Biomedical subjects

G Daculsi

Publications and source records attributed to G Daculsi.

At least 109 records · Page 6Linked to original sources

PubMed1996

Ultrastructural study of degradation of calcium phosphate ceramic by human monocytes and modulation of this activity by HILDA/LIF cytokine.

Biodegradation of ceramics in vivo is achieved essentially by monocytes and multinuclear cells (osteoclasts). Monocytes are the key element in this process because they intervene first at the biomaterial implantation site during inflammatory reaction. In this work, in vitro studies were conducted on an ultrastructural scale to determine the specific behavior of these cells with regard to a calcium phosphate (CaP) ceramic. Two types of phagocytosis were observed when cells came into contact with the biomaterial: either CaP crystals were taken up alone and then dissolved in the cytoplasm after disappearance of the phagosome membrane or they were incorporated together with large quantities of culture medium, in which case dissolution occurred after the formation of heterophagosomes. Phagocytosis of CaP coincided with autophagy and the accumulation of residual bodies in the cells. Addition of HILDA/LIF factor to these cultures induced a very marked decrease in phagocytotic activity directed at the capture of CaP crystals and culture medium. Autophagy was reduced, and residual bodies were rare or absent. This study specifies the role of monocytes in CaP biodegradation and demonstrates for the first time that HILDA/LIF has a biological effect on this cell line.

Animals↗

PubMed1996

[An experimental short-term study of intramuscular integration of macroporous biphasic calcium phosphate ceramics. Application to the achievement of biocomposite flaps].

The aim of this research is to prefabricate a bicomposite flap, which can be defined as a composite structure of foreign material and living tissue. An animal model was developed by vascularizing spherical implants of macroporous biphasic calcium phosphate by a latissimus dorsi muscle flap in rabbits. The experiment was divided into three stages to compare the role of blood flow in the flap and autologous marrow bone cells. Biological apatite precipitation inside the macropores requires both factors and allows further clinical applications.

Animals↗

PubMed1995

Culturing of cells from giant cell tumour of bone on natural and synthetic calcified substrata: the effect of leukaemia inhibitory factor and vitamin D3 on the resorbing activity of osteoclast-like cells.

Osteoclastic cells from giant cell tumour of bone (GCT) of bone provide a rich source for investigation of cellular mechanisms leading to formation of multinucleated cells, the resorption process and involvement of hormones and cytokines in these events. In the present study we investigated the effect of 1,25-dihydroxyvitamin D3 (VD3) and leukaemia inhibitory factor (LIF) on the resorbing potential of osteoclast of GCT origin using quantitative image-analysis of resorption lacunae in an in vitro dentine model. While VD3 unsignificantly increased the number of resorption pits and implicated surface after 7 days of GCT cell culturing, the stimulative effect of LIF was statistically significant. In cultures supplemented with LIF (5000 U/ml) the number of lacunae and resorption surface increased by 38% and 55%, respectively, when compared with control cultures. We suggest that both osteotropic agents increased osteoclastic activity, as the number of multinucleated cells was similar in control and experimental cultures. Seeding of GCT cells on biphasic calcium phosphate substratum revealed the relative inability of osteoclastic cells to resorb this synthetic material.

Adult↗

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

Utilization of activated U937 monocytic cells as a model to evaluate biocompatibility and biodegradation of synthetic calcium phosphate.

The use of calcium phosphate biomaterials as a bone substitute necessitates the use of normative biocompatibility and biodegradation techniques which must be fast, simple and reproducible. In the present study, we have developed an in vitro model to study and to compare different calcium phosphate ceramics. After activation with 1,25-dihydroxy-vitamin D3 and phorbol 12,13-dibutyrate, the monoblastic U937 cells became multinucleated, expressed tartrate-resistant acid phosphatase and several markers of monocyte/macrophage differentiation. Activated U937 cells did not express the vitronectin receptor (VNR) (as revealed using monoclonal antibodies 23C6 or 13C2) but around 25% of the cells were strongly reactive with 211D, a novel monoclonal antibody that recognizes an osteoclast-specific membrane antigenic determinant. These cells remain active/viable with hydroxyapatite (HA) or beta-tricalcium phosphate (beta-TCP) ceramics. In conclusion, activated U937 cells are good candidates to use in a normative in vitro method to evaluate new biomaterials.

Acid Phosphatase↗

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

[Dual-energy X-ray absorptiometry: value in orthopedics].

We emphasize the opportunity of an in vivo bone mass measurement with an easy and accurate technique for orthopedic practice. At the present time, Dual Energy X Ray Absorptiometry (DEXA) is the most used technique, and is a safe and short examination. It can assess the quantity of mineral of any region of the body with a remarkable reproducibility (1 to 3 per cent). New machines are improved, and they permit many practical applications beyond the osteoporosis field. Thus, in orthopedics, we can distinguish several interesting topics. Peripheral risk of fracture can be evaluated because of good correlation between bone mineral content and biomechanical properties of bone. Even if a peripheral fracture occurs after a fall, low bone mineral density plays an important role, as in the case of femoral neck fractures in elderly patients. In traumatological practice, a DEXA with a specialized advice has to be requested if the traumatism cannot fully explain the occurrence of the peripheral fracture. Low bone mineral density defines an osteoporotic state, with the possibility of selecting adequate therapy. The good reproducibility of the measurement allows early estimation of bone loss following a period of immobilization. Varying models of osteosynthesis can be compared in vivo, to evaluate a decrease of "stress shielding" bone resorption. The role of stiffness of an implant on regional bone mineral content can be assessed. Likewise, periprosthetic bone mineral content can be measured in various regions, and followed over time. Specific software allows the exclusion of the region where the metallic prosthesis is projected. The reproducibility of this peripheral bone mineral content is 2 to 3 per cent, which individually allows an estimation of variations of more than 5 per cent. It will be possible to evaluate in vivo the influence of various parameters of the prosthesis on bone mineral content in controlled studies, such as the role of the shape, the position, the structure, the coating. Mineral content of biomaterials and bone grafts are taken into account. Focusing the X Ray beam allows ultrahigh resolution. Precise measurements of very small parts of bone such as rodent tibia or vertebra are possible. The good reproducibility (2 per cent) authorizes the evaluation of various parameters which modify bone remodeling, such as immobilization or activity, ovariectomy. Preventive or curative therapeutics which change bone mass can be evaluated in animal pre clinical studies. There are other methods of measurement of bone mineral content. Digitalization of radiographs is not sufficiently accurate and CT Scan generate high levels of radiation. The DEXA is actually the best compromise for an accurate and reproducible measurement of the bone mineral content in vivo. This method will certainly be an important tool in orthopedics for several clinical or animal investigations in the future.

Absorptiometry, Photon↗

PubMed1994

Monocyte activity in the presence of calcium phosphate activated by 1,25 (OH)2 VD3 and interferon-gamma.

The monocyte is an essential element in cellular immunity. Consequently, its role in the biocompatibility process is important. A model study of the degradation of bioactive ceramics (calcium phosphate) using human peripheral blood monocytes activated by 1,25 (OH)2 VD3 and interferon (IFN)-gamma was implemented. Activated monocytes cultivated on calcium phosphate tablets led to cellular morphological modifications and to changes in the number of nuclei (from d 2 to 14). IFN-gamma promoted adhesion, the appearance of cytoplasmic extensions and multinuclei. Cavity resorption activity on the material was observed simultaneously.

Biocompatible Materials↗

PubMed1994

Synthetic calcium phosphates: models for biological crystals?

Characterization of the mineral phases of calcified tissues or ectopic calcifications has demonstrated the complexity of biological calcium phosphate salts. Chemists and numerous biologists involved in calcified tissue research have generally described bone and teeth crystallites as hydroxyapatite rather than biological apatites. All biological calcium phosphates have a non-stoichiometric formula, and numerous and variable substitutions. Moreover, in vivo transformations/maturations occur. There is no particular representative synthetic calcium phosphate crystal either for the normal mineral phases of calcified tissues or for the pathological phases. However, they constitute efficient models for the understanding of biological mineralization, and are good approaches to in vitro studies of biomaterials.

Calcification, Physiologic↗

PubMed1994

Rat long-term bone marrow culture as a model for transient production of multinucleated giant cells into suspension culture fraction and for steady mineralization process of adherent stromal cells.

Under in vitro conditions rat bone marrow stromal cells induced into osteogenic differentiation by beta-glycerophosphate, exogenous ascorbic acid and dexamethasone are able to produce a mineralized matrix. Here we describe adult rat long-term bone marrow cultures (LTBMC), deprived of these substances. Mineralization process in stromal adherent cells occurred after 1 month of incubation and was proved by means of X-ray electron microprobe. The high content of sulfur in the extracellular matrix surrounding the mineralized nodules suggests non-distrophic pathway of Ca/P deposition. During the first 2 weeks of incubation the extensive production of multinucleated tartrate-resistant acid phosphatase (TRAP) positive and TRAP negative giant cells occurred into the suspension fraction of the cultures. Rat LTBMC may serve as a model for the investigation of differentiation of osteoblastic progenitors and their interactions with multinucleated TRAP positive cells.

Animals↗

PubMed1994

Pelvic pseudotumoral calcium pyrophosphate dihydrate deposition: an ultrastructural study.

We analyzed large periarticular calcifications of the hips and pubis in a woman with diffuse primary chondrocalcinosis, symptomatic in the knees. Serial articular and periarticular biopsies were obtained during surgery for osteoporotic hip fracture. Histologic examination showed diffuse nonbirefringent clumps in red alizarin stained cartilage, capsula and tendon. Scanning electron microscopy with microanalysis indicated a calcium/phosphorus atomic ratio of about 1. Transmission electron microscopy, electron diffraction and Raman spectroscopy assessed calcium pyrophosphate dihydrate (CPPD) in cartilage, synovia, capsula, tendon and muscle. The cause of these hard to observe, bulky CPPD periarticular deposits, which resembled basic calcium phosphate on radiography, is still unclear.

Aged↗

PubMed1993

Osteoclastic resorption of Ca-P biomaterials implanted in rabbit bone.

The nature of the multinucleated cells involved in the resorption processes occurring inside macroporous calcium-phosphate biomaterials grafted into rabbit bone was studied using light microscopy, histomorphometric analysis, enzymatic detection of tartrate-resistant acid phosphatase (TRAP) activity, scanning, and electron microscopy. Samples were taken at days 7, 14, and 21 after implantation. As early as day 7, osteogenesis and resorption were observed at the surface of the biomaterials, inside the macropores. Resorption of both newly formed bone and calcium-phosphate biomaterials was associated with two types of multinucleated cells. Giant multinucleated cells were found only at the surface of the biomaterials; they showed a large number of nuclei, were TRAP negative, developed no ruffled border, and contained numerous vacuoles with large accumulation of mineral crystals from the biomaterials. Osteoclasts exhibited TRAP positivity and well-defined ruffled border. They were observed at the surface of both newly formed bone and biomaterials, around the implant, and inside the macropores. In contract with the biomaterials, infoldings of their ruffled border were observed between the mineral crystals, deeply inside the microporosity. The microporosity of the biomaterials (i.e., the noncrystalline spaces inside the biomaterials) increased underneath this type of cell as compared with underneath giant cells or to the depth of the biomaterials. These observations demonstrate that macroporous calcium-phosphate biomaterials implanted in bone elicit osteogenesis and the recruitment of a double multinucleated cell population having resorbing activity: giant multinucleated cells that resorb biomaterials and osteoclasts that resorb newly formed bone and biomaterials.

Animals↗

PubMed1992

Macroporous biphasic calcium phosphate efficiency in mastoid cavity obliteration: experimental and clinical findings.

Following our previous experimental studies on the performance of macroporous biphasic calcium phosphate (MBCP) in canine mastoid cavities, we used this material in patients requiring surgical intervention. Twenty-two cases were selected, and in eight specific cases a biopsy specimen was taken. Histologic, ultrastructural, and microanalysis studies were performed. This study demonstrates the effectiveness of MBCP implants as bone graft substitutes for mastoid cavity obliteration. Clinical evaluation of the series and histologic and ultrastructural results demonstrated the bioactivity and osteo-conduction of this material, with partial transformation of MBCP granules into lamellar bone after several months.

Adolescent↗

PubMed1992

Measurement of synovial fluid volume: a new dilution method adapted to fluid permeation from the synovial cavity.

A new dilution method was developed to measure the synovial fluid (SF) volume in a single knee joint of a rabbit. In this dilution method, we used 2 different kinds of dextrans, one having a mean molecular weight (M(r)) of 487,000 and labelled with fluorescein isothiocyanate (FITC) as a marker, and the other M(r) of 300,000 to give hypertonicity to the solution. By employing these high M(r) dextrans in their optimal concentrations, we were able to minimize the inevitable transsynovial shift of the fluid and marker after intraarticular injection. The original SF volume was then calculated using the fluorescence intensities of the injected and retrieved fluids. By determining the accurate volume of SF, it became possible to measure per joint the protein and hyaluronic acid contents in SF as well as the total and differential cell counts. The results obtained by this new method were reasonable and consistent, except for volume, with the reported results based on pooled samples from multiple joints. We believe that the method can contribute to the analysis of SF changes under various conditions in small laboratory animals.

Animals↗

PubMed1992

[Bone anchorage and surface condition of the implant. Validity of extraction tests].

The mechanical strength of the bone-implant interface depends on the morphology and the composition of the implant surface. The great variety of coating materials as well as the condition of the surfaces to be covered, makes a comparative and preclinical evaluation of the different materials for prostheses necessary. The results, the validity and the limits of the extraction tests are discussed in this article.

Animals↗

PubMed1990

Macroporous calcium phosphate ceramic for long bone surgery in humans and dogs. Clinical and histological study.

Our previous studies reported the performance of Macroporous Biphasic Calcium Phosphate (MBCP) in spine fusion. In the present study, this material was used in block forms in selected patients with tumoral resection in long bone. Two cases were chosen with large benign bone tumors. Clinical and radiographic assessments, CT scans, and NMR were performed after 16 months, and in one case control biopsies were taken. In order to understand the kinetic process of biodegradation of the MBCP blocks and bone formation at the expense of the ceramics, an experimental study in surgically created bond defects in canine femoral cortices was made. The MBCP blocks recovered after implantation period from 2 to 18 weeks were analyzed using histological, stereological, ultrastructural, electron microprobe, and IR spectroscopy analyses. This study demonstrated the efficiency of MBCP blocks for filling pathological defects in human long bone. The biointegration process of the MBCP blocks was due to a partial dissolution of the ceramics crystals (b-TCP content) by multinucleated cells. Simultaneously, bone ingrowth at the expense of the ceramic is observed. The new bone formation inside the MBCP macropores and in the spaces between the blocks, involved the formation of a new cortical bone on the outer part, and a trabecularlike bone with bone marrow in the inner part of the implant. The biological resorption of the MBCP ceramic decreased after 1 month implantation in dog, due to the protective role of the newly formed lamellar bone on the surface and in the core of the ceramics.

Animals↗

PubMed1990

Formation of carbonate-apatite crystals after implantation of calcium phosphate ceramics.

The aims of this study were (1) to determine at the crystal level, the nonspecific biological fate of different types of calcium phosphate (Ca-P) ceramics after implantation in various sites (osseous and nonosseous) in animals and (2) to investigate the crystallographic association of newly formed apatitic crystals with the Ca-P ceramics. Noncommercial Ca-P ceramics identified by X-ray diffraction as calcium hydroxylapatite (HA), beta-tricalcium phosphate (beta-TCP), and biphasic calcium phosphates (BCP) (consisting of beta-TCP/HA = 40/60) were implanted under the skin in connective tissue, in femoral lamellar cortical bone, articular spine bone, and cortical mandibular and mastoidal bones of animals (mice, rabbits, beagle dogs) for 3 weeks to 11 months. In humans, HA or beta-TCP granules were used to fill periodontal pockets, and biopsies of the implanted materials were recovered after 2 and 12 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Effect of the macroporosity for osseous substitution of calcium phosphate ceramics.

The main property of calcium phosphate ceramics (CaP ceramics) is to be gradually substituted by newly formed bone or at least to be coalescent with the host bone. In cortical bone in dogs three kinds of porosity were tested (from 100 to 600 microns). The results demonstrate that the macropores up to 100 microns are efficient for the bone ingrowth, however during the first months of implantation larger macropore sizes are more suitable for bone ingrowth.

Animals↗