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Biomedical subjects

R E Marchant

Publications and source records attributed to R E Marchant.

47 records · Page 3Linked to original sources
PubMed1987

Vascular graft-associated complement activation and leukocyte adhesion in an artificial circulation.

Complement-associated leukocyte adhesion appears to be a consistent in vitro and in vivo finding for many types of polymers; however, very little work has been done on the interaction of leukocytes with vascular graft materials. An in vitro perfusion system was used to study complement and leukocyte activation associated with the following vascular graft materials when tested with human blood: expanded polytetrafluoroethylene (ePTFE), crimped Dacron Bionit (DB) and preclotted Dacron Bionit. A decrease in the total leukocyte concentration with perfusion time was seen for all materials tested, and paralleled leukocyte adhesion to the graft surface as observed by scanning electron microscopy. The most dramatic decrease in leukocyte concentration was observed for the interaction of heparinized whole blood with Dacron. This was due to a selective decrease in neutrophils and monocytes, and was correlated with an increase in both leukocyte adhesiveness and complement activation, as measured by C5a elevation. Inhibiting complement activation by use of the anticoagulant, sodium citrate, curtailed Dacron-induced leukocyte adhesion. Little leukocyte or complement activation was observed for ePTFE or the silicone rubber control regardless of the anticoagulant used.

Adult↗
PubMed1987

In vivo leucocyte interactions with the NHLBI-DTB primary reference materials: polyethylene and silica-free polydimethylsiloxane.

In vivo leucocyte interactions with the NHLBI-DTB primary reference materials, low density polyethylene (LDPE) and silica-free polydimethylsiloxane (PDMS), were qualitatively and quantitatively characterized using a cage implant system over a 21 d implantation period. Scanning electron microscopy (SEM) and cytochemical staining procedures were utilized to observe the cellular events occurring at the leucocyte/biomaterial interface. The results showed that more cells adhered to the PDMS surface than the LDPE surface at days 4 and 7. The differential analysis revealed that mononuclear cells, presumably macrophages, preferentially adhered to both polymer surfaces. By day 21, there were more very large (greater than 20 nuclei per cell) foreign body giant cells (FBGCs) present on the PDMS surface than the LDPE surface. The phagocytic capabilities of the adhered cells, including the FBGCs, decreased to a greater extent on the PDMS surface, corresponding to the earlier and more extensive spreading of these cells observed in the morphological analysis.

Alkaline Phosphatase↗
PubMed1986

In vivo biocompatibility studies. VII. Inflammatory response to polyethylene and to a cytotoxic polyvinylchloride.

The cellular biocompatibility of low-density polyethylene and a cytotoxic polyvinylchloride were investigated using an in vivo cage implant system. Components of the inflammatory response (white cells, extra-cellular alkaline and acid phosphatase, the complement component C3, and total protein content) were monitored over a 21-day implantation period. Scanning electron microscopy was used to evaluate the morphologic condition of leukocytes adherent to the implanted polymers. Prior to implantation, each polymer was evaluated using an established primary acute toxicity screen. The results showed that the cytotoxic polyvinylchloride stimulated an intense acute phase inflammatory response, and at later observation periods, an intense and increasing chronic inflammatory response. In contrast, the polyethylene promoted relatively small increases in the acute and chronic phases of inflammation; the overall cellular response being essentially resolved by the third week after implantation. The initial toxicity screen of each polymer suggested that the observed differences in inflammation were primarily caused by the release from the polyvinylchloride of the added cytotoxic agent (dioctyltinbisoctylmercaptoacetate).

Acid Phosphatase↗
PubMed1986

The effects of an enhanced inflammatory reaction on the surface properties of cast Biomer.

The ability of a biomaterial to withstand the rigors of the harsh biologic environment is an important consideration when considering a material for long-term biomedical applications. Using a cage implant system, the effects of an intense inflammatory reaction on cast Biomer have been investigated. The inflammatory response to cast Biomer was greatly increased by coimplanting Biomer films with a cytotoxic poly(vinyl chloride) (PVC) in rats for a period of 21 days. Cast Biomer films were characterized by weight, advancing contact angle with water in air, attenuated total reflectance infrared spectroscopy and scanning electron microscopy (SEM). The analyses were performed before any treatment, after autoclaving and sonication, and after 21 days implantation with the cytotoxic (PVC) in rats. The results of the study indicated that cast Biomer does not undergo significant chemical degradation when subjected to the effects of an intense inflammatory reaction for 21 days. Implantation does, however, lead to rearrangement that results in a more polar and hydrophilic surface, suggesting that the polymer adapts to the hydrophilic environment of the inflammatory exudate.

Animals↗
PubMed1983

Type V collagen during granulation tissue development.

The collagen content, as determined by hydroxyproline assay, of experimental granulation tissue in rats was observed to increase rapidly 21 days, and less rapidly to 90 days of tissue development. Resistance of the collagen to pepsin digestion reached a maximum at 21 days, suggesting more extensive or more stable crosslinking at that time. Type V collagen and the expected collagen types I and III were present in pepsin extracts of the granulation tissue as determined by SDS-polyacrylamide gel electrophoresis. Over 3 months of tissue development the relative quantity of type V collagen, as evidenced by changes in the alpha B chain, varied in parallel with the changing vascularity of the tissue, suggesting an association with capillary endothelial cells and angiogenesis.

Animals↗
PubMedDate not supplied

In vivo biocompatibility studies. V. In vivo leukocyte interactions with Biomer.

A cage implant system was utilized to quantitatively and qualitatively characterize in vivo leukocyte interactions with cast Biomer. Scanning electron microscopy (SEM) in conjunction with cytochemical staining procedures were used to investigate the cellular events at the leukocyte/Biomer interface as well as in the inflammatory exudate over a 21-day implantation period. SEM was used to characterize leukocyte morphology on the Biomer surface and the cytochemical stains were used to differentially count leukocytes and to demonstrate intracellular alkaline and acid phosphatase activity. The results showed that the population density of leukocytes on the Biomer surface diminished with implantation time. The population density of multinucleated foreign body giant cells remained constant with time, while the numbers of nuclei per giant cell increased. The differential analysis revealed that macrophages preferentially adhered to the Biomer surface compared to other leukocytes in the exudate. The phagocytic capability of all adherent leukocytes, including giant cells, decreased with time and this corresponded to changes in leukocyte morphology observed with SEM.

Acid Phosphatase↗
PubMedDate not supplied

The biocompatibility of solution cast and acetone-extracted cast Biomer.

The cellular response to films of cast Biomer and acetone-extracted Biomer were investigated over a 21-day implantation period, using an in vivo cage implant system. Film samples were characterized by scanning electron microscopy (SEM), attenuated total reflectance infrared (ATR-IR), electron spectroscopy for chemical analysis (ESCA) and by contact angle measurements before implantation, and by SEM and ESCA after implantation and cleaning. Cellular and protein components of the inflammatory response were analyzed at periodic observation points after implantation. In addition, film samples were retrieved at 4, 7, and 21 days after implantation and analyzed for leukocyte adhesion by light microscopy and SEM. The results demonstrated that cast Biomer contains an extractable fraction, which when removed significantly improves the biocompatibility of the material.

Animals↗
PubMedDate not supplied

Activity of free and immobilized glucose oxidase: an electrochemical study.

The activity of free and immobilized glucose oxidase was determined using a sandwich type thin-layer electrochemical cell. The thin-layer cell consisted of a gold electrode deposited on a glass microscope slide, 165 microns thick Teflon TFE spacers, and a glass cover. Enzyme activity was determined by using cyclic voltammetry to measure the amount of hydrogen peroxide produced in the glucose oxidase catalyzed redox reaction between glucose and oxygen in the thin-layer cell. The specific activity of 13.4 nM glucose oxidase in 0.2 M aqueous sodium phosphate, pH 5.2 at room temperature, was calculated to be 4.34 U/mg GOx. Under the same experimental conditions, qualitative detection of the activity of glucose oxidase covalently immobilized to a thin radiofrequency plasma modified poly(etherurethaneurea) film was demonstrated.

Biosensing Techniques↗
PubMedDate not supplied

Use of Dacron as an alternative carrier for evaluating oxidizing sterilants in the AOAC sporicidal test.

The AOAC sporicidal method (966.04) recommends the use of porcelain penicylinders and black waxed silk sutures as carriers for demonstrating the sporicidal activity of sterilants. However, the silk carriers are not suitable for evaluating the sporicidal efficacy of oxidizing agents, and an inert polyester material (Dacron) is recommended as an alternative. Dacron provides an equivalent microbial and physical challenge to silk. Microbiologically, both materials demonstrated similar HCI resistance, which is required by the AOAC test, as well as equivalent spore loading and spore wash-off. Electron microscopy showed that both materials present the same braided microstructure, providing an equivalent physical challenge to the test sterilant. Dacron was more consistent than silk, and did not require extraction prior to spore loading. The extraction method for black waxed silk was variable and incomplete, which may compromise the activity of oxidizing sterilants and add to method variability. Silk was also structurally altered in the presence of oxidizing sterilants and increased sterilant degradation. Dacron did not affect the sterilant and was inert in the presence of oxidizing agents. Dacron sutures are proposed as inert alternatives to silk for evaluating the sporicidal efficacy of oxidizing agents.

Hydrochloric Acid↗
PubMedDate not supplied

Surface analysis of clinically used expanded PTFE endoscopic tubing treated by the STERIS PROCESS.

The repeated use of semicritical and critical medical instruments in clinical procedures carries an inherent risk of subsequent patient infection, necessitating "high-level" disinfection or sterilization. However, residual bio-organic contamination may hinder the ability of such processes to efficiently destroy infectious microbes. In this study, the inner surfaces of three clinically used expanded polytetrafluoroethylene endoscope tubes treated with glutaraldehyde disinfectant solutions were analyzed to quantify the efficacy of a buffered peracetic acid sterilization procedure, the STERIS PROCESS, in removing this contamination. Samples of the flexible distal biopsy channel of colonoscope tubes were examined before and after a variable number of STERIS processing cycles by three complementary surface characterization techniques: Fourier transform infrared spectroscopy (FTIR), electron spectroscopy for chemical analysis (ESCA), and atomic force microscopy (AFM). Glutaraldehyde fixed protein deposits identified on the tubing surface decreased with increased STERIS cycles. After 20 STERIS cycles, FTIR data indicated that approximately 30% of the contamination was removed, whereas ESCA indicated that 50% of the contamination was removed. AFM images showed considerable variation between control and processed samples, including evidence for cracks in the residual contamination layer. Clinical glutaraldehyde treatment and subsequent device drying are suggested to be two majors factors that limit effective cleaning of endoscopic tubing.

Biocompatible Materials↗