Lipolytic activity of porcine adipose tissue after preincubation

1. The stimulated lipolytic rate in porcine adipose tissue slices was markedly increased after preincubation with or without isoproterenol. 2. Preincubation with and without insulin, dibutyryl-cAMP or theophylline suggested that the activation of the stimulated rate resulted from inhibition or inactivation of cAMP-phosphodiesterase activity during preincubation. 3. Preincubation with isoproterenol also caused activation of the basal (no exogenous hormone) lipolytic activity. 4. However, much of this activation appeared to result from carry-over of isoproterenol into the incubation medium because it could be lowered by additional washing of the tissue, by lower isoproterenol concentration or by propranolol.     

Biological time and the effects of hydroxyurea on DNA synthetic activity of bone marrow and tumor cells in mice bearing the Ehrlich ascites carcinoma

The objective of this experiment was to attempt to induce, with hydroxyurea (HU), significant quantitative differences in the level of DNA-synthetic activity (DNA-SA) between a neoplastic cell population (the Ehrlich ascites carcinoma or EAC) and bone marrow in the same animal. Mice bearing a 5-day-old EAC were standardized to and kept on an LD 12:12 cycle (light 0600-1800 hr). They were treated with 500 mg/kg HU at 0500 hr (23 hr after lights on, or HALO) or at 1700 hr (11 HALO). DNA-SA was determined by liquid scintillation counting of 3H-thymidine incorporation into chemically isolated DNA. DNA-SA in bone marrow and EAC cells was monitored over the next 60 hr with subgroups of ten mice each killed every 3 hr beginning 3 hr after treatment with HU. The circadian system of the host influenced the response of the bone marrow to HU; i.e., the response to HU administered at 0500 hr was different both qualitatively and quantitatively from that for HU given at 1700 hr. Comparisons of DNA-SA in bone marrow and EAC from the same animal revealed time points after treatment with HU when DNA-SA in the EAC was high, but DNA-SA in bone marrow was low. These differences in the level of DNA-SA between a tumor cell population and bone marrow should be of therapeutic value; i.e., executor doses of anti-DNA-SA drugs such as cytosine arabinoside could be given at that point in time after treatment with HU when DNA-SA in the tumor was high, but DNA-SA in the bone marrow was low.     

Caffeine inhibits the development of Ehrlich ascites carcinoma cells in female mice

Long-term administration of caffeine at a dose of 20 mg /kg/day p.o. suppressed the viability, oxygen consumption and [3H]-thymidine incorporation of Ehrlich ascites carcinoma (EAC) cells. Though no significant change in the levels of plasma and adrenal corticosterone as well as both total and reduced adrenal ascorbic acid were observed following long-term caffeine consumption, pretreatment of caffeine and continuation of its treatment in the course of development of EAC cells restored the EAC Cell-induced changes in both corticosterone and ascorbic acid levels to control values. These results, thus, suggest that caffeine may suppress the growth of EAC cells by modulating the adrenal ascorbate level as well as corticosterone status.     

Neutral glycosphingolipids in Ehrlich ascites carcinoma cells

The structure of the neutral glycosphingolipids of the Ehrlich ascite carcinoma (EAC) cells was studied. The main four components were identified as glycosylceramide, lastosylceramide, N-acetylgalactosyllactosylceramide and galactosyl-N-acetyllactosylceramide (asialo-GM1). The neutral glycolipid pattern of the cells was found to depend on their density. Dilution of the cell suspension resulted in an increased content of asia-lo-GM1, whereas the content of the other neutral glycolipids remained unchanged. The possible connection between these changes and the earlier disclosed cell density dependence of the gangliosides in EAC cells is discussed.     

The antitumor effect of bleomycin combined with bestatin against Ehrlich ascites carcinoma in mice

The effect of bleomycin against Ehrlich ascites carcinoma transplanted subcutaneously to mice used in combination with bestatin was investigated. Male Balb/c mice weighting approximately 20 g and bred in our laboratories were used in this study. Each mouse was injected in its left lateral abdominal region subcutaneously with 7 X 10(6) tumor cells in 0.2 ml of ascites fluid. The mice were divided into four groups: control, bestatin alone (5 mg/kg intraperitoneally on Days 9-14), bleomycin alone (10 mg/kg intraperitoneally on Days 7 and 8), and bestatin plus bleomycin. Our results show that bestatin enhances the antitumor effect of bleomycin against Ehrlich ascites carcinoma as measured by the increased survival rates. Being an agent of very low toxicity, bestatin should be considered as a part of the chemoimmunotherapy protocol.     

Fluorescence study of Ehrlich ascites carcinoma cells after X-irradiation.

The mechanism of the increase in ultra-violet fluorescence (U.V.F.) intensity of Ehrlich ascites carcinoma cells after X-irradiation were investigated. It was shown that there were two mechanisms: size-dependent (mechanism I) and size-dependent (mechanism II). The basis of mechanism I is most probably an increase in protein content. Mechanism II is related to an increase in the U.V.F. quantum yield, though its biological nature is still unknown.