共查询到20条相似文献,搜索用时 31 毫秒
1.
Marc Dellinger Fernanda Ricchelli Giuliana Moreno Christian Salet 《Photochemistry and photobiology》1994,60(4):368-372
Abstract After 24 h incubation with Photofrinm® (PF), photodynamic action has been studied on Ca2+ transport in CV-1 cells. A moderate increase of the cytosolic free Ca2+ concentration [Ca2+ ] is observed immediately after a dose of irradiation which yields a survival rate of less than 5% at 48 h. In parallel, studies on digitonin-permeabilized cells indicate that such a treatment inhibits endoplasmic reticulum Ca2+ uptake with few alterations of this process in mitochondria. In contrast, ADP-stimulated respiration is impeded and intracellular ATP level decreases. It is suggested that direct damage to endoplasmic reticulum as well as mitochondrial disturbance are the primary mechanisms responsible for a nontransient elevation of [Ca2+] i preceding cell death. 相似文献
2.
An electrophysiological study of photodynamic action on the Paramecium membrane was carried out. In the presence of methylene blue (MB), light-spot stimulation of an anterior and a posterior part induced a depolarization and a hyperpolarization of the membrane, respectively. Under voltage-clamping, the anterior stimulation induced an inward current, while the posterior stimulation induced an outward current. The amplitudes of these currents were dependent on the membrane potential. When K+ channels were blocked with Cs+ and tetraethylammonium (TEA+ ), the posterior outward current was inhibited, while the anterior inward current was not inhibited. Intracellular application of the Ca2+ chelator, 1,2 -bis (2-aminophenoxy) ethane- N,N,N',N' -tetraacetic acid (BAPTA) also inhibited the posterior outward current, but the anterior inward current was unaffected. These results suggest that photodynamic action on the Paramecium membrane primarily opens the Ca2+ channels and the following influx of Ca2+ activates the Ca2+ -dependent K+ channels localized mainly on the posterior part of the membrane. 相似文献
3.
Giuliano ColombettiFrancesco LenciPill-Soon Song† 《Photochemistry and photobiology》1982,36(5):609-611
Extracellular K+ ions above a critical concentration induce ciliary reversal in unstimulated Stentor coeruleus and suppress step-up photophobic response. This threshold concentration of K+ ions depends on the extracellular Ca2+ concentration, and the subsequent backward gyration and light-sensitivity suppression seem to depend on the relative concentrations of K+ and Ca2+ . The concentration of Ca2+ necessary to overcome K+ -mediated inhibition of phobic response and backward swimming increases non-linearly with increasing K+ concentration. The Ca2+ -blocking agent. D-600, selectively inhibits photophobic responses of Stentor , thus further confirming the role of Ca2+ ions in photosensory transduction of this ciliate. 相似文献
4.
E. Ben-Hur M. Green A. Prager R. Kol I. Rosenthal 《Photochemistry and photobiology》1987,46(5):651-656
Abstract— The concentrations of Na+ , K+ , Ca2+ , Mg2+ and CI− ions in the cytoplasm of octopus photoreceptor cells were determined before and after illumination by electron probe X-ray microanalysis. The concentrations of these elements in the dark-adapted photoreceptor cells were: Na+ , 68.4; K+ , 111.4; Ca2+ , 4.0; Mg2+ , 16.4; and CI− , 102.9 m M /kg of cytoplasm. Illumination raised the concentration of Na+ by 58 m M and that of Cl− by 23 m M and reduced the K+ concentration by 47 m M /kg of cytoplasm. A trace increase of intracellular Ca2+ and a trace decrease of Mg2+ were observed. These results confirm the hypothesis that sodium ions flow in on illumination, and suggest the influx of chloride ions and the outflux of potassium ions during illumination. The intracellular concentrations of Na+ , K+ and Cl+ can give the basis for calculating the ion permeability of ion channels in octopus photoreceptor cell membranes, using values of the membrane potentials obtained by electrophysiological studies 相似文献
5.
Abstract— Effects of extracellular Ca2+ concentration and papaverine on the PIII response of the electroretinogram and the dark adaptation process of the visual cells were studied in the isolated, aspartate-treated bullfrog retina. The amplitudes of both the fast and slow PIII responses are increased in 0.01 m M Ca2+ solution, but decreased in Ca2+ -free solution containing 1 m M EDTA. The application of 0.1 m M papaverine in the presence of 1 m M Ca2+ led to the enhancement of the slow PIII response at lower stimulus intensity and the prolongation of the slow PIII response, but these effects of papaverine on the response were lost when Ca2+ was removed from the bathing fluid. The half-time of recovery of the fast PIII response amplitude after switching off the adapting light was a linear function of the amount of bleached rhodopsin. Papaverine in the absence of Ca2+ produced about 2-fold increase in the half-time of recovery of the response. These findings suggest that chemical reactions which are sensitive to papaverine in the absence of Ca2+ are implicated in the dark adaptation process of the visual cells. 相似文献
6.
CALCIUM CONTROL OF PHOTOTACTIC ORIENTATION IN Chlamydomonas reinhardtii: SIGN AND STRENGTH OF RESPONSE 总被引:3,自引:0,他引:3
Abstract— Chlamydomonas reinhardtii responds to a blue light stimulus by an oriented swimming (phototaxis) toward or away from the stimulus source. In this study it is established that the sign and strength of the phototactic response are a complex function of extracellular [Ca2+ ], stimulus fluence rate, time of analysis after onset of stimulation and light pretreatment. At very low extracellular [Ca2+ ] the response is weak and usually negative. At [Ca2+ ] close to the preconditioning level, phototactic response becomes stronger and positive. As [Ca2+ ] is raised further, the initial (2 s) response remains positive but the long term (20 s) becomes negative and very strong. At extremely high [Ca2+ ] the cells become immobile. This bimodal behavior suggests that two different mechanisms determine the direction of the turn. Data cannot be explained in terms of a simple model. The model which accounts for most of the details of the behavior is that of Kamiya and Witman (1984), which proposes that positive response is triggered by a transient increase in intracellular [Ca2+ ] and negative response by a decrease below unstimulated level of Ca2+ , at least in the range of 10-9 -10-6 M [Ca2+ ]. The strong negative orientation which follows an initial positive response above this level of [Ca2+ ], in these experiments, is best explained by an adaptation of the cells due to an increased (on average) intracellular [Ca2+ ]. 相似文献
7.
Abstract— The photodynamic effects of methylene blue (MB) on wild-type and mutant strains of Paramecium Were studied. From measurements of survival and cell motility under the continuous application of light in the presence of MB, the mutant strains remained alive for about three times longer than the wild-type strain. Although the resting potential of the mutant cells was similar to that of wild-type cells, the continuous photodynamic action shifted the membrane potentials of the mutant and wild-type cells to a depolarized level and a hyperpolarized level, respectively, from that before light application. Under voltage clamping, the mutant cells reduced not only the outward current elicited by the photodynamic action but also the outward tail current elicited by the preceding pulse of hyperpolarization. We conclude that the mutant strain is defective in the activation of Ca2 +-dependent K+channels. This defect might cause a reduction in the Ca2 +influx because of the suppression of the membrane hyperpolarization, which results in the elongation of survival time under the photodynamic action. 相似文献
8.
Abstract— White light irradiation of a microsomal fraction from etiolated plants affects their ATP-dependent Ca2+ accumulation by inhibiting active uptake and enhancing passive efflux. The succinate-dependent mitochondrial Ca2 + accumulation as well is decreased by light. The wavelength dependence of these light effects as well as their low quantum yield suggest non-phototransformable protochloro-phyll(ide) [PChl(ide)] to be the photoreceptor. PChlide has been isolated from corn leaves pretreated with 5-amino levulinic acid. Addition of Pchlide causes photosensitization of an otherwise light insensitive microsomal Ca2+ accumulation. The observed light effect may be due to contamination of the mitochondrial as well as the microsomal fractions with PChl(ide)‡ containing particles. Irradiation of the intact tissue leads to the almost complete disappearance of the light effect on the in vitro Ca2 + accumulation. 相似文献
9.
J. R. Blinks 《Photochemistry and photobiology》1978,27(4):423-432
Abstract—Calcium-sensitive photoproteins are "precharged bioluminescent proteins that are triggered to emit light by binding Ca2+ or certain other inorganic ions. Neither molecular oxygen nor any organic cofactor is required. The first such protein to be described was aequorin, and for various reasons that has been the one most widely studied. Photoproteins have been used as Ca2+ -indicators both in vitro and in living cells. Their chief advantages for this are (1) ease of signal detection, (2) high sensitivity, (3) relative specificity for Ca2+ , and (4) lack of toxicity. Difficulties in the experimental use of the photoproteins stem from (1) their one-time reactivity, (2) their large molecular size, (3) their scarcity, (4) the influence of experimental conditions on the sensitivity to Ca2+ , (5) the nonlinearity of the relation between [Ca2+ ] and light intensity, and (6) the limited speed with which light intensity follows sudden changes in [Ca2+ ]. Photoproteins have now been used as intracellular calcium indicators in more than two dozen types of cells, and experience with the method is rapidly growing. They are also useful in the determination of calcium binding constants for other substances in vitro , and as models for studies of receptor-ligand interactions in general. 相似文献
10.
Eitan Gross Benjamin Ehrenberg Fred M. Johnson † 《Photochemistry and photobiology》1993,57(5):808-813
Abstract— Two new sensitizers are introduced for a potential use in photodynamic therapy: Zn2+ - and MG2+ -tetrabenzoporphyrin (ZnTBP and MgTBP). A comparative study of the quantum yields of singlet oxygen generation (ΦΔ ) of hematoporphyrin derivative (HpD), Photofrin II (PF-II), Zn2+ -phthalocyanine tetrahydroxyl [ZnPC(OH)4 ] and the newly introduced sensitizers ZnTBP and MgTBP in liposomes, as well as the kinetics of a photochemical reaction sensitized by them, was made by employing the fluorescent membrane probe 9,10-dimethylanthracene (DMA). We followed the photosensitization of DMA in real time by monitoring its fluorescence decrease at 457 nm and found that DMA's photosensitization is oxygen mediated. The kinetic traces of the photosensitization reactions were fitted to an analytical function, and the ΦΔ values were evaluated. At 10 μ M sensitizer in an aqueous suspension of 2 mg/mL egg phosphatidylcholine (EPC), HpD was found to have the largest value of ΦΔ (0.215), followed by PF-II (0.191), ZnTBP (0.023), MgTBP (0.019) and ZnPC(OH)4 (0.005). As a test of the method, ΦΔ for methylene blue in ethanol was measured and found to be 0.45 as compared to 0.52 reported in the literature. Due to difference in the sensitizers' absorbances at the laser's wavelength, the reaction photosensitized by ZnTBP was the fastest with a time constant of 6.7 min, followed by MgTBP (8.7), PF-II (11.9), HpD (17.1) and ZnPC(OH)4 (31.2), all at equal sensitizers' concentrations and laser intensities. The binding constants of the sensitizers to EPC liposomes are also reported. 相似文献
11.
SALT AND pH-DEPENDENT CHANGES OF THE PURPLE MEMBRANE ABSORPTION SPECTRUM 总被引:19,自引:0,他引:19
Yoshiaki Kimura Akira Ikegami Walther Stoeckenius† 《Photochemistry and photobiology》1984,40(5):641-646
Abstract —Purple membrane suspensions change their color to blue and the absorption maximum shifts to 608 nm when the membrane is deionized on a cation exchange column or when it is washed first with < 2N NaCl followed by deionized water. The deionized chromophore is essentially identical with the chromophore produced by lowering the pH of the native membrane to < 4.0 (p K < 3.0). However, the deionized membrane does not aggregate and can be obtained in the pure state. The original purple color of the membrane is restored by addition of around 1 m M Na+ , K+ or 10 μ M Mg2+ , Ca2+ , Sr2+ , Mn2+ , Pb2+ or La2+ when the protein concentration is 5μ M . The required salt concentrations decrease with decreasing pH. Direct measurement of bound Ca2+ by atomic absorption spectroscopy yields a ratio of Ca2+ to protein of <2 and a binding constant of 1.4 × 106 . Titration of the spectral change with salts at different pH values shows a linear relation between the pH and the logarithm of the salt concentration, with a 1:1 ratio for Na+ and 1:2 ratio for Ca2+ . These relations are well predicted by Gouy-Chapman theory; however, the accompanying release of protons, changes of the CD spectrum, the complex kinetics of the spectral change during reconstitution with salt and preliminary X-ray diffraction results all suggest that conformational changes may be occurring in the protein. 相似文献
12.
Abstract— Perimycin, ouabain and elevation of extracellular K+ concentrations cause an increase in the fluence rate thresholds (white light) for the step-up photophobic response in Peranema trichophorum . Elevation of extracellular Na+ concentration decreases the thresholds for this response in comparison to the control level. The fluence rate threshold of perimycin-treated cells increases before the side effect of an antibiotic action appears. Removal of K+ ions from the medium of K+ -treated cells to a concentration of 1 mM depresses the threshold for the step-up response to the control level. By addition of K+ or Na + ions to perimycin- or ouabain-treated cells the threshold returns to the control value. It is suggested that the flagellar and cell membrane are responsible for changes of P. trichophorum photosensitivity. 相似文献
13.
Taek-Hyoun Chang Edward B. Walker Pill-Soon Song 《Photochemistry and photobiology》1981,33(6):933-936
Abstract— Two simple methods of phototaxis measurements have been applied to study the effects of ionophores on the negative phototactic response in Stentor coeruleus. The inhibitory effects of Ca2+ -ionophore (A23187), Ca2+ -blocking agent (Ruthenium Red), and K+ -ionophore (valinomycin) on photo-taxis have been determined. Results suggest that the influx of Ca2+ plays a transducing role in the phototaxis of Stentor. 相似文献
14.
Kenji Hasegawa Yasuo Tsukahara Shigeo Ishizaki Masakazu Shimamoto Takeshi Nakamura Masaki Sohma Toshiro Sato 《Photochemistry and photobiology》1998,67(2):256-262
It is known that the ciliated protozoan Paramecium multimicronucleatum has synchronized circadian rhythms of motility, resting membrane potential and cyclic adenosine 3',5'-monophosphate (cAMP) and cyclic guanosine 3',5'-monophosphate (cGMP) concentrations. The present study shows that (1) extracellularly added 4 m M tetraethylammonium (TEA)+ (a K+ channel blocker) almost completely abolishes the diurnal oscillation of intracellular cAMP concentrations; (2) even 32 mM TEA+ fails to abolish the circadian motility rhythm; but (3) the motility rhythm is highly damped when 4 mM TEA+ and 100 μM CdCl2 (a Ca2+ channel blocker) are added simultaneously. A cAMP analogue ( N 6 -monobutyryl-cAMP) added extracellularly accelerates swimming velocity. Both a K+ channel blocker ( e.g . TEA+ ) and an inhibitor (trifluoperazine) of adenylate cyclase (AC) suppress cAMP formation, supporting the hypothesis that AC in Paramecium has dual functions, as a K+ channel and as an enzyme for cAMP formation. It is hypothesized that the circadian synchrony is due to circadian fluctuations of AC causing separate circadian changes both in ciliary motion and membrane potential through a cAMP-dependent signal pathway that forms a sophisticated network of second messengers to govern the synchrony together with Ca2+ - and cGMP-dependent pathways in a manner antiphasic and/or complementary to one another. 相似文献
15.
Abstract The most widely used agents for photodynamic therapy are the porphyrin photosensitizers. It has been shown that hematoporphyrin derivative (HpD) can cause murine marrow hypercellularity and splenic hypertrophy. We have examined the effect on survival and marrow cellularity of high dose l,3-bis(2-chloroethyl)-l-nitrosourea (BCNU) after HpD or dihematoporphyrin ether (DHE) pretreatment in C57BL/6J mice.
The lethal toxicity of the LDS0 + 10% dose of BCNU (60 mg kg−1 ) was significantly reduced by pretreatment with HpD when the HpD was administered at least 3 days prior to the BCNU. HpD administered 1 or 2 days prior to BCNU or after BCNU had no effect. The percent death rate was reduced from 80 to 0% when HpD was administered 7 and 5 days prior to BCNU.
No alteration of the lethal toxicity rate of BCNU at doses of 80 mg kg−1 were identified with DHE pretreatment although some increase in median survival was noted in two groups. Some reduction in lethal toxicity was noted when 60 mg kg−1 BCNU was used and the pretreatment dose of DHE was 10 or 25 mg kg−1 given twice 3 days apart. Furthermore, a significant reduction of BCNU induced marrow cell depletion was found when low doses of DHE were used as pretreatment. High doses of DHE resulted in marrow depletion. Both HpD and DHE altered the toxicity of BCNU.
Should porphyrin photosensitizers, which alone have little toxicity, prove to protect against nitrosourea toxicity then an important dose limiting factor (myelotoxicity) could be altered if not reduction in the tumouricidal activity occurs. 相似文献
The lethal toxicity of the LD
No alteration of the lethal toxicity rate of BCNU at doses of 80 mg kg
Should porphyrin photosensitizers, which alone have little toxicity, prove to protect against nitrosourea toxicity then an important dose limiting factor (myelotoxicity) could be altered if not reduction in the tumouricidal activity occurs. 相似文献
16.
Abstract— The fluoroquinolone antibiotics can induce skin photosensitivity in some patients and this has been ascribed to the generation of reactive oxygen species, such as singlet oxygen (O2 [1 Δg ]). We have studied the photochemical properties of the different ionized forms of the fluoroquinolone norfloxacin upon complexation with Mg2 + and Ca2 + ions, as it is proposed that the antibiotic exists mainly as a complex in the blood plasma. We found that the norfloxacin cation (pH < 6) shows no photodegradation after UVA irradiation and has a low quantum yield of O2 (1 Δg ) generation. The norfloxacin cation does not complex. Ca2 + or Mg2 + ions; when these ions are added to the solution, we observed no changes in the fluorescence quantum yields (φflu ) and singlet oxygen yields (φΔ ). In contrast, the neutral (6 ± pH > 8.5) and anionic (pH > 9) forms of norfloxacin are able to complex calcium and magnesium, and their generation of O2 (1 Δg ) is decreased by complexation. The neutral zwitterionic form and the anionic form also quench singlet oxygen by both chemical and physical pathways regardless of complex formation, while physical quenching is observed for the cation. At pH > 7.4, norfloxacin photobleaches and complexation to Ca2 + and Mg2 + increases the rate at which photobleaching occurs. Thus, both the pH of the medium and complexation with metal cations may affect the phototoxic potential of this antibiotic. 相似文献
17.
Eric E. Kelley Frederick E. Domann Garry R. Buettner Larry W. Oberley C.Patrick Burns 《Journal of photochemistry and photobiology. B, Biology》1997,40(3):273-277
Photofrin®, a photosensitizer used in the photodynamic therapy of cancer, selectively localizes in cellular membranes. Upon exposure to visible light, Photofrin® produces singlet oxygen (1O2), which reacts with membrane polyunsaturated fatty acids forming lipid hydroperoxides. Transition metals, such as Fe2+, catalyze the production of cytotoxic free radicals from lipid hydroperoxides. Ascorbate reduces ferric to ferrous iron, further augmenting lipid peroxidation. Therefore, to increase the efficacy of Photofrin® photosensitization, we added 20 μM ferrous sulfate and 100 μM ascorbic acid, in an aqueous layer over SCC-25 oral squamous cell carcinoma cells during in vitro illumination. In electron paramagnetic resonance spin trapping experiments, using POBN (-(4-pyridyl-1-oxide)-N-tert-butylnitrone), we observed that the presence of this pro-oxidant combination greatly increases the production of membrane-derived lipid free radicals. The effect was time dependent but only partially concentration dependent. Trypan blue dye exclusion demonstrated that this increase in lipid radical formation correlated with cytotoxicity. These observations support the hypothesis that Photofrin® photosensitization leads to lipid hydroperoxide formation, which increases the cell's susceptibility to iron-induced Fenton chemistry. The resulting free radical-mediated lipid peroxidation results in cell death. From these data we hypothesize that the efficacy of photodynamic therapy of superficial cancer might be increased by the topical application of the pro-oxidant combination of iron and ascorbate. Furthermore, their use will probably allow lower doses of Photofrin® without compromising antitumor effect. 相似文献
18.
Kotaro T. Yamamoto William O. Smith Jr ‡ Masaki Furuya‡ 《Photochemistry and photobiology》1980,32(2):233-239
The aggregation of phytochrome purified from etiolated pea ( Pisum satirum cv. Alaska) and rye ( Secale cereale cv. Cougar) tissues was investigated by centrifugation and turbidimetry. Purified pea phytochrome (A669 /A280 = 0.88), if irradiated with red light, became precipitable in the presence of CaCl2 . The precipitation upon red-light irradiation was optimal at a Ca2- or Mg2+ concentration of 10–20 m M , was greater at increased phytochrome concentration or lower pH values, and was inhibited by 0.1 M KG. The precipitated phytochrome slowly became soluble after far-red light exposure.
Turbidity of pea phytochrome solutions after red-light irradiation also increased rapidly in the presence of either Ca2+ or Mg2+ . Far-red light exposure after the red light cancelled the turbidity increase. Rye phytochrome showed less turbidity increase than pea phytochrome and occurred only in the presence of Ca2+ . Partially degraded pea phytochrome produced by endogenous proteases in the extract did not show the turbidity increase. Undegraded pea phytochrome also associated with microsomal fractions under conditions similar to those described above, but the partially degraded phytochrome did not. 相似文献
Turbidity of pea phytochrome solutions after red-light irradiation also increased rapidly in the presence of either Ca
19.
Abstract— Etiolated turions of Spirodela polyrhiza are positively photoblastic and show a phytochrome-mediated low fiuence germination response. The far-red light (FR) reversibility decreased with the delay of FR irradiation (lag phase 1.06 ± 0.03 days after red light irradiation; half-maximal response 1.9 days). The action of the far-red-absorbing form of phytochrome (Pfr) was only realized by a germination response if exogenously applied Ca2 + was present. Calcium step-down (from 1 mM to 0.9 μ M Ca2 +) and Ca2 + step-up (from 0.9 μ M to 1 m M Ca2 +) experiments were carried out to determine the Ca2 +-sensitive phase. There was no time gap between the two phases determined by the step-down and step-up experiments but a clear coincidence of both curves. Pulse treatments (24 h) with Ca2 + (1 m M ) showed the upper part of this common curve to represent the most Ca2 +-sensitive phase. The Ca2 +-sensitive phase was within the Pfr-requiring phase. After reversion of Pfr by FR pulses there was only a negligible response to the high Ca2 +-concentration, independent of the delay between the red light (R) and FR pulses. These results are compatible with the assumption of Ca2 + acting as a second messenger of Pfr. However, the Ca2 +-insensitivity in the first 12 h after the R pulse points against this hypothesis. 相似文献
20.
GANAPATHY MUTHUKUMAR ELLEN C. JENSEN ANN W. NICKERSON MARK K. ECKLES KENNETH W. NICKERSON 《Photochemistry and photobiology》1991,53(2):287-291
Abstract— Penicillium isariaeforme is a photomorphogenic fungus which produces upright bundles of conidia-bearing mycelia (called coremia) when grown on a defined medium in visible (450–500 nm) light. We found that exogenous Ca2+ ions could substitute for light. In the dark 1–2 m M Ca2+ triggered coremia formation. Dark induction of coremia was specific for Ca2+ in that it could not be duplicated by 50 m M Ba2+ , Fe2+ , Mg2+ , Mn2+ , Sr2+ , or Zn2+ . Additionally, light-induced coremia formation was inhibited by both KI (2.5 m M ) and phenylacetic acid (0.25 m M ). 相似文献