Evidence for the transmission of information through electric potentials in injured avocado trees

Electrical excitability and signaling, frequently associated with rapid responses to environmental stimuli, have been documented in both animals and higher plants. The presence of electrical potentials (EPs), such as action potentials (APs) and variation potentials (VPs), in plant cells suggests that plants make use of ion channels to transmit information over long distances. The reason why plants have developed pathways for electrical signal transmission is most probably the necessity to respond rapidly, for example, to environmental stress factors.We examined the nature and specific characteristics of the electrical response to wounding in the woody plant Persea americana (avocado). Under field conditions, wounds can be the result of insect activity, strong winds or handling injury during fruit harvest. Evidence for extracellular EP signaling in avocado trees after mechanical injury was expressed in the form of variation potentials. For tipping and pruning, signal velocities of 8.7 and 20.9 cm/s, respectively, were calculated, based on data measured with Ag/AgCl microelectrodes inserted at different positions of the trunk. EP signal intensity decreased with increasing distance between the tipping and pruning point and the electrode. Recovery time to pre-tipping or pre-pruning EP values was also affected by the distance and signal intensity from the tipping or pruning point to the specific electrode position. Real time detection of remote EP signaling can provide an efficient tool for the early detection of insect attacks, strong wind damage or handling injury during fruit harvest.Our results indicate that electrical signaling in avocado, resulting from microenvironment modifications, can be quantitatively related to the intensity and duration of the stimuli, as well as to the distance between the stimuli site and the location of EP detection. These results may be indicative of the existence of a specific kind of proto-nervous system in plants.     

Effect of pollination and fertilization on the expression of genes related to floral transition, hormone synthesis and berry development in grapevine

In the present work, the effect of assisted fertilization on anatomical, morphological and gene expression changes occurring in carpels and during early stages of berry development in Vitis vinifera were studied. Inflorescences were emasculated before capfall, immediately manually pollinated (EP) and fruit development was compared to emasculated but non-pollinated (ENP) and self-pollinated inflorescences (NESP). The diameter of berries derived from pollinated flowers (EP and NESP) was significantly higher than from non-pollinated flowers (ENP) at 21 days after emasculation/pollination (DAE), and a rapid increase in the size of the inner mesocarp, together with the presence of an embryo-like structure, were observed. The expression of gibberellin oxidases (GA20ox and GA2ox), anthranilate synthase (related to auxin synthesis) and cytokinin synthase coding genes was studied to assess the relationship between hormone synthesis and early berry development, while flower patterning genes were analyzed to describe floral transition. Significant expression changes were found for hormone-related genes, suggesting that their expression at early stages of berry development (13 DAE) is related to cell division and differentiation of mesocarp tissue at a later stage (21 DAE). Expression of hormone-related genes also correlates with the expression of VvHB13, a gene related to mesocarp expansion, and with an increased repression of floral patterning genes (PISTILLATA and TM6), which may contribute to prevent floral transition inhibiting fruit growth before fertilization takes place.     

It takes guts to grow a brain: Increasing evidence of the important role of the intestinal microflora in neuro- and immune-modulatory functions during development and adulthood

A new study entitled "Normal gut microbiota modulates brain development and behavior", published in the Proceedings of the National Academy of Sciences, requires that we reconsider the notion that the brain is an immune-privileged site. The authors demonstrate that intestinal microbiota must be present within a set time-frame for normal synaptogenesis to occur in the brain. In the absence of intestinal microbiota, histopathological and behavioral abnormalities arise. These observations necessitate a new look at the many interconnections of the immune system and the brain, suggesting new frontiers for research and new therapeutic strategies for neurodevelopmental diseases.     

Glutathione transferase mu 2 protects glioblastoma cells against aminochrome toxicity by preventing autophagy and lysosome dysfunction

U373MG cells constitutively express glutathione S-transferase mu 2 (GSTM2) and exhibit ³H-dopamine uptake, which is inhibited by 2 µM of nomifensine and 15 µM of estradiol. We generated a stable cell line (U373MGsiGST6) expressing an siRNA against GSTM2 that resulted in low GSTM2 expression (26% of wild-type U373MG cells). A significant increase in cell death was observed when U373MGsiGST6 cells were incubated with 50 µM purified aminochrome (18-fold increase) compared with wild-type cells. The incubation of U373MGsiGST6 cells with 75 µM aminochrome resulted in the formation of autophagic vacuoles containing undigested cellular components, as determined using transmission electron microscopy. A significant increase in autophagosomes was determined by measuring endogenous LC3-II, a significant decrease in cell death was observed in the presence of bafilomycin A₁, and a significant increase in cell death was observed in the presence of trehalose. A significant increase in LAMP2 immunostaining was observed, a significant decrease in bright red fluorescence of lysosomes with acridine orange was observed, and bafilomycin A₁ pretreatment reduced the loss of lysosome acidity. A significant increase in cell death was observed in the presence of lysosomal protease inhibitors. Aggregation of TUBA/α-tubulin (tubulin, α) and SQSTM1 protein accumulation were also observed. Moreover, a significant increase in the number of lipids droplets was observed compared with U373MG cells with normal expression of GSTM2. These results support the notion that GSTM2 is a protective enzyme against aminochrome toxicity in astrocytes and that aminochrome cell death in U373MGsiGST6 cells involves autophagic-lysosomal dysfunction.     

A Novel Method to Evaluate the Community Built Environment Using Photographs – Environmental Profile of a Community Health (EPOCH) Photo Neighbourhood Evaluation Tool

Background

Previous research has shown that environments with features that encourage walking are associated with increased physical activity. Existing methods to assess the built environment using geographical information systems (GIS) data, direct audit or large surveys of the residents face constraints, such as data availability and comparability, when used to study communities in countries in diverse parts of the world. The aim of this study was to develop a method to evaluate features of the built environment of communities using a standard set of photos. In this report we describe the method of photo collection, photo analysis instrument development and inter-rater reliability of the instrument.

Methods/Principal Findings

A minimum of 5 photos were taken per community in 86 communities in 5 countries according to a standard set of instructions from a designated central point of each community by researchers at each site. A standard pro forma derived from reviewing existing instruments to assess the built environment was developed and used to score the characteristics of each community. Photo sets from each community were assessed independently by three observers in the central research office according to the pro forma and the inter-rater reliability was compared by intra-class correlation (ICC). Overall 87% (53 of 60) items had an ICC of ≥0.70, 7% (4 of 60) had an ICC between 0.60 and 0.70 and 5% (3 of 60) items had an ICC ≤0.50.

Conclusions/Significance

Analysis of photos using a standardized protocol as described in this study offers a means to obtain reliable and reproducible information on the built environment in communities in very diverse locations around the world. The collection of the photographic data required minimal training and the analysis demonstrated high reliability for the majority of items of interest.     

Non-equivalent Ligand Selectivity of Agonist Sites in (α4β2)2α4 Nicotinic Acetylcholine Receptors: A KEY DETERMINANT OF AGONIST EFFICACY*

The α4β2 nicotinic acetylcholine receptor (nAChR) is the most abundant nAChR type in the brain, and this receptor type exists in alternate (α4β2)₂α4 and (α4β2)₂β2 forms, which are activated by agonists with strikingly differing efficacies. Recent breakthroughs have identified an additional operational agonist binding site in the (α4β2)₂α4 nAChR that is responsible for the signature sensitivity of this receptor to activation by agonists, yet the structural mechanisms determining agonist efficacy at this receptor type are not yet fully understood. In this study, we characterized the ligand selectivity of the individual agonist sites of the (α4β2)₂α4 nAChR to determine whether differences in agonist selectivity influence agonist efficacy. Applying the substituted cysteine accessibility method to individual agonist sites in concatenated (α4β2)₂α4 receptors, we determined the agonist selectivity of the agonist sites of the (α4β2)₂α4 receptor. We show that (a) accessibility of substituted cysteines to covalent modification by methanesulfonate reagent depends on the agonist site at which the modification occurs and (b) that agonists such as sazetidine-A and TC-2559 are excluded from the site at the α4/α4 interface. Given that additional binding to the agonist site in the α4/α4 interface increases acetylcholine efficacy and that agonists excluded from the agonist site at the α4/α4 interface behave as partial agonists, we conclude that the ability to engage all agonist sites in (α4β2)₂α4 nAChRs is a key determinant of agonist efficacy. The findings add another level of complexity to the structural mechanisms that govern agonist efficacy in heteromeric nAChRs and related ligand-gated ion channels.