Phylogeography of the Chinese false gudgeon,Abbottina rivularis,in East Asia,with special reference to the origin and artificial disturbance of Japanese populations

Ichthyological Research - The Chinese false gudgeon, Abbottina rivularis, is a common cyprinid fish that is widely distributed throughout continental East Asia, but exhibits a restricted,...     

Annandale’s collection of freshwater fishes from Inle Lake,Myanmar, housed in the Kyoto University Museum

Ichthyological Research -     

Studies on aspartase. IV. Reversible denaturation of Escherichia coli aspartase.

Aspartase (L-aspartate ammonia lyase, EC 4.3.1.1) of Escherichia coli, denatured in 4 M guanidine-HCl, was renatured in vitro by simple dilution with a concomitant restoration of the activity. While the native enzyme exhibited a marked negative Cotton effect centered at 233 +/- 1 nm in optical rotatory dispersion, the enzyme denatured in 4 M guanidine-HCl retained little optical activity. Upon dilution of the denatured enzyme, however, more than 90% of the ordered structure was recovered in 1 min, while the restoration of the activity proceeded much more slowly. Estimation of molecular weights by gel permeation chromatography indicated that the tetrameric enzyme is subject to reversible dissociation into monomeric subunits under the experimental conditions. Various environmental factors such as temperature, pH and protein concentration exhibited profound influence on the rate and extent of the reactivation. In order to examine the correlation between the restoration of the activity and the quaternary structure, electron microscopic inspection of the kinetic processes of reversible denaturation was attempted. Upon dilution of the denatured enzyme at 4 degrees C, neither the activity nor tetrameric images were detected over several min. Upon the temperature shift up to 25 degrees C, however, the activity regain was rapidly proceeded concomitant with the appearance of tetrameric molecules. These results are compatible with the possibility that the subunit assembly is an essential prerequisite, thought not sufficient, for enzyme activity.     

Effects of culture conditions on molecular weights of poly(3-hydroxyalkanoates) produced byPseudomonas putida from octanoate

Summary Time-dependent changes in the molecular weights of poly(3-hydroxyalkanoates) (P(3HA)) produced byPseudomonas putida from octanoate were investigated. The mole ratio of carbon to nitrogen sources (C/N), incubation temperature, concentration of octanoate, and pH of culture solution were varied to study the effects of culture conditions on the yield and molecular weights of P(3HA). The molecular weights of P(3HA) decreased with time to reach a constant value during incubation. When the incubation temperature and the concentration of octanoate were low, P(3HA) polymers of high molecular weights were produced.     

H2 production from starch by a mixed culture of Clostridium butyricum and Enterobacter aerogenes

A mixed continuous culture of Clostridium butyricum and Enterobacter aerogenes removed O2 in a reactor and produced H2 from starch with yield of more than 2 mol H2/mol glucose without any reducing agents in the medium. Co-immobilized cells of the bacteria on porous glass beads evolved H2 from starch at 1.3 l/l.h, with H2 yield of 2.6 mol H2/ mol glucose at dilution rate of 1.0 h–1 in a continuous culture.     

Formation of the branching pattern of blood vessels in the wall of the avian yolk sac studied by a computer simulation

The present study was performed to provide data to support the notion previously believed but not proved experimentally or theoretically, that blood vessels are formed by the selection of capillaries in the network. In an attempt to understand the mechanism of formation of blood vessel branching structures, the transformation of a capillary network to a branching system in the wall of quail yolk sac was successively recorded by a series of photographs, and a computer simulation was carried out for the process of in vivo vascularization based on the photographs. The simulation demonstrated that a positive feedback system participated in the formation of a branching structure. That is, vessels which had been much used were enlarged, whereas less used vessels were reduced in their size and finally extinguished. The enlarged vessels became major components of the branching system. As the body of an embryo grew, it was observed that polygonal capillary networks enlarged, which led each polygon of the network to divide into a few finer polygons. Then, some of the capillary vessels were again selected and formed a branching system. This process repeated during the body growth, indicating that the vascular system developed adaptively to the body growth. A region where the growth was fast, received much blood flow and produced finer networks of capillaries. Thus, it was experimentally demonstrated for the first time that capillaries in the network are successively selected by a positive feedback mechanism and form blood vessels.     

Overproduction and crystallization of tryptophanase from recombinant cells of Escherichia coli

We have cloned the tryptophanase structural gene from Escherichia coli B/1t7-A into E. coli K-12 MD55 with a vector plasmid, pBR322. The cloned cells produced a large amount of the enzyme corresponding to more than 30% of the total soluble protein. With the enzyme obtained by this overproduction system, we have prepared three different crystals of tryptophanase, apo-enzyme, holo-enzyme, and a complex of holo-enzyme and L-alanine, by using polyethylene glycol 4000 or potassium phosphate as a precipitant and the hanging drop method. These single crystals appeared to be suitable for X-ray diffraction analysis.