DNA condensation by an oxidizable cationic detergent. Interactions with lipid vesicles.

Cationic amphiphile-mediated delivery of plasmid DNA is the non-viral gene transfer method most often used. In the present work, we considered a new cysteine-detergent, ornithinyl-cysteinyl-tetradecylamide (C(14)-CO), able to convert itself, via oxidative dimerization, into a cationic cystine-lipid. By using fluorescence techniques, we first characterized the structure of complexes of plasmid DNA with C(14)-CO molecules either kept as monomers, or oxidized into dimers. Both forms are able to condense DNA, with the formation of hydrophobic micelle-like domains along the DNA chain. Domains with a larger molecular order were obtained with dimeric C(14)-CO/DNA complexes. In a second step, the interactions of these complexes with lipid vesicles considered as membrane models were investigated. In the presence of vesicles, we observed a decondensation of the DNA involved in complexes obtained with C(14)-CO monomers. With anionic vesicles, the DNA is released into the bulk solution, while with neutral vesicles, it remains bound to the vesicles via electrostatic interactions with inserted C(14)-CO molecules. In sharp contrast, the complexes with C(14)-CO dimers are unaffected by the addition of either neutral or anionic vesicles and show no interaction with them. These results may partly explain the low transfection efficiency of these complexes at the +/-charge ratios used in this study.     

Mutants of Aspergillus nidulans with increased resistance to the alkylating agent, N-methyl-N'-nitro-N-nitrosoguanidine

The isolation and characterisation of mutants of Aspergillus nidulans showing resistance to MNNG is described. Such isolates were stable through prolonged subculture in the absence of the selective agent, and resistance segregated as an allele of a single gene in meiotic and mitotic analysis. MNNG-resistant strains showed an increase in resistance to EMS and UV irradiation but no cross-resistance to MMS was detected. Possible mechanisms of resistance to alkylating agents are discussed.     

Immune complex effects on murine macrophages. I. Immune complexes suppress interferon-gamma induction of Ia expression

We have studied the effects of immune complexes on the expression of macrophage surface proteins in vitro. Increased expression of the H-2 molecules I-A, I-E, and K on the macrophage membrane was induced by in vitro culture with crude lymphokine or interferon-gamma. Expression of all three of the molecules was additionally increased by stimulating the cultures with heat-killed Listeria monocytogenes. Addition of soluble immune complexes to the cultures did not have any effect on macrophage expression of these proteins. However, significant inhibition of lymphokine or interferon-gamma induction of I-A, I-E, and H-2K was observed when macrophages were cultured on plates to which immune complexes had been bound. This inhibition was dose dependent, required an immunoglobulin (Ig) molecule with an intact Fc portion, did not require the presence of T cells, and occurred in the presence of indomethacin. Complexes containing IgG1, IgG2a, IgG2b, and IgE, but not IgM or IgA, antibodies mediated the inhibitory effect.     

New matrices for the purification of pectinases by affinity chromatography

Polygalacturonic acid was used as a ligand in the affinity technique for pectinases purification from the filtrate of Aspergillus niger 71 culture. For this purpose four matrices were examined, namely, alkylamine controlled porous glass (CPG), alkylamine silica gel as well as keratin or polyamide coated silica gel. Good results of pectinase purification was obtained on silanized CPG or keratin coated silica gel supports.     

Cytochemical localization of alkaline phosphatase and ouabain-sensitive K+-dependent p-nitrophenylphosphatase activities in brain capillaries of the newt

The ultrastructural localization of alkaline phosphatase and K+-NPPase was investigated in brain capillaries of newt by a cytochemical study using whole brain perfusion. The alkaline phosphatase activity was present in both luminal and antiluminal membranes of the endothelial cells. By contrast, the K+-NPPase was located only in antiluminal membranes of the brain capillaries. This distinct enzymatic distribution suggested that the luminal and antiluminal membranes are functionally different. The role of alkaline phosphatase and K+-NPPase in the blood brain barrier is discussed.