In vitro lipid oxidation modifies proteins and functional properties of sarcoplasmic reticulum

Changes in protein and fatty acid compositions of flounder sarcoplasmic reticulum during NADH plus ascorbate-dependent lipid peroxidationin vitro were related to the ability of the sarcoplasmic reticulum to sequester Ca⁺². Progressive accumulation of high-molecular-weight protein components occurred concomitantly with loss of Ca⁺²-sequestering activity. Part of this polymerized protein may be the dimer or trimer of Ca⁺², Mg⁺²-ATPase. Loss in Ca⁺², Mg⁺²-ATPase protein could account for over 60% of the polymerized protein. Rate of loss of polyunsaturated fatty acids was C22:6>C20:4>C20:5>C22:5. Loss of polyunsaturated fatty acids and accumulation of thiobarbituric acid-reactive substances occurred concomitantly with protein polymerization.     

Direct evidence for Ca++-induced lateral phase separation in black membranes of lipid mixtures by the analysis of gramicidin A single-channels

Single-channel conductance fluctuations are analysed for gramicidin A incorporated into binary-mixed black lipid membranes of charged phosphatidic acid and neutral lecithin in different molar ratios. At very low Ca⁺⁺ concentrations in the electrolyte (i.e. in the presence of EDTA) homogeneous lipid mixtures are identified through their conductance and life time probability distributions for integral gramicidin pores. As for the pure lipid components, the conductance histograms each show a single maximum with regular width and for all channels a single mean lifetime is found.For Ca⁺⁺-levels (10^-6–10^-5 M) that are close to the critical demixing concentration (10^-4 M) unusually broad conductance distributions and reduced lifetimes are found provided the PC content, x, of the membrane is close to the critical mixture (x _crit0.5). We interpret this as a first example of the coupling of a membrane function (the transport of ions) to a lipid matrix with locally fluctuating composition close to a critical demixing point.For the conductance histogram of gramicidin A in an equimolar mixture of PA and PC shows two well-separated maxima. A correlation analysis between conductance and lifetime of the single pores shows that the two channel populations also differ significantly in their mean channel lifetime, ^*. This finding is interpreted as being direct evidence for Ca⁺⁺-induced lateral phase separation in black lipid membranes, as has been postulated recently.Abbreviations used HEPES N-2-hydroxyethyl-piperazine-N-2-ethane-sulfonic acid - EDTA ethylenediaminetetraacetic acid     

Hydrogen peroxide formation and lipid peroxidation in rat uterus—effect of hormones and vitamin E

The effect of estradiol-17β and progesterone given separately as well as in combination on the rate of hydrogen peroxide formation and lipid peroxidation in the uteri of ovariectomized rats was studied. Estradiol in 3μg dose per day per animal elicited maximum stimulatory response and progesterone (100μg), on the other hand, was without any such effect. However, progesterone given along with estradiol completely prevented the effect due to the latter. In the same way, vitamin E, a well known antioxidant was found to be extremelv effective in protecting the uterus from the highly peroxidative action of estradiol-17β.     

Ontogeny of human fetal catalase superoxide dismutase and lipid peroxidation: A comparative study

A comparative study on the activity profile of catalase and superoxide dismutase, the two scavenging enzymes, as well as the developmental profile of lipid peroxidation in the human fetal brain, liver and kidney have been done for gestation periods ranging from 12 weeks to 28 weeks and beyond. The activity of the scavenging enzymes increase gradually in_all the tissues with the advancement of pregnancy. Brain is an exception in case of catalase where the activity remains more or less same throughout the developmental period except in the case of fetuses, 28 weeks and above where significant decrease in the catalase activity is observed. A high level of lipid peroxidation is observed during early stages of development which declines thereafter.     

“SIF” cells in the sympathetic ganglia of the bullfrog,Rana catesbeiana: variety in population and innervation

Summary Small intensely fluorescent (SIF) cells appeared singly or, more frequently, in variably-sized clusters in the sacroccygeal 8th and 9th sympathetic ganglia of the bullfrog. Smaller clusters containing only two to nine SIF cells accounted for 61% of 1773 clusters examined. The largest cluster contained 283 cells. The number of cells in individual ganglia also varied from 21 to 3332. SIF cells, solitary as well as in smaller clusters, received no distinct form of the synaptic contact. In contrast, the cells in larger clusters were frequently innervated by nerve endings that were similar in vesicular constitution to the nerve endings on principal ganglion (PG) cells. No synaptic contact was found between SIF cells and PG cells. SIF cells were also characterized by their location in the vicinity of blood capillaries with a continuous endothelium. p]Our observation seems to suggest that larger clusters of SIF cells receiving nerve endings are linked to a paracrine and/or endocrine system. Chemical influence via the blood stream and intraganglionic milieu for non-innervated SIF cells in the solitary or smaller clusters is a subject for speculation. An interneuronal role of SIF cells to relay stimuli to PG cells seems unlikely. The possible functions here assigned to SIF cells could be variable in efficiency depending on their population and density.     

Thermodynamic analysis of nonelectrolyte sorption in plant cuticles: The effects of concentration and temperature on sorption of 4-nitrophenol

The sorption of 4-nitrophenol (4-NP) in enzymatically isolated cuticles ofLycopersicon esculentum fruits andFicus elastica leaves was studied as a function of temperature and solute concentration. Plots of the concentrations of 4-NP sorbed in the cuticle versus the equilibrium concentrations in the aqueous phase gave linear isotherms at low concentrations that tended to approach plateaus at higher sorbate concentrations ( 10 mmol·kg^-1). At low concentrations of sorbed 4-NP, cuticles have sorptive properties similar to those of organic solvents which are able to form intermolecular hydrogen bonds, while at higher concentrations their solid nature becomes apparent. During sorption of 4-NP the cutin matrix swells and new sorption sites are successively formed. The partition coefficients of 4-NP in the system cuticle/buffer are functions of temperature and concentration. At high sorbate concentrations (approx. 1 mol·kg^-1) they approach a value of 1. Different sorptive properties were observed for the cutin regions normally encrusted with soluble cuticular lipids (SCL) and those without SCL. Increasing temperature augmented the number of sorption sites in the cutin ofLycopersicon while no effect was observed withFicus. The changes of partial molar free energy (G ^o _tr), enthalpy (H ^o _tr), and entropy (S ^o _tr) for the phase transfer of 4-NP also depended on sorbate concentration: H ^o _tr and S ^o _tr were negative and steeply decreased at high sorbate concentrations. This is due to solute-solute interactions replacing solute-cutin interactions at high concentrations resulting in solid precipitates of solute within the cutin matrix. This formation of ordered solid domaines starting from a small number of nonelectrolyte molecules interacting with the cutin is proposed as a model for the intracuticular deposition of SCL.Abbreviations CM cuticular membrane - MX polymer matrix membrane - 4-NP 4-nitrophenol - SCL soluble cuticular lipids     

Liposome-mediated labeling of adrenocorticotropin fragments parallels their biological activity

To test our hypothesis that specific interactions of ACTH peptides with model lipid membranes reflect the biological importance of similar interactions on target cells, we investigated the liposome-mediated labeling of ACTH fragments with the extremely hydrophobic photolabel, 3-trifluoromethyl-3-(m-[125I]iodophenyl)diazirine. Correlations were found between the labeling rates and the agonistic and antagonistic potencies of the peptides for in vitro steroidogenesis and inhibition of a synaptosomal protein kinase. A model for the cross-reactivity between ACTH and opioid peptides is discussed.     

Capacitance--voltage relationship in phospholipid bilayers containing gangliosides

Changes in the position of the minimum of the parabolic capacitance-voltage curve allow the measurement of the amount of ganglioside present in artificial bilayers made with phosphatidylcholine-ganglioside mixtures and asymmetrically shielded with Ca2+. The screening effect of the ionic solution must be considered. With ganglioside/phospholipid molar ratios of up to 15%, all glycolipids can be found at the membrane surfaces.     

Schistosoma mansoni: schistosomulicidal activity of macrophages isolated from liver granulomas of infected mice

Mice infected with Schistosoma mansoni develop T cell-mediated granulomatous reactions around disseminated parasite eggs. In this study, granuloma-derived leucocytes have been examined for schistosomulicidal capacity by the use of in vitro cytotoxicity assays. Adherent macrophages, that were shown by electron microscopy to exhibit no gross morphological abnormalities, were unable to mediate significant mortality in the absence of serum factors. When cocultured with immune serum and complement, however, these cells killed +/- 26% of the larvae at a cell:target ratio of 5000:1. In contrast, granuloma-derived cell populations that were enriched for eosinophils (50-70% eosinophil content) showed only minimal cytotoxic potential. This may be related to observed structural changes in the eosinophil lysosomal granules, or perhaps to blocking of the cell-surface receptors by immune complexes. It is concluded that granuloma macrophages, activated by egg antigen-sensitised T lymphocytes, may serve as effector cells in immunity to schistosomules.     

Light-driven proton transport of bacteriorhodopsin incorporated into long-term stable liposomes of a polymerizable sulfolipid

The chromoprotein bacteriorhodopsin from Halobacterium halobium has been incorporated into liposomes made of a fully synthetic, polymerizable lipid. Bacteriorhodopsin is found to be active in these polymer liposomes. The advantage in the use of such polymer systems concerning long-term stability in comparison with liposomes made of natural lipid is demonstrated.