Effect of gentamicin on the auditory analyzer in sexually immature animals.

Auditory function of immature rabbits was evaluated using two electrophysiological methods, brainstem auditory evoked response (BAER) and distortion product otoacoustic emission (DPOAE), in chronic experiments following administration of therapeutic doses of gentamicin. Impairment of auditory function manifested in increased thresholds and decreased amplitude of the 1st BAER peak was established. DPOAE parameters were not significantly changed. It was suggested that gentamicin decreased activity of spiral ganglion neurocytes in animals with immature auditory analyzer.

Effects of amikacin on maturation of the auditory analyzer in rabbits.

We studied the dynamics of maturation of the hearing function by records of short-term latent brainstem evoked potentials and the effect of amikacin on maturation of the hearing function. The peripheral compartment of the auditory analyzer matures sooner than the central structures. Amikacin in therapeutic doses exhibited an ototoxic effect on the peripheral compartment of the auditory analyzer without impairing its central structures.

[Electrophysiological evaluation of the hearing function following cisplatin administration].

Experiments on guinea pigs with the use of electrophysiological methods (short-latency auditory evoked potentials, SLAEPs, and distortion product otoacoustic emission, DPOAE) have demonstrated damage of outer hair cells following application of therapeutic doses of cisplatin. It is concluded that finding of the logarithmic amplitude-time dependence for the first SLAEPs peak permits to diagnose an injury to outer hair cells.

[Specific ototoxic effects of monomycin in immature animals].

Dynamics of the hearing function was evaluated using immature animals based on the SSCP data. Morphological characteristics of the cochlear auditory ganglion were studied after administration of therapeutic doses of the ototoxic antibiotic monomycin. Untreated animals served as controls. The results of morphofunctional investigations were evaluated in comparison with the similar data obtained in adult cats after injection of the same doses of monomycin.

[Investigation of aggregates of dyes by the method of resonance light scattering: correction of spectra].

Resonance light scattering, a phenomenon of an abrupt enhancement of Rayleigh light scattering in close proximity to an absorption band, is easily detectable in solutions of strongly absorbing chromophores, which form large aggregates with strong pi-pi-electronic coupling among the chromophores. Resonance light scattering spectra need to be corrected for the sensitivity of spectrofluorimeter as well as for the effects of internal light filter. A method for correcting the measured resonance light scattering is described. It was shown by the method that the addition of KCl induces the formation of extended supramolecular aggregates (probably of H-type) of the anionic dye merocyanine 540 in water. The spectra of the resonance light scattering of the photosensitizer meta-tetra(hydroxyphenyl)chlorin (mTHPC, foscan ) indicate the formation of J-aggregates of this dye in aqueous medium.

[Impact of sound signals of high intensity on the acoustic analyzer].

Guinea-pig experiments were made for objective assessment of the effects of high-intensity noise on the acoustic analyzer. Noise with intensity above 100 dB for 11 hours is accompanied with thresholds rise by 20 dB. In some animals hearing loss was observed for several weeks after discontinuation of a sound impact. In the presence of initially high conductive hypoacusis intensive sound load may cause short-term sound threshold lowering with further damage to neurosensory cochlear elements.

[Ototoxic effect and its prevention in administration of cisplatin]. / Ototoksicheskoe deistvie tsisplatina i vozmozhnosti ego profilaktiki.

Short-latent acoustic evoked potentials were registered in examination of hearing function in guinea pigs given platinum compounds. A protective action of thiol compounds (sodium thiosulfate and unitiol) was tried in relation to hypoacusis induced by cisplatinum.

[Method of objective assessment of hearing function according to the findings of recording short-latency auditory evoked potentials (an experimental study)]. / Metod ob"ektivnoi otsenki slukhovoi funktsii po dannym registratsii korotkolatentnykh slukhovykh vyzvannykh potentsialov (éksperimental'noe issledovanie).

This experimental study was performed to compare amplitude and time characteristics of SLAEP spike 4 in healthy animals with those in animals having induced conductive and neurosensory hypoacusis. SLAEP analysis by the logarithmic function of spike 4 amplitude of its latent period provided distinctions in the curve shapes typical for conductive versus neurosensory hypoacusis. These differences may help in the practice of differential diagnosis.

[An analysis of the effect of different factors in early ontogeny on the behavior of sturgeon fry]. / Analiz vliianiia razlichnykh faktorov v rannem ontogeneze na povedenie molodi sevriugi.

The fractional factorial analysis of 2(5) type was carried put in order to estimate the influence of 5 different factors on stellate sturgeon fry behaviour in early ontogenesis. Different indices obtained in hydrodynamic test, in "open-field" test, in passive avoidance conditioning procedure were analysed. Statistically significant positive and negative influences on the indices were found for all the factors (level of illumination, food diets, high or low stream, presence or absence of predator fishes, character of a bottom). The most probable mechanism of stellate sturgeon behaviour modifications under the influence of different factors is the selection (predominant survival) of the samples which possess peculiarities the most adequate to environmental conditions.

[Comparative study of nerve stimulation factors by a single rectangular impulse and a series of rectangular impulses]. / Sravnitelnoe izuchenie parametrov stimuliatsii nerva odinochnym priamougolnym stimulom i seriei priamougolnykh impulsov.

The experiments were performed on the sciatic nerve of Rana temporaria. A single rectangular electric impulse and a series of rectangular microsecond impulses were used for stimulation. The threshold amplitude of a single impulse and the average voltage in series of impulses were compared. It was experimentally shown that application of a series of impulses as a stimulus necessitated less values of stimulation near the threshold. There was no significant difference between the average voltage in a series of impulses and the amplitude of a single rectangular impulse in stimulation far up the threshold.

[Extracochlear prosthesis in acute experiment]. / Ekstrakokhlearnoe protezirovanie v ostrom éksperimente.

Whether the transfer of coded sound intensity is possible was studied in acute experiments on cats with acquired deafness, using an original transducer of the signals with extracochlear position of the electrodes. The stimulation results were compared to intracochlear prosthesis. The type of the stimulation was not essential for threshold values of the total electric impact. In extracochlear position of the electrodes and the duration of potential 0.2 msec its amplitude increment was the highest, while the dynamic range turned out the lowest. With the impulse duration 0.5 msec, these differences disappeared. When compared to extracochlear, intracochlear bipolar stimulation proved superior.

[The effect of electrical and acoustic stimulation in early ontogeny on the characteristics of higher nervous activity and on the nucleic acid content of the tissues in chum salmon fry]. / Vliianie élektricheskoi i akusticheskoi stimuliatsii v rannem ontogeneze na kharakteristiki vysshei nervnoi deiatel'nosti i soderzhanie nukleinovykh kislot v tkaniakh molodi kety.

Stimulation of salmon larvae by electric current led further to unstable character of reactions in the open field. Acoustic stimulation both by tonal and musical signals favourably influenced the behaviour in the open field and the ability to elaborate conditioned reflexes. Changes of the content of nucleic acids were not found in the brain tissue but were found in the muscles, where they correlated with the growth speed and motor activity of the experimental fishes. The obtained data show the possibility of elaboration of applied methods of the control of CNS development and behaviour of young fishes at fishing plants.

[The effects of mono- and bipolar stimulations of the acoustic nerve by a pulse current]. / Effekty mono- i bipoliarnoi stimuliatsii slukhovogo nerva impul'snym tokom.

The amplitudes of the EPs during monopolar and bipolar stimulation of the acoustic nerve were analysed in the cat auditory cortex. Increasing number of trains of 0.2 and 0.5 msec duration of short (5 mu sec) electric pulses were delivered to the streptomycin-damaged cochlea. The comparison of the two types of stimulation revealed a larger dynamic range and a higher increase in the amplitude at the bipolar stimulation. The average value of the stimulation current was lower for the monopolar stimulation.

[Response of cortical evoked potentials to electric stimulation of the acoustic nerve in animals with damaged cochlea]. / Korkovye vyzvannye potentsialy na élektricheskoe razdrazhenie slukhovogo nerva u zhivotnykh s povrezhdennoi ulitkoi.

Evoked potentials of the auditory cortex during the electrical stimulation of the cochlea were studied in acute experiments on cats. A series of electric pulses of short duration and different frequency delivered to the streptomycin-damaged cochlea were used as a stimulus. It has been shown that an amplitude and latency of electrical cortex responses depended on the number of pulses in series and on the interpulse intervals. Amplitudes of evoked responses increased with the growth of the number of stimuli. Latent periods changed in a narrower stimulation frequency band. Dependence of the induced potentials' amplitude growth on the increase in the number of electric pulses changed as a result of the two-fold enhancement of the stimulation amplitude.

[Effect of low-energy laser irradiation on the functional state of the acoustic analyzer (experimental study)]. / Vliianie izlucheniia nizkoenergeticheskogo lazera na funktsional'noe sostoianie slukhovogo analizatora (eksperimental'noe issledovanie).

The acoustic function of guinea-pigs (in terms of ERA) before and after middle ear laser treatment (LHe-75, radiation intensity 15-17 mW, total dose 63 J/cm2, number of exposures 14) was investigated. The experiment was carried out using three groups of animals. Group 1 included healthy young animals. Group 2 consisted of adult animals with no signs of otitis media suppurativa. Group 3 involved adult guinea-pigs with chronic suppurative otitis media. After laser treatment all the animals showed increase of amplitudes of all ERA peaks, specifically of the first peak, an increase of the A1/A4 ratio, and an insignificant shortening of L1 at low sound intensities in group 1 and group 2 animals. This may suggest a greater excitation of the first component of the acoustic system. The group 3 animals exhibited a greater L1; this indicates that laser therapy of an untreated cavity during chronic otitis media may aggravate the pathological process. This pathology requires pretreatment of the middle ear cavity and laser therapy in combination with other therapeutic measures. None of the treated animals showed changes of the second time interval, whereas the third time interval (central time of conduction) became shorter, particularly on the side exposed to laser treatment. Our findings demonstrated differences in responses of adult and young animals to laser treatment (distinct shortening of the central time of conduction in those latter) which obviously needs further study.