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Suspension spinning of Bi1Sr1Ca1Cu2 oxide was examined to prepare a long filament with high-T c. The various starting powders were suspended in PVA solution. The viscous suspension was extruded as a filament and subjected to heat treatment to remove volatile components and to generate oxide in the superconducting phase. The filament obtained was about 300 µm in diameter and had a mixed phase of high-T c at 115 K and low-T c at 80 K. Superconductivity exceeding the liquid nitrogen temperature was detected for the filament through the starting powder prepared by coprecipitation of the oxalates.

A high-T c superconducting Bi-Pb-Sr-Ca-Cu-O filament was successfully prepared using a combined technique of suspension spinning and densification of the pyrolyzed filaments by two stages of pressing and sintering. Zero electrical resistivity was achieved at 99 K and the maximum J c of the filament was 1210 A/cm2 at 77 K, 0 T. The filament consisted of a single high-T c phase and the grains were oriented with the c-axis perpendicular to the longitudinal direction of the filament. The filament exihibited a tensile strength of 55 MPa and an elongation of 1.1%.

The preparation of a high-T c Ba2Y1Cu3O x superconducting filament was studied by nonaqueous suspension spinning. The fine powder of the oxide was suspended in PVA dimethyl sulfoxide solution containing a dispersant. The viscous suspension was extruded as a filament into a precipitating medium of methyl alcohol and coiled on a winding drum. The obtained filament, 200 µm in diameter, was heated to remove volatile components and to generate the layered perovskite phase. The heated filament with tensile strength of 37 MPa was a superconductor at 84 K and had a J c value of 680 A/cm2 at 77 K.

Background Vitamin K is essential for the posttranslational modification of various Gla proteins. Although it is widespread in several organs, including the testis, the function of vitamin K in these organs is not well characterized. In this study, we investigated the function of vitamin K in the testis and analyzed its role in steroidogenesis. Methods Eight-week-old male Wistar rats were fed a diet supplemented with menaquinone-4 (MK-4, 75 mg/kg diet), one of the predominant K2 vitamins present in the testis, for 5 weeks. In vivo testosterone levels of the rats' plasma and testes were measured by enzyme-linked immunosorbent assay, and in vitro testosterone levels of testis-derived tumor cells (I-10 cells) maintained in Ham's F-10 medium with 10% fetal bovine serum were measured following treatment with MK-4 (0 to 100 μM) at several time points. Testosterone and cellular protein levels were analyzed with respect to their effects on steroidogenesis. Results Testosterone levels in the plasma and testes of MK-4-fed rats were significantly increased compared to those of control rats, with no obvious differences in plasma luteinizing hormone levels. Secreted testosterone levels from I-10 cells were elevated by MK-4, but not by vitamin K1, in a dose-dependent manner independent of cAMP treatment. Western blot analysis revealed that expression of CYP11A, the rate-limiting enzyme in steroidogenesis, and phosphorylation levels of protein kinase A (PKA) and the cAMP response element-binding protein were all stimulated by the presence of MK-4. Enhancement of testosterone production was inhibited by H89, a specific inhibitor of PKA, but not by warfarin, an inhibitor of γ-glutamylcarboxylation. Conclusions MK-4 stimulates testosterone production in rats and testis-derived tumor cells via activation of PKA. MK-4 may be involved in steroidogenesis in the testis, and its supplementation could reverse the downregulation of testosterone production in elders.