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Biomedical subjects

P Valat

Publications and source records attributed to P Valat.

9 recordsLinked to original sources
PubMed2002

Infected mediastinitis secondary to perforation of superior vena cava by a central venous catheter.

We describe the first case of infected mediastinitis associated with central venous catheter insertion. The rare occurrence of this complication may be explained by the fact that it results from central venous catheter-related bloodstream infection and catheter perforation of superior vena cava. The symptoms of this complication (chest pain, dyspnoea) are not specific. Diagnosis should be confirmed by chest x-ray and computerized tomography which show hydromediastinum and pleural effusion. Removal and subsequent culture of the catheter tip will confirm infection. Appropriate antibiotic therapy, guided by sensitivities of the cultured organisms, should be commenced. Any pleural effusion should be drained by thoracocentesis, and the pleural fluid cultured. In case of fever, bacteraemia or shock, a thoracotomy to drain mediastinal and pleural effusions may be considered.

Catheterization, Central Venous↗
PubMed2001

A new photochromic 8pi-system based on an azaheptatriene-tetrahydroazepinoisoquinoline electrocyclization.

A new photochromic family of tetrahydroazepinoisoquinolines (THAI) 4a-i has been prepared. It undergoes light-induced ring opening from spiro compounds 4 to betaines 3 that decolorize in a very fast cyclizing reaction. Depending on substitution of the precursors 1 and 6, the photochromic styryltetrahydroindolizines (THI) 5k-q are formed in a periselective way. The conformation and configuration of the new photochromic THAI 4 and THI 5 were investigated by NMR and the structure of both compounds was proven by X-ray analysis. The photochromic properties were studied by laser flash photolysis, which afforded the lifetime of the colored form 3 and 3' in the micro- or nanosecond range.

Journal Article↗
PubMed1998

[Left ventricular diastolic function: physiology, physiopathology, evaluation, therapy, consequences of anesthesia].

With the exception of cardiac surgery, the acute disturbance of the left ventricular diastole occurs mainly in the elderly. Today it represents 30 to 40% of congestive cardiac failures, however with a lower mortality than for acute systolic disturbances. Generally indicated are relaxation anomalies, proto-mesodiastolic mechanism and problems with compliance, an indicator of the pressure/volume diastolic relationship. Invasive techniques remain the standard method. Doppler echocardiography is becoming increasingly important for the assessment of diastolic function. In most cardiopathies, relaxation anomalies occur early, whereas compliance disturbances are mainly associated with advanced cardiac diseases. During anaesthesia, adverse events (auricular fibrillation, hypovolaemia) may worsen a fragile situation. Anaesthetic agents, in particular volatile agents, act on the ventricular diastole. Long-term therapy of diastolic anomalies includes agents amending left ventricular hypertrophy. Emergency therapy has not yet been systematised.

Aged↗
PubMed1985

Ligand binding processes in hemoglobin. Chemical reactivity of iron studied by XANES spectroscopy.

K-absorption edge of coordinated ions exhibits a fine structure (through the use of XANES, or x-ray absorption near edge structures) that reflects the electronic repartition and the chemical reactivity of these ions. Comparative analysis of iron K-absorption-edge shape for hemoglobin derivatives with different ligand affinity suggests strongly that in hemoglobin, iron-forms with high and low affinity are highly improbable.

Adult↗
PubMed1983

Study of the Hansenula anomala yeast flavocytochrome-b2-cytochrome-c complex 2. Localization of the main association area.

The reversible association of the Zn2+-substituted Hansenula anomala cytochrome c dimer (Thomas et al., preceding paper in this issue) to flavocytochrome b2 in oxidized or lactate-reduced state has been investigated by fluorimetry. The same method has been used for the determination of Zn-cytochrome c complexing to defined proteolytic fragments of flavocytochrome b2, either heme-b2-containing monomers or a flavin-linked tetramer. All these fragments but the isolated cytochrome b2 core showed binding stoichiometries, Kd values and ionic strength dependences quite similar to those found for native flavocytochrome b2. These data allowed localization of the single high-affinity binding site of cytochrome c on a particular globule in the dehydrogenase domain of the flavocytochrome b2 protomers. Quenching of the Zn-porphyrin c fluorescence in the various complexes occurred with only minor changes of the fluorescence lifetime and did not show any direct relationship to the presence or the redox state of the heme b2 group.

Ascomycota↗
PubMed1980

Study of haem structure of photo-deligated haemoglobin by picosecond resonance Raman spectra.

It is well known that the oxygen affinity of haemoglobin depends on the number of combined oxygen molecules. This cooperative effect is considered to arise from a reversible protein transition between two forms which differ in tertiary and quaternary structure. However, the various steps of the structural changes concerning the protein and the haem have not been identified. Using time-resolved spectroscopy coupled to flash photolysis, we have attempted to elucidate the influence of protein on the relaxation processes of haem in haemoglobin. We now report our first results obtained in a picosecond time-resolved resonance Raman study of haemoglobin.

Carboxyhemoglobin↗