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Biomedical subjects

D Buchanan

Publications and source records attributed to D Buchanan.

At least 37 records · Page 2Linked to original sources
PubMed1999

Biopersistence and durability of nine mineral fibre types in rat lungs over 12 months.

The study objectives were to assess the ability of intratracheal injection methods to discriminate between nine fibre types in respect of pulmonary biopersistence, and to provide approximate estimates of relative biopersistence and durability for a study of general relationships with biological and toxicological responses. The test fibres included six samples of size-selected fibre types specially prepared for research purposes, two commercially available fibres, and amosite. A 1 mg dose of each fibre type was administered to rats by intratracheal injection. The relative biopersistence of fibres in different size categories was assessed from the changes in mean lung burden, as determined by electron microscopy, at 3 days and 1, 6 and 12 months after injection. The ability of the test materials to resist dissolution was measured in a parallel series of simple in vitro acellular experiments at two pHs and in a continuous flow dissolution test. The observed differences in the persistence of fibres of differing length recovered from rat lungs were consistent with the current hypothesis that short fibres are cleared by cellular processes and long fibres by dissolution and disintegration. Differences in persistence of long (> 20 microns) fibres were correlated with measured rates of dissolution in vitro. Differences in persistence among those fibre types also studied by others workers were consistent with their findings after inhalation and intratracheal injection. Overall, the differences in the biopersistences of the test fibres following intratracheal injection were sufficient to enable an examination of the relationship of biopersistence with other biological and toxicological responses. Biopersistence was influenced by both fibre dimensions and solubility.

Air Pollutants, Occupational↗
PubMed1999

Influence of fibre length, dissolution and biopersistence on the production of mesothelioma in the rat peritoneal cavity.

A range of respirable man-made mineral fibres were tested for evidence of carcinogenicity by injection into the peritoneal cavity of male SPF Wistar rats; and differences in carcinogenicity were related to the dimensions and biopersistence of the injected fibres. The fibres tested included an amosite asbestos, a silicon carbide whisker, a special purpose glass microfibre, and a range of other man-made vitreous fibres (MMVFs) and refractory ceramic fibres (RCFs) from the TIMA fibre repository. The injected dose of each was designed as the estimated mass required to contain 10(9) fibres > 5 microns in length, as determined by optical microscopy. The numbers of long fibres (> 15 microns) contained in these doses ranged across fibres from 0.1 x 10(9) to 0.8 x 10(9) fibres; the number of long fibres thinner than 0.95 micron ranged from 0.015 x 10(9) to 0.4 x 10(9). The treatment groups contained between 18 and 24 animals. Animals were killed when they showed signs of debilitation. At autopsy, the diagnosis of mesothelioma was usually obvious macroscopically. Otherwise, histological examination of peritoneal organs was used to search for early tumour development. Judged by median survival time, four of the fibre types, in the doses administered, presented higher mesothelioma activity than amosite asbestos. The other fibres tested were less carcinogenic than the amosite. Only a ceramic material derived by extreme heating to simulate the effect of furnace or oven conditions, produced no mesotheliomas. Attempts were made, using regression models, to relate these differences to fibre dimensions and to measures of durability from separate experiments. The results pointed principally to a link with the injected numbers of fibres > 20 microns in length and with biopersistence in the rat lung of fibres longer than 5 microns. Improved quantification of the relative importance of fibre dimensions and biopersistence indices requires experimentation with a range of doses.

Animals↗
PubMed1999

Influence of characteristics of inhaled fibres on development of tumours in the rat lung.

The objective was to examine and quantify the influence of fibre dimensions, persistence in the lung, and dissolution and cell toxicity in vitro, on the risks of developing lung tumours in rats. Data were brought together from the studies carried out at the IOM under the Colt Fibre Research Programme, and from studies carried out in Switzerland and the USA under the programme of the Thermal Insulation Manufacturers Association. In both studies, groups of rats were exposed by inhalation to a range of airborne fibres. At the end of their lives they were examined for the presence of benign and malignant lung tumours and mesothelioma. The studies differed in a number of details, but were combined on the basis of approximate equivalence of cumulative exposure to airborne fibres. Logistic regression models were used to relate differences in carcinogenicity to fibre characteristics; dimensions, persistence in the lung after intratracheal injection, dissolution rates from bench-top flow-through experiments, measures of inflammation, and other cell responses to fibres in vitro. Despite the small number of data points, the results suggested a primary influence of the airborne concentrations of the numbers of fibres thinner than 1 micron diameter and longer than 20 microns, and of the measured dissolution rate of the fibres. While these results are based on only a small number of fibre types, the statistical model fits the data reasonably well, and enables some cautious insights into the quantitative influences of dimensions and biopersistence. Results were broadly consistent with those from intraperitoneal injection studies of the same fibres, in that the responses were dependent on both the durability of the fibres and the numbers of long thin fibres. In vitro and in vivo cell responses did not predict significantly the risk of cancer following inhalation.

Air Pollutants, Occupational↗
PubMed1998

Development of a method for the determination of low contents of asbestos fibres in bulk material.

Asbestos is a category 1 carcinogen under the EU classification, but in the absence of a method to quantify asbestos in a matrix at the 0.1% level, there has been a delay in implementing relevant directives to asbestos. An analytical scheme for identification and quantification of asbestos using polarised light microscopy (PLM) and phase contrast optical microscopy (PCM) has now been developed. When used on artificial mixtures by an experienced laboratory, it achieved the required target performance, at 0.1% asbestos concentration by mass in a bulk sample, to obtain a result, which with 90% probability, is correct within a factor of two. The method of identification by PLM and quantification by PCM has been assessed by interlaboratory comparisons. The method begins with an initial identification using PLM, and depending on asbestos type and matrix a combination of preparation procedures are used to produce the analytical filter. A gentle comminution method was used which reduces the risk of overmilling. The asbestos mass percentage on the filter is quantified using PCM in combination with a PLM attachment for identification of possible non-asbestos fibres. The final method is supported by efficient methods for fibre identification for size determination and calculation of total fibre volume. A statistical analysis of mass concentration estimates was made and the effect of preferred orientation of fibres on the analytical filter was quantified.

Asbestos↗
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↗
PubMed1996

Re-engineering operating theatres: the perspective assessed.

Refers to the widely experienced and appreciated difficulties in scheduling hospital operating theatres to make effective use of resources, and to avoid delays and overruns that can adversely affect patient care and staff morale. Reports the findings and recommendations of a project based in the Surgical Directorate of Leicester General Hospital NHS Trust which sought to address these problems from a business process re-engineering perspective. Covering the whole patient trail, from referral to discharge describes the project's progress through four phases concerning process mapping, the collection of staff opinions and ideas through a combination of interviews and surveys, collection of data on patient flows and procedure times, and a final "handover" phase in which broad recommendations were passed back to the Surgical Directorate for implementation with staff involvement. Details the recommendations which include a shift to cross-functional teamworking in a number of areas, along with the development of a revised theatres policy and a strengthened theatres co-ordination function. In view of recent substantial and harsh criticisms of the re-engineering perspective, seeks to offer a balanced assessment of the perspective applied to a health care setting, exploring both the problems and benefits.

Appointments and Schedules↗
PubMed1995

Reproducibility of cardiorespiratory measurements during submaximal and maximal running in children.

With the increased use of oxygen consumption measurements in clinical and sporting studies, measurement variability has become more important to both the paediatric clinician and the sports scientist. In this study we assessed the reproducibility of cardiorespiratory measurements during submaximal and maximal running in children. Ten healthy, physically active boys (mean(s.d.) age 10.7(0.71) years) performed two submaximal and two maximal running tests within a 4 week period. The submaximal protocol consisted of three 6 minute runs at 7.2, 8.0 and 8.8 km/h. Every attempt was made to minimize the sources of non-biological variability at each testing session. During submaximal exercise, oxygen consumption (VO2), heart rate (HR) and fractional utilization appeared to be the most reliable measures accounting for over two-thirds of the total variation (coefficients of reliability (CR) of 68%, 94% and 82% respectively). Ventilation (Ve) and respiratory exchange ratio (RER) proved to be only moderately reliable accounting for less than half of the total variation (CR 50% and 45% respectively). At maximal exercise, VO2, Ve and time to exhaustion were most reliable, accounting for approximately two-thirds of the total variation (CR 65%, 63% and 63% respectively). Within this test environment, a two visit submaximal assessment was capable of estimating VO2 with a standard error of +/- 1.25 ml/kg/min. Similarly, for maximal testing a two visit assessment estimated peak VO2 with a standard error of +/- 2.28 ml/kg/min. On the evidence of these results a two visit assessment for submaximal and maximal exercise testing seems adequate to estimate the stability of submaximal cardiorespiratory measures and peak VO2 in healthy, normally active boys.

Body Weight↗
PubMed1995

Suicidal thought and self-transcendence in older adults.

1. The suicide rate for adults over 65 years of age is the highest rate for suicide in any age group, and the rate is projected to increase. 2. To address a clinical concern, such as suicide, clinicians and researchers must identify factors that are specific to each population at high risk. This study chose to examine self-transcendence, which is thought to be specific to older adults' success in meeting the multiple changes of later life. 3. Two questions that address self-transcendence are: "Who is most meaningful (important) to you now?" and "What is most meaningful (important) to you now?" If an older adult is unable to answer these questions, a suicide risk assessment should probably be done.

Adaptation, Psychological↗
PubMed1994

Validation of the sensormedics (S2900Z) metabolic cart for pediatric exercise testing.

The accuracy of many microprocessor controlled exercise testing systems has not been established, particularly for testing children. A metabolic cart (Sensormedics S2900Z) was validated against a reference system (Douglas bag) in children. The systems were tested using 10 active, healthy children (age 11.6 +/- 2.3 yrs) during physiological steady state at two exercise intensities, submaximal walking and running. Eight children performed a high ventilatory flow (HVF) protocol, running for 11 min. All 10 performed a low ventilatory flow (LVF) protocol, walking for 11 min. In both, gas samples were measured after 6 to 7 and 10 to 11 min into the Douglas bag, and after 8 to 9 min by the test system. There was minimal evidence of bias for VO2 at either ventilation rate. Greater variability was noted for FeCO2 and VCO2. In conclusion, the Sensormedics S2900Z appears to be adequate for testing children.

Bias↗
PubMed1991

Seroprevalence and demographic characteristics of injection drugs users among individuals at risk for HIV infection in Winnipeg, Manitoba, Canada.

From June 1986 to March 1990, a prospective seroprevalence survey and questionnaire of individuals at risk for HIV infection was conducted with volunteers in Winnipeg. Of 610 individuals enrolled, 146 were injected drug users (IDU). Fifteen IDU were in a methadone treatment program and all were seronegative. Three of 131 remaining IDU were HIV-1 seropositive (2.3%), a rate similar to 2.2% positive (20+ of 927) in diagnostic specimens from IDU tested in the province. Demographics and behaviour of 131 IDU were compared with 335 individuals, of whom 112 were gay/bisexual [24 of whom also had sexually transmitted diseases (STD)] and 223 heterosexuals who had STD. Males enrolled were significantly older than females. Multivariate analysis showed that factors independently associated with IDU were: a younger age, less education, mental health counselling, unemployment, and a history of jaundice or hepatitis. Drugs most commonly used were Ritalin/Talwin, cocaine, and heroin. Over 90% of individuals admitted to sharing needles. In spite of the low seroprevalence of HIV-1 infections, these individuals are important for the potential spread of HIV because of multiple means of acquiring and transmitting HIV and a high rate of needle sharing.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Mycobacterial infection in patients infected with the human immunodeficiency virus.

Of 207 homosexual or bisexual patients with the acquired immune deficiency syndrome (AIDS), 24 with the AIDS related complex, and 39 with asymptomatic HIV infection, 32 patients were found to have mycobacterial infection. Mycobacterium tuberculosis was found in 13 patients with AIDS and in two with the AIDS related complex. M avium-intracellulare was found in 15 patients with AIDS and was disseminated in 12. One patient was infected with M kansasii and one with M ulcerans. Invasive procedures were frequently required to obtain positive bacteriological results. Subclinical carriage of M avium-intracellulare and other mycobacteria thought to be nonpathogenic was common in patients seronegative for the human immunodeficiency virus and at all stages of human immunodeficiency virus infection. All but one isolate of M tuberculosis were fully sensitive to standard antimycobacterial antibiotics. Response to treatment was usually rapid. M avium-intracellulare isolates were all resistant to first line agents in vitro, and antibiotics such as ansamycin and amikacin were required to obtain a clinical response.

AIDS-Related Complex↗
PubMed1989

The effect of aminophylline on gastrointestinal blood flow and oxygen metabolism in the conscious newborn lamb.

Aminophylline, widely used in the neonatal period, has been reported to be associated with necrotizing enterocolitis. We hypothesized that aminophylline might alter gastrointestinal blood flow and oxygen delivery. The effects of this drug on gastrointestinal (GI) blood flow and oxygen delivery, consumption, and extraction were examined using the radioactive microsphere method in ten chronically catheterized, unanesthetized lambs aged 5-12 days. While cardiac output and systemic oxygen consumption did not change, we found statistically significant increases (p less than 0.05) in small intestinal blood flow as a function of lamb weight and as a percentage of cardiac output. Splanchnic oxygen consumption also increased significantly. The oxygen reserve available to the GI tract can be compromised by aminophylline at levels similar to those used in the human neonate for treatment of apnea.

Aminophylline↗
PubMed1989

Fetal distress associated with the anticardiolipin antibody and a history of intrauterine fetal demise. A case report.

A woman with a history of fetal demise, an elevated anticardiolipin antibody titer, lupus anticoagulant but no evidence of systemic lupus erythematosus received anticoagulation with heparin in adjusted subcutaneous doses. Daily fetal monitoring demonstrated reactive nonstress tests and normal biophysical profiles initially. At 30 weeks' gestation, however, repeated spontaneous decelerations developed, and fetal bradycardia necessitated delivery. The combination of a poor obstetric history and the presence of high cardiolipin antibody titers requires close fetal surveillance. The benefits of anticoagulation in this setting deserve further study.

Adult↗