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Biomedical subjects

G Lamoureux

Publications and source records attributed to G Lamoureux.

At least 19 recordsLinked to original sources
PubMed1991

Inhibition of tumor necrosis factor-alpha transcription by Epstein-Barr virus.

Tumor necrosis factor-alpha (TNF-alpha), which is produced mainly by monocyte/macrophage cells, has diverse physiological functions on lymphoid cells. Moreover, it has been shown that TNF-alpha exhibits antiviral activities. Here we report that Epstein-Barr virus (EBV), a B lymphotropic human herpes virus that interacts intimately with the immune system, exerts a strong inhibitory effect on TNF-alpha production by lipopolysaccharide-treated peripheral blood leukocytes as well as by monocytic cell lines, HL-60 and U-937. Flow cytometric analysis following staining with OKB7 monoclonal antibody showed that about 20% of cells from these monocytic lines express the CR2 antigen. Direct binding of fluorescein isothiocyanate-labeled EBV indicated that the virus binds to approximately 22% of cells of both monocytic lines. However, no virus-specific antigens were detected in the infected cells by immunofluorescence, suggesting that the infection was of the abortive type. The use of UV- or heat-inactivated EBV and inhibitory effect on TNF-alpha synthesis. These results suggest that infectious virus is necessary to obtain such an inhibitory effect. Analysis of TNF-alpha mRNA by polymerase chain reaction amplification indicated that the EBV suppressive effect is manifested at the transcriptional level. In contrast, EBV did not inhibit interleukin 1 mRNA production by these cells. These results indicate that EBV interacts directly with monocytes/macrophages to exert its immunomodulatory effect.

Antibodies, Monoclonal↗
PubMed1991

Rapid and sensitive sandwich enzyme-linked immunosorbent assay for detection of staphylococcal enterotoxin B in cheese.

A rapid and sensitive screening sandwich enzyme-linked immunosorbent assay (ELISA) was developed for the detection of staphylococcal enterotoxin B (SEB) in cheese by using a highly avid anti-SEB antibody (Ab) as the capture Ab (CAb) and as the biotinylated Ab conjugate. The glutaraldehyde fixation method for the immobilization of CAb on polystyrene dipsticks was superior to the adsorption fixation and the adsorption-glutaraldehyde fixation methods. The glutaraldehyde fixation method resulted in a higher surface-saturating CAb concentration as evaluated by the peroxidase saturation technique and by the ability of the CAb-coated dipstick to discriminate between positive and negative controls (index of discrimination). Of nine blocking agents used alone or in pairs, lysine-human serum albumin, bovine serum albumin, human serum albumin, and gelatin effectively saturated available sites on the CAb-coated dipsticks without causing interference with the antigen-Ab reactions. The addition of 1% polyethylene glycol to the diluent of the biotinylated anti-SEB Ab conjugate improved the detection of SEB. A concentration of 4% polyethylene glycol allowed a 5-min reaction time for the streptavidin-biotin-horseradish peroxidase conjugate. Cheddar cheese homogenate reduced the sensitivity of the SEB assay; however, the sensitivity was restored when 1.6% (wt/vol) of either a nonionic detergent (Mega-9) or two zwitterionic detergents (Zwittergent 3-10 and 3-12 detergent) was added to the diluent. By using the rapid sandwich ELISA, a minimum of 0.5 to 1.0 ng of SEB per ml was detected within 45 min. The whole procedure for the analysis of the cheddar cheese samples was completed within 1 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Cheese↗
PubMed1990

Peripheral blood lymphocytes resistant to Epstein-Barr virus immortalization manifest high natural killer (NK) type activity against NK-resistant target cells.

Epstein-Barr virus (EBV) readily immortalizes human peripheral blood lymphocytes (PBL) in vitro. We found recently that PBL from two EBV-seropositive healthy adults were exceptionally resistant to immortalization by EBV. In contrast to PBL from other EBV-seropositive donors sensitive to immortalization by EBV (S-PBL), the "resistant" PBL (R-PBL) respond to EBV infection with an early interleukin-2 (IL-2) synthesis and high interferon gamma (IFN gamma) production. In order to determine whether these differences in cytokine responses between R-PBL and S-PBL could be associated with a detectable difference in lymphocyte cytotoxicity, we compared the natural killer (NK) activity of R-PBL and S-PBL effectors by using both NK-sensitive (i.e. K562) and NK-resistant (i.e. Raji) targets. We found that, while effectors from EBV-infected R-PBL and S-PBL cultures exhibited comparable NK activity against the K562 targets, they differed remarkably in their cytolytic activity against Raji cells. At days 3 and 5 of culture, effectors from EBV-infected R-PBL showed a significantly higher lytic activity against Raji targets, whereas S-PBL did not. Culture of EBV-infected R-PBL and S-PBL effectors in the presence of recombinant IL-2 (rIL-2) for 5 days resulted in increases of their lytic activity against Raji cells, whereas pretreatment of these effectors with recombinant IFN gamma (rIFN gamma) was found to increase only R-PBL cytotoxicity. These results suggest that the resistance of R-PBL to EBV immortalization could be associated with a lymphokine-mediated early cellular cytotoxic response of the NK/LAK (lymphokine-activated killer cell) type against EBV-infected cells.

Adult↗
PubMed1990

"CORT-EX:" a program for quantitative analysis of brain SPECT data.

A program was developed to extract from brain SPECT data global as well as regional concentrations of a radiopharmaceutical while allowing for improved subjective evaluation of its distribution. This program was used to process the data obtained from 17 normal subjects, 20 min, 2 hr, and 4 hr after the injection of iodine-labeled iodoamphetamines. The mean absolute cortical uptake at these three time periods was 0.921 (+/- 0.185), 0.803 (+/- 0.107), and 0.748 (+/- 0.103) in arbitrary units (+/- s.d.), respectively. The regional distribution of the tracer became more uniform with time due to an uneven washout rate. The cerebellum was noted to have a very high variability in its uptake and a high washout rate, making it unsuitable as an internal standard for relative quantification. Finally, a repeat study was performed on 10 subjects. No significant difference could be demonstrated in the mean uptake of the group at 2 and 4 hr, however the difference observed in the 20 min uptake values was significant at the p = 0.05 level.

Adult↗
PubMed1989

Differential interleukin-2 and interferon-gamma production by human lymphocyte cultures exceptionally resistant to Epstein-Barr virus immortalization.

Epstein-Barr virus (EBV) readily immortalizes human peripheral blood lymphocytes (PBL) in vitro. However, during the past several years, we found that PBL from two exceptional EBV-seropositive healthy adult individuals were refractory to immortalization by EBV. We report here a study aimed at learning about the immunobiological features which differentiate these EBV-resistant (R) PBL from others which are susceptible (S) to EBV immortalization. Results of this investigation indicate that: (a) Following EBV infection, R-PBL produced significantly higher amounts of interferon gamma (IFN-gamma) than S-PBL. There were however no differences in regard to interferon alpha production between these two types (R and S) of EBV-infected cultures. (b) R-PBL had a maximal interleukin-2 (IL-2) production by S-PBL occurred at least 48 hr later, i.e., at Day 7. (c) The percentage of non-B cells expressing the IL-2 receptor was also higher in EBV-infected R-PBL than S-PBL. (d) In contrast, expression of IL-2 receptors after EBV infection was higher on B cells from S-PBL than on B cells from R-PBL. Interestingly, no differences were noted in regard to IL-2 receptor expression between R-PBL and S-PBL treated with mitogens (i.e., phytohemagglutinin and pokeweed mitogen). (e) Finally, using anti-IL-2 and anti-IFN-gamma antibodies in EBV-infected R-PBL cultures, we were able to obtain EBV-induced immortalization of these cultures. Taken together, these results suggest that an early IL-2 synthesis and high IFN-gamma production by EBV-infected PBL play an important role against lymphocyte immortalization by EBV.

Antigen-Antibody Reactions↗
PubMed1989

Hydrophilic polyurethane versus autologous femoral vein as substitutes in the femoral arteries of dogs: quantification of platelets and fibrin deposits.

Hydrophilic, microporous polyurethane vascular prostheses displayed good mechanical characteristics and the behaviour in vitro was excellent. The in-vivo results were, however, disappointing. To obtain a better understanding of the phenomena involved in the acute and early thrombosis, we implanted the polyurethane graft in the canine left femoral artery and an autologous femoral vein in the right for 4 and 24 h. At 4 h, one polyurethane graft was totally occluded and the other two were close to complete occlusion; at 24 h, none was patent. On the other hand, all autologous veins were patent. The thrombotic matrix incorporating both platelets and fibrinogen, quantified by labelling, was anchored along the anastomotic lines. This study confirms that polyurethane occlusion is initiated by hyperplastic reaction, but does not explain why.

Animals↗
PubMed1989

[The influence of previous infections on the development of experimental swine pleuropneumonia in specific pathogen free pigs].

This study was designed to determine in six-week old specific pathogen free pigs, the effect of previous experimental exposure to Mycoplasma hyopneumoniae and transmissible gastroenteritis virus on a challenge infection with Actinobacillus pleuropneumoniae. Pigs exposed simultaneously to M. hyopneumoniae and transmissible gastroenteritis virus appeared more resistant to challenge (one week later) with A. pleuropneumoniae. Four pigs out of a group of ten died following the challenge infection, compared to all ten pigs in the control group not submitted to previous infections. Clinical signs and lesions were also less severe in the previously infected group than in the control group. Pigs submitted to a single previous infection with M. hyopneumoniae only appeared to be less resistant to the challenge infection than pigs submitted to the dual previous infection with M. hyopneumoniae and the transmissible gastroenteritis virus. A correlation was found between the resistance of pigs to the challenge infection and their serum gammaglobulin levels.

Actinobacillus Infections↗
PubMed1989

Comparison of processed bovine internal mammary arteries and autologous veins as arterial femoral substitutes in dogs: blood compatibility and pathological characteristics.

This study was undertaken to compare the chemically processed internal mammary artery (BIMA) and the autologous femoral vein as arterial grafts. The BIMA prosthesis was implanted as a left femoral artery bypass and the femoral vein as a right femoral artery bypass graft in 27 dogs. In groups of three dogs the grafts were implanted for predetermined durations: 4, 24 and 48 hours (short term), 1, 2 and 4 weeks (medium term) and 3, 6 and 9 months (long term). All autologous veins were patent when the dogs were killed. The patency rates of the BIMA grafts were 100% in the short-term group, 67% in the medium-term group and 29% in the long-term group. The deposition of labelled fibrinogen and platelets on flow surfaces, the structural preservation of the wall of the BIMA prosthesis and accumulation of thrombi during the period of implantation were studied.

Animals↗
PubMed1988

Tac expression induced by Epstein-Barr virus is restricted on non-transformable B lymphocytes.

During the course of a comparative study dealing with the immortalization of lymphocytes from a large number of normal healthy donors, we found that B cells of two of these individuals could not be immortalized by Epstein-Barr virus (EBV) under the standard conditions. The expression of the Tac antigen on the membrane of EBV-infected B cells from these two donors was compared with that of B cells from EBV immortalization-susceptible ones. The method used was two-colour immunofluorescence cytofluorometer analysis. We found that the Tac antigen expression was significantly and repeatedly reduced in the case of the two immortalization-resistant donors. This difference might be related to a genetic control of the resistance to EBV-immortalization.

B-Lymphocytes↗
PubMed1987

Quantitative gallium 67 lung scan to assess the inflammatory activity in the pneumoconioses.

Gallium 67 lung scan has recently become increasingly used to evaluate the biological activity of alveolitis of interstitial lung diseases and to stage the disease process. In order to have a more precise and objective indicator of the inflammatory activity in the lung, we and others have developed computer-based quantitative techniques to process the 67Ga scan. In this report, we compare the results of three such computer-based methods of analysis of the scans of 38 normal humans and 60 patients suspected to have pneumoconiosis. Results of previous investigations on the mechanisms of 67Ga uptake in interstitial lung disease are reviewed. These data strengthen the view that quantitative 67Ga lung scan has become a standard technique to assess inflammatory activity in the interstitial lung diseases and that computer-based method of analysis of the scan provides an index of inflammatory activity of the lung disease that correlates with lung lavage and biopsy indices of inflammation in the lung tissue.

Asbestosis↗
PubMed1987

Clinical and sleep laboratory study of narcoleptic symptoms in multiple sclerosis.

Seventy white patients with a diagnosis of MS and typed for their HLA-A, B, C, and DR were studied. A clinical interview and a questionnaire were used to evaluate the presence of narcoleptic symptoms. The prevalence of sleep attacks, cataplexy, and sleep paralysis was significantly elevated among these patients. However, no difference was seen between DR2 and non-DR2 subjects with regard to the incidence of narcoleptic symptoms. Nine DR2 patients complaining of both sleep attacks and cataplexy were studied in the sleep laboratory for five consecutive naps, but no polygraphic evidence of narcolepsy was found.

Adult↗
PubMed1986

Hindgut dysgenesis as a cause of constipation with delayed colonic transit.

In a patient complaining of constipation since birth, delayed transit time in the ascending colon was related to a congenital malformation of the hindgut, different from Hirschsprung's disease. This was associated with absence of the left lobe of the liver. There was no propagating electrical muscular activity in the distal bowel.

Adult↗
PubMed1986

Gallium-67 uptake in the lung of asbestos exposed sheep: early association with enhanced macrophage-derived fibronectin accumulation.

To evaluate the time course and mechanisms of enhanced 67Ga lung uptake in asbestosis, we exposed two groups of sheep every 2 wk to either 100 ml saline (controls) or 100 mg UICC chrysotile fibers in 100 ml saline. The sheep were evaluated periodically by pulmonary function tests (PFT), thoracic radiograph (TR), 67Ga lung scan bronchoalveolar lavage (BAL), and transbronchial lung biopsy (TLB). By month 24 of the study, 9/15 exposed sheep had developed the initial alveolitis and had significant changes in PFT, TR, and TLB. The other six exposed sheep differed from controls only by a 75% increase in BAL fibronectin until month 30, where significant changes in albumin occurred and 67Ga scan score increased. The nine sheep with alveolitis had significant sustained increases in 67Ga scan and BAL levels from month 6, associated with a 150% increase in BAL fibronectin and other parameters of disease activity changed from month 18 to 30. We concluded that in the sheep model of asbestosis, significant changes in 67Ga scan, 67Ga BAL counts, and excessive elevation of BAL fibronectin preceded other parameters of disease activity. The data suggest that excessively activated macrophages are primarily responsible for the early 67Ga lung uptake.

Animals↗
PubMed1986

[Diagnosis of inflammatory sacroiliitis. Comparison of complementary examinations].

In order to test the sensitivity of different techniques in the diagnosis of sacroiliitis, we have made a prospective and non-controlled study of 22 patients using standard radiography of the sacroiliac joint; conventional tomography and axial scintigraphy (calculation of an ISI sacroiliac index). The normal upper limit of the sacroiliac index (1.42) was studied in parallel, using a group of 63 control subjects. Correlation between the radiological examinations was average, but was very poor between radiology and scintigraphy. Conventional tomography and calculation of the sacroiliac index were of equal value diagnostically. Clear images of juxta-articular geodes were seen during scanning, but were not taken into account in the diagnosis. They may represent the onset of larger erosions and need to be verified.

Adolescent↗