Rotation of the tectal primordium reveals plasticity of target recognition in retinotectal projection

Development ◽  
1990 ◽  
Vol 110 (2) ◽  
pp. 331-342 ◽  
Author(s):  
H. Ichijo ◽  
S. Fujita ◽  
T. Matsuno ◽  
H. Nakamura
Keyword(s):  
Ganglion Cells ◽  
Early Stage ◽  
Target Recognition ◽  
Experimental System ◽  
Caudal Part ◽  
Retinotectal Projection ◽  
Somite Stage ◽  
Retinal Axons ◽  
Stage Of Development ◽  
Rostral Part

Retinotectal projection is precisely organized in a retinotopic manner. In normal projection, temporal retinal axons project to the rostral part of the tectum, and nasal axons to the caudal part of the tectum. The two-dimensional relationship between the retina and the tectum offers a useful experimental system for analysis of neuronal target recognition. We carried out rotation of the tectal primordium in birds at an early stage of development, around the 10-somite stage, to achieve a better understanding of the characteristics of target recognition, especially the rostrocaudal specificity of the tectum. Our results showed that temporal retinal axons projected to the rostral part of the rotated tectum, which was originally caudal, and that nasal axons projected to the caudal part of the rotated tectum, which was originally rostral. Therefore, the tectum that had been rotated at the 10-somite stage received normal topographic projection from the retinal ganglion cells. Rostrocaudal specificity of the tectum for target recognition is not determined by the 10-somite stage and is acquired through interactions between the tectal primordium and its surrounding structures.

Anatomical mapping of retino-tectal connections in developing and metamorphosed Xenopus: evidence for changing connections

Development ◽  
1978 ◽  
Vol 45 (1) ◽  
pp. 249-270
Author(s):  
Alison Longley
Keyword(s):  
Optic Tectum ◽  
Wallerian Degeneration ◽  
Caudal Part ◽  
Electron Microscopic ◽  
Neural Connections ◽  
Retinal Axons ◽  
Retinal Lesion ◽  
Adult Pattern ◽  
Experimental Degeneration ◽  
Rostral Part

Neural connections between the eye and optic tectum in Xenopus laevis were anatomically traced by observing the tectal location of Wallerian degeneration after discrete retinal lesion. These retinotectal connections were mapped in postmetamorphic frogs and tadpoles at stage 51, the stage at which retinal axons have grown into about the rostral one-half of the tectum. The course of the experimental degeneration was the same in frogs and tadpoles, but degeneration proceeded faster in the younger animals. In the frogs, connections were ordered, with nasal retina mapping to the caudal part of the tectum and temporal retina mapping to the rostral tectum. In the tadpoles, within the innervated area at the rostral tectum, the retino-tectal connections were generally organized as in the adults, with the temporal retina mapping to the rostral part of the innervated tectum and nasal retina mapping primarily to the caudal part. But a portion of the nasal fibers consistently mapped to the far rostral tectum as well. Electron microscopic observations showed degenerating synaptic terminals at both rostral and caudal portions of the innervated tectum after lesion of just the nasal retina. Degeneration was not seen in control animals. These results indicate that some fibers (particularly from nasal retina) may shift their terminals caudally on the tectum to match tectal growth and produce the adult pattern of connections. If there is such connection readjustment, the ‘aberrant’ connections from nasal retina in tadpoles may be an indication of this process.

Direct exposure of postimplantation mouse embryos to 5-bromodeoxyuridine in vitro and its effect on subsequent chondrogenesis in the limbs

Development ◽  
1976 ◽  
Vol 36 (3) ◽  
pp. 623-638
Author(s):  
Narsingh D. Agnish ◽  
Devendra M. Kochhar
Keyword(s):  
Limb Development ◽  
Early Stage ◽  
Mouse Embryos ◽  
Complete Suppression ◽  
Duration Of Treatment ◽  
Whole Embryo Culture ◽  
Cartilage Development ◽  
Somite Stage ◽  
Stage Of Development ◽  
Long Term Treatment

As maternally administered 5-bromodeoxyuridine (BudR) is very quickly degraded by the liver, a combination of whole embryo culture and organ culture techniques was adopted to expose postimplantation mouse embryos to the analog and to study the effects of long-term treatment on the subsequent differentiation of limb-buds. Early and mid-11th-day mouse embryos were exposed to increasing concentrations of BudR for 12 or 24 h. Forelimbs of the treated embryos were then organ-cultured in drug-free medium and the extent of cartilage development in the explants examined. Exposure of embryos to 50–150µg/ml of BudR for 24 h resulted in significant inhibition of chondrogenesis in the subsequent limb cultures and the effect was related to dose. After treatment with 150 µg/ml of the drug, the forelimbs of the early 11-day embryos (somite stage 26–29) showed an almost complete lack of cartilage, while the limbs of mid-11th-day embryos (somite stage 32–34) were not nearly as sensitive and exhibited about 50% reduction in the amount of cartilage development. We conclude that if embryos in which the limb development is at a very early stage of development are exposed to BudR, the future course of limb differentiation is permanently and irreversibly damaged, resulting in a partial or even complete suppression of chondrogenesis in the organ. As both the dose and perhaps also the duration of treatment were critical, we suggest that the rather low frequency of reported limb malformations after in vivo injection of teratological doses of BudR may be due to only a small amount of the chemical reaching the embryos.

Regenerating axons from adult chick retinal ganglion cells recognize topographic cues from embryonic central targets

1991 ◽  
Vol 6 (6) ◽  
pp. 569-576 ◽  
Author(s):  
Jens Vanselow ◽  
Bernhard Müller ◽  
Solon Thanos
Keyword(s):  
Retinal Ganglion Cells ◽  
Axonal Regeneration ◽  
Ganglion Cells ◽  
Target Recognition ◽  
Growth Cones ◽  
Retinal Ganglion ◽  
Embryonic Growth ◽  
Retinal Axons ◽  
Order Of Magnitude ◽  
Mature Neurons

AbstractWe investigated whether regenerating mature axons recapitulate embryonic features essential to successful reconnectivity within the injured nervous system. Strips from embryonic and adult chick retinae were cultured, and outgrowing axons were examined morphometrically and immunohistochemically. In addition, the target-recognition properties of adult neurites were analyzed. Regenerating adult axons elongate on a poly-L-lysine/laminin substratum with a speed about one order of magnitude slower than that of embryonic axons. Morphologically, adult axonal tips differ dramatically from embryonic growth cones in that they possess only filopodial extensions whereas embryonic growth cones possess both lamellipodial and filopodial processes. Both embryonic and adult neurites express the growth-associated protein GAP-43. When cultured on alternating stripes of anterior and posterior embryonic tectal membranes, both adult and embryonic retinal axons distinguish between the two membrane preparations. Our results demonstrate that during axonal regeneration the mature neurons express embryonic properties that are involved in the recognition of tectal positional cues.

Memoirs: Variations in the Form of the Golgi Bodies during the Development of Neurones

1925 ◽  
Vol s2-69 (275) ◽  
pp. 509-517
Author(s):  
A. SUBBA RAU ◽  
R. J. LUDFORD
Keyword(s):  
Spinal Cord ◽  
Golgi Apparatus ◽  
Ganglion Cells ◽  
Early Stage ◽  
Golgi Body ◽  
Spinal Ganglia ◽  
Golgi Bodies ◽  
Stage Of Development ◽  
The Central Nervous System ◽  
High Degree

1. In the spinal ganglia of the chick of four days the Golgi apparatus or body is in the form of a cluster of granules or rodlets, grouped around the centrosphere, at one side of the nucleus (fig. 1, Pl. 39). 2. In a seven-day chick the Golgi body has increased in size and has begun to spread farther around the nucleus (fig. 3, Pl. 39). 3. All ganglion cells examined, both those of the spinal cord and of ganglia, have the Golgi apparatus in this compacted form during their early stage. 4. At a certain period which varies in the different cells the apparatus spreads out in the cytoplasm (fig. 4, Pl. 39), so that in the adult ganglia the apparatus is more or less scattered throughout the cell (figs. 5, 6, and 7, Pl. 39). 5. It is uncertain to what extent variations in the form of the apparatus, whether reticulate or in the form of individual rodlets, are due to differences in the degree of impregnation with the silver. The plane of the section is also an important factor in determining the appearance presented by the apparatus. 6. The medullary cells of the suprarenal body, which are derived from the central nervous system, have the apparatus in the form of a coiled network or cluster of granules at one pole of the nucleus, similar to the cells of the spinal ganglia at the early stage of development. 7. It is suggested that the scattered form of the Golgi apparatus in adult ganglion cells is an expression of the high degree of metabolism existing in these cells.

The Application of UX Research in New Energy Vehicle Innovation

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Menghan TAO ◽  
Ning XIAO ◽  
Xingfu ZHAO ◽  
Wenbin LIU
Keyword(s):  
Early Stage ◽  
Rapid Expansion ◽  
The Other ◽  
Innovative Product ◽  
Stage Of Development ◽  
New Energy ◽  
New Energy Vehicle ◽  
The One ◽  
New Energy Vehicles ◽  
Degree Of Innovation

New energy vehicles(NEV) as a new thing for sustainable development, in China, on the one hand has faced the rapid expansion of the market; the other hand, for the new NEV users, the current NEVs cannot keep up with the degree of innovation. This paper demonstrates the reasons for the existence of this systematic challenge, and puts forward the method of UX research which is different from the traditional petrol vehicles research in the early stage of development, which studies from the user's essence level, to form the innovative product programs which meet the needs of users and being real attractive.

scholarly journals Learning health systems in primary care: a systematic scoping review

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Danielle M. Nash ◽  
Zohra Bhimani ◽  
Jennifer Rayner ◽  
Merrick Zwarenstein
Keyword(s):  
Primary Care ◽  
Quality Improvement ◽  
Health Systems ◽  
Scoping Review ◽  
Early Stage ◽  
Point Of Care ◽  
The United States ◽  
Stage Of Development ◽  
Integrated Health ◽  
Google Search

Abstract Background Learning health systems have been gaining traction over the past decade. The purpose of this study was to understand the spread of learning health systems in primary care, including where they have been implemented, how they are operating, and potential challenges and solutions. Methods We completed a scoping review by systematically searching OVID Medline®, Embase®, IEEE Xplore®, and reviewing specific journals from 2007 to 2020. We also completed a Google search to identify gray literature. Results We reviewed 1924 articles through our database search and 51 articles from other sources, from which we identified 21 unique learning health systems based on 62 data sources. Only one of these learning health systems was implemented exclusively in a primary care setting, where all others were integrated health systems or networks that also included other care settings. Eighteen of the 21 were in the United States. Examples of how these learning health systems were being used included real-time clinical surveillance, quality improvement initiatives, pragmatic trials at the point of care, and decision support. Many challenges and potential solutions were identified regarding data, sustainability, promoting a learning culture, prioritization processes, involvement of community, and balancing quality improvement versus research. Conclusions We identified 21 learning health systems, which all appear at an early stage of development, and only one was primary care only. We summarized and provided examples of integrated health systems and data networks that can be considered early models in the growing global movement to advance learning health systems in primary care.

scholarly journals Open Research Data and Open Peer Review: Perceptions of a Medical and Health Sciences Community in Greece

Publications ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 14
Author(s):  
Eirini Delikoura ◽  
Dimitrios Kouis
Keyword(s):  
Peer Review ◽  
Evaluation System ◽  
Early Stage ◽  
Open Science ◽  
Health Sciences ◽  
Research Data ◽  
Stage Of Development ◽  
Open Research ◽  
Proper Training ◽  
To Receive

Recently significant initiatives have been launched for the dissemination of Open Access as part of the Open Science movement. Nevertheless, two other major pillars of Open Science such as Open Research Data (ORD) and Open Peer Review (OPR) are still in an early stage of development among the communities of researchers and stakeholders. The present study sought to unveil the perceptions of a medical and health sciences community about these issues. Through the investigation of researchers` attitudes, valuable conclusions can be drawn, especially in the field of medicine and health sciences, where an explosive growth of scientific publishing exists. A quantitative survey was conducted based on a structured questionnaire, with 179 valid responses. The participants in the survey agreed with the Open Peer Review principles. However, they ignored basic terms like FAIR (Findable, Accessible, Interoperable, and Reusable) and appeared incentivized to permit the exploitation of their data. Regarding Open Peer Review (OPR), participants expressed their agreement, implying their support for a trustworthy evaluation system. Conclusively, researchers need to receive proper training for both Open Research Data principles and Open Peer Review processes which combined with a reformed evaluation system will enable them to take full advantage of the opportunities that arise from the new scholarly publishing and communication landscape.

scholarly journals Primary Care Networks and Starfield’s 4Cs: A Case for Enhanced Chronic Disease Management

2021 ◽  
Vol 18 (6) ◽  
pp. 2926
Author(s):  
Chuan De Foo ◽  
Shilpa Surendran ◽  
Geronimo Jimenez ◽  
John Pastor Ansah ◽  
David Bruce Matchar ◽  
...  
Keyword(s):  
Primary Care ◽  
Chronic Disease ◽  
Disease Management ◽  
Chronic Disease Management ◽  
Early Stage ◽  
Healthcare Delivery ◽  
Stage Of Development ◽  
Facilitators And Barriers ◽  
Design Options ◽  
First Contact

The primary care network (PCN) was implemented as a healthcare delivery model which organises private general practitioners (GPs) into groups and furnished with a certain level of resources for chronic disease management. A secondary qualitative analysis was conducted with data from an earlier study exploring facilitators and barriers GPs enrolled in PCN’s face in chronic disease management. The objective of this study is to map features of PCN to Starfield’s “4Cs” framework. The “4Cs” of primary care—comprehensiveness, first contact access, coordination and continuity—offer high-quality design options for chronic disease management. Interview transcripts of GPs (n = 30) from the original study were purposefully selected. Provision of ancillary services, manpower, a chronic disease registry and extended operating hours of GP practices demonstrated PCN’s empowering features that fulfil the “4Cs”. On the contrary, operational challenges such as the lack of an integrated electronic medical record and disproportionate GP payment structures limit PCNs from maximising the “4Cs”. However, the enabling features mentioned above outweighs the shortfalls in all important aspects of delivering optimal chronic disease care. Therefore, even though PCN is in its early stage of development, it has shown to be well poised to steer GPs towards enhanced chronic disease management.

The magic bullet for rural development? Exploring the impacts of community telecenters in Bangladesh

2021 ◽  
pp. 026666692199750
Author(s):  
Noore Alam Siddiquee ◽  
Md Gofran Faroqi
Keyword(s):  
Service Delivery ◽  
Rural Areas ◽  
Early Stage ◽  
Rural Livelihoods ◽  
Value Added ◽  
Magic Bullet ◽  
Government Information ◽  
Individual Interviews ◽  
Stage Of Development ◽  
Marginalized Groups

This paper explores the impacts of Bangladesh’s Union Digital Centers (UDCs) as government information and service delivery hubs in rural areas. Drawing on user-surveys and semi-structured individual interviews it demonstrates that the UDCs have produced generally positive yet modest impacts on governance of service delivery. It shows that the UDCs are at an early stage of development, and that they offer only a limited set of services. While they helped extend ICT-enabled services to sections of population that would otherwise have missed them, the UDCs do not have much to do with rural livelihoods and empowerment of the poor and marginalized groups. These findings point to current inadequacies and pitfalls of the UDC approach to development. We argue that enhanced viability and effectiveness of the UDC experiment would warrant embedding more value-added governmental services and further strengthening of their capacity, mandate, and connectivity with government agencies at various levels, among others.

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