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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: An isocratic high–performance liquid chromatographic technique was developed to measure levels of γ–aminobutyric acid (GABA), glutamate, and taurine in the brain and pituitary of goldfish. Accuracy of this procedure for quantification of these compounds was established by evaluating anesthetic and postmortem effects and by selectively manipulating GABA concentrations by intraperitoneal administration of the glutamic acid decarboxylase (GAD) inhibitor 3–mercaptopropionic acid or the GABA transaminase inhibitor γ–vinyl GABA. The technique provided a simple, rapid, and reliable method for evaluating the concentrations of these amino acids without the use of complex gradient chromatographic systems. To investigate the relationship between neurotransmitter amino acids and the control of pituitary secretion of gonadotropin, the effects of injection of taurine, GABA, or monosodium glutamate on GABA, glutamate, taurine, and, in some instances, monoamine concentrations in the brain and pituitary were evaluated and related to serum gonadotropin levels. Injection of taurine caused an elevation in serum gonadotropin concentrations. In addition, injection of the taurine precursor hypotaurine but not the taurine catabolite isetheonic acid elevated serum gonadotropin levels. Intracerebroventricular injection of either GABA or taurine also elevated serum gonadotropin concentrations. Pretreatment of recrudescent fish with α–methyl–p–tyrosine reduced pituitary dopamine concentrations and also potentiated the serum gonadotropin response to taurine. Injection of monosodium glutamate caused an increase of glutamate content in the pituitary at 24 h; this was followed by a decrease at 72 h after administration. Pituitary GABA, taurine, and dopamine concentrations underwent a transient depletion after monosodium glutamate administration, and this was associated with an elevation of serum gonadotropin content. The increase in serum gonadotropin concentrations in response to a gonadotropin–releasing hormone analogue was potentiated by pretreatment with monosodium glutamate. This article demonstrates that procedures causing elevation in GABA and taurine concentrations stimulate gonadotropin release in a teleost fish.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 519 (1987), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1351
    Keywords: Goldfish ; Gonadotropin ; Olfaction ; Pheromone ; Steroid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. To determine the specificity of the goldfish (Carassius auratus) olfactory system to the reproductive pheromone 17α,20β-dihydroxy-4-pregnen-3-one (17α,20βP), and to determine if related sex steroids might also function as pheromones, electro-olfactogram (EOG) responses were recorded from mature male goldfish. 2. Of the 24 steroids tested, 17α,20βP was the most stimulatory. It had a detection threshold of 10−12 M and at a concentration of 10−8 M elicited an EOG response 3 times that elicited by 10−5 M L-serine 3. 17α,20β,21-triol-4-pregnen-3-one, a metabolite of 17α,20βP, was the only other highly stimulatory steroid. Its threshold was 10−11 M. 4. In cross-adaptation experiments EOG responses to all 21-carbon steroids were inhibited during adaptation to 17α,20βP: responses to this pheromone are transduced by a single receptor/transduction mechanism. 5. To verify the biological relevance of EOG recording whole animal responsiveness was determined by measuring blood gonadotropin. When goldfish were placed into homogeneous steroid solutions endocrine responsiveness strongly correlated with EOG recording. However, when steroids were added to aquaria containing fish, responses were less specific indicating that transient wisps of steroids trigger endocrine responses. 6. Although the extreme sensitivity and specificity of the goldfish olfactory system to 17α,20βP gives it the potential to serve as a highly specific cue, realization of this potential is probably determined by the dynamics of pheromone exposure.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0878
    Keywords: Gonadotrophin-releasing hormone ; Teleosts ; Immunohistochemistry ; Neuroendocrine control ; Reproduction ; Goldfish (Carassius auratus)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The organization of Gn-RH systems in the brain of teleosts has been investigated previously by immunohistochemistry using antibodies against the mammalian decapeptide which differs from the teleostean factor. Here, we report the distribution of immunoreactive Gn-RH in the brain of goldfish using antibodies against synthetic teleost peptide. Immunoreactive structures are found along a column extending from the rostral olfactory bulbs to the pituitary stalk. Cell bodies are observed within the olfactory nerves and bulbs, along the ventromedial telencephalon, the ventrolateral preoptic area and the latero-basal hypothalamus. Large perikarya are detected in the dorsal midbrain tegmentum, immediately caudal to the posterior commissure. A prominent pathway was traced from the cells located in the olfactory nerves through the medial olfactory tract and along all the perikarya described above to the pituitary stalk. In the pituitary, projections are restricted to the proximal pars distalis. A second immunoreactive pathway ascends more dorsally in the telencephalon and arches to the periventricular regions of the diencephalon. Part of this pathway forms a periventricular network in the dorsal and posterior hypothalamus, whereas other projections continue caudally to the medulla oblongata and the spinal cord. Lesions of the ventral preoptic area demonstrate that most of the fibers detected in the pituitary originate from the preoptic region.
    Type of Medium: Electronic Resource
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