• Journal of Korean Neurosurgical Society
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• v.64 no.2
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• pp.151-188
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• 2021

Spinal dysraphic lesions due to focal nondisjunction in primary neurulation are commonly encountered in paediatric neurosurgery, but the "fog-of-war" on these conditions was only gradually dispersed in the past 10 years by the works of the groups led by the senior author and Prof. Kyu-Chang Wang. It is now clear that limited dorsal myeloschisis and congenital spinal dermal sinus tract are conditions at the two ends of a spectrum; and mixed lesions of them with various configurations exist. This review article summarizes the current understanding of these conditions' embryogenetic mechanisms, pathological anatomy and clinical manifestations, and their management strategy and surgical techniques.

• Journal of Korean Neurosurgical Society
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• v.64 no.3
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• pp.326-328
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• 2021

• Applied Microscopy
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• v.29 no.1
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• pp.105-124
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• 1999

Histological and ultrastructural differentiations of the neuroepithelial cells in the mouse embryo during neurulation were observed. The neural plates and grooves consisted of pseudostratified columnar epithelium in the embryonic day (ED) 8 embryo were developed. In the ED 9 embryo, the neural tube was developed in all body length of embryo except both the cephalic and caudal ends. Secondary neurulation was shown at the tail bud of the ED 10 embryo. In the ED 8 embryo, the primitive streak was shown in the posterior end of the embryonic disc. The neuroepithelium, notochord and mesenchyme were well differentiated in the cephalic and cervical portions. In the ED 9 and 10 embryos, the roof plates of neural tubes were constituted of the closing of the surface ectodermal cells in the hindbrain and the neuroepithelial cells in the spinal cord. The floor plate of neural tube were consisted of the low pseudostratified columnar epithelium. The spinal motor nerve fibers were initially differentiated in the ED 10 embryo. According to the electron density of the cell and the differentiation of tell organelles, the neuroepithelial cells in the ED 9 and 10 embryos were classified into three types: dark, intermediate and light types. All types in the ED 9 embryo were observed but the dark cell in the ED 10 embryo was not done. The free ribosomes and polysomes in all neuroepithelial cells were developed. The RER and lipid droplets in the dark cell and the Golgi complex in the intermediate and light cells were observed. Many microfilaments in the cytoplasmic processes of intermediate cell and the microfilaments and microtubules in the light cell processes were observed to be well differentiated.

• Fisheries and Aquatic Sciences
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• v.16 no.1
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• pp.15-23
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• 2013

Normal embryonic development at a constant temperature ($18^{\circ}C$) has been described for the Siberian sturgeon Acipenser baerii (Acipenseriformes). Hormone-induced spawning and artificial insemination were performed to prepare embryonic batches for embryologic examination. After insemination, early cleavages of the Siberian sturgeon embryos continued for 7 h post-fertilization (HPF), showing the typical pattern of uneven holoblastic cleavage. Blastulation and gastrulation began at 9 HPF and 19 HPF, respectively. Epiboly formation (2/3 covered) was observed at 25 HPF during gastrulation. Neurulation was initiated with the formation of a slit-like neural groove from the blastopore at 33 HPF. During neurulation, the primary embryonic kidney (pronephros) and s-shaped heart developed. The embryos underwent progressive differentiation, which is typical of Acipenseriform species. A mass hatching was observed at 130 HPF, and the average total length of the hatched prolarvae was 10.5 mm. The hatched prolarvae possessed a typical pigment plug (yolk plug). The results of this study are valuable not only as a reference guide for the artificial propagation of Siberian sturgeon in hatcheries but also as the basis for the derivation of developmental gene expression assays for this species.

• Journal of Korean Neurosurgical Society
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• v.64 no.3
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• pp.380-385
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• 2021

Caudal agenesis refers to the congenital malformation with the essential feature of the agenesis of the sacrococcygeal bone. It is associated with various types of spinal cord anomaly as well as with complex anomalies of genitourinary or gastrointestinal system. The wide spectrum of the disease can be attributed to its pathoembryological origin, the secondary neurulation. This review presents the definition, etiology, classification, and clinical features of the disease.

• Toxicological Research
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• v.17
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• pp.11-16
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• 2001

The development of the central nervous system is a continuous process during the embryonic and fetal periods. For a better understanding of congenital anomalies of central nervous system, three major events of normal development, i.e., neurulation (3 to 4 weeks), brain vesicle formation (4 to 7 weeks) and mantle formation (over 8 weeks) should be kept in mind. The first category of anomalies is neural tube defect. Neural tube defects encompass all the anomalies arise in completion of neurulation. The second category of central nervous system anomalies is disorders of brain vesicle formation. This is anomaly that applies for "the face predicts the brain". Holoprosencephaly covers a spectrum of anomalies of intracranial and midfacial development which result from incomplete development and septation of midline structures within the forebrain or prosencephalon. The last category of central nervous system malformation is disorders involving the process of mantle formation. In the human, neurons are generated in two bursts, the first from 8 to 10 weeks and next from 12 to 14 weeks. By 16 weeks, most of the neurons have been generated and have started their migration into the cortex. Mechanism of migration disorders are multifactorial. Abnormal migration into the cortex, abnormal neurons, faulty neural growth within the cortex, unstable pial-glial border, degeneration of neurons, neural death by exogenous factors are some of the proposed mechanism. Agyria-pachygyria are characterized by a four-layerd cortex. Polymicrogyria is gyri that are too numerous and too small, and is morphologically heterogeneous. Cortical dysplasia is characterized by the presence Q[ abnormal neurons and glia arranged abnormally in focal areas of the cerebral cortex. Neuroglial malformative lesions associated with medically intractable epilepsy are hamartia or hamartoma, focal cortical dysplasia and microdysgenesis.ysgenesis.

• Journal of Korean Neurosurgical Society
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• v.64 no.3
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• pp.359-366
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• 2021

Neuromesodermal progenitors (NMPs) constitute a bipotent cell population that generates a wide variety of trunk cell and tissue types during embryonic development. Derivatives of NMPs include both mesodermal lineage cells such as muscles and vertebral bones, and neural lineage cells such as neural crests and central nervous system neurons. Such diverse lineage potential combined with a limited capacity for self-renewal, which persists during axial elongation, demonstrates that NMPs are a major source of trunk tissues. This review describes the identification and characterization of NMPs across multiple species. We also discuss key cellular and molecular steps for generating neural and mesodermal cells for building up the elongating trunk tissue.

• Journal of Korean Neurosurgical Society
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• v.37 no.1
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• pp.29-33
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• 2005

Objective: Congenital dermal sinus is a rare congenital disease that results from the failure of the neuroectoderm to separate from the surface ectoderm during the process of neurulation, where there is communication between the skin and the deeper structures. Their pathogenesis, clinical course and treatment strategy are well known. We analyze our series and compare our results with other series. Methods: Twenty patients were diagnosed as congenital dermal sinus and confirmed pathologically from October 1986 to July 2003 at our hospital. We studied the patients' clinical manifestations, radiological findings and pathological profiles. Results: Seven cases were located in the suboccipital area and 13 cases were located in the spinal area. Interestingly, 4 of 13 spinal lesion cutaneous openings were located lower than the 3rd sacral body level. 8 of 20 lesions were terminated at neural structures, 4 of 20 lesions were terminated at the intradural portion and others terminated at the extradural portion. Nine anomalies were combined with the dermal sinus, including 4 lipomas, 2 Currarino's triad, 1 encephalocele, 1 myelomeningocele and 1 diastematomyelia. Eleven patients had dermoid tumors. Conclusion: Congenital Dermal Sinus must be surgically removed immediately if they are diagnosed. The surgical procedure of congenital dermal sinus is complete removal, but in some cases, complete removal is impossible. In those cases, we removed all epithelial tissues. We consider sacrococcygeal dimple almost invariably have no connection with intraspinal structures. But, if other cutaneous manifestations are combined with cutaneous pits, it can communicate with the sacrococcygeal dimple.

• Journal of Korean Neurosurgical Society
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• v.64 no.3
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• pp.329-339
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• 2021

It has been recognised for over a century that the events of gastrulation are fundamental in determining, not only the development of the neuraxis but the organisation of the entire primitive embryo. Until recently our understanding of gastrulation was based on detailed histological analysis in animal models and relatively rare human tissue preparations from aborted fetuses. Such studies resulted in a model of gastrulation that neurosurgeons have subsequently used as a means of trying to explain some of the congenital anomalies of caudal spinal cord and vertebral development that present in paediatric neurosurgical practice. Recent advances in developmental biology, in particular cellular biology and molecular genetics have offered new insights into very early development. Understanding the processes that underlie cellular interactions, gene expression and activation/inhibition of signalling pathways has changed the way embryologists view gastrulation and this has led to a shift in emphasis from the 'descriptive and morphological' to the 'mechanistic and functional'. Unfortunately, thus far it has proved difficult to translate this improved knowledge of normal development, typically derived from non-human models, into an understanding of the mechanisms underlying human malformations such as the spinal dysraphisms and anomalies of caudal development. A paediatric neurosurgeons perspective of current concepts in gastrulation is presented along with a critical review of the current hypotheses of human malformations that have been attributed to disorders of this stage of embryogenesis.

• Fisheries and Aquatic Sciences
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• v.21 no.9
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• pp.23.1-23.8
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• 2018

Background: Russian sturgeon (Acipenser gueldenstaedtii) is an emerging candidate species in the Korean aquaculture domain owing to its highly valued caviar. Although the embryonic development of this species was previously described, the complete image data on the morphological differentiation of developing embryos have not been yet fully available. Further, with the viewpoint of larval production in hatchery, the effects of temperature on embryonic viability and the temporal window of hatching event have not been extensively studied. Hence, the objective of this study was to provide a complete set of photographic image data on the embryogenesis and also to examine the effects of incubation temperatures on embryonic viability and hatching event in farm-bred Russian sturgeon. Results: Typical characteristics of embryonic development including uneven, holoblastic cleavages with unequal blastomeres, followed by the formation of germ layer, neurulation, and organogenesis until hatching, were documented. Under different temperature conditions (12, 16, or $20^{\circ}C$), viability of embryos incubated at $12^{\circ}C$ was significantly lower as relative to those of 16 and $20^{\circ}C$ incubated embryos. Hatchability of embryos was higher, and the timing of hatching event was more synchronized at $20^{\circ}C$ than at 12 and $16^{\circ}C$. Conclusion: Data from this study suggest that the incubation of Russian sturgeon embryos at $20^{\circ}C$ would be desirable in the hatchery practice with respect to the good hatchability of embryos and the synchronization of hatching events. Additionally, the updated image data for complete embryonic development could be a useful reference guide for not only developmental researches but also artificial propagation of Russian sturgeon in farms.