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:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hepatotoxic doses of acetaminophen cause widespread alkylation of liver and early loss of cytosolic Ca2+ regulation. Although the precise location and target of lethal alkylation are not known, Ca2+ accumulation is viewed as a possible link between cell alkylation and cell death. We have recently shown that Ca2+ accumulates in the nucleus and that DNA fragments in vivo before the development of acetaminophen-induced necrosis in mice. The present study examined cultured hepatocytes for nuclear damage and its association with cell death in vitro. Positive results would argue for two key points. (1) Nonparenchymal cell damage does not explain DNA fragmentation induced by acetaminophen in vivo. (2) A chemical that causes necrosis can produce DNA damage considered characteristic of apoptosis. Hepatocytes from NIH Swiss mice were isolated by collagenase perfusion, cultured in Williams' E medium for 24 hr, and exposed to acetaminophen. Cytotoxicity was assessed by lactate dehydrogenase leakage and release of [3H]adenine from a prelabeled nucleotide pool. Genomic DNA fragmentation was assessed quantitatively by colorimetric analysis and qualitatively by agarose gel electrophoresis. Acetaminophen caused DNA damage from 1-4 hr onward and produced significant release of lactate dehydrogenase and [3H]adenine nucleotides at later times. Agarose gel electrophoresis revealed a "ladder" of DNA fragments characteristic of Ca(2+)-mediated endonuclease activation. Cytotoxicity correlated with nuclear Ca2+ accumulation (r greater than 0.895, p less than 0.05) and with percentage DNA fragmentation (r greater than 0.835, p less than 0.05). Nuclear changes in vitro generally reproduced those observed in vivo. Collectively, these findings demonstrate that nuclear Ca2+ accumulation and DNA fragmentation appear as early events that correlate directly with later cytotoxicity. These changes may contribute to acetaminophen-induced injury leading to cell death in vitro and necrosis in vivo.
...
PMID:Acetaminophen-induced cytotoxicity in cultured mouse hepatocytes: correlation of nuclear Ca2+ accumulation and early DNA fragmentation with cell death. 195 10

A lactate dehydrogenase (LDH) gene of Clostridium acetobutylicum B643 was cloned on two recombinant plasmids, pPC37 and pPC58, that were selected by complementation of Escherichia coli PRC436 (acd), a fermentation-defective mutant that does not grow anaerobically on glucose. E. coli PRC436(pPC37) and PRC436(pPC58) grew anaerobically and fermented glucose to mostly lactate. When pPC37 and pPC58 were transformed into E. coli FMJ39 (ldh pfl), an LDH-deficient strain, the resulting strains grew anaerobically on glucose and produced lactate. Crude extracts of E. coli FMJ39(pPC37) and FMJ39(pP58) contained high LDH activity only when assayed for pyruvate reduction to lactate, and the LDH activity was activated 15- to 30-fold by the addition of fructose 1,6-diphosphate (FDP). E. coli FMJ39 had no detectable LDH activity, and E. coli LDH from a wild-type strain was not activated by FDP. Maxicell analysis showed that both plasmids pPC37 and pPC58 expressed a protein with an apparent Mr of 38,000 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Restriction endonuclease mapping of pPC37 and pPC58 and DNA hybridization studies indicated that a 2.1-kb region of these two clones of C. acetobutylicum DNA encodes the FDP-activated LDH.
...
PMID:Cloning of a lactate dehydrogenase gene from Clostridium acetobutylicum B643 and expression in Escherichia coli. 208 23

Restriction endonuclease analysis (REA) was performed on the total cellular DNA from each of 396 strains of mutans streptococci (1) to determine its potential usefulness for the study of transmission of the organism and (2) to document the proportions and variety of strains harbored by members of a small group of families. The DNA was digested with restriction enzyme EcoRI and/or HindIII, electrophoresed on agarose gels, and the resulting patterns compared. The strains examined included fresh isolates from 58 subjects, including 19 strains from each member of five families. The sensitivity and reproducibility of REA patterns from the mutans streptococci seemed ideal for studies of their epidemiology and transmission. The pattern of each isolate from humans was unique, except for isolates from the same individual or from the same family. REA types from subjects from different families were always heterogeneous. A high frequency of multiple REA types (up to 5) was observed in many subjects. While evidence for intra-familial transmission was obtained, including transmission between spouses, there was also strong evidence of frequent sources of infection outside of the family. Mutations of strains to streptomycin resistance or to lactate dehydrogenase deficiency caused no detectable change in the REA patterns. The lack of plasmids in any of the 57 fresh isolates that were examined for them suggested that they may have contributed little to the heterogeneity of the patterns seen.
...
PMID:An investigation into the use of restriction endonuclease analysis for the study of transmission of mutans streptococci. 263

When thymocytes were cultured with adenosine, deoxyadenosine, or deoxyguanosine at 1 mM for 24 h, DNA cleavage at internucleosomal sites with multiples of approximately 180 bp was induced, followed by lactate dehydrogenase release into the medium. In the presence of coformycin, an adenosine deaminase inhibitor, or formycin B, a purine nucleoside phosphorylase inhibitor, DNA cleavage was induced by these nucleosides at concentrations of less than 50 microM. Other purine and pyrimidine ribo- and deoxyribonucleosides did not induce DNA cleavage or LDH release. Because thymocyte nuclei contain a Ca2+,Mg2+-dependent endonuclease, which preferentially cuts DNA in its linker regions, DNA fragmentation induced by the three purine nucleosides was suggested to occur through increased activity of the endonuclease. The DNA cleavage induced by the nucleosides required protein phosphorylation and synthesis, inasmuch as it was inhibited by an inhibitor of protein kinases, H-7, and by an inhibitor of protein synthesis, cycloheximide. The inhibition of DNA cleavage was accompanied by a reduction in lactate dehydrogenase release, suggesting a causal relationship between DNA cleavage and cell death. The DNA cleavage and subsequent cell lysis might be related to the selective thymocyte deletion observed in patients with adenosine deaminase or purine nucleoside phosphorylase deficiency.
...
PMID:Adenosine, deoxyadenosine, and deoxyguanosine induce DNA cleavage in mouse thymocytes. 326 57

The gene for L-lactate dehydrogenase (LDH) (EC 1.1.1.27) of Thermus caldophilus GK24 was cloned in Escherichia coli using synthetic oligonucleotides as hybridization probes. The nucleotide sequence of the cloned DNA was determined. The primary structure of the LDH was deduced from the nucleotide sequence. The deduced amino acid sequence agreed with the NH2-terminal and COOH-terminal sequences previously reported and the determined amino acid sequences of the peptides obtained from trypsin-digested T. caldophilus LDH. The LDH comprised 310 amino acid residues and its molecular mass was determined to be 32,808. On alignment of the whole amino acid sequences, the T. caldophilus LDH showed about 40% identity with the Bacillus stearothermophilus, Lactobacillus casei and dogfish muscle LDHs. The T. caldophilus LDH gene was expressed with the E. coli lac promoter in E. coli, which resulted in the production of the thermophilic LDH. The gene for the T. caldophilus LDH showed more than 40% identity with those for the human and mouse muscle LDHs on alignment of the whole nucleotide sequences. The G + C content of the coding region for the T. caldophilus LDH was 74.1%, which was higher than that of the chromosomal DNA (67.2%). The G + C contents in the first, second and third positions of the codons used were 77.7%, 48.1% and 95.5% respectively. The high G + C content in the third base caused extremely non-random codon usage in the LDH gene. About half (48.7%) the codons in the LDH gene started with G, and hence there were relatively high contents of Val, Ala, Glu and Gly in the LDH. The contents of Pro, Arg, Ala and Gly, which have high G + C contents in their codons, were also high. Rare codons with U or A as the third base were sometimes used to avoid the TCGA sequence, the recognition site for the restriction endonuclease, TaqI. Two TCGA sequences were found only in the sequence of CTCGAG (XhoI site) in the sequenced region of the T. caldophilus DNA. There were three segments with similar sequences in the two 5' non-coding regions, probably the promoter and ribosome-binding regions, of the genes for the T. caldophilus LDH and the Thermus thermophilus 3-isopropylmalate dehydrogenase.
...
PMID:Nucleotide sequence and characteristics of the gene for L-lactate dehydrogenase of Thermus caldophilus GK24 and the deduced amino-acid sequence of the enzyme. 353 39

Chronic exposure to dimethylnitrosamine produces hepatic tumors through recurrent DNA alkylation, whereas acute exposure can cause liver necrosis through mechanisms that remain largely unknown. Our laboratory recently demonstrated that DNA fragmentation occurs early on and may be a causal event in dimethylnitrosamine-induced necrosis in liver. A challenge to interpreting these results is that up to 30% of liver cells are non-parenchymal and could account for the observed DNA fragmentation. In the present study, we have examined whether dimethylnitrosamine induces early genomic DNA fragmentation in cultured mouse hepatocytes. Hepatic parenchymal cells isolated from male ICR mice were cultured in Williams E medium. DNA damage was assessed quantitatively as a fragmented fraction that was not sedimented at 27,000 x g, and qualitatively from agarose gel electrophoresis. Cellular response to DNA damage was assessed by measuring induction of the DNA repair enzyme DNA ligase. Toxic cell death was estimated from release of lactate dehydrogenase (LDH) or adenine nucleotides from cells prelabeled with [3H]adenine. Dimethylnitrosamine produced a twofold increase in [3H]adenine release by 6 h and LDH release at 36 h. DNA fragmentation and DNA ligase activity increased by as early as 1 h. The Ca(2+)-endonuclease inhibitor aurintricarboxylic acid and the Ca2+ chelator ethylenediamine tetraacetic acid (EDTA) prevented DNA fragmentation through 6 h and virtually abolished cytotoxicity through 30 h. DNA ligase induction was strongly associated with DNA fragmentation. Early increases in DNA fragmentation and DNA ligase were highly correlated with later toxic cell death. Such results strongly suggest that dimethylnitrosamine-induced fragmentation of DNA in target parenchymal cells is a causal factor in the toxic death of these liver cells.
...
PMID:Dimethylnitrosamine-induced DNA damage and toxic cell death in cultured mouse hepatocytes. 766 92

Exposure of renal proximal tubular epithelial cells (LLC-PK1) to the nephrotoxicants 2-bromo-6-(glutathion-S-yl)hydroquinone, 2-bromo-3-(glutathion-S-yl)-hydroquinone, and 2-bromo-(diglutathion-S-yl)hydroquinone caused DNA fragmentation and cytotoxicity. Viability measured by lysosomal neutral red accumulation was the most sensitive parameter of cytotoxicity, and preceded toxicity determined by either the mitochondrial MTT assay or by measuring intracellular lactate dehydrogenase activity. DNA fragmentation was detected as early as 15 min after exposure to 2-bromo-6-(glutathion-S-yl)hydroquinone (100 microM), 2-bromo-3-(glutathion-S-yl)hydroquinone (200 microM), and 2-bromo-(diglutathion-S-yl)hydroquinone (400 microM) and prior to other indices of toxicity. The ability of the cells to repair DNA damage was evident by the decrease in the extent of single strand breaks following removal of 2-bromo-3-(glutathion-S-yl)hydroquinone from the incubation medium. Moreover, inhibition of poly(ADP-ribose)polymerase with 3-amino-benzamide (10 mM), following exposure of LLC-PK1 cells to 0.5 mM 2-bromo-6-(glutathion-S-yl)hydroquinone or 2-bromo-(diglutathion-S-yl)hydroquinone, decreased cytotoxicity, indicating that DNA repair processes, activated in response to DNA damage, exacerbate toxicity. Treatment with the endonuclease inhibitor, aurintricarboxylic acid did not decrease cytotoxicity. A decrease in the cytotoxicity caused by 2-bromo-6-(glutathion-S-yl)hydroquinone and 2-bromo-(diglutathion-S-yl)hydroquinone was observed when cells were incubated with catalase or pretreated with deferoxamine (10 mM). The data suggest a mechanism whereby the conjugates generate hydrogen peroxide, and the subsequent iron-catalyzed generation of hydroxyl radicals causes DNA fragmentation and cytotoxicity.
...
PMID:Reactive oxygen species and DNA damage in 2-bromo-(glutathion-S-yl) hydroquinone-mediated cytotoxicity. 779 84

Alterations of cellular functions induced by recombinant human tumor necrosis factor alpha (TNF alpha) were compared in rat hepatocytes cultured under either periportal-equivalent (10 nM insulin; 10 nM glucagon; 13% O2) or perivenous-equivalent conditions (10 nM insulin; 1 nM glucagon; 4% O2). TNF alpha induced a time- and dose-dependent increase in nitric oxide (NO) production and an acute phase response (inhibition of albumin secretion and elevation of alpha 2-macroglobulin production) under both culture conditions. NO production was more pronounced in periportal cultures, while the acute phase response was stronger in pericentral cultures. This suggests that NO production and the acute phase response are controlled by different pathways. After exposure to TNF alpha, DNA content was measured fluorimetrically and biochemically. A marked decrease in nuclear DNA content was found exclusively in pericentral cultures after an 8-h exposure, followed by an elevation of lactic dehydrogenase (LDH) release after a 12-h exposure. Aurintricarboxylic acid (100 microM), an inhibitor of endonuclease, significantly inhibited the TNF alpha-induced decrease in nuclear DNA content but only partially inhibited the LDH release. This indicates that the loss of nuclear DNA content in pericentral cultures is due to an activation of endonuclease and the resulting DNA fragmentation and does not correlate with NO production. Furthermore, the release of LDH seems to be only partially associated with DNA damage. Dexamethasone (100 nM) completely inhibited both TNF alpha-induced DNA fragmentation and the elevation of LDH release. The results clearly indicate that the toxicity of TNF alpha is influenced by the metabolic state of hepatocytes. Accordingly, the preferential perivenous cell injury observed after exposure to endotoxins in vivo seems to be due to a higher sensitivity of the pericentrally localized hepatocytes towards TNF alpha rather than a TNF alpha concentration gradient.
...
PMID:Tumor necrosis factor alpha differentially modulates the cellular response of rat hepatocytes in periportal- and pericentral-equivalent cultures. 779 59

In this study, the endonuclease inhibitor aurintricarboxylic acid (ATA) was examined for its ability to attenuate both acute and delayed excitotoxicity mediated through NMDA and non-NMDA glutamate receptors. Ex vivo embryonic chick retina, a model system frequently used for studies of excitotoxicity, was exposed to either 100 microM NMDA or kainate (KA) +/- various concentrations of ATA for 60 min, then allowed to recover for 24 h. Lactate dehydrogenase release into the medium and histology were assessed as measures of delayed toxicity. ATA attenuated lactate dehydrogenase release due to NMDA or KA in a dose-dependent manner. Histology revealed that ATA decreased the number of pyknotic profiles in response to either glutamate agonist. The mechanism of ATA protection was addressed. ATA was found to block NMDA- but not KA-mediated 22Na+ influx and cyclic GMP formation. In membrane binding studies, ATA was relatively selective for displacement at the NMDA receptor. The IC50 values for displacement of [3H]CGS 19755, alpha-[3H]amino-3-hydroxy-5-methylisoxazole-4-propionic acid ([3H]AMPA), or [3H]KA were 29.9 +/- 1.3, 313 +/- 46, and > 1,000 microM +/- SEM, respectively. ATA also fully attenuated NMDA-induced and partially attenuated KA-induced acute excitotoxicity as monitored histologically by tissue swelling and by the increase in GABA in the medium. Temporal studies of ATA efficacy indicated that ATA needed to be present during NMDA exposure to afford protection but, versus KA, was equally effective if administered immediately after KA exposure. Questions regarding the cellular penetration of ATA were raised because incubation with 100 microM ATA for 60 min had no effect on lactate formation or [3H]leucine incorporation into trichloroacetic acid-precipitable material, even though, in cell-free systems, ATA is a potent inhibitor of phosphofructokinase activity and protein synthesis. These studies demonstrate that ATA can protect against excitotoxicity mediated through NMDA or non-NMDA glutamate receptors. The mechanism of protection versus NMDA is through interruption of NMDA receptor interactions. ATA has no direct effect at the KA receptor; thus, its mechanism of protection versus KA is distinct from that versus NMDA and is, at present, unknown.
...
PMID:Excitotoxicity at both NMDA and non-NMDA glutamate receptors is antagonized by aurintricarboxylic acid: evidence for differing mechanisms of action. 789 Nov 4

Aurintricarboxylic acid (ATA), an endonuclease inhibitor, has been shown to protect several cell types from an apoptotic form of cell death. We tested ATA for protective effects against glutamate excitotoxicity in 2-week-old cultured hippocampal neurons. Cell viability was determined 24 h after glutamate exposure either by trypan blue exclusion or by measurement of lactate dehydrogenase release. When ATA was added during exposure to glutamate, there was a dramatic increase in the number of viable neurons compared with cultures that did not receive ATA. If ATA was added after glutamate exposure, the rate of survival approached 100%. Several cellular processes may be the targets for ATA action. If the mechanisms of ATA protection are similar for excitotoxicity and apoptosis, then these distinct forms of cell death may share a common intracellular pathway.
...
PMID:Aurintricarboxylic acid protects hippocampal neurons from glutamate excitotoxicity in vitro. 809 52


1 2 3 Next >>

---