摘要:

AbstractEmbryonic retinae were transplanted onto the midbrain of neonatal congenitally anophthalmic mice and neonatal mice from which both eyes had been removed. When donor mice of the AKR strain were used, the detailed patterns of the transplant projections to the host brain were demonstrated with an antibody to Thy‐1.1, which specifically stains neural tissue derived from AKR donors. Many of the subcortical visual centers were innervated, and only small differences were encountered between anophthalmic and eye‐enucleated mice. The terminal arbors of transplant‐derived axons could not be classified as in normal animals, although several distinct arbor types were seen. In the superior colliculus, the laminar arrangements that characterize normal retinal arbors were disrupted. Despite this, the synaptic patterns formed by transplant derived axons in the superior colliculus of anophthalmic mice compared very closely with those of retinal axons in normal, sighted animals. These observations indicate that the ability of a retinal transplant to innervate the host brain and to form the synaptic arrays characteristic of optic terminals are not dependent on prior innervation, nor do they appear to be influenced by the events that follow eye removal. (e) 1993 Wiley‐Li

ISSN:0092-7317    

DOI:10.1002/cne.903270302

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractCell surface adhesion molecules N‐CAM and L 1 are implicated in central nervous system (CNS) cell migration and axon outgrowth in in vitro and in vivo developmental studies. These molecules show a differential distribution during CNS development, thus suggesting that they subserve different roles in process outgrowth and tissue organization. A variety of N‐CAM isoforms are known, and individual N‐CAMs undergo posttranslational modification. Such changes and the potential for generating numerous molecules may mediate development of specific neural cell contacts and circuitry. We evaluated immunohistochemical staining of polyclonal antibodies to L 1 and N‐CAM, as well as monoclonal antibodies directed against embryonic N‐CAM and the 140 and 180 kDa species of N‐CAM in human, rat, and mouse hippocampus. Staining patterns in the three species were qualitatively similar, but staining in the mouse hippocampus was quantitatively greater for some epitopes. A distinctive pattern of staining was found, corresponding to the known anatomy of the structure. Total N‐CAM staining was intense in the hilus and inner molecular layer (ML) of the dentate gyrus with lighter staining in the dentate outer ML. The mossy fiber tract (MFT), comprising axons traveling from the dentate granule cells to CA3 pyramidal cells, was strongly stained by polyclonal antibody to N‐CAM. There was abundant staining of the stratum radiatum (SR) and stratum oriens (SO) of CA1, but stratum lacunosum moleculare (LM) showed very little staining. The monoclonal antibody 12F11, which recognizes the 140 and 180 kDa forms of N‐CAM, intensely stained the MFT, hilus, and inner ML. With 12F11, SO and SR stained uniformly throughout CA1, with much reduced staining in CA2 and CA3. There was little staining in LM. L1 staining was more evenly distributed throughout the hippocampus and dentate, with light hilar and MFT staining, and even staining through the SR and SO. Stratum LM stained intensely for L1, with a narrow clear zone between SR and LM. The ML of the dentate gyrus stained intensely with anti‐L1, with a discrete clear zone separating the inner and outer ML. Embryonic N‐CAM had little staining in CA1 but strong hilar and MFT staining; thus, this “embryonic” determinant continues to be expressed in limited regions in the adult. In contrast to the adult rodent hippocampus, human hippocampus exhibited embryonic N‐CAM in the outer two‐thirds of the ML, but showed very little staining in the hilar region. These distinctive patterns suggest that the distribution of the N‐CAM and L1 molecular species have clear‐cut structural and functional roles in the laminated circuitry of the hipp

ISSN:0092-7317    

DOI:10.1002/cne.903270303

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe gene expression for α and γ subunits of enolase, a dimeric enzyme in the glycolytic pathway, was examined in the developing brain of rats by in situ hybridization. The expression for the γ subunit of enolase was first detected in post‐mitotic neurons settled in the mantle zone at E13, and it increased progressively until the adult stage. Expression signals for the α subunit were discerned in two discrete regions showing different developmental changes: the signals in the proliferative ventricular zone were intense at E13 and decreased and eventually disappeared around birth, whereas the signals in the mantle zone persisted until the adult stage. In the adult brain, mRNAs for the α and γ subunits were expressed widely in neurons, resulting in almost similar temporal patterns in the brain except for the cerebellum. Expression levels of the α subunit in adult glial cells were below the detection threshold of the in situ hybridization analysis. These findings suggest that both α and γ enolase subunits participate in energy production in neurons of the mature brain and that marked changes in the subunit composition of enolase occur according to both neuron type and maturation. (c) 1993 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903270304

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe distribution of the p75 nerve growth factor receptor (NGFr) was determined within the developing human basal ganglia in specimens between weeks 16 through 40 of gestation, 5 years of age, and adulthood. Although NGFr‐immunoreactive neurons were rarely seen in the caudate nucleus, a few such neurons were seen in the putamen between prenatal weeks 16 and 26 of development. At 26 and 40 weeks of gestation, the putamen also displayed NGFr‐immunoreactive fibers of putative basal forebrain origin. Some of these fibers coursed through the putamen en route to the cortex while others appeared to remain within the putamen. The external segment of the globus pallidus contained dense collections of NGFr‐immunoreactive neurons between 16 and 26 weeks of gestation, whereas the internal segment was devoid of immunoreactive perikarya. A few NGFr‐immunoreactive neurons were observed within the globus pallidus at embryonic week 40. The expression of NGFr‐immunoreactive neurons within the external segment of the globus pallidus was paralleled by a dense granular NGFr‐immunoreactive terminal‐like staining pattern within the subthalamic nucleus. This staining pattern was most intense at midgestation (weeks 21–26) and was not observed at 40 weeks of gestation or in adulthood. Interestingly, a similar NGFr‐immunoreactive terminal‐like pattern was also observed within the monkey subthalamic nucleus at embryonic day 120. These data indicate that NGF receptor mediated mechanisms may underlie developmental processes within the primate basal ganglia. The absence of NGFr‐immunoreactive neurons within the caudate nucleus, and the paucity of such neurons in the putamen, suggests that NGF receptors play a limited role in primate neostriatal development. Alternatively, developmental events mediated through NGF receptors may occur prior to embryonic week 16. Furthermore, an NGFr/trophic interaction appears to underlie the development of the pallidal‐subthalamic nucleus pathwa

ISSN:0092-7317    

DOI:10.1002/cne.903270305

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractVibrissal representations in the brainstem trigeminal complex (BTC) of rodents are manifested as architectural sub‐units called barrelettes. The development of barrelettes was studied by using Nissl staining, cytochrome oxidase histochemistry, and Golgi‐impregnation methods. On the day of birth (PND‐1), barrelettes are manifested as longitudinal, histochemical cylinders in sub‐nuclei principalis, interpolaris and caudalis of the BTC. One day later (PND‐2), fully formed histochemical barrelette formations are seen in the three sub‐nuclei. The development of cytoarchitectural barrelettes lags behind histochemical barrelettes by about two days. Between PND‐2 and PND‐3, longitudinal cytoarchitectonic cylinders begin to appear. By PND‐3, BTC neurons segregate into five rows of barrelettes in the coronal plane. Segmentation of rows into individual barrelettes begins on PND‐4, and complete cytoarchitectonic barrelette formations are seen by PND‐5. Golgi‐impregnation shows that on the day of birth, primary afferent terminals and dendritic arbors of second‐order trigeminal neurons within the BTC are short and poorly ramified. Over the next five post‐natal days, lengthening of these processes as well as elaboration into secondary and tertiary branches take place. Growth of these processes continues for two additional weeks, contributing to the increase in barrelette neuropils (hollows). As the neuropils expand, neuronal somata are pushed toward barrelette sides. Morphometric measurements show that there is a relatively constant rate of growth of barrelettes over the first three post‐natal weeks. The growth rate of the barrelette formations is identical to that of BTC as a whole. Thus, at the time of birth, the volume of neural tissue in the brainstem allotted to vibrissae is fixed relative to that allotted to other sensory receptors.Several features of the early development of barrelettes are identified: (1) Chemoarchitectural barrelettes appear before cytoarchitectural barrelettes, suggesting that terminal arbors of primary trigeminal afferents are organized before their target neurons form barrelettes. (2) Early cytoarchitecture is manifested in the form of unsegmented rows, suggesting that rough, row‐based topological maps are first formed, which are then fine‐tuned into individual sub‐units. Recent evidence shows that other vibrissal representations—thalamic barreloids and cortical barrels—also follow these “afferent‐before‐target” and “row‐before‐individual units” sequences of development. This gradual, afferent‐dependent fine‐tuning of topological organization is analogous to similar events during the early development of the visual system, and may be a general feature of developing sensory systems. In the visual system, sensory input plays an important role in fine‐tuning centers in the brain; the mechanisms by which barrelettes are org

ISSN:0092-7317    

DOI:10.1002/cne.903270306

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractAnatomical and immunohistochemical data indicate that, in addition to pyramidal neurons, nonpyramidal cells are exposed to perisomatic inhibition mediated by γ‐aminobutyric acid (GABA)‐containing terminals. However, no direct information is available as yet for the origin of GABAergic inputs to morphologically identified GABAergic neurons. In the present paper, we studied the topographical and synaptic relationship between identified GABAergic large basket cells and their immunohistochemically characterized target neurons revealed by parvalbumin‐(PV) and GABA immunostaining in the same material.Extracellularly applied biocytin labelled a total of 36 and 9 large basket cells in layers III and V, respectively. Of these, the axonal arborizations of two basket cells, BC1 and BC2, were reconstructed. The axon of BC1 occupied an area of about 2.3 × 2.2 mm2in layer III, providing a total of 2,755 terminals. The axon of BC2 showed an overall extent of 3.8 × 1.7 mm2in layer V elongated in the anteroposterior direction, and gave off 1,599 terminals. Immunostaining for PV was carried out to reveal putative nonpyramidal targets for BC1 and BC2. It was found that in addition to immunonegative cells, they established an average of 4–6 perisomatic contacts onto each of 58 (BC1) and 33 (BC2) PV‐immunopositive neurons. For electron microscopic verification, 23 terminals apposing the somata of 12 PV‐immunopositive neurons were selected. Each terminal was found to establish symmetrical (type II) contacts with its targeted cell. Furthermore, the distribution of soma area of the targeted PV‐immunopositive cells and of identified large basket cells showed remarkable similarity, implying that the two populations were actually the same. In addition, the average horizontal distance between neighbouring PV‐immunopositive target cells was found to be about 100 μm both in layers III and V.The results suggest that in area 18 the same large basket cell provides direct inhibition to certain pyramidal cells and facilitation to other pyramidal neurons, by inhibiting their presynaptic large basket cells at regular intervals. 1

ISSN:0092-7317    

DOI:10.1002/cne.903270307

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe chemical nature of the cells of the nucleus of the solitary tract (NTS) that project to the parabrachial nucleus (PB) was investigated in the pigeon by the use of fluorescent bead retrograde tracer and immunofluorescence for the detection of substance P (SP), leucineenkephalin (LENK), cholecystokinin (CCK), neurotensin (NT), somatostatin (SS), and tyrosine hydroxylase (TH). Cells immunoreactive for CCK were located in subnuclei lateralis dorsalis pars anterior (LDa) and medialis superficialis pars posterior, and caudal NTS (cNTS); 22–26.5% of these cells were double‐labeled bilaterally. Immunoreactive SP cells were found in ventral NTS subnuclei; 24–25% of these cells were double‐labeled bilaterally. Cells immunoreactive for LENK and NT were concentrated in the anterior NTS; 5.5–7.5% of the LENK cells were double‐labeled bilaterally, while 11% (ipsilateral) and 21% (contralateral) of the NT immunoreactive cells were double‐labeled. Many SS immunoreactive cells were found in peripherally located subnuclei; 5.5–6.5% of these cells were double‐labeled bilaterally. Catecholamine cells were distributed in LDa, peripheral subnuclei, and cNTS; 23% of these cells were double‐labeled ipsilaterally and 8.5% contralaterally. A two‐color double‐labeling immunofluorescence technique revealed many cells immunoreactive for both NT and LENK, only a rare cell immunoreactive for both SS and SP, and no cells immunoreactive for both TH and SP.Cells immunoreactive for SP, CCK, NT, and TH are major contributors to NTS projections to PB. The confinement of these substances to specific NTS subnuclei, which receive visceral sensory information from specific organs, may contribute to the chemical encoding of ascending visceral informatio

ISSN:0092-7317    

DOI:10.1002/cne.903270308

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractWound closure and repair of embryonic neuroepithelium were studied in organ‐cultured embryonic retinae. Eyes from 3 to 4‐day‐old embryos were cultured after removing pieces of retinal tissue. During the subsequent 24 hours of incubation, the 150 to 200 μm wide holes in the retina closed completely. Histological studies showed that the wound closure was not accomplished by cell migration or cell proliferation, but by an approximation of the wound edges mediated by extracellular matrix fibrils of the vitreous body. The wound contraction facilitated the integration of transplants into the retinal neuroepithelium with a perfect alignment of the implants with the host at the vitreal surface. Within 24 hours, a continuous inner limiting membrane between transplant and host retina was established. The effect of wound healing and tissue transplantation on the navigation of optic axons in the retina was investigated. The wound contraction in the retina caused the optic axons near the lesion site to grow to the wound center, where the axons traversed the retina and formed a neuroma at the ventricular side, resembling the organization of axons at the optic disc. In the transplantation paradigm, axons from the host retina migrated into the transplant and vice versa. However, due to the wound contraction around the transplant, most axons grew into the interface between the transplant and host tissue. 1993 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903270309

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper describes the ultrastructure of a sensory neuron found in the extraocular photoreceptive site on the butterfly genitalia. Our previous studies have shown that there are two pairs of the photoreceptive sites in a butterfly (four per individual). Each photoreceptive site is recognizable by a transparent area in the pigmented cuticle of the genitalia. From the nerve that extends from the transparent cuticle to the last abdominal ganglion, a sustained train of single unit spikes can be recorded in response to a light flash. The single unit spikes disappear when the transparent cuticle is covered, thus indicating that a single photoreceptor exists close to it.Here, we examined complete serial semithin sections of plastic‐embedded photoreceptive sites of both male and female, and observed an ovoid structure close to the transparent cuticle. The structure contained the cell body of a sensory neuron whose axon was in the nerve branch from which the photoresponse had been recorded. Further electron microscopy revealed that the cell body extended a few distal processes that protrude tubular membrane from the tip, forming a structure resembling the phaosome (from Greek;phaos= light,some= body) which was first described in the earthworm dermal photoreceptors. The sensory neuron was also found in a surgically isolated nerve‐photoreceptor preparation that responded to the light. We therefore propose that the phaosome‐containing sensory neuron is the butterfly genital photoreceptor. 1993 Wiley‐Li

ISSN:0092-7317    

DOI:10.1002/cne.903270310

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903270301

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY