[Studies on testicular function. Report 4. Studies on DNA synthesizing capacity of germinal cell, especially spermatogenic activity index in hypospermatogenesis (author's transl)].
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Biomedical subjects
Publications and source records attributed to M Terada.
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Cell populations enriched for erythroid precursor cells were fractionated from 13-day fetal-mouse livers by a method of immune hemolysis. These preparations of precursors, contaminated by less than 7% hemoglobinized erythroblasts, synthesize globin at a rate less than 6% that of the unfractionated liver erythroid cell population. RNA was isolated from these precursor cells and assayed for globin mRNA activity in a cell-free system from Krebs ascites tumor. The 6-16S RNA fraction from precursor cells has less than 5% of the globin mRNA activity of RNA isolated from unfractionated populations. Precursor cells incubated with erythropoietin show an increment in the rate of synthesis of globin only after 5-10 hr of incubation. After 10 hr of culture with this hormone, precursor cells show a 6- to 10-fold increase in globin mRNA activity. These results suggest that the precursor cells of hepatic erythropoiesis, responsive to erythropoietin, do not contain globin mRNA in a biologically active form. Erythropoietin-induced differentiation of these cells to erythroblasts is associated with an increase in globin mRNA.
Addition of a 0.5 M KCl wash fraction from rabbit reticulocyte ribosomes causes a 3- to 10-fold increase in the extent of translation of natural mRNAs by Krebs-cell lysates. In the presence of the wash fraction, 1 pmol of rabbit or mouse 10S RNA directs the incorporation of 80 pmol of leucine into rabbit globin. The addition of human 10S RNA results in the synthesis of equal amounts of human alpha and beta chains, identified by column chromatography. The stimulation by the wash fraction is almost completely dependent on added mammalian tRNA. In contrast to the wash fraction from rabbit reticulocytes, the wash fraction isolated from Krebs-cell ribosomes is inhibitory to both endogenous and exogenous mRNA translation. The stimulation by the wash fraction from rabbit ribosomes is not specific for globin mRNAs, but also increases endogenous, phage Qbeta, and viral RNA-directed protein synthesis.
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