Heme oxygenase (HO)-1 expression was investigated in rat isolated pancreatic islets. Freshly isolated islets showed no evidence of HO-1 expression. After a 20-h culture, there was a small increase in HO-1 in control islets, and interleukin-1beta (IL-1beta) induced HO-1 expression above control levels. N(G)-monomethyl-L-arginine inhibited the IL-1beta-induced increase in HO-1. Sodium nitroprusside-generated nitric oxide also increased HO-1 expression. CoCl2 induced a concentration- and time-dependent increase in HO-1, but not heat shock protein 70, expression. Cobalt chloride (CoCl2) protected islets from the inhibitory effects of IL-1beta on glucose-stimulated insulin release and glucose oxidation. Nickel chloride did not mimic the effects of CoCl2. An inhibitor of HO-1 activity, zinc-protoporphyrin IX (ZnPP), prevented the protective effect of CoCl2 on insulin release with IL-1beta but did not affect HO-1 expression or the inhibitory response to IL-1beta alone. ZnPP also inhibited the protective effect of hemin in IL-1beta-treated islets. CoCl2 inhibited the marked increase in islet nitrite production in response to IL-1beta. Cobalt-protoporphyrin IX (CoPP), which increased HO expression and activity, also protected islets from the inhibitory effects of IL-1beta, even though IL-1beta largely blocked the CoPP-induced increase in HO-1 expression. In betaHC9 cells, CoCl2 increased HO-1 expression and HO activity, whereas CoPP directly activated HO. ZnPP inhibited basal and CoCl2-stimulated HO activity. Thus, increased HO-1 expression and/or HO activity in response to CoCl2, CoPP, and hemin, seems to mediate protective responses of pancreatic islets against IL-1beta. HO-1 may be protective of beta-cells because of the scavenging of free heme, the antioxidant effects of the end-product bilirubin, or the generation of carbon monoxide, which might have insulin secretion-promoting effects and inhibitory effects on nitric oxide synthase.

High-quality Bi2Sr2CaCu2Ox/Ag superconducting tapes were fabricated directly from the nitrate salts of Bi, Sr, Ca, and Cu by the partial-melt-growth technique. Nitrate particles were deposited electrostatically on the Ag substrate and heat treated. After process optimization of the superconducting tapes, the best samples showed typical Tc of 89 K with zero applied field critical current density of 2×104 A/cm2 (Ic=11.2 A) at 77 K and 2.6×105 A/cm2 (Ic=190 A) at 4.2 K. Unlike films grown using solid state reacted precursor powders, these films lacked the typical Bi-free, needlelike defects and possessed a smooth morphology. X-ray diffraction patterns showed the film to be highly c-axis oriented. The processing of these tapes significantly reduces the overall fabrication time from precursor materials preparation to final heat treatment.

Spatial resolution/ variation as a function of distance from collimator surface in single photon emission computed tomography (SPECT) is a major obstacle for quantitative imaging. This work investigated two analytical inversion methods for correcting the distance-dependent resolution variation, as well as uniform attenuation in brain SPECT studies. The first one utilizes an accurately measured resolution variation kernel, but derives an approximated inversion formula. The second one derives an accurate inversion formula, but approximates the resolution variation kernel. Reconstructed images using the first method showed a better resolution recovery at the periphery of field-of-view (FOV), consistent with the theory that the inversion formula is approximated for far-field regions. The second method restored resolution better at the central area of FOV, consistent with the approach that the resolution kernel is approximated for near-field regions. The second method is more sensitive to the approximation. The first one is more robust I to the approximation and, therefore, can be a better choice for quantitative SPECT imaging.

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Critical current density above lo4 A/cm2 at 77 K and zero magnetic field have been achieved for both ~~a2~u306.8 '(YBCO) thin films on metallic substrates and Bi-based superconducting films on silver tapes. A transition buffer, consisting of sub-buffers deposited at different temperatures, was used to enhance the crystallinity and the transport properties' of YBCO films on metallic substrates. YBCO films were fabricated, using in-situ laser deposition, and they were strongly c-axis oriented. Critical temperature of 87 K and critical current density of 3x104 A/& at 77 K were obtained for a 0.5 mthick YBCO film. Also, the magnetic field dependence of Jc could be increased by using Pt-coated metallic substrates. For 10-20 pm-thick Bi-based superconducting tape, by using brush-on technique and heat treatment, critical current of lo4 A/cm2 at 77 K was obtained. This tape showed strong magnetic flux pinning at low temperature. The Bi-based thin films by laser deposition still suffered by the high temperature post-annealing.