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Biomedical subjects

E Shors

Publications and source records attributed to E Shors.

15 recordsLinked to original sources
PubMed1989

Patency and durability of small diameter silicone rubber vascular prostheses.

This study evaluated the long-term patency and durability of 6 mm internal diameter (ID), 18-30 micron pore size replamineform silicone rubber vascular prostheses as canine aortic interposition and arteriovenous (A-V) grafts. Six prostheses (6 mm ID x 8 cm length) were evaluated as aortic grafts for 24 to 30 months, and 10 prostheses (6 mm ID x 8-10 cm length) were studied as A-V grafts from 2 weeks to 10 months. Three of the A-V prostheses were punctured for sham dialysis once or twice/week with two 16 gauge needles (total of approximately 50 needle punctures). The porous wall of the silicone rubber prostheses was incorporated with capillaries and fibrohistiocytic cellular elements from 2 weeks of implantation. This cellular incorporation remained constant up to 2 1/2 years. Needle puncture of the arteriovenous grafts over a 3 to 5 month period produced no complications such as thrombosis, perigraft hematoma formation or bleeding through the puncture site. The silicone rubber sealed the holes with no evidence of tearing. Explanted prostheses had no evidence of enlargement or false aneurysm formation. This study supports our hypothesis that Replamineform silicone rubber prostheses are hemocompatable and demonstrate long-term durability for dialysis access. Clinical evaluation of this graft is planned in the near future.

Animals↗
PubMed1983

Effect of healing on small internal diameter arterial graft compliance.

Porosity is an essential component for long term function of small internal diameter synthetic vascular prostheses. Theoretically, porosity is required for healing by providing a scaffold for ingrowth of periprosthetic tissues. Porosity may be required for transfer of fluids and ions in prostheses even if tissue ingrowth does not occur. Increased permeability of vascular grafts has been shown to enhance tissue incorporation. Implants with pore sizes greater than 10 microns but less than 45 microns become ingrown with fibrohistiocytic tissue and capillaries. Implants with pore sizes greater than 45 microns are ingrown with organized fibrous tissue and minimal histiocytic response. The phenomenon of differential ingrowth may have important functional significance. Prostheses which heal with organized fibrous tissue have the potential for long term contracture, strangulation of vascularity and calcification. Fibrohistiocytic tissue has low mechanical strength and does not appear to contract or calcify. Elastomeric microporous vascular prostheses which are minimally ingrown or ingrown with fibrohistiocytic tissue maintain compliance after months of implantation. This study was designated to determine the effects of healing on the compliance of small internal diameter vascular replacements and to correlate the compliance to patency rates.

Animals↗
PubMed1983

Thrombogenicity and the interaction of proteins, platelets and white cells.

Radioactive labeled protein and platelet studies suggest that an ideal vascular surface absorbs albumin and prevents platelet adherence and aggregation. This study examines the interaction of serum and plasma proteins, white cells, and platelets in the thrombotic response to small internal diameter vascular prostheses. Thirty-seven replamineform silicone rubber vascular prostheses, 4 mm internal diameter and 6 cm length, had 5% aspirin and 5% theophylline by weight dispersed in a luminal coating (D); the remaining 37 control (C) prostheses had an identical silicone rubber coating without drugs. Scanning electron and darkfield microscopy confirmed similar surface topography in C and D grafts. One C and one D graft were studied in parallel using a modified canine arteriovenous fistula. Consistently, D prosthesis had increased bleeding through the graft wall. The 7 serum and 8 plasma experiments demonstrated greater accumulation on the D prostheses, the greatest deposition occurring within the first 30 minutes. In 8 platelet experiments, D grafts accumulated more radioactivity at both the 5 and 30 minute intervals. Six mononuclear and 8 PMN experiments had less accumulation on the D grafts at 15 minutes and no consistent difference at 60 minutes. Elution of C and D Grafts demonstrated significant drug levels in only the D grafts at the beginning of the experiments and after 15 minutes of exposure of blood. We conclude: (1) aspirin and theophylline have an effect on the initial interaction of plasma proteins, platelets and white cells in the thrombogenic response, (2) the effect diminishes as time released drug levels decrease.

Animals↗
PubMed1983

Neovascularity of a tracheal prosthesis/tissue complex.

Permanent bioincorporation of a microporous tracheal prosthesis will require a stable blood supply to connective tissue supporting an epithelial surface. In experience with over 80 tracheal implants in dogs, we have observed that end-on ingrowth and epithelialization does not occur in the absence of lateral ingrowth, epithelialization is marked by the appearance of a subepithelial network of vessels, and this process must be well advanced by 6 to 8 weeks for long-term stability. These observations were extended by using microangiography to delineate the blood supply of the prosthesis/tissue complex. Six implants of bioelectric polyurethane with 10% gentamicin (3 cm length, 2 cm diameter, 1 to 1.25 mm wall thickness, 60 to 120 mu micropore diameter) were interposed in the dog thoracic trachea and wrapped with an omental pedicle. The aorta was perfused with a barium suspension at elective sacrifice between 10 weeks and 21 months. Radiographs of specimens were correlated with bronchoscopic, gross, and histopathological findings. Neovascularity of the prosthesis/tissue complex can be described in three categories: outer capsule, prosthetic wall, and inner lining. Outer capsule vessels were oriented circumferentially immediately adjacent to the prosthetic wall. They resembled arteries up to 75 mu diameter on microscopy and appeared to develop from the omentum with connections developing to the bronchial circulation. Prosthetic wall vessels up to 75 mu with thin muscular walls were noted to traverse the porous prosthetic wall. The inner lining had a network of subepithelial vessels that connected to the lamina propria vasculature of the native trachea across the anastomoses with vessels up to 120 mu in diameter. We conclude that the omentum provides an immediate blood supply and a base for early connective tissue ingrowth. Epithelialization occurs as early as 3 weeks on the favorable bed, accompanied by vascular connections to the existing lamina propria tracheal vessels. This dual organization of blood supply with connections across the prosthetic wall is probably important to long-term stability of healing.

Animals↗
PubMed1981

Effect of surface porosity on early thrombogenicity using vascular grafts with two surfaces in sequence.

This experiment addresses the multifactorial dilemma of defining the ideal performance parameters of small internal diameter vascular grafts. We found silicone rubber vascular grafts with smooth surfaces remain acutely free of thrombotic deposits whereas grafts with rough surfaces promote a dispersed thrombus formation. This study also questions the concept that the thrombogenicity of one surface determines the thrombotic response of different and adjacent flow surfaces in the blood flow. Here the distinction between response to each surface was abruptly delineated and equal in intensity regardless of proximal or distal positioning. By studying the 2 surfaces in sequence, surface properties were evaluated using the minimal number of experiments by mitigating the effects of interanimal variability. This is an important consideration in an era of "cost accountability".

Animals↗
PubMed1977

Techniques for localized injections and topical applications of carcinogens at specific endobronchial sites in dogs.

We seek to create a canine lung cancer model with sharply localized carcinomas analogous to human lung cancers. Toward this goal techniques for recurrent endobronchial transbronchoscopic submucosal injections and topical applications of the carcinogens 3,4-benzo(a)pyrene and N-methyl-nitrosourea have been developed. After 2 years of experience with 2,868 endoscopic manipulations and varying dosage schedules in 59 dogs, safe effective techniques for recurrently delivering carcinogens and sequential biopsies of the same sites have evolved. Predominantly during the first year of experience, 10 dogs died as a consequence of technical problems such as exsanguinations after 1 mm. punch biopsies. There were also 39 instances of nonlethal technical complications of endoscopy in the face of immunosuppression and local irritation caused by the carcinogens. By the techniques and dosage schedules described, it has now become possible reliably and safely to create impressive localized bronchial preneoplasia with squamous metaplasia and atypia among the prominent features.

Administration, Topical↗
PubMedDate not supplied

Maintenance of compliance in a small diameter arterial prosthesis.

This study demonstrates that 20 to 30 microns porous, Replamineform silicone rubber prostheses remain isocompliant with adjacent arterial segments up to 8 months following implantation. This finding contrasts with the results of currently available prostheses, including autologous vein, which rapidly become minimally compliant. We conclude that this vascular construction is stable over the long-term following implantation and may improve the success of small internal diameter arterial reconstruction by eliminating failures caused by intimal hyperplasia.

Animals↗