Migration inhibitory action of bacterial lipopolysaccharide on progenitor cells of monocyte/macrophage lineage growing in culture in the presence of colony-stimulating factor (CSF-1)

Addition of lipopolysaccharide (LPS) to the culture of mouse myeloid stem cells (CFU_c) increased the incidence of compact colonies and decreased that of dispersed ones in the presence of colony-stimulating factor (CSF-1) which had not such an effect by itself even in high concentrations. Although colony morphology was thus changed, nearly all colonies were composed of monocytes. The incidence of compact colonies increased with the increase of LPS concentration but plateaued at about 50%. Bone marrow cells of LPS-tolerant mice responded to LPS in vitro to a slightly decreased extent. The activity of LPS was decreased by alkaline or acid hydrolysis of the LPS molecule and inhibited by polymixin B, but not by indomethacin, α-L-fucose, nor by α-methyl-D-mannoside. Other immunopotentiating substances, such as OK-432, Lentinan, and Levamisole, had no effect on the colony morphology. Both muramyl dipeptide and poly(I)poly(C) were also ineffective. Furthermore, the action of LPS was not abolished by the use of heat-inactivated serum in the culture. LPS was no longer stimulative for the induction of lysosomal enzymes in the CSF-stimulated culture, although it greatly enhanced the enzyme induction in the unstimulated culture. These results indicate that the cells of monocyte/macrophage lineage develop the capacity for migration before they become responsive to LPS, and that the LPS-responding monocytic cells can proliferate even in a state of confluence induced by LPS.     

Effects of inhibitors of DNA synthesis on spontaneous and ultraviolet light-induced sister-chromatid exchanges in Chinese hamster cells

Effects of inhibitors of DNA synthesis on spontaneous and ultraviolet light (UV)-induced sister-chromatid exchanges (SCE) were examined in a Chinese hamster cell line, V79 B-1. The inhibitors used were hydroxyurea (HU), 1-beta-D-arabinofuranosylcytosine (ara-C), aphidicolin (APC), 2',3'-dideoxythymidine triphosphate (ddTTP), neocarzinostatin (NCS), novobiocin (NB) and cycloheximide (CHX). HU, ara-C, and APC increased spontaneous SCE frequency, and had a synergistic effect on UV-induced SCE frequency. DdTTP, NCS and NB failed to show any statistically significant effect on either spontaneous or UV-induced SCE frequencies, though NCS and NB did slightly increase both spontaneous and UV-induced SCE frequencies. On the contrary, CHX decreased spontaneous SCE frequency, and more drastically, also UV-induced SCE frequency. These results are interpreted with respect to the replicating fork of DNA, a structure postulated to be involved in the formation of spontaneous and UV-induced SCE. A new model for SCE formation is proposed.     

Isolation, homogeneity, and properties of core particle from pyocin R1.

By a mild alkaline treatment of pyocin R1, the core particle was released from the contracted sheath. After sucrose density-gradient centrifugation, core-rich fractions were treated with anti-sheath serum and by a second density-gradient centrifugation, purified core particles were isolated. Homogeneity of the preparation was confirmed by observation under the electron microscope, immuno-precipitation reaction, and sucrose density-gradient centrifugation. The core particle exhibited a sedimentation coefficient of 37S. The quaternary structure of the core consists of a single kind of subunit protein with a molecular weight of 18,000. No contamination by other proteins was detected by SDS-disc electrophoreses. Amino acid analysis revealed that the core is rich in glycine, alanine, valine, leucine, aspartic acid (or asparagine), glutamic acid (or glutamine), and serine. This amino acid composition bears some resemblance to that of T-even bacteriophage tail-core.     

Formation of sulfhydryl groups in the culture medium by human diploid fibroblasts

When human diploid fibroblasts IMR-90 are cultured in routinely used medium (Eagle's basal medium supplemented with 10% fetal calf serum), sulfhydryl compounds appear in the medium. The major component of these sulfhydryl compounds is cysteine, and it is shown that a part of medium cystine is converted into cysteine by the cells. It is also shown that the sulfhydryl groups of serum albumin, which are masked and barely detectable before the culture, are restored. Probably cysteine formed by the cells reacts with serum albumin to give rise to the protein sulfhydryl groups via sulfhydryl–disulfide exchange reactions. Total sulfhydryl concentrations in the medium are maintained in a considerable level throughout the culture, and a possible physiological function of these sulfhydryl groups is discussed.     

Comparative study on fibers isolated from four R-type pyocins, phage-tail-like bacteriocins of Pseudomonas aeruginosa

Five R-type pyocins have been reported which are almost identical with one another in their morphology and subunit composition, though distinct in receptor-binding specificity. We isolated fibers from pyocin R2, R3, and R4 by essentially the same procedure as used in our previous isolation of pyocin R1 fiber with unimpaired receptor-binding ability. All the isolated fibers including R1 fiber were indistinguishable from one another, in terms of electron microscopic observation and subunit composition analysis by SDS gel electrophoresis. They consisted mainly of Subunit No. 2 (Mw 71,000) and No. 9 (31,000) proteins. Although Subunit No. 9 protein in every fiber was susceptible to trypsin and afforded a fragment with the same molecular weight (about 19,000) detectable in the SDS gel, Subunit No. 2 protein was cleaved with trypsin only after the fiber had been treated with an organomercurial, 4-(p-sulfophenylazo)-2-mercuriphenol. The cleavage of Subunit No. 2 protein proceeded to give several fragments with molecular weights ranging from 64,000 to 34,000, and the fragmentation patterns were electrophoretically distinct at least among R1 fiber, R3 fiber, and others (R2 and R4 fibers). The results indicate that Subunit No. 2 proteins of these fibers are different from one another in the structure surrounding trypsin-susceptible peptide bonds. Immunological investigations with anti-R1 fiber antibodies provided some additional information on the difference among R-type pyocins at the fiber level.     

Insulin-like activity of photochemically obtained monovalent monomeric concanavalin A in the presence of anti-concanavalin A antibodies: dependence on multivalency for stimulation of glucose oxidation of rat fat cells

Insulin-like action of monovalent monomeric concanavalin A (m-Con A) was examined in rat adipocytes in the presence of anti-m-Con A antiserum. The antisera from rabbits injected with m-Con A reacted with not only monovalent monomeric but also tetravalent tetrameric concanavalin A (alpha-Con A) in Ouchterlony double diffusion analysis. m-Con A alone did not show any appreciable effect on glucose oxidation of adipocytes while it slightly inhibited glycerol release stimulated by epinephrine. In contrast, exposure of adipocytes to m-Con A in the presence of antibodies to m-Con A resulted in stimulation of glucose oxidation and inhibition of epinephrine-stimulated lipolysis. The stimulation and the inhibition with m-Con A in the presence of the antibodies were of the same degree as those with alpha-Con A. Both alpha- and m-Con A were slightly active in inhibiting 125I-labeled insulin binding. These results demonstrate that the ability of anti-m-Con A antiserum to aggregate m-Con A bound to receptors on the isolated-adipocyte plasma membrane allowed m-Con A to mimic the biological activity of insulin and that the aggregation of receptors for ligands other than insulin can induce insulin-like action in rat fat cells.     

Chemical Characterization and Phytotoxic Effects of the Aerial Parts of Ruzigrass (Urochloa ruziziensis)

Studies of the phytotoxic effects between plants can be a crucial tool in the discovery of innovative compounds with herbicide potential. In this sense, we can highlight ruzigrass (Urochloa ruziziensis), which is traditionally used in the crop rotation system in order to reduce weed emergence. The aim of this work was to characterize the secondary metabolites of ruzigrass and to evaluate its phytotoxic effects. In total, eight compounds were isolated: friedelin, oleanolic acid, α‐amyrin, 1‐dehydrodiosgenone, sitosterol and stigmasterol glycosides, tricin and p‐coumaric acid. Phytotoxic effects of the crude methanolic extract and fractions of ruzigrass were assessed using germination rate, initial seedling growth, and biomass of Bidens pilosa, Euphorbia heterophylla and Ipomoea grandifolia. Chemometric analysis discriminated the weed species into three groups, and B. pilosa was the most affected by fractions of ruzigrass. The phytotoxic activities of 1‐dehydrodiosgenone, tricin, and p‐coumaric acid are also reported, and p‐coumaric acid and 1‐dehydrodiosgenone were active against B. pilosa.     

Kinetoplastid kinetochore proteins KKT2 and KKT3 have unique centromere localization domains

The kinetochore is the macromolecular protein complex that assembles onto centromeric DNA and binds spindle microtubules. Evolutionarily divergent kinetoplastids have an unconventional set of kinetochore proteins. It remains unknown how kinetochores assemble at centromeres in these organisms. Here, we characterize KKT2 and KKT3 in the kinetoplastid parasite Trypanosoma brucei. In addition to the N-terminal kinase domain and C-terminal divergent polo boxes, these proteins have a central domain of unknown function. We show that KKT2 and KKT3 are important for the localization of several kinetochore proteins and that their central domains are sufficient for centromere localization. Crystal structures of the KKT2 central domain from two divergent kinetoplastids reveal a unique zinc-binding domain (termed the CL domain for centromere localization), which promotes its kinetochore localization in T. brucei. Mutations in the equivalent domain in KKT3 abolish its kinetochore localization and function. Our work shows that the unique central domains play a critical role in mediating the centromere localization of KKT2 and KKT3.