Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.1.21 (thymidine kinase)
 7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hepatic thymidine kinase (TK) and ornithine decarboxylase (ODC) activities were used to quantify the regenerative response to injury with galactosamine. After massive damage with 1000 mg/kg galactosamine, TK activity (DNA synthesis) peaked between 62 and 120 hours. This peak of activity was depressed as much as 91% by six subcoma doses of dimethyl disulfide (DMDS) given between 24 hours and 64 hours after galactosamine administration. Similar doses of octanoic acid (OA) had no effect, and doses of NH4Cl had no effect except at 120 hours. The first peak of ODC activity (initiation of cell growth) at 45 hours was depressed about 60% by six subcoma doses of NH4Cl or DMDS injected between 27 hours and 42 hours. OA again had no effect. After 400 mg/kg galactosamine, a narrow but high peak of TK activity occurred at 62 hours. This peak of activity was depressed more than 50% by six subcoma doses of NH4Cl, OA, or DMDS given between 24 hours and 54 hours. The first peak of ODC activity at 36 hours was similarly reduced by more than 50% by similar doses of each of the toxins given between 24 hours and 34 hours. The overt neurologic effects of the toxins were dissipated within 1 hour of each injection. The depressive effect of NH4Cl and OA on TK and ODC activities during regeneration after massive centrolobular injury with acetaminophen was more consistently present and more extensive than that seen after injury with galactosamine.
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PMID:Effect of hepatic failure toxins on regenerative enzymes in the liver after injury with galactosamine in the rat. 270 58

Persistent slight or modest increments in blood ammonia level resulting from continuous intravenous infusion of NH4+ depressed hepatic thymidine kinase (TK) activity (DNA synthesis) by 30% after two-lobe (70%) hepatectomy, by 32% after subtotal (90%) hepatectomy, by 80% after massive injury with 1400 mg/kg acetaminophen, and by 92% after massive injury with 1000 mg/kg galactosamine. Ornithine decarboxylase activity (reflecting initiation of regeneration) was similarly depressed by 65% after 70% hepatectomy, by 58% after acetaminophen, and by 87% after galactosamine. It was not depressed after 90% hepatectomy. Intermittent marked but transient increments in blood ammonia level resulted in similar but slightly smaller enzyme reductions after the injuries with the toxins, and a reduction of 92% in TK activity after 70% hepatectomy. Thus, after toxic injury, both regenerative enzymes were substantially depressed by excess ammonia, whether present transiently in large amounts or persistently in small amounts. After partial hepatectomy, TK activity was similarly depressed by the large transient amounts of ammonia but was less affected by the persistent smaller amounts.
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PMID:Regenerative enzyme activity of the liver after partial hepatectomy or toxic injury depressed by continuous NH4+ infusion. 280 96

Massive liver injury with 1000 mg/kg D-galactosamine was followed by a broad peak of thymidine kinase (TK) activity over 62 to 120 hours. The highest mean value was a 29-fold increase in activity. Three peaks of ornithine decarboxylase (ODC) activity were observed over the same time span. The first peak occurred at 45 hours, showing a sevenfold to eightfold increase in activity. Histologic evidence of necrosis peaked at 12 to 24 hours and was prominent over 54 hours. Periportal inflammation in response to the cellular injury was prominent from 12 to 96 hours and peaked at 45 to 62 hours. The curve of mitoses peaked at the same time as that of TK activity but was only 68% as extensive. The first peak of ODC activity occurred before there was any significant presence of mitoses or of TK activity. A smaller dose of 400 mg/kg resulted in a narrow peak of TK activity at 62 hours that was a 37-fold increase in activity. The total TK response was 43% of that seen after the larger dose, about in proportion to the dose given. The first ODC peak, representing the earliest evidence of regeneration, was earlier and more prominent after the 400 mg/kg dose. On the basis of areas under the curves, the amounts of necrosis and of periportal inflammation after 400 mg/kg were 36% of those seen after 1000 mg/kg. Corresponding figures for other response curves were 29% for mitoses, 33% for serum SGPT, and 71% for total ODC activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Hepatic regenerative enzyme activity after diffuse injury with galactosamine: relationship to histologic alterations. 318 90

Connexins are subunits of gap junction channels, which allow direct transfer of ions, secondary messenger molecules, and other metabolites between contacting cells. Gap junctions are believed to be involved in tissue homeostasis, embryonic development, and control of cell proliferation. Several studies have shown that cell damage signals are transmitted through gap junctions when cells are irradiated or when cells bearing the herpes simplex virus-thymidine kinase (HSV-TK) gene are treated with ganciclovir. We established 2 lines of transgenic rats with a dominant-negative mutant of connexin 32 gene under control of the albumin promoter. In the livers of transgenic rats, membrane localization of normal endogenous connexin 32 protein is disturbed, and gap junction capacity measured by scrape dye-transfer assay in vivo is markedly decreased when compared with wild-type rats. The present investigation concerned susceptibility to the liver-toxic substances D-galactosamine and carbon tetrachloride. These toxicants induced massive liver cell death and elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the wild-type rats; however, much fewer liver cells were damaged and serum enzyme elevation was much lower in the transgenic rats. In conclusion, gap junctional intercellular communication (GJIC) plays an important role in toxic effects of chemicals; damage or death signals may pass through gap junctions in the rat liver in vivo.
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PMID:Connexin 32 dominant-negative mutant transgenic rats are resistant to hepatic damage by chemicals. 1523 4