Expression of human CD81 in transgenic mice does not confer susceptibility to hepatitis C virus infection

We previously demonstrated that hepatitis C virus (HCV) binds to human CD81 through the E2 glycoprotein. Therefore, expression of the human CD81 molecule in transgenic mice was expected to provide a new tool to study HCV infection in vivo, as the chimpanzee is the only species currently available as a laboratory animal model that can be infected with HCV. We produced transgenic mice expressing the human CD81 protein in a wide variety of tissues. We confirmed binding of recombinant E2 glycoprotein to the liver tissue as well as to thymocytes and splenic lymphocytes in the transgenic mice. We inoculated chimpanzee plasma infected with HCV into these animals. None of these transgenic animals showed evidence of viral replication. Furthermore, human CD81 transgenic mice that lack expression of endogenous mouse CD81 were also resistant to HCV infection. We conclude that expression of human CD81 alone is insufficient to confer susceptibility to HCV infection in the mouse. The presence of additional possible factors for HCV infection is discussed.     

Characterization of the rat neutrophil formyl peptide chemotaxis receptor.

Numerous synthetic N-formylated peptides, believed to be the analogs of the naturally occurring initiating signal peptides produced by bacteria, are potent chemotactic agents for phagocytic cells in several species. The authors have characterized the receptor with moderately high affinity for the chemotactic peptide f-Met-Leu-[3H]Phe on the rat peritoneal neutrophils. When neutrophils are incubated with f-Met-Leu-[3H]Phe at 24 C, the binding is saturable and reversible. The receptor on the inflammatory rat neutrophils has an equilibrium dissociation constant (KD) of 3.4 x 10(-8) M at 24 C, and there are approximately 65,000 sites per cell. In addition, the potency of several of these chemotactic peptides in inducing lysosomal enzyme secretion and superoxide production correlated well with their ability to compete with f-Met-Leu-[3H]Phe for receptor binding. Structure activity studies further demonstrate that the fine specificity of the formyl peptide receptor has been conserved across species lines.     

A pharmacological study of the angiotensin receptor and tachyphylaxis in smooth muscle.

The interaction of angiotensin with its receptor has been studied on the basis of the tachyphylaxis shown by the rat uterus towards angiotensin II when pH and Ca2+ concentration are below physiological levels. 14C-Angiotensin binding and 45Ca2+-uptake investigations suggest tachyphylaxis to be due to increased binding at low pH and Ca2+ concentration. Studies with alkylating (affinity labeled) angiotensin derivatives containing the N-mustard chlorambucil suggest a "Charnière type" inhibition at the Ca-binding site of receptor and an irreversible inhibition at an anionic site. Angiotensin inhibitors containing chlorambucil do not alkylate tissue but are competitive inhibitors suggesting that the aromatic side chain in angiotensin may induce conformational changes in the receptor. The results obtained lead to a logical model for the angiotensin receptor allowing for normal activation by the hormone as well as for production of tachyphylaxis.     

Determination of arylglycerol-beta-aryl ether linkages in enzymatic mild acidolysis lignins (EMAL): comparison of DFRC/(31)P NMR with thioacidolysis

Enzymatic mild acidolysis lignins (EMAL) isolated from different species of softwood and Eucalyptus globulus were submitted to comparative analysis that included thioacidolysis, derivatization followed by reductive cleavage (DFRC), and DFRC followed by quantitative (31)P NMR (DFRC/(31)P NMR). While gas chromatography (GC) was used to determine the monomer yields from both thioacidolysis and DFRC, (31)P NMR studies quantified the various phenolic hydroxy groups released by DFRC. The monomer yields from thioacidolysis and DFRC were substantially different, with thioacidolysis resulting in higher yields. In contrast, an excellent agreement was obtained in the total number of beta-aryl ether structures determined by thioacidolysis and DFRC/(31)P NMR, indicating that the combination of DFRC with quantitative (31)P NMR overcomes, at least in part, the limitations presented by the DFRC method. Both thioacidolysis and DFRC/(31)P NMR were further used to better understand the lignin isolation process from wood. The results show that mild rotary ball milling minimizes, but does not prevent, the degradation of beta-O-4 structures during the early stages of wood pulverization. The extent of such degradation was found to be higher for E. globulus than for a variety of softwoods examined. Furthermore, the structures of the EMALs isolated at yields ranging from 20% to 62% were very similar, indicating structural homogeneity in the lignin biopolymer within the secondary wall.