6,199 research outputs found
The Atlas of chick development /
No full textThe Atlas of Chick Development, Third Edition, a classic work covering all major event of chick development, is extensively updated with new and more detailed photographs, enlargements showing regions of special-interest and complexity, and new illustrations. The revised text and expanded illustrative material describe the intricate changes that take place during development, together with accounts of recent experimental and molecular research that has transformed our understanding of morphogenesis. These wide-ranging updates make this book an essential resource for development.The Atlas of Chick Development, Third Edition, a classic work covering all major event of chick development, is extensively updated with new and more detailed photographs, enlargements showing regions of special-interest and complexity, and new illustrations. The revised text and expanded illustrative material describe the intricate changes that take place during development, together with accounts of recent experimental and molecular research that has transformed our understanding of morphogenesis. These wide-ranging updates make this book an essential resource for development.Includes bibliographical references and index.The Hen's Egg and its Formation -- Techniques -- Early Stages -- Establishment of the Embryonic Body -- External Appearance and Polarity -- Heart, Blood Vessels and Lymphatics -- Urino-Genital System -- Gut, Coelom and Respiratory System -- Nervous System -- Skeleton and Muscles -- The Integument -- Endocrine Glands -- Extra-Embryonic Membranes.Print version record.Elsevie
Prospects for transgenesis in the chick
No full textResearch to develop a useful method for genetic modification of the chick has been on-going since the first demonstrations in the mouse in the 1980s that genetic modification is an invaluable tool for the study of gene function. Manipulation of the chick zygote is possible but inefficient. Considerable progress has been made in developing potentially pluripotent embryo stem cells and their contribution to somatic chimeric birds well-established. Germ line transmission of gametes derived from genetically modified embryo cells has not been described. Transfer of primordial germ cells from a donor embryo to a recipient and production of functional gametes from the donor-derived cells is possible. Genetic modification of primordial germ cells before transfer and their recovery through the germ line has not been achieved. The first transgenic birds described were generated using retroviral vectors. The use of lentiviral vectors may make this approach a feasible method for transgenic production, although there are limitations to the applications of these vectors. It is likely that a method will be developed in the next few years that will enable the use of transgenesis as a tool in the study of development in the chick and for many other applications in basic research and biotechnology
Expression and regulation of Cek-8, a cell to cell signalling receptor in developing chick limb buds
No full textThe Eph-related receptor tyrosine kinase gene, Cek-8, is expressed in mesenchyme at the tip of chick limb buds, with high levels of transcripts posteriorly and apically but fading out anteriorly. Expression of Cek-8 in distal mesenchyme is regulated by apical ridge- and FGF-polarising signals and retinoic acid, and is uniform across the anteroposterior axis in talpid3 mutants. These data indicate that Cek-8 expression responds to regulatory signals during limb patterning and suggest that this receptor tyrosine kinase may have a role in coordinating responses to signals in the progress zone of early buds. Later on in limb development, Cek-8 expression is associated with cell condensations that form tendons and their attachments to cartilage rudiments and then in developing feather buds
Modelling growth of chick embryo
No full textAn attenuated parabolic model has been proposed for determining the chick embryo weight depending on the time of incubation: Wem=0.00019119t^4.3482 exp(-0.052409t). This model described the chick embryo growth most precisely (r=0.948) in comparison with three others. Coefficients of correlation for the parabolic growth model, Gompertz function and exponential model were 0.802, 0.770 and 0.162, respectively
Effects of High Salt-Exposure on the Development of Retina and Lens in 5.5-Day Chick Embryo
No full textBackground/Aims: Excess maternal salt intake during pregnancy may alter fetal development. However, our knowledge on how an increased salt intake during pregnancy influences fetal eye development is limited. In this study, we investigated the effects of high-salt treatment on the developing eyes in chick embryos, especially focusing on the development of the retina and the lens. Methods: 5.5-day chick embryos were exposed to 280mosm/l (n=17), or 300mosm/l (n=16) NaCl. The treated embryos were then incubated for 96 hours before they were fixed with 4% paraformaldehyde for H&E staining, whole-mount embryo immunostaining and TUNEL staining. BrdU and PH3 incorporation experiments were performed on the chick embryos after high-salt treatment. RT-PCR analyses were conducted from chick retina tissues. Results: We demonstrated that high-salt treatment altered the size of eyes in chick embryos, induced malformation of the eyes and impaired the development of the lens and the retina. We found an impaired expression of Paired box 6 (PAX6) and neuronal cells in the developing retina as revealed by neurofilament immunofluorescent staining. There was a reduction in the number of BrdU-positive cells and PH3-positive cells in the retina, indicating an impaired cell proliferation with high-salt treatment. High-salt treatment also resulted in an increased number of TUNEL-positive cells in the retina, indicating a higher amount of cell death. RT-PCR data displayed that the expression of the pro-apoptotic molecule nerve growth factor (NGF) in chick retina was increased and CyclinD1 was reduced with high-salt treatment. The size of the lens was reduced and Pax6 expression in the lens was significantly inhibited. High salt-treatment was detrimental to the migration of neural crest cells. Conclusion: Taken together, our study demonstrated that high-salt exposure of 5.5-day chick embryos led to an impairment of retina and lens development, possibly through interfering with Pax6 expression.</p
Chick PTPσ regulates the targeting of retinal axons within the optic tectum
No full textChick PTP (cPTP), also known as CRYP, is a receptor-like protein tyrosine phosphatase found on axons and growth
cones. Putative ligands for cPTP are distributed within basement membranes and on glial end feet of the retina, optic nerve, and optic tectum, suggesting that cPTP signaling is occurring along the whole retinotectal pathway. We have shown previously that cPTP plays a role in supporting the retinal phase of axon outgrowth. Here we have now addressed the role of cPTP within retinal axons as they undergo growth and topographic targeting in the optic tectum. With the use of retroviruses, a secretable cPTP ectodomain was ectopically expressed in ovo in the developing chick optic tectum, with the aim of directly disrupting the function of endogenous cPTP. In ovo, the secreted ectodomains accumulated at tectal sites in
which cPTP ligands are also specifically found, suggesting
that they are binding to these endogenous ligands. Anterograde labeling of retinal axons entering these optic tecta revealed abnormal axonal phenotypes. These included the premature stalling and arborization of fibers,excessive pretectal arbor formation, and diffuse termination zones. Most of the defects were rostral of the predicted termination zone, indicating that cPTP function is necessary for sustaining the growth of retinal axons over the optic tectum and for directing axons to their correct sites of termination. This demonstrates that regulation
of cPTP signaling in retinal axons is required for their topographic mapping, the first evidence of this function for a receptor-like protein tyrosine phosphatase in the retinotectal projection
Neuronal induction of mouse embryonic stem cells following coculture with chick embryonic somites
No full textpurpose: The aim of the present study was to understand if EBs can promote generation of neurons following co – culture with chick embryo somites.
Materials and Methods: The mouse ES cells, line Royan B1, were cultured in hanging drops to induce embryoid bodies (EBs) formation. Then, RA was added to some EBs according to 2-/2+/2+ protocol to evaluate the potential of their neuron generation. Somites were isolated from the chick embryos and then embedded in alginate solution. Finally, alginate beads containing somites were co-cultured with EBs as 1:1 and 4:1 ratio.
Results: Mean percentage of EBs containing neurons in RA, somite 4:1, somite 1:1 and control were 82.8%, 35.3% ,21.1% and 4.8% , respectively. Our results showed that EBs can promote generation of neurons following co-culture with somites and somite 4:1 had more profound effect on neural induction compared to somite1:1. The neurons were formed rapidly in RA and somites groups than control group. The somite groups induced higher rosette formation which had the capacity to generate neurons upon isolation and replating. Finally, the neural properties were confirmed by immunocytochemistry procedures.
Conclusion: Chick embryonic somites can induce ES cells –derived EBs to generate neurons in vitro and may lead to formation of rosette structures with neuron formation capacity
An amino-terminal extension is required for the secretion of chick agrin and its binding to extracellular matrix.
No full textAgrin is an extracellular matrix (ECM) protein with a calculated relative molecular mass of more than 200 kD that induces the aggregation of acetylcholine receptors (AChRs) at the neuromuscular junction. This activity has been mapped to its COOH terminus. In an attempt to identify the functions of the NH2-terminal end, we have now characterized full-length chick agrin. We show that chick agrin encoded by a previously described cDNA is not secreted from transfected cells. Secretion is achieved with a construct that includes an additional 350 bp derived from the 5' end of chick agrin mRNA. Recombinant agrin is a heparan sulfate proteoglycan (HSPG) of more than 400 kD with glycosaminoglycan side chains attached only to the NH2-terminal half. Endogenous agrin in tissue homogenates also has an apparent molecular mass of > 400 kD. While the amino acid sequence encoded by the 350-bp extension has no homology to published rat agrin, it includes a stretch of 15 amino acids that is 80% identical to a previously identified bovine HSPG. The extension is required for binding of agrin to ECM. AChR aggregates induced by recombinant agrin that includes the extension are considerably smaller than those induced by agrin fragments, suggesting that binding of agrin to ECM modulates the size of receptor clusters. In addition, we found a site encoding seven amino acids at the NH2-terminal end of agrin that is alternatively spliced. While motor neurons express the splice variant with the seven amino acid long insert, muscle cells mainly synthesize isoforms that lack this insert. In conclusion, the cDNAs described here code for chick agrin that has all the characteristics previously allocated to endogenous agrin
Excess caffeine exposure impairs eye development during chick embryogenesis
No full textCaffeine has been an integral component of our diet and medicines for centuries. It is now known that over consumption of caffeine has detrimental effects on our health, and also disrupts normal foetal development in pregnant mothers. In this study, we investigated the potential teratogenic effect of caffeine over-exposure on eye development in the early chick embryo. Firstly, we demonstrated that caffeine exposure caused chick embryos to develop asymmetrical microphthalmia and induced the orbital bone to develop abnormally. Secondly, caffeine exposure perturbed Pax6 expression in the retina of the developing eye. In addition, it perturbed the migration of HNK-1 + cranial neural crest cells. Pax6 is an important gene that regulates eye development, so altering the expression of this gene might be the cause for the abnormal eye development. Thirdly, we found that reactive oxygen species (ROS) production was significantly increased in eye tissues following caffeine treatment, and that the addition of anti-oxidant vitamin C could rescue the eyes from developing abnormally in the presence of caffeine. This suggests that excess ROS induced by caffeine is one of the mechanisms involved in the teratogenic alterations observed in the eye during embryogenesis. In sum, our experiments in the chick embryo demonstrated that caffeine is a potential teratogen. It causes asymmetrical microphthalmia to develop by increasing ROS production and perturbs Pax6 expression.</p
Chick Lit in Historical Settings by Frida Skybäck
No full textChick lit is mostly contemporary portrayals of single women in cities. The Swedish author Frida Skybäck writes “chick lit in corsets”, that is, chick lit in a historical setting, and she writes primarily for teenage girls. Her two novels Charlotte Hassel (2011) and Den vita frun (2012) balance between chick lit jr. and romance. They can also be read as historical novels, and in my article I highlight how Skybäck has consciously played with the different genres to convey a feminist message and to strengthen young readers
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