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  • 1
    Electronic Resource
    Electronic Resource
    Pharmacological Properties of a New Selective Antiprogestagen: Org 33628 (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 761 (1995), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1995.tb31379.x
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  • 2
    Electronic Resource
    Electronic Resource
    Gonadal steroidogenesis and the possible role of steroid glucuronides as sex pheromones in two species of teleosts (1986)
    Springer
    Fish physiology and biochemistry 2 (1986), S. 101-107 
    Details
    ISSN: 1573-5168
    Keywords: Brachydanio rerio ; Clarias gariepinus ; teleosts ; ovary ; testis ; seminal vesicles ; steroidogenesis ; steroid glucuronides ; sex pheromones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In general, female zebrafish,Brachydanio rerio, ovulate only in the presence of males. The stimulant must be pheromonal as even male holding water is capable of inducing ovulation. After ovulation the mating phase begins. During this phase the male follows the female and oviposition as well as fertilization takes place. Both the ovulation and the mating are controlled by pheromones synthesized by the gonads. Ovulation can be induced by testicular homogenates. After the lipid material has been extracted from the testicular homogenates, the remaining aqueous phase can still induce ovulation. However, when the aqueous phase is treated with the enzymeβ-glucuronidase, it loses the ability to induce ovulation. This is an indication that glucuronides, probably steroid glucuronides, are the compounds responsible. During the mating phase, ovulated female zebrafish become attractive to males. It was found that, after ovulation, ovarian extracts contain the compounds responsible for attracting males. The attractant consists of a mixture of steroid glucuronides. After incubation of the gonads with3H-precursors seven steroid glucuronides have been identified in the testis and five in the ovary. Under fish culture conditions the African catfish,Clarias gariepinus, can produce postivitellogenic oocytes throughout the year. However, in capitivity neither males nor females spawn. In female catfish maturation and ovulation can be induced by treatment with gonadotropins. It might be possible that, analogous to the zebrafish, some reproductive processes in the catfish have to be induced by pheromones. It has been demonstrated that pheromonal compounds released by the seminal vesicles are involved in the attraction of female conspecifics. The steroid glucuronide synthesizing capability of the testes and the seminal vesicles of the male catfish are examined, as well as that of the ovary before and after ovulation of the female catfish. Both testes and seminal vesicles appear to be capable of steroid biosynthesis but only the latter synthesizes steroid glucuronides. Six of these conjugates have been isolated and identified. In the female catfish the ovaries are capable of synthesizing seven steroid glucuronides, but only after ovulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02264077
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  • 3
    Electronic Resource
    Electronic Resource
    Steroidogenesis during induced oocyte maturation and ovulation in the African catfish,Clarias gariepinus (1989)
    Springer
    Fish physiology and biochemistry 6 (1989), S. 61-78 
    Details
    ISSN: 1573-5168
    Keywords: oocyte maturation ; ovulation ; steroidogenesis ; teleosts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in ovarian steroidogenesis accompanying oocyte maturation and ovulation were studied in the African catfish,Clarias gariepinus. Laboratory-reared females with postvitellogenic ovaries were treated with pimozide and LHRH-analogue. The plasma gonadotropin levels were determined by means of a homologous radioimmunoassay, the condition of the ovaries was studied by histological examination of the follicles, and the steroidogenetic capacity of the ovaries was analyzed byin vitro incubation of tissue fragments for 3 h with [3H]-pregnenolone and [3H]androstenedione as precursors. Data were collected at regular intervals between 0 and 16 h after pimozide-LHRH analogue administration. Until 4 h after the beginning of the experiments the plasma gonadotropin levels did not rise above 25 ng/ml, the ovaries remained in the stage of postvitellogenesis, and testosterone was the main end product of steroidogenesis. Four hours later the gonadotropin concentration in the blood had risen to more than 150 ng/ml, and the ovaries had entered the stage of germinal vesicle migration. At the same time steroidogenesis shifted towards the production of 17α,20β-dihydroxy-4-pregnen-3-one, 5β-pregnane-3α, 17α-diol-20-one, 5β-pregnane-3α,6α,17α-triol-20-one, 5β-pregnane-3α,17α,20β-triol and 5β-pregnane-3α,6α,17α,20β-tetrol. During the subsequent stage of germinal vesicle breakdown the plasma gonadotropin level remained high, and the synthesis of the C21-steroids showed a further increase. Simultaneously, the production of some C19-steroid glucuronides was enhanced. The preovulation and especially the postovulation stages were accompanied by a gradual decrease in steroidogenic capacity of the ovaries, even though the plasma gonadotropin level remained high. It is concluded that the prematuration surge of gonadotropin influences the activity of enzymes involved in steroidogenesis, leading to a reduced C17,20-lyase and to an augmented activity of the enzymes 20β-hydroxysteroid dehydrogenase (HSD), 5β-reductase, 3α-HSD, 6α-hydroxylase and UDP-glucuronosyltransferase. During ovulation the activity of all steroidogenic enzymes, including such key enzymes as 3β-HSD and 17α-hydroxylase, gradually decreases. Not only 17α,20β-dihydroxy-4-pregnen-3-one, but also the 5β-reduced pregnanes may be involved in inducing oocyte maturation and/or ovulation. The very polar triol and tetrol products may function, together with the steroid glucuronides as sex pheromones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01875480
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  • 4
    Electronic Resource
    Electronic Resource
    Plasma profiles of fourteen ovarian steroids before, during and after ovulation in African catfish,Clarias gariepinus, determined by gas chromatography and mass spectrometry (1989)
    Springer
    Fish physiology and biochemistry 6 (1989), S. 79-89 
    Details
    ISSN: 1573-5168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The plasma concentrations of fourteen ovarian steroids were measured in postvitellogenic African catfish,Clarias gariepinus, which had been injected with pimozide and LHRHa. Postvitellogenesis persisted for at least four hours after pimozide and LHRHa administration. During this stage a limited rise in the plasma gonadotropin (GTH) level was accompanied by an increase in the testosterone concentration. The estradiol level was high and remained high except for a passing drop during the stage of germinal vesicle migration. At the stage of germinal vesicle migration a strong increase in the plasma GTH level coincided with a maximum in the testosterone concentration and a concomitant increase in the levels of 17α,20β-dihydroxy-4-pregnen-3-one and of five 5β-reduced pregnanes. During germinal vesicle breakdown the GTH concentration remained high, the plasma level of 17α-hydroxyprogesterone tended to increase, and the levels of 5β-pregnane-3α, 17α-diol-20-one, 5β-pregnane-3α,17α,20β-triol and 5β-pregnane-3α,17α,20α-triol reached a maximum. At pre-ovulation the GTH concentration did not change, and peak levels were reached of 17α,20β-dihydroxy-4-pregnen-3-one and 5β-pregnane-3α,6α,17α-triol-20-one. Shortly after ovulation the GTH concentration slightly decreased together with a sharp decline in the concentrations of 17α,20β-dihydroxy-4-pregnen-3-one and the 5β-reduced steroids, with the exception of 5β-pregnane-3α,17α,20α-triol, 5β-pregnane-3α,6α,17α,20β-tetrol and 5β-dihydrotestosterone. The plasma concentrations of androstenedione, estrone, etiocholanolone and 5β-androstane-3α,17β-diol showed marginal fluctuations during oocyte maturation and ovulation. Apart from 17α,20β-dihydroxy-4-pregnen-3-one, the 5β-reduced pregnanes might be candidates for the function of oocyte maturation inducing hormone inC. gariepinus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01875481
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  • 5
    Electronic Resource
    Electronic Resource
    Steroids and steroid glucuronides in the ovarian fluid of the African catfish,Clarias gariepinus, between ovulation and oviposition (1989)
    Springer
    Fish physiology and biochemistry 6 (1989), S. 91-112 
    Details
    ISSN: 1573-5168
    Keywords: gas chromatograhy-mass spectrometry ; steroids ; steroid glucuronides ; ovarian fluid ; pheromones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract As part of a series of experiments concerning a possible pheromonal function of steroids and steroid glucuronides excreted by the sex organs of the African catfish,Clarias gariepinus, qualitative and quantitative studies, using GCMS, were carried out to examine the presence of the steroids, that can be synthesized by the ovary during oocyte maturation and ovulation, and of the corresponding steroid glucuronides, in the fluid surrounding the eggs in the ovarian cavity shortly after ovulation. Full mass spectra were obtained of 5β-pregnane-3α,17α-diol-20-one, 5β-pregnane-3α,17α,20α-triol, 5β-pregnane-3α,6α,17α-triol-20-one, 5β-pregnane-3α,6α,17α,20β-tetrol, 5β-androstane-3α,17β-diol and 5β-androstane-3α,17β-diol-11-one. After selected ion monitoring the following steroids could be detected by the presence of at least two characteristic ions at the expected retention time: 5β-pregnane-3α, 17α,20β-triol, etiocholanolone, 5β-dihydrotestosterone, 5β-androstane-3α,11β-diol-17-one, testosterone and estradiol. After treatment with β-glucuronidase the following steroids could be determined in a similar way: 5β-pregnane-3α,17α-diol-20-one, 5β-pregnane-3α,17α,20α-triol, 5β-pregnane-3α,17α,20β-triol, 5β-pregnane-3α,6α,17α-triol-20-one, 5β-pregnane,3α,6α,17α,20β-tetrol, 5β-androstane-3α,17β-diol, etiocholanolone, 5β-dihydrotestosterone, testosterone and estradiol. The free steroids 5β-pregnane-3α,6α,17α,20β-tetrol and 5β-pregnane-3α,6α,17α-triol-20-one and the steroid glucuronides of testosterone, 5β-dihydrotestosterone and estradiol appeared to be the most abundant of these compounds. The results indicate that very polar steroids and steroid glucuronides, synthesized in the ovary, can be excreted via the ovarian fluid shortly before and during oviposition, and possibly function as sex attractants, inducing reproductive behaviour in male conspecifics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01875482
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  • 6
    Electronic Resource
    Electronic Resource
    A dual function of alcohol dehydrogenase in Drosophila (1983)
    Springer
    Genetica 60 (1983), S. 129-137 
    Details
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Alcohol dehydrogenase (ADH) of Drosophila not only catalyzes the oxidation of ethanol to acetaldehyde, but additionally catalyzes the conversion of this highly toxic product into acetate. This mechanism is demonstrated by using three different methods. After electrophoresis the oxidation of acetaldehyde is shown in an NAD-dependent reaction revealing bands coinciding with the bands likewise produced by a conventional ADH staining procedure. In spectrophotometric measurements acetaldehyde is oxidized in an NAD-dependent reaction. This activity is effectively inhibited by pyrazole, as specific inhibitor of ADH. By means of gas chromatographic analysis a quick generation of acetate from ethanol could be demonstrated. Our conclusion is further supported by experimental results obtained with either purified ADHF enzyme or genotypes with or without ADH, aldehyde-oxidase, pyridoxal-oxidase and xanthine-dehydrogenase activity. These results are discussed in relation to ethanol tolerance in the living organism in particular with respect to differences found between ADH in Drosophila melanogaster and D. simulans, and in relation to the possible implications for the selective forces acting on ADH-polymorphism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00127499
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