RESUMEN
In mammals, the central circadian oscillator is located in the suprachiasmatic nucleus (SCN). Hypothalamus-pituitary-thyroid axis components exhibit circadian oscillation, regulated by both central clock innervation and intrinsic circadian clocks in the anterior pituitary and thyroid glands. Thyroid disorders alter the rhythmicity of peripheral clocks in a tissue-dependent response; however, whether these effects are influenced by alterations in the master clock remains unknown. This study aimed to characterize the effects of hypothyroidism on the rhythmicity of SCN, body temperature (BT) and metabolism, and the possible mechanisms involved in this signalling. C57BL/6J adult male mice were divided into Control and Hypothyroid groups. Profiles of spontaneous locomotor activity (SLA), BT, oxygen consumption ( V Ì O 2 ${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ ) and respiratory quotient (RQ) were determined under free-running conditions. Clock gene expression, and neuronal activity of the SCN and medial preoptic nucleus (MPOM) area were investigated in light-dark (LD) conditions. Triiodothyronine (T3) transcriptional regulation of Bmal1 promoter activity was evaluated in GH3-transfected cells. Hypothyroidism delayed the rhythmicity of SLA and BT, and altered the expression of core clock components in the SCN. The activity of SCN neurons and their outputs were also affected, as evidenced by the loss of circadian rhythmicity in V Ì O 2 ${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ and RQ and alterations in the neuronal activity pattern of MPOM. In GH3 cells, T3 increased Bmal1 promoter activity in a time-dependent manner. Thyroid hormone may act as a temporal cue for the central circadian clock, and the uncoupling of central and peripheral clocks might contribute to a wide range of metabolic and thermoregulatory impairments observed in hypothyroidism. KEY POINTS: Hypothyroidism alters clock gene expression in the suprachiasmatic nucleus (SCN). Thyroid hypofunction alters the phase of spontaneous locomotor activity and body temperature rhythms. Thyroid hormone deficiency alters the daily pattern of SCN and medial preoptic nucleus neuronal activities. Hypothyroidism alterations are extended to daily oscillations of oxygen consumption and metabolism, which might contribute to the development of metabolic syndrome. Triiodothyronine increases Bmal1 promoter activity acting as temporal cue for the central circadian clock.
Asunto(s)
Factores de Transcripción ARNTL , Hipotiroidismo , Ratones Endogámicos C57BL , Núcleo Supraquiasmático , Triyodotironina , Animales , Masculino , Hipotiroidismo/fisiopatología , Hipotiroidismo/metabolismo , Hipotiroidismo/genética , Factores de Transcripción ARNTL/genética , Factores de Transcripción ARNTL/metabolismo , Ratones , Núcleo Supraquiasmático/metabolismo , Núcleo Supraquiasmático/fisiología , Ritmo Circadiano/fisiología , Temperatura Corporal/fisiología , Relojes Circadianos/genética , Relojes Circadianos/fisiología , Regulación de la Expresión GénicaRESUMEN
Objetivo: Avaliar o nível de conhecimento dos acadêmicos de Medicina sobre transplante e morte encefálica. Métodos: Questionário autoaplicado não identificado respondido pelos alunos do curso de Medicina do primeiro ao sexto ano, com base em informações da Associação Brasileira de Transplante de Órgãos e Tecidos, Registro Brasileiro de Transplantes e pela resolução que define os critérios para morte encefálica. Resultados: Dos 677 alunos do curso de Medicina, 310 (45,8%) concordaram em responder. Foram excluídos 22 (7,0%) pacientes. Dos que participaram, 41,3% informaram que já assistiram à aula sobre transplante de órgãos e 33% sobre morte encefálica; 9,7% se sentiram aptos a diagnosticar morte encefálica (p<0,01); apenas 66,8% responderam o rim como o órgão sólido mais transplantado no Brasil. Conclusão: O nível de conhecimento sobre morte encefálica e transplantes dos alunos de Medicina da instituição é limitado, o que pode ser resultado de uma abordagem inadequada durante o curso de Medicina. .
Objective: To evaluate the level of knowledge of medical students about transplantation and brain death. Methods: An anonymous self-administered questionnaire answered by medical students from the first through the sixth year that was based on information from the Associação Brasileira de Transplante de Órgãos e Tecidos, the Registro Brasileiro de Transplantes and the resolution that defines the criteria for brain death. Results: Of the 677 medical students asked, 310 (45.8%) agreed to answer the questionnaire. In total, 22 (7.0%) subjects were excluded. Of the students who participated, 41.3% reported having already attended a class on organ transplantation and 33% on brain death; 9.7% felt able to diagnose brain death (p<0.01); only 66.8% indicated the kidney as the most transplanted solid organ in Brazil. Conclusion: The level of knowledge of medical students at this institution regarding brain death and transplantation is limited, which may be the result of an inadequate approach during medical school. .
Asunto(s)
Adolescente , Adulto , Femenino , Humanos , Masculino , Adulto Joven , Muerte Encefálica , Conocimientos, Actitudes y Práctica en Salud , Trasplante de Órganos , Estudiantes de Medicina , Brasil , Estudios Transversales , Encuestas y Cuestionarios , Donantes de TejidosRESUMEN
OBJECTIVE: To evaluate the level of knowledge of medical students about transplantation and brain death. METHODS: An anonymous self-administered questionnaire answered by medical students from the first through the sixth year that was based on information from the Associação Brasileira de Transplante de Órgãos e Tecidos, the Registro Brasileiro de Transplantes and the resolution that defines the criteria for brain death. RESULTS: Of the 677 medical students asked, 310 (45.8%) agreed to answer the questionnaire. In total, 22 (7.0%) subjects were excluded. Of the students who participated, 41.3% reported having already attended a class on organ transplantation and 33% on brain death; 9.7% felt able to diagnose brain death (p<0.01); only 66.8% indicated the kidney as the most transplanted solid organ in Brazil. CONCLUSION: The level of knowledge of medical students at this institution regarding brain death and transplantation is limited, which may be the result of an inadequate approach during medical school.