摘要:

AbstractGiant ganglion cells (GGC) were demonstrated in retinas of adult dogfish by Golgi impregnation, reduced silver and vital methylene blue staining. All GGC have large, flattened perikarya, and dendrites which radiate in a single horizontal plane of the inner synaptic (plexiform) layer. They are identifiable as ganglion cells by their axons, which after a tortuous initial course enter the nerve fiber layer. We divide the GGC into three varieties: (1) ordinary, with perikarya in the layer of ganglion cells and nerve fibers, and with dendrites radiating in the inner (proximal) one‐fourth of the inner synaptic layer; (2) displaced or Dogiel's cells, with perikarya in the amacrine cell layer and dendrites radiating in the outer (distal) one‐fourth of the inner synaptic layer; and (3) intermediate, with both perikarya and dendritic trees at intermediate levels in the inner synaptic layer.Only the ordinary and displaced GGC in the ventral portion of retinas stained with methylene blue were studied in detail. Cells of both types are arranged in irregular patterns with perikarya about 0.8–1.0 mm apart. Dendrites of the ordinary GGC spread within an elliptical field having a major axis of about 1.7 mm (2.0 mm max) and a minor axis of about 1.5 mm (1.7 mm max). The major axis is vertical in the eye. Dendrites of the displaced GGC spread within a circular field having a diameter of about 1.9–2.0 mm (2.2 mm max). Quantitative comparison of the dendritic trees of ordinary and displaced GGC shows that they differ also in details of dendritic morphology, the dendrites of the ordinary GGC being on the average more numerous and highly branched but shorter than those of the displaced GGC. Ordinary and displaced GGC, therefore, comprise distinct populations which must be presumed to differ functionally.For both ordinary and displaced GGC, the dendritic density and, therefore, the total available postsynaptic surface per unit retinal area decline exponentially with distance from the center to the edge of the dendritic tree. In contrast, the sensitivity to light is constant throughout the receptive field centers of comparable diameter which have been analysed in parallel electrophysiological studies. While the diameters of the largest ganglion cell dendritic fields and receptive field centers are similar, therefore, more detailed correlations of structure and function cannot be made at

ISSN:0092-7317    

DOI:10.1002/cne.901480102

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

年代:1973

数据来源: WILEY

摘要:

AbstractPhotoreceptor and horizontal cells in retinas of the smooth dogfish were impregnated by the rapid Golgi method. Cones as well as rods are present; there are hundreds of rods per cone. The rod synaptic endings are small spherules which send out basal processes (telodendria). The cone synaptic endings are large pedicles which also extend telodendria.Horizontal cells of three distinctive varieties are segregated in vertically separate layers.Horizontal cells of the first (external) roware thick and cuboidal. They send out processes which enter into the invaginations in rod spherules. These cells and their processes cover a circular to elliptical field measuring 75–125 by 125–200 μm. They probably contact every rod in this field.Horizontal cells of the second (intermediate) roware flattened and stellate. Their processes also enter into the rod spherules. These cells cover a circular to elliptical field slightly larger than that covered by cells of the first row. Although they appear not to contact every rod in their field, the fields of adjacent cells of this type overlap. Every rod, therefore, probably contacts one horizontal cell of the second row as well as one of the first row.Horizontal cells of the third (internal) roware stellate, with a few long cylindrical horizontal processes. Finer vertical processes go from these to contact cone pedicles. Probably each cone contacts one such process, and each third‐row horizontal cell contacts on the order of ten cones. Although somewhat uncertain, the size, shape, and degree of overlap of the fields covered by third‐row cells are probably not very different from those of first‐ and second‐row cells. The vertical sequence of horizontal cells which contact rods or cones in dogfish is inverted from that

ISSN:0092-7317    

DOI:10.1002/cne.901480103

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

年代:1973

数据来源: WILEY

摘要:

AbstractRetinal bipolar cells of the smooth dogfish (Mustelus canis) were examined in the light microscope after vital staining with methylene blue or in Golgi‐impregnated preparations. Bipolars ofMustelusretina, as of other vertebrate retinas, were divisible into two broad categories: those with fine axons and those with bulbous axonal terminals. Further classification was made on the basis of the level of axonal termination within the inner synaptic layer (ISL). Thewide, monostratifiedaxons of some bipolar cells (typea1) ramify in the distal (outer) third of the ISL to a total horizontal span of 400–600 μm. These cells possess elliptical dendritic arbors 80–100 X 150–200 μm in diameter, variously shaped perikarya, and a cylindrical or bulbous Landolt's club. In flatmounted preparations, these cells often are seen to have all dendrites exiting horizontally from one side of the perikaryon, the axon exiting horizontally from the other side. Thenarrow, multistratifiedaxons of a second class of bipolars (typea2) ramify within the distal half of the ISL to a horizontal span of 45–130 μm. Their dendritic arbors are round or elliptical and of a diameter similar to that of axonal spread. A filamentous or flask‐shaped Landolt's club is generally present. The axons of bipolars withbulbousaxonal terminals (typeb) end in the middle of the ISL. The perikaryon is tulip‐shaped and a circular dendritic arbor, 70–100 μm in diameter, spreads concentrically about it. These cells always lack a Landolt's club. In the proximal (inner) half of the ISL, both wide monostratified (typec1) and narrow multistratified (typec2) bipolar cell axons are encountered. The axons of cells which have monostratified endings in theproximalISL (typec1) branch more frequently and have lesser horizontal extents than the axons of their counterparts (typea1) in thedistalISL. All bipolars ending in the proximal ISL lack a Landolt's club. The thick ISL ofMustelusretina is divided into at least three vertical sub‐layers, within each of which terminate axons of one or two classes of bipolar cells and dendrites of a single class of giant ganglion cells. If giant ganglion cells receive direct synaptic input from bipolar cells, the vertical strata of the ISL contain structurally distinct, and perhaps functionally different, bipolar

ISSN:0092-7317    

DOI:10.1002/cne.901480104

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe paleostriatal complex (PC) of the pigeon lies in the basolateral wall of telencephalon, and consists of three major subdivisions: the paleostriatum augmentatum (PA), paleostriatum primitivum (PP), and nucleus intrapeduncularis (INP). The lobus parolfactorius (LPO) lies on the medial aspect of PA and has often been considered to be part of PA. The present study of afferent and efferent connections of the paleostriatal complex supports earlier previous suggestions that the PC is directly comparable to the basal ganglia of mammalia. High concentrations of acetylcholinesterase were found in the PA, LPO and INP. Intense yellowish green fluorescence, probably dopamine, was confined to the PA and LPO.Stereotaxic lesions were placed in either the dorsal ventricular ridge structures above the PC (neo‐ and hyperstriatum), PA, LPO or PP‐INP, and animals sacrificed from one to six days postoperatively. The brains were stained with the Fink‐Heimer methods for the demonstration of degenerating axons and terminals. The region of the neo‐ and hyperstriatum was found to project upon the PA, in a seemingly topographic manner. PA was found to project topographically upon the PP and INP. In contrast, the LPO contributed to the medial forebrain bundle, terminating in the rostral lateral hypothalamus. LPO does not appear to project to the PP or INP.Lesions of PP‐INP resulted in massive degeneration of a descending tract, the ansa lenticularis. Terminal degeneration was found in the anterior and posterior nuclei of the ansa lenticularis of the ventral diencephalon, nucleus dorsalis intermedius posterior and nucleus spiriformis lateralis of the dorsal thalamus, and the nucleus tegmenti pedunculopontinus pars compacta et disseminata of the isthmic tegmentum. In these several features of histochemical and hodological organization the PC alone appears similar to the caudate‐putamen and globus pallidus complex of mammalian brains.More specifically, the PA resembles the caudate‐putamen, whereas PP and INP resemble the external and internal divisions of the globus pallidus, respectively. Similarities and differences between avian and mammalian brains, and the relationship of the present study of the PC and previous studies of the dorsal ventricular ridge structures are discussed (Karten, '69; Nauta and

ISSN:0092-7317    

DOI:10.1002/cne.901480105

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

年代:1973

数据来源: WILEY

摘要:

AbstractAn invaginating bipolar cell that has dendritic terminals forming the central elements of the cone triads is described for the retina of the cat. This type of bipolar contacts a minimum of four or five and a maximum of nine or ten cones. There is no evidence for a bipolar cell which contacts only one cone, i.e., a midget bipolar cell as in simians. There are flat bipolar cells that make superficial contacts with the bases of the cone pedicles and are postsynaptic to between 8 and 14 cones. One cone can be in contact with both an invaginating and a flat bipolar cell. There is evidence suggestive of two kinds of flat bipolars. A comparison is made between the bipolar connections in simians and the cat. The comparison is summarized in figures 29 and 30.

ISSN:0092-7317    

DOI:10.1002/cne.901480106

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe large peripheral horizontal cells of the retina of the rhesus monkey are compared with the smaller horizontal cells of the central area. There is most probably only one morphological type of horizontal cell in the rhesus monkey retina. Its dendrites go into cones and it has a single axon. From the fovea to the periphery of the retina there is a gradation in the number of cones an individual horizontal cell contacts. In the fovea a horizontal cell contacts six to nine cones; this ratio increases towards the periphery to between 30 and 40 cones to one horizontal cell.

ISSN:0092-7317    

DOI:10.1002/cne.901480107

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

年代:1973

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901480101

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

年代:1973

数据来源: WILEY