Possible repair action of Vitamin C on DNA damage induced by methyl methanesulfonate, cyclophosphamide, FeSO4 and CuSO4 in mouse blood cells in vivo

Interaction between Vitamin C (VitC) and transition metals can induce the formation of reactive oxygen species (ROS). VitC may also act as an ROS scavenger and as a metal chelant. To examine these possibilities, we tested in vivo the effect of two doses of VitC (1 and 30 mg/kg of mouse body weight) on the genotoxicity of known mutagens and transition metals. We used the alkaline version of the comet assay to assess DNA damage in peripheral white blood cells of mice. Animals were orally given either water (control), cyclophosphamide (CP), methyl methanesulfonate (MMS), cupric sulfate or ferrous sulfate. A single treatment with each VitC dose was administered after treatment with the mutagens or the metal sulfates. Both doses of VitC enhanced DNA damage caused by the metal sulfates. DNA damage caused by MMS was significantly reduced by the lower dose, but not by the higher dose of VitC. For CP, neither post-treatment dose of VitC affected the DNA damage level. These results indicate a modulatory role of Vitamin C in the genotoxicity/repair effect of these compounds. Single treatment with either dose of VitC showed genotoxic effects after 24 h but not after 48 h, indicating repair. Double treatment with VitC (at 0 and 24 h) induced a cumulative genotoxic response at 48 h, more intense for the higher dose. The results suggest that VitC can be either genotoxic or a repair stimulant, since the alkaline version of the comet assay does not differentiate "effective" strand breaks from those generated as an intermediate step in excision repair (incomplete excision repair sites). Further data is needed to shed light upon the beneficial/noxious effects of VitC.     

Interaction of pathogenic fungi with host cells: Molecular and cellular approaches

This review provides an overview of several molecular and cellular approaches that are likely to supply insights into the host-fungus interaction. Fungi present intra- and/or extracellular host-parasite interfaces, the parasitism phenomenon being dependent on complementary surface molecules. The entry of the pathogen into the host cell is initiated by the fungus adhering to the cell surface, which generates an uptake signal that may induce its cytoplasmatic internalization. Furthermore, microbial pathogens use a variety of their surface molecules to bind to host extracellular matrix (ECM) components to establish an effective infection. On the other hand, integrins mediate the tight adhesion of cells to the ECM at sites referred to as focal adhesions and also play a role in cell signaling. The phosphorylation process is an important mechanism of cell signaling and regulation; it has been implicated recently in defense strategies against a variety of pathogens that alter host-signaling pathways in order to facilitate their invasion and survival within host cells. The study of signal transduction pathways in virulent fungi is especially important in view of their putative role in the regulation of pathogenicity. This review discusses fungal adherence, changes in cytoskeletal organization and signal transduction in relation to host-fungus interaction.     

Crystallization and preliminary X-ray diffraction studies of two myotoxic Lys49-phospholipases A2 complexed with alpha-tocopherol

BnSP-7 and BnSP-6, two Lys49-phospholipase A2 isolated from Bothrops neuwiedi pauloensis snake venom, were co-crystallized with alpha-tocopherol and X-ray diffraction data were collected for both complexes (2.2 and 2.6 A). A new "alternative" quaternary conformation for these two complexes compared with all other dimeric Lys49-PLA2 has been observed.     

Functional characterization of the thi1 promoter region from Arabidopsis thaliana

The Arabidopsis thaliana THI1 protein is involved in thiamine biosynthesis and is targeted to both chloroplasts and mitochondria by N-terminal control regions. To investigate thi1 expression, a series of thi1 promoter deletions were fused to the beta-glucuronidase (GUS) reporter gene. Transgenic plants were generated and expression patterns obtained under different environmental conditions. The results show that expression derived from the thi1 promoter is detected early on during development and continues throughout the plant's life cycle. High levels of GUS expression are observed in both shoots and roots during vegetative growth although, in roots, expression is restricted to the vascular system. Deletion analysis of the thi1 promoter region identified a region that is responsive to light. The smallest fragment (designated Pthi322) encompasses 306 bp and possesses all the essential signals for tissue specificity, as well as responsiveness to stress conditions such as sugar deprivation, high salinity, and hypoxia.     

Colour discrimination in the black-tufted-ear marmoset (Callithrix penicillata): ecological implications

The dietary diversity of marmosets is substantial, which may reflect differences in their colour vision. This study examined the colour discrimination ability of a gummivore/insectivore callitrichid, Callithrix penicillata, which inhabits the Brazilian cerrado (bush savanna). A series of ecologically relevant tasks, involving a behavioural paradigm of discrimination learning in semi-natural conditions and the usage of ecologically relevant stimuli, was executed. Three marmosets, 2 males and a female, behaved like human dichromats, showing an impaired performance when orange and green stimuli had to be discriminated. In contrast, 2 females resembled human trichromats, discriminating those kinds of pairs. Our data suggest that Callithrix penicillata presents a polymorphic trichromacy, with dichromatic males and dichromatic or trichromatic females.     

Caspase-8 activity prevents type 2 cytokine responses and is required for protective T cell-mediated immunity against Trypanosoma cruzi infection

During Trypanosoma cruzi infection, T cells up-regulate caspase-8 activity. To assess the role of caspase-8 in T cell-mediated immunity, we investigated the effects of caspase-8 inhibition on T cells in viral FLIP (v-FLIP) transgenic mice. Compared with wild-type controls, increased parasitemia was observed in v-FLIP mice infected with T. cruzi. There was a profound decrease in expansion of both CD4 and CD8 T cell subsets in the spleens of infected v-FLIP mice. We did not find differences in activation ratios of T cells from transgenic or wild-type infected mice. However, the numbers of memory/activated CD4 and CD8 T cells were markedly reduced in v-FLIP mice, possibly due to defective survival. We also found decreased production of IL-2 and increased secretion of type 2 cytokines, IL-4 and IL-10, which could enhance susceptibility to infection. Similar, but less pronounced, alterations were observed in mice treated with the caspase-8 inhibitor, zIETD. Furthermore, blockade of caspase-8 by zIETD in vitro mimicked the effects observed on T. cruzi infection in vivo, affecting the generation of activated/memory T cells and T cell cytokine production. Caspase-8 is also required for NF-kappaB signaling upon T cell activation. Blockade of caspase-8 by either v-FLIP expression or treatment with zIETD peptide decreased NF-kappaB responses to TCR:CD3 engagement in T cell cultures. These results suggest a critical role for caspase-8 in the establishment of T cell memory, cell signaling, and regulation of cytokine responses during protozoan infection.     

Drosophila melanogaster P Transposable Elements: Mechanisms of Transposition and Regulation

The molecular mechanisms that control P element transposition and determine its tissue specificity remain incompletely understood, although much information has been compiled about this element in the last decade. This review summarizes the currently available information about P element transposition, P-M hybrid dysgenesis and P cytotype features, P element-encoded repressors, and regulation of transposition.     

Crystallization and preliminary X-ray diffraction analysis of an acidic phospholipase A(2) complexed with p-bromophenacyl bromide and alpha-tocopherol inhibitors at 1.9- and 1.45-A resolution

An acidic phospholipase A(2) (PLA(2)) isolated from Bothrops jararacussu snake venom was crystallized with two inhibitors: alpha-tocopherol (vitamin E) and p-bromophenacyl bromide (BPB). The crystals diffracted at 1.45- and 1.85-A resolution, respectively, for the complexes with alpha-tocopherol and p-bromophenacyl bromide. The crystals are not isomorphous with those of the native protein, suggesting the inhibitors binding was successful and changes in the quaternary structure may have occurred.