title: DNA synthesis and nucleoside metabolism in human tonsillar lymphocyte subpopulations.
abstract: High (HD) and low (LD) density cells were separated on 25% BSA gradient from tonsils of 3-6 years old children. Early B lymphocyte markers and sIg-s were found on the surface of 59-82% of the LD cells. This cell population was 5-6 times more active in DNA synthesis (3H-thymidine incorporation, DNA polymerase activity) than the HD cells. The total uptake of 3H-deoxycytidine was about the same as that of 3H-thymidine. As long as practically all thymidine taken up by the cells was immediately incorporated into DNA (90-95%), only 10-15% of deoxycytidine was incorporated into DNA under the same conditions, indicating different pool sizes for the DNA precursors. The majority of deoxycytidine (70%) was converted and incorporated as dTMP. A considerable part of labeled deoxycytidine could be detected in the soluble pool in form of nucleotides (3-8%), and in an unknown form, called substance X (8-14%). Substance X was purified by TL chromatography and identified by HPLC as deoxycytidine containing liponucleotides, probable precursors for plasmamembranes. The preferential utilisation of deoxycytidine for DNA and membrane synthesis in immature B lymphocytes draws the attention to its function in early events of lymphocyte maturation.
authors.affiliation: First Institute of Biochemistry, Semmelweis University Medical School, Budapest, Hungary.
authors.forename: M
authors.initials: M
authors.lastname: Staub
authors.forename: T
authors.initials: T
authors.lastname: Spasokukotskaja
authors.forename: M
authors.initials: M
authors.lastname: Benczur
authors.forename: F
authors.initials: F
authors.lastname: Antoni
mesh_terms: D000943:Antigens, Differentiation / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D004247:DNA / Q000096:biosynthesis*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D003841:Deoxycytidine / Q000378:metabolism; D003842:Deoxycytidine Kinase / Q000378:metabolism; D004229:Dithiothreitol / Q000378:metabolism; D006801:Humans; D008214:Lymphocytes / Q000145:classification / Q000201:enzymology / Q000378:metabolism*; D009705:Nucleosides / Q000378:metabolism*; D014066:Palatine Tonsil / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D013937:Thymidine Kinase / Q000378:metabolism
chemical_list: D000943:Antigens, Differentiation; D009705:Nucleosides; D003841:Deoxycytidine; D004247:DNA; D013937:Thymidine Kinase; D003842:Deoxycytidine Kinase; D004259:DNA-Directed DNA Polymerase; D004229:Dithiothreitol; D013936:Thymidine