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Biomedical subjects

A Lévesque

Publications and source records attributed to A Lévesque.

16 recordsLinked to original sources
PubMed1998

Analytical evaluation of the testosterone assay on the Bayer Immuno 1 system.

OBJECTIVES: To evaluate the analytical performance of the testosterone assay performed on the Bayer immuno 1 system from Bayer Corporation. DESIGN AND METHODS: The precision was measured using three Bayer TESTpoint Ligand controls, three Medical Decision Pools and the Bayer SETpoint Testosterone calibrators. The linearity was verified by diluting two serum samples containing high testosterone concentrations with the zero calibrator and the minimum detectable concentration determined by repetitive analysis of the zero calibrator. The assay was correlated with the Diagnostic Products Corporation (DPC) Total Testosterone assay using 342 serum samples. The reference values were determined using serum samples from 75 women and 60 men. RESULTS: The assay showed within-run coefficients of variation (CVs) varying from 1.1-8.4% and between-day CVs from 1.5-4.9% for testosterone concentrations varying from 1.77 to 66.96 nmol/L. The minimum detectable concentration was estimated at 0.11 nmol/L. The assay linearity proved excellent. A good correlation between the Bayer Immuno 1 and the DPC assays was observed with different categories of serum samples (Immuno 1 = 1.11 x DPC-0.32, r = 0.989, Sy[symbol: see text]x = 2.07 nmol/L). The reference values were estimated at 0.3-3.2 nmol/L for females and 9.3-35.6 nmol/L for males. CONCLUSIONS: The Bayer Immuno 1 Testosterone assay demonstrates the analytical characteristics required for its utilization in the clinical laboratory.

Adult↗
PubMed1997

Analytical evaluation of the CK-MB mass assay on the Technicon Immuno 1 system.

OBJECTIVES: To evaluate the performance of the Technicon Immuno 1 CK-MB mass assay. DESIGN AND METHODS: The precision was measured using the BioRad Liquichek CK-MB controls and the Technicon Immuno 1 SETpoint CK-MB calibrators. The linearity was verified by diluting 9 patient serum samples containing high CK-MB concentrations, and the minimum detectable concentration determined by repetitive analysis of the zero calibrator. The assay was compared with the Johnson & Johnson Vitros CK-MB activity assay using 111 patient serum samples. The reference range was determined using serum samples from 100 healthy adult volunteers. RESULTS: The assay shows within-run CVs varying from 1.5 to 7.5% and between-day CVs from 1.5 to 4.8% for CK-MB concentrations ranging from 3.9 to 99.0 micrograms/L. The linearity study gave correlation coefficients greater than 0.9961. There was a very good correlation between mass and activity assays (r = 0.985). The reference values were estimated at 0.0-4.2 micrograms/L and the minimum detectable concentration at 0.5 micrograms/L. CONCLUSIONS: The evaluation shows that the Technicon Immuno 1 CK-MB mass assay has the analytical characteristics suitable for its inclusion in the modern clinical repertoire.

Creatine Kinase↗
PubMed1997

Development of an assay for urinary free cortisol determination on the Technicon Immuno 1 system.

OBJECTIVES: To develop and evaluate a method using an ethyl acetate extraction procedure for the determination of urinary free cortisol on the Technicon Immuno 1 system from Bayer Corporation. DESIGN AND METHODS: We tested the assay precision, linearity, and correlation with the Urinary Kallestad Quanticoat Cortisol radioimmunoassay. We also studied the efficiency of the extraction procedure, performed a cross-reactivity study with different cortisol metabolites, and determined the reference values. RESULTS: The assay shows within-run CVs varying from 1.6 to 5.3% and between-day CVs from 2.7 to 6.1% for urinary free cortisol concentrations from 58 to 1097 nmol/L. The assay demonstrates an excellent linearity and a very good correlation with the Kallestad Quanticoat Cortisol assay (slope = 0.94, y-intercept = 29 nmol/L, Sy/x = 54 nmol/L, r = 0.996). The reference values were estimated at 42-281 nmol/d. The extraction procedure shows an average recovery of 99.0% and minimal interference with the cortisol metabolites tested with the exception of cortisone. CONCLUSIONS: The evaluation shows that the developed assay has the analytical characteristics required for its utilization in a clinical laboratory.

Cross Reactions↗
PubMed1997

Analytical performance of Bayer Immuno 1 estradiol and progesterone assays.

We evaluated the analytical performance of new estradiol and progesterone assays performed on the Bayer Immuno 1 system. Within-run and between-day CVs for estradiol at concentrations of 116.8-6645.8 pmol/L were < or = 6.4% and for 5.54-103.95 nmol/L progesterone were < or = 7.7%, thus meeting published analytical goals. The detection limits (2 SDs from mean of zero calibrator) were 27.1 pmol/L for estradiol (n = 72 over 20 days) and 0.51 nmol/L for progesterone (n = 47 over 20 days). The assays were linear to 9766 pmol/L and 113.0 nmol/L, respectively. Estradiol results agreed well with the Diagnostic Products Corporation (DPC) assays, except for serum samples from patients receiving estrogen replacement therapy; results for these samples agreed closely with the DPC estradiol-6 assay. The progesterone assay agreed closely with the DPC assay, except for samples from uremic patients. Reference values were estimated by the study of 29 women throughout the menstrual cycle with 15 samples per subject. We concluded that both assays demonstrate suitable precision, linearity, and intermethod agreement to allow their use in the clinical laboratory.

Automation↗
PubMed1996

Performance evaluation of automated immunoassays on the Technicon Immuno 1 system.

We performed an immunoassay evaluation for various analytes on a fully automated random-access analyzer, the Technicon Immuno 1 system from Bayer Corp. This system involves latex agglutination, magnetic separation sandwich, and magnetic separation competitive immunoassay configurations. The evaluated analytes were thyrotropin (TSH), triiodothyronine, thyroxine, free thyroxine, follitropin, lutropin, prolactin, beta subunit of human chorionic gonadotropin, cortisol, ferritin, alpha-fetoprotein, carcinoembryonic antigen, and prostate-specific antigen. We tested the assay precision, linearity, and correlation with comparison methods for these analytes. The functional sensitivity of the TSH assay and the sample-to-sample carryover were also studied. Excellent results were obtained for within-run and between-day precision studies, with most assays showing within-run CVs <4% and between-day CVs <6%. The linearity for all assays was acceptable and the correlation between Immuno 1 assays and comparison methods showed satisfactory results. The functional sensitivity of the TSH assay was estimated at 0.04 mU/L. No sample-to-sample carryover was detected.

Autoanalysis↗
PubMed1995

Measurement of tumor necrosis factor activity by flow cytometry.

Tumor necrosis factor-alpha (TNF-alpha) is a monokine of 17 kDa produced by activated macrophages and various cells involved in the immune system. We propose a new method for the measurement of TNF activity using flow cytometry. After an incubation with TNF, L929 cells were harvested and treated with a calcein-AM and ethidium homodimer-1 solution. Nonfluorescent calcein-AM is hydrolyzed by intracellular esterases to yield fluorescent calcein. The ethidium homodimer-1 is a high-affinity red fluorescent DNA dye that is internalized only through altered cell membranes. A very good correlation was observed between the calcein fluorescence intensity and the number of viable cells as well as the ethidium fluorescence and the number of cells with altered membranes. The assay is sensitive, inexpensive, and correlates with the already reported crystal violet assay while measuring membrane alteration by TNF. It allows the simultaneous measurement of total living and dead cells. There is no interference with culture medium components. This method is rapid and may be used for routine measurement of TNF activity.

Animals↗
PubMed1995

Improved fluorescent bioassay for the detection of tumor necrosis factor activity.

Tumor necrosis factor alpha (TNF-alpha) is a monokine of 17 kDa produced by activated macrophages and various cells involved in the immune system. We propose a new method for the measurement of TNF activity on mouse L929 fibroblast cells. After an incubation with TNF, the cells were stained with a solution of ethidium homodimer-1, a high-affinity red fluorescent DNA dye that is internalized only through altered cell membranes. The assay is sensitive, inexpensive and correlates with the already reported TNF assays while measuring the membrane alteration by TNF and not the cell detachment. It requires no rinsing before dye addition which may cause cell loss; there is no interference with culture medium components since the assay is performed in PBS. This method is more rapid and precise for routine measurement of TNF activity.

Animals↗
PubMed1994

Rapid purification method for human recombinant tumor necrosis factor alpha.

Human recombinant tumor necrosis factor alpha was purified in a single step to about 95% purity from Escherichia coli lysate by chromatography on hydroxyapatite. The last traces of contaminants were removed by fast protein liquid chromatography on a Mono Q column. The final product was found to be pure by gel electrophoresis with silver staining. A molecular mass of approximately 17,000 and a specific activity of 4.3 x 10(6) U/mg after a single purification step were found.

Amino Acids↗
PubMed1992

Effects of residency training in family medicine v. internship training on professional attitudes and practice patterns.

OBJECTIVES: To determine whether the professional attitudes and practice patterns of physicians with residency training in family medicine differ from those of generalists with internship training. DESIGN: Mail survey conducted in 1985-86. SETTING: Province of Quebec. PARTICIPANTS: A stratified random sample of French-speaking family and general practitioners who graduated after 1972 (325 physicians with residency training and 304 with internship training) (response rate 82%). MAIN RESULTS: Physicians with residency training were 3 years younger on average than those with internship training, were more likely to be female (38% v. 18%, p less than 0.001) and were more likely to work on a salaried basis in CLSCs (public community health centres) (36% v. 14%, p less than 0.001). Even after these confounding factors were controlled for, physicians with residency training seemed to be more sensitive to the psychosocial aspects of patient care and tended to attach more importance to informing patients about useful materials and resources concerning their health problems. They were not, however, more likely to value health counselling or integrate it in medical practice. CONCLUSION: Our findings provide some evidence that the new requirement that physicians complete a residency in family medicine to obtain medical licensure in general practice in Quebec may foster a more patient-centred approach to health care.

Adult↗
PubMed1991

Characteristics of physicians practicing in alternative primary care settings: a Quebec study of local community service center physicians.

Since the early 1970s, there have been two primary care networks in Quebec: the traditional one characterized by private practice remunerated on a fee-for-service basis, and the public one comprising 15 percent of physicians and characterized by salaried practice within publicly funded local community health service centers (CLSCs). Using data collected on 616 Quebec generalists, 333 in private practice and 283 in CLSCs, we compared physicians' profiles in both networks. In contrast to their colleagues in private practice, CLSC physicians are younger, more often women, and more often graduates of innovative primary care training programs. They are more sensitive to the biopsychosocial nature of health problems and to giving patients an active role in their care. Significant differences were also observed in physicians' self-reported clinical practices, more so for women than for men. The study suggests that alternative primary care settings attract physicians that are more preventive and socially oriented. As a result, they may contribute to the emergence of a more comprehensive type of medical practice in health care delivery systems.

Adult↗
PubMed1984

[Not Available].

Explore the source record for details and available documents.

Canada↗
PubMedDate not supplied

Synthesis of bombesin analogs by the Fmoc method.

Bombesin synthesis has previously been achieved by the Merrifield method. Severe conditions and repetitive acidic treatments have led to the selection of a milder method for improving effectiveness. This study describes a new technique for the synthesis of bombesin and its analogs based on the use of fluorenylmethoxycarbonyl (Fmoc) protected amino acids and continuous flow solid phase procedure. Peptide elongation is realized by the intermediaries of derived pentafluorophenyl ester amino acids. Peptides of different lengths were synthesized in order to determine the minimal length of peptide chain needed to obtain immunoreactivity comparable to that of natural bombesin. Purification and analysis of the products by FPLC and amino acid determination were performed. Immunoreactivity study of these peptides was measured by a competition radioimmunoassay with an antiserum directed against the C-terminal portion. Results suggest that a decapeptide analog is sufficient for bombesin to be recognized by the antibody or as a carrier in targeting therapy.

Amino Acid Sequence↗
PubMedDate not supplied

[Primary care in Québec: a comparison between private practitioners and physicians working in public community health centers].

Since the early 1970s, there have been two primary care networks in Quebec: the traditional one characterized by fee-for-service; and the public one regrouping 10% of physicians and characterized by a salaried practice within publicly funded local institutions known as CLSCs. Using 1984 data collected on 616 Quebec generalists, 333 in private practice and 283 in CLSCs, we compared the physicians' profile in both networks. In contrast to their colleagues in private practice, CLSC physicians were younger, more often female and more involved in rural practice as well as in community health. They also differed in their attitudes and to some extent in their clinical practices. Overall, the study suggests that the introduction of a public primary care network has served to facilitate the emergence of a more comprehensive type of medical practice in the Quebec health care system.

Adult↗
PubMedDate not supplied

The professional attitudes and practice characteristics of male and female specialists.

Using data obtained from a mail survey of 119 female and 140 male specialists conducted in Quebec in 1983-1984, we compared men and women on their attitudes and on the organizational, professional, and clinical characteristics of their medical practices. Analyses were performed separately for medical and surgical specialists. Gender differences in the clinical practice of medical specialists were found, with women reporting greater attention to the social, preventive, and human aspects of patient care than men. Among surgical specialists, women expressed more favorable attitudes toward the social component in health care than their male colleagues. They also differed from men on indicators measuring various practice characteristics. These findings may reflect gender differences in type of surgical specialty, since the majority of female surgeons were in ophthalmology. Overall, fewer women specialists reported that they had assumed administrative responsibilities. The implications of these results are discussed in the context of the increasing feminization of the medical profession.

Adult↗