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Biomedical subjects

J P Lefevre

Publications and source records attributed to J P Lefevre.

At least 19 recordsLinked to original sources
PubMed2001

Synthesis and photophysical and cation-binding properties of mono- and tetranaphthylcalix[4]arenes as highly sensitive and selective fluorescent sensors for sodium.

The syntheses and properties of two calixarene-based fluorescent molecular sensors are reported. These comprise tert-butylcalix[4]arene either with one appended fluorophore and three ester groups (Calix-AMN1). or with four appended fluorophores (Calix-AMN4). The fluorophore is 6-acyl-2-methoxynaphthalene (AMN), which contains an electron-donating substituent (methoxy group) conjugated to an electron-withdrawing substituent (carbonyl group); this allows photoinduced charge transfer (PCT) to occur upon excitation. The investigated fluoroionophores thus belong to the family of PCT fluorescent molecular sensors. In addition to the expected red shifts of the absorption and emission spectra upon cation binding, a drastic enhancement of the fluorescence quantum yield-in an "off- on" fashion comparable to that seen in photoinduced electron transfer (PET) molecular sensors-was observed. For Calix-AMN1. it increases from 10(-3) for the free ligand to 0.68 for the complex with Ca2+. This exceptional behaviour can be interpreted in terms of the relative locations of the npi* and pipi* levels, which depend on the charge density of the bound cation. For Calix-AMN4. in addition to the photophysical effects observed for Calix-AMN1, interactions between the chromophores by complexation with some cations have been found in the ground state (hypochromic effect) and in the excited state (excimer formation). Steady-state fluorescence anisotropy measurements for the system Na+ is included in Calix-AMN4, show a depolarization effect due to energy transfer (homotransfer) between the fluorophores. Regarding the complexing properties, a high selectivity for Na+ over K+, Li+, Ca2+ and Mg2+ was observed in ethanol and ethanol-water mixtures. The selectivity (Na+/other cations) expressed as the ratio of the stability constants was found to be more than 400.

Journal Article↗
PubMed1998

Evidence for the expression of urokinase-type plasminogen activator by human venous endothelial cells in vivo.

Endothelial cells (ECs) in culture synthesize and secrete urokinase-type plasminogen activator (u-PA), but the normal vascular endothelium is believed to synthesize only tissue plasminogen activator (t-PA), which is thought to be responsible for intravascular fibrinolysis. More recently, animal studies have shown that the biological role of u-PA in fibrinolysis has been underestimated, prompting a re-examination of its synthesis by the endothelium. In this study, we investigated whether u-PA was synthesized by non-atherosclerotic endothelial cells in vivo by testing ECs dislodged by venipuncture from 12 normal volunteers and 17 patients admitted for plasmapheresis. The ECs were isolated with an anti-endothelial monoclonal antibody coupled to immunomagnetic beads and characterized by morphology and by labelling for vWF, CD31, and UEA-1 binding. U-PA antigen was found in 50% of the ECs from the normal subjects and in 60% of those from patients. U-PA enzymatic activity on zymograms was detected in 50% of the normal samples and 60% of the patient samples, with the latter being more frequently and more strongly positive. U-PA mRNA was found in all the normal and patient samples tested. The results indicate that u-PA is synthesized by the venous endothelium in vivo but that its expression is highly variable.

Adult↗
PubMed1996

[Comparative study of the performance and ergonomics of nebulizers in cystic fibrosis].

This study had, as its aim, to test twelve nebulizers (6 jet, 6 ultrasonic) which are used in the treatment of cystic fibrosis. Devices were connected to a respirator in order to mimic the ventilation of a child and of an adult suffering from cystis fibrosis. Three medications: tobramycine, colistine and amiloride were nebulised. The volume of the recommended solution varied between 1.5 and 13 ml according to the manufacturer. During a session of ten minutes the ultrasonic nebulizer delivered an inhaled volume which was significantly greater than the jet (2.72 +/- 0.98 ml vs 1.22 +/- 0.59 ml, p < 0.0001) for the three drugs. Regarding granulometry, the fraction of particles between 0.5 and 5 microns, was higher with ultrasonic than with pneumatic nebulizer for tobramycine (67.1 +/- 10.7 vs 55.5 +/- 11.5%, p < 0.001) and amiloride (66.4 +/- 9.2% vs 58.1 +/- 15%, p < 0.05%). The variation of concentration due to nebulisation were independent of the type of apparatus but influenced by the drug since concentration was increased for tobramycine (+10.5 +/- 18.6%) and amiloride (+13.4 +/- 8/9%). In summary the effective fraction resulting from the inhalable fraction, from granulometry and from changes in concentration was significantly greater for ultrasonic than for jet nebrulizer (17.3 +/- 6.7% vs 9.7 +/- 9.6%, p < 0.001). This study underlines the great variability of the performance of aerosols generators and therefore the need for an accurate evaluation of nebulizer performances in order to prescribe the best nebulizer/drug association in clinical practice.

Administration, Inhalation↗
PubMed1986

[Prognosis of treated temporal arteritis. Retrospective study of 87 cases].

Eighty-seven patients (mean age 73 years) with histologically proven Horton's disease were followed up in 5 different specialized hospital units from 1970 to 1984. Except for one patient treated exclusively with antimalarials, all were under corticosteroids. The mean initial dose of prednisone or equivalent was 0.7 mg/kg/day and the mean maintenance dose, 10 mg/day. Steroids could be discontinued in 21 cases after 36 months on average; the other patients could not be weaned, even though 4 of them had been on steroids for more than 10 years. Side-effects were noted in 43 cases. Twenty-four patients died, mostly of cardiovascular diseases. Survival rates were 89 +/- 6.35% at 1 year, 60.2 +/- 8.7% at 5 years and 48 +/- 11.3% at 10 years. In the long run, mortality in our series proved to be exactly the same as in the general population. Nineteen patients had ocular manifestations of giant cell arteritis always from the onset, except for a fall in visual acuity; 26 relapses were observed in 18 patients, either during reduction of steroid dosage (21 cases) or after withdrawal (5 cases). In 2 cases histology showed typical lesions of giant cell arteritis after 41 and 50 months respectively under corticosteroid therapy.

Aged↗
PubMed1986

[Effects of the artificial pancreas on peripheral nerve function in the diabetic].

Twenty-one diabetic subjects were studied; all manifested fasting hyperglycemia and elevated Hb A1C. Motor conduction velocity of the median, ulnar and peroneal nerves; F wave of the peroneal nerve; sensory conduction velocity and sensory potential amplitude of the median and ulnar nerves and H reflex were determinated immediately before and after two days of strict glucose control with an artificial endocrine pancreas. A significant and acute improvement of some electrophysiological parameters led us to presume that repair of structural lesions would be unlikely. Only a metabolic disturbance, due to hyperglycemia, can be rapidly corrected.

Adolescent↗
PubMed1985

[Visuoverbal disconnection (optical aphasia) for objects, pictures, colors and faces with abstractive alexia].

The case is reported of a patient who, after a left occipital infarction, presented a deficit in naming visually presented objects with neither aphasia, nor perturbation in the perceptive and associative processing of visual informations. This visuo-verbal disconnection was accompanied by disturbance of the semantic function when this was explored via the visual channel. In addition the patient showed an alexia which could be described as an abstraction defect. Finally, the patient showed a deficit in naming colors and faces, without evidence for agnosia. This observation argues in favor of maintaining a distinction between visual associative agnosia and optic aphasia. It also demonstrates that the naming deficit implies a deficit in extracting semantic values from visual informations such as objects or graphic symbols.

Aged↗
PubMed1985

[The blink reflex and the diagnosis of multiple sclerosis. Clinical correlations in 66 patients].

The blink reflex obtained from 66 patients with multiple sclerosis (MS) shows 73% pathologic responses with MS considered as definite, 50% with MS considered as probable and only 18% with possible MS. These findings are of great diagnostical help, particularly in the absence of clinical evidence of involvement of the brain-stem. Among 8 electrological syndromes of alteration of the blink reflex, those due to large lesions of the brain-stem are often associated with definite MS, but small alterations of the blink reflex are more valuable for multifocal characterisation of the illness.

Blinking↗
PubMed1985

[Protein profile and immunoelectrophoresis of cerebrospinal fluid in neurology. Results and etiologies apropos of 430 tests].

The study of 430 cerebrospinal fluids resulting from a neurological department showed 67 pathological medical cases according to following tests: intrathecal IgG synthesis and/or restricted heterogeneity with immuno-electrophoresis. We established a biological classification to approach the different etiologies. This classification was used for multiple sclerosis for which various strictly clinical classifications are not always able to diagnose the illness, as we show it for one of them.

Blood Proteins↗