Biomedical subjects

L Poirier

Publications and source records attributed to L Poirier.

At least 19 recordsLinked to original sources

PubMed2002

Anomalous dispersion and superluminal group velocity in a coaxial photonic crystal: theory and experiment.

We demonstrate that coaxial cables with a periodic impedance exhibit dispersion properties specific to photonic crystals, albeit on a much lower frequency scale. Highly superluminal (>2c) pulse propagation is observed near the photonic band gap at 10 MHz. The influence of group velocity dispersion and crystal length on the traveling speed and shape of a Gaussian pulse are discussed. Results compare favorably with a simple multilayer theory and a coupled-mass model of the structure.

Journal Article↗

PubMed2002

Development and evaluation of a PCR method for detection of the Clostridium difficile toxin B gene in stool specimens.

A PCR assay detecting Clostridium difficile toxin B gene in stool specimens was compared to the cytotoxicity assay as the reference standard for the diagnosis of C. difficile antibiotic-associated diarrhea (CDAD). Overall, 118 stool samples were tested. All of the specimens that were negative by the cytotoxicity assay (59 out of 118) were also negative by the PCR method (specificity of 100%). Of the 59 cytotoxin-positive samples, 54 were PCR positive (sensitivity of 91.5%). This PCR method is promising for rapid diagnosis of CDAD.

Animals↗

PubMed2001

Effects of nebivolol and atenolol on insulin sensitivity and haemodynamics in hypertensive patients.

OBJECTIVES: To compare the effects of nebivolol and atenolol in 25 ambulatory hypertensive patients with impaired glucose tolerance. DESIGN: Clinic and ambulatory blood pressure, insulin sensitivity (euglycemic-hyperinsulinemic clamp), glucose tolerance (intravenous glucose tolerance test), systemic and regional haemodynamics were measured after 4 weeks of placebo and after each 16-week treatment period in a double-blind, crossover fashion. RESULTS: Nebivolol and atenolol similarly reduced (P< 0.001) clinic and ambulatory blood pressure by approximately 15/10 mmHg, systolic and diastolic. Clinic and ambulatory heart rate was reduced to a greater extent (P < 0.01) by atenolol than nebivolol. Atenolol was associated with an approximately 20% reduction in insulin sensitivity (insulin-induced glucose disposal rate/mean insulin concentration ratio, P < 0.01) and an approximately 10% reduction in glucose disappearance rate (K-value, P < 0.05), whereas these variables were not significantly modified with nebivolol. Cardiac output was reduced similarly (P < 0.05) by both drugs at rest but forearm blood flow, forearm vascular resistance or total peripheral resistance were unaffected. A significant inverse correlation coefficient between cardiac output and insulin sensitivity was found at baseline, suggesting that a compensatory increase in systemic blood flow occurs in hypertensive patients with progressively more marked insulin resistance. This relationship was unaffected by nebivolol but was lost with atenolol. CONCLUSIONS: These results indicate that insulin sensitivity was not modified significantly by nebivolol, whereas it was reduced by atenolol, although blood pressure was decreased to the same extent by both drugs. Neither drug induced systemic or forearm vasodilatation but the inverse relationship between cardiac output and insulin sensitivity was preserved with nebivolol but not with atenolol.

Adrenergic beta-Antagonists↗

PubMed2001

Yield of smear, culture and amplification tests from repeated sputum induction for the diagnosis of pulmonary tuberculosis.

OBJECTIVES: To assess the yield of repeated sputum induction for the diagnosis of active tuberculosis in patients who do not produce spontaneous sputum, or with smear-negative spontaneous samples. METHODS: Induced sputum was examined with fluorescent microscopy, two amplification methods (PCR Amplicor MTB, and MTD2), and cultured for mycobacteria using liquid (Bactec 12B) and Lowenstein-Jensen media. Bronchoscopy and collection of other specimens were performed at the discretion of the treating physician. RESULTS: A total of 1115 sputum inductions performed in 500 patients without adverse events yielded an adequate specimen in 1113 (99.8%), and microbiological confirmation in 43 of 44 (98%) culture-positive active TB cases. Yield increased with repeated sputum induction. The cumulative yield for acid-fast bacilli smear and mycobacterial culture was 64% and 70% respectively for one, 81% and 91% for two, 91% and 99% for three, and 98% and 100% for four induced samples. Yield of PCR also increased with the greater number of induced samples tested. CONCLUSIONS: Repeated sputum induction could considerably improve diagnostic accuracy for pulmonary TB.

Analysis of Variance↗

PubMed2000

Comparative evaluation of the MB/BacT and BACTEC 460 TB systems for the detection of mycobacteria from clinical specimens: clinical relevance of higher recovery rates from broth-based detection systems.

New broth-based detection systems have higher recovery rates of mycobacteria from clinical specimens than traditional cultures on solid media. The clinical significance of this higher sensitivity rate is largely unknown. We prospectively evaluated the performances of two liquid media detection systems (the MB/BacT system and the BACTEC 460 TB system) and an egg-based Lowenstein-Gruft solid medium (LG) on the recovery rates of mycobacteria from 849 clinical specimens. Mycobacteria (other then M. gordonae) were detected in 51 (6.0%) specimens. In 12/51 (23%) specimens, mycobacteria (five mycobacterium tuberculosis (MtB) and seven non-M tuberculosis complex (MOTT) were recovered only from the broth-based systems. Review of the patients' clinical charts revealed that failure of LG to recover Mtb were due to nonmycobacterial overgrowth and antibiotic treatment. The recovered MOTT were all clinically nonsignificant. Higher sensitivity of broth-based mycobacteria detection systems is largely due to their capability to recover mycobacteria from treated tuberculous patients or from partially decontaminated specimens. The high recovery rates of nonclinically significant MOTT could potentially increase inappropriate use of antibiotics.

Bacterial Typing Techniques↗

PubMed2000

Accuracy and utility of commercially available amplification and serologic tests for the diagnosis of minimal pulmonary tuberculosis.

Diagnosis of patients with minimal active tuberculosis (TB) is difficult, as there is no single test with high sensitivity and specificity. The yield and clinical utility of a combination of diagnostic tests were prospectively studied among 500 consecutive patients referred for sputum induction for diagnosis of possible active TB. Patients underwent sputum induction, chest X-ray, tuberculin testing, and had blood drawn for serologic testing (Detect-TB test; Biochem ImmunoSystems). Sputum was examined with fluorescent microscopy and PCR (Amplicor MTB-Roche) and cultured for mycobacteria using liquid (BACTEC) and solid media. For the diagnosis of the 60 cases of active TB, sensitivity and specificity, respectively, of the following diagnostic tests were mycobacterial culture, 73% and 100%; PCR, 42% and 100%; chest X-ray, 67-77% and 66-76%; tuberculin testing, 94% and 20%; and serology, 33% and 87%. After consideration of PCR and radiographic and clinical characteristics, a positive serologic test was independantly associated with diagnosis of active disease (adjusted odds of disease if positive, 2.6; 95% confidence limits, 1.1,6.1). No currently available test has sensitivity and specificity high enough for the accurate diagnosis of minimal pulmonary TB. Utilization of a combination of tests, together with consideration of key clinical characteristics, could improve diagnostic accuracy.

Adult↗

PubMed2000

A comparative review of the efficacy of antihypertensive agents on 24 h ambulatory blood pressure.

BACKGROUND: Ambulatory blood pressure (ABP) monitoring has contributed significantly to the diagnosis, prognosis and treatment of hypertension. However, most of the published reviews have not focused on the 24 h efficacy of conventional and new antihypertensive agents as measured by ABP monitoring. OBJECTIVES: To discuss the importance of 24 h blood pressure control, and to review the antihypertensive efficacy of conventional antihypertensive agents and of angiotensin II type I receptor (AT1R) blockers as assessed by ABP monitoring. PATIENTS AND METHODS: The 24 h antihypertensive efficacy of the different classes of agents was reviewed based on clinical, randomized, double-blind trials published in peer review journals. These trials were mainly performed in the authors' research unit but were performed in other centres as well. RESULTS AND CONCLUSIONS: Most antihypertensive agents provided 24 h ABP control. However, in the authors' experience, hydrochlorothiazide, some angiotensin converting enzyme inhibitors and low dosages of the calcium antagonist diltiazem did not permit satisfactory blood pressure reduction as assessed by ABP monitoring in truly hypertensive patients. AT1R blockers and especially those of the new generation characterized by tight and long lasting AT1-receptor binding produced adequate 24 h ABP control and continued effectiveness during the high risk early morning hours.

Adrenergic beta-Antagonists↗

PubMed1999

Group A Streptococcus carriage among close contacts of patients with invasive infections.

During the past few years, the incidence of invasive group A Streptococcus (GAS) infection has been increasing. However, there are presently no clear recommendations regarding antibiotic prophylaxis for close contacts of index patients. The aims of this study were 1) to determine the prevalence of carriage of the same GAS strain as the patient's among contacts of patients with invasive infections and 2) to assess the importance of exposure duration. From March 1995 to March 1996, the authors prospectively included in the study all patients with invasive GAS infection, as defined by the Working Group on Severe Streptococcal Infections, who came to Hôpital Maisonneuve-Rosemont in Montreal, Quebec, Canada. An epidemiologic investigation was systematically carried out for each index case. Contacts were divided into two groups: those who had spent 24 hours or more with the index patient during the week preceding the beginning of his or her illness and those who had spent 12-24 hours with the index patient during that week. Strains of GAS were examined by serotyping (proteins M and T and the presence or absence of the serum opacity factor) and by characterization of streptococcal pyrogenic exotoxins (exotoxins A, B, and C). One hundred and two contacts of 17 index cases with invasive GAS infection were systematically screened. Contacts were considered positive if they carried the same strain of the bacterium and the same streptococcal pyrogenic exotoxin as the index case. Among the contacts who had spent at least 24 hours per week with their respective index cases, 13 out of 48 (27%) were found to be harboring the same serotype of GAS as the index patient (95% confidence interval 14.5-39.5). By comparison, only one of the 54 contacts in the 12- to 24-hour group (1.8%) was found to be carrying the same strain of the bacterium (95% confidence interval 0-5.3). This difference between the two groups was statistically significant (p<0.001). The median age of the positive carriers (10 years) was significantly lower than the median age of the noncarriers (39 years) (p< or =0.0005). This study showed that close contacts who had spent 12-24 hours with the index patient were rarely colonized with GAS. If antibiotic prophylaxis against GAS is recommended, it should probably target contacts who spent at least 24 hours with an infected patient during the week preceding illness onset.

Adolescent↗

PubMed1999

Chronotherapeutics: are there meaningful differences among antihypertensive drugs?

In the past decade, many publications have dealt with the possible relationship between biological rhythms and the incidence of cardiovascular events. A high proportion of treated hypertensive patients have cardiovascular complications, and chronotherapy, which permits the use of drugs that are maximally effective at different points in the circadian cycle, may be an interesting and valuable approach to decreasing morbidity and mortality in these patients. This article summarizes current knowledge on the new science of chronopharmacology, as demonstrated in several clinical studies that have used conventional agents administered at various points in the circadian cycle as well as new chronotherapeutic agents, such as controlled onset extended release (COER)-verapamil. In addition, emphasis is given to a rigorous evaluation of antihypertensive agents in terms of efficacy and duration of effect to obtain adequate and sustained lowering of blood pressure over the 24-hour period.

Antihypertensive Agents↗

PubMed1998

Primary renal mucormycosis.

Primary renal mucormycosis is a rare infection capable of acute illness with sepsis. Few cases have been reported. We report a case of an acute primary renal mucormycosis and review the published reports. The incidence of primary renal mucormycosis has risen in recent years. The most frequently reported underlying predisposing disorders are human immunodeficiency virus infection, intravenous drug abuse, and diabetes mellitus. Primary renal mucormycosis should be suspected in patients with an immunocompromising illness or particular risk factors, when persistent flank pain and fever with sterile urine not responding to appropriate antibiotics are associated with enlarged heterogeneous kidneys.

Acute Disease↗

PubMed1998

Comparative effects of felodipine ER, amlodipine and nifedipine GITS on 24 h blood pressure control and trough to peak ratios in mild to moderate ambulatory hypertension: a forced titration study.

OBJECTIVE: To evaluate the 24 h antihypertensive efficacy and duration of action of felodipine extended release (ER) in comparison with two other long acting dihydropyridine calcium antagonists, amlodipine and nifedipine gastrointestinal therapeutic system (GITS), in patients with mild to moderate essential hypertension substantiated by ambulatory blood pressure (BP) monitoring. DESIGN: Randomized, forced titration, parallel group study. Clinic BP was measured at every patient's visit, and 24 h ambulatory BP was monitored at baseline and at the end of each dose-titration period. SETTING: Single centre: hypertension research unit in Quebec City, Quebec. PATIENTS: There were 89 patients enrolled into the study. Eighty-four eligible patients were randomized, and 83 completed the study and were included in the final efficacy analysis. INTERVENTIONS: Following a two-to four-week washout period (baseline), patients were randomly allocated to receive felodipine ER 5 mg, amlodipine 5 mg or nifedipine GITS 30 mg for four weeks (low dose). All study patients had their daily dose doubled to felodipine ER 10 mg, amlodipine 10 mg or nifedipine GITS 60 mg for a further four weeks (high dose). MAIN RESULTS: Significant (P < 0.001) and similar changes from baseline in clinic BP were observed in all treatment groups for low and high doses. Ambulatory BP profiles showed comparable blood pressure reductions with felodipine ER and amlodipine, and a trend towards a lesser reduction with nifedipine GITS during 24 h, daytime and night-time periods. BP loads were similarly reduced with the three treatments. Trough to peak ratios (T:Ps) were calculated from 24 h ambulatory BP curves according to two different approaches: for diastolic and systolic BP, respectively, the global approach produced T:Ps of 0.49 and 0.50 with felodipine ER 5 mg; 0.50 and 0.34 with felodipine ER 10 mg; 0.70 and 0.60 with amlodipine 5 mg; 0.88 and 0.82 with amlodipine 10 mg; 0.65 and 0.55 with nifedipine GITS 30 mg; 0.68 and 0.53 with nifedipine GITS 60 mg. T:Ps in the individual approach were 0.07 and 0.10 with felodipine ER 5 mg; 0.23 and 0.31 with felodipine ER 10 mg; 0.22 and 0.31 with amlodipine 5 mg; 0.45 and 0.58 with amlodipine 10 mg; 0.27 and 0.31 with nifedipine GITS 30 mg; and 0.24 and 0.40 with nifedipine GITS 60 mg. CONCLUSION: There was no evidence in this study of a difference among felodipine ER, amlodipine and nifedipine GITS in lowering ambulatory or clinic BP. Treatment based on ambulatory BP may be preferable to treatment guided by T:Ps because ambulatory BP is firmly established as a predictor of cardiovascular risk. Furthermore, there is no consensus on how to calculate T:Ps, and different methods of calculation may give divergent results.

Adult↗

PubMed1997

The antihypertensive efficacy of the novel calcium antagonist mibefradil in comparison with nifedipine GITS in moderate to severe hypertensives with ambulatory hypertension.

Mibefradil is a novel calcium antagonist that blocks selectively the T-type calcium channels. In this double-blind forced titration study design we compared the effects of mibefradil 50, 100, and 150 mg and nifedipine GITS 30, 60, and 90 mg monotherapies or combined with lisinopril 20 mg in 71 moderate to severe hypertensives (59 men and 12 women) with confirmed ambulatory hypertension. An incremental dose-response effect was observed both in clinic and ambulatory blood pressure parameters during treatment with mibefradil and nifedipine GITS alone and combined with lisinopril. At maximal dosage, patients treated with mibefradil experienced a greater (P < .05) reduction in clinic and ambulatory diastolic blood pressures as well as a greater response rate (86% v 69%). Trough:peak ratios for systolic and diastolic blood pressures were > 90% at each dose level. Significant decrease in baseline heart rate was observed with mibefradil 150 mg alone or combined with lisinopril, but no patients experienced clinically significant atrioventricular conduction abnormalities. Adverse events related to vasodilation were more prevalent in the nifedipine GITS group. Consequently, the results of the present study demonstrate that the novel calcium channel blocker mibefradil, either alone or in combination with lisinopril, is effective in reducing clinic and 24-h blood pressures while decreasing heart rate and is well tolerated in patients with moderate to severe hypertension.

Adult↗

PubMed1997

Physical performance is preserved after regression of left ventricular hypertrophy.

Reversal of left ventricular hypertrophy has been shown to improve left ventricular diastolic function in elderly patients with hypertension, but little is known about whether this affects physical performance. Left ventricular mass, cardiac function at rest and during submaximal exercise, and physical performance were assessed in 38 elderly patients with hypertension with left ventricular hypertrophy and normal systolic function before and after 8 and 14 months of therapy with amlodipine or hydrochlorothiazide or both. Blood pressure control was achieved with amlodipine in 18 patients, with hydrochlorothiazide in seven, and with the combination of these drugs in 13. Left ventricular mass index was similarly reduced from approximately 150 to approximately 100 g/m2 at 14 months' in each treatment group. Systolic function was maintained with the three treatment regimens, whereas similar decreases in time to peak filling rate and increases in first-third filling fraction occurred both at rest and during submaximal exercise after 8 months and further after 14 months of therapy. Exercise capacity did not significantly change in the group as a whole, but individual changes in peak oxygen uptake at the end of treatment correlated significantly with the decrease in time to peak filling rate during submaximal exercise (r = -0.49; p < 0.01). It is concluded that long-term blood pressure control with amlodipine or hydrochlorothiazide or both is associated with significant reductions in left ventricular mass and improved diastolic function in elderly patients with hypertension with left ventricular hypertrophy. Despite this reduction in left ventricular mass, left ventricular systolic function and physical performance are well preserved during submaximal exercise.

Aged↗

PubMed1997

The importance of screening for domestic violence in all women.

Both the current and past surgeon generals of the United States and the Public Health objectives for Healthy People 2000 have identified family violence as an epidemic and have called for an organized approach to screen, treat, and prevent further violence. Domestic violence is not, and never has been, a "disease" of the poor. Thousands of women from high socioeconomic levels are beginning to shatter our visual image of an abused woman and are forcing us to look at current primary care screening practices and interventions. Domestic violence is as common, and in some cases more prevalent, as diseases routinely screened for such as breast cancer, hypothyroidism, hypertension, and colon cancer. One of the barriers to universal screening of domestic violence is our reliance on the profile of the typical battered woman. One often neglected population is women from higher socioeconomic groups. This article provides the rationale for universal screening of all women for domestic violence.

Female↗

PubMed1996

Ethanol feeding of micropigs alters methionine metabolism and increases hepatocellular apoptosis and proliferation.

Chronic alcoholism is associated with increased cancer risk that may be related to ethanol-induced alterations in methionine and deoxynucleotide metabolism. These metabolic relationships were studied in micropigs fed diets for 12 months that contained 40% ethanol or cornstarch control with adequate folate. Ethanol feeding altered methionine metabolism without changing mean terminal liver folate levels. After initial equilibration to diet, ethanol feeding significantly increased monthly serum homocysteine levels while reducing serum methionine levels over the time course of the experiment. After 12 months, hepatic methionine synthase activity and the ratio of S-adenosylmethionine (SAM) to S-adenosylhomocysteine (SAH) were significantly reduced in ethanol-fed animals, whereas the ratio of liver deoxyuridine triphosphate (dUTP) to deoxythymidine triphosphate (dTTP) was increased and correlated inversely with methionine synthase activity. These findings were associated with increased frequency of hepatocytes with apoptotic bodies and positivity for proliferating cell nuclear antigen (PCNA) in livers from ethanol-fed minipigs. These studies suggest that chronic ethanol feeding perturbs methionine metabolism by impairment of methionine synthase activity, resulting in deoxynucleoside triphosphate (dNTP) imbalance, increased apoptosis, and regenerative proliferation. These biochemical alterations may provide a promoting environment for carcinogenesis during long-term ethanol exposure.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗

PubMed1996

A new urea broth-based test to detect Helicobacter pylori presence in upper gastrointestinal biopsies.

The aim of this study was to evaluate the performance of a simple and inexpensive homemade urea test (U-test) to detect Helicobacter pylori in upper digestive tract biopsies. We tested and compared the U-test with three other diagnostic methods: the Clo-test, and culture and pathology in 110 patients randomly chosen at the endoscopy clinic. When using culture and/or pathology as the "gold standard," H. pylori was found to exist in 54 patients. Pathology was positive in 50 cases (92.5%), culture in 49 (90.7%), the U-test in 45 (83.3%), and the Clo-test in 43 (79.6%). With regard to culture pathology, the sensitivities of the U-test and the Clo-test were 83.3% and 79.5%, respectively. Specificity was 100% for both methods. The kappa coefficient calculation between the U-test and the Clo-test was 0.98. The results show that the U-test is a reliable, fast, and inexpensive method for detecting H. pylori in upper gastrointestinal biopsies.

Adult↗

PubMed1996

Usefulness of ambulatory blood pressure monitoring in detecting the additional antihypertensive effect of non-pharmacologic treatment.

OBJECTIVE: The present study was designed to investigate whether a non-pharmacologic intervention program (NPIP) consisting of a weight-lowering diet, a reduction in alcohol consumption and physical training at 50% peak aerobic capacity could enhance the blood-pressure-lowering effect of calcium antagonists in obese sedentary, hypertensive patients. METHODS: Fifty-nine subjects were treatred with 5-10 mg isradipine once daily for 8 weeks and were then randomly allocated to either isradipine monotherapy or isradipine plus NPIP for 20 weeks. Clinic and ambulatory blood pressure were used for assessing the antihypertensive effect obtained in both treatment groups. RESULTS: Clinic and ambulatory systolic and diastolic blood pressures decreased significantly after 8 weeks of isradipine monotherapy. At week 28, the group treated with isradipine combined with NPIP and in which significant modifications in body weight (P < 0.0001), alcohol intake (P < 0.0001) and peak oxygen uptake (P <0.01) were observed, had significant (P < 0.05) additional decrements in ambulatory but not clinic blood pressure. CONCLUSIONS: These results demonstrate that the addition of lifestyle modifications in obese sedentary hypertensive patients already receiving pharmacological therapy can induce further blood pressure decrements. Because significant decrements were noticed only with ambulatory blood pressure monitoring, the results of the present study advocate this technique for assessing the magnitude of blood pressure reduction with non-pharmacological therapy.

Journal Article↗

PubMed1995

Clinical efficacy of force titrated doses of diltiazem extended-release. A placebo controlled study.

Thirty patients with clinical and ambulatory essential hypertension were treated in a double-blind fashion with force titrated doses of placebo or diltiazem once daily (OD) extended-release (ER) 120, 240, 360, and 540 mg to characterize the full-dose range of the new formulation. An incremental dose-response effect was observed both in clinic and ambulatory blood pressure parameters. Doses of > or = 240 mg significantly decreased clinic diastolic blood pressure, whereas systolic blood pressure was significantly lowered by the 540-mg dose. Moreover, compared with placebo, ambulatory blood pressure was significantly decreased by the 360- and 540-mg dose levels. Trough/peak ratios for systolic and diastolic blood pressures were 50% and higher at dose levels of 240 mg and above. Adverse reactions with diltiazem OD ER were generally mild and similar to those observed with placebo. The findings of this study indicate that the most favorable effects of diltiazem OD ER were observed in response to the 360- and 540-mg dose levels. The dose escalation forced titration study design appears to be a valuable tool in obtaining rigorous dose-response data of new antihypertensive agents.

Adolescent↗