摘要:

AbstractThe prothoracicotropic hormone is an insect neuropeptide released into the hemolymph to signal molting and metamorphosis through its stimulation of steroidogenesis. The only known source of the prothoracicotropic hormone in the tobacco hornworm,Manduca sexta, has been a group of lateral cerebral neurosecretory cells, the L‐NSC III. In this study, the developmental and spatial distribution of the prothoracicotropic hormone was examined throughout the life cycle ofManduca.In common with many vertebrates and invertebrates in which neuropeptides are located in several regions within the central nervous system (CNS), the prothoracicotropic hormone phenotype inManducais expressed by CNS neurons in addition to the L‐NSC III. These neurons are located in the brain, frontal ganglion, and subesophageal ganglion. One cerebral neurosecretory cell group, the ventromedial neurons, expresses the prothoracicotropic hormone phenotype and the behavioral neurohormone, eclosion hormone. Whereas the L‐NSC III and the ventromedial neurons express the peptide phenotype throughout the life cycle, the other neurons express the peptide only during the embryonic and larval stages. This precise spatial and temporal expression of the prothoracicotropic hormone by different groups of neurosecretory cells raises the possibility that inManducathe peptide may, in addition to its known neuroendocrine function, play other physiological roles in different ways at different stages of the life cycle. © 1993 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903270102

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractResponse properties of auditory nerve fibers (ANFs), including threshold sensitivity, vary systematically with spontaneous discharge rate (SR) (Liberman, M.C.: J. Acoust. Soc Amer. 63:442–455, 1978). Thus, an understanding of the mechanisms underlying signal transformation in the cochlear nucleus (CN) must include a description of any SR‐based difference in ANF projections. This study is the second of a pair describing the CN projections of intracellularly labeled ANFs of known SR, the first of which summarized projection to the anteroventral CN (Liberman, M.C.: J. Comp. Neurol. 313:240–258, (1991). For each swelling from each labeled fiber, the position (within CN subdivisions), the size, and the type of cell contacted (if determinable) was noted: roughly one in four labeled swellings appeared in intimate contact with the soma or proximal dendrites of a CN cell. In all such cases, cell size and swelling size were measured. As reported for auteroventral cochlear nucleus, the ANF innervation of the small‐cell regions of posteroventral CN (PVCN) was almost exclusively by low‐and medium‐SR fibers. Other significant SR‐based trends in ANF projections included (1) a tendency for high‐SR fibers to contact larger cells in PVCN, (2) a meager projection of low‐ and medium‐SR fibers to octopus cells, and 3) a tendency in the dorsal CN (DCN) for low‐SR terminals to end closer to the fusiform cell layer than high‐SR terminals. There were no significant SR‐based difference in ANF swelling sizes in any subdivision. A consideration of the average cell sizes, ANF swelling sizes and estimated numbers of ANFs of different CF and SR converging on each CN cell help explain some of the differences in response transformation associated with different cell types in the C

ISSN:0092-7317    

DOI:10.1002/cne.903270103

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have used electrophysiology and light microscopy of intracellularly labeled neurons in the nucleus of the tractus solitarius (nTS) in brainstem slices of the newborn rat (PO to P6) to examine the functional and morphological correlation of their development. Three‐dimensional reconstruction of neurons injected intracellularly with biocytin, following electrophysiological recording, revealed a close correspondence between morphological immaturity (appearing as polarization of the dendritic tree) and the absence of a ramp‐like voltage trajectory at the offset of hyperpolarizing current injections–lAnegativity (8 of the 8 cells examined showed this correlation). These morphologically polarized IAnegative neurons showed preferential dendritic sprouting in two diametrically opposite poles of the perikaryon.The orientation of the polarity differed according to the rostrocaudal location of the neuron. The appearance of a polarized dendritic tree during the first (immature) phase was transient and closely coincident with IAnegativity. Following the development of adult‐like electrophysiological characteristics, i.e., IApositivity, nucleus of the tractus solitarius neurons showed remarkably different morphological features (9 of 10 cells). These included a widespread branching of the dendritic tree in all directions, giving it a bushy appearance (cell body to dendrite ratio of 1:40). Numerous dendritic spines, growth cones on both dendrites and axons, and axon collateralization were present during both phases and indicate that nTS neurons during the two phases of early development demonstrate dynamic features of growth and maturation. The development of adult‐like electrophysiological characteristics, i.e., IApositivity, progressively increased in the postnatal period. During the later part of the first postnatal week, twice as many neurons showed IApositivity in days P3 to P6 as compared with days PO to P2. These results reveal the dynamic nature of neurons in the nTS during early development and illustrate the close link between morphology and functional characteristics in this region. We suggest that the establishment of adult‐like morphology can be modified by appropriate environmental clues provided to nTS neurons during the initial (immature) phase of early postnatal development. © 1993 Wil

ISSN:0092-7317    

DOI:10.1002/cne.903270104

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe ultrastructural organization of association nuclei in the primate thalamus is largely unexplored. In the present study we have combined electron microscopy with immunocytochemistry for the acetylcholine synthesizing enzyme choline acetyltransferase (ChAT) to assess the cholinergic synaptic organization of the mediodorsal (MD) nucleus in macaque monkeys. The cholinergic innervation of the MD nucleus showed striking regional variations with the greatest density of immunoreactive axons and varicosities found within the parvicellular division. Electron microscopic examination revealed that these ChAT immunoreactive (ChAT‐IR) axons were primarily small and unmyelinated. The majority of immunoreactive synaptic profiles were found within the extraglomerular neuropil (80.5%), with the remainder present in glomerular regions. Within the glomerular and extra‐glomerular neuropil ChAT‐IR profiles made contact with both conventional, presumably relay cell dendrites (CD), as well as with synaptic vesicle containing dendrites (SVCD) of local circuit neurons. In the glomeruli the frequency of synapses was approximately equal for CDs and SVCDs while in the extraglomerular areas 75% of the synaptic contacts were with CDs. ChAT‐IR synaptic profiles had a diversity of junctional complex morphologies. Within glomeruli they made symmetric synapses with CDs and predominantly asymmetric with SVCDs. The majority of extraglomerular contacts (60%) were classified as asymmetric and these as well as the smaller number of symmetric synapses contacted both CDs and SVCDs.In accord with results of physiological studies, these anatomical data indicate that cholinergic input to thalamic nuclei influences relay cell activity both directly and indirectly via local circuit neurons. © 1993 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903270105

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe dorsal cap of the inferior olive is involved in the control of eye movements and is excited by inputs from the midbrain. In the present study we attempted to determine the inhibitory input to this nucleus in rat and rabbit.The projection from the nucleus prepositus hypoglossi to the dorsal cap was studied in the light microscope by anterograde tracing of Phaseolus vulgaris‐leucoagglutinin and lesioninduced depletion of glutamic acid decarboxylase immunoreactivity, and in the electron microscope by anterograde tracing of wheat germ agglutinin‐coupled horseradish peroxidase combined with GABA immunocytochemistry. We show that the nucleus prepositus hypoglossi projects bilaterally to the dorsal cap, contralaterally to the ventrolateral outgrowth, and ipsilaterally to the medial accessory olive. After lesioning of the nucleus prepositus hypoglossi, the caudal dorsal cap was depleted of most of its glutamic acid decarboxylase‐immunoreactive terminals while the rostral dorsal cap and the ventrolateral outgrowth were depleted of a minor part. Ultrastructural analysis indicates that the majority, but not all, of the terminals from the nucleus prepositus hypoglossi in the dorsal cap are GABA‐positive. These GABA‐positive and GABA‐negative terminals form predominantly symmetric and asymmetric synapses; most of them synapse on dendrites outside and inside glomeruli, frequently in association with dendrodendritic gap junctions, while a small minority are axosomatic. None of the terminals from the nucleus prepositus hypoglossi was found to form a crest synapse, although synapses of this kind were predominantly formed by GABAergic terminals.This study shows that the dorsal cap receives a major inhibitory input from the nucleus prepositus hypoglossi, the terminals of which are located at strategic positions on the olivary neurons. © 1993 Wil

ISSN:0092-7317    

DOI:10.1002/cne.903270106

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractAge‐related increases and decreases have been described in cortical dendritic neuropil. Here, we examine age‐related changes in the basilar dendrites of supragranular pyramidal cells in human superior temporal gyrus (i.e., Wernicke's area) of left and right hemispheres. Tissue was obtained from 20 neurologically normal right‐handers from 18–79 years: 10 males (Mage= 52.2 years; SDage= 17.4) and 10 females (Mage= 47.8; SDage= 20.5). In tissue prepared by a modified rapid Golgi technique, ten pyramidal cells were sampled from each hemisphere and evaluated according to the following parameters: total dendritic length, mean dendritic length, and dendritic segment count.Despite considerable interindividual variation, the data exhibited significant dendritic degeneration with aging. There was an age‐related decrease in total dendritic length (r[20] = −0.44; P<0.05) and especially in mean dendritic length (r[20] = –0.69; P<0.001) with increasing age. Age‐mean dendritic length correlations were negative for all segment orders and revealed a progressive decrease in segment length in more distal branches. The number of dendritic segments remained relatively stable across the age span sampled. The data also indicated that interhemispheric dendritic asymmetries decreased with age. Individuals under 50 years of age had significantly greater total dendritic length values in the left hemisphere. Interhemispheric dendritic differences were not significant in individuals over 50. © 1993

ISSN:0092-7317    

DOI:10.1002/cne.903270107

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThis quantitative Golgi study extends our investigation of relationships between cortical dendrite systems in humans and higher cognitive functions. Here we examine the relationship between the basilar dendrites of supragranular pyramidal cells in Wernicke's area and selected intrinsic (i.e., gender and hemisphere) and extrinsic (i.e., education and personal history) variables. Tissue was obtained from 20 neurologically normal right‐handers: 10 males (Mage= 52.2) and 10 females (Mage= 47.8). Several independent variables were investigated: GENDER (male, female), HEMISPHERE (left, right), and EDUCATION (less than high school, high school, and university). These were evaluated according to Total Dendritic Length, Mean Dendritic Length, and Dendritic Segment Count. A distinction was made between proximal (1st, 2nd, and 3rd order) and ontogenetically later developing distal (4th order and above) branches.There was significant interindividual variation in dendritic measurements, which roughly reflected individuals' personal backgrounds. Females exhibited slightly greater dendritic values and variability than males across the age range examined. On the whole, the left hemisphere maintained a slight advantage over the right hemisphere for all dendritic measures when all subjects were pooled, but these differences were not in a consistent direction across individuals. Education had a consistent and substantial effect such that dendritic measures increased as educational levels increased. Dendritic differences between independent variable levels were most clearly illustrated in the total dendritic length of 3rd and 4th order branches. Distal dendritic branches appeared to exhibit greater epigenetic flexibility than proximal dendrites. The present findings concur with environmental enrichment research results in animals and suggest that dendritic systems in humans function as a sensitive indicator of an individual's (a)vocational activities. © 1993 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903270108

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractEstrogens play an important role in the control and differentiation of species‐typical behavior and in endocrine homeostasis of birds, but the distribution and evolution of cells that contain estrogen receptors in the avian brain are poorly understood. This study therefore surveys 26 species in the avian orders Anseriformes (1 species), Galliformes (2), Columbiformes (3), Psittaciformes (1), Apodiformes (2), and Passeriformes (3 suboscines, 14 oscines). Indirect immunocytochemistry with the estrogen receptor (ER) antibody H222Spy revealed a general pattern of ER‐antibody‐immunoreactive cells (ER‐IRC) in all 26 species, with ER‐IRC in consistent, well‐defined locations in the limbic forebrain, the midbrain striatum, the hippocampus, the hindbrain, and especially in the preoptic area and the tuberal hypothalamus. For some species, the microdistribution of ER‐IRC in some of these general areas differed, such as in the hippocampus and the anterior hypothalamus of suboscine species and in the preoptic area of the Japanese quail. Brains of oscine songbirds of both sexes, unlike brains of nonsongbirds, had ER‐IRC in three specific structures of the nonlimbic forebrain: in the area surrounding the nucleus robustus archistriatalis; in the rostral forebrain; and, for all individuals, in the caudale neostriatum, including the nucleus hyperstriatalis ventrale, pars caudale (HVc). Among songbird families or subfamilies, adult males of the Estrildinae had much lower numbers of ER‐IRC in HVc than did adult males of the Fringillidae, Paridae, Sturnidae, and Ploceinae. Differences occurred, too, among closely related species: the songbird canary (Serinus canaria) had an ER‐IRC area in the rostral forebrain that was lacking in all other songbird species, including other cardueline finches. The cells with ER that are found only in the songbird forebrain but not in reptiles, nonpasserine birds, and nonoscine passerine birds very likely coevolved with steroid‐dependent differentiation of vocal control areas. The songbird‐specific expression of ER in the forebrain could be an example in which taxon‐specific behavior is due to taxon specific neurochemical properties of the brai

ISSN:0092-7317    

DOI:10.1002/cne.903270109

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have studied the microglial reaction that accompanies cortical infarction induced by middle cerebral artery occlusion (MCAO). Lectin histochemistry with the B4‐isolectin fromGriffonia simplicifoliaas well as immunocytochemistry with a panel of monoclonal antibodies directed against major histocompatibility complex (MHC) and lymphocytic antigens were performed. Principal attention was focused on neocortical and thalamic regions, representative of primary and secondary ischemic damage, respectively. With the lectin procedure, activated microglial cells were abundant in the neocortex 24 hours after MCAO. In contrast, microglial activation in the thalamus was not apparent until day 2 after MCAO. On day 5, MHC class II antigen was expressed by reactive microglia in fiber tracts traversing the striatum, but was absent from activated microglia in the primary cortical infarction area. MHC class I and lymphocytic antigens were expressed differentially on microglia with class I antigens appearing early and lymphocytic antigens appearing late in the time course after focal ischemia. The findings are compatible with previous studies during global ischemia and confirm the early activation and the progressive nature of immunomolecule expression on activated microglia after an ischemic insult. In addition to neocortical and thalamic sites, our results showed an early microglial activation to be present also in forebrain regions outside of the middle cerebral artery (MCA) territory, such as the contralateral cortex and hippocampus. A unilateral microglial reaction was also detectable after long‐term survival (≥4 weeks) in the pyramidal tracts, as well as in the corticospinal tracts at cervical but not lumbar spinal cord levels. Ischemia‐induced neuronal damage, as evaluated by Nissl staining, was found only in cortical and thalamic regions. We conclude that the demonstration of reactive microglia indicates not only imminent ischemic neuronal damage within MCA territory but can also delineate extra‐focal disturbances, possibly reflecting subtle and transitory changes in neuronal activity. © 1993 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903270110

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractInoculation of the scarified cornea with herpes simplex virus (type 1) leads to herpetic infection of trigeminal ganglion cells. A recent study of the susceptibility of ganglion cells revealed that there may be at least four populations of trigeminal ganglion cells that are infectable by herpes. Two classes were identified by their neuropeptide content: Substance P or calcitonin gene‐related peptide. One class was identified by its affinity for a monoclonal antibody, SSEA‐3. The fourth class was recognized by its common affinity for both the monoclonal antibody LD2 and for the lectinBandeiraea simplicifoliaisolectin. However, there has been no direct evidence of which types are infected directly as a result of retrograde transport from the corneal site and which may be infected by cell‐to‐cell spread. The aim of this study was to determine which classes of neurons, which are known to become infected with HSV after ocular inoculation, supply corneal innervation.We have identified four classes of trigeminal ganglion neurons that supply axons to the central cornea of the mouse, on the basis of their ability to transport Fluoro‐Gold retrograde from axons in the central corneal epithelium and stroma. About 40% of the neurons that innervate the cornea contain Substance P or calcitonin gene‐related peptide; about 60% of the neurons that innervate the cornea react with the monoclonal antibody SSEA‐3. About 36% of all neurons in the whole ophthalmic division react with the LD2 orBandeiraea simplicifoliaisolectin, and Fluoro‐Gold labels only 2% of them. Thus, the population of LD2/Bandeiraea Simplicifolia Isolectin neurons that innervates the cornea represents less than 1% of the total neurons in the ophthalmic division, although it constitutes about 20% of the infected cells in that division at three days after viral inoculation. We conclude that most of the LD2/Bandeiraea simplicifolia isolectin‐positive ganglion cells that are infected with herpes at 3 days are infected as a result of HSV spread from nearby cells in the ganglion or proximal trigeminal root. Neurons labeled with antibodies to Substance P, calcitonin gene‐related peptide, or α‐SSEA‐3 that are primarily infected may be sources of the cell‐to‐cell spread of v

ISSN:0092-7317    

DOI:10.1002/cne.903270111

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY