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Biomedical subjects

A Zaragoza

Publications and source records attributed to A Zaragoza.

At least 19 recordsLinked to original sources
PubMed2005

Markov chains: computing limit existence and approximations with DNA.

We present two algorithms to perform computations over Markov chains. The first one determines whether the sequence of powers of the transition matrix of a Markov chain converges or not to a limit matrix. If it does converge, the second algorithm enables us to estimate this limit. The combination of these algorithms allows the computation of a limit using DNA computing. In this sense, we have encoded the states and the transition probabilities using strands of DNA for generating paths of the Markov chain.

Algorithms↗
PubMed2001

Induction of cell proliferation by cyclosporine A in primary cultures of rat hepatocytes.

Cyclosporine A (CsA) has been reported to be able to promote cell proliferation, although the precise mechanism by which CsA stimulates cell growth remains uncertain. In the present study, we examined, in hepatocyte cultures, the effect of CsA on parameters related to the cell cycle as well as the levels of proteins involved in the control and progression of the cycle. Flow cytometry analysis detected an increase in the percentage of cells involved in the S phase of the cycle, which correlated with increases in the levels of cyclins D1 and E (two G1-progression regulators), as well as in those of PCNA (proliferating cell nuclear antigen), and without modification in p27, an inhibitory protein of CDKs. We also examined in nucleus the levels of nuclear factor kappaB (a nuclear factor involved in the transcription of the cyclin D1 gene) and found that this transcription factor increased in the presence of CsA. We conclude that the increases in cyclin D1, PCNA, and cyclin E, together with the invariable level of p27, clearly show that CsA induces hepatocytes to proliferate. These results reinforce the idea of the growth-promoting effect of CsA in cultured hepatocytes.

Animals↗
PubMed2001

Mitochondrial involvement in cocaine-treated rat hepatocytes: effect of N-acetylcysteine and deferoxamine.

The cytotoxicity of cocaine (0 - 1000 microM), was studied on parameters related to the mitochondrial role and the cascade of events that lead to apoptosis in hepatocyte cultures from phenobarbitone (PB) pretreated rats. Cytotoxicity was dose-dependent and LDH leakage was significantly enhanced above 100 microM cocaine. Apoptosis was visualized by DNA fragmentation on agarose gel, and appeared at 50 and 100 microM cocaine. Cocaine induced biphasic changes in mitochondrial transmembrane potential and significantly increased the mitochondrial release of cytochrome c, the caspase-3 like DEVDase activity and the level of 20 kDa subunit, a product of pro-caspase-3 cleavage. The protective effect of N-acetylcysteine (NAC) and deferoxamine (DFO) on all these parameters confirmed the involvement of oxygen radicals in cocaine-induced necrosis/apoptosis. We conclude: first, that the biphasic changes recorded in mitochondrial inner membrane potential by the effect of cocaine, were parallel to apoptosis; second, that caspase-3 activity and cleavage to it p20 subunit increased sharply in parallel to the translocation of cytochrome c from mitochondria to cytosol; and third, that the antioxidants, NAC or DFO exerted a noticeable protective role in counteracting the cytotoxicity of cocaine, these effects being more pronounced in the case of DFO than NAC. These findings demonstrate that cocaine cytotoxicity involves mitochondrial damage.

Acetylcysteine↗
PubMed2000

Changes in antioxidant defence systems induced by cyclosporine A in cultures of hepatocytes from 2- and 12-month-old rats.

The in vitro effect of cyclosporine A (CsA) was studied in reference to the production of reactive oxygen species (peroxides and superoxide anion) and to cell enzyme-mediated antioxidant defence in hepatocytes isolated from rats aged 2 and 12 months. Primary cultures of hepatocytes were incubated in the presence of concentrations of cyclosporine in the range of 0 to 50 microM for 24 hr, and the release of lactate dehydrogenase into the culture medium was evaluated as a parameter of cytotoxicity and membrane lysis. Peroxides were quantified by using 2',7'-dichlorodihydrofluorescein diacetate, and superoxide anion levels were evaluated by the fluorescence of dihydroethidium. Enzyme activity and gene expression of catalase and Mn- and Cu,Zn-superoxide dismutase were also assayed. CsA cytotoxicity was significantly higher in hepatocytes from rats aged 12 months when compared to those aged 2 months. Intracellular peroxide content resulted in a dose-dependent increase, while the anion superoxide intracellular level slightly decreased as CsA increased from 0-50 microM. The progressive increase in intracellular peroxides in cell cultures in the range from 0-50 microM CsA was associated with the loss of cell viability and accompanied by significantly higher levels of Mn- and Cu, Zn-superoxide dismutase enzyme activities and mRNAs, and slight increases in catalase activity and mRNA. We conclude that, in primary hepatocyte cultures, the cytotoxicity of CsA was dose-dependent in both age groups and significantly higher in cultures from 12-month-old rats when compared to those from 2-month-old animals. The non-coordinated regulation of the gene expression of antioxidant enzyme systems, i.e. catalase and Mn- and Cu,Zn-superoxide dismutases, evidenced to a greater extent in hepatocytes from the older group of rats, could be one of the mechanisms involved in CsA toxicity.

Age Factors↗
PubMed2000

Effect of N-acetylcysteine and deferoxamine on endogenous antioxidant defense system gene expression in a rat hepatocyte model of cocaine cytotoxicity.

In the present study we investigated on cultures of hepatocytes from phenobarbital-pretreated rats, the effect of the antioxidants, 0.5 mM N-acetylcysteine (NAC) or 1.5 mM deferoxamine (DFO), previously incubated for 24 h and coincubated with cocaine (0-1000 microM) for another 24 h. Cocaine cytotoxicity was monitored by either the lysis of the cell membranes or apoptosis. Lysis of the cell membranes was evidenced by lactate dehydrogenase leakage, apoptosis was observed by detecting a hypodiploid peak (<2C) in DNA histograms obtained by flow cytometry, peroxide production was quantified with 2', 7'-dichlorodihydrofluorescein diacetate and gene expression of the antioxidant enzymes: Mn- and Cu,Zn-superoxide dismutases, catalase and glutathione peroxidase were measured by Northern blot analysis. NAC and DFO significantly decreased the extent of lysis of cell membranes and apoptosis, and the antiapoptotic effect was parallel to peroxide generation. By the effect of NAC and DFO, significant increases were detected in the levels of mRNA of catalase, manganese superoxide dismutase and glutathione peroxidase. From these results we conclude that NAC or DFO, when incubated in the presence of cocaine, exerted a protective effect against cocaine toxicity at the level of both lysis of the membranes and apoptosis. This protective effect, in the case of NAC, was directed towards an increase in antioxidant enzyme expression, and in the case of DFO against reactive oxygen species generation.

Acetylcysteine↗
PubMed2000

Potentiation of thioacetamide hepatotoxicity by phenobarbital pretreatment in rats. Inducibility of FAD monooxygenase system and age effect.

The ability of phenobarbital to induce the expression and activity of microsomal drug monooxygenases in the liver presents one of the most important issues in the field of chemical interactions and in the toxicity of xenobiotics. The model of rat liver injury induced by a single dose of thioacetamide (500 mg/kg intraperitoneally) was used to study the effect of phenobarbital (80 mg/kg/day intraperitoneally) for 5 days prior to thioacetamide. Serum parameters of liver injury such as aspartate aminotransferase activity, gamma-glutamyl transferase activity and the total bilirubin levels, as well as the activities of hepatic FAD and cytochrome P450 microsomal monooxygenases, were assayed in 2- and 12-month-old rats. Samples of blood and liver were obtained from controls (injected at 0 h with 0.5 ml of 0.9% NaCl) and at 12, 24, 48, 72 and 96 h of thioacetamide intoxication either to non-treated or phenobarbital pretreated rats. Potentiation of thioacetamide hepatotoxicity by phenobarbital pretreatment was demonstrated at morphological level, and by significant increases in the activities of serum aspartate aminotransferase and gamma-glutamyl transferase, and in the levels of total bilirubin. The extent of potentiation of thioacetamide-induced liver injury by phenobarbital pretreatment was similar in both age groups. Microsomal FAD monooxygenase activity, the enzyme responsible for thioacetamide biotransformation, was significantly enhanced (twofold) by phenobarbital pretreatment, and also underwent a further increase following thioacetamide, preceding the peak of necrosis. Cytochrome P450 monooxygenases were induced by phenobarbital pretreatment more than sixfold, and sharply decreased when phenobarbital was withdrawn and thioacetamide administered, showing at 48 h intoxication values close to basal. Phenobarbital pretreatment potentiated thioacetamide necrogenicity, and this potentiation was parallel to the induction of the microsomal FAD monooxygenase system, both by phenobarbital and by thioacetamide itself. The extent of thioacetamide-induced liver injury was significantly higher in 12-month-old rats, but the effect of phenobarbital pretreatment was similar in both age groups.

Age Factors↗
PubMed2000

HSP70 induction by cyclosporine A in cultured rat hepatocytes: effect of vitamin E succinate.

BACKGROUND/AIMS: The effect of vitamin E succinate was studied in vitro against cyclosporine A (CsA) cytotoxicity in reference to the induction of heat shock protein 70 (HSP70) in rat hepatocytes. METHODS: Primary cultures of hepatocytes were incubated with CsA, in the range of 0 to 50 microM, in the presence or absence of 50 microM vitamin E succinate for 24 h. Peroxides were quantified by using 2',7'dichlorodihydrofluorescein diacetate, HSP70 levels were measured by Western blot analysis and apoptosis was detected by the hypodiploid peak of propidium iodide stained DNA. RESULTS: At 24 h of incubation with CsA, intracellular peroxide content increased in a dose-dependent manner. HSP70 also increased in parallel to CsA concentration, and apoptosis showed a biphasic change, increasing at concentrations between 0 and 10 microM and decreasing from 10 to 50 microM. The effect of vitamin E was studied at 24 h of coincubation with CsA. The values obtained show that vitamin E significantly counteracted the effect of CsA, diminishing the CsA-induced increase in intracellular peroxides and the lysis of cell membrane. These vitamin E effects were accompanied by a decrease in HSP70 and an enhancement of apoptosis. CONCLUSIONS: We conclude that in primary hepatocyte cultures, peroxide generation and cytotoxicity induced by CsA was accompanied by HSP70 induction and that the CsA cytotoxicity significantly decreased in the presence of vitamin E succinate parallel to a disappearance in HSP70 and to an increase in apoptosis.

Animals↗
PubMed1999

Cocaine cytotoxicity in hepatocyte cultures from phenobarbital-induced rats: involvement of reactive oxygen species and expression of antioxidant defense systems.

The present study was designed to investigate whether cocaine modifies the production of reactive oxygen species, affects cellular enzyme-mediated antioxidant defense systems and, subsequently, promotes apoptosis and/or necrosis of hepatocytes. Primary cultures of hepatocytes isolated from phenobarbital-induced rats were exposed to cocaine (0-1000 microM) for 24 hr, and cell death (apoptosis or necrosis), antioxidant enzyme activities and mRNA levels, and peroxide generation were determined. Cocaine cytotoxicity by apoptosis was observed by detecting apoptotic nuclei using optic microscopy and by measurement of the hypodiploid peak (<2C) in DNA histograms obtained by flow cytometry. Necrosis was evidenced by lactate dehydrogenase (LDH) leakage, and peroxide production was quantified with 2',7'-dichlorodihydrofluorescein diacetate. Low concentrations of cocaine (less than 100 microM) resulted in an increase in dichlorofluorescein fluorescence, associated with an enhancement in apoptotic cell death and sharp decreases in the enzyme activities and RNAs of catalase and manganese-superoxide dismutase (Mn-SOD). The progressive decrease in peroxide production in cell cultures detected in the range of 250-1000 microM cocaine was associated with increases in LDH leakage and decreases in the percentage of apoptotic cells, accompanied by low levels in catalase and Mn-SOD enzyme activities and mRNAs, without apparent changes in apoptosis. These data indicate that oxygen radicals may contribute directly or indirectly to cocaine-induced apoptosis in cultured hepatocytes. We conclude that, in primary hepatocyte cultures, cocaine-induced cell death by necrosis was dependent on cocaine concentration, while cell death by apoptosis was parallel to peroxide concentration. The down-regulation of the gene expression of antioxidant enzyme systems should be one of the mechanisms involved in cocaine toxicity.

Animals↗
PubMed1998

Influence of aminoguanidine on parameters of liver injury and regeneration induced in rats by a necrogenic dose of thioacetamide.

1. When aminoguanidine, a nucleophilic hydrazine compound, was administered to rats (50 mg kg(-1) body wt) 30 min before a necrogenic dose of thioacetamide (500 mg kg(-1) body wt), significant changes related to liver injury and hepatocellular regeneration were observed. 2. The extent of necrosis was noticeably less pronounced, as detected by the peak of serum aspartate aminotransferase activity. Depletion of hepatic glutathione (GSH) and the increase in malondialdehyde concentration as markers of oxidative stress, produced by thioacetamide metabolism, were significantly diminished. However, the activity of microsomal FAD monooxygenase, the system responsible for thioacetamide oxidation, did not show significant alterations. Antioxidant enzyme systems involved in the glutathione redox cycle, such as glutathione reductase and glutathione peroxidase activities, slightly decreased following aminoguanidine pretreatment. 3. Primary cultures of peritoneal macrophages from control rats, when incubated in the presence of serum collected following thioacetamide intoxication, showed a significant decrease in nitric oxide (NO) release at 24 h, that was more pronounced in the group pretreated with aminoguanidine. However, the sharp and progressive increase in macrophage NO release, when incubated in the presence of serum obtained at 48, 72 and 96 h, were increased by aminoguanidine-pretreatment. 4. The cell population involved in DNA synthesis sharply increased in both groups at 48 h of intoxication, although the values at 0, 24, 72 and 96 h were markedly higher in the group pre-treated with aminoguanidine. Polyploidy at 72 and 96 h of intoxication was delayed by the effect of aminoguanidine and a progressive increase in the hypodiploid hepatocyte population, which reached 16% of the total at 96 h, was observed. 5. These results indicate that a single dose of aminoguanidine before thioacetamide administration, markedly diminished the severity of the liver injury by decreasing oxidative stress and lipoperoxidation, but hepatocellular regeneration was apparently unaffected probably due to an enhanced mitogenic activity.

Animals↗
PubMed1992

[The efficacy of Plantago ovata as a regulator of intestinal transit. A double-blind study compared to placebo].

The effect of Plantago ovata on patients with chronic constipation (CC) with or without irritable bowel syndrome (IBS) has been assessed by a double blind study comprising 20 patients with CC of which 10 had associated IBS. A clinical questionnaire, weight of feces and intestinal transit time measured with radiopaque markers were done. Patients were then randomly distributed, 10 receiving PO and 10 placebo. Similar tests were done after treatment one month later. All patients receiving PO had good results against only one in the placebo group. Frequency of stools increased from 2.5 +/- 1 vs 8 +/- 2.2 stools per week, p less than 0.001 for paired data). A decrease in consistency of stools was also observed in the treated group. Fecal weight and colonic transit time were not significantly modified in placebo patients, while weight increase was observed in the treated ones (124 +/- 71 vs 194 +/- 65, gr/d p less than 0.001 for paired data) as well as a decrease in transit time (48 +/- 15 vs 34 +/- 18 hours p less than 0.05 for paired data). No adverse effects were observed and particularly no flatulence as often seen in patients on bran.

Adult↗
PubMed1992

[Continuous monitoring of the upper esophageal sphincter with the Dent device, during acid perfusion or distension with balloon of the esophageal body].

The aim of the present study was to evaluate pressure changes of the UES under conditions that simulate the effects of gastroesophageal reflux (GER), that are, balloon esophageal distension and acid perfusion 0.1 N. Studies were performed in eight healthy subjects and fourteen patients with reflux esophagitis (RE), divided in two groups according to symptoms, 6 patients with heartburn and 8 patients with heartburn and regurgitation. We have employed the Dent sleeve to monitor UES pressure. The catheter was located with the help of a side-hole manometric catheter placed in the opposite side of the Dent sleeve; thereafter, it was anchorated. Perfusion of acid at 5 and 10 cm below the UES induces a pressure increase statistically significant, (paired data). This pressure increase is shown when mean values of the 5 minutes are considered as well for every minute. On the after hand, esophageal balloon distension did not produce pressure increases in any of the groups.

Adult↗
PubMed1992

[Response of the upper esophageal sphincter to various esophageal stimuli in patients with reflux esophagitis].

The clinical symptoms, including oropharingeal dysphagia and bronchial symptoms, have been analyzed in 18 normal controls and in 48 patients with reflux esophagitis. Patients with reflux and pyrosis and regurgitation usually have a disease of longer duration, more bronchial symptoms, greater severity of endoscopic lesions and less pressure in the U.E.S. area than those who only have heartburn. In 10 normals as well as in 28 patients (15 with pyrosis and 13 with both pyrosis and regurgitation) the pressure behavior of the superior esophageal sphincter has been studied with a specially designed instrument after different stimuli: acid perfusion at 5 and 10 cm of the U.E.S. during 5 minutes and esophageal balloon distention at 10 cm. In normal individuals none of the stimuli modified the pressure at rest of the U.E.S., while in patients with reflux esophagitis only HCl perfusion at 5 cm was able to significantly increase pressure. This finding was independent of the clinical symptoms of the patients.

Adult↗
PubMed1992

[Oropharyngeal functional assessment in patients with Zenker's diverticulum. Manometric and isotopic study].

Twenty patients with the diagnosis of Zenker's diverticulum were studied clinically and manometrically. In 8 patients oropharyngeal clearance of liquid isotopic markers was done. In three, esophageal emptying of a marked meal was also studied. Clinically, sixteen patients had oropharyngeal dysphagia, while for remained asymptomatic. Dysphagia was severe in only five patients. In half of the patients there were signs of hiatus hernia and/or reflux. Pharyngo-sphincteric incoordination was present in 70% of cases with a mean resting pressure of the LES significantly lower than in controls. There were no differences among patients with or without reflux. Isotopic esophageal clearance was not useful as a test, as there were no significant differences with the control group. On the other hand, esophageal emptying of solid isotopic meals may show the persistence of food in the diverticular sac long time after the meal.

Deglutition Disorders↗
PubMed1987

[Distribution of Langerhans cells in spinocellular epitheliomas].

The authors perform and study about Langerhans cell's distribution on squamous cell carcinomas and on one ecrine porocarcinoma. We used OKT6 and HLA-Dr antigens with fluorescein. We observed a higher density of these cells on the tumors more differentiated. On the other hand, we have seen that tumoral cells of the ecrine porocarcinoma display HLA-Dr antigens.

Adenoma, Sweat Gland↗