摘要:

AbstractThe heads of Long‐Evans rats were irradiated from the fourth day after birth with a schedule of repeated doses of low‐level x‐ray which essentially prevented the formation of basket, stellate and granule cells in all except the earliest‐forming lobules (nodulus and uvula). The morphogenic and synaptogenic effects of this treatment were examined with light and electron microscopy in 30 day old animals, with particular attention paid to the pyramis. Although when irradiation was started the Purkinje cells formed a monolayer and had upward oriented apical poles, they became scattered later and had randomly oriented dendrites. This secondary disorientation was attributed to insufficient space available in the arrested cerebellum for the rapidly expanding Purkinje cells. Although basket cell terminals were scarce, basket cell‐like terminals were formed on the somata of Purkinje cells, apparently by recurrent axon collaterals of these cells. The most common synapses with the thorns of Purkinje dendrites were formed by climbing fibers but other elements, including glial processes, were also in contact with postsynaptic loci on the thorns. Many mossy fiber terminals reached the surface. Where parallel fibers were present they were often thicker than in unirradiated animals and contained neurofilaments. No pathological changes were seen in these cerebella, with the possible exception of excessive lobulation of the nuclei of many Purki

ISSN:0092-7317    

DOI:10.1002/cne.901490202

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe heads of Long‐Evans hooded rats were irradiated daily from day 3, 4 or 6 onward with schedules of low‐level x‐ray which differentially delayed the regeneration of the subtotally eradicated external germinal layer or prevented its regeneration altogether. Most schedules that permitted regeneration led to the arrest of many granule cells in the molecular layer where they formed an ectopic zone. The dendrites of ectopic granule cells had synapses with mossy fibers located in their vicinity in the molecular layer. The position of the ectopic zone varied in different lobules depending on several factors: the time when regeneration began, the estimated date of descent of granule cells, regional differences in cortical maturation and in the estimated upward growth rate of mossy fibers. Within the same lobule, the longer regeneration was delayed the higher in the molecular layer the differentiating and descending granule cells were captured by the apparently autonomously ascending mossy fibers. If regeneration started early and allowed the descent of granule cells into the granular layer (early irradiation) or if regeneration of granule cells was prevented altogether (late irradiation) an ectopic zone was not formed. The technique was used for estimating the normal growth pattern of mossy fibers in the different lo

ISSN:0092-7317    

DOI:10.1002/cne.901490203

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe heads of Long‐Evans hooded rats were irradiated with a schedule of low‐level x‐ray which allowed regeneration of the external germinal layer. In the subsequently regenerated molecular layer, parallel fibers were often reoriented. In some cerebella this was restricted to a single lobule, frequently several lobules were affected, rarely almost the entire vermis. It was postulated that the reorientation of parallel fibers was determined by the invasion route of multiplying cells from spared foci of the external germinal layer. Where parallel fibers were rotated transversely, the axons of basket cells and the arborizing dendrites of Purkinje cells became oriented longitudinally. This, and other considerations indicated that parallel fibers exert a guiding influence on the pattern of growth of the spiny branchlets of Purkinje

ISSN:0092-7317    

DOI:10.1002/cne.901490204

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe brain and spinal cord of one adult sea lamprey,Petromyzon marinus, 12 cm in length, were fixed in glutaraldehyde and osmium, stained in toluidine blue, embedded in Araldite, and sectioned serially at 5 μ. Over 50 large axons were traced through the spinal cord to their probable cells of origin.The axon of one giant interneuron was followed from the posterior spinal cord rostrally into the lateral medulla of the brain.A formerly unrecognized pair of Müller axons was found to originate from the reticular cells I2.An unusual feature of some Müller axons was their migration out of the ventral columns and their subsequent branchi

ISSN:0092-7317    

DOI:10.1002/cne.901490205

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

年代:1973

数据来源: WILEY

摘要:

AbstractAn investigation of the habenular nuclei in tadpoles, young frogs, and fully matured Rana temporaria, revealed several consistent left‐right asymmetries. In tadpoles and young frogs, the left nucleus is partially divided by a vertical septum; lacks cells adjoining the third ventricle along part of its length; and contains fewer free cell bodies in its lumen than the nucleus on the right. In addition, the beginnings of a second nucleus on the left can be seen, lateral to the much larger main left nucleus. The fully grown adult has two distinct left habenular nuclei and only one on the righ

ISSN:0092-7317    

DOI:10.1002/cne.901490206

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe organization of the seventh lumbar dorsal root ganglion (DRG) of the cat has been investigated both anatomically and electrophysiologically. In the first two series of experiments an attempt was made to relate the topographic location of identified groups of cells in the ganglion with the rostro‐caudal position of their central processes in the filaments of the dorsal root.3H‐proline was injected into various sectors of the ganglion and the distribution of the axonically transported proteins, in individual dorsal rootlets, was determined by means of liquid scintillation spectroscopy and the location of the injections was determined by autoradiography of the sectioned ganglia. The projection pattern was also determined by antidromically activating DRG cells in various parts of the ganglion by sequentially stimulating each of six dorsal root filaments. The results of both groups of experiments indicate that cells located in the medial (caudal) parts of the ganglion project into the most caudal rootlets of the dorsal root; cells in the most lateral (rostral) parts of the ganglion project into the most rostral rootlets, while cells in the intermediate parts of the ganglion project into the middle rootlets. In a third series of experiments, a shifting pattern of overlapping receptive fields was demonstrated for a series of recordings that traversed the ganglion from medial to lateral. This pattern was shown to be nearly equivalent to the organization of receptive fields previously demonstrated by Kuhn ('53) for a rostral to caudal sequence of dorsal rootlets, i.e., foot and leg preaxial fields predominated in the lateral sectors, while postaxial fields were found in the medial sectors of the gangl

ISSN:0092-7317    

DOI:10.1002/cne.901490207

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe anlage of the substantia nigra compacta and the area ventralis tegmenti appears as a fluorescent zone in the midventral proliferation in the caudal mesencephalon of the rabbit at day 14 of gestation. Fluorescence is present in cell bodies and their processes in the mantle layer of the basal plate just ventral to the ependymal zone. By day 16 of gestation, the number of fluorescent cells and processes has increased, and they form an inverted “V” shaped zone in the midline mantle layer. A fluorescent fiber tract, the presumptive mesolimbic and nigroneostriatal pathway, extends from the fluorescent zone through the lateral hypothalamus as far as the caudal portion of the telencephalon. Electron microscopic studies of the inverted “V” shaped anlage show that most of the cells are spindle‐shaped bipolar neuroblasts, but some globular neuroblasts are present as well. The large 800 to 1000 Å dense core vesicle is found in the perikarya of the neuroblasts and also in processes in the neuropil. Axonal growth cones are common, but synaptic profiles are rare.By day 18 of gestation, some of the fluorescent cell bodies have migrated lateral to midline and as far rostral as the central portion of the midbrain. Fluorescent axons of the presumptive nigroneostriatal pathway have reached the putamen and have formed minute varicose terminals. These axons, therefore, have reached their terminal nucleus before their cell bodies have finished migrating to their final positions. Electron microscopic study of the anlage located lateral to midline shows that the cells are multipolar and exhibit extensive new growth of dendrites. Immature synaptic profiles and a few mature junctions are occasionally found in the neuropil.By day 20 of gestation, a distinct substantia nigra compacta and reticulata can be recognized lateral to the area ventralis tegmenti. The neurons of the substantia nigra have relatively abundant perikaryal cytoplasm and the cells are frequently adjacent to one another. The perikarya of the area ventralis are some what smaller and they are spaced more widely apart. Large dense core vesicles are present in some perikarya of both regions. Synaptic terminals are more common, but still not numerous. The meso‐limbic and nigroneostriatal pathway are well established a

ISSN:0092-7317    

DOI:10.1002/cne.901490208

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

年代:1973

数据来源: WILEY

摘要:

AbstractBecause sloths are among the slowest moving of mammals, it is of interest to determine whether the rate limiting factor is in their motivation, central nervous system, or their muscles.Muscle characteristics of ten sloths (Choloepus hoffmanni and Bradypus tridactylus) were studied by neuromuscular examination, electrophysiological, biochemical, and histological methods. Muscle twitch contraction averages 120 msec and one‐half relaxation time was 108 msec. Muscle contraction and relaxation are extremely sensitive to cold but were unaltered by calcium, quinine or procaine amide.Biochemical studies showed ATPase activity to be extremely low.Ultrastructure conformed closely to that of mammalian twitch fibers.Our data suggest that although muscle mechanics undoubtedly contribute to the slow movements of the sloth, they are not the only rate limiting facto

ISSN:0092-7317    

DOI:10.1002/cne.901490209

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.901490201

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

年代:1973

数据来源: WILEY