Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined the role of physiologic plasma concentrations of cholecystokinin (CCK) in the regulation of rat pancreatic gene expression. Postprandial plasma CCK concentrations, as determined by bioassay, were achieved by intraduodenal perfusion with soybean trypsin inhibitor (SBTI) or intravenous infusion of CCK-8. SBTI administration for 48h resulted in nonparallel regulation of digestive enzyme gene expression, as assessed by slot-blot analysis using cloned cDNA probes for trypsin, chymotrypsin, amylase and ribonuclease. As an indicator for pancretic growth stimulation, ornithine decarboxylase (ODC) gene expression was stimulated appr. 2-fold over the SBTI infusion period. Identical effects were seen with i.v. infusion of CCK-8. The CCK receptor antagonist L-364, 718 blocked the effects on pancreatic gene expression of both CCK infusion and SBTI administration. These data therefore indicate that postprandial plasma CCK concentrations regulate pancreatic digestive enzyme and ODC gene expression at a pretranslational level.
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PMID:Cholecystokinin as a regulator of rat pancreatic gene expression. 171 83

Previous studies in which investigators have induced the rate of polyamine uptake in vitro have used either inhibitors of polyamine biosynthesis or growth factors that induce cell proliferation. Recently, however, we have described the induction of putrescine uptake in cultured adult mouse hepatocytes and have shown that uptake is independent of both intracellular polyamine levels and proliferation. Although proliferation was not apparent in those studies, data suggested that, after isolation, the cells entered G1 of the cell cycle. In this study, we have examined whether the induction of putrescine uptake is a function of entry into the cell cycle and whether uptake activity is essential for optimal progression into the S phase. Using ribonuclease reductase subunit M1 as a marker of entry into the cell cycle, we have shown that hepatocytes enter G1 during the first 4 hr of culture. Both putrescine uptake and ornithine decarboxylase activity increased as the cells entered G1. Treatment of the cells with retinoic acid (10 to 33 mumol/L) prevented them from entering G1 and also inhibited the induction of the putrescine transporter by up to 90%. In contrast, initiation of G1 to S phase transition markedly down-regulated the activity of the transporter. Thus induction of the putrescine transporter in isolated hepatocytes appears to be a G1-specific event. Culturing the hepatocytes in the presence of 1,1'-bis[3-(1'-methyl-[4,4'-bipyridinium]-1-yl)-propyl]- 4,4'-bipyridinium, a potent competitive inhibitor of putrescine uptake, resulted in a 47% decrease in intracellular putrescine.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cell cycle-dependent uptake of putrescine and its importance in regulating cell cycle phase transition in cultured adult mouse hepatocytes. 195 75

Ornithine decarboxylase-antizyme was induced in mammary gland of fasted lactating rats by administration of 1,3-diaminopropan-2-ol. Antizyme from mammary gland showed similar chemical and kinetic behavior to that previously reported by Canellakis and co-workers for antizyme from liver [J. S. Heller, W. F. Fong, and E. S. Canellakis (1976) Proc. Natl. Acad. Sci. USA 72, 1858-1862]; specifically the inhibitor was nondialyzable, heat labile, and ribonuclease insensitive, and the inhibition was time independent, proportional to the concentration of antizyme present, and noncompetitive with respect to the substrate, ornithine. However, ornithine decarboxylase-antizyme from mammary gland eluted from Sephadex G-75 with an apparent molecular mass of 55 kDa, compared with 27 kDa, for antizyme from liver under identical conditions. The elution pattern was unaffected by the presence of high salt concentrations, indicating that the larger size was not due to macromolecular complexes. The presence of antizyme-ornithine decarboxylase complex was detected in mammary gland of untreated lactating rats fasted for 6 or 24 h, thus indicating that antizyme plays a role in the regulation of ornithine decarboxylase in mammary gland under physiological conditions.
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PMID:Properties of ornithine decarboxylase-antizyme from mammary gland of lactating rats. 357 21

Polyamines and RNA accumulate in the rat mammary gland during pregnancy, but the major increases occur after parturition. Therefore the major increases occur after the gland has obtained its maximal complement of epithelial cells. During lactation, the spermidine concentration rises above 5mm and RNA content in the lactating mammary gland reaches a value 16 times that of the unstimulated mammary gland. The ratio of spermidine/spermine, an increase of which initially signals an elevation in biosynthetic activity, is near 1 in the normal mammary gland and is greater than 10 in the lactating mammary gland. Putrescine concentration is very low during the entire course of mammary-gland development, with the exception of early pregnancy. The low putrescine concentration probably reflects the very rapid conversion of putrescine into spermidine. Both ornithine decarboxylase, the enzyme that synthesizes putrescine, and putrescine-stimulated S-adenosyl-l-methionine decarboxylase, the enzyme that synthesizes spermidine, increase in activity during middle and late pregnancy; during lactation, both enzyme activities are elevated until the 21st day of lactation, and then decline. These declines are concomitant with involution. Also, it was found that the amount of ribonuclease activity in the mammary gland was very high during lactation, almost double that in the gland during pregnancy.
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PMID:Polyamine biogenesis in the rat mammary gland during pregnancy and lactation. 465 54

Gene expression in mammalian cells can be suppressed by oligonucleotides complementary to the target mRNA. This strategy was explored as a means of arresting translation of the prohormone precursor proopiomelanocortin (POMC), used as a model system of peptide messengers that are synthesized and released from endocrine and neuronal cells. The synthesis of the POMC-derived peptides adrenocorticotropin (ACTH) and beta-endorphin (beta-END) was markedly reduced by an oligodeoxynucleotide (ODN) complementary to a region of beta-END mRNA in AtT-20 cells, which retain many of the differentiated phenotypes of corticotrophs; this treatment did not affect the steady-state levels of POMC mRNA. Antisense ODN was stable in cell culture medium for 24 h, and cellular uptake was low (approximately 2.5% of the added ODN); however, the intracellular levels of the ODN were sufficient to form a ribonuclease-resistant duplex with complementary cellular mRNA. Addition of ODN to the cell culture did not affect the cellular levels of chromogranin A-(264-314)/pancreastatin or cell viability and proliferation, as evidenced by bromodeoxyuridine incorporation and ornithine decarboxylase activity. Microinfusion of the antisense ODN in the rat hypothalamic arcuate nucleus, where the majority of POMC-positive brain perikarya are located, significantly reduced ACTH- and beta-END-immunopositive neurons, and antisense ODN-treated rats showed substantially less of the grooming behavior usually observed in a novel environment.
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PMID:Inhibition of proopiomelanocortin expression by an oligodeoxynucleotide complementary to beta-endorphin mRNA. 805 59