摘要:

AbstractHistological sections of the brains of eight species of turtles representing six different families were studied in order to delineate the cochlear nuclei. In addition, the posterior eighth cranial nerve root and its ganglion were sectioned in 15 specimens ofKinosternon leucostomum, and the distribution of the degenerated nerve fibers and terminals was determined. Two primary and one probably secondary nuclei were demonstrated by the terminal degeneration pattern of the cochlear fibers.A spherical nucleus angularis and an elongated nucleus magnocellularis together form a column of primary cochlear nuclei in the dorsal alar lamina of the medulla. Heavy terminal degeneration is seen associated with these cells following transection of the posterior eighth nerve and ganglion. Nucleus magnocellularis is probably homologous with the nucleus magnocellularis medialis of lizards and crocodiles, and has been described in turtles as nucleus dorsalis magnocellularis by previous authors.A probably secondary cochlear nucleus, nucleus laminaris, lies just ventral to the nucleus magnocellularis. It is associated with the nucleus magnocellularis throughout its length but is shorter. Nucleus laminaris remains free of terminal degeneration after destruction of the posterior eighth nerve and ganglion.The cochlear nuclei of other turtle species were very similar to those ofKinosternon leucostomum.

ISSN:0092-7317    

DOI:10.1002/cne.901850202

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractThe development of Purkinje cell dendrites was studied in the bullfrog from premetamorphic tadpoles to 10‐week‐old postmetamorphic froglets by the Golgi‐Kopsch method. In this species two distinct patterns of arbor formation may be seen, which appear to be related to differences in the timing of initial dendritic development. In Purkinje cells that begin development in early tadpole stages, the dendritic tree is elaborated by continuous and concomitant growth and branching, a process by which the developing arbor expands in both height and width. Arbor formation in Purkinje cells that begin development in metamorphosing tadpoles proceeds in two separate steps. Initially, dendrites of such cells elongate, but form only a few poorly developed branches; only when the arbor reaches near‐adult height does branching become extensive. Additional differences present in Purkinje cells are reflected in the paucity of growth cones and filopodia in the tadpole, and numerous filopodia and growth cones in the metamorphic period. An interesting feature of dendritic development in this species is a tendency to alter the arboreal domain by the formation of extra‐arboreal dendrites, and possibly by the occasional resorbtion of other partially formed dendrites.The pattern of dendritic development in the frog is different than in mammals and is difficult to interpret. Such unusual development may be due to disturbances in the timing of the formation of Purkinje cell dendrites and of the establishment of the external granular la

ISSN:0092-7317    

DOI:10.1002/cne.901850203

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractSensory neocortex of the tree shrew was divided into three main areas: the visual field, the auditory field, and the somatic field which includes motor cortex. Cortical cells which project to the tectum were identified by injecting HRP into superficial or deep layers of the superior colliculus and into various parts of the inferior colliculus. The main result is that these descending projections are well organized according to their origin in the three main sensory fields of the cortex. (1) Auditory field: labeled cells are found only in the core or auditory koniocortex, after injections of HRP in the pericentral area of the inferior colliculus; labeled cells are found in auditory belt areas after injections in posterior parts of the intermediate and deep layers of the superior colliculus, adjacent to the inferior colliculus. (2) Somatic field: labeled cells are also found in the somatic field after injections in the intermediate and deep layers of the superior colliculus, so that auditory and somatic fields probably overlap to some extent. The results do not exclude the possibility that somatic koniocortex has an exclusive target in the intermediate or deep layers of the superior colliculus. (3) Visual field: labeled cells are found only in the core or striate cortex after injections in the superficial layers of the superior colliculus. Labeled cells are found in the visual belt after injections in the rostral parts of the intermediate layers of the superior colliculus. When these results are related to ascending sensory pathways a picture emerges of a series of circuits or loops which interconnect parallel sensory pathways. These loops eventually reach the deep layers of the superior colliculus which of course have indirect access to motor neurons.

ISSN:0092-7317    

DOI:10.1002/cne.901850204

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractThe electrogenic developmental phase of the electric organ ofTorpedo marmoratabegins at 40 mm of embryo length and is characterized by a horizontal flattening of the vertically orientated myotubes. The first sign of this process is a rounding up of the ventral poles of the myotubes and a disassembly of the myofibrils located therein. Occurring concomitantly with this is a migration of the nuclei to the cell center which results in a horizontal plane of nuclei. Filament bundles are then found within the ventral cytoplasm often projecting upwards from the ventral plasma membrane. The filaments of the bundles are dimensionally similar to the myofilaments of muscle and it is suggested that the bundles play a role in cellular transformation.In contrast the dorsal pole of the cell appears to be integrated “passively” with the final cell shape as no morphological correlates of a retraction process have been found. A canalicular system, composed of a complex network of irregular tubules and vacuoles, appears just below the dorsal plasma membrane characterizing this region of the cell. A mononucleated satellite cell population lies in close proximity to the dorsal surface of the differentiating cell and fusion between the two cell types occurs throughout development.Cell shape transformation is complete by 55 mm of embryo length and the intercolumnar nerves begin to invade the interelectrocyte space. The ingrowing neurites preferentially course along the ventral electrocyte surface establishing junctions similar to motor endpla

ISSN:0092-7317    

DOI:10.1002/cne.901850205

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractIf cats are raised with monocular lid suture, cells in dorsal lateral geniculate (DLG) laminae which receive inputs from the deprived eye are smaller than normal when the animals reach maturity. Previous studies have shown that after a critical period of development, these morphological changes cannot be reversed by closing the initially experienced eye and opening the initially deprived eye (reverse suture). The present experiment investigated whether removal of the experienced eye, a procedure which rapidly reverses some of the physiological effects of monocular deprivation on striate cortex neurons (Kratz et al., '76), also would produce a reversal of the effects of monocular deprivation on DLG cell size. In addition, if a morphological reversal in DLG cell size could be observed, we were interested in knowing its time course relative to the physiological reversal in striate cortex.Nine control kittens were raised with monocular lid suture until they were four to eight months old (group MD). Comparison with a group of six normally reared kittens (group N) showed the usual effects of monocular deprivation on DLG cell size (cross‐sectional area) which have been reported previously; i.e., a marked reduction in cell size in the deprived binocular segments of laminae A and A1, and a smaller reduction in cell size in the deprived monocular segment of lamina A. Ten additional kittens were raised with monocular lid suture until they were four to five months old, at which time the experienced eye was enucleated. Five of these kittens (group MD‐DE‐Immed) were allowed to survive 30 hours after the enucleation. There was no significant difference in DLG cell size between these animals and the MD control animals. The remaining five kittens (group MD‐DE‐3 mo) were allowed to survive three months after enucleation of the experienced eye, and the deprived eye remained closed during this time. In these kittens, cells in the deprived DLG laminae were significantly larger than cells in the deprived laminae of kittens in both the MD‐DE‐Immed and the MD control groups. In addition, they were not significantly different from normal. The increased cell size in the MD‐DE‐3 mo cats was present in the deprived binocular segments of both laminae A and A1, and to a lesser extent in the deprived monocular segment of lamina A. Cell sizes also were measured in the deafferented (initially experienced) laminae of cats in the MD‐DE‐Immed and MD‐DE‐3 mo groups. They showed a slight decrease in size relative to DLG cells in the experienced laminae of MD control cats.These results indicate that deprived DLG cells can resume their growth after the previously defined critical period. Comparisons with previous studies indicate that it is necessary to completely remove the inputs from the experienced eye for the new growth to occur. However, it is not necessary to provide the deprived eye with visual experience. In addition, the increase in deprived DLG cell size occurs sometime after the increase in ability of the deprived eye to drive striate cortex cells (Kratz et al., '76). Thus, the functional recovery of cortical cells precedes the morphologi

ISSN:0092-7317    

DOI:10.1002/cne.901850206

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractThe morphology of the lateral cervical nucleus (LCN) and the organization of the cervicothalamic projection neurons were studied in cats which had received thalamic injections of horseradish peroxidase (HRP). The boundaries of the LCN were defined following very large thalamic HRP injections. Roughly 92–97% of LCN cells project contralaterally to thalamus; an additional 1‐5% project ipsilaterally. Computer‐assisted measurements of perikaryal areas demonstrated that there are two sizes of LCN cells, large (175–900 μm2) and small (<175 μm2); the small cells are localized in the medial third of the LCN. LCN cells which are not labeled after large thalamic HRP injections are predominantly small, medially‐located neurons.Small HRP injections into physiologically identified regions of ventroposterior thalamus demonstrated that cervicothalamic neurons are organized in a topography consistent with that observed physiologically in the LCN (Craig and Tapper, '78). Dorsolateral LCN cells are retrogradely labeled fromnucleus ventroposterolateralis, pars lateralis(VPL1), ventromedial LCN cells are labeled frompars medialis(VPLm), and a few medial cells are labeled fromnucleus ventroposteromedialis(VPM). A few cells in the medial portion of the LCN are also labeled from each part of ventroposterior thalamus. Some interspersion was observed even in the cases with the most well‐restricted labeling. We conclude that the LCN maintains a basic somatotopographic organization with an inherent variability, certain aspects of which are consistently demonstrable both physiologically and anatomically. Evidence was also obtained suggestive of a rostrocaudal inversion in the cervicothalamic projection. The cervicothalamic projection, the differentiation of the medial LCN subpopulation, and the possible redefinition of the LCN are discussed in light of

ISSN:0092-7317    

DOI:10.1002/cne.901850207

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractConsiderable evidence has accumulated indicating that one neurotransmitter in the excitatory cortico‐striatal tract is glutamate. Lesions of the tract result in reductions in the striatum of glutamate levels as well as high affinity uptake of glutamate into synaptosomes. Furthermore, such lesions leminate the neurotoxicity of the glutamate analog kainic acid when injected into the striatum. The fine structure of the cortico‐striatal pathway was studied to provide evidence regarding the morphology of glutamate nerve endings.Seven days after injection of3H‐proline (20–25 μCi) into the rat frontal cortex, axonally transported label appeared in the striatum with uniform distribution in a single type of nerve ending. The labeled boutons had common round vesicles and made asymmetrical contacts, mostly with dendritic spines. This morphology is typical of excitatory synapses, and similar to that previously shown for cholinergic boutons in the striatum.In four animals similarly injected with3H‐proline, kainic acid was administered directly into the striatum to induce degeneration of postsynaptic elements eight to ten hours before sacrifice. In areas affected by these injections, grains appear in pathches, possibly resulting from glial swelling. Labeled boutons were seen almost four times as often in synaptic contact with degenerating dendritic elements as with normal ones. The data provide morphological evidence as to the nature of the probable glutamatergic boutons in the striatum, and show the close relationship of such boutons with the neurotoxic effects of kainic acid. This would be anticipated in view of the dependency of kainic acid neurotoxicity on the intergrity of the cortico‐stri

ISSN:0092-7317    

DOI:10.1002/cne.901850208

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractAnatomical tracers were injected into electrophysiologically defined sites in somatosensory cortical Area 3b (SI proper) and Area I (posterior cutaneous field) of owl monkeys after these cortical subdivisions had been extensively explored in microelectrode mapping experiments. These mapping experiments revealed that both Areas 3b and 1 contain complete and separate representations of the body surface (Merzenich et al., '78). Restricted injections of the retrograde tracer, horseradish peroxidase (HRP), into either Area 3b or Area 1 labeled neurons within a band of cells in the ventroposterior nucleus (VP). The location of the labeled band in VP varied with the location of the injection site in both representations, and the labeled region of VP was overlapping for injections in corresponding body parts in the two representations. Neurons projecting to the hand and foot cortical representations were in architectonically identified subnuclei. Because injections into either Area 3b or Area 1 labeled over half of the neurons in the appropriate regions of VP, it appears that some neurons in VP project to both cortical representations. Finally, injections of HRP combined with the anterograde tracer,3H‐proline, indicate that VP neurons are reciprocally interconnected with both Areas 3b and

ISSN:0092-7317    

DOI:10.1002/cne.901850209

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractWe report a light‐ and electron‐microscopic examination of the inner plexiform layer of the central retina of young (c. 1 year) and old (3–4 year) goldfish. There were no new neurons added to this region during the growth period. Nonetheless, there were substantially more synapses (per cell, per mm2, or per degree2) in the older retinas. This result is discussed in the contexts of retinal function and neural develo

ISSN:0092-7317    

DOI:10.1002/cne.901850210

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase (HRP) was used to determine whether neurons in the rat superior cervical ganglion (SCG) are localized in regions of the ganglion as a function of the postganglionic trunk they utilize. In separate experiments, each of the two major postganglionic trunks was cut 1–3 mm from the SCG and solid HRP was applied to the cut end proximal to the ganglion. The results demonstrated that the cell bodies of neurons whose axons project out the internal carotid nerve (ICN) were located primarily in the rostral part of the ganglion. Cell bodies of neurons whose axons project out the external carotid nerve (ECN) were located primarily in the caudal part. The total percentages of neurons with axons in the ICN and ECN were about 35% and 45% respectively. When HRP was applied to both these trunks, 73% of the neurons in the SCG were labeled. In the caudal portion of the ganglion, an additional group of neurons was observed whose axons project into the cervical sympathetic trunk. Control studies indicated that the neuronal labeling observed in our experiments was due to retrograde axonal transport rather than the direct uptake of HRP by neuronal cell bodies. Thus, neuronal subpopulations exist in specific regions of the rat SCG. The significance of these results to biochemical and electrophysiological studies is discusse

ISSN:0092-7317    

DOI:10.1002/cne.901850211

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY