Pyruvate:NADP+ oxidoreductase from Euglena gracilis: mechanism of O2-inactivation of the enzyme and its stability in the aerobe

O2-inactivation of pyruvate:NADP+ oxidoreductase from mitochondria of Euglena gracilis was studied in vitro, and a mechanism which consists of two sequential stages was proposed. Initially, the enzyme is inactivated by the direct action of O2 in a process obeying second-order kinetics. Although the catalytic activity for pyruvate oxidation is lost by this initial inactivation, NADPH oxidation with artificial electron acceptors still occurs. Subsequently, a secondary, O2-independent inactivation occurs, rendering the enzyme completely inactive. Pyruvate stimulates the O2-inactivation while CoA and NADP+ protect the enzyme from O2. The O2-inactivation is accelerated by reduction of the enzyme with pyruvate and CoA. Reactivation of the O2-inactivated enzyme was studied in Ar by incubation with Fe2+ in the presence of some other reducing reagent such as dithiothreitol. The evidence obtained indicates that the partially inactivated enzyme, which retains catalytic activity for NADPH oxidation, can be reactivated, but the completely inactivated enzyme is not. When Euglena cells were exposed to 100% O2 the enzyme in the cells was inactivated by O2, but the rate was quite slow compared with that observed in vitro. The enzyme inactivated by O2 in the cells was almost completely reactivated in vitro by incubation with Fe2+ and other reducing reagents in Ar, suggesting that the secondary, O2-independent inactivation does not occur in situ. When the cells were returned to air, reactivation of the O2-inactivated enzyme in the cells began immediately. The enzyme, kept in isolated, intact mitochondria, was stable in air; however, the enzyme was inactivated by O2 when the mitochondria were incubated with a high concentration of pyruvate.     

Conformation and structure of 2-amino-8-(β-d-ribofuranosyl)imidazo [1,2-a]-s-triazin-4-one (5-aza-7-deaza guanosine), a potent antiviral nucleoside

The crystal and molecular structure of one imidazo[1,2-a]-s-triazine nucleoside and its antiviral activity are described. The crystal structure of 2-amino-8-(β-d-ribofuranosyl)imidazo-[1,2-a]-s-triazin-4-one monohydrate (C₁₀H₁₃N₅O₅·H₂O) was solved by X-ray counter data. The compound crystallizes in the monoclinic space group P2₁ with cell dimensions a = 7.353 (1), b = 6.465 (1), c = 13.701 (1) Å, β = 104.64 (1)°. The structure was solved by direct methods and refined by full matrix least-squares technique to a final value of the conventional R-factor of 0.049 using 1998 observed intensities. The orientation of the base relative to the sugar ring defined in terms of rotation about the C(1′)-N(8) glycosyl bond is anti (47.8°). The ribose moiety exhibits C(2′)-endo, ²E conformation. The conformation around C(4′)-C(5′) is gauche^?. Molecular packing is dominated by hydrogen bonds. Base stacking occurs long the b axis. 5-Aza-7-deazaguanosine has shown a marked antiviral activity in vitro against herpes simplex virus despite the fact that N(3) is effective as the hydrogen acceptor only.     

Arginase as an inhibitory principle in liver plasma membranes arresting the growth of various mammalian cells in vitro

Plasma membranes prepared from rat livers inhibited the in vitro growth of various mammalian cells including hepatoma cells in a concentration-dependent manner, showing an almost complete arrest of cell growth at 0.1 mg protein/ml. Some of these cells tested, i.e., leukemia (L1210 and P388) and myeloma (P₃-NS-1/1-Ag4-1) cells, were labile in the presence of plasma membranes (losing the viability), and CHO (Chinese hamster ovary) cells became round without detaching from the substratum. The culture medium preincubated with liver plasma membranes no longer supported the growth of hepatoma cells (AH13 and AH66F). However, the ‘conditioned’ medium supplemented with l-arginine, supported the growth of the cells. Moreover, the addition of l-ornithine to the cultures containing plasma membranes markedly reduced the inhibitory effect of plasma membranes. The plasma membrane preparations were found to possess considerable arginase activity. These results seem to indicate the possible involvement of arginase in the inhibition of cell growth by liver plasma membranes.     

Effects of pantolactone and butyrolaectone on the pleiotropic phenotypes of lon mutants and on thermal induction of the SOS phenomena in a tif mutant of Escherichia coli K12

Hydrophobic and charge-charge interactions of Salmonella typhimirium and Serratia marcescens were determined and related to their content of fimbriae and lipopolysaccharide (LPS). The cell surface structures were characterized with hydrophobic interaction chromatography (HIC), electrostatic interaction chromatography (ESIC) and particle electrophoresis measurements. The degree of interaction at the air-water interface was tested using a monolayered lipid film applied to an aqueous surface. The cell surface hydrophobicity of S. typhimurium in the presence of fimbriae was less in smooth than in rought bacteria. Examination of a series of rough mutants of S. typhimurium indicates that reduction of the O-side chain and core oligosaccharides was correlated with increased cell hydrophobicity. The enrichment factors at the air-water interface were significantly higher for fimbriated than for non-fimbriated S. typhimurium cells. Fimbriated S. marcescens cells were less hydrophobic and adhered to a lesser degree at the air-water surface than non-fimbriated counterparts. Electrophoretic measurements and adsorption to ion exchangers gives different information about the surface charge of bacteria. The latter technique gives the interaction between localized charged surfaces.Abbreviations HIC hydrophobic interaction chromatography - ESIC electrostatic interaction chromatography - LPS lipopolysaccharide - PBS phosphate buffered saline solution     

Endothelial specific granules in the umbilical veins of the postnatal rabbit

Summary A remarkable increase in number of endothelial specific granules was observed in the rabbit umbilical veins between 2 and 5 days after birth. Electron microscopy indicated that the granules were segregated in the Golgi complex of the endothelial cells and released into the vascular lumen during the postnatal obliteration stage of this vessel.Incubation of the postnatal vessels in Ringer solution containing a histamine releasing compound induced remarkable morphological alterations of these cytoplasmic components; a reduction of their osmiophilia, swelling with a widened space separating the granular matrix from the limiting membrane, fusion to each other and expulsion of their contents into the vascular lumen, as in mast cell degranulation by this drug, were noted.High-performance liquid chromatography of the homogenized vessels demonstrated appreciable concentrations of histamine in the postnatal samples. There was a correlation between the histamine concentration and the quantity of granules in the respective postnatal samples.The present study strongly suggests that the granules are reservoirs of histamine and have an important role in the obliteration of this vessel.This work was supported in part by Grant in Aid for Scientific Research (# 448087) to S. Fujimoto from the Ministry of Education of Japan     

The Remobilization of Nitrogen Related to Leaf Growth and Senescence in Rice Plants (Oryza sativa L.)

Rice plants (Oryzae sativa L.) grown in a nutrient solutionwere fed with (¹⁵NH₄)₂SO₄ during the 5 days of their young panicleformation. At the end of that time in the youngest leaf blade, which hadstarted to emerge during the labelling, absorbed-nitrogen accountedfor 37% of the increased nitrogen of the tissue; in the nextdeveloping leaf blade it accounted for 55%. Thus, remobilized-nitrogenoriginating from older patrs of the plant made up 63 and 45%,respectively, of their total nitrogen. The important contributionof the remobilized-nitrogen to the development of a leaf isevident. The remobilization of nitrogen in the 12th leaf blade on themain stem was examined in detail after labelling during itsdeveloping stage. The ¹⁵N level started to decrease soon afterthe end of the labelling period and continued to decrease untilfull senescence, although the total nitrogen in the same leafincreased until just after its complete expansion, suggestingthat even a young leaf plays a role as a supplier of remobilized-nitrogen. During the rapid decrease in the total nitrogen after its peakat full expansion of the leaf, the actual proportion of labelledabsorbed nitrogen remained nearly the same, indicating thatinflux of new nitrogen into a senescing leaf is very limited. (Received March 13, 1981; Accepted July 13, 1981)     

Reaction of some D-glucobioses with 2,2-dimethoxypropane

Laminarabiose, cellobiose, and gentiobiose were acetonated with 2,2-dimethoxy-propane under various conditions. Two isopropylidene acetals in which the reducing D-glucose residue had the furanoid form were obtained from laminarabiose, and two, in which the reducing D-glucose residue formed the acyclic dimethyl acetal, from cellobiose. Gentiobiose gave both types of isopropylidene compound.     

Cell surface changes accompanying aging in human diploid fibroblasts : III. Division age and senescence revealed by concanavalin A-mediated red blood cell adsorption

The relationship between cell size, [³H]thymidine incorporation capacity, and cell surface property of human diploid fibroblasts was investigated using the concanavalin A (ConA)-mediated red blood cell (RBC) adsorption assay. Small cells in late passage populations adsorbed RBCs well with the RBC coating method (in which ConA-coated RBCs are adsorbed to fibroblasts) as did large cells of this population, while small cells in early passage populations did not. The RBC adsorption capacity of rapidly dividing cells with this method differed among young, middle-aged and old cell populations. The results suggest that temporal cell size and [³H]thymidine incorporating capacity is not a measure of the division age of human diploid cells at the individual cell level. On the other hand, RBC adsorption with the fibroblast coating method (in which RBCs are adsorbed to ConA-coated fibroblasts) occurred to non-dividing cells of the populations. Thus, the increase in RBC adsorption with this method is considered to be a reflection of the increase in non-dividing cells at phase III. Our results support the hypothesis that RBC adsorption with the RBC and fibroblast-coating methods represents a cell surface marker for division age and senescence of human diploid cells, respectively, at the individual cell level.     

Studies on the population dynamics of a thistle-feeding lady beetle,Henosepilachna pustulosa (Kôno) in a cool temperature climax forest

1. A field study was carried out on the population dynamics of a thistle-feeding lady beetle, Henosepilachna pustulosa (Kôno ) living in a cool temperature climax forest in northern Kyoto Prefecture, central Japan.
2. Intensive marking, release and recapture program was carried out to estimate the adult population parameters by usingJolly-Seber method.
3. Sampling ratio was around 50%. Marking ratio rapidly rised as the census progressed and approached to 100%.
4. Sex ratio (% ♀) was 63–69% in both overwintered and new adults.
5. Daily survival rate was as high as 0.95 or more and constant throughout the season. Adult longevity in the spring was longer than 40 days.
6. Reproductive rate i. e., the ratio of the number of newly emerged adults in a given generation to that of overwintered adults in the preceding generation, is very small, ranging 1–3, whereas winter survival is higher than 50%, consequently the size of populations in the study area remain in a remarkably constant size and it never reached a level where intraspesific competition occurred.
7. The population characteristics of H. pustulosa are compared with those of the two closely related species, H. vigintioctopunctata and H. vigintioctomaculata, which are the pests of Solanaceous crops. Hp is more K-strategic than the two pest species.