Genetic mosaic dissection of Lis1 and Ndel1 in neuronal migration

Coordinated migration of newly born neurons to their prospective target laminae is a prerequisite for neural circuit assembly in the developing brain. The evolutionarily conserved LIS1/NDEL1 complex is essential for neuronal migration in the mammalian cerebral cortex. The cytoplasmic nature of LIS1 and NDEL1 proteins suggest that they regulate neuronal migration cell autonomously. Here, we extend mosaic analysis with double markers (MADM) to mouse chromosome 11 where Lis1, Ndel1, and 14-3-3? (encoding a LIS1/NDEL1 signaling partner) are located. Analyses of sparse and uniquely labeled mutant cells in mosaic animals reveal distinct cell-autonomous functions for these three genes. Lis1 regulates neuronal migration efficiency in a dose-dependent manner, while Ndel1 is essential for a specific, previously uncharacterized, late step of neuronal migration: entry into the target lamina. Comparisons with previous genetic perturbations of Lis1 and Ndel1 also suggest a surprising degree of cell-nonautonomous function for these proteins in regulating neuronal migration.     

Cocoa polyphenols attenuate hydrogen peroxide-induced inhibition of gap-junction intercellular communication by blocking phosphorylation of connexin 43 via the MEK/ERK signaling pathway

Cocoa, a good source of dietary antioxidative polyphenols, exhibited anticarcinogenic activity in animal models, but the molecular mechanisms of the chemopreventive potential of cocoa remain unclear. Inhibition of gap-junction intercellular communication (GJIC) is strongly related to tumorigenesis. Cocoa polyphenol extracts (CPE) dose dependently attenuated hydrogen peroxide (H₂O₂)-induced inhibition of GJIC in rat liver epithelial (RLE) cells. CPE inhibited the H₂O₂-induced phosphorylation and internalization of connexin 43, which is a regulating protein of GJIC in RLE cells. The H₂O₂-induced accumulation of reactive oxygen species and activation of extracellular signal-regulated kinase were inhibited by CPE treatment. However, CPE did not block H₂O₂-induced phosphorylation of p38 mitogen-activated protein kinase. An ex vivo kinase assay demonstrated that CPE inhibited the H₂O₂-induced mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK) 1 activity in RLE cell lysates. Ex vivo pull-down assay data revealed that CPE directly bound with MEK1 to inhibit MEK1 activity. These results indicate that CPE protects against the H₂O₂-induced inhibition of GJIC through antioxidant activity and direct inhibition of MEK activity, which may contribute to its chemopreventive potential.     

Epidemiological study of sun exposure and visual field damage in children in Primorsko-Goranska County--the risk factors of earlier development of macular degeneration

The aim of this study was to examine the possible harmful effects of solar exposure on visual field damage in children living in Primorsko-Goranska County. Our previous work has shown noxious influence on visual field in children with anamnesis long term exposure to sunlight. This is an extended study, including children in Novi Vinodolski and Gorski kotar. We measured possible defect in isopteric visual field and macular-meridian thresholds. In the area of island of Rab these changes were the biggest, subsequently is Novi Vinodolski and at least Gorski kotar with the smallest range of eye complicates according to exposure to sunlight. These damages correlate with the areas of great solar emission. Damages in periphery isopters of visual field have shown the characteristics of periphery defect invagination, while increased macular thresholds in complete visual field was from 5 to 15Asb. We can conclude that there is direct connection between increased sunlight and long-term exposure to sunlight on one side, and on the other side, damages of retinal perception. Increased sun exposure may represent very important factors in early occurrence and develop of Age-Related Macular Degeneration (AMD). It is recommended the children protection in summer months, as well as taking derivates of vitamin A and antioxidants. Nowadays, AMD is one of the most important causes of damaged visual field, pretend to be national problem if we don't use the adequate prevention. World Health Organization has to begin with prevention of AMD, including these risk factors.     

Alignment of the c-Type Cytochrome OmcS along Pili of Geobacter sulfurreducens

Immunogold localization revealed that OmcS, a cytochrome that is required for Fe(III) oxide reduction by Geobacter sulfurreducens, was localized along the pili. The apparent spacing between OmcS molecules suggests that OmcS facilitates electron transfer from pili to Fe(III) oxides rather than promoting electron conduction along the length of the pili.There are multiple competing/complementary models for extracellular electron transfer in Fe(III)- and electrode-reducing microorganisms (8, 18, 20, 44). Which mechanisms prevail in different microorganisms or environmental conditions may greatly influence which microorganisms compete most successfully in sedimentary environments or on the surfaces of electrodes and can impact practical decisions on the best strategies to promote Fe(III) reduction for bioremediation applications (18, 19) or to enhance the power output of microbial fuel cells (18, 21).The three most commonly considered mechanisms for electron transfer to extracellular electron acceptors are (i) direct contact between redox-active proteins on the outer surfaces of the cells and the electron acceptor, (ii) electron transfer via soluble electron shuttling molecules, and (iii) the conduction of electrons along pili or other filamentous structures. Evidence for the first mechanism includes the necessity for direct cell-Fe(III) oxide contact in Geobacter species (34) and the finding that intensively studied Fe(III)- and electrode-reducing microorganisms, such as Geobacter sulfurreducens and Shewanella oneidensis MR-1, display redox-active proteins on their outer cell surfaces that could have access to extracellular electron acceptors (1, 2, 12, 15, 27, 28, 31-33). Deletion of the genes for these proteins often inhibits Fe(III) reduction (1, 4, 7, 15, 17, 28, 40) and electron transfer to electrodes (5, 7, 11, 33). In some instances, these proteins have been purified and shown to have the capacity to reduce Fe(III) and other potential electron acceptors in vitro (10, 13, 29, 38, 42, 43, 48, 49).Evidence for the second mechanism includes the ability of some microorganisms to reduce Fe(III) that they cannot directly contact, which can be associated with the accumulation of soluble substances that can promote electron shuttling (17, 22, 26, 35, 36, 47). In microbial fuel cell studies, an abundance of planktonic cells and/or the loss of current-producing capacity when the medium is replaced is consistent with the presence of an electron shuttle (3, 14, 26). Furthermore, a soluble electron shuttle is the most likely explanation for the electrochemical signatures of some microorganisms growing on an electrode surface (26, 46).Evidence for the third mechanism is more circumstantial (19). Filaments that have conductive properties have been identified in Shewanella (7) and Geobacter (41) species. To date, conductance has been measured only across the diameter of the filaments, not along the length. The evidence that the conductive filaments were involved in extracellular electron transfer in Shewanella was the finding that deletion of the genes for the c-type cytochromes OmcA and MtrC, which are necessary for extracellular electron transfer, resulted in nonconductive filaments, suggesting that the cytochromes were associated with the filaments (7). However, subsequent studies specifically designed to localize these cytochromes revealed that, although the cytochromes were extracellular, they were attached to the cells or in the exopolymeric matrix and not aligned along the pili (24, 25, 30, 40, 43). Subsequent reviews of electron transfer to Fe(III) in Shewanella oneidensis (44, 45) appear to have dropped the nanowire concept and focused on the first and second mechanisms.Geobacter sulfurreducens has a number of c-type cytochromes (15, 28) and multicopper proteins (12, 27) that have been demonstrated or proposed to be on the outer cell surface and are essential for extracellular electron transfer. Immunolocalization and proteolysis studies demonstrated that the cytochrome OmcB, which is essential for optimal Fe(III) reduction (15) and highly expressed during growth on electrodes (33), is embedded in the outer membrane (39), whereas the multicopper protein OmpB, which is also required for Fe(III) oxide reduction (27), is exposed on the outer cell surface (39).OmcS is one of the most abundant cytochromes that can readily be sheared from the outer surfaces of G. sulfurreducens cells (28). It is essential for the reduction of Fe(III) oxide (28) and for electron transfer to electrodes under some conditions (11). Therefore, the localization of this important protein was further investigated.     

Alteration of cytokine profiles in mice exposed to chronic low-dose ionizing radiation

While a high-dose of ionizing radiation is generally harmful and causes damage to living organisms, a low-dose of radiation has been shown to be beneficial in a variety of animal models. To understand the basis for the effect of low-dose radiation in vivo, we examined the cellular and immunological changes evoked in mice exposed to low-dose radiation at very low (0.7 mGy/h) and low (3.95 mGy/h) dose rate for the total dose of 0.2 and 2 Gy, respectively. Mice exposed to low-dose radiation, either at very low- or low-dose rate, demonstrated normal range of body weight and complete blood counts. Likewise, the number and percentage of peripheral lymphocyte populations, CD4⁺ T, CD8⁺ T, B, or NK cells, stayed unchanged following irradiation. Nonetheless, the sera from these mice exhibited elevated levels of IL-3, IL-4, leptin, MCP-1, MCP-5, MIP-1α, thrombopoietin, and VEGF along with slight reduction of IL-12p70, IL-13, IL-17, and IFN-γ. This pattern of cytokine release suggests the stimulation of innate immunity facilitating myeloid differentiation and activation while suppressing pro-inflammatory responses and promoting differentiation of naïve T cells into T-helper 2, not T-helper 1, types. Collectively, our data highlight the subtle changes of cytokine milieu by chronic low-dose γ-radiation, which may be associated with the functional benefits observed in various experimental models.     

Cadmium activates Arabidopsis MPK3 and MPK6 via accumulation of reactive oxygen species

Cadmium (Cd) is a non-essential toxic heavy metal that influences normal growth and development of plants. However, the molecular mechanisms by which plants recognize and respond to Cd remain poorly understood. We show that, in Arabidopsis, Cd activates the mitogen-activated protein kinases, MPK3 and MPK6, in a dose-dependent manner. Following treatment with Cd, these two MAPKs exhibited much higher activity in the roots than in the leaves, and pre-treatment with the reactive oxygen species (ROS) scavenger, glutathione, effectively inhibited their activation. These results suggest that the Cd sensing signaling pathway uses a build-up of ROS to trigger activation of Arabidopsis MPK3 and MPK6.