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At least 235 records · Page 13Linked to original sources
PubMed1990

[Morphological studies of postnatal changes of the sound transport apparatus in the middle ear of humans and rabbits].

The dimensions of the tympanic membrane and middle ear ossicles, respectively, were measured, in order to investigate the postnatal development of sound transport function. In human we observed only a small increase of the tympanic membrane area between the 7th postconceptional month and the 32nd year of life. This growth has no functional effect on the sound transport. In contrast, in rabbits all measured parameters with the exception of the stapes plate area show an increase until the 12th day of life. Thus, the amplification factor doubles in this species during the first 2 weeks of life. The temporal parallelism of the middle ear development with the ontogenesis of the acoustic function seems to exist in humans, but does not in rabbits.

Adolescent↗
PubMed1987

Craniofacial dysmorphogenesis following hypervitaminosis A in mice.

Malformations of the temporomandibular joint (TMJ), zygomatic arch, middle ear ossicles, and mandibular musculature following hypervitaminosis A were described in fetal mice. Pregnant mice (Mus musculus) were each given a 0.2-ml solution of corn oil containing 10,000 IU of retinol palmitate by gavage on day 8.7. Thirty-eight fetal heads were collected and hemisected. The left hemiheads were serially sectioned, stained, and examined histologically. Right halves were cleared and double-stained with alizarin red and alcian blue. The craniofacial morphologies of the test mice were found to vary from normal to maximally involved (feature unidentifiable) even among littermates. Both inter- and intralitter variation were discussed. Errors in chondrogenesis were determined to have produced the variety of dysmorphologies observed. Changes in Meckel's cartilage affected both the TMJ and ossicles; the presence of ectopic cartilages affected the zygomatic arch; and the musculature was affected secondary to skeletal system changes. Several modes of vitamin A interference leading to craniofacial dysmorphogenesis have been proposed in the literature. It was determined that proposals implicating altered cellular differentiation were the most compatible with the in vivo data recorded here and elsewhere.

Animals↗
PubMedDate not supplied

Advances in the use of glass-ionomeric cement. Part 2: Functional results of fine application of low-viscosity glass-ionomeric cement: animal experimental results.

An experimentally developed technique for microapplication of low-viscosity glass-ionomeric cement (see part 1) was tested in animals over a 6-month period. The cement was used to firmly connect gold with titanium and gold with middle ear ossicles in 22 adult foxhounds. After a 6-month period of acoustic stimulation via parts of an implantable hearing aid, the finely applied glass-ionomeric cement was integrated in situ, stable and caused no adverse reactions. The microapplication technique used proved to be easy, effective and provided long-term stability.

Aluminum Silicates↗
PubMed1975

[Homologous transplants in the middle ear (author's transl)].

The original concept of tympanoplasty included besides the closure of the middle ear, the removal of pathological middle ear components leaving intact the functional and healthy components. The special conditions that prevail in the middle ear (aeration, absence of intrinsic trauma) allow the reconstruction of the middle ear mechanics to a great extent. Animal experiments and clinical experience reveal good transplantation properties of denatured and preserved ear ossicles. They are partly replaced by the body's own true tissue, and preserve the original form over a period of years. Denatured dear drums with malleus, incus, and parts of the stapes give astounding acoustic results. The posterior bony canal wall in old radical cavities can be replaced by the posterior wall of the human temporal bone which has been preserved in Cialit.

Bone Transplantation↗
PubMed1992

Induced and genetic mouse middle ear ossicular malformations: a model for human malformative ossicular diseases and a tool for clarifying their normal ontogenesis.

Oral administration of 13-cis retinoic acid (RA) to pregnant mice on the 9th gestation day provokes important malformations of the middle ear ossicles, associated with a general kind of craniofacial dysmorphogenesis evoking the human mandibulofacial dysostosis. The malleus, incus and stapes are affected. The malleus exhibits a handle separated from its head and keeping a persistant relationship with the tubotympanic recess. The stapes makes no contact with the otic capsule. The malformation pattern is visible early as shown by the appearance of an abnormally curved Meckel's cartilage at day 12, followed by the development of atypically shaped ossicular anlagen. The mouse "far" (first arch malformation) mutation is responsible for minor ossicular abnormalities which disrupts the normal relationships between the stapes, Reichert's cartilage and stapedial muscle. The administration of RA to pregnant mice and the comparison with a genetically induced malformation (the mutation far) provides some interesting information about the postulated mechanisms of human middle ear dysmorphogenesis, as well as precious data about the features of normal ossicular primordia formation. The comparison of these features with human middle ear abnormalities as revealed by medical imaging sheds light on human malformation patterns and provides a better understanding of normal and abnormal radiologic ossicular aspects.

Abnormalities, Drug-Induced↗
PubMed1985

Developments in contact X-ray microscopy in biomedical research.

Contact X-ray microscopy (microradiography) is a method of studying the microstructure of biological tissue. These techniques have been used to study the historadiological details of human breast tissue and sections of human ear ossicles. X-ray microscopy can also be used to demonstrate variations in structural densities seen in histological specimens including the detection of microcalcification. A modification of existing apparatus is described which has resulted in improved image-contrast and detail. The ability of X-rays to penetrate relatively thick sections of tissue makes it an ideal method for studying the morphology of biological structures, particularly in calcified tissue. The tissues may be further examined by conventional histology, elemental analysis, etc. The technique has a complementary role to alternative methods of tissue microscopy.

Breast↗
PubMed2006

Ossicular density in golden moles (Chrysochloridae).

The densities of middle ear ossicles of golden moles (family Chrysochloridae, order Afrosoricida) were measured using the buoyancy method. The internal structure of the malleus was examined by high-resolution computed tomography, and solid-state NMR was used to determine relative phosphorus content. The malleus density of the desert golden mole Eremitalpa granti (2.44 g/cm3) was found to be higher than that reported in the literature for any other terrestrial mammal, whereas the ossicles of other golden mole species are not unusually dense. The increased density in Eremitalpa mallei is apparently related both to a relative paucity of internal vascularization and to a high level of mineralization. This high density is expected to augment inertial bone conduction, used for the detection of seismic vibrations, while limiting the skull modifications needed to accommodate the disproportionately large malleus. The mallei of the two subspecies of E. granti, E. g. granti and E. g. namibensis, were found to differ considerably from one another in both size and shape.

Animals↗
PubMed2006

Severe hearing loss in Dlxl mutant mice.

The Dlx homeobox gene family participates in regulating middle and inner ear development. A significant role for Dlxl, in particular,has been demonstrated in the development of the middle ear ossicles, but the functional consequences of Dlx.l gene mutation on hearing thresholds has not been assessed. The present study characterizes auditory brainstem responses to click and tonal stimuli in a non-lethal variant of a Dlxl gene knockout. We found that peripheral hearing thresholds for click and tonal stimuli were significantly elevated in homozygous Dlxl knockout (Dlxl-/ ) compared to both heterozygous (Dlxl+/ ) and wild type (Dlxl+/+) mice. Thus, abnormal mor-phogenesis of the incus and stapes that has been documented previously with histological measures is now known to result in a severe peripheral hearing deficit.

Animals↗
PubMedDate not supplied

Bone resorption in chronic otitis media. The role of mast cells.

Twenty-two surgical specimens of eroded middle ear ossicles were removed from patients with chronic otitis media, with and without cholesteatoma. By using specific mast cell stains, increased numbers of mast cells were found in connective or granulation tissue adjacent to eroded surface of the bone. Mast cells possess the biological machinery necessary for enhancing bone resorption, and the population density of mast cells is increased in a variety of disorders that are associated with bone resorption. It is hypothesized that mast cells contribute to bone resorption in chronic otitis media, and the possible mechanisms by which mast cells exert their action are discussed.

Adolescent↗
PubMed1999

Neuronally modulated transcription of a glycine transporter in rat dorsal cochlear nucleus and nucleus of the medial trapezoid body.

Neurotransmitter transporters limit transmitter concentration at the postsynaptic membrane by removing neurotransmitters from the synaptic cleft. Not only do neurotransmitter transporters contribute to the regulation of synaptic transmission, but they themselves might be dynamically regulated by neuronal activity of the neurons in which they are expressed. In this experiment, we investigated the question of whether the transcription of two different glycine transporters, Glyt1 and Glyt2, is influenced by neuronal activity. These transporters are found in the dorsal cochlear nucleus (DCN) and medial nucleus of the trapezoid body. Glyt1 and Glyt2 mRNA were measured by using hybridization histochemistry and a semiquantitative reverse transcription polymerase chain reaction. Decreases in auditory primary afferent activity, caused by either unilateral labyrinthectomy or disruption of the middle ear ossicles, caused a reduction in Glyt2, but not Glyt1 mRNA in the ipsilateral DCN and in the contralateral medial nucleus of the trapezoid body. Acoustic stimulation at either 10 kHz or 40 kHz was used to provide controlled increases in primary afferent activity, evoking localized increases in Glyt2 mRNA in clusters of neurons in the DCN. The location of these clusters corresponded to the regions of the auditory tonotopic map devoted to these frequencies. The duration of changes in Glyt2 mRNA evoked by unilateral labyrinthectomy, measured with the reverse transcription polymerase chain reaction, was 5-10 days. These data provide the first example of in vivo regulation of transporter transcription by neuronal activity.

Amino Acid Transport Systems, Neutral↗
PubMed1983

Uptake and release of D-aspartate in the guinea pig cochlear nucleus.

This study attempted to determine if L-glutamate (L-Glu) and/or L-aspartate (L-Asp) might be the transmitters of neurons that provide synaptic endings to the cochlear nucleus of the medulla. The uptake and release of D-[3H]aspartate (D-Asp), a putative marker for L-Glu and L-Asp, were measured in the guinea pig cochlear nucleus before and after destruction of the cochlear afferents by cochlear ablation. The cochlear nucleus was dissected into the anteroventral (AVCN), posteroventral (PVCN), and dorsal (DCN) cochlear nuclei. Subdivisions from unlesioned animals took up D-Asp, achieving concentrations in the tissues that were 13-20 times that in the medium. Subsequently, electrical stimulation evoked a Ca2+-dependent release of part of the D-Asp from each subdivision. Disarticulation of the middle ear ossicles, which attenuates acoustic stimulation, produced a modest inhibition of D-Asp release in each subdivision, but did not alter the uptake of D-Asp. Cochlear ablation strongly depressed both the uptake and the release of D-Asp in each subdivision, presumably as a result of destruction of the cochlear nerve endings in the cochlear nucleus. Nevertheless, after lesions, there was a preservation of the uptake and release of D-Asp in the DCN relative to the AVCN and PVCN. These residual activities in the DCN may be mediated by the axonal endings of the granule cells of the cochlear nucleus. The present findings support the hypothesis that the granule cells of the cochlear nucleus, as well as the cochlear nerve fibers, use L-Glu and/or L-Asp as transmitters.

Animals↗
PubMed1986

The phenotypic interdependence of the musculoskeletal characters of the mandibular arch in mice.

Evidence from studies of craniofacial anomalies and the evolutionary transition from reptiles to mammals suggests that the temporomandibular joint (TMJ), bony zygomatic arch, middle ear ossicles and mandibular muscle pattern may form a correlated suite of characters. To test the degree of phenotypic interdependence among these features, mandibular arch defects were analysed in prenatal mice. Retinoic palmitate was administered to pregnant mice on day 8.7 to produce test foetuses with malformations of the mandibular arch. A rating scale was developed for each of the four characters so that numerical values could be assigned to each phenotype encountered. Control animals were used to establish normal phenotypes for each character which were assigned a value of 1. Data from each test age, 16, 18 and 19 days postconception, were pooled and Spearmann rank correlation coefficients between each of the traits were calculated. Coefficients (R) range from a high of 0.87, between the TMJ and zygomatic arch, to a low of 0.67 between the zygomatic arch and the mandibular musculature showing highly significant correlations (P less than 0.0001) among all characters. Therefore, the data suggest that the musculoskeletal features of the mandibular arch are phenotypically interdependent during development.

Abnormalities, Drug-Induced↗