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Biomedical subjects

W S Rehm

Publications and source records attributed to W S Rehm.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1970

A model for the long time-constant transient voltage response to current in epithelial tissues.

Upon passing a step current through the frog gastric mucosa, a transient response in voltage is observed, which can formally be represented by several types of model systems, although some models require elements which are hard to visualize in terms of the known morphology of the mucosa. A physically reasonable model can be constructed by considering the changes in intracellular ionic composition which arise due to current flow, and the consequent changes in diffusion potentials across the two cell membranes. A simple model has been developed which fits the observed long time-constant portion of the transient at low current densities, and predicts departures from exponential behavior at larger currents. Since reasonable values for membrane resistance and cell volume give a fit, it is proposed that this model may account for the long time-constant portion of the transient response. There is no reason to expect that similar considerations do not hold for epithelial tissues in general.

Animals↗