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E G Tombropoulos

Publications and source records attributed to E G Tombropoulos.

At least 19 recordsLinked to original sources
PubMed1984

Investigation of phospholipids of the pulmonary extracellular lining by electron paramagnetic resonance. The effects of phosphatidylglycerol and unsaturated phosphatidylcholines on the fluidity of dipalmitoyl phosphatidylcholine.

The membranous structures of the pulmonary extracellular lining were removed from the lungs of rabbits by pulmonary lavage and isolated by differential centrifugation. This membranous fraction contained 93% of the total extracellular phospholipids present in lavage effluents and consisted of membranous vesicles, membrane fragments, tubular myelin and secreted lamellar bodies. The fraction was rich in phosphatidylcholine (79.4%) containing 85.2% palmitic acid in the 1-position and 57.4% palmitic acid in the 2-position. Phosphatidylglycerol was the next most abundant phospholipid, accounting for 9.4% of the total. E.p.r. spectra, obtained by using 5-doxylmethylstearate as a probe, showed that the extracellular phospholipids of the pulmonary lining were organized into structures which were much more fluid than erythrocyte-ghost membranes. The fluidity of phosphatidylcholine isolated from the membranous fraction was similar to that of the fraction itself, indicating that the minor phospholipids had very little influence on the fluidity of the major phospholipid. At physiological temperature, the fluidity of dipalmitoyl phosphatidylcholine was relatively low, but could be markedly increased by the presence of 1-palmitoyl-2-oleoyl phosphatidylcholine or phosphatidylglycerol (10%). Protein present in the extracellular phospholipid fraction did not affect the fluidity of the fraction. These studies indicate that the unsaturated phosphatidylcholines could play a major role in determining the fluidity of the important surface-tension-lowering phospholipids such as dipalmitoyl phosphatidylcholine.

Animals↗
PubMed1983

Induction by morpholine of lysosomal alpha-mannosidase and acid phosphatase in rabbit alveolar macrophages in vivo and in vitro.

alpha-Mannosidase and acid phosphatase were induced in alveolar macrophages from the lungs of rabbits following exposure to morpholine. The induction was observed after inhalation of morpholine vapor or when macrophages were cultured in the presence of morpholine. Lysosomal hydrolases were not induced uniformly. In vivo, maximum induction of alpha-mannosidase and acid phosphatase in female rabbits was 1.7-fold and 2-fold, respectively, and in male rabbits, 3-fold and unchanged, respectively. In vitro, maximum hydrolase induction of alpha-mannosidase and acid phosphatase in macrophages from male rabbits was 1.4-fold and 1.3-fold, respectively, and from female rabbits, 1.3-fold and 1.5-fold, respectively. The induction of acid hydrolases in vitro was rapid, reaching a maximum within 4 hr in alveolar macrophages from male rabbits and within 8 hr in those from females. The induction was dose dependent. This study indicates that the lysosomal enzyme system of the alveolar macrophage may be stimulated by a low molecular weight xenobiotic.

Acid Phosphatase↗
PubMed1983

Isolation and characterization of rabbit lung lamellar bodies.

A method has been devised for the isolation of a highly purified preparation of lamellar bodies from rabbit lung. The purity of the preparation was confirmed by electron microscopy, marker enzymes, phospholipid composition, and isopycnic centrifugation on continuous density sucrose gradients. Contamination of the lamellar bodies by such subcellular components as mitochondria, nuclei, lysosomes and plasma membranes could be excluded; however, reduced nicotinamide adenine dinucleotide phosphate (NADPH) cytochrome c reductase, an enzyme specific for the endoplasmic reticulum components was a persistent contaminant in the preparation of the isolated lamellar bodies. When the lamellar bodies were subject to isopycnic centrifugation, all of the NADPH cytochrome c reductase activity was associated with the lamellar bodies in the low density peak; no reductase activity could be detected in the region of the density gradient demonstrated to localize microsomes. Use of 3H-radiolabeled microsomes confirmed that all of the NADPH cytochrome c reductase activity present in the lamellar body preparations could be accounted for by microsomal contamination. When lamellar bodies or liposomal membranes synthesized from the total phospholipid fraction of lamellar bodies were analyzed by the electron paramagnetic resonance probe, 5-dioxyl-methylstearate, they exhibited a high degree of fluidity at physiological temperature. This was in contrast to the low fluidity of liposomal membranes composed of pure dipalmitoylphosphatidylcholine, the major component (50%) of rabbit lamellar body phospholipids. Furthermore, the major temperature-dependent phase transition in lamellar body membranes occurred at a different temperature (30.5 degrees C) from that of dipalmitoyl-phosphatidylcholine (41.0 degrees C). It is clear, therefore, that the membrane fluidity of lamellar bodies must be highly influenced by the minor lipid component.

Animals↗
PubMed1976

Lipid synthesis by perfused lung.

An isolated lung ventilated with pulses of negative pressure and perfused through the pulmonary vasculature was utilized for the study of 3-sn-phosphatidylcholine synthesis. The perfusion fluid consisted of a Krebs-Ringer phosphate buffer with 6% bovine serum albumin, pH 7.4, and the appropriate substrate. The simultaneous incorporation of (1-14C) palmitate and (2-3H) glycerol and the simultaneous incorporation of (CH3-14C) choline and (CH3-3H) methionine were examined. From these experiments it is concluded: 1) lung tissue incorporates (2-3H) glycerol into 3-sn-phosphatidylcholine to a greater extent than any other lipid examined; 2) both choline and methionine contribute to the synthesis of 3-sn-phosphatidylcholine, and 50-70% of the label in its nitrogen base is derived from choline and 30-50% from methionine; and 3) a high PO2 appears to reduce the synthesis of 3-sn-phosphatidylcholine.

Animals↗