摘要:

AbstractIn order to study brainstem origins of spinal projections, ten Tegu lizards (Tupinambis nigropunctatus) received complete or partial hemisections of the spinal cord at the first or second cervical segment. Their brains were processed for conventional Nissl staining. The sections were surveyed for the presence or absence of retrograde chromatolysis. Based on analysis and comparison of results from lesions in the various spinal cord funiculi, the following conclusions were reached:The interstitial nucleus projects ipsilaterally to the spinal cord via the medial longitudinal fasciculus, as does the middle reticular field of the metencephalon. The red nucleus and dorsal vagal motor nucleus both project contralaterally to the spinal cord via the dorsal part of the lateral funiculus. The superior reticular field in the rostral metencephalon and the ventrolateral vestibular nucleus project ipsilaterally to the spinal cord via the ventral funiculus. The dorsolateral metencephalic nucleus and the ventral part of the inferior reticular nucleus of the myelencephalon both project ipsilaterally to the spinal cord via the dorsal part of the lateral funiculus.Several brainstem nuclei inTupinambisproject bilaterally to the spinal cord. The ventrolateral metencephalic nucleus, for example, projects ipsilaterally to the cord via the medial longitudinal fasciculus and contralaterally via the dorsal part of the lateral funiculus. The dorsal part of the inferior reticular nucleus projects bilaterally to the spinal cord via the dorsal part of the lateral funiculus. The nucleus solitarius complex projects contralaterally via the dorsal part of the lateral funiculus but ipsilaterally via the middle of the lateral funiculus. The inferior raphe nucleus projects bilaterally to the spinal cord via the middle part of the lateral funiculus.These data suggest that supraspinal projections in reptiles, especially reticulospinal systems, are more highly differentiated than previously thought. On the other hand, recent findings in cat, opossum, and monkey reveal that the organization of supraspinal pathways in the Tegu lizard bears a striking resemblance to that observed in mammals.

ISSN:0092-7317    

DOI:10.1002/cne.901980202

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

年代:1981

数据来源: WILEY

摘要:

AbstractCell types of the auditory neostriatum in the starling forebrain are described. This area in the caudal neostriatum is defined neurophysiologically by the appearance of auditory neurons.Through use of the rapid Golgi technique, four types of neurons are identified, mainly on the basis of their processes: Neurons with long descending axons and thick dendrites rich in spines (type 1), neurons with long ascending axons and thin dendrites poor in spines (type 2), short‐axon neurons (type 3), and microneurons (type 4).The axons of the long neurons pass outside the confines of the auditory neostriatum. Among neurons of type 1; some of the long descending axons directed toward the lower brain centers enter the capsula interna occipitalis (CIO). The descending axons give off many collaterals within the auditory neostriatum. With neurons of type 2; most of the ascending axons cross the lamina hyperstriatica, enter the hyperstraiatum ventrale, and arborize near its periventricular region. Some of the long ascending axons reach the overlying hyperstriatum ventrale, pars caudale (HVc, the vocal control area). Among neurons of types 3 and 4; the axons of short‐axon neurons and of microneurons end with fine branches within the auditory neostriatum.The dendrites of long‐axon neurons are oriented in specific directions, whereas those of short‐axon neurons and of microneurons do not show a definite pattern of orientation.In the region of the auditory neostriatum that lies immediately adjacent to the midline of the brain, the first three types of neurons are arranged around the central core known as field L, which is composed of the microneurons and the terminal ramifications of auditory afferents. Laterally the microneurons, along with the fibers of the input tract, undergo a rostral shift to occupy a more peripheral position within the auditory neostriatum.The neurons of the auditory neostriatum are compared with those of the mammalian auditory cortex, and a functional classification of nerve cells into projection neurons, association neurons, and interneurons is p

ISSN:0092-7317    

DOI:10.1002/cne.901980203

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

年代:1981

数据来源: WILEY

摘要:

AbstractElectron‐microscopic examination of the pigeon optic chiasm, tract, stratum opticum, and retino‐receptive layers of the optic tectum revealed regional differences at each level. Axonal size in the fiber pathways paralleled that previously reported for pigeon optic nerve, with mean diameter values of 0.96 μm for optic chiasm and 1.06 μm for optic tract. The dorsolateral aspects of these pathways contained a heterogeneous population of fibers (mean diameter ⋍ 1.44 μm) similar to that found in the nasal portion of optic nerve, while the ventromedial regions were occupied by a more homogeneous population of smaller fibers (mean diameter ⋍ 0.82 μm) resembling those observed in the temporal portion of the nerve.The retino‐receptive layers of anteroventral optic tectum (avT) differed ultrastructurally from those of posterodorsal tectum (pdT) with respect to the thickness of horizontal dendrites in layers 2–3, the size of optic terminals in layers 2–7, and the number of synaptic contacts per terminal. These findings point towards a regional variation in the processing of visual information throughout the retino‐tectal system and suggest that neurons in avT vs. pdT should show differences in the way they modify the neurophysiological characteristics of their resp

ISSN:0092-7317    

DOI:10.1002/cne.901980204

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

年代:1981

数据来源: WILEY

摘要:

AbstractThree types of synapses (S‐, F‐ and C‐types) were identified in the thin‐sectionedXenopusspinal cord and their structure was analyzed with the freeze‐fracturing technique.All three types of synapses showed similar specializations of the presynaptic membrane. This finding suggests that the three types of synapses may release their transmitters by a similar mechanism. By contrast, the three types of synapses revealed different specializations of the postsynaptic membrane. The E‐face of the S‐type postsynaptic membrane was characterized by a dense aggregate of large intramembrane particles, 12 to 15 nm in diameter. An aggregate of small particles, 8 to 9 nm, was evident on the E‐face of the postsynaptic membrane of the F‐type synapse. In the C‐type synapse, there was a striking aggregate of intramembrane particles, 10 to 14 nm in diameter, on the P‐face of the postsynaptic membrane. These characteristics features in the distribution of particles in the three types of postsynaptic membranes may reflect differences in the type of transmitter released or transmitter action on the postsynaptic neuron.The overall size of the area of aggregated particles on the P‐face of the C‐type postsynaptic membrane was coextensive with the underlying subsurface cistern (SSC) which showed partial occulsion of the lumen. This fact supports the view that the SSC is closely related to the C‐type synaptic action which might be distinct fr

ISSN:0092-7317    

DOI:10.1002/cne.901980205

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

年代:1981

数据来源: WILEY

摘要:

AbstractGangliosides were extracted, separated by thin layer chromatography, and quantitated in three cranial nerves of the garfish (Lepisosteus osseus): the completely unmyelinated olfactory nerve (OLF), and two nerves composed of both myelinated and unmyelinated fibers, viz., the main trunk of the maxillary nerve (MAX) and a branch of the maxillary nerve (BR‐MAX). Morphological studies on each of these nerves were done to verify that the OLF had been excised free of any contamination from the accompanying myelinated BR‐MAX, to aid in the interpretation of the biochemical findings, and to clarify the nature of the OLF supporting cell.The chief chemical findings were (1) documentation of the presence of gangliosides in nerves previously thought not to contain them, (2) demonstration that gangliosides can be associated with unmyelinated nerves, (3) demonstration of a greater proportion of one simple ganglioside (G‐6) in the OLF but greater proportions of two complex gangliosides (G‐2 and G‐O) in the MAX and BR‐MAX, and (4) that either GM4 or a variant of the GM3 is present in OLF. The morphological findings with respect to the difficulty of ascribing only peripheral nervous system characteristics to the OLF supporting cell are discussed in relation to the ganglioside band chromatographing slightly ahead of GM4

ISSN:0092-7317    

DOI:10.1002/cne.901980206

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe birthdates of neuronal populations comprising the chick telencephalon were determined by3H‐thymidine labeling and were mapped with respect to their terminal positions in the 16‐day embryo. Essentially all neurons were generated between four and nine days of embryonic development. Each telencephalic structure (based on terminology used by Karten and Hodos, '67) was characterized by a specific range of birthdates: some regions such as the core of the ectostriatum or the paleostriatum primitivum, were generated within a single day, while others, such as the hyperstriatum accessorium, required up to five days for generation of the complete population. Spatial‐temporal gradients of neuronal birthdates, lateromedial and ventrodorsal, were seen in the telencephalon as a whole and within individual subcompartments as well. An “outside‐in” pattern of histogenesis predominated throughout the entire telencephalon, including the dorsolateral cortex. However, notable exceptions pertaining to the paleostriatum augmentatum, hyperstriatum intercalatus and field “L” were observed. Glial cells, generated for the most part after day ten, were found to be distributed homogeneously throughout all areas of the telencephalon. These data provide the first birthdating data for an avian telencephalon and bring greater resolution to previous analyses of the histogenesis of this brain region. Further, the compartmentalization of the proliferative neuroepithelium is revealed by these data, and the possibility of a common time of origin in the neuroepithelium for neurons of related functi

ISSN:0092-7317    

DOI:10.1002/cne.901980207

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe movements of cells from their sites of origin in the proliferative neuroepithelium to their final positions in the chick telencephalon were traced by autoradiographic analysis of3H‐thymidine‐labeled brains. A series of chick embryos were labeled on successive days of development between days 5 and 9 and fixed for autoradiography between days 6 and 10. Isochrone maps visualizing neuronal positions on each day of development between days 6 and 10 provided direct information concerning cell migrations, displacements, and aggregations leading to compartmentalization of the telencephalic wall and the generation of the “outside‐in” pattern of histogenesis characteristic of the avian telencephalon. The topological divisions of the telencephalic wall appear to result from two factors: (1) the specification of neuronal precursors within the neuroepithelium and (2) the intrinsic associative and migratory properties of postmitotic neuronal populations expressed within the mantle layers. There was no evidence that glial cell barriers mediated the initial compartmentalization of neuronal po

ISSN:0092-7317    

DOI:10.1002/cne.901980208

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

年代:1981

数据来源: WILEY

摘要:

AbstractAn isolated perfused retina‐eyecup of the rabbit neonate was used to study the functional maturation of synaptic interactions in the outer plexiform layer. Intracellular recordings from receptors, horizontal cells, hyperpolarizing and depolarizing bipolar cells were obtained in the adult and at different stages of maturation. Three types of horizontal cells could be distinguished based on the relative amount of rod and cone input, response wave form, receptive field diameter, and amplitude‐intensity relationships. Two of the horizontal cell types were encountered with sufficient frequency such that maturation of these response characteristics could be followed over the developmental period of this study (8 days–adult). The growth rate of the amplitude‐intensity relationships was different for the two commonly encountered types of horizontal cells; the small diameter receptive field type achieved an adultlike amplitude‐intensity range at an earlier age than the large field type. Immature bipolar cell responses were initially monophasic potentials with transient‐sustained components appearing at a later stage. Center surround antagonism of bipolar cells developed after centermediated responses were first observed. This suggests some secondary modifications during synaptogenesis are responsible for the late maturation of center surround antagonism. The morphological appearance of synaptic contacts during different stages of synaptogenesis is discussed in reference to the different phases of functional, synaptic interactions of this study. It appears that some synapses in the vertebrate retina are functional at a time when synaptic structure is incomplete, based on ultrastructural observation. Maturation of receptive field diameter and amplitude‐intensity function is discussed in relationship to possible presynaptic and postsynaptic mechanisms which may influenc

ISSN:0092-7317    

DOI:10.1002/cne.901980209

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

年代:1981

数据来源: WILEY

摘要:

AbstractIntracellular recordings in an isolated perfused retina‐eyecup preparation of the neonate rabbit were used to study the physiological development of amacrine cells. By responding with transient depolarizations at the onset and termination of illumination, mature mammalianon‐offamacrine cell recordings appeared similar to those described in lower vertebrates. However, immature amacrine cell recordings showed a predominantlyonresponse, withoffresponses small and easily fatigued during repetitive stimulation. This underdevelopedoffcomponent of the amacrine cell response could also be abolished by decreasing the area of receptive field that was stimulated. The more slowly developingoffcomponent may reflect a different maturation rate of depolarizing (on) and hyperpolarizing (off) bipolar cells. In addition, properties of the maturing inner plexiform layer were examined with extracellular recordings of the proximal negative response (PNR). The PNR showed evidence of evidence of easy fatigability more evident in theoffresponse. These observations are consistent with the idea that the initial phase of light sensitivity is associated with labile synaptic input from bipolar ce

ISSN:0092-7317    

DOI:10.1002/cne.901980210

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe distribution of enkephalin‐like immunoreactivity in the hippocampal formation of the rat was analyzed. Two specific projection systems are described. The first emerges from the hilus of the dentate gyrus and appears to terminate with notably large boutons on the proximal apical and, to a lesser extent, basal dendrites of hippocampalregio inferiorpyramidal cells. This projection corresponds in source, position, and character to the hippocampal mossy fiber system. The second axonal population enters the temporal hippocampal formation from the medial wall of the subicular complex and follows the hippocampal fissure to occupystratum lacunosum‐moleculareof the hippocampus proper and the distal third of the dentate gyrus molecular layer; this pattern corresponds to the distribution of afferent input from the lateral entorhinal cortex and/or perirhinal area. Lesions of the hilus or retrohippocampal area caused a selective depletion of immunoreactivity in the mossy fiber fields and molecular layers of the dentate gyrus, respectively. Enkephalin‐like immunoreactivity was found within the somata of three types of hippocampal neurons: (1) granule cells of the dentate gyrus, (2) occasional pyramidal shaped cells of field CA1stratum pyramidale, and (3) varied scattered interneurons. Of this last group, two types of interneurons were consistently seen. The first occupy the border betweenstratum radiatumandstratum lacunosum‐moleculareand extend processes at right angles to the long axis of the pyramidal cell dendrites, whereas the second lie withinstratum radiatumof field CA1 and extend processes in alignment with the long axis of the pyramidal cell dendrites. Cells containing enkephalin‐like immunoreacactivity were also observed in the subiculum and retrohippocampal region, most notably including layers II and III of the lateral entorhinal cortex‐perirhinal area—the probable source of extrinsic immunoreactive input to the hippocampal formation. Intraventricular colchicine treatment intensified the immunoreactive staining of some hippocampal neurons but did not reveal any cell types not seen to be labeled in u

ISSN:0092-7317    

DOI:10.1002/cne.901980211

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

年代:1981

数据来源: WILEY