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Biomedical subjects

F Renault

Publications and source records attributed to F Renault.

At least 19 recordsLinked to original sources
PubMed1999

Identification of residues essential for human paraoxonase (PON1) arylesterase/organophosphatase activities.

Human serum paraoxonase (PON1) is a calcium-dependent organophosphatase. To identify residues essential for PON1 activity, we adopted complementary approaches based on chemical modification and site-directed mutagenesis. To detect 45Ca2+ binding to native and chemically modified PON1, we performed nondenaturating gel electrophoresis. The environment of calcium-binding sites was probed using the Ca2+ analogue, terbium. Tb3+ binds to calcium-binding sites as shown by displacement of 45Ca2+ by Tb3+. Binding of Tb3+ is accompanied by a complete loss of enzyme activity. PON1 chemical modification with the Trp-selective reagent, N-bromosuccinimide, and the Asp/Glu-selective, dicyclohexylcarbodiimide, established that Trp and Asp/Glu residues are components of the PON1 active center and calcium-binding sites. Additional evidence for the presence of a Trp residue in the PON1 calcium-binding sites was a characteristic fluorescence emission at 545 nm from the PON1-Tb3+ complex and abolishment of that fluorescence upon modification by N-bromosuccinimide. The importance of aromatic/hydrophobic character of the residue 280 was demonstrated by site-directed mutagenesis: the W280F mutant was fully active while the W280A and W280L mutants had markedly reduced activity. Twelve amino acids among conserved His and Asp/Glu residues were found essential for PON1 arylesterase and organophosphatase activities: H114, H133, H154, H242, H284, D53, D168, D182, D268, D278, E52, and E194. Finally, the cysteines constituting the PON1 disulfide bond (C41 and C352) were essential, but the glycan chains linked to Asn 252 and 323 were not essential for PON1 secretion and activity.

Amino Acids↗
PubMed1999

Neuropathy in two cobalamin-deficient breast-fed infants of vegetarian mothers.

We describe the electrophysiological findings in 2 infants with deficient cobalamin intake. After normal development, psychomotor regression appeared after the 6th month, leading to severe hypotonia and apathy before the 12th month. Electrodiagnostic evaluation showed sensory neuropathy in both cases, associated with motor neuropathy in 1 case. Thus, in an acquired floppy infant syndrome, electrophysiological signs of peripheral neuropathy contributed to the diagnosis of a curable metabolic disorder.

Action Potentials↗
PubMed1998

Purification, molecular characterization and catalytic properties of a Pseudomonas fluorescens enzyme having cholinesterase-like activity.

An enzyme with a cholinesterase (ChE) activity, produced by Pseudomonas fluorescens, was purified to homogeneity in a three-step procedure. Analysis by non-denaturing and SDS-PAGE, and by isoelectric focusing, indicated that the enzyme was a monomer of 43 kDa, with a pI of 6.1. The N-terminal sequence, AEPLKAVGAGEGQLDIVAWPGYIEA, showed some similarities with proteins of the ChE family and a strong similarity with a protein from Escherichia coli with unknown structure and function. Cholinesterase activity at pH 7.0 and 25 degreesC was maximum with propionylthiocholine as substrate (kcat,app=670 min-1), followed by acetylthiocholine, and significantly lower with butyrylthiocholine. Catalytic specificity (kcat/Km) was the same for propionylthiocholine and acetylthiocholine, but was two orders of magnitude lower for butyrylthiocholine. Kinetics of thiocholine ester hydrolysis showed inhibition by excess substrate which was ascribed to binding of a second substrate molecule, leading to non-productive ternary complex (Km=35 microM, KSS=0.49 mM with propionylthiocholine). There was low or no reactivity with organophosphates and carbamates. The enzyme inhibited by echothiophate (kII=0.44x102 M-1 min-1) was not reactivated by pralidoxime methiodide. However, the P. fluorescens enzyme had affinity for procainamide and decamethonium, two reversible ChE inhibitors used as affinity chromatography ligand and eluant, respectively. Although similarity of the N-terminal amino acid sequence of the enzyme with an internal sequence of ChEs is weak, its catalytic activity towards thiocholine esters, and its affinity for positively charged ligands supports the contention that this enzyme may belong to the ChE family. However, we cannot rule out that the enzyme belongs to another structural family of proteins having cholinesterase-like properties. The reaction of the enzyme with organophosphates suggests that it is a serine esterase, and currently this enzyme may be termed as having a cholinesterase-like activity.

Amino Acid Sequence↗
PubMed1997

Combined pressure/heat-induced inactivation of butyrylcholinesterase.

The combined effects of pressure and temperature on the activity of butyrylcholinesterase (BuChE) were investigated in the pressure range from 10(-3) to 5 kbar and temperature range from -10 degrees C to 70 degrees C. Inactivation of the enzyme showed a complex dependence on pressure and temperature. Under moderate pressures (1-3 kbar) at temperatures 40-65 degrees C BuChE was resistant to heat inactivation; under other conditions of pressure and temperature, the action of both parameters was synergistic and caused inactivation. Results allowed to construct a pressure-temperature kinetic phase diagram for the enzyme inactivation. The elliptic diagram for the irreversible transition active-->inactive BuChE as a function of both pressure and temperature has a positive angular coefficient. This indicates that pressure acts as a stabilizer of BuChE against heat denaturation.

Butyrylcholinesterase↗
PubMed1996

[Contribution of the electromyogram in the diagnosis of infantile spinal muscular atrophy in the neonatal period].

BACKGROUND: The acute form of Werdnig-Hoffman disease, infantile spinal muscular atrophy type I (SMA I), is characterized by severe paralytic hypotonia with neurogenic electromyographic (EMG) pattern and specific histologic features. PATIENTS: Four cases of very severe SMA I suffering from generalized muscle weakness at birth were included in the study. RESULTS: The neurogenic EMG pattern was observed at the first exam performed between D2 and D46. The muscular biopsy performed between D18 and D45 showed only a mild decrease of the muscle fiber size without grouping of fiber types. CONCLUSION: In those forms of SMA I with a neonatal clinical onset, the diagnosis is assessed by clinical and EMG findings while early muscular biopsy can be misleading. EMG is the relevant diagnostic test which confirms the anterior horn cell disease and can justify the DNA study.

Biopsy↗
PubMed1996

[Acute basal ganglia necrosis with favorable course during Mycoplasma encepahlitis].

BACKGROUND: Acute bilateral striatal necrosis complicating the course of a post-infectious encephalitis is rare. CASE REPORT: A previously healthy 5-year-old boy presented with an atypical pneumonia; he rapidly developed, encephalitis revealed by a generalized status epilepticus. After transient improvement, he became confused and mutic, with dystonic postures of his limbs. Painful stimulation resulted in prolonged facial grimacing and doleful cry. CT scan and MRI showed abnormal signals in the whole basal ganglia, typical of bilateral striatal necrosis. Serologic tests for Mycoplasma pneumoniae were positive. The child recovered almost completely. CONCLUSION: A parainfectious process is probably responsible for the transient bilateral striatal necrosis seen in this patient who had Mycoplasma pneumoniae infection several days before the onset of neurologic symptoms. MRI seemed more reliable than CT-scan for the diagnosis of this condition.

Acute Disease↗
PubMed1996

Maturation of the electroretinogram in children: stability of the amplitude ratio a/b.

We report the method and results of mesopic electroretinogram (ERG) recording by corneal electrode in 75 children aged from 0 to 15 years. This method gives an overall evaluation of the electrical activity of the retina in a rapid and acceptable manner, in the awake state and without sedation. The a- and b-waves were present at birth. The amplitude of these waves increased considerably throughout the period studied. The decrease in latencies was statistically significant only for the b-wave between birth and 6 months. The presence of oscillatory potentials increased with age. The amplitude ratio a/b remained constant at about 0.25 in all age groups. This a/b ratio thus constitutes, under the recording conditions described, a criterion of normality that is independent of age.

Adolescent↗
PubMed1995

Pressure-induced molten globule state of cholinesterase.

The denaturing effect of pressure on the structure of human butyrylcholinesterase was examined by gel electrophoresis under pressure and by 8-anilino-1-naphthalene sulfonate (ANS) binding. It was found that the fluorescence intensity of bound ANS is increased by pressure between 0.5 and 1.5 kbar and that the hydrodynamic volume of the enzyme swells when pressures around 1.5 kbar are applied. These findings indicate that pressure denaturation of butyrylcholinesterase is a multi-step process and that the observed transient pressure-denatured states have characteristics of molten globules.

Anilino Naphthalenesulfonates↗
PubMed1995

Raman spectroscopic study of conjugates of butyrylcholinesterase with organophosphates.

Raman spectra of human butyrylcholinesterase (BuChE; E.C. 3.1.1.8) were analyzed in the native state and after conjugation with organophosphates (soman, DFP and paraoxon). The secondary structure of the native BuChE in Tris-HCl buffer (pH 7.5), determined from analysis of the amide I polypeptide vibration band, indicates 47% alpha-helices, 26% beta-sheets, 16% turns and 12% undefined structure. We obtained the same values for paraoxon-phosphorylated BuChE, but 39% helical structure, 31% beta-sheets, 17% turns and 13% undefined structure for 'aged' DFP-BuChE conjugates and 36% helical structure, 34% beta-sheets, 20% turns and 10% undefined structure for 'aged' soman-BuChE conjugates. The approximately 10% decrease of alpha-helical structure observed upon phosphorylation by DFP and phosphonylation by soman, probably corresponds to the 'aging' process, which does not take place in the case of paraoxon. Considerable differences have been observed between native, paraoxon inhibited and 'aged' BuChE in aromatic ring vibrations, suggesting that the dealkylation of organophosphate conjugates modifies the environment or the interactions of aromatic amino-acid residues. In the aliphatic side chains an increase of the number of gauche configurations has been observed in 'aged' DFP-BuChE and soman-BuChE.

Butyrylcholinesterase↗
PubMed1995

Segmental myoclonus in a child with spinal cord tumour.

Segmental spinal myoclonus (SSM) involving a child's lower limb revealed the presence of a spinal cord tumour from T8 to T12. The clinical and electrophysiological features of SSM-during the child's development were studied. The presence of this disorder at two months of age did not disturb the development of walking, but did lead to orthopaedic complications. Four electromyographic recordings performed between 23 months and 7 years 10 months of age revealed the topographical extension of the SSM, its passage to rhythmicity, variable frequency and change in the sequence of activation of the muscles. These electroclinical features enable discussion of the pathophysiology of SSM by reference to neonatal motor automatisms and spinal generators.

Child↗
PubMed1994

Neurophysiological follow-up in two children with Creutzfeldt-Jakob disease after human growth hormone treatment.

A serial neurophysiological study has been performed of 2 children during the clinical course of Creutzfeldt-Jakob disease after human growth hormone (hGH) treatment. Evolution of the EEG pattern was typical: slow waves, periodic sharp wave complexes, then extinction. VEP components were moderately altered. BAERs performed in only 1 child were normal. The blink reflex (BR) showed an early alteration of the R1 component. The ERG exhibited early and profound anomalies. Pathological changes were obvious at the first recording, at the beginning of the second month after clinical onset: increase in peak latencies, morphological changes and important reduction of b wave amplitude (a/b amplitude ratio > or = 0.70; normal range 0.27-0.41). The ERG was completely absent a few months later. These results are compared with the similar retinopathy described in CJD- or scrapie-infected rodents. In the 2 children, pathological changes in ERG and in BR were obvious several months before the development of the typical EEG pattern. Therefore, early ERG and BR recording can be helpful in the diagnosis of CJD, especially in this ataxic form following hGH treatment.

Blinking↗
PubMed1994

An outbreak of Ochrobactrum anthropi bacteraemia in five organ transplant patients.

Nosocomial bacteraemia caused by Ochrobactrum anthropi occurred over a 1-month period in five organ transplant recipients, four of whom were in the same renal and pancreatic transplant unit. Bacteraemia occurred with cyclosporin A, azathioprine and steroids, and with a rabbit anti-thymocyte globulin (RATG) during the induction phase. RATG appeared to be the only common factor among the five cases. Over the period described, 71.4% of all patients receiving RATG developed O. anthropi bacteraemia. Three patients presented with fever and chills during or shortly after RATG infusion. Analysis of residues of the infusion, and the used vials of RATG, showed the presence of O. anthropi in concentrations of between 20 and 1000 cfu ml-1 in 5.3% of samples. Unused vials were found to be heavily contaminated with either O. anthropi or Microbacterium spp. in 23.5% of samples. All positive vials were of one particular lot number suggesting a malfunction in the manufacturing process. Many parenteral drugs such as the RATG used here do not contain preservatives and, although aseptically prepared, will not withstand thermal sterilization. Bacterial contamination of these small volume medications is not always easily detectable by conventional methods. This outbreak highlights the need for accurate quality control testing to detect small inocula that may occur during or after the manufacturing process.

Adult↗
PubMed1993

Muscle complications of malnutrition in children: a clinical and electromyographic study.

The authors report the clinical and electromyographic (EMG) findings in a series of 13 children with a pseudomyopathic motor deficit in the context of malnutrition (Body Mass Index < or = 3rd percentile) caused by primary protein-calorie deficiency or secondary to chronic disease. The infants (nine cases) manifested a regression or stagnation of motor abilities, with hypotonia and amyotrophy; older children and adolescents (four cases) presented clear amyotrophy with a deficit in muscle strength consisting primarily of proximal muscular weakness. Detection and stimulation-detection EMG demonstrated myogenic signs in at least two muscles in all patients. Myogenic signs were dominant in all proximal muscles. Latencies were normal in all patients. Motor nerve conduction velocities were slowed in three infants and in one adolescent. A temporal dispersion of motor responses was observed in 11 proximal muscles. The muscle biopsy, performed in five cases, revealed an inequality in the calibre of fibres, with atrophy dominating in type II fibres. The authors emphasize the value of EMG in disclosing the myopathic process, thereby contributing to the etiological diagnosis of motor difficulties in children suffering from malnutrition or a chronic disease.

Adolescent↗
PubMed1992

[Facial, lingual and pharyngeal electromyography in children: a method to study sucking and swallowing disorders and their pathophysiology].

The authors describe an electromyogaphic protocol developed with the aim of evaluating the sucking-swallowing function and of studying the pathophysiology of its disturbances in the newborn and in infants. This protocol consists of associating several techniques. Some of them are traditional: EMG of the facial muscles and nerves and blink reflex, while others are original: EMG of the tongue and hypoglossal nerve, EMG of the velum palatinum, and a dynamic study using a baby bottle, of the sucking and swallowing reflex for a liquid meal. For each technique, practical procedures are described together with normal results observed between birth and 3 years of age. The authors report on abnormalities observed in pathological conditions and discuss their significance in major nosological contexts. They emphasize the value of this EMG protocol in assessing the sucking-swallowing reflex, in revealing anatomo-functional disturbances in the brainstem and in tackling the pathophysiological aspects of aspiration pneumopathies, feeding difficulties and bucco-facial malformations.

Child, Preschool↗
PubMed1992

[Recurrent bronchopneumopathies in the infant due to swallowing dyspraxia. Two cases].

In two infants with recurrent lower respiratory tract infections starting within a few weeks of birth, dynamic electromyographic studies of sucking and swallowing evidenced a disorder of lingual and pharyngeal activities responsible for the episodes of aspiration. The central location of the anomaly was demonstrated by the absence of peripheral neuromuscular anomalies and by the presence of impaired blinking reflexes and brain stem potential anomalies. These neurofunctional anomalies improved over time and magnetic resonance imaging failed to disclose and structural anomalies of the central nervous system. The occurrence of the swallowing disorder as an isolated manifestation and its long duration, with follow-ups of 23 months and 4 years, are two unique features in these cases. Neurophysiologic investigations are essential for documenting the neurologic etiology of the swallowing disorders, demonstrating their location above or within the medulla oblongata, and differentiating functional and organic anomalies.

Deglutition Disorders↗