PubMed Health⌕ Search

Biomedical subjects

C Tiribelli

Publications and source records attributed to C Tiribelli.

At least 73 records · Page 4Linked to original sources
PubMed1994

Competition of bile acids on the sulfobromophthalein uptake in basolateral rat liver plasma membrane vesicles.

The effect of different bile acids (BA) on the hepatic uptake of sulfobromophthalein (BSP) was investigated in liver plasma membrane vesicles enriched in basolateral fraction. BSP uptake was measured either in the absence (electroneutral component) or in the presence of a membrane potential (electrogenic component) induced by the addition of valinomycin in the presence of an inwardly-directed potassium gradient. BSP uptake was also measured in the presence of different BA [cholate (C), taurocholate (TC), ursodeoxycholate (UDC) and tauroursodeoxycholate (TUDC)]. Electrogenic BSP uptake was not affected by BA. Conversely, the electroneutral portion of the BSP uptake was inhibited with an inhibition constant (Ki, microM) of 230 +/- 40 for C, 103 +/- 33 for TC, 99 +/- 34 for UDC and 120 +/- 39 for TUDC, respectively (means +/- SD, N = 4). The Dixon and Cornish-Bowden plot of the data revealed an uncompetitive type of inhibition for each BA. These data indicate that the electroneutral, but not the electrogenic, BSP transport system is modulated by BA.

Animals↗
PubMed1994

Role of BSP/bilirubin binding protein and bilitranslocase in glutathione uptake in rat basolateral liver plasma membrane vesicles.

Glutathione (GSH) efflux in the liver is mediated by carrier proteins sensitive to membrane potential (electrogenic), and it is inhibited by organic anions. The hepatic uptake of tetrabromosulfophthalein (BSP) is also a carrier-mediated function accomplished at least by two different transport mechanisms, bilitranslocase (BTL) and BSP/Bilirubin Binding Protein (BBBP). The two proteins operate in parallel, the former operating electro-genically, the latter being insensitive to membrane potential (electroneutral). To investigate the relationship between transport mechanisms for GSH and organic anions, the initial uptake rate of 35S-labelled BSP into basolateral rat liver plasma membranes was measured in the presence of external or intravesicular GSH. Electrogenic and electroneutral BSP uptake were neither cis-inhibited nor trans-stimulated by GSH. 3H glycine-GSH uptake in LPMV was not modified by pre-incubating LPMV with anti-BTL or anti-BBBP antibodies. These data indicate that GSH hepatic uptake is mediated neither by BBBP nor BTL.

Animals↗
PubMed1994

Prevalence of chronic liver disease in the general population of northern Italy: the Dionysos Study.

Data on the prevalence of chronic liver disease, derived from selected series of hospitalized patients or from mortality registers, underestimate the prevalence of chronic liver disease. The Dionysos Study is a cohort study that investigated for the first time the prevalence of chronic liver disease in a general population. All the citizens of two towns in northern Italy, Campogalliano and Cormons, aged 12 to 65 yr were contacted by letter. From March 1991 through March 1993, 6,917 of a total of 10,150 citizens were enrolled (compliance, 69%). The standardized protocol for each enrollee included (a) a color-illustrated food questionnaire on dietary habits and alcohol intake; (b) a detailed medical history, including questions on risk factors for chronic liver disease; (c) a physical examination; and (d) blood tests for AST, ALT, gamma-glutamyltranspeptidase, mean cell volume, platelet count and hepatitis B virus and hepatitis C virus markers. Signs suggestive of chronic liver disease were seen in 21.3% of the subjects, and who then underwent further liver function tests, upper abdominal ultrasonography and, when necessary, liver biopsy. Persistent signs of chronic liver disease were present in 17.5% of the subjects, including 1.1% with cirrhosis and 0.07% with hepatocellular carcinoma. The prevalence rates of hepatitis B virus and hepatitis C virus positivity (second-generation enzyme-linked immunosorbent assay) were 1.3% and 3.2%, respectively. Alcohol abuse was the etiological agent in 23%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Different genotypes of hepatitis C virus are associated with different severity of chronic liver disease.

The presence of the "Japanese type" NS4 region was investigated in two series of patients (53 from Italy and 58 from Japan) with hepatitis C virus (HCV)-related chronic liver disease. The two populations were homogeneous as regard to age, male/female ratio, histological diagnosis, and serum aminotransferase activities. Genomic amplification was carried out by "nested" polymerase chain reaction (PCR) with a pair of primers synthesized according to the sequence of JK-1 isolated in Japan. The presence of viral replication was confirmed further by PCR amplification of the 5'NC region. The NS4 region of the Japanese strain was detected in 24 sera (45%) from Italy and in 44 (71%) from Japan. NS4-positive patients were significantly older and showed an ALT serum level significantly lower (P < 0.01) than NS4 negative cases in each group. Cirrhosis was significantly (P < 0.0007) more common in NS4-positive than in NS4-negative patients. The HCV genotype was subsequently obtained according to Okamoto. All the NS4-positive patients were infected by Type II, whereas in NS4-negative patients all four genotypes were present though Type II still constituted the majority. Cirrhosis was associated exclusively with Type II both in NS4-positive and -negative subjects. These data indicate that, although the positivity for NS4 "Japanese" region seems to be associated with a more aggressive liver disease, the most prevalent Type II predicts more specifically those who are likely to develop cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1993

In vitro assessment of the ethanol-induced hepatotoxicity on HepG2 cell line.

This study reports on measurement of the ethanol-induced hepatotoxicity in vitro on using the human hepatocyte cell line HepG2. Cells were incubated in the presence of increasing ethanol concentrations (10-80 mM). Cytotoxicity was quantitated spectrophotometrically both by the metabolism of the tetrazolium dye MTT and by the release into the medium of LDH and other marker enzymes of ethanol damage (AST, GGT and GHD). No cytotoxicity was observed up to 40 mM ethanol whereas a dose-dependent increment was found at higher concentrations (60-80 mM ethanol). At 80 mM ethanol, cell viability after 24 hours was reduced to 68% and 60% as assessed by MTT and LDH release respectively (p < 0.0001 vs. controls). Exposure for additional 24 hours did not increase cytotoxicity. Transmission electron microscopy revealed the presence of fat droplets (steatosis) and mitochondrial damage. The method reported appears to be an useful and reproducible technique for the in vitro assessment of the ethanol-induced cytotoxicity in a human liver cell line.

Analysis of Variance↗
PubMed1993

Difference in hepatic uptake of tetra- and di-bromosulfophthalein in rat. Role of hydrophobicity, binding to plasma proteins and affinity for plasma membrane carrier protein.

The relative role of hydrophobicity, binding to plasma proteins and affinity for one of the plasma membrane transport proteins in the hepatic uptake of 3,4,5,6-tetra- (BSP) and 3,6-di- (DBSP) bromosulfophthalein was investigated in the rat. In terms of physicochemical characteristics, the two molecules show different pKa values and degrees of hydrophobicity, as determined from the n-octanol:water partition coefficient. In the intact animal, the plasma clearance and the plasma removal rate after a dose of 1.5 mumol/kg i.v. were significantly (P < 0.001) faster for BSP than DBSP, while no difference was found in the plasma distribution volume. The dissociation constant (Kd) of the high affinity binding sites of plasma proteins also differed for the two anions, being significantly lower for BSP than DBSP (0.95 +/- 0.02 vs 1.44 +/- 0.14 microM, P < 0.001). [35S]BSP uptake by liver plasma membrane vesicles was saturable with an apparent Km of 5.20 +/- 0.80 microM, and was competitively inhibited by DBSP (Ki 18.2 +/- 1.2 microM) indicating a common uptake system. The Kd value for binding of the organic anions to purified bilitranslocase, a plasma membrane protein involved in the electrogenic transport of pthaleins, was also significantly lower for BSP than DBSP (1.10 +/- 0.12 vs 3.02 +/- 0.27 microM, N = 3, P < 0.001), indicating a higher affinity of the former ligand for the carrier protein. No difference was observed in the capacity of the high affinity binding sites (32 +/- 3 vs 33 +/- 3 nmol/mg protein, BSP and DBSP, respectively). These data indicate that BSP and DBSP are two different cholephilic organic anions which share a common uptake mechanism, at least partly mediated by bilitranslocase. The greater affinity of BSP than DBSP for the carrier protein may account for the faster plasma disappearance rate of BSP observed in vivo, in spite of the higher plasma protein binding.

Animals↗
PubMed1993

Bilitranslocase and sulfobromophthalein/bilirubin-binding protein are both involved in the hepatic uptake of organic anions.

The hepatic uptake of cholephilic organic anions is a carrier-mediated process. Three distinct proteins [bilitranslocase (BTL), sulfobromophthalein (BSP)/bilirubin-binding protein (BBBP), and organic anion-binding protein] have been isolated from the basolateral plasma-membrane domain of the hepatocyte. To investigate the relative role of the first two of them in accounting for the hepatic uptake of organic anions, we measured the initial rates of uptake of 35S-labeled BSP into rat liver plasma-membrane vesicles. Because transport by BTL is electrogenic but transport by BBBP is electroneutral, studies were done either with or without a positive-inside membrane potential produced by adding valinomycin in the presence of an inwardly directed K+ gradient (outside K+ > inside K+). Both electrogenic and electroneutral transport systems followed saturation kinetics. Electroneutral uptake showed an apparent Km of 20 +/- 3 microM (mean +/- SD) and a Vmax of 1.0 +/- 0.13 nmol.(mg of prot)-1.15 sec-1, whereas the electrogenic portion of BSP uptake exhibited a Km of 5.2 +/- 0.8 microM and a Vmax of 1.1 +/- 0.1 nmol.(mg of prot)-1.15 sec-1. In this case, an overshoot was observed 15 sec after valinomycin addition. Electroneutral BSP uptake was inhibited by incubation with anti-BBBP antibody, whereas anti-BTL antibody did not show any inhibitory effect. Conversely, the electrogenic uptake was inhibited by anti-BTL antibody at a BSP concentration of 5 microM; no inhibition was seen either at 20 microM BSP or upon addition of anti-BBBP antibody. From these data we conclude that the hepatic uptake of organic ions occurs via two immunologically distinct carrier proteins (BTL and BBBP) operating in parallel. BTL is a higher affinity electrogenic transporting system of organic ions, whereas BBBP is a lower affinity electroneutral transporter.

Animals↗
PubMed1993

1H NMR spectroscopic studies of lipid extracts from human fatty liver.

Lipid extracts of biopsy samples from normal and non-alcohol-induced fatty human liver were studied by 1H-NMR at 200 MHz. Spectra of the lipid extracts from 10 mg samples were obtained in 6 min with routine acquisition parameters and allowed the calculation of the phosphatidylcholine to total fatty acyl chain ratio, the cholesterol to total fatty acyl chain ratio, the average fatty acyl chain length, the unsaturation ratio and the acylated glycerol to total fatty acyl chain ratio. The data suggest that lipids with a higher ratio of de novo synthesized fatty acyl chains are stored in non-alcohol-induced fatty liver. NMR lipid analysis appears to be a reliable method for the rapid assessment of hepatic lipid composition on bioptic specimens.

Biopsy↗
PubMed1993

Effect of ursodeoxycholic acid administration on bile duct proliferation and cholestasis in bile duct ligated rat.

The origin, mechanism, and significance of the bile duct proliferation (BDP) associated with cholestasis remain unexplained. This study examined the effect of oral administration of ursodeoxycholic acid (UDCA) on both BDP and cholestasis in the rat. After bile duct ligation, male Sprague-Dawley rats were treated for 30 days with either UDCA (5 mg/day) (group A) or saline solution (group B). Animals were sacrificed at day 30. The serum activity of aminotransferase (ALT, AST), alkaline phosphatase, and gamma-glutamyltransferase (GGT) was significantly lower (P < 0.01) in the UDCA-treated rats. Total serum bilirubin and total serum bile acids were lower (P < 0.001) in group A. Moreover, the control of BA in bile was reduced also (P < 0.02). Conversely, serum cholesterol levels were not different between the two groups. Histological examination showed that the number of ductular cells in the portal areas was significantly (P < 0.001) reduced in UDCA-treated as compared to saline-treated rats. The replication activity, assessed as the number of bromodeoxyuridine-positive cells, was also significantly lower in treated animals (33 +/- 11 vs 64 +/- 22 per 1000 cells; P < 0.001). Lobular bile ductules were three times larger in group B, and extrahepatic duct measurements confirmed this increase in size of the larger biliary ducts (P < 0.001). These findings demonstrate that UDCA reduces BDP in response to BD ligation. Although the mechanism(s) of this effect is still hypothetical, UDCA may reduce the level of irritating bile salts such as chenodeoxycholic acid and lithocolate and increase periductular bile acid recirculation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Ursodiol in the long-term treatment of chronic hepatitis: a double-blind multicenter clinical trial.

Ursodeoxycholic acid (UDCA or ursodiol) administration has been associated with a reduction of serum liver enzymes in patients with chronic liver disease and with improvement of liver histology in patients with primary biliary cirrhosis. To establish the potential therapeutic efficacy of ursodiol in chronic hepatitis, serum biochemistry and liver histology were investigated in a multicenter, double-blind placebo controlled clinical trial. Sixty patients with non-cholestatic chronic active (mild or severe) hepatitis, mainly of viral (virus C) etiology and almost completely asymptomatic, were enrolled in 3 centers: 29 were assigned to receive placebo and 31 UDCA (600 mg/day) for 1 year. Demographic, biochemical, virological and histological features were balanced between the 2 groups at the entrance into the study. Fifty-six patients (34 males, 22 females; 19 with cirrhosis; 5 HBsAg-positive; 45 anti-HCV positive) were included in the final analysis. Compliance was checked by measuring UDCA levels at the 3 follow-up visits (3, 6 and 12 months). Liver biopsy was performed at the beginning and at the end of treatment and was evaluated blindly by our pathologist (F.C.). Alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gammaglutamyltransferase (GGT) levels were significantly reduced by 25% from baseline values during treatment with ursodiol but not with placebo. The efficacy of UDCA in lowering serum AST and ALT was more pronounced in the presence of cirrhosis. The semiquantitative liver histological score used remained substantially unchanged after treatment and no differences between placebo and UDCA were found for portal or periportal necrosis or inflammation, intralobular degeneration, cholestasis or fibrosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Fatty infiltration of the liver. Quantification by 1H localized magnetic resonance spectroscopy and comparison with computed tomography.

RATIONALE AND OBJECTIVES: The authors evaluated the degree of fatty infiltration of the liver in subjects with diffuse liver steatosis using image-guided 1H localized MR spectroscopy and correlated the magnetic resonance (MR)-determined fat fraction with the computed tomography (CT) liver/spleen density ratio and histologic evaluation. METHODS: MR measurements were performed at 1.5 T by applying a double-spin-echo localization sequence. Twenty-six patients underwent MR and CT examinations and ultrasound (US)-guided biopsy. Additionally, three healthy volunteers underwent MR examination. Steatosis severity was estimated using 1) the ratio between fat and total MR signal areas; 2) the ratio between liver and spleen CT number; and 3) histologic score. RESULTS: The linear correlation between MR fat/fat-plus-water signal ratio and CT liver/spleen density values ratio is statistically significant. Both techniques correlate well with histologic score. No significant correlation exists between water or fat T2 values and the severity of steatosis. CONCLUSIONS: 1H MR spectroscopy allows a noninvasive estimate of the hepatic fat content.

Adult↗
PubMed1992

Transport of sulfobromophthalein and taurocholate in the HepG2 cell line in relation to the expression of membrane carrier proteins.

The transport of two different classes of organic anions (cholephilic dyes; the sulfobromophthalein, BSP, and bile acids; taurocholate, TC) was investigated in the HepG2 cell line. At 37 degrees C, BSP uptake was found to be biphasic with an apparent saturative curve in the concentration range between 0-6 microM followed by a linear component up to 18 microM. Kinetic constant determination showed an apparent Km of 26.6 +/- 3.1 microM and a Vmax of 5.64 +/- 0.82 nmol BSP.min-1.mg prot-1. At 4 degrees C, uptake was linear. By subtracting this latter component from the total uptake, a saturable, carrier mediated uptake was found with an apparent Km of 3.6 +/- 1.0 microM BSP and a Vmax of 0.37 +/- 0.04 nmol BSP.min-1.mg prot-1 (m +/- SEM, n = 6). These values were fully comparable with those found in freshly isolated male hepatocyte. Immunoblot analysis of HepG2 cell plasma membrane revealed the presence of bilitranslocase when tested against a monospecific antibody against this carrier molecule. On the contrary, TC uptake was linear up to concentration of 100 microM TC. No difference was observed in the presence or absence of Na+. Immunoprecipitation analysis showed the absence of the putative carrier of TC. These data indicate that the HepG2 cell line expresses a functioning bilitranslocase-mediated system. Conversely, carrier mediated bile acid uptake is absent in line with the lack of expression of the carrier protein.

ATP-Binding Cassette Transporters↗
PubMed1992

Effect of ethinylestradiol and epomediol on bile flow and biliary lipid composition in rat.

Epomediol (1,3,3-trimethyl-2-oxabicyclo(2.2.2.)octan-6,7-endo,endo-diol) (EPO) is a terpenoid compound shown to reverse 17 alpha-ethinylestradiol (EE)-induced cholestasis in rat. The effect is related to the restoration of normal liver plasma membrane fluidity values. To further characterize the effect of EPO, bile flow and biliary lipid composition were measured in rats treated either with EE or EE associated with EPO. EE significantly reduced the bile flow; this reduction was prevented by concomitant treatment with EPO with an increase in the bile salt secretion rate. EPO alone showed a choleretic effect. The biliary secretion rate of cholesterol was also significantly reduced by EE while being comparable to controls in EE-EPO-treated animals. Phospholipid (PL) biliary excretion was significantly (P less than 0.002) increased by EE either alone or combined with EPO. After EE treatment, the biliary PL composition showed a reduction in phosphatidylcholine (PC) concentration with a parallel increase in lyso-phosphatidylcholine (LPC) when compared to control animals (PC:LPC ratio 5.0 +/- 2.5 vs 26.8 +/- 9.9, mean +/- SD, P less than 0.005). EPO administration to EE-treated rats restored the biliary PC:LPC ratio to control values (27.6 +/- 10.6). EPO alone did not show any appreciable effect as compared to both control and EE-EPO treated animals. As increased concentrations of LPC have been reported to induce an alteration in the function of membrane lipids and membrane-associated proteins, such as regulatory enzymes for bile acid, cholesterol and phospholipid metabolism, these results suggest that the protective effect of EPO in EE-induced cholestasis may be related to the reversal of the alterations in membrane lipid composition and function induced by EE.

Animals↗