摘要:

AbstractPrevious studies demonstrated regional differences in the synthesis of extracellular matrix by astrocytes during optic nerve head (ONH) maturation and in glaucomatous optic neuro pathy, suggesting heterogeneity of astrocytes. To characterize different types of glial cells in human fetal and adult ONH, we used a variety of neural cell markers such as HNK‐1/N‐CAM, A2B5, galactocerebroside (GalC), myelin basic protein (MBP), and glial fibrillary acidic protein (GFAP). Cryostat or paraffin sections were prepared from fetal (16–25 weeks) and mature (8 months to 75 years old) ONH and processed for standard single/double immunocytochemistry. Two subpopulations of type 1 astrocytes were present in the mature prelaminar and laminar regions. Glial celia expressing only GFAP were identified as type 1A astrocytes at the edges of the cribriform plates. Cells forming the glial columns and lining the cribriform plates expressed both GFAP and fINK‐1/N‐CAM and were identified as type lB astrocytes. In the myelinated nerve, type 1A astrocytes form the glial limiting membrane. Cells labeled with GFAP and A2B5 were identified as type 2 astrocytes, and GFAP‐negative cells labeled with GaIC, MBP, and HNK‐1/N‐CAM were identified as oligodendrocytes. In fetal ONH, all glial cells expressed HNK‐1/N‐CAM. In older fetal ONH, some glial cells also expressed GFAP. No type 2 astrocytes or oligodendrocytes were present in the fetal ONH. In conclusion, at least two subpopulations of type 1 astrocytes exist in human ONH: Type 1A astrocytes may serve as structural support for a type lB astrocytes, which retain the developmental neural marker HNK‐1/N‐CAM, may have a more complex function by interfacing between blood vessels and other connective tissue surfaces. These findings demonstrate the heterogeneity of astrocytes in the human ONH and suggest differential regional responses to changes in their microenvironment

ISSN:0092-7317    

DOI:10.1002/cne.903620402

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe spinal projecting system of the sea lamprey (Petromyzon marinus) has been used extensively in studies of axonal regeneration in both larvae and adults. However, little is known about the changes that are undergone by this system during metamorphosis. In order to determine the developmental changes in the size of the descending spinal projection and in the morphology of its neurons, larval, transforming, and adult lamprey brains were labeled by retrograde transport of horseradish peroxidase (HRP) injected into the spinal cord at 25% of body length. Examination of brain wholemount preparations revealed that the total number of labeled neurons doubled during metamorphosis. Most of this increase could be explained by elongation of reticulospinal axons from the rostralmost segments of the spinal cord to locations caudal to the injection site. There were no additions or deletions of either identified reticulospinal neurons or of reticulospinal nuclear groups between the larval and the adult stages. The proportions of Müller and Mauthner cells that were labeled reached a maximum of 93% during the early stages of metamorphosis. Axons of these neurons are known to project almost the entire length of the cord, even in larvae. Therefore, the efficiency of retrograde transport appears to be greater during metamorphosis than during larval or adult stages. While changes in efficiency of retrograde transport could account for some of the apparent increase in reticulospinal neuron numbers between larvae and animals undergoing metamorphosis, this could not contribute to the further increase in the apparent size of the reticulospinal system in the adult, since efficiency of retrograde labeling in these animals was lower than that at earlier stages. With retrograde labeling, a significant increase was seen in the profusion of dendritic arborization of some Müller and Mauthner cells during the early stages of metamorphosis. This correlated with an increase in the incidence of extreme axonal die‐back, as indicated by the presence of retraction bulbs within the brainstem. However, intracellular injection of Neurobiotin in untransected animals showed similar degrees of dendritic arborization at all examined stages of development. Therefore, the dendritic profusion did not reflect developmental changes in neuronal morphology but rather reflected an increased sensitivity to axotomy during metamorphosis. We conclude that, during the transformation of the lamprey from the large larval to the adult form, there is little change in either the size or the dendritic morphology of the identified giant reticulospinal neurons. With respect to the smaller reticulospinal neurons, the distance of projection of many of their axons increases during metamorphosis, but there is very little increase in the number of reticulospinal neurons. © 1995 Wiley‐Li

ISSN:0092-7317    

DOI:10.1002/cne.903620403

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractNeurons in the dorsal lateral geniculate nucleus (dLGN) of normal and monocularly lid‐sutured squirrel monkeys were recorded electrophysiologically, and some were injected intracellularly with horseradish peroxidase (HRP) to examine and compare their synaptic inputs. Limited tests of the receptive field properties did not show any differences between the normal, nondeprived, or deprived neurons.Sixteen injected neurons were examined at the light microscopic level with most of these located in the P‐laminae (n = 14). Ten of these were either from normal monkeys (n = 9) or received input from the nondeprived eye of a monocularly deprived monkey (n = 1). The remaining six neurons received input from the deprived eye. The dendritic trees of deprived neurons did not differ from those of normal or nondeprived neurons. Three normal and five deprived neurons from the P‐laminae were examined at the electron microscopic level. Afferent distributions were not significantly different between normal and deprived neurons. Retinal, cortical, and gamma aminobutyric (GABA) ergic afferents accounted for nearly all inputs (avg., 42%, 23%, and 32%, respectively) and selectively contacted proximal, distal, or all parts of the dendrites.Overall, synaptic densities (synapses per length of dendrite) were high proximally and decreased with distance from the soma. However, the synaptic densities onto deprived neurons were higher at all distances compared to those onto normal neurons. Furthermore, HRP‐filled deprived neurons received an average of 25 synapses onto their somata compared with only an average of 7 somal synapses on the HRP‐fihled normal neurons. Most of the increase in the number of synapses onto the deprived neurons was from GABAergic type profiles. This abnormality of the deprived neurons of the dLGN could be the underlying cause of their lesser responses compared with normal or nondeprived dLGN neurons. It could also be the initial stage that causes blindness in monocularly lid‐sutured primates. © 1995 Wi

ISSN:0092-7317    

DOI:10.1002/cne.903620404

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractPrevious work has shown that the avian retina receives two types of centrifugal fibers from the brain. These types can be distinguished based on the size and the morphology of their terminal endings and have been termed convergent and divergent. The centrifugal fibers arise from the isthmooptic nucleus (ION) and the surrounding ectopic cell region (ECR). We used injections of anterograde tracers either to the ION/ECR or to the ECR only to determine the morphology, depth of termination, and regional distribution of the centrifugal fibers arising from each.We found that the ECR gives rise only to the divergent type of the centrifugal fiber, whereas the ION gives rise mainly to the convergent type but may also send some fibers of the divergent type. Most of the fibers project contralaterally, although a few from the ECR project ipsilaterally. The terminals of either type are not uniformly distributed throughout the retina; instead, they are found mainly in the inferior, midtemporal, to nasal portion of the retina and appear to avoid the fovea and most of the red field. By comparison, the ION receives a major projection from portions of the tectum that receive input from the fovea and the red field in a type of neural loop. The neural loop does not project to the same point (homotopic), but projects from the red field to the inferior retina (heterotopic), as was recently proposed by Holden (1990; Vis. Neurosci.4:493–497).The distribution of centrifugal axons corresponds to displaced ganglion cells that selectively innervate the nuclei of the accessory optic system (AOS), including the nucleus of the basal optic root (dorsal, ventral, and lateral) and the nucleus lentiformis mesencephali, pars magnocellularis. We suggest that the centrifugal axons act by increasing the gain on the AOS, thereby enhancing retinal stabilization of gaze with improved accuracy of pecking of small objects. © 1995 Wiley‐Liss

ISSN:0092-7317    

DOI:10.1002/cne.903620405

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe central nucleus of the amygdala (CNA) integrates visceral responses to stress partially through efferent projections to portions of the medial nuclei of the solitary tracts (mNTS) containing catecholaminergic neurons. To determine anatomical sites for CNA modulation of these neurons, immunoperoxidase detection of anterogradely transportedPhaseolus vulgarisleucoagglutinin (PHA‐ L) or biotinylated dextran amine (BDA) was combined with immunogold silver labeling of the catecholamine‐synthesizing enzyme, tyrosine hydroxylase, in adult rat mNTS. From 350 anterogradely labeled terminals identified within the intermediate mNTS, 30% formed symmetric, inhibitory‐type synapses and the remainder lacked recognized junctions as seen within a single plane of section. Of the terminals forming symmetric synapses, 16% were presynaptic to tyrosine hydroxylase immunoreactive dendrites and the remainder to unlabeled dendrites. The level of tyrosine hydroxylase immunoreactivity as assessed by density of gold‐silver particles was significantly lower in dendrites receiving synaptic input from CNA efferents as compared with dendrites of the same sizes (2. 0 μm2in mean area) which received synapses from unlabeled terminals or lacked recognizable synaptic inputs. When separately examined without regard to afferent input, the medium‐ and larger‐sized dendrites having mean cross‐sectional areas of 1–3 μ2m also contained significantly less tyrosine hydroxylase immunoreactivity than small (<1 μ2m) dendrites. These results suggest that CNA efferents to the mNTS inhibit non‐catecholamine‐containing neurons and a subpopulation of catecholamin ergic neurons distinguished by their low levels of tyrosine hydroxylase. The findings also indicate that small, presumably more distal, dendrites in the intermediate mNTS may synthesize and/or release catecholamines.

ISSN:0092-7317    

DOI:10.1002/cne.903620406

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe A7 cell line is an SV4O large T antigen‐immortalized astrocyte cell line produced from the neonatal rat optic nerve. Previous studies have demonstrated that A7 cells provide a favorable environment for the survival and growth of cultured neurons and can also stimulate axonal growth after grafting into the rat striatum. The current study was designed to investigate whether A7 cells grafted into adult rat striatum can migrate away from the implantation site. A7 cells were labelled in culture by incorporation of bromodeoxyuridine (BrdU) or by expression of an alkaline phosphatase transgene. The labelled cells were then transplanted into the left striatum of normal adult rats by introducing a blunt‐end 22 gauge needle through a trephine hole. The rats were euthanized at periods of up to 30 days after grafting. The A7 cells did not appear to alter the cytoarchitecture of the surrounding brain parenchyma. Labelled A7 cells were observed in both gray and white matter areas, and many were located in areas free of damage due to the implantation procedure. The migration of the BrdU‐labelled A7 cells with respect to the implantation needle track was determined on coronal sections. The radial migration distance from the needle tract was similarly determined on horizontal sections. A7 cells migrated progressively longer distances with increasing survival time of the animals: The largest migration distance (1,125 ± 52 μ) occurred at 30 days after grafting with an estimated migration rate of 31 μm per day. There was no significant directional polarity in the migration of these cells within the striatum. Some of the labelled A7 nuclear profiles were associated with blood vessels, some appeared to be associated with fiber bundles within the striatum, and some were found within the gray matter without apparent association with any anatomical structure. These results demonstrate that A7 immortalized astrocytic cells migrate away from a single implantation site following grafting into the adult rat striatum to populate a large area of the striatum. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903620407

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractFollowing middle cerebral artery occlusion in Wistar rats, the immunoreactivity of neuropeptide Y increased ipsilaterally in the insular cortex and basolateral nucleus of the amygdala. In addition, the immunoreactivity of leucine‐enkephalin, dynorphin, and neurotensin increased in the ipsilateral central nucleus of the amygdala. The amygdalar neurochemical changes are likely the result of damage to the insular cortex, although other cortical areas were also affected by the ischemia. To investigate whether damage to the insular cortex is essential in eliciting these changes, a localized lesion of the right or left insular cortex was produced by microinjection of D,L‐homocysteic acid. Control animals received injections of vehicle into the right or left insular cortex or D,L‐homocysteic acid into the right primary somatosensory cortex. Neurochemical changes were examined immunohistochemically with the peroxidase antiperoxidase reaction 5 lays after the injection. The immunoreactivity of neuropeptide Y increased locally after excitotoxic damage to the insular cortex or primary somatosenaory cortex. The amygdalar neurochemical changes, including neuropeptide Y increase in the basolateral nucleus and leucine‐enkephalin, dynorphin, and neurotensin increase in the central nucleus, were seen only when the ipsilateral insular cortex was lesioned. These neurochemical changes were similar to those seen 5 days after middle cerebral artery occlusion.Our findings indicat that damage to the insular cortex is essential in eliciting the neurochemical changes in the ipsilateral amygdala. In addition, the change in neuropeptide Y in the cortex appears to be a local reaction occurring irrespective of location of the lesion and glutamate receptor activation may be involved. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903620408

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractPostnatal development of Ruffini endings was ultrastructuraally investigated in the upper incisors of the rat from 1 day to 60 days after birth by means of protein gene product 9. 5 (PGP 9. 5) immunocytochemistry. The immunostaining with PGP 9. 5 antibody clearly demonstrated chronological alterations of the distribution and ultrastructure of the Ruffini endings during postnatal development. At 1 day after birth, the PGP 9. 5 positive nerve terminals contained a few mitochondria and vesicles immunonegative for PGP 9. 5. Dendritic terminals appeared at 4 days after birth, with a small number of expanded or bulbous portions. These expanded portions possessed morphological features similar to those of the growth cone: several mitochondria and various kinds of vesicles. Typical Ruffini endings with dendritic ramification and expanded portions appeared 7–11 days after birth. At this stage, parts of the axon terminals extended through the slits of Schwann cell covering and formed finger‐like projections called axonal spines. These Ruffini endings increased dramatically in number after 24–26 days and were identical in density and morphology to those seen in adult rats. After the commencement of the occlusion between the incisors, the number of large mitochondria increased, in contrast to the decrease of the vesicles in the axon terminals. Moreover, the axonal spines increased both in number and in length. Thus, the periodontal nerve endings showed stage‐specific morphological features intimately related in timing to tooth eruption and occlusion. Functional stimuli possibly contribute to the final differentiation and maturation of the periodontal Ruffini endings. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903620409

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractRadioactive complementary RNA probes, made from monkey‐specific cDNAs specific for the α1, α2, α4, α5, β1, β2, and γ2and γ2subunits of the γ‐aminobutyric acid A (GABAA) receptor were used for in situ hybridization histochemistry of the primary motor, somatosensory, and anterior parietal areas of thecerebral cortex in macaque monkeys.mRNAs for the α1, β2, and α2, subunit polypeptides, which form receptors with the full range of classical properties, are expressed at much higher levels in all areas and show laminar and sublaminar‐specific concentrations. α2, α4, α5, and β1subunit transcripts are expressed at much lower levels but also display individual, laminar‐specific concentrations; α5, expression, in particular, is highly expressed in layer IV in the somatosensory and parietal areas and in a layer IV‐like band in the motor cortex.In layers in which expression of a particular transcript is high, all neurons may express the gene, but in layers in which expression is moderate, it is possible to detect differences in the degree of labeling of individual neurons for a particular mRNA, and some neurons may not express certain subunit transcripts in detectable amounts.These findings indicate the variability in expression of different GABAAreceptor subunits in the cerebral cortex. Laminar differences may indicate the assembly of functional receptors from different arrangements of available subunits in different classes of ce

ISSN:0092-7317    

DOI:10.1002/cne.903620410

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe development of immunoreactivity for the putative inhibitory amino acid neurotransmitter glycine was investigated in the embryonic and posthatched chick lumbosacral spinal cord by using postembedding immunocytochemical methods. Glycine immunoreactive perikarya were first observed at embryonic day 8 (E8) both in the dorsal and ventral gray matters. The number of immunostained neurons sharply increased by ElO and was gradually augmented further at later developmental stages. The general pattern of glycine immunoreactivity characteristic of mature animals had been achieved by E12 and was only slightly altered afterward. Most of the immunostained neurons ware located in the presumptive deep dorsal horn (laminae IV‐VI) and lamina VII, although glycine‐imrnunoreactive neurons were scattered throughout the entire extent of the spinal gray matter. By using some of our previously obtained and published data concerning the development of gamma‐aminobutyric acid (GABA)‐ergic neurons in the embryonic chick lumbosacral spinal cord, we have compared the numbers, sizes, and distribution of glycine‐ and GABA‐immunoreactive spinal neurons at various develomental stages and found the following marked differences in the developmental characteristics of these two populations of putative inhibitory interneurons. (i) GABA immunoreactivity was expressed very early (E4), whereas immunoreactivity for glycine appeared relatively late (ES) in embryonic development. (ii) In the ventral horn, GABA immunoreactivity declined, whereas immunoreactivity for glycine gradually increased from ES onward in such a manner that the sum of glycinergic and GABAergic perikarya remained constant during the second half of embryonic development. (iii) Glycinergic and GABAergic neurons showed different distribution patterns in the spinal gray matter throughout the entire course of embryogenesis as well as in the posthatched animal. When investigating the colocalization of glycine and GABA immunoreactivities, perikarya immunostained for both amino acids were revealed at all developmental stages from E8 onward, and the proportions of glycine‐ and GABA‐immunoreactive neurons that were also immunostained for the other amino acid were remarkably constant during development. The characteristic features of the development of the investigated putative inhibitory spinal interneuroris are discussed and correlated with previous neuroanatomical and physiological studies. © 199

ISSN:0092-7317    

DOI:10.1002/cne.903620411

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY