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Biomedical subjects

J Barber

Publications and source records attributed to J Barber.

At least 19 recordsLinked to original sources
PubMed2006

Photosystem II: an enzyme of global significance.

Photosystem II (PSII) is a multisubunit enzyme embedded in the lipid environment of the thylakoid membranes of plants, algae and cyanobacteria. Powered by light, this enzyme catalyses the chemically and thermodynamically demanding reaction of water splitting. In so doing, it releases dioxygen into the atmosphere and provides the reducing equivalents required for the conversion of CO2 into the organic molecules of life. Recently, a fully refined structure of a 700 kDa cyanobacterial dimeric PSII complex was elucidated by X-ray crystallography which gave organizational and structural details of the 19 subunits (16 intrinsic and three extrinsic) which make up each monomer and provided information about the position and protein environments of 57 different cofactors. The water-splitting site was revealed as a cluster of four Mn ions and a Ca2+ ion surrounded by amino acid side chains, of which six or seven form direct ligands to the metals. The metal cluster was modelled as a cubane-like structure composed of three Mn ions and the Ca2+ linked by oxo-bonds with the fourth Mn attached to the cubane via one of its oxygens. The overall structure of the catalytic site is providing a framework to develop a mechanistic scheme for the water-splitting process, knowledge which could have significant implications for mimicking the reaction in an artificial chemical system.

Crystallography, X-Ray↗
PubMed2006

Ex vivo expansion of mafosfamide-purged PBPC products.

BACKGROUND: Multiple studies have demonstrated that 'purging' of autografts with 4-hydroperoxycyclophosphamide (4HC) or the related compound mafosfamide (Mf), to eradicate residual leukemia, produces the best results associated with autologous blood and marrow transplantation for AML. However, 4HC purging results in prolonged aplasia. Therefore, we evaluated the potential of ex vivo expansion of Mf-treated CD34+ cells from mobilized PBPC. METHODS: CD34+ cells were isolated from PBPC products and treated with 30 microg/mL Mf. The Mf-treated CD34+ cells were washed and cultured for 14 days in StemLine II-defined media containing recombinant human (rh) SCF, G-CSF and thrombopoietin (Tpo). RESULTS: Treatment with Mf resulted in 90% killing of progenitor cells (GM-CFC) but maintenance of SCID-repopulating cells (SRC). Ex vivo culture of the Mf-treated CD34+ cells resulted in decreased cell numbers (10-20% of the starting cell dose) during the first week. Nevertheless, in the second week of culture the total cell numbers expanded to approximately 20-fold above starting cell numbers and progenitor cells returned to approximately pre-treatment levels. DISCUSSION: These studies demonstrate the potential of ex vivo culture to expand both total cell numbers and progenitor cells following treatment of PBPC CD34+ cells with Mf. Clinical studies are currently being initiated to evaluate the engraftment potential of these purged and expanded products.

Adjuvants, Immunologic↗
PubMed2004

A meta-analysis of randomised trials suggests a survival benefit for combined radiotherapy and radical cystectomy compared with radical radiotherapy for invasive bladder cancer: are these data relevant to modern practice?

OBJECTIVE: Treatment options for muscle-invasive bladder cancer include radical cystectomy or radical radiotherapy, and the prevailing choice varies by country. The ideal treatment would be a bladder-preserving therapy without compromising survival. The objective of this review was to compare the overall survival after radical surgery (cystectomy) with radical radiotherapy in patients with muscle-invasive cancer. MATERIALS AND METHODS: We searched the Cochrane Controlled Trials Register, Medline, EMBASE, Cancerlit, Healthstar and the Database of Abstracts of Reviews of Effectiveness. Authors of unpublished data were contacted. Randomised trials comparing surgery (alone or with preoperative radiotherapy) with radiotherapy were eligible for assessment. Three reviewers assessed trial quality based on the Cochrane Guidelines. Data were extracted from the text of the article or extrapolated from the Kaplan-Meier plot. The Peto odds ratio was determined to compare the overall survival and disease-specific survival. Analysis was performed on an intention-to-treat basis and treatment actually received. RESULTS: No randomised trials comparing surgery alone with radiotherapy alone were identified. Three randomised trials comparing preoperative radiotherapy followed by radical cystectomy (surgery) versus radical radiotherapy with salvage cystectomy (radical radiotherapy) were eligible for assessment. These trials represented a total of 439 patients, 221 randomised to surgery and 218 to radical radiotherapy. Three trials were combined for the overall survival results, and one was evaluable for the disease-specific survival analysis. The mean overall survival (intention-to-treat analysis) at 3 and 5 years were 45% and 36% for surgery, and 28% and 20% for radiotherapy, respectively. Peto odds ratio (95% confidence interval [CI]) analysis consistently favoured surgery in terms of overall survival. The results were significantly in favour of surgery at 3 years (OR = 1.91, 95% CI 1.30-2.82) and at 5 years (OR = 1.85, 95% CI 1.22 -2.82). On a treatment-received basis, the results were significantly in favour of surgery at 3 years (OR 1.84, 95% CI 1.17-2.90) and 5 years (OR 2.17, 95% CI 1.39-3.38) for overall survival, and at 3 years (OR 1.96, 95% CI 1.06-3.65) for disease-specific survival. CONCLUSIONS: The analysis of this review suggests that there is an overall survival benefit with combined preoperative radiotherapy plus radical surgery compared with radical radiotherapy plus salvage cystectomy in patients with muscle-invasive bladder cancer. However, it must be considered that only three trials were included for analysis, the patient numbers were small and that many patients did not receive the treatment they were randomised to. It must also be noted that many improvements in radiotherapy and surgery have taken place since the initiation of these trials; therefore, the data may not be readily extrapolated to modern practice. Ideally, a new trial comparing modern bladder-sparing therapy with the latest surgical approach to this disease is required.

Cystectomy↗
PubMed2004

Virtual outreach: a randomised controlled trial and economic evaluation of joint teleconferenced medical consultations.

OBJECTIVES: To test the hypotheses that virtual outreach would reduce offers of hospital follow-up appointments and reduce numbers of medical interventions and investigations, reduce numbers of contacts with the health care system, have a positive impact on patient satisfaction and enablement, and lead to improvements in patient health status. To perform an economic evaluation of virtual outreach. DESIGN: A randomised controlled trial comparing joint teleconsultations between GPs, specialists and patients with standard outpatient referral. It was accompanied by an economic evaluation. SETTING: The trial was centred on the Royal Free Hampstead NHS Trust, London, and the Royal Shrewsbury Hospital Trust in Shropshire. The project teams recruited and trained a total of 134 GPs from 29 practices and 20 consultant specialists. PARTICIPANTS: In total, 3170 patients were referred, of whom 2094 consented to participate in the study and were eligible for inclusion. In all, 1051 patients were randomised to the virtual outreach group and 1043 to standard outpatient appointments. The patients were followed 6 months after their index consultation. INTERVENTIONS: Patients randomised to virtual outreach underwent a joint teleconsultation, in which they attended the general practice surgery where they and their GP consulted with a hospital specialist via a videolink between the hospital and the practice. MAIN OUTCOME MEASURES: Outcome measures included offers of follow-up outpatient appointments, numbers of tests, investigations, procedures, treatments and contacts with primary and secondary care, patient satisfaction (Ware Specific Visit Questionnaire), enablement (Patient Enablement Instrument) and quality of life (Short Form-12 and Child Health Questionnaire). An economic evaluation of the costs and consequences of the intervention was undertaken. Sensitivity analysis was used to test the robustness of the results. RESULTS: Patients in the virtual outreach group were more likely to be offered a follow-up appointment. Significant differences in effects were observed between the two sites and across different specialities. Virtual outreach increased the offers of follow-up appointments more in Shrewsbury than in London, and more in ENT and orthopaedics than in the other specialities. Fewer tests and investigations were ordered in the virtual outreach group, by an average of 0.79 per patient. In the 6-month period following the index consultation, there were no significant differences overall in number of contacts with general practice, outpatient visits, accident and emergency contacts, inpatient stays, day surgery and inpatient procedures or prescriptions between the randomised groups. Tests of interaction indicated that virtual outreach decreased the number of tests and investigations, particularly in patients referred to gastroenterology, and increased the number of outpatient visits, particularly in those referred to orthopaedics. Patient satisfaction was greater after a virtual outreach consultation than after a standard outpatient consultation, with no heterogeneity between specialities or sites. However, patient enablement after the index consultation, and the physical and psychological scores of the Short Form-12 for adults and the scores on the Child Health Questionnaire for children under 16, did not differ between the randomised groups at 6 months' follow-up. NHS costs over 6 months were greater for the virtual outreach consultations than for conventional outpatients, pound 724 and pound 625 per patient, respectively. The index consultation accounted for this excess. Cost and time savings to patients were found. Estimated productivity losses were also less in the virtual outreach group. CONCLUSIONS: Virtual outreach consultations result in significantly higher levels of patient satisfaction than standard outpatient appointments and lead to substantial reductions in numbers of tests and investigations, but they are variably associated with increased rates of offer of follow-up according to speciality and site. Changes in costs and technological advances may improve the relative position of virtual consultations in future. The extent to which virtual outreach is implemented will probably be dependent on factors such as patient demand, costs, and the attitudes of staff working in general practice and hospital settings. Further research could involve long-term follow-up of patients in the virtual outreach trial to determine downstream outcomes and costs; further study into the effectiveness and costs of virtual outreach used for follow-up appointments, rather than first-time referrals; and whether the costs of virtual outreach could be substantially reduced without adversely affecting the quality of the consultation if nurses or other members of the primary care team were to undertake the hosting of the joint teleconsultations in place of the GP. Qualitative work into the attitudes of the patients, GPs and hospital specialists would also be valuable.

Adult↗
PubMed2003

Low-light-adapted Prochlorococcus species possess specific antennae for each photosystem.

Prochlorococcus, the most abundant genus of photosynthetic organisms, owes its remarkably large depth distribution in the oceans to the occurrence of distinct genotypes adapted to either low- or high-light niches. The pcb genes, encoding the major chlorophyll-binding, light-harvesting antenna proteins in this genus, are present in multiple copies in low-light strains but as a single copy in high-light strains. The basis of this differentiation, however, has remained obscure. Here we show that the moderate low-light-adapted strain Prochlorococcus sp. MIT 9313 has one iron-stress-induced pcb gene encoding an antenna protein serving photosystem I (PSI)--comparable to isiA genes from cyanobacteria--and a constitutively expressed pcb gene encoding a photosystem II (PSII) antenna protein. By comparison, the very low-light-adapted strain SS120 has seven pcb genes encoding constitutive PSI and PSII antennae, plus one PSI iron-regulated pcb gene, whereas the high-light-adapted strain MED4 has only a constitutive PSII antenna. Thus, it seems that the adaptation of Prochlorococcus to low light environments has triggered a multiplication and specialization of Pcb proteins comparable to that found for Cab proteins in plants and green algae.

Adaptation, Physiological↗
PubMed2003

Improved methods of cultivation and production of deuteriated proteins from E. coli strains grown on fully deuteriated minimal medium.

AIMS: The aim was to develop reliable and economical protocols for the production of fully deuteriated biomolecules by bacteria. This required the preparation of deuterium-tolerant bacterial strains and an understanding of the physiological mechanisms of acquisition of deuterium tolerance. METHODS AND RESULTS: We report here improved methods for the cultivation of Escherichia coli on fully deuteriated minimal medium. A multi-stage adaptation protocol was developed; this included repeated plating and selection of colonies and resulted in highly deuterium-tolerant cell cultures. Three E. coli strains, JM109, MRE600 and MRE600Rif, were adapted to growth on deuteriated succinate medium. This is the first report of JM109 being adapted to deuteriated minimal media. The adapted strains showed good, consistent growth rates and were capable of being transformed with plasmids. Expression of heterologous proteins in these strains was reliable and yields were consistently high (100-200 mg l-1). We also show that all E. coli cells are inherently capable of growth on deuteriated media. CONCLUSIONS: We have developed a new adaptation protocol that resulted in three highly deuterium-tolerant E. coli strains. Deuterium-adapted cultures produced good yields of a deuteriated recombinant protein. We suggest that E. coli cells are inherently capable of growth on deuteriated media, but that non-specific mutations enhance deuterium tolerance. Thus plating and selection of colonies leads to highly deuterium-tolerant strains. SIGNIFICANCE AND IMPACT OF STUDY: An understanding of the mechanism of adaptation of E. coli to growth on deuteriated media allows strategies for the development of disabled deuterium-tolerant strains suitable for high-level production of deuteriated recombinant proteins and other biomolecules. This is of particular importance for nuclear magnetic resonance and neutron scattering studies of biomolecules.

Adaptation, Physiological↗
PubMed2003

Association of transforming growth factor beta-1 single nucleotide polymorphisms with radiation-induced damage to normal tissues in breast cancer patients.

PURPOSE: To investigate whether transforming growth factor beta-1 (TGFbeta1) single nucleotide polymorphisms were associated with the susceptibility of breast cancer patients to severe radiation-induced normal tissue damage. MATERIALS AND METHODS: PCR-RFLP assays were performed for TGFbeta1 gene polymorphisms on DNA obtained from 103 breast cancer patients who received radiotherapy. The G-800A, C-509T, T+869C and G+915C polymorphic sites were examined, and genotype and allele frequencies of two subgroups of patients were calculated and compared. RESULTS: The less prevalent -509T and +869C alleles were significantly associated with a subgroup of patients who developed severe radiation-induced normal tissue fibrosis (n=15) when compared with those who did not (n=88) (odds ratio=3.4, p=0.0036, and 2.37, p=0.035, respectively). Furthermore, patients with the -509TT or +869CC genotypes were between seven and 15 times more likely to develop severe fibrosis. CONCLUSIONS: These findings imply a role for the -509T and +869C alleles in the pathobiological mechanisms underlying susceptibility to radiation-induced fibrosis. Their predictive value would be limited to patients who are -509TT or +869CC, but if "fibrosis-associated" polymorphic sites in other genes could be identified, it may be possible to detect fibrosis prone individuals before radiotherapy with greater certainty.

Alleles↗
PubMed2002

Organization of transmembrane helices in photosystem II: comparison of plants and cyanobacteria.

Electron microscopy and X-ray crystallography are revealing the structure of photosystem II. Electron crystallography has yielded a 3D structure at sufficient resolution to identify subunit positioning and transmembrane organization of the reaction-centre core complex of spinach. Single-particle analyses are providing 3D structures of photosystem II-light-harvesting complex II supercomplexes that can be used to incorporate high-resolution structural data emerging from electron and X-ray crystallography. The positions of the chlorins and metal centres within photosystem II are now available. It can be concluded that photosystem II is a dimeric complex with the transmembrane helices of CP47/D2 proteins related to those of the CP43/D1 proteins by a twofold axis within each monomer. Further, both electron microscopy and X-ray analyses show that P(680) is not a 'special pair' and that cytochrome b559 is located on the D2 side of the reaction centres some distance from P(680). However, although comparison of the electron microscopy and X-ray models for spinach and Synechococcus elongatus show considerable similarities, there seem to be differences in the number and positioning of some small subunits.

Crystallography, X-Ray↗
PubMed2002

Joint teleconsultations (virtual outreach) versus standard outpatient appointments for patients referred by their general practitioner for a specialist opinion: a randomised trial.

BACKGROUND: The current model of general practitioner referral of patients to hospital specialists in the UK is sometimes associated with unnecessary duplication of investigations and treatments. We aimed to compare joint teleconsultations between general practitioners, specialists, and patients (virtual outreach) with standard outpatient referral. METHODS: Virtual outreach services were established in London and Shrewsbury. The general practitioners referred 3170 patients, of whom 2094 consented to participate in the study and were eligible for inclusion. 1051 patients were randomly assigned virtual outreach, and 1043 standard outpatient appointments. We followed up the patients for 6 months after their index consultation. The primary outcome measure was the offer of a follow-up outpatient appointment. Analysis was by intention to treat. FINDINGS: More patients in the virtual outreach group than the standard group were offered a follow-up appointment (502 [52%] vs 400 [41%], odds ratio 1.52 [95% CI 1.27-1.82], p<0.0001). Significant differences in effects were observed between the two sites (p=0.009) and across different specialties (p<0.0001). Virtual outreach increased the offers of follow-up appointments more in Shrewsbury than in London, and more in ear, nose, and throat surgery and orthopaedics than in the other specialties. Fewer tests and investigations were ordered in the virtual outreach group by an average of 0.79 per patient (0.37-1.21, p=0.0002). Patients' satisfaction (analysed per protocol) was greater after a virtual outreach consultation than after a standard outpatient consultation (mean difference 0.33 scale points [95% CI 0.23-0.43], p<0.0001), with no heterogeneity between specialties or sites. INTERPRETATION: The trial showed that allocation of patients to virtual outreach consultations is variably associated with increased offers of follow-up appointments according to site and specialty, but leads to significant increases in patients' satisfaction and substantial reductions in tests and investigations. Efficient operation of such services will require appropriate selection of patients, significant service reorganisation, and provision of logistical support.

Ambulatory Care Facilities↗
PubMed2002

Electron crystallographic study of photosystem II of the cyanobacterium Synechococcus elongatus.

The determination of the structure of PSII at high resolution is required in order to fully understand its reaction mechanisms. Two-dimensional crystals of purified highly active Synechococcus elongatus PSII dimers were obtained by in vitro reconstitution. Images of these crystals were recorded by electron cryo-microscopy, and their analysis revealed they belong to the two-sided plane group p22(1)2(1), with unit cell parameters a = 121 A, b = 333 A, and alpha = 90 degrees. From these crystals, a projection map was calculated to a resolution of approximately 16 A. The reliability of this projection map is confirmed by its close agreement with the recently presented three-dimensional model of the same complex obtained by X-ray crystallography. Comparison of the projection map of the Synechococcus elongatus PSII complex with data obtained by electron crystallography of the spinach PSII core dimer reveals a similar organization of the main transmembrane subunits. However, some differences in density distribution between the cyanobacterial and higher plant PSII complexes exist, especially in the outer region of the complex between CP43 and cytochrome b(559) and adjacent to the B-helix of the D1 protein. These differences are discussed in terms of the number and organization of some of the PSII low molecular weight subunits.

Cryoelectron Microscopy↗
PubMed2002

Air-surface exchange of polybrominated diphenyl ethers and polychlorinated biphenyls.

Air and leaf-litter samples were collected from a rural site in southern Ontario under meteorologically stable conditions in the early spring, prior to bud burst, over a three-day period to measure the simultaneous diurnal variations in polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs). PBDEs are used in a wide range of commercial products as flame retardants and are being assessed internationally as potential persistent organic pollutants. Total PBDE concentrations in the air ranged between 88 and 1250 pg m(-3), and were dominated primarily by the lighter congeners PBDEs 17, 28, and 47, and concentrations of total PCBs ranged between 96 and 950 pg m(-3), and were dominated by the lower chlorinated (tri- to tetra-) congeners. Slopes of Clausius-Clapeyron plots indicate that both PCBs and PBDEs are experiencing active air-surface exchange. Fugacities were estimated from concentrations in the air and leaf-litter and suggest near equilibrium conditions. Following the three-day intensive sampling period, 40 air samples were collected at 24-hour intervals in an attempt to evaluate the effect of bud burst on atmospheric concentrations. Total PBDE concentrations in the daily air samples ranged between 10 and 230 pg m(-3), and were dominated by the lighter congeners PBDE 17, 28, and 47, whereas concentrations of total PCBs ranged between 30 and 450 pg m(-3) during this period. It is hypothesized thatthe high PBDE concentrations observed at the beginning of the sampling period are the result of an "early spring pulse" in which PBDEs deposited in the snowpack over the winter are released with snowmelt, resulting in elevated concentrations in the surface and air. Later in the sampling period, following bud burst, PBDE concentrations in air fell to 10 to 20 pg m(-3), possibly due to the high sorption capacity of this freshly emerging foliage compartment.

Adsorption↗
PubMed2002

Three-dimensional electron cryo-microscopy study of the extrinsic domains of the oxygen-evolving complex of spinach: assignment of the PsbO protein.

Three independent three-dimensional reconstructions of the spinach photosystem II-light-harvesting complex supercomplex were derived from single particle analyses of non-stained, vitrified samples imaged by electron microscopy. Each reconstruction was found to differ significantly in the composition of the lumenal oxygen-evolving complex extrinsic proteins. From difference mapping, aided by electron microscopy of negatively stained selectively washed samples, regions of density were assigned to the PsbO and PsbP/PsbQ proteins. Interpretation of the density assigned to the PsbO protein was explored using computer-aided structural predictions. PsbO is calculated to be mainly a beta-protein (38% beta) composed of two domains within an overall elongated shape (Pazos, F., Heredia, P., Valencia, A., and De Las Rivas, J. (2001) Proteins Struct. Funct. Genet. 45, 372-381). The positioning and fitting of the proposed structural model for the PsbO protein within the three-dimensional map indicated that there is a single copy per reaction center. Moreover, the structural model derived for PsbO, together with difference mapping, indicates that this protein stretches across the surface of the reaction center with its N- and C-terminal domains located toward the CP47 and CP43 side, respectively. This structural assignment is discussed in terms of the recent x-ray-derived cyanobacterial model of PSII (Zouni, A., Witt, H.-T., Kern, J., Fromme, P., Krauss, N., Saenger, W., and Orth, P. (2001) Nature 409, 739-743).

Cryoelectron Microscopy↗
PubMed2002

Lycopene and prostate cancer.

The role of diet and dietary supplements in the development and progression of prostate cancer represents an increasingly frequent topic of discussion in the urologist's office. As access to information becomes forever easier, patients are more aware and educated about this subject than ever before. The role of antioxidants including carotenoids in all this has been the subject of great interest for some time. Lycopene, the carotenoid that gives tomatoes and other fruits and vegetables their red colour, has been of particular interest recently as regards its role in prostate cancer. The aim of this review is to briefly outline the biology and chemistry of lycopene, the scientific basis for its proposed anticancer properties and evaluate what conclusions the practicing urologist may draw from the data thus far. The media and industry have raced to encourage not only diets high in lycopene but also dietary lycopene supplements but there is probably only sufficient evidence to recommend to patients a diet rich in all vegetables and fruits of which tomatoes and tomato based products should certainly be a part.

Animals↗
PubMed2002

Design and performance of a multicentre, randomized controlled trial of teleconsulting.

We have designed and performed a multicentre, randomized controlled trial of teleconsulting. The trial investigated the effectiveness and cost implications in rural and inner-city settings of using videoconferencing as an alternative to general practitioner referral to a hospital specialist. The participating general practitioners referred a total of 3170 patients who satisfied the entry criteria. Of these, 1040 (33%) failed to provide consent or otherwise refused to participate in the trial. Of the patients recruited to the trial, a total of 1902 (91%) completed and returned the baseline questionnaire. Although the trial was successful in recruiting sufficient patients and in obtaining high questionnaire response rates, the findings will require careful interpretation to take account of the limits which the protocol placed on the ability of general practitioners to select patients for referral.

Family Practice↗