Antioxidant and pro-oxidant actions of flavonoids: effects on DNA damage induced by nitric oxide, peroxynitrite and nitroxyl anion

Antioxidant and pro-oxidant activities of flavonoids have been reported. We have studied the effects of 18 flavonoids and related phenolic compounds on DNA damage induced by nitric oxide (NO), peroxynitrite, and nitroxyl anion (NO-). Similarly to our previous findings with catecholamines and catechol-estrogens, DNA single-strand breakage was induced synergistically when pBR322 plasmid was incubated in the presence of an NO-releasing compound (diethylamine NONOate) and a flavonoid having an ortho-trihydroxyl group in either the B ring (e.g., epigallocatechin gallate) or the A ring (e.g., quercetagetin). Either NO or any of the above flavonoids alone did not induce strand breakage significantly. However, most of the tested flavonoids inhibited the peroxynitrite-mediated formation of 8-nitroguanine in calf-thymus DNA, measured by a new HPLC-electrochemical detection method, as well as the peroxynitrite-induced strand breakage. NO- generated from Angeli's salt caused DNA strand breakage, which was also inhibited by flavonoids but at only high concentrations. On the basis of these findings, we propose that NO- and/or peroxynitrite could be responsible for DNA strand breakage induced by NO and a flavonoid having an ortho-trihydroxyl group. Our results indicate that flavonoids have antioxidant properties, but some act as pro-oxidants in the presence of NO.     

An improved assay method for fibroblast gelatinolytic enzyme

A useful gelatinolytic enzyme assay for fibroblasts, utilizing a novel sample preparation method for collagenase with dithiothreitol (DTT) treatment to inactivate endogenous collagenase inhibitors, was developed using soluble fluorescein isothiocyanate (FITC)-labeled gelatin. The substrate, gelatin was prepared by heating commercially available FITC-labeled type I collagen. The denatured collagen was cleaved with purified trypsin and partially purified fibroblast gelatinase, and the digested FITC-fragments were measured fluorometrically. The intensity of the fluorescence was in proportion to the reaction time and enzyme concentration. Both enzyme activities were measurable within the nanogram range of enzyme preparations. The enzyme activity was detected after 4-aminophenylmercuric acetate (APMA) treatment which was completely inhibited by metalloproteinase inhibitors, but not by serine- and cysteine-proteinases' inhibitors. Conditioned media of human periodontal ligament fibroblasts (PLF) and gingival fibroblasts (GF) were separately treated with DTT prior to the enzyme assay, and then the assay was performed in the presence of APMA. The enzyme activities of PLF and GF were 106- and 55-fold higher than those of the conventional gelatinase assay which was carried out without DTT treatment. This assay method allowed the measurement of gelatinolytic enzyme activity when tissue inhibitors of metalloproteinases were present in the fibroblast culture medium.     

The growth of FeOOH microcrystals and chemisorption rate of NO

The adsorption of NO over a period of 1 ms–1 min on α- and γ-FeOOH with different degrees of crystallization has been examined in order to clarify the fast chemisorption phenomenon. The FeOOH crystals were prepared under the conditions of various reaction temperatures and ageing times. The changes in X-ray diffraction patterns, particle size, specific surface area and electrical conductivity were examined. The fast chemisorption rate constant, k_f, for NO was obtained at 30°C from the conductivity change in the initial stage of NO adsorption. The α-FeOOH aged for 2 days and 6 days, the crystallite size of which approximately 100 Å gave the highest k_f and the greatest amount of chemisorption; the high activity is assumed to be caused by a special surface structure accepting NO molecules. The maximum k_f for α-FeOOH was also for a crystallite size of approximately 100 Å. As the change of k_f with crystal growth for γ-FeOOH is similar to that of electrical conductivity, an electronic factor seems to be most important in the fast chemisorption process of NO on γ-FeOOH.     

A method of transient stability estimation for power systems by lyapunov function

The power system stability problem has been one of the major subjects concerning power system engineering, and is becoming much more significant today due to the increasing size and complexity of interconnected power systems. In this problem, it is well known that the direct method of Lyapunov is the most suitable method of on-line transient estimation for power systems, and several different techniques have been proposed for the construction of functions up to this time. However, the effectiveness of these Lyapunov functions for power systems have been demonstrated using only digital computer simulations. The purpose of this paper is to construct a microprocessor-based, on-line, transient-stability estimation system using the Lyapunov function constructed by the Lagrange-Charpit method, and to estimate the transient stability of an alternator connected to a large system. The experimental results show that this system can act satisfactorily for estimating the transient stability of the power systems.     

A 68-ns 4-Mbit CMOS EPROM with high-noise-immunity design

In a VLSI memory, noise generated by its own operation is a serious problem. The noise disturbs data sensing, especially in EPROMs which have a single-ended sensing scheme. To develop high-density and high-speed EPROMs, it is necessary to solve the noise problems. Incorrect EPROM functions due to the noise are discussed. High-noise-immunity circuit techniques for stable data sensing and high-speed access time are proposed. These are divided bit-line layout, reference line with dummy bit lines, and a chip-enable transition detector. Using these circuit techniques and 0.8-μm n-well CMOS technology, a 512 K×8-b CMOS EPROM was developed. A 68-ns access time was achieved. The die size is 5.62 mm×15.30 mm, and it is assembled in a 600-mil cerdip package     

Electrical and optical properties of electrochemically prepared polyselenophene film

The electrical, optical and magnetic properties of flexible shiny films of polyselenophene obtained by the electrochemical method are studied. The electrical conductivity of doped polyselenophene is found to be much lower than that of polythiophene and polypyrrole, which is consistent with its relatively wider ESR linewidth even after doping. The photovoltaic effect is also observed in this polymer and discussed in comparison with optical absorption spectra.     

Molecular evidence from retroposons that whales form a clade within even-toed ungulates

The origin of whales and their transition from terrestrial life to a fully aquatic existence has been studied in depth. Palaeontological, morphological and molecular studies suggest that the order Cetacea (whales, dolphins and porpoises) is more closely related to the order Artiodactyla (even-toed ungulates, including cows, camels and pigs) than to other ungulate orders. The traditional view that the order Artiodactyla is monophyletic has been challenged by molecular analyses of variations in mitochondrial and nuclear DNA. We have characterized two families of short interspersed elements (SINEs) that were present exclusively in the genomes of whales, ruminants and hippopotamuses, but not in those of camels and pigs. We made an extensive survey of retropositional events that might have occurred during the divergence of whales and even-toed ungulates. We have characterized nine retropositional events of a SINE unit, each of which provides phylogenetic resolution of the relationships among whales, ruminants, hippopotamuses and pigs. Our data provide evidence that whales, ruminants and hippopotamuses form a monophyletic group.     

Individual identification of cadaver parts after a bomb explosion using oligonucleotide fingerprinting by (GTG)5

A blind shell suddenly and unexpectedly exploded, and 20 dismembered human remains were discovered. DNA fingerprint was performed to determine whether the 20 human remains were derived from one person or not. DNA was isolated from each of the remains and digested by the restriction enzyme Hinf I and Hae III and hybridized with the oligonucleotide probe (GTG)5. DNA fingerprint using Hinf I demonstrated the same band pattern in 17 out of the 20 remains. However, in the remaining 3 samples, two novel strange bands were observed. DNA fingerprint using Hae III showed completely identical pattern in all of the remains.