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A Rigotti

Publications and source records attributed to A Rigotti.

46 records · Page 3Linked to original sources
PubMed1993

Biliary lipid secretion: immunolocalization and identification of a protein associated with lamellar cholesterol carriers in supersaturated rat and human bile.

Feeding a 0.5% diosgenin plus 0.02% simvastatin diet to rats increases biliary cholesterol concentration and saturation to levels generally found in human native supersaturated bile. By using preparative ultracentrifugation, gel filtration chromatography, and electron microscopy, we isolated, purified, and identified lamellar structures (unilamellar vesicles and multilamellae) as a major biliary cholesterol transport in supersaturated human and rat bile. It was estimated that more than 60% of biliary cholesterol is transported in these lamellar carriers, which were identified by transmission electron microscopy as unilamellar vesicles and multilamellar bodies within bile canaliculi of rats with cholesterol supersaturated bile. By SDS-PAGE, a characteristic and constant protein profile was found associated to the purified lamellar carriers. One of these proteins, a 130-kDa protein, was isolated from human biliary lamellae and used for preparation of a rabbit polyclonal antibody, which cross-reacted with the homologous rat protein. By Western blotting, it was established that the purified low density fraction of bile-Metrizamide gradients, containing lamellae, was enriched with the 130-kDa protein. The 130-kDa protein was characteristically detected at the canalicular membrane by Western blotting of hepatic subcellular fractions and by immunohistochemistry of rat and human liver biopsies. Amino acid sequencing of the amino terminus of the 130-kDa protein demonstrated a complete identity with aminopeptidase N, a canalicular transmembrane hydrophobic glycoprotein. These studies show that biliary lipids may acquire an ordered multilamellar structure that is present in the canaliculi of rats with supersaturated bile. These biliary lamellae are similar to lamellar bodies and surfactant-like material frequently found in other epithelia, suggesting common biogenetic, structural, and functional properties. The identification of aminopeptidase N associated with biliary lamellae is consistent with the involvement of the canalicular membrane in the secretory mechanism of biliary lipids.

Amino Acid Sequence↗
PubMed1992

Isolation and purification of human biliary vesicles with potent cholesterol-nucleation-promoting activity.

1. Cholesterol nucleation is a critical step in the formation of cholesterol gallstones. This nucleation takes place after aggregation and fusion of cholesterol-rich biliary vesicles, a process probably modulated by biliary proteins. The present study was conducted to identify specific proteins associated with native cholesterol-rich biliary vesicles and to explore their effect on the cholesterol-nucleation time of supersaturated artificial bile. 2. Hepatic bile was obtained from six patients with cholesterol gallstone disease. Biliary vesicles were isolated by ultracentrifugation and were purified by gel filtration chromatography. A small amount of protein (less than 1% by weight) remained associated with the purified cholesterol-rich biliary vesicles. The electrophoretic profile of these proteins was remarkably similar in all six patients, showing the presence of at least six polypeptides (of molecular mass from 52 to 200 kDa), five of them having carbohydrate residues (except the 52 kDa one). The effect of reconstituted biliary vesicle solutions, containing their specific vesicular proteins, on cholesterol-nucleation time was studied by mixing the vesicle solution with artificial supersaturated bile. A potent cholesterol-pronucleating activity, reflected in a 20-70% reduction in nucleation time, was present in the biliary vesicle solutions compared with control solutions having a similar lipid composition. The pronucleating activity disappeared on heating and was not detected in the micellar fraction containing the major proportion of biliary proteins. 3. These results indicate that cholesterol-rich biliary vesicles containing a unique and defined glycoprotein profile can be isolated and purified from human hepatic bile. The potent cholesterol-pronucleating activity of the biliary vesicles from patients with gallstones was unrelated to their lipid composition or cholesterol content.(ABSTRACT TRUNCATED AT 250 WORDS)

Bile↗
PubMed1991

[Conceptual evolution regarding the pathogenesis of biliary lithiasis due to cholesterol calculi].

In the recent 5 years, several important conceptual changes in the understanding of cholesterol gallstone formation have occurred. This article discusses the molecular basis of the disease, as we understand it today. The discovery of a vesicular carrier of biliary lipids and the metabolic regulation of biliary cholesterol secretion have markedly modified our understanding of the pathogenesis of cholelithiasis, giving more emphasis to molecular and cell biology aspects, rather than to physicochemistry, as occurred in the late seventies (micellar theory). The critical step in gallstone formation is cholesterol crystallization and it occurs after vesicle aggregation and fusion. This process is probably dependent of hepatic glycoproteins secreted into bile, presumably associated to the vesicular carrier of biliary cholesterol. Risk factors such as sex, obesity, sexual hormones, and diet seem to modify either biliary cholesterol secretion, and/or nucleation (crystallization) in the gallbladder, and/or gallbladder motility. It seems most likely that gallstones is a multifactorial disease, dependent of an interactions between environmental and genetic, or ethnic, factors.

Animals↗
PubMed1990

Acute bilateral renal vein thrombosis superimposed on calcified thrombus of the inferior vena cava in a patient with membranous lupus nephritis.

We report a case of membranous lupus nephritis with a previous history of long-standing nephrotic syndrome which developed an acute renal failure due to bilateral renal-vein thrombosis superimposed on a calcified thrombus of the inferior vena cava eight years after the diagnosis. The occurrence of acute renal-vein thrombosis is a possible but rarely described complication of systemic lupus erythematosus. The presence of a calcified thrombus of the inferior vena cava has been described in only one adult patient until now. An aggressive thrombolytic therapy with urokinase permitted the fresh thrombus to be dissolved with a marked improvement in renal function.

Acute Kidney Injury↗
PubMed1990

Secretion of biliary lipids from the hepatocyte.

A significant amount of biliary cholesterol is carried in unilamellar-phospholipid (lecithin) vesicles, in both supersaturated human hepatic bile and unsaturated rat bile. This fact supports the concept that biliary cholesterol is normally secreted in phospholipid vesicles from the hepatocyte into the canaliculus. The fundamental aspects of biliary lipid secretion relate first to the quantitative determinants of hepatocytic cholesterol secretion into the bile and, second, to the cell biology of this process. There is a tight curvilinear coupling between the rates of bile acids and biliary lipid secretion in all animal species. The hydrophobicity of the bile acid pool may modify this cosecretory mechanism in that more hydrophobic bile acids recruit more phospholipid and cholesterol per mole of bile acid secreted into the bile. The quantitative significance of this effect, however, is relatively minor. In contrast, intrahepatic determinants, such as the rates of hepatic cholesterol esterification and very low density lipoprotein production modulated by dietary factors, may markedly change the amount of cholesterol carried in vesicles into the bile. Recent studies provide strong evidence to support the concept that biliary cholesterol output is also modulated by the amount of free cholesterol available in specific regions of the endoplasmic reticulum for recruitment by the bile acid cosecretory mechanism. The origin of biliary lipids is in the smooth endoplasmic reticulum membranes. The intracellular transport and the canalicular secretory mechanism of the precursor of biliary lipid vesicles is mostly unknown. Two theories related to the cell biology of biliary lipid secretion are discussed in this article, the fusion-budding model and the exocytotic model.

Animals↗
PubMed1989

Effect of bean intake on biliary lipid secretion and on hepatic cholesterol metabolism in the rat.

We studied the effect of a bean diet on biliary lipid secretion, serum cholesterol concentration, and hepatic cholesterol metabolism in the rat. Rats fed a bean diet for 10-12 days had increased biliary cholesterol output and molar percentage by 300% and 200%, respectively, compared to rats fed an isocaloric and isoprotein casein diet. Biliary phospholipid output increased 180%. Bile flow and biliary bile salt output remained in the normal range. Total serum and VLDL cholesterol concentration significantly decreased 27% and 50%, respectively, in the rats fed the bean diet. Hepatic cholesterogenesis was increased 170% in the bean-fed animals. The relative contribution of newly synthesized hepatic cholesterol to total biliary cholesterol increased 200%, and that of endogenous origin only 50%. These results suggested that newly synthesized hepatic cholesterol was preferentially channelled to the biliary cholesterol secretory pathway in bean-fed rats. Although hepatic cholesteryl ester concentration increased 240%, the incorporation of [14C]oleate into hepatic cholesteryl esters was significantly decreased by 30% in isolated hepatocytes of bean-fed animals. These results were consistent with the possibility that the availability of hepatic free cholesterol for biliary secretion was increased in the bean-fed animals. This study demonstrates that bean intake has a profound effect on the metabolic channelling and compartmentalization of hepatic cholesterol, resulting in a significant decrease in total serum and very low density lipoprotein cholesterol concentrations and a high biliary cholesterol output.

Animals↗
PubMed1988

Regulation of biliary cholesterol secretion. Functional relationship between the canalicular and sinusoidal cholesterol secretory pathways in the rat.

The functional interrelationship between biliary cholesterol secretion, sinusoidal lipoprotein cholesterol secretion and bile salt synthesis was studied in the rat. Diosgenin, fructose, and colestipol in the diet were used to, respectively, influence biliary cholesterol output, VLDL production and bile salt synthesis. In the acute bile fistula rat, biliary cholesterol output was 700% increased by diosgenin and 50% decreased by fructose. In the rats fed both diosgenin and fructose, biliary cholesterol secretion was increased only by approximately 200%, whereas biliary bile salts and phospholipid outputs were unchanged. In the isolated perfused liver, VLDL-cholesterol output was 50% reduced by diosgenin alone, but was unchanged following feeding of diosgenin plus fructose. However, the livers of rats fed diosgenin plus fructose exhibited a 700% increase in VLDL-triglyceride production and a 200% increase in VLDL-cholesterol output. A significant reciprocal relationship between VLDL-cholesterol secretion and the coupling ratio of cholesterol to bile salts in bile was observed. Colestipol added to the diet maintained both sinusoidal and biliary cholesterol outputs within the normal range. In the chronic bile fistula rat, colestipol increased bile salt synthesis by 100% while diosgenin and fructose diets had no effect. Similarly, the addition of fructose to the colestipol diet did not decrease bile salt synthesis. These data suggest a reciprocal relationship between biliary cholesterol secretion and hepatic secretion of cholesterol as VLDL particles. The free cholesterol pool used for bile salt synthesis seems functionally unrelated to the pool from which VLDL-cholesterol and biliary cholesterol originate. These findings support the idea that metabolic compartmentalization of hepatic cholesterol is a major determinant of the quantity of cholesterol available for recruitment by the bile salt-dependent biliary cholesterol secretory mechanism.

Animals↗
PubMed1985

Plasma exchange therapy in rapidly progressive renal failure due to multiple myeloma.

Nineteen patients with severe renal failure due to multiple myeloma and with Bence Jones proteinuria greater than 1 gm/day were randomly assigned to group I or group II. Corticosteroids and cytotoxic drugs were given to all cases. The 9 patients of group I were also treated by peritoneal dialysis and the 10 patients of group II by plasma exchange and hemodialysis. Only 1 patient of group I, who was not oliguric at the onset, showed partial recovery from renal failure after 3 months of therapy, while 9 patients of group II (3 of whom were oliguric) had significant decrease in Bence Jones proteinuria and rapid improvement from the renal failure. In our experience, plasma exchange is more effective than peritoneal dialysis for reducing Bence Jones proteinuria and recovering from renal failure, even when there is oliguria.

Aged↗