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Summation of Basic Endocrine Data
Published in George H. Gass, Harold M. Kaplan, Handbook of Endocrinology, 2020
The anterior lobe in the fetus forms from an ectodermal evagination of the stomodeum (primordial mouth) just anterior to the buccopharyngeal membrane (Rathke’s pouch). At the third fetal week, this grows toward the infundibulum, which is a downward extension of the diencephalon. At the close of the second month, Rathke’s pouch loses its connection with the mouth and comes into contact with the infundibulum. Cells in the pouch proliferate and form the anterior lobe of the pituitary gland. The pars intermedia develops from the posterior wall of Rathke’s pouch. The infundibulum produces the stalk and the pars nervosa.
3.0: The development of gastric systems in children
Published in Clarissa Martin, Terence Dovey, Angela Southall, Clarissa Martin, Paediatric Gastrointestinal Disorders, 2019
Shomik Ghosal, Adrian G Martin
The cranial foregut, or pharyngeal gut, extends from the oropharyngeal membrane to (and includes) the respiratory diverticulum (lung bud). The derivatives of the pharyngeal gut include part of the mouth and tongue, pharynx, thyroid, parathyroid, thymus, lower respiratory tract and lungs. Development of the mouth comes from the pharyngeal gut and the stomodeum. After 4 weeks the lung bud appears – this will eventually become the lungs.
Mouth and throat, face, and the five senses
Published in Frank J. Dye, Human Life Before Birth, 2019
The mouth (or oral cavity) arises from the stomodeum, an inpocketing of ectoderm on the ventral side of the embryo's head. The stomodeum is separated from the end of the foregut by the oropharyngeal membrane. When the oropharyngeal membrane breaks down during the 24th day of development, the fetus's mouth opens for the first time. This breakdown of the oropharyngeal membrane occurs in the boundary between the oral cavity and the throat or pharynx, which becomes the tonsillar region (where the tonsils are located) of the adult.
Understanding Leishmania parasites through proteomics and implications for the clinic
Published in Expert Review of Proteomics, 2018
Infection in the vector sand fly begins with the intake of an infected bloodmeal. When the sand fly bites, it pierces its mouthpart into the skin and forms an hemorrhagic pool that causes ingestion of blood with amastigote-infected macrophages [20]. The blood meal moves into the midgut for digestion, where amastigotes are clustered and form a membranous structure called a peritrophic matrix to surround the bloodmeal and prevent its digestion by digestive enzymes of the gut. The amastigote then differentiates into the replicative ‘procyclic promastigote’ form, followed by rupture of the anterior portion of peritrophic matrix and release of promastigotes into the midgut epithelium. In the midgut, the parasite replicates via. binary fission and attaches to microvilli of the epithelium through LPG [21,22]. Upon detachment, the parasite moves toward the stomodeal valve in the anterior of the midgut where it continues to undergo replication. This process leads to the formation of the promastigote secretory gel, which serves as plug to obstruct the midgut and pharynx, and the parasite transforms into the infective metacyclic form [23]. The metacyclics then break the stomodeal valve, providing a way for movement of the metacyclics from the thoracic midgut [24]. This process leads to the next infection cycle upon sand fly bite and the release of metacyclics into the new mammalian host. The post-genomic era has greatly contributed to accessibility to different structural proteins and virulence factors in the parasite life cycle with therapeutic potential.
Comparative toxicity of three differently shaped carbon nanomaterials on Daphnia magna: does a shape effect exist?
Published in Nanotoxicology, 2018
Renato Bacchetta, Nadia Santo, Irene Valenti, Daniela Maggioni, Mariangela Longhi, Paolo Tremolada
Figure 2 shows sagittal sections from both controls and exposed samples. D. magna gut is composed by a short anterior region, the stomodeum or foregut, which is protected by a thick chitin layer with the function of transferring food from the mouth to the actual gut. This one, called midgut has anteriorly two diverticula or hepatic ceca, and both have digestive and absorptive functions. The final portion of the gut is called hindgut and is involved in the reabsorption of liquids (Quaglia, Sabelli, and Villani 1976). Microscopic analyses were performed mainly focusing at the midgut region, that is specifically involved in absorption. Contrary to controls, samples exposed to CNMs displayed large masses occupying the entire lumen of the gut (Figure 2(D–L)). These masses entered into contact with the apical cell portions, and in the most affected fields. caused disruption of the peritrophic membranes, whose role in protecting epithelial cells from mechanical damages was thus overcome. While at low concentrations some gut regions seemed to be perfectly conserved, at the highest concentrations the final portion of the midgut appeared completely altered. In these cases the epithelium was extremely reduced, the brush border eroded, and cells showed large empty spaces among them and between them and the basal lamina. These morphologies were mainly diffused in the 50 mg L−1 groups for all the tested CNMs.
Iron nanoparticle bio-interactions evaluated in Xenopus laevis embryos, a model for studying the safety of ingested nanoparticles
Published in Nanotoxicology, 2020
Patrizia Bonfanti, Anita Colombo, Melissa Saibene, Luisa Fiandra, Ilaria Armenia, Federica Gamberoni, Rosalba Gornati, Giovanni Bernardini, Paride Mantecca
In previous papers, Xenopus laevis embryos have been effectively used as experimental model to screen the comparative toxicity of metal and metal oxide NPs (Bacchetta et al. 2012; Colombo et al. 2017). It has been demonstrated that different metal oxides, like CuO, ZnO and TiO2 are able to exert variable embryotoxic effects (Bacchetta et al. 2012; Nations et al. 2011) and that the model is able to predict the teratogenicity of NMs, as in the case of surface coated Ag NPs (Colombo et al. 2017). Remarkably, the main target organ for the NMs studied always resulted to be the intestine. It occurs only at developmental stages following the stomodeum opening, when embryos begin to swallow NP suspensions (Bonfanti et al. 2015). At that point, ZnO NPs come in contact with the intestinal epithelium, where they are adsorbed through different mechanisms, induce oxidative damages and consequent histological lesions to the intestinal mucosa (Bacchetta et al. 2014). Together, these evidences suggest that Xenopus embryos might be profitably adopted to study the absorption mechanism and possible toxicity in a developing system of orally available NMs, like iron NPs that are potentially relevant for environmental or biomedical purposes. Moreover, it should be considered that Xenopus embryos represent a valuable model to bridge in vitro and in vivo studies using mammals, with negligible ethical implications. To confirm this, a study by Webster and collaborators (Webster et al. 2016) showed that after exposure to a range of NPs, the phenotypic score of Xenopus embryos showed a strong correlation with in vitro cell tests and, in particular, magnetite cored NPs, negative for toxicity in vitro and Xenopus, were further confirmed as nontoxic in mice.