Une évaluation des champs thermiques simulés par un modèle de circulation générale océanique dans l'Atlantique équatorial

Deux champs de vents différents ont été utilisés pour forcer le modèle de circulation du LODYC en Atlantique tropical (20°N-20°S) pour l'année 1984. Le premier champ de vents (MOA) provient des observations des bateaux marchands; le deuxième (FS2b) est issu des analyses d'un modèle de prévision atmosphérique (ECMWF). Les températures simulées sont comparées à un ensemble de 3600 profils thermiques mesurés au cours de l'année 1984. Le vent MOA restitue en particulier, le refroidissement superficiel lié à l'upwelling équatorial d'été ce que le vent FS2b ne fait pas. Toutefois, l'évènement anormal chaud du début de 1984 est bien représenté par les deux simulations ... Avec le champ de vent MOA, la température de surface est restituée de façon satisfaisante sur l'ensemble du domaine. Une simulation complémentaire a été réalisée pour évaluer les parts respectives de l'advection et des flux thermodynamiques dans les différences de température de la couche de surface des deux simulation

Lysosomes, a key target of hydrophobic photosensitizers proposed for photochemotherapeutic applications

Despite their important biological activity, lysosomes have been generally neglected as important primary targets of photosensitizers, because they are not easily accessible for experiments. This paper reviews factors favoring the localization of photosensitizers in lysosomes and the various experimental approaches which have been used so far for the characterization of the lysosomal staining by various photosensitizing dyes, including porphyrins, chlorins and phenoxazines. The experimental difficulties observed in combining several in vitro techniques for the unambiguous demonstration of lysosomal targeting are examined. New data on tetraphenylporphine derivatives and a pyropheophorbide, as well as previous data on photofrin II, are presented to illustrate the advantages and possibilities of microspectrofluorometry in the study of photosensitizer localization in single living cells. Both spectral and topographic information available from areas smaller than 1 μm2 make it possible to characterize fairly specific sites of localization through the use of specific and vital fluorescent probes of lysosomes, such as Lucifer Yellow. It is also shown by microspectrofluorometry on single living cells that the chronology of the photosensitized reactions induced by specific or unspecific lysosomal photosensitizers can be easily followed. The photosensitized lipofuscin formation observed at the plasma membrane level with the lysosomotropic tetraphenylporphine supports the contention that it is very rare to find a truly specific lysosomal photosensitizer. © 1993

Plasma Lipoproteins as Mediators of the Oxidative Stress Induced by UV Light in Human Skin: A Review of Biochemical and Biophysical Studies on Mechanisms of Apolipoprotein Alteration, Lipid Peroxidation, and Associated Skin Cell Responses

There are numerous studies concerning the effect of UVB light on skin cells but fewer on other skin components such as the interstitial fluid. This review highlights high-density lipoprotein (HDL) and low-density lipoprotein (LDL) as important targets of UVB in interstitial fluid. Tryptophan residues are the sole apolipoprotein residues absorbing solar UVB. The UVB-induced one-electron oxidation of Trp produces •Trp and O2•- radicals which trigger lipid peroxidation. Immunoblots from buffered solutions or suction blister fluid reveal that propagation of photooxidative damage to other residues such as Tyr or disulfide bonds produces intra- and intermolecular bonds in apolipoproteins A-I, A-II, and B100. Partial repair of phenoxyl tyrosyl radicals (TyrO•) by α-tocopherol is observed with LDL and HDL on millisecond or second time scales, whereas limited repair of α-tocopherol by carotenoids occurs in only HDL. More effective repair of Tyr and α-tocopherol is observed with the flavonoid, quercetin, bound to serum albumin, but quercetin is less potent than new synthetic polyphenols in inhibiting LDL lipid peroxidation or restoring α-tocopherol. The systemic consequences of HDL and LDL oxidation and the activation and/or inhibition of signalling pathways by oxidized LDL and their ability to enhance transcription factor DNA binding activity are also reviewed