摘要:

AbstractThe main purpose of this study was to examine the normal postnatal development of ocular dominance columns in the striate cortex of the macaque monkey and to determine how this developmental process is influenced by monocular lid‐suture. The physiological pattern of ocular dominance was studied in long, tangential electrode penetrations. For anatomical demonstration of the distribution of afferents we relied principally on the transneuronal transport of [3H]proline injected into one eye, and to a lesser extent on the Liesegang silver method. The effects of deprivation on cell size in the lateral geniculate nucleus (LGN) were also studied. Twenty‐six monkeys, divided into 5 groups (A–E), were used.AThe process of normal columnar development was examined in four monkeys aged from 1 to 6 weeks. At one week, there was both an anatomical and a physiological mixing of left‐ and right‐eye inputs to layer IVC, but the basic columnar pattern was evident, and some small regions were already monccular. At three weeks the columnar pattern resembled that seen in the adult, except for a suggestion that the borders between columns were not so sharply demarcated. By six weeks an adult degree of columnar segregation was established.BA series of ten monkeys had monocular suture performed at successively later ages, ranging from 2 days to adult, and they were allowed to survive for a long period. It was found that deprivation begun at any age from birth to about 6 weeks had approximately the same effect: the afferents for the open eye formed greatly expanded columns in layer IVC, and the columns for the closed eye were shrunken and fragmented. In the layers above and below IVC the open eye dominated almost completely. At 10 weeks, closure had only a mild effect on columnar size in layer IVC. With closures at 7–14 months there was no change in the size of columns in layer IVC, but when stained with the Liesegang silver method the deprived‐eye columns were paler than those for the open eye, suggesting a lower density of fibers. These late deprivations still caused a shift of ocular dominance in the upper cortical layers but not such an extreme change as with earlier closures. Lid suture in an adult had no detectable anatomical or physiological effects. Even monocular enucleation, in an adult, failed to induce sprouting of the geniculocortical afferents for the remaining eye.CIn order to investigate the rate at which monocular deprivation produces its effects, six monkeys were examined after short periods of deprivation in infancy. Eye‐closure from birth to 3 weeks was sufficient to produce the full anatomical and physiological effects. A nine‐day closure at 3 weeks, followed by reopening of the eye, also produced the full effects. A two‐week period of deprivation begun at five weeks of age, however, caused relatively mild columnar expansion in layer IVC, suggesting that late closures may require more time to produce anatomical changes than early closures.DThe effects of reopening the deprived eye and closing the experienced eye (reverse suture) were studied in three monkeys. The initial lid sutures were performed in the first few days of life. With reverse suture a t 3 weeks the relative sizes of the two sets of columns were reversed. This anatomical reversal was, however, limited to the afferents from the parvocellular laminae of the LGN; the magnocellular afferents remained in the pattern induced by the early deprivation. The layers outside of IVC were strongly dominated by the initially deprived eye. Reverse suture at 6 weeks allowed an anatomical recovery of the parvocellular afferents to a normal columnar size, but not a complete reversal. Again, the magnocellular afferents for the initially deprived eye were not induced t o enlarge their territory. Reverse suture at 1 year of age did not lead to any recovery.EOne monkey was reared in complete darkness from 3 days of age until 7 weeks of age. This animal, studied autoradiographically, showed a normal columnar pattern in layer IVC.We draw four conclusions from these experiments. (i) Ocular dominance columns are only partially formed a t birth but develop rapidly in the first few weeks of postnatal life. The process of segregation of the left‐ and right‐eye afferents‐in layer IV occurs in the presence or absence of visual experience. (ii) This developmental process may be redirected by early monocular deprivation, causing the segregation of the two sets of afferents into columns of unequal width, (iii) A rearrangement of the afferents can be induced for a short period after their segregation is complete. This is true of both normal and deprived animals. (iv) The eye preference of neurons in the upper and lower layers may be changed even after plasticity in layer‐

ISSN:0092-7317    

DOI:10.1002/cne.901910102

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe development of a group of club‐shaped sensilla called clavate hairs, located on the cerci of the cricket (Acheta domesticus), was examined morphologically. The clavate hairs are located on the base of the cercus and are thought to inform the animal of its orientation with respect to gravity. There are two groups of clavate hairs distinguished from one another by the orientation of their sockets: a dorso‐medial group whose sockets are oriented perpendicular to the long axis of the cercus and a ventro‐medial group inclined 45–60° away from the perpendicular. The ventro‐medial group consists of a series of rows of sensilla running parallel to the long axis of the cercus.By examining a cast‐off exoskeleton in the scanning electron microscope and comparing it with newly developed cuticle of the subsequent instar (Fig. 3), we showed how receptors were added to the ventro‐medial array of clavate hairs. The first ventral hair (#10, Fig.1) appeared in the second instar. Three more hairs were added in the third instar: two (#11 and #12) proximal to hair 10 forming the first row and one (#20) medial to 11 and initiating the second row. After the third instar one hair was usually added proximal to each row each time the specimen molted. Because of the regular positioning of hairs and their orderly addition to the array, it is possible to identify uniquely all of the hairs in the three largest rows of ventral hairs (Fig. 4).We developed a simple method for staining the neuron associated with each hair. A hair was injured by cutting off its tip. A bubble of cobaltous acetate was then placed on the hair for 18–20 hours and only the neuron associated with the injured hair took up the stain.The synaptic terminal arborizations of identified neurons examined in this manner were unique and reproducible from specimen to specimen (Fig. 6). Furthermore, there is a topographic order to the terminal arborizations. Within one row the oldest neurons project furthest into the nervous system and arborize over the greatest area, whereas younger neurons arborize in more restricted areas near the entrance of the cercal nerve. Thus it was concluded that birthday was corretated with the morphology of the synaptic arborization.By staining neurons that were the same age but located in different rows, we determined that birthday was not the only variable influencing the morphology of the terminal arbors. The terminal arbors of neurons 11 and 20, both of which first appear in the third instar, were very different from one another. Thus another variable, presumably position on the body surface, was also correlated with the morphology of a neuron's terminal arborization. We concluded from these results that position on the cercus as well as birthday is encoded in the developmental program of these neurons and that the morphology of their terminal arborizations is a joint function of the

ISSN:0092-7317    

DOI:10.1002/cne.901910103

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractParavertebral sympathetic ganglia from the lumbosacral region of a series of chick embryos have been studied with electron microscopic methods, including aldehyde‐osmium and permanganate fixatives, and correlative histofluorescence (Grillo et al., '74). Our purpose was to assess the differentiation of catecholaminergic (CA) cells during histogenesis in ovo. Examination of comparable adult ganglia as a baseline for differentiating stages confirmed that the principal sympathetic neuron (PN) is similar to those of other species in that it contains predominately small dense‐cored vesicles (SDCV) preserved only by permanganate, and does not histofluoresce following the method of Grillo et al. ('74). At embryonic day (E) 7–8, when ganglia have just formed, areas fluorescing bright yellow‐green are correlated with two types of cells: (1) Neuroblasts with vesicular nuclei and large dense‐cored vesicles (LDCV) are common. As the neuroblasts grow and differentiate, LDCV move away from perikaryal cytoplasm into developing processes. Around E13–15, SDCV appear in the neuroblasts which continue to develop until they resemble miniature adult PN in late embryos and hatchlings. (2) Granule (GR) cells with clumped chromatin and sparse cytoplasm are clustered in the ganglionic periphery at E7–8, but are rare. The GR cells increase somewhat in size and numbers by E11, but retain essentially the same characteristics as at earlier stages. Neither bright fluorescence nor GR cells appear later than stages E13–15. These results are interpreted to mean that when chick sympathetic stem cells have migrated from the primary ganglia into the paravertebral ganglia, they give rise to two separate lines of CA cells, one of which is not maintained and subsequently disappears. The results are significant as a basis for understanding how a mixed population of CA cells might arise within sympathetic

ISSN:0092-7317    

DOI:10.1002/cne.901910104

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe activity and distribution of the cholinergic neurotransmitter enzymes acetylcholinesterase (AChE) and choline acetyltransferase (ChAc) in the developing cerebellum of the mouse were investigated using biochemical assays and light microscopic histochemistry for AChE and ChAc, and electron microscopic histochemistry for AChE.Postnatal alterations in the levels of AChE and ChAc in the cerebellum of the mouse are characterized by a divergent pattern. During the first two postnatal weeks, AChE activity increases progressively, whereas ChAc activity remains low. Beyond day 14, when AChE activity is steady or gradually decreasing, ChAc increases sharply to reach a peak on day 32. Histochemically, AChE activity is associated with the glomeruli and the Golgi cells of the internal granular layer, the medullary layer, and the deep cerebellar nuclei. Purkinje cells exhibit transient staining between days 2 and 9. At the ultrastructural level, AChE staining is first demonstrated on day 6 within the Golgi cell soma, on day 9 at the mossy fiber–granule cell synapse, and on day 11 at the Golgi terminal–granule cell synapse. The staining intensity of these structures reaches that of the adult on day 19.The histochemical reaction for ChAc is localized to moderate number of presumed Bergmann glial cells, a few large cells of the deep cerebellar nuclei, small numbers of Golgi cells, and all immature Purkinje cells. The molecular layer, glomeruli, and the medullary layer fail to demonstrate ChAc activity. This distribution of ChAc sharply contrasts with the localization established by other methods previously and is interpreted in the light of the drawbacks of the histochemical procedure.The biochemical fluctuations in AChE activity, correlated with the histochemical and cytochemical data, suggest that the postnatal increases in the enzyme are related to the ingrowth of the mossy fibers and to the maturation of the AChE‐positive Golgi cells. Histochemical evidence for the correlation between the ontogenetic increases in cerebellar ChAc activity and progressive mossy fiber innervation must await the application of the immunohistochemical method to the developing cereb

ISSN:0092-7317    

DOI:10.1002/cne.901910105

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractSodium fluorescein (SF) was used as a very small tracer (mol wt 376; 5 A° diameter) to examine diffusion barriers in peripheral nerves and to compare them to those in other regions of the nervous system. The technique involved immobilization of the tracer by rapid freezing, followed by freezedrying and vacuum embedding in paraffin. The localization of the SF was then determined in tissue sections using fluorescence microscopy.Even at the highest doses of intravenously (IV) injected tracer, no extravasation could be detected in the cerebral cortex. On the other hand, SF penetrated very rapidly into peripheral ganglia and into the epineurium and perineurium of large peripheral nerves. The penetration of SF into the endoneurium of large nerves was, however, much more restricted with tracer detectable within the endoneurium only at high doses and long survival times. Even in such cases, the level of SF fluorescence was much lower within nerve fascicles than in the epineurium and the perineurium, and a sharp gradient in fluorescence intensity persisted at the inner border of the perineurium. The extent of extravasation into the endoneurium varied markedly between different fascicles of the same nerve and between different nerves in the same animal.Experiments involving injection of high doses of SF adjacent to the nerve indicated relatively little movement of SF across the perineurium, which indicates that the observed accumulation of tracer within the endoneurium was the result of direct extravasation of SF from the endoneural blood vessels. Small nerve branches (<100 μ in diameter) showed an earlier and more extensive penetration of SF into the endoneurium than large nerves like the sciatic, hypoglossal, or ventral tail nerve. This may be due to a diffusion of SF along the extracellular space of the endoneurium from nerve terminals where the perineurial barrier is open‐ended.In experiments involving IV injection of a solution containing both green fluorescent SF and red fluorescent Evans Blue (Evans Blue‐serum albumin complex, EBA = mol wt 69,000), the distribution of SF could be directly compared at various sites and sacrifice times to that of EBA, a much larger tracer. SF appeared more rapidly and extensively than EBA in the various compartments in ganglia and peripheral nerve. The distribution of EBA was the same as is typically seen when this tracer is injected alone, indicating that there was no change in vascular permeability associated with IV injection of SF.Since SF is of very small size, freely diffusible, nontoxic, and detectable at very low concentrations, it should be a useful complement to existing tracers. When tissues are processed according to the indicated procedure, one can obtain a very sensitive and reliable localization of this tracer which should be of value for studies in the nervous system concerning various pathological conditions associated with permeability altera

ISSN:0092-7317    

DOI:10.1002/cne.901910106

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe central fiber connections of the gustatory system (VII, IX, and X nerves) in the crucian carp were examined by the Fink‐Heimer method and its modification.The sensory and recurrence roots of the VII enter the brainstem separately and terminate in the ipsilateral half of the facial lobe (L‐VII). Afferent fibers of the IX terminate in the glossopharyngeal lobe (L‐IX). Most afferent fibers of the X terminate in the sensory layer of the vagal lobe (L‐X), in which degenerating terminals occur in some laminae. Some vagal afferents project bilaterally to the commissural nucleus of Cajal. The cutaneous component of the X projects to the nucleus of the spinal trigeminal tract (SpV) and the medial funicular nucleus (nFM).Ascending secondary fibers from the L‐VII project bilaterally to the secondary gustatory nucleus (nGS) in the isthmus region. Descending secondary fibers from the L‐VII turn caudally in the SpV. These fibers terminate mostly in the nucleus of the SpV and sparsely in the nFM. The L‐IX and L‐X give rise to the long and short secondary paths. The long path projects as the ascending secondary tract to the ipsilateral nGS. The short path includes secondary fibers projecting to the motor layer of the L‐X and the medullary reticular formation.Tertiary gustatory fibers arising in the nGS project ipsilaterally to two diencephalic nuclei: the nucleus glomerulosus and the nucleus diffusu

ISSN:0092-7317    

DOI:10.1002/cne.901910107

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractHistochemical, Golgi, and electron microscopic methods were used to study the superficial layers of the superior colliculus of the tree shrew. Following horseradish peroxidase injections in the dorsal lateral geniculate nucleus (LGd) and the pulvinar (Pul), retrogradely labeled somata were found in the upper two‐thirds and the lower third of the stratum griseum superficiale (SGS), respectively, as has been described by Albano et al. ('79). In tissue prepared with Golgi methods, somata, similar in location and shape to those projecting to the LGd, had narrow, vertically oriented dendritic arbors, which were confined to the upper two‐thirds of the SGS. Cells located in the lower third of the SGS had larger somata, similar to those projecting to the Pul, and wider dendritic arbors, which were confined to the lower two‐thirds of the SGS. Electron microscopic comparison of the number of degenerating terminals following enucleation and striate cortex lesion indicated that within the SGS terminals from the retina overwhelmingly outnumbered those from the cortex. In both types of material, degenerating terminals were observed throughout the SGS. However, the majority of the degenerating optic terminals were located in the upper SGS, whereas most of the degenerating striate terminals were found in the lower SGS. Thus, cells that project to the LGd and those that project to the Pul differ not only with respect to location, size, and dendritic morphology, but also with respect to the proportion of retinal and striate afferents which terminate in the region of their dendritic

ISSN:0092-7317    

DOI:10.1002/cne.901910108

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901910109

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901910111

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY