Disk-growing algorithm for phase-map unwrapping: application to speckle interferograms.

Interferometric techniques combined with phase shifting allow computation of the phase that is linked to the displacement of the object under study. The phases before and after displacement are computed from three or more interferograms (called specklegrams when speckle is used as the information carrier). Subtraction of these two phase patterns leads to a raw phase map. Phase unwrapping restores the 2π discontinuities and gives a continuous phase map. The disk-growing algorithm presented allows the inner and the outer propagation of the unwrapping from a growing disk and so avoids the main problem of anisotropic error propagation for noisy phase maps. It works successfully in speckle interferometry.

Design for polarizing holographic optical elements.

We present results of the application of a three-dimensional rigorous-vector coupled-wave theory to the design of polarizing holographic optical elements. Two different cases have been selected giving rise to two types of element, one of which is completely original. Experimental realizations were performed. The recording material was dichromated gelatin because of its outstanding performance related to diffraction efficiency. A fair agreement between the theoretical previsions and the experimental results was achieved.

Measurement of chromium content in dichromated gelatin by x-ray fluorescence.

X-ray fluorescence was applied to the determination of the chromium-ion content in developed dichromated gelatin after exposure. It was found that the Cr(3+) ions irreversibly linked to the gelatin molecules do not exceed one half of the original concentration of the ions. A similar study was carried out on the hardening of dichromated gelatin during dark reaction: as long as the degree of hardening of the gelatin allowed the chromium ions to migrate out of the film during development, the final Cr(3+) content was less than or equal to one half the original concentration.

Measure of the diffraction efficiency of a holographic grating created by two Gaussian beams.

We present a methodology for analyzing the characteristics of a photosensitive material for holography. When two Gaussian beams of equal intensities are exactly superimposed on the recording material, the modulation of the interference pattern is equal to unity. When they are no longer exactly superimposed, this modulation varies from one to zero depending on the analyzed point. On the other hand, the modulation is constant in a direction that is perpendicular to the incident plane. Therefore it is possible to consider a complete analysis (point by point) of only one holographic grating to measure the diffraction efficiency eta at a given modulation versus exposure or for varying modulation (or beam ratio K) for a given exposure. We present the results that are obtained with an experimental setup that was devised for that purpose. From these measurements it was possible to extract various parameters such as refractive-index modulation of the photosensitive support. The tested recording materials consist of film of dichromated gelatin and films of dichromate polyvinyl alcohol.

Adriamycin and derivatives interaction with the mitochondrial membrane: O2 consumption and free radicals formation.

Adriamycin induces the formation of semiquinone free radicals, O(2) and OH. species, in beef heart intact mitochondria, submitochondrial particles and complex I-III containing proteoliposomes. Free radicals were detected by the use of Electron Spin Resonance (ESR) spectroscopy with the spin trapping method. However, to observe transient oxygen species in intact mitochondria, a flow technique was mandatory. ESR results were compared with oxygen consumption measurements. Since free radicals could be involved in the mechanism of the adriamycin induced cardiotoxicity, it was essential to design new adriamycin derivatives which do not generate radicals. From the study of two adriamycin analogs (N-acetyl-adriamycin and 5-Iminodaunorubicin), it was shown that oxygen radicals formation require both the binding of the drug to the mitochondrial membrane and a quinone function associated with the drug structure. The data reported here might be useful in the synthesis of less cardiotoxic compounds.

Potentiation of oxygen toxicity by menadione in Saccharomyces cerevisiae.

The cytotoxicity of molecular oxygen can be sharply increased in the yeast Saccharomyces cerevisiae by the use of redox compounds capable of shunting electrons in vivo and of spontaneous reoxidation under aerobic conditions. Among these redox compounds, menadione (Vitamin K3) is particularly able to stimulate the cyanide-resistant respiration of the yeast cells. Under steady-state conditions, the efficiency of menadione is modulated by the physiological state of the yeast cells and also depends on the availability of reducing agents within the cell. Menadione shows lethal effects towards yeast cells in the presence of O2 only, as a result of the production of toxic metabolites like O2-. and H2O2 which are actually detected in the extracellular fluid. Inhibitors of the enzymes scavenging O2-. and H2O2 generally potentiate the lethal effects of this redox compound. On the other hand, superoxide dismutase and/or catalase supplemented into the incubation buffer have been found to protect the cells to various extents from the cytotoxic effects of menadione. Our data support the following conclusions: When the cellular enzymatic defences are functional, the moderate lethality induced by menadione is principally mediated by O2-. ions acting on the outer side of the cell (peripheral region). In the presence of cyanide, but not of azide, the loss of viability also results from additional damage occurring within the inner cell region. In this case, intracellular injury can be caused by H2O2 alone but our data also suggest that during redox cycling more reactive species--O2-. and probably OH.--are generally intracellularly and are involved in the cytotoxic process.

E.s.r. of spin-trapped radicals in gamma-irradiated polycrystalline DL-alanine. A quantitative determination of radical yield.

The quantitative aspects of determining free radicals in polycrystalline amino acids gamma-irradiated at room temperature and subsequently dissolved in spin-trap solutions were investigated. The deamination radical in DL-alanine was used for detailed studies and 2-methyl-2-nitrosopropane (MNP) was employed as the spin-trap. The spin-trapping efficiency (the number of radicals spin-trapped in solution divided by the number of radicals initially present in the gamma-irradiated solid) was found to be in the range 1 to 10 per cent for aqueous solutions depending on the experimental conditions. The effects of dose, particle size, pH, spin-trap concentration, age of spin-trap solution, MNP monomer to dimer ratio and the presence of organic solvents were investigated. Several reactions were found to decrease the spin-trapping efficiency; radical-radical recombination, the competition between the spin-adduct and the spin-trap for radicals and the reaction of radicals with the MNP dimer. The reaction of intact DL-alanine molecules with deamination radicals to produce H-abstraction radicals which are not spin-trapped does not significantly lower the spin-trapping efficiency. The results obtained with compounds such as glycine, glycylglycine, L-valine and L-proline suggest that the low spin-trapping efficiency found for DL-alanine may be representative of polycrystalline amino acids.

Visible-light-induced OH radicals in DNA-proflavine complexes: an e.p.r. and spin trapping study.

Using the spin-trapping technique, irradiation with visible light of complexes between DNA and proflavine was shown to generate OH radicals. The characteristic spectra were not obtained when proflavine or DNA were irradiated alone, nor when oxygen was absent. Using DMPO as a spin trap we found that the intensity of the DMPO-OH e.p.r. signal was enhanced when the molar ratio between bound proflavine and the DNA phosphorus increased up to a value of 0.15 demonstrating the efficiency of the intercalated dye molecules. A strong decrease of the e.p.r. signal was observed in the presence of various OH. scavengers like t-butanol, isopropanol or sodium benzoate. The OH. production was also decreased when the irradiation was made in the presence of SOD, ceruloplasmin or catalase and after addition of Chelex 100 resin.

E.S.R. of spin-trapped radicals in gamma-irradiated polycrystalline nucleic acid constituents and their halogenated derivatives.

Free radicals in gamma-irradiated polycrystalline nucleic acid constituents and their 5-halogenated derivatives have been studied by e.s.r. and spin-trapping. After gamma-irradiation at room temperature, the polycrystalline samples were dissolved in aqueous solutions of t-nitrosobutane (tNB) in the absence or presence of oxygen. For many of the nucleic acid constituents, two types of radicals, -C(5)RH-C(6)H- and -C(5)R-C(6)H2-, formed by H-addition to the double bond [-C(5)R=C(6)H-] of the base, were observed, where R is -CH3 or -H. In addition, radicals formed on the sugar moiety were found for some nucleosides. When oxygen was present in the tNB solution, the relative stability of trapped radicals was changed, and thus the presence of more than one radical species could be established. For halogenated bases, the radical produced by H-abstraction from N(1) was observed, and an additional radical species formed by H-addition to the C(6) position was found for 5-fluorouracil. For halogenated nucleosides, the same spectrum was observed in all compounds except the 5-fluoroderivatives, and was assigned to the radicals produced on the sugar moiety. For 5-fluorodeoxyuridine and 5-fluorouridine, the radical formed by H-addition to the C(6) position of the base was observed. In general, the present results are in good agreement with those of previous single crystal studies, but in the case of halogenated compounds other than the 5-fluoroderivatives, it was not possible to spin-trap the alpha-halo radicals which were the most prominent radicals formed from gamma-irradiation of single crystals at room temperature.

E.S.R. of spin-trapped radicals in aqueous solutions of 5-halo derivatives of nucleic acid constituents: reactions of hydrated electrons, hydroxyl radicals and U.V. photolysis.

In order to obtain information concerning the mechanism of radio- and photosensitization due to 5-halogen substituted nucleic acid constituents, the free radicals produced in iodo-, bromo-, chloro- and fluoro-derivatives of uracil, uridine and deoxyuridine by reaction with hydrated electrons and with hydroxyl radicals and by direct U.V. photolysis have been studied by e.s.r. and spin-trapping. t-Nitrosobutane was used as the spin-trap. From 5-halogenated bases (except 5-fluorouracil) U.V. photolysis and reactions with hydrated electrons produced the uracilyl radical which was subsequently spin-trapped. When hydroxyl radical reactions were studied, the free radical at the N(1) position of the base was identified. From 5-fluorouracil U.V. photolysis generated the alpha-halo radical at the C(5) position of the base. For 5-halogenated ribonucleosides and deoxyribonucleosides, free radicals located on the sugar moiety were observed for reactions with hydrated electrons, hydroxyl radicals and for U.V. photolysis. The implications of these results for understanding the mechanism of radio- and photosensitization by 5-halogenated nucleic acids are discussed.

[Photosensitization of consitutents of nucleic acids by proflavine. Mechanism of formation of hydrogen addition radicals in frozen aquenous solutions (author's transl)]. / Photosensibilisation des constituants des acides nucléiques par la proflavine Mécanisme de formation de radicaux d'addition d'hydrogène en solutions aqueuses gelées

It is shown that the insertion of nucleotides between proflavine molecules is favourable to photosensitization. Furthermore (1) each molecule of proflavine gives at the most one free radical in the substrate, (2) the chromophore is largely restored when oxygen is not present, (3) superoxide radicals are observed in the presence of oxygen, and (4) formyl radicals are detected. The scheme elaborated for the mechanism gives an explanation for all these observations.

Indirect EPR evidence for the production of singlet oxygen in the photosensitization of nucleic acid constituents by proflavine.

EPR spectroscopy is used to analyse the influence of D2O and NaN3 on the free radicals induced in frozen aqueous solutions of 5'-thymidine monophosphate photosensitized (lambda greater than 320 nm) by proflavine at 205 K. The results can be explained if the production of singlet oxygen during the process is assumed.

Triplet state population study in relation to the aggregation of proflavine in frozen solutions.

The evolution of the proflavine triplet state population with the extent of aggregation is examines, by ESRmeasurements, as a function of organic solvents and mineral salts, well known for their ability to influence the aggregation process. The intensity of the triplet state population has also been investigated as a function of pH. The insertion of aromatic molecules like DNA's nucleotides between dye molecules is shown to increase the intensity of the triplet state. It is put forward that the observed triplet state is characteristic of the singly protonated proflavine which seems to be the active species in in vivo experiments.