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Objective As the photostability of calcium ions (Ca2+) indicators is an important property for indicating the temporal features of cytosolic Ca2+ in cells, this study aims to quantitatively measure the light-induced fluorescence enhancement in cells stained with Ca2+ indicators. Methods Five cell lines, MC3T3-E1, RAW264.7, MLO-Y4, MEF3T3 and HEK293, were exposed to the light with five levels of optical power, respectively, so as to investigate the light induced responses of two commonly-used Ca2+ indicators, Fluo-4 AM and Oregon green. The light-induced fluorescence enhancement, the succeeding photobleaching and the thapsigargin (TG)-induced responsive peak followed by were observed. The characteristic parameters of responsive peaks were further analyzed. Results Light with higher power level would induce the fluorescence enhancement for both Fluo-4 AM or Oregon green, while the responsive percentage as well as the magnitude and time span of light-induced peak of Oregon green-stained cells were significantly lower than those of Fluo-4 AM-stained cells. Conclusions The use of Oregon green with low power level light shows better photostability to indicate the intracellular Ca2+.
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AIM: Accommodation is one of the most important functions of human eye, while its mechanism is still under discussion. This paper aimed to study accommodation mechanism with numerical simulation.METHODS: A simulation model was constructed to study the mechanism of accommodation based on the experimental data derived from published resources. The displacement and pressure are applied on the model to study the deformation of lens during accommodating.RESULTS: The simulation showed that, as the eye was accommodating, the thickness of the lens increased linearly,and the lens diameter decreased linearly. The optical power of the lens increased as the accommodation increased. This result was accord with the public facts in accommodation.Furthermore, the pressure was found to have a great influence on the shape of the lens and the optical power. The lens became thinner and flatter as the pressure increased and the pressure caused a remarkable increase of lens' optical power.CONCLUSION: The outcome of this paper is consistent with the Helmholtz's hypothesis on accommodation to some extent. The analytical model presented in this paper can be used in the theoretical study of the accommodation mechanism of the human lens.