Showing papers by "University of Seville published in 1993"

Release of secretory products during transient vesicle fusion

Abstract: Patch-Camp experiments have shown that fusion of secretory granules with the plasma membrane does not always occur as an all-or-none event, but can develop slowly in a fluctuating manner or can be transient. These observations suggested that release could be detected during such incomplete fusion events. To test this hypothesis we have combined patch-clamp measurements of the activity of single exocytotic fusion pores in beige mouse mast cells with the electrochemical detection of serotonin released during the exocytotic events. We report here that on fusion pore opening there is a small release of serotonin which is directly proportional to the pore conductance. We also show that a significant release occurs during transient fusion events. These results demonstrate, to our knowledge for the first time, release of a neurotransmitter from a secretory vesicle that did not undergo complete fusion.

Litter mass loss rates in pine forests of Europe and Eastern United States: some relationships with climate and litter quality

Abstract: The purpose of this study was to relate regional variation in litter mass-loss rates (first year) in pine forests to climate across a large, continental-scale area The variation in mass-loss rate was analyzed using 39 experimental sites spanning climatic regions from the subarctic to subtropical and Mediterranean: the latitudinal gradient ranged from 31 °N to 70 °N and may represent the the largest geographical area that has ever been sampled and observed for the purpose of studying biogeochemical processes Because of unified site design and uniform laboratory procedures, data from all sites were directly comparable and permitted a determination of the relative influence of climateversus substrate quality viewed from the perspective of broad regional scales Simple correlation applied to the entire data set indicated that annual actual evapotranspiration (AET) should be the leading climatic constraint on mass-loss rates (Radj 2 = 0496) The combination of AET, average July temp and average annual temp could explain about 70% of the sites' variability on litter mass-loss In an analysis of 23 Scots pine sites north of the Alps and Carpatians AET alone could account for about 65% of the variation and the addition of a substrate-quality variable was sufficiently significant to be used in a model The influence of litter quality was introduced into a model, using data from 11 sites at which litter of different quality had been incubated These sites are found in Germany, the Netherlands, Sweden and Finland At any one site most ( ≫ 90%) of the variation in mass-loss rates could be explained by one of the litter-quality variables giving concentration of nitrogen, phosphorus or water solubles However, even when these models included nitrogen or phosphorus even small changes in potential evapotranspiration resulted in large changes in early-phase decay rates Further regional subdivision of the data set, resulted in a range of strength in the relationship between loss rate and climatic variables, from very weak in Central Europe to strong for the Scandinavian and Atlantic coast sites (Radj 2 = 0912; AETversus litter mass loss) Much of the variation in observed loss rates could be related to continentalversus marine/Atlantic influences Inland locations had mass-loss rates lower than should be expected on the basis of for example AET alone Attempts to include seasonality variables were not successful It is clear that either unknown errors and biases, or, unknown variables are causing these regional differences in response to climatic variables Nevertheless these results show the powerful influence of climate as a control of the broad-scale geography of mass-loss rates and substrate quality at the stand level Some of these relationships between mass-loss rate and climatic variables are among the highest ever reported, probably because of the care taken to select uniform sites and experimental methods This suggest that superior, base line maps of predicted mass-loss rates could be produced using climatic data These models should be useful to predict the changing equilibrium litter dynamics resulting from climatic change

Mucoadhesive Drug Delivery Systems

Abstract: Pharmaceutical aspects of mucoadhesion have been the subject of great interest during recent years because mucoadhesion could be a solution for bioavailability problems that result from a too short length of stay of the pharmaceutical dosage form at the absorption site within the gastro-intestinal tract.This paper describes some aspects of bioadhesion such as mucus structure, stages of adhesion and the theories proposed that attempt to explain the adhesion mechanism. The factors that affect the bioadhesive power of a polymer, the methods that permit the evaluation of a bioadhesive system and the methods for surface characterization of biomaterials are discussed. Finally, the various polymers used and the bioadhesive systems designed for several therapeutic purposes are presented.

Current-mode techniques for the implementation of continuous- and discrete-time cellular neural networks

Abstract: A unified, comprehensive approach to the design of continuous-time (CT) and discrete-time (DT) cellular neural networks (CNNs) using CMOS current-mode analog techniques is presented. The net input signals are currents instead of voltages, which avoids the need for current-to-voltage dedicated interfaces in image processing tasks with photosensor devices. Outputs may be either currents or voltages. Cell design relies on exploiting current mirror properties for the efficient implementation of both linear and nonlinear analog operators. Basic design issues, the influence of nonidealities and advanced circuit design issues, and design for manufacturability considerations associated with statistical analysis are discussed. Experimental results are given for three prototypes designed for 1.6- mu m n-well CMOS technologies. One is discrete-time and can be reconfigured via local logic for noise removal, feature extraction (borders and edges), shadow detection, hole filling, and connected component detection (CCD) on a rectangular grid with unity neighborhood radius. The other two prototypes are continuous-time and fixed template: one for CCD and other for noise removal. >

Nonlinear switched-current CMOS IC for random signal generation

Abstract: A nonlinear switched-current circuit is presented that implements a chaotic algorithm for the generation of broadband, white analogue noise. The circuit has been fabricated in a double-metal, single-poly 1.6μm CMOS technology and uses a novel, highly accurate CMOS circuit strategy to realise piecewise-linear characteristics in the current-mode domain. Measurements from the silicon prototype show a flat spectrum from DC to ∼30% of the clock frequency, for a clock frequency of 500kHz.

Human papillomavirus and cervical intraepithelial neoplasia grade III/carcinoma in situ: a case-control study in Spain and Colombia.

Abstract: A case-control study of 525 cases of cervical intraepithelial neoplasia grade III (CIN III) and 512 controls was conducted in Spain and Colombia between 1985 and 1988 to assess the role of human papillomavirus (HPV) in the etiology of CIN III. HPV DNA in cytological scrapes from the cervix was assessed by Virapap and by polymerase chain reaction (PCR) based on the L1 consensus primers. A subsample of 268 specimens was also tested for HPV DNA using Southern hybridization. In Spain, the PCR-based prevalences of HPV DNA were 70.7% among cases and 4.7% among controls. Odds ratio (OR) and 95% confidence interval (numbers in parentheses) for HPV DNA were 56.9 (24.8-130.6). In Columbia HPV DNA was detected by PCR in 63.2% of the cases and in 10.5% of the controls. The OR was 15.5 (8.2-29.4). The estimated fractions of CIN III attributable to HPV were 72.4% in Spain and 60.3% in Colombia. HPV 16 was the predominant viral type and showed the strongest association with CIN III; in Spain the OR was 295.5 (44.8-1946.4) and in Colombia the OR was 27.1 (10.6-69.5). HPV DNA of unknown type was frequent in HPV-positive cases (18.3% in Spain and 38.0% in Colombia) and controls (66.7% in Spain and 47.4% in Colombia). The comparison of results from Virapap and PCR indicated that PCR is the method of choice for epidemiological studies. These data strongly support the hypothesis of the viral origin of CIN III, the common etiology of CIN III and invasive cervical cancer, and the causal nature of the association between HPV and CIN III.

CMOS design of chaotic oscillators using state variables: a monolithic Chua's circuit

Abstract: This paper presents design considerations for monolithic implementation of piecewise-linear (PWL) dynamic systems in CMOS technology. Starting from a review of available CMOS circuit primitives and their respective merits and drawbacks, the paper proposes a synthesis approach for PWL dynamic systems, based on state-variable methods, and identifies the associated analog operators. The GmC approach, combining quasi-linear VCCS's, PWL VCCS's, and capacitors is then explored regarding the implementation of these operators. CMOS basic building blocks for the realization of the quasi-linear VCCS's and PWL VCCS's are presented and applied to design a Chua's circuit IC. The influence of GmC parasitics on the performance of dynamic PWL systems is illustrated through this example. Measured chaotic attractors from a Chua's circuit prototype are given. The prototype has been fabricated in a 2.4- mu m double-poly n-well CMOS technology, and occupies 0.35 mm/sup 2/, with a power consumption of 1.6 mW for a +or-2.5-V symmetric supply. Measurements show bifurcation toward a double-scroll Chua's attractor by changing a bias current. >

Submerged macrophyte seed bank in a Mediterranean temporary marsh: abundance and relationship with established vegetation

Abstract: The abundance and composition of the submerged macrophyte seed bank in the Donana marsh (southwestern Spain) was evaluated to assess its relationship with the overlying vegetation. The results obtained demonstrate the existence of a dense seed-bank, both in terms of the number of seeds and their biomass, which represented about 10% (5% for angiosperms and >20% for Charophyta) of the total plant biomass, which ensures the maintenance of the annual submerged macrophyte populations of the seasonally inundated Donnana marsh. Seed bank and established vegetation were coupled, as reflected in the existence of significant correlations between their structure and abundance. This coupling was lacking for Charophyta, whose oospores are widespread and abundant across the marsh, even at locations where they are absent, or rare, in the established vegetation. These differences between the seed bank of annual angiosperms and Charophyta appear to reflect, in part, structural differences between angiosperm seeds and Charophyta oospores, with important ecological consequences. An important aspect of these differences is the allocation of Charophyta reproductive effort to many small propagules lacking embryo storage, compared to those of angiosperms, which ensures their efficient dispersal and numerical abundance in the seed bank.

Carbon source control on β-glucanases, chitobiase and chitinase from Trichoderma harzianum

Abstract: The cell-wall degrading enzymes β-glucanase and chitinase have been suggested to be essential for the mycoparasitic action of Trichoderma species against plant fungal pathogens. For this reason, the production in different carbon sources of extracellular β-1,3-glucanase, β-1,6-glucanase, chitobiase and chitinase was studied in a mycoparasitic strain of Trichoderma harzianum. Maximal β-glucanase specific activities were detected in media supplemented with either pustulan (β-1,6-glucan), nigeran (α-1,3-glucan alternating with α-1,4-glucan), chitin or Saccharomyces cerevisiae or Botrytis cinerea purified cell walls, whereas the highest chitinase specific activity was obtained in medium supplemented with chitin. Furthermore, β-glucanase, chitobiase and chitinase activities showed an increase parallel to increasing concentrations of either pustulan or chitin added to the cultures, although the extent of this increase varied with the different enzymes. The culture filtrates of T. harzianum grown in these carbon sources also showed lytic activity on purified cell walls of S. cerevisiae and B. cinerea. The enzyme synthesis seemed to be repressed by glucose, 8-hydroxyquinoline, which inhibits transcription, or cycloheximide, an inhibitor of protein synthesis.

Comparative Study of “Micrococcus sp.” Strains CCM 168 and CCM 1405 and Members of the Genus Salinicoccus

Abstract: Two culture collection strains, CCM 168 and CCM 1405, previously assigned to the genus Micrococcus were shown by molecular chemical characterization to belong to the genus Salinicoccus. A more detailed comparison of the physiological and biochemical properties of these strains and comparison with the type strain of Salinicoccus roseus indicated high degrees of relatedness among the three strains. DNA-DNA hybridization studies confirmed the high degrees of relatedness. All of the data demonstrate quite clearly that strains CCM 168 and CCM 1405 are members of the species S. roseus.

Reproductive biology of Cistus ladanifer (Cistaceae)

Abstract: The phenology, major floral characteristics, fruiting levels, and breeding system ofCistus ladanifer L. (Cistaceae), a common western Mediterranean shrub species, were studied in a southern Spanish population. The white, large (64 mm in diameter) flowers of this shrub appear during spring (March–May) and produce abundant pollen and nectar. In the year of study, flowers lasted up to three days, during which they were visited by a diverse array of insects including beetles, flies, and bees. Hand-pollinations revealed that flowers do not set any seed unless cross pollen is applied to the stigma. Microscopical observations indicate that self pollen tubes grow down the stigma but invariably fail to induce fruit maturation. At the plant level, all estimates of fecundity investigated (number of seeds per capsule, proportion of ovules developing into seed, and proportion of flowers setting fruit) were highly dependent on nearest neighbour distance, with isolated plants setting as little as 0% fruit. In contrast, plants within a clump often transformed into fruit as much as 90% of the flowers. At the population level, seed output was estimated to range between 3,000 and 270,000 seeds per plant during 1991.

Brainstem connections of the rat ventral respiratory subgroups: afferent projections

Abstract: Propriobulbar neurons having axonal projections to the Ventral Respiratory Group (VRG) were retrogradely labeled after discrete injections of Fast blue into one of the three physiologically identified subdivisions (Botzinger Complex, rostral inspiratory and caudal expiratory regions). Neurons that project to these regions were found throughout the rostrocaudal extent of the medulla and the pons in a variety of areas known to have cardio-respiratory function. Labeled somata were located within the nuclei of the solitary tract (commissural, intermediate and ventrolateral), other subdivisions of VRG, parabrachial nuclei (medial, dorsolateral and central lateral), Kolliker-Fuse nucleus, retrotrapezoid nucleus, lateral paragigantocellular nucleus and lateral tegmental field of the pons. Within the nuclei of the solitary tract and the Kolliker-Fuse nucleus, there was a topographical organization with respect to the three subdivisions of the VRG.

Latent inhibition and recall/recognition of irrelevant stimuli as a function of pre‐exposure duration in high and low psychotic‐prone normal subjects

Abstract: Learning to ignore non-relevant stimuli (coloured geometric shapes) was evaluated in high and low psychotic-prone normal subjects in two experiments. In the first, subjects were tested in a latent inhibition paradigm in a 2 times 2 × 3 factorial design (high vs. low psychotic proneness, as measured by MMPI subscales; pre-exposure of the stimuli such that they were non-relevant before the test but relevant in the test vs. absence of such pre-exposure; three levels of pre-exposure duration: 3-, 6-and 15-min). Low psychotic-prone subjects showed the latent inhibition effect (poorer learning as a result of pre-exposure to the non-relevant stimuli as compared to no pre-exposure) at 6- and 15-min durations, but not at 3-min. High psychotic-prone subjects failed to show latent inhibition at 3- and 6-min durations, but did show the effect at 15-min. The second experiment employed a 2 times 3 design (high vs. low psychotic proneness; three levels of pre-exposure duration of the same stimuli used in Expt 1). High psychotic-prone normal subjects recalled and recognized more previously non-relevant stimuli than low psychotic-prone subjects, particularly after 6-min pre-exposure to those stimuli. The data of the two experiments suggest that the attenuation of latent inhibition in high psychotic-prone subjects as compared to low psychotic-prone subjects is a result of the increased attention to non-relevant information.

Quercetin and naringenin; effects on ulcer formation and gastric secretion in rats

Abstract: The antiulcerogenic effect of two flavonoids, quercetin and naringenin, in acute gastric ulcer (cold-restraint and pylorus-ligated) has been investigated. In both models quercetin and naringenin presented a significant decrease in ulcer index with respect to the control group. Nevertheless, in the Shay-ligated method no decrease in either volume, acidity or pepsin were observed, however, a significant difference was found in histamine secretion values.

The horizontal vestibulo-ocular reflex in the hemilabyrinthectomized guinea-pig

Abstract: The horizontal vestibulo-ocular reflex (HVOR) in the alert guinea-pig elicited by sinusoidal rotations and by velocity steps was studied with scierai search coil measurement between 3 and 7 days (short term) and between 35 and 160 days (long term) after hemilabyrinthectomy. Animals of the short-term group were always tested after spontaneous nystagmus in darkness had disappeared. The HVOR gain in response to sinusoidal rotations (peak angular velocity: 40 deg/s) in the short-term group was bilaterally depressed compared to normal animals. The HVOR phase showed a shift towards larger phase leads over the whole frequency range tested (from 0.05 to 3 Hz). In addition, both the mean number of fast phases per half-cycle of sinusoidal rotation and the mean amplitude were reduced. HVOR responses to velocity steps at a constant acceleration of 300 deg/s2 up to final velocity (0 to 100 deg/s) and of 1000 deg/s2 up to final velocity (0 to 300 deg/s) were depressed bilaterally and asymmetrically such that the gain for rotation towards the intact side greatly exceeded that obtained for rotation towards the lesioned side. Finally, the latency of the vestibular responses was increased and the time constant reduced for both sides of rotation. The HVOR gain values for sinusoidal rotations in the long-term group were lower than normal but higher than in the short-term group: they were asymmetric as a result of a greater compensation for rotation towards the intact side. Neither the phase lead nor the HVOR latency and time constant recovered values close to normal. Finally, the mean number of fast phases per half-cycle remained depressed although the mean amplitude recovered. These results demonstrate that in the guinea-pig, the dynamic deficits show a certain degree of recovery after unilateral labyrinthectomy. However, compared to the compensation of the static deficits previously quantified, the rate of recovery is much lower. This suggests that different processes may be involved in the compensation of the static and dynamic deficits.

Sensitivity-based reactive power control for voltage profile improvement

Abstract: The authors present a procedure for dispatching reactive power when voltage deviations are not acceptable. The proposed method, intended for real-time use, determines which control variables are actually effective for solving voltage violations. Efficiency is measured according to sensitivities, current voltage profile and reserve margin of control variables. The selected control variables are rescheduled in proportion to their efficiency coefficients. State-of-the-art sparsity techniques are used to speed up computation of sensitivities. An example is included to show the effectiveness of the method. >

Ionic conductivity of ZrO2-12 mol % Y2O3 single crystals.

Abstract: Fast ionic conductors are important to study because of their use in the construction of technologically useful devices such as electrochemical cells, oxygen monitors, and the high-temperature fuel cell. Oxygen-ion conductors form a major subgroup of these materials, and, in particular, stabilized zirconia is one of the more important solid electrolytes. However, the ionic conductivity of this material is still only rather poorly understood. The aim of the present work is to describe, by means of a method of local fits (LF's) to Arrhenius's law, the experimental values of the ionic conductivity of ${\mathrm{ZrO}}_{2}$--12 mol % ${\mathrm{Y}}_{2}$${\mathrm{O}}_{3}$ single crystals in the temperature range from 200 \ifmmode^\circ\else\textdegree\fi{}C to 1600 \ifmmode^\circ\else\textdegree\fi{}C. This method yields two sets of data: the preexponential factor, ${\mathit{A}}_{\mathrm{LF}\mathit{i}}$, and the activation enthalpy, \ensuremath{\Delta}${\mathit{H}}_{\mathrm{LF}\mathit{i}}$. The ln${\mathit{A}}_{\mathrm{LF}\mathit{i}}$ versus \ensuremath{\Delta}S(T)/k plot [where \ensuremath{\Delta}S(T) is the entropy change in the process] is a very good test of the accuracy of the LF method. The \ensuremath{\Delta}${\mathit{H}}_{\mathrm{LF}\mathit{i}}$ values are fitted by a least-squares procedure to an empirical temperature-dependence function with four adjustable parameters. In order to interpret these results and to understand the physical meaning of the fitted parameters, a microscopic model is proposed that allows us to deduce a theoretical function of temperature for the activation enthalpy similar to the empirical function.Then, from this function, we determine the association (0.57 eV) and migration (0.73 eV) enthalpies for oxygen vacancies, and analyze the temperature variation of the free energy (\ensuremath{\Delta}G) and entropy (\ensuremath{\Delta}S), as well as the degree of dissociation of the vacancies in the conduction process for this material. A noteworthy result is that, for the range of temperature studied here, the extrinsic dissociated regime (where it is assumed that all oxygen vacancies are free) is never reached. Finally, taking into account the contribution of the jumps up to the second-next-nearest anionic neighbors, we obtain the value of 1.31\ifmmode\times\else\texttimes\fi{}${10}^{13}$ Hz for the attempt frequency of the oxygen vacancies.

Low selenium diet affects monoamine turnover differentially in substantia nigra and striatum.

Abstract: Turnover of dopamine, noradrenaline. serotonin, and their metabolites has been measured in striatum and substantia nigra of adult female rats that were fed control or selenium-deficient diets for 15 days. In addition, the glutathione peroxidase activity has been studied. The most striking result was the increase of dopamine turnover (63%) and 3- methoxytyramine turnover (55%) in substantia nigra between control and experimental animals. On the other hand, no changes were found in the turnover rate of dopamine and its metabolites in the striatum. Likewise, no changes were found in noradrenaline turnover in substantia nigra. In the striatum, there was a significant increase of serotonin turnover versus no change for 5-hydroxy-3-indoleacetic acid. However, in the substantia nigra, serotonin turnover did not show significant changes, whereas 5-hydroxy-3-indoleacetic acid turnover decreased. At the same time, glutathione peroxidase activity significantly decreased in both structures after selenium-deficient diets. These results suggest that a selenium-deficient diet for a short period of time decreases brain protection. principally in the substantia nigra, against oxidative damage.

Fluorescent detection‐polymerase chain reaction (FD‐PCR) assay on microwell plates as a screening test for salmonellas in foods

Abstract: This study evaluates a polymerase chain reaction assay coupled with a fluorescent detection in microwell plates for salmonellas in food samples. Chelex 100-extracted cultures and bulk and processed food samples were used as templates for a PCR assay in microwell plates, with a primer pair that amplifies a 206 bp segment of IS200. The PCR products were then denatured by heat and transferred to CovaLink NH plates (Nunc) to which capture oligonucleotides were covalently bound. Hybridization was performed for 1 h at 55 degrees C, the microwells were washed and an alkaline phosphatase-labelled probe, complementary of an internal sequence of the PCR product, was added. After stringent washes, 100 microliters of 1 mmol 1(-1) AttoPhos (JBL Scientific) was then added to the wells and the fluorescence measurement system (Millipore). The level of detection of the assay was as low as 1-10 cfu. A total of 172 food samples were tested, both by culture and FD-PCR. Of these 53 were culture positive and 119 culture negative. The sensitivity of the FD-PCR assay was 100% and the specificity was 90.1%. Positive and negative predictive values were 82.8 and 100%, respectively. Based on the results obtained in this study it appears that the FD-PCR assay described here can be useful to screen a large number of food samples for contamination by salmonellas.

Characterization of melatonin binding sites in human peripheral blood neutrophils.

Abstract: In this paper we show the presence of 2-[125I]melatonin binding sites in human neutrophils (hN). The specific binding of melatonin to hN cells and hN membranes was dependent on time and temperature, stable, saturable, and reversible. In competition studies, the specific binding of radioactive melatonin to hN cells or hN membranes was inhibited by increasing concentrations of native melatonin. Scatchard analysis showed the existence of a single class of binding sites with a Kd of 2.1 and 7.1 microM for hN cells and hN membranes, respectively. The binding capacity was of 84 and 132 pM for hN cells and hN membranes, respectively. The affinity of the binding sites for melatonin suggests that they may be relevant in studies on the pharmacological properties of melatonin in regulating human neutrophil activity.