Embryology of the Female Urogenital System and Clinical Applications
Linda Cardozo, Staskin David in Textbook of Female Urology and Urogynecology - Two-Volume Set, 2017
A growing dAtAbAse of murine genitoUrinary development exists within the GenitoUrinary Development MoleculAr AnAtomy Project (gudmAp.org), which includes seriAl sections of murine embryos At vArious stAges of development. over the pAst 10 yeArs, this multicenter collAborAtion hAs compiled A lArge dAtAbAse contAining the results of in situ hybridizAtions And immunohistochemistry performed for specific gene And protein expression, As well As microArrAy dAtA. These results Are AvAilAble As A common resource for All investigAtors viA the online portAl And serve As A rich stArting point from which new work cAn be plAnned or current findings cAn be compAred with. After initiAl fertilizAtion of two gAmetes, the resultAnt zygote undergoes A series of cell divisions. If this process occurs properly, the embryo ultimAtely implAnts within the endometriAl wAll of the uterine cAvity. Pluripotent stem cells then begin to differentiAte into three bAsic germ cell lAyers. by 22 dAys of gestAtion, the embryo is A disc-shAped structure contAining the 3 germ cell lAyers: the ectoderm-lined Amniotic cAvity, the mesoderm, And the endoderm Arising within the yolk sAc. At the crAniAl And cAudAl ends, the ectoderm And endoderm Are in direct contAct, And these bilAminAr AreAs Are described As the orophAryngeAl And cloAcAl membrAnes (Figure 22.1A) [1]. With further growth, this disc folds progressively both crAniocAudAlly And lAterAlly, resulting in yolk sAc invAginAtion. over the ensuing 6 weeks, the yolk sAc tubulArizes And differentiAtes into the stomAch, smAll
Biological Dimensions of Difference
Christopher J. Nicholls in Neurodevelopmental Disorders in Children and Adolescents, 2018
Fertilization involves the fusion of gametes into a new organism, the “zygote.” Cell division initially involves no growth, but rather cleavage of the cells into 2, 4, 16, and so on until 128 cells are reached, at which time the embryo becomes called a “blastula.” At about 7 days after fertilization, the blastula attaches itself to the uterus and becomes implanted. By day 9, two “germ” layers have become differentiated (an outer or “dorsal” ectoderm and an inner or “ventral” endoderm), and later as a result of the blastula folding inward, a third level (mesoderm) develops between the ectoderm and the endoderm. On day 18 of life, the nervous system begins to form on the dorsal surface (think of the dorsal fin on a shark) of the embryo, and in the third week of gestation, the ectodermal germ layer differentiates into a pear-shaped disk with an upper (cranial) and lower (caudal) end. This disk is called the “neural plate.” The more central cells on this plate become narrower on their inner surface, while the cells around them become narrower on their outer surface, which produces a “neural groove” which gradually deepens and eventually folds over onto itself, to become the “neural tube.” This tube closes from the middle toward each end, and gradually extends as a fluid filled tube with two open ends that eventually close by about 25 days of life. The cranial end of this tube ultimately becomes the brain, while the caudal end becomes the spinal cord. The reader is encouraged to review any of the multitude of YouTube videos showing the sequences of the above steps which are collectively termed “neurulation.”
Is the Human Embryo an Organism?
Nicholas Colgrove, Bruce P. Blackshaw, Daniel Rodger in Agency, Pregnancy and Persons, 2023
Early human development is summarized in Figure 1.1. Briefly, upon sperm-egg fusion at fertilization, a single cell (the zygote) is formed (Figure 1.1A). The zygote divides rapidly, producing a number of smaller cells known as blastomeres (Figure 1.1B). By the second or third day following sperm-egg fusion, the blastomeres have formed a ball-like structure known as a morula-stage embryo (Figure 1.1C). Cell division continues, and by the fifth day, the embryo has grown to about one hundred cells and formed a fluid-filled structure known as a blastocyst (Figure 1.1E). At this stage, the first two committed cell types have arisen. The cells that make up the outer layer of the blastocyst are known as trophectoderm (TE). Inside the blastocyst is a cluster of cells, known as the inner cell mass (ICM).
Effect of epigallocatechin-3-gallate (EGCG) on embryos inseminated with oxidative stress-induced DNA damage sperm
Published in Systems Biology in Reproductive Medicine, 2020
Man Chen, Wanmin Liu, Zhiling Li, Wanfen Xiao
A murine model of H2O2-induced sperm DNA damage had been established by Xiao et al. (2012) and provided the basis of our follow up experiments. In this model, the sperm exhibited the same level of DNA damage (evaluated using γH2AX level) as observed in the frozen-thawed sperm. However, the low fertilization rate observed in the frozen-thawed sperm was mitigated in the H2O2-treated sperm. The expression of γH2AX was detected in one- and four-celled embryos that were fertilized with 1-mM H2O2-treated sperm. However, the expression of γH2AX was not detected in the embryos inseminated with fresh spermatozoa (Xiao et al. 2012). Additionally, Wang et al (2013a) observed that the zygotes fertilized with H2O2-treated sperm exhibited G2/M cell cycle arrest. The expression of ATM (pSer-1981) and Chk1 (pSer-345) was detected in the zygotes fertilized with the H2O2-treated sperm. These results suggested that the DNA damage repair and the cell cycle checkpoints were functionally effective in the embryos inseminated with H2O2-treated sperm. ATM was activated and functioned as the co-upstream factor of DNA damage repair and cell cycle checkpoint mechanism to resolve the genomic stability in the sperm exhibiting H2O2-induced DNA damage. Hence, we investigated the potential protective mechanism of EGCG on embryos inseminated with H2O2-treated sperm by examining the effect of EGCG treatment on embryonic cleavage time and activation of ATM.
Towards the selection of embryos with the greatest implantation potential
Published in Journal of Obstetrics and Gynaecology, 2021
Dalia Khalife, Antoine Abu-Musa, Ali Khalil, Ghina Ghazeeri
Because of the few observations during the morphological assessment, several investigators have accepted the challenge to show that morphokinetic development of embryos presents a broader image of the embryo behaviour. It has been shown to be advantageous in providing more information on the timing of events such as fertilisation, the extrusion of polar bodies and the timing of cellular divisions (Fréour et al. 2013; Muñoz et al. 2013). Morphokinetic parameters used to predict the formation of a zygote into a blastocyst were based on the duration of the first cellular division, the time interval between 1 and 2 cell embryo and the synchronicity from 2 to 4 cell embryo. The development to high-grade blastocyst can be estimated in the first 2 days of embryo culture (Kirkegaard et al. 2013), as it is correlated to an early cellular division, to a shorter time of second division (3 to 4 cells) between 9.33 to 12.65 h and shorter time of third division (5 to 8 cells) between 0 to 4 h (Montag et al. 2011; Hashimoto et al. 2012; VerMilyea et al. 2014).
Pronuclear pattern does not predict morphokinetics behavior in human embryos
Published in Gynecological Endocrinology, 2018
Azita Faramarzi, Mohammad Ali Khalili, Marjan Omidi, Azam Agha-Rahimi, Fatemeh Taheri
We found that PN morphology associated with direct and arbitrary cleavage and arrested embryos. However, Z4 zygotes had higher rates of arrest compared to Z1–Z3 zygotes. Abnormal cleavage patterns, such as direct cleavage, which are not visualized by conventional assessments, result in lower developmental competence [19]. However, our TLM analysis showed that Z4 zygotes had higher prevalence of direct and arrested embryos. It has been reported that one of the possible reasons for abnormal cleavage pattern embryos is aneuploidy and genetic disorders [28]. This is also in line with the findings of Balaban and collaborate that showed the PN patterning can foretell risk of abnormal cleaving and arrest of embryos. Also, they found a strong association with occurrence of chromosomal aberration [25]. An early step of embryonic axis formation may be determined by chromatin and nucleoli polarization, which will from following embryo development. Also, it can be the reason of direct cleavage in embryos derived from Z4 zygotes. Although, Bar-Yoseph and coworkers suggested that PN scoring could not predict implantation rate compared to day 2 morphology assessments [13]. Also, these observations require handling of embryos outside the incubator, which expose the embryos to unstable ambient condition [29].