RESUMEN
The [Gd8(opch)8(CO3)4(H2O)8]·4H2O·10MeCN coordination cluster (1) crystallises in P1¯. The Gd8 core is held together by four bridging carbonates derived from atmospheric CO2 as well as the carboxyhydrazonyl oxygens of the 2-hydroxy-3-methoxybenzylidenepyrazine-2-carbohydrazide (H2opch) Schiff base ligands. The magnetic measurements show that the GdIII ions are effectively uncoupled as seen from the low Weiss constant of 0.05 K needed to fit the inverse susceptibility to the Curie-Weiss law. Furthermore, the magnetisation data are consistent with the Brillouin function for eight independent GdIII ions. These features lead to a magnetocaloric effect with a high efficiency which is 89% of the theoretical maximum value.
Asunto(s)
Dióxido de Carbono , Oxígeno , IonesRESUMEN
Members of the Ski/Sno family of gene products contain a characteristic peptide domain involved in protein-protein or protein-DNA interaction. Here, we characterize the developmental expression of xDawg, in Xenopus laevis, of a new gene, related to the Ski/Sno family of transcription regulators. The Ski/Sno domain of xDawg is predicted to present an electropositive surface, consistent with a role in DNA binding. This gene is expressed in the marginal zone of early gastrulae, and in the brain, sensory vesicles, and cranial neural crest of neurula and tailbud embryos.
Asunto(s)
Regulación del Desarrollo de la Expresión Génica , Factores de Transcripción/genética , Proteínas de Xenopus/genética , Xenopus laevis/embriología , Secuencia de Aminoácidos , Animales , Embrión no Mamífero/química , Embrión no Mamífero/metabolismo , Expresión Génica , Hibridación in Situ , Datos de Secuencia Molecular , Ribonucleoproteínas/análisis , Ribonucleoproteínas/metabolismo , Xenopus laevis/genéticaRESUMEN
The members of the FoxE subfamily of Fox (forkhead) genes are expressed in the developing pituitary, thyroid and lens. Mammalian Foxe1 is expressed primarily in the developing pituitary and thyroid gland, Foxe3 is expressed in the developing lens, while Xenopus FoxE4 is expressed in the developing lens and thyroid. Here we report the identification of Xenopus FoxE1, a gene that is primarily expressed in the developing pituitary and thyroid.
Asunto(s)
Factores de Transcripción Forkhead/metabolismo , Regulación del Desarrollo de la Expresión Génica , Hipófisis/embriología , Hipófisis/metabolismo , Glándula Tiroides/embriología , Glándula Tiroides/metabolismo , Proteínas de Xenopus/metabolismo , Xenopus laevis , Secuencia de Aminoácidos , Animales , Embrión no Mamífero/embriología , Embrión no Mamífero/metabolismo , Factores de Transcripción Forkhead/química , Factores de Transcripción Forkhead/genética , Datos de Secuencia Molecular , Filogenia , Hipófisis/química , Alineación de Secuencia , Glándula Tiroides/química , Proteínas de Xenopus/química , Proteínas de Xenopus/genética , Xenopus laevis/embriología , Xenopus laevis/metabolismoRESUMEN
Mutations in the aristaless-related homeobox (ARX) gene have been found in patients with a variety of X-linked mental retardation syndromes with forebrain abnormalities, including lissencephaly. Arx is expressed in the developing mouse, Xenopus, and zebrafish forebrain. We have used whole-mount in situ hybridization, overexpression, and loss-of-function studies to investigate the involvement of xArx in Xenopus brain development. We verified that xArx is expressed in the prospective diencephalon, as the forebrain is patterned and specified during neural plate stages. Expression spreads into the ventral and medial telencephalon as development proceeds through neural tube and tadpole stages. Overexpression of xArx resulted in morphological abnormalities in forebrain development, including loss of rostral midline structures, syn- or anophthalmia, dorsal displacement of the nasal organ, and ventral neural tube hyperplasia. Additionally, there is a delay in expression of many molecular markers of brain and retinal development. However, expression of some markers, dlx5 and wnt8b, was enhanced in xArx-injected embryos. Loss-of-function experiments indicated that xArx was necessary for normal forebrain development. Expansion of wnt8b expression depended on xArx function as a transcriptional repressor, whereas ectopic expression of dlx5, accompanied by development of ectopic otic structures, depended on function of Arx as a transcriptional activator. These results suggest that Arx acts as a bifunctional transcriptional regulator in brain development.
Asunto(s)
Regulación del Desarrollo de la Expresión Génica , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/fisiología , Prosencéfalo/embriología , Factores de Transcripción/genética , Factores de Transcripción/fisiología , Activación Transcripcional , Proteínas de Xenopus/genética , Proteínas de Xenopus/fisiología , Animales , Encéfalo/embriología , ADN Complementario/metabolismo , Diencéfalo/metabolismo , Proteína Doblecortina , Proteínas Fluorescentes Verdes/metabolismo , Proteínas de Homeodominio/biosíntesis , Hibridación in Situ , Microscopía Fluorescente , Cresta Neural/metabolismo , Neuronas/metabolismo , Oligonucleótidos Antisentido/química , Plásmidos/metabolismo , ARN/metabolismo , Telencéfalo/metabolismo , Factores de Transcripción/biosíntesis , Transcripción Genética , Proteínas Wnt , Proteínas de Xenopus/biosíntesis , Xenopus laevis , beta-Galactosidasa/metabolismoRESUMEN
The human aristaless-related homeobox ( ARX) gene is mutated in several patients with X-linked mental retardation and/or other neurologic pathologies. We report the isolation and expression pattern of a Xenopus arx gene. Similar to other vertebrate arx genes, Xenopus arx is expressed in the developing telencephalon, diencephalon, and floor plate.