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Biomedical subjects

A Fontaine

Publications and source records attributed to A Fontaine.

At least 73 records · Page 4Linked to original sources
PubMed1994

Intermediate states in ligand photodissociation of carboxymyoglobin studies by dispersive X-ray absorption.

The ligand photodissociation of sperm whale carboxymyoglobin (MbCO) at low temperature (15K-100K) under extended illumination has been studied by X-ray Absorption Near Edge Structure (XANES) spectroscopy using the dispersive technique. XANES simulations through the multiple scattering (MS) approach allow one to interpret the spectroscopic data in structural terms, and to investigate the Fe site structure configurations of the states that follow the CO photodissociation as a function of temperature. The Fe site in the photoproduct is unbound, with an overall structure similar to the deoxy-form (Mb) of the protein. The Fe site structure changes from T < 30K(Mb*) to T > 50K (Mb**), revealing the existence of a slower unbound state Mb**. A model is proposed which includes the faster state (Mb*) as a planar porphyrin ring with a displacement of Fe from the heme plane of less than 0.3 A, and the slower state (Mb**) with a domed heme.

Absorptiometry, Photon↗
PubMed1993

OmpC is involved in invasion of epithelial cells by Shigella flexneri.

Osmoregulation of the Shigella flexneri ompC gene and the role of OmpC in Shigella virulence have been investigated. OmpC was highly expressed when bacteria were grown in medium of either low or high osmolarity. This constitutive expression is in contrast with the regulation observed in Escherichia coli, in which the expression of OmpC is repressed at low osmolarity and induced at high osmolarity. In addition, the Shigella ompC gene was barely expressed by a delta ompB (delta ompR and delta envZ) mutant. We described in a previous report that such a mutant was severely impaired in virulence both in vitro and in vivo. Starting from this observation, and in order to assess which gene(s) regulated by ompR and envZ are involved in virulence, we constructed an S. flexneri delta ompC mutant. Three S. flexneri mutants, ompF'-lacZ, delta ompC, and delta ompB, were compared for virulence. The ompF'lacZ mutant behaved like the S. flexneri serotype 5 wild-type strain M90T in all in vitro and in vivo virulence tests. On the contrary, the delta ompB and delta ompC strains were considerably impaired in their virulence phenotypes. The ability of these two mutants to spread from cell to cell and to kill epithelial cells was severely affected. Consequently delta ompC, as previously described for delta ompB, was unable to elicit a positive Sereny test. The delta ompB mutant was restored to virulence by introducing a recombinant multicopy plasmid carrying the cloned E. coli ompC gene, indicating that a functional OmpC protein was necessary and sufficient to restore virulence to this mutant of S. flexneri.

Animals↗
PubMed1993

Carotid endarterectomy without angiography. The reliability of Doppler ultrasonography and duplex scanning in preoperative assessment.

OBJECTIVE: To validate the use of Doppler ultrasonography and duplex scanning as the only means of preoperative assessment in carotid disease. DESIGN: A retrospective study performed between January 1980 and December 1989. PATIENTS: Of 597 carotid endarterectomies carried out by one author, 130 procedures were performed on 118 patients (47 women, 71 men, ranging in age from 49 to 85 years) without preoperative cerebral angiography. Justifications for proceeding without angiography were risk of angiography (27 patients), iodine allergy (8 patients), renal insufficiency (5 patients), technical problems (4 patients) and surgeon's preference (74 patients). INTERVENTIONS: Doppler ultrasonography and duplex scanning were the only means of preoperative assessment on 130 occasions. The studies were done by fully trained radiologists. Until 1982 carotid stenosis was assessed with a continuous wave bidirectional Doppler flowmeter and gray-scale ultrasonography in equivocal cases. Thereafter, a real-time spectrum analyser connected on-line to a Doppler flowmeter was used. Duplex scanning was introduced in 1985. MAIN OUTCOME MEASURES: Surgical observations confirmed the preoperative assessment on 124 occasions (96%). RESULTS: Six patients had occlusion of the internal carotid artery (ICA); five patients had recent thrombosis that had occurred between the noninvasive assessment and the endarterectomy. Revascularization was successful in all. In one patient, the ICA was chronically occluded. In 63 patients, the mean pressure in the ICA stump and the mean gradient across the stenosis, measured intraoperatively, were 40 +/- 3 mm Hg (95% confidence interval: 34 to 48 mm Hg) and 55 +/- 3 mm Hg (95% confidence interval: 46 to 58 mm Hg), respectively, which confirmed the severity of the stenosis. CONCLUSION: The authors conclude that in their institution, carotid endarterectomy based on Doppler ultrasonography and duplex scanning only is reliable and safe.

Aged↗
PubMed1993

[Evaluation of the screening strategy for lead poisoning in 1-to-3-year-old children monitored in maternal-child welfare centers in Paris].

A procedure for screening for lead poisoning was implemented since 1987 in the maternal and child health centers of 6 Paris "arrondissements". It relies on a screening of the children through environmental and clinical information. Our study aimed at evaluating this procedure and at estimating the prevalence of lead poisoning in the children aged 1 to 3 years old attending free maternal and child health centers in Paris. We did a cross-sectional survey of a sample of 512 children. A questionnaire concerning each child's risk factors was answered by the paediatric nurses of the clinics. Potential lead poisoning cases were detected by capillary determining of free erythrocyte protoporphyrins (FEP). Blood lead level (PbB) was measured in children with FEP > or = 350 micrograms/l. The prevalence rate of lead poisoning was estimated at 1.9% +/- 1.7% for a PbB threshold > or = 250 micrograms/l and at 9.6% +/- 3.5% for a PbB threshold > or = 150 micrograms/l. The detection procedure identified 4 children out of 5 with a PbB > or = 250 micrograms/l and 2 children out of 3 with a PbB > or = 150 micrograms/l.

Child, Preschool↗
PubMed1992

X-ray absorption spectroscopy of carbonyl basket handle Fe(II) porphyrins: the distortion of the tetrapyrrolic macrocycle.

The distortion of the tetrapyrrolic macrocycle, the Fe-C-O bond angle and the Fe local electronic structure of carbonyl basket-handle Fe2+ porphyrins as a function of the basket-handle chain length have been studied by X-ray absorption near edge structure (XANES) spectroscopy, both in the solid state and in toluene solution. The Fe-C-O bond angle has been found to be linear in all compounds while the increasing distortion of the macrocycle with shortening of the chain length is indicated by the multiple scattering resonance in the heme plane appearing at 22 eV in the XANES spectrum.

Iron↗
PubMed1992

Stenosis of the renal artery: assessment of slowed systole in the downstream circulation with Doppler sonography.

Slowing and dampening of systole in the arterial network distal to stenosis is a well-known Doppler sign of severe arterial stenosis. To determine whether this sign is present in boys and girls with such stenosis, intrarenal Doppler curves (acceleration index [AI] and resistive index [RI]) were compared with findings on renal arteriograms in 20 boys and girls; the AI was also measured in 10 boys and girls without renal disease. Statistical analysis of AI and RI measurements was performed. Eleven of 32 renal arteries were normal. The normal AI was 4.0-7.0; in arteries with greater than 75% stenosis, the AI was 0.7-1.7. In five arteries studied after angioplasty, the AI had changed from 0.7-1.5 to 4.0-5.6 at the first posttreatment examination (performed 28 hours to 1 week after angioplasty), and it remained normal during the 3-year follow-up period. In kidneys with stenotic arteries, the RIs were lower (0.43-0.54) than in healthy subjects (0.56-0.63). Regression and correlation coefficients of AI and RI measurements were statistically significant, and discrimination between normal arteries and those with greater than 75% stenosis was excellent.

Child↗
PubMed1992

[Causes and modalities of pediatric ambulatory care in ten hospitals in the Ile-de-France region].

BACKGROUND: The increasing shortage of financial resources requires optimal use of hospital care by patients. However, the studies carried out to date in France have been limited to patients who are hospitalized, and have not included those seen as out-patients. POPULATION AND METHODS: All patients seen as out-patients in 10 hospitals in the Paris district (3 pediatric hospitals and 7 pediatric departments located in hospitals for adults and children), during the week of 19-26 April 1989, were given a questionnaire on the age, sex, nationality, socio-cultural and economic features of the family, history of earlier medical visits or admissions, the existence of pediatrician or practitioner, and the means and time taken to get to the hospital. Medical diagnosis was established for each patient following the WHO International Classification of Diseases (9th edition). RESULTS: 2,365 out of 2,675 questionnaires were usable. The main features were: 50% of patients were less than 3 years old, 55% were of French origin; 78% belonged to families with relatively low socio-economic status. Both parents had professional activities in 49% of families, 7% of mothers did not speak or write French. The ratio of patients aged less than 3 years admitted to the emergency ward was higher than the average. The most frequent diseases presented by these patients were respiratory (23%), infectious (14%), gastro-intestinal (10%) and neurological (7%); 14% of the patients were seen for symptoms that could not be assigned to a specific disease. 39% of patients were seen in out-patient clinics and 61% in emergency wards. 40% were sent by a health professional to out-patient clinics and only 25% to emergency wards. CONCLUSIONS: Despite the fact that this study is subject to particular conditions, i.e., relative frequency of infectious diseases due to seasonal causes, it suggests that the hospital is becoming the primary source of health care with an increasing percentage of patients seen in "emergency", even though this emergency is often more apparent than real. Health care networks should be established.

Ambulatory Care↗