摘要:

AbstractThe expression of the Fos and Jun families of nuclear phosphoproteins can be induced by a variety of extracellular stimuli and is known to participate in the transcriptional regulation of target genes. To examine the role of these transcription factors in retinal function, we used polyclonal antisera to localize these protein families in the turtle retina. Fos‐like immunoreactivity was in many somata in the inner nuclear and ganglion cell layers. In contrast, Jun‐like immunoreactivity was in a smaller number of amacrine cells and many somata in the ganglion cell layer. The monostratified dendritic arbors of one prominent amacrine cell type with Jun‐like immunoreactivity were also labeled. There were no dramatic differences in the levels of Fos‐like immunoreactivity or Jun‐like immunoreactivity between light‐ or dark‐adapted retinas.We examined the effects of excitatory amino acids and γ‐aminobutyric acid (GABA) on the expression of these proteins in vitro. In some experiments, cobalt was used to block synaptic transmission. The excitatory amino acids increased both Fos‐ and Jun‐like immunoreactivity, while GABA generally showed no such stimulatory effect. In cobalt‐treated retinas, the same cell types had Jun‐like immunoreactivity as seen in the controls, but overall levels of immunoreactivity were increased. In cobalt‐treated dark‐adapted retinas, some excitatory amino acids increased cytoplasmic Fos‐like immunoreactivity in the somata and processes of large cells in the ganglion cell layer. Our results suggest that Fos‐ and Jun‐related proteins may play an important role in the postsynaptic responses to amino acid transmitters in a wide variety of amacrine and gang

ISSN:0092-7317    

DOI:10.1002/cne.903540402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe early development of the uncrossed tectobulbar and the crossed tectospinal tracts was studied. These two projections arise from the same structure, the mesencephalon, and develop during the same time period, but follow divergent courses. We have traced the pathways followed by these projections and identified the positions at which axon guidance decisions are made. The first neurons differentiate either side of the entire rostrocaudal extent of the dorsal midline and initiate axons that extend dorsoventrally across the surface of the tectum. At the ventral edge of the tectum these axons turn abruptly and fasciculate to form a caudal descending projection to the hindbrain. These axons extend to the caudal hindbrain and do not project to the periphery along cranial nerve roots. We therefore consider this tract to be the teetobulbar, rather than the mesencephalic division of the trigeminal. While the tectobulbar projection is still developing, a second wave of axons is initiated, which arises from only the rostral part of the tectum. These axons grow beyond the tectobulbar turn point and continue toward the ventral midline, where they cross the floor plate, before turning caudally at the lateral edge of the main descending hindbrain tract, the ventrolateral tract. We discuss the development of these tracts with reference to possible guidance cues mediating their course. © 1995 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903540403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe connections of the lateral terminal nucleus (LTN) of the accessory optic system (AOS) of the marmoset monkey were studied with anterograde3H‐amino acid light autoradiography and horseradish peroxidase retrograde labeling techniques. Results show a first and largest LTN projection to the pretectal and AOS nuclei including the ipsilateral nucleus of the optic tract, dorsal terminal nucleus, and interstitial nucleus of the superior fasciculus (posterior fibers); smaller contralateral projections are to the olivary pretectal nucleus, dorsal terminal nucleus, and LTN. A second, mejor bundle produces moderate‐to‐heavy labeling in all ipsilateral, accessory oculornotor nuclei (nucleus of posterior commissure, interstitial nucleus of Cajal, nucleus of Darkschewitsch) and nucleus of Bechterew; some of the fibers are distributed above the caudal oculomotor complex within the supraoculornotor periaqueductal gray. A third projection is ipsilateral to the pontine and mesencephalic reticular formations, nucleus reticularis tegmenti pontis and basilar pontine complex (dorsolateral nucleus only), dorsal parts of the medial terminal accessory optic nucleus, ventral tegmental area of Tsai, and rostral interstitial nucleus of the medial longitudinal fasciculus. Lastly, there are two long descending bundles: (1) one travels within the medial longitudinal fasciculus to terminate in the dorsal cap (ipsilateral>>contralateral) and medial accessory olive (ipsilateral only) of the inferior olivary complex. (2) The second soon splits, sending axons within the ipsilateral and contralateral brachium conjunctivum and is distributed to the superior and medial vestibular nuclei.The present findings are in general agreement with the documented connections of LTN with brainstem oculomotor centers in other species. In addition, there are unique connections in marmoset monkey that may have developed to serve the more complex oculomotor behavior of nonhuman primates. © 1995 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903540404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractCell surface molecules with restricted spatial and temporal distributions are good candidates for mediators of the cell‐cell interactions that are necessary for the development of the nervous system. A monoclonal antibody (MAb 23A7) was produced that selectively and transiently labeled a limited subset of axons in the chick embryo spinal cord. Determination of the N‐terminal amino acid sequence and immunoprecipitation experiments demonstrated that the 23A7 antigen is identical to Bravo/Nr‐CAM, a previously described cell adhesion molecule with immunoglobulin‐like domains (E. J. de la Rosa, J. F. Kayyem, J. M. Roman, Y.‐D. Stierhof, W. J. Dreyer, and U. Schwartz [1989] J. Cell Biol. 111:3087–3096; M. Grumet, V. Mauro, M. P. Goon, G. M. Edelman, and B. A. Cunningham [1991]J. Cell Biol. 113:1399–1412).The temporal distribution of the 23A7 antigen is unusual in that, immunohistochemically, MAb 23A7 binding greatly decreases after 7 days of development, whereas Western blot analysis indicates increasing levels of the antigen until 17 days of development. In contrast, an antiserum against purified Nr‐CAM, which also binds only to the 23A7 antigen, labels nearly all the axons in the tissue throughout all the later stages of development. These anomalous observations are apparently not the result of differential sensitivity of the 23A7 epitope to fixation, the use of suboptimal concentrations of the MAb, or selective MAb binding to a subset of Bravo/Nr‐CAM molecules produced by alternative splicing of the transcript or by posttranslational modification. These findings could indicate the existence of multiple states of Bravo/Nr‐CAM, which during development, vary in the accessibility of their extracellular domains to the MAb. This suggests the existence of multiple conformation or aggregation states of this cell adhesion molecule, each of which might be performing a different function. ©

ISSN:0092-7317    

DOI:10.1002/cne.903540405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAnterograde and retrograde tracing with biotinylated dextran amine andPhaseolus vulgarisleukoagglutinin was used to assess projection patterns within the vibrissae representation of the rat's primary somatosensorycortex (S‐I). Large and small injections of either tracer into the center of the vibrissae representation yielded dense anterograde and retrograde labelling throughout much of the tangential extent of the vibrissae representation within S‐I. In all layers, the pattern and extent of retrograde and anterograde label was in rough congruence. The organization of this labelling varied across cortical layers. In layers II and III, labelled fibers extended away from injection sites in all directions and yielded a uniform pattern, which decreased in density with increasing distance from the tracer injection. There was a tendency for labelling to be more extensive along the representation of the row of vibrissae follicles that included the injection site than across rows. There was also a tendency for anterograde labelling to be more extensive in the direction of the representation of follicles more rostral on the face than that injected. In lamina IV, both labelled fibers and cells were restricted for the most part to the septa regions between the barrels. However, a small number of retrogradely labelled neurons were also located in the barrels (approximately one‐ninth of the number found in the septa). The pattern observed in laminae II–III was repeated in layers V and VI. In these laminae, there was no evidence of a pattern of intracortical connections related to the vibrissae representation in overlying lamina IV. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903540406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe predominantly neuronal, calcium‐binding protein calretinin is highly expressed in the guinea pig auditory system. Within the ventral cochlear nucleus (VCN), calretinin‐positive auditory nerve fibers terminate on many calretinin‐containing bushy, octopus, and multipolar cells. The abundance of calretinin in the cochlear nucleus provides an ideal system for examining the effects of altered neuronal input on the expression of this calcium‐binding protein.The present experiments examined the effects of unilateral cochlea ablation on calretinin immunoreactivity and mRNA levels in the VCN. Calretinin mRNA was labeled by in situ hybridization histochemistry using a radioactive oligonucleotide probe and was quantified by optical density measures on autoradiograms. Survival times of 1, 7, and 56 days postlesion were examined.The results revealed a consistent increase in calretinin mRNA in the rostral portion of the ipsilateral anterior VCN 1 day postlesion but no effect on calretinin mRNA in this region at 7 and 56 days postlesion. The intensity of immunohistochemical label was also increased at 1 and 7 days after surgery. In contrast, calretinin mRNA was not affected 1 day postlesion in the ipsilateral posterior VCN but was decreased at both 7 and 56 days postlesion. The decrease in calretinin mRNA in the posterior VCN at longer survival times was accompanied by decreased immunolabeling of fibers projecting from VCN cells to the superior olivary complex. These results suggest that calretinin gene expression is regulated in part by auditory nerve activity in some cochlear neurons but that additional factors related to the unique cellular milieu also control calretinin expression. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903540407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPrior morphological studies of individual retinal X and Y axon arbors based on intraaxonal labeling with horseradish peroxidase have been limited by restricted diffusion or transport of the label. We used biocytin instead as the intraaxonal label, and this completely delineated each of our six X and 14 Y axons, including both thalamic and midbrain arbors. Arbors in the lateral geniculate nucleus appeared generally as has been well documented previously. Interestingly, all of the labeled axons projected a branch beyond thalamus to the midbrain. Each X axon formed a terminal arbor in the pretectum, but none continued to the superior colliculus. In contrast, 11 of 14 Y axons innervated both the pretectum and the superior colliculus, one innervated only the pretectum, and two innervated only the superior colliculus. Two of the Y axons were quite unusual in that their receptive fields were located well into the hemifield ipsilateral with respect to the hemisphere into which they were injected. These axons exhibited remarkable arbors in the lateral geniculate nucleus, diffusely innervating the C‐laminae and medial interlaminar nucleus, but, unlike all other X and Y arbors, they did not innervate the A‐laminae at all. In addition to these qualitative observations, we analyzed a number of quantitative features of these axons in terms of numbers and distributions of terminal boutons. We found that Y arbors contained more boutons than did X arbors in both thalamus and midbrain. Also, for axons with receptive fields in the contralateral hemifield (all X and all but two Y axons), 90–95% of their boutons terminated in the lateral geniculate nucleus; the other two Y axons had more of their arbors located in midbrain. © 1995 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903540408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe performed experiments using retrograde and anterograde labeling with DiI to examine the development of basal forebrain (BFB) projections to the visual cortex in postnatal rats. DiI placed in occipital cortex led to retrograde labeling of BFB neurons as early as postnatal day 0 (P0); labeled cells were found mainly in the diagonal band complex but also in the medial septum, globus pallidus, and substantia innominata. The retrogradely labeled BFB cells displayed remarkably well‐developed dendritic arbors, even in younger animals, and showed increases in soma size, dendritic arbors, and dendritic spines over the first 2 postnatal weeks.Dil placements in the diagonal band led to anterogradely labeled axons in cortex. At early ages (P0–P1), labeled axons were largely confined to white matter. With increasing age, greater numbers of labeled axons were seen in the white matter and in deep cortical layers, and labeled axons extended into superficial layers. The leading edge of labeled fibers reached layer V of visual cortex by P2 and layer IV by P4 and were found throughout the cortical layers by P6. Numbers and densities of labeled axons in visual cortex were greater in older animals, at least through P14.The time of ingrowth of labeled BFB axons into visual cortex indicates that these afferents grow into particular cortical layers after those layers have differentiated from the cortical plate. These data indicate that basal forebrain projections arrive in occipital cortex after cortical lamination is well underway and after the entry of primary thalamocortical projections. © 1995 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903540409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903540401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY