Effects of procollagen C-proteinase enhancer protein on the growth of cultured rat fibroblasts revealed by an excisable retroviral vector

An excisable retroviral vector, TSN-lox, was developed by exploiting Cre-loxP homologous recombination. An integrated TSN-lox provirus could be excised, leaving a solo long terminal repeat at the integration site; inverse PCR, taking advantage of the solo long terminal repeat, was used to characterize cellular flanking sequences. A TSN-lox-transduced Rat2 cell clone, lox-7, was found to harbor the provirus in an intron of the procollagen C-proteinase enhancer protein (PCPE) gene, whose expression was lowered compared with that of the parental Rat2. When the vector provirus in lox-7 cells was excised, PCPE expression was elevated. The level of PCPE expression seemed to affect cell growth properties such as morphology, contact inhibition, and anchorage-independent growth. These results suggested that the excisable retroviral vector may be useful for studying the molecular basis for proviral insertion mutagenesis, and that PCPE may play a significant role in controlling cell growth and differentiation.     

High protein-adsorption characteristics of acicular crystal assembled TiO2 films and their photoelectric effect

Unique structures of TiO₂ films were prepared on F-doped SnO₂ transparent conductive films in aqueous solutions. They were then covered with dye-labeled proteins. Firstly, influence of film thickness on photoluminescence intensity (PL) and photocurrent (PC) was investigated. PL and PC were improved with the decrease of film thickness. Especially, PC was drastically improved to more than 30 times with the decrease of film thickness. Secondly, a novel technique of solution aging method was applied to form TiO₂ structures. PC was successfully improved with this technique. They were candidate materials for bio-semiconductor hybrid devices such as protein sensors.     

Structome of Saccharomyces cerevisiae determined by freeze-substitution and serial ultrathin-sectioning electron microscopy

The cell structure has been studied using light and electron microscopies for centuries, and it is assumed that the whole structure is clarified by now. Little quantitative and three-dimensional analysis of cell structure, however, has been undertaken. We have coined a new word, 'structome', by combining 'structure' and '-ome', and defined it as the 'quantitative and three-dimensional structural information of a whole cell at the electron microscopic level'. In the present study, we performed structome analysis of Saccharomyces cerevisiae, one of the most widely researched biological materials, by using freeze-substitution and serial ultrathin-sectioning electron microscopy. Our analysis revealed that there were one to three mitochondria, ~220 000 ribosomes in a cell, and 13-28 endoplasmic reticula/Golgi apparatus which do not form networks in the cytoplasm in the G1 phase. Nucleus occupied ~10.5% of the cell volume; cell wall occupied ~17%; vacuole occupied ~5.8%; cytoplasm occupied ~64%; and mitochondria occupied only ~1.7% in the G1 phase. Structome analysis of cells would form a base for the post-genome research.     

In situ microstructure observation techniques in welding

The results of investigations of the effect of the thermophysical conditions of argon-shielded arc welding on the properties of welded sheet components for stamping are presented.     

Atomic‐Scale Visualization of Polarization Pinning and Relaxation at Coherent BiFeO3/LaAlO3 Interfaces

Complex oxide heterointerfaces, which play host to an incredible variety of interface physical phenomena, are of great current interest in introducing new functionalities to systems. Here, coherent super‐tetragonal BiFeO₃/LaAlO₃ and rhombohedral BiFeO₃/LaAlO₃ heterointerfaces are investigated by using a combination of high‐angle annular dark‐field (HAADF) imaging and annular bright‐field (ABF) imaging in a spherical aberration (Cs) corrected scanning transmission electron microscope (STEM), and first‐principles calculations. The complicated ferroelectric polarization pinning and relaxation that occurs at both interfaces is revealed with atomic resolution, with a dramatic change in structure of BiFeO₃, from cubic to super‐tetragonal‐like. The results enable a detailed explanation to be given of how non‐bulk phase structures are stabilized in thin films of this material.     

In vitro and in vivo evaluation of ellagic acid on melanogenesis inhibition

The efficacy of ellagic acid (EA), one of the naturally occurring polyphenols, in inhibiting melanogenesis was examined in vitro and in vivo. When mushroom-derived tyrosinase, a metaloprotein containing copper, was incubated with EA, enzymatic activity tended to decrease with decreasing copper concentration. Enzyme activity partially recovered when copper was added to the inactivated enzyme. Tyrosinase activity in the B16 melanoma cells was observed to recover in a dose-dependent manner when copper ions were added to the medium containing EA. Based on these results, EA is thought to react specifically with the copper located at the active centre of the tyrosinase molecule. Furthermore, when EA was applied for 6 weeks to brownish guinea-pigs, which have melanocytes in their skin, at the same time as irradiating for 2 weeks with ultra-violet light, skin pigmentation was clearly suppressed and the skin to which EA had been applied showed features similar to that of non-irradiated skin. These areas were irradiated again when the application of EA had been completed, and skin pigmentation occurred at the former site of EA application. In similar studies with hydroquinone, re-pigmentation did not occur on the sites at which hydroquinone (1%) had been applied. Based on the results reported here, EA is thought to suppress melanogenesis by reacting with activated melanocytes and without injuring cells.