Effects of ganglion extracts on chloride-dependent electrical potentials and short-circuit currents across the mantle epithelium of Achatina fulica

1987 ◽  
Vol 65 (9) ◽  
pp. 2272-2275
Author(s):  
O. Enyikwola
Keyword(s):  
Cyclic Amp ◽  
Short Circuit ◽  
Achatina Fulica ◽  
Dibutyryl Cyclic Amp ◽  
Prolonged Heating ◽  
Electrogenic Transport ◽  
Electrical Potentials ◽  
Electrical Gradient ◽  
Short Circuit Currents

The left parietal and visceral ganglia of the giant African snail, Achatina fulica, and also nerves leading from them contain a compound that stimulates chloride-dependent electrogenesis by the mantle epithelium. Release of the substance in vitro is stimulated by 5–12 mM K+, provided Ca2+ is present. The active substance is inactivated by trypsin and prolonged heating, but not by brief heating or lipase. The electrical gradient was unaffected by adrenaline, acetylcholine, cyclic AMP, dibutyryl cyclic AMP, 5-hydroxytryptamine, or thyrotropin releasing factor. However, theophylline inhibited electrogenesis. It is suggested that the electrogenic transport of chloride by the mantle of Achatina may be under neuroendocrine control.

Chloride-dependent electrogenesis by the anterior intestine of Achatina fulica

1987 ◽  
Vol 65 (7) ◽  
pp. 1681-1684
Author(s):  
O. Enyikwola
Keyword(s):  
Chloride Transport ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Potential Difference ◽  
Achatina Fulica ◽  
Electrical Gradient ◽  
Anterior Intestine ◽  
Mucosal Side

The serosal side of the anterior intestine of the giant African snail, Achatina fulica, is a few millivolts negative to the mucosal side in vivo and in vitro. The potential difference ranged from 1.0 to 7.5 mV (average 2.8 ± 1.4 mV) and the short-circuit current difference, from 28.0 to 150.0 μA/cm2 (average 75.0 ± 12.8 μA/cm2). Good stirring is essential for the maintenance of the electrical gradient in vitro. The electrical potential does not depend on K+, Mg2+, Ca2+, or Na+ but requires Cl− on the mucosal side. The electrical gradient is reduced by cyanide, 2,4-dinitrophenol, and anoxia but not by ouabain, furosemide, or bumetanide. The transmural potential difference and short-circuit current were predominantly dependent upon aerobic metabolism. However, a finite residual component was dependent upon glycolytic energy. It is concluded that the role of chloride transport across the intestinal epithelium may be to facilitate fluid absorption from the lumen into the haemolymph.

Decreased ion transport by tracheal epithelium of the basenji-greyhound dog

1994 ◽  
Vol 76 (4) ◽  
pp. 1489-1493 ◽  
Author(s):  
T. L. Croxton ◽  
M. Takahashi ◽  
C. A. Hirshman
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Airway Epithelial Cells ◽  
Tracheal Epithelium ◽  
Airway Epithelial ◽  
Beta Adrenergic ◽  
Electrical Potentials ◽  
Short Circuit Currents

The Basenji-Greyhound (BG) dog model shows altered beta-adrenergic function in both airway smooth muscle and leukocytes. To investigate a possible beta-adrenergic pathway defect in airway epithelial cells of BG dogs, we studied the electrophysiological behavior of tracheal epithelia in vitro and measured tracheal electrical potentials in vivo. Baseline short-circuit currents of isolated tracheal epithelia from BG (n = 6) and mongrel control dogs (n = 7) were 18.7 +/- 3.4 and 43.7 +/- 4.2 microA/cm2, respectively (P = 0.001). Significant differences between short-circuit currents of BG and control epithelia persisted after inhibition of Cl- secretion by indomethacin or stimulation by isoproterenol or dibutyryl adenosine 3',5'-cyclic monophosphate. In vivo tracheal potentials were also significantly less (P = 0.01) in BG dogs (-22.3 +/- 2.5 mV; n = 12) than in control dogs (-32.5 +/- 2.6 mV; n = 10), and intravenous indomethacin reduced the tracheal potential of BG dogs but had no effect in control animals. There was no correlation in BG dogs between tracheal potential and the dose of methacholine required to double total lung resistance. These data suggest that ion transport by tracheal epithelium is decreased in BG dogs, that this difference is not due to diminished beta-adrenergic activity, and that cyclooxygenase products are important in maintaining tracheal potential in vivo in this model.

The inhibitory effects of some adenosine nucleolipids on the lipolysis in rat epididymal fat pads in vitro

1979 ◽  
Vol 44 (5) ◽  
pp. 1651-1656 ◽  
Author(s):  
Sixtus Hynie ◽  
Jiří Smrt
Keyword(s):  
Fatty Acids ◽  
Cyclic Amp ◽  
Dibutyryl Cyclic Amp ◽  
Inhibitory Effects ◽  
Epididymal Fat ◽  
Fat Pads

3'-Oleolyl-2,3-dihydroxypropyl-AMP, 3'-stearoyl-2,3-dihydroxypropyl-AMP, octadecyl-AMP and palmitamidoethyl-AMP inhibited in comparison with adenosine or fatty acids much stronger the lipolysis in rat epididymal fat pads in vitro stimulated by isoproterenol, theophylline and dibutyryl cyclic AMP. The inhibition of the effects of the two latter drugs suggest that the described effect is caused not only by the inhibition of the cyclic AMP production but also by the inhibition of its effect on the following steps in process of lipolysis.

TESTOSTERONE SECRETION BY FOETAL RAT TESTES IN VITRO

1976 ◽  
Vol 71 (2) ◽  
pp. 231-238 ◽  
Author(s):  
RÉGINE PICON
Keyword(s):  
Cyclic Amp ◽  
Synthetic Medium ◽  
Functional Differentiation ◽  
Dibutyryl Cyclic Amp ◽  
Testosterone Secretion ◽  
Testosterone Production ◽  
Foetal Rat

SUMMARY Testosterone secretion by foetal rat testes (13½–21½ days of gestation) explanted for 3 days in a synthetic medium was measured every 24 h by radioimmunoassay. During the first day of explantation, the foetal testis produced, respectively, 1013 ± 132, 8734 ± 1118, 9179 ± 2185 and 3886 ± 309 (s.e.m.) pg/testis when explanted at 14½, 16½, 18½ and 21½ days respectively. Testosterone production by 13½-day-old testes was not detectable on the first day of culture, but appeared on subsequent days. Daily testosterone secretion increased on the 2nd and 3rd days of culture in 14½-day-old testes and decreased in older stages. These results suggest that the functional differentiation of the testis is independent of stimulatory factors like gonadotrophins. Dibutyryl cyclic AMP was found to stimulate testosterone production significantly from 14½ days of gestation onwards.

scholarly journals Influence of A23187 and dibutyryl cyclic AMP on progestagen production by rat granulosa cells in vitro

Reproduction ◽  
1989 ◽  
Vol 86 (1) ◽  
pp. 373-381 ◽  
Author(s):  
B. K. Tsang ◽  
D. F. Mattice ◽  
M. Li ◽  
E. K. Asem
Keyword(s):  
Cyclic Amp ◽  
Granulosa Cells ◽  
Dibutyryl Cyclic Amp

scholarly journals Isolation of cDNA clones for genes exhibiting reduced expression after differentiation of murine teratocarcinoma stem cells.

1984 ◽  
Vol 4 (10) ◽  
pp. 2142-2150 ◽  
Author(s):  
R A Levine ◽  
G J LaRosa ◽  
L J Gudas
Keyword(s):  
Stem Cells ◽  
Retinoic Acid ◽  
Cyclic Amp ◽  
Cdna Library ◽  
In Vitro Transcription ◽  
In Vitro Translation ◽  
Transcriptional Level ◽  
Cdna Clones ◽  
Dibutyryl Cyclic Amp

In the absence of retinoic acid, PSA-G teratocarcinoma stem cells spontaneously differentiate at a moderate frequency into fibroblast-like cells. In the presence of retinoic acid and dibutyryl cyclic AMP, PSA-G stem cells differentiate into parietal endoderm cells. We prepared a cDNA library from undifferentiated PSA-G teratocarcinoma stem cells; this cDNA library was then screened for gene sequences which exhibit a reduction in expression during the differentiation of these stem cells. From ca. 1,000 clones screened, eight independent sequences were isolated. The level of expression of these cloned genes decreases by 3.0-fold to more than 10-fold after differentiation of PSA-G cells into fibroblast-like cells. After treatment of either PSA-G or F9 teratocarcinoma cells with retinoic acid and dibutyryl cyclic AMP for 72 h, the expression of seven genes is inhibited by two- to fourfold. This decrease of clone-specific transcripts can be detected within 12 h after the addition of retinoic acid. Hybridization-selection and in vitro translation experiments identified the proteins encoded by three of the cloned genes: pST 6-23 codes for a 89,000-dalton protein, pST 7-105 codes for a 41,000-dalton protein, and pST 9-31 codes for a 34,000-dalton protein. The 89,000-dalton protein encoded by pST 6-23 is a heat shock protein. In vitro transcription experiments demonstrate that the retinoic acid-mediated decrease in pST 6-135- and pST 1-68-specific RNA occurs at the transcriptional level and that dibutyryl cyclic AMP acts posttranscriptionally to further depress the levels of these RNAs.

Apical nonspecific cation conductances in rabbit cecum

1994 ◽  
Vol 266 (3) ◽  
pp. G475-G484 ◽  
Author(s):  
J. H. Sellin ◽  
W. P. Dubinsky
Keyword(s):  
Epithelial Transport ◽  
Apical Membrane ◽  
Divalent Cations ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Na Channel ◽  
Similar Response ◽  
Electrogenic Transport

Rabbit cecum exhibits electrogenic Na absorption in vitro. However, because this transport process is not inhibited by amiloride nor does it demonstrate saturation kinetics typical of the amiloride-inhibitable Na channel, we considered whether the cecal transporter represented one of a recently described family of nonselective cation conductances or channels (NSCC). Both transepithelial and vesicle studies demonstrated that K, Cs, and Rb were transported via an apical conductance. Electrogenic transport was inhibited by divalent cations including Ca, Mg, and Ba but was unaffected by either lanthanum or gadolinium. Parallel studies in distal colon did not exhibit a similar response to either K substitution or Ba inhibition. Phenamil, verapamil, and nicardipine significantly inhibited the short-circuit current (Isc). stimulated by nominal Ca- and Mg-free conditions. Flux studies demonstrated a correlation between changes in Isc and Na transport. Microelectrode impalement studies suggested that there may be both NSCC and K conductance in the apical membrane. Planar bilayer studies identified a 190-pS cation channel that may correlate with the macroscopic transport properties of this epithelium. These studies are consistent with a model of cecal Na absorption mediated by a NSCC in the apical membrane; this may be the mechanism underlying the distinct epithelial transport characteristics of this intestinal segment.

Effect of acetazolamide on sodium and chloride transport by in vitro rabbit ileum

1975 ◽  
Vol 228 (6) ◽  
pp. 1808-1814 ◽  
Author(s):  
HN Nellans ◽  
RA Frizzell ◽  
SG Schultz
Keyword(s):  
Cyclic Amp ◽  
Chloride Transport ◽  
Short Circuit ◽  
Electrical Potential ◽  
Direct Interaction ◽  
Short Circuit Current ◽  
Electrical Potential Difference ◽  
Membrane Component ◽  
Rabbit Ileum

Acetazolamide (8 mM) aboishes active Cl absorption and inhibits but does not abolish active Na absorption by stripped, short-circuited rabbit ileum. These effects are not accompanied by significant changes in the transmural electrical potential difference or short-circuit current. Studies of the undirectional influxes of Na andCl indicate that acetazolamide inhibits the neutral, coupled NaCl influx process at the mucosal membranes. This action appears to explain the observed effect of acetazolamide on active, transepithelial Na and Cl transport. Acetazolamide did not significantly inhibit either spontaneous or theophylline-induced Cl secretion by this preparation, suggesting that the theophylline-induced secretion may not simply be due tothe unmasking of a preexisting efflux process when the neutral influx mechanism is inhibited by theophylline. Finally, inhibition of the neutral NaCl influx process by acetazolamide does not appear to be attributable to an inhibition of endogenous HCO3production or an elevation in intracellular cyclic-AMP levels. Instead, it appearstheat the effect of acetazolamide is due to a direct interaction with a membrane component involved in the coupled influx process.

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