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Biomedical subjects

M MacLeod

Publications and source records attributed to M MacLeod.

At least 19 recordsLinked to original sources
PubMed2004

BETR-World: a geographically explicit model of chemical fate: application to transport of alpha-HCH to the Arctic.

The Berkeley-Trent (BETR)-World model, a 25 compartment, geographically explicit fugacity-based model is described and applied to evaluate the transport of chemicals from temperate source regions to receptor regions (such as the Arctic). The model was parameterized using GIS and an array of digital data on weather, oceans, freshwater, vegetation and geo-political boundaries. This version of the BETR model framework includes modification of atmospheric degradation rates by seasonally variable hydroxyl radical concentrations and temperature. Degradation rates in all other compartments vary with seasonally changing temperature. Deposition to the deep ocean has been included as a loss mechanism. A case study was undertaken for alpha-HCH. Dynamic emission scenarios were estimated for each of the 25 regions. Predicted environmental concentrations showed good agreement with measured values for the northern regions in air, and fresh and oceanic water and with the results from a previous model of global chemical fate. Potential for long-range transport and deposition to the Arctic region was assessed using a Transfer Efficiency combined with estimated emissions. European regions and the Orient including China have a high potential to contribute alpha-HCH contamination in the Arctic due to high rates of emission in these regions despite low Transfer Efficiencies. Sensitivity analyses reveal that the performance and reliability of the model is strongly influenced by parameters controlling degradation rates.

Air Pollutants↗
PubMed2004

Genotype, dietary manipulation and food allocation affect indices of welfare in broiler breeders.

1. An experiment was performed to compare the welfare of three broiler breeder genotypes (Label Rouge (LA), experimental dwarf (ER) and standard (SR)) fed on a Control or high Fibre diet. The LA birds were fed ad libitum and the other groups were reared to their recommended body weight targets. A group of standard broiler breeders was also fed a restricted amount of food, but to a lesser degree than SR, to achieve the same proportion of body weight (SE) as ER relative to ad libitum-fed dwarfs based on previous research. LA, ER, SR and SE are referred to as 'groups' in the text. 2. Welfare was assessed by comparing time budgets and heterophil-lymphocyte ratios (HL ratios) at 5, 10 and 15 weeks and immune responses at 15 weeks of age. In addition the weight and water content of the gastrointestinal tract at 4-h intervals at the end of the experiment were studied in LA and SR fed on both diets. 3. Body weights of LA, ER and SR fed on the Fibre diets were depressed and LA ate less of the Fibre than the Control diet. The coefficient of variation of body weight at 15 weeks was 7.9% in LA and similar (10.8 to 11.6%) in the other groups. 4. Drinking, litter-directed behaviour, resting and standing were affected by a group x age interaction with restricted birds showing increased drinking over time and less time spent resting compared to LA. The behaviour of ER birds was similar to SE. 5. HL ratios were within the normal biological range although all restricted-fed birds had an elevated HL ratio at 10 weeks of age relative to week 5 whereas LA birds had a reduced HL ratio at 15 weeks relative to 5 and 10 weeks of age. Immune responses were lower in ER and SE and the highest response was in SR. 6. No effects of diet were identified on behaviour, white blood cell counts or HL ratio. 7. With the exception of the crop, the dry weights of digesta in each section of the gut were similar in LA and SR birds. The results suggest that drinker-directed activity might be a substitute for foraging rather than an attempt to increase gut fill. 8. It is concluded that the replacement of standard with dwarf broiler breeders may improve the welfare of commercial flocks of broiler breeders by decreasing the degree of food restriction resulting in favourable changes in behaviour, for example, reduced 'drinker-directed' behaviour.

Aging↗
PubMed2003

Bladder dysfunction in Duchenne muscular dystrophy.

Although bladder function is thought to be unaffected in Duchenne muscular dystrophy, 46/88 boys interviewed had urinary problems. Nine underwent video urodynamics, showing in eight a small capacity, hyperreflexic bladder, and in the ninth (post spinal surgery) hyperreflexia and detrusor sphincter dyssynergia. Urinary dysfunction is a treatable feature of DMD.

Adolescent↗
PubMed2001

BETR North America: a regionally segmented multimedia contaminant fate model for North America.

We present the Berkeley-Trent North American contaminant fate model (BETR North America), a regionally segmented multimedia contaminant fate model based on the fugacity concept. The model is built on a framework that links contaminant fate models of individual regions, and is generally applicable to large, spatially heterogeneous areas. The North American environment is modeled as 24 ecological regions, within each region contaminant fate is described using a 7 compartment multimedia fugacity model including a vertically segmented atmosphere, freshwater, freshwater sediment, soil, coastal water and vegetation compartments. Inter-regional transport of contaminants in the atmosphere, freshwater and coastal water is described using a database of hydrological and meteorological data compiled with Geographical Information Systems (GIS) techniques. Steady-state and dynamic solutions to the 168 mass balance equations that make up the linked model for North America are discussed, and an illustrative case study of toxaphene transport from the southern United States to the Great Lakes Basin is presented. Regionally segmented models such as BETR North America can provide a critical link between evaluative models of long-range transport potential and contaminant concentrations observed in remote regions. The continent-scale mass balance calculated by the model provides a sound basis for evaluating long-range transport potential of organic pollutants, and formulation of continent-scale management and regulatory strategies for chemicals.

Air Movements↗
PubMed2001

Development of continental scale multimedia contaminant fate models: integrating GIS.

The incentives and approaches for modelling chemical fate at a continental scale are discussed and reviewed. It is suggested that a multi-media model consisting of some 20-30 regions, each of which contains typically seven environmental compartments represents a reasonable compromise between the issues of the need for detailed resolution, avoidance of excessive data demands and inherent complexity and transparency. Strategies adopted in compiling the Berkley-Trent (BETR) model for North America are discussed and used to illustrate the issues of selecting appropriate number and nature of segments, treatment of air and water flows and the acquisition of environmental data. It is suggested that GIS software can play a valuable role in gathering and processing such data and in the display and interpretation of the results of the model assessment. The BETR model will be a useful tool for describing the nature of persistence and long-range transport of chemicals of concern in the North American environment.

Air Movements↗
PubMed2001

Evaluation and comparison of multimedia mass balance models of chemical fate: application of EUSES and ChemCAN to 68 chemicals in Japan.

The European Union System for Evaluation of Substances (EUSES) and the ChemCAN chemical fate model are applied to describe the fate of 68 chemicals on two spatial scales in Japan. Emission information on the chemicals has been obtained from Japan's Pollutant Release and Transfer Registry and available monitoring data gathered from government reports. Environmental concentrations calculated by the two models for the four primary environmental media of air, water, soil and sediment agree within a factor of 3 for over 70% of the data, and within a factor of 10 for over 87% of the data. Reasons for certain large discrepancies are discussed. Concentrations calculated by the models are generally consistent with the lower range of concentrations that are observed in the environment. Agreement between modeled and observed concentrations is considerably improved by including an estimate of the advective input of chemicals in air from outside Japan. The agreement between the EUSES and ChemCAN models suggests that results of individual chemical assessments are not likely to be significantly affected by the choice of chemical fate model. Primary sources of discrepancy between modeled and observed concentrations are believed to be uncertainties in emission rates, degradation half-lives, and the lack of data on advective inflow of contaminants in air.

Biodegradation, Environmental↗
PubMed2001

The control of body orientation and center of mass location under asymmetrical loading.

This study examined how whole body center of mass (COM) in the medial-lateral direction and spatial orientation of body segments changed during quiet stance when a weight was loaded on asymmetrically on the right side of the pelvis. The load corresponded to 10 and 30% of body weight (BW) of each individual subject, and the stance width was varied from narrow (7.6 cm) to normal (20 cm) and to wide (33 cm). A total of 10 healthy young subjects (18-30 years of age) participated in the study. The results indicated that the COM location was significantly shifted towards the loaded side (about 1.2 cm with a 10% BW load and 3 cm with a 30% BW load). In addition, COM was closer to the center with a narrow stance (0.38 cm to the right of the center) than both normal and wide stance (about 1 cm to the right). However, the COM shifts for all test conditions were smaller (<50%) than that of the theoretically predicted values. The smaller shift in COM position appeared to be mostly due to the change in spatial orientation of the pelvis and lower extremity (about 2.5 degrees change with a 10% BW load, and 4.5 degrees change with a 30% BW load), while maintaining the upper body orientation relatively unchanged (less than 2 degrees with a 30% BW load). This strategy may allow increased stability of the upright stance with minimal amount of muscle activation.

Adolescent↗
PubMed2001

An exploratory study of clinical decision-making in five countries.

PURPOSE: To identify the cognitive processes nurses use in their decision-making in long- and short-term care settings in five countries, and the demographic variables associated with their decision-making. METHOD AND SAMPLES: The instrument used was a 56-item questionnaire that has been shown to be reliable in earlier studies. The sample consisted of five convenience samples of registered nurses working in either geriatric wards (n = 236) or acute medical-surgical wards (n = 223) in hospitals or nursing homes in Canada, Finland, Sweden, Switzerland, and the United States. FINDINGS: Five models of decision-making were identified on the basis of factor analysis. They represent both analytical and intuitive cognitive processes. Analytical cognitive processes were emphasized in information collection, problem definition, and planning of care, and intuitive cognitive processes were emphasized in planning, implementing, and evaluating care. Professional education, practical experience, field of practice, and type of knowledge were significantly associated with decision-making models as well as with country of residence of the participants. The highest proportion of analytically oriented decision-makers was found among nurses in long-term care, the decision-making of nurses in short-term care was more intuitively oriented. CONCLUSIONS: The results indicate that decision-making of participants varied from country to country and in different nursing situations. Future research should be focused on reasons for these differences, the relationship between the task and the nurses' type of knowledge, and how nurses use their knowledge to make decisions in different nursing situations.

Canada↗
PubMed2001

On the validity of classifying chemicals for persistence, bioaccumulation, toxicity, and potential for long-range transport.

It is argued that chemical substances can be meaningfully ranked or classified according to their persistence (P), bioaccumulation (B), toxicity (T), and potential for long-range transport (LRT) only if these attributes can be shown to be intensive, as distinct from extensive, properties of the substance, i.e., they are independent of quantity of substance. It is shown that P, B, and LRT can be considered intensive or quasi-intensive properties, but toxicity is more problematic. To obtain an intensive metric of toxicity requires selection of one of several possible extensive quantities that define exposure or dose. Ranking of a group of chemicals by toxicity is shown to be very dependent on which quantity is selected. It is suggested that toxicity metrics, such as lethal concentration to 50% of the population (LC50), lethal dose to 50% of the population (LD50), and threshold limit value (TLV) suffer the severe disadvantage of being dependent on the efficiency of delivery of the substance to the site(s) of toxic action in the organism. The use of measured or calculated internal dose is a preferable measure of toxicity since it reduces ambiguities inherent in the other metrics. Also, the primary concern is not the quasi-intensive property of toxicity; rather, it is the risk of toxic effects, an extensive quantity. To adequately assess the risk of toxic effects, both the toxic hazard and the degree of exposure must be characterized. Since exposure cannot be estimated without knowledge of the emission rate of chemicals to the environment, a compelling case can be made that screening to identify priority P, B, T, and LRT substances should be expanded to include quantity released to the environment as an additional factor.

Animals↗
PubMed1999

An assessment of the environmental fate and exposure of benzene and the chlorobenzenes in Canada.

Systematic modelling of the fate of benzene and the chlorobenzenes is presented which follows a four-stage process of chemical classification, quantifying discharge rates and environmental concentrations, evaluative assessment of fate and regional mass balance modelling has been carried out for the southern Ontario region. The EQC model was applied to determine the principal transport and transformation processes experienced by this group of chemicals, which vary considerably in volatility and hydrophobicity. Observed environmental concentrations are in satisfactory agreement with the predictions of the steady state Level III ChemCAN model of chemical fate. A multiple pathway human exposure model which estimates intake of contaminants by residents of southern Ontario has been developed and applied to these chemicals. A novel method of deducing maximum tolerable environmental concentrations is presented. Results suggest that benzene and 1,4-dichlorobenzene are present in the environment at levels sufficient to cause exposures near allowable daily intake (ADI) levels for the general population, but the other substances are present at levels which result in exposure ranging from 1/10 to 1/1000 of the ADI.

Benzene↗
PubMed1999

Transfer of the latissimus dorsi muscle after failed repair of a massive tear of the rotator cuff. A two to five-year review.

INTRODUCTION: Seventeen patients with an average age of fifty-five years (range, thirty-two to seventy-seven years) who had ongoing pain and impaired function following failed operative treatment of a massive tear of the rotator cuff were managed with a transfer of the latissimus dorsi muscle as a salvage operation. METHODS: The patients were examined at an average of fifty-one months (range, twenty-four to seventy-two months) after the operation. Pain, function, and satisfaction were assessed with use of a questionnaire, visual analog and ordinal scales, physical examination, and the University of California at Los Angeles shoulder score. RESULTS: Fourteen of the seventeen patients were found to have significant relief of pain (p<0.0001) and a significant improvement in function (p<0.001 for all activities except lifting more than fifteen pounds [6.8 kilograms], for which the p value was <0.0036) and were satisfied with the result of the operative procedure. Fifteen patients stated that they would have the operative procedure again under similar circumstances. Seven of eight patients with a detached or nonfunctional anterior portion of the deltoid had substantial improvement. Three operations were classified as failures because the patients were not satisfied with the result and had ongoing pain and impaired function. All three failures were in patients who had a work-related injury. Overall, six patients had a work-related injury, and only three of them had a satisfactory result. There were three complications, all related to contracture of a hypertrophic axillary scar. CONCLUSIONS: The results in this series indicate that transfer of the latissimus dorsi muscle is a reasonable approach for salvage after failed operative treatment of a massive tear of the rotator cuff.

Adult↗
PubMed1998

'Being there': learning through active participation.

Students engagement in learning is predicated not only on interest but on the perception of relevance to their needs. A hermeneutic interpretation of narrative student evaluation data from an introduction to nursing lecture course that was taught by means of a practice-based phenomenological approach revealed a pattern of student learning in which students moved from detachment to active participation in their learning. The stories shared by nurses in the practice setting were instrumental in introducing students to the world of nursing and facilitating a sense of belonging. Once engaged in the experience, students looked for opportunities to become active participants in their learning. A practice-based phenomenological approach to a theory course maximizes opportunities for student participation. Active reflection and integration allow students to make their own connections between theory and practice.

Curriculum↗
PubMed1998

Issues for nurses in rural and remote Canada.

Canada is a vast country with great diversity in its landscape, industry, culture and communities. The healthcare issues and concerns of people living in rural and remote areas are as fully diverse as the people and the landscape. This article describes the context of rural and remote nursing practice in Canada and discusses issues of health status and the social determinants of health, geographical isolation, professional isolation and cultural safety. It concludes with current initiatives in practice, education, research and policy. Particular issues facing nurses in rural and remote First Nations communities are highlighted.

Canada↗
PubMed1997

Evaluation of pelvic fractures. Clinical and radiologic.

This article gives the orthopedic surgeon a framework to use during the initial evaluation of a patient with a pelvic fracture in the emergency room. The essential elements of the assessment of instability, both clinically and radiologically, are given in this article. Examples of the major patterns of instability are provided.

Fractures, Bone↗
PubMed1996

A phase I study of combined radiation therapy with 5-fluorouracil and low dose folinic acid in patients with locally advanced pancreatic or biliary carcinoma.

PURPOSE: To evaluate the toxicities of a Phase I study of radiation therapy with concurrent 5-fluorouracil (5FU) and low dose folinic acid in patients with locally advanced pancreatic or biliary carcinoma. METHODS AND MATERIALS: Twenty-seven patients with locally advanced carcinoma of the pancreas (n = 19), bile duct (n = 7), and gall bladder (n = 1) were entered into a Phase I study of combined radiation therapy, 5FU, and folinic acid. Radiation was given as a split course of 40 Gy in 20 daily fractions with a gap of 2 weeks after 20 Gy. 5-Fluorouracil, 300 to 375 mg/m2/day and folinic acid, 20 mg/m2/day were given as an i.v. bolus daily for 5 days beginning on day 1 and again on day 29. RESULTS: Eight patients developed Grade 3 or 4 toxicities (National Cancer Institute common toxicity criteria) including nausea and vomiting (n = 4), oral mucositis (n = 4), myelosuppression (n = 2), infection (n = 2), and diarrhea (n = 1). Four patients did not complete the planned protocol due to treatment toxicities. There were two treatment deaths secondary to septic neutropenia. Treatment toxicity appeared to be related to age (> 70), performance status (ECOG = 2), and 5FU dose (> 350 mg/m2/day). CONCLUSION: This protocol is poorly tolerated by elderly patients or those with poor performance status, and 350 mg/m2/day is our recommended dose for 5FU as given in this protocol.

Adult↗
PubMed1995

Psychosocial adjustment in children with port-wine stains and prominent ears.

OBJECTIVE: To evaluate psychosocial adjustment in children with port-wine stain (PWS) and children with prominent ears (PE). METHOD: Thirty-two children aged 7 to 16 years with facial PWS and 42 children with PE were evaluated using the Harter Self-Perception Profile, the Revised Children's Manifest Anxiety Scale, the Children's Depression Inventory, the Disfigurement Perception Scale, and the Child Behavior Checklist. Results were compared with normative data for the local population or with a control group. Profile scores were correlated with severity of the PWS or prominence of the ears. RESULTS: Children with PE had poorer self-perception, higher concentration anxiety, and more internalizing and externalizing symptoms, and they were more withdrawn and had more social problems than children with PWS. The children with PWS functioned as well as or better than nondisfigured peers on measurements of psychosocial adjustment, while children with PE scored lower than nondisfigured peers on measures of self-perception and parent-rated social and attention problems. There was no correlation between degree of disfigurement and level of psychosocial adjustment. CONCLUSIONS: Psychosocial adjustment varied according to the nature of the disfigurement or deformity and was unrelated to the severity of the disfigurement.

Adaptation, Psychological↗