[Interleukin receptors and mechanism of target cell activation].
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Animals↗
Biomedical subjects
T Ide
Publications and source records attributed to T Ide.
Entrance of SV40-transformed cells into G0 phase as revealed by a study using the G0-specific ts mutant tsJT60.
The purpose of this study is to distinguish two possibilities that the transformed cells are blocked to enter a resting state (G0) and that they enter but are persistently stimulated to return to a growing cycle, using SV40-transformed tsJT60 cells as a model system. tsJT60 is a temperature-sensitive (ts) mutant of a Fischer rat cell line (3Y1), which is classified as a G0 mutant; i.e., the ts defect is not expressed within the growing cell cycle but is expressed only between G0 and S phases. We assumed that if the former possibility were the case, the transformed cells would not show any ts phenotype; and if the latter case, they might be ts. All SV40-transformed tsJT60 clones grew at 34 degrees C as well as SV40-transformed 3Y1 cells did at both temperatures. At 39.5 degrees C, some SV40-transformed tsJT60 clones grew (not ts) but others did not (ts) under conditions adequate for growth of untransformed cells. When clones that grew at 39.5 degrees C were cultured under conditions inadequate for growth of untransformed cells such as serum restriction or high cell density, they were ts for growth or even cytocidal at 39.5 degrees C. These results indicate that all clones of SV40-transformed tsJT60 cells are ts and the latter possibility is the case.
Animals↗
Expression of cell-cycle-dependent genes in serum stimulated cells whose entry into S phase is blocked by cytochalasin D.
A low concentration (0.6 micrograms/ml) of cytochalasin D inhibits the initiation of DNA synthesis after serum stimulation of growth-arrested GC-7 cells. Since actin-containing structures are suggested to be involved in the transfer of the growth signal to nuclei and in the synthesis and transport of nascent RNA, the effect of cytochalasin D on the expression of cell-cycle-regulated genes after serum stimulation was studied by Northern blot analysis. Cytoplasmic accumulation of such mRNAs as or c-fos, c-myc, beta-actin an ornithine decarboxylase occurred in serum-stimulated cells regardless of the presence of cytochalasin D, whereas that of thymidine kinase and histone H3 was blocked by the drug.
Actins↗
Activities of liver mitochondrial and peroxisomal fatty acid oxidation enzymes in rats fed trans fat.
The effect of trans fat on the activities of liver mitochondrial and peroxisomal fatty acid oxidation enzymes was examined in various strains of rats. When Wistar and Sprague-Dawley rats were fed for 30 days diets containing either olive oil or partially hydrogenated corn oil as a source of cis- or trans-octadecenoate, respectively, the activities of various enzymes of mitochondrial and peroxisomal beta-oxidation measured with cis- and trans-9-octadecenoic acid as substrates showed little dietary fat-dependent change. In Fischer 344 rats, feeding trans fat for 15 mo increased only moderately various enzymes of beta-oxidation except for carnitine acyltransferase. The rate of mitochondrial ketogenesis and the activity of carnitine acyltransferase measured with trans-9-octadecenoic acid as a substrate were about half those with the cis-counterpart. Peroxisomes oxidized trans-9-octadecenoyl-CoA at a rate comparable to the cis-counterpart. It was concluded from this study and previous ones that the difference in the geometry of dietary fatty acid had only a marginal effect in modulating the hepatic fatty acid oxidation system, in spite of marked differences in the metabolic behavior of cis- and trans fatty acid in cell-free preparations and perfused liver.
Animals↗
Induction of cellular DNA synthesis in G0-specific ts mutant, tsJT60, following infection with SV40 and adenoviruses.
tsJT60 cells, a temperature-sensitive G0 mutant of a Fischer rat cell line, grew normally in an exponential growth phase at both permissive (34 degrees C) and nonpermissive (39.5 degrees C) temperatures, but when stimulated with fetal bovine serum in the growth-arrested state (G0 phase) they entered S phase at 34 degrees C but not at 39.5 degrees C. Infection of G0-arrested tsJT60 cells with SV40, adenovirus (Ad) 5 wild type and its E1B mutant dl313, and Ad12 wild type and its E1B mutants in205B, in205C, dl205, and in206B induced DNA synthesis at both temperatures. The DNA synthesized after virus infection was shown to be cellular by Hirt separation of DNA from SV40-infected cells and by CsCl equilibrium density gradient centrifugation of DNA from Ad5-infected cells.
Adenoviruses, Human↗
Epidermal growth factor has a unique effect in combination with fetal bovine serum to bypass the ts-block of G0-specific ts mutant tsJT60.
tsJT60 cells are G0-specific temperature-sensitive mutants of the cell cycle from Fischer rats i.e., they grow exponentially at both 34 degrees and 39.5 degrees C, but when stimulated with fetal bovine serum (FBS) from the resting state (G0) they enter S phase at 34 degrees C but not at 39.5 degrees C. Epidermal growth factor (EGF) also induced DNA synthesis, although weakly, in G0-arrested tsJT60 cells at 34 degrees C but failed at 39.5 degrees C. When G0-arrested tsJT60 cells were stimulated at 39.5 degrees C with FBS plus EGF, they entered S phase and divided. Somatomedin C, insulin, or transferrin had a weak effect in inducing DNA synthesis in G0-arrested cells when applied at 34 degrees C or with FBS at 39.5 degrees C. Fibroblast growth factor, platelet-derived growth factor, or 12-O-tetradecanoylphorbol 13-acetate had no such stimulatory effect at 39.5 degrees C. Binding of 125I-somatomedin C was not temperature-sensitive. Several other ts mutant cells that were blocked at 39.5 degrees C from entering S phase from the resting state following FBS addition were stimulated by FBS plus EGF at 34 degrees C but not at 39.5 degrees C.
Animals↗
tsJT60, a cell cycle G0-ts mutant, becomes lethal at non-permissive temperature by transformation with adenovirus 5 when the expression of E1B gene is lacking.
tsJT60, a temperature-sensitive (ts) mutant cell line of Fischer rat, is viable at both permissive (34 degrees C) and non-permissive (39.5 degrees C) temperatures. The cells grow normally in exponential growth phase at both temperatures, but when stimulated with fetal bovine serum (FBS) from G0 phase they re-enter S phase at 34 degrees C but not at 39.5 degrees. When tsJT60 cells were transformed with adenovirus (Ad) 5 wild type, they grew well at both temperatures, expressed E1A and E1B genes, and formed colonies in soft agar. When tsJT60 cells were transformed with Ad5 dl313, that lacks E1B gene, the transformed cells grew well at 34 degrees C but failed to form colony in soft agar. They died very soon at 39.5 degrees C. 3Y1 cells (a parental line of tsJT60) transformed with dl313 grew well at both temperatures, although neither expressed E1B gene nor formed colonies in soft agar. The phenotype of being lethal at 39.5 degrees C of dl313-transformed tsJT60 cells was complemented by cell fusion with 3Y1BUr cells (5-BrdU-resistant 3Y1), but not with tsJT60TGr cells (6-thioguanine resistant tsJT60). These results indicate that the lethal phenotype is related to the ts mutation of tsJT60 cells and also to the deletion of E1B gene of Ad5.
Adenoviridae↗
GC-7 cells are growth arrested by cytochalasin D at two different points in the cell cycle.
GC-7 cells, a cell line from African green monkey kidney, which had been growth arrested in G0 phase by serum deprivation, entered S phase 15 h after serum stimulation. They were blocked from entering S phase in the presence of 0.6 micrograms/ml of cytochalasin D. The cells growth arrested between G0 and S phase by cytochalasin D entered S phase 6 h following the removal of the drug. The progression of S, G2, and M phases was not affected by cytochalasin D. On the other hand, when G0-arrested GC-7 cells were stimulated with serum for 23 h up to a late S/G2 phase and then cultured in the presence of cytochalasin D, or when an exponentially growing culture was treated with the drug, the cells were growth arrested at a point 15 h, not 6 h, before the next S phase. This point of growth arrest is kinetically similar to G0 phase, both occur 15 h before S phase, but is different from G0 in terms of c-fos expression after release from the block.
Animals↗
Colchicine activates cell cycle-dependent genes in growth-arrested rat 3Y1 cells.
When growth-arrested 3Y1 cells (Fischer rat fibroblasts) were exposed to 3 X 10(-5) M colchicine, they entered S phase after a 12-h lag period which is the same as that in serum-stimulated cells. The expression of genes such as c-fos, c-myc, JE, KC, ornithine decarboxylase, and histone H3, analyzed by Northern blotting, increased in a cell-cycle dependent manner after colchicine treatment. The increased level of mRNAs was much smaller in colchicine-stimulated cells than in serum-stimulated cells, corresponding to the lower frequency of the former cells entering S phase. The course of the prereplicative phase seems to be similar in terms of the expression of cell cycle-dependent genes in cells stimulated with colchicine and in those stimulated with serum.
Animals↗
Effects of short-term cholestyramine feeding on cholesterol metabolism in differently aged rats.
The effects of short-term (7 days) feeding of a diet containing cholestyramine (5%) on the cholesterol metabolism were studied in male Sprague-Dawley rats at ages of 5 weeks (young) and 9-10 months (adult). Cholestyramine significantly enhanced the activities of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase and cholesterol 7 alpha-hydroxylase both in young and adult rats; however, the absolute values were significantly higher in the former. The time-courses of changes in the activities of these enzymes after cessation of cholestyramine were comparable in both groups of rats. The rate of incorporation of mevalonate into sterol was also higher in young than in adult rats, while the stimulating effect of cholestyramine was markedly greater in adult rats. Hepatic acyl-CoA:cholesterol acyltransferase activity was comparable, but cholestyramine significantly decreased it only in adult rats. In adult rats hepatic cholesterol was decreased significantly by the resin while it remained uninfluenced in young rats. The serum cholesterol level tended to be higher in adult rats regardless of the dietary manipulation. The results indicate an appreciable age-dependent change in the hepatic cholesterol metabolism in response to the interruption of enterohepatic circulation of bile acids.
Aging↗
Age-related changes in the regulation of cholesterol metabolism in rats.
Activities of the hepatic cholesterol synthetic system including initial steps of the pathway and cholesterol 7 alpha-hydroxylase were all lower in adult (8 to 9-month-old) rats than in young (5 week-old) rats. The extent of diurnal fluctuation of 3-hydroxy-3-methylglutaryl coenzyme A reductase was, however, apparently greater in adult animals. When the cholesterol-enriched diet was fed to rats for 1 day, the extent of the depression of the cholesterogenic enzymes was dependent on age of animals. The enzyme activities rapidly increased on refeeding a cholesterol-free diet after the cholesterol challenge. In young rats the activity of cholesterol 7 alpha-hydroxylase exhibited a pattern inverse to that of HMG-CoA reductase whereas in adult rats it increased continuously during the entire experimental period. Cholesterol and triglyceride accumulated in the liver of adult animals, and their response to dietary cholesterol also depended on the age of the animals. The results indicate a specific modification of the cholesterol homeostatic mechanism with age.
Aging↗
Frequency of lymphocytes bearing surface membrane immunoglobulins in leukaemic cattle.
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Animals↗
Bypass of the ts block of tsJT60, a G0-specific ts mutant from rat fibroblasts, by fetal bovine serum and epidermal growth factor.
tsJT60, a temperature-sensitive (ts) G0-mutant cell line from a Fischer rat, grows normally in the exponential growth phase at 34 degrees C and 39.5 degrees C, but when stimulated with fetal bovine serum (FBS), from the G0 phase they reenter the S phase at 34 degrees C but not at 39.5 degrees C. The ts-block was bypassed when G0-arrested tsJT60 cells were stimulated at 39.5 degrees C with FBS plus epidermal growth factor (EGF). The presence of EGF for the first 6 h after serum stimulation caused tsJT60 cells to enter the S phase in the presence of FBS at 39.5 degrees C. When EGF was added 6 h after serum stimulation, entrance into the S phase was delayed by about 6 h. The sequential presence of two growth factors, EGF without FBS for 6 h then FBS without EGF, or the reversed sequence, failed to initiate DNA synthesis at 39.5 degrees C. The binding of EGF was not temperature sensitive. The amounts of RNA and protein present doubled after stimulation with both FBS and EGF at 39.5 degrees C. These and other findings suggest that EGF bypasses only some specific event in the entire prereplicative process that operates operating in serum-stimulated cells at 39.5 degrees C.
Animals↗
Blockage of prereplicative progression by cytochalasin D in serum-stimulated GC-7 cells.
When growth-arrested GC-7 cells, a cell line from African green monkey kidney, are stimulated with 10% calf serum, they enter S phase 14-15 h later. Cytochalasin D at 0.6 micrograms/ml blocks the entrance into S phase, and inhibits, though only partially, the increase in protein synthesis after serum stimulation. Since partial inhibition of protein synthesis by cycloheximide interferes with accumulation of labile proteins and thus blocks the entrance of serum-stimulated cells into S phase, the effects of these two inhibitors are compared. Cytochalasin D at lower concentrations reduced the rate of entry into S phase without affecting the length of the prereplicative phase, whereas cycloheximide extended the prereplicative phase dose dependently without affecting the rate of entry into S phase. Cytochalasin D affected neither individual [35S]methionine-labeled spots on two-dimensional polyacrylamide-gel nor degradation of cellular proteins. These results indicate that cytochalasin D, though it interferes with protein synthesis, blocks prereplicative progression of serum-stimulated GC-7 cells in a different manner than cycloheximide.
Animals↗
[Renal morphologic changes in pregnancy--ultrasonographic examination].
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Adult↗
Failure in S6 protein phosphorylation by serum stimulation of senescent human diploid fibroblasts, TIG-1.
When quiescent young or senescent human diploid cells, TIG-1, were metabolically labeled with 32Pi and stimulated with 10% fetal bovine serum, the phosphorylation of ribosomal S6 protein was enhanced in young cells but not in senescent cells while that of some other proteins were increased in both cells. Inability to stimulate the phosphorylation of S6 protein in senescent cells after serum addition may be the primary cause of the failure of enhancement in protein synthesis followed by the block of prereplicative events dependent on protein synthesis and thus of the failure of cells to enter S phase. However, when the cell-free preparation from serum-stimulated senescent cells was incubated with [gamma-32P]ATP, S6-kinase activity was stimulated and S6 in ribosomal fraction was susceptible to phosphorylation as observed in young cells. Differences in S6 phosphorylation of senescent cells between in vivo and in vitro was discussed.
Blood↗
Expression of growth-regulated genes in tsJT60 cells, a temperature-sensitive mutant of the cell cycle.
We have investigated the expression of growth-regulated genes in tsJT60 cells, a temperature-sensitive (ts) mutant of Fischer rat cells, which, on the basis of its kinetic behavior, can be classified as a G0 mutant. It grows normally at 34 degrees C and also at 39.5 degrees C if shifted to the higher temperature during exponential growth. However, if the cell population is first made quiescent by serum deprivation, subsequent stimulation by serum induces the cells to enter S phase at 34 degrees C but not at 39.5 degrees C. A panel of growth-regulated genes was used that included three protooncogenes (c-fos, c-myc, and p53), several genes that are induced in G0 cells stimulated by growth factors (beta-actin, 2A9, 2F1, vimentin, JE-3, KC-1, and ornithine decarboxylase), and an S-phase gene (histone H3). The expression of these growth-regulated genes was studied in both tsJT60 cells and its parental cell line, rat 3Y1 cells. All the genes tested, except histone H3, are similarly induced when quiescent tsJT60 cells are stimulated by serum at either permissive or restrictive temperatures. These results raise intriguing questions on the nature of quiescence and the relationship between G0 and G1 in cells in culture.
Animals↗
Strain dependence of the metabolism of cis- and trans-isomers of 9-octadecenoic acid in perfused liver and cell-free preparation in rats.
Hepatic metabolism of cis- and trans-9-octadecenoic acid was compared in various strains of rats and under different nutritional states. In Wistar rats triacylglycerol secretion was consistently higher in livers perfused with the cis isomer than with the trans isomer, while the difference was considerably attenuated in Sprague-Dawley rats. The difference in the hepatic triacylglycerol secretion disappeared when rats were fasted for 2 days. The rate of oxidation of trans fatty acid to ketone bodies was remarkably much higher than the cis isomer in Wistar but not in Sprague-Dawley rats. After fasting, the difference in the ketone body production disappeared in Wistar rats, whereas the oxidation rate was rather lower in the trans isomer than in the cis isomer in Sprague-Dawley rats. In isolated mitochondria, ketogenesis from trans-9-octadecenoic acid was markedly lower than that from the cis counterpart, irrespective of the nutritional states or strains of rats, and correlated well with the substrate specificity of carnitine acyltransferase. The molar concentration of malonyl-CoA to cause 50% inhibition of ketogenesis, the rate of peroxisomal beta-oxidation and the activity of acyl-CoA oxidase were all comparable, irrespective of the substrate sources. The Km value for acyl-CoA oxidase to the trans-acyl-CoA was 2-times higher than that of the cis counterpart in both strains of rats. Thus, peroxisomal as well as mitochondrial fatty acid oxidation systems apparently discriminated between the geometrical differences of the fatty acid substrate.
Acyl-CoA Oxidase↗