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1.
Ovarian steroidogenesis during final oocyte maturation (FOM) in the spotted seatrout (Cynoscion nebulosus) was investigated by incubating ovarian fragments with tritiated pregnenolone, followed by chromatographic separation of
the radioactive products. The major tritiated steroid produced during FOM comigrated with 17α,20β,21-trihydroxy-4-pregnen-3-one
(20β-dihydro-11-deoxycortisol, 20β-S) on HPLC and TLC. Only minor amounts of radioactive material coeluted with 17α,20β-dihydroxy-4-pregnen-3-one
(17α,20β-P), 11-deoxycorticosterone (DOC), estradiol-17β and testosterone standards in the HPLC system. Additional chromatography
by TLC confirmed the presence of radioactive estradiol-17β and testosterone but not 17α,20β-P and DOC.
All the ovarian steroids producedin vitro during FOM were assayed for their ability to induce germinal vesicle breakdown (GVBD) of spotted seatrout oocytes. Twenty
grams of ovarian tissue were incubated with human chorionic gonadotropin and exogenous pregnenolone. The steroidal products
were purified by HPLC and TLC. Most of the maturation-inducing activity was confined to steroidal material which comigrated
in these systems with 20β-S. This material was active at a concentration of 1 ng steroid/ml medium in the GVBD assay. Smaller
amounts of material which coeluted with 11-deoxycortisol, DOC, 17α,20β-P and several minor unidentified fractions induced
GVBD at concentrations of 10 ng steroid(s)/ml.
The structure-activity relationships of authentic steroids in inducing GVBD of spotted seatrout oocytes was investigated.
Hydroxylation at the 17α, 20β or 21 positions increased potency to induce GVBD. Steroids with multiple hydroxyl groups at
the 17α and 20β positions (17α, 20β-P) and at the 17α, 20β, and 21 positions (20β-S) had maximum biological activity in the
GVBD bioassay. The results suggest that 20β-S is a major maturation-inducing steroid in spotted seatrout. 相似文献
2.
M.L. Pinillos A.I. Guijarro M.J. Delgado P.C. Hubbard A.V.M. Canário A.P. Scott 《Fish physiology and biochemistry》2002,26(2):197-210
The present study is concerned with pheromone communication in tench (Tinca tinca L.), establishing firstly whether males have a high olfactory sensitivity to some typical teleost sex steroids and prostaglandins;
and secondly whether males and females might be able to synthesise and release some of these steroids into the water. The
C21 steroid, 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) was found to give large electro-olfactogram responses with an estimated
threshold of detection of 10−12 M. The male tench were equally sensitive to glucuronidated 17,20β-P (10−11.6 M) but 100 times less sensitive to sulphated 17,20β-P (11−9.7 M). Preliminary data from cross-adaptation studies suggest that both the free and conjugated forms are detected by the same
olfactory receptor(s). Male tench also had high olfactory sensitivity to prostaglandin F2α (PGF2α) and 15-keto PGF2α (11−11.5 and 10−11.4 M). They were relatively insensitive, however, to testosterone (T), androstenedione (AD), 11-ketotestosterone (11-KT), 17β-oestradiol
(E2), 17,20β,21-trihydroxy-4-pregnen-3-one (17,20β,21-P) and 17,20α-dihydroxy-4-pregnen-3-one (17,20α-P). Radioimmunoassays were
used to measure the steroids in plasma and water and all samples were processed for the measurement of free, sulphated and
glucuronidated fractions. In females, free 17,20β-P, 17,20α-P, free and glucuronidated T, and AD in plasma showed the largest
increases in response to injection with mammalian gonadotropin-releasing hormone analogue (GnRHa) or Ovaprim (a mixture of
GnRHa and a dopamine inhibitor). Free 17,20β-P was released into the water at the greatest rate. Plasma concentrations of
the two conjugated forms of 17,20β-P were also elevated 18 h after the administration of GnRHa, but not by as much as the
free steroid. In males, AD and 11-KT showed the greatest increase in response to GnRHa and were moreover released into the
water at a higher rate in the treated group than in the control. The data support a possible pheromonal role for free and
glucuronidated 17,20β-P.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
The in vitro effects of several steroids on the maturation of intact white sturgeon (Acipenser transmontanus) ovarian follicles were investigated. At the highest concentration (1024 ng ml–1 for the C21 steroids and 1139 ng ml–1 for the C19 steroids), all of the C21 steroids tested, progesterone (P4), 17-hydroxyprogesterone (17OHP), 17,20-dihydroxy-4-pregnen-3-one (17,20-P), 17,(20,21-trihydroxy-4-pregnen-3-one 20-S), 11-deoxycortisol (S) and cortisol (F), as well as testosterone (T) induced germinal vesicle breakdown (GVBD) at 14 and 22 h. At 6 h, only P4 and 17,20-P induced maturation at the highest concentration (1024 ng ml–1). At 14 and 22 h, 11-deoxycortisol was the most potent steroid inducer of GVBD followed by P4, 17OHP, 17,20-P, and 20-S. The steroid 11-hydroxytestosterone (11OHT) was completely ineffective at all concentrations and exposure times. The C21 steroids induced oocyte maturation at concentrations ranging from 4 to 1024 ng ml–1, whereas T induced GVBD at 225 to 1139 ng ml–1. Calculation of the mean effective concentration that induced 50% GVBD (EC50) from the 22 h incubations revealed the following order of potencies: S > P4 > 17OHP > 17,20-P > 20-S >> F > T. These bioassay results, together with previous findings on the endogenous production of steroids by ovarian follicles from gonadotropin-primed females, indicate that more than one steroid has a biological role in the resumption of meiosis in sturgeon oocytes and provides empirical evidence for P4, 17OHP, S, 20-S, and 17,20-P as maturation-inducing steroids in white sturgeon. 相似文献
4.
Makito Kobayashi Peter W. Sorensen Norm E. Stacey 《Fish physiology and biochemistry》2002,26(1):71-84
Species that employ sexual reproduction must synchronize gamete maturity with behavior within and between genders. Teleost
fishes solve this challenge by using reproductive hormones both as endogenous signals to synchronize sexual behavior with
gamete maturation, and as exogenous signals (pheromones) to synchronize spawning interactions between fish. This dual role
of hormonal products is best understood in the goldfish, an external fertilizer with a promiscuous mating system. Female gonadal
growth and vitellogenesis is stimulated by 17β-estradiol (E2) which also evokes release of a recrudescent pheromone. At the
completion of vitellogenesis, ovarian E2 production drops and plasma testosterone increases, sensitizing the female gonadotropin
II (luteinizing hormone; LH) system to environmental cues (temperature, spawning substrate, pheromones). These cues eventually
trigger a LH surge that alters steroidogenesic pathways to favor the production of progestins including 17,20β-dihydroxy-4-pregnen-3-one
(17,20β-P). Plasma 17,20β-P stimulates oocyte maturation but is also released to the water along with sulfated 17,20β-P and
androstenedione to serve as a preovulatory pheromone. This pheromone stimulates male behavior, LH release, and sperm production.
At the time of ovulation, females become sexually active in response to prostaglandin F2α (PGF2α) synthesized in the oviduct.
PGF2α and its metabolites are released as a postovulatory pheromone that induces male spawning behavior which further increases
male LH and sperm production. Androgenic hormones are required for male behavior and LH release. Although goldfish are gonochorists,
hormone treatments can induce heterotypical functions in adults. Similar findings in other fish demonstrate that a sexually
bipotential brain is not restricted to hermaphroditic fishes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Michiya Matsuyama Shinji Adachi Yoshitaka Nagahama Katsuhiko Maruyama Shuhei Matsura 《Fish physiology and biochemistry》1990,8(4):329-338
Ovarian developmental stages and serum steroid hormone levels were examined at six different times of day (0100, 0600, 1000,
1300, 1600, 2000 h) in a marine teleost, the Japanese whiting Sillago japonica, which has an asynchronous-type ovary containing oocytes at various stages of development and spawns every day during a period
ranging up to three months. The largest oocytes in the ovaries at the active vitellogenic or post-vitellogenic stages were
found between 0100 and 1300 h. Oocyte maturation indicated by germinal vesicle breakdown (GVBD) occurred at 1600 h, and ovulated
oocytes were observed in the ovaries collected at 2000 h. These processes were accompanied by a significant daily change in
serum steroid hormone levels. The serum level of estradiol-17β showed a peak in fish with mature oocytes sampled at 1600 h.
In these fish, the second-largest oocytes in the ovaries were at the initial stage of vigorous vitellogenesis, the secondary
yolk stage. Therefore the highest level of serum estradiol-17β was considered to be due to the second-largest oocytes. Testosterone
levels remained low and constant throughout the experimental period. The serum levels of 17α,20β-dihydroxy-4-pregnen-3-one
(17α,20β-diOHprog) peaked at 1600 h at which time all fish had mature oocytes. These results indicate that the Japanese whiting
possesses a diurnal rhythm of oocyte development including vitellogenesis, oocyte maturation and ovulation, and further suggest
that daily cycles in oocyte growth and maturation which simultaneously take place in an ovary are regulated by diurnal secretions
of estradiol-17β and the maturation-inducing steroid, 17α,20β-diOHprog. 相似文献
6.
William King V David L. Berlinsky Craig V. Sullivan 《Fish physiology and biochemistry》1995,14(6):489-500
Plasma estradiol-17 (E2), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E2 and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E2 and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass. 相似文献
7.
The gonad histology, gonado-somatic index (GSI), 17β-estradiol (E2) levels and acetylcholinesterase (AChE) activity in the carp species Chalcalburnus tarichi from Lake Van and the Karasu river, eastern Turkey, have been investigated. Fish between 5 and 7 years old were sampled from
November 2003 to February 2004. The ratio of female fish caught in Lake Van with abnormal ovaries (AbOF) was 43.3%, but the
fork length and body weight of these fish were not correlated with this abnormality. The weight of the ovaries and the GSI
values of AbOF were very low (P < 0.05). Histological observations on the samples caught each month revealed that the oocytes had degenerated in the perinucleolus
and early cortical alveolus stages and that the ovaries were full of somatic stromal tissue. In addition, the seminiferous
tubules of male fish with abnormal testes did not contain male reproductive cells at any stage. The ovaries of the fish caught
from the Karasu river were also full of oocytes in the perinucleolus and early cortical alveolus stages, but there were fewer
atretic follicles. Furthermore, apoptosis was observed in the ovary cells of these fish, in particular in the follicular cells,
and the plasma E2 levels of the AbOF was very low (P < 0.05). AChE activity was inhibited only in liver (P < 0.05). We conclude that our sample of C. tarichi must have been exposed to various polluting chemicals or another unknown factors (such as global warming) and that these
factors have irreversibly impaired oocyte development in a high percentage of fish. 相似文献
8.
David E. Kime Mohammad A. S. Abdullah Miroslawa Sokolowska-Mikolajczyk Piotr Epler 《Fish physiology and biochemistry》1994,13(4):317-324
Carp ovarian tissue was incubated with 3H-17-hydroxyprogesterone in the presence of 0, 0.1, 1, 10, and 100 μg ml−1 unlabeled 17-hydroxyprogesterone. The pattern of metabolites formed showed a marked variation with substrate concentration.
Formation of glucuronide and sulphate conjugates was important only at low substrate concentration. At high substrate concentration
(10 and 100 μg ml−1) 17,20α-dihydroxy-4-pregnen-3-one was the major metabolite, but at intermediate concentrations polar 7α-hydroxypregnanetetrols
predominated. The results support the hypothesis that at low substrate concentrations conjugating, 5α-reducing and 7α-hydroxylating
enzymes, of high activity but low capacity, act as scavengers to deactivate any steroids formed during the relatively low
pituitary gonadotrophin secretions which are necessary for oocyte development, but that during the prespawning gonadotrophin
surge when high levels of substrate are present these enzymes are saturated and 17,20α-dihydroxy-4-pregnen-3-one (17,20αP)
becomes the major ovarian steroid. The possible role of 17,20αP during oocyte final maturation requires further examination. 相似文献
9.
Growth hormone (GH) has recently been identified as co-gonadotropin regulating fish reproduction, hitherto, no effort has
been made to see its effect on oocyte maturation in fishes, though some reports demonstrate the role of insulin like growth
factor-I (IGF-I) in oocyte maturation in teleosts. Hence, effect of GH on oocyte maturation in post-vitellogenic H. fossilis has been worked out in the present study. Post-vitellogenic follicles in the ovarian tissue were challenged in vitro with H. fossilis pituitary homogenate (fPH), Clarias batrachus GH and GtH, barramundi IGF-I (IGF-I), 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) and testosterone alone, or in combination with IGF-I for 18 h at 26±1°C. Incubation of ovarian
tissue with GH in the presence of actinomycin d or cycloheximide or barramundi IGF-I antiserum was also made separately. In general, oocyte maturation was induced by fPH,
barramundi IGF-I, GtH, GH and DHP, which was augmented further by addition of barramundi IGF-I. Testosterone had no effect
on GVBD. Actinomycin d, cycloheximide and anti barramundi IGF-I abolished the GH induced oocyte maturation. Present study suggests for the first
time that GH has a role in egg maturation in fish. 相似文献
10.
Frederick W. Goetz Alexis Y. Fostier Bernard Breton Bernard Jalabert 《Fish physiology and biochemistry》1987,3(4):203-211
The plasma levels of estradiol-17 (E2), 17, 20-dihydroxy-4-pregnen-3-one (17,20-P) and gonadotropin (GTH) were measured in brook trout (Salvelinus fontinalis) during the period from the end of vitellogenesis to postovulation. Blood samples were taken according to specific stages of maturation, including germinal vesicle breakdown (GVBD) and ovulation. E2 levels were quite high (45 ng/ml) at the end of vitellogenesis (and prior to GVBD) and dropped precipitously by GVBD (2 ng/ml). They remained low through ovulation and postovulation. 17,20-P levels were low prior to GVBD (0.7 ng/ml) and increased dramatically at GVBD (148 ng/ml). The levels of 17,20-P remained high at ovulation (142 ng/ml) and then dropped significantly within 24 h to approximately half of the ovulatory values. They decreased even further by 7 days postovulation. GTH levels rose gradually through GVBD and ovulation from a postvitellogenic level of approximately 3 ng/ml to a 7 day postovulatory value of approximately 10 ng/ml. The overall results; 1) decrease in estradiol prior to GVBD, 2) increase in 17,20-P at GVBD and 3) gradual GTH rise through GVBD and ovulation, are similar to those reported for other salmonids. 相似文献
11.
Jeffrey A. Malison Lynne S. Procarione Terence P. Barry Anne R. Kapuscinski Terrence B. Kayes 《Fish physiology and biochemistry》1994,13(6):473-484
The annual reproductive cycle of walleye (Stizostedion vitreum) was characterized by documenting changes in gonadal development and serum levels of estradiol-17β (E2), testosterone (T), 17α,20β-dihydroxy-4-pregnen-3-one (17,20-P), and 11-ketotestosterone (11-KT) in wild fish captured from
upper midwestern lakes and rivers throughout the year. Fish from the populations used in this study spawn annually in early-
to mid-April. Walleye showed group synchronous ovarian development with exogenous vitellogenesis beginning in autumn. Oocyte
diameters increased rapidly from ∼ 200 μm in October to ∼ 1,000 μm in November, and reached a maximum of 1,500 μm just prior
to spawning. Changes in gonadosomatic indices (GSIs) paralleled changes in oocyte diameters. Serum E2 levels in females increased rapidly from low values in October (< 0.1 ng ml−1) to peak levels of 3.7 ng ml−1 in November, coinciding with the period of the most rapid ovarian growth. Subsequently, E2 levels decreased from December through spawning. Serum T levels exhibited a bimodal pattern, increasing to 1.6 ng ml−1 in November, and peaking again at 3.3 ng ml−1 just prior to spawning. We detected 11-KT in the serum of some females at concentrations up to 5.6 ng ml−1, but no seasonal pattern was apparent. In this study (unlike our results in a related study) 17,20-P was not detected. In
males, differentiation of spermatogonia began in late August, and by January the testes were filled (> 95% of germ cells)
with spermatozoa. Mature spermatozoa could be expressed from males from January through April. GSIs ranged from 0.2% (post-spawn)
to 3.2% (pre-spawn). Serum T levels rose from undetectable levels in post-spawn males to 1.6 ng ml−1 by November, remained elevated throughout the winter, and peaked at 2.8 ng ml−1 I prior to spawning. Levels of 11-KT in males remained low (< 10 ng ml−1, from post-spawning through January, then increased significantly by March and peaked just prior to spawning at 39.7 ng ml−1. Our results indicate that vitellogenesis and spermatogenesis are complete or nearly so, in walleye by early winter, and
suggest that it may be possible to induce spawning in this species several months prior to the normal spawning season by subjecting
fish to relatively simple environmental and hormonal treatments. 相似文献
12.
In order to study the possible homeostatic regulation of gonadal steroids in fishes, plasma steroid levels were measured in
hemi-castrated and sham-operated nesting male three-spined sticklebacks, Gasterosteus aculeatus, and in mature 2-year old male Atlantic salmon, Salmo salar. Hemi-castration significantly suppressed androgen levels in both species. In sticklebacks, plasma levels of 11-ketotestosterone
(11KT) were 56% and levels of testosterone (T) 55% of those found in sham-operated males. In hemi-castrated salmon the levels
of 11KT were 63%, and the levels of T were 75% of the levels in sham-operated males. In contrast, levels of 17α,20β-dihydroxy-4-pregnen-3-one
(17,20-P) in salmon (not measured in sticklebacks) were not different between hemi-castrated and sham-operated males. The
results suggest that, although levels of the steroid 17,20-P were compensated in hemi-castrated salmon, the androgen levels
in fish males in full spawning condition are not closely regulated by negative feedbacks.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
The relationship between plasma and ovarian levels of gonadal steroids was examined in two New Zealand fish species with multiple
spawning cycles of differing length. Snapper (Pagrus auratus) have a daily cycle of oocyte development, ovulation and spawning, whereas demoiselles (Chromis dispilus) spawn over 2–3 days during a repeat spawning cycle of 7–9 days. Ovarian and plasma levels of the gonadal steroids 17β-estradiol
(E2), testosterone (T), 17-hydroxyprogesterone (17P) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were measured in reproductively
active fish captured from the wild. Ovarian levels of E2, T and 17P changed in relation to spawning cycle and gonad stage in both snapper and demoiselles. E2 and T levels were detectable at all times, but highest during vitellogenesis in both species. Cyclic changes of 17P occurred
in both species, and levels appeared to depend on the rate of conversion of 17P to other hormones. No changes in ovarian levels
of 17,20βP were detected in relation to stage of the spawning cycle in snapper; however, ovarian levels of 17,20βP were highest
in demoiselles before spawning when fish undergoing final oocyte maturation predominated. Plasma levels of E2 and T were strongly correlated with ovarian concentrations (r=0.850 and r=0.819 for E2 and T respectively) in demoiselles but there was poor correlation between ovarian and plasma levels of 17P and 17,20βP (r=0.004
and 0.273 respectively), or between ovarian and plasma levels of E2, T, 17P or 17,20βP of snapper (r=0.135, 0.277, 0.131 and 0.279). The poor correlation between plasma and ovarian levels of
some steroid hormones suggests that plasma concentrations of steroids may not adequately reflect the reproductive status of
the fish during short-term cyclic ovarian changes. It is suggested that this disparity is likely to be most marked in species
with ovulatory periodicity of short duration. 相似文献
14.
This article briefly reviews the current status of investigations, mainly based on the amago salmon,Oncorhynchus rhodurus, on the mechanisms of synthesis and action of 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-diOHprog). Pituitary gonadotropin
is of primary importance in triggering meiotic maturation in teleost oocytes. However, the maturational action of gonadotropin
is not direct, but is mediated by the follicular production of maturation-inducing substance (MIS). It is now well established
that 17α,20β-diOHprog is the major MIS of salmonids. Production of this steroid occursvia the interaction of two distinct cell layers, the thecal and granulosa cell layers (2-cell type model). The first step of
the stimulating effect of gonadotropin in both layers is the receptor-mediated activation of adenylate cyclase and formation
of cAMP. Our findings suggest that the major stimulating action of gonadotropin on 17α,20β-diOHprog biosynthesis is due to
the stimulation of 17α-hydroxyprogesterone production by the thecal layer and the selective induction of thede novo synthesis of 20β-hydroxysteroid dehydrogenase in the granulosa layer. 17α,20β-diOHprog acts at the surface of the oocyte.
The early steps following 17α,20β-diOHprog action involve the formation of the major cytoplasmic mediator of this steroid,
maturation-promoting factor (MPF). It was shown that goldfish MPF induces meiotic maturation inXenopus oocytes andvice versa. The chemical characterization of fish MPF is important for our understanding of the precise mode of maturational action
of 17α,20β-diOHprog. 相似文献
15.
M. Matsuyama K. Ohta S. Morita M.M. Hoque H. Kagawa A. Kambegawa 《Fish physiology and biochemistry》1998,19(1):1-11
The female bambooleaf wrasse, Pseudolabrus japonicus, spawns daily during the spawning season, and exhibits a diurnal rhythm of ovarian development. In the present study, we have investigated: (1) circulating levels of 17a, 20-dihydroxy-4-pregnen- 17,20-P) and 17,20,21-trihydroxy-4-pregnen-3-one (20-S) in females sampled at different times of the day during spawning season in captivity, and (2) in vitro production of 17,20-P and 20-S by follicle-enclosed oocytes at seven different develo tal stages. In addition, we developed a microtiter plate enzyme-linked immunosorbent assay (ELISA) for 17,20-P. Serum levels of 17,20-P and 20-S showed similar diurnal changes; substantial increases in these levels occurred around the time of germinal vesicle breakdown (GVBD). In vitro experiments showed that massive production of 17,20-P and 20-S occurred in follicles collected just before or during GVBD. Further, acute decreases in 17,20-P and 20-S production were found in the ovarian follicles just prior to ovulation, suggesting inactivation of the maturation-inducing hormone (MIH). These results, taken together with our previous data on the occurrence of GVBD in vitro, suggest a role for both 17,20-P and 20b-S as MIHs in the bambooleaf wrasse. 相似文献
16.
Frederick William Goetz Priscilla Duman Amy Berndtson Erik G. Janowsky 《Fish physiology and biochemistry》1989,7(1-6):163-168
Previous studies have shown that 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P) can induce both germinal vesicle breakdown
and ovulationin vitro of yellow perch (Perca flavescens) oocytes. The stimulation of ovulation can be blocked by indomethacin and restored by the subsequent addition of several
primary prostaglandins (Goetz and Theofan 1979).
In the present investigation, medium levels of prostaglandin F (PGF) and E (PGE) were measured by radioimmunoassay duringin vitro 17α,20β-P-induced ovulation of perch oocytes. PGF levels increased significantly (compared to controls) from 30 to 36h of
incubation. Hourly samples taken through the time of ovulation revealed that the increase in PGF was very closely correlated
to the time of ovulation though it did not preceed it. Cortisol, testosterone, estradiol-17β, 17α,20α-dihydroxy-4-pregnen-3-one
and 17α-hydorxyprogesterone did not increase PGF levels by 48h of incubation, however, several other progestational steroids
including 20β-dihydroprogesterone (20β-P) and progesterone did. 17α,20β-P, 20β-P and progesterone also stimulated an increase
in PGF in spontaneously ovulating oocytes (in which all oocytes ovulated including controls), indicating that the increase
in PGF was not merely a result of the physical process of ovulation but was related to the presence of the steroid.
Based on work supported by the National Science Foundation under grant DCB-8517718 and DCB-8718178. 相似文献
17.
This study examined the changes in plasma steroids during natural (Experiment 1) and induced (Experiment 2) final maturation
in yellow perch Perca flavescens. In experiment 1, ovulating yellow perch were stripped of eggs and blood samples collected to determine the concentrations
of testosterone (T), estradiol-17β (E2), and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP). Eggs from individual females were
weighed and fertilized. Fertilization rate was determined at the embryo eyed stage. In experiment 2, females were randomly
assigned to one of the following treatment groups: (1) saline (0.7% NaCl), (2) des-Gly10[D-Ala6] LHRH-ethylamide (100 μg LHRHa/kg), and (3) LHRHa plus 17,20βP (100 μg LHRHa/kg + 2 mg 17,20βP/kg). Fish were injected intraperitoneally
with two doses at a two-day interval. Blood was collected prior to injections and at the time of ovulation/spawning and concentrations
of T, E2, and 17,20βP (free and conjugated) were determined. In experiment 1, low concentrations of 17,20βP were recorded
at spawning. In experiment 2, all surviving fish injected with LHRHa (5 of 5) released their eggs spontaneously during the
week following injections. None of the surviving control fish (0 of 5) ovulated during this period, whereas only 1 of 3 surviving
fish injected with LHRHa + 17,20βP released eggs. In the control group, concentrations of E2 and 17,20βP did not show significant
differences over the experimental period, whereas plasma T concentrations increased significantly. In fish injected with LHRHa,
the concentrations of T and 17,20βP increased significantly after the first injection but then declined at ovulation/spawning.
It also appears that 17,20βP was conjugated to its sulfated form. Mortality reached 62.5% in the group injected with LHRHa
+ 17,20βP indicating that this treatment was severe. Thus, LHRHa alone appears highly effective in inducing ovulation in yellow
perch.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
Coho salmon follicles obtained at various times throughout the periovulatory period were incubatedin vitro with graded amounts of partially purified salmon gonadotropin (SG-G100) for 24 h and the amounts of 17β-estradiol, testosterone and 17α20β dihydroxy-4-pregnen-3-one (17α20βP) released into the media determined by radioimmunoassay. By this approach, the pattern of steroid secretion by ovarian follicles
was shown to change in relation to the developmental status of the oocyte. Full-grown immature follicles produced large amounts
of 17β-estradiol but negligible amounts of testosterone and 17α20βP. Both basal and gonadotropin-stimulated 17β-estradiol production was subsequently reduced with advancing oocyte development. In contrast, the production of testosterone
and 17α20βP increased during the course of ovarian development with testosterone production highest in follicles with a peripheral germinal
vesicle and 17α20βP production highest in matured and postovulatory follicles. These data are discussed in relation to information on the preovulatory
changes in circulating levels of steriod hormones in salmonids. 相似文献
19.
In fish, oocyte maturation (resumption of meiosis after completion of vitellogenesis and before ovulation) is triggered by maturation inducing steroids (MIS) which generally appear to be secreted in the ovary in response to stimulation by a pituitary maturational gonadotropin. Converging data from different laboratories show that 17-hydroxy, 20-dihydroprogesterone (17, 20-OH-P) is the principal MIS in salmonoids; but clear identification remains to be done in other taxonomic groups.The experiments reported here in the rainbow troutSalmo gairdneri examine the possible involvement of oocyte cAMP on the mechanism of MIS action. The action of 17, 20-OH-P, on germinal vesicle breakdown (GVBD) in oocytes incubatedin vitro within the follicle, was inhibited by various substances expected to elevate the intraoocyte concentrations of cAMP: cAMP ( 1 mM) or dibutyril cAMP ( 2 mM), phosphodiesterase inhibitors such as theophylline ( 0.2 mM) or 3-isobutyl-1 methylxanthine (IBMX 0.1 mM), adenylate cyclase activators such as cholera toxin (> 100 nM) or forskolin ( 0.03 mM). In fact, the combined action of IBMX (1 mM) and forskolin (0.01 or 0.05 mM)in vitro was to promote accumulation of intraoocyte cAMP within 1 to 5 hours. Oocyte cAMP concentrations exhibited a large variability between different females, depending on the stage of oocyte development; a significant positive correlation between oocyte cAMP concentration and the follicular weight, and a significant negative correlation between oocyte cAMP concentration and the median efficient dose of 17, 20-OH-P for induction of GVBD, were observed. Finally, when intrafollicular oocytes were incubatedin vitro, the addition of a maturation-inducing concentration of 17, 20-OH-P (3×10–6M) induced a significant decrease of oocyte cAMP within the first 10 hours of incubation. These results show that cAMP appears to play a central role in the regulation of oocyte sensitivity to 17, 20-OH-P and in the intraoocyte mechanisms leading to GVBD in trout.These data are discussed together with the few indications available in fish concerning the mechanism of MIS action which can be compared to some extent with the amphibian model. 相似文献
20.
Ryusuke Sudo Ryota Tosaka Shigeho Ijiri Shinji Adachi Hiroaki Suetake Yuzuru Suzuki Noriyuki Horie Satoru Tanaka Jun Aoyama Katsumi Tsukamoto 《Fisheries Science》2011,77(4):575-582
To improve understanding of the mechanism of early ovarian development in eels, the effects of water temperature decrease
on oocyte development, plasma levels of sex steroids [estradiol 17β (E2), testosterone (T), 11-ketotestosterone (11-KT)],
and gonadotropin β-subunit [follicle-stimulating hormone (FSHβ), luteinizing hormone (LHβ)] messenger RNA (mRNA) expression
levels were investigated. A total of 27 female Japanese eels Anguilla japonica were divided into initial, control, and test (water temperature decrease) groups. Starting on 22 September 2009, eels in
the test group were reared in a tank with gradual temperature decrease from 25°C to 15°C over 39 days, while the control group
was maintained at 25°C. The test group accumulated more oil droplets in their oocytes than did the other groups. Levels of
sex steroids, especially 11-KT, were higher in the test group. In contrast, FSHβ and LHβ mRNA expression levels were lower
in the test group. These results suggest that water temperature decrease only induced an early stage of ovarian development
that was partly affected by an 11-KT increase. For further maturation, other environmental factors related to induction of
gonadotropin increase appear to be needed. 相似文献