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Biomedical subjects

F Lefebvre

Publications and source records attributed to F Lefebvre.

At least 19 recordsLinked to original sources
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↗
PubMed1995

Prenatal diagnosis of Smith-Lemli-Opitz syndrome is possible by measurement of 7-dehydrocholesterol in amniotic fluid.

Amniocentesis was performed at 17.3 weeks in a pregnancy with severe intrauterine growth retardation. Cytogenetic studies on amniocytes were normal, 46,XX, and the pregnancy was continued. The diagnosis of Smith-Lemli-Opitz syndrome was suspected in the neonatal period and confirmed by the presence of 7-dehydrocholesterol (7-DHC) in the plasma (0.4 mmol/l, normal = not detectable) associated with a low total cholesterol concentration (0.4 mmol/l, normal = 2.56 +/- 0.23). Retrospective analysis of the amniotic fluid sample revealed an elevated level of 7-DHC (0.022 mmol/l; normal = undetectable). Therefore measurement of 7-DHC levels in amniotic fluid during the second trimester of pregnancy is useful for the prenatal diagnosis of Smith-Lemli-Opitz syndrome in families at risk and should be considered in cases of severe growth retardation of unknown aetiology for which amniotic fluid is available and in which a normal chromosomal pattern in amniocytes is present.

Adult↗
PubMed1995

The effect of recombinant human basic fibroblast growth factor rhFGF-2 on human osteoblast in growth and phenotype expression.

This paper describes the studies of human recombinant basic fibroblast growth factor (rhFGF-2) for its effects on human osteoblast growth and phenotype expression. During a 24-h period of treatment, rhFGF-2 highly stimulated DNA synthesis in a dose-related fashion with a maximum stimulation of 150% for 1 ng/ml. On the other hand, rhFGF-2 decreases alkaline phosphatase activity, synthesis of type I collagen, and cumulative amount of osteocalcin. Moreover, rhFGF-2 provoked a threefold increase in the amount of intracellular cAMP. Scatchard plots show the presence of two classes of [125I] rhFGF-2 receptors. This data suggests that rhFGF-2 which stimulate cell replication may act indirectly as an anabolic agent and stimulate some of the phenotypic expression markers.

Adult↗
PubMed1995

Nonoperative management of biliary tract fistulas after blunt abdominal trauma in a child.

Nonoperative treatment was carried out in a 12-year-old girl who presented with biliary fistulas after blunt abdominal trauma with hepatic injury. A computed tomography-guided percutaneous puncture showed biliary peritonitis and permitted the positioning of an efficient intraperitoneal drainage. Endoscopic retrograde cholangiography was very helpful for visualization and accurate localization of biliary injuries. This permitted positioning a nasobiliary drain to reduce intrabiliary pressure and to bypass a lesion of the common hepatic duct. This nonoperative management allowed healing of fistulas within 20 days, without bile duct stricture (noted on the follow-up intravenous cholangiogram 18 months later).

Abdominal Injuries↗
PubMed1995

Beware of commercial human thrombins used to stimulate cultured endothelial cells.

In the field of in vitro biocompatibility testing, the investigation of cell response at the interface with a biomaterial is of great importance; there is a need for standard conditions and thus of well-defined and reliable sources of materials for an objective evaluation of cellular function. Thrombin is often used in vitro as a stimulating agent to check the specific functions of cultured endothelial cells. In the present work, and in order to select a thrombin of commercial origin, two criteria were borne in mind: purity towards the presence of the von Willebrand factor (vWF) and effectiveness towards vWF release by human umbilical venous endothelial cells (HUVEC) that have been submitted to four human commercial thrombins. We detected the presence of vWF in some thrombin solutions that have not yet been in contact with HUVEC. The different thrombins contained vWF antigen ranging from less than 0.1 mUnit per NIH unit of thrombin (from Diagnostica Stago and Sigma Chemical Co.) to 10-20 mUnit per NIH unit of Fibrindex thrombin (from Ortho Diagnostic Systems). Thus, if vWF is present in commercial thrombins, it contributes to and overestimates the vWF appearance in the media resulting from cell stimulation. Consequently, we fixed on thrombin from Diagnostica Stago for further studies involving HUVEC on biomaterials.

Biocompatible Materials↗
PubMed1995

New artificial connective matrix made of fibrin monomers, elastin peptides and type I + III collagens: structural study, biocompatibility and use as tympanic membranes in rabbit.

Experiments leading to the conception and development of a new artificial connective matrix based on collagen-elastin-fibrin associations are presented. Preliminary evaluation of this biomaterial as an artificial tympanic membrane is described. Morphological evaluation was performed by histopathological and scanning electron microscopic studies. Biocompatibility was documented by subcutaneous implantation and experimental grafting in rabbits was performed with histopathological studies of the tympanic grafted membranes. The positive results obtained in this experimental study enable future studies in humans to be prepared.

Animals↗
PubMed1995

New bioactivation mode for vascular prostheses made of Dacron polyester.

The performance of vascular prostheses, especially those of small calibre, still presents several problems. The use of polyesters such as the well-known poly(ethylene terephthalate) (Dacron) and, more recently, poly(tetrafluoroethylene) and polyurethanes provides a marked improvement. We have developed a process to increase the efficiency of such prostheses, using the ability of the Dacron polyester to be covalently modified by proteins under mild chemical conditions. The biomaterial is obtained from the particular interaction of elastin-solubilized peptides with type I + III collagens under very precise conditions. We have obtained an irreversible covalent bonding on Dacron. These biological conditions and the addition of connective proteins and glycosaminoglycans conferred on the resulting material a composition and a three-dimensional structure equivalent to the subendothelium, providing bioactive properties suitable for the development of a vascular prosthesis.

Biocompatible Materials↗
PubMed1995

A fractal approach to the segmentation of microcalcifications in digital mammograms.

This paper presents a computerized method for the automated segmentation of individual microcalcifications in a region of interest (ROI) known to contain a cluster in digital mammograms. Mammographic parenchyma caj be accurately modeled with the fractal approach, but not areas with microcalcifications. The digitized image is divided into 16 x 16-pixel overlapping windows and those accurately modeled by the fractal model are eliminated. The next steps include local thresholding of the ROIs using an iterative method, the elimination of some of the artifacts and identification of the clustered microcalcifications using a clustering algorithm. The evaluation was performed on 81 simulated clusters superimposed on normal mammographic backgrounds and on a representative database of 408 real mammograms. Microcalcification locations were identified by two radiologists independently. These locations were compared to those found by the computer algorithm. An average of 59% of the simulated microcalcifications and 69% of the microcalcifications common to both radiologists were detected. The algorithm described provides a fully automated method for the segmentation of individual microcalcifications in an area of the mammogram known to contain a cluster.

Biopsy↗
PubMed1995

An optimized parsing algorithm well suited to RNA folding.

The application of stochastic context-free grammars to the determination of RNA foldings allows a simple description of the sub-class of sought secondary structures, but it needs efficient parsing algorithms. The more classic thermodynamic model of folding, popularized by Zuker under the framework of dynamic programming algorithms, allows an easy computation of foldings but its use is delicate when constraints have to be introduced on sought secondary structures. We show here that S-attribute grammars unify these two models and we introduce a parsing algorithm whose efficiency enables us to handle problems until then too difficult or too large to deal with. As a matter of fact, our algorithm is as efficient as a standard dynamic programming one when applied to the thermodynamic model (yet it offers a greater flexibility for the expression of constraints) and it is faster and saves more space than other parsing algorithms used so far for stochastic grammars.

Algorithms↗
PubMed1995

[Treatment of hip dislocations and subluxations by Petit's splints].

PURPOSE OF THE STUDY: The management of DDH in infants less than one year old is not yet definite. Many ambulant therapeutic methods are described and Pavlik's harness is widely employed. The use of Petit's splints is less well known and we report our experience with 169 cases. MATERIAL AND METHOD: Between 1973 and 1991, Petit's splints were used in 112 cases, following abduction cushions in 55 cases and after Pavlik's harness in 2 cases. 103 hips were dislocated but reducible. This permitted progressive abduction of the hips in order to obtain the reduction of the dislocation and to ensure stabilization by retraction of the slack articular capsule. RESULTS: Only 8 dislocations (4,7 per cent) couldn't be reduced by this procedure and necessitated another treatment. Hips were normal after 5 years of follow up in 118 cases and there were 43 residual dysplasias. 6 post reductional avascular necrosis (3,7 per cent) were recorded as a complication of this method among which only one was a serlous from. DISCUSSION: This ambulatory method for treatment of congenital hip dislocation seems to be forsaken by many authors. Nevertheless its effectiveness has been demonstrated with a complication rate lower than with Pavlik's harness procedure.

Female↗