1,720,959 research outputs found
Effect of Brefeldin A on the synthesis and transport of cell-wall polysaccharides and proteins in pea root seedlings
No full textThe in vivo effect of Brefeldin A (BFA) on the synthesis and transport of cell wall polysaccharides and proteins in the roots of pea seedlings (Pisum sativum L. cv, Alaska) was investigated. BFA (10 mu g ml(-1)) inhibited the synthesis of cell wall matrix polysaccharides by approximately 43%. Under the same conditions, cellulose synthesis was inhibited by approximately 77%, The percentage of incorporation of L-[U-C-14]leucine and L-[U-C-14]proline into cytosolic, membrane and cell wall proteins was only slightly changed in the presence of BFA, In addition, the drug did not change the pattern of newly synthesized proteins in the three fractions as judged by SDS-PAGE fluorography. Double labelling of proteins and cell wall polysaccharides confirmed the above reported data. All these results showed that the synthesis and transport of proteins to the cell wall was only slightly affected by BFA under similar conditions to those which brought about a strong inhibition of the synthesis of matrix and cellulosic polysaccharides. BFA had no effect on the activity of membrane-bound and digitonin-solubilized mannan and glucomannan synthase isolated from the third internode of pea seedlings. This would exclude an effect of BFA at the level of the catalytic site of the synthases. The inhibition of polysaccharide synthesis by the drug was rapidly eliminated after its removal. It is concluded that the effect of BFA on the biosynthesis of cell wall polysaccharides could be caused by an interaction of the drug with the topological organization of the synthase complexes in the membranes. This effect would precede the action of the drug at the level of vesicle transport to the walls
Localization of pro- and anti- apoptotic product genes in lymphocytes aged under static magnetic fields exposure
No full textDifferentiation of monocytic U937 cells under static magnetic field exposure
No full textWe present here a morphological, cytochemical and biochemical study of the macrophagic differentiation of human pro-monocytic U937 cells exposed to moderate intensity (6 mT) static magnetic fields (MF). It was found that the following substances induced differentiation in U937 cells to a progressively lower degree: 50 ng/mL 12-0-tetradecanoyl-13-phorbol acetate (TPA), low concentration of glutamine (0,05 mM/L), 10% dimethyl sulfoxide (DMSO) and 100 mM/L Zn++. Differentiated U937 cells shift from a round shape to a macrophage-like morphology, from suspension to adhesion growth and acquire phagocytotic activity, the cytoskeleton adapting accordingly. Exposure to static MF at 6 mT of intensity decreases the degree of differentiation for all differentiating molecules with a consequent fall in cell adhesion and increased polarization of pseudopodia and cytoplasmic protrusions. Differentiation alone, or in combination with exposure to static MFs, affects the distribution and quantity of cell surface sugar residues, the surface expression of markers of macrophage differentiation, and phagocytotic capability. Our results indicate that moderate-intensity static MFs exert a considerable effect on the process of macrophage differentiation of pro-monocytic U937 cells and suggest the need for further studies to investigate the in vivo possible harmful consequences of this
Post-chronic whole-body exposure of rabbits to 650 MHz electromagnetic fields affects liver, spleen and brain.
No full textWe investigated the effects of post (i.e. 12 and 18 months) whole-body chronic (2 years) exposure of rabbits to 650 MHz electromagnetic fields, the same intensity of electromagnetic fields (EMF) produced by broadcasting station, on body-weight and body –mass fluctuation, on the morphological changes of the liver, spleen and brain, on the apoptotic rate modification and on the glycogen distribution in the liver. Two groups of rabbits were continuously exposed for 2 years to EMFs of 650 MHz followed by 12 or 18 months of post-exposure; a third group was sham exposed. Body-weight and –mass changes were evaluated by the conventional methods; morphological changes in the liver, spleen and brain were investigated at light and electron microscope level, by assessing tissue integrity, cell shape, apoptotic rate, glycogen presence and distribution. Significant changes, organ-, time- and individual-dependent, were observed between 2 years exposed rabbits plus 12 months versus 2 years exposed plus 18 months ones. In particular, apoptotic rate increasing or decreasing was exposure time- but not organ-dependent. In summary, whole-body chronic exposure of rabbits to 650 MHz electromagnetic fields gave rice to modifications whose type and intensity were related to time of post-exposure, to the type of organ and to the individual animal. Some of the exposure responses observed only for 2 years plus 12 months but not for 2 years plus 18 months years exposed rabbits, suggested adaptability of animals to long-time recovery after chronic exposure to 650 MHz electromagnetic fields
Anticancer drug resistance in drug-induced cell death of U937 cells.
No full textCell death and subsequent posmortem changes are integral pars of the normal development and maturation cycle. Cell death occurs by two alternative, oppisite modes: apoptosis, a programmed form of cell death, and necrosis, an unordered and accidental form
Expression of stress proteins 70 in Tilapia (Oreochromis mossambicus) during confinement and crowding stress
No full textThe knowledge of fish biology of stress response to unfavourable environmental conditions is of interest for both basic and applied purpose, providing useful information for fish farming and environmental risk assessment. In this study, tilapias (Oreochromis mossambicus), confined in nets inside the tanks for 4 or 5 hrs, were examined for induction of Hsp 70 in various organs by western blotting and for cortisol levels in the blood. In net-confined fish, cortisol, primary stress indicator, was found to consistently increase with differences between 4 and 5 hrs of confinement. Hsp 70 expression, evaluated in striated and cardiac muscle, gill, liver and brain showed fluctuation in confined animals. Indeed, increase or decrease of Hsp 70 expression in stressed fish was modified in organ- and stress duration-dependent manner and subjective fluctuation were minimal. Morphological observations (LM and EM) were carried out on liver, brain and gill from control and stressed animals. In particular, liver underwent major modifications while brain was only slightly modified and gills were unmodified during confinement stress. Taken together our data suggest that Hsp 70 expression could be an indicator of stress state in fish when measured in the significant responsive organs
Biological effects of 6 mT static magnetic fields: a comparative study in different cell types
Full text linkAim of the present work was the comparative study of the bio-effects induced by exposure to 6 mT static magnetic field (MF) on several primary cultures and cell lines. A particular attention was dedicated to apoptosis. Cell viability, proliferation, intracellular Ca2+ concentration and morphology were also examined during the exposure of cells to static MF. Primary culture of human lymphocytes, mice thymocytes and cultures of 3DO, U937, HeLa, HepG2 and FRTL-5 cells were cultured in the presence of 6 mT static MF and different apoptosis-inducing drugs (i.e. cycloheximide, H2O2, puromycin, heat shock, etoposide).
On all the different cells examined biological effects of static MF exposure were found. They were cell type-dependent but apoptotic inducer-independent. A common effect of the exposure to static MF was the promotion of apoptosis and mitosis but not of necrosis and modifications of the cell shape. Increase of the intracellular levels of Ca2+ ions were also observed. When pro-apoptotic drugs were added to static MF, the majority of cell types rescued from apoptosis. On the contrary, apoptosis of 3DO cells was significantly increased under simultaneous exposure to static MF and incubation with pro-apoptotic drugs. From these data it derives that 6 mT static MF exposure interfered with apoptosis in a cell type- and exposure time- dependent manner while the effects of static MF exposure on the apoptotic program were independent of the drugs used
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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