Characterization of translucent segments observed in an smbA mutant of Escherichia coli

Abstract The smbA gene of Escherichia coli is essential for cell proliferation. The smbA2 mutant shows cold-sensitive colony formation at 22°C. A novel morphological phenotype, formation of a translucent segment at midcell or at a cell pole, was observed by phase-contrastt microscopy at a high frequency in the smbA2 mutant cells incubated in L medium lacking NaCl at 22°C, but not observed in L medium containing 1% NaCl or 20% sucrose at the same temperature. No translucent segment was observed in the wild-type cells in any of the media used. Electron microscopic observation revealed that the translucent segments resulted from the enlargement of a periplasmic space by separation of the inner membrane from the peptidoglycan layer and the outer membrane.     

Two Phenolic Amides in the Seed Balls of Sugar Beet (Beta vulgaris L. var. saccharifera Alefeld)

Ferredoxin-dependent sulfite reductase (Fd-SiR) (EC 1.8.7.1) was purified about 1136-fold, with a yield of 11%, from fresh thalli of Porphyra yezoensis by a procedure involving ammonium sulfate precipitation, DEAE-cellulose chromatography, Buty 1-Toyopearl chromatography, Sephadex G-100 gel filtration and ferredoxin-Sepharose affinity chromatography. The purified enzyme was apparently homogeneous, as judged on polyacrylamide disc gel electrophoresis, with a specific activity of 100 units/mg of protein. The molecular weight of the enzyme was estimated to be 70 kilodaltons by gel filtration. On subunit analysis by SDS-PAGE, a single band corresponding to molecular weight of 65 kilodaltons appeared. The purified enzyme (Fd-SiR) showed 5-times higher ferredoxin-dependent activity than methyl viologen-linked activity. In the oxidized form, the enzyme exhibited absorption maxima at 278, 390 (Soret band), 586 (a band) and 714 (CT band) nm, indicating that siroheme is involved in the catalysis of sulfite reduction. The absorbance ratios, A₃₉₀: A₂₁₈ and A₅₈₆ :A₃₉₀, were 0.32 and 0.31, respectively. A plot of the substrate (sulfite) and electron donor (ferredoxin) concentrations versus enzymatic (Fd-SiR) activity yielded sigmoidal curves, giving Hill coefficients («) of 2.3 (for sulfite) and 2.7 (for ferredoxin), respectively. Antibody against the isolated enzyme was raised in rabbits. Analysis of the antiserum by immunodiffusion suggested that it was specific against isolated Fd-SiR. Using the antiserum, dot immunoblotting was performed to determine the immunological similarity of Fd-SiRs from Porphyra yezoensis, Spirulina platensis, Brassica chinensis and Spinacia oleracea. The tests revealed that the four forms of assimilatory Fd-SiR have antigenic determinants in common.     

Ca2+-dependent nuclear contraction in the heliozoon Actinophrys sol

Ca2+-dependent contractility was found to exist in the nucleus of the heliozoon protozoan Actinophrys sol. Upon addition of Ca2+ ([Ca2+]free = 2.0 x 10(-3) M), diameters of isolated and detergent-extracted nuclei became reduced from 16.5+/-1.7 microm to 11.0+/-1.3 microm. The threshold level of [Ca2+]free for the nuclear contraction was 2.9 x 10(-7) M. The nuclear contraction was not induced by Mg2+, and was not inhibited by colchicine or cytochalasin B. Contracted nuclei became expanded when Ca2+ was removed by EGTA; thus cycles of contraction and expansion could be repeated many times by alternating addition of Ca2+ and EGTA. The Ca2+-dependent nuclear contractility remained even after high salt treatment, suggesting a possible involvement of nucleoskeletal components in the nuclear contraction. Electron microscopy showed that, in the relaxed state, filamentous structures were observed to spread in the nucleus to form a network. After addition of Ca2+, they became aggregated and constructed a mass of thicker filaments, followed by re-distribution of the filaments spread around inside of the nucleus when Ca2+ was removed. These results suggest that the nuclear contraction is induced by Ca2+-dependent transformation of the filamentous structures in the nucleus.     

On periodic responses of a mathematical neuron model

The periodic responses of a mathematical neuron model, when periodically varying input stimuli are applied to the model, are investigated. An explicit representation of periodic responses is obtained. It is shown that a periodic response as a 0–1 string is a uniform string. That is, the 1's of the 0–1 string are distributed uniformly in the string.     

The multiple promoter methylation profile of PR gene and ERalpha gene in tumor cell lines

The changes of methylation status of various gene promoters are a common feature of malignant cells and these changes can occur early in the progression process. Therefore, abnormal methylation can be used as cancer marker. Such studies will first require the development of a panel of methylated markers that are methylated in cancer tissues but unmethylated in normal tissues or methylated status is different between cancer tissues and normal tissues. By using methylation-specific PCR (MSP) assay method, we observed alterations in DNA methylation at the double promoter regions of the progesterone receptor (PR) gene and estrogen receptor (ERalpha) gene in various tumor cell lines. Compared with normal white blood cell, the methylation status of PRA promoter in various cancer cell lines changed from unmethylation pattern to methylation pattern. That of PRB promoter changed from both unmethylated and methylated alleles to only methylated allele. The methylation status of ERalpha-A and ERalpha-B promoter in various cancer cell lines are cell -specific. This study indicates that PR promoter methylation may be a molecular marker in various cancer detections. And the methylation status of ERalpha-A and ERalpha-B is cell-specific.     

Uptake of Homologous Series of p-n-Alkylphenols by Phytopathogenic Fungi

Uptake of homologous series of p-n-alkylphenols by fungi from aqueous phase was studied using spores of Piricularia oryzae and Gibberella fujikuroi, and mycelia of P. oryzae as test organisms.

Process of uptake seemed to be physical, because dead cells took up as much phenol as did living cells. Amount of phenol taken up by fungal cells equilibrated with concentration of remaining phenol in external aqueous phase. Uptake was found to increase with increasing alkyl side chain length, and solubility of the homologous series decreases at higher rate than uptake increases. Uptake of higher homologue is not supposed to reach the level enough to inhibit growth of fungi, on account of its slight solubility.

These results explain the reason why antifungal activity of p-n-alkylphenol increases with increasing alkyl chain length up to a certain homologue, and decreases for the higher members.     

Studies on Oxidative Fermentation

It has been found that Gluconobacter liquefaciens metabolized 5-ketogluconic acid. In order to clarify metabolic pathways of this compound, the oxidation products by resting cells of this organism were investigated. Rubiginol, rubiginic, comenic, 2,5-diketogluconic, glycolic and tartronic acids were detected or identified in the reaction fluid. On the basis of these results and the data obtained by means of manometric experiments, the oxidation pathways of 5–ketogluconic acid were discussed.

Oxidation pathways of 5-ketogluconie acid by resting cells of Gluconobacter liquefaciens were further investigated. Arsenite inhibited the oxidation of this compound. The amount of carbonyl compounds in the oxidation products of 5–ketogluconic acid was increased by addition of 10^-3 m arsenite. Pyruvic and α-ketoglutaric acids were identified among these carbonyl compounds. Members of the tricarboxylic acid cycle were oxidized actively by resting cells or cell-free extracts of this organism. These results suggested the presence of the tricarboxylic acid cycle in the terminal oxidatjon of 5-ketogluconic acid by this organism.     

Establishment of a sandwich ELISA system to detect diapause hormone, and developmental profile of hormone levels in egg and subesophageal ganglion of the silkworm, Bombyx mori

In the silkworm Bombyx mori, diapause hormone (DH) is produced in the female subesophageal ganglion (SG) and induces embryonic diapause by targeting developing ovaries. DH is processed from a precursor protein consisting of DH, pheromone biosynthesis activating neuropeptide (PBAN) and three other neuropeptides (SGNPs). Because these five neuropeptides share a common sequence, FXPRLamide, at the C-terminus, a direct and specific assay for DH itself is required in order to understand the profile of concentration changes. In this study, we produced a mouse monoclonal antibody (anti-DH[N] mAb) against the N-terminal region of DH and developed a sandwich enzyme-linked immunosorbent assay using the anti-DH[N] mAb and a rabbit polyclonal antibody against the C-terminus of DH. This procedure enabled us to specifically quantify the DH molecule at femtomolar levels (equivalent to 1/10 of SG). We then plotted DH levels in eggs and SGs during embryonic and post-embryonic development. DH was present in late-stage embryos that had been destined for the production of both diapause and nondiapause eggs. DH levels in SG gradually increased in both types during larval development and peaked at the early pupal stage. At the middle pupal stage, DH levels in SG and SG-brain complex decreased markedly in the diapause-egg producing type, thus indicating active release of DH into the hemolymph. From 5th instar larva to adult, no sexual differences in DH levels were observed in SGs or SG-brain complexes from diapause and nondiapause egg-producing types.