摘要:

AbstractThe cells of origin of pathways descending to the spinal cord in the sharkScyliorhinus caniculaand in the rayRaja clavatahave been demonstrated by using the horseradish peroxidase (HRP) technique. Following HRP injections in the spinal cord ofScyliorhinus(fourth to sixth segment) and ofRaja(15th to 20th segment) labeled neurons could be identified in the rhombencephalon, the mesencephalon, and in the diencephalon. Cells of origin of diencephalic nuclei, which project to the spinal cord, were observed in the nucleus periventricularis hypothalami and in the thalamus ventralis pars medialis which can in this respect be considered hypothalamic. Descending pathways from mesencephalic structures originate from the interstitial nucleus of the fasciculus longitudinalis medialis, the tectum mesencephali, the nucleus intercollicularis, the tectotegmental junction zone, and from diffusely arranged tegmental neurons. A contralateral rubrospinal pathway could be recognized inRaja, but not inScyliorhinus.Rhombencephalic cells of origin of pathways descending to the spinal cord were found in all parts of the reticular formation, i.e., the nucleus raphes inferior, the nucleus reticularis inferior, medius, superior, and isthmi, in two vestibular nuclei, and in three nuclei, which have been tentatively indicated as nucleus B, F, and G. Furthermore cells of origin of descending pathways have been found in the nucleus tractus descendens nervi trigemini, in the nucleus funiculi lateralis, and in the nucleus tractus solitarii. The descending pathways of the two species studied have been compared with those of other vertebrates. It is concluded that the basic pattern in the organization of descending pathways to the spinal cord, as proposed by ten Donkelaar ('76) for terrestrial vertebrates, also holds for cartilaginous fishes.

ISSN:0092-7317    

DOI:10.1002/cne.902020403

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

年代:1981

数据来源: WILEY

摘要:

AbstractLesions were produced in the nasal‐superior quadrant of rat retinas at 1 day postnatal. Both the optic fiber and ganglion cell layers were destroyed at the lesion site. Retrograde changes in the more peripherally located ganglion cell bodies, their optic fibers, and neuroglia were monitored by light and electron microscopy. No optic fibers remained in the region peripheral to the lesion site after 2 days postoperative (DPO). Neither regenerative sprouting nor axonal ingrowth from late‐maturing ganglion cells in the retinal periphery was observed. Cell death of the large and the majority of medium ganglion cell bodies was very rapid, as was clearing of the degeneration products. These processes peaked at 1 DPO and were complete by 2 DPO. Microglia and Mueller cell cytoplasm actively phagocytized degenerating ganglion cell bodies and their optic fibers.A stable population of cell bodies in the ganglion cell layer peripheral to the lesion remained intact from 2 DPO to 21 DPO. The surviving somata were consistently 65% of the control ganglion cell population, and they remained after their axons had degenerated. The cell bodies measured 6–12.1 m̈m in diameter, a range which included the small cell population and a few of the medium cells. Dendritic patterning, used to designate ganglion cell types, corroborated their classification as small and medium ganglion cells. Morphological changes in these perikarya due to axotomy were limited to a mild chromatolytic re

ISSN:0092-7317    

DOI:10.1002/cne.902020404

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

年代:1981

数据来源: WILEY

摘要:

AbstractTectal tissue was dissected from fetal rats and transplanted adjacent to the superior colliculus of newborn rats. The recipient animals were then allowed to survive for 6 or more weeks. Subsequent examination revealed that the transplants generally lay over the host inferior colliculus and rostral part of the cerebellum and had substantial fiber connections with the host superior colliculus. To determine which host areas projected to the transplants, horseradish peroxidase (HRP) was injected into the transplants, and the host brain was examined for the presence of retrogradely filled neurons.Labeled cells were found in nearly 50 host areas. Most of these areas are known to project to normal superior colliculus. There was a consistency between one animal and another in the frequency and density of cell label in the various areas. The projection from host cortex (particularly from visual cortical areas) was the densest and most consistent projection. Other areas which commonly projected into the transplants included pretectum, parabigeminal nucleus, superior colliculus, and the brachial region of the inferior colliculus. Sparse and infrequent projections were found from ventral lateral geniculate nucleus, substantia nigra, zona incerta, and catecholaminergic nuclei. No unequivocally labeled retinal ganglion cells were found.The results indicate that the host projection into the transplants is limited to those areas with axons in the vicinity of the host/transplant interconnection. However, the data also suggest that (1) the relative maturity of particular host pathways at the time of transplantation and (2) some form of preferential or absolute affinity expressed between host axons and transplant cells are also factors which influence the pattern of connections formed between host and transplant.

ISSN:0092-7317    

DOI:10.1002/cne.902020405

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

年代:1981

数据来源: WILEY

摘要:

AbstractIt is well established that a congenital lack of ocular melanin (albinism) can lead to developmental abnormalities of the central visual pathways. However, it is yet unknown how the pigmentation per se acts to influence formation of the optic projection. In order to study the possible interaction between eye pigment and optic axons during development, we have examined, with the use of serial section techniques, a series of timed embryos at stages when the ocular pigment and outgrowing axons first become apparent. Our results have demonstrated that, in mice and rats, the upper wall of the distal half of the primitive eye stalk (a region which lies along the potential route to be taken by the earliest developing nerve fibers) is transiently pigmented prior to and during the migration of the pioneer optic axons. All outgrowing neurites avoid this stretch of melanotic tissue and instead grow preferentially through a system of extracellular tunnels in the ventral, pigment‐free zones of the distal eye stalk. The stalk remains unpigmented from about its midpoint and continuing toward the brain. At the pigment/pigment‐free interface many of the axons shift upward from their ventral positions, forming a marginal annulus. In the chick, on the contrary, pigmentation of the stalk does not occur and as the optic axons exit the globe they grow immediately in an annulus configuration. InXenopus, the entire stalk becomes pigmented and the optic fibers congregate in one discrete bundle of fascicles along the length of the stalk's most ventral margin. These observations suggest that melanin‐producing stalk cells may play a role in controlling the topographic patterning of optic fibers within the developing nerve by inhibiting the lateral spread of axonal growth cones into or within their territory. To test this hypothesis we have charted the distribution of optic fibers in the developing optic stalks of timed albino rat embryos. Indeed, as fibers leave the mutant eye, it was found that a small but consistent number of pioneering axons (day E15) become ectopic and immediataely invade nonpigmented regions (those normally pigmented and axon‐free) in the distal optic stalk. Thus, the usual topographic arrangement of the collection of pioneer optic fibers is altered in the

ISSN:0092-7317    

DOI:10.1002/cne.902020406

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe retrogradely transported horseradish peroxidase (HRP) method was used to study the areal and laminar distribution of neurons sending their axons to ipsilateral and contralateral visual cortical areas 17, 18, 19, and MT in the squirrel monkey. Further details regarding neuron type (stellate or pyramidal), size class, and spatial grouping of the cells making these corticocortical connections also were obtained.All interareal connections are reciprocal. Ipsilaterally, such connections exist between areas 17 and 18, 17 and MT, 18 and 19, 18 and MT, and 19 and MT. In addition, areas 18, 19, and MT receive association fibers from the ipsilateral frontal eye field; when combined with previous findings, these results indicate the existence of reciprocal connections between area 18 and the frontal eye field and between area MT and the frontal eye field. Each of areas 18, 19, and MT is also reciprocally connected with each of the contralateral areas 18, 19, and MT. Area 17 has only weak callosal connections. Both the ipsilateral and the contralateral connections are topographically organized such that they obey a hodological principle of visuotopic connectivity: that is, only representations of the same part of the visual field are interconnected.With regard to layers of origin, the callosal neurons of these visual areas conform to the general concept of corticocortical fibers arising from supragranular layers in that most of them are located in layer IIIb; only a few of them reside at the junction between layers V and VI. On the other hand, for all the visuocortical connections investigated, the anteriormost area of a reciprocally interconnected pair has its association neurons located predominantly in the infragranular layers while the posteriormost area has its association neurons located primarily in layer III.All callosal fibers and most association fibers arise from pyramidal cells. The callosal cells are larger and reside at a deeper level in layer III than neurons with ipsilateral corticocortical connections. However, some of the association cells at the junction of layers V and VI in area 17 which project to area MT are relatively large and may include the solitary cells of Meynert; but medium‐sized pyramidal cells also participate in this projection. In area 17, some association neurons in layers IIIb and IIIc which project to area 18, as well as some in layer IIIc which project to area MT, are most likely stellate cells.Several different patterns of cell groupings were observed for the central representation interconnections. Neither ipsilateral area MT nor any of the contralateral visuocortical areas had multiple groupings of labeled neurons. The ipsilateral projections from area 17 to 18, 17 to MT, and 18 to 19 were arranged similarly according to a plan involving separate, multiple loci of origin for cells projecting to a small ad isolated subregion of the central representation in the target cortical area; following larger injections, cells throughout the central representation of the projecting cortex were labeled. On the other hand area 18 appeared to have some subregions devoid of cells destined to project to area M

ISSN:0092-7317    

DOI:10.1002/cne.902020407

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe presence of specific oligosaccharides on the surface of retinal cells was examined by incubating FITC‐labeled lectins with cells dissociated from papain‐treated turtle retinas. The pattern and intensity of binding was found to vary among the cells examined. With Con A, there was strong surface staining of both rods and cones, with an intense ring of fluorescence above the nucleus. The bipolar and ganglion cells also showed strong surface labeling. In Müller (glial) cells there was intense fluorescence in the apical, microvillous region. In contrast, the horizontal cells and their axons showed weak staining. When RCA‐60, RCA‐120, and WGA were incubated with photoreceptors, bipolar cells, or horizontal cells, little fluorescence was visible. However, all three lectins bound strongly to the Müller cells. In contrast, theLotuslectin did not bind to any of the cells examined. In all the cases, lectin binding was inhibited by the appropriate haptene sugar. Further, prior treatment of cells with neuraminidase did not alter lectin binding to any cell type. These results suggest differences in the distribution of lectin receptors among specific cell types, and particularly between neurons and glial cells in the vertebra

ISSN:0092-7317    

DOI:10.1002/cne.902020408

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe cell bodies and dendrites of cat spinal α‐motoneurons were studied after intracellular staining with horseradish peroxidase.The mean diameter of the soma was positively correlated to both the mean diameter and the combined diameter of the first‐order dendrites, but not to the number of first‐order dendrites. On the average, 11.2 dendrites originated from the soma.The dendritic trees were more extensive than has been described previously. The mean value for the combined length of a whole dendrite was 4.7 mm, while the mean values for the total surface area and volume of a dendrite were 33.0 × 103m̈m2and 27.2 × 103m̈m3, respectively. The diameter of the first‐order dendrite was positively correlated to the combined length of the entire dendrite, the number of dendritic branching points, and the number of dendritic end branches. The diameter of the first‐order dendrite was also directly proportional to the volume and the surface area of the entire dendrite. About 75% of the dendritic surface area and 55% of the dendritic volume was located more than 300 m̈m away from the soma. The dendrites constituted about 97% of the surface area and about 75% of the volume of the entire motoneuron (excluding the axon).The dendritic tapering was moderate. On the average, the distal decrease in dendritic diameters caused a reduction in the combined dendritic parameter (Σ3/2) by 1.5% and 15% at 500 m̈m and 800 m̈m distance, respectiv

ISSN:0092-7317    

DOI:10.1002/cne.902020409

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

年代:1981

数据来源: WILEY

摘要:

AbstractBy the use of intracellular staining with horseradish peroxidase (HRP), the dendric systems of spinal γ‐motoneurons of the adult cat were studied with a light microscope.The dendrites extended in various directions up to 1.5 mm from the cell body. The dendric branching was sparse and even unbranched dendrites were occasionally seen. The number and combined diameter of the first‐order dendrites increased in parallel with the mean cell body diamter.The number of dendric end branches, the combined dendritic length, the membrane surface area, and the volume of the entire dendrite correlated positively with the diameter of the parent first‐order dendrite.In comparison with the α‐motoneurons (Ulfhake and Kellerth, '81) the γ‐motoneurons had smaller values for mean cell body diameter and mean diameter of the first‐order dendrites and they also had a smaller number of first‐order dendrites. The dendrites of the γ‐motoneurons were also found to have fewer branching points and larger values for combined dendritic length. The relation between the diameter of the first‐order dendrite and the surface area of the entire dendrite was almost identical for the two

ISSN:0092-7317    

DOI:10.1002/cne.902020410

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

年代:1981

数据来源: WILEY

摘要:

AbstractElectrophysiological data were collected from the forelimb region of somatosensory cortex in barbiturate‐anesthetized cats using low‐impedance microelectrodes in long slanting trajectories. Subsequently, the brains were fixed and stained with thionin to locate the electrode trajectories and to correlate cytoarchitecture with neural activity. Confirming earlier experiments, regions of cortex, preferentially responsive to one submodality of afferent input, were observed to stretch in mediolateral bands across SI. Separate magnification functions were calculated for each band. In the forelimb region the magnification functions for the deep and cutaneous RA bands could be approximated by linear functions while the data for the cutaneous SA band was best described by a second‐order equation. At least in the forelimb region this magnification function applied only along the anteroposterior dimension of the band because the body representation is anisotropic; along the anteroposterior dimension of the band, receptive field loci may change only millimeters on the skin when the electrode moves through 1 mm of cortex, whereas when an electrode moves in a mediolateral direction they change centimeters on the forearm for an equivalent cortical distance.Each representation is separated from the others by a transition zone having a minimal width less than 200 m̈m. Within the transition zones, neurons often have receptive field loci which are a compromise between loci found in the adjacent representations. In these zones responses are often difficult to elicit. Electrode penetrations encountering these transition zones contain data which fulfill the receptive field and modality criteria for the boundary of a cortical column. However, within the mediolateral length of each submodality band we have found no unit with a dimension greater than 200 m̈m which has a boundary or transition zone. Evidence for units of smaller size cannot be obtained because of limitations in the data collection techniques. Thus, within each submodality‐specific band, large portions of the somatotopic map appear to be a mediolateral continuum while relatively abrupt changes occur in receptive field locus and in submodality when the electrode passes through a transition zone between adjac

ISSN:0092-7317    

DOI:10.1002/cne.902020411

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

年代:1981

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902020402

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

年代:1981

数据来源: WILEY