Regional specificity of anuran larval skin during metamorphosis: dermal specificity in development and histolysis of recombined skin grafts

Summary Skins from back and tail were dissected from tadpoles of Rana japonica prior to resorption of the tail and separated into epidermis and dermis by treatment with neutral protease. Homotypically and heterotypically recombined skins were constructed from the separated epidermis and dermis and transplanted into the tail of the original tadpole. Skin grafts using dermis from tail region degenerated simultaneously with resorption of the tail. However, skin grafts containing dermis from back region survived on the posterior part of the juvenile frog beyond metamorphosis. Furthermore, all epidermis underlaid with dermis from back region formed secretory glands and became flattened epithelia characteristic of adult back skin, regardless of region from which the epidermis came. Even when epidermis isolated from tail skin was cultured inside a back skin graft, the tail epidermis survived forming an epithelial cyst and developed secretory glands. These results suggest that regional specificities of anuran larval skin, i.e., development of back skin and even histolysis of tail skin, are determined by regionally specific dermis. The results also suggest that some of epidermal cells of tail skin are able to differentiate into epithelial cells similar to back skin of the adult under the influence of back dermis.     

Induction of endoreduplication in Chinese hamsters V79 cells by cytosine arabinoside

Endoreduplication (ER) could be induced very effectively in Chinese hamster V79 cells exposed to cytosine arabinoside (1-β-D-arabinofuranosylcytosine; Ara-C). Cells were cultured for 48 hours in Ara-C containing medium. ER frequency increases rapidly after Ara-C release. About 60% of metaphase cells were endoreduplicated at 8–10 hours after release from Ara-C (5 μg/ml). Induction of ER also depends on Ara-C concentrations.     

Agromonas oligotrophica gen. nov., sp. nov., a nitrogen-fixing oligotrophic bacterium

Phenotypic and chemotaxonomic characteristics of five isolates of acetylenereducing (nitrogen-fixing) oligotrophic bacteria from a paddy soil were investigated. They showed similar phenotypic characteristics: they were aerobic, asporogenous, gram-negative, motile by a polar flagellum, and irregular rods. On full strength nutrient broth (NB) growth was severely suppressed, but well supported on 10-to 10000-fold diluted NB. They consumed glucose but produced no acid, and also utilized phenolic acids such as ferulic acid or p-coumaric acid. The cellular fatty acid composition, quinone system and DNA base composition of the isolates were investigated. Cellular fatty acids mainly consisted of straightchain unsaturated C_{18 : 1} (62–81% of total fatty acids). Ubiquinone Q-10 and a high guanine-plus-cytosine content (65.1–66.0 mol%) were found. The taxonomic status of the isolates is discussed and a new genus, Agromonas, with a single species Agromonas oligotrophica sp. nov., is proposed for these isolates. The type strain of A. oligotrophica is JCM 1494.     

Induced optical activity in poly-L-lysine-methyl orange system

The absorption and cicular dichroism spectra of the complex of poly-L -lysine (PLL) in the random coil form with methyl orange (MO) have been measured in aqueous solution. A new absorption band is observed at the shorter wavelength compared with that of the free dye. Although MO does not show a formation of dimer or aggregation with an increase in concentration, circular dichroism bands are observed at the wavelength corresponding to the wavelength of the new absorption band. These induced circular dichroism bands may arise from the dimeric MO molecules bound to PLL in the random coil form. The main contribution to the interaction between MO molecules is shown to be the electro static interaction. The observed circular dichroism spectra and the configuration of dimeric MO molecules bound to PLL can be explained by the dipole couping mechanism.     

Superinfection with R Factors by Transduction in Escherichia coli and Salmonella typhimurium

Superinfection immunity is found in the conjugal transfer of R factors between two fi(+) R factors and between two fi(-) R factors (fi = fertility inhibition), as we reported previously. In contrast, no reduction in the frequencies of transduction of an fi(+) R factor 222 was caused by the presence of fi(+) R factors in the recipients in transduction systems with phage P1kc in Escherichia coli K-12 and with phage P22 in Salmonella typhimurium LT-2. The absence of superinfection immunity in transduction may be due to the difference in the route of entry of the R factor. The frequencies of transduction of an fi(+) R factor were reduced, although slightly, by the presence of fi(-) R factors in the recipients. This reduction is probably due to host-controlled restriction of the entering fi(+) R factor by the fi(-) R factors in the recipients, since transduction of an fi(+) R factor by the transducing phage propagated on the strain carrying both fi(+) and fi(-) R factors was not reduced by the presence of homologous fi(-) R factors in the recipients. The fi(+) R factor 222, when transduced to the recipient strains carrying other R factors, recombined genetically at high frequencies with these resident R factors, regardless of their fi type.     

Effect of mutations at Lys250, Arg251, and Lys253 of cytochrome P450 1A2 on the catalytic activities and the bindings of bifunctional axial ligands.

Some eukaryotic cytochromes P450 (P450s) have a series of ionic amino acids, corresponding to Lys250, Arg251, and Lys253 residues in the P450 1A2 sequence. To understand the roles of those ionic amino acids in the catalytic function of P450, three single mutants, Lys250Leu, Arg251Leu, and Lys253Leu of P450 1A2 were obtained from yeast (Saccharomyces cerevisiae) expression system. Turnover numbers of the Arg251Leu mutant in dealkylation reactions of methoxy- and ethoxyresorufin catalyzed by the P450 reconstituted system were remarkably increased by sixfold compared to those of the wild type. The Lys250Leu and Lys253Leu mutants also showed turnover numbers higher than those of the wild type by three- to fourfold. Those catalytic activities were inhibited competitively by pyridine derivatives, nitrogenous axial ligands to the P450 heme. From those findings together with other spectral data, it was suggested that the ionic site of Lys250, Arg251, and Lys253 may be somehow located near the substrate recognition site and/or near the axial-ligand access channel of this enzyme.