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Biomedical subjects

J Kruh

Publications and source records attributed to J Kruh.

At least 37 records · Page 2Linked to original sources
PubMed1986

[Stimulation of human lymphocytes by phorbol acetate and a calcium ionophore induces an early transient expression of the c-fos oncogene followed by c-myc].

After stimulation of human lymphocytes by 12-0 tetradecanoyl phorbol acetate (TPA) and by the calcium ionophore A23187 an early transient expression of proto-oncogene fos followed by an expression of c-myc is observed, as has been described in rodent fibroblast stimulated by growth factors. This observation suggests a direct role of protein Kinase C and of calcium flux an the induction of cellular oncogenes fos and myc that may be associated with the early steps of activation and proliferation of lymphocytes.

Calcimycin↗
PubMed1985

The 25 kDa protein kinase inhibitor present in liver cell is absent in fast growing HTC cells and is induced in sodium butyrate treated cells.

We have recently characterized a cAMP independent protein kinase inhibitor in rat liver. This inhibitor is absent or inactive in fast growing HTC cells and is induced according to exponential kinetics by sodium butyrate, a compound which arrests cell growth at the G1 phase of the cell cycle. It is suggested that the inhibitor could be involved in cell growth regulation.

Animals↗
PubMed1985

A 25 000 dalton inhibitor of cAMP independent protein kinases present in rat liver HMG protein preparations.

A protein kinase inhibitor was found in rat liver cells as a component of HMG proteins. It is located in cytosol as well as in nuclei. It inhibits all tested cAMP independent protein kinases and has no effect on cAMP dependent protein kinases. This inhibitor is a 25 000 Da protein. It has no ATPase, phosphoprotein phosphatase or proteinase activity and is heat unstable.

Adenosine Triphosphatases↗
PubMed1985

Expression of c-fos oncogene during hepatocarcinogenesis, liver regeneration and in synchronized HTC cells.

We have studied the expression of c-fos gene in rat hepatoma induced by DENA. An increase of c-fos mRNA concentration was observed after 8 days, but the maximal 5- to 6-fold increase was observed after 70 weeks. This increase was found in perinodular hepatocytes as well as in cancer nodules. c-fos expression was also enhanced during liver regeneration at a period corresponding to cell proliferation. In HTC cells the arrest of the cell cycle at early G1 phase by addition of sodium butyrate was accompanied by a strong increase of c-fos gene expression. However the c-fos mRNA rapidly decreased after removal of sodium butyrate during the progression of the cells in the cell cycle and increased transiently when the cells entered again in G1 phase.

Animals↗
PubMed1985

Changes in poly (A) + RNA translational pattern during chemically induced hepatocarcinogenesis.

Hepatocarcinoma was induced by administration of diethylnitrosamine to rats. The rats were sacrificed 70 weeks after the administration and the carcinoma nodules were separated from the perinodular parenchymental cells after perfusion of liver with collagenase. The in vitro translational pattern of mRNAs from hepatocellular carcinomas, from perinodular hepatocytes and from regenerating liver after partial hepatectomy were compared by one- and two-dimensional electrophoreses to the pattern obtained with RNA from normal hepatocytes. An increased synthesis of several peptides was observed with RNAs from carcinoma and from regenerating liver and to a lesser extent with RNA from perinodular hepatocytes, which suggests that the increase in synthesis is at least partly related to cell proliferation. A decreased synthesis of several other peptides was observed with RNA from carcinoma nodules and to a lesser extent with RNA from perinodular hepatocytes, but not with RNA from regenerating liver, which suggests that this decrease in synthesis is related to some transformation specific process. These changes are observed as soon as 22 weeks after carcinogen administration. These observations also suggest that at least part of the perinodular hepatocytes have some characteristics of the transformed cells.

Animals↗
PubMed1985

Effect of sodium butyrate on the complexity and the translation activity of hepatoma tissue-cultured cell RNAs.

We have studied the effect of sodium butyrate on RNA populations and on the in vitro translation pattern of RNA from Hepatoma Tissue-Cultured (HTC) cells. Since sodium butyrate inhibits cell growth we have used stationary cells as control. Molecular hybridization study of cDNA with polyadenylated RNAs shows that sodium butyrate induces the formation of additional 15% new RNA sequences, essentially in the class of abundant sequences and of sequences of intermediary abundance. This drug also decreases 5-10 times the frequency of the sequences of intermediary abundance. One- and two-dimensional polyacrylamide gel electrophoreses of the translational products of RNAs show that sodium butyrate induces or strongly increases the synthesis of 13 polypeptides and decreases the synthesis of 6 polypeptides, which is consistent with the effect of sodium butyrate on RNA populations and could result from the effect of this drug at both transcriptional and early post-transcriptional steps. Electrophoretic analysis of the in vitro translation products of RNAs from cells submitted to sodium butyrate and transferred to a normal medium for various lengths of time shows that most of the polypeptides return to a normal pattern after a certain length of time which varies according to the polypeptide.

Animals↗
PubMed1984

Effect of sodium butyrate on gene expression in a rat myogenic cell line.

Sodium butyrate, when added in millimolar concentration to a culture of myoblasts of the L6 cell line, inhibits reversibly cell proliferation and differentiation. In the present work, we have studied the effect of Na butyrate on the translational efficiency of the overall poly (A)+ RNA. The mRNA from treated cells was translated in vitro as efficiently as proliferating myoblasts mRNA, while a decrease of translation efficiency was observed with myotubes mRNA. In addition this RNA directs the synthesis of several new polypeptides. on the switch on of alpha actin and myosin heavy chains (MHC), muscle specific genes by the dot blot and Northern blot techniques using cloned probes. Na butyrate prevented the expression of MHC and allowed the switch on of alpha actin gene but at a lesser extent than in normal myotubes. In addition the drug prevented the translocation of alpha actin mRNA into the cytoplasm.

Actins↗
PubMed1984

Correlated increase of the expression of the c-ras genes in chemically induced hepatocarcinomas.

The expression of the c-Ha-ras, the c-Ki-ras and the N-ras genes was measured by the dot blot technique in rat liver tumors induced by a short diethylnitrosamine (DENA) treatment and in the surrounding liver cells. A 2 to 25 times higher level of transcript was found as well in the surrounding cells, as in the tumor cells, as compared to the level in hepatocytes. In addition the increase of expression was parallel for the three ras genes. We conclude that this enhanced expression can be attributed to an epigenetic mechanism and it can, in certain cases, be dissociated from cell proliferation.

Animals↗
PubMed1984

Alpha actin gene exist in an active structural configuration in the proliferating myoblasts as well as in differentiated myotubes of the L6 line.

Single-stranded DNA (ssDNA) mainly consisting of transcription sites was probed with cDNA actin clones for studying the expression of actin specific genes during myogenesis in the L6 line of rat myogenic cells. As compared with total nuclear DNA, ssDNA from myoblasts and myotubes was found greatly enriched in sequences complementary to both muscular and non muscular actin sequences. In contrast, ssDNA from spleen, hepatocytes or hepatoma cells was found enriched only in sequences complementary to non muscle actin cDNA. Actin specific sequences accumulated in the ssDNA fraction are almost entirely derived from the coding DNA strand. The DNAase I sensitivity of the actin genes sequences in myogenic and non myogenic cells correlated the data obtained with the ssDNA fraction. It is concluded that the muscle specific actin genes is either transcriptionally active or at least exist in an active configuration in the proliferating myoblasts as well as in the terminally differentiated myotubes.

Actins↗
PubMed1984

Changes in gene expression following neoplastic transformation of rat myogenic cells.

Two malignant sublines, M4 and RMS4 , were previously derived from the recloned L6 line of rat myogenic cells. Comparative studies in tissue culture and inoculation into suckling rats indicated that M4 cells and RMS4 cells may be considered as low-malignant and high-malignant cells, respectively, while L6 cells are not malignant. In the present work, we used extracts from L6 cells, M4 cells, and RMS4 cells collected during the period of exponential growth, to compare their polyadenylic acid-containing messenger RNA (mRNA) populations and the corresponding cell-free translation products. Analysis of the hybridization kinetics between radioactive complementary DNA and homologous or heterologous cellular RNAs indicated that L6 cells contained about 28,000 distinct polyadenylic acid-containing mRNA sequences of 1.8 kilobases each, of which 2,000 to 2,500 and 4,000 to 5,000 were missing (or at least were very infrequent) in M4 cells and RMS4 cells, respectively. Using a minor fraction of the RMS4 cell complementary DNAs, partially purified through repeated complementary DNA-RNA hybridization cycles, it was further shown that RMS4 cells contained at least 700 to 800 distinct mRNA species, mainly belonging to the class of low abundance, which appeared to be absent in L6 cells. Most of these mRNA species were also found with a lower frequency in M4 cells. Bidimensional analysis of the cell-free translation products directed by polyadenylic acid-containing mRNA revealed some remarkable differences, in particular the synthesis in a RMS4 cell extract of at least three major polypeptides, possibly related either to the neoplastic process itself or to the stage of malignant transformation.

Animals↗
PubMed1983

A new cAMP independent protein kinase tightly bound to DNA, in rat liver nuclei.

A protein kinase has been characterized among the proteins tightly bound to DNA. It is not extracted with 1 M NaCl and is released by extensive DNase I digestion. This enzyme is able to phosphorylate nucleosomal histones, essentially H2B and H3, and several non-histone proteins associated with DNA, on serine residue(s). It does not phosphorylate protamine, casein, phosvitin and the chromosomal non-histone proteins extracted with 1 M NaCl and is cAMP independent. This protein kinase can be distinguished from the previously described enzymes.

Animals↗
PubMed1983

Early molecular events in rat heart after administration of triiodothyronine and isoproterenol.

Triiodothyronine (T3), isoproterenol and aminophylline injected daily into rats induce heart hypertrophy. We have compared the early effects of a single injection of each of these compounds to rats using myocardial RNA synthesis and translational efficiency. In rats injected with T3 4 h before death the synthesis of RNA was increased 2-fold, then the effect of T3 injection decreased with time. Injection of isoproterenol had no effect. Injection of T3 increased the amount of myocardial polysomes, heavy polysomes appeared approx. 15 h after the injection. Neither isoproterenol nor aminophylline modified the polysomal pattern. RNAs were translated in reticulocyte lysates in the presence of [35S]methionine. A small but significant increase in incorporation was observed with RNAs from rats injected with T3 4 and 18 h before death, whereas no modification were observed with RNAs from isoproterenol- and aminophylline-treated rats. Two-dimensional electrophoresis and radioautography showed significant qualitative and quantitative differences between the translational products of RNAs from control, T3-, isoproterenol- and aminophylline-injected rats. These observations are compatible with a mechanism of action of T3 at the transcriptional level and of cAMP on the processing and/or on the stability of various RNA species.

Animals↗
PubMed1983

A destabilized DNA conformation associated with tightly bound nuclear proteins in active genes of rat myoblast.

Purified nuclei from tissue cultured myoblasts were disrupted and centrifuged to equilibrium in a sarcosyl-caesium chloride gradient. A small portion (1.3% - 1.9%) of the non histone proteins (NHP) were banded with DNA in a high density region of the gradient. The DNA tightly bound to proteins representing about 0.6% of the total nuclear DNA was degraded after treating cell nuclei with S1 nuclease or DNAse I but resisted to mild micrococcal nuclease digestion. A large portion of the DNA sequences complementary to homologous RNA was concentrated in this DNA-proteins fraction. These finding suggest that a subset of NHP strongly associated to the active DNA regions play a role in the destabilisation of the double helical DNA during transcriptional processes.

Animals↗
PubMed1982

The small chromatin fragments released by micrococcal nuclease from hepatoma tissue cultured cell nuclei are strongly enriched in coding DNA sequences and are related to an actively transcribed single-stranded DNA fraction.

It was shown with the use of specific probes that mild micrococcal nuclease digestion released from chromatin actively-transcribed genes as small nucleosome oligomers. In the present work we demonstrate that most if not all of the active genes are accessible to the nuclease. It was found that the short released fragments are greatly enriched in transcribed DNA sequences, the most enriched being the dimers of nucleosomes since 35% of their DNA could be hybridized to cytoplasmic RNA. The results of cDNA-DNA hybridizations indicate that the monomers and dimers of nucleosomes contain most of the DNA sequences which encode poly(A+) RNAs, however larger released fragments include some transcribed sequences, while the nuclease resistant chromatin is considerably impoverished in coding sites. These evidences are the finding that about 25% of the DNA from the dimers of nucleosomes are exclusively located in this class of fragments, tend to prove that the active chromatin regions are attacked in a non-random way by micrococcal nuclease. We have previously isolated, without using exogenous nuclease, an actively transcribed genomic fraction amounting to 1.5-2% of the total nuclear DNA, formed of single-stranded DNA. In the present study we show that all or nearly all the single-stranded DNA sequences could be reassociated with the DNA fragments present in the released monomers and dimers of nucleosomes. Our observations confirmed our previous finding that the greatest part of single-stranded DNA selectively originates from the coding strand of genomic DNA.

Animals↗
PubMed1982

Effects of sodium butyrate, a new pharmacological agent, on cells in culture.

Sodium butyrate, at millimolar concentrations, when added to cell cultures produces many morphological and biochemical modifications in a reversible manner. Some of them occur in all cell lines. They concern regulatory mechanisms of gene expression and cell growth: an hyperacetylation of histone resulting from an inhibition of histone deacetylase and an arrest of cell proliferation are almost constantly observed. Some other modifications vary from one cell type to another: induction of proteins, including enzymes, hormones, hemoglobin, inhibition of cell differentiation, reversion of transformed characteristics of cells to normal morphological and biochemical pattern, increase in interferon antiviral efficiency and induction of integrated viruses. Most if not all these effects of butyrate could result from histone hyperacetylation, from changes in chromatin structures as measured by accessibility to DNases and from modifications in cytoskeleton assembly. We do not know at the present time whether butyrate acts on a very specific target site in cell or if it acts on several cell components.

Acetylation↗