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Showing papers by "University of Seville published in 1997"


Journal ArticleDOI
TL;DR: In this article, the scaling laws of the spray current and droplet size were obtained from a theoretical model of the charge transport, and the separation between two different behaviours strongly related to the viscosity and electrical conductivity of the liquid was found.

744 citations


Journal ArticleDOI
02 Oct 1997-Nature
TL;DR: Exocytosis of individual chromaffin granules is investigated by using cell-attached capacitance measurements, combined with electrochemical detection of catecholamines, achieved by inserting a carbon-fibre electrode into the patch pipette and finding that the fusion-pore diameter stays at <3 nm for a variable period, which can last for several seconds, before it expands.
Abstract: In mast cells and granulocytes, exocytosis starts with the formation of a fusion pore. It has been suggested that neurotransmitters may be released through such a narrow pore without full fusion. However, owing to the small size of the secretory vesicles containing neurotransmitter, the properties of the fusion pore formed during Ca2+-dependent exocytosis and its role in transmitter release are still unknown. Here we investigate exocytosis of individual chromaffin granules by using cell-attached capacitance measurements combined with electrochemical detection of catecholamines, achieved by inserting a carbon-fibre electrode into the patch pipette. This allows the simultaneous determination of the opening of individual fusion pores and of the kinetics of catecholamine release from the same vesicle. We found that the fusion-pore diameter stays at <3 nm for a variable period, which can last for several seconds, before it expands. Transmitter is released much faster through this pore than in mast cells, generating a 'foot' signals which precedes the amperometric spike. Occasionally, the narrow pore forms only transiently and does not expand, allowing complete transmitter release without full fusion of the vesicle with the plasma membrane.

549 citations


Journal ArticleDOI
TL;DR: In this paper, the levels of Cu, Zn, Pb, Hg, Cd, and Mn were significantly higher in the sample taken in the Province of Huelva than in the samples from the Province o f Cadiz.

364 citations


Journal Article
TL;DR: The results suggest that melatonin may be involved in the regulation of human immune functions by modulating the activity of Th1 cells and monocytes via nuclear receptor-mediated transcriptional control.
Abstract: This paper shows that melatonin is able to activate human Th1 lymphocytes by increasing the production of IL-2 and IFN-gamma in vitro. Th2 cells appear not to be affected by melatonin, since IL-4, which is mostly produced by Th2 cells, is not modified by the hormone. Melatonin also enhances IL-6 production by PBMCs. The activation by melatonin of IL-6 production is apparently related to the presence of monocytes, rather than to Th2 cells, in the cell preparation, since PBMCs depleted of monocytes (CD14+ cells) were not activated. Activation of PBMCs by melatonin was dependent on the dose and, measured by cytokine production, was observed only when cells were either not activated or only slightly activated by low concentrations of PHA, or when cell activation was achieved by incubating the cells with previously irradiated cells. Using a different approach to identify what type of cells among the PBMC subsets was activated by melatonin, the expression of CD69, a marker of cell activation, was studied. Melatonin increased the percentage of cells expressing the CD69 Ag in CD4+ but not in CD8+ cells. We have also achieved enhanced production of IL-2 and IL-6 using CGP 52608, a specific ligand of the putative nuclear melatonin receptor RZR/ROR, raising the possibility of direct effects of melatonin on gene regulation in both Th1 cells and monocytes. The results suggest that melatonin may be involved in the regulation of human immune functions by modulating the activity of Th1 cells and monocytes via nuclear receptor-mediated transcriptional control.

364 citations


Journal ArticleDOI
TL;DR: In this article, an analytical cone-jet solution for the electrohydrodynamic atomization of liquids was found for an asymptotic model assuming an infinitely long and thin emitted jet.
Abstract: An analytical cone-jet solution for the electrohydrodynamic atomization of liquids has been found for an asymptotic model assuming an infinitely long and thin emitted jet. Universal expressions for the emitted electric current, jet shape, charge distribution, surface charge, and other essential electrohydrodynamic quantities are obtained as functions of the liquid properties and the emitted liquid flow rate. The agreement with published experiments is good.

323 citations


Journal ArticleDOI
TL;DR: Results show that calmodulin appears to be involved in this process because its presence in the incubation medium was able to prevent the effect of melatonin on both NOS activity and cyclic GMP production, and polyacrylamide gel electrophoresis studies suggest that melatonin can interact with Calmodulin modifying the binding of the peptide to the synthetic NOS peptide.
Abstract: Constitutive rat cerebellar nitric oxide synthase (NOS) activity is shown to be inhibited by physiological concentrations of the pineal hormone melatonin. The inhibition was dose-dependent and was coupled to an inhibition of the cyclic GMP production activated by L-arginine. Results also show that calmodulin appears to be involved in this process because its presence in the incubation medium was able to prevent the effect of melatonin on both NOS activity and cyclic GMP production. Moreover, polyacrylamide gel electrophoresis studies suggest that melatonin can interact with calmodulin modifying the binding of the peptide to the synthetic NOS peptide encompassing the calmodulin-binding domain of constitutive NOS from rat cerebellum, the natural mechanism by which calmodulin activates cerebellar NOS. J. Cell. Biochem. 65:430–442. © 1997 Wiley-Liss, Inc.

287 citations


Journal ArticleDOI
TL;DR: The exopolysaccharide produced by a ropy strain of Pediococcus damnosus in a semi-defined medium was found to be an homopolymer composed of D-glucose.

200 citations


Journal ArticleDOI
TL;DR: In this article, the authors analyse the cost accounting system implemented in 1773 by a large, state owned, tobacco factory in Spain (the Royal Tobacco Factory, RTF) which operated as a monopolist.
Abstract: The aim of this paper is to analyse the cost accounting system implemented in 1773 by a large, state owned, tobacco factory in Spain (the Royal Tobacco Factory, RTF) which operated as a monopolist. Drawing on data extracted from original archives, the paper examines the characteristics of the cost system within the broader context of a strict control system. One of the main roles of the cost accounting system was to buttress a set of structural measures instituted in the RTF with the aim of minimising the scope for tobacco theft. Another aim was to impart visibility upon the various activities undertaken in the RTF. The paper also examines the role of the cost accounting practices as a disciplinary regime. A combination of physical measures, reflecting the rates and mixes of resource utilization and monetary measures were developed to facilitate monitoring and surveillance of the activities of the factory employees. These measures were used to establish a powerful regime of calculation which rendered human accountability visible. Such emphasis upon calculation created an environment at the RTF in which management could compare, differentiate, hierarchize, homogenize, and even exclude individuals.

194 citations


Journal ArticleDOI
12 Jan 1997
TL;DR: In this paper, the authors present the theoretic and methodological frame of the studies carried out by the authors on teacher's professional knowledge and epistemological conceptions, taking as a reference the bases of the Model of Investigation at the School and the IRES curricular project.
Abstract: We present in this article the theoretic and methodological frame of the studies carried out by the authors on teacher’s professional knowledge and epistemological conceptions, taking as a reference the bases of the Model of Investigation at the School and the IRES curricular project. In a latter article we will analyse the data there obtained.

193 citations


Journal ArticleDOI
TL;DR: In this paper, the dynamics for a system of hard spheres with dissipative collisions is described at the levels of statistical mechanics, kinetic theory, and simulation, where the Liouville operator and associated binary scattering operators are defined as the generators for time evolution in phase space.
Abstract: The dynamics for a system of hard spheres with dissipative collisions is described at the levels of statistical mechanics, kinetic theory, and simulation. The Liouville operator(s) and associated binary scattering operators are defined as the generators for time evolution in phase space. The BBGKY hierarchy for reduced distribution functions is given, and an approximate kinetic equation is obtained that extends the revised Enskog theory to dissipative dynamics. A Monte Carlo simulation method to solve this equation is described, extending the Bird method to the dense, dissipative hard-sphere system. A practical kinetic model for theoretical analysis of this equation also is proposed. As an illustration of these results, the kinetic theory and the Monte Carlo simulations are applied to the homogeneous cooling state of rapid granular flow.

180 citations


Journal ArticleDOI
TL;DR: Values for femoral neck BMD in the female population become statistically lower after the age of 49 years, while in the male population this effect was seen after the Age of 69 years, and values for lumbar spine BMD were higher in men than women at all ages.
Abstract: The aim of this study was to generate standard curves for bone mineral density (BMD) in a Spanish population using dual-energy X-ray absorptiometry (DXA), at both lumbar spine and femoral neck sites. The total sample size was 2442 subjects of both sexes aged 20-80 years, stratified according to survival rates, demographic distribution by local regions and sex ratio in the Spanish population. Subjects with suspected conditions affecting bone metabolism or receiving any treatment affecting bone mineralization were excluded. The study was carried out in 14 hospitals and bone density measurements were performed, using a QDR/ 1000 Hologic device. In the female population, the highest value for lumbar spine BMD was found within the 30-39 years age group, being significantly lower after the age of 49 years. In the male population, the highest values for lumbar spine BMD are found one decade earlier than in the female population and become significantly lower after the age of 69 years. The highest values for femoral neck BMD in men and women was found in the 20-29 year age group. Values for femoral neck BMD in the female population become statistically lower after the age of 49 years, while in the male population this effect was seen after the age of 69 years. Values for femoral neck BMD were higher in men than women at all ages.

Journal ArticleDOI
TL;DR: It is shown that HPR1 is not required for transcription activation and that the previously reported effects of hpr1Delta on the activation of different promoters is a consequence of the incapacity of hPR1Delta cells to elongate transcription through lacZ, used as reporter.
Abstract: The yeast HPR1 gene plays an important role in genome stability, as indicated by the observation that hpr1 mutants have high frequencies of DNA repeat recombination and chromosome loss. Here we report that HPR1 is required for transcriptional elongation. Transcription driven from constitutive and regulated yeast promoters cannot elongate through the bacterial lacZ coding region in hpr1D cells, but progresses efficiently through other sequences such as yeast PHO5. We show that HPR1 is not required for transcription activation and that the previously reported effects of hpr1D on the activation of different promoters is a consequence of the incapacity of hpr1D cells to elongate transcription through lacZ, used as reporter. Transcriptional defects are also observed in yeast DNA sequences of hpr1D cells in the presence of the transcription elongation inhibitor 6-azauracil. In all cases, the blockage of transcription elongation in hpr1D is associated with both the high frequency of deletions and the increase in plasmid instability that we report here. Therefore, in addition to the identification of a new element involved in transcriptional elongation, our work provides evidence for a new source of genomic instability.

Journal ArticleDOI
TL;DR: In this paper, the authors performed descriptive, sequential and principal components analyses to detect the overall structure of mouse behaviour on the elevated plus-maze test and found that sniffing is the main pattern, pSAP and pDip are highly linked 'anxiety-related' responses, and uSAP is an 'approach-avoid conflict' response usually followed by either sniffing on an open arm or closed arm entry.

Journal ArticleDOI
TL;DR: A CMOS chip for the parallel acquisition and concurrent analog processing of two-dimensional (2-D) binary images, based on the cellular neural/nonlinear network universal machine, which features 2-/spl mu/s operation speed and around 7-b accuracy in the analog processing operations.
Abstract: This paper presents a CMOS chip for the parallel acquisition and concurrent analog processing of two-dimensional (2-D) binary images. Its processing function is determined by a reduced set of 19 analog coefficients whose values are programmable with 7-b accuracy. The internal programming signals are analog, but the external control interface is fully digital. On-chip nonlinear digital-to-analog converters (DAC's) map digitally coded weight values into analog control signals, using feedback to predistort their transfer characteristics in accordance to the response of the analog programming circuitry. This strategy cancels out the nonlinear dependence of the analog circuitry with the programming signal and reduces the influence of interchip technological parameters random fluctuations. The chip includes a small digital RAM memory to store eight sets of processing parameters in the periphery of the cell array and four 2-D binary images spatially distributed over the processing array. It also includes the necessary control circuitry to realize the stored instructions in any order and also to realize programmable logic operations among images. The chip architecture is based on the cellular neural/nonlinear network universal machine (CNN-UM). It has been fabricated in a 0.8-/spl mu/m single-poly double-metal technology and features 2-/spl mu/s operation speed (time required to process an image) and around 7-b accuracy in the analog processing operations.

Journal ArticleDOI
TL;DR: In this article, the effects of traditional and conservation tillage on soil physical properties, soil water replenishment and depletion, and crop development and yield under southern Spanish conditions were investigated.
Abstract: Tillage methods affect soil physical properties and, thus, have a direct influence on the replenishment and depletion of soil water storage and crop performance. This study was conducted to determine the effects of traditional and conservation tillage on soil physical properties, soil water replenishment and depletion, and crop development and yield under southern Spanish conditions. The experiments were carried out from 1992 to 1995 in a sandy clay loam soil (Xerofluvent). The traditional tillage (TT) method consisted mainly of the use of mouldboard ploughing, and the conservation tillage (CT) was characterized by not using mouldboard ploughing, by reduction of the number of tillage operations and leaving the crop residues on the surface as mulch. In both tillage treatments a wheat (Triticum aestivum, L.)-sunflower (Helianthus annuus, L.) crop rotation was established. In each treatment, systematic measurements of bulk density, resistance to penetration, infiltration rate and hydraulic conductivity (using tension disc infiltrometers) in the soil top layer were carried out. Changes in water profiles through the experimental period were also followed using a neutron probe. Crop development and yield were determined. The soil bulk density in the 0 to 20 cm layer was significantly higher in the CT than in the TT treatment, mainly after tillage operations (between 10% and 24% higher in CT than in TT). After 3 years of continuous tillage treatments, the soil bulk density did not increase. The resistance to penetration at any time was higher in the CT than in the TT treatment, but not always significantly different. Infiltration rates were significantly higher in the TT than in the CT treatment (about 35% higher in TT than in CT). After 3 years of the tillage treatments the hydraulic conductivity of the soil surface layer, at a pressure head of 0 mm, was significantly higher in the CT (124 mm h−1) than in the TT (66 mm h−1). This is related to the existence of preferential paths created by an increase of the earthworm population in the CT treatment. Soil water profiles showed higher replenishment of soil water storage in the CT than in the TT treatment, particularly from October 1994 to June 1995 when the lowest precipitation of the experimental period was recorded. Plant height, leaf area index (LAI) and root length density (RLD) of the first sunflower crop were significantly higher in the TT than in the CT treatment. Nevertheless, the seed yield was slightly higher in the CT than in the TT treatment. In the second sunflower crop, plant height, LAI, RLD were significantly higher in the CT than in the TT treatment except early in the season, and yield was significantly (and extremely) higher in the CT (1521 kg ha−1) than in the TT (473 kg ha−1) treatment. During the wheat crop season, plant height and RLD were higher in the TT than in the CT treatment, but grain yield was again slightly higher in the CT than in the TT treatment. The conservation tillage applied seems to be highly effective in enhancing soil water recharge and water conservation, particularly in years with much lower than average precipitation.

Journal ArticleDOI
TL;DR: In this article, a quasi-one-dimensional electrohydrodynamically driven capillary jets are analyzed in the parametrical limit of negligible charge relaxation effects, i.e. when the electric relaxation time of the liquid is small compared to the hydrodynamic times.
Abstract: Electrohydrodynamically (EHD) driven capillary jets are analysed in this work in the parametrical limit of negligible charge relaxation effects, i.e. when the electric relaxation time of the liquid is small compared to the hydrodynamic times. This regime can be found in the electrospraying of liquids when Taylor's charged capillary jets are formed in a steady regime. A quasi-one-dimensional EHD model comprising temporal balance equations of mass, momentum, charge, the capillary balance across the surface, and the inner and outer electric fields equations is presented. The steady forms of the temporal equations take into account surface charge convection as well as Ohmic bulk conduction, inner and outer electric field equations, momentum and pressure balances. Other existing models are also compared. The propagation speed of surface disturbances is obtained using classical techniques. It is shown here that, in contrast with previous models, surface charge convection provokes a difference between the upstream and the downstream wave speed values, the upstream wave speed, to some extent, being delayed. Subcritical, supercritical and convectively unstable regions are then identified. The supercritical nature of the microjets emitted from Taylor's cones is highlighted, and the point where the jet switches from a stable to a convectively unstable regime (i.e. where the propagation speed of perturbations become zero) is identified. The electric current carried by those jets is an eigenvalue of the problem, almost independent of the boundary conditions downstream, in an analogous way to the gas flow in convergent–divergent nozzles exiting into very low pressure. The EHD model is applied to an experiment and the relevant physical quantities of the phenomenon are obtained. The EHD hypotheses of the model are then checked and confirmed within the limits of the one-dimensional assumptions.

Journal ArticleDOI
TL;DR: Melatonin receptor gene expression in the thymus and spleen supports the notion of the immunomodulatory role of melatonin, and the melatonin receptor mRNA was expressed in all the lymphocyte subpopulations studied from the rat thymuses.
Abstract: In the present work we analyze by reverse transcription, polymerase chain reaction, cDNA cloning, and sequence analysis the expression of membrane melatonin receptors in rat thymus and spleen. Results show, for the first time, that the melatonin receptor mRNA is expressed in both the thymus and spleen. Moreover, the melatonin receptor mRNA was expressed in all the lymphocyte subpopulations (CD4+,CD8+, double positive, double negative, and B cells) studied from the rat thymus. The Southern blot analysis with the melatonin receptor probe and sequence data also showed the identity of the DNA fragments in thymus, spleen, and the lymphocyte subpopulations studied. The melatonin receptor fragments amplified from rat brain, thymus, and spleen share identical nucleotide sequences with the rat Mel1a-melatonin receptor subtype. No signal was obtained with primers used to amplify the rat Mel1b-melatonin receptor subtype in both thymus and spleen. Finally, the melatonin receptor mRNA transcript distribution throughout the rat thymus was examined. Using digoxigenin-labeled cRNA probe to the specific melatonin receptor mRNA, examination of the whole thymus revealed a clear hybridization signal in both cortex and medulla. Melatonin receptor gene expression in the thymus and spleen supports the notion of the immunomodulatory role of melatonin.

Journal ArticleDOI
TL;DR: The hypothesis that anxiety is enhanced after test repetition is supported, and test-retest profiles are shown to be far from stable, except for exploratory locomotor activity.

Journal ArticleDOI
TL;DR: Two domains in REST that may mediate interactions with other proteins involved in restricting expression of a large set of genes to the vertebrate nervous system are revealed.
Abstract: The type II voltage-dependent sodium channel is present in neuronal cells, where it mediates the propagation of nerve impulses. Restricted expression of the type II sodium channel gene to neurons is due, at least in part, to binding of the repressor protein REST (also termed NRSF or XBR) to the RE1 (also called NRSE) sequence in the type II sodium channel gene. Previous studies have shown that a domain in REST containing eight GL1-Kruppel zinc finger motifs mediates DNA binding. Deletional and GAL4-fusion gene analyses now reveal repressor domains that lie outside of the DNA-binding domain in both the amino and carboxyl termini of REST. Mutational analysis further identifies a single zinc finger motif in the carboxyl-terminal domain as being essential for repressing type II sodium channel reporter genes. These studies reveal two domains in REST that may mediate interactions with other proteins involved in restricting expression of a large set of genes to the vertebrate nervous system.

Journal ArticleDOI
TL;DR: In this article, a six-step sequential extraction technique was used to determine the chemical association of heavy metals (Pb, Cd, Cu, Fe, Mn, Zn, Cr, Ni) with major sedimentary phases (exchangeable ions, carbonates, manganese oxides, iron oxides and organic matter and residual minerals) in samples from salt marshes on the southern Atlantic coast of Spain (Odiel and Bay of Cadiz Salt Marshes).

Journal ArticleDOI
TL;DR: The possibility of killing tumour cells by electroporation, as a variant of electrotherapy, constitutes, in the authors' opinion, a promising procedure in cancer therapy, avoiding the undesirable side effects normally derived from treatment with cytotoxic drugs.
Abstract: Cell death was induced by electroporation in HL60 cells, a human promyeloid leukaemia strain, in order to determine by both morphological and biochemical criteria whether necrotic or apoptotic processes occurred Cells sampled at several times after electroporation were analyzed for the assessment of the following end-points: (i) chromosomal DNA fragmentation; (ii) cell viability; (iii) mono- and oligonucleosomes in the cytoplasmic fraction; (iv) apoptotic index; and (v) morphology of treated cells The results indicate that about 50% of the cells killed by electroporation die through necrosis, while the remaining 50% of the cells undergo apoptosis Chromosome damage was also studied by cytogenetic analysis at metaphase The possibility of killing tumour cells by electroporation, as a variant of electrotherapy, constitutes, in our opinion, a promising procedure in cancer therapy, avoiding the undesirable side effects normally derived from treatment with cytotoxic drugs

Journal ArticleDOI
TL;DR: In this paper, it was shown that cold NaOH does not only extract iron-bound phosphate but also phytate and humic phosphates from aquatic sediments, which may be an important mechanism for anoxic phosphate release from sediments.
Abstract: NaOH is often used as an extractant for thefractionation of sediment-bound phosphates. Besidesorthophosphate, a certain quantity of phosphate whichis called ‘non-reactive NaOH-extractable phosphate’is also extracted. In recent literature it has beensuggested that this fraction consists of bacterialpolyphosphates and might be responsible for the phosphate release from aquatic sediments under anoxicconditions. In a previous publication we have already shown thatNaOH is not an accurate extractant as both theconcentration of NaOH and the duration of theextraction have an influence on the quantity ofphosphate extracted, due to the hydrolysis of organicphosphates. In this article we show that cold NaOH does not onlyextract iron-bound phosphate but phytate phosphate aswell. Non-reactive phosphate in this extract was notrelated to the presence of polyphosphate, but mainlyto phytate and humic phosphates. As it has been shownthat phytate may disappear from sediments when theybecome anoxic, we suggest that phytate mineralizationmay be an important mechanism for anoxic phosphaterelease from sediments.

Journal ArticleDOI
TL;DR: The findings confirm that prefrontocortical dopamine activation is necessary for coping with an anxiogenic challenge, allowing the animal to display adaptive exploratory responses in a fear-inducing environment.

Journal ArticleDOI
TL;DR: The moderate halophile Halomonas elongata Deustche Sammlung für Mikroorganismen 3043 accumulated ectoine, hydroxyectoine, glutamate, and glutamine in response to osmotic stress, providing the first evidence for the role of N-γ-acetyldiaminobutyric acid as osmoprotectant.

Journal ArticleDOI
TL;DR: A regulatory role for PKA activity in the production of constitutive transport vesicles from the TGN is indicated as a result of inhibition by H89 and a myristoylated form of the inhibitory peptide sequence contained in the thermostable PKA inhibitor.
Abstract: We have examined the role played by protein kinase A (PKA) in vesicle-mediated protein transport from the trans-Golgi network (TGN) to the cell surface. In vivo this transport step was inhibited by inhibitors of PKA catalytic subunits (C-PKA) such as the compound known as H89 and a myristoylated form of the inhibitory peptide sequence contained in the thermostable PKA inhibitor. Inhibition by H89 occurred at an early stage during the transfer of vesicular stomatitis virus G glycoprotein from the TGN to the cell surface. Reversal from this inhibition correlated with a transient increase in the number of free coated vesicles in the Golgi area. Vesicle budding from the TGN was studied in vitro using vesicular stomatitis virus-infected, permeabilized cells. Addition to this assay of C-PKA stimulated vesicle release while it was suppressed by PKA inhibitory peptide, H89, and antibody against C-PKA. Furthermore, vesicle release was decreased when PKA-depleted cytosol was used and restored by addition of C-PKA. These results indicate a regulatory role for PKA activity in the production of constitutive transport vesicles from the TGN.

Journal ArticleDOI
TL;DR: In this paper, a network observability analysis is formulated in a way to incorporate the conventional as well as unconventional measurements, including line currents, to detect not only unobservability but also uniqueness of the observed state.
Abstract: Network observability analysis is formulated in a way to incorporate the conventional as well as unconventional measurements, including line currents. This formulation has two essential advantages over the existing methods of network observability analysis: (1) it detects not only unobservability but also uniqueness of the observed state, and (2) it can directly identify the unobservable or nonuniquely observable branches without having to remove the irrelevant injections in an iterative manner. In addition, unlike the numerical observability analysis methods proposed so far, it can readily identify residual spread components and critical measurements. The proposed formulation is implemented and tested on sample power systems.

Journal ArticleDOI
TL;DR: Melatonin protects against gastric ischemia‐reperfusion injury in rats and is cytogenetically linked to central nervous system injury in mice.
Abstract: Lipid peroxidation and active oxygen metabolites have been suggested to play an important role in the pathogenesis of acute gastric mucosal injury induced by ischemia-reperfusion. The aim of this study was to examine the in vivo protective effects of melatonin on ischemia-reperfusion induced gastric damage in rats. The peroxidation of lipids and changes in the activities of related enzymes such as glutathione peroxidase and myeloperoxidase, as a marker of neutrophil infiltration, were also studied. Our results show that gastric injury was significantly increased after 30 min ischemia induced by clamping the celiac artery and 60 min reperfusion. Intraperitoneal administration of melatonin prevented postischemic mucosal injury. The mean ulcer indices of rats treated with 5, 10, and 20 mg kg(-1) were significantly lower (P<0.01, P<0.001) than that of control rats. These protective effects were likely in part related to a reduction of neutrophil infiltration (myeloperoxidase values). Lipid peroxidation in the stomach was increased by ischemia-reperfusion injury and this increase was inhibited by the administration of melatonin. In addition, treatment with melatonin limited the decreased glutathione peroxidase activity. The results suggest that melatonin confers a marked protection against ischemia-reperfusion gastric injury which could be due to melatonin's free radical scavenging activity and its ability to reduce neutrophil-induced toxicity.

Journal Article
TL;DR: A pertussis toxin-sensitive melatonin signal transduction pathway in human lymphocytes that involves the inhibition of adenylyl cyclase and the stimulation of phospholipase C is strongly suggested.
Abstract: We analyzed the melatonin signal transduction in human blood lymphocytes. High affinity melatonin receptors were identified by specific binding of 2-[125I]melatonin ([125I]MEL) to human lymphocyte membranes. Scatchard analysis of [125I]MEL binding revealed high affinity receptors, with a dissociation constant (Kd) of 0.45 nM and a binding capacity (Bmax) of 7.8 fmol/mg protein. Specific [125I]MEL binding was reduced markedly by GTP and its nonhydrolyzable analogues guanosine 5'-beta, gamma-imidotriphosphate (Gpp(NH)p) and guanosine 5'-O-(3-triphosphate) (GTP-gamma-S). Gpp(NH)p inhibited in a dose-dependent manner the [125I]MEL specifically bound to human lymphocyte membranes with a half-maximal inhibition (IC50) of 3.5 +/- 0.6 microM Gpp(NH)p. Treatment of human lymphocyte membranes with Gpp(NH)p increased the Kd value (Kd = 1.20 nM). Melatonin inhibited significantly and in a dose-dependent manner forskolin-stimulated cAMP production in intact human lymphocytes. Melatonin was able to stimulate diacylglycerol production in a dose-dependent manner in human lymphocyte membranes. Pertussis toxin treatment inhibited the specific [125I]MEL binding and blocked the ability of melatonin to both inhibit forskolin-stimulated cAMP production and stimulate diacylglycerol production. Pertussis toxin ADP-ribosylation and Western blot experiments demonstrated the protein expression of alpha i1/2, alpha i3/0, and beta gamma complexes of G proteins in human lymphocyte membranes. The results strongly suggest a pertussis toxin-sensitive melatonin signal transduction pathway in human lymphocytes that involves the inhibition of adenylyl cyclase and the stimulation of phospholipase C.

Journal ArticleDOI
TL;DR: The bisethene complex [Tp*IrH(π3-C3H4Me)] (6*) corresponds formally to the dimerisation of ethene by an unprecedented pathway that involves sequential C-H bond activation of a coordinated olefin molecule and C-C bond formation by coupling of the resulting vinyl and ethenes moieties as discussed by the authors.
Abstract: The bis(ethene) complex [Tp*Ir-(C2H4)2] (1*) (Tp* = tris(3,5-dimethyl-1-pyrazol-1-yl)hydroborato) undergoes thermal rearrangement to the hydrido–allyl complex [Tp*IrH(π3-C3H4Me)] (6*), through the intermediacy of the hydrido–vinyl complex [Tp*IrH(C2H3)(C2H4)] (2*). The overall conversion of 1* into 6* corresponds formally to the dimerisation of ethene by an unprecedented pathway that involves sequential C–H bond activation of a coordinated olefin molecule and C–C bond formation by coupling of the resulting vinyl and ethene moieties. Similar transformations have been observed for monosubstituted olefins like propene and 1-butene, while the internal alkene cis−2-butene experiences allylic activation of an sp3 C–H bond, which provides an alternative route to 6*. The extension of these investigations to the analogous complexes of the unsubstituted tris(pyrazolyl)hydroborato ligand Tp is also reported. Mechanistic studies on the formation of the C–C bond by coupling of the vinyl and the olefin ligands suggest the participation of a vinylidene complex (formed by α-H abstraction from the vinyl group), which then rearranges to an allene species. Evidence for the involvement of these and other key reaction intermediates is provided.

Journal ArticleDOI
TL;DR: The effects of organic effluents both inside and outside the Saladillo Harbour (Algeciras, southern Spain) are investigated in this article, where a clear gradient of decreasing pollution levels was observed from the interior to the exterior of the harbour, reflected both in physicochemical water and sediment parameters and in their respective microbiological parameters.