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Fertilization and normal embryonic and early fetal development
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
Asim Kurjak, Ritsuko K. Pooh, Aida Salihagic-Kadic, Iva Lausin, Lara Spalldi-Barisic
By the end of the 3rd week, the paraxial mesoderm condenses segmentally along the midline to form somite pairs. First the somites are recognized as conspicuous surface elevations and gradually increase in number craniocaudally. The somites give rise to most of the axial skeleton, trunk and limb musculature, and dermis of the skin. The formation and specification of somite segments are controlled by a unique combination of Hox genes (Hox code). Concurrent with somite differentiation, the intraembryonic coelom arises as isolated spaces between the layers of the lateral plate mesoderm, which is the primordium of body cavities. The coelomic cavities subsequently coalesce to form a single, horseshoe-shaped cavity that eventually gives rise to the pericardial, pleural, and peritoneal cavities.
Adult Stem Cell Plasticity
Published in Richard K. Burt, Alberto M. Marmont, Stem Cell Therapy for Autoimmune Disease, 2019
Skeletal muscle derives embryologically from somites.74 Signals from adjacent embryonic structures induce myogenesis in dorsal regions of the somites, giving rise to the dermomyotome, which in turn is the major source of muscle precursor cells, termed satellite cells.75,76 Satellite cells continue to be the major source of muscle cells in the adult, despite a significant drop in their numbers during postnatal development. In aged mice, satellite cells are reduced even farther.78 These precursor cells have unique morphology and express a unique set of proteins including M-cadherin, Myf-5, CD34, and Pax-7.79,80 Satellite cells are normally quiescent, but can be activated to both self-renew and produce more committed myocyte precursors upon muscle injury or weight bearing exercise.81,82 After activation, myocyte precursors undergo multiple cycles of cell division before fusing with existing myofibers or with each other to make new myofibers.77,81,83
Embryology of the Spinal Cord, Peripheral Nerves, and Vertebrae
Published in Bernard J. Dalens, Jean-Pierre Monnet, Yves Harmand, Pediatric Regional Anesthesia, 2019
Bernard J. Dalens, Jean-Pierre Monnet, Yves Harmand
In stage 14 (5- to 7-mm embryos, 32 d), the segmental division of somites has developed considerably. About 15 to 20 ventral and dorsal spinal roots have joined together, thus constituting the spinal nerves that grow medially and ventrally through the mesenchyma. The segmental disposition and growth of these nerves is responsible for a metameric disposition of the skin areas (dermatomes) they supply.
Development a high-throughput zebrafish embryo acute toxicity testing method based on OECD TG 236
Published in Toxicology Mechanisms and Methods, 2023
Shisan Xu, Fengyan Chen, Huan Zhang, Zhen-lie Huang, Jianjun Li, Desheng Wu, Xueping Chen
As an embryo acute toxicity testing model, zebrafish have several advantages, including the observation of numerous endpoints. Compared with the OECD 236 guidelines, we did not use the lack of somite as a mortality endpoint. This is underscored by the fact that we never observed zebrafish embryo die with the only symptom being lack of somite. This symptom was always included together with no heartbeat or tailbud non-detachment symptoms. In the present study, a 96-well microtiter plate was used (instead of 24-well plate) to perform the exposure assay. This modification can reduce the chemical used for the test and reduce toxic waste disposal. It was reported that smaller exposure volume may result to reduced chemical absorption and increased LC50 (Cassar et al. 2019). However, our experiments indicate that using a 96-well plate instead of a 24-well plate did not significantly affect testing results (Figure 2(C and B)). In our modified method, conserving the volume of the toxicity testing chemical and increasing the number of samples leads to a higher throughput assay.
In vitro antibacterial and anti-inflammatory effects of Anacardium occidentale L. extracts and their toxicity on PBMCs and zebrafish embryos
Published in Drug and Chemical Toxicology, 2022
Luana Souza Amorim, Pedro Everton Marques Goes, Rebeca Dantas Alves Figueiredo, Juliana Alves da Costa Ribeiro Souza, Josean Fechine Tavares, Lucio Roberto Cançado Castellano, Ricardo Dias de Castro, Davi Farias, Sabrina Garcia de Aquino
Following the guideline 236 of the Organization for Economic Cooperation and Development (OECD) for the fish embryo acute toxicity test (FET) (OECD 2013), zebrafish embryos up to 3 h post-fertilization (hpf) were exposed to one of five concentrations of A. occidentale leaf or bark extract (4.37, 8.75, 17.5, 35, and 70 µg/mL). For each concentration, a 24-well plate was prepared: 20 fertilized eggs (1 embryo per well) were exposed to the test sample, and the other four were used as internal controls (E3 embryo medium). An additional plate containing 20 embryos exposed only to E3 medium as a negative-control plate. Over the next 96 h, the embryos were analyzed every 24 h for the following apical endpoints: embryo coagulation, lack of somite formation, no detachment of the tail of the yolk sac, and lack of heartbeat. In the presence of any of these endpoints, the embryo/larva was considered dead. The number of deaths was used to calculate mortality (mortality% = number of deaths/total organisms × 100). In addition, sublethal effects such as eye malformation, otolith malformation, mouth malformation, spine malformation, changes in body pigmentation, egg hatching delay, yolk sac edema, body malformation, pericardial edema, head edema, blood clotting, thigmotaxis, and undersize were recorded daily. The exposures were performed under static conditions (without renewing the test sample or E3 medium). The observations were performed under a stereomicroscope (80× magnification) and photographed (Televal 31, Zeiss). After 96 h, the surviving larvae were euthanized with eugenol and properly discarded.
In vitro study of the toxic and teratogenic effects of prednisolone, azathioprine and mycophenolate mofetile on embryological development of rats
Published in Drug and Chemical Toxicology, 2022
Zeliha Fazliogullari, Ahmet Kagan Karabulut, Nadire Unver Dogan, Ismihan Ilknur Uysal, Hasan Acar
Finally, the study evaluated the embryos cultured within the combination of PRZ (20 µg/ml) and different doses of MMF (1–10 µg/ml). It was found that the drug combinations caused statistically significant developmental retardation in both the total morphological score (beginning at a dose of 5 µg/ml) and in the number of somites (beginning at a dose of 7.5 µg/ml) (Figures 13 and 14). When these combinations are evaluated regarding the malformations, oedema around the neural tube (p < 0.01, p < 0.001) was seen at 7.5 µg/ml and higher doses, and hematoma and pericardial oedema (p < 0.01, p < 0.001) were observed beginning at a dose of 5 µg/ml. The TUNEL test was positive in all cells cultured with the drug combinations, beginning at the lowest dose (Figure 9(b)).