Oxygen Enhancement of bactericidal activity of rifamycin SV on Escherichia coli and aerobic oxidation of rifamycin SV to rifamycin S catalyzed by manganous ions: the role of superoxide

Oxygen enhanced the bactericidal activity of rifamycin SV to Escherichia coli K12. Anaerobically grown cells, which had a low level of superoxide dismutase, were more susceptible to the bactericidal activity than aerobically grown cells, which contained a high level of superoxide dismutase. Oxygen also enhanced the inhibition of RNA polymerase activity of rifamycin SV, when Mn2+ was used as a cofactor. Rifamycin S was reduced to rifamycin SV by NADPH catalyzed by cell-free extracts of Escherichia coli K12. These results indicate that the inhibition of bacterial growth by rifamycin SV is due to the production of active species of oxygen resulting from the oxidation-reduction cycle of rifamycin SV in the cells. The aerobic oxidation of rifamycin SV to rifamycin S was induced by metal ions, such as Mn2+, Cu2+, and Co2+. The most effective metal ion was Mn2+. In the presence of Mn2+, accompanying the consumption of 1 mol of oxygen and the oxidation of 1 mol of rifamycin SV, 1 mol of hydrogen peroxide and 1 mol of rifamycin S were formed. Superoxide was generated during the autoxidation of rifamycin SV. Superoxide dismutase inhibited the formation of rifamycin S, but scavengers for hydrogen peroxide and the hydroxyl radical did not affect the oxidation. A mechanism of Mn2+-catalyzed oxidation of rifamycin SV is proposed and its relation to bactericidal activity is discussed.     

A Comparison of Purified Host Specific Toxin from Helminthosporium maydis, Race T, and Its Acetate Derivative on Oxidation by Mitochondria from Susceptible and Resistant Plants

NADH or succinate oxidation and malate oxidation were differentially affected in mitochondria from both susceptible and resistant corn by a purified and chemically characterized preparation of host-specific toxin from Bipolaris (Helminthosporium) maydis, race T. NADH and succinate oxidation by susceptible T corn mitochondria were stimulated 50 to 200% with apparent uncoupling from the cytochrome chain at approximately 10(-9)m toxin (5 to 20 ng/ml). Significant inhibition of malate oxidation was observed at slightly higher toxin concentrations, but oxidation was still coupled to ADP utilization. Inhibition of malate oxidation also was observed in N corn (resistant) and soybean mitochondria at approximately 1,000-fold greater concentrations, but stimulation of NADH and succinate oxidation was not found at any toxin concentration tested.A fully acetylated toxin derivative at approximately 1 microgram per milliliter also caused stimulation of NADH or succinate oxidation in T corn mitochondria, but not those of N corn or soybean mitochondria at 100 micrograms per milliliter. Malate oxidation was inhibited to the same extent by toxin acetate with mitochondria from T corn, N corn, and soybean. The blocking of hydroxyl groups in race T toxin by acetyl functions eliminated selectivity toward malate oxidation only. The data suggest that inhibition of malate oxidation is either a separate or secondary effect of selective action of toxin on T corn mitochondria, perhaps by interference with transport in or out of the matrix. Sensitivity of T, but not N, corn mitochondria to purified toxin decays within minutes after pellets are suspended in aqueous osmotica, with no obvious change in mitochondrial integrity. The action of race T toxin seems to involve a labile process, such as ion gradient(s), or an unstable structural conformation of T corn mitochondria.     

Corn leaf glutamate synthase: Purification and properties of the enzyme

An assay for ferredoxin-glutamate synthase is introduced thatuses an anion exchange resin to isolate the glutamate formedand subsequent determination with the ninhydrin procedure. Theenzyme was purified 200-fold from corn leaves by ammonium sulfatefractionation and chromatography on DEAE-cellulose, DEAE-Sephaceland ferredoxin- Sepharose. The purified enzyme had a specificactivity of 14 µmoles glutamate formed min^–1mg^–1protein. The enzyme has a molecular weight of 160,000. The pHoptimum for catalytic activity is 6.9. The isoelectric pointis at pH 4.2. The apparent Km values of the enzyme for L-glutamine,2-oxoglutarate and ferredoxin are 1,100, 240 and 1.7 µM.The enzyme has a high specificity toward these substrates witha stoichiometry between glutamate formation and glutamine consumption.Sulfhydryl reagents, bathophenanthroline, phthalein acids andazaserine produced strong inhibition of the enzyme activity. ¹Permanent address: Department of Agricultural Chemistry, KyotoUniversity, Kyoto 606, Japan. ²To whom inquiries should be addressed. (Received July 7, 1979; )     

Pili mediated agglutination of Serratia marcescens in human urine

Of 51 strains of Serratia marcescens isolated from patients with urinary or respiratory tract infections, 35 agglutinated in human urine. The agglutinating strains possessed numerous pili which were morphologically distinct from common pili or type I pili. The diameter of the pili was 3 nm and the average length was 0.3 micrometer. Electron microscopic examination showed that 80% or more of the cells of the agglutinating strains and 0 to 8% of the cells of the nonagglutinating strains were piliated. When an agglutinating strain was heated at 55 C for 10 min, it lost its agglutinating capacity and concomitantly its pili. These results suggest that the agglutination might occur because of interactions between the pili and some factors in human urine. The urinary slime appears to contain these agglutinating factors.     

Hormone-sensitive cAMP phosphodiesterase in liver and fat cells

Summary The enzymatic characteristics and the mode of hormone-dependent stimulation of cAMP phosphodiesterase are reviewed. The hormone-sensitive phosphodiesterase is a low Km enzyme, which has been found in liver and fat cells. The fat cell enzyme is mostly associated with the endoplasmic reticulum. The liver cell enzyme is also associated with certain subcellular structures.The hormone-sensitive phosphodiesterase appears to have catalytic and regulatory domains and is thought to be attached to subcellular structures at the regulatory portion of the enzyme. The catalytic domain of the fat cell enzyme can be obtained in a soluble form from the microsomal preparation by mild proteolysis or by dithiothreitol treatment at 0–4 °C. The catalytic domain of the liver enzyme can be solubilized by either hypotonic treatment or mild trypsin digestion. The catalytic domains solubilized from the basal and hormonally activated forms of the enzyme are apparently identical.The membrane-bound basal enzyme from adipocytes is activated in a concentrated salt solution without being solubilized. On the other hand, the plus-insulin activity is deactivated in a low salt solution or by a short dithiothreitol treatment at 37°, apparently without suffering any changes in the catalytic domain. In contrast, p-chloromercuriphenyl sulfonate seems to inactivate the enzyme by interacting with SH-groups in the catalytic domain. Although the liver enzyme is not similarly affected by salt concentrations, its catalytic activity is blocked by p-chloromercuribenzoate.The adipocyte enzyme can be solubilized with a mixture of Lubrol WX and Zwittergent 3–14. The apparent Stokes radius of the basal enzyme is approximately 87 A, while that of the hormone-stimulated enzyme is approximately 94 A.Apparently, the same species of phosphodiesterase is activated by both insulin and epinephrine in fat cells and by insulin and glucagon in liver, possibly being mediated by reactions involving phosphorylation. However, it is yet to be ascertained how phosphorylation is involved and how the apparent Stokes radius of the adipocyte enzyme is increased as a result of stimulation.     

Elimination of insulin-like activity present in certain batches of crude bovine serum albumin by trypsin treatment

A comparative study was carried out in order to determine which of the most commonly used alkalies for protein hydrolysis in tryptophan determination gave the best results. Hydrolyses were performed with 2.5 and 4 n Ba (OH)₂, 4 and 10 n NaOH, 5 n NaOH containing 5% SnCl₂, and with 4 n LiOH, not previously reported for use. The effect of temperature and hydrolysis time on the measured tryptophan content was also determined. Based on results obtained with lysozyme and with seven high protein preparations 4 n LiOH gave the best results. A temperature of 145°C was selected as the most convenient temperature since maximum tryptophan values were obtained with 4–8 h. The hydrolysis time required was inversely related to the protein content of the preparation. Lysozyme, casein, bovine plasma protein, and dehydrated whole egg gave maximum tryptophan content after 4 h hydrolysis while skimmed milk powder, rice flour, wheat flour, and wild legume flour required 8 h hydrolysis.     

43Ca NMR studies of Ca2+-Tetrahymena calmodulin complexes

⁴³Ca NMR spectra of Ca²⁺-Tetrahymena calmodulin(Tet. CaM.) complexes have been observed under various conditions. Off-rate of Ca²⁺ from Tet. CaM. is estimated to be approx. 2.7 × 10³ s^?1 under a certain assumption. Relaxation rates of ⁴³Ca NMR of Ca²⁺-Tet. CaM. are remarkably increased(by one order in magnitude) by adding trifluoperazine(TFP), a potent calmodulin antagonist. Relaxation parameters estimated suggest that Ca²⁺ mobility is reduced by the TFP binding. A stoichiometry of TFP is two moles per Tet. CaM. molecule. The relaxation rates of ⁴³Ca NMR signals are increased by adding excessive Mg²⁺ to the Ca²⁺-Tet. CaM. solutions. The addition of Mg²⁺ to the Ca²⁺-Tet. CaM. complex decreases apparent pKa value of the complex as well.     

Identification of encephalitogenic V beta-4-bearing T cells in SJL mice. Further evidence for the V region disease hypothesis?

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease of the central nervous system mediated by T cells bearing TCR of restricted heterogeneity. Thus, in the murine PL strain, V beta-8.2 is used by 80% of the encephalitogenic T cells. This observation has led to the successful prevention and reversal of EAE by the in vivo use of mAb directed to these restricted gene products. In SJL mice, the V beta-17a gene product has been shown to be used by approximately 50% of encephalitogenic T cells subsequent to immunization with a myelin basic protein (MBP)-derived peptide. However, the other V beta genes used by encephalitogenic T cells in SJL EAE have remained uncharacterized. We now report, for the first time, the beta-chain-encoding DNA sequence of two encephalitogenic, MBP-reactive, SJL-derived T cell clones. These clones which are specific for H-2s and the carboxyl-terminus (amino acid 92-103) of MBP, use TCR encoded by V beta-4. In addition, we demonstrate that the transfer of EAE by a heterogenous SJL-derived encephalitogenic T cell line can be prevented using an anti-V beta-4 antibody in vivo. V beta-4 usage has been previously described in a H-2u/MBP amino-terminus-reactive encephalitogenic T cell. The present findings may thus further support the "V region-disease" hypothesis.     

Development of vitrified mouse oocytes after in vitro fertilization

Mouse oocytes were cryopreserved by the vitrification method using vitrification solution (VSI) and the effects of dilution methods were examined on the rate of in vitro and in vivo development. Eighty-three percent and 75% of vitrified oocytes exhibited normal morphology when diluted in glycerol + sucrose and sucrose alone, respectively. In contrast, only 35% of the oocytes diluted by a stepwise method exhibited a normal appearance. A high proportion of vitrified oocytes was fertilized in vitro (84-94%), 80 to 87% of which were normal. Of the later embryos, 69 to 78% developed to blastocysts after 4 days of culture. Thirty-six live young (51%) were obtained when vitrified oocytes were transferred to recipient females. The overall rate of development to live young was 25% when vitrified oocytes were diluted with glycerol + sucrose solution. These results indicate that the simple and rapid procedure of vitrification and glycerol + sucrose dilution is suitable for the cryopreservation of mouse oocytes.     

Development of mouse enucleated oocytes receiving a nucleus from different stages of the second cell cycle.

The influence of the stage of the cell cycle of donor nuclei on the development of mouse oocytes enucleated at telophase I was examined. After nuclear transplantation and activation, a high proportion of the oocytes remodelled a nucleus, emitted a polar body and formed a pronuclear-like nucleus. Most of the reconstituted embryos that received an interphase nucleus 30-32 h or 34-36 h after treatment with human chorionic gonadotrophin (hCG) arrested at the 2-cell stage. The reconstituted embryos were able to develop to blastocysts when nuclei from late 2-cell embryos (44-46 and 48-50 h after hCG) were transferred to the oocytes. The resulting blastocysts were transferred to recipients and ten live young were obtained from the embryos that formed a pronuclear-like nucleus after extrusion of a polar body. Thus, the developmental ability of the reconstituted embryos was critically influenced by the stage of the cell cycle of the donor nuclei.