The influence of an abdominal support for a dental stool in the distributions and electrical activity of the longissimus and the superior trapezius muscle in dentists.

This study evaluated the influence an abdominal support attached to a traditional stool, of those used by dentists, has on the body's distribution of the electrical activity of the superior trapezius and the longissimus thoracic muscles of dental students during the execution of a clinical procedure. The results showed no significant difference in the body's distribution in the seat and backrest, but did reveal there was a weight discharge of 3.1 ± 1.9% of dentist's body weight in the abdominal support. The 9 o'clock position proved to be the best position to perform clinical procedures. It was also observed that the position was closer to the body's axis.

Effect of renoguanylin on hydrogen/bicarbonate ion transport in rat renal tubules.

Renoguanylin (REN) is a recently described member of the guanylin family, which was first isolated from eels and is expressed in intestinal and specially kidney tissues. In the present work we evaluate the effects of REN on the mechanisms of hydrogen transport in rat renal tubules by the stationary microperfusion method. We evaluated the effect of 1 muM and 10 muM of renoguanylin (REN) on the reabsorption of bicarbonate in proximal and distal segments and found that there was a significant reduction in bicarbonate reabsorption. In proximal segments, REN promoted a significant effect at both 1 and 10 muM concentrations. Comparing control and REN concentration of 1 muM, JHCO(3)(-), nmol cm(-2) s(-1)-1,76+/-0,11(control)x1,29+/-0,08(REN 10 muM); P<0.05, was obtained. In distal segments the effect of both concentrations of REN was also effective, being significant e.g. at a concentration of 1 muM (JHCO(3)(-), nmol cm(-2) s(-)1-0.80+/-0.07(control)x0.60+/-0.06(REN 1 muM); P<0.05), although at a lower level than in the proximal tubule. Our results suggest that the action of REN on hydrogen transport involves the inhibition of Na(+)/H(+)exchanger and H(+)-ATPase in the luminal membrane of the perfused tubules by a PKG dependent pathway.

Role of luminal anion and pH in distal tubule potassium secretion.

Potassium secretory flux (J(K)) by the distal nephron is regulated by systemic and luminal factors. In the present investigation, J(K) was measured with a double-barreled K(+) electrode during paired microperfusion of superficial segments of the rat distal nephron. We used control solutions (100 mM NaCl, pH 7.0) and experimental solutions in which Cl(-) had been replaced with a less permeant anion and/or pH had been increased to 8.0. J(K) increased when Cl(-) was replaced by either acetate ( approximately 37%), sulfate ( approximately 32%), or bicarbonate ( approximately 62%), and also when the pH of the control perfusate was increased ( approximately 26%). The majority (80%) of acetate-stimulated J(K) was Ba(2+) sensitive, but furosemide (1 mM) further reduced secretion ( approximately 10% of total), suggesting that K(+)-Cl(-) cotransport was operative. Progressive reduction in luminal Cl(-) concentration from 100 to 20 to 2 mM caused increments in J(K) that were abolished by inhibitors of K(+)-Cl(-) cortransport, i.e., furosemide and [(dihydroindenyl)oxy]alkanoic acid. Increasing the pH of the luminal perfusion fluid also increased J(K) even in the presence of Ba(2+), suggesting that this effect cannot be accounted for only by K(+) channel modulation of K(+) secretion in the distal nephron of the rat. Collectively, these data suggest a role for K(+)-Cl(-) cotransport in distal nephron K(+) secretion.