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G L Pool

Publications and source records attributed to G L Pool.

15 recordsLinked to original sources
PubMed1999

Subcellular localization of enzyme activities involved in the metabolism of platelet-activating factor in rainbow trout leukocytes.

The subcellular distribution of an alkyllyso-GPC: acetyl-CoA acetyltransferase (EC 2.3.1.67) and transacylase, two important enzyme activities involved in the remodeling pathway for the biosynthesis of platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, PAF) have been examined in leukocytes isolated from the pronephros of the rainbow trout, Oncorhynchus mykiss. Contrary to mammalian systems, in which the acetyltransferase is localized to intracellular membranes, the subcellular distribution of an acetyltransferase activity in rainbow trout leukocytes was localized to the plasma membrane. Analysis of the acetyltransferase products by thin-layer chromatography (TLC) and high performance liquid chromatography (HPLC) confirmed synthesis of two subclasses of PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine and 1-acyl-2-acetyl-sn-glycero-3-phosphocholine. The transacylase activity in this study was detected in membrane fractions in two domains of the intermediate density region which also contained the NADH dehydrogenase activity, a marker enzyme for the endoplasmic reticulum. Acylation of lysoPAF (1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine) exhibited approximately 95% specificity for omega-3 fatty acids. Acylation patterns were not significantly different in either domain of the endoplasmic reticulum. A model is proposed herein for the metabolism of PAF in rainbow trout leukocytes.

Acyltransferases↗
PubMed1999

Polyunsaturated fatty acids enhance the heat induced stress response in rainbow trout (Oncorhynchus mykiss) leukocytes.

The heat shock response has been studied extensively, yet the molecular signals that trigger the response remain elusive. The dogma of the heat shock response contends that denatured proteins initiate the response, but evidence is accumulating to point to a more complex system in which at least more than one signal is involved in this process. Thermal stress initiates changes in cellular phospholipid membrane physical state, which when acted upon by phospholipases may release lipid mediators that could serve as triggering signals during the heat shock response. We have examined the heat shock response in freshly isolated leukocytes from the pronephros of rainbow trout (Oncorhynchus mykiss). In this study, we show that leukocytes isolated from rainbow trout acclimated to 5 or 19 degrees C express elevated levels of heat shock protein 70 (hsp70) mRNA when heat shocked at 5 degrees C above their respective acclimation temperature and supplementation with exogenous docosahexaenoic acid or arachidonic acid followed by heat shock enhanced levels of hsp70 mRNA. The time course for docosahexaenoic acid induced enhancement of hsp70 mRNA was accelerated compared with heat shock alone, and staurosporine inhibited the docosahexaenoic acid induced increase of hsp70 mRNA. We also provide evidence that phospholipase A2 is involved in the heat shock response.

Animals↗
PubMed1991

Acylation of lyso platelet-activating factor by splenocytes of the rainbow trout, Oncorhyncus mykiss.

In mammalian systems, platelet-activating factor, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, (PAF) is rapidly inactivated by a deacetylation/reacylation system that produces 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine which is highly enriched in arachidonic acid. There is some evidence that n-3 fatty acids may have an impact on this system in humans but the nature of this impact is unclear. In rainbow trout, n-3 fatty acids are known to be essential dietary components which are derived through the food chain. Substantial quantities of n-3 fatty acids are found in trout membrane phospholipids. We show here that in sharp contrast to mammalian cells, trout cells acylate lyso platelet-activating factor, alkyl-GPC, 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine, (lyso-PAF) with a high degree of specificity for n-3 fatty acids. When [3H]lysoPAF was incubated with these cells, only three molecular species of alkylacylglycerophosphocholine were produced, and 92% contained n-3 fatty acids. Since isolated membranes yielded similar results, it appears that the acylation proceeds via a coenzyme A-independent transacylase as found in mammalian systems.

Acylation↗
PubMed1990

PAF-acether transfer activity in HL-60 cells is induced during differentiation.

Platelet-activating factor is a proinflammatory lipid active at subnanomolar concentrations. The intermembrane transfer of a biologically active PAF analog has been previously demonstrated in macrophages. Here we demonstrate that the specific activity of this transfer activity increases when HL-60 cells are induced to differentiate by treatment with dimethyl sulfoxide, dibutyryl cAMP or phorbol diester. In undifferentiated HL-60 cells, methylcarbamyl-PAF transfer activity was only 0.56 U.min-1.mg-1. This basal value was increased 2.6 and 6.7 times upon granulocytic and macrophagic differentiation, respectively. On the other hand, the transfer of 2-O-methyl-PAF, a cytotoxic analog with no PAF biological activity, remained very low and did not vary during differentiation.

Bucladesine↗
PubMed1984

Rat eustachian tube synthesizes disaturated phosphatidylcholine.

Otitis media results when the eustachian tube fails to adequately ventilate the middle ear. A surface tension-lowering substance may be required for normal tube opening, especially in young children with poorly developed naso-pharyngeal musculature. We report here that rat eustachian tube epithelium synthesizes disaturated phosphatidylcholine, which is recognized as the surface tension-lowering substance of pulmonary surfactant.

Animals↗
PubMed1983

Phospholipid-transfer activities in cytosols from lung, isolated alveolar type II cells and alveolar type II cell-derived adenomas.

We have examined phospholipid-transfer activities in cytosols from rat and mouse whole lung, isolated rat alveolar type II cells and alveolar type II cell-derived mouse pulmonary adenomas. We report an enrichment in phosphatidylcholine and phosphatidylglycerol (but not phosphatidylinositol) protein-catalysed transfer in the type II cell and adenoma cytosols compared with the whole-lung cytosols. The activities from these cytosols were resolved using column chromatofocusing, which clearly demonstrated the presence of a phosphatidylcholine-specific transfer protein in each of the four tissues. In addition, two proteins (rat) or three proteins (mouse) catalysing both phosphatidylcholine and phosphatidylglycerol transfer were resolved from whole lung, whereas in both the rat isolated alveolar type II cells and the mouse type II cell-derived adenomas one of these less specific proteins is not present.

Adenoma↗
PubMed1983

Spontaneous and protein-catalyzed transfer of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor) between phospholipid bilayers.

1-Alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor or alkylacetyl-GPC), a bioactive phospholipid that possesses hypotensive, platelet-aggregating and inflammatory properties, is known to be secreted by a variety of cell types. The biological activity of alkylacetyl-GPC is related to a precise chemical structure that implicates interaction with proteins. We have studied the spontaneous and protein-catalyzed transfer of alkylacetyl-GPC between phospholipid vesicles and have demonstrated the following: 1. There are at least two transferable pools of alkylacetyl-GPC in sonicated phospholipid vesicles. 2. These two pools differ in the rate at which they dissociate from the vesicles; one pool equilibrates between donor and acceptor vesicles instantaneously while the other pool is transferred much more slowly. 3. Dialysis of alkylacetyl-GPC between phospholipid vesicles through the aqueous phase is slow. 4. A protein fraction derived from rat lung cytosol catalyzes the transfer of the nonequilibrating pool of alkylacetyl-GPC between phospholipid vesicles; this transfer is superimposed on the spontaneous transfer and is unchanged in experiments using vesicles from which the rapidly equilibrating pool has been removed.

Kinetics↗
PubMed1968

Visual pigment fluorescence.

The fluorescence of cattle rod outer segments (dried) and of rhodopsin in solution lies in the range of 575 to 600 millimicrons with a quantum efficiency of 0.005 if excitation is in the visible band near 500 millimicrons. The emission is abolished by bleaching at -196 degrees C but can be reversibly regenerated by irradiation with light of longer wavelength (600 millimicrons). This behavior reflects the known interconversion of rhodopsin to prelumirhodopsin at this temperature.

Animals↗