摘要:

AbstractProjections from the high‐frequency representations of auditory cortical fields A and P were autoradiographically labeled using anterograde transport of a mixture of tritiated proline and leucine. A single injection of isotope into either cortical field resulted in multiple regions of dense labeling within ipsilateral AI. As the result of an injection of radioactive label into field A in one experiment, densely labeled regions were found to be systematically related to the binaural map throughout the high‐frequency representation of AI. Contralateral dominant suppression responses were located in regions of dense labeling while summation responses were located in regions of less dense labeling. In contrast, it was previously found that callosal axon terminations were more densely concentrated in summation columns than in contralateral dominant suppression columns (Imig and Brugge, '78). Thus, the two classes of binaural columns differ with respect to the density of innervation they receive from these ipsilateral and contralateral populations of neurons.In other experiments in which isotope was injected into field A, a systematic relationship between density of ipsilateral labeling and binaural response class was only seen in a portion of AI; in other regions no relationship was evident. A simple interpretation of these data follows. Within a contiguous territory in field A is a population of neurons whose axons provide more dense innervation to contralateral dominant suppression columns than to summation columns in ipsilateral AI. Injections of radioactivity confined to this territory result in a systematic relationship between the density of labeling and the binaural map throughout AI. Outside this territory is a population of neurons whose axonterminations are not systematically related to the binaural map in AI. Isotope injections which engage both territories may result in a systematic relation between density of labeling and the binaural map in one portion of AI, while in another, no relationship may be evident.There is some indication that projections from field P may also be related to binaural columns in AI in the same manner as are the projections from fiel

ISSN:0092-7317    

DOI:10.1002/cne.902030102

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

年代:1981

数据来源: WILEY

摘要:

AbstractPrevious histofluorescence studies have demonstrated that the caudal raphe nuclei (CRa) of the rat, particularly the ventral portion (VCRa), contains a very high density of noradrenaline (NA) terminals and in the present study we attempted to elucidate the origins and free structure of the NA terminals in this region.The majority of NA terminals found in the VCRa originated from A1and A3NA neurons and disclosed that a small number of very strongly fluorescent fibers located along the blood vessels arise from the superior cervical ganglion (SGC). Electron microscopic analysis after potassium permanganate fixation demonstrated that the NA terminals originated from A1and A3NA neurons are connected with neuronal elements, while NA fibers from the SGC were identified among the vascular elements. Axodendritic contacts were found to be predominant among the synapselike contacts of NA terminals in this area.

ISSN:0092-7317    

DOI:10.1002/cne.902030103

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe ingrowth, maturation, and aging of pulpal axons was followed by electron microscopy in permanent mandibular incisors of 44 cats aged 35 days–11 years. The first axons entered the incisor pulps about 2 months after birth. Cells resembling Schwann cells, but lacking an axonal relation, were also observed at this time. Axonal ingrowth and maturation continued until 7 months, when the pulps contained 92–394 axons, 81–88% of which were unmyelinated. Between month 7 and 20 months the character of the incisor pulpal axons remained largely unchanged. In adult cats the myelinated pulpal axons had diameters of 1–6 μm. The relation between the number of myelin lamellae and the axon size correlated better with linear + logarithmic than linear functions. The g‐ratios were higher than in most peripheral nerves, and tended to increase with axon diameter. In the old adult this tendency was more evident and the g‐ratios were generally lower. From 3 years on the incisors displayed various age‐related or pathological alterations. These were accompanied by axonal changes and axon loss. In contrast to earlier stages perineriumlike sheaths were frequent in old teeth. The findings are discussed in relation to axon development in the inferior alveolar nerve and in primary

ISSN:0092-7317    

DOI:10.1002/cne.902030104

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe life history of pulpal axons in primary mandibular incisors was examined by light and electron microscopy in 56 kittens aged from 25 days postconception to 120 days after birth. Cells resembling Schwann cells preceded the first arrival of pulpal axons, 1 week postnatally. Myelination was initiated during the second week. Two months after birth the incisors were fully grown and each pulp contained about 100 axons. Between 10 and 20% of these were myelinated and ranged in size from 1 to 5 μ. The relation between number of myelin lamellae and axon size appeared nonlinear and differed markedly from that in similarly sized inferior alveolar nerve axons. During the third month many unmyelinated axons showed signs of degeneration. With progress of root resorption an increasing proportion of both unmyelinated and myelinated axons degenerated. In highly resorbed incisors necrotic Schwann cells were associated with degenerating axons and there was a generalized pulpal tissue reaction. In some teeth with advanced root resorption pulpal axons were lacking. A progressive derangement of all pulpal tissue elements continued until shedding during the second half of the fourth month. In incisor nerve branches below the incisor teeth axon degeneration was very limited

ISSN:0092-7317    

DOI:10.1002/cne.902030105

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

年代:1981

数据来源: WILEY

摘要:

AbstractWe have studied the laminar position, morphology, and synaptic relationships of neurons in the cat superior colliculus which project to the interadjacent division of the lateral posterior nucleus (LPi), using the retrograde transport of horseradish peroxidase. The neurons which project to LPi are remarkably varied in depth, size, morphology, and synaptic density and appear to consist of at least four cell types. Labeled cells were found in four laminae. Forty‐seven percent were found in the superficial gray layer (50–550μm), all but a few within its deep subdivision. Forty‐seven percent were located in the optic layer (550–1,200μm), the majority of these being within the upper one‐half of the layer. Seven percent were found in the intermediate and deep gray layers (below 1,200μm). Cell body area varied widely, ranging from 37 to 768 μm2(mean of 243μm2). Based on cell size, shape, and dendritic field orientation, we identified four distinct cell morphologies which were labeled. Thirty‐five percent were stellate, 32% were vertical fusiform, 19% were granule, and 12% were horizontal cells. Electron microscope analysis confirmed that neurons projecting to the lateral posterior nucleus are a morphologically diverse group. A sample of 71 labeled cells varied significantly in density of synaptic input as well as in size, shape, depth, dendritic distributi

ISSN:0092-7317    

DOI:10.1002/cne.902030106

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

年代:1981

数据来源: WILEY

摘要:

AbstractSingle and double retrograde tracer experiments were performed in cats in order to investigate the organization of thalamic neurons projecting to the primary (SI) and secondary (SII) somatosensory cortical areas. In one series of animals, horseradish peroxidase (HRP) was injected in either SI or SII, and the distribution of retrogradely labeled neurons was reconstructed in serial coronal and horizontal sections through the thalamus. In a second series of experiments, cats received injections of HRP in SI and tritiated, enzymatically inactive HRP (3H‐apo‐HRP) in SII of the same hemisphere. The results from these experiments provide more exact information than can be obtained in single tracer experiments with regard to (1) the distribution and number of neurons projecting to both SI and SII by way of axon collaterals and (2) the topographical relationship among populations of thalamic neurons projecting to SI, SII, or both targets.SISingle tracer experiments demonstrate, in agreement with previous findings, that, after injection of SI which are focused on the representations of the limbs, heavy retrograde labeling is present throughout VPL. Within this complex, densely and lightly labeled neurons are found consistently and show some preferential pattern of organization. Thus, while both types of neurons are uniformly distributed in VPLl, densely labeled neurons tend to be arranged in clusters, particularly in the ventral portion of VPLm. Outside VPL, moderate but unequivocal retrograde labeling is present in POm, even in cases in which the spread of injected tracer did not encroach upon area 5; labeling of intralaminar nuclei and of a transitional zone between VP and VL, known to receive ascending spinal afferents, is also a consistent feature of all cats with SI injections, although it cannot be excluded that this results from the spread of injected HRP into area 4.SIIFrom cases with injection of HRP in the anterior ectosylvian gyrus, it appears that as the injection site is shifted from posterior to anterior, labeling of neurons in the thalamus shifts from the lateral portion of the posterior group (POl) and the caudal region of the medial portion of this same group (POm) to involve progressively more rostral portions of this nucleus and also VP. Within VP, SII‐projecting neurons are confined primarily within the lateral portion (VPLl) and posterior cap, while in VPLm they are confined mainly to the periphery of this nuclear subdivision and are sparse within its core region. Labeled neurons are also present in the transitional VP‐VL zone.Double tracerSimultaneous visualization of thalamic neurons projecting to SI, SII, or both targets shows that within VP these three neuronal populations are not distributed homogeneously. Rather, their differential distribution defines, on the basis of pattern of their cortical projections, three divisions of the thalamic somatosensory relay: (1) a central core region of VPLm, which contains predominantly neurons projecting to SI; (2) a shell of neuronswithinVPL, in which neurons projecting to SI are homogeneously distributed among neurons projecting to SII and neurons projecting to both SI and SII; and (3) a previously defined outer shell—outsideVPL—which is characterized, as a whole, by widely divergent cortical connections. It is suggested that these three regions, distinguished from one another by their patterns of cortical projection, may correspond to similar differential sites of afferent projections, such that each zone‐core, inner and outer shells—would be dominated by a different as

ISSN:0092-7317    

DOI:10.1002/cne.902030107

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

年代:1981

数据来源: WILEY

摘要:

AbstractA systemic immunological syndrome, graft‐versus‐host disease (GVHD), which does not cause inflammation or cell death in the cerebellum, is shown to retard granule cell production by decreasing the rate of DNA synthesis (S phase) and prolonging mitosis (M), at metaphase. The rate of cell production in diseased animals at postnatal day 14, quantitated by analysis of the rate of labeling of DNA with3H‐thymidine (3H‐Tdr), revealed decreased ability to synthesize new DNA. The number of cells taking up3H‐Tdr label per mm2, as detected by autoradiography, was similar in 14‐day‐old GVHD and control tissue as was the area of the germinal matrix zone and the number of mitotically active germinal cells per mm2in sagittal sections near the midline. However, because the total volume of the cerebellum was less, the total number of mitotically active cells in the whole cerebellum of 11‐, 14‐, and 17‐day‐old diseased animals was less than in littermate controls. Furthermore, DNA synthesis per mitotically active germinal cell was less in diseased animals at each age examined. The mitotic index was unaffected until late in the disease (day 17), suggesting that a prolongation of the cell cycle was responsible for this GVHD‐induced decrease in DNA synthesis. Consistent with a prolongation of the cell cycle was the finding that the mitotic figures in 14‐day‐old GVHD cerebella were mostly metaphase figures, whereas those in control cerebella were, as predicted, mostly prophase. Prolongation of the cerebellar cell cycle in 11‐ and 14‐day‐old diseased animals may explain the dramatic decrease in the mitotic index, the thickness of the germinal matrix zone, and the number of g

ISSN:0092-7317    

DOI:10.1002/cne.902030108

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

年代:1981

数据来源: WILEY

摘要:

AbstractSynaptic emergence and development in the duck olfactory bulb was quantiatively studied by electron microscopy from the 14th day of incubation (E 14) to the adult stage. Overall synaptic density in this bulb grew considerably during the last weeks of embryonic life and the first postnatal week.The pattern of synatpic density development was similar in the four main architectonic layers of the bulb. However, lower density values were observed in the mitral and inner granule cell layers.In the glomerular layer (GL), axodendritic synapse density was always higher than dendrodentritic synapse density. In the external plexiform layer, most synapses were dendrodendritic and were established between the gemmules of the granule cells (GC) and the dendrites of the mitral cells (MC) or tufted cells (TC). Synapses established by MC and TC on GC gemmules, or by GC on MC and TC dendrites had densities very similar to each other at all the stages studied. Reciprocal synapses already appeared at E 14; their density grew until a week after birth (P7) and thereafter remained stable. In the internal granular layer, the density of asymmetrical synapses was always higher than that of symmetrical synapses.Excitatory synapses formed earlier on MC and TC than inhibitory synapses. The ratio of inhibitory‐to‐excitatory synapses rose rapidly after birth, reaching 2.5 in the adult duck. The density of excitatory synapses received by granule cells was as high in the external plexiform layer as in the inner granule layer, at all stages of GC development. However, the ratio of received‐to‐formed synapses fell in these cells from 8.42 at E 14 to 2 after birth. These results are discussed as a function of the evolution of the different synaptic balances during olfactory bulb development.Synaptic development in the duck olfactory bulb at birth is relatively close to the adult state. It appears sufficiently advanced to enable the olfactory system to function in a way compatible with the relatively independent behavior displayed by the d

ISSN:0092-7317    

DOI:10.1002/cne.902030109

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe spatial distribution and temporal disappearance of Rohon‐Beard cells in the spinal cords of larval and newly metamorphosedRana pipienswere studied histologically to provide a basis for further research dealing with this particular cell type. It was found that a maximum number of approximately 250 Rohon‐Beard neurons have differentiated within the spinal cord ofRana pipiensby larval stage I. The majority of these cells are located in the cephalic end of the spinal cord, with a large number found near the boundary of the anterior quarter and the second quarter of the spinal cord. Fewer cells are found in the third and fourth quarters.There is a gradual degeneration of these cells during larval life so that by stage XXV, which is the completion of the metamorphic climax, there are no normally appearing Rohn‐Beard cells present. Degeneration of the Rohon‐Beard cells does not progress cephalocaudally with development, but rather there appears to be a nearly equal proportional loss of Rohon‐Beard cells in each quarter of the spinal cord at each of the stages studied. All Rohon‐Beard cells present during larval development ofRana pipiensare located in a dorsal position, close to the midline. At all ages and in each quarter of the spinal cord there are no significant bilateral differences in number of

ISSN:0092-7317    

DOI:10.1002/cne.902030110

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

年代:1981

数据来源: WILEY

摘要:

AbstractPrevious studies have demonstrated that in goldfish and tench inhibitory interneurons mediating both electrical and chemical inhibition of the Mauthner cell can be identified by a passive hyperpolarizing potential (PHP) which is recorded intracellularly when the latter is firing; some of them are crossed second‐order vestibular cells, the axons of which project ipsi‐laterally and contralaterally to their cell's body in several medullary nuclei. Since PHP‐exhibiting neurons and their target Mauthner cells can be simultaneously impaled, commissural interneurons were intracellularly stained with HRP contained in presynaptic microelectrodes and their synaptic features were correlated with electrophysiological findings. In this study we were able to confirm that commissural neurons are monosynaptically activated by VIIIth nerve afferents and that spikes selectively evoked in these cells produce monosynaptic Cl−‐dependent unitary IPSPs in their adjacent Mauthner cell; in addition to observations related to their general morphology, including their mode of termination within vestibular and reticular nuclei, new data were obtained, most of them with EM techniques. (1) The Mauthner cell is covered by well‐segregated synaptic endings of different shapes; among them, the unmyelinated club endings (which mediate field effect inhibition) penetrate within the peripheral part of the axon cap and terminate on this cell's soma and fine cap dendrites, while the small vesicle boutons which remain outside the axon cap (and can therefore only carry chemical inhibition) impinge on the Mauthner cell's soma and the proximal part of its large dendrites. An important finding was that endings of the two groups were stained by HRP, indicating that most commissural interneurons issue synaptic knobs of these two distinct classes. (2) The fine structure of labeled terminals was investigated: They exhibit the typical aspect of Gray type II synapses, with well‐differentiated presynaptic and postsynaptic differentiations and they contain pleiomorphic synaptic vesicles (mean diameter 40–46 nm; elongation coefficient 1.4–1.5; surface area 13–15.102nm2). A comparison with adjacent unstained equivalent terminals has revealed that HRP allows a reliable analysis of synaptic organelles with, however, a slight tendency of vesicles to be more spherical in presence of the enzyme. (3) Spikes do not propagate actively in unmyelinated club endings but the remaining passively transmitted depolarization is nevertheless above threshold for inhibitory transmitter release, as indicated by unitary IPSPs evoked by fibers terminating exclusively within the axon cap. Thus, club endings have a dual action, and they mediate part of the M‐cell's chemical inhibition. (4) Synapses established by commissural cells on vestibular neurons contain a pleiomorphic population of vesicles; they can be compared to those which were identified in the vestibular nuclei of other species and which were also postulated to have inhibitory functions. (5) The synaptic investment of HRP‐stained commissural neuronal cell bodies included mixed synapses associating gap junctions and active zones established by presumably VIIIth nerve afferents. This observation can be related to the fast‐occurring inhibition produced in both M‐cells by vestibular nerve stimulation. (6) Axons of commissural fibers are myelinated and the largest of them have an internal diameter of no less than 10 μm; the ratio g (axon/total fiber) is close to the optimal value for maximum conduction velocity. Thus, again, these cells are likely to carry the nearly simultaneous ipsi‐lateral and contralateral inhibition of the M‐cell following VIIIth nerve excitation and their widespread distribution suggests a diffuse and synchronous ipsi‐lateral and contralateral inhibitory action on other nuclei as well. (7) In contradiction to electrophysiological results suggesting that some of these neurons were efferent to the labyrinth, a stained process was only observed once in the vestibular tract; this case confirms that commissural cells can project to the labyrinth but its rarity raises questions about the criteria commonl

ISSN:0092-7317    

DOI:10.1002/cne.902030111

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

年代:1981

数据来源: WILEY