Background: Tau is secreted unconventionally, possibly explaining increased CSF phosphotau levels in early AD. Results: M1C cells secrete selectively phosphorylated, exosomal tau. These characteristics in early AD CSF tau suggest that CSF tau is secreted, not shed from dead neurons. Conclusion: Tau secretion occurs early and may explain lesion spreading in AD. Significance: Secretion biomarkers may become revolutionary prospective AD diagnostics.

A method was developed and tested which is suitable for the routine determination of the reserve-potassium (reserve-K) level of soili.e., K which is plant-available but not exchangeable to 1M ammonium acetate. The method is simple, relatively quick, and uses 2 g soil and 20 ml 0.03M sodium tetraphenylboron (NaTPB) in 1M sodium chloride with a 16 h extraction time. The KTPB precipitated is dissolved in an acetone medium and analysed directly by atomic absorption spectrophotometry. The NaTPB method was compared with 4 other measurements of soil K status: New Zealand Ministry of Agriculture and Fisheries Quick Test for K (STK), K exchangeable to ammonium acetate by leaching (1(..,), boiling nitric acid extractable K (1(..), and K extracted by 0.05M barium acetate at pH 5.0. These methods were tested by correlation of the extraction results with dry matter yield, total K uptake, and % K in ryegrass (Lolium perenne L.) grown to exhaustion on 13 soils of varying K status. The new method was then validated against the same ryegrass parameters for a further 25 soils exhausted of K in a separate glasshouse trial. K TPB , the quantity of K extracted by the NaTPB method, was highly correlated with K uptake by ryegrass (n = 13, r 2 = 0.90***; n = 25, r 2 = 0.94***), with yield (n = 13, r 2 = 0.74***; n = 25, r 2 = 0.56***), and with % K in herbage (n = 13, r 2 = 0.77***; n = 25, r 2 = 0.85***). It was generally superior to the other K measurements in all correlations examined. The method is sensitive to changes in K status caused by K uptake by plants and can identify K uptake from soil reserves after minimum levels of 1(.., (or STK) are reached. K T PB levels are less likely to be affected by seasonal variation than are STK levels. The NaTPB method is not suited to very large batch sizes and would be best used as a supplement to STK level measurements to establish the reserve-K content of soil. The method determines shortto medium-term availability of K, rather than the long-term availability indicated by the K, level. It would be most useful for soils which have significant reserve-K and in the low-medium STK range « 8).

Pasture yield responses to potassium (K) fertiliser were measured at 13 sites which had low levels of exchangeable K but varying amounts of non-exchangeable K.

Adsorption-desorption isotherms for nitrogen, argon, ethyl chloride and water on a disordered kaolinite are reported. Hysteresis in the amount adsorbed was observed with each system, but hysteresis at pressures below monolayer saturation was found only with the two polar species. Depletion of surface hydroxyl groups by high-temperature vacuum outgassing and by treatment with trimethylchlorosilane caused a disproportionate decrease in the monolayer capacity for ethyl chloride, and the destruction of low pressure hysteresis with that adsorbate. Low pressure hysteresis in the amount adsorbed is attributed to structural hysteresis of the monolayer resulting from the rearrangement of the adsorbate film under the influence of polar surface groups.

No abstract