Chloride channel blockers activate an endogenous cationic current in oocytes of Bufo arenarum.

A two-electrode, voltage-clamp technique was used to measure the effect of the Cl(-) channel blockers, 9-anthracene carboxylic acid and niflumic acid, upon the ionic currents of oocytes of the South American toad Bufo arenarum. The main results were: (1) both blockers produced a reversible increase of the outward currents on a dose-dependent manner; (2) the activated outward current was voltage dependent; (3) the 9-anthracene carboxylic acid-sensitive current was blocked with barium; and (4) the effect of 9-anthracene carboxylic acid was more pronounced in a zero-K(+) solution than in standard (2 mmol l(-1)) or high (20 mmol l(-1)) K(+) solutions, indicating that a K(+) conductance is activated. The effect of the Cl(-) channel blockers could be due to a direct interaction with endogenous cationic channels. Another possible explanation is that Cl(-) that enter the cell during depolarizing steps in control solution inhibit this cationic conductance; thus, the blockade of Cl(-) channels by 9-anthracene carboxylic acid and niflumic acid would remove this inhibition, allowing the cationic current to flow freely.

Effects of ionomycin and thapsigargin on ion currents in oocytes of Bufo arenarum.

In this study, two electrode voltage clamp technique was used to assess the ionic current of oocytes of the South American toad Bufo arenarum and to study the dependence of these currents on the extracellular and intracellular Ca2+ concentrations. Ca2+ chelators, ionomycin -a calcium ionophore- and thapsigargin, a blocker of the Ca2+ pump of the sarcoplasmic reticulum, were used. The main results were the following: Most oocytes showed a voltage activated rectifying conductance. Ionomycin (1 microM) increased inward and outward currents in control solution. The effect of ionomycin was blocked partially at negative potentials and was blocked completely at positive potentials in absence of extracellular Ca2+. When the oocytes were treated with thapsigargin (2 microM) or BAPTA-am, a membrane-permeant intracellular chelator in control solution (10 microM), ionomycin did not increased either inward nor outward currents. The conclusion of our experiments is that there are two sources of Ca2+ for activation of the current induced by ionomycin, the cytoplasmic stores and the extracellular space. We believe ionomycin directly translocates Ca2+ from the SER into the cytoplasm but not from the extracellular medium. Ca2+ entry probably occurs through store-operated-Ca-channels.

[Changes in the left ventricular function in hemodialyzed patients. Role of Doppler echocardiography]. / Modifiche della funzione ventricolare sinistra in pazienti emodializzati. Ruolo dell'ecocardiografia Doppler.

The aim of this study was to provide a further contribution to the study on the alterations of left ventricular diastolic function induced by dialysis, using simple indexes of diastolic function obtained with Doppler. The study is conduced in 15 patients with renal failure aged between 22 and 51 years old by means of echocardiography M-2D a pulsed Doppler analysis of the left ventricular refilling flow, evaluated before and after dialysis. By the results is risen up that the dLA has had a significant reduction (p = 0.032), the dSLV have undergone a reduction that is not being significant, while the dDLV has had a significant reduction (p = 0.029), shortening fraction is improved even if in a not significant manner. Also the Doppler indexes has had a behaviour homogeneous in the group of studied patients. Early ventricular refilling is reduced, as showed by the reduction of E, consequence of the reduction preload, while the diastolic late refilling has showed a little increment, expressed by the increase af the peak A. The variations of these indexes, even if not statistically significant, express an alteration of pattern diastolic Doppler caused by both the reduction of preload and the alteration of ventricular relaxation. Besides this alteration, to our notice, is not to consider expression of myocardial compromise in this group studied patients. It would be however useful enlargement of the study to greater number of patients with follow-up for better comprehension of this cardiopathy and makes a more individual treatment of these patients.

[The role of Doppler echocardiography in assessing left ventricular diastolic function. Case histories]. / Ruolo dell'ecocardiografia Doppler nella valutazione della funzione diastolica ventricolare sinistra. Contributo casistico.

The aim of this study was to provide a further contribution to evaluate the alterations induced by age on a number of simple Doppler indexes of left ventricular diastolic function. A population of 48 healthy subjects aged between 15 and 78 years old was examined using pulsed Doppler analysis of the left ventricular refilling flow. Linear regression analysis revealed a significant inverse correlation between age and peak speed during rapid refilling (r = -0.80); between age and the ratio between peak speed during rapid refilling and peak during atrial systole (r = -0.92); between age and deceleration time of peak E wave speed, although on the contrary the peak speed of diastolic refilling flow during the atrial systole (r = 0.81) increased significantly with age. Variance analysis showed that indexes of left ventricular diastolic function and age continued on the contrary to be significant n the population as a whole and in both sexes. From these findings it is clear that in the different age groups (15-29, 30-49, 50-65, and over 65) the peak speed of rapid refilling flow was significantly lower in over-65-year-olds than in elderly, middle-aged and young subjects (55 +/- 0.8, 60 +/- 0.5, 65 +/- 0.7 and 75 +/- 0.6 respectively; p < 0.001). The ratio between the peak speed of rapid refilling and that during the atrial systole was lower in over-65-year-olds compared to elderly subjects, middle-aged subjects or the youngest age group (0.94 +/- 0.09, 1.05 +/- 0.13, 1.96 +/- 0.21 and 2.68 +/- 0.50 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)