HISTOGENESIS OF CAMEL MESONEPHROS

SCVMJ, XIII (2) 2008
377
HISTOGENESIS OF CAMEL MESONEPHROS
(Camelus dromedarius)
A. H. K. Osman, S. M. Farouk, H. Eidaroos and A. A. M. Ahmed
Department of Cytology and Histology, Faculty of Vet. Med.,
Suez Canal University.
ABSTRACT
The mesonephros was firstly seen as a narrow strip along the roof of
thoracolumbar region of the vertebral column at 5 mm CVRL stage. At 8 mm
CVRL stage, the ramifications of the aorta gave rise to the first evidence of
glomerulogenesis. At 13-18 mm CVRL stage, the peritubular matrix showed
scarse mesenchymal cells and pronounced increase in the number of
hemopioetic cells. At 20 mm CVRL stage, two types of tubules were
demonstrated in the mesonephros, one of them lined with single layer of low
cuboidal cells, the other tubules lined with low columnar cells. The Mullerian
duct was firstly seen at the aforementioned stage. The maximum size of
mesonephros was observed at 35 mm CVRL stage and it began its retrogressive
apoptotic changes at 37 mm CVRL stage.
INTRODUCTION
The kidney development is an excellent model to study the different aspects of organogenesis for most known
developmental processes (Kuure, Vuolteenaho and Vainio (2000) because
its morphogenesis depends upon different ways of cell-cell and tissue interactions.
The present work was undertaken
with the aim of establishing the prenatal histological changes associating
with the morphogenesis of the mesonephros in dromedary camel.
MATERIAL & METHODS
The present study was carried out
on the kidney of 39 embryos and
fetuses of the one humped camel, their
crown vertebral rump lengths (CVRL)
ranging from 5 mm to 95 mm. These
samples were freshly collected from
El-Basateen Slaughter-house directly
after slaughtering of the pregnant animals; their uteri were opened and then
evacuated. After collection of the sam-
378
ples, they were immersed in 10% neutral buffered formalin for 4 weeks.
The fixed specimens were dehydrated into graded series of ethyl alcohol (70%, 80%, 90%, 95%, absolute
I, abs. II and abs. III), cleared in 3
changes of xylene, and then embedded
in paraffin wax. Cross and/or longitudinal serially sectios of 5 – 7 µm
thickness were obtained. The prepared
sections were stained using the following stains; Harris heamatoxylin and
Eosin (Harris, 1900) to study the general histmorphological features of the
different stages of the mesonephros,
Gomori's stain (Gomori, 1937) for demonestration of reticular fibers, Periodic-acid Schiffs (PAS) technique for
detection of neutral mucopolysaccharides (MC-Manus, 1946), Alcian blue technique, pH 2.5 for detection of
acidic mucopolysaccharides (Steedman, 1950), Heidenhain's iron haematoxylin stain for the detection of mitotic figures (Heidenhain, 1896).
RESULT
At 5 mm CVRL stage, the mesonephros was in the form of a narrow strip of epithelial tubular elements with
mesenchymal investment lying behind
the caudal end of the pronephric duct
(Fig. 1). The mesonephric mass was
made up of convoluted tubules, lined
with a single layer of cuboidal cells,
with an average diameter of 45.039
µm. The terminal caudal end of the
developing mesonephros showed a
Osman et al.,
comparatively wide epithelial duct representing the mesonephric duct (Wolffian duct) with an average diameter
about 121.228 µm which was lined
with simple cuboidal epithelium.
At 8 mm CVRL stage, the mesonephric masses were attached to the
dorsal surface of the coelomic cavity
by an augmented condensation of mesodermal cells investing the dorsal aorta and separated by the dorsal mesentery. Both mesonephri were surrounded by mesenchymal connective tissue
capsule which was covered externally
by flattened mesenchymal cells that
continued with the splanchnic mesoderm (Fig. 2). The dorsal aorta gave
two lateral branches, each of which
invaded the medial portion of the corresponding mesonephros (Fig. 3). The
ramifications of each branch gave rise
to the first evidence of glomerulogenesis. The developing glomerulus was
in the form of bulky mass of hemopioetic cells, mainly of the erythroblastic series, and mesenchymal cells.
The glomerular mass (mesonephric
corpuscle) was surrounded by flattened tubules; however, they were not
constructing a clear glomerular capsule. These developing corpuscles were
mainly found in the medial portion of
the mesonephros and none of them
was observed in the mid or lateral
(subcapsular) portion. The mesonephric tubules became differentiated according to their staining affinity into
two categories; a- superficial, subca-
SCVMJ, XIII (2) 2008
psular tubules in which their epithelial
lining tended to be acidophilic, bdeeper tubules of basophilic epithelial
lining (Fig. 3). The mitotic index in
the mesonephric tubules was about
49% (Fig. 4). The diameter of the
mesonephric tubules was about 45.064
µm.
At 13 – 18 mm CVRL stage, the
tubular epitheliocytes exhibited moderate to strong PAS reactivity (Fig. 5),
and their basophilic, centrally located
nuclei showed many mitotic figures
(the mitotic index was about 47%).
The peritubular matrix showed
scarse mesenchymal cells and pronounced increase in the number of hemopioetic cells. The mesonephric glomeruli became surrounded by clearly visible glomerular capsule comprising a
parietal and visceral layer forming
well developed mesonephric corpuscles (Fig. 5), with an average diameter
of 166.812 µm.
At 20 mm CVRL stage, progressive increase in the size of the mesonephros was noticed due to the increase
in the size and number of tubular and
glomerular elements. The mesonephric
tubules became differentiated into two
types (Fig. 6):
a- The first type was lined with a
single layer of low cuboidal cells devoid of any surface modification, with
spherical, centrally situated nuclei and
acidophilic cytoplasm.
b- The second type was lined by a
single layer of low columnar cells,
379
whose luminal domain was studded
with clearly visible microvilli, with
basally situated, spherical nuclei surrounded by appreciable amount of cytoplasm. The average diameter of the
mesonephric tubules was about 69.903
µm. In addition to the PAS reactivity,
the mesonephric corpuscles showed
moderate alcianophilia, and their average diameter was about 167.31 µm.
The Mullarian duct (paramesonephric
duct) was firstly observed besides the
enlarged mesonephric duct. Both structures were surrounded by enormous
mesenchymal cells with centrifugal orientation (Fig. 7). The former duct was
smaller in size than the latter one and
was situated in ventromedial aspect of
the mesonephros. It was lined with
simple columnar epithelium with oval,
basally situated nuclei and basophilic
cytoplasm.
At 35 mm CVRL stage, there were
no obvious qualitative changes among
the tubular and glomerular elements,
however, it was noticed that the argyrophilia and alcianophilia of the glomeruli demonstrated a consistent feature
(Fig. 8, 9). The size of the mesonephros has reached its maximum at this
stage. The diameter of the mesonephric tubules was about 83.61 µm
meanwhile that of the mesonephric
corpuscles was about 192.621 µm.
At 37 – 95 mm CVRL stage, the
mesonephric tubules and glomeruli were
characterized by gradual retrogressive
changes including apoptosis of their
380
lining epithelia (Fig. 10). Apoptotic
bodies were seen everywhere among
the tubular lumina and the fragmented
glomeruli. The apoptotic changes in
the glomeruli were associated with the
presence of multinucleated cells with
deeply basophilic nuclei and strongly
acidophilic cytoplasm giving the morphological features of gaint phagocytes (Fig. 11). There were gradual decr-
Osman et al.,
ease in the diameter of mesonephric
corpuscles, mesonephric tubules and
mesonephric ducts.The mitotic index
of the tubular epithelial lining became
about 39%.
Technical remark:
Beyond the 95 mm CVRL stage, we
couldn't observe any mesonephric structures because the technical possibility to obtain sections from wholemount fetuses not achieved.
Fig. (1): 5 mm CVRL stage: showing pronephric duct (arrow); mesonephric tubular
elements (arrow head), mesonephric duct (MD) and somite (S). (H&E).
Fig. (2): 8 mm CVRL stage: showing neural tube (NT); dorsal aorta (DA); dorsal
mesentery (DM); primitive gut (PG); two bilateral mesonephroi (M); coelomic
cavity (CC); mesonephric capsule (thin arrow); mesonephric ridge ( thick arrow)
and mesonephric duct (arrow head). (H&E).
Fig. (3): Mesonephros of 8 mm CVRL stage: showing dorsal aorta (DA) giving lateral
branching (L); dorsal mesentery (DM); coelomic cavity (CC); mesonephric tubule
(MT); mesonephric corpuscle (MC);; mesonephric capsule (arrow head) and
mesonephric ridge (arrow). (H&E).
Fig. (4): 8 mm CVRL stage: showing the mitotic activity (arrows) in the mesonephric
tubular epitheliocytes. (Heidenhain's iron haematoxylin).
SCVMJ, XIII (2) 2008
381
Fig. (5): 15 mm CVRL stage: showing moderate to strong PAS reactivity of the
mesonephric tubules (T) and corpuscles(C). Notice: the parietal (Thick arrow) and
visceral layer (Thin arrow) of the glomerular capsule became more differentiated.
(PAS).
Fig. (6): 20 mm stage: showing the two forms of mesonephric tubules, one of them lined
with low columnar cells (A) with apical clearly visible microvilli (arrows) and the
other one lined with low cuboidal cells (B). (H&E).
Fig. (7): 20 mm CVRL stage: showing mesonephric tubules (MT); mesonephric duct (MD)
and Mullerian duct (arrow). (H&E).
Fig. (8): 35 mm CVRL stage: showing the argyrophilia of mesonephric glomeruli.
(Gomori's reticulin).
382
Osman et al.,
Fig. (9): 35 mm CVRL stage: showing moderate to strong reaction of mesonephric
corpuscles (MC) to Alcian blue. Intestine (I) showed strong reaction to Alcian
blue. (Alcian blue).
Fig. (10): 37 mm CVRL stage: showing massive retrogressive changes including apoptotsis
of the lining epithelia of mesonephric tubules (MT) and corpuscles (MC). (H&E).
Fig. (11): 40 mm CVRL stage: showing some multinucleated gaint phagocytes (arrows)
among the fragmented mesonephric glomeruli. (H&E).
DISCUSSION
Our investigation has clarified
that the mesonephros was firstly observed at 5 mm CVRL stage. The mesonephros was in the form of a narrow
strip of epithelial tubular elements with
mesenchymal investment. Similar result was mentioned by Aly (2007) at 9
mm CVRL camel embryo. Bareedy,
Anis, Abbas, Ewais and Ammar (1982),
Emara (1989) and El-Harairy, Gaber
and Attia (1998) claimed that the first
appearance of the camel mesonephros
was at 8 mm, 6 mm and 10 mm CVRL
respectively. In pig, Haines and Mohiuddin (1972) stated that the first appearance of mesonephros was at 7 mm
CVRL embryo. In bovine it appeared
at the age of 28 - 42 days intrauterine
life (Canfield, 1980) and in the Egyptian water buffalo it appeared at 7 mm
CVRL embryos (Moustafa, Enany,
Osman and Amin, 1986). El-Gharbawy (2002) in rabbits, recorded that
SCVMJ, XIII (2) 2008
the bilateral mesonephroi appeared in
11 days old fetuses.
The mesonephric tubules were
differentiated according to their staining affinity into two categories:
a- superficial,
subcapsular
tubules in which their
epithelial lining ten-ded to be
acidophilic.
b- deeper tubules of basophilic epithelial lining. However, Smith
and MacKay (1991) described
proximal and distal tubules in the
mammalian mesonephros.
It was noticed that the first morphological evidence of mesonephric
glomerulogenesis initiated through the
invasion of few lateral branches from
the dorsal aorta into the medial portion
of the developing mesonephros at 8
mm CVRL Stage. The invading angiogenic mass, which was made up of a
predominance of hempoietic cells, represented an early glomerulus which
in turn became surrounded by flattened epithelial tubules forming a glomerular capsule. Both structures, glomerulus and its capsule, constructed the
developing mesonephric corpuscle.
Regarding glomerulogenesis, there is an agreement with Bareedy et
al., (1982), Emara (1989) and El-Harairy et al., (1998) in camel; Moustafa
et al., (1986) in buffalo and Haines
and Mohiuddin (1972) in pig, whom
emphasized the mesonephric invasion
by lateral branches from dorsal aorta.
In contrast to our findings, it was
383
mentioned that the terminal ends of
some mesonephric tubules became
ampullated forming the primordium of
the Bowman’s capsule which became
invaginated with few blood capillaries,
these capillaries were increased in
number forming the glomerular tuft
that contained immature hemopioetic
cells [Emara (1989) in 8 mm CVRL
and Aly (2007) in 14 mm CVRL camel embryo and El-Gharbawy (2002)
in 6 - 8 mm CVRL rabbit embryo].
Two types of tubules were demonstrated in the mesonephros of 20
mm CVRL stage, one of them was
lined with a single layer of low cuboidal cells whose luminal domain was
devoid of any surface modification
and the second type was lined with a
single layer of low columnar cells whose luminal domain was studded with
clearly visible microvilli. This tubular
differentiation was also described in
camel embryos by Bareedy et al.,
(1982) and Emara (1989) at 35 mm
CVRL and Aly (2007) at 20 mm
CVRL. It was also demonstrated in 40
mm CVRL buffalo embryo (Moustafa
et al., 1986) and at 10 mm CVRL
human embryo (Sadler, 2000).
The mesonephros reached its
maximum size at 35 mm CVRL stage.
According to Bareedy et al., (1982)
and Emara (1989), the maximal mesonephric size in camel is reached at 35
and 38 mm CVRL respectively. In
other species, the size of the mesonephros reached its peak in pig at 60
384
mm CVRL (Patten, 1964 ), in mouse
of 16 days post coitus (Vetter and
Gibley, 1966), in rabbit embryo of 18
days intrauterine life (Tiedmann and
Wettstein, 1980), in bovine embryo of
6 – 8 weeks intrauterine life (Canfield,
1980), in Egyptian water buffalo of 32
mm CVRL (Moustafa et al., 1986)
while in the marsupial native cat,
Nelson, Yuemin and Gemmell (1992),
mentioned that the mesonephros was
present at birth, reached a maximum
volume 11 days after birth.
The current findings revealed
that the mesonephros began its regression from 37 mm CVRL stage on.
The regression comprised apoptotic
changes among the tubular and glomerular elements of the mesonephros. In
camel, Bareedy et al., (1982) said that
the mesonephros gradually degenerates from 50 mm CVRL; Emara (1989)
recorded that the mesonephric degenerations occurred at 38 mm CVRL and
El-Harairy et al., (1998) in camel embryos mentioned that the mesonephros
started to degenerate at 150 mm CVRL,
meanwhile, Aly (2007) showed that at
47 mm CVRL, continuous regression
of the mesonephros takes place. In
rabbit, El-Gharbawy (2002) recorded
that degenerative changes began to occur in the mesonephroi of 15 days old.
In bovine fetuses, the degeneration occurs from the 8th week of gestation
(Canfield, 1980) while in buffalo, the
degeneration occurs at 47 mm CVRL
(Moustafa et al., 1986). In the native
Osman et al.,
cat, Nelson et al., (1992) mentioned
that the mesonephros had regressed
completely by day 30 after birth.
Kaufman, (1992) in mouse stated that
between 13 and 13.5 days post coitus
the mesonephros regressed, leaving
only few seemingly disorganized tubules.
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‫الملخص العـربى‬
‫"التطور النسيجى للكلية المتوسطة فى الجمل الدروميدرى"‬
‫اجري هذا البحث على كلى ‪ 93‬جنينا والتى تتراوح اطوالها ما بين ‪ 5‬مم – ‪ 35‬مم والتى تم جمعها من‬
‫مجزر البساتين اآللى بالقاهرة‪ .‬ولقد اظهرت نتائج تلك الدراسة ما يلى‪-:‬‬
‫ظهووور الكليووة المتوسووطة عنوود طووو ‪ 5‬مووم كيووريط نسوويجى مكووون موون عوودد كبيوور موون اانبيبووات الكلويووة‬
‫باالضافة الى قناة الكلية المتوسطة‪ .‬تستقب الكلية المتوسطة تفرعات دموية من اليريان االورطى والتى‬
‫تكون كبيبات الكلية عند طو ‪ 8‬مم‪ .‬تتمايزاانبيبات الكلوية عند طوو ‪ 02‬موم الوى نووعين احودهما تتفورد‬
‫خالياه الطالئية بوجود سطح هدبى‪ .‬يص حجم الكلية المتوسطة الوى اقصواه عنود طوو ‪ 95‬موم موم تذخوذ‬
‫فى االضمحال التدريجــى‪.‬‬

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