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The Blastoderm in Chicks During Early Gastrulation
This image shows a chicken (Gallus gallus) embryo undergoing gastrulation in stage four (18-19 hrs after laying) according to the Hamburger-Hamilton staging series. At this point in time the chicken embryo is a blastoderm (shown in blue). The first magnification of the embryo shows that the blastoderm cell layers have thickened to form the primitive streak and Hensen's node. The primitive streak extends from the posterior (P) region to the anterior (A) region. The second rectangular magnification shows the blastoderm cross-sectioned through the primitive streak.
Format: Graphics
A Fate Map of the Chick Embryo
A 3-D fate map of the chicken (Gallus gallus) embryo with the prospective point of ingression and yolk. The area where the primitive streak will form during gastrulation is shown. The anterior- posterior axis is shown by labeling the anterior and posterio ends (A) and (P). Different colors indicate prospective fates of different regions of the epiblast after gastrulation.
Format: Graphics
"Experiments on Embryonic Induction III. A Note on Inductions by Chick Primitive Streak Transplanted to the Rabbit Embryo" (1934), by Conrad Hal Waddington
Conrad Hal Waddington's "Experiments on Embryonic Induction III," published in 1934 in the Journal of Experimental Biology, describes the discovery that the primitive streak induces the mammalian embryo. Waddington's hypothesis was that a transplanted primitive streak could induce neural tissue in the ectoderm of the rabbit embryo. The primitive streak defines the axis of an embryo and is capable of inducing the differentiation of various tissues in a developing embryo during gastrulation.
Format: Articles
Subject: Experiments
"Induction and Patterning of the Primitive Streak, an Organizing Center of Gastrulation in the Amniote" (2004), by Takashi Mikawa, Alisa M. Poh, Kristine A. Kelly, Yasuo Ishii, and David E. Reese
"Induction and Patterning of the Primitive Streak, an Organizing Center of Gastrulation in the Amniote," (hereafter referred to as "Induction") examines the mechanisms underlying early amniote gastrulation and the formation of the primitive streak and midline axis. The review, authored by Takashi Mikawa and colleagues at Cornell University Medical College, was published in Developmental Dynamics in 2004.
Format: Articles
Subject: Publications
August Antonius Rauber (1841-1917)
August Antonius Rauber was an embryologist and anatomist who examined gastrulation in avian embryos. He examined the formation of the blastopore, epiblast, and primitive streak during chick development. Subsequent researchers have further studied Rauber's findings, which has led to new discoveries in embryology and developmental biology.
Format: Articles
Subject: People
"Experiments on the Development of Chick and Duck Embryos, Cultivated in vitro" (1932), by Conrad Hal Waddington
Conrad Hal Waddington's "Experiments on the Development of Chick and Duck Embryos, Cultivated in vitro," published in 1932 in Philosophical Transactions of the Royal Society of London, Series B, compares the differences in the development of birds and amphibians. Previous experiments focused on the self differentiation of individual tissues in birds, but Waddington wanted to study induction in greater detail. The limit to these studies had been the amount of time an embryo could be successfully cultivated ex vivo.
Format: Articles
Subject: Experiments
"A Series of Normal Stages in the Development of the Chick Embryo" (1951), by Viktor Hamburger and Howard L. Hamilton
The developmental stages of the chick embryo were examined by Viktor Hamburger and Howard L. Hamilton in "A Series of Normal Stages in the Development of the Chick Embryo," published in the Journal of Morphology in 1951. These stages were published to standardize the development of the chick based on varying laboratory conditions and genetic differences. The stages Hamburger and Hamilton assigned were determined by the visible features of the chick embryo.
Format: Articles
Subject: Experiments
Hensen's Node
A node, or primitive knot, is an enlarged group of cells located in the anterior portion of the primitive streak in a developing gastrula. The node is the site where gastrulation, the formation of the three germ layers, first begins. The node determines and patterns the anterior-posterior axis of the embryo by directing the development of the chordamesoderm. The chordamesoderm is a specific type of mesoderm that will differentiate into the notochord, somites, and neural tube. Those structures will later form the vertebral column.
Format: Articles
Subject: Processes
Gastrulation in Mus musculus (common house mouse)
As mice embryos develop, they undergo a stage of development called gastrulation. The hallmark of vertebrate gastrulation is the reorganization of the inner cell mass (ICM) into the three germ layers: ectoderm, mesoderm, and endoderm. Mammalian embryogenesis occurs within organisms; therefore, gastrulation was originally described in species with easily observable embryos. For example, the African clawed frog (Xenopus laevis) is the most widely used organism to study gastrulation because the large embryos develop inside a translucent membrane.
Format: Articles
Subject: Processes, Experiments
Hamburger-Hamilton Staging Series (1951)
In 1951 Viktor Hamburger and Howard Hamilton created an embryonic staging series from a combination of photographs and drawings from other researchers. The Hamburger-Hamilton stages are a sequence of images depicting 46 chronological stages in chick development. The images begin with a fertilized egg and end with a fully developed chick. The Hamburger-Hamilton staging series was produced in order to replace a previous chick staging series created in 1900. The earlier attempt lacked specific details and staged the chick embryo by using only morphological characteristics.
Format: Articles
Subject: Processes
Gastrulation in Gallus gallus (Domestic Chicken)
Gastrulation is an early stage in embryo development in which the blastula reorganizes into three germ layers: the ectoderm, the mesoderm, and the endoderm. Gastrulation occurs after cleavage but before neurulation and organogenesis. Ernst Haeckel coined the term; gaster, meaning stomach in Latin, is the root for gastrulation, as the gut is one of the most unique creations of the gastrula.
Format: Articles
Subject: Processes
Conrad Hal Waddington (1905-1975)
Conrad Hal Waddington was an embryologist and theoretical biologist. His early experimental work investigated aspects of embryonic induction and the properties of the organizer first identified by Hans Spemann and Hilde Mangold, while his later studies focused on genetic assimilation. Waddington is probably best known for developing the concept of the epigenetic landscape, and he also held significant interest in many different areas ranging from the visual arts and poetry to philosophy.
Format: Articles
Subject: People
Endoderm
Endoderm is one of the germ layers-- aggregates of cells that organize early during embryonic life and from which all organs and tissues develop. All animals, with the exception of sponges, form either two or three germ layers through a process known as gastrulation. During gastrulation, a ball of cells transforms into a two-layered embryo made of an inner layer of endoderm and an outer layer of ectoderm. In more complex organisms, like vertebrates, these two primary germ layers interact to give rise to a third germ layer, called mesoderm.
Format: Articles
Subject: Processes
Assisted Human Reproduction Canada (AHRC)
Established under the Assisted Human Reproduction (AHR) Act of 2004, Assisted Human Reproduction Canada (AHRC), also known as the Assisted Human Reproduction Agency of Canada, was created in 2006 to oversee research related to reproductive technologies and to protect the reproductive rights and interests of Canadian citizens. AHRC serves as a regulatory body for the development and use of such research and technology while enforcing the guidelines and restrictions laid out by the AHR Act.
Format: Articles
Subject: Organizations, Reproduction
Francis Maitland Balfour (1851-1882)
During the 1870s and early 1880s, the British morphologist Francis Maitland Balfour contributed in important ways to the budding field of evolutionary embryology, especially through his comparative embryological approach to uncovering ancestral relationships between groups. As developmental biologist and historian Brian Hall has observed, the field of evolutionary embryology in the nineteenth century was the historical ancestor of modern-day evolutionary developmental biology.
Format: Articles
Subject: People
"On the Origin of Mitosing Cells" (1967), by Lynn Sagan
On the Origin of Mitosing Cells by Lynn Sagan appeared in the March 1967 edition of the Journal of Theoretical Biology. At the time the article was published, Lynn Sagan had divorced astronomer Carl Sagan, but kept his last name. Later, she remarried and changed her name to Lynn Margulis, and will be referred to as such throughout this article. In her 1967 article, Margulis develops a theory for the origin of complex cells that have enclosed nuclei, called eukaryotic cells.
Format: Articles
Subject: Publications, Theories
Human Fertilisation and Embryology Act (1990)
The Human Fertilisation and Embryology Act 1990 established the legal framework that governs infertility treatment, medical services ancillary to infertility treatment such as embryo storage, and all human embryological research performed in the UK. The law also defines a legal concept of the parent of a child conceived with assisted reproductive technologies.
Format: Articles
Subject: Legal, Reproduction, Ethics
Carnegie Stages
Historically the exact age of human embryo specimens has long perplexed embryologists. With the menstrual history of the mother often unknown or not exact, and the premenstrual and postmenstrual phases varying considerably among women, age sometimes came down to a best guess based on the weight and size of the embryo. Wilhelm His was one of the first to write comparative descriptions of human embryos in the late 1800s. Soon afterward, Franklin P. Mall, the first director of the Carnegie Institution of Washington's (CIW) Department of Embryology, expanded upon His' work.
Format: Articles
Subject: Theories
“Annual Research Review: Prenatal Stress and the Origins of Psychopathology: An Evolutionary Perspective” (2011), by Vivette Glover
In 2011, fetal researcher Vivette Glover published “Annual Research Review: Prenatal Stress and the Origins of Psychopathology: An Evolutionary Perspective,” hereafter, “Prenatal Stress and the Origins of Psychopathology,” in the Journal of Child Psychology and Psychiatry. In that article, Glover explained how an evolutionary perspective may be useful in understanding the effects of fetal programming. Fetal programming is a hypothesis that attempts to explain how factors during pregnancy can affect fetuses after birth.
Format: Articles
Subject: Theories, Reproduction, Disorders
Neonatal Respiratory Distress Syndrome and Its Treatment with Artificial Surfactant
Neonatal respiratory distress syndrome, previously called hyaline membrane disease, is a respiratory disease affecting premature newborns. Neonatal respiratory distress syndrome involves shallow breathing, pauses between breaths that last a few seconds, or apnea, and a bluish tinge to the infant’s skin. The syndrome occurs when microscopic sacs called alveoli in infant lungs do not produce surfactant, a liquid that coats the inside of the lungs and helps them inflate during breathing.
Format: Articles
Subject: Disorders
Felix Anton Dohrn
Felix Anton Dohrn is best remembered as the founder of the Stazione Zoologica di Napoli, the world' s first permanent laboratory devoted to the study of marine organisms. Dohrn was born on 29 December 1840 in Stettin, Pomerania (now Poland), to a wealthy merchant family. Dohrn's paternal grandfather, Heinrich, trained as a surgeon and then established a sugar refinery, while Dohrn's father, Carl August Dohrn, who inherited the family business, became interested in natural history through Alexander von Humboldt, a family friend.
Format: Articles
Subject: People
Roy Chapman Andrews (1884-1960)
Roy Chapman Andrews traveled the world studying fossils, from mammals to dinosaurs, during the first half of the twentieth century. Andrews worked and collected fossil specimens for the American Museum of Natural History (AMNH) in New York City, New York. Throughout his career, Andrews collected bones of many animal species, including a previously unknown species of a horned, herbivorous dinosaur, later named Proceratops andrewsi in his honor. Andrews published widely read narratives about his travels and field experiences, such as On the Trail of Ancient Man and Across Mongolian Plains.
Format: Articles
Subject: People
Johann Friedrich Meckel, the Younger (1781-1833)
Johann Friedrich Meckel studied abnormal animal and human anatomy in nineteenth century Germany in an attempt to explain embryological development. During Meckel's lifetime he catalogued embryonic malformations in multiple treatises. Meckel's focus on malformations led him to develop concepts like primary and secondary malformations, atavism, and recapitulation- all of which influenced the fields of medicine and embryology during the nineteenth and twentieth centuries.
Format: Articles
Subject: People
Homeobox Genes and the Homeobox
Homeobox genes are a cluster of regulatory genes that are spatially and temporally expressed during early embryological development. They are interesting from both a developmental and evolutionary perspective since their sequences are highly conserved and shared across an enormously wide array of living taxa.
Format: Articles
Subject: Processes
Edwin Grant Conklin (1863-1952)
Edwin Grant Conklin was born in Waldo, Ohio, on 24 November 1863 to parents Nancy Maria Hull and Dr. Abram V. Conklin. Conklin's family was very religious and he seriously considered a theistic path before choosing a career in academics. Conklin's scientific work was primarily in the areas of embryology, cytology, and morphology, though many questions regarding the relationships between science, society, and philosophy had an influence on both his writings and academic lectures.
Format: Articles
Subject: People