Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Methods are described for preparing and analyzing single preimplantation mouse embryos for a variety of metabolites and cofactors (glucose-6-P, fructose-6-P, fructose-1,6-bisphosphate, ATP, AMP, Pi, citrate, isocitrate, alpha-ketoglutarate, and malate). Oil-well and enzymatic cycling techniques are combined to provide the sensitivity needed to measure the amounts present (10(-12) to 1o(-15) moles). After experimental treatment, embryos are collected on glass slides and freeze-dried. They can then be stored indefinitely under vacuum at -25 degrees C without deterioration. With these procedures, the embryos were collected at successive stages of development and subjected to starvation and refeeding with glucose, pyruvate or both. The results confirm the existence of a block at early stages at the P-fructokinase step. This may be due to inhibition by the very high citrate levels present. The data suggest that glycolysis is turned on late in preimplantation development by the rise in fructose-6-P, a deinhibitor of P-fructokinase. In the citrate cycle, no step between citrate and alpha-ketoglutarate is rate-limiting, but a step between alpha-ketaglutarate and malate appears to impede the flux at early embryonic stages.
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PMID:Measurement of metabolites in single preimplantation embryos; a new means to study metabolic control in early embryos. 58 Feb 93

We have examined the role of fructose as a substrate for the mammalian lung. Isolated and ventilated rat lungs were perfused for 2 h in the presence of either [U-14C]- or [5-3H]fructose. Fructose utilization, 3H2O production, and lactate and pyruvate production were measured. Insulin had no effect on the production of radiolabeled lactate. The 14C label from [U-14C]fructose was incorporated into the neutral lipids, phospholipids, fatty acid moiety, and deacylated fraction of lung. The apparent Km and maximum velocity of enzyme reaction for fructose utilization were 0.5 mM and 75 nmol X h-1 X g dry wt-1, respectively. Recovery of fructose 1-phosphate and fructose 1,6-diphosphate after perfusion with fructose, as well as detection of fructokinase, aldolase, and triokinase activities in the lung homogenates, suggested that fructose had been metabolized via phosphorylation through fructose 1-phosphate. Activities of fructose-metabolizing enzymes were not altered by the induction of diabetes, hypophysectomy, or starvation. These results suggest that mammalian lungs may utilize fructose to synthesize fatty acids, which in turn are used for phospholipid biosynthesis. The utilization of fructose by lung does not seem to be affected by nutritional or hormonal conditions.
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PMID:Fructose utilization by lung. 632 66

Starvation refeeding experiments were conducted in rats to test the hypothesis that adaptation of glucokinase (the high Km component of glucose phosphorylation) could be the major determinant of glucose metabolism of pancreatic islet cells and of glucose-stimulated insulin release. It was found that glucokinase of islet homogenates, glucose use by intact isolated islets, and glucose-induced insulin release as studied in a perifusion system were decreased after 24 h of fasting, whereas P-fructokinase and 3-P-glyceraldehyde DH were unaltered. After extended fasting (e.g., 120 h) all three enzymes were decreased but glucose use did not change any further. Refeeding normalized all parameters. These and previous results support the concept that glucokinase serves as the adaptive beta-cell glucoreceptor relating blood glucose to insulin release.
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PMID:Adaptation of glycolytic enzymes: glucose use and insulin release in rat pancreatic islets during fasting and refeeding. 645 66

We examined the relationship between glucose-induced insulin release and the intermediary metabolism of islets from fed and fasted rats. Isolated islets were perifused and insulin release measured in the effluent. At various times after switching islets from 2.4 to 8.6 or 14.5 mM glucose or from 2.4 to 14.5 and back to 2.4 mM glucose, islets were quickly frozen, freeze dried, and subsequently analyzed for tissue content of glucose-6-P, fructose-1,6-P2 plus triose-P, Pi, ATP, ADP, 5'-AMP, NADH, NADPH, total NAD, and total NADP using enzymatic fluorometric procedures. When islets from fed rats were exposed to high glucose, there were concomitant increases of insulin release and islet content of glucose-6-P, fructose-1,6-P2 plus triose-P, NADH, and NADPH. During stimulation Pi and 5'-AMP content fell markedly. The total adenine nucleotide content remained constant. Similar secretory and metabolic changes occurred when 1.5 mM Pi was added to the perifusion fluid. When glucose-stimulated islets were switched back to low glucose for 10 min, all substances but fructose-1,6-P2 plus triose-P, 5'-AMP, NADPH, and possibly ATP returned to the prestimulatory level. Starvation of rats for 3 days blocked the secretory response to 8.6 mM glucose. Fructose-1,6-P2 plus triose-P rose but it did not attain the level existing in islets from fed rats. The ratios (ATP)/(5'-AMP) and (ATP)/(Pi)(adp) increased to the values observed in glucose-stimulated islets of fed rats. The metabolic changes in islets from fed rats exposed to high glucose are consistent with an activation of glycolysis occurring concomitantly with stimulated rates of insulin release. This occurs despite the decrease of important activators of glycolysis--Pi and 5'-AMP. The enhanced glycolysis possibly results from P-fructokinase activation by increased fructose-6-P levels. Activation of glycolysis with 8.6 mM glucose was not as pronounced in islets from starved rats. Despite the different secretory response of islets from fet and fasted rats, the changes of phosphorylation state in the islets, in particular, Pi and 5'-AMP levels, were similar.
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PMID:Effects of glucose on insulin release and on intermediary metabolism of isolated perifused pancreatic islets from fed and fasted rats. 699 11

The plant cell cycle is equipped with two principal control points: PCP1 in G1 and PCP2 in G2 phase. These checkpoints can arrest the cell cycle in response to carbohydrate starvation, while sugar presence can revive the replication and mitotic activity. The process of cell cycle revival is strongly repressed by okadaic acid (OA) or 6-dimethylaminopurine (6-DMAP), inhibitors of specific protein phosphatases 1 or 2A or kinases (cyclin-dependent kinases), respectively. In the present study, it was investigated whether inhibition of cell cycle revival is performed through interference of the above-mentioned inhibitors with the metabolic pathway of sucrose applied to the cells. Changes of hexokinase (HK) and fructokinase (FK) activities, key enzymes of hexose metabolism, were analyzed in Vicia faba root meristem cells arrested in G1 and G2 phase by carbohydrate starvation as well as in those recovered with glucose or sucrose in the presence of OA or 6-DMAP. It was shown that in the sugar-starved cells, the activity of both enzymes decreased significantly. During cell regeneration with carbohydrates, the activity of HK was induced more by sucrose than by glucose, while FK remained inactive after glucose addition. Moreover, in situ investigation of the activities of HK and FK showed that OA-induced and 6-DMAP-induced repression of the cell cycle revival is connected with the interference of these drugs in the metabolic pathway of sucrose. It was also indicated that stronger OA-induced and 6-DMAP-induced inhibition of the replication and mitosis revival, at the early stages of sucrose regeneration, was correlated with the stronger influence of these inhibitors on HK and FK activities.
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PMID:In situ activities of hexokinase and fructokinase in relation to phosphorylation status of root meristem cells of Vicia faba during reactivation from sugar starvation. 1933 47