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Selected AbstractsEstrogenic effect of leachates and soil extracts from lysimeters spiked with sewage sludge and reference endocrine disruptersENVIRONMENTAL TOXICOLOGY, Issue 2 2002Halim Dizer Abstract Several experiments were conducted to evaluate the behavior and performance of some potential endocrine disrupters (ECDs). Two in vitro screening assays, one based on MCF7-cell proliferation (E-screen test) and the other on estrogenic receptor activity [enzyme-linked receptor assay (ELRA)], were used for the tests, which were done in lysimeters 80 cm in diameter with depths of 30 cm (shallow) or 90 cm (deep). A sandy soil was used to fill in all lysimeters, which were spiked on the surface with either: (a) a sewage sludge (SS) at a dose equivalent to 20 tons ha,1; (b) a mixture of reference ECDs, comprising 17,- and 17,-estradiol (E2), nonylphenol, octylphenol, and bisphenol A at doses 100 times higher than the maximum concentrations respectively found in the applied SS; or (c) a mixture of ECDs and SS. After percolation of the lysimeters with rain and/or artificial water, five leachates were sampled from each lysimeter during a period of 210 days. Immediately after the lysimeter percolation experiments, four and six soil fractions were dissected from, respectively, the 30-cm and 90-cm lysimeters and extracted by water. Both the leachate and soil extract samples were analyzed for their estrogenicity using the assays indicated above. The E-screen assay was highly sensitive only for some leachate and extract samples but gave no response for most leachates and soil extracts. The results of the ELRA assay suggests a significantly higher estrogenicity of leachate samples from shallow lysimeters compared with that of leachates from deep lysimeters. In contrast, the estrogenic effect measured for soil extracts of shallow lysimeters was lower than that measured for soil extracts of deep lysimeters. The results of the E-screen assay suggests the occurrence of a fast mobilization of applied ECDs and a moderate retardation effect of native ECDs contained in applied SS in the sandy soil used in the lysimeters. In lysimeters spiked with a mixture of SS and ECDs, the washing-out effect of ECDs in the first leachate fraction decreased, but the distribution of ECDs in the lysimeters increased. The relatively high estrogenic impact measured for soil water extracts suggests that the ECDs were mostly associated with water-soluble fractions of organic matter and/or water-suspended fractions of the mineral soil matrix. The application of SS to agricultural and forest fields may determine the immobilization of ECDs in soil or their movement to surface and/or groundwater. Therefore, an endocrine risk of exposure exists for the water and soil organisms. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 105,112, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10038 [source] Membrane-associated guidance cues direct the innervation of forebrain and midbrain by dorsal raphe-derived serotonergic axonsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2005Audrey Petit Abstract Unlike many neurons that extend an axon precisely to a single target, individual dorsal raphe 5-HT neurons project to multiple brain regions and their axon terminals often lack classical synaptic specializations. It is not known how 5-HT axon collaterals select between multiple target fields, or even if 5-HT axons require specific guidance cues to innervate their targets. Nor is it known how these axon collaterals are restrained within specific innervation target regions. To investigate this, we challenged explants of dorsal raphe with co-explants, or cell membrane preparations of ventral midbrain, striatum or cerebral cortex. We provide evidence for membrane-associated cues that promote 5-HT axon growth into each of these three target regions. The axon growth-promoting activity was heat-, protease- and phosphatidylinositol-phospholipase-C (PI-PLC)-sensitive. Interestingly, 5-HT axons specifically lost the ability to grow in heterotypic explants, or membrane carpets, following contact with ventral midbrain or striatal, but not cortical, explants or membranes. This inductive activity associated with striatal and ventral midbrain membranes was sensitive to both high salt extraction and PI-PLC treatment. By contrast, the activity that inhibited 5-HT axon growth onto heterotypic membranes was sensitive only to high salt extraction. These results provide evidence that a glycosylphosphatidylinositol (GPI)-linked membrane protein promotes 5-HT axon growth, and that short-range membrane-bound, as well as GPI-linked, molecules contribute to the guidance of 5-HT axon collaterals. These findings suggest that 5-HT axon collaterals acquire a target-induced growth-inhibitory response to alternative targets, increasing their selectivity for the newly innervated field. [source] Effects of task difficulty and time-on-task on mental workloadJAPANESE PSYCHOLOGICAL RESEARCH, Issue 3 2002Shigeru Haga Abstract: Twelve subjects performed a tracking task and a memory search task simultaneously on a computer screen. The dual task continued for approximately 10 min and was repeated three times, interrupted by a short break for subjective ratings: the NASA Task Load Index (NASA-TLX) and the Check List of Mental Condition. Event related potentials (ERP) evoked by the presentation of memory task stimuli were also recorded. All the subjects participated in three experimental sessions, which varied in difficulty of tracking task. Results demonstrated that the NASA-TLX and ERP were sensitive only to the change in task difficulty and were not affected by time-on-task or interaction between task difficulty and time-on-task. [source] Maintaining Cell Sensitivity to G-Protein Coupled Receptor Agonists: Neurotensin and the Role of Receptor Gene ActivationJOURNAL OF NEUROENDOCRINOLOGY, Issue 5 2001F. Souazé Abstract In the last few years, a number of studies have brought new insights into the fundamental mechanisms of cell desensitization and internalization of G-protein coupled receptors. Such studies have demonstrated that cells remain desensitized from a few minutes to several hours, after exposure to high concentrations of agonist. However, in vivo, agonists such as hormones are always present, even in small amounts, and such long desensitization is not conceivable, since constant stimulation of cells is required for physiological responses. Under such circumstances, cells would require a means to permanently maintain sensitivity to various internal or external stimuli. In the present review, we have taken as an example the expression of the high affinity neurotensin receptor, a seven transmembrane G-protein coupled receptor, upon prolonged exposure to its agonist, and observed that cells remained sensitive only if the receptor gene was activated by the agonist. Consequently, new receptors were synthesized, and either delivered to the cell surface or accumulated in submembrane pools. This regulation takes place only after prolonged and intense agonist stimulation. Under these conditions, it is proposed that receptor turnover is accelerated in proportion to the agonist concentration in order to allow the cells to produce an adapted cellular response to external stimuli. Such mechanisms thus play a key role in cell sensitivity to hormones. [source] A multiple-scattering theory of circular and linear dichroism for photoemission and photoabsorptionJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2002S. Di Matteo A unified treatment of circular dichroism, both natural and magnetic, in (spin-resolved) photoemission and photoabsorption from core levels is given, valid in the many-body case and for extended systems, together with an extension of the formalism to treat linear dichroism. The reduction of this scheme to a one-electron picture in the framework of multiple scattering theory is briefly discussed and shows the intimate connection of the two spectroscopies via a generalized optical theorem. Plausibility arguments are given that in correlated d -band systems screening and relaxation effects are not so drastic as in other cases, due to the autoscreening action of the excited photoelectron, so that the final density of states is much like the initial unperturbed one. It is shown how to exploit this point of view to obtain in favorables cases separated orbital and spin moment radial (surface) distribution maps from dichroic magnetic EXAFS spectra (photoelectron diffraction patterns) related to the ground state. Dichroic natural spectra, both in photoemission and absorption, are shown to be sensitive only to atoms in chiral geometry. [source] Cosmological implications of the PSCz PDF and its momentsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2001Manolis Plionis We compare the probability density function (PDF) and its low-order moments (variance and skewness) of the smoothed IRAS Point Source Catalogue Redshift Survey (PSCz) galaxy density field and of the corresponding simulated PSCz look-alikes, generated from N -body simulations of six different dark matter models: four structure-normalized with and , one COBE -normalized, and the old standard cold dark matter model. The galaxy distributions are smoothed with a Gaussian window at three different smoothing scales, , 10 and 15 h,1 Mpc. We find that the simulation PSCz look-alike PDFs are sensitive only to the normalization of the power spectrum, probably owing to the shape similarity of the simulated galaxy power spectrum on the relevant scales. We find that the only models that are consistent, at a high significance level, with the observed PSCz PDF are models with a relatively low power spectrum normalization . From the phenomenologically derived ,8,moments relation, fitted from the simulation data, we find that the PSCz moments suggest . [source] Photodynamic effect of hypericin in primary cultures of human umbilical endothelial cells and glioma cell linesPHYTOTHERAPY RESEARCH, Issue 6 2009Viktória Stupáková Abstract Hypericin is the most powerful naturally occurring photosensitizer and as such there is renaissant interest in the potentials of this compound for anticancer photodynamic therapy (PDT). The purpose of this study was to investigate the hypericin-mediated photodynamic therapy effects on normal human umbilical endothelial cells (HUVECs) in comparison with cancer human glioma cell lines U-87 MG and U-373 MG, in in vitro conditions. The data suggest that endothelial cells as well as glioma cell lines are sensitive only to photoactivated hypericin. The inhibitory effects of photoactivated hypericin did not differ in endothelial compared with tumor cells in cytotoxicity MTT and DNA fragmentation assays. However, an important difference in sensitivity was found between the above mentioned cell types in migration and metalloproteinases inhibition assays performed as cell function tests. The findings in both function tests were supported by the high sensitivity of endothelial cells in an additional angiogenesis test of tubular formation in vitro. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||