ABSTRACT
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.
Subject(s)
Carbon Dioxide , Oxygen , IonsABSTRACT
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.
Subject(s)
Forkhead Transcription Factors/metabolism , Gene Expression Regulation, Developmental , Pituitary Gland/embryology , Pituitary Gland/metabolism , Thyroid Gland/embryology , Thyroid Gland/metabolism , Xenopus Proteins/metabolism , Xenopus laevis , Amino Acid Sequence , Animals , Embryo, Nonmammalian/embryology , Embryo, Nonmammalian/metabolism , Forkhead Transcription Factors/chemistry , Forkhead Transcription Factors/genetics , Molecular Sequence Data , Phylogeny , Pituitary Gland/chemistry , Sequence Alignment , Thyroid Gland/chemistry , Xenopus Proteins/chemistry , Xenopus Proteins/genetics , Xenopus laevis/embryology , Xenopus laevis/metabolismABSTRACT
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.
Subject(s)
Gene Expression Regulation, Developmental , Transcription Factors/genetics , Xenopus Proteins/genetics , Xenopus laevis/embryology , Amino Acid Sequence , Animals , Embryo, Nonmammalian/chemistry , Embryo, Nonmammalian/metabolism , Gene Expression , In Situ Hybridization , Molecular Sequence Data , Ribonucleoproteins/analysis , Ribonucleoproteins/metabolism , Xenopus laevis/geneticsABSTRACT
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.
Subject(s)
Gene Expression Regulation, Developmental , Homeodomain Proteins/genetics , Homeodomain Proteins/physiology , Prosencephalon/embryology , Transcription Factors/genetics , Transcription Factors/physiology , Transcriptional Activation , Xenopus Proteins/genetics , Xenopus Proteins/physiology , Animals , Brain/embryology , DNA, Complementary/metabolism , Diencephalon/metabolism , Doublecortin Protein , Green Fluorescent Proteins/metabolism , Homeodomain Proteins/biosynthesis , In Situ Hybridization , Microscopy, Fluorescence , Neural Crest/metabolism , Neurons/metabolism , Oligonucleotides, Antisense/chemistry , Plasmids/metabolism , RNA/metabolism , Telencephalon/metabolism , Transcription Factors/biosynthesis , Transcription, Genetic , Wnt Proteins , Xenopus Proteins/biosynthesis , Xenopus laevis , beta-Galactosidase/metabolismABSTRACT
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.
