Toshishige Kido

Fine Structures of Utricle of Developing Chick Embryo Exposed to 2G Gravity

Utricular otoconia of the chick embryos incubated under continuous 2G load were examined under a scanning electron microscope. Morphological changes were confined to the process of otoconial formation and the otoconial size. Otoconial formation was remarkably delayed in the utricle of 2G centrifuged chick embryo. Giant otoconia, which sometimes amounted to over 100 microM in length, existed along the marginal zone of the utricular otolithic membrane. These results indicate that the 2G state influences the otoconical formation.

Glycoconjugates in the Otholithic Organ of the Developing Chick Embryo

The presence of glycoconjugates in the otolithic organ of developing chick embryos was investigated histochemically using lectins. On the 6-day-old chick embryo, intense labelling with lectins was observed in the sensory epithelium, on the surface of the epithelium and on the immature otoconia. The otoconia were intensely labelled with lectins at every stage of the chick embryos, while the labelling with lectins in the sensory epithelium became weaker with the maturing of the otoconia. In TEM observation, the secretory granules of the supporting cells of the sensory epithelium were labelled with lectin. The reaction of lectin was more intense in the electronic dense zone of the otoconium than in the electronic lucent zone at every stage of the chick embryos. These findings indicate that the precursors of the otoconia are secreted by the supporting cells of the sensory epithelium and that glycoconjugates play an important role in otoconial formation.

Effects of carbonic anhydrase inhibitor on the otolithic organs of developing chick embryos

Carbonic anhydrase appears to be involved in the process of otoconial formation. The purpose of this investigation was to observe the morphologic change in the surface structure of the otolithic organ in developing chick embryos after injection of the carbonic anhydrase inhibitor, acetazolamide. Acetazolamide (1.5, 3, or 6 mg/0.06 mL/egg) was injected into the yolk sac of the embryo of the fifth day of incubation. Embryo specimens were collected on the 11th, 13th, and 18th days of incubation. The chicks were killed on the third day posthatching, and the surfaces of the otolithic organs were observed under a scanning electron microscope. A marked disturbance in otoconial formation was noted in both utricle and saccule, marked by a decrease or absence of otoconia. A widely exposed meshwork structure of otolithic membrane was observed, with sensory cilia penetrating the meshwork small holes in many instances. There were also several otoconial abnormalities, such as the appearance of only a single giant otoconium, or from several to dozens of giant otoconia, and rough, spongy-surfaced global substances entirely covering the maculae. Clearly, carbonic anhydrase inhibitor (acetazolamide) injected into the yolk sac of developing chick embryos alters and inhibits normal otoconial morphogenesis.

Scanning electron microscopic study of amphibians otoconia.

The otoconia of three adult amphibian species were studied by scanning electron microscopy (SEM). Two calcium carbonate polymorphs (calcite and aragonite) were shown to be present at specific sites in the membranous labyrinth. The utricle contained only calcitic otoconia, whereas the saccule, lagena and endolymphatic sac contained only aragonitic otoconia. SEM examination demonstrated that there is a morphological difference in otoconia according to the site of origin in the membranous labyrinth, and that a mechanism for determining the range of otoconial sizes according to this difference in otoconial morphology may exist.

The otolithic organ in the developing chick embryo. Scanning electron microscopic study on the utricular macula.

The long and short axes of utricular maculae were measured to calculate growth curves using an ocular micrometer under stereomicroscope. The mean lengths of the long and short axes on the 6th incubation day were 0.06 mm and 0.05 mm, respectively. Thereafter: 1.00 mm and 0.74 mm on the 11th incubation day; 1.34 mm and 1.03 mm on the 15th incubation day; and on hatching 1.51 mm and 1.07 mm, respectively. The surface structure, particularly the otoconia and the sensory hairs of the utricular maculae, on the 4.5th incubation day to the 7th post-hatching day of White Leghorn chicks were observed with a scanning electron microscope (SEM). A number of microvilli and primary cilium on the inner surface of the otocyst were found between the 4.5th and the 5th incubation day. Immature sensory hairs appeared on the 5th incubation day. The polarity of the sensory hairs became evident on and after the 9th incubation day. Mature sensory hairs were seen all over the utricular maculae between the 1st and the 3rd post-hatching day. Mature sensory hairs were mainly seen near the striola, and immature ones peripherally. Then, the various forms in the maturation phase of sensory hairs were seen between the striola and the periphery. These arrangements suggest some process of maturity from the peripheral region to the central striola region. Immature otoconia were first seen on the 6th incubation day. Mature otoconia were recognized on and after the 11th incubation day, and they were observed on the whole surface of the utricular maculae. Global substances on the macula with a rough surface and spongy structure were observed suggesting otoconial precursors transforming themselves into otoconial crystals.

A case of cerebellar infarction occurred with the 8th cranial nerve symptoms.

A rare case, 32-year-old man, of cerebellar infarction with the occurrence of the 8th cranial nerve symptoms was reported. On the neuro-otological examination, hearing test and caloric test showed a severe hearing loss and no response on the right side, respectively, and the spontaneous horizontal nystagmus fixed to the left direction was observed. Magnetic resonance (MR) imaging showed the infarctions in the areas of anterior inferior cerebellar artery (AICA) and posterior inferior cerebellar artery (PICA) on the right side. On the 14th illness day, the 8th cranial nerve symptoms disappeared, and on the 12th illness day, right hearing level and caloric response were significantly improved. We suggested that such an early recovery of the subjective symptoms and neuro-otological findings may be attributable to the recanalized circulation disturbance or the development of collateral circulation.

Tortuosity of the internal carotid artery — report of three cases and MR-angiography imaging

Three cases of a tortuous internal carotid artery bulging the lateral pharyngeal wall that caused a persistent throat abnormal sensation were presented. Magnetic resonance angiography was non-invasive and useful for establishing its diagnosis. Otolaryngologists should recognize this anomaly, because it may cause a fatal hemorrhage during surgical procedures on the pharynx.

Vascular Leiomyoma of the Parotid Gland

Leiomyoma occurrence in the head and neck is rare. Vascular leiomyoma usually occurs in the skin of the limbs. Survey of the literature also revealed that there was no case of vascular leiomyoma in the parotid gland reported in Japan. A 50-year-old man with vascular leiomyoma which developed from the parotid gland was reported. The chief complaint of this patient was a painless preauricular mass on the right side. The tumor was a solitary mass of quail-egg size with round and smooth surface, elastic soft consistency and not tender. The tumor was completely removed under general anesthesia. This patient has been well without recurrence 5 years after operation.

Otoconial formation in the chick: changing patterns of tetracycline incorporation during embryonic development and after hatching

The antibiotic tetracycline (TC) is incorporated into calcifying tissues and serves as a fluorescent marker for identifying calcifying sites in bone and otoconia. Fluorescent labeling was performed at different stages in chick embryos and newly hatched chicks. The stagewise changes in the intensity, location and time course of fluorescent labeling were assessed. TC/egg (1-2 mg) was injected into the yolk sacs of embryos on the 4th, 8th and 11th embryonic days (ED), and the embryos were then killed at specified times after injection. In newly hatched chicks, TC was injected daily intraperitoneally with 0.06 mg TC/g body weight for 7 days and the chicks were killed on the 8th day after hatching. Embryos injected on the 4th ED and killed on the 6th ED showed intense fluorescence in the saccular otoconial layer. All maculae from embryos killed after injection on the 4th ED showed uniformly intense fluorescence throughout the otoconial layer. By the 9th ED, otoconia in all three maculae (saccular, utricular, and lagenar) fluoresced. Maculae from embryos killed after injection on the 8th ED showed uniformly intense fluorescence throughout the otoconial layer or intense localized fluorescence mainly in the upper half of the otoconial layer. All maculae from embryos killed after injection on the 11th ED showed moderate to weak fluorescence primarily in the lower half of the otoconial layer. All maculae from posthatched chicks showed very weak fluorescence throughout the otoconial layer. Otoconia at the periphery of the maculae generally showed weak fluorescence in embryos that had been injected on the 4th and 8th ED, but not in embryos injected on the 11th ED. TC, which competes for calcium binding sites, may inhibit the formation of some otoconia. The formation of giant otoconia may reflect subtle changes in the crystallization microenvironment on these occasions. In brief, the results suggest that: (a) otoconial formation in the saccule precedes that of the utricle and lagena; (b) otoconial formation occurs during the early period (beginning the 6th ED); (c) otoconial formation is stratified, with those in the upper layer forming first and those in the lower layer forming last.

Ultrastructure of the Chick Vestibular Ganglion and Vestibular Nucleus: A Scanning Electron Microscopic Study

The fine structure of the chick vestibular ganglion and vestibular nucleus was studied in three dimensions using a scanning electron microscope (SEM). NaOH and OSO4 maceration methods were applied to observe the configuration in the mechanically torn specimens. Also, Tanakas aldehyde prefix OSO4-DMSO-OSO4 method (A-O-D-O method) was applied to observe the intracellular structure in the fractured specimens. The surface of the ganglion cell and the nerve processes were seen to be covered with abundant thin fibrous tissues in the specimen treated with OSO4 maceration. This surface fibrous tissue was completely removed with the NaOH maceration method. As a result, the ganglion cell and nerve processes could be seen to be enveloped in the myelin sheath. In the fractured vestibular ganglion treated by the A-O-D-O method, there were three patterns of perikaryal myelination in the vestibular ganglion cells: heavily myelinated, lightly myelinated, and unmyelinated, respectively. In the perinuclear region of the vestibular ganglion cell, well developed and aggregated cytoplasmic organelles such as endoplasmic reticulum, mitochondria, and Golgi apparati were observed. In the perinuclear region of the Schwann cell relatively large mitochondria were characteristically observed. In the fractured view of the vestibular nerves, most of vestibular fibers were compactly myelinated. In the vestibular nucleus, the gathering of the neuronal cells were observed with the NaOH maceration method.