OXYGEN-DEPENDENT PHOTOSENSITIVITY and MITOTIC RECOMBINATION IN THE SMUT FUNGUS Ustilago violacea

Abstract— The effect of high intensity incandescent radiation on survival and mitotic recombination in the phlph + diploid strain of Ustilago violacea was studied with and without atmospheric O₂. In the presence of atmospheric O₂, strain phlph+ was characterized by photokilling to approximately 50% survival, and induction of mitotic recombination to about 60% by 90 min of light exposure. No photokilling and little induction of mitotic recombination were observed when light exposure was carried out in an 0₂ depleted environment. Photokilling and photo-induced mitotic recombination in U. violacea may be due to DNA damage or repair in response to a photosensitized reaction, involving an endogeneous photosensitizer.     

FORMATION BY HYDROGEN PEROXIDE OR 254 nm RADIATION OF A NEAR-UV CHROMOPHORE FROM PEPTIDE-BOUND CYSTEINE

Abstract Treatment of glutathione or N-acetylcysteinamide in water with hydrogen peroxide, or with 254 nm radiation together with molecular oxygen, results in the formation of a near-UV chromophore having maximal absorption at 305 nm. From examination of related compounds, it is apparent that the N-acylcysteinamide residue is the key element required for generation of the 305 nm chromophore. The structure of this near-UV chromophore is stable to base but unstable in aqueous acid, is relatively sensitive to oxidation by hydrogen peroxide but is only very slowly reduced by sodium borohydride and displays good thermal stability at 50°C.     

MITOTIC ACCELERATION INDUCED IN GRASSHOPPER NEUROBLASTS BY SMALL DOSES OF MONOCHROMATIC ULTRAVIOLET RADIATION

Abstract —Neuroblasts of the grasshopper, Chortophaga viridifasciata (DeGeer), in culture were exposed to 4–15 J/m² of monochromatic ultraviolet radiation in middle prophase and timed to prometaphase (breakdown of the nuclear membrane). At wavelengths 265 and 280 nm the times recorded for the treated cells were significantly less than those for the matched control cells. Wavelength 225 nm produced neither significant acceleration nor deceleration of mitotic rate.
Evidence from the present experiment does not implicate any particular chromophore in this response, though similar results of a previous microbeam study of neuroblasts point to the nucleic acid or protein of the nucleolus as the possible effective material.     

PHOTOSENSITIZATION BY ANTITUMORAGENTS–6. PRODUCTION OF SUPEROXIDE RADICAL AND HYDROGEN PEROXIDE DURING ILLUMINATION OF DIAMINOANTHRACENEDIONES IN THE PRESENCE OF NADH IN AQUEOUS SOLUTIONS: AN EPR STUDY

Abstract— Photosensitizing capabilities of anthracenedione anticancer agents to oxidize NADH in aqueous solutions have been studied by EPR and spin trapping techniques. It is demonstrated that 1,4-diamino substituted anthraquinones, like mitoxantrone and ametantrone, do not photosensitize NADH oxidation while 1,5- and l,8-bis[[(diethylamino)ethyl]amino]anthraquinones do, undergoing simultaneous one-electron reduction to their semiquinone radical forms upon illumination with visible light. In aerated aqueous solutions the reaction leads to the production of superoxide ion and hydrogen peroxide.     

PHOTOGENERATION OF SUPEROXIDE ION and HYDROGEN PEROXIDE FROM TRYPTOPHAN and ITS PHOTOOXIDATION PRODUCTS: THE ROLE OF 3a-HYDROPEROXYPYRROLIDINOINDOLE*

Abstract— Mechanism of the photogeneration of hydrogen peroxide and superoxide ion from tryptophan (Trp) and its photooxidation products was investigated. Near-ultraviolet irradiation of 3a-hydro-peroxypyrrolidinoindole, an intermediate in the photooxidation of Trp, has been shown to generate hydrogen peroxide efficiently under aerobic conditions. Irradiation of N-formylkynurenine in the presence of 3α-hydroxypyrrolidinoindole also produced hydrogen peroxide. The formation of superoxide ion in both reactions has been confirmed, whereas the reaction of Trp with chemically generated singlet oxygen did not produce any detectable amount of superoxide ion.     

HYDROGEN ABSTRACTION FROM LIPIDS BY TRIPLET STATES OF DERIVATIZED BENZOPHENONE PHOTOSENSITIZERS

Laser photolysis techniques have been used to characterize the reactivity of triplet state lipoidal benzophenone derivatives toward fatty acids and glycerides in benzene solution. The reactivities of benzophenone-4-heptyl-4'-pentanoic acid (BHPA) toward fatty acid compounds having different configurations of olefinic bonds have been determined. The rates of hydrogen abstraction are found to be lower when compared with similar measurements using benzophenone alone. However, the contribution of physical quenching of the triplet derivative by double bonds also appears to be slightly lower than that found with benzophenone itself. The hydrogen abstraction efficiencies of three other benzophenone derivatives toward linoleic acid in benzene have also been measured. For benzophenone incorporated into a fatty acid molecule, there is a limited relationship between structure and photoreactivity. Finally, these sensitizers have been incorporated into mixed SDS/linoleate micelles to determine the effects of molecular organization on photochemical behavior of the sensitizer and lipid.     

POTENTIOMETRIC and LASER FLASH PHOTOLYSIS STUDIES OF THE pH DEPENDENCE OF HYDROGEN PEROXIDE PRODUCTION BY THE SEMICARBAZIDE/LUMIFLAVIN/OXYGEN PHOTOSYSTEM

The effect of pH on hydrogen peroxide photoproduction by the semicarbazide/lumiflavin/ oxygen system has been investigated by using the potentiometric and laser flash photolysis techniques. Kinetic analysis of (a) primary and secondary reactions involved in the photoreduction of lumiflavin and (b) lumiflavin reoxidation by oxygen have been carried out at varying pH values, drastic differences being observed in the pH dependence of both types of reactions. The reaction mechanism appears to proceed by semicarbazide-quenching (reductive type) of the light-excited lumiflavin in its triplet state followed, depending on pH, either by reoxidation of the so formed flavosemiquinone by molecular oxygen or by flavosemiquinone disproportionation into oxidized and fully reduced lumiflavin.     

THE EFFECTS OF PLASMA LIPOPROTEINS ON in vitro TUMOR CELL KILLING and in vivo TUMOR PHOTOSENSITIZATION WITH BENZOPORPHYRIN DERIVATIVE

The influence of lipoprotein association on in vitro tumor cell killing and in vivo tumor photosensitization with benzoporphyrin derivative (BPD) has been investigated in M-1 tumor bearing mice. The association of benzoporphyrin mono acid ring A with either low or high density lipoprotein increased tumor cell killing in an in vivo/in vitro cytotoxicity assay performed 3 h post intravenous drug administration. Eight hours following photosensitizer injection only low density lipoprotein (LDL) mixtures produced significant (P less than or equal to 0.005) increases in tumor cell killing compared to BPD in unfractionated plasma. The efficacy of in vivo photosensitization in the presence of lipoproteins correlated with the in vivo/in vitro cytotoxicity. Association of BPD with low or high density lipoproteins resulted in delayed tumor regrowth and higher cure rates when light exposure (125J/cm2) was performed 3 h post drug administration. When light exposure was performed 8 h post-injection only LDL-BPD mixtures led to enhanced tumor eradication compared to BPD administered in aqueous solution or unfractionated plasma.     

ENHANCEMENT OF INTRAMOLECULAR EXCIMER FORMATION OF 1,3-BICHROMOPHORIC PROPANES VIA APPLICATION OF HIGH PRESSURE and VIA COMPLEXATION WITH CYCLODEXTRINS. PROTECTION FROM OXYGEN QUENCHING

Abstract— The emission of several 1,3-bichromophoric(BC) systems has been investigated in aqueous solutions containing various cyclodextrins (CD's). In all cases where molecular models reveal that the correspondence of the size and shape of the eclipsed conformation of the BC system and the cavity CD is high, a stable CD (host)-BC (guest) complex is formed and in these cases, the ratio of excimer to monomer emission intensity UE/IM) is much larger than that found in homogeneous solution. The effect of application of high pressure on the I_E/I_M ratio was investigated, as was the influence of 0₂ quenching of excimer and monomer in homogeneous solutions, in aqueous micellar solutions, and in aqueous solutions of CD complexes. A strong protection from 0₂ quenching is observed in the latter case.     

PHOTOPRODUCTION OF IONS FROM CHLOROPHYLL α IN SOLUTION STUDIED BY FLASH PHOTOLYSIS and PHOTOCONDUCTIVITY

Abstract— Ionic species were detected electrically on flash excitation of chlorophyll α following rapid production of the triplet state of the pigment. The action spectrum of photocurrent agreed well with the absorption bands of the pigment in the visible region; the threshold for the formation of ionic species in acetonitrile was 1.8 eV. Oxygen gas introduced into the solution completely prevented the appearance of the triplet and ionic species. The latter are suggested to result from electron-transfer between the triplet pigments. Decay processes of the ionic species varied markedly with changes in the solvent polarity. Direct photo-ionization of the pigment could be observed by UV excitation in some non-polar solvents.     

PROTECTION AGAINST ULTRAVIOLET-B RADIATION-INDUCED LOCAL and SYSTEMIC SUPPRESSION OF CONTACT HYPERSENSITIVITY and EDEMA RESPONSES IN C3H/HeN MICE BY GREEN TEA POLYPHENOLS

Abstract— Exposure of skin to UV radiation can cause diverse biological effects, including induction of inflammation, alteration in cutaneous immune cells and impairment of contact hypersensitivity (CHS) responses. Our laboratory has demonstrated that oral feeding as well as topical application of a poly-phenolic fraction isolated from green tea (GTP) affords protection against the carcinogenic effects of UVB (280–320 nm) radiation. In this study, we investigated whether GTP could protect against UVB-induced immunosuppression and cutaneous inflammatory responses in C3H mice. Immunosuppression was assessed by contact sensitization with 2,4-dinitrofluorobenzene applied to UVB-irradiated skin (local suppression) or to a distant site (systemic suppression), while double skin-fold swelling was used as the measure of UVB-induced inflammation. Topical application of GTP (1–6 mg/animal), 30 min prior to or 30 min after exposure to a single dose of UVB (2 kj/m²) resulted in significant protection against local (25–90%) and systemic suppression (23–95%) of CHS and inflammation in mouse dorsal skin (70–80%). These protective effects were dependent on the dose of GTP employed; increasing the dose (1–6 mg/animal) resulted in an increased protective effect (25–93%). The protective effects were also dependent on the dose of UVB (2–32 kJ/m²). Among the four major epicatechin derivatives present in GTP, (‐)-epigallocatechin-3-gallate, the major constituent in GTP, was found to be the most effective in affording protection against UVB-caused CHS and inflammatory responses. Our study suggests that green tea, specifically polyphenols present therein, may be useful against inflammatory dermatoses and immunosuppression caused by solar radiation.     

PHOTOSENSITIZED DAMAGE TO SUPERCOILED PLASMID DNA INDUCED BY 334-nm RADIATION IN THE PRESENCE OF 2-THIOURACIL CONSISTS OF ALKALI- and PIPERIDINE-LABILE SITES AS WELL AS FRANK STRAND BREAKS

A covalently closed, supercoiled plasmid was irradiated with 334-nm ultraviolet radiation in the presence of the naturally occurring photosensitizer 2-thiouracil (s2Ura). After irradiation, some DNA samples were treated to reveal labile sites. Agarose gel electrophoresis was then used to resolve the unrelaxed supercoils from the relaxed forms, and the DNA bands were quantitated by fluorescence scanning. Irradiation of the plasmid in the absence of s2Ura induced small numbers of frank DNA strand breaks (FSB), alkali-labile sites (ALS), and piperidine-labile sites (PLS). The induction of each of these lesions was enhanced 30 times when s2Ura was present during aerobic irradiation. Anoxia, as well as the hydroxyl radical scavengers acetate and formate, inhibited the formation of all three lesion types. The relative proportions of the three lesion types produced by several DNA damaging treatments were measured. Hydrogen peroxide, gamma-irradiation, and s2Ura photosensitization produced nearly identical damage proportions, with PLS: FSB ratios of 1.25:1, 0.78:1, and 0.84:1, respectively. Treatment with singlet oxygen [data from Blazek et al. (1989) Photochem. Photobiol. 48, 607-613] produced much different proportions, with a PLS:FSB ratio of 4.1:1. These results may indicate a role for hydroxyl radical in s2Ura-photosensitized DNA damage.     

云南褐煤蜡氧化精制的研究

本工作对云南潦浒、寻甸、昭通蒙旦蜡进行了脱树脂,氧化精制研究,探索国产蒙旦蜡能否经精制后满足合成改性浅色蜡的要求。实验结果表明,潦浒、寻甸两厂生产的蒙旦蜡经氧化精制不能达到完全脱色,而昭通蒙旦蜡在相同的精制条件下极易脱色,所得浅色蜡质量达到和超过国外同类产品的水平,因此昭通蒙旦蜡是生产浅色蜡的理想原料。在精制反应中,加入适量ＹＰＳＯ－１添加剂,对改善反应条件,产物的分离,提高得率和质量均有良好的影响。文中还讨论了潦浒、寻甸脱脂蜡经氧化精制不能完全脱色的原因