Advances in Anatomy, Embryology, and Cell Biology

The effects of ionizing radiation on centrosomes have been well documented and reviewed by Saladino et al. (2012) and are only briefly addressed here. These results showed that exposure of tumor cells to ionizing radiation causes centrosome overduplication and the formation of multipolar mitotic spindles, resulting in nuclear fragmentation and subsequent cell death (Sato et al. 2000). By using a variety of cell lines derived from different types of human solid tumors, it was shown that exposure to 10 Gy γ-radiation resulted in a substantial increase in cells containing an abnormally high number of aberrant centrosomes that formed multipolar spindles, resulting in imbalanced chromosome separation followed by mitotic cell death and formation of multi- or micronucleated cells...

Cellular polarization involves significant remodeling and decentralization of the nucleus-associated centrosome to focal points at the apical and basolateral surfaces which is associated with major remodeling of the microtubule system in which individual microtubules become nucleated and organized from the polarizing cell surfaces, as studied in polarizing epithelial cells (reviewed in Müsch 2004; Muroyama and Lechler 2017). These changes are associated with cellular asymmetry in preparation for cellular differentiation of previously non-committed cells...

Centrosome functions are vitally important for all aspects of reproduction with essential functions during meiosis, fertilization, cell division, centrosome remodeling during cellular polarization for tissue formation, and all stages of subsequent embryo development. Any defects in centrosome organization and dynamics can result in meiotic spindle formation errors, meiotic division errors, infertility, subfertility, arrested or failed development, and predisposition to various diseases including cancer. These aspects of reproduction will be addressed in more detail in the following sections...

One of the most interesting aspects of host cell-viral interactions is how the pathogen exploits the host cell cytoskeleton and centrosomes for survival in the host cell.

As major accomplishments and breakthroughs in centrosome research had been achieved by Theodor Boveri in reproductive cells with the invertebrate sea urchin being an ideal model system for such studies on fertilization, cell division, and embryo development, these studies also gave rise to Boveri's brilliant concept regarding cancer cells. He discovered that eggs fertilized with two sperm resulted in tripolar mitosis and abnormal cell division, similar to cells observed in cancer tissue.

Among the multiple and intriguing roles of centrosomes in cellular functions is the ubiquitin-proteasome-mediated protein degradation. It has been shown that proteasomes are concentrated at the mammalian centrosome which led to further studies to view the centrosome as a proteolytic center (Wojcik et al. 1996; Wigley et al. 1999; reviewed in Badano et al. 2005). Proteasomal components that are concentrated around the centrosome include ubiquitin, the 20S and 19S subunits of the proteasome, as well as the E3 enzyme parkin...

The synchronized distribution of centrosomal and genetic materials to the dividing daughter cells is critically important and depends on precisely orchestrated processes on structural and molecular levels. Structural and functional relationships between the nucleus and centrosomes facilitate cellular communication and coordination of cell cycle control and progression which becomes especially important during the transition from interphase to mitosis when synchrony between centrosomes and nuclear events is critical...

The centrosome field has seen enormous progress during the past few decades which spans the large areas of cell biology with new information on cell cycle controls and cellular health; immunology with centrosomes being essential for the formation of the immunological synapse; neurobiology with new insights into centrosome dysfunctions leading to disorders and disease; stem cell biology with fate-determining distribution of centrosomal material during asymmetric cell division; cancer biology with huge insights into the role of centrosomes in disease initiation, progression, and manifestation; reproductive biology with essential centrosome functions in oocytes, during fertilization and embryo development in which centrosome dysfunctions can be related back to abnormal centrosomal material in the meiotic spindle of oocytes; and several others that will be highlighted in the specific chapters of this book...

Chapter 8 was inadvertently published with errors and the following corrections were updated.

Placentation in humans is precocious and highly invasive compared to other mammals. Implantation is interstitial, with the conceptus becoming completely embedded within the endometrium towards the end of the second week post-fertilization. Villi initially form over the entire surface of the chorionic sac, stimulated by histotrophic secretions from the endometrial glands. The secondary yolk sac never makes contact with the chorion, and a choriovitelline placenta is never established. However, recent morphological and transcriptomic analyses suggest that the yolk sac plays an important role in the uptake of nutrients from the coelomic fluid...

Placenta forms as a momentary organ inside the uterus with a slew of activities only when the woman is pregnant. It is a discoid-shaped hybrid structure consisting of maternal and embryonic components. It develops in the mesometrial side of the uterus following blastocyst implantation to keep the two genetically different entities, the mother and embryo, separated but connected. The beginning and progression of placental formation and development following blastocyst implantation coincides with the chronological developmental stages of the embryo...

The female elephant shows a 3-week "follicular phase" to commence her 16-week estrous cycle at the end of which a second surge in pituitary luteinizing hormone (LH) release matures and ovulates an ovarian follicle in association with estrous behavior and mating, whereas the first LH surge at the start of the follicular phase causes luteinization of 3-5 partially developed follicles. The prolonged pregnancy of 22 months is supported by a zonary endotheliochorial placenta which secretes placental lactogen (ePL) from around 40 days of gestation in association with replacement of the lumenal epithelium of the endometrium by trophoblast and the development of large corpora lutea (CLs) in the maternal ovaries from the previously formed luteinized follicles in response to the first LH peak early in the follicular phase...

In the domestic dog, placentation arises from central implantation, passing through a transitional, yet important stage of choriovitelline placenta (yolk sac placenta), on the way to the formation of the definite, deciduate, zonary (girdle) allantochorionic endotheliochorial placenta.Sharing some similarities with other invasive types of placentation, e.g., by revealing decidualization, it is characterized by restricted (shallow) invasion of trophoblast not affecting maternal capillaries and maternal decidual cells...

In comparison to many other mammalian species, ruminant ungulates have a unique form of placentation. Ruminants initially display an epitheliochorial type of placentation; however, during the period of placental attachment, trophoblast giant binucleate cells (BNC) develop within the chorion to migrate and fuse with the uterine surface epithelium to form syncytial plaques. Binucleate cell migration and fusion continues throughout pregnancy but never appears to breach the basal lamina, beneath the uterine surface or luminal epithelium...

This chapter focuses on the early stages of placental development in horses and their relatives in the genus Equus and highlights unique features of equid reproductive biology. The equine placenta is classified as a noninvasive, epitheliochorial type. However, equids have evolved a minor component of invasive trophoblast, the chorionic girdle and endometrial cups, which links the equine placenta with the highly invasive hemochorial placentae of rodents and, particularly, with the primate placenta. Two types of fetus-to-mother signaling in equine pregnancy are mediated by the invasive equine trophoblast cells...

Pregnancy in pigs includes the events of conceptus (embryo/fetus and placental membranes) elongation, implantation, and placentation. Placentation in pigs is defined microscopically as epitheliochorial and macroscopically as diffuse. In general, placentation can be defined as the juxtapositioning of the endometrial/uterine microvasculature to the chorioallantoic/placental microvasculature to facilitate the transport of nutrients from the mother to the fetus to support fetal development and growth. Establishment of epitheliochorial placentation in the pig is achieved by: (1) the secretions of uterine glands prior to conceptus attachment to the uterus; (2) the development of extensive folding of the uterine-placental interface to maximize the surface area for movement of nutrients across this surface; (3) increased angiogenesis of the vasculature that delivers both uterine and placental blood and, with it, nutrients to this interface; (4) the minimization of connective tissue that lies between these blood vessels and the uterine and placental epithelia; (5) interdigitation of microvilli between the uterine and placental epithelia; and (6) the secretions of the uterine glands, called histotroph, that accumulate in areolae for transport though the placenta to the fetus...

It is sometimes implied that marsupials are "aplacental," on the presumption that the only mammals that have a placenta are the eponymous "placental" mammals. This misconception has persisted despite the interest in and descriptions of the marsupial placenta, even in Amoroso's definitive chapter. It was also said that marsupials had no maternal recognition of pregnancy and no placental hormone production. In addition, it was thought that genomic imprinting could not exist in marsupials because pregnancy was so short...

The preimplantation mammalian embryo is a simplistic, self-contained, and a superior model for investigating the inherent complexities of cell fate decision mechanisms. All mammals begin their humble journey from a single-cell fertilized zygote contained within a proteinaceous coat called the zona pellucida. The zygote embarks on a series of well-orchestrated events, beginning with the activation of embryonic genome, transition from meiotic to mitotic divisions, spatial organization of the cells, timely differentiation into committed trophectoderm (TE) and primitive endoderm (PrE), and ultimately escape from zona pellucida for implantation into the uterus...

In the vertebrate tree of life, viviparity or live birth has independently evolved many times, resulting in a rich diversity of reproductive strategies. Viviparity is believed to be a mode of reproduction that evolved from the ancestral condition of oviparity or egg laying, where most of the fetal development occurs outside the body. Today, there is not a simple model of parity transition to explain this species-specific divergence in modes of reproduction. Most evidence points to a gradual series of evolutionary adaptations that account for this phenomenon of reproduction, elegantly displayed by various viviparous squamates that exhibit placentae formed by the appositions of maternal and embryonic tissues, which share significant homology with the tissues that form the placenta in therian mammals...

Establishment of viviparity in mammals evolved through not only the long-term retainment of the fetus within the maternal uterus but differentiation and expansion of cell layers to form functional membranes to exchange O2 /CO2 and nutrients between the placenta and maternal circulations. Development of a fetal placental vascular circulation to interact with the maternal uterus is critical to the survival of all species. However, the fascination with the mammalian placenta is the robust variation in types, form, attachment, invasiveness, structure, cell differentiation, endocrine function, and regulation of the maternal immune system...