Inhibition of interferon secretion by vinblastine

The plant alkaloids vinblastine and colchicine are known to arrest cells in mitosis by virtue of their binding to spindle protein. These drugs are also capable of binding to microtubule protein and causing these structures to disaggregate into nonfunctional subunits (1, 2). Microtubular structures are thought to be involved in the secretory process of a number of proteins including insulin (7), collagen (4), and thyroid hormone (12). In this report we present our findings on the effects of these two drugs on the synthesis and secretion of interferon in a high producing human foreskin fibroblast strain (FS-4) (11).     

Conditions for cyanobacteria L-transformation

Anabaena variabilis and Chlorogloea fritschii can easily form L-like colonies that are characterized by their appearance and the morphology of component structures. The colonies consist of morphological elements typical of the L-variants of chemoheterotrophic bacteria: filaments, "grains", ring-shaped cells, etc. Data are presented pertinent to the functional activity of the photosynthetic apparatus of these organisms subjected to L-transformation.     

Incorporation of proteins labeled with H3-lysine into chromosomes of human leucocytes cultured in vitro

The experiments were carried out on human leucocytes cultured in vitro. We studied the distribution of silver grains over metaphase chromosomes after pulse-labeling of cells with H³-lysine in S- and G2 phases. It was found that the grain number per chromosome of the pairs No. 1–3, 13–15 is proportional to their lengths. The probability of incorporation of labeled proteins into each of the homologous chromosomes of the first pair is equal to 0.5 found from the results of statistical analysis of silver grain counts. In cells with karyotype XXX labeled in late-S, the grain number per chromosome in the subgroup 6-X-7 is uniform. In these cells there is no difference in labeling densities among chromosomes of the group A. The data obtained suggest that the formation of the protein component in autosomes of different groups as well as in homologous autosomes and sex-chromosomes proceeds simultaneously and at equal rate.     

Klenow fragment of DNA-polymerase I from E. coli. III. The role of internucleotide phosphate groups of the matrix in its binding with the enzyme

The modification of Klenow fragment of DNA polymerase I E. coli was investigated by the affinity reagents d(Tp)2C[Pt2+(NH3)2OH](pT)7 and d(pT)2pC[Pt2+(NH3)2OH](pT)7. The template binding site of the enzyme was modified by these reagents in the presence of NaF (5 mM), which inhibits selectively the 3'----5'-exonuclease activity of the enzyme and therefore prevents the reagent from degradation. NaCN destroyed covalent bonds between reagents and enzyme, restoring activity of the Klenow fragment. The affinity of different ligands (inorganic phosphate, nucleoside monophosphates, oligonucleotides) to the template binding site of Klenow fragment was estimated. Minimal ligands capable to bind with the template site were shown to be triethylphosphate (Kd 290 microM) and phosphate (Kd 26 microM). Ligand affinity increases by the factor 1.76 per an added (monomer unit from phosphate to d(pT) and then for oligonucleotides d(Tp)nT (n 1 to 19-20). At n greater than 19-20, the ligand affinity remained constant. The complete ethylation of phosphodiester groups lowers affinity of the oligothymidylates to the enzyme by approximately 10 times, and comparable decrease of Pt2+-oligonucleotide affinity to polymerase is caused by the absence of Mn2+-ions. The data obtained led to suggestion that one Me2+-dependent electrostatic contact of the template phosphodiester group with the enzyme takes place (delta G = -1.45...-1.75 kcal/mole). Formation of a hydrogen bond with the oxygen atom of P = O group of the same template phosphate is also assumed (delta G = -4.8...-4.9 kcal/mole). Other template internucleotide phosphates do not interact with the enzyme but the bases of oligonucleotides take part in hydrophobic interactions with the template binding site. Gibbs energy changes by -0.34 kcal/mole when the template is lengthened by one unit.     

The characteristics of the chemical composition and biological activity of Proteus antigens isolated using hydroxylamine

The comparative study of the chemical composition and biological properties of antigens isolated from Proteus vulgaris with the use of hydroxylamine and by two classical methods (Boivin's and Westphal's methods) has been made. As shown in this study, the treatment of bacteria with hydroxylamine makes it possible to obtain antigenic complexes with lower toxicity. At the same time hydroxylamine produces no denaturing effect on lipopolysaccharides and protein fractions of bacterial cells.