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W S Rehm

Publications and source records attributed to W S Rehm.

18 recordsLinked to original sources
PubMed1991

Effect of amphotericin B and Cl- removal on basolateral membrane K+ conductance in frog corneal epithelium.

Increase in stromal K+ concentration from 4 to 79 mM in an in vitro preparation of the frog cornea, in Cl(-)-free solutions, did not change the apical membrane fractional resistance, fR0, or the transepithelial conductance, gt; it depolarized the intracellular potential, V0, by 38 mV and decreased the short-circuit current, Isc by 2.9 microA/cm2. These changes were similar to those observed for the same increase in stromal K+ in control solutions except for the increase in gt in the latter. When stromal K+ was increased with 10(-5) M amphotericin B, AmB, in the tear solution, fR0 increased by 0.27 in control solutions and by 0.08 in Cl(-)-free solutions; respectively, gt increased by 0.40 and by 0.17 mS/cm2; Isc decreased by 12 and by 11 mS/cm2; V0 depolarized by 9 and by 9.5 mV. These results support the concept that: (i) entrance of Cl- into the cell is responsible in part for the bioelectrical changes observed when stromal K+ is increased; and (ii) AmB decreases the partial K+ conductance in the basolateral membrane of the frog cornea epithelium by a decrease in intracellular K+.

Amphotericin B↗
PubMed1990

Role of polarization of gastric EMFs in evaluation of contemporary HCl models.

The neutral proton pump (NP) model postulates a neutral exchange of K+ for H+ across the secretory membrane and the electrogenic proton pump (EP) model an electrogenic proton pump. Previous evidence is briefly reviewed and polarization of EMFs by transmucosal voltage clamping (VC) is presented. During VC, open circuit potential difference (PD) (VOC) is obtained by breaking the circuit for 2 s (after dielectric capacitors have discharged). The magnitude of polarization in Cl- media is less than in Cl(-)-free media, presumably due to the high conductance of Cl- paths. The magnitude in Cl(-)-free media is from 35 to 50 mV for a VC of 100 mV (nutrient side positive). The Na+/K(+)-ATPase is not essential because with choline sulphate media polarization is typical. With Cl(-)-free media, VOC versus IH (H+ rate) is exponential but (VC-VOC) versus IH is linear. Polarization on the basis of the NP model would be due to changes in K+ diffusion potentials. However, with 80 mM K+ on both sides (Cl(-)-free media) polarization is typical. We conclude that polarization cannot be due to a change in K+ diffusion potentials but to polarization of the EP model. The problem remains of how to incorporate the important finding of the H+/K(+)-ATPase into a model for the intact tissue.

Adenosine Triphosphatases↗
PubMed1979

Cell-to-cell communication of osteoblasts.

Osteoblasts were investigated by two methods, electrical conductance and dye injection. Current injection into one cell caused a change in the recorded transmembrane potential of a second cell, indicating high conductance pathways between the two cells. Dyes injected into a single osteoblast were transmitted to numerous surrounding cells.

Animals↗
PubMed1978

Transmembrane potentials of osteoblasts.

Transmembrane potentials were recorded in situ from osteoblasts on the parietal bones of albino rat pups, 3 to 24 days of age. Osteoblasts exhibit a uniquely low polarization of their cell membranes (3.93 mV, inside negative). Osteoblasts respond rapidly, but transiently, to parathyroid hormone by depolarization, and to thyrocalcitonin by hyperpolarization.

Animals↗
PubMed1977

A theory of endothelial control of corneal hydration.

The details of our previously described theory of how the endothelium controls corneal hydration in the absence of the epithelium are provided. A central postulate is that the endothelium can produce across its limiting plasma membranes an osmotic gradient that reduces stromal swelling pressure so that it does not exceed intraocular pressure during thinning of a swollen cornea.

Adenosine Triphosphatases↗
PubMed1977

Effect of nicotine on gastric acid secretion: evidence of electrogenic pump theory.

In vitro studies on H+ secretion, potential difference (PD), short-circuit current (Isc), and resistance across stripped mucosa of frog stomach in Cl-medium have shown that addition of nicotine in the serum bathing fluid caused a marked inhibition of the H+ secretory rate and an increase of PD and Isc without change of the transmucosal resistance. A dose-response correlation was indicated. During the first 8 min, the changes in the measured parameters, namely, PD versus Ih and Isc versus Ih, were linear. After 8 min, a deviation from linearity was observed. From the slope of the regression lines, the resistance of the electrogenic Cl- pump on the mucosal membrane (Rcl) was calculated to be 127 omega cm2 and the resistance of the chloride pathway on the serosal side (Rcl) was 407 omega cm2. The resistance of the H+ pump on the mucosal membrane (Rh) in Cl- medium was estimated to be 385 omega cm2. The sum of the emf's of the Cl+ pump on the mucosal membrane and of the Cl- gradient across the serosal membrane, namely Ecl + Ecl, was found to be 35 mV. The presence of such linear relationships between measured versus the H+ rate and Isc versus Ih lends support to the electrogenic theory of HCl secretion.

Animals↗
PubMed1977

Electrogenic HCl theory in light of effects of SCN- and Ba2+ on frog stomach.

It has been previously shown that a) thiocyanate (15 mM) inhibits H+ secretion and increases the resistance and potential difference (PD) which is explained on the basis of separate electrogenic mechanisms for H+ and Cl- and b) barium (1 mM) added to the nutrient side produces a large increase in the resistance and little change in the H+ rate and PD, and the site of the increased resistance is the nutrient membrane of the tubular cells. In the present paper we show that a) with Ba2+ on the nutrient side, addition of thiocyanate to the secretory side decreases the H+ rate to about zero and also decreases the resistance; and b) if the site of the decrease in resistance is the secretory membrane of the tubular cells, in which the HCl is produced, then these findings would be contrary to the predictions on the basis of the electrogenic theory. However, the transmucosal resistance is a function of the resistance across the surface epithelial cells and the resistance of the secretory and nutrient membranes of the tubular cells. With a 79 mM K+ pulse technique, the findings indicate that the resistance of the secretory membrane increases, and the decrease in the resistance is due to changes in the resistance of the surface cells and/or the nutrient membrane of the tubular cells.

Action Potentials↗
PubMed1977

Gastric secretion.

This review has attempted to cover some of the findings that have been made in the mechanism of gastric secretion in recent years. It is hard to offer any firm conclusions, whether at the level of stimulus, metabolism, or the terminal process of secretion. However, some generalizations may be possible. At least amphibian gastric secretion is stimulated by cAMP as a second messenger, with histamine presumably acting as the primary messenger. The resultant metabolic change is due largely to a direct stimulation of catabolism, which in dog appears to be the metabolism of hexose, through the glycolytic process, the hexose monophosphate shunt, and the Krebs' cycle with cytoplasmic reduction and mitochondrial oxidation of pyridine nucleotides. No evidence could be obtained for changes in high energy phosphate or for lipolysis. One would expect gastric mucosal membranes during secretion to contain an anion-restricted electrogenic H+ pump, but they in fact contain an ATPase stimulated by monovalent cations and are insensitive to ouabain. In addition, hog or dog gastric membranes have the vectorial properties of H+ absorption, Rb+ extrusion, and ANS fluorescence enhancement with the addition of ATP, as well as protein phosphorylation by 32P dependent on a K+ gradient.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1977

Electrical events during activation and inhibition of gastric HCl secretion.

A brief review of some of the relationships between the secretory rate and the electrophysiological characteristics of the canine and frog gastric mucosa is presented. There is no simple relationship between the potential difference (PD) and H+ rate in the in vitro frog gastric mucosa with standard Cl- bathing solutions. In contrast, with Cl- -free solutions (PD is inverted) there is a precise linear relationship between the PD and the H+ rate. This linear relationship is strong support for the concept that the H+ mechanism under these conditions is electrogenic. In the past it has been difficult rigorously to exclude the possibility that the inverted PD is due to a liquid junction potential between acid fluid in the lumina and the secretory bathing solution. Use of aminopyrine or imidazole essentially eliminates the possibility that the inverted PD is due to a liquid junction potential. Hence the linear relationship is solid evidence for the electrogenicity of the H+ mechanism. Recently we have shown that aminopyrine or imidazole can reverse thiocyanate inhibition of H+ secretion.

Aminopyrine↗
PubMed1976

Inhibition of H+ secretion in the frog gastric mucosa by ATP and related compounds.

Addition of adenosine triphosphate (ATP) to the nutrient (submucosal-facing) solution of the histamine-stimulated in vitro frog (Rana pipiens) gastric mucosa produces a marked reduction in the H+ secretory rate and an increase in transmucosal potential difference (PD) and resistance in both Cl- and Cl-free media. The effects are reversible upon removal of ATP. The threshold concentration is between 1 and 2 mM, and 5 mM produce maximal inhibition. It is shown that the effects of ATP are not due to a change in pH or osmolarity of the nutrient fluid, or to a decrease in the Ca2+ and/or Mg2+ activities of the nutrient fluid. It is also shown that the inhibitory action of ATP is not dependent on a chelation complex between Ca2+ or Mg2+. Adenosine diphosphate also produces effects essentially the same as ATP whereas 5'-adenosine monophosphate and adenosine produce relatively little or no change.

Adenosine↗
PubMed1976

An intact globe technique for electrophysiological studies on cornea.

An intact globe method was developed to determine the characteristics of the cornea of the bullfrog, Rana catesbeiana. With this method the anterior chamber could be perfused and the transcorneal potential difference (PD) and electrical resistance determined. It was found for the endothelium plus stroma (epithelium scraped) that the PD was essentially zero and the electrical resistance was only a small fraction of that of the intact cornea. Elevation of K+ or decrease in Cl- concentration in the anterior chamber produced in intact corneas a large and rapid change in PD while with the epithelium scraped (stroma and endothelium intact) these elevations produced a negligible change in PD. It is concluded that ions can rapidly move across the endothelium and stroma of the cornea.

Animals↗
PubMed1975

Diffusion resistance of endothelium and stroma of bullfrog cornea determined by potential response to K+.

Corneas of bullfrog (Rana catesbeiana) were mounted between lucite chambers. A four-electrode system was used and the potential difference (PD) and the electrical resistance were measured. In intact corneas, the PD averaged 25 mV (acqueous side positive) and the electrical resistance 1.5 kQ - cm2. perfusion of the aqueous side with high K+ solutions resulted in a marked decrease in PD and a drop in the electrical resistance. Scraping the epithelium (leaving the stroma plus endothelium) resulted in a drop of the PD to about zero and a decrease in electrical resistance to about 0.1 kQ - CM2 and a very small PD response to a marked elevation of the K+ concentration on the aqueous side. On the basis of the above, it is obvious that the large delta PD in intact corneas, due to elevation of the K+ concentration, must be due to K+ diffusing from the aqueous side across the endothelium and stroma and reaching the epithelium. The duration of the PD response is therefore a measure of the resistance to diffusion of the stroma plus endothelium. A quantitiative analysis shows that under in vitro conditions the resistance of the endothelium plus stroma to the diffusion of ions is very low.

Animals↗
PubMed1975

Reversibility of effects of very hypotonic fluids on in vitro frog gastric mucosa: a functional and morphological study.

Functional and morphological properties of the in vitro frog gastric mucosa were studied during and after exposure to very hypotonic (approximately 25 mOs M) solutions. Within 20 min the acid secretory rate decreased to zero, but it returned to normal levels after isotonic fluids had been restored. The potential difference (PD) dropped within the first minutes after the exposure to hypotonic solutions, and became inverted. Following the return of isotonic conditions the PD increased to levels higher than in the controls. The electrical resistance increased about 10-fold during the hypotonic period, but decreased to near normal values when isotonic conditions were restored. By light and electron microscopy the cells of the hypotonic mucosae appeared greatly swollen, and the alterations were assessed by morphometric methods. The gland lumina were almost obliterated, and the lamina propria was reduced to about 63% of its former volume. After the return to isotonic conditions normal morphology was restores. It is conceivable that the great increase in resistance duroing the hypotonic period was caused by the occlusion of the gland lumina. Quantitative analyses of the Na, K, and Cl tissue concentrations indicated a large loss of these ions during the hypotonic state. Presumably the epithelial cells in the hypotonic mucosae avoid bursting by rapidly letting large numbers of ions exit, which results in a celulular osmolarity close to that of the bathing fluids.

Animals↗