Biomedical subjects

F Ruiz

Publications and source records attributed to F Ruiz.

At least 37 records · Page 2Linked to original sources

PubMed2000

The role of oxidative stress in the toxicity induced by amyloid beta-peptide in Alzheimer's disease.

One of the theories involved in the etiology of Alzheimer's disease (AD) is the oxidative stress hypothesis. The amyloid beta-peptide (A beta), a hallmark in the pathogenesis of AD and the main component of senile plaques, generates free radicals in a metal-catalyzed reaction inducing neuronal cell death by a reactive oxygen species mediated process which damage neuronal membrane lipids, proteins and nucleic acids. Therefore, the interest in the protective role of different antioxidants in AD such as vitamin E, melatonin and estrogens is growing up. In this review we summarize data that support the involvement of oxidative stress as an active factor in A beta-mediated neuropathology, by triggering or facilitating neurodegeneration, through a wide range of molecular events that disturb neuronal cell homeostasis.

Alzheimer Disease↗

PubMed2000

Low cleavage activity of 15,15'dioxygenase to convert beta-carotene to retinal in cattle compared with goats, is associated with the yellow pigmentation of adipose tissue.

Two experiments (one with twelve heifers and the other with 14 goats) were designed to evaluate the effect of increasing dietary beta-carotene concentration on the activity of the cleaving enzyme 15,15' beta-carotene dioxygenase and the concentration of beta-carotene and retinol in selected tissues. The experiments lasted 120 days. During the first 90 days animals were offered a beta-carotene unsupplemented diet. In the following 30 days, they were distributed to one of three treatments: 0, 5.5 or 352 mg of beta-carotene/kg of dry matter intake. All animals were slaughtered at the end. In heifers the concentration of beta-carotene in plasma, reflected the level of beta-carotene fed. Goats had detectable levels of beta-carotene only on day 10 of supplementation. In the liver, beta-carotene concentrations were highest with the 352 dose in both species. Heifers had the highest concentration of beta-carotene in the adipose tissue. In bovines, no interaction between beta-carotene treatment and intestinal sampling site was found (P > 0.2) for the activity of 15,15 dioxygenase. Across beta-carotene levels, results of the enzyme assay were: 0.19, 0.32 and 0.45 nmol retinal/(mg S-9 protein/h) (P < 0.01) for 0, 5.5 and 352 mg beta-carotene.kg dry matter intake -1.d-1, respectively; across intestinal sampling sites results of the enzyme assay were 0.45, 0.43 and 0.08 nmol retinal/(mg S-9 protein/h) (P < 0.01) for duodenum, jejunum and ileum, respectively. Caprine data showed an interaction between beta-carotene treatment and intestinal sampling site (P < 0.05) for the activity of 15,15 dioxygenase. The results for treatment 0 were: 1.4, 1.4 and 0; for treatment 5.5: 1.41, 1.42 and 0.13; and for treatment 352: 1.46, 1.99 and 0.48 nmol retinal/mg S-9 protein/h for duodenum, jejunum and ileum, respectively. The lower levels of duodenal and jejunal 15,15'dioxygenase activity in cattle compared with goats, may explain the greater pigmentation of adipose tissue in the former ruminant specie.

Adipose Tissue↗

PubMed2000

Beta,gamma-methylene ATP but not alpha,beta-methylene ATP mimics the inhibitory effect of ATP on ventricular automaticity.

The effects of alpha,beta- and beta,gamma-methylene ATP on ventricular automaticity induced by local injury in the right ventricle of rats pretreated with reserpine, were investigated and compared with the effects of ATP and adenosine. Beta,gamma-methylene ATP but not alpha,beta-methylene ATP mimicked the inhibitory effect of both ATP and adenosine on the spontaneous automaticity In low concentrations, adenosine was more effective than ATP. Alpha,beta-methylene ATP caused little or no effect on ventricular automaticity. The results suggest that the effect of ATP might depend on its hydrolysis into AMP/adenosine.

Adenosine Triphosphate↗

PubMed2000

Stochastic risk estimate for barium radiological examinations in Malaga (Spain).

The aim of this research work has been the estimation of the stochastic risk for five barium examinations. The sample was the population attending the Radiological Service of the 'Nuestra Señora de la Victoria' University Hospital, who had been treated with some barium examinations, set in five different groups: oesophagus tract, oesophagus-gastric-duodenal tract, intestinal tract, enteroclysis and double enema. To estimate the stochastic risk, it is necessary to know the organ dose. This can be calculated from the dose-area product which allows us to determine the effective dose using software. The dose-area product is the most suitable quantity to measure in these types of examination. We have evaluated the contribution that each procedure provides to the genetically significant dose, somatically significant dose, collective effective dose, annual effective dose 'per capita' and detriment, which are useful for assessing the population risk of cancer or hereditary effects after x-ray exposure. The contribution to the genetically significant dose is 6.7 microGy, to the somatically significant dose 8.82 mSv-yr, 16.07 person-Sv for the collective effective dose, 0.03 mSv for the 'per capita' annual effective dose and the annual aggregated detriment is 0.33.

Age Factors↗

PubMed2000

Transpyloric enteral nutrition reduces the complication rate and cost in the critically ill child.

BACKGROUND: Studies in adults have shown that transpyloric enteral nutrition (TEN) is useful in certain patients who cannot tolerate oral or gastric feeding. This study was conducted to compare TEN with parenteral nutrition (PN) in critically ill pediatric patients. METHODS: A retrospective descriptive study conducted in the pediatric intensive care unit of a tertiary pediatric referral center. All patients in the pediatric intensive care unit (PICU) receiving PN and/or TEN from January 1993 through December 1996 were included in the study. RESULTS: Two hundred forty patients (14.6% of all patients admitted to the PICU) received PN and/or TEN (168 exclusively PN, 21 exclusively TEN, and 51 a combined regimen). The number of patients receiving PN and duration of PN declined significantly from 1993 (65 patients, 703 days) through 1996 (48 patients, 395 days). This was mirrored by the increase in the number of patients receiving TEN and duration of TEN. The incidence of complications (hyperglycemia, hypertriglyceridemia, and cholestasis) was higher in the PN group. There was no difference in the incidence of hospital-acquired infection or mortality between the two groups. The cost of TEN was lower than that of PN, with an estimated annual saving of $5,422. CONCLUSIONS: Transpyloric enteral nutrition is a suitable method of nutritional support for critically ill pediatric patients. It has fewer complications and a lower cost than PN.

Child↗

PubMed2000

Patient dose from barium procedures.

The objective of this work was to estimate patient doses (dose-area product, organ dose, effective dose and entrance surface dose) for barium procedures. A total of 175 procedures, in 175 patients, for five different examination categories was analysed. Dose-area product was determined using a transmission ionization chamber. Organ dose and effective dose were assessed using a knowledge of the examination and the software. For all patients, the contribution of fluoroscopy to the total dose was greater than that from radiography. Dose-area product from double contrast barium enema, enteroclysis and intestinal tract procedures was higher than that obtained for the other procedures. The average effective dose was 1.04 mSv and 13.99 mSv for oesophageal tract and enteroclysis examinations, respectively. Entrance surface dose in the oesophageal tract was 16 mGy, 10 times lower than for the other four procedures. Patient dose reduction in barium procedures may be achieved by improved training of resident radiologists, senior radiologists and other specialists in radiation protection.

Adult↗

PubMed2000

Assessing the effectiveness of direct digital radiography barrier sheaths and finger cots.

BACKGROUND: Effective cross-contamination prevention is critical for direct digital radiography, or DDR, sensors, which are not sterilizable; however, current manufacturers' recommendations for standard precautions are limited to the use of plastic barrier sheaths, which are commonly known to tear or leak. The authors sought to determine the incidence of digital radiography barrier-sheath leakage, with and without additional latex finger cot protection, as measured by a water pressure test. METHODS: Four hundred plastic barrier sheaths were randomly assigned to four groups based on intraoral radiograph positioning device use and supplemental barrier protection with a latex finger cot. Sheaths were carefully placed to cover DDR sensors for a single intraoral use, gently removed from the sensors and tested for leakage through a water pressure technique. RESULTS: Perforations occurred in 44 to 51 percent of plastic sheaths after a single radiographic exposure. However, only up to 6 percent of the plastic sheaths that were covered by a latex finger cot leaked during the water pressure test. CONCLUSIONS: At least 44 percent of the plastic barrier sheaths leaked after a single intraoral radiographic exposure. Use of a latex finger cot over the plastic sheath significantly reduced leakage to no more than 6 percent. CLINICAL IMPLICATIONS: Latex finger cots used in conjunction with the standard plastic sheaths that cover DDR sensors may more effectively prevent cross-contamination than do plastic sheaths alone. Dentists who use DDR sensors during highly invasive dental procedures such as dental implant surgery are encouraged to consider supplemental barrier protection for these delicate, expensive and nonsterilizable sensors to prevent patient cross-contamination.

Dental Equipment↗

PubMed2000

Sex differences in perceptions of romantic acts in Portuguese adolescents.

The study was done to examine sex differences in the importance attributed to romantic acts by adolescents. On a 15-item Romantic Acts questionnaire of Neto participants rated the importance of each act. Four factors of Offerings, Physical Intimacy, Altruistic Behavior, and Sexual Behavior were found. The 108 girls judged physical intimacy as more important than the 79 boys.

Adolescent↗

PubMed1999

Basal body duplication in Paramecium requires gamma-tubulin.

First discovered in the fungus Aspergillus nidulans[1], gamma-tubulin is a ubiquitous component of microtubule organizing centres [2]. In centrosomes, gamma-tubulin has been immunolocalized at the pericentriolar material, suggesting a role in cytoplasmic microtubule nucleation [3], as well as within the centriole core itself [4]. Although its function in the nucleation of the mitotic spindle and of cytoplasmic interphasic microtubules has been demonstrated in vitro [5] [6] and in vivo[7] [8] [9], the hypothesis that gamma-tubulin could intervene in centriole assembly has never been experimentally addressed because the mitotic arrest caused by the inactivation of gamma-tubulin in vivo precludes any further phenotypic analysis of putative centriole defects. The issue can be addressed in the ciliate Paramecium, which is characterized by numerous basal bodies that are similar to centrioles but the biogenesis of which is not tightly coupled to the nuclear division cycle. We demonstrate that the inactivation of the Paramecium gamma-tubulin genes leads to inhibition of basal body duplication.

Animals↗

PubMed1999

In vivo regulation by glutathione of methionine adenosyltransferase S-nitrosylation in rat liver.

BACKGROUND/AIMS: Ethanol consumption and pathological conditions such as cirrhosis lead to a reduction of hepatic glutathione. Hepatic methionine adenosyltransferase, the enzyme that synthesizes S-adenosylmethionine, the major methylating agent, is regulated in vivo by glutathione levels. We have previously shown that nitric oxide inactivates methionine adenosyltransferase in vivo by S-nitrosylation. In this study, we aimed to investigate the regulation by glutathione of methionine adenosyltransferase S-nitrosylation in rat liver. METHODS: Rat hepatocytes and whole animals were treated with buthionine sulfoximine, an inhibitor of glutathione synthesis, and methionine adenosyltransferase S-nitrosylation and activity were determined. RESULTS: In hepatocytes, buthionine sulfoximine led to the S-nitrosylation and inactivation of methionine adenosyltransferase. Restoring glutathione levels in hepatocytes treated with buthionine sulfoximine, by the addition of glutathione monoethyl ester, a permeable derivative of glutathione, led to the denitrosylation and reactivation of methionine adenosyltransferase. In whole animals, buthionine sulfoximine led also to methionine adenosyltransferase S-nitrosylation and inactivation. S-Nitrosylation and inactivation of methionine adenosyltransferase induced by buthionine sulfoximine in whole animals was prevented by glutathione monoethyl ester. CONCLUSIONS: These results indicate that in vivo hepatic methionine adenosyltransferase exists in two forms in equilibrium, nitrosylated (inactive) and denitrosylated (active), which are regulated by both the cellular levels of nitric oxide and glutathione.

Animals↗

PubMed1999

Meigs' syndrome with elevated CA125: case report and review of the literature.

A 51-year-old woman presented with acute ascites and hydrothorax is reported. Pelvic ultrasound showed two pelvic solid masses and serum CA125 level was elevated (577 IU/ml). Pathology revealed bilateral ovarian fibromas. We present this case of Meigs' syndrome and discuss its diagnostic problems and a review of the literature.

Abdomen↗

PubMed1999

Efficacy of ampicillin plus ceftriaxone in treatment of experimental endocarditis due to Enterococcus faecalis strains highly resistant to aminoglycosides.

The purpose of this work was to evaluate the in vitro possibilities of ampicillin-ceftriaxone combinations for 10 Enterococcus faecalis strains with high-level resistance to aminoglycosides (HLRAg) and to assess the efficacy of ampicillin plus ceftriaxone, both administered with humanlike pharmacokinetics, for the treatment of experimental endocarditis due to HLRAg E. faecalis. A reduction of 1 to 4 dilutions in MICs of ampicillin was obtained when ampicillin was combined with a fixed subinhibitory ceftriaxone concentration of 4 micrograms/ml. This potentiating effect was also observed by the double disk method with all 10 strains. Time-kill studies performed with 1 and 2 micrograms of ampicillin alone per ml or in combination with 5, 10, 20, 40, and 60 micrograms of ceftriaxone per ml showed a > or = 2 log10 reduction in CFU per milliliter with respect to ampicillin alone and to the initial inoculum for all 10 E. faecalis strains studied. This effect was obtained for seven strains with the combination of 2 micrograms of ampicillin per ml plus 10 micrograms of ceftriaxone per ml and for six strains with 5 micrograms of ceftriaxone per ml. Animals with catheter-induced endocarditis were infected intravenously with 10(8) CFU of E. faecalis V48 or 10(5) CFU of E. faecalis V45 and were treated for 3 days with humanlike pharmacokinetics of 2 g of ampicillin every 4 h, alone or combined with 2 g of ceftriaxone every 12 h. The levels in serum and the pharmacokinetic parameters of the humanlike pharmacokinetics of ampicillin or ceftriaxone in rabbits were similar to those found in humans treated with 2 g of ampicillin or ceftriaxone intravenously. Results of the therapy for experimental endocarditis caused by E. faecalis V48 or V45 showed that the residual bacterial titers in aortic valve vegetations were significantly lower in the animals treated with the combinations of ampicillin plus ceftriaxone than in those treated with ampicillin alone (P < 0.001). The combination of ampicillin and ceftriaxone showed in vitro and in vivo synergism against HLRAg E. faecalis.

Algorithms↗

PubMed1999

Role of antioxidants in the survival of normal and vitiliginous avian melanocytes.

Mutant feather melanocytes from Barred Plymouth Rock (BPR) and White Leghorn (WL) chickens are currently being used as avian models of vitiligo. Feather melanocytes in BPR and WL chickens die prematurely in vivo due to low (50-66%) antioxidant glutathione and superoxide dismutase levels when compared to the wild type Jungle Fowl (JF) melanocytes. Excess superoxide anions, generated by xanthine:xanthine oxidase (X:XO), caused a 15-20% increase in mortality after 1 and 2 hrs. in all three genotypes of in vitro melanocytes as compared to control values that received no X:XO. Overall, the JF wild type melanocytes had the lowest mortality rate, WL melanocytes had the highest mortality rate and the BPR melanocytes had an intermediate mortality rate. Superoxide anion and hydroxyl radical production in the WL feather were double the production in the JF wild type feather. The production of reactive oxygen species in BPR was intermediate to the other two genotypes. In an effort to mimic the low antioxidant levels of the BPR and WL feathers in the JF feather, JF in vitro feather melanocytes were treated with buthionine sulfoximine (BSO), a glutathione synthesis inhibitor. With BSO added to the medium, the JF mortality rates increased by 20-25%, reaching the mortality levels of the mutant BPR melanocytes. The addition of iron to the JF melanocyte X:XO medium increased their mortality rate by 20%, probably via the Fenton reaction. Thus, antioxidants play an extremely important role in both the viability of normal avian melanocytes and the premature death of the vitiliginous avian melanocytes. A working hypothesis, supported in part by the current results, is that the premature death of the mutant melanocytes could be precipitated in the poorly vascularized feather by low antioxidant protection due to both low turnover of tissue fluids which contain SOD and to genetically determined low levels of internal antioxidant protection in these melanocytes. This same mechanistic hypothesis could apply as "a" cause of premature melanocyte cell death in human vitiligo wherein the vitiliginous melanocytes may have a genetic defect in their antioxidant protection system and blood flow to an area may be restricted.

Animals↗

PubMed1998

Protection by pyruvate and malate against glutamate-mediated neurotoxicity.

Pyruvate and malate (P/M) increase the contribution of mitochondria to neuronal calcium homeostasis. We have now found that cortical neuronal cultures utilize pyruvate preferentially over glucose. The supply of pyruvate and malate protects hippocampal and cortical neurons against delayed cell death occurring 24 h after glutamate exposure. High [Ca2+]i levels attained during and after glutamate exposure were reduced when neurons were incubated in the presence of P/M. At the single cell level, this was reflected in a decrease in the number of neurons that respond to glutamate with high rises in [Ca2+]i. The results suggest that the ability to prevent large increases in [Ca2+]i may underlie the beneficial effects of pyruvate and malate during glutamate excitotoxicity.

Animals↗

PubMed1998

Chromosome diversity of the genus Aotus from Colombia.

Description of six Colombian karyomorphs is completed through an extensive cytogenetic characterization of 35 Aotus (owl monkeys) specimens. The description of a new karyomorph for Colombian Aotus by chromosome on Q, G, R, and C, sequential banding is included. Pairs of karyomorphs 2 and 3 and 6 and 9 with 2n of 54, and 50, respectively, as well as karyomorphs 7 and 8 with 46 and 58 chromosomes were strongly suspected to represent different species on the grounds of large karyotypic differences. A proposal for a chromosome nomenclature of Aotus karyomorphs that aims to clarify Aotus taxonomy is presented which achieves a precise correspondence of different banding patterns, based on Q, G, R, and C sequential banding and chromosome measurements. Although our contribution is not a universal nomenclature system, unique criteria for chromosome denomination within Aotus karyomorphs are established. Previous systems of chromosome nomenclature have not successfully addressed the nomenclature of chromosomes of the same karyotype.

Animals↗

PubMed1998

Specific interaction of methionine adenosyltransferase with free radicals.

Although free radicals have been traditionally implicated in cell injury, and associated to pathophysiological processes, recent data implicate them in cell signaling events. Free radicals are naturally occurring oxygen-,nitrogen-and sulfur-derived species with an unpaired electron, such as superoxide, hydroxyl radical or nitric oxide. In order to assess the role of free radicals in cell signaling, we have studies the modulator effect of oxygen and nitrogen active species on liver methionine adenosyltransferase (MAT), a key metabolic enzyme. The presence of 10 cysteine residues per subunit, makes liver MAT a sensitive target for oxidation/nitrosylation. Here we show that purified MAT from rat liver is nitrosylated and oxidized in vitro. Incubation with H202 or the NO donor S-nitrosylated GSH (GSNO), diminish MAT activity in a dose-and time-dependent manner. Furthermore, the inactivation derived from both oxidation and nitrosylation, was reverted by GSH. MAT inactivation originates on the specific and covalent modification of the sulphydryl group of cysteine residue 121. We also studied how free radicals modulate MAT activity in vivo. It was previously shown that MAT activity is strongly dependent on cellular GSH levels. Generation of oxygen and nitrogen active species in rats by injection of LPS, induced a decrease of liver MAT activity. This effect might derive from nitrosylation and/or oxidation of the enzyme. Modulation of liver MAT by NO is further supported by the inactivation of this enzyme observed in experimental models in which NO is produced; such as the administration of NO donors to rats and in hepatocytes cultured in hypoxia, a condition that induces the expression of the inducible nitric oxide synthase (iNOS). Oxidation also controls liver MAT activity in a cell environment as shown in CHO cells stably transfected with rat liver MAT cDNA upon addition of H2O2 to the culture medium. This effect depends upon the generation of the hydroxyl radical. On the basis of the metabolic implications of liver MAT, together with the structural features accounting for the sensitivity of this enzyme to active oxygen and nitrogen species, we propose that modulation of MAT by these agents could be a mechanism to regulate the consumption of ATP in the liver, and thus preserve cellular viability under different stress conditions.

Animals↗

PubMed1998

Nitric oxide inactivates rat hepatic methionine adenosyltransferase In vivo by S-nitrosylation.

We investigated the mechanism of nitric oxide (NO) action on hepatic methionine adenosyltransferase (MAT) activity using S-nitrosoglutathione (GSNO) as NO donor. Hepatic MAT plays an essential role in the metabolism of methionine, converting this amino acid into S-adenosylmethionine. Hepatic MAT exists in two oligomeric states: as a tetramer (MAT I) and as a dimer (MAT III) of the same subunit. This subunit contains 10 cysteine residues. In MAT I, S-nitrosylation of 1 thiol residue per subunit was associated with a marked inactivation of the enzyme (about 70%) that was reversed by glutathione (GSH). In MAT III, S-nitrosylation of 3 thiol residues per subunit led to a similar inactivation of the enzyme, which was also reversed by GSH. Incubation of isolated rat hepatocytes with S-nitrosoglutathione monoethyl ester (EGSNO), a NO donor permeable through the cellular membrane, induced a dose-dependent inactivation of MAT that was reversed by removing the NO donor from the cell suspension. MAT, purified from isolated rat hepatocytes, contained S-nitrosothiol groups and the addition of increasing concentrations of EGSNO to the hepatocyte suspension led to a progressive S-nitrosylation of the enzyme. Removal of the NO donor from the incubation media resulted in loss of most NO groups associated to the enzyme. Finally, induction in rats of the production of NO, by the administration of bacterial lipopolysaccharide (LPS), induced a fivefold increase in the S-nitrosylation of hepatic MAT, which led to a marked inactivation of the enzyme. Thus, the activity of liver MAT appears to be regulated in vivo by S-nitrosylation.

Animals↗

PubMed1998

Homology-dependent gene silencing in Paramecium.

Microinjection at high copy number of plasmids containing only the coding region of a gene into the Paramecium somatic macronucleus led to a marked reduction in the expression of the corresponding endogenous gene(s). The silencing effect, which is stably maintained throughout vegetative growth, has been observed for all Paramecium genes examined so far: a single-copy gene (ND7), as well as members of multigene families (centrin genes and trichocyst matrix protein genes) in which all closely related paralogous genes appeared to be affected. This phenomenon may be related to posttranscriptional gene silencing in transgenic plants and quelling in Neurospora and allows the efficient creation of specific mutant phenotypes thus providing a potentially powerful tool to study gene function in Paramecium. For the two multigene families that encode proteins that coassemble to build up complex subcellular structures the analysis presented herein provides the first experimental evidence that the members of these gene families are not functionally redundant.

Animals↗