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Biomedical subjects

F Ruiz

Publications and source records attributed to F Ruiz.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1998

In vitro activity of the new ketolide HMR3647 in comparison with those of macrolides and pristinamycins against Enterococcus spp.

Ninety-four erythromycin-susceptible and 107 erythromycin-resistant enterococcal strains (MIC of >/=512 microgram/ml) were inhibited by the ketolide HMR3647 at MICs of </=0.007 to 0.06 and 0.03 to 8 microgram/ml, respectively. Eighteen vanA-positive isolates and 29 high-level-penicillin-resistant isolates, all of them erythromycin resistant, were inhibited by HMR3647 at an MIC range of 0.015 to 4 microgram/ml. The new ketolide has excellent activity against Enterococcus species.

Anti-Bacterial Agents↗
PubMed1998

Uncoupling of basal body duplication and cell division in crochu, a mutant of Paramecium hypersensitive to nocodazole.

In Paramecium the development of cell shape and surface pattern during division depends on a precise spatial and temporal pattern of duplication of the ciliary basal bodies which are the organizers of the cortical cytoskeleton. According to their localization, basal bodies will duplicate once, more than once or not all and this duplication is coupled with cell division, as is centrosomal duplication in metazoan cells. We describe here a monogenic nuclear recessive mutation, crochu1 (cro1), resulting in abnormal cell shape and cortical pattern and hypersensitivity to nocodazole. The cytological analysis, by immunofluorescence and electron microscopy, demonstrates that the mutation causes hyper duplication of basal bodies and releases both spatial and temporal control of duplication as basal bodies continue to proliferate in interphase and do so at ectopic locations, beneath the surface and in cortical territories where no duplication occurs in the wild type. However, the abnormal surface organization of cro1 cells does not affect the program of basal body duplication during division. By genetic analysis, no interaction was detected with the sm19 mutation which impairs basal body duplication. In contrast, the cro1 mutation suppresses the nocodazole resistance conferred by nocr1, a mutation in a beta-tubulin gene. This interaction suggests that the primary effect of the mutation bears on microtubule dynamics, whose instability, normally increased during division, would persist throughout the interphase and provide a signal for constitutive basal body duplication.

Animals↗
PubMed1997

Genetic evidence for a role of centrin-associated proteins in the organization and dynamics of the infraciliary lattice in Paramecium.

Within the superfamily of "EF-hand Ca2+-modulated proteins," centrins constitute a family of cytoskeletal proteins that are highly conserved from lower eukaryotes to man. Their cytoskeletal specialization is manifest in their capacity to form filamentous contractile arrays of various shapes and functions and by their association with microtubule organizing centres (MTOCs). While the latter property has been conserved throughout the evolution of eukaryotes, centrin-based contractile structures are only found in protists where they form arrays of widely diverse organization and function. In the ciliate Paramecium tetraurelia, three centrin genes have been characterized, which may be part of a larger centrin gene family [Madeddu et al., 1996: Eur J. Biochem. 238:121-128]. The products of these genes were originally identified as components of the infraciliary lattice, a contractile cytoskeletal network [Garreau de Loubresse et al., 1991: Biol. Cell 71:217-225]. We show here that centrins are localized not only in this lattice but also in basal bodies and in the cord, a filamentous structure associated with the oral apparatus. We demonstrate that in the infraciliary lattice, but not in basal bodies, centrins are associated with high-molecular-weight proteins (ca. 350 kD). Their role in the biogenesis of the infraciliary lattice is documented by cytological and biochemical properties of the mutant "démaillé" (dem1) characterized by altered centrin-associated proteins and abnormal organization and dynamics of the infraciliary lattice.

Animals↗
PubMed1997

CCK-B receptors in the limbic system modulate the antidepressant-like effects induced by endogenous enkephalins.

Systemic administration of RB 101, a complete inhibitor of enkephalin catabolism, has been reported to induce antidepressant-like responses in mice which were potentiated by an ineffective dose of a CCK-B antagonist. The aim of this study was to investigate the neuroanatomical substrate involved in the facilitatory effects induced by CCK-B antagonists on RB 101 behavioural responses. Thus, the CCK-B antagonist PD-134,308 was locally administered into different brain structures (anterior nucleus accumbens, central amygdala and caudate nucleus) and its effects on the antidepressant-like response induced by systemic administration of RB 101 were evaluated in the conditioned suppression of motility (CSM) test in rats. RB 101 administered alone by the IV route decreased the CSM in rats, as previously obtained in mice. Systemic administration of a non effective dose of PD-134,308 facilitated the antidepressant-like effect induced by RB 101. Local injection of PD-134,308 into the anterior nucleus accumbens, the central amygdala or the caudate nucleus did not modify CSM. The antidepressant-like effects elicited by RB 101 in this test were potentiated by PD-134,308 after microinjection in the anterior nucleus accumbens and central amygdala, but not in the caudate nucleus. All these effects were observed only in shocked animals. The present results suggest that the mesolimbic system, particularly the anterior nucleus accumbens and the central amygdala, seems to play an important role in the interaction occurring between the endogenous CCK and opioid system in the control of behavioural responses.

Amygdala↗