Biomedical subjects

R Guidoin

Publications and source records attributed to R Guidoin.

At least 55 records · Page 3Linked to original sources

PubMed1997

Acute thrombogenicity of intact and injured natural blood conduits versus synthetic conduits: neutrophil, platelet, and fibrin(ogen) adsorption under various shear-rate conditions.

We investigated the acute thrombogenicity of synthetic arterial prostheses compared to biological arterial surfaces in contact with flowing nonanticoagulated blood. The acute events following blood/surface interactions were quantified using 51Cr-platelet deposition, 111In-neutrophil adhesion, and 125I-fibrin(ogen) adsorption on expanded polytetrafluoroethylene (ePTFE) synthetic arterial surfaces (Goretex and Impra) and on intact and injured biological arterial surfaces in ex vivo superfusion flow chambers at low (424/sec) and high (3397/sec) shear rates for 5 min at 37 degrees C. The hematological parameters were determined, and surface analysis was assessed by scanning electron microscopy. At low shear rate, the retention on intact arterial surfaces averaged 3.7 +/- 0.7 x 10(6) platelets/cm2, 26.5 +/- 4.2 x 10(3) neutrophils/cm2, and 10.7 +/- 2.2 cpm of fibrin(ogen)/cm2; retention remained statistically similar at the high shear rate on both Goretex and Impra ePTFE surfaces. In contrast, the deposition of platelets and neutrophils on injured arterial surfaces was significantly higher and increased with shear rate, although the significant increase in fibrin(ogen) adsorption was not influenced by the shear rate. At shear rates characterized by patent and stenosed arteries, ePTFE arterial prostheses demonstrated a low level of thrombogenicity compared to injured arteries. This favorable comparison can be considered as the first requirement for their successful use in arterial substitution.

Adsorption↗

PubMed1997

Multinuclear solid-state NMR spectroscopy of envelopes from virgin and explanted silicone breast prostheses: an exploratory study.

The structure and dynamics of silicone envelopes from virgin and explanted breast prostheses have been studied by 1H, 13C, and 29Si high-resolution solid-state NMR spectroscopy. The results indicate that this combination of techniques can be used to unambiguously identify the presence of methyltrifluoropropylsiloxane units and diphenylsiloxane units at concentrations of about 2.0% and 3.5%, respectively, in some of the envelopes. The presence of about 10% silica also was detected and a trace of lipids was found in the explanted silicone envelopes. We have also measured the proton T2 and T1 relaxation times of the envelopes to characterize the dynamics of the silicone in the envelopes.

Breast Implants↗

PubMed1997

The Dialine II graft: a new collagen-impregnated warp-knitted polyester arterial prosthesis.

The Dialine graft, a new prototype of knitted vascular prosthesis that uses a different brand of polyester fibers as an alternative to Dacron fibers, has been shown to offer excellent in vitro physical performance and in vivo healing. Although it still requires preclotting, the Dialine prosthesis was made impervious by impregnation of bovine type I collagen cross-linked with vapors of formalin. The purpose of the present investigation was to compare the in vitro physical characteristics of the Dialine II graft with those of the collagen-impregnated Hemashield graft. In addition, we studied the healing performance as a thoracoabdominal bypass in dogs for prescheduled periods of implantation ranging from 4 hours to 6 months. In vitro, the bursting strength, resistance to dilatation, and suture retention strength properties of the Dialine II prosthesis were all shown to exceed those of the Hemashield control graft. In the first weeks after implantation, the Dialine II grafts induced a discrete inflammatory response, as shown by the constant leukocyte counts observed both before implantation and when the animals were killed, as well as by the histologic observation of a few inflammatory cells in contact with the collagen. Consequently, the Dialine II grafts showed a slow rate of bioresorption of cross-linked collagen. At 1 month, a thin internal collagenous capsule was present at both anastomoses, laying over the original collagen coating. At 3 and 6 months, areas of thrombotic deposits and endothelialized areas were observed on the luminal surface. Because results of early clinical trials have been highly satisfactory, this prosthesis may be recommended for use without restriction as a medium- and large-diameter blood conduit.

Animals↗

PubMed1997

Shelf-life of bioprosthetic heart valves: a structural and mechanical study.

This study was undertaken to evaluate the influence of storage conditions on the shelf-life of porcine bioprosthetic valves. Fifty-five unimplanted porcine bioprostheses have been evaluated. The valves were stored in 0.5% buffered glutaraldehyde solution for different periods of time (7, 23 and 32 months). Twenty-eight valves were refrigerated while the remaining valves were stored at room temperature. The pH of the glutaraldehyde solution at room temperature decreased with time of storage, while that kept in the refrigerator remained stable over the course of the study. Macroscopic observations showed that the valve tissues kept at room temperature, especially for the periods of 23 and 32 months, became darker and more yellow in colour, whereas the refrigerated specimens exhibited no such changes in appearance. Scanning electron microscopy analysis revealed no noticeable differences on the surfaces of the leaflets stored under different conditions. Mechanical tests, including stress-strain response, stress relaxation and fracture behaviour, were carried out. Analysis of variance showed that the storage temperature, but not the length of storage, had a significant effect on some mechanical properties. The stress relaxation at 1000 s (P = 0.05), the ultimate tensile strength (P = 0.01) and the strain at fracture (P = 0.04) were all higher after storage at room temperature compared to the results after refrigeration. No statistically significant changes in the denaturation temperature of the collagen were observed between the different storage conditions. In conclusion, the storage temperature appears to have some influence on the bioprosthetic tissue. The bioprostheses stored under ambient conditions experience changes which may influence their longterm in vivo performance.

Animals↗

PubMed1997

Are intraaortic balloons suitable for reuse? A survey study of 112 used intraaortic balloons.

To assess the safety of reusing single-use intraaortic balloon devices (IABs), 112 used devices were investigated in terms of physical integrity, gas leakage inspection, mechanical performance, surface chemistry and morphology, and physical stability. These IABs were all used clinically only once, and the duration of the IABs in vivo ranged from 6 to 312 h. Macroscopic examination of the balloons and the outer catheters revealed no obvious change in either shape or color. No discernible abrasions or cracks were observed on the balloons. However, 61% of the balloons were creased, and 40% of the central lumens and 21% of the sheaths showed visible bending flaws. Moreover, 65% of the balloons and 38% of the central lumens were contaminated by visible residual organic debris. The physical integrity of each device was verified in a specially designed leakage-fatigue tester for 72 h. Ninety-seven percent of the devices passed the leakage inspection. Stress-strain testing, differential scanning calorimetry, attenuated total reflection-Fourier transform infrared, and scanning electron microscopy analyses clearly indicated that there were no significant differences in the mechanical properties, bulk material morphology, surface chemistry, and external surface morphology between the used balloons and virgin controls. Although some surface modifications occurred on the internal side of the balloons, the external surfaces of most balloons suffered no trauma. Most of the used IABs examined in this study maintained physical and mechanical properties similar to those of the virgin devices. The chemistry of the balloon material was stable after short-term in vivo use. However, it does not seem possible to establish a rigorous protocol of cleaning, sterilization, and inspection to guarantee a safer reuse of these devices. The presence of residual organic debris that cannot be eliminated results in an imperative preclusion not to reuse the IABs.

Calibration↗

PubMed1997

Importance of platelets in neutrophil adhesion and vasoconstriction after deep carotid arterial injury by angioplasty in pigs.

In previous studies we have shown that platelets can support neutrophil adhesion to the injured vessel wall in vitro and that neutrophils contribute to vascular tone regulation after arterial injury in vivo. In this study, we investigated the implication of platelets in neutrophil adhesion and the vasomotor response to arterial injury in vivo. 111In-labeled neutrophil adhesion and angiographic vasoconstriction were quantified after deep carotid arterial injury by balloon angioplasty in normal (n = 8), thrombocytopenic (n = 7), and aspirin-treated (2 mg/kg IV, n = 7) pigs. Thrombocytopenia was produced by a polyclonal antiplatelet serum that depleted circulating platelet count by 84% without influencing neutrophil count. In the control animals, neutrophil adhesion (x 10(4)/cm2) at the site of deep arterial injury averaged 26.8 +/- 4.0 and decreased significantly to 11.5 +/- 2.3 and 11.2 +/- 2.4 in the thrombocytopenic and aspirin groups, respectively. The degree of vasconstriction was also reduced significantly, from 55.5 +/- 3.8% in the control group to 31.4 +/- 6.2% after platelet depletion and to 23.6 +/- 4.5% in the aspirin-treated group. Neutrophil adhesion to intact noninjured adjacent arterial segments was low in all groups and was not affected by the antiplatelet serum or by aspirin. In in vitro superfusion flow chambers, neutrophil adhesion to damaged arterial segments increased in the presence of platelets in a concentration-dependent manner and was not influenced by the antiplatelet serum. This study demonstrates that platelets can modulate neutrophil adhesion to the deeply injured arterial wall and that both elements may influence the degree of postangioplasty vasoconstriction in vivo.

Angioplasty, Balloon↗

PubMed1997

Arterial wall mechanical characteristics after treatment in collagenase: an in vitro aneurysm model.

OBJECTIVE: To investigate the mechanical characteristics of canine aortas treated with buffered collagenase as a first step in developing an animal model of aortic aneurysm for the validation of stent-grafts. DESIGN: In vitro study of canine aortas. INTERVENTIONS: Canine thoraco-abdominal arteries were divided into the descending thoracic aorta the suprarenal artery and the infrarenal artery; these segments were incubated separately in a buffered collagenase solution for 1 to 6 hours. Some segments were left untreated as controls. OUTCOME MEASURES: Mean arterial wall thickness, measured with Vernier callipers and computerized histomorphometric methods and longitudinal tensile strength of control and treated vessel segments. RESULTS: The arterial wall thickness decreased with incubation time. After 1 hour of incubation the reduction was approximately 15% for the descending thoracic aorta, 16% for the suprarenal artery and 18% for the infrarenal artery. After 6 hours the total reduction in wall thickness was 32%, 41% and 44% respectively for the 3 segments. The tensile strength of the treated arterial segments also decreased with the incubation period. Initially, the infrarenal segment displayed the greatest strength; however, this was reversed as the period of incubation increased. The inelastic limit of the descending thoracic aorta control segment was reached at 100% elongation, whereas that of the suprarenal artery was reached at 80% and that of the infrarenal artery was reached at 60% elongation. All of the arterial segments became weaker as the period of incubation in buffered collagenase increased. CONCLUSION: This in vitro incubation technique successfully altered the structure of the collagen fibre network within the arterial wall. This method may be an option in developing an aneurysm model to test stent-grafts in vivo.

Aneurysm↗

PubMed1996

Selecting valid in vitro biocompatibility tests that predict the in vivo healing response of synthetic vascular prostheses.

We have investigated the usefulness of six in vitro biocompatibility tests in predicting the healing performance of polyester vascular prostheses as observed in previous canine in vivo trials. Vascular grafts were evaluated by using (i) a direct contact (DC) assay, (ii) an extract dilution (ED) assay on murine fibroblast cells, (iii) a DC assay on endothelial cells, (iv) a complement activation study, (v) a leucocyte activation study of CD18 integrin subunit expression on human polymorphonuclear cells (PMNs) and (vi) interleukin-2 receptor expression on lymphocytes. Uncleaned polyester grafts had previously been associated with poor healing and gelatin-impregnated polyester grafts with delayed but satisfactory healing, whereas commercially cleaned polyester grafts had demonstrated excellent healing. Lightweight and heavyweight knitted and woven polyester grafts supplied specifically for this project were studied, each with a different surface condition, i.e. commercially available (CP), uncleaned (UP) and impregnated with gelatin (GP). The UP grafts induced fibroblast cytotoxicity according to the ED assay, poor migration and viability of endothelial cells, and an elevated expression of CD18 and interleukin-2 receptor on PMNs and lymphocytes, respectively. In contrast, the CP grafts promoted good endothelial cell growth, no evidence of cytotoxicity and a weaker cell activation, and the GP grafts were found to be non-cytotoxic, to exhibit a good cellular response and to moderate cell activation. The complement activation assay and the DC assay on fibroblasts were found to be less useful and less discriminating. From this, it is concluded that the two cell activation measurements, the DC assay on endothelial cells and ED assay on fibroblasts, are useful in predicting the in vivo healing response of arterial polyester substitutes.

Analysis of Variance↗

PubMed1996

Chemical and morphological analysis of explanted polyurethane vascular prostheses: the challenge of removing fixed adhering tissue.

During in vivo experiments to evaluate the biocompatibility and biostability of alternative biomaterials, the ideal protocol for the handling and preservation of the explanted material is often compromised in order to meet the needs of both the pathologist and the materials scientist. Explants surrounded by tissue are often fixed in formalin or glutaraldehyde to facilitate later pathological and histological analysis, but the subsequent removal of such fixed tissue from thermally sensitive and less chemically stable polymers, such as polyurethanes, poses major problems for the materials scientist, who does not wish to modify the chemical, physical or morphological characteristics of the underlying biomaterial. The present study has attempted to find a solution to this problem by exposing virgin specimens of the microporous polyurethane Vascugraft vascular prosthesis to six different cleaning conditions, all known to be effective in removing fixed tissue. These conditions included the use of 20% aqueous potassium hydroxide solution for 48 h at room temperature, 5% sodium bicarbonate solution for 5 min at the boil, and 9, 10, 11 and 12N hydrochloric acid for 48 h at room temperature. The appearance and chemical properties of the virgin and treated specimens were compared using electron spectroscopy for chemical analysis, Fourier transform infrared spectroscopy, gel permeation chromatography for molecular weight and differential scanning calorimetry techniques. The use of temperatures close to the boil resulted in the formation of a translucent, rubbery material with gross changes in the microporous and microfibrous structure. The strongly acidic and alkaline conditions caused a loss in the surface carbonate group content. In addition, 12N hydrochloric acid reduced the molecular weight and urethane content. Consequently, 9N hydrochloric acid is recommended as the cleaning agent of choice for removing fixed tissue from this type of microporous polyurethane. Control experiments on virgin material should also be included in any cleaning protocol.

Adhesiveness↗

PubMed1996

An albumin-coated polyester arterial graft: in vivo assessment of biocompatibility and healing characteristics.

The albumin-coated vascular graft (ACG) and its uncoated polyester substrate, the Vascular II (V-II), were evaluated in terms of biocompatibility and biofunctionality using two in vivo animal studies. Biocompatibility and immunoreactivity were assessed by implanting intraperitoneally in the rat small segments of the ACG and the V-II graft and harvesting them with their surrounding tissue 3d, 1, 2 and 4 weeks later. Cytofluorometric determination of total T cells (CD3), the ratio of CD4/CD8 subsets and the percentage of IL-2 receptor-positive T cells in the peripheral blood has revealed that no significant difference in any of the T cell populations was found between the ACG and the V-II graft. The cellular reactivity of the ACG in terms of acid phosphatase activity at the implant side was significantly greater at 3 d but not at longer periods. Biofunctionality was evaluated by implanting both grafts as a thoracoabdominal vascular bypass in dogs for 11 different periods ranging from 4 h to 6 months. The rate of albumin resorption was such that traces were still present at 1 month, but no longer observable at 2 months. Tissue incorporation into the graft wall was earlier for the V-II (2 weeks) than for the ACG (4 weeks), which showed complete encapsulation, tissue incorporation and endothelialization after 2 months in vivo. Only small differences were observed between both grafts in terms of platelet and fibrin uptake on the luminal surface. The prostacyclin/thromboxane A2 ratio increased to a level higher that 1.0 aorta within 1 month for the V-II and 4 months for the ACG. In conclusion, the Bard ACG has demonstrated excellent biocompatibility in terms of blood T cell behaviour and acid phosphatase activity at the implant site. Finally, its healing response is equivalent to that of the uncoated Dacron prosthesis once the albumin coating has been resorbed.

Acid Phosphatase↗

PubMed1996

Efficiency of an external support to reduce lipid infiltration into venous grafts: in vitro evaluation.

Excessive distension of venous grafts due to arterial pressure enhances the convective water transport (filtration flow) through the vessel wall, and thus might affect the infiltration of macromolecules such as lipoproteins. In this paired experimental study, filtration velocities were measured at 100 mm Hg for canine jugular veins with or without external supports of expanded polytetrafluoroethylene (ePTFE) arterial prostheses. In addition, to assess the effect of filtration velocity on lipid infiltration or uptake, canine jugular veins were wrapped over half of their lengths with ePTFE arterial prostheses and perfused with dog serum containing 3H-cholesterol at a pressure of 100 mm Hg. At 100 mm Hg, the average filtration velocity of the wrapped jugular veins was 7.9 +/- 1.3 x 10(-6) cm/s whereas the average filtration velocity of the unwrapped veins was 27.3 +/- 2.7 x 10(-6) cm/s (p < 0.005). Moreover, the unwrapped veins had a significantly higher uptake rate of labeled cholesterol than the wrapped veins (10.9 +/- 7.3 x 10(-4) cm/h and 5.0 +/- 1.6 x 10(-4) cm/h, respectively, p < 0.005). In conclusion, under arterial pressure, veins experience excessive distention, which leads to significant increases in both filtration flow and cholesterol uptake. An external wrap or support of ePTFE material protects veins from excessive distension and thus may prevent atherosclerosis in venous grafts by reducing cholesterol uptake.

Animals↗

PubMed1996

Theoretical modelling of the release rate of low-density lipoproteins and their breakdown products at arterial stenoses.

Arterial stenoses and luminal-surface irregularities at anastomoses cause blood-flow disturbances with slow recirculation. The authors created a computer simulation to study the rates of the release into blood of atherogenic substances such as low-density lipoproteins and their breakdown products from within the arterial walls at stenoses. Finite-difference methods were used to solve the Navier-Stokes equations (in the form of stream function and vorticity function) and the steady-state mass transfer equation for bell-shaped stenoses with two different degrees of constriction. This simulation indicated that the efflux rates of lipids and their breakdown products from the vessel walls were suppressed in the region of disturbed flow, with slow circulation distal to stenoses. The lowest efflux rate was found at the point of flow separation, and this rate was much lower than rates in regions of undisturbed flow. Therefore, this mathematical model predicts that locally disturbed blood flow at arterial stenoses and arterial anastomoses is responsible for two distinct phenomena: first, it provides favourable conditions for lipid infiltration into vessel walls; and, second, it impairs the release into the blood of atherogenic substances accumulated in the vessel wall. Such mass transfer abnormalities may account for atherogenesis and the late failures of arterial reconstructions at these sites.

Animals↗

PubMed1995

Evaluating the Dialine vascular prosthesis knitted from an alternative source of polyester yarns.

The sudden and unilateral decision by E. I. DuPont de Nemours & Co., Inc., to withdraw its polymers for use in implantable devices has presented the medical device industry with an immediate and serious challenge to find alternative sources of biomaterials. In France, the company Cardial S.A. has already taken steps to find an alternative polyester yarn to replace Dacron by developing a new arterial prosthesis knitted from polyester yarns supplied by Rhône-Poulenc Fibres. This article describes an in vitro and in vivo study of this French device, called the Dialine prosthesis, with a view to determining its relative performance compared to current American and British prostheses, which rely on DuPont's Dacron yarn. In addition to analyses of the morphology and textile structure, and measurements of its physical and chemical properties, the Dialine graft was implanted as a thoracoabdominal bypass in dogs for periods ranging from 4 h to 6 months. In addition to our pathologic and histologic observations, we cleaned and evaluated the explanted prostheses for in vivo changes in dimensions, strength, and crystalline microstructure. The Dialine graft was found to differ structurally from other polyester prostheses because it is warp-knitted from a mixture of flat and texturized yarns with finer filaments. Its denser structure has a lower water permeability, greater flexibility and ease of handling, satisfactory strength, and dimensional stability, and it presents different textures on its luminal and external surfaces. The in vivo trial demonstrated that it has excellent biocompatibility and biostability over 6 months. With no thrombi observed on the luminal surface after 3 months, it has a faster rate of healing, generates compact external and internal capsules with a thinner neointima, and has an overall milder inflammatory response than is normally observed with Dacron-based prostheses.

Angiography↗

PubMed1995

Polyvinylidene fluoride (PVDF) as a biomaterial: from polymeric raw material to monofilament vascular suture.

This study identified the effects of various manufacturing processes on the crystalline microstructure, mechanical properties, and biocompatibility of a polyvinylidene fluoride (PVDF) suture. To achieve this, changes in the crystalline microstructure and the tensile behavior of PVDF monofilaments were monitored in vitro after different thermal processing, coloration, and sterilization treatments. In addition, the in vivo biocompatibility of the manufactured and sterilized PVDF suture was assessed by using it to anastomose a preclotted polyester vascular prosthesis as a thoracoabdominal bypass in a series of dogs. The tissue response was followed by histologic and scanning electron microscopy over implantation periods ranging from 4 h to 6 months. Differential scanning calorimetry and infrared spectroscopy (FTIR-ATR) showed that thermal processing and the addition of a coloring agent had a direct effect on modifying the crystalline microstructure and hence changing the mechanical properties. For example, thermal processing converted some of the alpha phase into the beta and gamma polymorphs, whereas coloration led only to a major increase in the beta-to-alpha ratio. The tensile properties were found to be optimized when the relative proportion of the beta and gamma phases combined compared to the alpha form gave rise to an FTIR A509/A532 absorption ratio between 4.0 and 4.5. Sterilization was found to cause some modifications to the crystalline microstructure near the surface of the monofilaments, but it did not change their mechanical properties. Pathologic examination of the anastomotic regions after different periods of implantation revealed a minimal cellular response, with no mineralization, intimal hyperplasia, or excessive fibrous tissue reaction. This good biocompatibility, together with other desirable characteristics such as ease of manipulation and satisfactory mechanical strength, makes PVDF an attractive alternative monofilament suture material for cardiovascular surgery.

Animals↗

PubMed1995

High resolution solid-state 29Si NMR spectroscopy of silicone gels used to fill breast prostheses.

We have used 29Si solid-state nuclear magnetic resonance (NMR) spectroscopy to study the chemical structure of the silicone gels in virgin and explanted breast prostheses. Despite evidences of alteration in the morphological appearance of the silicone gel inside the breast prosthesis, our results do not reveal changes in the chemical nature and structure of the silicone gels after implantation. In addition to the main 29Si resonance peak at -22.26 ppm that corresponds to the resonance frequency of the D repeat unit of the polysiloxane chains, the high sensitivity of our NMR technique allows the detection of very low concentrations of silicone compounds. Within our experimental detection limit of 0.2%, no signal between -90 ppm and -150 ppm are observed. This indicates that no silica products are present inside the gel of the prostheses. Furthermore, our 29Si NMR spectra indicate differences in the chemical compositions of the silicone gels from different manufacturers.

Breast Implants↗

PubMed1995

Increase of neutrophil adhesion and vasoconstriction with platelet deposition after deep arterial injury by angioplasty.

Physiopathologic events after arterial injury are largely influenced by blood element reactions with the injured surface. To determine acute arterial reactivity to injury, simultaneous chromium 51-labeled platelet deposition and indium 111-labeled neutrophil adhesion were quantified at the site of different degrees of carotid arterial injury by balloon dilatation in 21 normal pigs. The degree of vasoconstriction distally to the dilated areas was also quantified angiographically. Arteries were classified histologically as (1) uninjured with intact endothelium; (2) mildly injured with endothelial desquamation; or (3) deeply injured with lesions extending beyond internal elastic lamina, exposing the media. We found that, compared to mild injury, deep injury was associated with greater platelet deposition (38.2 +/- 5.7 x 10(6)/cm2 vs 7.8 +/- 0.9 x 10(6)/cm2; p < 0.05), neutrophil adhesion (30.6 +/- 4.1 x 10(4)/cm2 vs 10.2 +/- 2.9 x 10(4)/cm2; p < 0.05), and vasoconstrictive response (45.5% +/- 3.2% vs 26.7% +/- 2.8%; p < 0.05). Although distally to both types of injuries, noninjured arterial segments with intact endothelium were thromboresistant to platelet deposition, neutrophil adhesion to intact endothelium was much higher after deep injury (2.2 +/- 0.4 x 10(4)/cm2) compared to mild injury (0.36 +/- 0.1 x 10(4)/cm2; p < 0.05). Like platelet deposition, neutrophil adhesion is influenced by the severity of arterial injury; both may therefore be implicated in thrombogenesis and vascular responsiveness after arterial injury in vivo.

Angioplasty, Balloon↗

PubMed1995

Carbodiimide cross-linked gelatin: a new coating for porous polyester arterial prostheses.

The performance of a polyester arterial prosthesis impregnated with gelatin and cross-linked with carbodiimide (Uni-graft) was compared with its porous parent graft (Protegraft) using a canine thoraco-abdominal bypass model. The grafts were investigated in terms of their handling characteristics, imperviousness at implantation, surface thrombogenicity and healing behaviour. Prostheses 30 cm in length were implanted for the following periods: 4, 24 and 48 h, 1, 2 and 4 weeks, 2, 3, 4, 5 and 6 months. Both types of graft had good handling characteristics. The ready-to-use impregnated graft provided satisfactory haemostasis at implantation with no blood permeating through the wall after flow was restored. Both grafts exhibited low surface thrombogenicity, as determined by the uptake of labelled fibrin and platelets, and the healing sequence of the impregnated graft after resorption of the gelatin was equivalent to that of the preclotted control. Biodegradation of the gelatin was complete within 1 month of implantation with the subsequent development of a collagenous internal capsule at both anastomoses. Endothelial cells were observed between 4 and 6 months, but were confined to small islets distributed along the luminal surface. The prostacyclin/thromboxane A2 (PGI2/TXA2) ratio, which gives an indication of the level of endothelial cell activity, was greater than 1.0 after 1 week of implantation for the control graft. For the impregnated graft it reached 1.0 only after 3 months of implantation, but remained above 1.0 for periods of up to 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1995

Removing fresh tissue from explanted polyurethane prostheses: which approach facilitates physico-chemical analysis?

Chemical, physical and structural analyses of polymers from explanted vascular prostheses are frequently jeopardized because of incomplete removal of the encroaching host tissue. In this study, microporous polyurethane arterial prostheses implanted as a canine thoraco-abdominal bypass were explanted after 1 and 12 months and were cleaned without fixation using four different digesting enzyme treatments, including collagenase, pancreatin and trypsin alone and collagenase and pancreatin in series, followed by washing in a solution of Triton X-100 detergent. By following this approach all the fresh tissue attached to the external and internal walls of the prostheses was removed with minimal damage to the underlying synthetic polymer. The morphology of the explanted and cleaned polyurethane prostheses could be obtained readily by light and scanning electron microscopy. Surface microporous features and the presence of polyurethane microfibres that had experienced in vivo biodegradation could therefore be identified easily. The surface and bulk physico-chemical properties of the polyurethane polymer were determined by electron spectroscopy for chemical analysis, attenuated total reflectance-Fourier transform infrared spectroscopy and differential scanning calorimetry. It was found that the most successful approach for removing fresh tissue and exposing a clean and uncontaminated polyurethane surface was to incubate the explanted samples first in collagenase followed by digestion in pancreatin. This particular cleaning technique has proved valuable in enabling us to monitor small in vivo changes in the surface chemistry and in the bulk microphase segmented structure of polyurethane biomaterials.

Animals↗