PubMed Health⌕ Search

Biomedical subjects

R Antolini

Publications and source records attributed to R Antolini.

45 records · Page 3Linked to original sources
PubMed1984

Electrical properties of ionic channels formed by Helix pomatia hemocyanin in planar lipid bilayers.

Helix pomatia hemocyanin forms ion-conducting channels in planar lipid bilayer membranes when added at mg/ml concentration. These channels have several original features. They fluctuate between one conducting and some poorly conducting states and fluctuations can be grouped in bursts. Different channels can have widely different conductance amplitudes. Both channel conductance and burst lifetime are dependent on the applied voltage. Fluctuations within a burst show a complex kinetic behaviour which has been explained developing a multistate model. The model calls for one single open state and six different closed states. Transitions are allowed only between one of the closed states and the open one and obey first order kinetics. This model is able to fit all our experimental curves obtained in single channel experiments.

Animals↗
PubMed1984

Real-time beat-to-beat measurement of conduction intervals during cardiac electrophysiological studies.

The conduction times through different myocardial structures have been measured in real-time during clinical intracardiac investigations by means of a low-cost microprocessor-based system. Two endocavitary electrograms, a surface ECG and a pacemaker stimulus are analysed to detect the stimulus as well as atrial, His and ventricular waves and to measure, beat to beat, the time intervals between them. Measurements have been made in the course of 40 clinical studies, randomly chosen from about 500, and including different conditions such as sinus rhythm, acute drug tests and programmed atrial pacing. Our results show that the real-time measurement of the conduction intervals is feasible and may offer several advantages: it allows immediate data analysis which enables the investigator to better make decisions during the study; it reduces the time and effort required to perform and analyse the study; and it increases the quantity and quality of information gained on the cardiac status of the patient.

Adolescent↗
PubMed1982

The dependence of the conductance of the hemocyanin channel on applied potential and ionic concentration with mono- and divalent cations.

Incorporation of Megatura crenulata hemocyanin into phosphatidylcholine black lipid membranes results in the formation of ion channels. Channel properties depend on many factors, three of which are examined in this work: type and concentration of electrolyte and applied voltage. Eight cations at different concentrations have been used. Instantaneous conductance of the channel is a saturating function of both applied voltage and ionic strength of the bathing solution with monovalent cations, but only of ionic strength with divalent cations. Steady-state voltage-conductance relations are nonlinear for both signs but show slight saturation with ionic strength. Relaxation towards the steady state can be fitted by two exponentials with different time constants. All experimental data are fitted postulating the existence of a mechanism of voltage gating of the channel, and of discrete negative charge near its mouth. Specific and nonspecific binding of cations is required.

Cations, Divalent↗
PubMed1981

Ion transport through hemocyanin channels in oxidized cholesterol artificial bilayer membranes.

Incorporation of molluscan hemocyanins, obtained either from the blood of Megatura crenulata or Paludina vivipara, into oxidized-cholesterol black lipid films results in the formation of ionic channels. Channel conductance depends on the type of electrolyte present, ranging in our experiments from about 20 to 500 pS. It rises in a non-linear way as the salt concentration is increased, showing a saturation effect. An observed pH dependence of channel conductance suggests that there is a negative fixed charge associated with the pore. We discuss a model based on a simplified form of the Gouy-Chapman theory of the electrified double layer to explain the experimental results.

Animals↗
PubMedDate not supplied

Second-harmonic generation sensitivity to transmembrane potential in normal and tumor cells.

Second-harmonic generation (SHG) is emerging as a powerful tool for the optical measurement of transmembrane potential in live cells with high sensitivity and temporal resolution. Using a patch clamp, we characterize the sensitivity of the SHG signal to transmembrane potential for the RH 237 dye in various normal and tumor cell types. SHG sensitivity shows a significant dependence on the type of cell, ranging from 10 to 17% per 100 mV. Furthermore, in the samples studied, tumor cell lines display a higher sensitivity compared to normal cells. In particular, the SHG sensitivity increases in the cell line Balb/c3T3 by the transformation induced with SV40 infection of the cells. We also demonstrate that fluorescent labeling of the membrane with RH 237 at the concentration used for SHG measurements does not induce any measurable alteration in the electrophysiological properties of the cells investigated. Therefore, SHG is suitable for the investigation of outstanding questions in electrophysiology and neurobiology.

Animals↗