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Marianne Fillenz - One of the best experts on this subject based on the ideXlab platform.
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Extracellular brain Glucose levels reflect local neuronal activity a microdialysis study in awake freely moving rats
Journal of Neurochemistry, 2006Co-Authors: Lesley K. Fellows, M.g. Boutelle, Marianne FillenzAbstract:: The relationship between brain Extracellular Glucose levels and neuronal activity was evaluated using microdialysis in awake, freely moving rats. The sodium channel blocker tetrodotoxin and the depolarizing agent veratridine were administered through the dialysis probe to provoke local changes in neuronal activity. The Extracellular Glucose content was significantly increased in the presence of tetrodotoxin and decreased sharply following veratridine application. The systemic injection of a general anaesthetic, chloral hydrate, led to a large and prolonged increase in Extracellular Glucose levels. The brain Extracellular Glucose concentration was estimated by comparing dialysate Glucose efflux over a range of inlet Glucose concentrations. A mean value of 0.47 mM was obtained in five animals. The results are discussed in terms of the coupling between brain Glucose supply and metabolism. The changes observed in Extracellular Glucose levels under various conditions suggest that supply and utilization may be less tightly linked in the awake rat than has previously been postulated.
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continuous monitoring of Extracellular Glucose concentrations in the striatum of freely moving rats with an implanted Glucose biosensor
Journal of Neurochemistry, 2002Co-Authors: John P Lowry, M.g. Boutelle, Robert D Oneill, Marianne FillenzAbstract:Abstract: We have used a Glucose oxidase-based sensor implanted in the striatum of freely moving rats to determine the concentration of Extracellular Glucose in two distinct ways. With a modification of the zero net flux method, in which different concentrations of Glucose are infused through a dialysis probe glued to the biosensor, we calculated the concentration at which there was no change in Glucose current by regression analysis; this gave a concentration of 0.351 ± 0.016 mM. Calculating the concentration from the basal current and the in vitro calibration of the biosensor was not significantly different from this. The basal Extracellular Glucose concentration determined by either method remained constant over a period of several days. Infusion of 50 µM veratridine through the adjacent dialysis probe caused a steep decrease in Glucose current as soon as the drug reached the brain in contrast to the delayed fall (7.5 min) seen with microdialysis in previous experiments from this laboratory. These results demonstrate that this biosensor provides a direct, real-time measure of the Extracellular concentration of Glucose.
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Real-time monitoring of brain energy metabolism in vivo using microelectrochemical sensors: the effects of anesthesia.
Bioelectrochemistry, 2001Co-Authors: John P Lowry, Marianne FillenzAbstract:Rats were implanted in the striatum with a Pt/Ir electrode for measurement of regional cerebral blood flow (rCBF) (H2 clearance technique), a carbon paste electrode for monitoring tissue oxygen and a Glucose biosensor for monitoring Extracellular Glucose. Changes in all three parameters were recorded in response to the intraperitoneal (i.p.) administration of the anesthetics chloral hydrate (350 mg/kg), sodium pentobarbitone (60 mg/kg) and ketamine (200 mg/kg). An i.p. injection of normal saline, given as a control for the injection of the anesthetics, produced a parallel increase in rCBF and tissue oxygen accompanied by a brief decrease in Extracellular Glucose. Changes in tissue oxygen reflected the changes in rCBF; there was a decrease in both after sodium pentobarbitone, a decrease followed by a rebound after ketamine and a transient increase after chloral hydrate. All three anesthetics produced a decrease in Extracellular Glucose. The disparity between the changes in Glucose and the changes in rCBF and oxygen suggests that during anesthesia, the reduction in Extracellular Glucose is not due to a reduction in the direct delivery of Glucose from the blood vascular system. These results also indicate that levels of enzymatic substrates and mediators, which are intrinsic to the design and operation of amperometric biosensors, are clearly altered in a complex manner by anesthesia and suggest that caution should be exercised in extrapolating data from acute anesthetized experiments to normal physiology.
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Real-time monitoring of brain energy metabolism in vivo using microelectrochemical sensors: The effects of anesthesia
Bioelectrochemistry, 2001Co-Authors: John P Lowry, Marianne FillenzAbstract:Rats were implanted in the striatum with a Pt/Ir electrode for measurement of regional cerebral blood flow (rCBF) (H2clearance technique), a carbon paste electrode for monitoring tissue oxygen and a Glucose biosensor for monitoring Extracellular Glucose. Changes in all three parameters were recorded in response to the intraperitoneal (i.p.) administration of the anesthetics chloral hydrate (350 mg/kg), sodium pentobarbitone (60 mg/kg) and ketamine (200 mg/kg). An i.p. injection of normal saline, given as a control for the injection of the anesthetics, produced a parallel increase in rCBF and tissue oxygen accompanied by a brief decrease in Extracellular Glucose. Changes in tissue oxygen reflected the changes in rCBF; there was a decrease in both after sodium pentobarbitone, a decrease followed by a rebound after ketamine and a transient increase after chloral hydrate. All three anesthetics produced a decrease in Extracellular Glucose. The disparity between the changes in Glucose and the changes in rCBF and oxygen suggests that during anesthesia, the reduction in Extracellular Glucose is not due to a reduction in the direct delivery of Glucose from the blood vascular system. These results also indicate that levels of enzymatic substrates and mediators, which are intrinsic to the design and operation of amperometric biosensors, are clearly altered in a complex manner by anesthesia and suggest that caution should be exercised in extrapolating data from acute anesthetized experiments to normal physiology. © 2001 Elsevier Science B.V. All rights reserved.
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The relation between local cerebral blood flow and Extracellular Glucose concentration in rat striatum.
Experimental Physiology, 1998Co-Authors: Marianne Fillenz, John P LowryAbstract:The effect of anaesthetics on the relation between local cerebral blood flow (rCBF) and Extracellular Glucose was studied in rat striatum. Cerebral blood flow was measured using the hydrogen clearance method and Extracellular Glucose using an implanted Glucose oxidase-based biosensor. Rats were given an intraperitoneal (i.p.) injection of either sodium pentobarbitone (60 mg kg-1) or chloral hydrate (350 mg kg-1). The effect of the i.p. injection, as demonstrated by an i.p. saline injection, was a brief increase in rCBF accompanied by a decrease in Glucose. Sodium pentobarbitone produced a decrease in both rCBF and Glucose, whereas chloral hydrate caused a decrease in Glucose but an increase in rCBF. These findings show a dissociation between rCBF and Extracellular Glucose and suggest that Glucose in the Extracellular compartment is not derived directly from the blood vascular compartment.
David A. Hovda - One of the best experts on this subject based on the ideXlab platform.
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Intensive insulin therapy is associated with reduced Extracellular Glucose and increased oxygen extraction fraction after severe traumatic brain injury
Journal of Cerebral Blood Flow and Metabolism, 2005Co-Authors: Paul M. Vespa, Marvin Bergsneider, David L. Mcarthur, Hsiao-ming Wu, S.-c. Huang, Jeffry R. Alger, Thomas C. Glenn, David A. HovdaAbstract:Intensive Insulin Therapy is Associated with Reduced Extracellular Glucose and Increased Oxygen Extraction Fraction after Severe Traumatic Brain Injury
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persistently low Extracellular Glucose correlates with poor outcome 6 months after human traumatic brain injury despite a lack of increased lactate a microdialysis study
Journal of Cerebral Blood Flow and Metabolism, 2003Co-Authors: Paul M. Vespa, Marvin Bergsneider, David L. Mcarthur, Thomas C. Glenn, Kristine Ophelan, Maria Etchepare, Daniel F Kelly, Neil A Martin, David A. HovdaAbstract:Disturbed Glucose brain metabolism after brain trauma is reflected by changes in Extracellular Glucose levels. The authors hypothesized that posttraumatic reductions in Extracellular Glucose levels are not due to ischemia and are associated with poor outcome. Intracerebral microdialysis, electroencephalography, and measurements of brain tissue oxygen levels and jugular venous oxygen saturation were performed in 30 patients with traumatic brain injury. Levels of Glucose, lactate, pyruvate, glutamate, and urea were analyzed hourly. The 6-month Glasgow Outcome Scale extended (GOSe6) score was assessed for each patient. In regions of increased Glucose utilization defined by positron emission tomography, the Extracellular Glucose concentration was less than 0.2 mmol/l. Extracellular Glucose values were less than 0.2 mmol during postinjury days 0 to 7 in 19% to 30% of hourly samples on each day. Transient decreases in Glucose levels occurred with electrographic seizures and nonischemic reductions in cerebral perfusion pressure and jugular venous oxygen saturation. Glutamate levels were elevated in the majority of low-Glucose samples, but the lactate/pyruvate ratio did not indicate focal ischemia. Terminal herniation resulted in reductions in Glucose with increases in the lactate/pyruvate ratio but not in lactate concentration alone. GOSe6 scores correlated with persistently low Glucose levels, combined early low Glucose levels and low lactate/Glucose ratio, and with the overall lactate/Glucose ratio. These results suggest that the level of Extracellular Glucose is typically reduced after traumatic brain injury and associated with poor outcome, but is not associated with ischemia.
Connie E Short - One of the best experts on this subject based on the ideXlab platform.
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Low levels of Extracellular Glucose limit cardiac anaerobic metabolism in some species of fish.
The Journal of Experimental Biology, 2017Co-Authors: Kathy A Clow, Connie E Short, William R DriedzicAbstract:ABSTRACT There is a wide interspecific range in plasma Glucose levels in teleosts from less than 0.5 to greater than 10 mmol l −1 . Here we assessed how Glucose availability influences Glucose metabolism in hearts of Atlantic cod ( Gadus morhua ), rainbow trout ( Oncorhynchus mykiss ), lumpfish ( Cyclopterus lumpus ) and short-horned sculpin ( Myoxocephalus scorpius ) under normoxic and hypoxic conditions. These species had plasma Glucose levels of 5.1, 4.8, 0.9 and 0.5 mmol l −1 , respectively. Rates of Glucose metabolism and lactate production were determined in isolated hearts perfused with medium containing physiological levels of Glucose. Under normoxic conditions there was no significant difference in rates of either Glucose metabolism (average 15 nmol g −1 min −1 ) or lactate production (average 30 nmol g −1 min −1 ) across species. Under hypoxia (12% of air saturation) there were significant increases in rates of Glucose metabolism and lactate production in hearts from Atlantic cod (Glucose-130; lactate-663 nmol g −1 min −1 ) and rainbow trout (Glucose-103; lactate-774 nmol g −1 min −1 ); however, there was no change in rate of Glucose metabolism in hearts from either lumpfish or short-horned sculpin and only increases in lactate production to rates much lower than the other species. Furthermore, Atlantic cod hearts perfused with medium containing low non-physiological levels of Glucose (0.5 mmol l −1 ) had the same rates of Glucose metabolism under normoxic and hypoxic treatments. Anaerobic metabolism supported by Extracellular Glucose is compromised in fish with low levels of plasma Glucose, which in turn may decrease performance under oxygen-limiting conditions at the whole-animal level.
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Extracellular Glucose supports lactate production but not aerobic metabolism in cardiomyocytes from both normoglycemic Atlantic cod and low glycemic short-horned sculpin.
The Journal of Experimental Biology, 2016Co-Authors: Kathy A Clow, Connie E Short, William R DriedzicAbstract:ABSTRACT Fish exhibit a wide range of species-specific blood Glucose levels. How this relates to Glucose utilization is yet to be fully realized. Here, we assessed Glucose transport and metabolism in myocytes isolated from Atlantic cod ( Gadus morhua ) and short-horned sculpin ( Myoxocephalus scorpius ), species with blood Glucose levels of 3.7 and 0.57 mmol l −1 , respectively. Glucose metabolism was assessed by the production of 3 H 2 O from [2- 3 H]Glucose. Glucose metabolism was 3.5- to 6-fold higher by myocytes from Atlantic cod than by those from short-horned sculpin at the same level of Extracellular Glucose. In Atlantic cod myocytes, Glucose metabolism displayed what appears to be a saturable component with respect to Extracellular Glucose, and cytochalasin B inhibited Glucose metabolism. These features revealed a facilitated Glucose diffusion mechanism that accounts for between 30% and 55% of Glucose entry at physiological levels of Extracellular Glucose. Facilitated Glucose diffusion appears to be minimal in myocytes for short-horned sculpin. Glucose entry by simple diffusion occurs in both cell types with the same linear relationship between Glucose metabolism and Extracellular Glucose concentration, presumably due to similarities in membrane composition. Oxygen consumption by myocytes incubated in medium containing physiological levels of Extracellular Glucose (Atlantic cod 5 mmol l −1 , short-horned sculpin 0.5 mmol l −1 ) was similar in the two species and was not decreased by cytochalasin B, suggesting that these cells have the capability of oxidizing alternative on-board metabolic fuels. Cells produced lactate at low rates but glycogen levels did not change during the incubation period. In cells from both species, Glucose utilization assessed by both simple chemical analysis of Glucose disappearance from the medium and 3 H 2 O production was half the rate of lactate production and as such Extracellular Glucose was not available for oxidative metabolism. Overall, Extracellular Glucose makes only a minor contribution to ATP production but a sustained glycolysis may be necessary to support Ca 2+ transport mechanisms at either the sarcoplasmic reticulum or the sarcolemmal membrane.
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Extracellular Glucose can fuel metabolism in red blood cells from high glycemic Atlantic cod (Gadus morhua) but not low glycemic short-horned sculpin (Myoxocephalus scorpius).
The Journal of experimental biology, 2014Co-Authors: William R Driedzic, Kathy A Clow, Connie E ShortAbstract:Energy metabolism was assessed in red blood cells (RBCs) from Atlantic cod and short-horned sculpin, two species that have markedly different levels of blood Glucose. The objective was to determine whether the level of Extracellular Glucose has an impact on rates of Glucose metabolism. The blood Glucose level was 2.5 mmol l(-1) in Atlantic cod and 0.2 mmol l(-1) in short-horned sculpin, respectively. Oxygen consumption, lactate production and Glucose utilization were measured in whole blood and related to grams of RBCs. Glucose utilization was assessed by measuring both Glucose disappearance and the production of (3)H2O from [2-(3)H]-Glucose. RBCs from both species have an aerobic-based metabolism. In Atlantic cod, Extracellular Glucose is sufficient to provide the sum of glucosyl equivalents to support both oxidative metabolism and lactate production. In contrast, Extracellular Glucose can account for only 10% of the metabolic rate in short-horned sculpin RBCs. In both species, about 70% of Glucose enters the RBCs via facilitated transport. The difference in rates of Extracellular Glucose utilization is related to the extremely low levels of blood Glucose in short-horned sculpin. In this species energy metabolism by RBCs must be supported by alternative fuels.
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Glucose uptake and metabolism by red blood cells from fish with different Extracellular Glucose levels
The Journal of Experimental Biology, 2013Co-Authors: William R Driedzic, Kathy A Clow, Connie E ShortAbstract:SUMMARY The aim of the present study was to assess whether mechanisms of Glucose trafficking by red blood cells (RBCs) relate to species-specific Extracellular Glucose levels. Atlantic cod ( Gadus morhua ), Atlantic salmon ( Salmo salar ), cunner ( Tautogolabrus adspersus ) and short-horned sculpin ( Myoxocephalus scorpius ) had plasma Glucose levels of 4, 4.1, 1.95 and 0.73 mmol l −1 , respectively. Glucose uptake by isolated RBCs was measured by the initial incorporation of [6- 14 C]-Glucose and steady-state Glucose metabolism was determined by the production of 3 H 2 O from [2- 3 H]-Glucose. Saturation kinetics of Glucose uptake and inhibition of both Glucose uptake and metabolism by cytochalasin B and phloretin revealed that Atlantic cod, cunner and sculpin RBCs all had a facilitated transport component to Glucose trafficking. RBCs from Atlantic salmon showed a linear relationship between Glucose uptake and Extracellular Glucose level, but exhibited clear inhibition of Glucose metabolism by cytochalasin B and phloretin, suggesting a component of facilitated Glucose transport that is more elusive to detect. The production of 3 H 2 O was linear for at least 6 h and as such presents a rigorous approach to measuring glycolytic rate. Steady-state rates of Glucose metabolism were achieved at Extracellular levels of approximately 1 mmol l −1 Glucose for RBCs from all species, showing that within-species normal Extracellular Glucose level is not a primary determinant of the basal level of glycolysis. At physiological levels of Extracellular Glucose, the ratio of initial Glucose uptake to Glucose metabolism was 1.5 to 4 for all RBCs, suggesting that there is scope to increase metabolic rate without alteration of the basal Glucose uptake capacity.
William R Driedzic - One of the best experts on this subject based on the ideXlab platform.
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Low levels of Extracellular Glucose limit cardiac anaerobic metabolism in some species of fish.
The Journal of Experimental Biology, 2017Co-Authors: Kathy A Clow, Connie E Short, William R DriedzicAbstract:ABSTRACT There is a wide interspecific range in plasma Glucose levels in teleosts from less than 0.5 to greater than 10 mmol l −1 . Here we assessed how Glucose availability influences Glucose metabolism in hearts of Atlantic cod ( Gadus morhua ), rainbow trout ( Oncorhynchus mykiss ), lumpfish ( Cyclopterus lumpus ) and short-horned sculpin ( Myoxocephalus scorpius ) under normoxic and hypoxic conditions. These species had plasma Glucose levels of 5.1, 4.8, 0.9 and 0.5 mmol l −1 , respectively. Rates of Glucose metabolism and lactate production were determined in isolated hearts perfused with medium containing physiological levels of Glucose. Under normoxic conditions there was no significant difference in rates of either Glucose metabolism (average 15 nmol g −1 min −1 ) or lactate production (average 30 nmol g −1 min −1 ) across species. Under hypoxia (12% of air saturation) there were significant increases in rates of Glucose metabolism and lactate production in hearts from Atlantic cod (Glucose-130; lactate-663 nmol g −1 min −1 ) and rainbow trout (Glucose-103; lactate-774 nmol g −1 min −1 ); however, there was no change in rate of Glucose metabolism in hearts from either lumpfish or short-horned sculpin and only increases in lactate production to rates much lower than the other species. Furthermore, Atlantic cod hearts perfused with medium containing low non-physiological levels of Glucose (0.5 mmol l −1 ) had the same rates of Glucose metabolism under normoxic and hypoxic treatments. Anaerobic metabolism supported by Extracellular Glucose is compromised in fish with low levels of plasma Glucose, which in turn may decrease performance under oxygen-limiting conditions at the whole-animal level.
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Extracellular Glucose supports lactate production but not aerobic metabolism in cardiomyocytes from both normoglycemic Atlantic cod and low glycemic short-horned sculpin.
The Journal of Experimental Biology, 2016Co-Authors: Kathy A Clow, Connie E Short, William R DriedzicAbstract:ABSTRACT Fish exhibit a wide range of species-specific blood Glucose levels. How this relates to Glucose utilization is yet to be fully realized. Here, we assessed Glucose transport and metabolism in myocytes isolated from Atlantic cod ( Gadus morhua ) and short-horned sculpin ( Myoxocephalus scorpius ), species with blood Glucose levels of 3.7 and 0.57 mmol l −1 , respectively. Glucose metabolism was assessed by the production of 3 H 2 O from [2- 3 H]Glucose. Glucose metabolism was 3.5- to 6-fold higher by myocytes from Atlantic cod than by those from short-horned sculpin at the same level of Extracellular Glucose. In Atlantic cod myocytes, Glucose metabolism displayed what appears to be a saturable component with respect to Extracellular Glucose, and cytochalasin B inhibited Glucose metabolism. These features revealed a facilitated Glucose diffusion mechanism that accounts for between 30% and 55% of Glucose entry at physiological levels of Extracellular Glucose. Facilitated Glucose diffusion appears to be minimal in myocytes for short-horned sculpin. Glucose entry by simple diffusion occurs in both cell types with the same linear relationship between Glucose metabolism and Extracellular Glucose concentration, presumably due to similarities in membrane composition. Oxygen consumption by myocytes incubated in medium containing physiological levels of Extracellular Glucose (Atlantic cod 5 mmol l −1 , short-horned sculpin 0.5 mmol l −1 ) was similar in the two species and was not decreased by cytochalasin B, suggesting that these cells have the capability of oxidizing alternative on-board metabolic fuels. Cells produced lactate at low rates but glycogen levels did not change during the incubation period. In cells from both species, Glucose utilization assessed by both simple chemical analysis of Glucose disappearance from the medium and 3 H 2 O production was half the rate of lactate production and as such Extracellular Glucose was not available for oxidative metabolism. Overall, Extracellular Glucose makes only a minor contribution to ATP production but a sustained glycolysis may be necessary to support Ca 2+ transport mechanisms at either the sarcoplasmic reticulum or the sarcolemmal membrane.
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Extracellular Glucose can fuel metabolism in red blood cells from high glycemic Atlantic cod (Gadus morhua) but not low glycemic short-horned sculpin (Myoxocephalus scorpius).
The Journal of experimental biology, 2014Co-Authors: William R Driedzic, Kathy A Clow, Connie E ShortAbstract:Energy metabolism was assessed in red blood cells (RBCs) from Atlantic cod and short-horned sculpin, two species that have markedly different levels of blood Glucose. The objective was to determine whether the level of Extracellular Glucose has an impact on rates of Glucose metabolism. The blood Glucose level was 2.5 mmol l(-1) in Atlantic cod and 0.2 mmol l(-1) in short-horned sculpin, respectively. Oxygen consumption, lactate production and Glucose utilization were measured in whole blood and related to grams of RBCs. Glucose utilization was assessed by measuring both Glucose disappearance and the production of (3)H2O from [2-(3)H]-Glucose. RBCs from both species have an aerobic-based metabolism. In Atlantic cod, Extracellular Glucose is sufficient to provide the sum of glucosyl equivalents to support both oxidative metabolism and lactate production. In contrast, Extracellular Glucose can account for only 10% of the metabolic rate in short-horned sculpin RBCs. In both species, about 70% of Glucose enters the RBCs via facilitated transport. The difference in rates of Extracellular Glucose utilization is related to the extremely low levels of blood Glucose in short-horned sculpin. In this species energy metabolism by RBCs must be supported by alternative fuels.
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Glucose uptake and metabolism by red blood cells from fish with different Extracellular Glucose levels
The Journal of Experimental Biology, 2013Co-Authors: William R Driedzic, Kathy A Clow, Connie E ShortAbstract:SUMMARY The aim of the present study was to assess whether mechanisms of Glucose trafficking by red blood cells (RBCs) relate to species-specific Extracellular Glucose levels. Atlantic cod ( Gadus morhua ), Atlantic salmon ( Salmo salar ), cunner ( Tautogolabrus adspersus ) and short-horned sculpin ( Myoxocephalus scorpius ) had plasma Glucose levels of 4, 4.1, 1.95 and 0.73 mmol l −1 , respectively. Glucose uptake by isolated RBCs was measured by the initial incorporation of [6- 14 C]-Glucose and steady-state Glucose metabolism was determined by the production of 3 H 2 O from [2- 3 H]-Glucose. Saturation kinetics of Glucose uptake and inhibition of both Glucose uptake and metabolism by cytochalasin B and phloretin revealed that Atlantic cod, cunner and sculpin RBCs all had a facilitated transport component to Glucose trafficking. RBCs from Atlantic salmon showed a linear relationship between Glucose uptake and Extracellular Glucose level, but exhibited clear inhibition of Glucose metabolism by cytochalasin B and phloretin, suggesting a component of facilitated Glucose transport that is more elusive to detect. The production of 3 H 2 O was linear for at least 6 h and as such presents a rigorous approach to measuring glycolytic rate. Steady-state rates of Glucose metabolism were achieved at Extracellular levels of approximately 1 mmol l −1 Glucose for RBCs from all species, showing that within-species normal Extracellular Glucose level is not a primary determinant of the basal level of glycolysis. At physiological levels of Extracellular Glucose, the ratio of initial Glucose uptake to Glucose metabolism was 1.5 to 4 for all RBCs, suggesting that there is scope to increase metabolic rate without alteration of the basal Glucose uptake capacity.
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Anoxic performance of the american eel (Anguilla rostrata L.) heart requires Extracellular Glucose.
Journal of Experimental Zoology, 2000Co-Authors: John R. Bailey, Kenneth J. Rodnick, Robert Macdougall, Seana Clowe, William R DriedzicAbstract:The importance of Extracellular Glucose in the maintenance of performance of the heart of the American eel (Anguilla rostrata Le Sueur (L.) Under anoxia was assessed under a variety of experimental conditions. Ventricular strips, electrically paced at 36 bpm, in N2-gassed medium maintained the imposed pace rate and generated approximately 25% of the initial twitch force of contraction for at least 60 min when Glucose was present in the medium. But ventricular strips challenged without Glucose in the medium failed to maintain the pacing rate within 5–10 min. Isolated and intact, perfused hearts maintained pressure and followed an imposed pace rate of 24 bpm for at least 2 hr, under anoxic conditions, if Glucose was present in the medium. But without Glucose in the medium isolated hearts failed within 30 min. Endogenous glycogen stores were utilized in hearts perfused with medium containing NaCN to impair oxidative phosphorylation. The presence of Glucose in the medium did not protect against glycogen mobilization. The data indicate that exogenous Glucose is necessary to maintain performance under anoxia at high workloads and physiological Ca2+ levels. Finally, ventricular strips treated with NaCN and forced to contract at 24 bpm lost 70% of initial twitch force. Increasing Extracellular Ca2+ concentration stepwise from 1.5 to 9.5 mM restored twitch force to approximately 50% of the initial level and this response was not dependent on exogenous Glucose. However, Glucose was required to maintain resting tension even under normoxic conditions in the face of a Ca2+ challenge. J. Exp. Zool. 286:699–706, 2000. © 2000 Wiley-Liss, Inc.
Paul M. Vespa - One of the best experts on this subject based on the ideXlab platform.
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Intensive insulin therapy is associated with reduced Extracellular Glucose and increased oxygen extraction fraction after severe traumatic brain injury
Journal of Cerebral Blood Flow and Metabolism, 2005Co-Authors: Paul M. Vespa, Marvin Bergsneider, David L. Mcarthur, Hsiao-ming Wu, S.-c. Huang, Jeffry R. Alger, Thomas C. Glenn, David A. HovdaAbstract:Intensive Insulin Therapy is Associated with Reduced Extracellular Glucose and Increased Oxygen Extraction Fraction after Severe Traumatic Brain Injury
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persistently low Extracellular Glucose correlates with poor outcome 6 months after human traumatic brain injury despite a lack of increased lactate a microdialysis study
Journal of Cerebral Blood Flow and Metabolism, 2003Co-Authors: Paul M. Vespa, Marvin Bergsneider, David L. Mcarthur, Thomas C. Glenn, Kristine Ophelan, Maria Etchepare, Daniel F Kelly, Neil A Martin, David A. HovdaAbstract:Disturbed Glucose brain metabolism after brain trauma is reflected by changes in Extracellular Glucose levels. The authors hypothesized that posttraumatic reductions in Extracellular Glucose levels are not due to ischemia and are associated with poor outcome. Intracerebral microdialysis, electroencephalography, and measurements of brain tissue oxygen levels and jugular venous oxygen saturation were performed in 30 patients with traumatic brain injury. Levels of Glucose, lactate, pyruvate, glutamate, and urea were analyzed hourly. The 6-month Glasgow Outcome Scale extended (GOSe6) score was assessed for each patient. In regions of increased Glucose utilization defined by positron emission tomography, the Extracellular Glucose concentration was less than 0.2 mmol/l. Extracellular Glucose values were less than 0.2 mmol during postinjury days 0 to 7 in 19% to 30% of hourly samples on each day. Transient decreases in Glucose levels occurred with electrographic seizures and nonischemic reductions in cerebral perfusion pressure and jugular venous oxygen saturation. Glutamate levels were elevated in the majority of low-Glucose samples, but the lactate/pyruvate ratio did not indicate focal ischemia. Terminal herniation resulted in reductions in Glucose with increases in the lactate/pyruvate ratio but not in lactate concentration alone. GOSe6 scores correlated with persistently low Glucose levels, combined early low Glucose levels and low lactate/Glucose ratio, and with the overall lactate/Glucose ratio. These results suggest that the level of Extracellular Glucose is typically reduced after traumatic brain injury and associated with poor outcome, but is not associated with ischemia.
