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Changes in plasma concentrations of sex steroids were examined in male and female zebra finch chicks during the sensitive period for differentiation of sexually dimorphic brain nuclei associated with the control of song. Using a chromatographic separation procedure and radioimmunoassay, androstenedione, testosterone and 5 alpha-dihydrotestosterone were(More)
Human brain steroidogenic mechanisms, particularly aromatase, have been investigated in healthy and diseased conditions. Aromatase activity was measured in differentiated and undifferentiated neuroblastoma cell lines from mouse (TMN) and human (5H SY5Y) and in human post mortem brain samples. Neuroblastomas show much higher aromatase activity than human(More)
Estrogen formed by aromatization of testosterone (T) is involved in the activation of sexual behavior and control of the neuroendocrine system in the male Syrian hamster. Our study examined whether daylength influences formation of estrogen in the preoptic area (POA) and other neuroendocrine areas (anterior hypothalamus, AHT, and medial amygdala, MA) which(More)
Recent evidence indicates that 17beta-estradiol may have neuroprotective and neuroregenerative properties. Estradiol is formed locally in neural tissue from precursor androgens. The expression of aromatase, the enzyme that catalyses the conversion of androgens to estrogens, is restricted, under normal circumstances, to specific neuronal populations. These(More)
Oestrogens are formed from androgens in the mouse brain, but the localization of aromatase activity is unresolved. Immunocytochemistry has not detected aromatase in expected key androgen target areas such as the medial preoptic area. Using a micropunch method and a sensitive in vitro 3H2O product detection assay, we report significant aromatase activity in(More)
In vitro experiments were conducted to compare the steroid regulation of aromatase in preoptic and posterior hypothalamic areas. Kinetic analysis of aromatase activity in the preoptic area (POA) and posterior hypothalamus (AHP) of castrated and intact doves indicate that both areas have a similar, high substrate affinity (apparent Km less than 15 nM), but(More)
The effects of testosterone (T) treatment on androgen-metabolizing enzymes and especially on aromatase were examined in the developing hypothalamus of quail using an in vitro microassay. Testosterone propionate (TP) injected into the pectoral muscles of one-day-old chicks had no effect on formation of 5 alpha-dihydrotestosterone (5 alpha-DHT), 5(More)
The preoptic area (POA) of the male ring dove is a target for specific behavioral effects of estrogen that are separable from those of androgen. Activity of the aromatase system in the POA, which converts testosterone to 17 beta-estradiol (E2), is increased by systemic androgen. Using crystalline steroid implants positioned stereotaxically in the brain, we(More)
Steroid sex hormones have an organizational role in gender-specific brain development. Aromatase (cytochrome P450AR), converting testosterone (T) to estradiol-17 beta (E2) is a key enzyme in brain development and the regulation of aromatase determines the availability of E2 effective for neural differentiation. Gender differences in brain development and(More)