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At least 19 recordsLinked to original sources
PubMed1992

Lack of ubiquitin immunoreactivities at both ends of neuropil threads. Possible bidirectional growth of neuropil threads.

Immunocytochemically, neuropil threads (curly fibers) were investigated in the Alzheimer's disease brain using a confocal laser scanning fluorescence microscope by double labeling with tau/ubiquitin antibodies. Ubiquitin immunoreactivities were found to be lacking at one or both ends in more than 40% of tau-positive threads. Immunoelectron microscopy showed that bundles of paired helical filaments, which constitute neuropil threads, were positive for ubiquitin around their midportions, but often negative at their ends. Since it is reasonable to postulate that tau deposition as paired helical filaments precedes ubiquitination, the aforementioned observation suggests that the ends of the threads are newly formed portions, and thus the threads are often growing bidirectionally in small neuronal processes.

Aged↗
PubMed1983

Antennal neuropile in the brain of the crayfish: morphology of neurons.

The cellular composition of the antennal neuropile of the crayfish is described. As a context for this work the distribution of neuronal cell bodies throughout the supraoesophageal ganglion (brain) is also described. The neuronal cell bodies in the brain are concentrated in 19 distinct clusters. Three paired clusters are located on the dorsal side of the brain, four paired and one midline cluster bend around the brain laterally and frontally respectively. Fewer than ten somata lie outside of these clusters. The antennal neuropile is composed of primary afferent terminals, efferents, and projecting and local interneurons. The structures of individual neurons of all four types were determined by filling them with Lucifer yellow, and an overview of the neuropile structure was obtained with cobalt backfills of selected nerves. The antennal afferents are concentrated in four main tracts that run medially in the outer layer of the antennal neuropile. Up to 11 orthogonal side branches occur at equal distances (25-35 microns) along the main branches and penetrate the neuropile. The efferents contribute very thin dendrites to the antennal neuropile. The majority of the neuronal mass of the antennal lobe consists of projecting and local interneurons. The branching pattern of the interneurons within the antennal neuropile also shows an orthogonal arrangement of main branches and higher-order branches. Thus the antennal neuropile displays a strong geometrical regularity: Main processes of all four types of neurons run in bundles the length of the long axis of the neuropile (lateral to medial inside the brain) giving rise to orthogonal side branches at regular intervals. This branching pattern leads to a striped appearance of the antennal lobe.

Animals↗
PubMed1984

Microvascular permeability in induced astrocytomas and peritumor neuropil of rat brain. A high-voltage electron microscope-protein tracer study.

Brain tumors, benign and malignant, are characteristically more permeable to various types of tracer molecules than the neuropil in which they are embedded. Impermeability of brain neuropil capillaries is imparted by the blood-brain barrier, the anatomic basis of which is the network of interendothelial zonulae occludentes that seal capillary endothelial cells. To explore both the vascular elements of brain neoplasms and the route of tracer extravasation from them, as well as the possible effects of brain tumors on the permeability of peritumoral neuropil capillaries, brain tumors were induced in newborn Wistar rats by intracerebral (i.c.) injection of C-6 astrocytoma cells. The protein tracer horseradish peroxidase (HRP) was injected systemically into both normal and tumor-bearing rats to mark the pathway along which it flowed into the tumor parenchyma tissue spaces, and to signal any concomitant tracer loss from the tumor extracellular compartment or peritumoral brain capillaries, into the neuropil extracellular milieu. Electron-microscopic examination of thin plastic sections of tumor and peritumoral neuropil revealed massive extravasation of tracer into the tumor tissue spaces, but none was seen outside of the capillaries in the surrounding brain neuropil. Zonulae occludentes of both tumor capillary endothelium and brain capillary endothelium were devoid of tracer and judged tight (sealed). Tracer was seen in pinocytotic vesicles in the highly attenuated endothelium of tumor capillaries and also in cytoplasmic vesicles within the tumor cells. The peritumoral and contralateral neuropil capillary endothelium exhibited reaction product-filled pinocytotic vesicles and vesiculo-tubular conduits. Often, one end of a HRP-filled vesiculo-tubular channel appeared continuous with either the luminal or abluminal plasmalemma. High-voltage electron microscopy of these conduits often showed them to be continuous with both luminal and abluminal surfaces of the endothelium, thus forming a continuum across the capillary wall. In addition, these transendothelial channels, clearly constituted as chains of fused vesicles, were often seen in close proximity to, or fused with, dense bodies in the endothelial cytoplasm. In spite of the presence of HRP-filled structures in the peritumoral neuropil capillary endothelium of tumor-bearing rats, no evidence of tracer extravasation from these vessels was apparent. These results suggest that although peritumoral and contralateral neuropil capillaries possess the machinery for extravasation of tracer, likely as a response to the presence of the neoplasm, tracer is not lost but, instead, is degraded by endothelial enzymes.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

The structure of the fourth abdominal ganglion of the crayfish, Procambarus clarki (Girard). II. Synaptic neuropils.

Four discrete regions of synaptic neuropil in the crayfish fourth abdominal ganglion are described by light and electron microscopy. The largest is the horseshoe neuropil, a horseshoe-shaped mass of synaptic glomeruli that lies horizontally in the ventral ganglionic core. This neuropil has a substructure of three rings of fused glomeruli associated with the entry of small axons from the first and second nerve roots. The lateral neuropils are large, paired bulges of neuropil that define the sides of the ganglionic core. They contain neuronal profiles of various sizes, filled with clear or dense-cored vesicles. The neurons are randomly oriented except for occasional dendritic bundles. The tract neuropil is ultrastructurally similar to the lateral neuropils but it is distributed among the largest axons of the through-tracts and commissures. The midline neuropils are small, U-shaped clumps of uniformly sized neuronal profiles that contain large numbers of dense-cored vesicles and distinctive lamellar inclusions.

Animals↗
PubMed1976

Organization of crustacean neuropil. I. Patterns of synaptic connections in lobster stomatogastric ganglion.

The stomatogastric ganglion of the lobster consists of about thiry neurons, mainly large monopolar cells, which have been well characterized physiologically. This paper presents an anatomical description of this ganglion, emphasizing synaptic connections in the neuropil. The neuron cell bodies are located on the dorsal surface of the ganglion. They send processes into the underlying neuropil mass. The neuropil is differentiated into two regions: a core of coarse neuropil consists of large heavily ensheathed processes; a surrounding region of fine-textured synaptic neuropil consists of smaller unsheather processes. Synapses are found only in synaptic neuropil, not in the core of coarse neuropil. Synaptic contacts, about one million in the entire neuropil, are easily recognized by a set of criteria including presynaptic vesicles and pre- and postsynaptic membrane specializations. Most synaptic contacts invole at least three neural processes, usually one pre- and two postsynaptic elements. Synapses are clustered onto irregular swellings or varicosities on neural processes. These varicosities make both pre- and postsynaptic contacts. Three differenty types of presynaptic profile are recognized. Pyloric dilator, ventricular dilator and lateral posterior gastric neurons belong to type A with clear irregular synaptic vesicles. Lateral pyloric, pyloric, anterior median and dorsal gastric neurons belong to type B with larger clear round vesicles. Many unidentified fibres, presumably stomatogastric nerve afferents, blong to type C with both small clear irregular vesicles and also large dense-core vesicles. The synaptic vesicle types are tentatively correlated with neurotransmitter: type A with acetylcholine, type B with an unknown transmitter, possibly glutamate, and type C with dopamine. The distribution of synaptic contacts on the processes of identified neurons reconstructed from serial section is presented in the following paper.

Animals↗
PubMed1993

Compartmental loss of NADPH diaphorase in the neuropil of the human striatum in Huntington's disease.

The distribution of NADPH diaphorase staining in the human basal ganglia was compared in five cases who were neurologically normal with five cases who died with Huntington's disease. The normal cases showed an intense staining for NADPH diaphorase throughout all regions of the neuropil in the striatum (caudate nucleus, putamen and nucleus accumbens); the staining in the neuropil was largely homogeneous although a heterogeneous distribution was evident at rostral levels of the head of the caudate nucleus and in the nucleus accumbens where patches of reduced staining aligned with acetylcholinesterase-poor regions. The globus pallidus showed a moderately intense homogeneous pattern of staining for NADPH diaphorase. In comparison with control cases, sections of the striatum from the five cases with Huntington's disease showed a dramatic decrease in the intensity of NADPH diaphorase staining in the neuropil, especially in the caudate nucleus and putamen. In cases of early Huntington's disease where no discernible loss of neurons was seen [grade 0 using the grading criteria of Vonsatell et al. (1985) J. Neuropath. exp. Neurol. 44, 559-577], there was a marked heterogeneous pattern of staining in the caudate nucleus and putamen showing a patchy loss of NADPH diaphorase in the neuropil. This resulted in clearly delineated islands of greatly reduced staining surrounded by a matrix of moderately reduced staining; the patches of greatly reduced staining corresponded with acetylcholinesterase-poor striosomes. In cases of more advanced neuropathology (grades 1 and 2) the loss of NADPH diaphorase staining in the neuropil was even more marked, affecting both acetylcholinesterase-poor and acetylcholinesterase-rich regions of the caudate nucleus and putamen and resulting in an almost homogeneous loss of staining in these striatal regions. Despite this marked loss of staining in the neuropil, the numbers of NADPH diaphorase-stained neuronal somata in the striatum in Huntington's cases appeared comparable to those in the control cases. In the globus pallidus of one of the advanced Huntington's disease cases there appeared to be a minimal loss of NADPH diaphorase staining; however, staining in the other regions of the brain which were examined was similar to that in the control cases. These findings demonstrate a progressive compartmental loss of NADPH diaphorase in the neuropil of the human striatum in Huntington's disease which correlates with the extent of neurodegeneration; early in the disease the loss of neuropil staining is first evident in the striosome compartment, then followed by an additional loss in the matrix compartment in more advanced cases of the disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholinesterase↗
PubMed1985

[Postnatal development of barreloid neuropils in the ventrobasal complex of mouse thalamus: a histochemical study for cytochrome oxidase].

Postnatal development of barreloid neuropils was studied in the ventrobasal complex of mouse thalamus. A single barreloid neuropil which topographically represented a corresponding facial vibrissa on the contralateral side was demonstrated as a solid reaction mass with the method for cytochrome oxidase. This architectural unit was called a vibrissa compartment. On postnatal Day 0, the nuclear area of the ventrobasal complex showed higher activity for the enzyme than in regions around, but no barreloids were seen. Barreloid neuropils became detectable on postnatal Day 3 in the dorsomedial subnucleus of the ventrobasal complex and the septal delimitation of barreloids was established on postnatal Day 6. The arrangement of barreloids showed a distinct orderlines similar to that of facial vibrissae on a horizontal section. Barreloid neuropils contained synaptic glomeruli ensheathed with glial processes, in which dendritic processes and their excrescences of nerve cells received large terminal knobs in well-organized manner. On postnatal Day 10, immature glomerular forms were found in barreloid neuropils. The synaptic glomerulus of mature type, however, was not formed till postnatal Day 13. The number of synaptic junctions was examined in barreloid neuropils from postnatal Day 3 to 21. The result that the growth rate of synaptic junctions was the highest in a short period from postnatal Day 10 to 13 suggested rapid maturation of barreloid neuropils in this period. On postnatal Day 21, several types of synaptic contacts became remarkable in matured glomeruli. One of them, a filamentous type with association of clear synaptic vesicles at presynaptic sites was indicated. And non-synaptic junctional complex accompaning tubular structures beneath dense materials at dendritic sites was remarked between terminal knobs and dendritic processes. From results the following conclusions are remarked that at the level of mouse thalamus, septal delimitation of vibrissa compartments appeared on postnatal Day 3 and was established until postnatal Day 6. On the other hand, barreloid neuropils containing glomerular synaptic complexes became a maturing state on postnatal Day 13, that is, about one week later after architectural compartmentalization.

Animals↗
PubMed1997

Postnatal development of zinc-containing cells and neuropil in the hippocampal region of the mouse.

The present study describes the postnatal development of zinc-containing boutons and their neurons of origin in the hippocampal region of the mouse. Ages investigated for the development of zinc-containing neuropil were postnatal days 0 (P0), P3, P7, P11, P15, P21, and P28. For zinc-containing cell bodies P7, P15, P21, and P28 were studied. In the area dentata, zinc-containing neuropil appeared first by P3 adjacent to the suprapyramidal limb of the granule cell layer and extended later toward the infrapyramidal limb. By P15, inter- and intralaminar gradients corresponded to those seen in adult animals. The appearance of labeled granule cells followed closely, although temporally delayed, the pattern of granule cell neurogenesis. All granule cells were labeled by P28. In the hippocampus proper, zinc-containing neuropil was seen by P0, but staining of the incipient mossy fiber zone was first visible by P3. Staining pattern and intensity developed gradually until they reached their mature appearance by P15. The distribution of labeled cells was identical to that seen in mature animals by P7 in CA3, but first by P21 in CA1. In the subiculum, neuropil staining first appeared proximally by P7, included all of this area by P11, and appeared mature by P21. A few labeled cells were seen in the proximal subiculum at all ages at which labeled cells were present in CA1. Labeled cells which extended further distally became first visible by P21. Their number and labeling intensity reached mature levels by P28. In the presubiculum, retrosplenial area 29e, and parasubiculum, neuropil staining first appeared by P3. The retrosplenial area 29e could be distinguished by P11. This area and the presubiculum reached their adult appearance by P21. This occurred first by P28 in the parasubiculum due to the late maturation of the parasubiculum a. Labeled cells were first seen by P7 in layer III of the presubiculum and by P15 in the retrosplenial area 29e and the parasubiculum. Cell labeling appeared mature by the same times as the neuropil staining. In the entorhinal areas a very light neuropil stain was apparent in the deeper layers by P0. A distinct rise in staining intensity was first observed by P7 in layers I-III. Thereafter, mature characteristics developed gradually and were attained by P21. Cell labeling was not seen in the medial entorhinal area. A few labeled cells were apparent by P7 in the lateral entorhinal area. After a slight increase by P15, numerous labeled cells were found in layer II and layer VI by P21. Their distribution and labeling intensity appeared mature by P28. Zinc-containing cells appear to represent cells formed late in the course of neurogenesis in all areas aside from the lateral entorhinal area. As far as intrinsic connections are concerned, it is the development of projections from this subset of neurons which is monitored in this study. We suggest that the appearance of zinc may contribute via its different effects on N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors to the end of a developmental phase that is permissive to changes in synaptic efficacy. Species differences and alternative functions of zinc are considered.

Age Factors↗
PubMed1995

Distribution of fine neurites of stomatogastric neurons of the crab Cancer borealis: evidence for a structured neuropil.

The neuropil of the stomatogastric ganglion of the crab Cancer borealis contains many neuronal processes that may be arranged either at random or in some form of orderly structure. In this study, we provide evidence for two types of order in the neuropil, a segregation of the processes based on their size and a cell-specific distribution to the fine neurites. Identified neurons were injected with Lucifer yellow, fixed, and imaged as whole mounts with a confocal microscope. Four cell types were analyzed using the serial images, two pyloric neurons, one mixed pyloric/gastric neuron, and one gastric neuron. All of the neurons consisted of a approximately 60-microns-diameter soma, a approximately 20-microns-diameter primary neurite projecting into the center of the neuropil, a number of < 10-microns-diameter medium-sized neurites radiating away from the center, and many < 3-microns-diameter fine neurites around the periphery of the neuropil. The neuropil can, therefore, be divided into three layers, a central core containing the largest neurites, an intermediate region containing both medium-sized and fine neurites, and a peripheral neuropil containing mostly fine neurites. The distribution of the fine neurites was mapped using a three-dimensional grid. We found that the fine neurites were distributed not at random within the neuropil but in consistent, cell-specific patterns.

Animals↗
PubMedDate not supplied

Morphometric image analysis of neuropil threads in Alzheimer's disease.

Neuropil threads were quantitated in the neuropil (excluding senile plaques) of the superior frontal gyrus of 6 late stage patients with Alzheimer's disease (AD) and 6 age-matched control subjects using tau immunocytochemistry and computerized morphometric image analysis. The mean percent of the area of the neuropil occupied by neuropil threads was 10.6 for AD and 0.19 for controls (p < 1 x 10(-10)). The mean length of neuropil threads in AD was 21.9 mu compared with 19.7 mu for controls (p < 1 x 10(-10)). The mean area of neuropil threads was 25.3 mu 2 for AD and 21.3 mu 2 for controls (p < 1 x 10(-10)). In AD, the threads were most prominent in mid cortex (lamina 2 and 3) and least prominent in the lower cortex (lamina 5 and 6). Neuropil threads appear to lead to severe disorganization of intracortical and corticocortical connectivity and probably play a role in the cognitive failure in AD.

Aged↗
PubMed1991

Neuropil threads of Alzheimer's disease show a marked alteration of the normal cytoskeleton.

Abnormal neurites, neuropil threads, are a widespread and characteristic lesion of Alzheimer's disease likely to play a major role in the cognitive impairment of this disease. Contrary to normal neurites, neuropil threads contain straight and paired helical filaments that contain the microtubule-associated protein tau and ubiquitin. It is not known whether these abnormal filaments are added to or replace the normal cytoskeleton. In this study, we examined the fine structure of neuropil threads and carried out a morphometric analysis of the neurofilaments and abnormal filaments contained in the neuropil threads by using an antiserum to tau and colloidal gold immuno-electron microscopy. Almost 70% of the neuropil threads contained straight or paired helical filaments with no neurofilaments. The total number of filaments in each neuropil thread remained essentially unchanged either when straight or paired helical filaments were present alone or when they coexisted either together or with neurofilaments. When the three types of filaments were expressed as a proportion of the total, a linear inverse correlation was found between neurofilaments and straight filaments as well as between straight and paired helical filaments. Approximately 10% of the neuropil threads were found to be myelinated axons. It is concluded that straight filaments are likely to replace neurofilaments, that they in turn might be replaced by paired helical filaments, and that this process occurs in axons as well as dendrites.

Aged↗
PubMed1986

[The sensory neuropile of the nerve chain of Eurygaster integriceps P].

Structure of the sensory neuropil of the abdominal nervous chain has been studied in the Eurygaster integriceps P. by means of methylene blue and paraldehyde fuchsin with phloxin staining. The sensory neuropil consists of three parts: 1) main sensory neuropil, including terminal, T-shaped, antero- and posterconnective fibers; 2) lateral sensory neuropils of the extremities, that in the insect studied, as in the dragon-fly larva, have the form of the overturned eight; 3) system of thick T-shaped fibers getting into the first thoracic ganglion and running along the second nerves, as well as along the thoracic neuromeres of the synganglion, giving collateralies into the nuclei of the extremities and into the main neuropil and coming into both the abdominal and cranial parts. In the neuropil of the extremities certain fibers are revealed; they form collateralies in the nucleus itself and terminate in the main neuropil. Of all the insects investigated it is the Eurygaster integriceps P. that possesses the most developed sensitive nuclei in the extremities and the least developed nuclei in the wings.

Adaptation, Biological↗
PubMed1997

Distribution of astroglia in glomeruli of the rat main olfactory bulb: exclusion from the sensory subcompartment of neuropil.

During an entire lifetime, sensory axons of regenerating olfactory receptor neurons can enter glomeruli in the olfactory bulb and establish synaptic junctions with central neurons. The role played by astrocytes in this unique permissiveness is still unclear. Glomerular astrocytes have been identified by immunocytochemistry for glial fibrillary acidic protein and S100 proteins at the light and electron microscopic levels. The latter labeling included submicroscopic lamellar and filopodial extensions of astroglial processes. Cell bodies and processes accumulate along the border between juxtaglomerular walls and glomerular neuropil. Within glomeruli, a network of astroglial processes encloses mesh-like neuropil zones devoid of astroglia. Electron microscopy confirmed the division into subcompartments of glomerular neuropil: 1) The "sensory-synaptic subcompartment" includes all sensory axon terminals and terminal dendritic branches receiving sensory input, whereas astroglia are excluded; 2) in the "central-synaptic subcompartment," astroglial processes are intermingled with other neuropil components: dendrites of relay cells and interneurons, dendrodendritic synapses, centrifugal (cholinergic and serotonergic) axons, their axodendritic synapses, and blood vessels. Unevenly distributed astroglial processes in this subcompartment are attached to vascular basal laminae, stem dendrites, and subpopulations of dendrodendritic synapses, especially those colocalized with centrifugal projections ("triadic synapses"). Astroglia-free parts of the "central" subcompartment contain segments of dendrites and subpopulations of dendrodendritic synapses. Because of the subdivision of the glomerular neuropil into portions with and without glial components, glia do not completely demarcate the border between the "sensory" and the "central" subcompartments. Interdigitation between the subcompartments varies among glomeruli and even within a single glomerulus. The mesh width of astroglial networks covaries with numerical relations between sensory and dendrodendritic synapses. This distribution pattern of astrocytes suggests that these glial cells monitor brain-derived effects on olfactory glomerular neuropil rather than olfactory input and that astroglial processes are (re-)arranged accordingly.

Animals↗
PubMed1998

Nitric oxide synthase in the thoracic ganglia of the locust: distribution in the neuropiles and morphology of neurones.

Nitric oxide signaling is implicated in olfactory and visual pathways within the insect brain. In contrast, little is known about the distribution and function of nitric oxide synthase (NOS) in the ventral nerve cord. This study uses NADPH diaphorase histochemistry to describe the anatomy of NOS-containing neurones and the neuropilar distribution of NOS in the thoracic nerve cord of the locust. It is shown for the first time that mechanosensory neuropiles receive innervation from NOS-containing interneurones. Different cells innervate exteroceptive and proprioceptive projection neuropiles. In the projection neuropiles of tactile afferents, a dense meshwork of NOS-containing fibres is formed by collaterals of paired intersegmental axons that run through the entire thoracic nerve cord, innervating exclusively these exteroceptive neuropiles. In neuropile areas where proprioceptive afferents terminate, stained fibres are comparatively sparse and originate from local interneurones. The prothoracic ganglion showed strongly stained dense fibres in the dorsal neuropile that were not seen in the other neuromeres. This differential NOS-expression can be related to the branching pattern of a ventral group of neurones that was different in each neuromere. All thoracic neuromeres and the abdominal neuromeres A2 and A3 of the metathoraic ganglion contained a previously undescribed type of unpaired median neurone with bilaterally ascending and descending intersegmental projections that stained strongly for NOS. The distribution of NOS found in this study suggests a novel role for nitric oxide in an early stage of mechanosensory information processing in all thoracic neuromeres and an additional role in the prothoracic ganglion, which might be related to behavioural specializations of the forelegs.

Animals↗
PubMed1988

Organization of a sensory neuropile in the auditory pathway of two groups of Orthoptera.

The anterior intermediate sensory neuropile (aISN) is a prominent neuropile in the ventral nerve cord of locusts and bushcrickets. Previous studies have shown that it receives its main sensory input from auditory receptors. In this paper we examine the structural and physiological relationship between tympanal receptor terminations and the dendrites of sound-sensitive interneurones in the homologous neuropile of locusts and bushcrickets. Each individual receptor fibre of the bushcricket terminates in a somewhat different target area of the neuropile. The ordering is with respect to the characteristic frequency of the fibres (tonotopic) in the anterior-posterior and dorsoventral axis. In the locust, representatives of the four tympanal receptor groups branch in different areas of the aISN. Most of the dorsal neuropilar region, and the anterior ventral region, do not receive input from tympanal receptors. The dendrites of identified sound-sensitive interneurones were examined in the context of this afferent projection. Local interneurones as well as intersegmental interneurones in bushcrickets have dendritic branches in the whole aISN or part of it and thus overlap with at least some receptors. By recording intracellularly from their main neurites, short-latency synaptic potentials were found in response to receptor spikes indicating monosynaptic input. The tuning of these neurones could be predicted by their dendritic morphology. In contrast, in the locust only local and bisegmental neurones are monosynaptically connected with tympanal receptors, but not the studied intersegmental neurones. This is consistent with the finding that most or all branches of intersegmental neurones lie in the dorsal area of neuropile where no receptors terminate. Anatomical and physiological evidence is presented for identified local neurones providing the excitatory and inhibitory synaptic input for such intersegmental neurones. The difference in the basic wiring diagram in the homologous neuropile of the two orthopteran groups is discussed with respect to the possible different roles that sound plays in their behaviour.

Animals↗
PubMed1991

Alz-50 immunoreactive neuropil differentiates hippocampal complex subfields in Alzheimer's disease.

The topographic distribution of Alz-50 containing profiles was determined within the hippocampal formation and anterior parahippocampal gyrus by using a monoclonal antibody directed against the A68 protein in normal and Alzheimer's diseased (AD) brains. Although there was a paucity of immunoreactive neuropil in the normal hippocampal complex, there were a few Alz-50 positive neurons that occupied the hippocampal subfield, CA2. In most AD cases, Alz-50 immunoreactive neuropil was prominent in the outer two-thirds of the molecular layer of the dentate gyrus, although a few cases exhibited staining in the inner third of the molecular layer. CA2 was characterized by an increased density of neuropil staining within stratum pyramidale. The neuropil in subfield CA1 was stained densely with Alz-50 in strata oriens, pyramidale, and at the border between strata lacunosum-moleculare and radiatum. Alz-50 immunostained neurites occupied primarily the lateral two-thirds of the subiculum proper, whereas only sparse staining was seen in the adjacent presubiculum. Alz-50 neuropil and neuronal staining displayed three distinct laminar patterns along the mediolateral extent of the entorhinal cortex, whereas the perirhinal cortex exhibited a bilaminar pattern of immunoreactivity involving heavy staining in layers 1-3 as compared to layer 5. In general, the density of Alz-50 neurite staining in the neuropil appeared inversely proportional to the distribution of Alz-50 immunoreactivity within dendritic and somal compartments. Interestingly, the patterns of Alz-50 staining observed in the hippocampal complex in AD coincides with patterns of well-characterized afferent fiber pathways to these regions, thus further supporting the suggestion that hippocampal subfield specific pathology effectively disconnects medial temporal structures from adjacent neocortex in AD.

Aged↗
PubMed1989

Electrophysiological characterization of a nicotinic acetylcholine receptor on leech neuropile glial cells.

Ion-selective double-barrelled microelectrodes were used to measure the activities of intracellular K+, Na+, Cl-, and H+ (aiK, aiNa, aiCl, pHi) and membrane potential (Em) in neuropile glial cells as well as extracellular K+ activity (aeK) in the neuropile of the leech, Hirudo medicinalis, during bath application of carbachol. As measured with conventional single-barrelled microelectrodes, acetylcholine (ACh), nicotine, carbachol, tetramethylammonium (TMA), and choline elicited concentration-dependent (10(-6)-5 X 10(-3) M) transient membrane depolarizations of up to 60 mV amplitude whereas muscarine (10(-6)-10(-3) M) did not affect Em. alpha-Bungarotoxin (10(-7) M), decamethonium (10(-5) M), d-tubocurarine (5 X 10(-5) M), and strychnine (5 X 10(-5) M) blocked the carbachol depolarization by about 90%. Atropine (5 X 10(-5) M) blocked the response by about 75%, whereas hexamethonium was only effective at millimolar concentrations. Average baseline levels of aeK in the neuropile and of aiK, aiNa, and aiCl in the neuropile glial cells were about 3, 70, 10, and 7 mM, respectively. During the carbachol depolarization aeK and aiNa transiently increased, whereas aiK decreased. In contrast, a rise of aiK and a fall of aiNa were observed during glial depolarizations in solutions with elevated K+ concentration. aiCl increased during both the carbachol- and the K+-induced depolarization. During carbachol, pHi transiently fell by about 0.2 units from its average baseline level of 6.9, whereas an alkalinization of small amplitude was observed in high-K+ solutions. Bath-applied choline, TMA, and decamethonium rapidly accumulated in the neuropile glial cells as intracellularly monitored with double-barrelled microelectrodes filled with Corning K+ exchanger resin, which is highly selective for these agents. The results suggest that leech neuropile glial cells have a nicotinic ACh receptor coupled to a cation channel. It is hypothesized that this channel might also be permeable to choline, TMA, and decamethonium.

Animals↗
PubMed1984

Development of the axon cap neuropil of the Mauthner cell in the goldfish.

Development of the axon cap neuropil of the Mauthner neuron in post-hatching larval goldfish brains was observed electron-microscopically. The axonal initial segment of newly hatched (day-4) larvae is completely covered with synaptic terminals containing clear spherical synaptic vesicles. Profiles of thin terminal axons, the spiral fibers, containing similar synaptic vesicles, rapidly increase in number around the initial segment and form glomerular neuropil similar to the central core of the adult axon cap by day 7. Three types of synapses are formed in the core neuropil. Bouton-type synapses contacting the initial segment are most abundant in day-4 to -14 larvae; they decrease thereafter and are rare on the distal half of the initial segment of day-40 larvae. Asymmetric axo-axonic synapses are commonly observed between spiral fibers in the core neuropil of day-7 to -19 larvae, but become fewer by day 40. Unique symmetrical axo-axonic synapses showing accumulation of synaptic vesicles on either side of apposed membrane thickenings first appear in day-14 core neuropil, gradually increase in number, and become the predominant type in day-40 core neuropil. Thick myelinated axons, which lose their myelin sheaths in the glial cap cell layer, start to penetrate into the axon cap on day 10. They gradually increase in number and form the peripheral part of the axon cap together with the cap dendrites, which finally grow into the axon cap from the axon hillock region of the Mauthner cell by day 40.

Age Factors↗