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Biomedical subjects

A C Williams

Publications and source records attributed to A C Williams.

At least 145 records · Page 8Linked to original sources
PubMed1994

Loss of APC protein expressed by human colonic epithelial cells and the appearance of a specific low-molecular-weight form is associated with apoptosis in vitro.

APC (adenomatous polyposis coli) protein is differentially expressed in the normal colonic crypt and believed to be involved in colonic cell maturation. In this work we investigated whether expression of the APC protein is associated with cell death in colonic epithelial cells. We have previously reported an in vitro system to study apoptosis. Briefly, cells attached to the flask have a low frequency of apoptosis (1-3%), whereas cells that detach from the flask and float in the medium have a high proportion of apoptotic cells (36-96% depending on the cell line). The full-length 300-kDa or truncated APC protein, normally expressed by the attached cells (detected using the FE9 antibody), was found to be lost in the floating apoptotic cells in 8/11 colon tumour cell lines examined. In addition, the APC antibody FE9 detected a 90-kDa protein in the floating apoptotic cells of all cell lines investigated, which was not present in attached cells. Furthermore, loss of full-length APC and gain of the 90-kDa protein was observed in the apoptotic cells of 2 cell lines derived from other tissues: the SV40-transformed fibroblast cell line CMSV40fib and the lymphoblastoid B-cell line BJA-B. In cells repeatedly frozen and thawed, believed to induce necrotic cell death, full-length or truncated APC was also lost, though a 95-kDa protein distinct from that in apoptotic cells was observed. Specific loss of full-length or truncated APC (resulting in a 90-kDa protein in apoptotic cells but a 95-kDa protein in necrotic cells) is therefore associated with cell death. Our findings suggest a possible role for APC in cell survival.

Adenoma↗
PubMed1994

Pathways of cysteine metabolism in MND/ALS.

Analysis of plasma from MND/ALS patients has shown no significant differences in metabolism of cysteine derivatives, although a sub-set of the population has raised glutamate values. Cysteine dioxygenase was found to have reduced activity in vitro, consistent with previous findings of a high plasma cysteine/sulphate ratio.

Adult↗
PubMed1994

Comparison of Fourier transform Raman spectra of mammalian and reptilian skin.

Human skin offers potential advantages for the administration of therapeutic agents for both local and systemic use. However, in studies of transdermal drug delivery, problems with the supply, storage, and use of human tissue have encouraged workers to seek alternative animal materials to model drug diffusion across human skin. We obtained Fourier transform Raman spectra from mammalian (human and pig) and reptilian (snake) skins, and considered structural dissimilarities in the light of differences observed in the diffusion of drugs across the tissues.

Animals↗
PubMed1994

D-penicillamine metabolism in neurodegenerative diseases: an in vivo/in vitro sulphydryl methylation study.

1. D-Penicillamine (125 mg) was administered orally to control (healthy volunteers), Parkinson's and Motor Neurone Disease patients following an overnight fast. 2. Blood was collected at 08:00 h for the preparation of red blood cell membranes used in the in vitro S-methylation studies. Urine was collected from 08:00 to 16:00 h and analysed for D-penicillamine and its metabolites. 3. Metabolism occurred via S-methylation, N-acetylation and disulphide formation. Both the Parkinson's and Motor Neurone Disease patients excreted significantly higher median levels of S-methyl-D-penicillamine in the urine than the controls (177 and 209% more for the Parkinson's and Motor Neurone Disease patients respectively). 4. The in vitro and in vivo production of S-methyl-D-pencillamine was highly correlated in the control (rs = 0.936), Parkinson's (0.986) and Motor Neurone Disease (0.752) populations.

Adult↗
PubMed1994

Transfection and expression of mutant p53 protein does not alter the in vivo or in vitro growth characteristics of the AA/C1 human adenoma derived cell line, including sensitivity to transforming growth factor-beta 1.

Mutation of the p53 gene is thought to be a late event in human colorectal carcinogenesis, involved in the malignant conversion of the adenoma to the carcinoma. One of the questions that we hoped to address was whether, in vivo, a single mutational event in one p53 gene is sufficient to confer a significant growth advantage on a colonic epithelial cell. Such a growth advantage could result either from an increase in growth rate and/or loss of response to inhibitory growth signals naturally present in the colonic crypt. We therefore introduced the pC53-SCX3 143 (Val-Ala) p53 mutation into a non tumorigenic adenoma derived cell line, AA/C1, which contained a truncating APC mutation, activating K-ras mutation but was wild-type for the p53 protein. High levels of mutant p53 protein were detected in the pC53-SCX3 transfected AA/C1 cell lines but was found not to affect either the in vitro (colony forming efficiency, anchorage independence) or in vivo (tumorigenicity in nude mice) growth, when compared to vector control or the parental AA/C1 cell line. In addition, to test whether the cells become less sensitive to inhibitory growth factors, the response of the cell lines to the naturally occurring growth inhibitor TGF beta was also investigated. Even though TGF beta had previously been implicated in the control of growth of intestinal epithelium, expression of the mutant p53 protein did not affect the sensitivity of the parental AA/C1 cell line to TGF beta. Under the experimental conditions tested expression of the 143 (Val-Ala) p53 protein was unable to affect the in vitro or in vivo growth characteristics of the adenoma derived AA/C1 cell line. When compared to other studies, these results suggest that the genetic background of the individual recipient cell may greatly influence the effect of expression of a particular p53 mutation.

Adenoma↗
PubMed1993

A critical comparison of some Raman spectroscopic techniques for studies of human stratum corneum.

This study evaluates a variety of techniques and sampling conditions for Raman spectroscopic investigations of human stratum corneum. Using a Fourier-transform Raman system and samples of stratum corneum in vitro, we demonstrated minimal inter- and intracadaver variations in molecular vibrations. We have also shown Raman spectroscopy to be relatively insensitive to the hydration state of human stratum corneum, indicating that the technique should be valuable for monitoring the transdermal delivery of drugs from aqueous solutions. The stability of human stratum corneum to near-infrared laser excitation was verified by spectral collection for approximately 1 hr. We have also compared FT-Raman spectra from human stratum corneum in vitro and in vivo. Of the different types of Raman instruments used in this study (visible-light excitation microprobe, visible-light excitation macroscopic sampling, and Fourier-transform Raman), the FT-Raman system provided good-quality spectra with high sample throughput, but systems using visible-light excitation should provide unique information for use in specialist applications.

Epidermis↗
PubMed1993

Evaluation of a cognitive behavioural programme for rehabilitating patients with chronic pain.

The aim of this prospective longitudinal study was to evaluate an inpatient cognitive behavioural pain management programme for patients with chronic pain. A physical and psychological assessment of patients was carried out before and after treatment, and at one and six months follow up. A total of 212 patients with disabling chronic pain of mean duration 10.5 years, for whom no further medical or psychiatric treatment was appropriate or available, were admitted; their mean age was 50 years and 65% were women. The four week programme was delivered by a multidisciplinary team of two psychologists, a physiotherapist, nurse, occupational therapist and anaesthetist. The main components of therapy included: education, teaching behavioural and cognitive skills, a stretch and exercise programme, medication reduction, goal setting and pacing, and relaxation training. Outcome measures assessed quality of life, physical performance (for example walking speed), pain intensity and distress, depression severity and confidence. Assessment immediately after treatment revealed significant improvements on all measures. Improvements were well maintained at six month follow up. Cognitive behavioural treatment can be of value in improving the day-to-day functioning and quality of life of patients with chronic pain for whom conventional medical treatments have apparently failed.

Adult↗
PubMed1993

Biological consequences of the genetic changes which occur during human colorectal carcinogenesis.

Colorectal carcinogenesis is a complex multistage process and occurs through the accumulation of gene mutations in both oncogenes and tumour suppressor genes. Frequent genetic abnormalities include mutation of the familial adenomatous polyposis (APC) and/or the mutated in colorectal cancer (MCC) genes on chromosome 5q21, activation of K-ras and loss of the tumour suppressor genes p53 and DCC (deleted in colorectal cancer). In our laboratory we have developed human in vitro colonic cell culture model systems, to determine the biological consequences of these well characterised genetic changes, and how such changes can uncouple proliferation from differentiation and ultimately lead to the malignant phenotype.

Colorectal Neoplasms↗
PubMed1993

In vitro models of human colorectal cancer.

Epithelial cell lines that differentiate in vitro have been isolated from hereditary and sporadic colorectal adenomas representing different stages in tumour progression, from small adenomas with a low malignant potential to large adenomas with a relatively high malignant potential. The majority of cell cultures derived from small adenomas senesced, whereas the larger adenomas were more likely to give rise to an immortal cell line. Karyotypic analysis has shown that specific abnormalities of chromosomes 1, 6, 7, 13, 14, 17, 18 and 22 occur in these adenoma cell lines. Abnormalities of chromosome 1 have been implicated in tumour progression and the in vitro immortalization of colorectal adenomas. Molecular and cellular changes involving abnormalities of chromosomes 1 and 18, TP53 and ras gene mutations and reduced response to the growth inhibitory effects of TGFB and sodium butyrate, which occur during tumour progression, suggest that the in vitro model has relevance to in vivo carcinogenesis.

Adenoma↗
PubMed1993

Molecular events including p53 and k-ras alterations in the in vitro progression of a human colorectal adenoma cell line to an adenocarcinoma.

The aim of the current study was to identify genetic abnormalities in human colorectal adenoma and carcinoma derived cell lines, and to determine whether the genetic changes which occur in vitro are relevant to the in vivo situation. Loss of 1p(33-35) region was shown to be the most common chromosome 1 abnormality and loss of heterozygosity (LOH) of the DCC gene and/or adjacent sequences was detected in all adenoma derived cells as well as the carcinoma cell lines. The level of p53 protein was also investigated as increased cellular p53 protein had previously been associated with mutation of the p53 gene. A further aim was to investigate genetic changes in our in vitro model of tumour progression, where the adenoma derived PC/AA cell line has previously been converted in vitro to two distinct tumorigenic phenotypes, producing either an adenocarcinoma or a mucinous carcinoma in athymic nude mice. Progression to the adenocarcinoma phenotype was shown to involve a specific chromosome 1 rearrangement, loss of both normal copies of chromosome 18 (although DCC gene sequences were retained), loss of the remaining wild type allele of k-ras resulting in homozygosity for the k-ras codon 12 mutation and increased cellular p53 protein as detected by SDS-PAGE Western blotting. The increase in p53 protein was shown not to be due to the acquisition of a mutation in the p53 gene. Interestingly, progression of the adenoma derived PC/AA cell line to the mucinous malignant phenotype did not involve any of these molecular rearrangements, suggesting that different genetically distinct pathways are involved in colorectal carcinogenesis. These studies show that the genetic changes in our in vitro model of human colorectal tumour progression are similar to those observed in in vivo studies.

Adenocarcinoma↗
PubMed1992

Specific cytogenetic abnormalities and k-ras mutation in two new human colorectal-adenoma-derived cell lines.

Two new human epithelial cell lines from sporadic colorectal adenomas designated S/RR and S/BR are reported. Both cell lines have extended growth capacities in vitro, reaching passages 38 and 40 respectively and show no sign of senescence. S/RR and S/BR cell lines have retained the ability to differentiate in vitro, as shown by mucin production from goblet-like cells. S/BR was derived from a large colonic tubular villous adenoma (3 to 4 cm), whereas S/RR was derived from a small rectal adenoma (< 1 cm), and may represent a relatively early-stage adenoma. The parent S/RR cell line has given rise to a clonogenic variant, designated S/RR/Cl, which also has shown no sign of senescence and has currently reached passage 43. Both the S/BR and the S/RR cell lines had mutations in codon 12 of the K-ras gene, while retaining one normal allele. The presence of this mutation, particularly in the cell line S/RR derived from a small adenoma, is consistent with ras mutation being a relatively early event in colorectal carcinogenesis and is perhaps involved in the ability of the adenoma cells to progress and to give rise to an immortal cell line in vitro. The clonal derivatives of the S/RR cells have an isochromosome 1q and abnormalities of chromosome 13 which include an isochromosome 13q. The S/BR cells have a deletion on the short arm of chromosome 1 and trisomy 7. The common abnormality for S/RR and S/BR cells involves chromosome 1. The involvement of different chromosomes in the 2 cell lines also suggests different pathways for malignant progression of the premalignant adenoma cells.

Adenoma↗