Background: PCNA, an eukaryotic DNA sliding clamp interacts with replication factors and the cell cycle protein, p21(Cip1/Waf1) and functions as a molecular switch for DNA elongation. To understand how DNA replication is regulated through PCNA, elucidation of the precise mechanisms of these protein interactions is necessary.

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Quality control of tissues and organs for transplant is important to confirm their safety and effectiveness for regenerative medicine. However, quality evaluation is only carried out using a limited range of inspection criteria, because many of the available evaluation tests are invasive. In order to explore the potential of 2-[ 18 F]fluoro-2-deoxy-D-glucose ([ 18 F]FDG)-bioradiography as a non-invasive test for estimation of the safety, soundness, and effectiveness of tissues for transplantation, [ 18 F]FDG uptake and cell viability or metabolism were investigated using a reconstructed human epidermal model (RHEM). We developed an imaging system, and suitable bioradiographic image acquisition conditions and its effectiveness were investigated. [ 18 F]FDG uptake increased in agreement with DNA content as a marker of cell numbers and for histological assessment during cell proliferation and keratinization. [ 18 F]FDG uptake was significantly decreased in good agreement with the viability of tissues used with various hazardous chemical treatments. [ 18 F]FDG uptake by the tissues was decreased by hypothermia treatment and increased by hypoxia treatment while maintaining cell viability in the tissue. Therefore, [ 18 F]FDG-bioradiography can be useful to estimate cell viability or metabolism in this RHEM. This method might be utilized as a non-invasive test for quality evaluation of tissues for transplantation.

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Background:Reactive oxygen species (ROS) have been suggested to be involved in cellular damage caused by ischemia-reperfusion, anoxia-reperfusion, and hypoxia-reperfusion. We previously demonstrated that the generation of ROS was enhanced following hypoxia caused by an increased oxygen demand, and this was related to a shift in the tissue redox balance toward reduction. The aim of the present study was to elucidate the relationship among changes in ROS generation, tissue pO 2 levels, and redox balance changes in brain slices following hypoxia caused by a decreased oxygen supply. MethodsWe measured ROS-dependent chemiluminescence in cerebral cortex slices using a photonic imaging method as well as tissue pO 2 levels and the redox balance using micro sensors during reoxygenation after hypoxia caused by the deprivation of an adequate oxygen supply. ResultsROS-dependent chemiluminescent intensity was transiently enhanced during reoxygenation after the hypoxic treatment. Tissue pO 2 levels decreased and the tissue redox balance shifted towards reduction with the hypoxic treatment, followed by restoration to the steady-state condition. Increased ROS generation following hypoxia was related to a transient decrease in tissue pO 2 levels and a shift in the tissue redox balance towards reduction. ConclusionsThe present results demonstrated that ROS generation increased following hypoxia caused by a decreased oxygen supply. In addition, a transient redox shift to "hyper-reduction" with pO 2 changes may be involved in ROS generation in tissue.