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  • 1
    ISSN: 1432-0738
    Keywords: Methylmercury ; Aminoacyl tRNA synthetase ; Brain ; Protein synthesis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The activities of six aminoacyl-tRNA synthetase species were determined using enzyme preparations partially purified from the brains of control and methylmercury (MeHg)-treated rats. The activities of Asp-, Leu- and Tyr-tRNA synthetases were significantly reduced in the brains of MeHg-intoxicated rats, whereas those of Lysand Met-tRNA synthetases remained unchanged. In contrast, the activity of His-tRNA synthetase was significantly increased in the symptomatic phase of MeHg intoxication. The activities of these six aminoacyl-tRNA synthetases in the control brains were affected to different extents on the direct addition of MeHg to the assay system in vitro. No positive correlation was observed between the in vivo and in vitro effects of MeHg on the enzyme activities. These results indicate that the aminoacylation of tRNA is one of the actions of MeHg, which leads to inhibition of protein synthesis, and it is suggested that the syntheses of cellular proteins may be modified in different ways by MeHg, depending on their amino acid compositions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0533
    Keywords: Key word Ependymoma ; Lipidized cell ; Glial ; fibrillary acidic protein ; Collagenous metaplasia ; Spinal cord tumor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a 49-year-old woman with a spinal cord ependymoma located in the thoracolumbar region. At surgery, a soft dark-grayish tumor, which contained a hard whitish area, was removed. The specimen was a moderately cellular tumor with a central core made up of collagen nodules poor in cellular elements. Many of the tumor cells possessed ground glass-like eosinophilic cytoplasm, and frequently foamy tumor cells were evident. Perivascular pseudorosettes, ependymal rosettes and canals were present, the latter being rare. Many tumor cells, including those with foamy cytoplasm, were positive for glial fibrillary acidic protein. Similar tumor cells were also seen among, and even within, the collagen nodules. The MIB-1 labeling index was 0.66%. Ultrastructurally, the frequent lipidized tumor cells were ependymal in nature; cytoplasmic 10-nm-wide filaments, and intracytoplasmic lumina and intercellular microrosettes lined by microvilli were evident. Cilia were very rare. We considered the present case to be an unusual, lipidized variant of ependymoma. The collagen nodules appeared to be produced by the tumor cells themselves.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0738
    Keywords: Methylmercury accumulation ; Biotransformation ; Rat ; Hamster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The accumulation of mercury in tissues of the rat and hamster was determined after the administration of a single dose of 203Hg-methylmercury chloride (10mg/kg body weight). (1) On day 2, the mercury contents of hamster tissues were higher than those of rat tissues, except for red blood cells, in which the mercury content was about 6-fold higher in the rat than in the hamster. (2) After that time, the mercury content of hamster tissues decreased rather steeply and on day 16 it had reached 14–25% in nervous tissues and 7–15% in other tissues, of the levels on day 2. (3) In the rat, on the other hand, the mercury content of nervous tissues on day 16 was higher than that on day 2 (106–220%), except for dorsal roots and dorsal root ganglia, which showed slight decreases (75–94% of the levels on day 2). In non-neural tissues, the decreases up to day 16 were also small (71–92% of the levels on day 2). (4) Thus, both the uptake and elimination of mercury seem to be more rapid in the tissues of hamster compared with those of the rat. Similar trends of mercury accumulation and elimination were observed when animals received multiple injections of methylmercury that induced acute methylmercury intoxication. (5) Significant biotransformation of the injected methylmercury to inorganic mercury was detected in the liver, kidney and spleen of both animal species. Although the percentages of inorganic mercury in these tissues were not so different between the two species on day 2, they became exceedingly high in the tissues of hamster at the later stage, except in the kidney cytosol, in which the values were close in both animal species between day 2 and day 16.
    Type of Medium: Electronic Resource
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