Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.4 (ribonuclease)
 6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The fixation of CO2 into major classes of RNA in the mouse embryo was studied in culture. Total fixation of CO2 was low at the two-cell stage and no label was found in RNA. Between the eight-cell and morula/early blastocyst stages of development, total fixation increased markedly but decreased again at the late blastocyst stage. On a per cell basis, the level of incorporation of CO2 decreased steadily throughout the preimplantation period. A significant acceleration in the accumulation of 14CO2 into all classes of RNA occurred between eight-celled embryos and morulae/early blastocysts, and this effect was more evident when results were calculated in relation to cell number. At the late blastocyst stage, incorporation of label into RNA decreased on a per embryo and a per cell basis. Most of the label from CO2 was incorporated into the r-RNA fraction at all stages of development and incorporation into s-RNA was always less. The pattern of labelling of RNA with 14CO2 was similar to that previously obtained for the incorporation of [3H]uridine into embryonic RNA, suggesting that most of the CO2 entering the RNA pool may be incorporated into nucleotide bases. The s-RNA and r-RNA fractions were susceptible to digestion with both pancreatic ribonuclease and 0-3 M alkali. Approximately 31% of the label in the TD-RNA fraction remained after hydrolysis with ribonuclease and a similar proportion of the TD-RNA was resistant to alkali treatment. Incorporation of CO2 by morulae/early blastocysts was substantial during culture in substrate-free medium but was increased significantly in medium containing lactate plus pyruvate. Carbon dioxide fixation into RNA was decreased by preculture for 48 hr before incubation in radioactive medium. When compared with freshly collected morulae/early blastocysts, the proportion of the total label in the s-RNA fraction of precultured embryos was low, and a correspondingly greater proportion of the total label was found in the TD-RNA fraction.
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PMID:The incorporation of carbon dioxide into the major classes of RNA during culture of the preimplantation mouse embryo. 124 46

The in vitro metabolism of [14C]toluene by liver microsomes and liver slices from male Fischer F344 rats and human subjects has been compared. Rat liver microsomes produced only benzyl alcohol from toluene. Liver microsomes from human subjects metabolized toluene to benzyl alcohol, benzaldehyde, and benzoic acid. Liver microsomes from one human donor also produced p-cresol and o-cresol. The overall rate of toluene metabolism by human liver microsomes was 9-fold greater than by rat liver microsomes. Human liver microsomal metabolism of benzyl alcohol to benzaldehyde required NADPH and was inhibited by carbon monoxide and high pH (pH 10). but was not inhibited by ADP-ribose or sodium azide. These results suggest that cytochrome P-450, rather than alcohol dehydrogenase, was responsible for the metabolism of benzyl alcohol to benzaldehyde. Human and rat liver slices metabolized toluene to hippuric acid and benzoic acid. The overall rate of toluene metabolism by human liver slices was 1.3-fold greater than by rat liver slices. Cresols and cresol conjugates were not detected in human or rat liver slice incubations. Covalent binding of [14C]toluene to human liver microsomes and slices was 21-fold and 4-fold greater than to the comparable rat liver preparations. Covalent binding did not occur in the absence of NADPH, was significantly decreased by coincubation with cysteine, glutathione, or superoxide dismutase, and was unaffected by coincubation with lysine. Protease and ribonuclease digestion decreased the amount of toluene covalently bound to human liver microsomes by 78% and 27% respectively. Acid washing of human liver microsomes had no effect on covalent binding.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolism and covalent binding of [14C]toluene by human and rat liver microsomal fractions and liver slices. 198 39

The formate radical (CO2-) reacts with ribonuclease A to form the cystine disulfide radical as one of the products. CO2- reacts with the riboflavin binding protein of chicken egg white with the ultimate product being the neutral flavin semiquinone. Formation of the disulfide radical in ribonuclease is slower than the reaction between protein and CO2-; formation of the flavin semiquinone in the riboflavin binding protein is slower than the protein-CO2- reaction. We conclude for both proteins that CO2- must reduce an as yet unidentified group or groups, which in turn reduce(s) the disulfide of RNase or the flavin of riboflavin binding protein. This conclusion is supported in the case of ribonuclease by the observation of a transient, broad absorption band centered between 350 and 370 nm. The CO2--initiated reductions of the disulfide in ribonuclease and the flavin in the riboflavin binding protein are mixed first- and second-order processes. We propose that the transfer of an electron from the unknown intermediate(s) to the final product involves both inter- and intramolecular paths between groups that may not be in van der Waals contact. With the hydrated electron, in contrast to CO2-, as reductant of the riboflavin binding protein, the anionic semiquinone is observed as an intermediate. The anionic semiquinone is then rapidly protonated, yielding the stable neutral semiquinone. From the reaction kinetics and protein concentration dependence, we conclude that a group or groups on the protein donate(s) a proton to the anionic semiquinone by both inter- and intramolecular paths.
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PMID:Intramolecular electron and proton transfer in proteins: CO2- reduction of riboflavin binding protein and ribonuclease A. 299 79

Protein synthesis, normally a light-dependent process in isolated mature chloroplasts of Euglena gracilis var. bacillaris will take place in darkness if ATP and Mg2+ (ATP/Mg) are supplied. Either 5 or 10 mM ATP plus 15 mM MgCl2 are optimal and rates equal to those in the light can be obtained. Since ATP and Mg2+ are not stoichiometrically related, and since the optimal Mg2+ concentration is similar to that which stabilizes chloroplast ribosomes in vitro, it is suggested that the chloroplast is freely permeable to Mg2+ under these conditions. Protein synthesis under these conditions is not inhibited appreciably by DCMU, FCCP, cycloheximide, or by the addition of ribonuclease, but is highly sensitive to chloramphenicol. Carbon dioxide fixation is also a light-dependent process in isolated mature chloroplasts from Euglena, but addition of ATP (5 mM) and fructose bisphosphate (5 mM) plus aldolase (1.0 unit/ml) (fructose-1,6-bisphosphate/aldolase) yields CO2 fixation rates in darkness that are 43% of those normally obtained in the light. Mg2+ higher than 1.0 mM (e.g., 16 mM) is somewhat inhibitory. Chlorophyll synthesis from 5-aminolevulinate in 36 h developing chloroplasts from Euglena is also light-dependent, but addition of ATP/Mg and fructose-1,6-bis-phosphate/aldolase in darkness brings about the accumulation of a compound having the same RF on chromatography as protochlorophyllide from Barley; a subsequent brief illumination of the chloroplasts converts this compound to a compound with the RF of chlorophyll. Thus Euglena chloroplasts supplied with appropriate additions can carry out protein synthesis, carbon dioxide fixation and most of chlorophyll synthesis in darkness. This versatility is appropriate in photosynthetic organelles isolated from photo-organotrophic cells.
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PMID:Synthetic abilities of Euglena chloroplasts in darkness. 392 91

A hemolysin produced by Treponema hyodysenteriae, the etiological agent of swine dysentery, was investigated. A virulent isolate (B204) was inoculated into a standard culture medium consisting of Trypticase soy broth without dextrose (BBL Microbiology Systems) supplemented with 10% fetal calf serum in an atmosphere of 70:30 deoxygenated H2-CO2. Sterile cell-free filtrates were prepared at 2-h intervals and assayed for hemolytic activity by using washed sheep erythrocytes. The maximum hemolytic titer was obtained during the early log phase of growth (4 h). A loss of hemolytic activity was observed when cell-free filtrates were stored at 23 and 4 degrees C. Storage at -20 or -80 degrees C after lyophilization resulted in retention of the hemolytic titer for periods of up to 30 days. Enzymatic inactivation of the hemolysin was accomplished with pronase, but not with deoxyribonuclease, ribonuclease, lipase, or trypsin. Addition of exogenous ribonucleic acid-core to the standard culture medium resulted in a dose-dependent increase in the amount of hemolysin produced. The hemolysin could be purified by acid and ammonium sulfate precipitation followed by ion exchange and molecular sieve chromatography. The molecular weight of the hemolysin was 68,000 when determined by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis.
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PMID:Investigation of a hemolysin produced by enteropathogenic Treponema hyodysenteriae. 721 45

This study aimed to investigate the influence of acute tissue hypoxygenation on the expression of NO synthase (NOS) genes in vivo. To this end, male Sprague-Dawley rats were exposed either to 9% oxygen or to 0.1% carbon monoxide for 6 h, and mRNA levels of NOS-I, -II, and -III in kidneys, livers, lungs, and left and right heart ventricles were assayed by ribonuclease protection. For comparison, mRNA levels of erythropoietin were also measured in these tissues. NOS-III mRNA was highly abundant in all organs investigated. NOS-II mRNA was detected in lungs and hearts but not in kidneys and livers. NOS-I mRNA was found in kidneys, lungs, and hearts but not in livers. NOS-III mRNA levels were upregulated by hypoxia in all tissues examined, with the least effect (1.2-fold) in the left ventricle and the greatest effect (2.6-fold) in the lung. NOS-II mRNA was substantially downregulated in the ventricles by both treatments but not changed in the lung. NOS-I mRNA was upregulated by carbon monoxide in kidneys and lungs and by 9% oxygen in the lung. These findings suggest that NOS-III and possibly also NOS-I gene expression behave like oxygen-regulated genes, whereas the general effect of tissue hypoxygenation on NOS-II gene expression is less clear. Because NOS-III is primarily expressed in endothelial cells, a general upregulation of NOS in these cells may be of relevance for the regulation and maintenance of blood flow through hypoxic tissues.
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PMID:Acute hypoxia upregulates NOS gene expression in rats. 932 66

Gaseous CO2 was used as an antisolvent to induce the fractional precipitation of alkaline phosphatase, insulin, lysozyme, ribonuclease, trypsin, and their mixtures from dimethylsulfoxide (DMSO). Compressed CO2 was added continuously and isothermally to stationary DMSO solutions (gaseous antisolvent, GAS). Dissolution of CO2 was accompanied by a pronounced, pressure-dependent volumetric expansion of DMSO and a consequent reduction in solvent strength of DMSO towards dissolved proteins. View cell experiments were conducted to determine the pressures at which various proteins precipitate from DMSO. The solubility of each protein in CO2-expanded DMSO was different, illustrating the potential to separate and purify proteins using gaseous antisolvents. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS-PAGE) was used to quantify the separation of lysozyme from ribonuclease, alkaline phosphatase from insulin, and trypsin from catalase. Lysozyme biological activity assays were also performed to determine the composition of precipitates from DMSO initially containing lysozyme and ribonuclease. SDS-PAGE characterizations suggest that the composition and purity of solid-phase precipitated from a solution containing multiple proteins may be accurately controlled through the antisolvent's pressure. Insulin, lysozyme, ribonuclease, and trypsin precipitates recovered substantial amounts of biological activity upon redissolution in aqueous media. Alkaline phosphatase, however, was irreversibly denaturated. Vapor-phase antisolvents, which are easily separated and recovered from proteins and liquid solvents upon depressurization, appear to be a reliable and effective means of selectively precipitating proteins.
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PMID:Protein purification with vapor-phase carbon dioxide. 1009 36

This study aimed to investigate the role of endogenous nitric oxide (NO) in erythropoietin (EPO) gene expression in mice in vivo. For this purpose EPO mRNA was semiquantitated by ribonuclease protection assay in livers and kidneys of three groups of mice: wild-type (wt), endothelial NO-synthase (NOS) knockout mice (eNOS-/-), and wt treated with the NOS inhibitor N(G)-nitro-L-arginine methyl ester (50 mg x kg(-1) x day(-1)) for 4 days (wt+L-NAME). EPO gene expression was stimulated by normobaric hypoxia (8% O2) or by 0.1% carbon monoxide (CO) inhalation for 4 h each, or by intraperitoneal injection of 60 mg/kg cobaltous chloride (CoCl2) for 6 h. Renal EPO mRNA in wt increased 12-, 40-, and 13-fold over normoxic levels in response to hypoxia, CO and CoCl2 respectively. EPO mRNA was detectable in the livers only after CO exposure. Renal and hepatic EPO gene expression in wt+L-NAME appeared moderately increased relative to wt with a maximal 2.5-fold enhancement after CO exposure. EPO mRNA levels in eNOS-/- mirrored those of wt+L-NAME, but the effects were less prominent. Our data suggest that endogenous NO attenuates EPO gene expression in mice. This effect is dependent on the rate of EPO gene induction.
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PMID:Endogenous nitric oxide attenuates erythropoietin gene expression in vivo. 1067 40

An unforeseen side-effect on plant growth in reduced oxygen is the loss of seed production at concentrations around 25% atmospheric (50 mmol mol-1 O2). In this study, the model plant Arabidopsis thaliana (L.) Heynh. cv. 'Columbia' was used to investigate the effect of low oxygen on ethylene biosynthesis during seed development. Plants were grown in a range of oxygen concentrations (210 [equal to ambient], 160, 100, 50 and 25 mmol mol-1) with 0.35 mmol mol-1 CO2 in N2. Ethylene in full-sized siliques was sampled using gas chromatography, and viable seed production was determined at maturity. Molecular analysis of ethylene biosynthesis was accomplished using cDNAs encoding 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase in ribonuclease protection assays and in situ hybridizations. No ethylene was detected in siliques from plants grown at 50 and 25 mmol mol-1 O2. At the same time, silique ACC oxidase mRNA increased three-fold comparing plants grown under the lowest oxygen with ambient controls, whereas ACC synthase mRNA was unaffected. As O2 decreased, tissue-specific patterning of ACC oxidase and ACC synthase gene expression shifted from the embryo to the silique wall. These data demonstrate how low O2 modulates the activity and expression of the ethylene biosynthetic pathway during seed development in Arabidopsis.
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PMID:Oxygen control of ethylene biosynthesis during seed development in Arabidopsis thaliana (L.) Heynh. 1209 14