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E Rivedal

Publications and source records attributed to E Rivedal.

44 records · Page 3Linked to original sources
PubMed1982

Role of plasma fibronectin in the morphological transformation of hamster embryo cells.

Replacement of fetal bovine serum (FBS) by newborn serum in the hamster embryo cell transformation assay blocks the induction of morphologically transformed colonies by chemical carcinogens. Moreover, the addition of newborn serum strongly inhibits the formation of morphologically transformed colonies in the standard assay using 20% FBS. The present experiments show that the inhibitory factor is heat labile and not dialyzable, but is removed when the newborn serum is submitted to gelatin affinity chromatography. The inhibitory factor is recovered in the eluted gelatin bound material which gives essentially one band in SDS electrophoresis corresponding to that of plasma fibronectin. In separate experiments fibronectin from bovine plasma is shown to inhibit cell transformation in a similar way. The experiments suggest that fibronectin plays a central role in the mechanism of morphological cell transformation.

Animals↗
PubMed1982

Fibrinolytic activity and morphological transformation of hamster embryo cells.

Excretion of plasminogen activator from colonies of Syrian hamster embryo cells has been studied after sequential exposure of the cells to benzo[a]pyrene (3 days), and 12-O-tetradecanoyl-phorbol-13-acetate (3 days). The excretion of plasminogen activator was assayed using the fibrin/agarose overlay technique. The frequency of plasminogen activator-positive colonies was about two times higher for morphologically transformed colonies than for colonies with normal morphology growing on the same dish. Thus, 9% of the transformed colonies, compared to 4% of the colonies with normal morphology, gave clear zones of lysis in the fibrin/agarose overlay after 2 h of incubation. The frequency of plasminogen activator-positive colonies on untreated dishes was 2%. The addition of protease inhibitors strongly reduced the formation of clear zones of lysis, while they did not affect the frequency of morphologically transformed colonies. The data show that the expression of plasminogen activator is not an obligatory event in the process of morphological transformation.

Animals↗
PubMed1982

Evaluation of tumour promoters by the hamster embryo cell transformation assay.

Morphological transformation of hamster embryo cells has been used to study the effect of exposure to different combinations of compounds. Combined exposure to benzo[a]pyrene and cigarette smoke extract, to benzo[a]pyrene and nickel sulphate, and to cigarette smoke extract and nickel sulphate resulted in a synergistic increase in the formation of morphologically transformed colonies. This synergistic effect can be accounted for mainly by the finding that cigarette smoke extract and nickel sulphate promote or increase the number of transformed colonies following exposure to benzo[a]pyrene. Different tumour promoters and non-promoting analogues possess a potency for enhancing the transformation frequency similar to that of tumour promoters in experimental systems in vivo. Thus, our modification of the hamster embryo cell transformation assay may be a simple and quick method for studying modifiers of carcinogenesis.

Animals↗
PubMed1981

Metal salts as promoters of in vitro morphological transformation of hamster embryo cells initiated by benzo(a)pyrene.

The hamster embryo cell bioassay has been used to study the effect of metal salts on morphological transformation. A synergistic enhancement of the transformation frequency was found for the combined treatment with organic carcinogens [benzo(a)pyrene, N-hydroxy-2-acetylaminofluorene, and 4-nitroquinoline 1-oxide] and nickel sulfate, cadmium acetate, or potassium chromate. Chromic chloride and zinc chloride did not induce transformation themselves, and they had no effect on the transformation frequency when tested in combination with benzo(a)pyrene. The synergistic effect between benzo(a)pyrene and nickel sulfate or cadmium acetate was also apparent when the cells were treated sequentially with the chemicals. When the cells were first exposed to benzo(a)pyrene, both nickel sulfate and cadmium acetate showed a promotion-like effect similar to that obtained with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate. Moreover, when 12-O-tetradecanoylphorbol-13-acetate or benzo(a)pyrene were used as promoting agents, both nickel sulfate and cadmium acetate were able to initiate morphological transformation. The data suggest that the metal salts are more potent as promoters than they are as initiators. The present findings may be of importance in relation to carcinogenicity of metal compounds to humans.

Animals↗
PubMed1980

Synergistic effect on morphological transformation of hamster embryo cells by nickel sulphate and benz[a]pyrene.

Morphological transformation and induction of somatic mutation in the hamster embryo cell bioassay have been used to study whether the carcinogenicity of nickel is affected by polycyclic hydrocarbons. The transformation frequency was found to increase with increasing concentration of nickel sulphate, benz[a]pyrene (BP) and methylcholanthrene. In experiments with combinations of nickel sulphate and BP, the transformation frequencies used for all concentrations were higher than for compounds tested separately. The greatest enhancement was found using 5 micrograms/ml NiSO4 . 6H2O and 0.78 microgram/ml BP. The transformation frequency obtained with this combination was 10.7%, compared to 0.5% and 0.6% for the individual substances. No synergistic effect could be detected between nickel sulphate and methylcholanthrene (MC). In experiments measuring somatic mutation by selection for ouabain resistance, the mutation frequency was likewise found to be significantly higher than expected in mixtures of nickel sulphate and BP. The present demonstration of the synergistic effect between nickel sulphate and BP is of interest with the potentiating effect of cigarette smoking on development of lung cancer among nickel refinery workers.

Animals↗
PubMed1980

Potentiating effect of cigarette smoke extract on morphological transformation of hamster embryo cells by benzo[alpha]pyrene.

Morphological transformation in the hamster embryo cell bioassay has been used to study the possibility that carcinogenicity of benzo[alpha]pyrene (BP) is affected by cigarette smoke extract and whether smoke extract will promote transformations initiated by BP. The transformation frequency increases wth increasing concentrations of BP and smoke extract. In experiments with a combined treatment of BP and smoke extract, the transformation rates were higher than expected for all concentrations from experiments with the compounds tested separately. The greatest potentiating effect was found using 0.01 micrograms/ml BP and 1 microgram/ml smoke extract. The transformation frequency obtained with this combination was 4.3% compared to 1.4% and zero respectively for the individual substances. In experiments where cells were treated sequentially with BP (0.05 micrograms/ml) for 4 days followed by smoke extract (1 or 5 micrograms/ml) for the next 4 days, the transformation frequency was significantly higher than expected on the basis of the compounds tested separately. The demonstration of a synergistic effect between BP and cigarette smoke and the promotion-like effect of smoke extract on BP-initiated transformations of hamster embryo cells are of interest in relation to the higher frequency of lung cancer found in areas with high air pollution compared to rural areas.

Animals↗
PubMed1979

Role of ions in the regulation of porcine lactate dehydrogenase.

Different ions affect the H4 and M4 isoenzymes of porcine lactate dehydrogenase (L-lactate: NAD+ oxidoreductase, EC 1.1.1.27) in the same way, inhibiting the enzyme at low pyruvate concentrations, whereas at high pyruvate concentrations, the activities were enhanced. The inhibition was competitive with regard to pyruvate and NADH. The enhancement of the enzyme activity at high pyruvate concentration is due to the increase in the Km value for pyruvate, implying that higher substrate concentrations are needed to obtain substrate inhibition. Sulphate behaved differently from the other ions. It inhibited in a noncompetitive manner with regard to pyruvate and did not activate the enzyme at high pryvuate concentration. The effect of ions increased with the size of the anion. The ionic strength was of less importance.

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