摘要:

Abstract—Time‐gated fluorescence spectroscopy was performed on the tumor localizing fraction (TLF) of HpD in buffer at different concentrations of cationic surfactant. This technique obtains emission spectra with programmable delay relative to the excitation pulse. According to the measured fluorescence decay‐time constants (0.7, 3 and 15 ns) three gates were considered, delayed by 0, 5 and 18 ns, respectively, to evaluate the contribution of the emitting molecular species to the spectra. Simultaneous to these measurements, fluoresence decay waveforms and time‐integrated spectra were also detected. In buffer and in detergent micelles the fluorescence spectra are given by the superposition of the emission of the different molecular species present in the solution, and no appreciable interaction among the chromophores is observed. On the contrary, in the pre‐micellar range of the surfactant, evidence for the existence of an energy transfer mechanism was found. This effect seems to be related to the conflgurational state of the TLF polymeric chains and depends on the relative TLF/surfactant conc

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04142.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract—The tryptophanyl fluorescence decay of tuna apomyoglobin, a protein containing a single indole residue, has been compared to that of the monomeric tryptophanyl residue (NATA) in order to discriminate the effect determined by the protein matrix from those induced by physical and chemical agents. The fluorescence decay, obtained in the frequency domain, has been analyzed in terms of lifetime distributions having a Lorentzian shape. The results indicate that the incorporation of the chromophore into the protein matrix determines a broadening of the distribution pattern.A further increase of the distribution width has been observed on guanidine‐induced unfolding of the protein, whereas no effect has been detected for NATA in the presence of guanidine at concentrations as high as 6.0M.These observations lead to the conclusion that the tryptophanyl fluorescence lifetime is influenced by the protein matrix even in the fully unfolded state.The increase of temperature from 20 to 45oC produces an enlargement of the distribution width of NATA and unfolded tuna apomyoglobin. In the same thermal range, the native protein exhibits a narrowing of the tryptophanyl lifetime distribution. This different behaviour has been explained in terms of a larger distribution of microenvironmental states, generated by the chromophore‐solvent interaction (which is very limited in the native protein), at higher temperature.This conclusion has been further corroborated by the observation that a temperature increase changes the weight of the various components which contribute to the total emission of the free amino acid trypt

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04143.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract—Studies were carried out on two purpurins, NT2 and an analog, Sn.NT2H2. Both are photosensitizers, but the latter is substantially more effective against neoplastic cellsin vivo.These hydrophobic dyes can be solubilizedviaCremophor EL emulsions. We found both dyes to be approximately equitoxic to murine leukemia L1210 cells in culture, in terms of intracellular concentrations. But uptake of NT2 was 10‐fold less efficient than Sn.NT2H2, i.e. a 10‐fold higher extracellular level of NT2 was needed to produce an equitoxic response. Fluorescence measurements indicate that NT2 partitions to a very hydrophobic intracellular environments; its phototoxicity was related to inhibition of biosynthesis of DNA. In contrast, SN.NT2H2was accumulated at more hydrophilic loci (the apparent dielectric constant is consistent with a membrane interface) and mediated photodamage at sites of membrane tran

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04144.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract—The production of singlet oxygen was measured indirectly for three classes of photosensitizers: porphyrins (Photofrin II, TPPS4), chlorins (MACE, DACE), and a phthalocyanine (CASPc). Buffered solutions of sensitizers and singlet oxygen acceptors were irradiated with a CW dye laser and the oxygen depletion was monitored electrochemically with a Clark‐type microelectrode. A comparison of oxygen‐depletion rate constants and quantum efficiencies yields the order of efficiency of the sensitizers: TPPS4>MACE>PII>DACE>CASPc. For singlet oxygen acceptors the order was: furfuryl alcohol>imidazole>tryptophan. CHO cell suspensions were also used as acceptors. Here the order of efficiency (per absorbed photon) was PII>MACE = CASPc. Expressed in terms of oxygen depletion per cell the order was CASPc = PII>MACE. When performing cell clonogenicity studies the order of efficiencies, expressed as percentage cell kill per unit weight of sensitizer, was CASPc>PII>MACE = DACE. The discrepancy between the efficiencies of sensitizers to generate singlet oxygen and their cytotoxicity was explained in terms of photodegradation (for the chlorins), intracellular localization (for PII), and contributions from a Type I mechanism (for C

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04145.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract—A86Xenopuscells, cloned from aXenopusline that exhibited a high level ot photoreacti‐vation of UV‐induced lethal damage, and V79M1 hamster cells, cloned from a hamster line that did not exhibit efficient photoreactivation of such damage, were fused to produce the V79M1 A86 cell line ‐ a hybrid line in which approximately 84% of the cells contained the entire V79M1 and A86 genomes. Ultraviolet and UV plus photoreactivation fluence‐survival relations were then determined and compared for hybrid and parental Gl phase cells in a first attempt to elucidate interactions of the parental genetic potentials for photoreactivation in the hybrid. Specifically, it was anticipated that the combined V79M1 and A86 genomes in the hybrid would produce photoreactivating enzymes sufficient to efficiently photoreactivate UV‐induced lethal damage in both A86 and V79M1 DNA and little difference would be observed in the levels of photoreactivation exhibited by V79M1 A86 and A86 Gl phase cells. To the contrary, the level of photoreactivation observed for the hybrid did not closely approach that observed for the A86 line. To assist in the interpretation of this somewhat unexpected observation, three additional studies were performed: (1) comparison of ‘optimal’ schemes for photoreactivation of UV‐induced lethal damage in the hybrid and parental Gl phase cells, (2) comparison of the effects of some different types of growth medium on photoreactivation of UV‐induced lethal damage in hybrid and parental Gl phase cells, and (3) comparison of the levels of photoreactivation of UV‐induced chromatid deletions in the V79M1 and A86 chromosomes of Gl phase hybrid cells. The results suggested that the relatively low level of photoreactivation of UV‐induced lethal damage manifested by the hybrid cells could be attributed, at least in part, to their inability to efficiently photoreactivate pyrimidine dimers induced in the DNA of

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04146.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract—Exposure of mice to ultraviolet radiation (UV) followed by alloantigcn sensitization can suppress the immune response to that alloantigen. In order to assess the applicability of using UV‐induced immunosuppression in organ transplantation, the effectiveness of UV in prolonging the survival of vascularized organ allografts must be determined. Because, for technical reasons, rats are better suited than mice for such experiments, we first wanted to determine whether UV suppresses the immune response of inbred rats to alloantigens. The data presented here demonstrate that exposure of rats to UV (115–129 kJ/m2) prior to alloantigenic sensitization decreases the mixed lymphocyte response to alloantigen. The depression of the proliferative response to alloantigen was selective in that spleen cells from the UV‐treated rats could respond to mitogenic stimulation. In contrast to previous results with mice, suppressor cells could not be demonstrated in the spleens of the UV‐treated rats. In addition, UV treatment after sensitization inhibited the response to alloantigen. These data suggest that treatment of the recipient with UV before or after alloantigenic sensitization may provide a novel method of inhibiting immune responses to allogeneic

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04147.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract—The DNA repair capacities of three unrelated Cockayne syndrome(CS) fibroblast strains were compared to that of three unrelated xeroderma pigmentosum(XP) strains for three different DNA damaging agents using a sensitive host cell reactivation(HCR) technique. Adenovirus type 2(Ad 2) was treated with either UV light, γ‐rays or sunlamp‐irradiation and subsequently assayed for its ability to form viral structural antigens(Vag) in the CS and XP strains using immunofluorescent straining. D37values for the survival of Ad 2 Vag synthesis in the CS and XP strains, expressed as a percentage of those obtained in normal strains, were used as a measure of DNA repair capacity. Percent HCR values in the XP strains XP25RO, XP2BE and XP5BE respectively were lowest for UV(6, 14 and 6%), intermediate for sunlamp‐irradiation(18, 32 and 10%) and highest for 7‐irradiation(65, 61 and 60%), whereas for the CS strains CS1BE, CS3BE and CS278CTO respectively, percent HCR values were lowest for UV (26, 30 and 34%), intermediate for γ‐irradiation(61, 64 and 69%) and near normal for sunlamp‐irradiation(82, 73 and 89%). These results suggest that the spectrum of lesions' which is defectively repaired in CS is not the same as that which is defectively

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04148.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract—Spruce needles collected from several trees of the Black Forest were investigaled by EPR spectroscopy. These needles show in the g = 2.00 region a signal IIS(Tyr D+) and a light‐induced signal I(P700+) and a Mn2+hyperfine structure which superimposes the other absorptions. Difference spectra, light minus dark, partly eliminate the manganese hyperfine structure, and P700+can be observed. By comparison of these EPR signals with those of spinach chloroplast or thylakoid membranes described in the literature, significant deviations were observed, whereas several trees grown in the vicinity of Tubingen exhibit the well known D+and P700+EPR spectra. After treatment of branches of these ‘normal’ trees with herbicides like Amitrol and Roundup or chemicals like toluene or trichlormethane the EPR signals obtained are comparable with those observed with needles of the Black

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04149.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract—Oral retinoid therapy has been considered for the prevention of skin carcinogenesis in humans, although animal studies have failed to provide any evidence of a protective effect of these drugs in the one‐step photocarcinogenic system. In this study, oral therapy with vitamin A or a synthetic analogue, etretinate, was tested for ability to protect hairless mice(Skh‐hrl) from the development of skin tumours following exposure to broad‐band light(280–700 nm) for 25 weeks. Retinoids were given by gavage 3 times weekly either at low dosage(2000 IU vitamin A or 4 mg etretinate per kg body weight) or high dosage(10 000 IU vitamin A or 20 mg etretinate per kg body weight). None of the retinoid therapies compared to control mice(gavage vehicle only) modified skin tumour production in terms of time to onset of tumours, total tumour yield, or the types of tumours

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04150.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract—Monofunctional psoralens, plus UVA radiation are not erythemogenic and are less mutagenic than bifunctional psoralens plus UVA radiation. Thus, they have received considerable attention in recent years as potential therapeutic agents for various skin diseases. The purpose of this study was to examine the immunologic side effects following treatment of mice with a monofunctional psoralen plus UVA radiation. We report that angelicin plus UVA radiation suppressed the induction of contact hypersensitivity to dinitrofluorobenzene. This decreased immune response was associated with the presence of splenic suppressor cells that transferred suppression to normal recipients. Treatment with angelicin and UVA radiation also decreased the number of Thy‐1+and Ia+dendritic epidermal cells in the treated site. We conclude that although this monofunctional psoralen is not phototoxic, it has immunosuppressive activity in m

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb04151.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY