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.

Certain findings seemed to invalidate the author's separate site theory of HCl formation (separate H+ and Cl– ion electrogenic mechanisms). These findings are analyzed and further pertinent experimental data on the frog's stomach are presented. With an in vitro chamber method it was found that the onset of secretion (histamine stimulation) resulted in a sustained decrease in transmucosal resistance and a small initial increase in potential difference (PD) followed by a larger decrease. The ratio PD/resistance (the predicted short-circuit current, Isc) initially increased and then decreased. During short-circuiting, the onset of secretion resulted in the predicted changes in Isc. Following the establishment of secretion, changes in the H+ ion secretory rate frequently occurred without significant changes in Isc. Thiocyanate inhibition resulted in a transient increase in Isc and a sustained increase in both the PD and resistance. Clamping of the voltage across the mucosa at negative levels (nutrient negative) reversibly decreased the H+ ion rate. The average voltage necessary to reduce the H+ ion rate to zero was –140 mv. With a single loop equivalent circuit the average EMF of the H+ ion mechanism on the basis of the voltage-clamping experiments is 140 mv. Findings are explained by the separate site theory with the assumption of cytoplasmic biochemical coupling.

The freezing point depression of freshly excised frozen tissues, pulverized in a hydraulic press or in a mortar, is greater than that of plasma. Even at 0°C. the freezing point depression of such homogenates increases significantly with time. Dilution data indicate that such freezing point data are valid. The presence of intact cells has been shown in smears of tissues pulverized in a mortar, but not in smears of those crushed in a hydraulic press. The osmolarity of various diluent solutions affects the calculated osmotic activity of tissue homogenates presumably because of delayed diffusion between the diluent and cell fluid. With a hypertonic NaCl diluent, spuriously low values of tissue osmotic activity are found from calculations assuming instantaneous mixing between homogenates and diluents. The limitations of data from cryoscopic experiments and from tissue-swelling experiments are discussed in relation to the basic question of whether or not cell fluid is isotonic to extracellular fluid.

With an in vitro chamber method experiments were performed to determine the relative ionic conductances of the nutrient membrane (membrane facing muscularis mucosa). The concentration of a given ion in the nutrient bathing solution was changed, and the ensuing time course of the change in transmucosal potential difference (PD) was recorded. Changing K(+) from 4 to 79 mM produced a response in PD which occurred markedly faster than the response for the reverse change, and similar results were obtained by changing the Cl(-) concentration. It was found that these differences were predicted by the analysis of an idealized model consisting of a membrane in series with a diffusion barrier. When both the K(+) and Cl(-) were changed, such that the product of their concentrations remained constant, the time courses of the responses were again similiar to those predicted on the basis of the model. From the magnitudes of the total PD responses it is shown that in the presence of a 4 mM K(+) nutrient solution, the conductivity of the nutrient membrane appears to be entirely due to the K(+) and Cl(-) conductances, the K(+) conductance being about twice that of the Cl(-). It is also shown that with a 79 mM K(+) nutrient solution the parameters of the membrane were changed such that the conductances of the two ions were approximately equal. The time constant for diffusion of KCl or NaCl across the barrier consisting of the submucosa, muscularis mucosa, and lamina propria is about 1 min.