Dual-frequency picosecond optical parametric generator pumped by a Nd-doped vanadate bounce laser.

Dual-frequency MHz-repetition 1.5-µm optical parametric generation is demonstrated from a tandem system pumped by a picosecond Nd:YVO4 bounce laser. An average power of 1.0 W is obtained over the range 1571-1630 nm, corresponding to an optical-optical conversion efficiency and slope efficiency of 16% and 23%, respectively. Terahertz-wave with a frequency of 3.2 THz is also generated from the system in combination with an organic nonlinear DAST crystal.

Effect of flow direction on the morphological responses of cultured bovine aortic endothelial cells.

The effect of flow direction on the morphology of cultured bovine aortic endothelial cells is studied. Fully confluent endothelial cells cultured on glass were subjected to a fluid-imposed shear stress of 2 Pa for 20 min and 24 h using a parallel plate flow chamber. Experiments on shear flow exposure were performed for (i) one-way flow, (ii) reciprocating flow with a 30 min interval and (iii) alternating orthogonal flows with a 30 min interval. After flow exposure, the endothelial cells were fixed and F-actin filaments were stained with rhodamine phalloidin. Endothelial cells were observed and photographed by means of a microscope equipped with epifluorescence optics. The shape index (SI) and angle of cell orientation were measured, and F-actin distributions in the cells were statistically studied. Endothelial cells under the one-way flow condition showed marked elongation (SI = 0.39 +/- 0.16, mean +/- S.D.) and aligned with the flow direction. In the case of the reciprocating (SI = 0.63 +/- 0.14) and the alternating orthogonal flows (0.64 +/- 0.14), cells did not elongate so strongly as in the case of one-way flow. Although most cells in the reciprocating flow aligned with the flow direction, the cell axes in the alternate orthogonal flow distributed around a mean value of -45.1 degrees with a large S.D. value. Endothelial cells can be expected to recognise the flow direction, and change their shape and F-actin structure.

Highly sensitive flow detection of uric acid based on an intermediate regeneration of uricase.

The principle of the signal amplification of a uric acid sensor based on dithiothreitol (DTT)-mediated intermediate regeneration of uricase was applied to a flow-injection system with an immobilized uricase reactor and a DTT-containing carrier. Highly sensitive detection for nM to microM order of uric acid was achieved when 10 mM TRIS-HCl buffer (pH 10.0) containing 20 mM DTT was used as a carrier at 0.6 ml min-1 and 37 degrees C. The sensitivity of the uric acid was much improved over a batch method using a uricase membrane-coupling electrode, and the detection limit (ca. peak current 8 nA) of uric acid was found to be down to 3 x 10(-10) M (amplification factor; more than 10,000). This chemically amplified flow-system is very useful for the direct assay of uric acid in highly diluted biological fluids (urine and serum) without complicated pretreatment of the samples, because this sensor has the potential to detect trace amounts (nM to microM) of uric acid in highly diluted body fluids in which the concentration of interfering constituents was decreased to negligible levels. Good correlation was observed between this system and conventional spectrophotometry. The immobilized uricase reactor could be re-used for at least 4 months of repeated analysis without loss of activity and was stable if stored at 4 degrees C in 10 mM TRIS-HCl buffer, pH 9.0.

Studies of glucose metabolism in Bacillus subtilis. I. Purification of glucose-6-phosphate dehydrogenase from the vegetative cell and its properties in comparison with the spore enzyme.

1. Glucose-6-phosphate dehydrogenase [D-glucose-6-phosphate : NADP-+ 1-oxidoreductase, EC 1.1.1.49] from vegetative cells of Bacillus subtilis was purified about 2,400-fold. The purified enzyme was shown to be homogeneous as judged by chromatographic profile, polyacrylamide gel electrophoresis and ultracentrifugation. The correspondent enzyme from spores was also partially purified. 2. The molecular weight of the vegetative cell enzyme was estimated to be 350,000 by Sepharose 6B chromatography and sedimentation equilibrium studies, and that of its subunit was 58,000 as determined by SDS gel electrophoresis, indicating that the enzyme was found to be 240,000. 3. The vegetative cell enzyme and spore enzyme have the same Km values and pH optima. The optimum pH was about 9.2 for both enzymes and the Km values for NADP-+ and glucose-6-phosphate were determined to be 6.7 X 10-minus 6 and 7.5 X 10-minus 5M, respectively. 4. The amino acid composition of the vegetative cell enzyme was examined and was compared with those of enzymes from other sources.