SDF1 Antagonism of Axonal Repellents Requires Multiple G Protein Components and an Adam Metalloprotease

@font-face { font-family: Times New Roman ; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Times New Roman ; }table.MsoNormalTable { font-size: 10pt; font-family: Times New Roman ; }div.Section1 { page: Section1; } Growth cones of developing axons navigate by interpreting signals from multiple cues. Some of these are the familiar guidance cues netrin, semaphorin, slit, and ephrin. Growth cones are also influenced by GPCR ligands, including neurotransmitters such as glutamate and chemokines such as SDF1. Previous work from our lab demonstrated that either glutamate or SDF1, acting through their receptors mGluR1 or CXCR4, respectively, can reduce growth cone responsiveness to repellent cues. This effect is pertussis toxin-sensitive, implicating Gai/o proteins, yet dependent on increased cAMP, implicating Gas proteins. The antirepellent effect of SDF1 could also be mimicked by inhibition of Rho, suggesting that inhibition of Rho is a component of the antirepellent pathway. Here, I demonstrate that SDF1 antirepellent activity is blocked by peptides or proteins targeting Gai, Gaq, or Gbg. This suggests that multiple G protein components are required for SDF1 signaling. I also show that SDF1 antirepellent activity is mimicked by constitutively active forms of Gaq, Gai, or Gas. This suggests that higher-than-physiological levels of individual G protein components can substitute for a combination of G protein components in antirepellent signaling. A role for Gaq in antirepellent signaling is further supported by the ability of a phospholipase C (PLC) inhibitor to block the SDF1 antirepellent effect, consistent with Gaq’s canonical activation of PLC. My work also reveals an alternate mechanism for SDF1-induced antagonism of repellent signaling. I show that the metalloprotease ADAM10 can cleave the repellent receptor neuropilin-1. Further, SDF1 antirepellent activity is blocked by either the metalloprotease inhibitor TAPI-2 or a dominant-negative ADAM10. Thus, inhibitory shedding of repellent receptors may contribute to the antirepellent effect. Previous work has shown that the antirepellent effect is mimicked by pharmacologically increased cAMP or blocked by a cAMP antagonist. TAPI-2 does not block the antirepellent effects of a cAMP analogue, suggesting that ADAM activation belongs to a separate pathway not downstream of cAMP. This work supports a model wherein SDF1/CXCR4 activates multiple G protein components to both increase cAMP and activate ADAM10. This would reduce sensitivity to repellents through inactivation of Rho and clearing of repellent receptors from the growth cone surface

Correlation of the use of computers by education faculty with national standards for preservice students

The purpose of this research study was to provide information to faculty, administrators and state departments of education about the level of integration of computer technology into teacher education programs. The stated problem of this research was to determine the correlation of the use of computers by education faculty with national standards for preservice teachers. A review of the literature identified the continuing growth of computer use and a growing acceptance of national standards for computer literacy in K--12 and higher education settings. To determine the extent of computer use among education faculty, a three-part survey was developed. It including a Likert-type scale based on technology-use standards developed by the International Society for Technology in Education, questions regarding teaching experience and computer skills, and open-ended questions allowing for input on support for or obstacles to the integration of technology in the participating institutions. The study included only programs in Vermont which certified students to teach in K--12 settings. Surveys were sent to private and state institutions, with a total return rate of 46%.;Once data gathering was completed, analysis was done using JMPin, a version of SAS. Data were analyzed using descriptive statistics, and significance was tested using Pearson\u27s product-moment correlation for continuous data and chi-squares for ordinal data. Faculty were asked to what degree they modeled and/or required the specific standards for preservice teachers. Of those who responded, 83% reported modeling the standards to a low to moderate degree, while 90% reported requiring the standards at a low to moderate degree. Analysis of the correlation between teaching experience and the modeling and requiring of the standards showed little significance. There was a positive correlation to the faculty\u27s rating of their own computer skills. The open-ended questions brought forth comments including appreciation of strong institutional support, and concerns about technology training and time to use the skills learned. The results indicated that there were faculty at all the colleges who were modeling and requiring technology skills, which are now being required for certification in Vermont and 42 other states

Neighborhood Analyses Of Canopy Tree Competition Along Environmental Gradients In New England Forests

We use permanent-plot data from the USDA Forest Service's Forest Inventory and Analysis (FIA) program for an analysis of the effects of competition on tree growth along environmental gradients for the 14 most abundant tree species in forests of northern New England, USA. Our analysis estimates actual growth for each individual tree of a given species as a function of average potential diameter growth modified by three sets of scalars that quantify the effects on growth of (1) initial target tree size (dbh), (2) local environmental conditions, and (3) crowding by neighboring trees. Potential growth of seven of the 14 species varied along at least one of the two environmental axes identified by an ordination of relative abundance of species in plots. The relative abundances of a number of species were significantly displaced from sites where they showed maximum potential growth. In all of these cases, abundance was displaced to the more resource-poor end of the environmental gradient (either low fertility or low moisture). The pattern was most pronounced among early successional species, whereas late-successional species reached their greatest abundance on sites where they also showed the highest growth in the absence of competition. The analysis also provides empirical estimates of the strength of intraspecific and interspecific competitive effects of neighbors. For all but one of the species, our results led us to reject the hypothesis that all species of competitors have equivalent effects on a target species. Most of the individual pairwise interactions were strongly asymmetric. There was a clear competitive hierarchy among the four most shade-tolerant species, and a separate competitive hierarchy among the shade-intolerant species. Our results suggest that timber yield following selective logging will vary dramatically depending on the configuration of the residual canopy, because of interspecific variation in the magnitude of both the competitive effects of different species of neighbors and the competitive responses of different species of target trees to neighbors. The matrix of competition coefficients suggests that there may be clear benefits in managing for specific mixtures of species within local neighborhoods within stands

Social cognition and African American men: The roles of perceived discrimination and experimenter race on task performance

The Social Cognition Psychometric Evaluation (SCOPE) study consists of a battery of eight tasks selected to measure social-cognitive deficits in individuals with schizophrenia. The battery is currently in a multisite validation process. While the SCOPE study collects basic demographic data, more nuanced race-related factors might artificially inflate cross-cultural differences in social cognition. As an initial step, we investigated whether race, independent of mental illness status, affects performance on the SCOPE battery. Thus, we examined the effects of perceived discrimination and experimenter race on the performance of 51 non-clinical African American men on the SCOPE battery. Results revealed that these factors impacted social cognitive task performance. Specifically, participants performed better on a skills-based task factor in the presence of Black experimenters, and frequency of perceived racism predicted increased perception of hostility in negative interpersonal situations with accidental causes. Thus, race-related factors are important to identify and explore in the measurement of social cognition in African Americans

Inferring controls on the epidemiology of beech bark disease from spatial patterning of disease organisms

1 Spatial pattern in the distribution and abundance of organisms is an emergent property of collective rates of reproduction, survival and movement of individuals in a heterogeneous environment. 2 The form, intensity and scale of spatial patterning can be used to test hypotheses regarding the relative importance of candidate processes to population dynamics. 3 Using 84 plots across eastern North America, we studied populations of two associated plant parasites, the invasive felted beech scale Cryptococcus fagisuga Lind. and the native Neonectria fungi, which together cause beech bark disease (BBD). 4 We evaluated spatial patterns at the scales of trees within stands, stands within the forest and forests within the landscape to examine four hypothetically important factors in the ecology of the disease: (i) local contagion within stands; (ii) regional contagion, or among patch infection–reinfection dynamics; (iii) variation in host susceptibility linked to genetic and/or environmental heterogeneity; and (iv) climate effects on population growth of BBD organisms. 5 Analyses revealed an unexpected lack of spatial aggregation in BBD populations among trees, stands and forests. This implies that propagule pressure is generally sufficiently high throughout the infested region of North America such that neither trees nor stands are spared from the disease by dispersal limitations of the disease agents. Furthermore, variation in tree and stand level susceptibility has minimal impact on BBD dynamics and climate is not a conspicuous driver of abundance within the core range of BBD.This work was partially supported by the USDA Forest Service Northeastern Research Station, grant 04-JV-11242328-122.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1461-9563/hb2013ab201

Impact of soil and water conservation measuren on catchment hydrological response: a case in north Ethiopia

Impact studies of catchment management in the developing world rarely include detailed hydrological components. Here, changes in the hydrological response of a 200-ha catchment in north Ethiopia are investigated. The management included various soil and water conservation measures such as the construction of dry masonry stone bunds and check dams, the abandonment of post-harvest grazing, and the establishment of woody vegetation. Measurements at the catchment outlet indicated a runoff depth of 5 mm or a runoff coefficient (RC) of 1·6% in the rainy season of 2006. Combined with runoff measurements at plot scale, this allowed calculating the runoff curve number (CN) for various land uses and land management techniques. The pre-implementation runoff depth was then predicted using the CN values and a ponding adjustment factor, representing the abstraction of runoff induced by the 242 check dams in gullies. Using the 2006 rainfall depths, the runoff depth for the 2000 land management situation was predicted to be 26·5mm(RCD 8%), in line with current RCs of nearby catchments. Monitoring of the ground water level indicated a rise after catchment management. The yearly rise in water table after the onset of the rains (ΔT) relative to the water surplus (WS) over the same period increased between 2002-2003 (ΔT/WS D 3·4) and 2006 (ΔT/WS >11·1). Emerging wells and irrigation are other indicators for improved water supply in the managed catchment. Cropped fields in the gullies indicate that farmers are less frightened for the destructive effects of flash floods. Due to increased soil water content, the crop growing period is prolonged. It can be concluded that this catchment management has resulted in a higher infiltration rate and a reduction of direct runoff volume by 81% which has had a positive influence on the catchment water balance. © 2010 John Wiley & Sons, Ltd

SDF1-Induced Antagonism of Axonal Repulsion Requires Multiple G-Protein Coupled Signaling Components That Work in Parallel

SDF1 reduces the responsiveness of axonal growth cones to repellent guidance cues in a pertussis-toxin-sensitive, cAMP-dependent manner. Here, we show that SDF1's antirepellent effect can be blocked in embryonic chick dorsal root ganglia (DRGs) by expression of peptides or proteins inhibiting either Gαi, Gαq, or Gβγ. SDF1 antirepellent activity is also blocked by pharmacological inhibition of PLC, a common effector protein for Gαq. We also show that SDF1 antirepellent activity can be mimicked by overexpression of constitutively active Gαi, Gαq, or Gαs. These results suggest a model in which multiple G protein components cooperate to produce the cAMP levels required for SDF1 antirepellent activity

Intermediate-severity wind disturbance in mature temperate forests: legacy structure, carbon storage, and stand dynamics

Wind is one of the most important natural disturbances influencing forest structure, ecosystem function, and successional processes worldwide. This study quantifies the stand-scale effects of intermediate-severity windstorms (i.e., blowdowns) on (1) live and dead legacy structure, (2) aboveground carbon storage, and (3) tree regeneration and associated stand dynamics at four mature, mixed hardwood–conifer forest sites in the northeastern United States. We compare wind-affected forests to adjacent reference conditions (i.e., undisturbed portions of the same stands) 0–8 yr post-blowdown using parametric (ANOVA) and nonparametric (NMS ordination) analyses. We supplement inventory plots and downed coarse woody detritus (DCWD) transects with hemispherical photography to capture spatial variation in the light environment. Although recent blowdowns transferred a substantial proportion of live overstory trees to DCWD, residual live tree basal area was high (19–59% of reference areas). On average, the initial post-blowdown ratio of DCWD carbon to standing live tree carbon was 2.72 in blowdown stands and 0.18 in reference stands, indicating a large carbon transfer from live to dead pools. Despite these dramatic changes, structural complexity remained high in blowdown areas, as indicated by the size and species distributions of overstory trees, abundance of sound and rotten downed wood, spatial patterns of light availability, and variability of understory vegetation. Furthermore, tree species composition was similar between blowdown and reference areas at each site, with generally shade-tolerant species dominating across multiple canopy strata. Community response to intermediate-severity blowdown at these sites suggests a dynamic in which disturbance maintains late-successional species composition rather than providing a regeneration opportunity for shade-intolerant, pioneer species. Our findings suggest that intermediate-severity wind disturbances can contribute to stand-scale structural complexity as well as development toward late-successional species composition, at least when shade-tolerant regeneration is present pre-blowdown. Advance regeneration thus enhances structural and compositional resilience to this type of disturbance. This study provides a baseline for multi-cohort silvicultural systems designed to restore heterogeneity associated with natural disturbance dynamics