The present study evaluated the antimutagenic and anticancer activities of A. marina leaf extract. The antimutagenic activity of ethanol and water extracts of A. marina leaf (concentration 10 mg/plate for 48 h) was evaluated using the Salmonella typhimurium TA100 strain in the Ames test with (+S9) and without (−S9) metabolic activation, and its anticancer effect with concentrations of 200, 400, 450, 500, 600, and 800 µg/ml of ethanol extract for 24, 48, and 72 h on human leukaemic cell line HL-60 was assessed by MTT assay. The ethanol and water extracts of A. marina were revealed to have antimutagenic activity in the Salmonella mutation assay. The number of mutant colonies decreased in the presence of ethanol and water extract with (+S9) and without (−S9) metabolic activation. The ethanol extract showed a higher antimutagenic effect than the water extract, with an inhibition rate of 71% on the mutated bacterium. The MTT cell viability test showed an induction of cytotoxicity in HL-60 cells treated with the extract with IC50 values of 600, 400, and 280 µg/ml after 24, 48, and 72 h, respectively, in a concentration and time-dependent manner. Flow cytometric analysis confirmed the induction of apoptosis in the cells. Collectively, these results suggest that the Avicennia marina leaf extract contains bioactive compounds with antimutagenic and antileukaemic effects.
A series of measurements on the secondary-electron emission properties of a range of amorphous materials have been carried out under very stringent experimental conditions for various angles of incidence, over a wide range of primary energies. For these amorphous materials the effects of varying the angle of incidence of the primary beam agree with the predictions of simple theory. The measurements indicate that the rate of energy loss of a primary electron within the solid is reasonably well described over a limited range of energies by a power law. The value of the power-law exponent is slightly higher than the value of 1.35 suggested by Young and appears to vary with the atomic number of the target material. The inelastic reflection coefficient for these amorphous materials increases slightly with increasing angle of incidence.
A series of accurate measurements of the secondary-electron emission properties of a range of amorphous materials, carried out under stringent experimental conditions, have allowed an empirical test of the accuracy of the theoretical expressions derived by Dionne for the locations of the cross-over points on the yield curve. These expressions are found to be in good agreement with observation.
A variety of 'Universal Yield Curves' for the secondary emission process have been proposed. A series of precise measurements of the secondary emission properties of a range of related amorphous semiconducting materials, made under UHV on freshly vacuum-cleaved surfaces, and covering a wide range of primary energies, have recently made possible an accurate assessment of the validity of the various UYCs suggested. It is found that no truly universal curve exists; the atomic number of the target materials plays an important part in determining the secondary emission properties. Agarwal's semi-empirical expression, which takes account of the atomic number and weight, is found to give good agreement for all the materials studied. Further theoretical investigation is required.
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