A hydrodynamic model of labyrinth to study the stimulation of perilymph compartments by audioprostheses

CONCLUSIONS

The hydrodynamic model of the labyrinth spaces (LHM) is a useful tool for research on implantable audioprostheses, in particular to develop suitable actuators using MEMS technology (micro-electromechanic machine system). It has other potential applications for auditory research.

OBJECTIVES

The energy reaching the labyrinth fluids is crucial information for developing prostheses to substitute the tympanic-ossicular system because adequate stimulation of the cochlear partition is essential. However, in vivo measurements in human ears are not currently available. Therefore a model of the normal labyrinth resembling its hydrodynamic properties becomes a valuable tool. It could allow comparison of different processing systems, algorithms and transducers, to develop new audioprostheses and improve their effectiveness and efficiency.

MATERIALS AND METHODS

This work presents one LHM that emulates the conduction of the stimuli from the stapes footplate through the labyrinthine fluids, including its dimensions and physical properties, and some examples of measurements of perilymph stimulation by different audioprostheses and algorithms. RESULTS. As shown in the reported examples, this LHM provided effective measurement of acoustic stimulation across the whole human auditory frequency and intensity spectrum. Air-delivered and direct stimulation methods are possible. This provided convenient information for the actuator development and allowed comparison between different prototypes, stimulation patterns and algorithms.

The crystalline pattern of calcium in different topographical regions of the otoconial membrane. An electron probe and spectroscopic diffraction study

Quantitative electron probe microanalysis and electron spectroscopic diffraction analysis was used to determine the gradient of distribution of calcium and its crystalline pattern at different levels (lower gelatinous membrane, upper gelatinous membrane and otoliths) in the otoconial membrane of adult OF1 mice. Our quantitative electron probe microanalytical data, obtained with scanning-transmission electron microscopy, indicated that there was a gradient in calcium concentration which increased from the vestibular surface towards the otoliths. Differences between the three regions of the otoconial membrane were statistically significant in both the utricle and saccule. Our results with electron spectroscopic diffraction revealed an increasing crystalline development from the lower gelatinous membrane towards the otoliths. Our findings with both techniques suggest that the gelatinous membrane is involved in the maturation and crystallization of the otoliths.

[Late p53 mutation in head and neck oncogenesis]

p53 mutation are currently recognized as the commonest genetic event in human tumors. In this paper are studied, through immunochemistry, the p53 protein expression of 25 carriers from squamous cell carcinoma of the larynx and hypopharynx as well in the non tumoral mucosa of the larynx removed and corresponding metastases. Because of the great overexpression of this protein among tumors and its metastases, aside with the low expression in normal far-off mucous membranes of the studied growths, the AA. draw out the conclusion that p53 mutation is a late event by neck and head oncogenesis.

[Morphological and functional correlations of the protective action of coenzyme A in cisplatin ototoxicity (II)]

Earlier studies have shown that coenzyme A (CoA) protects against cisplatin (CP) induced deafness in guinea pigs. We studied the correlation between the latency of the N1 wave in electrocochleography and total loss of cilia in hair cells by scanning electron microscopy.

[Expression of proto-oncogene bcl-2 in squamous cell carcinoma of the larynx]

Apoptosis, or programmed cell death, is responsible for deleting cells in normal tissues to maintain homeostasis after DNA damage. Apoptosis has several physiological inhibitors, one of the most important being the proto-oncogene bcl-2. An immunohistochemical study was made of bcl-2 expression in 25 squamous cell carcinomas of the larynx, in laryngeal mucosa distant from the primary neoplasm, and in lymph node metastases. The relationship between bcl-2 expression and various clinical and pathological parameters was investigated. Bcl-2 was detected in 40% of primary tumors and in 71% of lymph node metastases; it seems to be a late event in laryngeal malignant transformation. We found no statistical association between bcl-2 expression and most of the clinical and pathological parameters examined. Only tumor differentiation was related to bcl-2 expression, bcl-2 positive tumors being moderately or poorly differentiated (p < 0.02).

[AIDS manifestations in otorhinolaryngology]

The otorhinolaryngological signs of AIDS are reviewed (both analysis and synthesis) following the chronological order of the literature. The earliest clinical pictures, their frequency and time of onset, are described by the authors studied. In 1986 the ENT signs of this disease were well known, and in our region the same multiple, polyfacetic aspects are seen. Personal experience of this is described, emphasizing how seldom the diagnosis has been made, except early on. Usually the cases seen and diagnosed by the Department of Infectious Diseases were referred for specialist opinion. The commonest findings were, amongst the opportunist infections: oropharyngeal and oesophageal candidiasis, and tuberculous adenopathies. Classical ENT pathology was represented by sinusitis and to a lesser extent by otitis and tonsillitis. The tumours seen were non-Hodgkin lymphomas, but no Hodgkin's or Burkitt's lymphomas. There was an unusual case of 'high grade centroblastic lymphoma', localized to the tonsil and presenting as necrotic tonsillitis and peritonsillar abscess. Recently a patient with a large pharyngeal tumour (still being investigated) has been provisionally diagnosed as having a cavernous angioma. Both these patients were diagnosed by us, since we saw the first sign of the disease. We have seen few Kaposi's sarcomas, since cutaneous and oral lesions are not usually referred to us.

Pantothenic acid and coenzyme A in experimental cisplatin-induced ototoxia

We have observed that pantothenic acid (PA) prevents deafness induced by cisplatin (CP) in the guinea pig if both drugs are administered jointly. When deafness was previously produced, recovery was sometimes obtained after the administration of PA; so, we studied the effects of PA on cisplatian-induced ototoxia in guinea pigs, both as a prophylactic agent in healthy animals, and as a therapeutic agent in animals previously made deaf by the drug. To elucidate why PA protects the ear from the toxic effects of CP, we used coenzyme A (CoA) instead of PA-since PA is a component of CoA-to test the hypothesis that the action of PA is due to CoA. The results were practically the same in both experiences, the compound action potential of the auditory nerve (CAP) was tested and cochleas were examined by scanning electron microscopy (SEM). Our results suggest that the protective effect of PA takes place through CoA. Both substances had the same effect on CP ototoxicity, but CoA appears to be much more active, since the dose tested here was much lower than that of PA.

[A CT cytomorphodensitometric study of the proliferating epithelial activity in middle ear cholesteatoma]

A cytomorphodensitometric study was made by analysis of the computerised image of the germinative and intermediate epithelial layers in a sample of five specimens of cholesteatoma and the corresponding skin from the external auditory canal. A morphometric variable corresponding to the nuclear area was determined and densitometric variables equivalent to the relative quantity of nuclear DNA were determined. Within the germinative layers of the cholesteatoma epithelium, we observed larger nuclei and more relative DNA per nucleus. The average densitometric values were in the range of 2C-4C, which is indicative of a greater cellular population in S phase in the cholesteatoma than in the skin.

[The study of proliferative epithelial activity in cholesteatoma of the middle ear during cytomorphophotometry]

Epithelial proliferation in colesteatoma and its influence on the subepithelial inflammatory reaction was studied using morphometry and nuclear photometry of specimens. Twenty specimens of colesteatoma and 15 specimens of skin from the external auditory canal were examined. Nuclear content was greater in the basal cells of colesteatoma epithelium than in the basal cells of external auditory canal epithelium, suggesting increased proliferative activity. This activity was found to be reted to the inflammatory infiltrate of the conjunctive tissue and varied in different specimens.

Early morphofunctional alterations induced by cisplatin in the cochlea. A quantitative and electrocochleographic study

The early morphological and functional alterations of the cochlea were studied in guinea pigs treated with cisplatin, administered to two groups of animals as a single dose of 4 or 10 mg/kg body weight. Morphological changes were observed by scanning electron microscopy, and functional alterations were investigated by electrocochleography to record compound action potentials. Statistically significant alterations in neurosensory stereocilia, consisting of partial or total denudation, were observed only after the experimental administration of the higher dose of cisplatin; these changes were consistently associated with distortions in the compound action potential.

Changes in immunologic response in tonsillectomized children. I. Immunosuppression in recurrent tonsillitis

The possible immunoregulatory role of the tonsils was studied by determining immunoglobulins IgG, A, M, E and factors C'3, C'4 and PFB of the complement system before and after tonsillectomy. The synthesis in vitro of IgG and IgM by lymphocytes stimulated with pokeweed mitogen was also measured. There were statistically significant differences between pre and post-operative levels of serum IgG, IgA and IgM, which decreased after surgery. Practically no change in the mean values of IgE and no significant differences in the levels of serum C'3, C'4, and PFB, were found. The in-vitro synthesis of both immunoglobulins (IgG, IgM) by lymphocytes increased significantly after tonsillectomy. Our results suggest that not only does tonsillectomy have no counterproductive effect on the immune system, but that, on the contrary, it seems to improve the immune response, since it appears to unblock the suppression to which the immune system was subject.

Effects of renal insufficiency on the cochlear absorptive-secretory areas. A morphological study in the Mongolian gerbil

In order to evaluate the effects of experimental renal insufficiency (RI) on the labyrinthine absorptive-secretory areas (ASA), 54 adult Mongolian gerbils were submitted to bilateral nephrectomy or to sham procedure. At different intervals (3, 6, 9, 12, 15, 18, 21, 24 hours) after the surgical procedures, or during the terminal stage (28 h) the animals were decapitated and both temporal bones were dissected to obtain selected specimens of the cochlear ASA. The specimens were processed and analysed by light and electron microscopy. Structurally, RI induced progressive thickening of the epithelial components (stria, prominentia, sulcus); separation by fluid accumulation between stria and mesodermal layer; and frequent dilatation of intraepithelial vessels. Ultrastructurally, diverse signs were observed parallel to the evolution of the RI. After 12 h a progressive enlargement of the intercellular spaces, which was particularly evident in the stria surrounding the vessels and in the other sulcus, was observed. Its latest expression was a marked widening of the basolateral spaces containing a granular substance. After 12 h the formation of large cytoplasmic perinuclear spaces containing small rounded vesicles, probably secondary to fluid accumulation, could be observed in the marginal cells. After 24 h diverse signs of organellar damage became evident (schedule: mitochondrial swelling, lysosome like figures, myelin like figures). In the terminal stage, a general homogenization of the cytosol was common. The findings suggest a definite re-distribution of fluids in the inner ear. A close relationship between renal dysfunction and labyrinthine microhomeostasis is therefore proposed.

[Cochleovestibular manifestations in hypothyroidism]

An study of cochleo-vestibular disturbances in different kinds of hypothyroidism is carried out. The majority of the patients suffered from sensorineural deafness of the flat type, lacking Recruitment. The evoked potentials of the brainstem were normal, where as myogenic ones showed a decrease in their amplitude. Evident central disturbances appeared on vestibular examination and a saccadic pursuit was frequently observed in the tracking test. The topography of the lesions is discussed.

Brainstem and middle latency auditory evoked responses in rabbits with halothane anaesthesia

The effects of different concentrations of halothane (0.5, 1 and 1.5%) in brainstem and middle latency auditory evoked responses were studied in 14 adult rabbits. The animals were firstly curarized, tracheostomized and ventilated mechanically. Various recording were made under these conditions for control purposes. During the experiment, arterial pressure, temperature, arterial concentrations of O2, CO2 and pH were monitored. Halothane produce an increase in latency a decrease in amplitude and at higher concentrations even abolished the later waves of middle latency auditory evoked responses. Brainstem potentials are stable, but slight changes in latency were observed at high concentrations (1.5%). Modifications of these potentials as a result of the different concentrations of this anaesthetic in relation with the recordings obtained in the animals curarized without anaesthesia are discussed and the results compared with previous reports in humans.

Otoconial mineralization in post-natal development

Otoconial mineralization has been studied in the utricle of post-natal rats, i.e. from birth to the 20th day. Calcium microanalytically detected is seen to decrease progressively until, after 20 days, when the level is rather lower than at birth. In the adult animal the calcium value is much higher, which leads us to believe that there is an immediate calcium loss that is later recovered. Calcium in the peripheral areas of the macula is proportionately less than in the central part.

Mineralization in the newborn rat statoconia. An EDAX study

Several types of statoconia, differing in size and shape, have been observed in macula utriculi, the smaller ones in the macular periphery. The larger statoconia seem to be formed by the association of smaller units and calcium presence is comparatively higher: In some parts of the marginal zone there exists a granular material in which the presence of calcium is significant.

The origin of the otoconia in the rat

The transitional zone of the saccule and the utricle--has been studied by transmission electron microscope in rats, days before birth. A noticeable secretory activity has been observed in their cells as well as the presence of inorganic spicular bodies that have also been observed in the lumen, some of them integrated into the otoconia. These findings were not seen in adult animals. It is assumed that both organic and inorganic components of the otoliths are produced in a critical period of the embryonal development in the transitional cells.

Degeneration and regeneration processes in experimental facial nerve paralysis

Facial nerve paralysis was provoked by compression of its extratemporal portion in rabbits and the degeneration and regeneration of the nerve fibres was studied ultrastructurally. The compression was removed to study the regenerative process in one group of animals. Axonal and myelin degeneration were the first events seen as a collagen tissue proliferation from the endoneurium and perineurium. Ultimately all the nerve was transformed into fibrous tissue. The myelin was disintegrated by Schwann's cells without any macrophagic activity. The regeneration process begins by the axons, that are orientated towards Büngner's bands of remnants of the Schwann's cells, in which a new myelin sheath appears. Schwann's cells play an important role, in both the degeneration and the regeneration process. The final aspect of the regenerated fibres is similar to normal but they contain more collagen tissue, thinner myelin sheaths, and a greater proportion of unmyelinated fibres.

Experimental ageusia

By administering acetyl-homocysteine and D-Penicillamine to the guinea pig, ageusia and hipogeusia respectively were obtained. Copper concentration was estimated in serum, saliva, liver, salivary glands, muscle, heart and tongue. A significant decrease in the concentration of this metal in the liver was observed and a slight increase in the rest (average values). The results were similar for both drugs. We believe that copper does not play any role in the taste process. The fact that this and other metals restore taste would indicate that those metals bind the SH groups of the drugs and that they are probably responsible for the ageusia.

Preneural phase of taste

The preneural phase of taste has been studied, describing first the pit region of taste buds and its dynamics. The biochemical regulation of the preneural phase is then analyzed, with emphasis on thiol and metal (certain metals) interactions: the first inhibit and the second facilitate. The equilibrium between thiol and metal ions regulates the flux of tastants, probably at the level of the microvilli membrane. The hypothetical role of the pore and dense substance is considered.

Desquamation on taste buds

Taste bud surface cells suffer from a desquamation process that modifies the pores' shape and size and the amount of amorphous substance in the pits region. We have studied this phenomenon-which probably plays an important functional role-by light, electron and scanning microscopy.

Ultrastructure of the organ of Jacobson and comparative study with olfactory mucosa

The organ of Jacobson has been studied in lizards, rats, guinea pigs, rabbits and dogs by means of embedding in nitrocellulose, semithin sectioning, and electron microscopy. The various elements of the organ in the species studied have been analysed and a comparative study carried out between the sensory portion of the organ and the olfactory epithelium.

Ultrastructural study of taste buds at rest and after stimulation, and comparative study between type III cell and Merkel cells

Changes in the pore region of the cell membrane have been studied in order to learn if this region plays an active part in the preneural phase of taste. We have observed, though not consistently, that the pore size is variable and that their contents are not constantly amorphous or homogeneous. The results are not so significant, however, as to allow of the formulation of any firm conclusions. The similarity between type III cells and Merkel cells (cells of the tactile system) was surprising. The probable role of the type III cell in taste is discussed.