No evidence for calcium electrogenic exchanger in frog semicircular canal hair cells.

We investigated the possibility that, in hair cells mechanically isolated from frog semicircular canals, Ca2+ extrusion occurs via a Na+ : Ca2+ (cardiac type) or a Na+ : Ca2+,K+ (retinal type) exchanger. Cells concurrently imaged during whole-cell patch-clamp recordings using the Ca2+ sensitive fluorescent dye Oregon Green 488 BAPTA-1 (100 micro m) showed no voltage dependence of Ca2+ clearance dynamics following a Ca2+ load through voltage-gated Ca2+ channels. Reverse exchange was probed in hair cells dialyzed with a Ca2+- and K+-free solution, containing a Na+ concentration that saturates the exchanger, after zeroing the contribution to the whole-cell current from Ca2+ and K+ conductances. In these conditions, no reverse exchange current was detected upon switching from a Ca2+-free external solution to a solution containing concentrations of Ca2+ alone, or Ca2+ + K+ that saturated the exchanger. By contrast, the same experimental protocol elicited peak exchange currents exceeding 100 pA in gecko rod photoreceptors, used as positive controls. In both cell types, we also probed the forward mode of the exchanger by rapidly increasing the intracellular Ca2+ concentration using flash photolysis of two novel caged Ca2+ complexes, calcium 2,2'-([1-(2-nitrophenyl)ethane-1,2-diyl]bis(oxy))bis(acetate) and calcium 2,2'-([1-(4,5-dimethoxy-2-nitrophenyl)ethane-1,2-diyl]bis(oxy)) bis(acetate), in the presence of internal K+ and external Na+. No currents were evoked by UV-triggered Ca2+ jumps in hair cells, whereas exchanger conformational currents up to 400 pA, followed by saturating forward exchange currents up to 40 pA, were recorded in rod photoreceptors subjected to the same experimental conditions. We conclude that no functional electrogenic exchanger is present in this hair cell population, which leaves the abundant plasma membrane Ca2+-ATPases as the primary contributors to Ca2+ extrusion.

[Chiari's network: persistence of the embryonic remnants of the valve of the sinus venosus in the right atrium. Echocardiographic and clinical analysis in a group of subjects]. / La rete di Chiari: persistenza dei residui embrionali delle valvole del seno venoso in atrio destro. Analisi ecocardiografica e clinica in un gruppo di soggetti.

As echocardiography is being used more often, its value and accuracy are becoming more fully appreciated, especially for identifying normal anatomic variants and their possible erroneous interpretation as pathologic states. We report the echocardiographic and clinical findings observed in sixteen subjects examined at our Cardiological Service in the period from January 1987 to April 1988. Mean age of these subjects is 40 +/- 27.04. Of these subjects, six are affected by other cardiac pathologies and ten are unaffected (Group A). First, we describe in all the patients M-mode and two dimensional patterns of persistence of the right venous sinus valve known as the Chiari network. This structure can present as a highly mobile, highly reflective echo target, which can be seen especially by means of the bi-dimensional technique. The Chiari network could be seen with all four standard approaches. The two most diagnostic views are, in our experience, the short axis parasternal view (62.5%), and the subcostal view (87.5%). In a great number of subjects (75%) the Chiari network could be seen in at least two approaches. Second, in Group A we make a clinical examination. Nine subjects in this group show the presence of a cardiac systolic murmur with vibratory characters from grade 1/6 to grade 3/6. 50% of the same patients presented supraventricular arrhythmias (particularly, two presented reciprocating paroxysmal supraventricular tachycardia and one paroxysmal atrial fibrillation). The significance of these findings is not clear yet. We, at least, emphasise that the Chiari network could be confused with other curvilinear highly mobile, echo targets such as right-heart vegetations, flail tricuspid leaflets, a small right-heart thrombus or even a pedunculated right heart tumor (especially right atrial myxoma). On the contrary, this structure might be considered a "normal anatomic variant".

[Partial rupture of biliary cyst of large dimensions. Clinical description and ultrasonic diagnosis]. / Rottura parziale di cisti biliare di grosse dimensioni. Descrizione clinica e diagnostica ecotomografica.

The clinical case of an elderly patient hospitalised for acute abdomen type syndrome is reported. Investigation, particularly echography, pointed to a diagnosis of partially ruptured giant biliary cyst of the liver. The clinical pictures and the unusual features of this rare condition are discussed. Differential diagnosis with respect to echinococcosis and polycystic liver is examined.

A theophylline dosage regimen which reduces round-the-clock variations in plasma concentrations resulting from diurnal pharmacokinetic variation.

Slower drug absorption at night can leave residual drug from an evening dose of a sustained-release product remaining to be absorbed at the time of the next morning's dose, thereby giving higher plasma concentrations of the drug during the day than the night. When a capsule product releasing theophylline over 12 h after a morning dose was given repetitively at 8 a.m. and 8 p.m. for 4 days, daytime plasma concentrations from 4 h to 8 h after the dose were about 40% greater than corresponding night-time concentrations, and the mean steady-state concentration during the night-time interval was only 81% of that during the daytime interval. Altering the regimen to one capsule at 12 noon and one at 10 p.m. eliminated all significant differences between a.m. and corresponding p.m. plasma concentrations of theophylline and between the mean steady-state concentrations for each of the interdose intervals within a day.