scholarly journals Gluconeogenesis from acetone in starved rats

1985 ◽  
Vol 231 (1) ◽  
pp. 151-155 ◽  
Author(s):  
G Hetenyi ◽  
C Ferrarotto
Keyword(s):  
Plasma Glucose ◽  
Time Course ◽  
Impulse Response Function ◽  
Metabolic Clearance ◽  
Plasma Lactate ◽  
Metabolic Clearance Rate ◽  
Unit Impulse ◽  
Anaesthetized Rats ◽  
Glucose Synthesis ◽  
Unit Impulse Response

To non-anaesthetized rats starved for 3 days, [U-14C]acetone, NaH14CO3, L-[U-14C]lactate, [2-14C]acetate or D-[U-14C]- plus D-[3-3H]-glucose was injected intravenously. From the change in the plasma concentration of labelled acetone versus time after the injection, the metabolic clearance rate of acetone was calculated as 2.25 ml/min per kg body wt., and its rate of turnover as 0.74 mumol/min per kg. The extent and time course of the labelling of plasma glucose, lactate, urea and acetoacetate were followed and compared with those observed after the injection of labelled lactate, acetate and NaHCO3. The labelling of plasma lactate was rapid and extensive. Some 1.37% of the 14C atoms of circulating glucose originated from plasma acetone, compared with 44% originating from lactate. By deconvolution of the Unit Impulse Response Function of glucose, it was shown that the flux of C atoms from acetone to glucose reached a peak at about 100 min after injection of labelled acetone. In comparable experiments the transfer from lactate reached a peak at 14 min after the injection of labelled lactate. It was concluded that acetone is converted into lactate to a degree sufficient to account for the labelling of plasma glucose and is thus a true, albeit minor, substrate of glucose synthesis in starved rats.

scholarly journals Spectral Analysis of Dynamic PET Studies

1993 ◽  
Vol 13 (1) ◽  
pp. 15-23 ◽  
Author(s):  
Vincent J. Cunningham ◽  
Terry Jones
Keyword(s):  
Impulse Response ◽  
Time Course ◽  
Arterial Input Function ◽  
Impulse Response Function ◽  
Impulse Response Functions ◽  
Dynamic Pet ◽  
Computer Algorithms ◽  
Arterial Blood ◽  
Unit Impulse ◽  
Unit Impulse Response

We describe a new technique for the analysis of dynamic positron emission tomography (PET) studies in humans, where data consist of the time courses of label in tissue regions of interest and in arterial blood, following the administration of radiolabeled tracers. The technique produces a simple spectrum of the kinetic components which relate the tissue's response to the blood activity curve. From this summary of the kinetic components, the tissue's unit impulse response can be derived. The convolution of the arterial input function with the derived unit impulse response function gives the curve of best fit to the observed tissue data. The analysis makes no a priori assumptions regarding the number of compartments or components required to describe the time course of label in the tissue. Rather, it is based on a general linear model, presented here in a formulation compatible with its solution using standard computer algorithms. Its application is illustrated with reference to cerebral blood flow, glucose utilization, and ligand binding. The interpretation of the spectra, and of the tissue unit impulse response functions, are discussed in terms of vascular components, unidirectional clearance of tracer by the tissue, and reversible and irreversible phenomena. The significance of the number of components which can be identified within a given datum set is also discussed. The technique facilitates the interpretation of dynamic PET data and simplifies comparisons between regions and between subjects.

scholarly journals Convolution-based time-domain simulation for fluidelastic instability in tube arrays

2021 ◽  
Author(s):  
Mingjie Zhang ◽  
Ole Øiseth
Keyword(s):  
Impulse Response ◽  
Response Function ◽  
Time Domain ◽  
Impulse Response Function ◽  
Time Domain Simulation ◽  
Unit Step ◽  
Tube Arrays ◽  
Unit Impulse ◽  
The Time Domain ◽  
Unit Impulse Response

AbstractA convolution-based numerical algorithm is presented for the time-domain analysis of fluidelastic instability in tube arrays, emphasizing in detail some key numerical issues involved in the time-domain simulation. The unit-step and unit-impulse response functions, as two elementary building blocks for the time-domain analysis, are interpreted systematically. An amplitude-dependent unit-step or unit-impulse response function is introduced to capture the main features of the nonlinear fluidelastic (FE) forces. Connections of these elementary functions with conventional frequency-domain unsteady FE force coefficients are discussed to facilitate the identification of model parameters. Due to the lack of a reliable method to directly identify the unit-step or unit-impulse response function, the response function is indirectly identified based on the unsteady FE force coefficients. However, the transient feature captured by the indirectly identified response function may not be consistent with the physical fluid-memory effects. A recursive function is derived for FE force simulation to reduce the computational cost of the convolution operation. Numerical examples of two tube arrays, containing both a single flexible tube and multiple flexible tubes, are provided to validate the fidelity of the time-domain simulation. It is proven that the present time-domain simulation can achieve the same level of accuracy as the frequency-domain simulation based on the unsteady FE force coefficients. The convolution-based time-domain simulation can be used to more accurately evaluate the integrity of tube arrays by considering various nonlinear effects and non-uniform flow conditions. However, the indirectly identified unit-step or unit-impulse response function may fail to capture the underlying discontinuity in the stability curve due to the prespecified expression for fluid-memory effects.

Glucose and lactate kinetics after endotoxin administration in dogs.

1977 ◽  
Vol 232 (2) ◽  
pp. E180 ◽  
Author(s):  
R R Wolfe ◽  
D Elahi ◽  
J J Spitzer
Keyword(s):  
Lactate Concentration ◽  
Constant Infusion ◽  
Glucose Turnover ◽  
Metabolic Clearance ◽  
Plasma Lactate ◽  
Metabolic Clearance Rate ◽  
Metabolic Substrate ◽  
E Coli ◽  
Lactate Kinetics ◽  
Plasma Lactate Concentration

We studied the effects of E. coli endotoxin on the glucose and lactate kinetics in dogs by means of the primed constant infusion of [6(-3)H] glucose and Na-L-(+)-[U-14C] lactate. The infusion of endotoxin induced a transient hyperglycemic level, followed by a steady fall in plasma glucose to hypoglycemic levels. The rate of appearance (Ra) and the rate of disappearance (Rd) of glucose were both significantly elevated (P less than .05) for 150 min after endotoxin, after which neither differed from the preinfusion value. The metabolic clearance rate of glucose was significantly elevated at all times 30 min postendotoxin. By 30 min postendotoxin, Ra and Rd of lactate, plasma lactate concentration, and the percent of glucose turnover originating from lactate were significantly elevated and remained so for the duration of the experiment. We concluded that after endotoxin hypoglycemia developed because of an enhanced peripheral uptake of glucose and a failure of the liver to maintain an increased Ra of glucose. We also concluded that lactate became an important precursor for gluconeogenesis and an important metabolic substrate.

Production rate, metabolic clearance rate and blood concentration of progesterone in conscious and anaesthetized pregnant rats

1984 ◽  
Vol 102 (3) ◽  
pp. 357-363 ◽  
Author(s):  
B. J. Waddell ◽  
N. W. Bruce
Keyword(s):  
Production Rate ◽  
Clearance Rate ◽  
Blood Concentration ◽  
Constant Infusion ◽  
Metabolic Clearance ◽  
Metabolic Clearance Rate ◽  
Short Term ◽  
Pregnant Rats ◽  
Pregnant Rat ◽  
Anaesthetized Rats

ABSTRACT Both production rate and metabolic clearance rate (MCR) of progesterone may vary rapidly and so effect short-term changes in blood concentration of the hormone. Here, a constant infusion and sampling technique was used to estimate these three characteristics of progesterone metabolism in seven conscious and ten anaesthetized rats on day 16 of pregnancy. After steady state was achieved, four samples were collected during a 1-h period from each rat. Mean values for production rate and MCR of progesterone in conscious rats were 14·0 ±1·4 μmol/day and 63·2 ± 6·2 litres/day respectively. Both values were substantially reduced in anaesthetized rats (8.6 ±0·8 μmol/ day and 39·4± 3·4 litres/day respectively) and so blood concentration was unchanged. The production rate was positively related to the total mass of luteal tissue (common correlation coefficient, r = 0·61, P <0·05). There were no consistent changes in the three characteristics with time but variation within rats was high. The estimated coefficients of variation for production rate, MCR and blood concentration within rats were 26, 18 and 17% in conscious and 27, 20 and 23% in anaesthetized rats respectively. Short-term changes in production rate and MCR generally were in the same direction (P <0·05). This reduced variation in blood concentration which would otherwise have occurred if production rate and MCR were unrelated. The pregnant rat is clearly capable of rapid shifts in production rate, MCR and blood concentration of progesterone and the positive relationship between production rate and MCR has a homeostatic effect on blood concentration. J. Endocr. (1984) 102, 357–363

Glucose uptake during centrally induced stress is insulin independent and enhanced by adrenergic blockade

1999 ◽  
Vol 87 (2) ◽  
pp. 722-731 ◽  
Author(s):  
Michael C. Lekas ◽  
Simon J. Fisher ◽  
Ban El-Bahrani ◽  
Mayliza van Delangeryt ◽  
Mladen Vranic ◽  
...  
Keyword(s):  
Plasma Glucose ◽  
Glucose Utilization ◽  
Glucose Production ◽  
Control Group ◽  
Adrenergic Blockade ◽  
Metabolic Clearance ◽  
Metabolic Clearance Rate ◽  
Marked Rise ◽  
Induced Stress ◽  
Adrenergic Activation

Glucose utilization increases markedly in the normal dog during stress induced by the intracerebroventricular (ICV) injection of carbachol. To determine the extent to which insulin, glucagon, and selective (α/β)-adrenergic activation mediate the increment in glucose metabolic clearance rate (MCR) and glucose production (Ra), we used five groups of normal mongrel dogs: 1) pancreatic clamp (PC; n = 7) with peripheral somatostatin (0.8 μg ⋅ kg−1⋅ min−1) and intraportal replacement of insulin (1,482 ± 84 pmol ⋅ kg−1⋅ min−1) and glucagon (0.65 ng ⋅ kg−1⋅ min−1) infusions; 2) PC plus combined α (phentolamine)- and β (propranolol)-blockade (7 and 5 μg ⋅ kg−1⋅ min−1, respectively; α+β; n = 5); 3) PC plus α-blockade (α; n = 6); 4) PC plus β-blockade (β; n = 5); and 5) a carbachol control group without PC (Con; n = 10). During ICV carbachol stress (0–120 min), catecholamines, ACTH, and cortisol increased in all groups. Baseline insulin and glucagon levels were maintained in all groups except Con, where glucagon rose 33%, and α, where insulin increased slightly but significantly. Stress increased ( P < 0.05) plasma glucose in Con, PC, and α but decreased it in β and α+β. The MCR increment was greater ( P < 0.05) in β and α+β than in Con, PC, and α. Raincreased ( P < 0.05) in all groups but was attenuated in α+β. Stress-induced lipolysis was abolished in β ( P < 0.05). The marked rise in lactate in Con, PC, and α was abolished in α+β and β. We conclude that the stress-induced increase in MCR is largely independent of changes in insulin, markedly augmented by β-blockade, and related, at least in part, to inhibition of lipolysis and glycogenolysis, and that Rais augmented by glucagon and α- and β-catecholamine effects.

scholarly journals Bile Acid Sequestration Reduces Plasma Glucose Levels in db/db Mice by Increasing Its Metabolic Clearance Rate

PLoS ONE ◽  
2011 ◽  
Vol 6 (11) ◽  
pp. e24564 ◽  
Author(s):  
Maxi Meissner ◽  
Hilde Herrema ◽  
Theo H. van Dijk ◽  
Albert Gerding ◽  
Rick Havinga ◽  
...  
Keyword(s):  
Bile Acid ◽  
Plasma Glucose ◽  
Clearance Rate ◽  
Metabolic Clearance ◽  
Metabolic Clearance Rate ◽  
Glucose Levels

Glucoregulation during rest and exercise in depancreatized dogs: role of the acute presence of insulin

1992 ◽  
Vol 262 (5) ◽  
pp. E574-E582 ◽  
Author(s):  
D. H. Wasserman ◽  
J. L. Bupp ◽  
J. L. Johnson ◽  
D. Bracy ◽  
D. B. Lacy
Keyword(s):  
Insulin Sensitivity ◽  
Plasma Glucose ◽  
Clearance Rate ◽  
Glucose Utilization ◽  
Metabolic Clearance ◽  
Metabolic Clearance Rate ◽  
Rest And Exercise

To determine the effects of the presence of insulin in poorly controlled diabetes, depancreatized (PX) dogs (n = 5) were studied during rest and 150 min of exercise in paired experiments in which saline alone was infused (IDEF) and in which insulin was replaced intraportally (200 microU.kg-1.min-1) with glucose clamped at the levels in IDEF (IR+G). PX dogs (n = 4) were also studied with insulin, but glucose was allowed to fall (IR). Insulin was not detectable, 6 +/- 1 and 6 +/- 2 microU/ml in IDEF, IR+G, and IR. Plasma glucose was 470 +/- 47, 480 +/- 48, and 372 +/- 35 mg/dl at rest in IDEF, IR+G, and IR, respectively. Levels were unchanged with exercise in IDEF and IR+G, but fell by 139 +/- 13 mg/dl in IR. Basal glucose rate of appearance (Ra) was 7.0 +/- 0.9, 1.3 +/- 1.1, and 6.0 +/- 0.7 mg.kg-1.min-1 in IDEF, IR+G, and IR, respectively. Exercise elicited a rise in Ra in only IDEF. The rises in Rd and metabolic clearance rate in IDEF were reduced (delta 2.6 +/- 0.7 and delta 0.8 +/- 0.3 ml.kg-1.min-1 at 150 min) compared with IR+G (delta 5.3 +/- 1.9 and delta 1.7 +/- 0.2 ml.kg-1.min-1 at 150 min) and IR (delta 3.7 +/- 1.2 and delta 2.4 +/- 0.8 ml.kg-1.min-1). The insulin sensitivity of glucose utilization (Rd) was elevated by approximately 75% at 150 min. Basal glycerol was similar in IDEF and IR but was reduced by approximately 70% in IR+G. Glycerol rose similarly with exercise in IDEF and IR.(ABSTRACT TRUNCATED AT 250 WORDS)

Another Look at Z-transform Technique for Deriving Unit Impulse Response Function

2007 ◽  
Vol 21 (11) ◽  
pp. 1829-1848 ◽  
Author(s):  
R. K. Rai ◽  
M. K. Jain ◽  
S. K. Mishra ◽  
C. S. P. Ojha ◽  
V. P. Singh
Keyword(s):  
Impulse Response ◽  
Response Function ◽  
Impulse Response Function ◽  
Unit Impulse ◽  
Unit Impulse Response

scholarly journals Fish-oil supplementation reduces stimulation of plasma glucose fluxes during exercise in untrained males

2003 ◽  
Vol 90 (4) ◽  
pp. 777-786 ◽  
Author(s):  
Jacques Delarue ◽  
Francois Labarthe ◽  
Richard Cohen
Keyword(s):  
Fish Oil ◽  
Lipid Oxidation ◽  
Olive Oil ◽  
Plasma Glucose ◽  
Clearance Rate ◽  
Carbohydrate Oxidation ◽  
Metabolic Clearance ◽  
Metabolic Clearance Rate ◽  
Fish Oil Supplementation ◽  
Stimulation Of

The present study examined the effects of a 3-week fish-oil supplementation (6 g/d) on the rate of plasma glucose disappearance (Rd glucose), hepatic glucose production (HGP), carbohydrate oxidation and lipid oxidation during exercise. Six untrained males (23±1 years; 67·6±2·7kg) performed two 90min cycling exercise sessions at 60% of maximal O2 output separated by 20 d. During the 20 d before the first test, they ingested 6g olive oil/d, then 6g fish oil/d during the 20 d before the second test. Plasma glucose fluxes and lipolysis were traced using 6,6-[2H2]glucose and 1,1,2,3,3-[2H5]glycerol respectively. Substrates oxidation was obtained from indirect calorimetry. At rest HGP and the Rd glucose were similar after olive oil and fish oil (1.83 (se 0·05) v. 1·67 (se 0·11) mg/kg per min). During exercise, fish oil reduced the stimulation of both the Rd glucose (5·06 (se 0·23) v. 6·37 (se 0·12) mg/kg per min; P<0·05) and HGP (4·88 (se 0·24) v. 5·91 (se 0·21) mg/kg per min; P<0·05). Fish oil also reduced glucose metabolic clearance rate (6·93 (se 0·29) v. 8·30 (se 0·57) ml/min). Carbohydrate oxidation tended to be less stimulated by exercise after fish oil than after olive oil (12·09 (se 0·60) v. 13·86 (se 1·11) mg/kg per min; NS). Lipid oxidation tended to be more stimulated by exercise after fish oil (7·34 (se 0·45) v. 6·85 (se 0·17) mg/kg per min; NS). Glycaemia, lactataemia, insulinaemia and glucagonaemia were similarly affected by exercise after fish oil and olive oil. Lipolysis at rest was similar after fish oil and olive oil (2·92 (se 0·42) v. 2·94 (se 0·28) μmol/kg per min) and similarly stimulated by exercise (6·42 (se 0·75) v. 6·77 (se 0·72) μmol/kg per min). It is concluded that fish oil reduced the Rd glucose by 26% by reducing glucose metabolic clearance rate, possibly by facilitating fat oxidation, and reduced HGP by 21%, possibly by a feedback mechanism.

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