Nora Bretón

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The 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta HSD) enzyme catalyzes the oxidation and isomerization of delta 5-3 beta-hydroxysteroid precursors into delta 4-ketosteroids, thus leading to the formation of all classes of steroid hormones. In addition, 3 beta HSD catalyzes the interconversion of 3 beta-hydroxy- and 3-keto-5(More)
Structures of cDNA clones encoding three members of the rat 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) family were characterized. To search for potential new types of 3 beta-HSD, rat types I and II 3 beta-HSD cDNAs were used as probes to screen a rat genomic DNA library. Among the clones isolated, one encodes a novel(More)
The enzyme 3 beta-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase (3 beta-HSD) catalyzes the oxidation and isomerization of 5-ene-3 beta-hydroxypregnene and 5-ene-hydroxyandrostene steroid precursors into the corresponding 4-ene-ketosteroids necessary for the formation of all classes of steroid hormones. We have recently characterized two types of human(More)
The conversion of 3 beta-hydroxy-5-ene steroids by the enzyme complex 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) is an obligatory step in the biosynthesis of all classes of hormonal steroids in classical steroidogenic as well as in peripheral tissues. To develop a model more closely related to the human, we have isolated and(More)
We have used our recently characterized human 3 beta-hydroxy-5-ene steroid dehydrogenase/delta 5-delta 4-isomerase (3 beta-HSD) cDNA as probe to isolate cDNAs encoding bovine 3 beta-HSD from a bovine ovary lambda gtll cDNA library. Nucleotide sequence analysis of two overlapping cDNA clones of 1362 bp and 1536 bp in length predicts a protein of 372 amino(More)
We study the stability of static spherically symmetric exact solutions of Einstein equations coupled with nonlinear electrodynamics, in the magnetic sector. These solutions satisfy the heuristic model proposed by Ashtekar-Corichi-Sudarsky for hairy black holes, meaning that the horizon mass is related to their Arnowitt-Deser-Misner (ADM) mass and to the(More)
We present a model for an inhomogeneous and anisotropic early universe filled with a nonlinear electromagnetic field of Born-Infeld (BI) type. The effects of the BI field are compared with the linear case (Maxwell). Since the curvature invaria nts are well behaved then we conjecture that our model does not present an initial big bang singularity. The(More)
The Aharonov–Anandan and Berry phases are determined for the cyclic motions of a non–relativistic charged spinless particle evolving in the superposition of the fields produced by a Penning trap and a rotating magnetic field. Discussion about the selection of the parameter’s space and the relationship between the Berry phase and the symmetry of the binding(More)