Neural Activation and Transformation in Explants of Competent Ectoderm under the Influence of Fragments of Anterior Notochord in Urodeles

Development ◽  
1954 ◽  
Vol 2 (3) ◽  
pp. 175-193
Author(s):  
P. D. Nieuwkoop ◽  
G. v. Nigtevecht
Keyword(s):  
Spinal Cord ◽  
Neural Induction ◽  
Spatial Relations ◽  
Neural Activation ◽  
Stages Of Development ◽  
Temporal And Spatial ◽  
Pass Through ◽  
Autonomous Development

Experiments in which folds of competent ectoderm were attached to neural plates of host embryos at various cranio-caudal levels (Nieuwkoop et al., 1952) suggested that two successive influences emanate from the underlying archenteron roof: a first one representing a more or less non-specific activation which leads autonomously to a differentiation in a prosencephalic direction; and a second one transforming these prosencephalic differentiation tendencies into more caudal ones leading to the formation of rhombencephalon and spinal cord. The work of Eyal-Giladi (1954) in which the temporal and spatial relations of neural induction were analysed by means of an interruption of the induction at various stages of development and at various cranio-caudal levels of the presumptive neural area showed very clearly that during gastrulation two successive waves of induction actually pass through the presumptive neuro-ectoderm in a caudo-cranial direction. The first wave, which emanates from the presumptive prechordal material, leads to an activation of the ectoderm and its autonomous development in a prosencephalic direction.

A Universe of Societies

2018 ◽  
Author(s):  
Didier Debaise
Keyword(s):  
Spatial Relations ◽  
The Third ◽  
The Status ◽  
History Of ◽  
Temporal And Spatial

Which kind of relation exists between a stone, a cloud, a dog, and a human? Is nature made of distinct domains and layers or does it form a vast unity from which all beings emerge? Refusing at once a reductionist, physicalist approach as well as a vitalistic one, Whitehead affirms that « everything is a society » This chapter consequently questions the status of different domains which together compose nature by employing the concept of society. The first part traces the history of this notion notably with reference to the two thinkers fundamental to Whitehead: Leibniz and Locke; the second part defines the temporal and spatial relations of societies; and the third explores the differences between physical, biological, and psychical forms of existence as well as their respective ways of relating to environments. The chapter thus tackles the status of nature and its domains.

Neural induction and regionalisation in the chick embryo

Development ◽  
1992 ◽  
Vol 114 (3) ◽  
pp. 729-741 ◽  
Author(s):  
K.G. Storey ◽  
J.M. Crossley ◽  
E.M. De Robertis ◽  
W.E. Norris ◽  
C.D. Stern
Keyword(s):  
Spinal Cord ◽  
Nervous System ◽  
Molecular Markers ◽  
Chick Embryo ◽  
Normal Development ◽  
Neural Induction ◽  
Stage 4 ◽  
Embryo Chick ◽  
Host Embryo ◽  
Embryonic Region

Induction and regionalisation of the chick nervous system were investigated by transplanting Hensen's node into the extra-embryonic region (area opaca margin) of a host embryo. Chick/quail chimaeras were used to determine the contributions of host and donor tissue to the supernumerary axis, and three molecular markers, Engrailed, neurofilaments (antibody 3A10) and XlHbox1/Hox3.3 were used to aid the identification of particular regions of the ectopic axis. We find that the age of the node determines the regions of the nervous system that form: young nodes (stages 2–4) induced both anterior and posterior nervous system, while older nodes (stages 5–6) have reduced inducing ability and generate only posterior nervous system. By varying the age of the host embryo, we show that the competence of the epiblast to respond to neural induction declines after stage 4. We conclude that during normal development, the initial steps of neural induction take place before stage 4 and that anteroposterior regionalisation of the nervous system may be a later process, perhaps associated with the differentiating notochord. We also speculate that the mechanisms responsible for induction of head CNS differ from those that generate the spinal cord: the trunk CNS could arise by homeogenetic induction by anterior CNS or by elongation of neural primordia that are induced very early.

scholarly journals The spinal control of locomotion and step-to-step variability in left-right symmetry from slow to moderate speeds

2015 ◽  
Vol 114 (2) ◽  
pp. 1119-1128 ◽  
Author(s):  
Charline Dambreville ◽  
Audrey Labarre ◽  
Yann Thibaudier ◽  
Marie-France Hurteau ◽  
Alain Frigon
Keyword(s):  
Spinal Cord ◽  
Step Length ◽  
Burst Duration ◽  
Relative Distance ◽  
Length Step ◽  
Spatial Parameters ◽  
Temporal And Spatial ◽  
Adult Cats ◽  
Left Right Asymmetry ◽  
Treadmill Locomotion

When speed changes during locomotion, both temporal and spatial parameters of the pattern must adjust. Moreover, at slow speeds the step-to-step pattern becomes increasingly variable. The objectives of the present study were to assess if the spinal locomotor network adjusts both temporal and spatial parameters from slow to moderate stepping speeds and to determine if it contributes to step-to-step variability in left-right symmetry observed at slow speeds. To determine the role of the spinal locomotor network, the spinal cord of 6 adult cats was transected (spinalized) at low thoracic levels and the cats were trained to recover hindlimb locomotion. Cats were implanted with electrodes to chronically record electromyography (EMG) in several hindlimb muscles. Experiments began once a stable hindlimb locomotor pattern emerged. During experiments, EMG and bilateral video recordings were made during treadmill locomotion from 0.1 to 0.4 m/s in 0.05 m/s increments. Cycle and stance durations significantly decreased with increasing speed, whereas swing duration remained unaffected. Extensor burst duration significantly decreased with increasing speed, whereas sartorius burst duration remained unchanged. Stride length, step length, and the relative distance of the paw at stance offset significantly increased with increasing speed, whereas the relative distance at stance onset and both the temporal and spatial phasing between hindlimbs were unaffected. Both temporal and spatial step-to-step left-right asymmetry decreased with increasing speed. Therefore, the spinal cord is capable of adjusting both temporal and spatial parameters during treadmill locomotion, and it is responsible, at least in part, for the step-to-step variability in left-right symmetry observed at slow speeds.

Dynorphin mRNA Expression in Dorsal Horn Neurons After Traumatic Spinal Cord Injury: Temporal and Spatial Analysis Using In Situ Hybridization

1998 ◽  
Vol 15 (7) ◽  
pp. 485-494 ◽  
Author(s):  
TOSHIYA TACHIBANA ◽  
KENJI MIKI ◽  
TETSUO FUKUOKA ◽  
AKIRA ARAKAWA ◽  
MUTSUMI TANIGUCHI ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
In Situ Hybridization ◽  
Spatial Analysis ◽  
Mrna Expression ◽  
Traumatic Spinal Cord Injury ◽  
Dorsal Horn Neurons ◽  
Cord Injury ◽  
Temporal And Spatial

scholarly journals Temporal and spatial relations in sentential reasoning

Cognition ◽  
2012 ◽  
Vol 122 (3) ◽  
pp. 393-404 ◽  
Author(s):  
Csongor Juhos ◽  
Ana Cristina Quelhas ◽  
P.N. Johnson-Laird
Keyword(s):  
Spatial Relations ◽  
Temporal And Spatial
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