ATP-induced cytoplasmic [Ca2+] increases in isolated cochlear outer hair cells. Involved receptor and channel mechanisms

Outer hair cells (OHC) of the mammalian cochlea are thought to preprocess the sound signal by active movements, which can be induced by electrical or chemical stimulation, e.g. depolarization evoked by high [K+] or increased cytoplasmic [Ca2+]. Extracellular ATP has been found to induce cytoplasmic [Ca2+] increases in OHC but involved mechanisms have not been elucidated. Cytoplasmic [Ca2+] was measured in non-enzymatically isolated single OHC using Fura-2 microspectrometry. Results, using ATP/derivatives and other P2-purinergic receptor (P2R) ligands, as well as Ca(2+)-channel blockers and pertussis toxin, revealed several signal transduction pathways that increase cytoplasmic [Ca2+] in OHC: a P2-purinergic receptor (P2R)--G-protein--effector (phospholipase C or an ion channel) system and a voltage-dependent Ca2+ channel. Agonist potency studies denote a pattern analogous to that found in skeletal muscle, i.e. ATP-alpha-S > ATP = 2-methyl-S-ATP >> ADP > alpha,beta-methylene-ATP, but no activation by ADP beta F or UTP, leaving a choice of P2y or P2zR subtypes. The latter possibility gained strength from calculations showing that up to 8% of ATP may have formed the P2zR agonist ATP4- in the experimental medium. Experiments in Ca(2+)-free medium and with pertussis toxin revealed that the main Ca2+ source was intracellular. Pertussis toxin did not affect [Ca2+] increase induced by carbachol. Acetylcholine, administered a few seconds before ATP, did not affect total cytoplasmic [Ca2+] increases. Induced cytoplasmic [Ca2+] increases were high enough (> 500 nM at 50 microM ATP/derivatives) to hyperpolarize the OHC membrane by opening K(+)-channels and decreased little with time.(ABSTRACT TRUNCATED AT 250 WORDS)

[Differential indications of free and pedicled transplants in reconstructive surgery in the head and neck area]

Since the microvascular tissue transfer has been introduced in the reconstructive surgery of the head and neck the question arises repeatedly which free transplant should be favoured and which advantages exist to pedicled flaps. Based on our experiences in 243 reconstructions we discuss the advantages and disadvantages of different operative techniques and their differential indications. Using free as well as pedicled flaps, reconstructions can be performed individually and the decision for a transplant depends on localisation, size and depth of the defect. In contrast to conventional techniques, like the deltopectoral flap, which we performed a decade ago, both new principles allow a one-stage procedure, which reduces the period of hospitalisation and improves the quality of life for the patients. The advantages of free tissue transfer can be seen especially in the reconstruction of the upper digestive tract after laryngopharyngectomy. The existing form of the jejunum segment like a tube allows an easy one-stage reconstruction, as well as better functional and aesthetic results. The radial forearm flap is a nearly ideal transplant in the anterior oral cavity because of the mechanical stability. In contrast the jejunum patch is more vulnerable and less qualified especially when fitting a prosthesis. In the posterior oral cavity we prefer the jejunum patch because it allows more mobility of the tongue. Deep defects, for instance after glossectomy, should be reconstructed with a free latissimus-dorsi-flap or a pedicled myocutaneous pectoralis major flap. In contrast to free tissue transfer, pedicled flaps have the advantage that the difficult technique of microanastomosis is avoided, which reduces the complication rate and the operation time.(ABSTRACT TRUNCATED AT 250 WORDS)

Structure, pharmacology and function of GABA-A receptors in cochlear outer hair cells

There is evidence that the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is released from some efferent olivocochlear nerve endings terminating at outer hair cells (OHCs). Using monoclonal antibodies against postsynaptic GABAA receptor from bovine cerebral cortex we confirm the presence of GABA and benzodiazepine bindings sites of alpha- and beta-subunits of GABAA receptors at the basal pole of isolated OHCs. Whole-cell recording with viable OHCs revealed that the application of 10(-3)-10(-8) M GABA to the cell surface was followed by a concentration-dependent hyperpolarization of the outer cell membrane. Hyperpolarization was increased in the presence of 2.5 x 10(-5) M chlorazepate, a benzodiazepine derivative. Electrophysiological effects caused by GABA alone or in combination with chlorazepate were specifically inhibited by 10(-6) M of the GABA-receptor antagonist picrotoxin. Moreover, 10(-5)-10(-7) M GABA caused reversible slow elongation of the cylindrical hair cell body in OHCs examined. These neurotransmitter-induced motile responses were specifically blocked by 10(-4) M picrotoxin. The results suggest that a subpopulation of OHCs express alpha- and beta-subunits of GABAA receptors which both form a GABA/benzodiazepine-receptor complex at the basal pole of isolated OHCs. These receptors are thought to allow GABA which is released from efferent auditory nerve terminals to bind to the cell surface of OHCs, resulting in GABAA-receptor activation. This probably gates a GABAA-receptor-associated chloride channel in the postsynaptic OHC membrane, allowing hyperpolarization and elongation of the cell.

Hyposmotic activation hyperpolarizes outer hair cells of guinea pig cochlea

The electrophysiological responses of isolated guinea pig outer hair cells (OHCs) to hyposmotic activation were studied using the whole-cell patch-clamp technique. The cell swelling by hyposmotic activation hyperpolarized OHCs by 6.6 +/- 2.3 mV from the resting membrane potential of -58.5 +/- 5.9 mV (n = 48). This hyperpolarization was associated with an outward current (97.7 +/- 22.2 pA, n = 15). The hyperpolarization was inhibited by 300 microM quinine, 5 mN Ba2+ and increasing the extracellular K+ to 30 mM from 5 mM. In the absence of extracellular Ca2+ (1 mM EGTA), the hyperpolarization during hyposmotic activation was also abolished while the following depolarization was preserved. 50 microM GdCl3, which is known to block stretch-activated non-specific cation channels, inhibited the hyperpolarization reversibly. 50 microM GdCl3 also inhibited [Ca2+]i increase during hyposmotic activation as shown by the calcium-sensitive dye fura-2. Simultaneously, the [Ca2+]i increase and the hyperpolarization during hyposmotic activation could be observed using the combined method of whole-cell patch clamp and fura-2 technique. It is concluded that the cell swelling by hyposmotic activation may activate the stretch-activated non-specific cation channels in the OHCs which allow a Ca2+ influx. In turn, this [Ca2+]i increase leads to an activation of the Ca(2+)-activated K+ channels at the basolateral membrane of OHCs which results finally in a reversible hyperpolarization of OHCs by K+ efflux.

Forces involved in length changes of cochlear outer hair cells

Motion or force generation of outer hair cells may contribute to active modulation of cochlear mechanics. In order to determine the force involved in length changes of outer hair cells, a new in vitro method was used. In the first series of experiments, apical and basolateral extracellular spaces of outer hair cells of the guinea-pig cochlea were separated. Changes of the voltage between the two extracellular spaces induced reversible, proportional changes of the cell length of 4.4 nm/mV if the cell had a length of 80 microns. In the second series of experiments, cell elongations in response to negative pressure applied to the basal end of the cells were measured and corrected for frictional effects. From these data, the compliance of the longitudinal axis of the hair cells was calculated. It was 220 +/- 130 m/N (n = 25) and 240 +/- 170 m/N (n = 24) for cells of the third and fourth cochlear turns, respectively, if the water permeability of the cell membrane was neglected. If the water permeability was taken into account, the compliance was probably around 500 m/N [corrected]. Thus, a mechanism that changes the cell length by 1 microm must generate a static force of at least around 2 nN in an outer hair cell of the organ of Corti [corrected]. Electromotility of outer hair cells, induced by changes of the electrical potential difference across the outer hair cell, is a mechanism that generates this force.

Possible roles of outer hair cell d.c. movements in the cochlea

Outer hair cells are expected to change the position of the cochlear partition in response to sound stimulation. This may contribute to the extended dynamic range of the cochlea. This paper explores the possible underlying mechanisms and the consequences for models of cochlear function of such position changes.

Sound preprocessing by ac and dc movements of cochlear outer hair cells

In inner and outer hair cells, a sound event results mechano-electrically in a receptor potential from the hair cells by the functioning of apical and lateral K(+)-channels. However, after this point, the signal transfer is divided. Inner hair cells (IHC) release an unknown afferent transmitter. By contrast, outer hair cells (OHC) are proposed to produce mechanical ac and dc responses. In our model, the ac components of the sound signal, the carrier frequencies, determine the response of the OHC. Usually, they respond by ac and dc movements. The rapid ac movements of OHC, for which the underlying mechanism is unknown, may respond cycle-by-cycle to and interfere with the carrier frequency of the traveling wave. Near hearing threshold, they could drastically amplify the traveling wave thus contributing to the postulated cochlear amplifier. Active dc movements of the cytoskeleton of the cell body, as well as of the cuticular plate with the sensory hairs, are proposed to respond to millisecond changes of the sound stimulus over time. Such changes could be a modulation of the amplitude (AM), i.e., an increase or decrease of the sound pressure level (SPL), which is reflected in the envelope of the traveling wave. The active mechanical dc response of OHC to the amplitude (AM) and frequency modulation (FM) pattern is then expected to result in dc position changes of the reticular lamina (RL). These should control the operation point of the stereocilia, thus influencing their transfer function and sensitivity. In addition, experimental data suggest that there are modulations of the compliance of the organ of Corti (OC) and changes of its geometry. This dc modulation of micromechanical properties and geometry of the OC by active force generation of OHCs might contribute to automatic gain control, adaptation, TTS, as well as to the homeostasis of the basilar membrane location. In particular, the motile mechanism may protect the vulnerable cochlear partition against high sound pressure levels. Moreover, according to this model, changes of the sound signal with time are expected to be encoded in the actively produced dc movements of the RL. As the signal changes may carry important information (e.g., complex sound signal modulations such as formant transitions in speech), this is extracted and mechanically encoded by the proposed active dc mechanism. It cannot be excluded that the information-carrying dc signal is transferred to inner hair cells contributing to their adequate stimulus.(ABSTRACT TRUNCATED AT 400 WORDS)

Volume regulation in guinea pig outer hair cells and the role of intracellular calcium

Single outer hair cells (OHCs) isolated from the guinea pig cochlea showed a regulatory volume decrease (RVD) after the initial cells swelling despite continued exposure to a hypotonic solution. The accompanying change of the intracellular Ca2+ concentration ([Ca2+]i) in the OHCs was investigated using the Ca(2+)-sensitive dye fura-2. Hyposmotic activation led to a [Ca2+]i increase which was accompanied by cell shortening and swelling. In a nominally Ca(2+)-free solution, however, [Ca2+]i was not significantly increased during hyposmotic activation although shortening and swelling of the OHCs were observed. These results suggest that the increase in [Ca2+]i during hyposmotic activation is mainly based on an influx of extracellular Ca2+.

Cochlear-motor, transduction and signal-transfer tinnitus: models for three types of cochlear tinnitus

The present paper reviews possible molecular and cellular mechanisms in the cochlea that might contribute to tinnitus. They constitute a part of a highly integrated network in cochlear sound processing and are divided for easier understanding into three different models, i.e. active motor tinnitus, transduction tinnitus and signal-transfer tinnitus. Some of the steps of the pathophysiological models can even be pharmacologically influenced (as exemplified by experimental applications of lidocaine, calcium channel blocker, benzodiazepine, glutamate and atropine). This provides a rationale for the efficient suppression of tinnitus in some patients by these drugs. The most evident problem of all models in tinnitus, including the ones proposed in this paper, is the lack of objective verification by measurement. Thus, the well-defined clinical situation of each patient is hardly attributable to one of the models suggested. In addition, adequate therapy--perhaps one of the drugs considered--still cannot be based upon a reliable clinical finding.

Characterization of marginal and Claudius' cells growing from cochlear explants in vitro

Tissue specimens of stria vascularis together with spiral ligament were transferred from the guinea pig cochlea to tissue culture dishes. To characterize and identify cells growing out from the explants, indirect immunofluorescence microscopy was used. The expression of the intermediate-sized filaments vimentin and cytokeratin 18 in cells on the surface of tissue specimens and in cells growing out from the explants after different cultivation periods were compared. Basically, three types of cells grew from the explants during several days: marginal cells, Claudius' cells and fibroblast-like cells. In primary cultures of explants, growth of marginal cells was observed in 25% of the dishes. Their proliferative activity, estimated by the use of the BrdUrd-DNA antibody, started in the stria vascularis and continued across the attachment of Reissner's membrane down to the bottom of the cell culture dish. The newly-formed marginal cells expressed cytokeratin 18 in the same way that original marginal cells on the tissue specimen do. If the newly-formed marginal cells were in contact with fibroblast-like cells or were forming groups (domes) on the bottom, they expressed vimentin. In 3% of the dishes growth of Claudius' cells was observed. Proliferative activity of these cells was found at the point where the basilar membrane was attached to the spiral ligament. New Claudius' cells spread at the opposite side of an explant when compared with the location of new marginal cells. Original as well as newly-formed Claudius' cells contained cytokeratin 18. Fibroblast-like cells were commonly present in cultures and contained only vimentin.

[Voice rehabilitation after laryngectomy with voice prostheses. Results of a prospective follow-up study]

Although the results of surgical rehabilitation by means of voice prostheses are on the average better than rehabilitation via oesophageal speech, the tracheoesophageal puncture (TEP)-technique has so far not been widely used in Germany. The majority of hospitals still prefer the "traditional" method of voice rehabilitation using oesophageal speech. The present prospective study was undertaken to compare the results of postlaryngectomy vocal rehabilitation, if patients were offered the surgical voice rehabilitation via voice prosthesis as an alternative to oesophageal speech. Taking into account all the patients who underwent laryngectomy from 1989 until 1990 in Tübingen, primary surgical voice rehabilitation was performed in 44 out of 54 patients (81.5%). Interestingly enough, 34 patients who underwent laryngectomy were able to perform communication via the telephone on the day of their discharge. Moreover, one-third of the laryngectomised patients showed a significant increase in speech intelligibility within the first six months after laryngectomy. 36 patients with laryngectomy were able to attain proficiency 6 months after surgery. In 12 patients the prosthesis had to be removed, since either phonation was impossible or patients successfully learned and preferred oesophageal speech. In conclusion, independent of the method of voice rehabilitation (prosthesis, electrolarynx, oesophageal speech), our results support the hypothesis that a voice rehabilitation regimen will yield a higher rehabilitation rate of patients if rehabilitation via surgical voice is offered as an alternative to learning the oesophageal voice. Therefore, it seems to be advisable that patients are allowed to have the choice between surgical rehabilitation and oesophageal speech restoration.(ABSTRACT TRUNCATED AT 250 WORDS)

High frequency radial movements of the reticular lamina induced by outer hair cell motility

Recently, it was shown in cochlear explants from the guinea pig cochlea that electrokinetic motile responses of outer hair cells can induce radial and transverse motion of the reticular lamina. Here we demonstrate, that the radial component of these motions can be measured up to high frequencies (15 kHz). Cochlear explants were taken from guinea pig inner ears and exposed to a sinusoidal electric field. A double photodiode was used as a linear position detector with high spatial and temporal resolution to detect radial movements in the plane of the reticular lamina. The organ of Corti of the second, third and fourth cochlear turns was stimulated with frequencies of the electrical field between 0.5 Hz and 20 kHz. Sinusoidal movements of up to 15 kHz were recorded. At higher frequencies the signal-to-noise ratio became too small. The largest responses were measured at the three rows of outer hair cells. If the strength of the electrical field was 2 kV/m, into which the cochlear explants were placed, the amplitudes of outer hair cell movements were around 1 micron at 1 Hz and 10 nm at 10 kHz. Uncoupling of the outer hair cells from the tunnel of Corti and from the inner hair cells decreased the oscillations of inner hair cells but did not affect outer hair cells. The movements showed frequency dependent amplitudes like a complex low-pass filter but no best frequency was observed.

C-type potassium channels in the lateral cell membrane of guinea-pig outer hair cells

The basolateral cell membrane of outer hair cells (OHC) from the mammalian cochlea is known to contain K(+)-channels. The prevailing type, a high-conductance K(+)-channel was further characterized in the present study in order to support its classification as C channel. OHC were isolated from the 3rd and 4th turn of the guinea-pig cochlea. Cell-attached and excised inside-out patches of the lateral cell membrane were investigated. The C-type channel had a selectivity for K+ over Na+ of 12:1 to 20:1 and displayed Goldman-type rectification and voltage-dependence of the open probability. The kinetics of both opening and closing could be described by time constants in the range of ms. The channel provides a calcium- and voltage-activated pathway through OHC lateral membranes for passive K+ transport.

[Speech perception and otoacoustic emissions by pre-processing sound in the inner ear]

Direct observations of the basilar membrane movements show that sound perception can no longer be regarded as a passive process: vulnerable, energy-consuming amplification processes are required in the cochlea. The outer hair cells (OHC) fulfil this demand morphologically and functionally. These sensory cells have a double role: they perceive sound and thus modulate the cochlear biomechanics through their motile activity. The key event of sound transduction is performed by the inner hair cells (IHC) after active sound amplification in the OHC. The control of the OHC is assured by the efferent olivocochlear fibres which release acetylcholine (ACh) and gamma-aminobutyric acid (GABA) into the synaptic cleft at the basal pole of the OHC. Nicotinergic acetylcholine and GABA receptors within the outer cell membrane of OHC were identified and characterised. The application of the neurotransmitter GABA to the basal pole of vital OHC leads to a reversible elongation of the cylindrical cell body while ACh induces a reversible, slow contraction of the sensory cells. These two neurotransmitters are supposed to counteract in the control of the cochlear amplifier. The reciprocal distribution of ACh and GABA receptors and their counteracting function (contraction vs elongation) has an additional impact on the modulation of OHC function. The result is an even more diversified control of the cochlear amplifier. The energy-consuming cochlear amplifications are reflected by an epiphenomenon, i.e. the otoacoustic emissions (OAE). These are emitted by the cochlea and can be divided into "spontaneous OAE", "transitory evoked OAE" (TEOAE), "stimulus frequency OAE" and "distortion product OAE". The TEOAE are now an integrated part of audiological diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrates in the cell surface of hair cells from the guinea pig cochlea

The presence of cell surface carbohydrates was investigated in intact, non-fixed outer hair cells (OHCs) of guinea pigs using fluorescein isothiocyanate (FITC) and rhodamine (TRITC) lectins. By means of wheat germ agglutinin (WGA) N-acetyl-D-glucosamine was shown in the entire OHC membrane, including the stereocilia. Binding of WGA in OHCs to neuraminic acid was excluded by preincubation with neuraminidase. Moreover, FITC-Limulus polyphemus, a specific lectin for neuraminic acid, showed no fluorescence on OHCs. Neutral saccharides, like alpha-D-mannose and/or alpha-D-glucose, were mainly observed at the cuticular plate and at the basal cell pole with FITC-concanavalin A. A weaker fluorescence was seen at the lateral cell wall. Two branched oligosaccharides, composed of beta-galactose, N-acetyl-D-glucosamine and mannose, were demonstrated by TRITC-Phaseolus vulgaris (PHA-E/L) in the entire OHC membrane. A spot-like binding of soybean agglutinin to N-acetyl-D-galactosamine could be demonstrated in the region of the cuticular plate. However, using Helix pomatia, the subtype N-acetyl-alpha-D-galactosamine was not detectable. Moreover, there was no binding of Ulex europaeus or of Arachis hypogea (PNA) to OHCs, suggesting the absence of considerable amounts of L-fucose and of galactose-beta-3-N-acetylgalactosamine. The results indicate that N-acetyl-D-glucosamine, alpha-D-mannose and alpha-D-glucose can be considered the major components of the OHC glycocalix. We suggest that they have a function as an anchoring structure in interstereociliary links as well as in hair bundle connections to the tectorial membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

gamma-Aminobutyric acid receptor activation of outer hair cells in the guinea pig cochlea

Gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter of the central nervous system, may also be released from olivocochlear efferent nerves reaching the outer hair cells of the cochlea. In the present study the cell potential of isolated outer hair cells of the third and fourth turns of the guinea pig cochlea was measured with patch-clamp electrodes. GABA-receptor agonists and antagonists were applied extracellularly. The cell membrane hyperpolarized in a reversible manner with increasing concentrations of extracellular GABA. Half-maximal hyperpolarization (2 mV) was achieved with approximately 10(-7) M GABA. Desensitization was not observed. The hyperpolarizing effect of GABA was potentiated by the benzodiazepine clorazepate and was blocked by picrotoxin.

Direct observation of living laryngeal carcinoma cells during invasion of healthy cell formation

After cloning of laryngeal carcinoma cells from tumor fragments obtained during surgery, the behavior of pure tumor cells was investigated under the inverted microscope. In tissue culture flasks, separately grown tumor cell layers and fibroblast layers were cocultured to visualize the invasion of malignant cells into healthy tissue. Using a time-lapse camera, the cells were recorded. The tumor cells often penetrated the healthy cell formation in a wedge-shaped cell formation. Near the tumor front, an elevated cell motility was found accompanied by continuous changes in the cell shape. Intercellular gaps were broader in the front line than in the more posterior parts of the tumor cell formation. The profound motility of the carcinoma cell enabled selected cells to leave the tumor cell formation completely and to migrate as single cells through healthy tissue. Eventually, some of the single tumor cells migrating through the fibroblast layer moved back to the tumor cell formation. Thus they left healthy appearing tissue behind which was earlier infiltrated by a malignant cell.

[Adjuvant and drug therapy of chronic pain in the head and neck area]

Head and neck pain caused of benign or malignant disease reduces remarkable the patient's quality of life. In the following are presented adjuvant and medicamentous methods for pain control. Surgery, irradiation and chemotherapy aim to diminish the tumor extension and reduce algesic transmitting substances in the periphery. Nerve blocs, cryoanalgesia and transcutaneous electrical nerve stimulation lead to an interruption of the painful spinal reflex arc. Active, passive and relaxation exercises prevent from dolorific muscular tensions. Psychological treatment, so as relaxation techniques in connection with behavior therapy, helps to develop coping strategies. The mainstay of pain relief is effective use of analgetics which should be given orally if possible, on a regular schedule and on an individualized basis according with the WHO guidelines.

Stiffness, compliance, elasticity and force generation of outer hair cells

Isolated outer hair cells (OHCs) were partially sucked into especially designed cell capillaries allowing an experimental reconstitution of the cells' electroanatomy. The experimental approach separated the apical from the basolateral parts of the cells thus forming an artificial scala media and scala tympani. Resistance between both was 121 +/- 42 M omega. A sequence of negative and positive pressures was applied to the basal cell pole allowing "pulling" or "pushing" of the sensory cell investigated. The resulting length changes together with the known pressures allowed the estimation of an actual longitudinal compliance of 354 +/- 35 m/N. Following "pulling" OHCs tended to resume their initial shape after the force had ceased to be effective indicating elastic distortions. The calculated elasticity modulus of OHCs amounted to 6.1 +/- 3.4 kN/m2. From this data an actual longitudinal whole cell stiffness of OHCs of 3 x 10(-3) N/m was calculated. Ultrasound scanning of immobilized OHCs identified the cuticular plate (CP) and a central core between CP and basal cell pole as structures contributing to the cells' acoustic stiffness. Changes of the potential differences between the artificial scala media and scala tympani resulted in active length changes following the command voltage with a slope of delta 1/(1 x U) = 0.055 V-1. Assuming the validity of Hooke's law, the force generation associated with the active length changes can be calculated since the compliance is known.(ABSTRACT TRUNCATED AT 250 WORDS)

[Speech intelligibility and psychosocial adaptation in various voice rehabilitation methods following laryngectomy]

Intelligibility and psychosocial adjustment are measured by the PLTT (Post-Laryngectomy-Telephone-Test) and a newly developed questionnaire (FPAL). 110 male patients with total or partial laryngectomies are tested. Three different groups are compared with each other: laryngectomees with voice prostheses, laryngectomees with oesophageal voice or artificial larynx, and patients with partial laryngectomies. As was to be expected, intelligibility (single words and sentences) was best in patients with partial laryngectomies. The intelligibility of the laryngectomees with voice prostheses is significantly higher than the intelligibility of patients with oesophageal voice or artificial larynx. There was no difference between the groups with regard to the subjective assessment of intelligibility in relation to various communication partners. Partial laryngectomies have the lowest negative impact on the social and psychological situation of the patients. Laryngectomees, however, are more lonely, indicate more psychological stress in social interactions, and have a less positive evaluation of their life. Statistical analyses reveal no difference in psychosocial adjustment between laryngectomees with voice prostheses, oesophageal voice and artificial larynges.

A nicotinic acetylcholine receptor-like alpha-bungarotoxin-binding site on outer hair cells

Acetylcholine (ACh) appears to be the major neurotransmitter liberated from olivocochlear efferents terminating on outer hair cells (OHC). Recently, cholinergic receptor epitopes were visualized at the basal pole of the OHCs. To evaluate the ACh receptor type at OHC we performed binding studies with [125I]-labelled alpha-bungarotoxin (alpha-bgtx), a close to irreversibly acting blocker of the nicotinic acetylcholine receptor (nAChR) of skeletal muscle and of electrocytes of Torpedo and Electrophorus. An irreversible and saturable binding (80 nM) of the radiolabelled compound to OHCs was observed. The number of alpha-bgtx sensitive binding sites present on each OHC was calculated to be about 2 X 10(-17) mol/OHC, which would amount to about 10(7) binding sites/cell. Preincubation with the reversibly acting cholinergic ligands, carbamylcholine (1 mM), nicotine (0.1 mM) and d-tubocurarine (1-100 microM) was found to inhibit alpha-bgtx binding to a varying degree. Atropine (0.05 mM), a muscarinic antagonist, had no influence on the binding of alpha-bgtx to OHCs. [3H]-QNB, a specific marker and antagonist for muscarinic AChR, and [125I]-kappa-toxin, known to react with neuronal and ganglionic nAChR, showed no specific binding to OHCs. The data indicate that a peripheral type nAChR is present on OHCs mediating ACh-induced modulation of the biomechanics of the cochlea by influencing OHC motility.

[Anxiety and coping with anxiety in patients with head and neck cancers]

In addition to their oncological symptoms, 82% of head and neck cancer patients showed anxiety. A high level of anxiety was found in 14% of the patients before surgery and 16% of the patients after surgery. In order to achieve a comprehensive treatment, it is very important to have some basic knowledge of conditions causing anxiety, reaction to anxiety, coping with anxiety, and anxiety-reinforcing conditions. In a longitudinal study of 50 men undergoing surgery for head and neck carcinoma, the subjective level of anxiety before and after surgery and the coping strategies were evaluated by a valid and reliable psychological method. The coping strategies "giving up" and "intake of medication, alcohol and nicotine" were positively correlated with higher levels of anxiety and anxiety reinforcement. The objective level of threat of surgery, such as the extent of impairment imposed by the operation or the individual prognosis, was not correlated with the subjective level of anxiety. It is possible for even minor diagnostic procedures to induce high anxiety. Talking to the patient about the outcome of investigations and the treatment is not enough to reduce anxiety. It is necessary to enhance the patient's feeling of personal control through continual contact with the doctor. A therapeutic approach for anxiety intervention which can be used by the physician is recommended. This intervention strengthens the level of the individual's self-control and reduces his anxiety-reinforcing behaviour, such as compulsive thinking, alcohol and nicotine use and social withdrawal.

The resting potential of marginal cells in stria vascularis explants

In order to examine the intracellular potential of stria vascularis marginal cells (MCs) under direct visual control, a short-term organ culture of guinea pig stria vascularis (SV) was developed. The experimental conditions allowed exposure of the luminal surface of the SV to artificial endolymph or perilymph. Using conventional microelectrodes and inverted bright-field microscopy, impalement of MCs from the endolymphatic side through the luminal cell membrane was achieved. With artificial perilymph at the luminal side a small positivity at the cell surface and low negative intracellular potentials were recorded at room temperature (23 degrees C). The initial recording was -6.5 +/- 5.0 mV while the stable recording was -4.0 +/- 3.6 mV. Similar results were obtained at a bath temperature of 37 degrees C. Furthermore, subtotal exposure of the luminal cell surface to artificial endolymph did not result in a significant potential change.

Motile responses of vestibular hair cells following caloric, electrical or chemical stimuli

Isolated, living vestibular hair cells (VHCs) from the guinea pig are capable of producing self-movements. Current injections and extracellular alternating current (a.c.) fields evoked mechanical responses of cell body or sensory hairs. Furthermore, superfusion in the presence of kainic acid or slow depolarizations by K-/gluconate evoked reversible slow motile responses of solitary vestibular sensory cells. If present in vivo, active VHC mechanics will influence the mechano-sensitive stereocilia and modulate stiffness and compliance of the receptor structure and its cupular or macular relationship. A tonic VHC motility might directly influence the displacement configuration in the cupula and macula organs and thus the micromechanical operating conditions of these sensory organs. Active mechanical events could contribute to adaptation processes (automatic gain control) and micromechanical non-linearities of stereociliary displacements. In addition, we demonstrate that direct caloric stimulation of isolated, living type I VHCs from guinea pig elicited mechanical responses of the sensory cells. This mechanism could contribute to the caloric induction of a nystagmus both under terrestrial and microgravitational conditions.

Cell potential and motility of isolated mammalian vestibular sensory cells

Vestibular hair cells (VHCs) were isolated from the guinea pig inner ear. Using the whole cell variant of the patch clamp recording technique a zero current cell potential of -63.1 +/- 9.9 mV was measured in macular hair cells. Depolarization and repolarization were accompanied by mechanical responses of the solitary VHCs. In addition to the evoked motile events spontaneous shape changes of VHCs were observed. Implications for vestibular micromechanics of the observed evoked force generation in VHCs are discussed.

Tinnitus associated spontaneous otoacoustic emissions. Active outer hair cell movements as common origin?

In the mammalian inner ear, active mechanical processes contribute to cochlear micromechanics. Direct evidence of these are spontaneous otoacoustic emissions (SOAE) which have been registered in the human and animal ear canal. In mammals, outer hair cells (OHC) seem to be the origin of this mechanical energy, because they exhibit motile responses to various stimuli. Here we report on bilateral tinnitus and bilateral SOAE with both acoustical phenomena located in the same frequency range. In a playback of the SOAEs their frequences were identified as the pitch of the tinnitus. An additional criterion favoring a common pathomechanism of SOAEs and tinnitus resulted from masking effects. Tinnitus and SOAEs from both sides were suppressed by the same tone, which indicates that the involved pathways are identical. Therefore we suggest that pathological long-term movements of only a small number of OHCs underlie both phenomena. From the SOAE emission spectra we calculated that not more than 60 OHCs might be involved.

Evaluation of otoacoustic emissions in high-risk infants by using an easy and rapid objective auditory screening method

Ninety-five ears of 53 infants at high risk for hearing impairment were examined using brainstem-evoked response audiometry (BERA), stapedial reflex audiometry (SRA) and click-evoked otoacoustic emissions (EOAEs). By taking BERA as a reference, the results obtained were compared in order to evaluate the significance of EOAEs for auditory screening. EOAEs were present in more than 90% of the ears when the BERA threshold was below 30 dB. In this group of infants, the stapedial reflex was positive in about 80% of the ears examined. In contrast, EOAEs were never observed with BERA thresholds exceeding 40 dB. In several cases with BERA thresholds above 30 dB, elevated SRA values could also be recorded. A further advantage of EOAEs and SRA was a recording time of less than 3 min. Since the non-invasive recording of EOAEs was fast and easy to perform and the results obtained were reproducible, we conclude that click-evoked otoacoustic emissions are a reliable technique for demonstrating normal cochlear function.

The cell potential of isolated inner hair cells in vitro

Inner hair cells (IHCs) were isolated from the 3rd and 4th turn of the guinea-pig cochlea using a new microsurgical technique. Microelectrode impalements in vitro with conventional microelectrodes yielded intracellular potentials of -14 +/- 7 mV (mean +/- SD, N = 43) at 24 degrees C. This suggested depletion of intracellular K+ in the isolated IHCs. Whole-cell recordings with patch-clamp suction electrodes of 11 +/- 3 M omega when filled with KCl Ringer demonstrated reloading of the cytoplasmic compartment with K+ (time constant t = 26.3 +/- 3.5 s), resulting in stable intracellular potentials after equilibration of -58.7 +/- 7.3 mV (mean +/- SD, N = 6) which is close to the K+ Nernst potential. The results suggest that IHC membranes are predominantly potassium-permeable. Assuming that in vivo the apical membranes of IHCs are exposed to endolymph-like fluid, the lower resting potentials of IHCs can be explained with the potassium permeability ratio of their apical and basolateral membranes. In whole-cell recordings, injection of hyperpolarizing current induced larger changes of the intracellular potential than depolarizing current. Oscillatory potential fluctuations were not observed, neither spontaneous nor in response to rectangular current pulses.

Visualization and functional testing of acetylcholine receptor-like molecules in cochlear outer hair cells

The efferent nerve endings at outer hair cells (OHCs) have been suggested to regulate active mechanical processes in the cochlea. The discovery of acetylcholine (ACh)-producing and -degrading enzymes in these synapses gave rise to the speculation that ACh might be one of the efferent transmitters. However, there has as yet been no identification and characterization of any corresponding receptor in OHCs which is required for further clarification of this question. In the present paper existence, location and first characterization of acetylcholine receptors (AChRs) in OHCs are reported. Using two anti-AChR monoclonal antibodies, AChR epitopes were found forming a cup at the basal end of the OHCs opposite to the efferent nerve endings. Furthermore, the studied molecules could be shown to extend through the cell membrane. In addition, the denervated OHC AChR-epitopes seem to move by lateral diffusion. Application of Carbachol and ACh to the basal pole of OHCs induced a weak, reversible cell contraction. Pharmacological controls revealed, that hte motile responses were mediated by the AChRs.

[Evoked otoacoustic emissions for hearing screening in infants]

The early detection of auditory dysfunction in neonates and infants is important for the development of language and other cognitive abilities. The registration of evoked otoacoustic emissions is a new way of detecting cochlear hearing disorders. Results in high-risk infants are reported. Evoked otoacoustic emissions promise to be a fast and noninvasive technique to screen auditory dysfunctions in newborns and high-risk infants.

Active radial and transverse motile responses of outer hair cells in the organ of Corti

In isolated outer hair cells (OHCs) electrically induced movements of high frequencies have been described. The experiments, however, gave no information whether fast OHC motility exists in situ. In the present report, we developed a technique to prepare viable half turn explants from the guinea-pig cochlea which could be kept as organ culture. Several video imaging methods and pixel-by-pixel, digital-image subtractions allowed simultaneous observations and quantitative measurements at video rates of 688 x 512 localizations of investigated segments of the organ of Corti (OC). When living cochlea explants were exposed to an electrical a.c. field, the OHCs in the OC followed this field by shortenings and elongations of their cell bodies and by radial movements of their cuticular plates (CP). This was accompanied by radial displacements of the hair bundles. In the apical turns video stroboscopy allowed recording of in situ movements of OHCs up to auditory frequencies. In all experiments motile responses were most prominent in the three rows of the OHCs. No or less pronounced passive motile responses could be observed at the tunnel of Corti (TC) and in the inner hair cells (IHCs). Mechanical decoupling of OHCs and IHCs at the TC resulted in a loss of IHC movements, whereas OHCs were uneffected. Motility was detectable in the presence of physiological salt solutions (300 mOsm/l) and in iso-osmolar mannitol or sorbitol solutions. The electrically induced motile responses were not suppressed in the presence of dinitrophenol or cytochalasin B. Thus, the present report shows active transverse and radial motile responses of OHCs in the OC, which are electro-mechanical in situ processes. The results indicate how outer hair cell electromotility may influence hearing when it occurs within the mechanical framework of the OC.

A subpopulation of outer hair cells possessing GABA receptors with tonotopic organization

The olivocochlear innervation has been postulated to regulate active mechanical processes in the mammalian cochlea. Histochemical studies led to the suggestion that a subpopulation of these efferent nerves, which predominantly terminate on outer hair cells (OHCs), are gamma-aminobutyric acid (GABA)-ergic. By means of two monoclonal antibodies, we were able to visualize GABAA-receptor immunoreactivity at the basal pole of isolated sensory cells. Both subunits of the GABAA receptor, the alpha- and beta-subunit, are known to form the transmembranous GABA/benzodiazepine-receptor complex and were present on OHCs. In addition, these inhibitory receptors were more numerous in the apical turns of the cochlea, indicating another criterion for distinguishing the apical from basal turns of the cochlea. These results support the concept that a subpopulation of axosomatic synapses at the basal pole of OHCs liberate the inhibitory neurotransmitter GABA into the synaptic cleft. Binding of the transmitter to these newly observed subsynaptic receptors is possibly followed by a change in OHC motility and a subsequent modulation of the movement of the basilar membrane.

[Transduction and motor disorders of cochlear hair cells in Menière and aminoglycoside hearing loss]

The auditory reception by cochlear hair cells is a mechano-electrical process of transducing based on ionic channels in the outer cell membrane. In addition, outer hair cells seem to control actively the non-linear micromechanics of the inner ear on the basis of fast and slow motor properties. These active motor properties of outer hair cells are obviously disturbed in acute attacks of Ménière's disease or in aminoglycoside intoxication. Their dysfunction may thus partly explain the resulting deafness.

[Microsurgically collected living inner hair cells allow measurements of ion channels and cell potential]

Living inner hair cells of the mammalian inner ear were dissected microsurgically from guinea-pig cochleae in the absence of proteolytic enzymes. They were kept in short-time culture for 2 hours. Viability of the preparation was monitored by registration of the cell potential with impaled microelectrodes. The patch-clamp technique allowed the identification of 3 types of ionic channels in the basolateral cell membrane. Isolated living inner hair cells are a new model allowing to investigate the cellular basis of physiological function and pathophysiological disorders of sound perception.

[Transmission electron microscopy of in vitro cultivated squamous cell carcinoma cell lines]

Despite a twofold recloning, ultrastructural analysis of squamous cell carcinoma lines of the head and neck showed morphologically a very heterogeneous picture in respect of the cytoplasmatic organelles, electron density of the cytoplasma, nucleus and differentiation of the cell membranes. Most prominent were the differences in the content of mitochondria and the formation of intracytoplasmatic filaments and desmosomes. Although the cells have been cultured as single cells, they developed desmosomes in vitro. The cell contact formation varied to such a degree that the plasma membranes of the cells from the tongue squamous cell carcinoma line SCC-25, as an example, were almost completely occupied by desmosomes.

Active movements of the cuticular plate induce sensory hair motion in mammalian outer hair cells

It has been suggested that active motor capacities may explain the high sensitivity and sharp tuning of auditory transduction in the mammalian cochlea. Recently, slow and fast motile responses of isolated outer hair cells (OHCs) have been demonstrated. These consist of reversible length changes in the cylindrical cell body. Here we show that isolated OHCs are also capable of slow and fast movements of the cuticular plate (CP) which cause passive displacements of the stereocilia. The molecular mechanisms that underlie the slow movements appear to reside in the highly organized actomyosin cytoskeleton in the CP. Additional, fast movements of the CP were observed in OHCs which were exposed to alternating electrical fields. These rapid mechanical events followed the electrical stimulus cycle-by-cycle, and unlike the slow movements, did not depend on the actomyosin skeleton in the CP. The fast motility of the CP and the attached stereocilia suggest an additional active mechanism which may contribute to the sensitivity and the sharp tuning of the cochlea near threshold. By controlling the operating point of the reticular lamina and of the hair bundles, the slow CP and stereociliary movements may influence basilar membrane homeostasis and temporary threshold shift at high sound pressure levels.

Outer hair cells as fast and slow cochlear amplifiers with a bidirectional transduction cycle

Cochlear hair cells fulfil the key function in hearing. However, possible differences in functions of inner and outer hair cells are the subject of a current scientific discussion. In the present paper, we present steps of the sensory transduction in living mammalian hair cells. The transduction is a mechano-electrical process based upon ionic channels in the outer cell membrane. These mechanisms are suggested to be similar in inner and outer hair cells, allowing inner hair cells the actual sound perception. By contrast, the outer hair cells seem to control actively the micromechanics of the inner ear on the basis of fast and slow motor properties. Our results revealed that in these cells, electro-mechanical mechanisms can induce fast and slow motile events. Together with the above-mentioned mechano-electrical transduction, the electro-mechanical mechanisms are assumed to establish a bidirectional transduction cycle in outer hair cells. These active motor properties of outer hair cells are obviously disturbed in acute attacks of Meniére's disease or in aminoglycoside intoxication, and may thus partly explain the resulting deafness.

Adenylate cyclase and G-proteins as a signal transfer system in the guinea pig inner ear

In many eukaryotic cells G-proteins play a key role in signal transduction through outer cell membranes. To study this pathway in the auditory organ of mammals we examined tissue preparations from the stria vascularis and the organ of Corti from the guinea pig inner ear. The activity of adenylate cyclase was measured by stimulation at the site of the enzyme, the hormone receptors and the modulating G-proteins. In the organ of Corti we found a low enzyme activity in all cochlear turns. The stria vascularis, however, showed a constant high concentration of beta 2-adrenergic receptors and of stimulating G-proteins in all cochlear turns. In contrast, the activity of the enzyme increased from the apical to the basal turn. Adenylate cyclase could be stimulated or inhibited in a concentration-dependent manner by drugs selectively effecting the G-proteins. Our results suggest a structure of the adenylate cyclase complex in the inner ear similar to other organs. Pathophysiological correlations to hearing loss associated with pseudohypoparathyroidism are discussed.

Motility of outer hair cells as an active, actin-mediated process

The cochlea of the inner ear is no longer regarded exclusively as a passive mechanical signal analyser. Active mechanical processes are thought to influence the vibration pattern of the basilar membrane. The source of these active mechanical processes is sought in the outer hair cells (OHC). These auditory sensory cells contain actin and actin-associated structural elements. Recently, isolated OHC have been demonstrated to be capable of reversible longitudinal contractions in vitro, whose molecular mechanism could not be documented, however. Furthermore, following an increase in the intracellular Ca2+ level, isolated OHC showed longitudinal motile responses in the presence of ATP. We now report that the observed Ca2+/ATP induced mechanical events in OHC are active processes, that are driven by the hydrolytic energy of ATP. Moreover, motile responses are frequently associated with a movement of the cuticular plate, including the stereociliary bundle. Cytochalasin B, inorganic bisphosphate, trifluoperazine and antiactin inhibit the motile response. Thus, our results show that outer hair cells possess actin-dependent Ca2+ and calmodulin-controlled motor properties, so that potentially they can actively adjust the mechanical properties of the basilar membrane during auditory stimulation.

Immunological aspects of tonsils and of tonsillitis

The human tonsils are responsible for the final antigen-induced differentiation of B-cells to plasma cells. Their main function could be the expansion of memory IgA-B-cells, allowing J-chain expression and final differentiation under secondary signals. IgA/J+-cells have been shown to migrate into mucosal membranes, allowing a protection against microorganisms. Recurrent tonsillitis obviously interferes with this complex immunological network, possibly resulting in a reduced mucosal protection by IgA. Furthermore, bacterial antigens can initiate the liberation of biochemical inflammatory mediators. Among these, arachidonic acid products can play a key role. They can induce epithelial damage and decreased ciliary function. Furthermore, they influence tonsillar immunological reactions.

Cytotoxic effects of recombinant human biological response modifiers on head and neck carcinoma cells

The present report shows that the simultaneous application of two biological response modifiers (recombinant human gamma-interferon plus recombinant human alpha-tumor necrosis factor) has a lethal effect on living laryngeal and salivary gland carcinomas. A cytostatic or cytotoxic effect of the two substances alone could only be observed in occasional cases. The results suggest a synergistic action of gamma-interferon and alpha-tumor necrosis factor that might be of therapeutic value for head and neck carcinomas in the future.

Evidence that phosphoinositides mediate motility in cochlear outer hair cells

Cochlear outer hair cells are postulated to modulate auditory transduction by their mechanical properties which presumably are controlled by efferent neurons and regulated by the levels of intracellular calcium. In a number of biological systems these calcium levels are controlled by inositol trisphosphate (InsP3), the second messenger of the phosphoinositide cascade. We have investigated whether the phosphoinositides function in the signal transfer in mammalian auditory sensory cells. Live isolated outer hair cells synthesize the lipids of the phosphoinositide cycle, phosphatidic acid (Ptd), phosphatidylinositol (PtdIns), phosphatidylinositol 4-phosphate (PtdInsP) and phosphatidylinositol 4,5-bisphosphate (PtdInsP2). After one hour of incubation with [32P]orthophosphate, Ptd constituted 21 +/- 7% of labeled lipids, PtdIns 19 +/- 5%, PtdInsP 28 +/- 7% and PtdInsP2 33 +/- 7%. Contractions were elicited in isolated cells after their membrane was permeabilized with Triton X-100. Addition of calcium and ATP resulted in contractions (average, 7.2% of initial cell length) in 81% of the cells studied; the omission of ATP or calcium (i.e. the presence of the calcium-chelator EGTA) reduced the incidence of contractions to 0% and 17%, respectively. In the absence of calcium, the putative second messenger, InsP3, caused contractions in 63% of the observed cells while the physiologically inactive agents inositol and inositol bisphosphate failed to elicit responses. The results are compatible with the suggestion that InsP3 mediates contractility in outer hair cells.

Fast motility of isolated mammalian auditory sensory cells

Auditory sensory cells (hair cells) are responsible for sound transduction in the cochlea of the inner ear. In the presence of a longitudinal a.c. field isolated living outer hair cells showed reversible motile responses. They followed the stimulus up to at least 1 kHz. Control experiments in the presence of cytochalasin B, phalloidin and dinitrophenol excluded actomyosin as a molecular basis of the high frequency motility. The results suggest, that outer hair cells might amplify sound-induced oscillations in the inner ear and thus increase sensitivity and frequency selectivity of hearing.

[Retrospect and perspective in rhinologic allergology]

The first classical description of allergic rhinitis was given by John Bostock in 1819, and Blackley demonstrated the etiology in 1873. In 1906 Clemens von Pirquet discussed a relationship between hypersensitivity and immunity: he called it allergy. In 1922 Prausnitz and Kustner described the transfer of the immediate type hypersensitivity by serum. Coca and Cooke called the factor atopic reagin. The breakthrough in 1967 was due to Ishizaka and Ishizaka who discovered the IgE-antibodies, and proved that these are identical with the postulated reaginic antibodies. The knowledge of the new IgE-antibody class allowed the incorporation of nasal allergy in clinical immunology.

[Demonstration and organizational structure of the DNA of human papillomaviruses in laryngeal and hypopharyngeal carcinomas]

Thirty biopsy specimens from various histological types of human carcinomas of the larynx and hypopharynx were analysed for the presence of human papillomavirus (HPV) DNA: DNA from the individual specimens were tested for the presence of homologous sequences to HPV genotypes 1, 2, 4, 8, 9, 10, 11, 13, 16 and 18. One squamous cell carcinoma of the hypopharynx (postcricoideal area) contained multiple copies of DNA hybridizing under stringent conditions with HPV 16 DNA. The latter DNA has been found to be frequently associated with human genital cancer. HPV 16 DNA was found mostly episomally as oligomeric circles of 7.9 kbp size, and as larger rear-ranged circular molecules. Integration of the viral DNA in the host cell DNA seems quite likely. Integration and rearrangement of viral DNA into cellular DNA may play a role in the induction and maintenance of the transformed state. The presence of sequences reacting under semistringent conditions with HPV DNA was observed in two additional biopsy specimens of this study. This could suggest that additional laryngeal cancers are associated with papilloma virus infections.

Three molecular steps of aminoglycoside ototoxicity demonstrated in outer hair cells

Previously postulated molecular mechanisms of aminoglycoside ototoxicity were investigated in outer hair cells in vitro. Cells were isolated by microdissection from the organ of Corti of the guinea pig and maintained in Hank's balanced salt solution. (1) Approx. 100 cells (the standard number per assay) bound 432 +/- 198 pmol calcium as determined with 45Ca2+ (1.2 mM). 1 mM neomycin or gentamicin lowered this value by 28% and 45%, respectively. (2) Binding of radiolabeled gentamicin (28 fmol per 100 cells at 0.1 microM gentamicin) was reduced by 55% by 1 mM neomycin or spermine. Washing with an excess of unlabeled gentamicin displaced only 60% of the drug, the remainder being tightly bound to a less accessible compartment. Incubation at low temperature essentially abolished gentamicin uptake. (3) Phospholipids were labeled with [32P]orthophosphate which was mostly incorporated into phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate, phosphatidylinositol, and phosphatidic acid. When the lipids were chromatographed over immobilized gentamicin PIP2, in contrast to other lipids, was strongly retained. These results are compatible with the following actions of aminoglycosides in outer hair cells: (1) competition with calcium; (2) energy-dependent uptake competitive with polyamines; and (3) binding to the phospholipid PIP2.