RESUMEN
Intrinsic topological insulators are realized by alloying Bi(2)Te(3) with Bi(2)Se(3). Angle-resolved photoemission and bulk transport measurements reveal that the Fermi level is readily tuned into the bulk bandgap. First-principles calculations of the native defect landscape highlight the key role of anti-site defects for achieving this, and predict optimal growth conditions to realize maximally resistive topological insulators.
Asunto(s)
Aleaciones/química , Bismuto/química , Selenio/química , Telurio/química , Impedancia EléctricaRESUMEN
Permanent or transient focal cerebral ischemia was induced in spontaneously hypertensive rats (SHR) using the intraluminal filament method. Successful occlusion of the middle cerebral artery (MCA) was achieved using 4/O filaments (terminal diameter 0.20-0.25 mm) coated with poly-L-lysine. The L-type calcium channel blocker isradipine (2.5 mg/kg) administered subcutaneously 30 min following permanent MCA occlusion significantly reduced the volume of ischemic brain damage in the cerebral hemisphere (25%; P = 0.0001), cerebral cortex (18%; P = 0.0034), and caudate nucleus (33%; P = 0.0002) when assessed at 24 h post-MCA occlusion. Isradipine did not affect the functional deficit (measured using a subjective neurological scoring system) induced by MCA occlusion. In SHR undergoing transient (2 h) MCA occlusion isradipine administered 30 min post-MCA occlusion produced a significant reduction (47%; P = 0.001) in hemispheric infarct volume, whereas isradipine administered at the onset of reperfusion did not confer any significant neuroprotection. No change in functional deficit was seen with isradipine with either dosing paradigm at 24 h post-MCA occlusion. These results demonstrate that the intraluminal filament method of MCA occlusion can be used in the SHR strain and also substantiates the neuroprotective efficacy of isradipine in SHR models of permanent and transient focal cerebral ischemia.
Asunto(s)
Isquemia Encefálica/tratamiento farmacológico , Bloqueadores de los Canales de Calcio/uso terapéutico , Canales de Calcio/efectos de los fármacos , Ataque Isquémico Transitorio/tratamiento farmacológico , Isradipino/uso terapéutico , Proteínas del Tejido Nervioso/efectos de los fármacos , Fármacos Neuroprotectores/uso terapéutico , Animales , Conducta Animal , Daño Encefálico Crónico/etiología , Daño Encefálico Crónico/prevención & control , Edema Encefálico/tratamiento farmacológico , Edema Encefálico/etiología , Edema Encefálico/patología , Isquemia Encefálica/complicaciones , Isquemia Encefálica/metabolismo , Isquemia Encefálica/patología , Bloqueadores de los Canales de Calcio/administración & dosificación , Bloqueadores de los Canales de Calcio/farmacología , Canales de Calcio Tipo L , Esquema de Medicación , Evaluación Preclínica de Medicamentos , Ataque Isquémico Transitorio/complicaciones , Ataque Isquémico Transitorio/metabolismo , Ataque Isquémico Transitorio/patología , Isradipino/administración & dosificación , Isradipino/farmacología , Masculino , Fármacos Neuroprotectores/administración & dosificación , Fármacos Neuroprotectores/farmacología , Ratas , Ratas Endogámicas SHRRESUMEN
Herbal medicines are widely perceived by the public as being healthful and innocuous. A number of herbal medicines have now been linked with hepatotoxicity. We report a case of acute hepatitis associated with the use of ma-huang, a herbal product derived from plants of the Ephedra species, which is advertised as being useful for causing weight loss and enhancing energy levels. Given the lack of reports in the literature of hepatotoxicity with ma-huang and ephedrine, we speculate that the ma-huang product our patient took contained some other ingredient or contaminant or was misidentified. Our report and others in the literature, which we review, indicate that the clinician should consider herbal medicines as a possible cause of unexplained liver injury.