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Biomedical subjects

J Prieto

Publications and source records attributed to J Prieto.

At least 55 records · Page 3Linked to original sources
PubMed2002

Postantifungal effect and effects of sub-MIC concentrations on previously treated Candida sp. influence of growth phase.

OBJECTIVES: This study evaluates the influence of growth phase on the postantifungal effect (PAFE) and on the effect of sub-MIC concentrations (1/4x MIC) on Candida sp. in PAFE stage (PAFSE). METHODS: This stage was induced by pre-treatments of 1.5 h of C. albicans or C. glabrata in their exponential or stationary phase, with 1x, 4x or 8x MIC of four antifungal agents that are fundamental for modern candidiasis therapy. RESULTS: Ketoconazole and fluconazole induced longer PAFSEs on microorganisms in logarithmic growth phase. However, this influence did not exist in the case of PAFSEs induced by AmB and 5-Fc or with the postantifungal effect induced by the four antifungal agents. In any way, significant PAFEs were always observed for Amphotericin B and 5-fluorocytosine (0.8-4.8 and 0.5-3 h, respectively, depending on the treatment dose). These values were increased (2.3-3.6 and 1.4-3.2 h respectively, depending on the pre-treatment dose) by posterior exposition to 1/4x MIC of the respective antifungal agent. In the case of ketoconazole and fluconazole, both antimycotics were not able to induce significant PAFEs, but posterior treatments to 1/4x MIC of each of the two azoles led in both yeast species to significant PAFSE of up to 2.6 h duration with ketoconazole, and 0.8 h with fluconazole, depending on the pre-treatment concentration. CONCLUSION: The growth phase of microorganisms should be considered in the planning of dosage protocols with azoles, because if the concentration applied is not high enough, the sub-MIC effects could be no significant for fungi in stationary phase of large wounds. Amphotericin B and 5-fluorocytosine induced significant postantifungal effect onCandida sp. This effect was increased by posterior exposition to sub-MIC concentration of the antifungal agents. Ketoconazole and fuconazole were not able to induce significant PAFEs at the concentrations tested, but posterior treatments to sub-MIC concentrations led to significant PAFSE. The growth phase of the culture at the time of its pre-treatment did not influence the length of the PAFE induced in it. However, the effect of the sub-MIC concentrations of Kz or Flu in yeast in PAFE phase was greater on yeast in exponential phase than for cultures in stationary phase.

Antifungal Agents↗
PubMed2002

Post-antifungal effect and effects of sub-MIC concentrations on previously treated Candida spp.: influence of exposure time and concentration.

This study evaluates the influence of exposure time and concentration on the post-antifungal effect (PAFE) and the effect of sub-MIC concentrations (1/4 x MIC) on Candida albicans and C. glabrata in the PAFE stage (PAFSE). This stage was induced by pretreatment for 1.5, 3 or 12 h with 1 x, 4 x or 8 x MIC of 4 antifungal agents fundamental to modern candidiasis therapy. The length of the 2 effects studied was dependent on the concentration of the antifungal agent applied during pretreatment, as well as on the exposure time. An increase in the dose and/or longer pretreatment prolonged the duration of the PAFE and PAFSE in both species and with all the antifungal agents. Significant PAFEs were always observed for amphotericin B and 5-fluorocytosine (0.8-13 h and 0.6-10.8 h, respectively). These values were increased (by 2.3-8.7 h and 1.5-7.8 h, respectively) by posterior exposure to 1/4 x MIC of the respective antifungal agent. Neither ketoconazole nor fluconazole were able to induce significant PAFEs, even with exposures of up to 12 h duration and a dose of 8 x MIC. However, treatment with 1/4 x MIC of each of the 2 azoles led to significant PAFSEs in both yeast species, of up to 6.5 h duration with ketoconazole and 1.7 h with fluconazole, if the concentrations and/or exposure times were sufficiently high.

Amphotericin B↗
PubMed2002

Antimicrobial resistance: a class effect?

Antibiotic use has led to increased resistance to certain group markers: penicillin, erythromycin and ciprofloxacin for beta-lactams, macrolides and quinolones, respectively. The influence of resistance to markers in decreasing susceptibility to the drugs included (on the basis of chemical structure) in the corresponding antibiotic group can be defined as 'resistance class effect'. In the case of macrolides, this effect is dependent on the prevalent resistant phenotype among the isolates of the target bacteria: the class effect exists completely if the mechanism of resistance is constitutive MLS(B) (all macrolides are affected by resistance to erythromycin), and only partially if the mechanism is the efflux M phenotype (all but 16-membered macrolides are affected). In Spain, the first case is exemplified by Streptococcus pneumoniae and the second by Streptococcus pyogenes. For beta-lactams and quinolones, resistance to the group markers results in large decreases in the antimicrobial activity of the less potent members of the group, penicillin being a better driver of resistance for oral cephalosporins than for aminopenicillins, and ciprofloxacin being a better driver for older rather than for the newer quinolones, which have enhanced anti-pneumococcal activity. Empirical prescription guidelines based on the pharmacoepidemiology of resistance, recommending the use of potent drugs that are less influenced by resistance to the marker, may help to counter the spread of resistance in the community.

4-Quinolones↗
PubMed2002

Effects of specific antibodies against Streptococcus pneumoniae on pharmacodynamic parameters of beta-lactams in a mouse sepsis model.

A dose-ranging study to investigate the in vivo effects of the presence of specific antibodies on the efficacy of beta-lactam treatment of sepsis caused by Streptococcus pneumoniae (non-beta-lactam-susceptible serotype 6B isolate) was performed with a BALB/c mouse model. Hyperimmune serum was obtained from mice immunized with the heat-inactivated strain. The rate of mortality was 100% in nontreated animals in the absence of specific antibodies. A single injection of a one-half or one-quarter dilution of hyperimmune serum produced 60 to 40% survival rates. In the absence of specific antibodies, the minimal effective doses of amoxicillin and cefotaxime that produced survival rates of 100 and 80% were 25 and 50 mg/kg of body weight (three times a day for up to six doses), respectively. These doses produced times that the levels in serum remained above the MIC (deltaT > MICs) approximately 30% of the dosing interval. When specific antibodies were present (by administration of a one-half or one-quarter dilution of hyperimmune serum), the minimal effective doses of the antibiotics were 3.12 and 6.25 mg/kg ( approximately 8 times lower), with the deltaT > MICs being approximately 3 and 5% of the dosing interval for amoxicillin and cefotaxime, respectively. This in vivo combined pharmacodynamic effect offers possibilities that can be used to address penicillin resistance.

Amoxicillin↗
PubMed2002

Gene therapy for liver diseases: recent strategies for treatment of viral hepatitis and liver malignancies.

Gene therapy has emerged as a powerful and very plastic tool to regulate biological functions in diseased tissues with application in virtually all medical fields. An increasing number of experimental and clinical studies underline the importance of genes as curative agents in the future. However, intense research is needed to evaluate the potential of gene therapy to improve efficacy and minimise the toxicity of the procedure.

Clinical Trials, Phase I as Topic↗
PubMed2002

Effect of ursodeoxycholic acid on methionine adenosyltransferase activity and hepatic glutathione metabolism in rats.

BACKGROUND AND AIMS: Both bile salts and glutathione participate in the generation of canalicular bile flow. In this work, we have investigated the effect of different bile salts on hepatic glutathione metabolism. METHODS: Using the isolated and perfused rat liver, we studied hepatic glutathione content, and metabolism and catabolism of this compound in livers perfused with taurocholate, ursodeoxycholate, or deoxycholate. RESULTS: We found that in livers perfused with ursodeoxycholate, levels of glutathione and the activity of methionine adenosyltransferase (an enzyme involved in glutathione biosynthesis) were significantly higher than in livers perfused with other bile salts. In ursodeoxycholate perfused livers, methionine adenosyltransferase showed a predominant tetrameric conformation which is the isoform with highest activity at physiological concentrations of substrate. In contrast, the dimeric form prevailed in livers perfused with taurocholate or deoxycholate. The hepatic activities of gamma-glutamylcysteine synthetase and gamma-glutamyltranspeptidase, enzymes involved, respectively, in biosynthetic and catabolic pathways of glutathione, were not modified by bile salts. CONCLUSIONS: Ursodeoxycholate specifically enhanced methionine adenosyltransferase activity and hepatic glutathione levels. As glutathione is a defensive substance against oxidative cell damage, our observations provide an additional explanation for the known hepatoprotective effects of ursodeoxycholate.

Animals↗
PubMed2002

Cytokine gene transfer into dendritic cells for cancer treatment.

Bone marrow-derived dendritic cells have been used to treat established experimental tumors by unleashing a cellular immune response against tumor antigens. Such antigens are artificially loaded onto dendritic cells' antigen-presenting molecules by different techniques including incubation with synthetic antigenic determinants, tumor lysates or nucleic acids encoding for those relevant antigens. Ex vivo gene transfer with viral and non-viral vectors is frequently used to obtain expression of the tumor antigens and thereby to formulate the therapeutic vaccines. Efficacy of the approaches is greatly enhanced if dendritic cells are transfected with a number of genes which encode immunostimulating factors. In some cases, such as with IL-12, IL-7 and CD40L genes, injection inside experimental malignancies of thus transfected dendritic cells induces complete tumor regression in several models. In this case tumor antigens are captured by dendritic cells by still unclear mechanisms and transported to lymphoid organs where productive antigen presentation to T-cells takes place. Many clinical trials testing dendritic cell-based vaccines against cancer are in progress and partial clinical efficacy has been already proved. Transfection of genes further strengthening the immunogenicity of such strategies will join the clinical club soon.

Bone Marrow Cells↗
PubMed2001

Antifibrogenic effect in vivo of low doses of insulin-like growth factor-I in cirrhotic rats.

Insulin-like growth factor-I (IGF-I) is produced mainly in the liver and it induces beneficial effects on the nutritional status, the liver function and oxidative hepatic damage in cirrhotic rats. The aim of this work was to analyze the effect of IGF-I on mechanisms of fibrogenesis in cirrhotic rats. Liver cirrhosis was induced by CCl(4) inhalation and phenobarbital in Wistar rats. Ten days after stopping CCl(4) administration (day 0), rats received either IGF-I (2 microg/100 g bw/day) (CI+IGF) or saline (CI) subcutaneously during 14 days. Animals were sacrificed on day 15. As control groups were used: healthy rats (CO) and healthy rats treated with IGF-I (CO+IGF). Liver histopathology, hydroxyproline content, prolyl hydroxylase activity, collagen I and III mRNA expression and the evolution of transformed Ito cells into myofibroblasts were assessed. Among the two control groups (CO+IGF), no differences were found in hydroxyproline content and these levels were lower than those found in the two cirrhotic groups. Compared with untreated cirrhotic rats, the CI+IGF-I animals showed a significant reduction in hydroxyproline content, prolyl hydroxylase activity and collagen alpha 1(I) and alpha1(III) mRNA expression. A higher number of transformed Ito cells (alpha-actin +) was observed in untreated cirrhotic animals as compared to CO and CI+IGF groups. In summary, treatment with IGF-I reduced all of the studied parameters of fibrogenesis. In conclusion, low doses of IGF-I induce in vivo an antifibrogenic effect in cirrhotic rats.

Actins↗
PubMed2001

Immunization with a tumor-associated CTL epitope plus a tumor-related or unrelated Th1 helper peptide elicits protective CTL immunity.

Immunization with cytotoxic T cell epitope SPSYVYHQF (AH1), derived from MuLV gp70 envelope protein expressed by CT26 tumor cells, does not protect BALB/c mice against challenge with CT26 tumor cells. By contrast, immunization with AH1 plus T helper peptides OVA(323-337) or SWM(106-118) eliciting Th1 and Th0 profiles, protected 83% and 33% of mice, respectively. Interestingly, immunization with AH1 plus both helper peptides reverted the efficacy to 33%. We identified the endogenous T helper peptide p(320-333) from gp70 which elicits a Th1 profile and is naturally processed. As for OVA(323-337), immunization with p(320-333) alone did not protect against tumor challenge. However, p(320-333) plus AH1 protected 89% of mice at day 10 after vaccination. Only 20% of mice vaccinated with AH1 + OVA(323-337) or AH1 + p(320-333) were protected when challenged 80 days after immunization. Treatment with OVA(323-337) or with p(320-333) around established tumors delayed tumor growth. Our results show that tumor-related as well as tumor-unrelated but strong Th1 peptides may be useful for inducing CTL responses in tumor immunotherapy.

Adjuvants, Immunologic↗
PubMed2001

Alpha(v)beta(3) integrin-mediated adenoviral transfer of interleukin-12 at the periphery of hepatic colon cancer metastases induces VCAM-1 expression and T-cell recruitment.

We previously reported that systemic injection of recombinant adenovirus resulted in a rim of gene transduction around experimental liver tumor nodules. This zone of higher infection is dependent on the alpha(v)beta(3) integrin, acting as an adenovirus internalization receptor, which is overexpressed in tissues surrounding liver metastases. When a recombinant adenovirus encoding interleukin-12 (AdCMVIL-12) is given into a subcutaneous tumor nodule in mice also bearing concomitant liver tumors, a fraction of AdCMVIL-12 reaches the systemic circulation and infects liver tissue, especially at the malignant/healthy tissue interface. As a result of the expression at this location of the interleukin-12 transgenes, VCAM-1 is induced on vessel cells and mediates the recruitment of adoptively transferred anti-tumor cytolytic T-lymphocytes. These studies provide mechanistic explanations for the potent therapeutic synergy observed between interleukin-12 gene transfer and adoptive T-cell therapy.

Adenoviridae↗
PubMed2001

Characterization of an immunologically conserved epitope from hepatitis C virus E2 glycoprotein recognized by HLA-A2 restricted cytotoxic T lymphocytes.

BACKGROUND/AIMS: Identification of epitopes recognized by cytotoxic T lymphocytes (CTL) in hepatitis C virus (HCV) proteins is of importance because they can be used for vaccination, treatment of infection or monitoring of immune responses. Our purpose was to characterize new CTL epitopes in HCV structural proteins. METHODS: Peptides were synthesized and tested in HLA-A2 binding assays. Binder peptides were used to stimulate peripheral blood mononuclear cells from HCV+ patients and controls, and activity measured in chromium release and ELISPOT assays. RESULTS: Twenty binder peptides were found, and stimulation of HCV+ patient cells with nine peptides showing high binding ability led to the growth of CD8+ CTL recognizing peptide E2(614-622) in association with HLA-A2. Peptide E2(614-622) was recognized by 30% of HLA-A2+ patients with chronic HCV infection, but no responses were observed in control groups. Five peptides derived from region E2(614-622) from 26 different viral isolates bound to HLA-A2 molecules, and all of them but one, containing Phe at position 622, were recognized by E2(614-622) specific CTL. CONCLUSIONS: These results show that peptide E2(614-622) belongs to a highly conserved region of HCV E2, and might be a good candidate to induce anti-HCV CTL responses in HLA-A2+ subjects.

Amino Acid Sequence↗
PubMed2001

T-helper cell response to woodchuck hepatitis virus antigens after therapeutic vaccination of chronically-infected animals treated with lamivudine.

BACKGROUND/AIMS: Immunotherapy of patients chronically-infected with hepatitis B virus (HBV) may have the risk of fulminant hepatitis. This risk might be diminished if immunotherapy was carried out under conditions of low viremia. METHODS: Five woodchucks chronically-infected with woodchuck hepatitis virus (WHV), a virus closely related to HBV, were treated with lamivudine for 23 weeks. At week 10, when viremia had decreased by 3-5 logs, three woodchucks were vaccinated with woodchuck hepatitis virus surface antigen (WHsAg) plus the T-helper determinant FISEAIIHVLHSR. RESULTS: It was found that the administration of lamivudine only, had no effect on the T-helper response against WHV antigens. By contrast, vaccination induced T-helper responses against WHV antigens, shifting the cytokine profile from Th2 to Th0/Th1, but was without effect on viremia, WHsAg levels, or anti-WHs antibodies. Analysis of liver biopsies showed that lamivudine administration may have reduced hepatic inflammation. By contrast, vaccination clearly enhanced hepatic inflammation. After lamivudine withdrawal, viremia returned to high levels. CONCLUSIONS: These results suggest that therapeutic vaccination of chronically-infected woodchucks under conditions of low viremia shifts the cytokine profile against viral antigens towards Th0/Th1. This shift may prevent the efficient induction of anti-WHs antibodies.

Animals↗
PubMed2001

Ductular morphogenesis and functional polarization of normal human biliary epithelial cells in three-dimensional culture.

BACKGROUND/AIMS: The understanding of the physiology and function of human biliary epithelial cells (hBEC) has been improved by studies in monolayer culture systems. The aim was to develop a polarized model to elucidate the mechanisms of ductular morphogenesis and functional differentiation of hBEC. METHODS: The morphological, phenotypic and functional properties of hBEC cultured as three-dimensional aggregates in collagen gel were assessed in medium supplemented with (or without) human hepatocyte growth factor (hHGF) and foetal bovine serum. RESULTS: In the absence of added mitogens and serum, cells maintained as morphologically polarized aggregates, organized around a central lumen, were positive for phenotypic markers of biliary epithelium and negative for markers of other cell types. Functional markers, gamma-glutamyl-transferase, anion exchanger-2, responses to gamma interferon and forskolin induced secretion, were preserved. hHGF increased both the size and number of aggregates and induced hBEC to invade the gel and lumena forming anastomosing networks of cells. CONCLUSIONS: Collagen gel culture in the absence of added growth factors and serum provides a model for analysis of the polarized functions of hBEC. The formation of poorly organized cords of cells in response to hHGF suggests that collagen gel culture may provide a model for the investigation of atypical ductular morphogenesis of the human biliary tract.

Adult↗
PubMed2001

[Plasmatic concentrations of fibronectin as marker of clinical course among septic patients].

INTRODUCTION: It is difficult to follow up the patients with sepsis because of the underlying pathology or the presence of complications. The attending physician needs to know as soon as possible the response to the antibiotic therapy. Is therefore necessary to find real time biological markers that will help to understand the clinical situation of the infected patient. It has been demonstrated that fibronectin (Fn) is an early marker of sepsis, so it seemed plausible its use in the clinical monitoring of the septic patient. MATERIAL: We have used plasmatic concentrations of Fn in the follow up of sepic patients admitted to the Hospital de Segovia from February to August, 1995. There were two control groups: one of healthy volunteers and another of varied pathology. RESULTS: We have applied the multiple comparison rule of Bonferroni to demonstrate that plasma Fn is a negative acute phase reactant, with almost undetectable levels while the patient is in critical condition. An effective treatment prompts plasma Fn to rise significantly within two days. DISCUSSION: Plasma Fn concentration by itself or in an score system could help in the follow up of the septic patients.

Acute-Phase Reaction↗
PubMed2001

Thrombopenic purpura induced by a monoclonal antibody directed to a 35-kilodalton surface protein (p35) expressed on murine platelets and endothelial cells.

OBJECTIVE: With the aim of obtaining monoclonal antibodies (mAbs) against mouse endothelial surface antigens, immunization of rats with a mouse-derived endothelial cell line (PY4.1) and subsequent hybridoma production were performed. MATERIALS AND METHODS: One of the mAbs produced by hybridoma EOL5F5 was selected for its surface binding to endothelial cell lines, and identification of the mAb-recognized antigen was performed by immunoprecipitation. Experiments were performed to analyze the effects of EOL5F5 on systemic administration to mice. RESULTS: EOL5F5-recognized antigen was a single band of 35 kDa under reducing and nonreducing conditions, features that do not match other known differentiation antigens with comparable tissue distribution. In vivo administration of purified EOL5F5 mAb to mice (n = 20) induced intense cutaneous purpura as well as severe but transient thrombocytopenia. Expression of EOL5F5-recognized antigen was detected on platelets from which it immunoprecipitated a moiety of identical electrophoretic pattern in SDS-PAGE, as the one recognized on endothelial cells. Immunohistochemically, EOL5F5-recognized antigen (p35) also was expressed on dermal capillaries, suggesting that, in addition to thrombocytopenia, damaging effects of the antibody on endothelial cells also might cause the observed purpura. CONCLUSIONS: Our results show induction of thrombocytopenic purpura in mice with an mAb against a single antigenic determinant expressed on both platelets and endothelium. EOL5F5 mAb injection sets the stage for useful experimental models that resemble immune thrombocytopenic purpura.

Animals↗
PubMed2001

Evaluation of two in vitro pharmacodynamic simulation models: microfiltration versus centrifugation-filtration.

Pharmacodynamic in vitro models that simulate serum antimicrobial concentrations provide more information about the activity of an antibiotic than MICs or traditional time-kill methods. The aim of this study was to compare two pharmacodynamic simulation models using ATCC strains of five different species and five antibiotics. In the first model (Centriprep-10 system), a filtration-centrifugation process was used to eliminate the antibiotic; in the second model (microfiltration system) no centrifugation was necessary. The antibiotic concentrations tested were similar to those in serum after normal doses of cefuroxime, clarithromycin, ciprofloxacin, gentamicin and cefotaxime. No significant differences were observed in the killing rates between the models except in the case of Haemophilus influenzae and cefotaxime. The new microfiltration model had the following advantages: lack of the carry-over effect, the absence of centrifugation that could damage bacteria and the possibility of increasing the number of incubation periods to give a better fit of the kinetic profile of man.

Anti-Bacterial Agents↗
PubMed2001

Influence of diminished susceptibility of Streptococcus pneumoniae to ciprofloxacin on the serum bactericidal activity of gemifloxacin and trovafloxacin after a single dose in healthy volunteers.

The serum bactericidal activity against 2 Streptococcus pneumoniae strains (ciprofloxacin MIC 1 and 4 mg/l) was measured in 12 volunteers who received oral single doses of gemifloxacin 320 mg and trovafloxacin 200 mg in a crossover fashion. The 4-fold increase in ciprofloxacin MIC from the susceptible to the resistant strain resulted in a 2-fold increase in MIC (from 0.015 to 0.03 mg/l), a 2-fold decrease in C(max)/MIC (104 vs 52) and in AUC(0-24 h)/MIC (532 vs 266), but a 5.6-fold decrease in area under the bactericidal curve (AUBC: 168 vs 30) for gemifloxacin. Trovafloxacin showed a 4-fold higher MIC (0.25 vs 0.06 mg/l), a 4-fold lower C(max)/MIC (8.6 vs 36), a 4-fold lower AUC(0-24 h)/MIC (85 vs 356) and a 11-fold lower AUBCs (2 vs 22) against the resistant isolate compared with the susceptible one. Trovafloxacin serum bactericidal titres against the ciprofloxacin-resistant strain were measurable generally only at 1 h after dosing (median titre=2). Gemifloxacin showed similar ex vivo bactericidal activity against the ciprofloxacin-resistant strain to that of trovafloxacin against the ciprofloxacin-susceptible strain.

Adult↗