摘要:

AbstractThe retinal projection to the brain inXenopushas been examined using autoradiographic techniques. The labelled moieties used were3H‐proline and3H‐fucose.There are three anterior thalamic optic terminal sites inXenopus. These are the nucleus of Bellonci, the corpus geniculatum thalamicum and the rostral visual nucleus. The first two of these are similar to the homonymous nuclei inRanawhile the last, the rostral visual nucleus, appears to correspond to the rostral end of the posterior entopeduncular nucleus ofRana. Both the nucleus of Bellonci and the rostral visual nucleus receive strong ipsilateral retinal inputs while the corpus geniculatum receives only a weak ipsilateral projection. In the posterior thalamic: pretectal region there is only one clearly defined optic terminal nucleus—the uncinate field. This structure receives a strong ipsilateral input. In addition there are two other labelled fields in this region whose nature (fibers v. terminals) cannot be clearly discerned in autoradiographs. These are the thalamopretectal field—a horizontal band which extends in the dorsomedial neuropil from midthalamus to the pretectum, and the pretectal field where diffuse labelling is evident, especially ipsilateral to the injected eye. The thalamopretectal field also receives an ipsilateral input. The optic tectum inXenopusreceives a dense contralateral retinal innervation but only a weak ipsilateral projection. Finally, the basal optic nucleus receives both contralateral and ipsilateral retinal innervation with the latter being, by far, the weaker of the two.In addition to other differences between the two species, it is obvious that there is a much denser and more extensive ipsilateral retinal projection to the thalamic and pretectal brain structures inXenopusthan inRana. This is presumably due to the greater size of the binocular field in

ISSN:0092-7317    

DOI:10.1002/cne.901890102

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

年代:1980

数据来源: WILEY

摘要:

AbstractA second type of horizontal cell with a distinctly different appearance from the previously known horizontal cell has been seen in Golgi‐impregnated monkey retinas. The new HII cell has a different dendritic branching pattern from the commonly described HI cell type, and it has a short convoluted axon with collaterals bearing small clusters of terminals. Comparisons of the two cell types at different retinal eccentricities show that HII cells have larger dendritic trees than HI cells in the foveal region but smaller dendritic trees than HIs in peripheral retina. Dendritic terminals of the new HII cell, like the HI cell, contact cone pedicles as lateral elements of the ribbon synapses. The isolated terminals or clusters of terminals borne by the short axon of the HII cell also contact cone pedicles as lateral elements rather than contacting rod spherules as lateral elements like HI terminal arborizations. Thus, the monkey like other vertebrates has at least two horizontal cell types which differ in morphology and synaptic connection

ISSN:0092-7317    

DOI:10.1002/cne.901890103

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

年代:1980

数据来源: WILEY

摘要:

AbstractDouble label‐emulsion autoradiography has been used in rhesus monkeys to study cortico‐cortical connections, arising from two separate sites of the striate cortex, and going in the same hemisphere into the cortex in the medial part of the posterior (or ventral) bank of the superior temporal sulcus (area STS). The projections from a single cortical locus are segregated into several patches of labeled terminals in layers III–IV, which from bands in consecutive sections. Fields of distribution of these bands from two sites of area 17 may completely overlap, when they arise from neighboring regions, or may partially overlap, when they arise from more separated regions. The latter show a retinotopical order in these connections and, consequently, of area STS itself: central visual field is lateral and ventral in STS to peripheral visual field, and upper visual field is ventral and medial to lower visual field. Connections from area 17 to area MT in owl monkey were analyzed in a comparative study. Results show that these connections are also highly segregated into bands, and that those arising in separate, but neighboring regions of 17, may greatly overlap in MT. The retinotopy of these connections was not studied, however. The similar divergent distribution of area 17 connections to STS and MT, and the similarity of the topography of STS connections and of the known retinotopy of area MT, are considered as elements of homologies between these areas. Functional implications of these divergent patterns of connections to these motion‐sensitive areas (Zeki, '74), are con

ISSN:0092-7317    

DOI:10.1002/cne.901890104

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe development of the trigeminal motor nucleus in the chick embryo was studied using autoradiographic, cell staining, fiber staining, and axonal transport techniques. It was found that this nucleus arises very early in neurogenesis, with the first cells produced at 48 hours of incubation (stage 12), peak cell production at 50–56 hours (stage 15), and neuroblast proliferation completed by 72 hours (stage 18). As has been described in mammalian embryos, the primordial trigeminal cells move from the ventricular layer to accumulate as part of the common medial column, and later migrate in a ventrolateral direction to form the definitive lateral motor nucleus. The first identifiable component of the trigeminal system is the semilunar ganglion, which flanks the neural tube at stage 12, and sends afferents into the metencephalon by stage 13. By stage 12–13, the medial column cells are first apparent, and at stage 14, a few of these medial column cells have moved to begin formation of a lateral nucleus. At this time, a thin motor root can be seen exiting the brainstem. During subsequent stages, migratory traffic from medial to lateral regions increases, with cells frequently moving in association with fiber processes in the marginal zone. These fibers are presumed to emanate from secondary sensory, reticular, and medial column neuroblasts. By day 5, the medial column is greatly depleted and by day 6–7, the definitive lateral motor nucleus is formed. Beginning at 5 days, the dorsal motor nucleus can be detected, with cells from the lateral nucleus appearing to stream in a dorsomedial direction for its formation. Injections of horseradish peroxidase (HRP) into the mandibular process of the first visceral arch resulted in retrograde labeling of lateral nucleus cells as early as 3.5 days of incubation. In addition, migrating cells, intermediate between medial column and lateral nucleus, were similarly labeled. These observations indicate that processes of the lateral nucleus cells and those of migrating cells are well into their peripheral field at this age, but we cannot conclude that neuromuscular affiliations have been established, due to the possibility of HRP diffusion and growth cone u

ISSN:0092-7317    

DOI:10.1002/cne.901890105

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

年代:1980

数据来源: WILEY

摘要:

AbstractThree dimensional reconstruction, with the use of serial, 1‐μm sections, has revealed a system of oriented intercellular spaces within the undifferentiated optic cup. These large openings appear in the marginal zone of the primitive retina and optic stalk prior to the formation of the first retinal ganglion cell axons. The spaces at the region of the optic disc form sets of long, interconnecting tunnels oriented in the direction of the stalk. The spaces at the back and rim of the cup form blind, radially arranged pockets. The extracellular tunnels of the optic disc region strictly maintain their positions in relation to the optic fissure and, thus, discrete portions of the retina become connected by continuous openings with equivalent regions in the stalk. The path taken by the earliest outgrowing optic fibers is identical to the one previously established by the intercellular tunnels. We propose that the tunnel and pocket layout may provide directional and topographic information to the first forming optic axo

ISSN:0092-7317    

DOI:10.1002/cne.901890106

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

年代:1980

数据来源: WILEY

摘要:

AbstractGround squirrel retinas contain a relatively small complement of rods (5–10% of all photoreceptors) which are thought to provide the basis for a weak scotopic visual capacity. In a previous investigation of the California ground squirrel (Spermophilus beecheyi) involving the recording of a retinal gross potential, the electroretinogram (ERG), electrophysiological evidence for a viable scotopic signal could be obtained from some, but not all of the ground squirrels examined. To further pursue the possibility that there is a structural/functional discrepancy in the relationship between rod photoreceptors and scotopic vision in the ground squirrel, several experiments involving electrophysiological, behavioral, and anatomical observations have been conducted. We found that although about one‐third of the ERGs recorded from a large sample of California ground squirrels lack those characteristics which would indicate the presence of a viable scotopic signal, the retinas of all the squirrels appear to contain the same small population of rod photoreceptors. Additional experiments on the golden‐mantled ground squirrel (Spermophilus lateralis), including behavioral as well as ERG measurements and anatomical observations, lead to this same concl

ISSN:0092-7317    

DOI:10.1002/cne.901890107

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

年代:1980

数据来源: WILEY

摘要:

AbstractThis study provides a description of the normal morphology of the inferior olive of the squirrel monkey,Saimiri sciureus, at the light and electron microscopic level. The cytoarchitecture of the inferior olive was mapped from serial transverse sections stained with cresyl violet. In common with other mammals, the inferior olive of the squirrel monkey consists of three subdivisions. The medial accessory olive includes seven subnuclei. Both the dorsal and medial accessory olives extend through approximately 90% of the total length of the inferior olivary complex. The principal olive, consisting of a dorsal and ventral lamella continuous with one another laterally, extends through the rostral 55% of the inferior olive. It is somewhat less convoluted than the principal olive of the macaque (Bowman and Sladek, '73). In most other respects, the inferior olive of the two primates is quite similar.Two patterns of dendritic arborization are noted in Golgi preparations from the caudal principal and accessory olives. Dendrites streaming away from the soma, and dendrites curling around the soma in a “ball‐like” pattern were observed in all three subdivisions of the inferior olive caudally. Simple spines are occasionally seen on the soma, and a few simple or club‐shaped spines were noted on the proximal portion of the dendritic arborization. Spines are more numerous on distal portions of the dendritic tree, however, and include simple, filiform, club‐shaped and occasionally complex, or racemous, spiny appendages.Viewed in the electron microscope, most inferior olivary neurons are seen to contain the typical organelles with the usual conformation and distribution. Rarely, a neuron with an indented nucleus and a thin rim of cytoplasm containing a paucity of organelles and a wispy endoplasmic reticulum is encountered. Axon terminals containing either clear round or clear pleomorphic vesicles are seen in all three olivary subdivisions. In a random survey of 706 axon terminals, 54% contained predominantly clear round vesicles. Large dense cored vesicles are seen in varying numbers in both types of terminals. Rarely, profiles containing mainly large dense cored vesicles are observed.Axosomatic synapses involving both types of clear vesicle containing terminals are occasionally encountered. Such synapses are symmetrical, regardless of the type of vesicle found in the axon terminal. Axodendritic synapses involving round vesicle containing terminals are asymmetrical, while those involving pleomorphic vesicle containing terminals are usually, but not invariably, symmetrical. Axodendritic synapses occur at all levels of the dendritic tree. Very rarely, synapses between an axon terminal and a profile resembling a dendrite, but containing pleomorphic vesicles, has been observed.Synaptic clusters, consisting of a central core of small dendritic elements surrounded by both round and pleomorphic vesicle containing terminals, are found in all three subdivisions of the inferior olive. The dendritic elements, which resemblespines, contain a flocculent cytoplasm, mitochondria, multivesicular bodies and smooth endoplasmic reticulum. Evidence from some electronmicrographs suggests that the dendritic core is composed of racemous processes. Gap junctions are occasionally encountered coupling adjacent dendrites within the core.Gap junctions are encountered in all three subdivisions of the inferior olive, but are commonest in the two accessory olives. While most gap junctions couple den‐drites, one example of an axosomatic gap junction has been

ISSN:0092-7317    

DOI:10.1002/cne.901890108

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe suprachiasmatic nucleus (SCN) has been proposed as a site for an endogenous circadian oscillator in mammals, since lesions of the nucleus abolish a wide spectrum of overt circadian rhythms. To demonstrate that a directly measurable property of the SCN itself in intact (unlesioned) animals is affected by environmental light and exhibits circadian rhythmicity, we used the autoradiographic 2‐deoxy‐D‐[14C]glucose method to determine glucose utilization of rat SCN under a variety of lighting conditions. Our experiments indicate an important role for the SCN in circadian rhythm organization, and we believe the deoxyglucose method will prove useful as a tool for better understanding the functions and mechanisms of circadian c

ISSN:0092-7317    

DOI:10.1002/cne.901890109

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe rabbit retinal ganglion cell layer contains a soma population which is morphologically distinct from the demonstrated ganglion cells. These “coronate cells” (Vaney, '80) have many features in common with classical neurons and are qualitatively different from typical glial cells. Detailed investigation by specific staining, ribonuclease treatment, and electron microscopy indicates that coronate cells are microneurons. The coronate cells contain somatic subsurface cisternae typical of rabbit amacrine cells, and are similar in appearance to some neurons of the amacrine cell layer. It is suggested that they represent, at least in part, a population of “displaced” amacrin

ISSN:0092-7317    

DOI:10.1002/cne.901890110

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

年代:1980

数据来源: WILEY

摘要:

AbstractExperimental evidence suggests that brain stem lesions producing paralysis of lateral gaze and dissociation of conjugate horizontal eye movements have certain common features. Both of these disturbances involve abducens internuclear neurons (Abd IN) or their projections. Attempts were made to determine the course and terminal distribution of Abd IN in the monkey by autoradiographic techniques. Tritiated amino acids injected in the abducens nucleus (Abd N) labeled: (1) root fibers ipsilaterally, and (2) fibers that ascended in medial parts of the contralateral medial longitudinal fasciculus (MLF). In the opposite oculomotor complex (OMC) silver grains were profuse over the ventral nucleus (VN, medial rectus muscle) and patchy over caudal parts of the dorsal nucleus (DN, inferior rectus muscle). Labeling of cells in the reticular formation ventral to Abd N resulted in transport ipsilaterally, outside the MLF, to the rostral interstitial nucleus of the MLF (RiMLF), a cell group considered to be concerned with vertical eye movements.Bilateral labeling of Abd N and cells of the nucleus prepositus (NPP) resulted in bilateral: (1) transport of isotope via root fibers and the MLF, and (2) selective distribution of silver grains in the OMC. Bilateral silver grain distribution in the OMC suggested profuse terminations in VN, patchy terminations in DN and vertical, linear terminations in caudal parts of the medial nucleus (MN, superior rectus muscle). Comparisons with more discrete unilateral labeling of cells in Abd N suggested that cells of the NPP project selectively to terminations in MN, and may be related to upward eye movements.Two conclusions were drawn: (1) The paresis of ocular adduction which occurs in both anterior internuclear ophthalmophlegia and in paralysis of lateral gaze results from involvement of Abd IN or their ascending projections, and (2) the NPP appears to project selectively to parts of MN of the OMC, a cell group said to provide crossed innervation for the superior rectus muscle.

ISSN:0092-7317    

DOI:10.1002/cne.901890111

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

年代:1980

数据来源: WILEY