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Biomedical subjects

M Boucher

Publications and source records attributed to M Boucher.

At least 55 records · Page 3Linked to original sources
PubMed1994

Evaluation of exposure data from men and women with the same job title.

In the epidemiological approach to occupational cancers, large bodies of data must be analyzed to find rare cases of cancer. The exposure status of workers must therefore be assessed. Inaccuracies will lead to bias toward the null value in certain cases. Job title has often been used as a proxy for exposure status. This study was undertaken to examine content (ie, tasks and activities) associated with job title among men and women in a large Québec municipality. Occupational accident reports were studied for 1589 accidents, and 113 men and women workers were interviewed about job content. Women and men did not seem to have the same accident rates. From interview data, it appeared that women and men with the same job title did not perform the same tasks. Thus, they might have different exposures. The data reported here support caution in using job title to estimate exposure for both genders if the job-exposure matrix has not previously been validated separately by gender. In addition, it may be unwise to adjust relationships between job title and cancer incidence for gender, thus treating gender as a confounder when it may be a proxy for specific exposures.

Adult↗
PubMed1993

Ontogeny of the humoral immune response to human immunodeficiency virus type 1 in infants.

In a cohort of infants born to human immunodeficiency virus type 1 (HIV-1)-infected mothers, changes in the levels of HIV-1 specific antibodies were measured during the first year of life. In uninfected children, the level of antibodies to six HIV-1 antigens (gp120, p66, p41, p31, p24, and p17) decreased continuously until becoming negative. In contrast, rising levels of one or more specific antibodies were detected in 9 of 12 infected children at a median age of 6 months. At 1 year of age, 8 infants were still asymptomatic and classified as P-1. All had serologic profiles consistent with de novo specific antibody production. In contrast, among the 4 infants who had early disease (class P-2), 3 had no significant rise in antibody to HIV-1. These results indicate that poor immune response, which could result from early infection of the infant, is often associated with rapid clinical progression.

Cohort Studies↗
PubMed1993

[Popliteal venous aneurysm. Apropos of 2 cases].

The authors report two cases of primary popliteal venous aneurysm. This condition is rare. The lesion may be clinically asymptomatic and may remain unrecognised since it is discovered most often during the investigation of thrombo-embolic complications. The diagnosis is based upon ultrasonography and phlebography. Asymptomatic forms should merely be monitored. Apart from anticoagulants, the treatment of symptomatic forms is surgical. Methods remain controversial.

Aged↗
PubMed1992

Membrane stabilizing activity and beta-adrenoceptor antagonist-induced bradycardia in conscious dogs.

The atrial effective refractory period (AERP) and atrial and ventricular chronotropic effects of the stereoisomers of propranolol, pindolol, metoprolol and penbutolol were studied in conscious atrio-ventricular blocked dogs. Atrial beta-adrenoceptor blocking activity was assessed for all the drugs against isoprenaline. All the drugs except dextro-pindolol lengthened AERP and decreased ventricular rate dose relatedly. At comparable levels of atrial beta-adrenoceptor blockade, dextro-propranolol, dextro-metoprolol and dextro-penbutolol were more potent to induce AERP lengthening than their respective levo-isomers, whereas dextro-pindolol was less potent than levo-pindolol. In addition, levo-pindolol and levo-metoprolol were more potent to produce ventricular bradycardia than the corresponding dextro-isomers, whereas the levo- and dextro-isomers of propranolol and penbutolol were equipotent. These results confirm that the ventricular bradycardia induced by the different beta-adrenoceptor antagonists is partly due to ventricular beta-adrenoceptor blockade and to the membrane stabilizing activity of these drugs, and partly to another as yet unknown factor seen especially with the levo-isomers and particularly marked with metoprolol.

Adrenergic beta-Antagonists↗
PubMed1992

Interactions with the cardiac cholinergic system: effects of disopyramide and its mono-N-dealkylated metabolite.

The cardiac vagolytic effects of disopyramide and its mono-N-dealkylated metabolite (MND), and their interactions with the cardiac cholinergic system, were assessed using in vivo and in vitro experiments. In chloralose anesthetized dogs, disopyramide phosphate (0.25 mg/kg/min) and MND at equimolar dose (0.173 mg/kg/min) reduced vagal bradycardia. As indicated by the ED80, MND exhibits a vagolytic activity 1.5-2 times less potent than disopyramide. Concomitantly, increases in heart rate and mean blood pressure were observed with disopyramide, whereas with MND only a rise in mean blood pressure occurred. In conscious dogs, where vagal tone is fully expressed, disopyramide and MND increased heart rate and, interestingly, prevented any atropine-induced additional tachycardia, though heart rate was relatively low. Binding studies on rat heart membranes yielded Ki values 2-2.5 times higher for MND than for disopyramide, and demonstrated that neither disopyramide nor MND binding modified the cardiac muscarinic receptor sites. Taken together, these results show that disopyramide exhibits a more potent cardiac vagolytic action than MND, very likely linked to a greater ability to bind to cardiac muscarinic receptors. They also show that disopyramide and MND are very potent in preventing atropine-induced "excess tachycardia", very likely by inhibiting the ionic pacemaker current(s) involved in its genesis.

Animals↗
PubMed1992

Contribution of vagal blockade to the tachycardia induced by the antimuscarinic agents atropine and pirenzepine.

1. The cardiac cholinergic blockade and the chronotropic effect of the widely differing antimuscarinic drugs atropine and pirenzepine were investigated in the dog. 2. In conscious dogs, suppression of the parasympathetic system with atropine (0.2 mg kg-1 h-1) causes marked brief cardioacceleration (234 +/- 13 beats min-1) while pirenzepine (3 mg kg-1 h-1) causes moderate but persistent cardioacceleration (179 +/- 13 beats min-1). After suppression of the influence of the cardiac sympathetic system these cardioaccelerator effects are attenuated, particularly those of pirenzepine. 3. The effects of vagal stimulation are blocked completely and persistently by both agents. 4. When the cardioinhibitory action of the vagus nerve is blocked by pirenzepine the induced tachycardia can be increased by atropine, which causes an additional cardioacceleration (25 +/- 9 beats min-1). 5. These results show that the tachycardia induced by antimuscarinic agents is not only due to vagal blockade. The different mechanisms which may be involved are discussed. The results suggest that pirenzepine can suppress cholinergic influence on the heart more electively than atropine, which induced an 'excess tachycardia'. Also, intrinsic heart rate can be approached more closely when pirenzepine is used to suppress the parasympathetic system, than with atropine.

Animals↗
PubMed1992

Possible association of benzalkonium chloride in nebulizer solutions with respiratory arrest.

OBJECTIVE: To report a case of possible association of benzalkonium chloride in nebulizer solutions with respiratory arrest and to review the involvement of various preservative agents in paradoxical bronchoconstrictive reactions. DATA SOURCES: Reference articles, case reports, and editorials are identified in the text. DATA SYNTHESIS: Many pharmacologic agents are available for nebulization. In addition to the active drug, these nebulizer solutions may contain preservatives. We describe a case of respiratory arrest in a 64-year-old man following nebulization therapy with albuterol and ipratropium solutions. These solutions contain benzalkonium chloride as a preservative. We are aware of only one report describing two deaths associated with such a severe reaction attributable to nebulization therapy. However, many reports of milder paradoxical bronchoconstriction are available in the medical literature. CONCLUSIONS: Clinicians should be aware of the possibility of paradoxical bronchoconstrictive reactions when patients are treated with nebulized bronchodilators.

Benzalkonium Compounds↗
PubMed1992

Diagnosis of vertical HIV-1 transmission using the polymerase chain reaction and dried blood spot specimens.

We have used the polymerase chain reaction (PCR) to detect HIV proviral sequences in minute amounts of peripheral blood collected onto newborn screening blotters. Forty-three newborns, infants, and children of HIV-infected mothers were serially studied: dried blood spot (DBS) specimens were processed for PCR; serum was assayed for HIV antibodies, p24 antigen, and immunoglobulins; mononuclear cells were cultured and CD4 cells were quantitated by immunofluorescence. There was excellent agreement between the results of blood spot PCR, viral culture, and clinical and immunological indicators of HIV infection. Eighteen of 19 infected children tested positive by both PCR and culture, including six asymptomatic infants who were less than 10 weeks of age. As expected, p24 antigen capture assays were insensitive, detecting only 13 of the 19 infected children. One infected infant tested positive by PCR, but negative by culture and antigen. This infant was seropositive at 27 months and had pronounced hypergammaglobulinemia in association with non-specific symptoms. Twenty-four of the 43 infants were asymptomatic with normal immune profiles, declining antibody levels and no evidence of infection. These children tested repeatedly negative by PCR, culture, and p24 antigen assays. Our results indicate that DBS PCR is a sensitive, specific, and cost-effective alternative to viral culture for the early diagnosis (or exclusion) of perinatal HIV infection. DBS sampling opens the way for large-scale prospective studies to determine the exact rates of vertical HIV transmission in industrialized, as well as, nonindustrialized countries.

Child, Preschool↗
PubMed1991

Intrauterine diagnosis of cytomegalovirus and rubella infections by amniocentesis.

OBJECTIVE: To establish a correlation between the presence of cytomegalovirus (CMV) or rubella virus in amniotic fluid obtained through amniocentesis and fetal infection. DESIGN: Case series. SETTING: Five hospitals in the Montreal region. Virology testing was done at the Virology Research Centre, Institut Armand-Frappier, Laval, Que. PATIENTS: Thirteen pregnant women infected with CMV, 3 with rubella, their 15 babies and 2 fetuses. Twelve of the women with CMV infection were recruited from a prospective study of CMV infection in pregnancy. Infection in the other women was detected through routine laboratory diagnostic testing. INTERVENTION: Amniotic fluid samples were cultured for CMV and rubella virus. Congenital infection of the neonates was established through isolation of either virus from pharyngeal mucus and urine specimens collected during the first 3 days of life or from fetal tissue if the pregnancy was terminated. MAIN RESULTS: CMV was cultured from the amniotic fluid of three of the CMV-infected women and from the pharyngeal mucus and urine specimens of their infants. Of the three women with rubella the amniotic fluid of one (who had a twin pregnancy) was positive for rubella virus. After the in-utero death of one fetus she underwent a therapeutic abortion of both. Examination of fetal tissue indicated that both fetuses had been infected with rubella virus. Each of the two other women with rubella gave birth to an uninfected, healthy infant. CONCLUSIONS: We found a strong correlation between the isolation of CMV or rubella virus from the amniotic fluid and the presence of congenital infection. This suggests that amniocentesis used to detect the presence of a virus is a useful method for the diagnosis of fetal infection.

Adult↗
PubMed1991

Paradoxal pharmacologic effects observed with beta-blocker agents on cardiac cells in culture.

The direct effects of propranolol and metoprolol were studied on cultured neonatal rat ventricular myocytes by recording cellular contraction with a video signal analyzer of cells movements. The experiments were performed on 3-d-old cultures forming a synchronously beating monolayer. The spontaneous beating frequency of preparations depended on cultures and varied from 100 to 330 beats/min with a peak for the interval 140 to 149 beats/min. Propranolol and metoprolol were tested at 1, 5, 10 microM and 10, 50, 100 microM, respectively. At these doses the two beta-blockers induced chronotropic and inotropic effects in the same range. The two agents induced rapid and short-lasting negative inotropic effects, which were dose-dependent and delayed negative chronotropic effects even with the lowest doses. In some preparations paradoxal effects were evidenced: an increase of the amplitude or frequency of the contractions was observed. The results obtained with 5 microM propranolol or 50 microM metoprolol could be separated in two groups depending on the basal beating rate (less than or greater than to 150 beats/min). In cultures with a rapid frequency, the drugs had a marked negative chronotropic effect and, surprisingly, a positive inotropic effect was observed. These findings confirm the interdependence of the two parameters frequency and amplitude of contraction on this model, and evidence the interest of taking into account the control parameters before any interpretation.

Adrenergic beta-Antagonists↗
PubMed1991

Effects of bepridil, diltiazem and verapamil on atrial refractoriness and heart rate in the conscious dog: comparison with quinidine.

1. Bepridil at cumulative doses between 1.25 and 8.75 mg/kg and quinidine between 2.5 and 17.5 mg/kg given in conscious dogs with chronic atrioventricular block and implanted atrial pacing electrodes, dose-relatedly lengthened atrial effective refractory period (AERP), as reflected by the decrease in maximal atrial frequency determined by pacing. 2. Diltiazem shortened AERP at 0.25 mg/kg and lengthened it at 1.75 mg/kg, but both effects were very slight. 3. Verapamil between 0.06 and 0.435 mg/kg did not alter AERP at all. 4. Except for diltiazem at 0.75 and 1.75 mg/kg and bepridil at 8.75 mg/kg, each dose of each drug increased atrial rate. Each drug produced an increase in ventricular rate and a short-lasting lowering in mean blood pressure. 5. Thus, these results indicate that bepridil exhibits more marked antiarrhythmic potentialities than quinidine and that the atrial and ventricular tachycardic effects observed are mainly baroreceptor reflex effects.

Animals↗
PubMed1991

Influence of pentobarbital and chloralose anesthesia on quinidine-induced effects on atrial refractoriness and heart rate in the dog.

The effects of pentobarbital and chloralose on the atrial effective refractory period (AERP), atrial and ventricular rates, and mean blood pressure and also on the effects of quinidine on the same parameters were investigated in dogs with chronic atrioventricular block and implanted atrial pacing electrodes. Pentobarbital (30 mg/kg) increased the AERP by up to 12%, atrial and ventricular rates by 39 and 40%, respectively, and after initial lowering (48%) it increased the mean blood pressure (46%). Chloralose (100 mg/kg) increased the AERP (less than 30 min) by up to 7%, the atrial rate by 49%, the ventricular rate (less than 5 min) by 18%, and the mean blood pressure by 47%. In conscious dogs, quinidine at cumulative doses of 2, 4, and 8 mg/kg, i.e., at plasma levels between 2.7 +/- 0.6 and 6.3 +/- 1.3 micrograms/ml, increased the AERP by up to 21, 28, and 46%, the atrial rate by 49, 65, and 72%, and the ventricular rate (less than or equal to 5 min) by 17, 14, and 14%, and lowered the mean blood pressure by 19, 33, and 43%, respectively. Pentobarbital increased the quinidine-induced lengthening of the AERP by up to 10, 21, and 25 ms, respectively, and reduced the corresponding atrial (38, 53, and 67 beats/min) and ventricular (4, 4, and 5 beats/min) chronotropic effects. In contrast, chloralose reduced the quinidine-induced lengthening of the AERP (5, 12, and 22 ms, respectively), but did not modify the corresponding atrial and ventricular chronotropic effects. Neither pentobarbital nor chloralose altered quinidine plasma levels or the hypotensive effects of this drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthetics↗
PubMed1990

Evidence for postsynaptic alpha 1- and alpha 2-adrenoceptors mediating catecholamine-induced negative chronotropic ventricular responses in the conscious dog.

1. Adrenaline (0.25-1 microgram/kg), noradrenaline (0.125-0.5 microgram/kg) and dopamine (25-100 micrograms/kg) given in the conscious dog with chronic atrio-ventricular block after beta-adrenoceptor blockade, increased ventricular cycle length (VCL) and mean blood pressure (MBP). 2. Atropine (muscarinic receptor blocker) reduced the catecholamine-induced effects on VCL without modifying their hypertensive effects. 3. Phenoxybenzamine or phentolamine (alpha-adrenoceptor blockers) only decreased the effects of adrenaline on VCL but suppressed those of noradrenaline and dopamine. They only reduced the effects of adrenaline and noradrenaline on MBP, but reversed that of dopamine. 4. Yohimbine (alpha-adrenoceptor blocker) suppressed the catecholamine-induced effects on VCL, and reduced strongly the hypertensive effects of adrenaline and noradrenaline and reversed that of dopamine. 5. Thus, these results show the existence of negative chronotropic postsynaptic alpha-adrenoceptors in the ventricles.

Adrenergic alpha-Antagonists↗
PubMed1990

Comparison of anticholinergic effects of cibenzoline, disopyramide, and atropine.

The anticholinergic effects of cibenzoline, disopyramide, and atropine were compared on experimental models. Using inhibition of specific binding of 3H-quinuclidinyl benzylate (3H-QNB) in rat heart and cerebral cortex, Ki values were 15.8 +/- 1.6, 12 +/- 3.5, and 0.013 +/- 0.001 microM, respectively, for heart membranes and 31.6 +/- 1.5, 7.8 +/- 1.3, and 0.006 +/- 0.001 microM, respectively, for cerebral cortex membranes. In isolated guinea pig ileum, disopyramide was about 15 times more anticholinergic than cibenzoline but about 900 times less so than atropine. In anesthetized dogs, the three drugs administered by intravenous bolus reduced bradycardia caused by vagal stimulation. The effect of cibenzoline at 7 mg/kg i.v. (double the antiarrhythmic dose) was approximately the same as that of disopyramide at 2.5 mg/kg (half the antiarrhythmic dose). The drugs were infused for 1 h at 0.17 mg/kg/h for atropine, 11.6 mg/kg/h for disopyramide, and 5.5 mg/kg/h for cibenzoline. The maximal inhibition of the vagal stimulation was 98, 95, and 52%, respectively, for the three drugs. In nonanesthetized dogs, inhibition of the vagal-tone-induced tachycardia reached 33 +/- 4, 134 +/- 20, and 206 +/- 19% for cibenzoline, disopyramide and atropine, respectively. These results show cibenzoline to exert less potent anticholinergic effects than disopyramide.

Animals↗
PubMed1989

Mechanisms of chronotropic cardiac effects of alinidine and plasma concentration-response relationships in the conscious dog with chronic atrioventricular block.

The chronotropic cardiac effects of alinidine were studied in the conscious dog with chronic atrioventricular block. Alinidine at 0.5 - 4 mg/kg, i.e., at plasma concentrations between 42 +/- 2 and 1625 +/- 371 ng/ml, initially increased atrial rate dose-dependently. This effect fell off rapidly, but atrial bradycardia was never observed. After atropine and pindolol, which raised basal atrial rate, alinidine (2 mg/kg) decreased atrial rate, whereas after phenoxy-benzamine, yohimbine or phentolamine, it produced atrial effects identical to those observed under basal conditions, i.e., initial tachycardia and no bradycardia. Alinidine dose-relatedly decreased ventricular rate. None of the pretreatments modified the maximal ventricular bradycardia, but interestingly after pindolol or yohimbine this effect developed more rapidly (maximal bradycardia between 3 and 5 against 30 min) and then declined progressively. Alinidine did not modify mean blood pressure at any dose. After atropine, phenoxybenzamine or phentolamine, alinidine remained without effect on mean blood pressure, but after pindolol or yohimbine, a hypotensive effect appeared concomitantly with the reduction of the ventricular bradycardia. These results show that the initial atrial cardioacceleration due to alinidine results from a direct vagolytic action of this drug and that the absence of atrial bradycardia results from buffering by the vagolytic effect and/or a relatively low basal atrial rate. They also suggest that the ventricular bradycardia does not involve either the muscarinic cholinoceptors or the alpha- or beta-adrenoceptors, though the results obtained after pindolol or yohimbine suggest possible involvement of a fall in sympathetic tone by stimulation of presynaptic or central alpha2-adrenoceptors, particularly in the persistence of the bradycardic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1989

Cardiac electrophysiological effects of cibenzoline in the conscious dog: plasma concentration-response relationships.

The cardiac electrophysiological effects of cibenzoline were studied in the conscious dog. Sinus rate, corrected sinus recovery time (CSRT), and Wenckebach point (WP) were measured in six intact dogs. Atrial and ventricular rates, and atrial effective refractory period (AERP) were measured in seven atrioventricular (AV)-blocked dogs. In both groups, blood pressure and cibenzoline plasma concentrations were also monitored. Each dog received three intravenous injections of 0.75, 1.5, and 3 mg base/kg cibenzoline 30 min apart. Cibenzoline increased sinus and atrial rates from the second dose onward, and ventricular rate slightly at the third dose. It lengthened CSRT and decreased WP at the first two doses only, and increased AERP from the first dose onward. In both groups, cibenzoline increased mean blood pressure at each dose. Taken together, these results indicate that in the conscious dog, cibenzoline at low plasma concentrations exhibits electrophysiological effects (lengthening of CSRT and AERP, and decrease in WP) attributable to its antiarrhythmic properties, and that at increasing concentrations it produces effects (increase in sinus rate, no effect on CSRT nor WP) which reflect competition between the effects related to its antiarrhythmic properties and those resulting from its direct vagolytic effect.

Animals↗