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Biomedical subjects

R Eloy

Publications and source records attributed to R Eloy.

At least 19 recordsLinked to original sources
PubMed2002

Influence of test protocol in determining the blood response to model polymers.

A multi-parametric, multi-center evaluation of three polymers was performed measuring their response to blood contact. The purpose of this study was to pinpoint differences in tests performed for assessing "basic" hemocompatibility on identical materials at different centers and attempt to rationalize. Assays for platelet adhesion, activation, aggregability and activation of the coagulation system in addition to an ex vivo patency assay were performed at four centers across Europe, using protocols favored by each center for determining the blood-contacting performance of a biomaterial. Three polymers were chosen for their expected blood response spanning the range of undesirable to desirable: ethylenevinylacetate (EVA), polyvinylchloride (PVC) and PVC modified with polyethylene oxide (PEO). The assays were ranked in terms of their efficacy compared to cost and simplicity. A correlation between assays was calculated, indicating the ability of one test to correctly determine the blood response compared to another. Some assays were unable to distinguish between materials, but of the assays which could, the materials were ranked in the following order: EVA; PVC; PVC-PEO, EVA producing the most undesirable response. It is concluded that many commonly used assays for determining hemocompatibility are inappropriate, but there are simple and reliable test methods available which correlate well with the more sophisticated protocols.

Journal Article↗
PubMed2001

Current and future issues in sensitisation testing.

Sensitisation is one of the biological risks that needs to be addressed for any medical device before clearance or clinical evaluation. This article describes the state of the art for this evaluation and also new variants of the procedure to increase the accuracy of these tests, particularly when some metals, latex-based products and macromolecular proteins such as collagen are concerned.

Dermatitis, Contact↗
PubMed2000

Biomaterial-induced sarcoma: A novel model to study preneoplastic change.

In the study of carcinogenesis most interest has focused on carcinomas, as they represent the majority of human cancers. The recognition of the adenoma-carcinoma sequence both in humans and in animal experimental models has given the field of basic oncology the opportunity to elucidate individual mechanisms in the multistep development of carcinoma. The relative scarcity of human sarcomas coupled with the lack of adequate animal models has hampered understanding of the molecular genetic steps involved. We present an experimental model in the rat in which a high incidence of malignant mesenchymal tumors arise around a subcutaneously implanted biomaterial. Nine commercially available biomaterials were implanted in a total of 490 rats of the Fischer strain for 2 years. On average, macroscopic tumors were found in 25.8% of implantation sites over a period from 26 to 110 weeks after implantation. The most frequent tumors were malignant fibrous histiocytomas and pleomorphic sarcomas, although fibrosarcomas, leiomyosarcomas, and angiosarcomas readily developed, the latter especially around polyurethane implants. Of particular interest are the results of a detailed histological study of the capsules around the implanted biomaterials without tumors. Here a spectrum of change from focal proliferative lesions through preneoplastic proliferation to incipient sarcoma could be observed. A parallel immunohistochemical study of peri-implant capsules showed that proliferating cell nuclear antigen was of particular help in identifying these atypical proliferative lesions. To our knowledge this is the first description of a sarcoma model in which preneoplastic lesions can be readily identified and also reproducibly induced. This model provides the molecular biologist with defined stages in the development of mesenchymal malignancy, with which the multistage tumorigenesis hypothesis can be tested, analogous to the well-known adenoma-carcinoma sequence.

Animals↗
PubMed1997

From cytotoxicity to biocompatibility testing in vitro: cell adhesion molecule expression defines a new set of parameters.

Determination of potential cytotoxicity is a central issue in current biocompatibility testing standards such as ISO and ASTM. Most of these tests do not assess biocompatibility of a biomaterial with regard to cell function. This study was aimed at screening a number of potential parameters that could be included in assessment of cell functional aspects of biocompatibility. Human umbilical vein endothelial cells (HUVEC) were seeded directly on titanium, NiCr alloy, CoCr alloy, PMMA, PE, PU, PVC, and silicone, or were exposed to the material extracts. Cytotoxicity was assessed for these materials through MTT conversion, crystal violet protein determination and Ki67 expression. In addition, expression of the cell adhesion molecules E-selectin, cadherin-5 and PECAM, as well as of the adhesion-associated proteins fibronectin and vinculin (focal adhesions), was determined by immunocytochemistry and western blotting. Cytotoxicity was not detected with the material extracts. Cells were able to adhere to bare metals, but not polymers. Fibronectin preadsorption resulted in adhesion and spreading also on the polymers. Cells were able to establish cell-cell contacts and focal adhesions. Western blotting, in combination with differential detergent extraction, indicated that linkage of cell-cell adhesion markers to the cytoskeleton may be used as an additional parameter relevant to cell function.

Journal Article↗
PubMed1994

In vitro biocompatibility evaluation of a heparinizable material (PUPA), based on polyurethane and poly(amido-amine) components.

The biocompatibility of a new heparinizable material based on polyurethane and poly(amido-amine) (PUPA) was evaluated both in the heparinized and non-heparinized forms. The quantity of heparin present on the material was measured using radiolabelled heparin and biological tests. Heparin release in plasma from heparinized PUPA was investigated using in vitro methods. The behaviour of PUPA towards cellular and plasmatic blood components was studied. The influence of sterilization on the cytocompatibility response of both heparinized and non-heparinized PUPA was investigated; gamma-rays were found to be a suitable method of sterilization as no toxic response was noticed.

Animals↗
PubMed1993

In vitro evaluation of inflammatory cell response after CF4 plasma surface modification of poly(methyl methacrylate) intraocular lenses.

The inflammatory cell response of tetrafluorocarbon (CF4) plasma surface modification of poly(methyl methacrylate) intraocular lenses (IOLs) was investigated in vitro. After two hours of lens contact with human granulocytes, scanning electron microscopy showed significantly less cell activation and granulocyte adhesion on the surface-modified IOL than on the untreated IOL (P < .01). The x-ray photo-electron spectroscopy analysis of the CF4 plasma surface modification demonstrated that new compounds containing fluorine were homogeneously grafted onto the PMMA lens surface, resulting in a marked increase of contact angle. These in vitro results must be confirmed by in vivo studies of CF4 plasma surface modification of IOLs.

Biocompatible Materials↗
PubMed1993

Treatment of experimental carotid aneurysms by endoprosthesis implantation: preliminary report.

Four experimental aneurysms were treated by implantation of an endoprosthetic stent. The aneurysms were surgically created by grafting a venous pouch on the carotid artery of mongrel dogs. Aneurysm patency was assessed angiographically. Under systemic heparinization and via a transfemoral approach, the stent measuring 20 mm in length and 5 mm in diameter, was implanted in the lumen of the parent artery at the level of the aneurysmal neck. Good angiographic results were obtained immediately following implantation, showing exclusion of the aneurysm from the circulation. Patency of the parent vessel was preserved in all the experimental aneurysms treated. In one case an angiogram performed 30 days later showed the same findings with excellent tolerance of the device. The technique of endovascular treatment of experimental aneurysms by stent implantation appears feasible and safe in vivo. Further investigations are still necessary before clinical applications.

Aneurysm↗
PubMed1992

[Diagnosis of bacterial infections on vascular prosthesis. Histological and microbiological analysis].

A retrospective study of 212 vascular graft failures, using different criteria of infection evidenced a relatively high incidence of infectious complications. Vascular graft infection was assessed on one of the following criteria: clinical infection, positive bacteriological and/or virological examination of the graft, presence of characterized micro-organisms and of microstructures 0.1 to 0.5 micron in size at the blood/prosthesis surface at scanning electron microscopy, and presence of foci of persistent polymorphonuclear cells and lymphocytes at histological microscopy. In the absence of overlapping between these criteria, the present results raise the question of the adequacy of conventional bacteriological sampling on explanted artificial surfaces.

Blood Vessel Prosthesis↗
PubMed1992

Physical and biological properties of a new synthetic amino acid copolymer used as wound dressing.

A new synthetic amino acid copolymer has been evaluated as wound covering. It is permeable to water vapor in the region of 4.1 kg/m2/24 h, it does not allow microbial proliferation after in vitro inoculation, it is impermeable to bacteria, and is stable and flexible. In vivo experiments were designed to provide qualitative and quantitative evaluation on its possible use as a skin substitute in full-thickness skin excision in the guinea pig. Two excisions, approximately 12-14 cm2 were performed on each side of the spine, leaving the panniculus carnosus. One site was treated with the membrane, the other with gauze. Each animal served as its own control. Photographs with a fixed focal-length camera were taken in identical conditions for all wounds immediately and 7, 14, and 21 days after excision. They were analyzed by planimetry. Histological studies were performed at 7, 14, and 21 days. The rate of healing between 0 and 21 days of the wounds treated with the copolymer membrane was significantly accelerated in comparison with wounds covered with a dry dressing (p less than 0.05). This increased epithelialization rate was confirmed by histology, which also suggested a reduction of the inflammatory response of the wound. In vivo biodegradation studies were also performed by subcutaneous implantation in the rat followed at 15, 30, 60, and 90 days by histology and physicochemical analyses. The results demonstrate that the membrane is not biodegradable.

Animals↗
PubMed1992

Wound healing of burns in rats treated with a new amino acid copolymer membrane.

A new amino acid copolymer (leucine + methylglutamate) membrane which is moderately permeable to water vapour, impermeable to bacteria, non-biodegradable and stable, has been developed as a burn wound covering. In an experimental model in the rat, excised burn lesions were covered either with the membrane or with conventional petrolatum-impregnated gauze. Morphometric analyses and histological investigations performed on days 7, 14, 21 and 42, suggested a significantly increased rate of healing for wounds covered with the polymeric membrane as compared with those covered with impregnated gauze. No wound dessication, fluid retention or exudate was observed under the membrane due to its moderate permeability to water vapour. The wounds covered with impregnated gauze also showed a marked inflammatory response in the granulation tissue, which remained even at day 42. This appearance was very different from a normal dermis or a polymeric membrane treated dermis.

Amino Acids↗
PubMed1991

Human vascular graft failure and frequency of infection.

Among 212 vascular prostheses collected in a vascular explant retrieval program, 50 exhibited one or more criteria of graft infection i.e., (a) clinical evidence of graft infection, (b) positive bacteriological analyses of the graft, and (c) presence at the blood-prosthetic interface of characterized microorganisms. Whereas each of these criteria was noted respectively in 25, 26, and 20 cases, there was no complete overlapping among the three criteria, but their combination led us to consider 50 cases of infected vascular grafts among the 212 collected. These results, and the occurrence in two cases among six investigations for viral infection, suggest that extensive bacteriological investigations of vascular explants should be included in an implant retrieval program, and that infection may represent a high risk in graft failure.

Aneurysm↗
PubMed1991

Evaluation of biocompatibility, based on quantitative determination of the vascular response induced by material implantation.

The biocompatibility of nine different materials, including positive and negative references, 4 polyurethane based and 3 latex based materials was investigated by (1) cytotoxic assay using V79 chinese hamster cells, (2) the thickness of inflammatory layer at 3 and 7 days after intramuscular implantation test, and (3) the course of the blood flow in tissue reaction around subcutaneously implanted materials using Laser Doppler Flowmetry (LDF) over 14 days following implantation. In addition, for some materials, different modes of sterilization were compared. Although the three methods explore different reactive systems, the material ranking obtained was highly similar for the three methods, suggesting a relative accuracy between them. For one latex however, an absence of cytotoxic effect in culture and a highly intense response by LDF investigation of the same order of magnitude as for the positive reference implant suggest that bioincompatibility may result from the material itself and cannot be exclusively investigated by the leaching of toxic components.

Anesthesia↗
PubMed1991

Contrast media for angiography: physicochemical properties, pharmacokinetics and biocompatibility.

Contrast agents are used as diagnostic molecules for the visualization of the vascular system. Despite their rapid pharmacokinetic distribution, and their excretion within a few minutes, their injection is associated with clinical symptoms of relative bioincompatibility. Allergoid reactions and disturbances of the hemostatic system represent the main fields of biological investigations. Due to the extent of clinical and experimental works the ubiquitous interactions between these molecules and cellular and/or protein systems have emerged. The development of a new family of low osmolality ionic or non-ionic contrast molecules had decreased the incidence of minor reactions, but did not modify the frequency of severe accidents and even led to the emergence of new iatrogenic syndromes. Despite extensive laboratory investigations there are still no predictive criteria nor any specific therapeutic prevention of these allergoid reactions. The suggested future line of investigation concerns the physicochemical interaction of CM and targeted biological systems which may allow the analysis and predictivity of these interactions at the molecular level.

Angiography↗
PubMed1991

Rat peritoneal macrophage procoagulant and fibrinolytic activities. An expression of the local inflammatory response.

1. Lysates of rat (Rattus norvegicus, Wistar strain) peritoneal macrophages selected by adherence were analysed for procoagulant activity (PCA) and plasminogen activator activity (PAA). 2. PCA is expressed following in vitro stimulation by lipopolysaccharide and in vivo (respectively 118 +/- 19.1 and 147.2 +/- 45.2 mUnits/10(6) M phi) very early after the intraperitoneal injection of thioglycollate. 3. PAA present in 24 hr thioglycollate stimulated cells (79.5 +/- 26.1 mI.U./10(6) M phi), disappears in a time dependent fashion after in vitro lipopolysaccharide stimulation. 4. Our findings indicate that rat peritoneal macrophages regulate their coagulolytic activities in a specific manner. 5. Rat peritoneal cavity may be proposed as a model for the study of inflammatory reaction with PCA and PAA as its indexes.

Animals↗
PubMed1991

[Coronary angioplasty using last generation materials. Immediate results].

PURPOSE: To present immediate results of percutaneous transluminal coronary angioplasty (PTCA) with the use of last generation catheter devices. METHODS: 74 patients underwent PTCA mean age 55 years the majority of them with disease of one vessel (92%) and good left ventricular function (88%). There was a total of 80 lesions treated, 26 type A and 54 type B according to the Task Force for Coronary Angioplasty of the American College of Cardiology--American Heart Association Classification. Results were analysed by separate observers: one clinical cardiologist (C), one cardiovascular surgeon (S) and two hemodynamicists (H1, H2). RESULTS: A significant fail in the degree of coronary obstruction was demonstrated post PTCA in the opinion of the observers: C = 83 +/- 10.7/9.0 +/- 14; S = 86 +/- 13.0/9.3 +/- 11; H1 = 88.6 +/- 7.0/8.5 +/- 12; H2 = 88.5 +/- 8.0/8.3 +/- 12 (P less than 0.001). Angiographic success was attained in 94.6% of the cases and the complication rate was low 2.7%. CONCLUSION: The high primary success and the low complication rates seen in this series can be attributed to the careful selection of cases and advanced performance of the catheterization devices that were used.

Adult↗