Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Catecholestrogens inhibit dopamine methylation in the gonadotrops of the African catfish,Clarias gariepinus (1989)
    Springer
    Fish physiology and biochemistry 6 (1989), S. 207-212 
    Details
    ISSN: 1573-5168
    Keywords: COMT ; gonadotropic cells ; dopamine ; catecholestrogens ; Clarias gariepinus ; teleosts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isolated gonadotrops of the African catfish,Clarias gariepinus, were incubated with dopamine (DA) and/or catecholestrone and the activity of the enzyme catechol-O-methyltransferase (COMT) was determined by measuring the methylated products. From the apparent Km values for DA and catecholestrone of 0.4–1.3 μM and 17.9–25.2 μM respectively, it was concluded that catecholestrone is a better substrate for the enzyme COMT, compared to DA. Moreover, the methylation of DA is inhibited by comparatively low concentrations of catecholestrone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01875023
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Seasonal changes in endocrine organs of the male common frog, Rana temporaria (1968)
    Springer
    Cell & tissue research 91 (1968), S. 96-111 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The annual cycle of the interrenal tissue in male common frogs, Rana temporaria, has been studied. From the changes in nuclear and cellular area, lipid and cholesterol content and mitotic activity it has been concluded that: 1. After a short resting phase in mid-winter the interrenal tissue shows a high secretory activity which reaches its maximum at the end of the breeding season. 2. After breeding secretion and production decrease to a minimum in mid-summer. 3. A restoration follows from late summer till early winter. During this period secretory activity is accompanied by a relatively high production. A comparison is made between the seasonal changes in the interrenal tissue and the corresponding changes of the testes and pars distalis of the same animals. The significance of pseudofollicles and chromotropic cells in the interrenal tissue is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336987
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Seasonal changes in endocrine organs of the male common frog,Rana temporaria (1968)
    Springer
    Cell & tissue research 88 (1968), S. 549-559 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The annual cycle of the five morphological cell types in the pars distalis of the adenohypophysis of male common frogs,Rana temporaria, was studied in variously stained sections of the pituitary, collected at monthly intervals. All cell types showed a maximal development at the end of hibernation, a strong extrusion of secretory granules in the breeding season, and a more gradual release during later spring and early summer. A minimal development occurred in mid-summer, and a restoration followed in autumn and the hibernation period. During the phase of extrusion production was low, and vice-versa. These seasonal changes correspond with those of the testes and interrenal tissue of the same animals as well as with those of the thyroids and other endocrine tissues, and seems to be an important part of the biphasic annual life cycle of the species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571799
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Histophysiological and immunocytochcmical study on the nature of the thyrotrops in the pituitary of immature rainbow trout, Salmo gairdneri (1983)
    Springer
    Cell & tissue research 231 (1983), S. 185-198 
    Details
    ISSN: 1432-0878
    Keywords: Thyroid ; Pituitary ; Thyrotrops ; Gonadotrops ; Immunocytochemistry ; Teleosts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Alcian blue and periodic acid-Schiff-positive “granular basophils” with electron-dense granules ±160 nm in diameter, and weakly developed irregular cisternae of the granular endoplasmic reticulum (GER) are present in the rostral pars distalis (RPD) and the proximal pars distalis (PPD) of immature rainbow trout. They all react with antisalmon αβ-gonadotropin. However, only granular basophils in the caudal RPD and the rostro-dorsal PPD, often bordering on and sometimes surrounded by neurohypophysial tissue, react with anti-human β-TSH. These cells, considered as the source of thyrotropin, show degranulation and dilatation of the GER-cisternae in fish treated with potassium perchlorate. The thyroids of the goitrogen-treated animals had relatively numerous small follicles with a high epithelium. The remaining granular basophils are gonadotrops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215785
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Glycoprotein gonadotropin in the plasma and its cellular origin in the adenohypophysis of sham-operated and ovariectomized rainbow trout, salmo gairdneri (1981)
    Springer
    Cell & tissue research 218 (1981), S. 439-448 
    Details
    ISSN: 1432-0878
    Keywords: Pituitary salmonids ; GTH-cells ; Ultrastructure ; Ovariectomy ; Radioimmunoassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Among the cells of the pituitary generally believed to produce glycoprotein gonadotropin (GTH) five forms were distinguished, based on the amount and the diameter of granules and globules and the appearance of the rough endoplasmic reticulum. In sham-operated trout so-called “globular” cells predominated, whereas after ovariectomy these were replaced by so-called “cisternal” cells, suggesting that both belong to one GTH-cell type. In addition, ovariectomy caused a strong increase in plasma GTH-levels. This indicates that the transition from globular to cisternal cells is accompanied by extrusion of GTH, and thus points to a storage of GTH in the granules and globules. It is argued that one of the five forms has the morphological characteristics of thyrotropic cells and may not produce glycoprotein GTH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210356
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    The brain-pituitary-gonadal axis in the rainbow trout, Salmo gairdneri: Gonadal hormones and the maturation of gonadotropic cells (1982)
    Springer
    Cell & tissue research 225 (1982), S. 45-56 
    Details
    ISSN: 1432-0878
    Keywords: Gonadotropic cells ; Maturation ; Gonadotropin ; Gonadal hormones ; Juvenile trout
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Intact and castrated juvenile male rainbow trout (Salmo gairdneri) were treated with testosterone and gonadotropic hormone (GTH) to determine the maturational effects of these hormones on the GTH-cells. Electron-microscopic studies of the GTH-cells revealed that GTH and testosterone in intact animals, and testosterone in castrated fish, caused GTH-cell maturation: These cells now displayed the same appearance as GTH-cells in adult trout, including the presence of globules, a well-developed Golgi apparatus and rough endoplasmic reticulum, all of which were absent in GTH-cells of control animals. Animals with stimulated GTH-cells also had an increased GTH content of the pituitary; release of GTH could not be demonstrated. Animals treated with GTH exhibited an accelerated development of the testes, resulting in complete gametogenesis and elevated plasma testosterone levels. These results indicate that exogenous steroids as well as endogenous gonadal steroids can stimulate the full development of GTH-cells and accelerate GTH synthesis. The significance of this stimulating effect of the gonadal hormones with respect to the development of the brain-pituitary-gonadal axis and the onset of puberty is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216217
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Anatomy of the ovaries of the starfish Asterias rubens (Echinodermata) (1981)
    Springer
    Cell & tissue research 217 (1981), S. 577-597 
    Details
    ISSN: 1432-0878
    Keywords: Ovaries ; Ovarian wall ; Oogenesis ; Steroid-synthesizing cells ; Asterias rubens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ovaries of the starfish Asterias rubens were studied histologically and ultrastructurally. The reproductive system in female specimens consists of ten separate ovaries, two in each ray. Each ovary is made up of a rachis with lateral primary and secondary folds: the acini maiores and acini minores. The ovarian wall is composed of an outer and an inner part, separated by the genital coelomic sinus. The ovarian lumen contains oocytes in various phases of oogenesis, follicle cells, nurse cells, phagocytosing cells and steroid-synthesizing cells. Oogenesis is divided into four phases: (i) multiplication phase of oogonia, (ii) initial growth phase of oocytes I, (iii) growth phase proper of oocytes I, and (iv) post-growth phase of oocytes I. The granular endoplasmic reticulum and the Golgi complex of the oocytes appear to be involved in yolk formation, while the haemal system, haemal fluid and nurse cells may also be important for vitellogenesis. The haemal system is discussed as most likely being involved in synchronizing the development of the ovaries during the annual reproductive cycle and in inducing, stimulating and regulating the function of the ovaries. Steroid-synthesizing cells are present during vitellogenesis; a correlation between the presence of these cells and vitellogenesis is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219366
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Changes in the pituitary of the common toad, Bufo bufo, during metamorphosis, and the identification of the thyrotropic cells (1966)
    Springer
    Cell & tissue research 75 (1966), S. 47-56 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Histological changes are described in the pituitary and thyroids of Bufo bufo at subsequent stages of metamorphosis. Special attention is paid to the differentiation of the chromophilic cell types in the pars distalis of the adenohypophysis. Dorso-caudally situated acidophils are functionally active during the larval growth period and gradually regress after the formation of an outer zone in the median eminence and the establishment of a haemal connection between neuro- and adenohypophysis. At the same time Alcian Blue positive, small basophils appear in the central area of the pars distalis. A close correlation exists between these cells and the activity of the thyroids; both reaching a maximum just before and during metamorphic climax. A second type of basophils, the Alcian Blue negative violet cells, develop in the rostral part of the adenohypophysis during metamorphic climax and in connection with the development of a portal circulation. It is concluded that the small basophils are the source of thyrotropic hormone. The larval acidophils are supposed to produce a growth promoting hormone with lactotropic properties, and the violet cells seem to secrete an ICSH-like hormone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00407143
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...