Biomedical subjects

M Dionne

Publications and source records attributed to M Dionne.

At least 19 recordsLinked to original sources

PubMed2001

Importance of attributable risk in monitoring adverse events after immunization: hepatitis B vaccination in children.

OBJECTIVES: Most vaccine safety data present only the postvaccination incidence of all adverse events rather than an estimate of attributable risk. This study sought to illustrate the difference between the 2 estimates with data from a hepatitis B immunization program. METHODS: The incidence of health problems occurring before and after each dose of hepatitis B vaccine in a cohort of 1130 children were compared. RESULTS: Although 47.5% of all children reported an adverse event during the 4 weeks following each of the 3 doses, adverse events attributable to immunization occurred in only 10.6% of children. CONCLUSIONS: Postimmunization incidence systematically overestimates the risk of adverse events. Estimating actual attributable risk is necessary to avoid false beliefs regarding immunization.

Adverse Drug Reaction Reporting Systems↗

PubMed2000

Autumnal biomass and potential productivity of salt marsh fungi from 29 degrees to 43 degrees north latitude along the United States Atlantic Coast.

It has been established that substantial amounts of fungal mass accumulate in standing decaying smooth cordgrass (Spartina alterniflora) marshes in the southeastern United States (e.g., in standing decaying leaf blades with a total fungal organic mass that accounts for about 20% of the decay system organic mass), but it has been hypothesized that in marshes farther north this is not true. We obtained samples of autumnal standing decaying smooth cordgrass from sites in Florida to Maine over a 3-year period. The variation in latitude could not explain any of the variation in the living fungal standing crop (as determined by ergosterol content) or in the instantaneous rates of fungal growth (as determined by acetate incorporation into ergosterol at a standard temperature, 20 degrees C), which led to the conclusion that the potential levels of fungal production per unit of naturally decaying grass are not different in northern and southern marshes. Twenty-one percent of the variation in the size of the living fungal standing crop could be explained by variation in the C/N ratio (the higher the C/N ratio the smaller the fungal crop), but the C/P ratio was not related to the size of the fungal crop. Instantaneous rates of fungal growth were negatively related to the size of the living fungal crop (r = -0.35), but these rates were not correlated with C/nutrient ratios. The same two predominant species of ascomycetes (one Phaeosphaeria species and one Mycosphaerella species) were found ejecting ascospores from standing decaying smooth cordgrass blades at all of the sites examined from Florida to Maine.

Acetates↗

PubMed1999

Molecular confirmation of hepatitis A virus from well water: epidemiology and public health implications.

An outbreak of hepatitis A in a rural river-island community was found to be associated with consumption of contaminated well water. Specimens from case-patients, the implicated well, and a cesspool suspected to be the source of contamination were all positive for hepatitis A virus (HAV) RNA by immunocapture reverse-transcription polymerase chain reaction. All isolates were identical over about 400 bases from two capsid-encoding regions of the genome, identifying the chain of transmission. Other wells up to 60 m from the cesspool also contained HAV RNA. In addition, HAV RNA was detected in the contamination source well 6 months after the initial contamination, when fecal coliform bacteria were no longer present. These findings demonstrate the utility of viral detection techniques to evaluate contaminated ground water.

Adolescent↗

PubMed1996

Impact of a mass immunization campaign against serogroup C meningococcus in the Province of Quebec, Canada.

A mass immunization campaign was conducted in the Province of Quebec, Canada, during the winter of 1993, following an increase in the incidence of meningococcal disease, which was mainly caused by a virulent clone of Neisseria meningitidis, serogroup C, serotype 2a. About 1.6 million doses of the polysaccharide vaccine were administered, covering 84% of the target population aged between 6 months and 20 years; the overall cost was about 25.5 million Canadian dollars. Cases notified to the regional health authorities by clinicians, hospital laboratories, and the provincial reference laboratory from January 1990 up to March 1994 have been included in the analysis. In the first year following the campaign, the incidence of the disease dropped markedly among vaccinees as well as the unvaccinated fraction of the target population, while it remained unchanged among persons aged more than 20 years. This suggests the existence of herd immunity. The overall field efficacy of the vaccine was 79%, more in teenagers and less in under-5-year-olds. A minimum of 37 cases were prevented during the first year.

Adolescent↗

PubMed1995

Obsessive compulsiveness and physical activity in anorexia nervosa and high-level exercising.

Although excessive physical activity and obsessive compulsiveness are both prevalent in anorexia nervosa (AN), to date, the association between these two factors has not been systematically investigated. The aim of the present study was to investigate the relationship between obsessive compulsiveness and both behavioral and psychological aspects of exercise in women with AN, and to compare them to a nonclinical sample of females classified as either moderate or high-level exercisers. Results indicated that obsessive compulsiveness, weight preoccupation, and pathological aspects of exercise were significantly related to the level of physical activity among the eating disorder patients. For the high-level exercisers, only obsessive compulsiveness was significantly related to the amount of physical activity. The findings are discussed in terms of a model in which physical activity, starvation, and obsessive compulsiveness are reciprocally and dynamically related, with each factor creating a destructive bidirectional loop that is resistant to change and difficult to break. We propose that this self-perpetuating loop may be a significant influence in the development and maintenance of eating disorders in a certain subgroup of women.

Adult↗

PubMed1994

Sentinel hospital surveillance of HIV infection in Quebec. Quebec Sentinel Hospital HIV-Seroprevalence Study Group.

OBJECTIVE: To measure the HIV seroprevalence rate in a surrogate sample of the general population in the province of Quebec, using a network of sentinel hospitals. DESIGN: Anonymous unlinked sentinel surveillance study. SETTING: Outpatient surgery units in 19 acute care hospitals throughout Quebec. PARTICIPANTS: All patients attending the outpatient surgery units from November 1990 to October 1992. A total of 61,547 plasma samples were obtained from leftover blood samples collected for cell counts. Fifty samples were excluded because of an insufficient amount of plasma and one because of an indeterminate result. INTERVENTION: HIV antibody testing with enzyme-linked immunosorbent assay; positive results confirmed with radioimmunoprecipitation assay. OUTCOME MEASURES: HIV antibody status, sex, year of birth and area of residence. RESULTS: The crude seroprevalence rate among the subjects aged 15 years or more was 0.4 per 1000 population (95% confidence interval [CI] 0.2 to 0.7) among the women and 3.6 per 1000 population (95% CI 2.8 to 4.4) among the men (p < 0.001). The rate after adjustment for age, sex and geographic distribution of the study population was 2.3 per 1000 population (95% CI 1.9 to 2.7). The seroprevalence rate among the male patients in the City of Montreal was much higher than the rates elsewhere in the province. It increased progressively during each of the four 6-month intervals of the study: 8.1, 8.7, 13.9 and 18.3 per 1000 respectively (chi 2 linear trend = 4.76; p = 0.029). No similar trends were observed outside Montreal for the male patients. There were too few seropositive female patients to draw any solid conclusion. CONCLUSIONS: Despite the possible drawbacks of a nonrandomized sampling scheme, this study suggests that in the male population the HIV seroprevalence rate is increasing in Montreal and is stable in all other areas of the province. The continued surveillance of HIV infection through anonymous unlinked studies is useful to monitor trends.

Adolescent↗

PubMed1994

The influence of body fat content and bone diameter measurements on body dissatisfaction in adult women.

This study investigated the simultaneous influence of various anthropometric factors on body dissatisfaction in adult women while controlling for psychological and behavioral factors known to covary with it. Multiple regression analyses confirmed that neuroticism, skeletal frame size, and percent body fat were positively, and age and physical activity inversely, related to dissatisfaction. Subsequent analyses substituted separate bone diameter measurements in place of the composite frame size variable and found that hip diameter, correcting for fatness, was a more salient factor in the determination of body dissatisfaction than the more general estimate of frame size. In pursuit of the perfect ultra-slender body women are encouraged to diet and exercise for weight loss more than ever before. It appears, however, that anatomical factors that are resistant to change by caloric restriction or physical activity, are a significant influence in the degree to which women report discontent with their body shape.

Adolescent↗

PubMed1994

The role of physical activity in the development and maintenance of eating disorders.

This study was intended to establish the pathogenic significance of sport and exercise in the development of eating disorders. Hospitalized eating disordered patients and an age-matched control group were assessed. Historical and current physical activity data were collected. An indepth interview was also conducted to ascertain the age of onset of the diagnostic symptoms for eating disorders, and to determine whether: (i) exercising predated dieting; (ii) patients had been involved in competitive athletics; (iii) exercise was excessive; and (iv) weight loss was inversely related to level of exercise. The results indicated that patients were more physically active than controls from adolescence onwards, and prior to the onset of the primary diagnostic criteria for anorexia nervosa. A content analysis of the interview data indicated that 78% of patients engaged in excessive exercise, 60% were competitive athletes prior to the onset of their disorder, 60% reported that sport or exercise pre-dated dieting, and 75% claimed that physical activity levels steadily increased during the period when food intake and weight loss decreased the most. Together our results suggest that overactivity should not be routinely viewed as a secondary symptom in anorexia nervosa, equivalent to other behaviours. For a number of anorexic women, sport/exercise is an integral part of the pathogenesis and progression of self-starvation.

Adolescent↗

PubMed1993

Body composition correlates of weight dissatisfaction and dietary restraint in young women.

Previous research found that when Body Mass Index (BMI) was statistically controlled in a multiple regression model, the percentage of body fat accounted for no additional variance in dietary restraint scores among women although, on its own, it was a significant predictor of this variable. These results imply that anatomical factors, besides fatness, influence dieting behaviour. The present study was designed to compare the relative influence on dietary restraint and weight dissatisfaction, of three body composition measures, each of which contributes in a different way to subjective impressions of body size (viz. BMI, body fat content, and skeletal frame size). Measures of emotional reactivity ('neuroticism'), body dissatisfaction, , and body focus were also included in the regression model. Results indicated that these psychological variables were strongly and positively related to restraint. Frame size was also a significant predictor of restraint and weight dissatisfaction. In fact, when frame size was controlled in the regression model, neither percentage of body fat nor BMI were able to explain any additional variance in restraint scores. These findings indicate that weight concerns and dieting behaviour are influenced, at least among young women, more by the size of their skeletal structure than their degree of adiposity. The irony of these findings is obvious and disheartening. An anatomical feature which is essentially resistant to change by dieting or exercise appears to be a primary influence in women's weight dissatisfaction and their tendency to diet. It is acknowledged, however, that this relationship may not obtain among very obese women.

Adipose Tissue↗

PubMed1990

Mutagenesis of essential functional residues in acetylcholinesterase.

The cholinesterases are serine hydrolases that show no global similarities in sequence with either the trypsin or the subtilisin family of serine proteases. The cholinesterase superfamily includes several esterases with distinct functions and other proteins devoid of the catalytic serine and known esterase activity. To identify the residues involved in catalysis and conferring specificity on the enzyme, we have expressed wild-type Torpedo acetylcholinesterase (EC 3.1.1.7) and several site-directed mutants in a heterologous system. Mutation of serine-200 to cysteine results in diminished activity, while its mutation to valine abolishes detectable activity. Two conserved histidines can be identified at positions 425 and 440 in the cholinesterase family; glutamine replacement at position 440 eliminates activity whereas the mutation at 425 reduces activity only slightly. The assignment of the catalytic histidine to position 440 defines a rank ordering of catalytic residues in cholinesterases distinct from trypsin and subtilisin and suggests a convergence of a catalytic triad to form a third, distinct family of serine hydrolases. Mutation of glutamate-199 to glutamine yields an enzyme with a higher Km and without the substrate-inhibition behavior characteristic of acetylcholinesterase. Hence, modification of the acidic amino acid adjacent to the serine influences substrate association and the capacity of a second substrate molecule to affect catalysis.

Acetylcholinesterase↗

PubMed1984