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In the present study we hypothesize that aquaporin 4 (AQP4) expression in the chicken oviduct would change during a pause in egg laying that was induced by fasting. Accordingly, the aim of this investigation was to examine the AQP4 mRNA and protein expression, and immunolocalization in the chicken oviduct during the course of regression. The experiment was carried out on laying hens subjected to a pause in laying that was induced by food deprivation for 5 days. Control hens were fed ad libitum. The birds were sacrificed on day 6 of the experiment and all segments of the oviduct were isolated, including the infundibulum, magnum, isthmus, shell gland, and vagina. Subsequently, the gene and protein expressions of AQP4 in the tissues were tested by real-time PCR and Western blot, respectively. The relative mRNA expression of AQP4 was the highest in the infundibulum and vagina and the lowest, and least detectable, in the magnum. The level of AQP4 protein was the highest in the infundibulum and the lowest in the magnum. Fasting resulted in a decrease of the AQP4 mRNA expression (${P} < 0.001$) in the infundibulum, a decrease in protein abundance (${P} < 0.01$) in the shell gland, and an increase in protein level (${P}< 0.001$) in the vagina. Immunohistochemistry demonstrated tissue- and cell-dependent localization of AQP4 protein in the oviductal wall. The intensity of staining was as follows: the infundibulum $>$ shell gland $>$ vagina ${\ge }$ isthmus ≫ magnum. In the control hens, the immunoreactivity for AQP4 in the vagina was similar, whereas in other oviductal segments, the immunoreactivity was stronger when compared with the chickens subjected to a pause in laying. In summary, these findings suggest that the AQP4 is an essential protein involved in the regulation of water transport required to create a proper microenvironment for fertilization and egg formation in the hen oviduct.

The centrohelid heliozoan Raphidocystis contractilis has many radiating axopodia, each containing axopodial microtubules. The axopodia show rapid contraction at nearly a video rate (30 frames per second) in response to mechanical stimuli. The axopodial contraction is accompanied by cytoskeletal microtubule depolymerization, but the molecular mechanism of this phenomenon has not been elucidated. In this study, we performed de novo transcriptome sequencing of R. contractilis to identify genes involved in microtubule dynamics such as the rapid axopodial contraction. The transcriptome sequencing generated 7.15‐Gbp clean reads in total, which were assembled as 31,771 unigenes. Using the obtained gene sets, we identified several microtubule‐severing proteins which might be involved in the rapid axopodial contraction, and kinesin‐like genes that occur in gene duplication. On the other hand, some genes for microtubule motor proteins involved in the formation and motility of flagella were not found in R. contractilis, suggesting that the gene repertoire of R. contractilis reflected the morphological features of nonflagellated protists. Our transcriptome analysis provides basic information for the analysis of the molecular mechanism underlying microtubule dynamics in R. contractilis. [ABSTRACT FROM AUTHOR]

A 7-nm-thick monolayer comprising myristate-capped silver nanoparticles (AgNPs) was fabricated by first drop casting an AgNP solution on the surface of a 10–100 μl water drop placed on a solid substrate. With the natural evaporation of the water, a monolayer slowly descended onto the substrate, the latter containing an array of 2.5-μm-diameter and 200-nm-deep holes, and finally formed circular freestanding monolayers in the holes. Nanoindentation measurement based on atomic force microscopy was carried out on the circular freestanding monolayer at its center, and the extending and retracting force–indentation curves were recorded to analyze further the mechanical properties of the monolayer. The force–indentation curves were evidently nonlinear, and so a two-term continuum-mechanics theory was used to interpret the results. By fitting the force–indentation curves using a two-term equation, the prestress and Young's modulus of the freestanding AgNP monolayer were obtained as approximately 0.05 N/m and several gigapascals, respectively, which are consistent with the results reported in the literature. For comparison, we also studied the mechanical responses of AgNP monolayers and bilayers on a soft polydimethylsiloxane (PDMS) substrate by using nanoindentation. Because the AgNP monolayer was stiffer than the PDMS substrate, it was possible to measure the mechanical response of the former despite it being only 7 nm thick. The mechanical strength of the freestanding AgNP monolayers was considered to be dominated by the attractive interactions between the interdigitated hydrocarbon chains of the myristate. [ABSTRACT FROM AUTHOR]

Purpose: Stent flexibility can influence clinical outcome, especially in bifurcation lesions. For instance, an overly rigid stent can impose mechanical stress on the artery at the stent edges and alter both arterial geometry and blood flow dynamics in bifurcations. This study investigated the influence of stent flexibility on vessel geometry, histology, wall stress, and blood flow dynamics in arterial bifurcations. Materials and Methods: We compared arterial angulation, stenosis, histopathology, simulated wall shear stress (WSS), and simulated blood flow velocity distribution in swine coronary artery bifurcations following placement of the less flexible Multi-link 8 or more flexible Kaname stent (4.1 ± 0.5 vs 1.5 ± 0.1 mN, p < 0.05, t-test). Stents were implanted into six coronary artery bifurcations each using the single-stent crossover technique without side branch strut dilatation. Outcomes were examined after 28 days. Results: Implantation of both stents significantly increased site angulation (Multi-link 8: 148° ± 8° to 172° ± 2°, p < 0.05, paired t-test; Kaname: 152° ± 5° to 164° ± 4°, p < 0.05, paired t-test), but the change tended to be greater after Multi-link 8 stent implantation (24° ± 15° vs 11° ± 7°, p = 0.1, t-test), suggesting greater straightening of the bifurcation. The Multi-link 8 stent induced greater neointimal thickness than the Kaname stent (0.53 ± 0.3 mm vs 0.26 ± 0.1 mm, p < 0.05, t-test). The distribution of neointimal hyperplasia following stent implantation as revealed by longitudinal histopathology matched the distribution of WSS simulated using computational fluid dynamics (CFD). The endothelium at low WSS areas exhibited aberrant cell morphology and leukocyte adhesion. A CFD model of a curved bifurcation suggested that the region of low WSS is expanded by artery straightening. Conclusion: In bifurcated lesions, stent flexibility influences not only mechanical stress on the artery but also WSS, which may induce local neointimal hyperplasia. [ABSTRACT FROM AUTHOR]

The centrohelid Raphidocystis contractilis is a heliozoan that has many radiating axopodia, each containing a bundle of microtubules. Although the rapid contraction of the axopodia at nearly a video rate (30 frames/s) is induced by mechanical stimuli, the mechanism underlying this phenomenon in R. contractilis has not yet been elucidated. In the present study, we described for the first time an adequate immunocytochemical fixation procedure for R. contractilis and the cellular distribution of a-tubulin before and after rapid axopodial contraction. We developed a flow-through chamber equipped with a micro-syringe pump that allowed the test solution to be injected at a flow rate below the threshold required to induce rapid axopodial contraction. Next, we used this injection method for evaluating the effects of different combinations of two fixatives (paraformaldehyde or glutaraldehyde) and two buffers (phosphate buffer or PHEM) on the morphological structure of the axopodia. A low concentration of glutaraldehyde in PHEM was identified as an adequate fixative for immunocytochemistry. The distribution of a-tubulin before and after rapid axopodial contraction was examined using immunocytochemistry and confocal laser scanning fluorescence microscopy. Positive signals were initially detected along the extended axopodia from the tips to the bases and were distributed in a non-uniform manner within the axopodia. Conversely, after the induction of a rapid axopodial contraction, these positive signals accumulated in the peripheral region of the cell. These results indicated that axopodial microtubules disassemble into fragments and/ or tubulin subunits during rapid axopodial contraction. Therefore, we hypothesize that the mechanism of extremely rapid axopodial contraction accompanied by cytoskeletal microtubule degradation in R. contractilis involves microtubule-severing at multiple sites. [ABSTRACT FROM AUTHOR]

Contents: This study was designed to examine whether aquaporin 4 (AQP4) is present in the chicken oviduct, and if so, whether its expression changes during pause in laying induced by tamoxifen (TMX; oestrogen receptor modulator) treatment. The control chickens were injected with a vehicle (ethanol) and the experimental ones with TMX at a dose of 6 mg/kg of body weight. Birds were treated daily until complete cessation of egg laying. The oviductal parts, that is the infundibulum, magnum, isthmus, shell gland and vagina were isolated from hens on day 8 of the experiment, and subsequently, the gene and protein expressions of AQP4 in tissues were examined by real‐time PCR and Western blot, respectively. Immunohistochemical localization of AQP4 in the wall of the chicken oviduct was also investigated. Both mRNA and protein of AQP4 were found in all segments of the chicken oviduct. The relative expression [RQ] of AQP4 was the highest in the infundibulum and the vagina and the lowest, less detectable, in the magnum and isthmus. The pattern of AQP4 protein expression was similar to that of mRNA. Treatment of hens with TMX decreased the mRNA and protein levels of AQP4 in the oviduct. Immunohistochemistry demonstrated tissue and cell‐dependent localization of AQP4 protein in the oviductal wall. The intensity of the immunopositive reaction was as follows: the infundibulum > vagina > shell gland ≥ isthmus >˃ magnum. In the control chickens, the immunoreactivity for AQP4 in all oviductal segments was stronger compared with the TMX‐treated hens. The results obtained indicate that AQP4 takes part in the regulation of water transport required for the formation of egg in the chicken oviduct. Moreover, a relationship between oestrogen action and AQP4 gene and protein expression is suggested. [ABSTRACT FROM AUTHOR]

Abstract: Arginine vasotocin (AVT) is expressed mainly in the paraventircular and supraoptic nuclei of the hypothalamus in chicken. This peptide is known to act as an antidiuretic hormone and its gene expression is stimulated by hyperosmolality. However, the transcription factors that regulate the AVT gene expression induced by hyperosmolality are still unknown. In this study, we examined the role of hyper-tonicity enhancer binding protein (TonEBP) in the transcriptional regulation of AVT gene in chicken. TonEBP mRNA expression levels increased at 1h after salt-loading treatment in the hypothalamus. This increase preceded that in AVT and c-fos mRNA expression. Intracerebroventricular injections of TonEBP antisense oligonucleotides, before the salt-loading treatment, prevented the increase in AVT gene expression. These results, all together, suggest that the transcription factor TonEBP may be involved in the regulation of AVT genes expression in response to a hyperosmotic environment in chicken. [Copyright &y& Elsevier]

Müllerian ducts of male chickens undergo regression around day 12 of incubation, but the underlining mechanisms remain unclear. The purpose of this study was to identify factors that contribute to regression of the Müllerian duct in the chicken. We first employed annealing control primer-based RT-PCR to screen candidate genes differentially expressed in the Müllerian ducts between male and female. Four differentially expressed genes (MSX2, GAL10, VCP and PLCH1) were partially sequenced. The expression of mRNA of the latter genes and MSX1 in the male and female Müllerian ducts were compared at 7.5, 8 and 9 days of incubation using semi-quantitative RT-PCR. The results indicated that both MSX1 and MSX2 mRNA was highly expressed in the male Müllerian duct at day 9 of incubation, whereas, PLCH1 mRNA was lower in the male duct at day 9 of incubation compared to that of the female duct. Although VCP mRNA was expressed in both left and right female Müllerian ducts, no expression was detected in the male duct. Whole mount in situ hybridyzation analysis showed that the expression of MSX1 and MSX2 mRNA were localized specifically in the mesenchymal cells of the male Müllerian duct at day 9 of incubation. In contrast, VCP mRNA expression was observed in both mesenchymal and epithelial cells of the female Müllerian duct but not detected in the male duct. These results suggest that both up-regulation of MSX1 and MSX2 mRNA expression is involved in the regression of the Müllerian duct in male chicken embryo, whereas VCP expression is involved in development of the female duct. [ABSTRACT FROM AUTHOR]

Abstract: Aquaporin (AQP) 4 is a member of the AQP gene family of water-selective transport proteins. We studied the effect of water deprivation on AQP4 gene expression in chickens. The nucleotide sequence of a chicken aquaporin 4 (AQP4) cDNA that encodes a protein of 335 amino acids showed high homology to mammalian AQP4. Using Northern blotting analysis, AQP4 mRNA in chickens was observed as a band of approximately 5.5 kb in several tissues in addition to the hypothalamus, proventriculus, kidney, and breast muscle. Quantitative analysis by real-time RT-PCR analysis showed that the mRNA expression of AQP4 in the hypothalamus significantly increased after dehydration. On the other hand, the mRNA expression of AQP4 in the kidney significantly decreased after dehydration. This suggests that AQP4 may play a pivotal role in osmoregulation in the chicken brain. [Copyright &y& Elsevier]

Literature data of the amount of liquid contained per crystal w L ( L ) measured for various chemicals are correlated only with the crystal size L as: w L ( L )∝ L 4 . Using the empirical equation, an equation of purity P for crystals produced from a continuous mixed-suspension, mixed-product-removal (CMSMPR) crystallizer at steady state is successfully derived as: P = 100 \times \left( 1 - {4k \cdot G \cdot \tau \over \rho_{\rm C} \cdot k_{\rm v} + 4k \cdot G \cdot \tau} \right). [ABSTRACT FROM AUTHOR]

Background: The plasma brain natriuretic peptide (BNP) level in elderly patients is elevated, but the mechanism of this increase is not clear.Objective: To examine the relationship between left ventricular geometry and BNP levels in elderly subjects.Methods: We investigated the effects of left ventricular (LV) geometry on plasma BNP levels by measuring these levels in elderly patients with or without LV hypertrophy. Patients were classified into 4 groups based on echocardiographic data: normal geometry; concentric remodeling; eccentric hypertrophy (EH), and concentric hypertrophy (CH). The samples were analyzed for BNP and endothelin-1 (ET-1).Results: Among the 4 groups, there were no differences in plasma ET-1 levels, ejection fraction, percent fractional shortening, or indices of diastolic function. Plasma BNP levels in EH and CH were higher than those in the normal geometry and concentric remodeling groups. There was a good correlation between plasma BNP levels and the relative wall thickness in EH, and between plasma BNP levels and the posterior wall thickness in CH (r = -0.474, r = 0.396, respectively, both p < 0.05). There were also good correlations between plasma BNP levels and LV mass index (LVMI). A stepwise multiple regression analysis showed that age and LVMI were significant independent contributors to plasma BNP levels.Conclusions: These results suggest that aging, increased wall stress and the extent of cardiac hypertrophy contribute to elevated BNP levels in the elderly. [ABSTRACT FROM AUTHOR]

Background and Objective: Recently, attention has been focused on endothelin-1 (ET-1) as an indicator of atherosclerosis. However, normal levels of ET-1 are frequently found in elderly patients. We investigated the relationships between echocardiographic findings and ET-1 in 117 inpatients for rehabilitation. Methods: The patients were 34 men and 83 women, 83.4 ± 0.8 years old (mean ± SE), with the following diseases: cerebrovascular diseases (n = 83), cardiovascular diseases of New York Heart Association Class I or II (n = 57), diabetes mellitus (n = 11) and hyperlipidemia (n = 12). Ejection fraction (EF) and left ventricular mass index (LVMI) were calculated by echocardiographic studies. Results: The average ET-1 was within the normal range, but a significant positive correlation was observed between age and ET-1 (ET-1 = 1.8 ± 0.1 pg/ml, r = 0.248, p < 0.01). Moreover, plasma ET-1 was positively correlated to total cholesterol and to low density lipoprotein cholesterol in patients with a history of hypertension (n = 41, r = 0.318 and r = 0.314, both p < 0.05). Gender was not a significant factor. There was no significant difference in ET-1 between patients with mild renal dysfunction (n = 54) and patients with normal renal function (n = 63) (blood urea nitrogen = 30.9 ± 2.4 vs. 15.1 ± 0.5 mg/dl, serum creatinine = 1.03 ± 0.06 vs. 0.59 ±0.02 mg/dl, ET-1 = 1.7 ± 0.1 vs. 1.8 ± 0.1 pg/ml), or between patients with (n = 50) and without (n = 67) left ventricular hypertrophy (LVMI = 146 ± 6 vs. 83 ± 2 g/m[sup 2] , ET-1 = 1.8 ± 0.1 vs. 1.8 ± 0.1 pg/ml). There was no difference in ET-1 between patients with EF <50% (n = 27) and EF ≥50% (n = 90) (ET-1 = 1.8 ± 0.2 vs. 1.7 ± 0.1 pg/ml). Conclusion: There were no significant relationships between echocardiographic findings and ET-1 in elderly subjects without overt heart failure. However, in patients with a history of hypertension, measuring ET-1 may be useful for estimating the extent of atherosclerosis.Copyright © 1999 S.Karger AG, Basel [ABSTRACT FROM AUTHOR]

Abstract: Food intake in chickens is regulated in a manner similar to that in mammals. Corticotropin-releasing factor (CRF), which increases the plasma corticosterone concentration, plays an important role as a mediator of many appetite-suppressive peptides in the central nervous system in both species. Central administration of glucagon suppresses food intake in rats. However, the anorexigenic action of glucagon in chicks has not yet been identified. In the present study, we investigated the effects of central administration of glucagon on food intake in chicks. Intracerebroventricular administration of glucagon in chicks significantly suppressed food intake and significantly induced hyperglycemia. In contrast, peripheral administration of the same dose of glucagon did not influence food intake and plasma glucose concentration. These results suggest that glucagon functions in chicks as an appetite-suppressive peptide in the central nervous system. Intracerebroventricular administration of glucagon in chicks also significantly increased CRF mRNA expression and plasma corticosterone concentration, suggesting that CRF acts as a downstream molecule for a glucagon-induced appetite-suppressive pathway in chicks. It is likely that the induction of hyperglycemia by central administration of glucagon is involved in its anorexigenic action, because peripheral administration of glucose in chicks suppressed food intake. These results suggest that CRF- and/or hyperglycemia-mediated pathways are involved in the anorexigenic action of glucagon in chicks. [Copyright &y& Elsevier]

Although asymmetric development of the ovary and the oviduct is a unique characteristic in birds, the mechanism of asymmetric development still remains unclear. Recently, degradation of extracellular matrix has been suggested as an important factor related to the regression of the Müllerian duct in mammals. The present study was conducted to examine a possible role of metalloproteinase-2 (MMP-2) in the regression of the right Müllerian duct in the developing chicken embryo. Morphological changes in the Müllerian ducts were studied on day 15 of incubation and mRNA expresseion of MMP-2 was studied on days 12, 15, and 18 of incubation. Morphological observation demonstrated the disappearance of basement membrane in the right Müllerian duct which undergoes the regression. RT-PCR analysis showed that MMP-2 mRNA expression of the right Müllerian duct increased on days 15 and 18 of incubation coincidently with the time of regression. In the right Müllerian duct, regression was prevented by diethylstilbestrol treatment on day 4 of incubation and a coincident decrease in MMP-2 expression was observed when compared to the control group. These results suggest that MMP-2 may be involved in the regression of the right Müllerian duct in the female embryos of the chicken. [Copyright &y& Elsevier]

We report the cloning of a chicken Transformer 2 (Tra 2) cDNA that encodes a protein of 289 amino acids which are 97.9% identical to those of mammalian splicing factor, Tra 2. Tra 2 mRNA was expressed in chicken embryonic tissues and was observed as a band of 1.5 kb by Northern blot analysis. Whole mount in situ hybridization showed an mRNA expression of Tra 2 in telencephalon, mandible, hyoid arch, wing and leg buds as early as day 3.5 of incubation. These results suggest that the Tra 2 gene may play a role in organogenesis in the chicken embryo. [Copyright &y& Elsevier]

The bed nucleus of the stria terminalis pars medialis (BSTM), medial preoptic nucleus (POM), and lateral septal region (LS) exhibit more vasotocin-immunoreactive (VT-ir) neural structures in male than in female adult quail. VT-ir cells and fibers in these regions are sensitive to gonadal steroids only in males. The insensitivity of adult female VT-ir neural structures to sex steroids is attributed to estradiol exposure during a critical period in embryonic life. Although the VT-ir system has been intensively examined in adult quail, information is limited in embryos and juveniles. Therefore, we herein investigated the development of VT-immunoreactive neural structures from embryonic day (E) 9 to adulthood with a particular focus on the BSTM, POM and LS of both sexes. VT-ir neural structures were more evident in female than in male embryos from E9 (BSTM and POM) and E11 (LS). This sex difference disappeared between E15 and post-hatch day 1 in the BSTM and POM, and during the first week of life in the LS. Male-biased sex differences in VT-ir structures appeared at puberty. Female-biased sexual dimorphism in the density of the VT-ir structures of BSTM was reflected by the stronger expression of VT mRNA in females than in males. However, the density of VT mRNA somata was comparable in the two sexes. The exposure of male embryos to estradiol resulted in the feminization of VT-ir neural structures in the BSTM, but not in the POM or LS at E11. Collectively, these results suggest that sex differences in VT-ir neural structures changes drastically throughout quail life. In embryos, endogenous estradiol may stimulate the expression of VT in females, resulting in a robust sex difference in VT-ir cells and fibers in favor of this sex. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the mechanism underlying central glucagon-induced hyperglycemia and anorexia in chicks. Male 8-day-old chicks (Gallus gallus) were used in all experiments. Intracerebroventricular administration of glucagon in chicks induced hyperglycemia and anorexia from 30min after administration. However, the plasma insulin level did not increase until 90min after glucagon administration, suggesting that glucose-stimulated insulin secretion from pancreatic beta cells may be suppressed by central glucagon. The plasma corticosterone concentration significantly increased from 30min to 120min after administration, suggesting that central glucagon activates the hypothalamic pituitary adrenal (HPA) axis in chicks. However, central administration of corticotropin-releasing factor (CRF), which activates the HPA axis in chicken hypothalamus, significantly reduced not only food intake but also plasma glucose concentration, suggesting that CRF and the activation of the HPA axis are related to the glucagon-induced anorexia but not hyperglycemia in chicks. Phentolamine, an α-adrenergic receptor antagonist, significantly attenuated the glucagon-induced hyperglycemia, suggesting that glucagon induced hyperglycemia at least partly via α-adrenergic neural pathway. Co-administration of phentolamine and α-helical CRF, a CRF receptor antagonist, significantly attenuated glucagon-induced hyperglycemia and anorexia. It is therefore likely that central administration of glucagon suppresses food intake at least partly via CRF-induced anorexigenic pathway in chicks. [Copyright &y& Elsevier]

Abstract: The biochemical properties, neuroanatomical location, and function of aromatase (ARO), the enzyme that converts testosterone to 17β-estradiol, have been studied extensively in the adult quail brain. Conversely, very little is known about ARO in quail embryos. This study investigated the distribution of ARO in quail prosencephalon at embryonic days (E) 9, 11, and 15 by immunocytochemistry. ARO-immunoreactive cells were observed within the walls of the cerebral ventricles, the ventral striatum, medial preoptic nucleus (POM), medial part of the bed nucleus of the stria terminalis (BSTM), lateral part of the BST, and in the tuberal region. The BSTM and to a lesser extent the POM showed transient, female-biased sex-differences. In the BSTM, the number of the ARO-immunoreactive cells, the fractional area covered by ARO-immunoreactive structures, and the overall extension of ARO-immunoreactivity were greater in females at E9 and E11, but these differences largely disappeared at E15 and post-hatch day 1. The sex differences were confirmed at the transcriptional level by in situ hybridization. In the lateral part of the POM, females showed slightly more ARO-immunoreactivity than males at E11. Treatment of E9 male embryos with estradiol completely feminized ARO-immunoreactivity at E11. The origins and the functional significance of these sex differences remain unknown. [Copyright &y& Elsevier]

Abstract: Brain can synthesize steroids de novo from cholesterol and this biochemical feature is a conserved property of vertebrates. There is growing evidence indicating that neurosteroids might participate in sexual differentiation of the brain. Therefore, in this study we investigated the presence, the sex differences, and the development-dependent variation of mRNAs coding for key neurosteroidogenic enzymes, namely cytochrome P450 side-chain cleavage enzyme (P450scc), 3β-hydroxysteroid-dehydrogenase/Δ5-Δ4-isomerase (3β-HSD), cytochrome P450 17α-hydroxylase/c17, 20-lyase (P450c17), and aromatase in embryonic prosencephali. Our results indicated that 3β-HSD mRNA levels were sexually dimorphic and developmental age-dependent. In particular, 3β-HSD mRNA levels were higher in females than in males at E7, whereas, this dimorphism was reversed at E9 and E15. In females, the relative levels of 3β-HSD mRNA were highest at E7, whereas, in males they were significantly higher at E9 and E15 than at E7 and at E11. This sexual dimorphism was a peculiar feature of the prosencephalon, it could not be observed before gonadal sexual differentiation and it was not paralleled by a dimorphism in the brain content of progesterone. The level of mRNA coding for P450scc and for P450c17 did not show obvious developmental- or sex-related variation. Aromatase mRNA varied as a function of the embryonic age but not of the sex. These results, taken together, are suggestive of a potential role of some neurosteroidogenic enzymes in the development of quail brain and suggest that sexual differences in the hormonal environment may occur during brain development. [Copyright &y& Elsevier]