Search PubMed⌕ Search

Biomedical subjects

J Prieto

Publications and source records attributed to J Prieto.

At least 145 records · Page 8Linked to original sources
PubMed1999

[Effect of subinhibitory concentrations of various antimicrobials on insoluble glucan production, polystyrene adherence and bacterial surface hydrophobicity of Streptococcus sobrinus].

The effect of subinhibitory concentrations (1/2, 1/4, 1/8 of the MIC) of amoxicillin, teicoplanin, clindamycin and erythromycin on the factors influencing the adherence and pathogenicity of Streptococcus sobrinus was evaluated. These factors included insoluble glucan, polystyrene adherence and bacterial surface hydrophobicity. Insoluble glucan was detected using a spectrophotometric method; polystyrene adherence was assessed using microtiter plates; and surface hydrophobicity was determined using a biphasic system (water/p-xiline). Amoxicillin and teicoplanin induced a statistically significant decrease in adherence at subinhibitory concentrations, and they also decreased the hydrophobicity. However, clindamycin and erythromycin were unable to decrease these parameters. The adherence and hydrophobicity of S. sobrinus was also dependent on the concentration of sucrose in the culture medium.

Anti-Bacterial Agents↗
PubMed1998

Transformed but not normal hepatocytes express UCP2.

Uncoupling protein 2 (UCP2) expression in liver is restricted to non-parenchymal cells. By means of differential display screening between normal rat liver and H4IIE hepatoma cells we have isolated a cDNA clone encompassing part of UCP2 cDNA. Northern blot analysis revealed that UCP2 is expressed in some hepatocarcinoma cell lines, while it is absent in adult hepatocytes. UCP2 mRNA in H4IIE cells was downregulated when cells were cultured for 36 h in 0.1% serum and its expression was restored upon addition of 10% serum or phorbol esters. Hypomethylation of UCP2 was observed in transformed UCP2 expressing cells. Our results indicate that UCP2 is expressed in some hepatocarcinoma cell lines and that serum components may participate in maintaining elevated UCP2 levels.

Animals↗
PubMed1998

Transmission of hepatitis C virus infection to tree shrews.

Although hepatitis C virus (HCV) infection can be reproduced in chimpanzees, these animals are rare and expensive. Tree shrews (tupaias) are small animals, closely related to primates, which adapt easily to a laboratory environment. In this work we have investigated the susceptibility of Tupaia belangeri chinensis to HCV infection. Tupaias caught in the wild in Yunnan (China) were inoculated in China with HCV genotype 1b (study A) and in Spain with a mixture of genotypes 1b, 1a, and 3 (study B). In study B tupaias were divided into three groups: group I was inoculated without previous manipulation, group II received 750 cGy of X-ray whole-body irradiation before inoculation, and group III was used as control. Transient or intermittent viremia occurred in 34.8% (8/23) and anti-HCV in 30.4% (7/23) of tupaias in study A. In study B a transient viremia was detected in 20% (2/10) in group I and in 50% (2/4) in group II. Anti-HCV was found in 1 tupaia from group I and in 3 from group II: Viremia lasted for longer and anti-HCV tended to reach higher titers in animals which received total body irradiation. ALT elevations and nonspecific pathological changes occurred in inoculated tupaias; however, the wild nature of the animals precludes the interpretation of these changes as solely due to HCV infection. In summary our results show that T.b. chinensis are susceptible to HCV and that whole-body irradiation may possibly increase the efficiency of the infection. These animals may serve as an in vivo system for culturing HCV and addressing pathophysiological and therapeutic issues of HCV infection.

Animals↗
PubMed1998

Granule associated DNase in T4 and T8 lymphocytes from patients with autoimmune diseases.

The presence of a DNase activity associated with secretion granules was detected in T4 and T8 lymphocytes from patients with autoimmune diseases. This activity was much higher in primary biliary cirrhosis (PBC) than in Graves' disease (GD) and multiple sclerosis (MS) or in healthy subjects. This granule associated DNase activity was Ca(2+)-dependent, inhibited by Zn2+, and higher at low pH; its molecular weight corresponded to 66kDa; it was more active with double-strand than single-strand DNA. Judging from its properties this enzyme differed from the three types of endonucleases described as involved in DNA fragmentation (DNase I, DNase II and NUC18). Flow cytometry analysis of T lymphocytes showed that DNase activity associated with CD4+ lymphocyte granules correlated with the ratio CD4+CD45RO+/CD4+CD45RA+ (memory and cytotoxic cells/naive cells, inducers of suppression). In contrast, T8 lymphocyte DNase activity correlated with the proportion of CD4+ lymphocytes with CD4+CD45RA- phenotype (helpers and inducers of cytotoxicity). The possible role of this DNase activity in the mechanisms of lysis or apoptosis mediated by CTL is discussed. We suggest that this DNase activity could be implicated in some of the alterations of the autoimmune response depending on cytotoxic T lymphocytes or T cell inducers of apoptosis.

Adult↗
PubMed1998

Cellular immunity to hepatitis C virus core protein and the response to interferon in patients with chronic hepatitis C.

To investigate the involvement of T-cell response against hepatitis C virus (HCV) antigens in viral clearance after interferon therapy, we measured interleukin-2 (IL-2) production by peripheral mononuclear cells in response to HCV core in patients with chronic hepatitis C. In a cohort of 43 patients, we investigated the frequency of circulating core-specific T-helper (Th) cell precursors by the limiting-dilution assay, and in a second cohort of 60 patients, we analyzed the response to specific core epitopes using 52 synthetic 15-mer overlapping peptides. We observed that the frequency of core-specific Th cell precursors was significantly higher in patients with sustained biochemical and virological response (SR) after interferon (IFN) therapy (median, 1/55,736) than in untreated patients (1/274,023) or that in patients who remained viremic after completion of the treatment-nonresponders (NR) plus transient responders (TR) (1/1,909,972). Patients who failed to respond to IFN (NR) and those who relapsed after IFN discontinuation (TR) had a similarly low number of precursors. The number of core peptides recognized by SR, TR, NR, UT, and healthy controls was 8.2 +/- 1.5, 6.5 +/- 1.2, 2.0 +/- 0.5, 2.7 +/- 0.9, and 0.3 +/- 0.2, respectively. In SR, the intensity of the proliferative response to core peptides as estimated by the summation of stimulation indexes (sigmaSI) was significantly higher than in NR and than in UT, but not different from that of TR. Our results indicate that both expansion of HCV-specific Th cell precursors and Th cell recognition of multiple core epitopes seem to be important in the elimination of HCV after IFN therapy.

Adult↗
PubMed1998

Risk factors for recurrence of hepatitis C after liver transplantation.

Recurrent hepatitis C is a frequent complication after liver transplantation for hepatitis C virus-related cirrhosis, but risk factors related to its development remain ill defined. Twenty-three patients receiving a primary liver graft for hepatitis C virus-related cirrhosis and with an assessable biopsy performed at least 6 months after liver transplantation were studied retrospectively. The end point of this study was to look for risk factors associated with the development of histologic hepatitis C in the graft. Thirty-six major variables were studied, and those reaching significance by univariate analysis were included in a multivariate analysis. Eighteen patients (78%) developed posttransplant hepatitis C. On univariate analysis, six variables showed significant predictive value: increased immunosuppression for treatment of acute rejection; pretransplant hepatocellular carcinoma; cumulative doses of prednisone at 3, 6, and 12 months after transplantation; and mean blood trough levels of cyclosporine in the first 6 months posttransplantation. On multivariate analysis, two variables retained independent statistical significance as predictors of hepatitis C recurrence, namely receipt of antirejection therapy (P = .0087) and lower mean cyclosporine levels in the first 6 months after transplantation (P = .0134). Therefore, recurrence of hepatitis C after liver transplantation seems to be at least partially related to posttransplantation immunosuppressive therapy.

Adult↗
PubMed1998

Effect of polymorphonuclear neutrophils on serum bactericidal activity against Streptococcus pneumoniae after amoxicillin administration.

The effect of phagocytic killing on serum bactericidal activity against Streptococcus pneumoniae was investigated 0, 1.5, 8 and 12 h after a single 875 mg oral dose of amoxicillin in healthy adults. Killing curves were determined with polymorphonuclear neutrophils (PMN), serum or PMN plus serum. Global killing (i. e. intracellular and extracellular killing) over 3 h of incubation was expressed as the area under the killing curve (AUKC; log cfu x h/ml). Amoxicillin did not affect the activity of PMN alone. For serum alone, the AUKC of post-administration samples (with supra-inhibitory amoxicillin concentrations) was significantly lower than in baseline samples. For serum plus PMN, significant bactericidal activity of serum was still found in samples after antibiotic concentrations had reached sub-inhibitory levels.

Adult↗
PubMed1998

In situ detection of AE2 anion-exchanger mRNA in the human liver.

Na+-independent anion exchangers, a family of membrane proteins that mediate electroneutral exchanges of chloride and bicarbonate ions across the cell membrane, are considered to be involved in intracellular pH regulation as well as in transepithelial acid/base transport. Previous immunohistochemical data have shown that anion-exchanger-2 (AE2) protein is expressed in the liver parenchyma, localizing at both the canaliculi and the luminal surfaces of intrahepatic bile ducts, where it may have a role in the biliary secretion of bicarbonate. In the present study, we have carried out in situ hybridization experiments on biopsies of human liver using three overlapping antisense anion-exchanger-2 riboprobes. Anion-exchanger-2 mRNA signals were localized mainly in the cytoplasm of terminal and interlobular bile-duct cells, whereas weaker signals were observed in bile-duct cells of larger intrahepatic ducts. Furthermore, some hepatocytes, mostly periportal, contained detectable anion-exchanger-2 mRNA signals in their cytoplasm. No hybridization signals were observed in controls with sense riboprobes, with omission of the antisense probe, or with treatment of the sections with RNase before hybridizations. Finally, intense anion-exchanger-2 hybridization signals were observed in lymphomononuclear cells in sinusoids and in portal infiltrates. Immunocytochemical data from reverse-phase sections suggest that these cells correspond to some of the CD45R+ (UCHL1+) T lymphocytes resident in the liver.

Adult↗
PubMed1998

Circulating adrenomedullin in cirrhosis: relationship to hyperdynamic circulation.

BACKGROUND/AIMS: Peripheral arterial vasodilation may be the key factor in the sodium and water retention of cirrhosis. The mechanism responsible for this vasodilation remains to be fully elucidated. Adrenomedullin is a novel peptide, highly expressed in cardiovascular tissues, with potent and long-lasting vasodilating activity. METHODS: The possible implication of adrenomedullin in the hemodynamic changes of cirrhosis has been investigated. We measured the plasma concentration of adrenomedullin in 20 cirrhotic patients and 11 healthy subjects. In addition, systemic, portal and renal hemodynamics, hormonal factors and renal function parameters were evaluated in the same patients. RESULTS: Circulating adrenomedullin was significantly higher in the group of patients with cirrhosis (72.1; 46-100 vs 21.6; 11-34 fmol/dl, respectively; p<0.02) and was directly correlated with the Pugh score (r: 0.6; p: 0.01), inversely correlated with the creatinine clearance (r: -0.6; p<0.01) and tended to inversely correlate with systemic vascular resistance index (r: -0.46; p: 0.07). There were no portal-peripheral differences in adrenomedullin levels. Transjugular intrahepatic portosystemic shunt insertion did not induce changes in the peripheral concentration of adrenomedullin, but baseline values of this hormone predicted the degree of hyperdynamic circulation after TIPS. CONCLUSIONS: Circulating adrenomedullin is increased in cirrhosis. These levels increase with the severity of the disease, especially in patients with hepatorenal syndrome. This peptide may contribute to vasodilation of cirrhosis.

Adrenomedullin↗
PubMed1998

Osteopenia in rats with liver cirrhosis: beneficial effects of IGF-I treatment.

BACKGROUND/AIMS: Liver cirrhosis is associated with osteopenia and also with low levels of IGF-I. This hormone has been reported to stimulate bone formation in states of undernutrition and low bone turnover. Our aims were to evaluate whether osteopenia develops in male Wistar rats with CCl4-induced cirrhosis and whether IGF-I is effective in the restoration of bone mass in these animals. METHODS: Cirrhotic rats were distributed into two groups: group CI (n = 12) which received placebo and group CI + IGF (n = 12) which was treated with human recombinant IGF-I (2 microg/100 g bw/day, s.c., 21 days). Twelve normal animals which received placebo constituted the control group. On the 22nd day, the animals were sacrificed, and bone parameters were analyzed in femur and/or tibia. RESULTS: Posterior-anterior and latero-medial diameters were similar in all groups. Also, no significant differences were observed in bone contents of calcium, total proteins, collagen and hydroxyapatite in CI rats as compared with controls. However, CI rats showed significant reductions in bone weight (-13.5%, p < 0.001), total bone density (-9.28%, p < 0.001), and increased perimedullar bone resorption and urinary levels of deoxypyridinoline (a marker of bone resorption). In CI + IGF rats these parameters improved significantly as compared with CI animals. CONCLUSIONS: Osteopenia characterized by loss of bone mass and preserved bone composition is found in rats with CCl4-induced cirrhosis. This bone disorder is partially corrected by treatment with low doses of IGF-I. Since osteoporosis seems to be the predominant form of osteopenia in patients with cirrhosis, IGF-I should be considered as a possible therapy for this disorder.

Alanine Transaminase↗
PubMed1998

Superoxide dismutase in patients with chronic hepatitis C virus infection.

It has been reported that hepatitis C virus (HCV) may cause oxidative stress in infected cells. Patients with chronic hepatitis C exhibit an increased production of tumor necrosis factor-alpha (TNF alpha), a cytokine that can produce oxidative stress by stimulating the generation of reactive oxygen species (ROS). Cell defense against ROS includes overexpression of Mn-superoxide dismutase (SOD), an inducible mitochondrial enzyme. To investigate cell defense against oxidative stress in HCV infection, we analyzed Mn-SOD mRNA in liver and in peripheral blood mononuclear cells (PBMC) from patients with chronic hepatitis C. Mn-SOD expression in PBMC was significantly increased in patients with HCV infection. Patients with sustained virological and biochemical response after therapy showed significantly lower Mn-SOD than patients with positive viremia. By contrast, Mn-SOD expression was not enhanced in the liver of patients with chronic hepatitis C. The values of Mn-SOD mRNA did not correlate with TNF alpha mRNA expression, viral load, or liver disease activity. Our results indicate that in HCV infection an induction of Mn-SOD was present in PBMC but absent in the liver, suggesting that this organ could be less protected against oxidative damage. Oxidative stress could participate in the pathogenesis of HCV infection.

Adult↗
PubMed1998

Antitumor effect of allogenic fibroblasts engineered to express Fas ligand (FasL).

Fas ligand is a type II transmembrane protein which can induce apoptosis in Fas-expressing cells. Recent reports indicate that expression of FasL in transplanted cells may cause graft rejection and, on the other hand, tumor cells may lose their tumorigenicity when they are engineered to express FasL. These effects could be related to recruitment of neutrophils by FasL with activation of their cytotoxic machinery. In this study we investigated the antitumor effect of allogenic fibroblasts engineered to express FasL. Fibroblasts engineered to express FasL (PA317/FasL) did not exert toxic effects on transformed liver cell line (BNL) or colon cancer cell line (CT26) in vitro, but they could abrogate their tumorigenicity in vivo. Histological examination of the site of implantation of BNL cells mixed with PA317/FasL revealed massive infiltration of polymorphonuclear neutrophils and mononuclear cells. A specific immune protective effect was observed in animals primed with a mixture of BNL or CT26 and PA317/FasL cells. Rechallenge with tumor cells 14 or 100 days after priming resulted in protection of 100 or 50% of animals, respectively. This protective effect was due to CD8+ cells since depletion of CD8+ led to tumor formation. In addition, treatment of pre-established BNL tumors with a subcutaneous injection of BNL and PA317/FasL cell mixture at a distant site caused significant inhibition of tumor growth. These data demonstrate that allogenic cells engineered with FasL are able to abolish tumor growth and induce specific protective immunity when they are mixed with neoplastic cells.

Animals↗
PubMed1998

Degree and distribution of variability in the 5' untranslated, E1, E2/NS1 and NS5 regions of the hepatitis C virus (HCV).

Hepatitis C virus (HCV) shows a high degree of variability resulting in many different variants. In this work we described the variability of several subgenomic fragments from the 5' untranslated region (5'-UTR) and E1, E2/NS1 and NS5 regions comparing, for every position, all the sequences published in GenBank v. 88 (July 1995) as well as new sequences obtained in this work. Variability was determined in two ways. First, we analysed the degree and type of substitutions found in these regions. Second, we defined the most variable and conserved segments in each region and compared our prediction with previous studies. Our results confirm that HCV variability changes along the different regions. Although we found four variable domains in the 5'-UTR, this region was the only one to contain conserved domains. Envelope (E1, E2/NS1) and NS5 regions showed high variability throughout; however, we were able to define six and three hypervariable domains, respectively. The degree and distribution of variability established in this work is supported by the high number of sequences and the different types included in the study. Knowledge of how variability is distributed along the different regions of the HCV genome could be of use in the design of new diagnostic and therapeutic strategies against HCV infection.

5' Untranslated Regions↗
PubMed1998

Postanitbiotic and sub-MIC effects of azithromycin and isepamicin against Staphylococcus aureus and Escherichia coli.

Investigations of pharmacodynamic parameters (postantibiotic effect [PAE], sub-MIC effects [SMEs], etc.) have been progressively employed for the design of dosing schedules of antimicrobial agents. However, there are fewer in vivo than in vitro data, probably because of the simplicity of the in vitro procedures. In this study, we have investigated the in vitro PAE, SME, and previously treated (postantibiotic [PA]) SME (1/2 MIC, 1/4 MIC and 1/8 MIC) of azithromycin and isepamicin against standard strains of Staphylococcus aureus and Escherichia coli by using centrifugation to remove the antibiotics. In addition, the in vivo PAE and SME have been studied with the thigh infection model in neutropenic mice. Finally, in vivo killing curves with two dosing schedules were determined to examine whether the PAE can cover the time that antimicrobial agents are below the MIC. The two antimicrobial agents induced moderate-to-high in vitro PAEs, SMEs, and PA SMEs against S. aureus (>8 h) and E. coli (3.38 to >7.64 h). The in vivo PAEs were also high (from 3.0 to 3.6 h), despite the fact that isepamicin had lower times above the MIC in serum. Only azithromycin showed a high in vivo SME against the two strains (1.22 and 1.75 h), which indicated that the in vivo PAEs were possibly overestimated. In the killing kinetics, no great differences (<0.5 log10) were observed between the schedule that took the PAE into account and the continuous administration of doses. These results are comparable with those of other authors and suggest that these antimicrobial agents could be administered at longer intervals without losing effectiveness.

Animals↗
PubMed1998

In vitro activities of co-amoxiclav at concentrations achieved in human serum against the resistant subpopulation of heteroresistant Staphylococcus aureus: a controlled study with vancomycin.

The effects of concentrations that simulated those in human serum after a single intravenous dose of amoxicillin (2 g), amoxicillin-clavulanic acid (2,000 and 200 mg, respectively), or vancomycin (500 mg), on the viability and beta-lactamase activity of two isogenic (beta-lactamase and non-beta-lactamase producer) heteroresistant Staphylococcus aureus strains were studied in an in vitro pharmacodynamic model. A reduction of > or = 97% of the initial inoculum was obtained with vancomycin and amoxicillin-clavulanic acid against both strains, with respect to the total bacterial population and the oxacillin-resistant subpopulation. The same pattern was observed with amoxicillin and the beta-lactamase-negative strain. beta-Lactamase activity in the beta-lactamase-positive strain changed over time parallel to viability, decreasing with amoxicillin-clavulanic acid or vancomycin and increasing in the amoxicillin and control groups. Clavulanic acid concentrations achievable in serum that changed over time allowed amoxicillin to act against the beta-lactamase-producing methicillin-resistant S. aureus to a similar extent as vancomycin.

Amoxicillin↗