ABSTRACT Milt from Pacific herring (Clupea harengus pallasi) was extracted and purified on revers... more ABSTRACT Milt from Pacific herring (Clupea harengus pallasi) was extracted and purified on reversed-phase high-performance liquid chromatography. The fractions were radioimmunoassayed for the following free and conjugated steroids: cortisol; 17α,20β-dihydroxy-4-pregnen-3-one; 17α,20α-dihydroxy-4-pregnen-3-one; 17α,21-dihydroxy-4-pregnene-3,20-dione; 17α,20β,21-trihydroxy-4-pregnen-3-one; 17α-hydroxy-4-pregnene-3,20-dione; 3α,17α,21-trihydroxy-5β-pregnan-20-one; testosterone; 11-ketotestosterone. Fractions containing significant amounts of immunoreactive material were subjected to further purification on thin-layer chromatography. Substantial amounts of cortisol (271 ng∙g−1 of milt) and 17α,20β-dihydroxy-4-pregnen- 3-one (ca. 38 ng∙g−1 of milt) were found in the free fractions of one of the extracts. Substantial amounts of cortisol (229 ng∙g−1 of milt), 17α,20β-dihydroxy-4-pregnen-3-one (25.7 ng∙g−1 of milt), and 3a, 17α,21-trihydroxy-5β-pregnan- 20-one (13 ng∙g−1 of milt) were found in the conjugated fractions of both extracts. Levels of the other steroids (free and conjugated) ranged from undetectable (<0.1) to 5.9 ng∙g−1 of milt. The possible reasons for the differences in free steroid levels between the extracts, and the potential role of the steroids as pheromones, are discussed.
Ovaries from a female plaice (Pleuronectes platessa) that had been injected with human chorionic ... more Ovaries from a female plaice (Pleuronectes platessa) that had been injected with human chorionic gonadotrophin were incubated in vitro with 17 alpha-hydroxy[1,2,6,7-3H]progesterone. The major steroids produced by the ovaries were tentatively identified as 17 alpha,21-dihydroxy-4-pregnene-3,20di-one (11-deoxycortisol; 17,21-P), 17 alpha,21-dihydroxy-5 beta-pregnane-3,20-dione (3 alpha, 17,21-P-5 beta). A high proportion of these steroids was found in a conjugated form (sulphates or glucuronides). Radioimmunoassays were developed for 11-deoxycortisol and for 3 alpha,17,21-P-5 beta and were applied to fractions of mature male and female plaice plasmas and plaice ovarian incubates that had been separated on thin-layer chromatography. The presence of all three steroids, in vivo and in vitro, was confirmed. Particularly high amounts of conjugated 3 alpha,17,21-P-5 beta were found in the plasma of mature females (200-400 ng ml-1). The 3 alpha,17,21-P-5 beta radioimmunoassay also identified 3 alpha,17 alpha-dihydroxy-5 beta-pregnane-20-dione in all three fluids, despite the fact that this steroid was not among the radioactive incubation products of the ovary. These findings are compared with those from another flatfish, the dab (Limanda limanda), where the major gonadal steroids have been shown to be 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one and its 5 beta-pregnane (3-keto and 3 beta-hydroxyl) metabolites.
In one previous paper we reported on the identification of 11-deoxycortisol and 3 alpha,17 alpha,... more In one previous paper we reported on the identification of 11-deoxycortisol and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one in the ovaries and plasma of mature female plaice and also described the development of radioimmunoassays for these two steroids. The present paper describes temporal changes in plasma levels of the free and conjugated forms of these and of some other steroids (17 alpha,20 beta-dihydroxy-4-pregnen-3-one, 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one, 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one, 17 alpha-hydroxy-4-pregnen-3-one, testosterone, and 17 beta-oestradiol) in female plaice injected with and without human chorionic gonadotrophin (HCG). Oocyte final maturation, but not ovulation, was induced by HCG injections. Levels of most of the steroids were also elevated by the HCG injections and were significantly higher than in control fish throughout the experiment (112 hr). The two most abundant steroids were 11-deoxycortisol and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one (up to 600 ng ml-1). Only relatively small amounts of 17 alpha-hydroxy-4-pregnen-3,20-dione (less than 15 ng ml-1), 17 alpha,20 beta-dihydroxy-4-pregnen-3-one, and 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one (less than 5 ng ml-1) were found. 17 alpha,20 beta,21-Trihydroxy-4-pregnen-3-one was not present. Testosterone and 17 beta-oestradiol levels rose briefly, in response to the first of the two HCG injections, and then fell significantly. The ratio of conjugated to free steroids (except for 17 alpha-hydroxy-4-pregnene-3,20-dione and 17 beta-oestradiol) was almost always greater than 1. In the HCG-injected fish, there was a significant negative correlation between the response of 17 beta-oestradiol levels and the response of 11-deoxycortisol and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one levels. This further confirms that, as teleosts approach the time of full maturity, there is switch-over in the ovaries from predominantly C19 and C18 steroid production to predominantly C21 steroid production.
Human chorionic gonadotrophin (HCG) effectively stimulated oocyte final maturation and ovulation ... more Human chorionic gonadotrophin (HCG) effectively stimulated oocyte final maturation and ovulation in female dabs (Limanda limanda) within 5 days of injection, and this was accompanied by significant changes in blood plasma steroid levels. The steroids which showed the greatest responses to the HCG injections were the ones previously found to be the major products of the ovaries in vitro: 17 alpha-20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P) and 3 beta,17 alpha,20 alpha-trihydroxy-5 beta-pregnane (3 beta,17,20 alpha-P-5 beta). 17,20 alpha-P responded more rapidly with peak levels after 32 hr of injection (115 ng ml-1), but 3 beta,17,20 alpha-P-5 beta reached higher levels ca. 12 hr later (320 ng ml-1). Levels of both steroids were not significantly different from initial values by the time of ovulation. 17 alpha,20 beta-Dihydroxy-4-pregnen-3-one, which is likely to be the oocyte maturation-inducing steroid (MIS) in the dab, showed a significant but very variable rise in levels (between 1 and 10 ng ml-1 in individual fish). 17 alpha-Hydroxy-4-pregnene-3,20-dione levels peaked at 6 ng ml-1 between 30 and 36 hr after HCG injection. Of the other C21 steroids identified in the ovaries of teleosts, 17 alpha,20 beta-21-trihydroxy-4-pregnen-3-one could not be detected, and 17 alpha,21-dihydroxy-4-pregnene-3,20-dione (11-deoxycortisol) showed nonsignificant changes compared to the saline-injected controls. HCG caused a decrease in estradiol-17 beta levels within 24 hr, but levels then rose again to a maximum of 8.2 ng ml-1 at ovulation time, possibly caused by the presence of vitellogenic oocytes in the ovaries. Changes in testosterone levels, however, were not significantly different between HCG- and saline-injected females. The role of HCG-responsive C21 steroids in the dab is discussed.
To examine the production of steroids with potential oocyte maturation-inducing or pheromonal act... more To examine the production of steroids with potential oocyte maturation-inducing or pheromonal activity in the goldfish (Carassius auratus) we have incubated mature ovaries of this species with 17-[3H]hydroxyprogesterone. The metabolites in the unconjugated, glucuronide, and sulfate fractions were identified by chromatography, microchemical reaction, and, in most cases, crystallization to constant specific activity. A major metabolite, present in all three fractions, was tentatively identified as 5 alpha-pregnane-3 beta,7 alpha,17,20 beta-tetrol. Although 17,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) was found in only low yield (as a sulfate), the presence of the tetrol indicates that it is synthesized in high yield but very rapidly metabolized. The relative proportions of 17,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P), 11-deoxycortisol (17,21-dihydroxy-4-pregnen-3,20-dione) and 17,20 beta,21-trihydroxy-4-pregnen-3-one (17,20 beta,21-P) varied significantly between incubations and may be affected by the maturational state of the ovary or the method used to stimulate oocyte maturation. Testosterone was present predominantly as its glucuronide. Significant production of glucuronides and sulfates was observed in all incubations. Twenty-five to 30% of the radioactivity remained associated with the tissue, but the distribution of activity between the metabolites did not differ greatly from that found in the medium. These results indicate that 11-deoxycortisol and its 20 beta-reduced derivative (17,20 beta,21-P) may be significant in spawning female goldfish.
Gonadotrophin-releasing hormone (GnRH) is the main neurohormone controlling gonadotrophin release... more Gonadotrophin-releasing hormone (GnRH) is the main neurohormone controlling gonadotrophin release in all vertebrates, and in teleost fish also of growth hormone and possibly of other adenohypophyseal hormones. Over 20 GnRHs have been identified in vertebrates and protochoordates and shown to bind cognate G-protein couple receptors (GnRHR). We have searched the puffer fish, Fugu rubripes, genome sequencing database, identified five GnRHR genes and proceeded to isolate the corresponding complementary DNAs in European sea bass, Dicentrachus labrax. Phylogenetic analysis clusters the European sea bass, puffer fish and all other vertebrate receptors into two main lineages corresponding to the mammalian type I and II receptors. The fish receptors could be subdivided in two GnRHR1 (A and B) and three GnRHR2 (A, B and C) subtypes. Amino acid sequence identity within receptor subtypes varies between 70 and 90% but only 50-55% among the two main lineages in fish. All European sea bass receptor mRNAs are expressed in the anterior and mid brain, and all but one are expressed in the pituitary gland. There is differential expression of the receptors in peripheral tissues related to reproduction (gonads), chemical senses (eye and olfactory epithelium) and osmoregulation (kidney and gill). This is the first report showing five GnRH receptors in a vertebrate species and the gene expression patterns support the concept that GnRH and GnRHRs play highly diverse functional roles in the regulation of cellular functions, besides the ''classical'' role of pituitary function regulation. Figure 3 Expression of dlGnRHRs in central and peripheral tissues detected by RT-PCR and Southern blotting. Amplification of rRNA 18s was used to standardize the quantity of mRNA. M,
Stellate sturgeon (Acipenser stellatus Pallas) females from the volga river were analysed for sex... more Stellate sturgeon (Acipenser stellatus Pallas) females from the volga river were analysed for sex steroids after hormonal stimulation. The results show a significant increase of sulfated sex steroid levels in serum and coelomic fluid (CF) at final maturation (FM). It is hypothesized that the steroid metabolites could be part of a chemical communication system related to reproduction.
Stellate sturgeon (Acipenser stellatus Pallas) males from volga river treated with LH-rH-a showed... more Stellate sturgeon (Acipenser stellatus Pallas) males from volga river treated with LH-rH-a showed an increase of free, sulfated and glucuronided sex steroid levels in serum and urine at spermiation. Conjugated forms of sex steroids could act as pheromones in sturgeon.
sprouting in the hippocampus and hippocampal slice cultures of animals (Scorza et al., 2003; Thom... more sprouting in the hippocampus and hippocampal slice cultures of animals (Scorza et al., 2003; Thomas et al., 2005). Pirocarpine-treated slice cultures have been widely used as an in vitro model of morphological changes observed in epileptic brains. Pilocarpine increases the firing rate of hippocampal neurons. Recently Koyama et al. (2004) have reported enhanced mossy fiber sprouting in picrotoxin-treated hippocampus. In these studies, mossy fibers in the hippocampal dentate gyrus have been observed with Neo-Timm staining after chemical fixation of the tissue. Therefore, the time course of the morphological changes of mossy fibers induced by pilocarpine has not been examined in detail. In this study we found that the neurites of GFP transfected neurons in the rat hippocampal dentate gyrus were transiently retracted and followed by extension when pilocarpine was applied; the retraction peaked at approximately 12 h and the elongation started at approximately 24 h after the drug application. A detailed analysis of 29 cases showed that neurites retracted toward the soma along the path of the original neuritis, the neurites started to regrow after the retraction, they almost restored their original shape during regrowing processes, and often extended more than the original length.
Abstract Thanks to the International Polar Year (IPY), international programme of research and ed... more Abstract Thanks to the International Polar Year (IPY), international programme of research and education, aiming to promote collaborative research in Polar regions in 2007-08, Portugal has been proposing to play an active role in various research disciplines. The main objectives, designed by the Portuguese Committee were: improving the knowledge in polar processes, implementing the capacity to detect climate change, assessing the global warming consequences in the preservation of marine and terrestrial biodiversity, and ...
Abstract Before the International Polar Year, in Portugal polar research was conducted by a very ... more Abstract Before the International Polar Year, in Portugal polar research was conducted by a very small group of scientists integrated in foreign projects or research institutions. Portugal was not member of the Scientific Committee for Antarctic Research (SCAR), the European Polar Board (EPB), neither a subscriber of the Antarctic Treaty. In 2004 Portuguese Polar researchers considered the IPY as an opportunity to change this situation and organized the national Committee for the IPY. The objectives were ambitious: to answer the ...
Estrogen is an essential hormone for many reproductive and non-reproductive functions. The functi... more Estrogen is an essential hormone for many reproductive and non-reproductive functions. The function of estrogen in the reproductive cycle of seabream (Sparus aurata), a protandrous hermaphrodite teleost fish, is complex but it is understood to be involved in sex inversion, a process that occurs in some individuals during the second reproductive season. Estrogen action is mediated by two estrogen receptor (ER) subtypes designated alpha and beta. As a step to understanding the mechanisms of estrogen action during natural and induced sex reversal in seabream, we have isolated two cDNAs encoding distinct forms of ER homologous to mammalian ER and ER . The seabream ER clone (sbER 1), which was truncated in the A/B domain, corresponded to a variant differing in five amino acids from another recently cloned sbER . The ER clone (sbER ) encoded a protein 559 amino acids long and showed only 40% identity to sbER . Northern blot analysis of liver and ovary mRNA indicated the presence of several transcripts of the two receptor subtypes. PCR analysis showed that the two receptors differed in their expression pattern. sbER had a more restricted distribution, occurring mainly in testis, liver and heart, and sbER was present in most tissues, being more abundant in ovary, testis, liver, intestine and kidney. The presence in seabream of two ERs with several ER transcripts and their pattern of distribution are consistent with the widespread effects of estrogen in different tissues.
ABSTRACT Milt from Pacific herring (Clupea harengus pallasi) was extracted and purified on revers... more ABSTRACT Milt from Pacific herring (Clupea harengus pallasi) was extracted and purified on reversed-phase high-performance liquid chromatography. The fractions were radioimmunoassayed for the following free and conjugated steroids: cortisol; 17α,20β-dihydroxy-4-pregnen-3-one; 17α,20α-dihydroxy-4-pregnen-3-one; 17α,21-dihydroxy-4-pregnene-3,20-dione; 17α,20β,21-trihydroxy-4-pregnen-3-one; 17α-hydroxy-4-pregnene-3,20-dione; 3α,17α,21-trihydroxy-5β-pregnan-20-one; testosterone; 11-ketotestosterone. Fractions containing significant amounts of immunoreactive material were subjected to further purification on thin-layer chromatography. Substantial amounts of cortisol (271 ng∙g−1 of milt) and 17α,20β-dihydroxy-4-pregnen- 3-one (ca. 38 ng∙g−1 of milt) were found in the free fractions of one of the extracts. Substantial amounts of cortisol (229 ng∙g−1 of milt), 17α,20β-dihydroxy-4-pregnen-3-one (25.7 ng∙g−1 of milt), and 3a, 17α,21-trihydroxy-5β-pregnan- 20-one (13 ng∙g−1 of milt) were found in the conjugated fractions of both extracts. Levels of the other steroids (free and conjugated) ranged from undetectable (<0.1) to 5.9 ng∙g−1 of milt. The possible reasons for the differences in free steroid levels between the extracts, and the potential role of the steroids as pheromones, are discussed.
Ovaries from a female plaice (Pleuronectes platessa) that had been injected with human chorionic ... more Ovaries from a female plaice (Pleuronectes platessa) that had been injected with human chorionic gonadotrophin were incubated in vitro with 17 alpha-hydroxy[1,2,6,7-3H]progesterone. The major steroids produced by the ovaries were tentatively identified as 17 alpha,21-dihydroxy-4-pregnene-3,20di-one (11-deoxycortisol; 17,21-P), 17 alpha,21-dihydroxy-5 beta-pregnane-3,20-dione (3 alpha, 17,21-P-5 beta). A high proportion of these steroids was found in a conjugated form (sulphates or glucuronides). Radioimmunoassays were developed for 11-deoxycortisol and for 3 alpha,17,21-P-5 beta and were applied to fractions of mature male and female plaice plasmas and plaice ovarian incubates that had been separated on thin-layer chromatography. The presence of all three steroids, in vivo and in vitro, was confirmed. Particularly high amounts of conjugated 3 alpha,17,21-P-5 beta were found in the plasma of mature females (200-400 ng ml-1). The 3 alpha,17,21-P-5 beta radioimmunoassay also identified 3 alpha,17 alpha-dihydroxy-5 beta-pregnane-20-dione in all three fluids, despite the fact that this steroid was not among the radioactive incubation products of the ovary. These findings are compared with those from another flatfish, the dab (Limanda limanda), where the major gonadal steroids have been shown to be 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one and its 5 beta-pregnane (3-keto and 3 beta-hydroxyl) metabolites.
In one previous paper we reported on the identification of 11-deoxycortisol and 3 alpha,17 alpha,... more In one previous paper we reported on the identification of 11-deoxycortisol and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one in the ovaries and plasma of mature female plaice and also described the development of radioimmunoassays for these two steroids. The present paper describes temporal changes in plasma levels of the free and conjugated forms of these and of some other steroids (17 alpha,20 beta-dihydroxy-4-pregnen-3-one, 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one, 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one, 17 alpha-hydroxy-4-pregnen-3-one, testosterone, and 17 beta-oestradiol) in female plaice injected with and without human chorionic gonadotrophin (HCG). Oocyte final maturation, but not ovulation, was induced by HCG injections. Levels of most of the steroids were also elevated by the HCG injections and were significantly higher than in control fish throughout the experiment (112 hr). The two most abundant steroids were 11-deoxycortisol and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one (up to 600 ng ml-1). Only relatively small amounts of 17 alpha-hydroxy-4-pregnen-3,20-dione (less than 15 ng ml-1), 17 alpha,20 beta-dihydroxy-4-pregnen-3-one, and 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one (less than 5 ng ml-1) were found. 17 alpha,20 beta,21-Trihydroxy-4-pregnen-3-one was not present. Testosterone and 17 beta-oestradiol levels rose briefly, in response to the first of the two HCG injections, and then fell significantly. The ratio of conjugated to free steroids (except for 17 alpha-hydroxy-4-pregnene-3,20-dione and 17 beta-oestradiol) was almost always greater than 1. In the HCG-injected fish, there was a significant negative correlation between the response of 17 beta-oestradiol levels and the response of 11-deoxycortisol and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one levels. This further confirms that, as teleosts approach the time of full maturity, there is switch-over in the ovaries from predominantly C19 and C18 steroid production to predominantly C21 steroid production.
Human chorionic gonadotrophin (HCG) effectively stimulated oocyte final maturation and ovulation ... more Human chorionic gonadotrophin (HCG) effectively stimulated oocyte final maturation and ovulation in female dabs (Limanda limanda) within 5 days of injection, and this was accompanied by significant changes in blood plasma steroid levels. The steroids which showed the greatest responses to the HCG injections were the ones previously found to be the major products of the ovaries in vitro: 17 alpha-20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P) and 3 beta,17 alpha,20 alpha-trihydroxy-5 beta-pregnane (3 beta,17,20 alpha-P-5 beta). 17,20 alpha-P responded more rapidly with peak levels after 32 hr of injection (115 ng ml-1), but 3 beta,17,20 alpha-P-5 beta reached higher levels ca. 12 hr later (320 ng ml-1). Levels of both steroids were not significantly different from initial values by the time of ovulation. 17 alpha,20 beta-Dihydroxy-4-pregnen-3-one, which is likely to be the oocyte maturation-inducing steroid (MIS) in the dab, showed a significant but very variable rise in levels (between 1 and 10 ng ml-1 in individual fish). 17 alpha-Hydroxy-4-pregnene-3,20-dione levels peaked at 6 ng ml-1 between 30 and 36 hr after HCG injection. Of the other C21 steroids identified in the ovaries of teleosts, 17 alpha,20 beta-21-trihydroxy-4-pregnen-3-one could not be detected, and 17 alpha,21-dihydroxy-4-pregnene-3,20-dione (11-deoxycortisol) showed nonsignificant changes compared to the saline-injected controls. HCG caused a decrease in estradiol-17 beta levels within 24 hr, but levels then rose again to a maximum of 8.2 ng ml-1 at ovulation time, possibly caused by the presence of vitellogenic oocytes in the ovaries. Changes in testosterone levels, however, were not significantly different between HCG- and saline-injected females. The role of HCG-responsive C21 steroids in the dab is discussed.
To examine the production of steroids with potential oocyte maturation-inducing or pheromonal act... more To examine the production of steroids with potential oocyte maturation-inducing or pheromonal activity in the goldfish (Carassius auratus) we have incubated mature ovaries of this species with 17-[3H]hydroxyprogesterone. The metabolites in the unconjugated, glucuronide, and sulfate fractions were identified by chromatography, microchemical reaction, and, in most cases, crystallization to constant specific activity. A major metabolite, present in all three fractions, was tentatively identified as 5 alpha-pregnane-3 beta,7 alpha,17,20 beta-tetrol. Although 17,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) was found in only low yield (as a sulfate), the presence of the tetrol indicates that it is synthesized in high yield but very rapidly metabolized. The relative proportions of 17,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P), 11-deoxycortisol (17,21-dihydroxy-4-pregnen-3,20-dione) and 17,20 beta,21-trihydroxy-4-pregnen-3-one (17,20 beta,21-P) varied significantly between incubations and may be affected by the maturational state of the ovary or the method used to stimulate oocyte maturation. Testosterone was present predominantly as its glucuronide. Significant production of glucuronides and sulfates was observed in all incubations. Twenty-five to 30% of the radioactivity remained associated with the tissue, but the distribution of activity between the metabolites did not differ greatly from that found in the medium. These results indicate that 11-deoxycortisol and its 20 beta-reduced derivative (17,20 beta,21-P) may be significant in spawning female goldfish.
Gonadotrophin-releasing hormone (GnRH) is the main neurohormone controlling gonadotrophin release... more Gonadotrophin-releasing hormone (GnRH) is the main neurohormone controlling gonadotrophin release in all vertebrates, and in teleost fish also of growth hormone and possibly of other adenohypophyseal hormones. Over 20 GnRHs have been identified in vertebrates and protochoordates and shown to bind cognate G-protein couple receptors (GnRHR). We have searched the puffer fish, Fugu rubripes, genome sequencing database, identified five GnRHR genes and proceeded to isolate the corresponding complementary DNAs in European sea bass, Dicentrachus labrax. Phylogenetic analysis clusters the European sea bass, puffer fish and all other vertebrate receptors into two main lineages corresponding to the mammalian type I and II receptors. The fish receptors could be subdivided in two GnRHR1 (A and B) and three GnRHR2 (A, B and C) subtypes. Amino acid sequence identity within receptor subtypes varies between 70 and 90% but only 50-55% among the two main lineages in fish. All European sea bass receptor mRNAs are expressed in the anterior and mid brain, and all but one are expressed in the pituitary gland. There is differential expression of the receptors in peripheral tissues related to reproduction (gonads), chemical senses (eye and olfactory epithelium) and osmoregulation (kidney and gill). This is the first report showing five GnRH receptors in a vertebrate species and the gene expression patterns support the concept that GnRH and GnRHRs play highly diverse functional roles in the regulation of cellular functions, besides the ''classical'' role of pituitary function regulation. Figure 3 Expression of dlGnRHRs in central and peripheral tissues detected by RT-PCR and Southern blotting. Amplification of rRNA 18s was used to standardize the quantity of mRNA. M,
Stellate sturgeon (Acipenser stellatus Pallas) females from the volga river were analysed for sex... more Stellate sturgeon (Acipenser stellatus Pallas) females from the volga river were analysed for sex steroids after hormonal stimulation. The results show a significant increase of sulfated sex steroid levels in serum and coelomic fluid (CF) at final maturation (FM). It is hypothesized that the steroid metabolites could be part of a chemical communication system related to reproduction.
Stellate sturgeon (Acipenser stellatus Pallas) males from volga river treated with LH-rH-a showed... more Stellate sturgeon (Acipenser stellatus Pallas) males from volga river treated with LH-rH-a showed an increase of free, sulfated and glucuronided sex steroid levels in serum and urine at spermiation. Conjugated forms of sex steroids could act as pheromones in sturgeon.
sprouting in the hippocampus and hippocampal slice cultures of animals (Scorza et al., 2003; Thom... more sprouting in the hippocampus and hippocampal slice cultures of animals (Scorza et al., 2003; Thomas et al., 2005). Pirocarpine-treated slice cultures have been widely used as an in vitro model of morphological changes observed in epileptic brains. Pilocarpine increases the firing rate of hippocampal neurons. Recently Koyama et al. (2004) have reported enhanced mossy fiber sprouting in picrotoxin-treated hippocampus. In these studies, mossy fibers in the hippocampal dentate gyrus have been observed with Neo-Timm staining after chemical fixation of the tissue. Therefore, the time course of the morphological changes of mossy fibers induced by pilocarpine has not been examined in detail. In this study we found that the neurites of GFP transfected neurons in the rat hippocampal dentate gyrus were transiently retracted and followed by extension when pilocarpine was applied; the retraction peaked at approximately 12 h and the elongation started at approximately 24 h after the drug application. A detailed analysis of 29 cases showed that neurites retracted toward the soma along the path of the original neuritis, the neurites started to regrow after the retraction, they almost restored their original shape during regrowing processes, and often extended more than the original length.
Abstract Thanks to the International Polar Year (IPY), international programme of research and ed... more Abstract Thanks to the International Polar Year (IPY), international programme of research and education, aiming to promote collaborative research in Polar regions in 2007-08, Portugal has been proposing to play an active role in various research disciplines. The main objectives, designed by the Portuguese Committee were: improving the knowledge in polar processes, implementing the capacity to detect climate change, assessing the global warming consequences in the preservation of marine and terrestrial biodiversity, and ...
Abstract Before the International Polar Year, in Portugal polar research was conducted by a very ... more Abstract Before the International Polar Year, in Portugal polar research was conducted by a very small group of scientists integrated in foreign projects or research institutions. Portugal was not member of the Scientific Committee for Antarctic Research (SCAR), the European Polar Board (EPB), neither a subscriber of the Antarctic Treaty. In 2004 Portuguese Polar researchers considered the IPY as an opportunity to change this situation and organized the national Committee for the IPY. The objectives were ambitious: to answer the ...
Estrogen is an essential hormone for many reproductive and non-reproductive functions. The functi... more Estrogen is an essential hormone for many reproductive and non-reproductive functions. The function of estrogen in the reproductive cycle of seabream (Sparus aurata), a protandrous hermaphrodite teleost fish, is complex but it is understood to be involved in sex inversion, a process that occurs in some individuals during the second reproductive season. Estrogen action is mediated by two estrogen receptor (ER) subtypes designated alpha and beta. As a step to understanding the mechanisms of estrogen action during natural and induced sex reversal in seabream, we have isolated two cDNAs encoding distinct forms of ER homologous to mammalian ER and ER . The seabream ER clone (sbER 1), which was truncated in the A/B domain, corresponded to a variant differing in five amino acids from another recently cloned sbER . The ER clone (sbER ) encoded a protein 559 amino acids long and showed only 40% identity to sbER . Northern blot analysis of liver and ovary mRNA indicated the presence of several transcripts of the two receptor subtypes. PCR analysis showed that the two receptors differed in their expression pattern. sbER had a more restricted distribution, occurring mainly in testis, liver and heart, and sbER was present in most tissues, being more abundant in ovary, testis, liver, intestine and kidney. The presence in seabream of two ERs with several ER transcripts and their pattern of distribution are consistent with the widespread effects of estrogen in different tissues.
Mendonca VM, Sprung M, Castro MM, Canario A. 2011. Particle retention efficiency of a coastal eco... more Mendonca VM, Sprung M, Castro MM, Canario A. 2011. Particle retention efficiency of a coastal ecosystem in the northeastern Atlantic Ocean. Wetlands 31(6):1175-1185.
ABSTRACT: Based on filtration rates obtained in situ at several habitats (mud flats, sand flats, and seagrass beds of Cymodocea nodosa), particle retention efficiency of benthic communities was estimated at Ria Formosa, a coastal lagoon in southern Portugal. The distinct physical characteristics of the water flow (water depth, current speed) at different tidal regimes (spring tide and neap tide) were also considered. Median filtration rates ranged 5.0−45.0 l m−2 h−1, despite the lack of dense bivalve beds or reefs. Based on median filtration rates of benthic communities on the studied substrate types, a model we developed showed that seagrass bed areas retained 15% of suspended particles during spring tide and 47% during neap tide. These retention efficiencies were much higher than those observed on mud flats (2.8% during spring tide, and 8% during neap tide), sand flats of finer grain size (8.8% during spring tide, and 50% during neap tide), and sand flats of coarser grain size (7% during spring tide, and 31% during neap tide). Removal of particles from water column was higher during the ebb tide than during flow tide, with particles of <5 μm diameter (especially diatoms, flagellates, and small-sized particulate matter) being the most commonly removed.
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Papers by Adelino V M Canario
http://www.springerlink.com/content/4244817675176620/
DOI: 10.1007/s13157-011-0228-x
ABSTRACT: Based on filtration rates obtained in situ at several habitats (mud flats, sand flats, and seagrass beds of Cymodocea nodosa), particle retention efficiency of benthic communities was estimated at Ria Formosa, a coastal lagoon in southern Portugal. The distinct physical characteristics of the water flow (water depth, current speed) at different tidal regimes (spring tide and neap tide) were also considered. Median filtration rates ranged 5.0−45.0 l m−2 h−1, despite the lack of dense bivalve beds or reefs. Based on median filtration rates of benthic communities on the studied substrate types, a model we developed showed that seagrass bed areas retained 15% of suspended particles during spring tide and 47% during neap tide. These retention efficiencies were much higher than those observed on mud flats (2.8% during spring tide, and 8% during neap tide), sand flats of finer grain size (8.8% during spring tide, and 50% during neap tide), and sand flats of coarser grain size (7% during spring tide, and 31% during neap tide). Removal of particles from water column was higher during the ebb tide than during flow tide, with particles of <5 μm diameter (especially diatoms, flagellates, and small-sized particulate matter) being the most commonly removed.