Inhibition Of Deoxyribonucleic Acid Synthesis Research Articles

Advances in Our Understanding of the Molecular Mechanisms of Action of Cisplatin in Cancer Therapy.

Cisplatin and other platinum-based chemotherapeutic drugs have been used extensively for the treatment of human cancers such as bladder, blood, breast, cervical, esophageal, head and neck, lung, ovarian, testicular cancers, and sarcoma. Cisplatin is commonly administered intravenously as a first-line chemotherapy for patients suffering from various malignancies. Upon absorption into the cancer cell, cisplatin interacts with cellular macromolecules and exerts its cytotoxic effects through a series of biochemical mechanisms by binding to Deoxyribonucleic acid (DNA) and forming intra-strand DNA adducts leading to the inhibition of DNA synthesis and cell growth. Its primary molecular mechanism of action has been associated with the induction of both intrinsic and extrinsic pathways of apoptosis resulting from the production of reactive oxygen species through lipid peroxidation, activation of various signal transduction pathways, induction of p53 signaling and cell cycle arrest, upregulation of pro-apoptotic genes/proteins, and down-regulation of proto-oncogenes and anti-apoptotic genes/proteins. Despite great clinical outcomes, many studies have reported substantial side effects associated with cisplatin monotherapy, while others have shown substantial drug resistance in some cancer patients. Hence, new formulations and several combinational therapies with other drugs have been tested for the purpose of improving the clinical utility of cisplatin. Therefore, this review provides a comprehensive understanding of its molecular mechanisms of action in cancer therapy and discusses the therapeutic approaches to overcome cisplatin resistance and side effects.

The effect of levocabastine hydrochloride on human Tenon’s capsule fibroblasts: Inhibition of proliferation, suppression of DNA synthesis and induction of apoptosis

Purpose: To investigate the effects of levocabastine hydrochloride on the profileration, Deoxyribonucleic acid (DNA) synthesis and induction of apoptosis, in human Tenon’s capsule fibroblasts. Methods: The maximum intoxicate concentration was determined by measuring the release of lactate dehydrogenase. Proliferation of fibroblasts was analyzed with a WST-1 method. DNA synthesis was examined by quantifying the incorporation of 5-bromo-2’-deoxyuridine into dividing cells, and apoptosis was analyzed using an Annexin-V-FLUOS Staining Kit. Results: Levocabastine hydrochloride (10−4 M), ketotifen fumarate (3 × 10−5 M) and tranilast (10−4 M) significantly inhibited proliferation of fibroblasts. Levocabastine hydrochloride (10−4 M), ketotifen fumarate (10−4 M) and tranilast (10−3 M) inhibited DNA synthesis and induced apoptosis. Conclusion: Levocabastine hydrochloride inhibited the proliferation of fibroblasts.

5-Fluorouracil incorporated into the tissue RNA of human and rat bladder carcinoma after administration of 1-(2-tetrahydrofuryl)-5-fluorouracil combined with uracil

UFT is an anticancer agent consisting of 1-(2-tetrahydrofuryl)-5-fluorouracil (5-FU) combined with uracil in a molar ratio of 1: 4. Its mechanisms of action are, presumably, inhibition of deoxyribonucleic acid (DNA) synthesis by thymidylate synthetase (TS) and impairment of ribonucleic acid (RNA) function by the incorporation of 5-fluorouridine-5'-triphosphate into RNA. This study was conducted to examine the TS inhibition rate (TS-IR) and the concentration of 5-FU incorporated in RNA per milligram of tissue treated with UFT (F-RNA). We administered UFT to 12 patients with bladder cancer. We also administered UFT to 20 rats bearing bladder tumors induced by N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN), and to 10 BBN-untreated control rats. We then determined the total TS concentration, TS-IR, and F-RNA in the human bladder tumor and normal tissues and in the BBN-treated and BBN-untreated rat organs, including the urinary bladder. In the bladder cancer patients, the mean F-RNAs in the bladder tumor and normal tissue were 0.133 +/- 0.137 and 0.056 +/- 0.062 ng/mg, respectively, without a significant difference (P < 0.1). The mean TS-IR was 35.3 +/- 19.6% in the tumor tissue and 38.0 +/- 16.6% in the normal bladder tissue, and this difference was also not significant. In the rat bladder cancer model, the total TS concentration and F-RNA in the tumor after the administration of UFT were 15.32 pmol/g and 0.780 ng/mg, respectively, being markedly higher than the corresponding values (1.22 pmol/g and 0.129 ng/mg) in the control normal bladder tissue. The impairment of RNA metabolism by F-RNA incorporated in RNA did not seem to be the critical mechanism of the antitumor effect of UFT at the usual clinical dose, as neither TS-IR nor F-RNA (as antitumor parameters) seemed to increase significantly after a clinical dose of UFT. However, the inhibition of DNA synthesis and the impairment of RNA were independent mechanisms of the action of high-dose UFT in the experimental rat bladder tumors, as both total is concentration and F-RNA were increased significantly.

Chromatographic Fractions from Croton cajucara Inhibit Cell Proliferation and Induce Differentiation in a Human Leukemia Cell Line

ABSTRACT Chromatographic fractions of the medicinal plant Crotoncajucara Benth. were studied in human promyelocytic leukemiaHL-60 cells for antiproliferative and cell differentiation–induc-ing properties. The chromatographic fractions F26–30, F39-42 ,F50–51, and F60–66, but not 19-nor-clerodane diterpene trans-dehydrocrotonin (t-DCTN) alone, inhibited cell proliferationbased on IC 50 values (the concentration that inhibits the 50% ofcell proliferation) obtained using the 3-(4,5-dimethylthiazol-2-yl) diphenyltetrazolium bromide (MTT) assay. These fractionsalso inhibited 5-bromodeoxyuridine incorporation, indicatingthat the growth-inhibitory effect involved the inhibition ofdeoxyribonucleic acid synthesis. The same fractions inducedmorphologic changes and caused significant nitroblue tetrazoli-um reduction in HL-60 cells as well. In summary, the results ofthis study demonstrate that the chromatographic fractions ofCroton cajucara contain substances differing from t-DCTN thatinhibit cell proliferation and also induce cell differentiation inHL-60 cells.Further studies are warranted to define the contribution ofeach component to these pharmacologic activities of the frac-tions.Key words: cell differentiation, cell proliferation, Crotoncajucara, HL-60, leukemia

Growth inhibition of esophageal squamous carcinoma cells by peroxisome proliferator-activated receptor-γ ligands

The growth of human cancer cells expressing peroxisome proliferator-activated receptor-γ (PPAR-γ) has been reported to be inhibited by PPAR-γ ligands. In esophageal squamous-cell carcinoma cell lines T.T, T.Tn, and EC-GI-10, we detected expression of PPAR-γ and investigated the effects of PPAR-γ ligands on these cell lines in vitro with the use of troglitazone, pioglitazone, and 15d-PGJ2. Marked growth inhibition by the PPAR-γ ligands was observed in all cases. The growth-inhibitory effect was evidenced by a dose-dependent inhibition of deoxyribonucleic acid synthesis and was associated with altered cell-cycle progression manifesting G1 arrest. Cell-cycle arrest in T.Tn cells induced by troglitazone could be correlated with an increased level of cyclin-dependent kinase inhibitor p27Kip1, p21Cip1/Waf1, and p18Ink4c. Moreover, troglitazone treatment increased the expression of interleukin-1α, a multifunctional cytokine implicated in antitumor immunity. These findings suggest that troglitazone and other PPAR-γ ligands have adjuvant or neoadjuvant therapeutic potentials in esophageal cancer. (J Lab Clin Med 2002;140:17-26)

Mechanisms of action of antimicrobials: focus on fluoroquinolones.

Five bacterial targets have been exploited in the development of antimicrobial drugs: cell wall synthesis, protein synthesis, ribonucleic acid synthesis, deoxyribonucleic acid (DNA) synthesis, and intermediary metabolism. Because resistance to drugs that interact with these targets is widespread, new antimicrobials and an understanding of their mechanisms of action are vital. The fluoroquinolones are the only direct inhibitors of DNA synthesis; by binding to the enzyme-DNA complex, they stabilize DNA strand breaks created by DNA gyrase and topoisomerase IV. Ternary complexes of drug, enzyme, and DNA block progress of the replication fork. Cytotoxicity of fluoroquinolones is likely a 2-step process involving (1) conversion of the topoisomerase-quinolone-DNA complex to an irreversible form and (2) generation of a double-strand break by denaturation of the topoisomerase. The molecular factors necessary for the transition from step 1 to step 2 remain unclear, but downstream pathways for cell death may overlap with those used by other bactericidal antimicrobials. Studies of fluoroquinolone-resistant mutants and purified topoisomerases indicate that many quinolones have differing activities against the two targets. Drugs with similar activities against both targets may prove less likely to select de novo resistance.

Stage-specific inhibition of deoxyribonucleic acid synthesis and induction of apoptosis by antracyclines in cultured rat spermatogenic cells.

A rapid in vitro method has been developed to detect early effects of cytostatic drugs on rat spermatogenesis. The induction of programmed cell death (apoptosis) and changes in DNA synthesis induced by doxorubicin and idarubicin were measured in specific stages of the cycle of seminiferous epithelium including mitotic (stage V) and meiotic (stage VIII-IX) S-phase cells. The model was used to investigate the protective effect of an organic thiophosphate, amifostine, against the toxicity of antracyclines. Premitotic DNA synthesis was found to be more sensitive than premeiotic DNA synthesis to antracyclines. Idarubicin was more toxic than doxorubicin to germ cells in inducing apoptosis and suppressing DNA synthesis. Amifostine had no protective effect against doxorubicin- or idarubicin-induced inhibition of DNA synthesis. In contrast, a significant stimulation of DNA synthesis in premitotic cells by amifostine was found, suggesting that this compound may have a stimulative effect on spermatogenic stem cells. These data show that stage-specific dissection of the seminiferous tubules and their in vitro exposure to predetermined doses of drugs may give us a unique possibility to detect drug action and protection against the cytotoxicity of antineoplastic agents at the cellular level of the spermatogenic cycle.

DNA signals for G2 checkpoint response in diploid human fibroblasts

DNA (deoxyribonucleic acid) signals that induce the G2 checkpoint response were examined using proliferative secondary cultures of diploid human fibroblasts. Treatments that generated DNA double-strand breaks (DSBs) directly were effective inducers of checkpoint response, generally producing >80% inhibition of mitosis (G2 delay) and the kinase activity of M-phase-promoting factor within 2 h of treatment. Effective inducers of G2 checkpoint response included γ-irradiation and the cancer chemotherapeutic drugs, bleomycin and etoposide. Treatments that produced DNA single-strand breaks, directly or indirectly through nucleotide excision repair, were not effective inducers of G2 delay. Ineffective treatments included incubation with camptothecin, an inhibitor of topoisomerase I (topo I), and irradiation with sublethal fluences of UVC, followed by incubation with aphidicolin. Transient severe inhibition of DNA synthesis with aphidicolin did not affect mitosis substantially, suggesting that the replication arrest input to the G2 checkpoint required more than brief inhibition of DNA synthesis. In contrast, moderate camptothecin-induced inhibition of DNA synthesis was associated with a strong inhibition of mitosis that developed 4–12 h after drug treatment. This result suggested that G2 delay was not expressed until the cells that were in S-phase at the time of treatment with camptothecin proceeded into G2. DNA damage was not necessary for induction of mitotic delay. An inhibitor of topoisomerase II (topo II), ICRF-193, which inhibits chromatid decatenation in G2 cells without damaging DNA, induced a severe inhibition of mitosis and M-phase-promoting factor kinase activity. The results suggest that DNA double-strand breaks and insufficiency of chromatid decatenation effectively induce the G2 checkpoint response, but DNA single-strand breaks do not.

Calcium-binding protein regucalcin inhibits deoxyribonucleic acid synthesis in the nuclei of regenerating rat liver.

The effect of regucalcin, a Ca(2+)-binding protein isolated from rat liver cytosol, on deoxyribonucleic acid (DNA) synthesis in the nuclei of regenerating rat liver was investigated. At 1 day after partial hepatectomy, the liver weight was increased about 50% of that of sham-operated rats, and it reached to the same levels as sham operation at 3 days after hepatectomy. Nuclear DNA synthesis was markedly increased at 1 day after hepatectomy, and this increase was also seen at 3 days. Nuclear DNA synthesis was clearly enhanced in the presence of EGTA (0.4 mM) in the incubation mixture. The presence of Ca2+ (1.0-25 microM) caused a significant decrease in the nuclear DNA synthesis of normal rat liver. Regucalcin (0.25 and 0.5 microM) clearly inhibited the nuclear DNA synthesis of normal rat liver. This inhibition was also seen in the presence of Ca2+ (1.0 microM). Moreover, in the liver nuclei obtained at 1 day after partial hepatectomy, the presence of regucalcin (0.05-0.5 microM) caused a remarkable inhibition of nuclear DNA synthesis. This effect was also revealed in the presence of EGTA (0.4 mM). Thus, the inhibitory effect of regucalcin was remarkable in regenerating rat liver nuclei in comparison with that of normal rat liver. The present results demonstrate that regucalcin can suppress nuclear DNA synthesis in regenerating rat liver. We suppose that regucalcin may have a role in the regulation of nuclear DNA synthesis in liver cell proliferation.

Inhibitors of protein tyrosine phosphorylation reduce the proliferation of two human glioma cell lines.

Epidermal growth factor (EGF) and platelet-derived growth (PDGF) are suggested to be involved in the proliferation of human gliomas. We examined the effects of these growth factors on two human malignant glioma cell lines. Treatment of the A172 glioblastoma and the Hs683 glioma cell line with EGF and PDGF resulted in the tyrosine autophosphorylation, and hence activation, of the respective growth factor receptors. In addition, both cell lines responded to EGF and PDGF with increased deoxyribonucleic acid (DNA) synthesis. Because the intrinsic protein tyrosine kinase activity of this class of growth factor receptors is indispensable for their functioning, we tested the effects of specific protein tyrosine kinase inhibitors on growth factor-induced DNA synthesis and glioma cell proliferation. Genistein inhibited both EGF- and PDGF-stimulated autophosphorylation of the receptors and induction of DNA synthesis. However, genistein seemed to be cytotoxic to the cells. The tyrphostins RG 50875 and RG 13022 dose-dependently inhibited DNA synthesis induced by EGF, PDGF, and serum. RG 13022 completely blocked the EGF- and PDGF-induced DNA synthesis at a concentration of 50 mumol/L. The tyrphostins showed no selectivity in blocking either EGF or PDGF signaling. With concentrations up to mumol/L, no cytotoxic side effects of the tyrphostins were observed. Both tyrphostins also inhibit serum-driven cell growth in a dose-dependent manner. These results support the hypothesis that activated protein tyrosine kinase receptors are involved in the proliferation of A172 and Hs683 glioma cells. Selective inhibitors of protein tyrosine kinases, therefore, might have the potential to contribute to the treatment of growth factor-dependent gliomas.

Inhibition of deoxyribonucleic acid synthesis during premeiotic stages of spermatogenesis by a factor from testis-associated lymphomyeloid tissue in the dogfish shark (Squalus acanthias).

To investigate factors controlling spermatogonial proliferation, we used premeiotic (PrM) spermatocysts (stage-synchronized germ cell/Sertoli cell clones) derived from the testis of the dogfish shark (Squalus acanthias) as an in vitro test system to estimate DNA synthesis by [3H]thymidine incorporation. Coculture of PrM spermatocysts with spermatocysts of the same (PrM) or more advanced stages (M, meiotic; PoM, postmeiotic) revealed the presence of an increasing gradient of inhibitory bioactivity from immature to mature stages (PoM > M > PrM). An even more potent and effective inhibition was detected when PrM spermatocysts were cocultured with equivalent amounts of epigonal organ, a lymphomyeloid tissue encapsulating the testis adjacent to the mature (PoM) region and immediately upstream in the vascular pathway. Inhibitory bioactivity also was present in spent media from cultured epigonal fragments and in cytosolic subfractions of epigonal homogenates but was undetectable in epididymis, muscle, serum, and red blood cells. Lower but significant inhibition was obtained with the white blood cell fraction of peripheral blood in one of two experiments. Effects of the epigonal growth-inhibitory factor (EGIF) were dose- and time-dependent, had a short response latency (3 h), were completely reversible (< 24 h after washout), and counteracted but did not block the stimulatory effects of insulin on [3H]thymidine incorporation by PrM spermatocysts. EGIF was equally inhibitory when tested on each of five PrM substages (stem cells-->preleptotene). Analysis of the entire series of experiments showed that testis-derived inhibitory activity varied seasonally, with maximum effectiveness correlated with periods of spermatogenic inactivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective Antimitotic Effects of Estramustine Correlate with Its Antimicrotubule Properties on Glioblastoma and Astrocytes

Estramustine is an estradiol-based agent that accumulates in cells containing estramustine binding protein. Previous studies have shown that this binding site is expressed in human glioblastoma cells and that estramustine accumulates in glioma cells, resulting in a concentration-dependent inhibition of proliferation. We have shown that estramustine treatment results in a rapid inhibition of deoxyribonucleic acid synthesis (within 4 h) in human glioblastoma cells associated with an alteration of cell size and shape, consistent with its known antimicrotubule activity. To extend these findings, we performed an immunohistochemical analysis of microtubules with a monoclonal antibody to beta-tubulin, using a colorimetric assay with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide to measure the antimitotic effects of estramustine on both human glioblastoma and astrocyte cultures. Within 4 hours, estramustine (10 mumol/L) caused a dramatic alteration in the tubulin staining in glioma cells, characterized by a disorganization in microtubules. Cell shape and microtubule staining in astrocytes were relatively preserved. Estramustine had a concentration-dependent cytotoxic effect in tumor cultures, whereas it had no effect on astrocyte viability at any concentration. Differences in the antimitotic effects do not appear to be related to variations in proliferation rates among these different types of cells. These data suggest that although estramustine is a potent inhibitor of proliferation in glioblastoma cells, it has modest antiproliferative effects on astrocytes and its selective activity is closely correlated with its antimicrotubule properties.

Inhibition of deoxyribonucleic acid synthesis by difluoromethylornithine: Role of polyamine metabolism in monocrotaline-induced pulmonary hypertension

Previously, we have shown that the protection provided by 2-difluoromethylornithine (DFMO) against the development of monocrotaline (MCT)-induced pulmonary hypertension (PH) is associated with inhibition of polyamine biosynthesis in the lungs of MCT-treated rats. Although these studies suggest that prevention of the development of MCT-induced PH is polyamine dependent, no one has demonstrated which cellular events of MCT-induced PH are polyamine dependent. In the present study, using DFMO we tested the hypothesis that inhibition of polyamine biosynthesis may protect against MCT-induced PH by limiting increases in DNA synthesis. We injected rats with MCT (60 mg kg ) or 0.9% NaCl and measured DNA synthesis 7 days after MCT by determining [ 3H]thymidine incorporation into whole lung DNA. We found that 7 days after MCT treatment DNA synthesis was increased compared to the control (0.9% NaCl). However, DFMO treatment (2% in drinking water) reduced the increase in DNA synthesis following MCT. To confirm that DFMO was acting as a specific inhibitor of polyamine biosynthesis in MCT-induced PH, we administered DFMO concurrently with exogenous ornithine (ORN) (2% in drinking water), the substrate for polyamine biosynthesis, to reverse the protection afforded by DFMO against MCT-induced PH. Twenty-one days after MCT injection we examined right ventricular hypertrophy (RVH), mean pulmonary arterial pressure (MPAP), lung wet weight, and lung polyamine levels. While animals given DFMO (MCT + DFMO) did not increase RVH, MPAP, lung wet weight, or lung polyamine levels, animals given ORN (MCT + DFMO + ORN) did develop increases paralleling those found in animals treated with MCT alone. Our results suggest that suppression of polyamine biosynthesis by DFMO may protect against the development of MCT-induced PH in part by preventing increases in DNA synthesis. This suppression of DNA synthesis may limit the proliferation of key lung cells involved in the inappropriate vascular remodelling associated with MCT-induced PH. These results are consistent with our working hypothesis that elevated lung polyamine levels are essential for the development of MCT-induced PH

Inhibition of deoxyribonucleic acid synthesis in vitro by anticancer platinum pyrimidine greens against Daudi cells.

Platinum pyrimidine greens inhibited the deoxyribonucleic acid (DNA) synthesis of tumor cells in the S phase of the cell cycle and exerted antitumor activity. Clear differences were observed in the activity between the samples prepared at 40 degrees C and at 75 degrees C. Using 3H-thymidine incorporation assay and cell cycle analysis we confirmed that the former had much stronger and more specific inhibitory activity against DNA synthesis than the latter. Reactivity of the 40 degrees C sample with deoxyguanosine monophosphate (dGMP) and deoxyadenosine monophosphate (dAMP) was, respectively, two and three times larger than that of the 75 degrees C sample.

Effects of glucocorticoids on deoxyribonucleic acid(DNA) synthesis stimulated by growth factors in cultured rat skin fibroblasts.

The effects of glucocorticoids on deoxyribonucleic acid (DNA) synthesis were studied by using confluent cultured rat skin fibroblasts prepared by enzymatic dispersion and expanded up to passage 3. Dexamethasone caused the inhibition of the DNA synthesis stimulated by 10% fetal calf serum (FCS) in a dose dependent manner. Maximum inhibition (90%-100%) was achieved by the concentration of 10(-7)M. A similar dose dependent inhibition was also obtained in the experiment using epidermal growth factor (EGF) (1 ng/ml) as a stimulant. Dexamethasone (10(-7)M) also inhibited the DNA synthesis stimulated by somatomedin C (100 ng/ml) or platelet derived growth factor (1 half-maximum unit/ml) almost to control levels. Binding studies with 125I-labeled EGF suggested that dexamethasone caused this inhibitory action without modulation of cell surface receptors for EGF. Furthermore, the effects of a variety of glucocorticoids on the DNA synthesis were studied to clarify the structural requirement of glucocorticoids for the inhibition of the DNA synthesis. The results showed that 11 beta-hydroxyl and 21-hydroxyl groups on the steroid nucleus were necessary for the inhibition of the growth factor-stimulated DNA synthesis. Meanwhile, the inhibitory action on the DNA synthesis was markedly diminished by the replacement of a 16 alpha-methyl group by a 16 beta-methyl group in the presence of a bulky group at C-17 (e.g. 17 alpha-valerate). For further elucidation of mechanisms of action of glucocorticoids on the inhibition of the growth factor-stimulated DNA synthesis, the relationships between the structural features of glucocorticoids and their binding ability to the glucocorticoid receptor ([3H]-dexamethasone-binding receptor) were studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of nordihydroguaiaretic acid on cultured rat and human glioma cell proliferation

When cultured malignant cells derived from rat gliomas (C6 and 9L) and human gliomas (A-172 and T98G) were treated for 4 hours with 1 to 80 microns nordihydroguaiaretic acid (NDGA) or 5,8,11,14-eicosatetraynoic acid (ETYA), a dose-dependent inhibition of deoxyribonucleic acid (DNA) synthesis occurred. In a series of three experiments for each cell line, 40 microM NDGA suppressed 3H-thymidine incorporation in the rat and human glioma lines to an average of less than 3.1% and 5.6% of control uptake (counts per minute), respectively. Incubation with a higher concentration of ETYA (80 microM) resulted in inhibition of rat and human DNA synthesis to less than 53% and 62% of control levels, respectively. This inhibition was not associated with any loss of cell viability, as judged by trypan blue exclusion studies. Prolonged incubation (for 72 hours) of the rat and human glioma cells with NDGA markedly decreased cell proliferation with no loss of cell viability. The inhibition of human glioma cell division by NDGA was rapidly reversible after incubation for 24 hours and at least partially reversible after incubation for 96 hours. It is concluded that the inhibitors of eicosanoid biosynthesis, NDGA and (to a lesser extent) ETYA, reduce in vitro cell proliferation in two glioma lines from both the rat and human. Since neither indomethacin nor acetylsalicylic acid altered DNA synthesis in these cell lines, this implicates the lipoxygenase products of arachidonic acid metabolism as important positive modulators in glioma cell division. These findings warrant further study in an in vivo system.

Inhibition of DNA synthesis in chick embryo retinas, in vitro, by a factor from fetal bovine serum

Fetal bovine serum inhibited deoxyribonucleic acid (DNA) synthesis in chick embryo retina explants. The inhibitory activity was precipitated from fetal bovine serum by 45% saturated ammonium sulfate and isolated by means of Sephadex G-100 and Bio-Gel P-60 columns as a peak with an apparent molecular weight of 7000 Da. DNA-inhibiting activity was heat- and acid-stable and was destroyed by dithiothreitol and alkaline treatment. The purified factor inhibited similarly both DNA synthesis and thymidine kinase activity; 50% inhibitory effect was found with 160 ng, 17 h after the addition into the incubation medium.

Antimalarial agents. III. Mechanism of action of artesunate against Plasmodium berghei infection.

The antimalarial agent, artesunate has been observed to suppress the infection growth rate of Plasmodium berghei in CF1 mouse red blood cells. The inhibition of growth was due to a number of biochemical mechanisms. Deoxyribonucleic acid (DNA) synthesis in the Plasmodium berghei was inhibited significantly by the drug with marginal inhibition of protein synthesis. The inhibition of DNA synthesis seemed to be due to a block of purine synthesis at the regulatory enzyme site of inosine monophosphate (IMP) dehydrogenase. Whereas there was no evidence to demonstrate that the drug alkylated nucleotide bases or caused cross linking of DNA strands of the plasmodium, the drug did appear to cause non-specific binding to bases that interfered with template activity. There was marked inhibition of messenger ribonucleic acid (mRNA) polymerase activity with moderate inhibition of DNA polymerase activity. The drug caused significant reduction of basal oxygen consumption of Plasmodium berghei with a significant inhibition of succinic acid dehydrogenase activity. The drug interacted with reduced nicotinamide adenine dinucleotide (NADH), suggesting the possibility that artesunate may interfere with energy required for cell growth.

Effect of nalidixic acid on the conversion of Staphylococcus aureus cells to L-forms in a liquid medium with 6-aminopenicillanic acid and lysozyme.

Microbiology and ImmunologyVolume 30, Issue 8 p. 811-818 Original ArticleFree Access Effect of Nalidixic Acid on the Conversion of Staphylococcus aureus Cells to L-Forms in a Liquid Medium with 6-Aminopenicillanic Acid and Lysozyme Kunihiko Yabu, Kunihiko Yabu Department of Biology, Hokuriku University School of Pharmacy, Kanazawa, Ishikawa, 920-11Search for more papers by this author Kunihiko Yabu, Kunihiko Yabu Department of Biology, Hokuriku University School of Pharmacy, Kanazawa, Ishikawa, 920-11Search for more papers by this author First published: August 1986 https://doi.org/10.1111/j.1348-0421.1986.tb03007.xCitations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL REFERENCES 1Bibel, D.J., and Lawson, J.W. 1975. Morphology and viability of large bodies of streptococcal L-forms. Infect. Immun. 12: 919– 930. 2Gellert, M., O'Dea, M.H., Itoh, T., and Tomizawa, J. 1976. Novobiocin and coumermycin inhibit DNA supercoiling catalyzed by DNA gyrase. Proc. Natl. Acad. Sci. U. S. A. 73: 4474– 4478. 3Goss, W.A., Deitz, W.H., and Cook, T.M. 1965. Mechanism of action of nalidixic acid on Escherichia coli. II. Inhibition of deoxyribonucleic acid synthesis. J. Bacteriol. 89: 1068– 1074. 4Green, M.T., Heidger, P.M., and Domingue, G. 1974. Proposed reproductive cycle for a relatively stable L-phase variant of Streptococcus faecalis. Infect. Immun. 10: 915– 927. 5Nagate, T., Komatsu, T., Izawa, A., Ohmura, S., Namiki, S., and Mitsuhashi, S. 1980. Mode of action of a new nalidixic acid derivative, AB206. Antimicrob. Agents Chemother. 17: 763– 769. 6Smith, D.H., and Davis, B.D. 1967. Mode of action of novobiocin in Escherichia coli. J. Bacteriol. 93: 71– 79. 7Staudenbauer, W.L. 1976. Replication of E. coli DNA in vitro: inhibition by oxolinic acid. Eur. J. Biochim. 62: 491– 497. 8Sugino, A., Peebles, C.L., Kreuzer, K.N., and Cozzarelli, N. 1977. Mechanism of action of nalidixic acid: purification of Escherichia coli nal A gene product and its relationship to DNA gyrase and a novel nicking-closing enzyme. Proc. Natl. Acad. Sci. U. S. A. 74: 4767– 4771. 9Wecke, J., Lahav, M., Ginsburg, I., and Giesbrecht, P. 1982. Cell wall degradation of Staphylococcus aureus by lysozyme. Arch. Microbiol. 131: 116– 123. 10Westmacott, D., and Perkins, H.R. 1979. Effect of lysozyme on Bacillus cereus 569: rupture of chains of bacteria and enhancement of sensitivity to autolysins. J. Gen. Microbiol. 115: 1– 11. 11Yabu, K. 1985. Conversion of Staphylococcus aureus cells to stable L-forms in a liquid growth medium. Microbiol. Immunol. 29: 157– 161. 12Yabu, K. 1986. Massive induction of Staphylococcus aureus unstable L-forms in a liquid medium. Microbiol. Immunol. 30: 275– 281. 13Yabu, K., Tomizu, H., and Kanda, Y. 1984. The effect of pipemidic acid on the growth of a stable L-form of Staphylococcus aureus. Microbiol. Immunol. 28: 1057– 1064. Citing Literature Volume30, Issue8August 1986Pages 811-818 ReferencesRelatedInformation

Studies on synthesis, structure, and antitumor activity of Pt(II) complexes containing 1,2-diamino-1,2-dideoxy-D-glucitol.

An attempt was made to develop new water-soluble antitumor Pt(II) complexes by introducing hydroxyl groups into a carrier ligand, 1, 2-diamino-1, 2-dideoxy-D-glucitol (1, 2-DAG), and their structures were determined by 13C nuclear magnetic resonance and circular dicroism spectral analyses. Only [Pt(NO3)2(1, 2-DAG)] and [Pt(SO4)(1, 2-DAG)] exhibited marginal effects against leukemia L1210 in vivo, among compounds with various leaving groups.The unexpectedly low antitumor activity of Pt(II) complexes containing 1, 2-DAG was investigated in in vitro experiments. The Pt(II) complexes of 1, 2-DAG showed the same binding mode with calf-thymus deoxyribonucleic acid (DNA) as cis-diamminedichloroplatinum(II), but inhibition of DNA synthesis in L1210 cells in vitro was not observed even at the concentration of 100 μM [PtCl2(1, 2-DAG)] or [Pt(oxalato)(1, 2-DAG)]. Consideration of the Pt contents taken into the cells indicated that the Pt(II) complexes have difficulty in passing through the cell membranes, which might account for the low antitumor effects observed in vivo.