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Biomedical subjects

M Bazin

Publications and source records attributed to M Bazin.

At least 19 recordsLinked to original sources
PubMed2002

Ultraviolet-B-induced inactivation of human OGG1, the repair enzyme for removal of 8-oxoguanine in DNA.

The OGG1 proteins are DNA N-glycosylases-apurinic-apyrimidinic lyases that are responsible for the removal of 8-oxo-7,8-dihydroguanine (8-oxoG) base in DNA. The human enzyme (hOGG1) is a monomer of 345 amino acids containing 10 buried tryptophan (Trp) residues that are very sensitive to UVB irradiation. The photolysis quantum yield of these Trp residues is about 0.3 and 0.1 in argon- and air-saturated solutions, respectively. Matrix-assisted laser desorption-ionization-time-of-flight mass spectrometry shows that several cleavage sites are identical under aerobic and anaerobic photolysis of Trp residues; one of them includes the active site. Western blots and polyacrylamide gel electrophoresis indicate that fragments of high molecular size are also formed. In addition to common photochemical paths with argon-saturated solutions, specific reactions occur in air-saturated solutions of hOGG1. The photolysis rate is inhibited by more than 50% on binding of hOGG1 to a 34mer oligonucleotide containing a single 8-oxoG-C base pair. Binding to the oligonucleotide with 8-oxoG-C induced a 20% quenching of the hOGG1 fluorescence, suggesting interaction of nucleic acid bases with the Trp residue(s) responsible for the photolysis. Using 2,6-diamino-4-hydroxy-5-N-methylformamidopyrimidine (Me-FapyG) and 8-oxoG as substrates, it is shown that protein photolysis induces photoinactivation of the DNA N-glycosylase activities. The excision of 8-oxoG is more affected than that of Me-FapyG at the same dose of UVB irradiation under both air and argon conditions. Besides the role of Trp residues, the possible involvement of Cys 253 in the photoinactivation process of hOGG1 is discussed.

Amino Acid Sequence↗
PubMed2000

Interactions of superoxide anion with enzyme radicals: kinetics of reaction with lysozyme tryptophan radicals and corresponding effects on tyrosine electron transfer.

The kinetics of O2*- reaction with semi-oxidized tryptophan radicals in lysozyme, Trp*(Lyz) have been investigated at various pHs and conformational states by pulse radiolysis. The Trp*(Lyz) radicals were formed by Br2*- oxidation of the 3-4 exposed Trp residues in the protein. At pH lower than 6.2, the apparent bimolecular rate is about 2 x 10(8) M(-1) s(-1); but drops to 8 x 10(7) M(-1) s(-1) or less above pH 6.3 and in CTAC micelles. Similarly, the apparent bimolecular rate constant for the intermolecular Trp*(Lyz) + Trp*(Lyz) recombination reaction is about (4-7 x 10(6) M(-1) s(-1)) at/or below pH 6.2 then drops to 1.3-1.6 x 10(6) M(-1) s(-1) at higher pH or in micelles. This behavior suggests important conformational and/or microenvironmental rearrangement with pH, leading to less accessible semi-oxidized Trp* residues upon Br2*- reaction. The kinetics of Trp*(Lyz) with ascorbate, a reducing species rather larger than O2*- have been measured for comparison. The well-established long range intramolecular electron transfer from Tyr residues to Trp radicals--leading to the repair of the semi-oxidized Trp*(Lyz) and formation of the tyrosyl phenoxyl radical is inhibited by the Trp*(Lyz) + O2*- reaction, as is most of the Trp*(Lyz) + Trp*(Lyz) reaction. However, the kinetic behavior of Trp*(Lyz) suggests that not all oxidized Trp residues are involved in the intermolecular recombination or reaction with O2*-. As the kinetics are found to be quite pH sensitive, this study demonstrates the effect of the protein conformation on O2*- reactivity. To our knowledge, this is the first report on the kinetics of a protein-O2*- reaction not involving the detection of change in the redox state of a prosthetic group to probe the reactivity of the superoxide anion.

Anions↗
PubMed2000

A laser flash photolysis and pulse radiolysis study of primary photochemical processes of flumequine.

The 355 nm laser flash photolysis of argon-saturated pH 8 phosphate buffer solutions of the fluoroquinolone antibiotic flumequine produces a transient triplet state with a maximum absorbance at 575 nm where the molar absorptivity is 14,000 M(-1) cm(-1). The quantum yield of triplet formation is 0.9. The transient triplet state is quenched by various Type-1 photodynamic substrates such as tryptophan (TrpH), tyrosine, N-acetylcysteine and 2-deoxyguanosine leading to the formation of the semireduced flumequine species. This semireduced form has been readily identified by pulse radiolysis of argon-saturated pH 8 buffered aqueous solutions by reaction of the hydrated electrons and the CO2*- radicals with flumequine. The absorption maximum of the transient semireduced species is found at 570 nm with a molar absorptivity of 2,500 M(-1) cm(-1). In argon-saturated buffered solutions, the semireduced flumequine species formed by the reaction of the flumequine triplet with TrpH stoichiometrically reduces ferricytochrome C (Cyt Fe3+) under steady state irradiation with ultraviolet-A light. In the presence of oxygen, O2*- is formed but the photoreduction of Cyt Fe3+ by O2*- competes with an oxidizing pathway which involves photo-oxidation products of TrpH.

Anti-Infective Agents↗
PubMed2000

[Vertebral osteomyelitis with epidural abscess in a child with sickle cell disease].

A case of paraplegia due to a thoracic epidural abscess in a 6-year-old black girl with sickle cell anemia is reported. MRI and CT scan showed abnormalities involving T6 vertebra which were consistent with osteomyelitis. A laminotomy, associated to antibiotic administration, permitted rapid neurological improvement. Although cultures were negative, the infection was probably due to salmonellae. Salmonellosis is a well-known complication in children with sickle cell disease but spinal localization is unusual. Its pathogenesis is unclear but immunological abnormalities associated to vascular obstructions by abnormal blood red cells have been advocated. The underlying etiology of vertebral abnormalities in these children is difficult to determine, but early diagnosis with modern investigations, as CT scan and MRI, is crucial to promptly begin therapy for osteomyelitis, minimizing the risk of spinal cord compression.

Anemia, Sickle Cell↗
PubMed1999

EPIMART: prospective incidence study of epileptic seizures in newly referred patients in a French Carribean island (Martinique).

PURPOSE: To identify, in the population living in the island of Martinique, persons who had their first epileptic seizure or first came to medical attention because of an epileptic seizure. METHODS: Between May 1, 1994, and April 30, 1995, we collected all suspected cases of provoked and unprovoked epileptic seizures admitted to the hospitals or addressed to the private neurologists or pediatricians of the island. RESULTS: Three hundred nine cases were collected. Rate of initial diagnosis of provoked and nonprovoked seizures (standardized to the U.S. population): 77.7/100,000, with a bimodal distribution of the cases with age (86 in 0- to 10-year age group and 203 in patients older than 60 years). Sixty-three cases were classified as provoked seizures (incidence, 16.4/100,000). Alcohol consumption, stroke, and cranial trauma were the most frequent causes (30.1, 20.6, and 18.7%, respectively). Two hundred forty-six cases were classified as unprovoked seizures (incidence, 64.1): seizures with a stable condition, 74 cases (I, 19.3); seizures with an evolutive condition, 17 cases (I, 4.5); seizures of unknown etiology, 155 cases (I, 40.4). These figures must be considered as the minimal rate. CONCLUSIONS: The global incidence rate of newly referred persons with a diagnosis of epileptic seizures in this study is clearly higher than those observed in industrialized countries but lower than those in developing countries. The major risk factors are represented by alcohol consumption, followed by stroke, cranial trauma, and infectious diseases.

Adolescent↗
PubMed1999

Ultraviolet-B-induced damage to Escherichia coli Fpg protein.

We investigated the effect of UVB light (290 < or = lambda < or = 320 nm) on the structure and enzymatic activities of Escherichia coli Fpg protein (2,6-diamino-4-hydroxy-5N-methylformamidopyrimidine-DNA glycosylase), a DNA repair enzyme containing a zinc finger motif and five chromophoric Trp residues. Irradiation with UVB light of air-saturated pH 7.4 buffered aqueous solutions of Fpg induces the formation of polymers as shown by sodium dodecyl sulfate polyacrylamide gel electrophoretic analysis. In argon-saturated solutions, polymer formation produces a precipitate. The polymerization quantum yield is 0.07 +/- 0.01 and 0.15 +/- 0.02 in air- and argon-saturated solutions, respectively. In the polymerized Fpg protein, second-derivative absorption spectroscopy indicates that three and one Trp residues are destroyed in air- and argon-saturated solutions, respectively. Polymers are devoid of all three activities of the Fpg protein, whereas the unpolymerized protein retains full activities. Matrix-assisted laser desorption/ionization experiments demonstrate that polymer formation is accompanied by the formation of short polypeptides containing the first 32 or 33 residues of the N-terminal domain. Theses polypeptides are most probably formed by the photolytic cleavage of Fpg protein induced by light absorption by the adjacent Trp-34 residue.

Amino Acid Sequence↗
PubMed1999

Lysosomes are sites of fluoroquinolone photosensitization in human skin fibroblasts: a microspectrofluorometric approach.

The fluoroquinolone antibiotics are widely used despite their strong phototoxicity under solar UV irradiation. Although they are known as good photodynamic photosensitizers, other factors than production of activated oxygen species may play a role in the effectiveness of the phototoxic effect. Subcellular localization is one of the important parameters that may determine this strength. Using microspectrofluorometry, it is shown that norfloxacin, ofloxacin, lomefloxacin, ciproflaxin and BAYy3118 are readily incorporated into lysosomes of HS68 human skin fibroblasts although weak staining of the whole cytoplasm also occurs especially with norfloxacin. Consistent with their photoinstability in solutions, the fluoroquinolones under study are readily photobleached by UVA in the HS68 fibroblasts. The BAYy3118 derivative that has the fastest bleaching rate also shows the strongest phototoxicity toward HS68 fibroblasts. Photosensitization with these fluoroquinolones induces lysosomal membrane damage as shown by the increased rate of leakage of the lysosomal probe lucifer yellow as compared to that observed with untreated cells.

Anti-Infective Agents↗
PubMed1998

Effect of single mutations on the structural dynamics of a DNA repair enzyme, the Escherichia coli formamidopyrimidine-DNA glycosylase--a fluorescence study using tryptophan residues as reporter groups.

The effects on the structure dynamics of the Escherichia coli wild-type formamidopyrimidine-DNA glycosylase (Fpg) protein of the single mutations Lys57-->Gly (FpgK57G), Pro2-->Gly (FpgP2G) and Pro2-->Glu (FpgP2E) were studied by fluorescence techniques, namely: lifetime measurements and acrylamide quenching of the fluorescence of Trp residues. The fluorescence decays of Fpg and its mutant forms were analysed by the maximum-entropy method and lifetime distributions in the range 200 ps to 9 ns were obtained. The lifetime distribution profiles of FpgK57G, FpgP2G and FpgP2E are different from that of wild-type Fpg. Both dynamic and static quenching by acrylamide were observed for all the proteins. At 20 degrees C, the bimolecular collisional quenching rate constant of the FpgP2E fluorescence by acrylamide was only 0.8 M(-1) s(-1) as compared to about 1.4 M(-1) s(-1) for the three other proteins. At 6 degrees C, all the spectroscopic properties of these four proteins are about the same. The analysis of experimental data demonstrates that all three mutations induce a structural reorganization of the Fpg protein. However, only the P2E mutation lead to a reduced accessibility of some Trp residues to acrylamide quenching. It is concluded that the single P2E replacement induces a conformational change leading to a more rigid globular structure as opposed to the wild type and K57G and P2G mutations. The influence of the single mutations on the enzyme activities of the Fpg protein is discussed.

Acrylamide↗
PubMed1998

Intra and intermolecular charge effects on the reaction of the superoxide radical anion with semi-oxidized tryptophan in peptides and N-acetyl tryptophan.

The reaction of the superoxide radical anion (O2-*), with the semi-oxidized tryptophan neutral radical (Trp*) generated from tryptophan (Trp) by pulse radiolysis has been observed in a variety of functionalized Trp derivatives including peptides. It is found that the reaction proceeds 4-5 times faster in positively charged peptides, such as Lys-Trp-Lys, Lys-Gly-Trp-Lys and Lys-Gly-Trp-Lys-O-tert-butyl, than in solutions of the negatively charged N-acetyl tryptophan (NAT). However, the reactivity of O2-* with the Trp* radical is totally inhibited upon binding of these peptides to micelles of negatively charged SDS and is reduced upon binding to native DNA. By contrast, no change in reactivity is observed in a medium containing CTAB, where the peptides cannot bind to the positively charged micelles. On the other hand, the reactivity of the Trp* radical formed from NAT with O2-* is reduced to half that of the free Trp* in buffer but is markedly increased in CTAB micelles. The models studied here incorporate elements of the complex environment in which Trp* and O2-* may be concomitantly formed in biological system and demonstrate the magnitude of the influence such elements may have on the kinetics of reactions involving these two species.

Amino Acid Sequence↗
PubMed1998

[Epileptic seizures, epilepsy and risk factors. Experiences with an investigation in Martinique. Epimart Group].

A prospective incidence study was carried out in the French Caribbean island of Martinique between May 1st 1994 and April 31st 1995. incidence was 80.6 (77.7 when standardized with 1990 U.S. population). This incidence was higher than that observed in the Swiss canton of Geneva where the same methodology was used. The individualized risk factors of first provoked and unprovoked seizures in Martinique were alcoholism, head trauma and cerebro-vascular accidents.

Epilepsy↗
PubMed1997

N-conjugates of 2,5-disubstituted pyrrole and glutathione. Evaluation of their potency as antioxidants against photosensitization of NCTC 2544 keratinocytes by excess endogenous protoporphyrin IX.

A novel glutathione compound in which the amino group has been derivatized by a 2,5-dimethyl pyrrole is shown to be very effective against cell photosensitization in vitro. Protoporphyrin IX either added to the medium or produced endogenously by incubation of NCTC 2544 keratinocytes with 5-aminolevulinic acid has been chosen as the photosensitizer. The antioxidant effectiveness of glutathione-pyrrole derivatives against protoporphyrin photosensitization depends critically on the type of 2,5 substitution on the pyrrole ring. This structure-function relationship may be attributed to the difference in compartmentation and/or uptake of the various glutathione-pyrrole derivatives under study. The 2,5-dimethyl pyrrole derivative is much more effective than glutathione as a protective agent against phototoxic reactions induced by protoporphyrin IX.

Aminolevulinic Acid↗
PubMed1996

Alteration of lipoproteins of suction blister fluid by UV radiation.

Suction blister fluid is a good representative of the interstitial fluid feeding the epidermal cells. Lipoproteins contained in the suction blister fluid of healthy volunteers are readily photo-oxidized by UV radiation in the wavelength range 290-385 nm. Absorbed light doses equivalent to one minimal erythemal dose absorbed by skin exposed to UVB (e.g. 290-320 nm) are sufficient to induce lipid peroxidation and modification of apolipoproteins A-I, A-II and B. Albumin, which is known to protect serum fully from oxidative stresses, is not so effective against photo-oxidation. Although tryptophan (Trp) residues of proteins contained in the suction blister fluid are photo-oxidized, apolipoprotein A-II, which does not contain any chromophoric Trp residue, is also altered by the UV radiation. With regard to results obtained with a model reconstituted fluid, it is suggested that the radical chain reaction of the lipid peroxidation can transfer the initial photodamage at sites not directly susceptible to photo-oxidation. The biological implications of these results are discussed.

Apolipoprotein A-I↗
PubMed1995

The diffusion-controlled reaction of semioxidized tryptophan with the superoxide radical anion.

From pulse radiolysis measurements in oxygenated aqueous solution, the semioxidized tryptophan radical (Trp.- formed by the one-electron oxidation of Trp by Br2- radical--has been shown to oxidize the superoxide radical anion with a rate constant of k = 2 x 10(9) M-1 s-1. Proof of this reaction is found in addition of superoxide dismutase (SOD) to the system, which totally eliminates the contribution of the Trp. + O2- mechanism to Trp. decay. Little, if any, reaction of molecular oxygen with Trp. may be observed on the time scale of the pulse radiolysis experiment.

Anions↗
PubMed1995

Subcellular localization of and photosensitization by protoporphyrin IXhuman keratinocytes and fibroblasts cultivated with 5-aminolevulinic acid.

The subcellular localization of protoporphyrin (PP) has been studied by microspectrofluorometric techniques in NCTC 2544 keratinocytes incubated with 5-aminolevulinic acid (ALA) for times up to 42 h. Whereas the plasma membrane shows strong staining, fluorescent spots are observed within the cytoplasm especially in the perinuclear region. Although the topographic pattern of the PP distribution does not change much with the incubation time with ALA, the fluorescence spectra suggest that the PP microenvironments are quite different at short and long incubation times. Addition of 18 microM desferrioxamine almost doubles the ALA-induced PP concentration. Colocalization experiments with rhodamine 123, a mitochondrial probe, and lucifer yellow (LY) or neutral red (NR), two lysosome probes, demonstrate that at least some of these spots are of lysosomal origin. Study of the time evolution of the NR fluorescence under irradiation with visible light in the presence and absence of ALA demonstrates that lysosomes are damaged cells that have synthesized PP. No PP fluorescence can be detected in mitochondria after incubation with ALA. However, photosensitization of mitochondria occurs under irradiation with visible light. Very little formation of lipofuscins by photosensitization with exogenous PP or ALA-induced PP is observed with the NCTC 2544 keratinocytes, as compared to normal human fibroblasts.

Aminolevulinic Acid↗
PubMed1994

Glutathione peroxidase and glutathione reductase activities towards glutathione-derived antioxidants.

A new class of glutathione derivatives with antioxidant properties has been prepared by transformation of the NH2 group into a pyrrole ring with various substitutions at the 2 and 5 positions. Due to steric hindrance and/or hydrophobicity of the 2-5-disubstituted pyrrole ring, the reduced glutathione derivatives are poor substrates of the glutathione peroxidase and do not effectively compete with GSH. The oxidized glutathione derivatives are, in turn, relatively good substrates (Km = 1.5 mM) of the glutathione reductase as compared to natural oxidized glutathione (Km = 0.51 mM) but are not effective competitors of the enzyme. It can be considered that the new glutathione derivatives do not strongly interfere with the natural enzymatic defence against fatty acid hydroperoxides formed during an oxidative stress.

Animals↗
PubMed1994

A pulse radiolysis study of one-electron oxidation and .OH radical reaction of a new class of antioxidants: 2,5 dimethylpyrrole--amino acid N-conjugates.

A new class of 2,5 dimethylpyrrole functionalized amino acid and peptide antioxidants has been synthesized. Pulse radiolysis studies have been carried out on these compounds to determine their reactivity in one-electron oxidation reactions with Br2- and (SCN)2-, as well as their reactivity toward the water radicals .OH and eaq-. When compared to similar reactions with parent amino acids and peptides, both rate constants and transient spectra indicate considerable interaction between the electronic states of the pyrrole moiety and amino acid or peptide. Where comparison data is available, radical reactions are significantly more rapid with these derivatives than with the parent compounds. Exceptions occur in some cases of .OH attack where steric hindrance may be evoked to explain a lower rate constant in the derivative compounds. Electron attachment rates are also found to be enhanced by the presence of the pyrrole ring.

Amino Acids↗
PubMed1991

Type I and type II photosensitization by the antibacterial drug nalidixic acid. A laser flash photolysis study.

The 355 nm laser flash photolysis of nalidixic acid at pH 9.2 leads to the formation of the nalidixate anion triplet state (absorption lambda max = 620 nm; 5700 less than or equal to epsilon T less than or equal to 9000 M-1cm-1; 0.6 less than or equal to phi T less than or equal to 1). The first order triplet state decay (kT = 7.7 x 10(3) s-1) is accompanied by a diffusion controlled triplet-triplet annihilation. Oxygen efficiently quenches the triplet state (k = 3.2 x 10(9) M-1s-1). The nalidixate radical dianion (absorption lambda max = 650 nm; epsilon = 3000 M-1cm-1) is produced by the diffusion controlled reductive quenching of the triplet state by tryptophan and tyrosine. The superoxide anion (O2-.) is produced by diffusion controlled reaction of the radical dianion with oxygen. The O2-. is characterized by its reactions with ferricytochrome c and superoxide dismutase. The physiological form of nalidixic acid is thus a good Type I and Type II photosensitizer.

Anions↗