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Biomedical subjects

A Axelsson

Publications and source records attributed to A Axelsson.

At least 163 records · Page 9Linked to original sources
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Cochlear vascular and sensory cell changes induced by elevated temperature and noise.

The vascular anatomy of the chinchilla cochlea was quantitatively analyzed and compared in animals exposed to 155- or 160-dB impulse noise at normal (37 degrees C) and elevated (40 degrees C) body temperatures. Vascular changes persisted 45 days after noise exposure in all experimental animals. Six variables were most susceptible to change in one or more of the vessels studied: 1) irregularities in the vessel lumen, 2) plasma spaces between red blood cells (RBCs) and the vessel wall, 3) columns of RBCs, 4) variability in density of RBCs, 5) pigment clumps in the stria vascularis, and 6) perivascular cells compressing the vessel lumen. These vascular changes, which indicate a reduction in blood flow, were present throughout the length of the cochlea, with a tendency toward maximum change in areas of maximum hair cell loss. There was no evidence in the vascular results to support an interaction between noise and increased body temperature. However, the cochleograms from the experimental animals indicate that at the 160-dB exposure level the noise and high temperature may have interacted to increase hair cell loss.

Animals↗
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The vascular anatomy of the gerbil cochlea.

The vascular pattern of the cochlea was studied in 12 adult gerbils (Meriones unguiculatus) using the Berlin blue (Prussian blue) contrast injection technique. The capillary areas of the gerbil cochlea are similar to those of other mammals studied. As in some other mammals, the vessel of the basilar membrane was inconsistently identified in the basal turn. It was usually replaced by a larger uninjected channel, supporting the suggestion that the vessel of the basilar membrane may be more functionally important in fetal life than in adulthood. The vascular pattern of the external cochlear wall is well maintained from base to apex, although a simplification of vasculature can be observed apically.

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Comparative anatomy of cochlear blood vessels.

The vascular anatomy of most mammalian cochleas is similar. Of those examined to date, the human cochlea is the most unusual. The blood flow is segmentally, centrifugally, and centripetally arranged, with many spirally perpendicular vessels shunted in, suggesting good possibilities for variations of circulation. There is a pronounced apical simplification of the vascular pattern probably more than corresponding to the decreasing volume of the turns. The blood supply of the scala vestibuli is mainly arterial; that of the scala media is capillary or by-pass, and that of the scala tympani is venous. The vessel of the basilar membrane shows great variations among species, from presence in all turns to complete non-existence. Its importance and size is greater during embryonic life.

Animals↗
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Measurement of diffusion coefficients in gels using holographic laser interferometry.

The accuracy and precision of holographic interferometry as a method to measure diffusion coefficients in gels are investigated both experimentally and theoretically. The standard deviations in the experimentally determined diffusion coefficient for ethanol in 4% (w/v) agarose gel were 3.3% for diffusion into the gel and 6.1% for diffusion out of the gel. These are in good agreement with the standard deviations obtained using Monte Carlo simulations. Systematic errors derived from an assumption of constant diffusion coefficients were also investigated.

Computer Simulation↗
PubMedDate not supplied

Pop music and hearing.

Several factors indicate the possibility of sensorineural hearing loss in connection with pop music. However, very few investigations have examined the hearing in pop musicians and their audience. Sensorineural hearing loss was only demonstrated in 5% of musicians. In our own material, we found a sensorineural hearing loss in 13% defined as a mean pure-tone threshold at 3, 4, 6, and 8 kHz of more than 20 dB HL. The hearing loss was, as expected, correlated with age, duration of exposure, military service, etc. Temporary threshold shift measurements showed that musicians were more resistant to pop music noise than the audience and that female listeners were more resistant than male listeners. The findings leave many interesting questions concerning the relationship between noise and hearing loss.

Adult↗
PubMedDate not supplied

Temporary threshold shift after exposure to noise and music of equal energy.

Ten voluntary subjects were exposed to 10 min of recorded pop music on five occasions. On five other occasions these subjects were exposed to a noise with level-, frequency-, and time-distribution characteristics, measured in octave-band steps, equal to those of the music. Measurements of temporary threshold shift showed almost equal sensitivity to the two stimuli in four subjects, whereas six others demonstrated marked differences in sensitivity. Differences were always due to more temporary threshold shift after exposure to the nonmusical noise stimulus. These findings imply that factors other than physical properties of the fatiguing sound contribute to the degree of temporary threshold shift.

Adolescent↗
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Anatomical effects of sudden middle ear pressure changes.

Acute middle ear (ME) and inner ear changes following brief unilateral phasic ME pressure changes (up to +/- 6000/mm H2O) were studied in the guinea pig. Middle ear findings included perforation of the tympanic membrane, serous and serosanguinous exudate and hemorrhage of tympanic membrane and periosteal vessels. Changes were related to magnitude of applied pressure. Perforation and hemorrhage were more commonly seen with negative rather than positive pressure. Air bubbles behind the round window were seen with positive pressures. Occasional distortion, but never perforation of the round window, was noted. Hemorrhage of the scala tympani was observed with both positive and negative pressures; scala vestibuli hemorrhage was found with negative ME pressure. In some instances pressure direction and magnitude related changes were seen in the contralateral ear.

Animals↗
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Chronic effects of phasic middle ear pressure changes.

In an attempt to better define the mechanisms of barotrauma, middle and inner ear pathology was studied in guinea pigs three weeks following exposure to a brief, sudden middle ear pressure change. Findings included tympanic membrane perforations (particularly dependent upon high negative pressure exposures), vascular hemorrhage (primarily dependent upon high positive pressure exposures), serosanguineous effusions (predominantly dependent upon infection) and serous effusion (dependent upon negative pressure exposure). Round window perforations were common in high pressure animals with infection. Other inner ear membrane changes were infrequent or minimal. Lymphatic hemorrhage was observed as a function of exposure. The clinical implications of these findings and possible mechanisms underlying these changes are discussed in terms of our previously reported study of the immediate effects of such pressure change.

Animals↗
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Comparison of subjective and radiological findings during the course of acute maxillary sinusitis.

Some of the most common symptoms and signs of acute maxillary sinusitis were graded and compared with the radiological findings during the course of the disease. Four different treatment modes were used in 176 patients. The radiological and the subjective findings did not differ among the groups, which consequently were evaluated as an entity. The radiographic results demonstrated that the healing course during the first 15 treatment days follows an even regression line. The subjective findings show a more marked improvement during the first five days than subsequently, and also a more rapid initial improvement than radiography shows. The cough symptom showed the slowest recovery subjectively and also compared most closely with radiological findings. Patients with sinusitis which did not show an initial healing radiographically also had more marked symptoms the fifth day, and vice versa: patients who showed less than average healing subjectively also showed a slower healing radiographically.

Acute Disease↗
PubMedDate not supplied

Effect of high intensity impulse noise on the vascular system of the chinchilla cochlea.

Changes in the vasculature of the chinchilla cochlea were quantitatively assessed 45 days after impulse noise exposure of either 155- or 160-dB peak sound pressure level. The condition of the vessels in the lateral wall and spiral lamina of each cochlea was evaluated in terms of 20 morphological parameters. Multivariate statistical analysis identified the parameters that were significantly affected by the noise exposure. Evaluation of these significant parameters indicated a net reduction in blood flow to the cochlea. All of the noise-exposed cochleas showed vascular changes when compared to controls, and the magnitude of these changes was related to the amount of hair cell loss. The vascular changes are presumed to be permanent.

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