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G Porcellati

Publications and source records attributed to G Porcellati.

At least 73 records · Page 4Linked to original sources
PubMed1979

Synthesis of phosphatidylcholine and phosphatidylethanolamine at different ages in the rat brain in vitro.

The de novo synthesis of choline and ethanolamine phosphoglycerides in brain microsomes from 18 month-old male rats was investigated in vitro by using labeled cytidine-5'-diphosphate choline and cytidine-5'-diphosphate ethanolamine as lipid precursors. The rate of synthesis of the two phospholipid classes was found to be noticeably decreased, as compared to that of adult animals. The addition of exogenous diacyl glycerols to microsomes from ageing rat brain brings the rate of synthesis nearly to the adult levels. The synthesis of choline and ethanolamine phosphoglycerides is not affected in the liver microsomes of ageing rats. The molar distribution of fatty acids in brain microsomal diacyl glycerols of ageing rats is noticeably different from that of adult animals. The content of monoenoic and dienoic species is increased, whereas that of the tetraenoic species is decreased. Base exchange reaction for choline and ethanolamine incorporation into respective phospholipids is not affected in the brain microsomes of the aged rats.

Aging↗
PubMed1979

The effect of acute ethanol administration on phosphorylcholine uptake and metabolism in rat liver slices.

Liver slices obtained from normal and acutely ethanol-intoxicated rats were incubated with labelled choline plus unlabelled orthophosphate or labelled phosphorylcholine (PC). After variable times of incubation hydrosoluble compounds and choline phosphoglycerides (CPG) were extracted from the tissue and analyzed. When compared to controls, the slices obtained from intoxicated livers accumulated more PC and synthesized more CPG when incubated with PC; on the other hand, when incubated with choline, they accumulated less PC. From these results it can be concluded that PC is a better lipid precursor in intoxicated livers, than in normal ones. In any case CPG becomes better labelled after incubation with choline than with PC; base-exchange could be liable for this result.

Alcoholic Intoxication↗
PubMed1978

Studies of rat brain choline ethanolamine phosphotransferases using labeled alkylacylglycerol as substrate with evidence for reversibility of the reactions.

Cholinephosphotransferase activity in brain microsomes may be assayed with labeled alkylacylglycerols or with CDP-choline with label in the phosphocholine with nearly identical results. The direct linear plot method was used for evaluation of Michaelis-Menten kinetic parameters. Most of the cholinephosphotransferase activity is in microsomes and a stimulatory factor seems to be present in the cytosol. Incubation of microsomes with labeled alkylacylglycerols and CDP-choline, in the initial absence of CDP-ethanolamine, produced labeled ethanolamine glycerophospholipids as well as labeled choline glycerophospholipids. Since the labeling of ethanolamine glycerophospholipids was increased by the addition of CMP, the labeling was probably due to the reversal of ethanolamine phosphotransferase to yield CDP-ethanolamine produced by the choline phosphotransferase reaction. Cholinephosphotransferase was reversed more readily than ethanolaminephosphotransferase in brain as it is in liver (Kanok and Ohno, 1973). Only trace quantities of plasmalogens were formed with labeled alkylacylglycerols. Previous results of plasmalogen labeling from labeled CDP-nucleotides were apparently due to reversal of phosphotransferase reactions. Alkylacylglycerophospholipids are not good substrates for plasmalogen formation, even when they are incorporated into microsomes.

Animals↗
PubMed1978

Membrane-bound base-exchange reactions in animal tissues.

The calcium-stimulated incorporation of ethanolamine, L-serine and choline into rabbit synaptosomal phospholipids in vitro has been investigated. The synaptosomal membranes were prelabelled in vitro in their choline-, ethanolamine- or serine-phosphoglycerides by base-exchange and then chasing experiments were performed by displacing the lipid-bound base by ethanolamine, choline or L-serine labelled with a different isotope. The results indicate that membrane phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine are substrates for the exchange with all the three mentioned bases. A very small phospholipid pool (0.5-2% of the total available pool) is active in the calcium-dependent exchange between membrane phosphatidylcholine or phosphatidylethanolamine and free bases, whereas the pool of exchanging phosphatidylserine is sensibly larger (2-9%). In another series of experiments the effect of the base-exchange reaction upon the production of cyclic-AMP at the level of rat brain synaptic membranes has been examined. An exchange with ethanolamine produces a significant decrease of the NaF-stimulated production of the cyclic nucleotide, whereas it increases the noradrenaline-induced production. With some exceptions, the exchange with L-serine produces opposite effects. The possible physiological importance of phospholipid pool at the synaptosomal level is discussed.

Adenylyl Cyclases↗
PubMed1978

A possible mechanism for cholesteryl ester formation during demyelination: lecithin:cholesterol acyltransferase (LCAT) activity in rat brain.

Lecithin:cholesterol acyltransferase (LCAT) activity has been examined in the rat by using a brain homogenate preparation as the phospholipid substrate and blood plasma as the enzyme source. LCAT activity was detected on using 60 mul of serum onwards. Successive experiments have also shown that LCAT activity is present in the edematous rat brain tissue homogenate when incubated with inactivated rat plasma as substrate. The results are discussed in relation to cholesteryl ester accumulation in brain during demyelinating diseases.

Animals↗
PubMed1977

Biosynthesis of rat brain phosphatidylethanolamines from intracerebrally injected ethanolamine.

[2-3H]Ethanolamine was injected intracerebrally into male rats and the brains of the animals immediately removed by particular procedures at regular intervals over the first 1200 sec. The incorporation of radioactivity into brain phosphorylethanolamine, cytidine-5'-diphosphate (CDP) ethanolamine and phosphatidylethanolamines was examined and quantitated. The nature of phosphatidylethanolamine molecular subspecies, which became labelled, was also investigated after isotope administration. Phosphorylethanolamine, CDP-ethanolamine and phosphatidylethanolamines were all labelled already 5 sec after the administration of labelled ethanolamine. The specific radioactivities of different phosphatidylethanolamine molecular subspecies varied according to the time elapsed from the injection to the sacrifice of the animals. This last result, together with the data on time course of labelling of ethanolamine phosphoglycerides and their precursors, provides indications that this base may be incorporated into lipids not only by net synthesis pathway, but also by base-exchange reaction.

Animals↗