Showing papers by "University of Seville published in 1999"
TL;DR: Measurements of the fluid velocity as a function of frequency and position across the electrode indicate that the flow occurs due to electroosmotic stress arising from the interaction of the electric field and the electrical double layer on the electrodes.
500 citations
TL;DR: In this paper, the authors investigate the fate of single secretory vesicles after fusion with the plasma membrane by measuring capacitance changes and transmitter release in rat chromaffin cells using the cell-attached patch-amperometry technique.
Abstract: Exocytosis, the fusion of secretory vesicles with the plasma membrane to allow release of the contents of the vesicles into the extracellular environment, and endocytosis, the internalization of these vesicles to allow another round of secretion, are coupled. It is, however, uncertain whether exocytosis and endocytosis are tightly coupled, such that secretory vesicles fuse only transiently with the plasma membrane before being internalized (the 'kiss-and-run' mechanism), or whether endocytosis occurs by an independent process following complete incorporation of the secretory vesicle into the plasma membrane. Here we investigate the fate of single secretory vesicles after fusion with the plasma membrane by measuring capacitance changes and transmitter release in rat chromaffin cells using the cell-attached patch-amperometry technique. We show that raised concentrations of extracellular calcium ions shift the preferred mode of exocytosis to the kiss-and-run mechanism in a calcium-concentration-dependent manner. We propose that, during secretion of neurotransmitters at synapses, the mode of exocytosis is modulated by calcium to attain optimal conditions for coupled exocytosis and endocytosis according to synaptic activity.
404 citations
TL;DR: It is concluded that the phenolics found in virgin olive oil possess an array of potentially beneficial lipoxygenase-inhibitory, prostaglandin-sparing, and antioxidant properties.
346 citations
TL;DR: In this paper, a plant homologue of APC activators involved in mitotic cyclin degradation, called ccs52, was identified from Medicago sativa root nodules, which exhibit the highest degree of endopolyploidy in this plant.
Abstract: Plant organs develop mostly post-embryonically from persistent or newly formed meristems. After cell division arrest, differentiation frequently involves endoreduplication and cell enlargement. Factors controlling transition from mitotic cycles to differentiation programmes have not been identified yet in plants. Here we describe ccs52, a plant homologue of APC activators involved in mitotic cyclin degradation. The ccs52 cDNA clones were isolated from Medicago sativa root nodules, which exhibit the highest degree of endopolyploidy in this plant. ccs52 represents a small multigenic family and appears to be conserved in plants. Overexpression of ccs52 in yeast triggered mitotic cyclin degradation, cell division arrest, endoreduplication and cell enlargement. In Medicago, enhanced expression of ccs52 was found in differentiating cells undergoing endoreduplication. In transgenic M.truncatula plants, overexpression of the ccs52 gene in the antisense orientation resulted in partial suppression of ccs52 expression and decreased the number of endocycles and the volume of the largest cells. Thus, the ccs52 product may switch proliferating cells to differentiation programmes which, in the case of endocycles, result in cell size increments.
341 citations
TL;DR: Current evidence for oxidative damage in chronic inflammatory periodontal disease, and the possible therapeutic effects of anti-oxidants in treating and/or preventing such pathology, are reviewed, with special attention to vitamin E and Co-enzyme Q.
Abstract: In recent years, there has been a tremendous expansion in medical and dental research concerned with free radicals, reactive oxygen species, and anti-oxidant defense mechanisms. This review is intended to provide a critical, up-to-date summary of the field, with particular emphasis on its implications for the application of "anti-oxidant therapy" in periodontal disease. We have reviewed the nomenclature, mechanisms of actions, features, and sources of most common free radicals and reactive oxygen species, as well as analyzed the typical biological targets for oxidative damage. Based on a review of direct and indirect anti-oxidant host defenses, particularly in relation to the key role of polymorphonuclear neutrophils in periodontitis, we review current evidence for oxidative damage in chronic inflammatory periodontal disease, and the possible therapeutic effects of anti-oxidants in treating and/or preventing such pathology, with special attention to vitamin E and Co-enzyme Q.
330 citations
TL;DR: A revision on intra-laboratory testing of accuracy of analytical methods from recovery assays is given and procedures based on spiked matrices and spiked samples are presented and discussed.
299 citations
TL;DR: It is concluded that melatonin inhibits NO production mainly by inhibition of iNOS expression, and the inhibition of NO levels may account for the protection of the indoleamine against LPS‐induced endotoxemia in rats.
Abstract: We evaluated the role of melatonin in endotoxemia caused by lipopolysaccharide (LPS) in unanesthetized rats. The expression of inducible isoform of nitric oxide synthase (iNOS) and the increase in the oxidative stress seem to be responsible for the failure of lungs, liver, and kidneys in endotoxemia. Bacterial LPS (10 mg/kg b. w) was i.v. injected 6 h before rats were killed and melatonin (10-60 mg/kg b.w.) was i.p. injected before and/or after LPS. Endotoxemia was associated with a significant rise in the serum levels of aspartate and alanine aminotransferases, gamma-glutamyl-transferase, alkaline phosphatase, creatinine, urea, and uric acid, and hence liver and renal dysfunction. LPS also increased serum levels of cholesterol and triglycerides and reduced glucose levels. Melatonin administration counteracted these organ and metabolic alterations at doses ranging between 20 and 60 mg/kg b. w. Melatonin significantly decreased lung lipid peroxidation and counteracted the LPS-induced NO levels in lungs and liver. Our results also show an inhibition of iNOS activity in rat lungs by melatonin in a dose-dependent manner. Expression of iNOS mRNA in lungs and liver was significantly decreased by melatonin (60 mg/kg b. w., 58-65%). We conclude that melatonin inhibits NO production mainly by inhibition of iNOS expression. The inhibition of NO levels may account for the protection of the indoleamine against LPS-induced endotoxemia in rats.
284 citations
TL;DR: Isolate-A showed a partial dissociation of the 11S protein because of the high pH used for the protein extraction, and this probably explains the differences observed in the functional characteristics of both isolates.
260 citations
TL;DR: It is shown that STAT3 is a transcription factor whose activity is modulated by H2O2 in human lymphocytes, in which endogenous catalase had previously been inhibited, and that H 2O2 and vanadate are likely to inhibit the activity of intracellular tyrosine phosphatase(s), leading to enhanced STAT3 tyosine phosphorylation and hence its translocation to the nucleus.
249 citations
TL;DR: Porin loss can augment resistance provided either by TEM- or SHV-type ESBLs or by plasmid-mediated AmpC enzymes to include the latest oxyimino-β-lactams and carbapenems in K. pneumoniae.
Abstract: Two clinical isolates of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae were noted to be less susceptible than expected to imipenem. Both were missing outer membrane proteins that serve as channels for antibiotic entry. The role of beta-lactamase in resistance was investigated by eliminating the original ESBL and introducing plasmids encoding various ESBLs and AmpC beta-lactamase types, by studying the effect of an increased inoculum, and by evaluating interactions with beta-lactamase inhibitors. The contribution of porin deficiency was investigated by restoring a functional ompK36 gene on a plasmid. Plasmids encoding AmpC-type beta-lactamases provided resistance to imipenem (up to 64 microg/ml) and meropenem (up to 16 microg/ml) in strains deficient in porins. Carbapenem resistance showed little inoculum effect, was not affected by clavulanate but was blocked by BRL 42715, and was diminished if OmpK36 porin was restored. Plasmids encoding TEM- and SHV-type ESBLs conferred resistance to cefepime and cefpirome, as well as to earlier oxyimino-beta-lactams. This resistance was magnified with an increased inoculum, was blocked by clavulanate, and was also lowered by OmpK36 porin restoration. In addition, SHV-2 beta-lactamase had a small effect on carbapenem resistance (imipenem MIC, 4 microg/ml, increasing to 16 microg/ml with a higher inoculum) when porins were absent. In K. pneumoniae porin loss can thus augment resistance provided either by TEM- or SHV-type ESBLs or by plasmid-mediated AmpC enzymes to include the latest oxyimino-beta-lactams and carbapenems.
244 citations
TL;DR: It is concluded that the induction of AQP4 mRNA expression is related to disruption of the blood-brain barrier and under brain edema conditions this water channel plays a key role in the reestablishment of the brain osmotic equilibrium.
TL;DR: It is reported here that IL-1β provokes a marked repression of genes, such as fragile X mental retardation 1 (FMR1) and hypoxanthine phosphoribosyltransferase (HPRT), having a CpG island in their promoter region.
Abstract: Interleukin (IL)-1beta is a pleiotropic cytokine implicated in a variety of activities, including damage of insulin-producing cells, brain injury, or neuromodulatory responses. Many of these effects are mediated by nitric oxide (NO) produced by the induction of NO synthase (iNOS) expression. We report here that IL-1beta provokes a marked repression of genes, such as fragile X mental retardation 1 (FMR1) and hypoxanthine phosphoribosyltransferase (HPRT), having a CpG island in their promoter region. This effect can be fully prevented by iNOS inhibitors and is dependent on DNA methylation. NO donors also cause FMR1 and HPRT gene silencing. NO-induced methylation of FMR1 CpG island can be reverted by demethylating agents which, in turn, produce the recovery of gene expression. The effects of IL-1beta and NO appear to be exerted through activation of DNA methyltransferase (DNA MeTase). Although exposure of the cells to NO does not increase DNA MeTase gene expression, the activity of the enzyme selectively increases when NO is applied directly on a nuclear protein extract. These findings reveal a previously unknown effect of IL-1beta and NO on gene expression, and demonstrate a novel pathway for gene silencing based on activation of DNA MeTase by NO and acute modification of CpG island methylation.
TL;DR: In this article, a universal value of the surface charge on the liquid microjet and the resulting charged droplets, independent of their size and of the liquid permittivity, has been found.
TL;DR: In this paper, the authors define and study both bi-slant and semisupermanifolds of an almost contact metric manifold and, in particular, of a Sasakian manifold.
Abstract: We define and study both bi-slant and semi-slant submanifolds of an almost contact metric manifold and, in particular, of a Sasakian manifold We prove a characterization theorem for semi-slant submanifolds and we obtain integrability conditions for the distributions which are involved in the definition of such submanifolds We also study an interesting particular class of semi-slant submanifolds
TL;DR: Results showed that both melatonin and TAS in human serum exhibited 24 hr variations with nocturnal peak values at 01:00 hr, and suggested that melatonin contributes to the total antioxidative capability of human serum.
Abstract: This work evaluates whether physiological concentrations of the pineal secretory product melatonin contribute to the total antioxidant status (TAS) of human serum. Day and nighttime serum samples were collected from healthy volunteers ranging from 2 to 89 years of age and used to measure melatonin and TAS. Results showed that both melatonin and TAS in human serum exhibited 24 hr variations with nocturnal peak values at 01:00 hr. Moreover, exposure of volunteers to light at night resulted in clear decreases of both TAS and melatonin. Furthermore, when melatonin was removed from sera collected at night, the TAS value of the sample was reduced to basal daytime values. In aging studies, it was found that nocturnal serum values of TAS and melatonin exhibited maximal values during the first four decades; thereafter, these values decreased as age advanced. In 60-year-old individuals, day/night differences in serum melatonin and TAS levels were clearly diminished, by more than 80%, with these differences being completely abolished in older individuals. Our results suggest that melatonin contributes to the total antioxidative capability of human serum. This antioxidant contribution of melatonin is reduced as age advances correlating with the age-related reduction of melatonin.
TL;DR: Optimal resolution of the two K. pneumoniae porins by electrophoresis on polyacrylamide gels is not achieved using gel systems already described for E. coli, and application of this identification system showed that most isolates lacking expression of extended-spectrum beta-lactamases express the two porins.
Abstract: Two porins, OmpK36 and OmpK35, have been described previously in Klebsiella pneumoniae, and they are homologous to the Escherichia coli porins OmpC and OmpF, respectively, at both the DNA and amino acid levels. Optimal resolution of the two K. pneumoniae porins by electrophoresis on polyacrylamide gels is not achieved using gel systems already described for E. coli and requires modifications of the bisacrylamide content of the resolving gels. Once resolved, identification of porins OmpK36 and OmpK35 cannot be based solely on their apparent molecular masses since in some strains the OmpK36 porin migrates faster than the OmpK35 porin, whilst in other strains OmpK35 is the faster-migrating porin. Expression of OmpK35 porin is increased in low-osmolarity medium and, combined with Western blot analysis, this allows for the identification of both porins. Application of this identification system showed that most isolates lacking expression of extended-spectrum β-lactamases express the two porins, whereas most isolates producing these β-lactamases express only porin OmpK36, and the OmpK35 porin is either very low or not expressed.
TL;DR: This study strongly suggests that the VPP reflects an early visual stage of face processing in the fusiform gyrus that is strictly stimulus-related and independent of familiarity, and shows that source localization algorithms may give reliable solutions on single subject averages for early visual components despite high inter-subject variability of the surface characteristics of ERPs.
TL;DR: Data support the view that GMAP-210 serves to link the cis-Golgi network to the minus ends of centrosome-nucleated microtubules, and appears essential for ensuring the proper morphology and size of the Golgi apparatus.
Abstract: We report that a peripheral Golgi protein with a molecular mass of 210 kD localized at the cis-Golgi network (Rios, R.M., A.M. Tassin, C. Celati, C. Antony, M.C. Boissier, J.C. Homberg, and M. Bornens. 1994. J. Cell Biol. 125:997-1013) is a microtubule-binding protein that associates in situ with a subpopulation of stable microtubules. Interaction of this protein, now called GMAP-210, for Golgi microtubule-associated protein 210, with microtubules in vitro is direct, tight and nucleotide-independent. Biochemical analysis further suggests that GMAP-210 specifically binds to microtubule ends. The full-length cDNA encoding GMAP-210 predicts a protein of 1, 979 amino acids with a very long central coiled-coil domain. Deletion analyses in vitro show that the COOH terminus of GMAP-210 binds to microtubules whereas the NH2 terminus binds to Golgi membranes. Overexpression of GMAP-210-encoding cDNA induced a dramatic enlargement of the Golgi apparatus and perturbations in the microtubule network. These effects did not occur when a mutant lacking the COOH-terminal domain was expressed. When transfected in fusion with the green fluorescent protein, the NH2-terminal domain associated with the cis-Golgi network whereas the COOH-terminal microtubule-binding domain localized at the centrosome. Altogether these data support the view that GMAP-210 serves to link the cis-Golgi network to the minus ends of centrosome-nucleated microtubules. In addition, this interaction appears essential for ensuring the proper morphology and size of the Golgi apparatus.
TL;DR: In this paper, the relation between structural and process quality in preschool classrooms is examined and compared across four countries (Germany, Portugal, Spain, and the United States) using the Early Childhood Environment Rating Scale and the Caregiver Interaction Scale.
Journal Article•
TL;DR: Findings support the idea that under toxicity conditions associated with high LPS doses, VIP and PACAP could act as protective mediators that regulate the excessive release of TNF-alpha to reduce inflammation or shock.
Abstract: Vasoactive intestinal peptide (VIP) is a neuropeptide synthesized by immune cells that can modulate several immune aspects, including the function of cells involved in the inflammatory response, such as macrophages and monocytes. The production and release of cytokines by activated phagocytes are important events in the pathogenesis of ischemia-reperfusion injury. There is abundant evidence that the proinflammatory cytokine TNF-α is an important mediator of shock and organ failure complicating Gram-negative sepsis. VIP has been shown to attenuate the deleterious consequences of this pathologic phenomenon. In this study we have investigated the effects of VIP and the structurally related neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP38) on the production of TNF-α by endotoxin-activated murine peritoneal macrophages. Both neuropeptides rapidly and specifically inhibit the LPS-stimulated production of TNF-α, exerting their action through the binding to VPAC1 receptor and the subsequent activation of the adenylate cyclase system. VIP and PACAP regulate the production of TNF-α at a transcriptional level. In vitro results were correlated with an inhibition of both TNF-α expression and release in endotoxemic mice in vivo. The immunomodulatory role of VIP in vivo is supported by the up-regulation of VIP release in serum and peritoneal fluid by LPS and proinflammatory cytokines such as TNF-α, IL-1β, and IL-6. These findings support the idea that under toxicity conditions associated with high LPS doses, VIP and PACAP could act as protective mediators that regulate the excessive release of TNF-α to reduce inflammation or shock.
TL;DR: The topical antiinflammatory activity of the hexane extract and of stigmasterol was evaluated by auricular oedema, induced by 12‐0‐tetradecanoylphorbol acetate (TPA), in the mouse, using single and multiple applications of the phlogistic agent.
Abstract: Eryngium foetidum L. (Apiaceae) is a Caribbean endemic plant, used in folk medicine for the treatment of several antiinflammatory disorders. A preliminary phytochemical study showed that the hexane extract is rich in terpenic compounds. Chromatographic fractionation of this extract yielded: alpha-cholesterol, brassicasterol, campesterol, stigmasterol (as the main component, 95%) clerosterol, beta-sitosterol, delta 5-avenasterol, delta (5)24-stigmastadienol and delta 7-avenasterol. The topical antiinflammatory activity of the hexane extract and of stigmasterol was evaluated by auricular oedema, induced by 12-0-tetradecanoylphorbol acetate (TPA), in the mouse, using single and multiple applications of the phlogistic agent. Both reduced the oedema in a similar proportion in the two model assays (acute and chronic). Meloperoxidase activity was strongly reduced by both the extract and the compound, in the acute but not the chronic model. These results indicate that the leaves of Eryngium foetidum L may be effective against topical inflammation processes. Stigmasterol also exerts a significant topical antiinflammatory activity although it cannot be considered to be a major antiinflammatory agent, therefore other bioactive components are probably involved in the activity of the hexane extract.
TL;DR: It is shown that melatonin seems to promote a Th1-response by increasing IL-12 production by cultured monocytes under suboptimal stimulation in a dose-dependent way.
TL;DR: It is shown that hpttg is highly expressed in the majority of pituitary adenomas while only very low levels of mRNA can be detected in normal pituitaries by Northern blot analysis, and hPTTG protein was immunolocalized mainly in the cytoplasm of adenoma cells.
Abstract: The role of oncogenes in pituitary tumorigenesis remains elusive since few genetic changes have been identified so far in pituitary tumors. Pituitary tumor-transforming gene (pttg) has been recently cloned from rat GH4 pituitary tumor cells. We have previously isolated and characterized hpttg from human thymus. In the present study, we analyse the expression of hpttg mRNA in a series of human pituitary adenomas. We show that hpttg is highly expressed in the majority of pituitary adenomas while only very low levels of mRNA can be detected in normal pituitary gland by Northern blot analysis. hPTTG protein was immunolocalized mainly in the cytoplasm of adenoma cells. Other common extra-cranial malignant tumors were also analysed by immunohistochemistry. Interestingly, strong hPTTG immunoreactivity was detected in most adenocarcinomas of mammary and pulmonary origins.
01 Jan 1999
TL;DR: In this paper, it was shown that for a Banach space X there are bounded linear operators having hypercyclic vectors if and only if X is separable and dim X = oo.
Abstract: We provide in this paper a direct and constructive proof of the following fact: for a Banach space X there are bounded linear operators having hypercyclic vectors if and only if X is separable and dim X = oo. This is a special case of a recent result, which in turn solves a problem proposed by S. Rolewicz.
TL;DR: Phenotypic and phylogenetic studies indicate that isolate 4A represents a new species, Halomonas campisalis, and this organism, and similar ones, hold promise for the treatment of saline, alkaline waste.
TL;DR: In this article, the load flow equations are written in terms of new variables resulting in a set of 3N equations (2N linear plus N quadratic) for a network with N+1 buses.
Abstract: This paper presents a method to solve the power flow problem in radial distribution networks. In the proposed formulation, the load flow equations are written in terms of new variables resulting in a set of 3N equations (2N linear plus N quadratic) for a network with N+1 buses. A computationally efficient solution scheme based on the Newton-Raphson method is proposed, and possible simplifications are discussed. Finally, a comparative evaluation of the proposed method's performance against existing algorithms is provided.
TL;DR: It is shown that these new basis functions ensure a very quick convergence of the numerical results obtained via the Galerkin's method with respect to the number of basis functions, and a very efficient technique is presented, which makes possible the fast computation of the infinite integrals arising from the application of Galerkins's method in the HTD.
Abstract: Galerkin's method in the Hankel transform domain (HTD) is used for computing the resonant frequencies, quality factors, and radiation patterns of the resonant modes of circular microstrip patches. The patches are assumed to be embedded in multilayered dielectric substrates. In this paper, the dyadic Green's function of the problem in the HTD is determined in terms of the two-dimensional Fourier transform of a related Green's function. New basis functions for the current density on the patches are introduced. It is shown that these new basis functions ensure a very quick convergence of the numerical results obtained via the Galerkin's method with respect to the number of basis functions. Also, a very efficient technique is presented, which makes possible the fast computation of the infinite integrals arising from the application of Galerkin's method in the HTD. At the end of this paper, the numerical results obtained are compared with previously published numerical results, with numerical results computed by means of the electromagnetic simulator "Ensemble", and with measurements carried out by the authors. Good agreement is found in all cases among all sets of results.
TL;DR: In the paper, the application of MIMO frequency-domain methods to predict the existence of multiple equilibria and of limit cycles and a new and more general stability index which could be used to perform a bifurcation analysis of fuzzy control systems is presented.
Abstract: Points out how the nonlinearities involved in multivariable Takagi-Sugeno (T-S) fuzzy control systems could originate complex behavior phenomena, such as multiple equilibrium points or limit cycles, that cannot be detected using conventional stability analysis techniques. In the paper, the application of MIMO frequency-domain methods to predict the existence of multiple equilibria and of limit cycles are presented. The proposed method is based on the formulation of a Lur'e problem from the original structure of a T-S fuzzy system with a fuzzy controller. Furthermore, this technique makes straightforward the application of input-output stability techniques such as the multivariable circle criterion, also called the conicity criterion, and the harmonic balance method. Moreover, in the paper, the application of the harmonic balance method has been generalized to the case of a MIMO fuzzy system with asymmetric nonlinearities and improved by the decreasing conservatism. A new and more general stability index which could be used to perform a bifurcation analysis of fuzzy control systems is presented. The paper includes a collection of examples where the advantages of the proposed approach are made explicit comparing it to the input-output conicity criterion and the Lyapunov direct method.
TL;DR: Functional characterization suggested a narrower pore for the OmpK37 porin, which correlated with the susceptibility to certain beta-lactam antibiotics, since a K. pneumoniae strain expressing porin OMPK37, but not porin ompK36 or Omp k35, was less susceptible to beta- lactamiotics than the same strain expressing either porinOmpK 36 or OMP k35.
Abstract: Klebsiella pneumoniae porin genes were analyzed to detect mutations accounting for the porin deficiency observed in many beta-lactam-resistant strains. PCR and Southern blot analysis revealed the existence of a third porin gene in addition to the OmpK36 and OmpK35 porin genes previously described. This new porin gene was designated ompK37 and is present in all of the clinical isolates tested. The OmpK37 porin gene was cloned, sequenced, and overexpressed in Escherichia coli. In contrast to that of the major porins, OmpK37 porin expression was only detectable by Western blot analysis in porin-deficient beta-lactam-resistant strains, suggesting strong down regulation under standard laboratory conditions. Functional characterization suggested a narrower pore for the OmpK37 porin than for K. pneumoniae porins OmpK36 and OmpK35. This correlated with the susceptibility to certain beta-lactam antibiotics, since a K. pneumoniae strain expressing porin OmpK37, but not porin OmpK36 or OmpK35, was less susceptible to beta-lactam antibiotics than the same strain expressing either porin OmpK36 or OmpK35.
TL;DR: In this article, the authors identify empirically the specific combinations of conflict handling styles that result in differentiated patterns within groups of managers, by using hierarchical and non-hierarchical cluster analyses of a sample of managers.
Abstract: Most studies of conflict handling styles in organizations analyze these styles separately. These studies assume that individuals are oriented towards the use of one of the styles of conflict management. As a result, different styles are compared one by one as if they were independent. In contrast, from a more all‐embracing perspective people are seen as adopting configurations of styles. The interest in this alternative perspective lies in exploring the relations between these styles, how they combine and form patterns of conflict styles. This article presents an exploratory study that seeks to identify empirically the specific combinations of conflict handling styles that result in differentiated patterns within groups of managers. By using hierarchical and non‐hierarchical cluster analyses of a sample of managers, different patterns of conflict management were identified. The effectiveness of each of the resulting patterns was analyzed in terms of its influence on the parties' joint substantive outcomes and their mutual relationship. Results show that patterns using multiple conflict handling styles were more effective than patterns based on a single style.