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ABSTRACT: Since the Kalman filter and Monte Carlo techniques, much theoretical work has been put into the development of signal deconvolution tools. Among recent developments taking place in neuroscience are Dynamic Expectation Maximization, Generalized Filtering and the Cubature Kalman Filter. While there are exciting prospects to use these tools for Dynamic Causal Modeling and other analyses of networks, there has been comparatively little work to validate the algorithms on controlled experimental data. In this work, the latest evolution of these tools, the square-root cubature Kalman smoother (SCKS), is tested for its effectiveness on multimodal neurovascular data. Multispectral intrinsic optical imaging and electrophysiological measurements of Wistar rats are used in combination with somatosensory stimulation. The Buxton-Friston (B-F) balloon model is then deconvolved with the SCKS algorithm to obtain the estimated neuronal inputs u(t) from the hemodynamic measurements (flow, oxy- and deoxygenated hemoglobin). RESULTS: The estimated neuronal inputs are compared to the stimulation protocol and a sensitivity and specificity analysis is carried out. SCKS succeeds in recovering most of the stimulations. Next, the estimated inputs are compared to actual measures of neuronal activity: local field potentials (LFPs) and multiunit activity (MUA). Good sensitivity of the technique is obtained with both LFPs and MUA over the whole recordings, with the area of the ROC curves favoring LFPs. A weak correlation between SCKS estimated inputs and LFPs is found outside stimulation periods, significant at one standard deviation. Finally, the accuracy of state reconstructions is studied and SCKS reconstructed states are highly concordant with measured states.
Journal of neuroscience methods 07/2012; 210(2):247-58. · 2.30 Impact Factor
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ABSTRACT: The LOU/c rat is an inbred strain considered a model of healthy aging. It exhibits a longer free disease lifespan and a low adiposity throughout life. While this animal model has been shown to maintain eating behavior and neuroendocrine, metabolic and cognitive functions with age, no study has yet investigated vascular correlates in this model of healthy aging. In the present work, multispectral optical imaging was used to investigate the hemodynamic response in the somatosensory cortex of LOU/c rats following forepaw stimulation in three age groups, 4, 24 and 40months. Results indicate reduced hemodynamic responses in the contralateral somatosensory cortex between young (4months) and older groups following stimulation. This decrease was associated with an increase in the spatial extent of activation. The ipsilateral response did not change with aging leading to decreased laterality. Estimations of the relative change in the local cerebral metabolic rate of oxygen during stimulation based on multimodal data showed no significant change with age. The exponent describing the relation between blood volume and blood flow changes, Grubb's parameter, did display a significant change with age which may suggest vessel compliance modifications. This work finds its relevance in recent findings underlying the importance of vascular changes with aging and its impact on neurodegenerative disease.
NeuroImage 06/2011; 56(4):1892-901. · 5.89 Impact Factor
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ABSTRACT: Neuronal, vascular and metabolic factors result in a deterioration of the cerebral hemodynamic response with age. The interpretation of neuroimaging studies in the context of aging is rendered difficult due to the challenge in untangling the composite effect of these modifications. In this work we integrate multimodal optical imaging in biophysical models to investigate vascular and metabolic changes occurring in aging. Multispectral intrinsic optical imaging of an animal model of healthy aging, the LOU/c rat, is used in combination with somatosensory stimulation to study the modifications of the hemodynamic response with increasing age. Results are fitted with three macroscopic biophysical models to extract parameters, providing a phenomenological description of vascular and metabolic changes. Our results show that 1) biophysical parameters are estimable from multimodal data and 2) parameter estimates in this population change with aging.
NeuroImage 04/2011; 57(4):1480-91. · 5.89 Impact Factor
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ABSTRACT: To determine if changes in patients' nutritional status during hospitalization are related to daily energy and protein intakes when cachectic/inflammatory conditions are controlled for.
Prospective study.
A total of 32 non-cachectic patients (21 women; 65-92 y).
Nutritional status was evaluated at admission and discharge using the Protein-Energy Malnutrition Index which includes BMI, %IBW, TS, MAC, albumin, hemoglobin and lymphocyte count. Food intake was assessed 3 meals/day every other day for an average of 46.2 +/- 14.6 meals/participant.
In all, 47% of the study sample was malnourished at admission. Nutritional status improved in 73% of patients who had been identified as malnourished and in 30 % of non-malnourished patients at admission. Total energy intake correlated with improvements in BMI, %IBW and total lymphocyte count (all p < 0.04). Improvement in PEMI score for the whole group was associated with functional status (p < 0.05). Controlling for this variable, energy (kj/kg body weight) and protein (g/kg body weight) intakes correlated positively with improvements in BMI, %IBW and MAC (Energy: partial r = 0.644, 0.624, 0.466 respectively; Protein: partial r = 0.582, 0.554, 0.433 respectively; all p < 0.05).
Results from this study offer strong evidence that when cachectic/inflammatory conditions are controlled for, standard nutrition care is compatible with the maintenance or improvement of nutritional status during the hospital stay.
The Journal of Nutrition Health and Aging 02/2009; 13(2):83-8. · 2.69 Impact Factor
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ABSTRACT: To examine the nutritional implications of the interactions taking place between patients and care providers during mealtimes in hospital settings. Specifically, we tested research propositions that the amount and nature of interpersonal behaviours exchanged between patients and providers impact patients' food intake. These propositions were derived from prior evidence of social influences on eating behaviour and a well-established framework that identifies two fundamental modalities of human interaction: striving for mastery and power (agency) and efforts to promote union with others (communion).
In a within-subject naturalistic study, participants were observed on multiple meals (n=1477, 46.2 meals/participant on average), during which participants' and providers' agency- and communion-related behaviours and patients' protein and energy intake were recorded. Meal-level frequency and complementarity of patients' and providers' behaviours were computed to test research propositions.
Dining room of a geriatric rehabilitation unit.
Thirty-two elderly patients (21 females, mean age:78.8, 95% CI: 76.4, 81.1).
Meal-level frequency of patient-provider exchanges (P=0.016) and patients' agency-related behaviours (P=0.029), as well as mutual reciprocation of patients' and providers' communion-related behaviours (P=0.015) on a given meal were positively linked to protein intake. Higher energy intake was found during meals where patients expressed more agency-related behaviours (P=0.029).
Results present evidence that the amount and nature of patient-provider interpersonal exchanges on a given meal influence the nutritional quality of food intake in hospitalized elderly. They provide insights into how to improve the design and delivery of routine care to this malnutrition-prone population.
This study was supported by the Canadian Institutes of Health Research (Operating grant to Laurette Dubé, Doctoral Fellowship to Catherine Paquet) the Fonds de la Recherche en santé du Québec and by the Danone Institute (Doctoral fellowship to Danielle St-Arnaud McKenzie).
European Journal of Clinical Nutrition 06/2007; 61(5):664-72. · 2.46 Impact Factor
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ABSTRACT: The mechanisms responsible for the pathological deposition of iron and other redox-active metals in the aging and degenerating mammalian CNS remain poorly understood. We previously demonstrated that normal aging and pharmacological (oxidative) stressors promote the transformation of astroglial mitochondria to iron-laden, diaminobenzidine (DAB)-positive cytoplasmic inclusions in sub-cortical regions of the rat brain. In the current study, we demonstrate that (1) numbers of DAB-positive glial granules in the rat dorsal hippocampus, an area implicated in learning and memory, progressively increase between 3, 12 and 22 months of age; (2) dietary restriction (40%), a manipulation that attenuates many mammalian aging processes, has no effect on the age-related accumulation of these gliosomes in the rat hippocampus; and (3) the latter can be accelerated by dietary supplementation of iron and copper. Our data support the view that dietary exposure to iron and/or copper in adult life can impact the sequestration of redox-active metals in aging hippocampal astroglia.
Biogerontology 02/2004; 5(2):81-8. · 3.34 Impact Factor
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ABSTRACT: Sociodemographic, lifestyle and dietary characteristics were studied to gain insights into determinants of total diet quality and diversity in a weighted sample of 460 participants aged 55-74 (53% female) from the 1990 Enqu te qu b coise sur la nutrition (EQN) dataset.
Dietary data consisted of an interviewer-administered 24-hour recall and food frequency questionnaire, and a self-administered questionnaire on dietary behaviours, attitudes and perceptions. 24-hour recall data were coded into food groups as described in Canada's Food Guide for Healthy Eating. Diet quality was scored using the categorical Dietary Diversity Score (DDS, range 0-4) and continuous Dietary Adequacy Score (DAS, range 0-18). A second nonconsecutive recall (10% of subjects) permitted correction of food group portions for intraindividual variability and subsequent calculation and validation of usual DDS and DAS. Relationships were examined between the scores and independent variables. Forward leastwise logistic regession (DDS) and stepwise multiple regression (DAS) analyses were conducted with independent variables showing significant bivariate relationships.
Among men, breakfast consumption and eating commercially-prepared meals were positively associated with usual DDS, but poor social support and supplement use negatively predicted this score. Eating fewer than 3 meals daily, smoking, and dietary supplement use were negative predictors of usual DAS (r2=0.155). Among women, eating commercial foods was a negative predictor of usual DDS, as was preferring overweight to depriving themselves of favourite foods. Reporting that health concerns influenced food choices and disagreeing with the statement that effort is needed to have a nice body were positive determinants of usual DAS in women. On the other hand, eating fewer than 3 meals daily negatively predicted this dietary index (r2 = 0.162).
Gender differences in predictors of diet quality suggest the need to target nutrition health promotion to the needs of older men and women to encourage optimal eating habits.
The Journal of Nutrition Health and Aging 02/2004; 8(2):83-91. · 2.69 Impact Factor
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ABSTRACT: The mechanisms responsible for the pathological deposition of iron and other redox-active metals in the aging and degenerating mammalian CNS remain poorly understood. We previously demonstrated that normal aging and pharmacological (oxidative) stressors promote the transformation of astroglial mitochondria to iron-laden, diaminobenzidine (DAB)-positive cytoplasmic inclusions in sub-cortical regions of the rat brain. In the current study, we demonstrate that (1) numbers of DAB-positive glial granules in the rat dorsal hippocampus, an area implicated in learning and memory, progressively increase between 3, 12 and 22 months of age; (2) dietary restriction (40%), a manipulation that attenuates many mammalian aging processes, has no effect on the age-related accumulation of these gliosomes in the rat hippocampus; and (3) the latter can be accelerated by dietary supplementation of iron and copper. Our data support the view that dietary exposure to iron and/or copper in adult life can impact the sequestration of redox-active metals in aging hippocampal astroglia.
Biogerontology 01/2004; 5(2):81-88. · 3.34 Impact Factor
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ABSTRACT: Decentralized bulk food distribution was implemented in a nursing home. Employees working with elderly residents with dementia were asked their opinion of the impact of the new system on residents and workload. A convenience sample of 24 employees (57% of the staff) completed a 31-item, self-administered Likert-scale questionnaire that allowed open-ended comments. Responses were subjected to descriptive quantitative analysis, and a qualitative approach was used to explore themes that emerged in comments. Qualitative analysis indicated that 52% of responses were negative in tone, 30% were positive, and 18% were neutral. Initially, three categories of comments emerged, with specific multiple themes related to the residents (41%), the employees (37%), or the food-service system (22%). Most comments in the employee category were negative, and suggested that the decentralized food-service system caused hardship for the staff. This problem was resolved by adding one staff-hour at the midday meal. One year later, an abbreviated repeat survey of 29 employees revealed adaptation and general acceptance of the system. Because a motivated patient care staff is essential to the successful feeding of nursing home residents with dementia, employees' concerns must be considered when operational changes are planned.
Canadian Journal of Dietetic Practice and Research 02/2001; 62(1):18-25. · 0.81 Impact Factor
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ABSTRACT: To evaluate the nutritional and clinical consequences of changing from a centralized food delivery system to decentralized bulk food portioning; a system in which meal portioning occurs on residents' floors of a nursing home.
A pilot study with a pre-post design
The study took place on one floor of a home for elderly persons with dementia. Of the 34 residents, 22 (1 man) participated in this study. Average age was 82 years (range = 55 to 94 years). Nutritional status was verified before introduction of the bulk food portioning system by 3 nonconsecutive days of observed food intakes, anthropometric measurements (height, weight, triceps skinfold thickness, mid-upper-arm circumference), and biochemical parameters (albumin, lymphocytes, glucose, sodium, potassium, transferrin, vitamin B-12, folate, hemoglobin). Trained dietitians collected the dietary and anthropometric data and validated the food intake estimates and anthropometric measurements. Data were also collected 10 weeks after implementation of the new food distribution system.
Paired t tests adjusted by a Bonferroni correction assessed differences between values measured before and after introduction of the new food distribution system.
Average food consumption increased substantially and significantly after introduction of the bulk food portioning system. Mean energy intakes rose from 1,555 to 1,924 kcal/day and most other nutrients also increased, many significantly, but there were no changes in anthropometric values or biochemical parameters, except for albumin level which decreased to the lower normal limit.
Portioning of food in the residents' dining room simulates a homelike atmosphere thereby encouraging increased food consumption. With well-trained and enthusiastic staff, this system could contribute to improved nutritional status in the very elderly, even those who have dementia. Dietitians have a key role to play in overseeing residents' nutritional needs and in training, supervising, and motivating foodservice personnel.
Journal of the American Dietetic Association 12/2000; 100(11):1354-60. · 3.59 Impact Factor
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G Ferland
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ABSTRACT: Historically known for its role in blood coagulation, vitamin K also has been shown to be required for the physiologic activation of numerous proteins that are not involved in hemostasis. Over the last 20 years, vitamin K-dependent proteins have been isolated in bone, cartilage, kidney, atheromatous plaque, and numerous soft tissues. Although the precise mechanism of action of many of these proteins remains to be determined, their discovery has proven important from a physiologic point of view.
Nutrition Reviews 09/1998; 56(8):223-30. · 4.47 Impact Factor
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ABSTRACT: In mammals, middle age and late adulthood is characterized by a decrease of growth hormone (GH) secretion and insulin-like growth factor 1 (IGF-1) serum levels, contributing to tissue and organ atrophy. This condition is related, at least in part, to alterations of pituitary GH-releasing hormone (GHRH) receptor-binding sites. Prevention of age-related deterioration of tissues and organs, retardation of the onset or progression of a wide range of age-related diseases and extension of both mean and maximum life span can be achieved through life-long moderate calorie restriction (CR). Because CR has been reported to positively modulate the somatotropic axis resulting in the maintenance of a youthful GH secretory pattern in aged rats, we investigated whether or not benefits of a long-term (10 months) 40% CR, started in 8-month-old male Sprague-Dawley rats, was accomplished by preventing age-related alterations of pituitary GHRH receptor binding sites. We also studied whether or not a short-term (50 days) 40% CR, started in 16-month-old rats, could revert them. Potential hormonal and metabolic modulators of the GHRH receptors were investigated as well. GHRH binding parameters were derived from saturation studies performed in pituitary homogenates with [125I-Tyr10]hGHRH (1-44)NH2. As previously reported, the high affinity GHRH receptor-binding sites were blunted in 18-month-old ad libitum-fed rats and the apparent concentration of total binding sites was reduced. Short-term CR neither restored high affinity GHRH binding sites nor increased the apparent concentration of total binding sites. On the contrary, long-term calorie-restricted 18-month-old rats exhibited high and low affinity GHRH binding sites (Kd1: 1.73 +/- 0.35 nM; Kd2: 310 +/- 41 nM; Bmax1: 183 +/- 55 fmol/mg protein; Bmax2: 30 +/- 3 pmol/mg protein) as found in 2-month-old rats (Kd1: 0.68 +/- 0.15 nM; Kd2: 350 +/- 47 nM; Bmax1: 219 +/- 53 fmol/mg protein; Bmax2: 84 +/- 9 pmol/mg protein). Our results imply that CR must be implemented before age-related alterations of GHRH receptor-binding sites become too severe or that CR has to be carried out for a long period of time, independently from the age at which it begins. Protection of pituitary GHRH binding sites from age-related alterations could not be attributed to changes in circulating levels of total or free T4 or free fatty acids. Finally, the anti-aging effect of a long-term CR observed at the level of pituitary GHRH receptors does not result in a significant increase of total IGF-1 circulating levels. Identification of molecular and cellular mechanisms responsible for these actions will deserve attention in order to identify centrally and/or peripherally active classes of molecules that could preserve, in aging mammals, the functionality of the somatotropic axis through selective regulation of pituitary GHRH receptors.
Neuroendocrinology 08/1998; 68(1):21-9. · 2.38 Impact Factor
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ABSTRACT: Earlier studies have shown that hepatic vitamin A stores increase with age and that rats subjected to life-long dietary restriction (DR) have greater hepatic retinoid concentrations than ad libitum-fed rats. It was suggested that these changes may be attributed to altered intestinal absorption, and so we measured retinol absorption in 3, 12, and 22 month-old female Sprague-Dawley rats fed ad libitum (AL) or a restricted diet (40%) enriched (DR+) or not (DR) with vitamins and minerals. An in vivo model was used and lymph collected from the mesenteric duct while rats were infused a micellar solution containing [3H]retinol into the proximal duodenum. Aging significantly decreased lymph flow, and at all ages DR and DR+ rats exhibited a higher flow than age-matched AL rats. Absorption of retinol was not significantly modified by age in AL and DR+ rats. However, in the DR group, there was a marked decrease in absorption between 3 and 12 months of age. Retinol absorption was significantly higher in 12 and 22 month-old DR+ rats than in age-matched AL rats, a finding that may be explained by both higher lymph flow rate and higher long-term vitamin A intake per body weight. In conclusion, the increased content of vitamin A in the livers of older AL rats is not associated with changes in intestinal absorption. In DR rats, however, retinoid accumulation in the liver may be explained by increased intestinal absorption of the vitamin, though other mechanisms may be involved. A possible explanation may be a decreased output of retinol from the liver as a result of lower metabolic needs. The lower serum vitamin A concentrations observed in DR rats would tend to support this hypothesis.
The FASEB Journal 08/1996; 10(9):1085-90. · 5.71 Impact Factor
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ABSTRACT: Precision grip, such as lateral pinching, is an essential
component of independent hand function. This apparently simple motor
task, relies on a complex interaction of sensory and motor mechanisms.
Patients with impaired input from proprioceptors and cutaneous receptors
may experience difficulty with timing and scaling motor recruitment
during manipulative manoeuvres. To help evaluate and retrain motor
control of the hand, an instrumented pinching device with a computerized
on-line visual feedback system responding to pinch force variation was
designed and constructed. Mechanical testing of the device included step
loading, loading-unloading cycles and 4 hours of constant loading to
evaluate hysteresis, nonlinearity and signal shift over time.
Calibration coefficients were calculated in the active range of 0 to 100
Newtons. A pilot test was then conducted using normal subjects (n=6).
The experimental session for each subject consisted of a total of 30
trials: one trial per pinch span (12.3, 31.4 and 51.7 mm) to determine
the maximal force (MF), and three repeated measures per force target
(FT) level (25, 50 and 75 per cent of MF) per span. Data was filtered
(Fc=10 Hz) and then normalized in terms of Ff level. Overall, subjects
achieved better pinch force control at lower FT levels and at the
thickest span tested. This study provided the basis for a clinical pilot
test to determine the effectiveness of this rehabilitation tool in
re-educating functional pinch in patients with sensorimotor impairments
Biomedical Engineering Conference, 1996., Proceedings of the 1996 Fifteenth Southern; 04/1996
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ABSTRACT: The accumulation of lysosomal bodies has long been considered to be an important correlate of aging. However it is not well established whether these age related changes interfere with cellular function. In this study, an evaluation of lysosomes by ultrastructural analysis was performed in livers of 4-6 and 20-24-month-old Sprague-Dawley female rats, fed ad libitum (A) or a restricted diet (R). An attempt was made to relate this parameter to hepatic protein synthesis, a liver function known to decrease with age and increase with dietary restriction. Aging was accompanied in both A and R animals with higher number and size of secondary lysosomes (lipofuscin) and by a decrease in total protein synthesis in hepatocytes. When compared to age matched ad libitum fed animals, livers of food restricted rats contained higher number of secondary lysosomes, yet exhibited higher protein synthetic capacity. Thus in hepatocytes, lipofuscin accumulation does not seem to interfere with cellular function.
Mechanisms of Ageing and Development 07/1992; 64(1-2):49-59. · 3.44 Impact Factor
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ABSTRACT: The size and number of fat-storing cells (FSC), considered to be the main liver storage site of vitamin A, as well as hepatic vitamin A content, were studied in aging female Sprague-Dawley rats subjected soon after weaning to dietary restriction (R), that is, 60% of food consumed by their ad libitum-fed controls (A). In A or R rats, the FSC index (number of cells per 1000 hepatocytes) and volume density (% of hepatic volume) were increased significantly at 24-27 months compared with the younger age groups. The lipocyte index and volume density were also found to be significantly higher, after the first year, in R rats when compared to corresponding age-matched A controls. An increase in total vitamin A content was also noted with age in both groups. R rats exhibited higher retinol, retinyl ester, and total retinoid content than their corresponding controls, but the differences were statistically significant only at 12-14 and 24-27 months. These results indicate that, during aging, dietary restriction markedly increases vitamin A content in liver tissue, a change that may be relevant to the beneficial effect of this dietary manipulation on liver function.
Journal of Gerontology 02/1992; 47(1):B3-8.
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ABSTRACT: The specific activity of 4 lysosomal enzymes was studied in homogenate, hepatocytes, Kupffer and endothelial cells isolated from the livers of female Sprague-Dawley rats aged 3.5, 12 and 24 months. Cells were obtained by enzymatic digestion and centrifugal elutriation. Cell viability was not affected by age or diet. In hepatocytes, the activities of all enzymes (acid phosphatase, beta-galactosidase, arylsulfatase B and cathepsin D) increased with age in rats fed ad libitum (A) but were not altered significantly by dietary restriction. The activities of all enzymes except acid phosphatase were systematically higher at 3.5 months of age in Kupffer and endothelial cells than in hepatocytes. Acid phosphatase, arylsulfatase B and cathepsin D activities increased with age in both Kupffer and endothelial cells. Beta galactosidase was decreased significantly with age in Kupffer cells but was elevated in endothelial cells. Rats exposed to dietary restriction (R) showed higher activities of beta-galactosidase, arylsulfatase B and cathepsin D when compared to corresponding A animals with the exception of the younger age group. No clear cut pattern was observed in acid phosphatase activity. Thus, the activities of liver lysosomal enzymes increase with age but the pattern of change differs with respect to enzyme and cell populations. The heightened enzyme activity in Kupffer and endothelial cells from R rats may reflect a more efficient phagocytic capacity in these animals.
Mechanisms of Ageing and Development 12/1990; 56(2):143-54. · 3.44 Impact Factor
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ABSTRACT: The aim of the present study was to determine whether increased output of phospholipid in bile during aging may be due to alteration of bile acid composition and stimulated hydrophobic bile acid formation. In female Sprague-Dawley rats we examined the influence of aging and life long dietary restriction (60% of the ad libitum intake) on bile flow, total bile acid secretion, bile acid composition and conjugation pattern, as well as phospholipid output. Rats were cannulated at 3.5, 8-12 and 24-27 months of age and bile collected for analysis. With age, there was a significant reduction in bile flow and total bile acid secretion, however, phospholipid output increased. Restriction of dietary intake exerted a beneficial effect on the age-related decline in bile formation. Studies of bile composition indicated that 12 alpha-hydroxylated bile acids (cholic acid and deoxycholic acid) secretion decreased in aged rats compared to 3.5-month-old rats. This was associated with a corresponding increase in secretion of chenodeoxycholic acid and hyodeoxycholic-ursodeoxycholic acid. However, the magnitude of the change in secretion of these bile acids could not account for the increased output of phospholipid in bile.
Lipids 11/1989; 24(10):842-8. · 2.13 Impact Factor
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ABSTRACT: Food restriction is one of the most effective interventions which increases the survival of rodents and influences a variety of physiologic and pathologic processes. Thus, we examined whether life-long caloric restriction would influence bile formation, one of the important hepatic functions. Female Sprague Dawley rats were subjected soon after weaning to a restricted diet (60% of the diet consumed by the rats fed ad libitum) and bile formation determined at 3.5, 12 and 24 months of age. Rats had their bile ducts cannulated under nembutal anesthesia and bile collected at 10 min. intervals. Bile flow rate decreased 35% between 3.5 and 24 months of age. This decrease was associated with a reduction of the bile acid dependent fraction of bile flow (BADF) up to 12 months of age, thereafter the bile acid independent fraction (BAIF) also decreased. Phospholipid and cholesterol secretion rates increased with age, but did not correlate with bile acid secretion. In rats fed the restricted diet, bile flow was about 20% higher at 3-5 months of age when compared with the ad libitum fed group. This bile flow rate remained constant until 24 months of age. The increased bile flow was attributed to higher BADF and BAIF. The phospholipid and cholesterol secretion followed that of bile acids. It thus appears that dietary restriction exerts a beneficial effect on the age related decline in bile formation.
Life Sciences 12/1987; 41(18):2091-9. · 2.53 Impact Factor
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ABSTRACT: This review summarizes current knowledge on mechanisms involved in hepatic bile formation and the role of diet as a modulator of this important liver function. It also includes cholestasis and nutritional interventions known to exert a beneficial effect in this pathology. Two components of the bile flow have been described: bile acid dependent (BADF) and bile acid independent (BAIF) flows and, several cellular structures are known to be involved in their generation. The membrane's enzyme activities, transporters and pumps play a particularly important role in bile secretion. Of the macronutrients, dietary protein has been shown to markedly affect bile flow. Protein deficient diet results in a decrease of both BADF and BAIDF, and in increased susceptibility to bile acid (BA)-induced cholestasis. Amino acid mixtures included in TPN solutions as well as certain individual amino acids can induce cholestasis mainly through alterations of plasma membrane composition and function. Supplementation with taurine and S-adenosyl methionine prevents these forms of cholestasis by maintaining membrane integrity and function. The quantity and quality of dietary lipid influences bile secretion. Enhanced bile flow was observed with high polyunsaturated fat intake and was attributed to both higher BADF and BAIDF. Diets enriched in fish oil were found to result in the generation of greater bile flow when compared to diets enriched in corn oil. Dietary phospholipid (soybean lecithin) supplementation increases bile secretion and exerts a beneficial effect against BA-induced cholestasis probably by maintenance of membrane integrity. Although there is much information on the role of dietary carbohydrates, fibers, minerals and vitamins on cholesterol and BA metabolism, relatively little is known about their implication in bile formation. Finally certain dietary strategies such as energy restriction and starve-refeed regimen can enhance bile secretion by their effects on BADF and BAIDF through maintenance of membrane function. In conclusion, diet is an important modulator of bile formation and secretion by affecting BA synthesis and metabolism as well as membrane structure and function.
Nutrition Research.
