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Biomedical subjects

J Clément

Publications and source records attributed to J Clément.

At least 37 records · Page 2Linked to original sources
PubMed1986

[Correlation between the steady state and turnover of gamma-aminobutyric acid during brain maturation in mice].

In 2 inbred strains of mice (C57Bl/6J, DBA/2J) in 15 areas, the in vivo GABA turnover rates are significantly correlated with the GABA steady-state levels in 21 day-old mice. In 3 month-old mice the correlation stands only in some areas, the same ones in the 2 strains: olfactory bulbs, frontal cortex, septum, amygdala, hypothalamus, hippocampus, cerebellum. Moreover, the turnover rates decrease sharply with age.

Aging↗
PubMed1985

Forced oscillation technique: comparison of two devices.

The respiratory impedances in healthy subjects and patients with advanced obstructive lung disease were measured between 2 and 32 Hz, using two forced oscillation techniques: the setup used previously by Grimby et al. (J. Clin. Invest. 47: 1455-1465, 1968) and a modified device in which the pneumotachograph is replaced by a 2-m-long tube and the ratio of pressures at both ends of the tube is determined. The advantages of the latter device are that 1) its impedance and frequency characteristics can be predicted by classical physics, 2) the only requirement for correct measurements are a match of the pressure transducers, and 3) high-pass filters are not needed to suppress the influence of breathing. On the other hand, the device is more sensitive to the turbulences induced by the subject's own breathing. This drawback can be avoided by interposing a piece of tubing between the mouth and proximal pressure recording site.

Airway Resistance↗
PubMed1984

Frequency dependence of pulmonary compliance and resistance in patients with obstructive lung disease.

The frequency dependence of pulmonary compliance and resistance was investigated in 27 patients with obstructive lung disease. Compliance and resistance were determined either by the conventional zero crossing (Cdyn) and isovolume (RL) technique or by a modified Fourier analysis following a smoothing procedure (auto- and cross-correlation function) yielding an effective compliance and resistance, CL and RL. The latter technique was used to calculate CL and RL from the fundamental and third and fourth harmonics present in the flow and transpulmonary pressure signals. Three breathing frequencies were investigated: 0.5, 1, and 2 Hz. Both Cdyn and CL, calculated from the fundamental component, decreased progressively with frequency. However, Cdyn showed less frequency dependence than CL. CL calculated from the harmonics was significantly smaller than CL from the fundamental at the same breathing frequency. RL, as well as RL calculated from the fundamental, tended to increase with frequency. A decline of resistance with frequency became apparent, however, when RL from the fundamental was compared with RL obtained from the corresponding higher order harmonics. These results suggest that the frequency dependence of resistance can be masked by the usual procedure of breathing at several frequencies. Instead the measurements should be performed at a single frequency, for instance spontaneous breathing, by computing resistance from the higher order harmonics present in the breathing signals.

Adolescent↗
PubMed1984

Pulmonary resistance and compliance by auto- and cross-correlation functions of transpulmonary pressure and flow.

A technique is described on how to calculate the pulmonary resistance and compliance from the higher order harmonics present in mouth flow and transpulmonary pressure signals during spontaneous breathing. The estimates of resistance and compliance (or rather reactance) obtained from these harmonics following a conventional Fourier transform are not reliable because of a lack of reproducibility. This is obviated by a preliminary smoothing of the signals by means of auto- and cross-correlation functions. Both the conventional and the modified technique yield identical results for the fundamental component of breathing.

Adolescent↗
PubMed1984

[Demonstration of the correlation of the degree of synthesis and 4-aminobutyric acid levels in the central nervous system; effect of repeated convulsive seizures].

GABA turnover rates have been determined in 15 brain areas in five inbred strains of Mice or sublines (DBA/2J, C57/6J, Swiss Rb1, Swiss Rb2, Swiss Rb3). GABA turnover rates and levels are correlated (2 P less than 0.05). After repeated seizures (twice a day for 15 days), induced by an acoustic stimulus in Swiss Rb1 Mice selected for audiogenic seizures, this correlation is no longer observed.

Acoustic Stimulation↗
PubMed1983

Lymphatic transport of cholesterol from exogenous and biliary origins in nonfasting rats after intraduodenal infusions of triolein.

Labelled thoracic-duct lymph was collected from nonfasting rats with a bile fistula after simultaneous intraduodenal infusions of bile labelled with [1-2 3H] cholesterol and a nutritive mixture containing [4-14C] cholesterol. The gastrointestinal tract, feces, chylomicrons and infranatants were analysed. Both biliary and exogenous cholesterol were absorbed by lymphatic way but the recovery of 3H labelling in total lymph was markedly higher than that of 14C activity. This fact might be due to different rates of cholesterol exchanges from the two origins with the nonlabelled cholesterol present in the enterocytes and further exchanges of the enterocytes cholesterol with plasma cholesterol. Most of radioactivity was detected in chylomicrons. The relative [3H] and [14C] cholesterol specific activities were always low; thus when a little exogenous cholesterol is brought the major part of lymph cholesterol had an endogenous--other than biliary--source.

Animals↗
PubMed1983

Total resistance and reactance in patients with respiratory complaints with and without airways obstruction.

A comparison was made of the frequency dependence of total respiratory resistance, (Rrs), and reactance (Xrs), determined by a forced oscillation technique in 442 healthy subjects and in 126 patients with respiratory complaints, with or without slight airways obstruction. The comparison was performed by means of a discriminant analysis. The latter demonstrated that the Rrs and Xrs data, measured between 8 and 24 Hz, of patients differ from those of healthy subjects primarily by a decrease of Rrs with frequency associated with more negative Xrs (and thus with an increase in resonant frequency). This probably also applies to patients with more advanced airways obstruction. The addition of the FEV1 values to the analysis provides only a small amount of independent information. The forced oscillation technique thus appears to be a sensitive tool to separate healthy subjects (smokers and nonsmokers) from patients with respiratory complaints associated or not with a reduced FEV1.

Airway Obstruction↗
PubMed1982

[Bromazepam against anxiety in psychiatric patients (author's transl)].

In this study involving 30 hospital patients (23 inpatients and 7 out-patients) with neurosis or depressive syndrome, bromazepam 12 mg/24 hours in 2 or 3 divided doses proved effective in controlling anxiety symptoms. The results, as measured by the Hamilton scale, were satisfactory in two-thirds of the cases, notably in neurotic anxiety. Free-floating anxiety and somatic symptoms were relieved. Undesirable reactions consisted of daytime somnolence (5 cases), feeling of dizziness (1 case) and fatigue (1 case).

Adult↗
PubMed1982

Rapidly decreasing forced expiratory volume in one second or vital capacity and development of chronic airflow obstruction.

In a prospective study of 2,406 members of the Belgian Air Force, followed for 3 to 15 yr, 325 demonstrated a yearly decline in FEV1 and/or in vital capacity (VC) that was significantly faster than that expected in healthy nonsmokers. Such rapid declines were met more frequently in heavy smokers and in subjects with a reduced FEV1 or VC. There was no clear-cut association between rapid declines and a history of respiratory diseases. It may be predicted, if the rates of declines do not vary with aging, that about 0.5% of nonsmokers and 4% of heavy smokers in the investigated population will reach disabling airway obstruction (FEV1 of 1.2 L or less) at 65 yr of age. At least 6 to 8 yr of follow-up are required to appreciate with precision the rates of declines in FEV1 or in VC.

Forced Expiratory Volume↗
PubMed1982

Normal values of total respiratory resistance and reactance determined by forced oscillations: influence of smoking.

In 407 healthy male subjects, smokers and nonsmokers, the resistance and reactance of the respiratory system were determined between 4 and 24 Hz, using a forced oscillation technique. The values are significantly correlated with age, weight, height, FEV1, and vital capacity. After standardization of the data for the latter variables, there are no differences between smokers and nonsmokers. The technique thus lacks sensitivity for the detection of the effects of smoking.

Adolescent↗
PubMed1981

Model of elasticity of the human lung.

A model of the elasticity of the human lung has been developed to evaluate the relative importance of the characteristics of the lung parenchyma, of thorax configuration, and of gravity on the vertical gradients of pleural pressure and regional volumes, and on the linear displacements of lung tissue, of various lung volumes. The predictions of the model are compared with available experimental data. It is suggested that the bulk elasticity modulus of the human lung is high with respect to that of canine lungs, that the shearing forces are low ("effective" Poison's ratio of about 0.4-0.45), and that the variations of regional pleural pressures and volumes during deflation are determined primarily by the interaction between lung weight and changes in thorax configuration.

Adult↗
PubMed1980

Influence of flow amplitude on pulmonary resistance determined near zero flow.

Pulmonary resistance, determined near zero flow by means of the isovolume technique, increases with the total amplitude of flow. This variation observed in healthy subjects at two frequencies, and documented also by other investigators, was stimulated in a model study. The main factor responsible for the amplitude dependence of pulmonary or airway resistance appears to be the asymmetrical elastic characteristics of the airways.

Adult↗
PubMed1980

Mechanical properties of lungs and chest wall during spontaneous breathing.

Using a forced oscillation technique, we measured the resistance (Rrs) and reactance (Xrs) of the respiratory system between 2 and 32 Hz at three different lung volumes in 15 healthy subjects and 7 patients with chronic obstructive pulmonary disease. Rrs and Xrs were partitioned, by means of a pressure recording in the esophagus, into the resistance and reactance of lung and airways (L) and the chest wall. The measurements were validated by checking the adequacy of the frequency response of the esophagus, by the lack of difference between thoracic and mouth flow, by an estimation of the error introduced by the shunt impedance of the cheeks, and by comparisons with the values of pulmonary compliance and resistance determined in the same subjects with classical techniques. In both healthy subjects and patients, the chest wall has a low resistance that increases somewhat at low lung volumes and behaves functionally as a two-compartment system, with low capacitance at frequencies exceeding 4 Hz. Rrs varies with lung volume and is markedly frequency dependent in patients; both phenomena are due primarily to corresponding variations of RL. In healthy subjects, at and above functional residual capacity (FRC) level, the lungs behave as a one-compartment system, the reactance of which is mainly determined by the gaseous inertance, at least beyond 2 Hz. In patients and in healthy subjects breathing below FRC, the observed frequency dependence of resistance and the simultaneous increase in resonant frequency can be simulated satisfactorily by Mead's two-compartment model, assuming a large increase in peripheral airways resistance.

Animals↗