Evidence for post-transcriptional regulation of clustered microRNAs in Drosophila

BACKGROUND: MicroRNAs (miRNA) are short 21-23nt RNAs capable of inhibiting translation of complementary target messenger RNAs. Almost half of D. melanogaster miRNA genes are grouped in genomic clusters. RESULTS: The peculiarities of the expression of clustered miRNAs were studied using publicly available libraries of sequenced small RNAs from different Drosophila tissues. We have shown that although miRNAs from almost all clusters have similar tissue expression profiles (coordinated clusters), some clusters contain miRNAs with uncoordinated expression profiles. The predicted transcription start sites (TSSs) of such clusters are located upstream of the first miRNA, but no TSSs are found within the clusters. The expression profiles of miR and miR* sequences in uncoordinated clustered miRNAs do not correlate while their profiles from the coordinated clustered miRNAs are similar. CONCLUSIONS: The presence of exclusively upstream promoters in miRNA clusters containing uncoordinated miRNAs means that the clusters are transcribed as single transcription units. The difference of tissue expression profiles of uncoordinated miRNAs and the corresponding miRs* suggests a post-transcriptional regulation of their processing or stability. [KEYWORDS: Animals, Drosophila/ genetics, Gene Expression Profiling, MicroRNAs/ genetics/ metabolism, Multigene Family, Promoter Regions, Genetic, RNA Processing, Post-Transcriptional, Transcription Initiation Site]

Efficiency of Electron-Positron Pair Productionby Neutrino Flux from Accretion Disk of a Kerr Black Hole

Dominant processes of neutrino production and neutrino-induced \ep-pair production are examined in the model of a disk hyper-accreting onto a Kerr black hole. The efficiency of plasma production by a neutrino flux from the disk, obtained for the both cases of presence and absence of a magnetic field, is found to be no more than several tenths of percent and, therefore, not enough for the origin of cosmological gamma-ray bursts.Comment: 8 pages, 1 figur

Control of elastic-hysteretic characteristics of multilayer all-metal vibration insulators with structural damping

The use of all-metal vibration insulators is one of the most effective ways to eliminate the harmful effects of vibrations in mechanical systems. However, a similar type of parametrically controlled all-metal vibration insulators is little studied. In this research, the possibility of control of elastic-hysteretic characteristics of multilayer vibration insulators from metal is proved on the basis of the theory of similarity and theory of structural damping. It was found that the use of the square law of distribution of the friction coefficient on the height of the multilayer package and uniform compression of layers provides the high damping at resonance. The obtained results can be useful for design of effective parametrically controlled systems of vibration protection for any field of technology

On the Possible Enhancement of the Magnetic Field by Neutrino Reemission Processes in the Mantle of a Supernova

URCA neutrino reemission processes under the conditions in the mantle of a supernova with a strong toroidal magnetic field are investigated. It is shown that parity violation in these processes can be manifested macroscopically as a torque that rapidly spins up the region of the mantle occupied by such a field. Neutrino spin-up of the mantle can strongly affect the mechanism of further generation of the toroidal field, specifically, it can enhance the field in a small neighborhood of the rigid-body-rotating core of the supernova remnant.Comment: 8 pages, late

The differences between Cis-and Trans-Gene inactivation caused by heterochromatin in Drosophila

Position-effect variegation (PEV) is the epigenetic disruption of gene expression near the de novo-formed euchromatin-heterochromatin border. Heterochromatic cis-inactivation may be accompanied by the trans-inactivation of genes on a normal homologous chromosome in trans-heterozygous combination with a PEV-inducing rearrangement. We characterize a new genetic system, inversion In(2)A4, demonstrating cis-acting PEV as well as trans-inactivation of the reporter transgenes on the homologous nonrearranged chromosome. The cis-effect of heterochromatin in the inversion results not only in repression but also in activation of genes, and it varies at different developmental stages. While cis-actions affect only a few juxtaposed genes, trans-inactivation is observed in a 500-kb region and demonstrates а nonuniform pattern of repression with intermingled regions where no transgene repression occurs. There is no repression around the histone gene cluster and in some other euchromatic sites. trans-Inactivation is accompanied by dragging of euchromatic regions into the heterochromatic compartment, but the histone gene cluster, located in the middle of the trans-inactivated region, was shown to be evicted from the heterochromatin. We demonstrate that trans-inactivation is followed by de novo HP1a accumulation in the affected transgene; trans-inactivation is specifically favored by the chromatin remodeler SAYP and prevented by Argonaute AGO2

The influence of strong magnetic field on photon-neutrino reactions

The two-photon two-neutrino interaction induced by magnetic field is investigated. In particular the processes $\gamma \gamma \to \nu \bar \nu$ and $\gamma \to \gamma \nu \bar \nu$ are studied in the presence of strong magnetic field. An effective Lagrangian and partial amplitudes of the processes are presented. Neutrino emissivities due to the reactions $\gamma \gamma \to \nu \bar \nu$ and $\gamma \to \gamma \nu \bar \nu$ are calculated taking into account of the photon dispersion and large radiative corrections. A comparison of the results obtained with previous estimations and another inducing mechanisms of the processes under consideration is made.Comment: 16 pages, LATEX, 3 EPS figures, based on the talk presented at XXXI ITEP Winter School of Physics, Moscow, Russia, February 18 - 26, 200

Optical properties of colloidal solutions of metal nanoparticles

nanoparticles, spectroscopy, light absorption, plasmon, plasmon resonanceNanoparticles are finding more practical applications in various fields of human activity, including veterinary and medicine. Due to the fact that the effectiveness of colloidal solutions of nanoparticles is directly related to their aggregate state, convenient methods for assessing the physicochemical characteristics of such preparations is of high priority. Nanoparticles have unique optical properties that depend on their size and shape. They can be determined by the refractive index of light on the surface of nanoparticles in a phenomenon known as plasmon resonance, which makes the UV-Vis spectroscopy a valuable tool for studying and evaluating the properties of nanomaterials. Optical characteristics of NPs colloidal solutions of noble metals (silver) or bioelements (copper, silicon dioxide) were determined at various wavelengths (nm): 300–800 nm. The surface plasmon resonance has been found in all test preparations, while all of them exhibited obvious nonlinear optical properties. The most pronounced plasmon resonance peak was found in the colloidal solution of silver NPs within a wavelength of 420 nm. In the case of a colloidal solution of copper NPs, the peak of plasmon resonance was less pronounced and had a red shift (peak at 560 nm). In the colloidal solution of silicon dioxide, the plasmon resonance was less pronounced than in other test preparations, being shifted to the blue side of the spectrum (360 nm). UV-Vis spectroscopy of metal NPs requires further studies to assess their stability and influence of various external factors on their activity