Proneural clusters: equivalence groups in the epithelium of Drosophila

Development ◽  
1990 ◽  
Vol 110 (3) ◽  
pp. 927-932 ◽  
Author(s):  
P. Simpson ◽  
C. Carteret
Keyword(s):  
Nervous System ◽  
Cell Lineage ◽  
Cellular Interactions ◽  
Equivalence Group ◽  
Neural Fate ◽  
Axonal Projections ◽  
The Central Nervous System ◽  
Neuronal Specificity ◽  
Proneural Cluster ◽  
Do So

The segregation of neural precursors from epidermal cells during development of the nervous system of Drosophila relies on interactions between cells that are thought to be initially equivalent. During development of the adult peripheral nervous system, failure of the cellular interactions leads to the differentiation of a tuft of sensory bristles at the site where usually only one develops. It is thus thought that a group of cells at that site (a proneural cluster) has the potential to make a bristle but that in normal development only one cell will do so. The question addressed here is do these cells constitute an equivalence group (Kimble, J., Sulston, J. and White, J. (1979). In Cell Lineage, Stem Cells and Cell Determination (ed. N. Le Douarin). Inserm Symposium No. 10 pp. 59–68, Elsevier, Amsterdam)? Within clusters mutant for shaggy, where several cells of a cluster follow the neural fate and differentiate bristles, it is shown that these display identical neuronal specificity: stimulation of the bristles evoke the same leg cleaning response and backfilling of single neurons reveal similar axonal projections in the central nervous system. This provides direct experimental evidence that the cells of a proneural cluster are developmentally equivalent.

Lateral inhibition and the development of the sensory bristles of the adult peripheral nervous system of Drosophila

Development ◽  
1990 ◽  
Vol 109 (3) ◽  
pp. 509-519 ◽  
Author(s):  
P. Simpson
Keyword(s):  
Small Groups ◽  
Neural Cells ◽  
Cellular Interactions ◽  
Equivalence Group ◽  
Neural Fate ◽  
Neurogenic Genes ◽  
Sensory Bristles ◽  
Proneural Cluster ◽  
Molecular Nature ◽  
Bristle Pattern

Cells in the neurectoderm of Drosophila face a choice between neural and epidermal fates. On the notum of the adult fly, neural cells differentiate sensory bristles in a precise pattern. Evidence has accumulated that the bristle pattern arises from the spatial distribution of small groups of cells, proneural clusters, from each of which a single bristle will result. One class of genes, which includes the genes of the achaete-scute complex, is responsible for the correct positioning of the proneural clusters. The cells of a proneural cluster constitute an equivalence group, each of them having the potential to become a neural cell. Only one cell, however, will adopt the primary, dominant, neural fate. This cell is selected by means of cellular interactions between the members of the group, since if the dominant cell is removed, one of the remaining, epidermal, cells will switch fates and become neural. The dominant cell therefore prevents the other cells of the group from becoming neural by a phenomenon known as lateral inhibiton. They, then, adopt the secondary, epidermal, fate. A second class of genes, including the gene shaggy and the neurogenic genes mediate this process. There is some evidence that a proneural cluster is composed of a small number of cells, suggesting a contact-based mechanism of communication. The molecular nature of the protein products of the neurogenic genes is consistent with this idea.

scholarly journals Immune System in the Brain: A Modulatory Role on Dendritic Spine Morphophysiology?

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Oscar Kurt Bitzer-Quintero ◽  
Ignacio González-Burgos
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Immune System ◽  
Dendritic Spines ◽  
Cell Lineage ◽  
Myeloid Cell ◽  
Brain Parenchyma ◽  
Immune Mediators ◽  
The Central Nervous System ◽  
The Brain

The central nervous system is closely linked to the immune system at several levels. The brain parenchyma is separated from the periphery by the blood brain barrier, which under normal conditions prevents the entry of mediators such as activated leukocytes, antibodies, complement factors, and cytokines. The myeloid cell lineage plays a crucial role in the development of immune responses at the central level, and it comprises two main subtypes: (1) resident microglia, distributed throughout the brain parenchyma; (2) perivascular macrophages located in the brain capillaries of the basal lamina and the choroid plexus. In addition, astrocytes, oligodendrocytes, endothelial cells, and, to a lesser extent, neurons are implicated in the immune response in the central nervous system. By modulating synaptogenesis, microglia are most specifically involved in restoring neuronal connectivity following injury. These cells release immune mediators, such as cytokines, that modulate synaptic transmission and that alter the morphology of dendritic spines during the inflammatory process following injury. Thus, the expression and release of immune mediators in the brain parenchyma are closely linked to plastic morphophysiological changes in neuronal dendritic spines. Based on these observations, it has been proposed that these immune mediators are also implicated in learning and memory processes.

scholarly journals Order and coherence in the fate map of the zebrafish nervous system

Development ◽  
1995 ◽  
Vol 121 (8) ◽  
pp. 2595-2609 ◽  
Author(s):  
K. Woo ◽  
S.E. Fraser
Keyword(s):  
Nervous System ◽  
Neural Development ◽  
Expression Patterns ◽  
Time Lapse ◽  
Cellular Interactions ◽  
Fate Map ◽  
Dorsal Midline ◽  
Vertebrate Model ◽  
The Central Nervous System ◽  
Mutant Phenotypes

The zebrafish is an excellent vertebrate model for the study of the cellular interactions underlying the patterning and the morphogenesis of the nervous system. Here, we report regional fate maps of the zebrafish anterior nervous system at two key stages of neural development: the beginning (6 hours) and the end (10 hours) of gastrulation. Early in gastrulation, we find that the presumptive neurectoderm displays a predictable organization that reflects the future anteroposterior and dorsoventral order of the central nervous system. The precursors of the major brain subdivisions (forebrain, midbrain, hindbrain, neural retina) occupy discernible, though overlapping, domains within the dorsal blastoderm at 6 hours. As gastrulation proceeds, these domains are rearranged such that the basic order of the neural tube is evident at 10 hours. Furthermore, the anteroposterior and dorsoventral order of the progenitors is refined and becomes aligned with the primary axes of the embryo. Time-lapse video microscopy shows that the rearrangement of blastoderm cells during gastrulation is highly ordered. Cells near the dorsal midline at 6 hours, primarily forebrain progenitors, display anterior-directed migration. Cells more laterally positioned, corresponding to midbrain and hindbrain progenitors, converge at the midline prior to anteriorward migration. These results demonstrate a predictable order in the presumptive neurectoderm, suggesting that patterning interactions may be well underway by early gastrulation. The fate maps provide the basis for further analyses of the specification, induction and patterning of the anterior nervous system, as well as for the interpretation of mutant phenotypes and gene-expression patterns.

scholarly journals Pre-existing neuronal pathways in the leg imaginal discs of Drosophila

Development ◽  
1989 ◽  
Vol 107 (4) ◽  
pp. 855-862 ◽  
Author(s):  
S. Tix ◽  
M. Bate ◽  
G.M. Technau
Keyword(s):  
Nervous System ◽  
Cell Lineage ◽  
Imaginal Discs ◽  
Postembryonic Development ◽  
The Other ◽  
Sense Organs ◽  
Adult Cell ◽  
A Cell ◽  
The Central Nervous System ◽  
Drosophila Embryos

Injection of a cell lineage tracer (HRP) into Drosophila embryos before cellularization provides a way of selectively labelling cells at later stages that have undergone only a few mitoses. All cells born and differentiating during embryogenesis become labelled, whereas further proliferation and growth during postembryonic development causes an almost complete dilution of the marker in the adult cell complement. Early born neurons visualized in this way are good candidates for executing a pioneering function during postembryonic differentiation of the adult nervous system. In all three pairs of leg imaginal discs, a stereotyped set of larval sense organs becomes selectively labelled. Their axons fasciculate with a larval nerve, which connects the leg disc with the central nervous system. Larval sense organs are not present in the other imaginal discs. Larval neurons are not present in the transformed antennal discs of Antp 73B flies. Nonetheless adult axons successfully navigate to the base of these discs as they differentiate to form ectopic legs. We conclude that embryonically formed larval nerves are not essential for the guidance of adult axons within the leg discs.

The Influence of Functional Circulatory Disturbances on the Central Nervous System

1930 ◽  
Vol 76 (315) ◽  
pp. 641-645 ◽  
Author(s):  
W. Spielmeyer
Keyword(s):  
Internal Medicine ◽  
Central Nervous System ◽  
Nervous System ◽  
Point Of View ◽  
The Central Nervous System ◽  
Circulatory Disturbances ◽  
Do So

If I may be allowed to speak to you about the importance of functional impediments to the circulation, I would like to do so from the point of view of the anatomist. I shall not speak about the clinical and physiological observations in neuropathology and internal medicine; I want rather to begin with the deductions to which the anatomist is led by his own methods, independent of clinical facts and questions.

scholarly journals Streptococcus pneumoniae Causes Experimental Meningitis following Intranasal and Otitis Media Infections via a Nonhematogenous Route

2001 ◽  
Vol 69 (12) ◽  
pp. 7318-7325 ◽  
Author(s):  
Andrea Marra ◽  
Daniel Brigham
Keyword(s):  
Central Nervous System ◽  
Cerebrospinal Fluid ◽  
Nervous System ◽  
Streptococcus Pneumoniae ◽  
Otitis Media ◽  
Intranasal Inoculation ◽  
The Central Nervous System ◽  
Human Infections ◽  
The Brain ◽  
Do So

ABSTRACT Using two different animal models of Streptococcus pneumoniae infection, we have demonstrated that this organism is able to spread to the central nervous system and cause meningitis by bypassing the bloodstream. Following respiratory tract infection induced via intranasal inoculation, bacteria were rapidly found in the bloodstream and brains in the majority of infected mice. A similar pattern of dissemination occurred following otitis media infection via transbullar injection of gerbils. However, a small percentage of animals infected by either route showed no bacteria in the blood and yet did have significant numbers of bacteria in brain tissue. Subsequent experiments using a galU mutant of S. pneumoniae, which is impaired in its ability to disseminate to the bloodstream following infection, showed that this organism is able to spread to the brain and cerebrospinal fluid. These results demonstrate that, unlike many bacterial pathogens that cause meningitis, S. pneumoniae is able to do so independent of bloodstream involvement upon different routes of infection. This may address the difficulty in treating human infections caused by this organism.

Comprehensive examination of the human fetus

1989 ◽  
Vol 1 (2) ◽  
pp. 125-176 ◽  
Author(s):  
CR Harman
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Human Fetus ◽  
Indirect Evidence ◽  
Specific Detail ◽  
Critical Areas ◽  
Salient Points ◽  
Comprehensive Examination ◽  
The Central Nervous System ◽  
Do So

We cannot talk to the fetus. Our ability to place the fetal condition accurately in context, therefore, lies with indirect evidence and inferred responses. We can examine the fetus. We can do so in a most comprehensive fashion, addressing the salient points of fetal anatomy, both structural and functional. We are able to perform routine evaluation of every system and the methodology is available to assess critical areas such as the heart and the central nervous system in specific detail.

Transcriptional regulation of Notch and Delta: requirement for neuroblast segregation in Drosophila

Development ◽  
1997 ◽  
Vol 124 (10) ◽  
pp. 2015-2025 ◽  
Author(s):  
L. Seugnet ◽  
P. Simpson ◽  
M. Haenlin
Keyword(s):  
Nervous System ◽  
Transcriptional Regulation ◽  
Transcriptional Control ◽  
Notch Signalling ◽  
Heterogeneous Distribution ◽  
A Cell ◽  
The Central Nervous System ◽  
Regulatory Loop ◽  
Proneural Cluster ◽  
Control Activation

Segregation of a single neural precursor from each proneural cluster in Drosophila relies on Notch-mediated lateral signalling. Studies concerning the spacing of precursors for the microchaetes of the peripheral nervous system suggested the existence of a regulatory loop between Notch and its ligand Delta within each cell that is under transcriptional control. Activation of Notch leads to repression of the achaete-scute genes which themselves regulate transcription of Delta, perhaps directly. Here we have tested a requirement for transcriptional regulation of Notch and/or Delta during neuroblast segregation in embryos, by providing Notch and Delta ubiquitously at uniform levels. Neuroblast segregation occurs normally under conditions of uniform Notch expression. Under conditions of uniform Delta expression, a single neuroblast segregates from each proneural group in 80% of the cases, more than one in the remaining 20%. Thus transcriptional regulation of Delta is largely dispensable. We discuss the possibility that segregation of single precursors in the central nervous system may rely on a heterogeneous distribution of neural potential between different cells of the proneural group. Notch signalling would enable all cells to mutually repress each other and only a cell with an elevated neural potential could overcome this repression.

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