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Biomedical subjects

M François

Publications and source records attributed to M François.

At least 19 recordsLinked to original sources
PubMed2002

Electromagnetic-field distribution measurements in the soft x-ray range: full characterization of a soft x-ray laser beam.

We report direct measurement of the electromagnetic-field spatial distribution in a neonlike Ar capillary discharge-driven soft x-ray laser beam. The wave front was fully characterized in a single shot using a Shack-Hartmann diffractive optics sensor. The wave front was observed to be dependent on the discharge pressure and capillary length, as a result of beam refraction variations in the capillary plasma. The results predict approximately 70% of the laser beam energy can be focused into an area 4 times the size of the diffraction-limited spot, reaching intensities of approximately 4 x 10(13) W/cm(2).

Journal Article↗
PubMed2001

Anhydrous lead(II) heptanoate.

The title compound, catena-poly[[(heptanoato-O,O')lead(II)]-micro-heptanoato-O,O':O:O'], [Pb(C(7)H(13)O(2))(2)], is a metallic soap which can be used as a corrosion inhibitor since it forms a passive film at the Pb surface. Its structure is characterized by two-dimensional layers parallel to the bc plane. The layers are packed through van der Waals interactions along the a direction and form blocks parallel to (001). The 6s(2) lone pair of electrons on Pb(II) is stereochemically active in this compound, which leads to a hemidirected octahedral geometry for the O-environment around the Pb atoms.

Journal Article↗
PubMed2001

[Acute external mastoiditis in children: report of a series of 48 cases].

DESIGN: To determine the impact of the emergence of penicillin-resistant strains of pneumococci on the frequency of acute mastoiditis in children, and to assess the importance of laboratory and imaging studies in the treatment of acute mastoiditis. METHOD: Retrospective review of the medical records of children with postauricular swelling and otoscopic signs of acute otitis media from January 1993 through December 2000. RESULTS: Forty-eight children aged three months to 14 years (median 17 months) were identified. The number of cases was almost the same from one year to another. All children had bacteriological examinations. The mastoid pus and the otorrhea was sterile in 22 cases. The most frequent pathogen was Streptococcus pneumoniae (17 cases), which was resistant to penicillin in 71% of cases. The initial body temperature, the number of polymorphonuclears and the CRP were not different between the group of 18 children with periostitis, which required medical treatment alone, and the group of 30 children who had a mastoid abscess which required surgery. The difference between periostitis and mastoid abscess was seen on clinical examination and CTscan.

Abscess↗
PubMed2001

Congenital nasal pyriform aperture stenosis: diagnosis and management of 20 cases.

The objective of this study was to review the characteristics of congenital nasal pyriform aperture stenosis (CNPAS) in a series of 20 children seen between 1993 and 1996. The diagnosis was made by physical examination and computed tomography scan. A single central maxillary incisor was detected in 12 cases (60%). Three children had morphological abnormalities of the pituitary gland shown on magnetic resonance imaging. One child had an antidiuretic hormone deficiency, and another child had a growth hormone deficiency. Two children had craniosynostoses, 1 of which was Apert's syndrome. All patients underwent operation by a sublabial approach, and 1 was referred for a columellar necrosis after nasal stenting. After surgery, all patients showed improvement, and the nasal stenting was usually removed 1 week after surgery. Follow-up revealed normal breathing. In conclusion, CNPAS was previously considered to be an unusual cause of nasal obstruction in neonates and infants. The number of cases treated recently in our department suggests that this newly recognized entity is more common than expected.

Abnormalities, Multiple↗
PubMed2001

[Tympanostomy tube otorrhea: microbiological epidemiology, pathogen susceptibility to local antibiotics and bactericidal power of the rifamycin-olfloxacin combination].

OBJECTIVE: We studied the microbiological epidemiology of tympanostomy tube otorrhea, rifamycin and ofloxacin sensitivity of pathogens isolated from these otorrheas, and the bactericidal power of the rifamycine-ofloxacin combination. MATERIAL AND METHODS: A prospective study was conducted in 1997 with cultures of otorrhea aspirates, in vitro study of pathogen resistance to rifamycin and ofloxacin, bacteriocidal study of the rifamycin-ofloxacin combination. RESULTS: One hundred eight aspirates were obtained from 98 children (mean age 5 years). Ten aspirates were sterile, 32 had more than one pathogen. The more frequent pathogens were Pseudomonas aeruginosa (Pa) (n=35), Staphylococcus aureus (Sa) (n=27), Haemophilus influenae (Hi) (n=12) and Streptococcus pneumoniae (Sp) (n=9). All Hi, all Sp, 86.3% of the Sa (MIC(90) 0.25 mg/l) and none of the Pa were rifamycin sensitive. All Hi, 97.7% of the Pa (MIC(90) 0.5 mg/l), 73,1% of the Sa (MIC(90) 0.24 mg/l) and none of the Sp were ofloxacin sensitive. The rifamycin-ofloxacin combination led to a 4 log CFU/ml decrease in 6 hours for Sp, and in 24 hours for Pa, Hi and Sa. CONCLUSION: The rifamycin-ofloxacin combination is bactericidal for bacteria causing tympanostomy tube otorrhea. Otic drops with this combination should be considered as the first line treatment for such otorrhea.

Anti-Bacterial Agents↗
PubMed2000

MR imaging features of acute bilateral renal cortical necrosis.

Bilateral renal cortical necrosis (BRCN) is an uncommon cause of acute renal failure. Kidney biopsy, arteriography, and contrast-enhanced computed tomography (CT) are usually used to diagnose BRCN. However, these methods can have potentially serious side effects. We report two cases in which magnetic resonance imaging (MRI) evidenced characteristic features of BRCN, which were confirmed by histological findings and arteriography and correlated with clinical evolution. In the first case report, the diagnosis of a massive and complete cortical necrosis variety was suggested on MRI that showed a thin rim of low signal intensity along border of kidneys. It was confirmed on kidney biopsy, and the renal function did not recover. The second case is an incomplete form with cortical patchy areas of low signal intensity. In these two patients, MRI helped to establish an early diagnosis of BRCN with characteristic representative findings, without the potential nephrotoxic effects of iodinated contrast that has to be used in CT and arteriography. Kidney biopsy, besides the risks of complications, provides only a parceled analysis of the renal tissue and therefore does not allow any conclusion as to the extension of cortical necrosis. MRI may be of great help for the diagnosis and follow-up of acute renal cortical necrosis.

Adult↗
PubMed2000

[What is the role of tonsillectomy in children?].

Tonsillectomy is mandatory in the case of chronic airway obstruction associated with tonsillar hypertrophy and in the case of a unilateral enlarged tonsil which may be malignant. Tonsillectomy may be indicated in recurrent tonsillitis. More rarely, tonsillectomy is performed in children for tonsil bleeding or chronic tonsillitis. Allergy and bleeding disorders are not a contraindication for tonsillectomy.

Airway Obstruction↗
PubMed2000

Induction of necrosis in human neutrophils by Shigella flexneri requires type III secretion, IpaB and IpaC invasins, and actin polymerization.

Infection by Shigella flexneri is characterized by infiltration of neutrophils in the intestinal mucosa and by a strong inflammatory reaction. Although neutrophils are constitutively programmed to die by apoptosis, we show that isolated human neutrophils undergo necrosis 2 h after infection with virulent S. flexneri strain M90T but not with the virulence plasmid-cured strain BS176. This was demonstrated by the release of azurophil granule proteins concomitant with the release of lactate dehydrogenase (LDH), disruption of the plasma membrane, and absence of DNA fragmentation. Mutants with the mxiD1 gene, coding for an essential component of the secretion type III machinery, or the genes coding for IpaB or IpaC invasins deleted were not cytotoxic. Neutrophil necrosis occurred independently of the bacterial ability to leave phagosomes, and it involved actin polymerization, as the addition of cytochalasin D after phagocytosis of Shigella inhibited the release of LDH. In conclusion, Shigella kills neutrophils by necrosis, a process characterized by the release of tissue-injurious granular proteins. This probably contributes to disruption of the epithelial barrier, leading to the dysentery observed in shigellosis and allowing Shigella to enter its host cells.

Actins↗
PubMed2000

[Direct foreign body footplate trauma: 3 cases].

3 cases of direct foreign body footplate trauma are described in children. A surgical exploration was decided on history, cochleovestibular signs and/or CT abnormalities. Hearing improved in all cases after surgery.

Adolescent↗
PubMed1999

Transnasal endoscopic repair of congenital defects of the skull base in children.

OBJECTIVE: To examine imaging findings and methods of endoscopic treatment of congenital skull base defects in children. DESIGN: Retrospective study and case series. SETTING: Academic tertiary care center. PATIENTS: Four patients (aged 12 and 14 months and 8 and 13 years) were included from 1995 to 1997. Three presented with a nasal glioma, which was recurrent in 1 case. The fourth patient presented with bacterial meningitis due to a spontaneous cerebrospinal fluid leak. Computed tomography and magnetic resonance imaging were used to locate the defect of the skull base. INTERVENTION: Transnasal endoscopic resection of the glioma or the meningocele, with immediate repair of the skull base defects using free mucosal flaps and/or pediculized mucosal flaps and/or conchal cartilage together with fibrin glue and nasal packing during a 3-week period. RESULTS: None of the 4 patients has experienced recurrent cerebrospinal fluid leaks or postoperative meningitis. CONCLUSIONS: The transnasal endoscopic repair of congenital meningoceles is a reliable technique in select pediatric patients. Computed tomography and magnetic resonance imaging provide information that can be used to help the surgical procedure.

Adolescent↗
PubMed1999

Crystallographic and chemical composition of otoconia in the salamander Pleurodeles waltl.

The aim of the present study was to define the morphology and the crystallographic and chemical composition of otoconia in different regions of the inner ear in Pleurodeles waltl (urodele amphibian). The inner ear of adults was microdissected and otoconia were analyzed by scanning electron microscopy (SEM), X-ray diffraction, energy dispersive X-ray (EDX) and transmission electron microscopy. Two types of crystals were detected by SEM. Otoconia had different shapes depending on their location in the membranous labyrinth. One type had a cylindrical body with a triplanar smooth facet at each end, the other ones had either a prismatic shape with flat sides and end faces or a fusiform shape with rounded body and pointed end. The forms corresponded to those previously identified by other authors. These two types of otoconia had different X-ray diffraction patterns. The cylindrical otoconia were calcitic and located in the utricle, the other ones were aragonitic and located in the saccule, lagena and endolymphatic sac. An analysis by EDX indicated that both types of otoconia contained about 95% calcium with trace quantities of sodium, magnesium, phosphorus, sulfur, chlorine and potassium. Trace amounts of strontium was only found in the aragonitic otoconia.

Animals↗
PubMed1999

Appearance and evolution of calcitic and aragonitic otoconia during Pleurodeles waltl development.

The aim of this study is to determine the stages of appearance, morphology, crystallographic structure and chemical composition of otoconia during the inner ear development of an urodele amphibian, Pleurodeles waltl. The first otoconia are detected in the otocyst. Near hatching, calcitic otoconia are polyhedral in the saccule and cylindrical in the utricle. During the following stages, the saccular otoconia agglomerate and constitute a polyhedral calcitic otolith. At larval stage 44, aragonitic fusiform otoconia appear on the otolithic surface. At stage 52, X-ray diffraction analysis shows calcite and aragonite patterns. In adults, all the saccular otoconia are aragonitic. In contrast, the utricular otoconia do not show any modification up to adulthood. In the endolymphatic sac, otoconia appear at stage 45 and in the lagena at stage 49. They remain aragonitic up to adulthood. Energy dispersive X-ray spectroscopy (EDXS) elemental analysis of the otoconia reveals a high quantity of calcium with trace quantities of sodium, magnesium, phosphorus, sulfur, chlorine and potassium. However, magnesium and sulfur have a lower concentration in lagenar aragonitic otoconia than in utricular and saccular calcitic ones. As in adults, trace amounts of strontium are only found in aragonitic otoconia.

Animals↗