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Biomedical subjects

J A McLean

Publications and source records attributed to J A McLean.

At least 19 recordsLinked to original sources
PubMed2001

Cognitive dietary restraint is associated with higher urinary cortisol excretion in healthy premenopausal women.

BACKGROUND: Cognitive dietary restraint, assessed by the Three-Factor Eating Questionnaire restraint subscale, is associated with subclinical menstrual cycle disturbances. This association may be mediated by stress-activated cortisol release. OBJECTIVE: We assessed whether 24-h urinary cortisol excretion differs between women with high and low restraint scores. DESIGN: Participants (aged 21.6+/-2.5 y; n = 62) with normal-length menstrual cycles and high (n = 33) or low (n = 29) restraint scores completed a questionnaire describing weight history, dietary practices, and exercise. Cortisol, calcium, and creatinine were measured in urine collected over 24 h on a day when all food and beverages were provided and measured. Previously, 3-d food records and anthropometric measurements were obtained. RESULTS: Age, height, weight, body mass index, and length of menstrual cycle were similar between groups. The reported amount of exercise was higher (3.4+/-1.7 compared with 2.2+/-1.8 h/wk; P<0.05) and energy intakes (assessed from 3-d and 24-h food records) were lower in the high- than in the low-restraint group. Ratios of urinary cortisol (nmol) to creatinine (mmol) were higher in the high-restraint than in the low-restraint group (42.9+/-12.9 compared with 36.3+/-8.9; P<0.05), whereas ratios of urinary calcium (mmol) to creatinine were lower (0.3+/-0.1 compared with 0.4+/-0.2; P<0.05) in the high-restraint group. Urinary cortisol was not associated with exercise, nutrient intakes, or anthropometric measurements. CONCLUSIONS: High dietary restraint scores are associated with urinary cortisol, a biological marker of stress, and high cortisol excretion may affect bone health. Our results suggest that further research is warranted to clarify these associations and to determine whether they persist over time.

Adult↗
PubMed2001

Dietary restraint, exercise, and bone density in young women: are they related?

PURPOSE: Women with high scores for dietary restraint have been found to have higher 24-h urinary cortisol excretion and a higher prevalence of subclinical ovulatory disturbances, both of which may be risk factors for bone loss. The purpose of this study was to explore relationships between dietary restraint and bone health in regularly menstruating young women. METHODS: 62 women (age: 21.7 +/- 2.5 yr) had body composition and total body and lumbar spine bone mineral density (BMD) and content (BMC) assessed using dual-energy x-ray absorptiometry. Dietary restraint was assessed using the restraint subscale from the Three-Factor Eating Questionnaire: 29 women had low restraint (LR; restraint score 0--5), 33 had high restraint (HR; restraint score 13--21). Exercise (h x wk(-1)) was assessed by questionnaire on two occasions. RESULTS: LR and HR women were similar in age and body composition (fat mass = 15.0 +/- 4.7 kg, lean mass = 40.9 +/- 4.9 kg), but HR women exercised more (3.4 +/- 1.7 vs 2.2 +/- 1.8 h x wk(-1), P < 0.05). Exercise was correlated with BMD and BMC, and when it was included as a covariate, total body BMC was significantly lower in HR than LR women. In multiple regression analysis, weekly hours of exercise and restraint score were significant predictors of total body BMD and BMC. CONCLUSION: The observations of this cross-sectional study suggest that high levels of cognitive dietary restraint, or associated factors such as higher cortisol, may attenuate the positive effects of exercise on bone in young women.

Adult↗
PubMed2000

Basic life support.

Explore the source record for details and available documents.

Cardiopulmonary Resuscitation↗
PubMed1998

A direct injection high-efficiency nebulizer for inductively coupled plasma mass spectrometry.

A simple, relatively low-cost direct injection high-efficiency nebulizer (DIHEN) is introduced for argon inductively coupled plasma (Ar ICP) spectrometry. The DIHEN may be operated at solution uptake rates of 1-100 microL/min. Analytical performance indexes for the DIHEN and fundamental characteristics of the aerosol produced are obtained using an ICP mass spectrometer (ICPMS) and a two-dimensional phase Doppler particle analyzer (2D PDPA), respectively. Results are compared to those obtained with a conventional crossflow pneumatic nebulizer (PN), equipped with a Scott-type spray chamber. Droplet sizes and velocities produced with the DIHEN are smaller than those reported for the direct injection nebulizer (DIN). The DIHEN offers optimal sensitivity at low injector gas flow rates (approximately 0.25 L/min) and high rf power (approximately 1.5 kW). For the 17 elements tested, detection limits (ppt) and sensitivities achieved with the DIHEN (at 85 microL/min) are similar to, or better than, those obtained on the same instrument using the PN (at 1 mL/min). However, because the primary aerosol is injected directly into the plasma, oxide-to-metal ion ratios (MO+/M+) are high, as in the case of the DIN. The utility of the DIHEN for the analysis of small-volume samples is demonstrated by microscale flow injection analysis (muFIA) of Cr bound to human lung DNA. Detection of Cr at the femtogram level is feasible.

Argon↗
PubMed1998

Sensitive quantitation of chromium-DNA adducts by inductively coupled plasma mass spectrometry with a direct injection high-efficiency nebulizer.

A novel method is described for the sensitive detection of chromium-DNA adducts. Chromium-DNA adducts were determined in 1 microgram of DNA from normal human lung fibroblasts exposed to sodium chromate using microscale flow injection analysis with a direct injection high-efficiency nebulizer and inductively coupled plasma mass spectrometry detection. The frequency of Cr-DNA adducts increased in a dose-dependent sigmoidal manner, indicating saturation and toxicity. The low detection limits (on the order of parts per trillion) allows the detection of as few as two Cr adducts per 10,000 bases, which, coupled with the small DNA sample requirement, makes this technique suitable for measuring metal-DNA adducts as biomarkers of exposure to toxic and carcinogenic metals such as Cr, in cultured cells, animals, and humans.

Chromium↗
PubMed1997

Improvement of hemispatial neglect with cold-water calorics: an electrophysiological test of the arousal hypothesis of neglect.

Introducing ice-water into the left ear of right-brain-damaged patients attenuates unilateral neglect symptoms. By examining EEG changes over each hemisphere during this procedure, we were able to test a hypothesis concerning the mechanism of cold-water calorics and the attention-arousal hypothesis of hemispatial neglect. We present a case study of an 83-year-old woman with a massive right-hemisphere CVA exhibiting severe hemispatial neglect. Caloric stimulation produced a leftward eye deviation to central position, and a temporary partial remission of neglect symptoms. Significant changes in EEG activation indicated a central mechanism associated with the regularization of eye gaze. Caloric stimulation also produced a significant interaction between EEG frequency band and hemisphere, indicating that while both hemispheres increased in cortical activation, the right hemisphere increase was significantly greater. This supports the activation-arousal hypothesis of neglect over the mutual inhibition model.

Aged↗
PubMed1995

Elimination rate of 65Zn as a measure of food intake: a validation study in the mouse (Mus sp.).

We measured elimination of 65Zn in white mice (Mus musculus) using daily whole body counting. Thirteen male mice were randomly divided into three groups, each maintained at a different temperature. Each animal was labeled with 65Zn on day 0 and monitored over days 0-48 postinjection. Daily food intake and body masses of all the animals were measured. We evaluated the ability of derived components of the 65Zn elimination curves to predict food intake over different phases of the measurement period. Food intake was significantly different between temperature groups; temporal variation in food intake was not intercorrelated between groups. Whole body elimination of 65Zn involved a rapid decline over days 0-1, followed by a biexponential decline in counts over days 1-48. Components of the first phase of the biexponential elimination curve were not significantly related to food intake. The rate (k2) of isotope elimination in the second phase was significantly related to mean food intake over days 25-48, 13-24, and 37-48. Rate of turnover in the second phase of elimination, incorporating the variation in zinc body pool size (k2 x 1/N2), where N2 is the constant of the second phase of elimination, was the best predictor of food intake and accounted for 60% of the variability over days 37-48.

Animals↗
PubMed1994

Immediate hypersensitivity reaction to cyclophosphamide.

We report a case of an acute anaphylactic reaction to intravenous cyclophosphamide in a patient with systemic lupus erythematosus. Skin testing for reactivity to cyclophosphamide and one of its metabolites, 4-hydroperoxycyclophosphamide, was performed on the patient and on 6 controls. The patient exhibited positive skin test responses; all controls had negative responses. The results suggest an acute hypersensitivity reaction related to sensitivity to cyclophosphamide and to 4-hydroperoxycyclophosphamide, through a shared antigenic determinant or dual sensitization.

Adult↗
PubMed1993

Direct muscle neurotization recovers gastrocnemius muscle function.

This case report describes a devastating injury in which a distal motor nerve had been avulsed from the muscle belly and was not available for reconstruction. This otherwise irreparable posterior tibial nerve injury was successfully treated by direct neurotization of the muscle belly. The patient did have one small, intact, muscular branch to the medial gastrocnemius muscle; however, electrodiagnostic and clinical examination and recovery pattern suggested the neurotization procedure was responsible for the functional recovery. In the rare situation where no distal nerve is available, and tendon transfers or arthrodesis are inappropriate, direct muscle neurotization can be considered as a salvage technique.

Adult↗
PubMed1991

An evaluation of the Deltatrac indirect calorimeter by gravimetric injection and alcohol burning.

We evaluated a 'state of the art' open hood type of indirect calorimeter (Deltatrac, Datex) to determine its stability and precision, and related these to in vivo measurements made with the same type of calorimeter. Three Deltatrac Metabolic Monitors were investigated at two centres over a period of twelve months by two methods of recovery: (i) gravimetric injection of a nitrogen/CO2 gas mix and (ii) ethanol burning using the manufacturers approved apparatus. We compared machine variation with in vivo variation in measurements of oxygen uptake and carbon dioxide production at rest in healthy subjects. The Deltatrac recovery of both oxygen and carbon dioxide was on average 4.8% and 4.7% higher respectively for the alcohol burning method. We suspected that this apparent over-recovery was because the alcohol burner produced a resistance to the airflow generated across the canopy. By gravimetrically injecting the gas mix into the canopy hose whilst the alcohol burner was attached we were able to confirm this error. There was no significant change in recovery for any of the Deltatracs by either method over the year of evaluation. The between-study variation for the machine and in vivo measurements were less than 4%, and the within-study variations were less than 6% and less than 7%, respectively. These studies re-emphasise that careful evaluation of commercially produced indirect calorimeters is essential before clinical measurements are made.

Calorimetry↗
PubMed1991

Efficacy of feedback training in long-standing facial nerve paresis.

An efficacious treatment has not been available to patients with aberrant regeneration of the facial nerve as a result of Bell's palsy or after acoustic neuroma excision. This prospective controlled trial examines the efficacy of electromyographic feedback versus mirror feedback as treatment strategies for patients suffering from long-standing (18 months minimum) facial nerve paresis. Twenty-five patients were randomly assigned to electromyography with mirror feedback or mirror feedback alone. Seven rural patients who did not undergo treatment served as controls. At 0, 6, and 12 months, facial motor function was objectively quantified by linear measurement of facial movement, visual assessment of voluntary movement, and electrical measurement of facial nerve response to maximal stimulation. Statistically significant improvements were noted in both electromyography and mirror-feedback groups with respect to symmetry of voluntary movement (P less than .03) and linear measurement of facial expression (P less than .01). The positive results of this controlled trial demonstrate that feedback training in combination with a structured home rehabilitation program is a clinically efficacious treatment for patients with facial nerve paresis.

Adult↗
PubMed1990

Driving experience and the risk of traffic accident among motorcyclists.

In a case-control study on the risk of traffic accidents among motorcyclists in Singapore, we demonstrated an inverse monotonic relationship between accident risk and driving experience. As compared to drivers with less that 1 yr of driving experience, the odds ratios (adjusted for race, age and frequency of riding) for those with driving experience of 1-4, 5-9 and 10 yr or more were 0.60, 0.50 and 0.36, respectively. We propose that intensive in-circuit training of learner motorcyclists should replace the conventional on-the-road training on the basis that the former serves to increase their driving experience without subjecting the learner motorcyclists to the risk of sustaining road accident.

Accidents, Traffic↗
PubMed1986

Evaluation of interclonal elemental-profile variation in Sitka spruce seed.

Elemental profiles of seeds collected from four ramets in each of 10 clones growing in a 12-year-old Sitka spruce [Picea sitchensis (Bong.) Carr.] seed orchard were determined by X-ray energy-dispersive spectrometry. The data collected from the resultant spectra were used to assess differences among clones and among ramets of a single clone and to determine the mechanism governing the observed differences. The spectra were shown to be different from each other and were specific to each clone. Results from analyses of variance (ANOVA) indicated that the clonal differences accounted for the majority of variation (77%), while among ramets within clones differences rated second (17%). Broad-sense heritability estimates were highly significant and ranged from 0.46 to 0.95. The multivariate analyses conducted on the data further emphasized the results obtained from ANOVA and a high degree of success (90%) was achieved in classifying seed samples to their source clone. Results support the hypothesis that the elemental uptake and assimilation of minerals of Sitka spruce is under genetic control.

Genotype↗
PubMed1986

The significance of carbon dioxide and methane measurements in the estimation of heat production in cattle.

1. Records of metabolic measurements on cattle by open-circuit indirect calorimetry have been examined to determine the practical significance in the calculation of heat production of including measurements of carbon dioxide and methane in addition to the measurement of oxygen. 2. It was found that the combined effects of CO2 and CH4 made only a small contribution to the total estimation of heat production which could be calculated with approximately +/- 1% accuracy from analysis of O2 alone.

Animals↗
PubMed1986

Evoked electromyography in Bell's palsy: a clinically useful test?

One hundred and forty-four patients presenting with a Bell's palsy were seen at Sunnybrook Medical Centre, University of Toronto, between the years 1978 and 1985. Only patients with a complete paralysis and not treated with either steroids or surgical decompression of the facial nerve were included in the study. The results of electrical tests performed on days 8, 9 or 10 after the onset of paralysis in 23 patients were used to predict clinical recovery at 12 weeks, six months and 12 months. There was good statistical correlation for values of conduction latency and amplitude with good clinical recovery after 12 weeks (p = 0.01). Electrical tests could not be used to predict clinical recovery at six months and at 12 months. The rationale for any surgical intervention based on the results of electrical tests is questioned.

Adolescent↗
PubMed1985

Aspirin-sensitive asthma.

Aspirin intolerance is particularly common in asthmatic patients who additionally have chronic rhinitis and/or nasal polyps. These individuals differ in several respects from patients who experience urticaria and/or angioedema after aspirin administration, and differing mechanisms may be involved. Data regarding the latter are indirect and incomplete, but suggest that ASA-sensitive asthma is most likely to be related in some manner to the capacity of ASA to inhibit cyclooxygenases, enhanced lipoxygenase metabolism perhaps playing a crucial role. Current research employing ASA "desensitization" may help to elucidate these enigmas.

Arachidonic Acid↗
PubMed1984

Calibration methods in respiratory calorimetry.

Methods for calibration of respiratory gas exchange measurement systems are evaluated. A new method is described in which O2 is removed from the subject chamber or gas stream and measured gravimetrically in a small combustion chamber containing steel wool. The "Fe-burner" method was tested by comparison with the N2-injection method and found to be of similar accuracy. The new method is easy to perform, quick, and readily applicable to both open- and closed-circuit respiratory systems. It has a rate of O2 uptake that can be adjusted to be similar to the rate by an experimental subject (10-600 kg). Complete calibration of open- and closed-circuit indirect calorimetric systems can be achieved when the Fe-burner method, involving measurement of O2 uptake, is combined with the gravimetric injection of specific gases (CO2, methane) produced by the subject.

Calibration↗