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Biomedical subjects

A Radford

Publications and source records attributed to A Radford.

At least 37 records · Page 2Linked to original sources

Patient perceptions of continuity of care: is there a socioeconomic factor?

This study aimed to assess perceptions of continuity of care by patients from different socioeconomic areas using focus group interviews augmented by postal replies. Patients were randomly selected from two contrasting primary medical care locations: a middle class suburb and a less affluent suburb in Adelaide, South Australia. The Ethnograph was used to analyse the content of the interviews and postal responses. Analysis used the framework described by Curtis and Rogers in the USA and Freeman in the UK. The response rate was much lower from the lower socioeconomic group (5% focus group; 20% when postal replies included). They emphasized access factors and importance of records, and alleged situations where they were taken too casually and their problems were not dealt with. Those from the middle class area (response rate 25%) emphasized interpersonal ('art of care') factors and were more likely to use their presenting problem as a criterion to decide whether they needed to postpone the problem to a time when they could see their personal doctor. Focus groups can be useful evaluation tools in general practice, but oversampling of lower socioeconomic groups is needed. Continuity of care should be considered as an aid to consistent quality of care, rather than its essence. Well controlled intervention-outcome studies in different types of practice organization in differing socioeconomic situations will increase our understanding of continuity of care.

Adult↗

Cellulase production by Neurospora crassa: purification and characterization of cellulolytic enzymes.

In studies on cellulase production by the cell-1 mutant of Neurospora crassa, eight enzymes (three exoglucanases, four endoglucanases, and one beta-glucosidase) were identified and characterized by gel filtration, ion exchange chromatography, and chromatofocusing. After purification, each of the proteins ran as a single band in polyacrylamide gel electrophoresis, using both native and denaturing gels. The molecular weights of the proteins were found to be between 70,000 and 22,000 daltons, and all were glycosylated, with carbohydrate contents ranging between 5.6% and 36%.

Amino Acid Sequence↗

Cloning, sequencing and homologies of the cbh-1 (exoglucanase) gene of Humicola grisea var. thermoidea.

Studies on the enzymes of the cellulase complex of the thermophilic fungus Humicola grisea var. thermoidea are described. A genomic library was constructed in the phage vector EMBL 4, and from this library two clones were isolated using as a probe the cloned cbh-1 (exoglucanase, EC 3.2.1.91) gene of Phanerochaete chrysosporium, a cellulolytic basidiomycete fungus. These clones were analysed by restriction mapping and Southern blotting, and one of them (lambda 3) was sub-cloned into the M13 phage vectors mp18 and mp19. The gene sequence was determined by the dideoxy chain-termination method. Sequence comparison with the equivalent genes from P. chrysosporium and Trichoderma reesei was made: in terms of primary sequence there is about 60% homology between the three species. Secondary structure prediction of the H. grisea sequence was also computed.

Amino Acid Sequence↗

The cellulase complex of Neurospora crassa: activity, stability and release.

The temperature and pH optima, and the temperature and pH stability, of crude and purified enzymes of the cellulase complex of the cellulolytic ascomycete fungus Neurospora crassa were investigated. The effects of some non-ionic surfactants and fatty acids on the production/release of enzymes of cellulase complex were also examined. For the different enzymes of the complex, activity maxima occurred between pH 4.0 and 7.0, with pH 5.0 being close to optimal for stability of all. Temperature optima for activity ranged between 45 and 65 degrees C, with the stability optimum between 45 and 50 degrees C. The presence of C18 fatty acids and surfactants resulted in increased production of both endoglucanase and exoglucanase in the medium. Oleic acid was the most effective fatty acid tested, and Tween 80 the most effective surfactant. Oleic acid had no detectable effect on production of beta-glucosidase, and Tween 80 actually reduced its production.

Cellulase↗

Recurrent issues in traveller health.

The questions concerning the health of travellers discussed in this paper are which antimalarial to prescribe; whether to immunise against hepatitis, typhoid or cholera; and which, if any, antidiarrhoeal to prescribe.

Antidiarrheals↗

Comparison of the orotidine 5'-monophosphate decarboxylase sequences of eight species.

Predicted amino acid sequences of the enzyme orotidine 5'-phosphate decarboxylase (EC 4.1.1.23) from eight different organisms are compared. The comparisons are made on the basis of primary structural differences, primary amino acid sequence, hydropathy profiles, and secondary structure predictions. The organisms compared are Mus musculus, Aspergillus nidulans, Neurospora crassa, Kluyveromyces lactis, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Escherichia coli, and Salmonella typhimurium.

Amino Acid Sequence↗

Molecular genetic analysis of the pyr-4 gene of Neurospora crassa.

By means of S1 nuclease mapping, one transcription origin and three termini are identified for the pyr-4 gene of Neurospora crassa, the same origin being used also by Escherichia coli on the cloned gene. Translation of the clone in mini-cells gives a 50,000 dalton gene product, the same size as that determined for the Neurospora native enzyme. Putative CAAT and TATA boxes, and upstream and downstream potential secondary structures, are identified.

Amino Acid Sequence↗

Obstetric ultrasonography: wider role for radiographers?

Most obstetric ultrasound scanning is carried out by radiographers, who have professional constraints that forbid them to disclose the result of any investigation to any patient or to hold themselves as professionally qualified to diagnose. A nationwide survey was carried out to explore the paramedical aspects of obstetric ultrasound services and determine how radiographers reconcile their professional constraints with the needs and expectations of patients. It was concluded that over 70% of obstetric scanning in the United Kingdom is carried out by radiographers who tell patients some results and report both numerical and interpretational data to referring clinicians. This survey suggests that constraints on radiographers who perform obstetric ultrasonography are excessively restrictive and conflict with everyday clinical demands. The medical supervision of some obstetric ultrasound units should be improved, and partners of patients should not be encouraged to expect access to obstetric scans unless radiographers have close medical support.

Female↗

Sequence analysis of the pyr-4 (orotidine 5'-P decarboxylase) gene of Neurospora crassa.

The pyr-4 gene of Neurospora crassa encodes orotidine-5' -phosphate decarboxylase, which catalyses the sixth step in the pyrimidine biosynthetic pathway. The complete nucleotide sequence of a 1.8-kb genomic fragment containing the pyr-4 gene has been determined. Using transposon mutagenesis, the coding region has been identified, and the amino acid (aa) sequence deduced. Comparison of the pyr-4 aa sequence with URA3, the equivalent gene of Saccharomyces cerevisiae, showed extensive blocks of homology, with non-homologous sequences between these blocks being generally much longer in Neurospora than in yeast. Computer-predicted protein secondary structure of pyr-4 and URA3 was conserved within equivalent blocks. Upstream sequences of pyr-4 were compared with other sequenced Neurospora genes and possible promoter sequences identified.

Amino Acid Sequence↗

Cloning of the structural gene for orotidine 5'-phosphate carboxylase of Neurospora crassa by expression in Escherichia coli.

A Neurospora gene bank in plasmid pRK9 was used to complement pyrimidine auxotrophs in E. coli. Two plasmids were obtained that complement a pyrF mutant of E. coli. These plasmids hybridise to Neurospora DNA and transform a pyr-4 strain of Neurospora. The promoter used in expressing the orotidine 5'-monophosphate carboxylase in E. coli is within the Neurospora sequence.

Carboxy-Lyases↗

Investigation of binding sites in the complex pyrimidine-specific carbamoyl-phosphate synthetase/aspartate carbamoyltransferase enzyme of Neurospora crassa.

The pyr-3 gene of Neurospora crassa codes for the bifunctional enzyme pyrimidine-specific carbamoyl-phosphate synthetase/aspartate carbamoyltransferase (carbon dioxide: ammonia ligase (ADP-forming, carbamate-phosphorylating)/carbamoylphosphate: L-aspartate carbamoyltransferase), EC 6.3.4.16/EC 2.1.3.2). We describe the investigation of substrate- and product-binding sites of the enzyme by affinity chromatography, using the ligands aspartate, glutamate, and adenosine 5'-diphosphate, and investigate the channelling of carbamoyl phosphate, the product of the first function and substrate of the second, through the pathway. For this latter aspect of the investigation, two new enzyme assays were devised and described. The results of the competition studies on carbamoyl phosphate-binding are consistent with the existence of two different binding sites within the enzyme for this metabolic intermediate, one for it as the product of the first step and the other for it as the substrate of the second.

Aspartate Carbamoyltransferase↗

Nitrogen metabolite repression of fluoropyrimidine resistance and pyrimidine uptake in Neurospora crassa.

Wild type Neurospora crassa was shown to be more resistant to 5-fluoro-uracil, 5-fluoro-uridine and 5-fluoro-2'-deoxyuridine in the presence of ammonia than in its absence. This differential resistance may in part be accounted for by the observation that both uracil and uridine uptake in germinating conidia is under nitrogen metabolite regulation. The uptake of uracil and uridine is increased on poor nitrogen sources in wild type, is unaffected by nitrogen source in a nit-2 mutant strain while a gln-1 mutant strain showed intermediate behaviour. Wild type also showed increased resistance to all three fluoropyrimidines with increased temperature and both uracil and uptake in the wild type increased with temperature and both uracil and uridine uptake in the wild type increased with temperature.

Ammonia↗

The involvement of proteolysis in conformational stability of the carbamoyl-phosphate synthetase/aspartate carbamoyltransferase enzyme of Neurospora crassa.

The pyrimidine-3 gene of Neurospora crassa codes for a bifunctional enzyme catalysing the first two steps of the pyrimidine biosynthetic pathway. Difficulties have been experienced in purification due to the lability of the enzyme. The enzyme loses carbamoyl-phosphate synthetase (carbon-dioxide: ammonia ligase (ADP-forming, carbamate-phosphorylating), EC 6.3.4.16) activity and undergoes a change in apparent molecular weight from the native 650,000 to 100,000 of the only detectable fragment. Attempts have been made therefore to stabilize the enzyme so as to minimise these effects. Elastinal, a protease inhibitor, reduces the effects, as do certain ultraviolet-sensitive mutant strains which lack a minor protease. The nature of the loss of carbamoyl-phosphate synthetase suggests an instability in the tertiary structure of the enzyme which can be reduced by the use of glycerol. Glycerol also exhibits a protease-inhibiting effect in this system. Although a range of protease inhibtors and use of uvs mutants can reduce the rate of decay of carbamoyl-phosphate synthetase activity, only glycerol can stabilize the native molecular weight. Our results support the hypothesis that the loss of carbamoyl-phosphate synthetase activity and change in molecular weight of the enzyme is a three-step sequence of proteolysis, conformational shift and cleavage of a further non-covalent bond.

Aspartate Carbamoyltransferase↗