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Biomedical subjects

A Csordas

Publications and source records attributed to A Csordas.

26 records · Page 2Linked to original sources
PubMed1986

Increased acetylation of histones at an early stage of oestradiol-mediated gene activation in the liver of immature chicks.

The vitellogenin system of chicken was used to examine alterations in the microheterogeneity of chromosomal proteins in the course of steroid hormone-mediated gene expression. After administration of oestradiol-17 beta there is a dramatic increase in the number of copies of vitellogenin m-RNA in the liver of male oviparous animals, like Xenopus and chicken. According to earlier reports the rapid increase in transcriptional activity starts after a lag of 4 h. The system has also been examined as to the number of DNase I hypersensitive sites which appear to correlate with the degree of differentiation and hormonal activation. The time course of [3H]acetate incorporation into the histone fraction was monitored and the microheterogeneity of histones analysed by acid-Triton-urea gel electrophoresis. The results show that there is an increased degree of acetylation of histones in the liver of immature chicks as a result of oestradiol-17 beta administration. The change in the modification pattern of histones was found to be an early event, correlated with the time course of appearance of new DNase I hypersensitive sites and the onset of vitellogenin m-RNA synthesis. These observations are in agreement with an earlier report about the increase in the acetylation of histones in fetal guinea pig uterus after oestradiol treatment [1]. The results suggest that the acetylation of histones might be a prerequisite for the removal of structures for efficient gene repression and the establishment of DNase I hypersensitive sites.

Acetylation↗
PubMed1984

Structure- and configuration-dependent effects of C18 unsaturated fatty acids on the chicken and sheep erythrocyte membrane.

High concentrations of unsaturated fatty acids are known to cause hemolysis. At low concentrations, however, unsaturated cis fatty acids have been found to protect erythrocytes against hypotonic hemolysis. In the present experiments we examined the effect of oleic (18:1), linoleic (18:2), linolenic (18:3), and elaidic (18:1) acid on the osmotic fragility of chicken and sheep erythrocytes, which markedly differ in their resistance to osmotic rupture. The results are summarized as follows: (A) The phenomenon of stabilization was observed in both species alike. (B) Interaction of cells with the fatty acids under isotonic conditions led to a persistent stabilization, i.e., the cells remained more resistant against osmolysis even after several washings. (C) Oleic and elaidic acid protected against osmotic rupture with a high degree of specificity. Linoleic and linolenic acid were much less protective. Thus, this effect appears to be specific for one double bond. (D) Contrary to the unsaturated fatty acids with cis configuration, elaidic acid with the trans configuration showed no biphasic behaviour, and even at the highest concentrations applied no hemolysis was observed.

Animals↗
PubMed1984

Transcription of chemically acetylated chromatin with homologous RNA polymerase B.

Homologous RNA polymerase B was used to examine the template properties of rat liver chromatin modified by acetic anhydride. Transcription of chromatin was strongly stimulated on the chemically acetylated template. Under conditions of reinitiation inhibition there was an approximately two-fold increase in the number of initiation sites on the acetylated chromatin. A new method of chemical acetylation of histones, with a high degree of specificity, is presented.

Acetylation↗
PubMed1984

Depression of histone acetylation by alkylating antitumor agents: significance for antitumor activity and possible biological consequences.

Treatment of Ehrlich ascites tumor cells with the alkylating antitumor agents triaziquonum, N-mustard and cyclophosphamide leads to a reduction in the posttranslational incorporation of 3H-acetate into histones and the extent of histone acetylation in Ehrlich ascites tumor cells. All core histones are affected. The depression of histone acetylation is not the result of a decrease in acetyl-CoA. Evidence is presented for an activation of histone deacetylase by alkylating agents. A reduction of histone deacetylation is observed after exposure to all concentrations of alkylating agents which inhibit cell proliferation. In order to evaluate the biological consequences of a reduction of histone acetylation, the extent of acetylation was modulated by either chemical acetylation or treatment with butyrate. In all cases an increase in histone acetylation leads to an enhancement of the rate of transcription. In accord with previous reports from our laboratory (1), it is concluded that the reduction of histone acetylation affects RNA synthesis. It is emphasized, however, that besides a regulation of transcription, histone acetylation may be involved in other cell functions. Thus, the complete biological consequences of the reduction of histone acetylation remain to be elucidated. In view of the antitumor activity of the alkylating agents it seems noteworthy that hepatoma AS30D cells are characterized by a remarkably higher extent of histone H4-acetylation compared to normal, adult, fetal, or regenerating liver.

Alkylation↗
PubMed1983

Conservation of the acetylation pattern of histones and the transcriptional activity in Ehrlich ascites tumor cells by sodium butyrate.

Histone deacetylases of Ehrlich ascites tumor cells are active at low temperatures (0-4 degrees C). The so-called hyperacetylated state of histones is the physiological state of histones in intact Ehrlich ascites tumor cells which is conserved by the continuous presence of 10 mM sodium butyrate during the preparation of nuclei and histones. Isolation of histones in the absence of butyrate causes an artificial decrease in histone acetylation. This artificial loss of histone acetylation produces a decrease of the elongation reaction in the RNA synthesis. The initiation of RNA synthesis is not affected.

Acetylation↗
PubMed1982

Cell-cycle-dependent effects of sodium-n-butyrate in Physarum polycephalum.

Sodium-n-butyrate affects the length of the mitotic cycle of Physarum polycephalum. Application during S- or early G2-period results in a delay of the subsequent mitosis, whereas application later in the cycle has no delaying effect. Interestingly, the second mitotic cycle after application is considerably shortened when butyrate has been administered during S- or early G2-period of the preceding cycle. In comparison, other homologous short-chain fatty acids were tested; the retarding effect on mitosis increases with the number of carbon atoms, although only butyrate can shorten the second mitotic cycle. It is shown that butyrate causes an immediate depression of synthesis of DNA, RNA and protein. After a certain time-interval the plasmodium overcomes the butyrate block. DNA synthesis is fully recovered and the inhibition of RNA and protein synthesis is even overcompensated until the next mitosis, as reflected by elevated levels of RNA and protein.

Butyrates↗
PubMedDate not supplied

Very alkaline immobilized pH gradients for two-dimensional electrophoresis of ribosomal and nuclear proteins.

Basic proteins normally lost by the cathodic drift of carrier ampholyte focusing, or separated by NEPHGE with limited reproducibility, could be well separated by two-dimensional (2-D) electrophoresis under equilibrium conditions using immobilized pH gradients (IPGs) 4-10 and 6-10 using a previously published protocol (Görg et al., Electrophoresis 1988, 9, 531-546). In the present study we have extended the pH gradient to pH 12 with IPGs 8-12, 9-12 and 10-12 for the analysis of very basic proteins. Different optimization steps with respect to pH engineering, gel composition and running conditions, such as substitution of acrylamide by dimethylacrylamide and addition of isopropanol with and without methylcellulose to the IPG rehydration solution (in order to suppress the reverse electroosmotic flow) were necessary to obtain highly reproducible 2-D patterns of ribosomal proteins from HeLa cells and mouse liver. Histones from chicken erythrocyte nuclei as well as total cell extracts of erythrocytes were also successfully separated under steady-state conditions. Due to the selectivity of isoelectric focusing in IPG 9-12, where the more acidic proteins abandon the gel, the tedious procedure of nuclei preparation prior to histone extraction can be omitted.

Animals↗