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M Gagnon

Publications and source records attributed to M Gagnon.

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

Effect of glucose, glucose regulation, and word imagery value on human memory.

Changes in memory performance were examined after intake of a glucose (50 g) or saccharin (50 mg) solution in fasted men and women. Glucoregulation was estimated by using a recovery index to categorize participants within each gender as having poor or good recovery. Memory was assessed with word-learning tasks in which the imagery-evoking value of the words was systematically manipulated to yield high- and low-imagery lists. The results showed that men and women characterized as having poor glucose regulation had significantly worse memory performance under the saccharin condition. This decrement was reversed by glucose ingestion. These effects were observed for both low- and high-imagery words. This study supports the hypothesis that poor glucoregulation is associated with poor memory performance even in young healthy participants and that the ingestion of glucose can improve their memory.

Adult↗
PubMed1999

Economic evaluation of donepezil for the treatment of Alzheimer's disease in Canada.

BACKGROUND: Donepezil is a new drug recently approved in the United States and Canada for the treatment of Alzheimer's disease (AD). We estimated the cost-effectiveness of donepezil 5 mg daily as an adjunct to usual care in the management of persons with mild-to-moderate AD defined as a Mini-Mental Health State Examination (MMSE) score in the range 10 to 26. METHODS: Treatment effect data as MMSE change-over-baseline scores were obtained from a 30-week placebo-controlled trial of donepezil. MMSE scores beyond observed trial data were estimated using a Markov model with 10 cycles of 24 weeks based on the placebo MMSE progression observed in the trial. Data from AD subjects in the Canadian Study of Health and Aging were used to estimate costs of nursing home care, community services, medications, and caregiver time as a function of MMSE score. A clinic-based cohort study from Alberta was used to estimate the distribution of AD patients by MMSE score presenting for treatment. The effectiveness measure for the economic model was expected time (over 5 years) spent with nonsevere AD (MMSE > or = 10). RESULTS: Over 5 years of treatment, donepezil is predicted to reduce health care costs by CA$929 per patient but increase caregiver time costs by CA$48 per patient for an overall cost saving to society of CA$882 per patient. Patients not receiving donepezil are predicted to spend 2.21 years of the 5 years in nonsevere AD compared with 2.41 years for treated patients (a gain of just over 2 months). Sensitivity analysis reveals that cost savings per patient increase if more AD patients are assumed to survive to 5 years; however, if donepezil treatment continues when patients' MMSE score falls below 10, the incremental cost is higher for treatment at CA$1554 per patient. CONCLUSION: Based on the limited available data, our model predicts that the use of donepezil for mild-to-moderate AD in Canada is associated with lower 5-year costs and less time spent with severe AD when compared with the alternative of usual care with no donepezil therapy. As more reliable long-term data become available, these predictions should be confirmed and/or updated.

Aged↗
PubMed1999

Effects of age and gender on autonomic control of blood pressure dynamics.

Both age and gender influence cardiovascular autonomic control, which in turn may influence the ability to withstand adverse cardiac events and respond to orthostatic stress. The purpose of this study was (1) to quantify age- and gender- related alterations in autonomic control of blood pressure (BP) and (2) to examine the impact of these autonomic alterations on BP response to orthostatic stress. We measured continuous BP and R-R intervals and vasoactive peptide levels in the supine and 60 degrees head-up tilt positions during paced respiration (0.25 Hz) in 89 carefully screened healthy subjects (41 men, 48 women, aged 20 to 83 years). Data were analyzed by gender (age adjusted) and by age group (gender adjusted). During tilt, women had greater decreases in systolic BP than men (-10.2+/-2 versus -1.2+/-3 mm Hg; P=0.02) and smaller increases in low-frequency (sympathetically mediated) BP power (P=0.02). Upright plasma norepinephrine was lower in women (P=0.02). Women had greater supine high-frequency R-R interval power than men (P=0.0001). In elderly subjects, the tilt-induced increase in low-frequency BP power was also diminished (P=0.01), despite higher supine (P=0.02) and similar upright norepinephrine levels compared with younger subjects. Thus, healthy women have less sympathetic influence on BP and greater parasympathetic influence on R-R interval than men. Elderly subjects also have reduced sympathetic influence on BP, but this appears to be more consistent with a reduction in vasomotor sympathetic responsiveness.

Adult↗
PubMed1998

Functional and physical association of a cell surface phospholipid and interleukin-2 receptor p55(alpha) subunits.

A phosphatidylcholine-like phospholipid expressed in the outer leaflet of the cell membrane shortly after mitogenic activation of T-cells is described, based on the binding of monoclonal antibody 90. 60.3. Expression of the 90.60.3 phospholipid antigen in T-cells is activation-dependent. Once expressed, the 90.60.3 phospholipid is in direct physical association with the interleukin-2 (IL-2) binding domain of IL-2 receptor alpha subunits, but does not affect IL-2 binding. The association is specific, because the 90.60.3 phospholipid is not found in association with other domains of IL-2 receptor alpha subunits, or near IL-2 receptor beta or gamma subunits. Culturing cytokine-dependent cell lines in the presence of monoclonal antibody 90.60.3 potentiates IL-2-dependent cell survival and proliferation in a dose-dependent manner. In contrast, IL-4-dependent responses are not potentiated. Taken together, the data suggest that specific plasma membrane phospholipids expressed in the outer leaflet after T-cell activation associate with the IL-2 binding domain of IL-2 receptor alpha subunits (and perhaps other cytokine receptors), and may play a role in regulating receptor mobility or signal transduction.

Animals↗
PubMed1998

Relation between severity of Alzheimer's disease and costs of caring.

BACKGROUND: Data from the Canadian Study of Health and Aging (CSHA) were used to examine the relation between severity of Alzheimer's disease, as measured by the Mini-Mental State Examination (MMSE), and costs of caring. METHODS: The CSHA was a community-based survey of the prevalence of dementia, including subtypes such as Alzheimer's disease, among elderly Canadians. Survey subjects with a diagnosis of possible or probable Alzheimer's disease were grouped into disease severity levels of mild (MMSE score 21-26), mild to moderate (MMSE score 15-20), moderate (MMSE score 10-14) and severe (MMSE score below 10). Components of care available from the CSHA were use of nursing home care, use of medications, use of community support services by caregivers and unpaid caregiver time. Costs were calculated from a societal perspective and are expressed in 1996 Canadian dollars. RESULTS: The annual societal cost of care per patient increased significantly with severity of Alzheimer's disease. The cost per patient was estimated to be $9451 for mild disease, $16,054 for mild to moderate disease, $25,724 for moderate disease and $36,794 for severe disease. Institutionalization was the largest component of cost, accounting for as much as 84% of the cost for people with severe disease. For subjects living in the community, unpaid caregiver time and use of community services were the greatest components of cost and increased with disease severity. INTERPRETATION: The societal cost of care of Alzheimer's disease increases drastically with increasing disease severity. Institutionalization is responsible for the largest cost component.

Alzheimer Disease↗
PubMed1998

Sensitivity analysis of segment models to estimate the net reaction moments at the L5/S1 joint in lifting.

This paper deals with the mathematics of inverse dynamic analysis for calculating the net reaction moments; the sensitivity of the net reaction moments to nine experimental values is quantified and two dynamic models are compared. The results indicate that, among all terms, the external forces in the case of a lower body model and the segment masses in the case of an upper body model contributed the most to differences in the sensitivity of the lumbosacral reaction moment about the transverse axis. About the other axes there was no clear difference between the two body models.

Adult↗
PubMed1997

Development and application of predictive equations of maximal static moments generated by the trunk musculature.

OBJECTIVE: To develop and apply regression equations that predict the maximal static moments generated by the extensor, axial rotator and lateral flexor muscles of the trunk as a function of forward bending angles and asymmetrical positions of the torso in human subjects. DESIGN: Using experimental data, polynomial predictive equations were developed. The equations were applied in an algorithm to estimate the maximal moment generated by individual subjects. METHODS: Three groups of male subjects participated in the evaluation of the effect of forward bending and trunk asymmetry on the static moment of the extensor, right axial rotator, and right lateral flexor muscles of the trunk, respectively. Two other groups of male subjects were evaluated to test the validity of the algorithm. During the dynamometric tests, the three-dimensional position of the trunk was determined using cinematography techniques. RESULTS: For the extensor muscles, a curvilinear increase of the maximal moment was observed with forward bending, with a slight decrease of the moment on each side of the neutral position. For the right axial rotator muscles, both forward bending and left asymmetrical position of the trunk increased the maximal moments generated by these muscles. The right lateral flexors were stronger in the standing and mid-flexion positions than in other positions. First-order, second-order and interaction terms appear in the regression equations to account for the effect of forward bending and asymmetrical positions. The regression equation for the extensors and right axial rotator muscles have R(2) coefficients (range 0.56-0.76) higher than those of the lateral flexor regression equations (range 0.09-0.12). The algorithm results in an average error of 13% in predicting the strength of extensor and axial rotator muscles of individual subjects. CONCLUSION: The results have shown that strength of the extensor and axial rotator muscles is affected by forward bending and the asymmetry of the trunk, while strength of the lateral flexor muscles is only dependent on the forward bending position. The regression equations and the corresponding algorithm are applicable for the range of positions used in the study.

Journal Article↗
PubMed1997

Box tilt and knee motions in manual lifting: two differential factors in expert and novice workers.

OBJECTIVE: It was the objective of this study to investigate the kinematic and kinetic effects of two specific handling factors that differentiate expert and novice workers, namely the level of knee flexion and box tilt. DESIGN: Seven inexperienced subjects were required to lift a 12-kg box in the sagittal plane using three different strategies: (1) reduced knee flexion and a backward box tilt (more typical of experts); (2) large knee flexion and a backward box tilt; (3) large knee flexion and no box tilt (more typical of novices). BACKGROUND: The lifting techniques of highly skilled workers differ substantially from those of novices but only limited information is available to compare their biomechanical differences. METHODS: The methods included dynamic segmental analyses to calculate the net moments at all body joints and a planar single-muscle equivalent to estimate compression loadings at L5/S1; total work and joint work distribution were calculated using the integration of joint power. The 3-D kinematic data were acquired with three video cameras and force data were obtained with one AMTI force platform which were synchronized with the film data. RESULTS: Box tilt reduced the load trajectory and loadings on the lower back and shoulders; a reduced knee flexion affected body posture and reduced mechanical work and loadings on all body joints. The combination of these two factors, box tilt and reduced knee flexion, showed added effects for almost all variables. CONCLUSIONS: These two factors proper to experts were, in this context, biomechanically more advantageous.

Journal Article↗
PubMed1997

Effect of pelvic tilt on lumbar spine geometry.

The purpose of this study was to use a noninvasive method to determine the effect of pelvic tilt on the lumbar spine geometry in the sagittal plane. Five healthy male subjects were instructed in performing active forward and backward pelvic tilt manoeuvres in the standing position. The lumbar spine geometry (severity of lordosis, pelvis and lumbar vertebrae orientations) was estimated with a lumbar spine geometric model. The voluntary backward pelvic tilt succeeded in reducing the depth of the lumbar spine curvature, but the forward tilt did not change it. Both pelvic tilt manoeuvres influenced the absolute orientations of the lower lumbar vertebrae and the relative orientations of some lumbar vertebrae. Interestingly, the L5/S1 joint showed was little affected by the pelvic tilt manoeuvres.

Adult↗
PubMed1997

Vasomotor instability preceding tilt-induced syncope: does respiration play a role?

This study aimed to determine whether alterations in cardiovascular dynamics before syncope are related to changes in spontaneous respiration. Fifty-two healthy subjects underwent continuous heart rate (HR), arterial blood pressure (BP), and respiratory measurements during 10-min periods of spontaneous and paced breathing (0.25 Hz) in the supine and 60 degrees head-up tilt positions. Data were evaluated by power spectrum and transfer function analyses. During tilt, 27 subjects developed syncope or presyncope and 25 remained asymptomatic. Subjects with tilt-induced syncope had significantly greater increases in low-frequency (0.04-0. 15 Hz) systolic BP, diastolic BP, and HR power during tilt than the asymptomatic subjects (P </= 0.01). This difference was present during spontaneous but not paced breathing. However, average tidal volume, respiratory rate, minute ventilation, proportion of breaths below 0.15 Hz, and low-frequency respiratory power during tilt did not differ between syncopal and nonsyncopal subjects. Transfer magnitudes between low-frequency respiration and BP, and between BP and interbeat interval, were also similar between groups. Thus vasomotor instability before syncope is not related to alterations in respiration or the cardiovagal baroreflex but may reflect oscillating central sympathetic outflow to the vasculature.

Baroreflex↗
PubMed1996

Sex differences in estrogen receptor and progestin receptor induction in the guinea pig hypothalamus and preoptic area.

Quantitative in vitro autoradiography was used to determine if regional sex differences in estrogen receptor (ER) content and/or estrogen responsiveness, as indicated by an increase in progestin receptor (PR), are present in the adult guinea pig brain. Adult male and female guinea pigs were gonadectomized 1 week before subcutaneous injection of 25 micrograms estradiol benzoate (EB)/kg body wt or the sesame oil vehicle. Animals were killed by decapitation 44 h after injection. Unoccupied PRs, and unoccupied and occupied ERs, were measured in discrete brain regions by quantitative in vitro autoradiography using [3H]R5020 and [3H]estradiol as ligands, respectively. In vehicle-injected controls, a higher level of ER was found in the arcuate nucleus (ARC), dorsal medial nucleus (DMN) and ventrolateral nucleus (VLN) of females as compared to males. At 44 h after EB injection, 32-55% of the ERs were occupied; however, EB treatment caused a marked down-regulation of total receptor (calculated as occupied+ unoccupied receptor) in most of the brain regions examined, including the periventricular preoptic area (PVP), medial preoptic area (MPO), bed nucleus of the stria terminalis, paraventricular nucleus, ARC, ventrolateral hypothalamus (VLH), VLN, and DMN. In EB-treated animals, PR binding was detectable in the PVP, MPO, ARC, VLH, and VLN, with higher levels of binding observed in the PVP, MPO, and VLN of the female as compared to the male. No PR binding was observed in oil-injected control animals. These results demonstrate region-specific sex differences in ER as well as estrogen-induced regulation of progestin and ERs in the guinea pig brain. The discordance between the regional distributions of sex differences in ER and estrogen-induced PR implies that sex differences in ER and estrogen-induced PR implies that sex differences in estrogen response may not be clearly linked to a sex difference in receptor number. Instead, sex differences in response may involve differences in receptor number within specific subpopulations of estrogen target cells or may involve differences in ER dynamics.

Animals↗
PubMed1996

Factors influencing subject willingness to participate in clinical gerontologic research.

To identify factors influencing willingness to participate (WTP) in clinical gerontologic research, a questionnaire containing descriptions of seven research projects with a corresponding set of questions about perceived intrusiveness (discomfort and inconvenience), stipend, and other incentive factors was sent to 1004 community-dwelling research subject registry members. There was an inverse relationship between perceived level of intrusiveness and WTP. The more intrusive the study, the greater the relative influence of a stipend on WTP. Male gender and a new experience with an opportunity to learn were independently related to WTP. Subject ratings of perceived intrusiveness for each study component were entered into a factor analysis to guide the development of a three-tier "Level of Intrusiveness" scale. Although prospective validation is necessary, the Level of Intrusiveness scale may be useful in predicting WTP, and determining when other incentives are needed to improve subject recruitment for clinical research.

Aged↗
PubMed1996

Knee movement strategies differentiate expert from novice workers in asymmetrical manual materials handling.

One way to generate hypotheses on appropriate handling principles is to compare the strategies of highly skilled workers (experts) with those of novice workers (novices). This study was conducted to determine whether experts differ from novices in their handling strategies and to determine the effects of these differences in joint motions and net reaction moments at the trunk (L5/S1) and knees. Six experts and five novices were compared transferring two loads (12 and 22 kg) from four different initial low positions to a standardized low position on a trolley. The external forces were obtained from two AMTI force platforms, and two 16 mm Locam cameras coupled with two mirrors were used to obtain the three-dimensional kinematic data. An inverse dynamic analysis was performed on each segment and the net reaction moments were evaluated at L5/S1 and the knees; trunk posture, knee flexion angles and feet spacings were also calculated. Results showed that both groups minimized trunk asymmetries of posture and efforts; however, the experts were characterized by reduced knee flexion (31 degrees vs 53 degrees) and total knee excursion (20 degrees vs 38 degrees), increased flexion moments (72 vs 58 Nm) but reduced extension moments (4 vs 26 Nm) and valgus moments (30 vs 54 Nm). The experts' strategies appear safer overall because they reduce trunk asymmetry, asymmetrical efforts on the knee and stress on the femoropatellar joint. Moreover, these strategies present a potential for reduced mechanical energy expenditure due to lower knee excursions and increased knee stability due to reduced knee flexion.

Adult↗
PubMed1996

Glucose regulation and cognitive functions: relation to Alzheimer's disease and diabetes.

Glucose has been found to improve memory in animals and humans. Animal research has revealed that glucose may improve memory through a facilitation of acetylcholine (ACh) synthesis and release in the brain. This glucose-related memory improvement has prompted research in elderly humans. These studies have shown that the memory-improving action of glucose depends on each individuals' blood glucose regulation. Based on these data, researchers have evaluated the effect of glucose on memory in patients with Alzheimer's disease (AD). Results demonstrated that glucose could improve memory in a subset of patients that had abnormalities in their blood glucose regulation. Interestingly, these alterations in blood glucose regulation were believed to depend on the severity of the disease process. Another line of investigation has focused on alterations in brain glucose metabolism. Both animal models and studies with Type II diabetic elderly patients have shown that altered glucose regulation impairs learning and memory processes. It is possible that in AD patients, hyperglycemia exerts a deleterious effect by potentiating the neuronal death produced by other pathological processes taking place such as amyloid deposition. Based on these data, it appears important to find the prevalence of altered glucoregulation at various stages of AD. Secondly, it may be of interest to determine prospectively whether altered glucoregulation is linked to a faster progression of the disease. Finally, if such a relationship is observed, the next logical step would be to determine whether AD patients could benefit from treatments aimed at normalizing blood glucose regulation and improving insulin sensitivity.

Alzheimer Disease↗
PubMed1996

Validation of two 3-D segment models to calculate the net reaction forces and moments at the L(5)/S(1) joint in lifting.

The purpose of this study was to examine the validity and sensitivity of two three-dimensional segment models to estimate the net reaction forces and moments at the L(5)/S(1) joint. The two dynamic three-dimensional multisegment models, applied to lifting activities, were a lower body model and an upper body model. Three healthy male subjects participated in this study. The asymmetrical task consisted of lifting a load of 9.6 kg in a normal speed condition and in a fast condition. Results from the two models in terms of joint reaction forces and joint reaction moments at L(5)/S(1) were compared and were then used to validate them. The correlation between the reaction moments from both models were generally above 0.95 and the root mean square (RMS) differences were generally below 10 Nm but could reach 38 Nm. Similar trends were observed in the sensitivity analysis. A proportion of the error was attributable to errors in the segment accelerations because of an increase in the RMS differences between the models with an increase in lifting speed. The use of the lower body model seemed to present some advantages over the upper body model because of the nature of the task analysed which did not require large accelerations from the lower part of the body.

Journal Article↗