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Cite this page: Hill, M.A. (2020, October 19) Embryology Sheep Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Talk:Sheep_Development
10 Most Recent Papers
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<pubmed limit=5>Sheep Development</pubmed>
<pubmed limit=5>Sheep Embryology</pubmed>
A stereotaxic, population-averaged T1w ovine brain atlas including cerebral morphology and tissue volumes
Front Neuroanat. 2015 Jun 4;9:69. doi: 10.3389/fnana.2015.00069. eCollection 2015.
Nitzsche B1, Frey S2, Collins LD2, Seeger J3, Lobsien D4, Dreyer A5, Kirsten H6, Stoffel MH7, Fonov VS2, Boltze J8.
Standard stereotaxic reference systems play a key role in human brain studies. Stereotaxic coordinate systems have also been developed for experimental animals including non-human primates, dogs, and rodents. However, they are lacking for other species being relevant in experimental neuroscience including sheep. Here, we present a spatial, unbiased ovine brain template with tissue probability maps (TPM) that offer a detailed stereotaxic reference frame for anatomical features and localization of brain areas, thereby enabling inter-individual and cross-study comparability. Three-dimensional data sets from healthy adult Merino sheep (Ovis orientalis aries, 12 ewes and 26 neutered rams) were acquired on a 1.5 T Philips MRI using a T1w sequence. Data were averaged by linear and non-linear registration algorithms. Moreover, animals were subjected to detailed brain volume analysis including examinations with respect to body weight (BW), age, and sex. The created T1w brain template provides an appropriate population-averaged ovine brain anatomy in a spatial standard coordinate system. Additionally, TPM for gray (GM) and white (WM) matter as well as cerebrospinal fluid (CSF) classification enabled automatic prior-based tissue segmentation using statistical parametric mapping (SPM). Overall, a positive correlation of GM volume and BW explained about 15% of the variance of GM while a positive correlation between WM and age was found. Absolute tissue volume differences were not detected, indeed ewes showed significantly more GM per bodyweight as compared to neutered rams. The created framework including spatial brain template and TPM represent a useful tool for unbiased automatic image preprocessing and morphological characterization in sheep. Therefore, the reported results may serve as a starting point for further experimental and/or translational research aiming at in vivo analysis in this species. KEYWORDS: SPM; atlas; brain; sheep; stereotaxy; structural MRI; tissue segmentation
Development of morulae from the oocytes of cultured sheep preantral follicles
Arunakumari G, Shanmugasundaram N, Rao VH. Theriogenology. 2010 Sep 15;74(5):884-94. Epub 2010 Jul 7. PMID: 20615540
LH pulse frequency and the emergence and growth of ovarian antral follicular waves in the ewe during the luteal phase of the estrous cycle
Seekallu SV, Toosi BM, Rawlings NC. Reprod Biol Endocrinol. 2009 Jul 28;7:78. PMID: 19638235
Pregnancy recognition and conceptus implantation in domestic ruminants: roles of progesterone, interferons and endogenous retroviruses
Reprod Fertil Dev. 2007;19(1):65-78.
Spencer TE, Johnson GA, Bazer FW, Burghardt RC, Palmarini M.
Center for Animal Biotechnology andGenomics, Department of Animal Science, Texas A&M University, College Station, TX 77843, USA. email@example.com Abstract The present review highlights new information on pregnancy recognition and conceptus development and implantation in sheep with respect to regulation by progesterone, interferons and endogenous retroviruses. After formation of the corpus luteum, progesterone acts on the endometrium and stimulates blastocyst growth and elongation to a filamentous conceptus (embryo/fetus and associated extra-embryonic membranes). The envelope of endogenous retroviruses related to Jaagsiekte sheep retroviruses appears to intrinsically regulate mononuclear trophectoderm cell proliferation and differentiation into trophoblast giant binucleate cells. The mononuclear trophectoderm cells of elongating sheep conceptuses secrete interferon-tau, which acts on the endometrium to prevent development of the luteolytic mechanism by inhibiting transcription of the gene for the oestrogen receptor alpha in the luminal and superficial ductal glandular epithelia. These actions prevent oestrogen-induced transcription of the oxytocin receptor gene and, therefore, oxytocin-induced luteolytic pulses of prostaglandin F2alpha. Progesterone down regulation of its receptors in luminal and glandular epithelia correlates temporally with a reduction in anti-adhesive mucin land induction of secreted galectin 15 (LGALSI5) and secreted phosphoprotein 1, which are proposed to regulate trophectoderm proliferation and adhesion. Interferon-c acts on the endometrial lumenal epithelium to induce WNT7A and to stimulate LGALS 15, cathepsin L and cystatin C, which are candidate regulators of conceptus development and implantation. The number of potential contributors to maternal recognition and establishment of pregnancy continues to grow and this highlights our limited appreciation of the complexity of the key molecules and signal transduction pathways that intersect during these key developmental processes. The goal of improving reproductive efficiency by preventing embryonic losses that occur during the peri-implantation period of pregnancy in domestic ruminants provides the challenge to increase our knowledge of endometrial function and conceptus development.
Ontogeny and nutritional programming of uncoupling protein-2 and glucocorticoid receptor mRNA in the ovine lung
J Physiol. 2005 May 15;565(Pt 1):159-69. Epub 2005 Mar 17.
Gnanalingham MG, Mostyn A, Dandrea J, Yakubu DP, Symonds ME, Stephenson T. Source Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, UK.
This study investigated the developmental and nutritional programming of uncoupling protein-2 (UCP2), glucocorticoid receptor (GR) and 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) mRNA in the sheep lung from the time of uterine attachment to 6 months of age. The effect of maternal nutrient restriction on lung development was determined in early to mid gestation (i.e. 28-80 days gestation, period of maximal placental growth, and embryonic and pseudoglandular stages of fetal lung development) and late gestation (i.e. 110-147 days gestation, period of maximal fetal growth, and canalicular and saccular stages of fetal lung development). Fetal lungs were sampled at 80 and 140 days (term approximately 148 days) gestation, and sheep lungs at 1, 7, 30 days and 6 months. GR and 11betaHSD1 mRNA were maximal at 140 days gestation, whereas UCP2 mRNA peaked at 1 day of age and then declined with postnatal age. Maternal nutrient restriction in both early-to-mid and late gestation had no effect on lung weight, but increased UCP2, GR and 11betaHSD1 mRNA abundance at every sampling age. These findings suggest that the developmental ontogeny of UCP2 mRNA in the ovine lung is under local glucocorticoid hormone action and that maternal nutrient restriction has long-term consequences for UCP2 and GR mRNA abundance in the lung irrespective of its timing.
Fig 1 Phases of fetal lung development and postnatal lung growth in relation to periods of maternal nutrient restriction in the sheep
phases of fetal lung development are as follows:
- embryonic, 0–40 days
- pseudoglandular, 40–80 days
- canalicular, 80–120 days
- saccular, 120 to term 148 days gestation.
Implantation mechanisms: insights from the sheep
Reproduction. 2004 Dec;128(6):657-68.
Spencer TE, Johnson GA, Bazer FW, Burghardt RC.
Center for Animal Biotechnology and Genomics, Animal Science and Veterinary Anatomy and Public Health, Texas A&M University, College Station, Texas 77843, USA. firstname.lastname@example.org Abstract Implantation in all mammals involves shedding of the zona pellucida, followed by orientation, apposition, attachment and adhesion of the blastocyst to the endometrium. Endometrial invasion does not occur in domestic ruminants; thus, definitive implantation is achieved by adhesion of the mononuclear trophoblast cells to the endometrial lumenal epithelium (LE) and formation of syncytia by the fusion of trophoblast binucleate cells with the LE. This review highlights new information on mechanisms regulating the implantation cascade in sheep. The embryo enters the uterus on day 4 at the morula stage of development and then develops into a blastocyst by day 6. The blastocyst sheds the zona pellucida (day 8), elongates to a filamentous form (days 11-16), and adheres to the endometrial LE (day 16). Between days 14 and 16, the binucleate cells begin to differentiate in the trophoblast and subsequently migrate and fuse with the endometrial LE to form syncytia. Continuous exposure of the endometrium to progesterone in early pregnancy downregulates the progesterone receptors in the epithelia, a process which is associated with loss of the cell-surface mucin MUC1 and induction of several secreted adhesion proteins. Recurrent early pregnancy loss in the uterine gland knockout ewe model indicates that secretions of the endometrial epithelia have a physiologic role in blastocyst elongation and implantation. A number of endometrial proteins have been identified as potential regulators of blastocyst development and implantation in sheep, including glycosylated cell adhesion molecule 1 (GlyCAM-1), galectin-15, integrins and osteopontin. The epithelial derived secreted adhesion proteins (GlyCAM-1, galectin-15 and osteopontin) are expressed in a dynamic temporal and spatial manner and regulated by progesterone and/or interferon tau, which is the pregnancy recognition signal produced by the trophoblast during blastocyst elongation. The noninvasive and protracted nature of implantation in domestic animals provides valuable opportunities to investigate fundamental processes of implantation that are shared among all mammals. Understanding of the cellular and molecular signals that regulate uterine receptivity and implantation can be used to diagnose and identify causes of recurrent pregnancy loss and to improve pregnancy outcome in domestic animals and humans.
Biology of progesterone action during pregnancy recognition and maintenance of pregnancy
Front Biosci. 2002 Sep 1;7:d1879-98.
Spencer TE, Bazer FW.
Center for Animal Biotechnology and Genomics and Department of Animal Science, Texas AM University, College Station, Texas 77843-2471, USA. Abstract Progesterone is the hormone of pregnancy and unequivocally required in all mammals for maternal support of conceptus (embryo/fetus and associated membranes) survival and development. The actions of progesterone are mediated by the progesterone receptor (PR). However, the endometrial lumenal (LE) and glandular epithelia (GE) of a number of species exhibit a loss of PR expression prior to the stages of uterine receptivity and implantation. In sheep, PR expression becomes undetectable in the endometrial LE after Day 11 and then in the GE after Day 13. Loss of PR in the GE appears to be required for onset of differentiated functions in terms of production of secretory proteins, such as uterine milk proteins (UTMP) and osteopontin (OPN). Therefore, the actions of progesterone on endometrial epithelia during most of gestation appear to be mediated by the endometrial stroma that remains PR-positive throughout pregnancy. Stromal cells produce several growth factors, such as hepatocyte growth factor (HGF) and fibroblast growth factors-7 and -10 (FGF-7, FGF-10), that have receptors expressed specifically in the endometrial epithelia. These factors may be progesterone-responsive and mediate epithelial-mesenchymal interactions that are crucial for support of pregnancy. Studies of the uterine gland knockout (UGKO) ewe indicate that uterine glands and, by default, their secretions are required for peri-implantation conceptus survival and growth. A complex servomechanism, involving hormones from the ovary and conceptus as well as endogenous betaretroviruses expressed in the endometrial LE and GE, is proposed to regulate endometrial gland differentiation and function during gestation. At estrus, estrogen increases PR expression in the endometrial epithelia. High levels of endogenous Jaagsiekte sheep retroviruses (enJSRVs) are expressed in the PR-positive endometrial LE and GE in response to increasing progesterone and are hypothesized to stimulate trophoblast proliferation and production of interferon (IFN) tau. IFN tau, the pregnancy recognition hormone produced by the trophoblast from Days 10 to 21, acts in a paracrine manner on the PR-negative endometrial LE and superficial GE to inhibit transcription of estrogen receptor alpha (ER) and oxytocin receptor (OTR) genes. These actions of IFN tau maintain progesterone production from the corpus luteum by abrogating release of luteolytic pulses of prostaglandin F2 alpha (PGF) from the endometrial epithelium. The antiluteolytic effects of IFN tau are dependent on progesterone. Progesterone stimulation over 8-10 days suppresses expression of the PR gene in the LE and then GE. Loss of the PR in the LE is concomitant with decreases in mucin glycoprotein one (MUC-1), an inhibitor of blastocyst implantation. As the conceptus begins implantation on Day 15, the binucleate trophectodermal cells then differentiate and produce placental lactogen (PL), a member of the prolactin (PRL) and growth hormone (GH) family. PL stimulates GE proliferation and production of secretory proteins, such as UTMP and OPN. Interestingly, the effects of PL on the GE appear to require the absence of PR and prior exposure to IFN tau. During mid-pregnancy, the mononuclear trophectodermal cells produce GH that can also act on a progestinized uterus to stimulate GE hypertrophy and secretory function. The actions of this servomechanism are proposed to stimulate GE hyperplasia from Days 20 to 50 and then GE hypertrophy and maximal differentiated function after Day 50 when the majority of fetal growth and development occurs during gestation.
Fetal sheep development on ultrasound and magnetic resonance imaging
Fetal sheep development on ultrasound and magnetic resonance imaging: a standard for the in utero assessment of models of congenital abnormalities.
Ontogeny of ovine lymphocytes. II. An immunohistological study on the development of T lymphocytes in the sheep fetal spleen
Immunology. 1987 Sep;62(1):107-12.
Maddox JF, Mackay CR, Brandon MR.
Department of Veterinary Preclinical Sciences, University of Melbourne, Parkville, Victoria, Australia.
The development of T and B lymphocytes in the ovine fetal spleen was studied immunohistologically using a panel of monoclonal antibodies. A specific sequence of appearance of lymphocyte markers on cells was observed. At 43-44 days of gestation, SBU-T1- and SBU-T8-positive lymphocytes were present in low numbers. However, no SBU-T4, 20.96-, 25.69-, 38.38-, or 46.66-positive lymphocytes were seen until 50-55 days of gestation. Surface immunoglobulin (sIg) was first detected on fetal spleen cells at 45-50 days of gestation. SBU-T19 lymphocytes appeared later in gestation, being observed in fetal spleens at 57 days gestational age (g.a.). The distribution of T cells, B cells and MHC antigens in the developing spleen of the ovine fetus is described.
The evolution and involution of Peyer's patches in fetal and postnatal sheep
Eur J Immunol. 1983 Aug;13(8):627-35.
Reynolds JD, Morris B.
The Peyer's patches (PP) of sheep have a number of important anatomical features and functional characteristics which are similar to tissues that have been classified as primary lymphoid organs. The prenatal maturation of PP occurs in the absence of any antigenic stimulus as immunogenic molecules are not normally encountered by the sheep fetus. Primordial PP were first detected in the small intestine of fetal sheep at about 60-days gestation; lymphoid follicles were present by 75-days gestation and vigorous lymphopoiesis was occurring in these follicles by 100 days. From 120-days gestation until birth, at about 150 days, the PP follicles were histologically mature and they had the greatest density of proliferating lymphoid cells found anywhere in the body. The total number of PP and their constituent follicles had developed before birth when there were 25-40 discrete PP in the jejunum and proximal ileum and one single continuous PP in the terminal ileum. There was no evidence of any change in the rate of growth of the PP follicles at birth which could be related to the advent of the first antigens in the gut. The total weight of PP tissue was greater than any other single lymphoid tissue by about 6 weeks after birth weighing around 120 g or about 1.2% of the body weight; about 50-60 g of the PP tissue was calculated to be lymphoid tissue. At this time the ileocecal PP (IPP) extended 2.5 m along the terminal ileum and accounted for about 90% of the total mass of PP. From about 12 weeks after birth the IPP began to involute and only a few PP follicles remained in this region of the intestine by 18 months of age. Follicles in PP in other parts of the small intestine remained and continued to produce lymphocytes throughout the life of the animal. PP contain a number of anatomically and functionally distinct lymphoid compartments that could play different roles in the body's immune defense. Explicit in most theories on the function of PP is the notion that antigenic stimulation is the cause of the lymphopoiesis in the follicles; our results do not support this view. Instead they suggest that the follicles in the PP of sheep may play a role similar to that played by the bursa of Fabricius in birds. PMID 6884422 DOI: 10.1002/eji.1830130805
Placental vessels of the foetal lamb
J Anat. 1968 Nov;103(Pt 3):539-52.
Steven DH. PMID 5693293