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Biomedical subjects

B Crabtree

Publications and source records attributed to B Crabtree.

At least 19 recordsLinked to original sources
PubMed2006

A case study of regional catchment water quality modelling to identify pollution control requirements.

There are four ecologically important river catchments that contain candidate Special Areas of Conservation (cSACs) under the Habitats Directive in the Lake District National Park located in the North of England. These are the rivers Ehen, Kent, Derwent and Eden. For each cSAC, there are defined ecological criteria that include water quality targets to protect the designated species. Stretches of the riverine cSACs in each catchment are failing to meet these and other water quality targets. The Environment Agency commissioned a study of each catchment to provide the underpinning scientific knowledge to allow it to deliver its statutory obligations under the Habitats Directive. SIMCAT river water quality models were produced and used to predict the water quality impacts resulting from a number of water quality planning scenarios aimed at achieving full compliance with the Habitats Directive and other national and EEC water quality targets. The results indicated that further controls on effluent discharges will allow the majority of targets to be met but other sources of pollution will also need to be controlled. The outcome of the study also recognised that water quality improvements alone will not necessarily produce the required improvement to the ecological interest features in each cSAC.

Ammonia↗
PubMed2003

Modelling the influence of irrigation abstractions on Scotland's water resources.

Legislation to control abstraction of water in Scotland is limited and for purposes such as irrigation there are no restrictions in place over most of the country. This situation is set to change with implementation of the European Water Framework Directive. As a first step towards the development of appropriate policy for irrigation control there is a need to assess the current scale of irrigation practices in Scotland. This paper presents a modelling approach that has been used to quantify spatially the volume of water abstractions across the country for irrigation of potato crops under typical climatic conditions. A water balance model was developed to calculate soil moisture deficits and identify the potential need for irrigation. The results were then combined with spatial data on potato cropping and integrated to the sub-catchment scale to identify the river systems most at risk from over-abstraction. The results highlight that the areas that have greatest need for irrigation of potatoes are all concentrated in the central east-coast area of Scotland. The difference between irrigation demand in wet and dry years is very significant, although spatial patterns of the distribution are similar.

Agriculture↗
PubMed2002

Effective environmental regulation to maximise the benefits of integrated wastewater management.

On the 25 November 1999, the Secretary of State for the Environment in England and Wales announced the outcome of the water companies' third Periodic Review. As a result, a major environmental investment programme will be completed during the period 2000/2005. Overall in England and Wales, it is planned that almost 3,600 km of rivers will be protected or improved and 3,800 unsatisfactory CSOs will be improved to allow receiving water objectives to be met. This means that over the next 5-year period an average of nearly 18 discharges will be improved every week. The implementation of the programme will involve a large workload for the Environment Agency in planning and authorising the individual schemes for delivery by the water companies. The paper illustrates how the Urban Pollution Management procedure and associated environmental standards are to be used to underpin the Environment Agency's policy, to encourage the use of integrated wastewater planning and, as a result, ensure that the anticipated environmental improvements will be delivered.

Cities↗
PubMed2001

Rural, urban and suburban comparisons of preventive services in family practice clinics.

Numerous studies have compared health services provided in rural and urban areas, and overall they have found that utilization is lower in rural areas. A significant factor in lower utilization is that rural residents have less access to health services. Much less is known about rural and urban utilization differences once a patient has access to a service provider. This paper focuses on preventive services received when a patient is already in a clinic. Using data from an in-depth qualitative study of 16 family practice clinics in Nebraska, comparisons of physician-specific preventive service rates are made across three geographic categories: rural, urban and suburban. Results from a one-way multivariate analysis of variance show that preventive services rates for nine services examined were as high or higher in rural areas, suggesting that rural health services do not lag for patients with access.

Adolescent↗
PubMed2000

Historical reflections on current preventive practice.

BACKGROUND: Preventive care in medicine and public health has evolved through historical stages. Recently, developments within the contemporary health care environment have pressured primary care physicians to deliver more preventive care, but little was known about the actual delivery of such services. The Direct Observation of Primary Care study investigated the delivery of preventive services. METHODS: In the study's qualitative portion, research nurses observed 138 family physicians in northeast Ohio, dictating observational fieldnotes. After transcription, the fieldnotes were content analyzed to identify patterns and themes. Further consideration led to a secondary historical analysis of ideas influencing medicine and public health. Fieldnotes were then re-analyzed from a historical perspective. RESULTS: The primary analysis showed variations among physician's philosophies and styles of practice that influenced the delivery of preventive services. The secondary analysis highlighted competing historical ideas that have shaped medicine and public health. The authors argue that contemporary physician's philosophies and styles of practice have parallels in the history of ideas informing medical and public health practice. CONCLUSIONS: The implications of these findings, particularly a lost appreciation of ideas that continue to be operational in practice, may be important if there is to be improvement in the delivery of preventive services.

Family Practice↗
PubMed1994

Case managers and physicians: communication and perceived problems.

OBJECTIVE: To describe case managers' perceptions of the physician-case manager relationship. DESIGN: A qualitative field study using in-depth open-ended interviews was used to elicit case managers' experiences and practices. A multidisciplinary team analyzed transcripts using an adaptation of the "grounded theory" approach of Glaser and Strauss. PARTICIPANTS/SETTING: Case managers were selected for interview using a maximum variation sampling strategy within an established state-wide case management agency. MAIN OUTCOME MEASURES: Transcript analysis allowed for the organization of observations into themes, which were merged across interviews to generate theses. RESULTS: Case managers report that: (1) The case manager role is poorly understood by physicians. (2) Physicians lack insight into the social and environmental aspects of home-bound elderly people. (3) Access to physician services is often difficult to obtain. (4) Power struggles occasionally surface in care planning. (5) Decisions by physicians and case managers regarding the care of frail elderly are often made from different agenda. CONCLUSIONS: From the perspective of case managers, gaps in interprofessional communication may hinder the optimal care of frail elderly individuals.

Aged↗
PubMed1994

Contradictions in case management: client-centered theory and directive practice with frail elderly.

New long-term care legislation and managed care legitimate case management for gatekeeping and advocacy for frail elderly. Qualitative in-depth interviews with case managers who are social workers and nurses were used to address the question: To what extent is client-centered theory reflected in case management practice? Differences between reported client-centered theory and directive practice were identified by five themes: (a) client wishes versus system constraints; (b) the paradox of working to keep clients home versus the perceived inevitability of nursing home placement; (c) client centeredness versus the case manager's care plan; (d) client self-determination versus strategies of persuasion; (e) informing the client about case management versus the reality of practice. Ethical implications, competing demands, and environmental constraints are discussed. Suggestions are made to better integrate client-centered theory with directive practice.

Aged↗
PubMed1993

Serum albumin and prealbumin as predictors of clinical outcomes of hospitalized elderly nursing home residents.

OBJECTIVE: To investigate the prevalence of hypoalbuminemia and hypoprealbuminemia in hospitalized, elderly, skilled nursing facility residents and to correlate these findings with clinical outcomes. DESIGN: Prospective cohort study. SETTING: A 300-bed community hospital. PARTICIPANTS: Eighty-one hospitalized, skilled nursing facility patients, average age 83.1 years. INTERVENTIONS: None. OUTCOME MEASURES: Serum albumin and prealbumin (transthyretin) were measured at admission, mid-week, 1 week, and 1 month. Patients were followed for 90 days for the outcomes of length of hospitalization and mortality. RESULTS: The prevalence of hypoalbuminemia was 99% and of hypoprealbuminemia, 79%. Both means dropped significantly from admission to midweek nadirs of 25 g/L for albumin and 14 mg/L for prealbumin. Severe hypoalbuminemia at mid-week predicted mortality (RR = 4.1 95%, CI 2.0-8.5) and extended length of hospitalization (RR = 5.2 95%, CI 2.8-9.8). Severe hypoprealbuminemia predicted extended hospitalization (RR = 3.2, CI 1.5-6.7) but not mortality. CONCLUSIONS: Hypoalbuminemia and hypoprealbuminemia are very common in this clinical setting and vary in parallel fashion over time. Severe hypoalbuminemia was a stronger predictor than hypoprealbuminemia of 90-day mortality and extended length of stay. Serum albumin on admission was not as strong a predictor of outcomes as serum albumin at mid-week.

Aged↗
PubMed1992

The effects of propionate and butyrate on acetate metabolism in rat hepatocytes.

1. Two mM propionate or butyrate inhibited the mitochondrial uptake of acetate by rat hepatocytes. 2. With propionate the inhibition was so strong that the net formation of acetate in the cytoplasm, usually masked by the mitochondrial uptake, appeared directly as a net output of acetate into the medium; showing that this net formation of acetate, reported by [Crabtree B., Gordon M.-J. and Christie S. L. (1990) Biochem. J. 270, 219-225] is not an artefact arising from a misinterpretation of isotopic data. 3. The results also suggest that propionate and butyrate inhibit peroxisomal metabolism.

Acetates↗
PubMed1992

A method for identifying external control sites in metabolic systems.

A graphic method is presented for the identification of control sites in a metabolic system. This method is based on the matrix method for calculating net sensitivities developed by Crabtree and Newsholme (Biochem. J. 247: 113-120, 1987) and avoids the misidentification of control sites that can result from a simple inspection of a system. The method is easily adapted for analysis by computer and may be used for preliminary investigations of metabolic systems to identify potential control sites for further more quantitative investigations.

Animals↗
PubMed1991

A method for testing the stability of a steady-state system during the calculation of a response to large changes in regulator concentrations.

A modification of the 'finite decomposition' method (Crabtree and Newsholme (1985) Curr. Top. Cell. Regul. 25, 21-76) for calculating physiological responses from sensitivities is described, to enable the system to be tested for stability at each step of the procedure. Instability is indicated by a change of sign of the determinant of the square matrix (N) in the governing equation for the system. The method cannot be used to predict a change of sign of the determinant of the square matrix (N) in the governing equation for the system. The method cannot be used to predict responses beyond any step at which instability occurs.

Allosteric Regulation↗
PubMed1990

Measurement of the rates of acetyl-CoA hydrolysis and synthesis from acetate in rat hepatocytes and the role of these fluxes in substrate cycling.

1. Acetyl-CoA hydrolysis, acetyl-CoA synthesis from acetate and several related fluxes were measured in rat hepatocytes. 2. In contrast with acetyl-CoA hydrolysis, most of the acetyl-CoA synthesis from acetate occurred in the mitochondria. 3. Acetyl-CoA hydrolysis was not significantly affected by 24 h starvation or (-)-hydroxycitrate. 4. In the cytoplasm there was a net flux of acetyl-CoA to acetate, and substrate cycling between acetate and acetyl-CoA in this compartment was very low, accounting for less than 0.1% of the total heat production by the animal. 5. A larger cycle, involving mitochondrial and cytoplasmic acetate and acetyl-CoA, may operate in fed animals, but would account for only approx 1% of total heat production. 6. It is proposed that the opposing fluxes of mitochondrial acetate utilization and cytoplasmic net acetate production may provide sensitivity, feedback and buffering, even when these fluxes are not linked to form a conventional substrate cycle.

Acetates↗
PubMed1990

Seat belt use and stress in adolescents.

This study explored the association of adolescent seat belt use with psychosocial risk factors in an urban minority population after the enactment of a mandatory seat belt law. Data on seat belt use, family support, feelings of being down, suicidal ideation, substance abuse, sexual activity, school troubles, and problems with the law were obtained from 541 self-report intake forms administered to an adolescent medicine clinic population from 1986 to 1987. Respondents were almost exclusively black and Hispanic; 315 (59%) were females and 222 (41%) males, with a mean age of 15.4. Seat belt use was reported by 249 (46%) and no or intermittent use by 292 (54%). Chi-square and Wilcoxon rank sums tests were used to examine associations between seat belt use and risk factors. Results showed that the group comprised of those reporting no and intermittent seat belt use was significantly more likely to feel down, have decreased home support, have problems with school and the law, have been on probation, and feel that life in general was not going very well. No association was found between seat belt use and cigarette, drug, or alcohol use or sexual activity without contraceptives. Taking into account the lack of observed behavioral information to validate such self-report questionnaires, these data nevertheless point to the nonuse or intermittent use of seat belts as a possible manifestation of a lack of self-care due to feeling down and/or preoccupation with family, school, or societal problems.

Adolescent↗
PubMed1989

A simplified method for calculating complex metabolic sensitivities by using matrix partitioning.

The matrix method for calculating the overall sensitivities (including control coefficients) of a metabolic system, described by Crabtree & Newsholme [Biochem. J. 247, 113-129 (1987)], is simplified by a preliminary partitioning of the initial matrix equation. This reduces the size of the matrix to be inverted and thereby removes a major drawback with the original method. The resulting procedure is simpler and more systematic than the alternative methods currently available, especially when the system is extensively branched.

Mathematics↗
PubMed1989

Evidence that the production of acetate in rat hepatocytes is a predominantly cytoplasmic process.

By using [1-14C]butyrate, the fluxes of butyrate to acetate and fatty acids were measured in rat hepatocytes. Both fluxes were inhibited to a similar extent by (-)-hydroxycitrate, with no significant effect on butyrate uptake. These results indicate that acetate formation takes place in the cytoplasm, presumably via ATP-stimulated acetyl-CoA hydrolase. Since acetate formation occurred despite a net uptake of acetate, the results are also consistent with the operation of a substrate cycle between acetate and acetyl-CoA, recently proposed by other workers, and suggest that this cycle is cytoplasmic.

Acetates↗
PubMed1987

The derivation and interpretation of control coefficients.

1. Equations for control coefficients are derived by using a method that generates all the control coefficients for a system in a single procedure. This requires solving fewer simultaneous equations than an equivalent method based on 'control theorems'. 2. The interpretation of control coefficients is discussed: in particular, it is shown that these functions are unsatisfactory as measures of 'control' and are perhaps best used as a means of testing control theories (models).

Mathematics↗