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  • 1
    ISSN: 1573-4935
    Keywords: Neurosecretion ; Vasopressin ; Guanine nucleotides ; G-proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In SLO-permeabilized isolated nerve endings from the rat neurohypophysis, GTP, guanosine 5′[y-thio]triphosphate (GTPyS) and guanosine 5′(ßy-imido]triphosphate (GMPPNP) inhibit the Ca2+-evoked vasopressin release. Pretreatment with pertussis toxin enhances the inhibitory effects of both GTP-analogues. Omission of Mg2+ overcomes the effect of GMPPNP and reverses the inhibitory effect of GTP and GTPyS. In the absence of Mg2+, GTP and GTPyS now potentiate Ca2+-evoked secretion.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 205 (1980), S. 31-42 
    ISSN: 1432-0878
    Keywords: Neurosecretion ; Invertebrate (crab) ; Exocytosis ; Membrane retrieval
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural aspects of hormone release from the sinus gland of the crab Carcinus maenas, have been studied by incubation of glands in vitro (i) in high potassium-containing media to induce hormone release; (ii) in a high potassium-containing calcium-free medium in which depolarisation but no hormone release would be expected; and (iii) in control saline. Uptake of horseradish peroxidase into subcellular organelles was also studied. Many neurosecretory granules could be found in the nerve terminals but, in contrast to mammalian neurosecretory systems, structures resembling microvesicles were extremely scarce. High potassium stimulation in the presence of calcium caused an 18 % loss of granules from the nerve terminals associated with images of single and multiple exocytosis. It further caused an increase in vacuoles which could have accounted for 33 % of the membrane of the granules exocytosed. After incubation in high potassium-containing, calcium-free media there was no evidence either of exocytosis of granules or of an increase in the vacuole population. The population of sparse microvesicle-like structures was not significantly altered by incubation in either high potassium medium. Horseradish peroxidase reaction product could be found only in vacuoles of tissues stimulated by high potassium concentrations in the presence of calcium. It is concluded that this depolarising stimulus produces, in the presence of calcium, the release by exocytosis of about one sixth of all the granules in the sinus gland, and that vacuoles are the organelle responsible for the recapture of membrane after the exocytosis.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0878
    Keywords: Neurosecretion ; Sinus gland ; Isolated nerve endings ; Potassium stimulation ; Digitonin permeabilization ; Cardisoma carnifex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The preparation of isolated peptidergic nerve terminals from the sinus gland (a neurohemal organ) of the crab (Cardisoma carnifex) is described. In this species the nerve endings can have diameters up to 30 μm. They release neurosecretory material as judged by the decrease in the volumetric density of granules upon depolarization with potassium. Similar results were obtained after permeabilization of the nerve terminals with digitonin, but only in the presence of micromolar concentrations of calcium. This preparation should prove useful in correlating electrical events with other cellular processes involved in stimulus-secretion coupling.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0878
    Keywords: Vasopressin ; Oxytocin ; Opioid peptides ; Neurosecretion ; Neural lobe ; Co-localization ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The content of vasopressin, oxytocin, neurophysin, leucine-enkephalin, methionine-enkephalin, dynorphin-(1–13), and α-neoendorphin in the rat neurohypophysis was measured after different periods of dehydration and after depolarisation of isolated neural lobes and of neurosecretory nerve endings. The rates at which the amount of neurohypophysial hormone and opioid peptides decreased, and the changes in the ratios between the amount of vasopressin or oxytocin and opioid peptide in the neurohypophysis after dehydration and in the incubation medium after depolarization in vitro cast some doubt on, and can be explained by mechanisms other than co-localisation of the different peptides.
    Type of Medium: Electronic Resource
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