scholarly journals Studies of the ethylation of rat liver transfer ribonucleic acid after administration of l-ethionine

1972 ◽  
Vol 128 (1) ◽  
pp. 59-68 ◽  
Author(s):  
A. E. Pegg
Keyword(s):  
Rat Liver ◽  
Ribonucleic Acid ◽  
Major Part ◽  
Actinomycin D ◽  
Major Product ◽  
The Other ◽  
Methyl Donor ◽  
Principal Product

1. The ethylated nucleosides present in tRNA isolated from the livers of rats treated with 0.5g of l-ethionine/kg body wt. were investigated. Evidence that this tRNA contained N2-ethylguanine, N2N2-diethylguanine, N2-ethyl-N2-methylguanine, 7-ethylguanine, two ethylated pyrimidines and ethylated ribose groups was obtained. 2. Ethylation of bacterial tRNA was catalysed by extracts containing tRNA methylases prepared from rat liver by using S-adenosyl-l-ethionine as an ethyl donor, but the rate of ethylation was 20 times less than the rate of methylation with S-adenosyl-l-methionine as a methyl donor. 3. The principal product of such ethylation in vitro was N2-ethylguanine and traces of the other ethylated guanines and pyrimidines found in tRNA isolated from rats treated with ethionine in vivo were also found. 1-Ethyladenine was not formed, although 1-methyl-adenine is a major product of methylation of bacterial tRNA by these extracts, and 1-ethyladenine was not present in the rat liver tRNA isolated from ethionine-treated animals. 4. After injection of actinomycin D (15mg/kg body wt.) or l-methionine (1.0g/kg body wt.) before the ethionine, ethylation of tRNA was diminished by about 80% but not completely abolished. Administration of 1-aminocyclopentanecarboxylic acid (2.5g/kg body wt.) to inhibit the formation of S-adenosyl-l-ethionine inhibited ethylation of tRNA by 44%. 5. These results suggest that not all of the ethylation of tRNA that occurs in the livers of rats treated with ethionine is mediated by the action of tRNA methylases acting with S-adenosyl-l-ethionine as a substrate, but that this pathway does occur and accounts for a major part of the observed ethylation. 6. The results are discussed with reference to ethionine-induced hepatocarcinogenesis.

scholarly journals The effects of salicylate on the activity of rat liver tyrosine–2-oxoglutarate aminotransferase in vitro and in vivo

1972 ◽  
Vol 126 (2) ◽  
pp. 347-350 ◽  
Author(s):  
A. A.-B. Badawy
Keyword(s):  
Rat Liver ◽  
Pyridoxal Phosphate ◽  
Actinomycin D ◽  
Sodium Salicylate ◽  
Intraperitoneal Administration ◽  
Tyrosine Aminotransferase ◽  
Major Effect ◽  
Endogenous Activity

1. Salicylate, in concentrations of 0.25mm and above, enhances the basal activity of tyrosine–2-oxoglutarate aminotransferase in homogenates of rat liver incubated in the absence of added pyridoxal 5′-phosphate (endogenous activity). The effect is decreased by increasing the concentration of the cofactor. 2. The intraperitoneal administration of sodium salicylate enhances the activity of rat liver tyrosine aminotransferase; the major effect during the first hour being on the enzyme in the absence of added pyridoxal phosphate. Actinomycin D prevents the induction of the enzyme by cortisol and tryptophan. Induction by pyridoxine or salicylate is 50% inhibited by actinomycin D. The effects of the injections of various combinations of cortisol, pyridoxine and salicylate were also studied in the absence or presence of actinomycin D. 3. It is suggested that salicylate induces rat liver tyrosine aminotransferase by displacing its protein-bound cofactor and that a cofactor-type induction of the hepatic enzyme occurs in pyridoxine-treated rats.

scholarly journals ANTIGENIC MODULATION

1968 ◽  
Vol 127 (3) ◽  
pp. 523-539 ◽  
Author(s):  
Lloyd J. Old ◽  
Elisabeth Stockert ◽  
Edward A. Boyse ◽  
Jae Ho Kim
Keyword(s):  
Actinomycin D ◽  
Progressive Increase ◽  
The Other ◽  
Antigenic Modulation ◽  
Cytotoxic Test ◽  
Cell Divisions ◽  
Wide Range ◽  
D Region

Antigenic modulation (the loss of TL antigens from TL+ cells exposed to TL antibody in the absence of lytic complement) has been demonstrated in vitro. An ascites leukemia, phenotype TL.1,2,3, which modulates rapidly and completely when incubated with TL antiserum in vitro, was selected for further study of the phenomenon. Over a wide range of TL antibody concentrations modulation at 37°C was detectable within 10 min and was complete within approximately 1 hr. The cells were initially sensitized to C' by their contact with antibody, thereafter losing this sensitivity to C' lysis together with their sensitivity to TL antibody and C' in the cytotoxic test. The capacity of the cells to undergo modulation was abolished by actinomycin D and by iodoacetamide, and by reducing the temperature of incubation to 0°C. Thus modulation apparently is an active cellular process. Antigens TL. 1,2, and 3 are all modulated by anti-TL.1,3 serum and by anti-TL.3 serum. This modulation affects all three TL components together, even when antibody to one or two of them is lacking. aAnti-TL.2 serum does not induce modulation and in fact impairs modulation by the other TL antibodies. The influence of the TL phenotype of cells upon the demonstrable content of H-2 (D region) isoantigen, first shown in cells modulated in vivo, has been observed with cells modulated in vitro. Cells undergoing modulation show a progressive increase in H-2 (D region) antigen over a period of 4 hr, with no change in H-2 antigens of the K region. Restoration of the TL+ phenotype of modulated cells after removal of antibody is less rapid than TL+ → TL- modulation and may require several cell divisions.

scholarly journals Ribonucleic acid synthesis in porphyric rat liver induced by 3,5-dicarbethoxy-1,4-dihydrocollidine

1973 ◽  
Vol 136 (1) ◽  
pp. 209-215 ◽  
Author(s):  
Hajime Nawata ◽  
Kenichi Kato
Keyword(s):  
Rat Liver ◽  
Liver Cell ◽  
Ribonucleic Acid ◽  
Rna Synthesis ◽  
Actinomycin D ◽  
Acid Synthesis ◽  
Rapid Decrease ◽  
Aminolaevulinic Acid ◽  
Induction Mechanism

1. Administration of 3,5-dicarbethoxy-1,4-dihydrocollidine to rats caused a marked increase in the activity of δ-aminolaevulinic acid synthetase as well as a slight net increase in RNA in the livers. 2. 3,5-Dicarbethoxy-1,4-dihydrocollidine primarily stimulated the synthesis of RNA in the nucleus of the liver cell. 3. The decrease in RNA synthesis after administration of this drug resulted in a rapid decrease in the activity of this induced enzyme. This was also confirmed by treatment with actinomycin D. 4. From kinetic experiments on synthesis of RNA and δ-aminolaevulinic acid synthetase in vivo the induction mechanism of this enzyme was discussed.

Enhanced Melanization of Harding-Passey Mouse Melanoma Cells Following Treatment with Exogenous Melanosomes in Monolayer Culture

1979 ◽  
Vol 34 (1-2) ◽  
pp. 124-130 ◽  
Author(s):  
H. B. Leising ◽  
D.O. Schachtschabel
Keyword(s):  
Monolayer Culture ◽  
Actinomycin D ◽  
Melanoma Cells ◽  
Tyrosinase Activity ◽  
The Other ◽  
Monolayer Cultures ◽  
Protein Portion ◽  
Inhibitor Treatment

Abstract Purified melanosomes isolated from subcutaneously growing Harding-Passey melanomas of NMRI-mice were labeled either in vitro with [14C] tyrosine or [14C]DOPA in the melanin portion, or in vivo in the melanin and protein portion following i. p. injection of [14C] tyrosine. Treatment of monolayer cultures of Harding-Passey melanoma cells (HPM-73 line) with such labeled melanosomes resulted in rapid uptake of label during the first 4 h which leveled off thereafter. A portion of the “incorporated” label could be removed by a 15 min chase with unlabeled melanosomes.Uptake of labeled melanosomes by HPM-73 cells was followed by increased cellular melaniza­tion which was not only due to melanin derived from incorporated melanosomes but primarily to newly formed melanin. Tyrosinase activity was elevated in melanosome-treated cells. Tyrosinase activity of control cells was significantly reduced following a 24 h exposure to actinomycin D or cycloheximide. On the other side, the same inhibitor treatment of melanosome-pretreated cells resulted in less inhibition of tyrosinase activity.The present findings suggest “melanophagic” properties of cultured melanoma cells resulting in enhanced melanogenesis after phagocytotic uptake of functionally active exogenous melanosomes.

Comparison of binding and removal of remnants of triglyceride-rich lipoproteins of intestinal and hepatic origin by rat liver in vitro

1982 ◽  
Vol 243 (5) ◽  
pp. G389-G395
Author(s):  
A. D. Cooper ◽  
M. A. Shrewsbury ◽  
S. K. Erickson
Keyword(s):  
Rat Liver ◽  
Plasma Membranes ◽  
Low Density Lipoproteins ◽  
The Other ◽  
Very Low Density Lipoproteins ◽  
Rat Liver Plasma Membranes ◽  
Chylomicron Remnants ◽  
Fold Excess

Chylomicrons were isolated from intestinal lymph and very low-density lipoproteins (VLDL) from the perfusate of isolated perfused livers. In vivo the initial phase of clearance of these particles was very rapid. Chylomicrons appeared to be cleared more quickly than VLDL (t1/2 = 3.7 +/- 1.4 vs. 10.6 +/- 4.0 min). Remnants were prepared from these particles in eviscerated rats and isolated using conditions under which contamination of particles from one organ by particles from the other organ was minimal. The removal of these remnant particles by isolated perfused livers was studied. VLDL remnants were removed more rapidly than the nascent VLDL. The removal of 125I-labeled VLDL remnants was inhibited by the presence of unlabeled VLDL remnants or chylomicron remnants in the perfusate. A 15- to 20-fold excess of either particle inhibited about 50% of the uptake of the labeled lipoprotein. The two types of remnants had comparable potency as competitors of uptake. Similarly, the two types of remnants inhibited uptake of a trace of labeled chylomicron remnants. The binding of these particles to rat liver plasma remnants. The binding of these particles to rat liver plasma membranes was also investigated. Both labeled chylomicron remnants and VLDL remnants bound specifically to the membranes, and either type of remnant displaced the binding of the other with equal potency. Taken together, these results indicate that chylomicron and VLDL remnants share the same hepatic removal mechanism and suggest that the rate of removal of a remnant is not a function of the organ of origin of the precursor lipoprotein.

Constitutive and Induced Synthesis of Heat Shock Proteins in Transplantable Hepatomas

1987 ◽  
Vol 73 (6) ◽  
pp. 559-565 ◽  
Author(s):  
Luisa Schiaffonati ◽  
Lidia Bardella ◽  
Gaetano Cairo ◽  
Emilia Rappocciolo ◽  
Lorenza Tacchini ◽  
...  
Keyword(s):  
Heat Shock ◽  
Heat Shock Proteins ◽  
Rat Liver ◽  
Growth Rates ◽  
The Other ◽  
Constitutive Synthesis ◽  
Shock Proteins ◽  
Slow Growing

The synthesis of heat shock proteins (HSP) was studied in rat liver and in a series of transplantable Morris hepatomas with different growth rates, subjected to heat shock in vivo and in vitro. Different from the liver, hepatomas synthesized HSP constitutively, i.e., also before exposure to heat. This constitutive synthesis was low and limited to one HSP in the slowest-growing tumor, more marked and involving other HSP in the intermediate- and fast-growing hepatomas. In tumor that synthesized HSP constitutively, the induction of HSP in response to heat was proportionately reduced. These patterns of reaction were essentially similar in vivo ad in vitro. The amount of HSP 68 was well correlated to the levels of its mRNA in liver and in all hepatomas, whereas the increase in HSP 89 was accompanied by a corresponding increase in the related mRNA in liver and in slow-growing hepatoma, not in the other tumors, thus suggesting a different mechanism of control of HSP 89 synthesis in the more malignant hepatomas.

scholarly journals The effects of salicylate on the activity of rat liver tryptophan pyrrolase in vitro and in vivo

1971 ◽  
Vol 123 (2) ◽  
pp. 171-174 ◽  
Author(s):  
A. A.-B. Badawy ◽  
M. J. H. Smith
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Binding Sites ◽  
Actinomycin D ◽  
Sodium Salicylate ◽  
Progressive Increase ◽  
Tryptophan Pyrrolase ◽  
Enzyme Ratio

1. Salicylate, in concentrations of 0.05mm and above, inhibits the basal activity of tryptophan pyrrolase in homogenates of rat liver and the activity induced by cortisol but not that induced by tryptophan. The inhibition is abolished by adding haematin to the reaction mixtures. 2. The intraperitoneal injection of 400mg of sodium salicylate/kg in the rat causes a decrease in the tryptophan pyrrolase activity in the liver at 30min, the activity is restored to normal at 2h, increases to sixfold after 5h and returns to the basal value at 12h. The activation of the enzyme by salicylate is prevented by the administration of cycloheximide but not by pretreatment with actinomycin D. The effects of the combined injection of salicylate and cortisol are additive, whereas those of salicylate plus tryptophan are not. The injection of salicylate causes a progressive increase in the holo-/apo-enzyme ratio and an increased content of tryptophan in the liver over a period of 3h. 3. It is suggested that salicylate inhibits tryptophan pyrrolase activity in vitro and in vivo by interacting with iron protoporphyrins and causes a later enhancement of the enzyme activity in vivo by a mechanism involving the release of tryptophan from its binding sites on circulating albumin and on other proteins.

Enhancement of ADP-induced Platelet Aggregation by Adrenaline in Vivo and Its Prevention

1973 ◽  
Vol 29 (02) ◽  
pp. 490-498 ◽  
Author(s):  
Hiroh Yamazaki ◽  
Itsuro Kobayashi ◽  
Tadahiro Sano ◽  
Takio Shimamoto
Keyword(s):  
Platelet Count ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
The Other ◽  
Endothelial Surface ◽  
Important Interaction ◽  
Blood Coagulability ◽  
The Difference

SummaryThe authors previously reported a transient decrease in adhesive platelet count and an enhancement of blood coagulability after administration of a small amount of adrenaline (0.1-1 µg per Kg, i. v.) in man and rabbit. In such circumstances, the sensitivity of platelets to aggregation induced by ADP was studied by an optical density method. Five minutes after i. v. injection of 1 µg per Kg of adrenaline in 10 rabbits, intensity of platelet aggregation increased to 115.1 ± 4.9% (mean ± S. E.) by 10∼5 molar, 121.8 ± 7.8% by 3 × 10-6 molar and 129.4 ± 12.8% of the value before the injection by 10”6 molar ADP. The difference was statistically significant (P<0.01-0.05). The above change was not observed in each group of rabbits injected with saline, 1 µg per Kg of 1-noradrenaline or 0.1 and 10 µg per Kg of adrenaline. Also, it was prevented by oral administration of 10 mg per Kg of phenoxybenzamine or propranolol or aspirin or pyridinolcarbamate 3 hours before the challenge. On the other hand, the enhancement of ADP-induced platelet aggregation was not observed in vitro, when 10-5 or 3 × 10-6 molar and 129.4 ± 12.8% of the value before 10∼6 molar ADP was added to citrated platelet rich plasma (CPRP) of rabbit after incubation at 37°C for 30 second with 0.01, 0.1, 1, 10 or 100 µg per ml of adrenaline or noradrenaline. These results suggest an important interaction between endothelial surface and platelets in connection with the enhancement of ADP-induced platelet aggregation by adrenaline in vivo.

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