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Johan W M Hekking - One of the best experts on this subject based on the ideXlab platform.
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multistep role for actin in initial closure of the mesencephalic Neural Groove in the chick embryo
Developmental Dynamics, 2002Co-Authors: H W M Van Straaten, I J P Sieben, Johan W M HekkingAbstract:In a previous study, we have demonstrated that initial closure of the mesencephalic Neural Groove in the chick embryo is different from neurulation elsewhere. The Neural Groove invaginates, the walls appose and make contact in a ventrodorsal direction, and subsequently separate ventrally, forming an incipient Neural tube lumen, which finally widens into a definitive lumen. In this study, a role for actin in the processes of this initial mesencephalic closure is studied. Based on rhodamine-phalloidin–stained sections, three distinct actin distribution patterns emerged, and time-lapse video microscopy revealed cytochalasin-D–reversible neurulation movements. We propose that actin is involved in formation and stabilization of the Neural Groove hinge point, in invagination of dorsal neuroepithelial cells into the Neural Groove, in the origin of the incipient lumen and the reinforcement of adhesion of the dorsal Neural folds, and finally in the development of a wide lumen. Such a multifunctional effect of actin microfilaments within a narrow time window and at specific sites has not been reported yet. © 2002 Wiley-Liss, Inc.
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Neurulation in the rabbit embryo.
Anatomy and Embryology, 1998Co-Authors: Marian C.e. Peeters, Johan W M Hekking, Christoph Viebahn, H W M Van StraatenAbstract:Among a broad range of factors and mechanisms involved in the complex process of neurulation a relationship between the curvature of the craniocaudal body axis and rate of Neural tube closure has been proposed, but more examples and models are needed to further substantiate the existence of this relationship. This is particularly true for mammals, where marked differences in embryonic body curvature between species exist. The rabbit embryo has virtually no curvature during the main phase of neurulation and is therefore a suitable model, but neurulation is hardly documented in this species. In the present study, therefore, Neural tube closure in the rabbit embryo is presented in detail by morphological and morphometrical parameters, as well as from scanning electron microscopic investigations. At the stages of 6–8 somites, the flat Neural plate transforms into a V-shaped Neural Groove, beginning at the rhombo-cervical level. Between the stages of 8 and 9 somites, multiple closure sites occur simultaneously at three levels: at the incipient pros-mesencephalic transition, at the incipient mes-rhombencephalic transition, and at the level of the first pairs of somites. This results in four transient neuropores. The anterior and rhombencephalic neuropores close between the stages of 9–11 somites. The mesencephalic neuropore is very briefly present. The posterior neuropore is the largest and remains longest. Its tapered (cranial) portion closes fast within somite stages 9–10. Subsequently its wide (caudal) portion closes up to a narrow slit, but further closure slows down till full closure is achieved at the 22-somite stage. In comparing rabbit neurulation with that of chick and mouse, the sequence of multiple site closure resembles that of the mouse embryo, but other important aspects of neurulation resemble those of the chick embryo. In contrast to mouse and chick, no time lag between closure at the three closure sites in the rabbit was seen.
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Initial closure of the mesencephalic Neural Groove in the chick embryo involves a releasing zipping-up mechanism.
Developmental Dynamics, 1997Co-Authors: H W M Van Straaten, Marian C.e. Peeters, Karin F.w. Szpak, Johan W M HekkingAbstract:According to a traditional viewpoint, initial closure of the anterior Neural Groove involves bilateral elevation of the edges of the Neural plate, flattening of the midline area, subsequent convergence of the dorsal Neural folds, and finally adhesion and fusion of the medial fold edges. In a transverse view, the shape of the Neural Groove thereby changes from V > U > toppled C > O. This sequence implicates that the Neural Groove is wide almost from its inception. In the present study, a new mechanism of initial closure is proposed, based on observations in living chick embryos and on light and scanning electron microscopic observations during neurulation in the presumptive mesencephalic region. The medial part of the Neural plate invaginates in ventral direction. The walls of the arising Neural Groove appose, beginning in the depth, and make subsequent contact. During continued invagination the Neural walls extend in ventral direction, the apposition/contact zone shifts in dorsal direction up to the Neural folds and the Neural walls separate ventrally, resulting in the incipient Neural tube lumen. The mechanism is best compared with a zipping-up releasing model. In a transverse view, the shape of the Neural Groove changes from V > Y > I > O. While, according to the traditional view, the Neural folds have to converge from a distance in order to contact each other, in the present mechanism the walls and folds are sequentially in contact by the ventro-dorsal zipping-up mechanism, thereby avoiding the possibility of mismatch of the Neural folds. The above process is initiated over a considerable longitudinal distance along the Neural plate, but only at the mesencephalic level does the dorsal shift of the contact zone become complete. At other levels of the neuraxis, the contact zone releases prematurely and the Neural walls become widely separated well before their dorsal Neural folds are in contact. These folds have to converge, therefore, in order to close, but their matching is facilitated by the alignment of the previously contacted Neural folds at the mesencephalic level as well as by guidance underneath the vitelline membrane.
H W M Van Straaten - One of the best experts on this subject based on the ideXlab platform.
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multistep role for actin in initial closure of the mesencephalic Neural Groove in the chick embryo
Developmental Dynamics, 2002Co-Authors: H W M Van Straaten, I J P Sieben, Johan W M HekkingAbstract:In a previous study, we have demonstrated that initial closure of the mesencephalic Neural Groove in the chick embryo is different from neurulation elsewhere. The Neural Groove invaginates, the walls appose and make contact in a ventrodorsal direction, and subsequently separate ventrally, forming an incipient Neural tube lumen, which finally widens into a definitive lumen. In this study, a role for actin in the processes of this initial mesencephalic closure is studied. Based on rhodamine-phalloidin–stained sections, three distinct actin distribution patterns emerged, and time-lapse video microscopy revealed cytochalasin-D–reversible neurulation movements. We propose that actin is involved in formation and stabilization of the Neural Groove hinge point, in invagination of dorsal neuroepithelial cells into the Neural Groove, in the origin of the incipient lumen and the reinforcement of adhesion of the dorsal Neural folds, and finally in the development of a wide lumen. Such a multifunctional effect of actin microfilaments within a narrow time window and at specific sites has not been reported yet. © 2002 Wiley-Liss, Inc.
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Neurulation in the rabbit embryo.
Anatomy and Embryology, 1998Co-Authors: Marian C.e. Peeters, Johan W M Hekking, Christoph Viebahn, H W M Van StraatenAbstract:Among a broad range of factors and mechanisms involved in the complex process of neurulation a relationship between the curvature of the craniocaudal body axis and rate of Neural tube closure has been proposed, but more examples and models are needed to further substantiate the existence of this relationship. This is particularly true for mammals, where marked differences in embryonic body curvature between species exist. The rabbit embryo has virtually no curvature during the main phase of neurulation and is therefore a suitable model, but neurulation is hardly documented in this species. In the present study, therefore, Neural tube closure in the rabbit embryo is presented in detail by morphological and morphometrical parameters, as well as from scanning electron microscopic investigations. At the stages of 6–8 somites, the flat Neural plate transforms into a V-shaped Neural Groove, beginning at the rhombo-cervical level. Between the stages of 8 and 9 somites, multiple closure sites occur simultaneously at three levels: at the incipient pros-mesencephalic transition, at the incipient mes-rhombencephalic transition, and at the level of the first pairs of somites. This results in four transient neuropores. The anterior and rhombencephalic neuropores close between the stages of 9–11 somites. The mesencephalic neuropore is very briefly present. The posterior neuropore is the largest and remains longest. Its tapered (cranial) portion closes fast within somite stages 9–10. Subsequently its wide (caudal) portion closes up to a narrow slit, but further closure slows down till full closure is achieved at the 22-somite stage. In comparing rabbit neurulation with that of chick and mouse, the sequence of multiple site closure resembles that of the mouse embryo, but other important aspects of neurulation resemble those of the chick embryo. In contrast to mouse and chick, no time lag between closure at the three closure sites in the rabbit was seen.
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Initial closure of the mesencephalic Neural Groove in the chick embryo involves a releasing zipping-up mechanism.
Developmental Dynamics, 1997Co-Authors: H W M Van Straaten, Marian C.e. Peeters, Karin F.w. Szpak, Johan W M HekkingAbstract:According to a traditional viewpoint, initial closure of the anterior Neural Groove involves bilateral elevation of the edges of the Neural plate, flattening of the midline area, subsequent convergence of the dorsal Neural folds, and finally adhesion and fusion of the medial fold edges. In a transverse view, the shape of the Neural Groove thereby changes from V > U > toppled C > O. This sequence implicates that the Neural Groove is wide almost from its inception. In the present study, a new mechanism of initial closure is proposed, based on observations in living chick embryos and on light and scanning electron microscopic observations during neurulation in the presumptive mesencephalic region. The medial part of the Neural plate invaginates in ventral direction. The walls of the arising Neural Groove appose, beginning in the depth, and make subsequent contact. During continued invagination the Neural walls extend in ventral direction, the apposition/contact zone shifts in dorsal direction up to the Neural folds and the Neural walls separate ventrally, resulting in the incipient Neural tube lumen. The mechanism is best compared with a zipping-up releasing model. In a transverse view, the shape of the Neural Groove changes from V > Y > I > O. While, according to the traditional view, the Neural folds have to converge from a distance in order to contact each other, in the present mechanism the walls and folds are sequentially in contact by the ventro-dorsal zipping-up mechanism, thereby avoiding the possibility of mismatch of the Neural folds. The above process is initiated over a considerable longitudinal distance along the Neural plate, but only at the mesencephalic level does the dorsal shift of the contact zone become complete. At other levels of the neuraxis, the contact zone releases prematurely and the Neural walls become widely separated well before their dorsal Neural folds are in contact. These folds have to converge, therefore, in order to close, but their matching is facilitated by the alignment of the previously contacted Neural folds at the mesencephalic level as well as by guidance underneath the vitelline membrane.
Kohei Shiota - One of the best experts on this subject based on the ideXlab platform.
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Development and Developmental Disorders of the Forebrain
2020Co-Authors: Hans Ten J Donkelaar, Kohei Shiota, Akira Hori, Martin Lammens, Johannes R. M. Cruysberg, Berit M. VerbistAbstract:Neurulation has been extensively studied in amphibian, avian and mammalian embryos and occurs in four stages: formation of the Neural plate, shaping of the Neural plate, bending of the Neural plate and closure of the Neural Groove. The rostral part of the Neural tube develops into the brain, whereas the caudal part becomes the spinal cord. This is the primary type of neurulation (Sect. 4.2). The most caudal part of the Neural tube forms by aggregation of cells into a medullary cord which then cavitates and connects to the main Neural tube. This process is called secondary neurulation (Sect. 4.3).
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neurulation and Neural tube defects
2014Co-Authors: Hans Ten J Donkelaar, Kohei Shiota, Mireille Bekker, Willy O Renier, Akira HoriAbstract:Neurulation has been extensively studied in amphibian, avian and mammalian embryos and occurs in four stages: formation of the Neural plate, shaping of the Neural plate, bending of the Neural plate and closure of the Neural Groove. The rostral part of the Neural tube develops into the brain, whereas the caudal part becomes the spinal cord. This is the primary type of neurulation (Sect. 4.2). The most caudal part of the Neural tube forms by aggregation of cells into a medullary cord which then cavitates and connects to the main Neural tube. This process is called secondary neurulation (Sect. 4.3).
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Neural tube closure in humans initiates at multiple sites: evidence from human embryos and implications for the pathogenesis of Neural tube defects
Anatomy and Embryology, 2000Co-Authors: T. Nakatsu, Chigako Uwabe, Kohei ShiotaAbstract:The closure of the Neural tube (NT) in the human embryo has generally been described as a continuous process that begins at the level of the future cervical region and proceeds both rostrally and caudally. On the other hand, multiple initiation sites of NT closure have been demonstrated in mice and other animals. In humans, based on the study of Neural tube defects (NTD) in clinical cases, van Allen et al. (1993) proposed a multi-site NT closure model in which five closure sites exist in the NT of human embryos. In the present study, we examined human embryos in which the NT was closing (Congenital Anomaly Research Center, Kyoto University) grossly and histologically, and found that NT closure in human embyos initiates at multiple sites but that the mode of NT closure in humans is different from that in many other animal species. In addition to the future cervical region that is widely accepted as an initiation site of NT closure (Site A), the mesencephalic-rhombencephalic boundary was found to be another initiation site (Site B). The second closure initiating at Site B proceeds bidirectionally and its caudal extension meets the first closure from Site A over the rhombencephalon, and the rostral extension of the second closure meets another closure extending from the rostral end of the Neural Groove (Site C) over the prosencephalon, where the anterior neuropore closes. The caudal extension of the first closure initiating at Site A was found to proceed all the way down to the caudal end of the Neural Groove where the posterior neuropore is formed, indicating that in humans, NT closure does not initiate at the caudal end of the Neural Groove to proceed rostrally. Since there is a considerable species difference in the mode of NT closure, we should be careful when extrapolating the data from other animals to the human. It seems that the type of NTD affects the intrauterine survival of abnormal embryos. Almost all the embryos with total dysraphism appear to die by 5 weeks of gestation, those with an opening over the rhombencephalon by 6.5 weeks, and those with a defect at the frontal and parietal regions survive beyond 7 weeks.
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The induction of Neural tube defects by maternal hyperthermia: a comparison of the guinea‐pig and human
Neuropathology and Applied Neurobiology, 1992Co-Authors: M. S. R. Smith, Kohei Shiota, J. B. Upfold, Marshall J. Edwards, J. Cawdell-smithAbstract:In our recent studies on the effects of maternal hyperthermia on the embryonic guinea-pig, we have demonstrated two ‘teratogenic windows’ at embryonic days 13 and 21 (E13 and E21). E13 encompasses the period of the closure of the Neural Groove and anterior neuropore, and E21 the commencement of the cortical plate. The approximate equivalent developmental times in the human are E23-E25 and E49-E56 respectively. In the guinea-pig, maternal hyperthermia at E13 results in a high incidence of Neural tube defects (NTD), many open, and associated with other defects such as microphthalmia, and scoliosis or kyphosis. The NTD were most common in the developing hindbrain and all demonstrated considerable infoldings of Neural tissue, rosettes of neuroepithelial cells, outpocketings of Neural tissue and large cystic cavities beneath the defect. In human examples from the Kyoto Human Embryo Collection, 16 had verified hyperthermic insults at E23-E25 and all had NTD which showed similar deformities to the guinea-pig. Most embryos with such gross defects are aborted in the early fetal period in both species.
I J P Sieben - One of the best experts on this subject based on the ideXlab platform.
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multistep role for actin in initial closure of the mesencephalic Neural Groove in the chick embryo
Developmental Dynamics, 2002Co-Authors: H W M Van Straaten, I J P Sieben, Johan W M HekkingAbstract:In a previous study, we have demonstrated that initial closure of the mesencephalic Neural Groove in the chick embryo is different from neurulation elsewhere. The Neural Groove invaginates, the walls appose and make contact in a ventrodorsal direction, and subsequently separate ventrally, forming an incipient Neural tube lumen, which finally widens into a definitive lumen. In this study, a role for actin in the processes of this initial mesencephalic closure is studied. Based on rhodamine-phalloidin–stained sections, three distinct actin distribution patterns emerged, and time-lapse video microscopy revealed cytochalasin-D–reversible neurulation movements. We propose that actin is involved in formation and stabilization of the Neural Groove hinge point, in invagination of dorsal neuroepithelial cells into the Neural Groove, in the origin of the incipient lumen and the reinforcement of adhesion of the dorsal Neural folds, and finally in the development of a wide lumen. Such a multifunctional effect of actin microfilaments within a narrow time window and at specific sites has not been reported yet. © 2002 Wiley-Liss, Inc.
Bhiwgade Dayan - One of the best experts on this subject based on the ideXlab platform.
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comparative evaluation of ultrastructural modifications and changes in the interhaemal membrane of the short nosed fruit bat cynopterus sphinxgangeticus during early trilaminar Neural Groove and full term stages of development
European Journal of Experimental Biology, 2015Co-Authors: Deshbhratar M Shantaj, Mahaley A Jyotsna, Raut R Sonali, Hile K Vijay, Bhiwgade DayanAbstract:The present investigation deals with the holistic information & knowledge of the interhaemal membrane of the megachiropteran bat, Cynopterus sphinx gangeticus during early (trilaminar, Neural Groove) & full-term stages of development. The morphology and histology of the definitive placenta of Pteropodidae bat, Cynopterus comprised of a discoidal, symmetrical and labyrinthine with haemodichorial condition. The orientation of the embryonic mass of the blastocyst was mesometrial and the attachment of the blastocyst being circumferential along with superficial attachment. The ultra-structural studies on the interhaemal membrane reflected that, initially the placenta was endotheliochorial in origin with the presence of maternal endothelium that persisted till the Neural Groove stage. The maternal endothelium was well-developed with large irregularly shaped blood lacunae which beared a unicellular layer of endothelial cells and later eroded & the maternal blood space came in direct confluence with syncytiotrophoblast. Free-floating amoeboid-shaped cells were also noted in the Maternal Blood Space. The interstitial membrane became highly inconspicuous by the subsequent developing stage. Most uniquely the intrasyncytial lamina was absent and later noticed only at few sites as a double-layered discontinuous membrane with homogenous maternal inside during the full-term stage. As such the conventional history of conversion of the interstitial membrane into intra-syncytial lamina did not hold true in this case. Occasional “Blebbing” or ballooning of the intra-syncytial lamina was also noted. The cytotrophoblast immensely vacuolated and sometimes it was such greatly attenuated at sites that it resembled a haemomonochorial condition with the presence of only syncytiotrophoblast. Certain binucleate cytotrophs or Giant cells were also observed. The confirmative absence of maternal endothelium and the presence of syncytio & cytotrophoblast at full-term stage resolved that the placenta is haemodichorial and thus the ambiguity of it being haemomonochorial or haemodichorial is finally resolved.