Changes in lipid composition of oat root membranes as a function of water-deficit stress

1985 ◽  
Vol 63 (2) ◽  
pp. 77-84 ◽  
Author(s):  
C. Liljenberg ◽  
M. Kates
Keyword(s):  
Fatty Acids ◽  
Plasma Membrane ◽  
Water Deficit ◽  
Lipid Composition ◽  
Membrane Fraction ◽  
Plasma Membranes ◽  
Root Tip ◽  
Water Deficit Stress ◽  
Root Cells ◽  
Steryl Esters

The effect of repeated water-deficit stress on the lipid composition of root cells from 5-day-old oat (Avena sativa L. cv. Seger) seedlings was studied. The content of total acyl lipids was found to decrease with increasing degree of water-deficit stress, owing largely to decreases in free fatty acids, triglycerides, phosphatidylethanolamine (PE), wax esters, steryl esters, and acylated steryl glycosides. Major polar lipids both in total root cells and in the plasma membrane enriched fraction, as well as the microsomal membrane fraction, were PE, phosphatidylcholine (PC), digalactosyldiacylglycerol (DGDG), monogalactosyldiacylglycerol (MGDG), and polyglycolipid. Decreases in the degree of unsaturation of the fatty acids as a funtion of increased water-deficit stress were observed for the MGDG and polyglycolipid components of total root cells and for the MGDG, DGDG, and polyglycolipid of the plasma membrane fraction. Electron microscopy showed that stressed root tip cells had much smoother plasma membranes than those of control unstressed root cells. These results suggest that root cells of oat seedlings respond to water-deficit stress by reducing the total plasma membrane mass and degree of lipid fluidity, which would reduce the water permeability of the plasma membranes and help maintain cell turgidity.

The lipid composition of plasma membrane from goat mammary gland

1988 ◽  
Vol 66 (12) ◽  
pp. 1355-1359 ◽  
Author(s):  
Arun Sharma ◽  
Rajvir Dahiya
Keyword(s):  
Fatty Acids ◽  
Plasma Membrane ◽  
Liquid Chromatography ◽  
Mammary Gland ◽  
Thin Layer ◽  
Lipid Composition ◽  
Cholesterol Ester ◽  
Plasma Membranes ◽  
Neutral Lipids ◽  
Gas Liquid Chromatography

Experiments were conducted to examine and characterize the lipid composition of the plasma membrane from the lactating goat mammary gland. The plasma membranes were purified by discontinuous sucrose density centrifugation. Lipids were extracted from these membranes and analyzed by thin-layer and gas–liquid chromatography. The results of these studies demonstrate that (i) the principal phospholipids of mammary-gland plasma membranes are phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin; (ii) the principal neutral lipids are triacylglyceride and cholesterol ester; (iii) the major glycolipids are globotetraosylceramide and globotriaosylceramide; and (iv) the major fatty acids are oleic (18:1), palmitic (16:0), stearic (18:0), and myristic (14:0) acids.

Mechanism of hypoxic injury to pulmonary artery endothelial cell plasma membranes

1989 ◽  
Vol 257 (2) ◽  
pp. C223-C231 ◽  
Author(s):  
E. R. Block ◽  
J. M. Patel ◽  
D. Edwards
Keyword(s):  
Fatty Acids ◽  
Plasma Membrane ◽  
Endothelial Cell ◽  
Pulmonary Artery ◽  
Lipid Composition ◽  
Plasma Membranes ◽  
Membrane Lipid ◽  
Conjugated Dienes ◽  
Membrane Phospholipids ◽  
Cell Plasma

We exposed monolayer cultures of pulmonary artery endothelial cells or plasma membranes derived from these cells to hypoxic (0 and 5% O2) and normoxic (20% O2; control) conditions and measured cellular contents of malondialdehyde and conjugated dienes, plasma membrane fluidity and lipid composition, and plasma membrane-dependent transport of 5-hydroxytryptamine (5-HT). Hypoxia caused significant increases in malondialdehyde and conjugated dienes, in fluidity, and in 5-HT transport. Hypoxia also caused a significant decrease in plasma membrane total phospholipids and a marked increase in plasma membrane free fatty acids that appeared to be due to release of fatty acids from the plasma membrane phospholipids. The increases in fluidity and 5-HT transport and the alterations in fatty acids were reversible after return to control conditions. These results indicate that hypoxia alters the physical state, lipid composition, and function of endothelial cell plasma membranes by a combination of stimulation of membrane lipid peroxidation and accelerated degradation of membrane phospholipids, the latter probably secondary to activation of membrane phospholipases.

A study of membrane lipids from dehydration-acclimated Brassica napus root cells: formation of a cubic phase under physiological conditions

1990 ◽  
Vol 68 (1) ◽  
pp. 102-105 ◽  
Author(s):  
P. Norberg ◽  
K. Larsson ◽  
C. Liljenberg
Keyword(s):  
Water Deficit ◽  
Membrane Lipids ◽  
Phase Behaviour ◽  
Water Deficit Stress ◽  
Cubic Phase ◽  
Polarization Microscopy ◽  
Root Cells ◽  
X Ray ◽  
X Ray Crystallography ◽  
Microsomal Membranes

Rape seedlings were acclimated to evaporative dehydration by exposure to repeated moderate water-deficit stress. The stress program started after 19 days of growth and consisted of three, 24-h stress periods interspersed with 24-h rewatering periods. After the third stress period the roots were harvested and microsomal membranes were isolated. Control plants were grown under equivalent conditions without stress (nonacclimated cells). Total lipids were extracted from the membranes and investigated with X-ray crystallography and polarization microscopy at different degrees of hydration and temperatures. In excess water, the membrane lipids from both acclimated and nonacclimated cells exhibited a cubic phase. The lipids from the nonacclimated cells formed a hexagonal (HII) phase on dehydration. The lipids from the acclimated cells behaved in a different way during dehydration, where the cubic phase was transformed to an L2 phase via an intermediate HII phase. At increasing temperatures, the hydrated cubic phase started to form an L2 phase at 30 °C and was fully converted to the liquid-type state at 42 °C. The mesomorphic phase behaviour is discussed in relation to membrane activity.Key words: water-deficit stress, microsomal membranes, X-ray crystallography, polarization microscopy.

The isolation of plasma membrane from protoplasts of soybean suspension cultures

1977 ◽  
Vol 24 (1) ◽  
pp. 295-310
Author(s):  
D.W. Galbraith ◽  
D.H. Northcote
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Membrane Fraction ◽  
Sucrose Gradient ◽  
Plasma Membranes ◽  
Gradient Centrifugation ◽  
Buoyant Density ◽  
Membrane Systems ◽  
Enzymic Digestion ◽  
Nadh Cytochrome

A procedure for the isolation of plasma membranes from protoplasts of suspension-cultured soybean is described. Protoplasts were prepared by enzymic digestion of the cell wall and the plasma membrane was labelled with radioactive diazotized sulphanilic acid. The membrane systems from broken protoplasts were separated by continuous isopycnic sucrose gradient centrifugation. Radioactivity was localized in a band possessing a buoyant density of 1–14 g ml-1. The activities of NADPH- and NADH-cytochrome c reductase, fumarase, Mg2+-ATPase, IDPase and acid phosphodiesterase in the various regions of the density gradient were determined. A plasma membrane fraction was selected which was relatively uncontaminated with membranes derived from endoplasmic reticulum, tonoplasts and mitochondria. The results indicated that Mg2+-ATPase and possibly acid phosphodiesterase were associated with the plasma membrane.

scholarly journals Plasma membrane association of Acanthamoeba myosin I.

1989 ◽  
Vol 109 (4) ◽  
pp. 1519-1528 ◽  
Author(s):  
H Miyata ◽  
B Bowers ◽  
E D Korn
Keyword(s):  
Plasma Membrane ◽  
Binding Site ◽  
Heavy Chain ◽  
Membrane Fraction ◽  
Plasma Membranes ◽  
Actin Binding ◽  
Plasma Membrane Fraction ◽  
Myosin I ◽  
Membrane Bound ◽  
Actin Binding Site

Myosin I accounted for approximately 2% of the protein of highly purified plasma membranes, which represents about a tenfold enrichment over its concentration in the total cell homogenate. This localization is consistent with immunofluorescence analysis of cells that shows myosin I at or near the plasma membrane as well as diffusely distributed in the cytoplasm with no apparent association with cytoplasmic organelles or vesicles identifiable at the level of light microscopy. Myosin II was not detected in the purified plasma membrane fraction. Although actin was present in about a tenfold molar excess relative to myosin I, several lines of evidence suggest that the principal linkage of myosin I with the plasma membrane is not through F-actin: (a) KI extracted much more actin than myosin I from the plasma membrane fraction; (b) higher ionic strength was required to solubilize the membrane-bound myosin I than to dissociate a complex of purified myosin I and F-actin; and (c) added purified myosin I bound to KI-extracted plasma membranes in a saturable manner with maximum binding four- to fivefold greater than the actin content and with much greater affinity than for pure F-actin (apparent KD of 30-50 nM vs. 10-40 microM in 0.1 M KCl plus 2 mM MgATP). Thus, neither the MgATP-sensitive actin-binding site in the NH2-terminal end of the myosin I heavy chain nor the MgATP-insensitive actin-binding site in the COOH-terminal end of the heavy chain appeared to be the principal mechanism of binding of myosin I to plasma membranes through F-actin. Furthermore, the MgATP-sensitive actin-binding site of membrane-bound myosin I was still available to bind added F-actin. However, the MgATP-insensitive actin-binding site appeared to be unable to bind added F-actin, suggesting that the membrane-binding site is near enough to this site to block sterically its interaction with actin.

scholarly journals Lipid composition of the isolated rat intestinal microvillus membrane

1968 ◽  
Vol 109 (1) ◽  
pp. 51-59 ◽  
Author(s):  
G. G. Forstner ◽  
K. Tanaka ◽  
K. J. Isselbacher
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Neutral Lipid ◽  
Lipid Composition ◽  
Plasma Membranes ◽  
Membrane Lipids ◽  
Saturated Fatty Acids ◽  
Polar Lipids ◽  
Published Data ◽  
Microvillus Membrane

1. Rat intestinal microvillus plasma membranes were prepared from previously isolated brush borders and the lipid composition was analysed. 2. The molar ratio of cholesterol to phospholipid was greatest in the membranes and closely resembled that reported for myelin. 3. Unesterified cholesterol was the major neutral lipid. However, 30% of the neutral lipid fraction was accounted for by glycerides and fatty acid. 4. Five phospholipid components were identified and measured, including phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, sphingomyelin and lysophosphatidylcholine. Though phosphatidylethanolamine was the chief phospholipid, no plasmalogen was detected. 5. In contrast with other plasma membranes in the rat, the polar lipids of the microvillus membrane were rich in glycolipid. The cholesterol:polar lipid (phospholipid+glycolipid) ratio was about 1:3 for the microvillus membrane. Published data suggest that this ratio resembles that of the liver plasma membrane more closely than myelin or the erythrocyte membrane. 6. The fatty acid composition of membrane lipids was altered markedly by a single feeding of safflower oil. Membrane polar lipids did not contain significantly more saturated fatty acids than cellular polar lipids. Differences in the proportion of some fatty acids in membrane and cellular glycerides were noted. These differences may reflect the presence of specific membrane glycerides.

scholarly journals PREPARATION AND CHARACTERIZATION OF A PLASMA MEMBRANE FRACTION FROM ISOLATED FAT CELLS

1970 ◽  
Vol 44 (2) ◽  
pp. 417-432 ◽  
Author(s):  
Daniel W. McKeel ◽  
Leonard Jarett
Keyword(s):  
Plasma Membrane ◽  
Cytochrome C ◽  
Membrane Fraction ◽  
Plasma Membranes ◽  
Reductase Activity ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Adenyl Cyclase Activity ◽  
Cytochrome C Reductase ◽  
Plasma Membrane Fraction

A rapid method of preparing plasma membranes from isolated fat cells is described. After homogenization of the cells, various fractions were isolated by differential centrifugation and linear gradients. Ficoll gradients were preferred because total preparation time was under 3 hr. The density of the plasma membranes was 1.14 in sucrose. The plasma membrane fraction was virtually uncontaminated by nuclei but contained 10% of the mitochondrial succinic dehydrogenase activity and 25–30% of the RNA and reduced nicotinamide adenine dinucleotide cytochrome c reductase activity of the microsomal fraction. Part of the RNA and NADH-cytochrome c reductase activity was believed to be native to the plasma membrane or to the attached endoplasmic reticulum membranes demonstrated by electron microscopy. The adenyl cyclase activity of the plasma membrane fraction was five times that of Rodbell's "ghost" preparation and retained sensitivity to epinephrine. The plasma membrane ATPase activity was five times that of the homogenate and microsomal fractions. Electron microscopic evidence suggested contamination of the plasma membrane fraction by other subcellular components to be less than the biochemical data indicated.

scholarly journals Rhizophagy Cycle: An Oxidative Process in Plants for Nutrient Extraction from Symbiotic Microbes

2018 ◽  
Vol 6 (3) ◽  
pp. 95 ◽  
Author(s):  
James White ◽  
Kathryn Kingsley ◽  
Satish Verma ◽  
Kurt Kowalski
Keyword(s):  
Cell Walls ◽  
Plasma Membranes ◽  
Reactive Oxygen ◽  
Root Tip ◽  
Free Living ◽  
Root Cells ◽  
Cell Plasma ◽  
Cell Shapes ◽  
Bacteria And Fungi ◽  
Nutrient Extraction

In this paper, we describe a mechanism for the transfer of nutrients from symbiotic microbes (bacteria and fungi) to host plant roots that we term the ‘rhizophagy cycle.’ In the rhizophagy cycle, microbes alternate between a root intracellular endophytic phase and a free-living soil phase. Microbes acquire soil nutrients in the free-living soil phase; nutrients are extracted through exposure to host-produced reactive oxygen in the intracellular endophytic phase. We conducted experiments on several seed-vectored microbes in several host species. We found that initially the symbiotic microbes grow on the rhizoplane in the exudate zone adjacent the root meristem. Microbes enter root tip meristem cells—locating within the periplasmic spaces between cell wall and plasma membrane. In the periplasmic spaces of root cells, microbes convert to wall-less protoplast forms. As root cells mature, microbes continue to be subjected to reactive oxygen (superoxide) produced by NADPH oxidases (NOX) on the root cell plasma membranes. Reactive oxygen degrades some of the intracellular microbes, also likely inducing electrolyte leakage from microbes—effectively extracting nutrients from microbes. Surviving bacteria in root epidermal cells trigger root hair elongation and as hairs elongate bacteria exit at the hair tips, reforming cell walls and cell shapes as microbes emerge into the rhizosphere where they may obtain additional nutrients. Precisely what nutrients are transferred through rhizophagy or how important this process is for nutrient acquisition is still unknown.

Isolation and characterization of plasma membranes from bovine carotid arteries

1986 ◽  
Vol 250 (1) ◽  
pp. C65-C75 ◽  
Author(s):  
R. V. Sharma ◽  
R. C. Bhalla
Keyword(s):  
Plasma Membrane ◽  
Cytochrome C ◽  
Membrane Fraction ◽  
Plasma Membranes ◽  
Carotid Arteries ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Cytochrome C Reductase ◽  
Plasma Membrane Fraction

A plasma membrane fraction from bovine carotid arteries has been isolated by extraction of a crude microsomal fraction with a low-ionic-strength buffer containing ATP and Ca2+. This step was followed by sucrose-density-gradient centrifugation in the presence of 0.6 M KCl. The plasma membrane vesicles were enriched 60- to 80-fold in Na+-K+-adenosinetriphosphatase, 5'-nucleotidase, and phosphodiesterase I activities. The final yields of these marker enzymes were 12-18% of the total activities in the postnuclear supernatant, and the protein yield was 100-120 micrograms/g wet wt of carotid arteries. Contamination of the plasma membrane fraction by mitochondria and sarcoplasmic reticulum was low as judged by low activities of succinate--cytochrome-c reductase and NADPH--cytochrome-c reductase, respectively. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoprecipitation with smooth muscle-specific actin antibodies showed that the plasma membrane fraction was substantially free from myosin and actin contamination. The plasma membrane vesicles accumulated Ca2+ in the presence of ATP, and the accumulation was increased by calmodulin. Ca2+ accumulated in the presence or absence of calmodulin could be released almost completely from the vesicles by the addition of the Ca2+ ionophore A23187 but not by ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid, indicating that Ca2+ uptake in the presence of ATP is intravesicular. The effects of phosphate and oxalate on Ca2+ uptake in the plasma membranes were different from one another. Phosphate increased Ca2+ uptake in a concentration- and time-dependent manner, and the increase in Ca2+ uptake could be observed as early as 1 min. On the other hand, oxalate at concentrations up to 5 mM did not increase Ca2+ uptake significantly during the 30-min incubation. These plasma membranes can prove useful for the study of ion transport across plasma membranes, hormone binding, characterization of calcium channels, and preparation of antibodies against plasma membrane proteins.

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