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F Nervi

Publications and source records attributed to F Nervi.

At least 37 records · Page 2Linked 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↗
PubMed1993

Hepatic production of very low density lipoprotein, catabolism of low density lipoprotein, biliary lipid secretion, and bile salt synthesis in rats fed a bean (Phaseolus vulgaris) diet.

Rats fed a bean diet develop a significant hypocholesterolemia. The catabolism of low density lipoprotein (LDL; d 1.019-1.063 g/ml) was studied in vivo and in vitro in the isolated perfused liver of rats fed either a casein or a bean diet. The clearance of LDL was significantly increased by 100% from 0.38 +/- 0.04 to 0.63 +/- 0.04 ml/h x 100 g body wt in vivo in the bean-fed rat. Similarly, the clearance of homologous and heterologous (human) LDL was also increased by 100% in the isolated perfused liver of bean-fed animals. Spleen, kidney, and hepatic cholesterogenesis was increased by 150% in these animals. Bile salt synthesis was increased from 1.54 +/- 0.02 to 2.84 +/- 0.09 nmol/min x g liver wt (P < 0.02) and biliary cholesterol output by 200% from 0.81 +/- 0.03 to 2.18 +/- 0.04 nmol/min x g (P < 0.02) in the isolated perfused liver of rats fed a bean diet. These results explained the depletion of hepatic cholesterol and were consistent with the LDL turnover studies, suggesting that apoB/E receptor activity was increased in these animals. ApoB and triglyceride secretion in the d < 1.060 g/ml lipoprotein fraction of liver perfusates remained normal in the bean-fed rats. In contrast, total sinusoidal cholesterol output isolated in the d < 1.060 g/ml fraction significantly decreased by 100% after 90 min of perfusion. Cholesterol output in the d > 1.060 g/ml lipoprotein fraction was unmodified by the bean diet. These data demonstrate that key metabolic pathways of hepatic cholesterol are modified in the bean-fed rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
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↗
PubMed1992

[Epidemiology and natural history of biliary calculi. Implication for clinical management].

The knowledge of the epidemiology of cholesterol gallstones is mainly descriptive in Chile. Prevalence data has been gathered from several autopsy studies. The prevalence in these studies is similar to the prevalence determined in a cholecystographic study in a sample of the population of Santiago: 51% of women and 17% of men harbor gallstones, or have been cholecystectomized. The risk factors of the disease are well known and include sex, age, obesity, pregnancy, female sex hormones and hypotriglyceridemic drugs, there is scarce data on the natural history of gallstone disease. In this article we review the present knowledge of both the epidemiology and natural history of gallstones. In addition, we present some specific questions related to the potential identification of environmental and genetic risk factors in epidemiological studies. It is stressed that the knowledge of the natural history of gallstone disease is critical for the appropriate rational management of silent gallstones.

Cholelithiasis↗
PubMed1991

[Dentistry and seropositivity. Therapeutic protocol].

The Authors wanted to give a basis for oral hygiene in order to reduce gingival bleed in risk patients. The experimental study tested for 21 days 63 people ex addicts divided into 3 groups: 4 periodontal probings with the Ainamo e Bay method. The statistical calculus showed an improvement in the group that had been using 3 garglings a day for 7 days and afterwards 1 gargling a day for 7 days with clorexidina glucosed 8 ml in 80 ml water for 60 seconds. It is necessary to remind risk patients of the importance of removing the plaque through brushing, without having too confidence in the garlings.

Adult↗
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

Catabolism of chylomicron remnants in patients with previous acute pancreatitis.

A recent study reports that patients with previous acute pancreatitis commonly have an abnormal clearance of serum triglycerides after an oral fat load. This observation supports the hypothesis that patients with previous acute pancreatitis and normal fasting serum triglyceride levels may have a preexistent abnormality in the metabolism of chylomicrons. To test this hypothesis, the catabolism of chylomicrons and their remnants was studied in a series of 7 patients who had sustained an attack of pancreatitis (2, gallstone related; 2, alcohol ingestion; 1, hydatid cyst; and 3, no associated pathological condition) at least 18 mo earlier. All the patients had previously had abnormal oral-fat tolerance test results. These patients were compared with a series of 6 healthy volunteers. Chylomicrons were endogenously labeled with an oral dose of retinyl palmitate, and their plasma elimination half-life was calculated. The retinyl palmitate absorption rate constants were similar in control and pancreatitis patients. The chylomicron t1/2 were 2.3 +/- 0.8 (SD) h and 3.9 +/- 1.8 h in the control and pancreatitis groups, respectively (p = 0.07). The chylomicron remnant t1/2 was 2.7 +/- 1.1 h in the control group and 5.2 +/- 2.4 h in the pancreatitis group (p less than 0.05). This study supports the hypothesis that subjects with previous acute pancreatitis may have an abnormality in the catabolism of chylomicron particles. This abnormality may represent a preexistent genetic condition expressed in either the apoprotein composition of chylomicrons or in the hepatic apolipoprotein E-receptor activity.

Acute Disease↗
PubMed1990

[Gallbladder cancer mortality in Chile and its relation to cholecystectomy rates. An analysis of the last decade].

Extrahepatic biliary tract cancer (mainly gallbladder cancer) mortality rates have increased from 7.84 x 100.000 to 9.6 x 100.000 in Chile during the last decade. The most significant risk factor for gallbladder cancer is gallstone disease. However, no apparent changes in the prevalence of gallstone disease has occurred during this period. In contrast, cholecystectomy rates have consistently decreased during the decade. The aim of this study was to correlate extrahepatic biliary tract cancer mortality and cholecystectomy rates of previous years during the last decade in our country. The best correlation coefficient between both variables was obtained when mortality was correlated with cholecystectomy rates two years prior to the mortality rate (r = -0.92). This finding is consistent with the hypothesis that changes in the number of cholecystectomies performed in a specific geographic area would reciprocally change gallbladder cancer mortality rate. It was estimated that increasing cholecystectomies by 12,500 per year would decrease at mortality rate from this cancer by approximately 1.0 x 100.000 two years in Chile.

Chile↗
PubMed1990

Separation and quantitation of cholesterol carriers in native bile by ultracentrifugation.

The vesicular and micellar carriers of biliary cholesterol were isolated and quantitated from native bile by a simple and short isopyknic ultracentrifugal method. The method was designed to decrease the potential pitfalls of classic ultracentrifugation: osmotic effects of the centrifugation media and hydrostatic pressure effects generated in the centrifuge tube. This was accomplished by using metrizamide as an inert centrifugation medium for isopyknic separation and a vertical rotor. The buoyant density of vesicles isolated from human native bile varied between 1.010 and 1.030 gm/ml, as determined in preformed bile-metrizamide density gradients after 285 min of centrifugation. When 16% metrizamide was directly dissolved in bile, its density increased to 1.060 gm/ml. After 120 min of centrifugation, it was found that more than 95% of total vesicular cholesterol floated at the top of the centrifuge tube. This fraction appeared as one or two white opalescent bands. The present ultracentrifugal method was validated by gel filtration chromatography. It was found that more than 95% of vesicular cholesterol migrated to the top 0.4 ml of the centrifuge tube after the short-run centrifugation. Approximately 5% of total biliary cholesterol present in the vesicular fractions was in fact solubilized in mixed micelles as assessed by gel filtration chromatography. Although the proportion of vesicles and micelles estimated with the present ultracentrifugal method is in the range reported by other authors using the more common chromatographic method, we believe that our method has two major advantages. First, it eliminates the dilutional effect of buffers necessary for gel filtration chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)

Bile↗
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↗
PubMed1990

Rapid isolation of vesicular and micellar carriers of biliary lipids by ultracentrifugation.

A simple, rapid, and new method has been developed to isolate and to quantitate the vesicular carrier of biliary lipids by isopycnic ultracentrifugation. The method combines the use of Metrizamide, as an inert centrifugation media to change the density of bile for isopycnic separation of vesicles, and a vertical rotor, to decrease both the time of centrifugation and the pressure of the hydrostatic column in the ultracentrifuge tube. Vesicles harvested from bile-Metrizamide density gradients were identified by negative staining electron microscopy. The buoyant densitites of biliary vesicles varied between 1.010 and 1.030 g/ml. The diameter of vesicles in fractions with d less than 1.020 g/ml was 82 +/- 10 nm and in fraction with d approximately 1.030 g/ml was 57 +/- 8 nm. Gel filtration chromatography with Ultrogel AcA 34 was used to validate the quantitive isolation of vesicles by the ultracentrifugal method. In experiments with bile-Metrizamide continuous preformed density gradients, greater than 93% of vesicular cholesterol was found in fractions with d less than 1.030 g/ml after 285 min of centrifugation at 50,000 rpm in a VTi vertical rotor (Beckman Instruments, Inc.). When 16% Metrizamide was dissolved in bile and centrifuged for 120 min, greater than 96% of total vesicular cholesterol was found in the top 0.4 ml of the 5-ml centrifuge tube, as assessed by gel filtration chromatography. This fraction contained less than 8% of cholesterol carried in micelles, as assessed by gel filtration chromatography. The variation coefficient of this short ultracentrifugal method to isolate biliary vesicles was 4.6%.(ABSTRACT TRUNCATED AT 250 WORDS)

Bile↗
PubMed1989

[Acute pancreatitis and hypertriglyceridemia].

The etiology and pathogenesis of acute pancreatitis are unknown in the majority of patients. However, it is well known that there are several relevant clinical conditions associated to acute pancreatitis such as, gallstone disease, alcoholism and hypertriglyceridemia. The possible pathogenic relationships between acute pancreatitis and hypertriglyceridemia are discussed in this article. It has recently been shown that a significant proportion of patients with a history of acute pancreatitis have an abnormal clearance of exogenous triglycerides, indicating the presence of a preexistent metabolic abnormality in this population. This observation supports the hypothesis of a possible genetic heterogeneity related to either an abnormal apoprotein profile of chylomicrons, or hepatic receptor mechanism of chylomicron remnants uptake in the liver. If this hypothesis proves to be correct, then a genetic marker may be available to identify the subjects at high risk for acute pancreatitis.

Acute Disease↗
PubMed1989

[Characterization of lipoprotein catabolism in biliary cholesterol hypersecretion conditions in rats].

The liver represents the principal pathway for sterol excretion from the organism. In addition, the major proportion of serum lipoproteins is catabolized in the liver. It is known that diosgenin and bean diet markedly induce biliary cholesterol output. In this series of studies we characterized the catabolism of several lipoprotein particles in animals fed diosgenin or a bean-rich diet (biliary cholesterol output is increased greater than 300% in these animals). Human low density lipoprotein (hLDL) and rat high density lipoprotein apo-E free (rHDL) were labeled with 125I. Rat chylomicrons were labeled with cholesterol-(3H)-oleate. hLDL clearance increased from 381 +/- 39 to 628 +/- 44 (microliters/h x 100 g body wt) (p less than 0.005) in bean-fed rats. The half life (t1/2) decreased from 12.4 +/- 1 to 9.8 +/- 0.7 h (p less than 0.005) in these rats. The clearance of rHDL apo-E free increased from 579 +/- 8 to 680 +/- 36 (microliters/h x 100 g body wt) (p less than 0.05) in diosgenin-fed animals. The t1/2 significantly decreased from 8.2 +/- 0.7 h to 7.0 +/- 0.3 h (p less than 0.05) in these rats. In contrast, chylomicron clearance and t1/2 were not modified by the diosgenin or bean diets. These results are consistent with the hypothesis that the number and/or affinity of the B/E and A-I receptors, but not E receptors are increased in rats fed biliary cholesterol hypersecretory diets. These studies suggests the presence of a functional inter-relationship between the biliary and sinusoidal pathways of hepatic cholesterol.

Animals↗
PubMed1989

Influence of legume intake on biliary lipids and cholesterol saturation in young Chilean men. Identification of a dietary risk factor for cholesterol gallstone formation in a highly prevalent area.

Chileans and North American Indians have one of the highest prevalence rates of cholesterol gallstones in the world. The most common theory to explain this has been the operation of some as yet undefined genetic risk factor in these populations. Searching for some common environmental factor for gallstones in Chileans and North American Indians, we found that beans and other legumes are common foods consumed by both populations. In this study we tested the hypothesis that legume intake may favor the production of biliary cholesterol supersaturation. We studied 20 young men subjected to a diet containing 120 g/day of legumes and a control diet without legumes for a period of 1 mo each. Both diets supplied identical quantities of energy, carbohydrates, protein, total fat, fiber, and cholesterol. Low-density lipoprotein cholesterol concentration decreased by 16% (p less than 0.001) after the legume diet. Biliary cholesterol saturation increased in 19 of the 20 subjects; the mean of the group markedly increased from 110% to 169% (p less than 0.001) after the legume diet. These results are consistent with the hypothesis that legume intake is a potential risk factor for cholesterol gallstone disease.

Adult↗
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↗