Biomedical subjects

T A Willis

Publications and source records attributed to T A Willis.

11 recordsLinked to original sources

PubMed2002

Cardioversion by venepuncture in sustained stable supraventricular tachycardia.

Two cases are described of cardioversion from stable supraventricular tachycardia after venepuncture. In both cases usual vagal manoeuvres at home and in the casualty department were unsuccessful. However, attempts to site intravenous cannulas by the attending medical staff terminated his supraventricular tachycardia. Venepuncture is probably the commonest vagal manoeuvre performed in hospital but has not previously been reported as a method of cardioversion.

Adolescent↗

PubMed2001

Biocompatibility of NDGA-polymerized collagen fibers. I. Evaluation of cytotoxicity with tendon fibroblasts in vitro.

The material properties of tendon type I collagen fibers polymerized with nordihydroguaiaretic acid (NDGA) are equivalent to native tendon, suggesting that NDGA crosslinking may provide a viable approach to stabilizing collagenous materials for repairing ruptured, lacerated, or surgically transected fibrous tissues, such as tendon and ligament (Koob & Hernandez, Biomaterials, in press). Using standard cytotoxicity tests, the present study evaluated the biocompatibility of these fibers with cultured bovine tendon fibroblasts. Primary fibroblasts obtained from calf digital extensor tendons were exposed to NDGA, reaction products generated from the polymerization protocol, and the crosslinked fibers. NDGA was cytotoxic to these cells at concentrations above 100 microM. NDGA oxidation products were similarly cytotoxic. At concentrations below 100 microM, fibroblast viability was not affected by NDGA or its oxidation products. At these lower concentrations, fibroblast proliferation was unaffected compared to controls not exposed to NDGA. Fibers crosslinked with NDGA contained no unreacted NDGA, but they did contain soluble reaction products that were cytotoxic to tendon fibroblasts in both the elution and the direct contact tests. Washing the fibers in 70% ethanol and phosphate-buffered saline eliminated cytotoxicity of the fibers. Ethanol simultaneously sterilized the fibers. Tensile tests established that the ethanol/phosphate buffer wash did not adversely affect the material properties of the fibers. The results of these experiments indicate that NDGA-crosslinked fibers can be rendered nontoxic to tendon fibroblasts and may provide a novel approach for producing biologically based, biocompatible, tendon bioprostheses.

Animals↗

PubMed2001

Biocompatibility of NDGA-polymerized collagen fibers. II. Attachment, proliferation, and migration of tendon fibroblasts in vitro.

The material properties of collagen fibers polymerized with nordihydroguaiaretic acid (NDGA) are equivalent to native tendon, suggesting that NDGA crosslinking may provide a viable approach to stabilizing collagenous materials for use in repairing ruptured, lacerated, or surgically transected fibrous tissues, such as tendons and ligaments (Koob & Hernandez, Biomaterials, in press). The present study evaluated the biocompatibility of these fibers with cultured bovine tendon fibroblasts. Fibroblast attachment, migration, and proliferation on NDGA-crosslinked materials were compared to those on prepolymerized type I tendon collagen constructs as well as on tissue-culture-treated plastic. Fibroblast attachment on NDGA-crosslinked collagen fibrils was equivalent to attachment on plates coated with collagen alone. Over a period of 8 days in culture, attached fibroblasts proliferated on NDGA-crosslinked collagen at a rate identical to that of fibroblasts attached to native collagen. In order for the biomaterial effectively to bridge gaps in fibrous tissues, fibroblasts must be able to migrate and replicate on the bridging fiber. Control and crosslinked fibers were inserted in calf tendon explants, with a portion of the fiber extending out of the sectioned end of the tendon. Explants were cultured for 9 weeks, and the number of cells was measured at weekly intervals. Cells appeared on the fibers after 1 week of culture. By 2 weeks, cells had colonized the entire fiber. The number of cells continued to increase throughout the 9 weeks in culture, forming a layer several cells thick. Histologic analysis indicated that the fibroblasts populating the fibers appeared to originate in the epitenon. There was no difference in the rate of fibroblast migration and replication, nor in the ultimate number of colonizing cells, between control collagen fibers and NDGA-crosslinked fibers. NDGA-crosslinked fibers may provide a means of bridging gaps in ruptured, lacerated, or surgically transected tendons by providing a mechanically competent scaffold on which tendon fibroblasts can migrate, attach, and proliferate.

Animals↗

PubMed2000

Cytochrome oxidase deficiency presenting as birth asphyxia.

Hypoxic-ischaemic encephalopathy (HIE) was diagnosed in an infant with acidosis. At 7 weeks of age further investigations revealed abnormal neuroimaging (CT and MRI scans) and a raised plasma and CSF lactate. A skeletal-muscle biopsy at 2 months of age confirmed the diagnosis of cytochrome oxidase deficiency. The course of the patient's disorder has taken that of a static encephalopathy (cerebral palsy). Inborn disorders of the respiratory chain should be considered in the differential diagnosis of HIE.

Acidosis, Lactic↗

PubMed1998