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Biomedical subjects

F Lefebvre

Publications and source records attributed to F Lefebvre.

At least 37 records · Page 2Linked to original sources
PubMed1998

Automatic three-dimensional reconstruction and characterization of articular cartilage from high-resolution ultrasound acquisitions.

Three-dimensional (3D) high-resolution ultrasonography has proved to be useful for in vitro assessment of cartilage remodeling due to osteoarthritis. The diagnosis is performed by computation of the mean thickness of the cartilage, which reveals hypertrophy or thinning, and by 3D reconstruction of the data, which provides essential information about the size, extent, and localization of the lesion. In both cases, preliminary segmention of the cartilage is necessary. This article proposes an algorithm for automatic segmentation of the cartilage from 3D ultrasonic acquisitions of the rat patella, which includes the detection of the cartilage surface and the cartilage/bone interface. The method was designed on the assumption of regularity and smoothness of the interfaces. The use of a global threshold was sufficient to separate the patella area from the background. The cartilage/bone interface was detected by selection of regions of interest (ROIs) encompassing the interface, followed by the detection of the interface within these ROIs using the graph theory. The method was applied to 162 samples. The detection accuracy was judged to be very good or good in 99% of the cases for the cartilage surface and in 86% of the cases for the cartilage/bone interface. The mean cartilage thickness value in the central part of the patella obtained from the automatic detection method was compared to that obtained manually. The coefficient of correlation between the two measurements was 0.92. These results show that our method is reliable. Thus, fast processing of a large number of acquisitions and a more complete analysis of the cartilage surface become possible.

Aging↗
PubMed1998

Interest of direct radionuclide cystography in repeated urinary tract infection exploration in childhood.

108 children with repeated urinary tract infection were examined both with direct contrast cystography and radionuclide cystography. There was a good correlation between the two procedures in the majority of the cases (79), but in 21 cases, direct radionuclide cystography alone was positive and for 8 other children, direct contrast cystography showed a low-grade vesico-ureteric reflux even though radionuclide cystography was negative. When comparing the two procedures and taking into consideration the age of the patients we find that radionuclide cystography is more sensitive to detect vesico-ureteric reflux in the younger population (p < 0.02). This advantage is less clear for older children who more often present a low-grade reflux. Low radiation exposure is also a great advantage of radionuclide cystography, but anatomic definition is better with contrast cystography. It seems thus that the two procedures complement rather than rival each other. Their respective interest for evaluation of repeated urinary tract infection in children therefore depends on age, attain-ability of the procedure, and the possibility of a bladder or ureteral abnormality. Quite a few authors consider radionuclide cystography as at least as valid as contrast cystography, and even more sensitive. We have attempted to compare both procedures and to determine their respective role in repeated urinary tract infection exploration.

Adolescent↗
PubMed1998

Nursery Neurobiologic Risk Score and outcome at 18 months.

The aim of this study was to confirm the predictive value of the nursery Neurobiologic Risk Score. Prospectively, 121 infants (mean birthweight 961 +/- 179 g, gestation 27.0 +/- 1.2 weeks) were followed at 18 months. The nursery Neurobiologic Risk Score was correlated to the developmental quotient (r = -0.54). From low (scores 0-4), to moderate (scores 5-7) to high (scores > or = 8) risk groups, respectively, significant differences were found in mean developmental quotient (101 +/- 9 vs 92 +/- 19 vs 76 +/- 24) and in prevalence of developmental quotients < 90 (12 vs 24 vs 71%), of cerebral palsy (4 vs 19 vs 41%), of severe disabilities (0 vs 24 vs 50%) and of any disability (16 vs 30 vs 71%). Sensitivity, specificity, positive and negative predictive values for any disability were 81, 54, 49 and 84% for a score > or = 5 and 56, 87, 71 and 78% for a score > or = 8. The nursery Neurobiologic Risk Score was useful in predicting 18 months outcome of very premature infants.

Developmental Disabilities↗
PubMed1998

Developmental pathways leading to externalizing behaviors in 5 year olds born before 29 weeks of gestation.

Longitudinal data for 62 infants born before 29 weeks of gestation were used to assess the influence of four factors (i.e., neonatal health, family environment, language skill, and nonverbal ability) on the parental report of hyperactive and oppositional behaviors of children at 5 years 9 months. The proposed path analysis model tested the following: (1) whether neonatal health and family environment have a direct influence on language skill and nonverbal ability both measured at 18 months corrected age, (2) the predictive value of language skill and nonverbal ability on oppositional and hyperactive behaviors, and (3) whether the effects of neonatal health and/or family environment on oppositional and hyperactive behaviors can be conceived as mediated by language skill and/or nonverbal ability. The results revealed three main pathways. First, family environment predicted language skill, which, in turn, was negatively associated with children's hyperactivity. Second, neonatal health predicted nonverbal ability, which was positively linked to oppositional behaviors. Third, a direct negative relation between neonatal health and hyperactive outcome was observed. The implications of these substantially different pathways for hyperactive and oppositional behaviors are discussed.

Causality↗
PubMed1998

Automatic detection of the boundary of the calcaneus from ultrasound parametric images using an active contour model; clinical assessment.

This paper presents a computerized method for automated detection of the boundary of the os calcis on in vivo ultrasound parametric images, using an active dynamic contour model. The initial contour, defined without user interaction, is an iso-contour extracted from the textural feature space. The contour is deformed through the action of internal and external forces, until stability is reached. The external forces, which characterize image features, are a combination of gray-level information and second-order textural features arising from local cooccurrence matrices. The broadband ultrasound attenuation (BUA) value is then averaged within the contour obtained. The method was applied to 381 clinical images. The contour was correctly detected in the great majority of the cases. For the short-term reproducibility study, the mean coefficient of variation was equal to 1.81% for BUA values and 4.95% for areas in the detected region. Women with osteoporosis had a lower BUA than age-matched controls (p = 0.0005). In healthy women, the age-related decline was -0.45 dB/MHz/yr. In the group of healthy post-menopausal women, years since menopause, weight and age were significant predictors of BUA. These results are comparable to those obtained when averaging BUA values in a small region of interest.

Adult↗
PubMed1998

Health and developmental outcomes at 18 months in very preterm infants with bronchopulmonary dysplasia.

OBJECTIVE: To determine whether very preterm infants who are oxygen-dependent at 28 days of life but not at 36 weeks' gestational age are at high risk of morbidities at 18 months. POPULATION: A total of 217 infants born in a tertiary care center at 24 to 28 weeks' gestation in 1987 to 1992, classified into three groups: neonatal comparison group, O2 <28 days of life (n = 76); bronchopulmonary dysplasia (BPD)-1, O2 >/=28 days but not at 36 weeks' gestational age (n = 48); and BPD-2, O2 >/=36 weeks (n = 93). OUTCOME MEASURES: Growth, persistent respiratory problems (asthma, tracheostomy, home oxygen therapy), surgery, hospitalizations, and neurodevelopmental impairments. RESULTS: Among the three groups, no differences were found in weight, height, head circumference, or total number of days of rehospitalizations for any causes, or in rate of rehospitalizations to the intensive care unit, persistent respiratory problems, cerebral palsy, or sensory impairment. Children with BPD-2 needed more hernia repairs compared with the other two groups (comparison group: 12% vs BPD-1: 10% vs BPD-2: 30%), had more days of readmissions for respiratory problems (comparison group: 2.0 vs BPD-1: 2.0 vs BPD-2 6.3 [BPD-1 vs BPD-2]), had a lower mean developmental quotient (comparison group: 97.4 +/- 15.0 vs BPD-1: 97.9 +/- 11.6 vs BPD-2: 90.7 +/- 19.3). Intraparenchymal cerebral lesions, high family adversity, and prolonged ventilation were the most important factors influencing the developmental outcome. CONCLUSION: Children with BPD-1 are similar in all respect at 18 months to children in the comparison group. Children with BPD-2 are similar to the other groups at 18 months in growth, general health, and neurologic outcome but differ in having a higher number of days of rehospitalizations for respiratory causes, more hernia repairs, and more developmental delays.

Bronchopulmonary Dysplasia↗
PubMed1998

Extreme prematurity in healthy 5-year-old children: a re-analysis of sex effects on event-related brain activity.

A male disadvantage has been reported in several outcome studies of children born preterm. Twenty-two healthy premature children (10 girls, 12 boys) born between 25 and 28 weeks of gestation and 20 controls born full-term (10 boys, 10 girls) were matched on socioeconomical status and age. Event-related potentials (ERPs) were recorded by using 14 electrodes in a visual oddball task, with 75% frequent and 25% rare stimuli. This task elicited a larger P3 to the rare than to the frequent stimuli, with a prominent parietocentral localization. However, the amplitude was larger in full-term boys than in full-term girls, a difference that was not observed between preterm boys and preterm girls, especially to targets and on the central electrodes. In addition, the preterm group was characterized by a frontal slow wave larger in boys than in girls. In these prematures, the lack of the sex-related difference may be accounted by differences in the strength of the neuronal generators in males, as they might have been affected by the high level of androgens by the fetal testis under the control of placental gonadotropes during the first two thirds of gestation.

Attention↗
PubMed1997

A topographical ERP study of healthy premature 5-year-old children in the auditory and visual modalities.

The aim of this research is to study the impact of extreme prematurity on the cognitive development of the child as assessed at age 5 years 9 months. Our samples include 15 healthy prematures born between 25 and 28 weeks of gestational age carefully matched with 15 full-term controls. In the first experiment, two different auditory stimuli were presented to the subjects who listened passively without instruction. The second experiment consisted of a standard visual oddball task in which the subjects were instructed to 'catch' two different animals, by pushing a left or right button for a moose (n = 120) or a raccoon (n = 40), respectively. In the auditory task, 3 ERP peaks were analyzed (frontal N100 and P3a, temporal P2). All premature children demonstrated normal early frontal N100 and temporal P2 responses. The group differences were apparent in the late positivity (P3a) where controls showed a larger amplitude to the rare tones applied evenly to both ears. In contrast, the prematures did not show sensitivity to rare tones but showed a larger P3a upon left ear stimulation, when compared to the right. Also, the ERPs to the visual oddball task showed normal early positivities (P250-300) in the premature group. Once again, deviations from the normal were evident in late waves. The ERPs recorded from prematures showed a more diffuse topography especially between 500 and 600 ms post-stimulus and around the posterior area (P550). The succeeding negativity (SW) was not altered in the premature group. The ERP data suggest that premature children, even without clinically apparent problems, convey specific ERP singularity when engaged in a task that involves complex processing.

Acoustic Stimulation↗
PubMed1996

Ability of various inserts to promote endothelium cell culture for the establishment of coculture models.

To select an insert suitable for human umbilical vein endothelial cell (HUVEC) culture, we compared several available inserts of 0.2 to 0.45 micron porosity: Cellagen (ICN), Transwell-COL (Costar), Millicell-HA and CM (Millipore), Anopore (Nunc), Cyclopore (Falcon) in comparison with a control surface (Thermanox). The requirements were: (i) to promote attachment, adhesion and proliferation of HUVEC (judged by [3H]thymidine incorporation into DNA at days 1, 3, 7); (ii) to allow HUVEC visualization by inverted, fluorescence microscopy for uptake of DiI-Ac-LDL and scanning electron microscopy, performed at day 9 after seeding. Because Transwell and Cellagen are collagen precoated and CM has to be coated for cell culture, we performed collagen coating (types I + III or IV) for non-pretreated inserts for the purpose of comparison. Our preferences comprise Transwell-COL, Cyclopore not coated or coated (whatever the collagen type), and Cellagen. However, on a quality/price ratio criterion, Cyclopore, even uncoated, is the insert of choice. The HA, CM and Anopore inserts, even coated, do not allow HUVEC growth but do not alter positive uptake of acetylated LDL.

Cells, Cultured↗
PubMed1996

New preparation and microstructure of the EndoPatch elastin-collagen containing glycosaminoglycans.

Several improvements of the basic reaction between elastin-solubilized peptides and type I + III collagens are presented. They concern the prior incubation of the proteins in an adequate medium as well as the addition of heparan sulphate or hyaluronic acid (HA) and the consequent effects on the physical properties of yielded matrices. The addition of HA in small amounts enabled us to make membranes with good performances.

Biocompatible Materials↗
PubMed1996

Neonatal survival and disability rate at age 18 months for infants born between 23 and 28 weeks of gestation.

OBJECTIVE: Our purpose was to determine gestational age-specific outcomes of infants born in a period of surfactant use. STUDY DESIGN: All 465 consecutive births between 23 and 28 weeks' gestation in a tertiary center from 1987 to 1992 were analyzed prospectively. At 18 months' corrected age, 217 of 254 (85%) survivors were evaluated. RESULTS: From 1987 and 1988 to 1991 and 1992 there was an increase in survival for infants born at 24 weeks (from 0% to 33% p = 0.17), 25 to 26 weeks (38% to 71%, p < 0.005), and 27 to 28 weeks (66% to 84%, p < 0.05). At each weekly interval from 24 to 28 weeks of gestation the respective incidence of normality was 44%, 71%, 57%, 76% and 72% (not significant) and the respective mean developmental quotient was 91 +/- 17, 89 +/- 25, 90 +/- 24, 96 +/- 15 and 96 +/- 14 (not significant). CONCLUSIONS: Gestational age was strongly associated with outcome in terms of survival. Overall, 70% of children followed up were developing within the normal range.

Analysis of Variance↗
PubMed1996

Interest of umbilical fold incision for pyloromyotomy.

We report the results of a study concerning 80 infants undergoing a pyloromyotomy over a 3-and-a-half-year period. 40 infants had a right upper quadrant transverse rectus incision and 40 infants had an umbilical fold incision. Morbidity and cosmetic aspect of the two techniques were compared. We insist on the umbilical fold incision which presents the same advantages as the classic one and a better cosmetic result.

Humans↗
PubMed1996

Evaluation of bioabsorbable elastin-fibrin matrix as a barrier in surgical periodontal treatment.

The purpose of this investigation was to test clinically the efficiency of a recently described bioabsorbable matrix as a guided tissue regeneration membrane. This matrix was prepared from an original reaction between elastin and fibrin monomers and is now extensively used in several domains of surgery. The study group was composed of 26 patients, with a total of 35 lesions (22 intrabony defects, 8 Class II furcations and 5 Class III furcations) presenting moderate to advanced adult periodontitis. After initial therapy, measurements were made with a calibrated periodontal probe. Probing depth (PD) and gingival margin location (GM) measurements were taken twice: immediately before surgery and after 6 months before re-entry. Clinical attachment level (CAL), vertical osseous level (VOL) and alveolar crest location (AC) measurements were taken during surgery and after 6 months with re-entry procedures for all the patients. Color change of the gingival margin was only observed in 4 defects and device exposure occurred in the proportion of 2 out of the 35 defects. No foreign body reaction was observed in any case. At the intrabony defects mean PD reduction was 5 mm (P < 0.001), and mean gain of CAL was 4 mm (P < 0.001). Mean VOL was 4.3 mm (P < 0.001), mean gingival recession was 0.9 mm (P < 0.05) and mean AC was 0.2 mm (NS). At the Class II furcation defects the mean PD reduction was 4.5 mm (P < 0.001), mean gain CAL vertical was 3.2 mm and CAL horizontal was 4.5 mm (P < 0.001). Gingival recession averaged 1 mm (NS). A complete closure was observed in 2 out of the 8 defects. At the Class III furcation defects the mean PD reduction was 3.6 mm (P < 0.05) and mean CAL-V gain was 1.5 mm (P < 0.02). However the 5 sites showed no horizontal attachment gain and none were unchanged. A very low gingival recession, gingival reaction, crestal bone loss, and device exposure occurred during this study. This preliminary study suggests that the use of a biosynthetic barrier may have beneficial effects in the treatment of intrabony defects and Class II furcation defects. Randomized controlled trials are necessary to evaluate the efficacy and safety of this bioabsorbable membrane in periodontal therapy.

Adult↗
PubMed1996

Imaging and microanalysis of 14N and 15N by SIMS microscopy in yeast and plant samples.

We have investigated the usefulness of Secondary Ion Mass Spectrometry (SIMS) for studying the tissue distribution of 15N labelling in yeast cells and soybean leaf tissues. The secondary ions best suited for this are 12C14N- and 12C15N-. Using a mass resolution of 6000, all problems of interference by other ions were avoided. The lateral resolution was of the order of 300 nm, i.e. well suited for subcellular studies. The sensitivity was good enough to allow the detection and the mapping of 15N, even when it was present at its natural value concentration of the isotopic ratio of only 0.37%. Using yeast cells at isotopic equilibrium with their nutrient medium, the nitrogen isotopic ratios in the cells were consistent with those in the medium. In the soybean leaf samples, the mapping of 14N and 15N was well correlated with the anatomical structures of the tissues. The mean isotopic ratios (100 15N/14N, at/at), measured in the leaf tissues by SIMS, were slightly below those in the nutrient medium as well as those measured in the leaf tissue by conventional mass spectrometry. This may be explained by differences in the methods of preparation of the leaf samples for SIMS and for mass spectrometry, and by the fact that the plants were probably still not perfectly at isotopic equilibrium with their external medium at the time the experiments were performed.

Cell Compartmentation↗
PubMed1996

A grammar-based unification of several alignment and folding algorithms.

We show in this paper that many popular models of folding and/or alignment may be described by a new formalism: multi-tape S-attribute grammars (MT-SAG's). This formalism relieves the designer of biological models of implementation details which may hinder his inventiveness. To complete this formalism, we designed and implemented a tool which, given a MTSAG, will output an efficient parser for this grammar. We also show that MTSAG's offer a new, efficient and useful way to handle stochastic context-free grammars and tools that generate them.

Algorithms↗
PubMed1996

Functional upregulation of granulocytes labeled with technetium-99m-HMPAO and indium-111-oxinate.

UNLABELLED: Indium-111-oxinate-labeled granulocytes have been used in vivo for several years for the detection of abscesses. Technetium-99-m-hexamethylpropyleneamine oxime (99mTc-HMPAO) labeling has more recently been described. METHODS: The influence of radiolabeling by both radiotracers on adhesion glycoprotein CD11b quantification was studied in quiescent and formyl-methionylleucylphenylalanine (fMLP)-activated neutrophils (PMN). Adhesion was assessed on human umbilical endothelial cells (HUVEC) as well as the repercussion of the granulocyte labeling on HUVEC viability (neutral red) and metabolic activity (MTT). Chemotaxis of PMN was evaluated by measuring migration under agarose with fMLP as chemoattractant. We also measured phagocytosis and the production of hydrogen peroxide induced by staphylococcus aureus. RESULTS: Whereas whole functional integrity is maintained after labeling, most of the functions (CD11b expression, adhesion, HUVEC metabolic activity) are up-regulated while chemotaxis is decreased in the presence of both radiotracers. Indium-111-oxinate induces larger alterations than 99mTc-HMPAO. CONCLUSION: These data were obtained in normal volunteers. In patients, alterations due to the in vitro labeling procedure, in addition to potential functional alterations caused by the underlying pathology, should be taken into account during image interpretation.

Cells, Cultured↗