Cresta neural, cuarta hoja, germinativa embrionaria / Neural crest, fourth embryonary germinative leaf

RESUMEN Las células de la cresta neural son pluripotenciales y son llamadas la cuarta hoja germinativa del embrión. Con el objetivo de estructurar los referentes teóricos actualizados que sustenten la afirmación precedente y que constituirá material de estudio para los estudiantes de las Ciencias Médicas, se realizó la revisión de 28 referencias bibliográficas, de ellas 89% actualizadas. Estas células aparecen durante la neurulación y pasado este proceso transitan de epitelial a mesenquimatosa; migran siguiendo señales de la matriz extracelular a todo el cuerpo del embrión diferenciándose en tejidos disimiles. Muy vinculados en su evolución a mecanismos epigenéticos, hacen a esta población celular vulnerables a ser dañadas invocándose en la etiología de diferentes defectos congénitos y enfermedades crónicas no trasmisibles como cáncer. Como conclusión por su pluripotencialidad y por los mecanismos moleculares que distinguen su evolución son consideradas por muchos autores la cuarta hoja germinativa del embrión (AU).

SUMMARY Neural crest cells are pluripotentials, and are called the fourth germinative leaf of the embryo. With the objective of structuring the updated theoretical referents backing up the precedent affirmation that will be study material for the students of Medical Sciences, the authors reviewed 28 bibliographic references, 89 % of them updated. These cells appear during neurulation and after this process they transit from epithelial to mesenchymal; following extracellular matrix signals, they migrate to the whole embryo body differentiating themselves in dissimilar tissues. Tightly related in their evolution to epigenetic mechanisms, this cell population is very likely to be damaged and so they are invoked in the etiology of different congenital defects and noncommunicable chronic diseases like cancer. In conclusion, due to their pluripotentiality and the molecular mechanisms distinguishing their evolution, many authors consider them the embryo´s fourth germinative leaf (AU).

Progress in biomechanical mechanism of neurulation / 国际儿科学杂志

Neurulation is a critical step in the early embryonic development of chordate and its failure causes the occurrence of neural tube defect (NTD).This is a type of serious birth defects of the nervous system,including anencephaly,spina bifida,meningeal or encephalocele and myelomeningocele.The average incidence of NTD is 1 per 1000 pregnancies worldwide.Its pathogenesis is not yet clear.Currently,research on neural tube defect has always been elucidated from the perspective of nutrition such as folic acid,or from a molecular potion related to neural tube closure.These efforts have been successful in identifying numerous cell biological processes essential to neurulation and genes associated with neural tube defect.However,as an event of tissue morphogenesis,neurulation is the result of a series of events involving the signaling pathway,cytoskeletal components,cellular,and tissue-level mechanical interactions.Only when the various aspects of neurulation are determined can it be better understood.Developmental biologists have been discussing biomechanical mechanisms that drive neurulation for many years,but there is still a lack of a unified understanding of them.The biomechanical mechanisms involved in neurulation are reviewed.

Understanding of Human Embryo Development for Teratogen Counselling

Human embryology is the study of development from a single cell to a baby in 9 months. Implantation occurs at the end of the first week of development. The second week of development is known as the week of 2's. Gastrulation, the most characteristic event occurring in the third week, establishes three germ layers composed of ectoderm, mesoderm, and endoderm. The three germ layers and neural crest cells lead to the development of their own tissues and organs during the embryonic period, which extends from the third to the eighth week. Major congenital malformations occur in the embryonic period. The fetal period, from the third month to the day of birth, is the time for maturation of tissues and organs, and growth of the body. Because of the close relationship between embryology and congenital abnormalities, knowledge of human development is essential to assess the effects on the embryo when the mother has been exposed to teratogens. This paper briefly reviews the normal embryonic development and associated congenital malformation.

The differential expression of P57kip2 and CDK5 in retinoic acid-induced neural tube defects / 重庆医学

Objective To investigate the differential expression of P57kip2 and CDK5 in neural tube defects t(NTD) from the normal ,and provide the clue for the research of the molecular mechanism of the normal neurula formation .Methods A cDNA mi-croarray containing 1 100 known genes was used to compare differences in P57kip2 and CDK5 gene expression between the normal control group and the retinoic acid(RA)-induced NTD group on embryonic(E) day 9 .5 and 10 .5 .Two differentially expressed genes were randomly selected from the two groups for Northern blotting to verify the results of the cDNA microarray .Results Compared the differences of between P57kip2 and CDK5 in normal and E9 .5 d ,E10 .5 d ,E9 .5 d-NTD ,E10 .5 d-NTD ,P57kip2 and CDK5 expression was significantly up-regulated in the before and after the formation of the normal neurulation ,but them showed a downward trend in retinoic acid (RA)-induced NTD(including two phase E9 .5 d and E10 .5 d) .Conclusion P57kip2 and CDK5 in-volved in the physiological process of NTD ,and provide the useful clue for the research of the molecular mechanism of the normal neurula formation .

Desarrollo embrionario del sistema nervioso central y órganos de los sentidos: revisión / Embryonic central nervous system and sense organ development: review

El sistema nervioso tiene origen en la capa germinal ectodérmica. Así como en la vida posnatalel sistema nervioso está claramente diferenciado en sistema nervioso central y periférico,en su etapa embrionaria la formación de cada uno sigue caminos diferentes, pero cercanos.Esta revisión hace hincapié en la formación del sistema nervioso central y de estructurasespecíficas, como los órganos de los sentidos. Se presenta un breve recorrido por procesoscomo la gastrulación, la neuralización y la formación de placodas hasta llegar a las diferentesestructuras que conforman el sistema nervioso central y los órganos de los sentidos...

The nervous system has its origin in the well-known ectodermic germinal layer. During thepostnatal life, the nervous system is clearly differentiated in central nervous system andperipheral nervous system. During the embryonic stage, all the components follow differentpaths but they are still close to each other. This review focuses on the central nervoussystem and development of the sense organs. It includes a brief review of processes suchas gastrulation, neurulation and development of cranial placodes and the structures thatmake up the central nervous system and the sense organs...

Experimental Study on the Effects of Cabarmazepine on the Neurulation in Early Chick Embryos and Immunohistochemical Staining for Fibronectin

Teratogenic effects of carbamazepine, an anticonvulsant, on the neurulation of the explanted early chick embryos were studied utilizing the punched-out filter paper explantation and culture technique. Fresh fertilized white leghorn hen eggs were incubated for 20-30 hours in an egg incubator. The Hamburger and Hamilton stage 4-11 chick embryos were explanted using the punched-out filter paper explantation technique and cultured in the CO2 cell culture incubator for 6-10 hours. They were randomly divided into a control group and an experimental group. The experimental group was divided into five subgroups according to the carbamazepine concentrations of 20micrometer 40micrometer 100micrometer 200micrometer 400micrometer with which the Ham's F-10 culture media were treated. The morphological characteristics and the incidences of teratogenic effects on the neurulation of early chick embryos in the control and experimental groups were compared with each other using the stereomicroscope and the electron microscope. The chick embryos of the same developmental stage were selected from the control and experimental groups, and immunohistochemical staining for fibronectin was done by the double-bridge PAP method. The results were as follows. 1) Of the 41 chick embryos cultured in the Ham's F-10 media without carbamazepine, 38 embryos(92.7%) developed normally, and 3 embryos(7.3%) developed abnormally. In contrast, among the 98 embryos cultured in the carbamazepine-treated media, 54 embryos(55.1%) developed abnormally. The frequent anomalous features were deformities of the neural folds, failure of neural tube closure, derangement of somites, and developmental arrest. 2) The frequency and severity of abnormal embryos increased in dose-dependent fashion. The embryos cultured in the media treated each with 20micrometer 40micrometer 100micrometer 200micrometer 400micrometer of carbamazepine developed abnormally in 12.5%, 21.1%, 60.0%, 81.0%, 86.4% respectively. 3) The scanning electron microscopic findings in neuroepithelial cells of abnormally developed embryos were flattened and smooth cellular surface with diminished surface blebs and microvilli, and size irregularity of the cells. On transmission electron microscope, underdevelopment of intracellular microfilaments was seen, but there was no significant change in the intracellular organelle. 4) The immunohistochemical stainability of the extracellular fibronectin at the basal side of the neuroepithelium was decreased in the carbamazepine-treated embryos.

Ultrastructural Changes in the Neurulation of Early Chick Embryos Treated with Diphenylhydantoin

Teratogenic effects of a diphenylhydantoin on the neurulation of the explanted early chick embryos were studied using the punched-out filter paper explantation technique. The 6th to 9th Hamburger and Hamilton staged chick embryos were explanted and cultured in the Ham's F-10 media treated with 15 microgram/ml, 30 microgram/ml, 60 microgram/ml, 90 microgram/ml, 120 microgram/ml of diphenylhydantoin in the CO2 incubator for 6-9 hours. The morphological chracteristics and the ultrastructural changes of the neuroepithelium of early chick embryos were compared with the control and experimental group using the stereomicroscope and the electron microscope. Of th 40 chick embryos cultured in the Ham's F-10 media without drug, 37 embryos(92.5%) developed normally and 3 embryos(7.5%) developed abnormally in 94 embryos(61.4%). The frequent anomalous features of the embryos were deformities of the neural folds in the cranial regions, failure of neural tube closure, dispersion of somites and developmental arrest. The scanning electron microscopic findings of neuropithelial cells of abnormally developed embryos were diminished surface blebs and microvilli, flattened and smooth cellular surfaces, and irregular size of cells. The transmission electron microscopic findings of neuroepithelial cells of abnormally developed embryos showed no significant changes of the development of intracellular organelles except the smooth cellular surface and mild underdevelopment of microfilaments.

The Effect of Ca++ on Neurulation of Early Chick Embryos

Chick embryos have been used widely as model systems for studies in experimental embryology and teratology. Especially early chick embryos are very useful for studies of neural tube defects. We made a try to figure out the effect of Ca++ on neurulation using Ca++ antagonist and Ca++ free media in early chick embryo, which is stage 8 by Hamburger & Hamilton classification. After 6~9 hours incubation in media treated with verapamil and media without Ca++, we observed the effects of these agents by LM and EM. All of 12 embryos incubated in Ca++ free media showed that neural tube was diffusely opened along the whole axis and other deformity was not found. The chick embryos cultured in medium treated with verapamil revealed various abnormalities in dose related manner. The case of arrest of the growth was also observed, which was not found Ca++ free media group. On scanning electron microscopic examination, the surface of neuroepithelium was flattened in embryos cultured in Ca++ free media.

The Effect of Local Anesthetics on Neurulation of Early Chick Embryos

Chick embryos have been used widely as model systems for studies in experimental embryology and teratology. Especially early chick embryos are very useful for studies of neural tube defects. Local anesthetics such as lidocaine, tetracaine and ketamine are known to inhibit the formation of microfilaments and cause neural tube defects. We made a try to figure out the effect of local anesthetics on neurulation in early chick embryo, which is stage 8 by Hamburger & Hamiliton classification. After 6~9 hours incubation in media treated with above local anesthetics, we observed the effects of these agents by LM and EM. Stage 8 chick embryos responded to local anesthetics in a dose related manner. Tetracaine showed most potent effects. Neural folds failed to make a contact, so the neural tube was left open. In high dosage, the case of no growth or little growth of embryo was also observed. On scanning electron microscopic examination, the surface of neuroepithelium was flattened in embryos treated with ketamines. On transmission electron microscopic examination. neuroepithelium of embryos cultured in ketamine showed the decrease of microfilaments and less conspicuous feature of mitochondria and rough ER(endoplasmic reticulum)'s.