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Biomedical subjects

W S Rehm

Publications and source records attributed to W S Rehm.

At least 55 records · Page 3Linked to original sources
PubMed1981

Origins of positive potential difference of frog gastric mucosa in Cl--free solutions.

Experiments were performed on gastric mucosae of Rana pipiens with an in vitro method. Bathing both sides of the mucosae in Cl--free solutions resulted in an inverted potential difference (PD) (i.e., nutrient negative). Cimetidine in a concentration of 10(-4) or 10(-3) M in the nutrient solution gave a positive PD when the H+ secretory rate was zero or near zero and confirmed that the PD versus H+ rate was linear. the origins of the positive PD were examined by ion replacement, e.g., choline for Na+ in both solutions. When both solutions had 25 mM HCO(-)3 (i.e., no HCO(-)3 gradient), the difference in PD between choline sulfate and Na2SO4 solutions indicated a possible small active transport of Na+ from the secretory to nutrient side. Similar experiments indicated no active K+ transport. A residual PD occurred without Na+. With H+ rate zero, 100% O2, and no HCO(-)3, a base secretion of about 0.4 mueq.h-1.cm-2 was obtained in a direction to contribute to the positive PD. Active SO2(-)4 transport may occur.

Animals↗
PubMed1981

Explanation of the effects of imidazole, aminopyrine, and thiocyanate on gastric secretion.

On the basis of the model of figure 9 and its equivalent circuit of figure 10, explanations have been presented for the inhibition of the SCN type of inhibitors and the reversal of their inhibition by the weak bases, imidazole and aminopyrine. On the basis of the model, we have presented explanations for the changes in PD and resistance associated with the SCN type of inhibitors. Explanations of the other effects of the SCN type inhibitors and the effects of the weak bases are possible on the basis of the model. However, these explanations involve some lengthy analysis beyond the scope of the present paper. The model supplies the conceptual basis for a considerable number of further substantive experiments.

Aminopyrine↗
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↗