Neuropile

Hilbig, H. Punkt, K. (1997). 24-hour rhythmicity of NADPH-diaphorase activity in the neuropil of rat visual cortex. Brain Res. Bull. 43, 337-40. 

While NPs are also labeled by Ap antibodies, the total area of this labeling is a small fraction of the total area of diffuse Ap immunoreactivity. Thus, these studies sought to correlate dementia with a form of Ap that seems to have little effect on associated neuropil. These studies, not surprisingly, were for the most part negative. Other studies have restricted their analysis to fibrillar forms of Ap that are relevant to NPs and have been more equivocal in their reporting of a link between plaque load and dementia [29]. 

FIGURE 1-15 A myelinating oligodendrocyte, nucleus (N), from the spinal cord of a 2-day-old kitten extends cytoplasmic connections to at least two myelin sheaths arrows). Other myelinated and unmyelinated fibers at various stages of development, as well as glial processes, are seen in the surrounding neuropil. Xl2,750. 

The astrocyte-neuron lactate shuttle hypothesis is controversial. In recent years the possibility that lactate, formed within the brain and released by astrocytes, is an important neuronal substrate both for energy and incorporation into neurotransmitters has been the subject of many studies and considerable controversy. There is evidence that suggests transient release of lactate in human brain on stimulation [48,8,88], Little is known about the highly active metabolism that takes place in the many elaborate, lamellar distal processes of astrocytes dispersed through the neuropil and interacting with an estimated >100,000 synapses [82, and references therein]. However, it is well established that astrocytes do respond to neuronal activity [89], For example, in the isolated mouse optic nerve preparation, upon stimulation, astrocytic glycogen... 

The adult brain is endowed with nuclear as well as cytosolic and membrane T3 receptors that have been visualized by autoradiography and studied biochemically [30-33]. Both neurons and neuropil are labeled by [ 1251]T3, and the labeling is selective across brain regions. Functionally, one of the most prominent features of neural action of thyroid hormone in adulthood is subsensitivity to norepinephrine as a result of a hypothyroid state [27], These changes may be reflections of loss of dendritic spines in at least some neurons of the adultbrain. Clinically, thyroid hormone deficiency increases the probability of depressive illness, whereas thyroid excess increases the probability of mania (Ch. 52) in susceptible individuals [27],... 

The remarkable similarity of glomerular organization in the first-order central olfactory neuropils of essentially all invertebrates and vertebrates that have a differentiated olfactory system has been noted often (e.g., refs. 9-12). Indeed, Dethier (1) argued persuasively that olfactory systems similar to those of contemporary insects and vertebrates, with comparable glomerular organization, were probably already in place 500 million years ago. Referring to environmental odor substances produced, first by photosynthesis and later by mankind s organic chemistry, in varieties far... 

Axons of antennal ORCs project through the antennal nerve to enter the brain at the level of the ipsilateral antennal lobe (AL) of the deutocerebrum (52). ORC axons project from the flagellum to targets in the AL, but axons from antennal mechanosensory neurons bypass the AL and project instead to an "antennal mechanosensory and motor center" in the deutocerebrum posteroventral (with respect to the body axis of the animal) to the AL (52, 58, 64). In moths and certain other insect groups, sex-pheromonal information is processed in a prominent male-specific neuropil structure in each AL called the macroglomerular complex (MGC) (16, 52, 64, 65). 

With very few exceptions, the neurons in the medial, lateral, and anterior cell groups of the AL fall into two main classes (19,65,67,72,73). Projection neurons (PNs or output neurons) have dendritic arborizations in the AL neuropil and axons that project out of the AL, and local... 

Axons of male-specific antennal ORCs specialized to detect components of the sex pheromone project exclusively to the MGC (64, 89), and all AL neurons that respond to antennal stimulation with sex pheromone components have arborizations in the MGC (65, 72, 73). The MGC in M. sexta has two major, easily distinguishable divisions a donut-shaped neuropil structure (the "toroid") and a globular structure (the "cumulus") adjacent to the toroid and closer to the entrance of the antennal nerve into the AL (74). AL PNs that respond to antennal stimulation with sex pheromone component A have arborizations in the toroid and PNs responsive to component B, in the cumulus (74). Thus first-order synaptic processing of sensory information about these key components of the sex pheromone apparently is confined to different, distinctive neuropil regions of the MGC. 

PNs terminate (67, 72, 73). The LALs are also linked to each other by bilateral neurons with arborizations in each LAL. Neuropil adjacent to the LAL contains branches of many neurons that descend in the ventral nerve cord. Local neurons link the LAL to this adjacent neuropil. Some descending neurons also have arborizations in the LAL. Thus, the LAL is interposed in the pathway of olfactory information flow from the AL through the lateral protocerebrum to descending neurons. 

Protein aggregation is a common feature of all of the chronic human neurode-generative disorders. The intraneuronal inclusions in many of these diseases contain deposits of ubiquitylated proteins, indicating that perturbations of ubiquitin-dependent proteolysis may occur. The neuropathological hallmarks of AD are intraneuronal NFTs composed of hyperphosphorylated protein tau and extracellular amyloid plaques (12,23,24,191,207). Most of the ubiquitylated, hyperphosphorylated tau protein in NETs is monoubiquitylated, with the remainder polyubiquitylated, as the substrate of the 26S proteasome (258). The protein deposits in NET, neuritic plaques, and neuropil threads in the cerebral cortex of AD patients and those with... 

Similar to axons, synapses are initially overproduced in the infant primate, reaching their maximum number during infancy (2-4 months of age) (Rakic et ah, 1986). Cortical synapses are eventually pruned down to a density of approximately 15 to 20 synapses/100 lm of neuropil. Axons and synapses are eliminated through different time courses (Fig. 1.7). In primates, the adult number of synapses in the primate cerebral cortex is not achieved until near adolescence (Rakic et ah, 1986). 

Nicotine shows protective effects against Ap-induced neurotoxicity in vivo and in vitro. Although nicotine acts on nAChRs, it also contains metal chelating abilities. It has been shown that maternal nicotine exposure resulted in a reduction of the copper content in the neonatal lung. In addition, evidence has been accumulated that nicotine might chelate metals. Indeed, nicotine reduces the levels of copper and zinc in senile plaques and neuropil, counteracting the undesirable metal accumulation. 

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