Biomedical subjects

F Marra

Publications and source records attributed to F Marra.

At least 73 records · Page 4Linked to original sources

PubMed1996

Defective aggregation in cirrhosis is independent of in vivo platelet activation.

BACKGROUND/AIMS: Platelet function abnormalities contribute to the hemostatic defect in patients with cirrhosis. In this study we evaluated the occurrence of in vivo platelet activation as a possible mechanism of defective platelet aggregation in patients with cirrhosis. METHODS: Nine patients with severe (Child B-C) cirrhosis and defective platelet aggregation were studied in comparison with age- and sex-matched healthy controls. The presence of activated platelets in the bloodstream was evaluated by fluorescence-activated flow cytometry using antibodies directed against activation-dependent platelet proteins and by measuring plasma levels of beta-thromboglobulin and platelet factor 4. Urinary levels of 11-dehydro-TXB2 and of 2,3-dinor-TXB2 were assayed by radioimmunoassay following chromatographic separation. RESULTS: In unstimulated platelets, the expression of both GMP 140 and GP 53 was not significantly different in patients with cirrhosis and in controls. After stimulation with ADP and epinephrine, expression of activation-dependent antigens was lower in platelets from patients (GMP 140: 0.64 +/- 0.09 vs 0.73 +/- 0.04, p = 0.02; GP 53: 0.41 +/- 0.13 vs 0.54 +/- 0.14). Plasma levels of beta-thromboglobulin and platelet factor 4, as indexes of in vivo platelet activation, were also comparable in the two groups of subjects. Urinary levels of 11-dehydro-TXB2 and of 2,3-dinor-TXB2, the major systemic metabolites of TXA2, were significantly higher in patients with cirrhosis (1807 +/- 518 vs 341 +/- 121 ng/pg creatinine and 693 +/- 512 vs 205 (93 ng/pg creatinine, respectively, p < 0.001). However, increased excretion of TXB2 metabolites was also observed in three patients with chronic autoimmune thrombocytopenia. CONCLUSIONS: These data indicate that circulating platelets are not activated in cirrhosis, and that defective aggregation is most likely dependent on the alteration of the transmembrane signaling pathways. The increased urinary excretion of systemic TXA2 metabolites may be related to increased intrasplenic platelet destruction.

Aged↗

PubMed1996

Pharmacokinetics and pharmacodynamics of torasemide and furosemide in patients with diuretic resistant ascites.

BACKGROUND/AIM: To evaluate the pharmacokinetics and pharmacodynamics of furosemide and torasemide in patients with cirrhosis and diuretic resistant ascites. METHODS: Eighteen patients were randomly allocated to receive intravenous torasemide (40 mg) or furosemide (80 mg). The renal response to these drugs was assessed in baseline conditions and in the 24 h following drug administration together with plasma and urinary concentrations of furosemide, torasemide and its metabolites. RESULTS: Torasemide induced significantly greater diuretic and natriuretic effects than furosemide in the first hour after drug administration. No other significant differences between the two drugs were observed with respect to the renal response to these drugs. Torasemide reached a lower maximum plasma concentration than furosemide, but the former drug had a longer apparent terminal half-life and lower renal and non-renal clearances. Comparing these results with those previously reported in healthy subjects, both drugs showed a reduced elimination rate through renal and non-renal routes, and a larger distribution to body fluids. As a consequence, the half-life of both drugs was longer than in healthy subjects. Urinary excretion of pharmacologically active species, however, was quantitatively unchanged after torasemide administration, whereas it was reduced after furosemide. Finally, the natriuretic potency of both drugs was markedly reduced in these patients. CONCLUSIONS: The pharmacokinetics and pharmacodynamics of torasemide and furosemide are markedly altered in patients with diuretic resistant ascites.

Adult↗

PubMed1996

PDGF stimulates tyrosine phosphorylation of JAK 1 protein tyrosine kinase in human mesangial cells.

Platelet-derived growth factor (PDGF) exerts multiple effects in glomerular mesangial cells, including transcription of genes that mediate its biological activity. We have partially characterized PDGF-mediated early mitogenic signal transduction pathways that include activation of protein kinase C alpha and phosphatidylinositol 3 kinase. However, the precise mechanism of PDGF-induced gene transcription is not yet clear. A family of cytoplasmic transcription factors referred to as signal transducers and activators of transcription (STAT) has recently been identified. This group of transcription factors is activated by different cytokines via tyrosine phosphorylation. We studied the effect of PDGF on STATs in human mesangial cells. Using a gel retardation assay, nuclear and cytoplasmic extracts from PDGF-stimulated mesangial cells contained protein factors that bind to a DNA sequence representing the sis-inducible element (SIE) present in the c-fos gene promoter. These protein factors also bind to the enhancer element present in interferon-gamma responsive genes, suggesting the involvement of STAT proteins. The addition of monoclonal antibody that recognizes STAT 1 results in "supershift" of the DNA-protein complex stimulated by PDGF indicating the presence of STAT 1. Immunoblotting experiments with a monoclonal STAT 1 antibody revealed the presence of STAT1 alpha and STAT1 beta in mesangial cells. Since certain cytokines activate STATs via tyrosine phosphorylation mediated by JAK family of tyrosine kinases, we studied the effect of PDGF on JAK kinases. Antiphosphotyrosine immunoblotting of JAK 1 immunoprecipitates from PDGF-stimulated mesangial cell lysate showed increased tyrosine phosphorylation of this tyrosine kinase. In vitro immune complex kinase assay of JAK 1 immunoprecipitates from PDGF-stimulated mesangial cell lysate revealed activation of this tyrosine kinase. Taken together, these data demonstrate that PDGF activates the transcription factor STAT 1 in mesangial cells. The data also provide the first evidence that PDGF stimulates tyrosine phosphorylation of JAK 1, the cytoplasmic tyrosine kinase stimulated by many other cytokines to activate transcription via STATs. These observations indicate that JAK 1 is a downstream tyrosine kinase in PDGF receptor signaling and is a candidate for activation of STAT 1.

Binding Sites↗

PubMed1996

Inhibition by pentoxifylline of extracellular signal-regulated kinase activation by platelet-derived growth factor in hepatic stellate cells.

1. It has been proposed that pentoxifylline (PTF) acts an antifibrogenic agent by reducing the synthesis of extracellular matrix components, and this possibility has been confirmed in animal models of hepatic fibrosis. In this study the effects of PTF on the proliferation of extracellular matrix producing cells induced by platelet-derived growth factor (PDGF) were evaluated. The study was performed on hepatic stellate cells, currently indicated as the major source of extracellular matrix in fibrotic liver. 2. PTF caused a dose-dependent reduction of PDGF-induced mitogenesis with an IC50 of 170 microM, identical to the EC50 for the increase in intracellular cyclic AMP levels. Preincubation with PTF did not affect either PDGF-receptor autophosphorylation or phosphotidylinositol 3-kinase activity, whereas it markedly reduced PDGF-stimulated extracellular signal-regulated kinase (ERK) activity and ERK isoform phosphorylation. PTF also reduced PDGF-induced c-fos mRNA expression, which is dependent on activation of the RAS/ERK pathway. In addition, the PDGF-induced increase in cytsolic-free calcium was almost completely prevented by pretreating the cells with PTF. 3. The results of the present study indicate that PTF, in addition to its effect on collagen deposition and degradation, may exert an antifibrogenic effect by reducing the PDGF-induced proliferation of extracellular matrix producing cells. This effect appears to be mediated by a reduction of PDGF-stimulated ERK activity as well as of other intracellular signalling pathways such as the PDGF-induced elevation of cytosolic-free calcium.

Adipocytes↗

PubMed1996

Thrombin stimulates association of src homology domain containing adaptor protein Nck with pp125FAK.

Thrombin stimulates mitogenesis and tyrosine phosphorylation of several proteins in glomerular mesangial cells [T. Force, J. M. Kyriakis, J. Avruch, and J. V. Bonventre, J. Biol. Chem. 266: 6650-6656, 1991; and G. Grandaliano, G. Ghosh Choudhury, P. Biswas, and H. E. Abboud, Am. J. Physiol. 267 (Renal Fluid Electrolyte Physiol. 36: F528-F536, 1994]. However, none of the tyrosine phosphorylated proteins have been identified. Here we show that thrombin stimulates phosphorylation of four major proteins of molecular masses 170, 125, 97, and 47 kDa in antiphosphotyrosine immunoprecipitates in vitro. Immunoblot analysis of antiphosphotyrosine immunoprecipitates from lysates of thrombin-treated cells with anti-Nck antibody revealed the presence of this src homology domain-containing adaptor molecule in the tyrosine-phosphorylated protein fraction. In addition, in thrombin-treated cells, direct immunoblotting of Nck immunoprecipitates with antiphosphotyrosine antibody showed no tyrosine phosphorylation of Nck. In these immunoprecipitates, we detected a 125-kDa tyrosine-phosphorylated protein. We identified this protein as pp125FAK (FAK, focal adhesion kinase) after analyzing Nck immunoprecipitates by anti-FAK immunoblotting. Treatment of mesangial cells with thrombin resulted in stimulation of the tyrosine kinase activity of pp125FAK in vitro. We conclude that activation of the cytoplasmic protein tyrosine kinase pp125FAK by thrombin stimulates its association with the src homology domain-containing adaptor protein Nck. This indicates that Nck is a direct target for FAK in the thrombin-induced signal transduction pathway.

Adaptor Proteins, Signal Transducing↗

PubMed1996

Epidermal growth factor, epidermal growth factor receptor, and transforming growth factor-alpha in human hyperplastic prostate tissue: expression and cellular localization.

It is widely accepted that polypeptide growth factors are involved in the growth and development of normal and neoplastic human prostate. It has been previously reported that epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) receptors are present in the human hyperplastic prostate tissue (BPH). To add information on the mechanism of action of EGF and transforming growth factor-alpha (TGF alpha), a peptide correlated to EGF, and the EGF receptor (EGF-R) in the human prostate, we studied the expression and cellular localization of messenger ribonucleic acid (RNA) encoding EGF, EGF-R, and TGF alpha in BPH tissue. Reverse transcriptase-PCR of total RNA extracted from BPH tissues documented the presence of specific transcripts for EGF, EGF-R, and TGF alpha. In situ hybridization with specific RNA probes synthesized from the respective complementary DNA demonstrated that EGF, EGF-R, and TGF alpha messenger RNAs were mainly localized in the epithelial cells. Immunprecipitation and Western blot analysis showed that BPH tissue contained the corresponding proteins, EGF and TGF alpha. Our findings provide additional support for the idea that EGF and TGF alpha may be considered specialized symbols in the language of cell-cell interactions and for the hypothesis that in the human prostate they seem to act in an autocrine fashion.

Epidermal Growth Factor↗

PubMed1996

Monocyte chemotactic peptide-1 expression in acute and chronic human nephritides: a pathogenetic role in interstitial monocytes recruitment.

Tubulointerstitial damage is a common histopathological feature of acute and chronic renal diseases and a prognostic indicator of renal function outcome. Monocytes infiltrating the interstitium, through the release of cytokines and/or growth factors, may play a key role in the pathogenesis of tubulointerstitial damage. Monocyte chemotactic peptide-1 (MCP-1) is a specific and powerful chemoattractant and activating factor for monocytes. This study investigated MCP-1 expression and its correlation with monocyte infiltration and tubulointerstitial damage in biopsies of patients with acute interstitial nephritis (AIN) and a chronic glomerulonephritis, namely immunoglobulin. A nephropathy (IgAN), often characterized by tubulointerstitial involvement. Six patients with AIN and 20 patients with IgAN, nine with mild (G1 to 2) and 11 with moderate to severe histologic lesions (G3 to 5), were studied. MCP-1 gene and protein expression were evaluated by in situ hybridization and immunohistochemistry. Infiltrating CD68-positive cells were identified as monocytes. MCP-1, weakly expressed in normal kidneys, was clearly upregulated in AIN biopsies. The gene and the protein expression were primarily localized in tubular and glomerular parietal epithelial cells, as well as in infiltrating mononuclear cells. In IgAN, a striking increase in MCP-1 mRNA and protein expression was observed only in the biopsies with moderate to severe lesions, with a pattern of expression similar to AIN. The MCP-1 expression strictly correlated with monocyte infiltrates and tubulointerstitial damage. In addition, the urinary excretion of this chemokine was studied in 17 IgAN patients. MCP-1 protein concentration was higher, compared with healthy subjects, in IgAN patients, especially in the G3 to 5 group, and directly correlated with the renal MCP-1 gene expression. In conclusion, these data suggest that production of MCP-1 in the tubulointerstitial compartment may play a key role in modulating monocytes influx and, consequently, tubulointerstitial damage.

Acute Disease↗

PubMed1996

Aminoglycoside administration as a single daily dose. An improvement to current practice or a repeat of previous errors?

Despite the availability of newer and safer antibacterials, aminoglycosides continue to play a major role in the management of infections in hospitalised patients. The concept of single daily dose (SDD) regimens was introduced many years ago and is now receiving much attention as an alternative regimen for this class of drugs. To evaluate the rationale and clinical support for SDD schemes, we conducted a 'MEDLINE' search to locate relevant preclinical and clinical literature pertaining to this issue. The results of animal model and noncomparative clinical data tended to be variable and inconclusive. We were able to identify 28 prospective comparative clinical trials; however, only one was randomised, double-blind and of sufficient sample size to detect differences in efficacy between treatment arms, should any exist. Despite these flaws, our review suggests that SDD schemes appear to be no more efficacious and no less toxic, but may be less costly, than traditional multiple daily dose schemes. We also assessed the predicted disposition of tobramycin/gentamicin in 415 patients with known pharmacokinetic parameters. With doses of 7 mg/kg at intervals of between 24 and 60 hours (depending upon renal function), the maximum serum concentration at steady-state (Cmaxss) varied from 8.5 to 55.6 mg/L, while the Cminss was < 2.0 mg/L in the majority of patients. Mid-interval serum aminoglycoside concentrations were < 0.5 mg/L in up to 23% of patients, suggesting possible underdosage in certain patients with this scheme. More conclusive clinical evidence is necessary before SDD schemes should be adopted as standard clinical practice. Empirical weight-based dosage schemes appear to yield widely variable serum aminoglycoside concentrations which could be considered therapeutically inadequate or toxic.

Aminoglycosides↗

PubMed1996

[Viral liver cirrhosis: natural course, pathogenesis and clinical implications of the complications].

The role of hepatitis B virus (HBV) and hepatitis C virus (HCV) as a major cause of chronic liver disease is now accepted worldwide. This study was aimed at evaluating the natural history of the disease in patients with virus-induced chronic active hepatitis or cirrhosis, and the influence played by age, sex and etiology, liver function tests and by the occurrence of different complications. We retrospectively examined the clinical records of 506 inpatients: 194 were affected by chronic active hepatitis (125 males, 69 females, mean age 45 +/- 11 years, 146 HCV- and 48 HBV-related), and 312 by cirrhosis without clinical evidence of portal hypertension (178 males, 134 females, mean age 53 +/- 9 years, 249 HCV- and 63 HBV-related). The occurrence of cirrhosis in the chronic active hepatitis group was then calculated, together with the occurrence of complications and the cumulative mortality rate of established cirrhosis. During follow-up 93 patients with chronic hepatitis developed cirrhosis. The cumulative probability of developing cirrhosis in this group was 6.64% at 5 years, 56.1% at 10 years and 86.8% at 15 years. These patients were therefore included in the cirrhosis group for the final analysis, so that a total of 405 cirrhotic patients were evaluated: these patients had a cumulative survival rate of 99.1% at 5, 76.8% at 10 and 49.4% at 15 years. Comparing the age-adjusted death rate of our patients with the general Italian population, we observed that in patients with liver cirrhosis it was 3.14 and 2.84 times higher in men and women, respectively. Bilirubin was an independent indicator of survival. Several complications, such as esophageal varices, ascites, jaundice, hemorrhage, hepatic encephalopathy and hepatocellular carcinoma significantly reduced the survival rate and were indicated as major complications, while thrombocytopenia, cholelithiasis and diabetes did not affect survival and thus were called minor complications. Incidence of hepatocellular carcinoma was very high especially in males, without correlation with etiology. In conclusion, the progression of virus-induced chronic active hepatitis to cirrhosis is not influenced by sex and etiology. Similarly, the different etiology does not modify the natural history of cirrhosis while the occurrence of one or more major complications significantly shortens survival. The longer survival rate observed in patients with cirrhosis included in this study is probably due to the selective inclusion of patients with early disease and no evidence of portal hypertension.

Adult↗

PubMed1995

Involvement of phosphatidylinositol 3-kinase in the activation of extracellular signal-regulated kinase by PDGF in hepatic stellate cells.

Phosphatidylinositol 3-kinase (PI 3-K) is a lipid and protein kinase which associates with the activated platelet-derived growth factor (PDGF) receptor and other tyrosine kinases. We studied the effects of wortmannin, a selective inhibitor of PI 3-K, on the activation of extracellular-signal regulated kinase (ERK) by PDGF in cultured hepatic stellate cells, mesenchymal cells responsible for extracellular matrix synthesis within the liver. Incubation with 100 nM wortmannin, a dose which almost completely blocks PI 3-K, resulted in 50% reduction of ERK activity. Direct inhibition of ERK by wortmannin could not be considered responsible for this effect, since wortmannin did not inhibit ERK activity in vitro. Rather, inhibition of PI 3-K acts on the kinase cascade that leads to ERK activation, since PDGF-dependent phosphorylation of ERK was found to be reduced after incubation with wortmannin. Wortmannin also inhibited the increase in c-fos mRNA induced by PDGF, which is dependent on ERK activation. The results of this study show that in hepatic stellate cells PI 3-K is involved in ERK activation, although it is not necessary. These data indicate cross-talk between PI 3-K and the Ras/ERK pathway in PDGF-stimulated cells.

Androstadienes↗

PubMed1995

A nuclear protein in mesangial cells that binds to the promoter region of the platelet-derived growth factor-A chain gene. Induction by phorbol ester.

Mesangial cells predominantly express platelet-derived growth factor (PDGF)-A chain mRNA and release PDGF. Mesangial cell PDGF-A chain mRNA abundance is regulated by several agents including phorbol esters. We have recently demonstrated that induction of PDGF-A chain mRNA abundance in response to phorbol 12-myristate 13-acetate is primarily due to gene transcription. We have now analyzed the 5'-flanking region of the PDGF-A chain promoter to identify DNA binding protein(s) which have the potential to regulate PDGF-A chain gene transcription in human mesangial cells. DNase I footprint analysis of the 5'-flanking region of the PDGF-A chain promoter identifies a DNase I protected region at the location -82 to -102 corresponding to the sequence 5'-GGCCCGGAATCCGGGGGAGGC-3'. Therefore, nuclear extracts from human mesangial cells contain a protein, PDGF-A-BP-1, that binds to a DNA sequence (-82 to -102) in the promoter region of the PDGF-A chain gene. Gel mobility shift analysis using labeled oligomer corresponding to the binding site for PDGF-A-BP-1 indicates that PDGF-A-BP-1 is induced by phorbol ester in mesangial cells as well as fat-storing cells (> 20 fold). Egr-1 protein does not bind to labeled PDGF-A-BP-1 oligomer and does not compete with the binding of PDGF-A-BP-1. In addition, SP-1 binding sequence does not compete with the binding sequence of the mesangial cell protein. PDGF-A-BP-1 appears to represent a novel protein which is induced by phorbol ester and thus has the potential for an important role in the transcriptional regulation of the PDGF-A chain gene in mesangial cells and other vascular pericytes.

Base Sequence↗

PubMed1995

Thrombin stimulates proliferation of liver fat-storing cells and expression of monocyte chemotactic protein-1: potential role in liver injury.

Liver fat-storing cells (FSC) proliferate and secrete extracellular matrix in experimental models of liver injury. In this study, we determined if thrombin, a serine protease produced during acute and chronic tissue injury, modulates the functions of FSC. Thrombin stimulated DNA synthesis and proliferation of FSC, as assessed by [3H]-thymidine incorporation assay and measurement of cell number, respectively. Thrombin also increased the secretion of monocyte chemotactic protein-1 (MCP-1) in a time- and dose-dependent fashion. The effect of thrombin on both DNA synthesis and MCP-1 secretion was neutralized by pretreatment of thrombin with hirudin. The increased MCP-1 secretion was associated with increased steady-state levels of MCP-1 messenger RNA. Pretreatment of FSC with 5 mumol/retinol for 48 hours inhibited the mitogenic effects of thrombin but not the induction of MCP-1 secretion. FSC express specific transcripts encoding for the human thrombin receptor, as shown by Northern blot analysis of poly(A)+ RNA. Proteolytic activation of the thrombin receptor results in the formation of a new N-terminus that functions as a tethered ligand. We studied the effects of a thrombin receptor activating peptide (TRAP) corresponding to the newly formed N-terminus on FSC. TRAP mimicked the effects of thrombin on [3H]-thymidine incorporation, MCP-1 secretion, and MCP-1 gene expression. This study suggest that thrombin may be involved in modulating FSC proliferation and monocyte chemotaxis during human liver disease, through proteolytic activation of its receptor.

Adipocytes↗

PubMed1995

Transforming growth factor-beta 1 regulates platelet-derived growth factor receptor beta subunit in human liver fat-storing cells.

Activated liver fat-storing cells (FSC) are known to play a key role in the development of liver fibrosis. An important element in FSC activation process is the increased expression of receptors for platelet-derived growth factor (PDGF), a potent mitogen for FSC. The aim of the present study was to evaluate the expression PDGF-receptor alpha and beta subunits in cultured human FSC and their regulation induced by transforming growth factor-beta 1 (TGF-beta), a cytokine potentially involved in an autocrine loop. TGF-beta induced a significant increase of the mitogenic effect of PDGF-BB and did not affect the mitogenicity of PDGF-AA and PDGF-AB, suggesting a selective action of the PDGF-receptor-beta subunit. This hypothesis was confirmed by regulation experiments showing selective and time-dependent upregulation of the messenger (m)RNA encoding for the PDGF-receptor-beta subunit and the relative protein induced by TGF-beta. In addition, binding studies showed a parallel increase of PDGF-BB binding sites after incubation of human FSC with TGF-beta. These studies provide evidence for an additional mechanism leading to the perpetuation of FSC activation and proliferation and contribute to a better understanding of the role of TGF-beta and PDGF in the development of liver fibrosis.

Becaplermin↗

PubMed1994

Biosynthesis of platelet-activating factor and its 1O-acyl analogue by liver fat-storing cells.

BACKGROUND/AIMS: Platelet-activating factor (PAF) is an important mediator of proinflammatory cell-to-cell interactions with powerful vasoactive properties. We evaluated the biosynthesis of PAF by cultured human fat-storing cells (FSC), liver-specific pericytes involved in the inflammatory and fibrogenic process of liver tissue. METHODS: PAF synthesis was evaluated by measuring [3H]acetate incorporation under basal conditions and upon stimulation with A23187, thrombin, and lipopolysaccharide. Further analysis of PAF species synthesized by FSC was performed using gas chromatography/mass spectrometry. RESULTS: All stimuli induced a significant increase of basal PAF synthesis by FSC. Further analysis showed that > 50% of the newly synthesized PAF species was secreted whereas the remaining fraction was cell-associated. PAF species produced by FSC were able to induce aggregation of rabbit washed platelets with an effectiveness correspondent to 10(-9) mol/L authentic PAF. Gas chromatography/mass spectrometry analysis revealed that a large percentage (74%) of PAF-like lipids synthesized by FSC consisted of 1O-acyl PAF. Finally, stimulation of FSC with PAF caused an increase in cytosolic free calcium, thus suggesting a possible involvement of this pericyte in the well-known effects of PAF on portal pressure. CONCLUSIONS: These results expand the available knowledge concerning the role of PAF in conditions characterized by extensive activation and damage of the liver sinusoidal endothelium and decreased hepatic scavenger activity.

Acetates↗

PubMed1994

Regulation of platelet-derived growth factor secretion and gene expression in human liver fat-storing cells.

BACKGROUND/AIMS: Liver fat-storing cells (FSCs) actively proliferate and secrete extracellular matrix during liver injury. Platelet-derived growth factor (PDGF) is a potent mitogen for cultured FSCs. In the present study, we investigated the regulation of PDGF gene expression and production in cultured human liver FSCs. METHODS: PDGF A-chain and B-chain expression was analyzed by Northern blotting and ribonuclease protection assay, respectively. Secretion of PDGF was evaluated by immunoprecipitation and immunoblotting of conditioned medium and metabolic labeling of FSC followed by immunoprecipitation. RESULTS: Three PDGF A-chain transcripts were detectable. Stimulation of FSC with phorbol myristate acetate (10(-7) mol/L) or PDGF BB (20 ng/mL) increased steady-state levels of PDGF A-chain and B-chain messenger RNA. PDGF AA had a small stimulatory effect on A-chain but not B-chain messenger RNA levels. FSCs secrete PDGF in the conditioned medium. The secreted protein is bioactive, because concentrated conditioned medium induced an increase in thymidine incorporation that was inhibited by anti-PDGF antibodies. CONCLUSIONS: This study shows that cultured FSCs express PDGF A- and B-chain genes and release bioactive PDGF in the culture medium. These data raise the possibility of an autocrine or short-loop paracrine effect of PDGF in FSCs as a mechanism contributing to the maintenance of the proliferative state during liver injury.

Cells, Cultured↗

PubMed1993

Torasemide in the treatment of patients with cirrhosis and ascites.

The effects of torasemide (20 mg/day) and furosemide (50 mg/day), each given over 4 days, were compared in a randomized and crossover study carried out in seven patients with cirrhosis and tense ascites. Patients also received a low-sodium (40 mmol/day) diet and the aldosterone antagonist, potassium canrenoate (100 mg b.i.d.). Torasemide induced a remarkably higher natriuretic (120 +/- 15 vs. 33 +/- 6 mmol/day, p < 0.02) and diuretic (1450 +/- 63 vs. 900 +/- 58 ml, p < 0.005) effect than furosemide. Body weight loss was also significantly higher (2.5 +/- 1.6 vs. 0.2 +/- 1.3 kg, p < 0.01) during the torasemide period. Kaliuresis was similar during the two treatment periods, despite the striking differences observed in natriuresis. Neither torasemide nor furosemide induced any significant change in serum electrolyte or creatinine concentrations, or in ammonia levels. The results of this study indicate that torasemide is suitable for the treatment of sodium retention in patients with cirrhosis and ascites.

Adult↗

PubMed1993

Defective signal transduction in platelets from cirrhotics is associated with increased cyclic nucleotides.

BACKGROUND: Patients with advanced cirrhosis show defective platelet aggregation, which is dependent, at least in part, on intrinsic platelet abnormalities. The aim of this study was to evaluate the activating and inhibitory pathways of platelet signal transduction in cirrhotic patients. METHODS: Twelve cirrhotic patients and 12 control subjects participated in this study. Measurements were performed on washed platelets. RESULTS: Thrombin-stimulated inositol 1,4,5-trisphosphate production was reduced fivefold, and the increase in cytosolic calcium concentration was significantly lower in platelets from cirrhotic patients following stimulation with thrombin, platelet activating factor, or U-46619. In addition, the activity of the platelet Na+/H+ antiporter, evaluated after an acid load, was significantly lower in platelets from cirrhotic patients (0.90 +/- 0.19 vs. 1.37 +/- 0.16 delta pHi/min, P = 0.07). Cirrhotic patients also showed a significantly increased basal intraplatelet content of both 5'-cyclic adenosine monophosphate (cAMP) (2724 +/- 330 vs. 1561 +/- 258 fmol/10(8) platelets, P < 0.05) and 5'-cyclic guanosine monophosphate (cGMP) (217 +/- 18 vs. 159 +/- 29 fmol/10(8) platelets, P < 0.05). CONCLUSIONS: Our results indicate that in platelets from cirrhotic patients, defective early signal transduction is associated with an increase in platelet cAMP and cGMP, thus revealing new mechanisms contributing to the defective platelet function in this disease.

Adult↗

PubMed1993

Impaired superoxide anion, platelet-activating factor, and leukotriene B4 synthesis by neutrophils in cirrhosis.

BACKGROUND: Several alterations of polymorphonuclear leukocyte (PMN) function were found in alcoholic cirrhotics that may contribute to augmented susceptibility to infections. We evaluated function and synthesis of lipid mediators in PMN obtained from nonalcoholic cirrhotics. METHODS: We evaluated the phagocytic and chemotactic response together with superoxide anion (O2-), leukotriene B4, (LTB4) and platelet-activating factor (PAF) production in response to different stimuli in PMN from nonalcoholic cirrhotics as compared with controls. RESULTS: PMN from cirrhotics showed, after stimulation with opsonized zymosan (STZ) and phorbol-12-myristate-13-acetate, a reduced capacity to produce O2- when compared with controls. [3H]acetate incorporation into PAF was significantly higher in PMN obtained from controls in respect to cirrhotics. Gas chromatography/mass spectrometry analysis confirmed a reduced PAF synthesis by PMN obtained from cirrhotics. LTB4 production from PMN, after stimulation with calcium ionophore (A23187) and STZ, was significantly reduced in cirrhotics. [3H]arachidonic acid release from prelabeled PMN, measured upon stimulation with A23187 and STZ, was higher in controls than in cirrhotics. CONCLUSIONS: An altered synthesis of LTB4 and PAF is associated with an impaired O2- production by PMN in nonalcoholic cirrhosis. Reduced synthesis of lipid mediators may be related to an altered phospholipase A, activity.

Adult↗