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F Leclerc

Publications and source records attributed to F Leclerc.

At least 19 recordsLinked to original sources
PubMed1996

Using SAR and QSAR analysis to model the activity and structure of the quinolone-DNA complex.

A set of 78 quinolone derivatives were used in a structure-activity study to identify structural features correlating with antibacterial activity. Distinct combinations of functional properties were identified for Gram-negative and Gram-positive bacteria. 3-D Quantitative structure-activity relationship (QSAR) studies identified specific hydrophobic, topologic and electronic properties of the molecules for both in vitro and in vivo activities. From these results, a three-dimensional model of a DNA-quinolone complex was built using molecular modeling techniques. It was based on the intercalation of quinolone into the double helix of DNA. We conclude that the intercalation model is consistent with most available data on the structure of the quinolone complex. This predicted structure is stabilized by the binding of magnesium ion with the sp2 oxygens present in quinolone, a phosphate and a purine base of the DNA. Substituents R1 and R7 are predicted to make hydrophobic interactions in the major and minor groove of DNA, respectively. R7 could also form hydrogen bonds with amino groups of guanines and the aspartic acid residue at position 87 in DNA gyrase subunit A.

DNA Topoisomerases, Type II↗
PubMed1995

Salicylate poisoning: two-dimensional J-resolved NMR urinalysis.

Identification of a case of acute salicylate intoxication using 300 MHz 1H NMR spectroscopy of a urine sample is reported. It has been achieved by using a combination of a one-dimensional experiment with water presaturation and a two-dimensional homonuclear J-resolved experiment. By these means, lysine and the three major metabolites of acetylsalicylic acid have been assigned in the crude urine. The results are compared with those obtained at 600 MHz and with classical biochemical methods. The use of this method for routine diagnosis in biological analysis is discussed.

Adolescent↗
PubMed1995

[Vascular tracheal compression presenting as bronchiolitis in infants].

BACKGROUND: Anomalies of the aortic arch and pulmonary arteries may produce compression of the trachea with chronic stridor or wheezing aggravated by crying, feeding and flexion of the neck. CASE REPORTS: Three infants, 3, 5 and 2 months-old, respectively, were admitted suffering from acute bronchiolitis. The first patient had intermittent wheezing for one month; lateral chest X-rays showed an opaque area inserted between the trachea and oesophagus and computed tomography showed pulmonary artery sling with tracheal stenosis which was successfully operated. The second patient displayed pulmonary atelectasia which required bronchoscopy; this technique showed tracheal stenosis which was due to pulmonary artery sling. The third patient had a history of congenital stridor: he required endotracheal intubation; a bronchoscopy performed because persistent pulmonary atelectasia showed tracheal stenosis which was secondary to a double aortic arch. The condition was improved after surgical correction. CONCLUSIONS: A history of stridor and/or wheezing in patients admitted for bronchiolitis must lead to consider the possibility of vascular compression of the trachea and to perform specific investigations.

Aorta, Thoracic↗
PubMed1995

[Modality and causes of 259 deaths in a pediatric intensive care unit].

BACKGROUND: There are few data available from European pediatric intensive care units (PICU) regarding the modes of death and their causes. POPULATION AND METHODS: Two hundred and fifty nine children, not including neonates, died in the PICU over a 7-year period (1987-1993). Data were obtained from a computerized data base and the retrospective review of medical records by two intensivists. Deaths were classified into three groups according to the terminal event: brain death (BD), unsuccessful resuscitation (UR), do-not-resuscitate order and limitation and/or withdrawal of therapy (LWT). RESULTS: BD was the most common mode of death (38%); UR accounted for 34% and LWT for 28% of deaths. There was no significant annual variation in the proportion of BD, UR and LWT. Age and sex were similar in the three groups. The predominant organ system failure involved upon admission was the central nervous system (52%) in the LWT group, and the cardiovascular system (54%) in the UR group. Severe chronic disease (37%) and immunosuppression (19%) were more prevalent in the LWT group than in the BD group. Time from admission to death was longer in the LWT group (median = 119 hours) as compared to the UR group (10 hours) and the BD group (54 hours). Ten percent of the BD patients became organ transplant donors. Sixty-seven per cent of BD patients had medical contraindication for organ donation: parents did not accept organ donation in 61% of potential cases. Thirty deaths (12%) seemed to be avoidable; dehydration from acute infectious gastroenteritis (n = 7) was the most common cause of avoidable death. CONCLUSIONS: The modes of death in our PICU were statistically not different from those seen in two of four North-American PICUs; LWT was less prevalent than in the two other PICUs, but the patient populations were very different (presence of neonates and many cardiovascular surgery patients). Assessment of the severity of illness at admission and of functional outcome in the survivors are mandatory in future studies.

Adolescent↗
PubMed1995

[Effects of hypocaloric diet on respiratory manifestations in Willi-Prader syndrome].

BACKGROUND: Prader-Willi syndrome (PWS) is a multisystem disorder with hyperphagia and obesity. Breathing disorders such as snoring, sleep apnea syndrome, and sleep hypoventilation have also been reported. CASE REPORT: Jonathan was born with the typical features of PWS. He developed exercise dyspnea, cyanosis and nocturnal sweating at the age of 3 years. A few months later, a respiratory failure required his admission to the intensive care unit. His weight was then 48 kg (300% ideal body weight (IBW); physical examination showed polypnea (60 breaths/min), cyanosis, fat deposition on the chest wall. Transcutaneous oxygen saturation was 65%, carbon dioxide tension 81 mmHg (capillary sample). Pulmonary hypertension was found (mean arterial pulmonary pressure = 55 mmHg). Polysomnography detected hypoventilation with persistent hypoxemia increasing during the night and transient dips of oxygen saturation with bradycardia. He was treated with oxygen, mechanical ventilation (facial mask) and a low caloric diet (600 cal/day). Four months later, he weighed 33 kg (200% IBW); the respiratory features had resolved and gazometric values and pulmonary pressure returned to the normal ranges. Polysomnography showed only obstruction apnea and hypopnea without oxygen desaturation. CONCLUSIONS: Patients with PWS may develop respiratory symptoms sufficient by severity to be life threatening. They are related to morbid obesity and are influenced by a hypocaloric diet. Follow-up of patients with this syndrome must include repeated respiratory evaluation.

Child, Preschool↗
PubMed1994

Inhaled nitric oxide for a severe respiratory syncytial virus infection in an infant with bronchopulmonary dysplasia.

OBJECTIVE: To report the first case of ARDS in children treated with nitric oxide (NO) inhalation. METHODS: A 13-months infant presented with BPD and severe hypoxemia related to RSV infection and ARDS. Inhaled NO was delivered in the ventilatory circuit of a continuous flow ventilator (Babylog 8000, Dräger) in a concentration of 20-80 ppm for 7 days. NO and NO2 were continuously monitored (Polyton Draeger). Respiratory mechanics were evaluated by using the method of passive inflation by the ventilator. RESULTS: NO inhalation improved oxygenation (tcSaO2) and reduced respiratory system resistance without affecting arterial pressure. NO2 level remained below 5 ppm, and methaemoglobin level below 1%. The child survived without neurologic sequela. CONCLUSIONS: Two mechanisms to explain oxygenation improvement can be suggested: selective improvement in perfusion of ventilated regions and bronchodilation.

Blood Gas Analysis↗
PubMed1994

A three-dimensional model of the Rev-binding element of HIV-1 derived from analyses of aptamers.

Coordinated variations in the sequence of the Rev-binding element of HIV-1, identified by in vitro genetic selections, have been used as distance and conformational constraints for molecular modelling. Three-dimensional models of the wild-type Rev-binding element and several, evolved RNA ligands (aptamers) have been constructed. These models demonstrate that non-Watson-Crick pairings open the major groove allowing access of an alpha-helical peptide from Rev, and explain why some selected RNA sequences can bind Rev more tightly than others.

Base Composition↗
PubMed1994

[Treatment with intermittent high dosage corticotherapy in chronic interstitial pneumonia in an infant. A case report].

Chronic interstitial pneumonia (PIC) are rare in infants. We report a case of an infant who presented with a chronic interstitial pneumonia following an infection with a respiratory syncytial virus. The diagnosis was confirmed histologically (open lung biopsy). The failure of oral steroid therapy (Prednisolone 2 mg/kg/day) led to the use of boluses of methylprednisone (30 mg/kg/day, daily for three days in three series one month apart). The treatment led to a progressive improvement and thirty months after the last bolus the respiratory examination was normal as was the radiology. The efficacy of bolus steroid therapy observed by other authors should be confirmed in multicentre trials using surgical biopsy to precise the pulmonary lesions.

Administration, Oral↗
PubMed1993

Modelling velocity profiles of rapid movements: a comparative study.

In this paper we compare 23 different models that can be used to describe the asymmetric bell-shaped velocity profiles of rapid-aimed movements. The comparison is performed with the help of an analysis-by-synthesis experiment over a database of 1052 straight lines produced by nine human subjects. For each line and for each model, a set of parameters is extracted that minimizes the error between the original and the reconstructed data. Performance analysis on the basis of the mean-square-error clearly reflects the superiority of the support-bounded lognormal model to globally describe the velocity profile characterizing rapid movements.

Biomechanical Phenomena↗
PubMed1993

Sudden death revealing Chiari type 1 malformation in two children.

We report the first two fatal cases of sudden unprovoked cardiorespiratory arrest in children with previously undiagnosed Arnold-Chiari type 1 malformation. This diagnosis should be considered in children with unexplained cardiorespiratory arrest. The risk of sudden death in Arnold-Chiari type 1 malformation reinforces the indication for early neurosurgical procedure.

Adolescent↗
PubMed1992

Respiratory mechanics in mechanically ventilated newborns: a comparison between passive inflation and occlusion methods.

A passive inflation method was described for measuring total respiratory elastance and resistance during mechanical ventilation in adult patients (Rossi et al., J Appl Physiol 58:1849, 1985). We applied this method to preterm and full-term mechanically ventilated newborn infants and we compared the results with those obtained by the occlusion method. We performed 37 tests in 16 newborn infants (B.W. 880-4,500 g; G.A. 28-42 weeks), between 1 and 45 days of postnatal age, ventilated with a Servo Ventilator 900C, set in controlled-volume mode. Flow was measured through a pneumotachograph inserted between the endotracheal tube (ETT) and the breathing circuit, tidal volume by integration of flow and airway pressure directly at the airway opening. Flow, volume, and pressure were recorded on an X/Y plotter to obtain pressure-volume (P/V), flow-volume (V/V) loops, and pressure-time curves. Occlusion was performed by using the end-inspiratory and the end-expiratory pause buttons of the ventilator. Analysis of P/V and V/V loops provided respiratory system compliance (Crs, infl.), resistance (Rrs, infl.), and "intrinsic positive end-expiratory pressure" (PEEPi, infl.). These values were compared with Crs, occl., Rrs, occl., and PEEPi, occl. measured by the occlusion method. The measurements were well correlated (Crs, infl./Crs, occl.: r = 0.90; Rrs, infl./Rrs, occl.: r = 0.91; PEEPi, infl./PEEPi, occl.: r = 0.91). Rrs, infl./Rrs, occl. and PEEPi, infl./PEEPi, occl. did not differ significantly. However, Crs, occl. was 15% higher than Crs, infl. (P less than 0.01). The passive inflation method is simple to use and well tolerated in preterm and full-term ventilated newborn infants, it provides accurate results, and can be a good alternative to occlusion methods. It requires, however, a constant inflation flow and adaptation to the ventilator.

Airway Resistance↗