Evidence for overlapping, but not identical, protein machineries operating in vegetal RNA localization along early and late pathways in Xenopus oocytes

RNAs that localize to the vegetal cortex of Xenopus oocytes are involved in early embryonic patterning and cell fate specification. Two mechanistically distinct pathways lead to RNA enrichment at the vegetal cortex: the early and the late. While several candidate proteins that seem to operate in the late localization pathway have been identified, proteins involved in the early pathway remain to be identified. In this study, we report on the isolation of a novel vegetally localized RNA in Xenopus oocytes that makes use of the early pathway and encodes a protein with a conserved but functionally uncharacterized NIF-motif. The localization signal of XNIF was mapped to a 300-nucleotide region in the 5'-UTR, which is able to mediate both accumulation to the mitochondrial cloud in stage I oocytes, as well as vegetal transport in later stage oocytes. The XNIF-LE contains 16 copies of the previously defined CAC-containing signal motifs for RNA localization. A critical number of such repeats seems to be required for accumulation in the mitochondrial cloud along the early pathway, but additional repeats seem to be required for localization along the late pathway. Cross-linking experiments identify two novel proteins of 62 and 64 kDa that interact with the XNIF-LE but not with the Vg1-LE that operates in the late pathway. Conversely, at least two of the previously identified VgRBPs, Vg1RBP1 and Prrp, also bind to the XNIF-LE. Thus, overlapping, but not identical, protein machineries mediate vegetal RNA localization along early and late pathways in Xenopus oocytes.     

Temporal integration in nasal lateralization and nasal detection of carbon dioxide

Two experiments examined time/concentration trading for the detection of carbon dioxide, an irritant with little or no odor. Experiment 1 employed the nasal lateralization method: subjects attempted to determine which nostril received carbon dioxide and which received pure air when presented simultaneously. Experiment 2 employed a temporal, two-alternative, forced-choice, detection paradigm with monorhinal stimulation. In both experiments, stimulus duration was varied at a number of fixed concentrations to determine the shortest, detectable pulse. Under both conditions, threshold pulse duration decreased as stimulus concentration increased. Power functions with exponents of less than negative one described the data quite well: More than a twofold increase in duration was needed to compensate for a twofold decrease in concentration. Thus, for carbon dioxide, the nasal trigeminal system functions as an imperfect integrator at threshold-level.     

Endocytosis by random initiation and stabilization of clathrin-coated pits

Clathrin-coated vesicles carry traffic from the plasma membrane to endosomes. We report here the real-time visualization of cargo sorting and endocytosis by clathrin-coated pits in living cells. We have detected the formation of coats by monitoring incorporation of fluorescently tagged clathrin or its adaptor AP-2; we have also followed clathrin-mediated uptake of transferrin and of single LDL or reovirus particles. The intensity of a cargo-loaded clathrin cluster grows steadily during its lifetime, and the time required to complete assembly is proportional to the size of the cargo particle. These results are consistent with a nucleation-growth mechanism and an approximately constant growth rate. There are no strongly preferred nucleation sites. A proportion of the nucleation events are weak and short lived. Cargo incorporation occurs primarily or exclusively in a newly formed coated pit. Our data lead to a model in which coated pits initiate randomly but collapse unless stabilized, perhaps by cargo capture.     

5-Hydroxyindoleacetic acid and homovanillic acid concentrations in cerebrospinal fluid in patients with Alzheimer's disease, depression and mild cognitive impairment

In this study we investigated the cerebrospinal fluid (CSF) concentrations of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) in Alzheimer (AD) patients (n=75), patients with mild cognitive impairment (MCI, n=9) and patients with depression (n=7). CSF HVA was significantly elevated in AD with depression (Geriatric Depression Scale, 15 point version GDS>5) in comparison to AD without depression (p<0.05, ANOVA) and CSF HVA showed a significant positive correlation with the GDS score of AD-patients (p=0.03, Spearman Rho: 0.38, Spearman Rank Correlation). In the group of AD patients CSF 5-HIAA was positively correlated with cerebrospinal fluid beta-amyloid 1-42 (Abeta42), p<0.05, Spearman Rho: 0.3, Spearman Rank Correlation, but not with CSF tau. Additionally, there was a significant positive correlation between cerebrospinal fluid 5-HIAA and HVA in the group of AD patients (p<0.0001, Rho: 0.47, Spearman Rank correlation). Neither 5-HIAA nor HVA in CSF could differentiate between mild cognitive impairment, depression and AD. The results of this study support the hypothesis that the serotonergic system plays a role in the course of AD. They further suggest an important role of dopamine metabolism in depression within AD patients.     

Effects of dynamin inactivation on pathways of anthrax toxin uptake

Internalization and traffic to acidic endosomes of anthrax lethal factor (LF) and protective antigen (PA), bound to the anthrax toxin receptor (ATR), is required for LF translocation into the cytosol, where it can elicit its toxic effects. Dynamin is required for clathrin-mediated endocytosis, and long-term disruption of dynamin function blocks internalization of PA. We have used LFn-DTA, a surrogate of LF consisting of the N-terminal domain of LF fused to the catalytic subunit of diphtheria toxin, to differentiate the effects of acute and long-term block of dynamin function on LFn-DTA toxicity. Both forms of interference reduce LFn-DTA toxicity only partially, consistent with alternative routes for LFn-DTA endocytosis. In contrast, a long-term block of dynamin activity results in a further interference with LFn-DTA toxicity that is consistent with an altered endosomal environment, probably an increase in endosomal pH.     

Synthesis and biological activity of some structural modifications of pancratistatin

Structurally modified derivatives of 7-deoxypancratistatin have been synthesized and evaluated in cancer cell line inhibition studies.     

Population Genetic Structure and Conservation of the Lesser White-Fronted GooseAnser erythropus

The lesser white-fronted goose is a sub-Arctic species with a currently fragmented breeding range, which extends from Fennoscandia to easternmost Siberia. The population started to decline at the beginning of the last century and, with a current world population estimate of 25,000 individuals, it is the most threatened of the Palearctic goose species. Of these, only 30–50 pairs breed in Fennoscandia. A fragment of the control region of mtDNA was sequenced from 110 individuals from four breeding, one staging and two wintering areas to study geographic subdivisions and gene flow. Sequences defined 15 mtDNA haplotypes that were assigned to two mtDNA lineages. Both the mtDNA lineages were found from all sampled localities indicating a common ancestry and/or some level of gene flow. Analyses of molecular variance showed significant structuring among populations ( _ST 0.220, P < 0.001). The results presented here together with ecological data indicate that the lesser white-fronted goose is fragmented into three distinctive subpopulations, and thus, the conservation status of the species should be reconsidered.