Integrin Function in Early Vertebrate Development: Perspectives from Studies of Amphibian Embryos
Yoshikazu Takada in Integrins: The Biological Problems, 2017
Mechanistically, the process of gastrulation may be considered on several levels that include: (1) the “behavior” of the individual cells that collectively serve to “drive” morphogenesis at gastrulation, (2) the molecules mediating the shape changes and adhesive properties of these cells, and (3) the control of the timing and patterning of the cellular movements involved. Following the progression through early cleavage and blastula stages, gastrulation begins with the appearance of a slit-like invagination of bottle cells, termed the blastopore, on the dorsal side of the embryo as illustrated in Figure 1. The involuting mesoderm subsequently comes in contact with the blastocoel roof and travels along it in the direction of the animal pole. The zone of involution initiated at the dorsal lip of the blastopore spreads laterally and ventrally to enclose the endoderm, which remains visible as a yolk plug through late gastrulation. The superficial cells of the animal pole and equatorial marginal zone spread by epiboly during this process, thus covering the entire outer surface of the embryo. Inside the embryo, the endodermally derived archenteron forms as the mesoderm advances, resulting in the displacement of the blastocoel (Figure 1).
Magnetic Resonance Imaging in Developmental Biology
Michel M. J. Modo, Jeff W. M. Bulte in Molecular and Cellular MR Imaging, 2007
Although the resolution of the three-dimensional MRM does not permit us to visualize thin structures such as Brachet’s cleft directly, its location and time of appearance can be deduced in the MRM renderings by discontinuities in the intrinsic contrast between the vegetal cell mass and animal cap and the extrinsic contrast between the inner subclone and the unlabeled ectodermal tissue. In our MRM images, the formation of the cleft first becomes evident at stage 10,when the outwardly rotating vegetal cell mass apposes the ectoderm (stage 10, large open arrow). The cleft runs through the labeled C1 clone, separating it into inner mesendodermal and outer ectodermal subclones (stages 10.5 to 12). The inner and outer subclones then behave differently. The vegetal limits of the two parts move together ventral-ward with the blastopore (asterisk). However, the animal limit of the outer subclone remains stationary (solid arrow), while the animal limit of the inner subclone moves anteriorly, following the leading edge of gastrulation (open arrow). The final configuration of the labeled clone confirms the tissue identity of the inner and outer subclones as mesendodermal and ectodermal, respectively. At the end of gastrulation (stage 12), the inner subgroup of the C1 clone lies within the mesendoderm, dorsal to the developing archenteron. The dorsal view of the embryo (Figure 16.4, middle column) shows how the clone changes its morphology from a somewhat squat appearance to an elongated one, consistent with the normal convergent-extension behavior of the axial mesoderm during gastrulation.
The Twentieth Century
Arturo Castiglioni in A History of Medicine, 2019
Gastrulation had long been recognized as a significant step in the sequence of events associated with organization of the embryo. It was known that a large portion of the ectoderm (the outermost of the three primitive layers) of the blastula swept downward to the blastopore (the mouth of the primitive gut, or archenteron), where it invaginated to produce the mesoderm and roof of the archenteron. Attempts at tracing the subsequent fate of different regions of this presumptive mesoderm were at first confined to the production of an injury in a single region, until W. vogt mapped out the fate of the different surface areas of the amphibian gastrula (1929), by staining circumscribed regions with vital dyes and tracing their subsequent migrations.
Complex split cord malformation with split conus
Published in British Journal of Neurosurgery, 2021
Tobin George, Ganesh Divakar, Biren Patel, Sreenath P. R., Krishnakumar K., Easwer H. V., Prakash Nair
Gastrulation is a formative process by which the ectoderm, mesoderm and the endoderm, which are precursors of all embryonic tissues, and the axial orientation, are established in embryos.1 During gastrulation, epiblastic cells from the edges on either side of the of the Primitive node flow through the primitive pit to wedge between ectoderm and endoderm.2 They then undergo midline integration under the ectoderm to form the solid midline notochord. Spinal dysraphism involves a spectrum of congenital anomalies which occur due to embryogenic defects in either gastrulation, primary, secondary or junctional neurulation. While these processes are fundamentally different, each contributes to the formation of the spinal neuraxis.3 Failure of midline integration of the notochord has been speculated to result in split cord malformation. In a type I split cord malformation (SCM) there are two hemicords, each contained within its own dural tube, separated by a dura-sheathed rigid osseocartilaginous median septum.4
Nanopolystyrene beads affect motility and reproductive success of oyster spermatozoa (Crassostrea gigas)
Published in Nanotoxicology, 2020
K. Tallec, I. Paul-Pont, M. Boulais, N. Le Goïc, C. González-Fernández, F. Le Grand, A. Bideau, C. Quéré, A.-L. Cassone, C. Lambert, P. Soudant, A. Huvet
Healthy spermatozoa are crucial for ensuring the sustainability of C. gigas through the transfer of genetic heritage to oocytes and offspring. Among the parameters that define the quality of spermatozoa, the motility (e.g. the percentage of motile spermatozoa and the swimming speed) and reproductive success are predominant (Taylor et al. 2014). Here, despite a very short exposure of 1h, the 50-NH2 beads reduced the percentage of motile spermatozoa and their VAP, leading to a decrease in the D-larval yield, which was used as a proxy for reproductive success. While the present study showed that toxic effects on spermatozoa appeared from 10µg mL−1 of 50-NH2 beads, embryotoxicity was observed from 0.1µg mL−1 in oyster embryos exposed to the same particles (Tallec et al. 2018). Higher embryotoxicity than spermiotoxicity has been previously observed in oysters and sea urchins embryos/spermatozoa exposed to PAH-contaminated sediments and xenobiotics (Geffard et al. 2001; Manzo, Buono, and Cremisini 2006). This difference can be related to the set of intense metabolic and morphological modifications (e.g. numerous cleavages, gastrulation, organogenesis, shell calcification) triggered during embryogenesis (Fitzpatrick et al. 2008).
Sirenomelia and maternal chlamydia trachomatis infection: a case report and review
Published in Fetal and Pediatric Pathology, 2019
Gabriella Fuchs, Ekaterina Dianova, Sunny Patel, Sonia Kamanda, Rita Prasad Verma
The etiopathogenesis of sirenomelia is explained by two proposed pathophysiological hypotheses. The first mechanism postulated by Stocker and Heifetz in 1987 [13] is the “defective blastogenesis hypothesis” where a teratogenic insult during the gastrulation stage of embryogenesis, corresponding to the third human gestational week, causes malformation of the notochord and results in abnormal development of the caudal somites and tailbud [8]. The second mechanism hypothesized by Stevenson et al. (1986) [14] suggests a “vascular steal hypothesis” where a single aberrant umbilical artery diverts blood and nutrients away from caudal parts of the developing embryo, leading to underdevelopment or absence of caudal structures, as seen in sirenomelia. This single umbilical artery originates from a persistent vitelline artery which branches superiorly off of the abdominal aorta. These two hypotheses may not be mutually exclusive, since a defect in early blastogenesis may result in aberrant vessel development that can lead to ischemia and nutrient deficiency of target tissues [1,6]. The agents reported to be linked to sirenomelia in humans or animal models are illicit or prescription drugs, such as, cocaine, retinoic acid, anticonvulsants, and some antibiotics [1,6,9,15]. Other agents include tobacco and heavy metals. Maternal complications tentatively associated with sirenomelia are diabetes mellitus and fever >38 °F in the 1st trimester of pregnancy [1,6,9,15]. Infectious agents in the mother have not been so far linked to the anomaly.
Related Knowledge Centers
- Animal
- Epithelium
- Gastrointestinal Tract
- Embryo
- Cellular Differentiation
- Blastocyst
- Animal Embryonic Development
- Blastulation
- Cell
- Cell Lineage