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  • Gonadotropin secretion  (2)
  • testis  (2)
  • African catfish (Clarias lazera)  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Isolation of gonadotrops from the pituitary of the African catfish, Clarias lazera (1984)
    Springer
    Cell & tissue research 236 (1984), S. 669-675 
    Details
    ISSN: 1432-0878
    Keywords: Gonadotrops ; Isolation ; Cell culture ; Gonadotropin secretion ; African catfish (Clarias lazera)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Dispersed pituitary cells from male African catfish, Clarias lazera, were fractionated in a density gradient of Percoll. Five fractions were isolated, consisting of about 6, 19, 39, 95 and 83% gonadotrops, respectively. The gonadotrops were identified by their ultrastructural characteristics, by immunocytochemistry, and by measuring their hormone content. After one day in culture, in each fraction the secretion of gonadotropin could be stimulated by a luteinizing hormone-releasing hormone analogue, indicating that the cells had retained their functional integrity. Since the regulatory mechanisms of different cell types from the pituitary have some similarity, purification of the gonadotrops provides a model to study the regulation of gonadotropin secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217237
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Pubertal development of male African catfish,Clarias gariepinus. In vitro steroidogenesis by testis and interrenal tissue and plasma levels of sexual steroids (1997)
    Springer
    Fish physiology and biochemistry 16 (1997), S. 129-138 
    Details
    ISSN: 1573-5168
    Keywords: Clarias gariepinus ; African catfish ; teleost fish ; puberty ; spermatogenesis ; steroidogenesis ; testis ; interrenal tissue ; androgen blood levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In fish, sex steroids initiate and/or accelerate the maturation of the brain-pituitary-gonad axis. In order to obtain information on the steroid milieu during the pubertal development of male African catfish, we have monitored the conversion of [3H]-pregnenolone and [3H]-androstenedione by testis and [3H]-pregnenolone by interrenal tissue fragmentsin vitro. Pubertal development occurs between two and six months of age. Testicular development proceeds through four main stages that are characterised histologically by the presence of spermatogonia (stage I), spermatogonia and spermatocytes (stage II), spermatogonia, spermatocytes and spermatids (stage III), and all germ cells including spermatozoa (stage IV). 11β-Hydroxyandrostenedione and cortisol were the main products of testes and interrenal tissue, respectively, in all stages of the pubertal development; a change in the steroidogenic pattern was not observed during this period. The interrenal tissue displayed no significant conversion of [3H]-pregnenolone to 11-oxygenated androgens. Blood plasma was analyzed for the presence of five androgens; testosterone, 11β-hydroxytestosterone, 11β-hydroxyandrostenedione, androstenetrione, and 11-ketotestosterone. 11-Ketotestosterone was the quantitatively dominating androgen in the circulation at all stages of development, which was more pronounced in stages III and IV. The obvious differences between thein vitro andin vivo results, namely 11β-hydroxyandrostenedione being the main testicular productvs. 11-ketotestosterone dominating in the blood, may indicate that 11β-hydroxyandrostenedione is converted to 11-ketotestosterone at extratesticular sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00004670
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Steroid hormone secretion by testicular tissue from African catfish, Clarias gariepinus, in primary culture: identification and quantification by gas chromatography — mass spectrometry (1993)
    Springer
    Fish physiology and biochemistry 12 (1993), S. 21-30 
    Details
    ISSN: 1573-5168
    Keywords: gas chromatography-mass spectrometry ; teleosts ; testis ; steroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract With the final aim of identifying the testicular steroids involved in the feedback mechanism of the hypothalamus-pituitary-gonad axis, steroid secretion by the testis of African catfish, Clarias gariepinus, was studied in vitro, by means of gas chromatography followed by mass spectrometry. Testicular fragments of sexually mature catfish raised in captivity were incubated in L-15 medium with and without catfish pituitary extract (cfPE). Without adding cfPE, 22 steroids could be identified, amongst which 11β-hydroxyandrostenedione, 11β-hydroxytestosterone, 11-ketotestosterone and 11-ketoandrostenedione were dominating. After incubation in the presence of cfPE, the concentrations of the four 11-oxygenated steroids were increased about 4-fold. The amounts of pregnane derivatives in the incubation medium showed the largest increases in the presence of cfPE. 5β-Pregnane-triol levels, for example, were 60-fold higher than in the medium from control incubations. The secretion of 5α- and 5β-androstanes was also stimulated by cfPE. The stimulation was not equal for all steroids, indicating that cfPE not only stimulates total steroidogenesis by increasing the availability of cholesterol, but also by influencing specific steroid converting enzyme activities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00004319
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The brain-pituitary-gonadal axis in the rainbow trout, Salmo gairdneri (1983)
    Springer
    Cell & tissue research 233 (1983), S. 377-388 
    Details
    ISSN: 1432-0878
    Keywords: Gonadotrops ; Gonadotropin secretion ; Steroids ; Brain-pituitary-gonadal axis ; Juvenile teleost
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In a cytophysiological study it was investigated whether in juvenile trout gonadal steroids stimulate the gonadotropic (GTH)-cells directly or indirectly via the brain. Pituitaries of donor animals were transplanted into the caudal musculature of testosterone-treated and non-testosterone-treated host fish. Testosterone treatment caused an increase in GTH-content in the in situ pituitaries and in the grafts. Accordingly, the gonadotrops displayed ultrastructural changes such as the appearance of well-developed Golgi systems and large globules. The stimulation of the morphological development of gonadotrops and of synthesis and storage of GTH in the allografted pituitaries indicates that testosterone affects the GTH-cells directly. In untreated juvenile trout the gonadotropin content of the pituitary and the gonadotropin concentration in the plasma vary with the time of year. This variation and the role of testosterone and gonadotropin-releasing hormone on the release of GTH are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238304
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    Paper (German National Licenses)
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