Auditory pathway and auditory brainstem response in mice lacking NMDA receptor epsilon 1 and epsilon 4 subunits.

There is considerable evidence that the N-methyl-D-aspartate receptor (NMDAR) is a component of excitatory amino acid synapses in the ascending auditory pathway. The availability of mice that are defective in NMDAR epsilon 1 or NMDAR epsilon 4 subunit paves the way for investigations on the role of this receptor in auditory function. Non-radioactive in situ hybridization was used in the parent C57/6J wild strain to determine if these subunits are normally expressed in cochlear nucleus (CN) and superior olivary complex (SOC) and to confirm their absence in the respective mutant mice. Evoked auditory brainstem response (ABR) to normal acoustic stimulation was investigated to assess function. In situ hybridization revealed the expression of NMDAR epsilon 1 and epsilon 4 subunits mRNAs in major neuronal types in the CN and SOC of the wild type mice while epsilon 1 and epsilon 4 expression were absent in their respective mutant mice. The ABR threshold for the epsilon 1 mutant mice was similar to that of wild type mice however the threshold for the epsilon 4 mutant mice was significantly elevated. These results suggest a role for the NMDAR epsilon 4 in normal auditory functions while the NMDAR epsilon 1 may have a less critical function under normal conditions.

Autoradiographic localization of somatostatin mRNA in the adult rat lower brainstem: observation by the double illumination technique.

Using in situ hybridization histochemistry and observation with a double (dark and bright) illumination apparatus, the precise localization of preprosomatostatin mRNA was studied in the adult rat lower brainstem and cerebellum. It has previously been hard to localize the somatostatin precursor gene in the adult rat brainstem, because the level of expression is low or undetectable in some brain areas in adulthood, in contrast to the high levels in the neonatal period. The present study in adult rats showed the clear localization of this mRNA in the same areas where it is found in the perinatal period. The results showed that somatostatin neurons in such areas continue the minimal production of the precursor gene even at the adult stage.

Sympathetic nerve disturbance and fine structure of adrenergic nerve terminals in nasal mucosa after experimentally-induced nasal hypersensitivity.

Electron microscopic observations were used to study the relation between the adrenergic nerve terminal and the effector cell in the nasal mucosa of toluene diisocyanate-sensitized and non-sensitized guinea pigs. Adrenergic nerve terminals were abundantly distributed in the adventitia of arterioles, however, no synapse formation was observed in smooth muscle cells of the mesothelium, i.e., effector cells. Adrenergic nerve terminals were observed separated from smooth muscle cells of the mesothelium of the arteriole by distances of 1000 A-3000 A. Neurotransmission by the sympathetic nerve in the nasal mucosa is assumed to be by diffusion of norepinephrine (NE) or by diffusive synaptic conduction. The mechanism of sympathetic hypofunction in the nasal mucosa in nasal hypersensitivity is assumed to be as follows: Released histamine directly stimulates H-1 receptors at the sympathetic nerve terminal, leading to the release of NE. Once released, NE is not readily reabsorbed, and is gradually depleted in the sympathetic nerve terminal, leading to hypofunction of the sympathetic nerve.

Effects of topical capsaicin on autonomic nerves in experimentally-induced nasal hypersensitivity. An immunocytochemical study.

Effects of capsaicin on autonomic nerves in the nasal mucosa and olfactory bulb of toluene diisocyanate sensitized guinea pigs were studied using immunocytochemistry. In the nasal mucosa, substance P (SP)- and tyrosine hydroxylase (TH)-like immunoreactive (SPI and THI) fibers seemed to decrease after capsaicin application. Calcitonin gene-related peptide (CGRP)-like immunoreactive (CGRPI) fibers did not show obvious alterations. In the olfactory bulb, SPI and CGRPI fibers were few and the effects of capsaicin on those fibers were difficult to evaluate. THI fibers seemed not to be affected by capsaicin. It is suggested that capsaicin affects not only sensory nerves but that it also impacts on THI sympathetic nerves in the nasal mucosa.

Immunolocalization of tyrosine hydroxylase and vasoactive intestinal polypeptide in nerve fibers innervating human palatine tonsil and paratonsillar glands.

The presence of tyrosine hydroxylase (TH) and vasoactive intestinal polypeptide (VIP) in the nerve fibers of the human palatine tonsil and paratonsillar secretory glands is reported. By immunohistochemistry TH-immunoreactive nerves and those immunoreactive to VIP were localized to the tonsil, in particular, the tonsillar vessel wall, extranodular lymphoid tissue and lymph nodule, and to the acinar basal surface of the paratonsillar glands. In the lymph nodule, immunoreactive varicose nerve profiles were observed inside the marginal zone. The germinal center was devoid of immunoreactive fibers.

Electron microscopic observation of calcitonin gene-related peptide-like immunoreactivity in the organ of Corti of the rat.

Calcitonin gene-related peptide (CGRP)-like immunoreactive (CGRP-IR) nerve terminals in the organ of Corti of rats were studied by light and electron microscopy. Surface preparation of the organ of Corti were immunostained using anti-CGRP antiserum for avidin-biotin immunohistochemistry. Dense CGRP-IR fiber bundles were observed by light microscopy in the inner spiral bundles, tunnel spiral bundles and outer spiral bundles. Electron microscopic analysis indicated that CGRP-IR fibers belong to efferent nerves. In the inner spiral bundles, the CGRP-IR fibers showed a direct contact mainly with non-immunoreactive afferent fibers. Some CGRP-IR nerve endings in the inner spiral bundles formed contacts directly with inner hair cells. In the outer spiral bundles, CGRP-IR fibers formed synaptic contacts exclusively with the outer hair cells. It should be noted that the number of synapses of CGRP nerve endings with outer hair cells varied depending upon the sub-row: a falling gradient in number occurred along the inner-outer axis. Our results suggest that CGRP acts as an efferent neuromodulator in the organ of Corti.

Ontogeny of calcitonin gene-related peptide in the organ of Corti of the rat.

The ontogeny of calcitonin gene-related peptide (CGRP)-like immunoreactive (CGRPI) fibers in the rat cochlea was examined using immunocytochemistry. It was found that the CGRPI cochlear system developed markedly in the postnatal period; CGRPI fibers first appeared in the inner spiral bundle at postnatal day 8, then at the base of the outer hair cells, tunnel spiral bundle and tunnel radial fibers at postnatal day 19. The ontogenetical profile elucidated by this study suggests that CGRP has a role as a neuromodulator or neurotransmitter in this system.

Postnatal development of the eustachian tube and its surrounding structures. Preliminary study.

The postnatal development of the eustachian tube and its surrounding structures (tubal cartilage, tubal gland, tensor veli palatini muscle, and levator veli palatini muscle) was investigated in serial vertical histologic sections from 12 normal temporal bones of individuals whose ages ranged from 39 weeks' gestation to 19 years of age. After projecting tissue sections onto paper and tracing the structures, several measurements were made in order to analyze this development. Findings revealed that the eustachian tube and its accessory structures developed postnatally up to the age of 19 years. The lumen area in a 19-year-old specimen was 4.7 times that of the 1-day-old infant. The development of the tube was greatest in the pharyngeal part. Postnatal development of the eustachian tube appears to be related to growth of the face. The cartilage area in the 19-year-old specimen was 3.6 times that of the 1-day-old infant. The mucosal acinar cells were predominant in infants but no greater than the number of serous acinar cells by the age of 19 years. The areas of the tensor and levator veli palatini muscles in a 19-year-old specimen were 5.1 and 11.1 times, respectively, those of the 1-day-old infant. This preliminary study reports the postnatal development of the eustachian tube and its accessory structures, a subject never thoroughly investigated to date. However, because of the limited number of cases available, further investigation of a greater number of cases should be performed so that the relationship between tubal development and alterations in function that occur with age can be understood clearly.

A method for the histopathological analysis of the temporal bone and the eustachian tube and its accessory structures.

A very important contribution to the study of otitis media, one of the diseases most often seen in pediatric patients, is the collection, processing, and study of the specimens of the temporal bone and the entire eustachian tube. During the last few years, we have collected, processed, and studied 100 such specimens, and through these experiences our technique has become refined. We now have some important suggestions for otologists interested in the histological study of otitis media as well as in the pathology of the eustachian tube and its relation to middle ear abnormalities. This report details the most successful method for the study of eustachian tube abnormalities and their relationship to middle ear effusion.

The presence of a calcitonin gene-related peptide in the olivocochlear bundle in rat.

The origins of calcitonin gene-related peptide immunoreactive (CGRPI) fibers in the cochlea were examined in rats. Parasagittal transection of the brain just medial to the principal sensory trigeminal nucleus resulted in the ipsilateral disappearance of CGRPI fibers in the cochlea, indicating that the origins of these fibers lie in the central nervous system. Next, we used a highly sensitive method combining retrograde tracing and immunohistochemistry to identify the origins of the CGRPI fibers in the cochlea. After injection of biotin-wheat germ agglutinin (b-WGA) into the cochlea, CGRPI neurons in the ipsilateral lateral superior olivary nucleus also contained b-WGA granules. These findings indicated that CGRPI efferent fibers are major components of the olivocochlear bundle.

Adrenergic innervation of the Eustachian tube. Histochemical and electron-microscopic study.

The presence of adrenergic nerves in the Eustachian tubes of guinea pigs was observed using the Falck-Hillarp fluorescence method. Abundant adrenergic nerve are forming networks around blood vessels in all tubal regions. Adrenergic fibers also surround the tubal glands. The precise locations of adrenergic nerve terminals in the tube were demonstrated by electron microscopy following application of a false transmitter. Adrenergic nerve terminals were found in abundance just beneath the smooth muscle layer of the arteries in each part of the tube and close to the myoepithelial cells of the tubal gland.

Localization of calcitonin gene-related peptide in the organ of Corti of the rat: an immunohistochemical study.

The localization of calcitonin gene-related peptide (CGRP)-like immunoreactive (CGRPI) structures in the cochlea was examined in the rat using immunocytochemistry. Numerous CGRPI fibers entered the organ of Corti in the intraganglionic spiral bundle and formed a dense fiber patch at the base of the inner hair cells. Much fewer, but still a significant number of CGRPI fibers were seen at the synaptic region of the outer hair cells. Since no immunoreactive cells were seen in the organ of Corti and spinal ganglion, these fibers may be one of the major components of the olivocochlear bundles originated from the superior olivary complex.

How to remove, process, and study the temporal bone with the entire eustachian tube and its accessory structures: a method for histopathological study.

A very important contribution to the study of otitis media, one of the diseases most often seen in pediatric patients, is the collection and study of temporal bone specimens which include the entire Eustachian tube. During the last few years, we have collected, processed, and studied more than 100 such specimens. Through these experiences, our technique has become so refined that we have some important suggestions to make to otologists who are interested in the histological study of otitis media as well as in the pathology of the Eustachian tube and its relation to middle ear abnormalities. This report describes the method we have found to be most successful for the study of Eustachian tube abnormalities and their relationship to middle ear effusion.

Histopathology of otitis media in infants with cleft and high-arched palates.

The middle ear and the bony and cartilaginous portions of the eustachian tube (ET) were studied histopathologically in 20 temporal bones from 19 infants, aged 45 minutes to 12 months. Otitis media (OM) was observed in 17 of 20 bones, and 16 bones with OM had an effusion. Otitis media was more severe in the ears of cleft palate infants compared to those with high-arched palates. Inflammation was present in the bony portion of the ET in 15 of 17 temporal bones with OM, but appeared to be less marked than that present in the middle ear. In addition, inflammation of the cartilaginous portion of the ET appeared to be less severe than in its bony portion. Inflammation of the middle ear and the ET appeared to be more pronounced in older infants, particularly in those with cleft palates.

Metastatic squamous cell carcinoma in the neck invading the facial canal--a case report.

The results of histopathologic examination of the temporal bone of a 71-year-old woman with squamous cell carcinoma of the tonsil and ipsilateral facial palsy are presented. The right temporal bone was directly involved by metastatic spread of the primary lesion to the right upper cervical lymph nodes. Tumor cells had invaded the canal of the facial nerve, the chorda tympani nerve, and the stapedius muscle, as well as the air cells in the mastoid region. However, although tumor cells had infiltrated the facial canal to a considerable distance from the metastatic tumor mass, the facial nerve had not been infiltrated. Slight degeneration of the facial nerve, however, was observed and appeared to have been caused by compression by the tumor.

The anatomy of the auditory tube and paratubal musculature in a one month old cleft palate infant.

The auditory tube, middle and inner ear, and paratubal musculature were removed en bloc at autopsy from a 1 month old white cleft palate female. The specimen was serially sectioned in a coronal plane and studied under light microscopy. Severe inflammatory changes were observed in the middle ear and osseous portion of the auditory tube in association with the presence of a middle ear effusion. While the posterior tubal lumen, tubal cartilage, and tensor veli palatini (TVP) and tensor tympani muscles were similar to those of an age-matched control specimen, the anterior tubal lumen was seen to be superoinferiorly abbreviated with a large intrusive malpositioned levator veli palatini (LVP) muscle occupying the inferior tubal floor. This muscle was noted to divide into two bundles on proceeding posteriorly with the more superior bundle taking an abnormal origin from the inferior surface of the tube. The luminal compression observed in this specimen is reminiscent of that previously described in cleft fetuses though the abnormal morphology of the LVP muscle has not been reported for the few cleft palate specimens studied. It is probable that this morphology is idiomatic to the present specimen and not a characteristic of the cleft palate condition.

Autonomic innervation of the middle ear.

The distribution of nerve fibers in the middle ear mucosa and eardrum of the cat and guinea pig was studied using immunocytochemical and histofluorescence techniques. Nerve fibers containing noradrenaline, vasoactive intestinal peptide, substance P, enkephalin or immunoreactive avian pancreatic polypeptide were demonstrated in the middle ear mucosa. After extirpation of the superior cervical ganglion, nerve fibers containing noradrenaline and avian pancreatic polypeptide disappeared while fibers containing vasoactive intestinal peptide, substance P and enkephalin seemed to remain unaffected.