scholarly journals COMPOSITION OF CELLULAR MEMBRANES IN THE PANCREAS OF THE GUINEA PIG

1971 ◽  
Vol 49 (1) ◽  
pp. 130-149 ◽  
Author(s):  
J. Meldolesi ◽  
J. D. Jamieson ◽  
G. E. Palade
Keyword(s):  
Fatty Acids ◽  
Guinea Pig ◽  
Neutral Lipids ◽  
Liver Microsomes ◽  
Zymogen Granule ◽  
Protein Ratio ◽  
Hepatic Microsomes ◽  
Microsomal Membranes ◽  
E 600 ◽  
Exocrine Cell

The lipid composition of rough and smooth microsomal membranes, zymogen granule membranes, and a plasmalemmal fraction from the guinea pig pancreatic exocrine cell has been determined. As a group, membranes of the smooth variety (i.e., smooth microsomes, zymogen granule membranes, and the plasmalemma) were similar in their content of phospholipids, cholesterol and neutral lipids, and in the ratio of total lipids to membrane proteins. In contrast, rough microsomal membranes contained much less sphingomyelin and cholesterol and possessed a smaller lipid/protein ratio. All membrane fractions were unusually high in their content of lysolecithin (up to ∼20% of the total phospholipids) and of neutral lipids, especially fatty acids. The lysolecithin content was shown to be due to the hydrolysis of membrane lecithin by pancreatic lipase; the fatty acids, liberated by the action of lipase on endogenous triglyceride stores, are apparently scavenged by the membranes from the suspending media. Similar artifactually high levels of lysolecithin and fatty acids were noted in hepatic microsomes incubated with pancreatic postmicrosomal supernatant. E 600, an inhibitor of lipase, largely prevented the appearance of lysolecithin and fatty acids in pancreatic microsomes and in liver microsomes treated with pancreatic supernatant.

scholarly journals COMPOSITION OF CELLULAR MEMBRANES IN THE PANCREAS OF THE GUINEA PIG

1971 ◽  
Vol 49 (1) ◽  
pp. 150-158 ◽  
Author(s):  
J. Meldolesi ◽  
J. D. Jamieson ◽  
G. E. Palade
Keyword(s):  
Electron Transport ◽  
Guinea Pig ◽  
Enzyme Activities ◽  
Transport Systems ◽  
Zymogen Granule ◽  
Electron Transport Chains ◽  
Microsomal Membranes ◽  
Pancreatic Exocrine ◽  
Exocrine Cell ◽  
Secretory Products

A comparative study of the enzymic activities of membrane fractions derived from guinea pig pancreatic homogenates has yielded the following results: Rough microsomal membranes (derived from the rough ER) have the reductase activities of the two microsomal electron transport systems but lack enzyme activities of Golgi-type (TPPase) and plasmalemmal-type (5'-nucleotidase, ß-leucyl naphthylamidase, Mg-ATPase). Smooth microsomal membranes (derived primarily from the Golgi complex), zymogen granule membranes, and plasmalemmal fractions possess overlapping enzyme activities of plasmalemmal type, in different relative concentrations for each fraction. In addition, the smooth microsomal membranes exhibit TPPase and ADPase activity and share with rough microsomes the reductase activities of the two electron transport chains. Taken together with recent data on the lipid composition of the same fractions (2), these results indicate that the membranes of the pancreatic exocrine cell are chemically and functionally distinct, and hence do not mix with one another during the transport of secretory products.

Convenient biosynthetic preparation of isomeric spin-labelled radioactive phosphatidic acids

1982 ◽  
Vol 60 (11) ◽  
pp. 1014-1017 ◽  
Author(s):  
L. Stuhne-Sekalec ◽  
N. Z. Stanacev
Keyword(s):  
Fatty Acids ◽  
Guinea Pig ◽  
Stearic Acid ◽  
Liver Microsomes ◽  
Enzymatic Preparation ◽  
Pig Liver ◽  
Secondary Hydroxyl ◽  
Phosphatidic Acids ◽  
Guinea Pig Liver Microsomes ◽  
Guinea Pig Liver

A convenient method for the enzymatic preparation of sn-3-[2-3H]phosphatidic acids carrying also 5-, 12-, or 16-nitroxide stearic acids, from sn-3-[2-3H]glycerophosphate and isolated guinea pig liver microsomes, is described in detail. The procedure allows a simultaneous preparation of three spin-labelled sn-3-[2-3H] phosphatidic acids of yields 3–3.5 μmol of each compound which is > 99% pure in respect to the radioactivity and which contains 25 mol% of spin-labelled fatty acids. These phosphatidic acids were approximately equally distributed between the primary and the secondary hydroxyl when 12- or 16-nitroxide stearic acids were used or predominantly (75%) associated with the secondary hydroxyl of sn-3-[2-3H]phosphatidic acid when 5-nitroxide stearic acid was present in the incubation mixture.

scholarly journals COMPOSITION OF CELLULAR MEMBRANES IN THE PANCREAS OF THE GUINEA PIG

1971 ◽  
Vol 49 (1) ◽  
pp. 109-129 ◽  
Author(s):  
J. Meldolesi ◽  
J. D. Jamieson ◽  
G. E. Palade
Keyword(s):  
Guinea Pig ◽  
Gradient Centrifugation ◽  
Secretory Proteins ◽  
Zymogen Granule ◽  
Marker Enzymes ◽  
Zymogen Granules ◽  
Terminal Web ◽  
Granule Fraction ◽  
Pancreatic Exocrine ◽  
Exocrine Cell

The subcellular components involved in the synthesis, transport, and discharge of secretory proteins in the guinea pig pancreatic exocrine cell have been isolated from gland homogenates by differential and gradient centrifugation. They include rough and smooth microsomes derived respectively from the rough endoplasmic reticulum and Golgi periphery, a zymogen granule fraction consisting mainly of mature zymogen granules and a smaller population of condensing vacuoles, and a plasmalemmal fraction. Membrane subfractions were obtained from the particulate components by treatment with mild (pH 7.8) alkaline buffers which extract the majority (>95%) of the content of secretory proteins, allowing the membranes to be recovered from the extracting fluid by centrifugation. The purity of the fractions was assessed by electron microscopy and by assaying marker enzymes for cross-contaminants. The rough and smooth microsomes were essentially free of mitochondrial contamination; the smooth microsomes contained <15% rough contaminants. The zymogen granule fraction and its derived membranes were free of rough microsomes and contained <3% contaminant mitochondria. The plasmalemmal fraction was heterogeneous as to origin (deriving from basal, lateral, and apical poles of the cell) and contained varying amounts of adherent fibrillar material arising from the basement membrane and terminal web. The lipid and enzymatic composition of the membrane fractions are described in the following reports.

Mitochondrial importation of lipids and liponucleotides from microsomes independent of and facilitated by purified cytosol proteins

1980 ◽  
Vol 58 (10) ◽  
pp. 1082-1090 ◽  
Author(s):  
L. Stuhne-Sekalec ◽  
N. Z. Stanacev
Keyword(s):  
Guinea Pig ◽  
Neutral Lipids ◽  
Protein S ◽  
Mitochondrial Import ◽  
Pig Liver ◽  
Conventional Procedure ◽  
Independent Mechanism ◽  
Microsomal Membranes ◽  
Experimental Findings ◽  
Guinea Pig Liver

The mitochondrial importation of microsomal lipids and liponucleotides in the presence and in the absence of partially purified cytosol protein(s) isolated from guinea pig liver was studied by the aid of isomeric (5-, 12-, and 16-(N-oxyl-4′,4′-dimethyloxazolidine)stearoyl) spin-labelled radioactive phosphatidic acid, phosphatidylcholine, neutral lipids, and CDP-diglycerides. Using a conventional procedure for the protein purification, cytosol protein(s) was purified approximately 1000-fold in respect to its ability to catalyze the translocation of isomeric spin-labelled lipids and liponucleotides from the microsomal to mitochondrial membranes. The highest activity of this protein was exhibited with biosynthesized spin-labelled lipids and liponucleotides bound to the microsomal membranes as substrates and the lowest, with the synthetic liponucleotides and derived lipids bound to the microsomal membranes. The partially purified protein was active in catalyzing the mitochondrial import of phospholipids from microsomes after heat treatment up to 90 °C.In addition to the cytosol protein catalyzing mechanism of mitochondrial import of lipids and liponucleotides from microsomal membranes, another cytosol protein independent mechanism of the mitochondrial importation of the same lipids and liponucleotides was also demonstrated in an agreement with our previous reports on the existence of cytosol protein independent intermembranous translocation of phospholipids. These experimental findings are discussed in terms of possible physiological significance and reaction mechanisms involved in the mitochondrial import of lipids and liponucleotides from the microsomal membranes of guinea pig liver.

scholarly journals Effects of CoA and acyl-CoA on Ca2+-permeability of endoplasmic-reticulum membranes from rat liver

1995 ◽  
Vol 306 (3) ◽  
pp. 703-708 ◽  
Author(s):  
G T Rich ◽  
J G Comerford ◽  
S Graham ◽  
A P Dawson
Keyword(s):  
Fatty Acids ◽  
Membrane Fusion ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Short Term ◽  
Esterified Fatty Acids ◽  
Chain Acyl ◽  
Microsomal Membranes ◽  
Long Chain

We have studied the effects of CoA and palmitoyl-CoA on Ca2+ movements and GTP-dependent vesicle fusion in rat liver microsomes. (1) Inhibition of membrane fusion by CoA depends on esterification of CoA to long-chain acyl-CoA using endogenous non-esterified fatty acids. (2) Binding of long-chain acyl-CoA to microsomal membranes is inhibited by BSA, which also relieves inhibition of membrane fusion. (3) Under conditions where acyl-CoA binding is inhibited, CoA causes increased Ca2+ accumulation, apparently by decreasing the Ca2+ leak rate. (4) Conversely, palmitoyl-CoA, in the presence of BSA, causes Ca2+ efflux. (5) The decrease in Ca(2+)-permeability caused by CoA does not depend on the presence of ATP or GTP, and is irreversible in the short term. (6) Using 14C-labelled CoA we show that CoA derivatives can be formed from endogenous components of microsomal membranes in the absence of ATP. (7) The results are interpreted in terms of a Ca(2+)-permeability which is controlled by CoA and/or long-chain acyl-CoA esters.

scholarly journals Effect of diet on the rate of depletion of n–3 fatty acids in the retina of the guinea pig

1998 ◽  
Vol 39 (6) ◽  
pp. 1274-1279
Author(s):  
Harrison S. Weisinger ◽  
Algis J. Vingrys ◽  
Lavinia Abedin ◽  
Andrew J. Sinclair
Keyword(s):  
Fatty Acids ◽  
Guinea Pig
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