Selforganization of ependyma in regenerating teleost spinal cord: evidence from serial section reconstructions

Development ◽  
1986 ◽  
Vol 96 (1) ◽  
pp. 1-18
Author(s):  
Marilyn J. Anderson ◽  
Chi Y. Choy ◽  
Stephen G. Waxman
Keyword(s):  
Spinal Cord ◽  
Serial Section ◽  
De Novo ◽  
Serial Sections ◽  
Developmental Sequence ◽  
Morphological Organization ◽  
Ependymal Layer ◽  
Undifferentiated Cells

Multiple ependymal structures have been observed in regenerating spinal cord of the teleost Apteronotus albifrons. Evidence is presented for two modes of formation of the secondary ependymas: budding off from the primary ependyma, and de novo origin of a tube-like ependymal structure within a group of undifferentiated cells. Serial sections of regenerated cord provide evidence that undifferentiated cells not in immediate contact with the main ependymal layer can organize and differentiate into an ependymal structure in the regenerating spinal cord. These findings suggest that a significant amount of morphological organization can take place independent of the normal developmental sequence and environment.

Cell morphology, volume, and surface area determinations from multilevel contouring within HVEM micrographs of serial sections and whole-cell mounts

1987 ◽  
Vol 45 ◽  
pp. 588-589
Author(s):  
M. Marko ◽  
A. Leith ◽  
D. Parsons
Keyword(s):  
Surface Area ◽  
Electron Micrographs ◽  
Cell Morphology ◽  
Individual Variation ◽  
Serial Section ◽  
Stereo Pair ◽  
Complex Structures ◽  
Serial Sections ◽  
Surface Areas ◽  
Computer Based

The use of serial sections and computer-based 3-D reconstruction techniques affords an opportunity not only to visualize the shape and distribution of the structures being studied, but also to determine their volumes and surface areas. Up until now, this has been done using serial ultrathin sections.The serial-section approach differs from the stereo logical methods of Weibel in that it is based on the Information from a set of single, complete cells (or organelles) rather than on a random 2-dimensional sampling of a population of cells. Because of this, it can more easily provide absolute values of volume and surface area, especially for highly-complex structures. It also allows study of individual variation among the cells, and study of structures which occur only infrequently.We have developed a system for 3-D reconstruction of objects from stereo-pair electron micrographs of thick specimens.

scholarly journals EXTIRPATION OF THE THYMUS IN THE GUINEA PIG

1917 ◽  
Vol 25 (1) ◽  
pp. 129-152 ◽  
Author(s):  
Edwards A. Park
Keyword(s):  
Guinea Pig ◽  
Serial Section ◽  
Guinea Pigs ◽  
Close Association ◽  
Main Lobe ◽  
Technical Error ◽  
Serial Sections ◽  
Pharyngeal Pouch ◽  
The Third ◽  
Third Pharyngeal Pouch

1. Accessory lobes of thymus, derived from the third pharyngeal pouch, occurring in close association with the parathyroids from the third pouch, were found in serial section of the cervical tissues of eleven out of fourteen guinea pigs, and probably would have been found in all fourteen but for a technical error. 2. It is probable, therefore, that accessory lobes of thymus having this situation and origin are usually, if not always, present in the guinea pig. 3. Additional accessory lobes of thymus belonging to, but at some distance from the main lobe were also present in several of the animals. 4. The discovery of these accessory lobes makes it certain that the guinea pig is unsuitable material for complete thymectomy, and probably complete extirpation of the thymus in this animal is rarely, if ever accomplished. 5. The extirpation experiments of previous investigators in the guinea pig must now be regarded as partial extirpations, and their results interpreted in that light. 6. Extirpation of the thymus in the guinea pig produced no changes in the writer's experiments. 7. The study of the serial sections of the cervical tissues of the guinea pig indicates that Ruben's statements regarding the parathyroid derived from the fourth pharyngeal pouch in the guinea pig are correct,—that it is much smaller than parathyroid III, may be rudimentary, and is sometimes absent at least on one side. 8. No accessory lobe of thymus was found accompanying the parathyroid from the fourth pouch, a finding also bearing out Ruben's statement that no thymus anlarge springs from the fourth pouch in the guinea pig.

Low risk of radiation myelopathy with relaxed spinal cord dose constraints in de novo, single fraction spine stereotactic radiosurgery

2020 ◽  
Vol 152 ◽  
pp. 49-55
Author(s):  
Kevin Diao ◽  
Juhee Song ◽  
Peter F. Thall ◽  
Gwendolyn J. McGinnis ◽  
David Boyce-Fappiano ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Stereotactic Radiosurgery ◽  
De Novo ◽  
Low Risk ◽  
Radiation Myelopathy ◽  
Single Fraction ◽  
Dose Constraints

Histoenzymatic profile of human muscle cultured in monolayer and innervated de novo by fetal rat spinal cord

1988 ◽  
Vol 11 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Giuseppe Vita ◽  
Valerie Askanas ◽  
Andrea Martinuzzi ◽  
W. King Engel
Keyword(s):  
Spinal Cord ◽  
De Novo ◽  
Human Muscle ◽  
Rat Spinal Cord ◽  
Fetal Rat

Cell Death in Spinal Cord Injury (SCI) Requires de Novo Protein Synthesis

2006 ◽  
Vol 939 (1) ◽  
pp. 436-449 ◽  
Author(s):  
SWAPAN K. RAY ◽  
DENISE D. MATZELLE ◽  
GLORIA G. WILFORD ◽  
EDWARD L. HOGAN ◽  
NAREN L. BANIK
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Cell Death ◽  
Protein Synthesis ◽  
De Novo ◽  
Cord Injury ◽  
De Novo Protein Synthesis

scholarly journals Two applications of developmental genetics to paleontology: segmentation genes in molluscs and preoral appendages in taxa of uncertain affinity

1992 ◽  
Vol 6 ◽  
pp. 145-145 ◽  
Author(s):  
David K. Jacobs
Keyword(s):  
Fossil Record ◽  
De Novo ◽  
Ectopic Expression ◽  
Cell Types ◽  
The Body ◽  
Developmental Genetics ◽  
Switching Function ◽  
Developmental Sequence ◽  
Homologous Genes ◽  
Organ Systems

Resolution of deep evolutionary problems, including the origin of the metazoa and the morphologic evolution of higher taxa within the metazoa, have long been sought in the developmental sequence. Haeckel's gastraea theory is perhaps the best example of this endeavor. Since Haeckel's time it has become apparent that the early evolution of animal life cannot be read directly from the developmental sequence. Ontogeny itself evolves making it difficult to even identify homologies in the early development between many phyla and classes. However, all may not be lost; during metazoan development gene expression must be localized in order to differentiate cell types in the body during development. It is this regionalized transcription and translation to protein product that differentiates cell types, organ systems, and the morphologic features that we can identify in the fossil record. The functional importance of the genes in question, and the fact that portions of the protein products of these genes must bind to DNA in order to perform their switching function, leads to extreme sequence conservation. This permits the identification and comparison of homologous genes important in the development of divergent taxa even after the passage of the entire Phanerozoic. If these genes retain a pattern of expression in development as well as conservation of the DNA sequence, then we can identify a homologous process derived from the development of the shared ancestor of the two taxa.This approach can be used to address the homology of metameric units. Preliminary results indicate that the segmentation gene engrailed is expressed in chiton trochophores in associated with each of the developing plate fields. The engrailed gene is known to control segmentation processes in arthropods and annelids. Evidently the plates in chitons evolved from serial features in a shared ancestor of annelids, arthropods and molluscs. This indicates that the serial features found in molluscs are ancestral (plesiomorphic), and that the evolution of the mollusca has involved the loss or reduction of serial features rather than their de novo evolution in chitons and monoplacophorans as has been suggested by a number of neontologists. The fossil record suggests successive reduction of serial features in molluscs. This paleontological interpretation now finds support in developmental genetics.Developmental genetics also provides a basis for evolution of body plans. Unusual preoral appendages have evolved in chelicerates, Burgess Shale arthropods such as Yohoia and Leanchoilia, and non arthropod forms such as Opabinia and Tullimonstrum. The differentiation of the vertebral column of vertebrates and the segments of arthropods are controlled by homologous genes that are expressed in a anterior to posterior sequence. Out of place (ectopic) expression of posterior genes in the anterior region produces posterior features in the antennal field of arthropods and in the most anterior vertebrae of the vertebrates. This potential for conversion of anterior features was present in the shared ancestor of vertebrates and arthropods. Thus evolution of novel anterior features resulting from ectopic expression could occur in both deuterostomes and protostomes and may account for a range of novel fossil forms. This suggests that parallel evolution of unusual anterior features could occur, and the presence of these features may not be the best character to use in a phylogenetic analyses.

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