University of Córdoba (Spain)

About: University of Córdoba (Spain) is a education organization based out in Cordova, Spain. It is known for research contribution in the topics: Population & Catalysis. The organization has 12006 authors who have published 22998 publications receiving 537842 citations. The organization is also known as: University of Córdoba (Spain) & Universidad de Córdoba.

Leptin inhibits testosterone secretion from adult rat testis in vitro

Abstract: Leptin, the product of the ob gene, has emerged recently as a pivotal signal in the regulation of fertility. Although the actions of leptin in the control of reproductive function are thought to be exerted mainly at the hypothalamic level, the potential direct effects of leptin at the pituitary and gonadal level have been poorly characterised. In the present study, we first assessed the ability of leptin to regulate testicular testosterone secretion in vitro. Secondly, we aimed to evaluate whether leptin can modulate basal gonadotrophin and prolactin (PRL) release by incubated hemi-pituitaries from fasted male rats. To attain the first goal, testicular slices from prepubertal and adult rats were incubated with increasing concentrations (10(-9)-10(-7) M) of recombinant leptin. Assuming that in vitro testicular responsiveness to leptin may be dependent on the background leptin levels, testicular tissue from both food-deprived and normally-fed animals was used. Furthermore, leptin modulation of stimulated testosterone secretion was evaluated by incubation of testicular samples with different doses of leptin in the presence of 10 IU human chorionic gonadotrophin (hCG). In addition, analysis of leptin actions on pituitary function was carried out using hemi-pituitaries from fasted adult male rats incubated in the presence of increasing concentrations (10(-9)-10(-7) M) of recombinant leptin. Serum testosterone levels, and basal and hCG-stimulated testosterone secretion by incubated testicular tissue were significantly decreased by fasting in prepubertal and adult male rats. However, a significant reduction in circulating LH levels was only evident in adult fasted rats. Doses of 10(-9)-10(-7) M leptin had no effect on basal or hCG-stimulated testosterone secretion by testes from prepubertal rats, regardless of the nutritional state of the donor animal. In contrast, leptin significantly decreased basal and hCG-induced testosterone secretion by testes from fasted and fed adult rats. In addition, 10(-9) M leptin inhibited LH and FSH secretion by incubated hemi-pituitaries from fasted adult males, whereas, at all doses tested, it was ineffective in modulating PRL release. Our results show that leptin, depending on the state of sexual maturation, is able to inhibit testosterone secretion acting at the testicular level. Furthermore, the present data suggest that the actions of leptin on the reproductive system are complex and are probably carried out at different levels of the hypothalamic-pituitary-gonadal axis.

Dynamical dark energy in light of the latest observations

Abstract: A flat Friedman-Roberson-Walker universe dominated by a cosmological constant ($\Lambda$) and cold dark matter (CDM) has been the working model preferred by cosmologists since the discovery of cosmic acceleration. However, tensions of various degrees of significance are known to be present among existing datasets within the $\Lambda$CDM framework. In particular, the Lyman-$\alpha$ forest measurement of the Baryon Acoustic Oscillations (BAO) by the Baryon Oscillation Spectroscopic Survey (BOSS) prefers a smaller value of the matter density fraction $\Omega_{\rm M}$ compared to the value preferred by cosmic microwave background (CMB). Also, the recently measured value of the Hubble constant, $H_0=73.24\pm1.74 \ {\rm km}\ {\rm s}^{-1} \ {\rm Mpc}^{-1}$, is $3.4\sigma$ higher than $66.93\pm0.62 \ {\rm km}\ {\rm s}^{-1} \ {\rm Mpc}^{-1}$ inferred from the Planck CMB data. In this work, we investigate if these tensions can be interpreted as evidence for a non-constant dynamical dark energy (DE). Using the Kullback-Leibler (KL) divergence to quantify the tension between datasets, we find that the tensions are relieved by an evolving DE, with the dynamical DE model preferred at a $3.5\sigma$ significance level based on the improvement in the fit alone. While, at present, the Bayesian evidence for the dynamical DE is insufficient to favour it over $\Lambda$CDM, we show that, if the current best fit DE happened to be the true model, it would be decisively detected by the upcoming DESI survey.

Analytical Supercritical Fluid Extraction

Abstract: 1 Preliminary Operations of the Analytical Process.- 1.1 Analytical Chemistry Today.- 1.2 The Analytical Process.- 1.3 Preliminary Operations of the Analytical Process.- 1.3.1 Basic Features.- 1.3.2 Most Common Steps.- 1.3.3 Recent Developments.- 1.4 Analytical Separation Techniques.- 1.4.1 Objectives.- 1.4.2 Classifications.- 1.4.3 Continuous Separation Techniques.- 1.5 Extraction Systems in Analytical Chemistry.- 1.6 Analytical Leaching Methodologies.- 1.7 Ideal Features of an Analytical Leaching System.- 1.8 Supercritical Fluids and Analytical Chemistry.- References.- 2 Physico - Chemical Properties of Supercritical Fluids.- 2.1 Definition of Supercritical Fluid.- 2.2 Physical Properties of Supercritical Fluids.- 2.2.1 Properties at or near the Critical Point.- 2.2.2 Properties of the Supercritical Region.- 2.2.2.1 Density.- 2.2.22 Diffusivity.- 2.2.2.3 Viscosity.- 2.2.2.4 Dielectric Constant.- 2.3 Binary Systems.- 2.4 Polarity.- 2.4.1 The ?* Polarizability/Polarity Scale.- 2.5 Reactions in or with Supercritical Fluids.- 2.5.1 Reactions in Supercritical Fluids.- 2.5.1.1 Influence of Pressure on the Reaction Rate.- 2.5.1.2 Catalytic Effects.- 2.5.1.3 Supercritical Water as an Exceptional Reaction Medium.- 2.5.1.4 Enzymatic Reactions in Supercritical Fluids.- 2.5.2 Reactions with Supercritical Fluids.- 2.6 Other Properties of Supercritical Fluids.- 2.7 General Applications of Supercritical Fluids.- 2.7.1 Industrial Processes.- 2.7.1.1 Supercritical Fluids in the Food Industry.- 2.7.1.2 Polymer Processing with Supercritical Fluids.- 2.7.2 Processing of Heavy Hydrocarbons.- 2.7.3 Analytical Applications of Supercritical Fluids.- 2.7.4 Waste Detoxification with Supercritical Fluids.- 2.7.5 Other Applications of Supercritical Fluids.- References.- 3 Theoretical and Practical Aspects of Supercritical Fluid Extraction.- 3.1 Introduction.- 3.2 Foundation of Leaching.- 3.3 Purity of Supercritical Fluids.- 3.4 Solubility in Supercritical Fluids.- 3.4.1 Solubility Measurements in Supercritical Fluids.- 3.4.2 Solubility and Chemical Structure.- 3.4.2.1 Hydrocarbons.- 3.4.2.2 Hydroxyl Compounds.- 3.4.2.3 Carboxylic Acids.- 3.4.2.4 Ethers.- 3.4.2.5 Esters.- 3.4.2.6 Aldehydes.- 3.4.2.7 Nitrogen-Containing Compounds.- 3.4.3 The Solubility Parameter.- 3.4.4 Theoretical Models.- 3.4.5 Influence of Cosolvents on Solubility: the Entrainer Effect.- 3.4.5.1 Clustering.- 3.4.5.2 Effect of the Cosolvent on Selectivity.- 3.4.6 Entrainer Effect of a Second Solute.- 3.4.7 Solubility near a UCEP.- 3.5 Transport Phenomena.- 3.5.1 Desorption of Adsorbed Species.- 3.5.2 Diffusion in the Solid.- 3.5.2.1 The Spherical Model.- 3.5.2.2 The Infinite Slab Model.- 3.6 Factors Influencing Supercritical Leaching.- 3.6.1 Properties of the Supercritical Fluid.- 3.6.2 Properties of the Solid.- 3.6.3 Properties of the Solute.- 3.6.4 Presence of a Modifier.- 3.6.5 Additives.- 3.6.6 Derivatization.- 3.6.7 Temperature.- 3.6.8 Dynamic Factors.- References.- 4 The Analytical-Scale Supercritical Fluid Extractor.- 4.1 Introduction.- 4.2 The Supercritical Fluid Extractor: A Broad View.- 4.3 Basic Elements of a Supercritical Fluid Extractor.- 4.3.1 The Fluid Reservoir.- 4.3.1.1 Description.- 4.3.1.2 Connection to the Extractor.- 4.3.1.3 Functioning, Cautions.- 4.3.1.4 Measurement of the Cylinder Contents.- 4.3.2 The propulsion system.- 4.3.2.1 Single Systems.- 4.3.2.2 The Need for a Dual Propulsion System: Use of Modifiers.- 4.3.3 The Extraction Chamber.- 4.3.3.1 General Features.- 4.3.3.2 Cell Size.- 4.3.3.3 Sample Size to Cell Volume Ratio.- 4.3.3.4 Cell Geometry.- 4.3.3.5 Special Cells.- 4.3.3.6 Multi-Extraction Systems.- 4.3.3.7 Performance of Extraction Chambers.- 4.3.4 The Depressurization System.- 4.3.4.1 Types of Restrictors.- 4.3.4.2 Problems Arising from Depressurization.- 4.3.5 Collection Systems.- 4.3.5.1 Types.- 4.3.5.2 Special Collection Systems.- 4.3.6 Thermostating.- 4.3.7 Ancillary Components.- 4.4 Extraction Modes.- 4.5 Off-Line Coupled SF Extraction/Detection.- 4.6 On-Line Coupled SF Extraction/Detection.- 4.6.1 Types of Interfaces Used.- 4.6.2 Coupled SFE/Gas Chromatography.- 4.6.3 Coupled SFE/SFC.- 4.6.4 Coupled SFE/HPLC.- 4.6.5 Comparison of SFE Hyphenated Techniques with GC, SFC and HPLC.- 4.6.6 Other Hyphenated Techniques.- 4.7 Comparison of the Off-Line and On-Line Modes.- 4.8 Commercially Available Supercritical Fluid Extractors.- References.- 5 Analytical Applications of Supercritical Fluid Extraction.- 5.1 Introduction.- 5.2 Variables Affecting Extraction Quality.- 5.2.1 Nature and Composition of the Extractant.- 5.2.2 Pressure.- 5.2.3 Temperature.- 5.2.4 Flow-Rate.- 5.2.5 Extraction Time.- 5.2.6 Sample and Analyte Properties.- 5.2.7 Collection Systems.- 5.2.8 In-situ Derivatization.- 5.2.9 Other Factors.- 5.2.10 Quality Parameters.- 5.3 Sequential Extractions.- 5.4 General Applications of SFE.- 5.4.1 Types of Samples.- 5.4.1.1 Solid Samples.- 5.4.1.2 Liquid Samples.- 5.4.1.3 Gaseous Samples.- 5.4.1.4 Sample Size.- 5.4.2 Types of Analytes.- 5.4.3 Scope of Application of SFE.- 5.5 SFE and Other Extraction Techniques.- 5.5.1 Advantages of Supercritical Fluid Extraction.- 5.5.2 Disadvantages of Supercritical Fluid Extraction.- 5.6 Trends in SFE.- References.

Climate, soil and plant functional types as drivers of global fine-root trait variation

Abstract: 1.Ecosystem functioning relies heavily on belowground processes, which are largely regulated by plant fine-roots and their functional traits. However, our knowledge of fine-root trait distribution relies to date on local- and regional-scale studies with limited numbers of species, growth forms and environmental variation. 2.We compiled a worldwide fine-root trait dataset, featuring 1115 species from contrasting climatic areas, phylogeny and growth forms to test a series of hypotheses pertaining to the influence of plant functional types, soil and climate variables, and the degree of manipulation of plant growing conditions on species fine-root trait variation. Most particularly, we tested the competing hypotheses that fine-root traits typical of faster return on investment would be most strongly associated with conditions of limiting versus favourable soil resource availability. We accounted for both data source and species phylogenetic relatedness. 3.We demonstrate that (1) Climate conditions promoting soil fertility relate negatively to fine-root traits favouring fast soil resource acquisition, with a particularly strong positive effect of temperature on fine-root diameter and negative effect on specific root length (SRL), and a negative effect of rainfall on root nitrogen concentration; (2) Soil bulk density strongly influences species fine-root morphology, by favouring thicker, denser fine-roots; (3) Fine-roots from herbaceous species are on average finer and have higher SRL than those of woody species, and N2-fixing capacity positively relates to root nitrogen; (4) Plants growing in pots have higher SRL than those grown in the field. 4.Synthesis. This study reveals both the large variation in fine-root traits encountered globally and the relevance of several key plant functional types and soil and climate variables for explaining a substantial part of this variation. Climate, particularly temperature, and plant functional types were the two strongest predictors of fine-root trait variation. High trait variation occurred at local scales, suggesting that wide-ranging belowground resource economics strategies are viable within most climatic areas and soil conditions.