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Development of continental aridity has been linked to late Cenozoic global cooling, but the evidence is indirect, based on terrestrial loess deposits and eolian silt in marine sediments, whereas direct dating of the inception of arid landforms has been frustrated by a lack of suitable methods. Here we report the first age determination of a major arid-zone dune field, based on cosmogenic [sup.10]Be and [sup.26]Al measurements of drill cores from dunes in the Simpson Desert, central Australia. Results show that the dune field began to form ca. 1 Ma, whereas dating using quartz optically stimulated luminescence indicates episodic dune building during late Quaternary ice ages. Less intense desertification began earlier; the previous cosmogenic exposure dating showed that neighboring stony deserts began to form at the onset of Quaternary ice ages 2-4 Ma. Aridity deepened and the dune field formed when ice age cycles increased their amplitude and switched their periods from 40 k.y. to 100 k.y. ca. 1 Ma.

Stony deserts are durable indicators of aridity but until now have not been directly dated. Using [sup.21Ne] and [sup.10Be] produced in surface rocks by cosmic rays, we show that Australian stony deserts formed 2-4 Ma, at the time when global cooling initiated the Quaternary ice ages and intensified aridity-induced major landscape changes in central Australia. This is the first direct determination of stony desert ages, using a new method for determining cosmogenic [sup.21Ne] in the presence of various neon components from other sources. Keywords: late Cenozoic, stony deserts, silcrete, exposure age, cosmogenic Ne/Be.

The effects of sphingosine 1-phosphate (S-1-P) and lysophosphatidic acid (LPA) on glycogen phosphorylase stimulation were analyzed in freshly prepared and primary cultured hepatocytes isolated from adult rats. The presence of S-1-P and LPA in primary cultured rat hepatocytes induced the stimulation of glycogen phosphorylase which was mediated by phospholipase C activation and elevations in [Ca2+]i. Furthermore, S-1-P attenuated adenosine 3',5'-cyclic monophosphate accumulation in rat hepatocytes.