Developmental Aspects of Pediatric Pharmacology and Toxicology
Sam Kacew in Drug Toxicity and Metabolism in Pediatrics, 1990
An important component to consider is the stage of fetal development at the time of chemical exposure. During the first week of development after fertilization, the embryo undergoes the process of cleavage and gastrulation. Exposure to drugs such as antimetabolites, ergot alkaloids, or diethylstilbestrol at this stage can result in termination of pregnancy.3 Organogenesis is the next developmental stage covering weeks two to eight of gestation. Exposure to drugs including thalidomide, alcohol, lithium, phenytoin, and isotretoin during this phase can result in serious structural abnormalities.3,5 Chemicals such as cigarette smoke, heavy metals, or carbon monoxide may affect development during the remaining gestational period, ranging from 9 weeks to 9 months. Predominant effects are alteration in the differentiation of the reproductive and central nervous systems.3 Consequently, altered brain function and growth retardation are some of the principle adverse effects due to exposure at this stage. The relationship between stage of development and type of effect is illustrated in Table 2.
Epigenetic Reprogramming in Early Embryo Development
Cristina Camprubí, Joan Blanco in Epigenetics and Assisted Reproduction, 2018
Early embryo development is usually understood as the stage between fertilization and blastocyst implantation, and the places where it physically befalls in mammals involve the uterine tube (oviduct, fallopian tube) and the uterus itself. Under the biological point of view, what happens during the early embryo development is that two highly specialized cells, the spermatozoon and the oocyte, fuse to later originate a number of “undifferentiated” or “non-specialized” cells, the 2, 4, 8, or successive multiples of blastomeres in the early embryos. Under the DNA methylation context, what happens is that two methylated genomes (the ones from the spermatozoon and the oocyte) fuse to originate one common genome that is progressively less methylated, as the blastomere divisions follow one another (1–3). In other words, and combining the biological and DNA methylation views, during early embryo development the cell type-specific epigenetic program disappears temporarily to, shortly after, begin to be re-written differentially according with the cell type.
Aedes Mosquitoes: The Universal Vector
Jagriti Narang, Manika Khanuja in Small Bite, Big Threat, 2020
Aedes are known as indoor breeding mosquitoes, that is, they breed in freshwater containers usually found inside or around human dwellings (domestic and peri-domestic containers, respectively). For laying eggs in foci favorable within these dwellings, the females search for damp or moist places that form little water bodies (Gubler, 1989). The preferable sites where eggs are seen are the water collected in tree holes, on the edges of artificial containers such as cement, clay, metallic, and plastic tanks. (Fig. 1.3). They lay around 50–100 eggs at one time. The eggs when laid appear white but change to black as they meet the atmosphere after 2 h (Nelson, 1986). They are oval shaped, covered with shell, and 1 mm in length (Fig. 1.4). The shell is partly secreted by the mother and partly by the embryo. They are soft and flexible when laid but later become hard and waterproof. The embryo develops inside the eggs within 2–3 days depending on atmospheric conditions. These eggs can remain viable up to a year (Foster and Walker, 2002). If an infected female has laid the eggs, then there are chances of the progeny getting infected; in other words, the female is capable of vertical transmission (egg to progeny). The process of laying eggs at a suitable place is termed oviposition, and this is done with the help of fine sensory hairs present on the lower parts of the abdomen (Clements, 2000).
Clinical Presentations and Diagnostic Imaging of VACTERL Association
Published in Fetal and Pediatric Pathology, 2023
Gabriele Tonni, Çağla Koçak, Gianpaolo Grisolia, Giuseppe Rizzo, Edward Araujo Júnior, Heron Werner, Rodrigo Ruano, Waldo Sepulveda, Maria Paola Bonasoni, Mario Lituania
The word “association”, by definition, is different from “syndrome”. A set of related symptoms characterizes syndromes, whereas associations are nonrandom interactions. Associations represent the idiopathic occurrence of multiple congenital anomalies during blastogenesis. The key concept is the implication that different causal factors, acting at certain stages in development, cause similar patterns of defects [17]. Developmental defects occurring during blastogenesis are polytopic and originate in two or more progenitor fields, for instance, anorectal anomalies. Monotopic defects arise during organogenesis, which involves one genetic field. Polydactyly, one of the many clinical symptoms of VACTERL association, is caused by a monotopic defect during organogenesis. “Clinical heterogeneity” depends on when the different factors (genetic and/or environmental) act, therefore resulting in either an isolated developmental field defect (DFD) or a DFD associated with other patterns of malformations. The development field is a region or part of the embryo which responds as a coordinated unit to embryonic induction and results in complex or multiple anatomic structures [18]. Etiological heterogeneity is one of the known characteristics of the DFD.
A narrative analysis of anti-abortion testimony and legislative debate related to Georgia’s fetal “heartbeat” abortion ban
Published in Sexual and Reproductive Health Matters, 2020
Dabney P. Evans, Subasri Narasimhan
Supporters of HB 481 consistently used the term “unborn child,” which served as a lexical bridge to link the concepts of “heartbeat” and personhood. Other similar terms were, “early infant in the womb,” “early infant,” “child in utero,” and “child” to attribute personhood to embryos and fetuses at “any or all stages of development.” By definition, the term embryo describes the period of development from conception to the six weeks gestation/eight weeks post-fertilisation and the term fetus from six weeks gestation/eight weeks post-fertilisation until birth.27 Therefore, the sponsor’s terms are inaccurate. Yet, the language deliberately mimics biological, human, and child development terminology in an attempt to add an air of medical credibility to the claim, which cannot be backed by scientific sources. One legislator stated: “What I’m telling you when you think about a child … early infants is an infant that is in their early stages of development.”
The effect of short-term disturbance of day 3 embryo culture on the development and implantation
Published in Gynecological Endocrinology, 2019
Kseniya Vladislavovna Krasnopolskaya, Anastasia Nikolaevna Beketova, Nina Igorevna Sesina, Nataliya Kirillovna Сhinchenko, Gohar Vigenovna Badalyan, Nataliya Mihailovna Sudarikova, Tatyana Viktorovna Bocharova, Ekaterina Olegovna Zakharchenko
The present common practice requires embryo cultivation for up to 5 days of development. It has been proved that pregnancy frequency, as well as childbirth, is statistically higher in case of 5th-day transfer, which is determined by a possibility to select best quality embryos, having achieved the blastocyst stage [2–4]. Best strategy of embryo cultivation is to keep them in optimal conditions. Modern incubators along with upgraded culture medium allow controlling most of the parameters without interference. There are two reasons for breaking ‘ideal culture conditions’: necessity to obtain information of fertilization and embryo development and also applying multistage culture medium, which inevitably leads to transferring embryos from one culture medium into another of the next stage. This causes short-term variations of several parameters: pH, temperature, illumination intensity. The listed disorders are risk factors affecting embryo quality and their implantation potential.
Related Knowledge Centers
- Egg Cell
- Multicellular Organism
- Sexual Reproduction
- Sperm
- Blastomere
- Zygote
- Animal Embryonic Development
- Fertilisation
- Cleavage
- Cell