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Biomedical subjects

F Antoni

Publications and source records attributed to F Antoni.

At least 91 records · Page 5Linked to original sources
PubMed1983

A third DNA-dependent ATPase from Bacillus cereus free of ATP-dependent DNase activity.

The purification of ATP-dependent DNase from Bacillus cereus led to the isolation and characterization of a third DNA-dependent ATPase. The enzyme called ATPase III has been purified free of nuclease activity. None of the expected ATPases proved to be identical with ATP-dependent DNase-DNA-dependent ATPase. Separation of ATPase I, II and III and a DNase specific for single-stranded DNA from the same source excludes the possibility of ATP-dependent DNase being the action of a single enzyme molecule.

Adenosine Triphosphatases↗
PubMed1983

Discrepancies between flow cytometric analysis and [3H]thymidine incorporation in stimulated lymphocytes.

The DNA synthesis system of freshly isolated tonsillar lymphocytes and those stimulated by phytohaemagglutinin were compared by different methods. Both cell populations had high DNA polymerase alpha and thymidine kinase activities, as well as a high rate of incorporation of [3H]thymidine into DNA. However, the two cell populations differed when their DNA distributions were compared by flow cytometry. Freshly isolated cells contained many less (6%) cells in S phase than were found in phytohaemagglutinin-stimulated lymphocytes (18%) as detected by flow cytometry. The labelling of different subpopulations of lymphocytes was studied by sorting them electrically with a fluorescence-activated cell sorter. Analysis of the radioactivity of [3H]thymidine pulse-labelled cells, sorted according to their DNA content, showed that cells in the G1 peak of DNA distribution had a significant amount of incorporated [3H]thymidine. Sorting of cells according to their size (i.e., by light scattering) revealed that only large cells were labelled with [3H]thymidine.

Child↗
PubMed1983

Ethanol potentiates the inhibitory effect of D-galactosamine on protein synthesis in isolated hepatocytes.

The effect of the combined addition of D-galactosamine and ethanol on hepatic protein synthesis was studied in isolated mouse hepatocytes. 2.5 mM D-galactosamine or 40 mM ethanol alone caused slight or no inhibition of amino acid incorporation into proteins. However, a profound inhibition (about 80%) was observed if D-galactosamine of the same dose was added after a preincubation of the cells with 40 mM ethanol and vice versa. It shows that there is a strong mutual potentiation between D-galactosamine and ethanol in the inhibition of protein synthesis.

Animals↗
PubMed1983

Differences between lymphoid organs with respect to the phosphorylation of deoxycytidine and thymidine.

The specific activity of thymidine kinase (TK) was higher in spleen than in thymus or unseparated tonsillar lymphocytes, while deoxycytidine kinase (dCK) specific activity was lowest in spleen and was much higher in thymus and in unseparated tonsillar lymphocytes. The ratio of dCK to TK was always high in thymus, in unseparated and in B-cell-enriched tonsillar lymphocytes (between 2 and 5), but it was always low in spleen (0.3-0.4). The difference in the pyrimidine nucleoside phosphorylating enzyme activities of the thymus and spleen does not seem to be a mere consequence of different DNA synthesis rates, because the activities of DNA polymerase-alpha were practically the same in these organs. Unseparated and B-cell-enriched tonsillar lymphocytes resemble the thymus with respect to the ratio of dCK to TK activities, while the T-cell-enriched fraction contained 3-5 times lower activities of both enzymes. These results suggest that the metabolic pathways of CdR and TdR utilization for DNA synthesis differ in the lymphocyte populations independently from their rate of DNA polymerization and they may be in connection with their maturation processes.

Animals↗
PubMed1983

Pokeweed mitogen, Bordetella pertussis and breast milk cell factor induce preferentially the synthesis of different immunoglobulin classes.

Human tonsillar lymphocytes were cultured in the presence of different activators and [14C]-isoleucine. De novo synthesized, [14C]-labeled immunoglobulin was determined after separation of the different classes by immunoadsorbants carrying class-specific anti-human IgA, IgG, IgM, IgD or IgE. Pokeweed mitogen and whole killed Bordetella pertussis enhanced the synthesis and secretion of IgA, IgG and IgM. Maximum stimulation was found with pokeweed mitogen in IgM secretion (up to 5-fold), while Bordetella pertussis had the largest impact on IgA and IgG (4-5 fold increase). The human milk cell factor (demonstrated by Pittard and Bill., Cell. Immunol. 1979, 42, 437.) in the supernatant of cultured milk cells stimulated selectively the synthesis of IgA (4-fold).

Bordetella pertussis↗
PubMed1982

Specific binding of thrombin-antithrombin III complex to hepatocytes.

Thrombin-antithrombin III complex binds selectively to isolated hepatocytes, whereas antithrombin III alone does not. The binding is time and concentration dependent at 37 degrees C: the apparent Km value is 0.8/microM. The rate of binding is approximately 1.6 X 10(5) molecules h-1 cell-1 at this concentration. At 4 degrees C there is no measurable interaction between the complex and the hepatocytes. The binding is also prevented by pretreatment of cells with trypsin. On the other hand, about 80% of the thrombin-antithrombin III complex bound to hepatocytes is releasable by trypsin digestion. NaF or carboxyatractyloside does not inhibit the process. The interaction of thrombin-antithrombin III complex with hepatocytes seems to be specific, since the complexes of antithrombin III with other proteinases, like trypsin or plasmin, are not bound at the concentrations used. Based on these data, a mechanism for the binding of the inactive complexed form of thrombin to hepatocytes is suggested.

Animals↗
PubMed1982

Reversible inhibition of RNA synthesis and irreversible inhibition of protein synthesis by D-galactosamine in isolated mouse hepatocytes.

The inhibition of RNA synthesis of isolated mouse liver parenchymal cells caused by 10 mM D-galactosamine was reversible, while the inhibition of protein synthesis remained unaltered after the removal of galactosamine. 10(-5)M epinephrine and 10(07)M glucagon have been shown to decrease aminoglycogen formation and thus to reduce the inhibitory effect of galactosamine on protein synthesis (II). However, these hormones did not decrease the inhibition of RNA synthesis. 10 mM D-galactosamine did not effect the nucleoside and amino acid incorporation of isolated non-parenchymal mouse liver cells. The predominant role of aminoglycogen in the inhibition of protein synthesis in galactosamine induced liver injury is discussed.

Animals↗
PubMed1982

The site of histone H2b phosphorylated by a cyclic nucleotide independent histone kinase.

A cyclic nucleotide independent histone kinase was demonstrated in bovine thymus extract. This enzyme was very similar to that found previously in the cytoplasm and nucleus of human tonsillar lymphocytes (Faragó et al., 1973, Biochim. Biophys. Acta 297, 517 and 1974, ibid 370, 459). High-performance liquid chromatography of the tryptic phosphopeptides of calf thymus histones H1 and H2b phosphorylated by the histone kinase or by the catalytic subunit of cylic AMP dependent protein kinase showed that the intrinsic substrate specificity of these enzymes differed significantly. Under our experimental conditions the histone kinase phosphorylated preferentially the Ser-32 residue, and it did not phosphorylate the Ser-36 residue of histone H2b, while Ser-36 was phosphorylated preferentially by the cyclic AMP dependent protein kinase. A peptide containing the amino acid sequence of histone H2b from Gly-26 to Lys-34 (Gly-Lys-Lys-Arg-Lys-Arg-Ser-Arg-Lys-Ala) was synthesized. This peptide was a competitive inhibitor of histone H1 phosphorylation by the histone kinase and it was also a substrate for this enzyme.

Amino Acid Sequence↗
PubMed1982

Effect of arabinosyl cytosine on the level of DNA polymerase and thymidine kinase activity in PHA-stimulated human tonsillar lymphocytes.

The effect of arabinosyl cytosine (ara-C) was studied on the uptake, phosphorylation and incorporation of 3H-thymidine in human tonsillar lymphocyte cultures is described along with its effect on the level of DNA polymerase and thymidine Kinase activities induced by phytohaemagglutinin (PHA). Freshly isolated tonsillar lymphocytes are stimulated cells with a remarkably high activity of DNA polymerase alpha and thymidine kinase. During in vitro culture, these stimulated cells are transformed to the resting state with low DNA polymerase and thymidine kinase activity. However, a new DNA synthesising cycle can be induced by PHA with maximum at 48 h. 10(-6) M ara-C inhibited the incorporation of 3H-thymidine by 90-95%. This inhibition may be reversed by rinsing the cells. The inhibition of the transport of 3H-thymidine seems to be only a consequence of the inhibitory effect of ara-C on the DNA polymerisation reaction, because at 10 degrees C, where DNA synthesis was arrested, ara-C does not influence the uptake and the phosphorylation of 3H-thymidine. Ara-C (10(-6) M) abolished also the PHA induced elevation of DNA polymerase alpha and thymidine kinase activities without influencing protein synthesis of the cell. This supports a coordinated regulation mechanism between DNA synthesis and the synthesis of enzymes involved in DNA replication.

Cells, Cultured↗
PubMed1982

DNA polymerase and thymidine kinase activities in MC-29 virus-induced transplantable hepatoma and the effect of cytostatic treatment of these activities.

The activity of DNA polymerases and thymidine kinase was compared in the MC-29 leukosis virus-induced transplantable hepatoma and in the livers of rats treated with cyclophosphamide (CP), cytosine-arabinoside (ara-C) and 5-fluoro-uracil (5-FU). The specific activity of DNA polymerase was twenty times greater in the MC-29 leukosis virus-induced hepatoma, while thymidine kinase was only 3-5 times greater than in liver. All three enzymes showed Michaelis-Menten kinetics in their substrate and template saturation curves. The template utilization of DNA polymerases from hepatoma and from liver was compared. Both had higher activities on a poly(dA) . poly(dT) template at pH 8.0, than on DNA at pH 7.5. After chromatography on a phosphocellulose column two polymerases were separated. The first peak eluted by 0.15 m KCl preferred DNA as template (polymerase alpha). The second eluted by 0.5 M KCl worked better on poly(dA) . poly(dT) (polymerase beta). Thymidine kinase was eluted by 0.25 m KCl. Inhibition by N-ethylmaleimide (NEM) showed the polymerase alpha to be sensitive and the polymerase beta to be resistant to the sulfhydryl blocking agent; similar to the respective enzymes of other eukaryotic cells. The specific activity of DNA polymerase decreased after CP treatment at 6 h and 72 h and after ara-C treatment at 72 h. The specific activities of thymidine kinase were not changed significantly in response to the drug administrations.

Animals↗
PubMed1982

Cytotoxic material released from Staphylococcus epidermidis. I. Effects on [3H]thymidine incorporation of human lymphocytes.

Incorporation of [3H]thymidine ([3H]TdR) into tonsil lymphocytes was inhibited by native Staphylococcus epidermidis while Staphylococcus aureus Cowan I caused stimulation. The inhibitory effect of S. epidermidis was abolished by formalin treatment but not by heat killing. A toxic agent was released from S. epidermidis on gentle water extraction without lysing the bacteria. The extract contained protein and other UV-absorbing material, but did not exhibit haemolytic, lysozyme, catalase or protease activity. The heat-resistant, formalin-sensitive inhibitor present in the aqueous extract of S. epidermidis inhibited [3H]TdR incorporation of lymphocytes in a dose-dependent manner and decreased the viability of lymphocytes.

Cytotoxins↗
PubMed1982

Cytotoxic material released from Staphylococcus epidermidis. II. Fractionation and some effects of the fractions on lymphocytes and hepatocytes.

Cytotoxic substance(s) of about 4 X 10(3) molecular weight, containing 9.5% peptide and 73% carbohydrate was released from Staphylococcus epidermidis in phosphate buffered saline. The material was soluble in ethanol and was heat-resistant. It blocked amino acid uptake and E-rosette formation of human tonsillar and blood lymphocytes. In isolated mouse hepatocytes the toxin inhibited protein synthesis, but only in the presence of calcium ions. The results suggest that eukaryotic cell membranes are damaged by the coccal agent.

Animals↗
PubMed1981

The effect of ATP on the incorporation of deoxyribonucleoside triphosphates by Escherichia coli DNA polymerase I.

The effect of ATP on Escherichia coli DNA polymerase I has been investigated as a function of the concentration of substrates and divalent metal ions in the presence of activated DNA as template. At saturating Mg2+ concentration 1.5 mM ATP stimulated 2.5-times the incorporation of [3H]dGTP when only one substrate (dGTP) was present, and had no significant effect in the presence of all four dNTPs, whereas under similar conditions, a saturating concentration of dATP increased the reaction rate only 1.5-times. At optimal Mn2+ concentrations ATP also showed a similarly marked effect only in the case when one substrate (dGTP) was present in the reaction. The optimal concentration of Mn2+ was shifted by ATP to higher concentrations both in the presence of one and of all four substrates. ATP did not influence the apparent Km for dGTP, while V was increased by a factor of about 2.5. The possible presence of dNTP in ATP, as inpurity, was ruled out by isotope dilution analysis. Thus, ATP stimulated the polymerization reaction only under limited conditions, i.e., when one substrate was present in the reaction.

Adenosine Triphosphate↗