Biomedical subjects

A Meunier

Publications and source records attributed to A Meunier.

At least 19 recordsLinked to original sources

PubMed2002

Monosodium urate monohydrate crystal-induced inflammation in vivo: quantitative histomorphometric analysis of cellular events.

OBJECTIVE: To quantify the inflammatory cell response in rat air pouch pseudosynovial membrane during monosodium urate monohydrate (MSU) crystal-induced inflammation. METHODS: In the rat air-pouch model, we used a computer-assisted histomorphometric method to quantify cell distributions, based on cell linear densities, in histologic sections of membranes from pouches injected with MSU or saline. The volume, white blood cell (WBC) count, and histamine content of the pouch exudates were determined at several time points. RESULTS: Injection of 10 mg of MSU crystals into the pouch produced an acute exudate. After peaking at 24 hours, the exudate volume and WBC count decreased spontaneously over the next 3 days, simulating the self-limited course of acute gout. Membrane thickness followed a parallel course. Membrane polymorphonuclear cell (PMN) linear densities were closely correlated with exudate WBC counts, suggesting PMN recruitment from the subintimal synovial membrane. Both monocyte/macrophage and mast cell linear densities increased in the subintimal layer 2 hours after crystal injection (P = 0.038 and P = 0.03, respectively, versus controls), whereas PMN linear densities showed 2 peaks, one at 4 hours and the other 24 hours. The exudate histamine content peaked 6 hours after crystal injection, when mast cell linear densities were minimal in the membranes, suggesting mast cell degranulation. CONCLUSION: An increase in monocyte/macrophage and mast cell densities in the membrane preceded the PMN influx in the pouch membrane and exudate, suggesting that mast cells may be involved in the early phase of MSU crystal-induced inflammation, at least in this rat model.

Animals↗

PubMed2002

Hip fracture risk and proximal femur geometry from DXA scans.

In this retrospective study of hip fracture risk evaluation from hip dual-energy X-ray absorptiometry (DXA) scans, our objectives were to determine which part of the femoral neck length contributes most to the fracture risk and to define a geometric parameter better than hip axis length (HAL) for discriminating hip fracture patients. Forty-nine Caucasian women with a nontraumatic femoral neck fracture were matched on age to 49 normal women and on both age and femoral neck bone mineral density (BMD) to 49 unfractured women. In addition to BMD, geometric parameters including neck-shaft angle, neck width and several HAL segments were evaluated by discriminant analysis to determine which was the best hip fracture discriminator. Neck-shaft angle had a limited influence on the hip fracture risk. Age-related bone loss was associated with a neck width increase in unfractured and fractured patients. HAL was significantly longer in fractured patients and was a significant discriminator between fractured patients and normal controls. HAL was not significant as a discriminator between fractured and low-BMD unfractured patients. The intertrochanter-head center distance (from the intertrochanteric line to the femoral head center) coincides with the femoral lever arm and includes no segments that adapt to BMD changes, such as the greater trochanter-intertrochanter distance. Among all tested lengths, this segment was the part of HAL that discriminated best between fractured and low-BMD unfractured patients. A longer intertrochanter-head center distance increased the risk of femoral neck fracture among low-BMD patients. Including automatic measurement of this segment in standard DXA protocols may prove useful in identifying patients at high risk for hip fracture. At present, HAL remains the easier neck length to measure, but automatic evaluation of the intertrochanter-head center distance must be a goal for future image analysis development.

Absorptiometry, Photon↗

PubMed2001

In vivo tracking of bone marrow fibroblasts with fluorescent carbocyanine dye.

Recent advances in the field of tissue engineering have culminated in new tissue substitutes that combine a biomaterial and precursor cells. The effectiveness of these materials is generally assessed in animals, but few studies explore the fate of the transplanted cells in vivo, despite its paramount importance for understanding the function of the engineered tissues. Current methods that use reporter genes or chimeric animals are not always well suited to solving tissue-engineering problems. We therefore developed a new method for irreversible labeling of cells to track their fate in vivo. We used a fluorescent lipophilic probe, CM-Dil, that avidly binds to the cell membrane. Human bone marrow stromal fibroblasts could be labeled with 20 microM CM-Dil in 30 min. The CM-Dil was not cytotoxic and did not affect cell proliferation in vitro. Cells could be monitored for up to 30 days when placed in a coral scaffold and implanted intramuscularly or in a bony site. However, the fluorescence intensity decreased roughly in parallel with the number of cell divisions. This fact needs to be taken into account during the design and interpretation of experiments. We believe that this technique is also of interest for other cell types.

Bone Marrow Cells↗

PubMed2001

Long-term in vivo bioactivity and degradability of bulk sol-gel bioactive glasses.

Melt-derived bioactive glasses have been used with success in various clinical applications for over 10 years. Recently, particles of sol-gel-derived bioactive glasses with an initial high specific surface area have been shown to exhibit excellent osteoconductive properties as well as significant degradability. In this work, we explored the long-term in vivo bioactivity and degradability of bulk sol-gel-derived glasses in a rabbit model. Two sol-gel compositions (58S and 77S Bioglass) were used. Bulk 45S5 Bioglass was used as a control. Both sol-gel-derived glasses demonstrated osteoconductive properties similar to 45S5 Bioglass. In addition, absorbability was observed for both sol-gel-derived glasses starting after 12 weeks of implantation. Total absorption reached 40% after 52 weeks. No degradation could be measured in the case of bulk 45S5 melt-derived Bioglass within 1 year of implantation. The degradation process was highly time dependent, as demonstrated by regression analysis. New bone formation was found to fill in areas that had been resorbed, similar to bone remodeling. This absorbability can be assumed to be at least partially related to an osteoclastic resorption as viable osteoclasts-like cells were found to be in direct contact with the glass surfaces.

Absorbable Implants↗

PubMed2001

There are some benefits for eradicating Helicobacter pylori in patients with non-ulcer dyspepsia.

BACKGROUND: The relationship between Helicobacter pylori infection and non-ulcer dyspepsia is not established. AIM: To determine whether eradication of H. pylori might be of benefit in non-ulcer dyspepsia patients. METHODS: We randomly assigned 129 H. pylori infected patients with severe epigastric pain, without gastro-oesophageal reflux symptoms, to receive twice daily treatment with 300 mg of ranitidine, 1000 mg of amoxicillin, and 500 mg of clarithromycin for 7 days and 124 such patients to receive identical-appearing placebos. RESULTS: Treatment was successful (decrease of symptoms at 12 months) in 62% of patients in the active-treatment group and in 60% of the placebo group (N.S.). At 12 months, the rate of eradication of H. pylori was 69% in the active-treatment group and 18% in the placebo group (P < 0.001). Complete relief of symptoms occurred significantly more frequently in patients on the active treatment (43%) than in placebo-treated patients (31%, P=0.048). Within the active-treatment group, therapeutic success was significantly more frequent in the non-infected patients (84% vs. 64%, P=0.04). CONCLUSIONS: Although eradicating H. pylori is not likely to relieve symptoms in the majority of patients with non-ulcer dyspepsia, a small proportion of H. pylori-infected patients may benefit from eradication treatment.

Adolescent↗

PubMed2001

Frequency- and duration-dependent effects of cyclic pressure on select bone cell functions.

The present study demonstrated unique correlations between characteristic parameters of mechanical loading and osteoblast functions. Specifically, osteoblast proliferation was dependent on the frequency and on the duration of the applied cyclic pressure stimulus: decreased cell proliferation was only observed when these cells were exposed to cyclic pressure at 1.0-Hz (but not at 0.25-Hz) frequency for 1 h (but not for 20 min) daily for 5 days. In contrast, endothelial cells were not responsive to cyclic pressure, whereas fibroblast proliferation increased under similar test conditions. Most important, cyclic pressure affected various osteoblast genes differently: exposure of osteoblasts to cyclic pressure (at 1.0-Hz frequency for 1 h daily) resulted in enhanced transcription and translation of alkaline phosphatase after 5 days; the same mechanical stimulus, however, did not affect osteopontin mRNA expression during the same time periods. These findings provide cellular and molecular level information, which is not only important in elucidating the correlation between mechanical loading and bone homeostasis, but can be useful in development of new technology in skeletal tissue engineering.

Animals↗

PubMed2001

Hydroxyapatite-coated versus grit-blasted femoral stems. a prospective, randomised study using EBRA-FCA.

We have carried out a prospective, randomised study designed to compare the long-term stability of the stem of cementless femoral implants with differing surface configurations. A total of 50 hips (46 patients) was randomised into two groups, according to whether the medullary stem had been grit blasted (GB) or coated with hydroxyapatite (HA). Both femoral prostheses were of the same geometrical design. We used Ein Bild Roentgen Analyse femoral component analysis (EBRA-FCA) to assess the stability of the stem. The mean follow-up was for 8.66 years. The mean migration of the stem was 1.26 mm in the HA group compared with 2.57 mm in the GB group (Mann-Whitney U test, p = 0.04). A mixed model ANOVA showed that the development of subsidence was statistically different in the two groups during the first 24 months. After this subsidence increased in both groups with no difference between them. Our results indicate that, with the same design of stem, HA coating enhanced the stability of the femoral stem when compared with GB stems.

Adult↗

PubMed2001

Distribution of intracortical porosity in human midfemoral cortex by age and gender.

The purpose of this study was to describe the age-specific distribution of midfemoral intracortical porosity throughout the cortical width in males and females. Microradiography and an automated image analysis system were used to study midfemoral cortical bone specimens from 163 white people, including 77 males and 86 females, in a recent anthropological collection covering a broad age range. In each specimen, porosity (percentage of the cortical bone area occupied by pores), pore number, and pore size were measured throughout the entire cortex and in three cortical subregions of equal width labeled the periosteal, midcortical, and endosteal subregions. For each gender, relationships linking age to porosity, pore number, and mean pore size were assessed using regression analysis. In addition, age- and site-related changes in these three variables were tested for significance using two-way analysis of variance (ANOVA). Age explained 52% of the porosity variance in females and 13.5% in males. In each gender, there were significant age- and site-related differences in porosity, pore number, and pore size. In adults aged 60 years or younger, both pore size and pore number increased with increasing age, whereas in adults older than 60 years, pore size continued to increase but pore number decreased. In males, the age-related changes in pore size and pore number were proportionally similar in the three cortical subregions. In females, in contrast, the changes predominated in the endosteal subregion and resulted in significant cortical thinning.

Adolescent↗

PubMed2001

Total hip arthroplasty for the treatment of ankylosed hips : a five to twenty-one-year follow-up study.

BACKGROUND: The purpose of the present retrospective study was to report the long-term results of total hip arthroplasty following a hip fusion. Special attention was paid to the resulting function of both the involved joint and the neighboring joints, as pain in the lower back or knee was the usual indication for conversion. The factors that were likely to influence the functional outcome were analyzed. METHODS: Forty-five consecutive total hip arthroplasties were performed in forty-five patients from 1969 through 1993. The mean age of the patients at the time of the operation was 55.8 years (range, twenty-eight to eighty years). Ankylosis of the hip had been spontaneous in twenty patients and postoperative in twenty-five patients. The mean duration of the ankylosis had been thirty-six years (range, three to sixty-five years). The mean duration of follow-up was 8.5 years (range, five to twenty-one years). No patient was lost to follow-up. RESULTS: The mean hip score, according to the scale of Merle d'Aubigné, was 16.5 1.5 points at the latest follow-up evaluation. Hip function was considered to be satisfactory for forty-one (91%) of the forty-five patients. The definitive score for walking ability was not achieved by the one-year evaluation; it improved notably for two to three years and then it remained stable. At the time of the latest follow-up, the mean arc of flexion was 88 degrees (range, 30 degrees to 130 degrees ). Forty-three (96%) of the forty-five patients had no pain in the involved joint. The only factor that was predictive of the final functional result with regard to walking ability was the intraoperative status of the gluteal muscles. Most patients had effective pain relief in the neighboring joints. The cumulative survival rate at eight years, with revision as the end point, was 96.7% (95% confidence interval, 90.2% to 100%). CONCLUSIONS: The long-term effectiveness of total hip arthroplasty for the treatment of an ankylosed hip was clearly demonstrated in both the involved and the neighboring joints in the present study. However, the preoperative and intraoperative status of the gluteal muscles should be carefully evaluated when this procedure is being considered, as this was the only factor that was predictive of the final walking ability.

Adult↗

PubMed2001

Comparative analysis of two different types of alumina-alumina hip prosthesis retrieved for aseptic loosening.

We compared and quantified the modes of failure and patterns of wear of 11 Mittelmeier and 11 Ceraver-Ostal retrieved alumina-alumina hip prostheses with reference to the corresponding clinical and radiological histories. Macroscopic wear was assessed using a three-dimensional co-ordinate measuring machine. Talysurf contacting profilometry was used to measure surface roughness on a microscopic scale and SEM to determine mechanisms of wear at the submicron level. The components were classified into one of three categories of wear: low (no visible/measurable wear), stripe (elliptical wear stripe on the heads and larger worn areas on the cups) and severe (macroscopic wear, large volumes of material lost). Overall, the volumetric wear of the alumina-alumina prostheses was substantially less than the widely used metal and ceramic-on-polyethylene combinations. By identifying and eliminating the factors which accelerate wear, it is expected that the lifetime of these devices can be further increased.

Adolescent↗

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↗