摘要:

AbstractThe distribution of callosal cells and terminals was studied in the posterior neocortex of pups whose ages ranged from 3 to 16 days and in adult rats 2 months of age or older. Callosal cells and terminations were revealed using retrograde (horseradish peroxidase) and anterograde (horseradish peroxidase; tritiated proline) tracing techniques, respectively, and the distribution of callosal connections was analyzed in tangential or coronal histological sections.In agreement with previous studies, we observed that the pattern of callosal connections in areas 17 and 18 of adult rats contains the following features: (1) a dense band of callosal cells and terminations separating the interiors of areas 17 and 18a, (2) a ringlike configuration anterolateral to area 17, (3) a region of dense labeling lateral to area 18a, (4) several narrow bands of labeling that bridge area 18a at different anteroposterior levels, and (5) one or more labeled regions in area 18b. In all these callosal regions, labeled cells and terminations are densely aggregated in layers II–III, Va, and Vc–VIa, and less densely in layer IV and the remaining portions of layers V and VI. High densities of isotope‐labeled fibers are also observed in the lower half of layer I. Throughout the interiors of areas 17 and 18a, a significant number of labeled cells are observed in layers Vc–VIa.In contrast to adult rats, in neonates no distinct tangential pattern of callosal connections is apparent. Instead, labeled cells are densely aggregated in two continuous horizontal bands located in cortical layers Va and Vc–VIa, and callosal axons are largely restricted to white matter. During the first 2 postnatal weeks there is a progressive loss of callosal cells in regions that normally have few callosal cells in the adult (e.g., interiors of areas 17 and 18a) and an increase in the number of cells in layers II–IV in regions that are densely callosal in the adult (e.g., callosal regions at the 17/18a border, lateral border of area 18a, and in area 18b). The decrease in the number of callosal cells in the interiors of areas 17 and 18a is more severe in the upper than in the lower band of the immature labeling pattern, and our data from tangential sections indicate that this loss of callosal neurons occurs synchronously across the interiors of these areas. During this period there is also a localized invasion of labeled callosal axons into those regions of gray matter where they will be found in adult life. By 7 days of age, all major features of the mature callosal pattern can be clearly recognized, and by 12 days of age—a few days before eye opening—the pattern appears v

ISSN:0092-7317    

DOI:10.1002/cne.902390102

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

年代:1985

数据来源: WILEY

摘要:

AbstractA small injection of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) was injected into dorsal or ventral peripheral retina in normal goldfish and in goldfish with prior optic nerve crush. Serial sections of tectum were subsequently taken for horseradish peroxidase (HRP) histochemistry 18 hours after injection and studied with light microscopy and densitometric reconstructions. In normals, a small, sharply delineated patch of product 200–300 μm wide was observed at the appropriate medial or lateral periphery of tectum. This product filled the entire SFGS, the main optic termination layer, and fell off abruptly at its edges. No labelling was detected in the optic pathways.In regenerates at about 20 days after nerve crush, these retinal injections yielded product that was dispersed across 1,000 μm or more of tectum but not in a uniform fashion. The densest product was biased toward the appropriate tectal position while product of intermediate density was mainly distributed along a path from the anterior end of tectum to this region. Product in the inappropriate half of tectum was much lighter and typically fiberlike in appearance. By about 40 days, product had condensed considerably at roughly the correct region of tectum but it was not as sharply delimited as in normals. Dense label occupied a single area about twice that of normals and exhibited flanking regions of light label extending for several hundred micrometers. At 59–148 days, a further condensation was observed but into more than one patch of product. The patches were of variable size and consisted of sharply delimited dense product which filled the entire SFGS at each position. Morphologically, these patches bore a remarkable resemblance to the ocular dominance columns previously seen in this

ISSN:0092-7317    

DOI:10.1002/cne.902390103

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe fine structure of the tyrosine hydroxylase (TH) immunoreactive neurons of the hypothalamic arcuate nucleus was examined by means of immunocytochemistry [peroxidase‐antiperoxidase (PAP) method], utilizing an antibody against TH. Immunolabeled axon terminals were observed infrequently and were located predominantly in the lateral region, whereas numerous labeled perikarya and dendrites were found throughout the nucleus. The labeled terminals, containing primarily clear and occasionally dense core vesicles, were never observed in synaptic contact. On the other hand, unlabeled axon terminals were frequently seen synapsing on labeled dendrites. In addition, the labeled dendrites were often seen in direct apposition to other neuronal elements such as both labeled and unlabeled perikarya. In contrast, unlabeled dendrites were never seen apposed to labeled perikarya. Labeled dendrites also occurred in direct contact with one another and with unlabeled dendrites. Moreover, numerous labeled dendrites were encountered along tanycytic processes. Dendrites engaged in tanycytic appositions were occasionally partially encompassed by thin sheaths emanating from the tanycytic process. The extensive contact made by the labeled dendritic profiles on both labeled perikarya and dendrites suggests that tubero‐infundibular dopaminergic (TIDA) cells may communicate with each other by means of dendritic release of dopamine. The presence of appositions between labeled dendrites and both unlabeled perikarya and dendrites suggests that the TIDA system also influences other neuronal populations through its dendrites. Finally, the dendrotanycytic relationship suggests that the TIDA system may play some role in the regulation of tanycytic funct

ISSN:0092-7317    

DOI:10.1002/cne.902390104

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

年代:1985

数据来源: WILEY

摘要:

AbstractUsing the peroxidase antiperoxidase immunocytochemical method, we were able to demonstrate within the brain and retrocerebral complex ofPeriplaneta americanaseveral neuronal structures which were very specifically stained with an anti‐methionine‐enkephalin antiserum. From the precise localization of this immunoreactive material some speculations about its possible functions could be derived, such as a neurotransmitter‐ or neuromodulatorlike function and/or a neurohormonal role. These data present new evidence for the recently developed concept that opiate peptides, identical or related to those found in higher species, occur also in inverteb

ISSN:0092-7317    

DOI:10.1002/cne.902390105

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

年代:1985

数据来源: WILEY

摘要:

AbstractPrevious studies have shown that suturing one eyelid closed in a newborn kitten results in profound changes in the development of the visual system. Among these is a retardation in the growth of neurons in the layers of the dorsal lateral geniculate nucleus receiving retinal input from the closed eye. Moreover, the greatest effect appears to be in the largest neurons. The present study examines the effects of monocular deprivation en the perikaryal size of select group of small lateral geniculate neurons, GABAergic neurons, that may be interneurons. These cells were selectively labeled by an antiserum to glutamic acid decarboxylase (GAD) and immunocytochemical methods. The results demonstrate that GAD+ neurons are among the smallest in the lateral geniculate nucleus and that they are insensitive to the effects of monocular deprivation. That is, GAD+ neurons in deprived laminae A and A1 are similar in size to those in the corresponding, nondeprived laminae. These findings are consistent with the hypothesis that GAD+ neurons are interneurons and therefore not subject to binocular competition in the visual cortex. This interpretation, however, is complicated by additional studies of the postnatal development of GAD+ neurons which reveal that GAD+ neurons grow to their adult size relatively early, before the onset of the critical period. Thus the insensitivity of the perikarya of GAD+ neurons to monocular deprivation may be attributable to their precocious growth.

ISSN:0092-7317    

DOI:10.1002/cne.902390106

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

年代:1985

数据来源: WILEY

摘要:

AbstractWe report a comparative immunofluorescence and immunoblotting study of GFA protein, the subunit of glial filaments, in nonmammalian vertebrates. The study was conducted with polyclonal antibodies raised to human and shark antigen and with monoclonal antibodies isolated from mice immunized with chicken and bovine antigen. With the exception of cyclostomes, glial filaments appeared remarkably conserved in vertebrate phylogeny, both with respect to the molecular weight and immunoreactivity of their protein subunit. In most species, the antibodies decorated a single band in brain, spinal cord, and optic nerve extracts by the immunoblotting procedure. This band had the same molecular weight in the different CNS regions. With the exception of the turtle, species differences in the molecular weight of the band were not greater than those observed among mammalian vertebrates (human, bovine, and rat). However, there were some exceptional findings in fish. In goldfish and trout brain and spinal cord extracts, the antibodies decorated with the same intensity two bands. In accordance with previous immunofluorescence findings, goldfish optic nerve extracts were negative by the immunoblotting procedure. In four fishes (sea bass, tautog, trout, and scup), optic nerves reacted with the antibodies. However, the band decorated by the antibodies was higher in molecular weight than that obtained from brain and spinal cord extracts. Glial fibers were demonstrated by immunofluorescence in the brain, spinal cord, optic nerve, and retina of most species studied. In amphibia immunofluorescent structures were comparatively few, probably accounting for the negative results by immunoblotting. A comparative immunohistological study of the cerebellum showed the presence of perpendicular glial fibers in the molecular layer of most species examined. Birds and amphibia were different in this respect. Bergmann glia in chicken were GFA negative. In the frog and the toad, immunofluorescent fibers in the molecular layer of the cerebellum were haphazardly oriented. Ependymal radial glia was GFA‐negative in the cerebellum of subavian vertebrates. Antisera raised in rabbit to shark GFA protein reacted with the same bovine GFA fragments recognized by polyclonal and monoclonal antibodies raised to human and bovine antigens, respectively, i.e., 30‐kDa N‐bromosuccinimide fragment (tryptophan cleavage); 35‐kDa 2‐nitro‐5‐thiocyanobenzoic acid fragment (cysteine cleavage); 18‐kDa cyanogen bromide fragment (methionine cleavage). Conversely, the chicken GFA monoclonal antibodies selected for this study only reacted with non

ISSN:0092-7317    

DOI:10.1002/cne.902390107

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe geometry of the somata and dendritic trees of motoneurons innervating neck and shoulder muscles was investigated by using intracellular injections of HRP. In general, these motoneurons did not belong to a homogeneous population of motoneurons. Differences in average primary dendritic diameter, number of primary dendrites, and other measures of dendritic tree size were found between different neck and shoulder motoneuron groups. Several indices of proximal dendritic tree size (number of primary dendrites, sum of dendritic diameters, Rall's dendritic trunk parameter, and the sum of dendritic holes) were weakly correlated with the diameter or surface area of the soma. Some of these correlations depended on the muscle supplied by the motoneuron.The total combined dendritic length ranged from 66,660 to 95,390 μm. There was a weak, but positive, correlation between the diameter of primary dendrites and combined dendritic length. This relationship varied from motoneuron to motoneuron.The diameters of all dendrites of three trapezius motoneurons were examined in detail. The total dendritic surface area examined ranged from 415,000 to 488,100 μm2and represented approximately 99% of the total neuronal surface area. Last‐order dendrites showed a high degree (39.9%) of taper. Dendritic tapering, by itself, was a major factor in the decrease of the (sum of dendritic diameters)3/2measured at progressively distal sites from the soma. Although few parent and daughter dendrites obeyed the “three‐halves law,” the average exponent was 1.57. The diameters of primary dendrites and dendritic surface area were weakly correlated. The correlation between dendritic diameter and combined dendritic length or surface area improved if the weighted average of the diameter of second‐order dendrites was used as a measure of dendrite size. Second‐order dendrites, whose branches terminated in different regions of the spinal cord, showed different relationships between dendritic diameter and combined dendritic length or surface area.Comparisons between the motoneurons examined in the present study and motoneurons innervating other muscles indicate that, although all spinal motoneurons share several common features (e.g., long dendrites, dendritic tapering), each motoneuron group has a set of unique features (e.g., soma shape, relationship between primary dendrite diameter and dendritic surface area). Thus, the rules governing motoneuron dendritic geometry are not fixed but depend on the species of t

ISSN:0092-7317    

DOI:10.1002/cne.902390108

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

年代:1985

数据来源: WILEY

摘要:

AbstractBoth the dorsal and ventral optic tracts of goldfish have similar shapes when they are sectioned perpendicularly to their longitudinal axes. Each tract is pear‐shaped, consisting of a narrow and a deep apex, a wide mid‐span, and a progressively curved and tapered superficial base. The tracts differ in that the apex of the dorsal optic tract points caudally, while the apex of the ventral optic tract points medially. In addition, upon segregating from the main optic tract, the dorsal optic tract courses dorsally while the ventral optic tract courses caudally. Thus, the two optic tracts have similar shapes and are orthogonal to one another.The topography of the retinal fibers within the optic tracts was determined either by ablating part of the retina and subsequently filling the axons from the intact hemiretina with cobaltous‐lysine or by applying cobaltous‐lysine to a slit in the retina. Both optic tracts contain a similar arrangement of optic fibers. Axons of central retinal ganglion cells (RGCs) are in the apex of each tract and optic fibers of peripheral RGCs are located along the base of each tract. Axons of temporal RGCs are located dorsally in the ventral optic tract and laterally in the dorsal optic tract, while axons of nasal RGCs are located ventrally in the ventral optic tract and medially in the dorsal optic tract. These findings indicate that the optic axons are organised as laminae. Deeper laminae contain the axons of older annuli of RGCs and superficial laminae contain the axons of younger annuli of RGCs. This type of chronological organization appears to be consistent across vertebrates. Furthermore, the organization of the optic axons across laminae is constant. Temporal RGC axons are at one end, and nasal RGC axons are at the other end of each lamina. These results are consistent with those found in other nonmammalian vertebrates. Moreover, these findings preclude the possibility that the axons of a half‐annulus of RGCs in goldfish travel together as a fascicle in the optic tracts that is continuous with a fascicle in the stratum opticum of the tectum.The general position of the fibers from different retinal quadrants in the optic tracts may lead to a probabilistic determination as to which part of the tectum they innervate. Namely, temporal RGC axons, destined for the rostral tectum, are situated in the optic tracts so that they are close to the rostral tectum. Nasal RGC axons, destined for caudal tectum, are situated in the optic tracts so thay they are farthest from the rostral tectum. Thus, axons of nasal, RGCs have a lower probability of innervating the rostr

ISSN:0092-7317    

DOI:10.1002/cne.902390109

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe population dynamics of internal granule cells in the rat olfactory bulb during adult life were analyzed in histological sections and in autoradiograms with (1) counts of granule cells, (2) counts of labeled granule cells 1 month after injection of3H‐thymidine at various ages, and (3) counts of labeled granule cells at varying survival times (up to 18 months) after injection at 3 months and 24 months. The total number of granule cells increases linearly throughout life, approximately doubling between 3 and 31 months. Autoradiographic studies show that the rate of production of new granule cells decreases from 3 to 12 months and then is approximately constant during the rest of the life span. The number of labeled cells found 6 months after injection at 3 and 24 months is about one‐fourth and one‐half, respectively, that of the number at a 1‐month survival, suggesting that many of the cells produced to do not survive. However, at least some granule cells labeled at 3 months survive for 18 months. A model is suggested in which granule cells are produced continuously throughout life and control of the total number of granule cells is effected chiefly through the rate of cel

ISSN:0092-7317    

DOI:10.1002/cne.902390110

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

年代:1985

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902390101

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

年代:1985

数据来源: WILEY