Evolution of MicroRNA Biogenesis Genes in the Sterlet (Acipenser ruthenus) and Other Polyploid Vertebrates

MicroRNAs play a crucial role in eukaryotic gene regulation. For a long time, only little was known about microRNA-based gene regulatory mechanisms in polyploid animal genomes due to difficulties of polyploid genome assembly. However, in recent years, several polyploid genomes of fish, amphibian, and even invertebrate species have been sequenced and assembled. Here we investigated several key microRNA-associated genes in the recently sequenced sterlet (Acipenser ruthenus) genome, whose lineage has undergone a whole genome duplication around 180 MYA. We show that two paralogs of drosha, dgcr8, xpo1, and xpo5 as well as most ago genes have been retained after the acipenserid-specific whole genome duplication, while ago1 and ago3 genes have lost one paralog. While most diploid vertebrates possess only a single copy of dicer1, we strikingly found four paralogs of this gene in the sterlet genome, derived from a tandem segmental duplication that occurred prior to the last whole genome duplication. ago1,3,4 and exportins1,5 look to be prone to additional segment duplications producing up to four-five paralog copies in ray-finned fishes. We demonstrate for the first time exon microsatellite amplification in the acipenserid drosha2 gene, resulting in a highly variable protein product, which may indicate sub- or neofunctionalization. Paralogous copies of most microRNA metabolism genes exhibit different expression profiles in various tissues and remain functional despite the rediploidization process. Subfunctionalization of microRNA processing gene paralogs may be beneficial for different pathways of microRNA metabolism. Genetic variability of microRNA processing genes may represent a substrate for natural selection, and, by increasing genetic plasticity, could facilitate adaptations to changing environments.     

On the structure of self-similar detonation waves in TNT charges

Combustion, Explosion, and Shock Waves - A phase-plane method is proposed to model flow fields bounded by constant-velocity detonation waves propagating in TNT charges. Similarity transformations...     

Volitional facilitation of difficult intentions: Joint activation of intention memory and positive affect removes Stroop interference.

Removal of Stroop interference was obtained after exposure to words eliciting positive affect. This effect was predicted by personality systems interactions (PSI) theory, which assumes that (a) an abstract (high-level) representation of a difficult intention is generated in intention memory under certain conditions (e.g., when an action plan contains more than 1 step); (b) positive affect releases the inhibition of the pathway between intention memory and its output system. Interference removal is interpreted in terms of volitional facilitation. This effect posits a challenge to current cognitive models of the Stroop effect. Compared with alternative explanations, PSI theory can explain the data in a broader context: Implications of volitional facilitation and volitional inhibition for the study of prospective memory, alienation, procrastination, and rumination in depression are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Kinetochores,cohesin, and DNA breaks: Controlling meiotic recombination within pericentromeres

In meiosis, DNA break formation and repair are essential for the formation of crossovers between homologous chromosomes. Without crossover formation, faithful meiotic chromosome segregation and sexual reproduction cannot occur. Crossover formation is initiated by the programmed, meiosis-specific introduction of numerous DNA double-strand breaks, after which specific repair pathways promote recombination between homologous chromosomes. Despite its crucial nature, meiotic recombination is fraud with danger: When positioned or repaired inappropriately, DNA breaks can have catastrophic consequences on genome stability of the resulting gametes. As such, DNA break formation and repair needs to be carefully controlled. Within centromeres and surrounding regions (i.e., pericentromeres), meiotic crossover recombination is repressed in organisms ranging from yeast to humans, and a failure to do so is implicated in chromosome missegregation and developmental aneuploidy. (Peri)centromere sequence identity and organization diverge considerably across eukaryotes, yet suppression of meiotic DNA break formation and repair appear universal. Here, we discuss emerging work that has used budding and fission yeast systems to study the mechanisms underlying pericentromeric suppression of DNA break formation and repair. We particularly highlight a role for the kinetochore, a universally conserved, centromere-associated structure essential for chromosome segregation, in suppressing (peri)centromeric DNA break formation and repair. We discuss the current understanding of kinetochore-associated and chromosomal factors involved in this regulation and suggest future avenues of research.     

Time integration in the context of energy control and locking free finite elements

Summary In the present paper two main research areas of computational mechanics, namely the finite element development and the design of time integration algorithms are reviewed and discussed with a special emphasis on their combination. The finite element techniques are designed to prevent locking and the time integration schemes to guarantee numerical stability in non-linear elastodynamics. If classical finite element techniques are used, their combination with time integration schemes allow to avoid any modifications on the element or algorithmic level. It is pointed out, that on the other hand Assumed Stress and Enhanced Assumed Strain elements have to be modified if they are combined with energy conserving or decaying time integration schemes, especially the Energy-Momentum Method in its original and generalized form. The paper focusses on the necessary algorithmic formulation of Enhanced Assumed Strain elements which will be developed by the reformulation of the Generalized Energy-Momentum Method based on a classical one-field functional, the extension to a modifiedHu-Washizu three-field functional including enhanced strains and a suitable time discretization of the additional strain terms. The proposed method is applied to non-linear shell dynamics using a shell element which allows for shear deformation and thickness change, and in which the Enhanced Assumed Strain Concept is introduced to avoid artificial thickness locking. Selected examples illustrate the locking free and numerically stable analysis.     

Motivation, affect, and hemispheric asymmetry: Power versus affiliation.

In 4 experiments, the authors examined to what extent information related to different social needs (i.e., power vs. affiliation) is associated with hemispheric laterality. Response latencies to a lateralized dot-probe task following lateralized pictures or verbal labels that were associated with positive or negative episodes related to power, affiliation, or achievement revealed clear-cut laterality effects. These effects were a function of need content rather than of valence: Power-related stimuli were associated with right visual field (left hemisphere) superiority, whereas affiliation-related stimuli were associated with left visual field (right hemisphere) superiority. Additional results demonstrated that in contrast to power, affiliation primes were associated with better discrimination between coherent word triads (e.g., goat, pass, and green, all related to mountain) and noncoherent triads, a remote associate task known to activate areas of the right hemisphere. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compression of femtosecond optical pulses with dielectric multilayer interferometers

The group velocity dispersion of a multilayer thin film Gires-Tournois interferometer used for reflection of ultrashort optical pulses can be continuously tuned from positive to negative values at an extremely low loss in pulse energy. Thus, this device can be applied for compression of femtosecond pulses independent of the sign of the frequency chirp by simple angle tuning of the interferometer. This has been demonstrated with up-chirped 210 fs pulses which have been compressed to an almost transform-limited duration of 115 fs.     

Cognitive control factors in speech perception at 11 months.

The development of speech perception during the 1st year reflects increasing attunement to native language features, but the mechanisms underlying this development are not completely understood. One previous study linked reductions in nonnative speech discrimination to performance on nonlinguistic tasks, whereas other studies have shown associations between speech perception and vocabulary growth. The present study examined relationships among these abilities in 11-month-old infants using a conditioned head-turn test of native and nonnative speech sound discrimination, nonlinguistic object-retrieval tasks requiring attention and inhibitory control, and the MacArthur-Bates Communicative Development Inventory (L. Fenson et al., 1993). Native speech discrimination was positively linked to receptive vocabulary size but not to the cognitive control tasks, whereas nonnative speech discrimination was negatively linked to cognitive control scores but not to vocabulary size. Speech discrimination, vocabulary size, and cognitive control scores were not associated with more general cognitive measures. These results suggest specific relationships between domain-general inhibitory control processes and the ability to ignore variation in speech that is irrelevant to the native language and between the development of native language speech perception and vocabulary. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vowel categorization by very young infants.

Six-month-old infants are known to categorize vowels despite variation in talker voice and pitch contour. Using the observer-based psychoacoustic procedure, this study asked whether 2- and 3-mo-olds could categorize similarly. Infants were trained to respond whenever the vowel category alternated from /a/ to /i/ and to refrain from responding when the vowel category remained the same, despite variation in spectral cues associated with pitch and talker changes. 80% of 2-, 3-, and 6-mo-olds did not respond the first time a talker change occurred in the absence of a vowel change, suggesting that even the younger infants recognize these spectrally different sounds as perceptually equivalent. This study establishes the observer-based psychoacoustic procedure as a viable research tool in the field of infant speech perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)