Sub-Poissonian statistics in order-to-chaos transition

We study the phenomena at the overlap of quantum chaos and nonclassical statistics for the time-dependent model of nonlinear oscillator. It is shown in the framework of Mandel Q-parameter and Wigner function that the statistics of oscillatory excitation number is drastically changed in order-to chaos transition. The essential improvement of sub-Poissonian statistics in comparison with an analogous one for the standard model of driven anharmonic oscillator is observed for the regular operational regime. It is shown that in the chaotic regime the system exhibits the range of sub- and super-Poissonian statistics which alternate one to other depending on time intervals. Unusual dependence of the variance of oscillatory number on the external noise level for the chaotic dynamics is observed.Comment: 9 pages, RevTeX, 14 figure

Water table fluctuations in the riparian zone: comparative results from a pan-European experiment

Soil saturation is known to be of crucial importance to denitrification and other nitrogen cycling processes within the riparian zone. Since denitrification potential generally increases towards the soil surface, water table elevation can control the degree to which nitrate reduction is optimised. Given their topographic location and sedimentary structure, most floodplains are characterised by high water tables. However, detailed field data on water table levels, hydraulic gradients and flow patterns within the riparian zone are generally lacking. This paper presents data collected as part of a pan-European study of nitrate buffer zones, the Nitrogen Control by Landscape Structures in Agricultural Environments project (NICOLAS). An identical experimental design was employed at each site, allowing riparian zone hydrology and nitrogen cycling processes to be explored across a wide range of temperate climates; only the hydrological data are discussed here. A grid of dipwells at 10-metre spacing was installed at each site and manual measurements made at least once a month for a minimum of one year. In addition, at least one dipwell in each grid was monitored continuously using a data logger. All the riparian zones studied displayed a clear annual cycle of water table elevation, although other factors seemed equally important in influencing the range of variation. Where the riparian zone was flat, the water level in the adjoining river or lake proved more significant in controlling water table levels within the riparian zone than was originally anticipated

Activation of p42 Mitogen-activated Protein Kinase (MAPK), but not c-Jun NH(2)-Terminal Kinase, Induces Phosphorylation and Stabilization of MAPK Phosphatase XCL100 in Xenopus Oocytes

Dual-specificity protein phosphatases are implicated in the direct down-regulation of mitogen-activated protein kinase (MAPK) activity in vivo. Accumulating evidence suggests that these phosphatases are components of negative feedback loops that restore MAPK activity to low levels after diverse physiological responses. Limited information exists, however, regarding their posttranscriptional regulation. We cloned two Xenopus homologs of the mammalian dual-specificity MAPK phosphatases MKP-1/CL100 and found that overexpression of XCL100 in G2-arrested oocytes delayed or prevented progesterone-induced meiotic maturation. Epitope-tagged XCL100 was phosphorylated on serine during G2 phase, and on serine and threonine in a p42 MAPK-dependent manner during M phase. Threonine phosphorylation mapped to a single residue, threonine 168. Phosphorylation of XCL100 had no measurable effect on its ability to dephosphorylate p42 MAPK. Similarly, mutation of threonine 168 to either valine or glutamate did not significantly alter the binding affinity of a catalytically inactive XCL100 protein for active p42 MAPK in vivo. XCL100 was a labile protein in G2-arrested and progesterone-stimulated oocytes; surprisingly, its degradation rate was increased more than twofold after exposure to hyperosmolar sorbitol. In sorbitol-treated oocytes expressing a conditionally active ΔRaf-DD:ER chimera, activation of the p42 MAPK cascade led to phosphorylation of XCL100 and a pronounced decrease in the rate of its degradation. Our results provide mechanistic insight into the regulation of a dual-specificity MAPK phosphatase during meiotic maturation and the adaptation to cellular stress

Tyrosine hydroxylase in the brain and its regulation by glucocorticoids

Early life stress events can produce long-lasting changes in neurochemistry and behaviors related to monoamine systems, with increased risks of cardiovascular, metabolic, neuroendocrine, psychiatric disorders, generalized anxiety and depression in adulthood. Tyrosine hydroxylase (TH), the key enzyme for catecholamine synthesis, also plays an important role in the activity of the noradrenergic system and may be a target for glucocorticoids during the perinatal programming of physiological functions and behavior. Administration of hydrocortisone or dexamethasone to female rats on day 20 of pregnancy and to 3-day-old neonatal pups significantly increased TH mRNA levels (real-time PCR) and enzyme activity as well as protein levels determined by ICH in the locus coeruleus. Moreover, our treatment led to increase in TH mRNA levels in 25- and 70-day-old animals, as well as an increase in enzyme activity in the brainstem and cerebral cortex of adult rats. The long-term changes in TH expression are limited by the perinatal period of development. Administration of hormones on day 8 of life was not accompanied by changes in TH mRNA levels or enzyme activity. Glucocorticoids use several mechanisms to bring about transactivation or transrepression of genes. The main mechanism includes direct binding of the hormone-activated GRs to glucocorticoid responsive elements (GREs) in the promoter region of genes. However, despite optimistic claims made the classical GRE was not found in the TH gene promoter. Protein – protein interactions between hormone-activated GR and other transcription factors, for example, AP-1, provide an additional mechanism for the effects of glucocorticoids on gene expression. An important feature of this mechanism is its dependence on the composition of proteins formed by AP-1. Hormone-activated GRs are able to enhance gene expression when AP-1 consists of the Jun / Jun homodimer, but do not do that when AP-1 appears as the Jun / Fos heterodimer. Furthermore, as has been shown recently, the GRE / AP-1 composite site is the major site of interaction of glucocorticoids with  the TH gene in the pheochromocytoma cell line. Ontogenetic variation in the expression of Fos and Jun family proteins, which affects their ratio, can be one of the reasons for the TH gene regulation by glucocorticoids at near-term fetuses and neonates. However, to date this hypothesis has been supported only by in vitro data, and the existence of this mechanism in in vivo conditions needs to be explored in further studies