Title Histochemical Analysis of the Vomeronasal Organ of the One

Title
Histochemical Analysis of the Vomeronasal Organ of the OneHumped Camel (Camelus dromedarius)( 要約版(Digest) )
Author(s)
Dalia Ibrahim Tawfik Mohamedien
Report No.(Doctoral
Degree)
博士(獣医学) 甲第432号
Issue Date
2015-03-13
Type
博士論文
Version
none
URL
http://repository.lib.gifu-u.ac.jp/handle/123456789/50998
※この資料の著作権は、各資料の著者・学協会・出版社等に帰属します。
学
位
論
文
要
約
氏
名
Dalia Ibrahim Tawfik Mohamedien
題
目
Histochemical Analysis of the Vomeronasal Organ of the One-Humped Camel
（Camelus dromedarius）
（ヒトコブラクダ鋤鼻器の組織化学的解析）
ラクダ嗅覚系の解剖学的および組織学的特徴は過去にも報告されているが，レクチン
組織化学や，免疫組織化学，および嗅覚器の発生に関する解析はまだない。そこで本研
究では，ヒトコブラクダの成体および胎子における嗅覚器の組織化学的特徴を明らかに
するため，それらを組織化学，免疫組織化学，およびレクチン組織化学によって調べた。
さらに，砂漠に棲む動物の鼻腔では様々な領域に特殊な構造が見つかるのに対し，鋤鼻
器では砂漠での生活に対する適応について何も分かっていない。そこで本研究では特に
ラクダ鋤鼻器に着目した。
ラクダ鋤鼻器の形態学的特徴を明らかにするため，HE 染色，PAS 染色，およびアル
シアン青染色（pH 2.5）によって解析した。成ラクダの鋤鼻器は鼻中隔の基部に位置す
る一対の管で，固有層と共に鋤鼻軟骨によって囲まれ，内側を感覚上皮，外側を非感覚
上皮によって裏打ちされていた。支持細胞，感覚細胞，および基底細胞の核は，鋤鼻感
覚上皮の浅層，中間層，および深層にそれぞれ位置していた。また，鋤鼻器の非感覚上
皮は偽重層線毛円柱上皮で，PAS 強陽性の杯細胞を含んでいた。
鋤鼻器の感覚上皮と非感覚上皮両方の周囲には毛細リンパ管が認められた。このよう
な特徴はヒツジ鋤鼻器には認められなかった。これらのリンパ管は，細胞外空間の水や
液体の吸収と放出を制御することによって鋤鼻感覚上皮を乾燥から守り，砂漠でラクダ
鋤鼻器の機能を維持するのに関わっているのかも知れない。
感覚上皮と非感覚上皮の糖鎖組織化学的特徴を明らかにするため，21 種類のビオチ
ン化レクチンを用いてレクチン組織化学を行った。鋤鼻感覚上皮において，WGA，LEL，
BSL-I，および Con A は感覚細胞を標識し，8 種類のレクチンすなわち，WGA，LEL，DSL，
DBA，SBA，BSL-I，VVA，および PHA-L は，基底細胞を標識した。
13 種類のレクチンすなわち，WGA，s-WGA，LEL，STL，DSL，DBA，SBA，BSL-I，VVA，
RCA-I，PNA，ECL，および UEA-I は，鋤鼻器の感覚上皮と非感覚上皮両方の自由縁を標
識した。これらの内 ECL を除く 12 種類のレクチンはまた鋤鼻腺を染色し，その内 5 種
類のレクチンすなわち，WGA，DBA，SBA，VVA，および RCA-I は，杯細胞を染色した。こ
れらの知見は，感覚上皮と非感覚上皮両方の自由縁の糖鎖組織化学的特徴が互いに似て
いることを示し，自由縁の染色が鋤鼻腺と杯細胞からの粘液性の分泌物に由来すること
が示唆された。
DBA はラクダ鋤鼻器の非感覚上皮に散在する紡錘形細胞の細胞質および自由縁上の細
胞突起先端を標識した。ヒツジ鋤鼻器では，DBA は鋤鼻感覚上皮の特別な細胞を染色し
た。その細胞は鋤鼻感覚細胞と同じ高さに位置するが，細胞の分布や形態，数は鋤鼻感
覚細胞のそれと一致しなかった。
感覚細胞の分布，分化，および成熟度を明らかにするため，また孤在性化学感覚細胞
（SCC）のような特殊な要素の存在を明らかにするため，成ラクダの鋤鼻器を免疫組織
化学的に調べた。成ラクダの嗅覚器において，PGP9.5 は鋤鼻感覚上皮のほとんどの感
覚細胞を標識し，支持細胞や基底細胞を標識しなかった。OMP は幾つかの感覚細胞を染
色し，成ラクダの鋤鼻感覚細胞が成熟し機能的であることが示された。
PLCβ2 は感覚上皮に散在する SCC を標識し，非感覚上皮ではより多くの SCC を標識し
た。二重免疫組織化学によって両上皮の SCC はサブスタンス P 陽性の神経線維に囲まれ
ていることが示された。ラクダ鋤鼻器における SCC の分布は，それが刺激物質や有害物
質が鋤鼻器の管腔へ過剰に侵入しないよう制御し，砂漠で鋤鼻感覚細胞を傷害から守る
働きをもつことを示唆する。
胎子嗅覚器の分化度を評価するため，ラクダ鋤鼻器と嗅上皮の発生および感覚細胞の
分化を免疫組織化学とレクチン組織化学によって調べた。頭尾長 395 mm と 510 mm の胎
子では，PGP9.5 が鋤鼻器と嗅上皮の感覚細胞を強く標識し，OMP は標識しなかった。こ
れは，鋤鼻器と嗅上皮の両方で感覚細胞は分化しているが完全には成熟してないことを
示している。頭尾長 187 mm の胎子において，WGA と LEL の強い染色は鋤鼻器と嗅上皮
の両方に感覚細胞が存在することを示していたが，PGP9.5 は鋤鼻器を弱く染め，嗅上
皮を染めなかった。すなわち，ラクダの鋤鼻器と嗅上皮は分化してはいるが未成熟な感
覚細胞を含んでおり，胎生期の半ばまで，神経細胞の分化は鋤鼻器の方が嗅上皮よりも
幾分早いらしい。
まとめると，本研究によって成体および胎子ラクダ鋤鼻器の組織化学，レクチン組織
化学，および免疫組織化学に関する詳細な情報が得られ，ラクダが砂漠の生活に適応す
るのを助けると予想される，鋤鼻器の形態学的および機能的特徴が明らかになった。
学
氏
名
題
目
位
論
文
要
約
Dalia Ibrahim TawfikMohamedien
Histochemical Analysis of the Vomeronasal Organ of the One-Humped Camel
(Camelusdromedarius)
（ヒトコブラクダ鋤鼻器の組織化学的解析）
The capacity of the dromedary camel to live under desert conditions is due to its
biological and physiological particularities. All the functions of the dromedary organism are
conceived to be physiologically adapted to “water and food restrictions” and to a very hot
climate. Thus, it is expected that morphological adaptations for the desert environment exist in
camel olfactory organs.The anatomical and histological features of the camel olfactory organs
have been reported previously. However, lectinhistochemical analysis, immunohistochemical
analysis, and analysis for the development of olfactory organs are lacking. In this study the
olfactory organs of both adult and fetal one-humped camels have been studied using traditional,
immuno- and lectinhistochemistry aiming to clarify their morphological and histochemical
features. In addition, in contrast to the information about some special structures which have
been elucidated in the nasal cavity of desert animals, no information is available to date on the
adaptations of the VNO for the desert life. Therefore, using a breed of sheep which live in the
cold climate for comparison, I also focused on the camel VNO to identify the adaptations to the
desert environment.
The camel VNO was examined by Hx&E, PAS or alcian blue (pH 2.5) staining in order
to clarify its morphological features. The adult camel VNO was a pair of tubes situated at the
base of the nasal septum. The VNO and its associated lamina propria were surrounded by an
incomplete ring of vomeronasal cartilage which was hyaline in nature. The camel VNO was
lined by the sensory epithelium medially and the non-sensory epithelium laterally. Nuclei of the
supporting cells, receptor cells, and basal cells were arranged in the apical, middle, and
basalregions of the vomeronasal sensory epithelium, respectively. The supporting cells had dark,
oval nuclei arranged in three to five layers. While, the receptor cells were pear-shaped and their
nuclei were arranged in one or two layers and were pale with a distinct nucleolus. Nuclei of the
basal cells were oval or round and smaller than those of the receptor and supporting cells. Some
superficially-situated cells were detected, which were different from the basal, receptor or
supporting cells in their morphology, distribution or frequency.
The non-sensory epithelium of the VNO was a pseudostratified ciliated columnar
epithelium with goblet cells, which reacted intensely-positive to PAS. The number of goblet cells
decreased caudally till they disappear at the middle of the anterior-posterior axis of the VNO.
Morphological adaptation represented by several lymphatic capillaries has been detected
underlying the whole camel vomeronasal epithelium of both sensory and non-sensory sides.
Such morphological feature is not known in other animals and I could not detect it in sheep. This
may indicate an involvement of these lymphatics in the adaptation to the water deficiency in the
desert environment by regulating the absorption and release of water and fluids of the extra
cellular spaces to protect the vomeronasal epithelium from dehydration and thus maintaining the
function of the camel VNO.
In order to clarify the glycohistochemical characteristics of the sensory and non-sensory
epithelia, lectinhistochemistry has been done using 21 types of biotinylatedlectins. In the
vomeronasal sensory epithelium of camel, WGA, LEL, BSL-I and Con A labeled the receptor
cells and eight lectins: WGA, LEL, DSL, DBA, SBA, BSL-I, VVA and PHA-L, labeled the
vomeronasal basal cells. In the non-sensory epithelium of camel VNO, none of the lectins used
in this study except DBA labeled the ciliated cells and four lectins: WGA, LEL, DSL and PHA-L,
labeled the basal cells of the non-sensory epithelium only in the anterior region. In camel,
thirteen lectins: WGA, s-WGA, LEL, STL, DSL, DBA, SBA, BSL-I, VVA, RCA-I, PNA, ECL
and UEA-I, labeled the free border of both sensory and non-sensory epithelia of the VNO.
Twelve of these lectins except ECL also stained the vomeronasal glands, while five of these
lectins: WGA, DBA, SBA, VVA and RCA-I, stained the goblet cells. These findings indicated
that the glycohistochemical characteristics of the free borders of both sensory and non-sensory
epithelia of camel VNO are similar to each other, suggesting that the staining in the free border
may originate from the mucous secretions of the vomeronasal glands and goblet cells.
DBA labeled the cytoplasm and tip of the cell processes on the free border of some
columnar-shaped cells scattered in the non-sensory epithelium of the camel VNO. In the sheep
VNO, DBA stained particular cells in the vomeronasal sensory epithelium, located at the same
level as the vomeronasal receptor cells, although the distribution, shape and number of the
stained cells did not correspond to those of the vomeronasal receptor cells.
Aiming to clarify the distribution, degree of differentiation and maturation of the receptor
cells, in addition to elucidate the existence of other specialized elements such as solitary
chemosensory cells (SCCs), the adult camel VNO was investigated immunohistochemically. In
the camel VNO, PGP 9.5 labeled the majority of the receptor cells in the vomeronasal sensory
epithelium, but not the supporting or basal cells. OMP stained some receptor cells, but no
immunoreactive signals for OMP were detected in the non-sensory epithelium. This assures that
the adult camel vomeronasal receptor cells are mature and functioning.
PLCβ2 labeled scattered SCCs in the sensory epithelium and a larger number of SCCs in
the non-sensory epithelium of camel VNO. Double labeling immunohistochemistry revealed that
some of the SCCs in both epithelia were surrounded by substance P-positive nerve fibers.
Moreover, OMP did not label the SCCs, either in the sensory or non-sensory epithelium. The
distribution of the SCCs in the camel VNO suggests a substantial role in avoiding the over access
of irritant and harmful substances to the lumen of the VNO and thus protecting the vomeronasal
receptor cells from damage in the desert environment.
In order to distinguish the degree of differentiation of the fetal olfactory organs,
development and neuronal differentiation of the VNO and the OE of camel were studied by
immunohistochemistry and lectinhistochemistry. PGP 9.5, but not OMP, intensely labeled the
olfactory receptor cells of the VNO and OE at 395 mm- and 510 mm-fetal ages. This indicates
that the olfactory receptor cells are differentiated, but not fully-matured both in the VNO and OE.
In 187 mm-fetus, PGP 9.5 yielded faint immunoreactive signals in the VNO, but not in the OE,
although the presence of receptor cells were indicated in both tissues by intense WGA and LEL
stainings. Thus, the camel VNO and OE bear differentiated, but are still immature receptor cells,
even though the neuronal differentiation seems to be somewhat faster in the camel VNO than in
the OE till half of the prenatal life. This may suggest earlier maturity of the VNO than the OE.
In conclusion, detailed information on the histology, lectinhistochemistry and
immunohistochemistry of the adult and fetal camel VNO has been obtained. Moreover, several
lymphatic capillaries have been detected underlying the whole vomeronasal epithelium and
numerous SCCs have been identified in the camel VNO. Such special morphological and
functional features of the VNO are expected to help the camel adaptations for desert life.

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