PubMed Health⌕ Search

Biomedical subjects

A Loiseau

Publications and source records attributed to A Loiseau.

71 records · Page 4Linked to original sources
PubMed1989

Exercise tolerance in chronic obstructive pulmonary disease: importance of active and passive components of the ventilatory system.

We investigated which components of ventilatory function are related to exercise tolerance in chronic obstructive pulmonary disease (COPD) patients. Physical characteristics, usual lung function, timing and neuromuscular components of ventilation were measured in 113 outpatients in whom FEV1/VC was less than 75% of the predicted value and exercise was limited by breathlessness. These variables were used to predict the maximum work load during progressive bicycle exercise. The prediction was obtained using a stepwise procedure in men and women separately. Among the variables selected, age, body weight, FEV1/VC, PImax, and P0.1/VT/TI accounted for 79% of the variability in maximum performance in men. The predictive model was statistically verified and was stable. The mean prediction error was 12 Watts. Among these variables, P0.1/VT/TI, PImax, and FEV1/VC were the main determinants of maximum work load (MWL). These results show that exercise limitation in COPD is related to impairment of both the active (inspiratory muscles) and passive (respiratory impedance) components of the ventilatory system. The same conclusions concerning passive components are proposed for women, despite a smaller population which prevented verification of the prediction.

Adult↗
PubMed1988

T-lymphocytes recovered by bronchoalveolar lavage from normal subjects and patients with sarcoidosis are refractory to proliferative signals.

Granuloma formation in the lung of patients with sarcoidosis is preceded by the accumulation of large numbers of activated T-lymphocytes, which results, at least in part, from the proliferation of T-lymphocytes within the lung. To determine whether the increased proliferation of lung T-lymphocytes in sarcoidosis results from a failure of mechanisms responsible for limiting their proliferation, we have compared the ability of purified T-lymphocytes present in bronchoalveolar lavage fluid and peripheral blood from normal subjects and patients with sarcoidosis to respond to proliferative signals. The mitogen-induced proliferative response of lavage T-lymphocytes from normal subjects and patients with sarcoidosis was similar, but the response of lavage T-lymphocytes was much less than that observed using normal or sarcoid blood T-lymphocytes. The reduced proliferative response of sarcoid lavage T-lymphocytes could not be overcome by addition of accessory cells or exogenous interleukin-2, and it did not result from the presence of suppressor cells. Furthermore, sarcoid lavage lymphocytes are capable of being activated by "mitogenic" signals, as indicated by the ability of phytohemagglutinin to induce expression of the 4F2 surface antigen and stimulate interleukin-2 production. However, the expression of interleukin-2 receptors was reduced on stimulated sarcoid lavage T-lymphocytes compared with that observed on normal blood T-lymphocytes, which may account in part for their reduced proliferative capacity. Because mechanisms that render lavage T-lymphocytes from normal subjects refractory to proliferative signals appear to operate in sarcoidosis as well, these findings suggest that a defect in the inhibition of T-lymphocyte proliferation is unlikely to be an important cause of lymphocyte accumulation in this disorder.

Adult↗
PubMed1987

The effects of halothane on the human beta-adrenergic receptor of lymphocyte membranes.

The effects of halothane on beta-adrenergic receptor antagonist interaction were studied using the membranes of human lymphocytes as a model. Membrane preparations of lymphocytes were obtained from blood samples withdrawn from seven healthy young volunteers. Beta-receptor studies were performed using (-)125I iodocyanopindolol (125ICP) binding. Non-specific binding was determined in the presence of (-)isoproterenol. Beta-receptor density (Bmax) and the dissociation constant (KD) for 125ICP were determined from saturation curves. Beta-receptor affinity for agonists evaluated by the IC50 (the concentration of isoproterenol required to inhibit 50% of specific 125ICP binding) and the dissociation constant (KL) for isoproterenol was established from competition curves. The effect of halothane 1%, in an air oxygen mixture (oxygen fraction: 0.3) administered by tonometry during ligand membrane incubation, on beta-adrenergic receptor, was compared to that of control experiments not exposed to halothane. Halothane produced a moderate but significant decrease of Bmax (-10%) and a significant increase in non-specific binding (+30%), while KD, IC50, and KL were unchanged. The authors conclude that halothane, in vitro, decreases beta-adrenergic receptor density. This effect could be mediated by an alteration of the receptor in the membrane due to action of halothane on the lipid phase of the membrane.

Adult↗
PubMed1985

Servo-controlled air pump for calibration of respiratory measurement systems.

We describe a servo-controlled piston pump driven by a stepping motor. The analogue controller is a single non-linear second-order feedback loop with adjustable speed and acceleration limits. This system, designed to simulate slowly-moving, active and non-linear systems, can be used as a low (0-6.5 litre s-1) flow volume generator in calibration procedures.

Calibration↗
PubMed1985

[Familial sarcoidosis. Apropos of 22 families].

Twenty-two families, the ethnic origins of which were Caucasian (16) or mixed Caribbean (6), each with two or three members suffering from sarcoidosis, were studied. The frequency of familial sarcoidosis when all races are considered is 2.4 p. 100 but it is higher in people born in the Caribbean. Clinically, this form is no different from non-familial cases but there is a tendency, especially in homozygotic twins, for the dates of revelation of the disease to be very close to each other, and for the clinical and radiological features and the evolution to be the same. A higher frequency of pairs of the same sex with equal numbers of parent-sibling and sibling-sibling pairs were observed. There was no predominance of mother-sibling with respect to father-sibling pairs. The HLA system study was too fragmented to draw any conclusion about the mode of transmission of familial sarcoidosis.

Black People↗
PubMed1979

Course of pulmonary hemodynamics in patients with chronic obstructive pulmonary disease.

Eighty-five patients with chronic obstructive pulmonary disease, mainly chronic bronchitis (71 patients), who had arterial hypoxemia and moderate to severe obstruction of the airways underwent at least two right cardiac catheterizations in a clinical steady state, with a delay of three years or more between the first and the last catheterization. The average delay was 60 +/- 19 months (range, 36 to 119 months). Patients were regularly examined (quarterly clinical and functional checkups). The changes in pulmonary hemodynamic data were small. In the group of 53 patients with an initial mean pulmonary arterial pressure of 20 mm Hg or less, this pressure varied from 15.4 +/- 3.1 to 18.3 +/- 6.6 mm Hg (P less than 0.001); in the group of 32 patients with an initial mean pulmonary arterial pressure greater than 20 mm Hg, this pressure varied from 27.7 +/- 6.0 to 31.0 +/- 9.3 mm Hg (P less than 0.05). The mean pulmonary arterial pressure increased by 5 mm Hg or more in only 28 patients. In these patients with hemodynamic "worsening," the final arterial oxygen pressure (PaO2) was lower and the final arterial carbon dioxide tension was higher than in the remaining patients. A significant negative correlation (r = -0.39; P less than 0.001) was observed between changes in PaO2 and mean pulmonary arterial pressure. There was a generally good agreement between the course of pulmonary hemodynamics (mean pulmonary arterial pressure), on the one hand, and the clinical, radiologic (transverse diameter of the heart), and electrocardiographic evolution, on the other hand. In the 33 patients who died, a relatively long survival was observed after the first episode of right-sided heart failure or after ascertaining pulmonary hypertension.

Adult↗
PubMed1978

The relationship of age to pulmonary membrane conductance and capillary blood volume.

The lung transfer components of 70 normal, adult nonsmokers 18 to 78 years of age were measured by the single-breath diffusing capacity of the lung for CO. The membrane conductance and the pulmonary capillary blood volume were estimated by several measurements of the diffusing capacity at increasing alveolar PO2. Diffusing capacity, membrane conductance, and pulmonary capillary blood volume are functions of biometric references (height or alveolar volume) and of age. The observed decrease with age was more evident after 40 years of age for diffusing capacity and membrane conductance. Pulmonary capillary blood volume decreases at a later age. The changes in membrane conductance and pulmonary capillary blood volume with age may be due either to morphologic changes in the alveolar capillary surface or increasing inhomogeneities of distribution or both.

Adolescent↗
PubMedDate not supplied

Pathophysiology of middle ear epithelium: a new role for prostaglandin E2.

INTRODUCTION: Otitis media with effusion is a disease of the middle ear epithelium resulting from a decreased sol layer as well as increased mucus secretion and plasma-derived protein transudation, which causes mucus plugging. Because the epithelium keeps the middle ear cavities fluid-free and air-filled, we investigated its fluid transport capacities, which may be involved in both efficacy of the mucociliary clearance and drying-out of the posterior ear cavities (Yen PT et al: Acta Otolaryngol (Stockh) 113, 1993). We have established the absorptive capacity of middle ear epithelial cells in primary culture (Herman P, et al: Am J Physiol 262, 1992). However, the paucity of cells obtained by enzymatic digestion led us to develop a new model for further investigation of middle ear epithelial cell. METHODS: We established a middle ear cell line (MESV) using simian virus 40 (SV40) infection of middle ear epithelial cells from the Mongolian gerbil. RESULTS: Investigation of the transport processes using the short-circuit current technique showed that MESV cells retain most characteristics of the original middle ear epithelial cells. Transepithelial sodium transport from the apical to the basal side was responsible for the transepithelial lumen-negative potential difference. CONCLUSION: The presence of high concentrations of prostaglandin E2 in the middle ear effusions has been documented. This work investigates the effect of prostaglandin E2 on the rate of transepithelial ion transport of MESV cells. Prostaglandin E2 increased the rate of electrogenic sodium transport by means of increase in the intracellular cyclic adenosine monophosphate (cAMP) content. Such a modulation of sodium transport in the course of otitis media could be responsible for the reduced periciliary sol layer that impairs the mucociliary clearance.

Animals↗
PubMedDate not supplied

Different levels of food restriction have opposite effects on adipocyte cellularity and lipoprotein-lipase activity in obese rats.

The effects of several levels of chronic energy restriction on epididymal and perirenal adipose tissue cellularity and lipoprotein lipase activity, serum glucose and insulin and hepatic enzyme activities were studied in lean Fa/- and genetically obese fafa rats. The restricted rats were compared to rats fed ad libitum 24/24h or 8/24h. Restricting time of feeding was associated with increases in fat cell number in the lean, increases in perirenal adipose tissue fat cell size and serum insulin in the obese and increases in lipoprotein lipase activity in both phenotypes. Mild food restriction (-25%) had similar effects in the obese: perirenal adipose tissue fat cell size and serum insulin levels were even higher but fat cell hyperplasia was reduced. Restriction by 50% normalized lipoprotein lipase activity and markedly reduced fat cell size in the lean; in the obese, lipoprotein lipase activity and insulin levels were similar to or lower than those of the corresponding ad libitum 24/24h group but fat cell hypertrophy was not particularly affected. Restriction by 75% in the obese prevented adipocyte hyperplasia. Furthermore, lipoprotein lipase activity in adipose tissue was normalized, serum insulin and lipids being within normal limits. However, these animals had large adipocytes and were still fat.

Adipose Tissue↗
PubMedDate not supplied

Lung transfer factor for carbon monoxide measured during a slow single breath without breath-holding and during slow exhalation.

We considered whether a slow single breath with neither breath-holding nor carefully controlled flows could provide estimates of lung transfer factor for CO (TLCO) similar to those obtained with the usual standardized single breath technique. This technique requires actual flow rates and volume variations to be taken into account [10], as well as the use of a fast CO analyser and computerized calculations. TLCO values found with this method (TLCOsb) for 5 normal subjects and 29 patients with various respiratory diseases did not differ from those obtained with the standardized test (p less than 0.001). TLCO was also measured during exhalation only, by the use of a single compartment, constant TLCO equation and a computational procedure which provided a mean TLCO value for a given expired volume range (TLCOex). A unique TLCOex was sufficient to account for the whole exhalation in normal subjects and certain patients. In most patients two TLCOex were necessary, one for large lung volume after dead space washout and the other one accounting for the second half of expiration until closing volume. Most TLCOex were larger than TLCOsb calculated during the same slow breath. This over-estimation was found to be correlated (p less than 0.001) with the phase III argon slope. In patients where two TLCOex values were required to describe the exhaled CO course, we found that TLCOex decreased with lung volume. This decrease was also correlated with the argon slope (p less than 0.001). The observed difference between TLCOsb and TLCOex values and the decrease of TLCOex with lung volume probably reflect inhomogeneous ventilation distribution.

Adult↗