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Biomedical subjects

R Haigh

Publications and source records attributed to R Haigh.

52 records · Page 3Linked to original sources
PubMed1991

Analysis of the haemolysin transport process through the secretion from Escherichia coli of PCM, CAT or beta-galactosidase fused to the Hly C-terminal signal domain.

Secretion of haemolysin (HlyA) is secA independent, but depends upon two accessory membrane proteins, HlyB and HlyD, encoded by the hly determinant. A fourth (cytoplasmic) protein, HlyC, is required to activate HlyA post-translationally, but has no role in export. Deletion studies have previously shown that the HlyA molecule contains a targeting signal close to the C-terminus which specifically directs its secretion to the medium. This targeting signal has been variously located within the terminal 27, 53, 60 or 113 amino acids. In this paper, we have sought to confirm the presence of a C-terminal targeting signal and to analyse the specificity of the Hly transport system through fusion of C-terminal fragments of HlyA to heterologous polypeptides. A C-terminal fragment (23 kDa) of HlyA, when fused at the C-terminus, efficiently promoted the secretion of the eukaryotic protein prochymosin (PCM) to the medium via HlyB and HlyD. This result is in contrast to previous findings that prochymosin, preceded by the alkaline phosphatase signal sequence, cannot be translocated across the Escherichia coli inner membrane. The HlyA targeting domain was also used to secrete to the medium varying portions of chloramphenicol acetyltransferase (CAT) and 98 per cent of the beta-galactosidase (LacZ) molecule (both E. coli cytoplasmic proteins). In the case of the PCM and CAT fusions the efficiency of secretion was reduced as the proportion of the PCM and CAT molecule increased. This result is consistent with inhibition of secretion through the irreversible folding of the larger passenger protein fragments, or the occlusion of the HlyA targeting signal by upstream sequences. Analysis of the nature of the C-terminal domain promoting secretion of prochymosin, demonstrated that shortening the signal domain from 218 to 113 amino acids significantly reduced the efficiency of secretion. This result may also reflect the importance of maintaining an independently folded signal motif well separated from a passenger domain.

Amino Acid Sequence↗
PubMed1989

Automatic speech recognition for disabled people.

It has been suggested that one of the most promising areas for the application of speech recognition is in helping handicapped people (Leggett and Williams, 1984). Within the last decade, many improvements have been made in the performance of automatic speech recognisers and current technology is discussed in relation to the needs of the disabled population. Recent research developments in the field of automatic speech recognition are reviewed, with particular reference to voice control of robotic arms and environmental control units. This includes a description of a Voice Activated Domestic Appliance System (VADAS), whose evaluation has just been completed. The general conclusion reached is that although speech recognition applications for disabled people are well within the capacity of available technology, it is primarily a lack of human factors work which is impeding developments in this field. Several human factors issues are identified; the most important of these being the need to increase the reliability of present speech recognisers, before they can confidently be incorporated into the lives of the disabled population.

Journal Article↗
PubMed1989

Human amniotic fluid urogastrone (epidermal growth factor) and fetal lung phospholipids.

Urogastrone was measured by radioimmunoassay in amniotic fluid obtained from 186 complicated pregnancies at 22 to 40 weeks gestation. Amniocentesis was performed for a variety of indications to obtain information about fetal lung maturity or bilirubin levels before induction of labour or caesarean section in various obstetric conditions. In 114 specimens lung phospholipids extracted from amniotic fluid were also assayed using two-dimensional thin layer chromatography. Urogastrone concentrations became measurable at approximately 30 weeks gestation and thereafter there was a 10-fold rise in concentrations between 30 and 40 weeks gestation. This increase in urogastrone concentration was positively correlated with a rise in phosphatidylcholine and phosphatidylglycerol concentrations and the phosphatidylcholine (lecithin)/sphingomyelin ratio (L/S). These results are compatible with a role for urogastrone in human fetal lung maturation.

Amniotic Fluid↗
PubMed1989

A novel C-terminal signal sequence targets Escherichia coli haemolysin directly to the medium.

Escherichia coli haemolysin (HlyA), a 107K (K = 10(3) Mr) protein, is secreted to the medium in an hlyB, hlyD-dependent process. Secretion, however, depends on neither an N-terminal signal sequence nor on SecA, which is part of the normal cellular export machinery for periplasmic and outer membrane proteins. In contrast, HlyA contains a novel C-terminal secretion signal encompassing the last 27 amino acids and possibly some additional residues immediately upstream. This region is characterized by a 16 residue 'aspartic acid box' composed largely of small amino acids which we propose constitutes an important element in recognition of the membrane translocation complex constituted by HlyB and HlyD. This feature is also found at the C-terminus of the adenyl cyclase and leukotoxin A molecules and resembles a recently identified eukaryotic C-terminal signal for targeting to glycosomes. A domain of the HlyB component of the haemolysin transport system is also similar to a domain widely distributed in nature, apparently acting as an ATP-dependent transport protein for a wide variety of molecules. Secretion of haemolysin, however, is the first example of a protein translocation system involving an HlyB-like molecule. This suggests that a major role of HlyB or at least its C-terminal domain is the coupling of energy to translocation of the haemolysin. It is more likely therefore that HlyD is more involved in the actual translocation through the membrane. On the basis of genetical and biochemical studies we propose that the haemolysin is translocated directly to the medium bypassing the periplasm. We further propose that HlyB and HlyD together constitute a membrane-bound translocator specific for molecules bearing the HlyA targeting sequence, and that the organization of this complex (conceivably involving other E. coli membrane proteins) must somehow straddle the inner and outer membranes. Finally, the HlyA C-terminal domain has been successfully used to promote the secretion to the medium of a number of heterologous polypeptides, in an HlyB,D-dependent manner.

Amino Acid Sequence↗
PubMed1987

Release of a chimeric protein into the medium from Escherichia coli using the C-terminal secretion signal of haemolysin.

Recently, we have identified a novel topogenic sequence at the C terminus of Escherichia coli haemolysin (HlyA) which is essential for its efficient secretion into the medium. This discovery has introduced the possibility of using this secretion system for the release of chimeric proteins from E. coli directly into the medium. We have now successfully fused this C-terminal signal to a hybrid protein containing a few residues of beta-galactosidase and the majority of the E. coli outer membrane porin OmpF lacking its own N-terminal signal sequence. We find that this chimeric protein is specifically translocated across the inner and outer membranes and is released into the medium. In addition, we have further localized the HlyA secretion signal to the final 113 amino acids of the C terminus. In fact, a specific secretion signal appears to reside at least in part within the last 27 amino acids of HlyA.

Amino Acid Sequence↗
PubMed1987

Acute mastitis; a novel presentation of relapsing polychondritis.

A 30 year old female with previous Crohn's disease presented with recurrent cutaneous vasculitis and polyarthritis. She subsequently developed recurrent transient bilateral mastitis with auricular and laryngotracheal chondritis typical of relapsing polychondritis. Acute mastitis is a previously unrecognized association of this disorder.

Acute Disease↗
PubMed1986

An ergonomic assessment of BS 5810: 1979 access for the disabled to buildings, through a survey of architects.

This article describes a project which was undertaken to assess the British Standard 5810: 1979 Access for the Disabled to Buildings, with a view to it being improved at the next review. This code of practice 'concentrates on the essential provisions that need to be incorporated in buildings to ensure that they are conveniently usable by disabled people'. The aim of the project was to make suggestions for improvements to the Standard, both qualitatively and in its range of provision, by discovering what additional data, if any, architects require, what level of detail they need and the preferred method of presentation. Research was also undertaken to ascertain whether the information contained in the Standard is based on empirical data. The project involved a literature search, sending postal questionnaires to architects and visiting architectural practices to complete structured interviews. The method used, the results and the conclusions on how the British Standard could be improved are described.

Journal Article↗
PubMed1979

The approach of the European communities to the assessment of the carcinogenic risk of environmental chemicals, in particular, artificial colourings.

A brief outline is given of the rationale of the Environmental Research Programme of the European Economic Community and of its implementation. The major part of the programme is devoted to research on the exposure-effect relationships for mutagens and carcinogens and to the establishment of criteria. As a first step, a battery of test systems for mutagenicity screening is being established. These will be evaluated in a comparative test programme. The second part of the paper describes the specific legislative actions of the European Communities on food colourings. The historical background is given; and the criteria used by the Scientific Committee for Food for classifying and evaluating colouring matters are listed. Proposed regulatory action, on the basis of the report of the Committe, includes lists of colouring matters which are 'unacceptable', 'temporarily acceptable' and 'acceptable'.

European Union↗
PubMedDate not supplied

Safety and necessity of antioxidants: EEC approach.

As neither 'safety' nor 'necessity' in the context of food additives is absolute, it is not surprising that agreement on conditions of use of additives requires patient consultation between governments and scientists. The Scientific Committee for Food (SCF) of the European Economic Community plays an important role in advising government authorities on the safety of food additives, including antioxidants. This paper identifies important factors contributing to the development of a single rule applying to the use of antioxidants throughout the EEC. The legislative framework, the need for antioxidants, and estimates of antioxidant intake by persons within the 12 independent States of the EEC are reviewed. Also presented are the results of the SCF's recent review of ascorbates, BHA, BHT, TBHQ, gallates and erythorbic acid.

Antioxidants↗
PubMedDate not supplied

Management of myocardial infarction in the elderly: admission and outcome on a coronary care unit.

A data base of 1,511 patients admitted to a single Coronary Care Unit was analysed to examine the potential impact of thrombolytic therapy in elderly patients with myocardial infarction. Age was confirmed as a highly significant prognostic factor, and cost utility analysis showed that the cost of thrombolytic therapy with streptokinase in the elderly was lower per quality adjusted life year than in younger patients. However, median delay time of admission from onset of symptoms was significantly greater in this age-group, suggesting a need for a greater awareness of the benefits of thrombolytic therapy in elderly people.

Aged↗
PubMedDate not supplied

Thymic eicosanoid profiles and cyclooxygenase localization in prenatal and postnatal CBA/J mice.

Previous work in our laboratory has implicated arachidonic acid metabolites as modulators of fetal murine thymocyte development in vitro. Therefore, we determined whether distinct temporal patterns existed with regard to the capacity for eicosanoid synthesis by fetal and postnatal thymic lobes which might relate to early proliferative and differentiation events within the thymus. Thin layer chromatography was used to demonstrate differential synthesis of 15-HETE, 5-HETE, PGD2, 6-keto PGF1 alpha, and PGF2 alpha by both fetal and postnatal thymic lobes. In contrast, PGE2 and TXB2 were synthesized at a constant level. These findings were in part substantiated by radioimmunoassay of culture media for PGE2 and 6-keto PGF1 alpha following fetal thymic organ culture for 7 or 8 days. In addition, we were able to demonstrate immunoreactive cells for cyclooxygenase in early embryonic and postnatal thymic lobes. Taken together, the above findings permit the suggestion that metabolites of arachidonic acid modulate development of thymocytes and, in turn, their capacity for synthesis is modulated as the thymus develops.

6-Ketoprostaglandin F1 alpha↗