japan. Quartz grains 50-150 microns in size extracted from the samples were analyzed for their thermoluminescence (TL) intensities. Conversion of TL intensity to 60Co gamma exposure resulted in the following estimates: 40.5 to 27.6 mC kg-1 (157 to 107 R) for five samples (one each) collected from five sites at distances of 1.27 to 1.34 km from the hypocenter of the atomic bomb detonated in 1945; 23.7 +/- 1.4 mC kg-1 (92 +/- 5 R) for three samples from one site at a distance of 1.39 km; 21.4 to 17.0 mC kg-1 (83 to 66 R) for three samples (one sample per site) from three sites at distances of 1.40 to 1.43 km; 19.8 +/- 1.3 mC kg-1 (77 +/- 5 R) for four samples from one site at a distance of 1.45 km; and 13.2 mC kg-1 (51 R) for one sample at a distance of 1.46 km. At face value, these estimates are greater by a factor of about 2.5 than previous estimates based on the tentative 1965 radiation dose estimates for atomic bomb survivors (a tentative dosimetry model proposed in 1965), but agree within +32% to -13% (+15% on the average) with recent estimates using modern computational techniques using an improved model of the atomic bomb explosion.

Cobalt Radioisotopes↗