Search PubMed⌕ Search

Biomedical subjects

A Tardieu

Publications and source records attributed to A Tardieu.

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

[Short and intermediate-term hemodynamic study at rest and during exercise of cardiac insufficiency treated by captopril].

Administration of 25 mg of captopril to 10 patients with heart failure (NYHA II, III) produces at rest after 60 min bradycardia (-7 per cent, p less than 0.01), hypotension (-8 per cent) and improvement of the preload (-30 per cent, p less than 0.01). This effect is still apparent after two months of treatment where PAP is decreased by 20 per cent (p less than 0.05). A prolonged effect of captopril is present in these 10 patients. The capacity to perform a muscular exercise on an ergometric bicycle is prolonged by 10 per cent (p less than 0.01) on the first day and by 18 per cent (p less than 0.01) after two months of treatment. This improvement seems to be related to improvement of the hemodynamic parameters, especially of preload indices. In 5 patients, lactacidemia, the arterio-venous difference and the extraction coefficient of O2 were studied at rest and during exercise. No significant difference are noted after the treatment with the inhibitors of conversion enzymes.

Adult↗
PubMed1986

Effects of captopril on myocardial perfusion in patients with coronary insufficiency: evaluation by the exercise test and quantitative myocardial tomoscintigraphy using thallium-201.

Nine patients with coronary insufficiency were investigated using an exercise test coupled with quantitative myocardial tomoscintigraphy with thallium-201 before and after 48 hours' treatment with captopril. After captopril treatment, an improvement in ST segment depression was noted during exercise. The quantitative tomoscintigraphy showed a reduction in the ischaemic zone with captopril during exercise. However, in three patients, although there was an overall improvement in myocardial perfusion during exercise, aggravation of wash-out was observed in some regions, reminiscent of a coronary steal effect.

Adult↗
PubMed1985

[Late chronic constrictive pericarditis following aortic valve replacement].

The authors report a case of chronic constrictive pericarditis in a 54 year old patient who had undergone aortic valve replacement 6 years previously. The valve was replaced with a Starr-Edwards prosthesis because of aortic regurgitation due to infective endocarditis. The outcome after pericardectomy was favourable with a 3 year follow-up. This complication of cardiac surgery, of which there are now 45 reported cases, should not be overlooked because it can be cured surgically. The diagnosis is based on phonomechanographic, echocardiographic and, above all, haemodynamic investigations to distinguish the condition from irreversible myocardial dysfunction.

Aortic Valve↗
PubMed1985

[A case of electrically and mechanically stunned myocardium].

The authors report the case of a 72 year old patient with ECG changes of anterior myocardial infarction complicated by left ventricular failure and shock which has a favourable outcome with regression of the pathological Q waves on the 7th day. Radionuclide investigation and coronary angiography showed no myocardial sequellae and the coronary arteries appeared normal. This case, an example of stunned myocardium, confirms that severe myocardial ischaemia, even of short duration, may induce reversible but prolonged metabolic disturbances. The practical implications of this concept are discussed.

Aged↗
PubMed1985

[Outcome of patients with inoperable multivessel coronary disease].

The authors studied the clinical course of 100 patients with two or three vessel coronary artery disease who were unsuitable for surgery because of the poor quality of the distal vascular bed or excessively depressed left ventricular function. The 6 year actuarial survival was 58 per cent; 43 of the 100 patients did not present any serious cardiac events causing death or requiring further admission to hospital, over this follow-up period. The severity of the clinical course in women and the presence of heart failure prior to coronary angiography were considered to be among the most important clinical prognostic factors. On the basis of the haemodynamic survey, the probability of survival or the risk of a further coronary accident appears to depend more on the extent of the left ventricular kinetic abnormalities than on the ejection fraction or the severity of the coronary lesions.

Adult↗
PubMed1984

X-ray analysis of the kinetics of Escherichia coli lipid and membrane structural transitions.

Synchrotron radiation was used to follow the time course of the transitions, induced by temperature jump, in Escherichia coli membranes and their lipid extracts isolated from a fatty acid auxotroph grown with different fatty acids. We measured the relaxation times associated with the phase transitions as well as with the conformational transition of the hydrocarbon chains and observed different behavior as a function of chemical composition. Relaxation times of about 1-2 s were found at a hexagonal to lamellar phase transition and within a lamellar phase whose parameters display important variations with temperature when the conformational transition takes place. On the other hand, no delay was observed for a phase transition where large lipid or water diffusion was not needed. We have shown that phase transitions and conformational transitions are, to a large extent, uncoupled and that the relaxation times corresponding to the latter transition could be related to the size of the ordered domains. In all cases, the order to disorder conformational transition is more rapid than the disorder to order transition. Finally, the relaxation times of the disorder to order transition observed with the membranes and with their lipid extracts were found to be strongly correlated, indicating that the proteins do not play a role in this transition.

Cell Membrane↗
PubMed1984

Spatial reorganization of low-molecular-weight proteins during cold cataract opacification.

Freeze-fracture electron microscopy of calf lens nuclear cytoplasm undergoing a cold cataract opacification shows the formation of domains within the bulk cytoplasm. The size distribution of these domains (from a few tens of nanometers to a few micrometers) is compatible with previous size evaluations obtained from light scattering experiments for the 'large scattering elements' responsible for cold cataract opacification. In addition, these domains appear to be devoid of crystallins of higher molecular weight and enriched in low-molecular-weight species.

Animals↗
PubMed1984

Solution X-ray scattering studies of the yeast phosphofructokinase allosteric transition. Characterization of an ATP-induced conformation distinct in quaternary structure from the R and T states of the enzyme.

The allosteric transition of yeast phosphofructokinase has been studied by solution x-ray scattering. The scattering curves corresponding to the native enzyme (T conformation) were found to be similar to the curves recorded in the presence of saturating concentrations of fructose 6-phosphate (R conformation) or AMP (R or R' conformation). However, the curves obtained in the presence of ATP are clearly different: the radius of gyration increases and the secondary minima and maxima are systematically shifted to lower angles, suggesting a swelling of the enzyme in the presence of ATP. These results give the first direct evidence for the existence of an ATP-induced T' conformation, distinct in quaternary structure from the R and T states of the enzyme oligomer, in agreement with our previous modeling of yeast phosphofructokinase regulation. X-ray scattering data are discussed in relation to the distinct molecular mechanisms of the ATP and fructose 6-phosphate allosteric effects involving, respectively, sequential and concerted conformational changes of the enzyme oligomer.

Allosteric Regulation↗
PubMed1984

Studies on the structure of yeast phosphofructokinase.

In this paper, we describe an efficient procedure for the purification of yeast phosphofructokinase. This procedure eliminates any time delay and enables to obtain an enzyme with minimum proteolytic alterations. The molecular weights of the oligomeric enzyme and of its constitutive subunits were both evaluated by means of several independent methods. However, the accuracy of each measurement was not sufficient to discriminate between an hexameric and an octameric structure of the enzyme oligomer. On the other hand, crosslinking experiments demonstrated the octameric structure of yeast phosphofructokinase. Obviously, some methods of molecular weight determination have led to erroneous results. In particular, our experiments show that the reliability of molecular weight determinations performed by gel filtration of native proteins must be considered with caution.

Cross-Linking Reagents↗
PubMed1983

Self-assembly of brome mosaic virus capsids. Kinetic study using neutron and X-ray solution scattering.

The self-assembly of brome mosaic virus capsid has been studied kinetically by means of X-ray and neutron scattering. It appears to be a very fast process: for the concentrations used (5 to 8 mg/ml) the forward scattering reaches 50% of its maximal value in less than one second. Further, the assembly seems to proceed through intermediate states whose nature is still speculative.

Capsid↗
PubMed1982

Analysis of models of irregular shape by solution X-ray scattering: the case of the 50S ribosomal subunit from E. coli.

Structural models of biological macromolecules can be tested by comparing calculated and experimental solution scattering curves. We have developed an approach for computing scattering shape functions at medium resolution from models proposed on the basis of other techniques such as electron microscopy. We present the results obtained with the 50S ribosomal subunit from Escherichia coli; two models are considered, one proposed by Lake (1976), the other one by Tischendorf et al. (1975). Although the two models are similar in many respects, their scattering shape functions are significantly different. The comparison with the experimental scattering curve allows us to check the scale of the models and, after scaling, to quantitate the agreement between the observed and the calculated curves. Finally, it can provide a starting point for the structural interpretation of the X-ray data.

Journal Article↗
PubMed1980

Chromatin repeat length in somatic hybrids.

In order to study the mechanisms by which a characteristic repeat length is inherited in somatic cells, it was necessary to develop a method for determining repeat length with a precision of 1 to 2 base pairs. Hybrid clones between parental cell lines differing in repeat length by 6 base pairs were isolated. The four independent hybrid clones characterized had repeat lengths intermediate between those of the parental lines; however, it could be demonstrated that these repeat lengths are unique values and do not arise from a double distribution of the parental repeat lengths. It therefore is concluded that repeat length in somatic cells is determined by a common pool of diffusible substances.

Animals↗