How does the unicellular <Emphasis Type="Italic">Tetrahymena</Emphasis> utilise the hormones that it produces? Paying a visit to the realm of atto-and zeptomolar concentrations

Changes in the hormone content of Tetrahymena pyriformis GL were investigated during histamine, serotonin or insulin treatment at concentrations of 10⁻⁶M to 10⁻²¹M for 30 min. The immunologically demonstrable hormone content was studied by using specific antibodies, flow cytometry and confocal microscopy. Histamine at the higher ranges elevated the serotonin content of Tetrahymena, whereas serotonin at the lower ranges (down to 10⁻²¹M) decreased its histamine levels. Insulin did not affect its serotonin content, whereas serotonin increased its insulin content at each concentration studied (down to 10⁻²¹M). Insulin between 10⁻⁶M and 10⁻²¹M increased the hista-mine levels of Tetrahymena, although histamine influenced its insulin level only at 10⁻⁶M. Our results call attention to the presence of hormonal interactions even at “low” levels of phylogeny and to the extreme sensitivity of the hormone receptors of Tetrahymena. These data might explain (1) the requirement of Tetrahymena for (vertebrate) hormone production and hormone receptors and (2) the way that it uses these hormones under natural conditions.This work was supported by the National Research Fund (OTKA-T-037303), Hungary.     

Cladocerans as indicators in the importance of passive nature conservation

The aim of our study was to verify the effectiveness of passive nature conservation with regard to the preservation of species, by examining a typical mesozooplankton community. We investigated five oxbow lakes which were similar to each other in terms of size, depth and close-to-each, but which differed markedly from one to another in terms of lake management. One is under passive protection, the others are under different forms of management. Based on the NMDS (Non-metric Dimensional Scaling) analysis, we identified the variable (transparency) which is responsible for the segregation. In the case of rare species IndVal (Indicator Value) analysis was used to evaluate the occurrence and significance of indicator species. We also found marked differences in the species composition; seven species showed indicator values for the protected oxbow lake, five of which were significant (p <?0.001). In contrast, in the case of the other four oxbow lakes, a total of one species showed an indicator value. Finally, regression tree analysis was used to distinguish the oxbow lakes from each other for both common and mass-occurring species. Among the mass-occurring species, the protected oxbow lake is characterized by a large number of Acropreus harpae (Baird, 1835), while in case of the other, non-protected, oxbow lakes Alona guttata (Sars, 1862) and Alonella excisa (Fischer, 1854) are the basis for the separate classification. There is a positive effect of passive protection regarding the quantitative and qualitative occurrence of the zooplankton community. Our study highlights the importance of this kind of passive protection in the life of a particular water body and advocates that their protection should be maintained.     

Prp19/Pso4 Is an Autoinhibited Ubiquitin Ligase Activated by Stepwise Assembly of Three Splicing Factors

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Fission yeast homologue of Tip41-like proteins regulates type 2A phosphatases and responses to nitrogen sources

A fission yeast (Schizosaccharomyces pombe) gene encoding a member of the TIP41-like protein family was identified and characterized. Deletion of the fission yeast tip41 gene leads to slower growth when ammonium chloride is the nitrogen source, but the growth rate is not affected when adenine is the nitrogen source. The tip41 mutant cells also enter the G1 phase of the cell cycle earlier than wild-type cells in response to nitrogen starvation. Overexpression of tip41(+) causes cell death, spherical cell morphology and blocks the shift to G1 phase upon nitrogen starvation. Overexpression of tip41(+) increases the activity of type 2A phosphatase. In a ppa2 deletion strain with reduced PP2A activity, overexpression of tip41(+) no longer blocks the shift to G1 upon nitrogen starvation. These results suggest that fission yeast Tip41 plays a role in cellular responses to nitrogen nutrient conditions at least partly through regulation of type 2A phosphatase activity.     

mGluR7 Genetics and Alcohol: Intersection Yields Clues for Addiction

Development of addiction to alcohol or other substances can be attributed in part to exposure-dependent modifications at synaptic efficacy leading to an organism which functions at an altered homeostatic setpoint. Genetic factors may also influence setpoints and the stability of the homeostatic system of an organism. Quantitative genetic analysis of voluntary alcohol drinking, and mapping of the involved genes in the quasi-congenic Recombinant QTL Introgression strain system, identified Eac2 as a Quantitative Trait Locus (QTL) on mouse chromosome 6 which explained 18% of the variance with an effect size of 2.09 g/kg/day alcohol consumption, and Grm7 as a quantitative trait gene underlying Eac2 [Vadasz et al. in Neurochem Res 32:1099–1112, 100, Genomics 90:690–702, 102]. In earlier studies, the product of Grm7 mGluR7, a G protein-coupled receptor, has been implicated in stress systems [Mitsukawa et al. in Proc Natl Acad Sci USA 102:18712–18717, 63], anxiety-like behaviors [Cryan et al. in Eur J Neurosci 17:2409–2417, 14], memory [Holscher et al. in Learn Mem 12:450–455, 26], and psychiatric disorders (e.g., [Mick et al. in Am J Med Genet B Neuropsychiatr Genet 147B:1412–1418, 61; Ohtsuki et al. in Schizophr Res 101:9–16, 72; Pergadia et al. in Paper presented at the 38th Annual Meeting of the Behavior Genetics Association, Louisville, Kentucky, USA, 76]. Here, in experiments with mice, we show that (1) Grm7 knockout mice express increased alcohol consumption, (2) sub-congenic, and congenic mice carrying a Grm7 variant characterized by higher Grm7 mRNA drink less alcohol, and show a tendency for higher circadian dark phase motor activity in a wheel running paradigm, respectively, and (3) there are significant genetic differences in Grm7 mRNA abundance in the mouse brain between congenic and background mice identifying brain areas whose function is implicated in addiction related processes. We hypothesize that metabotropic glutamate receptors may function as regulators of homeostasis, and Grm7 (mGluR7) is involved in multiple processes (including stress, circadian activity, reward control, memory, etc.) which interact with substance use and the development of addiction. In conclusion, we suggest that mGluR7 is a significant new therapeutic target in addiction and related neurobehavioral disorders.     

Arabidopsis S6 kinase mutants display chromosome instability and altered RBR1�CE2F pathway activity

The 40S ribosomal protein S6 kinase (S6K) is a conserved component of signalling pathways controlling growth in eukaryotes. To study S6K function in plants, we isolated single‐ and double‐knockout mutations and RNA‐interference (RNAi)‐silencing lines in the linked Arabidopsis S6K1 and S6K2 genes. Hemizygous s6k1s6k2/++ mutant and S6K1 RNAi lines show high phenotypic instability with variation in size, increased trichome branching, produce non‐viable pollen and high levels of aborted seeds. Analysis of their DNA content by flow cytometry, as well as chromosome counting using DAPI staining and fluorescence in situ hybridization, revealed an increase in ploidy and aneuploidy. In agreement with this data, we found that S6K1 associates with the Retinoblastoma‐related 1 (RBR1)–E2FB complex and this is partly mediated by its N‐terminal LVxCxE motif. Moreover, the S6K1–RBR1 association regulates RBR1 nuclear localization, as well as E2F‐dependent expression of cell cycle genes. Arabidopsis cells grown under nutrient‐limiting conditions require S6K for repression of cell proliferation. The data suggest a new function for plant S6K as a repressor of cell proliferation and required for maintenance of chromosome stability and ploidy levels.