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Claudio Cobelli - One of the best experts on this subject based on the ideXlab platform.
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insulin Secretion Rate during glucose stimuli alternative analyses of c peptide data
Annals of Biomedical Engineering, 2001Co-Authors: Elena Breda, Claudio CobelliAbstract:The ability to evaluate the pancreatic insulin Secretion Rate (ISR) is essential for a quantitative understanding of the glucose regulation system in man. Various approaches have been developed for evaluation of the ISR in vivo. The aim of this study was to compare input/output and compartmental models of C-peptide to reconstruct the ISR in response to both physiological and nonphysiological glucose stimuli in healthy humans. In particular we applied the nonparametric stochastic deconvolution and the C-peptide minimal model approaches to the graded up&down glucose infusion protocol, where glucose was infused at progressively increasing and then decreasing Rates, and to the intravenous glucose tolerance test (IVGTT), where an impulse dose of glucose was administered. Our results show that the two models give virtually identical results when glucose and C-peptide (and thus ISR) profiles are smooth and regular, but when vigorous nonstationarities are present, like during the first 4 min of the IVGTT, the two ISR profiles are different (but not their areas under the curve). The C-peptide minimal model, albeit requiring, at variance with deconvolution, the knowledge of glucose data, has the advantage of providing quantitative indices of the β-cell function, which is important in the parametric definition of different physiopathological states. © 2001 Biomedical Engineering Society.
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Reconstructing insulin Secretion Rate after a glucose stimulus by an improved stochastic deconvolution method
IEEE Transactions on Biomedical Engineering, 2001Co-Authors: G. Pillonetto, Giovanni Sparacino, Claudio CobelliAbstract:Reconstructing insulin Secretion Rate (ISR) after a glucose stimulus by deconvolution is difficult because of its biphasic pattern, i.e., a rapid Secretion peak is followed by a slower release. Here, the authors refine a recently proposed stochastic deconvolution method by modeling ISR as the multiple integration of a white noise process with time-varying statistics. The unknown parameters are estimated from the data by employing a maximum likelihood criterion. A fast computational scheme implementing the method is presented. Monte Carlo simulation results are developed which numerically show a more reliable ISR profile reconstructed by the new method.
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a stochastic deconvolution method to reconstruct insulin Secretion Rate after a glucose stimulus
IEEE Transactions on Biomedical Engineering, 1996Co-Authors: Giovanni Sparacino, Claudio CobelliAbstract:Insulin Secretion Rate (ISR) is not directly measurable in man but it can be reconstructed from C-peptide (CP) concentration measurements by solving an input estimation problem by deconvolution. The major difficulties posed by the estimation of ISR after a glucose stimulus, e.g., during an intravenous glucose tolerance test (IVGTT), are the ill-conditioning of the problem, the nonstationary pattern of the Secretion Rate, and the nonuniform/infrequent sampling schedule. In this work, a nonparametric method based on the classic Phillips-Tikhonov regularization approach is presented. The problem of nonuniform/infrequent sampling is addressed by a novel formulation of the regularization method which allows the estimation of quasi time-continuous input profiles. The input estimation problem is stated into a Bayesian context, where the a priori known nonstationary characteristics of ISR after the glucose stimulus are described by a stochastic model. Deconvolution is tackled by linear minimum variance estimation, thus allowing the derivation of new statistically based regularization criteria. Finally, a Monte-Carlo stRategy is implemented to assess the uncertainty of the estimated ISR arising from CP measurement error and impulse response parameters uncertainty.
M Follenius - One of the best experts on this subject based on the ideXlab platform.
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slow oscillations of plasma glucose and insulin Secretion Rate are amplified during sleep in humans under continuous enteral nutrition
Sleep, 1994Co-Authors: C Simon, G Brandenberger, J Saini, J Ehrhart, M FolleniusAbstract:Concomitant oscillations of plasma glucose and insulin Secretion Rate with a periodicity of about 80 minutes have been identified in normal humans. To determine whether these slow oscillations are influenced by sleep, peripheral levels of glucose and C-peptide were measured at 10-minute intervals over 24 hours in seven subjects, once with a normal nocturnal sleep from 2300 to 0700 hours, and once with a shifted daytime sleep from 0700 to 1500 hours. The subjects received continuous enteral nutrition and remained supine for the 8 hours preceding blood sampling and throughout the whole experiment. Insulin Secretion Rate was estimated by deconvoluting peripheral C-peptide levels using an open two-compartment model. The amplitude of glucose and insulin Secretion Rate oscillations increased by 160% during the 8-hour sleep periods, at whatever time they occurred, whereas the influence of the time of day was not significant. Glucose and insulin Secretion Rate mean levels were also significantly increased during normal nocturnal sleep compared to the remaining 8-hour waking periods, but this effect did not persist when sleep was shifted to the daytime. The number of oscillations was similar in both experimental series and was not affected by sleep. No systematic concordance was found between glucose and insulin Secretion Rate oscillations and the rapid eye movement-nonrapid eye movement sleep cycles, despite them having similar periodicities. This study demonstRates that increased amplitude of glucose and insulin Secretion Rate oscillations is related to sleep rather than to the time of day, without any associated frequency variations.(ABSTRACT TRUNCATED AT 250 WORDS)
I.d. Miletic - One of the best experts on this subject based on the ideXlab platform.
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Effect of taste and smell on Secretion Rate of salivary IgA in elderly and young persons.
The journal of nutrition health & aging, 1999Co-Authors: Susan S. Schiffman, I.d. MileticAbstract:Two experiments were performed to determine the effect of taste and odor stimuli on Secretion Rate of salivary IgA in young and elderly individuals. In Experiment 1, three stimuli were applied to the tongue: 1) "flavor" drops (60% sugar, 5% cocoa powder, and 0.1 % Irish cream odor); 2) sugar (60%); and 3) water. In Experiment 2, four different foods (chicken broth, onion soup, corn, and carrots) were tested with and without monosodium glutamate (MSG). The stimuli in both experiments were delivered three times in a one hour period: t=0, t=30 minutes, t=60 minutes. The results of Experiment 1 indicated that application of sugar (taste alone) and flavor (taste and odor combined) to the tongue induced significantly higher Secretion Rates of sIgA than the application of water in both elderly and young subjects. In addition, flavor application produced significantly higher Secretion Rates of sIgA than sugar application alone. Secretion Rates of sIgA in young persons were significantly higher than those in elderly persons. In Experiment 2, the increase in Secretion Rate of sIgA at 30 and 60 minutes for each food with MSG was greater than the same food without MSG for the elderly subjects. The increases in Secretion Rates of sIgA were produced by elevated salivary flow (Experiments 1 and 2) as well as increased absolute concentrations of sIgA (Experiment 1). The elevation of absolute concentrations of sIgA by chemosensory stimuli may involve neural-immune connections. The improvements in salivary flow and secretory immunity by repeated taste and smell stimulation found here have clinical potential for treatment of immune deficiencies and dry mouth which frequently occur in elderly individuals.
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Salivary IgA Secretion Rate in young and elderly persons
Physiology & behavior, 1996Co-Authors: I.d. Miletic, Susan S. Schiffman, V.d. Miletic, Elizabeth A. Sattely-millerAbstract:Immunoglobulin A (IgA) is the dominant immunoglobulin isotype on all mucosal surfaces where it acts as a first line of defense against microbial invasion. Recent investigations suggest that secretory IgA (sIgA) concentrations vary over the day due to a range of variables including dietary factors, daily mood, and exercise. In this study, salivary IgA was determined by ELISA in samples of 48 persons grouped as "young" (20-30 years old) and "elderly" (60-80 years old). Unstimulated, stabilized morning and afternoon saliva was collected during 7 consecutive days. Saliva flow, total proteins, sIgA concentrations, and sIgA Secretion Rates were determined. The main finding was that saliva flow and sIgA Secretion Rate were significantly lower in the elderly than in the young. Salivary IgA Secretion Rate was found to be independent of total proteins secreted in all samples. There is individual variability within a particular age group. It was also found that stress and daily events influence the sIgA Secretion Rate.
G Brandenberger - One of the best experts on this subject based on the ideXlab platform.
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twenty four hour rhythms of plasma glucose and insulin Secretion Rate in regular night workers
American Journal of Physiology-endocrinology and Metabolism, 2000Co-Authors: Chantal Simon, L Weibel, G BrandenbergerAbstract:To determine whether the ultradian and circadian rhythms of glucose and insulin Secretion Rate (ISR) are adapted to their permanent nocturnal schedule, eight night workers were studied during their...
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slow oscillations of plasma glucose and insulin Secretion Rate are amplified during sleep in humans under continuous enteral nutrition
Sleep, 1994Co-Authors: C Simon, G Brandenberger, J Saini, J Ehrhart, M FolleniusAbstract:Concomitant oscillations of plasma glucose and insulin Secretion Rate with a periodicity of about 80 minutes have been identified in normal humans. To determine whether these slow oscillations are influenced by sleep, peripheral levels of glucose and C-peptide were measured at 10-minute intervals over 24 hours in seven subjects, once with a normal nocturnal sleep from 2300 to 0700 hours, and once with a shifted daytime sleep from 0700 to 1500 hours. The subjects received continuous enteral nutrition and remained supine for the 8 hours preceding blood sampling and throughout the whole experiment. Insulin Secretion Rate was estimated by deconvoluting peripheral C-peptide levels using an open two-compartment model. The amplitude of glucose and insulin Secretion Rate oscillations increased by 160% during the 8-hour sleep periods, at whatever time they occurred, whereas the influence of the time of day was not significant. Glucose and insulin Secretion Rate mean levels were also significantly increased during normal nocturnal sleep compared to the remaining 8-hour waking periods, but this effect did not persist when sleep was shifted to the daytime. The number of oscillations was similar in both experimental series and was not affected by sleep. No systematic concordance was found between glucose and insulin Secretion Rate oscillations and the rapid eye movement-nonrapid eye movement sleep cycles, despite them having similar periodicities. This study demonstRates that increased amplitude of glucose and insulin Secretion Rate oscillations is related to sleep rather than to the time of day, without any associated frequency variations.(ABSTRACT TRUNCATED AT 250 WORDS)
C Simon - One of the best experts on this subject based on the ideXlab platform.
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slow oscillations of plasma glucose and insulin Secretion Rate are amplified during sleep in humans under continuous enteral nutrition
Sleep, 1994Co-Authors: C Simon, G Brandenberger, J Saini, J Ehrhart, M FolleniusAbstract:Concomitant oscillations of plasma glucose and insulin Secretion Rate with a periodicity of about 80 minutes have been identified in normal humans. To determine whether these slow oscillations are influenced by sleep, peripheral levels of glucose and C-peptide were measured at 10-minute intervals over 24 hours in seven subjects, once with a normal nocturnal sleep from 2300 to 0700 hours, and once with a shifted daytime sleep from 0700 to 1500 hours. The subjects received continuous enteral nutrition and remained supine for the 8 hours preceding blood sampling and throughout the whole experiment. Insulin Secretion Rate was estimated by deconvoluting peripheral C-peptide levels using an open two-compartment model. The amplitude of glucose and insulin Secretion Rate oscillations increased by 160% during the 8-hour sleep periods, at whatever time they occurred, whereas the influence of the time of day was not significant. Glucose and insulin Secretion Rate mean levels were also significantly increased during normal nocturnal sleep compared to the remaining 8-hour waking periods, but this effect did not persist when sleep was shifted to the daytime. The number of oscillations was similar in both experimental series and was not affected by sleep. No systematic concordance was found between glucose and insulin Secretion Rate oscillations and the rapid eye movement-nonrapid eye movement sleep cycles, despite them having similar periodicities. This study demonstRates that increased amplitude of glucose and insulin Secretion Rate oscillations is related to sleep rather than to the time of day, without any associated frequency variations.(ABSTRACT TRUNCATED AT 250 WORDS)
