Stability of 3' dangling ends on the core helix of AUGCAU at various Na+ concentrations.

Stability increments of 3' dangling ends on the core helices AUGCAU at various Na+ concentrations are reported. The results show that all 3' dangling ends except 3'U dangling at low Na+ concentrations can stabilize the helix and this stabilization is very sequence dependent.     

Reactivity and activation of dioxygen-derived species in aprotic media (a model matrix for biomembranes)

In aprotic media the electrochemical reduction of dioxygen yields superoxide ion (O2-), which is an effective Br?nsted base, nucleophile, one-electron reductant, and one-electron oxidant of reduced transition metal ions. With electrophilic substrates (organic halides and carbonyl carbons) O2- displaces a leaving group to form a peroxy radical (ROO.) in the primary process. Superoxide ion oxidizes the activated hydrogen atoms of ascorbic acid, catechols, hydrophenazines and hydroflavins. Combination of O2- with 1,2-diphenylhydrazine yields the anion radical of azobenzene, which reacts with O2 to give azobenzene and O2- (an example of O2--induced autoxidation). With phenylhydrazine, O2- produces phenyl radicals. The in situ formation of HO2. (O2- plus a proton source) results in H-atom abstraction from allylic and other groups with weak heteroatom--H bonds (binding energy (b.e.) less than 335 kJ). This is a competitive process with the facile second-order disproportionation of HO2. to H2O2 and O2 (kbi approximately equal to 10(4) mol-1 s-1 in Me2SO). Addition of [FeII(MeCN)4] (ClO4)2 to solutions of hydrogen peroxide in dry acetonitrile catalyses a rapid disproportionation of H2O2 via the initial formation of an adduct [FeII(H2O2)2+----Fe(O)(H2O)2+], which oxidizes a second H2O2 to oxygen. In the presence of organic substrates such as 1,4-cyclohexadiene, 1,2-diphenylhydrazine, catechols and thiols the FeII-H2O2/MeCN system yields dehydrogenated products; with alcohols, aldehydes, methylstyrene, thioethers, sulphoxides, and phosphines, the FeII(H2O2)2+ adduct promotes their monoxygenation. The product from the FeO2+-H2O2 reaction, [FeII(H2O2)22+], exhibits chemistry that is closely similar to that for singlet oxygen (1O2), which has been confirmed by the stoichiometric dioxygenation of diphenylisobenzofuran, 9,10-diphenylanthracene, rubrene and electron-rich unsaturated carbon-carbon bonds (Ph2C = CPh2, PhC = CPh and cis-PhCH = CHPh). In dry ligand-free acetonitrile (MeCN), anhydrous ferric chloride (FeIIICl3) activates hydrogen peroxide for the efficient epoxidation of alkenes. The FeIIICl3 further catalyses the dimerization of the resulting epoxides to dioxanes. These observations indicate that strong Lewis acids that are coordinatively unsaturated, [FeII(MeCN)4]2+ and [FeIIICl3], activate H2O2 to form an effective oxygenation and dehydrogenation agent.(ABSTRACT TRUNCATED AT 400 WORDS)     

Thy-1 inhibits mitogen-induced Ca2+ oscillation in ras-transformed mouse fibroblasts.

Cell surface glycoprotein Thy-1 functions as a transformation suppressor in v-ras-transformed NIH/3T3 cells [Sugimoto et al., (1991) Cancer Res. 51, 99-104.]. In order to understand the mechanism of action of Thy-1, we examined the effect of Thy-1 expression on mitogen-induced Ca2+ oscillation which was correlated with v-ras-transformation [Fu et al., (1991) FEBS Lett. 281, 263-266.]. Forced expression of Thy-1 in v-ras-transformed cells inhibited mitogen-induced Ca2+ oscillation. Although v-Ras-free, Thy-1-positive NIH/3T3 cells (major population) did not show Ca2+ oscillation, whereas in Thy-1-negative NIH/3T3 cells (less than 1% of the population) Ca2+ oscillation was observed. Finally, replacement of the carboxyl-half of Thy-1 with that of CD4 abolished the inhibitory effect of Thy-1. These results suggest that Thy-1 directly or indirectly participates in the negative regulation of Ca2+ response by inhibiting Ca2+ oscillation.     

Temporal and Spatial Expression of the {alpha}-Amylase Gene during Seed Germination in Rice and Barley

We have analyzed the in situ hybridization of     

A Simple Bile-Disk Method for the Identification of Bacteroides fragilis

A simple method for the separation and identification of Bacteroides fragilis from other Bacteroides species through the use of oxgall-impregnated filter paper disks is described. As in the antibiotic sensitivity test, filter paper disks containing defined amounts of bile salt were placed on a lawn of bacterial cells on Gifu anaerobic medium agar plates. Bile-resistant bacteria were identified as strains of Bacteroides fragilis after incubation in anaerobic jars containing hydrogen and carbon dioxide generators at 35 C for 24 hr. The optimum concentration of bile salt, yielding results very similar to those of the conventional tube method, was determined to be 25 mg per disk, empirically. Since this method is easy to perform, time saving, economical and gives clear results, it may be readily used as a daily routine test in the clinical microbiology laboratory.     

Purification and characterization of benzoyl-L-tyrosine ethyl ester hydrolase from the yolk sac membrane of chicken egg

An enzyme which hydrolyzes benzoyl-L-tyrosine ethyl ester (BTEE) was purified from yolk sac membranes of day-18 chick embryos. The purified BTEE hydrolase has a molecular weight of 110,000, being composed of 70,000 and 40,000 subunits, and preferred synthetic substrates for chymotrypsin to those for trypsin. The optimum pH and temperature of this enzyme were 6.5-7.0 and 40 degrees C, respectively. The Km value for BTEE of the enzyme was 16 mM at pH 6.5 and 30 degrees C. The enzyme was inhibited markedly by some chymotrypsin inhibitors but scarcely inhibited by trypsin inhibitors. Magnesium ion acted as potent activator, depending on the enzyme purity and its concentration, whereas p-chloromercuribenzoate and zinc ion inactivated the activity markedly. The BTEE hydrolase was found to hydrolyze proteins such as casein and hemoglobin. These data indicated that the enzyme is a proteinase similar to chymotrypsin. This proteinase could act on yolk proteins, suggesting that it plays an important role in the metabolism of yolk at the yolk sac membrane layer.     

Magnesium ion: a possible physiological regulator of aldosterone production

We examined the direct effect of magnesium ion on aldosterone production by adrenal cells using collagenase-dispersed zona-glomerulosa cells in rats. The effects of magnesium on aldosterone production stimulated by angiotensin II or ACTH were also investigated. Both magnesium sulphate (MgSO4) and magnesium chloride (MgCl2) (0 to 2 mM) decreased aldosterone production in a dose-dependent manner. In comparison with magnesium-free medium, 2 mM MgSO4 inhibited aldosterone production by 73% and MgCl2 by 65%. In addition, MgSO4 showed an inhibitory effect on aldosterone production stimulated by angiotensin II (10pM to 10nM), whereas it had no significant effect on aldosterone production due to ACTH stimulation (10pM to 10nM). These data suggest that magnesium has an inhibitory action on aldosterone production in vitro and may be a physiological regulator of aldosterone production.