scholarly journals Long-term maintenance of low concentrations of fructose for the study of hepatic glucose phosphorylation

1999 ◽  
Vol 337 (3) ◽  
pp. 497-501 ◽  
Author(s):  
John W. PHILLIPS ◽  
Debra C. HENLY ◽  
Michael N. BERRY
Keyword(s):  
Isolated Hepatocytes ◽  
Maximal Rate ◽  
Prolonged Incubation ◽  
Low Concentrations ◽  
Hepatic Glucose ◽  
Incubation Periods ◽  
Glucose Phosphorylation ◽  
Term Maintenance ◽  
Stimulation Of

The stimulation of glucose phosphorylation in isolated hepatocytes by low fructose concentrations is transient due to the rapid metabolism of fructose. To prolong this stimulatory effect fructose was enzymically generated in the incubation medium from either sucrose with invertase or inulin with inulinase. A maximal rate of glucose phosphorylation was achieved when fructose was formed at at least 0.01 µmol/min, which maintained a concentration of 70 µM fructose in the medium. In the presence of a fructose concentration of 70 µM, the rate of phosphorylation with 5 mM glucose was doubled and remained constant over a 2.5 h period. Under these conditions the rate of glycolysis was increased more than 3-fold. The stimulation of flux through glucokinase by low concentrations of fructose decreased the proportion of glucose phosphorylated, which was cycled between glucose and glucose 6-phosphate, and increased the proportion that was glycolysed. The method described for maintaining the stimulation of glucose phosphorylation by isolated hepatocytes over prolonged incubation periods is especially suited to the further study of the control of glucokinase activity, in particular how the variation of flux through glucokinase affects the flux through all the pathways that utilize the product, glucose 6-phosphate.

scholarly journals Prostaglandins E2 and F2α increase fructose 2,6-bisphosphate levels in isolated hepatocytes

1991 ◽  
Vol 274 (1) ◽  
pp. 309-312 ◽  
Author(s):  
A M Gómez-Foix ◽  
J E Rodríguez-Gil ◽  
J J Guinovart ◽  
F Bosch
Keyword(s):  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Glycolytic Flux ◽  
Dependent Manner ◽  
Hepatic Glucose Metabolism ◽  
Prostaglandin F2 Alpha ◽  
Hepatic Glucose ◽  
Dose Dependent ◽  
Prostaglandins E2 And F2α ◽  
Stimulation Of

In hepatocytes isolated from fed rats, prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) increased, in a time- and dose-dependent manner, fructose 2,6-bisphosphate [Fru(2,6)P2] levels and stimulated the glycolytic flux. The rise in Fru(2,6)P2 was related to an increase in glucose 6-phosphate levels which resulted from the stimulation of glycogenolysis. In cells obtained from 24 h-starved rats, no effects of either PGE2 or PGF2 alpha could be observed. In addition, when the stimulation of glycogenolysis was abolished by incubation of fed-rat hepatocytes in a Ca2(+)-depleted medium, Fru(2,6)P2 levels did not increase. Furthermore, no effects of PGs on 6-phosphofructo-2-kinase activity could be observed. These results indicate that PGE2 and PGF2 alpha show similar actions to Ca2(+)-dependent hormones on hepatic glucose metabolism.

scholarly journals A novel Ca2+ indicator for long-term tracking of intracellular calcium flux

BioTechniques ◽  
2021 ◽  
Author(s):  
Jinfang Liao ◽  
Deven Patel ◽  
Qin Zhao ◽  
Ruogu Peng ◽  
Haitao Guo ◽  
...  
Keyword(s):  
Organic Anion ◽  
Organic Anion Transporter ◽  
Calcium Flux ◽  
Major Drawback ◽  
Prolonged Incubation ◽  
Anion Transporter ◽  
Incubation Periods ◽  
Time Required ◽  
Intracellular Calcium Flux

The major drawback of using Fluo-4 AM is that it requires an organic anion transporter inhibitor, such as probenecid, to prevent leakage. This can hinder the studies that require extended monitoring time and longer cellular retention. To address the issue, a novel Ca2+ indicator, Calbryte 520 AM, was developed. We compared the performance of Fluo-4 AM and Calbryte 520 AM following prolonged incubation periods after cell loading. Cells loaded with Calbryte 520 AM retained the dye for up to 24 h while exhibiting significant fluorescence brightness and superior Fmax/F0 ratios (Fmax: fluorescence intensity upon stimulation; F0: intensity before stimulation). It demonstrated that the longer retention of Calbryte 520 AM can be exploited to accommodate for the extended time required when monitoring calcium dynamics.

scholarly journals Uptake and metabolism of propionate in the liver isolated from sheep treated with glucagon

1997 ◽  
Vol 77 (5) ◽  
pp. 783-793 ◽  
Author(s):  
Abdulhamid Mohamed Ali ◽  
Markandeya Jois
Keyword(s):  
Jugular Vein ◽  
Isolated Hepatocytes ◽  
Maximal Rate ◽  
Caudal Lobe ◽  
Sterile Saline ◽  
Sheep Liver ◽  
Net Uptake ◽  
Perfusion Experiment ◽  
Uptake And Metabolism ◽  
Stimulation Of

The uptake and metabolism of propionate in the isolated perfused caudal lobe of the liver and in isolated hepatocytes were examined following treatment of sheep with glucagon or saline. Glucagon or sterile saline was infused at 9·8 µg/min for 3 h into the jugular vein and then the caudal lobe of the liver was removed surgically under anaesthesia. The caudal lobe was used either to prepare hepatocytes or in a non-recirculating perfusion experiment. Uptake and metabolism of propionate were studied using [2-14C]propionate. In studies using the non-recirculation perfusion of the caudal lobe of the sheep liver it was shown that the treatment of sheep with glucagon resulted in an increased rate of gluconeogenesis from propionate and in an increased net uptake of propionate by the caudal lobe. The uptake of propionate into the hepatocytes was saturable, concentrative and exhibited a Km for propionate of 0·24 (SE 0·07) mM and a maximal rate of uptake (Vmax) of 6·7 (SE 0·6) nmol/mg dry cells per min and was unaffected by glucagon treatment of sheep. After incubation of cells in medium containing 0·5 mM-[2-14C]propionate for 10 min, the rate of gluconeogenesis from propionate was 22 % higher in the hepatocytes isolated from glucagon-treated sheep. Concentrations in the medium of 1·35 mM butyrate and 1 mM-caproate inhibited propionate uptake by about 50 % and abolished the glucagon-induced stimulation of gluconeogenesis from propionate. The results are consistent with a regulatory role for glucagon in the gluconeogenesis from propionate in the sheep liver.

scholarly journals Direct evidence for antipseudomonal activity of macrolides: exposure-dependent bactericidal activity and inhibition of protein synthesis by erythromycin, clarithromycin, and azithromycin.

1996 ◽  
Vol 40 (10) ◽  
pp. 2271-2275 ◽  
Author(s):  
K Tateda ◽  
Y Ishii ◽  
T Matsumoto ◽  
N Furuya ◽  
M Nagashima ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Bactericidal Activity ◽  
Direct Evidence ◽  
Dependent Manner ◽  
Intracellular Accumulation ◽  
Prolonged Incubation ◽  
Incubation Periods ◽  
Inhibition Of Protein Synthesis ◽  
Term Administration

Several previous investigators have reported that long-term administration of certain macrolides is efficacious in patients with persistent pulmonary Pseudomonas aeruginosa infections, even though the clinically achievable concentrations of these medications are far below their MICs. In the present study, we examined how sub-MICs of macrolide antibiotics affect the viability of and protein synthesis in several strains of P. aeruginosa. We report that 48 h, but not 12 or 24 h, of growth on agar containing a clinically achievable concentration of azithromycin (0.5 microgram/ml, 1/128 the MIC) significantly reduces the viability of strain PAO-1. Similar effects were seen with erythromycin and clarithromycin at 2 micrograms/ml (1/128 and 1/64 the respective MICs), whereas josamycin, oleandomycin, ceftazidime, tobramycin, minocycline, and ofloxacin had no effect on viability, even following 48 h of incubation with concentrations representing relatively high fractions of their MICs. The bactericidal activity of azithromycin seen following 48 h of incubation was not limited to strain PAO-1 but was also seen against 13 of 14 clinical isolates, including both mucoid and nonmucoid strains. Although viability was not decreased prior to 48 h, we found that 4 micrograms of azithromycin per ml inhibits protein synthesis after as little as 12 h and that protein synthesis continues to decrease in a time-dependent manner. We likewise found that P. aeruginosa accumulates azithromycin intracellulary over the period from 12 to 36 h. These results suggested that sub-MICs of certain macrolides are bactericidal to P. aeruginosa when the bacteria are exposed to these antibiotics for longer periods. Exposure-dependent intracellular accumulation of the antibiotic and inhibition of protein synthesis may partially account for the antipseudomonal activity of macrolides over relatively prolonged incubation periods.

Prescription of Calcium Concentration and Pth Control

1996 ◽  
Vol 16 (1_suppl) ◽  
pp. 300-305 ◽  
Author(s):  
Eberhard Ritz ◽  
Jutta Passlick-Deetjen ◽  
Martin Zeier ◽  
Adam Stefanski
Keyword(s):  
Calcium Concentration ◽  
Calcium Uptake ◽  
Calcium Content ◽  
Phosphate Binders ◽  
Calcium Balance ◽  
Frequent Episodes ◽  
Prospective Trials ◽  
Term Maintenance ◽  
Stimulation Of

The use of calcium-containing oral phosphate binders, introduced in an effort to avoid aluminum-containing compounds, has led to more frequent episodes of hypercalcemia. This prompted the introduction of continuous ambulatory peritoneal dialysis (CAPD) solutions with diminished calcium content. The problems raised by such solutions included stimulation of parathyroid hormone (PTH) secretion and long-term maintenance of calcium balance. Some of these issues can today be answered on the basis of controlled prospective trials. Variability of the rate of intestinal calcium uptake of bone turnover, of baseline parathyroid activity, and other factors make it necessary to individualize the indication for the use of CAPD solutions with low calcium content.

scholarly journals Synergistic stimulation of Ca+ uptake by glucagon and Ca2+-mobilizing hormones in the perfused rat liver. A role for mitochondria in long-term Ca2+ homoeostasis

1986 ◽  
Vol 238 (3) ◽  
pp. 653-661 ◽  
Author(s):  
J G Altin ◽  
F L Bygrave
Keyword(s):  
Cyclic Amp ◽  
Calcium Content ◽  
Fold Increase ◽  
Maximal Response ◽  
Similar Response ◽  
Long Term Effects ◽  
Low Concentrations ◽  
Order Of Magnitude ◽  
Stimulation Of

A perfused liver system incorporating a Ca2+-sensitive electrode was used to study the long-term effects of glucagon and cyclic AMP on the mobilization of Ca2+ induced by phenylephrine, vasopressin and angiotensin. At 1.3 mM extracellular Ca2+ the co-administration of glucagon (10 nM) or cyclic AMP (0.2 mM) and a Ca2+-mobilizing hormone led to a synergistic potentiation of Ca2+ uptake by the liver, to a degree which was dependent on the order of hormone administration. A maximum net amount of Ca2+ influx, corresponding to approx. 3800 nmol/g of liver (the maximum rate of influx was 400 nmol/min per g of liver), was induced when cyclic AMP or glucagon was administered about 4 min before vasopressin and angiotensin. These changes are over an order of magnitude greater than those induced by Ca2+-mobilizing hormones alone [Altin & Bygrave (1985) Biochem. J. 232, 911-917]. For a maximal response the influx of Ca2+ was transient and was essentially complete after about 20 min. Removal of the hormones was followed by a gradual efflux of Ca2+ from the liver over a period of 30-50 min; thereafter, a similar response could be obtained by a second administration of hormones. Dose-response measurements indicate that the potentiation of Ca2+ influx by glucagon occurs even at low (physiological) concentrations of the hormone. By comparison with phenylephrine, the stimulation of Ca2+ influx by vasopressin and angiotensin is more sensitive to low concentrations of glucagon and cyclic AMP, and can be correlated with a 20-50-fold increase in the calcium content of mitochondria. The reversible uptake of such large quantities of Ca2+ implicates the mitochondria in long-term cellular Ca2+ regulation.

Purine synthesis de novo and its regulation in rat hepatocytes

1980 ◽  
Vol 58 (8) ◽  
pp. 599-606 ◽  
Author(s):  
Christine Des Rosiers ◽  
Marcel Lalanne ◽  
Joan Willemot
Keyword(s):  
Pentose Phosphate Pathway ◽  
De Novo ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Pentose Phosphate ◽  
Male Rats ◽  
P Availability ◽  
Prolonged Incubation ◽  
Purine Synthesis ◽  
Stimulation Of

Purine synthesis de novo and its regulation were studied in freshly isolated hepatocytes from fed adult male rats. These cells incorporated [14C]formate mainly into purine ribonucleotides. The immediate effect of increasing the concentration of inorganic phosphate in the incubation medium was an increase in 5-phosphoribosyl 1-pyrophosphate (PP-ribose-P) availability and a stimulation of purine synthesis de novo. However, prolonged incubation of cells in 25 mM phosphate resulted in a decreased PP-ribose-P availability and purine synthesis de novo. Methylene blue and phenazine methosulfate decreased PP-ribose-P availability and purine synthesis de novo although they stimulated considerably the pentose phosphate pathway. In contrast, epinephrine and glucagon increased significantly PP-ribose-P availability and purine synthesis de novo, but they did not change the activity of the pentose phosphate pathway. These results show a relationship between PP-ribose-P availability and purine synthesis de novo in rat hepatocytes. They emphasize the complexity of the regulation of PP-ribose-P availability.

Efficacious long-term maintenance therapy with pantoprazole (PAN) in patients with Zollinger-Ellison syndrome

2001 ◽  
Vol 120 (5) ◽  
pp. A613-A613
Author(s):  
P BORNMAN ◽  
K RADEBOLD ◽  
H DEBAERE ◽  
L VENTER ◽  
H HEINZE ◽  
...  
Keyword(s):  
Maintenance Therapy ◽  
Zollinger Ellison Syndrome ◽  
Term Maintenance
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