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Biomedical subjects

G Arienti

Publications and source records attributed to G Arienti.

At least 55 records · Page 3Linked to original sources
PubMed1988

Incorporation of glycerol and ethanolamine into glycerophospholipid in rat brain areas during bicuculline-induced convulsive seizures.

The effect of bicuculline-induced convulsive seizures on lipid metabolism has been studied in four brain areas (cerebellum, cerebral cortex, hippocampus, and brainstem) using [2-3H]glycerol and [1,2-14C]ethanolamine as radioactive lipid precursors administered simultaneously with bicuculline. Twelve minutes after the administration, the uptake of radioactivity depended both on brain area and treatment, being generally higher in convulsing rats. The uptake of glycerol was influenced to a larger extent than that of ethanolamine and increased during convulsions, but its incorporation into lipids did not. In contrast, the amount of ethanolamine incorporated into lipids increased during bicuculline-induced seizures. The difference in behavior of glycerol and of ethanolamine is also indicated by the decrease of the 3H/14C ratio of phosphatidyl-ethanolamine in various brain areas during convulsions. It is, therefore, evident that the metabolism of the two precursors is affected differently by seizures.

Animals↗
PubMed1987

Factors affecting the reaggregation of rat brain microsomes solubilized with octyl glucoside and their relationship with the base-exchange activity of reaggregates.

Rat brain microsomal membranes disaggregated by exposure to octyl glucoside were recovered by centrifugation after dialytic removal of the detergent. The composition of the dialysis medium (divalent cations, pH) was important to this effect; indeed, the reaggregation process which occurred during the dialytic step required the presence of either Ca2+ or Mg2+ and a slightly acidic pH. The lipid protein/ratio and choline and ethanolamine base-exchange of recovered particles depended on the conditions of dialysis although their lipid composition did not. The lipid composition of membranes was also varied by adding PE or PC to octyl glucoside-microsome suspensions. This treatment produced reaggregates possessing a low content of cholesterol and varying PC/PE ratios. Both choline and ethanolamine base-exchange activities were related to this parameter.

Animals↗
PubMed1987

Glycerol incorporation into brain lipids in rat pups born to ethanol-intoxicated dams.

The incorporation of labeled glycerol into glycerolipid of rat brain was influenced by the age of the animal (2-month-old vs. newborn); indeed, 12 min after the administration, diglyceride was the most heavily labeled glycerolipid in the newborn brain, whereas the labeling of glycerophospholipid was highest in the adult. Various amounts of ethanol (0% to 36% of total energy intake) were administered to pregnant female rats, and the brains of their pups were examined for the ability to incorporate labeled glycerol into glycerolipid. The radioactivity incorporated into lipid diminished with increasing the amounts of alcohol consumed. The labeling pattern of lipid classes was also influenced; indeed, the radioactivity of diglyceride decreased markedly, whereas that of triglyceride and glycerophospholipid was affected to a lower degree. The distribution of radioactivity among different phospholipids also varied with age; on a percent basis, phosphatidylcholine was labeled less and phosphatidylinositol was labeled more in the newborn than in the adult. Ethanol influenced the pattern of glycerophospholipid labeling, increasing the radioactivity of phosphatidylserine and decreasing that of phosphatidylinositol.

Age Factors↗
PubMed1987

Cerebellar metabolism of phosphatidylethanolamine and its water-soluble precursors during bicuculline-induced convulsive seizures.

The incorporation of labeled ethanolamine into phosphatidylethanolamine (PE) and its water-soluble precursors, phosphoethanolamine and CDP-ethanolamine, is measured in rat cerebella during the course of bicuculline-induced convulsive seizures. The labeling of CDP-ethanolamine and phosphoethanolamine diminishes 6 min after the administration of both bicuculline and radioactive ethanolamine whereas that of PE is unaffected in these conditions. Time is very important to this effect; indeed, no differences of the labeling of PE water-soluble precursors can be found in rat cerebellum of normal and convulsing animals 12 min after the administration. The cerebellar pool of CDP-ethanolamine doubles after 6 min of convulsions, which means that unlabeled CDP-ethanolamine forms from a non-radioactive source, such as lipid, may be through the reversal of the ethanolamine phosphotransferase reaction. This effect disappears 12 min after the injection of the convulsant.

Animals↗
PubMed1986

The reaggregation of rat brain microsomal membranes after the treatment with octyl-beta-D-glucopyranoside. A study on ethanolamine base-exchange.

The ethanolamine base-exchange activity of rat brain microsomes has been studied after treating the membranes with the non-ionic detergent n-octyl-beta-D-glucopyranoside. The detergent could solubilize membrane lipid and protein. The concentrations of the detergent and of membrane protein were both important for this effect. The presence of disaggregating concentrations of octylglucopyranoside in the base-exchange incubation mixture strongly inhibited the incorporation of radioactive ethanolamine into lipid; however, the removal of the detergent through dialytic procedures before assaying the base-exchange reaction restored the enzymic activity almost completely. As shown by exposing the membranes to trinitrobenzenesulfonic acid (TNBS), the phosphatidylethanolamine (PE) which was newly synthesized by base-exchange was also compartmented in the microsomal membrane. The treatment with the detergent after the base-exchange reaction abolished the compartmentation of the newly synthesized lipid. However, if microsomes were solubilized and the detergent was removed by dialysis before the assay of base-exchange, the reassembly of membranes occurred with a recovery of the compartmentation of the newly synthesized PE. The presence of Ca2+ in the dialytic medium was important for the preservation of base-exchange activity, probably affecting the reassembly of membrane components.

Animals↗
PubMed1986

Cerebellar metabolism of phosphatidylcholine and its hydrosoluble precursors during bicuculline-induced convulsive seizures.

The cerebellar incorporation of labeled choline into phosphatidylcholine (PC) and its hydrosoluble choline-containing precursors has been examined during the course of bicuculline-induced convulsive seizures. The labeling of phosphocholine and of PC diminished in these conditions whereas that of cytidine-5'-diphosphate choline (CDP-choline) was practically unaffected. Moreover, the cerebellar pools of phosphocholine and CDP-choline increased by 75-100% after 6 min of convulsions; these compounds were formed from lipid through the action of phospholipases or through the reverse action of choline phosphotransferase. From the data reported in this paper it should also be inferred that the cytidylyltransferase reaction was activated. It is therefore concluded that the cerebellar metabolism of PC and its precursors was affected in various ways by the bicuculline-induced convulsive seizures.

Animals↗
PubMed1986

Compartmentation of newly synthesized phosphatidylethanolamine in rat brain microsomes.

The 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 difluorodinitrobenzene 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.

Animals↗
PubMed1986

Ethanolamine base-exchange reaction in rat brain microsomal subfractions.

Crude microsomal fractions have been subfractionated by differential ultracentrifugation into subfractions A, B, and C, corresponding to light smooth, heavy smooth, and rough microsomal membranes, respectively. The purity and the vesiculation of the membranes were checked biochemically. Subfraction C showed the highest ethanolamine base-exchange activity, both on phospholipid and protein bases. The other two subfractions had roughly similar activities. The kinetic behavior of the enzyme activity, although anomalous, was similar in the three subfractions. Treatment of the vesicles with Pronase or with mercury-dextran produced inactivation of the ethanolamine base-exchange reaction in the three subfractions. These findings suggest that the active site of base-exchange activity would be localized on the external leaflet of the vesicles. Treatment of the membranes with trinitrobenzenesulfonic acid (TNBS) has shown that the newly synthesized phosphatidylethanolamine (PE) belongs to a pool easily reacting with the probe, independent of the subfraction investigated. On the other hand, the distribution of the bulk membrane PE reacting with TNBS differs in the three subfractions examined. It is concluded that the newly synthesized PE and probably the active site of the enzyme are on the external leaflet of the membrane in all subfractions and that the ethanolamine base-exchange reaction has similar properties in all subfractions.

Animals↗
PubMed1985

Effect of various drugs producing convulsive seizures on rat brain glycerolipid metabolism.

Convulsive 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 [2-3H]glycerol, 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 min), whereas the opposite was true for the radioactivity of DG and PA. The radioactivity of other lipid classes did not appreciably 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 administration of bicuculline affected lipid metabolism in cerebellum.

Animals↗
PubMed1985

Sidedness of phosphatidylcholine-synthesizing enzymes in rat brain microsomal vesicles.

The sidedness of CDP-choline:1,2-diradylglycerol choline phosphotransferase (EC 2.7.8.2) and of the choline base-exchange activity has been studied in rat brain microsomal vesicles. Proteases (trypsin and pronase) and mercury-dextran have been used as reagents for membrane surface components. All of them could inactivate both enzymes to a good extent, without affecting the morphology or the permeability to sucrose of the vesicles. It is therefore concluded that CDP-choline:1,2-diradylglycerol choline phosphotransferase and the choline base-exchange activity are localized on the outer surface of rat brain microsomal vesicles.

Animals↗
PubMed1984

The effect of pyridoxal phosphate-induced convulsive seizures on rat brain phospholipid metabolism.

The intraventricular injection of pyridoxal phosphate (PLP; 1 mumole/brain) to rats causes convulsive seizures beginning 3 min after injection and lasting for about 20 min. The incorporation of [2-3H] glycerol into rat brain glycerides has been studied to ascertain whether treatment with PLP affects the incorporation of label into various lipid classes. The labeling pattern of glycerides is changed by the administration of PLP. The observed alterations begin a few min after injection, together with the convulsive seizures. 1 h after the injection the pattern of labeling of brain glycerides returns to normal. Different glycerides are differently affected by PLP. This work demonstrates that the labeling of diglyceride increases whereas that of phosphatidylethanolamine decreases following PLP administration.

Animals↗
PubMed1984

The effect of polyunsaturated phosphatidylcholine on lipid synthesis in ethanol-intoxicated cultured rat hepatocytes.

Rat liver cells in primary culture have been used to study the influence of ethanol and of a polyunsaturated phosphatidylcholine preparation from soybean lecithin on glycerol incorporation into lipids. Ethanol decreases the incorporation of glycerol into choline and ethanolamine phosphoglycerides and increases that into diglyceride, either when added to the incubation medium or when administered to rats prior to hepatocyte preparation. The addition of the polyunsaturated lipid material (EPL) is able to counteract the effect of ethanol modifying the labeling of glycerol in favour of phospholipids.

Animals↗
PubMed1983

Compartmentation of membrane phosphatidylethanolamine formed by base-exchange reaction in rat brain microsomes.

The compartmentation of membrane phosphatidylethanolamine (PE) formed by base-exchange reaction in rat brain microsomal vesicles has been investigated. After labelling membrane PE by base-exchange in vitro, microsomal vesicles 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 concluded that PE labelled by base-exchange is completely localized in the cytoplasmic leaflet of microsomal vesicles.

Animals↗
PubMed1983

Cholinephosphotransferase activity in human platelets.

Disrupted human platelets possess a cholinephosphotransferase activity (EC 2.7.8.2) whose properties have been studied in this work. The labeling of choline glycerophospholipid (CGP) from radioactive cytidine-5'-diphosphate choline (CDP-choline) in vitro shows a maximum at pH 8.0 (using Hepes [4-(2-hydroxyethyl)-piperazine-1-ethane-2-sulfonic acid] as a buffer) and is stimulated by Mn2+, Mg2+ and diacylglycerol. The enzymic activity is inhibited by Ca2+. The dependence of human platelet cholinephosphotransferase upon CDP-choline concentration does not follow the Michaelis-Menten equation. CMP strongly inhibits the reaction. The functional implications of this newly discovered platelet activity are briefly considered.

Blood Platelets↗