Amsacrine: An aminoacridine derivative that intercalates into DNA and is used as an antineoplastic agent.Aminoacridines: Acridines which are substituted in any position by one or more amino groups or substituted amino groups.DNA Topoisomerases, Type II: DNA TOPOISOMERASES that catalyze ATP-dependent breakage of both strands of DNA, passage of the unbroken strands through the breaks, and rejoining of the broken strands. These enzymes bring about relaxation of the supercoiled DNA and resolution of a knotted circular DNA duplex.Topoisomerase II Inhibitors: Compounds that inhibit the activity of DNA TOPOISOMERASE II. Included in this category are a variety of ANTINEOPLASTIC AGENTS which target the eukaryotic form of topoisomerase II and ANTIBACTERIAL AGENTS which target the prokaryotic form of topoisomerase II.Teniposide: A semisynthetic derivative of PODOPHYLLOTOXIN that exhibits antitumor activity. Teniposide inhibits DNA synthesis by forming a complex with topoisomerase II and DNA. This complex induces breaks in double stranded DNA and prevents repair by topoisomerase II binding. Accumulated breaks in DNA prevent cells from entering into the mitotic phase of the cell cycle, and lead to cell death. Teniposide acts primarily in the G2 and S phases of the cycle.Intercalating Agents: Agents that are capable of inserting themselves between the successive bases in DNA, thus kinking, uncoiling or otherwise deforming it and therefore preventing its proper functioning. They are used in the study of DNA.Dipodomys: A genus of the family Heteromyidae which contains 22 species. Their physiology is adapted for the conservation of water, and they seldom drink water. They are found in arid or desert habitats and travel by hopping on their hind limbs.Aminacrine: A highly fluorescent anti-infective dye used clinically as a topical antiseptic and experimentally as a mutagen, due to its interaction with DNA. It is also used as an intracellular pH indicator.Etoposide: A semisynthetic derivative of PODOPHYLLOTOXIN that exhibits antitumor activity. Etoposide inhibits DNA synthesis by forming a complex with topoisomerase II and DNA. This complex induces breaks in double stranded DNA and prevents repair by topoisomerase II binding. Accumulated breaks in DNA prevent entry into the mitotic phase of cell division, and lead to cell death. Etoposide acts primarily in the G2 and S phases of the cell cycle.Cytarabine: A pyrimidine nucleoside analog that is used mainly in the treatment of leukemia, especially acute non-lymphoblastic leukemia. Cytarabine is an antimetabolite antineoplastic agent that inhibits the synthesis of DNA. Its actions are specific for the S phase of the cell cycle. It also has antiviral and immunosuppressant properties. (From Martindale, The Extra Pharmacopoeia, 30th ed, p472)Razoxane: An antimitotic agent with immunosuppressive properties.Vomiting, Anticipatory: Vomiting caused by expectation of discomfort or unpleasantness.Antineoplastic Agents: Substances that inhibit or prevent the proliferation of NEOPLASMS.Mitoxantrone: An anthracenedione-derived antineoplastic agent.AcridinesTopoisomerase I Inhibitors: Compounds that inhibit the activity of DNA TOPOISOMERASE I.Daunorubicin: A very toxic anthracycline aminoglycoside antineoplastic isolated from Streptomyces peucetius and others, used in treatment of LEUKEMIA and other NEOPLASMS.Asparaginase: A hydrolase enzyme that converts L-asparagine and water to L-aspartate and NH3. EC Resistance: Diminished or failed response of an organism, disease or tissue to the intended effectiveness of a chemical or drug. It should be differentiated from DRUG TOLERANCE which is the progressive diminution of the susceptibility of a human or animal to the effects of a drug, as a result of continued administration.Cardiotoxins: Agents that have a damaging effect on the HEART. Such damage can occur from ALKYLATING AGENTS; FREE RADICALS; or metabolites from OXIDATIVE STRESS and in some cases is countered by CARDIOTONIC AGENTS. Induction of LONG QT SYNDROME or TORSADES DE POINTES has been the reason for viewing some drugs as cardiotoxins.Databases, Chemical: Databases devoted to knowledge about specific chemicals.Antineoplastic Combined Chemotherapy Protocols: The use of two or more chemicals simultaneously or sequentially in the drug therapy of neoplasms. The drugs need not be in the same dosage form.Leukemia, Erythroblastic, Acute: A myeloproliferative disorder characterized by neoplastic proliferation of erythroblastic and myeloblastic elements with atypical erythroblasts and myeloblasts in the peripheral blood.Friend murine leukemia virus: A strain of Murine leukemia virus (LEUKEMIA VIRUS, MURINE) producing leukemia of the reticulum-cell type with massive infiltration of liver, spleen, and bone marrow. It infects DBA/2 and Swiss mice.Leukemia, Experimental: Leukemia induced experimentally in animals by exposure to leukemogenic agents, such as VIRUSES; RADIATION; or by TRANSPLANTATION of leukemic tissues.Chlorophyllides: Products of the hydrolysis of chlorophylls in which the phytic acid side chain has been removed and the carboxylic acids saponified.Neuropeptides: Peptides released by NEURONS as intercellular messengers. Many neuropeptides are also hormones released by non-neuronal cells.Nonprescription Drugs: Medicines that can be sold legally without a DRUG PRESCRIPTION.Pharmacopoeias as Topic: Authoritative treatises on drugs and preparations, their description, formulation, analytic composition, physical constants, main chemical properties used in identification, standards for strength, purity, and dosage, chemical tests for determining identity and purity, etc. They are usually published under governmental jurisdiction (e.g., USP, the United States Pharmacopoeia; BP, British Pharmacopoeia; P. Helv., the Swiss Pharmacopoeia). They differ from FORMULARIES in that they are far more complete: formularies tend to be mere listings of formulas and prescriptions.Preservatives, Pharmaceutical: Substances added to pharmaceutical preparations to protect them from chemical change or microbial action. They include ANTI-BACTERIAL AGENTS and antioxidants.Injections, Intravenous: Injections made into a vein for therapeutic or experimental purposes.Food Preservatives: Substances capable of inhibiting, retarding or arresting the process of fermentation, acidification or other deterioration of foods.Xylitol: A five-carbon sugar alcohol derived from XYLOSE by reduction of the carbonyl group. It is as sweet as sucrose and used as a noncariogenic sweetener.Patents as Topic: Exclusive legal rights or privileges applied to inventions, plants, etc.Biofuels: Hydrocarbon-rich byproducts from the non-fossilized BIOMASS that are combusted to generate energy as opposed to fossilized hydrocarbon deposits (FOSSIL FUELS).Body Composition: The relative amounts of various components in the body, such as percentage of body fat.Tablets: Solid dosage forms, of varying weight, size, and shape, which may be molded or compressed, and which contain a medicinal substance in pure or diluted form. (Dorland, 28th ed)Excipients: Usually inert substances added to a prescription in order to provide suitable consistency to the dosage form. These include binders, matrix, base or diluent in pills, tablets, creams, salves, etc.Foramen Ovale, Patent: A condition in which the FORAMEN OVALE in the ATRIAL SEPTUM fails to close shortly after birth. This results in abnormal communications between the two upper chambers of the heart. An isolated patent ovale foramen without other structural heart defects is usually of no hemodynamic significance.GermanyLeukemia, Myeloid, Acute: Clonal expansion of myeloid blasts in bone marrow, blood, and other tissue. Myeloid leukemias develop from changes in cells that normally produce NEUTROPHILS; BASOPHILS; EOSINOPHILS; and MONOCYTES.Leukemia, Myeloid: Form of leukemia characterized by an uncontrolled proliferation of the myeloid lineage and their precursors (MYELOID PROGENITOR CELLS) in the bone marrow and other sites.Remission Induction: Therapeutic act or process that initiates a response to a complete or partial remission level.Hematopoietic Stem Cell Transplantation: Transfer of HEMATOPOIETIC STEM CELLS from BONE MARROW or BLOOD between individuals within the same species (TRANSPLANTATION, HOMOLOGOUS) or transfer within the same individual (TRANSPLANTATION, AUTOLOGOUS). Hematopoietic stem cell transplantation has been used as an alternative to BONE MARROW TRANSPLANTATION in the treatment of a variety of neoplasms.Nuclear Reprogramming: The process that reverts CELL NUCLEI of fully differentiated somatic cells to a pluripotent or totipotent state. This process can be achieved to a certain extent by NUCLEAR TRANSFER TECHNIQUES, such as fusing somatic cell nuclei with enucleated pluripotent embryonic stem cells or enucleated totipotent oocytes. GENE EXPRESSION PROFILING of the fused hybrid cells is used to determine the degree of reprogramming. Dramatic results of nuclear reprogramming include the generation of cloned mammals, such as Dolly the sheep in 1997.Epigenesis, Genetic: A genetic process by which the adult organism is realized via mechanisms that lead to the restriction in the possible fates of cells, eventually leading to their differentiated state. Mechanisms involved cause heritable changes to cells without changes to DNA sequence such as DNA METHYLATION; HISTONE modification; DNA REPLICATION TIMING; NUCLEOSOME positioning; and heterochromatization which result in selective gene expression or repression.Inventions: A novel composition, device, or process, independently conceived de novo or derived from a pre-existing model.Lower Gastrointestinal Tract: The segment of GASTROINTESTINAL TRACT that includes the small intestine below the DUODENUM, and the LARGE INTESTINE.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Fibrocystic Breast Disease: A common and benign breast disease characterized by varying degree of fibrocystic changes in the breast tissue. There are three major patterns of morphological changes, including FIBROSIS, formation of CYSTS, and proliferation of glandular tissue (adenosis). The fibrocystic breast has a dense irregular, lumpy, bumpy consistency.Calcium Phosphates: Calcium salts of phosphoric acid. These compounds are frequently used as calcium supplements.Bone Substitutes: Synthetic or natural materials for the replacement of bones or bone tissue. They include hard tissue replacement polymers, natural coral, hydroxyapatite, beta-tricalcium phosphate, and various other biomaterials. The bone substitutes as inert materials can be incorporated into surrounding tissue or gradually replaced by original tissue.Porosity: Condition of having pores or open spaces. This often refers to bones, bone implants, or bone cements, but can refer to the porous state of any solid substance.Bone and Bones: A specialized CONNECTIVE TISSUE that is the main constituent of the SKELETON. The principle cellular component of bone is comprised of OSTEOBLASTS; OSTEOCYTES; and OSTEOCLASTS, while FIBRILLAR COLLAGENS and hydroxyapatite crystals form the BONE MATRIX.Minerals: Native, inorganic or fossilized organic substances having a definite chemical composition and formed by inorganic reactions. They may occur as individual crystals or may be disseminated in some other mineral or rock. (Grant & Hackh's Chemical Dictionary, 5th ed; McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Phosphates: Inorganic salts of phosphoric acid.Bone Cements: Adhesives used to fix prosthetic devices to bones and to cement bone to bone in difficult fractures. Synthetic resins are commonly used as cements. A mixture of monocalcium phosphate, monohydrate, alpha-tricalcium phosphate, and calcium carbonate with a sodium phosphate solution is also a useful bone paste.

Effect of cellular ATP depletion on topoisomerase II poisons. Abrogation Of cleavable-complex formation by etoposide but not by amsacrine. (1/246)

Topoisomerase (topo) II poisons have been categorized into ATP-independent and -dependent drugs based on in vitro studies. We investigated drug-induced topoII-DNA complexes in intact cells almost completely depleted of ATP. Virtually no DNA single-strand breaks (SSBs), as measured by alkaline elution, were detected in energy-depleted cells treated with the topoII poisons etoposide, teniposide, daunorubicin, doxorubicin, mitoxantrone, or clerocidin. This inhibition was reversible; subsequent incubation with glucose restored the level of DNA SSBs. The effect of ATP depletion was specific for topoII, because topoI-mediated cleavable complexes induced by camptothecin were unaffected by ATP depletion. Furthermore, etoposide-induced DNA-protein complexes and DNA double-strand breaks, as measured by filter elution techniques, and topoIIalpha and -beta trapping, as measured by a band depletion assay, were completely inhibited by energy depletion. Differences in drug transport could not explain the effect of ATP depletion. The topoII poison amsacrine (m-AMSA) was unique with respect to ATP dependence. In ATP-depleted cells, m-AMSA-induced DNA SSBs, DNA double-strand breaks, DNA-protein complexes, topoIIalpha and -beta trapping were only modestly reduced. The accumulation of m-AMSA was reduced in ATP-depleted cells, which indicates that drug transport could contribute to the modest decrease in m-AMSA-induced cleavable complexes. In conclusion, drug-induced topoII-DNA complexes were completely antagonized in ATP-depleted cells, except in the case of m-AMSA. One possible interpretation is that m-AMSA mainly produces prestrand passage DNA lesions, whereas the other topoII poisons tested exclusively stabilize poststrand passage DNA lesions in intact cells.  (+info)

Human small cell lung cancer NYH cells selected for resistance to the bisdioxopiperazine topoisomerase II catalytic inhibitor ICRF-187 demonstrate a functional R162Q mutation in the Walker A consensus ATP binding domain of the alpha isoform. (2/246)

Bisdioxopiperazine drugs such as ICRF-187 are catalytic inhibitors of DNA topoisomerase II, with at least two effects on the enzyme: namely, locking it in a closed-clamp form and inhibiting its ATPase activity. This is in contrast to topoisomerase II poisons as etoposide and amsacrine (m-AMSA), which act by stabilizing enzyme-DNA-drug complexes at a stage in which the DNA gate strand is cleaved and the protein is covalently attached to DNA. Human small cell lung cancer NYH cells selected for resistance to ICRF-187 (NYH/187) showed a 25% increase in topoisomerase IIalpha level and no change in expression of the beta isoform. Sequencing of the entire topoisomerase IIalpha cDNA from NYH/187 cells demonstrated a homozygous G-->A point mutation at nucleotide 485, leading to a R162Q conversion in the Walker A consensus ATP binding site (residues 161-165 in the alpha isoform), this being the first drug-selected mutation described at this site. Western blotting after incubation with ICRF-187 showed no depletion of the alpha isoform in NYH/187 cells in contrast to wild-type (wt) cells, whereas equal depletion of the beta isoform was observed in the two sublines. Alkaline elution assay demonstrated a lack of inhibition of etoposide-induced DNA single-stranded breaks in NYH/187 cells, whereas this inhibition was readily apparent in NYH cells. Site-directed mutagenesis in human topoisomerase IIalpha introduced into a yeast Saccharomyces cerevisiae strain with a temperature-conditional yeast TOP2 mutant demonstrated that R162Q conferred resistance to the bisdioxopiperazines ICRF-187 and -193 but not to etoposide or m-AMSA. Both etoposide and m-AMSA induced more DNA cleavage with purified R162Q enzyme than with the wt. The R162Q enzyme has a 20-25% decreased catalytic capacity compared to the wt and was almost inactive at <0.25 mM ATP compared to the wt. Kinetoplast DNA decatenation by the R162Q enzyme at 1 mM ATP was not resistant to ICRF-187 compared to wt, whereas it was clearly less sensitive than wt to ICRF-187 at low ATP concentrations. This suggests that it is a shift in the equilibrium to an open-clamp state in the enzyme's catalytic cycle caused by a decreased ATP binding by the mutated enzyme that is responsible for bisdioxopiperazine resistance.  (+info)

Enhanced amsacrine-induced mutagenesis in plateau-phase Chinese hamster ovary cells, with targeting of +1 frameshifts to free 3' ends of topoisomerase II cleavable complexes. (3/246)

Previous work showed that the DNA double-strand cleaving agents bleomycin and neocarzinostatin were more mutagenic in plateau-phase than in log-phase cells. To determine whether topoisomerase II poisons that produce double-strand breaks by trapping of cleavable complexes would, likewise, induce mutations specific to plateau-phase cells, aprt mutations induced by amsacrine in both log-phase and plateau-phase CHO cells were analyzed. The maximum aprt mutant frequencies obtained were 7 x 10(-6) after treatment with 0.02 microM amsacrine in log phase and 27 x 10(-6) after treatment with 1 microM amsacrine in plateau phase, compared with a spontaneous frequency of < 1 x 10(-6). Base substitutions dominated the spectrum of mutations in log-phase cells, but were much less prevalent in plateau-phase cells. Both spectra also included small deletions, insertions and duplications, as well as few large-scale deletions or rearrangements. About 5% of the log-phase mutants and 16% of the plateau-phase mutants were +1 frameshifts, and all but one of these were targeted to potential free 3' termini of cleavable complexes, as determined by mapping of cleavage sites in DNA treated with topoisomerase II plus amsacrine in vitro. Thus, these insertions may arise from templated extension of the exposed 3' terminus by a DNA polymerase, followed by resealing of the strand, as shown previously for acridine-induced frameshifts in T4 phage.  (+info)

Autologous bone marrow transplantation in non-Hodgkin's lymphoma patients: effect of a brief course of G-CSF on harvest and recovery. (4/246)

This study compares harvest and hematological recovery data of 100 lymphoma patients who underwent BM harvest either after a short course of G-CSF (16 microg/kg for 3 days) (n = 57) or in steady-state conditions (n = 43). G-CSF allowed the attainment of a significantly higher median number of total nucleated cells x 10(8)/kg (4.4, range 1.4-17, vs 2.1, range 0.6-4.2; P < 0.0001), mononuclear cells x 10(8)/kg (0.55, range 0.20-1.4, vs 0.41, range 0.15-0.76, P < 0.0001) and CFU-GM/ml (310, range 10-5500, vs 80, range 10-3800, P = 0.008), with lower volumes of blood collected (17.5 ml/kg, range 8-31 vs 21.0, range 15-30, P = 0.0001). Hematological recovery was faster in patients who received pre-treated BM (median time to PMN >0.5 x 10(9)/l and to platelets >20 x 10(9)/l was 12, range 10-14, and 13, range 10-18, days, respectively) than in those autotransplanted with steady-state BM (median time to PMN >0.5 x 10(9)/l and to platelets >20 x 10(9)/l 13, range 10-18 and 14, range 10-20 days, respectively, P = 0.004 and P = 0.01). Transfusional requirement was significantly different and patients of the G-CSF group needed shorter hospitalization (17 days, range 12-24, vs 20 days, range 14-32; P = 0.02). These data suggest that treating patients with G-CSF before BM harvest improves the quality of the harvest and accelerates engraftment and hematological recovery.  (+info)

Transfection of 9-hydroxyellipticine-resistant Chinese hamster fibroblasts with human topoisomerase IIalpha cDNA: selective restoration of the sensitivity to DNA religation inhibitors. (5/246)

In the Chinese hamster lung cell line DC-3F/9-OH-E, selected for resistance to 9-OH-ellipticine and cross-resistant to other topoisomerase II inhibitors, the amount of topoisomerase IIalpha is 4-5-fold lower than in the parental DC-3F cells, whereas topoisomerase IIbeta is undetectable. Cloning and sequencing of topoisomerase IIalpha cDNAs from DC-3F and DC-3F/9-OH-E cells revealed an allele polymorphism, one allele differing from the other by the presence of seven silent mutations and three mutations in the noncoding region. In addition, the mutated allele contains three missense mutations located close to the ATP binding site (Thr371Ser) or to the catalytic site (Ala751Gly; Ile863Thr). To analyze the contribution of these topoisomerase IIalpha alterations to their resistance phenotype, DC-3F/9-OH-E cells were transfected with an eukaryotic expression vector containing the human topoisomerase IIalpha cDNA. In one transfected clone, the amount of topoisomerase IIalpha isoform and the catalytic activity were similar to that in the parental DC-3F cells. These cells, which contain only topoisomerase IIalpha, are then a unique mammalian cell line to analyze the physiological and pharmacological properties of this enzyme. However, the restoration of a nearly normal topoisomerase IIalpha activity in the DC-3F/9-OH-E cells did not have the same effect on their sensitivity to different enzyme inhibitors; a 75% reversion of the resistance, associated with a 2-3-fold increased stabilization of the cleavable complex, was observed with both etoposide and m-AMSA, two drugs that inhibit the DNA religation step in the enzyme catalytic cycle; in contrast, the transfected cells remained fully resistant to ellipticine derivatives that did not induce the stabilization of the cleavable complex. We hypothesized that a trans-acting factor, inhibiting the induction of cleavable complex formation by drugs that are not religation inhibitors, might be present in the resistant cells. However, such a factor was not detected in in vitro experiments, and other hypotheses are discussed.  (+info)

Murine transgenic cells lacking DNA topoisomerase IIbeta are resistant to acridines and mitoxantrone: analysis of cytotoxicity and cleavable complex formation. (6/246)

Murine transgenic cell lines lacking DNA topoisomerase II (topo II)beta have been used to assess the importance of topo IIbeta as a drug target. Western blot analysis confirmed that the topo IIbeta -/- cell lines did not contain topo IIbeta protein. In addition, both the topo IIbeta +/+ and topo IIbeta -/- cell lines contained similar levels of topo IIalpha protein. The trapped in agarose DNA immunostaining assay (TARDIS) was used to detect topo IIalpha and beta cleavable complexes in topo IIbeta -/- and topo IIbeta +/+ cells. These results show that both topo IIalpha and beta are in vivo targets for etoposide, mitoxantrone, and amsacrine (mAMSA) in topo IIbeta +/+ cells. As expected, only the alpha-isoform was targeted in topo IIbeta -/- cells. Clonogenic assays comparing the survival of topo IIbeta -/- and topo IIbeta +/+ cells were carried out to establish whether the absence of topo IIbeta caused drug resistance. Increased survival of topo IIbeta -/- cells compared with topo IIbeta +/+ cells was observed after treatment with amsacrine (mAMSA), methyl N-(4'-[9-acridinylamino]-2-methoxyphenyl) carbamate hydrochloride (AMCA), methyl N-(4'-[9-acridinylamino]-2-methoxyphenyl)carbamate hydrochloride (mAMCA), mitoxantrone, and etoposide. These studies showed that topo IIbeta -/- cells were significantly more resistant to mAMSA, AMCA, mAMCA, and mitoxantrone, than topo IIbeta +/+ cells, indicating that topo IIbeta is an important target for the cytotoxic effects of these compounds.  (+info)

Altered drug interaction and regulation of topoisomerase IIbeta: potential mechanisms governing sensitivity of HL-60 cells to amsacrine and etoposide. (7/246)

Topoisomerase II (topo II), an enzyme essential for cell viability, is present in mammalian cells as the alpha- and beta-isoforms. In human leukemia HL-60/S or HL-60/doxorubicin (DOX)0.05 cells, the levels of topo IIalpha- or beta-protein were similar in either asynchronous exponential or synchronized cultures. Although topo IIalpha was hypophosphorylated in HL-60/DOX0.05 compared with HL-60/S cells, both overall and site-specific hyperphosphorylation of topo IIbeta was apparent in HL-60/DOX0.05 compared with HL-60/S cells. The phosphorylation of topo IIalpha and not beta was enhanced in the S and G(2) + M phases of HL-60/S cells. In contrast, an increase in the phosphorylation of topo IIbeta compared with alpha was apparent in the G(1) and S phases of HL-60/DOX0.05 cells. The cytotoxicity and depletion of topo IIalpha or beta in cells treated with drug for 1 h revealed that mole-for-mole, amsacrine was 2-fold more effective than etoposide in killing HL-60/S or HL-60/DOX0.05 cells and in depleting the beta versus alpha topo II protein. Present results demonstrate that: 1) hyperphosphorylation of topo IIbeta in HL-60/DOX0.05 cells may be a compensatory consequence of the hypophosphorylation of topo IIalpha to maintain normal topo II function during proliferation, and 2) enhanced sensitivity of HL-60/S or HL-60/DOX0.05 cells to amsacrine may be due to the preferential interaction and depletion of topo IIbeta.  (+info)

An antitumor drug-induced topoisomerase cleavage complex blocks a bacteriophage T4 replication fork in vivo. (8/246)

Many antitumor and antibacterial drugs inhibit DNA topoisomerases by trapping covalent enzyme-DNA cleavage complexes. Formation of cleavage complexes is important for cytotoxicity, but evidence suggests that cleavage complexes themselves are not sufficient to cause cell death. Rather, active cellular processes such as transcription and/or replication are probably necessary to transform cleavage complexes into cytotoxic lesions. Using defined plasmid substrates and two-dimensional agarose gel analysis, we examined the collision of an active replication fork with an antitumor drug-trapped cleavage complex. Discrete DNA molecules accumulated on the simple Y arc, with branch points very close to the topoisomerase cleavage site. Accumulation of the Y-form DNA required the presence of a topoisomerase cleavage site, the antitumor drug, the type II topoisomerase, and a T4 replication origin on the plasmid. Furthermore, all three arms of the Y-form DNA were replicated, arguing strongly that these are trapped replication intermediates. The Y-form DNA appeared even in the absence of two important phage recombination proteins, implying that Y-form DNA is the result of replication rather than recombination. This is the first direct evidence that a drug-induced topoisomerase cleavage complex blocks the replication fork in vivo. Surprisingly, these blocked replication forks do not contain DNA breaks at the topoisomerase cleavage site, implying that the replication complex was inactivated (at least temporarily) and that topoisomerase resealed the drug-induced DNA breaks. The replication fork may behave similarly at other types of DNA lesions, and thus cleavage complexes could represent a useful (site-specific) model for chemical- and radiation-induced DNA damage.  (+info)

  • Amsacrine and continuous-infusion high-dose cytosine arabinoside as induction therapy for patients with newly-diagnosed acute myelogenous leukemia. (
  • Use with diuretics or nephrotoxic drugs such as the aminoglycosides may theoretically increase the risk of cardiotoxicity with amsacrine by precipitating hypokalaemia. (
  • Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of amsacrine in children with use in other age groups. (
  • Amsacrine should be given with caution to patients with liver or kidney disease, who may require dosage adjustments. (
  • Rapidly dividing cells are two to four times more sensitive to amsacrine than are resting cells. (
  • NSC 343499), a lipophilic and water-soluble derivative of amsacrine (NSC 249992), on cell viability, growth, clonogenicity, and progression through the cell cycle were investigated in suspension cultures of Friend erythroleukemic cells and in adherent cultures of Chinese hamster ovary cells. (
  • Since the growth of normal body cells may also be affected by amsacrine, other effects will also occur. (
  • Amsacrine is incompatible with sodium chloride 0.9% injection and with other chloride-containing solutions, apparently because of the poor solubility of the hydrochloride salt in aqueous solution. (
  • Amsacrine is prepared as a solution in lactic acid and dimethylacetamide, and is given, diluted in glucose 5%, by intravenous infusion over 60 to 90 minutes. (