• 한국가축번식학회지
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• 제20권1호
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• pp.71-76
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• 1996

This experiment was carried out to investigate the developmental ability of bovine embryos matured and fertilized in vitro to the gastrulation stage. The bovine oocytes were collected from 2∼5mm follicles, matured for 20∼24hrs in 5% CO2 incubator and then fertilized with frozen-thawed semen. On day 9 after IVF and after freezing and thawing the hatching abilities of expanding blastocysts were examined. Cleavage rate and production rate to expanding blastocysts were 59.7%(955/1604) and 20.7%(333/1604), respectively. Hatching rate of day-9 expanding blastocysts was 54%(40/74), that after freezing and thawing was 56%(79/141). Also, developmental ability of hatched blastocysts to the primitive streak stage was 26%(6/23).

• Journal of Korean Neurosurgical Society
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• 제64권3호
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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.

• Asian-Australasian Journal of Animal Sciences
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• 제7권4호
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• pp.459-466
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• 1994

Primordial germ cells (PGCs) in aves are the progenitor cells for the gametes. These cells first appear in the epiblast (Eyal-Giladi et al.. 1981). Then translocate and concentrate to endoderm of germinal crescent area in the junction of the area opaca and area pellucida lateral to the primitive streak in stage 4 through 7. They separate from the endoderm, temporarily circulate via the blood vascular system, leave the blood vessels, and finally settle down in the gonadal anlagen at stage 20-24 where they rapidly proliferate to form germ cells. Recently, several attempts have been made to introduce foreign gene into the avian genome to form a transgenic chicken. The stem cells most readily available as vehicles for genetic manipulation of germline in avian species are the PGCs. PGCs have recently been manipulated genetically and used successfully as a vector for gene transfer.

• Applied Microscopy
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• 제20권1호
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• pp.17-35
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• 1990

Effect of 5-hydroxytryptamine(5-HT, serotonin) and its precursor tryptophan on the cell proliferation of brain and somite parts of 4 day chick embryo in Dulbeco's modified essential medium was examined morphologically at cellular level. It was realized that the externally added 5-HT and/or tryptophan disturbed cell proliferation and severve necrosis occured. Electron micrograph showed that the development of cell organelles were greatly impaired. The activities of both acetylcholine esterase and $Mg^{2+}$ -dependent ATPase of the brain tissues of 5 day chick embryo, which received 1mg of tryptophan and/or 0.1mg of 5-HT at primitive streak stage after 24 hrs incubation of the fertilized egg, were much lower(about 20-25%) than those of control group. These results were supported by the electron micrographs of chemically treated cells. Control cells showed clear densed bands of acetylcholine esterase activity around nucleus and rough endoplasmic reticulum but tryptophan or 5-HT treated groups showed discontinued activity bands. In the case of $Mg^{2+}$-ATPase, the control groups showed clear continuous activity bands but tryptophan and/or 5-HT treated groups were discontinuous. From the previous and present studies, it seems that the intracelluar 5-HT level is very important for the cell proliferation and normal morphogenesis.

• 의료법학
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• 제10권1호
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• pp.11-38
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• 2009

"Bioethics" may have various meanings depending on its roles. It may mean professional ethics for scientists and physicians, etc. It may also mean an academic discipline using interdisciplinary approach as well as a philosophical or a legal approach. "Bioethics" as an interdisciplinary study should often deal with public policy on bioethical issues. I call this role bioethics as a study of bioethics policy, which has to be developed as a new discipline. From this perspective, I deal with bioethical issues relevant to a human life before birth. There are various and often conflicting arguments about the moral status of a human life before birth such as the fertilization argument, the argument of genetic identity, so-called the "14 days" argument focusing on the formation of primitive streak, the argument of sentient being, and Michael Sandle's argument of an embryo as a being between a thing and a person. I argue that each of them is reasonable. Thus we are faced with reasonable disagreement on the views over whether a human life before birth has the same right to life as that of a person or whether right to life may be considered to be a matter of degree. If we acknowledge reasonable disagreement, as John Rawls pointed out, we should tolerate the views from ours in a plural society. Therefore, we cannot help making a policy that allows abortion and embryonic research with some limitations. When we say a certain act is morally permissible, "moral permissibility" does not mean that the act is morally right for all. Rather it means that the act cannot help being morally allowed for some persons although the others do not believe its moral rightness because they cannot right now rationally persuade others to accept their view.

• Journal of Korean Neurosurgical Society
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• 제64권3호
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• pp.386-405
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• 2021

Recent advancements in basic research on the process of secondary neurulation and increased clinical experience with caudal spinal anomalies with associated abnormalities in the surrounding and distal structures shed light on further understanding of the pathoembryogenesis of the lesions and led to the new classification of these dysraphic entities. We summarized the changing concepts of lesions developed from the disordered secondary neurulation shown during the last decade. In addition, we suggested our new pathoembryogenetic explanations for a few entities based on the literature and the data from our previous animal research. Disordered secondary neurulation at each phase of development may cause corresponding lesions, such as failed junction with the primary neural tube (junctional neural tube defect and segmental spinal dysgenesis), dysgenesis or duplication of the caudal cell mass associated with disturbed activity of caudal mesenchymal tissue (caudal agenesis and caudal duplication syndrome), failed ingression of the primitive streak to the caudal cell mass (myelomeningocele), focal limited dorsal neuro-cutaneous nondisjunction (limited dorsal myeloschisis and congenital dermal sinus), neuro-mesenchymal adhesion (lumbosacral lipomatous malformation), and regression failure spectrum of the medullary cord (thickened filum and filar cyst, low-lying conus, retained medullary cord, terminal myelocele and terminal myelocystocele). It seems that almost every anomalous entity of the primary neural tube may occur in the area of secondary neurulation. Furthermore, the close association with the activity of caudal mesenchymal tissue in secondary neurulation involves a wider range of surrounding structures than in primary neurulation. Although the majority of the data are from animals, not from humans and many theories are still conjectural, these changing concepts of normal and disordered secondary neurulation will provoke further advancements in our management strategies as well as in the pathoembryogenetic understanding of anomalous lesions in this area.

• Applied Microscopy
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• 제29권1호
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• pp.105-124
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• 1999

마우스(ICR mouse)의 신경배형성에 따른 뇌 및 척수 신경상피의 조직학적 및 미세구조적 분화를 관찰하여 다음과 같은 결과를 얻었다. 배발생 8일 (embryonic day 8) 마우스배 (mouse embryo)에서 위중층원주상피의 신경판 및 신경고랑이 형성되었고, 배발생 9일에서는 두부의 전단부 및 말단부를 제외한 전 체장에서 신경관이 형성되었으며, 배발생 10일에서는 미아에서 이차신경배형성이 이루어졌다. 배발생 8일 마우스배의 미부 말단부에서는 신경상피와 중간엽과의 경계가 불분명한 원시선이 관찰되었고, 두부에서는 신경상피, 척삭 및 중간엽세포의 구분이 분명하였다. 배발생 9일과 10일 마우스배의 경우, 후뇌 부위에서는 표피 외배엽세포의 결합에 의하여, 척수 부위에서는 신경상피세포의 결합에 의하여 덮개판을 이루어졌고, 바닥판은 높이가 낮은 위중층원주상피세포로 이루어겼다. 배발생 10일 마우스배에서 척수의 운동신경이 처음 분화되었다. 배발생 9일과 10일 마우스배에서 신경상피세포들은 세포소기관의 분화 및 전자밀도의 차이에 따라 암세포, 중간형세포 및 명세포로 구분되었다. 배발생 9일에서는 모든 형의 세포가 관찰되었으나, 배발생 10일에서는 중간형 및 명세포들 만이 관찰되었다. 모든 신경상피세포에서 free ribosome 및 polysome들이 다같이 발달하였으나, 암세포에서는 RER과 lipid droplet들, 중간형세포와 명세포에서는 Golgi체들이 발달하였다. 중간형세포의 세포질돌기에서는 신경미세섬유, 명세포의 세포질들기에서는 신경미세섬유 뿐만 아니라 미세소관들도 다수 관찰되었다.