摘要:

AbstractThe development of the retina and tectum in goldfish was studied using light and electron microscopy. Soon after hatching the retina is well differentiated in that all the layers of the adult retina are present. The tectum at this time lacks the characteristic layered structure of the adult and innervation in the stratum opticum is extremely sparse, being confined mainly to the rostral region. The retina grows rapidly and retinal layers increase in thickness. This continues into adulthood. Optic innervation of the tectum increases and in fish 19 mm in body length the adult pattern of layers seen by silver staining and by electron microscopy is recognizable. At this time the optic nerve contains large number of unmyelinated axons. The thickness of tectal layers continues to increase over the entire size range of fish studied, well into adulthood. Synaptic densities in the layer of optic termination also change. Density falls in the rostral region as the fish increase in size. In the caudal region there is an initial decrease followed by a small increase. Total numbers of synapses in the main layer of optic termination increase both rostrally and caudally over the entire range of fish studied. Optic and nonoptic fibers contribute to this. The optic nerve at this stage is almost completely myelinated. The continuing growth of both the retina and tectum, including synaptogenesis, may provide a basis for the remarkable regeneration and plasticity shown by this system.

ISSN:0092-7317    

DOI:10.1002/cne.901930202

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

年代:1980

数据来源: WILEY

摘要:

AbstractIn previous studies we have described vibrissae‐related segmentation in the brainstem, thalamus, and cortex of the neonatal rat. Using succinic dehydrogenase (SDH) histochemistry, we delineated the time course in development of the normal segmentation at each level of the trigeminal system and the aberrant segmentation resulting from follicle damage at birth (Killackey and Belford, '79; Belford and Killackey, '79a, b). The present study examines the aberrant patterns that result from damage to the vibrissae follicles at different ages, comparing the patterns at the different levels of the trigeminal system.The present study indicates a number of similarities between the central representations of the vibrissae. First, the patterns are similar within each of the three representations in the trigeminal nuclei for removal at a given age in a particular animal. These changes include a decrease in SDH density but a maintenance of normal row widths. Second, the patterns are similar within both the ventrobasal complex and layer IV of somatosensory cortex for removal at a given age in a particular animal. These changes include a fusion of individual clusters into bands, and a decrease in band width, but maintenance of normal SDH density. Third, the effects of damage to a row of vibrissae follicles at different ages are graded. Earlier damage produces more marked aberrations. Fourth, for all of the structures, the transition between bands and clusters occurs with damage at the same age. Further, the last age at which damage produces aberrant patterns is Day 3 for all of the structures. Thus, the data suggest that there is one sensitive period for pattern alteration in the entire central trigeminal syste

ISSN:0092-7317    

DOI:10.1002/cne.901930203

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

年代:1980

数据来源: WILEY

摘要:

AbstractAs a first step in analyzing the influence of various afferent projections on the development of the hamster lateral posterior nucleus, its normal organization was studied using both light and electron microscopic techniques. Rostrolateral, rostromedial, and caudal subdivisions were identified. Therostrolateral subdivisionreceives dense projections from the ipsilateral superior colliculus and posterior neocortex, as well as sparser, more restricted projections from the contralateral colliculus and retina. The ipsilateral colliculus is by far the major source of medium‐sized (M)terminals with round vesicles. These terminals synapse around the shafts of large central dendrites to form distinctive synaptic clusters. The contralateral colliculus and retina contribute a few M‐terminals to the clusters. In contrast, axons from the posterior neocortex form very large (RL‐)terminals with round vesicles from the posterior neocortex form very large (RL)terminals with round vesicles which synapse onto numerous appendages of a single proximal dendrite, are surrounded by glial lamellae, and rarely participate in the clusters. Axons from all four sources also form small (RS)terminals with round vesicles which synapse on the shafts of small dendrites. Finally, F‐terminals with flat or pleomorphic vesicles form symmetric synaptic contacts both within and outside the clusters. The only identified projection to therostromedial subdivisionis from the ipsilateral posterior neocortex, which contributes RL‐ and RS‐ terminals. F‐terminals are also found, but neither M‐terminals nor synaptic clusters are present. Thecaudal subdivisionalso receives RL‐ and RS‐terminals from the ipsilateral posterior neocortex. Small inputs from the ipsilateral and contralateral colliculi are present, but their axons form only RS‐terminals. No M‐terminals or synaptic clusters are found.These results indicate that a large neonatal superior colliculus lesion would eliminate the vast majority of the M‐terminals in the synaptic clusters of the ipsilateral lateral posterior nucleus. In subsequent studies (Crain and Hall, '80 a, b, c), we will examine how the remaining inputs from the retina, contralateral superior colliculus, and posterior neocortex contribute to the synaptic organization when it dev

ISSN:0092-7317    

DOI:10.1002/cne.901930204

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe present series of experiments was designed to study how synaptic relationships in the lateral posterior nucleus are altered after neonatal superior colliculus lesions. In this paper, we studied the lateral posterior nucleus with light and electron microscopic techniques at two critical stages: at the time of the initial neonatal tectal lesion and at the onset of the consequent proliferation of retinal axons.At birth, the lateral posterior nucleus is very immature. Very few synapses are present and no degenerating terminals were found 6 hours after a tectal lesion. Thus, very few, if any, tectal axons have established connections in the nucleus by this time and the optic tract terminals which proliferate as a result of a neonatal tectal lesion are not simply taking over vacated postsynaptic sites.Optic tract terminal proliferation begins 4 to 6 days after removal of the superior colliculus and parallels the development of the normal retinal projections to the superior colliculus and to the dorsal and ventral lateral geniculate bodies (So et al., '78). Thus, the proliferation appears to be an example of increased synapse formation during normal development rather than a case of true “axonal sprouting”.At 6 to 7 days of age, when optic tract terminal proliferation is beginning, the neuropil is still very immature. The terminal types found in the adult nucleus cannot be identified and synaptic clusters have not yet formed. Thus, following neonatal tectal lesions, the lateral posterior nucleus must undergo most of its development not only in the absence of one of its normal projections, but also in the presence of at least one anomalous project

ISSN:0092-7317    

DOI:10.1002/cne.901930205

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe reorganization of the adult hamster's lateral posterior nucleus after neonatal superior colliculus lesions was studied using primarily light and electron microscopic degeneration techniques. Two types of experiments were conducted.First, the distributions of the remaining afferents from the contralateral superior colliculus, the contralateral retina, and the ipsilateral posterior neocortex were determined using the Fink‐Heimer ('67) technique. Normally the projections from the contralateral superior colliculus and retina are sparse and restricted to small areas in the rostrolateral subdivision. After neonatal lesions of the ipsilateral colliculus, however, these two minor projections greatly increase in density and expand to share a common border. In contrast, the normal projection from the posterior neocortex is dense throughout the rostrolateral subdivision. After a neonatal colliculus lesion, however, this projection is greatly decreased in the region occupied by the optic tract terminals.Second, the ultrastructural organization of the rostrolateral subdivision was studied in adult animals which had received neonatal colliculus lesions. Normally, this region is characterized by synaptic clusters in which numerous medium‐sized terminals (M‐terminals), almost all from the ipsilateral colliculus, synapse around the shaft of a large central dendrite. The contralateral colliculus and retina normally contribute only a few M‐terminals. After a neonatal colliculus lesion, typical clusters still form, but now the expanded projections from the contralateral colliculus and retina contribute numerous M‐terminals. The cortex does not contribute M‐terminals in either normal or experimental animals.These results suggest that the afferents to the rostrolateral subdivision normally compete for synaptic space. The various factors that might be involved in determining the outcome of such competition ar

ISSN:0092-7317    

DOI:10.1002/cne.901930206

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

年代:1980

数据来源: WILEY

摘要:

AbstractAfter a neonatal lesion of the ipsilateral superior colliculus, the projections to the lateral posterior nucleus from the contralateral superior colliculus and retina expand their terminal fields until they share a common border. In the first experiment described in this paper, we removed both superior colliculi at birth and used the Fink‐Heimer method to show that the optic tract projection could expand even further and enter the region which would have been occupied by the terminals of the crossed colliculus projection. Similarly, in the second experiment, we showed that the crossed collicular projection could be increased even more if the contralateral eye as well as the ipsilateral colliculus was removed at birth.Another result of a neonatal superior colliculus lesion is that the projection from the optic tract shares a border with the posterior neocortical projection. In the third experiment, we removed both the ipsilateral superior colliculus and the posterior neocortex at birth and demonstrated that the optic tract projection expanded more than after an ipsilateral colliculus lesion alone.Our results support the hypotheses that the projections from the ipsilateral and contralateral superior colliculi and the retina compete for synaptic space in the lateral posterior nucleus, and that a similar competition between the retinal and cortical projections may also occu

ISSN:0092-7317    

DOI:10.1002/cne.901930207

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe pattern of motor innervation to the cutaneous‐pectoris muscle of the frog is altered after injuring the motor nerve to the contralateral muscle in that muscle fibers innervated by a single motor nerve cell become polyneuronally innervated. This polyneuronal pattern of innervation was detected by single cell recordings of multiple end‐plate potentials from muscle fibers. The present study shows that the anatomical basis for this electrophysiological observation is the formation of new additional synapses by intact motor neurons on already innervated muscle fibers at new sites. Light and electron microscopical examination of muscles stained with Zinc Iodide and Osmium revealed that the sources for the new axon terminals were the intact motor axons and nerve endings that gave rise to sprouts that formed synaptic connections with muscle fibers apparently not innervated by their parent axons. Furthermore, new synapses were formed at new synaptic sites. The increased incidence of polyneuronal innervation that was detected electrophysiologically was associated, in the same muscles, with a proportional increase in the average end‐plate size estimated from the measurements of cholinesterase‐stained sites. Additional evidence that synapses were formed at new sites was that the shape of the different components of multiple end‐plate potentials in some polyneuronally innervated muscle fibers differed in their rise‐times. No such recordings were observed in polyneuronally innervated muscle fibers of n

ISSN:0092-7317    

DOI:10.1002/cne.901930208

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

年代:1980

数据来源: WILEY

摘要:

AbstractQuail neural crest cells were grown in vitro at clonal density for 7 or 10 days. Mixed neural crest colonies and clones (containing both pigmented and unpigmented cells) were implanted into the trunk region of 2 1/2‐day‐old host chicken embryos by a previously described injection technique (Bronner and Cohen, '79). Here we describe the migratory behavior and subsequent phenotypic expression of the injected cells. Unpigmented cells and pigmented cells both migrated along the ventral neural crest pathway; there were, however, some differences in migratory behavior between the two cell types. After 3 days in vivo, unpigmented quail neural crest cells contributed to the sympathetic ganglion, adrenal medulla, and/or aortic plexus in the host. Many of the unpigmented cells became catecholamine‐containing neuroblasts. Unpigmented cells were never observed in the gonads or the gut, but localized only in regions normally populated by trunk neural crest precursors to neurons and supportive cells. Melanocytes derived from the same precursor, however, were often found in the gonads or gut, in addition to normal neural crest locations in the trunk. These results demonstrate that quail neural crest cells grown in tissue culture for 7 days or more retain the ability to migrate and contribute to normal neural crest structures when placed in the embryonic environment. Under the conditions described, a single neural crest cell gave rise to daughter cells expressing the melanotic phenotype (detected in tissue culture) and adrenergic phenotypes (detected after injection in vivo). This demonstrates that at least some single cells of the premigratory crest in the trunk region are plurip

ISSN:0092-7317    

DOI:10.1002/cne.901930209

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe motor and sensory connections of the cervical vagus nerve and of its inferior ganglion (nodose ganglion) have been traced in the medulla oblongata of 32 adult cats with the neuroanatomical methods of horseradish peroxidase (HRP) histochemistry and amino acid autoradiography (ARG). In 14 of these subjects, an aqueous solution of HRP was applied unilaterally to the central end of the severed cervical vagus nerve. In 13 other cases, HRP was injected directly into the nodose ganglion. Three of these 13 subjects had undergone infranodose vagotomy 6 weeks prior to the HRP injection. A mixture of tritiated amino acid was injected into the nodose ganglion in five additional cats. The retrograde transport of HRP yielded reaction product in nerve fibers and perikarya of parasympathetic and somatic motoneurons in the medulla oblongata. Furthermore, a tetramethyl benzidine (TMB) method for visualizing HRP enabled the demonstration of anterograde and transganglionic transport, so that central sensory connections of the nodose ganglion and of the vagus nerve could also be traced. The central distribution of silver grain following injections of tritiated amino acids in the nodose ganglion corresponded closely with the distribution of sensory projections demonstrated with HRP, thus confirming the validity of HRP histochemistry as a method for tracing these projections. The histochemical and autoradiographic experiments showed that the vagus nerve enters the medulla from its lateral aspect in multiple fascicles and that it contains three major components—axons of preganglionic parasympathetic neurones, axons of skeletal motoneurons, and central processes of the sensory neurons in the nodose ganglion. Retrogradely labeled neurons were seen in the dorsal motor nucleus of X(dmnX), the nucleus ambiguus (nA), the nucleus retroambigualis (nRA), the nucleus dorsomedialis (ndm) and the spinal nucleus of the accessory nerve (nspA). The axons arising from motoneurons in the nA did not traverse the medulla directly laterally; rather, all of these axons were initially directed dorsomedially toward the dmnX, where they formed a hairpin loop and then accompanied the axons of dmnX neurons to their points of exit. Afferent fibers in the vagus nerve reached most of the subnuclei of the nTS bilaterally, with the more intense labeling being found on the ipsilateral side. Labeling of sensory vagal projections was also found in the area postrema of both sides and around neurons of the dmnX. These direct sensory projections terminating within the dmnX may provide an anatomical substrate for vagally mediated monosynpatic reflexes. Following deefferentiation by infranodose vagotomy 6 weeks prior to HRP injections into the nodose ganglion, a number of neurons in the dmnX were still intensely labeled with the HRP reaction product. The axons of these HRP‐labeled perikarya may constitute the bulbar component of the accessory ne

ISSN:0092-7317    

DOI:10.1002/cne.901930210

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe central sensory and motor connections of various respiratory, cardiovascular, and gastrointestinal viscera were analyzed using the transganglionic and retrograde transport of horseradish peroxidase (HRP).In 42 adult cats, we examined the brain stem and peripheral ganglia following microinjections of HRP (10 μl) into individual visceral organs—larynx, extrathoracic trachea, intrathoracic trachea, right main bronchus, right lung (upper lobe), heart, and stomach. Comparison of individual cases led to the conclusion that distinct patterns of sensory and motor projections to the medulla exist for each visceral organ studied.The nucleus of the tractus solitarius (nTS) receives the sensory projections from all the viscera listed above, with two exceptions: (1) a few sensory fibers from the larynx terminate in the ipsilateral spinal tract of the trigeminal nerve (spV), and (2) some sensory fibers from the bronchus, lung, and stomach terminate in the area postrema (ap). Within the nTS, the sensory fibers from each visceral organ terminate in a number of subnuclei. The dnTS, mnTS, and ncom receive sensory projections from all the viscera studied. The remaining five subnuclei (dlnTS, ni, nI, vlnTS, vnTS) of the nTS are not connected to all viscera, and the density of projections to these regions varies for different viscera. However, there does not seem to be any specific region of the medulla which is devoted entirely to receiving the sensory fibers from a particular visceral organ. Rather, the rostrocaudal extent of sensory fibers, from most of the viscera studied, spans the entire length of the medulla. Differences in the central representation of viscera were found to be subtle and to lie within the organization of the nuclear subgroups of the nTS.The central representation of unpaired or midline viscera (e.g., trachea and heart) is bilateral for both sensory and motor innervation. However, for unilateral, paired viscera (e.g., bronchi and lungs), it was consistently found that over one third of the sensory and motor representation is contralateral. Control experiments involving vascular injections of HRP excluded the possibility that this contralateral labeling could have been due to vascular uptake of the enzyme. The localization of sensory perikarya of visceral afferents in the “principal visceral ganglion” of the vagus—the nodose ganglion—was overlapping, and no well‐demarcated regions in the nodose ganglion could be identified that received projections primarily from a given visceral organ.The motor nuclei providing parasympathetic (preganglionic) and somatic motor innervation to the viscera were primarily the dmnX, nA, and nRA. The entire dmnX (extending over 10–15 mm rostrocaudally), contributed fibers to each area injected with HRP, with the exception of the extrathoracic trachea. No region in the dmnX was found where preference was given to a specific viscus. The nA contributed efferents to all the viscera studied, and this contribution came from the entire 6 mm of nA contributing vagal efferents. Visceral containing smooth muscle as well as skeletal muscle were innervated by the nA. The caudal nRA provided motor fibers to the larynx, trachea, and stomach, and again no preferred rostrocaudal representation of motoneurons to a given viscus was found. Postganglionic sympathetic innervation to the viscera studied was found to be localized to the stellate and superior cervical ganglia. Within these sympathetic ganglia, some regional preference for different viscera was detected. In the case of motor innervation, unilateral paired viscera received motor fibers from both ipsilateral and contralateral sides of the medulla via bot

ISSN:0092-7317    

DOI:10.1002/cne.901930211

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

年代:1980

数据来源: WILEY