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Pregnancy is the main event in the life of a female mammal to reproduce its progeny and maintain the integrity of the species. It is a very coordinated process involving reproductive organs and changes in the tissue concentration of various hormones, cytokines, enzymes and growth factors, of which hormones are most important. Various hormones are involved in the preparation of the uterus of ewe for conception of embryo, growth and development of embryo and foetus, maintenance of pregnancy and birth of a healthy lamb. However, pregnancy mainly involved two hormones, namely progesterone and oestrogens. Other hormones involved in this process are prostaglandin, cortisone, relaxin and oxytocin, which are mainly important for parturition. The endocrine changes in the ewe during the oestrous cycle, pregnancy and parturition dramatically affect the structure of the endometrium as well as the uterine immune system. During the 17-day oestrus cycle, progesterone dominates for about 13 days and oestrogens dominate for 3−4 days. In the pregnant ewe, oestogens are necessary for the growth and development of the ovarian follicles. However, once the ewe become pregnant progesterone become the key hormone to maintain the pregnancy and, therefore, known as 'pregnancy hormone'. Progesterone dominates until the onset of parturition when endometrium switches from a progesterone-dominated state to an oestrogen-dominated state. Therefore, this paper reviews the hormonal profiles and endocrinological changes that occur during oestrous cycle and different stages of pregnancy in the ewe. The paper also illustrates the important immunological changes of the uterus that occur with the endocrinological changes.
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J Agric Rural Dev 4(1&2), 1-7, June 2006 ISSN 1810-1860
JARD
Journal of Agriculture
& Rural Development
Hormonal Changes in the Uterus During Pregnancy Lessons from
the Ewe: A Review
ABU NASAR MD. AMINOOR RAHMAN *
School of Agriculture and Rural Development, Bangladesh Open University, Gazipur, Bangladesh
Received 18 July 2004; received in revised form 18 May 2005; accepted 22 June 2006
ABSTRACT
Pregnancy is the main event in the life of a female mammal to reproduce its progeny and maintain the
integrity of the species. It is a very coordinated process involving reproductive organs and changes in
the tissue concentration of various hormones, cytokines, enzymes and growth factors, of which
hormones are most important. Various hormones are involved in the preparation of the uterus of ewe
for conception of embryo, growth and development of embryo and foetus, maintenance of pregnancy
and birth of a healthy lamb. However, pregnancy mainly involved two hormones, namely
progesterone and oestrogens. Other hormones involved in this process are prostaglandin, cortisone,
relaxin and oxytocin, which are mainly important for parturition. The endocrine changes in the ewe
during the oestrous cycle, pregnancy and parturition dramatically affect the structure of the
endometrium as well as the uterine immune system. During the 17-day oestrus cycle, progesterone
dominates for about 13 days and oestrogens dominate for 34 days. In the pregnant ewe, oestogens
are necessary for the growth and development of the ovarian follicles. However, once the ewe
become pregnant progesterone become the key hormone to maintain the pregnancy and, therefore,
known as ‘pregnancy hormone’. Progesterone dominates until the onset of parturition when
endometrium switches from a progesterone-dominated state to an oestrogen-dominated state.
Therefore, this paper reviews the hormonal profiles and endocrinological changes that occur during
oestrous cycle and different stages of pregnancy in the ewe. The paper also illustrates the important
immunological changes of the uterus that occur with the endocrinological changes.
Key words: Oestrous cycle, pregnancy, parturition, endometrium, immune cells, ewe.
INTRODUCTION
Pregnancy is the most important event in the life of any female organism to reproduce its progeny. It is
a very coordinated process among the mammalian species involving reproductive organs and
hormones. The endocrine changes, i.e. changes in the profile of oestrogens and progesterone in
the ewe (female sheep) during the oestrous cycle, pregnancy and parturition dramatically affect the
structure of the endometrium as well as the uterine immune system. Hunter (1980), Pineda (1989),
Liggins and Thorburn (1994), and Lye (1996) have significant contribution in the sheep
reproductive endocrinology. It is to be mentioned here that the hormonal profiles in the ewe varies
those from the cow, the buffalo cow and the doe (female goat). Hormonal changes in the uterus might
also regulate the immune cells and immunity of the uterus. Therefore, it is important to understand the
* Corresponding author: Associate Professor, SARD, BOU. Phone: 603-0196186718, E-mail: aminoor69@yahoo.com
2006, School of Agriculture and Rural Development, Bangladesh Open University. All rights reserved.
A. N. M. A. Rahman
2
hormonal interaction that happens in the uterus of the ewe during oestrus cycle, pregnancy and
parturition. Although, the sheep in Bangladesh are non-descriptive type, however, they provide us meat
and carpet wool. So, if we can improve their productivity it may contribute to our national livestock
economy. Therefore, we need to be aware of the scientific information on the hormonal profiles and
changes in the uterus of ewe during pregnancy.
ENDOCRINE PROFILES OF THE OESTROUS CYCLE
Like other mammals, the uterus of the ewe is subject to morphological and functional changes
which span a 17-day oestrous cycle. The stages of the oestrous and reproductive cycles of the ewe
are briefly presented in Fig. 1.
Fig. 1. The oestrous and reproductive cycles of the ewe. Adapted from Pineda (Pineda, 1989)
Cyclic changes in the circulating levels of the ovarian hormones, progesterone and oestrogen have
direct effects on the growth and metabolism of cells in the reproductive tissues. The main events of
the oestrous cycle are related to the periods of growth of the ovarian follicles and the corpus
luteum. During the 17-day cycle, progesterone dominates for about 13 days and oestrogen
dominates for 34 days. The endocrine patterns of lutenizing hormone (LH), oestrogen (oestradiol),
progesterone and prostaglandin F
2
α
(PGF
2
α
) during the oestrous cycle in the ewe are presented in Fig. 2
.
Fig. 2. Changes in the concentration of progesterone and oestradiol during the oestrous cycle in the
ewe. Uterine PGF2α pulses prior to oestrous cause the demise of the corpus luteum resulting
in decreasing progesterone and elevated oestradiol levels and the occurrence of the oestrus.
Adapted from Caldwell and colleagues (1972)
Hormonal changes in the ewe uterus during pregnancy
3
Day 0 of the cycle is generally designated as the first day of behavioural oestrus, which is the result
of increasing oestrogen levels produced by the developing pre-ovulatory follicles. High oestrogen
levels are believed to cause a surge of gonadotrophin releasing hormone (GnRH) and
consequently an LH peak at oestrus resulting in spontaneous ovulation towards the end of oestrus.
Following ovulation the ruptured follicle becomes a functional corpus luteum, which is the main
source of progesterone in the cycling ewe. Blood levels of progesterone are low at oestrus (less
than 1.0 ng/ml) through to day 3 of dioestrous, and then rapidly increase to maximal levels at day 8,
and remain elevated until days 11
12 (Fig. 2). Regression of the corpus luteum (luteolysis), induced
by PGF2α, occurs if an embryo is not present in the uterus, resulting in a rapid drop in plasma
progesterone. Ovarian oxytocin stimulates endometrial secretion and release of prostaglandins.
The onset of the follicular phase of the next cycle is characterised by low progesterone levels and
increasing GnRH and LH levels, while the follicle-stimulating hormone (FSH) levels present at the
onset of this phase are progressively decreased. These events are controlled by oestrogen and
inhibin, which are produced in increasing amounts by the developing follicles.
ENDOCRINE PROFILES DURING PREGNANCY
Once mating and fertilization are successfully completed the trophoblast must signal its presence to
the maternal system to prevent luteolysis and maintain progesterone production, which is essential
for the establishment of pregnancy (Geisert and Malayer, 2000). The blastocyst, before it attaches
to the endometrium, secretes substances that directly or indirectly prolong the lifespan of the
corpus luteum and prevent a return to ovarian cyclicity (Jainudeen and Hafez, 2000). The timing of
this phenomenon is known as ‘maternal recognition of pregnancy’. The substance/molecule that
inhibits the synthesis and/or release of luteolytic PGF2α from the endometrial cells and prevent
corpus luteum regression (Bazer, 1989; Bazer et al., 1989) is an embryonic protein first known as
ovine trophoblast protein-1 (oTP-1) (Imakawa et al., 1987). The oTP-1 was later classified as ovine
interferon-tau (oIFN-τ) (Bazer et al., 1997), when it was found to be a member of the interferon
family. The oIFN-τ is a cytokine that acts locally on the uterine endometrium rather than
systemically (Jainudeen and Hafez, 2000). The oIFN-τ has antiluteolytic, immunosuppressive,
antiviral and possibly antiproliferative properties (Bazer, 1989; Bazer et al., 1989). The anti-
luteolytic effect of oTP-1 is dependant upon the presence of progesterone and endometrial
progesterone receptors (Ott et al., 1992). Granulocyte macrophage-colony stimulating factor (GM-
CSF), which is produced in the maternal uterine endometrium, stimulates the production of oIFN-τ
by the trophoblast (Imakawa et al., 1993). Secretion of oIFN-τ from the conceptus trophectoderm at
1215 days post coitus (dpc) in the ewe (Bazer et al., 1997) and 1417 dpc in the cow and the doe
(Bazer et al., 1997; Gnatek et al., 1989) is essential for maternal recognition of pregnancy.
Once the trophoblast established the ‘maternal recognition of pregnancy’ then it proceeds to the
next step for implantation into the luminal epithelium of the endometrium of the ewe. The
implantation event is accompanied by significant changes in the tissue concentration of various
cytokines, adhesion molecules, hormones, enzymes and growth factors, all of which may be crucial
in initiating the feto-maternal relationship (Rice and Chard, 1998; Saito, 2000). Like hormones,
cytokines are very important for maintaining pregnancy. While IFN-τ is important for ‘maternal
recognition of pregnancy’ other cytokines such as interleukin-1 beta (IL-1β), tumor growth factor
beta (TGF-β), IL-6, leukaemia inhibition factor (LIF), IL-10 are important for embryo growth and
development, and IL-6 and LIF are important for elongation of embryo and placentation (Rahman,
2002; Rahman et al., 2004). The reproductive hormones believed to interact and regulate these
cytokines in the uterus of the ewe (Rahman, 2002).
Progesterone is the key hormone of pregnancy and is thus often called the ‘pregnancy hormone’. It
acts to prevent the resumption of cyclicity, prepares the uterus for implantation and maintains
myometrial quiescence (Lye, 1996). Actually, myometrial quiescence during pregnancy is achieved
by the combined action of progesterone, relaxin, prostacyclin and nitric oxide (Lye, 1996). In the
cow, progesterone is found to stimulate the production of a variety of endometrial secretions, which
are required for the successful development of embryos (Geisert et al., 1992). Low concentrations
of progesterone in the ewe can lead to poor embryo development (Nephew et al., 1991) and
A. N. M. A. Rahman
4
progesterone supplementation enhances embryo growth in both the bovine (Garrett et al., 1988)
and the ovine (Kleemann et al., 1994) species. Together with oestrogen, progesterone acts to
transform the endometrium into a secretory tissue capable of supporting both the pre- and post-
implantation conceptus. The plasma concentration of progesterone during pregnancy in the ewe is
depicted in Fig. 3. The progesterone concentration in the peripheral plasma gradually rises from the
luteal phase level during the first half of pregnancy, markedly increases at about 90 dpc, peaks at
about 125 dpc (Bassett et al., 1969; Liggins and Thorburn, 1994; Thorburn et al., 1977) and falls in
the last few days before parturition (Bassett et al., 1969; Challis and Lye, 1994; Liggins and
Thorburn, 1994; Stabenfeldt et al., 1972). In the ewe, during the first third of pregnancy,
progesterone is produced by the corpus luteum, and as with humans (Lye, 1996), production is taken
over by the placenta at about 50 dpc and subsequent removal of the ovaries does not compromise
development of the foetus (Casida and Warwick, 1945; Denamur and Martinet, 1955).
Progesterone also believed to aid in the maintenance of uterine immune system during pregnancy in the
ewe (Rahman, 2002). It has been reported that a systemic hormonal signal of maternal or foetal
origin activates and increase the number of a specific immune cells in the uterine endometrium of
ewe (Majewski et al., 2001) which protect the foetus from maternal immune rejection. These cells
are known as intraepithelial large granulated lymphocytes (LGL) or gamma-delta TcR positive large
granulated lymphocytes (γδ TcR+ LGLs). Progesterone could be a prime candidate for this systemic
hormonal signal (Hansen, 1998). These γδ TcR+ LGLs remain highest level in the uterus of the ewe
throughout the final stage of pregnancy and even just before the onset of parturition (Rahman et
al., 2002).
Fig. 3. Progesterone levels in the peripheral plasma of the ewe throughout the pregnancy period.
Adapted from Bassett and colleagues (1969)
The major oestrogens present in the maternal plasma of the ewe are the sulpho-conjugates of oestrone
and oestradiol-17α, the concentration of which increases progressively from 70 dpc to parturition
(Carnegie and Robertson, 1978; Currie et al., 1973). Until 120 dpc, the concentration of free oestrone
and oestradiol-17β in the maternal plasma remains at a low level, but then increases gradually, before
undergoing a sudden and rapid rise in the last days of pregnancy (reviewed in Liggins and Thorburn,
1994). This dramatic increase in free oestrogens coincides with a major increase in the oestrogen
sulpho-conjugates in the foetal and maternal plasma (Liggins and Thorburn, 1994).
Prostaglandins, particularly PGF, are very important in the parturition of the ewe and the doe, with
increasing levels in the venous plasma in the last days before parturition (Liggins et al., 1972). The
concentration of progesterone, oestradiol-17α and PGF in the venous plasma of a doe during the
last week of pregnancy, parturition and post-partum is depicted in Fig. 4.
Hormonal changes in the ewe uterus during pregnancy
5
Fig. 4. Changes in the concentration of oestradiol-17α (¡), progesterone (---¨---) and
PGF () in the uterine venous plasma of a doe before and after parturition.
Adapted from Umo and colleagues (1976)
ENDOCRINE PROFILES AT PARTURITION
Parturition is the physiological process by which the pregnant uterus delivers the foetus/foetuses
and placenta from the mother. The onset of parturition is associated with a switch from a
progesterone-dominated state to an oestrogen-dominated state (Liggins and Thorburn, 1994). The
foetus of an ewe attains a weight of about 4 kilograms close to parturition. Parturition is triggered by
the foetus and is completed by a complex interaction of endocrine, neural, and mechanical factors
(Jainudeen and Hafez, 2000) in which both the foetal and maternal mechanisms play essential
roles. In the ewe, the foetal endocrine system plays a major role. During the final stage of
gestation, the production and secretion of cortisol by the foetal adrenal gland (Bazer and First,
1983; Thorburn, 1991) induces a fall in the maternal progesterone concentration, which initiates
parturition. This cortisol induces the placental 17α-hydroxylase to catalyse the conversion of
progesterone to oestrogen (Liggins and Thorburn, 1994) resulting in increased oestrogen:
progesterone ratios, which play an important role in the increased synthesis and release of
prostaglandins, activation of the myometrium and ripening of the cervix (Challis and Lye, 1994).
Prostaglandins, particularly PGF, play a central role in myometrial contraction, which begins 618
hours before delivery (Lye, 1996). Along with relaxin, oestrogen causes a relaxation of the birth
canal, especially the cervix and the vagina (McDonald, 1989), and helps to facilitate the birth of the
foetus. Oxytocin is not a pre-requisite for the parturition in the ewe (Liggins and Thorburn, 1994)
but it facilitates the delivery of the foetus and placenta by inducing forceful uterine contractions
(Glatz et al., 1981).
It has been reported that at the onset of parturition when progesterone concentration decline in
the blood plasma a dramatic decline in the proportion of γδ TcR+ LGLs occur (Fox et al., 1998,
Rahman et al., 2002). This is mainly due to the apoptosis of LGL in the luminal epithelium and
migration of these cells to the uterine lumen (Rahman et al., 2002). Withdrawal of progesterone
during the onset of parturition (Basset et al., 1969; Wooding and Flint, 1994), which could in turn
cause the onset of apoptosis, would lead to the disappearance of the LGLs (Rahman et al., 2002).
It has also been reported that the LGLs seem to play a major role through de-granulation to
facilitate detachment of fetal membranes and to protect the uterus from microbial infection at a time
when the uterine cervix is open to the environment (Rahman, 2002; Rahman et al., 2002).
A. N. M. A. Rahman
6
Therefore, the interaction of hormones with immune cells have very important roles in the healthy
birth of a lamb as well as for the protection of infection and maintenance of uterine integrity in the ewe.
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... We could not find any reference to ISG15 mRNA and ISG17 mRNA levels at 7 days post NM. Blood concentration of P4 in estrus is low (less than 1.0 ng/ ml) through day 2 of diestrus and then quickly increases to maximum concentrations at 7 days, and remains elevated for up to days 13-15 following estrus (Rahman, 2006). Therefore, no difference between concentrations of serum P4 of both pregnant and non-pregnant occurs on days 1-7 from the estrous cycle, but regression of the corpus luteum (luteolysis), induced by prostaglandin F2, (PGF 2α ), occurs if an embryo is not present in the uterus, which leads to rapid decline in plasma P4 (Rahman, 2006). ...
... Blood concentration of P4 in estrus is low (less than 1.0 ng/ ml) through day 2 of diestrus and then quickly increases to maximum concentrations at 7 days, and remains elevated for up to days 13-15 following estrus (Rahman, 2006). Therefore, no difference between concentrations of serum P4 of both pregnant and non-pregnant occurs on days 1-7 from the estrous cycle, but regression of the corpus luteum (luteolysis), induced by prostaglandin F2, (PGF 2α ), occurs if an embryo is not present in the uterus, which leads to rapid decline in plasma P4 (Rahman, 2006). Conversely, when an embryo is present in the uterus PGF 2α secretion is inhibited. ...
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Authors' Contribution KS and MH designed and performed the experiment. HM and MA analysed the data and helped in reviewing the manuscript. SG and HM finalized the writing. The accuracy of interferon-stimulated gene 15 (ISG15) and interferon-stimulated gene 17 (ISG17) mRNA levels in early detection of pregnancy in Aardi goats compared to progesterone and ultrasound (US) were evaluated. Female goats were synchronized using the ovsynch protocol level in combination with natural mating (NM). Blood samples were collected at 1, 7, 15, 23, 35, and 60 days post NM. Levels of ISG15 and ISG17 mRNAs were assayed using real-time PCR, and serum progesterone (P4) concentrations were assayed using an ELISA kit. Pregnancy detection was performed by US on 23, 35, and 60 days post NM. Serum P4 concentration was significantly higher in pregnant than non-pregnant goats at 15, 23, 35, and 60 days post NM. Relative expression of mRNA of ISG15 and ISG17 was significantly higher in pregnant goats at 7, 15, and 35 days post NM. ISG15 and ISG17 were not significantly different compared to P4 and US in the pregnant and non-pregnant goats. The accuracy of ISG15 and ISG17 was not significantly different than P4 on days 7 and 15 or from P4 and US on day 23 post NM. Decreased accuracy of ISG15 and ISG17 on day 35 might be done to lower levels. US provided accurate pregnancy diagnoses on day 35 (96.97%) and 60 (100%) post NM. ISG15 and ISG17 mRNA levels could be considered good indicators of goat pregnancy on day 23 post NM. These methods will provide early and precise detection of pregnancy compared to the routinely used serum P4 and US methods.
... In sheep, estrogens predominate for approximately 3-4 days in the estrous cycle, while progesterone predominates for about 13 days. The latter becomes the main hormone during pregnancy, reaching a maximum concentration around 130 days (Rahman, 2006). Similar to hArg, the retrospective analysis of the earlier study shows that progesterone concentrations were also higher in ewes bearing-multiple fetuses (Fig. 3). ...
Article
A striking increase in homoarginine concentrations, about more than 100-fold that observed in humans, was recently reported during pregnancy in a nutritionally induced model of intra-uterine growth restriction in ewes. To determine whether this phenomenon is at least partially related to the nutritional regimen, estrus synchronization, or analytical method, thirty-four one-year-old primiparous, non-synchronized, and well-fed Sarda breed ewes were exposed to fertile rams allowing those who came into estrus to naturally mate. Plasma arginine, homoarginine, asymmetric dimethylarginine, symmetric dimethylarginine, mono methylarginine, and citrulline concentrations were measured in each sample using LC-MS/MS. Homoarginine concentrations showed a 44-fold variation between the highest and the lowest values while the fluctuations of arginine and its analogues and metabolites were much smaller, between 1.1 and 1.6-fold. Repeated-measures correlation analysis showed a significant negative correlation between homoarginine/arginine and arginine/asymmetric dimethylarginine ratios (Rm = −0.40; P < 0.000001). Furthermore, median homoarginine concentrations significantly increased with the number of fetuses. The marked increase in homoarginine concentrations with advancing gestational age is genuine and independent of mating, feeding, diet, and hormone treatment. The higher homoarginine concentrations found in ewes bearing multiple fetuses suggest the presence of a physiological link between this arginine analog and energy metabolism in pregnancy that warrants further investigation.
... Sheep will often have multiples at birth, which can be physically challenging, stressful and a painful process for the mother and offspring that may require a farmer's intervention [10]. The parturition period is associated with several physiological, hormonal and behavioral changes in the pregnant animal, with restless behavior exhibited by nesting and reduced appetite along with birth contractions, which increase in frequency and intensity as birth progresses [10,11]. Studying cows, Huzzy et al. [12] found a dramatic increase in the number of positional changes such as lying or standing at calving, and reported that the animals tended to isolate themselves from the rest of the herd. ...
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The aim of this study was to assess the duration and frequency of behavioral observations of pregnant ewes as they approached lambing. An understanding of behavioral changes before birth may provide opportunities for enhanced visual monitoring at this critical stage in the animal’s life. Behavioral observations for 17 ewes in late pregnancy were recorded during two separate time periods, which were 4 to 6 weeks before lambing and before giving birth. It was normal farm procedure for the sheep to come indoors for 6 weeks of close monitoring before lambing. The behaviors of standing, lying, walking, shuffling and contraction behaviors were recorded for each animal during both time periods. Over both time periods, the ewes spent a large proportion of their time either lying (0.40) or standing (0.42), with a higher frequency of standing (0.40) and shuffling (0.28) bouts than other behaviors. In the time period before giving birth, the frequency of lying and contraction bouts increased and the standing and walking bouts decreased, with a higher frequency of walking bouts in ewes that had an assisted lambing. The monitoring of behavioral patterns, such as lying and contractions, could be used as an alert to the progress of parturition.
... Estrogen is essential for the growth and development of the ovarian follicles, while, once pregnant, progesterone would become the crucial hormone that maintain pregnancy. At the time of delivery, the content of estrogen decreases greatly but progesterone reaches a high level above usual condition (Rahman, 2006). Therefore, AM recovered the postpartum sex hormone levels to normal state. ...
Article
Background Apios Americana Medicus (AM), a potential staple food substitution characterized as mass production, abundant nutrition and low cost, has been consumed with a long history in eastern North American. Nowadays, AM have been cultured, consumed and studied worldwide. Nevertheless, present studies focused on AM are mainly about its nutritional values, chemical compositions and biological activities, whereas these studies only remain at their infancy, and investigations concerning AM's deep processing and application are still insufficient. Besides, current studies have dedicated to learn edible AM tuber (AMT), while less studies paid attention other parts, such as flower, leaf and vine. Scope and approach In this review, we comprehensively reviewed and analyzed the current research progress of AM based on the literature published from 1924 to 2021, then systematically categorized and summarized the bioactive substances in different parts, presented and exemplified their biological activities. Furthermore, we have also thoroughly discussed the present shortage and challenges that AM faces, and predicted AM's possible orientation and perspectives in the future. Key findings and conclusions AM has abundant bioactive chemicals in different parts, and demonstrates remarkable bioactivities in antioxidant, anti-inflammation, anti-diabetes, anti-atherosclerosis, anti-hypertension, immunoregulation, anti-tumor and improvement in post-partum uterine involution. Therefore, it is suggested that AM shows potential to become future staple food candidate with diverse bioactivities, which would enlighten some innovate ideas on increasing farmers’ income, and provide potential promising strategies to solve global hunger.
... These observations agree with the results obtained by Guseva et al. (2003) [10], who observed that female swine cells collected from the reproductive tract in the estrogen-dominant phase of the oestrous cycle were more susceptible to Chlamydia suis infection than cells obtained in the progesterone-dominant phase. Finally, it has been shown that the recrudescence of C. abortus in late-term pregnancy in sheep coincides with the marked physiological change in the serum estradiol/ progesterone ratio that takes place during the final stage of gestation [11]. ...
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Background: Chlamydia abortus, an obligate intracellular pathogen with an affinity for placenta, causes reproductive failure. In non-pregnant animals, an initial latent infection is established until the next gestation, when the microorganism is reactivated, causing abortion. The precise mechanisms that trigger the awakening of C. abortus are still unknown. Sexual hormones such as estradiol and progesterone have been shown to affect the outcome of infection in other species of the family Chlamydiaceae, while estrogens increase chlamydial infection, progesterone has the opposite effect. To try to establish whether there is a relationship between these events and the latency/ reactivation of C. abortus in the reproductive tract of small ruminants, ovine endometrial (LE) and trophoblastic (AH-1) cells were treated with estradiol or progesterone prior to their infection with C. abortus. The results are compared with those obtained for treatment with penicillin prior to infection, which is a well-established model for studying persistent infection in other chlamydial species. Cells were examined by transmission electron microscopy, and an mRNA expression analysis of 16 genes related to the chlamydial developmental cycle was made. Results: The changes observed in this study by the action of sex hormones seem to depend on the type of cell where the infection develops. In addition, while the changes are morphologically similar to those induced by treatment with penicillin, the patterns of gene expression are different. Gene expression patterns therefore, seem to depend on the persistence induced models of C. abortus used. Hormone treatments induced aberrant forms in infected endometrial cells but did not affect the chlamydial morphology in trophoblast cells. At the genetic level, hormones did not induce significant changes in the expression of the studied genes. Conclusions: The results suggest that penicillin induces a state of persistence in in vitro cultured C. abortus with characteristic morphological features and gene transcriptional patterns. However, the influence of hormones on the C. abortus developmental cycle is mediated by changes in the host cell environment. Furthermore, a persistent state in C. abortus cannot be characterised by a single profile of gene expression pattern, but may change depending on the model used to induce persistence.
... As mechanism of prostaglandin action requires active CL presence, serum progesterone concentration should be elevated at the time of PG application. As stated by Nasar and Rahman [ 14 ], blood levels of progesterone are low at oestrus (less than 1.0 ng/ml) through to day 3 of dioestrus, and then rapidly increase to maximal levels at day 8, and remain elevated until days 11-12. However, in the present study, initial levels of serum progesterone, measured at the time of PG injection, were not indicative of CL presence, but ewes that responded to treatment had higher serum progesterone level (0.47 and 0.95 ng/mL) than nonresponsive ewes (0.02 and 0.44 ng/mL). ...
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The study investigates the possibility of oestrus synchronization in ewes of MIS sheep population using prostaglandin (PG) outside the breeding season, serum progesterone concentration for pregnancy diagnosis and effect of hCG (human chorionic gonadotropin) on reproductive parameters. Prostaglandin was used to induce oestrus at the dose of 2.5 ml/ewe, administered intramuscularly in two injections (with 11 days interval). Responsive ewes were bred to rams and were divided into two groups, one of which was administered with hCG at the dose of 300 IU i/m 7th day post mating and the second group which was used as a control. Serum progesterone was measured on the day of prostaglandin administration and 17 days post mating. Oestrus response was 66.67%, lambing rate was 70%, average litter size was 1.7 lambs/ewe and twinning rate was 60%. Administration of hCG 7 days post mating did not improve fertility results. Lambing, prolificacy and twinning rates were higher in control than in hCG group, but no statistical difference was found between these groups. From a total of 20 ewes that were mated after PG treatment in 18 of them (90%), on the basis of progesterone concentration measured on the 17th day after mating and subsequent lambing results, gestation was confirmed or denied.
... Implantation and decidualization are tightly regulated by common endocrine changes. In women, menstrual cycle, early pregnancy, and parturition processes are marked by immune homeostasis and endocrine regulation (Nasar and Rahaman, 2006;Singh et al., 2011). Accommodation of semiallogeneic transplant as well as implantation, decidualization and parturition are supported by steroid hormones (Progesterone, estradiol, corticosteroids) and peptide hormones (human chronic gonadotropin, prolactin, relaxin, oxytocin) (Schumacher et al., 2014). ...
Article
The success of pregnancy depends mostly on a synchronized immune-endocrine crosstalk at the maternal-fetal interface. Hormones are important in terms of maintaining the suitable environment and sufficient nutrition for the developing fetus. They also play a major role during the process of parturition and lactation. Maternal immunomodulation is important for the tolerance of semiallogeneic fetus. This is achieved in concert with a variety of endocrine stimulation. Estrogen, progesterone, and Human Chorionic Gonadotropin play a major role in immune modulation during pregnancy. Hormones modulate B cells, dendritic cells, uterine natural killer cells, macrophages, neutrophils to adopt fetal friendly immune phenotypes. Recently the use of hormones in assisted reproductive technology has been found to improve the pregnancy outcome. The present review focuses on the pregnancy-related hormones, their role in immunomodulation for successful pregnancy outcome. This also shed light on the immune-endocrine crosstalk at maternal-fetal interface during pregnancy.
... In livestock systems, based on grazing and concentrate supplementation at milking, BCS monitoring is very essential to allow rapid changes in the dietary management in animals with low condition score (Molina et al., 1991). Progesterone, " the hormone of gestation " , is the key hormone important for preparing the uterus for implantation and maintaining myometrial quiescence (Rahman, 2006). The inspection of blood progesterone as well as ultrasonography are commonly used to determine the number of fetuses in pregnant animals (Medan et al., 2004) which is important for organizing the technological regimen of feeding and breeding, herd replacement, and to protect animals from metabolic diseases during the late stage of pregnancy. ...
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This study aimed at evaluating the effect of reproductive stage on nutritional status, and hormonal and trace mineral levels in sheep and goats reared in harsh arid conditions in South Sinai, Egypt. Egyptian local breeds of sheep (n=74) and goats (n=58) raised in South Sinai were examined by means of transabdominal ultrasonography to verify single vs. multiple feti pregnancy or non-pregnant status. Serum samples were collected for assessment of progesterone and trace minerals (selenium (Se), zinc (Zn), copper (Cu) and iron (Fe)) levels. Evaluation of the nutritional status of animal flocks showed that the mean body condition score was below the average levels, but did vary noticeably with pregnancy or between sheep and goats. Serum progesterone concentrations were significantly higher in pregnant animals with multiple fetuses than those bearing single fetus (p < 0.01), and both were higher than the respective values in non-pregnant animals (p < 0.001). Serum trace mineral levels were too low with no significant differences caused by pregnancy, number of fetuses or animal species. From these results, we could conclude that the state of pregnancy and fetal number have a significant influence on serum levels of progesterone. However, the harsh conditions in South Sinai in terms of scarce precipitation, low cultivation chances and high water salinity are the major factors influencing nutritional status or trace mineral levels in the reared small ruminants, regardless of the reproductive state or species.
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Selenium is a mineral that contributes to animal reproduction. The objective of this work was to evaluate conception rate and progesterone concentration in landrace ewes, during the reproductive season by organic selenium intake. 27 multiparous ewes were used with a body condition of 2.5; two groups were randomly designed: 11 ewes without selenium and 16 with selenium. Estrus was synchronized with intravaginal sponges containing fluorogestone acetate for 14 days, at the time of sponges removal, application of 400 UI of eCG was made. Artificial insemination (IA) was developed at a fixed time (55 hours after removal of sponges), consecutive application of 0.3 ppm day-1 of oral organic selenium was started seven days before IA. Progesterone concentration was evaluated in blood samples obtained along one estrus cycle (21 days), gestation diagnosis was developed at 35 days after the IA. Progesterone concentrations, between without selenium (5.28 ng mL-1) and treatment with organic selenium (6.58 ng mL-1), were not different between groups or between days (p ≥ 0.05), although in both groups the maximum progesterone concentration was observed on day 14 after the IA, in coincidence with a normal corpus luteum time. Also, conception rate was not different (p ≥ 0.05); in the group without selenium 81.8 % and with organic selenium 75 %. Based on the results, it is concluded that organic selenium application for seven days before IA did not influence progesterone concentration and conception rate in ewes.
Chapter
Intrauterine migration and equidistant spacing between embryos is essential to embryonic survival in polytocous species. The conceptus of the mare probably demonstrates a spectacular form of intrauterine migration of any species. Following hatching from its zona pellucida, the equine conceptus is surrounded by an acellular capsule that forms between the trophoblast and zona when the embryo enters the uterus on day 5. The origin of the capsule appears to be from uterine secretions. The capsule remains for several weeks and may play a role in conceptus migration and protection. During and following implantation in domestic farm animals, an outgrowth of extraembryonic mesoderm originates from the embryoblast, and migrates between the trophectoderm and endoderm. This mesodermal layer splits and combines with the trophectoderm to form the yolk sac. The mesoderm also contributes to formation of the amnion and the allantois, which is formed from an outgrowth of the embryo hindgut.
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This review of vertebrate placental structure attempts to integrate some of the considerable body of work done using electron microscopic and other techniques since Amoroso’s classic 1952 chapter. The reference list concentrates on the most recent work. Mossman (1987) provides the best comprehensive list of placental references. This chapter is mainly concerned with providing data to facilitate broad comparisons of structures and secretions both during development and in their final form with a view to relating them to the functional activity of the placenta. The remarkably wide variety of structures in the mature placenta develops from a basically similar repertoire of extraembryonic membranes as typified in the amniote egg, and the diversity can be further simplified by use of straightforward structural criteria. The major problem is to relate those criteria to the wide range of functions served by the placenta. A few non-amniotes have developed analogous structures which serve similar functions to the extraembryonic membranes, and these offer further insights into the requirements for successful fetal development (Hagan, 1951; Woollacott and Zimmer, 1975; Amoroso et al., 1979; Bone et al., 1985).
Article
Dysfunctional parturition is a major contributor to perinatal mortality and morbidity, yet our knowledge of the mechanisms that initiate labor is limited. While the endocrine profiles across species are quite diverse, several common threads are apparent, foremost of which is a requirement for progesterone to maintain pregnancy. I propose that at term, progesterone must be physically or functionally removed, resulting in a switch from a progesterone dominated to an estrogen dominated system. This increase in the estrogen:progesterone ratio causes the mobilization of two parallel molecular/biochemical pathways. One leads to myometrial ACTIVATION, an increase in myometrial spontaneous excitability, responsiveness to uterotonic stimulants and cell-cell coupling as a result of the increased expression of a cassette of ‘contraction-associated’ proteins, such as ion channels, agonist receptors and gap junctions. The other leads to the increased production and release of the uterotonic agonists to STIMULATE the activated myometrium. The temporal coordination and synchronzation of these pathways ensures the efficient and expeditious delivery of the fetus(es). Understanding the mechanisms regulating these pathways should enable the development of protocols to prevent premature labor in women, and also effectively manipulate the timing of birth in domestic species, thereby reducing perinatal loss and enhancing productivity.
Article
Experimental evidence from the sheep and other species is used to develop a hypothetical model of the mechanisms involved in protection of the ruminant placenta from maternal immunological attack. According to this model, the trophoblast is at risk of cytolysis mediated by cytolytic αβ-T cell receptor (TCR)+ T cells and cells of the natural killer lineage. Destruction of trophoblast cells is inhibited through several processes. First, expression of major histocompatibility proteins on the trophoblast is limited. Moreover, several types of molecules are secreted locally that inhibit lymphocyte activation. These include molecules produced by the trophoblast (e.g. interferon-τ (IFN) and prostaglandin E2 (PGE2)) and endometrium (e.g. PGE2 and uterine milk proteins (UTMP)) as well as inhibitory cytokines such as transforming growth factor-β from activated luminal γδ TCR+ cells. In addition to producing suppressor factors, activated luminal γδ TCR+ lymphocytes may also secrete cytokines that stimulate placental growth and hormone secretion.