RESUMEN
A new orthorhombic phase of the multiferroic BiFeO3 has been created via strain engineering by growing it on a NdScO(3)(110)(o) substrate. The tensile-strained orthorhombic BiFeO3 phase is ferroelectric and antiferromagnetic at room temperature. A combination of nonlinear optical second harmonic generation and piezoresponse force microscopy revealed that the ferroelectric polarization in the orthorhombic phase is along the in-plane {110}(pc) directions. In addition, the corresponding rotation of the antiferromagnetic axis in this new phase was observed using x-ray linear dichroism.
RESUMEN
We report a UV-Raman study of folded acoustic vibrations in epitaxial ferroelectric BaTiO3/SrTiO3 superlattices. The folded acoustic doublets show an anomalous temperature dependence disappearing above the ferroelectric transition, which is tuned by varying the thickness of the BaTiO3 and SrTiO3 layers. A mechanism involving the acoustic phonon modulation of the spatially periodic ferroelectric polarization explains the observed temperature dependence. These results demonstrate the strong coupling between sound, charge, and light in these multifunctional nanoscale ferroelectrics.
RESUMEN
The effects of chronic ethanol feeding on the binding of transforming growth factor-alpha (TGF-alpha) and TGF-alpha-stimulated receptor autophosphorylation were investigated in isolated rat hepatocytes. When hepatocytes were isolated from rats that were fed an ethanol liquid diet for 6-8 weeks, these cells exhibited a marked impairment of TGF-alpha-stimulated autophosphorylation of the receptor that binds this growth factor compared with hepatocytes from the pair-fed controls. This impaired autophosphorylation of receptor tyrosine residues was accompanied by significant decreases in the amount of surface-bound TGF-alpha. Immunoanalysis indicated no changes in receptor number, indicating that decreased receptor content was not responsible for decreased TGF-alpha binding in the hepatocytes from the ethanol-fed rats. In conclusion, chronic ethanol feeding reduced TGF-alpha binding to hepatocytes with a concomitant decrease in the ability of the receptor tyrosine kinase to autophosphorylate its tyrosine residues. These changes were not accompanied by decreased receptor protein content. These defects could lead to altered signal transduction and to impaired reparative and regenerative processes in the liver.
Asunto(s)
Receptores ErbB/metabolismo , Etanol/administración & dosificación , Factor de Crecimiento Transformador alfa/farmacología , Animales , Humanos , Técnicas de Inmunoadsorción , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Fosforilación , Ratas , Ratas Wistar , Proteínas Recombinantes/farmacología , Transducción de Señal , Factor de Crecimiento Transformador alfa/metabolismoRESUMEN
The effects of chronic ethanol administration on the endocytosis of three representative cytokines were investigated in isolated rat hepatocytes. When hepatocytes were isolated from rats that were fed an ethanol liquid diet for 12 to 13 weeks, these cells exhibited a decreased ability to internalize and degrade transforming growth factor-alpha, tumor necrosis factor-alpha and interleukin-6, compared with hepatocytes from the pair-fed controls. This impaired endocytosis of all three cytokines was accompanied by significant decreases in the amount of hepatocyte surface-bound cytokine. Changes in cytokine binding to surface receptors and reduced rates of receptor-cytokine complex internalization into the cells seem to be major contributors to defective endocytosis in hepatocytes from the ethanol-fed rats. Impaired hepatocyte endocytosis could lead to altered steady-state levels of cytokines in the liver and modified physiological responses to cytokines. These changes could affect homeostasis among the various cell types in the liver and could contribute to liver dysfunction and injury.