Studies involving estrogen treatment of ovariectomized rats or mice have attributed to this hormone a neuroprotective effect on the substantia nigra pars compacta (SNpc) neurons. We investigated the effect of estradiol replacement in ovariectomized rats on the survival of dopaminergic mesencephalic cell and the integrity of their projections to the striatum after microinjections of 1 microg of 6-hydroxydopamine (6-OHDA) into the right SNpc or medial forebrain bundle (MFB). Estradiol replacement did not prevent the reduction either in the striatal concentrations of DA and metabolites or in the number of nigrostriatal dopaminergic neurons following lesion with 1 microg of 6-OHDA into the SNpc. Nevertheless, estradiol treatment reduced the decrease in striatal DA following injection of 1 microg of 6-OHDA into the MFB. Results suggest therefore that estrogen protect nigrostriatal dopaminergic neurons against a 6-OHDA injury to the MFB but not the SNpc. This may be due to the distinct degree of lesions promoted in these different rat models of Parkinson's disease.
Neonatal handling has long-lasting effects on behavior and stress reactivity. The purpose of the present study was to investigate the effect of neonatal handling on the number of dopaminergic neurons in the hypothalamic nuclei of adult male rats as part of a series of studies that could explain the long-lasting effects of neonatal stimulation. Two groups of Wistar rats were studied: nonhandled (pups were left undisturbed, control) and handled (pups were handled for 1 min once a day during the first 10 days of life). At 75-80 days, the males were anesthetized and the brains were processed for immunohistochemistry. An anti-tyrosine hydroxylase antibody and the avidin-biotinperoxidase method were used. Tyrosine hydroxylase-immunoreactive (TH-IR) neurons were counted bilaterally in the arcuate, paraventricular and periventricular nuclei of the hypothalamus in 30-µm sections at 120-µm intervals. Neonatal handling did not change the number of TH-IR neurons in the arcuate (1021 ± 206, N = 6; 1020 ± 150, N = 6; nonhandled and handled, respectively), paraventricular (584 ± 85, N = 8; 682 ± 62, N = 9) or periventricular (743 ± 118, N = 7; 990 ± 158, N = 7) nuclei of the hypothalamus. The absence of an effect on the number of dopaminergic cells in the hypothalamus indicates that the reduction in the amount of neurons induced by neonatal handling, as shown by other studies, is not a general phenomenon in the brain. Environmental stimuli during the neonatal period have lasting effects on emotional behavior and reactivity to stress in adult animals (1,2). Neonatal handling has been used as an experimental model to examine the mechanisms by which early environmental changes could affect neural systems, leading to stable behavioral and neuroendocrine changes (3-6). This apparently harmless procedure in infancy reduces fear in novel environments (5-7) and the secretion of corticosterone, adrenocorticotrophin and prolactin in response to stressors in adulthood (4-6). Furthermore, preliminary results from our laboratory showed that neonatal manipulation reduced the number of neurons in the medial amygdala, the prefrontal cortex (8) and the locus coeruleus (9), and decreased the number of somatostatinergic neurons in the hypothalamic periventricular nucleus
Cerro Largo -RS, Brasil. Pesquisamos as concepções de ensino e de currículo presentes nos resumos publicados na seção de Ensino de Zoologia do Congresso Brasileiro de Zoologia (CBZ), organizado pela Sociedade Brasileira de Zoologia (SBZ), entre os anos de 2004 e 2014. Os 167 trabalhos analisados inicialmente foram separados em três categorias de análise, sendo as concepções de ensino técnico, prático e emancipatório/crítico. Quando analisamos as concepções de currículo, utilizamos as concepções: tradicionais, críticas e pós-críticas. Os resultados que obtivemos referentes a concepções expressam um ensino de Zoologia 49.1% na perspectiva técnica, 31,1% concepção prática e apenas 19,8% das concepções de ensino eram emancipatório/crítico. Quanto aos resultados das concepções de currículo, o ensino de Zoologia pode ser considerado: 85% tradicional, em seguida tivemos 12,6% de concepção crítica e por fim as concepções pós-críticas com 2,4%. Também apresentamos uma análise sobre as concepções de ensino e de currículo, promovendo um diálogo com a literatura para que os leitores possam melhor compreendê-las. Concepções estão presentes na atividade docente e tem um papel muito importante ao influenciar no ensino e aprendizado. Defendemos a ideia de que as concepções docentes não sejam fixas, neutras e imutáveis, ao contrário, sejam fluentes para que possam ser transformadas e aperfeiçoadas de acordo com o contexto escolar, cabendo ao docente pensar a própria prática, em um processo flexível de açãoreflexão-ação, buscando desenvolver um ensino de excelência, contextualizado, inovador ao longo de sua carreira e desenvolvimento profissional.
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