Intrinsic Motivations Drive Learning of Eye Movements: An Experiment with Human Adults

Intrinsic motivations drive the acquisition of knowledge and skills on the basis of novel or surprising stimuli or the pleasure to learn new skills. In so doing, they are different from extrinsic motivations that are mainly linked to drives that promote survival and reproduction. Intrinsic motivations have been implicitly exploited in several psychological experiments but, due to the lack of proper paradigms, they are rarely a direct subject of investigation. This article investigates how different intrinsic motivation mechanisms can support the learning of visual skills, such as “foveate a particular object in space”, using a gaze contingency paradigm. In the experiment participants could freely foveate objects shown in a computer screen. Foveating each of two “button” pictures caused different effects: one caused the appearance of a simple image (blue rectangle) in unexpected positions, while the other evoked the appearance of an always-novel picture (objects or animals). The experiment studied how two possible intrinsic motivation mechanisms might guide learning to foveate one or the other button picture. One mechanism is based on the sudden, surprising appearance of a familiar image at unpredicted locations, and a second one is based on the content novelty of the images. The results show the comparative effectiveness of the mechanism based on image novelty, whereas they do not support the operation of the mechanism based on the surprising location of the image appearance. Interestingly, these results were also obtained with participants that, according to a post experiment questionnaire, had not understood the functions of the different buttons suggesting that novelty-based intrinsic motivation mechanisms might operate even at an unconscious level.     

Endothelial-Mesenchymal Transition of Brain Endothelial Cells: Possible Role during Metastatic Extravasation

Cancer progression towards metastasis follows a defined sequence of events described as the metastatic cascade. For extravasation and transendothelial migration metastatic cells interact first with endothelial cells. Yet the role of endothelial cells during the process of metastasis formation and extravasation is still unclear, and the interaction between metastatic and endothelial cells during transendothelial migration is poorly understood. Since tumor cells are well known to express TGF-β, and the compact endothelial layer undergoes a series of changes during metastatic extravasation (cell contact disruption, cytoskeletal reorganization, enhanced contractility), we hypothesized that an EndMT may be necessary for metastatic extravasation. We demonstrate that primary cultured rat brain endothelial cells (BEC) undergo EndMT upon TGF-β1 treatment, characterized by the loss of tight and adherens junction proteins, expression of fibronectin, β1-integrin, calponin and α-smooth muscle actin (SMA). B16/F10 cell line conditioned and activated medium (ACM) had similar effects: claudin-5 down-regulation, fibronectin and SMA expression. Inhibition of TGF-β signaling during B16/F10 ACM stimulation using SB-431542 maintained claudin-5 levels and mitigated fibronectin and SMA expression. B16/F10 ACM stimulation of BECs led to phosphorylation of Smad2 and Smad3. SB-431542 prevented SMA up-regulation upon stimulation of BECs with A2058, MCF-7 and MDA-MB231 ACM as well. Moreover, B16/F10 ACM caused a reduction in transendothelial electrical resistance, enhanced the number of melanoma cells adhering to and transmigrating through the endothelial layer, in a TGF-β-dependent manner. These effects were not confined to BECs: HUVECs showed TGF-β-dependent SMA expression when stimulated with breast cancer cell line ACM. Our results indicate that an EndMT may be necessary for metastatic transendothelial migration, and this transition may be one of the potential mechanisms occurring during the complex phenomenon known as metastatic extravasation.     

RNA binding properties of the coat protein from bacteriophage GA.

The coat protein of bacteriophage GA, a group II RNA phage, binds to a small RNA hairpin corresponding to its replicase operator. Binding is specific, with a Ka of 71 microM -1. This interaction differs kinetically from the analogous coat protein-RNA hairpin interactions of other RNA phage and also deviates somewhat in its pH and salt dependence. Despite 46 of 129 amino acid differences between the GA and group I phage R17 coat proteins, the binding sites are fairly similar. The essential features of the GA coat protein binding site are a based-paired stem with an unpaired purine and a four nucleotide loop having an A at position -4 and a purine at -7. Unlike the group I phage proteins, the GA coat protein does not distinguish between two alternate positions for the unpaired purine and does not show high specificity for a pyrimidine at position -5 of the loop.     

Brutperiode des Steinhuhns (Alectoris graeca) in Griechenland

Ohne Zusammenfassung

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Breeding season of the Rock Partridge (Alectoris graeca) in Greece

     

State-of-the art data normalization methods improve NMR-based metabolomic analysis

Extracting biomedical information from large metabolomic datasets by multivariate data analysis is of considerable complexity. Common challenges include among others screening for differentially produced metabolites, estimation of fold changes, and sample classification. Prior to these analysis steps, it is important to minimize contributions from unwanted biases and experimental variance. This is the goal of data preprocessing. In this work, different data normalization methods were compared systematically employing two different datasets generated by means of nuclear magnetic resonance (NMR) spectroscopy. To this end, two different types of normalization methods were used, one aiming to remove unwanted sample-to-sample variation while the other adjusts the variance of the different metabolites by variable scaling and variance stabilization methods. The impact of all methods tested on sample classification was evaluated on urinary NMR fingerprints obtained from healthy volunteers and patients suffering from autosomal polycystic kidney disease (ADPKD). Performance in terms of screening for differentially produced metabolites was investigated on a dataset following a Latin-square design, where varied amounts of 8 different metabolites were spiked into a human urine matrix while keeping the total spike-in amount constant. In addition, specific tests were conducted to systematically investigate the influence of the different preprocessing methods on the structure of the analyzed data. In conclusion, preprocessing methods originally developed for DNA microarray analysis, in particular, Quantile and Cubic-Spline Normalization, performed best in reducing bias, accurately detecting fold changes, and classifying samples.

     

Akustische Barrieren beim Waldbauml?ufer (Certhia familiaris)?

Zusammenfassung Waldbaumläufer besitzen je nach geographischer Herkunft deutlich verschiedene Reviergesangs-Strophen. Zusammenfassen lassen sich jene aus Mittel- und W-Europa (Certhia familiaris macrodactyla, mWb;C. f. britannica undC. f. corsa), aus dem weiteren Himalaya-Gebiet (Nepal,C. f. mandellii, nWb; und SW-China,C. f. khamensis, cwb) und als weitere Gruppe die aus Japan (C. f. orientalis, jWb). Differenzen im Gesang bestehen hinsichtlich der Zahl der Elemente in der Strophe, Frequenzumfang der Strophe, Frequenzverlauf der Elemente und deren Frequenzumfang. Der nWb reagiert nicht auf Gesang des mWb, umgekehrt besteht hohe Reaktionsfreudigkeit des mWb auf Str. des nWb. Freiland-Experimente mit unveränderten, gekürzten und künstlichen Str. aus gereihten Einzel-El. zeigen, daß bestimmter Frequenz-Verlauf der El. die Reaktion hervorruft. Es sind solche El. des nWb, die beim mWb in ähnlicher Form auftreten. Vielfach sind es aber El., die zwar vordergründig geringe oder keine Übereinstimmungen aufweisen, in einzelnen El.-Abschnitten jedoch erkennbare Frequenz-Entsprechungen besitzen. Einzelne dieser El. von mWb und nWb sind als homolog zu betrachten. In den meisten Fällen kann über die mögliche Homologie nicht entschieden werden, denn über El.-Veränderungen in der Evolution akustischer Signale ist bei Baumläufern zu wenig bekannt.

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Acoustic barriers in the Tree Creeper (Certhia familiaris)?

Summary Tree Creepers use according to their distributional origin different territorial songs. Populations with similar songs occur in Central and W Europe (C. f. macrodactyla, mWb;C. f. britannica, C. f. corsa), in Himalayan East Asia (Nepal,C. f. mandellii, nWb; SW China,C. f. khamensis, cWb) and Japan (C. f. orientalis, jWb). Differences in the territorial songs refer to number of elements in the verse, frequency volume of the verse, frequency modulation of the elements and their frequency volume. The Tree Creeper from Nepal (mandellii) does not react on the song of Central European Tree Creepers (macrodactyla), but the latter is very responsive tomandellii verses. Field experiments using unchanged, shortened or artificial verses consisting of one natural element arranged in a row, demonstrate that only certain frequency modulations evoke reactions. Such elements occur at least in similar expression in nWb and mWb as well. Often also such elements are answered which at first sight do not correspond or only to a low degree to mWb elements, but do so in certain small sections of mWb elements. Several of the similar elements in mWb and nWb are to be considered homologous. But in most cases where reaction in field experiments is high, the homology of the elements concerned cannot be substantiated. Changes of element structures in the course of vocal evolution in the [familiaris] superspecies is too poorly known.

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Results of the Himalaya Expeditions ofJ. Martens, No. 146. — For No. 145 see: Stuttgarter Beitr. Naturk., (A) 411: 1–43, 1987. — J. M. sponsored by Deutscher Akademischer Austauschdienst and Deutsche Forschungsgemeinschaft.     

‘Mild mitochondrial uncoupling’ induced protection against neuronal excitotoxicity requires AMPK activity

The preconditioning response conferred by a mild uncoupling of the mitochondrial membrane potential (Δψ_m) has been attributed to altered reactive oxygen species (ROS) production and mitochondrial Ca^2 + uptake within the cells. Here we have explored if altered cellular energetics in response to a mild mitochondrial uncoupling stimulus may also contribute to the protection. The addition of 100 nM FCCP for 30 min to cerebellar granule neurons (CGNs) induced a transient depolarization of the Δψ_m, that was sufficient to significantly reduce CGN vulnerability to the excitotoxic stimulus, glutamate. On investigation, the mild mitochondrial ‘uncoupling’ stimulus resulted in a significant increase in the plasma membrane levels of the glucose transporter isoform 3, with a hyperpolarisation of Δψ_m and increased cellular ATP levels also evident following the washout of FCCP. Furthermore, the phosphorylation state of AMP-activated protein kinase (AMPK) (Thr 172) was increased within 5 min of the uncoupling stimulus and elevated up to 1 h after washout. Significantly, the physiological changes and protection evident after the mild uncoupling stimulus were lost in CGNs when AMPK activity was inhibited. This study identifies an additional mechanism through which protection is mediated upon mild mitochondrial uncoupling: it implicates increased AMPK signalling and an adaptive shift in energy metabolism as mediators of the preconditioning response associated with FCCP-induced mild mitochondrial uncoupling.     

Two distinct proteolytic systems responsible for glucose-induced degradation of fructose-1,6-bisphosphatase and the Gal2p transporter in the yeast Saccharomyces cerevisiae share the same protein components of the glucose signaling pathway.

Addition of glucose to Saccharomyces cerevisiae inactivates the galactose transporter Gal2p and fructose-1,6-bisphosphatase (FBPase) by a mechanism called glucose- or catabolite-induced inactivation, which ultimately results in a degradation of both proteins. It is well established, however, that glucose induces internalization of Gal2p into the endocytotic pathway and its subsequent proteolysis in the vacuole, whereas FBPase is targeted to the 26 S proteasome for proteolysis under similar inactivation conditions. Here we report that two distinct proteolytic systems responsible for specific degradation of two conditionally short-lived protein targets, Gal2p and FBPase, utilize most (if not all) protein components of the same glucose sensing (signaling) pathway. Indeed, initiation of Gal2p and FBPase proteolysis appears to require rapid transport of those substrates of the Hxt transporters that are at least partially metabolized by hexokinase Hxk2p. Also, maltose transported via the maltose-specific transporter(s) generates an appropriate signal that culminates in the degradation of both proteins. In addition, Grr1p and Reg1p were found to play a role in transduction of the glucose signal for glucose-induced proteolysis of Gal2p and FBPase. Thus, one signaling pathway initiates two different proteolytic mechanisms of catabolite degradation, proteasomal proteolysis and endocytosis followed by lysosomal proteolysis.     

Seasonal root growth in the arctic tussock tundra

Summary The quantity of growing root tips per unit of soil volume was analyzed in a central Alaskan tussock tundra site. By June 10, the aboveground fraction of the vegetation had initiated the flush of spring growth and flowering while less than 5 active root tips cm^-3 were found. By June 25 this value had increased to 30 root tips cm^-3. Similar values in July were followed by a complete cessation of root growth after the first week of August. By then, leaf senescence had also become visible. In the spring, low root temperatures were responsible for the time lag between shoot growth initiation and the beginning of root growth. In early August, root growth stopped in spite of adequate soil temperatures and accumulated carbohydrate for root growth. It is proposed that use of reserve carbohydrate for root growth in August would compromise the flush of spring growth in the following year.