Activity-dependent adenosine release may be linked to activation of Na+-K+ ATPase : an in vitro rat study

In the brain, extracellular adenosine increases as a result of neuronal activity. The mechanisms by which this occurs are only incompletely understood. Here we investigate the hypothesis that the Na+ influxes associated with neuronal signalling activate the Na+-K+ ATPase which, by consuming ATP, generates intracellular adenosine that is then released via transporters. By measuring adenosine release directly with microelectrode biosensors, we have demonstrated that AMPA-receptor evoked adenosine release in basal forebrain and cortex depends on extracellular Na+. We have simultaneously imaged intracellular Na+ and measured adenosine release. The accumulation of intracellular Na+ during AMPA receptor activation preceded adenosine release by some 90 s. By removing extracellular Ca2+, and thus preventing indiscriminate neuronal activation, we used ouabain to test the role of the Na+-K+ ATPase in the release of adenosine. Under conditions which caused a Na+ influx, brief applications of ouabain increased the accumulation of intracellular Na+ but conversely rapidly reduced extracellular adenosine levels. In addition, ouabain greatly reduced the amount of adenosine released during application of AMPA. Our data therefore suggest that activity of the Na+-K+ ATPase is directly linked to the efflux of adenosine and could provide a universal mechanism that couples adenosine release to neuronal activity. The Na+-K+ ATPase-dependent adenosine efflux is likely to provide adenosine-mediated activity-dependent negative feedback that will be important in many diverse functional contexts including the regulation of sleep

Wakefulness affects synaptic and network activity by increasing extracellular astrocyte-derived adenosine

Loss of sleep causes an increase in sleep drive and deficits in hippocampal-dependent memory. Both of these responses are thought to require activation of adenosine A1 receptors (adorA1Rs) and release of transmitter molecules including ATP, which is rapidly converted to adenosine in the extracellular space, from astrocytes in a process termed gliotransmission. Although it is increasingly clear that astrocyte-derived adenosine plays an important role in driving the homeostatic sleep response and the effects of sleep loss on memory (Halassa et al., 2009; Florian et al., 2011), previous studies have not determined whether the concentration of this signaling molecule increases in response to wakefulness. Here, we show that the level of adorA1R activation increases in response to wakefulness in mice (Mus musculus). We found that this increase affected synaptic transmission in the hippocampus and modulated network activity in the cortex. Direct biosensor-based measurement of adenosine showed that the net extracellular concentration of this transmitter increased in response to normal wakefulness and sleep deprivation. Genetic inhibition of gliotransmission prevented this increase and attenuated the wakefulness-dependent changes in synaptic and network regulation by adorA1R. Consequently, we conclude that wakefulness increases the level of extracellular adenosine in the hippocampus and that this increase requires the release of transmitters from astroctyes

Influence of Gibberellic Acid and Indole-3-Acetic Acid on the Morphology and Population Dynamics of Eudorina elegans

Assuming optical density to be a function of population density, colorimetric techniques were used to determine the effects of two growth regulator substances, indole-3-acetic acid and gibberellic acid, on the morphology and population dynamics of Eudorina elegans. A tube of culture medium without organisms was used as a reference point to calibrate the colorimeter. Chemically-treated cultures and soil-water control cultures were compared to the reference reading and growth curves were plotted. Colony counts were made at the termination of the experiment and comparisons were made with the colorimeter readings. Results demonstrated gibberellic acid to be a promoter of cell division and/or growth in concentrations below 75 ppm and to be inhibitory at concentrations of 75 ppm and above. Indole-3-acetic acid produced little effect on populations at low concentrations and was strongly inhibitory above concentrations of 5 ppm

Monte Carlo Electron Trajectory Calculations of Electron Interactions in Samples with Special Geometries

Implementing a Monte Carlo simulation for application to electron sample interactions requires use of accurate treatments of elastic and inelastic scattering. In formulating a Monte Carlo simulation, careful testing must be carried out to ensure that the calculation yields sensible and useful results. A suitable testing procedure includes calculation of (1) electron backscatter coefficients as a function of atomic number, including any necessary adjustment of scattering parameters; (2) backscatter coefficients as a function of specimen tilt; (3) backscatter and transmission coefficients for thin foils; (4) backscattered electron energy distributions; (5) electron spatial distributions; and (6) x-rays, including x-ray depth distributions, and relative and absolute yields. Adapting a Monte Carlo simulation to a particular problem involving special sample geometry requires careful consideration of the interaction of the electron with the target. When the electron trajectory crosses a boundary, the segments of the trajectory in each phase must be calculated in a logical, stepwise fashion, allowing for modification of the step lengths due to variable scattering power in phases of different composition. The particular example of a planar boundary between phases of different composition is considered

Initial Findings on Visual Acuity Thresholds in an African Elephant (\u3cem\u3eLoxodonta africana\u3c/em\u3e)

There are only a few published examinations of elephant visual acuity. All involved Asian elephants (Elephas maximus) and found visual acuity to be between 8′ and 11′ of arc for a stimulus near the tip of the trunk, equivalent to a 0.50 cm gap, at a distance of about 2 m from the eyes. We predicted that African elephants (Loxodonta africana) would have similarly high visual acuity, necessary to facilitate eye-trunk coordination for feeding, drinking and social interactions. When tested on a discrimination task using Landolt-C stimuli, one African elephant cow demonstrated a visual acuity of 48′ of arc. This represents the ability to discriminate a gap as small as 2.75 cm in a stimulus 196 cm from the eye. This single-subject study provides a preliminary estimate of the visual acuity of African elephants

Fourth Symposium on Chemical Evolution and the Origin and Evolution of Life

This symposium was held at the NASA Ames Research Center, Moffett Field, California, July 24-27, 1990. The NASA exobiology investigators reported their recent research findings. Scientific papers were presented in the following areas: cosmic evolution of biogenic compounds, prebiotic evolution (planetary and molecular), early evolution of life (biological and geochemical), evolution of advanced life, solar system exploration, and the Search for Extraterrestrial Intelligence (SETI)

The X-33 Extended Flight Test Range

Development of an extended test range, with range instrumentation providing continuous vehicle communications, is required to flight-test the X-33, a scaled version of a reusable launch vehicle. The extended test range provides vehicle communications coverage from California to landing at Montana or Utah. This paper provides an overview of the approaches used to meet X-33 program requirements, including using multiple ground stations, and methods to reduce problems caused by reentry plasma radio frequency blackout. The advances used to develop the extended test range show other hypersonic and access-to-space programs can benefit from the development of the extended test range

Effects of Lineup Modality on Witness Credibility

Three experiments were conducted to explore the credibility of earwitness versus eyewitness testimony among American college students. Experiment 1 demonstrated that subjects were less likely to identify the perpetrator of a simulated crime in auditory lineups than in visual or auditory-visual lineups. In Experiment 2, subjects observed a videotaped witness from Experiment 1 make an identification. Contrary to actual accuracy data, subjects were as believing of the identifications made by auditory witnesses as they were of the identifications made by visual or auditory-visual witnesses. In Experiment 3, mock jurors in a simulated robbery trial believed auditory lineup identifications as much as they did visual or auditory-visual lineup identifications

Automatic Detection of Seizures with Applications

There are an estimated two million people with epilepsy in the United States. Many of these people do not respond to anti-epileptic drug therapy. Two devices can be developed to assist in the treatment of epilepsy. The first is a microcomputer-based system designed to process massive amounts of electroencephalogram (EEG) data collected during long-term monitoring of patients for the purpose of diagnosing seizures, assessing the effectiveness of medical therapy, or selecting patients for epilepsy surgery. Such a device would select and display important EEG events. Currently many such events are missed. A second device could be implanted and would detect seizures and initiate therapy. Both of these devices require a reliable seizure detection algorithm. A new algorithm is described. It is believed to represent an improvement over existing seizure detection algorithms because better signal features were selected and better standardization methods were used

Flashbulb Memories? The Effects of When the Initial Memory Report was Obtained

Why have some researchers found reports of flashbulb memories to be stable, while others have observed inconsistencies? Paradoxically, it appears that relatively long delays between event and initial documentation have produced greater consistency of participants\u27 reports. To investigate this directly, we collected the initial documentation of hearing about O.J. Simpson\u27s acquittal either five hours or one week after the acquittal was read. Observed consistency of memories varied as a function of documentation time; following an eight-week retention, the delayed reports were more consistent. The delayed group also reported fewer propositions in their initial documentation. We proposed a consolidation model to explain these results: during the days immediately following a newsworthy event, the narrative structure of these memories changes in that some details are forgotten. After this consolidation period, the memories may solidify. Thus, it may have been easier for the delayed group to provide consistent memories at the two intervals