Mumtaz A. Dinno

The effect of therapeutic ultrasound on electrophysiological parameters of frog skin

There are two groups of mechanisms through which ultrasound can affect biological systems, those of thermal origin and others of nonthermal origin. Since in almost every therapeutic application of ultrasound, movement of ions across cellular membranes is involved, it becomes important to study the effect of ultrasound on active and passive ionic conductance. In order to differentiate between thermal and nonthermal effects, a study was conducted on model systems in which the effect of temperature is known. The well-known sodium transporting epithelium, the epidermis of abdominal frog skin, was investigated and the effect of therapeutic ultrasound on its electrophysiological properties was determined. It was found that under open circuit conditions, irradiation of the skin with 1 MHz cw (60-480 mW/cm2) ultrasound caused a significant decrease (5-50%, depending on the applied power) in the transepithelial potential and resistance at room temperature (20-22 degrees C). Under short circuit conditions, also at room temperature, there was an increase in total ionic conductance (20-250%, depending on the applied power) and a decrease in the net actively transported current, measured as the short circuit current. These effects are reversible within the range of powers used. Furthermore, it was found that the magnitude of the observed changes was strongly dependent on the perfusion rate and the gas content of the bathing medium. The effect of ultrasound diminished in the presence of CO2 and was enhanced with faster perfusion rates. Pulsed ultrasound delivered at the same energy (Isata) as that of cw caused a significantly larger effect. At lower temperatures (12-14 degrees C) the effect of ultrasound was reduced. Analysis of the data reveals that the effects of ultrasound on ion transport reported here are not primarily of thermal origin but are probably due to cavitation and related effects, such as microsteaming.

Microelectrode studies of amphotericin B on Na+ and K+ conductance in bullfrog cornea

Addition of 10(-5) M amphotericin B to the tear solution of an in vitro preparation of the frog cornea increased the transepithelial conductance, gt, and decreased the apical membrane fractional resistance, f(R0), in the presence or absence of tear Na+ and Cl-. In the presence of tear Na+ and Cl-, amphotericin B increased the short-circuit current, Isc, from 3.9 to 8.8 microA.cm-2 and changed the intracellular potential, V0, from -48.5 to -17.9 mV probably due to a higher increase in the Na+ than in the K+ conductance. In the absence of tear Na+ and Cl-, amphotericin B decreased Isc from 5.5 to about 0 microA.cm-2 due to K+ (and possibly Na+) flux from cell to tear and changed V0 from -35.4 to -63.6 mV due to the increase in conductance of both ions. Increase in the tear K+ from 4 to 79 mM (in exchange for choline), in the presence of amphotericin B and absence of tear Na+ and Cl-, decreased f(R0) from 0.09 to 0.06, increased gt from 0.23 to 0.31 mS, increased Isc from 0.63 to 7.3 microA.cm-2, and changed V0 from -65.5 to -17.3 mV due to the change in EK in the presence of a high conductance in the tear membrane. Similar effects were observed with an increase of tear Na+. Results support the concept that the Na+ conductance opened by amphotericin B in the apical membrane is greater than the K+ conductance. Previously observed transepithelial effects of the ionophore may be explained mostly on the basis of its effect on the apical membrane.

Determination of Electrogenicity of Frog Gastric Mucosa in Chloride-Free Solutions by Using Barbiturates

Conclusion Barbiturates can be used to reveal the linear relationship between the PD and the H+ rate and to obtain estimates of electrical parameters of the H+ secretory mechanism in Cl--free solutions.

Potential difference responses to nutrient K+, Cl- and Na+ changes in secreting and resting states of frog stomach.

The effects of changes in nutrient concentrations of K+, Cl- and Na+ on the transmucosal potential difference (PD) and the resistance were compared for secreting fundus and resting fundus of Rana pipiens. Increase of K+ from 4 to 40 mM, decrease of Cl- from 81 to 8.1 mM and decrease of Na+ from 102 to 10 mM gave, 10 min after the change in the secreting fundus, delta PD values of -28.2, -19.8 and -7.5 mV, respectively. In the resting fundus with SCN- inhibition, the same changes in nutrient ion concentration gave delta PD values of -20.1, -17.0 and -10.2 mV, respectively. Changes in Na+ concentration were considered in a set of experiments of high acid secreting stomachs (4 to 6 mu equiv. . h-1 . cm-2). Here, delta PD gave for 10-fold decreases in Na+ concentration in secreting fundus -4.8 mV and in resting fundus with SCN- inhibition -22.6 mV. Omeprazole inhibition gave results quite similar to those with SCN- inhibition. From these results in going from secretion to inhibition, it follows that the increment of K+ conductance if it increased was lower than the increase in NaCl symport conductance since the change in delta PD for K+ decreased and that for Na+ increased. Also HCO3- conductance increased with inhibition. After SCN- inhibition the transmucosal resistance initially increased and later decreased. The decrease can be accounted for by the increase in conductance of the NaCl symport pathway and of the HCO3- pathway.

The effect of extracorporeal shock wave lithotripsy (ESWL) on electrophysiological parameters across abdominal frog skin: Real time observations

The side effects of ESWL, such as increased sodium excretion and proteinuria, may be explained by structural and functional changes that lead to an increase in permeability across the renal tubule. This preliminary study was undertaken to examine the feasibilty of such an explanation. Frog skin was used in this investigation, since sodium transport across it is similar to that of the distal convoluted tubule in the kidney. Exposure of the skin to a single shock at 20‐kV electrode voltage caused a significant but reversible decrease in transepithelial membrane potential, a decrease in ionic current (primarily sodium), and an increase in total ionic permeability. It is of interest to note here that these results are similar to those reported by Dinno et al. [Ultrasound Med. Biol. 15, 461–470 (1989)] on the effect of therapeutic ultrasound (1 MHz, 60–480 mW/cm2) on frog skin. Those similarities suggest a common mechanism. On the basis of this observation and other unpublished results, acoustic cavitation, an...

Inhibition of acid secretion of fundus of Rana pipiens with a high concentration of potassium on the secretory side

Inhibition of acid secretion of the frog fundus is generally accompanied by an increase in transmucosal resistance, Rt, and in potential difference, PD (nutrient normally positive). These results are predicted for the intact tissue by an electrogenic proton pump. It has been suggested that the increase in PD with inhibition can also be explained by a neutral proton pump. The latter model postulates a K+ diffusion potential across the secretory (lumen-facing) membrane tending to make the secretory side positive. Upon inhibition, the [K+] in the lumen is assumed to increase, which decreases the diffusion potential, resulting in an increase in the positivity of the nutrient side. To test this theory, we determined the effects of inhibition with a high [K+] on the secretory side. With a high [K+] in the lumina, inhibition would result in only a small change in the ratio of K+ in the cell to that in the lumina, and hence a small change in the diffusion potential. We found, however, that inhibition increased the PD essentially the same as in the controls. With inhibition the resistance also increased with high secretory K+. Elevating the secretory K+ during secretion produced a 44% decrease in Rt indicating a large increase in luminal K+. We conclude that the results are not compatible with the K+ diffusion potential model but are those predicted by the electrogenic concept.

Microelectrode study of effects of luminal K+ on surface cells of frog stomach

Abstract Microelectrode studies were conducted to determine whether increasing the K + concentration from 4 to 80 mM in the secretory solution affected the surface cells of the frog gastric mucosa (fundus) of Rana pipiens . The short-circuit current ( I sc ) increased by 10% and the conductance ( G t ) increased by 19%. The potential difference ( V sc ) from secretory solution to cell and the fractional resistance ( F o ) remained essentially unchanged. On the basis of the constancy of the latter two parameters, it was inferred that the change in K + concentration did not affect the surface epithelial cells.

The effects of ultrasound on membrane‐bound ATPase activity.

Ultrasound frequencies ranging from 26 kHz–10 MHz are used in a number of applications varying from cell disruptions to therapeutic and diagnostic procedures. Previous results from our laboratory have demonstrated that 1‐MHz ultrasound at therapeutic intensities causes significant changes in the electrophysiological properties of epithelial tissues. The nature of these alterations indicated that, among other effects, the Na/K‐dependent ATPase activity of the tissue was reduced. In this study, the effects of ultrasonic irradiation (30 kHz) on enzyme activities in two model systems have been examined: one membrane incorporated (Na/K‐dependent ATPase in inverted erythrocyte ghosts from rat blood) and the other in ‘‘free’’ solution (ATP‐dependent firefly luciferin/luciferase reaction). Ultrasonic irradiation produced irreversible decreases in the activity of the enzyme in each system. At present, the analysis leads one to conclude that sono‐chemical (including free radical) and not thermal effects on the enzy...

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+.

The effect of ultrasound on the ionic conductance across frog skin in the presence of free‐radical scavengers

In a recent study, Dinno et al. [Ultrasound Meal. Biol. 15, 461–470 (1989).] reported that the increase in ionic conductance across frog skin is primarily due to effects of nonthermal origin. Cavitation was considered to be the major mechanism response for the change in the conductance. Since free radicals (FR), under certain conditions, are known to be generated during cavitation, it was decided to investigate the effect of ultrasound in the presence of free‐radical scavengers (FRS). It was found that the presence of 5 mM of either vitamin C or cysteamine caused a significant block to the increase of ionic conductance induced by ultrasound. On the other hand, cystamine, which does not permeate into the cell as readily as the other two FRS, did not interfere as strongly with the action of ultrasound. On the basis of these results, the following indications are suggested: (1) The increase in ionic conductance in the presence of ultrasound is triggered by FR produced by cavitation and (2) in some as‐yet‐unk...