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Biomedical subjects

A Meunier

Publications and source records attributed to A Meunier.

At least 37 records · Page 2Linked to original sources
PubMed2001

Histologic changes associated with experimental partial anterior disc displacement in the rabbit temporomandibular joint.

AIMS: To correlate histologic changes with the stress developed by various disc interferences via a model of partial anterior disc displacement in the rabbit temporomandibular joint (TMJ). METHODS: Eighteen male New Zealand rabbits were operated on to expose the temporomandibular disc without severing its attachments. A suture was passed around the lateral part of the disc over the condylar attachments and the 2 strands were fixed in the orbital cavity. In 9 rabbits, a resorbable suture was used to secure the disc displacement. In the other 9, a nonresorbable suture was fixed with a nickel-titanium spring to displace and maintain tension on the disc. Three non-operated animals served as controls. The animals were sacrificed at 12 and 24 weeks after surgery, and the TMJs were prepared for undecalcified histology. RESULTS: In the first group, the disc remained in a normal position, but its morphology was modified and small histologic changes were observed in the cartilage. In the second group, the disc was displaced in various positions corresponding to the strength delivered by the spring. CONCLUSION: Adaptive changes were observed in joints with a slightly displaced disc, while degenerative changes were associated with larger disc displacements. In each experimental joint, histologic changes increased from the medial to lateral parts. This phenomenon was related to the stress gradient induced by axial disc rotation over the condyle. Any disc displacement always resulted in changes in the cartilage.

Absorbable Implants↗
PubMed2001

The Beet soilborne pomovirus in Belgium and relationship with rhizomania.

The objective of this study was to determine the extend of the Beet soilborne pomovirus (BSBV) and the Beet virus Q in sugar beet fields in Belgium. During the 2000 sugar beet growing season, more than 80 fields located in Belgium were investigated for the presence of the Beet necrotic yellow vein benyvirus (BNYVV), the BSBV and Polymyxa betae, the plasmodiophorid vector of both viruses. Fields investigated were identified either using previous recorded data or by visual identification of yellow leaves on sugar beets or root symptoms. Sampling position (longitude-latitude) was recorded using the global positioning system (G.P.S.) with the view to follow-up infested fields in the following years. Three different techniques were used to evidence the aforementioned biological agents: enzyme-linked immunosorbent assay (ELISA), a RT-PCR assay to detect the viruses and direct coloration of Polymyxa betae in plant root tissues, using lactophenol-aniline blue. ELISA allowed the detection of 43 BSBV-infested soils, largely distributed in all Belgian sugar beet growing areas. These results were largely confirmed by RT-PCR using two different primers pairs targeting respectively a 400 bp fragment of the 145K ORF located on virus RNA-1 and a 970 bp fragment of the conserved 3' end of the viral genome. Five other primer's pairs have also been evaluated for BSBV identification. The detection of BSBV-infested soils without BNYVV, as well as BNYVV-infested soils without BSBV allowed the design of a competition assay between both viruses. Among the samples, 21 were selected randomly and tested for the presence of Beet virus Q by RT-PCR. Here also, six fields were detected positive for this virus. Sequence data reveal a clonal population of BSBV isolates in Belgium though a high level of diversity is observed for the coat protein region. Compared to BSBV, BVQ isolates show less diversity at sequence level.

Belgium↗
PubMed2000

New approach for separating Bacillus subtilis metalloprotease and alpha-amylase by affinity chromatography and for purifying neutral protease by hydrophobic chromatography.

Proteases are commonly used in the biscuit and cracker industry as processing aids. They cause moderate hydrolysis of gluten proteins and improve dough rheology to better control product texture and crunchiness. Commercial bacterial proteases are derived from Bacillus fermentation broth. As filtration and ultrafiltration are carried out as the only recovery steps, these preparations contain also alpha-amylase and beta-glucanase as the main side activities. The aim of this study is to purify and characterize the Bacillus subtilis metalloprotease from a commercial preparation, in order to study separately the impact of the protease activity with regards to its functionality on biscuit properties. Purification was achieved by means of affinity chromatography on Cibacron Blue and HIC as a polishing step. Affinity appeared to be the most appropriate matrix for large scale purification while ion exchange chromatography was inefficient in terms of recovery yields. The crude product was first loaded on a Hi Trap Blue column (34 microm, Pharmacia Biotech); elution was carried out with a gradient of NaCl in the presence of 1 mM ZnCl2. This step was only efficient in the presence of Zn cations, because this salt promoted both protease stabilization resulting in high recovery yields and also complexation of amylase units into dimers resulting in amylase retention on the column and a better separation of the 3 activities. Beta-glucanase was mostly non retained on the column and a part was coeluted with the protease. This protease fraction was then loaded on a Resource Phe column (15 microm, Pharmacia Biotech) in a last step of polishing. Elution was carried out with a linear gradient of 100-0% ammonium sulfate 1.3 M; protease was eluted at the beginning of the gradient and well separated from amylase and glucanase trace impurities. The homogeneity of the purified protease was confirmed by SDS-PAGE, which showed that its MW was about 38. pH and temperature optima were also determined on the fraction.

Bacillus subtilis↗
PubMed2000

Bioactivity of sol-gel bioactive glass coated alumina implants.

Alumina on alumina total hip arthroplasty has been in use for more than 25 years with encouraging results. However, an improvement of the alumina/bone interface still is required. The objective of this study was to investigate the in vitro and in vivo osteoconductive properties of sol-gel bioactive glass coated alumina implants. Two sol-gel glass compositions (58S Bioglass(R) and 77S Bioglass(R)) were used as coatings on alumina substrates and implanted in a rabbit model. The 58S sol-gel coating was employed in two configurations, single (A58S1) and double layer (A58S2). SEM analysis after one week in simulated body fluid revealed small crystals assumed to represent the initial phase of hydroxyapatite formation, whereas no clear conclusion could be drawn from Fourier transform infrared spectroscopy data. The percentage of bone in direct contact was greater for coated implants when compared to bulk alumina implants (p <0.001). In the case of A58S1 implants, bone percentage significantly increased from 45.1% after 3 weeks up to 87. 8% after 24 weeks of implantation (p = 0.0004). The presence of osteoid tissue, related to an aluminum release from the alumina substrates, was greatly diminished when compared to melt-derived glass-coated alumina implants.

Aluminum Oxide↗
PubMed2000

Tissue-engineered bone regeneration.

Bone lesions above a critical size become scarred rather than regenerated, leading to nonunion. We have attempted to obtain a greater degree of regeneration by using a resorbable scaffold with regeneration-competent cells to recreate an embryonic environment in injured adult tissues, and thus improve clinical outcome. We have used a combination of a coral scaffold with in vitro-expanded marrow stromal cells (MSC) to increase osteogenesis more than that obtained with the scaffold alone or the scaffold plus fresh bone marrow. The efficiency of the various combinations was assessed in a large segmental defect model in sheep. The tissue-engineered artificial bone underwent morphogenesis leading to complete recorticalization and the formation of a medullary canal with mature lamellar cortical bone in the most favorable cases. Clinical union never occurred when the defects were left empty or filled with the scaffold alone. In contrast, clinical union was obtained in three out of seven operated limbs when the defects were filled with the tissue-engineered bone.

Animals↗
PubMed2000

Wear of alumina-on-alumina total hip arthroplasties at a mean 11-year followup.

The surface topography of 11 alumina-on-alumina hip arthroplasties retrieved for aseptic loosening at a mean 11-year followup was investigated. Macroscopic wear was assessed using a coordinate measuring machine. Microscopic wear features were evaluated by Talysurf analysis. Scanning electron microscopy was used to look at the alumina microstructure. Components were classified into three groups: (1) low wear with no sign of wear and average arithmetic roughness values below 0.05 microm; (2) stripe wear with a visible oblong worn area on the femoral heads and penetration rates below 10 microm/year; and (3) severe wear with a visible loss of material on both components, showing total roughness values as much as 4 microm and maximum penetrations higher than 150 microm. Alumina quality assessed by grain size measurements and porosity percentages improved progressively from 1977 to 1988. This resulted in a correlated decrease of the microscopic wear magnitude. However, on a macroscopic scale, factors responsible for either a load increase (weight, young age, and male gender) or impairment in the load distribution over the component surfaces (large grain size, nonoptimal initial cup inclination, and cup migration and/or tilting) increased the penetration rates.

Adolescent↗
PubMed2000

CT of the middiaphyseal femur: cortical bone mineral density and relation to porosity.

PURPOSE: To determine whether computed tomography (CT) can be used to quantify age- and site-related changes in cortical bone mineral density (cBMD) at the middiaphyseal femur and whether cBMD differences are related to intracortical porosity. MATERIALS AND METHODS: Cortical bone specimens from 163 femurs were studied with CT and microradiography. Femurs were from 77 males and 86 females in a white anthropologic collection covering a broad age spectrum. In each sample, the cBMD was measured in the entire cortical width and in periosteal, midcortical, and endosteal subregions of interest. Age- and site-related changes in cBMD were tested for significance by using a two-way analysis of variance for both sexes. By using linear regression, cBMD was compared with porosity in the entire cortical width and in each subregion. RESULTS: There were significant age-related differences in cBMD (P <.001 in females, P =.008 in males). In addition, cBMD values were significantly different between the three cortical subregions (P <.001 for both sexes), decreasing from the periosteum to the midcortex to the endosteum. The cBMD values were closely related to porosity, and porosity contributed to 71.6% of the variance in cBMD in the overall population. CONCLUSION: CT is effective in the measurement of age- and site-related changes in cBMD. Decreases in cBMD are closely correlated with increased cortical porosity.

Adolescent↗
PubMed2000

[Osteoconductive properties of bioactive glasses in a bulk form and as a coating on alumina].

INTRODUCTION: Alumina on alumina friction couple has proven its reliability in the field of total hip arthroplasty. However, loosening of the alumina socket has been responsible for most of the failures. An improvement of the bone/alumina interface could be achieved with the use of an osteconductive material as a coating on alumina. The aim of this study was to evaluate the osteconductive properties of two types of bioactive glasses as a coating on alumina substrates. MATERIALS AND METHODS: Two types of coated implants (silicate glass coated alumina - AVSi, and phosphate glass coated alumina - AVP) were evaluated in a rabbit cancellous bone model. Pure alumina implants (A) were used as negative controls and bulk glasses (silicate - VSi and original 45S5, and phosphate glasses -VP) as negative controls. Sacrifices were performed at 3, 12 and 24 weeks. The interface evaluation included histomorphometry using an image analyzer. RESULTS: Silicate glasses demonstrated high osteoconductive properties. However, non mineralized osteoid tissue was the main tissue in contact with both coated implants and bulk phosphate glasses. This tissue covered over 70 p. 100 after 24 weeks of implantation, while it was never observed around pure alumina implants after 3 weeks. DISCUSSION: Amongst the hypotheses that could explain this mineralization inhibitory process, the one involving an Al(3+) glasses contamination from Al(2) O(3) is the likeliest. The high temperature coating procedure could be responsible for alumina transformation into a more soluble phase.

Aluminum Oxide↗
PubMed2000

Cell mechanotransduction and interactions with biological tissues.

The biomechanical mechanisms involved in the processes of tissue remodeling and adaptation are reviewed with emphasis on mechanotransduction at the cellular level. New theoretical models associated with experimental rheological techniques are briefly commented.

Adaptation, Physiological↗
PubMed2000

[Cementless acetabular fixation with solid alumina sockets. Apropos of 62 total hybrid prostheses with press-fit alumina sockets at 6-year mean follow-up].

PURPOSE OF THE STUDY: In order to avoid polyethylene wear observed in total hip replacement, an alumina-alumina combination has been used since 1977. The aim of this prospective study was to assess the results of an alumina-alumina total hip arthroplasty with a cementless press-fit plain alumina socket and a cemented titanium alloy stem with special attention for socket fixation because of previously encountered problems. MATERIALS AND METHODS: Fifty-five patients (62 hips) were operated on between 1982 and 1990. The main parameter for inclusion was a high level activity demand. The bearing surfaces were a 32 mm alumina head articulating within the alumina socket. Mean follow-up was 6 years. RESULTS: Four revisions occurred in this series: 3 for aseptic loosenings of the socket and 1 for femoral head fracture. Considering acetabular revision for aseptic loosening as the end point, the survival rate was 93.2 % at six years and 78.8 % at six years when considering acetabular loosening as the end point. At a mean of 72.1 month-follow-up, 92.4 % of the remaining hips were graded as very good or good while 44.6 % showed radiolucent lines around the socket and 4 had migrated with no radio-clinical correlation. On the femoral side, there was no radiolucent line nor loosening, and the value of the colar calcar resorption was low (mean 0.4 mm). In all four revisions, the stem was left in place, and there was no bone loss, which allowed simple revisions. DISCUSSION: Thin radiolucent lines around bulk alumina press-fit sockets can be understood as a normal bone reaction to material as the Young's modulus is much higher. They do not necessarily signify mechanical failure of the fixation. However when considering the rate of acetabular loosening, an improvement of the alumina/bone interface is still required.

Adult↗
PubMed1999

Osteogenesis with coral is increased by BMP and BMC in a rat cranioplasty.

Autologous bone marrow cells (BMC), bone morphogenetic protein (BMP) and natural coral exoskeleton (CC) were used to enhance the repair of large skull bone defects in a craniotomy model. Nine millimeter calvarial defects were created in adult rats and were either left empty (control defects) or implanted with CC alone, CC-BMC, CC-BMP, or CC-BMC-BMP. After 1 or 2 months, osteogenesis was insufficient to allow union when defects were left empty or filled with CC. Addition of BMC alone to CC had no positive influence on osteogenesis at any time and increased CC resorption at 2 months (0.1 +/- 0.1 mm2 versus 0.5 +/- 0.3 mm2). In contrast addition of BM P or BM P/BMC to CC led to a significant increase in osteogenesis and allowed bone union after 1 month. At 2 months, the combination of CC-BM P-BMC was the most potent activator of osteogenesis. Filling a defect with CC-BMP-BMC resulted in significantly increased bone surface area (11 +/- 2.7 mm2) in comparison to filling a defect with CC-BMP (7.0 +/- 1.4 mm2), CC-BMC (3.5 +/- 1.1 mm2) or CC (4.5 +/- 0.4 mm2). CC resorption was significantly decreased in the presence of BMP with or without BMC at both times. These data are in accordance with the presence of progenitor cells in bone marrow that are inducible by BMP to the osteogenic pathway in a cranial site. The increase in material resorption in defects filled with CC-BMC could suggest that cells from the granulocyte-macrophage lineage survived the grafting procedure and were still active after 2 months.

Analysis of Variance↗
PubMed1999

Effects of chitosan on rat knee cartilages.

The aim of this work is to study the effects of chitosan on rat knee cartilages. 0.2 ml of 0.1% chitosan solution pH = 6.9 were injected inside rat knees articular cavity. One, three and six weeks after injection, histological and histomorphometric studies were performed on undecalcified samples embedded in polymethylmetacrylate. Results show that after 1 and 6 weeks: (i) chitosan slows significantly (P < 0.005) the decrease in epiphyseal cartilage thicknesses and (ii) increases significantly articular cartilage chondrocyte densities (P < 0.002). However chitosan solution induces a proliferation of fibrous tissue with abundant fibroblasts, fibrocytes and monocytes inside the joint and this proliferation is still present after 6 weeks. This study suggests that chitosan could act on the growth of epiphyseal cartilage and wound healing of articular cartilage.

Animals↗
PubMed1999

Cementless bulk alumina socket: preliminary results at 6 years.

To avoid polyethylene wear observed in total hip replacement, an alumina-alumina combination has been used since 1977. The aim of this study is to report the results of a hybrid alumina-alumina total hip arthroplasty with a cementless press-fit bulk alumina socket and a cemented titanium alloy stem in 55 patients (62 hips) operated on between 1982 and 1990. The bearing surfaces were a 32-mm alumina head articulating within the alumina socket. Four failures occurred: 3 aseptic loosenings of the socket and 1 femoral head fracture. Considering aseptic loosening as the endpoint, the survival rate was 93.2% after 6 years. At a mean of 72.1 months' follow-up, 92.4% of the surviving hips were graded as very good or good using the Merle d'Aubigné-Postel hip score. Radiolucent lines were observed on the acetabular side in 68.1 of the hips. The future of this interface, which is probably fibrous, remains questionable. With the exception of 1 femoral head fracture, all revisions were related to failure of the bony fixation of the socket, and no problem was encountered related to the alumina-alumina friction coupling. Alumina sockets with other types of cementless fixation have therefore been designed and are presently under clinical investigation.

Adult↗
PubMed1999

Coral grafting supplemented with bone marrow.

Limited success in regenerating large bone defects has been achieved by bridging them with osteoconductive materials. These substitutes lack the osteogenic and osteoinductive properties of bone autograft. A direct approach would be to stimulate osteogenesis in these biomaterials by the addition of fresh bone-marrow cells (BMC). We therefore created osteoperiosteal gaps 2 cm wide in the ulna of adult rabbits and either bridged them with coral alone (CC), coral supplemented with BMC, or left them empty. Coral was chosen as a scaffold because of its good biocompatibility and resorbability. In osteoperiosteal gaps bridged with coral only, the coral was invaded chiefly by fibrous tissue. It was insufficient to produce union after two months. In defects filled with coral and BMC an increase in osteogenesis was observed and the bone surface area was significantly higher compared with defects filled with coral alone. Bony union occurred in six out of six defects filled with coral and BMC after two months. An increase in the resorption of coral was also observed, suggesting that resorbing cells or their progenitors were present in bone marrow and survived the grafting procedure. Our findings have shown that supplementation of coral with BMC increased both the resorption of material and osteogenesis in defects of a clinical significance.

Animals↗
PubMed1999

Induction of Toxoplasma gondii cystogenesis and multiplication arrest by treatments with a phosphatidylcholine-specific phospholipase C inhibitor.

A model of tissue cyst formation was developed using D609, a specific inhibitor of phosphatidylcholine specific-phospholipase C. The phospholipase inhibitor induced a decrease in Toxoplasma gondii multiplication and several successive treatments could lead to an arrest in parasite multiplication and full encystment of the parasites. This could be a first step towards an in vitro model of T. gondii reactivation.

Animals↗
PubMed1999

[Biomaterials and the living system].

Biomaterials, whatever their applications: cardiovascular surgery, orthopaedic surgery, ophthalmology, plastic surgery, urology, membranes for renal dialysis have some common approach. It is a very interdisciplinary field that needs intervening bioengineers, M.D, biologists and materials scientists. It is a domain with special emphasis on responsability because of the very severe consequence of these material failures. After an overview of these materials and their applications, we will briefly present here the evaluation systems of these biomaterials, including laboratory tests, mechanical tests as well as biological ones. Then we will project in the future to insist on three main orientations: tissue engineering, optimised materials for some precise function and also how new techniques of applied genetic could modify this field in deep in the future.

Biocompatible Materials↗
PubMed1998

Addition of fibrin sealant to ceramic promotes bone repair: long-term study in rabbit femoral defect model.

Despite their impact on the healing of soft connective tissue, fibrin sealants have not been shown conclusively to have an important role in the healing of bone defects. We report the positive influence of fibrin sealants on repair of cancellous bone cavities filled with a porous, resorbable ceramic. We studied two fibrin sealants: Autocolle and Tissucol. Autocolle is enriched in platelet factors during its preparation. Tissucol is a commercially available fibrin glue prepared from pooled human plasma that has no enrichment in platelet factors. Cavities 10 mm in depth and 5 mm in diameter were drilled in lateral condyles of 45 New Zealand rabbits. These defects were filled with either coral granules or a mixture of fibrin sealant (Autocolle or Tissucol) and coral granules or left empty. At 1 month addition of a fibrin sealant (Autocolle or Tissucol) to the coral led to a significant increase in bone formation in comparison to coral alone. At 2 months significant fibrin sealant mediated enhancement of bone repair was observed with Autocolle only. At 6 months bone formation was similar to the adult bone amount in nonoperated animals, whatever the initial material. Control cavities, on the other hand, were invaded with fibrous tissue only at each time period.

Animals↗