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Personne :
Lachance, Dominic.

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Lachance

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Dominic.

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Département de Médecine expérimentale, Faculté de Médecine, Université Laval

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Voici les éléments 1 - 4 sur 4
  • PublicationRestreint
    Angiotensin-converting enzyme inhibitor captopril prevents volume overload cardiomyopathy in experimental chronic aortic valve regurgitation
    (National Research Council of Canada., 2004-03-12) Lachance, Dominic.; Roussel, Élise; Gauthier, Cindy; Couët, Jacques; Lapointe, Évelyne; Drolet, Marie-Claude.; Gaudreau, Martin.; Plante, Éric; Arsenault, Marie
    L'efficacité des inhibiteurs de l'enzyme de conversion de l'angiotensine I (IECA) dans le traitement de l'insuffisance aortique (IA) chronique est encore mal comprise et controversée. Les mécanismes par lesquels les IECA ont un effet protecteur dans la surcharge de volume du ventricule gauche (VG) sont encore peu clairs et les études cliniques ont jusqu'à maintenant donné des résultats contradictoires. Dans cette étude, nous avons cherché à comparer l'efficacité de deux doses différentes d'un IECA (captopril) dans un modèle animal d'IA chronique. Chez des rats Wistar ayant une IA sévère, nous avons étudié les effets d'un traitement de 6 mois avec une faible dose de captopril (FD; 25 mg/kg) ou une haute dose (HD; 75 mg/kg) sur la fonction et l'hypertrophie du VG. Les rats IA témoins ont tous développé une hypertrophie excentrique du VG ainsi qu'une dysfonction systolique. Le traitement FD n'a pu prévenir l'hypertrophie et n'a procuré qu'une protection modeste contre la dysfonction systolique. Le traitement HD a préservé la fonction systolique et a eu tendance à ralentir le développement de l'hypertrophie du VG. L'index cardiaque est demeuré élevé et similaire pour chacun des groupes traités ou non. L'activité du système rénine–angiotensine (SRA) a aussi été étudiée. L'activité de l'ECA a augmenté dans les VGs des animaux IA et le traitement HD a fortement abaissé l'expression des ARNm encodant les différents récepteurs à l'angiotensine II dans ce tissu. L'expression de la fibronectine a augmenté dans les VG des animaux IA mais le traitement HD a presque complètement renversé cet effet de l'IA. L'inhibiteur de l'ECA captopril s'est avéré efficace à haute dose dans notre modèle d'IA. Cette efficacité pourrait être liée à une modulation du SRA tissulaire et de la fibrose dans le VG.
  • PublicationAccès libre
    Gender differences in left ventricular remodeling in chronic severe aortic valve regurgitation in rats.
    (Hertfordshire : ICR, 2006-05-03) Lachance, Dominic.; Roussel, Élise; Couët, Jacques; Drolet, Marie-Claude.; Plante, Éric; Arsenault, Marie
    BACKGROUND AND AIM OF THE STUDY: Aortic valve regurgitation (AR) can result in heart failure from chronic overloading of the left ventricle. As little is known of gender-specific responses of the left ventricle to this condition, the study aim was to compare left ventricular (LV) remodeling in male and female rats with severe AR. In order to assess the impact of estrogens on LV remodeling in AR, the effect of ovariectomy (OVX) was also evaluated. METHODS: AR was created in adult Wistar rats (females (control or OVX) and males). Animals were followed for 26 weeks and compared to sham-operated groups. Heart function was evaluated in vivo using echocardiography, and the hearts were subsequently harvested for tissue analysis. RESULTS: The LV ejection fraction was decreased similarly in both sexes. Despite similar echocardiographic AR severity, females had higher indexed cardiac output and the largest increase in LV weight, cardiomyocyte hypertrophy and eccentric remodeling. No differences were observed between control and OVX females. Ovariectomy had no significant impact on any of the parameters monitored. CONCLUSION: Female rats developed more LV remodeling in response to chronic AR than males. AR appears to impose a greater LV workload on females due to their smaller body and heart size. Hormonal status did not have any impact on LV remodeling in this experimental model.
  • PublicationAccès libre
    Impact of anesthesia on echocardiographic evaluation of systolic and diastolic function in rats
    (Elsevier, 2006-11-28) Lachance, Dominic.; Roussel, Élise; Couët, Jacques; Drolet, Marie-Claude.; Plante, Éric; Arsenault, Marie
    Background : Echocardiography is used on rats but general anesthesia is usually necessary to be able to obtain a good quality echocardiogram. Each type of anesthetic agent has specific impacts on hemodynamics and, therefore, may affect differentially the echocardiographic measurements. Objectives : We sought to compare the echocardiograms of normal rats and rats with chronic aortic regurgitation under anesthesia using ketamine-xylazine or isoflurane. Methods : Animals underwent an echocardiogram with both drugs sequentially. Echocardiographic measurements were compared. Results : Mitral diastolic Doppler measurements (early diastolic filling wave [E] and late atrial diastolic filling wave [A] velocities) were significantly affected by the type of anesthesia in the normal group but not left ventricular dimensions or ejection fraction. Left ventricular dimensions were affected by the type of anesthesia in the aortic regurgitation group and diastolic Doppler flow. Conclusion : The anesthetic agent has significant specific impacts on many echocardiographic measurements. Investigators working with rat models should be aware of those potential effects.
  • PublicationAccès libre
    Effectiveness of β-blockade in experimental chronic aortic regurgitation
    (American Heart Association, 2004-09-13) Lachance, Dominic.; Roussel, Élise; Couët, Jacques; Drolet, Marie-Claude.; Gaudreau, Martin.; Plante, Éric; Arsenault, Marie
    Background— Past studies have suggested that the adrenergic system becomes abnormally activated in chronic volume overload, such as in severe aortic valve regurgitation (AR). However, the effectiveness of agents directed against this adrenergic activation has never been adequately tested in chronic AR. We therefore tested the effects of metoprolol treatment on the left ventricular (LV) function and remodeling in severe chronic AR in rats. Methods and Results— Severe AR was created in adult male Wistar rats by retrograde puncture of the aortic leaflets under echocardiographic guidance. Two weeks later, some animals received metoprolol treatment (25 mg/kg) orally for 24 weeks, and some were left untreated. LV dimensions, ejection fraction, and filling parameters were evaluated by echocardiography. Hearts were harvested at 1, 2, 14, and 180 days for the evaluation of hypertrophy, β-adrenergic receptor status, and extracellular matrix remodeling. We found that metoprolol treatment prevented LV dilatation and preserved the ejection fraction and filling parameters compared with untreated animals. Metoprolol increased the expression of β1-adrenoreceptor mRNA and reduced G protein receptor kinase 2 levels. Collagen I and III mRNA levels were reduced. Cardiac myocyte hypertrophy was also prevented. Conclusions— In our experimental model of severe AR, metoprolol treatment had a significant beneficial global effect on LV remodeling and function. These results suggest that the adrenergic system is important in the development of volume-overload cardiomyopathy in AR and that adrenergic-blocking agents may play a role in the treatment of this disease.