The chicken embryo as a model for ductus arteriosus developmental biology: cracking into new territory.
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Results for “embryo model”
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[Chick embryos as a model for studying colicine biosynthesis in bacteria of the enteric family].
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Animals↗
The chick embryo: a leading model in somitogenesis studies.
The vertebrate body is built on a metameric organization which consists of a repetition of functionally equivalent units, each comprising a vertebra, its associated muscles, peripheral nerves and blood vessels. This periodic pattern is established during embryogenesis by the somitogenesis process. Somites are generated in a rhythmic fashion from the presomitic mesoderm and they subsequently differentiate to give rise to the vertebrae and skeletal muscles of the body. Somitogenesis has been very actively studied in the chick embryo since the 19th century and many of the landmark experiments that led to our current understanding of the vertebrate segmentation process have been performed in this organism. Somite formation involves an oscillator, the segmentation clock whose periodic signal is converted into the periodic array of somite boundaries by a spacing mechanism relying on a traveling threshold of FGF signaling regressing in concert with body axis extension.
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Mouse embryos in culture: models for understanding diabetes-induced embryopathies and gene function.
Both the metabolic studies on diabetes and the genetic studies using antisense oligodeoxynucleotides clearly demonstrate the importance and usefulness of rodent whole embryo culture. Without this technique, these studies would be impossible and, consequently, our knowledge of both normal and abnormal development would not be as advanced as it is today. The culture system fills a unique niche in studies in the fields of developmental biology and teratology and these sciences would have been less well served without Dr. New's contribution.
3-Hydroxybutyric Acid↗
In vitro simulations of embryo transfer in a laboratory model of the uterus.
Embryo transfer (ET) is the final manual intervention during which the newly formed embryo is placed within the uterus by a transcervical catheter. The loading of the syringe-catheter complex with the transferred volume consists of the transfer media (which contains the embryos) separated by air spaces on both sides. The dynamics involved in injecting the syringe-catheter complex is not well understood nor has it been investigated to date. We developed an in vitro experimental setup for simulations of ET into a rigid transparent uterine model. The catheter was loaded in sequences of liquid and air as it is in the clinical setting. The transferred liquid was colored with a dye and its dispersion within the uterine cavity was recorded by a video camera. The results demonstrated, for the first time, the importance of having a gas phase in the catheter load. The resulting air bubbles within the uterus were carried upward towards the fundus by buoyant forces, thereby dragging behind them the transferred liquid which contained the embryos. This could be expected to substantially increase the probability for the embryos to be present near the fundal wall at the time window for implantation. There was also evidence of a dependency of the rate of injection upon the catheter load into the uterus: a low speed generated several air bubbles which led to more of the transferred liquid being carried towards the fundal end, thus possibly enhancing the potential for implantation.
Embryo Transfer↗
Developmental expression of thrombin in zebrafish embryos: a novel model to study hemostasis.
A partial cDNA encoding zebrafish prothrombin has been cloned and used as a probe to study the temporal expression of prothrombin mRNA during early embryonic development. The results revealed accumulation of prothrombin mRNA in diverse tissues such as the eyes and myotomes in early embryogenesis. We have also examined the enzymatic activity of thrombin in converting fibrinogen to fibrin in individual embryos at different stages of development. We found that the fibrin-forming activity does not temporally correlate with the first presence of thrombin mRNA in the early stages of embryogenesis, but does correlate with the initiation of blood formation. Our ability to observe the fibrin-forming activity in single individual embryo will facilitate studies on identifying recessive mutations affecting blood coagulation, such as the regulatory gene mutations controlling the clotting factor genes. Furthermore, the observation of thrombin activity will also facilitate studies on the blood coagulation pathways in the early embryogenesis in this zebrafish model.
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[CHICK EMBRYOS AS THE MODEL FOR THE STUDY OF ANTI-TRICHOMONAL ANTIBIOTICS].
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Anti-Bacterial Agents↗
Amphibian embryos as a model system for organ engineering: in vitro induction and rescue of the heart anlage.
Beating hearts can be induced under in vitro conditions when the dorsal blastopore lip (including the zone of Spemann organizer) is treated with Suramin. In contrast, untreated organizer forms dorsal mesodermal derivatives as notochord and somites. When those in vitro produced heart precursor tissues are transplanted ectopically in the posterior trunk area of early larvae, secondary beating heart structures will be formed. Furthermore, the replacement of the heart primordium of the host embryo by heart tissue induced under in vitro conditions will result in the rescue of the heart anlage. This model could be a valuable tool for the study of the multi-step molecular mechanisms of heart structure induction under in vitro conditions and vasculogenesis after transplantation into the host embryo.
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Pathogenesis of diastematomyelia: can a surgical model in the chick embryo give some clues about the human malformation?
To reproduce diastematomyelia, a sagittal incision was carried out at the level of the rhomboidal sinus of 36- to 40-h-old chick embryos. A small piece of membrane shell, a small agar screen, or a piece of quail isochronous isotopic notochord was inserted into the gap. The embryos were killed and fixed after 9 days' incubation. Diastematomyelia was obtained in several embryos treated with interposition of a membrane screen or a piece of quail notochord. Microscopic examination revealed two hemicords, each containing its own central canal; in some cases one of the cords showed hydromyelia. Absence of the rump was seen in association with experimental diastematomyelia. The interposition of a resorbable agar screen did not succeed in reproducing diastematomyelia. The results of these surgical manipulations suggest that diastematomyelia cannot be explained by a primary disorder of neurulation. It supports the theory of noninvolution of a firm midline structure (probably the neurenteric canal, rapidly surrounded by mesodermal cells originating from the notochord), which prevents the fusion of the separated parts.
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Cooperation between multiple oncogenes in rodent embryo fibroblasts: an experimental model of tumor progression?
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Adenoviridae↗
Calculating the implantation potential of day 3 embryos in women younger than 38 years of age: a new model.
For optimal embryo selection in IVF/intracytoplasmic sperm injection (ICSI), knowledge of the implantation potential is essential. This is a retrospective analysis of morphological characteristics and cleavage kinetics of day 3 embryos resulting in an objective assessment of the relative implantation potential of each distinct type of embryo. Therefore transferred embryos were sampled according to their documented implantation behaviour: all embryos without any implantation on the one hand and all those with 100% ongoing implantation on the other. There were 213 such embryos in the latter group of which only seven (3%) had >20% fragmentation and only one embryo (0.5%) showed multinucleation (an embryo containing >20% fragmentation). For this reason, only embryos with < or =20% fragmentation and without multinucleation were analysed. They were split up according to the amount of fragmentation and the number of blastomeres on day 2 and on day 3. For each type, the implanted fraction was calculated, i.e. the number certainly implanted divided by the sum of the number certainly implanted and the number certainly not implanted, thus describing its relative implantation potential. By extrapolation to the entire population it was possible to establish the implantation potential for each type of embryo. Optimal day 3 embryos were calculated to reach a mean of 47% ongoing implantation. By establishing the implantation potential for most embryos, this model also provides useful information about which embryos are worth freezing in a cost-effective cryopreservation policy.
Adult↗
Retroviruses and mouse embryos: a rapid model for neurovirulence and transplacental antiviral therapy.
A murine model in which neurotropic retroviral infection can be studied over short periods of time was developed. Microinjection of Cas-Br-E virus into midgestation mouse embryos caused paralysis and death within 25 days after birth, in contrast to virus-infected neonates which develop disease only after 4 months. To evaluate whether antiviral drugs could cross the placental barrier and influence the course of the disease, the drug 3'-azido-3'-deoxythymidine (AZT) was administered to infected embryos through the drinking water of pregnant females. AZT treatment markedly retarded the onset and course of virus-induced central nervous system disease, permitting animals to survive beyond 4 months of age. These results are evidence for effective antiviral treatment during gestation and in the perinatal period and are of potential significance for the management of maternal transmission of the acquired immune deficiency syndrome (AIDS) virus.
Animals↗
The sea urchin embryo as a model for studying efflux transporters: roles and energy cost.
We describe the use of the sea urchin as a model for studying efflux transporters and estimating energy cost for the cytotoxin protective system provided by these transporters. The unfertilized egg has low transport activity, which increases to a new steady state shortly after fertilization. Activity results from p-glycoprotein (p-gp) and MRP type transporters which protect the embryo from cytotoxic drugs that can disrupt cell division or induce apoptosis. The energy cost is estimated from a novel use of calcein-AM as a substrate; keeping 0.25 microM substrate levels out of the cell utilizes only 0.023% of steady state respiration.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
Factors affecting the efficiency of embryo cryopreservation and rederivation of rat and mouse models.
The efficiency of embryo banking for rat and mouse models of human disease and normal biological processes depends on the ease of obtaining embryos. Authors report on the effect of genotype on embryo production and rederivation. In an effort to establish banks of cryopreserved embryos, they provide two databases for comparing banking efficiency: one that contains the embryo collection results from approximately 11,000 rat embryo donors (111 models) and another that contains the embryo collection results from 4,023 mouse embryo donors (57 induced mutant models). The genotype of donor females affected the efficiency of embryo collection in two ways. First, the proportion of females yielding embryos varied markedly among genotypes (rats: 16-100 %, mean =71 %; mice: 24-95 %, mean =65 %). Second, the mean number of embryos recovered from females yielding embryos varied considerably (rats: 4-10.6, mean =7.8; mice 5.3-32.2, mean =13.7). Genotype also affected the efficiency of rederivation of banked rat and mouse embryos models by embryo transfer. For rats, thawed embryos (n =684) from 33 genotypes were transferred into 66 recipient females (pregnancy rate, 78 %). The average rate of developing live newborns for individual rat genotypes was 30 % with a range of 10 to 58 %. For mice, thawed embryos (n =2,064) from 59 genotypes were transferred into 119 pseudopregnant females (pregnancy rate: 76 %). The average rate of development of individual mouse genotypes was 33 % with a range of 11 to 53 %. This analysis demonstrates that genotype is an important consideration when planning embryo banking programs.
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Sea urchin embryo as a model organism for the rapid functional screening of tubulin modulators.
Identification of antimitotic molecules that affect tubulin dynamics is a multistep procedure. It includes in vitro tubulin polymerization assay, studies of a cell cycle effect, and general cytotoxicity assessment. To simplify this lengthy screening protocol, we have introduced and validated an assay system based on the sea urchin embryos. The proposed two-step procedure involves the fertilized egg test for mitotic arrest and the behavioral assessment of a free-swimming blastula. In order to validate the assay, we have analyzed the effect of a panel of known antiproliferative agents on the sea urchin embryo. For all tubulin destabilizing drugs, we observed rapid spinning and lack of forward movement of an embryo. Both effects are likely to result from the in vivo microtubule disassembly caused by test molecules. Notably, the described assay yields rapid information on antiproliferative, antimitotic, cytotoxic, and tubulin destabilizing activities of the molecules along with their solubility and permeability potential. Moreover, measured potencies of the test articles correlated well with the reported values in both in vitro and cell based assays.
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Regulatory models for human embryo cloning: the free market, professional guidelines, and government restrictions.
Both experimental and therapeutic uses of the new reproductive technologies have been governed not by the medical ideology of the best interests of patients and their children, but by the market ideology of profit maximization under the guise of "reproductive liberty." Government in our constitutional, democratic society has the authority and obligation to make and enforce reasonable regulations to manage the new reproductive market in order to protect the interests of the public, prospective parents, and their future children. The "cloning" debate provides a useful opportunity to compare and contrast the competing regulatory models of the free market, professional guidelines, and government restrictions.
Advisory Committees↗
Study of upper extremity growth and development using human embryos and computer-reconstructed models.
This study investigated the apical ectodermal ridge and early vasculature of the human limb bud by use of histologic techniques and a new method of computer modeling. Fourteen human embryos were studied (more than 10,000 sections) microscopically and the embryonic limbs were reconstructed three-dimensionally by use of a serialized programming method. The apical ectodermal ridge consists of an extensive band of specialized cells, located over the rim of the limb surmounting a strip of rapidly-dividing mesenchymal cells. It is consistently supplied by a large vessel that shows extensive central branching.
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Ascidian embryos as a model system to analyze expression and function of developmental genes.
Ascidians have served as an appropriate experimental system in developmental biology for more than a century. The fertilized egg develops quickly into a tadpole larva, which consists of a small number of organs including epidermis, central nervous system with two sensory organs, endoderm and mesenchyme in the trunk, and notochord and muscle in the tail. This configuration of the ascidian tadpole is thought to represent the most simplified and primitive chordate body plan. Their embryogenesis is simple, and lineage of embryonic cells is well documented. The ascidian genome contains a basic set of genes with less redundancy compared to the vertebrate genome. Cloning and characterization of developmental genes indicate that each gene is expressed under discrete spatio-temporal pattern within their lineage. In addition, the use of various molecular techniques in the ascidian embryo system highlights its advantages as a future experimental system to explore the molecular mechanisms underlying the expression and function of developmental genes as well as genetic circuitry responsible for the establishment of the basic chordate body plan. This review is aimed to highlight the recent advances in ascidian embryology.
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