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Biomedical subjects

S Crisp

Publications and source records attributed to S Crisp.

At least 19 recordsLinked to original sources
PubMed1998

A new enzyme-linked immunosorbent assay to measure anti-endothelial antibodies after cardiac transplantation demonstrates greater inhibition of antibody formation by tacrolimus compared with cyclosporine.

BACKGROUND: Chronic rejection or transplant-associated coronary artery disease (TxCAD) is the most serious complication after human cardiac transplantation. Previous studies, using Western blotting, have shown formation of antibodies against endothelial antigens of 56 and 58 kDa, which are associated with early TxCAD. These antigens were later identified as being vimentin and its breakdown products. The aims of the present study were to devise a robust assay for detection of anti-vimentin antibodies and to compare antibody formation in patients taking different immunosuppressive drugs. METHODS: 106 sequential serum samples from 19 patients taking tacrolimus and 68 sera from 12 patients taking cyclosporine were examined by enzyme-linked immunosorbent assay (ELISA) for anti-vimentin antibodies and Western blotting for reactivity against bands at 56/58 kDa. Serum samples were taken before transplantation and at 1, 3, 6, 9, and 12 months. RESULTS: The vimentin ELISA produced significantly higher numbers of positive episodes per patient (3.92+/-1.08) compared with use of Western blotting (2.54+/-0.52). Serum from patients taking tacrolimus contained significantly less antibodies measured by ELISA (15.8%) or Western blotting (6.5%) than sera from patients taking cyclosporine (46.8% for ELISA; P=0.001 and 21% by Western blotting, P=0.01). Intravascular ultrasound performed on six patients at 12 months showed a correlation between anti-vimentin antibody formation and detection of early coronary disease. CONCLUSIONS: The results demonstrate first, that differences in antibody profiles produced by different immunosuppressive drugs, and second, that detection of anti-vimentin antibodies may be a noninvasive method of detecting disease activity in transplanted vessels.

Antibodies↗
PubMed1996

The medical device directives and their impact on the development and manufacturing of medical implants.

The introduction of a legal framework for the supply of medical implants is discussed with reference to the Active Implantable Medical Device Directive and the Medical Device Directive. The definitions of medical device and manufacturer are discussed. The application of the Directives to device/drug combinations is considered. All implants must meet certain essential requirements to ensure that they do not harm the patient, clinician or any third party. For most implants this will be indicated on the product or its packaging by CE; marking involving an independent organization called a Notified Body; the latter are appointed by the Competent Authority of the Member State. Devices are classified in proportion to the risk associated with them. The steps needed to be taken by manufacturers are outlined and the verification options discussed. The role of standards and the new approach to writing them in Europe is presented. After placing a product on the market, the manufacturer must set up a system of post-market surveillance, including a vigilance procedure, in order to monitor product performance. Individual Member States can exercise the safeguard clause when a product appears to have had the CE marking incorrectly applied.

Equipment Design↗
PubMed1995

A method of two-dimensional mapping of cortical perfusion by cylindrical transformation of HMPAO SPET data.

In order to synthesize three-dimensional information on relative regional blood flow (rCBF) from the cortical grey matter in 99Tcm-hexamethylpropyleneamine oxime (HMPAO) single photon emission tomographic (SPET) images into a single two-dimensional 'cortical peel' (CP) image, we developed a program that performs cylindrical transformation of SPET data. A sub-routine of this program performs measurements of cortex-to-cerebellum rCBF ratios for 54 cortical regions in the CP image. This program was used to establish a normative database derived from 30 young normal control subjects aged 28.7 +/- 6.9 years. The database was then used to express cortex-to-cerebellum rCBF ratios in four colour-coded ranges of normal standard deviation of the mean rCBF ratio across the cortical regions in the CP image. This CP method was implemented for 30 clinical HMPAO SPET studies in patients (n = 30, aged 71.8 +/- 4.2 years) with suspected dementia as well as several studies in aged healthy subjects (n = 8, aged 67 +/- 9.8 years). In 25/30 (83%) patients, all abnormalities seen on the tomographic display were evident on the corresponding CP image. No aged healthy subjects showed abnormalities on either the tomographic display or the corresponding CP image. An advantage of this technique is that the extent and severity of rCBF abnormalities are readily appreciated in one single image. This technique, in conjunction with the conventional multi-slice tomographic display, was a useful tool in identifying various patterns of rCBF abnormalities in the patients with clinically suspected dementia.

Adult↗
PubMed1987

The prevalence of human isolates of Salmonella subspecies II in southern Africa.

The Salmonella Reference Centre in Johannesburg received 14059 strains of human origin between 1979 and 1984. A significant proportion (6.3%) proved to belong to subspecies II. The majority were cultured from faecal material, usually associated with symptoms related to the gastrointestinal tract. They comprised 884 isolates, represented by 203 serotypes, of which 45 were new serotypes. The poor hygienic conditions found in many rural areas, together with possible contamination of food and water by wild animals, may contribute to the greater frequency of human S.II infections and the widespread occurrence of unusual serotypes in man in this geographic region.

Adult↗
PubMed1980

Zinc oxide eugenol cements. V. Instrumental studies of the catalysis and acceleration of the setting reaction.

Zinc oxide eugenol (ZOE) cements were prepared by mixing powders of widely differing reactivity with a variety of liquid formulations. The course of the setting reaction was followed by penetrometer, rheological and electrical techniques. Small amounts of water, organic acids, and the reactivity of water, organic acids, and the reactivity of the zinc oxide all have a profound influence on the setting characteristics of cement pastes.

Acids↗
PubMed1979

The hydration of dental cements.

A study was made of the hydration of dental cements, water being classified as "non-evaporable" and "evaporable". The ratio of these two types of water was found to vary greatly among different cement types, being lesser in zinc oxide and ionic polymer cements and greater in ion-leachable glass and phosphoric acid cements. The cement with the least "non-evaporable" water, i.e., showing least hydration (the zinc polycarboxylate cement), had the lowest strength and modulus and the greatest deformation at failure. A linear relationship was found to exist between strength and the degree of hydration of dental cements. All the cements were found to become more highly hydrated and stronger as they aged.

Absorption↗
PubMed1979

The quantitative measurement of the opacity of aesthetic dental filling materials.

A method is described for measuring the opacity of anesthetic dental filling materials using a goniophotometer. Procedures are given for converting measured opacity values to those referred to a 70% reflectance background (C0.7 values) as required by existing specifications. The conversion is involved, and, since most available white surfaces have reflectance of about 80%, it is recommended that in future specifications opacity be recorded as C0.8 values. Opacity values for 28 materials are reported. It was found that the opacity of dental cement decreases for several days following preparation and that powder/liquid ratio has little effect, while pigmentation has a marked effect on opacity.

Acrylic Resins↗
PubMed1978

A study of temperature changes occurring in setting dental cements.

A study has been made of the rise in temperature associated with the setting of dental cements. Results are discussed in terms of the chemistry of the cement systems and are related to specification testing and clinical usage. Zinc oxide cements evolve more heat than those based on ion-leachable glasses, and phosphate bonded cements evolve more heat than polycarboxylate cements.

Acrylic Resins↗
PubMed1978

Infrared spectroscopic studies on the development of crystallinity in dental zinc phosphate cements.

An infrared spectroscopic study has been made of the development of crystallinity (hopeite) in dental zinc phosphate cements. Crystallization in the bulk of a cement is prevented only by the incorporation, in the liquid, of aluminum which forms complexes with phosphoric acid. The development of surface crystallinity is related to the chemical composition of the cement and the speed of the reaction. No acid phosphates are to be found in the matrix which consists solely of neutral orthophosphates.

Aluminum↗