Role of active potassium transport by integumentary epithelium in secretion of larval-pupal moulting fluid during silkmoth development

1975 ◽  
Vol 62 (2) ◽  
pp. 357-366
Author(s):  
A. M. Jungreis ◽  
W. R. Harvey
Keyword(s):  
Short Circuit ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Potassium Transport ◽  
Open Circuit ◽  
Ratio Test ◽  
Potassium Flux

1. The exuvial side of the pharate pupal integument is usually positive to the haemolymph-side, both in vivo and in vitro, during the period when the moulting fluid is being secreted. 2. The ratio of potassium flux toward the exuvial space is higher than that toward the haemolymph, under both open-circuit conditions and short-circuit conditions, demonstrating by the Flux Ratio test that potassium is actively transported across the isolated integument during this secretion period. 3. Just prior to ecdysis, while moulting fluid is being reabsorbed, the potassium flux ratios become unity, suggesting that active potassium transport has ceased, but the short-circuit current that remains suggests that some other ion is actively transported at this time. 4. We argue that the potassium salt solution, formed in the exuvial space (as water presumably follows the actively transported potassium), has three functions (1) to accomplish the gel--sol transformation, (2) to activate the gel enzymes and (3) to buffer the enzyme solution at a pH favourable to the activity of the gel enzymes.

Enhancement of the performance of CdS/CdTe heterojunction solar cell using TiO2/ZnO bi-layer ARC and V2O5 BSF layers: A simulation approach

2020 ◽  
Vol 92 (2) ◽  
pp. 20901
Author(s):  
Abdul Kuddus ◽  
Md. Ferdous Rahman ◽  
Jaker Hossain ◽  
Abu Bakar Md. Ismail
Keyword(s):  
Solar Cell ◽  
Short Circuit ◽  
Photovoltaic Performance ◽  
Short Circuit Current ◽  
Short Circuit Current Density ◽  
Open Circuit ◽  
Heterojunction Solar Cell ◽  
Back Surface ◽  
Heterojunction Solar Cells

This article presents the role of Bi-layer anti-reflection coating (ARC) of TiO2/ZnO and back surface field (BSF) of V2O5 for improving the photovoltaic performance of Cadmium Sulfide (CdS) and Cadmium Telluride (CdTe) based heterojunction solar cells (HJSCs). The simulation was performed at different concentrations, thickness, defect densities of each active materials and working temperatures to optimize the most excellent structure and working conditions for achieving the highest cell performance using obtained optical and electrical parameters value from the experimental investigation on spin-coated CdS, CdTe, ZnO, TiO2 and V2O5 thin films deposited on the glass substrate. The simulation results reveal that the designed CdS/CdTe based heterojunction cell offers the highest efficiency, η of ∼25% with an enhanced open-circuit voltage, Voc of 0.811 V, short circuit current density, Jsc of 38.51 mA cm−2, fill factor, FF of 80% with bi-layer ARC and BSF. Moreover, it appears that the TiO2/ZnO bi-layer ARC, as well as ETL and V2O5 as BSF, could be highly promising materials of choice for CdS/CdTe based heterojunction solar cell.

Active transport of magnesium across the isolated midgut of Hyalophora cecropia

1975 ◽  
Vol 63 (2) ◽  
pp. 313-320
Author(s):  
J. L. Wood ◽  
A. M. Jungreis ◽  
W. R. Harvey
Keyword(s):  
Steady State ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Potassium Transport ◽  
Magnesium Concentration ◽  
Magnesium Transport ◽  
Wet Weight ◽  
Net Flux ◽  
Burk Plot

1. The 28Mg-measured net flux of magnesium from lumen-side to haemolymph-side of the isolated and short-circuited midgut was 1.97 +/− 0.28 mu-equiv cm(−2) /(−1) in 8 mM-Mg2+. 2. The magnesium-influx shows a delay before the tracer steady-state is attained, indicating the existence of a magnesium-transport pool equivalent to 6.7 mu-equiv/g wet weight of midgut tissue. 3. Magnesium depresses the short-circuit current produced the midgut but not the potassium transport, the depression being equal to the rate of magnesium transport. 4. Magnesium transport yields a linear Lineweaver-Burk plot with an apparent Km of 34 mM-Mg2+ and an apparent Vmax of 14.9 mu-equiv cm(−1) /(−1). 5. Magnesium is actively transported across the midgut and contributes to the regulation of the haemolymph magnesium concentration in vivo.

Protein kinase C potentiates cAMP-stimulated mouse duodenal mucosal bicarbonate secretion in vitro

2004 ◽  
Vol 286 (5) ◽  
pp. G814-G821 ◽  
Author(s):  
Bi-Guang Tuo ◽  
Jimmy Y. C. Chow ◽  
Kim E. Barrett ◽  
Jon I. Isenberg
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Duodenal Mucosa ◽  
Bicarbonate Secretion ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Ussing Chambers ◽  
Duodenal Bicarbonate Secretion

PKC has been shown to regulate epithelial Cl- secretion in a variety of models. However, the role of PKC in duodenal mucosal bicarbonate secretion is less clear. We aimed to investigate the role of PKC in regulation of duodenal mucosal bicarbonate secretion. Bicarbonate secretion by murine duodenal mucosa was examined in vitro in Ussing chambers using a pH-stat technique. PKC isoform expression and activity were assessed by Western blotting and in vitro kinase assays, respectively. PMA (an activator of PKC) alone had no effect on duodenal bicarbonate secretion or short-circuit current ( Isc). When PMA and dibutyryl-cAMP (db-cAMP) were added simultaneously, PMA failed to alter db-cAMP-stimulated duodenal bicarbonate secretion or Isc ( P > 0.05). However, a 1-h preincubation with PMA potentiated db-cAMP-stimulated duodenal bicarbonate secretion and Isc in a concentration-dependent manner (from 10-8 to 10-5M) ( P < 0.05). PMA preincubation had no effects on carbachol- or heat-stable toxin-stimulated bicarbonate secretion. Western blot analysis revealed that PKCα, -γ, -ϵ, -θ, -μ, and -ι/λ were expressed in murine duodenal mucosa. Ro 31–8220 (an inhibitor active against PKCϵ, -α, -β, and -γ), but not Gö 6983 (an inhibitor active against PKCα, -γ, -β, and -δ), reversed the potentiating effect of PMA on db-cAMP-stimulated bicarbonate secretion. PMA also time- and concentration-dependently increased the activity of PKCϵ, an effect that was prevented by Ro 31–8220 but not Gö 6983. These results demonstrate that activation of PKC potentiates cAMP-stimulated duodenal bicarbonate secretion, whereas it does not modify basal secretion. The effect of PKC on cAMP-stimulated bicarbonate secretion is mediated by the PKCϵ isoform.

Calcium secretion in canine tracheal mucosa

1985 ◽  
Vol 59 (4) ◽  
pp. 1191-1195 ◽  
Author(s):  
F. J. Al-Bazzaz ◽  
T. Jayaram
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Potential Difference ◽  
Secretory Process ◽  
Metabolic Inhibitor ◽  
Tracheal Mucosa ◽  
Transepithelial Potential ◽  
Transepithelial Potential Difference

Calcium (Ca) affects many cellular functions of the respiratory tract mucosa and might alter the viscoelastic properties of mucus. To evaluate Ca homeostasis in a respiratory epithelium we investigated transport of Ca by the canine tracheal mucosa. Mucosal tissues were mounted in Ussing-type chambers and bathed with Krebs-Henseleit solution at 37 degrees C. Unidirectional fluxes of 45Ca were determined in tissues that were matched by conductance and short-circuit current (SCC). Under short-circuit conditions there was a significant net Ca secretion of 1.82 +/- 0.36 neq . cm-2 . h-1 (mean +/- SE). Under open-circuit conditions, where the spontaneous transepithelial potential difference could attract Ca toward the lumen, net Ca secretion increased significantly to 4.40 +/- 1.14 compared with 1.54 +/- 1.17 neq . cm-2 . h-1 when the preparation was short-circuited. Addition of a metabolic inhibitor, 2,4-dinitrophenol (2 mM in the mucosal bath), decreased tissue conductance and SCC and slightly decreased the unidirectional movement of Ca from submucosa to lumen. Submucosal epinephrine (10 microM) significantly enhanced Ca secretion by 2.0 +/- 0.63 neq . cm-2 . h-1. Submucosal ouabain (0.1 mM) failed to inhibit Ca secretion. The data suggest that canine tracheal mucosa secretes Ca; this secretory process is augmented by epinephrine or by the presence of a transepithelial potential difference as found under in vivo conditions.

scholarly journals Further Observations on the Regulation of KCl ABSORPTION ACROSS LOCUST RECTUM

1985 ◽  
Vol 116 (1) ◽  
pp. 153-167
Author(s):  
J. W. HANRAHAN ◽  
J. E. PHILLIPS
Keyword(s):  
Chloride Transport ◽  
Short Circuit ◽  
Membrane Conductance ◽  
Short Circuit Current ◽  
Membrane Resistance ◽  
Open Circuit ◽  
High K ◽  
K Concentration ◽  
K Permeability

1. Electrophysiological and tracer flux techniques were used to studyregulation of KC1 reabsorption across locust recta. Physiologically high K+levels (100 mmolI−1) on the lumen side stimulated net 36Cl flux and reduced the theoretical energy cost of anion transport under open-circuit conductions. 2. The stimulation of short-circuit current (Ibc i.e. active C− absorption) by crude corpora cardiaca extracts (CC) was not dependent on exogenous Ca2+. Stimulations of Ibc were greatly enhanced in the presence of theophylline, indicating that the rate of synthesis of cAMP is increased by CC extracts. High CC levels lowered transepithelial resistance (Rt), suggesting that chloride transport stimulating hormone (CTSH) regulates both active Cl− absorption and counter-ion (K+) permeability. 3. High mucosal osmolarity or K+ concentration decreased Ibc and caused a disproportionately large increase in Rt, consistent with a decrease in theshunt (K+) conductance. Measurements of relative mucosal-to-serosal membrane resistance confirmed that high mucosal K+ levels reduced apical membrane conductance. Lowering mucosal pH to values observed in vivo atthe end of resorptive cycles also inhibited Ibc, apparently without affecting K+ permeability.

Role of nutrient HCO3(-) in protection of amphibian gastric mucosa

1980 ◽  
Vol 239 (6) ◽  
pp. G536-G542
Author(s):  
R. Schiessel ◽  
A. Merhav ◽  
J. B. Matthews ◽  
L. A. Fleischer ◽  
A. Barzilai ◽  
...  
Keyword(s):  
Gastric Mucosa ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Experimental Conditions ◽  
Slow Decline ◽  
Alkaline Tide ◽  
Artificial Gastric Juice ◽  
Rapid Drop

In in vitro bullfrog fundic mucosa inhibited with 10(-3) M metiamide and exposed to a luminal pH of 2 a progressive slow decline in potential difference (PD) and short-circuit current (Isc) and a rise in resistance (R) were observed when the nutrient solution (N) contained 18 mM HCO3(-), but these changes were restored by an N containing 50 mM HCO3(-). Substitution of PO4(3-) or N-tris(hydroxymethyl)-methyl-2-aminoethanesulfonic acid for NHO3(-) in N caused a rapid drop in PD and Isc in inhibited tissues, changes that could be prevented by 10(-4) M histamine. Ulceration occurred more frequently in metiamide-inhibited gastric sacs exposed to artificial gastric juice with an N of 18 mMHCO3(-) than with 50 mM HCO3(-), but histamine prevented ulceration in the 18 mM HCO3(-) solution. JnetCl approximated Isc under most experimental conditions in inhibited mucosa and was reduced dramatically as were both Jn leads to sCl and Js leads to nCl when HCO3(-) was removed from N. In histamine-stimulated tissues, removal of nutrient HCO3(-) did not influence Cl- transport. Our results are consistent with the proposal that HCO3(-) in N supports normal Cl- flux and that the alkaline tide of actively secreting oxyntic cells can do the same in the absence of ambient HCO3(-).

Prolactin effects on ion transport across cultured mouse mammary epithelium

1981 ◽  
Vol 240 (3) ◽  
pp. C110-C115 ◽  
Author(s):  
C. A. Bisbee
Keyword(s):  
Cell Cultures ◽  
Short Circuit ◽  
Collagen Gel ◽  
Mammary Epithelium ◽  
Short Circuit Current ◽  
Sodium Absorption ◽  
Collagen Gels ◽  
Mouse Mammary Epithelium

Prolactin is a known osmoregulatory hormone in lower vertebrates, and recent evidence indicates that this hormone modulates ionic concentrations in milk. In an ultrastructurally and biochemically differentiated primary cell culture system in which mouse mammary epithelium is maintained on floating collagen gels, prolactin causes an increase in short-circuit current (Isc) of monolayers of cells derived from midpregnant (24.6 to 48.0 microA . cm-2) and lactating (10.4 to 16.1 microA . cm-2) glands. Transepithelial potential differences (basal side ground) average about -12 mV and are similar to those seen in vivo. Prelactating mammary epithelial cell cultures have transepithelial resistances ranging from 374 omega . cm2 (prolactin present) to 507 omega . cm2 (prolactin absent), and lactating cell cultures have resistances averaging almost 1,000 omega . cm2. Prolactin effects require at most one day of culture maintenance in prolactin-containing medium, and the effects are not due to known contamination of prolactin preparations with arginine vasopressin or growth hormone. Medium concentrations of prolactin as low as 1 ng/ml can elicit these effects. In prelactating cell cultures not treated with prolactin, the Isc is equal to the rate of sodium absorption. Prolactin increases sodium absorption fourfold but increases Isc only twofold. Clearly, prolactin induces other active transport; neither potassium nor chloride movements can account for this additional transport. Resistance values, current-voltage plots, and permeability coefficients indicate that in vitro mammary epithelium is a moderately “tight” tissue. Comparisons with intact glands indicate that in vitro mammary epithelium closely resembles its in vivo counterpart. Floating collagen gel cultures appear suitable for elucidating transport properties in cellularly heterogeneous and structurally complex mammalian tissues.

Water and electrolyte transport by rabbit esophagus

1975 ◽  
Vol 229 (2) ◽  
pp. 438-443 ◽  
Author(s):  
DW Powell ◽  
SM Morris ◽  
DD Boyd
Keyword(s):  
Sodium Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Electrolyte Transport ◽  
Potential Difference ◽  
Sodium Absorption ◽  
Bathing Solution ◽  
Electrical Potential Difference

The nature of the transmural electrical potential difference and the characteristics of water and electrolyte transport by rabbit esophagus were determined with in vivo and in vitro studies. The potential difference of the perfused esophagus in vivo was -28 +/- 3 mV (lumen negative). In vitro the potential difference was -17.9 +/- 0.6 mV, the short-circuit current 12.9 +/- 0.6 muA/cm2, and the resistance 1,466 +/- 43 ohm-cm2. Net mucosal-to-serosal sodium transport from Ringer solution in the short-circuited esophagus in vitro accounted for 77% of the simultaneously measured short-circuit current and net serosal-to-mucosal chloride transport for 14%. Studies with bicarbonate-free, chloride-free, and bicarbonate-chloride-free solutions suggested that the net serosal-to mucosal transport of these two anions accounts for the short-circuit current not due to sodium absorption. The potential difference and short-circuit current were saturating functions of bathing solution sodium concentration and were inhibited by serosal ouabain and by amiloride. Thus active mucosal-to-serosal sodium transport is the major determinant of the potential difference and short-circuit current in this epithelium.

An Investigation of the Role of Possible Neural Mechanisms in Cholera Toxin-Induced Secretion in Rabbit Ileal Mucosa in Vitro

1989 ◽  
Vol 77 (2) ◽  
pp. 161-166 ◽  
Author(s):  
K. J. Moriarty ◽  
N. B. Higgs ◽  
M. Woodford ◽  
L. A. Turnberg
Keyword(s):  
Cholera Toxin ◽  
Fluid Transport ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Electrical Potential Difference ◽  
Rabbit Ileum ◽  
Ileal Mucosa

1. Cholera toxin stimulates intestinal secretion in vitro by activation of mucosal adenylate cyclase. However, it has been proposed that cholera toxin promotes secretion in vivo mainly through an indirect mechanism involving enteric neural reflexes. 2. We examined this hypothesis further by studying the influence of neuronal blockade on cholera toxin-induced changes in fluid transport across rabbit ileum in vitro. Mucosa, stripped of muscle layers, was mounted in flux chambers and luminal application of crude cholera toxin (2 μg/ml) caused a delayed but sustained rise in the short-circuit current, electrical potential difference and Cl− secretion. Pretreatment with the nerve-blocking drug, tetrodotoxin (5 × 10−6 mol/l serosal side), failed to influence the secretory response to cholera toxin, and addition of tetrodotoxin at the peak response to cholera toxin also had no effect. 3. That tetrodotoxin could block neurally mediated secretagogues was confirmed by the demonstration that the electrical responses to neurotensin (10−7 mol/l and 10−8 mol/l) were blocked by tetrodotoxin (5 × 10−6 mol/l). Furthermore, the response to cholera toxin of segments of ileum, which included the myenteric, submucosal and mucosal nerve plexuses, was not inhibited by tetrodotoxin. 4. We conclude that cholera toxin-induced secretion in rabbit ileum in vitro is not mediated via a neurological mechanism.

NaCl transport across equine proximal colon and the effect of endogenous prostanoids

1990 ◽  
Vol 259 (1) ◽  
pp. G62-G69 ◽  
Author(s):  
L. L. Clarke ◽  
R. A. Argenzio
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Proximal Colon ◽  
Nacl Transport ◽  
Apparent Lack ◽  
Ussing Chambers ◽  
Cl Secretion

In contrast to in vivo findings, the equine proximal colon fails to demonstrate significant net absorption of Na+ and Cl- under in vitro conditions. The present study was undertaken to determine if endogenous prostanoids are responsible for this apparent lack of ion transport. Proximal colonic tissues from ponies were preincubated in either normal Ringer solution or in Ringer containing 1 microM indomethacin and studied in Ussing chambers containing these solutions. Untreated colonic mucosa demonstrated negligible Na(+)-Cl- absorption in the basal state. In contrast, indomethacin-treated colon significantly absorbed Na+ and Cl-, primarily as the result of an equivalent increase in the mucosal-to-serosal flux of these ions. Preincubation of proximal colon in 0.1 mM ibuprofen-treated Ringer yielded similar results. Treatment of indomethacin colon with 1 mM mucosal amiloride eliminated net Na(+)-Cl- absorption without affecting the short-circuit current (Isc). The Isc in control tissue was significantly greater than in indomethacin-treated tissue and was reduced by 0.1 mM serosal furosemide. Serosal addition of 0.1 microM prostaglandin E2 or 10 mM serosal plus mucosal theophylline to indomethacin-treated tissues abolished net Na(+)-Cl- absorption and increased the Isc to levels indistinguishable from control. In contrast, control tissues were essentially unaffected by these secretagogues. These findings indicated that Na(+)-Cl- absorption in equine proximal colon was electroneutral (possibly involving Na(+)-H+ exchange) and that the tissue was capable of electrogenic Cl- secretion. However, under the in vitro conditions, basal ion transport was dominated by endogenous prostanoids that abolished Na(+)-Cl- absorption and elicited near-maximal electrogenic Cl- secretion.

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