Talk:Sheep Development: Difference between revisions

Revision as of 13:25, 12 October 2010

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

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. tspencer@tamu.edu 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.

PMID: 15579583 [

Fetal sheep development on ultrasound and magnetic resonance imaging

http://www.ncbi.nlm.nih.gov/pubmed/16912495

Fetal sheep development on ultrasound and magnetic resonance imaging: a standard for the in utero assessment of models of congenital abnormalities.

estrous cycle

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

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 ===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
+===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. tspencer@tamu.edu
+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.
+PMID: 15579583 [
 ===Fetal sheep development on ultrasound and magnetic resonance imaging===