ISSN:0092-7317    

DOI:10.1002/cne.903610302

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractIn situ hybridization was used to document the distribution of mRNA encoding six subunit isoforms of non‐N‐methyl D‐aspartic acid (NMDA) glutamate receptors (GluR1, GluR2, GluR3, GluR4, GluR5 and GluR6) in the inner ears of embryonic, postnatal and adult rats. GluR2 and GluR3 expression in the spiral ganglion appeared well before birth, and reached adult levels several days before the onset of function in the cochlea. In the spiral limbus, expression of GluR2 and GluR3 mRNA reached very high levels at around the time of birth, then declined after a few days. Low levels of GluR1, GluR4 and GluR6 expression were detected in various tissues of the cochlea during development. In the adult cochlea, GluR expression was limited to GluR2 and GluR3 mRNAs in the spiral ganglion neurons and GluR2 mRNA in fibrocytes of the spiral limbus, a non‐neural tissue. The ontogenetic expression of additional GluR subunit genes and their appearance in different cochlear tissues could reflect different roles for these genes during development, or less precise regulation of gene expression within the GluR family. In particular, the very high levels of GluR gene expression in the spiral limbus during the perinatal period support a non‐neural function, perhaps as cell surface receptors during tissue differentiation. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903610303

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the rat, fibers from the prelimbic cortex terminate in the medial nucleus accumbens. Anterior paraventricular thalamic and parvicellular basal amygdaloid fibers reach both the prelimbic cortex and the medial nucleus accumbens. All three afferent systems have an inhomogeneous distribution within the nucleus accumbens, and whether or not these projections actually reach the same areas is unknown. Our aim was to evaluate the relationships of the three afferents with respect to the shell, the core, and the cell clusters of the nucleus accumbens. Double anterograde tracing and single anterograde tracing combined with immunohistochemistry for calbindin (D28k) or Nissl stain was used. Following tracer injections in the prelimbic cortex and the anterior paraventricular thalamus, a complementary (i. e., nonoverlapping) pattern of was found in the shell. Thus, afferents from the prelimbic cortex are associated with cell clusters, whereas those from the anterior paraventricular thalamus avoid these cells but are affiliated with regions exhibiting weak homogeneous calbindin immunoreactivity. In the calbindin‐poor patches of the core, the situation is reversed as both sets of fibers overlap. In cases with injections in the prelimbic cortex and the parvicellular basal amygdala, a pattern of overlap was seen in the shell and core. Thus, the fibers in the shell were found together in association with cell clusters, whereas regions of weak homogeneous calbindin immunoreactivity were avoided. In the core, overlap was seen in the patch compartment. Finally, with parvicellular basal amygdala/paraventricular thalamus injections, a complementary fiber organization was present in the shell, but overlap was prominent in the patches of the core.The results demonstrate that the relationships of prelimbic cortical, paraventricular thalamic, and parvicellular basal amygdaloid afferents in the nucleus accumbens vary according to their compartmental (immunohistochemical and cellular) affiliation. Compartmentalization is therefore a possible anatomical substrate for condensation or segregation of neuronal signals passing through the nucleus accumbens. © 1995 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903610304

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractInvestigations into the biological actions of nerve growth factor (NGF) have shown that dorsal root ganglion (DRG) neurons subserving nociception require NGF for survival and maintenance of phenotype. This discovery suggests that the signaling NGF receptor, TrkA, can be used as a marker for nociceptive neurons. In this study, we have used antibodies to TrkA, in conjunction with cell biological markers that show a restricted distribution in the DRG, to further characterize subsets of DRG neurons that are dependent upon NGF. Staining for TrkA labeled small and medium‐sized neurons that composed 47% of all neurons in thoracic ganglia. Double‐labeling with antibodies to the high molecular weight neurofilament protein (NFH), a marker for neurons with myelinated axons, demonstrated that TrkA staining is found in only a small subset of myelinated neurons. Surprisingly, many DRG neurons were not labeled by either TrkA or NFH. These neurons had small soma areas, contained the intermediate filament protein peripherin, and were labeled by the lectin BSI, identifying them as neurons likely to have unmyelinated axons. In addition, small TrkA–negative neurons were extensively labeled by antibodies to the intermediate filament protein γ‐internexin, the delta isoform of protein kinase C, and by the BSI isolectin BSI‐B4. In order to assess the potential functions of TrkA–negative small neurons, we examined their projections to the dorsal horn of the spinal cord. TrkA–immunoreactivity in the spinal cord was restricted to lamina I and the outer region of lamina II (II0), similar to staining for calcitonin gene‐related peptide. In contrast, the central projections of TrkA–negative neurons, as visualized by BSI‐B4staining, were particularly dense in lamina IIi. Our results suggest that TrkA‐expressing and non‐TrkA‐expressing small neurons compose functionally distinct populations of DRG neuro

ISSN:0092-7317    

DOI:10.1002/cne.903610305

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe distribution of synaptic terminals onto spinothalamic tract cells (types I and II) of the superficial dorsal horn was determined with special reference to the amino acid transmitters glutamate and γ‐aminobutyric acid. Fifteen spinothalamic cells retrogradely labeled from the thalamus with the neuroanatomical tracer wheatgerm agglutinin conjugated to horseradish peroxidase were sectioned for electron microscopy. Serial sections from several levels through each cell were immunostained for glutamate and γ‐aminobutyric acid using a postembedding immunogold technique. Perimeter measurements of spinothalamic cell somata and dendrites and the lengths of apposition for all terminal profiles in contact with the spinothalamic cells were obtained from electron micrographs using a digitizing tablet. These data were used to determine the density of terminals on the soma and dendrites. In addition, the terminal population on these cells was categorized by transmitter content (glutamate, γ‐aminobutyric acid, or unlabeled). The results demonstrate that terminal density increased on dendrites relative to their distance from the soma. Glutamatergic and GABAergic input composed 37% and 20% of the terminal population, respectively, and these percentages remained uniform for the soma and dendrites. There were no significant differences among the 15 cells analyzed for this study. The results, therefore, suggest that both type I and type II STT cells of the superficial DH have similar synaptic organizations. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903610306

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractWe have studied the morphogenetic reorganization that occurs in the grasshopper brain during embryogenesis. We find that morphogenetic movements occur at three organizational levels during brain development. First, the entire developing brain changes its orientation with respect to the segmental chain of ventral ganglia. A 90° shift in the attitude of the brain neuraxis occurs during embryogenesis due to a gradual upward movement of the cerebral structures in the head. Second, the clusters of proliferating neuroblasts and progeny that generate the neuroarchitecture of the mature brain move relative to one another and to nonneural structures such as the stomodeum. This is especially pronounced for the pars intercerebralis and for the tritocerebrum, as shown by annulin and engrailed immunoreactivity. Third, individual neuroblasts within a given proliferative cluster undergo positional reorganization during embryogenesis. Identified neuroblasts of the tritocerebrum and the pars intercerebralis are displaced within the brain. We conclude that the transformation of the simple sheet‐like structure of the early embryonic brain into the highly differentiated structure of the mature brain involves a series of morphogenetic movements that occur in virtually all parts of the brain. © 1995 Wiley‐Liss

ISSN:0092-7317    

DOI:10.1002/cne.903610307

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractNerve terminals and associated cells on the muscle's surface were visualized in the crayfish opener muscle with several fluorescent dyes in conjunction with confocal microscopy and conventional fluorescence microscopy. The nerve terminals of the excitatory and inhibitory axons were best seen with 4‐diethylaminostyryl‐N‐methylpyridinium iodide (4‐Di‐2‐Asp). This dye is selectively accumulated in mitochondria, which are numerous both in the axons and in synapse‐bearing terminal varicosities. Muscle nuclei were also clearly visualized, because they excluded 4‐Di‐2‐Asp but were stained by acridine orange (AO). A positive attraction between muscle nuclei and nerve terminals was evident by visual inspection and was confirmed by spatial statistics. Additional flat cells on the muscle's surface appeared as bright rings with elongated processes that were often close to or overlapped nearby nerve terminals. The structure of these cells was established by electron microscopy after labeling them with fluorescent polystyrene beads, which could be found over structures on the muscle surface in sections of embedded specimens. The flat surface cells were distinct from peripheral glial cells closely associated with axons and nerve terminals. Nevertheless, spatial statistics showed that the surface cells were grouped near nerve terminals. They occupied a small fraction of the muscle cell's surface. Their functional role has not been determined in crustacean muscles. ©

ISSN:0092-7317    

DOI:10.1002/cne.903610308

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractMature perivascular sympathetic axons associated with the intradural segment of the internal carotid artery (ICA) of the adult rat respond by sprouting following a two week infusion of nerve growth factor (NGF) into the lateral ventricle of the brain. Because nonsympathetic axons such as those comprising the sensory and parasympathetic population have been shown to respond to NGF, the present study was carried out to determine whether mature sensory axons respond toin vivoNGF infusion and whether competitive interactions between the innervating populations might affect the responsiveness of these axons to NGF. Standard electron microscopic techniques as well as calcitonin‐gene‐related peptide (CGRP) immunohistochemistry at the light microscopic level were used to examine the effects of intracerebroventricular NGF infusion on mature perivascular fibers with and without prior sympathetic denervation (i. e., bilateral superior cervical ganglionectomy). Following NGF infusion, CGRPimmunoreactive fibers appeared thicker and more numerous in the longitudinal plane when compared with vehicle controls. However, at the ultrastructural level, a significant increase in the total number of axons was not observed, although there was an increase in the number of large granular vesicles, suggesting that the CGRP fibers responded to exogenous NGF with an increase in neurotransmitter content, but not by sprouting. Sympathetic denervation, on the other hand, resulted in a significant increase in the number of fibers passing in the circumferential plane. The most dramatic change in CGRP immunoreactivity was observed following combined sympathetic denervation and subsequent NGF infusion, where, in addition to the presence of thicker immunoreactive fibers, a significant increase in the perivascular density of immunoreactive fibers associated with the intradural blood vessels was observed. These findings suggest that exogenous NGF has different effects on mature sympathetic and nonsympathetic fibers that innervate intradural blood vessels. The former exhibit robust sprouting, whereas the latter do not sprout in response to NGF but show evidence for increased neuropeptide content. In addition, the heightened response by sensory axons following denervation and subsequent NGF infusion provides support for the idea that sensory and sympathetic axons normally compete for target space and/or target‐derived neurotrophic factors. © 1995 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903610309

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractWe studied the morphology of bipolar cells in fixed vertical tissue sections of the rat retina by injecting the cells with Lucifer Yellow and neurobiotin. In addition to the rod bipolar cell, nine different putative cone bipolar cell types were distinguished according to the position of their somata in the inner nuclear layer and the branching pattern and stratification level of their axon terminals in the inner plexiform layer. Some of these bipolar cell populations were labeled immunocytochemically in vertical and horizontal sections using antibodies against the calcium‐binding protein recoverin, the glutamate transporter GLT‐1, the alpha isoform of the protein kinase C, and the Purkinje cell marker L7. These immunocytochemically labeled cell types were characterized in terms of cell density and distribution.We found that rod bipolar cells and GLT‐1‐positive cone bipolar cells occur at higher densities in a small region located in the upper central retina. This area probably corresponds to the central area, which is the region of highest ganglion cell density. A second peak of rod bipolar cell density in the lower temporal periphery matches the retinal area of binocular overlap. The population densities of the immunocytochemically characterized bipolar cells indicate that at least 50% of all bipolar cells are cone bipolar cells. The variety and total number of cone bipolar cells is surprising because the retina of the rat contains 99% rods. Our findings suggest that cone bipolar cells may play a more important role in the visual system of the rat than previously thought. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903610310

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractMany branched patterns in nature are hypothesized to be fractal, i. e., statistically self‐ similar across a range of scales. We tested this hypothesis on the two‐dimensional arbors of retinal neurons and blood vessels. First, we measured fractalness on synthetic fractal and nonfractal patterns. The synthetic fractal patterns exhibited self‐similarity over a decade of scale, but the nonfractal “controls” showed hardly any self‐similarity. Neuronal and vascular patterns showed no greater self‐similarity than the controls. Second, we manipulated a synthetic fractal pattern to remove its self‐similarity and found this to be reflected in a loss of measured fractalness. The same manipulation of the nonfractal control and also of the neural and vascular patterns did not alter their measured fractalness. Third, we “grew” patterns of branched line segments according to a variety of nonfractal algorithms. These patterns were, if anything slightly more fractal than the neural and vascular patterns. We conclude that the biological patterns studied here are not fractal. Finally, we measured extended versions of these patterns: a contiguous array of homotypic neuron arbors and a vascular pattern with a high degree of total detail. These patterns showed a “fractal dimension” of 2, which implies that down to some cut‐off scale they fill space completely. Thus, neural and vascular patterns might best be described as quasi‐regular latti

ISSN:0092-7317    

DOI:10.1002/cne.903610311

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY