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slides3/26/12
BIO361Exam3
| Question | Answer |
|---|---|
| What happens first in Neuralation of Amphibians? | the embryo elongates and a flattened region of the dorsal epithelium (neural plate) appears on its dorsal surface |
| What happens 2nd in Neuralation of Amphibians? | A neural groove is evident along the midline of the plate, with a widened depression at the anterior end. |
| What happens 3rd in Neuralation of Amphibians? | The lateral edges of the plate become prominent and fold in (neural fold) toward the midline of the embryo . |
| What happens last in Neuralation of Amphibians? | At the end of neurulation, the neural folds become contiguous along most of the dorsal midline and begin to fuse. |
| What happens in first phase of neurulation of Amphibians? | formation of the neural plate and it concludes with the formation of the keyhole stage |
| What happens in 2nd phase of neurulation of Amphibians? | the closure of the neural plate into a neural tube |
| What is bottle cell in neurulation of amphibians? | 1 Bottle cells appear at time of neurulation 2 Change in shape of epithelial to bottle cell is one of driving forces for event 3 Cytoskeletal changes lead to bottle cell shape |
| Cells undergo ______ with alignment of their microtubules, then contraction of the ____ filaments at the apex of cell form ____shape. | columnarization, actin, bottle shape |
| Inhibition of F-actin of microtubules can inhibit what? | neurulation |
| F-actin acts like strings to pull what? | apex of cell |
| F-actin can be inhibited by what? | Cytochalasin |
| Microtubules elongate cell to give what? | polarity for movement |
| Microtubules can be inhibited by? | Colchicine |
| The neural plate is also shaped by what? | convergent extension |
| What is convergent extension? | during neurulation, a central posterior region of nueral plate undergoes dramatic elongation |
| What region undergoes dramatic elongation? | Notoplate |
| What two process contribute to generating the keyhole shape? | Both columnarization and cell intercalation |
| The convergence and extension behavior originates in ____ and are transmitted to ___ tissue. | DIMZ and adjacent tissues |
| The induction of convergance and extension behavior is associated with neural induction also known as? | primary embryonic induction |
| At the neural fold, the neural ___cells crawl under the ___. | Neural plate cells, epidermis |
| T or F: The isolated plate rolls into a tube only when the margin is present | True |
| What three things are also responsible in neural tube closure? | Apical constriction, rapid anteroposterior extension, and cell crawling. |
| In amphibians, Neural plate is associated with? | Columnarization and convergent extension |
| In amphibians, Neural tube closure is associated with? | Apical constriction, rapid anteroposterior extension, and cell crawling |
| During gastrulation, Nieuwkoop center cells remain? | Endodermal |
| During gastrulation, the cells of the organizer becomes __________ and migrate underneath the _______. | dorsal mesoderm and dorsal ectoderm |
| During gastrulation, the tissue that forms the dorsal lip of blastopore and moves into embryo is called? | Chordamesoderm |
| What will chordamesoderm form? | the notochord |
| Why is the chordamesoderm important? | It induces proper development of overlying ectodermal tissue into neural tube. |
| What does notochord serve as? | internal support structure for body |
| In mammals, notochord forms by invagination of what? | the mesoderm |
| In birds and mammals, the cells at midline of neural plate are called? | Medial hinge point (MHP) cells |
| The notochord induces what cells to decrease their height and become wedge-shaped? | MHP cells |
| What cells anchor to the surface of ectoderm of neural folds? | Dorsolateral hinge points (DLHPs) cells |
| ____increase height and become wedge-shaped. | DLHPs |
| The pushing of epidermis toward center and furrowing of neural tube creates what? | Neural folds |
| The key region is the _____. It thickens and folds to produce the neural folds and neural groove before closing to form the neural tube. | Neural plate |
| How is the neural tube formed? | By separation from the surface ectoderm |
| What is this separation of neural tube mediated by? | the expression of different cell adhesion molecules |
| The cells that become neural tube stop expressing ____, and instead synthesize ___and ____. | E cadherin, N cadherin and N-CAM |
| If one side of an embryo is injected with N-cadherin mRNA, is there separation of neural tube? | No. N-cadherin is expressed in epidermal cells and presumptive neural tube. |
| T or F: The closure of neural tube does not occur simultaneously throughout ectoderm. | True. |
| What are the two ways of forming a neural tube? | Primary and secondary nuerulation |
| What is primary neurulation? | the cells surrounding the neural plate direct the neural plate cells to proliferate, invaginate, and pinch off from the surface to form a hollow tube. |
| What is secondary neurulation? | the neural tube arises from a solid cord of cells that sinks into the embryo and subsequently hollows out to form a hollow tube. |
| In birds and mammals, what region of the neural tube is constructed by primary neurulation? | The rostral (anterior) region |
| In birds and mammals, what region of the neural tube is made by secondary neurulation? | The caudal (posterior) region |
| The anterior portion of the neural tube forms what? | The BRAIN |
| The posterior portion forms what? | The SPINAL CORD |
| How was regional specificity of induction demonstrated? | by implanting different regions of the archenteron roof into early gastrulae. |
| What did the resulting embryos develop in regional specificity? | secondary dorsal structures. |
| Dorsal blastopore lips from early gastrulae transplanted into other ____ gastrulae induced secondary ______. | early, heads. |
| Dorsal blastopore lips from later gastrulas transplanted into ______ gastrulae induced the secondary ______. | early, tails. |
| What happens if ectodermal cells are exposed to BMP? | They assume an epidermal fate |
| The epidermal face is avoided in drsal side of embryo by what? | Local activity of the organizer molecules |
| All of the organizer molecules bind to BMPs preventing their binding to what? | BMP receptors |
| In this way, the ____is rescued from becoming epidermis. | Neuroectoderm |
| What molecules secreted by organizer that induce head structures? | Cerberus, Frzb, Dickkopf, IGFs |
| What is ceberus? | a secreted protein that induces the most anterior head |
| what is Frzb? | small, soluble form of Frizzled, the Wnt receptor, and is capable of binding Wnt proteins in solution |
| WHat is dickkopf? | protein that appears to interact directly with Wnt proteins extracellularly. |
| what is IGFs? | inhibit the RTK cascade that interfere with the induction pathway of both BMP and Wnt. |
| The trunk inducer involves what protein? | Xwnt8 |
| What is Xwnt8? | primary protein involved in posteriorizing the neuronal tube |
| A gradient of Xwnt8 is highest in the _________ and absent in the _______ | posterior, and absent in anterior |
| _____ and ______ seem also involved in posteriorizing the neuronal tube in concentration manner. | FGFs and Retinoic acid |
| What is the double gradient model? | A gradient of BMP expression specifies the frog dorsal-ventral axis, while a gradient of Wnt proteins specifies the anterior-posterior axis. |
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