[Electroimmunodiffusion reaction in the diagnosis of syphilis (author's transl)]

A group of 800 human sera, obtained from syphilitic and nonsyphilitic individuals were tested in the counterimmunoelectrophoresis (CIE) technique with Reiter protein antigen. The sera were assayed for comparison in the following treponemal and nontreponemal tests: standard serologic tests for syphilis with cardiolipin; complement fixation (Kolmer 1/5 vol) with Reiter protein antigen (RPCF); T. pallidium immobilization (TPI) test; haemoagglutination test for T. pallidum antibodies (TPHA). The sensitivity and specificity of CIE test, its simplicity, the low cost, the possibility of practical application as a routine test for syphilis serology were discussed.

In vitro cell response of Treponema pallidum-infected rabbits. I. Lymphocyte transformation

Lymphocyte response to phytohaemagglutinin (PHA), Treponema pallidum, cultivable Reiter strain and cardiolipin reagent were examined using peripheral lymphocytes of T. pallidum-infected rabbits and control animals injected intratesticularly with saline extract of normal rabbit testes mixed with T. pallidum-free saline extract of infected testes. The response to PHA was significantly suppressed only in the infected animals, reaching the lowest level at 30 days after infection. A substantial increase of lymphocyte stimulation in the presence of cardiolipin reagent at 20 days after infection correlated well with the appearance of the maximum titre of Wassermann antibodies. Significant (P less than 0.02) increase in spontaneous response of cells incubated for 5 days made the response to T. pallidum and the Reiter strain difficult to interpret. An explanation for the spontaneous response is offered.

Interaction of calcium with negative lipids in planar bilayer membranes. Influence of the solvent

The interaction of Ca++ with acidic phospholipids in black lipid films and lipid bilayers formed from two monolayers was studied by measuring their physical stability and conductance. It was found that the addition of CaCl2 to only one side of lipid bilayers formed from phosphatidylserine or cardiolipin does not appreciably change these parameters. In contrast, black films are unstable to the asymmetric addition of CaCl2. Therefore, the destabilizing effect of Ca++ cannot be attributed to a surface charge difference. The only variation in composition between both bilayer membranes, namely the solvent content of the bilayer, seems to be responsible for the distinctive effect of Ca++. A tentative explanation is presented.

Stimulation by acidic phospholipids of protein-catalyzed phosphatidylcholine transfer

1. The catalyzed transfer of phosphatidylcholine from unilamellar liposomes to mitochondria by phospholipids exchange protein from beef heart or from beef liver is stimulated by the presence of up to 20 mol% acidic phospholipid (phosphatidylinositol or phosphatidic acid) in the liposome. Co-sedimentation of liposomes with mitochondria increases with increasing mol% acidic phospholipid. 2. The catalyzed transfer of phosphatidylcholine from unilamellar liposomes to multilamellar vesicles by beef heart or beef liver exchange proteins is also stimulated by the presence of acidic phospholipid. No co-sedimentation of negatively charged transfer of phosphatidylcholine from multilamellar vesicles to unilamellar liposomes by phospholipid exchange protein from beef heart or beef liver reaches a maximum at 7.5% phosphatidylinositol in the liposomes. Inhibition of phosphatidylcholine transfer was observed at levels of liposome phosphatiylinositol of greater than 15 mol% only in the presence of beef liver exchange protein. 4. Changes in the surface charge of liposomes by the addition of acidic phospholipid were verified by a novel application of polyvinylchloride block electrophoresis that allows the direct measurement of the relative electrophoretic mobility of sonicated vesicles.

Temperature-induced changes in lecithin model membranes detected by novel covalent spin-labelled phospholipids

Several spin-labelled phospholipids carrying covalently bound 5-doxylstearic acid (2-(3-carboxydecyl)-2-hexyl-4,4-dimethyl-3-oxazolidinoxyl) were intercalated in liposomes of saturated and unsaturated lecithins. Temperature-induced changes of these liposomes, detected by the spin-labelled phospholipids, were found to be in agreement with the previously described transitions of hydrocarbon chains of host lecithins detected by different probes and different techniques, establishing that spin-labelled phosopholipids are sensitive probes for the detection of temperature-induced changes in lecithin model membranes. In addition to the detection of already-known transitions in lecithin liposomes, the coexistence of two distinctly different enviroments was observed above the characteristic transition temperature. This phenomenon was tentatively attributed to the influence of the lecithin polar group on the fluidity of fatty acyl chains near the polar group. Combined with other results from the literature, the coexistence of two environments could be associated with the coexistence of two conformational isomers of lecithin, differing in the orientation of the polar head group with respect to the plane of bilayer. These findings have been discussed in view of the present state of knowledge regarding temperature-induced changes in model membranes.

A spin label study of lipid oxidation catalyzed by heme proteins

Rapid loss of the electron spin resonance signal from a variety of spin labels is observed when ferricytochrome c or metmyoglobin are combined with lipids. Evidence is presented that this loss of signal can be used as a sensitive method to study lipid oxidation catalyzed by heme proteins. Under aerobic conditions and with lipids which bind the heme protein, the kinetics of the oxidation process as observed by the spin label method are identical to the kinetics previously observed by measurements of oxygen uptake. Use of pre-oxidized lipids under anaerobic conditions indicates that cytochrome c reacts with a product of lipid oxidation. Kinetic studies of the anaerobic reaction indicate that cytochrome c reacts rapidly with lipid oxidation products in membrane areas far larger than the area occupied by cytochrome c, implying rapid transport of reactive species within the membrane interior in directions parallel to the membrane surface. Under anaerobic conditions, reaction of cytochrome c with lipid oxidation products appears to produce a relatively long lived (hours) species located in the hydrophobic portion of the membrane, which is capable of subsequent reaction with lipid-soluble spin labels.

[Changes of the phospholipid bilayer structure under the adsorption of ferricytochrome c on its surface]

Changes in the mobility of phospholipid molecules in liposomes membranes under adsorption ferricytochrome c on its surface were studied by means of NMR and EPR spectroscopy. It is found that the interaction of cytochrome molecules with vesicles causes the broadening of 1H-NMR signals of hydrophobic as well as polar groups in cardiolipin and phosphatidylcholine in the presence of lauric or phosphatidic acid. This broadening of 1H-NMR signals in hydrophobic groups may be caused by decrease in the rate of lateral diffusion of phospholipid molecules. The changes in the correlation time of hydrophobic spin-proub in liposomes containing phosphatydiloholine and cardiolipin with the increase of ferricytochrome c concentration were also observed. These changes suggest that the formation of protein-phospholipid clusters results in the impair of the regular structure of phospholipid bilayer.

Cytidine diphosphate diglyceride of bovine brain. Positional distribution of fatty acids and analysis of major molecular species

A method is described for the isolation of CDP-diglyceride from bovine brain. Yields of the product ranged from 9.2-15.5 mumol per kilogram of tissue, which corresponds to about 1% of the level of phosphatidic acid. Mild alkaline hydrolysis of the product gave three water-soluble phosphate esters which had the same electrophoretic mobilities as CMP, CDP-glycerol and glycerol 3-phosphate. The liponucleotide was quantitatively hydrolysed by CDP-diglyceride hydrolase from Escherichia coli to phosphatidic acid and CMP. No dCMP was recovered in enzymatic or alkaline hydrolysates and it is concluded there can be little or no dCDP-diglyceride in bovine brain. Brain CDP-diglyceride was similar to phosphatidylinositol in that in both lipids stearate was the major saturated fatty acid and arachidonate the most abundant unsaturated fatty acid. This differed significantly from the fatty acid patterns of other metabolically related phospholipids, phosphatidic acid and cardiolipin. Brain CDP-diglyceride was hydrolysed with phospholipase C from Clostridium welchii with the liberation of the diglyceride moiety in high yield. Treatment of the diglyceride with pancreatic lipase showed CDP-diglyceride with the asymmetric distribution of fatty acids characteristic of most mammalian phospholipids, saturated fatty acids being found mostly at position 1 and polyunsaturated fatty acids at position 2. The derived diglyceride acetates were separated into different molecular species by argentation thin-layer chromatography. These analyses showed that 1-stearoyl, 2-arachidonoyl was the major species of brain CDP-diglyceride.

Stacking of safranine in liposomes during valinomycin-induced efflux of potassium ions

Liposomes were prepared from phosphatidylcholine and cardiolipin in a KCl medium and suspended in a choline chloride medium with safranine. When efflux of K+ was induced by valinomycin, spectral shifts characteristic of stacking were observed. Ca2+ inhibited the rate of stacking in a competitive manner with a Ki of about 200 muM, while La3+ was about 10 times more potent. When liposomes were prepared from phospholipids with a higher ratio of cardiolipin to phosphatidylcholine the inhibition was more potent. No effect on the stacking phenomena was seen when CA2+ was added after the stacking was completed. When CA2+ or an organic cation with four charges, spermine was trapped in the intraliposomal compartment, no significant change in the rate of stacking was seen. However, the extent of stacking was decreased. It is suggested that safranine is driven by a diffusion potential to a site that is inaccessible to CA2+ in the medium, presumably to the inner boundaries of the liposomal membranes.

[Positional distribution of fatty acids in the phospholipids of regenerating rat liver]

The fatty acid composition and positioning in the glycerophospholipids from regenerating rat liver were investigated at different stages of the regeneration process. In the lecithins and phosphatidylethanolamines of the regenerating liver the content of arachidonic acid is lower and that of linoleic acid is higher than in the corresponding lipid fractions of normal rat liver. These deviations are maximal at 24 hours after hepatectomy i.e. at the onset of the mitosis. At any stage of the regeneration the high specifity of the fatty acid positioning characteristical for the normal liver is retained completely. The fatty acid composition of cardiolipin is not changed during the regeneration process.

[TPHA test. Comparison with classical lues reactions and the FTA-ABS test (author's transl)]

1. 227 sera from a mixed group of patients were investigated by the TPHA test, FTA-ABS test, the complement fixation reaction with cardiolipin and pallida antigens, the Meinicke test II and the VDRL test, and compared. 2. 124 sera with a diagnosis of "latent seropositive syphilis" were compared in the same way. The TPHA, FTA-ABS and VDRL tests were in very good agreement with a high specificity and sensitivity, so that all 3 methods are suitable for routine diagnosis. 3. A change in the diagnostic methods for lues is discussed in the light of our own results and those published in the literature and the fact that no unclarified cases remain after using the TPHA and the FTA-ABS tests.

Isolation and characterization of cytidine diphosphate diglyceride from beef liver

Cytidine diphosphate diglyceride was isolated from beef liver by a combination of silicic acid column, DEAE-cellulose column, and this layer chromatography. The product (5.8 to 17.4 mumol/kg of liver) contained cytidine/phosphate/fatty acids in the molar proportions 1.05/2.0/2.05 (theoretical, 1.0/2.0/2.0) (average for three preparations). The liponucleotide was split quantitatively by a partially purified hydrolase from Escherichia coli, specific for CDP-diglyceride, (Raetz, C. R. H., Hirschberg, C. B., Dowhan, W., Wickner, W. T., and Kennedy, E. P. (1972) J. Biol. Chem. 247, 2245-2247) into phosphatidic acid and a water-soluble nucleotide that was chromatographically identical with CMP. No dCMP was located in these hydrolysates. The liver liponucleotide was more effective than a synthetic preparation of CDP-diglyceride in promoting the formation of phosphatidylinositol with guinea pig brain microsomes. The fatty acid composition of CDP-diglyceride was compared with metabolically related phospholipids from beef liver. The liponucleotide had a similar composition to phosphatidylinositol, characterized by a high level of stearate and with arachidonate as the major unsaturated fatty acid. The content of arachidonate in both lipids was significantly higher than that in phosphatidic acid. The profile of fatty acids of cardiolipin was quite unlike that of CDP-diglyceride. These findings suggest several alternatives for the metabolic origins of beef liver CDP-diglyceride: (a) CDP-diglyceride is formed from an atypical pool of phosphatidic acid, (b) the enzyme is selective for arachidonoyl-containing species of phosphatidic acid, (c) the liponucleotide may also be derived from phosphatidylinositol by the back-reaction of CDP-diglyceride: inositol phosphatidyltransferase.

Effect of polymyxin B on liposomal membranes derived from Escherichia coli lipids

The specificity of the action of polymyxin B was studied using liposomes as a model membrane system. Liposomes prepared from total lipids of Gram-negative bacteria Escherichia coli, a mixture of purified E. coli phosphatidylethanolamine and cardiolipin and a mixture of phosphatidylethanolamine and phosphatidylglycerol, were extemely sensitive to polymyxin while those prepared from lipids of Gram-positive bacteria Streptococcus sanguis, lipids of sheep erythrocyte membranes, mixtures of egg lecithin and negatively charged amphiphatic molecules, were less sensitive to the action of the antibiotic. Cholesterol was shown to suppress the polymyxin-induced response in liposomes.