1) This document discusses genes involved in embryo-endometrium interactions in mares during Maternal Recognition of Pregnancy (MRP). It provides an overview of early embryonic development in mares and key events in the first 3 weeks of pregnancy.
2) Specific proteins expressed by the conceptus capsule, such as β2-microglobulin, uterocalin, and uteroglobin, are believed to play roles in communication between the conceptus and endometrium before the embryo fixes to the uterus.
3) Understanding molecular crosstalk between the embryo and endometrium is important as it allows the conceptus to signal its presence and prevent luteolysis, thereby establishing pregnancy in mares
Endocrinology --- control of parturitiondrmcbansal
This document provides information about Prof. Mahesh Chandra Bansal, including his educational background and professional experience as the Founder Principal & Controller of Jhalawar Medical College And Hospital, Jhalawar and former Principal & Controller of Mahatma Gandhi Medical College And Hospital in Sitapura, Jaipur. It then discusses the mechanisms of myometrial quiescence during pregnancy and the initiation of labor, focusing on the roles of hormones like progesterone, estrogen, relaxin, corticotropin releasing hormone, prostaglandins, and other factors in maintaining uterine quiescence and triggering the start of labor.
Induction of parturition & elective termination of pregnancyMahalingeshwara Mali
this ppt briefs about induction of parturition and elective termination of pregnancy in farm and pet animals, which may be helpful for the veterinary undergraduates, field veterinarians, and farm managers to extend their knowledge in this aspect.
Uterine infections are a major cause of reduced fertility in cattle. Puerperal uterine infections (metritis) occur within 21 days after calving and involve mixed bacterial flora. Post-puerperal uterine infections (endometritis) occur after 21 days and can lead to irregular cycles or anestrus. Treatment involves antibiotics, often parenterally, and may include prostaglandins to aid uterine involution. Accurate diagnosis is important for selecting the appropriate treatment protocol to resolve the infection and restore fertility.
This document summarizes the process of parturition (childbirth) and lactation. It discusses the roles of hormones like relaxin, prostaglandins, and oxytocin in softening the cervix and inducing labor contractions. It also mentions mechanical factors that can trigger labor, like fetal movements and cervical stretching. The stages of labor and delivery are outlined. Finally, it briefly discusses the changes in hormone levels after birth that support lactation and the immune benefits breastfeeding provides to the baby.
The placenta serves many essential functions:
1) It acts as a barrier and protects the fetus from harmful substances in maternal blood while allowing oxygen, nutrients, and waste to pass through.
2) The placenta provides nutrition to the fetus by selecting and transporting nutrients like amino acids, glucose, fatty acids, vitamins and minerals from maternal blood.
3) It produces important hormones like hCG, estrogen, progesterone, and human placental lactogen that help maintain the pregnancy and support fetal development.
Fraternal twins develop from two separate zygotes and have two placentas, chorions, and amniotic sacs. Identical twins develop from one zygote, with 65% sharing one placenta and chorion but having two amniotic sacs, and 35% having two separate placentas, chorions, and amniotic sacs. The placenta facilitates nutrient and gas exchange between the mother and fetus, and transfers IgG antibodies, providing passive immunity to the fetus.
Determining pregnancy in cattle is an important
management tool. The ability to determine
pregnancy can allow us to make timely
culling decisions and focus the resources of our
operation on sound, reliable breeders.
Endocrinology --- control of parturitiondrmcbansal
This document provides information about Prof. Mahesh Chandra Bansal, including his educational background and professional experience as the Founder Principal & Controller of Jhalawar Medical College And Hospital, Jhalawar and former Principal & Controller of Mahatma Gandhi Medical College And Hospital in Sitapura, Jaipur. It then discusses the mechanisms of myometrial quiescence during pregnancy and the initiation of labor, focusing on the roles of hormones like progesterone, estrogen, relaxin, corticotropin releasing hormone, prostaglandins, and other factors in maintaining uterine quiescence and triggering the start of labor.
Induction of parturition & elective termination of pregnancyMahalingeshwara Mali
this ppt briefs about induction of parturition and elective termination of pregnancy in farm and pet animals, which may be helpful for the veterinary undergraduates, field veterinarians, and farm managers to extend their knowledge in this aspect.
Uterine infections are a major cause of reduced fertility in cattle. Puerperal uterine infections (metritis) occur within 21 days after calving and involve mixed bacterial flora. Post-puerperal uterine infections (endometritis) occur after 21 days and can lead to irregular cycles or anestrus. Treatment involves antibiotics, often parenterally, and may include prostaglandins to aid uterine involution. Accurate diagnosis is important for selecting the appropriate treatment protocol to resolve the infection and restore fertility.
This document summarizes the process of parturition (childbirth) and lactation. It discusses the roles of hormones like relaxin, prostaglandins, and oxytocin in softening the cervix and inducing labor contractions. It also mentions mechanical factors that can trigger labor, like fetal movements and cervical stretching. The stages of labor and delivery are outlined. Finally, it briefly discusses the changes in hormone levels after birth that support lactation and the immune benefits breastfeeding provides to the baby.
The placenta serves many essential functions:
1) It acts as a barrier and protects the fetus from harmful substances in maternal blood while allowing oxygen, nutrients, and waste to pass through.
2) The placenta provides nutrition to the fetus by selecting and transporting nutrients like amino acids, glucose, fatty acids, vitamins and minerals from maternal blood.
3) It produces important hormones like hCG, estrogen, progesterone, and human placental lactogen that help maintain the pregnancy and support fetal development.
Fraternal twins develop from two separate zygotes and have two placentas, chorions, and amniotic sacs. Identical twins develop from one zygote, with 65% sharing one placenta and chorion but having two amniotic sacs, and 35% having two separate placentas, chorions, and amniotic sacs. The placenta facilitates nutrient and gas exchange between the mother and fetus, and transfers IgG antibodies, providing passive immunity to the fetus.
Determining pregnancy in cattle is an important
management tool. The ability to determine
pregnancy can allow us to make timely
culling decisions and focus the resources of our
operation on sound, reliable breeders.
The placenta develops from fetal and maternal tissues to function as the respiratory, nutritive, excretory, barrier and endocrine organ of pregnancy. It transfers oxygen, nutrients and waste between the mother and fetus. The placenta can develop abnormalities in its shape, size, position or adhesion to the uterine wall which may cause complications like preterm birth or hemorrhage. Placental lesions like infarcts may also occur due to conditions like hypertension.
The document discusses the placenta, parturition, and lactation. It provides details on:
- The structure and functions of the placenta, including nutrient, waste, and gas exchange between mother and fetus. Hormones produced by the placenta like estrogen, progesterone, hCG, and HPL are also discussed.
- The process of parturition or labor, including the three stages of labor and the mechanisms involved like hormones like progesterone and oxytocin that regulate the initiation and progression of labor.
- The stages of lactation including mammogenesis, lactogenesis when milk production begins, and galactokinesis which is the let-down reflex stimulated by suckling that
HORMONAL REGULATION OF OVULATION,PREGNANCY,PARTURITIONSudarshan Gokhale
The document discusses the hormonal regulation of ovulation, pregnancy, and parturition. It describes the key hormones involved in each process, including estrogen, progesterone, LH, FSH, hCG, relaxin, corticotropin, and oxytocin. Ovulation is regulated by the hypothalamus and pituitary gland releasing hormones like LH and FSH. Pregnancy involves changes in the maternal body and is maintained by hormones like estrogen, progesterone, hCG, and corticotropin. Parturition is triggered by a drop in progesterone and rise in oxytocin, relaxing ligaments and stimulating uterine contractions.
The document summarizes hormonal control of pregnancy. It discusses the steps of fertilization, including sperm being attracted to the ovum, binding to the zona pellucida, and the fusion of membranes allowing the male pronucleus to enter the ovum. Implantation typically occurs 5-7 days after ovulation, aided by trophoblast cells and progesterone. The placenta then develops, serving functions like nutrient exchange and endocrine activity. Estrogens and progesterone produced during pregnancy impact development of the fetus and preparation of the mother's body for childbirth and lactation.
The document discusses gestation periods in farm animals. It describes gestation as consisting of three classes: the ovum period from fertilization to implantation, the embryo period from implantation to early organ formation, and the fetus period from organ formation to birth. The roles of the placenta, hormones, and changes to the female genital organs during gestation are also examined. Factors influencing the length of gestation and methods for examining gestation in farm animals are outlined.
The document discusses the process of cervical ripening in cows. Cervical ripening involves the softening and dilation of the cervix to allow for birth. It is a two-stage process beginning with softening in late pregnancy and ripening just before birth. Key factors that influence cervical ripening include changes in hormones like progesterone and estrogen, degradation of cervical connective tissue by enzymes like MMPs, and an inflammatory response. Together these various biological mechanisms work to decrease the cervix's mechanical strength and increase its hydration in preparation for parturition.
1. Fertilization involves the sperm binding to and penetrating the egg's coat and membrane, fusing with the egg and releasing its contents. This blocks further sperm from entering.
2. During the first trimester, the fertilized egg undergoes cleavage and forms a blastocyst that implants in the uterus. The placenta and fetus develop through organogenesis.
3. In the second trimester, the fetus grows substantially as the placenta takes over hormone production. In the third trimester, the fetus grows more while the mother's body prepares for birth through hormonal changes.
The document discusses gestation and parturition (birth) across several species. It covers topics like fertilization, fetal development, placental structures and types, recognition of pregnancy, fetal growth, the stages and hormones of parturition, dystocia (difficult birth), and lactation. Key details are provided on the placental characteristics, birth processes and signals, and gestation lengths of cows, sheep, sows, and mares.
This document discusses sexual growth and development from pre-puberty through adolescence. It covers sex determination by chromosomes during fertilization, genetic and gonadal differentiation leading to the formation of either testes or ovaries. The roles of genes and hormones like testosterone and Müllerian inhibiting substance in testicular and ovarian development are described. Disorders of sexual development that can occur from chromosomal abnormalities like Klinefelter syndrome or hormonal defects are also outlined.
The distinctive features of camel reproduction are explained in this lecture delivered in a Webinar on Camel Reproduction 12 July 2020, Bikaner, Rajasthan, India
The document summarizes the biological processes involved in parturition or childbirth. As pregnancy advances, the placenta increases expression of the hormone corticotropin-releasing hormone (CRH). Rising maternal CRH levels peak at delivery. In the mother and fetus, CRH binds to receptors stimulating changes that initiate parturition, including increased cortisol and lung maturation in the fetus. Contraction of the myometrium at term involves interaction between actin and myosin proteins, excitability of myometrial cells, and intercellular connectivity mediated by prostaglandins and calcium. Understanding these pathways may help predict preterm birth risk and reduce associated complications.
The document discusses the anatomy and physiology of the male reproductive system in domestic animals. It describes how the male reproductive tract develops from the Wolffian duct and mesonephric tubules in the embryo. The male reproductive organs include two testes located in the scrotum, ducts, accessory sex glands, penis, and prepuce. The testes produce sperm and male sex hormones. Various structures then transport the sperm from the testes to the female's vagina during copulation.
This document summarizes the physiology of lactation. It discusses the development of breasts from embryogenesis through pregnancy and lactation. It describes the anatomy and histology of breasts. It explains the role of hormones such as prolactin, estrogen, and progesterone in breast development and milk production. It discusses the phases of lactation including mammogenesis, lactogenesis, galactokinesis, and galactopoiesis. It also covers the composition and formation of human milk and the advantages of breastfeeding for both mothers and babies.
This document summarizes Heera KC Parajuli's seminar on conception and fetal development. It begins with an overview of gametogenesis - the processes of sperm and egg formation. It then discusses ovulation, explaining how a mature ovarian follicle ruptures monthly to release an egg. The next section covers fertilization, describing the steps where a sperm and egg fuse together in the fallopian tube to form a zygote. The document concludes with an introduction to the development of the zygote and early embryo.
Successful implantation of the embryos in the uterus after IVF cycle is about 20%. It represents the bottleneck in the procedure of in vitro fertilization and embryo transfer. In this presentation we look at factors affecting implantation and how to improve it.
This document summarizes the mammalian reproductive physiology seminar on parturition (birth process). It discusses the three stages of parturition including cervical dilation and effacement, birthing process, and delivery of the placenta. It also describes the neuroendocrine control of parturition triggered by the fully formed fetus and placenta. Finally, it discusses the postpartum period known as puerperium, where the mother's body returns to its non-pregnant state over 6 weeks.
The document describes placement tests for the Corrective Reading Comprehension program. It consists of three tests - Test 1 is a screening test, Test 2 places students into specific lessons or programs based on errors, and Test 3 also places students into lessons based on errors. The document provides details on administering and scoring each test, including sample questions, answer keys, and placement guidelines.
The placenta develops from fetal and maternal tissues to function as the respiratory, nutritive, excretory, barrier and endocrine organ of pregnancy. It transfers oxygen, nutrients and waste between the mother and fetus. The placenta can develop abnormalities in its shape, size, position or adhesion to the uterine wall which may cause complications like preterm birth or hemorrhage. Placental lesions like infarcts may also occur due to conditions like hypertension.
The document discusses the placenta, parturition, and lactation. It provides details on:
- The structure and functions of the placenta, including nutrient, waste, and gas exchange between mother and fetus. Hormones produced by the placenta like estrogen, progesterone, hCG, and HPL are also discussed.
- The process of parturition or labor, including the three stages of labor and the mechanisms involved like hormones like progesterone and oxytocin that regulate the initiation and progression of labor.
- The stages of lactation including mammogenesis, lactogenesis when milk production begins, and galactokinesis which is the let-down reflex stimulated by suckling that
HORMONAL REGULATION OF OVULATION,PREGNANCY,PARTURITIONSudarshan Gokhale
The document discusses the hormonal regulation of ovulation, pregnancy, and parturition. It describes the key hormones involved in each process, including estrogen, progesterone, LH, FSH, hCG, relaxin, corticotropin, and oxytocin. Ovulation is regulated by the hypothalamus and pituitary gland releasing hormones like LH and FSH. Pregnancy involves changes in the maternal body and is maintained by hormones like estrogen, progesterone, hCG, and corticotropin. Parturition is triggered by a drop in progesterone and rise in oxytocin, relaxing ligaments and stimulating uterine contractions.
The document summarizes hormonal control of pregnancy. It discusses the steps of fertilization, including sperm being attracted to the ovum, binding to the zona pellucida, and the fusion of membranes allowing the male pronucleus to enter the ovum. Implantation typically occurs 5-7 days after ovulation, aided by trophoblast cells and progesterone. The placenta then develops, serving functions like nutrient exchange and endocrine activity. Estrogens and progesterone produced during pregnancy impact development of the fetus and preparation of the mother's body for childbirth and lactation.
The document discusses gestation periods in farm animals. It describes gestation as consisting of three classes: the ovum period from fertilization to implantation, the embryo period from implantation to early organ formation, and the fetus period from organ formation to birth. The roles of the placenta, hormones, and changes to the female genital organs during gestation are also examined. Factors influencing the length of gestation and methods for examining gestation in farm animals are outlined.
The document discusses the process of cervical ripening in cows. Cervical ripening involves the softening and dilation of the cervix to allow for birth. It is a two-stage process beginning with softening in late pregnancy and ripening just before birth. Key factors that influence cervical ripening include changes in hormones like progesterone and estrogen, degradation of cervical connective tissue by enzymes like MMPs, and an inflammatory response. Together these various biological mechanisms work to decrease the cervix's mechanical strength and increase its hydration in preparation for parturition.
1. Fertilization involves the sperm binding to and penetrating the egg's coat and membrane, fusing with the egg and releasing its contents. This blocks further sperm from entering.
2. During the first trimester, the fertilized egg undergoes cleavage and forms a blastocyst that implants in the uterus. The placenta and fetus develop through organogenesis.
3. In the second trimester, the fetus grows substantially as the placenta takes over hormone production. In the third trimester, the fetus grows more while the mother's body prepares for birth through hormonal changes.
The document discusses gestation and parturition (birth) across several species. It covers topics like fertilization, fetal development, placental structures and types, recognition of pregnancy, fetal growth, the stages and hormones of parturition, dystocia (difficult birth), and lactation. Key details are provided on the placental characteristics, birth processes and signals, and gestation lengths of cows, sheep, sows, and mares.
This document discusses sexual growth and development from pre-puberty through adolescence. It covers sex determination by chromosomes during fertilization, genetic and gonadal differentiation leading to the formation of either testes or ovaries. The roles of genes and hormones like testosterone and Müllerian inhibiting substance in testicular and ovarian development are described. Disorders of sexual development that can occur from chromosomal abnormalities like Klinefelter syndrome or hormonal defects are also outlined.
The distinctive features of camel reproduction are explained in this lecture delivered in a Webinar on Camel Reproduction 12 July 2020, Bikaner, Rajasthan, India
The document summarizes the biological processes involved in parturition or childbirth. As pregnancy advances, the placenta increases expression of the hormone corticotropin-releasing hormone (CRH). Rising maternal CRH levels peak at delivery. In the mother and fetus, CRH binds to receptors stimulating changes that initiate parturition, including increased cortisol and lung maturation in the fetus. Contraction of the myometrium at term involves interaction between actin and myosin proteins, excitability of myometrial cells, and intercellular connectivity mediated by prostaglandins and calcium. Understanding these pathways may help predict preterm birth risk and reduce associated complications.
The document discusses the anatomy and physiology of the male reproductive system in domestic animals. It describes how the male reproductive tract develops from the Wolffian duct and mesonephric tubules in the embryo. The male reproductive organs include two testes located in the scrotum, ducts, accessory sex glands, penis, and prepuce. The testes produce sperm and male sex hormones. Various structures then transport the sperm from the testes to the female's vagina during copulation.
This document summarizes the physiology of lactation. It discusses the development of breasts from embryogenesis through pregnancy and lactation. It describes the anatomy and histology of breasts. It explains the role of hormones such as prolactin, estrogen, and progesterone in breast development and milk production. It discusses the phases of lactation including mammogenesis, lactogenesis, galactokinesis, and galactopoiesis. It also covers the composition and formation of human milk and the advantages of breastfeeding for both mothers and babies.
This document summarizes Heera KC Parajuli's seminar on conception and fetal development. It begins with an overview of gametogenesis - the processes of sperm and egg formation. It then discusses ovulation, explaining how a mature ovarian follicle ruptures monthly to release an egg. The next section covers fertilization, describing the steps where a sperm and egg fuse together in the fallopian tube to form a zygote. The document concludes with an introduction to the development of the zygote and early embryo.
Successful implantation of the embryos in the uterus after IVF cycle is about 20%. It represents the bottleneck in the procedure of in vitro fertilization and embryo transfer. In this presentation we look at factors affecting implantation and how to improve it.
This document summarizes the mammalian reproductive physiology seminar on parturition (birth process). It discusses the three stages of parturition including cervical dilation and effacement, birthing process, and delivery of the placenta. It also describes the neuroendocrine control of parturition triggered by the fully formed fetus and placenta. Finally, it discusses the postpartum period known as puerperium, where the mother's body returns to its non-pregnant state over 6 weeks.
The document describes placement tests for the Corrective Reading Comprehension program. It consists of three tests - Test 1 is a screening test, Test 2 places students into specific lessons or programs based on errors, and Test 3 also places students into lessons based on errors. The document provides details on administering and scoring each test, including sample questions, answer keys, and placement guidelines.
English for Secretaries by Regina RezendeRegina Efs
O documento resume as qualificações e experiência de Regina Rezende como professora de inglês há mais de 20 anos, incluindo sua graduação pela Cultura Inglesa e certificações da Universidade de Cambridge. Ela também oferece workshops e treinamentos de Business English para secretárias em empresas multinacionais.
This document outlines the design of an English for Specific Purposes (ESP) course for banking personnel. It begins with an introduction to ESP and a literature review covering definitions of ESP, classifications of ESP, needs analysis, and course design in ESP. It then describes the context and needs analysis conducted for banking staff, which included a questionnaire and interviews. The needs analysis identified key language skills required. The document concludes by outlining the proposed ESP course design plan, including the course description, methodology, learning outcomes, evaluation criteria, and syllabus. The course aims to meet the identified language needs of banking personnel through targeted content and activities.
The lesson plan is for a two hour intermediate/advanced ESP poster workshop. It focuses on reading, listening, speaking and writing skills related to selling. The 28 students will learn selling vocabulary and techniques, assess their own sales skills, discuss strengths and weaknesses, write product advertisements, and listen to and discuss a conversation between an estate agent and buyer. The goals are for students to learn skills for successful selling and reflect on how to improve their performance.
Conversation at the bank Additional English M.4Chawin Maninun
This document provides vocabulary and sample conversations related to banking services. It includes terms for checking balances, ordering statements, paying bills, accessing accounts by phone, and cashing cheques. Sample dialogs demonstrate cashing a cheque at the bank and inquiring about telephone banking services. The telephone banking summary explains that customers can access their accounts 24/7 by phone to check balances, pay bills, transfer funds and more. Assistance is available via an automated system or during business hours.
The document is a lesson plan for a class on writing letters confirming orders as part of a business English course. The lesson plan outlines identifying parts of confirmation letters, phrases used in confirmations, and writing draft and full confirmation letters. It provides sample materials including a sample confirmation letter and assessment rubric for student work. The goal is for students to learn to write effective order confirmation letters.
Needs analysis questionnaire 10 may 2010 maf.mod.gov.mypendidikanborangborang...Hameed Al-Zubeiry
This document contains a needs analysis questionnaire to assess the requirements for an English curriculum design course. It collects information about the purpose, students, duration and target course for the curriculum being designed. It asks questions about the type of English course (general, ESP, EAP), level, skills focus (listening, speaking, reading, writing), content materials, and language requirements for students. The questionnaire aims to gather details about the curriculum project that will be used to design, develop and document an English course specific to the respondent's unit or command during the curriculum design course.
1) The document contains a 25 question placement test covering math and geometry concepts such as rounding, operations with fractions and decimals, word problems, properties of shapes, coordinate geometry, statistics, and more.
2) The questions range from simple computations and word problems to more complex problems involving multiple steps.
3) The test is designed to assess a student's current math skill level and place them in the appropriate math course.
Este cuestionario busca establecer el nivel de inglés de los estudiantes mediante preguntas sobre sus preferencias de aprendizaje, actitudes hacia el idioma, uso actual y futuro del inglés. Las preguntas indagan sobre temas como habilidades, comodidad al trabajar individualmente o en grupo, necesidades de aprendizaje y razones para tomar el curso.
Needs Analysis: A Valuable Tool for Designing and Maintaining Effective ESP C...Abdeslam Badre, PhD
This is a descriptive article about the definition, value, and operational procedures of the design and implementation of needs analysis in foreign language teaching institutions.
This document discusses various English placement tests used internationally and within Malaysia to assess students' English proficiency levels. It describes tests such as the Cambridge Placement Test (CPT), Oxford Online Placement Test, TOEFL, IELTS, and MUET used in Malaysia. These tests measure abilities in reading, listening, grammar, and vocabulary and place students in appropriate ability levels and courses. Placement tests benefit students by allowing them to study at their level and complete language requirements for university in a timely manner through grouped proficiency levels.
The document discusses the results of a study on the impact of COVID-19 lockdowns on air pollution. The study found that lockdowns led to short-term reductions in nitrogen dioxide and fine particulate matter concentrations globally. However, the decreases in air pollution were temporary and levels rose back to normal once lockdown restrictions were lifted and activity resumed.
This document summarizes the results of a needs analysis survey of 113 English teachers in Zhejiang, China. The survey aimed to identify teachers' main problems, learning needs, and preferences for training. It found that teachers' top problems included student motivation, classroom management, and language skills. Their main learning needs centered around improving teaching skills, language proficiency, and activity design. Most teachers preferred hands-on, practical training focused on classroom observations and reflections rather than lectures. The results informed the design of an in-service teacher training program for the region.
An English for Specific Purposes (ESP) lesson plan on business communications. The lesson focuses on making introductions and exchanging business greetings. Includes small group discussion and roleplay. Used for Grade 11-12 or equivalent students.
The document discusses a placement test being administered to 500 newly admitted students at HCMC Industry and Trade College. It notes students come from different backgrounds and English proficiency levels vary greatly. The test aims to properly place students into appropriate English courses. A placement test is important for students, teachers and the school. It allows students to be challenged at their level, helps teachers design suitable lessons, and improves the school's educational quality overall. The document also provides details on test takers, their expected English knowledge, and common test task types.
The document discusses various methods for conducting a learning needs analysis (LNA) at the organizational, job, and individual level. It describes LNA as a systematic process of collecting and analyzing information to identify learning requirements and determine current competency levels. Common methods discussed include interviews, examining documentation like performance reviews, using analysis models like SWOT, and assessments, observations, testing, skills matrices, focus groups, and questionnaires/surveys. The goal of LNA is to identify performance gaps and determine if learning interventions can address the root causes.
Mammary gland and its birth anomalies with characteristics in other mammalian...Visith Dantanarayana
The mammary glands develop differently in males and females due to hormone levels. In females, the breasts develop further during puberty, pregnancy, lactation, and are influenced by the menstrual cycle. They are composed of glandular, adipose, and connective tissues. Hormones like estrogen, progesterone, and prolactin stimulate development of the breasts at different stages through their receptors. The Cooper's ligaments provide internal support to the breasts but sagging is influenced by multiple genetic and environmental factors rather than the ligaments alone. The breasts have arterial blood supply and venous drainage and lymph from different areas of the breasts drains to different lymph node groups.
1) Maternal recognition of pregnancy refers to the signals sent by the conceptus to prevent luteolysis and allow the pregnancy to continue.
2) In ruminants like sheep and cattle, the conceptus produces interferon tau which blocks oxytocin receptors in the uterus and prevents a decline in progesterone levels.
3) In pigs, the conceptus produces estrogen which reroutes prostaglandin F2alpha into the uterine lumen instead of allowing it to cause luteolysis.
The onset of parturition, commonly known as labor, is a complex physiological process that marks the culmination of pregnancy and the initiation of the birthing process. This intricate sequence of events involves a series of hormonal, mechanical, and neurological changes that ultimately lead to the expulsion of the fetus from the mother's uterus. Understanding the onset of parturition requires a comprehensive exploration of the various stages and factors involved.
The process of parturition can be broadly categorized into three main stages: pre-labor, labor, and post-labor. The pre-labor stage encompasses the preparatory changes occurring in the days and weeks leading up to labor, while the labor stage involves the actual contractions and cervical dilation facilitating delivery. The post-labor stage involves the expulsion of the placenta and the initial postpartum adjustments.
The hormonal regulation of parturition is a crucial aspect of its onset. Throughout pregnancy, the placenta produces progesterone, a hormone that maintains the uterine environment and prevents premature contractions. As term approaches, the ratio of progesterone to estrogen changes, leading to a decline in progesterone levels and a subsequent increase in estrogen. This shift triggers a cascade of events, including the activation of uterine contractions and the initiation of cervical ripening.
The role of oxytocin, often referred to as the "love hormone" or "cuddle hormone," is paramount in the onset of labor. Produced by the hypothalamus and released by the pituitary gland, oxytocin stimulates uterine contractions. Additionally, oxytocin plays a crucial role in the positive feedback loop of labor – as contractions intensify, more oxytocin is released, further promoting labor progression.
Mechanical factors also contribute to the onset of parturition. The growing fetus applies pressure on the cervix and uterine walls, leading to the release of prostaglandins. Prostaglandins are lipid compounds that promote uterine contractions and cervical ripening. The combination of hormonal changes and mechanical pressure creates a synergistic effect, fostering the progression of labor.
The intricate interplay between the maternal-fetal unit and the surrounding environment further influences the onset of parturition. Maternal stress, for instance, can impact the release of corticotropin-releasing hormone (CRH), which, in turn, influences the production of other hormones involved in labor. Moreover, the fetus itself plays an active role in signaling its readiness for delivery through various molecular signals.
The onset of labor is often heralded by a set of common signs. These may include the engagement of the fetal head into the pelvis, the "bloody show" – a discharge of mucus mixed with blood resulting from cervical changes, and the rupture of the amniotic sac, leading to the release of amniotic fluid. These signs, in conjunction with regular and increasingly intense contractions.
This document discusses the anatomy and physiology of lactation. It describes the parts of the female breast including lobes, glandular tissue, milk ducts, nipples, areolae, blood vessels, and nerves. It explains the processes of mammogenesis during pregnancy, lactogenesis after delivery as milk production begins, and galactopoiesis which is the maintenance of milk production through regular removal of milk from suckling. Key hormones involved are prolactin, estrogen, progesterone, and oxytocin which works through the milk ejection reflex.
1. Fertilization occurs through the acrosomal reaction and fusion of the egg and sperm membranes, allowing entry of a single sperm.
2. This triggers the fast block to polyspermy within 1/10th of a second and the cortical reaction, which changes the egg cytoplasm and hardens membranes to prevent multiple fertilization.
3. Pregnancy is divided into three trimesters. The first trimester involves rapid development and differentiation of the embryo. The placenta forms and the embryo implants in the uterine wall.
1) Maternal recognition of pregnancy (MRP) refers to signals from the developing embryo that prevent regression of the corpus luteum and allow pregnancy to be established.
2) In ewes, the conceptus secretes ovine interferon-tau (oIFN-tau) between days 10-21 of gestation which suppresses uterine prostaglandin F2α release and luteolysis.
3) In cattle, the interferon-tau homolog is bovine interferon-tau (bIFN-tau) which is secreted from days 16-19 of gestation and acts through similar antiluteolytic mechanisms.
The document discusses the placenta and its functions. It begins by defining the placenta and its origins from Latin. It then discusses:
1) Companies in Japan that produce extracts from human placenta to treat conditions like menopause and hepatitis.
2) The placenta's roles in transporting nutrients, gases, and waste between the mother and fetus. It has endocrine functions and produces hormones to maintain pregnancy and support fetal development.
3) The development of the placenta from the blastocyst stage through implantation and formation of the chorion and villi to facilitate exchanges between mother and fetus.
The mammary gland develops from embryonic ectoderm layers. In humans, mammary buds form and develop into primary sprouts that become openings in the nipple called galactophores. Secondary sprouts form mammary ducts. After birth, ducts branch and elongate during puberty and pregnancy due to sex hormones. During pregnancy, alveoli and lobules form to produce milk under control of hormones like progesterone and prolactin. Colostrum is the first milk produced after birth that protects the newborn.
The placenta functions to transfer nutrients and waste between the mother and fetus through respiratory, excretory, and nutritive processes. It produces hormones like human chorionic gonadotropin (hCG), human chorionic somatomammotropin (hCS), estrogen, and progesterone that are crucial to maintaining the pregnancy. The placenta, fetus, and maternal systems form an integrated unit where hormones are transferred between compartments to regulate processes of pregnancy and fetal development.
This topic includes menstruation:- its definition, anatomical aspects- follicular growth and atresia, germ cells, premodial follicle; menstrual cycle/ ovarian cycle:- definition, phases- recruitment of groups of follicles (premature phase), selection of dominant follicle and its maturation, ovulation, follicular atresia; Endometrial cycle:- division of endometrium- basal zone, functional zone and its phases- stage of regeneration, stage of proliferation, secretory phase, menstrual phase, mechanism of menstrual bleeding, role of prostaglandins, hormones in relation to ovarian and menstrual cycle, ovulation, luteal-follicular shift, menstrual symptoms, menstrual hygiene, anovular menstruation, artificial postponement; cervical cycle, vaginal cycle and general changes in follicular and luteal phase.
The document discusses hormonal changes during pregnancy and lactation. It identifies the placenta as an endocrine organ that produces hormones like hCG, HPL, estrogen, progesterone, and relaxin. It describes the roles and actions of these hormones in maintaining pregnancy and preparing the breasts for lactation. The document also discusses theories for the initiation of labor like the progesterone deprivation theory, oxytocin theory, and prostaglandin theory. It explains the three phases of lactation - mammogenesis, lactogenesis, and galactopoiesis - and the roles of prolactin, oxytocin, progesterone, and estrogen in breast development and milk production.
This document discusses oogenesis, the process of egg formation in ovaries. It begins by defining oogenesis as the formation of eggs from the ovary. It then describes the key stages of oogenesis, including the development of primary oocytes from oogonia in the embryo, the resumption of meiosis at puberty, and the unequal cell divisions that result in a larger secondary oocyte retaining most of the cytoplasm. The document also compares oogenesis to spermatogenesis, noting the differences in gamete number, size, and timing of meiosis between the two processes.
First week of development: Ovulation to Implantation Jwan AlSofi
The document summarizes key aspects of ovulation, fertilization, and early embryonic development. It describes the ovarian and menstrual cycles controlled by hormones like FSH and LH. Ovulation occurs mid-cycle due to an LH surge, releasing an egg. Sperm travel through the reproductive tract while undergoing capacitation. Fertilization typically occurs in the fallopian tubes, involving penetration of the egg's layers and fusion of gametes. This activates the egg and forms pronuclei, leading to cell division and pregnancy if implantation occurs. Otherwise, the corpus luteum regresses and menstruation begins.
The document summarizes key differences between spermatogenesis and oogenesis. Spermatogenesis produces four small equal gametes from each primary spermatocyte, while oogenesis produces one large gamete and polar bodies from each primary oocyte. The ovum stores nutrients and cytoplasmic information important for development, undergoing growth and yolk deposition during the vitellogenic phase prior to ovulation.
The document summarizes the structure and physiology of lactation. It describes the 5 stages of lactation: mammogenesis, lactogenesis, galactokinesis, galactopoiesis, and involution. Key points include the hormonal control of lactation, the composition of breast milk, and factors that can affect milk production such as medications, stress, and infant feeding patterns. The summary provides an overview of the essential information on the structure, process, and factors involved in human lactation.
This document provides an overview of female reproductive physiology, including:
1. The process of oogenesis in the ovaries where primordial follicles develop into mature ova.
2. The roles of the ovaries, fallopian tubes, uterus, cervix, and vagina in the female reproductive system.
3. How the ovarian and menstrual cycles are regulated by hormones and synchronize the development of ova and the endometrium.
4. Fertilization occurs when an ovum is picked up by the fallopian tubes and transported to the uterus for potential implantation.
This document discusses engineering the microenvironment of ovarian follicles for in vitro culture through the application of tissue engineering principles. It begins with an overview of follicle development in vivo and the current state of in vitro follicle culture systems. Two-dimensional culture systems disrupt follicle architecture, while three-dimensional systems better maintain cell-cell interactions but have room for improvement. The field of tissue engineering can provide tools to better control the biochemical and mechanical signals within engineered follicle culture systems. The challenges of selecting appropriate biomaterials and manipulating their properties to regulate factor transport and mechanical cues throughout follicle development are discussed.
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Genes involved in embryo- endometrium interactions in mares during Maternal
Recognition of Pregnancy (MRP)
Abstract
Introduction
There are many important reasons for studying equine reproduction and improving its
efficiency for its own sake [1]. 16% of thoroughbreds experience pregnancy failure, with
60% happening within the first three weeks of gestation [2]. Economically, the equine
industry is substantial in many countries and poor reproductive results are very costly.
Although equine reproductive studies are still in their early stages, it is known that genes
expressed in the endometrium (the lining of the uterus) of mares play a necessary role in the
establishment and maintenance of maternal pregnancy. The actions of the conceptus (the
spherical shaped sac containing the embryo proper, its associated membranes and fluid) in the
uterus must be considered as it is also important in MRP [3].
Using biochemical pathways, the conceptus signals its presence causing arrest of the
oestrous cyclic process and maintains primary Corpus Luteum (CL) function. The events
controlling these processes are known as “maternal recognition of pregnancy” (MRP) [4]. For
all ruminants it is therefore understood that for MRP to transpire, communication between the
conceptus and the endometrium is necessary, thus creating a synchronous uterine
environment for embryonic development. Very little is known about the molecular crosstalk
between the embryo and endometrium in equines because their MRP mechanisms are
different to other ruminants [5].
Progesterone is a principal hormone involved in maintaining pregnancy in all
mammals. In the presence of an embryo in the uterus, the life span of the CL (corpus luteum)
is prolonged and endometrial release of prostaglandin F2α (PGF2α) into the bloodstream is
blocked, preventing luteolysis (regression of the CL) [3]. MRP depends on species- specific
signals produced by the embryo and recognised by the uterine lining and vice versa.
The aim of this review is to first, give an overview of the first 3 weeks of pregnancy
in the mare and its embryonic development. Secondly, to highlight key prostaglandins and
genes that have a strong influence on MRP involved in the conceptus- endometrium
interactions, especially those leading up to implantation in equids and in ruminants. Finally,
to discuss the values of studying equine embryology.
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Early stage development of the equine embryo
After fertilisation, the zygote cleaves via first mitosis to give two cells called
blastomeres surrounded by the zona pellucida. Cleavages are divisions of cells in the early
embryo. The cleavage ends with the formation of the blastula. These begin during the
transport of the embryo through the oviduct into the uterus but, this process is a species-
specific stage during development. Mares are unusual to other animals with regard to passage
through the oviduct, whereby only developing embryos can pass through unlike unfertilised
oocytes which cannot [3,6].
The equine blastocyst enters the oviduct around day 6.5 after ovulation has occurred.
The blastocyst contains an inner cell mass and a blastocyst cavity surrounded by a monolayer
of trophectoderm. By day 7 the zona pellucida has shed and the embryo is surrounded by a
tough acellular mucin-like glycoprotein capsule [7]. The capsule acts to protect, and prevents
the trophoblast from elongating, unlike other domestic animals such as cattle and pigs, and
gives it its spherical structure. It facilitates rapid growth between days 11 and 16, nutrition
and migration of the conceptus in the uterine lumen via peristaltic myometrial forces [5].
During the migration from one uterine horn to the other, the conceptus has surface
contact with the endometrium. The conceptus signals its presence in the uterus via anti-
luteolytic signals thus, the embryo prevents luteolysis by first, placing itself near to the
endometrium then attaching to it [3], between day 17 and 21 [8]. This event is known as
fixation, where the conceptus containing the embryo proper becomes attached to the
endometrial surface. Fixation is the termination of the extended mobility stage in the uterus,
positioning and fixing the embryo at the base of one of the uterine horns. This termination is
because of an increase in uterine tone and embryo growth, predominantly in the right horn of
mares [8]. In rodents and primates the term implantation is used here but, in these animals the
embryo penetrates the epithelium and advances into the endometrial connective tissue where
it is implanted [3]. Fig.1 outlines the stages of development of an equine embryo during MRP
from day 0 to day 28.
In mares luteolysis can occur as early as days 11 and 13 [5,9]. Luteolysis can be
defined as the functional and/ or structural regression of the CL [10]. It is a crucial process in
the ovarian cycle whereby, post-ovulation, luteolysis is initiated by an Oxytocin-dependant
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Fig. 1: The approximate timing of key developmental stages of growth in the equine embryo during the first 4
weeks of gestation .Taken from [1]
high- frequency burst release of PGF2α (prostaglandin F2α) from the posterior pituitary and the
CL [1]. Simultaneously, the oxytocin receptor is upregulated in the endometrium, this is
similar for cows and sheep [10]. Luteolysis is abrogated by the conceptus for the pregnancy to
continue, usually from day 14 [5].
The relationship between endometrium and embryo
For the establishment of pregnancy, a number of complex interactions are necessary.
This is during the pre-fixation period. These interactions take place between the ovary,
endometrium and embryo. The ovaries produce oestradiol and progesterone, these hormones
act on the endometrium to produce various proteins and prostaglandins. When an embryo is
present in the uterus, proteins nourish the developing embryo. As already mentioned,
prostaglandin acts on the CL causing luteolysis if a viable embryo is not present in the animal
[11]. Depending on the species, the conceptus secretes steroids, prostaglandins, growth
factors and cytokines. These factors influence the endometrium: preventing prostaglandin
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secretion and stimulating protein secretion, or by directly acting on the ovary to stimulate
progesterone secretion [12].
The pig, horse and guinea pig are oxytocin dependant species. During MPR the CL
produces progesterone and oxytocin stimulating endometrial synthesis of prostaglandin thus,
causing luteolysis. Interferon- tau (IFN-τ) is the MRP factor in ruminants such as sheep,
cows, goats [13, 14]. IFN-τ genes are not present in horses and equine conceptuses do not
produce interferon like proteins during early pregnancy but, it is an important factor in other
ruminants and therefore must be acknowledged [15]. IFN-τ silences expression of the
estrogen receptor (ESR1) preventing expression of endometrial oxytocin receptors. If an
embryo is present, oxytocin cannot induce PGF2α synthesis preventing luteolysis. It is
released from the endometrial glands and stimulates histotrophe production, i.e. secretions
that nourish the embryo in the uterine cavity. Pigs have a different mechanism to halt
luteolysis. Oxytocin is produced in the CL and promotes synthesis of PGF2α like ruminants.
The trophectoderm of a pig trophoblast produces oestradiol, thus preventing luteolysis. PGF2α
is secreted into the uterine cavity where it is degraded by rate limiting enzymes instead of the
maternal bloodstream as in equids and ruminants [3].
Conceptus associated proteins involved in endometrium communication
The components of systems for the exchanging of materials between the conceptus
and the mare are often found in the cellular yolk sac wall called the capsule. The proteins
β2M, uterocalin, uteroglobulin, ganglioslide activator protein (GM2AP) and phospholipase
A2 (PLA2) are mostly expressed in large amounts approaching the time before fixation.
A major luteolysis- associated protein of the conceptus capsule is β2 Microglobulin
(β2M). It is the most abundant protein within the capsule. β2M undergoes proteolysis in the
capsule and its sequence is shortened around the time of fixation [16]. The removal of amino
acids is due to the conversion of the intact form of β2M to its cleaving form to the
endometrium around day 17, when the embryo becomes fixed to the uterine lumen. The
origin of the β2M has not been determined but Quinn et al. state that it is likely to stem from
the endometrium or yolk sac wall tissue. Its function is the light chain complex of various
MHC class 1 complexes. It is believed to also have an earlier function in the capsule before
degradation occurs [17].
Uterocalin/ P19 is a characterised lipocalin which act as a small hydrophilic carrier
protein. It is secreted by the endometrial glands in late diestrus and in early pregnancy in
equines. The cationic protein binds to capsule and its main function is to transport and deliver
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lipophillic substances such as nutrients into the yolk sac [16]. It is only present in the yolk sac
fluid before fixation. Uterocalin has only been demonstrated in equines so far. Similar to β2M
it lessens as the capsule degrades, therefore uterocalin and β2M only appear to be essential
during early embryonic growth [17].
The uteroglobin gene is expressed in the equine uterus. First identified in the uterine
of rabbits, it is a member of the large secretoglobulin super family of proteins. Like
Uterocalin it binds small lipophillic molecules and also, is present in ample amounts in the
uterine lavage fluids but, only in the yolk sac before fixation [16, 17]. Uteroglobulin is found
in various mammals including some without encapsulate conceptuses.
The ganglioslide activator protein (GM2AP) is expressed in large amounts by the
equine capsule up until around day 18.5 of pregnancy. This protein is involved in the
transport of glycolipids. It has only been found to be expressed by the capsule so far [18].
Phospholipase A2 (PLA2) are a complex group of enzymes that cleave glycerol based
phospholipids and a fatty acid, usually arachidonic acid, a cyclooxygenase substrate from the
eicosanoid family (a group of signalling molecules constructed by the oxidation of twenty-
carbon essential fatty acids) [16, 17, 19]. The PLA2 enzymes play a valuable role in
regulating ovarian function, pregnancy and delivery, they are also important in inflammation
and haemostasis. PLA2 synthesis in the equine uterus was found to bind to the capsule and
increase its concentration when PGF2α was administered to block fixation [16, 17, 19]. It is
also believable that synthesis of PLA2 assists in the degradation and removal of the
conceptus capsule.
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Membrane phospholipids
PLA2
Arachidonic acid
COX-1 COX-2
PGH2
PGE2 PGF2α
PGE
synthesis
PGF
synthesis
Fig. 2 Systematic mechanisms of the expression of prostaglandin E2 and prostaglandin F2α in the equine uterine
lining. Endometrial membrane phospholipids are converted to arachidonic acid by active phospholipase A2
(PLA2). Arachidonic acid is metabolised to an intermediate prostaglandin H2 (PGH2) by two cyclooxygenase
enzymes (COX-1 and COX-2). Prostaglandin E (PGE) is synthesised to prostaglandin E2 (PGE2) and
prostaglandin F is synthesised to prostaglandin F2α (PGF2α).
Prostaglandin synthase expression in the equine endometrium
Boerboom et al. hypothesise that the conceptus could inhibit luteolysis by altering
expression of enzymes involved in prostaglandin (PG) synthesis [10]. The effects of
prostaglandins are mediated by membrane bound receptors in the uterus. Prostaglandin F
receptor (PGFR) is a contractile receptor that binds PGF2α and prostaglandin E2 receptor
(PGER) acts as a relaxant and may play an important role in uterine receptivity. The PGER
(prostaglandin E2 receptor) has four subtypes [20]. Prostaglandins are synthesised in response
to many pathological and physiological stimuli that activate phospholipase A2 (PLA2)
converting membrane phospholipids to arachidonic acid then metabolises to cyclic
endoperoxide prostaglandin H2 (PGH2) by two cyclooxygenase isoform enzymes COX-1 and
COX-2 [9, 10]. This is shown in fig 2. COX-1 and COX-2 catalyse arachidonic acid and they
are considered to be the rate-limiting enzymes in prostaglandin production. The receptors
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PGER and PGFR along with the cyclooxygenase enzymes play an important role in
degrading prostaglandin during MRP [20].
COX-1 expression was shown to remain low in the uterus during the oestrus cycle and
become upregulated during MRP. It is understood that its expression may be influenced by
oestradiol [20]. COX-2 is a key modifier of PG metabolism during early pregnancy in mares.
It can be stimulated in different cell types by different factors, i.e. Follicle stimulating
hormone and luteinising hormone in ovarian follicles or by cytokines influencing epithelial
cells [20]. PGH2 is the intermediate prostaglandin formed from the prostaglandin synthesis
reaction, it is then converted to prostaglandin E2 (PGE2) and PGF2α by prostaglandin E
synthesis (PGEs) and prostaglandin F synthesis (PGFs) [15]. Balances between these two
biosynthesis are considered important in ruminants for successful pregnancy to take place. It
is not fully understood whether the relative expression of enzymes PGE2 and PGF2α changes
throughout the oestrous cycle and pregnancy in equid endometrium [21]. Ealy et al. state that
in equids, the primary target for conceptus secretions is COX-2, which leads to believe that
endometrial COX-2 is blocked by the presence of the conceptus but, the amount of PGEs and
PGFs is not affected [10, 13].
In relation to differences in the biological roles in the reproductive tracts interactions
in equid verses ruminant, Boerboom el al’s findings were that there was a lack of endometrial
expression of PGE2 in equines and also, that it does not have an effect on the lifespan of the
CL or in luteolysis. In bovine endometrium PGE2 regulation plays an important role in
parallel with COX-2 in the establishment of pregnancy. PGE2 is produced in large quantities
by the conceptus, Boerboom et al. hypothesise that it may have the responsibility of acting as
a supplement for the endometrium rather than serving to stimulate myometrial contractions
therefore, moving the conceptus around the uterus distributing antiluteotic signal molecules
which is a process common in ruminants. By targeting the expression of the COX-2 enzyme
the equine conceptus can regulate endometrial prostaglandin synthesis [10, 15].
In cows and sheep endometrial COX-1 expression was almost undetectable and COX-
2 was found to increase and be temporarily expressed around the time of luteolysis (i.e., day
15) [10]. COX-2 expression levels in these ruminants is prolonged by pregnancy, of which
does not affect the amount of PGF2α released by the uterus of the ewe but affects the
pulsatility of its secretion [10].
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There are fundamental differences in the molecular mechanisms underlying MRP in
mares, cows and ewes. Oxytocin stimulation of PGF2α secretion is reduced when pregnant in
these animals but in mares the receptor number is higher at time of luteolysis resulting in
prevention of luteolysis being more dependent on inhibiting the up-regulation of COX-2
rather than oxytocin receptor [22].
Gene regulation in the equine endometrium during MRP
Equine gene homologue Gene symbol Function
Up regulated genes
Homo sapiens GM2 ganglioside activator GM2A Lipid transport
Heat shock proteins
Equus caballus similar to heatshock 22kDa protein 8 HSPB8 Response to stress
Homo sapiens heat shock 27kDa protein family member 7 HSPB7 Response to stress; cardiovascular
Equus caballus similar to crystallin Alpha B CRYAB Protein tyrosine kinase signalling; anti apoptosis
Cell- cell signalling
Equus caballus siminlar to interferon stimulated gen 15 ISG15 Cell-cell signalling; protein modification process
Equus caballus similar to ATPase, H+ transporting ATP6V0A4 Ion/proton transport
Equus caballus siminlar to stanniocalin STC1 Cell-cell signalling: calcium ion homeostasis
Transport
Homo sapiens proton/ amino acid transporter 2 (PAT2) SLC36A2 Amino acid transporter
Equus caballus similar to solute carrier family 46 member 2 SLC46A2 Transport
Putative Secretory Proteins
Equus caballus similar to fibroblast growth factor 9 FGF9 Growth factor activity
Equus caballus TIMP metallopeptidase inhibitor 1 TIMP1 metallopeptidase inhibitor
Equus caballus similar to fibroblast growth factor binding protein FGFBP Growth factor binding
Down regulated genes
Equus caballus insulin-like growth factor binding protein 1 IGFBP1 Regulation of cell growth
Equus caballus similar to connective tissue growth factor CTGF Cell adhesion; regulation of cell growth; angiogenesis
Equus callabus estrogen receptor 1 ESR1 Estrogen receptor signalling
Table 1. A gene profile of genes which are up and down-regulated within the endometrium during MRP.
Adapted from [9, 23].
Regulation of genes within the endometrium in response to a conceptus
Many of the identified genes that are regulated in the endometrium are involved in the
endometrial remodelling in response to a conceptus. After looking at the conceptus response to
the endometrium it is necessary to study the endometrial response with respect to the conceptus. It
is important the conceptus- endometrium interactions remain synchronous for MRP to occur and
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for embryo growth and development to be successful. Table 1 shows a summary of commonly
upregulated and down regulated genes that are expressed in the endometrium during early
pregnancy in response to the conceptus.
Merkl et al. determined differential expression of genes in the endometrium on day 8
and 12 of pregnant and cyclic mares, taking endometrial biopsies on the relevant days and using
qPCR and microarrays to show total mRNA expression in response to a conceptus. By day 12,
they noticed a significant difference in the expressions recorded. They found the higher mRNA
levels were due to a response to the conceptus that prevented the down regulation of the genes
they analysed, except for FGF9 gene, a fibroblast growth factor, which was additionally
upregulated. Merkl et al. stated that the regulation of steroid hormones may be responsible for
these interactions [9].
Heat shock proteins are proteins whose expression is upregulated when introduced to
a stressful environment. The three main proteins regulated by oestrogens and involved in the
equine endometrium are heat shock proteins B7 and B8 (HSPB7 and HSPB8) and Crystalin, alpha
B (CRYAB). The endometrium is sensitive and receptive towards the conceptus. Klein et al.
hypothesised that these proteins prepare the endometrium for fixation in the conceptus [23].
Cell-cell signalling mediates the transfer of information from one cell to another [24].
This process and its upregulation of genes are essential for the successful establishment of
pregnancy. Stanniocalcin 1 (STC1) is a pregnant-specific uterine gene which is upregulated in the
endometrium across species. In the endometrium of equids STC1 expression has not been
reported but, its expression has been recorded in sheep, pigs, humans and mice. In sheep, STC1
mRNA and protein are required for regulating growth and differentiation of the embryo and its
placenta, and act as a marker for implantation in pigs. In humans and mice STC1 expression is
highest during embryo implantation in the endometrium. It therefore plays a species- independent
role in early pregnancy [9, 23].
During MRP, amino acid transport is necessary for embryo development. Transport
mediator protein, solute carrier 36 member 2 (SLC36A2) is a proton/ amino acid symporter. This
simply means that two molecules can be transported by this protein in the same direction through
the conceptus capsule using a common carrier mechanism. Klein et al. assume that its
upregulation is due to the demands of rapidly growing conceptus for nutrients [23].
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Secretory proteins make up a considerable amount of gene material upregulated in the
uterine cavity. When secretory protein production is poor, pregnancies often show detrimental
effects [25]. Commonly upregulated secretory proteins were luteinizing hormone (LH), tissue
inhibitor of metalloproteinase 1 (TIMP1) and insulin growth factors (IGFs). LHB has been
observed in women and is believed to prepare the uterus for implantation. It interrupts cellular
apoptosis, encourages angiogenesis and employs a particular immune responses [11, 25]. This is
understood to be similar in equids in preparing the endometrium for fixation. TIMPs regulate the
extracellular matrix production and tissue reconstruction during implantation and fixation thus, it
is a contributing factor to endometrial reconstruction in various species and equine pregnancies
[23]. As described earlier, FGF9 a fibroblast growth factor is also potentially involved in
endometrial reconstruction [9, 23]. IGFBP1 and IGF1 are both found to be upregulated and
expressed in Klein et al. and Merkl et al. studies on expressions in the endometrium. It is
suggested IGFBP1 and IGF1 have a function as transporters of IGFs between the endometrium
and uterine lumen of the horse [9, 23].
A gene of interest is estrogen receptor 1 (ESR1), involved in the initiation of
luteolysis in cyclic mares. Pre-fixation period ESR1 is down regulated. This is due to the intrusion
of the conceptus [23]
The value of equines in reproductive studies
When it comes to looking at maternal recognition of pregnancy, equines exhibit many
differences in comparison to other domestic ruminants (goats, sheep, pigs, cattle). But there
are also similarities. For example in cattle 70%- 80% of total embryonic loss occurs between
days 8-16 after insemination, a similar time-frame like equines in embryonic loss. Equines
have many advantages in using them as models over other ruminants for the study of
pregnancy in the first month, and for the total embryonic loss that occurs during this time.
There is no other domestic species of which a conceptus can be collected intact i.e within the
first four weeks of pregnancy while undergoing advanced organogenesis. It can be obtained
from the uterus repeatedly, atraumatically and easily with no maternal tissues attached [1].
Although methods and techniques for this research have developed greatly over the past
decade, there are still many unanswered questions in embryonic development and its
interactions within the uterus. Fortunately, this acts as an incentive to undertake this research
and combat the problem of early embryonic loss and extend our knowledge of endometrium-
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embryo cross-talk. Betteridge states that “research will quite certainly also pay dividends in
unanticipated ways in the broader field of reproductive biology” [1].
A disadvantage is that the embryo cannot be accessed easily until around day 6.5
after the blastocyst has been released from the oviduct. At present, surgery or slaughter is the
necessary procedure to collect a blastocyst from the oviduct. Once the blastocyst enters the
uterus it can be accessed easily using harmful techniques. Surgery or slaughter is most
certainly not efficient. It is possible to successfully culture cleavage stage embryos in vitro.
There is not a system that can meet the requirements of a growing blastocyst and provide it
with the correct environment to allow it to produce a capsule as it does in the uterus [26].
Therefore, there is a need to improve methods to produce embryos in vitro.
From an immunological point of view, the embryo- maternal interactions has
highlighted events that struggle to be detected in other species [25].
Conclusion
It is clear that embryo- endometrial interactions are not detected by a single gene, but
by a series of individual genes and pathways regulating specific phases of endometrial
function, conceptus development, and the influences the conceptus has on endometrial
function during maternal recognition of pregnancy. In only very recent years has there been
much understanding of the embryo- maternal cross talk. Transcriptional profiling of the equid
endometrium during MRP has only been published this year, of which are the first few of
their kind to be reported. Common features have been found in equine and human
pregnancies [11, 25, 27]. Equines have proven to be a positive addition in the studies of
early reproductive research. Many questions remain in this area of research, such as further
investigations into communication between the embryo and endometrium via gene
expression, the physical relationship between the capsule and the yolk sac and its signalling
efforts towards the endometrium and the conceptus synchronisation in the uterine cavity. By
focusing on particular genes that are expressed during early pregnancy it will be possible to
improve methods for diagnosis and treatment of mares that are prone to losing the conceptus
during the first three weeks of pregnancy. There is the need for rigour in the study of
embryonic development and its products presumed to play an important role in
communication between embryo and mother in any species.
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