Altered synaptic glutamate homeostasis contributes to cognitive decline in young APP/PSEN1 mice.

Non-convulsive epileptiform activity is a common and under-studied comorbidity of Alzheimer's disease that may significantly contribute to onset of clinical symptoms independently of other neuropathological features such as ß-amyloid deposition. We used repeated treatment with low dose kainic acid (KA) to trigger sub-threshold epileptiform activity in young (less than 6 months) wild-type (WT) and APP/PSEN1 mice to test the role of disruption to the glutamatergic system in epileptiform activity changes and the development of memory deficits. Short-term repeated low-dose KA (five daily treatments with 5 mg/kg, IP) impaired long-term potentiation in hippocampus of APP/PSEN1 but not WT mice. Long-term repeated low-dose KA (fourteen weeks of bi-weekly treatment with 7.5-10 mg/kg) led to high mortality in APP/PSEN1 mice. KA treatment also impaired memory retention in the APP/PSEN1 mice in a Morris water maze task under cognitively challenging reversal learning conditions where the platform was moved to a new location. Four weeks of bi-weekly treatment with 5 mg/kg KA also increased abnormal spike activity in APP/PSEN1 and not WT mice but did not impact sleep/wake behavioral states. These findings suggest that hyperexcitability in Alzheimer's disease may indeed be an early contributor to cognitive decline that is independent of heavy ß-amyloid-plaque load, which is absent in APP/PSEN1 mice under 6 months of age.

Solar flare acceleration of solar wind: influence of active region magnetic field.

The direction of the photospheric magnetic field at the site of a solar flare is a good predictor of whether the flare will accelerate solar wind plasma. If the field has a southward component, high-speed solar wind plasma is usually observed near the earth about 4 days later. If the field has a northward component, such high-speed solar wind is almost never observed. Southward-field flares may then be expected to have much larger terrestrial effects than northward flares.

Origin of the warped heliospheric current sheet.

The warped heliospheric current sheet for early 1976 is calculated from the observed photospheric magnetic field by a potential field method. Comparisons with measurements of the interplanetary magnetic field polarity for early 1976 obtained at several locations in the heliosphere by Helios 1, Helios 2, Pioneer 11, and at the earth show a rather detailed agreement between the computed current sheet and the observations. It appears that the large-scale structure of the warped heliospheric current sheet is determined by the structure of the photospheric magnetic field and that "ballerina skirt" effects may add small-scale ripples.

Interplanetary Magnetic Field Polarity and the Size of Low-Pressure Troughs Near 180{degrees}W Longitude.

When the interplanetary magnetic field is directed away from the sun, the area of wintertime low-pressure (300-millibar) troughs near 180 degrees W longitude is significantly larger than when the field is toward the sun. This relation persists during most of the winters of 1951 to 1973.

Solar structure and terrestrial weather.

If there is indeed an effect of the variable sun on the weather, the physical cause for it remains quite elusive (12). We should keep in mind the possibility that there may be several causes and several effects. The situation may change through the 11-year sunspot cycle and the 22-year solar magnetic cycle, as well as on longer time scales. Work is proceeding at a lively pace at the institutions mentioned in this article and at many others around the world. The Soviet Union has long had considerably more workers interested in this field than has any other country. A bilateral agreement between the Soviet Union and the United States has considerably increased the interactions between workers interested in this subject, including an exchange of extended visits between the two countries. A detailed knowledge of solar causes of geomagnetic activity is only now beginning to emerge after many years of scientific efforts. This suggests that a possible successful solution to the sun-weather problem will require a similar magnitude of effort. We look forward with interest and optimism to the results of the next few years.

The spiral interplanetary magnetic field: a polarity and sunspot cycle variation.

Spacecraft observations near the earth of the average direction of the interplanetary magnetic field during the sunspot maximum year 1968 showed a deviation from the spiral field of Parker's classical description. The included angle between the average field direction when the field polarity was away from the sun and the average direction when the field polarity was toward the sun was 168 degrees , rather than 180 degrees as predicted by Parker. This effect appears to have a sunspot cycle variation.

Solar Magnetic Sector Structure: Relation to Circulation of the Earth's Atmosphere.

The solar magnetic sector structure appears to be related to the average area of high positive vorticity centers (low-pressure troughs) observed during winter in the Northern Hemisphere at the 300-millibar level. The average area of high vorticity decreases (low-pressure troughs become less intense) during a few days near the times at which sector boundaries are carried past the earth by the solar wind. The amplitude of the effect is about 10 percent.