Cat Ears Research Articles

Histopathological findings in the inner ear of cats following stapes operation

This paper presents the histopathological findings in the inner ear of cats following the stapes surgery. With the surgical technique modified by us, it is possible to diminish the chance of operative failures and offer more chances of success

A critical level for auditory damage at high intensities

Evidence from a number of different studies in which the ear was exposed to intense sounds can be interpreted as showing that there is a critical level (Lc) above which the loss mechanism changes. Based on the research of Price [J. Acoust. Soc. Am. 66, 456–465 (1979)], the physiological basis for Lc is thought to be mechanical stress at the level of the hair cell. When measured with conventional instruments, Lc depends on the spectrum of the sound as well as its specific pressure-time history. For an exponentially damped 1 kHz impulse, Lc has been calculated to be about 145 dB for the median human ear and about 155 dB for a rifle shot. For the cat ear, Lc may be about 20–25 dB lower than for the human ear. The presence of a spectrum-dependent critical level resulting from mechanical stress in the inner ear has significance for efforts to limit hazard from intense stimulation. It suggests not only how intense a sound is acceptable; but also how it should be measured. In addition, the presence of species dependent differences in Lc also has implications for use of animal models in noise effects research.

Loss of auditory sensitivity following exposure to spectrally narrow impulses.

Damage-risk criteria (DRC) for impulse noise do not presently take the spectrum of an impulse into direct account; yet it is clear that the ear is spectrally tuned. In order to establish the sensitivity of various sections of the cochlear duct to trauma from impulses, ears were exposed to 100 spectrally narrow impulses (1.0, 5.0, or 10.0 kHz) delivered in 10 min. Changes in auditory sensitivity were measured by an electrocochleographic technique in 43 cat ears and a threshold of loss established for each type of impulse. Expressed in SPL at the ear drum, the loss threshold rose at 3.2 dB/octave between 1.0 and 10.0 kHz. Expressed in stapes displacements, the loss threshold fell at 5.4 dB/octave in the same region. This curve was used to establish a tentative shape for a DRC for the human ear for impulse noise. The patterns of loss, rates of loss, lack of recovery, and loss thresholds are discussed with respect to their probable physiological basis with conclusion that mechanical displacement rather than metabolic exhaustion is the most reasonable causative factor.

Function of the Acoustic Reflex in Discrimination of Intense Speech

It is known that the middle ear acoustic reflex (AR) alters the transmission characteristics of the auditory system; however, disagreement exists on how these changes may influence the ears; transfer of speech stimuli. In this study, speech with and without a competing message was delivered at supra-AR levels to cat ears that demonstrated an active and a pharmaceutically inactivated middle ear reflex mechanism. Resulting cochlear potentials were tape recorded and subsequently presented to 18 human subjects with normal hearing. Findings suggest word and sentence discrimination is enhanced in the presence of a functioning AR, with implications for hearing aid use and stapedectomy procedure.

Action potentials in the cat at low sound intensities: thresholds, latencies, and rates of change.

The interpretation of whole-nerve action potentials is a topic of increasing importance in both clinical and research settings. This effort has been hampered by a lack of data on the action potential that are theoretically interpretable and systematically measured over a wide range of frequencies and at low sound intensities. Therefore, the present study was designed to measure the thresholds, latencies, and rates of change in the whole-nerve action potential in response to constant-spectral-width tone pips at eight frequencies between 0.5 and 20 kHz in the cat ear. These quantities were calculated by a linear regression technique from round-window potentials in 28 normal ears. They were found to be consistently within approximately 18 dB of previously published behavioral measures, a difference attributable to temporal integration. The interanimal variability had a standard deviation of about 5 dB and the intra-animal variability was extremely low. The growth of amplitude across frequencies, the rate of change of latency with intensity changes, and the latency at threshold all demonstrated orderly relationships which are presented. The data were all consistent with contention that the potentials were being produced by a single population of cells located at a place consistent with the frequency of the eliciting tone. The methods used provide exceedingly stable measures and should be applicable in both clinical and research settings.

Some hosts, properties and possible affinities of a labile virus from Hypochoeris radicata (Compositae)

SUMMARYHypochoeris mosaic virus (HMV) is common in Hypochoeris radicata (‘cat's ear’) in western Canada. It infected 10 of 53 mechanically inoculated species in five of twelve families, but was not transmitted by aphids or through seed or soil. Sap from infected Nicotiana clevelandii was sometimes infective after dilution to 10‐1 and occasionally 102, after 10 min at 45 but not 50°C, and after 1 but not 2 days at 20°C. Infectivity of crude nucleic acid extracts from infected leaves was rapidly abolished by RNase but not by DNase.Host sap contained very few rod‐shaped particles or particle fragments mostly 21.0–22.5 nm in diameter, and up to 420 nm long but with predominant lengths of 120–140 and 240–260 nm. Many rods in purified virus preparations were less than 240 nm long, and the majority were c. 140 nm or shorter. The particles had a helical substructure with a pitch of 2.58 nm and contained a single type of protein of estimated mol. wt 24.5 × 103.HMV showed no serological relationship to eight morphologically similar viruses (beet necrotic yellow vein, broad bean necrosis, barley stripe mosaic, peanut clump, potato mop‐top, Nicotiana velutina mosaic, wheat soil‐borne mosaic and defective strains of tobacco mosaic). It is probably a hitherto undescribed tobamovirus.

Activity of propriospinal neurons during the scratch reflex in cats

Fictitious scratching, i.e., rhythmic activity of hind-limb motoneurons at the characteristic scratching frequency, was evoked by tactile stimulation of the ear in thalamic cats immobilized with flaxedil. Activity of propriospinal neurons in segments C1, C2, and T4–T7 was recorded extracellularly. The neurons were identified by their antidromic response to stimulation of their axons in segment L1. Most neurons did not respond to stimulation of the ear. Some neurons, however, were activated during fictitious scratching. Neurons of the cervical segments responded not only to stimulation of the ear, but also to tactile stimulation of the forelimbs and also to passive movements of those limbs. Neurons of the thoracic segments were activated only by stimulation of the ipsilateral ear; these neurons were inhibited by stimulation of the contralateral ear. The role of the propriospinal neurons in the activation of the spinal mechanisms of scratching is discussed.

The effects of experimentally-produced middle ear lesions on tympanometry in cats.

Tympanometry was performed before and after producing specific lesions in the middle ears of cats. The lesions selected for study included stapes fixation, ossicular discontinuity, and scarred tympanic membranes. Stapes fixation resulted in marked increases in middle ear impedance, easily detected with tympanometry. Ossicular discontinuity resulted in complex tympanometric shapes which were easily accounted for by simple interactions between acoustic resistance and reactance. The complex shapes that occurred in normal and abnormal ears with pressure changing from negative to positive resulted from more complicated interactions. Large surgical incisions in the posterior-superior quadrant of the eardrum were quite visible at otoscopy but could not be detected tympanometrically one month after surgery.

Response of first order vestibular neurons to lidocaine hydrochloride.

Changes in behavior and electrical activity of primary vestibular neurons were observed following injection of lidocaine hydrochloride into the middle ear of cats. After injection the cats exhibited head and ocular nystagmus, head and neck deviation and pupillary changes. Mean preinjection resting discharge rate for first order vestibular neurons was 46.0 spikes/sec. Two hours after lidocaine application the resting rate decreased to a mean of 22.2 spikes/sec and then recovered to 43.0 spikes/sec four hours, and 47.4 spikes/sec six hours after the experimental treatment. The increment sensitivity (increased rate of firing) of horizontal canal neurons to constant angular acceleration for the control period was 2.0 extra spikes/sec/deg/sec2; two hours after the application, 70% of the recorded neurons were unresponsive to angular acceleration or tilt. The sensitivity after four hours was 1.0 spikes/sec/deg/sec2 and 2.1 spikes/sec/deg/sec2 at six hours. The distinct depression of sensitivity by lidocaine at four hours compared to normal mean resting rate at this time suggests these functions may be governed by two modes of action in the receptor or first order afferents.

Toward a theoretically based DRC for impulse noise

The presently accepted damage‐risk criterion for impulse noise [CHABA. Rep. WG‐57 (1968)] makes no specific allowance for the spectral tuning of the ear. Data from the cat ear, reported at the 9th ICA (G. R. Price, 1977), indicate that the stapes displacement at the threshold of loss for spectrally simple impulses declines as a function of frequency at about 6 dB/octave. Assuming a similar pattern to hold for the human ear, a curve relating the free‐field peak pressure levels of gunfire impulses to the threshold of loss has been developed. The curve allows progressively less pressure (−3 dB/octave) as the spectral peak of the impulse rises to the midrange and allows increases in pressure if the spectral peak is higher than that. For the low‐frequency impulses (most gunfire) this is the opposite of the CHABA prediction. Validation with experimental ears and weapons impulses remains to be done.

Proplast in the Middle Ear and Oval Window of Cats

Poly(tetrafluoroethylene) carbon fiber implant material (Proplast), an all-plastic material, was evaluated for use in otologic surgery. Response to the implant was studied in the middle ear and vestibule of 14 cats by placing the Proplast in the oval window after stapedectomy. After a one year follow-up, it appears that Proplast was tolerated well, causing no inflammatory reaction in either the vestibule or cochlea, or in the middle ear cavity. Fibrous tissue ingrowth was found throughout the implant, and a fibrous tissue membrane covered both the vestibular and the tympanic surfaces of the Proplast. Being well tolerated by both middle ear and inner ear tissues, this porous, all-plastic material offers several otologic applications.

External and middle ears, the determinants of the auditory threshold curves

The pressure transformation ratio of the cat's ear under auditory free-field conditions was calculated from Nedzelnitzky's data [pressure in scala vestibuli (sc. v.) for a constant SPL at the tympanic membrane] with appropriate corrections applied for his open bulla and the tympanic membrane reference. For a constant SPL at the pinna, the pressure in sc. v. followed a curve identical to an inverted plot of the cat's free-field threshold. Therefore, when expressed in terms of threshold SPLs at the pinna, the pressure in sc. v. became independent of frequency, its absolute value being 0. 003 dyn/cm2. These results demonstrate the importance of the acoustic properties of ear canal and pinna. They also suggest that the free-field threshold curve is mainly determined by properties of the external and middle ears, including the inner-ear input impedance. The power entering the inner ear at threshold was calculated from cat impedance data of Lynch and Peake. Its value is about 10−18 W for frequencies between 50 and 7000 Hz. [Supported by NIH grants.]

The association of Pityrosporum pachydermatis with the normal external ear canal of dogs and cats

ABSTRACTThe frequency of Pityrosporum pachydermatis within the non‐otitic external ear canals of dogs and cats has been investigated and an assessment of the abundance of the yeast made by microscopic and cultural techniques. It was present in varying amounts in 49% of clean dog ears and 23% of clean cat ears. Microscopically, 14% of the ears were found to contain the yeast in large numbers. A further 3 % of ears examined showed excessive cerumen production and all these contained the yeast.The prevalence of P. pachydermatis in non‐otitic ears of both dogs and cats was similar to that previously reported in otitic ears.

Eye of Newt, Tongue of Carp, Ear of Cat, Paw of Monkey …

Eye of Newt, Tongue of Carp, Ear of Cat, Paw of Monkey …

A fluorescence and electron microscopic study of the adrenergic innervation in the vestibular ganglion and sensory areas.

The adrenergic innervation in the vestibular ganglion and sensory areas in rabbit and cat was studied with fluorescence and electron microscopic techniques. All adrenergic nerve fibres consisted of postganglionic axons from the ipsilateral superior cervical ganglion. In rabbit, postganglionic nerve fibres passed via the carotic plexus. Probably because of the anatomical difference, the feline internal carotic artery being rudimentary, all sympathetic nerve fibres to the inner ear in cat passed via the tympanic plexus. In the vestibular ganglion there was a uniform distribution of adrenergic nerve fibres and there was no difference in distribution patterns between rabbit and cat. There was a continuous blood vessel innervation and an innervation independent of blood vessles. The adrenergic innervation extended to the sensory areas but did not seem to penetrate the basement membrane and no adrenergic nerve terminals were found in direct contact with sensory or secretory cells.

Interruption of recovery during intermittent stimulation produces greater loss in sensitivity

Recent work on hearing loss to intermittent stimulation [G. R. Price, J. Acoust. Soc. Am. 56 (1974)] has documented an early recovery process (ERP) in the cochlear microphonic (CM) and led to the hypothesis that if the ERP is interrupted by subsequent exposures, loss in CM sensitivity would be greater than the loss to an equivalent amount of continuous stimulation or to an equal amount of intermittent stimulation timed to avoid interrupting it. This hypothesis .was tested by exposing anesthetized cat ears to 5.0-kHz pure-tone stimulation at an intensity 30 dB above that producing a maximum in CM output at the round window. Stimuli were on for 1 min and off for an appropriate period until a total of 30 rain of stimulation had been delivered. In one experimental group (N = 10), the exposure schedule interrupted the ERP when it had 5 dB left to run and for a second group (N = 10), the inte rexposure interval was 9 min, a period allowing the ERP to run to completion. Interrupting the ERP did result in significantly more loss than continuous stimulation. Allowing the ERP to go to completion resulted in less loss, although the difference was not statistically significant. Data from studies using human ears indicate that similar processes may also be acting in the human ear as well.

Granulomatous reaction in experimental stapedectomy.

Inner ear granuloma reactions following bilateral stapedectomy were studied in 21 cats. In the protocol, nonsensitized cats received homologous or heterologous fat in their left oval window after stapedectomy. Cats sensitized by skin grafting received homologous fat in their left ear. Absorbable gelatin sponge oval window seal was used on the right ear of all cats in the series. Of 22 nonsensitized cat ears, only one developed an inner ear granulomatous reaction, but 7 out of 20 sensitized cat ears developed the reaction. Prior sensitization increases the chances of an inner ear granuloma response, and delayed or cellular hypersensitivity may be the cause of the reactions.

Loss and recovery processes operative at the level of the cochlear microphonic during intermittent stimulation.

It has become increasingly apparent that the ear's behavior in response to intermittent stimulation is complex. In order to study the loss processes operative at the most peripheral level, CM sensitivity at the round window was monitored in a series of acute experiments on 150 cat ears as they were exposed to intermittent or continuous 5.0-kHz pure-tone stimulation. Stimuli were delivered at a SPL either 10 or 30 dB above that intensity necessary to produce a maximum CM output. Stimuli were on a 20% duty cycle with on-times varying from 10 msec to 2 min. Recovery processes taking place between stimuli were also measured. At all but the shortest on-times, loss was bimodally distributed, i.e., ears lost either much more or much less sensitivity than ears exposed to equivalent amounts of continuous stimulation. The shortest on-times, in contrast, tended to produce predominantly large losses. An early recovery process at the level of the CM was explored and found to have the following properties: it proceeded in log-time and the amount of recovery was proportional to the log of the on-time but was unrelated to the amount of residual sensitivity shift. The data were interpreted as showing the possibility that large losses to intermittent stimuli were likely to result when successive stimuli in the intermittent train interrupted the early recovery process before it has run to completion. These data were compared with TTS data from the human ear and parallels noted.

The use of tissue adhesive (isobutyl cyanoacrylate) and topical steroid (0.1 percent dexamethasone) in experimental tympanoplasty.

AbstractTwo main purposes in the present study were: 1. to determine the feasibility of using the tissue adhesive isobutyl 2‐cyanoacrylate in reconstructive middle ear surgery; and 2. to learn whether a potent topical corticosteroid (0.1 percent dexamethasone) would have beneficial anti‐inflammatory effects when placed in the tympanic cavity at the time of middle ear surgery.Tympanoplastic surgery was performed on 26 cat ears and six squirrel monkey ears; the animals were followed for six weeks to nine months postoperatively.The conclusions to be drawn from this experimental study are that presently the tissue adhesive isobutyl cyanoacrylate appears too toxic for use on the delicate middle ear structures; likewise, corticosteroids placed in the middle ear do not appear to have any beneficial effects in tympanoplasty surgery.

Unusual Ciliated Cell Group in the Utricle of a Cat

Using a scanning electron microscope, a group of ciliated cells was found in the area of the utricular macula of an adult cat. A cross section of the same specimen viewed with a transmission electron microscope revealed that the hairs observed had the characteristic inner structure of true cilia. As the same cell group was not found in either the contralateral ear of the same cat or in any of three other cats examined, the presence of these ciliated cells seems to be exceptional.