Polymerase chain reaction fingerprints.
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DNA↗
Biomedical subjects
R Salvi
Publications and source records attributed to R Salvi.
Anatomical correlates of impulse noise-induced mechanical damage in the cochlea.
Changes in the surface morphology of the organ of Corti in the chinchilla were studied following exposure to blast waves at 160 dB peak SPL. The generation and development of a mechanically induced lesion on the organ of Corti was followed over a period of 30 days using scanning electron microscopy. The most prominent feature of the lesion was the complete separation of a 5-7 mm strip of the sensory epithelia consisting of outer hair cells, Deiter cells and Hensen cells from the reticular lamina and the basilar membrane. The inner hair cells in this same area survived for several days in a remarkably normal condition. A spectrum of ciliary changes was observed on the inner and outer hair cells that differ somewhat from those commonly reported following continuous noise exposure. Some of the observed changes in morphology can be related to a variety of inferred mechanical events on the basilar membrane.
Animals↗
Amplitude modulation thresholds in chinchillas with high-frequency hearing loss.
Estimates of auditory temporal resolution were obtained from normal chinchillas using sinusoidally amplitude modulated noise. Afterwards, the animals were exposed to noise whose bandwidth was progressively increased toward the low frequencies in octave steps. The first exposure was to an octave band of noise centered at 8 kHz. Three additional octave bands of noise were subsequently added to the original exposure in order to progressively increase the extent of the high-frequency hearing loss. The first exposure produced a temporary hearing loss of 50 to 60 dB near 8 kHz and elevated the amplitude modulation thresholds primarily at intermediate (128 Hz) modulation frequencies. Successive noise exposures extended the temporary hearing loss toward lower frequencies, but there was little further deterioration in the amplitude modulation function until the last exposure when the hearing loss spread to 1 kHz. The degradation in the amplitude modulation function observed after the last exposure, however, was due to a reduction in the sensation level of the test signal rather than to a decrease in the hearing bandwidth. The results of this study suggest that the high-frequency regions of the cochlea may be important for temporal resolution.
Animals↗
[Hemodynamic changes during multilevel stress tests in supine and in sitting positions and during training on cycloergometer in recent myocardial infarction].
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Adult↗
Influence of vibration on asymptotic threshold shift produced by impulse noise.
Monaural chinchillas were exposed for 10 days to one of these conditions: (1) whole-body vibration (30 Hz, 1 g rms acceleration); (2) impact noise (113 dB peak SPL 1/s) or (3) a combination of whole-body vibration and impact noise. Thresholds were monitored before, during and after the exposure using the auditory-evoked response or behavioral conditioning techniques. Vibration alone had essentially no effect on threshold. Exposure to impact noise produced a stable asymptotic level of threshold shift 2-8 h after exposure onset. The asymptotic threshold shift was roughly 35 and 43 dB SPL at 0.5 and 8.0 kHz, respectively. Exposure to impact noise plus vibration produced an asymptotic threshold shift at 0.5 and 8.0 kHz that was approximately 10 dB greater than noise alone. The combination group also showed greater permanent threshold shifts and greater hair cell losses than the group exposed only to impact noise. The results imply that impact noise and whole-body vibration, at levels commonly found in industrial settings, can interact to increase the susceptibility of the chinchilla cochlea to noise-induced hearing loss.
Animals↗
[Recent myocardial infarction: incidence of the ventricular arrhythmias and correlations with some ecgraphic and hemodynamic parameters at rest and during exercise (author's transl)].
UNLABELLED: To assess incidence of ventricular premature beats (VPB) and correlate ECGraphic and hemodynamic data of parameters at rest and during exercise, 176 oligo or asymptomatic patients (167 males and 9 females) with recent myocardial infarction (RMI) (20-60 days after AMI) underwent a maximal symptom limited exercise test in supine position during hemodynamic monitoring (Swan-Ganz cath. 7F placed in pulmonary artery) without medical therapy. During the following 24 hours the patients underwent a continuous ambulatory ECG. 71 patients (40%) had no VPB (class 0), 56 patients (32%) had less than 1 VPB/hour (class 1), 35 patients (20%) had less than 6 VPB/minute and less than 30 VPB/hour (class 2) and 14 patients (8%) had greater than 6 VPB/minute and greater than 30 VPB/hour (class 3). Patients with VPB were then divided into qualitative classes: class A: 57 patients (54%) with isolated and unifocal VPB; class B: 38 patients (36%) with polifocal, bigeminal and paired VPB; class C: 10 patients (10%) with R on T or consecutive beats (3 or more). 28% of the patients had complex VPB (class B and C). 20% of all the patients (36/176) had VPB during exercise, 8 patients had VPB only during exercise, increasing the percentage of arrhythmias from 60% to 64%. VPB were more frequent and complex in patients with inferior or anterior + inferior MI than in patients with anterior MI and patients aged more than 60. Patients with complex VPB had cardiac volume index higher (p less than 0.05) than patients without VPB or with isolated VPB. Patients of different classes showed work capacity of 75-80 watts with 75-80% of maximal theoretic heart rate. Infarct size (NQ) was not correlated with number of VPB. Arrhythmias were slightly more frequent in patients with exercise ST depression (66%) than in patients without exercise ST depression (57%) (NS). No significant difference was found between ST elevation at rest and during exercise and VPB. PWP was, on the average, normal at rest (10 mmHg in the different classes) and slightly pathological during exercise with no differences between patients without VPB (class 0 = 21.7 mmHg) and patients with VPB (class 1 = 22.4 mmHg, Class 2 = 24.4 mmHg, Class 3 = 20.8 mmHg). IN CONCLUSION: in oligo or asymptomatic patients with RMI: a) exercise slightly increased the sensitivity of continuous ambulatory ECG to reveal VPB b) poor correlations were found between VPB and ECGraphic and hemodynamic parameters both at rest and during exercise.
Adult↗
VIII nerve response to click stimuli in normal and pathological cochleas.
A flat 30--50 dB hearing loss was established in chinchillas following a 5 day exposure to an octave band of noise (354--708 Hz, 95 dB SPL). After exposure, single auditory nerve fiber recordings were obtained using click and tone burst stimuli. The thresholds of units from the noise-treated animals were elevated 30--70 dB and the tuning curves were abnormally broad. At the threshold for click stimulation, the fiber latencies were shorter in the noise-treated animals than those in normal animals. However, the latencies for the two groups were similar when stimulated at the same intensities. As indicated by the number of peaks in the PST histograms obtained with clicks, the units from the noise-treated animals showed considerably more damping in the neural response than those from normal units. The temporal spacing between the peaks in the histograms for units of similar CF was the same in the normal and noise-treated groups, although this cannot be taken to infer that an individual unit PST histogram would remain the same after noise exposure as before. These limited neural data therefore show changes in the same direction as those in the transient mechanical response of the basilar membrane reported by Robles et al.
Animals↗
Gap detection by the chinchilla.
Five monaural chinchillas were trained with a method of shock-avoidance conditioning to respond to silent intervals, or gaps, in an otherwise noise. The noise was low-pass filtered at either 10 or 6 kHz and presented at six intensities ranging between 23- and 77- dB sound-pressure level (SPL). Gap detection thresholds were determined according to the method of constant stimuli. For both noise bands, gap thresholds were approximately 3 ms at the highest intensity levels and increased to approximately 6 ms at the lowest level. The results obtained from the chinchilla are in general agreement with those obtained from man.
Animals↗
Auditory fatigue: retrocochlear components.
Changes in auditory sensitivity were measured at the VII nerve, cochlear nucleus, and inferior colliculus after a fatiguing sound exposure. Losses in sensitivity progressively increased from peripheral to central auditory sites. The results suggest that there is a retrocochlear component to auditory fatigue when it is induced by low-level sounds of short duration.
Acoustic Stimulation↗
Letter: Evoked-response audibility curve of the chinchilla.
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Acoustic Stimulation↗
2f1-f2 distortion product otoacoustic emissions in White Leghorn chickens (Gallus domesticus): effects of frequency ratio and relative level.
The effects of primary tone frequency ratio (f2/f1 ratio) and relative level (L2/L1) on the amplitude of the cubic difference tone (CDT: 2f1-f2) distortion product otoacoustic emissions (DPOAEs) were investigated in adult White Leghorn chickens (Gallus domesticus). In experiment 1, 9 f2/f1 ratios ranging from 1.05 to 1.8 were investigated. Measurements were obtained from both ears of 4 chickens at 7 f1 frequencies ranging from 0.8 to 4.0 kHz. The primary tones were equal in level, and varied from 20 to 80 dB SPL. The mean CDT amplitude increased with increasing primary tone level once the measurement noise floor was exceeded. The input/ output functions assumed one of two shapes: one in which there was a systematic increase in DPOAE amplitude with increasing primary tone level, and the other in which there was a plateau in the input/output function near 65-70 dB SPL. At the highest primary tone level (80 dB SPL), there was a decrease in the CDT amplitude with increasing f2/f1 ratio. At high primary tone levels, the f2/f1 ratio which produced the largest CDT was 1.05 or 1.1, while at lower primary tone levels the largest CDT occurred at f2/f1 ratios of 1.2-1.3. In experiment 2, L2 was held constant at 70 dB SPL, and L1 varied from 50 to 80 dB SPL. For f1 frequencies of 0.8 and 3.2 kHz, there was an increase in the CDT amplitude with increasing L1, followed by an asymptote at higher levels. In contrast, for 1.6 and 2.0 kHz f1 frequencies, the amplitude increased, plateaued and then increased again at higher levels. Informal measurements suggest that spontaneous otoacoustic emissions (SOAEs) are rarely seen in chickens. However, a reliable SOAE was observed in 1 chicken, which could be suppressed by external sounds and anoxia.
Acoustic Stimulation↗
Magnitude and pattern of inner and outer hair cell loss in chinchilla as a function of carboplatin dose.
We examined the relationship between carboplatin dose and pattern of IHC and OHC loss in five groups of chinchillas treated with carboplatin: (I) single dose, 38 mg/kg, (II) double dose, 38 mg/kg, (III) double dose, 63 mg/kg, (IV) double dose, 75 mg/kg, and (V) double dose, 100 mg/kg. The pattern of IHC loss was relatively uniform along the length of the cochlea with all doses. Average IHC loss increased from approximately 20 per cent in group I to approximately 100 per cent in groups III, IV and V. Average OHC loss was small or negligible in groups I, II, III and IV; only group V consistently showed large (> 40 per cent) OHC losses. OHC loss progressed along a base-to-apex gradient. The dose of carboplatin which reliably destroyed OHCs was four to five times greater than that needed to damage IHCs.
Animals↗
Anatomical, metabolic and genetic aspects of age-related hearing loss in mice.
Because of their short lifespan and genetic homogeneity, mice can provide valuable insights into the biological basis of age-related hearing loss. In C57BL/6 mice, hair cell loss begins around 1-2 months of age and progresses rapidly along a base-to-apex gradient, whereas CBA mice show relatively little hair cell loss until late in life. This anatomical difference is reflected in dehydrogenase histochemistry, an indirect measure of aerobic energy metabolism. A small, but significant, decrease in hair cell dehydrogenase staining occurred in CBA mice between 1.5 and 18 months of age. Significantly, dehydrogenase levels in 1.5-month C57 mice were substantially lower than in CBA mice of any age. Thus, deficits in aerobic energy metabolism presage degeneration of the hair cells. The superoxide radical, O2*-, a normal byproduct of cellular metabolism, is potentially toxic and can cause cellular damage if it is not inactivated by superoxide dismutases. Cytosolic copper/zinc superoxide dismutase (SOD1) is highly expressed in the cochlea. Knockout mutant mice with a single (HET) or double deletion (KO) of the Sod1 gene coding for SOD1 showed greater age-related losses than wild-type (WT) mice. KO mice had the worst hearing, WT the best, and HETs were intermediate. KOs exhibited considerably greater hair cell loss than WT mice; however, losses in KOs were only slightly greater than in HETs. KO mice showed significantly greater loss of spiral ganglion cells and nerve fibers than WT mice. These results indicate that SOD1 and O2*- play important roles in age-related hearing loss. Intervention strategies targeting O2*- may reduce age-related hearing loss.
Aging↗