Neuroprotection with the N-methyl-D-aspartate antagonist dizocilpine (MK-801) in a model of focal ischaemia

Ischaemic brain damage, due to cerebrovascular disease ("stroke"), head injury, cardiac arrest, surgery (cardiopulmonary bypass and intracranial) and perinatal hypoxia, is a major cause of death and disability in the western world. Stroke alone is the third most common cause of death after cancer and heart disease, accounting for some 10% of all deaths, approximately 60,000 per year in England and Wales. Recently there has been rapidly growing evidence supporting the "excitotoxic" theory of neuronal damage in ischaemia, in which excitatory amino acid neurotransmitters are implicated as agents of damage to ischaemic brain. Excitatory amino acid antagonists, in particular N-methyl-D-aspartate (NMDA) antagonists, have proved to be dramatically effective in the protection of brain parenchyma in experimental models of ischaemia, especially focal ischaemia. The role of excitatory amino acid neurotransm itters in ischaemia and the experimental evidence for amelioration of ischaemic brain damage by NMDA antagonists, is reviewed. A model of focal ischaemia in the rat is described, which can be used for assessing drugs that might be useful clinically. A method of volumetric analysis of infarct size using conventional histopathology is compared to a much cheaper and faster m ethod using the m itochondrial redox stain, 2,3,5,triphenyltetrazolium chloride (TTC). The later method can be used for the rapid screening of compounds, but it has limitations which are fully explored. The neuroprotective effects of the NMDA antagonist, dizocilpine (MK-801) in acute and chronic ischaemia are compared and the chronic model is used to establish a "dose response" and "therapeutic window" for dizocilpine. Hypertension is a major risk factor in stroke and the neuroprotective effects of dizocilpine are examined in both normotensive and spontaneously hypertensive strains of rat, with pure cortical and combined cortical and striatal lesions. Finally, release of neuron-specific enolase into the CSF is correlated with infarct size in dizocilpine treated and control animals with a view to the possible clinical use of NSE in the quantification of ischaemic damage

Processing and Transmission of Information

Contains reports on two research projects.National Aeronautics and Space Administration (Grant NsG-334)National Aeronautics and Space Administration (Grant NGR 22-009-304

A flexible flight display research system using a ground-based interactive graphics terminal

Requirements and research areas for the air transportation system of the 1980 to 1990's were reviewed briefly to establish the need for a flexible flight display generation research tool. Specific display capabilities required by aeronautical researchers are listed and a conceptual system for providing these capabilities is described. The conceptual system uses a ground-based interactive graphics terminal driven by real-time radar and telemetry data to generate dynamic, experimental flight displays. These displays are scan converted to television format, processed, and transmitted to the cockpits of evaluation aircraft. The attendant advantages of a Flight Display Research System (FDRS) designed to employ this concept are presented. The detailed implementation of an FDRS is described. The basic characteristics of the interactive graphics terminal and supporting display electronic subsystems are presented and the resulting system capability is summarized. Finally, the system status and utilization are reviewed

Temperature extremes: Effect on plant growth and development

AbstractTemperature is a primary factor affecting the rate of plant development. Warmer temperatures expected with climate change and the potential for more extreme temperature events will impact plant productivity. Pollination is one of the most sensitive phenological stages to temperature extremes across all species and during this developmental stage temperature extremes would greatly affect production. Few adaptation strategies are available to cope with temperature extremes at this developmental stage other than to select for plants which shed pollen during the cooler periods of the day or are indeterminate so flowering occurs over a longer period of the growing season. In controlled environment studies, warm temperatures increased the rate of phenological development; however, there was no effect on leaf area or vegetative biomass compared to normal temperatures. The major impact of warmer temperatures was during the reproductive stage of development and in all cases grain yield in maize was significantly reduced by as much as 80−90% from a normal temperature regime. Temperature effects are increased by water deficits and excess soil water demonstrating that understanding the interaction of temperature and water will be needed to develop more effective adaptation strategies to offset the impacts of greater temperature extreme events associated with a changing climate

Canopy Resistance as Affected by Soil and Meteorological Factors in Potato

Precision irrigation requires a method of quantifying the crop water status or root zone depletion of water to determine when and how much water to apply to the soil. Changes in canopy resistance (rc) and canopy temperatures have the potential of being used as a crop water status indicator for irrigation management. A study was conducted on potato (Solanum tuberosum L.) grown in northern Egypt at Shibin El-Kom on an alluvial loamy soil for winter (20 Sept. 2001 through 20 Jan. 2002) and spring (1 Feb. 2002 through 20 May 2002) seasons to determine if rc derived from energy balance and plant parameters could be used to determine the onset of water stress and the amount of water required to refill the soil profile. Diurnal rc was determined for well-watered conditions and achieved minimum values of 20 and 10 s m-1 at noontime during winter and spring periods, environmenrespectively. A power relationship of -0.86 for well-watered conditions was developed between rc and net radiation (Rn) at various plant growth stages. In deficit soil water conditions, rc increased linearly with decreasing available soil water (ASW), with a change in potato rc of 0.75 and 0.39 s m-1 per percentage ASW for 1 and 2 MJ m-2 h-1 of Rn at midgrowth, respectively. A ratio of actual/potential canopy resistance (rc/rcp) was derived to normalize the meteorological differences between growing seasons. This ratio was 2.5 when 50% of ASW was removed and can be used as a parameter to determine the need for irrigations using weather factors and canopy temperature. Canopy resistance increased linearly with increasing soil solution salinity, electrical conductivity, when the soil solution was above the threshold soil salinity value. A ratio of rc/rcp was found to normalize the effects of different environments across saline and water deficit conditions