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Biomedical subjects

M Montpetit

Publications and source records attributed to M Montpetit.

11 recordsLinked to original sources
PubMed1998

Socioeconomic geographical links to human immunodeficiency virus seroprevalence among childbearing women in Montreal, 1989-1993.

BACKGROUND: To describe the socioeconomic profiles of geographical areas on Montreal Island in which human immunodeficiency virus (HIV) seropositive women delivering live births between 1989 and 1993 reside. METHODS: Leftover dried blood spot filter paper specimens collected from newborns were irretrievably unlinked from identifying information prior to testing. Seroprevalence estimates were calculated based on Western blot confirmed positive samples. Using data from the Canadian census, Revenue Canada, and provincial birth records, the socioeconomic characteristics of postal zones in which seropositive mothers reside were described. RESULTS: Montreal Island had an overall 5-year HIV seroprevalence rate estimate of 16.6 (95% CI: 14.1-19.3) per 10000 childbearing women. Areas in which at least one seropositive woman gave birth had lower mean infant birthweights and higher percentages of single mothers and single-parent families. The HIV-positive neonatal blood specimens were more likely to originate from areas where a higher proportion of residents reported less education, greater unemployment, and lower income. CONCLUSIONS: Higher HIV infection rates were found among childbearing women from lower socioeconomic areas of Montreal. Increased understanding of the relationship between socioeconomic status and HIV acquisition and transmission is required to inform the development of targeted HIV prevention programmes.

Adult↗
PubMed1995

Regulation of Lewis lung carcinoma invasion and metastasis by protein kinase A.

Metastatic Lewis lung carcinoma (LLC-LN7) cells have increased protein kinase A (PKA) activity and are more invasive in vitro than are non-metastatic (LLC-C8) cells. To determine whether PKA mediates the in vitro invasiveness and in vivo metastatic capabilities of these tumor cells, the LLC variants were stably transfected to over-express the C alpha subunit of PKA, and thus to have increased PKA activity, or to express a mutant cAMP-resistant PKA R1 alpha subunit which blocks PKA activation. Wild-type LLC-LN7 tumor cells were invasive in vitro and in vivo, recurred after tumor excision and metastasized to the lungs. However, they lost these properties after transfection to express the mutant R1 alpha that blocks PKA activation. The non-invasive, non-recurring and non-metastatic LLC-C8 cells gained the capacity to invade, to recur following tumor excision and to metastasize when transfected to express the PKA C alpha subunit.

Animals↗
PubMed1995

Potential applications of proviral load measurement in clinical retrovirology.

We have previously noted an association between proviral load and the severity of immune disease in individuals with a wide range of CD4 cell counts. Using the quantitative DNA polymerase chain reaction technology developed in our laboratory, we sought to extend these observations, with a view to establishing guidelines for the use of proviral load in a clinical context. We studied 199 patients with a range of CD4 cell counts attending an urban tertiary care center. Proviral load/10(6) peripheral blood mononuclear cells (PBMCs) was measured using a microtiter plate assay designed specifically for this purpose. Human immunodeficiency virus proviral DNA was detected in 193 of 199 clinical samples. Levels of proviral load were tabulated for patients and evaluated in seven categories defined by CD4 cell counts. Although a wide range of proviral loads was observed in each category of patients, there was a trend toward increasing proviral load with decreasing CD4 cell count. Statistically significant relationships were observed between proviral load and the CD4 cell count and the CD4 cell percentage (Spearman's correlation coefficient -0.19, p = 0.01 for both absolute CD4 and CD4 percentage). These relationships were quite weak and could not be taken to explain disease progression in isolation. If we defined a cutoff between low and high proviral loads at 100 copies/10(6) PBMCs, we noted that 52% (24 of 46) of patients with CD4 cell counts > 400/microliters had lower loads, as compared with 16% (24 of 143) of those with more advanced disease (p < 0.01). There is a weak, but statistically significant association between proviral load and CD4 cell depletion.(ABSTRACT TRUNCATED AT 250 WORDS)

CD4 Lymphocyte Count↗
PubMed1994

Effects of cold and warm blood cardioplegia assessed by myocardial pH and release of metabolic markers.

The optimal temperature of blood cardioplegia remains controversial. Interstitial myocardial pH was monitored online with a probe that was inserted in the anterior wall of the left ventricle. Venous pH, lactate production, and creatine kinase and troponin T release were measured in coronary sinus blood obtained in 14 dogs after ischemic arrest periods of 5, 10, 20, and 40 minutes with warm (n = 7; mean myocardial temperature, 35 degrees +/- 2 degrees C) and cold (n = 7; mean myocardial temperature, 12 degrees +/- 1 degree C) blood cardioplegic protection. Blood cardioplegic solution was delivered at a rate of 100 mL/min during the 10 minutes between each ischemic arrest. The interstitial myocardial pH decreased significantly (p < 0.05) from 7.1 +/- 0.3 to 6.53 +/- 0.3 after ischemia in animals perfused with warm blood cardioplegia and from 7.04 +/- 0.3 to 6.64 +/- 0.1 in those receiving cold blood cardioplegic protection; however, the difference between the groups was not significant (p > 0.05). Lactate production and creatine kinase and troponin T release increased significantly after ischemia, but there was no difference in the changes between the warm and cold blood cardioplegia groups. In conclusion, ischemia caused significant changes in all variables measured, and these changes were directly proportional to the duration of ischemia. However, there was no significant difference (p > 0.05) in the myocardial metabolic changes between the warm and cold blood cardioplegia groups in terms of the duration of ischemic arrest studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

Rapid DNA fingerprinting to control for specimen errors in HIV testing by the polymerase chain reaction.

Variable-number-tandem-repeats (VNTRs) are highly polymorphic and provide informative genetic markers for distinguishing between individuals. We have used PCR amplification of VNTR locus pMCT118 to identify mislabelled specimens submitted for HIV PCR testing. The method is rapid, can be applied to large numbers of samples and eliminates the need for radioactive probes. DNA samples (10 ng) are amplified for 25 cycles using fluorescence-labelled oligonucleotide primers (blue dye). An aliquot of the PCR product is then combined with an internal lane size standard (labelled with a red dye), electrophoresed through a 2% agarose gel on an automated fluorescence DNA fragment analyser and the size and quantity of the fragments determined automatically relative to the internal standard. Fifteen alleles, ranging in size from 398 tp 709 bp were readily identified in a random sampling of DNA from 63 unrelated HIV-infected patients. Fragment size was reproducible and corresponded to alleles containing from 16 to 35 repeats of a 16 bp unit. VNTR genotyping will prove useful for resolving discordant results due to specimen mix-up and ensuring that the correct samples have been analyzed.

Alleles↗
PubMed1992

Stability of dried blood spot specimens for detection of human immunodeficiency virus DNA by polymerase chain reaction.

Blood sampling on filter paper has many advantages for the detection of perinatal human immunodeficiency virus (HIV) infection by the polymerase chain reaction (PCR). However, if the method is to be widely used, an assessment of its performance under field conditions is required. To simulate conditions in the field, 50-microliters aliquots of whole blood containing low levels of HIV proviral DNA (4 to 1,024 copies per 100,000 nucleated cells) were spotted onto filter paper; dried; and subjected to heat, humidity, and prolonged storage at room temperature. After exposure, the DNA was recovered and amplified with primers to human leukocyte antigen DQ alpha- and HIV-specific sequences. Treatment at 37 degrees C and 60% humidity for 7 days, storage for 12 weeks at 22 degrees C, and freeze-thawing twice had no adverse effect on PCR reactivity when compared with the results obtained with reference spots stored at -20 degrees C. The lower limits of HIV detection in all tests ranged from 4 to 16 HIV copies per 100,000 cells. Fixation in 70% ethanol improved the amplification of low levels of HIV DNA and reduced biohazard risks. These findings suggest that dried blood spots will provide a powerful new resource for testing for HIV by PCR, especially in remote areas where refrigeration and immediate sample processing are unavailable.

Blood Specimen Collection↗
PubMed1991

Physical and dynamic characteristics of DC ablation in relation to the type of energy delivery and catheter design.

We evaluated and compared the in vitro characteristics of direct current ablation using high energy ablation (Hewlett-Packard defibrillator) and a new form of low energy ablation (low energy ablation power supply, Cardiac Recorders, UK). Two new catheters with a large distal electrode have been recently introduced for catheter ablation: a low energy 7F bipolar catheter (Bard) with a contoured distal electrode, and a 7F deflectable catheter with a 4-mm tip (Mansfield). In vitro studies were carried out in a large tank filled with physiological saline while recording voltage, current, and pressure. High speed cinematography at 32,000 frames per second (Cordin, Utah) was done to assess the dynamic behavior of the vapor globe with both systems of energy delivery. We evaluated shocks of 50, 100, 150, 200, and 300 joules with the conventional system, and shocks of 10, 15, 20, 30, and 40 joules with the new system, and also compared the effects of varying catheter design with both systems of energy delivery. The conventional system using high energy showed significant arcing and increases in pressure. Low energy direct current ablation produces nonarcing shocks with 20 joules or less, and significantly less vapor globe and gas formation during arcing shocks, with a shorter duration of increase in pressure. This new system using low energy direct current may reduce the risk and complications reported with high energy ablations.

Cardiology↗
PubMed1991

In vitro and in vivo effects within the coronary sinus of nonarcing and arcing shocks using a new system of low-energy DC ablation.

DC shocks within the coronary sinus have been abandoned because of the risk of cardiac rupture and tamponade. Catheter ablation using DC energy to electrodes straddling the ostium of the coronary sinus, when used clinically, has been reported to result in cardiac tamponade in as many as 16% of patients. A new system of energy delivery maximizes voltage while decreasing the undesirable effects caused by barotrauma. This system includes 1) a low-energy ablation power supply with a brief time-constant capacitive discharge that delivers up to 40 J and 3,000 V and 2) a low-energy ablation catheter with a contoured distal electrode. We performed in vitro and in vivo studies of this new system and compared arcing shocks with nonarcing shocks. Ablations were performed using unipolar distal shocks (D) and unipolar shocks to both electrodes made electrically common (P-D). In vitro studies were done in a large tank filled with physiological saline while recording voltage, current, and pressure. High-speed cinematography (32,000 frames/sec) of shocks of 10-40 J permitted detailed analysis of the vapor globe. Anodal shocks of less than 20 J showed no arcing or only minimal vapor globe formation. For D and P-D anodal shocks of 40 J, the diameters of the vapor globe were 31 and 22 mm, respectively, corresponding to pressure recordings of 11 and 4.9 atm. The pressure rise lasted less than 50 mu sec. In vivo studies involved 18 dogs that received nonarcing shocks (one to six shocks of 15 J) and 18 dogs that received arcing shocks (one to three shocks of 40 J). Each group was divided between D and P-D shocks; catheter ablation was performed at a mean +/- SEM distance of 2.94 +/- 0.92 cm within the coronary sinus. All dogs tolerated the procedure without cardiac rupture or tamponade. When killed 2-4 days later, the dogs had edema and hyperemia or hemorrhage in the area of the coronary sinus. We compared the effects of multiple (three to six) nonarcing shocks with the effects of one to three arcing shocks. Disruption or rupture of the coronary sinus within the epicardial fat space occurred in two of 12 dogs (17%) with multiple nonarcing shocks but in 13 of 18 dogs (72%) with arcing shocks (p less than 0.003). Occlusion of the coronary sinus occurred in two of 12 dogs (17%) with multiple nonarcing shocks and in nine of 18 dogs (50%) with arcing shocks (p less than 0.06).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Androgen-independent epithelial cells of the rat ventral prostate.

Androgen-independent cell lines have been clonally selected from primary cultures of androgen-dependent epithelial cells from the rat ventral prostate. These rapidly dividing epithelial-like cells (RDE) have altered morphology and adherence characteristics. Unlike normal prostate epithelial cells, the RDE cell lines do not require androgens for cell division or cell survival. In the presence of physiological concentrations of testosterone, the isoelectric focusing patterns of prostatic acid phosphatases are abnormal in these RDE cells, and the prostate steroid-binding protein genes are not expressed. The loss of androgen dependence is not due to the inability of RDE cells to metabolize testosterone to 5 alpha-dihydrotestosterone, the active androgen, since the RDE cell lines metabolize testosterone in a manner similar to normal androgen-dependent epithelial cells. When RDE cells are grown on collagen matrices, the cells assume ductlike structures, similar to prostatic acini, although PSBP gene expression is not induced. When seeded into soft agar these cell lines form distinct foci, suggesting that they are potentially tumorigenic.

Acid Phosphatase↗
PubMed1986

Multiple conductance states of the acetylcholine receptor channel complex.

The acetylcholine-activated channel of vertebrate skeletal muscle, as manifested in cultured, developing cells, is able to adopt more than one conductance state. This paper briefly reviews the evidence for such multiple conductance channels and presents results showing that the amplitude of subconductance states does not depend on agonist size and (or) valence. This seems to rule out the possibility that subconductances occur during partial occlusion of the channel (by agonist molecules) and supports the idea that subconductances represent discrete, allosterically activated channel conformations.

Animals↗