摘要:

AbstractThis inquiry began with the discovery that just tow layers of the lateral geniculate nucleus (GL) ofGalagocontain large amounts of acetyl‐cholinesterase (AChE). These two layers (layers 3 and 6) are similar in cell size and Nissl‐staining characteristics and project to the same layer in the striate cortex.To find out whether the pattern of staining is unique in theGalago, We examined the distribution in AChE in the lateral geniculate nucleus of the owl monkey,Aotus trivirgatus.In this species we found that the parvocellular layers (3 and 4) stained darkly for AChE while the magnocellular layers (1 and 2) were only slightly stained. The interlaminar zones as well as the “S” layers were also distinguished by a high level of AChE staining.In order to determine the source of the cholinesterase staining in layers 3 and 6 ofGalago, we studies, in separate experiments, the effects of kainic acid injections into GL, of eye enucleations, and of lesions of the striate cortex. Injections of kainic acid, followed by survival time of 2 and 11 days, produced severe cellular destruction in GL, yet the AChE staining of layers 3 and 6 was undiminished. Eye enucleations had no effect upon the AChE staining of GL even after a survival period of 3 years. In contrast, a small lesion of the striate cortex, followed by a 9‐day survival period, produced conspicuous gaps in the AChE staining of layers 3 and 6. These results indicate that the AChE in layers 3 and 6 is not attributable to the cells within the layers, or to retinal fibers, but is dependent upon descending projections form the striate cortex.Because of the dependence of AChE reaction product in layers 3 and 6 of GL upon and intact striate cortex, we turned our attention to the distribution of AChE in the striate cortex. InGalago, cholinesterase‐positive cells were found in layer VI of the striate cortex; and in bothGalagoandAotus, the striate cortex was distinguished from other cortical areas by a prominent band of cholinesterase activity within layer IV. This band ended abruptly at the 17‐‐18 border. The precise origin of this cholinesterase staining within layer IV of the striate cortex remains t

ISSN:0092-7317    

DOI:10.1002/cne.901940402

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe inferior olivary complex (IOC) in the opossum is not present as a discernible nuclear group at birth (12–13 days post‐conception), but it is seen by the third day in the pouch (postnatal day 3). At this age the IOC is a homogeneous mass of cells with no apparent nuclear subdivisions. Furthermore, cells destined for the IOC can be seen in migratory positions termed the marginal and submarginal migratory strands similar to those described for the rat (Altman and Bayer, '78a, b; Ellenberger et al., '69). By pouch day 5–7 the marginal migratory strand is no longer present; however, the submarginal stream of cells is still evident. As in 3‐day‐old opossums no nuclear subdivisions can be identified in the 5–day old animal. Analysis of both Nissl and Golgi preparations from 5–7 day old opossums reveals that olivary neurons are 5–7 μ in diameter and exhibit relatively short dendrites with infrequent spines. By 10–14 days in the pouch the rostral IOC has begun to separate into major nuclear subdivisions, whereas intermediate and caudal areas have not separated. Individual olivary cell bodies at this age are 6–9 μm dendritic shafts exhibit irregular contours and moniliform threads at their terminations, and spines arising from the dendrites are either pedunculated or sessile. In the 21–25‐day‐old opossum individual principal and accessory nuclei can be identified in a form similar to those in the adult; however, the entire IOC is less that one‐fourth the length of its adult counterpart (Bowman and King, '73). Neuronal perikarya have increased in size to 10–12 μm, while the dendrites are varicose and often end as moniliform threads. Spines have similarly increased in number and complexity since the previous age and include sessile, pedunculated, multilobed, and elongate forms. Dendritic spines reach their greatest density in 36–40‐day‐old animals and decrease in number by pouch day 65–68. At this latter age the nerve cell bodies measure 15–22 μm in diameter. The time span between pouch days 21–25 and days 65–68 is characterized by tremendous growth as the length of the IOC increases to three‐fourths of the adult size.The cerebellum was also examined from day 1 through day 68. At birth a rudimentary cerebellum contains darkly stained cells dorsal to the mitotically active ventricular epithelium. By pouch days 5–7 the immature cerebellum retains its plate‐like appearance, but includes a superficial band of darkly stained cells. Two dense bands of cells, one superficial and one deeper, are present in the cerebellum by pouch days 10–14. Throughout pouch days 10–14 to 65–68 the developing cerebellum is acquiring its adult laminar appearance; however, an external granular layer is still conspicuous at 68 days of age.The present results indicate that the development of the IOC, from its initial appearance in the ventral medulla through its separation into discrete subnuclei, is markedly extended in the opossum when compared to the rat (Altman and Bayer, '78b). Moreover, the adult nuclear configuration of the opossum IOC is apparent prior to the appearance of distinct cortical laminae in the cerebellum. The significance of some of the morphological aspects of IOC development, e.g., the temporal relationship between spine density and t

ISSN:0092-7317    

DOI:10.1002/cne.901940403

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractAt birth the inferior olivary complex (IOC) is not present in the caudal ventro‐medial brainstem of the opossum. In the 3‐‐7‐day‐old animal (15–19 days post‐conception), this same region does contain neurons of the developing IOC. The immature neurons are characterized by large, centrally numerous small‐diameter profiles which contain bundles of filaments and scattered microtubules. Occasional synaptic endings, containing round clear vesicles, contact large, flocculent profiles which contain bundles of filaments and scattered microtubules. Occasional synaptic endings, containing round clear vesicles, contact large, flocculent profiles. By 10–14 days of age, the olivary cell bodies and the surrounding neuropil exhibit many of the same features as in the 3–7 day‐old opossums. In opossums 21–25 days old, there is an increase in varicosities and irregular contours along many of the dendritic shafts. Furthermore, synaptic terminals, possessing round clear vesicles, now contact the soma, dendritic shafts, dendritic varicosities, spines, and large, flocculent profiles. Terminals containing pleomorphic vesicles or a mixture of clear and large granular vesicles are presynaptic only to dendritic spines or large, flocculent profiles. Neuroglial cell bodies have been identified at all ages examined.It is not until days 65–68 that pre‐ and postsynaptic elements are organized into synaptic clusters (glomeruli), which are typical of the adult. Spiny appendages and small‐diameter dendrites comprise the central core of the clusters which are surrounded by synaptic endings containing a variety of vesicle types. Thus it would appear that subsequent to their initial arrival (day 16–17), the synaptic relationships of cerebellar and midbrain afferents are modified to reflect their adult configuration by days 65–68. This extended period of development (postnatal days 3–68) for the olivary complex provides a good model for assessing the ef

ISSN:0092-7317    

DOI:10.1002/cne.901940404

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe axonal arborization of chandelier cells is characterized by its conspicuous, vertically oriented, bouton aggregates. The efferent synaptic relationships established by these terminal formations were investigated by electron microscopy of Golgi preparations after gold toning and deimpregnation. In all cases examined form layers II and III of cat areas 17 and 18, the terminal formations, here denominatedspecific terminal portions(stp), make symmetric synapses upon axon initial segments of pyramidal neurons. Some identified stp's were reconstructed from ultrathin serial sections with the aid of a microcomputer‐based system, and the number of synaptic contacts established on axon initial segments was evaluated. No evidence was found that parts of the axonal tree other than stp's also engage in synaptic contacts.Specific terminal portions are rather variable in complexity. However, the synaptic contacts they engage in are constant and the complexity of stp's from the same axonal arborization varies. It is, therefore, clear that all stp's are terminal axonal formations of a unique, specialized type of neuron.Computer techniques and conventional Golgi observations were used to study further details of chandelier cell morphology. Axonal plexuses are preferentially, although not exclusively, local and distribute within spheric, ovoid, or disk‐shaped spaces In most chandelier cells, the main axonal trunk descends to the white matter, where we have been unable to follow it furt

ISSN:0092-7317    

DOI:10.1002/cne.901940405

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractTwo major interneurons of the outer part of Rexed's layer II (IIa) were impaled with microelectrodes, had their primary inputs characterized, and were subsequently filled with horseradish peroxidase. Their fine structural characteristics and synaptic connections were then analyzed electron microscopically. Two islet cells, whose rostrocaudally oriented dendrites were largely confined within layer IIa, received primary input form small myelinated axons. A stalked cell, whose cell body was situated on I/II border had a cone‐shaped dendritic arbor which traversed layer IIa as well as the inner part of Rexed's layer II (IIb) and rostrocaudal dendritic branches which ran for part of their course along the I/IIa border. It received primary input from small myelinated as well as form unmyelinated axons. Both cell types received asymmetrical axodendritic synapses from primary endings in layer IIa and IIb glomeruli and widely separated symmetrical axodendritic synapses from small nonprimary endings outside of glomerli.The presence of aggregates of synaptic vesicles in the dendrites of the layer IIa islet cells but not in the staked cell dendrites constitutes the major fine structural difference between these interneurons. Islet cell dendtrites from symmetrical synapses on several different kinds of neural processes. They usually send either a single type 2 spine (spines which contain synaptic vesicles) or dendtritic shaft into layer IIa and IIb glomeruli, where they form dendrodendritic synapses on adjacent type 1 spines (spines without synaptic vesicles) and on other small dendritic shafts. Some islet cell type 2 spines also form dendroaxonic synapses on the primary endings.Outside of the glomeruli, islet cell dendrites also form dendrodendritic synapses on type 1 spines and different sized dendritic shafts. They often approach other dendritic shafts. They often approach other dendritic shafts forming small bundles of dendrites in which they are reciprocally linked by dendrodendritic synapses to other synaptic vesicle‐containing dendrites. At bead‐like enlargements of their dendritic shafts and along some of the shafts of unmyelinated axons. The unmyelinated axon of the islet cell forms symmetrical synapses on layer II dendritic shafts and spines outside of glomeruli. The role of the layer IIa islet cell as an inhibitory interneuron is disc

ISSN:0092-7317    

DOI:10.1002/cne.901940406

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractNeurons in Rexed's layer II were physiologically characterized with natural and electrical stimuli applied to their cutaneous receptive field. The neurons were then intracellularly stained with horseradish peroxidase. Three general patterns of physiological responses were found Nociceptive specific neurons did not respond to gentle mechanical stimulation. Most responded exclusively to tissue‐damaging stimuli. Some also responded to moderately heavy pressure, but these responded to noxious stimuli with an increased discharge frequency. Wide dynamic range neurons responded to both gentle mechanical stimulation and to tissue‐damaging stimulation. Low‐threshold mechanoreceptive neurons responded only to gentle mechanical stimulation. Some of the low‐threshold mechanoreceptive neurons were innervated by primary afferents with unmyelinated axons. Excepting those low‐threshold mechanoreceptive neurons with input form unmyelinated afferents, the patterns of primary afferent innervation of layer II neurons were similar to the patterns innervation that gave been found for neurons in layers I and IV‐V.All nut 2 of the 22 neurons that we found were recognized as being of two general morphological types. Stalked cells had their perikarya situated along the superficial border of layer II. Most of their dendrites traveled ventrally while spreading out rostrocaudally. This gave their dendritic arbors a fan‐like shape. Stalked cell axons arborized largely in layer I. Islet cell perikarya were found throughout layer II. Most of their dendrites traveled rostrocaudally. Their dendritic arbors were shaped like cylinders with their long axes parallel to the long axis of the spinal cord. Islet cell axons arborized in the immediate vicinity of their dendtritic territories, within layer II.Stalked cells and those islet cells whose dendritic arbors were largely contained within the superficial one‐third of layer II (layer IIa) were either nociceptive specific or wide dynamic range neurons. The islet cells whose dendritic arbors were largely within the deeper two‐thirds of layer II (layer IIb) were all low‐threshold mechanoreceptive neurons. These observations suggest that layers IIa and IIb have different functional roles and that stalked cells and islet cells are separate and distinct components of the neural circuitry of the supe

ISSN:0092-7317    

DOI:10.1002/cne.901940407

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractTritiated thymidine (3H‐TdR) injected before a stab wound of the spinal cord or transection of the hypoglossal nerve has resulted in many labeled reactive cells in the CNS after injury, most of which have the ultrastructural features of microglia. To test for the possible origin of these labeled cells from monocytes, we examined them for the presence of sodium, fluoride‐ (NaF) sensitive non‐specific esterase (NSE), an enzyme characteristic of monocytes. Some of the labeled cells in stab wounds had NaF‐sensitive NSE, but no such cells were found in the nucleus of the injured hypoglossal nerve. To test for the possibility that the NSE‐negative labeled cells had been labeled by reutilization of3H‐TdR, we used125I‐5‐iodo‐2'deoxyuridine (125I‐UdR), a thymidine analogue with a much lower rate or reutilization, to label blood mononuclear cells prior to either a spinal cord stab wound or hypoglossal axotomy. The number of labeled cells was decreased in the spinal cord wound, but more than half were NSE‐negative. No labeled blood mononuclear cells were found in the hypoglossal nucleus, although there was no decrease in the hyperplasia of unlabeled non‐neuronal cells. When125I‐UdR was injected on the fourth day after hypoglossal axotomy, or when both3H‐TdR and125I‐RdR were injected simultaneously before hypoglossal axotomy, many labeled cells were found in the hypoglosaal nucleus, indicating that125I‐UdR can be used by the reactive cells and that it did not inhibit their proliferation. Therefore, the microglial cells that proliferate in response to peripheral nerve injury are not recently derived from any type of circulating large blood mononuclear cell. The most likely explanation for the presence of the3H‐TdR‐labeled cells in the nucleus of the injured hypoglossal nerve in that they were proliferating intrinsi

ISSN:0092-7317    

DOI:10.1002/cne.901940408

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractNeurogenesis in the rat amygdala was examined with3H‐thymidine radiography. The animals were the offspring of pregnant females given two injections of3H‐thymidine on consecutive days in an overlapping series: Embryonic day (E) 12 + E13, + E14. E21 + E22. On 60 days of age, the percentage of labelled cells and the proportion of cells added during each day of formation were determined at several anatomical levels within the following components of the amygdala: anterior amygdaloid area, bed nuclei of the lateral and accessory olfactory tracts, central, medial, anterior cortical, posterolateral cortical, posteromedial cortical, basomedial, basolateral, and lateral nuclei, the amygdalo‐hippocampal area, and the intercalated masses.All large and many small neurons originate in most nuclei between E13 and E17, those in the intercalated masses between E15 and E19, those in the amygdalo‐hippocampal area between E16 and E19. The anterior amygdaloid area, intercalated masses, central, medial, posterolateral cortical, posteromedial cortical, basomedial, basolateral, and lateral nuclei have strong rostral‐to‐caudal intranuclear gradients. There are five additional intranuclear gradients: 1) medial to lateral in the central nucleus, anterior amygdaloid area, and anterior intercalated masses; 2) lateral to medial in the bed nucleus of the lateral olfactory tract and basolateral nucleus; 3) superficial to deep in the amygdalo‐hippocampal area, posterolateral, and posteromedial cortical nuclei; 4) ventral to dorsal in the medial nucleus; and 5) dorsal to ventral between the small and large‐celled parts of the lateral nucleus. Only the bed nucleus of the accessory olfactory tract and the anterior cortical nucleus do not have intranuclear gradients. Between 10 and 15% of the total cell population in most nuclei are very small neurons and/or glia which originate simultaneously between E18 and E20. This population is absent in the ventral part of the medial, anterior cortical, and anterior basomedial nuclei; these contiguous areas may form a distinct subunit in the amygdala.In contrast to the pronounced intranuclear gradient, internuclear gradients are weak. Neurogenesis in the central nucleus and corticomedial and basolateral complexes appears to take place both concurrently and independently. There are groups of early‐originating neurons in the central, medial, and basolateral nuclei located near the periphery of the amygdala. Each of these groups is surrounded by younger neurons farther within the interior. The youngest calls are in the centrally placed intercalated masses. These settling patterns suggest that cells in the amygdala arise simultaneously from more than one neuroepithelial source during morphogenesis.The chronology of neurogenesis in the amygdala can be related to some of its anatomical connections. Rostral‐to‐caudal gradients in the corticomedial complex may be timed to coincide with early vs. late arrival of olfactory fibers. The subdivisions bases on intranuclear gradients in the central, medial, and basolateral nuclei match the subdivisions based on patterns of a

ISSN:0092-7317    

DOI:10.1002/cne.901940409

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractGroups of pregnant rats were injected with two successive daily doses of3H‐thymidine form gestational days 12 and 13 (E12 + 13) until the day before parturition (E21 + 22). In adult progeny of the injected rats the proportion of neurons generated on specific embryonic days was determined quantitatively in the vestibular and auditory nuclei of the upper medulla. In the vestibular nuclei, neurons are generated between days E11 and E15 in an overlapping sequential order, yielding a lateral‐to‐medial and a rostral‐to‐caudal internuclear gradient. In the lateral vestibular nucleus peak production time is day E12; in the superior nucleus, E13; in the inferior nucleus, E13 and E14; and in the medial nucleus, E14. The early generation of neurons of the lateral vestibular nucleus may reflect the early differentiation of the circuit from the gravity receptors (utricle) to neurons of the spinal cord controlling postural balance. The later production of neurons of the superior vestibular nucleus may reflect the subsequent differentiation of the circuit from the rotational receptors (semicircular canals) to the neurons of the brain stem controlling eye movements. The generation time of neurons of the nucleus prepositus hypoglossi overlaps with that of the medial vestibular nucleus.The neurons of the anteroventral and posteroventral cochlear nuclei are produced form days E13 to E17, with no temporal differences between the two nuclei. The neurons of the dorsal cochlear nucleus are generated over a very long time span, beginning on day E12 and extending into the postnatal period. There is a sequence in the production of neurons forming the different layers of the dorsal cochlear nucleus in the following order: pyramidal cells, cells of the inner layer, cells of the outer layer and, finally, cells of the granular layer. There is also a sequential production of neurons in four nuclei of the superior olivary complex. In the lateral trapezoid nucleus peak production time is day E12; in the medial superior olivary nucleus, day E13; in the medial trapezoid nucleus, day E15; and in the lateral superior olivary nucleus, day E16. This order yields a medial‐to‐lateral gradient in the dorsal aspect of the superior olivary complex, and a lateral‐to‐medial gradient ventrally. These mirror‐image gradients were also seen intranuclearly in the lateral superior olivary nucleus and the medial trapezoid nucleus. The cytogenetic gradients could not be related to tonotopic representation; however, they could be related to the lateral location of ipsilateral cochlear nucleus input to the lateral superior olivary nucleus and the medial location of the contralateral cochlear nucleus input to the media

ISSN:0092-7317    

DOI:10.1002/cne.901940410

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractGroups of pregnant rats ware injected with two successive daily doses of3H‐thymidine form gestational day 12 and 13 (E12 + 13) until the day before parturition (E21 + 22) in order to label in their embryos the proliferating precursors of neurons. At 60 days of age the proportion of neurons generated (or no longer labeled) on specific embryonic days was determined quantitatively in 14 nuclei of the pontine region. Peak production time of neurons of the trigeminal mesencephalic nucleus was on day E11 or earlier, with a small proportion generated on day E12. Peak production time of the trigeminal motor neurons was on day E12, with a small proportion produced earlier. Neurons of the principal sensory nucleus were generated between days E13 and E16, with a peak on day E14; the late‐produced neurons tended to belong to a class of intermediate and large cells. The bulk of the neurons of the supratrigeminal and infratrigeminal nuclei arose on day E15 and E16.Neurons of the locus coeruleus are produced mostly on day E12, with about 20% of the cells arising on day E13. The bulk of the neurons of the dorsal tegmental nucleus (Gudden's) are produced between days E13 and E15, whereas most of the neurons of the deep (ventral) tegmental nucleus are produced on day E15. A dorsal‐to‐caudal gradient was also obtained between the dorsal and vental nuclei of the lateral lemniscus, the neurons of the former being generated between days E12 and E15; the latter, between days E13 and E17. The neurons of both the pars lateralis and the pars medialis of the parabrachial nucleus were produced simultaneously between days E13 and E15, with a peak on day E13. the heterogeneous collection of neurons of the pontine paramedial reticular formation was produced from day E11 (or earlier) until day E15. Finally, the neurons of the raphe pontis parvicellularis were generated at an even rate between days E13 and E15, whereas the bulk of the neurons of the raphe pontis magnocellularis were produced on days E15 and E16.On the basis of datings obtained for 9 subdivisions of the entire brain stem trigeminal complex, hypotheses were offered of the cytogenetic components of the system. The sequence of neuron production in the dorsal and deep tegmental nuclei was related to their connections with divisions of the mammillary and habenular nuclei on a “first come‐first s

ISSN:0092-7317    

DOI:10.1002/cne.901940411

出版商:Alan R. Liss, Inc.    

年代:1980

数据来源: WILEY