PubMed Health⌕ Search

Biomedical subjects

R Eloy

Publications and source records attributed to R Eloy.

At least 19 recordsLinked to original sources
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

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↗
PubMed1991

Evaluation of macrophage procoagulant and fibrinolytic activities induced by peritoneal dialysis solutions.

To investigate the coagulant and fibrinolytic potential of peritoneal macrophages, after short-term exposure to dialysis solutions intraperitoneal (IP) injection of these hyperosmolar glucose solutions was performed in rats. During the 72-hour postinjection period, the dialysis solutions and, as controls, Ringer's lactate and Ringer's lactate-glucose all induced a similar increase in the number of polymorphonuclear cells and macrophages within a maximum of 24 or 48 hours after their IP injection. These findings demonstrate that IP injection of any dialysis solution results in a moderate non-specific inflammatory cell harvesting. Compared with activity induced by the control solutions, no significant increase of procoagulant and fibrinolytic activities, identified respectively by the presence of thromboplastin and plasminogen activator, was observed in peritoneal macrophages obtained 48 hours after injection of the solution with the highest glucose concentration. However, the level of procoagulant activity could increase as a result of different manufacturers' processing of the solutions. That the basal level of macrophage functions may be modified suggests that this cell may initiate coagulolytic conditions in the peritoneal cavity, especially in the course of IP injection of dialysis solutions.

Animals↗
PubMed1990

[The Dacron vascular prosthesis in men. Mechanical performance, lesions and molecular stability].

The causes of failure of vascular prostheses implanted in man were investigated by means of histological, ultrastructural and scanning electron microscopic techniques as well as mechanical performance and macromolecular structure studies. These investigations concerned 22 out of 212 explanted prostheses from about 10 vascular surgery departments, examined over a 3-year period. The changes observed in the mechanical properties of the explanted prostheses (2 to 75 per cent reduction of resistance to rupture) and the finding of broken fibers and migrating polyester particles were confirmed by the presence of structural alterations in the polymer with, in particular, diminution of its crystalline structure. No correlation was found between the occurrence of these lesions and the type of prosthesis used and/or the duration of implantation.

Blood Vessel Prosthesis↗
PubMed1990

Quantitative in vivo studies of hyperemia in the course of the tissue response to biomaterial implantation.

Hyperemia associated with an inflammatory response has been investigated in rats, by using four different experimental models, i.e., "positive" and "negative" polymer implants from the pharmacopea, operative control, and abscess induced by turpentine oil. 133Xenon clearance, infrared thermography and Laser Doppler Flowmetry (LDF) were used to monitor the subcutaneous local hemodynamic changes from 1 to 40 postoperative days. LDF proved to be a sensitive, reproducible method, able to discriminate positive from negative implants already at the 3rd postoperative day and up to 40 days. This increased local blood flow was also visualized at the site of positive implants at the 14th and 21st postoperative days by means of 133Xe Clearance. Additional information obtained by infrared thermography allowed discrimination between positive implants and control sites but only at the very early stage (1 to 3 days). The significance of the different data collected by the three techniques was correlated with histological events occurring at the different implant sites. LDF may therefore represent a useful technique for noninvasive semiquantitative assessment of tissue response to biomaterials.

Animals↗
PubMed1990

[Epikeratoplasty without sutures using collagen IV lens in monkeys: description of the surgical technic].

The authors describe their original epikeratoplasty technic without sutures which is compatible with the use of collagen IV lens. They describe the first four observations of primates operated on using this technic. At first the epithelium is removed at the cornea center and a trepanation is made of 4 mm diameter and 0.1 mm depth. The bottom of the trepanation is then cut horizontally, and the periphery of the lens is put in the cornea stroma. Later the epithelium will recover the collagen lens. The lens is perfectly set in the cornea. We don't use any suture and so we avoid astigmatism and neovascularisation. The follow-up consisted of biomicroscopic examination photography, specular microscopy, pachymetry, photokeratoscopy (Nidek System) tonometry and histology. Clinical observance showed a perfect lens tolerance. The cornea is immediately transparent and within a week epithelial cells recovered the lens of three animals out of four. The photokeratoscopy study proved the important cornea refraction modification. This technic is reversible and the lens can be exchanged. A study of histology has begun and already shows a pluristratified epithelium. Further studies will test the biomaterial stability and ultra structural relations between the collagen IV lens and epithelial cells.

Animals↗
PubMed1990

[Use of human placental type IV collagen in tympanoplasty. Results of initial animal experimentation].

This study presents the use of human type IV collagen film in myringoplasty in dogs. Evaluation criteria were clinical (repeated otoscopies) and histological (histological analysis of cicatrised membranes). This new biomaterial should seem to be a technological advance on temporal bone aponevrosis or perichondria auto-grafts. This study constitutes the necessary preliminary research to any application in man.

Animals↗
PubMed1990

Lipid accumulation in prosthetic vascular grafts. Experimental study.

The present study demonstrates that the endoprosthetic tissue, developed at the contact of Dacron and Gore-Tex vascular prostheses replacing the infrarenal aortae of healthy dogs, presents a particular lipidic pattern as compared with the adjacent intimal arterial layer. The modified lipidic pattern is characterized by a significant increase in the total amounts of cholesterol, phospholipids, and triglycerides, despite a normal lipidic plasma profile. Histochemical studies showed that lipid droplets are accumulated in the cytoplasm of deeply situated cells and in the extracellular matrix. These findings support the idea that lipids may be trapped within the pseudo-intima of synthetic vascular grafts, even in the absence of a major plasma lipid disorder, and contribute to the prosthesis failure.

Animals↗
PubMed1989

Biosynthesis of factor V by normal adult rat hepatocytes.

The synthesis of coagulation factor V was investigated in isolated rat hepatocytes maintained in long-term primary culture. Two culture conditions were compared. A clotting assay and an immunoprecipitation experiment with rabbit anti rat factor V IgG were used to demonstrate not only the presence of factor V in the cells but also active secretion into the culture medium. Both the inhibition of the clotting reaction in presence of the antibody and absence of thrombin in culture media confirmed the specificity of the clotting assays. Electron microscopic examination located factor V in the endoplasmic reticulum and Golgi apparatus of hepatocytes in common with other liver specific plasma proteins. Examination of liver tissue sections confirmed the production of factor V in hepatocytes but not in hepatic endothelial cells although it did not exclude a transit pathway of factor V through these cells. Addition of Russell viper venom factor V activating enzyme to the culture medium had no effect on the factor V activity. In contrast, treatment of cell extracts did increase the coagulant activity. This suggests that hepatocytes contained principally an unactivated form or procofactor, whereas factor V present into the culture medium was mainly in an activated form. These data provide evidence for synthesis and secretion of an hepatocytic factor V.

Animals↗
PubMed1989

Effect of iodinated contrast media on blood clotting.

Recently, blood clot formation in catheters used for the injection of nonionic contrast media (CM) during angiography has been reported as being due to activation of hemostasis in the catheter. However, CM exhibit inhibitory properties regarding coagulation and platelet functions. The effect on blood clotting of iohexol, iopamidol, ioxaglate, diatrizoate, and ioxitalamate at a ratio of 10% v/v with nonanticoagulated human whole blood was evaluated using the kinetics of fibrinopeptide A (FpA) generation. Blood aliquots were taken every 2 minutes until blood clot occurred. Two groups of contrast media were identified: (1) iohexol and iopamidol, which increased the clotting time, and (2) ioxaglate, diatrizoate, and ioxitalamate, for which all clotting times were over 30 minutes and no FpA generation occurred.

Blood Coagulation↗