Showing papers on "Toad published in 1972"
TL;DR: It was found that indomethacin potentiated the response to high concentrations of theophylline, indicating that endogenous prostaglandins could have a regulatory role to play in the normal cell function.
Abstract: FLORES, AURA G. A., AND GEOFFREY Mr. G. SHARP. Endogenous prostaglandins and osmotic waterflow in the toad bladder. Am. J. Physiol. 223 (6) : 1392-1397. 1972.-Prostaglandins, at low concentrations, inhibit the osmotic water-flow response to antidiuretic hormone (ADH) and to theophylline in toad bladder. They have no effect upon the response to dibutyryl cyclic AMP. Thus the prustaglandins inhibit adenyl cyclase in this tissue and decrease the stimulation of adenyl cyclase by ADH. It is not known, however, whether endogenous prostaglandins have any physiological role in reducing basal adenyl cyclase activity and hormone responses. As indomethacin inhibits prostaglandin synthetase and thus blocks prostaglandin synthesis and release, it has been used to assess the physiological role of prostaglandins. Indomethacin enhanced the osmotic water-flow response to submaximal concentrations of antidiurelic hcrmone and to dibutyryl cyclic AMP. The effect on the latter was ascribed to the inhibitory effect of indomethacin on phosphodiesterase. On a molar basis, indomethacin was estimated to be more than lo-fold more effective than theophylline in its ability to inhibit phosphodiesterase. Thus potentiation cf the response to ADH by indomethacin, even at low concentrations, is not by itself an indication that endogenous release of prostaglandins exerts a continual restraining influence on adenyl cyclase. However, it was found that indomethacin potentiated the response to high concentrations of theophylline (which alone inhibit phosphodiesterase activity). This effect is ascribed to the lifting of prostaglandin inhibition of adenyl cyclase and indicates that endogenous prostaglandins could have a regulatory role to play in the normal cell function.
129 citations
TL;DR: The present findings indicate that the frequency of the amphibian bladder to water and enhance of such membrane continuities is greatly increased the transport of sodium across the mucosal in cells stimulated by oxytocin or the dibutyryl epithelium.
Abstract: It is well established that neurohypophyseal observations (40) of çontinuity between the hormones and cyclic 3',5'-adenosine monogranule membrane and the plasma membrane . phosphate (cAMP) increase the permeability The present findings indicate that the frequency of the amphibian bladder to water and enhance of such membrane continuities is greatly increased the transport of sodium across the mucosal in cells stimulated by oxytocin or the dibutyryl epithelium (16, 17, 27) . Recently, we reported derivative of cAMP as compared to unstimulated that in the toad bladder mucosal epithelium, the controls . altered permeability is paralleled by a marked increase in the endocytic uptake of horseradish MATERIALS AND METHODS peroxidase from the lumen (31-33) . One of the The following compounds were used in this study : possible explanations was that the observed oxytocin, prepared by Miss P. L. Hoffman at Mt . endocytosis might be a secondary effect . The Sinai School of Medicine by the solid-phase method primary effect in the response to hormone and of peptide synthesis (35) . The hormone was found cyclic nucleotide might conceivably be a stimuto possess an activity of 500 units/mg when tested in lation of exocytosis, the fusion of membranes the fowl vasodepressor assay just before use . N 6 -2'surrounding secretion granules with the plasma O-dibutyryl adenosine 3',5'-cyclic monophosphate membrane. This would result in the addition of (dibut . cAMP) was purchased from Schwarz Bio
117 citations
94 citations
84 citations
TL;DR: Lithium has a similar effect on the antidiuretic activity of oxytocin and choline on the serosal surface also inhibits the transport of water facilitated by vasopressin in the toad bladder.
Abstract: 1. The effect of intravenous infusions of various ions on the antidiuretic action of antidiuretic hormone has been studied in rats.
2. Lithium (13 mmol/l.) reversibly inhibits the antidiuretic responses. Similar concentrations of potassium, rubidium, strontium, magnesium, choline and calcium do not. Lithium has a similar effect on the antidiuretic activity of oxytocin.
3. The inhibition is not simply related to blood nor whole body lithium concentrations.
4. Lithium (2 mmol/l.) in contact with the serosal surface also inhibits the transport of water facilitated by either 0·5 U/l. antidiuretic hormone or 1·1 mmol/l. cyclic adenosine monophosphate in the isolated toad bladder.
5. Choline (2 mmol/l.) on the serosal surface also inhibits the transport of water facilitated by vasopressin in the toad bladder.
66 citations
TL;DR: The apical portions of the cells containing the enzyme were discretely stained as noncontiguous polygonal forms and allowed an estimation of the luminal surface representation of this epithelium, an observation consonant with the known localization of carbonic anhydrase primarily in supernatant fractions.
Abstract: Carbonic anhydrase activity was demonstrated in a distinct population of mucosal cells of whole stretched bladder of turtle and toad. The apical portions of the cells containing the enzyme were discretely stained as noncontiguous polygonal forms and allowed an estimation of the luminal surface representation of this epithelium. The slight luminal surface (O.8� or less) occupied by cells with carbonic anhydrase activity in the toad bladder contrasted with a greater representation in turtle bladder (6.4-12.2%) and correlated with the relative capacity of these tissues to acidify. After completion of the enzyme staining reaction the tissues of the turtle bladder were directly processed for electron microscopic observations without osmium tetroxide postflxation. The deposition of the electron-opaque cobalt sulfide compound was selective and was found only in cells with luminal representation and small apical granules, the recently described “third cell type”; cobalt sulfide was mainly present in the cytoplasm, an observation consonant with the known localization of carbonic anhydrase primarily in supernatant fractions.
60 citations
TL;DR: It is suggested that cyclic AMP directly affects the permeability of the mucosal face of the epithelial cells to water and to sodium and that there are two separate adenyl cyclase systems responsible for controlling the permeabilities to waterand to sodium.
Abstract: THERE is overwhelming evidence to connect cyclic 3′,5′-adenos-ine monophosphate (cyclic AMP) with hormone action in various tissues1. For example, the toad bladder responds to neurohypophyseal hormones (ADH) with an increase in water permeability2 and with an increase in the mucosal to serosal transport of sodium3. ADH also causes an increase in cyclic AMP levels in the tissue4 and the actions of the hormone can be mimicked by addition of the cyclic nucleotide2,5. Orloff and Handler5 have suggested that cyclic AMP directly affects the permeability of the mucosal face of the epithelial cells to water and to sodium and that there are two separate adenyl cyclase systems responsible for controlling the permeability to water and to sodium6,7.
57 citations
TL;DR: Observations support the view that mitochondriarich cells arc in a way involved in the osmoregulation controlled by aldosterone.
46 citations
44 citations
TL;DR: It is suggested that the responsiveness of the toad bladder to antidiuretic hormones diminishes as the effective osmotic pressure of the interstitial fluids declines.
Abstract: The effect of dilution of the interstitial fluids on the responsiveness of the toad urinary bladder to antidiuretic hormones has been examined in vivo and in vitro. Toads were given periodic injections with vasopressin while in water so that their plasma osmolality fell below 190 mosmoles/kg H2O. The hydraulic conductivity of bladders which had been removed from the animal and fixed with 1% glutaraldehyde was 10-fold less in overhydrated toads than in normally hydrated controls. A similar inhibitory phenomenon was observed in in vitro studies, when the tonicity of Ringer's fluid in which the bladders were suspended was lowered from its isotonic value. Mannitol, but not urea, could be effectively substituted for one-half of the NaCl content of Ringer's fluid. In other experiments it has been shown that the responsiveness of the bladder to vasotocin is depressed during bulk water movement across the tissue. This "flux inhibition" was found to depend upon the velocity and the duration of water flow from mucosa to the serosa. It is suggested that the responsiveness of the toad bladder to antidiuretic hormones diminishes as the effective osmotic pressure of the interstitial fluids declines.
42 citations
TL;DR: The increase of short-circuit current seen in the presence of vasopressin is reduced by Li+.
TL;DR: Insofar as the early rise in SCC represents a rise in active Na transport, the data suggest that hypotonicity acts by increasing energy metabolism with a resultant activation of the transport mechanism via increased supply of high-energy substrate.
Abstract: LIPTON, PETER. E$ect of changes in osmolarity on sodium transport across isolated toad bladder. Am. J. Physiol. 222(4) : 82 l-828. 1972. -Reducing the osmolarity of the solution bathing the serosal surface of the isolated toad bladder by one-third (hypotonicity) doubled short-circuit current (SCC) across the tissue (osmotic response). 22Na tracer studies showed that in the steady state this was due to an increase in active transepithelial Na transport. Increasing serosal osmolarity by 20yo halved transepithelial Na transport. Hypotonically induced alterations in cell volume and electrolyte concentration were complete well before the SCC was maximal, indicating that the increase did not result from a direct effect of altered environment upon the transport mechanism itself. Hypotonicity reduced epithelial cell Na concentration by ~25%. If this reduction occurs in the Na pool participating in the osmotic response, then, assuming the twobarrier transport model, hypotonicity must lead to a stimulation of the basally located Na pump which is not a result of increased availability of Na. Hypotonicity caused an ouabain-inhibitable increase in respiration which rose faster than the SCC. Insofar as the early rise in SCC represents a rise in active Na transport, the data suggest that hypotonicity acts by increasing energy metabolism with a resultant activation of the transport mechanism via increased supply of high-energy substrate.
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TL;DR: Toad splenic lymphocytes undergo blastogenic conversion in vitro in response to both phytohemagglutinin (PHA) and allogeneic splenocytes, and the maximum response to PHA and to alloantigens varies from toad to toad, and is influenced by the type of serum used to supplement the culture medium.
Abstract: Toad splenic lymphocytes undergo blastogenic conversion in vitro in response to both phytohemagglutinin (PHA) and allogeneic splenocytes. At 26°C, maximum incorporation of tritiated thymidine occurs on day 3 in response to PHA, and on day 7 in a mixed lymphocyte culture (MLC). The response to PHA is concentration-dependent. The maximum response to PHA and to alloantigens varies from toad to toad, and is influenced by the type of serum used to supplement the culture medium. More lymphocytes cultured with xenogeneic serum and PHA undergo mitosis than those cultured with PHA and allogeneic serum. In contrast, allogeneic serum suppresses transformation in the MLC.
TL;DR: The experimental evidence presently suggests that some species may not possess an active transport system linked to the Ca 2+ ion requirement for hormone release, and suggests that MSH release from pars intermedia cells may be regulated by a Na + K + pump (active transport) mechanism.
TL;DR: The study discusses the requirement for adjuvant in the production of precipitating antibodies to human serum proteins in Xenopus laevis ; long-term persistence of human albumin in the toad's circulation was also noted.
TL;DR: The specificity of the peptides on inhibition of the hormone is demonstrated by the fact that oxytocin, lysine vasopressin, and pressinoic acid and pressinamide (ring structures of the vasopressingins) do not show such inhibitory activity.
Abstract: Tocinamide and tocinoic acid, ring structures of oxytocin, are potent inhibitors of the release of melanophore stimulating hormone from the rat and hamster pituitary in vitro. Tocinamide is effective at concentrations as low as 10-(14)M on the mammalian pituitary. These peptides do not affect release of the hormone on the frog (Rana pipiens) pars intermedia, but they do inhibit release in the bullfrog (Rana catesbeiana) and the toad (Bufo marinus). The specificity of the peptides on inhibition of the hormone is demonstrated by the fact that oxytocin, lysine vasopressin, and pressinoic acid and pressinamide (ring structures of the vasopressins) do not show such inhibitory activity. Hypothalamic extracts of either the frog (Rana pipiens) or the rat inhibit release of the hormone from pituitaries of either species. The inhibitory effects of tocinamide and tocinoic acid, like that of hypothalamic extracts, are reversible.
TL;DR: A cyclic AMP-dependent protein kinase was partially purified from toad urinary bladder epithelium and found to be inhibitory at concentrations higher than 5 × 10-4 M, while Ca2+ was found to have a role in neurohypophyseal hormone-induced permeability changes.
Abstract: SummaryA cyclic AMP-dependent protein kinase was partially purified from toad urinary bladder epithelium. Cyclic AMP-stimulated protein kinase activity as well as the unstimulated (control) activity of the enzyme was maximal at pH 6.5 using Tris-maleate, sodium cacodylate or sodium acetate buffers. The apparent Km value of cyclic AMP for the stimulation of the enzyme (in sodium acetate buffer and in the presence of 10 mM Mg2+) was 1.5 × 10-9M. The acyclic nucleotide 5'-AMP (in the concentration range 5 × 10-10 to 5 × 10-5M) failed to activate bladder protein kinase. Ca2+ was found to be inhibitory at concentrations higher than 5 × 10-4M. A role for cyclic AMP-dependent protein kinase in neurohypophyseal hormone-induced permeability changes is discussed.
TL;DR: The data support the concept that not only net water flow, but also changes in smooth muscle tone can appreciably affect the epithelial geometry, and demonstrate continuity between the epithelium and underlying smooth muscle.
Abstract: Vasopressin has been noted to increase the size of the intercellular spaces of toad bladder epithelium even in the absence of an osmotic gradient. The present studies demonstrate that the same phenomenon may be obtained in the presence or absence of a transepithelial gradient of glutaraldehyde indicating that the effect is not a fixation artifact. Morphologic evidence is presented demonstrating continuity between the epithelium and underlying smooth muscle. The data support the concept that not only net water flow, but also changes in smooth muscle tone can appreciably affect the epithelial geometry.
TL;DR: Results in vitro confirm the previous ones in vivo indicating that the hypothalamic inhibitory control of the pars intermedia of amphibians is achieved through catecholamines.
TL;DR: It is concluded that the predominant cause of the reduction of respiration induced by ouabain is inhibition of transepithelial sodium transport.
TL;DR: Evidence is presented in terms of temperature coefficients measured for the short circuit current across toad bladder and the Na + /K + ATPase activity, supporting the idea that sodium transport across the toads bladder is normally limited by mucosal sodium permeability and that the major effect of aldosterone is to increase this permeability.
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TL;DR: Acetylsalicylic acid by itself has no effect on net water movement but clearly potentiates the response to oxytocin and to an increase in medium tonicity in toad urinary bladder, suggesting the control mechanism based on cellular osmolarity as previously described is operated via the liberation of prostaglandin E1.
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