Biochemical studies of pigments from a pathogenic fungus Microsporum cookei. V. Evidence for the transmembrane permeability of xanthomegnin across phospholipid bilayer membranes.

Direct evidence is provided for the transmembrane permeation of xanthomegnin across phospholipid bilayer membranes using ascorbate-loaded liposomes. This process may be associated with an uncoupling effect on the oxidative phosphorylation of mitochondria.     

Biochemical studies of pigments from a pathogenic fungusMicrosporum cookei. V. Evidence for the transmembrane permeability of xanthomegnin across phospholipid bilayer membranes

Summary Direct evidence is provided for the transmembrane permeation of xanthomegnin across phospholipid bilayer mebranes using ascorbate-loaded liposomes. This process may be associated with an uncoupling effect on the oxidative phosphorylation of mitochondria.     

Peptide-polysaccharides isolated from the culture medium of the fungus Paracoccidioides brasiliensis pathogenic to man

A peptido-polysaccharide isolated from the culture medium of Paracoccidioides brasiliensis has been studied. The crude product is a mixture of several polysaccharides releasing, by hydrolysis glucose, mannose and galactose. The purified fraction contains mannose (88%) and galactose (12%). This galactomannan has a molecular weight varying between 4.6.10(4) and 2.6.10(4). It is associated with a peptide containing four amino-acids.     

Net transport of cholesterol from cells of the human EA.hy 926 endothelial cell line to high density lipoproteins

EA.hy 926 cells, a human endothelial cell line, show characteristics of differentiated endothelial cells. The cells express saturable binding of apo E-free¹²⁵I-high density lipoprotein₃ (HDL₃). B_max increased from 71 to 226 ng HDL₃ bound/mg cell protein after cholesterol loading of the confluent endothelial cells with cationized low density lipoprotein (LDL). The affinity did not change after cholesterol enrichment (K_d was 37 g HDL₃ protein/ml for control cells and 31 g/ml, for loaded cells). Incubation of cholesterol-loaded EA.hy 926 cells with native HDL and LDL had different effects on cellular cholesterol levels. Incubation with HDL decreased both esterified and unesterified cellular cholesteryl, but LDL did not change total cellular cholesterol However, LDL tended to increase cellular cholesteryl esters, with a concomitant decrease of unesterified, cellular cholesterol. Incubation of endothelial cells with both HDL and LDL also resulted in decreased total cellular cholesterol levels. These data show that cationized LDL-loaded human endothelial EA.hy 926 cells can be used to study the net transport of cellular cholesterol to HDL, the first step in reverse cholesterol transport.     

Comparative studies on the covalent binding of the carcinogen benzo(a)pyrene to DNA in various model systems.

The covalent binding of tritiated benzo(a)pyrene (BP) to DNA has been determined in rat liver in vivo, in rat liver perfused in situ, after incubation of BP with liver single cells, with liver homogenate, with liver microsomes and DNA, with fibroblasts from a rat granuloma pouch, and with 2 cell lines. Liver single cells were found to be a valuable compromise between the most sensitive system (microsomal incubation of BP and DNA) and the biologically most relevant system (in vivo).     

Sensitivity of transformed EHSVi fibroblasts to the antibody-complement lytic system. Cooperation between the lytic units, and existence of a cellular defense]

The sensitivity of transformed EHSVi fibroblasts to the antibody-complement lytic system was evaluated, at various antibody concentrations (Ac), in conditions in which a variation of the lytic activity proportional to Ac3, 1 may be observed. This points out, not the expected cooperation between IgG molecules in activating C1 within a definite lytic unit, but a cooperation between the lytic units themselves, and therefore the existence of a cell defence.     

Paracelsin; characterization by NMR spectroscopy and circular dichroism,and hemolytic properties of a peptaibol antibiotic from the cellulolytically active mnoldTrichoderma reesei. Part B

Summary Paracelsin, a hemolytic and membrane active polypeptide antibiotic of the peptaibol class which is excreted by the moldTrichderma reesei, was obtained by a simplified and isolation procedure utilziing hydrophobic adsorber resin. Investigation by¹³C nuclear magnetic resonance spectroscopy and circular dichroism revealed considerable helical portions in solution, and the very recently accomplished sequence determination of paracelsin allows the discussion of the results with regard to the closely related analogues, alamethicin and suzukacillin. A selective cleavage of the peptide was achieved by careful treatment with various acids, and a buffer of pH 8.25 and of high ionic strength made possible the quantitative determination of the C-terminal phenylalaninol released by means of ion-exchange chromatography. The significance of the production of paracelsin and related mycotoxins of the peptaibol class, exhibiting various kinds of biological activity, is discussed with respect to the extensive effort being made towards biotechnological applications of species, strains and cellulolytically highly active mutants of the fungusTrichoderma.Presented in part at the 5th European Symposium on Animal, Plant and Microbial Toxins, Hannover, August 29–September 2, 1983 and a lecture given at Ciby-Geigy/Basel in March 1984.Acknowledgment. We thank I. Ackermann for excellent and skilled technical assistance and gratefully acknowledge the help of R. Ratz for support in CD spectroscopy.