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PubMed1992

Three-dimensional analysis of the relationship between synaptic pathology and neuropil threads in Alzheimer disease.

Recent studies have shown that the Alzheimer disease (AD) neocortex is characterized by a loss of large neurons, the presence of dilated terminal axons, widespread loss of synapses, and a disruption of the dendritic cytoskeleton which is manifested as Tau immunoreactive threads. In the present study we have investigated the relationship between synaptic and dendritic abnormalities in the neocortex of Alzheimer patients and examined the extent to which these structural alterations correlate with the severity of cognitive impairment in AD. Quantitative neuroanatomical data were obtained from immunofluorescence-labeled specimens using a laser-scanning confocal microscope, computer-assisted image processing and serial section reconstruction techniques. We found that the AD cases showed a 34% loss in the number of presynaptic terminals per 100 square (sq) microns, many of which showed structural abnormalities. The AD neuropil had an average of 10 +/- 7 dendritic threads per 1,000 sq microns, with the average thread measuring 2 sq microns. Severe AD cases had thicker threads compared with mild to moderate AD cases. Three-dimensional analysis showed clustering of synapses around threads, as well as presynaptic boutons apposed to dendritic neuropil threads. Statistical analysis showed that the strongest correlation was between synapse density and Blessed score of cognitive impairment. Thread counts did not correlate with either but were correlated with tangle counts. Stepwise multiple regression analysis showed that tangle counts, but not threads, strengthened the correlation between Blessed score and synapses. We conclude that synaptic damage may precede dendritic thread and tangle formation, and that threads do not necessarily induce synaptic pathology. Instead, dendrite sprouting in the denervated regions could be associated with increased accumulation of cytoskeletal proteins observed in the dendritic threads.

Aged↗
PubMed1993

A brain-specific protein p25 is localized and associated with oligodendrocytes, neuropil, and fiber-like structures of the CA3 hippocampal region in the rat brain.

Developmental expression and cellular localization of a novel brain-specific 25-kDa protein (p25), a substrate of tau protein kinase II, were investigated in the rat brain using polyclonal antibodies raised against peptides synthesized based on the p25 amino acid sequence. By western immunoblotting, p25 was found to be expressed only slightly in the embryonic period; the expression increased from 11 days up to 5 weeks of age, and continued to increase gradually until 1-2 years of age. Immunohistochemistry revealed distinct staining of glial cells in most regions of the central nervous system in the adult rat brain. These positively immunostained cells were especially abundant in the white matter, such as the corpus callosum, cingulum, external capsule, and internal capsule. The glial cells were identified as oligodendrocytes, and the nuclei of the cells remained unstained. Whereas the neuropil in most parts of the brain was immunostained less intensely than glias, the neuropil in the first and second layers of the cerebral cortex and the dentate gyrus was relatively strongly stained. Fiber-like structures were also stained in the CA3 region of hippocampus.

Aging↗
PubMed1981

Amino acid incorporation in medial hypothalamic nuclei: circadian, perikarya, and neuropil variations.

Amino acid, [3H]lysine, incorporation was examined with autoradiographic techniques in four nuclei of the medial hypothalamus during four consecutive 6-h periods. Rats which had previously been maintained under 12:12 light-dark conditions were kept in constant darkness during the day of [3H]lysine administration to prevent any direct influence of light on hypothalamic activity. Forty-five minutes after intraperitoneal injection of the tritiated amino acid, animals were killed. After autoradiography processing, grain counting revealed that the suprachiasmatic and magnocellular paraventricular nuclei showed a statistically significant circadian variation in the number of grains over neural perikarya. A time-of-day effect was also found in the grain count over neuropil of the arcuate, ventromedial, and paraventricular nuclei. A corresponding behavioral study found that feeding continued to occur primarily during the 12 h of night, even with lights out for 24 h. These data suggest an endogenous circadian variation in one or more factors that influence amino acid uptake and protein synthesis in some hypothalamic neurons. When [3H]lysine uptake was analyzed in terms of grains/100 micrometer 2 of cell area, the arcuate and paraventricular nuclei showed a significantly greater (double) uptake of [3H]lysine than did the suprachiasmatic or ventromedial nuclei. Four times more grains were counted over somata than over an equal area of cell-free neuropil.

Amino Acids↗
PubMed1990

Mechanism of potassium uptake in neuropile glial cells in the central nervous system of the leech.

1. Ion-selective double-barreled microelectrodes (ISME) were used to measure intracellular K+ (aKi), Na+ (aNai), and Cl- (aCli) activities of neuropile glial (NG) cells in the central nervous system of the medicinal leech Hirudo medicinalis. Ion fluxes were induced by an increase in extracellular K+ concentration [( K+]o) and analyzed to elucidate the ionic mechanism of the K+ uptake occurring under such conditions. 2. In addition, the K+ concentration of the extracellular space of the nerve cell body region (NCBR) and the neuropile (N) was measured with neutral carrier K(+)-ISME. In normal saline (4 mM K+), a concentration of 4.2 mM was measured in both extracellular spaces. No differences between the K+ concentration of the bathing fluid and the extracellular spaces were found at higher (i.e., 10 and 40 mM) K+ concentrations. 3. In normal saline, the mean membrane potential (Em) was -68 mV, and the mean aKi, aNai, and aCli were found to be 77, 10, and 7 mM, respectively. The corresponding equilibrium potentials were -81, 56, and -66 mV. The chloride equilibrium potential (ECl) was similar to Em, and it is concluded that chloride is passively distributed across the NG cell membrane. 4. When [K+]o was transiently increased 10-fold (i.e., to 40 mM), aKi and a Cli increased transiently by 22 and 25 mM, respectively, and the membrane depolarized to -28 mV, which was similar to both K+ equilibrium potential (EK) and ECl. The KCl uptake was accompanied by a transient decrease in aNai to 5 mM. 5. After incubation for at least 1 h in Na(+)-free saline, NG cells accumulated K+ in the absence of extracellular Na+ to levels similar to those observed in the presence of Na+. Therefore the uptake of K+ was not dependent on external--and probably also internal--Na+. 6. Changes in cell volume induced by the increase in [K+]o were estimated by loading NG cells with choline and monitoring its intracellular concentration with Corning-K(+)-ISME. In saline containing 40 mM K+, NG cell volume increased to approximately 150% of its volume in normal saline. 7. It is concluded that the mechanism of K+ uptake in NG cells is by passive KCl and water influx, which causes cell swelling.

Animals↗
PubMedDate not supplied

Synaptophysin immunoreactivity of the cortical neuropil in vascular dementia of Binswanger type compared with the dementia of Alzheimer type and nondemented controls.

It has been shown recently that in Alzheimer's disease the degree of dementia is strongly correlated with a reduction of the synaptophysin reactivity of the cortical neuropil as a measure of synapse density, while counts of neuritic plaques showed a weak correlation. This suggests that mechanisms acting at the synaptic level, finally resulting in a numerical decline of synapses, may represent an important factor in the pathogenesis of dementia. Under these aspects, we wanted to examine whether changes of synaptophysin immunoreactivity may also occur in dementia of vascular origin such as Binswanger's disease, where the white matter atrophy is usually conceived to be the main morphologic correlate of dementia. However, infrequently patients with morphologically typical Binswanger's subcortical encephalopathy including white matter atrophy are not demented. We found in 9 cases of vascular dementia of Binswanger type a significant reduction in synaptophysin immunoreactivity of the cortical neuropil (9.1%), the magnitude of which was not much less than in Alzheimer type dementia (10.9%). These results suggest that a reduction in cortical synaptic population density may also play a significant role in the pathogenesis of dementia in Binswanger's disease. In view of the fact that similar conditions have been shown to occur in neurodegenerative disorders with dementia other than Alzheimer type dementia, there seems to be evidence for a possible common pathogenetic link between these forms of dementia at the synaptic level, where different etiologic factors may result in similar changes.

Aged↗
PubMedDate not supplied

Rare neuropil threads in amyotrophic lateral sclerosis and parkinsonism-dementia on Guam and in the Kii Peninsula of Japan.

Using three different silver impregnation methods and antisera against microtubule-associated protein-tau (MAP-tau) and amyloid beta/A4 protein, we demonstrated abundant neurofibrillary tangles (NFTs), rare senile plaques, absence of amyloid angiopathy and rare MAP-tau- and silver-positive neuropil threads in the hippocampus of patients with amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia (PD) on Guam and in the Kii Peninsula of Japan. In contrast, abundant neuropil threads, NFTs, senile plaques with associated dystrophic neurites and amyloid angiopathy were confirmed in Alzheimer disease patients. These observations indicate that there may be important factor(s) responsible for the difference in the deposition and distribution of amyloid beta/A4 protein and MAP-tau between Pacific ALS and PD and Alzheimer disease.

Aged↗
PubMed2001

Localization of the clock controlling circadian rhythms in the first neuropile of the optic lobe in the housefly.

The visual system of a fly expresses several circadian rhythms that have been detected in the photoreceptors of the compound eye and in the first neuropile, the lamina, of the underlying optic lobe. In the lamina, axons of two classes of interneuron, L1 and L2, exhibit cyclical size changes, swelling by day and shrinking by night. These rhythmic size changes may be generated by circadian oscillators located inside and/or outside the optic lobe. To localize such oscillators, we have examined changes in the axonal cross-sectional areas of L1 and L2 within the lamina of the housefly (Musca domestica) under conditions of 12 h of light and 12 h of darkness (LD12:12), constant darkness (DD) or continuous light (LL) 24 h after the medulla was severed from the rest of the brain. After the lesion, the axon size changes of L1 and L2 were maintained only in LD conditions, but were weaker than in control flies. In DD and LL conditions, they were eliminated. This indicates that circadian rhythms in the lamina of a fly are generated central to the lamina and medulla neuropiles of the optic lobe. Cyclical changes of light and darkness in LD conditions are still able, however, to induce a weak daily rhythm in the axon sizes of L1 and L2.

Animals↗
PubMed2006

Chromosome 17 abnormalities in pediatric neuroblastic tumor with abundant neuropil and true rosettes.

Although as a group, embryonal central nervous system tumors share a common background of primitive round cells, numerous distinctive histologic features allow for further subclassification. One tumor with a unique microscopic appearance is the recently described pediatric neuroblastic tumor with abundant neuropil and true rosettes (PNTANTR). We report 2 additional cases of this unusual tumor; both arose in 4-year-old children, one a midpontine tumor and the other a large cerebral lesion. The tumors contained hypercellular sheets of undifferentiated cells, broad zones of neuropil, and scattered perivascular, Homer Wright, and multilayered ependymoblastic-like rosettes. Isochromosome 17q was detected in multiple samples from one tumor, while the other tumor showed polysomy 17. No deletions of INI1 or amplifications of MYC or MYCN were detected. This report adds 2 cases to our experience of PNTANTR and is the first to demonstrate isochromosome 17q, a molecular alteration typical of medulloblastomas.

Brain↗
PubMed1999

Effects of roundabout on growth cone dynamics, filopodial length, and growth cone morphology at the midline and throughout the neuropile.

roundabout (robo) encodes an axon guidance receptor that controls midline crossing in the Drosophila CNS. In robo mutants, axons that normally project ipsilaterally can cross and recross the midline. Growth cones expressing Robo are believed to be repelled from the midline by the interaction of Robo and its ligand Slit, an extracellular protein expressed by the midline glia. To help understand the cellular basis for the midline repulsion mediated by Robo, we used time-lapse observations to compare the growth cone behavior of the ipsilaterally projecting motorneuron RP2 in robo and wild-type embyros. In wild-type embryos, filopodia can project across the midline but are quickly retracted. In robo mutants, medial filopodia can remain extended for longer periods and can develop into contralateral branches. In many cases RP2 produces both ipsilateral and contralateral branches, both of which can extend into the periphery. The growth cone also exhibits longer filopodia and more extensive branching both at the midline and throughout the neuropile. Cell injections in fixed stage 13 embryos confirmed and quantified these results for both RP2 and the interneuron pCC. The results suggest that Robo both repels growth cones at the midline and inhibits branching throughout the neuropile by promoting filopodial retraction.

Animals↗
PubMedDate not supplied

[Ultrastructural organization of the anterior sensory neuropile in the metathoracic ganglion of the locust Locusta migratoria].

The study of serial sections of the metathoracic ganglion of Locusta migratoria showed that the fibres of the tympanal nerve terminate in the dorsal half of the anterior sensory neuropile (ASN). Three types of synaptic endings were found in the ASN. Endings type I contain dense-core vesicles 600-850 A in diameter, more or less uniformly distributed in the axoplasm. They do not form specialized contacts with postsynaptic fibres and are localized only in the most ventral part of the ASN. Endings type II contain clear round vesicles 400-450 A in diameter (rare 250-300 A) and form typical synapses with dense pre-and postsynaptic membranes and synaptic cleft 150-200 A. Four types of contacts formed by these endings with postsynaptic fibres were found: 1 : 1 synapses; convergent, divergent and serial. All of them are well presented in the auditory neuropile. Endings type III contain both dense-core and clear vesicles in different relation. Only clear vesicles of these endings are connected with the active sites of the membrane.

Animals↗
PubMed1986

[Structure of the neuropile of the abdominal trunk of Oweniidae (Polychaeta, Oweniidae)].

By means of vital staining with methylene blue, structural organization of the abdominal nerve trunk has been studied in the Polychaeta--Myriochele oculata Zachs. Topographic relations of sensitive, motor and associative neurons of the neuropil are demonstrated. Overwhelming majority of the trunk nerves are unipolar, and a small part--bipolar. The sensitive and motor elements of the neuropil have not any strict zonal localization and are situated in it both dorsally and ventrally. The associative apparatus is presented by a system of short links. The abdominal trunk is a non-paired formation. During evolution of the Oweniidae, there, probably, took place a process on inclusion of the sensitive bipolar neurons into the composition of the associative apparatus of the abdominal trunk.

Animals↗
PubMedDate not supplied

Cellular lesions in the central nervous system of Periplaneta americana following insecticide treatment in vitro and in vivo. I. Nerve cell bodies and the neuropile.

Cellular lesions in the metathoracic ganglion of P. americana following insecticide treatment have been examined. Treatment of the isolated ganglia with dieldrin (10 microM) and bioresmethrin (5 microM) induced mitochondrial damage in the neuropile and nerve cell bodies. The mitochondria in treated nerve cells were swollen with broken cristae and devoid of normal morphological appearance. Following in vivo treatment of cockroaches with these insecticides, this type of mitochondrial damage was observed even at the onset of poisoning. In the prostrate cockroaches, however, the mitochondrial swelling was accompanied by the accumulation of electron dense granules. In addition, the neuropiles of insecticide-treated ganglia contained secondary lysosomes which increased in size and number with the progress of poisoning and showed signs of depletion of synaptic vesicles. The action of dieldrin upon the ultrastructure was completely abolished by pretreatment of ganglia with 10 mM Mg2+. On the other hand, pretreatment of ganglia with tetrodotoxin and pentobarbital-sodium had very little effect on the action of dieldrin though these compounds blocked the action of bioresmethrin. The results of this study suggest that cellular lesions in the insect CNS, caused by dieldrin, are due to an enhanced uptake of calcium into nerve terminals which may occur independent of membrane depolarization. The effects of bioresmethrin upon the ultrastructure of the CNS are apparently mediated by nerve excitation and membrane depolarization. It is concluded that treatment of intact cockroaches with dieldrin and bioresmethrin initiates catabolic processes in the nerve cells leading to cellular lesions which are indicative of neuronal degeneration.

Animals↗
PubMed1978

[Structure of the neuropile of the abdominal brain of polychaetes].

By means of vital staining of neuronal elements with methylene blue, new data were obtained on the structure of neuropil in the abdominal brain of Polychaete (Nereis diversicolar). Neuronal composition and interrelationship between sensory, motor and associative areas are clarified. Dorsoventral differentiation of the neuropil is analyzed; common level of intraneural relations of Polychaetes in the line of Annelida is determined.

Animals↗
PubMed1998

Molecular cloning of a lobster Gbeta subunit and Gbeta expression in olfactory receptor neuron dendrites and brain neuropil.

We have isolated from the olfactory organ of the American lobster (Homarus americanus) two cDNA clones with homology to beta subunits of G proteins. LobGbeta1 contained a complete open reading frame that predicted an amino acid sequence with >80% identity to Gbeta sequences from other species. LobGbeta2 was a fragment of an open reading frame whose predicted amino acid sequence had 65-69% identity to other Gbeta sequences. LobGbeta2 mRNA was not detectable in the brain, eye plus eyestalk, leg, dactyl, olfactory organ, or tail muscle. In contrast, lobGbeta1 was expressed in all these tissues as a single mRNA species of 6.4 kb and a protein of 37 kD. In the brain and olfactory organ, Gbeta immunoreactivity was almost exclusively confined to neurites: the neuropil regions of the brain and the outer dendrites of the olfactory receptor neurons. Coimmunoprecipitation revealed that lobster Gbeta interacted with both Galpha s and Galpha q. LobGbeta1 is likely to be involved in a wide range of signaling events including olfactory transduction and synaptic transmission in the brain.

Amino Acid Sequence↗
PubMed2001

Visualization of synaptic markers in the optic neuropils of Drosophila using a new constrained deconvolution method.

The fruitfly Drosophila melanogaster offers compelling genetic advantages for the analysis of its nervous system, but cell size precludes immunocytochemical analysis of wild-type structure and mutant phenotypes beyond the level of neuronal arborizations. For many antibodies, especially when immunoelectron microscopy is not feasible, it would therefore be desirable to extend the resolution limit of confocal microscopy as far as possible. Because high-resolution confocal microscopy suffers from considerable blurring, so-called deconvolution algorithms are needed to remove, at least partially, the blur introduced by the microscope and by the specimen itself. Here, we present the establishment and application of a new deconvolution method to visualize synaptic markers in Drosophila optic neuropils at the resolution limit of light. We ascertained all necessary parameters experimentally and verified them by deconvolving injected fluorescent microspheres in immunostained optic lobe tissue. The resulting deconvolution method was used to analyze colocalization between the synaptic vesicle marker neuronal synaptobrevin and synaptic and putative synaptic markers in photoreceptor terminals. We report differential localization of these near the resolution limit of light, which could not be distinguished without deconvolution.

Animals↗
PubMed2003

Early development of the Drosophila brain: III. The pattern of neuropile founder tracts during the larval period.

The Drosophila N-CAM homolog Fasciclin II (FasII) is expressed during the embryonic period in a subset of central neurons that pioneer the neuropile of the larval brain. Toward the end of embryogenesis, FasII expression in axon tracts diminishes but resumes from the late first larval instar in an increasingly complex pattern of axon tracts that join the tracts laid down in the embryo. We present evidence that FasII is expressed in a major fraction of the long axon tracts that interconnect different domains of the larval brain. For many tracts, FasII expression remains stable throughout larval development and pupal development. Therefore, the FasII pattern of axon tracts, along with the mushroom body and optic lobe, both of which are also FasII-positive, represents a useful set of landmarks that define different regions in the Drosophila brain throughout development. In this study, serial confocal brain sections were used to generate digital three-dimensional models of larval axon tracts at different stages. These models form part of our effort to generate an anatomic framework of Drosophila larval brain structure required for accurate localization of gene expression and gene function in experimental studies of neural development.

Animals↗
PubMed2005

Localization of nitric oxide synthase in the central complex and surrounding midbrain neuropils of the locust Schistocerca gregaria.

Nitric oxide (NO), generated enzymatically by NO synthase (NOS), acts as an important signaling molecule in the nervous systems of vertebrates and invertebrates. In insects, NO has been implicated in development and in various aspects of sensory processing. To understand better the contribution of NO signaling to higher level brain functions, we analyzed the distribution of NOS in the midbrain of a model insect species, the locust Schistocerca gregaria, by using NADPH diaphorase (NADPHd) histochemistry after methanol/formalin fixation; results were validated by NOS immunohistochemistry. NADPHd yielded much higher sensitivity and resolution, but otherwise the two techniques resulted in corresponding labeling patterns throughout the brain, except for intense immunostaining but only weak NADPHd staining in median neurosecretory cells. About 470 neuronal cell bodies in the locust midbrain were NADPHd-positive positive, and nearly all major neuropil centers contained dense, sharply stained arborizations. We report several novel types of NOS-expressing neurons, including small ocellar interneurons and antennal sensory neurons that bypass the antennal lobe. Highly prominent labeling occurred in the central complex, a brain area involved in sky-compass orientation, and was analyzed in detail. Innervation by NOS-expressing fibers was most notable in the central body upper and lower divisions, the lateral accessory lobes, and the noduli. About 170 NADPHd-positive neurons contributed to this innervation, including five classes of tangential neuron, two systems of pontine neuron, and a system of columnar neurons. The results provide new insights into the neurochemical architecture of the central complex and suggest a prominent role for NO signaling in this brain area.

Animals↗
PubMed2003

The unusual visual system of the Strepsiptera: external eye and neuropils.

Adult males of the insect order Strepsiptera are characterized by an unusual visual system that may use design principles from compound as well as simple eyes. The lenses of this eye are unusually large and focus images onto extended retinae. The light-gathering ability of the lens is sufficient to resolve multiple points of an image in each optical unit. We regard each unit as an independent image-forming eye that contributes an inverted partial image. Each partial image is re-inverted by optic chiasmata between the retinae and the lamina, where the complete image could be assembled from the neighboring units. The lamina, medulla and lobula are present, but their organization into cartridges is not clearly discernable. Fluorescent fills, whole-tissue stains, and synaptotagmin immunohistochemistry show that the optic neuropils nevertheless are densely packed, and that several parallel channels within the medulla underlie each of the lenses. The size and shape of the rhabdoms, as well as a relatively slow flicker-fusion frequency could suggest that these eyes evolved through a nocturnal life stage.

Animals↗