Effect of addition of water-soluble polysaccharides on bacterial cellulose production in a 50-L airlift reactor.

Bacterial cellulose (BC) production was carried out in a batch cultivation of Acetobacter xylinum in a 50-L internal loop airlift reactor by addition of water-soluble polysaccharides into the medium. When 0.1% (w/w) agar was added, BC production reached 8.7 g/L compared with 6.3 g/L in the control, and duration of the cultivation period to reach the maximum concentration of BC was almost half of that without addition of polysaccharides. During cultivation, BC was formed into pellets whose size was smaller when the productivity of BC was higher, indicating that increase in the relative viscosity by addition of polysaccharides hindered formation of large clumps of BC and increase in the volumetric oxygen transfer coefficient at high flow rate led to increase in BC productivity.

Conformational stability and warfarin-binding properties of human serum albumin studied by recombinant mutants.

Correctly folded recombinant wild-type human serum albumin and the single-residue mutants K199A, W214A, R218H and H242Q were produced with the use of a yeast expression system. The changes in R218H resulted in a pronounced decrease in intrinsic fluorescence. Thermodynamic parameters for thermal denaturation of the present mutants and of five additional mutants have been determined, showing small increases in stability for two mutants (R218H and H242Q) and a larger decrease in stability for one (W214A). In the last of these, denaturation was a heterogeneous process starting at physiological temperature. The high-affinity binding constant for warfarin at pH 7.4 was determined by fluorescence spectroscopy: there was a significant increase in affinity for binding of warfarin to H242Q and K199A and a smaller decrease in affinity for W214A and R218H. The findings show that Trp-214 is not as essential for the high-affinity binding of warfarin as has previously been thought.

New stacking variant of Laves phase found in (Ti0.95 V0.05) Co2 alloy.

Microstructures of the Laves phase alloy, (Ti0.95 V0.05) Co2, were studied by high resolution electron microscopy and electron diffraction. In this alloy system, coexistence of several kinds of layered structures was observed. Among these structures, a new stacking variant was found and was analyzed to be ABCAB'A'C'BCA'C'B'. This structure belongs to the trigonal system of the space group P3m1 (no. 164). The lattice parameters presented in the hexagonal system are a = 0.4727 +/- 0.0009 nm and c = 4.628 +/- 0.008 nm. This structure is called 12T in the Ramsdell notation and 4323 in the Zhdanov symbol, and is classified into hP3m1-(6i)5(3f)(3e)(2d)12(2c)6 using the Wyckoff notation.

Pathological study on mucosal changes in small intestine of rat by oral administration of ricin. I. Microscopical observation.

A histological study on small intestine of Wistar rats after oral administration of ricin, a proteinous toxin from castor bean seeds, was carried out. In Experiment I, the jejunum was examined at 1, 2, 5, 10, 15, 20, 24, and 40 hours after oral administration of ricin 30 mg/kg. In Experiment II, ricin was administered at dose of 1, 3, 5, 10, 15, 30, and 60 mg/kg, and after 5 hours the jejunum, mid-portion, and ileum were examined. For comparison, ricin 0.5 mg/kg was administered intraperitoneally and castor bean hemagglutinin (CBH) 30 mg/kg orally. In both experiments, the changes of mucosa were essentially similar dependent on time-lapse and dose respectively, which were atrophy of villus, elongation of crypt, degeneration of epithelium, decrease of goblet cell, fusion of intervillous epithelia, infiltration of neutrophils and eosinophils, and dissociation between epithelium and lamina propria. These changes were most manifest in the jejunum that was contacted with ricin first in a high concentration. In contrast, intraperitoneal administration of ricin caused only dissociation between epithelium and lamina propria and oral administration of CBH caused only milder atrophic changes. The evidences suggest that the mucosal changes by oral administration were caused by direct contact with ricin.