115 research outputs found
Protein traffic is an intracellular target in alcohol toxicity
Eukaryotic cells comprise a set of organelles, surrounded by membranes with a unique composition, which is maintained by a complex synthesis and transport system. Cells also synthesize the proteins destined for secretion. Together, these processes are known as the secretory pathway or exocytosis. In addition, many molecules can be internalized by cells through a process called endocytosis. Chronic and acute alcohol (ethanol) exposure alters the secretion of different essential products, such as hormones, neurotransmitters and others in a variety of cells, including central nervous system cells. This effect could be due to a range of mechanisms, including alcohol-induced alterations in the different steps involved in intracellular transport, such as glycosylation and vesicular transport along cytoskeleton elements. Moreover, alcohol consumption during pregnancy disrupts developmental processes in the central nervous system. No single mechanism has proved sufficient to account for these effects, and multiple factors are likely involved. One such mechanism indicates that ethanol also perturbs protein trafficking. The purpose of this review is to summarize our understanding of how ethanol exposure alters the trafficking of proteins in different cell systems, especially in central nervous system cells (neurons and astrocytes) in adult and developing brains
Searching free zinc at the ultrastructural level in cultured astrocytes
Zinc is an element that is necessary for many physiological functions in the body but may play an important role in diseases affecting most systems in the body if its balance is altered by environmental, toxicological or idiosyncrasy of subjects. We have centred our investigation in central nervous system, using cultured astrocytes since they are involved in clearance of zinc exocytated to the extracellular medium during synaptic transmission.
In previous works we have used a zinc fluorochrome, i.e., the TSQ (6-Methoxy-(8-p-toluenesulfonamido)quinoline) to in vivo zinc uptake in cultured astrocytes and its accumulation in organelles named zincosomes. However, the precise location of these zinc-enriched structures (zincosomes) at the ultrastructural level is a very hard task. In a previous attempt at the electron microscopy level, only topographical approximation by combining light and electron microscopy allowed us to identify selected zincosomes previously marked with TSQ.
Now, our objective is to adapt zinc autometallography (Timm’s method) to TSQ labelled cultured astrocytes.
For the electron microscopic detection of zincosomes, the first important step is to achieve a good zinc precipitation during or previous to glutaraldehyde fixation. Surprisingly, neither ditizone nor selenite were successful as zinc precipitating agents; only sodium sulphide gave us good results. We also found that while glutaraldehyde is the best option for animal experimentation, paraformaldehyde prefixation gave us best results. Paraformaldehyde prefixation allowed both ultrastructure preservation as well as zinc-precipitated-detection with Timm autometallography in semithin sections. These semithin sections were included again and zincosomes become clearly visible in ultrathin sections
Ethanol impairs extracellular zinc intake in cultured astrocytes
Zinc (Zn) deficiency is present in many physiological and health problems. Among
circumstances involved in Zn deficiency, ethanol consumption appears as a prominent
cause. In the CNS substantial amounts of Zn appear accumulated in synaptic vesicles of a
particular class of neurons: the Zn enriched neurons very abundant in the telencephalon and
cerebral cortex. This is the so called synaptic Zn which is simultaneously released with the
neurotransmitter thus exerting a neuromodulator role during synaptic transmission.
Neighbour astrocytic processes have to capture the excess of both extracellular Zn and
neurotransmitter in order to maintain efficient synaptic transmission between neurons. In this
work we analyze the effect of exposure to 30 mM ethanol for 7 days in the ability of cultured
rat astrocytes to capture and manage extracellular Zn. Intracellular Zn levels were visualized
by using the TSQ Zn fluorochrome, either in normal culture conditions or after supplementary
addition of 50 μM ZnSO4 to the culture. Fluorescence was recorded with an Olympus
microscope BX50WI, equipped with a Hamamatsu ORCA digital camera controlled with the
Aquacosmos software. Basal Zn levels in cultured astrocytes was greatly and significantly
lower in ethanol treated cells (about 30% of control cultures). These differences were
consistently maintained after addition of extracellular Zn to cell monolayers, resulting in a
lower ability to uptake or retain Zn. The Zn was uptaked by the endocytic pathway, as
demonstrated by the marker FM1-43 and was mainly confined to bright organelles that were
more abundant in control cells. In conclusion, ethanol impairs astrocyte Zn management
resulting in a lower capacity for extracellular Zn intake in resting conditions and after
extracellular addition. It has been proposed that an efficient method to palliate Zn deficiency
it could be a dietary supplement. Nevertheless, this study suggests that a dietary Zn
supplementation may not be enough for recovery of cellular normal function in alcoholic
cultured astrocytes
El porqué, el cómo y el dónde de la internacionalización de la empresa.
La internacionalizacion de las empresas es cada vez mayor, siendo un proceso en continuo y acelerado crecimiento. Los cambios producidos en el entorno empresarial y los que previsiblemente se han de producir en un futuro próximo, hacen pensar que este proceso seguirá intensificandose. Es por ello, que al tratar de conocer el porqué se internacionalizan las empresas, como lo hacen, y dónde ó en qué paises desarrollan alguna(s) de las actividades de la cadena de valor adquiere especial importancia, si se desea entender y estudiar correctamente este fenomeno. El analisis de las teorias acerca de la internacionalizacion consideradas como más relevantes en el contexto actual, se hace necesario para verificar su alcance, validez y capacidad explicativa y, consiguientemente, precisar en qué medida permiten responder a las cuestiones formuladas. Este trabajo tiene, pues, por objeto el estudio de las teorias de la internacionalizacion, del paradigma ecleptico, del modelo de Uppsala, y del modelo Porter
Prenatal exposure to ethanol alters plasma membrane glycoproteins of astrocytes during development in primary culture as revealed by concanavalin a binding and 5?-nucleotidase activity
Prenatal alcohol exposure affects galactosyltransferase activity and glycoconjugates in the Golgi apparatus of fetal rat hepatocytes
Effect of cholesterol and its autooxidation derivatives on endocytosis and dipeptidyl peptidases of aortic endothelial cells
The effects of cholesterol (CHO) and
cholesterol autooxidation derivatives (CAD) on the
endocytosis of cationized ferritin (CF) by endothelial
cells have been investigated. The effect of both
substances on the activity of lysosomal enzymes
dipeptidyl peptidase 1 (DPP 1) and dipeptidyl
peptidase 11 (DPP 11) was also studied. Treatment of
rats with CAD induced striking alterations in the
ultrastructure of endothelial cells and makes it
impossible to analyze the effect of this toxin on
endocytosis processes. In contrast, CHO-treated cells
displayed a good ultrastructural preservation and
showed an increased ability to endocyte ferritin, as
compared with controls. Both DPPI and DPP 11
activities increased after 3 weeks of CAD or CHO
treatment. Our results indicate that although CHO
damage endothelial cells, the most important effects
could be attributed to CAD which usually
accompanies CHO-supplemented diets
A Comparative Morphometrical Study of the Ultrastructural Organization in Six Dinoflagellate Species Using Stereology
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