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Biomedical subjects

A Nicol

Publications and source records attributed to A Nicol.

6 recordsLinked to original sources
PubMed1992

Cell adhesion and growth on synthetic elastomeric matrices containing Arg-Gly-Asp-Ser-3.

Synthetic elastomeric polypeptide matrices based on the repeating amino acid sequences of elastin have biophysical and biological properties which are favorable for prosthetic materials. An important requirement envisaged for some applications is the ability to support cell adhesion and growth. The X20-poly-(GVGVP), the gamma-irradiation cross-linked elastomeric matrix based on the repeating pentamer Val-Pro-Gly-Val-Gly, and X20-poly[n(GVGVP), (GRGDSP)] containing the covalently incorporated cell adhesion sequence Arg-Gly-Asp-Ser (RGDS) were synthesized. These matrices were tested for their ability to support the adhesion and growth of bovine aortic endothelial cells and of bovine ligamentum nuchae fibroblasts. Adhesion experiments carried out in albumin-containing media showed that matrices containing 60:1, 40:1, and 20:1 ratios of (GVGVP):(GRGDSP) supported maximal cell attachment, that matrices containing 100:1 exhibited an intermediate level of attachment and that matrices composed of 500:1 and (GVGVP) alone were very poor supports for cell attachment. Serum in the media promoted submaximal cell attachment to X20-poly(GVGVP) but did not permit substantial cell growth. Cell growth was supported by matrices having high ratios of (GRGDSP). Ratios of 60:1, 40:1, and 20:1 supported three population doublings of endothelial cells over 3 days resulting in confluent matrix-adherent monolayers. Ratios of 40:1 and 20:1 similarly supported the growth of fibroblasts.

Amino Acid Sequence↗
PubMed1979

The sorting out of embryonic cells in monolayer, the differential adhesion hypothesis and the non-specificity of cell adhesion.

It has been reported previously that sorting out of chick embryonic liver parenchyma and limb bud mesenchymal cells would take place in monolayer culture. The distribution of cell types obtained (liver formed the internal, discontinuous phase) was interpreted in terms of the differential adhesion hypothesis. It was suggested that, in monolayer, liver cells were more cohesive than limb bud cells. In this paper we set out to extend the previous observations with 2 particular questions in mind: (i) Is sorting out in monolayer a general phenomenon occurring between a wider range of cell types? (ii) Can evidence be provided for or against the interpretation of results in terms of the differential adhesion hypothesis? Sorting-out experiments were conducted on circular hydrophilic islands, on an otherwise hydrophobic substratum. Under these conditions, sorting-out in monolayer was obtained with binary combinations of 4 chick embryonic tissue types: liver parenchyma, limb bud mesenchyme, pigmented epithelium of the eye and corneal epithelium. With every combination but one, the cells of one type surrounded the cells of the other type, generating what we have called a 'circle-within-a-circle' configuration. With the remaining combination, liver parenchyma and corneal epithelium, only localized sorting was obtained. The 'circle-within-a-circle' configuration is consistent with an interpretation in terms of the differential adhesion hypothesis, according to which the distribution of cells is determined by the relative strengths of cohesions between their lateral surfaces. In direct support of this is the finding from plating the different cell types at sub-confluent density on hydrophilic substrata that limb bud is the cell tye having the weakest lateral cohesion in monolayer. Limb bud surrounded the other 3 tissues on hydrophilic island. A hierachy of lateral cohesiveness between the 4 cell types has been constructed. It is unlikely that the results can be explained in terms of specific cohesion. When plated together at subconfluent density, the 3 epithelial cell types aggregate together to form mixed monolayered islands, suggesting that they share common adhesive mechanisms.

Animals↗
PubMed1978

An assessment of the accuracy of modern endoscopic diagnosis of oesophageal stricture.

The results of 135 fibreoptic endoscopic examinations of oesophageal strictures carried out in a district general hospital are reported. The endoscopic diagnosis was correct in 90 per cent, uncertain in 3 per cent and incorrect in 7 per cent of these cases. This study indicates that endoscopic examination should include tissue sampling; this not only allows a precise tissue diagnosis to be made but also is shown to increase the accuracy of diagnosis. Tissue sampling should include cytological as well as histological material. Analysis of cases of stricture correctly diagnosed has shown that target biopsy and brush cytology each makes a significant contribution to diagnosis. The routine collection of cytological specimens in addition to the more commonly obtained histological specimens in addition to the more commonly obtained histological speciments is strongly advocated. The natural history of malignant oesophageal strictures in this study is reviewd. The mean survival in 58 cases was 6.9 months.

Adult↗
PubMed1978

Mutual cohesion and cell sorting-out among four species of cellular slime moulds.

Interspecific cell cohesion among 4 species of cellular slime moulds, Dictyostelium discoideum, D. mucoroides, D. purpureum and Polysphondylium violaceum has been studied. Binary mixtures of aggregation-stage cells of the 4 species were shaken in suspension, one species of each pair being labelled with [3H]thymidine. Cell aggregates were sampled at intervals over 24 h and their composition examined by autoradiography. The following results were obtained: (i) Cells of each species were capable of cohesion with those of the other 3 species. (ii) In general cells of both species in any mixture were present in aggregates after 1 h, but were not localized according to species. (iii) Within 8-h aggregates cells of different species were regionally localized, i.e. sorting-out appeared to have taken place. (iv) 24-h aggregates were more varied: in mixtures of Dictyostelium species, the different species were localized within the aggregates; in mixtures of Dictyostelium species with Polsphondylium, there was a tendency for cells of the different species to become segregated into completely separate aggregates. The significance of these results in relation to both previous descriptive work and recent biochemical studies on the mechanism of slime mould cell cohesion is discussed.

Adhesiveness↗
PubMed1976

Severe pseudomembranous colitis after lincomycin and clindamycin.

Four cases of severe pseudomembranous colitis following the use of lincomycin and clindamycin are described; 2 required emergency total colectomy and 2 died. Cases of such gravity after the use of these drugs have not been previously reported. On hundred and fifty-six orthopaedic cases where clindamycin and lincomycin were used postoperatively are reviewed; 34 had diarrhoea (22 per cent), and 3 of the severe cases occurred in this group. The diagnosis of pseudomembranous colitis may be difficult as the latent period from initiation of drug therapy to commencement of diarrhoea may be as much as 18 days, and that from cessation of drug therapy may be as much as 11 days. The value of early sigmoidoscopy in cases of diarrhoea of obscure aetiology is emphasized, and the characteristic sigmoidoscopic and histological appearances of pseudomembranous colitis are described. As these drugs may produce a lethal condition it is suggested that they should be used with appropriate discretion, especially in the elderly female who appears to be most at risk.

Aged↗