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Biomedical subjects

M Nadeau

Publications and source records attributed to M Nadeau.

At least 19 recordsLinked to original sources
PubMed1996

Priming of human peripheral blood mononuclear cells with lipopolysaccharides for enhanced arachidonic acid release and leukotriene synthesis.

In a previous study, we have shown that the ability of lipopolysaccharides (LPS) to prime isolated neutrophils for enhanced leukotriene B4 (LTB4) synthesis was dependent on the presence of plasma and involved the CD 14 antigen. In the present study, we have investigated the priming of human peripheral blood mononuclear cells (PBMC) with LPS for the subsequent release and metabolism of arachidonic acid. When PBMC were incubated with LPS for up to 2 h or when freshly isolated PBMC were stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP) or with LPS alone, little or no synthesis of 5-lipoxygenase products nor arachidonic acid liberation were detected. However, the preincubation of PBMC with LPS for as little as 5 min primed cells for the subsequent synthesis of LTB4 upon stimulation with fMLP. Maximal priming was observed following a 15-min preincubation period and the priming effect was transient as cells preincubated with LPS for 90 min or more were no longer primed for leukotriene synthesis. Monocytes were found to be responsible for the enhanced response to fMLP since purified lymphocytes did not produce LTB4 nor LTC4 in contrast to monocyte-enriched suspensions. The priming for leukotriene synthesis coincided with an increased capacity for the release of free arachidonic acid as measured by mass spectrometry; LPS-primed cells released 8-15 times more arachidonic acid than unprimed cells within 1 min of stimulation with fMLP. Priming was observed with as little as 0.001-0.01 microg LPS/mL when cells were incubated in the presence of 10% autologous plasma. Interestingly, in the absence of plasma, priming was only observed at LPS concentrations of 0.1 microg/mL or greater. Pretreatment of cells with anti-CD14 antibodies significantly decreased the priming effect observed with 0.01 microg/mL LPS but did not affect priming with 1 microg/mL LPS. These results indicate that the priming of human PBMC with LPS for the subsequent synthesis of arachidonic acid metabolites via the 5-lipoxygenase pathway is dependent on plasma and CD14 at lower concentrations of LPS (0.001-0.01 microg/mL) but not at LPS concentrations of 0.1 microg/mL or greater.

Arachidonate 5-Lipoxygenase↗
PubMed1995

Hyperhomocysteinemia and traditional cardiovascular disease risk factors in end-stage renal disease patients on dialysis: a case-control study.

Hyperhomocysteinemia occurs frequently in end-stage renal disease (ESRD), but its prevalence in comparison with traditional cardiovascular disease (CVD) risk factors is unknown. Fasting total plasma homocysteine, potential determinants of plasma homocysteine (i.e., plasma B-vitamins and serine), total and HDL cholesterol, glucose, and creatinine, were determined in 24 ESRD patients on dialysis, and 24 age, gender, and race matched Framingham Offspring Study controls with normal renal function. Presence of clinical CVD and CVD risk factors was established by standardized methods. Mean plasma homocysteine was markedly higher in the ESRD patients versus controls (22.7 vs. 9.5 mumol/l). ESRD patients were 33 times more likely than controls to have hyperhomocysteinemia (> 15.8 mumol/l) (95% confidence interval, 5.7-189.6). Hyperhomocysteinemia persisted in the ESRD patients despite normal to supernormal B-vitamin status. Plasma serine levels below the tenth percentile of the control distribution were found in 75% of the ESRD patients. Oral serine supplementation caused a 37% increase in mean plasma serine, but had no effect on plasma homocysteine in four ESRD patients with supernormal plasma folate, low plasma serine, and hyperhomocysteinemia. Given its unusually high prevalence, improved management of hyperhomocysteinemia might reduce CVD sequelae in ESRD.

Adult↗
PubMed1994

High dose ascorbate supplementation fails to affect plasma homocyst(e)ine levels in patients with coronary heart disease.

Pharmacologic doses of folate, in the absence of clinical folate deficiency, can reduce plasma levels of the putatively atherothrombotic amino acid, homocysteine (H(e)). Data suggesting that H(e) may accumulate in experimental scurvy prompted us to explore the efficacy of high dose ascorbate supplementation as a H(e)-lowering treatment, in the absence of clinical ascorbate deficiency. A randomized, placebo-controlled trial of 12 weeks of high dose (4.5 g/day) ascorbate supplementation was completed by 44 patients with established coronary heart disease. No significant change in mean fasting total plasma H(e) levels was demonstrable despite a marked increase in mean fasting plasma ascorbate levels amongst those patients randomized to active treatment. Ascorbate supplementation to prevent the development of fasting hyperhomocysteinemia may only be relevant at scorbutic levels of plasma ascorbate.

Ascorbic Acid↗
PubMed1994

Severe folate deficiency causes secondary depletion of choline and phosphocholine in rat liver.

It has previously been shown that choline deficiency causes depletion of hepatic folate concentration in rats. Two separate experiments were undertaken to investigate the converse phenomenon: whether folate deficiency would lead to depletion of hepatic choline. In Experiment 1, severe folate deficiency was induced in rats by feeding an amino acid-defined diet containing (per kg diet) 1.4 g choline, 0 mg folate and 10 g succinylsulfathiazole. Control rats were fed the same diet containing 8 mg folate/kg. After 4 wk, plasma and hepatic folate concentrations were significantly depleted in the severely folate-deficient rats compared with controls (P < 0.001), and hepatic choline and phosphocholine concentrations were 65 and 80% lower, respectively (P < 0.001). In Experiment 2, moderate folate deficiency was induced in rats by feeding the same diet as described above, but with the succinylsulfathiazole omitted. After 24 wk, significant systemic folate deficiency was present in the moderately folate-deficient rats compared with controls (P < 0.001). A modest reduction (36%, P = 0.087) in hepatic choline concentration was observed in the moderately folate-deficient rats compared with controls. No significant differences in hepatic phosphocholine concentrations were detected between the two groups. These results indicate that severe folate deficiency causes secondary hepatic choline deficiency in rats.

Animals↗
PubMed1994

BIRM 270: a novel inhibitor of arachidonate release that blocks leukotriene B4 and platelet-activating factor biosynthesis in human neutrophils.

(S)-N-[2-Cyclohexyl-1-(2-pyridinyl)ethyl]-5-methyl-2-benzoxazolamine+ ++ (BIRM 270) was identified as a potent and enantiomerically selective inhibitor of calcium ionophore A23187-stimulated leukotriene B4 biosynthesis in human neutrophils. The (S)- and (R)-enantiomers exhibited IC50 values of 1 nM and 40 nM, respectively. BIRM 270 did not inhibit 5-lipoxygenase activity in a cell-free assay. In addition, the compound did not interfere with the conversion of exogenous 5-lipoxygenase substrate (15S)-hydroperoxyeicosatetraenoic acid to (5S, 15S)-dihydroxyeicosatetraenoic acid in intact, ionophore-stimulated neutrophils. Under the same experimental conditions, BIRM 270 inhibited the production of 5-lipoxygenase products from endogenous substrate, suggesting that the compound affected arachidonate availability rather than metabolism. Consistent with this concept, the inhibition of leukotriene B4 biosynthesis by BIRM 270 was overcome by the addition of exogenous arachidonic acid to the leukocyte preparation. Direct measurement of free arachidonate by gas chromatography-mass spectrometry confirmed that BIRM 270 inhibited arachidonate release from ionophore-stimulated neutrophils. The compound did not affect arachidonate reacylation. The blockage of arachidonate release coincided with inhibition of leukotriene B4 biosynthesis in these cells. BIRM 270 also inhibited ionophore-stimulated platelet-activating factor biosynthesis by human neutrophils. Although these results suggest that BIRM 270 inhibited phospholipase A2-mediated deacylation of membrane phospholipids, the compound did not directly inhibit the high molecular weight, cytosolic phospholipase A2 derived from human neutrophils or U937 cells. Thus, suppression of arachidonate mobilization by BIRM 270 may be due to indirect inhibition of intracellular phospholipase A2 or to inhibition of another acylhydrolase activity.

Arachidonic Acid↗
PubMed1992

Serological characterization of Actinobacillus pleuropneumoniae strains isolated from pigs in Quebec.

A total of 3306 isolates of A. pleuropneumoniae originating from lung tissues of pigs that died of acute pleuropneumonia and 140 isolates recovered from tonsils or nasal cavities of apparently healthy pigs from chronically infected herds were serotyped. Various serotyping methods, such as slide agglutination, tube agglutination, ring precipitation, coagglutination, immunodiffusion, indirect hemagglutination and counterimmunoelectrophoresis either alone or in combination were used. The techniques used for serotyping continued to evolve during the last 10 years depending on the problem encountered in serotyping. Antisera prepared in rabbits against formalinized whole cell suspensions of reference strains of A. pleuropneumoniae of serotypes 1 to 12 were employed for serotyping. Serotype 1 was predominant ranging from 55 to 87% from year to year during the last 10 years with an average prevalence of 68%. Serotype 5 was second in prevalence ranging from 9 to 30% with a mean of 23%. Both subtypes of serotype 5 (5a and 5b) were present in Quebec. Serotypes 3, 6, 7, 8, 10 and 12 were isolated in small numbers together accounting for about 9%. Serotypes 4, 9 and 11 were not present. Cross-reactions were observed among isolates of serotypes 3, 6 and 8, and 1, 9 and 11 and were easily differentiated from each other by quantitation of type and group specific antigens by coagglutination and immunodiffusion tests. Serotypes 1, 5 and 7 were isolated most frequently from tonsils of pigs from chronically infected herds. Prevalence of different serotypes in different countries has also been reviewed.

Actinobacillus Infections↗
PubMed1990

Obesity, hypertension, hyperuricemia and diabetes mellitus among the Cree and Inuit of northern Québec.

In the last thirty years, sociocultural and political changes have profoundly affected the way of life of the Cree and Inuit of Northern Québec. Their health status profile has also changed. This study presents the main results of a health survey performed among the Cree and Inuit in 1982-1984 by a multidisciplinary team. Obesity, arterial hypertension, hyperuricemia and diabetes mellitus while almost unknown in the past, have now been added to the list of Cree and Inuit health problems. Crees have the highest risk for obesity, hypertension and diabetes mellitus. Hyperuricemia for unknown reasons seems more prevalent among the Inuit. Our findings suggest that further in-depth studies of chronic conditions in these communities are needed.

Adolescent↗
PubMed1990

Prevalence of Streptococcus suis in four to eight week old clinically healthy piglets.

The study was undertaken to determine the prevalence, in the nasal cavities, of Streptococcus suis in four to eight week old clinically healthy piglets. Streptococci biochemically compatible with S. suis were isolated from 94% of piglets and 98% of farms. Of the 782 isolates submitted to serotyping, only 164 (21%) were included in the nine official serotypes. These 164 typable isolates originated from 121 (31%) of the 388 piglets and from 36 (73%) of the 49 farms included in the study. The most frequent serotypes found in piglets were, in decreasing order, 3, 4, 8 and 2. Serotype 1 was not detected in this survey. As many as 32% of piglets were found positive for two different serotypes and three different serotypes were found in 1%.

Animals↗
PubMed1989

Rapid detection of Streptococcus suis serotype 2 in weaned pigs.

A survey to detect Streptococcus suis serotype 2 in 1,716 weaned pigs was done in Quebec. Forty-nine sow herds were included in this survey: in 26 herds, S suis serotype 2 had been isolated during the preceding 12 months and in 23 herds (control), the organism had not been detected during a previous study. Swab specimens of the nasal cavity and tonsils of pigs were obtained for bacteriologic culture, and S suis serotype 2 was easily detected by the use of brain-heart infusion agar containing a Streptococcus-selective supplement and 5% goat antiserum raised against S suis serotype 2. After measurement of the diameter of the precipitation zone of 539 isolates, a slide agglutination test was performed to identify the S suis serotype 2 isolates. The mean precipitation zone diameter obtained for group S suis serotype 2 was larger (P less than 0.001) than that for the group designated as "others". With slide agglutination test results as reference and on the basis of discriminant analysis to stimulate detection of S suis serotype 2, 93.1% of all isolates were correctly classified, using the precipitation zone diameter as unique classification criterion. Relative specificity was 94.5% and relative sensitivity was 88.7%. Use of the precipitation zone diameter on a quantitative basis led to the proposal of a simple and reliable technique to screen swine herds for S suis serotype 2 in weaned pigs. Nasal and tonsillar swab specimens were obtained and analyzed concurrently for S suis serotype 2. The organism was found in both sites in only 20.4% of 103 carrier pigs.(ABSTRACT TRUNCATED AT 250 WORDS)

Agglutination Tests↗
PubMed1988

Isolation of Streptococcus suis from diseased pigs in Canada.

A total of 260 isolates of streptococci collected over a 9-year period from diseased pigs submitted for necropsy were studied. Seventy-seven percent of isolates were identified as S. suis and 32% of S. suis isolates were retrieved in pure culture. S. suis was found more frequently in lungs and was often isolated in conjunction with Actinobacillus pleuropneumoniae, Pasteurella multocida, Escherichia coli and other microorganisms. A total of 151 (76%) of S. suis isolates could be serotyped within the 9 recognized serotypes. Serotype 2 was the most prevalent with 33%, followed by serotypes 3, 5 and 7. All isolates were sensitive to ampicillin, penicillin, cephradine, chloramphenicol and trimethoprim-sulfamethoxazole. Resistance to streptomycin, neomycin and tetracycline appeared to be very high.

Animals↗
PubMed1988

Minimal inhibitory concentrations of antimicrobial agents against Actinobacillus pleuropneumoniae.

Forty-five isolates of Actinobacillus pleuropneumoniae were tested for susceptibility to 12 antimicrobial agents using a microdilution method for the minimal inhibitory concentration determinations. These results confirmed the high prevalence of A. pleuropneumoniae strains resistant to antibiotics as reported earlier using the disc diffusion method (Kirby-Bauer method). While 36% of the isolates were resistant to the penicillins, 47% were resistant to chloramphenicol and 68% were resistant to tetracycline. Minimal inhibitory concentrations for the resistant isolates were approximately 32 times higher than those for the susceptible isolates to the above antibacterial agents. The isolates were in general weakly susceptible or resistant to spectinomycin, lincomycin, tiamulin and spiramycin whereas most of them were susceptible to gentamicin, trimethoprim and erythromycin. The susceptibility pattern was similar throughout the 1980 to 1984 period. The 14 serotype 5 isolates were more resistant to tetracycline but less resistant to chloramphenicol and the penicillins than the 28 serotype 1 isolates.

Actinobacillus↗
PubMed1984

Liver lysosomal enzymes in rats during long-term dietary restriction. 1. Changes during the developmental period of life.

The specific activities of the lysosomal enzymes acid phosphatase, beta-galactosidase, arylsulphatase B and cathepsin D were determined in homogenates of livers of rats fed ad libitum and of rats subjected to long-term dietary restriction (10%, 30% and 50% of diet consumed by the ad libitum group). Dietary restriction began soon after weaning and animals were sacrificed 3, 9, 15 and 24 weeks later. Dietary restriction influenced all four enzymes but the changes depended on the enzyme as well as on the degree and duration of the dietary restriction. Total activity of acid phosphatase increased significantly at 3 weeks of restriction but only in the 50% group. The activity returned to normal values at 9 weeks. Arylsulphatase B increased in all experimental groups with a more pronounced change observed at 3 weeks and in the more severely restricted rats. No notable change in the activities of beta-galactosidase and cathepsin D activities was observed. Changes in the liver ultrastructure paralleled the biochemical changes seen at 3 weeks. Numerous autophagic vacuoles and dense bodies resembling age pigments were formed in the hepatocytic cytoplasm. Mitochondrial enlargement, increased matrical density and rough endoplasmic reticulum fragmentation were also noted. Few of these changes were observed at 9 weeks, and the hepatocyte's morphology was virtually normal at 15 and 24 weeks. The marked changes seen at 3 weeks may be a manifestation of the body's adaptive processes to the nutritional stress.

Acid Phosphatase↗
PubMed1984

Studies on leukotriene B4 omega-oxidation in human leukocytes.

The kinetics of the transformation of arachidonic acid into 5-lipoxygenase products in human blood leukocytes stimulated with the ionophore A23187 (2 microM) was studied using high performance liquid chromatography. The levels of 5-hydroxyeicosatetraenoic acid (5-HETE), leukotriene B4 (LTB4), delta 6-trans-LTB4, and leukotriene C4 (LTC4) were maximum after 4-5 min of incubation; at longer incubation times, the levels of delta 6-trans-LTB4 and LTC4 remained unchanged, whereas those of 5-HETE and LTB4 decreased rapidly. The disappearance of LTB4 was concomitant with the formation of omega-hydroxy-LTB4 and omega-carboxy-LTB4. When synthetic LTB4 was added to a suspension of unstimulated human leukocytes, a similar pattern of omega-oxidation products was observed. This omega-oxidation process showed some specificity for LTB4, as indicated by the slower reaction of three stereoisomers of LTB4. Studies with subpopulations of human blood cells and human plasma clearly indicated that the polymorphonuclear leukocytes were the main source of enzymic activity for the omega-oxidation of LTB4. The liquid chromatographic behaviors of natural omega-hydroxy-LTB4 and omega-carboxy-LTB4 were studied in two systems.

Calcimycin↗
PubMed1983

The bicycle ergometer for muscle power testing.

The force-velocity relationship implies that the faster a contracting muscle is permitted to shorten, the weaker it becomes or the slower a contracting muscle is permitted to shorten, the stronger it becomes until it reaches maximal isometric tension. The relationship is hyperbolic for a denervated muscle but is inverse and linear for functionally innervated muscle groups. When the force of contraction is multiplied by the velocity of contraction, a power production curve is obtained. The purposes of the study were to examine the force-velocity relationship on a standard bicycle ergometer, to deduce a power-velocity curve, to compare the results of young men and women and to see if the measures were reproducible. Fifty-eight young men and women volunteered for the study. Testing consisted of pedalling as quickly as possible for five seconds at resistance settings from 2 to 7-kg. In order to evaluate the reproducibility of the scores, retesting was done one hour later. It was shown that the relationship between the resistance settings and the number of revolutions completed by the male and female subjects was inverse and linear. The higher the resistance setting was, the larger was the difference in the scores of the young men and women. When a power curve was derived for each group, a peak power was only identified in the female subjects and this was encountered at a 5-kg resistance setting. The scores obtained at a resistance setting of 5 and 7 kg for female and male subjects respectively showed the best reproducibility. The bicycle ergometer may not be used as an alternative but as a complementary tool to an isokinetic dynamometer.

Exercise Test↗
PubMed1983

Iron status of French-Canadian children: a three year follow-up study.

Dietary iron intake and hematocrit, hemoglobin, serum iron, transferrin saturation and serum ferritin were studied longitudinally in 425 French-Canadian children from upper-middle class families at 3, 6, 9, 12, 15, 18, 24 and 36 months. At 3 to 9 months, the median iron intake exceeded the amount recommended (7 mg/d), at 12 to 36 months it was close to the amount recommended (8 mg). The proportion of anaemic children as diagnosed by low hematocrit and hemoglobin values did not exceed 5 percent except at three months of age. Transferrin saturation lower than 16 percent was detected in 12 percent of the children aged 12-18 months and 8 percent of those aged 24-36 months. Serum ferritin increased from 18 to 36 months of age; between 18 months and 3 years, the proportion of children with deficient serum ferritin (SF less than 10 ng/ml) and low iron reserves (SF 10-20 ng/ml) declined respectively from 29 to 2 percent and 55 to 26 percent. Thus, as the children grew older the iron intake still permitted the improvement of hematologic parameters of iron status in most subjects. The progressive increase of hematological values with age emphasizes the need for more specific standards for children of various ages.

Canada↗