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G Porcellati

Publications and source records attributed to G Porcellati.

At least 55 records · Page 3Linked to original sources
PubMed1981

Glycerophospholipid metabolism in neuronal and glial cell-enriched fractions.

The metabolism of phospholipids in separated glial and neuronal cells has been reviewed in this paper. Lipids are more abundant in glia; on the other hand, in vivo experiments performed with labeled precursors have indicated that lipid turnover is faster in neurons (with the possible exception of oligodendroglia). Biosynthetic and catabolic enzymes of lipid metabolism have been studied in separated cells (mainly in neurons and astroglia) and have been shown to be almost always more active in neurons. Also base exchange is probably more active in these cells. Therefore the results of in vitro and in vivo experiments indicate that neurons are more active than astroglia in metabolizing glycerophospholipids.

Aging↗
PubMed1981

Occurrence and properties of phospholipases A1 of plasma membranes prepared from neuronal- and glial-enriched fractions of the rabbit cerebral cortex.

Exogenously added glycerophosphatides, specifically radioactively labelled either in the 1 or in the 2 position, were used to investigate the occurrence and properties of phospholipase A1 in plasma membranes prepared from neuronal- and glial-enriched fractions of rabbit brain. Phospholipase A1 activity was maximal at pH values ranging between 8.0 and 9.0 for the plasma membranes of both cell types. The enzyme activity was most abundant in the microsomal fraction, with a neuronal/glial ratio of about 2. The plasma membranes displayed about half the enzymic activity of the microsomal fraction, whereas only small amounts of phospholipase A1 were present in the neuronal and glial mitochondria. Investigations on the substrate specificity showed a different pattern for the enzyme of neuronal and glial origin. The release of labelled fatty acids from phosphatidylcholine by the neuronal plasma membrane phospholipase A1 decreased with increasing degree of unsaturation of the fatty acids at the 1 position. The presence of plasmalogens and plasmalogen precursors in the incubation mixture appreciably inhibited the hydrolysis of the corresponding diacyl compounds.

Animals↗
PubMed1981

The effect of some flavolignans on lipid synthesis in ethanol-intoxicated hepatocytes in primary culture.

Rat liver cells in primary culture have been used to investigate the effect of ethanol and of two flavolignans 3,7-dihydroxy-2-(1,4-benzodioxan-6-yl)chroman-4-one (I) and 3,7-dihydroxy-2-[(2,3-diphenyl)-1,4-benzodioxan-6-yl]chroman-4-one (II) on the incorporation of [2-3H]-glycerol into lipids. Ethanol produces a decrease of the incorporation of labelled glycerol into lipids, whereas at the longest times of incubation flavolignans have an opposite effect. Neutral lipid/phospholipid labelling ratio is modified by ethanol in favour of neutral lipids. This action is counteracted by both flavolignans, which are therefore able to hinder, at least partially, the actions of ethyl alcohol on liver lipid metabolism.

Animals↗
PubMed1981

Cyclic GABA-GABOB analogues. III - Synthesis and biochemical activity of new alkyl and acyl derivatives of 4-hydroxy-2-pyrrolidinone.

The synthesis of new N-substituted 4-hydroxy (III) and 4-acyloxy- or 4-alkoxy-2-pyrrolidinones (IV), as analogues of oxiracetam (III c), is reported. For this purpose, a convenient procedure for N-alkylation of the base-labile 4-hydroxy-2-pyrrolidinones (II a, c, d) was developed. Compounds (III) and (IV) were examined on phospholipid synthesis in brain microsomal membranes of rats, both in vivo and in vivo-in vitro, and on protein synthesis in brain slices. Results showed that only oxiracetam (III c), and to a lesser extent piracetam, are active both on phospholipid and brain protein synthesis.

Animals↗
PubMed1980

Increased activity of a phospholipid base-exchange system by the differentiation of neoplastic cells from the nervous system.

The activity of a base-exchange enzyme system, specific for the polar head-groups of brain phospholipids, was measured in both C 1300 mouse neuroblastoma (clone 41A3) and human glioma 138 MG cell lines. This base-exchange is thought to occur between free nitrogenous bases and membrane-bound phospholipids. The incorporation of free 14C-labeled ethanolamine and L-serine was determined in undifferentiated and morphologically differentiated cells. Both cell lines showed a significant increase in ethanolamine and L-serine incorporation upon differentiation.

Animals↗
PubMed1980

Synaptosomal phospholipid pool in rabbit brain and its effect on GABA uptake.

Rabbit synaptosomes have been used to study the effect of the base-exchange reaction in membrane phospholipids on gamma-aminobutyric acid (GABA) transport in vitro. The uptake of GABA was measured after a base-exchange reaction with ethanolamine, choline, or L-serine and after subsequent displacement of these exchanged moieties from lipid by bases of similar or different structures which were added to the synaptosomal medium. Serine incorporation stimulated GABA transport, but its displacement from membrane lipid by choline or ethanolamine induced an inhibition of GABA transport. Ethanolamine incorporation inhibited GABA transport, but its displacement of serine or choline resulted in stimulation of GABA uptake. Choline incorporation also inhibited GABA transport, although less than ethanolamine. The pool size of synaptosomal phospholipids, presumably involved in GABA uptake, accounted for 0.2 to 10% of the total content of membrane phospholipid. Thus, alteration of phospholipid composition by exchange of the lipid hydrophilic head-groups influences the extent of GABA uptake into rabbit synaptosomes.

Animals↗
PubMed1980

Synthesis of molecular species of glycerophospholipids from diglyceride-labeled brain microsomes.

Selectivity 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 rate.

Animals↗
PubMed1980

An improved procedure for the synthesis of 14C-labeled phosphatidylserine from cerebral phosphatidic acid.

A complete procedure to prepare a highly labeled phosphatidyl-L-[U-14C]serine possessing the same fatty acid composition of brain phospholipids is reported. CDP-diglyceride was synthesized by reaction between phosphatidic acid and CMP-morpholidate as the dicyclohexylcarboxamidium salt. The reaction between CDP-diglyceride and L-[U-14C]serine to produce the labeled phosphatidylserine was catalyzed by the CDP-diglyceride: L-serine phosphatidyl transferase (EC 2.7.8.8) from E. coli. A selective inhibition of phosphatidylserine decarboxylase activity, present as contaminant in the enzyme extract, was introduced in order to avoid a low yield of product. Traces of phosphatidylethanolamine (about 1%) were easily removed by preparative thin-layer chromatography. The yield of the labeled product was as high as 87% and it specific radioactivity was 170 mCi/mmol.

Animals↗
PubMed1980

The effect of chronic ethanol administration on membrane-bound enzymes of rat liver.

The chronic treatment with small amounts of ethanol associated with a fat-poor diet produces enzyme modifications in rat liver subcellular fractions. All the enzymic activities tested in this paper increased or remained unaffected after alcohol treatment. Part of the observed effects could be ascribed to the proliferation of the endoplasmic reticulum which follows to ethanol intoxication; the increase of some enzyme activities, in the plasma membranes of treated animals seems to be probably due to modification of the environment of the membrane.

Alcoholism↗
PubMed1979

[Preliminary data on activation of the enzyme of the metabolism of phospholipid bases in various areas of the brain].

The scope of this work was to study the effect of imydazole on base-exchange enzymic system in selected cerebral areas. We have previously demonstrated that imydazole was an activator of phosphatidylserine synthesis in slices of caudate nucleus. This effect lacked in the omogenate we had supposed that this activation by imydazole was not directed on base-exchange enzymic system, but was induced by decrease of cellular cyclic nucleotides amount. Therefore we have investigated the effect of dibutirril-AMPciclic in selected cerebral areas. In addition it was useful to state if activation by imydazole was area-specific or not.

Animals↗
PubMed1979

Quantitative evaluation of two pathways for ethanolamine phosphoglyceride biosynthesis in rat brain in vivo.

[3H]Ethanolamine and [32P]orthophosphate were injected intraventricularly into adult female rats. At varying time intervals after the injection (1--10 min), the animals were killed by means of a microwave apparatus, and phosphorylethanolamine and ethanolamine phosphoglycerides were extracted from the brains and counted after separation. The kinetic constants for phosphorylethanolamine incorporation into ethanolamine lipids were calculated both from 3H data and from 32P data. From our results, it seems that base exchange reactions for ethanolamine incorporation into ethanolamine lipids are a pathway active in brain in vivo.

Animals↗
PubMed1979

Activity and subcellular distribution of phospholipase A1 from neuronal cell-enriched fractions of the rabbit cerebral cortex.

Glycerophosphatides, specifically labeled either in the 1 or in the 2 position, were used to measure the activity of neuronal phospholipase A1 and to investigate the subcellular distribution of the enzyme. The microsomes were found to possess the highest phospholipase activity, with a threefold increase as compared to the cell homogenate. A considerable enzymatic activity could still be observed in the plasma membranes isolated from the neuronal-enriched cell fraction. Microsomal phospholipase possessed the highest activity with phosphatidylcholine, whereas phosphatidylserine was cleaved at a much lower rate. The rate of release of labeled fatty acids from the substrates by the microsomal phospholipase decreased with increasing degree of unsaturation of the fatty acids at the 1 position. The presence of plasmalogens and of alkylacyl analogues in the incubation mixture caused an appreciable inhibition of the hydrolysis of the diacyl glycerophosphatides.

Animals↗