Skin test results but not serology reflect immediate type respiratory sensitivity: a study performed with recombinant allergen molecules.

The diagnosis of type I allergy, an IgE-antibody-mediated hypersensitivity disease affecting more than 25% of the population, is based on the measurement of allergen-specific serum IgE levels and provocation testing. Whether the determination of allergen- specific serum IgE levels can replace in vivo provocation testing for allergy diagnosis is a controversial issue. We used purified recombinant timothy grass and birch pollen allergens to compare by skin prick and nasal provocation testing as well as by serology in vivo sensitivity with antibody-binding capacity in 24 pollen allergic patients and eight control individuals. Results from biologic tests were correlated with each other and with allergen-specific IgE and IgG1-4 levels. IgE-reactive allergens induced immediate skin and nasal reactions, but the intensity of the allergic tissue reactions was not correlated with either the levels of allergen-specific IgE or the levels of allergen-specific IgG antibodies. Less frequently detected allergens with low IgE-binding capacity were able to induce strong allergic reactions comparable to those caused by major allergens with high IgE-binding capacity. In contrast, skin test and nasal provocation results were significantly correlated (r = 0.63, p < 0.01). Our study thus demonstrates on a molecular level that skin testing provides a better reflection of immediate type respiratory sensitivity than serologic measurements. These results have implications for allergy diagnosis and, in particular, for the selection of relevant allergen components for specific immunotherapy.

Radiation of jejunal interposition in T3-T4 upper aerodigestive tumours.

30 patients with T3 and T4 tumours of the upper aerodigestive tract had their tumours resected by pharyngolaryngectomy. This was followed by reconstruction of a gullet or creation of a siphon as a tracheohypopharyngeal shunt for voice restoration with a free jejunal autograft. All patients were treated postoperatively with 60Co gamma radiation, 6 MeV photons or 7.5 to 10 MeV electrons of a beta-tron, with a dose of 50-65 Gy in the area of the primary tumour and 50-65 Gy to the neck. 4 patients refused further treatment after a depth dose of between 16 and 32 Gy. Local recurrence occurred in 40% of cases. The survival rate was 36.6% (11/30) after a mean follow-up time of 21.5 months, although 2 patients died of intercurrent diseases without recurrence of their tumours. The results obtained justify active surgical intervention with postoperative irradiation even at an advanced stage of the tumour.

Caroverine depresses the activity of cochlear glutamate receptors in guinea pigs: in vivo model for drug-induced neuroprotection?

With the aid of microiontophoretic techniques the action of caroverine, a quinoxaline-derivative, was tested on the receptor-linked depolarisation of the subsynaptic membrane of cochlear afferents. This membrane can be depolarised by the afferent transmitter agonist glutamate, mediated by NMDA and non-NMDA receptors and by acetylcholine, one of the different transmitter substances, released physiologically on axodendritic efferent synapses. Caroverine antagonized the membrane response to glutamate in an enduring but reversible manner. In contrast, the drug exhibited no effect on the depolarising action of acetylcholine. Therefore, the pharmacological profile of caroverine corresponded to the action of selective glutamate receptor antagonists. Since glutamate is likely to be the major mediator of neurotoxicity in the central nervous system, the selective glutamate-antagonism of caroverine is of particular interest, due to its putative neuroprotective competence. Caroverine is currently available clinically in some countries as a spasmolytic drug. Following these results it is proposed to test the drug for clinical efficacy in putatively glutamate-induced, excitotoxic disorders of the brain.

Autotransplanted jejunum in patients with carcinomas of the head and neck: transport of immunosurveillance against tumor cells?

Autologous jejunum, transplanted as a functional replacement immediately after radical dissection of advanced stages of squamous cell carcinomas of the head and neck and subsequently irradiated, was examined by immunohistochemistry (APAAP/PAP-technique). Biopsies from 9 patients were taken at the time of transplantation and up to 24 months thereafter (group 1) and from 5 patients only once after transplantation (group 2). Twenty-six monoclonal antibodies (mAbs) were used as surface markers to give an overview about phenotypical changes with respect to T-, B- and M phi-antigens. 1) B cells: a general increase of CR2+ (CD21, p less than 0.01) could be noticed after transplantation, immunoglobulin positive cells remained unchanged expect for a significant decrease of IgM+ (p less than 0.01) and IgA1+ (p less than 0.01) cells. 2) The number of T cells (CD3+) showed no significant differences although TcR gamma/delta+ cells decreased (p less than 0.01) in the autotransplant. ICAM-1 (CD54) and IL-2R (CD25) were found on a significant (p less than 0.01) higher number of cells after transplantation. 3) Cells with M/M phi morphology showed increased expression of the Fc gamma receptors (CD64, p less than 0.001; CD32, n.s.; CD16, p less than 0.001), of the complement receptors CR1 (CD35, (p less than 0.001) and CR3 (CD11b, p less than 0.02), of HLA-DQ (p less than 0.01), and of the antigens 25F9 (mature M phi; p less than 0.01) and CD4 (p less than 0.02). Correlation analyses of data obtained from the biopsies of the 14 autotransplanted jejunum cases revealed a CD35+ and a 25F9+ subpopulation of M/M phi. Our findings indicate that despite irradiation autotransplanted jejunum contained cells with immunological capacities. Therefore, the replacement of larynx by autologous jejunum may facilitate not only mechanical but also immunological functions.

Origin of auditory fractal random signals in guinea pigs.

In guinea pigs, the constant iontophoretic release of transmitter agonists in the synaptic cleft of inner hair cells (IHC) triggers chemically an irregular and bursting mode of spiking discharge, subsynaptically recorded in the afferent dendrites. The tendency to form spike clusters appears to be independent of the quality and quantity of the used test substances, the excitatory amino acids N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4- isoxazole-propionic acid (AMPA). The recorded spike trains show a remarkable stability of the calculated individual box-counting dimension characterizing the bursting behaviour as a fractal random point process. The fractal kinetics seems to reflect molecular instabilities of cochlear afferent glutamate receptors, determining the mode of the signal transmission in the auditory periphery.

Metabotropic glutamate receptors group I are involved in cochlear neurotransmission.

All three types of ionotropic glutamate receptors, AMPA, NMDA and kainate, contribute to the neurotransmission between inner hair cells (IHC) and afferent neurons in the mammalian cochlea. We used microiontophoretic techniques to investigate whether metabotropic glutamate receptors group I (mGluR I) are also involved in the transmission of IHC afferents of the guinea pig. The mGluR I agonist DHPG produced an increase in afferent firing, which lasted significantly longer than that of the ionotropic agonists AMPA and NMDA. The activation was reversibly blocked by the mGluR I antagonist AIDA in a dose-dependent manner. AIDA also diminished spontaneous activity, but only slightly affected the AMPA- or NMDA-induced firing rate. Our results suggest that mGluR I are involved in peripheral auditory processing.

Reconstruction of the facial nerve in acoustic neurinoma surgery. Juxtapontine-intratemporal nerve graft.

Five cases of large acoustic neurinomas (diameter 2.5 cm) with involvement of the facial nerve in the tumour capsule are presented. The preoperative function of the facial nerve was normal. During surgery, in order to achieve a radical tumour removal, the facial nerve was severed juxtapontine. Reconstruction was performed at the same procedure using a 5-6 cm long sural nerve graft. Thus the central juxtapontine stump was joined to the peripheral stump in the facial nerve canal of the petrous bone. After six months, all five patients exhibited a well functioning mimic and a good eyelid function. At the one year control four patients had normal nerve function clinically and one patient still showed asymmetrical mimic.

The efferent modulation of mammalian inner hair cell afferents.

The results of immunocytochemical, enzymatic and electrophysiological studies have indicated that acetylcholine and GABA may act as neurotransmitters in lateral olivocochlear efferent endings on inner hair cell afferent dendrites. Since spike activity can be recorded in the dendritic region of inner hair cells, microiontophoretic techniques were used testing the possible neurotransmitter candidates, acetylcholine and GABA, on spontaneous and induced firing of the afferent dendrites. The experiments were carried out in anaesthetised guinea-pigs, the third and fourth turns of the cochlea being exposed for electrode penetration. Ejection of acetylcholine resulted in a pronounced dose-dependent increase in subsynaptic spiking activity. Furthermore, acetylcholine enhanced glutamate-induced activity. In contrast, even at high doses, GABA had very little effect on the spontaneous cochlear firing rate. When the firing rate had first been enhanced by glutamate or N-methyl-D-aspartate, however, this activation could be reduced by the ejection of GABA. A similar reduction was observed when the firing rate had been enhanced with acetylcholine. The results of our studies support the hypothesis that these substances are involved in efferent neurotransmission on inner hair cell afferent fibres. It should be pointed out, however, that besides acetylcholine and GABA, several opioids such as enkephalins and dynorphins seem to be involved in efferent cochlear innervation.

Glutamate receptors in afferent cochlear neurotransmission in guinea pigs.

With the aid of microinotophoretic techniques we tested the action of the transmitter candidate glutamate (Glu) at the afferent synapses of inner hair cells (IHC) in guinea pigs. In order to determine the various types of glutamate receptors, further agonistic excitatory amino acids (EAA) as well as competitive EAA-antagonists were used. Applied perisynaptically, Glu, aspartate, N-methyl-D-aspartate (NMDA), quisqualate (Q) and kainate (K) activate the subsynaptic, phasic firing activity of the afferent dendrites. The NMDA-induced activation is augmented by simultaneous application of glycine. The firing rate induced by Glu and NMDA is blocked by the specific NMDA-antagonist D-2-amino-7-phosphonoheptanoate (AP-7). Furthermore, activity induced by Glu and Q decreases under the influence of the selective Q-antagonist glutamic acid diethylester (GDEE). These results are consistent with the hypothesis that Glu acts as a possible afferent neurotransmitter of the IHC. This neurotransmission is mediated by postsynaptic EAA-receptor subpopulations which are sensitive to NMDA, Q and K. The activity of the NMDA-receptors depends, however, on the amount of glycine available. Our data suggest that the afferent synapses of the IHC possess functional properties which are equivalent to the properties of glutamatergic NMDA-sensitive and NMDA-non-sensitive synapses in the central nervous system.

Dopamine regulates the glutamatergic inner hair cell activity in guinea pigs.

Recent immunocytochemical and biochemical studies support a possible neurotransmitter function of dopamine (DA) in the efferent olivocochlear innervation of the guinea pig cochlea. However, the physiological role of DA in cochlear neurotransmission remains unknown. In the present study microiontophoretic techniques were used for testing the action of DA as well as D1- and D2-agonists and -antagonists on spontaneous and N-methyl-D-aspartic acid (NMDA)-, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-, kainic acid- or glutamate-induced firing of afferent fibres in the dendritic region of inner hair cells. Subsynaptic spike activities of anaesthetised guinea pigs were recorded after exposing the third or fourth turn of the cochlea for electrode penetration. Application of DA alone had very little effect on the spontaneous afferent firing rate. In contrast, firing induced by NMDA or AMPA could be depressed by additional administration of DA in a dose-dependent manner. A similar reduction of the induced spike activity was seen after co-administration of D1- or D2-agonists. The action of DA on glutamate agonist-induced firing could be blocked by D1- as well as D2-antagonists. These results show that DA can depress the activated firing rate of the afferent fibres and that this action is mediated by both D1- and D2-receptor subtypes.

GABA(A) receptor modulates the activity of inner hair cell afferents in guinea pig cochlea.

The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is mediated by two main categories of receptors: the GABA(A) and GABA(B) receptor. Recent immunocytochemical and electron microscopical studies revealed the existence of GABA at the efferent olivocochlear innervation of the guinea pig cochlea. In this microiontophoretic study we examined the effect of GABA on spontaneous and glutamate or acetylcholine induced activity of afferent fibres in the dendritic region of inner hair cells. Furthermore, the receptor subtypes being responsible for this GABA action were analysed using specific agonists and antagonists on alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and N-methyl-D-aspartic acid (NMDA) induced activity. The spike activities of the subsynaptic area were recorded in the third or fourth turn of the cochlea of anaesthetised guinea pigs. Application of GABA had little effect on spontaneous activity whereas the glutamate or acetylcholine induced firing rate could be depressed by GABA. AMPA and NMDA induced activity was reduced by the GABA(A) agonist muscimol but not by the GABA(B) agonist baclofen. The GABA(A) antagonist blocked the inhibition of both GABA and the GABA(A) agonist. In contrast, the GABA(B) antagonist saclofen was without effect. These results reveal that GABA reduces the activated firing rate of inner hair cell afferents mediated by the GABA(A) receptor subtype.

Receptor pharmacological models for inner ear therapies with emphasis on glutamate receptors: a survey.

With the aid of microiontophoretic techniques we evaluated the action of different postsynaptic glutamate receptor subtypes that mediate neurotransmission between the inner hair cell and the afferent neuron. The sensory input is modulated by axodendritic efferents. In the central nervous system, excessive activation of glutamate receptors is thought to be responsible for a wide variety of neurotoxic actions, and calcium is involved in the etiology of glutamate-induced cell damage. Glutamatergic neurotoxicity may form an appropriate pathophysiological model to explain a variety of inner ear diseases characterized by acute or progressive hearing loss and tinnitus. In clinical trials, three sites of action are thought to attenuate glutamatergic otoneurotoxicity: presynaptically, via the reduction of excessive transmitter release; postsynaptically, via competitive or noncompetitive receptor antagonism; and intracellularly, via blockage of glutamate receptor-dependent calcium stores. The drugs discussed in this paper are currently available clinically and have only recently been found to attenuate glutamate toxicity. Magnesium and the quinoxaline derivative Caroverine, which have already been tested in humans, exhibit a statistically significant otoneuroprotective action in noise-induced hearing loss and tinnitus. The intensive search for further drugs that enhance the survival of cochlear afferents without disrupting acoustic signal processing is one of the main goals of research in clinical otoneuropharmacology in the near future.

Cochleo-vestibular correlations in Meniere's disease.

The cochlear and vestibular functions were investigated in a sample of 36 patients with unilateral Meniere's disease. Caloric reactions and hearing thresholds were compared separately at several frequencies. A topodiagnostic relationship between the cochlear and vestibular function was discovered. Using four qualitative categories, a significantly high correlation was obtained between the basal hearing loss (4000 Hz) and unilateral weakness, whereas no correlation was obtained when evaluating the more apical hearing loss (lower frequencies 250-1 000 Hz). A normal caloric reaction can be reasonably expected in cases of unilateral Meniere's disease if the hearing loss is less than approx. 40 dB HL at 4 000 Hz.

Glutamic acid and glutamic acid diethylester in tinnitus treatment.

Numerous recent findings indicate that in mammals glutamic acid (Glu) functions as the primary and secondary afferent cochlear transmitter, or at least as an agonist of the main transmitter. Glutamic acid diethylester (GDEE) is one of the known antagonists of Glu. A long term suppression of certain forms of tinnitus was observed dependent on the sequence, amount and perfusion rate upon i.v. application of Glu and GDEE. Consecutive controls with tinnitus detecting as well as blind studies helped to objectify the subjective sensations of the patients.

The action of putative neurotransmitter substances in the cat labyrinth.

Possible neurotransmitter candidates were tested in the labyrinth of the cat with the aid of microiontophoretic techniques. Depending on the recording site, spontaneous regular or irregular fibre activity was obtained in the subsynaptic region of the macula sacculi. Ejection of GABA enhances the firing rate, whereas acetylcholine reduces the spontaneous activity. A similar application of glycine and proline produced no effect. The action of GABA was specifically blocked by the GABA antagonists bicuculline and picrotoxin. The alkaloids further induced a decrease in the spontaneous activity which lasted for several minutes.

Receptorpharmacological models for the therapy of labyrinthine vertigo.

In the mammalian labyrinth, GABAA receptor subtypes are involved in the excitatory neurotransmission between the vestibular type II hair cells and the afferent neurons. Additional afferent ionophoric receptor channels, sensitive to further transmitter candidates, are discussed for both types I and II hair cells. GABA accelerates excitotoxic cell death in cortical neurons. This GABA-ergic neurotoxic action forms an appropriate pathophysiological model explaining peripheral labyrinthine disorders characterized by the spontaneous labyrinthine nystagmus and vertigo in man. A calculated GABAA receptor antagonism was envisaged in order to attenuate the pathological vestibular imbalance following one-sided GABA-accelerated vestibular neurotoxicity. Moderate allosteric blockers of the GABAA receptor channel and weak inverse agonists of the benzodiazepine binding site meet some requirements for potentially successful clinical application. The suppressing action of the suitable drugs picrotoxin and flumazenil on labyrinthine nystagmus and vertigo, tested in clinical trials, supports the hypothesis that GABAA receptors are involved in vestibular neurotransmission, even in humans. The test results promise the development of a successful vestibular receptorpharmacology in the near future.

Suppressive action of picrotoxin, a GABA antagonist, on labyrinthine spontaneous nystagmus and vertigo in man.

There is evidence that GABA acts as the excitatory neurotransmitter at synapses between vestibular hair cells and the afferent fibres in the mammalian labyrinth. The question arose as to whether certain vestibular dysfunctions such as labyrinthine vertigo could be treated in patients by influencing the peripheral GABA system by means of the GABA antagonist picrotoxin, a well known analeptic drug. With the application of slow infusion rates of only milligrams of picrotoxin a distinct suppression of peripheral spontaneous nystagmus, caloric excitability of labyrinths, and labyrinthine vertigo, without general CNS-induced arousal effect, was observed. A latent central spontaneous nystagmus can become manifest, whereas a manifest central spontaneous nystagmus remains unchanged. A future application of picrotoxin as a diagnostic and therapeutic tool in cases involving vestibular disorders is discussed.

Efferent controlled integrating fuctions of primary vestibular afferents.

The vestibular type II receptor cells of mammalians are multiply innervated. Their afferents are integrating neurons consisting of many inputs but only one output. They transform the irregular spontaneous input activity into a regular output. Under the influence of efferent activity following the stimulation of the contralateral labyrinth, this regular output activity becomes irregular. This efferent influence upon afferent spontaneous activity is analysed by means of an existing computer model of an integrating cell. The analysis confirms a high functional interdependence of both labyrinths.

Stochastic resonance in cochlear signal transduction.

The use of a stochastic resonance model contributes crucially to our comprehension of the intensity resolution characteristics of the mammalian cochlea. In guinea pigs, as demonstrated by different statistical methods, the temporal distribution of the interspike intervals of the spontaneous activity reflects an intrinsic cochlear white noise process, demanded as basic requirement for manifest stochastic resonance phenomena. Brownian motion of cochlear fluids is discussed as the underlying white noise motor. Following our model, the amount of white noise, adjusted at the level of the stereocilia of the inner hair cells, determines the threshold, dynamic range and intensity discrimination limen of an individual afferent neuron of the mammalian cochlea.

New approaches for inner ear therapy with glutamate antagonists.

In the mammalian cochlea neurotransmission between inner hair cells and afferent auditory neurons is probably mediated by glutamate or another related excitatory amino acid. Neurotoxicity induced by excessive glutamate release seems to play a crucial role in some pathological conditions of the cochlea, such as ischaemia or noise trauma. Thus, glutamate antagonists may be a new therapeutic strategy for different inner ear diseases. Because of their potential severe side-effects only a few glutamate antagonists have so far been adopted for clinical use. We used microiontophoretic techniques to compare the effects of memantine and caroverine on the glutamatergic transmission of inner hair cells of the guinea pig and tested the possibility of a local administration of memantine to the cochlea with a micropump. Memantine selectively inhibited the NMDA (N-methyl-D-aspartate) stimulated activity while caroverine blocked NMDA as well as AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) induced activity of inner hair cell afferents. With a flow rate of 1 microl/h the local administration of memantine via a cochleotomy was succeeded in a reversible blockade of the spontaneous and the NMDA induced firing of inner hair cell afferents. These results suggest that local application to the cochlea could be a feasible way to administer glutamate antagonists in sufficient amounts while avoiding systemic side-effects.