Effect of radon on Yoshida sarcoma.
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GMP synthetase was found in the cytosolic fraction of Yoshida sarcoma ascites cells. However, prolonged centrifugation resulted in precipitation of the enzyme. On sucrose density gradient centrifugation of a crude extract of Yoshida sarcoma ascites cells, a part of this enzyme showed high sedimentability at low ionic strength. On the basis of these observations, GMP synthetase was purified from Yoshida sarcoma ascites cells by means of procedures including centrifugal fractionation. The purified enzyme was shown to be homogeneous on SDS-polyacrylamide gel electrophoresis and isoelectric focusing in polyacrylamide gel. The molecular weight of the GMP synthetase was estimated to be 78,000 by SDS-polyacrylamide gel electrophoresis and gel filtration on Sephadex G-150. Its isoelectric point was estimated to be 5.6. The Km values of this enzyme for XMP, ATP, and glutamine were calculated to be 4.6, 120, and 300 microM, respectively. Although ammonia could substitute for glutamine as a donor of the amino group, the Km value was as high as 120 mM, indicating that it cannot be considered to be a physiological substrate. This enzyme showed high activity only in the presence of Mg2+, and very low activity in the presence of other divalent cations. Inhibition by nucleoside monophosphates was not significant. The enzyme required reduced sulfhydryl compounds for its activity.
The solid Yoshida sarcoma implanted on the feet of rats was subjected to local hyperthermia by water bath immersion. Tumor response was governed by the temperature and duration of heating (i.e., the degree of heating) and by tumor volume. With small tumors (1.0- to 1.5-ml volume) an intratumor temperature of 42 degrees maintained for 1 hr led to tumor regression in 11 to 13 days, and the tumor volume was halved every 2.6 days. Following 2 hr hyperthermia (42 degrees) the tumors disappeared in 6 to 7 days, and tumor volume was halved every 1.2 days. Tumors of 2 to 3-mol volume had left the exponential phase of the growth curve and required 2 hr at 42 degrees for cure. Following heating at 40 degrees for 1 hr, there was a 50% increase in O2 uptake and anaerobic CO2 production by the tumor, accompanied by enhanced dissemination by lymphatic, vascular, and direct routes, and tumor was found in organs not usually the site of metastases (e.g., testis and stomach). With large tumors (3.0 to 4.5 ml), the survival time of the rats was significantly reduced. These results occurred in the absence of a rise in body temperature of the animals. It is concluded that in this animal-tumor system, hyperthermia at a temperature inadequate for tumor destruction (40 degrees) can result in changes in the tumor that represent a hazard to the host.
The effects of cytochalasin B (CB) and colchicine on the motility and growth of cultured Yoshida sarcoma cells are studied by cinematographic methods. CB was found to reduce the average locomotory rate of motile Yoshida sarcoma cells and to enhance the frequency of non-motile cells. On the other hand, colchicine enhanced only the frequency of non-motile cells and did not affect the locomotory rate of motile cells. CB inhibited the growth of Yoshida sarcoma cells at the concentration range of 0.6 to 5 microgram/ml.
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