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Biomedical subjects

E S Wilkins

Publications and source records attributed to E S Wilkins.

9 recordsLinked to original sources
PubMed1991

Tissue reaction to intraperitoneally implanted catheter materials.

The limiting factor that introduces long-term complications of intraperitoneal (i.p.) catheters used, for example, with the Programable Implantable Medication System (PIMS) is the encapsulation of the catheter tip with tissues due to tissue reaction. The objective is the development of new catheters for PIMS or other systems for i.p. insulin delivery that allow continued insulin flow. The study is based on two hypotheses: (1) vascularized tissue will grow into a porous end plug mounted at the catheter tip (100-300 microns pore diameter), with sufficient blood supply to carry the insulin to the circulation; (2) use of a narrow pore diameter (25 microns or less) end plug will prevent tissue ingrowth yet allow insulin flow. The biological response to the following materials, all designed for use in catheters, were studied: polyurethane, segmented polyether-urethane, alumina coated on Teflon (proplast regular and micro-pore), pyrolytic carbon, high density polyethylene, ultra high molecular weight polyethylene, hydroxyapatite, bioglass, and expanded Teflon. Some of these materials also are used for several other applications: vascular grafts, in the cardiovascular system, and for dental, orthopaedic, and other purposes. The shape and size of the end plugs made from each of the materials were as similar as possible to minimize size effects. The test materials were implanted i.p. in 12 dogs for a period of 12 weeks. The cylindrical plugs were typically 1.5-2.5 cm long, with an inside diameter of 0.3 cm, and an outside diameter of 0.6 cm. When the explants were retrieved, thin capsules were observed, of varying thickness and blood supply, surrounding the end of the catheters.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Towards implantable glucose sensors: a review.

The clinical treatment procedures to monitor and control diabetes mellitus include the use of mechanical devices. Of these devices, closed-loop devices are preferred to open loop devices. However, the development of such devices depends to a great extent on the availability of reliable, long-lasting glucose sensors. In this paper, the status of implantable glucose sensors is reviewed. Glucose sensors are classified and discussed under the following headings: Enzyme catalysed electrodes; metal catalysed sensors; affinity sensors; and coated wire sensors. The relative merits of each of the sensor types are presented and experimental results for both in vitro and in vivo studies are summarized.

Biosensing Techniques↗
PubMed1988

The coated wire electrode glucose sensor.

Previous techniques for sensing and measuring glucose are briefly reviewed and compared. The genesis of the glucose coated wire electrode lies in liquid membrane technology, and the basic principle of the electrode is described. The electrode utilizes a quaternary ammonium salt with a sparingly soluble metallic salt of glucose, in a matrix such as poly(vinyl chloride). Fabrication procedures are detailed. Typical sensor responses are illustrated with experimental data. The sensor generally shows a voltage that decreases linearly with increasing glucose concentration over approximately 40 mg/dl to 200 mg/dl. The time response of the sensor is of the order of seconds, and the lifetime observed to date is of the order of several months. Initial studies of mechanism are discussed, using liquid NMR. Preliminary interference effect studies to date are summarized, in which common compounds such as ascorbic acid, uric acid, L-cystine, glycine, and bilirubin were used. Singly these compounds show no significant interference effects.

Barium↗
PubMed1986

Optimization of an implantable coated wire glucose sensor.

An effective glucose sensor should have a short response time and show a strong linear relationship with concentration changes. This paper describes the methods used in an optimization experiment designed to minimize the response time and maximize the coated wire glucose sensor output (voltage or current for glucose concentrations ranging from 40 to 200 mg%). The sensor used for the experiments was a coated wire type. The object was to find the optimum membrane composition performance in relation to different glucose solution concentrations. Four experimental designs were used to analyse the effects of Aliquat: decanol (vol%), glucose salt concentration, and polymer: solvent ratio on the response time and voltage or current differences. Regression models for response time and output were used to establish the optimum experimental conditions. These models were calculated using the statistical analysis system (SAS) general linear model (GLM) procedure. Both polarographic and potentiometric models were used to determine the sensitivity of the sensor. The coated wire sensor developed during the present study had a response time of about one minute, a marked improvement over earlier designs. In addition, it yielded reproducible voltage or current differences with changes in glucose concentration.

Analysis of Variance↗
PubMed1979

Effect of aspirin and vitamins C and E on synovial rheumatoid arthritic and other cells.

Normal and rheumatoid arthritic human synovial cells, normal rat muscle and bone cells, were cultured with combinations of aspirin (acetylsalicytic acid), vitamins C and E. Aspirin reduced percent growth of all cells by about 1/5 relative to controls. High vitamin C eradicated arthritic cells. In combinations, vitamin C was most important in eradicating arthritic cells. A low-vitamin C combination was most effective in reducing arthritic cell populations, while having little effect on normal cells. Vitamin E retarded but did not prevent the action of vitamin C.

Arthritis, Rheumatoid↗
PubMed1979

Rheological properties of skin components under compressive load.

Characterization was made of the mechanical properties under compression of four major skin components (collagen, elastin, chondroitin sulfate, and hyaluronic acid) placed in a gel matrix. Using the previous theoretical work of Bert et al., thickness under compression was related to degree of hydration and the results expressed in terms of pressure vs. hydration. All measurements were conducted at 14 degrees C, 21 degrees C, and 25 degrees C. Application of the findings to a model based on the finite deformation strain-energy theory of Aubert indicate that collagen, elastin, and chondroitin sulfate show a viscoelastic response under compression. On the other hand, hyaluronic acid and gelatin exhibit rubber-like behavior.

Chondroitin↗