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Biomedical subjects

C Sawyer

Publications and source records attributed to C Sawyer.

14 recordsLinked to original sources
PubMed1998

Two erbB-4 transcripts are expressed in normal breast and in most breast cancers.

ErbB-4 is a recently described member of the epidermal growth factor receptor (EGFR) family which together with erbB-3 acts as a receptor for a group of ligands known as the neuregulins (NRGs) or heregulins (HRGs). Unlike the EGFR and erbB-2 relatively little is known about the expression of erbB-4 in human tumours. Using RT-PCR and Southern blotting analysis we have investigated the expression of erbB-4 mRNA in a range of human tumour cell lines and in normal and malignant breast tissue. Using primers which amplified a 658 base pair (bp) region corresponding to part of the cytoplasmic domain of c-erbB-4 we found the receptor was expressed in some but not all breast and ovarian tumour cell lines and also in a glioma cell line. The highest level of erbB-4 expression was found in the ovarian carcinoma OVCAR-3 and the breast carcinoma T-47D. In all cell lines where the 'full-length' erbB-4 was detected, a second previously undescribed c-erbB-4 sequence was also found as a 610 bp PCR product. The alternative PCR product was identical in sequence to c-erbB-4 except for a deletion of 48 bp which encodes a consensus phosphatidylinositol 3-kinase (PI3K) binding site. This suggested that the two forms of erbB-4 might interact with different intracellular signalling pathways and therefore influence a wider variety of cellular responses to heregulin than previously thought. Expression of both erbB-4 variants was found in 7/7 normal breast tissues but only in 9/12 breast tumours analysed. In line with the terminology of Elenius et al. (1997b) we have designated the two isoforms of the C-terminal transcripts as CT-a (full-length) and CT-b which lacks the P13K binding motif. These results identify suitable cell lines for the further investigation of erbB-4 expression and function and suggest that the role of erbB-4 in breast cancer warrants further investigation with larger numbers of normal and malignant breast tissues.

Alternative Splicing↗
PubMed1997

Methodology for selection of human antibodies to membrane proteins from a phage-display library.

We describe a simple antigen capture technique for the selection of a specific human antibody to p185erbB-2, a transmembrane glycoprotein, from a library of human Fab genes expressed on the surface of bacteriophage. Magnetic beads coated with the rat antibody ICR55 have been used to capture erbB-2 antigen from Triton X-100 extracts of SKOV3 cells. The antigen-coated beads have then been used to select bacteriophage displaying human Fab with affinity for p185erbB-2. After 4 rounds of selection, 65 phage clones were isolated which bound specifically to p185erbB-2 in a capture assay. Nine of the clones which gave the strongest reaction in an ELISA were selected for further development and the Fab genes were subcloned into the expression vector pUC119his6mycXba and electroporated into E. coli TG1. Colonies were grown, induced and the supernatants tested for the presence of secreted human Fab. Supernatants from two of the 9 clones contained human Fab and one of these bound specifically to erbB-2 in a capture assay, stained the membranes of the erbB-2 overexpressing cell lines BT474 and SKBR3 and immunoprecipitated a protein of molecular weight 185 000 kDa from SKOV3 cells. We conclude that a membrane antigen captured by specific monoclonal antibody can be used successfully to select phage displaying human antibodies specific for the antigen.

Animals↗
PubMed1997

A novel culture morphology resulting from applied mechanical strain.

To demonstrate that cells both perceive and respond to external force, a strain/relaxation regimen was applied to normal human fetal and aged dermal fibroblasts cultured as monolayers on flexible membranes. The precisely controlled protocol of stretch (20% elongation of the culture membrane) at 6.67 cycles/min caused a progressive change in the monolayers, such that the original randomly distributed pattern of cells became a symmetric, radial distribution as the cell bodies aligned parallel to the applied force. High cell density interfered with the success of re-alignment in the fetal cell cultures observed, which may reflect a preference in this cell strain for cell-cell over cell-matrix contacts. The chronologically aged cells observed did not demonstrate this feature, aligning efficiently at all seeding densities examined. The role of microfilaments in force perception and transmission was investigated through the addition of cytochalasin D in graded doses. Both intercellular interactions and cytoskeletal integrity mediate the morphological response to mechanical strain.

Actins↗
PubMed1992

Preliminary assessment of the Dex Frame for assisting children with specific learning difficulties.

A device called the Dex Frame has recently been marketed as an aid for children with specific learning difficulties. Using a test of reading speed and a test of reading accuracy we have attempted to evaluate the device. Two groups of children with learning difficulties were used, one having sole use of the device and being allowed to carry it with them and a second group who only used the device when attending for remedial tuition and assessment. The results show that no significant improvement occurred in reading performance of the groups with learning difficulties using the Dex Frame as compared with a control group. The teachers of the groups did, however, feel that on an individual basis some children (< 10%) expressed that they felt more comfortable using the device.

Audiovisual Aids↗
PubMed1991

An inducible gene expression system for Neurospora crassa.

Neurospora crassa acetyl CoA synthetase is highly induced when the growing mycelium is transferred from sucrose- to acetate-based medium. The inducible promoter of this gene has been isolated and used to control the expression of glutamate dehydrogenase. Transformants containing this expression cassette show gdh levels up to 25 times higher than the nontransformed host strain. This expression cassette will form the basis of a system of heterologous gene expression.

Acetate-CoA Ligase↗
PubMed1989

Mild cystic fibrosis in a consanguineous family.

Cystic fibrosis is an autosomal recessive genetic disorder linked to chromosome 7q in all families studied. Expression of the disease varies, but the genetic basis for clinical heterogeneity is unknown. We describe an extended consanguineous family with pulmonary disease and the sweat gland phenotype of cystic fibrosis. In the members of this family, clinical expression of the disease was mild, as manifested by the absence of severe childhood lung disease and increased longevity with better functional status than that expected for age. The degree of pancreatic exocrine insufficiency varied (4/10), but the older patients had normal pancreatic function. The pedigree suggested the likelihood of common ancestry, and eight of the ten affected persons were clearly related. At least three of the family members with the mildest clinical disease had consanguineous parents and may therefore have been homozygous for a variant cystic fibrosis gene. The mild expression of cystic fibrosis in this family provides evidence for a form of cystic fibrosis that is intrinsically less debilitating than the classic form.

Adolescent↗
PubMed1988

Bacterial survival and thermal responses of beef loaf after microwave processing.

The effects of wrapping product in polyvinylidene chloride (PVDC) film, load size (150, 600 and 1200 g loaves), microwave output power (713 +/- 5 W and 356 +/- 3 W at 2450 MHz) and processing time on bacterial survival were evaluated in beef loaf. Specifically the survival of aerobic flora, and inoculated Staphylococcus aureus (ATCC 6538) and Escherichia coli (O157:H7) were assessed. Results showed that beef loaf wrapped in PVDC film had lower levels of survival for aerobic bacteria, S. aureus and E. coli than unwrapped beef loaf. When beef loaf was exposed to the same microwave dose (watts x minutes processed/grams of food), the percent of survival remained the same, regardless of load size or microwave output power. Exposed microwave dose, which correlated highly to percent of bacterial survival (R2 = 0.8-0.83) and end point temperature (R2 = 0.84), is suggested in place of output power, time or temperature as a predictor of microbial quality in foods that have been microwave processed.

Animals↗
PubMed1984

Calculation of carcinogenic potency from long-term animal carcinogenesis experiments.

An index of carcinogenic potency for chemicals tested in chronic animal experiments is described. By analogy with the well-known 'lethal dose 50' (LD50) of quantal bioassay, a 'tumorigenic dose 50' (TD50) may be defined (in the absence both of tumors in the control group and of intercurrent deaths) as that (daily) dose of chemical which gives 50% of the test animals tumors by some fixed age. Tumors in the control (zero-dose) group are handled exactly as for the LD50, and intercurrent deaths are handled by life-table methods. Nonparametric procedures are developed for estimating the TD50 and for constructing confidence intervals. These are based on likelihoods which assume that the tumor hazard is linear in dose.

Aniline Compounds↗
PubMedDate not supplied

Clinical research within the chiropractic profession: status, needs and recommendations.

In the current climate of accountability, health care financing reform and the demand on all health professions for evidence, there is an urgent need to expand clinical research activity within the profession. Those randomized clinical trials that have been reported in the literature have focused primarily on low back and headache pain. Only recently have studies been initiated to investigate the effectiveness of chiropractic interventions for conditions other than back pain. The ability of chiropractic colleges to develop research infrastructures and productive clinical research programs depends on removing or minimizing a number of impediments. A shortage of chiropractic clinicians who have the experience and training to conduct clinical research is compounded by a dependency on tuition revenue, limited external funding and a lack of institutional emphasis on research. The profession generally, and chiropractic colleges specifically, must address the impediments that limit the growth of research capacity. We present several recommendations and the action steps required to achieve specific outcomes.

Academic Medical Centers↗