scholarly journals Estimation of the Total Entry Rate and Resynthesis of Glucose in Sheep Using Glucoses Uniformly Labelled With 14C and Variously Labelled With 3H

1972 ◽  
Vol 25 (6) ◽  
pp. 1313 ◽  
Author(s):  
GJ Judson ◽  
RA Leng
Keyword(s):  
Glucose Metabolism ◽  
Plasma Glucose ◽  
Single Injection ◽  
Specific Radioactivity ◽  
Constant Infusion ◽  
Daily Ration ◽  
Entry Rate

Comparisons have been made of [6_3H]-, [3-3H]-, and [2-3H]glucose with [U-14C]glucose for measuring parameters of glucose metabolism in sheep given their daily ration in 24 equal amounts at hourly intervals. The specific radioactivity (R) of plasma glucose was measured at frequent intervals from 0 to 10 hr and 0 to 32 hr after the start of a constant infusion. or single injection, of mixtures of these isotopes respectively.

scholarly journals Evaluation of three isotope-dilution techniques for studying the kinetics of glucose metabolism in sheep

1969 ◽  
Vol 114 (2) ◽  
pp. 203-214 ◽  
Author(s):  
R. G. White ◽  
J. W. Steel ◽  
R. A. Leng ◽  
J. R. Luick
Keyword(s):  
Glucose Metabolism ◽  
Isotope Dilution ◽  
Plasma Glucose ◽  
Single Injection ◽  
Specific Radioactivity ◽  
Injection Technique ◽  
Entry Rate ◽  
Exponential Equation ◽  
Time Curve ◽  
Feeding Regimes

1. Comparisons have been made of three isotope-dilution techniques for measuring parameters of glucose metabolism in sheep given their daily ration in 12 equal amounts (i.e. from 07.00 to 18.00hr.) 2. [U−14C]Glucose was used in all experiments. After a single injection the specific radioactivity of plasma glucose was measured at specific times for up to 24hr. Primed infusions were made with various ratios of P, priming injection (nc), to F, infusion rate (nc/min.) (P/F ratios varying from 23:1 to 147:1) and the specific radioactivity of plasma glucose was measured at 60, 120, 150, 180, 210 and 240min. In continuous infusions the specific radioactivity of plasma glucose was followed for 9hr.; a constant specific radioactivity was observed after approximately 180min. 3. A computer programme was used to fit a multi-exponential equation to the log(specific radioactivity)–time curve after a single injection. A second- or third-order exponential equation was found to fit the results. 4. Conventional analyses of all results showed that similar estimates of the irreversible loss of glucose were obtained by using all three techniques. Estimates of glucose pool size and space by using the primed infusion technique were both significantly higher than estimates obtained by the single injection technique. In these experiments total entry rate could only be determined from the single-injection results and a wide variation in estimates was obtained. 5. Comparisons of the specific radioactivity–time relationships after a single injection of [U−14C]glucose in sheep given their ration either once daily or as a proportion at hourly intervals indicated that there were fluctuations in glucose synthesis in the former over the period of the experiment. The multi-exponential curves fitted to these results had larger residual variances than in sheep given food at hourly intervals. All parameters of glucose metabolism estimated were similar under both feeding regimes. 6. A number of methods of analysis are discussed and a model for glucose metabolism in sheep in suggested.

Glucose lactate interrelations in sheep.

1978 ◽  
Vol 235 (5) ◽  
pp. E487
Author(s):  
P E Reilly ◽  
L G Chandrasena
Keyword(s):  
Plasma Glucose ◽  
Glucose Concentration ◽  
Lactate Concentration ◽  
Lactate Production ◽  
Plasma Glucose Concentration ◽  
Constant Infusion ◽  
Dilution Method ◽  
Entry Rate ◽  
Net Production ◽  
Arterial Plasma

The constant-infusion, isotope-dilution method was used to investigate the interrelationships between the glucose and lactate pools of six trained sheep deprived of food overnight. Arterial plasma lactate concentration was a linear function of the net lactate entry rate as was the net production of glucose from lactate, which suggests that the net rate of formation of glucose from lactate is dependent on the availability of lactate. Similarly the arterial plasma glucose concentration was correlated with the net entry rate of glucose as was the net production rate of lactate from glucose, suggesting that the net rate of lactate production from glucose is a function of arterial plasma glucose concentration. The demonstration of these two interrelations between glucose and lactate in normal sheep suggests that, in the absence of external factors producing hormonal or other changes that could cause perturbations of carbohydrate homeostasis, the net rates of conversion of glucose to lactate and of lactate to glucose may be largely determined by the arterial concentrations of glucose and lactate, respectively.

Effects upon glucose metabolism of feeding a low-or high-roughage diet at two levels of intake to sheep

1975 ◽  
Vol 33 (1) ◽  
pp. 33-44 ◽  
Author(s):  
Essi Evans ◽  
J. G. Buchanan-Smith
Keyword(s):  
Glucose Metabolism ◽  
Half Life ◽  
Venous Blood ◽  
Specific Radioactivity ◽  
Dietary Treatment ◽  
Pool Size ◽  
Entry Rate ◽  
Soya Bean Meal ◽  
Subsequent Withdrawal ◽  
Dietary Treatments

1. To determine the effect of diet and level of energy intake on glucose metabolism in sheep, four dietary treatments consisting of feeding a low-roughage (LR) and a high-roughage (HR) diet at each of two intake levels estimated to provide 586 and 1172 kJ (140 and 280 kcal) digestible energy (DE)/kg body-weight0·75 per d were given to each of eight yearling rams in four different time periods each of 4 weeks duration. Both diets contained 140 g crude protein/ kg using ground maize, mixed hay and soya-bean meal and were given in two meals/d. Estimated DE values of food were verified during the study and actual intakes of DE were within 9·5% of the estimated values.2. To study glucose metabolism, a single intravenous injection of [2-3H]glucose and subsequent withdrawal of nine venous blood samples within 3 h were made in each experiment. Two experiments were conducted on consecutive days for each sheep on each dietary treatment.3. Coefficients of determination (r2) for linear regressions to measure the effect of time after a single injection of [2-3H]glucose on log specific radioactivity of plasma glucose were calculated for fifty-eight experiments. In fifty-six of the experiments, r2 values exceeding 0·95 were obtained.4. Compared to the HR diet, the LR diet increased (P < 0·05) the pool size and decreased (P < 0·05) the half-life of glucose. At both intake levels, the LR diet increased (P < 0·05) the plasma concentration and the entry rate of glucose compared to the HR diet but interaction (P < 0·05) between diet and intake level was attributed to a greater difference obtained between diets at the higher compared to the lower level of food intake. Increasing the level of intake caused a greater (P < 0·05) pool size and space, and a shorter (P < 0·05) half-life of glucose.5. It was concluded that substitution of roughage by concentrate in a ruminant's diet may increase the rate of glucose entry during a short time period after eating.

Acute Effects of Central Neuropeptide Y Injection on Glucose Metabolism in Fasted Rats

1995 ◽  
Vol 89 (5) ◽  
pp. 543-548 ◽  
Author(s):  
J. P. H. Wilding ◽  
Y. T. Kruszynska ◽  
P. D. Lambert ◽  
S. R. Bloom
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Glucose Metabolism ◽  
Neuropeptide Y ◽  
Plasma Glucose ◽  
Hepatic Glucose Production ◽  
Constant Infusion ◽  
Initial Increase ◽  
Acute Effects ◽  
Fasted Rats

1. Neuropeptide Y is a potent appetite stimulant and has been found to modulate glucose metabolism when given chronically. The acute effects of neuropeptide on peripheral glucose handling have not been studied in detail. We have studied the acute effects of central nervous system injection of neuropeptide on glucose metabolism in vivo in the rat. 2. Rats implanted with chronic cannulae in the third cerebral ventricle were injected with either neuropeptide Y or saline and peripheral insulin sensitivity was assessed during a hyperinsulinaemic euglycaemic clamp. The effect of centrally injected neuropeptide Y on post-absorptive glucose metabolism was studied using a constant infusion of [6-3H]glucose. 3. Infusion of neuropeptide Y resulted in a 18% increase in glucose requirement during the clamp, suggesting increased peripheral tissue responsiveness to insulin. Neuropeptide Y injection in 10 h fasted rats increased plasma glucose (area under curve 9.9 ± 0.2 versus 9.1 ± 0.1 mmol h−1 I−1, P < 0.01), insulin (103 ± 23 versus 33 ± 8 pmol/l, P < 0.01, at 30 min) and glucagon (5.5 ± 0.5 versus 3.1 ± 0.3 pmol/l, P < 0.05, at 30 min). The increase in plasma glucose was due to an initial increase in the rate of appearance, which peaked between 20 and 30 min after neuropeptide Y infusion; over the entire 90 min 16% more glucose entered the systemic circulation in the neuropeptide Y-treated rats than in control rats, and the total quantity of glucose removed was also greater. 4. Neuropeptide Y in the central nervous system influences glucose metabolism by altering secretion of islet hormones, hepatic glucose production and the peripheral response to insulin.

scholarly journals Glucose metabolism in cattle given sugar cane based diets supplemented with varying quantities of rice polishings

1979 ◽  
Vol 42 (2) ◽  
pp. 341-347 ◽  
Author(s):  
H. M. Ferreiro ◽  
A. Priego ◽  
J. Lopez ◽  
T. R. Preston ◽  
R. A. Leng
Keyword(s):  
Glucose Metabolism ◽  
Sugar Cane ◽  
Specific Radioactivity ◽  
Daily Basis ◽  
Entry Rate ◽  
Low Protein ◽  
Time Period ◽  
Limiting Nutrient ◽  
Short Time ◽  
Protein Diets

1. Glucose entry rates were measured with [2−3H]glucose in groups of cattle given sugar-cane diets and between o and 1200 g rice polishings.2. In the first experiment measurements of glucose metabolism were estimated in four animals (one of each being given 0, 400, 600 and 1000 g supplement) over 24 h using a repeated single injection at 6 h intervals and sampling blood for 3 h.3. The results indicated that in a short time period of each isotope experiment relatively steady-state conditions existed since the plot of log specific radioactivity v. time was linear with a high correlation coefficient.4. The pattern of glucose entry rates was variable over the 24 h period being highest shortly after feeding and then declining to quite low levels immediately before the next feed, 24 h later. However, the more rice polishings that were made available to the cattle, the higher the glucose entry rate at 4–7 h, and it remained higher for a longer time.5. In the second experiment with nineteen animals there was a linear relationship between the glucose entry rate (measured 4–7 h after feeding) and the amount of rice polishings consumed by the animal.6. The results suggest that glucose is being made available in quite large quantities from the supplement. Using the means of these estimates over 24 h to predict glucose entry rate on a daily basis, it is suggested that at least 50% of the starch in the rice polishings was made available to the animal as glucose.7. The results are discussed in relation to the suggestion that the availability of glucose may be limiting nutrient in cattle given low-protein diets.

The reliability of rates of glucose appearance in vivo calculated from single tracer injections

1979 ◽  
Vol 57 (11) ◽  
pp. 1267-1274 ◽  
Author(s):  
John R. Allsop ◽  
Robert R. Wolfe ◽  
Joseph J. DiStephano III ◽  
John F. Burke
Keyword(s):  
Plasma Glucose ◽  
Infusion Rate ◽  
Specific Radioactivity ◽  
Glucose Production ◽  
Endogenous Glucose Production ◽  
Constant Infusion ◽  
Glucose Turnover ◽  
Time Curve ◽  
The Mean

The rate of appearance of unlabelled glucose was calculated from changes in plasma glucose specific radioactivity after a single intravenous injection of labelled glucose and compared with the actual constant infusion rate of unlabelled glucose into an anaesthetized dog with all sources of endogenous glucose production surgically removed. The mean steady-state rate of appearance of unlabelled glucose calculated from the area under the specific radioactivity versus time curve was 7% higher than the actual infusion rate (n = 4), but the difference was not statistically significant. The variability in the rate calculated in this manner was, however, greater than the variability we have reported with rates determined from a primed constant infusion of tracer. Using 15- to 60- or 60- to 120-min specific radioactivity data the mean rate of appearance of glucose, calculated on the assumption of a one-pool model for glucose turnover in vivo, was approximately 60% higher than the actual infusion rate. The results also indicate that it is possible to construct multi-pool models, but it is difficult to equate specific physiological events with the individual terms of the multi-exponential equation which describes the changes in plasma glucose specific radioactivity.

scholarly journals Evaluation of glucose turnover, body mass and recycling with reversible and irreversible tracers

1974 ◽  
Vol 142 (1) ◽  
pp. 161-170 ◽  
Author(s):  
Joseph Katz ◽  
H. Rostami ◽  
Arnold Dunn
Keyword(s):  
Steady State ◽  
Glucose Metabolism ◽  
Single Injection ◽  
Mean Transit Time ◽  
Specific Radioactivity ◽  
Glucose Turnover ◽  
Glucose Carbon ◽  
Multicompartmental Model ◽  
Labelled Compound ◽  
Total Body

1. Methods are presented for the calculation of rates of synthesis or loss, mean transit time and total body pool of compounds from specific-radioactivity curves, without assuming a multicompartmental model and without fitting the data by exponential expressions. The methods apply to the steady state after either single injection or continuous infusion of a labelled compound. 2. The use of irreversible and reversible tracers and the effects of recycling of carbon on the estimations of the parameters of glucose metabolism are discussed. Methods for quantitatively determining recycling of glucose carbon by the use of glucose doubly labelled with 14C and 3H are presented.

Studies on the mechanism of the selective suppression of plasma levels of follicle-stimulating hormone in the female rat after administration of steroid-free bovine follicular fluid

1983 ◽  
Vol 97 (3) ◽  
pp. 327-338 ◽  
Author(s):  
W. J. de Greef ◽  
F. H. de Jong ◽  
J. de Koning ◽  
J. Steenbergen ◽  
P. D. M. van der Vaart
Keyword(s):  
Follicular Fluid ◽  
Plasma Levels ◽  
Single Injection ◽  
Constant Infusion ◽  
Metabolic Clearance ◽  
Female Rat ◽  
Clearance Rates ◽  
Lh Rh ◽  
Lh Releasing Hormone ◽  
Hypophysial Portal

Steroid-free bovine follicular fluid (bFF) selectively suppresses the plasma levels of FSH in the female rat, demonstrating that bFF contains inhibin-like material. The present study was concerned with the effects of bFF on the hypothalamic release of LH releasing hormone (LH-RH) into hypophysial stalk blood and on the metabolic clearance rates of gonadotrophins. The metabolic clearance rates of FSH, LH and prolactin were determined after a single injection of and during a constant infusion with adenohypophysial extract. Similar results were obtained with both methods, and treatment with bFF did not alter the metabolic clearance rates of FSH, LH and prolactin. Anaesthesia with urethane, used for surgery involved in the collection of hypophysial stalk blood, did not interfere with the effect of bFF on plasma levels of FSH. The administration of bFF did not change the hypothalamic content of LH-RH, but caused a 30% decrease in the levels of LH-RH in hypophysial stalk plasma. However, a fraction isolated from bFF, which contained 20 times more inhibin-like activity per mg protein than bFF, did not alter the hypothalamic release of LH-RH into the hypophysial portal blood while this fraction was effective in specifically suppressing the plasma levels of FSH. It was concluded that the inhibin-like activity in bFF does not suppress the plasma levels of FSH by affecting its plasma clearance or by influencing the hypothalamic release of LH-RH, but that it has a direct effect on the adenohypophysis in inhibiting the release of FSH. Besides the inhibin-like activity, bFF also contains another factor which can decrease the levels of LH-RH in hypophysial stalk plasma.

scholarly journals Examination of Potential Mechanisms in the Enhancement of Cerebral Blood Flow by Hypoglycemia and Pharmacological Doses of Deoxyglucose

1997 ◽  
Vol 17 (1) ◽  
pp. 54-63 ◽  
Author(s):  
Naoaki Horinaka ◽  
Nicole Artz ◽  
Jane Jehle ◽  
Shinichi Takahashi ◽  
Charles Kennedy ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Glucose Metabolism ◽  
Plasma Glucose ◽  
Plasma Lactate ◽  
Insulin Hypoglycemia ◽  
Glucose Levels ◽  
Arterial Blood ◽  
Arterial Plasma

Cerebral blood flow (CBF) rises when the glucose supply to the brain is limited by hypoglycemia or glucose metabolism is inhibited by pharmacological doses of 2-deoxyglucose (DG). The present studies in unanesthetized rats with insulin-induced hypoglycemia show that the increases in CBF, measured with the [14C]iodoantipyrine method, are relatively small until arterial plasma glucose levels fall to 2.5 to 3.0 m M, at which point CBF rises sharply. A direct effect of insulin on CBF was excluded; insulin administered under euglycemic conditions maintained by glucose injections had no effects on CBF. Insulin administration raised plasma lactate levels and decreased plasma K+ and HCO3– concentrations and arterial pH. These could not, however, be related to the increased CBF because insulin under euglycemic conditions had similar effects without affecting CBF; furthermore, the inhibition of brain glucose metabolism with pharmacological doses (200 mg/kg intravenously) of DG increased CBF, just like insulin hypoglycemia, without altering plasma lactate and K+ levels and arterial blood gas tensions and pH. Nitric oxide also does not appear to mediate the increases in CBF. Chronic blockade of nitric oxide synthase activity by twice daily i.p. injections of NG-nitro-L-arginine methyl ester for 4 days or acutely by a single i.v. injection raised arterial blood pressure and lowered CBF in normoglycemic, hypoglycemic, and DG-treated rats but did not significantly reduce the increases in CBF due to insulin-induced hypoglycemia (arterial plasma glucose levels, 2.5-3 m M) or pharmacological doses of deoxyglucose.

Effects of oral administration of polystyrene nanoplastics on plasma glucose metabolism in mice

Chemosphere ◽  
2021 ◽  
pp. 132607
Author(s):  
Xingpei Fan ◽  
Xiangjuan Wei ◽  
Hailong Hu ◽  
Boya Zhang ◽  
Daqian Yang ◽  
...  
Keyword(s):  
Glucose Metabolism ◽  
Oral Administration ◽  
Plasma Glucose
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