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Search Results: 1 - 10 of 3226 matches for " Pavel Stopka "
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Way-marking behaviour: an aid to spatial navigation in the wood mouse (Apodemus sylvaticus)
Pavel Stopka, David W Macdonald
BMC Ecology , 2003, DOI: 10.1186/1472-6785-3-3
Abstract: In an experiment, conspicuous natural candidate way-marks were removed from a simple arena and wood mice were given white plastic discs instead. The wood mice picked up these discs and re-distributed them about their arena; as the mice moved, they repeatedly re-positioned the discs and usually spent a considerable time near recently repositioned discs. Analysis revealed a statistically significant association between the location of places in which the mice had positioned way-marks and the subsequent pattern of their movements. In a separate analysis, based on the context in which each behaviour occurred, we used the components and sequences of wood mouse behaviour to deduce the motivation behind each activity. One set of behaviour patterns, the elements of which were closely linked by the high transition probabilities amongst them, were interpreted as linked elements of exploration; whenever the mice transported a disc it was in association with these exploratory behaviours. This evidence that transporting discs is set in the motivational context of exploratory behaviour supports the conclusion that way-marking is part of the wood mouse's system of spatial orientation.We conclude that way-marking – a behaviour not previously described in mammals other than humans – serves solely as an aid to spatial navigation during exploration.All animals face at least occasional problems of orientation. Especially for vertebrates, this can involve periods of almost continuous decisions. Much remains unknown about the processes involved in spatial orientation, and the behaviour patterns through which navigation is achieved. As a general model, mammals are thought to use fixed external cues as points of reference during their movements [1]. This model holds that an individual's spatial references are updated, with respect to the array of fixed land-marks, so that it is able to return to its refuge, feeding places, or other places of interest. This system (termed 'path integration'
Individual variation evades the Prisoner's Dilemma
Dominic DP Johnson, Pavel Stopka, Josh Bell
BMC Evolutionary Biology , 2002, DOI: 10.1186/1471-2148-2-15
Abstract: We show that relaxing the assumption of fixed payoffs leads to frequent violations of the payoff structure required for a Prisoner's Dilemma. With variance twice the payoff interval in a linear PD matrix, for example, only 16% of matrices are valid.A single player lacking a valid PD matrix destroys the conditions for a Prisoner's Dilemma, so between any two players, PD games themselves are fewer still (3% in this case). This may explain why the Prisoner's Dilemma has hardly been found in nature, despite the fact that it has served as a ubiquitous (and still instructive) model in studies of the evolution of cooperation.The Prisoner's Dilemma (PD) has generated many hundreds of publications [1,2] spanning the biology, moral philosophy, sociology, economics and political science literature [1,3-6]. It received special attention because it sets paradoxical conditions to examine how and when cooperation can evolve even when a rational player is bound to defect. As a result, a large body of literature has grown up around the problem of finding optimal strategies for playing the game but "the preoccupation with new and improved strategies has sometimes distracted from the main point: explaining animal cooperation" [7]. Recent publications have concentrated on how special conditions such as kin selection [3], iterated interactions [8], spatial structuring [9] or indirect reciprocity through reputation [10] can escape the paradox and lead to evolution of cooperation. Other studies pushed the iterated PD concept further to identify optimal strategies when players' decisions are not made simultaneously [11-13] or when players have payoffs that are not symmetrical [14].Our aim is not to criticise these theoretical developments at all. Rather, we suggest a reason for why PD may be relatively rare in the first place, and therefore point out that such special conditions (to permit cooperation despite the PD) need not be invoked if the game is not common in nature anyway. As Clemen
Variation in Apical Hook Length Reflects the Intensity of Sperm Competition in Murine Rodents
Martin ?andera, Tomá? Albrecht, Pavel Stopka
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0068427
Abstract: Background Post-copulatory sexual selection has been shown to shape morphology of male gametes. Both directional and stabilizing selection on sperm phenotype have been documented in vertebrates in response to sexual promiscuity. Methodology Here we investigated the degree of variance in apical hook length and tail length in six taxa of murine rodents. Conclusions Tail sperm length and apical hook length were positively associated with relative testis mass, our proxy for levels of sperm competition, thus indicating directional post-copulatory selection on sperm phenotypes. Moreover, our study shows that increased levels of sperm competition lead to the reduction of variance in the hook length, indicating stabilizing selection. Hence, the higher risk of sperm competition affects increasing hook length together with decreasing variance in the hook length. Species-specific post-copulatory sexual selection likely optimizes sperm morphology.
Novel OBP genes similar to hamster Aphrodisin in the bank vole, Myodes glareolus
Romana Stopková, Zbyněk Zdráhal, ?těpán Ryba, Ond?ej ?edo, Martin ?andera, Pavel Stopka
BMC Genomics , 2010, DOI: 10.1186/1471-2164-11-45
Abstract: Here we show that Aphrodisin-like proteins exist in other species, belong to a group of Odorant Binding Proteins (Obp), and contrary to the expression of Aphrodisin only in hamster genital tract and parotid glands of females, we have detected these transcripts in both sexes of M. glareolus with the expression confirmed in various tissues including prostate, prepucial and salivary glands, liver and uterus. On the level of mRNA, we have detected three different gene variants. To assess their relevance for chemical communication we investigated the occurrence of particular proteins in saliva, urine and vaginal discharge. On the protein level we confirmed the presence of Obp2 and Obp3 in both saliva and urine. Appropriate bands in the range of 17-20 kDa from vaginal discharge were, however, beyond the MS detection limits.Our results demonstrate that three novel Obps (Obp1, Obp2, and Obp3) are predominant lipocalins in Myodes urine and saliva. On the protein level we have detected further variants and thus we assume that similarly as Major Urinary Proteins in mice, these proteins may be important in chemical communication in this Cricetid rodent.Lipocalins are known to be involved in many important biological processes, of which one of them is chemical communication. Due to a conservative tertiary structure forming typical beta barrel all lipocalins share ability to bind various ligands of different size and structure. For some of the lipocalin members there already exists evidence for causing significant behavioural effects by their specific pheromonal ligands. The main lipocalin proteins studied to date in association with chemical communication are the mouse Major Urinary Proteins (Mup) secreted predominantly in the urine and saliva and Odorant Binding Proteins (Obp) with predominant site of expression in nasal tissue.In mice, urine is an important source of chemical information, frequently investigated by conspecifics and having the ability to elicit various behaviou
Expression patterns of microRNAs associated with CML phases and their disease related targets
Kate?ina Machová Poláková, Tereza Lopotová, Hana Klamová, Pavel Burda, Marek Trněny, Tomá? Stopka, Jana Moravcová
Molecular Cancer , 2011, DOI: 10.1186/1476-4598-10-41
Abstract: Using microarrays we identified differential expression profiles of 49 miRNAs in CML patients at diagnosis, in hematological relapse, therapy failure, blast crisis and major molecular response. The expression deregulation of miR-150, miR-20a, miR-17, miR-19a, miR-103, miR-144, miR-155, miR-181a, miR-221 and miR-222 in CML was confirmed by real-time quantitative PCR. In silico analyses identified targeted genes of these miRNAs encoding proteins that are involved in cell cycle and growth regulation as well as several key signaling pathways such as of mitogen activated kinase-like protein (MAPK), epidermal growth factor receptor (EGFR, ERBB), transforming growth factor beta (TGFB1) and tumor protein p53 that are all related to CML. Decreased levels of miR-150 were detected in patients at diagnosis, in blast crisis and 67% of hematological relapses and showed significant negative correlation with miR-150 proved target MYB and with BCR-ABL transcript level.This study uncovers microRNAs that are potentially involved in CML and the annotated functions of in silico filtered targets of selected miRNAs outline mechanisms whereby microRNAs may be involved in CML pathogenesis.Mammalian microRNAs (miRNA, miR) are short non-coding RNAs that regulate preferentially gene expression by inhibiting translation of specific target mRNAs. MiRNA-mRNA matching is based on imperfect sequence base-pairing with the required complementarity centered over positions 2 - 8 of mRNA's seed sequence [1]. Depending on specific target genes, miRNAs regulate many cellular functions such as developmental timing, signal transduction, apoptosis, cell proliferation and tumorigenesis [2-5]. Thus, gene expression and role of miRNAs are currently being largely studied in human malignancies and chemical compounds that regulate miRNA levels are potentially very important for developing new treatment strategies in chronic myeloid leukemia (CML). The first miRNA molecules that have been associated with human leuk
Absence of spermatozoal CD46 protein expression and associated rapid acrosome reaction rate in striped field mice (Apodemus agrarius)
Leanne E Clift, Petra Andrlikova, Michaela Frolikova, Pavel Stopka, Josef Bryja, Brian F Flanagan, Peter M Johnson, Katerina Dvorakova-Hortova
Reproductive Biology and Endocrinology , 2009, DOI: 10.1186/1477-7827-7-29
Abstract: Reverse transcription polymerase chain reaction (RT-PCR) was used to assess whether A. agrarius transcribe testicular CD46 mRNA. RT-PCR was supplemented with 3'- and 5'-rapid amplification of cDNA ends to determine the complete nucleotide sequence of A. agrarius CD46. Fluorescence microscopy was used to assess whether CD46 protein is expressed by A. agrarius sperm. The acrosome status of A. agrarius sperm was calculated over time by immunocytochemistry using peanut agglutinin lectin.We demonstrate that A. agrarius mice transcribe two unique alternatively spliced testicular CD46 mRNA transcripts, both lacking exon 7, which differ from those described previously in other Apodemus species. The larger A. agrarius CD46 transcript has an insert between exons 10 and 11 which, if translated, would result in a novel cytoplasmic tail. In addition, A. agrarius CD46 transcripts have an extended AU-rich 3'-untranslated region (UTR) and a truncated 5'-UTR, resulting in failure to express spermatozoal CD46 protein. We show that A. agrarius has a significantly faster spontaneous acrosome reaction rate than A. sylvaticus and Mus.Absence of CD46 protein expression is associated with acrosomal instability in rodents. A. agrarius mice express novel CD46 transcripts, resulting in the trade of spermatozoal CD46 protein expression for a rapid acrosome reaction rate, in common with other species of field mice. This provides a strategy to increase competitive sperm advantage for individuals, leading to faster fertilisation in this highly promiscuous genus.There is pronounced sperm competition in species belonging to the Apodemus genus (field mice), which is reflected by their disproportionately large testes [1,2]. There is also an association between relative testis mass and the shape of the apical hook in the falciform head of murine sperm [3]. The extremely long apical hook of A. sylvaticus spermatozoa enables them to intertwine, forming in vivo trains of up to 100 cells [4]. These sperm
Toxoplasma gondii Decreases the Reproductive Fitness in Mice
Katerina Dvorakova-Hortova, Adela Sidlova, Lukas Ded, Denisa Hladovcova, Markus Vieweg, Wolfgang Weidner, Klaus Steger, Pavel Stopka, Agnieszka Paradowska-Dogan
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0096770
Abstract: Toxoplasma gondii is a common protozoan parasite that infects warm-blooded animals throughout the world, including mice and humans. During infection, both, the parasite and the host, utilize various mechanisms to maximize their own reproductive success. Mice and humans are both the intermediate hosts for Toxoplasma gondii, which forms specialized vacuoles containing reproductive cysts in the formers’ tissue. As half of the human population is infected, developing a disease called toxoplasmosis, along with an ever-growing number of couples suffering with idiopathic infertility, it is therefore surprising that there is a lack of research on how Toxoplasma gondii can alter reproductive parameters. In this study, a detailed histometric screening of the testicular function along with the levels of the pituitary luteinizing hormone (LH) were analysed in infected mice. Data on relative testis and epididymis weight, and sperm count were also collected. Based on the results obtained, the level of LH in the urine of Toxoplasma gondii infected mice was lower compared to the control. In direct correlation with the hormone level, testicular function and sperm production was also significantly lower in Toxoplasma gondii positive group using sperm count and histometric analysis as a marker. Not only were the number of leptotene primary spermatocytes and spermatids lowered, but the number of Sertoli cells and the tubule diameter were elevated. In parallel, a pilot epigenetic study on global testicular methylation, and specific methylation of Crem, Creb1 and Hspa1genes essential for successfully ongoing spermatogenesis was performed. Global methylation was elevated in Toxoplasma infected mice, and differences in the DNA methylation of selected genes were detected between the Toxoplasma positive and control group. These findings demonstrate a direct relation between Toxoplasma gondii infection and the decrease of male reproductive fitness in mice, which may contribute to an increase of idiopathic infertility in humans.
The Relief of Plasma Pressure and Generation of Field-Aligned Currents in the Magnetosphere  [PDF]
Pavel Sedykh
International Journal of Astronomy and Astrophysics (IJAA) , 2011, DOI: 10.4236/ijaa.2011.12004
Abstract: A combined action of plasma convection and pitch-angle diffusion of electrons and protons leads to the formation of plasma pressure distribution in the magnetosphere on the night side, and, as it is known, steady electric bulk currents are connected to distribution of gas pressure. The divergence of these bulk currents brings about a spatial distribution of field-aligned currents, i.e. magnetospheric sources of ionospheric current. The projection (mapping) of the plasma pressure relief onto the ionosphere corresponds to the form and position of the auroral oval. This projection, like the real oval, executes a motion with a change of the convection electric field, and expands with an enhancement of the field. Knowing the distribution (3D) of the plasma pressure we can determine the places of MHD-compressor and MHD-generators location in the magnetosphere. Unfortunately, direct observations of plasma distribution in the magnetosphere are faced with large difficulties, because pressure must be known everywhere in the plasma sheet at high resolution, which in situ satellites have been unable to provide. Modeling of distribution of plasma pressure (on ~ 3-12 Re) is very important, because the data from multisatellite magnetospheric missions for these purposes would be a very expensive project.
Simulation as a Support for Ultrasonic Testing  [PDF]
Pavel Mares
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.513118

Ultrasonic testing is a very important non-destructive method for testing components for safety of nuclear power plants and other security and delicate parts in other industries. Nowadays, thanks to the development of computer technology, it is possible to simulate processes which occur during ultrasonic testing. That is why numerical simulations are becoming an integral part of non-destructive testing. Simulations are used to determine parameters of ultrasonic examination, especially parameters of probes and scan plan and also in the analysis of results. They are used in such cases, when it is necessary to verify applicability of probes and methods. This verification could be provided on the weld and test block which are not manufactured. It could be also provided on defects, which are not manufactured in test block, but their presence is possible in given weld joint. Simulations are very useful for verifying the propagation of ultrasonic signal in given area (e.g. weld area). If movement of probe is limited, possibility of whole volume scan should be verified.

Methodology for Evaluating and Monitoring of Waterworks Performance Efficiency —Part 1: Methods and Testing Procedures  [PDF]
Pavel Polasek
Advances in Chemical Engineering and Science (ACES) , 2014, DOI: 10.4236/aces.2014.42024

This paper presents a methodology for evaluating the water purification process efficiency attained by 1) jar tests, which are commonly used to determine the treatability of water, and 2) waterworks performance in different phases of the purification process as well as in its entirety. This methodology provides an important tool for the following: 1) determination of optimised reaction conditions under which water is treatable to its best attainable quality; 2) evaluation of the purification process efficiency attained by waterworks during different periods and under different operational conditions; 3) comparisons of performance efficiency of different waterworks; and 4) comprehensive commissioning of waterworks and identification of bottlenecks if any exist in process and plant design. This paper describes procedures for pre-processing of water samples to be analysed as well as mathematical formulas for processing of the results obtained. A few examples of the practical application of the methodology are included and the potential to obtain the optimization of waterworks’ purification processes is herein illustrated.

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