The High Resolution Fly's Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes' measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of 6 x 10(19) eV, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of 4 x 10(18) eV. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described.

Arachidonic acid is metabolized to prostaglandin H(2) (PGH(2)) by cyclooxygenase (COX). COX-2, the inducible COX isozyme, has a key role in intestinal polyposis. Among the metabolites of PGH(2), PGE(2) is implicated in tumorigenesis because its level is markedly elevated in tissues of intestinal adenoma and colon cancer. Here we show that homozygous deletion of the gene encoding a cell-surface receptor of PGE(2), EP2, causes decreases in number and size of intestinal polyps in Apc(Delta 716) mice (a mouse model for human familial adenomatous polyposis). This effect is similar to that of COX-2 gene disruption. We also show that COX-2 expression is boosted by PGE(2) through the EP2 receptor via a positive feedback loop. Homozygous gene knockout for other PGE(2) receptors, EP1 or EP3, did not affect intestinal polyp formation in Apc(Delta 716) mice. We conclude that EP2 is the major receptor mediating the PGE2 signal generated by COX-2 upregulation in intestinal polyposis, and that increased cellular cAMP stimulates expression of more COX-2 and vascular endothelial growth factor in the polyp stroma.

We have identified a strong candidate cDNA for the mouse reeler gene. This 5 kb transcript encodes a 99.4 kD protein consisting of 881 amino acids and possessing two EGF-like motifs. We assayed two independent mutant alleles--'Jackson reeler', which has a deletion of the entire gene, and 'Orleans reeler' which exhibits a 220 bp deletion in the open reading frame, including the second EGF-like motif and resulting in a frame shift. In situ hybridization reveals that the transcript is detected exclusively in the pioneer neurons which guide neuronal cell migration along the radial array. Our findings offer an explanation for how the reeler mutant phenotype causes a disturbance of the complex architecture of the neuronal network.

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The advent of thermostable enzymes has led to great advances in molecular biology, such as the development of PCR and ligase chain reaction. However, isolation of naturally thermostable enzymes has been restricted to those existing in thermophylic bacteria. Here, we show that the disaccharide trehalose enables enzymes to maintain their normal activity (thermostabilization) or even to increase activity at high temperatures (thermoactivation) at which they are normally inactive. We also demonstrate how enzyme thermoactivation can improve the reverse transcriptase reaction. In fact, thermoactivated reverse transcriptase, which displays full activity even at 60°C, was powerful enough to synthesize full length cDNA without the early termination usually induced by stable secondary structures of mRNA.The usefulness of thermostable enzymes is indisputable; they allowed the development of outstanding techniques such as PCR and ligase chain reaction (1, 2). However, the isolation of thermostable enzymes has been restricted to those existing in thermophylic organisms. To expand the availability of thermostable enzymes, we explored a completely new way-the thermal stabilization of those enzymes that are normally thermolabile by the addition of structure stabilizing molecules. In particular, we explored the properties of molecules that are normally involved in heat shock response, and we anticipated being able to confer thermal stability to enzymes. Among them, there is the disaccharide trehalose. Trehalose synthesis is induced by heat shock in the Saccharomyces cerevisiae yeast (3), suggesting its possible role in this response and in desiccation tolerance (4). In fact, yeast mutants defective in trehalose synthesis show a significant reduction in thermotolerance (5). It has been reported that enzymes could be protected from irreversible heat aggregation-heat denaturation in vitro by trehalose, suggesting its chaperonin-like function (6). Trehalose also has been used to confer stability to dried enzymes (7).In the present study, we discovered that trehalose can be used as a reaction additive to stabilize or stimulate enzymatic activity at unusually high temperatures, enabling the use of thermosensitive enzymes as though they would be thermostable. This property should be useful for converting a wide range of thermosensitive enzymes to thermostable and thermoactive ones for wide applications in biological, medical, and industrial fields.To show the power of trehalose-mediated thermal activation, we subsequently applied this new method to the synthesis of full length cDNA. The major obstacle to preparing high quality cDNA libraries has been the low efficiency of reverse transcriptase (RT) to synthesize full length cDNA, which is due to the strong secondary structure of mRNA, which cause the RT to stop the synthesis and subsequently to be released from the hybrid mRNA͞incomplete cDNA. To overcome problems associated with the secondary structure of mRNA, both denaturing of sample before the reaction and increased temper...