RESUMO
While there has been increasing support for the existence of cerebral sex differences, the mechanisms underlying these differences are unclear. Based on animal data, it has long been believed that sexual differentiation of the brain is primarily linked to organizational effects of fetal testosterone. This view is, however, in question as more recent data show the presence of sex differences before the onset of testosterone production. The present study focuses on the impact that sex chromosomes might have on these differences. Utilizing the inherent differences in sex and X-chromosome dosage among XXY males, XY males, and XX females, comparative voxel-based morphometry was conducted using sex hormones and sex chromosomes as covariates. Sex differences in the cerebellar and precentral gray matter volumes (GMV) were found to be related to X-chromosome dosage, whereas sex differences in the amygdala, the parahippocamus, and the occipital cortex were linked to testosterone levels. An increased number of sex chromosomes was associated with reduced GMV in the amygdala, caudate, and the temporal and insular cortices, with increased parietal GMV and reduced frontotemporal white matter volume. No selective, testosterone independent, effect of the Y-chromosome was detected. Based on these observations, it was hypothesized that programming of the motor cortex and parts of cerebellum is mediated by processes linked to X-escapee genes, which do not have Y-chromosome homologs, and that programming of certain limbic structures involves testosterone and X-chromosome escapee genes with Y-homologs.
Assuntos
Encéfalo/anatomia & histologia , Hormônios Esteroides Gonadais/sangue , Caracteres Sexuais , Cromossomos Sexuais/genética , Adulto , Encéfalo/patologia , Feminino , Humanos , Síndrome de Klinefelter/patologia , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
Circumferential strips of rabbit aorta were subjected to 60-second graded stretches in vitro. Before and after each stretch, the vasoconstrictor dose-responses to potassium and norepinephrine were measured. For stretch between 130 to 190% of resting length, vasoconstrictor response was progressively enhanced. However, arteries stretched 190 to 220% of resting length showed a significant fall in developed tension in response to either vasoconstrictor. Since arteries in vivo operate at 150 to 180% of resting length due to physiologic distention, it is likely that effective angioplasty does induce paralysis of vascular smooth muscle.
Assuntos
Músculo Liso Vascular/fisiologia , Norepinefrina/farmacologia , Potássio/farmacologia , Vasoconstrição/efeitos dos fármacos , Angioplastia com Balão/efeitos adversos , Animais , Aorta Abdominal/efeitos dos fármacos , Aorta Abdominal/fisiologia , Masculino , Contração Muscular/efeitos dos fármacos , Músculo Liso Vascular/efeitos dos fármacos , Coelhos , Estresse Mecânico , Fatores de TempoRESUMO
Angioplasty was performed on rabbit aortas in vivo. During balloon catheter inflations, the aortic diameters increased by 29%-75%; after deflation, there was persistent dilation of the treated segments by 11%-45%. Aortic strips removed from dilated and nondilated segments were tested for vasoconstrictor response in vitro. The vasoconstrictor response was attenuated in proportion to the effective stretch applied to the aorta in vivo. It was concluded that angioplasty can induce paralysis of smooth muscle.
Assuntos
Angioplastia com Balão , Aorta/fisiologia , Músculo Liso Vascular/fisiologia , Potássio/farmacologia , Vasoconstrição/efeitos dos fármacos , Angiografia , Animais , Técnicas In Vitro , Coelhos , VasodilataçãoAssuntos
Glicogênio/análise , Lipídeos/análise , Miocárdio/análise , Animais , Colorimetria , Matemática , Métodos , Ratos , EspectrofotometriaRESUMO
El botulismo en lactantes - enfermedad hasta hace poco desconocida - esta siendo descripta cada vez con mayor frecuencia en la medida en que se conocen mejor su epidemiologia y formas clinicas, muy peculiares en esta edad de la vida. Los primeros casos fueron registrados en 1976. A partir de esa fecha ha aumentado el numero de hallazgos comunidados desde que se reconocio la posibilidad de ocurrencia del botulismo como una toxiinfeccion,distinta de la clasica forma de intoxicacion alimentaria.Las esporas de Clostridium botulinum libres de toxicidad, llegan al intestino, donde germinan, eleborando su poderosa exotoxina, situacion que se produce con selectividad en esta etapa de la infancia. La extraordinaria abundancia de esporas de C. botulinum en los suelos de Mendoza y San Luis, la gran variedad de tipos serologicos identificados (A, B, F) y el descubrimiento del nuevo tipo G junto al subtipo Af en nuestro medio determinan la busqueda sistematica de esta patologia entre los lactantes de nuestra region. Se presenta en esta comunicacion el caso de un lactante de 3 meses de edad, con un cuadro clinico caracterizado por: constipacion, paralisis flaccida simetrica y reflejo fotomotor perezoso. Se detecto C. botulinum tipo A en heces. El presente caso confirma la existencia universal de esta patologia y constituye un alerta para su busqueda sistematica. El conocimiento acabado de su epidemiologia y clinica incrementara la frecuencia de diagnosticos