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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 31 (1992), S. 164-171 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 6457-6466 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a general theory of equilibrium polymerization in a binary mixture by applying the n-vector model for magnetism in a weak field. Results are given for the temperature dependence of the order parameters, polymer length, and phase diagrams in the concentration–temperature plane. In addition to phase separations between two monomer phases and between a monomer and a polymer phase, the phase diagrams show the possibility of coexistence between two polymer phases with a critical point. It is shown that our theory becomes identical to the earlier theory for equilibrium copolymerization of Tobolsky and Owen when the molecular field approximation and some additional approximations are used.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 639 (1991), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0843
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of our investigations is to evaluate whether the sensitivity patterns of small-cell lung-cancer (SCLC) cell lines in vitro can be used in evaluating new drugs and in selecting drugs for the optimization of combination therapy. In our attempts to obtain a panel of cell lines demonstrating differential patterns in sensitivity, we have developed three SCLC lines exhibiting different types of multidrug resistance (MDR). In the present investigations we compared the sensitivity patterns shown by five wild-type SCLC lines and three MDR lines in response to six different types of drugs: doxorubicin, cytarabine, carmustine, cisplatin, vincristine, and etoposide. In the wild-type SCLC cell lines, the range of variation in sensitivity to all drugs was within a factor of 10. Cell lines showing low sensitivity to doxorubicin also exhibited low sensitivity to etoposide and vincristine, and vice versa. In contrast, the pattern of sensitivity to carmustine was almost the opposite of that to doxorubicin. A tendency to an inverse relationship between doxorubicin and carmustine sensitivity was also observed when doxorubicin sensitivity was reduced in near stationary cells and in cells exposed to the metabolic inhibitor 2-deoxy-d-glucose. In agreement with the pattern observed for the wild-type lines, all of the MDR sublines demonstrated collateral sensitivity to carmustine. As to cytarabine, the wild-type lines expressed a sensitivity pattern similar to that shown in response to doxorubicin. Interestingly, the opposite pattern was found in the MDR lines, as all three demonstrated cytarabine hypersensitivity. The combination of alkylating agents and “MDR” drugs are of proven clinical benefit in the treatment of solid tumors, as is the combination of anthracycline and cytarabine in acute myeloid leukemia. The experimentally derived sensitivity data on cytarabine, alkylating agents, and MDR drugs (i.e., etoposide, doxorubicin, vincristine) thus resemble the clinical experience with these drugs, and we conclude that the use of a clonogenic asay on the described panel of SCLC cell lines can give valuable information for the selection of agents for combination therapy.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0843
    Keywords: Etoposide ; Topoisomerase II ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A number of clinically important drugs such as the epipodophyllotoxins etoposide (VP-16) and teniposide (VM-26), the anthracyclines daunorubicin and doxorubicin (Adriamycin), and the aminoacridine amsacrine exert their cytotoxic action by stabilizing the cleavable complex formed between DNA and the nuclear enzyme topoisomerase II. We have previously demonstrated in several in vitro assays that the anthracycline aclarubicin (aclacinomycin A) inhibits cleavable-complex formation and thus antagonizes the action of drugs such as VP-16 and daunorubicin. The present study was performed to validate these in vitro data in an in vivo model. At nontoxic doses of 6 and 9 mg/kg, aclarubicin yielded a marked increase in the survival of non-tumor-bearing mice given high doses of VP-16 (80–90 mg/kg) in six separate experiments. In therapy experiments on mice inoculated with Ehrlich ascites tumor cells, aclarubicin given at 6 mg/kg roughly halved the increase in median life span induced by VP-16 at doses ranging from 22 to 33 mg/kg. An attempt to determine a more favorable combination of VP-16 and aclarubicin by increasing VP-16 doses failed, as the two drugs were always less effective than VP-16 alone. The way in which VP-16-induced DNA strand breaks lead to cell death remains unknown. However, VP-16 has been reported to cause apoptosis (programmed cell death) in several cell lines. To ascertain whether the protection given by aclarubicin could have a disruptive effect on the apoptotic process, we used the small intestine as an in vivo model. Whereas VP-16-induced apoptosis in crypt stem cells was detectable at a dose as low as 1.25 mg/kg, aclarubicin given at up to 20 mg/kg did not cause apoptosis. Indeed, aclarubicin caused a statistically significant reduction in the number of cells rendered apoptotic by VP-16. The present study thus confirms the previous in vitro experiments and indicates the value of including an in vivo model in a preclinical evaluation of drug combinations.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0843
    Keywords: Key words: Etoposide – Topoisomerase II – Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. A number of clinically important drugs such as the epipodophyllotoxins etoposide (VP-16) and teniposide (VM-26), the anthracyclines daunorubicin and doxorubicin (Adriamycin), and the aminoacridine amsacrine exert their cytotoxic action by stabilizing the cleavable complex formed between DNA and the nuclear enzyme topoisomerase II. We have previously demonstrated in several in vitro assays that the anthracycline aclarubicin (aclacinomycin A) inhibits cleavable-complex formation and thus antagonizes the action of drugs such as VP-16 and daunorubicin. The present study was performed to validate these in vitro data in an in vivo model. At nontoxic doses of 6 and 9 mg/kg, aclarubicin yielded a marked increase in the survival of non-tumor-bearing mice given high doses of VP-16 (80 – 90 mg/kg) in six separate experiments. In therapy experiments on mice inoculated with Ehrlich ascites tumor cells, aclarubicin given at 6 mg/kg roughly halved the increase in median life span induced by VP-16 at doses ranging from 22 to 33 mg/kg. An attempt to determine a more favorable combination of VP-16 and aclarubicin by increasing VP-16 doses failed, as the two drugs were always less effective than VP-16 alone. The way in which VP-16-induced DNA strand breaks lead to cell death remains unknown. However, VP-16 has been reported to cause apoptosis (programmed cell death) in several cell lines. To ascertain whether the protection given by aclarubicin could have a disruptive effect on the apoptotic process, we used the small intestine as an in vivo model. Whereas VP-16-induced apoptosis in crypt stem cells was detectable at a dose as low as 1.25 mg/kg, aclarubicin given at up to 20 mg/kg did not cause apoptosis. Indeed, aclarubicin caused a statistically significant reduction in the number of cells rendered apoptotic by VP-16. The present study thus confirms the previous in vitro experiments and indicates the value of including an in vivo model in a preclinical evaluation of drug combinations.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0843
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The epipodophyllotoxines VP-16 and VM-26 are chemically closely related. VM-26 has been found to be considerably more potent than VP-16 in vitro in a number of investigations. Although the drugs have been known for 〉20 years, they have not been compared at clearly defined equitoxic doses on an optimal schedule in vivo and it has not been clarified as to whether a therapeutic difference exists between them. A prolonged schedule is optimal for both drugs; accordingly we determined the toxicity in mice using a 5-day schedule. The dose killing 10% of the mice (LD10) was 9.4 mg/kg daily (95% confidence limits, 7.4–11.8) for VP-16 and 3.4 (2.5–4.5) mg/kg daily for VM-26. In vitro, we found VM-26 to be 6–10 times more potent than VP-16 in a clonogenic assay on murine tumors P388 and L1210 leukemia and Ehrlich ascites. This pattern was also demonstrated in a multidrug-resistant subline of Ehrlich selected for resistance to daunorubicin (Ehrlich/DNR+), as it was 30 times less sensitive than Ehrlich cells to both VP-16 and VM-26. Using 90%, 45%, and 22% of the LD10 on the same murine tumors in vivo, we found that the effect of the two drugs was equal as evaluated by both the increase in life span and the number of cures. The drugs were also compared in nude mice inoculated with human small-cell lung cancer lines OC-TOL and CPH-SCCL-123; however, they were more toxic to the nude mice and only a limited therapeutic effect was observed. In conclusion, the complete cross-resistance between the two drugs suggests that they have an identical antineoplastic spectrum. VM-26 was more potent than VP-16 in vitro; however, this was not correlated to a therapeutic advantage for VM-26 over VP-16 in vivo
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The catalytic domain of PAC1 (amino acids 127-314; cPACl) was expressed as a soluble glutathione S-transferase (GST) fusion protein, and the enzymatic activity of the highly purified GST-cPACl was assayed using a variety of substrates. In a screen of potential physiological substrates, we used ...
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cancer chemotherapy and pharmacology 30 (1992), S. 219-220 
    ISSN: 1432-0843
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0843
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Recent studies by Boesch et al. have demonstrated that a nonimmunosuppressive cyclosporin analog, SDZ PSC 833 (an analog of cyclosporin D), is an active multidrug-resistance modifier that is at least 10 times more potent than cyclosporin A. In vitro accumulation and cytotoxicity experiments using daunorubicin (DNR) and vincristine (VCR) under the influence of SDZ PSC 833 and cyclosporin A were performed in wild-type (EHR2) and the corresponding highly DNR-resistant (about 80-fold) Ehrlich ascites tumor cells (EHR2/DNR+). In accumulation experiments, both SDZ PSC 833 and cyclosporin A were found to reverse the multidrug-resistant (MDR) phenotype, but to the same degree at equimolar concentrations. Thus, in EHR2/DNR+ cells, both cyclosporins at 5 μg/ml enhanced DNR and VCR accumulation to sensitive levels, but only a negligible effect on DNR accumulation in the drug-sensitive cells was seen. In the clonogenic assay, the cytotoxicity of the two modulators was equal. The lethal dose for 50% of the cell population (LD50) was approx. 7 μg/ml for both compounds, and no toxicity was observed at concentrations below 2 μg/ml. At nontoxic doses, both cyclosporins effectively increased the cytotoxicity of DNR and VCR in a concentration-dependent manner. The dose-response curves were nearly identical and did not demonstrate differences in modulator potency. These data permit the conclusion that cyclosporin A and SDZ PSC 833 do raise the intracellular accumulation of DNR and VCR to the same levels and that SDZPSC 833 does not potentiate cytotoxicity better than cyclosporin A in EHR2/DNR+ cells. However, since the new compound is nonimmunosuppressive and causes less organ toxicity, clinical studies of its MDR modulating effect seem highly relevant.
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