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D Lacroix

Publications and source records attributed to D Lacroix.

At least 55 records · Page 3Linked to original sources
PubMed1997

IFN-tau increases PGE2 production and COX-2 gene expression in the bovine endometrium in vitro.

Prostaglandins (PGs) are well known for their role in reproductive processes. At the time of pregnancy recognition, PGF2alpha is luteolytic and PGE2 may be antiluteolytic and luteotropic. During the preimplantation period, interferon-tau (IFN-tau) is produced by the conceptus and plays a crucial role in maternal recognition of pregnancy in domestic ruminants. We have demonstrated previously that recombinant bovine and ovine interferon-tau (rbIFN-tau and roIFN-tau) stimulate PGE2 production in epithelial cells, changing the primary PG produced by these cells from F2alpha to E2. In stromal cells, where PGE2 is the major PG produced, roIFN-tau induced an increase of both types of PGs. The aim of this paper is to identify the possible involvement of cyclooxygenases (COXs) in the modulation of PG production by trophoblastic interferons. Epithelial and stromal cells cultured in vitro were isolated from bovine endometrium and stimulated with increasing doses (1, 10 and 20 microg/ml) of roIFN-tau. PG levels in the culture media were measured by enzyme immunoassays (EIA) and total RNA was extracted from the cells. Northern blot analysis was performed to quantify cyclooxygenase COX-1 (constitutive), COX-2 (inducible) and phospholipase A2 (PLA2) messenger RNA (mRNA) production in response to treatment. The results indicate that roIFN-tau treatment did not affect COX-1 and PLA2 mRNA production in either cell type, whereas COX-2 expression was upregulated in both. The up-regulation of COX-2 transcript was greater in stromal than in epithelial cells. The increase in COX-2 mRNA levels was concurrent with increased production of PGE2 and PGF2alpha in stromal cells and principally PGE2 in epithelial cells. Furthermore, addition of indomethacin (1 microM) and a specific COX-2 inhibitor (NS-398, 1 microM) blocked the roIFN-tau-stimulation of PG production in both cell types. The mechanism whereby elevated COX-2 expression results in a selective increase of PGE2 in epithelial cells remains to be elucidated. In stromal cells, an increase in COX-2 mRNA levels may explain increased PG production. The overall effect of roIFN-tau in the two cell types is a net increase in PGE2 output.

Animals↗
PubMed1997

Expression of CYP3A in the human liver--evidence that the shift between CYP3A7 and CYP3A4 occurs immediately after birth.

CYP3A isoforms are responsible for the biotransformation of a wide variety of exogenous chemicals and endogenous steroids in human tissues. Two members of the CYP3A subfamily display developmentally regulated expression in the liver; CYP3A7 is expressed in the fetal liver, whereas CYP3A4 is the major cyrochrome P-450 isoform present in the adult liver. To gain insight into the descriptive ontogenesis of CYP3A isoforms during the neonatal period, we have developed several approaches to explore a neonatal liver bank. Although CYP3A4 and CYP3A7 are structurally closely related, they differ in their capacity to carry out monooxygenase reactions. We have cloned CYP3A4 and CYP3A7 and established stable transfectants in Ad293 cells to investigate their substrate specificities. The 16alpha hydroxylation of dehydroepiandrosterone is catalyzed by both proteins, but CYP3A7 has a higher affinity and maximal velocity than CYP3A4. Conversely, the conversion of testosterone into its 6beta derivative is essentially supported by CYP3A4. We used these two probes to determine the ontogenic evolution at the protein level; CYP3A7 was very active in the fetal liver and its activity was maximal during the first week following birth before to progressively decline and reached a very low level in adult livers. Conversely, the activity of CYP3A4 was extremely weak in the fetus and began to raise after birth to reach 30-40% of the adult activity after one month. CYP3A4 RNA accumulation displays a similar pattern of evolution; when probed with an oligonucleotide, its concentration increased rapidly after birth to reach a plateau as soon as the first week of age. These data supports the assumption that CYP3A4 expression is transcriptionally activated during the first week after birth and is accompanied by a simultaneous decrease of CYP3A7 expression, in such a way that the overall CYP3A protein content and the level of pentoxyresorufin dealkylase catalyzed by the two proteins remain nearly constant.

Adult↗
PubMed1997

Systemic infection related to endocarditis on pacemaker leads: clinical presentation and management.

BACKGROUND: Endocarditis related to pacemaker (PM)-lead infection is a rare but serious complication of permanent transvenous pacing. To determine in which situations the diagnosis should be evoked and to determine optimal management, we reviewed our experience with endocarditis related to PM-lead infection. METHODS AND RESULTS: Fifty-two patients were admitted for endocarditis related to PM-lead infection. The presentation was acute in 14 patients, with onset of symptoms in the first 6 weeks after the last procedure on the implant site, and chronic in 38 patients. Fever occurred in 86.5%. Clinical and/or radiological evidences of pulmonary involvement were observed in 38.4%. Pulmonary scintigraphy disclosed pulmonary infarcts in 31.2%. Local complications were found in 51.9%. Elevated C-reactive protein was found in 96.2%. A germ was isolated in 88.4% of patients and was a Staphylococcus in 93.5%. Transthoracic echocardiography demonstrated vegetations in only 23% of patients, whereas transesophageal echocardiography disclosed abnormal appearances on the PM lead in 94%. We systematically tried to ablate all the material. Two techniques were used: percutaneous ablation or surgical removal during extracorporeal circulation. All patients were treated with antibiotics after removal of the infected material. Two patients died before lead removal and 2 after surgical removal; the predischarge mortality was 7.6%, and the overall mortality was 26.9% after a follow-up of 20.1+/-13 months. CONCLUSIONS: The diagnosis of endocarditis related to PM-lead infection should be suspected in the presence of fever, complications, or pulmonary lesions after PM insertion. Transesophageal echocardiography should be performed to look for vegetations. Staphylococci are involved in the majority of these infections. The endocardial system must be entirely removed and appropriate antibiotic therapy pursued for 6 weeks.

Aged↗
PubMed1997

Asystolic cardiac arrest during head-up tilt test: incidence and therapeutic implications.

Occasionally, the cardioinhibitory response may be profound during tilt induced syncope. Whether this response is associated with more severe symptoms or predicts a poor response to pharmacotherapy remains controversial. The aim of this study was to characterize patients with vasovagally mediated asystole occurring during head-up tilt test and to evaluate the respective interests of sequential pacing and beta-blockers to treat them. We performed 60 degree tilt testing in 179 consecutive patients with unexplained syncope (91 women and 88 men, age 36.6 +/- 20.1 years). Asystole was defined as a ventricular pause > 5 seconds. All patients with tilt induced asystole received therapy with either beta-blockers or sequential pacing, the efficacy of which was evaluated with serial tilt tests. Of 77 patients with positive tilt test, 10 developed syncope related to asystole (mean duration 11.9 +/- 4.9 s), 2 with spontaneous recovery, and 8 with seizures needing a brief cardiopulmonary resuscitation. When compared with patients without asystole, asystolic patients had more severe symptoms (seizures: 6/10 vs 9/67, P = 0.05, injury 9/10 vs 27/67, P = 0.0048). In the first six patients in whom cardiac pacing was considered, syncope or presyncope still occurred despite atrioventricular pacing at 45 beats/min. Five of these 6 patients, as well as the remaining 4 asystolic patients, were tilted with beta-blockers: 3 patients became tilt-negative; 3 were significantly improved; and 3 did not respond. During follow-up (mean 22.7 +/- 11.7 months) with every patient taking beta-blockers and seven having a permanent pacemaker, no syncopal recurrence was observed. Tilt-induced asystole that may require resuscitative maneuvers occurs especially in patients with a history of seizures or injury. Therapy with beta-blockers in often effective to prevent induction of syncope as well as recurrences.

Adolescent↗
PubMed1997

Stress analysis of glenoid component designs for shoulder arthroplasty.

Secure and lasting fixation of the glenoid component in total shoulder arthroplasty is difficult because there is an insufficient volume of strong bone in the scapula. Consequently, radiolucencies of the glenoid component are common (much more common than radiolucencies of the humeral component). Early glenoid component designs were fabricated wholly from polyethylene, were fixated with PMMA cement, and had various degrees of constraint and conformity between the glenoid surface and the ball of the humeral component. More recent design variations include metal backing and non-cemented anchorage systems. In this study, various designs of cemented glenoid component are analysed using the finite element method. These are examined for (a) two different abduction angles; 60 degrees and 90 degrees; (b) high and low conformity and (c) high and low constraint. Stress distributions are compared with the failure strengths of the components and the influence of the various design factors can be observed.

Biocompatible Materials↗
PubMed1997

[Determinants of malignant vasovagal syncopes with asystole disclosed by the tilting test and therapeutic implications].

UNLABELLED: In order to evaluate the determinants of malignant vasovagal syncope with asystole revealed by the tilting test and to determine the possible therapeutic implications, 179 patients (91 women and 88 men, mean age 36.6 +/- 20.1 years) referred for the assessment of unexplained a were studied. The test was performed with a tilt of 60 degrees for 45 minutes. A bolus of isoprenaline (0.02 to 0.08 microgram/kg.min) was injected in the case of a negative passive test. Asystole was defined as a ventricular pause lasting > or = 5 seconds. RESULTS: Ten (13%) of the 77 patients with a positive tilting test experienced a cardio-inhibitory reaction with prolonged asystole lasting an average of 11.9 +/- 4.9 seconds. Compared to the other 67 patients with a positive test, those with asystole were younger (23/9 +/- 14.8 years vs 32.9 +/- 18.5 years, NS) and had a more frequent history of convulsions (6/10 vs 9/67, p = 0.05) during spontaneous episodes and trauma (9/10 vs 27/67, p = 0.005). Implantation of a pacemaker was chosen first-line treatment for the first 6 patients. Their follow-up tilting tests remained positive (pre S = 4, S = 1) despite DDD stimulation of 45 bpm. Five of these patients and the following 4 patients were retested under beta-blockers. In six patients treated with beta-blockers, the clinical symptoms resolved completely (n = 3) or improved (n = 3), in contrast with 3 other patients in whom the tilting test remained positive with recurrence of asystole. The mean follow-up for the 169 patients is 22.7 +/- 11 months and the ten patients with asystole remained totally asymptomatic. CONCLUSION: An asystolic response during the tilting test is characteristic of vasovagal syncope described as malignant. The syndrome essentially affects young patients, with a more frequent history of trauma and convulsions. Beta-blockers appear to be at least as effective as permanent pacemaker to prevent symptoms in this specific subgroup.

Adrenergic beta-Antagonists↗
PubMed1997

[Ventricular fibrillation after radiofrequency ablation of the atrioventricular node].

The authors report the case of a 77 year old patient who underwent radiofrequency ablation of the atrioventricular node for chronic. Invalidating atrial fibrillation, refractory to pharmacological therapy. A single chamber ventricular pacemaker was implanted one week before interruption of AV conduction. Eleven applications (7 on the right and 4 on the left side of the interventricular septum) were required for successful ablation. Four hours later, the patient developed episodes of non-sustained polymorphic ventricular tachycardia and torsades de pointe. These arrhythmias were initiated by long cycle-short cycle sequences and preceded by changes of ventricular repolarisation (prolongation of the spontaneous and paced QTc and JTc intervals). Eight days after ablation, the patient had an episode of ventricular fibrillation reduced by external DC shock. This arrhythmia was also preceded by changes in ventricular repolarisation. This case demonstrates the potential proarrhythmogenic effect of radiofrequency ablation of the AV node with changes in ventricular repolarisation which induces malignant ventricular arrhythmias. The authors suggest an appropriate preventive attitude. The progression in two distinct phases (immediate and late) imposes prolonged arrhythmia monitoring.

Aged↗
PubMed1997

[An update of surgery for ventricular tachycardia].

The implantable defibrillator has, to a certain degree, taken over some of the indications of antiarrhythmic surgery in ventricular tachycardia resistant to drug therapy. Initially reserved for patient with ventricular aneurysms, this form of surgery may also be proposed for patients with localised infarction. The multiplicity of forms of tachycardia, the variability of their mechanism which is not always limited to the subendocardial layers requires mapping procedure to guide the surgical intervention on the arrhytmogenic substrate. The so-called regional procedures which, for most workers, combine resection and cryo-ablation, is a good compromise between risk and efficacy. This surgery used to be associated with a high mortality but this has been considerably reduced by technical advances in myocardial protection. Similarly, the failure rate has also been reduced by the identification of "atypical" mechanisms. These improvements have been obtained thanks to systems of mapping which allow investigation of the epicardium/endocardium relationship and activation of the deep septal regions. Although the two techniques are not designed for the same type of patient, global mortality of surgically treated patients in the long term is not different to that of patients with an implantable defibrillator. Clinical efficacy of antiarrhythmic surgery is over 90% at 5 years in the majority of large scale trials. This type of surgery is the only really radical approach because of the limitations of catheter ablation and should be considered to be complementary to the implantable defibrillator in the management of post-infarction ventricular tachycardia.

Adult↗
PubMed1997

[Value of the tilt-table test in the management of unexplained syncope in children and adolescents].

The value of the tilt test in assessing unexplained syncope in children and adolescents was investigated in 79 patients (41 girls and 38 boys, 12.3 +/- 2.9 years). The test was performed with a tilt of 60 degrees for 45 minutes. A pharmacological provocation with isoprenaline was carried out in negative passive test. The tilt test was considered to be positive in cases of symptomatic falls of the systolic blood pressure with or without bradycardia. Asystole was defined as a ventricular pause > or = 5 seconds. During the investigation, 52 patients (66%) reproduced symptoms related to vasovagal syncope in 45 patients (57%) or panic attack in 7 others (9%). Of the 45 presenting vasovagal syncope, 7 had a cardio-inhibitory reaction with asystole of 11.2 +/- 3.3 seconds. The other responses were vasodepressive in 17 patients and mixed in 21 patients. A comparative study did not reveal any significant difference between patients with a positive or negative test including those with panic attacks. Seventy-five patients were followed up for an average of 32 +/- 22.3 months. Preventive therapy was prescribed in 34 patients because of the frequency or severity of their symptoms. At the end, 10 patients (13%) had at least one recurrence of syncope, 3 in the group with panic attacks, 5 in non-treated patients (irrespective of the result of the tilt test) and only 1 in the group of 23 patients treated with beta-blockers. The authors conclude that with a diagnostic return of 66% in this series, the tilt test seems to be the non-invasive investigation of choice in unexplained syncope in children and adolescents. In addition, true vasovagal syncope can be differentiated from psychogenic.

Adolescent↗
PubMed1997

[VDD mode single electrode cardiac stimulation: indications, results and limitations of the method].

UNLABELLED: Several authors have reported the single atrioventricular (AV) electrode, comprising an atrial dipole floating in the right atrium, to be a system capable of providing results which are just as satisfactory as those of conventional systems (DDD). Between August 1992 and March 1995, a VDD single electrode pacemaker was implanted in 65 patients (mean age: 73 years +/- 17.2). The indication for implantation was isolated high degree AVB with no apparent sinus dysfunction. Four pacemakers were used: Vitatron (n = 24), Intermedics (n = 23), Medico (n = 13), Biotronik (n = 5). Intraoperative atrial endocavitary recording was 1.8 mV +/- 0.74. 17 patients died from a cause unrelated to pacemaker dysfunction. 4 patients were lost to follow-up. The remaining 44 patients were reviewed in our centre with a mean follow-up of 14.5 months +/- 7 months. Seven pacemakers (16%) were reprogrammed in VVI or VVI (R) mode, because of permanent atrial fibrillation in 3 cases, complete loss of atrial reception in 2 cases and late onset sinus dysfunction in 1 case. In the 41 patients in sinus atrial rhythm, the atrioventricular synchronization rate was greater than 90% in 88% of patients, equal to 76.3% in 2.4% of patients and atrioventricular synchronization was impossible in 9.6% of cases. CONCLUSION: The overall results of our preliminary experience of VDD mode single electrode pacemaker are moderate. The poor results essentially concerned patients with paroxysmal atrial arrhythmias prior to pacing.

Adolescent↗
PubMed1996

The selection of needs indicators for regional resource allocation in the fields of health and social services in Québec.

In Québec, recent political statements have strengthened the necessity to allocate resources according to regional population needs. A regional-provincial working group was set up to propose needs indicators in 8 different fields-or client-oriented programs-which subdivide the entire spectrum of health and social services in Québec. These programs include physical health, mental health, public health, functionally impaired elderly people, physical deficiency, intellectual deficiency, alcoholism and drug abuse and problems (abuse, neglect, delinquency) among young people and their families. The following paper summarizes the main proposals of the working group. Some comments are made on the definition of client-oriented programs, basic concepts, research questions and methodological approaches. Concrete examples are given in order to illustrate the type of data and methods used. Furthermore, the indicators selected for resource allocation (in each of the 8 client-oriented programs) are presented on a regional basis (n = 18) and introduced in a principal component analysis. Their variations are discussed and recommendations to facilitate their use and promote their development are made. Finally, the actual utilization of these indicators is reported.

Adolescent↗
PubMed1996

Isoform-dependent effects of halothane in human skinned striated fibers.

BACKGROUND: Reports of the effects of halothane on isoform contractile proteins of striated muscles are conflicting. To determine whether halothane affects cardiac and skeletal contractile proteins differently, the authors examined the effects of two doses of halothane (0.44 and 1.26 mM, equivalent to 0.75 and 2.25 vol%, respectively) on the Ca++ sensitivity and maximal force in human skinned cardiac, type I (slow twitch), and type II (fast twitch) skeletal muscle fibers. METHODS: Left ventricular muscle strips and skeletal muscle biopsy specimens were obtained from eight and ten patients undergoing cardiac and orthopedic surgery, respectively. Sarcolemma and sarcoplasmic reticulum were destroyed with ethylene glycol bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid plus Brij 58. Ca++ sensitivity was studied by observing the isometric tension developed by skinned fibers challenged with increasing concentrations of Ca++. Muscle fiber type was determined in each skeletal fiber by the difference in strontium-induced tension measurements. RESULTS: Halothane shifted the Ca++ tension curves toward higher Ca++ concentrations and increased the Ca++ concentrations for half-maximal activation in both cardiac and type I skeletal muscle fibers (from 1.96 microM and 1.06 microM under control conditions to 2.92 microM and 1.71 microM in presence of 0.75 vol% halothane, respectively) without changing the slope of this relationship (Hill coefficient). In contrast, no significant effect was observed in type II fibers. Halothane also decreased the maximal activated tension in the three groups of fibers with a lesser effect in type II fibers. CONCLUSIONS: Halothane decreases Ca++ sensitivity and maximal force in human skinned cardiac and type I fibers at 20 degrees C. It is concluded that the negative inotropic effects of halothane depend on contractile proteins isoforms.

Anesthetics, Inhalation↗
PubMed1996

Late diagnosis of pericardial constriction associated with defibrillator patches and deformation of the left ventricle.

We report a case of pericardial constriction associated with defibrillator patches developing 4.5 years after implantation. This constriction was related to the presence of a large pericardial mass that had developed above the defibrillator patch. This mass, which had a calcified superior border, suggested former hematoma associated with pericardial fibrosis. It induced significant compression of the right ventricle and a dumb-bell deformity of the left ventricle. The hemodynamic picture was of elastic-form constrictive pericarditis. Because of previous cerebral stroke during cardiac surgery, the patient was discharged on pharmacologic treatment after improvement of his functional status. Since removal of epicardial patches is an effective treatment of constriction, constrictive pericarditis should be systematically considered in patients with epicardial patch electrodes and impairment of functional status.

Cardiac Catheterization↗
PubMed1996

[Value of mapping in surgical treatment of ventricular tachycardia].

Surgery may be proposed for patients with a localised aneurysm or akinesia for treatment of monomorphic ventricular tachycardia resistant to antiarrhythmic therapy after myocardial infarction. The multiplicity of tachycardia forms in the same patient, the variability of their mechanism which is not necessarily limited to the subendocardia layers, require mapping to guide the surgeon in the destruction of the anatomical substrates. In a series of 57 ventricular tachycardias recorded in 17 patients with myocardial infarction the authors demonstrated that a system of computerised mapping of the epicardial and endocardial regions optimised the results of this form of surgery. Mapping localised, sometimes at a distance from the scar, classical subendocardial reentry, implicated on occasion the mitral papillary muscle in the mechanism or a tachycardia in cases of inferior or lateral infarction and localised the reentry in the epicardium of the lower layers of the septum. The identification of these "atypical" mechanisms significantly improves the number of patients without inducible arrhythmias after surgery (from 50 to 87% in the authors' experience), without changing the operative mortality. The only really curative approach because of the limitations of catheter ablation, this surgery is a complementary method to implantable defibrillators in the management of post-infarction ventricular tachycardia.

Aged↗
PubMed1996

[Surgical management of ventricular arrhythmia after myocardial infarction].

From December 1986 to December 1994, 36 patients underwent surgical treatments for intractable ventricular tachyarrhythmias after myocardial infarction. Preoperative electrophysiological studies confirmed inducibility of sustained monomorphic ventricular tachycardia and its resistance to antiarrhythmic drugs in all patients, 2 different concepts were assessed: 1) 22 non-guided surgical procedures were performed. 17 patients underwent Encircling thermic exclusion by Nd-Yag laser beam (Group A) and 5 patients underwent extended cryoablations (n = 5) with endocardial resections. Mean preoperative value of left ventricular function in Groups A and B were 35.23% and 30.20% respectively. 10 coronary bypasses (Group A: n = 8; Group B: n = 2) and 1 mitral valve replacement (Group A) were also performed. Perioperative mortality was 5.5% in Group A. No perioperative deaths occurred in Group B. Ventricular tachycardias recurred spontaneously in 2 patients (Group A) and 7 remained inducible after evaluation by electrophysiological studies. 2) 14 patients underwent extended cryoablations guided by intraoperative cardiac mapping, including endocardial resections in all cases. Mean preoperative value of left ventricular function was 32.80%. Mitral valve replacements were achieved in 2 cases, 1 perioperative death occurred (7.14%). Clinical recurrence of ventricular tachycardias concerned 1 patient (7.69%) and 2 remained inducible after electrophysiological studies (15.38%). We conclude that the better results obtained with cardiac mapping and cryoablations may be due to available detection and destruction of deep septal arrhythmogenic substrates. Moreover, cryoablation creates a nonarrhythmogenic scar and can be performed in papillary muscles while preserving the structure of the tissue. No postoperative alteration of left ventricular function was therefore observed.

Adult↗