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

---

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

Hypoglycemia may develop in patients with severe untreated malaria and can complicate the course of treatment with parenteral quinine as a result of quinine-induced hyperinsulinemia. Intravenous quinine is used increasingly as the therapy of choice in patients with severe malaria, most of whom are children. To assess the importance of both pretreatment and quinine-related hypoglycemia in children in an area in which the disease is endemic, we prospectively studied 95 Malawian children with falciparum malaria and altered consciousness who were treated with intravenous quinine. Nineteen patients had hypoglycemia before treatment. Seven (37 percent) died, and five of the survivors (26 percent) had neurologic sequelae. The corresponding values for patients who were initially normoglycemic were 4 percent and 4 percent, respectively (P less than 0.0001). Hypoglycemia was associated with low plasma insulin concentrations and with elevated plasma concentrations of lactate, alanine, and 5'-nucleotidase--a finding that suggests that impaired hepatic gluconeogenesis but not hyperinsulinemia contributes to the pathogenesis of pretreatment hypoglycemia. All patients were given quinine dihydrochloride in a 5 percent dextrose infusion, and those with hypoglycemia received 50 percent dextrose. Hypoglycemia recurred in seven of the patients with pretreatment hypoglycemia, but these episodes were also not associated with hyperinsulinemia. Of the 76 children who were initially normoglycemic, none became hypoglycemic during the course of treatment with intravenous quinine. We conclude that hypoglycemia is a frequent complication of falciparum malaria in children and that it reflects severe disease and is associated with a poor prognosis. We did not find it to be a complication of quinine treatment.
...
PMID:Blood glucose levels in Malawian children before and during the administration of intravenous quinine for severe falciparum malaria. 305 May 16

Insulin receptors in human colon tumours, normal colon tissue and mesenteric fat removed at surgery have been identified by measuring the binding of labelled insulin to cell membrane preparations. Insulin binding sites were readily detected in all tissues, with mean +/- SD binding site concentrations of 43 +/- 41, 44 +/- 39, and 44 +/- 35fmol/mg membrane protein, and dissociation constants of 0.73 +/- 0.61, 0.66 +/- 0.41, and 0.78 +/- 0.58nM for microsomal plasma membrane preparations of tumour (n = 23) respectively. The specificity of binding of labelled insulin was similar in tumour and normal colon samples. Binding in normal colon preparations was highest in the epithelium (84fmol/mg membrane protein) and lower in lamina propria (19fmol/mg), submucosa (25fmol/mg) and muscle wall (13fmol/mg). Degradation of labelled insulin was similar in tumour and normal colon preparations. Mean receptor levels were not significantly different between microsomal membrane preparations and plasma membranes partially purified on discontinuous sucrose gradients, quantitated against either unit membrane protein or unit 5'-nucleotidase specific activity. There was a significant negative correlation between insulin levels, but no significant relationship was seen between serum insulin and receptor levels in either colon tumour or tissue preparations from full-thickness normal colon wall. An inverse correlation between serum insulin and receptor levels was, however, apparent in preparations of colonic musosa. These data indicate that although insulin receptors in colon tumours share the same biochemical characteristics as those present in the normal colon, receptors in tumour tissue are less sensitive to down-regulation by ambient insulin than receptors in mesenteric fat cells and normal colonic mucosa.
...
PMID:Insulin binding by normal and neoplastic colon tissue. 388 82

The importance of estrogens in the dietary lipid alteration of R3230AC mammary carcinoma growth and insulin binding was studied. Animals were divided into three groups [intact, ovariectomized, and ovariectomized treated with estradiol valerate (EV)] and were fed diets containing either 0% fat (fat free), 0.5% corn oil (low fat), or 20% corn oil (high fat). An alteration of tumor burden between animals fed high-fat versus either low-fat or fat-free diets was observed and appeared to be influenced by the estrogen status of the animal. The difference in tumor burden attributed to dietary lipid seen in intact rats was less in ovariectomized rats and greater in ovariectomized rats treated with EV, despite the fact that absolute tumor burden was reduced by this treatment. A similar relationship was observed for dietary lipid-induced differences in insulin binding to plasma membranes from these tumors. Reduction of tumor growth resulting from estrogen treatment was greater in low-fat- and fat-free-fed animals than in high-fat-fed rats. Again, tumor growth behavior appeared to be related to the reduction of insulin binding induced by estrogen treatment; insulin binding to plasma membranes from animals fed a low unsaturated lipid diet was decreased to a greater extent by EV treatment than in membranes from high-fat-fed rats. Altered tumor growth and membrane insulin binding, resulting from dietary perturbations and/or EV treatment, were not invariably related to serum insulin levels, nor to differences in membrane preparation, as reflected by 5'-nucleotidase activity, nor to membrane fatty acid composition or uptake of proline. Taken together, these results suggest a potential role of estrogens and insulin receptors as mediators of the dietary lipid alterations of growth of the R3230AC mammary carcinoma.
...
PMID:A role of estrogens and insulin binding in the dietary lipid alteration of R3230AC mammary carcinoma growth in rats. 388 27

1. A method for the preparation of brush border from rabbit kidneys is described. Contamination by other organelles was checked by electron microscopy and by the assay of marker enzymes and was low. 2. Seven enzymes, all hydrolases, were substantially enriched in the brush-border preparation and are considered to be primarily located in this structure. They are: alkaline phosphatase, maltase, trehalase, aminopeptidase A, aminopeptidase M, gamma-glutamyl transpeptidase and a neutral peptidase assayed by its ability to hydrolyse [(125)I]iodoinsulin B chain. 3. Adenosine triphosphatases were also present in the preparation, but showed lower enrichments. 4. Alkaline phosphatase was the most active phosphatase present in the preparation. The weak hydrolysis of AMP may well have been due to this enzyme rather than a specific 5'-nucleotidase. 5. The two disaccharidases in brush border were distinguished by the relative heat-stability of trehalase compared with that of maltase. 6. The individuality of the four peptidases was established by several means. The neutral peptidase and aminopeptidase M, both of which can attack insulin B chain, differed not only in response to inhibitors and activators but also in the inhibitory effect of a guinea-pig antiserum raised to rabbit aminopeptidase M. This antiserum inhibited both the purified and the brush-border activities of aminopeptidase M. The neutral peptidase and gamma-glutamyl transpeptidase were unaffected but aminopeptidase A was weakly inhibited. The characteristic responses to Ca(2+) and serine with borate served to distinguish aminopeptidase A and gamma-glutamyl transpeptidase from other peptidases. 7. No dipeptidases, tripeptidases or carboxypeptidases were identified as brush-border enzymes. 8. Incubation of brush border with papain released almost all the aminopeptidase M activity but only about half the activities of maltase, gamma-glutamyl transpeptidase and aminopeptidase A. No release of alkaline phosphatase, trehalase or the neutral peptidase was observed.
...
PMID:Studies on the enzymology of purified preparations of brush border from rabbit kidney. 414 72

Heart sarcolemmal membranes were isolated by the hypotonic shock-LiBr treatment from rats with chronic diabetes induced by a streptozotocin (65 mg/kg, iv) injection. Sarcolemmal Mg2+-dependent ATPase activity was elevated, whereas 5'-nucleotidase and K+-p-nitrophenylphosphatase activities in diabetic heart were depressed in comparison to control preparations. Although patent Na+-K+-ATPase and patent ouabain-sensitive Na+-K+-ATPase activities were unaltered, latent Na+-K+-ATPase activities, as determined in membranes after alamethicin or deoxycholate treatments, were found to be significantly depressed in diabetic animals. A depression in the latent Na+-K+-ATPase activity in diabetic preparations was also observed in membranes prepared by the sucrose density gradient method. Insulin-treated diabetic rats were observed to have normalized latent Na+-K+-ATPase activities. Total phospholipid content did not differ, but cholesterol content of the sarcolemmal membranes was significantly increased in diabetic heart preparations. Sarcolemmal Na+-K+-ATPase activity in diabetic heart was more resistant to treatments with filipin, an agent known to bind with cholesterol residues. These results suggest that chronic experimental diabetes is associated with some defects in sarcolemmal enzymatic activities and composition.
...
PMID:Sarcolemmal Na+-K+-ATPase activity in diabetic rat heart. 613 47

A high affinity Ca2+-stimulated, Mg2+-dependent ATPase (Ca2+-Mg2+-ATPase) was identified in microsomes and plasma membrane vesicles isolated from rat hepatocytes. The distribution of this enzyme was similar to that of the plasma membrane marker enzymes alkaline phosphodiesterase and 5'-nucleotidase. The Ca2+-Mg2+-ATPase had an apparent half-saturation constant of approximately 75 nM for Ca2+. After incubation of rat hepatocytes with 25 nM vasopressin for 3 min, the activity of Ca2+-Mg2+-ATPase was decreased 15-30%. The effect of vasopressin on the activity of this enzyme was near maximal after incubating hepatocytes with vasopressin for only 15 sec. The concentration of vasopressin needed for half-maximal inhibition of this enzyme in hepatocytes was approximately 6 nM. Treatment of the hepatocytes with 10 microM phenylephrine caused about a 10% decrease in ATPase activity while 10 nM glucagon or 200 microU/ml insulin did not affect the enzyme. These findings suggest that inhibition of the Ca2+-Mg2+-ATPase activity may be part of the mechanism by which vasopressin and alpha-adrenergic agonists elevate cytosolic Ca2+ in hepatocytes.
...
PMID:Regulation of Ca2+-Mg2+-ATPase activity in hepatocyte plasma membranes by vasopressin and phenylephrine. 613 76

The subcellular distribution in rat liver of non-latent and latent NADH pyrophosphatase was determined by analytical sucrose density gradient centrifugation. Non-latent NADH pyrophosphatase activity was distributed similarly to the plasma membrane marker, 5'-nucleotidase. However, latent NADH pyrophosphatase was found at the low density region of the gradient, similar to the distribution of galactosyl transferase, a Golgi marker. A population of membranes, corresponding to those from the low density region, was prepared by discontinuous sucrose gradient centrifugation. Radiolabelled insulin was used, to monitor the involvement of these membranes in ligand internalization. The membrane perturbant, digitonin, was used to effect a partial separation between membranes bearing NADH pyrophosphatase and those bearing galactosyl transferase. The mechanism by which this separation is effected has been investigated and it was shown that, although digitonin caused a loss of enzyme latency, the density shift was not due to this effect. The partially purified ligandosome-rich fraction was characterized by enzymic and ultrastructural analysis. A novel EM cytochemical stain for NADH pyrophosphatase identified a vesicular fraction distinct from Golgi lamellae.
...
PMID:Isolation and partial characterization of the rat liver ligandosome fraction. 614 45

The effect of streptozocin (STZ)-induced diabetes on the plasma membrane calcium uptake of rat liver was investigated. Plasma membrane preparations from diabetic rats showed a 2-3-fold increase in calcium uptake activity over controls 3-4 wk after the initial injections. Such an increase can be either reversed or blocked by treating the diabetic rats with exogenous insulin or administering nicotinamide 15 min before and 3 h after the STZ injection, respectively. The activity of 5'-nucleotidase and the [3H]ouabain binding to the plasma membranes were similar in samples from both the control and diabetic rats. These findings made it unlikely that preferential enrichment of plasma membranes or increased proportion of inside-out vesicles was the cause of the enhanced calcium uptake activity in membranes from diabetic animals. In addition, the effect of diabetes on the calcium uptake activity did not diminish even when the assay was performed in the presence of 2.5 microM ruthenium red, an inhibitor of calcium uptake by mitochondria, or when oxalate was omitted from the assay, suggesting that the effect was specifically on the plasma membrane pump. The enhanced calcium uptake activity was a result of an increase in the Vmax (58.8 versus 113.1 pmol calcium/mg protein/min for control and diabetic rats, respectively). No significant change in Km for calcium was detected.
...
PMID:The effect of streptozocin-induced diabetes on the plasma membrane calcium uptake activity of rat liver. 620 83

1. A rapid method was developed for the preparation of plasma membranes from either isolated rat fat-cells or intact epididymal fat-pads with the use of density-gradient centrifugation in the presence of Percoll. On the basis of 5'-nucleotidase activity, the yield of plasma membranes was about 50% and purification over 10-fold. Activities of marker enzymes indicated that contamination by mitochondria and microsomal fraction was small. 2. Incorporation of 32Pi into proteins associated with plasma membranes within isolated fat-cells was investigated. Four major bands of labelled phosphoproteins were separated by sodium dodecyl sulphate/polyacrylamide-slab-gel electrophoresis; the apparent subunit mol.wts. were 67 000, 61 000, 26 000 and 20 000. None of these phosphoprotein bands corresponded to periodate/Schiff-staining glycoproteins. The extent of phosphorylation of the 61 000 mol.wt phosphoprotein band was increased by about 30 and 60% after exposure of fat-cells for 15 min to insulin or adrenaline respectively.
...
PMID:Use of a novel rapid preparation of fat-cell plasma membranes employing Percoll to investigate the effects of insulin and adrenaline on membrane protein phosphorylation within intact fat-cells. 626 55

In rabbit liver plasma membranes (LPM), specific binding of 125I-insulin rapidly increased in late gestation and peaked at birth, declining thereafter. In contrast, 125I-glucagon binding was lowest in late gestation, somewhat higher at birth, and increased by 48 h although only to 20-25% of adult. These changes in binding were due to changing numbers of receptors involving predominantly high affinity sites for insulin and low affinity sites for glucagon, with only minor changes in affinity. Despite measurable glucagon receptors by birth, fetal LPM produced no increment above basal in cAMP production with maximal doses of glucagon (10(-6) M), prostaglandin E1 (10(-4) M), or epinephrine (10(-4) M). Near birth only NaF (10 mM) produced a modest but significant increment in cAMP. By 2 h postbirth, all stimuli evoked significant increments in cAMP production that increased progressively but was still only 15-20% of adult at 48 h. Furthermore, although specific binding of cholera toxin was greater in fetal LPM (11 +/- 1 vs. 6 +/- 1%), cholera toxin-stimulated cAMP production increased by only 12-26% above basal in the fetus compared with 220% in adult. Markers of membrane purity including 5'-nucleotidase, phosphodiesterase, and insulin or glucagon degradation were not different in fetus and adult. We conclude that receptors and components of the adenylate cyclase complex mature independently; initial coupling occurs between the G/F regulatory protein and the catalytic unit (NaF but not hormonal activation) followed within hours of birth by coupling to the hormone receptor.
...
PMID:Ontogeny of hepatic insulin and glucagon receptors and adenylate cyclase in rabbit. 630 5


<< Previous 1 2 3 4 5 6 7 Next >>

---