Wachstumsminderung

X-ray absorption near edge structure (XANES) analysis in combination with synchrotron radiation induced total reflection X-ray fluorescence (SR-TXRF) acquisition was used to determine the oxidation state of Fe in human cancer cells and simultaneously their elemental composition by applying a simple sample preparation procedure consisting of pipetting the cell suspension onto the quartz reflectors. XANES spectra of several inorganic and organic iron compounds were recorded and compared to that of different cell lines. The XANES spectra of cells, independently from the phase of cell growth and cell type were very similar to that of ferritin, the main Fe store within the cell. The spectra obtained after CoCl2 or NiCl2 treatment, which could mimic a hypoxic state of cells, did not differ noticeably from that of the ferritin standard. After 5-fluorouracil administration, which could also induce an oxidative-stress in cells, the absorption edge position was shifted toward higher energies representing a higher oxidation state of Fe. Intense treatment with antimycin A, which inhibits electron transfer in the respiratory chain, resulted in minor changes in the spectrum, resembling rather the N-donor Fe-,′-dipyridyl complex at the oxidation energy of Fe(III), than ferritin. The incorporation of Co and Ni in the cells was followed by SR-TXRF measurements

Geochemical Aspect of Chemolithoautotrophic Bacterial Activity in the Role of Black Shale Hosted Mn Mineralization, Jurassic Age, Hungary, Europe

出版者照会後に全文公開The black shale-hosted ÚRKÚT Mn-mineralization is among the 10 largest deposits in the World. In this study optical and electron microscopy demonstrated the biological formation of Mn-Fe minerals in Mn-carbonate ores. The ED-XRF elemental content maps and SEM-EDX observation of the ores showed distribution of Mn, Fe, and Si banded layer structure whereas the Mg, Al, and K are randomly distributed, as well as to explain the role of microorganisms associated with Ca and P. In both samples abundant microorganisms were found in the dark brown and white layers. Optical micrographs of thin sections clearly showed various shapes of cellular materials, such as spherule, oval, and filamentous morphologies. SEM-EDX observation revealed Fe-rich and P-Ca components around microorganisms showing spherule, tubular, and filamentous cells. The present investigation strongly suggests that the Mn-Fe and Si minerals were associated with microorganisms as a biological organic product. The identity of the bacteria responsible for Mn mineral formation is unknown, but is tentatively assigned to Mn and Fe bacteria on the basis of morphology. The genesis of rocks and minerals have played a pivotal role in Toarcian age, and they may even have acted as life genetic system

Where and when to look: Sequential effects at the millisecond level

International audienceLearning and imitating a complex motor action requires to visually follow complex movements, but conscious perception seems too slowfor such tasks. Recent findings suggest that visual perception has a higher temporal resolution at an unconscious than at a conscious level. Here we investigate whether high-temporal resolution in visual perception relies on prediction mechanisms and attention shifts based on recently experienced sequences of visual information. To that aim we explore sequential effects during four different simultaneity/asynchrony discrimination tasks. Two stimuli are displayed on each trial with varying stimulus onset asynchronies (SOA). Subjects decide whether the stimuli are simultaneous or asynchronous and give manual responses. The main finding is an advantage for different-order over same-order trials, when subjects decided that stimuli had been simultaneous on Trial t − 1 , and when Trial t is with an SOA slightly larger than Trial t − 1, or equivalent. The advantage for different-order trials disappears when the stimuli change eccentricity but not direction between trials (Experiment 2), and persists with stimuli displayed in the centre and unlikely to elicit a sense of direction (Experiment 4). It is still observed when asynchronies on Trial t − 1 are small and undetected (Experiment 3). The findings can be explained by an attention shift that is precisely planned in time and space and that incidentally allows subjects to detect an isolated stimulus on the screen, thus helping them to detect an asynchrony