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Asymmetric expression of proteins in the granules of the placentomal Binucleate cells in Giraffa camelopardalis

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  • Sharjah Equine Hospital

Abstract and Figures

Introduction: Mature granulated trophoblast binucleate cells (BNC) have been found in all ruminant placentas examined histologically so far. BNC are normally fairly evenly distributed throughout the fetal villus and all their granules contain a similar variety of hormones and pregnancy associated glycoproteins (PAGs). Only the Giraffe is reported to show a different BNC protein expression, this paper is designed to investigate that. Results: Gold labelled Lectin histochemistry and protein immunocytochemistry were used on deplasticised 1 μm sections of a wide variety of ruminant placentomes with a wide range of antibodies and lectins. Results: In the Giraffe placentomes, even though the lectin histochemistry shows an even distribution of BNC throughout the trophoblast of the placental villi, the protein expression in the BNC granules is limited to the BNC either in the apex or the base of the villi. Placental lactogens and Prolactin (PRL) are present only in basally situated BNC: PAGs only in the apical BNC. PRL is only found in the Giraffe BNC which react with many fewer of the wide range of antibodies used here to investigate the uniformity of protein expression in ruminant BNC. Discussion: The possible relevance of these differences to ruminant function and evolution is considered to provide a further example of the versatility of the BNC system.
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Received: November 2, 2021. Revised: December 20, 2021. Accepted: January 15, 2022
© The Author(s) 2022. Published by Oxford University Press behalf of Society for the Study of Reproduction.
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Biology of Reproduction, 2022, 106(4), 814822
https://doi.org/10.1093/biolre/ioab247
Advance access publication date 17 January 2022
Research Article
Asymmetric expression of proteins in the granules of the
placentomal Binucleate cells in Giraffa camelopardalis
F. B. P. Wooding1,*,A. J. Forhead1,S. Wilsher2, W. R. Allen2,,R. M. Roberts3,J. A. Green3,
J. F. Beckers4,N. Melo Sousa de4and G. Charpigny5
1The Physiological Laboratory, University of Cambridge, Downing Site, Cambridge, CB2 3EG
2The Paul Mellon Laboratory of Equine Reproduction, Newmarket, Suffolk, CB8 9BJ
3Division of Animal Sciences, University of Missouri, Columbia, Missouri, USA
4Physiologie de la Reproduction, Faculte de Medecine Veterinaire, B-4000, Liege, Belgique
5INRA, UMR1198, Biologie Devel Reprod, F-78532 Jouy et Josas, France
*Correspondence: E-mail Address: fbpw2@cam.ac.uk (FBP Wooding)
Grant Support: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.
Deceased
Abstract
Mature granulated trophoblast binucleate cells (BNC) have been found in all ruminant placentas examined histologically so far. BNC are normally
fairly evenly distributed throughout the fetal villus and all their granules contain a similar variety of hormones and pregnancy associated
glycoproteins (PAGs). Only the Giraffe is reported to show a different BNC protein expression, this paper is designed to investigate that.
Gold labelled Lectin histochemistry and protein immunocytochemistry were used on deplasticised 1 μm sections of a wide variety of ruminant
placentomes with a wide range of antibodies and lectins. In the Giraffe placentomes, even though the lectin histochemistry shows an even
distribution of BNC throughout the trophoblast of the placental villi, the protein expression in the BNC granules is limited to the BNC either in
the apex or the base of the villi. Placental lactogens and Prolactin (PRL) are present only in basally situated BNC: PAGs only in the apical BNC.
PRL is only found in the Giraffe BNC which react with many fewer of the wide range of antibodies used here to investigate the uniformity of
protein expression in ruminant BNC. The possible relevance of these differences to ruminant function and evolution is considered to provide a
further example of the versatility of the BNC system.
Keywords: Ruminant placenta, Trophoblast binucleate cell, Giraffe granule protein asymmetry
Introduction
Mature granulated trophoblast BNC have been found in
all ruminant placentas examined histologically so far [13].
Recent investigations suggest that all mature BNC undergo
the same characteristic migration out of the trophoblast fol-
lowed by fusion with a uterine epithelial cell or derivative
to form fetomaternal tissue throughout pregnancy [4]. The
granules are released to the maternal compartment by exocy-
tosis from this fetomaternal tissue. BNC are normally fairly
evenly distributed throughout the fetal villus and all their
granules contain a similar variety of hormones and pregnancy
associated glycoproteins (PAGs) [1].
The one exception to this uniformity so far is the giraffe,
(Giraffa camelopardalis) which is reported to show BNC
whose granules react uniquely with a Prolactin antibody but
are restricted to the base of the fetal villi [2].
The giraffoid clade now consists only of Giraffes, Okapis
and Pronghorns [5] but they were much more widespread
in the Miocene era [6]. They are now restricted to a few
species in marked comparison with the enormous expansion
of the other ruminant clades, in particular the Bovidae. For-
tunately samples of Okapi and Pronghorn placentas were
available, as well as a wide variety of other ruminant placentas
[Supplementary Table S1].
Antibodies to Prolactin and purified Placental lactogens
from three different species were used (Tabl e 1 ) together with
examples from the two phylogenetically distinct ancient and
modern groups of PAGs [7,14].
This paper reports a qualitative and quantitative study of
ruminant BNC position and granule content in the species
detailed above using the range of antibodies and lectins.
This variety of results should facilitate investigation of the
possible relevance of any differences to ruminant function and
evolution.
Methods and materials
Animals
Mid to late pregnant placental material was used from
a wide variety of ruminants collected over many years
(Supplemental Table S1 and see Wooding references in [1]).
They were fixed by aldehyde immersion or perfusion.
Wild animals were shot as part of Wild life management or
culling procedures and placentomes removed and immersion
fixed within 20 minutes of the death of the animals. Fixa-
tives used included Bouins, phosphate buffered Paraformalde-
hyde or Glutaraldehyde, and Surgipath (methyl alcohol and
formaldehyde). The quality of fixation varied, but crucially, all
produced comparable results with the antibodies and lectins
(Tabl e 1 ) used on the placentome sections.
Small pieces of Horse Anterior Pituitary were also fixed and
processed as the placentome samples.
Wooding et al., 2022, Vol. 106, No. 4 815
Ta b l e 1 . Antibodies and Lectins used
Abbreviations Antibody Antibody origins
“ancient”PAGs
RA Anti native bovine-PAGs Wooding et al 2005 [13]
RD Anti-boPAG 2
BJ Anti-boPAG 2 Beckers et al 1994 [18]R438
“new”PAGs
RB Anti native bo-PAGs Wooding et al 2005 [13]
RC Anti –ovinePAG 1
RU
FPIR Anti bo PAG 1 Touzard et al 2013 [14]
BG Anti-bo PAG 1 Zoli et al 1991 [15]R726
Buffalo PAGs
BK Anti-wbPAGs Barbato et al 2013 [19]R858
BM Anti-wbPAGs (different N
terminal sequence)
R859
Goat PAGs
BB Anti-capPAG55+59 kDa Garbayo et al 1998 [16]R708
BE Anti-capPAG55+62 kDa R706
Ovine PAG Anti-ovPAG57 El-Amiri et al 2004 [20]R780
BN Anti-bovine PAG 1 Zoli et al 1991 [15]
Placental Lactogens
Friesen oPL Anti ovinePL Chan et al 1978 [22]
BF Anti- bovine PL Alvarez-Oxiley et al 2007 [17]
PROLACTIN Anti humanPRL NIH
SBU3 Monoclonal ab, Homologous to
ovine PAG
Gogolin-Ewens et al,1987 [21]
LECTINS Vector Laboratories, Peterboro, UK
DSA
DBA
ePHA
lPHA
For the differences between “ancient” and “new” PAGs see [14], the Touzard et al reference and Wallace et al [7].
For details of the animals and origins see Supplemental
Tabl e S 1 .
At least two placentomes from a single animal were used in
the case of the Wildebeest, at least two or more animals from
each of the other species were used.
A central slice was cut from each fixed placentome. “Match-
stick” samples from the central region of each slice from
maternal to fetal edge were used. The samples were then
embedded in epoxy resin with no osmium postfixation.
Semithin sections were cut, picked up on cover glass squares
treated with APES, deresinated in sodium ethoxide and thor-
oughly washed in PBS.
Immunocytochemistry
The cover glass squares were then floated section side down
on drops of antibody (see Tabl e 1 ) followed by immunogold
colloid (goat anti-rabbit G5, Jackson Immunoresearch Labs,
USA) and then intensified with silver reagent (Aurion, Wageni-
gen, Netherlands). The coverslips were washed thoroughly
between each incubation.
The antibodies used (Tabl e 1 ) were to purified lactogens
or Pregnancy Associated Glycoproteins (PAGs) from a variety
of species (see Supplementary Table S1) used at a dilution of
1:1000.
Lectin histochemistry
The cover glass squares were floated section side down
on drops of biotinylated lectins (see Tabl e 1 ) followed by
immunogold colloid.
(Goat antibiotin G5) and then intensified with silver reagent
(Aurion, Wagenigen, Netherlands). The lectins used were cho-
sen as the most BNC reactive although the silver enhancement
did produce some background with the giraffe specimens.
The antibodies and lectins identified BNC granules in all
species used. Controls with buffer substituted for antibody or
lectin showed no significant labelling.
Assessment of Labeling
Visual estimate of antibody reaction on BNC granules, scale
used: —, no reactivity, (+) sporadic/occasional: +,++,+++
indicate increasing levels of reactivity.
Quantitation of BNC
The number of BNC visible in the X10 objective field of
view was counted at random positions along the axis of the
fetomaternal “matchstick” from the fetal to maternal side.
The area of the field of view was converted to mm 2and
the position along the “matchstick” estimated by eye.
The results for any particular lectin or antibody are consis-
tent but the standard deviations are high mainly because of the
variable areas of core villus connective tissue on the sections.
To minimise this problem semiserial sections were used for
any one comparative run.
Results
Our results show a remarkable degree of uniformity in the
binucleate cell granule immunoreactivity in thirteen of the
fourteen ruminant species we examined (Tabl e s 2 and 4,
Supplementary Fig. S1,Fig. 1).
We used a wide range of Pregnancy Associated Glyco-
proteins (PAGs) and Placental Lactogen antibodies (Ta ble 1)
raised against proteins purified from ruminant placentas of
816 BNC protein distribution in Giraffe placenta, 2022, Vol. 106, No. 4
Ta b l e 2 . Assessment of the immunoreactivity of non giraffoid Ruminant BNC
ANTIBODY COW EWE BISON Tragulus Springbok Impala Red deer Chinese water deer Wildebeest White tail Wapi t i
“ancient”PAGs
RA +++ +++ ++ +++ +++ ++++ ++ +++ +++
RD +++ +++ ++++ ++ ++ +++
BJ ++ ++ +++ ++++
“new”PAGs
RB +++ +++ +++ +++ ++ +++ ++++ +++ +++
RC ++++ +++ +++ ++ ++ ++++ +++ +++
RU ++ +++ +++ ++ ++ +++ +++ +++ +++ +++
FPIR +++ ++ +++ ++ ++ +++
BC ++ ++ ++ +++ ++ + + +++ +++
BO ++ +++ ++ +++ +++ +++ ++
Buffalo PAGs
BK ++ ++ +++ +++ + + ++ ++ ++ +++ +++
BM ++ +++ +++ +++ ++ +++ +++ +++
Goat PAGs
BB +++ +++ +++ +++ +++ ++++ ++ +++ +++ +++
BE +++ +++ +++ ++ +++ +++ +++ +++ +++
Ovine PAG
BN +++ +++ +++ +++ +++ +++ ++++ +++
SBU3 ++ ++ ++ ++ +++ ++ ++
Placental Lactogens
Friesen bPL +++ ++ +++ ++ ++ ++ ++ ++
BF ++ ++ +++ + ++ ++++ ++++
PROLACTIN
SBU3 ++ ++ ++ ++ +++ ++ ++
LECTINS
DSA ++ ++ +++ ++
DBA +++ +++ +++ +++ +++ +++
ePHA +++
lPHA +++
Scale used: —, no reactivity, +,++,+++ indicate increasing levels of reactivity. Empty oblong: assessment not done
Wooding et al., 2022, Vol. 106, No. 4 817
Figure 1. Pronghorn and Tragulus; placentomal semiserial sections showing similar localisations and even distributions of BNCs throughout the sections
using PAG antibody or lectin localisations. Maternal villus, mv. Arrows indicate different levels of the same BNCs on the pairs of sections. Arrowheads
identify the fetal basal chorionic layer on the Pronghorn. Scale bar =250 μm. Tragulus; Scale bar = 80 μm.
different species. The BNC granules were detected by gold
labelled immunocytochemistry by most of the antibodies and
lectins used on deplasticised araldite sections which included
the full depth of the placentomal villi from maternal to fetal
sides.
In the thirteen, BNC were evenly distributed throughout
the fetal villi with no consistent indication of any zonation
(Tabl e s 2 and 4,Supplementary Fig. S1,Fig. 1).
There have been reports of differences in zonation [eg,
3], but there are no previous quantitative studies confirm-
ing them.
All the BNC granules on any one section showed similar
levels of expression of PAGs or lactogens or lectin reactivity,
although the levels of expression differed between the various
species and the PAGs, lactogens and lectins (Tabl e s 3 and 5,
Figs 1, 2, 3).
818 BNC protein distribution in Giraffe placenta, 2022, Vol. 106, No. 4
Ta b l e 3 . The immunoreactivity of the BNC in the Giraffoid clade
GIRAFFE OKAPI PRONGHORN
ANTIBODY Different
Placentomes
Different
animal
Different
Placentomes
Different
animal
“ancient”PAGs G1A G1B G2 P1 P1G P6
RA (+) (+) (+)+++ ++++ ++ ++
RD −−−+++ +++ ++ +++
BJ +Mend +Mend ++ ++ +++ ++
“new”PAGs
RB −−−++++ ++
RC +Mend −+++ ++ ++
RU ++Mend
only
+++Mend ++Mend + + + +
FPIR −−−+++ ++ ++
BC −−−−+++ ++ ++
BO −−− ++ ++++
Buffalo PAGs
BK +Mend −+++ ++ ++
BM −−−−−−−
Goat PAGs
BB ++Mend ++Mend +++ ++ ++ ++
BE ++Mend ++Mend +++Mend ++ +++ +++ ++
Ovine PAG
BN ++Mend ++Mend ++Mend ++ ++++
SBU3 −−−−−−−
Placental Lactogens
Friesen bPL ++Fend ++Fend +++Fend
BF ++Fend ++Fend ++Fend +
PROLACTIN ++Fend ++Fend ++Fend
LECTINS
DSA +++ +++ +++ ++ +++ +++
DBA + + + + +
ePHA ++ +++ +++ +++
lPHA ++ ++ ++ ++
Scale used: —, no reactivity, (+) sporadic/occasional: +,++,+++ indicate increasing levels of reactivity. Empty oblong: assessment not done. M/F ends:
Maternal or Fetal ends of the Fetal villus
In sharp contrast to the uniform immunoreactive BNC
distribution in the 13 species described above, the Giraffe
immunoreactive BNC distribution is unique. In this species
the placental BNC granules react with many fewer of the
antibodies used and when they do react it is in strictly localised
areas, either the top or bottom 25% of the fetal villus length
(Tabl e s 3 and 5). This is more difficult to recognise when the
entire length of the Giraffe sections are shown on Supplemen-
tal Fig. S2 and better appreciated at higher magnification on
Figs. 2, 3).
All the antibodies expressed in the top 25% are against
PAGs whereas all the basal group are anti PLs or Prolactin.
The prolactin expression is unique to Giraffe, and it seems def-
inite as the antibody can be absorbed against NIH prolactin
on both placentome and Horse anterior pituitary sections
(Supplementary Fig. S3).
One of the PLs (BF) does show a wider distribution than the
top 25% of the villus but with a rapidly decreasing frequency
towards the maternal end.
However localising giraffe BNC with the most strongly
reacting lectin clearly demonstrates a uniform distribution
throughout the fetal villi (Tabl e s 3 and 4,Figs. 2, 3).
The two other members of the giraffoid clade, Okapi
(Okapi johnstoni) and Pronghorn (Antilocapra americana)
show no zonation of immunoreactive BNC positioning and
their BNC react with many more of the antibodies than
the giraffe. (Ta ble 3) They also show individual differences
compared to the giraffe no Prolactin or placental lactogen
expression for example.
Discussion
This paper establishes the asymmetry of the PAG and the
PRL/lactogen distributions in the BNC granule content of the
Giraffe placentomal villi compared with the uniformity of
BNC granule content in the placentomal villi of all the other
ruminant groups investigated so far. This asymmetry is also in
contrast to the uniform distribution of the BNC in the Giraffe
placentomal villi as clearly indicated by the lectin content of
the BNC granules.
The Giraffe BNC granules react with many fewer of
the antibodies used here but do show a unique content of
PRL. This does not seem to be an artefact as shown by the
ability to absorb the reactivity with pure PRL in both the
giraffe placentome and the horse anterior pituitary sections
(Supplementary Fig. S3).
There is also a clear difference in type at the two ends of the
fetal villi with PRL and placental lactogens at the base and a
range of PAGs at the top.
These peculiarities are not shared by the other members of
the giraffoid clade, Okapi and Pronghorn, both of which show
similar distribution of BNC granule immunoreactivity to the
ruminant majority, although there are individual differences
Wooding et al., 2022, Vol. 106, No. 4 819
Figure 2. Giraffe placentomal fetal villus chorionic ends. Lactogen antibodies are present at the bases of the fetal chorionic villi (eg, at arrows); no BNCs
can be identified using PAG antibody; BNCs are localised throughout the villi the using lectin. Arrows indicate different levels of probably the same BNCs
on the sections using the lactogen antibody or lectin localisation. Scale bar =50 μm.
such as no reaction with the SBU3 or one of the Buffalo PAG
antibodies.
It is perhaps of interest that the only other placental PRL
trophoblast localisation reported is in the Elephant (Lox-
odonta africana) but the localisation is throughout the epithe-
lium [8] and not restricted to any specialised cells.
The lectins used in this investigation were chosen for
maximum reactivity. There are differences in lectin reactivity
between Giraffoids and the other ruminants which are
detailed in our previous papers [911].
The typical uniform BNC distribution with the unique
formation of fetomaternal tissue by migration and fusion was
established early in evolution as exemplified by the Tragulid
line [12], and probably was a key factor in the success of the
ruminant grouping. All of the mature ruminant placentas so
far investigated show this characteristic pattern as do the BNC
of Giraffe and Pronghorn [4].
There is no obvious or apparent functional reason for the
PAG asymmetry unless it is necessary to establish a high
concentration of PAGs in the caruncle. This could camouf lage
820 BNC protein distribution in Giraffe placenta, 2022, Vol. 106, No. 4
Figure 3. Giraffe placentomal fetal villus caruncular ends. PAG antibodies are present at the apices of the fetal chorionic villi (eg, at arrows); no BNCs can
be identified using lactogen antibody; BNCs are localised throughout the villi using lectin. Arrows indicate BNCs in very similar positions using the PAG
antibody or lectin localisation. Scale bar =50 μm.
the area from invasive maternal lymphocytes to maintain
the fetomaternal balance. This strategy has been suggested
to be the case in the development of the bovine placental
villi but no BNC asymmetry was necessary to produce that
[13].
PRL and lactogens are considered to play important roles
in the fetal metabolism but there is no reason to think that the
asymmetric localisation would speed up the delivery to the
fetus.
We have shown previously [2] that the stimulation of the
protein expression is very precisely localised since the villus
base (arcade) chorion presumably stimulates expression of
BNC PRL and the lactogens but no significant PAGs whereas
BNC in the adjacent intercotyledonary chorion express PAGs
but no PRL or lactogens.
Both giraffe placentomal samples show a very similar
unique BNC distribution and protein expression so it is
unlikely to be a methodological artefact. Also the even
Wooding et al., 2022, Vol. 106, No. 4 821
Ta b l e 4 . Quantitation of the number of immunoreactive BNC per mm2in four non giraffoid Ruminants
VILLUS COUNT AREA
SPECIES ANTIBODY OR LECTIN FETAL END 0 -50% n = 5 MATERNAL END 50 100%
n=5
COW(Bos taurus)BB 80±12 85 ±11
BC 90 ±695 ±9
BF 90 ±12 85 ±10
BG 88 ±10 85 ±15
BK 88 ±15 80 ±10
DBA 45 ±850 ±11
EWE (Ovis aries)RA 68 ±965 ±10
RB 36 ±840 ±11
ovinePL 28 ±10 30 ±8
bovinePL 30 ±832 ±10
TRAGULUS spp RU 48 ±14 50 ±10
PHA 61 ±969 ±10
PRONGHORN (Antilocapra americana)97±12 84 ±15
RU 78 ±11 69 ±12
DSA 68 ±770 ±7
No significant differences were detected between fetal and maternal end counts
Ta b l e 5 . Quantitative estimates of the number of immunoreactive BNC cells per mm2in Giraffe
Antibody or Lectin Villus count position
0 25% 25% -50% 50% -75% 75%- 100%
Animal Fetal end Maternal end
Giraffe A DSA 61 ±13 60 ±11 63 ±12 62 ±14
bovinePL 27 ±6 1 ±2 1 ±1 0
PRL 29 ±6 1 ±1 1 ±1 0
BF 67 ±227 ±811 ±2 5 ±2
BE 00065 ±16
RU 00060 ±9
Giraffe B DSA 56 ±958 ±11 55 ±11 56 ±12
bovinePL 28 ±1 3 ±1 2 ±1 1 ±1
ovinePL 14 ±2 0 0 0
PRL 24 ±1 0 0 0
BF 53 ±429 ±924 ±921 ±6
BE 00026 ±6
RU 00027 ±5
BB 00020 ±5
BJ 00014 ±7
BN 00015 ±5
No significant differences were detected between fetal and maternal end counts of the Lectins
distribution of the lectins here (and other antibodies used
previously [2]) throughout the giraffe sections support this
assumption.
Maybe it shows the versatility of the BNC system in solving
the problems of maternofetal immunological balance in the
extreme evolutionary niche occupied by the giraffe.
Supplementary material
Supplementary material is available at BIOLRE online.
Acknowledgements
The authors are very grateful to the many individuals (see
Supplementary Table S1) who provided the wide range of suitable
Ruminant samples.
Funding
This research did not receive any specific grant from any funding agency
in the public, commercial or not-for- profit sector.
Conflict of interest
There is no potential Conflict of Interest with any public or commercial
organisations.
Data availability
The data underlying this article are available in the article and in its
online supplementary material.
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... In Giraffe, as expected, all BNCs contain lectin binding granules throughout the fetal villus, but PAGs are only expressed in BNC at the tips and lactogen proteins are expressed only in the basal trophoblast BNC. Since the Giraffe BNCs show the normal migration and fusion process [32], this is another example of the flexibility of the BNC system [45]. ...
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Introduction The impala is a widely distributed African ungulate. Detailed studies of the placenta and ovaries in impala undertaken in the 1970s did not address the endocrine functions of the placenta. Methods The uteri of 25 pregnant impala estimated to be between 49 and 113 days of the 190 day gestation were examined grossly, histologically and immunohistochemically. Results A single corpus luteum was present in either maternal ovary but the conceptus was always situated in the right uterine horn. The fetal membranes extended to the tips of both uterine horns. The amnion was in intimate contact with, but not fused to, the allantochorion. Placentation was typically ruminant with fetal macrocotyledons attached to the rows of maternal caruncles. The fetal villi were highly branched, especially in the centre of each placentome where the attenuated maternal epithelium lining the placental crypts was absent in some places. Both the corpus luteum and the uninucleate trophoblast cells of the interplacentomal allantochorion stained strongly for 3-β hydroxysteroid dehydrogenase, and progestagen concentrations in allantoic and amniotic fluids increased significantly as gestation progressed, with a tendency to do likewise in maternal serum. Binucleate trophoblast cells stained positively for bovine placental lactogen, but neither the placenta nor the maternal corpus luteum showed evidence of oestrogen synthesis. Discussion Despite exhibiting the same basic type of placentation, both the gross and histological structure of the impala placenta, along with its immunohistochemical properties, demonstrates that great variation exists across ruminant placentas.
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Introduction: The unicellular trophoblast epithelium of all ruminants so far investigated contains 15-20% binucleate cells with numerous secretory granules. Electron microscope (EM) studies of the domesticated cow, ewe, goat and deer species have established that these BNC migrate out of the trophoblast epithelium to fuse with the apposed maternal uterine epithelial cells or derivative to form fetomaternal tissue throughout pregnancy. However there is one careful EM study of the trophoblast of a wild ruminant, the White-tail deer, which found the usual number of BNC but no evidence of any migration or fusion. Since there are up to 200 species of wild ruminants, it was important to establish whether there really are two possible scenarios for BNC function. Materials and methods: This paper reports a light microscope (LM) immunocytochemical study of cell dynamics in ruminant placentas using 1-2 mμ deresinated sections. Results: The results clearly demonstrate that the White-tail deer and all of the other 15 (see Table 1) randomly selected wild ruminants show the same BNC migration and fusion pattern. Discussion: These results suggest that this remarkable cellular behaviour is fundamental to the ruminant evolutionary success.
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Although the pronghorn (Antilocapra americana) resembles an antelope, its nearest relatives are the giraffe and okapi. In this study we have examined the placentae of 6 pronghorns using lectin- and immunocytochemistry to identify giraffid and bovid features. Binucleate cells (BNC) of the placenta exhibited features intermediate between those of the giraffe and bovine; Dolichos biflorus agglutinin binding – strong in the bovine BNC and absent in the giraffe – was evident in only a subpopulation of BNC while binding to blood vessels, as in the giraffe. Binding of Phytolacca americana agglutinin resembled that of the giraffe and okapi whereas many other glycans were found in all four clades. PAG antigens were similar to bovine and okapi but not giraffe. In summary, although the pronghorn outwardly resembles an antelope, placental BNC show giraffid features. Although each clade has its own individual characteristics, there are far more similarities than differences between them, emphasizing the common ancestry of all four clades.
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Science produces fascinating puzzles: why is there such a range of placental structures when other mammalian organs are so structurally uniform ? Why and how did the different placental structures evolve ? Comparative placental studies can facilitate the identification of the common factors in placental growth, differentiation and function and their relevance to possible evolutionary pathways. Comparative Placentation is the only book presenting up-to-date data illustrating the great variety of structure but uniform function of vertebrate placentas from fish to man. This information is essential for selection of suitable models to investigate particular practical problems of impaired or anomalous growth in human and animal placentation. The unique collection of the best light and electron micrographs from the last thirtyfive years which precisely illustrate the structural range in each taxon, make the book the most authoritative publication in this field and a vital source of information for anyone interested on reproductive physiology, anatomy and medicine.
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Pregnancy-associated glycoproteins (PAGs) are abundantly expressed products of the placenta of species within the Cetartiodactyla order (even-toed ungulates). They are restricted to this order and they are particularly numerous in the Bovidae. The PAGs exhibit a range of temporal and spatial expression patterns by the placental trophoblasts and probably represent a group of related proteins that perform a range of distinct functions in the epitheliochorial and synepitheliochorial placental forms. This review presents an overview of the origins of the PAGs, a summary of PAG expression patterns, and their use as markers of pregnancy status. Speculations about their putative role(s) in pregnancy are also presented. © 2015 Society for Reproduction and Fertility.
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The trophoblast binucleate cell [BNC] is central to the structure and function of all ruminant placentas so far investigated. The Giraffidae are considered to form a separate family within the ruminant suborder.Methods The structure and function of two [mid and late pregnant] giraffe placentas and two term okapi placentas have been investigated immunocytochemically.ResultsTheir major characteristics: polycotyledonary epitheliochorial structure, sequential glucose transport using two transporter isoforms, expression of water transporters in the interplacentomal [IP] and placentomal [P] trophoblast and restriction of calcium transport to the IP trophoblast are similar to those of the ruminant family Bovidae. . Giraffe and okapi also show characteristic ruminant trophoblast binucleate cells (BNC) which migrate and fuse with individual uterine epithelial cells as in the cow. However, there are many fewer BNC, of limited distribution, when compared with other ruminants so far investigated. The giraffe and okapi BNC also show a different range of proteins, Pregnancy Associated Glycoproteins (PAGs) and glycans which clearly distinguish the Giraffidae from the Bovidae.Conclusions The results support a separate giraffid family derived from a common ancestry, possessing subpopulations of BNC with potentially different functions.
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