摘要:

AbstractThe cytoarchitecture and fiber connections of the nucleus lateralis valvulae of the carp (Cyprinus carpio) were studied by Nissl, Bodian, Golgi, and horseradish peroxidase methods. Chief cells composing the nucleus lateralis valvulae (NLV) are small and granular, and their axons terminate in the cerebellum. These neurons have no dendrite, and the cell body is enveloped in a single terminal of afferent fibers to the NLV. In order to observe local cell clustering, the NLV was three‐dimensionally reconstructed with the aid of a computer image analysis system.Afferent sources to the NLV were the nucleus pretectalis superficialis pars magnocellularis (Northcutt and Braford, '84:Brain Res. 296:181–184), nucleus ventromedialis thalami (Ito et al., '86:J. Comp. Neurol 250:215–227), and the inferior lobe. The NLV projects to the inferior lobe and the cerebellum. In particular, the cerebellar projections were strong and topographically arranged. Some larger neurons lying just beneath the NLV, some of which were intermingled with the NLV neurons, projected to the torus longitudinalis.On the basis of the local cell clustering as well as NLV‐cerebellar connections, three subdivisions of the NLV could be recognized, i.e., anterior, central, and posterior portions. The posterior portion was further subdivided into lateral and media

ISSN:0092-7317    

DOI:10.1002/cne.902980402

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

年代:1990

数据来源: WILEY

摘要:

AbstractAnatomical organization of the central auditory system in the mole was studied at the lower brainstem levels. The cyto‐, myelo‐, and chemoarchitectures were examined in Nissl, myelin, and acetylcholinesterase stained materials, and then the origins of the ascending afferents to the inferior colliculus (IC) were identified by injecting wheatgerm agglutinin conjugated to horseradish peroxidase (WGA‐HRP) into the unilateral IC and processing the tissue according to the standard retrograde tracing techniques. The results indicate that the auditory nuclei and pathways in the lower brainstem of the mole conform to the basic plan common to many other mammals. Nevertheless, several characteristic features are evidenced in the present study: (1) in the cochlear nucleus (CochN), granule cell fields are very large in both the ventral (VCN) and dorsal (DCN) nuclei; among several populations of neurons, fusiform cells in the DCN, multipolar cells in the VCN and DCN, and small spherical cells in the VCN project to the IC directly, (2) in the superior olivary complex (SOC), the medial nucleus (MSO) is well developed in comparison with that in the hedgehog, the opossum, the mouse, and the rat, although the general configuration of the SOC is similar to that in those mammals, most strikingly, the MSO projects to the IC bilaterally in the mole, and (3) the nuclei of the lateral lemniscus (NLL) show a great development and consist of three well‐differentiated parts of the dorsal, intermediate, and ventral nuclei. The projections from these subnuclei to the IC conform to the basic mammali

ISSN:0092-7317    

DOI:10.1002/cne.902980403

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

年代:1990

数据来源: WILEY

摘要:

AbstractWe characterized the motoneuron pool positions and projection patterns in the embryonic quail hindlimb and compared them to those in the chick to determine the degree of similarity and to form a baseline for future chimeric experiments. We find that the most similar parameters of pool position correlate with the major axonal pathway choices. First, the medial‐lateral pool position, which is highly conserved among birds and mammals, is identical in the quail and chick and correlates with the dorsal‐ventral pathway choice, the first and least plastic of the choices within the limb. Second, although quail pools were known to be compressed into seven rather than eight segments, we show that the map of pools is compressed about a central point (segment three) that preserves the spatial relationships between anterior pools and the crural plexus, and between posterior pools and the sciatic plexus. Access to guidance cues that are restricted to each plexus region is thus maintained between species. Third, pool position along the anterior‐posterior axis is the least similar parameter between species. In fact, the entire lumbosacral motor complex may shift by ± half a segment in individual quail. Despite the consequent differences in segmental projections, the specific projection pattern within each quail hindlimb is identical to that in the chick. There is no need to preserve the exact segmental pattern either phylogenetically or during development, because motoneurons accommodate to modest variations in their position along the anterior‐posterior axis by sorting out at the limb base. The contrast between variable segmental and constant limb projections also demonstrates that neither the specification nor the precise projection of motoneurons is dependent upon the specification or development of

ISSN:0092-7317    

DOI:10.1002/cne.902980404

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn order to clarify the neuroanatomical basis for postulated muscarinic cholinergic control of a wide array of physiological processes in birds, the distribution of muscarinic cholinergic receptors in the brain of three avian species was investigated by quantitative autoradiography. The species consisted of two passerines (songbirds), the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia), and one galliform, the Japanese quail (Coturnix coturnix japonica). [3H] N‐methyl scopolamine (NMS), a muscarinic cholinergic antagonist was used as the ligand to label the receptors. Initial experiments demonstrated that the binding of this ligand in the three species is saturable in the nanomolar range and has a high affinity (Kd= ±0.6 nM). Displacement experiments revealed that three muscarinic ligands competed ii an order of potency characteristic of the mammalian muscarinic receptor (i.e., atropine ≥ oxotremorine ≥ carbachol) for NMS binding in the avian brain.In all three species, portions of the basal ganglia, such as the parolfactory lobe and the paleostriatum augmentatum, exhibited the highest density of binding. On the other hand, the paleostriatum primitivum, the avian homologue of the mammalian globus pallidus, contained very few binding sites. Other telencephalic sites, such as the ventral and dorsal hyperstriatum, also revealed relatively high receptor density. However, the neostriatum and especially the ectostriatum showed much lower levels. In the hypothalamus, in all three species, specific binding could be observed in the ventromedial nucleus and adjacent areas. The paraventricular nucleus also showed moderate levels of binding density, especially in the two songbird taxa. At a more rostral level, the preoptic area showed low levels of binding. In the quail, the sexually dimorphic nucleus of the preoptic area was clearly outlined in the autoradiograms by the low level of binding sites compared to the surrounding areas. In the two passerine species, nuclei of the song system were identified by either high or low levels of NMS binding. High binding defined area X and the mesencephalic nucleus, intercollicularis (ICo). In contrast, the robust nucleus of the archistriatum and the magnocellular nucleus of the anterior neostriatum showed low levels of binding in comparison with the surrounding tissue. None of these nuclei were visible in the quail autoradiograms except for ICo, which appeared as in the passerines as i heavily labelled area surrounding the lightly labelled nucleus mesencephalicus lateralis par dorsalis. In all three species, the hippocampal complex was devoid of NMS binding except for two lateral dark bands that were present along the entire rostral to caudal extent of the hippocampus. These results suggest general similarities between the distribution of muscarinic cholinergic binding sites in birds and mammals. Among the three species, the qualitative pattern of receptor density is similar, with the exception of the telencephalic nuclei controlling vocal behavior in songbirds, which have no apparent homologues in the

ISSN:0092-7317    

DOI:10.1002/cne.902980405

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

年代:1990

数据来源: WILEY

摘要:

AbstractTransection of the fimbria‐fornix pathway is a paradigm that has been richly exploited in rats to assess the structural and functional correlates of cognitive behavior, neural grafting, and growth factor administration. Principally, the degeneration of cholinergic neurons within the septal/diagonal band region has received detailed attention following this manipulation. In contrast, no studies have examined the response of the cholinergic septal/diagonal neurons following axotomy in nonhuman primates. This study examined the neuronal and glial responses within the septal region to selective fornix transection (without cingulate gyrus ablation) in fourCebus apellamonkeys. One month following unilateral transection of the fornix by means of an open microsurgical approach, a comprehensive loss of acetylcholinesterase [AChE]‐containing fibers was observed throughout the hippocampal formation and dentate gyrus ipsilateral to the lesion. Decreases in AChE fiber densities were also observed within the entorhinal cortex ipsilateral to the lesion. No such changes in AChE‐fiber density were consistently observed within the subicular region. The decrease in hippocampal AChE‐positive fibers was paralleled by a 49.5% reduction in cholinergic medial septal neurons as revealed by Nissl stains and immunohistochemical staining for the receptor for nerve growth factor, a marker of cholinergic basal forebrain neurons in primates. In contrast, no significant changes in the number of neurons within the vertical limb of the diagonal band were noted. Following the transection, a relatively intense reactive gliosis was observed within the dorsal half of the septal region ipsilateral to the transection and within the overlying transected corpus callosum. These data provide the foundation in nonhuman primates on which novel therapeutic factors can be evaluated in paradigms relevant to the study of Alzheimer's

ISSN:0092-7317    

DOI:10.1002/cne.902980406

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

年代:1990

数据来源: WILEY

摘要:

AbstractExperiments were designed to find the degree to which regenerated optic axons occupied their previous locations in the optic tracts. Following optic nerve crush and regeneration, either the dorsal, Ventral, Peripheral, Temporal, or nasal part of the retina was ablated. The axons of the remaining retinal ganglion cells (RGCs) were labeled with cobalt. Density of the regenerated dorsal and ventral axons in the dorsal vs. ventral optic tracts was determined digitally. In addition, we determined the density of temporal and nasal axons in the temporal vs. nasal compartments of each optic tract and the density of central axons in the central vs. peripheral compartments of both optic tracts.Regenerated axons were not distributed randomly in the optic tracts. Instead, they were slightly but significantly biased toward growing through the tract or compartment that they had occupied previously. Still, the pathway specificity exhibited by the regenerated axons was closer to random than it was to the pathway specificity seen in normal animals. Dorsal, ventral, and central RGC axons were significantly better localized to their correct tract or compartment than were temporal or nasal RGC axons. Also, over time, dorsal and ventral axons tended to disappear from incorrectly chosen optic tracts. The slight bias toward choosing the appropriate optic tract or optic tract compartment may be enough to account for the topographic specificity of the regenerated retinotectal projection. Near‐randomness of the axonal positions in the tracts argues against the presence of any specific guidance cues in the optic tracts of adult animals. Axonal density was highest in the correct compartment and diminished progressively with increasing distance into the incorrect compartment. Such a gradient of axonal density suggests that regenerating axons “drift” away from their previous positions in the optic pat

ISSN:0092-7317    

DOI:10.1002/cne.902980407

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

年代:1990

数据来源: WILEY

摘要:

AbstractRedistributions of monkey cones and rods during the first year after birth include a fivefold increase in peak foveal cone density from 43,000 to 210,000 cones/mm2, a decrease in the diameter of the rod‐sparse area, and a two‐ to threefold decrease in peripheral photoreceptor density. Two weeks before birth, higher cone density is already apparent in the future fovea, as are the nasotemporal asymmetry in cone distribution, a higher density “cone streak” along the horizontal meridian, a large rod‐sparse central fovea, and a ring of high rod density. Despite the early appearance of these basic patterns, photoreceptor distribution is not mature until 1 to 5 years postnatally.Total cones varied from 4 million at birth to 3.1 million in the average adult. The two oldest eyes had fewer cones, suggesting up to a 25% loss late in development. There were 60 to 70 million rods in the adult macaque retina and little evidence of postnatal changes in number. Neither of these small changes is sufficient to account for the reduction in peripheral photoreceptor density and both are in the wrong direction to explain increasing foveal density, ruling out a major role for either photoreceptor death or generation.Retinal area increased by a factor of 2.4 from 2 weeks before birth to adulthood. In contrast, the posterior pole of the retina was dimensionally stable throughout this period, with the distance between the fovea and optic disc varying nonsystematically from 3.37 to 4.05 mm. Retinal coverage of the globe was also stable at 48–60%. Thus postnatal growth can be ruled out as a factor in the density changes occurring in central retina. Adult retinas have a higher proportion of both cones and rods in midperiphery, whereas young retinas have a higher proportion of photoreceptors in far periphery. It appears that photoreceptors are radially redistributed from peripheral toward central retina during postnatal development, resulting in the marked increase in foveal cone density and the decrease in the eccentricity of the rod ring. Up to 13 weeks postnatally, midperipheral growth of the retina is substantial and increases with eccentricity. At later ages, expansion continues only in the very far periphery. Retinal growth appears sufficient to explain the decreases in peripheral rod and cone density with age.These and previous data strongly suggest that differentiated photoreceptors, with complex cytology and synaptic contacts, migrate toward the foveal center, explaining the increase in foveal photoreceptor density. The distance that cones migrate between E152 and adulthood increases from 0 at the foveal center to a maximum of 0.230 mm for cones originally located at 1mm of eccentricity in the immature retina. This migration is equal to published measurements of the length of fibers of Henle for cones located at 0.75 mm in the adult. These data suggest that at the center of the fovea, the length of the fiber of Henle is due to outward migration of the bipolar neuron to which the photoreceptor is connected, but that by 0.75 mm, the length of the fiber is due to the centralward migration of the ph

ISSN:0092-7317    

DOI:10.1002/cne.902980408

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

年代:1990

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902980401

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

年代:1990

数据来源: WILEY