Finite-size effects in continuum percolation.
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Journal Article↗
Biomedical subjects
A Tremblay
Publications and source records attributed to A Tremblay.
Fermi surface of the one-dimensional Hubbard model.
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Journal Article↗
Infinite set of crossover exponents of the XY model and f( alpha ) approach.
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Journal Article↗
Effects of dietary sodium restriction and potassium intake on cholesterol side-chain cleavage cytochrome P-450 and adrenodoxin mRNA levels.
We studied the effect of dietary sodium restriction (3 weeks) and high potassium intake (7 days) on transcriptional regulation of cytochrome P-450 cholesterol side chain cleavage (P-450 scc) and adrenodoxin (Adx) in rat adrenal glands. Northern blotting analysis demonstrated that both treatments markedly increased P-450scc and Adx mRNA levels in the zona glomerulosa (Z-G) and the zona fasciculata-reticularis (Z-F-R) compared with controls. The Z-G appears to be more sensitive to variations in electrolytes than does the Z-F-R. The low sodium diet provoked a 2.9-fold increase in P-450scc mRNA level in the Z-G compared to 2.1-fold in the Z-F-R, whereas Adx mRNA levels were enhanced 2.2- and 1.7-fold respectively in these two zones. Restriction of sodium intake provoked significant increases in plasma ACTH, aldosterone and corticosteroids compared with controls. In the Z-G of KCl-loaded rats, we found a 1.6-fold increase in P-450scc and a 2.1-fold increase in Adx mRNA levels, and in the Z-F-R there was a 1.7- and 1.8-fold enhancement. There were no changes in beta-actin mRNA levels upon dietary treatments. These results thus indicate that both sodium depletion and high potassium intake in rats could act at the transcriptional level of P-450scc and Adx, two components of a rate-limiting step in steroidogenesis leading to aldosterone production. In addition, the elevation in plasma ACTH level in response to Na+ restriction suggests a possible involvement of ACTH in the response of the adrenal glands to sodium depletion.
Actins↗
Familial lipoprotein lipase-activity deficiency: study of total body fatness and subcutaneous fat tissue distribution.
Total body fatness and subcutaneous fat tissue distribution were evaluated in 19 hyperchylomicronemic patients. Eleven were males, aged 10 to 57 years, and eight were females, aged 13 to 46 years. Familial lipoprotein-lipase-activity deficiency was diagnosed by the absence of lipoprotein-lipase activity in the plasma withdrawn ten and 20 minutes after intravenous injection of ten units of heparin per kilogram of body weight. The 19 patients had skin-fold measurements for evaluation of subcutaneous fat distribution. Fifteen also underwent body density measurements by underwater weighing. Percent body fat was calculated from body density. These anthropometric data were plotted against the regression curves of 1638 normal controls of both sexes (aged 10 to 54 years) for fat tissue weight, percent body fat, subcutaneous fat/total fat mass ratio and trunk/extremity skin-fold ratio. Impairments in the process of building fat tissue reserves could not be shown in the 19 hyperchylomicronemic patients, in spite of the absence of lipoprotein-lipase activity in their postheparin plasma. It is hypothesized that normal fat tissue mass in these patients could be due partly to de novo synthesis of fatty acids by adipocytes, hydrolysis of plasma triglycerides by hepatic lipase, and/or contribution of a specific fat-tissue lipase to the catabolism of plasma triglyceride-rich lipoproteins.
Adipose Tissue↗
Genetic effect in resting and exercise metabolic rates.
Two studies dealing with the contribution of the genotype in individual differences for resting metabolic rate (RMR), thermic effect of a 4.2 MJ carbohydrate meal (TEM), and energy cost of submaximal exercise are reported. The genetic effect for RMR and TEM was studied in 31 pairs of parent-child, 21 pairs of dizygotic (DZ) twins, and 37 pairs of monozygotic (MZ) twins, whereas the heritability of the energy cost of submaximal exercise was determined from data on 22 pairs of DZ twins and 31 pairs of MZ twins. The heritability of RMR reached approximately 40% of the variance remaining after adjustment for age, gender, and fat-free mass, (FFM). The genetic effect for TEM was equivalent to at least 40% to 50% of the variation in the energy expended during four hours after the meal test. A highly significant genetic effect was found for fasting plasma glucose (greater than .72), but the results for fasting plasma insulin are unclear. No significant genetic variance was seen for the glucose and insulin response to the carbohydrate meal. Finally, heritability for the metabolic rate during cycle exercise was high (greater than or equal to .46) at low power output, but it became nonsignificant when the energy cost reached about 6 times the RMR.
Adolescent↗
Computed tomography-measured trunk fat and plasma lipoprotein levels in nonobese women.
The associations between total adiposity, adipose tissue distribution measured by computed axial tomography (CAT), regional variation in fat cell size, and plasma lipoprotein levels were studied in a sample of 22 premenopausal healthy nonobese women aged 34.6 +/- 3.1 years (mean +/- SD) (% body fat, 27.8 +/- 5.8). In these nonobese women, no associations were found between total adiposity, adipose tissue distribution, and plasma triglyceride or very-low-density lipoprotein levels. However, total adiposity (as reflected by the body density-derived fat mass and by the adipose tissue volume measured by CAT), as well as the total trunk fat areas (measured at the abdominal and thoracic levels) were positively correlated with plasma low-density lipoprotein (LDL) cholesterol (.05 greater than P less than .01) and LDL apolipoprotein (apo) B (.05 greater than P less than .0005) levels. Because of these associations with LDL-C and LDL apo B levels, these body fatness indicators were negatively correlated with the HDL-cholesterol/LDL-cholesterol and HDL-apo A-I/LDL-apo B ratios. However, few significant associations were observed between the proportion of abdominal fat estimated by the waist/hip circumference ratio (WHR) and the lipoprotein-lipid profile (r = .45 and r = .44, P less than .05 with HDL triglyceride (TG) and LDL-apo B/LDL-cholesterol ratio, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
Abdomen↗
Assessment of adipose tissue distribution by computed axial tomography in obese women: association with body density and anthropometric measurements.
1. Abdominal obesity is associated with numerous metabolic complications. Deep abdominal adipose tissue is critical in the association between the level of abdominal obesity and cardiovascular risk factors. 2. Adipose tissue localization was assessed by computed axial tomography (CAT), and its association with body density and anthropometric measurements was investigated in a sample of fifty-one obese women (percentage body fat 45.9 (SD 5.6)) aged 35.7 (SD 5.5) years. The CAT scans were performed at three levels: lower chest, abdomen and mid-thigh. 3. The total adipose tissue volume computed from these three scans was highly correlated with body fat mass (r 0.94, P less than 0.001). The proportion of deep abdominal fat as measured by the ratio of deep: total adipose tissue areas at the abdominal level was not significantly correlated with body fat mass, but it was moderately associated with the ratio of waist: hip circumferences (WHR) (r 0.49, P less than 0.001). The absolute amount of deep abdominal fat was, however, significantly correlated with body fat mass (r 0.72, P less than 0.001). 4. The subscapular (r 0.38) and the abdominal (r 0.38) skinfolds were the only two skinfolds that were significantly associated with the proportion of deep abdominal fat (P less than 0.01). These skinfolds were also those which showed the highest correlation with the absolute amount of deep abdominal fat (r 0.65, P less than 0.001, for both skinfolds). 5. A three-site CAT-scan procedure can be used for the estimation of body fat mass in premenopausal obese women. 6. In these obese women, there was no significant association between total adiposity and the proportion of deep adipose tissue at the abdominal level. 7. In premenopausal obese women, the absolute amount of deep abdominal fat can be predicted from anthropometric measurements with more accuracy than the relative amount of deep abdominal fat.
Adipose Tissue↗
Impact of dietary fat content and fat oxidation on energy intake in humans.
Three studies were performed to assess the effects of a high-fat diet and exercise-induced changes in fat oxidation on energy intake in humans. In the first study the short-term effect of a high-fat diet on spontaneous energy intake was investigated. The second study evaluated the long-term effect of a high-fat diet on adiposity and the third study evaluated the effect of exercise-induced changes in fat oxidation on short-term regulation of energy intake when subjects were consuming a high-fat diet. The results of these studies indicate that a high-fat diet induces a short-term hyperphagia, a high percentage of lipids in the usual diet is associated with a higher adiposity, and exercise may attenuate or amplify the high-fat, diet-induced hyperphagia, depending on the magnitude of the exercise-induced increase in fat oxidation.
Adaptation, Physiological↗
Genetic and environmental influences on level of habitual physical activity and exercise participation.
In order to quantify genetic and environmental determinants of physical activity level, 1,610 subjects from 375 families who lived in the greater Québec city area completed a three-day activity record in 1978-1981. Level of habitual physical activity, which includes all the usual activities of life, and exercise participation, which includes activities requiring at least five times the resting oxygen consumption and more, were derived from this record. Familial correlations were computed in several pairs of biologic relatives and relatives by adoption after adjustment for the effects of age, sex, physical fitness, body mass index, and socioeconomic status, and analyzed with a model of path analysis that allows the separation of the transmissible effect between generations (t2) into genetic (h2) and cultural (b2) components of inheritance. The transmission was found to be statistically significant, but was accounted for by genetic factors for level of habitual physical activity (t2 = h2 = 29%), and by cultural factors for exercise participation (t2 = b2 = 12%). Although non-transmissible environmental factors remain the major determinants of these two physical activity indicators in this population, the results suggest that children can acquire from their parents certain customs regarding exercise behavior and that the propensity toward being spontaneously active could be partly influenced by the genotype.
Activities of Daily Living↗
The effect of prior exercise and caffeine ingestion on metabolic rate and hormones in young adult males.
The purposes of this study were to examine (a) the effects of acute exercise on metabolic rate 24 and 48 h postexercise and (b) the interaction of acute exercise and the thermic effect of caffeine on metabolic rate and hormonal changes during the late postexercise recovery period. In six young males, who were regular consumers of caffeine, resting energy expenditure was measured before and after caffeine (5 mg.kg-1) and placebo ingestion under the following conditions: (i) control (e.g., no prior exercise), (ii) 24 h postexercise, and (iii) 48 h postexercise. Blood samples were drawn for plasma glucose, insulin, glycerol, free fatty acids, catecholamines, and thyroid hormones (triiodothyronine, thyroxine, and free thyroxine). Results showed that acute exercise did not exert a detectable effect on resting metabolic rate in the late postexercise recovery period, that is, resting metabolic rate was similar among the conditions of control (1.17 +/- 0.12 kcal.min-1), 24 h postexercise (1.16 +/- 0.12), and 48 h postexercise (1.16 +/- 0.11). Caffeine ingestion increased metabolic rate (approximately 7%), but the thermic effect was not different among the experimental conditions. Plasma insulin and norepinephrine were lower after caffeine ingestion, whereas an increase in plasma free fatty acids was noted. Other hormones and substrates did not change significantly in response to caffeine ingestion. Furthermore, the hormonal and substrate milieu was not significantly different 24 and 48 h postexercise when compared with the control condition. Our results support the view that acute exercise does not alter the resting metabolic rate in the late postexercise recovery period.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Role of deep abdominal fat in the association between regional adipose tissue distribution and glucose tolerance in obese women.
Computed tomography (CT) was used to study the association between adipose tissue localization and glucose tolerance in a sample of 52 premenopausal obese women aged 35.7 +/- 5.5 yr (mean +/- SD) and with a body fat of 45.9 +/- 5.5%. Body-fat mass and the body mass index (BMI) were significantly correlated with plasma glucose, insulin, and connecting peptide (C-peptide) areas after glucose (75 g) ingestion (.40 less than or equal to r less than or equal to .51, P less than .01). Trunk-fat accumulation and the size of fat cells in the abdomen displayed highly significant correlations with postglucose insulin levels. The C-peptide area was also positively correlated with abdominal fat cell size (r = .76, P less than .01) and was more closely associated with the sum of trunk skin folds (r = .59, P less than .001) than with the extremity skin folds (r = .29, P less than .05). Subcutaneous and deep-abdominal-fat areas measured by CT displayed comparable associations with the plasma insulin area (r = .44 and .49, respectively; P less than .001) but marked differences in the associations with glucose tolerance. Indeed, subcutaneous abdominal fat was not significantly correlated with the glucose area, whereas deep abdominal fat showed a significant correlation (r = .57, P less than .001) with the glucose area. Midthigh fat deposition measured by CT was not, however, correlated with plasma glucose, insulin, or C-peptide areas.(ABSTRACT TRUNCATED AT 250 WORDS)
Abdomen↗
Relation of high plasma triglyceride levels associated with obesity and regional adipose tissue distribution to plasma lipoprotein-lipid composition in premenopausal women.
Abdominal obesity is associated with high plasma triglyceride (TG) and with low plasma high density lipoprotein (HDL)-cholesterol (CHOL) levels. As plasma TG and HDL-CHOL are negatively correlated, the associations between obesity, the regional distribution of body fat, plasma TG levels, and plasma lipoprotein concentration and composition were studied in a sample of 76 premenopausal women (52 obese and 24 non-obese). Obese women had significantly higher plasma levels of VLDL-TG, low density lipoprotein (LDL)-CHOL, LDL-TG, LDL-apolipoprotein (apo) B and reduced HDL-CHOL levels compared to non-obese controls (p less than 0.01). However, plasma concentrations of HDL-apo A-I and HDL-TG were not different between obese and non-obese women. Partial correlation analyses revealed that both fat mass and abdominal fat accumulation significantly contributed to VLDL-TG and HDL-CHOL variances. After control for body fat mass, the waist-to-hip circumference ratio (WHR) remained significantly correlated with plasma LDL-apo B levels and with the LDL-apo B/LDL-CHOL ratio (0.01 greater than p less than 0.05). Body fat mass was, however, associated with TG enrichment of LDL (p less than 0.01). After control for WHR, body fat mass showed no significant association with plasma HDL-TG levels, whereas the WHR was positively correlated with HDL-TG levels (p less than 0.05). Partial correlation analyses indicated that adjustment for fat mass or for the WHR failed to eliminate the associations between plasma VLDL-TG levels and lipoprotein lipid composition. This study emphasizes the importance of plasma VLDL-TG level as a correlate of plasma LDL and HDL lipid composition in abdominal obesity.
Adipose Tissue↗
Metabolic characteristics of postobese individuals.
The metabolic characteristics of nine postobese and six lean control male individuals were investigated to identify factors potentially associated with the predisposition to become obese. The postobese subjects had been maintaining their body weight stable for at least six months following a 24.8 kg mean weight loss. Body weight, fat mass and fat-free mass were comparable to values of the control subjects. Data obtained in postobese and control subjects were also compared to those of seven obese male individuals whose mean body weight was comparable to the body weight of postobese subjects before they initiated their weight-reducing program. Resting metabolic rate (RMR) was significantly higher (P less than 0.05) in the obese than in the two other groups. Thermic effect of food and participation in physical activities were similar in the three groups of subjects. Daily energy intake tended to be higher in control subjects but not to a statistically significant extent. However, energy intake above RMR was statistically higher in control subjects than in the two other groups. As expected, fasting and postprandial plasma glucose and insulin were substantially higher in obese than in postobese and control subjects. Moreover, fasting and postprandial hyperglucagonemia was observed in both obese and postobese subjects, suggesting that weight loss did not normalize plasma glucagon levels as was the case for glucose and insulin. From an energetic standpoint, results of the present study suggest that people predisposed to obesity may be characterized by reduced energy needs over resting metabolic rate, a phenomenon that would not be explained by a reduced physical activity level.
Blood Glucose↗
Effect of exogenous insulin on plasma free carnitine levels during exercise in normal man.
Preliminary data from our laboratory have shown that the decrease in plasma free carnitine levels normally found during prolonged exercise is blunted in type 1 diabetic man. This study was designed to test the hypothesis that this might be due to the sustained peripheral hyperinsulinemia seen during exercise in diabetics treated by subcutaneous insulin. Ten male subjects underwent 90 min of cycle ergometry at 60% of their maximal oxygen uptake capacity on two occasions, one with and the other without a constant 0.13 mU.kg-1.min-1 i.v. insulin infusion. Blood samples were taken at rest, during exercise, and after exercise for measurement of plasma glucose, insulin, C-peptide, free fatty acids, and carnitine. Plasma glucose dropped significantly (p less than 0.01) from basal during both infusions, but values at 30, 45, and 60 min of exercise were lower (p less than 0.05) during insulin infusion compared with the saline infusion. Exercise produced a significant (p less than 0.01) fall in plasma insulin in both infusions. However, from 30 to 90 min of exercise, the plateau insulin level was higher during the insulin infusion compared with the saline infusion (91.4 +/- 3.0 vs. 32.9 +/- 3.0 pmol/L; p less than 0.001). Plasma C-peptide decreased significantly (p less than 0.01) during exercise and recovery in both infusions, but values between infusions were not significantly different. Plasma free fatty acids increased significantly (p less than 0.01) at 90 min of exercise during the saline infusion, while during the insulin infusion this was noted during recovery only.(ABSTRACT TRUNCATED AT 250 WORDS)
Adipose Tissue↗
Evidence for the existence of small eaters and large eaters of similar fat-free mass and activity level.
The objective of this study was to identify individuals of the same age, sex, activity level and fat-free mass who differed in their level of energy intake (EI). Estimates of energy intake and physical activity level were derived from three-day food and activity records from 430 individuals 17-54 years of age. Body composition was measured by underwater weighing and body fat and fat-free mass were obtained. Subjects were grouped into four categories based on age and sex (females aged 17-34 and 35-54 years and males aged 17-34 and 35-54 years). Subjects were identified as small eaters (SE) or large eaters (LE) according to kJ of EI per kg body weight, SE being from the lower quartile and LE from the upper quartile of their distributions. The results showed that, on average, LE consumed almost twice as many kJ per kg body weight as SE (about 200 versus 100). In addition middle-aged male and female SE were significantly (P less than 0.001) heavier than middle-aged male and female LE respectively. The mean body weight for the male SE was 82 +/- 12 kg (mean +/- s.d.) against 69 +/- 9 kg for the LE, while it was 66 +/- 10 kg against 52 +/- 5 kg for the female SE and LE. The male and female SE also had a significantly higher percentage body fat in both age groups. In general, there was no difference in fat-free mass and activity level between the SE and LE. It is concluded that there exist groups of individuals who have a considerable difference in their EI and adiposity even though they have similar levels of activity and fat-free mass.
Activities of Daily Living↗
Reply to "Comment on the conductivity exponent in continuum percolation"
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Journal Article↗
Effect of the amount of body fat on the age-associated increase in serum cholesterol.
This study investigates the contribution of body fat stores on the age-associated increase in serum cholesterol and triglyceride levels. Percentage of body fat was measured by hydrostatic weighing, and serum cholesterol, triglyceride, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol levels were determined in a sample of 472 healthy men and women ages 18-50 years. In both sexes, body fat mass was significantly correlated with serum cholesterol (r = 0.21 in men and r = 0.24 in women, P less than 0.01) and triglyceride (r = 0.33 in men and r = 0.24 in women, P less than 0.01) levels. After adjustment for the association between age and serum cholesterol, no correlation was observed between body fat mass and serum cholesterol (r = 0.01 in men and r = 0.09 in women). After correction for age, serum triglyceride levels remained significantly correlated with body fat mass (r = 0.26 and r = 0.17 in men and women, respectively, P less than 0.05). As body fat also increases with age, the possibility that a partial correlation coefficient procedure eliminated a portion of the age effect mediated by an age-related increase in fat, was addressed by performing further analyses. Within each sex subsample two sets of analyses were performed on (a) three groups of subjects individually paired for age but with different levels of body fat stores, and (b) three groups of subjects paired for the amount of body fat but differing in age.(ABSTRACT TRUNCATED AT 250 WORDS)
Adipose Tissue↗