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Biomedical subjects

F Antoni

Publications and source records attributed to F Antoni.

At least 127 records · Page 7Linked to original sources
PubMed1978

Two types of cyclic GMP binding site associated with the cyclic AMP-dependent protein kinase from lymphocytes.

Low- and high-affinity binding sites for cyclic GMP were found to be associated with the cyclic AMP-dependent protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) from human tonsillar lymphocytes, but neither of them was identical with the cyclic AMP binding site. The enzyme activated by cyclic GMP phosphorylated the same site of calf thymus H2b histone as the cyclic AMP activated enzyme; however, more complex kinetics of activation were found with cyclic GMP. Two classes of cyclic GMP binding site were demonstrated by kinetic analysis of cyclic [3H]GMP binding in the enzyme preparations eluted by 0.1 M potassium phosphate (pH 7.0) from DEAE cellulose. The high-affinity cyclic GMP binding site (Kd about 4 . 10(-8) M) belonged to some complex form of the protein kinase, as evidenced by the mutual inhibition of cyclic AMP binding and high affinity cyclic GMP binding. However, the high-affinity cyclic GMP binding site disappeared on Sephadex G-100 gel chromatography of the enzyme preparation, whereas the cyclic AMP binding activity was recovered quantitively as separate fractions. The low-affinity cyclic GMP binding site (Kd 2--5 . 10(-6) M) was demonstrated by the inhibitory effect of 10(-5) M cyclic GMP on cyclic AMP binding in each cyclic AMP binding fraction obtained by gel chromatography. However, cyclic AMP did not inhibit the binding of cyclic GMP to the low-affinity binding site.

Binding Sites↗
PubMed1978

Excretion of newly synthesized DNA by tonsil lymphocytes.

The main part of newly synthesized DNA is preferentially released in vitro both by non-stimulated or phytohemagglutinin-stimulated tonsil lymphocytes. Freshly isolated cells excrete DNA faster than phytohemagglutinin-stimulated ones. The acid-precipitable 3H-thymidine lost can be accounted for in the culture medium as labeled, double stranded DNA isolated on hydroxyapatite column.

Cell Survival↗
PubMed1978

Effect of released lymphocyte proteins on human lymphocytes in vitro. II. Protein synthesis of nylon-wool separated cells in the presence of proteins derived from lymphocytes.

Protein synthesis of nylon-wool adherent (B) and non-adherent (T) human tonsillar lymphocytes was examined in the presence of three protein fractions precipitated with ammonium sulfate from the medium of the above lymphocytes incubated in vitro for 4 hours. One fraction precipitated with ammonium sulfate at 0--30% saturation was found to inhibit amino acid incorporation into proteins mainly in unseparated cells while the fraction precipitated at 30--70% saturation decreased the rate of protein synthesis in B cells. The fraction precipitated at 70--100% saturation inhibited protein synthesis slightly in T lymphocytes. Protein synthesis in B and T as well as in unseparated cells was also examined in the presence of proteins obtained from the medium of B and T lymphocytes. It is assumed that proteins released by lymphocytes without mitogenic activation in vitro are involved in the mediation of lymphocyte interactions and may be related to lymphokines synthesized and released by activated cells.

B-Lymphocytes↗
PubMed1977

Lethla effect of nitrous acid on Escherichia coli.

The effect of nitrous acid (NA) on viability, integrity of cellular DNA and on membrane transport were studied in 5 strains of Escherichia coli. Stationary phase cells, grown on mineral salts medium, were exposed to NA. The viability of strains decreased in thefollowing order: W3110 wild-type greater than WP2 wild-type, WP2 uvrA greater than NG30 recA greater than P3478 polA. Alterations were found in the DNA sedimentation profile in alkaline sucrose gradient. Disturbance of DNA synthesis was measured by 3H-labelled thymidine ([3H]Thd) incorporation. No degradation of DNA was found after NA treatment. Low doses of NA caused significant inhibition of leucine and glucose transport into whole cells. The results are interpreted in terms of the multi-target action of NA causing the death of cells.

Biological Transport, Active↗
PubMed1977

Fate of foreign DNA taken up by tonsillar lymphocytes.

The uptake of heterologous (B. cereus) DNA by tonsillar lymphocytes was followed for 22 hours. Acid-precipitable DNA became associated with the cells as soon as they were mixed with DNA. The uptake was linear from 0 to 3 hours, between 3 to 6 hours part of the cell-associated DNA was released into the incubation medium, and at 22 hours the amount of label in the cells reached the values measured at 2--3 hours. In respect of the size of DNA the uptake seemed to follow the same saturation curve. There was no difference between the uptake pattern of native DNA and that of heat-denatured DNA. The decrease of size of foreign DNA in the cells in the incubation medium was followed by agarose-gel electrophoresis. In tonsillar lymphocytes enzyme activities capable of degrading heterologous DNA were found. The enzyme activities present in the cells could be detected in the culture medium as well for at least 24 hours.

Bacillus cereus↗
PubMed1977

Studies on human tonsillar lymphocyte membranes. I. Isolation and characterization of a membraneous glycoprotein fraction from human lymphocytes.

A microsomal fraction containing high amounts of plasma membrane has been isolated from human tonsillar lymphocytes. The subcellular fractions were characterized on the basis of their chemical composition and enzyme activities. A glycoprotein fraction solubilized by lithium-diiodo-salicylate (LIS) was purified by ion-exchange chromatography. The purified glycoprotein was analyzed by various methods and its carbohydrate content was determined. The glycoprotein contained large amounts of hexoses and sialic acid and this fraction represented 3--4% of the whole plasma membrane protein. The fraction was shown to consist of three individual proteins (4 X 10(4), 4.6 X 10(4) and 4.8 X 10(4) daltons) determined by SDS-polyacrylamide gel electrophoresis.

Carbohydrates↗
PubMed1977

Studies on human tonsillar lymphocyte membranes. II. Biological properties of membraneous glycoprotein fractions derived from human tonsillar lymphocytes.

Microsomal and mitochondrial glycoprotein fractions were isolated from human tonsillar lymphocytes. The microsomal glycoprotein was purified by DEAE-Sephadex chromatography. Yielding three subfractions. The different glycoprotein fractions were studied and characterized in two different ways. The isolated glycoproteins inhibited spontaneous (E) rosette formation. This effect was similar to that exhibited by some immunosuppressive drugs and the inhibitory property was heat-labile. The microsomal and mitochondrial glycoproteins and the DEAE-Sephadex subfractions of the microsomal glycoprotein inhibited the mitogenic effect of phytohaemagglutinin and concanavalin A. This inhibition was much stronger than the effect of monosaccharide haptens (N-acetyl-D-galactose-amine and D-glucose) and may be attributed to the lectin-binding property of the glycoprotein fraction.

Concanavalin A↗
PubMed1977

Cytoplasmic aggregates in D-galactosamine induced liver injury.

D-galactosamine treatment leads to the formation of PAS-positive granules or aggregates in the cytoplasm of mouse liver cells. Ultrastructural observations show that the granules consist of particles surrounded by membranes of rough endoplasmic reticulum. Cytochemical results reveal that part of the particles is pronase-sensitive and amylase resistant, staining positively by the Thiéry silver proteinate method. The other part is stained positively by EDTA preferentional staining. According to the cyto-and histochemical results the granules consist of ribosomes and abnormal basic glycogen. The aggregates are removed from the cytoplasm mostly by lysosomal degradation.

Animals↗
PubMed1976

The use of agarose gels for the assay of the deoxyribonuclease activity associated with the soluble penton of adenoviruses.

Evidence is presented that the excess pool of penton complexes purified from adenovirus type 1-infected HEp-2 cells also carry an endonucleolytic activity. The effect was measured with both E. coli and adenovirus type 1 double-stranded DNA substrates. The use of agarose gels for assaying the endonuclease activity allowed the approximative calculation of the number of penton molecules which might produce one DNA double-strand break under the experimental conditions selected.

Adenoviruses, Human↗
PubMed1976

Myasthenia gravis: mitotic activity of thymus-dependent and blood-lymphocytes.

The thymus and blood lymphocytes of 20 thymectomized patients with myasthenia gravis, including 3 cases of thymoma, have been studied for mitotic activity (spontaneous mitotic activity of native thymocytes, responsiveness of cultured cells to PHA, DNA-polymerase specific activity). The myasthenic thymus gland was found to be the site of a spontaneous DNA-synthesis of similar intensity as the mitotic activity of the thymus in infancy. This was also reflected by the DNA-polymerase activity of the cells. While the thymocyte cultures responded well to PHA stimulation in 50% of the cases, the blood-lymphocytes were found unresponsive. There was a partial correlation between the individual parameters of mitotic activity, but practically none between the mitotic activity and the clinical severity of myasthenia or the histological features of the thymus or of thymoma. Except in the latter cases, a correlation was found between mitotic activity and preoperative immunosuppressive treatment. It is suggested that the T-lymphocytes are not directly involved in the pathomechanism of myasthenia gravis.

Adolescent↗
PubMed1976

Demonstration of adenovirus associated endonuclease.

In HEp-2 and amnion cell cultures infected with type 1 adenovirus the DNase activity of cell extracts was measured on 32P-labelled Escherichia coli DNA substrate. Enzyme activity was demonstrated by the acid soluble nucleotides released from the 32P-DNA and by the decreased sedimentation rate of labelled DNA. High DNase activity was measured in both adenovirus infected and in untreated HEp-2 cell extracts. Nuclease activity of the amnion host cells being much lower than that of HEp-2 cells, virus-associated endonuclease activity was successfully demonstrated in them. Purified type 1 adenovirus decreased the sedimentation rate of 32P-labelled E. coli DNA. The phenomenon is explained by the virion-associated endonuclease activity. Trypsin inactivated and anti HEp-2 IgG failed to inhibit the virion nuclease. An association between endonuclease and trypsin sensitive penton is assumed.

Adenoviridae↗
PubMed1975

Determination of UTP and ATP pool sizes in human tonsillar lymphocytes by using Escherichia coli RNA polymerase.

The present paper describes a rapid, specific and sensitive method for quantitating ribonucleoside triphosphates (ATP and UTP) in cell extracts. The principle of the method is based on the synthesis of a ribonucleotide polymer in the presence of UTP, ATP and poly(dA-dT) as template. A method for calculation is also described, making the determination of UTP and ATP pool sizes in the cells possible under the same experimental conditions. The calculation takes into account the isotope dilution effect caused by the intracellular ATP. Our experiments show that the neutralized perchloric acid soluble fraction of human tonsillar lymphocytes contains no inhibitors for the RNA polymerase test. According to our results, this cell extract contains 80 pmol of UTP and 340 pmol of ATP per mug RNA.

Adenosine Triphosphate↗