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Biomedical subjects

G Atlan

Publications and source records attributed to G Atlan.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

cAMP-dependent modulation of L-type calcium currents in mouse diaphragmatic cells.

The regulation of calcium channels by cAMP-dependent phosphorylation was investigated in the diaphragm muscle. Experiments were performed on dissociated costal diaphragmatic cells from 16- to 17-day-old fetal mice. The ionic current through calcium channels was measured using the whole cell clamp technique with barium as the charge carrier. A depolarizing pulse delivered from a holding potential of -80 mV elicited a low-threshold dihydropyridine (DHP)-insensitive T-type current and a high-threshold DHP-sensitive L-type current. Agents that either increase intracellular cAMP levels (forskolin, 10(-4) M, and dibutyryladenosine 3'-5' cyclic monophosphate, 10(-4) M) or inhibit cAMP degradation (theophylline, 10(-4) M) produced relative increases in L-type current amplitude of 24.4 +/- 13.8%, 13.4 +/- 4.6%, and 15.9 +/- 2.8% (p < 0.05), respectively. Current intensity increased after application of the beta-adrenergic agonist isoproterenol (10(-5) M, 16.5 +/- 3.6%, P < 0.005). None of these agents affected the T-type current. These results suggest that L-type calcium channel activities of the diaphragm muscle are regulated by cAMP-dependent phosphorylation.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMedDate not supplied

[Study of ventilatory mechanics - its application to artificial ventilation (author's transl)].

Study of ventilatory mechanics implies collection of input variables (stresses estimated by pressures) and output variables (strains), from which the parameters (compliance, resistance, etc.) of a model reproducing the functioning system can be computed. From this point of view, patients under artificial ventilation show a twofold difficulty: the one is the collection of variables, very difficult in consideration of the patients' precarious state, the other the type of the model: the first order linear model, used for lack of better solution, can be criticized, on the one hand by severe pulmonary changes in these patients, and by the special mode of applying constraints during artificial ventilation on the other. All these facts explain the methodologic and theoretical difficulties encountered in ventilatory mechanics analysis in resuscitation, which actually leads to the expression of one parameter as representative of the pulmonary parenchymal elasticity: the static compliance, and to the determination of the balancing point of the system: the functional residual capacity.

Airway Resistance↗
PubMedDate not supplied

Correlation between lung structure and respiratory function in hamsters with experimental emphysema.

The correlation between lung structure and respiratory function was studied in normal hamsters and hamsters with elastase-induced emphysema. Four physiological parameters related to the elasticity of the respiratory system were determined from the quasi-static deflation pressure-volume curve: the shape constant (K) of the mono-exponential model fitted to the curve, the inflated volume (VI) taken as the volume change from a tracheal pressure of 0 to 30 cmH2O, the total respiratory compliance (C), determined near the relaxation volume and the normalized compliance (C/VI). The lung structure was morphologically described by the mean alveolar linear intercept (Lm) and the internal surface area (ISA). The correlations between these indices showed that 1) the four physiological parameters correlate better with Lm than with ISA, and 2) a simple index such as the normalized compliance allows to predict the severity of emphysema satisfactorily (r = 0.85; p less than 10(-6)).

Animals↗
PubMedDate not supplied

[Effects of histamine on the pressure-volume curve of the respiratory system in the guinea pig].

Intravenous infusion of histamine has been shown to constrict smooth muscle of alveolar ducts. In this study, we have assessed the effects of a prolonged infusion of histamine to obtain a steady state response on quasistatic pressure-volume curves (P-V curves) together with the changes in dynamic compliance (Cdyn) and conductance (G) of the respiratory system. Increasing doses of histamine were given in order to obtain the dose-response characteristics of the changes in Cdyn, G and P-V curves. In nine anesthetized guinea-pigs under mechanical ventilation, administration of histamine resulted in a fall in Cdyn and G with a decrease of 50% of initial value approximately for 150 ng X kg-1 X s-1 of histamine. Modifications of the P-V curves were characterized by a decrease in the maximal volume, and an increase in the hysteresis of the P-V loop due to the downward displacement of the inflation limb. With infusion of histamine, there was a large decrease of quasi-static compliance which appeared to account for most of the decrease in dynamic compliance. Such changes in P-V curves can be related both to a closure of alveolar ducts and to an alteration of lung distensibility. Comparison of the dose-response curves for the different parameters indicated that Cdyn and G reflect, at least in part, events occurring in the periphery of the lung.

Animals↗
PubMedDate not supplied

[Plethysmographic measurement of lung volume in chronic obstructive pulmonary disease. Influence of the panting pattern].

In 9 healthy subjects and 22 patients with chronic obstructive disease, we computed total lung capacity (TLC) using an integrated flow pressure-corrected body plethysmograph. During panting manoeuvre, TLC derived from oesophageal pressure (TLCes) was compared to TLC derived from mouth pressure (TLCm). In healthy subjects, TLCm was identical to TLCes. Patients with obstructive disease exhibited different behaviours according to experimental conditions: a) in free frequency panting with mouth occlusion close to functional residual capacity (FRC) (9 patients), TLCm appeared to be significantly higher than TLCes (mean difference: 0.25 1; p less than 0.05); b) in panting with both low (less than 1 Hz) and high (2 Hz) frequencies and mouth occlusion close to FRC (7 patients), TLCm appeared to be significantly higher than TLCes only at a high frequency (p less than 0.05); c) in panting with both low and high frequencies and mouth occlusion close to TLC (6 patients), no significant difference was observed between TLCm and TLCes. These results suggest that in patients with chronic obstructive disease plethysmographic lung volume measurements are subject to error, due to the influence of extrathoracic airways. During occlusion at FRC, panting frequency was found to influence the results obtained, the error being minimized with low frequencies. In contrast, by occluding at TLC, we found that panting frequency was less likely to influence the results. However, potential sources of error still exist: for instance, the influence of abdominal gas or the panting pattern.

Adult↗