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Biomedical subjects

D Preston

Publications and source records attributed to D Preston.

At least 19 recordsLinked to original sources
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↗
PubMed1993

Stable chromosome aberrations among A-bomb survivors: an update.

Analysis of data on stable chromosome aberrations collected between 1968 and 1985 by the Radiation Effects Research Foundation (RERF) on 1703 individuals exposed to A-bomb radiation in Hiroshima and Nagasaki, Japan, reveals different dose-response relationships in the two cities, as well as significant effects of both time of assay and age at exposure. In Hiroshima, the proportion of cells with aberrations increased by 0.080 per sievert at low doses, assuming a constant neutron radiation RBE of 10 relative to gamma radiation, for assays performed during the latest period (1981-1985). In Nagasaki, the low-dose increase was 0.0126 per sievert. There was evidence that radiation exposure was more effective for producing stable aberrations at some younger ages at exposure, although the interpretation of this interaction is difficult. Modeling neutron and gamma-ray components of dose separately in a way which allows the neutron RBE to vary with dose yielded an estimated low-dose limiting value of RBE of 707 (95% confidence bound 200-infinity), with a low-dose response of approximately 0.008 aberrations per sievert. This RBE is much higher than the published RBEs for induction of aberrations in vitro. The high estimated RBE and the differences in dose response by city both are suggestive of systematic dose estimation errors in which either neutrons were underestimated in Hiroshima or gamma rays were overestimated in Nagasaki.

Adolescent↗
PubMed1993

Deliberate self-harm and public holidays: is there a link?

It has previously been reported [Davenport & Birtle, 1990] that there is a positive association between nonfatal deliberate self-harm in adolescents and emotionally charged festivals, such as St Valentine's Day and Christmas Day. We studied all cases of nonfatal deliberate self-harm presenting to three Central London hospitals on St Valentine's Day and Christmas Day and on two control dates, between 1983 and 1989. No association was found between cases of deliberate self-harm and St Valentine's Day, but a negative association was found with Christmas Day.

Adolescent↗
PubMed1991

Frequent chest X-ray fluoroscopy and breast cancer incidence among tuberculosis patients in Massachusetts.

The incidence of breast cancer was determined in 4940 women treated for tuberculosis between 1925 and 1954 in Massachusetts. Among 2573 women examined by X-ray fluoroscopy an average of 88 times during lung collapse therapy and followed for an average of 30 years, 147 breast cancers occurred in contrast to 113.6 expected [observed/expected (O/E) = 1.29; 95% confidence interval (CI) = 1.1-1.5]. No excess of breast cancer was seen among 2367 women treated by other means: 87 observed versus 100.9 expected. Increased rates for breast cancer were not apparent until about 10 to 15 years after the initial fluoroscopy examination. Excess risk then remained high throughout all intervals of follow-up, up to 50 years after first exposure. Age at exposure strongly influenced the risk of radiation-induced breast cancer with young women being at highest risk and those over age 40 being at lowest risk [relative risk (RR) = 1.06]. Mean radiation dose to the breast was estimated to be 79 cGy, and there was strong evidence for a linear relationship between dose and breast cancer risk. Allowing for a 10-year minimum latent period, the relative risk at 1 Gy was estimated as 1.61 and the absolute excess as 10.7 per 10(4) woman-years per gray. When compared to other studies, our data suggest that the breast is one of the most sensitive tissues to the carcinogenic force of radiation, that fractionated exposures are similar to single exposures of the same total dose in their ability to induce breast cancer, that risk remains high for many years after exposure, and that young women are especially vulnerable to radiation injury.

Breast Neoplasms↗