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.     

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.     

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.     

Some characteristics of monolayers of 1-palmitoyl-2-oleoyl-phosphatidylglycerol with and without dipalmitoylphosphatidylcholine during dynamic compression and expansion

Some properties of monolayers of $\text{1-}\text{palmitoyl}\text{-2-}\text{oleoyl}\text{-sn-}\text{glycero}\text{-3-}\text{phospho}\text{-rac-}\text{glycerol}$ (POPG) alone or of POPG in mixtures with $\text{1,2-}\text{dipalmitoyl}\text{-sn-}\text{glycero}\text{-3-}\text{phosphocholine}$ (DPPC) have been measured near 35°C during dynamic compression and expansion at 3.6 cm²·s^?1. (2) The mean values of minimum surface tension (corresponding to maximum surface pressure) which could be obtained with pure POPG monolayers at high compression ranged from 15 to 18 mN·m^?1 in the presence of Na⁺, Ca²⁺ or low pH (2.0) in the subphase. (3) The presence of Ca²⁺ or low pH in the subphase increased the collapse plateau ratios obtained on cyclic compression. This might represent enhanced respreading into the monolayer of pure POPG from a collapsed form during reexpansion of the surface. (4) Monolayers containing 10% or 30% POPG and 90% or 70% DPPC could be compressed to surface tensions approaching zero. (5) In such mixed monolayers, 10% or 30% POPG did not appear to enhance respreading, as measured by collapse plateau ratios, in the presence of Na⁺ or Ca²⁺ in the subphase.     

Analysis of retinal and 3-dehydroretinal in the retina by high-pressure liquid chromatography

A sensitive analytical method was developed in order to study the rhodopsin-porphyropsin system in the eye. Oximes of 11-cis-retinal, all-trans-retinal, 11-cis-3-dehydroretinal, and all-trans-3-dehydroretinal were determined quantitatively by high-pressure liquid chromatography. This method was applied to the analysis of retinal and 3-dehydroretinal in the retinas of bullfrog and goldfish. The results agreed with those obtained from the bleaching kinetics of visual pigment extracted with detergent. A reliable result is obtained if the tissue contains more than 5 pmol of retinal (or 3-dehydroretinal). The chromophore composition could be determined in the eye of a small freshwater prawn, Palaemon pancidence, using 50 pmol of 11-cis-retinal and no 3-dehydroretinal.     

On the Phospholipid Metabolism of Glial Cell Primary Cultures.

Abstract: Primary cultures were prepared from newborn rat brain. After 16-18 days, they consisted mainly of mature and immature astrocytes and oligodendrocytes, as judged by immunohistochemistry. To study the metabolism of ethanolamine glycerophospholipids, the cells were incubated with 1-[1-³H]alkyl- sn -glycero-3-phosphoethanolamine (1-alkyl-GPE), for 1–20 h. Five main products were formed: 1-alkyl-2-acyl-GPE; 1-alkyl-2-acyksn-glycero-3-phosphocholine (1-alkyl-2-acyl-GPC); 1-alkenyl-2-acyl-GPE (ethanolamine plasmalogen); 1-alkenyl-2-acyl-GPC (choline plasmalogen); and 1-alkyl-glycerol. Acylation of the substrate was the main reaction during the first 3 h of incubation, whereas desaturation to plasmaiogen reached a maximum after 12 h. Greater amounts of radioactivity were observed in the phosphatidylcholine fraction after longer incubation times. Only small amounts of choline plasmalogen were observed. The phosphatidylethanolamine fraction consisted of 26.5% diacyl-, 27.5% alkyl-acyl-, and 46.0% alkenyl-acyl- compounds, whereas the corresponding data for the phosphatidylcholine fraction were 78.5, 16.4, and 5.1%, respectively, after 20 h of incubation. Hydrolysis of the substrate to 1-alkyl-glycerol was a minor reaction.     

Electrical conductivity of bilayer lipid membranes in electrolytic solution

The electrical conductivity of bilayer lipid membranes (BLM) of oxidized cholesterol has been measured separately in bathing solutions of sodium sulphate, sodium chloride, sodium bromide, sodium iodide and also in bathing solutions of iodine and iodine containing these salts. An attempt has been made to explain the conduction of electric current across the membranes.     

The Utilization of Glucose and Proline by Culture Forms of Trypanosoma brucei*

Exponentially dividing culture forms of Trypanosoma brucei did not utilize glucose provided in the culture medium. The inclusion of 2-deoxyglucose in the medium had no effect on the growth of the trypanosomes. Glucose could be replaced by proline in the liquid phase of biphasic medium without affecting the doubling time of the organisms. Proline added to the culture medium in this way disappeared during the log phase of growth. Glucose in the culture medium was used by the trypanosomes only when the stationary growth phase had been reached. Lipid accumulated in stationary phase trypanosomes grown in glucose-containing medium, but there was no lipid accumulation in log phase organisms or in those which had been grown in proline-containing medium. Bloodstream trypanosomes transferred to liquid medium rapidly utilized glucose over the first 12 hr of culture, and this was accompanied by an accumulation of free pyruvate in the medium. The rate of glucose utilization fell off over the next 36 hr; this was accompanied by a lowering of free pyruvate in the medium and a rise in the proline oxidase activity of the trypanosomes. The possible biologic significance of proline to trypanosomes developing in the midgut of the tsetse vector is discussed.