Biomedical subjects

G Arienti

Publications and source records attributed to G Arienti.

At least 37 records · Page 2Linked to original sources

PubMed1996

Formylcolchicine bound to lactosaminated serum albumin is a more active antifibrotic agent than free colchicine.

Liver fibrosis was induced by chronically (7 weeks) administering CCl4 to rats. Animals were divided into four groups: (a) controls, (b) treated with CCl4 alone, (c) treated with CCl4 and colchicine and (d) treated with CCl4 and formyl-colchicine bound to lactosaminated serum albumin (FC-LASA). Liver dysfunction was monitored by biochemical tests (alkaline phosphatase [ALP], gamma-glutamyltransferase [gamma GT], aspartate and alanine transaminases [AST and ALT], albumin and total bilirubin). Fibrosis was evaluated by determining hydroxyproline and by microscopic examination. The exposure to CCl4 produced major alterations of liver structure and collagen deposition. These effects were partially counteracted by colchicine and to a greater extent by FC-LASA. Morphological findings paralleled biochemical data. The information reported here indicates that colchicine has an antifibrotic activity on the liver of intoxicated rats and that FC-LASA is more active than colchicine itself as an antifibrotic agent.

Amino Sugars↗

PubMed1996

Red blood cell ghosts are affected by adrenoleucodystrophy.

X-linked adrenoleucodystrophy is a disorder occurring in different clinical forms, characterized by adrenal, gonadal and nervous system dysfunction. The basis of the illness is a derangement of the peroxisomal system necessary to oxidize very long-chain fatty acids that accumulate in various tissues. The diagnosis relies on clinical signs and symptoms and on biochemical findings. The six reported cases presented idiopathic adrenal insufficiency. We measured the lipid composition of red blood cell (RBC) ghosts of patients and control subjects. The distribution of phosphorus among phospholipid classes was unaffected; we could not demonstrate any differences between the fatty acid patterns of RBC membrane, either in total lipid extracts or in separated lipid classes. However, we found an increase in total lipid (both phospholipid and cholesterol), in membrane viscosity and in the Na+/K(+)-dependent ATPase. Therefore, we report four main findings on ghosts in adrenoleucodystrophy patients: (a) very long-chain fatty acids do not accumulate; (b) the lipid-protein ratio increases; (c) fluidity decreases; and (d) the activity of ATPase increases. The last finding is proposed as a possible biochemical marker of the illness. We conclude that adrenoleucodystrophy affects deeply RBC membranes.

Adrenoleukodystrophy↗

PubMed1995

Liver alcoholic cirrhosis and spur-cell (acanthocytic) anaemia. A study of erythrocyte ghost composition and fluidity.

BACKGROUND: The occurrence of spur-cell anaemia in the course of cirrhosis is rare. Alterations of the lipid composition and fluidity of erythrocyte (RBC) ghosts may be present and participate in the phenomenon. METHODS: A 59-year-old male patient with alcoholic cirrhosis developed severe spur-cell haemolytic anaemia before death. We compared his RBC ghosts with those of 10 cirrhotic patients and used a group of 9 healthy subjects as controls. RESULTS: The cholesterol to protein ratio was higher in cirrhotic patients; besides, they had less unsaturated fatty acid. The ratio of phospholipid phosphorus to protein did not change; yet, the distribution of phosphorus among phospholipid classes was altered. No difference in 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy (membrane fluidity) was observed between the ghosts of cirrhotic patients and those of healthy people. However, the ghosts of the patient with spur-cell anaemia were more rigid than those of either group. CONCLUSIONS: The values of most variables of cirrhotic patients' ghosts lay between those of healthy subjects and those of the one who developed spur-cell anaemia. It is concluded that some homeostatic mechanisms must control fluidity during cirrhosis; in some cases alterations are particularly great, and fluidity cannot be maintained.

Acanthocytes↗

PubMed1995

Derivatives of colchicine preferentially taken up by the liver: an approach to the treatment of liver fibrosis.

The distribution in the mouse of colchicine and of two colchicine derivatives, namely formylcolchicine/formylated serum albumin (FC/FTSA) and formylcolchicine/lactosaminated serum albumin (FC/LASA), was studied. The presence of radioactivity after the intravenous injection of labelled colchicine or of its derivatives was determined in liver, small intestine, kidney and blood. The radioactivity of the derivatives was better retained than that of colchicine. The derivatives accumulated in the liver to a much greater extent than colchicine, but were scarcely present in the gut. Tropism towards the liver might be important for the use of FC/LASA and FC/FTSA to control liver fibrosis.

Animals↗

PubMed1994

The effect of maternal ethanol intoxication on erythrocyte ghost fluidity in new-born rat pups.

We administered ethanol to pregnant rats and determined cholesterol, lipid phosphorus and fluorescence anisotropy of diphenylhexatriene (DPH) and of trimethylaminophenyl hexatriene (TMA-DPH) in erythrocyte ghosts of newborn pups and of their mothers. Cholesterol content was different in dams and pups and changed after treatment. Age, but not ethanol, affected lipid phosphorus. Either age (dams versus pups) or treatment affected the curves of DPH fluorescence anisotropy (r) versus temperature (T), but those of TMA-DPH did not change, indicating that only the inner core of the membrane was influenced. We conclude that adult and erythrocyte ghosts differed for the lipid composition, for the dependence of r on T (for DPH) and for the effects of ethanol dosing on these parameters.

Animals↗

PubMed1993

Rat brain microsome fluidity as modified by prenatal ethanol administration.

The fluorescence anisotropy (r) of diphenylhexatriene (DPH) and of trimethylamino-diphenylhexatriene (TMA-DPH) as a function of temperature (10 degrees to 54 degrees C) was measured in brain microsomes of newborn rats prenatally exposed to ethanol. In this temperature range, the relationship between r and T was linear. The addition of ethanol in vitro to microsomal suspensions influenced the slope of the line of r versus T only when DPH was used as a probe and with high concentrations of the alcohol (> or = 0.3 M). The administration of ethanol (18% of total energy intake) in vivo to pregnant dams affected the slope of the lines of r versus T of the microsomes of pups, either using DPH or TMA-DPH as probes. The slope was also affected in brain microsomes obtained from dams, yet, only with TMA-DPH and in the opposite sense than in pups. We conclude that the effect of prenatal exposure to ethanol depended on metabolic alterations induced by the alcohol and not on its detergent properties for the following reasons: (a) The effects in vitro and in vivo were different and (b) in vitro effects could be obtained only with high concentrations (> or = 0.3 M), whereas in vivo effects were produced by small doses of ethanol. Besides, the effects of the administration of the alcohol in vivo were different in adult and intrauterine life.

Animals↗

PubMed1993

Transport of phosphatidylserine from microsomes to the inner mitochondrial membrane in brain tissue.

Phosphatidylserine was labeled by incubating rat brain homogenates with [3-14C]serine in the presence of Ca2+ (base-exchange conditions). Some labeled phosphatidylethanolamine also forms, in spite of the inhibition of Ca2+ on phosphatidylserine decarboxylase. Phosphatidylserine labeling and decarboxylation also occur on incubating a mixture of purified mitochondria and microsomes, suggesting that no soluble factors are necessary for the synthesis and the decarboxylation of phosphatidylserine. Ca2+ favors the transfer of phosphatidylserine from microsomes (where it forms) to mitochondria (where it is decarboxylated). The specific radioactivity of the phosphatidylserine transferred to mitochondria is higher than that of microsomal phosphatidylserine. This finding supports the hypothesis that the lipid is compartmentalized in microsomes and that radioactive, newly synthesized phosphatidylserine is much better exported than the bulk of microsomal phospholipid.

Animals↗

PubMed1993

The fate of phosphatidylethanolamine formed by decarboxylation in rat brain mitochondria.

In the liver, the synthesis and the decarboxylation of phosphatidylserine (PS) are a part of a metabolic cycle forming choline from serine. Yet, in the brain, the methylation of PE to phosphatidylcholine is a minor path. Therefore it is possible that the decarboxylation of PS has different biological meanings in the two organs. In this paper, we follow the formation and the fate of radioactive PE; to this purpose, we load brain mitochondria with PS by incubating cell homogenates with labelled serine in base-exchange conditions. Then, we isolate mitochondria and incubate them for PS decarboxylase. We also subfractionate mitochondria to investigate the distribution of PE in inner and outer membranes. We conclude that newly formed PE slowly moves from its site of synthesis (inner mitochondrial membranes). Besides, it reacts better with TNBS and with FLA than the pre-existing PE. This suggests that the newly-synthesised lipid does not mix quickly with the rest of mitochondrial PE. Therefore, our data demonstrate that the fate of PE formed through the decarboxylation path in the brain is different from that reported for the liver where newly-formed PE is rapidly exported to outer mitochondrial membranes.

Animals↗

PubMed1992

Acetyl-L-carnitine influences the fluidity of brain microsomes and of liposomes made of rat brain microsomal lipid extracts.

The fluorescence anisotropy (r) of diphenylhexatriene (DPH) was measured in different preparations (bovine spinal cord phosphatidylserine liposomes, rat brain microsomes, liposomes made with rat brain microsomal lipid having different phospholipid:cholesterol ratios) at temperatures ranging from 10 degrees to 55 degrees C. Phosphatidylserine liposomes exhibited an exponential relationship of r versus temperature, whereas the relationship shown by microsomes and liposomes prepared with microsomal lipid extracts was a linear one. The removal of protein and high phospholipid:cholesterol ratios decreased the slope of the lines (fluidity increased), although the intercept was unaffected. This means that differences were better appreciated at high temperatures and were well evident at 37 degrees C. Acetyl-L-carnitine decreased r in rat brain microsomes and in liposomes made with microsomal lipids with different phospholipid:cholesterol ratios. The fluidifying effect of acetyl-L-carnitine was mild but statistically significant and could explain, at least in part, the data reported in the literature of acetyl-L-carnitine acting on some parameters affected by ageing. Besides, acetyl-L-carnitine seemed to oppose the changes of viscosity due to lipid peroxidation, which has been reported to increase in ageing and dementia. L-carnitine shares the properties of its acetyl ester, but only in part.

Acetylcarnitine↗

PubMed1992

The transfer of phosphatidylserine from rat brain microsomes to mitochondria is regulated by microsomal lipid pattern.

We label the phosphatidylserine of rat brain microsomes through the base-exchange reaction and study the export of this lipid to mitochondria in a reconstituted system. We fuse microsomes to liposomes to vary the lipid composition of donor membranes and investigate the effect of membrane lipid pattern on phosphatidylserine movement. The specific radioactivity of the phosphatidylserine transferred to mitochondria is higher than that of microsomal phosphatidylserine. This finding supports the hypothesis that the lipid is compartmented in microsomes and that the radioactive, newly synthesized phosphatidylserine is much better exported than the bulk of microsomal phospholipid. The transfer of phosphatidylserine from microsomes, where it forms through the base-exchange reaction, to mitochondria, where it decarboxylates to phosphatidylethanolamine, is enhanced by phosphatidylserine itself, and by other lipid classes. This is proposed as a part of a possible mechanism for regulating phosphatidylserine metabolism in the brain.

Animals↗

PubMed1992

Serine base-exchange in rat liver microsomes: effect of phospholipids.

We enriched liver microsomes in lipid classes and molecular species disrupting membranes with octyl glucoside and reassembling them by detergent removal. Phosphatidylethanolamine incorporated into membranes better than phosphatidylserine or phosphatidylcholine. In addition, the degree of incorporation depended on the unsaturation of fatty acyl-chains. The enrichment of the membranes with phosphatidylserine or phosphatidylcholine inhibited serine base-exchange, whereas the addition of phosphatidylethanolamine usually stimulated it. The effect of exogenous lipids also depended on molecular species; egg yolk phosphatidylcholine and dipalmitoyl phosphatidylcholine inhibited base-exchange whereas the effect of palmitoyl-oleoyl phosphatidylcholine depended on the incorporated amount. The degree of unsaturation also modulated the effect of phosphatidylethanolamine.

Animals↗

PubMed1991

Regulation of liver base-exchange activity by acidic phospholipids.

Liver microsomes were enriched in liposomal acidic lipids by Ca(2+)-dependent fusion of liposomes at pH 7.0. The extent of fusion was monitored by the transfer of radioactive cholesteryl oleate. The enrichment of membranes in phosphatidylserine inhibited ethanolamine base-exchange, whereas the fusion with phosphatidylinositol inhibited both ethanolamine and serine base-exchange reactions. In contrast, these two phospholipids had scarce effects on choline base-exchange. Phosphatidic acid did not suppress any of the three base-exchange activities. Possible functional implications are discussed.

Animals↗

PubMed1991

The fusion of liposomes to rat brain microsomal membranes regulates phosphatidylserine synthesis.

Rat brain microsomal membranes were fused to liposomes prepared with several pure lipids, namely, phosphatidylserine, phosphatidylinositol, phosphatidic acid, and mixtures of phosphatidic acid and phosphatidylcholine or phosphatidylethanolamine. The fusion between liposomes and microsomes was measured by the octadecyl rhodamine B chloride method. The extent and other properties of fusion largely depend on the lipid used to prepare liposomes; phosphatidic acid and phosphatidylinositol fuse more extensively than other lipid classes. The activity of serine base exchange is affected by the fusion between rat brain microsomes and lipids. It is strongly inhibited by phosphatidylserine, but it is activated by phosphatidic acid. The inhibition produced by phosphatidylserine on its own synthesis is proposed as a mechanism for controlling the formation of phosphatidylserine in rat brain microsomes.

Animals↗

PubMed1990

The effect of membrane lipid molecular species on rat brain base-exchange reactions: an appraisal of phosphatidylserine and of polyunsaturated phosphatidylcholine.

Rat brain microsomal membranes were solubilized with octyl glucoside and reassembled by removing the detergent. The composition of reconstituted membranes was modified by adding exogenous lipid to the detergent-membrane mixtures. The base-exchange reactions were sensitive to these procedures. The inhibiting or activating capacity of added lipid was related to the charge of polar head groups; indeed, the addition of phosphatidylserine always resulted in inhibition and that of phosphatidylcholine very often in activation. The addition of phospholipid possessing unsaturated acyl chains inhibited less (or activated more) serine and choline base-exchange than the addition of saturated species. It is concluded that phosphatidylserine and polyunsaturated phosphatidylcholine have opposite effects on base-exchange.

Animals↗

PubMed1989

Effect of pyridoxal 5'-phosphate and valproic acid on phospholipid synthesis in neuroblastoma NA.

Phospholipid metabolism in neuroblastoma cells in monolayer culture after acute exposure to pyridoxal phosphate (PLP) has been studied. (a) A strong depression of the rate of biosynthesis of cellular phospholipids from labeled choline and ethanolamine, is demonstrated in neuroblastoma cells grown in culture media containing PLP. (b) Valproic acid reverses the effect of PLP on ethanolamine and choline incorporation into cell lipid. Other anticonvulsants (clonazepam, diazepam, carbamazepine, diphenylhydantoin and ethosuximide) have little or no effect on reversing the inhibition of lipid synthesis produced by PLP. (c) PLP decreases the cellular uptake of choline. This effect might be responsible for the decreased lipid synthesis and is partially reversed by valproic acid. (d) The energy charge of the cell is not affected by either PLP or valproic acid, but it is diminished by the two compounds together. (e) The degradation of choline lipids is decreased by PLP and valproic acid. The hydrolysis of phosphocholine and the outflow of choline from cultured cells is also affected by the drugs. Variations of ethanolamine and choline transport should not be due to any effects of PLP or valproic acid on the lipid phase of the membranes since these molecules have no effect on the permeability of liposomes. (f) It is concluded that ethanolamine and choline lipid metabolism in cultured neuroblastoma cells is influenced by PLP and/or valproic acid, probably through a mechanism involving the transport of precursors across the membrane, although other mechanisms cannot be ruled out.

Energy Metabolism↗

PubMed1989

Fusion of liposomes and rat brain microsomes examined by two assays.

Liposomes are prepared from rat brain microsomal lipid and loaded with either Tb3+ or dipicolinic acid (DPA) to test fusion with the Tb-DPA assay. They are also loaded with octadecyl Rhodamine B chloride (R18) to test fusion with the R18 assay. The addition of either Ca2+ or Mg2+ to loaded liposomes develops fluorescence with both assays. The fluorescence elicited by Mg2+ is similar to that elicited by Ca2+ if assessed with R18, but much higher if determined by Tb-DPA. The Ca2(+)-dependent fluorescence of the Tb-DPA complex is not suppressed by the addition of EDTA, and therefore it is internal to vesicles. The contrary is true for the Mg2(+)-dependent fluorescence. Rat brain microsomes can be disrupted by adding octylgucoside and reconstituted by removing it by dialysis. We use this procedure to load microsomes with DPA. This allows the use of the Tb-DPA assay for testing the fusion of rat brain microsomes. Reconstituted microsomes fuse with liposomes. This fusion has characteristics similar to those of liposome-liposome fusion. However, no microsome-microsome fusion could be detected with either method. The two methods give different results, owing to the chemical properties of the assays. Indeed Tb-DPA implies the retention of vesicle content, whereas this is not required by the R18 assay.

Animals↗

PubMed1989

Effect of subconvulsive doses of bicuculline on the incorporation of radioactive precursors into glycerolipids in rat brain areas.

Bicuculline (either 25 mumol or 12.5 mumol/kg body wt) was administered to rats by intraperitoneal route. Animals treated with 25 mumol/kg experienced convulsions, whereas those receiving 12.5 mumol/kg did not. Controls received saline instead of the drug. Radioactive precursors [2-3H] glycerol and/or [1,2 14C] ethanolamine were injected into cerebral ventriculi simultaneously with bicuculline and the rats were killed 12 min afterwards. Their brains were dissected by hand into four parts (cerebellum, brain stem, hippocampus, cerebral cortex) and the labeling of lipid classes determined after extraction and separation. Although glycerol was incorporated into lipid better than ethanolamine in all areas, the fate of the injected radioactive precursors varied according both to area and treatment. The lowest uptake of radioactivity was in the cerebral cortex and the highest in the brain stem and hippocampus. Moreover, the administration of bicuculline influenced the distribution of radioactivity among lipid classes; these variations, however, were not dependent on the administered doses of bicuculline. We conclude that the effects on glycerolipid metabolism observed in convulsing animals are due to several causes including alterations of systemic parameters (hypertension, hypoxia, etc.). The distribution of glycerol label between phospholipid and neutral lipid is proposed as a biochemical model for the study of convulsive and subconvulsive states.

Animals↗

PubMed1988

The incorporation of intracranially injected glycerol into brain glycerides of young rats born to normal and alcohol-fed mothers.

Growth alters the ability of rat brain to incorporate [2-3H]glycerol into glycerides; indeed, 12 min after the intracranial administration of the precursor, diglyceride becomes more radioactive in newborn than in 19-day-old brain, the reverse being true for total glycerophospholipid and triglyceride. The ratio between the labeling of phospholipid and that of neutral lipid in the experimental conditions described in this paper is proposed as a marker of brain maturity. The distribution of labeling among phospholipid classes also varies with age, and the increase of labeling in total phospholipid occurring with increasing age is almost entirely due to phosphatidylethanolamine and phosphatidylcholine. The metabolism of myelin lipids might be responsible for these age-dependent variations. The administration of ethanol to dams during pregnancy and lactation alters the distribution of the label among neutral glycerolipid and total glycerophospholipid in an age-dependent manner. The labeling distribution among phospholipid classes is also affected.

Aging↗