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Biomedical subjects

V V Popov

Publications and source records attributed to V V Popov.

At least 55 records · Page 3Linked to original sources
PubMed1993

Direction-dependent spectral sensitivity and interaural spectral difference in a dolphin: evoked potential study.

Sensitivity and interaural intensity difference (IID) dependence on sound frequency and direction was measured in an Amazon river dolphin Inia geoffrensis by recording the auditory nerve evoked response from the body surface. The maximal sensitivity in the horizontal plane was found when the sound direction was 5 degrees to 10 degrees ipsilateral to the recorded ear; the direction dependence of sensitivity was more pronounced at higher frequencies than at lower ones. The IID reached its peak at small azimuthal angles (7.5 degrees to 15 degrees) and higher sound frequencies (100 kHz), or at large azimuthal angles (30 degrees to 45 degrees) and lower sound frequencies (20 to 30 kHz). Each sound direction featured its specific pattern of spectral sensitivity and of interaural spectral difference. The interaural spectral difference fluctuated within a range of more than 20 dB depending on sound direction. The data indicate that interaural intensity as well as spectral difference may be cues for binaural localization of sound direction by dolphins.

Acoustic Stimulation↗
PubMed1991

Interaural intensity and latency difference in the dolphin's auditory system.

Binaural hearing mechanisms were measured in dolphins (Inia geoffrensis) by recording the auditory nerve evoked response from the body surface. The azimuthal position of a sound source at 10-15 degrees from the longitudinal axis elicited interaural intensity disparity up to 20 dB and interaural latency difference as large as 250 microseconds. The latter was many times greater than the acoustical interaural time delay. This latency difference seems to be caused by the intensity disparity. The latency difference seems to be an effective way of coding of intensity disparity.

Acoustic Stimulation↗
PubMed1991

[10 years' experience of heart valve bioprostheses. Present status and future development].

Long-term results of mitral valve replacement with bioprostheses of three original designs are overviewed. Refinement of the supporting framework design, and of modelling and conservation methodologies has made it possible to improve the survival rates and provided for the absence of specific complications in two groups of patients. Experimental evidence allows for anticipating an increase in the terms of bioprostheses performance.

Adolescent↗
PubMed1990

Location of an acoustic window in dolphins.

Auditory brainstem responses (ABR) to sound clicks from sources in different positions were recorded in dolphins Inia geoffrensis. The position of the acoustic window was determined by measurement of acoustic delays. The acoustic window was found to lie close to the auditory meatus and the bulla rather than on the lower jaw.

Animals↗
PubMed1990

Auditory brain stem responses in characterization of dolphin hearing.

Auditory brain stem responses (ABR) were recorded from the head surface of non-anesthetized and non-relaxed bottle-nosed dolphins, Tursiops truncatus. The region of best ABR recording was shown to be located 6-9 cm caudal to the blowhole. The threshold values were about 1 mPa for noise bursts and -3 dB re 1 mPa for tone bursts of the optimal frequency (80 kHz). The maximum frequency at which ABR could be evoked was 140 kHz. The duration of temporal summation reached 0.5 ms at intensities near the threshold and decreased with an increase in intensity. When the stimuli were paired clicks of the same intensity, the time to complete recovery from the second response was about 5 ms, while that to its 50% recovery was 0.7 ms. When the conditioning click exceeded the testing one in intensity, prolongation of the recovery period was observed. A 40-dB intensity difference led to an approximately 10-fold prolongation of this period.

Acoustic Stimulation↗
PubMed1989

[Treatment of patients with gonarthrosis by intra-articular administration of drugs].

The effectiveness of intra-articular administration of kenalog, hydrocortisone, gordox and polyvinylpyrrolidone to patients with gonarthrosis and concurrent synovitis was studied. Kenalog and hydrocortisone were more effective than placebo, while gordox, polyvinylpyrrolidone and placebo had similar effect. Kenalog and hydrocortisone had nearly the same favourable effect in synovitis. Only one patient treated with gordox had side effects. Signs of synovitis were analysed and its most typical symptoms specified.

Adult↗
PubMed1986

Evoked potentials of the auditory cortex of the porpoise, Phocoena phocoena.

Evoked potential (EP) recordings in the auditory cortex of the porpoise, Phocoena phocoena, were used to obtain data characterizing the auditory perception of this dolphin. The frequency threshold curves showed that the lowest EP thresholds were within 120-130 kHz. An additional sensitivity peak was observed between 20 and 30 kHz. The minimal EP threshold to noise burst was 3 X 10(-4) - 10(-3) Pa. The threshold for response to modulations in sound intensity was below 0.5 dB and about 0.1% for frequency modulations. Special attention was paid to the dependence of the auditory cortex EP on the temporal parameters of the acoustic stimuli: sound burst duration, rise time, and repetition rate. The data indicate that the porpoise auditory cortex is adapted to detect ultrasonic, brief, fast rising, and closely spaced sounds like echolocating clicks.

Acoustic Stimulation↗
PubMed1986

[Hemodynamic results of replacing the mitral valve with an aortic xenobioprosthesis].

Results of an analysis of clinico-hemodynamic data obtained in 66 patients with bioprosthesis of the mitral valve are presented. The data of intraoperative examination as well as of catheterization of heart cavities within the period from 6 to 62 months after operation show the xenoaortic bioprosthesis to give an adequate correction of the mitral valve defect, their implantation was followed by a substantial improvement of the patients's state.

Adult↗
PubMed1985

[Topical organization of somatic projections to the cerebral cortex of the seal Callorhinus ursius].

Somatotopic projections in the cerebral cortex of the fur seal (Callorhinus ursinus) were determined by microelectrode recordings of the multiple unit activity. Somatosensory cortical area is restricted rostrally by postcruciate and coronal sulci, caudally by anterior suprasylvain sulcus and dorsomedially by ansate sulcus. The somatotopic map in this area is oriented in such a way that the head projection is positioned ventrolaterally and that of the hindlimb dorsomedially. The projection area of the forelimb is immersed in the coronal sulcus. Marked disproportions are observed in the projections of different parts of the soma; the head projection has a relatively large magnification factor and within it the vibrissae are presented with the largest magnification.

Animals↗