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Deoxyuridine: 2'-Deoxyuridine. An antimetabolite that is converted to deoxyuridine triphosphate during DNA synthesis. Laboratory suppression of deoxyuridine is used to diagnose megaloblastic anemias due to vitamin B12 and folate deficiencies.Deoxyuracil Nucleotides: Uracil nucleotides which contain deoxyribose as the sugar moiety.Pyrophosphatases: A group of enzymes within the class EC 3.6.1.- that catalyze the hydrolysis of diphosphate bonds, chiefly in nucleoside di- and triphosphates. They may liberate either a mono- or diphosphate. EC 3.6.1.-.Bromodeoxyuridine: A nucleoside that substitutes for thymidine in DNA and thus acts as an antimetabolite. It causes breaks in chromosomes and has been proposed as an antiviral and antineoplastic agent. It has been given orphan drug status for use in the treatment of primary brain tumors.Floxuridine: An antineoplastic antimetabolite that is metabolized to fluorouracil when administered by rapid injection; when administered by slow, continuous, intra-arterial infusion, it is converted to floxuridine monophosphate. It has been used to treat hepatic metastases of gastrointestinal adenocarcinomas and for palliation in malignant neoplasms of the liver and gastrointestinal tract.DCMP Deaminase: An enzyme that catalyzes the hydrolytic deamination of deoxycytidylic acid to deoxyuridylic acid and ammonia. It plays an important role in the regulation of the pool of deoxynucleotides in higher organisms. The enzyme also acts on some 5-substituted deoxycytidylic acids. EC 3.5.4.12.ThymidineDeoxyribonucleosides: A purine or pyrimidine base bonded to DEOXYRIBOSE.Thymidylate Synthase: An enzyme of the transferase class that catalyzes the reaction 5,10-methylenetetrahydrofolate and dUMP to dihydrofolate and dTMP in the synthesis of thymidine triphosphate. (From Dorland, 27th ed) EC 2.1.1.45.Thymidine Monophosphate: 5-Thymidylic acid. A thymine nucleotide containing one phosphate group esterified to the deoxyribose moiety.UracilIn Situ Nick-End Labeling: An in situ method for detecting areas of DNA which are nicked during APOPTOSIS. Terminal deoxynucleotidyl transferase is used to add labeled dUTP, in a template-independent manner, to the 3 prime OH ends of either single- or double-stranded DNA. The terminal deoxynucleotidyl transferase nick end labeling, or TUNEL, assay labels apoptosis on a single-cell level, making it more sensitive than agarose gel electrophoresis for analysis of DNA FRAGMENTATION.Megaloblasts: Red blood cell precursors, corresponding to ERYTHROBLASTS, that are larger than normal, usually resulting from a FOLIC ACID DEFICIENCY or VITAMIN B 12 DEFICIENCY.Idoxuridine: An analog of DEOXYURIDINE that inhibits viral DNA synthesis. The drug is used as an antiviral agent.Uracil-DNA Glycosidase: An enzyme that catalyzes the HYDROLYSIS of the N-glycosidic bond between sugar phosphate backbone and URACIL residue during DNA synthesis.Deoxyribonucleotides: A purine or pyrimidine base bonded to a DEOXYRIBOSE containing a bond to a phosphate group.Deoxycytidine Monophosphate: Deoxycytidine (dihydrogen phosphate). A deoxycytosine nucleotide containing one phosphate group esterified to the deoxyribose moiety in the 2'-,3'- or 5- positions.UridineMitochondrial Encephalomyopathies: A heterogenous group of disorders characterized by alterations of mitochondrial metabolism that result in muscle and nervous system dysfunction. These are often multisystemic and vary considerably in age at onset (usually in the first or second decade of life), distribution of affected muscles, severity, and course. (From Adams et al., Principles of Neurology, 6th ed, pp984-5)Uracil NucleotidesNucleotide Deaminases: Catalyze the hydrolysis of nucleotides with the elimination of ammonia.Thymine Nucleotides: Phosphate esters of THYMIDINE in N-glycosidic linkage with ribose or deoxyribose, as occurs in nucleic acids. (From Dorland, 28th ed, p1154)Apoptosis: One of the mechanisms by which CELL DEATH occurs (compare with NECROSIS and AUTOPHAGOCYTOSIS). Apoptosis is the mechanism responsible for the physiological deletion of cells and appears to be intrinsically programmed. It is characterized by distinctive morphologic changes in the nucleus and cytoplasm, chromatin cleavage at regularly spaced sites, and the endonucleolytic cleavage of genomic DNA; (DNA FRAGMENTATION); at internucleosomal sites. This mode of cell death serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth.Sarcoma, YoshidaRhodotorula: A red yeast-like mitosporic fungal genus generally regarded as nonpathogenic. It is cultured from numerous sources in human patients.Thymidine Phosphorylase: An enzyme that catalyzes the transfer of 2-deoxy-D-ribose from THYMIDINE to orthophosphate, thereby liberating thymidine.Uridine Phosphorylase: An enzyme that catalyzes the transfer of ribose from uridine to orthophosphate, forming uracil and ribose 1-phosphate.Methotrexate: An antineoplastic antimetabolite with immunosuppressant properties. It is an inhibitor of TETRAHYDROFOLATE DEHYDROGENASE and prevents the formation of tetrahydrofolate, necessary for synthesis of thymidylate, an essential component of DNA.DNA: A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).Deamination: The removal of an amino group (NH2) from a chemical compound.Cytidine: A pyrimidine nucleoside that is composed of the base CYTOSINE linked to the five-carbon sugar D-RIBOSE.Pyrimidine Nucleosides: Pyrimidines with a RIBOSE attached that can be phosphorylated to PYRIMIDINE NUCLEOTIDES.Pyrimidine Nucleotides: Pyrimidines with a RIBOSE and phosphate attached that can polymerize to form DNA and RNA.Folic Acid Deficiency: A nutritional condition produced by a deficiency of FOLIC ACID in the diet. Many plant and animal tissues contain folic acid, abundant in green leafy vegetables, yeast, liver, and mushrooms but destroyed by long-term cooking. Alcohol interferes with its intermediate metabolism and absorption. Folic acid deficiency may develop in long-term anticonvulsant therapy or with use of oral contraceptives. This deficiency causes anemia, macrocytic anemia, and megaloblastic anemia. It is indistinguishable from vitamin B 12 deficiency in peripheral blood and bone marrow findings, but the neurologic lesions seen in B 12 deficiency do not occur. (Merck Manual, 16th ed)Anemia, Megaloblastic: A disorder characterized by the presence of ANEMIA, abnormally large red blood cells (megalocytes or macrocytes), and MEGALOBLASTS.Thymidine Kinase: An enzyme that catalyzes the conversion of ATP and thymidine to ADP and thymidine 5'-phosphate. Deoxyuridine can also act as an acceptor and dGTP as a donor. (From Enzyme Nomenclature, 1992) EC 2.7.1.21.Fluorodeoxyuridylate: 5-Fluoro-2'-deoxyuridylate. An inhibitor of thymidylate synthetase. Formed from 5-fluorouracil or 5-fluorodeoxyuridine.ThymineTritiumPentosyltransferases: Enzymes of the transferase class that catalyze the transfer of a pentose group from one compound to another.Tetrahydrofolates: Compounds based on 5,6,7,8-tetrahydrofolate.N-Glycosyl Hydrolases: A class of enzymes involved in the hydrolysis of the N-glycosidic bond of nitrogen-linked sugars.Cell Proliferation: All of the processes involved in increasing CELL NUMBER including CELL DIVISION.Folic Acid Antagonists: Inhibitors of the enzyme, dihydrofolate reductase (TETRAHYDROFOLATE DEHYDROGENASE), which converts dihydrofolate (FH2) to tetrahydrofolate (FH4). They are frequently used in cancer chemotherapy. (From AMA, Drug Evaluations Annual, 1994, p2033)Trimetrexate: A nonclassical folic acid inhibitor through its inhibition of the enzyme dihydrofolate reductase. It is being tested for efficacy as an antineoplastic agent and as an antiparasitic agent against PNEUMOCYSTIS PNEUMONIA in AIDS patients. Myelosuppression is its dose-limiting toxic effect.Cell Division: The fission of a CELL. It includes CYTOKINESIS, when the CYTOPLASM of a cell is divided, and CELL NUCLEUS DIVISION.Nucleosides: Purine or pyrimidine bases attached to a ribose or deoxyribose. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Kinetics: The rate dynamics in chemical or physical systems.Cytidine Deaminase: An enzyme that catalyzes the deamination of cytidine, forming uridine. EC 3.5.4.5.Folic Acid: A member of the vitamin B family that stimulates the hematopoietic system. It is present in the liver and kidney and is found in mushrooms, spinach, yeast, green leaves, and grasses (POACEAE). Folic acid is used in the treatment and prevention of folate deficiencies and megaloblastic anemia.Vitamin B 12 Deficiency: A nutritional condition produced by a deficiency of VITAMIN B 12 in the diet, characterized by megaloblastic anemia. Since vitamin B 12 is not present in plants, humans have obtained their supply from animal products, from multivitamin supplements in the form of pills, and as additives to food preparations. A wide variety of neuropsychiatric abnormalities is also seen in vitamin B 12 deficiency and appears to be due to an undefined defect involving myelin synthesis. (From Cecil Textbook of Medicine, 19th ed, p848)Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Bone Marrow: The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells.Antimetabolites: Drugs that are chemically similar to naturally occurring metabolites, but differ enough to interfere with normal metabolic pathways. (From AMA Drug Evaluations Annual, 1994, p2033)DNA Glycosylases: A family of DNA repair enzymes that recognize damaged nucleotide bases and remove them by hydrolyzing the N-glycosidic bond that attaches them to the sugar backbone of the DNA molecule. The process called BASE EXCISION REPAIR can be completed by a DNA-(APURINIC OR APYRIMIDINIC SITE) LYASE which excises the remaining RIBOSE sugar from the DNA.Leukemia L1210Nucleotides: The monomeric units from which DNA or RNA polymers are constructed. They consist of a purine or pyrimidine base, a pentose sugar, and a phosphate group. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Mitosporic Fungi: A large and heterogenous group of fungi whose common characteristic is the absence of a sexual state. Many of the pathogenic fungi in humans belong to this group.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.DNA, Neoplasm: DNA present in neoplastic tissue.Nucleoside Deaminases: Catalyze the hydrolysis of nucleosides with the elimination of ammonia.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Pyrimidines: A family of 6-membered heterocyclic compounds occurring in nature in a wide variety of forms. They include several nucleic acid constituents (CYTOSINE; THYMINE; and URACIL) and form the basic structure of the barbiturates.DNA Replication: The process by which a DNA molecule is duplicated.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Proliferating Cell Nuclear Antigen: Nuclear antigen with a role in DNA synthesis, DNA repair, and cell cycle progression. PCNA is required for the coordinated synthesis of both leading and lagging strands at the replication fork during DNA replication. PCNA expression correlates with the proliferation activity of several malignant and non-malignant cell types.DNA Fragmentation: Splitting the DNA into shorter pieces by endonucleolytic DNA CLEAVAGE at multiple sites. It includes the internucleosomal DNA fragmentation, which along with chromatin condensation, are considered to be the hallmarks of APOPTOSIS.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Fluorouracil: A pyrimidine analog that is an antineoplastic antimetabolite. It interferes with DNA synthesis by blocking the THYMIDYLATE SYNTHETASE conversion of deoxyuridylic acid to thymidylic acid.Staining and Labeling: The marking of biological material with a dye or other reagent for the purpose of identifying and quantitating components of tissues, cells or their extracts.Cell Survival: The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability.Caspase 3: A short pro-domain caspase that plays an effector role in APOPTOSIS. It is activated by INITIATOR CASPASES such as CASPASE 9. Isoforms of this protein exist due to multiple alternative splicing of its MESSENGER RNA.Neurogenesis: Formation of NEURONS which involves the differentiation and division of STEM CELLS in which one or both of the daughter cells become neurons.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.