Shell-less chick embryo culture is the process of growing chick embryos in vitro, without their protective egg shells, for scientific observation. Chick embryos and other avian embryos have been used as biological models to visualize the developmental stages of embryos for education and to perform embryological manipulations. Using this technique, observations can be made, whether it is an induced-malformation caused due to the effect of teratogens or inoculations with viruses such as HIV or herpes simplex. Furthermore, methods for preservation of endangered avian species and the development of transgenic birds using surrogate egg shell culture have been created by scientists across the globe. Scientists have designed drug delivery tests in mammalian embryos to treat degenerative diseases. The technique was used in India to scrutinize glucose-induced deformities in chick embryos.
Early history The earliest example of a formal study removing chick embryo cultures from their shells to study was Aristotle in his work History of Animals in the fourth century BC, who would observe and dissect chick embryos at different development stages, noting, among other things, the formation of the heart and other organs at specific time intervals after conception. Although Aristotle did not focus on growing chick embryo cultures outside of the egg, this work is one of the first systemic and formal studies on chick embryo cultures in a shell-less setting at different development stages, as well as one of the first formal studies on embryology and animal development in general. In the 17th century, William Harvey conducted extensive studies on embryology, particularly on chick embryos. Using the process of epigenesis, he observed and documented the stages of chick embryo development. Although he did not culture embryos in vitro, he opened eggs at various stages to observe development and drew conclusions about the circulation of blood and organ formation. His work On the Generation of Animals, published in 1651, details his studies on the development of chick embryos, including his ideas on epigenesis and the circulation of blood. Marcello Malpighi an Italian anatomist, was one of the first scientists to use a microscope to study chick embryos. His 1672 work On the Formation of the Chick in the Egg detailed the early stages of chick development, which he documented through a series of highly detailed illustrations. His observations were not of shell-less embryos per se, but they represented some of the earliest systematic investigations into chick embryology. He illustrated and documented stages of chick embryo development using microscopy, one of the first applications of this tool in embryology. Christian Heinrich Pander (1794–1865): Pander's studies in the early 19th century, published in 1817, focused on chick embryo development. He introduced the concept of germ layers, describing how the ectoderm, mesoderm, and endoderm formed in the chick embryo. His work laid the groundwork for later embryological studies and was influential in developmental biology. His work in 1817, Dissertatio Inauguralis quaedam de Ovi Avium atque Hominis Incubatione [Dissertation on the Incubation of the Avian Egg and Humans]. Würzburg: University of Würzburg. This dissertation introduced the concept of germ layers, describing the ectoderm, mesoderm, and endoderm in the developing chick. Karl Ernst von Baer built on Pander's work and is often called the "father of embryology." His studies in the 1820s focused on vertebrate embryology, including that of the chick, and he formulated von Baer's laws, describing the stages of development. He did not use shell-less techniques but dissected eggs at different stages to observe development. In 1828 his work On the Developmental History of Animals: Observation and Reflection laid the foundation of comparative embryology and described developmental stages, including his renowned laws of development. While these studies did not involve full in vitro culture of chick embryos without shells, they were significant for embryology, marking advances in observing and understanding developmental processes. True shell-less chick embryo culturing methods emerged only in the 20th century, with improved understanding of environmental needs for sustaining embryos outside the shell. These set the foundation for practical shell-less embryo culturing to emerge with the advent of modern laboratory techniques.
Growth in vitro
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