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Summary Kidney cells from primary cultures of 15-day old mouse embryos were incubated for 2, 5 or 10 min with H3-uridine, then either fixed immediately or incubated again for various periods in a chase medium containing an excess of unlabeled uridine and cytidine. The number of grains over the non-nucleolar part of the nucleus (chromatin), the nucleolus and the cytoplasm were counted on the autoradiograms.The grain count showed that both chromatin and nucleolus incorporate very rapidly H3-uridine from the medium, whereas a time lag elapses before any H3-radioactivity above background is detected in the cytoplasm. Incorporation of H3-uridine into the RNA of the nucleus and the nucleolus is not immediately blocked after chase, suggesting that the labeled precursor pool is not completely washed out from the living cell, or diluted by the excess of unlabeled uridine present in the medium. The grain count over the nucleus and the nucleolus rises for a certain time after chase and then gradually declines; H3-radioactivity appears in the cytoplasm 10 min after chase and keeps rising through a 110-min interval. The experiment, then — even though it suggests that the bulk of cellular RNA is synthesized in the chromatin and the nucleolus and then continuously released into the cytoplasm — does not rule out the possibility that some RNA fraction, characterized by a low turnover rate, is synthesized independently in the cytoplasm.Synthesis of RNA is a continuous process throughout the cell cycle, except during metaphase and anaphase. It ceases at prometaphase after the disappearance of the nucleolus and disintegration of the nuclear membrane, and resumes in early telophase. Part of the chromosomal RNA does not remain associated with the chromosomes through division, but is suddenly released into the cytoplasm when the cell enters metaphase. 相似文献
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Selenalysine transamination by a bovine brain enzyme 总被引:1,自引:0,他引:1
C Blarzino R Coccia C Foppoli B Pensa G De Marco 《Physiological chemistry and physics and medical NMR》1989,21(4):295-300
Selenalysine is deaminated by glutamine transaminase from bovine brain, leading to the production of the corresponding alpha-ketoacid, which spontaneously cyclizes to a ketimine form. Selenalysine shows a good affinity for the enzyme. 相似文献
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L A Marco R Pendleton T F Reed T E Brigham L D Aldes R B Chronister 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1989,94(1):29-33
1. The purpose of this study was to demonstrate that ketamine anesthesia (100 mg/kg) induces tongue protrusions (P) in addition to retrusions (R) and swallows (S) in adult rats. 2. These linguo-pharyngeal events occur alone or combined in various sequential patterns. 3. The SPR sequence is not the predominant pattern in all preparations suggesting profound disruption of physiological linkages by ketamine. 4. Haloperidol administration suppresses these events for 1-120 min depending on the dose (0.75-2.5 mg/kg). 5. Swallows are the least vulnerable to haloperidol. 6. This and previous findings provide further evidence that ketamine induced linguo-pharyngeal activity can serve as a model for acute or tardive dyskinesia better than stereotypies. 相似文献
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Presence of glyoxalase II in mitochondria from spinach leaves: comparison with the enzyme from cytosol 总被引:1,自引:0,他引:1
V Talesa G Rosi S Contenti C Mangiabene M Lupattelli S J Norton E Giovannini G B Principato 《Biochemistry international》1990,22(6):1115-1120
Glyoxalase II has been purified from cytosol and mitochondria of spinach leaves. Electrophoresis and isoelectric focussing have resolved cytosolic and mitochondrial glyoxalase II in multiple forms: pl 5.3, 5.8 and 6.2 (cytosol) and pl 4.8 (mitochondria). The enzyme of both localizations is a monomer showing a relative molecular mass of about 26 kDa. The values of kinetic constants using several glutathione thiolesters as substrates, are similar for the enzymes from cytosol and mitochondria. These results extend also to plant the presence in mitochondria of peculiar forms of glyoxalase II, likewise recently demonstrated in mammalians. 相似文献