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Synthesis of molecular species of glycerophospholipids from diglyceride-labeled brain microsomes
No full textSelectivity of CDP-choline: diacylglycerol choline phosphotransferase and CDP-ethanolamine: diacylglycerol ethanolamine phosphotransferase for molecular species of diglyceride has been studied in rat brain microsomes in vitro.
Diglyceride-labeled microsomes were prepared by incubation with labeled sn-glycerol-3-phosphate; the microsomes were then incubated with CDP-choline or CDP-ethanolamine for different time intervals. Experimental data extrapolated to zero-time incubation were taken into account for evaluating species specificity. A small selectivity for diglyceride species has been demonstrated for the choline phosphotransferase, but the ethanolamine phosphotransferase was found to convert hexaenoic diglyceride into phospholipid at the highest rat
Enzymic synthesis of 1-alkyl-2-acyl-sn-glycero-3-phosphorylethanolamine through ethanolaminephosphotransferase activity in the neuronal and glial cells of rabbit in vitro
No full text
The effect of prostaglandin F2alpha on arachidonate and lipid-choline metabolism in rat brain slices in vitro.
No full textCompartmentation of Newly Synthesized Phosphatidylethanolamine in Rat Brain Microsomes
No full textThe compartmentation of the phosphatidylethanolamine
newly synthesized in brain microsomes in vitro either by
base exchange or net synthesis has been studied, using difluorodinitrobenzene as a chemical probe. The experimental results demonstrate that in rat brain microsomes the phosphatidylethanolamine molecules synthesized by base exchange and the bulk membrane lipid belong to different pools. Ca2+ bound to microsomes seems to be involved in the maintenance of the compartmentation of phosphatidylethanolamine. In the presence of Ca2+ the newly synthesized phosphatidylethanolamine molecules react with difìuorodinitrobenzene as though they are organized
in clusters. After biosynthesis in vivo or in vitro through
the cytidine pathway, the compartmentation of the newly formed
phosphatidylethanolamine appears less marked than after the
synthesis through base exchange
Involvement of CDP-choline in phospholipid metabolism of brain tissue in vitro
No full textThe ability of phosphorylcholine and CDP-choline to act as
lipid precursors was tested in chick brain microsomes (plus
supernatant).
CDP-choline was, in every case, a much better precursor of
choline glycerophospholipids than phosphorylcholine. The cytìdylyltransferase reaction which forms CDP-choline appears, therefore, as the limiting step of the metabolic pathway which introduces phosphorylcholine into lipids. This reaction can be
stimulated by the addition of phospholipids to the incubation
mixture. Choline lysoglycerophospholipids are the most active
in this connection.
Compartmentation of membrane phosphatidylethanolamine formed by base-exchange reaction in rat brain microsomes
No full textThe compartmentation of membrane phosphatidylethanolamine (PE) formed by base-exchange reaction in rat brain microsomal vesicIes has been investigated. After labelling membrane PE by base-exchange in vitro, microsomal vesicIes were treated with trinitrobenzenesulfonic acid (TNBS). The amount of membrane PE
reacting with TNBS depends on the duration and the temperature of the reaction as well as on the TNBS concentration. It was found that almost all of the labelled PE molecules, but only about 24% of membrane PE, were accessible to TNBS, under very mild reaction conditions. It is concIuded that PE labelled by
base-exchange is completely localized in the cytoplasmic leaflet of microsomal vesicIes
EFFECT OF VARIOUS DRUGS PRODUCING CONVULSIVE SEIZURES ON RAT BRAIN GLYCEROLIPID METABOLISM
No full textConvulsive seizures were elicited in the rat by the injection of several different drugs (pyridoxal phosphate, bicuculline, penicillin and ouabain). Glycerolipid metabolism was studied after the intraventricular injection of [2-3Hlglycerol, which was incorporated into rat brain glycerides. The percentage of total lipid label found in each lipid class (phosphatidylethanolamine, PE; phosphatidylcholine, PC; phosphatidylserine, PS; phosphatidic acid, PA; phosphatidylinositol, PI; diacylglycerol (+ monoacylglycerol), DG and triacylglycerol, TG) depended on the time elapsed from the injection of the labeled precursor. The percent of total lipid radioactivity as PE and PC increased with time (3-60 rnin), whereas the opposite was true for
the radioactivity of DG and PA. The radioactivity of other lipid classes did not appreciabily vary between 3 and 60 min from the injection of the labeled glycerol.
The intraventricular administration of pyridoxal phosphate together with labeled glycerol decreased the percent of lipid radioactivity as PE and increased that as DG. This 'lipid effect' was detected also after the administration of other convulsants,
such as ouabain and penicillin. The intraperitoneal administratio
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