摘要:

Abstract—The excited state behavior of an anionic ruthenium(II) complex, RuL34‐(L=bathophen‐anthroline disulfonate), that is electrostatically bound to positively charged alumina‐coated silica particles is investigated. The apparent association constant for the binding of RuL34‐to the particles is 1.2 × 104M‐1. Surface photochemical processes result in decreased emission yields and multiexponential excited state decay. Excited state quenching by ground‐state molecules is evident at high surface coverages. The non‐exponential decay kinetics observed at low surface coverages can be attributed either to clustering of the RuL34‐molecules or photoionization promoted by Lewis acid sites on th

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04223.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—It has been demonstrated that UVB radiation (290–320 nm) suppresses mammalian cell‐mediated immunity by effecting thetranstocisisomerization of urocanic acid (UCA) in the stratum corneum, the uppermost layer of the skin.Trans‐urocanic acid has been shown to be the photoreceptor for UVB‐induced immune suppression and thecis‐isomer has been demonstrated to be immunosuppressive. Little is known, however, about how the isomerization of UCA may affect the proximal or distal cells of the skin or the immune system. We report here thattrans‐UCA is biologically activein vitroin human dermal fibroblasts, inducing adenyl cyclase as measured by cAMP (adenosine 3', 5'‐cyclic monophosphate) formation in a dose‐dependent manner similar to the action of histamine.Trans‐UCA and histamine stimulate 50% of maximum activity at concentrations of 3.3 μMend 13.8 μMrespectively.Cis‐UCA does not increase cAMP in these human fibroblasts but actively down regulates the increase of cAMP induced by either histamine ortrans‐UCA.Cis‐UCA down regulated the histamine response by 75% and thetrans‐UCA response by 60% at a concentration range of 1 mMto 1 nM.Thetrans‐UCA induction of cAMP can also be downregulated with an H2 histamine receptor antagonist cimetidine. These results support the hypothesis that a cellular target forcis‐UCA is the dermal fibroblast and the effects reported here may represent the initial biochemical and cellular event for UVB‐induced immune suppressioni.e.the immediate step following the isomerizationof transtocis‐UCA is the down regulation of cAMP bycis‐UCA. Regulation of such an important second messenger such as cAMP could then allow cascading signals

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04224.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—Single‐ and double‐stranded calf thymus DNA and two polynucleotides (0.4 mM) were studied in aqueous solution at pH ≅ 7 using pulsed, 20 ns laser excitation at 193 nm. Monophotonic ionization of the nucleic acids is suggested from the linear dependences of the concentration of ejected electrons and the number of single‐ and double‐strand breaks (ssb, dsb, respectively) on laser intensity (IL) in the range (0.2–3) × 106W cm‐2. The quantum yields of formation of hydrated electrons (φe‐) and ssb and dsb (φSSband φdsb) are therefore independent ofIL. In contrast, under 248 nm excitation these quantum yields increase linearly withILunder otherwise comparable conditions. Nevertheless, several effects and mechanistic implications are analogous using Λexc= 193 and 248 nm. For polycytidylic acid, poly(C), in Ar‐saturated solution for example, the efficiency of ssb per radical cation (ηRC=φssb/φe‐) is similar to the efficiency of ssb per OH radical (ηOH). For polyadenylic acid, poly(A), and single‐ and double‐stranded DNA ηRC(Λexc= 193 nm) is significantly smaller than ηOH. The ratio φssb(N2O)/φssb(Ar) is =2 for poly(C), =4 for poly(A) and =10 for DNA; the conversion of hydrated electrons into OH radicals in N2O‐saturated solution and smaller ηRCthan ηOHvalues in the case of DNA account for these results. For double‐stranded DNA φdsbdoes not depend onILbut increases linearly with the dose, indicating an accumulative effect of two ssb to generate one dsb. The critical distance for thi

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04225.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—The quantum yield, φZE, for configurational photoisomerization (4Z,15Z→ 4Z,15E) of bilirubin bound non‐covalently to human serum albumin was determined (at 23 ± 2°C) by laser excitation and chromatographic analysis of products. Values obtained for photoexcitation at 465 nm were about one‐half those previously reported. The quantum yield was dependent on excitation wavelength, decreasing from a value of 0.109 ± 0.010 for excitation at 457.9 nm to a value of 0.054 ± 0.005 for excitation at 514.5 nm. The wavelength dependence is consistent with rapid transfer of excitation energy between the two non‐identical pyrromethenone chromophores of bilirubin in the singlet excited state. Since the quantum yields for photoisomerization and luminescence of bilirubin bound to serum albumin at room temperature are both low, internal conversion processes, rather thanZ→Econfigurational isomerizations, are probably the major pathways for deactivation of photo

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04226.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—When whole retinal pigmented epithelium (RPE) cells isolated from bovine eyes are incubated with14C‐labeled ascorbic acid and exposed to a visible laser, the ascorbic acid is oxidized to dehydro‐L‐ascorbic acid (DHA). The amount of ascorbic acid which is oxidized is proportional to the radiant exposure of the sample (i. e.the total amount of radiation per unit area delivered over the exposure time). Blue light is more effective than red light in driving the reaction. The amount of label appearing in the DHA fraction is increased if unlabeled DHA is present in the reaction mixture, indicating that some redox cycling of ascorbate is occurring in the RPE cells. The ascorbic acid oxidizing activity does not depend on intact cells, is not inactivated by heating the cells to 80°C, and appears to reside mainly in the subcellular fraction which contains melanin pigment granules. The ascorbic acid oxidation may be caused by free radicals formed when melanin is illuminated with light. This reaction appears to be a useful method for quantifying the production of free radicals during photooxidativ

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04227.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—The relative abilities of UV‐A, B and C radiations to initiate lipid peroxidation and apolipoprotein (apo) B modification of human purified low density lipoproteins have been compared. Ultraviolet‐B and C (at 310 and 254 nm, respectively) exhibited similar efficacy as shown by the increase in lipid peroxidation markers (conjugated dienes, thiobarbituric acid reactive substances and fluorescent lipid soluble products) and in oxysterols, as well as by the decrease of the contents of natural antioxidants (tocopherols and carotenes) and in polyunsaturated fatty acids. In contrast, UV‐A (at 360 nm) was found poorly effective and only at very high radiation intensities. Under all the conditions used, apoB was not affected by the UV radiations as shown by the stability of amino acid composition (except tryptophan level) and of trinitrobenzenesulfonic acid reactive amino group content. Similarly, the low density lipoprotein size was not altered. By comparison, low density lipoproteins oxidized by transition metal presented strong alterations of apoB and major changes of the apparent low density lipoprotein size.Finally, low density lipoproteins irradiated by UV‐B or C exhibited a much higher cytotoxicity on cultured cells than those irradiated by UV‐A. Under the conditions used in this paper, the cytotoxic effect of the irradiated low density lipoproteins was positively correlated with their content in lipid peroxidation products and inversely correlated with their tocophe

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04228.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—Pheophorbidea‐induced photo‐oxidation,in vitro, of cytochrome c oxidase and cytochromecresults in irreversible modifications to both protein components. Photo‐oxidation of cytochromec, as exhibited by change in its heme oxidation state, displays exponential kinetics and is detected with a lag period. Both the photo‐induced inactivation of the enzyme, and destruction of the substrate ability of cytochromecoccur as complex multi‐process events. Under similar experimental conditions, the loss of the substrate capability of cytochrome c develops approximately three times faster than inactivation of the enzyme. The slight lag in the photo‐oxidation of cytochrome c is due to pheophorbidea‐induced superoxide production. However, the relative amount of photo‐oxidant produced is considerably more effective than the cytochrome c reducing capacity of the superoxide. Neither hydroxyl radical nor hydrogen peroxide are involved in the photo‐oxidation of the heme function. The possibilities of heme oxidation by a singlet oxygen mediated pathway or direct electron abstraction involving the heme or apoprotein are not excluded. It is proposed that a multi‐site oxidation of numerous reduced energy cofactors within cells may augment collateral enzyme inactivation in maximizing photosensitizer‐induced cytotoxicity. Accordingly, amphipathic photosensitizers, capable of accessing both lipid and aqueous compartments containing reduced cofactors, may be more effective agents for photodynamic therapy than those which exhibit a high specificity of s

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04229.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—C3H/10T1/2 mouse fibroblasts were grown to different cell densities either by plating at low density and allowing different growth periods, or by plating at a series of increasing densities and allowing the same growth period. These plates were UV irradiated at 7.5 J/m2or mock irradiated and 24 h later infected with UV‐irradiatedHerpes simplextype I virus which had been UV irradiated at 50 or 125 J/m2or mock irradiated. The numbers and sizes of plaques were measured and these data used to calculate the extent of UV‐enhanced host cell reactivation, the capacity enhancement, the large plaque effect (LPE) and the small plaque effect (SME). The influence of cell density on these phenomena was similar for both series of density experiments. Ultraviolet‐enhanced host cell reactivation could be demonstrated only for cultures of lower density. The capacity of the cells forHerpes simplextype I virus decreased with cell density, but UV irradiated cells showed an increase in capacity with cell density. Plaque sizes decreased in all cases with cell density but the LPE and SPE were not significantly altered. The greatest variation in the above parameters occurred just as the cells were approaching confluence, where most host cell reactivation experiments are carried out. We conclude that the reproducibility of such experiments depends critically on cell density, a dependence which may be relevant to mechanistic interpretations of the UV‐dependent

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04230.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—The biological activity of some benzopsoralen derivatives, prepared with the aim of obtaining new drugs for photochemotherapy, has been studied. The more interesting compounds are 4‐hydroxy‐methyl‐4',5'‐benzopsoralen and 4‐hydroxymethyl‐4',5'‐tetrahydro‐benzopsoralen, which were found to be active in the dark also: DNA and RNA synthesis were both inhibited in Ehrlich cells, even if in a partially reversible fashion, while protein synthesis remained unaffected. In Chinese hamster ovary cells culturedin vitro, the clonal growth was strongly inhibited by incubation in the dark with both drugs, while a number of chromosomal aberrations was observed in the fraction of growing cells. Using alkaline elution, DNA strand breaks were detected. In addition, in the presence of aphidicolin, a specific inhibitor of DNA polymerase, the clonal growing capacity was completely restored; in contrast, the number of DNA strand breaks remained unchanged. All these results suggest that DNA topoisomerases are probably the target of these two benzopsoralens. These compounds are also good sensitizers; by UV‐A irradiation they have a good capacity to produce singlet oxygen, but they appeared to be unable to induce erythemas on guinea‐pig skin. Under UV‐A light, they induced a strong inhibition of DNA synthesis in Ehrlich cells. Thus, benzopsoralens appear to be capable of inducing strong antiproliferative effects by two different mechanisms, by UV‐A ir

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04231.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—When a dilute F‐solution was added to a culture of Chinese hamster cells that had been preincubated with an aluminium phthalocyanine sensitizer derived from AlPcCI, the photosensitivity of the cells was markedly reduced compared to control cells not treated with F‐. Under the same treatment conditions, the reduction in [3H]thymidine incorporation into cellular DNA caused by light and this sensitizer and the production of DNA‐protein crosslinks caused by light and this sensitizer were also inhibited by F‐. In contrast, the killing of Chinese hamster cells, the reduction of thymidine incorporation by the cells, and the production of DNA‐protein crosslinks in the cells caused by the combination of light and either Photofrin II or the silicon phthalocyanine HOSiPcOSi(CH3)2(CH2)3‐N(CH3)2were not inibited by F‐. We conclude that the aluminium phthalocyanine sensitizer used is largely or completely AlPc(OH)(H2O), that it is converted to a fluoro complex by F‐that this compound probably is a less efficient generator of photochemical damage at a critical cellular target(s) than is AlPc(OH)(H2O). The inhibition of thymidine incorporation and DNA‐protein crosslink formation indicates that the effects of F‐can be expressed at intracellular sites. It is further concluded that the silicon phthalocyanine sensitizer and Photofrin II do not interact

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04232.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY