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R S Wright - One of the best experts on this subject based on the ideXlab platform.
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Seasonal changes in the levels of 11‐Oxotestosterone and testosterone in the serum of male salmon, Salmo salar L., and their relationship to growth and maturation cycle
Journal of Fish Biology, 2006Co-Authors: S V Hunt, T H Simpson, R S WrightAbstract:Levels of 11-Oxotestosterone (17 β-hydroxyandrost-4-ene-3, 11-dione) and testosterone in the blood serum of individually marked adult male Atlantic salmon held in captivity, were measured by radioimmunoassay at approximately monthly intervals for periods of up to 18 months. In addition to peak concentrations of both hormones shown by all the maturing fish at the time to full sexual maturation during October and November, a majority of maturing fish also showed a significant elevation of 11-Oxotestosterone during the early months of the year. The possible involvement of this early elevation of 11-Oxotestosterone in controlling the mitotic multiplication of spermatogonia is discussed. Weight and length increases expressed as specific values GW and GL and weight to length relationships for the maturing males for each sampling period are presented and compared with those of non-maturing fish.
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Effects of rearing density on sexual maturation and growth in sea-cage reared Atlantic salmon, Salmo salar L.
Aquaculture Research, 1992Co-Authors: H. A. Mclay, R S Wright, A. F. Youngson, R. JohnstoneAbstract:. Paired subgroups of fish were derived in January from each of two parent sea-cages of Atlantic salmon, Salmo salar L. The proportion of fish which later became sexually mature in each parent group, after one winter (as grilse) and under commercial rearing density, was determined. Maturity rates in the subgroups, reared in sea-cages at lower density, were significantly greater than in the parent groups. Rearing at reduced density was associated with increased growth in some, hut not all, comparisons. Periodic anaesthesia, handling and sampling of blood for steroid hormone determinations did not consistently affect maturation rate or growth among fish in one of each pair of subgroups. Sexual development was assessed by determining levels of the steroid hormones 11-Oxotestosterone or 17β-oestradiol in samples of blood serum taken monthly from individually marked fish in one of each pair of subgroups. Between February and April specific growth rates in maturing male grilse were significantly higher than in fish subsequently shown to have remained immature. Growth rates in maturing female grilse differed similarly between March and April. Between July and August, however, growth rates of non-maturing salmon exceeded those of grilse.
John E. Thain - One of the best experts on this subject based on the ideXlab platform.
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Relationship between Sex Steroid and Vitellogenin Concentrations in Flounder ( Platichthys flesus ) Sampled from an Estuary Contaminated with Estrogenic Endocrine-Disrupting Compounds
Environmental Health Perspectives, 2006Co-Authors: Alexander P. Scott, Ioanna Katsiadaki, Mark F. Kirby, John E. ThainAbstract:High concentrations of vitellogenin (VTG; egg yolk protein) have previously been found in male flounder (Platichthys flesus) from several UK estuaries; these levels have been ascribed to the presence of estrogenic endocrine-disrupting compounds (EDCs). Gonadal abnormalities, including intersex, have also been recorded in these estuaries. However, there is no firm evidence to date that these two findings are causally linked or that the presence of estrogenic EDCs has any adverse population effects. In the present study, we examined the relationship between concentrations of VTG and sex steroids (11-Oxotestosterone in males and 17β-estradiol in females) in specimens of flounder captured from the estuary of the River Mersey. We first questioned whether the high concentrations of VTG in male and immature female flounder were indeed caused by a direct effect of exogenous EDCs and not indirectly via the endogenous secretion of 17β-estradiol. The data favored the direct involvement of estrogenic EDCs. We then questioned whether the presence of estrogenic EDCs not only stimulated inappropriate VTG synthesis but whether it might also have had a negative effect on endogenous steroid secretion. It should be noted that the predicted consequences of a drop in steroid secretion include smaller gonads, smaller oocytes, fewer numbers of sperm, and depressed spawning behavior. This question was more difficult to answer because of the strong effect of the seasonal reproductive cycle and stage of maturation on steroid concentrations. However, matched by month of capture and stage of maturation, both 17β-estradiol in females and 11-keto-testosterone in males were in most cases significantly lower in those years when VTG concentrations were higher. Key words: 17β-estradiol, endocrine disruption, estrogens, flounder, sex steroids, vitellogenin. Environ Health Perspect 114(suppl 1):27–31 (2006). doi:10.1289/ehp.8049 available vi
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Relationship between Sex Steroid and Vitellogenin Concentrations in Flounder (Platichthys flesus) Sampled from an Estuary Contaminated with Estrogenic Endocrine-Disrupting Compounds
Environmental Health Perspectives, 2005Co-Authors: Alexander P. Scott, Ioanna Katsiadaki, Mark F. Kirby, John E. ThainAbstract:High concentrations of vitellogenin (VTG; egg yolk protein) have previously been found in male flounder (Platichthys flesus) from several UK estuaries; these levels have been ascribed to the presence of estrogenic endocrine-disrupting compounds (EDCs). Gonadal abnormalities, including intersex, have also been recorded in these estuaries. However, there is no firm evidence to date that these two findings are causally linked or that the presence of estrogenic EDCs has any adverse population effects. In the present study, we examined the relationship between concentrations of VTG and sex steroids (11-Oxotestosterone in males and 17β-estradiol in females) in specimens of flounder captured from the estuary of the River Mersey. We first questioned whether the high concentrations of VTG in male and immature female flounder were indeed caused by a direct effect of exogenous EDCs and not indirectly via the endogenous secretion of 17β-estradiol. The data favored the direct involvement of estrogenic EDCs. We then questioned whether the presence of estrogenic EDCs not only stimulated inappropriate VTG synthesis but whether it might also have had a negative effect on endogenous steroid secretion. It should be noted that the predicted consequences of a drop in steroid secretion include smaller gonads, smaller oocytes, fewer numbers of sperm, and depressed spawning behavior. This question was more difficult to answer because of the strong effect of the seasonal reproductive cycle and stage of maturation on steroid concentrations. However, matched by month of capture and stage of maturation, both 17β-estradiol in females and 11-keto-testosterone in males were in most cases significantly lower in those years when VTG concentrations were higher.
S T H Chan - One of the best experts on this subject based on the ideXlab platform.
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In vivo effects of oLH and LHRH-analog on sex reversal and plasma sex steroid profiles in the female Monopterus albus
General and Comparative Endocrinology, 1993Co-Authors: W S B Yeung, Hai-yong Chen, S T H ChanAbstract:Abstract The effects of ovine-luteinizing hormone (oLH) or a synthetic analog of luteinizing hormone-releasing hormone, Des-Gly 10 [S-Ala 6 ]-LHRH ethylamide acetate salt (LHRH-A), on the female phase of the protogynous Monopterus albus were investigated, and the plasma levels of androstenedione (Ad), testosterone (T), 11-Oxotestosterone (KT), 11β-hydroxytestosterone (OHT), 17β-estradiol (E2) and progesterone were determined. In the postspawning stage, oLH induced precocious sex reversal in the gonad from female to male and increased plasma levels of Ad, T, KT and OHT. However, such oLH effects in M. albus females were slight at the early prespawning stage, and no significant signs of precocious sex reversal were found either in gonadal structure or in plasma hormones as those in postspawning treatment. After LHRH-A treatment of M. albus females in both postspawning and early prespawning stages, the gonadal structure remained "female type" with no sign of proliferation of either Leydig cells or male germ cells. The plasma levels of E2 were greatly increased after the treatment.
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The in vitro metabolism of radioactive androstenedione and testosterone by the gonads of the protogynous Monopterus albus at different sexual phases: a time-course and seasonal study.
General and Comparative Endocrinology, 1993Co-Authors: W S B Yeung, Hai-yong Chen, S T H ChanAbstract:Abstract The seasonal gonadal steroidogenesis of Monopterus albus in relation to natural sex reversal was studied by in vitro time-course incubations. In vitro steroid metabolisms varied with the developmental stages of the gonad. In the female stage, the major products were either 3β-hydroxy-5α-androstan-17-one or unidentified metabolites, depending on the season. In the males, 11-Oxotestosterone was the major product during the prespawning, reproductively active period, while in other periods of the seasonal cycle, 5α-reduced metabolites were more abundant. In the intersexes, the steroidogenic pattern changed from a female to a male pattern, i.e., the production of 11-Oxotestosterone increased and that of the unidentified metabolites decreased.
S V Hunt - One of the best experts on this subject based on the ideXlab platform.
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Seasonal changes in the levels of 11‐Oxotestosterone and testosterone in the serum of male salmon, Salmo salar L., and their relationship to growth and maturation cycle
Journal of Fish Biology, 2006Co-Authors: S V Hunt, T H Simpson, R S WrightAbstract:Levels of 11-Oxotestosterone (17 β-hydroxyandrost-4-ene-3, 11-dione) and testosterone in the blood serum of individually marked adult male Atlantic salmon held in captivity, were measured by radioimmunoassay at approximately monthly intervals for periods of up to 18 months. In addition to peak concentrations of both hormones shown by all the maturing fish at the time to full sexual maturation during October and November, a majority of maturing fish also showed a significant elevation of 11-Oxotestosterone during the early months of the year. The possible involvement of this early elevation of 11-Oxotestosterone in controlling the mitotic multiplication of spermatogonia is discussed. Weight and length increases expressed as specific values GW and GL and weight to length relationships for the maturing males for each sampling period are presented and compared with those of non-maturing fish.
R. Johnstone - One of the best experts on this subject based on the ideXlab platform.
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Effects of rearing density on sexual maturation and growth in sea-cage reared Atlantic salmon, Salmo salar L.
Aquaculture Research, 1992Co-Authors: H. A. Mclay, R S Wright, A. F. Youngson, R. JohnstoneAbstract:. Paired subgroups of fish were derived in January from each of two parent sea-cages of Atlantic salmon, Salmo salar L. The proportion of fish which later became sexually mature in each parent group, after one winter (as grilse) and under commercial rearing density, was determined. Maturity rates in the subgroups, reared in sea-cages at lower density, were significantly greater than in the parent groups. Rearing at reduced density was associated with increased growth in some, hut not all, comparisons. Periodic anaesthesia, handling and sampling of blood for steroid hormone determinations did not consistently affect maturation rate or growth among fish in one of each pair of subgroups. Sexual development was assessed by determining levels of the steroid hormones 11-Oxotestosterone or 17β-oestradiol in samples of blood serum taken monthly from individually marked fish in one of each pair of subgroups. Between February and April specific growth rates in maturing male grilse were significantly higher than in fish subsequently shown to have remained immature. Growth rates in maturing female grilse differed similarly between March and April. Between July and August, however, growth rates of non-maturing salmon exceeded those of grilse.
