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Biomedical subjects

D Preston

Publications and source records attributed to D Preston.

At least 19 recordsLinked to original sources
PubMed2006

Diversity of 16S rRNA gene, ITS region and aclB gene of the Aquificales.

The Aquificales are prevalent members of the microbial communities inhabiting many marine and terrestrial hydrothermal systems. Numerous new strains were obtained from deep-sea and terrestrial hydrothermal systems. In order to resolve the phylogenetic relationships within this group, three different phylogenetic datasets were used, namely the 16S rRNA gene, the intergenic transcribed spacer region between the 16S rRNA and 23S rRNA genes (ITS) and the gene coding for the ATP citrate lyase (aclB), a key enzyme in the reductive TCA cycle. The data were analyzed using neighbor-joining, parsimony and maximum likelihood. The resulting phylogenies appeared to be consistent between the three markers. The three genes confirmed the presence of isolates that merit further characterization and descriptions as new species and perhaps even new genera. The detailed phylogenetic interrelationships of these isolates are described here.

ATP Citrate (pro-S)-Lyase↗
PubMed2004

Heavy metal contamination of water, soil and produce within riverine communities of the Río Pilcomayo basin, Bolivia.

The Río Pilcomayo heads on the Cerro Rico de Potosí precious metal-polymetallic tin deposits of Southern Bolivia. Mining of the Potosí deposits began in 1545 and has led to the severe contamination of the Pilcomayo's water and sediments for at least 200 km downstream of the mines. This investigation addresses the potential human health affects of metal and As contamination on four communities located along the upper Río Pilcomayo by examining the potential significance of human exposure pathways associated with soils, crops and water (including river, irrigation and drinking water supplies). The most significantly contaminated agricultural soils occur upstream at Mondragón where Cd, Pb and Zn concentrations exceed recommended guideline values for agricultural use. Further downstream the degree of contamination decreases, and metal concentrations are below Dutch, German and Canadian guideline values. Metal and As concentrations in agricultural products from the four communities were generally below existing guidelines for heavy metal content in commercially-sold vegetables. Thus, the consumption of contaminated produce does not appear to represent a significant exposure pathway. A possible exception is Pb in carrots, lettuce and beetroots from Sotomayor and Tuero Chico; 37% and 55% of the samples, respectively, exceeded recommended guidelines. Most communities obtain drinking water from sources other than the Río Pilcomayo. In general, dissolved concentrations of metals and As in drinking water from the four studied communities are below the WHO guideline values with the exception of Sb, which was high at Tasapampa. The inadvertent ingestion of contaminated water from irrigation canals and the Río Pilcomayo represents a potential exposure pathway, but its significance is thought to be minimal. Given the degree of soil contamination in the area, perhaps the most significant exposure pathway is the ingestion of contaminated soil particles, particularly particles attached to, and consumed with vegetables. The risks associated with this pathway can be reduced by thoroughly washing or peeling the vegetables prior to consumption. Other exposure pathways that are currently under investigation include the consumption of contaminated meat from livestock and poultry, which drink polluted waters and the ingestion of contaminated wind-blown dust.

Agriculture↗
PubMed2004

[Medical and biological consequences of human's chronic exposure to radiation].

The authors considered medical consequences of radiation accidents (burial of radioactive waste into Techa river and accident in 1957) in "Majak" Industrial Association. Results of long-term observations helped to evaluate health state of people who underwent chronic exposure to radiation and of their descendants.

Catchment Area, Health↗
PubMed2003

Fatal chemotherapy-induced encephalopathy following high-dose therapy for metastatic breast cancer: a case report and review of the literature.

Chemotherapy-induced encephalopathies occur in a variety of clinical settings and the most detailed accounts have been described following combination methotrexate and radiation therapy. The case described herein developed severe encephalopathy following a high-dose chemotherapy protocol used in the treatment of metastatic carcinoma of the breast. Visual symptoms developed 3 weeks after completing high-dose chemotherapy and peripheral blood hematopoietic stem cell transplantation. Over the next several weeks, additional neurologic deficits developed and continued to progress despite various treatment interventions. Diffuse deep gray matter damage was identified on MR imaging and a brain biopsy revealed pathological findings similar in many respects to those described for methotrexate/radiation, cisplatin, BCNU and/or 5 FU/levamisole-related leukoencephalopathy. The patient succumbed to complications resulting from the CNS disorder, 8 weeks after the onset of symptoms. This case is unusual for two reasons. First, the patient developed severe encephalopathy following a high-dose chemotherapy protocol commonly used in the treatment of metastatic breast carcinoma and second, the encephalopathy involved primarily deep gray matter structures rather than white matter.

Adult↗
PubMed2001

Stable chromosome aberrations in atomic bomb survivors: results from 25 years of investigation.

Frequencies of stable chromosome aberrations from more than 3,000 atomic bomb survivors were used to examine the nature of the radiation dose response. The end point was the proportion of cells with at least one translocation or inversion detected in Giemsa-stained cultures of approximately 100 lymphocytes per person. The statistical methods allow for both imprecision of individual dose estimates and extra-binomial variation. A highly significant and nonlinear dose response was seen. The shape of the dose response was concave upward for doses below 1.5 Sv but exhibited some leveling off at higher doses. This curvature was similar for the two cities, with a crossover dose (i.e. the ratio of the linear coefficient to the quadratic coefficient) of 1.7 Sv (95% CI 0.9, 4). The low-dose slopes for the two cities differed significantly: 6.6% per Sv (95% CI 5.5, 8.4) in Hiroshima and 3.7% (95% CI 2.6, 4.9) in Nagasaki. This difference was reduced considerably, but not eliminated, when the comparison was limited to people who were exposed in houses or tenements. Nagasaki survivors exposed in factories, as well as people in either city who were outside with little or no shielding, had a lower dose response than those exposed in houses. This suggests that doses for Nagasaki factory worker survivors may be overestimated by the DS86, apparently by about 60%. Even though factory workers constitute about 20% of Nagasaki survivors with dose estimates in the range of 0.5 to 2 Sv, calculations indicate that the dosimetry problems for these people have little impact on cancer risk estimates for Nagasaki.

Adolescent↗
PubMed2000

The NHS manager. A view from the bridge.

The changing role of the manager has been a growing area of both academic and popular literature over recent years. In addition, the interest of the popular press has made terms like "grey suit" and "fat cat" common terminology. Management roles and managerial authority within today's organisations have seen many changes. This has led to frustration and anxiety for managers as they have watched their role change. In the NHS, like other sectors, managers have become a target for organisational redundancies and have experienced increased responsibility, closer monitoring of performance and heightened job insecurity. This paper aims to offer a contribution to the empirical data on managers by investigating one group of NHS managers' own perceptions of how others see their role. The findings suggest that NHS managers are very aware of the largely negative perceptions that surround them but accept this as an integral part of their role.

Administrative Personnel↗
PubMed2000

Bringing Canadian healthcare closer to home: the initial stages of change for senior managers within the province of British Columbia.

This paper explores some recent healthcare reforms within the Canadian healthcare sector. As in most countries across the world, healthcare managers in Canada have been faced with the dilemma of how to achieve a balance between equity of provision and expenditure control. This study explores the external and internal pressures for change at the provincial and national levels within Canada. More significantly, it focuses on how the early stages of these changes have resulted in altered work roles and relationships for healthcare managers. A case study of British Columbia is described, where radical changes occurred in the healthcare sector in the mid-1990s. Interviews conducted with a sample of senior healthcare managers in the province illustrate how the restructuring of healthcare impacted upon management roles, structures and communication. The qualitative interview data is intended to provide an important addition to the body of largely quantitative, statistical data that is collected on international health systems on a regular basis. How the findings of the case study can contribute to learning and practice within the health services management arena is discussed.

Attitude of Health Personnel↗
PubMed1999

Treatment of posttraumatic ocular dysmotility using autogenous buccal fat grafts in a porcine model.

Diplopia occurring after orbital trauma is a complex and difficult clinical problem. Numerous potential mechanisms exist by which it may occur. Restrictive ocular dysmotility caused by intraorbital scarring is a major component in diplopia's pathogenesis. The current large animal study was conducted to develop an experimental model of restrictive ocular dysmotility that would quantitatively characterize the biomechanical properties of the globe rotations. Using this model, a novel method of restoring the low-friction milieu within the orbit by interposing a buccal fat graft was tested. In the initial stage, the baseline force duction was measured in 20 pig eyes using a highly sensitive, digital tensiometer. Traumatic violation of Tenon's fascia with electrocautery into the extraconal fat and the periorbita was followed by direct suturing of the extraocular muscle to the nearest orbital periosteum. After 6 weeks, the measurements (again in the field of the traumatized muscle) were repeated, and the eyes were divided into two treatment groups (n = 10 eyes per group). The left eye received the standard lysis of adhesion, whereas the right eye received lysis and buccal fat interposition grafting. The third and final force measurements were performed 6 weeks after treatment. The results showed a baseline linear load-displacement curve of 0 to 8 mm, with the globe rotating 400 microm for every 1000 mg of tensile load. Surgical trauma increased the slope as defined by load/displacement but, surprisingly, the relationship remained linear in the entire range from 2 to 8 mm. This linear relationship was seen in all stages: baseline, after trauma to Tenon's fascia, after surgical lysis alone, and after lysis with buccal fat interposition. The difference was in the slope, or stiffness. Lysis alone partially reduced the slope, but it was still higher than baseline. Lysis and buccal fat grafting returned the slope to near baseline. This, however, did not reach the level of statistical significance. It seems that a focal intervention along the course of an extraocular muscle altered the composite behavior of orbital resistance to globe rotation. Although buccal fat grafting did not significantly improve motility, it did not worsen it.

Adipose Tissue↗
PubMed1998

Quantitative forced ductions in an animal model--characterization of passive forces.

PURPOSE: Our purpose was to characterize the passive tissue forces involved in ocular rotation in a controlled animal model and to evaluate the influence of manual versus mechanized ductions, repeated measurements, speed of rotation, and the influence of the nondepolarizing muscle relaxant mivacurium. METHODS: Forced ductions were performed under general anesthesia on 20 eyes of 10 pigs, with or without mivacurium, with use of a highly sensitive force gauge attached to the eye by a traction suture. The eye was moved either manually or at constant speed with a motorized platform. Eyes were rotated a total of 8 mm from their resting position under anesthesia. The force-displacement relationship was analyzed and compared between groups. RESULTS: A linear (elastic) relationship between force and displacement was noted, with a slope of 0.4 g per degree with use of the mechanized technique. Neither speed of rotation, use of mivacurium, nor repeated ductions significantly influenced the shape or slope of the relationship. Hysteresis averaged 2 to 4 g. Measurements performed with use of the motorized platform showed significantly improved reliability over those made manually. CONCLUSIONS: The passive length-tension data correlate well with data reported by others in humans. Within a wide range of eye movement, this force is elastic in nature. For relatively low angular velocities, such as might be produced in smooth pursuit, the passive forces do not change appreciably with changes in velocity. The nondepolarizing muscle relaxant mivacurium has no effect on accurate performance of passive forced ductions under general anesthesia. Studies collecting quantitative data on passive orbital forces should be performed, when feasible, with an automated duction and recording apparatus.

Anesthesia, General↗
PubMed1998

Restricted ocular motility after orbital trauma--studies with an animal model.

OBJECTIVE: Our purpose was to develop a quantitative model of restricted ocular motility (fat adherence syndrome) in the pig orbit to facilitate research into pathogenesis and treatment. METHODS: Twenty eyes of 10 pigs were used in an attempt to create a fibrous adhesion between either the inferior rectus or the medial rectus muscle and the adjacent periorbita. Quantitative forced ductions were performed preoperatively and 6 weeks postoperatively with an electronic force gauge. RESULTS: Forced ductions displayed a linear relationship to displacement over the range tested, both preoperatively and postoperatively. Although increased resistance to forced ductions was produced in 10 of the 20 (50%) eyes, the average changes were not statistically significant. The absolute change in force (Postoperative--Preoperative) was linearly related to the amount of ocular rotation. Reproducibility of measurements was markedly improved by the use of a motorized forced duction apparatus compared with manual rotation. CONCLUSIONS: The results from this study, and those from previous work, suggest that the classic fat adherence syndrome is an uncommon event, even after significant soft tissue injury in the orbit. Further studies are needed to more completely define the risk factors and pathogenesis of the fat adherence syndrome and the suitability of the pig orbit as a model.

Adipose Tissue↗
PubMed1997

Doctor in the process. The engagement of clinical directors in hospital management.

Aims to examine medical involvement in hospital management processes, and to consider the implications of current experience for the next generation of clinical directors. Doctors who move into a formal management role often find themselves unprepared for their new responsibilities. Research has thus concentrated on identifying the management competences which doctors lack, and with designing ways to remedy the deficit. Seeks to move beyond this deficit model by adopting a perspective which focuses on the engagement of doctors in the management process. Draws data from in-depth interviews with six clinical directors and 19 other members of the hospital management team at Leicester General Hospital NHS Trust (LGH). Content analysis of interviews suggest that the engagement of clinical directors in the hospital management process at this site can be described as reluctant, transient, service-driven, power-pulled and pressured. This negative portrayal of the role, however, must be set in the context of the "management expectation" held of clinical directors by other hospital managers and staff--an expectation that is not currently fulfilled.

Clinical Medicine↗
PubMed1997

The importance of being earnest: reflections on an attempt to create an information-led organizational culture in the NHS.

Presents a study of organizational culture in a community health-care Trust in the UK. The Trust has been involved in attempting to create what was described as an information-led culture and is concurrent with the implementation of a new information system. Describes some of the recent management initiatives which were intended to improve communications within the Trust and to provide employees with a better understanding of the changes which have been taking place. Identifies findings which suggest that there was some distance between the perceptions of management and those of employees. While the senior management team appear to have been in earnest in attempting to ensure that staff have the information and understanding they need, the results of an organizational culture survey suggest that these efforts may have been ineffective.

Administrative Personnel↗
PubMed1996

Communications between professional groups in an NHS trust hospital.

Discusses an audit of communications between doctors and other professional groups in a National Health Services trust hospital. The project was undertaken as a result of senior management's perception that there were problems regarding the interface between professionals and junior doctors particularly, and that these have a potentially detrimental impact on patient care. The aim of the study was to improve the work environment of medical practitioners and professional staff by researching the factors affecting communication and the sources of conflict which exist between the groups. Describes the methodology and provides an overview of the main findings grouped into themes. A large number of recommendations for change have been made to the hospital concerning systems, procedures, structures, training and inter-professional boundaries. Implementation of some of these recommendations has taken place already. Full evaluation of their impact is yet to be determined.

Communication↗
PubMed1995

Cancer risks and biomarker studies in the atomic bomb survivors.

This paper describes recent studies on cancer incidence among Japanese atomic bomb survivors. The report includes a brief description of the primary atomic bomb survivor cohorts. The results illustrate the magnitude of the excess risks and show how these risks vary with sex, age at exposure and time. Descriptions are presented in terms of both excess relative risks and excess absolute rates. The paper also includes a summary of the current status of research on biomarkers of radiation exposure in the atomic bomb survivors.

Adolescent↗