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M Hoshi

Publications and source records attributed to M Hoshi.

At least 109 records · Page 6Linked to original sources
PubMed1998

The relative biological effectiveness of accelerated carbon ions with different LET for inducing mitotic crossing over and intragenic reversion of the white-ivory allele in Drosophila larvae.

PURPOSE: To evaluate the relative biological effectiveness (RBE) of accelerated carbon ions generated with a synchrotron for inducing mutations as a function of linear energy transfer (LET), using the loss of heterozygosity for wing-hair mutations and the reversion of the mutant white-ivory eye-colour in Drosophila melanogaster. MATERIALS AND METHODS: The measurements were made using a combined mutation assay system so that induced mutant wing-hair clones as well as revertant eye-colour clones can be detected simultaneously in the same fly. Larvae were irradiated at the age of 72+/-6 h post-oviposition with X-rays or carbon ions with LET values of 13, 60 and 95 keV/microm. RESULTS: The RBE of carbon ions for producing wing-hair mosaic spots increased with increasing LET values. The RBE for the induction of eye-colour mutants did not change with LET. The estimated RBE values were found to be in the range 2 to 6.5 for the wing-hair and nearly unity for the eye-colour mosaic spot mutations. CONCLUSIONS: RBE-LET relationships were obtained for the induction of wing-hair and eye-colour mosaic spots. These relationships suggest that more complex types of DNA damage, such as nonrejoinable strand breaks that increase with LET, may be responsible for inducing the wing-hair mutation, while more simple forms of molecular damage induce reversion in the white-ivory allele.

Animals↗
PubMed1998

Track structure in radiation biology: theory and applications.

PURPOSE: A brief review is presented of the basic concepts in track structure and the relative merit of various theoretical approaches adopted in Monte-Carlo track-structure codes are examined. In the second part of the paper, a formal cluster analysis is introduced to calculate cluster-distance distributions. METHOD: Total experimental ionization cross-sections were least-square fitted and compared with the calculation by various theoretical methods. Monte-Carlo track-structure code Kurbuc was used to examine and compare the spectrum of the secondary electrons generated by using functions given by Born-Bethe, Jain-Khare, Gryzinsky, Kim-Rudd, Mott and Vriens' theories. The cluster analysis in track structure was carried out using the k-means method and Hartigan algorithm. RESULTS: Data are presented on experimental and calculated total ionization cross-sections: inverse mean free path (IMFP) as a function of electron energy used in Monte-Carlo track-structure codes; the spectrum of secondary electrons generated by different functions for 500 eV primary electrons; cluster analysis for 4 MeV and 20 MeV alpha-particles in terms of the frequency of total cluster energy to the root-mean-square (rms) radius of the cluster and differential distance distributions for a pair of clusters; and finally relative frequency distribution for energy deposited in DNA, single-strand break and double-strand breaks for 10MeV/u protons, alpha-particles and carbon ions. CONCLUSIONS: There are a number of Monte-Carlo track-structure codes that have been developed independently and the bench-marking presented in this paper allows a better choice of the theoretical method adopted in a track-structure code to be made. A systematic bench-marking of cross-sections and spectra of the secondary electrons shows differences between the codes at atomic level, but such differences are not significant in biophysical modelling at the macromolecular level. Clustered-damage evaluation shows: that a substantial proportion of dose ( 30%) is deposited by low-energy electrons; the majority of DNA damage lesions are of simple type; the complexity of damage increases with increased LET, while the total yield of strand breaks remains constant; and at high LET values nearly 70% of all double-strand breaks are of complex type.

Alpha Particles↗
PubMed1998

Localization of LewisX, sialyl-LewisX and alpha-galactosyl epitopes on glycosphingolipids in lens tissues.

Mammalian lens contains several neutral and acidic glycosphingolipids, the core structures of which are ganglio-, neolacto-, globo-, and isoglobo-series sugar chains. Old World monkey lens shows glycosphingolipid compositions similar to those of human cataractous lens, in particular the presence of Lewisxand sialyl-Lewisxepitopes and the absence of alpha-galactosyl epitope. Dog and pig lenses contain globotriaosylceramide and the sialyl-Lewisxcontaining neolactotetraosylceramide, respectively, which were found in primate lens, together with the alpha-galactosyl epitope containing neolactotetraosylceramide. Thin-layer chromatography immunostaining revealed the enrichment of some neolacto-series glycosphingolipids in the cortical and nuclear fibers, but not in lens epithelia, of dog, pig, and Japanese monkey lenses. Immunohistochemical studies confirmed the expression of Lewisx, sialyl-Lewisx, and alpha-galactosyl epitopes in the inner cortical and nuclear fibers, in association with the differentiation and maturation of lens epithelial cells to lens fibers. Glycobiological approaches thus suggested that some neolacto-series glycosphingolipids are involved in lens fiber development, in which the physiological roles of the alpha-galactosyl epitope are evolutionarily replaced by the Lewisxand sialyl-Lewisxepitopes in Old World monkeys and humans.

Animals↗
PubMed1998

Monte Carlo simulation of in vivo measurements of 90Sr + 90Y bremsstrahlung.

The purpose of this study was to calculate the 90Sr + 90Y bremsstrahlung yield generated in bone quantitatively, and to determine the optimum conditions required for in vivo measurements of the yield, assuming that a given amount of contamination, due to the ordinary activities of 137Cs and 40K, is present within the human body. Several approximations in the distribution of activities in various body phantoms, simulating the human leg, waist and head, were made for simplicity. All the calculations were carried out using an in-house Monte Carlo code. The photon spectra incident on a detector window, of diameter 200 mm, positioned 1 mm from the surface of each phantom were obtained. A pseudo-peak of 90Sr + 90Y bremsstrahlung was observed at approximately 50 keV with a full width at half maximum of 60 keV (FWHM). The signal-to-background ratio, eta, where eta represents the ratio of the number of photons in the energy interval between 30 to 160 keV in the bremsstrahlung spectrum produced by 1 Bq kg(-1) of 90Sr and the background spectrum, which is assumed to comprise of 1 Bq kg(-1) of 137Cs and 60 Bq kg(-1) of 40K, was evaluated in order to determine the optimum measuring conditions. An optimum eta value of 0.0353 was obtained for the leg phantom, of bone diameter 30 mm, covered by a 1 mm layer of soft tissue. Combining the present calculations with the conventional measurements, a new and simpler method for evaluating the body burden activity of a beta emitter, such as 90Sr, is proposed.

Beta Particles↗
PubMed1998

Residual 60Co activity in steel samples exposed to the Hiroshima atomic-bomb neutrons.

Residual 60Co radioactivity produced by the neutrons from the Hiroshima atomic bomb has been measured by means of gamma-ray spectrometry for seven steel samples located up to 1,800 m slant range and one control sample obtained at 4.5 km from the hypocenter. After removing the main constituent of iron ions from the steel sample by the solvent extraction method, nickel and cobalt were chemically separated by the ion exchange process. Gamma-ray measurements were performed with a low background well-type germanium detector. Derived specific activities 60Co:Co were compared with previous measurements and with the calculation based on the neutron fluence of current dosimetry system DS86. It has been shown that a systematic discrepancy exists between the measured and calculated activity. The calculated-to-measured ratios for 60Co are consistent with those of 152Eu and 36Cl activity.

Chlorine↗
PubMed1998

Genomic analysis of DUSP6, a dual specificity MAP kinase phosphatase, in pancreatic cancer.

DUSP6 (alias PYST1), one of the dual-specificity tyrosine phosphatases, is localized on 12q21, one of the regions of frequent allelic loss in pancreatic cancer. This gene is composed of three exons, and two forms of alternatively spliced transcripts are ubiquitously expressed. Although no mutations were observed in 26 pancreatic cancer cell lines, reduced expressions of the full-length transcripts were observed in some cell lines, which may suggest some role for DUSP6 in pancreatic carcinogenesis.

Blotting, Southern↗
PubMed1998

Estimation of dose absorbed fraction for 131I-beta rays in rat thyroid.

The dose absorbed fraction of rat thyroid by internal deposit of 131I has been calculated as a function of effective diameter of thyroid. The calculations were done using two types of Monte Carlo simulations: one was by a simple energy-loss calculation in spherical volume according to the electron stopping power, and another by a more realistic simulation using Monte Carlo N-Particle Transport code system Version 4A (MCNP). These two calculations were consistent with each other within a deviation of 5%. The absorbed fractions in spherical thyroid were drastically changed up to 5 mm diameter, and then almost all energy was deposited within 10 mm diameter. For the practical application to the animal experiment, the absorbed fractions of ellipsoid-shaped thyroids were also calculated for 1-, 4- and 9-week-old rats, where the fractions were estimated to be 0.61, 0.67 and 0.68, respectively. It was also found that the absorbed fraction of the ellipsoid with various dimensions can be simulated by a calculation for spherical volume with a comparable effective diameter.

Animals↗
PubMed1998

Radiation therapy among atomic bomb survivors, Hiroshima and Nagasaki.

As a follow-up to the two previous surveys of radiation therapy among the atomic bomb survivors, a large-scale survey was performed to document (1) the number of radiation therapy treatments received by the atomic bomb survivors and (2) the types of radiation treatments conducted in Hiroshima and Nagasaki. The previous two surveys covered the radiation treatments among the Radiation Effects Research Foundation Adult Health Study (AHS) population, which is composed of 20,000 persons. In the present survey, the population was expanded to include the Life Span Study (LSS), including 93,611 atomic bomb survivors and 26,517 Hiroshima and Nagasaki citizens who were not in the cities at the times of the bombings. The LSS population includes the AHS population. The survey was conducted from 1981 to 1984. The survey teams reviewed all the medical records for radiation treatments of 24,266 patients at 11 large hospitals in Hiroshima and Nagasaki. Among them, the medical records for radiation treatments of 1556 LSS members were reviewed in detail. By analyzing the data obtained in the present and previous surveys, the number of patients receiving radiation therapy was estimated to be 4501 (3.7%) in the LSS population and 1026 (5.1%) in the AHS population between 1945-1980. During 1945-1965, 98% of radiation treatments used medium-voltage X rays, and 66% of the treatments were for benign diseases. During 1966-1980, 94% of the radiation treatments were for malignant neoplasms. During this period, 60Co gamma-ray exposure apparatus and high-energy electron accelerators were the prevalent mode of treatment in Hiroshima and in Nagasaki, respectively. The mean frequency of radiation therapy among the LSS population was estimated to have been 158 courses/year during 1945-1965 and 110 courses/year during 1966-1980. The present survey revealed that 377 AHS members received radiation therapy. The number was approximately twice the total number of cases found in the previous two surveys. Thus the data on radiation therapy in the AHS members have been updated well by this survey, and will provide information for more precise dose-response analyses of radiation effects in the AHS population. The information extracted from the medical records of the hospitals consisted of hospital names, treatment periods, body sites treated, diagnoses, treatment doses, radiation sources, the field sizes of the exposures and the data for identification of the patients. These data will be essential in estimating the organ doses from scattered radiation and in evaluating the effects of therapeutic radiation.

Adolescent↗
PubMed1997

In vivo dielectric analysis of free water content of biomaterials by time domain reflectometry.

A method of in vivo analysis of the free water content in living organisms by dielectric analysis in the time domain is described. Human skin is chosen as an example of living tissue. The cells suitable for the measurement of various layers of human skin and calculation procedures for the waveform reflected from the probe end are described. The approach was confirmed to be effective for the determination of the water content through measurement of the standard samples, keratin-water mixtures. This method was also applied to human skin in vivo. Water content data measured with a probe specially designed for surface layer analysis were sensitive to humidity around the subject. The formula expressing the relation between the electrical field character of the probe, the permittivity depth profile, and the measured permittivity was used to analyze the water content profile as a function of the depth from the skin surface. The use of several kinds of probes, differing in their electric field characteristics, permitted evaluation of the water content depth profile of human skin. This procedure is easy and applicable to any sample due to its simplicity. The measurement needs only a touch of the probe on a sample spot. It is therefore a promising method of physicochemical research on living organisms and biomaterials.

Body Water↗
PubMed1997

Structure of the main saccharide chain in the acrosome reaction-inducing substance of the starfish, Asterias amurensis.

The structure of the main saccharide chain of the acrosome reaction-inducing substance in the egg jelly coat of the starfish, Asterias amurensis, is composed of the following pentasaccharide repeating units (Structure I). A polymer consisting of 10-11 repeating units has been observed to induce the acrosome reaction in starfish sperm at high calcium concentrations. [STRUCTURE I:see text] The identities and linkage positions of constituent sugars were established using sugar, methylation, and sulfate analyses together with one- and two-dimensional nmr spectroscopy. The structure was supported by the data obtained for desulfation products and the Smith degradation of the polysaccharide.

Acrosome↗
PubMed1997

Nontoxic amyloid beta peptide 1-42 suppresses acetylcholine synthesis. Possible role in cholinergic dysfunction in Alzheimer's disease.

We show here that amyloid beta peptide1-42 (Abeta1-42) may play a key role in the pathogenesis of the cholinergic dysfunction seen in Alzheimer's disease (AD), in addition to its putative role in amyloid plaque formation. Abeta1-42 freshly solubilized in water (non-aged Abeta1-42), which was not neurotoxic without preaggregation, suppressed acetylcholine (ACh) synthesis in cholinergic neurons at very low concentrations (10-100 nM), although non-aged Abeta1-40 was ineffective. Non-aged Abeta1-42 impaired pyruvate dehydrogenase (PDH) activity by activating mitochondrial tau protein kinase I/glycogen synthase kinase-3beta, as we have already shown in hippocampal neurons (Hoshi, M., Takashima, A., Noguchi, K., Murayama, M., Sato, M., Kondo, S., Saitoh, Y., Ishiguro, K., Hoshino, T., and Imahori, K. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 2719-2723). Neither choline acetyltransferase activity nor choline metabolism was affected. Therefore, the major cause of reduced ACh synthesis was considered to be an inadequate supply of acetyl-CoA owing to PDH impairment. Soluble Abeta1-42 increases specifically in AD brain (Kuo, Y.-M., Emmerling, M. R., Vigo-Pelfrey, C., Kasunic, T. C., Kirkpatrick, J. B., Murdoch, G. H., Ball, M. J., and Roher, A. E. (1996) J. Biol. Chem. 271, 4077-4081). This increase in soluble Abeta1-42 may disturb cholinergic function, leading to the deterioration of memory and cognitive function that is characteristic of AD.

Acetylcholine↗
PubMed1997

Correlation between MIB-1 staining indices and recurrence in low-grade astrocytomas.

Although low-grade astrocytomas are histologically benign, some of them recur frequently. We retrospectively investigated the relationship between MIB-1 staining index (SI) and recurrence in 47 low-grade astrocytomas that were treated in Keio University Hospital from 1981 to 1991. We found a correlation between SI and recurrence. MIB-1 SIs recurrent low-grade astrocytomas have been shown to be almost similar to those of astrocytoma grade 3. We concluded that it was very important to examine MIB-1 SI in all astrocytomas especially in low-grade astrocytomas, because MIB-1 SI is one of the factors from which we could predict-recurrence and decide whether radiotherapy or chemotherapy should be performed.

Adolescent↗
PubMed1997

Analysis of cancer mortality among atomic bomb survivors registered at Hiroshima University.

The aim of this study was to investigate the late effect on cancer mortality risk of the radiation exposure of atomic bomb survivors who comprised a study population different from that previously studied by the Radiation Effects Research Foundation (RERF). We examined survivors residing in Hiroshima Prefecture, who were followed up between 1968 and 1989 by the Research Institute for Radiation Biology and Medicine (RIRBM) at Hiroshima University. We used the dose-evaluation system known as Atomic Bomb Survivors 1993 Dose (ABS93D), which was based on the Dosimetry System 1986 for the survivors registered with RERF. The dose estimation was applied in a total of 35,123 subjects. Among survivors who had been alive for > 20 years after the bombing, the relative mortality risk of leukaemia at 1 Gy of organ dose was 2.37 (90% confidence interval: 1.36-3.39), which was significantly higher than the zero dose control group. Similarly, significantly higher risks were observed for all cancers except leukaemia, including cancers of the lung, colon and female breast. Comparison is made with RERF results regarding temporal changes in the relative risk. Although we observed slightly lower relative risks than RERF values for the cancer of the stomach and lung, and for all cancer except leukaemia, no marked trends for any cancer were observed in this study. Though there were some differences in population between RERF and RIRBM, no marked discrepancies were observed.

Adolescent↗
PubMed1997

Association of the major ganglioside in sea urchin eggs with yolk lipoproteins.

The predominant ganglioside in sea urchin eggs, M5 (NeuGc alpha 2-6Glc beta 1-1'Cer), exists mainly in the cytoplasm before and after fertilization. Using immunofluorescence microscopy, M5 ganglioside has been shown to localize in the network of cortical endoplasmic reticulum and unidentified vesicles in the eggs. In this study, the subcellular localization of M5 ganglioside in unfertilized eggs was further examined by immunoelectronmicroscopy using preembedding and postembedding labeling techniques. In order to prevent lipid extraction during dehydration and embedding, fixed eggs were subjected to rapid-freezing and freeze-substitution, and then embedded in hydrophilic resin. When ultrathin sections were treated with the anti-M5 ganglioside monoclonal antibody, the labeling of M5 ganglioside localized in the endoplasmic reticula, yolk granules, and microvilli. M5 ganglioside in yolk granules was not restricted to the membrane, suggesting that M5 ganglioside associated with soluble proteins or components in yolk granules. Indeed, gel filtration of the soluble fraction of the yolk lysate showed that M5 ganglioside was coeluted with yolk lipoproteins which were one of the main components in yolk granules. Moreover, M5 ganglioside was extracted from the electrophoretically purified yolk lipoproteins. These results demonstrate that M5 ganglioside in yolk granules associate with yolk lipoproteins. These data suggest that much of M5 ganglioside may be taken up into growing oocytes during oogenesis and transported from yolk granules to other cellular components during embryogenesis. M5 ganglioside associating with yolk lipoproteins in yolk granules may be a significant stored material to be utilized for early embryogenesis.

Animals↗
PubMed1997

Developmental changes in carbohydrate antigens in embryonic rat lens.

The functions of glycosphingolipids, especially those containing the alpha-galactosyl epitope, were investigated during the development and differentiation of rat lens. Glycosphingolipids in embryonic lens tissue were mainly composed of neolacto-series glycosphingolipids and sialic acid-containing ganglio-series gangliosides GM3 and GD3. These glycosphingolipids and gangliosides were widely expressed on cell membranes in the lens vesicle and the elongating lens fibers. In particular, the expression of neolacto-series glycosphingolipids with the alpha-galactosyl epitope was found to be associated with the differentiation and interaction of lens fibers. Glycoproteins with the alpha-galactosyl epitope was also involved in the elongation of lens fibers. The expression of the glycoproteins was highly specific in elongating lens fibers when these were examined in head sections obtained at various embryonic stages. Thus, the alpha-galactosyl epitope on glycosphingolipids and glycoproteins appears to be associated with the differentiation and elongation of lens fibers in the rat. Evolution-related changes in the expression of carbohydrate antigens are also discussed in relation to the development and cell-to-cell interaction of lens fibers in mammals.

Animals↗
PubMed1997

Detection of in vivo proteasome activity in a starfish oocyte using membrane-impermeant substrate.

A method was investigated for monitoring the activity of protease(s) in cytosol of a single starfish oocyte using succinyl-Phe-Leu-Arg-coumarylamido-4-methanesulfonic acid as the substrate, which was injected into the cell. After preincubation of immature oocytes with a proteasome inhibitor, N-carbobenzoxy-L-leucinyl-L-leucinyl-L-norvalinal, the initial hydrolysis of the substrate was remarkably inhibited. The inhibitor blocked 1-methyladenine-triggered cyclin degradation, which is known to be mediated by proteasome. However, calpain inhibitor E-64 did not inhibit the hydrolysis of the substrate. These results suggested that the protease activity measured by this method is mainly attributable to cytoplasmic proteasome. The hydrolysis of the substrate was partially inhibited by bestatin, suggesting that the substrate was cleaved by aminopeptidase. Thus, the initial velocity of hydrolysis of the substrate (V0) by proteasome was assayed in a living oocyte after preinjection of bestatin. The values of V0 increased gradually after 1-methyladenine addition and reached the maximum level at the time corresponding to cyclin degradation. The calculated maximum velocity of hydrolysis by a mature oocyte was approximately three times higher than that by an immature oocyte. The Michaelis-Menten constant value was also higher in mature than immature oocytes. These results suggest that proteasome-dependent proteolysis is regulated not only by ubiquitination of substrates, as is generally believed, but also by the proteasome activity itself.

Adenine↗