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Biomedical subjects

A Cantafora

Publications and source records attributed to A Cantafora.

At least 73 records · Page 4Linked to original sources
PubMed1992

Altered insulin receptor processing and membrane lipid composition in erythrocytes of cirrhotic patients.

Insulin binding and insulin receptor down-regulation characteristics were evaluated, as well as cholesterol and phospholipid levels in erythrocytes from 22 patients with liver cirrhosis. These parameters were correlated with clinical characteristics and with scores related to severity of the liver injury. Nine healthy subjects were studied as a control group. It was observed that insulin binding was generally greater in patients than in controls because of an increase in surface insulin receptor numbers, rather than from a change in receptor affinities. In cirrhotic patients, the erythrocyte insulin receptors did not undergo the normal down-regulation process but, in most cases, increased in response to insulin incubation. The alterations in insulin processing characteristics were more frequent in patients with alcoholic cirrhosis and more severe liver impairment and correlated with the changes in the lipid composition of erythrocyte membranes. In particular, an increase in the cholesterol to phospholipid molar ratio and a decrease in polyunsaturated fatty acid content of phospholipids in erythrocyte membranes of cirrhotic patients was associated with impairments in insulin receptor processing. Similar changes in insulin receptor processing were observed when the molar ratio of cholesterol to phospholipid in normal erythrocytes was modified in vitro by incubation with cholesterol-rich liposomes.

Adult↗
PubMed1991

The cesium-induced delay in myoblast membrane fusion is accompanied by changes in cellular subfraction lipid composition.

We have recently demonstrated that the delay in myoblast membrane fusion induced by cesium is accompanied by changes in isolated membrane lipids (Santini, M.T., Indovina, P.L., Cantafora, A. and Blotta, I. (1990) Biochim. Biophys. Acta 1023, 298-304). In the present study, we have investigated changes in the lipid profile of total cell homogenates and microsomal membrane fractions during myoblast membrane fusion as well as the effects that addition of cesium may have on these lipid variations in order to try to understand the production and translocation of lipids during this myogenic process. The data presented here indicate that the lipid composition of cell homogenates and microsomes varies in a different manner from isolated plasma membranes during myogenic fusion. In addition, cesium affects, in a different manner, the normally-occurring lipid production and distribution which takes place in each subcellular fraction.

Animals↗
PubMed1991

Gallstones in cystic fibrosis: a critical reappraisal.

Radiolucent gallstones are common in young adults with cystic fibrosis. In the mid-1970s, it was suggested that gallstones are made of cholesterol, but this hypothesis has never been tested. Several recent studies have shown that the detection of cholesterol monohydrate crystals in bile has high sensitivity and specificity for the diagnosis of cholesterol gallstones. We therefore used this approach to study 17 young adults with cystic fibrosis, 10 of whom had radiolucent gallstones. The two groups of patients were comparable in age and gender (all patients but one were male). Duodenal bile was obtained after gallbladder contraction with intravenous cerulein; it was used for lipid and protein chemistry studies and for polarizing microscopy. The latter was performed both in whole bile and in the postultracentrifugation (100,000 g) sediment. Bile cholesterol saturation did not significantly differ between patients with (1.21 +/- 0.28) or without gallstones (0.99 +/- 0.54). Slight cholesterol supersaturation was found in 7 of 10 gallstone and three of seven nongallstone patients. At no time were cholesterol crystals detected in either the group, even after bile ultracentrifugation. Two more cystic fibrosis patients with gallstones died of severe bronchopneumopathy, and small pigment gallstones were obtained at autopsy. At stone analysis, cholesterol content was 44% and 28% of dry weight, respectively. Infrared spectroscopy of stone powder was compatible with the presence of calcium bilirubinate and proteins as major components. We conclude that radiolucent gallstones of cystic fibrosis are not of the conventional cholesterol type.

Adolescent↗
PubMed1991

Impaired hepatic handling and processing of lysophosphatidylcholine in rats with liver cirrhosis.

Lysophosphatidylcholine is a major metabolic product in the plasma and cellular turnover of phospholipids, with well-known membrane-toxic and proinflammatory properties. Because the liver plays a key role in plasma lysophosphatidylcholine removal and biotransformation and because virtually nothing is known of these processes in a diseased organ, the hepatobiliary metabolism of lysophosphatidylcholine was investigated in rats with carbon tetrachloride-induced liver cirrhosis. Twelve adult male Wistar rats with histologically confirmed cirrhosis and 8 control animals were fitted with jugular and biliary catheters and allowed to recover. The animals were kept under constant IV infusion of taurocholate (1 mumol/min). Two microcuries of sn-1[14C]palmitoyl-lysophosphatidylcholine was administered as a single bolus. The fate of the injected radioactivity, including removal from plasma, uptake, and subcellular location in the liver and molecular and aggregative forms, was studied by combined chromatographic and radiochemical methods. Major findings were (a) that lysophosphatidylcholine has a prolonged permanence in plasma of cirrhotic rats, due both to decreased hepatic clearance and to depressed conversion into phosphatidylcholine; (b) that the rate of lysophosphatidylcholine acylation is much slower in the cirrhotic than in the normal liver, both at the microsomal and at the cytosolic level; (c) that cytosolic lysophosphatidylcholine in the cirrhotic liver, but not in the normal liver, is predominantly non-protein bound; (d) that the strict molecular selectivity of lysophosphatidylcholine acylation observed in controls is partially lost in cirrhosis; and (e) that a consistent fraction of lysophosphatidylcholine is converted into triacylglycerols in cirrhotics but not in controls. These findings show a profound derangment of lysophosphatidylcholine handling and processing in the cirrhotic liver, which is of potential pathogenetic significance.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1991

Dietary taurine content changes liver lipids in cats.

Adult female cats were fed a completely defined purified diet (taurine-free) alone or containing 0.05% taurine (the normal dietary requirement) or 1% taurine (20-fold the normal dietary requirement) for greater than 2 y. The relative composition of conjugated biliary bile acids was not different among the three groups and virtually all bile acids were conjugated with taurine. The taurine concentration in liver varied dramatically with the amount of taurine in the diet. Total liver lipid content decreased with increasing dietary taurine. Individual lipid components also varied, especially free fatty acids (which decreased with increasing dietary taurine) and triglycerides (which increased with increasing dietary taurine), indicating that taurine has a metabolic effect on lipid metabolism. Taurine deficiency also caused significant changes in the fatty acid distribution of sphingomyelin. In particular, a decrease of lignoceric acid and an increase of nervonic acid were observed. The present data suggest that hepatocellular levels of taurine can modulate the mobilization of liver lipid stores and the utilization by the liver of circulating free fatty acids. These effects are probably mediated by factors affecting membrane fluidity, such as the ratio of cholesterol to phospholipids, the degree of unsaturation of phospholipids and the changes in sphingomyelin fatty acid composition.

Administration, Oral↗
PubMed1991

Improvement of estradiol 17 beta-D-glucuronide cholestasis by intravenous administration of dimethylethanolamine in the rat.

The intravenous administration of dimethylethanolamine in the rat promotes a selective enrichment of liver membranes with polyunsaturated phosphatidylcholines. The effect of dimethylethanolamine pretreatment on cholestasis induced by estradiol 17 beta-D-glucuronide, a potent cholestatic agent, was assessed in this study. Dimethylethanolamine, dissolved in sodium-taurocholate was infused intravenously (0.3 mg/kg/min) for 15 hr. One group of control rats (estradiol 17 beta-D-glucuronide controls) received the bile salt only. An estradiol 17 beta-D-glucuronide bolus was then injected intravenously (10.4 mg/kg) into dimethylethanolamine-pretreated and estradiol 17 beta-D-control rats, and its effect on bile flow and biliary lipid secretion was compared for 3 hr. The estradiol 17 beta-D-glucuronide inhibitory effect on bile flow and biliary lipid secretion was significantly antagonized by dimethylethanolamine pretreatment. The maximum inhibition of bile flow was found 30 min after estradiol 17 beta-D-glucuronide administration, when it decreased from 3.5 +/- 0.4 microliters/min/100 gm (basal) to 0.9 +/- 0.3 microliters/min/100 gm in estradiol 17 beta-D-glucuronide controls, whereas in dimethylethanolamine-pretreated rats this decreased only from 3.2 +/- 0.4 (basal) to 2.3 +/- 0.4 microliters/min/100 gm. Bile flow and the biliary secretion of cholesterol, phosphatidylcholine and bile salts were significantly higher in the dimethylethanolamine-pretreated rats than in estradiol 17 beta-D-glucuronide controls (p less than 0.02) during the cholestatic phase. The inhibitory effect of estradiol 17 beta-D-glucuronide on bile flow was associated with a marked decrease of membrane fluidity (p less than 0.001) assessed by 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy and with a cholesterol enrichment of microsomes, sinusoidal and canalicular liver plasma membranes and inhibition of sinusoidal Na+,K(+)-ATPase activity (p less than 0.05). These membrane alterations persisted 180 min after estradiol 17 beta-D-glucuronide administration despite complete normalization of bile flow. Dimethylethanolamine pretreatment significantly counteracted the reduction of membrane fluidity (p less than 0.001), the cholesterol enrichment and the inhibition of Na+,K(+)-ATPase (p less than 0.05) promoted by estradiol 17 beta-D-glucuronide administration in all membrane subfractions 30 and 180 min after administration. In addition, dimethylethanolamine-pretreated rats had more polyunsaturated fatty acids in membrane phosphatidylcholine with respect to the control groups. Dilatation of canaliculi and loss of microvilli were evident in estradiol 17 beta-D-glucuronide controls 180 min after estradiol 17 beta-D-glucuronide administration.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Hepatic uptake and processing of free cholesterol from different lipoproteins with and without sodium taurocholate administration. An in vivo study in the rat.

The metabolic fate of [14C]cholesterol carried in the VLDL, LDL, HDL2 and HDL3 lipoprotein fractions has been investigated in bile-fistula rats with jugular vein cannulation. After the depletion of bile salt pool, the labelled lipoprotein fraction was administered either with or without the continuous infusion of sodium taurocholate. The proportion of labelled steroids secreted in the bile within 3 h after the lipoprotein administration was generally higher when the exogenous bile salt was infused. Specifically, the HDL2 fraction induced the secretion of relatively high proportions of labelled steroids, mainly bile salts, either with or without the taurocholate infusion. The other lipoprotein fractions increased the proportion of free cholesterol in steroid bile secretion under taurocholate administration. The label associated to the LDL fraction showed a higher biliary secretion and a more steady clearance from plasma if the exogenous bile salt was not administered. In this same condition, the administration of HDL3 fraction gave the highest values of radioactivity recovered in the liver (mainly as free cholesterol) and a significant increase of cholesterol in the biliary secretion. The present results suggest that each lipoprotein fraction tested may contribute in a peculiar manner to bile salt and cholesterol biliary secretion. Both the expression of apo-E and apo B,E receptors and the levels of circulating bile salts appear to have a role in this process.

Animals↗
PubMed1990

Separation and determination of molecular species of phosphatidylcholine in biological samples by high-performance liquid chromatography.

A method for determining the molecular species composition of phosphatidylcholine in biological samples by reversed-phase high-performance liquid chromatography with dual-wavelength ultraviolet detection is described. The optimum compromise between analysis time and chromatographic resolution under isocratic and isothermal conditions (0.8 ml/min and 32 degrees C, respectively) was obtained with the mobile phase methanol-ethanol (6:4, v/v) containing 20 mM choline chloride-water-acetonitrile (90:7:3, v/v/v). The problems of quantification at 205 nm, due to large differences in the detector response with the degree of unsaturation, were resolved by using the appropriate calibration factors chosen with the ratio of absorbances at 205 and 215 nm. The proposed procedure gave results in good agreement with fatty acid composition in samples of rat bile, liver, liver mitochondria and microsomes determined by gas-liquid chromatography.

Animals↗
PubMed1990

The cesium-induced delay in myoblast membrane fusion is accompanied by changes in isolated membrane lipids.

We have recently demonstrated that cesium ions delay the sharp decrease in both membrane conductivity and membrane permittivity of chick embryo myoblasts seen at fusion (Santini, M.T., Bonincontro, A., Cametti, C. and Indovina, P.L. (1988) Biochim. Biophys. Acta 945, 56-64). Analysis of the conductivity dispersion data (obtained in the radiowave frequency range) indicated that cesium delays fusion by about 30 h. We suggested that cesium is affecting both active ionic transport by blocking potassium channels as well as interfering with membrane lipid and/or protein charges. In the present study, we have investigated both the possible role of membrane lipids in myoblast fusion and the possible effects of cesium on these lipids. Our data indicate that lipid changes do occur in the isolated myoblast plasma membrane of controls during myogenic differentiation especially prior to fusion and that in cesium cultures these variations do not occur. These variations are in accordance with current membrane fusion theory. Specifically, there is a decrease in bilayer-stabilizing lipids (phosphatidylcholine) and an increase in bilayer-destabilizing ones (phosphatidylethanolamine and phosphatidic acid) and cholesterol during the fusion process. In addition, although slight, during fusion there appears to be a decrease in phosphatidylinositol which is believed to be involved in the inositol phosphate second messenger system. In cesium cultures, in which fusion is greatly delayed, the same lipid changes do not take place and those that are observed seem to reflect the fusion delay.

Animals↗
PubMed1990

Alterations of lipid composition in Friend leukemia cell tumors in mice treated with tumor necrosis factor-alpha.

Lipid analyses were carried out on transplantable murine Friend leukemia cell tumors, 6 h after intratumoral administration of tumor necrosis factor-alpha (TNF). The levels of the major phospholipid classes were uniformly decreased to about 70% of control values; free fatty acids were increased to about 170%; diacylglycerol was decreased to about 50% and triacylglycerol, the main lipid component, was not significantly altered. These results analysed in the light of concomitant alterations in the levels of phospholipid precursors and catabolites (determined in previous 31P NMR studies) and histological modifications demonstrated that at early stages of TNF-induced inhibition of tumor growth (a) phospholipid catabolism was significantly enhanced; (b) morphological changes were apparently correlated with alterations in the levels of phosphatidylcholine and its catabolic products.

Animals↗
PubMed1989

Selective hepatic enrichment of polyunsaturated phosphatidylcholines after intravenous administration of dimethylethanolamine in the rat.

The content of polyunsaturated phosphatidylcholines (PCs) is one of the parameters which regulate membrane functions. Polyunsaturated PCs are preferentially synthesized in the liver by the microsomal enzyme phosphatidylethanolamine N-methyltransferase. The activity of this enzyme may be stimulated in vitro in isolated rat hepatocytes by supplementation with dimethylethanolamine (DME), the polar head group of the precursor of PC along this pathway. The aim of this study was to evaluate in vivo the effect of an intravenous infusion of DME in the rat on the hepatic phospholipid composition. Bile fistula rats were intravenously infused for 15 h with sodium taurocholate (1 mumol/kg per min), with or without the addition of 0.3 mg/kg per min of [14C]DME. The concentration per gram of wet liver of individual phospholipid classes, PC molecular species and of total triacylglycerols, as well as the distribution of radioactivity in liver phospholipids, in rat tissues and body fluids were analyzed. A significant (P less than 0.01) enrichment in PC was found in the liver of DME-infused rats with respect to controls. No differences in the other phospholipid classes were found. DME-infused rats showed a significant (P less than 0.01) decrease in the hepatic concentration of triacylglycerols. At HPLC analysis, the enrichment in PC in DME-infused rats was found to be selectively due to three molecular species (i.e., sn-1 stearoyl/sn-2 arachidonoyl, sn-1 stearoyl/sn-2 linoleoyl, sn-1 stearoyl/sn-2 docosahexanoyl molecular species). In agreement with quantitative data, more than 70% of hepatic radioactivity was recovered in polyunsaturated PC species, with the highest specific activity in the sn-1 stearoyl PCs. The specific activity of hepatic PC approximates that of phosphatidyldimethylethanolamine. This finding together with the effective incorporation of DME in PC suggests that this amino base is methylated after its incorporation into phosphatidyldimethylethanolamine, throughout the stimulation of hepatic N-methyltransferase activity. The selective hepatic enrichment with polyunsaturated PC species after DME infusion may offer a new experimental tool for studying hepatic membrane metabolism.

Animals↗
PubMed1989

Hepatic uptake and metabolism of free cholesterol from different lipoprotein classes. An in vivo study in the rat.

Hepatic metabolism of [14C]cholesterol, vehiculated by LDL, HDL2 and HDL3 lipoprotein particles, has been studied in rats with a permanent biliary drainage. The lipoprotein fractions were infused individually by a jugular vein catheter and bile was collected for 180 min after the administration. At the end of this period, the animals were killed and the blood and livers were collected. The free cholesterol of the HDL2 fraction was secreted into bile, mainly as bile salt, preferentially to that associated with HDL3 and LDL fractions (11.7% vs. 2.3% and 0.3%, respectively). The free cholesterol of the HDL3 fraction, on the other hand, was taken up by liver more quickly and in a higher proportion than that associated with other lipoprotein fractions. The label incorporation in this lipoprotein fraction was secreted earlier and not transformed into bile. The contribution of LDL-vehiculated free cholesterol to bile secretion was small and the hepatic uptake amounted to no more than 12% of the injected label.

Animals↗
PubMed1989

Characterization of vesicles, containing an acylated oligopeptide, released by human colon adenocarcinoma cells. NMR and biochemical studies.

RNA-containing vesicles, recovered from the supernatant of high-density cell samples of human colon carcinoma, produce a high-resolution 1H NMR spectrum of lipids characterized by isotropic tumbling; these vesicles contain large amounts of triglycerides and cholesterol esters. Both findings have strict analogies to what is displayed by the proteolipid complexes isolated from the sera of tumor-bearing patients [(1985) Proc. Natl. Acad. Sci. USA 82, 3455-3459; (1986) FEBS Lett. 203, 164-168]. Lipid analysis and enzymatic tests indicate that these vesicles are selected micromaps of plasma membranes, analogous to those that can be recovered from culture media in which tumor cells are grown [(1985) Dev. Biol. 3, 33-57]. Peculiar lipids, an acylated oligopeptide and a modified phospholipid, are also present in the vesicles.

Acylation↗
PubMed1989

Carbon tetrachloride-induced experimental cirrhosis in the rat: a reappraisal of the model.

The goal of this study was to evaluate the presence of extrahepatic damage and the uniformity and reversibility of the histological findings in CCl4-induced liver cirrhosis in the rat. To verify these findings rats were sacrificed 2 and 10 weeks after a treatment consisting of ten intragastric doses of CCl4, administered weekly. All treated rats developed an irreversible micronodular cirrhosis with no damage to the brain, kidney and pancreas. Moreover, rats sacrificed 2 weeks after the last CCl4 dose showed a number of functional alterations usually observed in man. In particular, low branched chain/aromatic amino acids (BCAA/AAA) plasma ratio, high ammonia, low zinc and high insulin with normal blood glucose were obtained.

Amino Acids↗
PubMed1988

Determination of phospholipids in biological samples by an improved densitometric method on thin-layer chromatograms.

The quantitative determination of the different phospholipids present in samples of bile, liver or plasma has been performed by densitometric scanning of high-performance thin-layer chromatography plates. These have been developed as follows: pre-treatment with sulphuric acid-ethanol mixture, staining with ethanol-modified molybdenum blue reagent and post-treatments with water and ethanol added with a small quantity of sulphuric acid. The sequential treatment, which introduces some modifications in a previously described procedure, allowed a linear and stable colour response for phosphorous-containing lipids on uniform and colourless background. The calibration of each plate with standard mixture was required for obtaining results in good agreement with other routine methods of determination.

Bile↗
PubMed1988

On the mechanism of action of lonidamine: a study on human erythrocyte membrane.

The incubation of human erythrocytes with increasing levels of the antineoplastic drug Lonidamine clearly indicated a dose-dependent effect on the lipid composition of the plasma membranes. A selective transfer of phosphatidylcholine and cholesterol from membrane to incubation medium and the consequent enrichment in phosphatidylethanolamine of the membrane itself was observed. Moreover, the membranes were found to contain increasing levels of the drug which was incorporated at a constant membrane/medium partition ratio. The changes in composition appeared to be consistent with morphological alterations observed by scanning and freeze-fracture electron microscopy demonstrating changes in cell shape, the presence of numerous intracellular vesicles, and a membrane protein rearrangement. The analysis of intact red cells by nuclear magnetic resonance ruled out the possibility that the alterations described above could be due to an ATP depletion. This further confirmed that cell membranes were the primary target of the Lonidamine action, the previously described energy metabolism impairment being a consequence of a selective damage of cellular membranes, probably originating from the incorporation of the drug into the lipid bilayer.

Cholesterol↗