Search PubMed⌕ Search

Biomedical subjects

F Antoni

Publications and source records attributed to F Antoni.

At least 109 records · Page 6Linked to original sources
PubMed1981

Role of metabolic activation in the sister chromatid exchange-inducing activity of ethyl carbamate (urethane) and vinyl carbamate.

Ethyl carbamate (EC, urethane) at 10(-2) M concentration induced more sister chromatid exchanges (SCEs) in cultured human peripheral blood lymphocytes in the absence of S9 mix than did 10(-2) M vinyl carbamate (VC), a possible proximate carcinogenic metabolite (Dahl et al., 1978) of EC. VC itself doubled SCE frequency over the control. In the presence of native S9 mix from Aroclor-induced rat liver, the SCE-inducing activity of VC was highly increased whereas that of EC was suppressed. This opposite effect of S9 mix on VC and EC seems to be due to two different factors. Activation of VC by the S9 fraction seems to be due to the presence of mixed-function oxidases in the S9 mix, because neither the native S9 fraction in the absence of co-factors nor the heat-inactivated S9 fraction in the incubation mixture led to the activation of VC. Deactivation of EC by S9 mix, on the other hand, seems to involve the presence of excess protein and/or substances of low molecular weight in the incubation mixture, because this deactivating effect did not change considerably when the S9 fraction was supplied in the absence of co-factors or when it originated from non-induced rat liver. Heat denaturation of the S9 fraction led to an increased deactivating effect on the SCE-inducing ability of EC. This result is in line with the assumption that reactive -SH groups in the S9 protein are at least partly responsible for the deactivation of EC by S9. Heat denaturation of the S9 fraction led to an about 1.5-fold increase in reactive -SH groups.

Animals↗
PubMed1981

Separation of ATP-dependent DNAse to ATPase and DNAse.

A 250-fold purified ATP-dependent DNase from Bacillus cereus has been separated to DNA-dependent ATPase I and II and a DNase specific for single-stranded DNA (ssDNase) by means of high resolution of DEAE cellulose chromatography. Simultaneously with the separation of ATPase and ssDNase, a decrease in ATP-dependent DNase activity was observed. Complete separation resulted in the total loss of ATP-dependent DNase activity. Reconstitution of ATP-stimulated DNase activity was dependent on the ratio of the combined ATPase II and ssDNase.

Adenosine Triphosphatases↗
PubMed1981

Surface immunoglobulins of tonsil lymphocytes.

Human tonsillar lymphocytes bound 14C-labelled homologous IgG, IgA, and IgM at 5 degrees C and released them at 35 degrees C. B cells were found to be more active in this type of Ig binding. The amount of lymphocytes which could be labelled with fluoresceinated anti-human Ig-s decreased during preincubation of the cells at 35 degrees C. Intrinsic Ig-s (determinants of lymphocytes) were demonstrated by immunofluorescent staining preceded by preincubation of the cells at 35 degrees C for 60 min. The ratios of IgG, IgA, and IgM bearing cells in the human tonsillar lymphocyte population were 16.0, 8.0 and 7.4% respectively. The weak binding of Ig-s to the surface of lymphocytes is discussed with regard to the demonstration of surface Ig determinants of lymphocytes.

Fluorescent Antibody Technique↗
PubMed1981

Studies on human tonsillar lymphocyte membrane. III. Isolation and characterization of plasma membrane fractions after hypotonic lysis.

Hypotonic lysis was applied for the preparation of lymphocyte plasma membranes. By this method it was possible to separate membrane fractions with a high sialic acid to protein and cholesterol to phospholipid ratio. The plasma membrane fractions had a lower content of endoplasmatic reticulum than the preparations described earlier but were slightly contaminated with DNA. The isolation method proved to useful for the preparation of surface membranes from human lymphocytes

Cell Fractionation↗
PubMed1980

Low molecular weight cyclic AMP binding protein isolated from the extract of human tonsillar lymphocytes.

A protein fraction of molecular weight 33,000-36,000 accounted for about 40% of the cyclic AMP binding capacity of the cytoplasmic extract of human tonsillar lymphocytes. This cyclic AMP binding fraction (designated as R' protein [10]) proved to be a proteolytic fragment of the regulatory subunit of the cyclic AMP-dependent protein kinase. The Scatchard plot of cyclic AMP binding by the isolated R' fraction indicated positive cooperativity. 50% saturation of the cyclic AMP binding sites was achieved at about 4 . 10(-9) M cyclic AMP. An upward concave curve was obtained in the Scatchard plot of cyclic GMP binding by the R' protein. These results strongly suggest that more than one molecule of cyclic nucleotide can be bound by one molecule of the R' protein. The R' protein could not be detected in the physiological salt extract of isolated nuclei in which type I cyclic AMP-dependent protein kinase was the dominating isoenzyme (according to the terminology used by Corbin, S.D., Keely, S.L. and Park, C.R. (1975) J. Biol. Chem. 250, 218-225). The cytoplasm of cells contained a higher amount of type II than type I regulatory subunit. In the cytoplasm the predominant part of RII was present in the dissociated state in all preparations, while when the RII was found in the nucleus it was mainly in the holoenzyme form. The R' protein presumably from the dissociated type II regulatory subunit.

Carrier Proteins↗
PubMed1980

A lymphokine-like factor isolated by deoxycholate from the membrane of human lymphocytes.

1. Membranous protein fractions containing carbohydrates were solubilized from human tonsillar lymphocytes in the presence or basence of deoxycholate. The optimal conditions for the detergent treatment, high solubilized protein yield without cell disruption, temperature and time of the treatment and concentration of the detergent were elucidated. 2. The protein fractions inhibited both the mitogen-activated and the nonactivated DNA synthesis in human lymphocyte targets in vitro but did not affect the uptake of [3H]thymidine. The fractions had a slight effect on the amino acid incorporation into proteins and failed to influence the uptake of amino acids. 3. It is assumed that the investigated membranous proteins are lymphokine-like materials produced continuously by lymphocytes in vivo and are incorporated into the membrane of the cells.

Amino Acids↗
PubMed1980

Purification and characterization of a DNA-dependent ATPase from Bacillus cereus.

A DNA-dependent ATPase (molecular weight 71 000) free of nuclease activity has been purified from Bacillus cereus. The enzyme shows similar characteristics as the enzyme isolated from Escherichia coli and Bacillus subtilis. Heat denatured DNA stimulates the rate of ATP hydrolysis to ADP and Pi to an extent about tenfold higher than the native DNA. Double stranded DNA without single stranded regions is not a suitable cofactor for the enzyme. The ATPase is inhibited by adenosine 5'-(beta, gamma-imino)-diphosphate, while another ATP analogue, adenosine 5'-(beta, gamma-methylene)-diphosphate has no effect on ATPase activity. KM for ATP is 0.38 mM, the apparent KM for nucleotide equivalent DNA is 1.2 microM. Evidence of the unwinding function of the enzyme is presented.

Adenosine Triphosphatases↗
PubMed1980

The adherence of Staphylococcus epidermidis to human tonsil lymphocytes.

Attachment of various bacteria to human, peripheral blood and tonsil lymphocytes was investigated in vitro. About 20% of tonsil lymphocytes bound Staphylococcus epidermidis, whereas the binding of other strains was negligible. The influence on cytoadherence of human serum, immunoglobulins (human IgM, IgG, IgA, as well as their respective anti-Ig's), and carbohydrates (mono and polysaccharides) was measured. It was found that heterogenous surface structures of the lymphocytes participate in the attachment.

B-Lymphocytes↗
PubMed1980

[Analysis and fractionation of human tonsillar lymphocytes].

Among the human tonsillar cells, 28.0 +/- 3.1 and 45.14 +/- 2.16% were found to be E and EAC rosette forming cells, resp. In the course of the separation procedure with nylon cotton, in the authors' modification, the cells failing to form rosettes were almost entirely adhering irreversibly to the nylon wool. The 3H-thymidine incorporation in these cells was very intensive, and we supposed them to be T and B lymphoblasts. On the basis of E and EAC rosette formation, the percentage of T and B lymphocytes in human tonsils--as reported by various authors--is different. It may be supposed that methods employed by these authors did not demonstrate the equal extent of transformed forms of lymphocytes, i.e. lymphoblasts, whose amount may be influenced by the functional condition of tonsils.

B-Lymphocytes↗
PubMed1979

Epinephrine and glucagon counteract inhibition of protein synthesis induced by D-galactosamine in isolated mouse hepatocytes.

10 mM D-galactosamine enhibited protein synthesis (1 h incubation time) by 67% in isolated mouse liver cells. Counteracting uridylate deficiency induced by D-galactosamine by preventive administration of 20 mM uridine did not decrease the extent of protein synthesis inhibition. 20 mM D-galactose reverted the inhibition of protein synthesis by D-galactosamine. 10(-5) M epinephrine and 10(-7) M glucagon decreased the incorporation of D-galactosamine into glycogen to 38% and 26% of the control value, respectively, after a 35 min incubation and reduced the inhibition of protein synthesis by D-galactosamine effectively. Experimental evidence supports the view that aminoglycogen formed after D-galactosamine treatment is responsible for the inhibition of protein synthesis.

Amino Sugars↗
PubMed1979

Cyclic nucleotide binding properties and molecular forms of the cyclic-AMP-dependent protein kinase from bovine eye lens.

The activity of the cyclic-AMP-dependent protein kinase found in the crude extract of bovine eye lens cortical fibers was increased by 10(-6) M cyclic AMP or 10(-5) M cyclic GMP to the same extent, However, the interaction between cyclic AMP and cyclic GMP in the course of binding to the cyclic-AMP-dependent protein kinase did not seem to be competitive. Scatchard analysis of cyclic GMP binding by the crude extract indicated the presence of two type of cyclic GMP binding sites (Kd1 about 2 . (10(-7) M, Kd2 about 5 . 10(-6) M). Different species of cyclic nucleotide binding fractions were separated by Sephadex G-200 gel chromatography of the crude extract. The bulk of the low affinity cyclic GMP binding activity was found in the exclusion volume. The cyclic-AMP-dependent protein kinase eluted in two fraction (apparent molecular weight 300 000 and 150 000) and both protein kinase fractions were accompanied by the high affinity cyclic GMP binding activity. However, the ratios of this activity to the cyclic AMP binding activity were different in the two fraction, suggesting that different molecular weight forms of the holoenzyme had different cyclic nucleotide binding properties.

Animals↗
PubMed1979

Localization of deoxyribonucleic acid-stimulated adenosine triphosphatases in human lymphocytes.

Two enzymes hydrolyzing ATP (ATPase A and ATPase B) were purified from freshly isolated lymphocytes of human tonsils. Both enzymes are stimulated by single-stranded DNA and seem to be localized in the chromatin. ATPase A and ATPase B appear to be distinct enzymes as judged from their elution profiles obtained after DEAE-cellulose and ATP-Sepharose column chromatography, from their behavior towards actinomycin D, a DNA intercalating agent, and from their sensitivity to monovalent salt concentration.

Adenosine Triphosphatases↗
PubMed1979

An adenosine triphosphate dependent deoxyribonuclease with adenosine triphosphatase, activity from Bacillus cereus.

An adenosine triphosphate-stimulated deoxyribonuclease was purified to about 4200 fold from Bacillus cereus. The enzyme activity of the crude extract increased by a factor of about 5 after dialysis. One of the low molecular weight inhibitors of the crude extract was found to be inorganic phosphate. During enzyme purification two nucleases were identified. One of them was specific to denatured DNA and the other one degraded both denatured DNA and native DNA. The activity towards native DNA could be increased several times by ATP. Through all steps of purification the ATP-independent DNase always accompanied the ATP-dependent one and the ratio of their activity was found to be constant. The ATP-dependent DNase also possessed ATPase activity stimulated both by native and denatured DNA. The fact that ATPase was stimulated by DNA and went together with ATP-dependent DNase during purification suggests that these functions belong to the same enzyme complex. Maximal activity of ATPase had broader pH, Mg2+ and ATP concentration ranges than that of DNase. Cooperation of the two functions may be limited only to a narrow range of ATP concentration. Km for ATPase was 1.6x10-4 M ATP.

Adenosine Triphosphatases↗
PubMed1979

Binding of exogenous DNA by human lymphocytes and by their isolated plasma membranes.

The binding of labeled bacterial DNA to human tonsil lymphocytes and to plasma membranes isolated from these cells involved macromolecules mainly located at the cell surface, since plasma membrane preparations showed properties in common with those of viable cells. DNA binding to lymphocytes was a dissociable, saturable, time, temperature, pH and concentration dependent process. A double reciprocal plot of the data obtained from DNA saturation curves gave an apparent dissociation constant of about 4 X 10(-10) M. The process of interaction of 3H-DNA with lymphocyte membranes gave a complex Scatchard plot, whose first slope yielded an apparent dissociation constant similar to that obtained for DNA-cell interaction. Binding was shown to be specific for DNA because RNA did not displace the bound DNA. Double stranded DNA was preferentially bound relative to single stranded DNA. Temperatures greater than 55 degrees C abolished the binding capacity. Results of experiments in which pH and salt concentration were varied point to the importance of conformational changes of the nucleic acid in the binding process.

Bacillus cereus↗