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R. Webb - One of the best experts on this subject based on the ideXlab platform.
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Extra- and intracellular effects of divergent selection for pituitary responsiveness to gonadotropin-releasing hormone in prepubertal ram lambs.
Biology of reproduction, 1997Co-Authors: N. P. Evans, J R Mcneilly, T. A. Bramley, R. WebbAbstract:Divergent selection based on the response of 10-wk-old male lambs to a GnRH challenge has produced two Lines of sheep, referred to as high and low Lines, that differ in their ability to release LH in response to pharmacological and physiological doses of GnRH. The aim of this study was to determine whether the between-Line Differences in pituitary sensitivity were related to Differences in GnRH receptor number and/or the transduction of the intracellular signal following GnRH receptor activation. Pituitary glands were collected from fourteen 20-wk-old ram lambs from each Line, weighed, and sampled for GnRH receptor analysis. The remaining tissue from 9 lambs from each Line was dispersed. Of the resultant cell suspension, a sample was stored for measurement of GnRH receptor content and the remainder was plated and cultured for 24 h. The LH responses of cultured cells were measured after exposure to GnRH, A23187, or the phorbol ester phorbol 12,13 dibutyrate (PDB). The results indicated that the pituitary glands of the high Line contained significantly higher concentrations of GnRH receptors than did those of the low Line and released significantly more LH after stimulation with either GnRH or the Ca2+-calmodulin or protein kinase C intracellular second messenger systems. Therefore, the between-Line difference in the regulation of pituitary LH secretion occurs at a step distal to the stimulatory sites of action of A23187 and PDB.
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Effects of indirect selection for pituitary responsiveness to gonadotropin-releasing hormone on the storage and release of luteinizing hormone and follicle-stimulating hormone in prepubertal male lambs.
Biology of reproduction, 1995Co-Authors: N. P. Evans, J R Mcneilly, R. WebbAbstract:Divergent selection based on the LH response to a 5-micrograms dose of GnRH in 10-wk-old Finn Dorset ram lambs has created two Lines of sheep that differ significantly in their response to both physiological and pharmacological dosages of GnRH. The aims of this study were to investigate whether there are between-Line Differences in endogenous LH and FSH secretion in ram lambs, as in the adult ewes, and to determine whether these Differences are related to Differences in storage of gonadotropins within the pituitary glands of the two Lines. To address the first aim, endogenous LH and FSH secretion was monitored in 20 ram lambs from each Line for a 6-h period at 2, 6, and 10 wk of age. To investigate potential between-Line Differences in gonadotropin storage, the LH responses to two acute challenges with either 0.5, 5.0, or 50.0 micrograms of GnRH were examined in 10-wk-old ram lambs from each Line. The results demonstrated that the between-Line difference in the LH response to a 5-micrograms GnRH challenge in ram lambs is accompanied by significant between-Line Differences in the regulation of endogenous gonadotropin secretion. Specifically, lambs from the High Line secreted LH pulses of significantly greater amplitude than did lambs from the low Line at 2 and 10 wk of age.(ABSTRACT TRUNCATED AT 250 WORDS)
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Alterations in endogenous gonadotropin secretion and pituitary responsiveness to gonadotropin-releasing hormone in adult ewes, following indirect selection in prepubertal male lambs.
Biology of reproduction, 1994Co-Authors: N. P. Evans, J R Mcneilly, R. WebbAbstract:Indirect selection to improve reproductive performance in the female, through use of a physiologically related trait in prepubertal males, the LH response to a GnRH challenge, has created two Lines of sheep with altered pituitary gland sensitivity to both physiological and pharmacological doses of GnRH. These Lines also exhibit correlated between-Line Differences in female reproductive performance during the first, and at the beginning of the second, breeding season. This study was designed to determine whether the observed between-Line Differences in female reproductive performance were related to between-Line Differences in endogenous gonadotropin secretion during the luteal and follicular phases of the estrous cycle and whether the between-Line difference in the LH response to a GnRH challenge was maintained in adult females. The results indicated that, despite similar mean gonadotropin and steroid concentrations during the luteal and follicular phases of the estrous cycle, significant between-Line Differences in LH pulse amplitude were present during the follicular phase (high Line > low Line). In addition, the results indicated that the between-Line difference in the LH response to a GnRH challenge was maintained in adult ewes, being most apparent during the follicular phase, when the magnitude of the difference was similar to that in prepubertal female lambs. Therefore, in addition to showing maintenance of the between-Line difference in the selected characteristic in postpubertal females, the results demonstrate that adult ewes from the two Lines differ in additional, unselected but physiologically related traits and provide a model system with which to study steroidal regulation of gonadotropin secretion in the ewe.
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Role of gonadal negative feedback on the gonadotrophin responses to gonadotrophin-releasing hormone (GnRH) in ram lambs from two Lines of sheep selected for their luteinizing hormone response to GnRH.
Journal of reproduction and fertility, 1991Co-Authors: N. P. Evans, J R Mcneilly, R. B. Land, R. WebbAbstract:Divergent selection has resulted in two Lines of lambs (high and low) that have a 5-fold difference in their ability to release luteinizing hormone (LH) in response to 5 micrograms of gonadotrophin-releasing hormone (GnRH). BaseLine gonadotrophin concentrations, the gonadotrophin responses to a GnRH challenge and the concentrations of testosterone and oestradiol were compared in lambs which were castrated at birth and intact lambs from both selection Lines at 2, 6, 10 and 20 weeks of age. The pattern of LH and follicle-stimulating hormone (FSH) secretion was similar in the two Lines, but differed between the intact and the castrated lambs. Basal LH and FSH secretion were significantly higher in the castrates than in the intact lambs from both selection Lines. The high-Line lambs had significantly higher basal FSH concentrations at all ages tested and significantly higher basal LH concentrations during the early postnatal period. The magnitude of the gonadotrophin responses to GnRH differed significantly between the intact and the castrated lambs within each Line, the amount of gonadotrophins secreted by the castrated lambs being significantly greater. The removal of gonadal negative feedback by castration did not alter the between-Line difference in either LH or the FSH response to the GnRH challenge. Throughout the experimental period, the concentration of testosterone in the intact lambs was significantly greater than in the castrated lambs in both selection Lines, but no significant difference was seen in the concentrations of oestradiol. No significant between-Line Differences were found in the peripheral concentrations of testosterone or oestradiol in the intact lambs from the two selection Lines. Therefore, despite similar amounts of gonadal negative feedback in the selection Lines, there were significant between-Line Differences in basal gonadotrophin concentrations, at 2 and 6 weeks of age, and in the LH and FSH responses to an exogenous GnRH challenge, at all ages tested. Removal of gonadal negative feedback did not affect the magnitude of the between-Line difference in the response of the Lines to GnRH stimulation. The results indicate that the effects of selection on gonadotrophin secretion are primarily at the level of the hypothalamo-pituitary complex.
J K Belknap - One of the best experts on this subject based on the ideXlab platform.
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Mu-opiate receptor binding is up-regulated in mice selectively bred for high stress-induced analgesia.
Brain research, 1994Co-Authors: J S Mogil, P Marek, L A O'toole, M L Helms, B Sadowski, J C Liebeskind, J K BelknapAbstract:Pain perception and sensitivity to opiate analgesics strongly depend on genotype. Mice selectively bred for high (HA) and low (LA) swim stress-induced analgesia display markedly divergent morphine analgesia, a difference that appears to be determined by one or at the most two major genes. In an attempt to provide candidate genes mediating the supranormal analgesia displayed by HA mice, we performed mu-opiate receptor binding on 27th generation HA, LA, and control (C) mice using [3H]naloxone. HA mice were found to have significantly higher whole-brain receptor density (Bmax) than LA mice in whole brain homogenates; no significant difference in affinity (Kd) was observed. Quantitative autoradiography confirmed the Line difference in whole-brain receptor binding. In the medial thalamus, a brain area implicated in ascending pathways of pain inhibition, HA mice were found to display significantly higher [3H]naloxone binding than C mice (a 64% increase) and LA mice (a 128% increase). No significant Line Differences were observed in any other brain locus. Thalamic mu receptors may therefore play an important role in a central 'volume control' mechanism of pain inhibition, and underlie individual Differences in the responses of mice to opiate analgesic drugs.
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μ-Opiate receptor binding is up-regulated in mice selectively bred for high stress-induced analgesia
Brain Research, 1994Co-Authors: J S Mogil, P Marek, L A O'toole, M L Helms, B Sadowski, J C Liebeskind, J K BelknapAbstract:Abstract Pain perception and sensitivity to opiate analgesics strongly depend on genotype. Mice selectively bred for high (HA) and low (LA) swim stress-induced analgesia display markedly divergent morphine analgesia, a difference that appears to be determined by one or at the most two major genes. In an attempt to provide candidate genes mediating the supranormal analgesia displayed by HA mice, we performed μ-opiate receptor binding on 27th generation HA, LA, and control (C) mice using [ 3 H]naloxone. HA mice were found to have significantly higher whole-brain receptor density ( B max ) than LA mice in whole brain homogenates; no significant difference in affinity ( K d ) was observed. Quantitative autoradiography confirmed the Line difference in whole-brain receptor binding. In the medial thalamus, a brain area implicated in ascending pathways of pain inhibition, HA mice were found to display significantly higher [ 3 H]naloxone binding than C mice (a 64% increase) and LA mice (a 128% increase). No significant Line Differences were observed in any other brain locus. Thalamic μ receptors may therefore play an important role in a central ‘volume control’ mechanism of pain inhibition, and underlie individual Differences in the responses of mice to opiate analgesic drugs.
N. P. Evans - One of the best experts on this subject based on the ideXlab platform.
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Extra- and intracellular effects of divergent selection for pituitary responsiveness to gonadotropin-releasing hormone in prepubertal ram lambs.
Biology of reproduction, 1997Co-Authors: N. P. Evans, J R Mcneilly, T. A. Bramley, R. WebbAbstract:Divergent selection based on the response of 10-wk-old male lambs to a GnRH challenge has produced two Lines of sheep, referred to as high and low Lines, that differ in their ability to release LH in response to pharmacological and physiological doses of GnRH. The aim of this study was to determine whether the between-Line Differences in pituitary sensitivity were related to Differences in GnRH receptor number and/or the transduction of the intracellular signal following GnRH receptor activation. Pituitary glands were collected from fourteen 20-wk-old ram lambs from each Line, weighed, and sampled for GnRH receptor analysis. The remaining tissue from 9 lambs from each Line was dispersed. Of the resultant cell suspension, a sample was stored for measurement of GnRH receptor content and the remainder was plated and cultured for 24 h. The LH responses of cultured cells were measured after exposure to GnRH, A23187, or the phorbol ester phorbol 12,13 dibutyrate (PDB). The results indicated that the pituitary glands of the high Line contained significantly higher concentrations of GnRH receptors than did those of the low Line and released significantly more LH after stimulation with either GnRH or the Ca2+-calmodulin or protein kinase C intracellular second messenger systems. Therefore, the between-Line difference in the regulation of pituitary LH secretion occurs at a step distal to the stimulatory sites of action of A23187 and PDB.
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Effects of indirect selection for pituitary responsiveness to gonadotropin-releasing hormone on the storage and release of luteinizing hormone and follicle-stimulating hormone in prepubertal male lambs.
Biology of reproduction, 1995Co-Authors: N. P. Evans, J R Mcneilly, R. WebbAbstract:Divergent selection based on the LH response to a 5-micrograms dose of GnRH in 10-wk-old Finn Dorset ram lambs has created two Lines of sheep that differ significantly in their response to both physiological and pharmacological dosages of GnRH. The aims of this study were to investigate whether there are between-Line Differences in endogenous LH and FSH secretion in ram lambs, as in the adult ewes, and to determine whether these Differences are related to Differences in storage of gonadotropins within the pituitary glands of the two Lines. To address the first aim, endogenous LH and FSH secretion was monitored in 20 ram lambs from each Line for a 6-h period at 2, 6, and 10 wk of age. To investigate potential between-Line Differences in gonadotropin storage, the LH responses to two acute challenges with either 0.5, 5.0, or 50.0 micrograms of GnRH were examined in 10-wk-old ram lambs from each Line. The results demonstrated that the between-Line difference in the LH response to a 5-micrograms GnRH challenge in ram lambs is accompanied by significant between-Line Differences in the regulation of endogenous gonadotropin secretion. Specifically, lambs from the High Line secreted LH pulses of significantly greater amplitude than did lambs from the low Line at 2 and 10 wk of age.(ABSTRACT TRUNCATED AT 250 WORDS)
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Alterations in endogenous gonadotropin secretion and pituitary responsiveness to gonadotropin-releasing hormone in adult ewes, following indirect selection in prepubertal male lambs.
Biology of reproduction, 1994Co-Authors: N. P. Evans, J R Mcneilly, R. WebbAbstract:Indirect selection to improve reproductive performance in the female, through use of a physiologically related trait in prepubertal males, the LH response to a GnRH challenge, has created two Lines of sheep with altered pituitary gland sensitivity to both physiological and pharmacological doses of GnRH. These Lines also exhibit correlated between-Line Differences in female reproductive performance during the first, and at the beginning of the second, breeding season. This study was designed to determine whether the observed between-Line Differences in female reproductive performance were related to between-Line Differences in endogenous gonadotropin secretion during the luteal and follicular phases of the estrous cycle and whether the between-Line difference in the LH response to a GnRH challenge was maintained in adult females. The results indicated that, despite similar mean gonadotropin and steroid concentrations during the luteal and follicular phases of the estrous cycle, significant between-Line Differences in LH pulse amplitude were present during the follicular phase (high Line > low Line). In addition, the results indicated that the between-Line difference in the LH response to a GnRH challenge was maintained in adult ewes, being most apparent during the follicular phase, when the magnitude of the difference was similar to that in prepubertal female lambs. Therefore, in addition to showing maintenance of the between-Line difference in the selected characteristic in postpubertal females, the results demonstrate that adult ewes from the two Lines differ in additional, unselected but physiologically related traits and provide a model system with which to study steroidal regulation of gonadotropin secretion in the ewe.
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Role of gonadal negative feedback on the gonadotrophin responses to gonadotrophin-releasing hormone (GnRH) in ram lambs from two Lines of sheep selected for their luteinizing hormone response to GnRH.
Journal of reproduction and fertility, 1991Co-Authors: N. P. Evans, J R Mcneilly, R. B. Land, R. WebbAbstract:Divergent selection has resulted in two Lines of lambs (high and low) that have a 5-fold difference in their ability to release luteinizing hormone (LH) in response to 5 micrograms of gonadotrophin-releasing hormone (GnRH). BaseLine gonadotrophin concentrations, the gonadotrophin responses to a GnRH challenge and the concentrations of testosterone and oestradiol were compared in lambs which were castrated at birth and intact lambs from both selection Lines at 2, 6, 10 and 20 weeks of age. The pattern of LH and follicle-stimulating hormone (FSH) secretion was similar in the two Lines, but differed between the intact and the castrated lambs. Basal LH and FSH secretion were significantly higher in the castrates than in the intact lambs from both selection Lines. The high-Line lambs had significantly higher basal FSH concentrations at all ages tested and significantly higher basal LH concentrations during the early postnatal period. The magnitude of the gonadotrophin responses to GnRH differed significantly between the intact and the castrated lambs within each Line, the amount of gonadotrophins secreted by the castrated lambs being significantly greater. The removal of gonadal negative feedback by castration did not alter the between-Line difference in either LH or the FSH response to the GnRH challenge. Throughout the experimental period, the concentration of testosterone in the intact lambs was significantly greater than in the castrated lambs in both selection Lines, but no significant difference was seen in the concentrations of oestradiol. No significant between-Line Differences were found in the peripheral concentrations of testosterone or oestradiol in the intact lambs from the two selection Lines. Therefore, despite similar amounts of gonadal negative feedback in the selection Lines, there were significant between-Line Differences in basal gonadotrophin concentrations, at 2 and 6 weeks of age, and in the LH and FSH responses to an exogenous GnRH challenge, at all ages tested. Removal of gonadal negative feedback did not affect the magnitude of the between-Line difference in the response of the Lines to GnRH stimulation. The results indicate that the effects of selection on gonadotrophin secretion are primarily at the level of the hypothalamo-pituitary complex.
Michal Zeman - One of the best experts on this subject based on the ideXlab platform.
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maternally derived egg hormones antibodies and antimicrobial proteins common and different pathways of maternal effects in japanese quail
PLOS ONE, 2014Co-Authors: Monika Okuliarova, Zuzana Kankova, Michal Zeman, Aline Bertin, Erich Möstl, Christine LeterrierAbstract:Avian eggs contain a variety of maternally-derived substances that can influence the development and performance of offspring. The levels of these egg compounds vary in relation to environmental and genetic factors, but little is known about whether there are correlative links between maternal substances in the egg underlying common and different pathways of maternal effects. In the present study, we investigated genetically determined variability and mutually adjusted deposition of sex hormones (testosterone-T, androstenedione-A4 and progesterone-P4), antibodies (IgY) and antimicrobial proteins (lysozyme) in eggs of Japanese quail (Coturnix japonica). We used different genetic Lines that were independently selected for yolk T concentrations, duration of tonic immobility and social reinstatement behaviour, since both selections for behavioural traits (fearfulness and social motivation, respectively) produced considerable correlative responses in yolk androgen levels. A higher selection potential was found for increased rather than decreased yolk T concentrations, suggesting that there is a physiological minimum in egg T levels. Line Differences in yolk IgY concentrations were manifested within each selection experiment, but no consistent inter-Line pattern between yolk IgY and T was revealed. On the other hand, a consistent inverse inter-Line pattern was recorded between yolk IgY and P4 in both selections for behavioural traits. In addition, selections for contrasting fearfulness and social motivation were associated with changes in albumen lysozyme concentrations and an inverse inter-Line pattern between the deposition of yolk IgY and albumen lysozyme was found in Lines selected for the level of social motivation. Thus, our results demonstrate genetically-driven changes in deposition of yolk T, P4, antibodies and albumen lysozyme in the egg. This genetic variability can partially explain mutually adjusted maternal deposition of sex hormones and immune-competent molecules but the inconsistent pattern of inter-Line Differences across all selections indicates that there are other underlying mechanisms, which require further studies.
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Genetic Differences in yolk testosterone levels influence maternal hormone deposition in the second laying cycle in Japanese quails.
Comparative biochemistry and physiology. Part A Molecular & integrative physiology, 2012Co-Authors: Michal Zeman, Peter Škrobánek, Monika OkuliarovaAbstract:Maternally-derived yolk androgens exhibit distinct among- and within-female variations but limited data refer to inter-seasonal changes of maternal hormones in the yolk. We investigated the deposition of yolk testosterone (T) across two laying cycles in Japanese quail. To test how genetically-determined Differences influence between cycle variations in yolk androgens we compared females from low (LET) and high (HET) egg T Lines at the end of the first and at the beginning of the second laying cycle after an induced moult. Line Differences in yolk T levels exhibited high consistency exceeding two reproductive cycles. Yolk T concentrations increased in the second laying cycle in HET but not in LET females. Plasma T levels did not differ between cycles in both Lines and no Line Differences were found either before or after the moult indicating the presence of mechanisms limiting the increase of T concentrations in the circulation. Differences in the yolk T levels were not accompanied by changes in the egg and yolk mass. The HET quail laid eggs with heavier eggshell than the LET quail. Our results demonstrate different abilities of mothers to deposit T in their eggs over two reproductive seasons with expected consequences on the development of their progeny.
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Effects of divergent selection for yolk testosterone content on growth characteristics of Japanese quail.
Comparative biochemistry and physiology. Part A Molecular & integrative physiology, 2011Co-Authors: Monika Okuliarova, Kostal L, Michal ZemanAbstract:Effects of yolk androgens on postnatal growth of offspring have been widely studied but their physiological role in the growth control is not fully understood due to an inconsistency in obtained results. We investigated androgen-mediated maternal effects on postnatal growth in relation to endocrine control mechanisms using two Lines of Japanese quail divergently selected for high (HET) and low (LET) egg testosterone (T) content. Embryonic growth did not differ between the Lines. During the growth period HET quail were heavier and displayed longer tarsi as compared with LET quail, with more pronounced Line Differences in males than females. HET males were heavier than LET males from the age of 2 weeks, reached the age of maximum growth rate earlier, and displayed higher asymptotic body weight than LET males. Accelerated growth in HET males was not accompanied by increased postembryonic plasma T concentrations. Plasma triiodothyronine levels did not differ between Lines while plasma thyroxine levels were decreased in HET as compared with LET female chicks. Line Differences in body weight disappeared in adult quail suggesting that yolk androgens, increased in a physiological way, resulted in stimulation of juvenile growth rate in precocial Japanese quail under stable social and environmental conditions.
C. J. P. Eriksson - One of the best experts on this subject based on the ideXlab platform.
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Hepatic aldehyde and alcohol dehydrogenases in alcohol-preferring and alcohol-avoiding rat Lines
Biochemical pharmacology, 1994Co-Authors: T. Koivisto, C. J. P. ErikssonAbstract:The alcohol-avoiding ANA (Alko, Non-Alcohol) and alcohol-preferring AA (Alko, Alcohol) rat Lines are known to differ in their acetaldehyde metabolism and were originally found to differ in hepatic alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activities in the 1970s. At the beginning of the 1980s, these rat Lines were revitalized and some previously found Line Differences were lost. Thus, the purpose of this study was to determine whether these enzymatic Line Differences still exist and, if so, to study them further at the isoenzyme level. ADH and ALDH activities were measured from liver homogenates and different subcellular fractions of the rats. The ANA rats were found to have lower hepatic ALDH and higher ADH activities than AA rats, in accordance with the previous study. The Line difference in ALDH activity was observed in all fractions, but was more apparent with millimolar than micromolar substrate concentrations and generally more pronounced in females than in males. The Line difference in the microsomal ALDH activity was found to be quantitative, and it seemed to concern both microsomal ALDH isoenzymes. A qualitative Line difference concerning mitochondrial high Km ALDH isoenzyme was found, and three different cytosolic ALDH isoenzyme patterns were observed, the frequencies of which were found to be different in the two Lines. In conclusion, the results of the present study support the assumption that Line Differences in hepatic ADH and ALDH activities may be relevant to the acetaldehyde accumulation and the particularly low ethanol consumption of the ANA rats.
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Mitochondrial aldehyde dehydrogenase (ALDH2) polymorphism in AA and ANA rats: Lack of genotype and phenotype Line Differences
Pharmacology biochemistry and behavior, 1993Co-Authors: T. Koivisto, Lucinda G. Carr, C. J. P. ErikssonAbstract:Polymorphism of the gene coding for mitochondrial ALDH2 in humans is known to be associated with Differences in alcohol drinking behavior. Recently, two different alleles of the ALDH2 gene, ALDH2R and ALDH2Q, have been found in rats also and a possible relationship between the frequencies of the two alleles and drinking behavior has been proposed. In this study, we examined whether this polymorphism of ALDH2 was the underlying cause for the previously reported acetaldehyde accumulation in the alcohol-avoiding ANA rat Line and, thus, could be one of the factors explaining the Differences in alcohol drinking behavior between the ANA and the alcohol-preferring AA rat Lines. The experimental animals were genotyped and their mitochondrial ALDH activities and blood acetaldehyde concentrations after ethanol injection were measured. The two Lines did not differ in their frequencies of ALDH2R and ALDH2Q alleles. Thus, the polymorphism in the ALDH2 gene does not explain the acetaldehyde accumulation in ANA rats and it does not seem to be associated with Differences in the alcohol drinking behavior in these rat Lines.