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Biomedical subjects

M Bazin

Publications and source records attributed to M Bazin.

At least 37 records · Page 2Linked to original sources
PubMed1991

Photoreactivity of 5-geranoxypsoralen and lack of photoreaction with DNA.

5-Geranoxypsoralen, commonly called bergamottin, a major furocoumarin contained in bergamot oil, is reported in vitro as a highly photoreactive psoralen. In ethanol, it exhibits quite a high triplet state quantum yield (approximately 0.37). The triplet state is involved in subsequent photochemistry which depends on the initial concentration and on the presence of oxygen. In contrast to most psoralens, absorption and fluorescence data suggest that 5-geranoxypsoralen does not interact with DNA in the dark. No UVA-induced interstrand cross-links in DNA were shown.

DNA↗
PubMed1990

Degradation of crystallins from a psoriatic patient undergoing PUVA therapy.

Comparative physico-chemical and spectroscopic analyses were carried out in human lens proteins obtained from extracts of normal, senile and PUVA cataracts. Mass recovery analysis reveals a large protein concentration loss in the PUVA cataract relative to the normal lens and senile cataract. This protein loss parallels an increase in the degraded polypeptide chains. However, the tryptophan content (2.1 mol/mol of 20 kDa protein subunit) and the apparent fluorescence quantum yield (phi f = 0.056) of the tryptophan residues which are believed to be involved in the development of UV-induced cataracts are unchanged after age-related alterations and/or in vivo photochemistry associated with psoralen (8MOP) photosensitized reactions.

Aging↗
PubMed1990

Ultra-structure and localisation of formazan formed by human neutrophils and amoebae phagocytosing virulent and avirulent Legionella pneumophila.

Legionella pneumophila (LP) strains of differing virulence were incubated with a solution of nitroblue-tetrazolium (NBT) at a concentration of 1 mg.ml-1 in the presence of Acanthamoeba polyphaga or human polymorphonuclear neutrophils (PMN). Reduction of NBT to formazan occurred at a faster rate in the presence of virulent strains. Reduction appeared to be temperature dependent; at 37 degrees C the reaction rate was higher than at 20 degrees C. On microscopic examination, deposits of formazan around Legionella cells were observed inside amoebae similar to those deposited in human neutrophils. Electron microscopy revealed electron-dense particles surrounding virulent legionellae, which appeared to be associated with formazan formation. Formazan formation inside amoebae may suggest the presence of a respiratory burst against LP, which is more intense with virulent strains.

Acanthamoeba↗
PubMed1990

Is rhodamine 123 a photosensitizer?

Because of conflicting reports on the photoxicity of rhodamine 123 (Rh 123), we have undertaken a study of Rh 123 photosensitization in several in vitro systems. First, Rh 123 is not a photodynamic agent and does not react with singlet oxygen. Second, when bound to cytochrome c (Cyt c), Rh 123 photosensitizes ferro Cyt c but not ferri Cyt c degradation by an oxygen-independent process. When delivered to skin fibroblasts where it specifically stains mitochondria, Rh 123 photosensitizes membrane damage. These results are consistent with the hypothesis that Rh 123 is a phototoxic stain. The lack of photosensitivity of Rh 123-stained mitochondria in some cell lines might therefore be due to specific structural features.

Animals↗
PubMed1989

Photosensitization with alpha-terthienyl: the formation of superoxide ion in aqueous media.

It is well known that alpha-terthienyl generates singlet oxygen in organic solvents with high quantum yields. In an aqueous medium, the production of superoxide radical-anion is readily detected by comparing the reduction of ferricytochrome c or nitro blue tetrazolium in the presence and in the absence of superoxide dismutase. Electron transfer reactions from the electronically excited sensitizer are also detected in an argon atmosphere.

Cytochrome c Group↗
PubMed1989

[Neutralizing activity against herpes simplex in maternal milk].

Human milk could play a role in the protection of the newborn from Herpes simplex virus 2 contamination. Neutralizing activity against Herpes simplex virus 2 was measured in 94 human milk samples and in 31 sera from healthy women. A weak neutralizing activity was detected in 48 milk samples. They were neither correlated to anti-Herpes simplex virus antibodies found in milk, nor to the neutralizing activity in sera. The origin and non immunologic nature of this activity are discussed.

Antibodies, Viral↗
PubMed1988

Determination of the dioxygen quenching constant for protein and model indole triplets.

The decay of the indole triplet of single tryptophan-containing proteins and model compounds can be readily determined at room temperature in solution by monitoring the triplet absorption or emission following an exciting laser pulse. The dioxygen triplet quenching constants, can be measured for all these molecules and compared to the analogous singlet values determined by fluorescence methods. The dioxygen triplet quenching constant (tkq) ranged from a high of 5.1.10(9) M-1.s-1 for the exposed indole of corticotropin to a low of 0.1.10(9) M-1.s-1 for the buried indole of asparaginase. The ratio of these values with their respective dioxygen singlet quenching constants (skq), tkq/skq, ranged from 0.3 to 0.6 for aqueous exposed polypeptide indoles. For globular proteins the tkq/skq value is observed to be 0.2 +/- 0.1. This lower value for protein indoles is not attributable to 'bulk' environmental or hydrogen bonding effects, since the magnitude of tkq/skq (= 0.5 +/- 0.1) for model indoles was independent of solvent dielectric constant, polarity, and proticity. Temperature-dependence studies were done to test whether tkq could be used to characterize the nature of the protein matrix. The activation energy (Ea) for tkq was found to be 11 +/- 2 kcal/mol for most proteins. This Ea was independent of whether the indole side-chain was solvent exposed or buried in the non-aqueous protein interior. Large Ea values were also obtained for model indoles, naphthalene and nalidixic acid, dissolved in water, whereas the same compounds dissolved in 95% ethanol exhibited much smaller Ea values. These data, in combination with the observation that the tkq of model indoles is insensitive to changes in solvent viscosity, indicate that dioxygen quenching at the triplet level can not be easily used to characterize the dynamics of proteins.

Indoles↗
PubMed1988

Characterization of the indole triplet excited state in proteins utilizing laser flash photolysis.

The triplet-triplet absorption spectrum of the sole indole side chain of human serum albumin and its decay kinetics were previously characterized, at room temperature, by using a conventional flash photolysis method [(1978) Proc. Natl. Acad. Sci. USA 75, 1172-1175]. Exploitation of this potentially useful long lived reporter group in protein studies was limited by the excessively large sample size required by that apparatus. The 265 nm laser flash instrument used in the present work avoids this problem at the price of a loss in photo-selectivity. We report that the latter concern can be mitigated. Melittin was studied first because this polypeptide contains a single aromatic residue (W-19), and because its monomeric and tetrameric forms are good models for solvent exposed and buried indole side chains of proteins. For both forms, the indole triplet and neutral radical absorption spectra could be readily time resolved and identified on the basis of shape and differential dioxygen sensitivity. The single tryptophan containing protein human serum albumin was studied next because it contains a large number of other 265 nm absorbing moieties whose transient spectra might complicate the detection of the indole triplet. These transients were shown to not interfere significantly in the wavelength region 450 nm to 600 nm, and, in contrast to the indole triplet, they were relatively dioxygen insensitive. Thus, a facile means is available by which the indole triplet of proteins may be characterized. Subsequently the question of whether this species could be detected in the presence of nuclei acid components was investigated by flashing the phage fd. The putative nucleic acid transients were shown not to interfere and the absorbance of the indole triplet was readily time resolved. The spectral assignment was persuasively confirmed by showing that the indole triplet absorption and phosphorescence emission spectra decay with the same lifetime. The present work thus provides additional evidence for the general applicability of the indole triplet excited state as a long lived intrinsic protein reporter group.

Bacteriophages↗
PubMed1987

Phototoxic effects of fluoranthene, a polycyclic aromatic hydrocarbon, on bacterial species.

Fluoranthene, a non-carcinogenic polycyclic aromatic hydrocarbon, inactivates Escherichia coli cells in the presence of near-ultraviolet light (NUV; 300-400 nm). E coli cells carrying defects in the uvrA6 or katF genes are sensitized to inactivation by the simultaneous treatment with fluoranthene and NUV, suggesting that DNA is a target and that hydrogen peroxide is generated. Haemophilus influenzae transforming DNA can be inactivated by the simultaneous treatment with fluoranthene and NUV confirming DNA as a target. Using the photooxidation of imidazole and histidine as probes, fluoranthene was found to generate singlet oxygen in organic and aqueous media. In water, it participated in electron transfer reactions, reducing nitro blue tetrazolium as well as ferricytochrome C. This reduction took place both in the presence of air, where superoxide anion was formed, and under argon. Simultaneous treatment with fluoranthene and NUV was incapable of inducing histidine-independent mutations. Simultaneous treatment with fluoranthene and NUV was incapable of inducing the uvrA gene product as evidenced by the absence of the induction of beta-galactosidase in an E coli operon fusion strain [uvrA215::Mud(Ap,lac)].

DNA Damage↗
PubMed1987

Complement-mediated solubilization of rat IgA immune precipitates.

The complement-mediated solubilization (CMS) of immunoprecipitates (IP) consisting of DNP-rat serum albumin (RSA) and rat monoclonal anti-DNP antibodies of the IgA [both polymeric (p-) and monomeric (m-)] or IgG2b (sub)class was studied. In contrast to IgG2b IP, solubilization of IgA IP was only observed in an autologous system, with rat serum as the source of complement. IP prepared using m-IgA were solubilized faster than those prepared using p-IgA. Analysis of both affinity and avidity of the antibodies, indicated that this difference may be due to the lower avidity of the m-IgA antibodies as compared to p-IgA. Analysis of the solubilized IP revealed deposition of C3 and C4 on IgG2b, and only C3 on IgA IP. These results point toward a role of the alternative pathway in the solubilization of IgA IP. Size analysis of the solubilized IgA IP employing sucrose density gradient ultracentrifugation, indicated that these were heterogeneous, with a size generally larger than 19 S.

Animals↗
PubMed1986

Proximity relations between tyrosine and tryptophan residues in fd phage determined by luminescence measurements.

Resonance energy transfer from tyrosine to tryptophan residues was detected in the phage fd. The magnitude of the transfer efficiency was estimated by both a traditional and an alternative method. The latter involved comparison of the indole acceptor excitation spectrum full-width half-maximum with a set of standard values differing in the amount of absorbance contributed by tyrosine donor. Both methods lead to the same conclusion: essentially all the tyrosine residues of the viral coat are within 0.9 nm of a tryptophan residue. Also, fluorescence lifetime measurements provide additional support for the hypothesis that there are at least two different environments for the coat protein's sole indole side-chain. Little if any DNA phosphorescence was seen, consistent with the nucleic acid bases being stacked in the DNA core.

Coliphages↗
PubMed1986

Evidence from pulse radiolysis and flash photolysis of the environment of tryptophan and tyrosine in the coat protein of fd phage.

Charge transfer has been observed between oxidised tryptophan-26 units and the tyrosine-21 or -24 of the coat protein of fd phage. The transfer is likely to be intramolecular. The rates suggest that the aromatic units are in a rigid region and that they may have at least two different environments. No apparent interaction occurs with the DNA, consistent with tryptophan and tyrosine units not being in contact with the bases.

Bacteriophages↗
PubMed1986

Oxic and anoxic photodamage triggered at the subcellular level by the synergistic action of haematoporphyrin derivative and nitroimidazoles.

A first attempt to impair a biological function by the synergistic effects of HpD and nitroimidazoles (metronidazole or misonidazole) under anaerobic conditions is reported. A function tightly linked to a membrane has been chosen as model and the Ca2+ movements through the inner mitochondrial membrane have been studied. When isolated mitochondria (1 mg/cm3) are irradiated in oxic condition with 25 micrograms/cm3 HpD and 1 mmol dm-3 nitroimidazole in the medium, Ca2+ uptake is stopped after 15 s of irradiation. When irradiated in anoxic conditions with 25 micrograms/cm3 HpD alone, addition of ATP triggers a normal Ca2+ uptake even after 10 min of irradiation. In contrast Ca2+ uptake is stopped by 1 min irradiation after addition of 1 mmol dm-3 misonidazole to HpD and by 2 min irradiation after addition of 1 mmol dm-3 metronidazole. Thus, under these experimental conditions, the enhancement ratio of the HpD action (defined as the ratio of the durations of irradiation necessary to obtain the cessation of Ca2+ uptake before and after addition of a component other than HpD) is of the order of 40, 10 and 5 for oxygen, misonidazole and metronidazole, respectively. Misonidazole is still efficient at a concentration of 0.1 mmol dm-3.

Adenosine Triphosphate↗