The Effects of L(+), D(-), and DL-2-amino-4-phosphonobutyrate (APB) on Electroretinogram and Ganglopn Cell Activity in the Cat Retina

L(+)-, D(-)-, or DL-2-amino-4-phosphonobutyric acid (APB; 2.5- 16 μmol) were injected into the vitreous body of anesthetized adult cats. The retina was stimulated by diffuse square wave light flashes (10- 60 ms). The flash-induced electroretinogram (ERU) and responses of single retinal ganglion cells (RGC) were recorded simultaneously. Intravitreal injection of L(+)APB led to a decrease in the ERG b-wave amplitude and the unmasking of the a-wave. The magnitude and rate of the b-wave reduction were different for the two enantiomers. The threshold dose of D(-)APB was 6 times higher than for L(+)APB. L(+)APB (8.2 ± 1.6 μmol; n=7) decreased the b-wave with an average time constant r = 88.5 min, D(-)APB (13.2 ± 1.1 μmol; n=6) with r = 357.1 min, and DL-APB (8.35 ± 1.1 μmol; n=5) with r = 101.0 min. Concomitant with the reduction of the b-wave, L(+)APB (2.7μmol) inhibited both the spontaneous and light-evoked firing in ON-center ganglion cells. The threshold doses of L(+), D(-) and DL-APB for inhibition of spontaneous adivity and the light response in ON-center cells paralleled those in reducing the ERU h-wave. Low doses of L(+)APB or DL-APB that were effective in blockng ON-center cell activity caused only very small changes in the activity of OFF-center ganglion cells. However, high doses of L(+)APB (≥8.2μmol) or DL-APB (≥13.7 μmol) also decreased the spontaneous and light-evoked activity in OFF-center RGC and first shortened than prolonged the light-induced inhibition of OFF-center RGC.Whitehall Foundation (S93-24

Level density and gamma strength function in 162-Dy from inelastic 3-He scattering

Complementary measurements have been performed for the level density and gamma strength function in 162-Dy using inelastic 3-He scattering. Comparing these results to previous measurements using the 163-Dy(3-He,alpha) reaction, reveals that the measured quantities above 1.5 MeV do not depend significantly on the nuclear reaction chosen.Comment: 15 pages, including 7 figure

Community Ecology and Capacity: Advancing Environmental Communication Strategies among Diverse Stakeholders

1. Introduction Many socioeconomically and geographically diverse communities in the United States have been challenged by occurrences of environmental contamination and the related complex public health issues. The investigations associated with such concerns have traditionally been the responsibility of governmental agencies. Communities facing potential environmental exposures often believe that government-based environmental agencies are not adequately addressing their concerns regarding risk, thus resulting in their misunderstanding and distrust of the regulatory process. A schism develops whereby the community perceives that government is either not doing enough to address their concerns and/or are being influenced by the relevant industry. The governmental agencies involved perceive that the community possesses an inaccurate or irrational perception of the potential risks. As a result, a stressful relationship often arises. Recommendations for effective risk communication have been developed and published (Covello & Sandman, 2001; Hance et al., 1989; Sandman, 1989). Research has also demonstrated the importance of developing relationships among stakeholders and its impact on information delivery and reception (ATSDR, 2004). Given that stakeholder groups perceive risk differently, it is imperative for each group to appreciate the viewpoints of all involved to engage in effective dialog (Park et al., 2001; Tinker et al., 2001). Cox (2006) defines environmental communication as “…the pragmatic and constitutive vehicle for our understanding of the environment as well as our relationships to the natural world; it is the symbolic medium that we use in constructing environmental problems and negotiating society’s different responses to them.” Although opportunities for public participation in environmental assessments have greatly increased, the environmental communication process among key stakeholders needs further evaluation (Charnley & Engelbert, 2005; McKinney & Harmon, 2002). The purpose of this chapter is to describe an evaluative process to develop and propose recommendations that could improve the environmental communication that occurs among diverse stakeholders, such as an environmental regulation and protection agency, waste disposal and energy producing facilities, community activists and the general public. Two case studies will be presented; the first describes the management of environmental permitting decisions in several disparate communities; and the second describes the management and perception of health risks from a single-owner waste-to-energy facility in two distinct communities. To accomplish this goal, this chapter will: 1.) examine how a state environmental agency and waste disposal and energy producing facilities describe their environmental communication experiences regarding various permitting operations and the risk perceptions of the impacted communities; 2.) identify effective communication methods; 3.) discuss the strengths and limitations of these activities; and 4.) propose recommendations for practitioners to advance environmental communication strategies among these key stakeholders

Level density and thermal properties in rare earth nuclei

A convergent method to extract the nuclear level density and the gamma-ray strength function from primary gamma-ray spectra has been established. Thermodynamical quantities have been obtained within the microcanonical and canonical ensemble theory. Structures in the caloric curve and in the heat capacity curve are interpreted as fingerprints of breaking of Cooper pairs and quenching of pairing correlations. The strength function can be described using models and common parameterizations for the E1, M1 and pygmy resonance strength. However, a significant decrease of the pygmy resonance strength at finite temperatures has been observed.Comment: 15 pages including 8 figures. Proceedings article for the conference Nuclear Structure and Related Topics, Dubna, Russia, June 6-10, 200

Barnes Hospital Bulletin

https://digitalcommons.wustl.edu/bjc_barnes_bulletin/1205/thumbnail.jp

Saccade learning with concurrent cortical and subcortical basal ganglia loops

The Basal Ganglia is a central structure involved in multiple cortical and subcortical loops. Some of these loops are believed to be responsible for saccade target selection. We study here how the very specific structural relationships of these saccadic loops can affect the ability of learning spatial and feature-based tasks. We propose a model of saccade generation with reinforcement learning capabilities based on our previous basal ganglia and superior colliculus models. It is structured around the interactions of two parallel cortico-basal loops and one tecto-basal loop. The two cortical loops separately deal with spatial and non-spatial information to select targets in a concurrent way. The subcortical loop is used to make the final target selection leading to the production of the saccade. These different loops may work in concert or disturb each other regarding reward maximization. Interactions between these loops and their learning capabilities are tested on different saccade tasks. The results show the ability of this model to correctly learn basic target selection based on different criteria (spatial or not). Moreover the model reproduces and explains training dependent express saccades toward targets based on a spatial criterion. Finally, the model predicts that in absence of prefrontal control, the spatial loop should dominate