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The Emergence of Order in Space
Published in Pier Luigi Gentili, Untangling Complex Systems, 2018
Chemical waves of Ca+2 are relevant not only for the control of rapid and frequently repeated responses such as heartbeat, neurotransmitter release, and muscle contraction. They are apparently ubiquitous. They are present in somatic cells and sex cells. Calcium waves are known to trigger transformations of the cell cortex (that is the layer of proteins on the inner face of the plasma membrane of the cell) and cytoplasm, as well as to stimulate many enzymatic and metabolic processes (Whitaker 2006). For example, the activation of eggs by sperm is accompanied by a significant transient in intracellular calcium concentration. The calcium wave initiates at the point of the sperm entry and crosses the egg as a tsunami-like wave at a speed of about 5–50 μm/s (Table 9.2 reports the values relative to mammal eggs of 100 μm crossed by calcium waves in ~2 s) up to reach the antipode of the egg. The large calcium signal triggers a reorganization of the entire egg cortex and cytoplasm (Sardet et al. 1998). There is evidence that calcium signals are important in all three relevant stages of embryogenesis: in embryonic axis formation (anterior-posterior, dorsoventral and left-right axes), in coordinated cell migrations forming tissues (like in gastrulation forming gut and in neurulation generating the spinal cord), and in organogenesis (once the overall body plan is laid out, local differentiation gives rise to organs) (Whitaker 2006).
Morphogenesis
Published in A. Šiber, P. Ziherl, Cellular Patterns, 2018
Also left out are some of the more mature topics, not just the recent developments. Among the processes not discussed we mention neurulation, a process in vertebrates where the so‐called neural plate infolds and closes so as to form the neural tube, which later develops into brain and spinal cord [190], and branching morphogenesis, that is, the formation of hierarchical structures such as lung or gland ducts [191] as well as organoids [140, 192]. We touched upon the specific features of dividing tissues but not upon the subtleties of the mechanical feedback loop controlling cell size and shape so as to ensure stable and uniform growth [193]. Nonetheless, the diverse range of approaches presented here do illustrate the possible ways of viewing tissue deformations in a comparative fashion, inviting readers to approach their own projects from more than a single angle.
Embryotoxic effects of Rovral® for early chicken (Gallus gallus) development
Published in Journal of Toxicology and Environmental Health, Part A, 2021
Beatriz Mitidiero Stachissini Arcain, Maria Cláudia Gross, Danúbia Frasson Furtado, Carla Vermeulen Carvalho Grade
Defects in the cranial region of the embryos treated with Rovral® were predominantly incomplete formation of the head/brain, absence of the beak and microphthalmia. The formation of the head depends upon the coordination of several complex processes, which include neurulation and correct closure of the neural tube (Schoenwolf 2018), as well as cephalic folding of the embryo’s body (Gilbert and Barresi 2016). Further, neural crest cells released from neural ridges migrate to the rostral region, filling the pharyngeal arches and contributing to the formation of the skeleton, melanocytes, connective tissue, smooth muscle, fascia and parts of the peripheral nervous system of the face and neck (Creuzet, Couly, and Le Douarin 2005). Defects in neurulation and incorrect cephalic formation lead to anencephaly or encephalocele (Wolujewicz and Ross 2019). Poor neural crest migration in the rostral region might affect structures of the face and neck, and, in humans, results in conditions such as the Waardenburg syndrome (Dourmishev et al. 1999) and CATCH 22 syndrome (Boyarchuk, Volyanska, and Dmytrash 2017).