1,590 research outputs found
Cholesterol metabolism. Its regulation at the hepatic and intestinal level
Aunque todas las células del organismo tienen capacidad para sintetizar colesterol, la mayor parte de la síntesis de éste, que da lugar a lo que se conoce como colesterol endógeno, se realiza en el hígado. El hepatocito tiene además capacidad de captar colesterol de las lipoproteínas circulantes, y a la vez de excretarlo formando parte de nuevas lipoproteínas de origen hepático o transformado en ácidos biliares. El colesterol de origen extrahepático procede principalmente de la mucosa intestinal. Aquí se realiza la absorción del colesterol de la dieta (colesterol exógeno), la biosíntesis de nuevo colesterol y la esterificación para ser almacenado en la célula o secretado a sangre en las lipoproteínas de origen intestinal. A nivel celular, la importancia del colesterol radica en que forma parte de la mayoría de las estructuras membranosas de todas las células del organismo. En este artículo se revisan algunos de estos aspectos del metabolismo del colesterol, y se analiza la influencia de la composición lipídica de un tipo de membranas celulares, las membranas microsomales, en la actividad de los enzimas reguladores del metabolismo de colesterol.Although all the cells in the body are able to form cholesterol, most part of this synthesis, leading to which is called
endogenous cholesterol, occurs in the liver. Hepatocytes can also obtain cholesterol from the plasma lipoproteins. At the same time, cholesterol is either secreted from the liver in new plasma lipoproteins or transformed in bile acids. The extrahepatic cholesterol is mainly produced in the intestinal mucosa. In the site, it takes place the absorption of cholesterol from the diet (exogenous cholesterol), along with the biosynthesis of new cholesterol and the esterification of the molecule to be stored in the cell or secreted as plasma lipoproteins. At the cellular level, the importance of cholesterol comes from the fact that many of the membranous structures of all cells are partially composed of these substance. In this article some of these aspects of the colesterol metabolism are reviewed. We also describe the influence of lipid composition of microsomal membranes on the activity of colesterol metabolism regulating enzymes
Hidrógeno electrolítico para la gestión de la red eléctrica
La variabilidad de la demanda a lo largo de las horas del día y las estaciones del año, junto a la generación aleatoria de la mayoría de las fuentes de energía renovable, sitúan al sistema eléctrico ante un nuevo y fascinante paradigma; ello resulta especialmente relevante en redes relativamente aisladas y con una notable penetración de los parques eólicos, como sucede actualmente en España. La figura 1 muestra una curva típica, con dos puntas que reflejan sobretodo las necesidades de climatización durante las horas cálidas del estío e iluminación en los días cortos del invierno
Variación estacional del contenido de esporas de cladosporium en la atmósfera de Córdoba
En este trabajo se estud ia l a incidencia de esporas del género Cladosporium en l a atmósfera de Córdoba durante el período comprendido entre Abril de ¡gs3 a Narzo de 1984, med i ante la utilización de los mét odos de muestreo grav imétr ico y volumétrico . Se comparan los resultados obtenidos con los aportados por otros autores y se relacionan con los parámetros climatológicosIn this paper the incidente of spores of Cladosporium f rom Apri l 1983 to March 1984 in the atmosphere of Córdoba , by means of g.ravirnetric and volumetric methods is studied. The data obtained related wi t h t he clima tic parameters are comparated wi th those published by other author
Salutogenic interventions and health effects : a scoping review of the literature
Objective
To explore the typology of implemented salutogenic interventions and the health effects described by the authors.
Method
A scoping review of the literature published (PubMed, Embase, Web of Science and Scopus) over the last ten years (2007-2016) was conducted. Articles that included interventions with assessments of health outcomes were selected for this review. The kappa index (86.4%) was calculated for the classification and extraction of information.
Results
61 papers were selected out of the 676 works identified. These were categorized into individual, grouped, mixed and intersectoral interventions. A total of 85% of the interventions described positive effects. Adverse effects were not reported. Methodological limitations were identified in 75% of the papers. The interventions addressed a large variety of topics, especially in the field of mental health and chronic diseases. Collective actions described more positive effects. Intersectoral actions were the only type of interventions to have approached the impact of mortality reduction.
Conclusions
Findings support the existence of positive health effects of salutogenic approaches. Important methodological limitations were identified, such as biases in the selection of participants and sample sizes. Studies need to be conducted with improved monitoring and evaluation designs. A more robust theoretical framework and tools to evaluate the salutogenic contents are needed
Long-term effects of chronic khat use: impaired inhibitory control
So far no studies have systematically looked into the cognitive consequences of khat use. This study compared the ability to inhibit and execute behavioral responses in adult khat users and khat-free controls, matched in terms of age, race, gender distribution, level of intelligence, alcohol and cannabis consumption. Response inhibition and response execution were measured by a stop-signal paradigm. Results show that users and non-users are comparable in terms of response execution but users need significantly more time to inhibit responses to stop signals than non-users
LISA, binary stars, and the mass of the graviton
We extend and improve earlier estimates of the ability of the proposed LISA
(Laser Interferometer Space Antenna) gravitational wave detector to place upper
bounds on the graviton mass, m_g, by comparing the arrival times of
gravitational and electromagnetic signals from binary star systems. We show
that the best possible limit on m_g obtainable this way is ~ 50 times better
than the current limit set by Solar System measurements. Among currently known,
well-understood binaries, 4U1820-30 is the best for this purpose; LISA
observations of 4U1820-30 should yield a limit ~ 3-4 times better than the
present Solar System bound. AM CVn-type binaries offer the prospect of
improving the limit by a factor of 10, if such systems can be better understood
by the time of the LISA mission. We briefly discuss the likelihood that radio
and optical searches during the next decade will yield binaries that more
closely approach the best possible case.Comment: ReVTeX 4, 6 pages, 1 figure, submitted to Phys Rev
Statistical physics and stromatolite growth: new perspectives on an ancient dilemma
This paper outlines our recent attempts to model the growth and form of
microbialites from the perspective of the statistical physics of evolving
surfaces. Microbialites arise from the environmental interactions of microbial
communities (microbial mats). The mats evolve over time to form internally
laminated organosedimentary structures (stromatolites). Modern day
stromatolites exist in only a few locations, whereas ancient stromatolitic
microbialites were the only form of life for much of the Earth's history. They
existed in a wide variety of growth forms, ranging from almost perfect cones to
branched columnar structures. The coniform structures are central to the heated
debate on the oldest evidence of life. We proposed a biotic model which
considers the relationship between upward growth of a phototropic or
phototactic biofilm and mineral accretion normal to the surface. These
processes are sufficient to account for the growth and form of many ancient
stromatolities. These include domical stromatolites and coniform structures
with thickened apical zones typical of Conophyton. More angular coniform
structures, similar to the stromatolites claimed as the oldest macroscopic
evidence of life, form when the photic effects dominate over mineral accretion.Comment: 8 pages, 3 figures. To be published in Proceedings of StatPhys-Taiwan
2004: Biologically Motivated Statistical Physics and Related Problems, 22-26
June 200
The Proteome of Biologically Active Membrane Vesicles from Piscirickettsia salmonis LF-89 Type Strain Identifies Plasmid-Encoded Putative Toxins
Indexación: Scopus.Piscirickettsia salmonis is the predominant bacterial pathogen affecting the Chilean salmonid industry. This bacterium is the etiological agent of piscirickettsiosis, a significant fish disease. Membrane vesicles (MVs) released by P. salmonis deliver several virulence factors to host cells. To improve on existing knowledge for the pathogenicity-associated functions of P. salmonis MVs, we studied the proteome of purified MVs from the P. salmonis LF-89 type strain using multidimensional protein identification technology. Initially, the cytotoxicity of different MV concentration purified from P. salmonis LF-89 was confirmed in an in vivo adult zebrafish infection model. The cumulative mortality of zebrafish injected with MVs showed a dose-dependent pattern. Analyses identified 452 proteins of different subcellular origins; most of them were associated with the cytoplasmic compartment and were mainly related to key functions for pathogen survival. Interestingly, previously unidentified putative virulence-related proteins were identified in P. salmonis MVs, such as outer membrane porin F and hemolysin. Additionally, five amino acid sequences corresponding to the Bordetella pertussis toxin subunit 1 and two amino acid sequences corresponding to the heat-labile enterotoxin alpha chain of Escherichia coli were located in the P. salmonis MV proteome. Curiously, these putative toxins were located in a plasmid region of P. salmonis LF-89. Based on the identified proteins, we propose that the protein composition of P. salmonis LF-89 MVs could reflect total protein characteristics of this P. salmonis type strain. © 2017 Oliver, Hernández, Tandberg, Valenzuela, Lagos, Haro, Sánchez, Ruiz, Sanhueza-Oyarzún, Cortés, Villar, Artigues, Winther-Larsen, Avendaño-Herrera and Yáñez.https://www.frontiersin.org/articles/10.3389/fcimb.2017.00420/ful
A case for biotic morphogenesis of coniform stromatolites
Mathematical models have recently been used to cast doubt on the biotic
origin of stromatolites. Here by contrast we propose a biotic model for
stromatolite morphogenesis which considers the relationship between upward
growth of a phototropic or phototactic biofilm () and mineral accretion
normal to the surface (). These processes are sufficient to account
for the growth and form of many ancient stromatolities. Domical stromatolites
form when is less than or comparable to . Coniform structures with
thickened apical zones, typical of Conophyton, form when . More
angular coniform structures, similar to the stromatolites claimed as the oldest
macroscopic evidence of life, form when .Comment: 10 pages, 3 figures, to appear in Physica
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