[The hearing function in the one-year old children with intrauterine growth retardation evaluated by two objective audiological methods].

The objective of the present study was to collect objective information about the hearing function in the prematurely born infants suffering intrauterine growth retardation (IUGR). The audiological examination of 77 patients at the age of 12 months was performed using two different methods making use of distortion product otoacoustic emission (DPOAE) and evoked auditory steady state responses (ASSRs). Hearing disorders were diagnosed in the children presenting with grade II and III IUGR born prior to the 34th week of pregnancy. The results of the study indicate that the children with grade II and III intrauterine growth retardation born earlier than the 34th week of pregnancy are at risk of developing hearing impairment and should be under dynamic audiological observation with the use of two objective methods, namely DPOAE and ASSR.

[Tympanometry in the premature infants of different gestational age during the primary audiological examination].

The objective of the present work was to study specific approaches of tympanometry in the premature infants of different gestational age. A total of 122 typmanograms (243 ears) were available for the analysis. Peculiarities of recording tympanograms and their characteristics in the premature infants of different gestational age (including static compliance, intratympanic pressure, and tympanogram width) have been demonstrated. The optimal frequency of tympanometry in the premature infants of different gestational age was determined.

[Changes in auditory function during first 6 months in premature children with intrauterine growth retardation].

AIM: To define an influence of intrauterine growth restriction to forming of hearing function of preterm infants. PATIENTS AND METHODS: The audiological test by the method of distortion product otoacoustic emission (DPOAE) was performed 3 times (during supposed dates of birth; 3 months old; 6 months old) in 136 premature children born while different gestation periods. Children were divided into 2 groups: premature children with intrauterine growth restriction (IUGR) and premature children with normal weight for their gestation age (normotrophy). RESULTS: During checkup in supposed date of birth of children with IUGR, DPOAE was detected less than children with normotrophy and with the same gestation period. Test results in all 3 months old premature children of gestation period less than 32 weeks were significantly lower in comparison with children of another date of gestation. Results in 6 months old children with IUGR and with normotrophy were almost identical. In 17% of children with IUGR born at term gestation less than 32 weeks of auditory function is not available. Children with normotrophy from the same subgroup lack of auditory function were noted in 12% of cases. CONCLUSIONS: Premature children with IUGR maturing of auditory function is likely not to end in 6 months and can continue after 6 months.

[The study of maturation of the auditory analyzer rabbit according distortion-product otoacoustic emissions].

AIM: In our chronic experiment to register changes of acoustic response of Distortion-Product Otoacoustic Emissions (DPOAE) of intact rabbits in postnatal ontogenesis for the purpose of getting normative data which can be used for studying impact of pathological factors on auditory function and maturation of activity of outer hair cell in ontogenesis. MATERIALS AND METHODS: Study of otoacoustic emissions used mature chinchilla rabbits with a 19 day life of up to 3 months. RESULTS: In the course of ripening were obtained functional activity of outer hair cells of the cochlea. CONCLUSION: normative data obtained allow us to study using a rabbit model, the pathological effects of agents on the maturation of the outer hair cells of the cochlea in the experiment.

[The functional state of the auditory analyzer in prematurely born infants (after 29 weeks of gestation) at 6 months of life].

The objective of the present study was to evaluate the functional state of the auditory analyzer in infants born prematurely (after 29 weeks of gestation) and examined at 6 months of life. The evoked otoacoustic emission (EOAE) techniques were used for the purpose. Testing with the help of two different modes of EOAE yielded virtually identical results which confirms the possibility to apply both delayed EOAE (dEOAE) and distortion-product frequency OAE (dpOAE) for the assessment of the auditory function. It is concluded that the degree of cochlear development in prematurely born infants (after 29 weeks of gestation) examined by the dpOAE technique at 6 months of life is significantly different from that in children born between the gestation age of 33 and 37 weeks.

[The functional state of the cochlea in premature infants born before 28 weeks gestation on the 6th month of life].

The objective of the present study was to assess the state of the peripheral portion of the auditory analyzer based on induced otoacoustic emissions (IOAEs), distortion product otoacoustic emissions (DPOAEs), and delayed IOAEs (DIOAEs). The study included 31 premature infants born before 28 weeks gestation and examined later on the 6th month of postnatal life. All of them were shown to have the underdeveloped cochlea. It was shown that the DPOAEs technique makes it possible to record induced otoacoustic emissions more frequently than the DIOAEs method. It is concluded that the hearing function in premature infants born before 28 weeks gestation should be evaluated on the 6th month of postnatal life based on two classes of emission.

[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.

[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.

[Morphofunctional characteristics of the cat spiral ganglion in neurosensory hypoacusis]. / Morfofunktsional'naia kharakteristika spiral'nogo gangliia koshek v usloviiakh neirosensornoi tugoukhosti.

Morphofunctional disorders in spiral ganglion in animals of different groups of age with neurosensory hardness of hearing due to ototoxic antibiotics have been shown. Antibiotic intoxication in kittens in early postnatal period arouses essential deviation from normal process of development of neurocytes in spiral ganglion. In the first rate low level of their metabolic activity must be shown. Delay of differentiation of neurocytes makes essential influence on the development of spiral ganglion as the unit of transmission of audio-information. The main feature of morphofunctional disorders in neurocytes of ganglion of grown-up animals is inhibition of protein synthesis mechanism activity.

[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 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.

[Coronary blood outflow along parasinoidal pathways in the left heart (possible pathogenesis of angina attacks with normal coronary circulation)]. / Sbros koronarnoi krovi po parasinusnym putiam v levye otdeli serdtsa (vozmozhnyi patogenez pristupov stenokardii pri normal'nom koronarnom krovotoke).

Acute experiments on isolated cat hearts were made to study the involvement of the parasinus pathways of the left heart in the blood outflow from the myocardium. The magnitude of the blood outflow to the left heart via the parasinus pathways may vary within a wide range, depending on heart function conditions. During heart work normalization, the specific values of the outflow to the left heart are minimal, amounting on an average to 10%, those under heart perfusion with venous blood to 39%, reaching 64% after 30 minutes of ischemia. The data obtained indicate that the assessment of myocardial supply by the blood inflow to the coronary arteries cannot be regarded as adequate and that angina pectoris attacks may occur because of the shunt drainage of the coronary blood, by-passing the myocardial capillaries.