Thymidine

About: Thymidine is a research topic. Over the lifetime, 6178 publications have been published within this topic receiving 194386 citations. The topic is also known as: 1-(2-deoxy-beta-D-erythro-pentofuranosyl)-5-methylpyrimidine-2,4(1H,3H)-dione & 2'-deoxy-5-methyluridine.

Monoclonal antibody to 5-bromo- and 5-iododeoxyuridine: A new reagent for detection of DNA replication

Abstract: Monoclonal antibodies specific for 5-bromodeoxyuridine have been produced and applied in detecting low levels of DNA replication on a cell-by-cell basis in vitro. The immunoglobulin-producing hybridomas were derived from spleen cells of mice immunized with a conjugate of iodouridine and ovalbumin. The cells were fused with the plasmacytoma line SP2/0Ag14. The antibodies produced are highly specific for bromodeoxyuridine and iododeoxyuridine and do not cross-react with thymidine. DNA synthesis in cultured cells exposed to bromodeoxyuridine for as short a time as 6 minutes can be detected easily and rapidly by an immunofluorescent staining method and quantitated by flow cytometry.

3'-Azido-3'-deoxythymidine (BW A509U): an antiviral agent that inhibits the infectivity and cytopathic effect of human T-lymphotropic virus type III/lymphadenopathy-associated virus in vitro.

Abstract: The acquired immune deficiency syndrome (AIDS) is thought to result from infection of T cells by a pathogenic human retrovirus, human T-lymphotropic virus type III (HTLV-III) or lymphadenopathy-associated virus (LAV). In this report, we describe the antiviral effects of a thymidine analogue,3'-azido-3'-deoxythymidine (BW A509U), which, as a triphosphate, inhibits the reverse transcriptase of HTLV-III/LAV. This agent blocks the expression of the p24 gag protein of HTLV-III/LAV in H9 cells following exposure to virus. The drug also inhibits the cytopathic effect of HTLV-IIIB (a virus derived from a pool of American patients) and HTLV-III/RF-II (an isolate obtained from a Haitian patient that differs by about 20% in the amino acid sequence of the envelope gene from several isolates of HTLV-III/LAV, including HTLV-IIIB, analyzed so far). 3'-Azido-3'-deoxythymidine also completely blocks viral replication as assessed by reverse transcriptase production in normal human peripheral blood mononuclear cells exposed to HTLV-IIIB. Finally, at concentrations of 3'-azido-3'-deoxythymidine that block the in vitro infectivity and cytopathic effect of HTLV-IIIB, the in vitro immune functions of normal T cells remain basically intact.

Selectivity of action of an antiherpetic agent, 9-(2-hydroxyethoxymethyl)guanine

Abstract: A guanine derivative with an acyclic side chain, 2-hydroxyethoxymethyl, at position 9 has potent antiviral activity [dose for 50% inhibition (ED50) = 0.1 μM] against herpes simplex virus type 1. This acyclic nucleoside analog, termed acycloguanosine, is converted to a monophosphate by a virus-specified pyrimidine deoxynucleoside (thymidine) kinase and is subsequently converted to acycloguanosine di- and triphosphates. In the uninfected host cell (Vero) these phosphorylations of acycloguanosine occur to a very limited extent. Acycloguanosine triphosphate inhibits herpes simplex virus DNA polymerase (DNA nucleotidyltransferase) 10-30 times more effectively than cellular (HeLa S3) DNA polymerase. These factors contribute to the drug's selectivity; inhibition of growth of the host cell requires a 3000-fold greater concentration of drug than does the inhibition of viral multiplication. There is, moreover, the strong possibility of chain termination of the viral DNA by incorporation of acycloguanosine. The identity of the kinase that phosphorylates acycloguanosine was determined after separation of the cellular and virus-specified thymidine kinase activities by affinity chromatography, by reversal studies with thymidine, and by the lack of monophosphate formation in a temperature-sensitive, thymidine kinase-deficient mutant of the KOS strain of herpes simplex virus type 1 (tsA1).

Phosphorylation of 3'-azido-3'-deoxythymidine and selective interaction of the 5'-triphosphate with human immunodeficiency virus reverse transcriptase.

Abstract: The thymidine analog 3'-azido-3'-deoxythymidine (BW A509U, azidothymidine) can inhibit human immunodeficiency virus (HIV) replication effectively in the 50-500 nM range [Mitsuya, H., Weinhold, K. J., Furman, P. A., St. Clair, M. H., Nusinoff-Lehrman, S., Gallo, R. C., Bolognesi, D., Barry, D. W. & Broder, S. (1985) Proc. Natl. Acad. Sci. USA 82, 7096-7100]. In contrast, inhibition of the growth of uninfected human fibroblasts and lymphocytes has been observed only at concentrations above 1 mM. The nature of this selectivity was investigated. Azidothymidine anabolism to the 5'-mono-, di-, and -triphosphate derivatives was similar in uninfected and HIV-infected cells. The level of azidothymidine monophosphate was high, whereas the levels of the di- and triphosphate were low (less than or equal to 5 microM and less than or equal to 2 microM, respectively). Cytosolic thymidine kinase (EC 2.7.1.21) was responsible for phosphorylation of azidothymidine to its monophosphate. Purified thymidine kinase catalyzed the phosphorylations of thymidine and azidothymidine with apparent Km values of 2.9 microM and 3.0 microM. The maximal rate of phosphorylation with azidothymidine was equal to 60% of the rate with thymidine. Phosphorylation of azidothymidine monophosphate to the diphosphate also appeared to be catalyzed by a host-cell enzyme, thymidylate kinase (EC 2.7.4.9). The apparent Km value for azidothymidine monophosphate was 2-fold greater than the value for dTMP (8.6 microM vs. 4.1 microM), but the maximal phosphorylation rate was only 0.3% of the dTMP rate. These kinetic constants were consistent with the anabolism results and indicated that azidothymidine monophosphate is an alternative-substrate inhibitor of thymidylate kinase. This conclusion was reflected in the observation that cells incubated with azidothymidine had reduced intracellular levels of dTTP. IC50 (concentration of inhibitor that inhibits enzyme activity 50%) values were determined for azidothymidine triphosphate with HIV reverse transcriptase and with immortalized human lymphocyte (H9 cell) DNA polymerase alpha. Azidothymidine triphosphate competed about 100-fold better for the HIV reverse transcriptase than for the cellular DNA polymerase alpha. The results reported here suggest that azidothymidine is nonselectively phosphorylated but that the triphosphate derivative efficiently and selectively binds to the HIV reverse transcriptase. Incorporation of azidothymidylate into a growing DNA strand should terminate DNA elongation and thus inhibit DNA synthesis.

Tumor Chemosensitivity Conferred by Inserted Herpes Thymidine Kinase Genes: Paradigm for a Prospective Cancer Control Strategy

Abstract: The lack of highly exploitable biochemical differences between normal tissues and some tumors can theoretically be circumvented by a strategy utilizing gene insertion prophylactically to create tissue mosaicism for drug sensitivity, thereby ensuring that any tumor arising clonally will differ from part of the normal cell population. Elements of the strategy were tested with neoplastic BALB/c murine cell lines bearing the herpes thymidine kinase gene. Exposure to the herpes thymidine kinase-specific substrate 9-([2-hydroxy-1-(hydroxymethyl)ethoxy]methyl)guanine ablated the clonogenic potential of the cells in vitro, and administration of this drug to BALB/c mice bearing tumors produced by the cell lines uniformly induced complete regression of the tumors. The observed responses to therapy imply that the strategy may prove valuable when the genetic technology needed for its human implementation becomes available.