ABSTRACT
Male Wistar rats were fed a choline-deficient, L-amino acid-defined (CDAA) diet alone or in combination with a nitrone-based free radical trapping agent, phenyl N-tert-butyl nitrone (PBN) in the drinking water at the concentrations of 0.013, 0.065, and 0.130% for 12 weeks. PBN inhibited the changes that are normally induced in the livers of rats by the CDAA diet feeding, i.e., development of putative preneoplastic lesions, proliferation of connective tissue, reduction of glutathione S-transferase activity, formation of 8-hydroxyguanine in DNA, and an increase in inducible cyclo-oxygenase (COX2) activity. PBN, however, did not prevent the increases in the COX2 mRNA or protein levels brought on by the CDAA diet These results indicate that the loss of glutathione S-transferase activity and COX2 induction may play significant roles in rat liver carcinogenesis by the CDAA diet and that PBN prevents neoplasia not only by its radical scavenging activity but also by inhibiting COX2 activity at the catalytic level.
Subject(s)
Amino Acids/deficiency , Choline Deficiency/complications , Free Radical Scavengers/pharmacology , Liver Neoplasms, Experimental/prevention & control , Nitrogen Oxides/pharmacology , Animals , Cyclic N-Oxides , Cyclooxygenase 2 , Glutathione/metabolism , Isoenzymes/drug effects , Liver Neoplasms, Experimental/etiology , Male , NF-kappa B/physiology , Nitric Oxide Synthase/physiology , Nitric Oxide Synthase Type II , Prostaglandin-Endoperoxide Synthases/drug effects , Rats , Rats, WistarABSTRACT
A new dual-ported, floating-point, digital signal processor has been evaluated for compressing 512 and 1,024 digital radiographic images using a full-frame, two-dimensional, discrete cosine transform (2D-DCT). The floating point digital signal processor operates at 49.5 million floating point instructions per second (MFLOPS). The level of compression can be changed by varying four parameters in the lossy compression algorithm. Throughput times were measured for both 2D-DCT compression and decompression. For a 1,024 x 1,024 x 10-bit image with a compression ratio of 316:1, the throughput was 75.73 seconds (compression plus decompression throughput). For a digital fluorography 1,024 x 1,024 x 8-bit image and a compression ratio of 26:1, the total throughput time was 63.23 seconds. For a computed tomography image of 512 x 512 x 12 bits and a compression ratio of 10:1 the throughput time was 19.65 seconds.