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Biomedical subjects

A Cantafora

Publications and source records attributed to A Cantafora.

At least 37 records · Page 2Linked to original sources
PubMed1998

The human gallbladder increases cholesterol solubility in bile by differential lipid absorption: a study using a new in vitro model of isolated intra-arterially perfused gallbladder.

In this study, we first developed and validated a new in vitro isolated, intra-arterially perfused, gallbladder model and then applied the method to investigate the absorption of biliary lipids by the gallbladder wall and the effect of this process on the composition of human bile. Oxygenated and glucose-added buffer was perfused through the cystic artery to maintain organ viability. A standard pooled natural bile, radiolabeled with H3-cholesterol and C14-palmitoyl-linoleoyl-phosphatidylcholine, was instilled in the lumen via a cystic duct catheter. Changes in bile volume and lipid concentrations were monitored at time intervals to evaluate the disappearance of lipids from bile caused by gallbladder absorptive function. Organ viability was demonstrated by stable lactate dehydrogenase (LDH) organ release and oxygen consumption throughout the experiments. In the pig, disappearance rates of lipids from bile were similar in vitro and in vivo, demonstrating the validity of the isolated in vitro model for functional studies. By applying our in vitro isolated preparation to the human gallbladder, we found that 23% of cholesterol and 32% of phosphatidylcholine, but only 9% of bile salts, disappeared from bile in 5 hours. As a consequence, at the end of the experiments, cholesterol (P < .05) and phospholipid (P < .05) molar percentages were significantly reduced, while the bile salt (P < .05) molar percentage was significantly increased with respect to values at the beginning of the studies. Our findings are of pathophysiological relevance and support the concept that the human gallbladder modifies the relative composition of biliary lipids in such a way as to increase cholesterol solubility in bile.

Absorption↗
PubMed1998

The mechanism underlying the hypocholesterolemic effect of chronic fish oil feeding in rats is not due to increased excretion of dietary cholesterol.

The role of the excretion of dietary cholesterol in the hypocholesterolaemic effect of chronic fish oil feeding in rats was investigated. The hepatic uptake and processing of [3H]cholesterol carried in chylomicrons derived from fish oil was studied in vivo in rats fed a low fat diet or a diet supplemented with fish oil for 21 days. In addition, the effects of the fish oil diet on cholesterol esterification, cholesteryl ester hydrolysis, bile acid synthesis and biliary lipid secretion were determined. In rats fed the fish oil as compared to the low fat diet, the uptake of [3H]cholesterol from the blood and its secretion into bile as bile acids was significantly slower, and this was entirely due to a decrease in the bile acid fraction. Biliary bile acid mass secretion was unchanged by fish oil feeding, while biliary cholesterol and phospholipid secretion was increased. No significant differences were observed either in the expression of mRNA for cholesterol 7alpha hydroxylase or the secretion of bile acids into bile after 20 h biliary drainage between the fish oil and low fat diet groups, suggesting that bile acid synthesis is not affected. These results indicate that the access of chylomicron cholesterol to the hepatic substrate pool for bile acid formation is decreased in the fish oil fed rats, and this, together with its slower uptake from the blood, accounts for the retardation of its excretion via the bile. Thus, the hypocholesterolemic effect of dietary fish oil in rats is not due to more rapid metabolism of cholesterol originating from the diet.

Animals↗
PubMed1998

Long-term cultures of human fetal liver cells: a three-dimensional experimental model for monitoring liver tissue development.

BACKGROUND/AIMS: The present study describes an embryonic-fetal liver culture system which allows morphogenetic interactions consistent with the development of the hepatocellular function. METHODS: Intact livers from 8-12-week embryos were soaked in an extracellular matrix at 4 degrees C and gently dissociated without any enzymatic treatment. The resulting spherical hepatic units were cultured in a chemically defined serum-free medium and seeded into an extracellular matrix layer. Adherent three-dimensional tissue specimens were examined at various times by light and electron microscopy to evaluate the maintenance of hepatocyte morphology. RESULTS: The liver cells were viable for over 4 months; erythropoietic burst colonies were detected for longer than 6 weeks. Parallel detection of bile salt production in the medium by high performance liquid chromatography proved liver tissue functionality. Bile salt composition revealed predominance of taurine-conjugates rather than glycine. Maximum bile salt concentration (approximately 3 months) coincided with structural and ultrastructural observations indicating a marked decline in hematopoiesis, well-defined biliary canaliculi and formation of an organ-like structure. CONCLUSIONS: This three-dimensional culture system recapitulates fetal liver development with: (i) initial proliferation of both fetal erythropoietic and hepatic cells and (ii) subsequent shut-off of erythropoiesis and a shift to a more advanced stage of hepatocyte function, such as bile salt secretion.

Bile Acids and Salts↗
PubMed1998

Effect of S-adenosyl-L-methionine and dilinoleoylphosphatidylcholine on liver lipid composition and ethanol hepatotoxicity in isolated perfused rat liver.

We investigated whether S-adenosyl-L-methionine (SAMe), dilinoleoylphosphatidylcholine (DLPC), or SAMe + DLPC influence liver lipid composition as well as acute ethanol hepatotoxicity in the isolated perfused rat liver (IPRL). SAMe (25 mg/kg intramuscularly three times a day) was administered for five consecutive days, while DLPC was administered intraperitoneally for five days. The liver was then isolated, perfused with taurocholate to stabilize bile secretion, and exposed to 0.5% ethanol for 70 min. SAMe, without changing total phospholipid (PL) content, induced an increase in the phosphatidylcholine/phosphatidylethanolamine (PC/PE) molar ratio in both liver homogenate and microsomes and a significant enrichment of 16:0-20:4 and 18:0-20:4 PC molecular species. DLPC induced a significant enrichment of PL in liver homogenate and microsomes due to a contemporary increase in PC and PE. The PC enrichment specifically involved 16:0-20:4 and 18:0-20:4 PC molecular species besides the HPLC peak containing the administered 18:2-18:2 PC species. DLPC + SAMe increased the concentration of PC in liver homogenate and microsomes due to a specific enrichment of 16:0-22:6, 16:0-20:4, and 18:0-20:4 PC molecular species, and the HPLC peak containing the administered 18:2-18:2 PC species. Ethanol acute exposure in the control IPRLs for 70 min induced a depletion of cholesterol in both liver homogenate and microsomes without significant changes in the composition of PL classes and PC molecular species. SAMe, DLPC, or SAMe + DLPC counteracted the cholesterol depletion induced by ethanol, indicating that phospholipid changes promoted by these treatments all induce a major resistance of liver membranes to the effect of ethanol. Ethanol administration in control IPRLs induced a fivefold increase of AST and LDH release in the perfusate, depletion of glutathione in homogenates and mitochondria, decreased oxygen liver consumption, and inhibition of bile flow. These effects of ethanol were significantly antagonized by SAMe. In contrast, DLPC alone only minimally attenuated enzyme release in the perfusate and the inhibitory effect of ethanol on bile flow, but it failed to influence the depletion of total and mitochondrial glutathione or the depressed oxygen consumption induced by ethanol. DLPC, administered together with SAMe, added nothing to the protective effect of SAMe against ethanol hepatotoxicity and cholestasis. In conclusion, this study demonstrates that both SAMe and DLPC induced marked modifications in the lipid composition of liver membranes with a similar enrichment of polyunsaturated PC molecular species. Only SAMe, however, significantly protected against the hepatotoxic and cholestatic effect of acute ethanol administration, an effect associated with maintained normal glutathione mitochondrial levels and oxygen liver consumption. This indicates that the protective effect of SAMe against ethanol toxicity is linked to multiple mechanisms, the maintenance of glutathione levels probably being one of the most important.

Animals↗
PubMed1998

Simple detection of a point mutation in LDL receptor gene causing familial hypercholesterolemia in southern Italy by allele-specific polymerase chain reaction.

Polymerase chain reaction (PCR) amplification of specific alleles allowed the rapid detection of a point mutation (missense Gly528 --> Asp) in exon 11 of the low density lipoprotein receptor gene which was otherwise not detectable by exon amplification and enzymatic digestion as it does not modify the normal restriction pattern. The mutant allele, designated as FH-Palermo-1 from the origin of the first carrier family identified, gave a specific PCR product of 109 bp clearly distinct from the product of 168 bp obtained from other alleles with a nonspecific couple of primers. This method allowed us to distinguish one positive sample mixed with up to 11 parts of normal DNA. Furthermore, the specific amplification product was characterized by a Bsm I restriction site not present in nonspecific products.

Alleles↗
PubMed1997

The lipolysis of chylomicrons derived from different dietary fats by lipoprotein lipase in vitro.

The lipolysis of chylomicrons derived from palm, olive, corn or fish oil (enriched in saturated, monounsaturated, n - 6 polyunsaturated and n - 3 polyunsaturated fatty acids, respectively) by rat post-heparin lipoprotein lipase in vitro was compared by measuring the release of [3H]oleate from their triacylglycerol. Chylomicrons derived from corn oil were lipolysed more rapidly than the other types in the first 20 min of the reaction, but after 120 min the total amount of triacylglycerol hydrolysed was similar with all types of chylomicrons used. The rate of lipolysis of the different types of chylomicrons also showed different dependencies on the substrate concentration. The highest Vmax values were obtained when the chylomicrons were derived from olive and corn oil and the lowest when they were derived from palm oil, while olive oil chylomicrons gave the highest Km and palm oil chylomicrons the lowest. These results indicate that differential metabolism of chylomicrons of different fatty acid composition by lipoprotein lipase may play a part in the differential rates of clearance from the blood of lipid of dietary origin demonstrated in earlier work from our laboratory.

Animals↗
PubMed1997

Comparison of the uptake and processing of cholesterol from chylomicrons of different fatty acid composition in rats fed high-fat and low-fat diets.

The fate of [3H]cholesterol carried in chylomicrons prepared from rats given a meal of palm oil (rich in long-chain saturated fatty acids), olive oil (rich in monounsaturated fatty acids) or corn oil (rich in n-6 polyunsaturated fatty acids) was investigated in vivo in rats fed a low-fat diet or a diet supplemented with the corresponding oil (to provide 40% of the calories) for 21 days. In the low-fat-fed groups, radioactivity was removed from the blood and secreted into bile over 180 min more rapidly when the chylomicrons were derived from corn oil as compared to palm or olive oil. After feeding the corresponding high-fat diets, however, both parameters were decreased in rats fed palm and corn oil, but not olive oil. As a result of these changes, the rates of removal of radioactivity from the blood and secretion into bile were similar in animals given the olive oil and corn oil diets, and higher than those in rats fed the palm oil diet. All the high-fat diets tended to increase the proportion of the radioactivity in the plasma found in the 1.006-1.050-g/ml fraction (low-density lipoprotein) and decrease that in the 1.050-1.25-g/ml (high-density lipoprotein) fraction in comparison to the respective low-fat diet groups, but the transfer of radioactivity to the plasma high-density lipoprotein fraction was particularly slow in palm-oil-fed rats. These findings indicate that diets high in saturated or n-6 polyunsaturated fat retard the metabolism of chylomicron cholesterol in comparison to diets low in fat, while those high in monounsaturated fat do not have this effect. As a consequence of this, the rate of removal of cholesterol of dietary origin from the body is slower in animals fed saturated as compared to monounsaturated or n-6 polyunsaturated fat. Thus, differential metabolism of chylomicron cholesterol clearly plays an important role in the hyper- and hypo-cholesterolaemic effects of these dietary fats.

Animals↗
PubMed1997

Age-related variations in hepatic biosynthesis of phosphatidylcholine: a study of choline metabolism with perfused rat liver.

This study investigated the age-related increase in phospholipid secretion previously described in perfused rat livers. The hypothesis of this study was that the increased secretion is mainly due to an enhanced hepatic biosynthesis of phosphatidylcholine (PC). Specifically, we evaluated the contribution to this increase of the major hepatic pathway of phosphatidylcholine formation (i.e., the conversion of choline into phosphatidylcholine via cytidine diphosphate [CDP]-choline). The measurements of [3H]choline incorporation into phosphatidylcholine and its precursors in liver and bile throughout the 2-hr duration of the experiments showed significant differences in the amount of newly synthesized labeled PC secreted in the bile produced by adult and young rat livers. However, the present findings do not support the idea that the age-related increase in phosphatidylcholine hepatic secretion was due only to a strong increase in phosphatidylcholine synthesis by via CDP-choline. Conversely, they suggest that future research should be directed towards the mechanisms regulating the diacylglycerol metabolism in the hepatocytes, as the alteration of the splitting ratio of hepatic diacylglycerol flow could lead to an age-related increase in conversion of diacylglycerol into phosphatidylcholine, rather than into triacylglycerol. This, in turn, may decrease the availability of triacylglycerol for hepatic very low density lipoprotein (VLDL) assembly and contribute to altered VLDL synthesis, as previously observed in the aging process.

Aging↗
PubMed1996

Probucol reduces hepatic cholesterol secretion in hyperlipidemic Yoshida rats.

In this study, perfused livers from Yoshida rats, either on a normal diet or on a diet with 0.3% probucol, were examined. The analysis of liver lipid content and of bile and lipoprotein secretion changes showed that probucol had a relevant effect on liver lipid biosynthesis. In particular, it reduced the production of triacylglycerols and, to a much greater extent that of cholesterol. In addition, probucol reduced plasma cholesterol concentration by decreasing esterified cholesterol in HDL1 and HDL2 fractions. Furthermore, HDL1 composition of both hepatic neosynthetized and circulating particles was strongly modified by probucol. Finally, probucol did not appear to induce significant differences in lipid bile secretion while phospholipid secretion from perfused livers was increased. These facts suggest that the hypolipidemic action of probucol is not mediated by an increase in bile steroid secretion, but rather by a direct reduction in hepatic lipoprotein cholesterol secretion. This secretion induces a modified plasma profile of HDL particles such that these variations are advantageous in terms of reverse cholesterol transport.

Animals↗
PubMed1996

Differential effects of chylomicron remnants derived from corn oil or palm oil on bile acid synthesis and very low density lipoprotein secretion in cultured rat hepatocytes.

The effects of chylomicron remnants derived from corn oil (rich in n-6 polyunsaturated fatty acids) and palm oil (rich in long chain saturated fatty acids) on bile acid synthesis and very low density lipoprotein secretion in cultured rat hepatocytes were studied. Incubation of the cells with corn oil remnants led to increased bile acid production, while the secretion of lipid in very low density lipoprotein remained unchanged. In contrast, addition of palm oil remnants to the medium did not affect bile acid synthesis, but resulted in the secretion of cholesterol-rich very low density lipoprotein. These findings show that chylomicron remnants of different fatty acid composition have differential effects on cholesterol metabolism in liver cells, and provide part of the explanation for the hyper- and hypocholesterolaemic effects of saturated and polyunsaturated fatty acids.

Animals↗
PubMed1996

Age-related changes in lipid secretion of perfused livers from male Wistar rats donors.

Male Wistar rats show typical age-related variations in the distribution of high-density lipoprotein subfractions that include an increase in HDL1 and a decrease in HDL2 proportion. The role of liver in these variations was evaluated by studying the lipoprotein and bile secretions from perfused livers of 14 +/- 1 and 3.5 +/- 0.5 month old Wistar rats (adult and young animals, respectively). The lipid content of lipoproteins secreted from adult livers was higher in HDL2 fraction and lower in VLDL fraction. The lipid output did not show significant age-related variations in the case of HDL1 fraction. However, the lipoproteins secreted from adult livers contained a higher proportion of phospholipids, and a lower proportion of triacylglycerols in comparison with lipoproteins secreted by young livers. Therefore, the molar ratio of core to surface lipids was lower in lipoproteins secreted by adult livers. Adult livers showed a reduction in bile flow by about 37% with a significantly higher phospholipid secretion. These findings suggest that both the hepatic metabolism of glycerophospholipids and their repartition between plasma and bile compartments are affected by aging process. In conclusion, present data show that the age-related increase in plasma HDL1 proportion, previously observed in this rat strain in vivo, are not due to a higher liver secretion of these particles. Conversely, liver appears to have a major role in the age-related VLDL increase and in the variations of phospholipid lipoprotein secretion.

Aging↗
PubMed1995

Comparison of the hepatic uptake and processing of cholesterol from chylomicrons of different fatty acid composition in the rat in vivo.

The effect of the fatty acid composition of chylomicrons on the uptake and processing of the cholesterol they carry was investigated in the rat in vivo. Rats kept on a standard low fat pellet diet and tube fed a single dose of palm, olive, corn or fish oil (rich in saturated, n-9 monounsaturated, n-6 polyunsaturated and n-3 polyunsaturated fatty acids, respectively) were used to prepare [3H]cholesterol-labelled chylomicrons of different fatty acid composition. These were then injected intravenously into rats (kept on the standard diet), and the clearance of radioactivity from the blood, distribution in the plasma lipoprotein density fractions, uptake by the liver and appearance in the bile were studied. [3H]Cholesterol from fish and corn oil chylomicrons was cleared from the blood more rapidly than that from palm and olive oil chylomicrons. After 180 min the proportion of the radioactivity present in the plasma in high density lipoprotein (HDL) was less when the chylomicrons were derived from palm oil as compared to any of the other oils. Approx. 40% of the administered label was recovered in the liver after 180 min in all experiments. The percentage of the injected radioactivity secreted into bile during 180 min was significantly higher with corn and fish oil chylomicrons than with palm oil chylomicrons, with chylomicrons from olive oil in an intermediate position, and these differences were most pronounced between 60 and 120 min after administration of the label. These studies clearly demonstrate that the fatty acid composition of chylomicrons has important effects on the hepatic uptake and processing of the cholesterol they carry, with enrichment with polyunsaturated fatty acids leading to an increased rate of uptake and more rapid removal from the body via the bile as compared to enrichment with saturated or monounsaturated fatty acids.

Adrenal Glands↗
PubMed1995

Matrix-assisted laser desorption mass spectrometry for the detection of recombinant bovine growth hormone in sustained-release form.

We employed matrix-assisted laser desorption mass spectrometry (LD-MS) to detect recombinant bovine growth hormone (r-bGH) in sustained-release preparations. After preliminary extraction in phosphate buffer, LD-MS provided a precise determination of the molecular mass (M(r)) of the r-bGH contained in 38 sustained-release preparations. The hormone was characterised using enzyme immunoassay, immunoblotting and amino acid sequencing. Rapid detection is essential for analysing large numbers of samples, and for monitoring the use of r-bGH in zootechnical productions and its administration as a "high-tech" drug for therapeutic purposes.

Amino Acid Sequence↗
PubMed1995

Age-related variations in plasma and liver lipids of Yoshida rats: a comparison with Wistar rats.

Lipoprotein and liver lipids of spontaneously hyperlipidemic Yoshida rats were compared with those of normolipidemic Wistar animals for studying their age- and strain-related differences. Both strains showed an age-related increase in the total plasma cholesterol concentration. However, the Yoshida strain had a higher content of cholesteryl esters and triglycerides than the Wistar strain in both young and adult animals (2- and 8-month-old animals, respectively). The free cholesterol content was also higher, but only in the 8-month-old animals. Both strains showed an age-related increase in the proportion of HDL1 and a symmetrical decrease in both the HDL2 and HDL3 subfractions, but the variations were more evident in the Yoshida strain. The study of strain-related differences suggested that the spontaneous hypertriglyceridemia of the Yoshida strain was not only related to the higher amount and proportion of the VLDL fraction, but also to the higher content of triglycerides in the LDL fraction. The livers of Yoshida rats accumulated more triglycerides (with an age-related progression) than those of Wistar rats. The major lipid classes in the liver of Yoshida rats contained a significantly higher proportion of monounsaturated fatty acyls. Furthermore, this proportion showed an age-related increase in all the lipid classes, but in cholesteryl esters. This suggested that liver desaturases had a relevant role in the development of hyperlipidemia, and of its age-related variations, in the Yoshida strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗