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Zona Pellucida: A tough transparent membrane surrounding the Ovum. It is penetrated by the sperm during Fertilization.

Fertilization

JoVE 10907

During fertilization, an egg and sperm cell fuse to create a new diploid structure. In humans, the process occurs once the egg has been released from the ovary, and travels into the fallopian tubes. The process requires several key steps: 1) sperm present in the genital tract must locate the egg; 2) once there, sperm need to release enzymes to help them burrow through the protective zona pellucida of the egg; and 3) the membranes of a single sperm cell and egg must fuse, with the sperm releasing its contents—including its nucleus and centrosome—into the egg’s cytoplasm. If these steps are successful, the genetic material of the male and female gametes combine, and mitotic cell division commences, giving rise to a diploid embryo. The binding of the sperm and egg cell brings about various changes, among them the production of waves of calcium ions (Ca2+) pulsing through the egg cell. Such oscillations are initiated by sperm-egg fusion and result from both the release and uptake of endogenous Ca2+ in the endoplasmic reticulum of an egg cell and the simultaneous discharge and intake of such ions from the egg’s extracellular environment. Importantly, calcium signaling modifies the egg by causing vesicles, called cortical granules, that lay directly below its plasma membrane to release their contents into the open space bene

 Core: Reproduction and Development

Spermatogenesis

JoVE 10905

Spermatogenesis is the process by which haploid sperm cells are produced in the male testes. It starts with stem cells located close to the outer rim of seminiferous tubules. These spermatogonial stem cells divide asymmetrically to give rise to additional stem cells (meaning that these structures “self-renew”), as well as sperm progenitors, called spermatocytes. Importantly, this method of asymmetric mitotic division maintains a population of spermatogonial stem cells in the male reproductive tract, ensuring that sperm will continue to be produced throughout a man’s lifespan. As spermatogenesis proceeds, spermatocytes embark on meiosis, and each ultimately divides to form four sperm—each with only 23 chromosomes— that are expelled into the male reproductive tract. Interestingly, this is in contrast to oogenesis in women, during which only a single egg is generated for every progenitor cell. At the end of spermatogenesis, sperm demonstrate their characteristic shape: a “head” harboring minimal cytoplasm and a highly condensed nucleus, as well as a motile tail (flagellum). They are small cells, with no organelles such as ribosomes, ER or Golgi, but do have many mitochondria around the flagellum for power. Just below the head is the acrosomal vesicle which contains hydrolytic enzymes to penetrate the egg outer coat—th

 Core: Reproduction and Development

Cleavage and Blastulation

JoVE 10908

After a large-single-celled zygote is produced via fertilization, the process of cleavage occurs while zygotes travel through the uterine tube. Cleavage is a mitotic cell division that does not result in growth. With each round of successive cell division, daughter cells get increasingly smaller.

At the beginning of embryogenesis, maternal mRNAs control development. However, by the eight-cell stage of cleavage, embryonic genes become activated in a process called zygotic genome activation (ZGA). As a result, maternal mRNAs get degraded, and ZGA causes a transition from maternal to zygotic genetic control of developing an embryo. Although maternal mRNAs get degraded, previously translated proteins may remain in the embryo through later stages of development. Cleavage patterns vary between organisms depending on the presence and distribution of egg yolk amongst other factors. For example, mammals have a holoblastic rotational cleavage pattern. They are holoblastic because they have sparse, but evenly distributed yolk and therefore end up with a cleavage furrow that extends through the entire embryo as opposed to being meroblastic where the cleavage furrow does not extend through the yolk-dense portion of the cytoplasm. At the onset of cleavage, rotational cleavage begins when the zygote first divides to form two smaller daughter cells called blas

 Core: Reproduction and Development

Bottlenose Dolphin (Tursiops truncatus) Spermatozoa: Collection, Cryopreservation, and Heterologous In Vitro Fertilization

1Department of Animal Reproduction, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), 2Department of Animal Medicine and Surgery, School of Veterinary Medicine, Universidad Complutense de Madrid, 3Department of Physiology, Faculty of Veterinary Science, University of Murcia, Campus Mare Nostrum, 4Mundomar, Benidorm, 5Veterinary Services, L'Oceanográfic, Ciudad de las Artes y las Ciencias, Junta de Murs i Vals, s/n, 46013

JoVE 55237

 Developmental Biology

Measuring Intracellular Ca2+ Changes in Human Sperm using Four Techniques: Conventional Fluorometry, Stopped Flow Fluorometry, Flow Cytometry and Single Cell Imaging

1Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología-Universidad Nacional Autónoma de México, 2Math and Sciences Department, Edison State College

JoVE 50344

 Biology

Laser-assisted Lentiviral Gene Delivery to Mouse Fertilized Eggs

1Neurobiology Laboratory, National Institute of Environmental Health Sciences, 2Comparative Medicine Branch, National Institute of Environmental Health Sciences, 3Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, 4Signal Transduction Laboratory, National Institute of Environmental Health Sciences

JoVE 58327

 Biology

Combinational Treatment of Trichostatin A and Vitamin C Improves the Efficiency of Cloning Mice by Somatic Cell Nuclear Transfer

1Division of Biological Science, Graduate School of Biology-Oriented Science and Technology, Kindai University, 2Faculty of Biology-Oriented Science and Technology, Kindai University, 3Wellcome Trust/Cancer Research UK Gurdon Institute and Department of Zoology, University of Cambridge, 4Laboratory of Reproductive Biology, Graduate School of Agriculture, Kyoto University, 5Institute of Advanced Technology, Kindai University

JoVE 57036

 Developmental Biology

Analysis of Chromosome Segregation, Histone Acetylation, and Spindle Morphology in Horse Oocytes

1Department of Health, Animal Science and Food Safety, University of Milan, 2IRCCS. Istituto Ortopedico Galeazzi, 3PRC, CNRS, IFCE, Université de Tours, INRA, 4PAO, INRA, 5Clinique des Animaux de Compagnie et des Équidés, Université de Liège, 6University of Agricultural Sciences and Veterinary Medicine, Cluj-Napoca, Romania

JoVE 55242

 Developmental Biology

Structure-function Studies in Mouse Embryonic Stem Cells Using Recombinase-mediated Cassette Exchange

1Department of Biomedical Molecular Biology, Ghent University, 2Inflammation Research Center, VIB, 3Center for Medical Genetics, Ghent University Hospital, 4Cancer Research Institute Ghent (CRIG), 5Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, 6Helmholtz Center for Infection Research, 7Mammalian Functional Genetics Laboratory, Division of Blood Cancers, Australian Centre for Blood Diseases, Department of Clinical Haematology, Monash University and Alfred Health Alfred Centre

JoVE 55575

 Developmental Biology

In Vitro Growth of Mouse Preantral Follicles Under Simulated Microgravity

1Reproductive Medicine Center, The First Affiliated Hospital of Wenzhou Medical University, 2Department of Orthopaedics, The Second Affiliated Hospital of Wenzhou Medical University, 3Department of Obstetrics, The First Affiliated Hospital of Wenzhou Medical University, 4School of Laboratory Medicine and Life Science, Wenzhou Medical University, 5School of Pharmaceutical Science, Wenzhou Medical University, 6Stem Cells and Genetic Engineering Group, AgriBioscience Research Centre, Department of Economic Development, Jobs, Transport and Resources, 7Department of Histology and Embryology, Wenzhou Medical University

JoVE 55641

 Developmental Biology

Inactivation of mTor: A Tool to Investigate Meiotic Progression and Translational Control During Bovine Oocyte Maturation

1BVN Neustadt/Aisch, 2Faculty of Veterinary Medicine, Clinic for Obstetrics, Gynecology and Andrology of Large and Small Animals, Justus-Liebig-University Giessen, 3Reproductive Cell Biology Unit, Leibniz Institute for Farm Animal Biology, 4Reproductive Biochemistry Unit, Leibniz Institute for Farm Animal Biology

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JoVE 53689

 JoVE In-Press
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