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Fetus: The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after Conception until Birth, as distinguished from the earlier Embryo, Mammalian.

Oogenesis

JoVE 10906

In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from the equivalent procedure of spermatogenesis in males. First, meiotic divisions during oogenesis are asymmetric, meaning that a large oocyte (containing most of the cytoplasm) and minor polar body are produced as a result of meiosis I, and again following meiosis II. Since only oocytes will go on to form embryos if fertilized, this unequal distribution of cell contents ensures that there are enough cytoplasm and nutrients to nourish the early stages of development. Second, during oogenesis, meiosis “arrests” at two distinct points: once during embryonic growth and a second time during puberty. In mammals, oocytes are suspended in prophase I until sexual maturation, at which point meiosis I continues under hormonal influence until an egg precursor cell is released into a fallopian tube. At ovulation, the precursor exits the ovary and, only if fertilization occurs, is stimulated to complete meiosis II and form a complete egg. Defects during oogenesis can result in severe consequences. In particular, problems with chromosome segregation during either meiosis I or meiosis II may lead to an embryo being aneuploid, meaning that it contains an abnormal number of chromosomes. Increased age elevates a woman

 Core: Biology

Antibody Structure

JoVE 10898

Antibodies, also known as immunoglobulins (Ig), are essential players of the adaptive immune system. These antigen-binding proteins are produced by B cells and make up 20 percent of the total blood plasma by weight. In mammals, antibodies fall into five different classes, which each elicits a different biological response upon antigen binding.

Antibodies consist of four polypeptide chains: two identical heavy chains of approximately 440 amino acids each, and two identical light chains composed of roughly 220 amino acids each. These chains are arranged in a Y-shaped structure that is held together by a combination of covalent disulfide bonds and noncovalent bonds. Furthermore, most antibodies carry sugar residues. The process of adding sugar side chains to a protein is called glycosylation. Both the light chain and heavy chain contribute to the antigen binding site at each of the tips of the Y structure. These 110-130 amino acids are highly variable to allow recognition of an almost unlimited number of antigens. This region is also called the variable region and is part of the antigen binding fragment. Each arm of the Y-shaped unit carries an identical antigen binding site. Antibodies can crosslink antigens: when one arm binds to one antigen and the other arm binds to a second, structurally identical antigen. Crosslinking is facilitated by the f

 Core: Biology

Natural Selection- Concept

JoVE 10632

Fitness

Widespread variation of phenotypes in natural populations provides the raw material for evolution, which is the change in the inherited traits of populations over successive generations. Natural selection is one of the main mechanisms of evolution and requires variable traits to be heritable and associated with differential survival and/or reproductive success. Phenotypes that…

 Lab Bio

Tissue Regeneration with Somatic Stem Cells

JoVE 5339

Somatic or adult stem cells, like embryonic stem cells, are capable of self-renewal but demonstrate a restricted differentiation potential. Nonetheless, these cells are crucial to homeostatic processes and play an important role in tissue repair. By studying and manipulating this cell population, scientist may be able to develop new regenerative therapies for injuries and diseases.


 Developmental Biology

Explant Culture for Developmental Studies

JoVE 5329

Explant culture is a technique in which living cells or tissues are removed from an embryo for continued development outside of the organism. This ex vivo approach allows researchers to manipulate and observe developing tissues in ways that are not possible in vivo. Once established, explant culture is frequently used to understand the role of genes and signaling molecules in …

 Developmental Biology

A Novel Surgical Approach for Intratracheal Administration of Bioactive Agents in a Fetal Mouse Model

1Molecular Virology and Gene Therapy, KU Leuven, 2Department of Woman and Child, KU Leuven, 3Neurobiology and Gene Therapy, KU Leuven, 4Division of Nuclear Medicine, KU Leuven, 5Biomedical NMR Unit/ MoSAIC, KU Leuven

JoVE 4219

 Medicine

Instrumentation of Near-term Fetal Sheep for Multivariate Chronic Non-anesthetized Recordings

1Département de sciences cliniques, CHUV, Université de Montréal, St-Hyacinthe, QC, 2Département d'obstetriques et de gynécologie, CHU Ste-Justine Research Centre, Université de Montréal, 3Département de neurosciences, CHU Ste-Justine Centre de recherche, Université de Montréal, 4Centre de recherche en reproduction animale (CRRA), Université de Montréal, St-Hyacinthe, QC

JoVE 52581

 Developmental Biology
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