摘要:

AbstractThe dorsomedial region of the nucleus of the tractus solitarius termed the subnucleus gelatinosus (SNG) was studied at the light and electron microscopic level in the cat. In cresyl violet and luxol fast blue stained sections the SNG contained small neuronal somata that were scattered throughout a pale‐staining neuropil containing few myelinated fibers. These neurons were difficult to impregnate with Golgi staining techniques, but in successful impregnations the somata were observed to be 10–19 μm in diameter and bore few sparsely branching primary dendrites. Spines were present on the dendrites of some neurons and were more numerous on distal portions of the dendritic tree.Ultrastructural examination of the SNG revealed that the neuronal complement consisted of round, oval, or spindle shaped neurons with little or no organized Nissl substance. Rare myelin‐like ensheathments of neuronal perikarya were also observed. Bundles of fine unmyelinated axons that coursed mainly longitudinally were a prominent feature of the area. The most common type of axon terminal observed contained mainly round clear vesicles, approximately 31 nm in diameter, and made asymmetrical synaptic contact with a dendritic profile. Pleomorphic vesicle‐containing terminals involved in symmetrical synaptic contact were also commonly seen. Axodendritic and axosomatic synapses were associated with terminals containing either round clear vesicles or pleomorphic vesicles. Less commonly, dendrodendritic and dendrosomatic synapses were seen, the presynaptic elements of which contained pleomorphic vesicles.Following removal of a nodose ganglion, degenerating terminals of vagal afferent fibers were observed throughout the neuropil. Such terminals contained round, clear vesicles with an occasional large, dense‐cored vesicle, and made axodendritic and axosomatic synapti

ISSN:0092-7317    

DOI:10.1002/cne.902060202

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractRetinotectal map formation was studied during regeneration in young adultXenopus.Right compound double‐temporal eyes (TT) were formed in tailbud stage embryos by the fusion of two temporal halves of the eye blastema in the same orbit. In other animals right compound double‐nasal eyes (NN) were prepared. In both combinations the left eye was kept intact. After metamorphosis the right and left optic nerves were sectioned to induce optic fiber regeneration from each eye to both tecta. The patterns of retinotectal projections from the compound and normal eyes were studied from 37 to 364 days after optic nerve section, using electrophysiological recording of the visuotectal projections and3H‐proline autoradiographic assay from one of the two eyes.The left normal eyes projected in a retinotopic fashion, across the entire extent of the right and left dually innervated tecta. In contrast, the right compound eye projections were confined to the rostrolateral or to the caudomedial part of the right and left tecta in TT and NN animals, respectively. These tectal areas corresponded to the termination of temporal and nasal hemiretinal fibers of the normal eye. Discontinuous, interdigitating projection patterns from the right and left eyes were found in parts of the tecta where the compound and the normal eye projections overlapped.These results indicate that the normal optic fiber projections caused the originally expanded compound eye projections to be restricted to the corresponding part of the dually innervated tecta. It is suggested that the orderliness and the extent of the retinotectal map are established by the competition and interaction of optic fibers based on stable positional programming of the retinal ganglion

ISSN:0092-7317    

DOI:10.1002/cne.902060203

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe apical surface of the retinal pigment epithelial cells (RPE) in the cat extend long sheetlike membranes that wrap concentrically above and around cone outer segments forming the cone sheath. The origin and organization of these sheetlike projections were studied in serial sections by electron microscopy. The apical surface of the RPE cells was found to consist of a thin zone of anastomosing ridges, or microplicae, from which longer projections extend. The lamellar projections forming the cone sheath originate from the microplicae as small cytoplasmic tabs that rapidly expand into broader sheets. Growth of individual sheets to their final size and shape continues by lateral and longitudinal expansion, fusion, and subdivision of the membrane. The small area of connection to the cell body allows the lamellae to overlap and interdigitate in forming the complex organization of the sheath. Microfilaments but not microtubules extend into the apical processes. RPE cilia (9 + 0 microtubules) with associated basal bodies, striated rootlets, and microtubules mark the location of retinal cones. These structures may be part of a microtubule organizing center that participates in morphogenesis of the cone sheath. They also may be involved in anchoring the apical projections forming the sheath, or in the movement of apical projections during the phagocytosis of outer segment discs shed from cone tips.

ISSN:0092-7317    

DOI:10.1002/cne.902060204

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThere is considerable evidence that the midbrain periaqueductal gray (PAG) is involved in visceral, emotive, and sexual responses and in endogenous analgesic effects. To see which of the forebrain areas directly influence the PAG, small injections of horseradish peroxidase were made into the various regions of monkey, cat, and rat PAG.Despite the fact that different regions of the PAG were injected in separate animals the majority of the forebrain areas labeled remained constant. Retrogradely filled pyramidal neurons in layer V were found in the frontal lobe in areas 6, 8, 9, 10, 13, and 24. Labeled neurons also appeared in the amygdala, preoptic area, and the anterior, dorsal, periventricular, ventromedial, periarcuate, lateral, and posterior hypothalamic nuclei. The main route for the hypothalamic → PAG projection appeared to be via the periaqueductal bundle which immediately borders on the cerebral aqueduct. Labeled neurons were also observed in the zona incerta, mesencephalic reticular formation, deep layers of the superior colliculus, and the nucleus cuneiformis. Most labeling was ipsilateral to the injection site although a small but consistent contralateral labeling was present. Therefore a strict subdivision of the PAG based on each subnucleus having its own unique set of connections seems inappropriate. There were few striking differences found in the forebrain areas that project to the PAG in the three species examined.These results are discussed in terms of the possible contribution these forebrain areas have in regulating the PAG with regard to its functions as a visceral, nociceptive, and cognitive integrato

ISSN:0092-7317    

DOI:10.1002/cne.902060205

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe cortical afferent connections of the amygdaloid complex of the cat have been studied by means of retrograde tracing of horseradish peroxidase and the fluorescent substances bisbenzimid and nuclear yellow. Subsequently, anterograde tracing experiments were carried out in order to define more precisely the termination areas of the corticoamygdaloid fibers.The results of the present study indicate that the main and accessory olfactory bulbs, the anterior olfactory nucleus, the prepiriform cortex and discrete regions of the medial frontal lobe, the insular and temporal cortices, as well as the perirhinal and entorhinal cortices and the ventral subiculum project to the amygdaloid complex. The main termination sites of these projections are the central, basolateral, and lateral amygdaloid nuclei. Neocortical regions project to the lateral nucleus and the lateral division of the lateral central nucleus. The mesocortical regions project predominantly to the basolateral nucleus and a medial division of the lateral central nucleus. In addition, area 35 distributes fibers to the lateral nucleus and the entorhinal cortex projects to the cortical nuclei of the amygdaloid complex. Fibers from the infralimbic area only reach the region of the medial central nucleus. Of the allocortical regions the prepiriform cortex distributes its fibers to the lateral, basolateral, and cortical nuclei, whereas the ventral subiculum projects to the medial division of the lateral central nucleus and the cortical nuclei.In the neocortical and most of the mesocortical regions the cells which project to the lateral and basolateral amygdaloid nuclei lie in layer III, whereas the cells which project to the central nucleus are located in layer V.

ISSN:0092-7317    

DOI:10.1002/cne.902060206

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractTwo types of neuron in the upper superficial gray layer of the cat superior colliculus accumulated exogenous3H‐gamma‐aminobutyric acid intensely. The first type was a horizontal cell with a fusiform cell body, horizontal dendrites, a low synaptic density, but a high percentage of cortical synaptic contacts. This cell had presynaptic dendrites. The second type was a granule cell (type A) with a small round cell body, thin and obliquely oriented dendrites, a moderate synaptic density, and few cortical synaptic contacts. These two types differed in size, shape, dendritic morphology, and patterns of synaptic input. They likely participate in different inhibitory mechanisms.Four types of unlabeled neurons were also identified. Type B granule cells were found only within the upper subdivision of the superficial gray layer. They had moderate‐sized cell bodies, a high synaptic density, and numerous somatic spines. A third type of granule cell (type C) was found only in the deep subdivision of the superficial gray. This type had a low synaptic density and spines that contained synaptic vesicles. Vertical fusiform and stellate forms were also found. We conclude that at least six types of neurons populate the upper superficial gray layer of the cat superior colli

ISSN:0092-7317    

DOI:10.1002/cne.902060207

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractAn anatomical technique based on the retrograde transport of horseradish peroxidase (HRP) was used to investigate the projections of spinal cord neurons to the mesencephalic tegmentum in the rat. Restricted unilateral injections were confined to central grey, cuneiformis area, and superior colliculus. Injections into all these loci produced labeling in similar spinal areas. Only quantitative differences were noted.In the spinal grey matter, numerous labeled cells were regularly encountered in the marginal zone, the lateral part of the neck of the dorsal horn, and the dorsal grey commissure. Projections from the marginal zone and neck of the dorsal horn were predominantly contralateral. In the white matter, a pronounced bilateral labeling was observed in the nucleus of the dorsolateral funiculus, thus confirming our previous electrophysiological findings (Menétrey et al., '80). This distribution of labeled cells was commonly observed throughout the whole length of the cord. Additional sites of projecting cells have also been identified at the most rostral levels (obex, C1, C2). They mostly derived from spinal extensions of the dorsal column nuclei and lateral cervical nucleus contralaterally; from the lateral ventral horns bilaterally and from the nucleus commissuralis ipsilaterally.This study is thus a clear confirmation that the mesencephalic tegmentum constitutes a target for various somatosensory inputs originating from spinal cord, dorsal column nuclei, and lateral cervical nucleus. Moreover, from these results together with those obtained for the spinothalamic tract in the rat, it appears that marginal and dorsolateral funiculus neurons preferentially project to the mesencephalic tegmentum. The importance of marginal zone projections underlines the involvement of the spinomesencephalic tract in pain mechanisms

ISSN:0092-7317    

DOI:10.1002/cne.902060208

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902060201

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY