A Method for Studying the Effects of Neurochemicals on Long-Term Compensation in Unilaterally Labyrinthectomized Rats

A new method has been developed to study the influence of drugs and toxicants on longterm recovery of dynamics in the horizontal vestibulo-ocular reflex of the rat after hemilabyrinthectomy (HL). HL was performed by injecting sodium arsanilate into the middle ear. The lesion was confirmed by histology. Eye movements elicited by sinusoidal vestibular stimulation, in both light and darkness, were recorded by a search-coil technique and then analyzed by a computer program created with virtual instrument soft-ware, which calculated the gain of the slow-phase velocity (SPV) and the saccades para-meters (frequency, amplitude, and peak velocity) to the lesioned side and to the intact side separately. During the 2-10 week period after HL, repeated analysis of the spontaneous long-term recovery of such parameters revealed a slight but significant reduction of the post-HL asymmetry between SPV gain to the lesioned side and to the intact side. During the follow-up period, a post-HL increase of the phase lead remained unchanged. The reduced number of saccades/min was not completely restored. To test the usefulness of the experimental model for neurochemical investigation of such adaptation, we administered baclofen and toluene to rats 8–12 wk after hemilabyrinthectomy. Baclofen, a specific GABAB agonist, immediately restored the symmetry of SPV gain. By contrast, toluene, which has some effects on the central vestibular system that are related to GABAB transmission, aggravated the asymmetry in both the SPV gain and the number of saccades. We suggest that the experimental model would be useful for studying neurochemical mechanisms in vestibular adaptation processes

Transformational leadership in sports : a case study exploring leadership in practice

Teorin om transformellt ledarskap är den mest studerade ledarskapsstilen inom organisationsforskning, men är inte så utforskat i en idrottskontext. Transformellt ledarskap bygger på de fyra dimensionerna idealiserad påverkan, inspirerande motivation, intellektuell stimulans och individuellt hänsynstagande. Syftet med denna uppsats har varit att studera det transformella ledarskapet i ett idrottslag och hur ledarskapet inom laget upplevs från ett tränar- och spelarperspektiv, samt att undersöka hur en ny tränare kan förändra laget. Detta har utförts med en fallstudie där huvudtränaren och tre av spelarna har intervjuats för åsikter och erfarenheter av ledarskapet. Semistrukturerade intervjuer, baserade på en omformulering av påståenden av Transformational Teaching Questionnaire, har använts för att få djupgående information och mer noggranna förklaringar och ge exempel hur det transformella ledarskapet uppfattas i praktiken. Resultatet visar att upplevelsen av tränaren som ledare till stor del delas av både tränaren som spelarna. Genom att tränaren har en stark personlighet har hen lyckats influera spelarna och förändra beteendet hos dem. Tränaren har även, sedan hen tog vid, lyckats skapa en bra lagsammanhållning i gruppen vilket har framkommit under samtliga intervjuer. Spelarna upplever att de får vara delaktiga i vissa delar av besluten där målsättningen är en betydande del, dock sätter tränaren strukturen för hur denna ska nås. Resultaten visar att det är den assisterande tränaren som tar de individuella samtalen med spelarna medan huvudtränaren ansvarar för det övergripande för hela laget. Från dessa resultat kan vi argumentera för att tränaren, vill viss grad, är en transformell ledare även om alla kriterier inte möts. Denna slutsats påverkas starkt av de yttre omständigheter som omgav laget förra säsongen.The theory of transformational leadership is the most commonly studied leadership style in organizational research, but not so well explored in a sport context. The aim of this thesis has been to study the transformational leadership in a sports team and how the leadership within the team is perceived from both a coach and players perspective by also taking into consideration how a new coach can change the team. This has been performed as a case study where the head coach and three of the players has been interviewed for opinions and experiences of the leadership. Semistructured interviews, based on reformulated statements of the Transformational Teaching Questionnaire, have been used to get in-depth information and more thorough explanations and get examples how the transformational leadership is perceived in practice. The result shows that the perception of the coach as a leader is to a big part shared by both the coach and the players. With the results from the thesis we can argue that the coach, to some points, is a transformational leader although not meeting all criteria’s. The results also show that the coach has been a big part in changing the team dynamic and their performance. The conclusion is strongly affected by the circumstances that surrounded the team last season

A ratchet mechanism for amplification in low-frequency mammalian hearing

The sensitivity and frequency selectivity of hearing result from tuned amplification by an active process in the mechanoreceptive hair cells. In most vertebrates the active process stems from the active motility of hair bundles. The mammalian cochlea exhibits an additional form of mechanical activity termed electromotility: its outer hair cells (OHCs) change length upon electrical stimulation. The relative contributions of these two mechanisms to the active process in the mammalian inner ear is the subject of intense current debate. Here we show that active hair-bundle motility and electromotility can together implement an efficient mechanism for amplification that functions like a ratchet: sound-evoked forces acting on the basilar membrane are transmitted to the hair bundles whereas electromotility decouples active hair-bundle forces from the basilar membrane. This unidirectional coupling can extend the hearing range well below the resonant frequency of the basilar membrane. It thereby provides a concept for low-frequency hearing that accounts for a variety of unexplained experimental observations from the cochlear apex, including the shape and phase behavior of apical tuning curves, their lack of significant nonlinearities, and the shape changes of threshold tuning curves of auditory nerve fibers along the cochlea. The ratchet mechanism constitutes a general design principle for implementing mechanical amplification in engineering applications.Comment: 6 pages, 4 figures, plus Supplementary Information. Animation available on the PNAS website (http://dx.doi.org/10.1073/pnas.0914345107)

Dendrogenin A and B two new steroidal alkaloids increasing neural responsiveness in the deafened guinea pig

Aim: To investigate the therapeutic potential for treating inner ear damage of two new steroidal alkaloid compounds, Dendrogenin A and Dendrogenin B, previously shown to be potent inductors of cell differentiation. Methods: Guinea pigs, unilaterally deafened by neomycin infusion, received a cochlear implant followed by immediate or a two-week delayed treatment with Dendrogenin A, Dendrogenin B, and, as comparison artificial perilymph and glial cell-line derived neurotrophic factor. After a 4-week treatment period the animals were sacrificed and the cochleae processed for morphological analysis. Electrically-evoked auditory brainstem responses were measured weekly throughout the experiment. Results: Following immediate or delayed Dendrogenin treatment the electrical responsiveness was significantly maintained, in a similar extent as has been shown using neurotrophic factors. Histological analysis showed that the spiral ganglion neurons density was only slightly higher than the untreated group. Conclusions: Our results suggest that Dendrogenins constitute a new class of drugs with strong potential to improve cochlear implant efficacy and to treat neuropathy/synaptopathy related hearing loss. That electrical responsiveness was maintained despite a significantly reduced neural population suggests that the efficacy of cochlear implants is more related to the functional state of the spiral ganglion neurons than merely their number

Влияние параметров торцовой фрезы на характер обработанной поверхности

Материалы ХI Международной науч.-техн. конф. студентов, магистрантов и аспирантов [28-29 апреля 2011 г., г. Гомель]. - Гомель, 2011

Single molecule analysis of combinatorial splicing

Alternative splicing creates diverse mRNA isoforms from single genes and thereby enhances complexity of transcript structure and of gene function. We describe a method called spliceotyping, which translates combinatorial mRNA splicing patterns along transcripts into a library of binary strings of nucleic acid tags that encode the exon composition of individual mRNA molecules. The exon inclusion pattern of each analyzed transcript is thus represented as binary data, and the abundance of different splice variants is registered by counts of individual molecules. The technique is illustrated in a model experiment by analyzing the splicing patterns of the adenovirus early 1A gene and the beta actin reference transcript. The method permits many genes to be analyzed in parallel and it will be valuable for elucidating the complex effects of combinatorial splicing

Aminoglycoside antibiotics impair calcium entry but not viability and motility in isolated cochlear outer hair cells

Cochlear outer hair cells have been well established as primary targets of the ototoxic actions of aminoglycoside antibiotics. These cells, isolated from the guinea pig cochlea and maintained in short-term culture, were used as a model for evaluating the acute effects of gentamicin on cell viability, depolarization-induced transmembrane calcium flux, and depolarization-induced motile responses. On the basis of morphology and fluorochromasia, the presence of extracellular gentamicin as high as 5 mM did not affect the viability of the cells for up to 6 hr, the longest time tested. Viable cells showed binding of fluorescently tagged gentamicin to their base but excluded the drug from their cytoplasm. In response to [K + ]-depolarization, intracellular calcium levels (monitored with the fluorescent calcium-sensitive dye fluo-3) increased from a resting value of 218 ± 102 nM to 2,018 ± 1,077 nM concomitant with a cell shortening of 0.7% ± 1.3%. The depolarization-induced calcium increase was apparently caused by calcium entry into the cell as it was inhibited by the calcium-channel blocker methoxyverapamil and prevented in the absence of extracellular calcium. Both gentamicin and neomycin blocked the [K + ]-induced calcium increase at an IC 50 of 50 ΜM. Despite the inhibition of calcium entry the ability of the outer hair cells to shorten under [K + ]-depolarization was not impaired; in fact, cell shortening was even more pronounced in the absence of calcium influx (2.6% ± 1.4%). This argues effectively against the existence of a calcium-dependent actomyosin-mediated component in [K + ]-induced shape changes. The results suggest the existence of voltage-gated calcium channels in outer hair cells and that calcium influx through these channels is impaired by the aminoglycoside antibiotics neomycin and gentamicin. This action may be part of the acute ototoxic mechanism of these molecules. Furthermore, the results not only confirm the calcium independence of the depolarization-induced motility but also suggest that calcium influx into outer hair cells opposes cell shortening.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50224/1/490240226_ftp.pd

The 5′-end heterogeneity of adenovirus virus-associated RNAI contributes to the asymmetric guide strand incorporation into the RNA-induced silencing complex

Human Adenovirus type 5 encodes two short RNA polymerase III transcripts, the virus-associated (VA) RNAI and VA RNAII, which can adopt stable hairpin structures that resemble micro-RNA precursors. The terminal stems of the VA RNAs are processed into small RNAs (mivaRNAs) that are incorporated into RISC. It has been reported that VA RNAI has two transcription initiation sites, which produce two VA RNAI species; a major species, VA RNAI(G), which accounts for 75% of the VA RNAI pool, and a minor species, VA RNAI(A), which initiates transcription three nucleotides upstream compared to VA RNAI(G). We show that this 5′-heterogeneity results in a dramatic difference in RISC assembly. Thus, both VA RNAI(G) and VA RNAI(A) are processed by Dicer at the same position in the terminal stem generating the same 3′-strand mivaRNA. This mivaRNA is incorporated into RISC with 200-fold higher efficiency compared to the 5′-strand of mivaRNAI. Of the small number of 5′-strands used in RISC assembly only VA RNAI(A) generated active RISC complexes. We also show that the 3′-strand of mivaRNAI, although being the preferred substrate for RISC assembly, generates unstable RISC complexes with a low in vitro cleavage activity, only around 2% compared to RISC assembled on the VA RNAI(A) 5′-strand

Waves on Reissner's membrane: a mechanism for the propagation of otoacoustic emissions from the cochlea

Sound is detected and converted into electrical signals within the ear. The cochlea not only acts as a passive detector of sound, however, but can also produce tones itself. These otoacoustic emissions are a striking manifestation of the cochlea's mechanical active process. A controversy remains of how these mechanical signals propagate back to the middle ear, from which they are emitted as sound. Here we combine theoretical and experimental studies to show that mechanical signals can be transmitted by waves on Reissner's membrane, an elastic structure within the cochea. We develop a theory for wave propagation on Reissner's membrane and its role in otoacoustic emissions. Employing a scanning laser interferometer, we measure traveling waves on Reissner's membrane in the gerbil, guinea pig, and chinchilla. The results accord with the theory and thus support a role for Reissner's membrane in otoacoustic emissions.Comment: 30 pages, 6 figures, and Supplemental informatio