Arch. Oto-Rhino-Laryng.,212, 141--146 (1976)
Archivesof Oto-Rhino-Laryngology 9 by Springer-Verlag 1976
Short Communication/Kurze Mitteilung
Scanning Electron Microscopic Study of the Cat Papilla Neglecta* T. Hoshino and A. Kodama Department of Otolaryngology,Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo, Japan 173 (Prof. Jun-Ichi Suzuki)
Summary. The papilla neglecta in the cat vestibule was studied under a scanning electron microscope. This papilla appears as a small mound of cells on the utricle near the posterior semicircular canal crista. The number of sensory hair bundles on the papilla ranged from 1 1 - 6 4 in 7 ears examined (average, 37). Although this crista-like endorgan was regularly found in the cat, its function may not be important in that the number of sensory hair cells is only 1/150 of those counted on guinea pig posterior semicircular canal crista. Key words: Papilla neglecta - Histology - Scanning electron microscopy
The papilla neglecta is a sensory apparatus found in the vestibule. This structure has been given various names such as the crista quarta, macula neglecta and sensura neglecta. Retzius (1872) originally described the papilla neglecta in the fish inner ear. In mammals, this structure is commonly found in the feline species (Gacek, 1961) and some other mammalian forms (Igarashi, 1965). The papilla neglecta was seen in 6 out of 640 human temporal bone specimens by Montandon et al. (1970). In mammalian inner ears the papilla neglecta is located on the postero-inferior part of the utricle near the posterior crista ampullaris. An electron microscopic study of the cat has shown that the papilla neglecta has the same structure as the crista ampullaris in that there are two types of nerve endings and sensory hair cells which are covered on the luminal surface by a cupular structure (Montandon et al., 1970). In the present study a scanning electron microscope was used to obtain a stereoscopic view of the papilla neglecta of the cat. Material and Method
Several young and adult cats were used in this study. After decapitation, 2% glutaraldehyde bufferred with phosphate (0.1 M, pH 7.4) was perfused into the inner ear through the oval and round windows. After glutaraldehyde fixation the specimens were further fixed in 1% osmium tetroxide. The membra~ *
This study was partly supported by U.S.P.H.S. Research Grant No. NS 10412--03
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nous labyrinth was dissected out under 70% ethanol following serial ethanol dehydration. The specimens were then transferred from absolute ethanol to amyl acetate and dried in a critical point dryer with liquid carbon dioxide. After coating with gold the specimens were studied under a Hitachi HHS2R scanning electron microscope.
Findings The papilla neglecta was found in all c a t specimens examined under the scanning electron microscope. This papilla was identified as a small dot, even at a low magnification under a dissecting microscope, near the posterior canal crista. The distance between the papilla neglecta and the posterior canal crista was about 0.7 ram. Under the light microscope, the papilla neglecta appeared as a small mound of sensory and supporting cells collared by cells with thicker cytoplasm than the surrounding ampullary wall cells. These were probably transitional cells (Fig. 1). A small cuputa-like structure was seen overlying the sensory cells, thus, the structure of the papilla was similar to that of the crista ampullaris. Under the scanning electron microscope, the papilla neglecta appeared as a small mound surrounded by an elevated ridge of transitional cells (Fig. 3). Sensory hair bundles were clearly visible amongst the supporting cells (Fig. 4) and the hairs on these bundles were arranged in graded heights. Next to the longest hairs of each bundle a singular, much longer cilium was detected (probably a kinoeilium) which differed slightly from the other hairs (Fig. 4). In general, these sensory hairs were longer than hairs seen on the otolithic maculae but their lengths were similar to hairs on the crista ampullaris.
Fig, 1. Light microscopic view of the cat papilla neglecta. Papilla neglecta (arrow) appears as a low mound of cells near the posterior semicircular canal crista (P). A cupula-like structure is seen covering the mound (insertion, arrow)
Papilla Neglecta of the Cat
143
Fig. 2. Scanning electron microscopic view of the cat papilla neglecta (long arrow). Sensory hair bundles are clearly visible. Short arrow indicates the eminentia cruciata. P: posterior semicircular canal crista. Bar equals 0.i mm
Fig. 3. Scanning electron microscopic view of the cat papilla neglecta. The number of sensory hair bundles varys considerably across cats
T h o u g h the s e n s o r y hairs were s o m e t i m e s c o v e r e d with a fine fibrous m a s s s t a t o c o n i a were n e v e r f o u n d o n this mass. P o l a r i z a t i o n o f these s e n s o r y hairs was utriculo-fugal with o n l y a few exceptions. T h e n u m b e r o f s e n s o r y hair bundles on one papilla n e g l e c t a r a n g e d f r o m 11--64 ( a v e r a g e o v e r 7 ears: 37). In one case, the
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Fig. 4. Sensory hair bundles on the cat papilla neglecta. Sensory hairs are very similar to the hairs on the crista ampullaris. These hairs are polarized in one direction with a few exceptions (arrows). Bar equals 5 micra number of sensory hair bundles counted on one ear was 11 whereas 31 were counted on the opposite ear. The luminal surfaces of both the supporting and transitional cells had a single short cilium and a smooth luminal surface. Discussion
The papilla neglecta was first described by Retzius in the fish and it is a bipartite structure consisting of two mounds (Fig. 5) located near the utriculo-saccular duct. De Burlet (1934) and others have verified the existence of this small sensory endorgan in various classes of vertebrates. Some structural features found in previous investigations and also the present study indicate that the papilla neglecta is structur: ally similar to the crista ampullaris rather than the otolithic macula. These features include a crest-shape of the papilla, long sensory hairs from the sensory cells, a cupulalike structure without otoconia and unidirectional polarization of sensory hairs.
Papilla Neglecta of the Cat
145
Fig. 5. Papilla neglecta of the goldfish. This papilla consists of two separate mounds (arrows) which each bear many sensory hair bundles. Bar equals 0.05 mm
As the number of the sensory hair bundles in the papilla neglecta with an average of 37 is very small as compared to the number of the hair cells on the posterior canal crista [5430 in the guinea pig (Lindeman, 1969), 7600 in humans (Rosenhall, 1973)], the papilla neglecta m a y not have a significant function in the cat although it was regularly found as a separate endorgan. The number of sensory cells on the cat posterior canal crista ampullaris has not as yet been reported. Gacek (1961) found approximately 35 nerve fibers innervating the cat's papilla neglecta. This finding considered in light of the actual hair cell population (i: 37) yields an innervation ratio as high as 1 : 1. In the human, the presence of this papilla is rather exceptional and therefore its functional significance m a y be negligible, as indicated by its name. This structure thus seems to be a rudimentary endorgan in the mammals. Igarashi and Yoshinobu (1966) mentioned that some correlation m a y exist between the papilla neglecta and another rudimentary structure in the mammalian inner ear, the eminentia cruciata. Both structures have been frequently observed in the cat (Fig. 2) and the dog vestibule and thus an intimate relationship between these structures m a y exist in both these species. However, this relationship does not seem to be consistent in other classes of vertebrates in that the fish, for example, does not have an eminentia cruciata although a well-developed papilla neglecta has been found. The authors are deeply indebted to Professor Jun-Ichi Suzuki (Teikyo University) for his encouragement in this study. Mr. Dominic W. Hughes kindly helped in English compilation.
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References de Burlet, H. M.: Vergleichende Anatomie des statoakustischen Organs. In: Handbuch der vergleichenden Anatomie der Wirbeltiere, 2 (2), p. 1293. Berlin-Wien: Urban & Schwarzenberg 1934 Gacek, R. R.: The macula neglecta in the feline species. J. Comp. Neurol. 116, 317-323 (1961) Igarashi, M.: Redefinition of the macula neglecta in mammals. J. Comp. Neurol. 125, 287-294 (1965) Igarashi, M., Yoshinobu, T.: Comparative observation of the eminentia cruciata in birds and mammals. Anat. Rec. 155, 269--277 (1966) Lindeman, H. H.: Studies on the morphology of the sensory regions of the vestibular apparatus. Ergebn. Anat. Entwickl.-Gesch. 42, 1-113 (1969) Montandon, P., Gacek, R. R., Kimura, R. S.: Crista neglecta in the cat and human. Ann. Otol. 79, 105-112 (1970) Retzius, G.: Das GehSrorgan der Knochenfische. Anat. Untersuchungen. Erste Lieferung. Stockholm (1872). Cited from Jorgensen, J. M.: The avian neglecta Retzii. Acta Zoologica 53, 155--163 (1972) Rosenhall, U.: Degenerative patterns in the aging human vestibular neuro-epithelia. Acta oto-taryng. 76, 208--220 (1973)
Received December 18, 1976
Archivesof Oto-Rhino-Laryngology 9 by Springer-Verlag 1976
Short Communication/Kurze Mitteilung
Scanning Electron Microscopic Study of the Cat Papilla Neglecta* T. Hoshino and A. Kodama Department of Otolaryngology,Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo, Japan 173 (Prof. Jun-Ichi Suzuki)
Summary. The papilla neglecta in the cat vestibule was studied under a scanning electron microscope. This papilla appears as a small mound of cells on the utricle near the posterior semicircular canal crista. The number of sensory hair bundles on the papilla ranged from 1 1 - 6 4 in 7 ears examined (average, 37). Although this crista-like endorgan was regularly found in the cat, its function may not be important in that the number of sensory hair cells is only 1/150 of those counted on guinea pig posterior semicircular canal crista. Key words: Papilla neglecta - Histology - Scanning electron microscopy
The papilla neglecta is a sensory apparatus found in the vestibule. This structure has been given various names such as the crista quarta, macula neglecta and sensura neglecta. Retzius (1872) originally described the papilla neglecta in the fish inner ear. In mammals, this structure is commonly found in the feline species (Gacek, 1961) and some other mammalian forms (Igarashi, 1965). The papilla neglecta was seen in 6 out of 640 human temporal bone specimens by Montandon et al. (1970). In mammalian inner ears the papilla neglecta is located on the postero-inferior part of the utricle near the posterior crista ampullaris. An electron microscopic study of the cat has shown that the papilla neglecta has the same structure as the crista ampullaris in that there are two types of nerve endings and sensory hair cells which are covered on the luminal surface by a cupular structure (Montandon et al., 1970). In the present study a scanning electron microscope was used to obtain a stereoscopic view of the papilla neglecta of the cat. Material and Method
Several young and adult cats were used in this study. After decapitation, 2% glutaraldehyde bufferred with phosphate (0.1 M, pH 7.4) was perfused into the inner ear through the oval and round windows. After glutaraldehyde fixation the specimens were further fixed in 1% osmium tetroxide. The membra~ *
This study was partly supported by U.S.P.H.S. Research Grant No. NS 10412--03
142
T. Hoshino and A. Kodama
nous labyrinth was dissected out under 70% ethanol following serial ethanol dehydration. The specimens were then transferred from absolute ethanol to amyl acetate and dried in a critical point dryer with liquid carbon dioxide. After coating with gold the specimens were studied under a Hitachi HHS2R scanning electron microscope.
Findings The papilla neglecta was found in all c a t specimens examined under the scanning electron microscope. This papilla was identified as a small dot, even at a low magnification under a dissecting microscope, near the posterior canal crista. The distance between the papilla neglecta and the posterior canal crista was about 0.7 ram. Under the light microscope, the papilla neglecta appeared as a small mound of sensory and supporting cells collared by cells with thicker cytoplasm than the surrounding ampullary wall cells. These were probably transitional cells (Fig. 1). A small cuputa-like structure was seen overlying the sensory cells, thus, the structure of the papilla was similar to that of the crista ampullaris. Under the scanning electron microscope, the papilla neglecta appeared as a small mound surrounded by an elevated ridge of transitional cells (Fig. 3). Sensory hair bundles were clearly visible amongst the supporting cells (Fig. 4) and the hairs on these bundles were arranged in graded heights. Next to the longest hairs of each bundle a singular, much longer cilium was detected (probably a kinoeilium) which differed slightly from the other hairs (Fig. 4). In general, these sensory hairs were longer than hairs seen on the otolithic maculae but their lengths were similar to hairs on the crista ampullaris.
Fig, 1. Light microscopic view of the cat papilla neglecta. Papilla neglecta (arrow) appears as a low mound of cells near the posterior semicircular canal crista (P). A cupula-like structure is seen covering the mound (insertion, arrow)
Papilla Neglecta of the Cat
143
Fig. 2. Scanning electron microscopic view of the cat papilla neglecta (long arrow). Sensory hair bundles are clearly visible. Short arrow indicates the eminentia cruciata. P: posterior semicircular canal crista. Bar equals 0.i mm
Fig. 3. Scanning electron microscopic view of the cat papilla neglecta. The number of sensory hair bundles varys considerably across cats
T h o u g h the s e n s o r y hairs were s o m e t i m e s c o v e r e d with a fine fibrous m a s s s t a t o c o n i a were n e v e r f o u n d o n this mass. P o l a r i z a t i o n o f these s e n s o r y hairs was utriculo-fugal with o n l y a few exceptions. T h e n u m b e r o f s e n s o r y hair bundles on one papilla n e g l e c t a r a n g e d f r o m 11--64 ( a v e r a g e o v e r 7 ears: 37). In one case, the
144
T. Hoshino and A. Kodama
Fig. 4. Sensory hair bundles on the cat papilla neglecta. Sensory hairs are very similar to the hairs on the crista ampullaris. These hairs are polarized in one direction with a few exceptions (arrows). Bar equals 5 micra number of sensory hair bundles counted on one ear was 11 whereas 31 were counted on the opposite ear. The luminal surfaces of both the supporting and transitional cells had a single short cilium and a smooth luminal surface. Discussion
The papilla neglecta was first described by Retzius in the fish and it is a bipartite structure consisting of two mounds (Fig. 5) located near the utriculo-saccular duct. De Burlet (1934) and others have verified the existence of this small sensory endorgan in various classes of vertebrates. Some structural features found in previous investigations and also the present study indicate that the papilla neglecta is structur: ally similar to the crista ampullaris rather than the otolithic macula. These features include a crest-shape of the papilla, long sensory hairs from the sensory cells, a cupulalike structure without otoconia and unidirectional polarization of sensory hairs.
Papilla Neglecta of the Cat
145
Fig. 5. Papilla neglecta of the goldfish. This papilla consists of two separate mounds (arrows) which each bear many sensory hair bundles. Bar equals 0.05 mm
As the number of the sensory hair bundles in the papilla neglecta with an average of 37 is very small as compared to the number of the hair cells on the posterior canal crista [5430 in the guinea pig (Lindeman, 1969), 7600 in humans (Rosenhall, 1973)], the papilla neglecta m a y not have a significant function in the cat although it was regularly found as a separate endorgan. The number of sensory cells on the cat posterior canal crista ampullaris has not as yet been reported. Gacek (1961) found approximately 35 nerve fibers innervating the cat's papilla neglecta. This finding considered in light of the actual hair cell population (i: 37) yields an innervation ratio as high as 1 : 1. In the human, the presence of this papilla is rather exceptional and therefore its functional significance m a y be negligible, as indicated by its name. This structure thus seems to be a rudimentary endorgan in the mammals. Igarashi and Yoshinobu (1966) mentioned that some correlation m a y exist between the papilla neglecta and another rudimentary structure in the mammalian inner ear, the eminentia cruciata. Both structures have been frequently observed in the cat (Fig. 2) and the dog vestibule and thus an intimate relationship between these structures m a y exist in both these species. However, this relationship does not seem to be consistent in other classes of vertebrates in that the fish, for example, does not have an eminentia cruciata although a well-developed papilla neglecta has been found. The authors are deeply indebted to Professor Jun-Ichi Suzuki (Teikyo University) for his encouragement in this study. Mr. Dominic W. Hughes kindly helped in English compilation.
146
T. Hoshino and A. Kodama
References de Burlet, H. M.: Vergleichende Anatomie des statoakustischen Organs. In: Handbuch der vergleichenden Anatomie der Wirbeltiere, 2 (2), p. 1293. Berlin-Wien: Urban & Schwarzenberg 1934 Gacek, R. R.: The macula neglecta in the feline species. J. Comp. Neurol. 116, 317-323 (1961) Igarashi, M.: Redefinition of the macula neglecta in mammals. J. Comp. Neurol. 125, 287-294 (1965) Igarashi, M., Yoshinobu, T.: Comparative observation of the eminentia cruciata in birds and mammals. Anat. Rec. 155, 269--277 (1966) Lindeman, H. H.: Studies on the morphology of the sensory regions of the vestibular apparatus. Ergebn. Anat. Entwickl.-Gesch. 42, 1-113 (1969) Montandon, P., Gacek, R. R., Kimura, R. S.: Crista neglecta in the cat and human. Ann. Otol. 79, 105-112 (1970) Retzius, G.: Das GehSrorgan der Knochenfische. Anat. Untersuchungen. Erste Lieferung. Stockholm (1872). Cited from Jorgensen, J. M.: The avian neglecta Retzii. Acta Zoologica 53, 155--163 (1972) Rosenhall, U.: Degenerative patterns in the aging human vestibular neuro-epithelia. Acta oto-taryng. 76, 208--220 (1973)
Received December 18, 1976
