Neural epithelium

Figure 1.10 Some characteristics of neuroglial cells. A. The neural epithelium derives embry-onally from the ectoderm and differentiates in neuroblasts and neurons and in spongioblasts that will differentiate in astrocytes, oligodendrocytes, and ependymal cells as well as migratory spongioblasts that may give rise to neurons. B. Major functions of neuroglial cells. C. Schematic shape of astrocytes and oligodendrocytes and their respective locations with respect to the neuron. (Courtesy of Dr. S. Oklund.)...

The onset of neural crest cell migration involves two basically different events, which are simultaneous in birds and mammals, but which are sequential in urodele amphibians. The events are (a) egress of crest cells from the neural epithelium and... 

These results indicate that innate locomotory competence does increase before crest migration begins in trunk levels of avian embryos, but such locomotory ability does not necessarily ensure that crest cells leave the neural epithelium. 

An especially interesting example of mitochondrial differentiation is seen in neuroglia and neurons from the cerebral cortex, for these cells stem from a near common ancestor —the neural epithelium. Mitochondria from neuron-enriched and glia-enriched cell fractions of beef and rabbit brains have been isolated. These mitochondria show no striking... 

Transplantations of brain vesicles are made at the 12- to 14-somite stages, which are favorable for the following reasons Brain vesicles, still uncovered by the amnion, are clearly demarcated by constrictions in the absence of brain curvature the notochord is no longer strongly adherent to the ventral part of the neural epithelium at this level the neuroepithelium is not yet vascularized. Some neural aest cells and cephalic mesoderm are transferred along with the brain vesicles. Their presence does not interfere with the development of the brain, and presence of melanocytes in the head feathers of the chimera indicates the level of the brain graft. 

The retina comprises two principal components, the non-neural retinal pigment epithelium and the neural retina. The retinal pigment epithelium is an essential component of the visual system both structurally and functionally. It is important for the turnover and phagocytosis of photoreceptor outer segments, the metabolism of retinoids, the exchange of nutrients between the photoreceptors, and the choroidal blood vessels and the maintenance of an efficient outer blood-retinal barrier. 

The origin of the nervous tissue which comprises the sensory epithelium of the vomeronasal organ is in the anterior neural crest, from which the anterior neurogenic placode appears at the rostral tip (Fig. 4.1). 

SD Klyce, KA Palkama, M Harkonen, WS Marshall, S Huhtaniitty, KP Mann, AH Neufeld. (1982). Neural serotonin stimulates chloride transport in the rabbit corneal epithelium. Invest Ophthalmol Vis Sci 23 181-192. 

The neural tube is a pseudostratified epithelium, with cells extending between the apical and basal surfaces of the epithelial wall. The neuroepithelium contains undifferentiated populations of stem cells and radial glia (see Ch. 29). With time, both of these cell types give rise to the three main lineages for neurons, astrocytes and oligodendrocytes. After the final mitotic division, neurons migrate away from the ventricular surface of the neural... 

Pioneering efforts to understand the nature of olfactory coding were reported by Adrian (24-27). His work introduced the ideas that different odors activate ORCs in different regions of the olfactory epithelium and that spatiotemporal patterns of ORC firing would suffice to encode different odors. Subsequent studies by many investigators and involving various recording methods (reviewed in refs. 13 and 28) led to the conclusion that, at various levels of the pathway, the olfactory system uses distributed neural activity to encode information about olfactory stimuli. 

Radioactivity from " C-labeled chloroform was detected in the placenta and fetuses of mice shortly after inhalation exposure (Danielsson et al. 1986). In early gestation, accumulation of radioactivity was observed in the embryonic neural tissues, while the respiratory epithelium was more involved in chloroform metabolism in the late fetal period. 

In most organs and tissues the injury and the underlying mechanism for that injury are complex and may involve a combination of events. The extent and severity of this tissue injury are dependent upon the radiosensitivity of the various cell types in that organ system. Rubin and Casarett (1968) describe and schematically display the events following radiation in several organ system types. These include a rapid renewal system, such as the gastrointestinal mucosa a slow renewal system, such as the pulmonary epithelium and a nonrenewal system, such as neural or muscle tissue. In the... 

Second, the neural processing of this code defines a percept, called an odor . The first process takes place in a heterogeneous population of olfactory receptor neurons (ORNs) distributed in the epithelium. It determines which volatiles can be detected. The second process occurs in a series of neuropiles in the brain. It leads to some form of perception and can drive a behavioral response, depending on the animal s internal state and integration with other sensory modalities. How do individual neurons handle the transfer of information How do they connect to form a network in which this information is distributed, and what are the coding properties of this network ... 

Tight junctional complexes zonula occludens ) in the retinal pigment epithelium prevent the ready movement of antibiotics and other drugs from the blood to the retina and vitreous. The retina is a developmental derivative of the neural tube wall and can be viewed as a direct extension of the brain it is not surprising that the blood-retinal barrier somewhat resembles the blood-brain barrier in form and function. Experimental evidence has shown that histamine does not alter the vascular permeability of the retina but does affect that of all other ocular tissues. The retina closely resembles the brain with respect to this trait. 

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