摘要:

AbstractConnections between the primary motor cortex (MI) and the corpus striatum were studied in the owl monkey. Representations of specific body movements were elicited in MI by microstimulation techniques, and the efferent projections from these stimulation sites were labeled with wheat germ agglutinin‐horseradish peroxidase conjugate (WGA‐HRP).Dense projections were found in the putamen ipsilateral to the injection site and sparser projections occupied comparable areas in the contralateral putamen. Representations of hindpaw regions projected to the dorsomedial portion of the putamen with only slight extensions across cell bridges into the caudate nucleus. Representations of the forepaw and head projected to progressively more ventrolateral zones of the dorsal two‐thirds of the putamen. Projections from injections of cortex representing discrete body movements terminated in an irregular or patchy distribution over a relatively large portion of the putamen. Extensive projections from relatively discrete injections in MI are indicative of a large degree of divergence and provide evidence for possible overlap from representations of relatively disparate body parts. The results are consistent with observations reported in other species of primates, but different from those seen in carnivores. This difference is discussed with regard to possible general features of corticostriate organiz

ISSN:0092-7317    

DOI:10.1002/cne.903070202

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

年代:1991

数据来源: WILEY

摘要:

AbstractWe have examined the formation of myenteric ganglia in the developing avian enteric nervous system. The monoclonal antibody HNK‐1 was used to identify neural‐crest‐derived cells in whole mounts of fore‐ and midgut of chick embryos. We find that the crest‐derived cells extend processes to their neighbors and form a complex network in the wall of the gut. Formation of this network is an unusual behavior of crest‐derived cells and suggests the gut microenvironment is critical to this behavior. This cellular network disappears after ablation of the vagal neural crest, indicating the HNK‐1‐stained cellular network arises from crest‐derived cells. The network is found in the gut wall before the vagal nerve fibers are present. This network is first found in the primordium of the proventriculus, distal to the evagination of the lung buds, and progresses just proximal to the yolk stalk at embryonic day (E)3.5 and almost to the ileocecal junction at E5.5. The number of cells and the complexity of the network decrease in a rostral‐caudal direction down the length of the gut at these stages. The leading edge of the network consists of cells serially arranged in longitudinally running strands. The organization of the network changes with increasing embryonic age; we have focused on network changes in the proventriculus. In the primordium of the proventriculus at E3.5, the network consists of a cluster of one or two adjacent crest‐derived cells, which extend processes to a number of neighboring crest‐derived cells. At E5.5 large increases in the number of cells per cluster and in the length of cellular connectives between clusters are apparent. At E6.5 a crude meshwork of clusters is seen. At E10.5 the arrangement of cell clusters resembles the pattern of ganglia found in the adult myenteric plexus. This network may provide the environmental cues for the differentiation of enteric neurons and a framework for the pattern of ganglia found in the adult

ISSN:0092-7317    

DOI:10.1002/cne.903070203

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

年代:1991

数据来源: WILEY

摘要:

AbstractImmunocytochemical techniques were used to study the effects of tactual deprivation on glutamic acid decarboxylase (GAD) containing neurons in rat somatosensory barrel cortex. In normal rats GAD immunoreactive neurons and puncta are present in all laminae, with dense patches of GAD immunoreactive puncta centered on the barrels in lamina IV. Trimming whiskers of adult rats leads to a reversible decrease of GAD immunoreactivity in barrels corresponding to trimmed hairs. Intensity of GAD staining also is reversibly altered in supragranular laminae ofnondeprivedbarrel columns flanked by deprived barrels. This indicates that GAD levels in the barrel cortex ordinarily fluctuate with changes in sensory input. By contrast, animals whose whiskers are trimmed from birth have normal GAD staining in both deprived and nondeprived barrels. Moreover, if trimmed whiskers of neonatally deprived animals are allowed to grow to normal lengths and are retrimmed later in adulthood GAD staining is not affected. Thus early tactual deprivation disrupts mechanisms that permit modulation of transmitter enzyme levels in cortical neurons following changes in sensory experience.

ISSN:0092-7317    

DOI:10.1002/cne.903070204

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe distribution of dopamine and dopamine‐immunoreactive neurones was studied in the central nervous system of the snailLymnaea stagnalis.The results from immunocytochemical labelling were compared with those from the application of the glyoxylic acid fluorescence method and 6‐hydroxydopamine‐induced pigment labelling. Comparisons were also made between the number of dopamine immunoreactive neurones and the dopamine content of the ganglia, measured by high‐performance liquid chromatography.Dopamine immunocytochemistry proved to be superior to the other two histochemical techniques in terms of specificity and sensitivity. The 6‐hydroxydopamine‐induced pigment labelling failed to prove a useful tool for the in vivo identification of all dopamine‐containing neurones. The distribution and number of dopamine‐immunoreactive neurones and levels of biochemically measured dopamine in specific ganglia showed a close correspondence. By using the results of the dopamine immunocytochemistry and glyoxylic acid technique, a detailed map of dopamine‐containing neurones was constructed. Dopamine‐containing inter‐ and intra‐ganglionic axon tracts were also demonstrated. The mapping of dopamine‐containing neurones will facilitate further neurophysiological analysis of dopaminergic ne

ISSN:0092-7317    

DOI:10.1002/cne.903070205

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

年代:1991

数据来源: WILEY

摘要:

AbstractBending of the neural plate has long been considered to be driven by principallyintrinsicforces generated by wedging of neurepithelial cells. Our previous studies have shown that during neural fold elevation, significant neurepithelial cell wedging occurs only within the median hinge point (MHP), the midline region of neural plate anchored to the notochord. We have also shown that neural fold elevation can still occur when MHP cells are prevented from becoming wedge‐shaped but fails to occur when the neural plate is separated from lateral nonneurepithelial tissues, even though MHP cells still become wedge‐shaped and the midline neural plate still furrows. Together, these results suggest that neural fold elevation, rather than being driven by neurepithelial cell wedging, is driven, at least in part, by extrinsic forces generated by lateral nonneurepithelial tissues. However, it could be argued that in the absence of localized neurepithelial cell wedging, compensatory and atypical cell wedging occurred uniformly throughout the neural plate, providing forces adequate for neural fold elevation. Likewise, it could be argued that in the process of separating the neural plate from lateral nonneurepithelial tissues, the neural plate was damaged to the extent that the neural folds were unable to elevate. To investigate the validity of these arguments, we removed the following tissues microsurgically prior to neural fold elevation: MHP cells, varying amounts of lateralneurepithelialcells (L cells), and the tissues directly underlying these two populations of neurepithelial cells. We found that the neural folds still formed and underwent elevation, convergence, and fusion, resulting in an essentially normal neural tube, even though MHP cells, the underlying notochord, and some L cells were absent for long craniocaudal distances. These results demonstrate that microsurgery alone does not damage the neural plate sufficiently to prevent neural fold elevation, convergence, and fusion. Moreover, the fact that each of the two persisting remnants of lateral neurepithelium generally remained straight and consistently changed their orientation from horizontal to vertical rather than curling suggests very strongly that bending of the neural plate in these embryos is not the result of compensatory and atypical cell wedging. Finally, the results provide further direct evidence ofextrinsicforces in bending because the two remnants of lateral neurepithelium, which were oriented horizontally at the time of tissue extirpation, could not have become oriented vertically in the absence of such for

ISSN:0092-7317    

DOI:10.1002/cne.903070206

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

年代:1991

数据来源: WILEY

摘要:

AbstractModern neuronanatomical techniques were used to investigate the development of the avian sympathetic preganglionic cell column in the spinal cord of the chick embryo. [3H]thymidine autoradiography indicated that the majority of these preganglionic, or “Terni column” neurons are generated between stages 18 and 24 (days 2–4). This coincides with the genesis of the somatic motoneurons in the thoracic levels of the cord, and therefore differences in the time of origin cannot explain the divergent fates of these two neuronal populations. Data obtained from short‐survival autoradiographic experiments indicated that many early born cells remain close to the ventral region of the ventricular epithelium until day 5 of incubation. Ventral root injections used to label retrogradely neurons projecting an axon into the ventral root (Terni cells and somatic motoneurons) have labeled neurons next to the ventricular epithelium at the same early stages. Thus, it seems likely that some Terni cells, if not all, maintain medial positions and do not migrate laterally to join a common motor column before initiating a dorsal migration. Analysis of a closely staged series of embryos, whose Terni column neurons were retrogradely labeled with wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP), revealed that between days 5 and 8 of incubation, Terni column neurons migrated dorsally to attain their adult position adjacent to the central canal. These changes in position were reflected in the changing morphology of the Terni column neurons, visualized by the Golgi‐like HRP labeling. The positions of the migrating Terni cells differed from those of commissural cells, indicating that these fibers are not the substrate for the dorsal migration. The dorsal migration of Terni column cells was not disrupted by the surgical removal of the sympathetic ganglia, the synaptic targets of these neurons, nor by disruption of spinal afferents. Taken together, these results suggest that the migratory behavior of Terni cells is distinctive when compared to that of somatic motoneurons, and that local and/or intrinsic cues within the spinal cord guide the dorsal migration of Terni

ISSN:0092-7317    

DOI:10.1002/cne.903070207

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe purpose of the present study was to compare the frequency of different classes of axon terminals on selected regions of the somatodendritic surface of dorsal neck motoneurons. Single motoneurons supplying neck extensor muscles were antidromically identified and intracellularly stained with horseradish peroxidase. By using light microscopic reconstructions as a guide, axon terminals on the somata, proximal dendrites (within 250 μm of the soma), and distal dendrites (more than 540 μm from the soma) were examined at the electron microscopic level.Axon terminals were divided into several classes based on the shape, density, and distribution of their synaptic vesicles. The proportion of axon terminals belonging to each axon terminal class was similar on the somata and proximal dendrites. However, there were major shifts in the relative frequency of most classes of axon terminals on the distal dendrites. The most common classes of axon terminals on the somata and proximal dendrites contained clumps of either spherical or pleomorphic vesicles. These types of axon terminals accounted for more than 60% of the axon terminals on these regions. In contrast, only 11% of the axon terminals found on distal dendrites belonged to these types of axon terminals. The most commonly encountered axon terminal on distal dendrites contained a dense collection of uniformly distributed spherical vesicles. These types of axon terminals accounted for 40% of all terminals on the distal dendrites, but only 5–7% of the axon terminals on the somata and proximal dendrites. Total synaptic density on each of the three regions examined was similar. However, the percentage of membrane in contract with axon terminals was approximately four times smaller on distal dendrites than somata or proximal dendrites. Axon terminals (regardless of type) were usually larger on somata and proximal dendrites than distal dendrites.These results indicate that there are major differences in the types and arrangement of axon terminals on the proximal and distal regions of dorsal neck motoneurons and suggest that afferents from different sources may preferentially contact proximal or distal regions of the dendritic trees of these ce

ISSN:0092-7317    

DOI:10.1002/cne.903070208

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

年代:1991

数据来源: WILEY

摘要:

AbstractPossible estrogen influences on oxytocin mRNA expression were studied in preoptic and anterior hypothalamic regions as might be important for behavioral as well as neuroendocrine controls. In situ hybridization for oxytocin mRNA determination was supported by immunocytochemical identification and was compared with vasopressin mRNA in situ hybridization. With these techniques, oxytocin‐expressing neurons were identified in medial preoptic, anterior commissural, periventricular, paraventricular, supraoptic, and perifornical nuclei as well as the bed nucleus of the stria terminalis and intersupraopticoparaventricular (internuclear) islands. Distribution and number of oxytocin mRNA‐containing neurons and oxytocin mRNA levels were compared between ovariectomized control rats given cholesterol implants and ovariectomized rats given short‐term (2 days) or long‐term (2 months) estradiol treatment (10% estradiol, subcutaneous silastic implants). Effectiveness of long‐term estrogen treatment was confirmed behaviorally. While there was a trend in several cell groups for a larger number of oxytocin‐mRNA‐containing neurons to be observed following 2 days of estrogen treatment, this was not statistically significant. Moreover, additional oxytocin‐mRNA containing cell groups were not seen after short or long estradiol treatment. With computer‐aided analysis, mean pixels per oxytocin‐mRNA expressing neuron (reflecting oxytocin mRNA content) were compared between groups: In the supraoptic nucleus and the anterior commissural nucleus, these were increased both by 2 days and 2 months of estradiol treatment. These differences may be important in modulating female reproductive behavior. Present findings also suggest that estradiol can affect the oxytocinergic system via an indirect route since the cell groups influenced here by estradiol do not contain estrogen receptors. Oxytocinergic neurons may serve as a good system to compare direct transcriptional with indirect

ISSN:0092-7317    

DOI:10.1002/cne.903070209

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

年代:1991

数据来源: WILEY

摘要:

AbstractA semiquantitative, electron microscopic immunocytochemical procedure based on the use of colloidal gold particles as markers was employed to analyze the subcellular distribution of glutamate and glutamine, a major glutamate precursor, in a subpopulation of spinocerebellar mossy fiber terminals. These terminals were identified by anterograde transport of a horseradish peroxidase‐wheat germ agglutinin conjugate, injected in the thoracic spinal cord. Gold particles signalling glutamate‐like immunoreactivity were enriched over clusters of synaptic vesicles relative to organelle‐free cytoplasmic matrix, and there was a strong positive correlation between gold particle and synaptic vesicle densities (correlation coefficient 0.94). Gold particles indicating glutamine‐ike immunoreactivity showed a much weaker correlation with vesicle density (correlation coefficient 0.36) and were about equally concentrated over cytoplasmic matrix as over clusters of synaptic vesicles.Compared with the mossy fibers, the putative GABAergic Golgi cell terminals exhibited a lower level of glutamate‐like immunoreactivity, which was very weakly correlated with the vesicle density (correlation coefficient 0.27). The level of glutamine‐like immunoreactivity in the Golgi cell terminals was similar to that in mossy fibers, but much lower than that in glial cells.The anterogradely labelled mossy fiber terminals were not enriched in immunoreactivities for aspartate or GABA.These results suggest that the level and subcellular distribution of glutamate in presumed glutamatergic terminals differs from that in terminals in which glutamate only serves metabolic or precursor roles, and that these differences can be exploited in immunocytochemical studies aimed at identifying glutamate‐using neurons. In contrast, glutamine immunocytochemistry does not seem to be generally useful i

ISSN:0092-7317    

DOI:10.1002/cne.903070210

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

年代:1991

数据来源: WILEY

摘要:

AbstractThree neuroanatomical tracers have been employed to map the axonal projections formed between transplants of fetal spinal cord tissue and the surrounding host spinal cord in adult rats. Solid pieces of embryonic day 14 (E14) rat spinal cord were placed into hemisection aspiration cavities in the lumbar spinal cord. Injections of either (1) a mixture of horseradish peroxidase and wheat germ agglutinin‐ conjugated horseradish peroxidase, (2) Fluoro‐Gold, or (3)Phaseolus vulgarisleucoagglutinin (PHA‐L) were made into the transplants or the neighboring segments of the host spinal cord at 6 weeks to 14 months post‐transplantation.Injections of anterograde and retrograde tracers into the transplants revealed extensive intrinsic projections that often spanned the length of the grafts. Axons arising from the transplants extended into the host spinal cord as far as 5 mm from the host‐graft interface, as best revealed by retrograde labeling with Fluoro‐Gold. Consistent with these observations, iontophoretic injections of PHA‐L into the transplants also produced labeled axonal profiles at comparable distances in the host spinal cord, and in some instances elaborate terminals fields were observed surrounding host neurons. The majority of these efferent fibers labeled with PHA‐L, however, were confined to the immediate vicinity of the host‐graft boundary, and no fibers were seen traversing cellular partitions between host and transplant tissues.Host afferents to the transplants were also revealed by these tracing methods. For example, the injection of Fluoro‐Gold into the grafts resulted in labeling of host neurons within the spinal cord and nearby dorsal root ganglia. In most cases, retrogradely labeled neurons in spinal gray matter were located within 0.5 mm of the graft site, although some were seen as far as 4–6 mm away. The distance and relative density of ingrowth exhibited by host axons into the grafts, however, appeared modest based upon the results of HRP and Fluoro‐Gold retrograde labeling. This was further confirmed with the PHA‐L anterograde method. Whereas some host fibers were seen extending into the transplants, the majority of PHA‐L containing axons formed terminal‐like profiles at or within 0.5 mm of the host‐graft interface.The Comprehensive view of intrinsic connectivity and host‐graft projections obtained in these studies indicates that intraspinal grafts of fetal spinal cord tissue can establish a short‐range intersegmental circuitry in the injured, adult spinal cord. These observations are consistent with the view that such grafts may contribute to the formation of a functional relay between separated segments of the spinal cord after injury. The fact, however, that the majority of host‐ and graft‐derived axons were concentrated within the vicinity of the host‐graft border raises several considerations about the dynamics of axonal growth and cellular interactions. In that regard, the present findings provide a useful baseline for elucidating mechanisms that regulate axonal elongation in this experimental setting. These results also provide a framework for future tests of surgical, pharmacological, or molecular manipulations that may enhance the degree of axonal i

ISSN:0092-7317    

DOI:10.1002/cne.903070211

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

年代:1991

数据来源: WILEY