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:3.1.26.9 (ribonuclease)
6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calcium signaling critical to neural functions is mediated through Ca(2+) channels localized on both the plasma membrane and intracellular organelles such as endoplasmic reticulum. Whereas Ca(2+) influx occurs via the voltage- or/and ligand-sensitive Ca(2+) channels, Ca(2+) release from intracellular stores that amplifies further the Ca(2+) signal is thought to be involved in more profound and lasting changes in neurons. The ryanodine receptor, one of the two major intracellular Ca(2+) channels, has been an important target for studying Ca(2+) signaling in brain functions, including learning and memory, due to its characteristic Ca(2+)-induced Ca(2+) release. In this study, we report regional and cellular distributions of the type-2 ryanodine receptor (RyR2) mRNA in the rat brain, and effects of spatial learning on RyR2 gene expression at mRNA and protein levels in the rat hippocampus. Using in situ hybridization, reverse transcription polymerase chain reaction, and ribonuclease protection assays, significant increases in RyR2 mRNA were found in the hippocampus of rats trained in an intensive water maze task. With immunoprecipitation and immunoblotting, protein levels of RyR2 were also demonstrated to be increased in the microsomal fractions prepared from hippocampi of trained rats. These results suggest that RyR2, and hence the RyR2-mediated Ca(2+) signals, may be involved in memory processing after spatial learning. The increases in RyR2 mRNA and protein at 12 and 24 h after training could contribute to more permanent changes such as structural modifications during long-term memory storage. Zhao, W., Meiri, N., Xu, H., Cavallaro, S., Quattrone, A., Zhang, L., Alkon, D. A. Spatial learning induced changes in expression of the ryanodine type II receptor in the rat hippocampus.
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PMID:Spatial learning induced changes in expression of the ryanodine type II receptor in the rat hippocampus. 1065 85

This study was designed to investigate the possible role of cyclo-oxygenase-2 (COX-2) and prostaglandin E(2)(PGE(2)) in endometrial adenocarcinoma. COX-2 RNA expression was confirmed in various grades of adenocarcinoma by ribonuclease protection assay. COX-2 and microsomal glutathione-dependent prostaglandin E synthase (mPGES) expression and PGE(2)synthesis were localised to the neoplastic epithelial cells and endothelial cells. In order to establish whether PGE(2)has an autocrine/paracrine effect in adenocarcinomas, we investigated the expression of 2 subtypes of PGE(2)receptors, namely EP2 and EP4, by real time quantitative PCR. Expression of EP2 and EP4 receptors was detected in adenocarcinomas from all grades of differentiation and was significantly higher than that detected in normal secretory phase endometrium (P< 0.01). The fold induction of expression in adenocarcinoma compared with normal secretory phase endometrium was 28.0 +/- 7.4 and 52.5 +/- 10.1 for EP2 and EP4 receptors respectively. Immunohistochemistry localised the site of expression of EP4 receptor in neoplastic epithelial cells and in the endothelium of carcinomas of all grades of differentiation. Finally, the functionality of the EP2/EP4 receptors was assessed by investigating cAMP generation following in vitro culture of adenocarcinoma tissue in the presence or absence of 300 nM PGE(2). cAMP production in response to PGE(2)was significantly higher in carcinoma tissue than that detected in normal secretory phase endometrium (3.42 +/- 0.46 vs 1.15 +/- 0.05 respectively; P< 0.001). In conclusion, these data suggest that PGE(2)may regulate neoplastic cell function in an autocrine/paracrine manner via the EP2/EP4 receptors.
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PMID:Expression of COX-2 and PGE synthase and synthesis of PGE(2)in endometrial adenocarcinoma: a possible autocrine/paracrine regulation of neoplastic cell function via EP2/EP4 receptors. 1159 75

Rat liver, liver homogenates, and microsome fractions separated therefrom were examined systematically in the electron microscope in sections of OsO(4)-fixed, methacrylate-embedded tissue and pellets. It was found that most microsomes are morphologically identical with the rough surfaced elements of the endoplasmic reticula of hepatic cells. They appear as isolated, membrane-bound vesicles, tubules, and cisternae which contain an apparently homogeneous material of noticeable density, and bear small, dense particles (100 to 150 A) attached to their outer aspect. In solutions of various osmolar concentrations they behave like osmometers. The findings suggest that they derive from the endoplasmic reticulum by a generalized pinching-off process rather than by mechanical fragmentation. The microsome fractions contain in addition relatively few vesicles free of attached particles, probably derived from the smooth surfaced parts of the endoplasmic reticula. Dense, peribiliary bodies represent a minor component of the same fractions. The microsomes derived from 1 gm. wet weight liver pulp contained (averages of 10 experiments) 3.09 mg. protein N, 3.46 mg. RNA (RNA/protein N = 1.12), and 487 microg. phospholipide P. They displayed DPNH-cytochrome c reductase activity and contained an alcohol-soluble hemochromogen. The microsome preparations proved resistant to washing and "aging." Treatment with versene and incubation with ribonuclease (30 minutes at 37 degrees C.) resulted in appreciable losses of RNA and in partial or total disappearance of attached particles. Treatment with deoxycholate (0.3 to 0.5 per cent, pH = 7.5) induced a partial clarification of the microsome suspensions which, upon centrifugation, yielded a small pellet of conglomerated small, dense particles (100 to 150 A) with only occasionally interspersed vesicles. The pellet contained approximately 80 to 90 per cent of the RNA and approximately 20 per cent of the protein N of the original microsomes. The supernatant accounted satisfactorily for the materials lost during deoxycholate treatment. The findings suggest that the microsomal RNA is associated with the small particles whereas most of the protein and nearly all of the phospholipide, hemochromogen, and DPNH-cytochrome c reductase activity are associated with the membrane or content of the microsomes.
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PMID:Liver microsomes; an integrated morphological and biochemical study. 1331 80

Microsomes were isolated from the pancreas of starved and fed guinea pigs. In the first case, the gland was removed from animals starved for 48 hours; in the second, the pancreas was excised 1 hour after the beginning of a meal that ended a fast of 48 hours. These are referred to below as fed animals. In both cases the tissue was homogenized in 0.88 M sucrose and the microsomes obtained by centrifuging the mitochondrial supernatant at 105,000 g for 60 minutes. In starved animals the content of the endoplasmic reticulum of the exocrine cells and the content of the microsomes were found to be of low or moderate density. In fed guinea pigs the cavities of the reticulum frequently contained dense intracisternal granules and the microsomes were distinguished by a content of high density sometimes in the form of recognizable intracisternal granules. In starved animals, the microsomes were found to account for 5 to 20 per cent of the trypsin-activatable proteolytic activity and ribonuclease activity of the whole cell, whereas in fed animals they contained uniformly almost 30 per cent of these activities. In fed animals the dense, cohesive content of the microsomes (intracisternal granules) could be isolated by breaking up the microsomes with dilute (0.1 per cent) deoxycholate solutions and separating microsomal subfractions by differential centrifugation. The specific enzymatic activities of a heavy microsomal subfraction rich in intracisternal granules were almost equal to those of isolated purified zymogen granules. The ribonucleoprotein particles attached to the microsomal membranes could be isolated by the same technique and found also to exhibit some of the same enzymatic activities. Corresponding subfractions isolated from the microsomes of starved animals were considerably less active. The relevance of these findings for the synthesis and intracellular transport of protein in the exocrine cell of the pancreas is discussed.
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PMID:A cytochemical study on the pancreas of the guinea pig. II. Functional variations in the enzymatic activity of microsomes. 1354 3

The various cellular components of immune rabbit histiocytes have been analyzed for their ability to induce cellular resistance in normal animals. The results of these investigations have shown that the nuclear and mitochondrial fractions were inactive and that the microsomal and ribosomal fractions were active. The importance of ribonucleic acid in induction of cellular resistance was established by isolation of an active ribosomal RNA and by demonstration of inactivation of this material with ribonuclease but not with deoxyribonuclease or trypsin. The possibility that viable bacilli were present in immune ribosomes was tested; the absence of complement-fixing antibodies and of skin reactivity to tuberculin in animals inoculated with ribosomes was considered as partial evidence of absence of living bacilli.
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PMID:STUDIES OF TUBERCLE BACILLUS-HISTIOCYTE RELATIONSHIPS. VI. INDUCTION OF CELLULAR RESISTANCE BY RIBOSOMES AND RIBOSOMAL RNA. 1407 98

Schlessinger, David (Washington University School of Medicine, St. Louis, Mo.), Vincent T. Marchesi, and Benjamin C. K. Kwan. Binding of ribosomes to cytoplasmic reticulum of Bacillus megaterium. J. Bacteriol. 90:456-466. 1965.-As many as 60% of the cellular ribosomes are bound to membrane "ghosts" in lysozyme lysates in 0.02 m Mg(2+). Bound ribosomes labeled with C(14)-uracil do not exchange with added unlabeled ribosomes, even after disruption of the cell membrane by sonic treatment. Electron micrographs of thin sections of ghosts, or of fragments produced by sonic disruption of protoplasts, indicate that the ribosomes are distributed on a reticular matrix which extends throughout the cytoplasm. The binding of ribosomes to this matrix is insensitive to ribonuclease or deoxyribonuclease, and has many other features in common with the binding of ribonucleoprotein to the membranous elements of the mammalian microsomal fraction, though the reticulum does not appear to be membranous. Thus, functioning ribosomes may be bound to a cytoplasmic structure in all cell types.
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PMID:BINDING OF RIBOSOMES TO CYTOPLASMIC RETICULUM OF BACILLUS MEGATERIUM. 1432 62

To determine the possible significance of in vivo or in vitro enzyme action in ribonucleoprotein systems, rat liver microsomes and ribonucleoprotein particles (RNP) prepared from them by deoxycholate treatment were incubated for 1 hour at 37 degrees C. with crystalline pancreatic ribonuclease (RNase) or various RNase-free crystalline proteolytic enzymes. The extent of the degradation of the RNA of the microsomes and RNP was determined and the protein degradation estimated in both cases. With either microsomes or RNP, RNase (0.5 to 1.0 mg. per ml.) degraded from 75 to 95 per cent of the RNA, with little protein breakdown being apparent when microsomes were used but with significant protein degradation in the RNP. When microsomes were treated with proteolytic enzymes approximately 40 to 50 per cent of the original microsomal protein became nonsedimentable while at the same time 60 to 80 per cent of the RNA was also found to be non-sedimentable. Of the non-sedimentable RNA, approximately one-third was in the form of acid-precipitable RNA while the remainder was in the form of acid-soluble nucleotides. When RNP was treated with proteolytic enzymes, about 95 per cent of the RNA could no longer be sedimented. About half of this appeared as acid-precipitable RNA and half as acid-soluble nucleotides. Both microsomes and RNP contained significant RNase activity with RNP exhibiting about 10 times the specific activity of microsomes. Some of the characteristics of this RNase activity were determined and the results with proteolytic enzymes interpreted in light of this activity.
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PMID:Studies on the function of intracellular ribonucleases. II. The interaction of ribonucleprotein and enzymes. 1443 7

A study was made of the permeability of the microsomes to C(14)-sucrose and to C(14)-carboxypolyglucose, a branch-chained glucose polymer with a molecular weight of approximately 50,000. It was concluded that the microsomal membranes are permeable to sucrose on the basis of the following evidence: the volume of distribution of C(14)-sucrose was 84 per cent of the total microsomal pellet water; the sucrose unavailable volume, the per cent dry weights of the microsomal pellets, and the optical density of microsomal suspensions were independent of the concentration of sucrose in the suspending medium. It is suggested that the microsomal water which is unavailable to sucrose may be bound to protein and/or ribonucleic acid of the microsomes. The volume of distribution of C(14)-carboxypolyglucose was 44 per cent of the total pellet water, and it is considered that the microsomal membranes may be impermeable to this compound. Pretreatment with ribonuclease resulted in small increases in the volumes of distribution of both C(14)-sucrose and C(14)-carboxypolyglucose.
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PMID:Permeability of rat liver microsomes to sucrose and carboxypolyglucose in vitro. 1444 67

The absence of L-ascorbic acid (L-AA, or AA) synthesis in scurvy-prone organisms, including humans, other primates, guinea pigs, and flying mammals, was traced to the lack of L-gulonolactone oxidase (GULO) activity. GULO is a microsomal enzyme that catalyzes the terminal step in the biosynthesis of L-AA. Clinical cases of scurvy were described in a family of Danish pigs. This trait is controlled by a single autosomal recessive allele designated od (osteogenic disorder). Here we demonstrate that the absence of GULO activity and the associated vitamin C deficiency in od/od pigs is due to the occurrence of a 4.2-kbp deletion in the GULO gene. This deletion includes 77 bp of exon VIII, 398 bp of intron 7 and 3.7 kbp of intron 8, which leads to a frame shift. The mutant protein is truncated to 356 amino acids, but only the first 236 amino acids are identical to the wild-type GULO protein. In addition, the od allele seems to be less expressed in deficient and heterozygous pigs compared with the normal allele in heterozygous and wild-type animals as determined by ribonuclease protection assay. We also developed a DNA-based test for the diagnosis of the deficient allele. However, we failed to identify the mutated allele in other pig populations.
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PMID:Intragenic deletion in the gene encoding L-gulonolactone oxidase causes vitamin C deficiency in pigs. 1511 10

At 22 degrees in Earle's medium, Krebs cells synthesize proteins. After a brief ;pulse' with [(14)C]valine followed by a ;chase' of [(12)C]valine the radioactivity appears first in microsomes and is transferred after ;chase' to the cell sap. Kinetics of labelling of the mitochondrial protein are different from that of either microsomal or cell-sap protein. When Krebs cells in buffer are mixed with ribonuclease in water the nuclease penetrates the cell membrane. The ribonuclease-treated cells are still viable but have lost most of their cytoplasmic ribosomes (electron micrograph). Such cells still synthesize mitochondrial protein at near normal rate but synthesis of microsomal protein is severely inhibited. The results indicate that some mitochondrial proteins are synthesized independently of the microsome-cell-sap system.
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PMID:The site of synthesis of mitochondrial proteins in Krebs II ascites-tumour cells. 1674 81


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