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  • 1
    Electronic Resource
    Electronic Resource
    Effects of a transplantable insulinoma upon regulatory peptide concentrations in the gastrointestinal tract of the rat (1986)
    Springer
    Diabetologia 29 (1986), S. 334-338 
    Details
    ISSN: 1432-0428
    Keywords: Insulinoma ; substance P ; neurokinin A ; vasoactive intestinal polypeptide ; somatostatin ; gastrin-releasing peptide ; enteroglucagon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The rapid growth (0.8±0.3 g/day) of a transplantable insulinoma, which also contained substance P (2.9±2.3 pmol/g) and gastrin-releasing peptide (3.2± 2.1 pmoll/g), resulted in the development of hyperphagia, hyperinsulinaeinia and hypoglycaemia in rats (n=8). After a 14-day growth period, the insulinoma-bearing rats showed an increase (49%; p〈0.01) in the weight of the small intestine but no significant change in stomach weight compared with control animals. The content (pmol/organ) of somatostatin, substance P, neurokinin A and vasoactive intestinal peptide in the stomachs of the tumour rats was unchanged. A depletion in the content (53% p〈0.01) and concentration (57%; p〈0.01) of gastrin-releasing peptide, however, suggested either hypersecretion, possibly mediated through hypoglycaemia-induced vagal stimulation, or inhibition of synthesis. The concentration and content of glucagon-like immunoreactivity (enteroglucagon) in the small intestine of the insulinoma rats increased markedly (47%; p〈0.01 and 120%; p〈0.01). This increase is consistent with a proposed role of this peptide as a factor trophic to the intestinal mucosa. No significant changes in the concentrations of somatostatin, substance P, neurokinin A, vasoactive intestinal peptide and gastrin-releasing peptide in the small intestine were observed. However, the increase in gut weight resulted in a greater content of vasoactive intestinal peptide (40%; p〈0.01) and substance P (37%; p〈0.05) in the insulinoma rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00452072
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Selective depletion of the acetylcholine and vasoactive intestinal polypeptide of the guinea-pig myenteric plexus by differential mobilization of distinct transmitter pools (1988)
    Springer
    Experimental brain research 72 (1988), S. 535-542 
    Details
    ISSN: 1432-1106
    Keywords: Myenteric plexus ; Guinea pig ; Acetylcholine ; Vasoactive intestinal polypeptide ; Differential release ; Cotransmission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of electrical field stimulation on the release of acetylcholine (ACh) and vasoactive intestinal polypeptide (VIP) from superfused strips of myenteric plexus-longitudinal muscle (MPLM) of guinea-pig ileum and on the transmitter content of the tissue was investigated at different frequencies and in the presence and absence of choline hemicholinium-3 and colchicine. Low frequency electrical field stimulation released ACh by more than 4 times the basal release; the simultaneously detected VIP secretion was increased only slightly above the resting level. During high frequency stimulation (50 Hz) the release of VIP was greatly increased (to 5 times the resting release) whereas the release of ACh increased to only 150% of the basal output. When choline was present, the ACh content of the tissue itself was not altered by electrical stimulation indicating a rate of synthesis sufficient to maintain release. It was reduced in a frequency-dependent manner in the absence of exogenous choline or in the presence of 10 μM hemicholinium-3 (an inhibitor of choline uptake) by up to 54% of the original content. A similar but even larger reduction took place in the amount of ACh released. Neither the secretion of VIP nor the tissue VIP content was altered by these treatments. Long-lasting (〉60 min) high-frequency (50 Hz) stimulation resulted in the depletion of the VIP pool (by 25%) while the ACh content remained unaltered. The stimulus-induced depletion of the VIP pool was increased when colchicine reduced the amount of VIP released and the VIP content of the stimulated tissue up to 50%; it caused a small hemicholinium-like effect on the release of ACh and on the ACh content of the tissue when the tissue was stimulated for an extended length of time (120 to 180 min) at low frequency (5 Hz) but otherwise had little effect. Depolarization by elevated potassium concentration or by veratridine increased the ACh release by 150–280% and the VIP release by 125–200% of the resting release and was thus equivalent to electrical stimulation at 8–10 Hz. At the end of prolonged chemical depolarization (60 min) the ACh content was reduced to 60–80% and the VIP content to 80–90% of the non-stimulated values respectively. These results are interpreted in terms of the different intracellular dynamics of ACh and VIP and their respective storage vesicles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00250599
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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