Biomedical subjects
Publications and source records attributed to A C Robinson.
A case of idiopathic midline destructive disease (IMDD) in a 39-year-old male is described. Clinical features and diagnosis are discussed. The value of radiotherapy in management is highlighted.
DNA clones containing foldback sequences, derived from Physarum polycephalum nuclear DNA, can be classified according to their pattern of hybridisation to Southern blots of genomic DNA. One group of DNA clones map to unique DNA loci when used as a probe to restriction digests of Physarum nuclear DNA. These cloned segments appear to contain dispersed repetitive sequence elements located at many hundreds of sites in the genome. Similar patterns of hybridisation are generated when these cloned DNA probes are annealed to DNA restriction fragments of genomic DNA obtained from a number of different Physarum strains, indicating that no detectable alteration has occurred at these genomic loci subsequent to the divergence of the strains as a result of the introduction or deletion of mobile genetic elements. However, deletion of segments of some cloned DNA fragments occurs following their propagation in Escherichia coli. A second, distinct group of clones are shown to be derived from highly methylated segments of Physarum DNA which contain very abundant repetitive sequences with regular, though complex, arrangements of restriction sites at their various genomic locations. It is suggested that these DNA segments contain clustered repetitive sequence elements. The results lead to the conclusion that foldback elements in Physarum DNA are located in segments of the genome which display markedly different patterns of sequence organisation and degree of DNA methylation.
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Values for alkaline phosphatase and gamma glutamyl transpeptidase (GGTP) and the prevalence of their elevation was significantly higher in 35 patients with ankylosing spondylitis (AS) than in 35 age and sex matched controls. The abnormal enzyme levels appeared to reflect a non-specific reaction to inflammation and could thus aid in assessment of disease status.
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It has been found that in BHK 21 cells caffeine potentiates cell killing by both UV irradiation and N-methyl-N-nitrosoguanidine (MNNG). The potentiating effect is greater with UV than with MNNG. While non-toxic concentrations of caffeine inhibit the joining of newly-replicated DNA fragments into large molecular weight DNA (post-replication repair) after UV irradiation, they have no such effect after MNNG treatment. Furthermore, the joining of DNA fragments continues in the cells treated with 3 microgram/ml of MNNG, a dose which leads to less than 5% cell survival. While inhibition of the synthesis of large molecular weight DNA can explain the synergistic effect of caffeine upon cell survival after UV irradiation, it cannot explain the similar effect after MNNG treatment.
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Mutagenesis of a strain of Escherichia coli carrying a temperature-sensitive (Ts) mutation in the cell division gene ftsA yielded a number of temperature-resistant variants. In certain cases, restoration of viability at the restrictive temperature could not be attributed to suppressor mutations occurring in other genes or to structural gene reversion. DNA sequencing of the variants demonstrated the continuing presence of the original Ts mutation (ftsA13) and revealed secondary mutations within the same gene. These secondary mutations are able to rescue the ftsA13 mutation in cis, but not in trans.
Single amino acid substitutions increase the activity and stability of subtilisin E in mixtures of organic solvents and water, and the effects of these mutations are additive. A variant of subtilisin E that exhibits higher activity in mixtures of dimethylformamide (DMF) and water (Q103R) was created by random mutagenesis combined with screening for improved activity (K. Chen and F. H. Arnold, in preparation). Another mutation, N218S, known to improve both the activity and stability of subtilisin BPN', also improves the activity and stability of subtilisin E in the presence of DMF. The effects of the two substitutions on transition-state stabilization are additive. Furthermore, the Q103R mutation that improves activity has no deleterious effect on subtilisin stability. The double mutant Q103R+N218S is 10 times more active than the wild-type enzyme in 20% (v/v) DMF and twice as stable in 40% DMF. Although the effects of single mutations can be impressive, a practical strategy for engineering enzymes that function in nonaqueous solvents will most likely require multiple changes in the amino acid sequence. These results demonstrate the excellent potential for engineering nonaqueous-solvent-compatible enzymes.
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We have estimated that in 1995 more than 2 million pounds was spent by the National Health Service on throat swabs used to investigate chronic tonsillitis in the UK. This study was devised to assess the value of this investigation. The surface microflora, obtained using a throat swab, was compared with the microflora of the deep tonsil in 30 cases of chronic tonsillitis. None of the throat swabs grew pathogenic organisms, while in 16 cases, heavy growths of recognised pathogens were grown from the tonsillar tissue. This paper demonstrates that throat swabs have little value in the management of chronic tonsillitis, and if the investigation was omitted in this condition, a substantial saving could be made.