Luis Valladares - Academia.edu (original) (raw)
Papers by Luis Valladares
Journal of Steroid Biochemistry, 1974
The fate of [3H]-testosterone in female rat bone marrow cells has been studied. The hormone is ta... more The fate of [3H]-testosterone in female rat bone marrow cells has been studied. The hormone is taken up by.the cytosol and nuclear fractions to a different extent, the nucleus taking up the larger amount of the hormone. Receptor proteins have not hccn detected in the cytosol and the free hormone is transported from cytoplasm to nucleus, where it becomes bound to a soluble nuclear receptor. The hormone-nuclear soluble receptor complex is then bound to chromatin components in a process that seems to be hormone and tissue specific.
Revista médica de Chile, 1999
We report a 16 year old girl presenting with secondary amenorrhea, a history of voice coarsening,... more We report a 16 year old girl presenting with secondary amenorrhea, a history of voice coarsening, hirsutism and a body mass index of 35 kg/m2. Pelvic ultrasound and CT scans showed a retro uterine dense mass. She was operated and a left ovarian tumor was excised. Pathological examination disclosed a Sertoli-Leydig tumor.
Revista médica de Chile, 1984
Pediatric Research, Oct 1, 1990
1 1 R o m a l d i n i J .H. D e p t o f ! 3 n d o c r i n o l o g y and N e o n a t o l o g y , H... more 1 1 R o m a l d i n i J .H. D e p t o f ! 3 n d o c r i n o l o g y and N e o n a t o l o g y , HSPE-IAMSPE, CP 8R0, S a o P a u l o , B r a s i l . d h o rmone r e p l a c e m e n t . O u r s c r e e n i n g p r o g r a m f o r c o n g e n i t a l h y p ot h y r o i d i s m e v a l u a t e d 4 , 4 5 n e w b o r n s w i t h s i m u l t a n e o u s d e t e r m i n at i o n s o f TSH a n d T 4 i n t h e u m b i l i c a l c o r d b l o o d a f t e r immediate c l a m p i n g . N e w b o r n s p r e s e n t i n g TSH c o n c e n t r a r i o n s h i g h e r than 40 u U / m l ( n = 38; 0.7%) H e r e r e c a l l e d . I n i l l i s g r o u p , 9 o u t o f t h e m ( 0 . 8 ) h a d TSH v a l u e s a b o v e 60 u U / m l .
Revista médica de Chile, 2003
Human diet contains a series of bioactive vegetal compounds that can improve human health. Among ... more Human diet contains a series of bioactive vegetal compounds that can improve human health. Among these, there has been a special interest for phytoestrogens. This article reviews the evidence about the potential benefits of phytoestrogens for human health. Forty eight manuscripts were selected for their study design and relevance to human health. The cell growth inhibitory effects of phytoestrogens and their implication in breast cancer are reviewed. Also the effects of these compounds on serum lipid levels and the effectiveness of a phytoestrogen derivate, ipriflavone, on the prevention of osteoporosis are analyzed. Although these compounds have a great potential for improving health, there is still not enough evidence to recommend the routine use of phytoestrogens.
Revista chilena de pediatría, 1995
Premature thelarche: evidence of increased serum total estrogenic activity Hormone profile end pe... more Premature thelarche: evidence of increased serum total estrogenic activity Hormone profile end pelvic ultrasonography were studied in 41 girls with premature thelarche aged 21 .2 ± 9.7 months and in 39 non affected conrrol girls of the same age and social status. Estrogenic contaminants were looked for both in girls sera and in poultry samples through serum and tissue levels of zearalenone and diethilbestrol. Total estrogenic activity was measured by radioreceptor assay. Basal serum levels or LH, FSH, prolactine and estradiol [E2] were not different between both groups. Total estrogenic activity was significantly higher in girls with thelarche [201 ± 102 vs 78 ± 20 pg E2 eauivalent), turning later to sim'lar levels than in controls in five patients in which thelarche eventually subsided. After LHRH greater FSH than LH peak response was observed (28.7 ± 1 7.5 Up/ml vs 5, ~; ± 2.7 Uu/m!|. No differences were detected in uterine size and squeletal maturation, but a greater mean ovarian volume was seen in patients with thelarquia. No estrogenic contaminants v/ere detected in poultry samples. Partial activation of ihe hypothalamus-pituitary-axis, mainly through FSH secretion, might thus be the responsible of ovarian secretion of E2 or another substance w ; tn estrogenic action.
Advances in experimental medicine and biology, 2008
A stable cyclized 9-mer peptide (cP) containing the active site of alpha-alpha fetoprotein (alpha... more A stable cyclized 9-mer peptide (cP) containing the active site of alpha-alpha fetoprotein (alphaFP) has been shown to be effective for prevention of estrogen-stimulated tumor cell proliferation in culture or of xenographt growth in immunodeficient mice. cP does not block 17beta-estradiol (E2) binding to its receptors, but rather appears to interfere with intracellular processing of the signal that supports growth. To obtain insight on that mechanism we studied the effect of cP on the proliferation of MCF-7 cells in culture. Proliferation in the presence of 2 microM E2 is decreased up to 40% upon addition of 2 microg ml(-1) cP to the medium; the presence of cP did not increase cell death, cP reduced also the proliferation of estrogen-dependent ZR75-1 cells but had no effect on autonomous MDA-MB-231 cells, cP did not modify the number of binding sites for labeled E2 or affected cell death. We detected increased nuclear p21Cip1 immunoreactivity after cP treatment. Our results suggest ...
Thrombosis Research, 2009
Introduction: Several dietary intervention studies examining the health effect of soy isoflavones... more Introduction: Several dietary intervention studies examining the health effect of soy isoflavones allude to the importance of equol in establishing the cardiovascular response to soy protein. Although, the specific mechanism by which this action occurs has not been established. The aim of this study was to investigate the inhibitory effect of soy-isoflavones and the metabolite of daidzein, equol, on agonist-induced platelet responses dependent on thromboxane A 2 (TxA 2) receptor. Material and methods: Competitive radioligand binding assay was used to screen for affinity of these compounds to the TxA 2 receptor. The effect of equol on platelet activation, evaluate through of release of the ATP, by analogs of TxA 2 was analyzed. The effect of equol on platelet aggregation was investigated with ADP, U46619 (a TxA 2 mimic) and the calcium ionophore A23187. Results: The data showed that aglycone isoflavones and equol bind to TxA 2 receptor in the µmol/L range, whereas their glucoside derivates had very low binding activity for this receptor. Under equilibrium conditions, the following order of the relative affinity in inhibiting [ 3 H]-SQ29585 binding was: equol N genistein N daidzein N glycitein ≫ genistin, daidzin, glycitin. Equol interaction was reversible and competitive for labeled-SQ29548 with not apparent decrease in the number of TxA 2 binding sites. In addition, from platelet activation studies, equol effectively inhibited ATP secretion elicited by the TxA 2 analog U46619. On the other hand, equol inhibited the platelet aggregation induced by U46619 and A23187, while it failed to inhibit that induced by ADP. Conclusions: The aglycone isoflavones from soy, and particularly equol, have been found to have biological effects attributable to thromboxane A 2 receptor antagonism. These findings may help elucidate how dietary isoflavone modulate platelet function and explain why soy-rich foods are claimed to have beneficial effects in the prevention of thrombotic events.
Neuroscience Letters, 2004
Systemically administered melatonin has been reported to produce antinociception and to inhibit s... more Systemically administered melatonin has been reported to produce antinociception and to inhibit spinal nociceptive transmission in rats. The present study was designed to investigate in anesthetized rats (i) whether intrathecally administered melatonin can depress synaptic potentiation (wind-up) in the spinal cord, and (ii) whether this effect is prevented by intrathecal (i.t.) administration of the MT2 receptor antagonist luzindole. Results showed that melatonin i.t. (10, 30 and 90 microg) induced dose-dependent inhibition of wind-up activity (ED50=52.06 microg i.t.), an effect that was prevented by 100 microg i.t. of luzindole. Since wind-up is dependent on NMDA receptor activation, the results suggest that melatonin can interfere with the NMDA-mediated glutamatergic component of pain transmission in rat spinal cord by acting on MT2 receptors.
Neuroreport, 2002
Melatonin has been shown to exert potent antinociception but the sites and mechanisms of action u... more Melatonin has been shown to exert potent antinociception but the sites and mechanisms of action underlying this effect have not yet been clarified. The effect of melatonin on spinal cord nociceptive transmission was studied in rats by assessing wid-up activity in a C-fiber reflex responses paradigm evoked by repetitive (0.6 Hz) electric stimulation. Intraperitoneal administration of 1.25, 2.5, 5.0 and 10.0 mg/kg melatonin induced a dose-dependent inhibition of spinal wind-up activity, the higher dose of the drug used being able to depress completely the C reflex gain. Results indicate that melatonin markedly depresses spinal wind-up in rats, probably through hyperpolarization of dorsal horn neurons consecutive to melatonin binding to membrane receptors, and/or via intracellular interference with a NMDA receptor-dependent nitric oxide generating pathway.
Journal of Endocrinological Investigation, 1992
The present study was performed to determine the in vitra steroidogenic capacity of a gonadal sam... more The present study was performed to determine the in vitra steroidogenic capacity of a gonadal sam pie from a patient suffering from a complete androgen resistance syndrome. Testosterone and estradiol production by the testicular tissue from this patient as weil as gonadotropin binding to a membrane fraction prepared from this tissue were measured. hCG bound with high affinity but with a
Evolution & Development, 2005
Summary DNA methylation is one of the epigenetic and hereditary mechanisms regulating genetic exp... more Summary DNA methylation is one of the epigenetic and hereditary mechanisms regulating genetic expression in mammalian cells. In this review, we propose how certain natural agents, through their dietary consumption, could induce changes in physiological aspects in mammalian mothers, leading to alterations in DNA methylation patterns of the developing fetus and to the emergence of new phenotypes and evolutionary change. Nevertheless, we hypothesize that this process would require (i) certain key periods in the ontogeny of the organism where the environmental stimuli could produce effects, (ii) particular environmental agents as such stimuli, and (iii) that a genomic persistent change be consequently produced in a population. Depending on the persistence of the environmental stimuli and on whether the affected genes are imprinted genes, induced changes in DNA methylation patterns could become persistent. Moreover, some fragments could be more frequently methylated than others over seve...
Brain Research Bulletin, 2010
-Adrenergic receptor stimulation can significantly facilitate synaptic potentiation in the hippo... more -Adrenergic receptor stimulation can significantly facilitate synaptic potentiation in the hippocampus and enhance memory processes, but its effect on neocortical plastic mechanisms is less conclusive. In the present study we determined the effect of propranolol, a -adrenoceptor antagonist, on long-term potentiation (LTP) induced in vivo in rat occipital cortex by tetanizing stimulation of corpus callosum and observed a dose-dependent inhibition of LTP. We further administered propranolol through mini-osmotic pumps during 3 days, and observed the performance of rats in a complex operant conditioning learning paradigm and assessed the expression of brain-derived neurotrophic factor (BDNF) in the occipital cortex. Propranolol exposure depressed both the number of reinforced responses in the operant conditioning task and BDNF expression in occipital cortex. Taken together, our results suggest that propranolol impairs memory formation by inhibiting cortical LTP induction and associated BDNF expression.
Latin American Journal of Aquatic Research, 2017
A detailed study of gametes development and characterization of plasma sex steroid hormones durin... more A detailed study of gametes development and characterization of plasma sex steroid hormones during the maturation cycle was performed for the first time in the southern hake (Merluccius australis). Fish were caught in the inland waters of the Reloncaví Sound, Interior Sea of Chiloé, Chile. Samples of gonads and blood were collected for histology and sex steroid hormone (17 β-estradiol, 11-ketotestosterone and 17,20 βdihydroxy-4-pregnen-3-one) analysis, respectively. Sex steroid hormone quantification was performed using enzyme-immunoassay (ELISA). Results showed that M. australis males and females have asynchronous development of testicles and ovaries, in all stages of maturation. Most spawning fish were found during the spring months. Regarding the sex steroid hormones, serological fluctuations of 17 β-estradiol and 11- ketotestosterone were found during gonadal maturation of M. australis. These hormones are the main hormones responsible for vitelogenesis and spermatogenesis proces...
International Journal of Medical and Surgical Sciences, 2018
Journal of Steroid Biochemistry, 1986
In order to characterize the effects of androgens and anabolics on muscle, a tissue culture syste... more In order to characterize the effects of androgens and anabolics on muscle, a tissue culture system has been established which allows exact control of experimental conditions and therefore does not suffer from disadvantages present in other systems, i.e. animal models. Myoblasts derived from fetal and neonatal rat muscles undergo functional alterations in monolayer cultures which are similar to those observed in vivo, including withdrawal from the cell cycle and subsequent fusion to form multinucleate rnFt= capable of contraction. Therefore, using this system it is possible to study the influence of androgens and anabolics on proliferation and differentiation of myoblasts as well as metabolism of mature myotubes. Furthermore, the system allows for evaluation of the effects of these compounds on "atrophic" muscle, e.g. reduction of muscle mass induced by glucocorticoids or tetrodotoxin, or "trained" muscle when coupled with electrical stimulation of the cultures. Proliferation is evaluated using 'H-thymidine incorporation and cell counts. Morphological observation and measurement of lactate dyhydrogenase and creatine kinase serve to define the time course of differentiation. Effects on mature myotubes are determined at varying time intervals by measurement of amino acid and glucose transport, protein synthesis, enzymes of energy metabolism and myosin synthesis.
Revista chilena de pediatría, 1995
Premature thelarche was looked for among 460 healthy girls of different socioeconomic level (SEL]... more Premature thelarche was looked for among 460 healthy girls of different socioeconomic level (SEL], aged 6 to 36 months. Sixty five girls (14.1%) had palpable, diameter 10 mm or more, breast tissue. No significant difference was observed in the prevalence of palpable breast tissue between girls of different socioeconomic levels. Fixty three girls with prernalure thelarche, who had never been given hormones, were compared to fourty seven girls without premature thelarche and their corresponding mothers were asked to answer a written questionare. No significant differences were found in evolution of pregnancy, delivery, neonatal period, medical history or nutrition between patients and controls. In 26 cases premature thelarche represented persistence of neonatal thelarche up to the time of the study. Growth and bone age of patients were appropriate for chronological age. Breast tissue size decreased in 21 {75%}, disappeared in 5 |18%) and increased without other signs of puberty in 2 (7%) of 28 patients who were followed up 5 to 15 months. Premature thelarche is a benign condition that tends to improve spontaneously, not apparently related to hormonal contamination of food, although it is rot possible to exclude other environmental agents. It probably represents a variant form of normal development in youngs females.
Steroids, 2000
In previous reports we have demonstrated high plasma levels of sex hormone-binding globulin (SHBG... more In previous reports we have demonstrated high plasma levels of sex hormone-binding globulin (SHBG) in asymptomatic alcoholic men. In the present work the physicochemical properties of SHBG from plasma of noncirrhotic alcoholic patients have been further compared with SHBG of control subjects. Steroid binding to SHBG was similar for the two groups: alcoholic men, K d of 0.62 Ϯ 0.07 nM and control individuals, K d of 0.70 Ϯ 0.10 nM. The structure of oligosaccharides attached to SHBG from controls and alcoholic men were determined by using serial chromatography. Our data indicated that 7% of SHBG of control individuals was not retarded by the Con-A column, whereas ϳ30% of SHBG of alcoholic men eluted in the void volume of Con A. Approximately 46% of SHBG of alcoholics applied to Con A, possessed biantennary complex oligosaccharides, as indicated by the fact that it could be eluted with methyl-␣-D-glucopyranoside and by its retention on wheat germ agglutinin; in contrast, when SHBG from control men was analyzed, ϳ51% was eluted with methyl-␣-Dglucopyranoside. Approximately 9% of the biantennary complex oligosaccharides on SHBG of control men and none of those on SHBG from alcoholic men were fucosylated on the chitobiose core, as determined by chromatography on Lenn culinaris lectin. Galactosylated oligosaccharides were also present on the SHBG fraction as indicated by its interaction with Ricinus communis-I. Approximately 24% of SHBG of alcoholic men and 39% of those on SHBG from control individuals applied to Con-A were retained and could be eluted with methyl-␣-D-mannopyranoside. Evidence based on the binding on mannoside-eluted SHBG to Con-A, wheat germ agglutinin, and R. communis-I indicated that at least the SHBG in this fraction, from alcoholics or controls, contained two glycosylation sites and that the sites were differentially glycosylated.
Journal of Steroid Biochemistry, 1974
The fate of [3H]-testosterone in female rat bone marrow cells has been studied. The hormone is ta... more The fate of [3H]-testosterone in female rat bone marrow cells has been studied. The hormone is taken up by.the cytosol and nuclear fractions to a different extent, the nucleus taking up the larger amount of the hormone. Receptor proteins have not hccn detected in the cytosol and the free hormone is transported from cytoplasm to nucleus, where it becomes bound to a soluble nuclear receptor. The hormone-nuclear soluble receptor complex is then bound to chromatin components in a process that seems to be hormone and tissue specific.
Revista médica de Chile, 1999
We report a 16 year old girl presenting with secondary amenorrhea, a history of voice coarsening,... more We report a 16 year old girl presenting with secondary amenorrhea, a history of voice coarsening, hirsutism and a body mass index of 35 kg/m2. Pelvic ultrasound and CT scans showed a retro uterine dense mass. She was operated and a left ovarian tumor was excised. Pathological examination disclosed a Sertoli-Leydig tumor.
Revista médica de Chile, 1984
Pediatric Research, Oct 1, 1990
1 1 R o m a l d i n i J .H. D e p t o f ! 3 n d o c r i n o l o g y and N e o n a t o l o g y , H... more 1 1 R o m a l d i n i J .H. D e p t o f ! 3 n d o c r i n o l o g y and N e o n a t o l o g y , HSPE-IAMSPE, CP 8R0, S a o P a u l o , B r a s i l . d h o rmone r e p l a c e m e n t . O u r s c r e e n i n g p r o g r a m f o r c o n g e n i t a l h y p ot h y r o i d i s m e v a l u a t e d 4 , 4 5 n e w b o r n s w i t h s i m u l t a n e o u s d e t e r m i n at i o n s o f TSH a n d T 4 i n t h e u m b i l i c a l c o r d b l o o d a f t e r immediate c l a m p i n g . N e w b o r n s p r e s e n t i n g TSH c o n c e n t r a r i o n s h i g h e r than 40 u U / m l ( n = 38; 0.7%) H e r e r e c a l l e d . I n i l l i s g r o u p , 9 o u t o f t h e m ( 0 . 8 ) h a d TSH v a l u e s a b o v e 60 u U / m l .
Revista médica de Chile, 2003
Human diet contains a series of bioactive vegetal compounds that can improve human health. Among ... more Human diet contains a series of bioactive vegetal compounds that can improve human health. Among these, there has been a special interest for phytoestrogens. This article reviews the evidence about the potential benefits of phytoestrogens for human health. Forty eight manuscripts were selected for their study design and relevance to human health. The cell growth inhibitory effects of phytoestrogens and their implication in breast cancer are reviewed. Also the effects of these compounds on serum lipid levels and the effectiveness of a phytoestrogen derivate, ipriflavone, on the prevention of osteoporosis are analyzed. Although these compounds have a great potential for improving health, there is still not enough evidence to recommend the routine use of phytoestrogens.
Revista chilena de pediatría, 1995
Premature thelarche: evidence of increased serum total estrogenic activity Hormone profile end pe... more Premature thelarche: evidence of increased serum total estrogenic activity Hormone profile end pelvic ultrasonography were studied in 41 girls with premature thelarche aged 21 .2 ± 9.7 months and in 39 non affected conrrol girls of the same age and social status. Estrogenic contaminants were looked for both in girls sera and in poultry samples through serum and tissue levels of zearalenone and diethilbestrol. Total estrogenic activity was measured by radioreceptor assay. Basal serum levels or LH, FSH, prolactine and estradiol [E2] were not different between both groups. Total estrogenic activity was significantly higher in girls with thelarche [201 ± 102 vs 78 ± 20 pg E2 eauivalent), turning later to sim'lar levels than in controls in five patients in which thelarche eventually subsided. After LHRH greater FSH than LH peak response was observed (28.7 ± 1 7.5 Up/ml vs 5, ~; ± 2.7 Uu/m!|. No differences were detected in uterine size and squeletal maturation, but a greater mean ovarian volume was seen in patients with thelarquia. No estrogenic contaminants v/ere detected in poultry samples. Partial activation of ihe hypothalamus-pituitary-axis, mainly through FSH secretion, might thus be the responsible of ovarian secretion of E2 or another substance w ; tn estrogenic action.
Advances in experimental medicine and biology, 2008
A stable cyclized 9-mer peptide (cP) containing the active site of alpha-alpha fetoprotein (alpha... more A stable cyclized 9-mer peptide (cP) containing the active site of alpha-alpha fetoprotein (alphaFP) has been shown to be effective for prevention of estrogen-stimulated tumor cell proliferation in culture or of xenographt growth in immunodeficient mice. cP does not block 17beta-estradiol (E2) binding to its receptors, but rather appears to interfere with intracellular processing of the signal that supports growth. To obtain insight on that mechanism we studied the effect of cP on the proliferation of MCF-7 cells in culture. Proliferation in the presence of 2 microM E2 is decreased up to 40% upon addition of 2 microg ml(-1) cP to the medium; the presence of cP did not increase cell death, cP reduced also the proliferation of estrogen-dependent ZR75-1 cells but had no effect on autonomous MDA-MB-231 cells, cP did not modify the number of binding sites for labeled E2 or affected cell death. We detected increased nuclear p21Cip1 immunoreactivity after cP treatment. Our results suggest ...
Thrombosis Research, 2009
Introduction: Several dietary intervention studies examining the health effect of soy isoflavones... more Introduction: Several dietary intervention studies examining the health effect of soy isoflavones allude to the importance of equol in establishing the cardiovascular response to soy protein. Although, the specific mechanism by which this action occurs has not been established. The aim of this study was to investigate the inhibitory effect of soy-isoflavones and the metabolite of daidzein, equol, on agonist-induced platelet responses dependent on thromboxane A 2 (TxA 2) receptor. Material and methods: Competitive radioligand binding assay was used to screen for affinity of these compounds to the TxA 2 receptor. The effect of equol on platelet activation, evaluate through of release of the ATP, by analogs of TxA 2 was analyzed. The effect of equol on platelet aggregation was investigated with ADP, U46619 (a TxA 2 mimic) and the calcium ionophore A23187. Results: The data showed that aglycone isoflavones and equol bind to TxA 2 receptor in the µmol/L range, whereas their glucoside derivates had very low binding activity for this receptor. Under equilibrium conditions, the following order of the relative affinity in inhibiting [ 3 H]-SQ29585 binding was: equol N genistein N daidzein N glycitein ≫ genistin, daidzin, glycitin. Equol interaction was reversible and competitive for labeled-SQ29548 with not apparent decrease in the number of TxA 2 binding sites. In addition, from platelet activation studies, equol effectively inhibited ATP secretion elicited by the TxA 2 analog U46619. On the other hand, equol inhibited the platelet aggregation induced by U46619 and A23187, while it failed to inhibit that induced by ADP. Conclusions: The aglycone isoflavones from soy, and particularly equol, have been found to have biological effects attributable to thromboxane A 2 receptor antagonism. These findings may help elucidate how dietary isoflavone modulate platelet function and explain why soy-rich foods are claimed to have beneficial effects in the prevention of thrombotic events.
Neuroscience Letters, 2004
Systemically administered melatonin has been reported to produce antinociception and to inhibit s... more Systemically administered melatonin has been reported to produce antinociception and to inhibit spinal nociceptive transmission in rats. The present study was designed to investigate in anesthetized rats (i) whether intrathecally administered melatonin can depress synaptic potentiation (wind-up) in the spinal cord, and (ii) whether this effect is prevented by intrathecal (i.t.) administration of the MT2 receptor antagonist luzindole. Results showed that melatonin i.t. (10, 30 and 90 microg) induced dose-dependent inhibition of wind-up activity (ED50=52.06 microg i.t.), an effect that was prevented by 100 microg i.t. of luzindole. Since wind-up is dependent on NMDA receptor activation, the results suggest that melatonin can interfere with the NMDA-mediated glutamatergic component of pain transmission in rat spinal cord by acting on MT2 receptors.
Neuroreport, 2002
Melatonin has been shown to exert potent antinociception but the sites and mechanisms of action u... more Melatonin has been shown to exert potent antinociception but the sites and mechanisms of action underlying this effect have not yet been clarified. The effect of melatonin on spinal cord nociceptive transmission was studied in rats by assessing wid-up activity in a C-fiber reflex responses paradigm evoked by repetitive (0.6 Hz) electric stimulation. Intraperitoneal administration of 1.25, 2.5, 5.0 and 10.0 mg/kg melatonin induced a dose-dependent inhibition of spinal wind-up activity, the higher dose of the drug used being able to depress completely the C reflex gain. Results indicate that melatonin markedly depresses spinal wind-up in rats, probably through hyperpolarization of dorsal horn neurons consecutive to melatonin binding to membrane receptors, and/or via intracellular interference with a NMDA receptor-dependent nitric oxide generating pathway.
Journal of Endocrinological Investigation, 1992
The present study was performed to determine the in vitra steroidogenic capacity of a gonadal sam... more The present study was performed to determine the in vitra steroidogenic capacity of a gonadal sam pie from a patient suffering from a complete androgen resistance syndrome. Testosterone and estradiol production by the testicular tissue from this patient as weil as gonadotropin binding to a membrane fraction prepared from this tissue were measured. hCG bound with high affinity but with a
Evolution & Development, 2005
Summary DNA methylation is one of the epigenetic and hereditary mechanisms regulating genetic exp... more Summary DNA methylation is one of the epigenetic and hereditary mechanisms regulating genetic expression in mammalian cells. In this review, we propose how certain natural agents, through their dietary consumption, could induce changes in physiological aspects in mammalian mothers, leading to alterations in DNA methylation patterns of the developing fetus and to the emergence of new phenotypes and evolutionary change. Nevertheless, we hypothesize that this process would require (i) certain key periods in the ontogeny of the organism where the environmental stimuli could produce effects, (ii) particular environmental agents as such stimuli, and (iii) that a genomic persistent change be consequently produced in a population. Depending on the persistence of the environmental stimuli and on whether the affected genes are imprinted genes, induced changes in DNA methylation patterns could become persistent. Moreover, some fragments could be more frequently methylated than others over seve...
Brain Research Bulletin, 2010
-Adrenergic receptor stimulation can significantly facilitate synaptic potentiation in the hippo... more -Adrenergic receptor stimulation can significantly facilitate synaptic potentiation in the hippocampus and enhance memory processes, but its effect on neocortical plastic mechanisms is less conclusive. In the present study we determined the effect of propranolol, a -adrenoceptor antagonist, on long-term potentiation (LTP) induced in vivo in rat occipital cortex by tetanizing stimulation of corpus callosum and observed a dose-dependent inhibition of LTP. We further administered propranolol through mini-osmotic pumps during 3 days, and observed the performance of rats in a complex operant conditioning learning paradigm and assessed the expression of brain-derived neurotrophic factor (BDNF) in the occipital cortex. Propranolol exposure depressed both the number of reinforced responses in the operant conditioning task and BDNF expression in occipital cortex. Taken together, our results suggest that propranolol impairs memory formation by inhibiting cortical LTP induction and associated BDNF expression.
Latin American Journal of Aquatic Research, 2017
A detailed study of gametes development and characterization of plasma sex steroid hormones durin... more A detailed study of gametes development and characterization of plasma sex steroid hormones during the maturation cycle was performed for the first time in the southern hake (Merluccius australis). Fish were caught in the inland waters of the Reloncaví Sound, Interior Sea of Chiloé, Chile. Samples of gonads and blood were collected for histology and sex steroid hormone (17 β-estradiol, 11-ketotestosterone and 17,20 βdihydroxy-4-pregnen-3-one) analysis, respectively. Sex steroid hormone quantification was performed using enzyme-immunoassay (ELISA). Results showed that M. australis males and females have asynchronous development of testicles and ovaries, in all stages of maturation. Most spawning fish were found during the spring months. Regarding the sex steroid hormones, serological fluctuations of 17 β-estradiol and 11- ketotestosterone were found during gonadal maturation of M. australis. These hormones are the main hormones responsible for vitelogenesis and spermatogenesis proces...
International Journal of Medical and Surgical Sciences, 2018
Journal of Steroid Biochemistry, 1986
In order to characterize the effects of androgens and anabolics on muscle, a tissue culture syste... more In order to characterize the effects of androgens and anabolics on muscle, a tissue culture system has been established which allows exact control of experimental conditions and therefore does not suffer from disadvantages present in other systems, i.e. animal models. Myoblasts derived from fetal and neonatal rat muscles undergo functional alterations in monolayer cultures which are similar to those observed in vivo, including withdrawal from the cell cycle and subsequent fusion to form multinucleate rnFt= capable of contraction. Therefore, using this system it is possible to study the influence of androgens and anabolics on proliferation and differentiation of myoblasts as well as metabolism of mature myotubes. Furthermore, the system allows for evaluation of the effects of these compounds on "atrophic" muscle, e.g. reduction of muscle mass induced by glucocorticoids or tetrodotoxin, or "trained" muscle when coupled with electrical stimulation of the cultures. Proliferation is evaluated using 'H-thymidine incorporation and cell counts. Morphological observation and measurement of lactate dyhydrogenase and creatine kinase serve to define the time course of differentiation. Effects on mature myotubes are determined at varying time intervals by measurement of amino acid and glucose transport, protein synthesis, enzymes of energy metabolism and myosin synthesis.
Revista chilena de pediatría, 1995
Premature thelarche was looked for among 460 healthy girls of different socioeconomic level (SEL]... more Premature thelarche was looked for among 460 healthy girls of different socioeconomic level (SEL], aged 6 to 36 months. Sixty five girls (14.1%) had palpable, diameter 10 mm or more, breast tissue. No significant difference was observed in the prevalence of palpable breast tissue between girls of different socioeconomic levels. Fixty three girls with prernalure thelarche, who had never been given hormones, were compared to fourty seven girls without premature thelarche and their corresponding mothers were asked to answer a written questionare. No significant differences were found in evolution of pregnancy, delivery, neonatal period, medical history or nutrition between patients and controls. In 26 cases premature thelarche represented persistence of neonatal thelarche up to the time of the study. Growth and bone age of patients were appropriate for chronological age. Breast tissue size decreased in 21 {75%}, disappeared in 5 |18%) and increased without other signs of puberty in 2 (7%) of 28 patients who were followed up 5 to 15 months. Premature thelarche is a benign condition that tends to improve spontaneously, not apparently related to hormonal contamination of food, although it is rot possible to exclude other environmental agents. It probably represents a variant form of normal development in youngs females.
Steroids, 2000
In previous reports we have demonstrated high plasma levels of sex hormone-binding globulin (SHBG... more In previous reports we have demonstrated high plasma levels of sex hormone-binding globulin (SHBG) in asymptomatic alcoholic men. In the present work the physicochemical properties of SHBG from plasma of noncirrhotic alcoholic patients have been further compared with SHBG of control subjects. Steroid binding to SHBG was similar for the two groups: alcoholic men, K d of 0.62 Ϯ 0.07 nM and control individuals, K d of 0.70 Ϯ 0.10 nM. The structure of oligosaccharides attached to SHBG from controls and alcoholic men were determined by using serial chromatography. Our data indicated that 7% of SHBG of control individuals was not retarded by the Con-A column, whereas ϳ30% of SHBG of alcoholic men eluted in the void volume of Con A. Approximately 46% of SHBG of alcoholics applied to Con A, possessed biantennary complex oligosaccharides, as indicated by the fact that it could be eluted with methyl-␣-D-glucopyranoside and by its retention on wheat germ agglutinin; in contrast, when SHBG from control men was analyzed, ϳ51% was eluted with methyl-␣-Dglucopyranoside. Approximately 9% of the biantennary complex oligosaccharides on SHBG of control men and none of those on SHBG from alcoholic men were fucosylated on the chitobiose core, as determined by chromatography on Lenn culinaris lectin. Galactosylated oligosaccharides were also present on the SHBG fraction as indicated by its interaction with Ricinus communis-I. Approximately 24% of SHBG of alcoholic men and 39% of those on SHBG from control individuals applied to Con-A were retained and could be eluted with methyl-␣-D-mannopyranoside. Evidence based on the binding on mannoside-eluted SHBG to Con-A, wheat germ agglutinin, and R. communis-I indicated that at least the SHBG in this fraction, from alcoholics or controls, contained two glycosylation sites and that the sites were differentially glycosylated.