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Biomedical subjects

R Eloy

Publications and source records attributed to R Eloy.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1989

[The neoartery, myth or reality? Study of 79 explanted arterial prostheses].

This study represents the third stage of a personal study on the long term fate of reconstruction and arterial restoration materials presented to the Academie de Chirurgie. 79 explanted prostheses were studied. First of all by an in depth histological study (8 cases selected from 70 reinterventions carried out before 1980), and then by a more complete protocol: scanning electron microscopy, resistance testing, programmed differential calorimetry, X-ray diffraction and biochemical analysis (71 reinterventions carried out after 1980). Our findings agree with the studies of R. Guidoin. With the exception of structural manufacturing defects or defects related to surgical manipulation, mechanical fatigue in a Dacron (PET) arterial prosthesis is inevitable: on average by the 7th to 10th year, a prosthesis looses one half of its mechanical resistance. The covering tissue, like that of the external capsule, which has poor mechanical properties, cannot compensate for prosthetic deterioration which may be considered to be complete by the 25th year. Knitted arterial prostheses, especially aortic, more rapidly undergo dilatation than woven prostheses which are much more resistant. On the other hand, the poor compliance of the latter compared with the recipient artery, perhaps favorises late anastomotic rupture. At internal capsule or pseudo-intimal level, endothelium is never present, but rather there is a permanent turnover with a variable time course, the mechanisms of which are poorly understood (role of prostaglandins?). Rather than a neo-artery, the vascular surgeon is only capable of producing an imperfect arterial tube, fragile from many points of view, and having an evolution which remains poorly understood.

Aneurysm↗
PubMed1989

Biocompatibility of human collagen type IV intracorneal implants.

A new biomaterial made from human placental collagen type IV has been developed in corneal inlays for refractive keratoplasty. Eight dogs received intracorneal lenses to investigate biocompatibility. Postoperative follow-up observation of 2 years revealed that the eyes remained clear and without inflammatory reaction. Endothelial cells were unaltered. Histological and ultrastructural studies showed no signs of inflammation, ulceration, or encapsulation. No fibroblastic activity was evident at the lens stroma interface.

Animals↗
PubMed1988

An in vitro evaluation of the hemostatic activity of topical agents.

An in vitro method has been developed for human non-anticoagulated blood to evaluate the enhancing effect of hemostatic agents on both plasmatic and cellular activation of the coagulation cascade. The coagulation time and the sequential generation of fibrinopeptide A (FpA) have been used as parameters. The kinetics of generation of FpA has been modelized and mathematically analyzed using the latence time, the slope of the linear part of the curve, and the time necessary to reach half maximal amplitude of FpA in the tube. A maximal amplitude of FpA in the tube. A very precise evaluation of the hemostatic activity of five different molecules, four being collagenous in nature, is given.

Analysis of Variance↗
PubMed1988

Stability of performances of vascular prostheses retrospective study of 22 cases of human implanted prostheses.

Twenty-two cases of vascular graft failures (thrombosis, pseudoaneurysm, dilation, infection) were investigated by means of physicochemical, histological, and ultrastructural studies. A general decrease of mechanical resistance to stress of the prostheses was observed. Its magnitude ranged from 2 to 75% of the values of identical virgin prostheses and there was no relation with the duration of implantation. In addition to the breakage of yarn filaments (SEM), migration of fiber debris (histology) was observed in 7 cases. The structure of the polyester molecule had evolved after implantation. A decrease of crystallinity (x-ray diffraction and differential scanning calorimetry) was noted. These observations raise the question of the established stability of vascular prostheses and emphasize the need for further investigations in human graft retrieval programs.

Biocompatible Materials↗
PubMed1988

Evaluation of histamine release following intravenous injection of ionic and nonionic contrast media.

To evaluate histamine release (HR) following injection of radiocontrast media and to test the predictive value of peak-expiratory-flow rate (PEFR) in detecting high-risk patients, the authors performed in two series 90 intravenous pyelograms (IVPs). In the first group, HR was measured by a fluorometric method after injection of Hexabrix (25 patients) and Iopamiron (25 patients). In the second group, HR measured by a radioimmunoassay, and PEFR measured by a peak flowmeter were investigated after injection of Hexabrix (10 patients), Telebrix (10 patients), Omnipaque (10 patients) and Iopamiron (10 patients). Histamine release in groups 1 and 2, and PEFR in group 2, were not significantly modified by the injection of each radiocontrast media. For the four patients (two per group) who experienced minor allergic side effects, the levels of HR and PEFR were always within the normal ranges.

Contrast Media↗
PubMed1988

In vitro interactions of gadolinium DOTA meglumine and gadolinium DTPA meglumine on hemostasis.

The interactions of two gadolinium complexes (Gd-DOTA meglumine and Gd-DTPA meglumine) with hemostatic function have been analyzed using: (1) coagulation reactions (extrinsic and intrinsic pathways and fibrinoformation) and (2) platelet function investigations (aggregation, release of Ca++ and ATP after stimulation with collagen 2.5 micrograms/mL). The data obtained with Gd-DTPA meglumine (Mgl) exhibited a significant increase of the intrinsic coagulation pathway and a delay in fibrinoformation, although there is no alteration of the effect of thrombin on fibrinogen (fibrinopeptid A determinations). Platelet aggregation and release are moderately modified. In contrast, Gd-DOTA Mgl exerts no effect on the coagulation system and only minor effects on platelet functions. It is suggested that at least one mechanism involves the complexation of ionized calcium because Gd-DTPA Mgl and Gd-DOTA Mgl complex, respectively, 45% and 23% of ionized calcium in plasma. However, other mechanisms such as an alteration of fibrin polymerization are not unlikely.

Contrast Media↗
PubMed1988

[A trial use of lenses of human placental collagen in epikeratoplasty procedures].

Epikeratoplasty is a refractive surgery procedure described by Werblin and Kaufman which is simple, effective and reversible. However its development is hampered by the need of human corneas. We evaluated this procedure in rabbits and monkeys using lenticules of human collagen. The collagen is obtained from frozen human placentas, washed and subjected to pepsin digestion; it is contained in the supernatant of centrifugation and can be isolated by a physico-chemical treatment. 15 days after surgery the lenses of 14 rabbits were completely covered with a layer of epithelial cells. 6 months after surgery, the eyes of 14 monkeys were quiet and the lenses were covered with an epithelium made up of 2 to 5 layers of cells. The lens exhibited no inflammatory infiltration and there was no inflammatory reaction around the lens. These studies are still preliminary and longer term tests are necessary. These initial results are very encouraging, prompting us to develop the use of this type of material in refractive surgery.

Animals↗