摘要：

When reticulocyte polysomes are dissociated with sodium dodecyl sulfate and analyzed by sucrose density gradient centrifugation, a ribonucleic acid of 9 S (9S ribonucleic acid) is observed. This ribonucleic acid exhibits many of the properties expected for the hemoglobin messenger ribonucleic acid, such as size, per cent of total ribonucleic acid, and involvement in polysomal structure. Because of these unique features it was of interest to study its synthesis in relation to ribosomal ribonucleic acid synthesis during erythroid cell development. This was accomplished by injecting [3H]uridine into anemic mice at various times prior to collecting the circulating reticulocytes. Cells obtained shortly after injection of the ribonucleic acid precursor are those reticulocytes originating from more mature nucleated erythroid cells while those reticulocytes obtained at longer times originate from more immature precursor cells. The data indicate that ribosomal ribonucleic acid is synthesized early in erythroid cell development while 9S ribonucleic acid synthesis is maximal in later cells.

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