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Biomedical subjects

M Bélisle

Publications and source records attributed to M Bélisle.

9 recordsLinked to original sources
PubMed1994

Acetylcholinesterase adaptation to voluntary wheel running is proportional to the volume of activity in fast, but not slow, rat hindlimb muscles.

Chronic enhancement of neuromuscular activity by forced exercise training programmes results in selective adaptation of the G4 acetylcholinesterase (AChE) molecular form in hindlimb fast muscles of the rat, with only minor and non-selective AChE changes in the soleus. In order to shed further light on the physiological significance of this G4 adaptation to training, we turned to a voluntary exercise model. The impact of 5 days and 4 weeks of voluntary wheel cage running on AChE molecular forms was examined in four hindlimb fast muscles and the slow-twitch soleus from two rat strains. Inbred Fisher and Sprague-Dawley rats, placed in live-in wheel cages, exercised spontaneously for distances which progressively increased up to an average of approximately 3 and 18 km/day, respectively, by the end of week 4. Fast muscles responded to this voluntary activity by massive G4 increases (up to 420%) with almost no changes in A12, so that by week 4 the tetramer became the main AChE component of these muscles. The additional G4 was composed primarily of amphiphilic molecules, suggesting a membrane-bound state. The G4 content of fast muscles was highly correlated with the distance covered by the rats during the 5 days before they were killed (r = 0.850-0.879, P < 0.001 in three muscles). The soleus muscle, in turn, responded to wheel cage activity by a marked selective reduction of its asymmetric forms--up to 45% for A12. This A12 decline, already maximal by day 5 of wheel cage running, showed no relationship with the distance covered.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1993

Increased insulin suppression of plasma free fatty acid concentration in exercise-trained rats.

The effect of exercise training on the insulin suppression of plasma free fatty acid (FFA) concentrations was studied in unanesthetized rats with the hyperinsulinemic-euglycemic clamp technique. Seven rats trained (TR) for 3 h/day by continuous swimming during 8 wk were compared with 6 untrained (UT) body weight-matched rats. Both TR and UT rats were submitted to an exercise swimming session 18 h before the clamp. A smaller mean diameter of adipocytes sampled from the epididymal fat depot was measured in TR animals. The total quantity of glucose infused to maintain euglycemia was 2.2 times higher in TR than in UT animals. No significant differences in plasma insulin concentrations were found between the two groups throughout the experiment. Insulin infusions resulted in a 60% decrease of plasma FFA in TR rats (mean value: from 0.46 to 0.18 mM) compared with 27% in UT animals (mean value: from 0.45 to 0.33 mM). The data indicate a greater ability of insulin to suppress plasma FFA levels with exercise training, which suggests an increased antilipolytic action of insulin in adipocytes under this condition.

Adipose Tissue↗
PubMed1987

Improving adherence to physical activity.

Two studies tested the efficacy of Marlatt and Gordon's relapse-prevention approach in increasing attendance during an exercise program (short-term adherence) and continuation of exercise activities for 12 weeks following termination of the formal program (longer term adherence). Participants in both studies were registrants in 10-week exercise groups (jogging, aerobic dance, and pre-ski training) sponsored by the Université de Montréal Sports Centre. The intervention, designed to increase awareness of obstacles to exercise and to develop appropriate techniques for coping with them, was delivered by group leaders within the context of the regular program. Results of both studies indicate a small but consistent superiority of adherence in the experimental condition compared to the control condition. The low cost of this intervention, however, makes even small gains cost effective. Possible methods for strengthening the treatment effect are discussed.

Adult↗
PubMed1982

Characterization of human placental neuraminidases. Stability, substrate specificity and molecular weight.

1. At least two components of neuraminidase can be distinguished on the basis of thermolability and sedimentability by using the artificial fluorogenic substrate 4-methylumbelliferyl N-acetyl-alpha-D-neuraminate. 2. In crude homogenates, thermodenaturation at 25 degrees C showed a biphasic curve corresponding to component A (half-life, 21 min) and B (half-life, 85 min). The two components were partially resolved by centrifugation. A being soluble and B sedimentable. Both had similar pH-activity curves (pH optimum, 4.4), Km values (A, 0.10 mM; B, 0.06 mM) and molecular weight as determined by radiation inactivation (A, 67000; B, 63000). 3. The soluble A form was still aggregated or bound to membranous debris since almost all neuraminidase activity was eluted near or at the void volume of a Sephacryl S-300 column. 4. Both soluble and sedimentable fractions of placenta hydrolysed the GD1A ganglioside and N-acetyl-neuraminyl-D-lactose linearly for 12 h but no fetuin hydrolysis was detected. 5. The neuraminidase activity with the artificial fluorogenic substrate was inhibited by N-acetylneuraminyl-D-lactose but not by the GD1A ganglioside. These preliminary results suggest that there exist two closely related enzymes hydrolysing both the artificial substrate and N-acetylneuraminyl-D-lactose and a third one hydrolysing the GD1A ganglioside exclusively.

Chromatography, Gel↗
PubMed1980

Studies on the sialidoses: properties of human leucocyte neuraminidases.

At least two components of neuraminidase (acylneuraminyl hydrolase, EC 3.2.1.18) can be distinguished in human leucocytes on the basis of pH optimum, thermolability at 30 degrees C and the effect of the detergent octyl-beta-D-glucoside. With 4-methylumbelliferyl-alpha-D-N-acetylneuraminate as substrate, the A component has a pH optimum of 5.0, is labile at 30 degrees C and is unaffected by 0.2 M octyl-beta-glucoside. The B component has a pH optimum of 4.0-4.2, is stable at 30 degrees C but loses most of its activity in the presence of 0.2 M octyl-beta-glucoside. Both A and B components are membrane-bound but only the A component is solubilized by octyl-beta-glucoside in an active form. Molecular weights of neuraminidases by gamma-ray radiation inactivation (a method that does not require solubilization of the enzyme) were found to be 240 000 +/- 19 000 for the B component, 203 000 +/- 17 000 for the A component and 238 000 +/- 8000 for the octyl-beta-glucoside-solubilized A component. Gel filtration of soluble A component on Sephacryl S-300, in the presence of octyl-beta-glucoside, showed a single peak of activity eluted at or near the void volume suggesting that the enzyme is still in an aggregated form. Profound deficiency of neuraminidase activity was found for both A and B components in leucocytes of patients affected with sialidoses type 1 and 2 (less than 15% normal) and intermediate activity in obligate heterozygotes. These results suggest that the A and B components of leucocyte neuraminidase are closely related from the genetic point of view and that rapid diagnosis of sialidoses can be done by fluorimetric assay of neuraminidase in leucocytes.

Adolescent↗
PubMed1979

Neuraminidase activity in the mucolipidoses (types I, II and III) and the cherry-red spot myoclonus syndrome.

Two neuraminidase (EC 3.2.1.18) comonents, A and B, were distinguished in cultured skin fibroblasts on the basis of thermolability at 37 degrees C. The more labile component (A) t1/2 = 4.7--5.3 min at 37 degrees C, comprises 66--90% of total neuraminidase activity when determined using sodium (4-methylumbelliferyl-alpha-D-N-acetylneuraminate) (MU-alpha-N) as substrate. Activity was assayed at 0 degrees C for 18 h instead of 37 degrees C to fully determine both thermolabile and thermostable components. Diminished activity was noted in cultured fibroblasts from mucolipidoses I, II and III (MLI, MLII, MLIII) and the cherry-red spot myoclonus syndrome (CRSM) patients when assayed at both 0 and 37 degrees C with either MU-alpha-N or each of a series alpha (2 leads to 3)- and alpha (2 leads to 6)-linked N-acetylneuraminyloligosaccharides. Increased sensitivity and rapidity of analyses were achieved using MJ-alpha-N as substrate in determining neuraminidase activity. Results from two obligate heterozygote MLI cell lines (14.5 and 8.0% of control activity) indicate that the MU-alpha-N substrate could be useful for heterozygote detection.

Cells, Cultured↗
PubMed1979

Neuraminidase in cultured fibroblasts and leucocytes of homozygotes and heterozygotes for the mucolipidosis II gene (I-cell disease).

The significance of neuraminidase deficiency reported to be the primary defect in mucolipidosis II has been evaluated by determination of this enzyme activity in cultured fibroblasts, culture medium, and leucocytes from homozygote and heterozygous carriers of the disease. A new and sensitive fluorometric assay of neuraminidase was used with sodium (4-methylumbeliferyl-alpha-D-N-acetylneuraminate) as substrate. We report: 1) nearly total deficiency of neuraminidase in mucolipidosis fibroblasts, 2) partial deficiency of this enzyme in leucocytes of one patient, 3) this decreased activity ceases to exist following Triton X-100 treatment, and 4) intermediary mean neuraminidase activity in fibroblasts and leucocytes from obligate heterozygotes. Although these results would be consistent with the suggestion that neuraminidase deficiency is the primary defect in this disease, evidence from the work of other authors suggests that the enzyme deficiency results from a secondary effect of the mucolipidosis II mutation.

Cells, Cultured↗