Search PubMed⌕ Search

Biomedical subjects

J Heighway

Publications and source records attributed to J Heighway.

At least 55 records · Page 3Linked to original sources
PubMed1991

Transcription of a stem/loop region of a tumour-amplified sequence induces bacterial aggregation.

A sequence of human DNA, amplified in a lung tumour, was shown to induce expression-dependent effects on Escherichia coli phenotype. Previous studies have demonstrated the induction of abnormal plasmid supercoiling and bacterial aggregation in host strains harbouring various constructs encoding this region. Subcloning identified a short stretch of 50 bp crucial for these effects. This study details further characterization of the active sequence. Computer analysis of the region predicted the formation of a stem/loop structure in transcribed RNA. Transcription, in the absence of translation, of a 22 bp sequence comprising this structure was sufficient to induce bacterial aggregation. Site-directed and random mutagenesis of the sub-region were carried out in order to identify critical factors in the induction of this phenotypic shift. It was found that changes in the loop sequence modulated activity, and mutations increasing predicted stem stability produced more active constructs. The wild-type sequence induced high level aggregation in only a limited number of strains but using the mutagenesis data, a sequence was synthesized that induced high level aggregation in most E. coli strains tested.

Bacterial Adhesion↗
PubMed1990

N-myc gene is amplified in alveolar rhabdomyosarcomas (RMS) but not in embryonal RMS.

DNA from 13 (6 alveolar and 7 embryonal) childhood rhabdomyosarcomas (RMS) was examined to determine the incidence and prognostic relevance of N- and c-myc genes. Southern analysis showed 5- to 20-fold amplification of N-myc gene in 4 of 6 alveolar but in none of 7 embryonal RMS (p less than 0.04; Fisher's exact test). The number of children who died with multiple- and single-copy N-myc gene was 4/4 and 5/9 respectively (p greater than 0.05; Chi-squared test). There was no statistically significant correlation between N-myc amplification and age, gender, site, stage or survival time. There was no amplification or gross rearrangement of c-myc in any of the 13 RMS.

Blotting, Southern↗
PubMed1989

Unexpected effects on bacterial phenotype induced by expression of a tumour-amplified human sequence.

An amplified human sequence was isolated from a metastatic human lung carcinoma. A fragment of this sequence situated behind the lac promoter of pUC19 appeared to affect plasmid DNA supercoiling in certain E. coli strains. Subclones were constructed to identify the smallest region of the human insert that conferred the activity and a 369 bp fragment was identified, expression of which appeared to result in abnormal plasmid supercoiling. In order to study this phenotype, various constructs were introduced into the minicell-producing strain E. coli DS410 and an unexpected effect was observed. The bacteria, after normal early growth, clumped together in late log phase, leaving virtually clear medium. Other E. coli strains were also shown to be affected to a lesser degree. The sequence producing this effect was also mapped to the 369 bp fragment and a critical region of approximately 50 bp was identified using site-directed in vitro mutagenesis and Bal31 deletion analysis. The plasmid encoded product responsible for this phenotypic alteration did not appear to be a peptide and clumping was observed when the human DNA was expressed from several bacterial promoters. It would seem likely that this sequence encodes a biologically active RNA which affects gene expression in the host cell.

Carcinoma, Squamous Cell↗
PubMed1987

A cell line from Wilms' tumour with deletion in short arm of chromosome II.

A cell line (T3/73) from a Wilms' tumour has been established from a 9 month-old boy with aniridia. The tumour was removed in 1973. On histological examination a diagnosis of Wilms' tumour was made which showed undifferentiated areas, marked tubule formation and abundant striped muscle fibres. The tumour cells, which are fusiform, grew rapidly in culture without the addition of growth factors, and have undergone over 100 passages. Approximately 95% and 5% were positive for desmin and cytokeratin, respectively. The cell doubling time was 28 hr. Cytogenetic studies revealed a karyotype of 46,XY,del(11) (p12::p14). Although the cells stained very intensely with a monoclonal antibody that detects oncogene ras p 21 antigen, Southern blot analysis using c-Ha-ras as a probe failed to reveal an obvious deletion or amplification of either Ha-ras allele.

Antibodies, Monoclonal↗
PubMed1987

Isolation of a human genomic fragment, co-amplified with c-Ki-ras, that affects plasmid supercoiling in E. coli.

Amplification of cellular proto-oncogenes has been implicated in the development of human malignancies. A library was constructed from genomic DNA extracted from a lung tumour, previously shown to carry an amplified c-Ki-ras 2 gene. Using a v-Ki-ras probe, a fragment with ras homology was isolated and shown to be amplified in the original tumour DNA to the same level as c-Ki-ras. Studies with human hamster hybrids demonstrated that it is normally located on human chromosome 12 (as is c-Ki-ras). The restriction map of the fragment is different from that of the known Ha, Ki or N-ras genes and its sequence shows evolutionary conservation, as demonstrated by hybridisation to the genomic DNA of several mammalian species. A pUC19 subclone (pK42), carrying a 1.3kb insert, shows supercoil heterogeneity in plasmid preparations, as does a second compatible plasmid introduced into the same bacterial host with pK42. It appears therefore that the subclone is encoding a product that affects DNA topoisomerase activity in E. coli.

Animals↗
PubMed1986

Genetic predisposition to human lung cancer.

The influence of polymorphic variants of the human c-Ha-ras gene on predisposition to lung cancer has been investigated. The human c-Ha-ras gene has been shown to reside on a polymorphic BamH1 restriction fragment. This restriction fragment length polymorphism (RFLP) results from variation in the size of a region of repetitive DNA 3' to the gene. An attempt has been made to characterise and compare the c-Ha-ras RFLP's in a normal population and in a group of cancer patients. DNA was extracted from the white blood cells of 101 normal donors and four common Ha-ras alleles identified, with occasional rare alleles of various sizes. The allele frequencies were examined in 132 lung cancer patients, comprising 66 individuals with small cell carcinoma of the lung (SCCL) and 66 with non-small cell carcinoma of the lung (non-SCCL). An abnormal allele distribution was found in individuals with non-SCCL compared to both control and SCCL values suggesting a degree of genetic pre-position to non-SCCL. In addition, analysis of the Ha-ras RFLP's in solid samples inferred a deletion of material from the short arm of chromosome 11 in two of 16 informative samples.

Adenocarcinoma↗