Exposure of isolated frog rod outer segments (ROS) to ferrous sulfate in a Krebs-bicarbonate medium causes a time-dependent disruption of the membrane organization of the discs. Ferrous sulfate also causes ROS swelling and aggregation. Addition of taurine (5-20 mM) and zinc sulfate (250 microM) to the incubation medium markedly protected ROS from the disrupting effect of ferrous sulfate. Of other amino acids tested, only beta-alanine had a protective effect on ROS structure. Ferrous sulfate caused an increase in lipid peroxidation, measured by malonaldehyde formation. The protective effect of taurine and zinc is not accompanied by a reduction of lipid peroxidation. Water accumulation occurs as a consequence of the peroxidative action of ferrous sulfate, and this effect was counteracted by taurine and zinc. Ferrous sulfate did not cause damage to ROS structure when incubation was carried out in sucrose-HEPES. Sodium, chloride, and bicarbonate ions caused ferrous sulfate to disrupt ROS structure. It is concluded that taurine and zinc protect ROS membranes from ion and/or water entry occurring as a consequence of membrane lipid peroxidation.
The resolution of fluorescence microscopy images is limited by the physical properties of light. In the last decade, numerous super-resolution microscopy (SRM) approaches have been proposed to deal with such hindrance. Here we present Mean-Shift Super Resolution (MSSR), a new SRM algorithm based on the Mean Shift theory, which extends spatial resolution of single fluorescence images beyond the diffraction limit of light. MSSR works on low and high fluorophore densities, is not limited by the architecture of the optical setup and is applicable to single images as well as temporal series. The theoretical limit of spatial resolution, based on optimized real-world imaging conditions and analysis of temporal image stacks, has been measured to be 40 nm. Furthermore, MSSR has denoising capabilities that outperform other SRM approaches. Along with its wide accessibility, MSSR is a powerful, flexible, and generic tool for multidimensional and live cell imaging applications.
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