摘要:

Abstract—Aromatic cationic dyes have a potential as photo‐chemotherapeutic agents because they are selectively concentrated into the mitochondria of cancerous cells. The mechanism of cytophototoxicity has been proposed to be primarily due to dye sensitized photogeneration of highly toxic singlet oxygen (1O2) at the mitochondria. We tested this hypothesis by measuring the relative phototoxicity of a collection of aromatic cationic dyes towards respiring rat‐liver mitochondria (RLM), upon addition of 514 nm laser light. Effectiveness of dye photosensitization towards destruction of RLM function was assayed by its effect on the RLM membrane potential. Three physical parameters of dye phototoxicity were independently measured and a relative phototoxicity calculated assuming adherence of mechanism to the1O2hypothesis. Quantum yields of dye sensitized1O2production were estimated, either from time‐resolved luminescence measurements of photosensitized1O2formed, or by comparing rates of photobleaching of1O2trap; the relative partition of dye into mitochondrial lipid was determined gravimetrically; and the optical density of dye was determined in a lipid like Triton X‐100 micellar environment. Under the assumption of the1O2hypothesis, these parameters were used to predict a relative phototoxicity which was compared with that observed. For 12 of the 14 dyes investigated, the observed and predicted phototoxicities were linearly correlated (r=0.85) suggesting support of the1O2hypothesis. Carbocyanines DiOC2(3) and DiSC2(3) did not correlate and were found to be 10 and 1000 times more potent than predicted, suggesting an additional factor at play in their phot

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04212.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—Photosensitization ofEscherichia coliandPseudomonas aeruginosacells by deuteroporphyrin (DP) is shown to be possible in the presence of the polycationic agent polymyxin nonapeptide (PMNP). Previous studies established complete resistance of Gram‐negative bacteria to the photodynamic effects of porphyrins. The present results show that combined treatment ofE. coliorP. aeruginosacultures with DP and PMNP inhibit cell growth and viability. No antibacterial activity of PMNP alone could be demonstrated and cell viability remained unchanged. Spectroscopically, PMNP was found to bind DP, a mechanism which probably assists its penetration into the cell's membranes. Insertion of DP into the cells was monitored by the characteristic fluorescence band of bound DP at 622 nm. Binding times were 5–40 min and the extent of binding increased with decreasing the pH from 8.5 to 6.5. DP binding constants, as well as the concentrations of PMNP which were required for maximal effect on the various Gram‐negative bacteria, were determined fluorometrically. By the treatment of DP, PMNP and light the growth ofE. coliandP. aeruginosacultures was stopped and the viability of the culture was dramatically reduced. Within 60 min of treatment the survival fraction ofE. coliculture was 9 × 10–6that ofP. aeruginosawas 5.2 × 10–4. Electron microscopy depicted ultrastructural alterations in the Gram‐negative cells treated by DP and PMNP. The completion of cell division was inhibited and the chromosomal domain was a

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04213.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—The enhancement of photorepair of UV‐induced pyrimidine dimers by preillumination with fluorescent light, previously reported with RBCF‐1 cells derived from caudal fin of a goldfish, was studied in terms of clonogenic ability and yields of dimers. In the logarithmic growth phase, the ability of photorepair increased with the time after preillumination, reached a maximum at 8 h, and gradually declined. At 8 h, the dose decrement with the photorepair‐treatment for 20 min at 7.5 J/m2UV increased by preillumination for 1 h from 1.6 to 3.1 J/m2in terms of restoration of survival and from 1.2 to 4.3 J/m2in terms of the disappearance of dimers. Incubation of the preilluminated cells in the medium containing cyclohexirnide (0.5 μg/mL) after preillumination until UV‐irradiation diminished their enhancement of photorepair. In the density‐inhibited state, the ability of photorepair was higher than in the log phase, and it was hardly enhanced by pre

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04214.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—Survival of wild‐type and four radiation‐sensitive (rad) mutants of the nematodeCaenorhubditis elegunswas determined after near‐UV irradiation in the presence of 8‐methoxypsoralen (8‐MOP). Three sets of inactivation profiles were generated for each strain by irradiating synchronous populations of either early embryos, late embryos or first‐stage larvae (L1s). Late embryos were consistently the most sensitive. Curiously, none of the fourradmutants were even moderately hypersensitive. Split‐dose experiments indicated that DNA‐DNA crosslinks were primarily responsible for lethality. Crosslink induction and repair were determined using two different assays. In both cases, little if any repair was observed in wild‐type. This lack of repair thus explains why theradmutants were not hypersensitive to 8‐MOP photoinactivation. Since early embryos undergo extensive cell cycling, their resistance to 8‐MOP photoinactivation suggests that replication is highly refractory to both monoadducts and crosslinks, as has been demonstrated previously for UV radiation‐induced photoproducts (Hartmanet al., 1991,Muta

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04215.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—The binding of hematoporphyarin derivative (HpD) to brain tumor cells and their photo‐sensitivity was studied as a function of HpD concentration, time of incubation and growth phase of cells. Upon binding to cells, HpD showed three fluorescence bands at 616, 636 and 678 nm. In plateau phase cells a fluorescence band at 636 nm was predominant, which was further enhanced by increasing HpD concentration and/or increasing incubation time. In exponential phase cells the maximum fluorescence was exhibited at 616 nm. After 1 h incubation of exponential phase cells with increasing HpD concentration an overall intensity enhancement occurred with no change in the distribution of bands, whereas longer incubation time caused an increase in relative intensity of the 636 nm band similar to that observed in plateau phase cells. After 1 h incubation with HpD plateau phase cells were more photosensitive than exponential phase cells, although cell bound HpD was much less in the former case. Incubation of cells for 24 h drastically enhanced the photosensitivity irrespective of the growth phase. Our results suggest a relationship between the fluorescence emission band of HpD at 636 nm and photosensitivity of ce

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04216.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—Phycoerythrocyanin or fractions enriched in it have been isolated from the filamentous cyanobacteria,Westiellopsis prolificaARM 365 andNostoc rivulareARM 212. Both show the photoreversible photochromism (difference maxima at 503 and 570 nm) characteristic of this pigment, which is related to the phycoviolobilin chromophore on the α‐subunit. Native phycoerythrocyanin and its β‐subunit show little if any reversible photochemistry in the 600–620 nm region, where the phycocyanobilin chromophores absorb maximally. Instead the phycocyanobilin chromophores are bleached irreversibly. At the same time, the data show that reversible photochemistry is a useful analytical tool to detect phycoerythrocyanin in cyanobacterial extracts. Fluorescence measurements indicate that: (i) the 510 nm absorbing isomer of the violobilin chromophore has only little fluorescence; and (ii) the energy transfer from the violobilin chromophores to the cyanin chromophores is efficient only in the 57

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04217.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—We have previously used chlorophyll fluorescence measurements atFmaxconditions (i.e. with Photosystem II electron acceptor QAreduced) to monitor the action of 9,10‐anthraquinones on photosynthetic electron transport in plant chloroplasts. The present investigation employs two additional techniques to characterize the extent of electron transport inhibition induced by the addition of substituted anthraquinones to the suspending medium of spinach chloroplasts. Results are presented for spectrophotometric assays of the rate of electron transfer to an exogenous electron acceptor, 2.6‐dichloroindophenol (DCIP) and for electrochemical determinations of the rate of oxygen evolution in anthraquinone‐treated chloroplasts. In general, amino‐substituted anthraquinones are ineffective inhibitors, maintaining electron transfer rates to DCIP at levels ranging from 50 to 90% of normal rates and yielding rates of O2evolution averaging at 70% of the rate in untreated chloroplasts. In contrast, hydroxy‐substituted anthraquinones efficiently block Photosystem II electron transport, resulting in low rates of DCIP photoreduction ranging from 0 to 20% of normal values and reducing O2evolution rates to an average of 30% of the rate observed for untreated chloroplasts. Relative rates of DCIP photoreduction for anthraquinone‐treated chloroplasts show a strong linear correlation with the reported relativeFmaxchlorophyll fluorescence intensities. Relative O2evolution rates are observed to correlate with the Stern‐Volmer fluorescence quenching parameterKsv. We suggest that slight differences in the extent of inhibitory activity of an anthraquinone as measured by the three techniques are consistent with certain known Photosystem II heterogeneities. The similarities in relative rankings of inhibitory effects for the 9,10‐anthraquinones, however, demonstrate that the three techniques employed (measurements ofFmaxchlorophyll fluorescence, DCIP photoreduction rates, and O2evolution rates) are alternative assays of anthraquinone‐induced Photosystem II electron t

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04218.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—An improved synthesis of benzochlorins is reported. Demetallation of themeso‐hydroxymethylvinyl derivative of octaethylporphyrin, followed by treatment with sulfuric acid results in cyclization to generate the corresponding octaethylbenzochlorin in high yield. Prolonged treatment with acid generates the sulfonated derivative. These sensitizers were shown to be efficient photodynamic agentsin vivo.Animals bearing a transplantedN‐{4‐(5‐nitro‐2‐furyl)‐2‐thiazolyl}formamide induced urothelial tumor were treated with either the benzochlorin or its sulfonated derivative. Irradiation of tumors 24 h later resulted in a significant tumoricidal effect in a short term assay. We conclude that benzochlorins warrant further examination as potential agents for use in pho

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04219.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—Chemiluminescence (CL) caused by photosensitization of porphyrins in phosphate buffered saline (PBS) solution containing 3% human serum albumin (HSA) was observed for the first time. Irrespective of porphyrins concerned, CL shows a spectrum ranging from 380 to 520 nm with a peak near 450 nm and decays almost single‐exponentially with a lifetime of about 15 s. The intensity of CL depends on concentrations of porphyrins and HSA in PBS solution. We have examined a number of porphyrins and observed CL for the compounds with triplet lifetimes longer than 0.1 ms. The appearance and quenching of CL by photosensitization of porphyrin‐HSA systems indicate that type II reaction by singlet oxygen occurs significantly in photodynamic therapy resulting in hypoxic regions in environments surrounding the sensi

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04220.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—Comparison of spectroradiometric and meter measurements of a series of ultraviolet radiation sources indicates that a wide divergence between readings can occur. We found that with a xenon are filtered as a solar simulator producing UV‐A (320–400 nm) and UV‐B (290–320 nm) radiation, the meter can either over‐or underestimate the emission of the source when different cutoff filters are used. The most severe discrepancy appears with the UV‐B meter reading, although the UV‐A reading can also be problematic. Meters should be calibrated against the specific sources they will be

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb04221.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY