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Colchicine inhibition of ADH effect on frog skin permeability.
No full textADH and AMPc enhance both thiourea unidirectional fluxes in frog skin. This effect is completely abolished by colchicine pretreatment. The ADH increase of thiourea discharge with or without colchicine led us to suppose that colchicine does not directly affect ADH action on outer membrane permeability, but exerts its effects on a site which is limiting for the ADH action on transepithelial permeability
Colchicine effect on the permeability of the whole epithelium and of isolated cells of frog skin
No full textThe effect of 2 X 10(-5) M colchicine on epithelial cells isolated from frog skins was investigated. Three hours of treatment with colchicine did not change either Na+ and K+ content of isolated cells or nonelectrolyte permeability. When ADH (50 mU/ml) was added, thiourea uptake values became greater than without the hormone; the same values were found in the cells previously treated with colchicine. Na+ transepithelial transport, measured by means of short-circuit current, was inhibited by the antimitotic agent both under control conditions and after ADH stimulation. These results support the view that colchicine does not directly affect ADH action on membrane permeability, but influences some mechanism that controls ADH action on transepithelial transport. Intercellular junctions appear to be the location of such a mechanism
Noradrenaline induced secretion of nonelectrolytes through frog skin
No full textAddition of noradrenaline (4 x 10(-5) M) to the inner bathing fluid in the skin of the frog Rana esculenta results in increased unidirectional fluxes of urea, thiourea, N-methyl-thiourea, N-N'-dimethylthiourea and mannitol. Fluxes towards the external medium (phi o) undergo a much greater increase than those moving the opposite direction (phi i). The effect of noradrenaline on phi o is higher for urea and thiourea than mannitol, while its effect on phi o thiourea derivatives is related to lipid solubility. This phenomenon does not occur for phi i of the same molecules. FCCP (10(-6) M) pretreatment strongly inhibits the noradrenaline effect on phi o. In skin pretreated with colchicine (2 x 10(-5) M) both urea fluxes are increased to the same extent by noradrenaline. Noradrenaline is concluded to exert two separate effects: (1) a change in permeability in both directions; (2) a secretion of nonelectrolytes towards the external fluid. Such secretion is most probably associated with the hormone-induced secretion of fluid and electrolytes, perhaps mediated by an exocytotic mechanism
Inositol 1,4,5-trisphosphate and ryanodine receptors mobilize calcium from a common functional pool in human U373 MG cells
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Bradykinin stimulation does not induce intracellular Ca2+ elevation in cells from desmoid tumors
No full textThe nature of Cl- secretion, induced by carbaryl, across the isolated skin of Rana esculenta.
No full text1. The pesticide carbaryl induces Cl- secretion through the isolated frog skin.
2. This effect is due to the activation of both processes responsible for this
phenomenon: (a) Na+/K+/2Cl- cotransport on the serosal membrane; (b) Cl-
selective channels on the external membrane. 3. Cl- outflux is inhibited by
bumetanide (10(-5) M) on the serosal side and by diphenylamine-2-carboxylic acid
(DPC) (10(-3) M) on the external side. 4. The DPC action is not mimicked by
Naproxen, a specific inhibitor of cyclooxygenase. 5. A comparison with
isoprenaline, demonstrates that the carbaryl action is, paradoxically, more
selective than that of isoprenaline. 6. This selectivity of carbaryl action on
Cl- permeability is confirmed by the fact that, unlike isoprenaline, carbaryl
does not affect the permeability of Na+ and thiourea
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