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Biomedical subjects

A C Edwards

Publications and source records attributed to A C Edwards.

At least 19 recordsLinked to original sources
PubMed2006

Reducing fluxes of faecal indicator compliance parameters to bathing waters from diffuse agricultural sources: the Brighouse Bay study, Scotland.

The European Water Framework Directive requires the integrated management of point and diffuse pollution to achieve 'good' water quality in 'protected areas'. These include bathing waters, which are regulated using faecal indicator organisms as compliance parameters. Thus, for the first time, European regulators are faced with the control of faecal indicator fluxes from agricultural sources where these impact on bathing water compliance locations. Concurrently, reforms to the European Union (EU) Common Agricultural Policy offer scope for supporting on-farm measures producing environmental benefits through the new 'single farm payments' and the concept of 'cross-compliance'. This paper reports the first UK study involving remedial measures, principally stream bank fencing, designed to reduce faecal indicator fluxes at the catchment scale. Considerable reduction in faecal indicator flux was observed, but this was insufficient to ensure bathing water compliance with either Directive 76/160/EEC standards or new health-evidence-based criteria proposed by WHO and the European Commission.

Agriculture↗
PubMed2002

Calcite saturation in the River Dee, NE Scotland.

The spatial and temporal variations in calcite (calcium carbonate) solubility within the Dee basin of NE Scotland were assessed using water chemistry data gathered from a network of 59 sites monitored for water quality from June 1996 to May 1997. Calcite solubility, expressed in terms of a saturation index (SIcalcite), was determined from measured streamwater pH, Gran alkalinity and calcium concentrations and water temperature. In general, the waters of the Dee system are undersaturated with respect to calcite, though the saturation index is higher during the summer months indicating a dependency on flow conditions and biological activity. Under low-flow conditions, the streamwaters are dominated by water derived from the lower soil horizons and deeper groundwater stores and therefore, ions such as Gran alkalinity and calcium are at their highest concentrations as they are derived mainly from bedrock weathering. The influence of biological activity on the carbonate system is also evident as the observed pH and estimated EpCO2 values indicate strong seasonal patterns, with the highest pH and lowest EpCO2 values occurring during the summer low-flow periods. Only at three sites in the lowland region of the catchment, during the summer low-flow period, are the waters oversaturated. As such, the Dee system represents an extreme 'end-member' case when compared to many UK rivers that span both under- and oversaturated conditions during the year. Regression analysis highlights a systematic change in the SIcalcite-pH relationship in a broad east-west direction across the Dee system. At sites draining the relatively impermeable upland areas, the regression of SIcalcite against pH gives a straight line with a gradient in the range 1.6-2.4. Correspondingly, under the most extreme alkaline conditions found at sites draining lowland agricultural areas, a straight-line relationship exists but with a gradient of unity. It is concluded that these changes in the SIcalcite-pH relationship are due to variations in the bicarbonate system induced by the flow conditions and biological activity. Given the waters are undersaturated, then calcite precipitation and hence phosphorus co-precipitation cannot occur within the water column.

Agriculture↗
PubMed2001

CD18 activation epitopes induced by leukocyte activation.

The cell surface adhesion molecule LFA-1 coordinates leukocyte trafficking and is a costimulatory molecule for T cell activation. We developed a panel of mAbs that recognize activation epitopes on the CD18 subunit, and show that stimulation of T lymphocytes appears to be accompanied by a conformational change in a subpopulation of LFA-1 that does not require ligand binding. Activation epitope up-regulation requires divalent cations, is sensitive to cellular signal transduction events, and correlates with cell adhesion. In addition, the stimulated appearance of these activation epitopes is absent in cell lines from patients with leukocyte adhesion deficiency-1/variant that has previously been shown to be defective in LFA-1 activation. Thus, these activation epitope Abs can be used to dissect signal transmission to CD18. Evidence suggests that these CD18 activation epitopes are induced early in cellular activation and are independent of actin rearrangement necessary for avid adhesion. We have also determined that function-blocking CD18 Abs inhibit the induction of activation epitopes. One activation epitope Ab binds to a site on CD18 distinct from that of the blocking Abs, indicating that the blocking Abs suppress a conformational change in LFA-1. We also find that these neoepitopes are present on rLFA-1 with high affinity for ICAM-1 and their binding is modulated in parallel with the affinity of LFA-1 for ICAM-1. Collectively, these neoepitope Abs identify a subpopulation of LFA-1 most likely with high affinity for ICAM-1 and necessary for LFA-1 function.

Adjuvants, Immunologic↗
PubMed2001

Inorganic and organic losses of nitrogen from upland regions of Britain: concentrations and fluxes.

The nitrogen (N) composition of streams draining eight upland regions of Britain was compared using monthly samples collected between April 1997 and April 1998. Stream samples were analysed for total N (TN), particulate N (PN), nitrate (NO3), ammonium (NH4), and dissolved organic nitrogen (DON). Concentrations of TN were small, generally less than 1.5 mg N l(-1), were dominated by dissolved forms of N, and varied significantly between regions. NO3 accounted for the majority of variability. Concentrations of DON also varied between regions but to a smaller extent than those of NO3. There were considerable variations in TN fluxes between upland regions, which ranged between 3.8 and 16.1 kg N ha(-1) year(-1). The majority of the variation was due to NO3 fluxes, which were largest in regions receiving largest inputs of atmospheric N deposition and ranged between 1.4 and 13.5 kg N ha(-1) year(-1). Fluxes of DON ranged between 1 and 3.5 kg N ha(-1) year( -1), while fluxes of PN were generally less than 0.5 kg N ha(-1) year(-1) , and NH4 fluxes ranged between 0.1 and 0.4 kg N ha(-1) year(-1). NO3 was the dominant fraction (47-84%) of N exported from all upland regions except the Highlands, where DON accounted for 52% of the TN flux. This study has shown that the DON fraction is an important component of the total N transported by upland streams in Britain.

Altitude↗
PubMed2001

The nitrogen composition of streams in upland Scotland: some regional and seasonal differences.

The nitrogen (N) composition of streams draining four upland regions of Scotland was compared in samples collected monthly between April 1997 and April 1998. Stream samples were analysed for total N (TN), particulate N (PN), nitrate (NO3), ammonium (NH4), dissolved organic N (DON) and dissolved organic carbon (DOC). Concentrations of TN were small, generally less than 1 mg l(-1) , dominated by dissolved forms of N, and varied significantly between upland regions. Nitrate accounted for most of the variability in TN; largest concentrations were observed in the Southern Uplands and smallest concentrations were observed in the Highlands. Nitrate concentrations were positively correlated with the percentage cover of improved grasslands and brown forest soils and negatively correlated with the percentage cover of peat. Concentrations of DON also varied between regions, but to a lesser extent than those of NO3. Largest concentrations occurred in SW Scotland and smallest concentrations in the Cairngorms. Although a significant positive correlation between DON and DOC was observed, stream water DON content was not related to the percentage cover of peat in the catchment, as was the case for DOC. The average DOC:DON ratio was narrower for streams in the Southern Uplands than for those in the Cairngorms and Highlands. Nitrate and DON displayed contrasting seasonal trends; NO3 concentrations were larger in the winter while DON concentrations were larger in the summer. Only a small proportion, < 8% and < 7%, of TN was PN and NH4, respectively, the majority of N was present as either NO3 or DON. Nitrate was the dominant fraction (58-65%) in all regions except the Highlands where DON accounted for 57% of TN. However, the relative importance of the DON component increased in the summer in all regions. This study has demonstrated that the DON fraction is an important component of the total N transported by streams from upland catchments in Scotland. Thus, assessments of anthropogenic impacts on N losses from upland ecosystems need to consider not only the dissolved inorganic species but also DON.

Agriculture↗
PubMed2001

Modelling instream nitrogen variability in the Dee catchment, NE Scotland.

The Integrated Nitrogen in CAtchments model (INCA) was applied to the River Dee, Aberdeenshire, NE Scotland. To a first approximation the model was able to simulate the annual mean streamwater NO3-N concentrations observed along the length of the main channel. This provided the basis for using INCA to subsequently explore the effects of N deposition and land use management on streamwater NO3-N concentrations and loads. On an annual timescale, the model predictions suggest that NO3-N concentrations will decrease by 5% following a 20% reduction in fertiliser application. Furthermore, model results also suggest that a 50% increase in N deposition will cause a 15% increase in the streamwater NO3-N concentrations. The utility of INCA as a tool for catchment management is discussed, current limitations are highlighted and possible improvements are suggested.

Agriculture↗
PubMed2001

Water quality of Scottish rivers: spatial and temporal trends.

The Harmonised Monitoring Scheme (HMS) was initiated in 1974 and represents the best-organised source of temporal and spatial data describing water quality for the major mainland rivers of Scotland, England and Wales. This paper presents the first detailed analysis of HMS data for Scotland, and identifies temporal changes in water quality from 1974 to 1995. From a concomitant analysis of catchment land cover characteristics, water quality indices have been linked with potential 'drivers' of change, influencing both point and diffuse sources. Nitrate concentrations between rivers are highly correlated with the amount of arable land, and relationships exist between grassland cover, orthphosphate-P and suspended solids concentrations. Similarly, urban catchments are highly correlated with ammonium-N, orthophosphate-P and suspended solids. Spatial and temporal trends in water quality for the rivers of Scotland are discussed.

Agriculture↗
PubMed2000

A review of water quality concerns in livestock farming areas.

Post-war changes in farming systems and especially the move from mixed arable-livestock farming towards greater specialisation, together with the general intensification of food production have had adverse affects on the environment. Livestock systems have largely become separated into pasture-based (cattle and sheep) and indoor systems (pigs and poultry). This paper reviews water quality issues in livestock farming areas of the UK. The increased losses of nutrients, farm effluents (particularly livestock wastes), pesticides such as sheep-dipping chemicals, bacterial and protozoan contamination of soil and water are some of the main concerns regarding water quality degradation. There has been a general uncoupling of nutrient cycles, and problems relating to nutrient loss are either short-term direct losses or long-term, related to accumulated nutrient surpluses. Results from several field studies indicate that a rational use of manure and mineral fertilisers can help reduce the pollution problems arising from livestock farming practices. Several best management practices are suggested for the control of nutrient loss and minimising release of pathogen and sheep-dip chemicals into agricultural runoff.

Agriculture↗
PubMed2000

Knowledge of cardiovascular disease risk factors among the Canadian population: relationships with indicators of socioeconomic status.

BACKGROUND: We examined the ability of adult Canadians to recall cardiovascular disease risk factors to determine the associations between their ability to recall risk factors for cardiovascular disease and their socioeconomic status. METHODS: This study used the database assembled by the Canadian Heart Health Surveys Research Group between 1986 and 1992--a stratified representative sample comprising 23,129 Canadian residents aged 18 to 74. Nurses administered a standard questionnaire asking respondents to list the major risk factors for cardiovascular disease: fat in food, smoking, lack of exercise, excess weight, elevated blood cholesterol and high blood pressure. Six logistic regressions examined the multivariate associations between ability to recall each risk factor with education, income adequacy, occupation, sex, age, marital status and province of residence. RESULTS: More people knew about the behaviour-related risk factors for cardiovascular disease than about the physiologic risk factors: 60% recalled fat in food, 52% smoking and 41% lack of exercise, but only 32% identified weight, 27% cholesterol and 22% high blood pressure. Education was the socioeconomic status indicator most strongly and consistently associated with the ability to recall risk factors for cardiovascular disease. The odds ratios of reporting an association of the risks between people with elementary education and those with university degrees varied between 0.16 (95% confidence interval 0.12 to 0.22) for lack of exercise to 0.55 (95% confidence interval 0.39 to 0.77) for smoking. INTERPRETATION: People in categories at greater risk of cardiovascular disease, such as those aged 65 or more or those with only elementary education, are less able to recall important cardiovascular disease risk factors.

Adolescent↗
PubMed2000

Distribution of cardiovascular disease risk factors by socioeconomic status among Canadian adults.

BACKGROUND: This study was designed to describe the distribution of risk factors for cardiovascular disease by socioeconomic status in adult men and women across Canada using the Canadian Heart Health Surveys Database. METHODS: The data were derived from provincial cross-sectional surveys done between 1986 and 1992. Data were obtained through a home interview and a clinic visit using a probability sample of 29,855 men and women aged 18-74 years of whom 23,129 (77%) agreed to participate. The following risk factors for cardiovascular disease were considered: elevated total plasma cholesterol (greater than 5.2 mmol/L), regular current cigarette smoking (one or more daily), elevated diastolic or systolic blood pressure (140/90 mm Hg), overweight (body mass index and lack of leisure-time physical activity [less than once a week in the last month]). Education and income adequacy were used as measures of socioeconomic status and mother tongue as a measure of cultural affiliation. RESULTS: For most of the risk factors examined, the prevalence of the risk factors was inversely related to socioeconomic status, but the relationship was stronger and more consistent for education than for income. The inverse relationship between socioeconomic status and the prevalence of the risk factors was particularly strong for smoking and overweight, where a gradient was observed: 46% (standard error [SE] 1.4) of men and 42% (SE 4.3) of women who had not completed secondary school were regular smokers, but only 12% (SE 1.0) of men and 13% (SE 0.9) of women with a university degree were regular smokers. Thirty-nine percent (SE 1.4) of men and 19% (SE 3.8) of women who had not completed secondary school were overweight, compared with 26% (SE 2.6) of male and 19% of female university graduates. The prevalence of leisure-time physical inactivity and elevated cholesterol was highest in both men and women in the lowest socioeconomic category, particularly by level of education. INTERPRETATION: The differences in the prevalence of risk factors for cardiovascular disease between socioeconomic groups are still important in Canada and should be considered in planning programs to reduce the morbidity and mortality from cardiovascular disease.

Adolescent↗
PubMed1999

Systemic sclerosis (scleroderma) in two iron ore mines.

Six males with systemic sclerosis were observed in the work forces of two iron ore mines. The usual spectrum of clinical features encountered in systemic sclerosis patients were present. Histologic examination of pulmonary tissue was performed on three of the cases and showed features of both silicosis and scleroderma but to different degrees and stages of development. Exposure to high levels of silica-containing dusts had occurred in all six cases.

Adult↗
PubMed1998

Gender differences in marital support following a shared life event.

Previous work has established that women with good marriages are less at risk of depression of clinical severity following a crisis than women in poor quality relationships. Evidence for such protectiveness is less clear for men. The paper examines the relationship between marital quality, onset of depression, and gender following a severely threatening life event. The results show that good quality of marriage related to lower rates of depression for both men and women, although the overall rate for women was higher. For women with a good marital relationship, but for whom support from partner was not forthcoming at the time of the crisis (i.e. the person was "let down"), risk was increased, confirming a result from a study in Islington. The current study shows that the same set of findings holds for men. Gender differences did emerge when the subjective need for support within the marital relationship is taken into account, with women expressing greater need. However, such a desire for support was not necessarily translated into support-seeking behaviour as in a poor relationship turning to a partner was frequently inopportune. Women were also more likely to seek support outside the marriage; as in the earlier Islington research this was related to a lower risk of depression for those in a poor relationship. An unexpected finding was that men who received support outside marriage had an increased risk of depression.

Adult↗
PubMed1997

Gender differences in the onset of depression following a shared life event: a study of couples.

BACKGROUND: Gender differences in clinically relevant depression are well established, appear to be greatest in childbearing years and may be the result of gender differences in social roles. METHODS: A community sample of 100 couples who had recently experienced at least one threatening life event that was potentially depressogenic for both of them was studied using a semi-structured interviewer-rated interview. Onset of depression was assessed using the Present State Examination, and, rather than assuming that a gender difference in roles existed uniformly across the couples, they were characterized according to their actual role activity and commitment. RESULTS: Women were found to have a greater risk of a depressive episode following the life event than men, and this difference was of a similar magnitude to other reports of gender differences in depression. Consistent with a role hypothesis, this greater risk was entirely restricted to episodes that followed events involving children, housing or reproductive problems. In addition, it was found that women's greater risk of a depressive episode following such events was only present among those couples where there were clear gender differences in associated roles. There was some suggestion that differences in roles on the one hand resulted in women being more likely to hold themselves responsible for such events and, on the other hand, enabled men to distance themselves from them. CONCLUSIONS: These results support the hypothesis that gender differences in rates of depression in the general population are, to a considerable extent, a consequence of role differences.

Adult↗
PubMed1996

Comparison of optimised planar scintigraphy with SPECT thallium, exercise ECG and angiography in the detection of coronary artery disease.

BACKGROUND: Thallium SPECT has been shown to be more sensitive than planar imaging in the detection of coronary heart disease (CAD) in a number of reported series. Early (< 10 minutes) redistribution on planar imaging has been demonstrated in clinical studies and this may partly contribute to its lower sensitivity. AIM: To determine whether thallium SPECT is superior to planar scintigraphy (with the timing of imaging performed optimally so that it was commenced within five minutes of injection) in the detection of CAD. METHODS: Planar and SPECT studies were performed in 44 patients with significant (> 70% stenosis) CAD, seven patients with borderline stenoses (50-69%) and in 18 patients with no significant CAD. RESULTS: The sensitivity of planar imaging was 66% which was higher than exercise ECG 54% (ns) but significantly lower than SPECT 86% (p < 0.005). The specificity of planar thallium scintigraphy was 100% which was higher than SPECT (83%) and significantly higher than exercise ECG 72% (p < 0.05). SPECT had a significantly higher sensitivity for LAD and single vessel disease than planar imaging and this was unrelated to a history of prior myocardial infarction. CONCLUSION: Even when planar imaging is timed optimally to minimise the impact of early redistribution, SPECT is more sensitive than either planar imaging or exercise ECG in the detection of CAD, but its specificity is lower.

Adult↗
PubMed1995

Long-term nutrient enrichment of an estuarine system: Ythan, Scotland (1958-1993).

A comprehensive review is given of past and current annually averaged nutrient concentrations (total oxidised nitrogen [TON], phosphate and silicate) in the River Ythan and its estuary. TON concentrations in the River Ythan have increased from ca 100-150 microm in the late 1960s to ca 500-550 microm in the early 1990s, changes which are also shown in the estuary. The interpretation of the phosphate data is more complex but concentrations in the estuary also appear to have increased. Silicate concentrations have remained constant with time. The results of 11 surveys of the estuary completed during 1993 are given. TON and silicate behave conservatively in the estuary, with concentrations determined by those of the fresh water end-member and hence by processes within the catchment. Phosphate and ammonia concentrations at low salinity are affected by the discharge from the Ellon sewage treatment facility at the head of the estuary. Throughout the estuary there is evidence of an input of ammonia to the water column from the sediments, but it represents only ca 0.2-2% of the nitrogen entering from the River Ythan. Despite the increased nutrient loading to the estuary there is no evidence that this has resulted in higher chlorophyll concentrations in the water column, this observation is attributed to the relatively short flushing period of the estuary.

Journal Article↗
PubMed1994

Redistribution of zinc from sewage sludge applied to a range of contrasting soils.

An incubation study has been performed to investigate the rates of redistribution of 65Zn from spiked sewage sludge into different soil fractions. The labeled zinc in soils amended with sludge was fractionated by operationally defined procedures at three different times (1, 7 and 30 days after incubation) into exchangeable, organically bound, amorphous iron oxide-bound, crystalline iron oxide-bound and residual fractions. The rates of redistribution of zinc from sewage sludge mainly depended on soil pH. In acid soils, most of the sludge-derived zinc (70-80%) went to the exchangeable pools, and was retained in this form at high concentration for at least a month. The effect of the time during digestion of the incorporation of a 65Zn spike into sludge was also studied. Although the results were significantly effected by spike timing, the effects of the latter on subsequent zinc fractionation results were minor compared with the effect of soil pH.

Hydrogen-Ion Concentration↗