DNA replication and H5 histone exchange during reactivation of chick erythrocyte nuclei in heterokaryons

Fusion of terminally differentiated chick erythrocytes (CE) with replicating quail myoblasts or established L6J1 rat myoblasts results in reactivation of DNA synthesis in the dormant CE nuclei and in suppression of DNA synthesis in the myoblast nuclei. The nuclei of primary quail myoblasts are more effectively inhibited than the nuclei of established rat myoblasts. Inhibition of DNA replication occurs not only by preventing G1 nuclei from entering S-phase but also by blocking nuclei in S-phase and by delaying nuclei in G2 from undergoing mitosis and starting a new DNA replication cycle. No inhibition of DNA synthesis could be observed when mouse erythrocytes, i.e., erythrocytes lacking nuclei, were fused with rat myoblasts to generate mouse-globin-containing L6J1 cybrids. — Reactivation of CE nuclei is associated with a loss of the tissuespecific H5 histone variant. Complete elimination of H5 histone, however, does not seem to be a necessary prerequisite for the initiation or completion of DNA replication in CE nuclei since H5 antigens are found on reactivated G1, S, and G2 nuclei.     

Synthesis of dinucleoside tetraphosphates by RNA polymerase B (II) from calf thymus

Highly purified RNA polymerase B (II) from calf thymus catalyses the synthesis of dinucleoside tetraphosphates from ribonucleoside triphosphates in the absence of an oligonucleotide primer or additional protein factors. The reaction requires a DNA template and bivalent cations such as Mn2+ or Mg2+. It is strongly inhibited by heparin and high concentrations of alpha-amanitin but not by rifampicin. On a given template various dinucleoside tetraphosphates of different sequence are formed although the yield depends on the nature of the template.     

Chromatographic studies on the radiolysis of DNA in aqueous solution

Radiation-induced degradation of double-stranded DNA from calf thymus in aqueous solution with sodium phosphate was studied by conventional gel chromatography and by high-performance liquid-gel permeation chromatography. Comparison of the data after radiolysis of aqueous solutions of DNA under anaerobic and aerobic conditions indicates that double-strand breakage is not enhanced by oxygen. An increase of ionic strength impedes the break-down of the DNA molecules, so that loss of DNA can only be observed at doses above 100 Gy. Only reactions of OH-radicals contribute to the fragmentation of DNA, while the presence of hydrated electrons, H.-or formate radicals does not lead to a loss of highly polymerized DNA up to doses of 1500 Gy. High-performance liquid-chromatography proved to be an excellent method of studying the degradation of macromolecules as a function of dose.     

Role of serum and urinary Tamm-Horsfall protein in the surveillance of kidney transplants

The study of 24-h urinary excretion proves to be quite interesting from a theoretical point of view on account of its topographic origin in the nephron and from a practical point of view to control renal transplant patients with favourable or unfavourable course. In both cases, the results we obtain are in accordance with that of blood creatinine assay and ratio N-acetyl-beta-D-glucosaminidase (NAG)/creatinine in urine. The prolonged study of serum THG concentration confirms the previous data regarding the outcome of renal grafts. Moreover, particularly low concentration rates probably imply the interference of factors such as: renal toxins or anti-THG autoantibodies.     

Interaction of histone H1 from sea urchin sperm with superhelical and relaxed DNA

Complexes of histone H1 from sea urchin sperm (H1S) and calf thymus (H1T) with superhelical DNA I and relaxed circular DNA II have been analyzed by analytical sedimentation. Similar to H1T, the highly basic and relatively arginine-rich histone H1S preferentially interacts with DNA I compared to DNA II under competition conditions. However, H1S induces a stronger aggregation of bothforms of DNA than H1T. Below 0.05 M NaCl, the soluble complexes formed by both histones have similar properties, but aggregation proceeds in a different manner: H1S induces a stronger aggregation of DNA II as compared to DNA I, whereas H1T fails to aggregate DNA I.The results are explained on the basis of differences in amino acid sequence and structure of the two histones and related to the special chromatin condensing ability of histone H1S.     

Covalent immobilization of the multienzyme enniatin synthetase

Summary The multienzyme enniatin synthetase was covalently immobilized to N-hydroxysuccinimide activated agarose. The stability of the immobilized enzyme at 25°C was enhanced compared to the soluble enzyme. Immobilization experiments also indicated that the enniatins are synthesized by a single molecule and thus do not require interactions of several enzyme molecules.     

Production and characterization of KDO-specific monoclonal antibodies recognizing lipopolysaccharides from heptoseless mutants of Salmonella

Abstract Hybrid cell lines producing monoclonal antibodies with specificity for the lipopolysaccharide (LPS) from the deep rough mutant Salmonella minnesota R595 have been established. Spleen cells from BALB/c mice immunized with live R595 bacteria were fused with Sp 2/0 myeloma cells and three hybridomas producing antibodies specific for heptoseless LPS from Salmonella were selected. All three monoclonal antibodies were shown to bind only to heptoseless, but 3-deoxy- d -manno-octulosonic acid (KDO) containing LPS when tested in enzyme-linked immunosorbent assay (ELISA) against a set of structurally defined LPS and lipid A from Salmonella, Shigella and Escherichia coli . Synthetic KDO was an efficient inhibitor of the antibody-R595 LPS interaction defining that KDO is in an immunodeterminant position interacting with the monoclonal antibodies.     

Primary structure of the glycan chains of normal C 1 esterase inhibitor (C 1-INH) after NMR analysis at 400 MHz

The primary structural analysis of O- and N-linked carbohydrate chains of the C-1-esterase inhibitor purified from normal serum was carried out by 400-MHz 1H-NMR spectroscopy. C-1-esterase inhibitor protein of a molecular weight of 116,000 daltons contains 24 O-glycans: NeuAc (alpha 2-3) Gal (beta 1-3) GalNAc, 4 N-glycans: NeuAc (alpha 2-6) Gal (beta 1-4) (GlcNAc (beta 1-2) Man (alpha 1-3) [NeuAc (alpha 2-6) Gal (beta 1-4) GlcNAc (beta 1-2) Man (alpha 1-6)] Man (beta 1-4) GlcNAc (beta 1-4) GlcNAc and 2 N-glycans: NeuAc (alpha 2-3) Gal (beta 1-4) GlcNAc (beta 1-2) Man (alpha 1-3) [NeuAc (alpha 2-3) Gal (beta 1-4) GlcNAc (beta 1-2) Man (alpha 1-6)] Man (beta 1-4) GlcNAc (beta 1-4) GlcNAc. 30% of the N-glycans are fucosylated.