Electrophysiological effects of cholinergic agonists in surface epithelium of Necturus gastric antrum

1996 ◽  
Vol 270 (3) ◽  
pp. G449-G462
Author(s):  
A. E. Gadacz ◽  
M. E. Klingensmith ◽  
D. I. Soybel
Keyword(s):  
Basolateral Membrane ◽  
Membrane Conductance ◽  
Early Spring ◽  
Transport Processes ◽  
Surface Epithelium ◽  
Antral Mucosa ◽  
Cholinergic Stimulation ◽  
Cholinergic Agonists ◽  
Ion Substitution

Intracellular microelectrode techniques were used to characterize voltage and conductance properties of the basolateral membrane of surface epithelial cells in in vitro Necturus antral mucosa. Flux studies confirmed that this tissue secretes HCO3- under resting conditions and during response to cholinergic stimulation. In studies using intracellular microelectrodes, exposure to cholinergic agonists such as acetylcholine, bethanechol, or carbachol elicited an initial hyperpolarization followed by depolarization of the basolateral cell membranes associated with up to fourfold increases in basolateral membrane conductance. Effects of acetylcholine were dose dependent (10(-6) - 10(-4) M) and prevented by pretreatment of tissues with the nonselective muscarinic receptor blocker atropine. Some variation in this response to cholinergic stimulation was observed and appeared to be related to the season (fall/winter/early spring vs. late spring/summer). Despite such variability, circuit analysis and ion substitution studies indicated that the carbachol-induced increases in basolateral conductance were due to increases in conductance to K+ and Cl- . These increases in basolateral transport processes may serve to stabilize cell ion composition and membrane electrical properties during cholinergic stimulation of mucus and HCO3- secretions.

Characteristics of basolateral Cl- transport by gastric surface epithelium in Necturus antral mucosa

1993 ◽  
Vol 264 (5) ◽  
pp. G910-G920 ◽  
Author(s):  
D. I. Soybel ◽  
M. B. Davis ◽  
L. Y. Cheung
Keyword(s):  
Nutrient Solution ◽  
Cell Membranes ◽  
Basolateral Membrane ◽  
Membrane Potentials ◽  
Gastric Antrum ◽  
Ion Exchanger ◽  
Surface Epithelium ◽  
Antral Mucosa ◽  
Liquid Ion Exchanger ◽  
Electrochemical Equilibrium

Conventional and ion-selective microelectrodes were used to characterize transport of Cl- across the basolateral cell membranes of gastric surface epithelium in isolated preparations of gastric antrum of Necturus. Conventional, voltage-sensing electrodes were used to evaluate changes in membrane potentials and resistances during removal of Cl- from the nutrient perfusate. Liquid ion exchanger Cl(-)-selective microelectrodes were constructed and validated to measure intracellular Cl- activity (aiCl). Our data indicate that 1) aiCl (range 12-25 mM) is close to that predicted if Cl- is distributed across the cell membranes by electrochemical equilibrium, 2) aiCl is not influenced by changes in luminal Cl- content but is susceptible to changes in nutrient Cl- content, 3) Cl- conductances cannot be detected in the basolateral membrane and changes in membrane potentials do not influence aiCl, and 4) Cl- accumulation across the basolateral membrane depends on Na+ and the level of [K+] in the nutrient solution. Inhibition of K(+)-dependent Cl- accumulation, in the absence of nutrient Na+ or in the presence of the inhibitor bumetanide, was demonstrated. These findings suggest that basolateral Na(+)-K(+)-Cl- cotransport is important in regulating cell Cl- levels in surface cells of the gastric antrum in Necturus.

Characterization of the apical membrane ionic permeability of the rabbit proximal convoluted tubule

1986 ◽  
Vol 250 (2) ◽  
pp. F339-F347
Author(s):  
J. Y. Lapointe ◽  
R. Laprade ◽  
J. Cardinal
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Conductance ◽  
Transference Number ◽  
Membrane Resistance ◽  
Transference Numbers ◽  
Vitro Analysis ◽  
Convoluted Tubules

Basolateral membrane potential (psi BL), transepithelial potential (psi T), and the ratio of apical to basolateral membrane resistance (RA/RBL) were measured in rabbit proximal convoluted tubules (PCT) perfused in vitro. Analysis of RA/RBL changes using several luminal perfusates indicates that the cotransport of Na with glucose and alanine would represent 19% of the apical conductance in normal conditions; the cotransport of Na with acetate, citrate, sulfate, and phosphate would represent 7%, whereas Na, K, and Cl diffusion would represent 10, 4, and 0% of this apical conductance, respectively. On the other hand, psi BL values can also be analyzed using the equivalent circuit of the epithelium to obtain the apical membrane equivalent electromotive force (EA) in the presence of each perfusate. These values, as well as the preceding values obtained from RA/RBL measurements, indicate that in the absence of cotransported solutes the transference number for Na diffusion is several times larger than for K diffusion. Among the conductance pathways studied, the transference number sequence would be as follows: Na cotransport with alanine and glucose greater than Na cotransport with anions greater than Na diffusion greater than K diffusion greater than Cl diffusion. This study also suggests the presence of another important but unidentified apical ionic permeation pathway, since the total of the transference numbers obtained from RA/RBL analysis represents only 40% of the total apical membrane conductance and the absolute values of EA are difficult to account for using only the tested apical membrane permeation pathways.

Basolateral K+ conductances in surface epithelium of Necturus antrum: effects of Ca2+ and divalent cations

1992 ◽  
Vol 262 (4) ◽  
pp. G651-G659
Author(s):  
D. I. Soybel ◽  
S. W. Ashley ◽  
L. Y. Cheung
Keyword(s):  
Membrane Permeability ◽  
Divalent Cations ◽  
Basolateral Membrane ◽  
Membrane Resistance ◽  
Membrane Potentials ◽  
Time Dependent ◽  
Physiological Significance ◽  
Surface Epithelium ◽  
Antral Mucosa ◽  
Microelectrode Techniques

Intracellular microelectrode techniques were used to characterize basolateral membrane K+ conductances in isolated Necturus antral mucosa. Exposure of tissues to progressively higher levels of serosal K+ (4, 20, 40, or 60 mM) resulted in progressively greater depolarizations of basolateral membrane potentials and decreases in membrane resistance, consistent with the presence of a significant K+ conductance. Ba2+ (2 mM) partially blocks these conductances. Exposure of tissues to increased levels of serosal Ca2+ (from 1.8 to 6.8 mM) elicited significant hyperpolarization of basolateral potentials and decreases in basolateral resistance. These effects are also elicited by Sr2+ (5 mM), but not by Mg2+ (5 mM). Ba2+ (5 mM) elicits complex and time-dependent effects, but transiently elicits an effect similar to high Ca2+. Ion substitutions in the serosal perfusate suggest that the Ca(2+)-induced effects are due to enhancement of basolateral K+ conductances. Further work is necessary to identify the processes that mediate this increase in basolateral K+ conductance and to evaluate the physiological significance of this change in membrane permeability to K+.

scholarly journals Cholinergic stimulation blocks endothelial cell activation and leukocyte recruitment during inflammation

2005 ◽  
Vol 201 (7) ◽  
pp. 1113-1123 ◽  
Author(s):  
Rubina W. Saeed ◽  
Santosh Varma ◽  
Tina Peng-Nemeroff ◽  
Barbara Sherry ◽  
David Balakhaneh ◽  
...  
Keyword(s):  
Endothelial Cell ◽  
Cell Activation ◽  
Leukocyte Recruitment ◽  
Dependent Manner ◽  
Cholinergic Stimulation ◽  
Endothelial Cell Activation ◽  
Cholinergic Agonists ◽  
Α7 Nachr

Endothelial cell activation plays a critical role in regulating leukocyte recruitment during inflammation and infection. Based on recent studies showing that acetylcholine and other cholinergic mediators suppress the production of proinflammatory cytokines via the α7 nicotinic acetylcholine receptor (α7 nAChR) expressed by macrophages and our observations that human microvascular endothelial cells express the α7 nAChR, we examined the effect of cholinergic stimulation on endothelial cell activation in vitro and in vivo. Using the Shwartzman reaction, we observed that nicotine (2 mg/kg) and the novel cholinergic agent CAP55 (12 mg/kg) inhibit endothelial cell adhesion molecule expression. Using endothelial cell cultures, we observed the direct inhibitory effects of acetylcholine and cholinergic agents on tumor necrosis factor (TNF)-induced endothelial cell activation. Mecamylamine, an nAChR antagonist, reversed the inhibition of endothelial cell activation by both cholinergic agonists, confirming the antiinflammatory role of the nAChR cholinergic pathway. In vitro mechanistic studies revealed that nicotine blocked TNF-induced nuclear factor–κB nuclear entry in an inhibitor κB (IκB)α- and IκBε-dependent manner. Finally, with the carrageenan air pouch model, both vagus nerve stimulation and cholinergic agonists significantly blocked leukocyte migration in vivo. These findings identify the endothelium, a key regulator of leukocyte trafficking during inflammation, as a target of anti-inflammatory cholinergic mediators.

scholarly journals Effects of floral thermogenesis on pollen function in Asian skunk cabbage Symplocarpus renifolius

2009 ◽  
Vol 5 (4) ◽  
pp. 568-570 ◽  
Author(s):  
Roger S. Seymour ◽  
Yuka Ito ◽  
Yoshihiko Onda ◽  
Kikukatsu Ito
Keyword(s):  
Growth Rate ◽  
Pollen Germination ◽  
Narrow Range ◽  
Temperature Tolerance ◽  
Early Spring ◽  
Long Period ◽  
Pollen Tube Growth Rate ◽  
Skunk Cabbage ◽  
Effects Of Temperature

The effects of temperature on pollen germination and pollen tube growth rate were measured in vitro in thermogenic skunk cabbage, Symplocarpus renifolius Schott ex Tzvelev, and related to floral temperatures in the field. This species has physiologically thermoregulatory spadices that maintain temperatures near 23°C, even in sub-freezing air. Tests at 8, 13, 18, 23, 28 and 33°C showed sharp optima at 23°C for both variables, and practically no development at 8°C. Thermogenesis is therefore a requirement for fertilization in early spring. The narrow temperature tolerance is probably related to a long period of evolution in flowers that thermoregulate within a narrow range.

scholarly journals High-level expression of IκB-β in the surface epithelium of the colon: in vitro evidence for an immunomodulatory role

1999 ◽  
Vol 66 (6) ◽  
pp. 1049-1056 ◽  
Author(s):  
Gary D. Wu ◽  
Ning Huang ◽  
Xiaoming Wen ◽  
Sue A. Keilbaugh ◽  
Hongyun Yang
Keyword(s):  
Surface Epithelium ◽  
High Level Expression ◽  
High Level

scholarly journals Tobacco Mosaic Virus Movement Protein Functions as a Structural Microtubule-Associated Protein

2006 ◽  
Vol 80 (17) ◽  
pp. 8329-8344 ◽  
Author(s):  
Jamie Ashby ◽  
Emmanuel Boutant ◽  
Mark Seemanpillai ◽  
Adrian Sambade ◽  
Christophe Ritzenthaler ◽  
...  
Keyword(s):  
Tobacco Mosaic Virus ◽  
Mosaic Virus ◽  
Movement Protein ◽  
Cell Extract ◽  
Transport Processes ◽  
In Vitro Assays ◽  
Protein Functions ◽  
Intercellular Spread

ABSTRACT The cell-to-cell spread of Tobacco mosaic virus infection depends on virus-encoded movement protein (MP), which is believed to form a ribonucleoprotein complex with viral RNA (vRNA) and to participate in the intercellular spread of infectious particles through plasmodesmata. Previous studies in our laboratory have provided evidence that the vRNA movement process is correlated with the ability of the MP to interact with microtubules, although the exact role of this interaction during infection is not known. Here, we have used a variety of in vivo and in vitro assays to determine that the MP functions as a genuine microtubule-associated protein that binds microtubules directly and modulates microtubule stability. We demonstrate that, unlike MP in whole-cell extract, microtubule-associated MP is not ubiquitinated, which strongly argues against the hypothesis that microtubules target the MP for degradation. In addition, we found that MP interferes with kinesin motor activity in vitro, suggesting that microtubule-associated MP may interfere with kinesin-driven transport processes during infection.

The location and mechanism of hyperosmotic fluid secretion in the rectum of the saline-water mosquito larvae Aedes taeniorhynchus

1977 ◽  
Vol 66 (1) ◽  
pp. 111-126
Author(s):  
T. J. Bradley ◽  
J. E. Phillips
Keyword(s):  
Saline Water ◽  
Fluid Secretion ◽  
Opposite Polarity ◽  
Posterior Segment ◽  
Transport Processes ◽  
Cell Border ◽  
Experimental Conditions ◽  
Ultrastructural Studies ◽  
Aedes Taeniorhynchus

1. Ligation between the anterior and posterior segments of the rectum in vitro was used to demonstrate that the posterior rectum is the site of hyperosmotic secretion to the lumen side. Observations were consistent with a reabsorptive function for the anterior rectum. These results support predictions from ultrastructural studies of these two segments. 2. The initial potential of the rectal lumen, relative to the haemocoel side, was of opposite polarity in the anterior (−10 mV) and posterior (+ 10 mV) segments and these values decreased to −2 and +6 mV respectively in ligated recta which had secreted for 2 h. 3. A comparison of these potential difference measurements with concentration differences developed across the rectal epithelium under the same experimental conditions indicates that Na+, K+, Mg2+, and Cl- are all actively transported by the posterior segment to the lumen side. 4. The influence of different haemolymph concentrations of Na+, K+, and Cl- on the potential differences across the basal cell border and across the whole rectal epithelium are reported. Based on this and previous data, we propose a model for the organization of transport processes within the single celltype present in the posterior rectal epithelium.

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