摘要:

AbstractThe granule cell clusters in the rat olfactory tubercle were studied in Nissl‐stained and Golgi‐impregnated sections. Discrete cell clusters that vary in size and shape occur mainly in the multiform layer and less often in the molecular layer. In cell‐stained sections they consist of small, round granule cells, 5–8 μm in diameter, that often surround a core or hilar area, which may contain larger neurons. In Golgi sections, the uni‐ or bipolar granule cells have a globular‐shaped soma and varicose dendrites that are thin, have few branches, and are usually less than 100 μm long. The dendrites remain within the border of the cluster. There are few spines on most granule cells; however, a small population of granule cells is spine‐rich. The axons are beaded, seldom have collaterals, and do not appear to exit from the cluster.Either in the hilus or in among granule cells are the special large hilar neurons, whose somata measure 15–17 × 18–22 μm. Unlike most of the neurons that are near a granule cell cluster, the dendrites, and perhaps axons, of the special large hilar neurons spread throughout a cluster. Differences in their dendrites suggest that there may be several varieties of them, but not enough examples have been studied to produce a useful classification. Some of their dendrites have bushlike terminal endings. Only the initial, beaded segment of their axons has been impregnated.Three types of afferent fibers have been identified: (1) Axons that are probably afferent to the olfactory tubercle course along a granule cell cluster giving off short collaterals that end in the periphery of a cluster. (2) Axon bundles that arise mainly from medium‐sized densely spined neurons in the tubercle travel through a cluster, emitting boutons en passant or short collaterals that may end on granule cells. (3) Thick axons, which are among the thickest fibers in the olfactory tubercle, enter a cluster and develop a number of collaterals that in turn divide, and finally produce a unique terminal arborization in the cluster.The granule cell clusters are frequently identified as the islands of Calleja. A comparison of the structure of granule cells with that of the cells Calleja (La Region Olfactoria del Cerebro, Madrid: N. Moya, 1893) described in the “islotes olfativos,” or islands of Calleja, indicates that he was pointing to the thickened, ruffled portions of the dense cell layer and not to the granule cell clusters. Since the time of their original description, the islands of Calleja have been defined in different ways, have been divided into various types, and have not been consistently identified with a specific cell type or cell group. Consequently, the term has little descriptive value.The possible significance of the granule cells is discussed, particularly in relation to the concept of the ventral striatopallidal system. Because the granule cells are structurally unlike any neuron that has been identified in the corpus striatum, it is difficult to fit them into the ventral striatopallidal system. Because the granule cells are structurally unlike any neuron that has been identified in the corpus striatum, it is difficult to fit them into the ventral striatopallidal system. The granule cells, however, structurally resemble uni‐ and bipolar neurons in the hypothalamic suprachiasmatic and arcuate nuclei. Further critical structural, cytochemical, and functional comparisons between the granule cells and these hypothalamic neurons could provide valuable clues to understanding the significance

ISSN:0092-7317    

DOI:10.1002/cne.902650102

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

年代:1987

数据来源: WILEY

摘要:

AbstractWith the aid of specific antisera to the retinal proteins S‐antigen and α‐transducin and to the rhodopsin apoprotein opsin, we have labeled various cell populations in the pineal organ, parapineal organ, habenular nucleus, and subcommissural organ in two teleost species: the rainbow trout and the European minnow. Although these proteins are associated with photoreceptor functions, not only photoreceptor cells but also the majority of parenchymal cells in the pineal organ were immunoreactive. Immunoreactive cells with dendrite‐ and axonlike processes were observed also in the parapineal organ and the habenular nucleus. Furthermore, S‐antigen‐immunoreactive, long, axonal processes were observed in the pineal organ and could be traced from the pineal organ to the habenular nucleus and to the pretectal area. In the light of recent HRP electron microscopical and immunocytochemical studies we propose (1) that not only the classical pineal photoreceptor cells of poikilothermic vertebrates but also other types of CSF‐contacting neurons may be the phylogenetic ancestors of mammalian pinealocytes, and (2) a close interrelationship between the pineal organ and the limbic system, effectuated by the direct projections from pineal photoreceptors/CSF‐contacting neurons/pinealocytes to the habenular nucleus, and by displaced “pinealocytelike” elements scattered in the

ISSN:0092-7317    

DOI:10.1002/cne.902650103

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

年代:1987

数据来源: WILEY

摘要:

AbstractTo study qualitative and quantitative changes in the glial cell population of young postnatal dogs, the cervical spinal cords of 20 beagle pups, ranging in age from 1 to 28 days, were prepared for light and electron microscopy. Glial cells in the lateral corticospinal tract were classified and quantified directly on the electron microscope. Quantification was performed by means of a stereological method designed to correct for sampling bias, and glia were classified according to morphological criteria as immature glial cell precursors, light and dark oligodendrocytes, astrocytes, and microglia.Glial cell precursors, which include undifferentiated glioblasts, oligodendroblasts, and astroblasts, predominated in the first few days after birth, constituting 43% of the glial cell population, and then declined to less than 5% by 28 days. Light and dark oligodendrocytes differed morphologically in their electron density and the appearance of their organelles. Light oligodendrocytes increased slightly prior to myelination, and then declined, whereas dark oligodendrocytes continued to increase throughout the 4‐week period and became the predominant cell type at 28 days (66%). In contrast to the oligodendroglial population, the sizes of the astroglial and microglial cell populations were relatively stable.This study shows that the population of immature glial cell precursors, abundant at birth in the lateral corticospinal tract, appear to be differentiating primarily into oligodendroglia, because this population exhibits a rapid increase in size, and relatively little change occurs in the astrocyte population. The trends in glial cell development in the dog are similar to those reported for rodents, although there may be some variation in the maturation and activity of oligodendrocyte

ISSN:0092-7317    

DOI:10.1002/cne.902650104

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

年代:1987

数据来源: WILEY

摘要:

AbstractNeurogenesis and morphogenesis in the rat bed nucleus of the stria terminalis (strial bed nucleus) were examined with [3H]thymidine autoradiography. For neurogenesis, the experimental animals were the offspring of pregnant females given an injection of [3H]thymidine on 2 consecutive gestational days. Nine groups of embryos were exposed to [3H]thymidine on E13–E14, E14–E15,…E21–E22, respectively. On P60, the percentage of labeled cells and the proportion of cells originating during 24‐hour periods were quantified at six anteroposterior levels in the strial bed nucleus. On the basis of neurogenetic gradients, the strial bed nucleus was divided into anterior and posterior parts. The anterior strial bed nucleus shows a caudal (older) to rostral (younger) neurogenetic gradient. Cells in the vicinity of the anterior commissural decussation are generated mainly between E13 and E16, cells just posterior to the nucleus accumbens mainly between E15 and E17. Within each rostrocaudal level, neurons originate in combined dorsal to ventral and medial to lateral neurogenetic gradients so that the oldest cells are located ventromedially and the youngest cells dorsolaterally. The most caudal level has some small neurons adjacent to the internal capsule that originate between E17 and E20. In the posterior strial bed nucleus, neurons extend ventromedially into the posterior preoptic area. Cells are generated simultaneously along the rostrocaudal plane in a modified lateral (older) to medial (younger) neurogenetic gradient. Ventrolateral neurons originate mainly between E13 and E16, dorsolateral neurons mainly between E15 and E16, and medial neurons mainly between E15 and E17. The youngest neurons are clumped into a medial “core” area just ventral to the fornix.For morphogenesis, pregnant females were given a single injection of [3H]thymidine during gestation, and their embryos were removed either 2 hours later (short survival) or in successive 24‐hour periods (sequential survival). The embryonic brains were examined to locate areas of intensely labeled cells in the putative neuroepithelium of the strial bed nucleus, to trace migratory waves of young neurons, and to establish their final settling locations. Two different neuroepithelial sources produce neurons for the strial bed nucleus. The anterior strial bed nucleus is generated by a neuroepithelial zone at the base of the inferior horn of the lateral ventricle from the anterior commissural decussation area forward to the primordium of the nucleus accumbens. The posterior strial bed nucleus is generated by a neuroepithelial zone at the base of the transient medial horn of the lateral ventricle, lateral to the fusion with the anterior thalamus. Neurons destined for the anterior strial bed nucleus migrate radially from their neuroepithelial source so that older neurons settle ventromedially, and younger neurons settle dorsolaterally, closest to the inferior horn. Older neurons destined for the lateral parts of the posterior strial bed nucleus migrate radially, reflecting the curve taken by the neuroepithelium in the medial horn. Younger neurons in the medial part also migrate radially, accumulating adjacent to the lateral neurons. The youngest neurons in the core and medial shell migrate ventromedially past older neurons and settle in clumps or diffusely throughout the medial part, Taken as a whole, these observations suggest that there is a developmental basis for the structural and functional hetero‐geneity found in the adult bed nucleus of the

ISSN:0092-7317    

DOI:10.1002/cne.902650105

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

年代:1987

数据来源: WILEY

摘要:

AbstractNeurogenesis and morphogenesis in the rat preoptic area were examined with [3H] thymidine autoradiography. For neurogenesis, the experimental animals were the offspring of pregnant females given an injection of [3H]thymidine on two consecutive gestational days. Nine groups were exposed to [3H]thymidine on embryonic days E13–E14, E14–E15, E21–E22, respectively. On postnatal day P5, the percentage of labeled cells and the proportion of cells originating during 24‐hr periods were quantified at four anteroposterior levels in the preoptic area. Throughout most of the preoptic area there is a lateral to medial neurogenetic gradient. Neurons originate between E12–E15 in the lateral preoptic area, between E13–E16 in the medial preoptic area, between E14–E17 in the medial preoptic nucleus, and between E15–E18 in the periventricular nucleus. These structures also have intrinsic dorsal to ventral neurogenetic gradients. There are two atypical structures: (1) the sexually dimorphic nucleus originates exceptionally late (E15–E19) and is located more lateral to the ventricle than older neurons; (2) in the median preoptic nucleus, where older neurons (E13–E14) are located closer to the third ventricle than younger neurons (E14–E17).For an autoradiographic study of morphogenesis, pregnant females were given a single injection of [3H] thymidine during gestation, and their embryos were removed either two hrs later (short survival) or in successive 24‐hr periods (sequential survival). Short‐survival autoradiography was used to locate the putative neuroepithelial sources of preoptic nuclei, and sequential survival autoradiography was used to trace the migratory waves of young neurons and their final settling locations. The preoptic neuroepithelium is located anterior to and in the front wall of the optic recess. The neuroepithelium lining the third ventricle is postulated to contain a mosaic of spatiotemporally defined neuroepithelial zones, each containing precursor cells for a specific structure. The neuroepithelial zones and the migratory waves originating from them are illustrated. Throughout most of the preoptic area, neurons migrate predominantly laterally. The older neurons in the lateral preoptic area migrate earlier and settle adjacent to the telencephalon. Younger neurons migrate in successively later waves and accumulate medially. The sexually dimorphic neurons are exceptional since they migrate past older cells to settle in the core of the medial preoptic nucleus. The median preoptic nucleus originates from a midline neuroepithelial zone that is continuous with the neuroepithelium in the midline basal telencephalon, and is, therefore, considered to represent a transitional area between the telenceph

ISSN:0092-7317    

DOI:10.1002/cne.902650106

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe sources of descending spinal tracts in the goldfish,Carassius auratus, were visualized by retrograde transport of horseradish peroxidase (HRP) administered to the hemisected spinal cord. In the diencephalon, HRP‐positive neurons were identified in the nucleus preopticus magnocellularis pars magnocellularis and ventromedial nucleus of the thalamus of the ipsilateral side. In the mesencephalic tegmentum, a few somata of the contralateral nucleus ruber and several ipsilateral neurons of the nucleus of the median longitudinal fasciculus were labeled. The reticular formation of the rhombencephalon was the major source of descending afferents to the spinal cord. A larger number of neurons were retrogradely labeled in the ipsilateral superior, middle, and inferior nuclei than in the contralateral nuclei. A few raphe neurons and the contralateral Mauthner neuron were also HRP‐positive. The octaval area showed retrogradelyl labeled neurons in the anterior, magnocellular, descending, and posterior octaval nuclei of the ipsilateral side. A large number of neurons in the facial lobe and a few somata located adjacent to the descending trigeminal tract were labeled on the ipsilateral side. The pattern of descending spinal projections in goldfish is comparable to that of tetrapods and suggests that the spinal tracts have originated quite early in the course of vertebrate evolut

ISSN:0092-7317    

DOI:10.1002/cne.902650107

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn the rat, the numbers and locations of motoneurons innervating the short plantar muscles of the hindlimb (supplied by the medial and lateral plantar nerves, as well as a branch of the sural nerve) were determined by using both horseradish peroxidase (HRP) and fluorochromes as retrograde labels.Topographical organization within the plantar motor nucleus was examined by exposing individually the cut ends (encapsulated in low melting‐point paraffin) of medial plantar, lateral plantar, and sural nerves to HRP. In addition, double‐labeling experiments were conducted in which the medial plantar nerve was labeled with one fluorochrome (either true blue or diamidino yellow) and the lateral plantar nerve with another.The plantar motor pool is located in the extreme dorsolateral portion of the ventral horn, usually concentrated in the fifth lumbar (L5) spinal segment. Labeled motoneurons extended caudally into the sixth lumbar (L6) segment and rostrally into portions of the fourth lumbar (L4) segment. Motoneurons of the medial plantar, lateral plantar, and sural nerve have overlapping territories. Sural motoneurons (about 70 cells per side) are generally confined to L5, medial plantar motoneurons (about 180 cells per side) tend to be concentrated in caudal L5 and rostral L6, whereas the lateral plantar motoneurons (about 310 cells per side) extend throughout the entire length of the plantar motor pool.The distribution of motoneuronal cell size is unimodal (mean cross‐sectional area = 610 ± 150 μm2). Cell bodies of plantar motoneurons tend to have similar geometries in all three major planes of sectioning.In all, the combined plantar plus sural nerve population amounts to about 560 motoneurons on each side of the spinal cord. On the basis of these data, and those published by others, the innervation of the small muscles of the foot accounts for about 25% of the motor axons carried by the entire sciati

ISSN:0092-7317    

DOI:10.1002/cne.902650108

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

年代:1987

数据来源: WILEY

摘要:

AbstractThalamocortical projections to four tonotopic fields (A, AI, P, and VP) of the cat auditory cortex were studied by using combined microelectrode mapping and retrograde axonal transport techniques. Horseradish peroxidase (HRP) or HRP combined with either tritiated bovine serum albumin or nuclear yellow was injected into identified best‐frequency sites of one or two different fields in the same brain. Arrays of labeled neurons were related to thalamic nuclei defined on the basis of their cytoarchitecture and physiology. In some cases, patterns of labeling were directly compared with thalamic best‐frequency maps obtained in the same brain. We compared only patterns of labeling resulting from injections into similar parts of the frequency representation in different fields to insure that observed differences in patterns of labeling did not simply reflect differences in the frequency representation at the injection sites.The thalamic projection to the four fields is divided among seven nuclei, three tonotopic nuclei (ventral nucleus, V; lateral part of the posterior group of thalamic nuclei, Po; and dorsal cap nucleus, d) and four nontonotopic nuclei (caudodorsal nulceus, cd; ventrolateral nucleus, vl; and small, Ms, and medium‐large, Mg, cell regions of the medial division). Projections to each field differ, and each field receives inputs from tonotopic and nontonotopic nuclei. Field A receives its major inputs from Po and Mg, and a minor input from V. Field AI receives its major inputs from V, Po, and Mg, although Po and Mg have heavier projections to field A. Field P receives its major inputs from V, d, and vl; and minor inputs from cd, Ms, Mg, and Po. Field VP receives major inputs from V, vl, and cd; and minor inputs from d, Ms, and Mg.There are segregated territories in V and Po in which most neurons project to one cortical field (major projection), and a smaller proportion projects to one or more other fields (minor projections). Field VP receives a major projection from the caudal pole of V. Field P receives a major projection from the caudal half of V, and from a thin band along the dorsal border of rostral V. Field AI receives a major projection from most of the rostral one‐half of V, and smaller areas in Po and the caudal half of V exclusive of its caudal pole. Field A receives a major projection from most of Po.Neurons with collateral projections to at least two cortical fields have been found in small proportions in most areas projecting to tonotopic cortex. In V and Po at least one‐third of the minor‐projection fibers appear to be collaterals of major‐proj

ISSN:0092-7317    

DOI:10.1002/cne.902650109

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe segmental origins of the cricket giant interneuron system have been studied by staining these neurons with cobalt during the last half of embryonic development. The results demonstrate that the interneurons are derived from three distinct clusters of embryonic neurons that form a serially repeating pattern in each abdominal ganglion. Some of the neurons previously described in adults (Mendenhall and Murphey, '74; Murphey, '85) have been identified in embryos and are described here with respect to this pattern. These neurons include both giant interneurons and several non‐giant mechanosensory interneurons that mediate several different sensory modalities. The anatomical organization of this system is compared to similar mechanosensory systems in other insects and crustace

ISSN:0092-7317    

DOI:10.1002/cne.902650110

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

年代:1987

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902650101

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

年代:1987

数据来源: WILEY