Sex Steroid Profiles Research Articles

Annual reproductive cycle of black rockfish Sebastes schlegeli in captivity

: The gonadal development and serum profiles of vitellogenin and sex steroids in rearing Sebastes schlegeli were monitored for one full year. Female fish began vitellogenesis from November and completed it in March. Gestation occurred from April, and parturition occurred in June. A thin chorion and scanty cortical alveoli are oogenetic peculiarities of this fish. Male fish began spermatogenesis from June, and matured in November and December. It appears that copulation occurs in November and December, and that the sperm are stored freely in the ovary during the early vitellogenic period and under the ovigerous lamellae epithelium during the late vitellogenic period. Serum vitellogenin levels in female fish had a good correlation with oocyte growth. Serum estradiol-17β (E2) levels in female fish were elevated from November to February, suggesting that E2 controls vitellogenesis. Serum 17,20β-dihydroxy-4-pregnen-3-one (DHP) in female fish increased in the late vitellogenic period, suggesting that DHP was a maturation-inducing steroid. High levels of serum DHP during gestation suggest that it may be one of the endocrine factors for maintaining gestation. Serum 11-ketotestosterone (11-KT) levels in male fish were elevated from June to October, suggesting that 11-KT controls spermatogenesis. Serum DHP in male fish had a single peak in October, suggesting that DHP plays some role in the late stages of spermatogenesis.

Plasma sex steroid and vitellogenin profiles during gonad development in wild Mediterranean amberjack ( Seriola dumerilii )

Mediterranean amberjacks, Seriola dumerilii Risso, were caught off the Pelagie Islands, in the south Mediterranean Sea, between May 1997 and June 1999. Fish blood was sampled, and gonads were collected at 10-day intervals throughout the spawning period and at monthly intervals during the resting period. Concentrations of plasma estradiol-17s (E2), testosterone (T), 17,20s-dihydroxy-4-pregnen-3-one (DHP) and vitellogenin (Vtg) in females; and plasma T and 11-ketoT (11-KT) in males were correlated with changes in gonadal development. The first females that had already ovulated (F5) were found in late May. Most mature females (F4) were caught in June. Post-spawned females (F6) were found from late July until September. Estradiol-17s was at baseline levels (<0.02 ng ml−1) during autumn/winter and rapidly peaked (6.29±0.68 ng ml−1) from May to early July. Plasma T levels showed a similar profile and were positively correlated to E2 (r 2=0.668) during the spawning period. Continuously elevated levels of E2 and T were observed during the spawning season in vitellogenic females (stages F3, F4 and F5). Resting females were found during the autumn/winter months. Vitellogenin levels increased during May and peaked in June, reverting to undetectable levels in August, in parallel with sex steroid changes. Plasma DHP levels peaked in June (283.45±97.3 pg ml−1), falling to basal values (<5 pg ml−1) in August. DHP levels were higher in mature females (F4) than in maturing (F3) and in partially ovulated (F5) females. DHP values increased during germinal vesicle migration, peaked during germinal vesicle breakdown and decreased again during complete oocyte hydration. In males, changes in T and 11-KT plasma levels were related to testis development. The highest levels of T (5.76±2.64 ng ml−1) were measured during spermatogenesis and highest 11-KT (5.28±3.6 ng ml−1) in males with milt, from May to June. This study provides information, for the first time, on the relation between plasma sex steroid profiles and gonad development in wild Mediterranean amberjack, a useful benchmark for broodstock monitoring under controlled conditions.

Photoperiod regulates the timing of sexual maturation, spawning, sex steroid and thyroid hormone profiles in the Atlantic cod ( Gadus morhua)

Atlantic cod of both sexes were held under four different photoperiod regimes from age 1 year until second sexual maturation at 3 years. Annual photoperiod cycles were compressed into 6 or 9 months, held at 12 months, or extended to 18 months, in each case followed by one 12-month cycle (termed 6+12, 9+12, 12+12, and 18+12, respectively). Photoperiod alterations caused shifts in the cyclic patterns of plasma calcium, sex steroid, and thyroid hormones, and also produced correlative changes in the timing of spawning. Initial spawning was advanced in the compressed (6+12) photoperiod group, followed by further advancement in the timing of the second spawning. Conversely, spawning was delayed in the 18+12 group. Patterns in circulating hormones observed under these experimental conditions were consistent with the coupling of photoperiod to spawning by way of established endocrine transducers. These results demonstrate that manipulation of the annual photoperiod cycle is a powerful hatchery technique in the maintenance of reproductive stocks of Atlantic cod that spawn at various times of the year.

Estrogen receptor beta messenger ribonucleic acid expression in the forebrain of proestrous, pregnant, and lactating female rats.

Estrogen receptor (ER)beta is present in hypothalamic and limbic neurons of female rat brains, but little is known about its regulation under physiological conditions. To determine whether ER beta expression varies during physiological conditions in which sex steroid hormone profiles are significantly different, we used in situ hybridization to assess ER beta mRNA expression in the periventricular preoptic area, bed nucleus of stria terminalis, paraventricular nucleus, supraoptic nucleus, and the posterodorsal medial amygdala of female rats on proestrus, on d 22 of pregnancy, or on d 10 of lactation (L10). In the periventricular preoptic area, d-22 pregnant females had fewer ER beta-mRNA-expressing cells than did females at proestrus, but the level of ER beta mRNA expression per cell in pregnant females was higher than in the two other groups. In the paraventricular nucleus, no changes in ER beta mRNA expression were observed; whereas in the supraoptic nucleus, proestrous females had fewer ER beta-mRNA-expressing cells than L10 females. In the posterodorsal medial amygdala, proestrous females had a greater number of ER beta-mRNA-expressing cells than did L10 females. These results demonstrate that ER beta mRNA expression is differentially regulated in a brain-region-specific and temporal manner under physiological conditions and suggest that ER beta may participate in the regulation of estrogen-sensitive reproductive functions in female rats.

Estrogen synthesis in fetal sheep brain: effect of maternal treatment with an aromatase inhibitor.

The aim of the present study was to determine whether the fetal lamb brain has the capacity to aromatize androgens to estrogens during the critical period for sexual differentiation. We also determined whether administration of the aromatase-inhibitor 1,4,6-androstatriene-3,17-dione (ATD) could cross the placenta and inhibit aromatase activity (AA) in fetal brain. Eight pregnant ewes were utilized. On Day 50 of pregnancy, four ewes were given ATD-filled Silastic implants, and the other four ewes received sham surgeries. The fetuses were surgically delivered 2 wk later (Day 64 of gestation). High levels of AA (0.8-1.4 pmol/h/mg protein) were present in the hypothalamus and amygdala. Lower levels (0.02-0.1 pmol/h/mg protein) were measured in brain stem regions, cortex, and olfactory bulbs. The Michaelis-Menten dissociation constant (K(m)) for aromatase in the fetal sheep brain was 3-4 nM. No significant sex differences in AA were observed in brain. Treatment with ATD produced significant inhibition of AA in most brain areas but did not significantly alter serum profiles of the major sex steroids in maternal and fetal serum. Concentrations of testosterone in serum from the umbilical artery and vein were significantly greater in male than in female fetuses. No other sex differences in serum steroids were observed. These data demonstrate that high levels of AA are found in the fetal sheep hypothalamus and amygdala during the critical period for sexual differentiation. They also demonstrate that AA can be inhibited in the fetal lamb brain by treating the mother with ATD, without harming fetal development.

Ovarian growth and plasma sex steroid and vitellogenin profiles during vitellogenesis in Tasmanian female Atlantic salmon ( Salmo salar)

In order to provide detailed information on the reproductive development of female Atlantic salmon ( Salmo salar) in Tasmania, Australia, fish were sampled from sea cages during the main period of vitellogenesis over the austral summer and autumn (October–March). Plasma levels of the gonadal steroids 17β-estradiol (E 2) and testosterone (T), and vitellogenin (Vtg), as well as a range of indices of ovarian development, were measured. Somatic growth and gonadal development were consistent with the stock's growth and development as an austral autumn spawning stock. Mean body weight increased from 3.4 to 5.4 kg and gonadosomatic index (GSI) increased from 0.5% to 17%. Plasma levels of E 2 and T increased from ∼3 to ∼20 ng ml −1 and plasma levels of Vtg increased from ∼2.5 to greater than 35 mg ml −1. However, increases in GSI, oocyte volume, etc., tended to occur later than expected on the basis of Northern hemisphere data and plasma levels of E 2 and T did not increase significantly until the last month of sampling. Plasma levels of Vtg were also static (∼10 mg ml −1) during mid-summer (December–January). Together these observations indicate possible temperature-related impairment of reproductive development during summer.

Sex steroid profiles in female and male stellate sturgeon (Acipenser stellatus Pallas) during final maturation induced by hormonal treatment

Journal of Applied IchthyologyVolume 18, Issue 4-6 p. 375-381 Sex steroid profiles in female and male stellate sturgeon (Acipenser stellatus Pallas) during final maturation induced by hormonal treatment T. Semenkova, T. Semenkova Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorI. Barannikova, I. Barannikova Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorD. E. Kime, D. E. Kime Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorB. G. McAllister, B. G. McAllister Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorL. Bayunova, L. Bayunova Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorV. Dyubin, V. Dyubin Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorN. Kolmakov, N. Kolmakov Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this author T. Semenkova, T. Semenkova Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorI. Barannikova, I. Barannikova Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorD. E. Kime, D. E. Kime Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorB. G. McAllister, B. G. McAllister Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorL. Bayunova, L. Bayunova Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorV. Dyubin, V. Dyubin Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this authorN. Kolmakov, N. Kolmakov Central Laboratory of Fish Reproduction, St Petersburg; Physiological Institute St Petersburg University, Universiteskaya Embankment, St Petersburg, Russia; Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UKSearch for more papers by this author First published: 17 December 2002 https://doi.org/10.1046/j.1439-0426.2002.00368.xCitations: 39AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume18, Issue4-6December 2002Pages 375-381 RelatedInformation

Inhibition of gonadotropin-induced oviposition and ovarian steroidogenesis in the African clawed frog ( Xenopus laevis) by the pesticide methoxychlor

Concern over the role of environmental toxicants in amphibian population declines has highlighted the need to develop more comprehensive ecotoxicological test methods for this at-risk group. With continued interest in environmental endocrine disrupters (EDs), and the paucity of data pertaining to endocrine disrupting effects in amphibia, such tests should incorporate reproductive and endocrine endpoints. We investigated the effects of in vivo exposure to the pesticide methoxychlor (MXC) on reproductive and endocrine function in adult female African clawed frogs, ( Xenopus laevis). Frogs were exposed to MXC (0.5–500 μg/l) in tank water throughout a cycle of oogenesis stimulated by exogenous gonadotropins. Gonadotropin-induced oviposition was delayed, and reduced numbers of unfertilizable eggs of increased size were oviposited by frogs exposed to 500 μg/l MXC. Reduced egg output was mirrored by increased gonado-somatic index in MXC-treated frogs. Post-oviposition, plasma sex steroid profiles were altered in MXC-exposed frogs as estradiol/progesterone and estradiol/testosterone ratios were elevated. Ex vivo synthesis of progesterone by ovarian explants was significantly reduced for frogs exposed to MXC≥0.5 μg/l. Additionally, plasma vitellogenin concentrations were significantly depressed in frogs exposed to 500 μg/l MXC. These data indicate that reproductive and endocrine dysfunction can occur in adult amphibia exposed to high concentrations of an environmental toxin with endocrine disrupting activity. Such effects may be indicative of the potential for adverse effects on amphibian wildlife exposed to environmental EDs.

Plasma insuline, IGF-I et cancer du sein

Several recent epidemiological studies have shown an increase in breast cancer risk among women who have elevated plasma levels of testosterone, reduced levels of sex hormone-binding globulin (SHBG), and hence elevated levels of bioavailable androgens and estrogens not bound to SHBG. This endocrine profile is generally associated with obesity and chronic hyperinsulinemia, of which it is most likely a result. Lack of physical activity, obesity, and a diet rich in rapidly digestible carbohydrates and poor in fibre favour the development of insulin resistance and hyperinsulinemia. The elevated insulin levels, in turn are related to decreases in plasma and tissue levels of IGFBP-1 and IGFBP-2 (insulin-like growth factor-binding proteins), and this may increase the availability of insulin-like growth factor-I (IGF-I) to its receptors. Like insulin, IGF-I also inhibits the hepatic synthesis of SHBG, whereas both hormones stimulate the ovarian synthesis of sex steroids. Moreover, insulin and IGF-I can both enhance the development of breast tumours, through their cognate receptors within the mammary tissue. Taken together, these observations lead to the hypothesis that breast cancer risk may be increased in women with elevated plasma insulin levels, and/or with elevated levels of bioactive IGF-I. Hyperinsulinemia and an increased IGF-I bioactivity could thus be an important physiological link between a western lifestyle, overnutrition, a hyperandrogenic sex steroid profile, and increased breast cancer risk. Prospective cohort studies will be needed to test this hypothesis, and to study in greater detail the possible relationships of breast cancer risk with plasma levels of IGF-I and IGFBPs. Confirmation of a relationship of breast cancer risk with plasma insulin levels, on the one hand, or with total plasma IGF-I, on the other hand, could open up new prespectives for breast cancer prevention, either by changes in dietary intake patterns and physical activity, or by the use of certain chemopreventive drugs.

Identification of novel metabolites of the xenoestrogen 4- tert-octylphenol in primary rat hepatocytes

A number of environmental pollutants, including 4- tert-alkylphenols, can mimic the actions of endogenous steroids and have the potential to disrupt the endocrine function in humans and animals. The biotransformation of a 4- tert-alkylphenol in isolated rat hepatocytes was studied in order to determine the possible fate and activity of these xenoestrogens in higher vertebrates. Hepatocytes were incubated with 30 μM 4-(1′,1′,3′,3′-tetramethylbutyl)[U- 14C]phenol (4- tert-octylphenol; t-OP) for up to 60 min. Radiolabelled metabolites were detected by radio-HPLC and the structures determined by gas chromatography–mass spectrometry (GC–MS) analysis of the conjugated or aglycone products. After a 15 min incubation, over 97% of t-OP was metabolised to a complex mixture of metabolites. The initial metabolites formed were identified as products of hydroxylation of the aromatic ring to form catechols and methylated catechols, as well as glucuronide conjugates of the catechol metabolites or parent phenol. These products were further metabolised by hydroxylation of the alkyl chain followed by glucuronide conjugation of the alkoxy group. The conjugated metabolites of t-OP are unlikely to retain estrogen receptor activity, however t-OP is metabolised by some pathways that are similar to that of estrogen catabolism, namely by ortho-hydroxylation to form catechols, methylation by catechol O-methyltransferases and ring conjugation by uridine diphosphoglucuronosyl transferases. Further investigations are needed to determine whether 4- tert-alkylphenols can alter circulating sex steroid profiles by acting as substrates of enzymes determining estrogen metabolism and excretion.

Profiles of Gonadal Development, Sex Steroids, Aromatase Activity, and Gonadotropin II in the Controlled Sex Change of Protandrous Black Porgy, Acanthopagrus schlegeli Bleeker

The objectives of the present study were to investigate the effects of oral administration of estradiol-17β (E2) on the sex steroids and gonadotropin II (GTH II) in plasma, aromatase activity in gonad and brain, and sex change in protandrous black porgy, Acanthopagus schlegeli Bleeker. Two-year-old black porgy were divided into two groups, one fed a control diet and the other a diet mixed with E2 (4.0 mg/kg feed) for 7 months. Significantly higher GSI was observed in the E2 group. Fish treated with E2 showed complete suppression of spermatogenesis and spermiation and induced sex change with vitellogenic oocytes and large primary oocytes. Lower levels of plasma 11-ketotestosterone and higher levels of plasma vitellogenin were shown in the E2 group. Higher gonadal aromatase activity in concordance with elevated plasma levels of GTH II was observed in the E2 group. The highest aromatase activity in the forebrain in the control group was observed in January. Higher aromatase activity in forebrain, midbrain, and hindbrain was also detected in the E2 group than the control group. The change of aromatase activity in brain was more susceptible than that in gonad. The data showed that the increase of plasma GTH II levels and gonadal aromatase activity may be important to the controlled sex change by administration in black porgy.

Methallibure inhibition of testicular and seminal vesicle activity in catfish, Clarias batrachus (Linn.): A study correlating changes in serum sex steroid profiles

The administration of methallibure (2 microg/g BW, daily for 15 days) in Clarias batrachus in prespawning phase (May-June) resulted in decreased weights of seminal vesicle (SV) and testis, and reductions in the concentrations of total proteins, fructose, hexosamines, and sialic acid in SV and testis. The inhibitory changes can be attributed to impairment of steroidogenesis, serum levels of testosterone and estradiol -17beta decreased significantly. Withdrawal of methallibure treatment for 7 and 15 days resulted in gradual recovery and restoration of all the above parameters except the sialic acid levels in the SV and testis, and fructose level in the SV. The methallibure induced regressive changes in the SV and testis were discussed in the light of its GTH inhibiting property.

Sex steroid and prolactin profiles in male American black bears (Ursus americanus) during denning.

Serum sex steroid and prolactin profiles were examined in the male American black bear, Ursus americanus during denning. Sera collected in December and the following March from 8 denning male black bears in Minnesota, U.S.A. were assayed for testosterone, estradiol-17 beta and prolactin. Eight bears were confirmed to be the denning mode based on a serum urea to creatinine ratio less than 10. Serum testosterone concentrations tended to increase from December to the subsequent March whereas serum estradiol-17 beta concentrations tended to decrease during this period. There were few changes in serum prolactin concentrations between December and March. These findings suggest that spermatogenesis and testicular steroidogenesis initiated during denning may be influenced by changes in serum sex steroid concentrations in the American black bear.

Annual sex steroid profiles and effects of gender and season on cytochrome P450 mRNA induction in atlantic tomcod (Microgadus tomcod)

AbstractAs a preliminary step in a 4‐year biomonitoring program, sex steroid levels (testosterone and 11‐ketotestosterone in males, and testosterone and estradiol in females), gonad weights, and diameter of vitellogenic oocytes were measured in tomcod collected bimonthly from the Miramichi (industrialized site) and Kouchibouguac (reference site) rivers from September 1993 to September 1994. As well as the reproductive indices, hepatic levels of cytochrome P4501A mRNA (CYP1A mRNA) were also measured. The preparatory period for spawning began in September, with maximal steroid levels in November, and spawning took place from late December to January. The CYP1A mRNA levels in female tomcod appeared inversely related to plasma steroids, with the lowest amounts of CYP1A mRNA coinciding with maximal steroids. The CYP1A mRNA levels in male tomcod did not exhibit this relationship. River–river comparisons of female tomcod showed significantly smaller vitellogenic oocytes in the Miramichi, along with lower plasma testosterone, estradiol, and relative gonad weight. Miramichi CYP1A mRNA levels were higher than Kouchibouguac in the fall but lower in the spring sample. The CYP1A mRNA–sex steroid relationship observed in this study will facilitate meaningful interpretation of data collected during the full 4‐year study.

Gametogenesis and sex steroid profiles in cultured coho salmon (Oncorhynchus kisutch, Walbaum)

The gametogenesis of a 2-year-old coho salmon broodstock population cultured in a fish farm in southern Chile was studied. Gonadosomatic index (GSI), microscopic gonadal traits, and serum levels of estradiol-17β(E2), testosterone, and 17α,20β-dihydroxy-4-pregnene-3-one (17,20P) in both sexes were recorded beginning 9 months before spawning in bimonthly samplings. Maximum GSI means were reached during May, the month of spawning, with 16.8 ± 4.1% for females and 8.4 ± 0.8% for males, both values within the range described in the literature. GSI in males, however, was triple that of females during January, showing a faster rate of gonadal growth in males in early summer. Gonadal microscopy for both sexes showed stages corresponding to those described by different authors for other salmonids such as rainbow trout. The secondary vitellogenesis period was 4 to 5 months and corresponded with the short vitellogenesis model described in rainbow trout for broodstocks maturing at 2 years of age. The serum profiles of sex steroids in both sexes are consistent with those described in coho salmon and other salmonid species. In females, E2 and 17,20P show opposite profiles, reaching their maximum levels (E2: 45.13 ± 11.3 ng/ml; 17,20P: 24.47 ± 7.34 ng/ml) during vitellogenesis (March) and ovulation (May), respectively. In both sexes, testosterone concentration shows maximum levels in May (females: 61.68 ± 15.75 ng/ml; males: 107.8 ± 11.6 ng/ml), suggesting the physiological importance of this hormone during maturation, either directly or as a substrate for the synthesis of other hormones. In males, the maximum level of 17,20P (22.33 ± 4.5 ng/ml) also occurs in May during total spermiation, which confirms its role in semen production and semen fluid regulation as described in the literature about this hormone in salmonid males. On the basis of the data obtained, a reproductive pattern is proposed for 2-year-old salmon cultured in southern Chile. J. Exp. Zool. 280:429–438, 1998. © 1998 Wiley-Liss, Inc.

Impaired ovulation and breast cancer risk.

Conflicting results have been reported on the association between breast cancer risk and symptoms of luteal insufficiency, such as irregular or prolonged menstrual cycles and difficulty in becoming pregnant. Studies on the association between breast cancer risk and hormonal markers of impaired ovulation have also yielded conflicting results. Inadequate allowance for body mass and fat distribution may lead to inconsistent results when assessing the association between luteal insufficiency in premenopausal women and breast cancer risk. Ovulatory function is impaired by obesity, especially if it is predominantly abdominal in distribution. The Western diet and lifestyle favour early manifestation of hyperinsulinaemic insulin resistance in genetically-predisposed women. It is commonly associated with obesity which is predominantly abdominal in distribution. In a subset of premenopausal women, the concomitants of hyperinsulinaemia may impair maturation of ovarian follicles by a direct effect of insulin or insulin-like growth factors on ovarian tissue. Even when women are ovulating regularly, obesity may be associated with luteal insufficiency as shown by decreased levels of progestins or other changes in the sex steroid profile. Insulin resistance is likely to be involved and might explain the weak reduction in breast cancer risk associated with overweight in premenopausal Western women, in contrast with the increased risk widely reported in obese post menopausal women.

Comparative study of reproductive biology in single and multiple‐spawner cyprinid fish. II. Sex steroid and plasma protein phosphorus concentrations

The dynamics and regulation of oogenesis in single and multiple‐spawner cyprinid fish showing group‐synchronous oocyte development, was investigated in three species from the River Meuse (Belgium): the roach Rutilus rutilus as a single spawner, and the bleak Alburnus alburnus and the white bream Blicca bjoerkna as multiple spawners. This paper compares the seasonal profiles of sex steroids (oestradiol‐17β, testosterone and 17,20β‐dihydroxy‐4‐pregnen‐3‐one) and plasma alkali‐labile protein phosphorus. Different patterns of plasma oestradiol‐17β (E2) and plasma protein phosphorus (PPP) have been observed not only between the single and the multiple spawner fish, but also among the two multiple spawners. In roach, two increases of E2 levels were observed. The first occurred in September after a short gonadal quiescent period, and coincided with the increase of the PPP at the onset of exogenous vitellogenesis. The second took place in spring before the spawning season. The low PPP recorded during that period probably reflected its rapid incorporation by the oocytes. In both multiple spawners, highest values of PPP were recorded just before the spawning season. In white bream, the PPP declined progressively once the differentiation of exogenous vitellogenic oocytes was completed before the onset of the spawning season. In bleak, PPP levels remained high throughout the spawning season and corresponded to a sustained oocyte recruitment during the whole of this period. Regardless of the pattern of oocyte growth recruitment, the E2 concentrations were high in both multiple spawner species during the breeding season. In the three species, testosterone levels remained low regardless of the maturation stage (ranging from 0.6 to 13.4ng ml−1). Except for relatively high concentrations of 17,20βP in roach during final maturation and postspawning stages (20 and 28 ng ml−1, respectively), low levels of this steroid were measured in these cyprinids, and especially in the multiple spawner fish. The role of this progestogen as the maturation inducing Steroid is discussed.

Ovarian development and serum sex steroid and vitellogenin profiles in the female cultured sturgeon hybrid, the bester

Changes in serum levels of estradiol‐17/J (E2), testosterone (T), 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β‐P) and vitellogenin (VTG), in cultured adult female bester were examined in relation to ovarian development during a 1‐year sampling period. Considerable variations in oocyte development were found among fish. Oocytes at previtellogenic stage (≥0–6mm in diameter) generally started to develop concomitantly with the degeneration of the first batch of oocytes. In vitellogenic individuals, ovaries were comprised of more advanced oocytes with diameter ranging from 0–6 to 2–6 mm and in the post‐vitellogenic class, oocytes attained their largest size (&gt;2–6mm) while the germinal vesicle was migrating towards the animal pole. Oocytes with a migrating nucleus were maintained during the winter period and massive degeneration started in April–May without germinal vesicle breakdown (GVBD) or ovulation occurring. Seasonal changes in E2, T and VTG levels were well correlated with the advancement of oogenesis. Their levels increased during vitellogenesis, whereas in the post‐vitellogenic (migratory nucleus) stage the levels of E2 declined from 2–4 ng ml −1± to 1–2 ng ml −1 and VTG from 4–10 mg ml −1 to 0.–0.5 mg ml −1 while T levels remained high (50–60 ng ml −1). In contrast, serum levels of 17,20†‐P were constantly low (less than 0.2 ng ml−L) throughout the reproductive cycle. These results indicate that the time appropriate for induction of artificial reproduction would be from October–November to April–May when the oocytes are in the late Stages of the development.

Ovarian development and serum sex steroid and vitellogenin profiles in the female cultured sturgeon hybrid, the bester

Changes in serum levels of estradiol-17/J (E2), testosterone (T), 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) and vitellogenin (VTG), in cultured adult female bester were examined in relation to ovarian development during a 1-year sampling period. Considerable variations in oocyte development were found among fish. Oocytes at previtellogenic stage (≥0–6mm in diameter) generally started to develop concomitantly with the degeneration of the first batch of oocytes. In vitellogenic individuals, ovaries were comprised of more advanced oocytes with diameter ranging from 0–6 to 2–6 mm and in the post-vitellogenic class, oocytes attained their largest size (>2–6mm) while the germinal vesicle was migrating towards the animal pole. Oocytes with a migrating nucleus were maintained during the winter period and massive degeneration started in April–May without germinal vesicle breakdown (GVBD) or ovulation occurring. Seasonal changes in E2, T and VTG levels were well correlated with the advancement of oogenesis. Their levels increased during vitellogenesis, whereas in the post-vitellogenic (migratory nucleus) stage the levels of E2 declined from 2–4 ng ml −1± to 1–2 ng ml −1 and VTG from 4–10 mg ml −1 to 0.–0.5 mg ml −1 while T levels remained high (50–60 ng ml −1). In contrast, serum levels of 17,20†-P were constantly low (less than 0.2 ng ml−L) throughout the reproductive cycle. These results indicate that the time appropriate for induction of artificial reproduction would be from October–November to April–May when the oocytes are in the late Stages of the development.

Testicular development and serum sex steroid profiles during the annual sexual cycle of the male sturgeon hybrid the bester

Testicular development in the adult male F1 sturgeon hybrid, the bester (Huso huso L. female x Acipenser ruthenus L. male), was examined monthly in relation to serum sex steroid levels. Spermatogenesis lasted for 1 year, with meiosis generally starting in September and spermiogenesis in November, although there was considerable variation in testicular developmental stages between fish sampled monthly. Testicular development continued, slowly, during the winter months until April. Fish did not exhibit spontaneous spermiation, and phagocytotic activity of Sertoli cells became prominent from May onwards. Androgen levels increased during Spermatogenesis and remained high throughout the pre‐spermiation period. In the degeneration stage, 11‐ketotestosterone concentrations declined to low levels, while testoster‐ one levels remained high. The serum concentration of 17,20β‐dihydroxy‐4‐pregnen‐3‐one was low throughout the reproductive cycle. Based on these results, it is suggested that the time appropriate for induction of final maturation would be from November–December to April when the testes are in the late stage of development.