A depletable pool of adenosine in area CA1 of the rat hippocampus

Adenosine plays a major modulatory and neuroprotective role in the mammalian CNS. During cerebral metabolic stress, such as hypoxia or ischemia, the increase in extracellular adenosine inhibits excitatory synaptic transmission onto vulnerable neurons via presynaptic adenosine A1 receptors, thereby reducing the activation of postsynaptic glutamate receptors. Using a combination of extracellular and whole-cell recordings in the CA1 region of hippocampal slices from 12- to 24-d-old rats, we have found that this protective depression of synaptic transmission weakens with repeated exposure to hypoxia, thereby allowing potentially damaging excitation to both persist for longer during oxygen deprivation and recover more rapidly on reoxygenation. This phenomenon is unlikely to involve A1 receptor desensitization or impaired nucleoside transport. Instead, by using the selective A1 antagonist 8-cyclopentyl-1,3-dipropylxanthine and a novel adenosine sensor, we demonstrate that adenosine production is reduced with repeated episodes of hypoxia. Furthermore, this adenosine depletion can be reversed at least partially either by the application of exogenous adenosine, but not by a stable A1 agonist, N6-cyclopentyladenosine, or by endogenous means by prolonged (2 hr) recovery between hypoxic episodes. Given the vital neuroprotective role of adenosine, these findings suggest that depletion of adenosine may underlie the increased neuronal vulnerability to repetitive or secondary hypoxia/ischemia in cerebrovascular disease and head injury

A Partial Magnetometer Survey of The Archaeological Conservancy’s Portion of the A. C. Saunders Site (41AN19)

The Texas Archeological Research Laboratory (TARL) at The University of Texas at Austin conducted a partial magnetometer survey of The Archaeological Conservancy-owned portion of the A. C. Saunders site (41AN19) during the period between 6-8 December 2005. This survey was sponsored by the Texas Department of Transportation Environmental Affairs Division (TxDOT/ENV) due to a proposed expansion of the right-of-way of U.S. Highway 175 and was conducted under a research design approved by The Archeological Conservancy and TxDOT/ENV. The work was conducted under the direction of Dale Hudler (Principal Investigator) from TARL with a joint TARL/Prewitt and Associates, Inc. field crew (Jonathan Jarvis, TARL and Tim Griffith, Prewitt and Associates, Inc.)

Analysis of Log Hauling Vehicle Accidents in the State of Georgia, USA, 1988–2004

Mechanical failure rates associated with logging vehicle accidents in Georgia are dramatically lower today than they were in 1988–1991 before these trucks became subject to random roadside inspections. Mechanical failure dropped by half for logging tractor-trailers (from 10.9% to 4.8%) and by two-thirds for logging trucks (from 12.9% to 4.2%). Mechanical failure is now the seventh most cited contributing factor in logging tractor-trailer accidents instead of first as it was prior to 1991. Specific types of mechanical failures have also declined sharply. Three potential failure items that are visually checked during roadside inspections – brakes, slick tires, and lights – have seen the most dramatic declines. Brake failure has dropped by two-thirds and improper lights as a factor have almost disappeared. Driver impairment due to use of alcohol or drugs today occurs in less than 0.5 percent of accidents. Factors associated with logging vehicle accidents today in Georgia closely resemble those associated with all trucking accidents generally. Accidents per million tons of wood consumed, however, has increased steadily from 11 in 1991 to 19 per million tons in 2003

VECTOR POTENTIAL FORMULATION FOR THE IMPEDANCE BOUNDARY CONDITION

The paper introduces a vector potential formulation applying the Impedance Boundary Condition for 3D eddy current problems involving muitiply connected regions with exterior circuit conditions