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Biomedical subjects

G Gagnon

Publications and source records attributed to G Gagnon.

At least 37 records · Page 2Linked to original sources
PubMed1987

Clinical results after 12 months from a study of the incidence and progression of dental caries in relation to consumption of chewing-gum containing xylitol in school preventive programs.

This study was designed to evaluate the effect of chewing-gum containing xylitol on the incidence and the progression of dental caries. A sample of 433 children, aged 8 and 9 years, of low socio-economic status and high caries rate, was divided into two experimental groups (15% or 65% xylitol chewing-gum distributed three times a day at school) and one control group (without chewing-gum). The three groups were exposed to the same basic preventive program. Children who chewed gum had a significantly smaller DMF(S) increment over a 12-month period than did the control group. The former had increments of 1.58 surfaces, compared with 3.28 for the latter. No statistically significant difference, however, was demonstrated between the two experimental groups. The net progression of decay (progressions-reversals) showed a significant difference between the two experimental groups and the control group. In addition, 65% xylitol chewing-gum produced better results than did that containing 15% xylitol, suggesting a dose-response relationship. Chewing xylitol gum had a beneficial effect on the caries process for all types of tooth surfaces, but chewing gum with a higher xylitol content had an additional positive effect on buccolingual surfaces. A questionnaire asking the participants about stomach pain indicated that there was no difference between the experimental and control groups. The feasibility of such a preventive measure has been demonstrated by the excellent level of participation of both children and teachers. This activity could easily be integrated into existing preventive public health programs.

Chewing Gum↗
PubMed1985

Cloning of hybridomas by a single-cell transfer technique.

A method for cloning hybridomas is described which involves transfer of single cells with a capillary tubing connected to a suction apparatus. This method enables the efficient recovery of antibody-producing clones of differing abundances from the parent hybridoma cultures. The 4 cell lines submitted to this cloning procedure produced a 100% yield of positive wells upon recloning by the same method.

Animals↗
PubMed1985

Isolated late asthmatic reaction due to nickel sulphate without antibodies to nickel.

A worker with occupational exposure to nickel developed asthma a few months after starting work. Skin prick tests to nickel sulphate were negative. Inhalation challenge with nickel sulphate, at a concentration of 10 mg/ml for 30 min induced a late asthmatic reaction, starting 3 hr after the end of exposure leading to severe nocturnal attack. Tests for antibodies with nickel reactivity were negative.

Adult↗
PubMed1985

Slope of the dose-response curve to inhaled histamine and methacholine and PC20 in subjects with symptoms of airway hyperexcitability and in normal subjects.

Slopes of the dose-response curves to inhaled histamine or methacholine and PC20 were compared in 14 subjects with symptoms of bronchial hyperexcitability and in 10 normal subjects. Slopes were obtained by analyzing curves with 3 to 6 points by the least squares method. Only curves with satisfactory correlation coefficients corresponding to p values less than 0.05 were kept for analysis. Twelve of the 14 subjects with symptoms of bronchial hyperexcitability and 1 of the 10 normal subjects had slopes greater than 20 (percent change in FEV1/log histamine or methacholine concentration) (chi-square = 13.5, p less than 0.001). Eleven of the 14 subjects with symptoms of bronchial hyperexcitability and 1 of the 10 normal subjects had PC20 results less than or equal to 16 mg/ml (chi-square = 11.0, p less than 0.001). It is concluded that, using the method described in our study, slopes of the dose-response curve to inhaled histamine or methacholine are different in subjects with and without symptoms of bronchial hyperexcitability.

Adult↗
PubMed1983

Improving appointment-keeping by patients new to a hospital medical clinic with telephone or mailed reminders.

A randomized trial of telephone and mailed reminders was conducted to assess their effect in reducing the rate of failure to keep appointments among patients new to a general medical clinic. Only 10% of the patients who received a telephone call and 12% of those who received a letter failed to keep their appointments compared with 20% of the control group (p less than 0.05). The most common reason given for failure to keep the appointment was lack of awareness of the appointment. Thus, telephone or mailed reminders can lower the rate of failure to keep appointments and result in greater satisfaction by patients and health care personnel.

Appointments and Schedules↗
PubMed1980

Sexual dimorphism in body composition changes during the pubertal period: as shown by French-Canadian children.

Size and velocity growth curves of stature to represent skeletal growth, lean arm circumference to represent muscle growth, and the sum of three skinfolds to represent fat tissue changes, are presented for a longitudinal study of Montreal school-age chidren. Both a chronological age scale, and one relative to the individual ages of peak growth velocity in stature, are used. Intercorrelations between the various components are tabulated for age groups based on the two scales. The three skinfolds are also analyzed separately. The results show that such simple anthropometric measures can be usefully taken to represent the growth of different body components. Longitudinal analysis reveals that, whereas the relationship of muscular to statural growth in boys is purely maturational, it is not so for girls, and that the different skinfolds show complex sexual differences in growth during the pubertal period.

Adipose Tissue↗
PubMed1980

Studies on the mechanism of action of glucagon in strips of rabbit renal artery.

1 The vasodilator effects of glucagon and adenosine cyclic 3',5'-monophosphate (cyclic AMP) were evaluated in strips of rabbit renal artery contracted with noradrenaline (NA) in the absence and presence of phosphodiesterase inhibitors or calcium (Ca(2+)) antagonists.2 The vascular relaxant effect of glucagon was markedly potentiated by various concentrations of four different phosphodiesterase inhibitors (papaverine, theophylline, 3-isobutyl-l-methylxanthine (IBMX) and indomethacin), while that of cyclic AMP was potentiated by only two of them (papaverine and indomethacin) and inhibited by the others (theophylline and IBMX).3 Amongst the four phosphodiesterase inhibitors, IBMX (10 mug/ml) was found to produce the largest potentiation (e.g. the sensitivity increased by a factor of 10) of glucagon-induced vascular relaxations (ED(50) of glucagon in the presence of IBMX = 9.2 +/- 1.0 ng/ml).4 Ca(2+) antagonists such as verapamil and SKF 525A produced a dose-dependent inhibition of the vasodilator action of glucagon. Verapamil (2.5 mug/ml) also antagonized cyclic AMP-induced vascular relaxations.5 The vasodilator effect of verapamil was inhibited dose-dependently by raising the concentration of extracellular Ca(2+) from 0.05 to 0.2 g/l (or 1.25 to 5.0 mM) while those elicited by glucagon or cyclic AMP were not influenced, thus suggesting that the latter two drugs do not interfere with Ca(2+) influx.6 Disodium edetate (Na(2)EDTA, 210 to 840 mug/l) produced a dose-dependent vasodilator effect which was attributed to the facilitation of Ca(2+) extrusion from the smooth muscle cells and/or Ca(2+) binding to the cell membrane. The relaxation produced by Na(2)EDTA was significantly blocked by verapamil (10 mug/ml) or SKF 525A (10 mug/ml).7 The results were taken as an indication that glucagon produces at least a fraction of its vasodilator effect by promoting Ca(2+) extrusion from the vascular smooth muscle cells and/or Ca(2+) binding to or sequestration into intracellular sites, presumably via a cyclic AMP-dependent mechanism.

1-Methyl-3-isobutylxanthine↗
PubMed1980

Studies on the mechanism of action of various vasodilators.

1 The vascular relaxant effects of histamine, adenosine, isoprenaline nitroglycerine, papaverine and 3-isobutyl-l-methylxanthine (IBMX) were assessed individually, in strips of rabbit renal artery moderately contracted with noradrenaline (NA) in the absence or presence of phosphodiesterase inhibitors (papaverine and IBMX) or verapamil, a Ca(2+) antagonist.2 The vasodilator effect of histamine was potentiated by papaverine (6.1 x 10(-7) M) and IBMX (4.4 x 10(-5) M) but inhibited dose-dependently by verapamil (5.1 and 51.0 x 10(-7) M).3 Adenosine-induced vascular relaxations were greatly increased in the presence of papaverine (6.1 x 10(-7) M) but significantly reduced in the presence of IBMX (4.4 x 10(-5) M) or verapamil (5.1 and 51.0 x 10(-7) M).4 The vasodilatation produced by isoprenaline was increased in the presence of IBMX (4.4 x 10(-5) M) or papaverine (6.1 x 10(-7) M), but inhibited by verapamil (5.1 and 51.0 x 10(-7) M).5 The vascular relaxant effects of nitroglycerine and papaverine were inhibited in the presence of IBMX (4.4 x 10(-5) M) or verapamil (5.1 and 51.0 x 10(-7) M). Papaverine (6.1 x 10(-7) M) also antagonized nitroglycerine-induced vascular relaxation.6 The vasodilator effect of IBMX was greatly reduced in the presence of papaverine (6.1 x 10(-7) M) or verapamil (5.1 and 51.0 x 10(-7) M).7 The vascular relaxant effect of verapamil was reduced proportionally by raising the extracellular Ca(2+) concentration from 1.25 to 5.0 mM while those elicited by histamine, adenosine, isoprenaline, nitroglycerine, papaverine and IBMX were not modified by this procedure.8 These results were taken as an indication that several vasodilators (e.g. histamine, adenosine, isoprenaline, nitroglycerine, papaverine and IBMX), but not a Ca(2+) antagonist such as verapamil, produce a fraction of their vasodilator effects by promoting Ca(2+) extrusion from and/or Ca(2+) sequestration into the vascular smooth muscle cells, via a cyclic adenosine 3',5'-monophosphate-dependent mechanism.

1-Methyl-3-isobutylxanthine↗
PubMed1978

A new bioassay for glucagon.

1 The relaxant action of glucagon has been studied in strips of rabbit renal arteries partially contracted by a low concentration (1 ng/ml) of noradrenaline.2 The preparation was relaxed in a dose-dependent manner by concentrations of glucagon varying between 25 ng/ml and 420 ng/ml.3 The relaxant effect of glucagon (0.1 mug/ml approximately ED(60)) on this preparation was not affected by propranolol (5.0 mug/ml), cimetidine (10 mug/ml), diphenhydramine (10 mug/ml), indomethacin (5.0 mug/ml), phentolamine (1.2 mug/ml), atropine (10 mug/ml) and 8-Leu-AT(II) (1.0 mug/ml) but was slightly potentiated by Des-Arg(9) Leu-OMe(8)-Bk (25 mug/ml) and indomethacin (50 mug/ml).4 The dose-response curve to glucagon remained parallel in the presence of papaverine (2.5 mug/ml) but was shifted to the left by a factor of 2.5 to 2.8. Theophylline (250 mug/ml) also potentiated the vascular relaxation induced by glucagon.5 Insulin (10 mug/ml) did not influence the relaxant effect of glucagon.6 The removal of the N-terminal amino acid (His) of glucagon reduced by 89% the biological activity of this fragment on the vascular preparation. The removal of the C-terminal amino acids Met-27, Asn-28 and Thr-29 of glucagon resulted in a fragment which was inactive either as an agonist or as an antagonist when tested at concentrations as high as 925 ng/ml.7 It is concluded that the relaxation of partially contracted strips of rabbit renal arteries by glucagon constitutes a simple, sensitive, relatively specific and reliable bioassay which may be useful for the determination of glucagon in biological materials and for structure-activity relationship studies with this hormone.

Animals↗
PubMed1978

Stimulating actions of various prostaglandins and noradrenaline in strips of rabbit renal artery.

The myotropic effects of prostaglandins E1, E2, F2alpha, A1, and noradrenaline were evaluated in spirally cut strips of rabbit renal arteries suspended in a physiological salt solution maintained at 37 degrees C. The four prostaglandins as well as noradrenaline elicited contractions of the isolated rabbit renal artery. At concentrations higher than 1.0 X 10(-7) g ml-1 the contracting effect of prostaglandin E1 diminished. The vasoconstrictor actions of prostaglandins E2 and F2alpha were potentiated by cocaine and inhibited by phentolamine. On the other hand, phentolamine did not inhibit the vasoconstrictor effect of prostaglandins E2 and F2alpha on strips of rabbit renal arteries removed from rabbits pretreated with reserpine. These results were taken as an indication that part of the contractile effects of prostaglandins E2 and F2alpha on the isolated rabbit renal artery may be due to the release of noradrenaline from adrenergic nerve terminals.

Animals↗
PubMed1977

Elevation of prostaglandin and cyclic AMP levels by arachidonic acid in primary epithelial cell cultures of C3H mouse mammary tumors.

Arachidonic acid causes a sharp transient increase in cyclic AMP levels in primary epithelial cell cultures obtained from C3H mouse mammary tumors. The effect is evident within two minutes and is enhanced by theophylline or 3-isobutyl-1-methylxanthine. Maximum increase in cyclic AMP levels are observed with a dose of 100 mug/ml of arachidonic acid (AA). At higher dose levels the increase in cyclic AMP levels is reduced. Naproxen, an inhibitor of prostaglandin synthesis in this system markedly reduces the stimulation of cyclic AMP by arachidonic acid but it does not affect the increase in cyclic AMP levels observed after the addition of prostaglandin E's, epinephrine or cholera enterotoxin. Arachidonic acid, under the same conditions, also causes a significant elevation of PGE and PGF media levels which is slower and more sustained than the cAMP response. The data strongly suggest that a metabolic of arachidonic acid is responsible for the cyclic rise, however, it is not certain whether this is due to PGE2 or some other product.

Animals↗
PubMed1976

Prostaglandin biosynthesis and stimulation of cyclic AMP in primary monolayer cultures of epithelial cells from mouse mammary gland.

Cyclic AMP levels in primary monolayer cultures of epithelial cells prepared from mid-pregnant mice are stimulated by prostaglandin E1 and E2. Prostaglandin F1alpha and F2alpha have only a slight effect upon cyclic AMP levels. In the absence of phosphodiesterase inhibitors the rise in cyclic AMP produced by PGE1 is only transient and the levels return to normal within 30 minutes. High concentrations (16 mM) of theophylline are needed to prevent this decline, suggesting that the phosphodiesterase activity of epithelial cells in culture is high. However, theophylline alone produced only a small increase in basal cyclic AMP levels even over a 2-hour period indicating that basal cyclic AMP is turned over more slowly than cyclic AMP produced in response to stimulation with PGE1. Both PGE and PGF synthesis were monitored using radioimmunoassay procedures previously reported. The observed levels were found to decrease as cell density increased and were sensitive to the addition of agents such as collagen and naproxen.

Animals↗