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Biomedical subjects

J Raftery

Publications and source records attributed to J Raftery.

At least 55 records · Page 3Linked to original sources
PubMed1999

Determination of the structure of seleno-methionine-labelled hydroxymethylbilane synthase in its active form by multi-wavelength anomalous dispersion.

The enzyme hydroxymethylbilane synthase (HMBS, E.C. 4.3.1.8) catalyzes the conversion of porphobilinogen into hydroxymethylbilane, a key intermediate for the biosynthesis of heme, chlorophylls, vitamin B12 and related macrocycles. The enzyme is found in all organisms, except viruses. The crystal structure of the selenomethionine-labelled enzyme ([SeMet]HMBS) from Escherichia coli has been solved by the multi-wavelength anomalous dispersion (MAD) experimental method using the Daresbury SRS station 9.5. In addition, [SeMet]HMBS has been studied by MAD at the Grenoble ESRF MAD beamline BM14 (BL19) and this work is described especially with respect to the use of the ESRF CCD detector. The structure at ambient temperature has been refined, the R factor being 16.8% at 2. 4 A resolution. The dipyrromethane cofactor of the enzyme is preserved in its reduced form in the crystal and its geometrical shape is in full agreement with the crystal structures of authentic dipyrromethanes. Proximal to the reactive C atom of the reduced cofactor, spherical density is seen consistent with there being a water molecule ideally placed to take part in the final step of the enzyme reaction cycle. Intriguingly, the loop with residues 47-58 is not ordered in the structure of this form of the enzyme, which carries no substrate. Direct experimental study of the active enzyme is now feasible using time-resolved Laue diffraction and freeze-trapping, building on the structural work described here as the foundation.

Binding Sites↗
PubMed1999

Bound-solvent structures for microgravity-, ground control-, gel- and microbatch-grown hen egg-white lysozyme crystals at 1.8 A resolution.

A number of methods can be used to improve the stability of the protein crystal-growth environment, including growth in microgravity without an air-liquid phase boundary, growth in gels and growth under oil ('microbatch'). In this study, X-ray data has been collected from and structures refined for crystals of hen egg-white lysozyme (HEWL) grown using four different methods, liquid-liquid dialysis on Earth and in microgravity using the European Space Agency's (ESA) Advanced Protein Crystallization Facility (APCF) on board the NASA Space Shuttle Life and Microgravity Spacelab (LMS) mission (STS-78), crystallization in agarose gel using a tube liquid-gel diffusion method and crystallization in microbatch under oil. A comparison of the overall quality of the X-ray data, the protein structures and especially the bound-water structures has been carried out at 1.8 A. The lysozyme protein structures corresponding to these four different crystallization methods remain similar. A small improvement in the bound-solvent structure is seen in lysozyme crystals grown in microgravity by liquid-liquid dialysis, which has a more stable fluid physics state in microgravity, and is consistent with a better formed protein crystal in microgravity.

Amino Acid Sequence↗
PubMed1998

Evaluation of total purchasing pilots in England and Scotland and implications for primary care groups in England: personal interviews and analysis of routine data. The Total Purchasing National Evaluation Team.

OBJECTIVES: To evaluate the reported achievements of the 52 first wave total purchasing pilot schemes in 1996-7 and the factors associated with these; and to consider the implications of these findings for the development of the proposed primary care groups. DESIGN: Face to face interviews with lead general practitioners, project managers, and health authority representatives responsible for each pilot; and analysis of hospital episode statistics. SETTING: England and Scotland for evaluation of pilots; England only for consideration of implications for primary care groups. MAIN OUTCOME MEASURES: The ability of total purchasers to achieve their own objectives and their ability specifically to achieve objectives in the service areas beyond fundholding included in total purchasing. RESULTS: The level of achievement between pilots varied widely. Achievement was more likely to be reported in primary than in secondary care. Reported achievements in reducing length of stay and emergency admissions were corroborated by analysis of hospital episode statistics. Single practice and small multipractice pilots were more likely than large multipractice projects to report achieving their objectives. Achievements were also associated with higher direct management costs per head and the ability to undertake independent contracting. Large multipractice pilots required considerable organisational development before progress could be made. CONCLUSION: The ability to create effective commissioning organisations the size of the proposed primary care groups should not be underestimated. To be effective commissioners, these care groups will need to invest heavily in their organisational development and in the short term are likely to need an additional development budget rather than the reduction in spending on NHS management that is planned by the government.

Budgets↗
PubMed1998

Day case surgery trends in England: the influences of target setting and of general practitioner fundholding.

OBJECTIVES: To describe the trends in the proportion of elective surgery carried out as day cases, and the impact of the setting of targets and the introduction of general practitioner (GP) fundholding on the use of day surgery. METHODS: Cross-sectional analysis of Hospital Episode Statistics for England. 1990/1991 to 1994/1995, comparing procedures for which targets were and were not set, and comparing types of purchaser (GP fundholder and health authority). RESULTS: Elective surgical procedures increased from 2.7 million in 1990/1991 to 3.9 million in 1994/1995, a 44% increase. Increased numbers of day cases (up 117%) accounted for almost all of the increased total activity. The proportion of day cases rose from 35% to 53% over the period. Those procedures for which targets were set (over 25% of elective surgery) had a slightly lower day case proportion in 1990/1991 (34% compared to 36%) but slightly higher by 1994/1995 (57% compared to 52%). GP fundholders generally had slightly lower proportions treated as day cases compared to health authorities. CONCLUSIONS: Day cases were additional to, rather than a substitute for, inpatient treatments. Setting day case targets may have been associated with growth in use of day surgery, but there was no association with type of purchaser.

Ambulatory Surgical Procedures↗
PubMed1997

Impact of the NHS reforms on English hospital productivity: an analysis of the first three years.

OBJECTIVES: To evaluate the effect of purchaser mix, market competition, and trust status on hospital productivity within the NHS internal market. METHODS: Hospital cost and activity data were taken from routinely collected data for acute NHS hospitals in England for 1991-2 to 1993-4. Cross sectional and longitudinal regression methods were used to estimate the effect of trust status, competition, and purchaser mix on average hospital costs per inpatient, after adjusting for outpatient activity levels, casemix, teaching activity, regional salary variation, hospital size, scale of activity, and scope of cases treated. RESULTS: Real productivity gains were apparent across the study period for NHS hospitals on average. Casemix adjustment drastically improved cross sectional comparisons between hospitals. Gaining trust status and increasing host district purchaser share were associated with productivity increases after adjustment for casemix, regional salary differences, and hospital size and scope. Hospitals that became trusts during the study period were on average less productive at the beginning of the period than those that did not, and there were no significant productivity differences between trust waves at the end of the period in 1993-4. Market concentration was not associated with productivity differences. CONCLUSION: Further analysis is needed to determine whether overall and trust associated productivity gains are transient effects, one off shifts, or self perpetuating reorientations of organisational behaviour. Hospitals may have chosen to become trusts because they anticipated being able to increase productivity. Increases in the proportions of small purchasers were associated with increasing costs. Importantly, this study could not adjust for changes in the quality of care.

Cross-Sectional Studies↗
PubMed1997

Estimating the burden of disease in an English region.

BACKGROUND: Health Authorities seeking to make appropriate investments in health care require information about the nature of the burden of disease in their populations. The World Bank instrument called DALY-Disability Adjusted Life Year-has been used in the South and West Region to measure this burden. METHOD: The burden of disease caused by a selection of diseases has been calculated using DALYs, which combine premature mortality and disability. An estimate of the total burden has been estimated by ICD chapter. RESULTS: Premature mortality accounts for 52 per cent of the burden of disease and disability 48 per cent. Mental illness, for which its DALY value is largely derived from disability not premature mortality, contributes the third largest component of the total burden, after heart disease and cancer. DISCUSSION: DALYs can be calculated using UK data, and, with an appreciation of the theoretical issues which surround the calculations, can be used to describe the burden of disease in a population. Although designed to assist investment decisions in developing countries, the DALY is likely to be valuable in established market economies.

Algorithms↗
PubMed1996

Case mix measurement in English hospitals: an evaluation of five methods for predicting resource use.

OBJECTIVES: The introduction of an internal market in the British National Health Service (NHS) has highlighted the importance of developing appropriate, valid and timely measures of hospital activity, both for the purposes of specifying and monitoring contracts and for evaluating the success of the NHS reforms in general. This paper compares the validity of five case mix methods (Diagnosis Related Groups (DRGs); Healthcare Resource Groups (HRGs) versions 1 and 2; specialty classification; a simple age categorization) in predicting resource use. METHODS: Two data sets were used to compare different case mix methods. A 3% random sample (n approximately equal to 300,000) of the 1992/3 Hospital Episodes Statistics was used to test their ability to predict variation in length of stay, and a second set of individually costed patient episodes from two hospitals (n approximately equal to 40,000) was used to test their ability to explain cost variation. Analysis of variance models were used to assess the fit of each of the case mix systems to test data and a simple significance test of differences in mean squared error between models was applied. RESULTS: All case mix methods performed poorly on untrimmed data. When lengths of stay greater than 29 days were excluded, version 2 of HRGs explained 31% of total variance in length of stay and 25% of cost variation. DRGs explained less variance but performed better than HRGs version 1. For a typical hospital patient population consisting of a range of specialties, the difference in explanatory power between HRGs V2 and DRGs was statistically significant at the 5% level for sample sizes of approximately 2000 or greater. For individual specialties, the minimum sample size required for the difference between the groupers to be significant ranged from around 300 to over 2000. CONCLUSIONS: The locally developed HRGs version 2 system appears to offer superior performance in terms of resource homogeneity to other currently available approaches. It is also more adaptable and cheaper than imported alternatives and has been formally endorsed by the UK medical Royal Colleges.

Analysis of Variance↗
PubMed1995

Image-plate synchrotron laue data collection and subsequent structural analysis of a small test crystal of a nickel-containing aluminophosphate.

Image plates have advantages over photographic films, which include wider dynamic range, higher detector quantum efficiency, reduced exposure time and large size. In this study, an on-line image-plate system has been used to record crystallographic data from a small crystal. In particular, synchrotron Laue data were recorded with lambda(min) = 0.455, lambda(max) = 1.180 A, in 20 images 10 degrees apart and with an exposure time of 0.3 s each from a crystal (0.02 x 0.05 x 0.25 mm) of a nickel-containing aluminophosphate, NiAPO. The Laue data were analyzed with the Daresbury Laue software, including the application of an absorption correction. The structure was solved by a combination of the Patterson method and successive difference Fourier calculations using SHELXS86 and SHELXL93; the final R value for 1934 unique reflections (all data) and 310 parameters was 7.90%. The structure agrees with that determined by monochromatic diffractometry using the same crystal and reported by Helliwell, Gallois, Kariuki, Kaucic & Helliwell [Acta Cryst. (1993), B49, 420-428] with an r.m.s. deviation of 0.03 A. Hence, this study shows the image-plate device to be very effective for synchrotron data collection and subsequent structure analysis from small crystals, i.e. 0.02 x 0.05 x 0.25 mm, in chemical crystallography as well as providing further confirmation of the practicability of Laue data in structure solution and refinement.

Journal Article↗
PubMed1995

Differences in hospital casemix, and the relationship between casemix and hospital costs.

BACKGROUND: The aim of the study was to examine the relationship between hospital costs and casemix, and after adjustment for casemix differences, between cost and institutional size, number of specialties, occupancy and teaching status. METHODS: A retrospective analysis of all admissions to nine acute-care NHS hospitals in the Oxford region during the 1991-1992 financial year was undertaken. All episodes were assigned to a diagnosis-related group (DRG) and a cost weight assigned accordingly. Costs per finished consultant episode, before and after adjustment for casemix differences, were analysed at the hospital and specialty level. RESULTS: Casemix differences were significant, and accounted for approximately 77 per cent of the difference in costs between providers. Costs per casemix-adjusted episode were not significantly associated with differences in hospital size, scope, occupancy levels or teaching status, but sample size was insufficient to investigate these relationships adequately. Specialty costs were poorly correlated with specialty casemix. This was probably due to poor apportionment of specialty costs in hospital accounting returns. CONCLUSIONS: Casemix differences need to be taken into account when comparing providers for the purposes of contracting, as unadjusted unit costs may be misleading. Although the methods used may currently be applied to most NHS hospitals, widespread use would be greatly facilitated by the development of indigenous cost weights and better routine hospital data coding and collection.

Bed Occupancy↗
PubMed1994

Refined structure of concanavalin A complexed with methyl alpha-D-mannopyranoside at 2.0 A resolution and comparison with the saccharide-free structure.

The three-dimensional structure of the complex between methyl alpha-D-mannopyranoside and concanavalin A has been refined at 2.0 A resolution. Diffraction data were recorded from a single crystal (space group P2(1)2(1)2(1), a = 123.7, b = 128.6, c = 67.2 A) using synchrotron radiation at a wavelength of 1.488 A. The final model has good geometry and an R factor of 19.9% for 58 871 reflections (82% complete), within the resolution limits of 8 to 2 A, with F > 1.0sigma(F). The asymmetric unit contains four protein subunits arranged as a dimer of dimers with approximate 222 point symmetry. Each monomer binds one saccharide molecule. Each sugar is bound to the protein by hydrogen bonds and van der Waals contacts. Although the four subunits are not crystallographically equivalent, the protein-saccharide interactions are nearly identical in each of the four binding sites. The differences that do occur between the four sites are in the structure of the water network which surrounds each saccharide; these networks are involved in crystal packing. The structure of the complex is compared with a refined saccharide-free concanavalin A structure. The saccharide-free structure is composed of crystallographically identical subunits, again assembled as a dimer of dimers, but with exact 222 symmetry. In the saccharide complex the tetramer association is different in that the monomers tend to separate resulting in fewer intersubunit interactions. The average temperature factor of the mannoside complex is considerably higher than that of the saccharide-free protein. The binding site in the saccharide-free structure is occupied by three ordered water molecules and the side chain of Asp71 from a neighbouring molecule in the crystal. These occupy positions similar to those of the four saccharide hydroxyls which are hydrogen bonded to the site. Superposition of the saccharide-binding site from each structure shows that the major changes on binding involve expulsion of these ordered solvents and the reorientation of the side chain of Tyrl00. Overall the surface accessibility of the saccharide decreases from 370 to 100 A(2) when it binds to the protein. This work builds upon the earlier studies of Derewenda et al. [Derewenda, Yariv, Helliwell, Kalb (Gilboa), Dodson, Papiz, Wan & Campbell (1989). EMBO J. 8, 2198-2193] at 2.9 A resolution, which was the first detailed study of lectin-saccharide interactions.

Journal Article↗
PubMed1994

High-resolution structures of single-metal-substituted concanavalin A: the Co,Ca-protein at 1.6 A and the Ni,Ca-protein at 2.0 A.

The molecular structures of cobalt- and nickel-substituted concanavalin A have been refined at 1.6 and 2.0 A resolution, respectively. Both metal derivatives crystallize in space group I222 with approximate cell dimensions a = 89, b = 87 and c = 63 A and one monomer in the asymmetric unit. The final R factor for Co-substituted concanavalin A is 17.8% for 29 211 reflections with F > 1.0sigma(F) between 8.0 and 1.6 A. For Ni-substituted concanavalin A the final R factor is 15.9% for 16 128 reflections with F > 1.0sigma(F) between 8.0 and 2.0 A resolution. Both structures contain a transition-metal binding site and a calcium-binding site but, unlike Cd-substituted concanavalin A, do not have a third metal-binding site. The Co-substituted concanavalin A structure diffracts to the highest resolution of any concanavalin A structure reported to date. A comparison of the structures of Ni-, Co-, Cd-substituted and native concanavalin A gives an indication of coordinate errors, which is a useful baseline for comparisons with saccharide complexes of concanavalin A described in other work. We also give a detailed account of multiple conformations which were found for five side-chain residues.

Journal Article↗
PubMed1993

Capitation funding: population, age, and mortality adjustments for regional and district health authorities in England.

OBJECTIVE: To assess the effect of each of the components of the national capitation funding formula--population projections and age and mortality weighting--at regional and district level. DESIGN: Application of age-cost and mortality weights to the projected 1997 populations of regions and districts, based on the Department of Health public health common dataset. SETTING: Regional and district health authorities in England. RESULTS: The application of the age-cost and mortality weights to projected populations resulted in greater changes in the shares of weighted populations relative to the estimated 1991 population at district level (mean 0, range -17% to 28%) than at regional level (mean 0, range -9% to 6%). At district level mortality weights had less scope for influence (mean 0, range -9% to 14%) than population projections (mean 0, range -16% to 31%) or age weights (mean 0, range -20% to 30%). CONCLUSIONS: The adjustments to the 1991 population shares due to the application of the national capitation funding formula depend on the interaction of three elements: the projected population by age group, the age-cost weight, and the mortality weight. Since each is open to uncertainty, either in terms of measurement (projected population, particularly for births and the over 85s) or method (derivation of the age-cost and mortality weights), the formula should be implemented cautiously at district level. Ways should be considered of incorporating elements of uncertainty into the model. Further research is required on the elements and degree of uncertainty in each of these components, as well as on the relative health needs of different populations.

Adolescent↗