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9 results on '"Kuppers, E."'

2. OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

Author

Pommerol, A., Thomas, N., El-Maarry, M.R., Pajola, M., Groussin, O., Auger, A.-T., Oklay, N., Fornasier, S., Feller, C., Davidsson, B., Gracia-Berna, A., Jost, B., Marschall, R., Poch, O., Barucci, M.A., Bertaux, J.-L., La Forgia, F., Keller, H.U., Kührt, E., Lowry, S.C., Mottola, S., Naletto, G., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo, R., Koschny, D., Rickman, H., Agarwal, J., A'Hearn, M.F., Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., De Cecco, M., Debei, S., Güttler, C., Fulle, M., Gutiérrez, P.J., Hviid, S.F., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kuppers, E., Lara, L., Lazzarin, M., Lopez Moreno, J.L., Marzari, F., Michalik, H., Preusker, F., Scholten, F., Tubiana, C., Vincent, J.-B., Pommerol, A., Thomas, N., El-Maarry, M.R., Pajola, M., Groussin, O., Auger, A.-T., Oklay, N., Fornasier, S., Feller, C., Davidsson, B., Gracia-Berna, A., Jost, B., Marschall, R., Poch, O., Barucci, M.A., Bertaux, J.-L., La Forgia, F., Keller, H.U., Kührt, E., Lowry, S.C., Mottola, S., Naletto, G., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo, R., Koschny, D., Rickman, H., Agarwal, J., A'Hearn, M.F., Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., De Cecco, M., Debei, S., Güttler, C., Fulle, M., Gutiérrez, P.J., Hviid, S.F., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kuppers, E., Lara, L., Lazzarin, M., Lopez Moreno, J.L., Marzari, F., Michalik, H., Preusker, F., Scholten, F., Tubiana, C., and Vincent, J.-B.

Abstract

Since OSIRIS started acquiring high-resolution observations of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, over one hundred meter-sized bright spots have been identified in numerous types of geomorphologic regions, but mostly located in areas receiving low insolation. The bright spots are either clustered, in debris fields close to decameter-high cliffs, or isolated without structural relation to the surrounding terrain. They can be up to ten times brighter than the average surface of the comet at visible wavelengths and display a significantly bluer spectrum. They do not exhibit significant changes over a period of a few weeks. All these observations are consistent with exposure of water ice at the surface of boulders produced by dislocation of the weakly consolidated layers that cover large areas of the nucleus. Laboratory experiments show that under simulated comet surface conditions, analog samples acquire a vertical stratification with an uppermost porous mantle of refractory dust overlaying a layer of hard ice formed by recondensation or sintering under the insulating dust mantle. The evolution of the visible spectrophotometric properties of samples during sublimation is consistent with the contrasts of brightness and color seen at the surface of the nucleus. Clustered bright spots are formed by the collapse of overhangs that is triggered by mass wasting of deeper layers. Isolated spots might be the result of the emission of boulders at low velocity that are redepositioned in other regions. © 2015 ESO.

Published
2015

7. Regulation of gene expression in the developing midbrain by estrogen: implication of classical and nonclassical steroid signaling.

Author

Beyer C, Pawlak J, Brito V, Karolczak M, Ivanova T, and Kuppers E

Subjects
Animals, Astrocytes drug effects, Astrocytes metabolism, Cells, Cultured, Female, Gene Expression Regulation, Developmental physiology, Mesencephalon embryology, Mesencephalon metabolism, Mice, Mice, Inbred BALB C, Neurons drug effects, Neurons metabolism, Pregnancy, Signal Transduction physiology, Estrogens pharmacology, Gene Expression Regulation, Developmental drug effects, Mesencephalon drug effects, Signal Transduction drug effects, Signal Transduction genetics
Abstract

Estrogen plays an important role during midbrain development. This is indicated by the presence of nuclear estrogen receptors and the transient expression of the estrogen-forming enzyme aromatase. A number of recent studies have shown that estrogen promotes the differentiation and survival, as well as physiological performance, of midbrain dopaminergic cells. In addition, we have reported that both ways of cellular estrogen signaling (classical and nonclassical) as well as interactions with nonneuronal target cells are involved in the transmission of intra- and intercellular estrogen effects in this brain region. This study provides additional evidence that (i) estrogen is capable of regulating gene expression in cultured embryonic neurons and astrocytes differently and (ii) both signaling mechanisms, i.e., classically through nuclear receptors and nonclassically through the stimulation of membrane-estrogen receptors, which are coupled to distinct intracellular signal transduction cascades, contribute diversely to gene regulation. These data reveal a high degree of complexity of estrogen action at the genomic level in the developing brain. Further studies are warranted to unravel the exact contribution of the differently regulated genes for developmental estrogen action.

Published
2003
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