Low doses of ultraviolet radiation and oxidative damage induce dramatic accumulation of mitochondrial DNA replication intermediates,fork regression,and replication initiation shift

Mitochondrial DNA is prone to damage by various intrinsic as well as environmental stressors. DNA damage can in turn cause problems for replication, resulting in replication stalling and double-strand breaks, which are suspected to be the leading cause of pathological mtDNA rearrangements. In this study, we exposed cells to subtle levels of oxidative stress or UV radiation and followed their effects on mtDNA maintenance. Although the damage did not influence mtDNA copy number, we detected a massive accumulation of RNA:DNA hybrid–containing replication intermediates, followed by an increase in cruciform DNA molecules, as well as in bidirectional replication initiation outside of the main replication origin, O_H. Our results suggest that mitochondria maintain two different types of replication as an adaptation to different cellular environments; the RNA:DNA hybrid–involving replication mode maintains mtDNA integrity in tissues with low oxidative stress, and the potentially more error tolerant conventional strand-coupled replication operates when stress is high.     

Accumulation of the labdane diterpene Marrubiin in glandular trichome cells along the ontogeny of Marrubium vulgare plants

The content of the diterpene Marrubiin was assessed by GC-FID in leaves of Marrubium vulgare plants along their ontogeny. Maximum accumulation occurred just before flowering time and in fully expanded leaves. After feeding the plants with radio labeled [³H]-geranyl geranyl diphosphate, up to 70% of the radioactivity was recovered in HPLC-Rt coincidental with authentic Marrubiin, which was also characterized by GC-EIMS, thus confirming that the biosynthesis of Marrubiin proceeds through the 1-deoxy-D-xylulose-5-phosphate pathway. The major accumulation of radioactivity occurred in glandular trichome cells, and the product remained stable throughout.     

Influence of protein nutrition on calpain activity of mouse kidney: Modulation by calpastatin

The effect of protein depletion and refeeding with a normal diet on calpain activity was examined in mouse kidney soluble homogenate. In terms of units per gram of protein, it increased 2.9 times with depletion and decreased upon refeeding. After a DEAE-Sephacel chromatography, the homogenate yielded three enzymatic activities. Their sum, assessed as total calpain activity, was higher than the activity measured before fractionation and did not appreciably change during protein depletion and refeeding. Because the proportion of total activity displayed by the complete homogenate increased with depletion and decreased with refeeding, a low calpastatin content in depleted kidney was envisaged. This was confirmed by direct estimations: depleted kidney had 6 times less calpastatin compared to both normal and 16 h refed tissue. We concluded that a decrease in calpastatin content contributes to an increased calpain activity related to degradable protein in protein depleted kidney. In view of this, it seems not unlikely that the in vivo rate of protein breakdown depicted by kidney during protein depletion and refeeding is in part effected through modulation of the calpain proteolytic system. (Mol Cell Biochem 166: 95-99, 1997)     

PARP-1 Regulates Metastatic Melanoma through Modulation of Vimentin-induced Malignant Transformation

PARP inhibition can induce anti-neoplastic effects when used as monotherapy or in combination with chemo- or radiotherapy in various tumor settings; however, the basis for the anti-metastasic activities resulting from PARP inhibition remains unknown. PARP inhibitors may also act as modulators of tumor angiogenesis. Proteomic analysis of endothelial cells revealed that vimentin, an intermediary filament involved in angiogenesis and a specific hallmark of EndoMT (endothelial to mesenchymal transition) transformation, was down-regulated following loss of PARP-1 function in endothelial cells. VE-cadherin, an endothelial marker of vascular normalization, was up-regulated in HUVEC treated with PARP inhibitors or following PARP-1 silencing; vimentin over-expression was sufficient to drive to an EndoMT phenotype. In melanoma cells, PARP inhibition reduced pro-metastatic markers, including vasculogenic mimicry. We also demonstrated that vimentin expression was sufficient to induce increased mesenchymal/pro-metastasic phenotypic changes in melanoma cells, including ILK/GSK3-β-dependent E-cadherin down-regulation, Snail1 activation and increased cell motility and migration. In a murine model of metastatic melanoma, PARP inhibition counteracted the ability of melanoma cells to metastasize to the lung. These results suggest that inhibition of PARP interferes with key metastasis-promoting processes, leading to suppression of invasion and colonization of distal organs by aggressive metastatic cells.     

Dormancy in peach (Prunus persica L.) flower buds

Morphological studies were carried out with peach flower buds collected monthly in 1989 and 1990, from two months before leaf fall (7 March) until two to three weeks before bloom (7/8 August). Chilled (2–4°C for 30 days) and unchilled buds were exposed to 20 to 25°C, 100% RH and continuous light. Gibberellin A₃ (3 ng or 30 ng) was applied to some of the non-chilled cuttings at three days intervals. Then, 12, 19, and 26 days after they were planted, the buds were sampled and processed for histological studies. Cultured flower buds (chilled or unchilled) had accelerated anther and gynoecium morphogenesis after 12 days under controlled conditions, compared to buds processed immediately after collection from the field. Chilling treatment augmented the bud culture effect, while Gibberellin A₃ applications to the excised buds retarded bud morphogenesis to a stage comparable to that of buds collected directly from the field. This, suggests that the comparatively high levels of Gibberellin A_1/3 we previously found in mid winter [15, 18] could be at least one of the factors that controls floral bud dormancy by retarding anther and gynoecium development.     

Relation between Belief and Performance in Perceptual Decision Making

In an uncertain and ambiguous world, effective decision making requires that subjects form and maintain a belief about the correctness of their choices, a process called meta-cognition. Prediction of future outcomes and self-monitoring are only effective if belief closely matches behavioral performance. Equality between belief and performance is also critical for experimentalists to gain insight into the subjects'' belief by simply measuring their performance. Assuming that the decision maker holds the correct model of the world, one might indeed expect that belief and performance should go hand in hand. Unfortunately, we show here that this is rarely the case when performance is defined as the percentage of correct responses for a fixed stimulus, a standard definition in psychophysics. In this case, belief equals performance only for a very narrow family of tasks, whereas in others they will only be very weakly correlated. As we will see it is possible to restore this equality in specific circumstances but this remedy is only effective for a decision-maker, not for an experimenter. We furthermore show that belief and performance do not match when conditioned on task difficulty – as is common practice when plotting the psychometric curve – highlighting common pitfalls in previous neuroscience work. Finally, we demonstrate that miscalibration and the hard-easy effect observed in humans'' and other animals'' certainty judgments could be explained by a mismatch between the experimenter''s and decision maker''s expected distribution of task difficulties. These results have important implications for experimental design and are of relevance for theories that aim to unravel the nature of meta-cognition.     

Host-association as major driver of microbiome structure and composition in Red Sea seagrass ecosystems

The role of the microbiome in sustaining seagrasses has recently been highlighted. However, our understanding of the seagrass microbiome lacks behind that of other organisms. Here, we analyse the endophytic and total bacterial communities of leaves, rhizomes, and roots of six Red Sea seagrass species and their sediments. The structure of seagrass bacterial communities revealed that the 1% most abundant OTUs accounted for 87.9% and 74.8% of the total numbers of reads in sediment and plant tissue samples, respectively. We found taxonomically distinct bacterial communities in vegetated and bare sediments. Yet, our results suggest that lifestyle (i.e. free-living or host-association) is the main driver of bacterial community composition. Seagrass bacterial communities were tissue- and species-specific and differed from those of surrounding sediments. We identified OTUs belonging to genera related to N and S cycles in roots, and members of Actinobacteria, Bacteroidetes, and Firmicutes phyla as particularly enriched in root endosphere. The finding of highly similar OTUs in well-defined sub-clusters by network analysis suggests the co-occurrence of highly connected key members within Red Sea seagrass bacterial communities. These results provide key information towards the understanding of the role of microorganisms in seagrass ecosystem functioning framed under the seagrass holobiont concept.     

The 46359CT polymorphism of DNMT3B is associated with the risk of cervical cancer

Abnormal methylation is related to cancer development. Since DNMT3B is an enzyme that modulates genomic methylation, we hypothesized that genetic variants of the promoter DNMT3B may be associated with an increased risk of developing cervical cancer. Our aim was to investigate the association between ?579GT and 46359CT polymorphisms of DNMT3B and cervical cancer, high-grade squamous intraepithelial lesions (HSIL), and low-grade squamous intraepithelial lesions (LSIL). Samples from 200 healthy women and 130 women with squamous intraepithelial lesions (70 with cervical cancer, 30 with HSIL, and 30 with LSIL) were analyzed. Polymorphism genotyping was performed using PCR and restriction fragment length polymorphism. The ?579GT polymorphism was not associated with cervical cancer, HSIL, or LSIL. The CT genotype of 46359CT polymorphism was significantly associated with cervical cancer risk (OR 8.75, CI 1.27–374.1), whereas the TT genotype was associated with a significantly decreased risk of HSIL (OR 0.66, CI 0.01–0.32) and LSIL (OR 0.11, CI 0.026–0.45). Our results suggest that genotyping the 46359CT polymorphism in DNMT3B may help identify women who are genetically susceptible to cervical cancer development. Additional studies with larger sample sizes are necessary to confirm our findings.     

Summer staging areas of non-breeding Short-toed Snake Eagles Circaetus gallicus

Capsule Immature Short-toed Snake Eagles hatched in Spain leave their Sahelian wintering grounds to spend the summer in northern Africa.