Interaction and orientation of an alpha-aminoisobutyric acid- and tryptophan-containing short helical peptide pore-former in phospholipid vesicles, as revealed by fluorescence spectroscopy

The interaction and orientation of a membrane protein ion channel model, an alpha-aminoisobutyric acid analogue of gramicidin B (GBA), in egg yolk phosphatidylcholine vesicles was studied by means of fluorescence spectroscopic techniques. GBA helices form stable ion-conducting pores in membranes [Jelokhani-Niaraki et al. (1995) J. Chem. Soc. Perkin Trans. 2, 801-808]. In an alpha-helical model for the peptide, all Trp residues (intrinsic fluorophores) are distributed near the C-terminus. Fluorescence quenching experiments revealed the exposure of the helical peptides' C-termini to aqueous environments. Dansyl-labeled vesicles were used to investigate the GBA dynamism of the interaction with membranes. It was shown that considerable amounts of peptide reside on and in the vicinity of the outer surface of lipid bilayers. The transmembrane transfer to the inner layer is slow due to the high affinity of Trp residues for bilayer interfaces which anchor the peptide to the outer surface. A structural-functional interpretation of the GBA interaction with membranes is presented.     

Hyperlipoproteinemia enhances susceptibility to acute disseminated Candida albicans infection in low-density-lipoprotein-receptor-deficient mice

Recent studies have suggested the use of lipoproteins as an adjuvant treatment of lethal gram-negative infections. However, other important microorganisms for the etiology of sepsis, such as Candida species, grow better in lipid-rich environments. We investigated the effect of hyperlipoproteinemia on systemic candidiasis in low-density-lipoprotein-receptor-deficient (LDLR-/-) mice, in which the loss of the receptor results in a seven- to ninefold-higher plasma LDL level than that in their wild-type littermates (C57BL/6J). LDLR-/- mice died earlier, and the outgrowth of Candida albicans in the kidneys and livers of LDLR-/- mice was significantly higher compared with that of controls. After infection, circulating cytokine concentrations were significantly higher in LDLR-/- mice. In vitro, C. albicans grew better in plasma samples of LDLR-/- mice than in control plasma samples and peritoneal macrophages of LDLR-/- mice challenged with heat-killed C. albicans produced more cytokines than did those of controls. This latter phenomenon was probably due to increased binding of yeast cells to macrophages of LDLR-/- mice. These data suggest that hyperlipoproteinemia is deleterious in systemic candidiasis.     

Effects of antiallergic drug, pemirolast potassium on phospholipase D activation in antigen-stimulated rat basophilic leukemia (RBL-2H3) cells

An anti-allergic drug, permirolast potassium (TBX), inhibited antigen (Ag)-induced phospholipase D (PLD) activation in rat basophilic leukemia (RBL-2H3) cells. The concentration-dependent inhibitory profile for Ag-induced PLD activation was parallel to those for secretory response and inositol phosphate formation. In contrast, TBX had no effect on PLD activation caused by calcium ionophore A23187 or phorbol myristate acetate. These results suggest that TBX inhibits Ag-induced PLD activation by interfering with the signal transduction pathway upstream of Ca2+ mobilization and protein kinase C activation.     

Nuclear analysis of a laser fusion reactor,SENRI-I

A neutronic analysis of the laser-driven inertial-confinement fusion reactor SENRI-I is presented. Three-dimensional Monte Carlo calculations were performed to examine the effects of laser beam ports on the flux distribution, tritium breeding ratio, thermal energy deposition in the blanket, and radiation streaming. A Monte Carlo code was also used for the time-dependent radiation-damage analysis accounting for the time of the flight spread of neutrons and the results are compared to the analysis for the HIBALL design. Induced radioactivity was estimated, based on the one-dimensional transport calculation and depletion analysis. The calculated results reveal the advantages of the SENRI-I design with a thick Li layer compared to other reactor systems employing a dry-wall scheme.     

The effects of fibroblast growth factors in long-term primary culture of dystrophic (mdx) mouse muscle myoblasts

Neutralizing monoclonal antibodies specific for human interleukin-6 (IL-6) bind two distinct sites on the IL-6 protein (sites I and II). Their interference with IL-6 receptor binding suggested that site I is a receptor-binding site of IL-6, whereas site II is important for signal transduction. Mutagenesis of site II could therefore result in the isolation of IL-6 receptor antagonists. To test this hypothesis, a panel of IL-6 mutant proteins was constructed that did not bind to a site II-specific monoclonal antibody. One such site II mutant protein (with double substitution of Gln-160 with Glu and Thr-163 with Pro) was found to be an antagonist of human IL-6. It was inactive on human CESS cells, weakly active on human HepG2 cells, but active on mouse B9 cells. It could specifically antagonize the activity of wild-type IL-6 on CESS and HepG2 cells. The binding affinity of this variant for the 80-kDa IL-6 receptor was similar to that of wild-type IL-6. High affinity binding to CESS cells, however, was abolished, suggesting that the mutant protein is inactive because the complex of the 80-kDa IL-6 receptor and the mutant protein cannot associate with the signal transducer gp130. The human IL-6 antagonist protein may be potentially useful as a therapeutic agent.     

Trace elements in spinocerebellar degeneration

Cocaine and cocaethylene concentrations in blood and tissues at early stages postmortem (0-6 h) were investigated using alcohol-treated rats. Gas chromatography/mass spectrometry following a liquid/liquid extraction procedure was employed to detect these drugs. Calibration curves showed good linearity in the range of 0 to 2,500 ng/mL with correlation coefficients of 0.9999 and 0.9998 for cocaine and cocaethylene, respectively. In a group treated with cocaine and ethanol orally, the liver lost over 25% of the cocaine present at death after 1 h. Conversely, the hepatic cocaethylene concentrations at this time reached more than twice those at death. Thereafter, the hepatic concentrations of cocaine and cocaethylene were maintained at a constant level until 6 h postmortem. Similar results were obtained with rats given cocaine intramuscularly. No changes in the cocaine and cocaethylene concentrations in any other tissues during the 6-h of postmortem period were observed. The forensic pathologist and toxicologist should be aware of these phenomena when selecting postmortem specimens for the analysis of cocaine and cocaethylene and take them into account when interpreting the results.