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Biomedical subjects

D C Cameron

Publications and source records attributed to D C Cameron.

At least 19 recordsLinked to original sources
PubMed1992

Enhancement of 1,3-propanediol production by cofermentation in Escherichia coli expressing Klebsiella pneumoniae dha regulon genes.

1,3-Propanediol (1,3-PD) is an intermediate in chemical and polymer synthesis. We have previously expressed the genes of a biochemical pathway responsible for 1,3-PD production, the dha regulon of Klebsiella pneumoniae, in Escherichia coli. An analysis of the maximum theoretical yield of 1,3-PD from glycerol indicates that the yield can be improved by the cofermentation of sugars, provided that kinetic constraints are overcome. The yield of 1,3-PD from glycerol was improved from 0.46 mol/mol with glycerol alone to 0.63 mol/mol with glucose cofermentation and 0.55 mol/mol with xylose cofermentation. The engineered E. coli also provides a model system for the study of metabolic pathway engineering.

Acetates↗
PubMed1991

1,3-Propanediol production by Escherichia coli expressing genes from the Klebsiella pneumoniae dha regulon.

The dha regulon in Klebsiella pneumoniae enables the organism to grow anaerobically on glycerol and produce 1,3-propanediol (1,3-PD). Escherichia coli, which does not have a dha system, is unable to grow anaerobically on glycerol without an exogenous electron acceptor and does not produce 1,3-PD. A genomic library of K. pneumoniae ATCC 25955 constructed in E. coli AG1 was enriched for the ability to grow anaerobically on glycerol and dihydroxyacetone and was screened for the production of 1,3-PD. The cosmid pTC1 (42.5 kb total with an 18.2-kb major insert) was isolated from a 1,3-PD-producing strain of E. coli and found to possess enzymatic activities associated with four genes of the dha regulon: glycerol dehydratase (dhaB), 1,3-PD oxidoreductase (dhaT), glycerol dehydrogenase (dhaD), and dihydroxyacetone kinase (dhaK). All four activities were inducible by the presence of glycerol. When E. coli AG1/pTC1 was grown on complex medium plus glycerol, the yield of 1,3-PD from glycerol was 0.46 mol/mol. The major fermentation by-products were formate, acetate, and D-lactate. 1,3-PD is an intermediate in organic synthesis and polymer production. The 1,3-PD fermentation provides a useful model system for studying the interaction of a biochemical pathway in a foreign host and for developing strategies for metabolic pathway engineering.

Anaerobiosis↗
PubMed1990

The "Carpentier" thoracic aortic by-pass technique for management of descending aortic aneurysms and dissections--a radiological perspective.

The "Carpentier" thoracic aortic bypass procedure is a recently described and, until now, little used surgical technique for the treatment of descending thoracic aortic aneurysms and dissections. It involves the placement of a large conduit from the ascending aorta to the distal abdominal aorta through a midline sternotomy incision extended to the umbilicus and the subsequent interruption of the aorta just distal to the left subclavian artery via a left postero-lateral thoracotomy. As radiologists we should be aware of this alternative surgical option so that, in addition to diagnosing and classifying these aneurysms and dissections, we can assist our surgical colleagues in:-- a. The pre-operative assessment of the aorta for bypass grafting including the distal abdominal aorta b. The post-operative monitoring of the anticipated thrombotic occlusion of the descending thoracic aorta to the coeliac axis.

Aged↗
PubMed1989

Erosive spondylo-arthropathy and tertiary hyperparathyroidism.

A patient on long term haemodialysis for analgesic nephropathy, with known teriary hyperparathyroidism developed a rapidly evolving, erosive, non-infective spondylo-arthropathy at two vertebral levels. In addition, erosions were noted adjacent to the right sacroiliac joint. Subsequent postmortem material from the affected vertebral levels demonstrated changes consistent with hyperparathyroidism alone and this is suggested as the possible aetiology underlying this recently recognised destructive spondyloarthropathy.

Female↗
PubMed1989

A second global regulator gene (arcB) mediating repression of enzymes in aerobic pathways of Escherichia coli.

In Escherichia coli anaerobic growth lowers the basal or induced levels of numerous enzymes associated with aerobic metabolism. Mutations in arcA (dye) at min 0 relieve this pleiotropic anaerobic repression and render the cell sensitive to the redox dye toluidine blue. In this study we identified a second pleiotropic control gene, arcB, at min 69.5. Mutations, including a deletion, in this gene also relieved the anaerobic repression and caused sensitivity to toluidine blue. Mutations in arcA or arcB did not significantly change the catabolite repression of the target phi(sdh-lacZ) operon, in which lacZ is fused to a structural gene for succinate dehydrogenase, nor did the mutations strikingly influence the pattern of excretion products during glucose fermentation. The presence of arcA+ in a multicopy plasmid restored anaerobic repression in arcB mutants, as indicated by the expression of phi(sdh-lacZ). The arcB product might be a sensor protein for the redox or energy state of the arc regulatory system.

Aerobiosis↗
PubMed1978

Radiographic patterns of pulmonary involvement in acute mycoplasmal infections.

The radiological appearances and the progress of the pulmonary manifestations of serologically-proven acute Mycoplasma pneumoniae infection were studied in 29 patients. The radiological changes seen at and after admission were not helpful in establishing an aetiological diagnosis except in three patients, in whom a "classical" pattern of mycoplasma pneumonia, based on the radiological appearnaces at different histopathological stages of the disease, could be recognised retrospectively. The patterns seen were varied and generally non-specific, and were not related to the age of the patient or to the duration of disease prior to admission. Specific anti-mycoplasma therapy may have prevented the progress of the disease after admission, although five of six patients in whom radiological deterioration occurred after admission were receiving such treatment.

Acute Disease↗
PubMed1977

The radiographic patterns of acute mycoplasma pneumonitis.

Twenty-two cases of serologically proven pulmonary mycoplasma infection have been reviewed. All showed abnormality on plain chest radiographs. A definitive diagnosis could not be made on initial or individual films. However, studies of sequential films enabled diagnostic patterns to be distinguished.

Adolescent↗