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Description: We have previously reported the chemotherapeutic effect of rifamycin derivatives on an ascites tumor, using increased life span as a criterion. These derivatives inhibit (1) RNA-instructed DNA polymerase in crude viral extracts; (2) virus-induced transformation in tissue cultures; and (3) the growth of tumors in vivo. One rifamycin derivative, rifazone-8{sub 2} (R-8{sub 2}), not only inhibits transformation in chick fibroblasts but affects the growth of transformed cells. The present study demonstrates that rifampicin and R-8{sub 2} act as cytocidal (rather than cytostatic) agents against some ascites cell lines.
Date: August 1, 1978
Creator: Hughes, Ann M. & Calvin, Melvin
Partner: UNT Libraries Government Documents Department


Description: Iodoacetamide has been shown by others to be a radiation sensitizer for bacteria and for certain mammalian cells tested in vitro. This work describes an examination of the effectiveness of iodoacetamide used in vivo. Survival of ascites tumor cells maintained in the peritoneal cavity of mice was used as an indicator of sensitization. Survival was assessed using TD{sub 50} and total tumor cell population determination methods. A comparison of results obtained by these methods is made. The effects of oxygen tension and radiation dose rate upon results was examined. Iodoacetamide was found to be effective as a radiation sensitizer under all conditions although to a lesser degree than that reported by others for in vitro experiments with bacteria. Radioactive tracer studies indicate that iodoacetamide has rapid and total access to most if not all tissues of the body. This fact coupled with the observation of a sensitization in an in vivo system where the anoxia so prevalent in well developed tumors was present, suggests the possibility of clinical usefulness of iodoacetamide in cancer radiation therapy. Certain observations are reported on the effect of various cell and host treatment procedures upon cell population growth kinetics seen subsequent to inoculation of hosts with the cells. A hypothesis is presented which can account for the observations made by the author and also for those made by some others who report that large inocula, i.e., greater than 10 cells, are required to give rise to a lethal tumor in isologous hosts of the strain of tumor origin. The hypothesis may also account for what is known in the literature as the 'Hybrid Effect.'
Date: October 1, 1970
Creator: Richards, F. Robert & Kelly, Lola S.
Partner: UNT Libraries Government Documents Department

Biological effects of negative pions

Description: From thirteenth international congress of radiology; Madrid, Spain (15 Oct 1973). A brief review is presented of studies on biological effects of negative pions. Studies on biological effectiveness at the plateau were conducted using mice with ascites tumors, the RBE relative to /sup 60/Co gamma radiation was nearly 1.0. Studies on biological effectivenes s and oxygen enhancement ratio using root growth of Vicia faba showed that the RBE was 1.31 and the OER was 2.04. RBE and OER were measured in various biologica1 systems and the results at the peak of the depth-dose distribution are tabulated. Results of studies on human kidney- cells, bean roots, and HeLa cells are reviewed with regard to variations in biologica1 effectiveness within the peak regdon. Ce1l survival calculations are reviewed with emphasis on cell survival data at various descrete LET values. A discussion is presented of the biological effects of negative pion beams of interest for therapy-. (HLW-)
Date: January 1, 1973
Creator: Raju, M.R.
Partner: UNT Libraries Government Documents Department

(Accumulation of methyl-deficient rat liver messenger ribonucleic acid on ethionine administration). Progress report. [Methyltransferase activity in Ehrlich ascites tumor cells and effects of phorbol ester on methyltransferase activity]

Description: Enzyme fractions were isolated from Ehrlich ascites cells which introduced methyl groups into methyl deficient rat liver mRNA and unmethylated vaccinia mRNA. The methyl groups were incorporated at the 5' end into cap 1 structures by the viral enzyme, whereas both cap 0 and cap 1 structures were formed by the Ehrlich ascites cell enzymes. Preliminary results indicate the presence of adenine N/sup 6/-methyltransferase activity in Ehrlich ascites cells. These results indicate that mRNA deficient in 5'-cap methylation and in internal methylation of adenine accumulated in rats on exposure to ethionine. The methyl-deficient mRNA isolated from the liver of ethionine-fed rats differed in its translational properties from mRNA isolated from control animals. Preliminary experiments indicate that single topical application of 17n moles of TPA to mouse skin altered tRNA methyltransferases. The extent of methylation was increased over 2-fold in mouse skin treated with TPA for 48 hours. These changes have been observed as early as 12 hours following TPA treatment. In contrast, the application of initiating dose of DMBA had no effect on these enzymes. It should be emphasized that the changes in tRNA methyltransferases produced by TPA are not merely an increase of the concentration of the enzyme, rather that they represent alterations of specificity of a battery of enzymes. In turn the change in enzyme specificity can produce alterations in the structure of tRNA. (ERB)
Date: January 1, 1980
Creator: Borek, E.
Partner: UNT Libraries Government Documents Department