Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.3.5 (5'-nucleotidase)
3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Five enzymes concerned with the metabolism of adenine derivatives were assayed in seven regions of the rat brain. A region which included the hypothalamus had the highest AMP deaminase and adenosine deaminase activities, while its 5'-nucleotidase activities were relatively low. The enzymes named and also the uptake of [14C]adenine by incubated tissue samples were more active with hypothalamic than with neocortical tissues. On superfusion with glucose-bicarbonate saline after assimilating [14C]adenine, the hypothalamic tissues released about 0.2 per cent of their 14C content per minute. This release was increased fourfold with electrical excitation but the presence of 0.25 muM tetrodotoxin prevented most of this increase. The compounds released during superfusion and electrical stimulation were preponderantly hypoxanthine, inosine, and adenosine, with only small amounts of adenine nucleotides. The output of all these compounds increased during the period of stimulation and also the proportion of adenine nucleotides increased when stimulation was carried out in the presence of tetrodotoxin. The output of the nucleotides and adenosine increased more promptly when stimulated than did that of the other compounds named. The results are discussed in terms of the metabolic roles of the enzymes concerned. and in relation to whether the enzymes are acting on intracellular or extracellular substrates.
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PMID:The metabolism of adenine derivatives in different parts of the brain of the rat, and their release from hypothalamic preparations on excitation. 126 67

The subcellular distribution of glucose transporters in rat hepatocytes and HepG2 cells was studied in the absence and in the presence of insulin. Glucose transporters were quantitated by measuring glucose-sensitive cytochalasin B binding and by protein immunoblotting using isoform-specific antibodies. Plasma membrane contamination into subcellular fractions was assessed by measuring distribution of 5'-nucleotidase and cell surface carbohydrate label. In hepatocytes, GLUT-2 occurred in a low-density microsomal (LDM) fraction at a significant concentration, and as much as 15% of cellular GLUT-2 was found intracellularly that cannot be accounted for by plasma membrane contamination. In HepG2 cells which express GLUT-1 and GLUT-2, the two isoforms showed distinct subcellular distribution patterns: GLUT-2 was highly concentrated in LDM while very little GLUT-1 was found in this fraction, indicating that a large portion of GLUT-2 occurs in intracellular organelles. Insulin treatment did not change the subcellular distribution patterns of glucose transporters in both cell types. Our results suggest that rat hepatocytes and HepG2 cells possess an intracellular storage pool for GLUT-2, but lack the insulin-responsive glucose transporter translocation mechanism.
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PMID:Demonstration of an insulin-insensitive storage pool of glucose transporters in rat hepatocytes and HepG2 cells. 161 23

Microvessels were isolated from bovine and rat cerebral cortex by simple procedures involving mechanical homogenization, differential and density-gradient centrifugation, and chromatography on a column of glass beads. The preparations were composed of short capillaries with a diameter of 1-10 microns. Both purifications were monitored by assaying the activity of the marker enzyme gamma-glutamyl transpeptidase (gamma-GTase). The final bovine and rat preparations were enriched 20- and 14-fold over the homogenate respectively. gamma-GTase activity was measured in different fractions after bovine and rat membranes were solubilized with 0.5% and 0.3% Triton X-100 respectively. Measurement of 5'-nucleotidase and acetylcholinesterase activities indicated very low levels of contamination of the microvessel preparations by glial cells and neurons. The integrity of the capillary membranes was confirmed by the assay of a cytosolic marker enzyme, lactate dehydrogenase. Viability of the microvessels was demonstrated by the presence of detectable levels of adenylates and by tissue respiration induced by glucose and succinate. Comparison of the proteins of homogenized bovine and rat brain cortex with those of purified capillaries separated by SDS/PAGE revealed enrichment of at least three predominant proteins of 14, 16 and 18 kDa in the capillary preparations. It is concluded that these methods allow rapid isolation of small blood vessels of the blood-brain barrier which are suitable for metabolic and structural studies in vitro.
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PMID:Purification and characterization of metabolically active capillaries of the blood-brain barrier. 171 99

The subcellular origin of membranes from rat skeletal muscle that contain insulin-responsive glucose transporters was investigated. Rat skeletal muscle membranes were prepared by isopycnic centrifugation in sucrose gradients. In vivo insulin treatment increased the content of GLUT-4 glucose transporters in the 25% sucrose fraction (enriched in the plasma membrane marker 5'-nucleotidase) and decreased it in the 35% sucrose fraction (devoid of plasma membrane markers). The possibility of endothelial cell membrane contamination in these fractions was investigated using a mouse monoclonal antibody, MRC OX-43, raised against a cell surface protein specific to rat vascular endothelium. MRC OX-43 did not react with any of the muscle membrane fractions, but did recognize a protein of around 100 kDa in extracts of human endothelial cells and rat aorta. An antibody to the dihydropyridine receptor of skeletal muscle, IIC12, was used to determine the presence of transverse tubules in these fractions. IIC12 reacted positively with a 180-kDa protein in purified rat transverse tubules. In contrast, this antibody did not cross-react with the 25% or 35% sucrose fractions. The 25% sucrose fraction was devoid of calsequestrin and ryanodine receptor, cisternal sarcoplasmic reticulum markers. However, small amounts of these proteins were detected in the 35% sucrose fraction. The results suggest that the 25% sucrose fraction represents plasma membranes, while the 35% sucrose fraction is an insulin-sensitive intracellular fraction that contains, but is not enriched in, sarcoplasmic reticulum cisternae. The results further show that insulin-induced recruitment of GLUT-4 transporters in skeletal muscles can be demonstrated independently of GLUT-4 recruitment in endothelial cells.
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PMID:Characterization of glucose transporter-enriched membranes from rat skeletal muscle: assessment of endothelial cell contamination and presence of sarcoplasmic reticulum and transverse tubules. 198 44

Thioacetamide (100 mg/kg), when administered to normal rats, caused a significant increase in the activities of 5'-nucleotidase and gamma-glutamyl transpeptidase and a decrease in the activities of glucose 6-phosphatase and succinate dehydrogenase enzymes in the liver. DNA, RNA, and proteins were increased while the cytochrome P450 in the microsomal fraction and the glycogen content in the liver were decreased significantly. Elevations in the activities of GOT, GPT, and alkaline phosphatase and bilirubin content in serum were also observed. Picroliv, a standardised glycoside fraction of Picrorhiza kurroa, in doses of 12.5 and 25 mg/kg prevented most of the biochemical changes induced by thioacetamide in liver and serum. The hepatoprotective activity of Picroliv was comparable with that of silymarin, a known hepatoprotective agent obtained from seeds of Silybum marianum.
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PMID:Picroliv affords protection against thioacetamide-induced hepatic damage in rats. 206 53

Horseradish peroxidase (HRP, 10 mg/100 g body weight) was intravenously injected into rats in order to investigate the nature of the compartments involved in the transcellular transport of the protein through hepatocytes into bile. Double cytochemistry for HRP and the marker enzymes for cytoplasmic organelles was used. HRP was shown to be taken up by hepatocytes via vesicles at the sinusoidal surface, some of which were positive for 5'-nucleotidase activity. HRP was then found in the smooth-surfaced vesicles and tubules which were negative in 5'-nucleotidase, glucose 6-phosphatase, thiamine pyrophosphatase and acid phosphatase activity, suggesting that the tubular structures are neither the endoplasmic reticulum, the Golgi apparatus nor lysosomes. Biochemical studies revealed that the lead procedures used for the double cytochemistry did not inhibit the peroxidatic activity of HRP, and conversely that HRP did not interfere with the marker enzyme activity. Such cytochemical observations seemed to be supported by the observation that administration of monensin (3.5 mg/100 g) and chloroquine (5 mg/100 g), which markedly altered the structure of the Golgi apparatus and lysosomes, respectively, slightly altered the biliary excretion of HRP but not to a significant extent.
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PMID:Cytochemical examination of the compartments involved in the transcellular transport of horseradish peroxidase in rat hepatocytes. 208 41

The purpose of this study was to simultaneously isolate skeletal muscle plasma and microsomal membranes from the hind limbs of male Sprague-Dawley rats perfused either in the absence or presence of 20 milliunits/ml insulin and to determine the effect of insulin on the number and distribution of glucose transporters in these membrane fractions. Insulin increased hind limb glucose uptake greater than 3-fold (2.4 +/- 0.7 versus 9.2 +/- 1.0 mumol/g x h, p less than 0.001). Plasma membrane glucose transporter number, measured by cytochalasin B binding, increased 2-fold (9.1 +/- 1.0 to 20.4 +/- 3.1 pmol/mg protein, p less than 0.005) in insulin-stimulated muscle while microsomal membrane transporters decreased significantly (14.8 +/- 1.6 to 9.8 +/- 1.4 pmol/mg protein, p less than 0.05). No change in the dissociation constant (Kd approximately 120 nm) was observed. K+-stimulated-p-nitrophenol phosphatase, 5'-nucleotidase, and galactosyltransferase specific activity, enrichment, and recovery in the plasma and microsomal membrane fractions were not altered by insulin treatment. Western blot analysis using the monoclonal antibody mAb 1F8 (specific for the insulin-regulatable glucose transporter) demonstrated increased glucose transporter densities in plasma membranes from insulin-treated hind limb skeletal muscle compared with untreated tissues, while microsomal membranes from the insulin-treated hind limb skeletal muscle had a concomitant decrease in transporter density. We conclude that the increase in plasma membrane glucose transporters explains, at least in part, the increase in glucose uptake associated with insulin stimulation of hind limb skeletal muscle. Our data further suggest that these recruited transporters originate from an intracellular microsomal pool, consistent with the translocation hypothesis.
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PMID:Identification of an intracellular pool of glucose transporters from basal and insulin-stimulated rat skeletal muscle. 210 34

A freely mobile jacket and tether system was developed for the investigation of total parenteral nutrition (TPN)-induced metabolic bone disease and complications of prolonged TPN in 12 Macaca fascicularis nonhuman primates. The animals received TPN for 49 +/- 7 d (means +/- SEM), providing 82 +/- 2 kcal.kg-1.d-1. Serum glucose increased from 3.6 +/- 0.2 mmol/L at baseline to 8.3 +/- 1.9 mmol/L (p less than 0.01) during TPN, and serum albumin decreased from 38 +/- 1 g/L at baseline to 29 +/- 1 g/L (p less than 0.001) during 2.75% amino acid TPN and 30 +/- 2 g/L (p less than 0.01) during 5% amino acid TPN infusion. No significant changes were seen in serum prealbumin, total protein, bilirubin, alanine aminotransferase, and 5'-nucleotidase during TPN infusion. Major complications included catheter sepsis, hyperglycemia, diarrhea, and premature death in six animals. Thus, metabolic complications of prolonged TPN support may be investigated in a freely mobile nonhuman primate.
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PMID:Long-term parenteral nutrition in unrestrained nonhuman primates: an experimental model. 210 76

Exercise training has been shown to enhance the ability of insulin to stimulate glucose uptake in responsive tissues. The purpose of this study was to determine the effects of exercise training on the levels of the insulin-regulatable glucose transporter (IRGT) in rat skeletal muscle. After 6 wk of voluntary running in exercise-wheel cages, male Sprague-Dawley rats were rested for approximately 27 h and fasted overnight before removal of plantaris and soleus muscles. The concentration of glucose transporters per unit of muscle protein or DNA was quantitated by immunoblotting with an anti-IRGT polyclonal antibody raised against a synthetic peptide. The IRGT protein was increased by 60% (141 +/- 14 vs. 229 +/- 24 counts/min [cpm]/25 micrograms protein, P less than 0.01) in plantaris muscle from exercise-trained rats compared with controls. Total protein yield, DNA content, and 5'-nucleotidase activity were not different in plantaris muscle from control and exercise-trained rats. In contrast, there was no significant increase in the IRGT protein in soleus muscle after training when data were expressed per unit of muscle protein (292 +/- 22 vs. 346 +/- 16 cpm/25 micrograms protein). These data indicate that the increase in the IRGT in plantaris muscle is a selective response to exercise training that does not reflect an overall increase in muscle protein. The changes in IRGT for these muscles with exercise training parallel changes observed in insulin-mediated glucose uptake. We propose that this increase in the total number of glucose transporters may be a major component of the increase in insulin-mediated glucose uptake that is observed with exercise training.
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PMID:Effects of exercise training on insulin-regulatable glucose-transporter protein levels in rat skeletal muscle. 222 15

The acute toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was examined in male C57BL/6J mice differing only at the Ah locus. Wild type mice (Ahb/b, "b/b") were treated once with 0, 50, 100, 200, 300, and 400 micrograms TCDD/kg po while congenic mice (Ahd/d, "d/d") received a single dose of 0, 400, 800, 1600, 2400, and 3200 micrograms TCDD/kg. Mice were checked daily, weighed twice a week, and those that survived, killed 35 days post-treatment. The LD50 values were 159 and 3351 micrograms/kg for b/b and d/d mice, respectively. Mean time to death was 22 days and was independent of dose and genotype. Decrease in body weight gain was noted in both strains 5 days after treatment and occurred at doses greater than or equal to 100 micrograms/kg in b/b mice and 1600 micrograms/kg in d/d mice. Dose-related increases in liver weight (both absolute and relative to body weight) and decreases in thymus, spleen, testes, and epididymal fat pad weights were observed at 8-24-fold higher doses in d/d than in b/b mice. A dose-related increase in segmented neutrophils was observed in both strains. Serum chemistry values indicated that 8-24X greater doses of TCDD were needed to elevate sorbitol dehydrogenase, alanine aminotransferase, and 5'-nucleotidase and to decrease total and esterified cholesterol in d/d than in b/b mice. Few effects were seen on total bile acids, serum triglycerides, glucose, or nonesterified cholesterol. In the liver, hepatocellular cytomegaly, fatty change, and bile duct hyperplasia occurred in both strains in a dose-related manner, as did thymic and splenic atrophy. Necrosis of germinal epithelium in the testes and edema in the stomach submucosa occurred at acutely toxic doses. These lesions also occurred at doses 8-24X greater in d/d than in b/b mice. Thus, the spectrum of toxicity is independent of the allele at the Ah locus, but the relative dose needed to bring about various acute responses is approximately 8-24X greater in congenic mice homozygous for the "d" allele than for the wild type animals carrying two copies of the "b" gene.
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PMID:Differential toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in C57BL/6J mice congenic at the Ah Locus. 237 98


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