DNA PHOTOREACTIVATING ENZYME FROM SILKWORM

An ammonium-sulfate-precipitable (33–70%) fraction in extracts from eggs of silkworm Bombyx mori contains photoreactivating enzyme that reactivates the transforming activity of UV inactivated Hemophilus influenzae DNA. The action spectrum for in vitro photoreactivation with the enzyme has a broad peak around 365–385 nm, with a shoulder extending to 460 nm. This relatively higher photoreactivation efficiency at wavelengths longer than 450 nm seems to be a unique feature of DNA photoreactivating enzyme of silkworm. Using gel filtration, a mol wt of 42,000 was estimated for the enzyme. Optimum and isoionic pH of the enzyme were 7.2 and 5.4, respectively. These properties of silkworm enzyme are within the range of variations in reported biochemical characteristics of photoreactivating enzymes from different species.     

ACTION SPECTRUM FOR PHOTOREACTIVATION OF ULTRAVIOLET-INDUCED MORPHOLOGICAL ABNORMALITY IN SEA URCHIN EGGS

Abstract An action spectrum was obtained for photoreactivation (PR) of morphological abnormality arising from ultraviolet (UV)-irradiation of sea urchin sperm. The wavelength dependence of PR was measured by the restoration of the formation of normal pluteus larvae after the exposure of fertilized eggs to various fluences of monochromatic PR light (313 to 500 nm). The PR action spectrum showed a maximum around 365 nm and a secondary peak somewhere above 400 nm. High PR activity beyond 400 nm wavelengths may reflect an advantageous or adaptational ability to cope with harmful effects of solar UV radiation.     

Photoreactivating Enzyme for (6–4) Photoproducts in Cultured Goldfish Cells

We previously reported that when cultured goldfish cells are illuminated with fluorescent light, photorepair ability for both cyclobutane pyrimidine dimers and (6–4) photoproducts increased. In the present study, it was found that the duration of the induced photorepair ability for cyclobutane pyrimidine dimers was longer than that for (6–4) photoproducts, suggesting the presence of different photolyases for repair of these two major forms of DNA damage. A gel shift assay was then performed to show the presence of protein(s) binding to (6–4) photoproducts and its dissociation from (6–4) photoproducts under fluorescent light illumination. In addition, at 8 h after fluorescent light illumination of the cell, the binding of pro-tein(s) to (6–4) photoproducts increased. The restriction enzymes that have recognition sites containing TT or TC sequences failed to digest the UV-irradiated DNA pho-toreactivated by using Escherichia coli photolyase for cyclobutane pyrimidine dimers, indicating that restriction enzymes could not function because (6–4) photoproducts remained in recognition sites. But, when UV-irradiated DNA depleted of cyclobutane pyrimidine dimers was incubated with extract of cultured goldfish cells under fluorescent light illumination, it was digested with those restriction enzymes. These results suggested the presence of (6–4) photolyase in cultured goldfish cells as in Dro-sophila, Xenopus and Crotalus.     

PHOTOREACTIVATION OF ULTRAVIOLET LIGHT-INDUCED DAMAGE IN CULTURED FISH CELLS AS REVEALED BY INCREASED COLONY FORMING ABILITY AND DECREASED CONTENT OF PYRIMIDINE DIMERS

Abstract— Cultured cells derived from a goldfish were irradiated with 254nm ultraviolet light. Cell survival and splitting of pyrimidine dimers after photoreactivation treatment with white fluorescent lamps were examined by colony forming ability and by a direct dimer assay, respectively. When UV-irradiated (5 J/m²) cells were illuminated by photoreactivating light, cell survival was enhanced up to a factor of 9 (40min) followed by a decline after prolonged exposures. Exposure of UV-irradiated (15 J/m²) cells to radiation from white fluorescent lamps reduced the amounts of thymine-containing dimers in a photoreactivating fluence dependent manner, up to about 60% reduction at 120 min exposure. Keeping UV-irradiated cells in the dark for up to 120min did not affect either cell survival or the amount of pyrimidine dimers in DNA, indicating that there were not detectable levels of a dark-repair system in the cells under our conditions. Correlation between photoreactivation of colony forming ability and photoreactivation of the pyrimidine dimers was demonstrated, at least at relatively low fluences of photoreactivating light.     

Characteristics of the Na/beta-alumina/Na cell as a sodium vapor pressure sensor

The EMF and voltage-current characteristics for a galvanic cell with the configuration Na vapor (P₁)/sodium beta-alumina/Na vapor (P₂) were studied. It was verified that the EMF followed the Nernst relation over a wide pressure range. For example, when P₁ = 2 × 10^-2 mm Hg and beta-alumina temperature = 340°C, the measured EMF agreed with the calculated value in P₂ range from 10^-5 to 10^-2 mm Hg. At lower pressure range, the measured EMF showed a negative deviation. Coexisting argon gas did not influence the cell EMF characteristic. In an atmosphere containing oxygen, the measured EMF was very high at first. Then it decreased and finally approached a value which agreed with the Nernst equation after several hours. At low beta-alumina temperatures, current saturation was observed in the voltage versus current relation with the anode on the P₂ side. Although the sodium pressure could be determined from saturating current measurement, the measurable pressure range was narrower than that for EMF measurement. At high beta-alumina temperature, current saturation was not clear. Values of 6 × 10^-6 (Ω cm)^-1 for the electron conductivity and 6 × 10^-10 (Ω cm)^-1 for the hole conductivity at 340° were obtained for beta-alumina from the voltage-current characteristics at low sodium pressure.     

Reactions of quinolinium and pyridinium N-imines with cyclopentadienone derivatives

The novel reactions of quinolinium and pyridinium N-imines with cyclopentadienones are described.     

REPAIR OF THYMINE DIMERS AND (6–4) PHOTOPRODUCTS IN GROUP A XERODERMA PIGMENTOSUM CELL LINES HARBORING A TRANSFERRED NORMAL CHROMOSOME 9

Transfer of a normal chromosome 9 into a xeroderma pigmentosum (XP)-A cell line partially restored its DNA repair activity. XP-A cell lines harboring a transferred chromosome were much more UV-resistant than parental XP-A cells but still more UV-sensitive than normal cells. The amount of UV-induced unscheduled DNA synthesis was only one-third of that in normal cells. The repair of thymine dimers and (6-4) photoproducts in these cell lines was analyzed by using monoclonal antibodies raised against them. Although these XP-A cell lines carrying a normal chromosome 9 could repair (6-4) photoproduct with a little lower efficiency than normal cells, the repair of thymine dimers was completely absent in these cells. The present results suggest a gene-dosage effect in DNA excision repair mechanisms in human cells or a rather complicated mechanism which involves two or more pathways.     

Suppression Of Ages Formation In Spontaneous Diabetic OLETF Rat By Organic Germanium Compound [Poly-trans-(2-carboxyethyl) Germasesquioxane] (Ge-132)

The model rat for the type 2 diabetes mellitus (NIDDM) in human were observed for 72 weeks after birth, administering an organic germanium compound [Bis(2-Carboxyethyl) germasesquioxane, Ge-132] perorally 100 mg/kg/day since 24 weeks old. Clinical examinations were followed throughout the observation period. Blood and urinary glucose in positive control OLETF rats tended to be higher than those treated with Ge-132. At the end of the 72nd week, animals were sacriificed to examine the pathological changes, specifically in pancreas, kidney and brain. Anti-AGE antibody stained proximal and distal tubles and basement membrane of glomerules in kidney, and accumulated AGE masses in cortex, hippocampus and cerebellum of OLETF rat's brain. Amyloid stains by basic congo red on kidney and brain revealed that the deposits of amyloid in kidney mesangium and in cortex, hippocampus and cerebellum were observable in OLETF rats. Ge-132 suppressed the deposition of amyloid tangles in kidneys and brains. Anti rat complement C'3 antibody reacted with AGE and amyloid tangles that were sensitive to anti-AGE antibody. AGE generated in vitro by incubating human serum, human gammaglobulin (HGG), or bovine serum albumin (BSA) with glucose activated complements, showing the consumption of complements in the hemolysis of hemolysin-coated sheep red blood cells. A novel device Quantum Resonance Spectrometer (QRS) could read the subtle bio-magnetism memorized in serum samples, demonstrating quantitative values reflecting the patho-physiology of OLETF rats.