Reduction of 7-ketolithocholic acid to chenodeoxycholic acid by rat liver preparations in vitro

The formation of chenodeoxycholic acid via 7-ketolithocholic acid by rat liver preparations was examined in vitro. Results showed that a rat liver preparation reduced 7-ketolithocholic acid mainly to chenodeoxycholic acid and to ursodeoxycholic acid in a smaller amount, and that the reductase required NADPH but not NADH as coenzyme and was mainly localized in the microsomes.     

Cholinesterase activity in some species of theAllium genus

In partly purified protein complexes obtained from 22 species of theAllium genus and 6 cultivars ofAllium cepa the activity of cholinesterases was detected and measured using the method of Ellman et al. The degree of its inhibition with 10^-4 M neostigmine was also tested. It was found that the activity of cholinesterase differed in individual species up to two hundred times, while the differences in the inhibitory activity of 10^-4 M neostigmine occurred only in a few cases. Individual sections and cultivars could not be characterized on the basis of the differences in the activities of the cholinesterases. Of all the sections that ofPhyllodolon shows the highest average activity. In the case of the tested cultivars distinctly the lowest activity was observed in cv. Kastická. The values of the enzymatic activity measured by Ellman’s method in this plant material include the activity of specific and unspecific cholinesterases and the part uninhibitable by neostigmine.     

Improvement of serum amino acid profile in hepatic failure with the bioartificial liver using multicellular hepatocyte spheroids

We designed a bioartificial liver support system in which encapsulated multicellular spheroids of rat hepatocytes were utilized as a bioreactor in a hollow fiber cartridge. The spheroids, formed in a positively charged polystyrene dish that contained hormonally defined medium, were encapsulated into microdroplets of agarose that contained about 9 x 10(7) rat hepatocytes. The medium, including 150 mL reservoir volume, was circulated in a closed circuit in which the cartridge was inserted. The pH and levels of dissolved oxygen were monitored and automatically regulated so that they were maintained within a constant range for 72 h. Albumin accumulated in the circuit at the rate of 2.0 mg/L/h in this system. When the bioreactor cells in the system were replaced with Hep G2 cells, a human hepatoblastoma cell line, albumin accumulated at the rate of 0.15 mg/L/h. The spheroids of primary culture hepatocytes had 13 times higher albumin-producing capacity than the aggregates of Hep G2. The serum of a patient with fulminant hepatic failure was circulated in this system with the spheroids of primary culture hepatocytes. The concentration of branched amino acid (BCAA) in the circuit significantly increased during the 48 h circulation, while the concentration of aromatic amino acid (AAA) and methionine decreased. The ratio of BCAA/AAA increased from 0.640 to 0.772, indicating that the hepatocyte spheroids had improved the imbalance of the amino acid profile in the serum. These findings indicate that this system may be a useful model for an artificial liver support. (c) 1996 John Wiley & Sons, Inc.     

Incidence of Plasmids in Marine Vibrio spp. Isolated from an Oil Field in the Northwestern Gulf of Mexico

Presumptive marine Vibrio spp. were collected from an operational oil field and control site located in the northwestern Gulf of Mexico. Of 440 isolates analyzed for the presence of extrachromosomal deoxyribonucleic acid elements or plasmids by using the cleared lysate and agarose gel techniques, 31% showed distinct plasmid bands on agarose gels. A majority of the plasmids detected were estimated to have molecular masses of 10 × 10⁶ or less. Multiple plasmids were observed in approximately half of the plasmid-containing strains. A number of isolates contained plasmids with similar banding and mobility patterns. The oil field area had noticeably more plasmid-containing strains (35 versus 23% in the control site) and a greater number of plasmids per plasmid-containing strain (an average of 2.5 plasmids, versus 1.5 in the control site). Oil field discharges might have resulted in increased plasmid incidence and diversity.     

Species diversity of mangrove and continental drift

The mangrove formation on the coasts of S. Atlantic is very poor in species (only 6) compared with mangrove in S. and SE. Asia or E. Africa (more than 30). This fact cannot be explained by ecology. It is suggested that the main cause is the historically late origin of the Atlantic due to the continental drift.     

Decoy engineering of the receptor-like cytoplasmic kinase StPBS1 to defend against virus infection in potato

Potato virus Y (PVY) is an important pathogen of potato (Solanum tuberosum). Although the PBS1–RPS5 immune system is well documented in Arabidopsis thaliana, it has not been reported in potato. In Arabidopsis, the bacterial effector AvrPphB cleaves AtPBS1 to trigger an immune response. Here, we show that the AvrPphB-triggered immune response is mediated by StPBS1, a close homologue of AtPBS1 in potato. However, downstream signalling of StPBS1 was mediated by unknown resistance (R) proteins other than potato orthologues of AtRPS5 and HvPBR1, which is important for HvPBS1 signalling in barley. Immune signalling of StPBS1 is mediated by the AvrPphB C-terminal cleavage domain and an STKPQ motif, in contrast to AtPBS1-mediated immunity in which both AvrPphB cleavage fragments and an SEMPH motif are essential. The cleavage sequence of AvrPphB in StPBS1 was replaced with that of the PVY NIa-Pro protease to obtain StPBS1^NIa. StPBS1^NIa overexpression potato displayed stronger immunity to PVY infection than did the StPBS1 transgenic lines. StPBS1^NIa was cleaved at the expected target site by NIa-Pro protease from PVY. Thus, we characterized the function of StPBS1 in potato immunity and provide a biotechnology control method for PVY via transformation of decoy-engineered StPBS1^NIa.