PubMed · 13477377
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
1957-10-10. CURRENT concepts in therapy.. https://doi.org/10.1056/nejm195710102571507
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Explore the source record for details and available documents.
Allograft function may become impaired during rejection after human liver transplantation. Cytokines induce nitric oxide (NO) production in hepatocytes, Kupffer cells and infiltrating mononuclear cells. NO inhibits cytoplasmatic cytochrome p450 (CYP) enzyme activity in vitro. It is not known whether this mechanism plays a role in vivo. In order to characterize the role of locally produced cytokines in the pathogenesis of liver dysfunction, we analysed human liver transplant biopsy material for the expression of proinflammatory cytokines as well as for NO synthase and we compared these results to the microsomal liver function in vivo [aminopyrine breath test (ABT)] and in vitro (enzymatic analysis of CYP). Microsomal liver function decreased in vivo during rejection while ABT levels decreased by 40% and increased again by 59% after the acute rejection episode. Similarly, CYP 1A2 and 2E1 activity dropped 42% and 24% in rejecting samples, respectively. Competitive reverse transcriptase polymerase chain reaction (RT-PCR) showed a fivefold upregulation of interferon gamma (IFN-gamma) gene expression. Inducible, but not constitutive NO-synthase gene expression was upregulated fivefold in samples from rejecting patients suggesting a local induction of NO in response to immune events. Our data show a marked impairment of CYP enzyme activity during allograft rejection which is presumably secondary to an increased intragraft production of proinflammatory cytokines and NO.
The first example of a working model of the photosynthetic antenna-reaction center complex, constructed via self-assembled supramolecular methodology, is reported. For this, a supramolecular triad is assembled by axially coordinating imidazole-appended fulleropyrrolidine to the zinc center of a covalently linked zinc porphyrin-boron dipyrrin dyad. Selective excitation of the boron dipyrrin moiety in the boron dipyrrin-zinc porphyrin dyad resulted in efficient energy transfer (k(ENT)(singlet) = 9.2 x 10(9) s(-)(1); Phi(ENT)(singlet) = 0.83) creating singlet excited zinc porphyrin. Upon forming the supramolecular triad, the excited zinc porphyrin resulted in efficient electron transfer to the coordinated fullerenes, resulting in a charge-separated state (k(cs)(singlet) = 4.7 x 10(9) s(-)(1); Phi(CS)(singlet) = 0.9). The observed energy transfer followed by electron transfer in the present supramolecular triad mimics the events of natural photosynthesis. Here, the boron dipyrrin acts as antenna chlorophyll that absorbs light energy and transports spatially to the photosynthetic reaction center, while the electron transfer from the excited zinc porphyrin to fullerene mimics the primary events of the reaction center where conversion of the electronic excitation energy to chemical energy in the form of charge separation takes place. The important feature of the present model system is its relative "simplicity" because of the utilized supramolecular approach to mimic rather complex "combined antenna-reaction center" events of photosynthesis.