摘要:

AbstractWith the aid of cultured rat microglial cells as immunogen, we raised two monoclonal antibodies, designated murine clone (MUC) 101 and 102, which recognised subsets of resident microglial cells in the normal central nervous system and cells of the mononuclear phagocyte system in peripheral organs. These antibodies were characterised by immunoperoxidase immunocytochemistry, immunoelectron microscopy, and immunoblotting.The immunostained cells were identified as microglial cells by double‐immunofluorescence labelling with the B4‐isolectin fromGriffonia simplicifolia, an established microglial cell marker. Under normal conditions, both antibodies labeled resident microglia but with different distribution patterns. Under pathological conditions, e.g., after facial nerve transection, they labeled activated, perineuronal microglia in the operated facial nucleus. Immunoelectron microscopy demonstrated a membrane localisation of the antigen recognised by MUC 102.In peripheral organs, MUC 101 and 102 reacted with different cell populations of the mononuclear phagocyte system, particularly in thymus, spleen, and peripheral lymph node. Western blot experiments showed that MUC 101 recognised two proteins of 116 and 95 kD in fractions obtained from operated facial nucleus while MUC 102 reacted with two proteins of 62 and 70 kD molecular weight.These immunocytochemical results (1) confirm the antigenic similarity between microglia and cells of the monocyte–macrophage cell lineage, and (2) indicate that considerable antigen heterogeneity might exist among resident microglia. MUC 101 and 102 could thus become useful for studying the function of microglial cells both under normal and pathological condi

ISSN:0092-7317    

DOI:10.1002/cne.903130302

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractAs part of an on‐going study of segmental differentiation in the central nervous system (CNS) of the leechHirudo medicinalis, a search was made for putative segmental homologs of the heart accessory (HA) neurons, which exist exclusively as a bilateral pair in the ganglia of the fifth and sixth body segments. As it is not yet feasible to obtain adequate cell lineage information inH. medicinalispotential homologs of the HA neurons were determined using morphological, immunohistochemical, and electrophysiological criteria. Among cells in other body ganglia with somata in the same locations as HA neurons, a pair was found having extensive morphological and physiological similarities to HA neurons. These we have called HA‐like (HAL) neurons.Adult HA and HAL neurons have closely related patterns of primary branching, in terms of shape, intraganglionic pathways taken, and extraganglionic projections. The number, location, and relative thickness of branches are also similar among these cells. In embryos 10 to 11 days old, HA and HAL neurons have virtually identical branching patterns, with primary and secondary branches of nearly uniform caliber. Differences in branch thickness develop gradually; by embryonic day 20, they resemble those found in adult neurons. Two features found to differ between HA and HAL neurons were the cell body diameter (larger for the HA cells) and the expression of antigens recognized by the monoclonal antibody Laz1‐1 (absent at a detectable level in the HA neurons). At a physiological level, the HA and HAL neurons showed action potentials of similar size and shape, as well as inhibitory synaptic inputs from a common source, the heart interneurons (HN).The observations presented here suggest that there is a common developmental origin for the HA and HAL neurons, and hence that their fates are positionally determined by as yet unknown fa

ISSN:0092-7317    

DOI:10.1002/cne.903130303

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractAndrogens influence the postnatal development of motoneurons in the spinal nucleus ofthe bulbocavernosus (SNB) by regulating neuromuscular synapse elimination, the process through which multiple axonal inputs are retracted from each muscle fiber until single innervation is established. In the rat levator ani (LA), one of the target muscles for SNB motoneurons, much of this loss of multiple innervation can be prevented by prepubertal androgen treatment. We used steroid autoradiography to measure the ontogeny of steroid accumulation in the SNB and the retrodorsolateral nucleus (RDLN), two motoneuronal groups thought to differ in their sensitivity to androgens. Spinal cord tissue was analyzed from castrated male rats at 7, 14,21, and 60 days of age after injection of radiolabelled testosterone. SNB and RDLN motoneurons differ in the ontogeny of androgen accumulation. Over 80% of SNB motoneurons develop the capacity to accumulate androgen during the second week after birth, during the period when androgen regulates synapse elimination in the LA. In contrast, androgen accumulation in RDLN motoneurons develops much later (after 21 days). These data suggest that androgen may act directly on SNB motoneurons to influence synapse elimination.

ISSN:0092-7317    

DOI:10.1002/cne.903130304

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractSemipermeable guidance channels have been shown to support nerve regeneration in the peripheral nervous system (PNS) possibly through interactions with the wound healing environment. This study quantitatively assesses the ability of such channels to support regeneration in the PNS segment of the spinal roots across a 4 mm gap and compares the resultant dorsal and ventral root regeneration. Acrylic copolymer guidance channels with a molecular weight (Mw) cutoff of 50,000 Da were used in a transected rat spinal root model. Cohorts of 23 animals (11 ventral, 12 dorsal) were examined at four weeks; 6 animals (3 ventral, 3 dorsal) at ten weeks; and 10 animals (5 ventral, 5 dorsal) at twenty‐four weeks post‐implantation. Both the dorsal and ventral roots were able to regenerate across the gap within the semipermeable channel. At all time periods, the regenerated dorsal roots contained fewer myelinated axons than found in the contralateral control root and consisted of an abundance of collagenous tissue. In contrast, by ten weeks the regenerated ventral roots contained twice the contralateral control number of myelinated axons and were composed predominantly of large, myelinated axons. At twenty‐four weeks the number of unmyelinated axons was also quantified, with the regenerated dorsal root containing only one‐fifth of the control number and the regenerated ventral root containing more than four times the control. Due to the proximity of the dorsal root lesion to the axonal cell bodies, the dorsal root ganglion (DRG) neuronal cell loss was investigated at four weeks post‐implantation. A comparison of the cell numbers on the experimental side to those on the contralateral control side yielded a mean E/C ratio of 1.07, suggesting that a significant cell loss is an unlikely causative factor in the impairment of regeneration in the dorsal root. This study reports a difference in the regenerative capacities of dorsal and ventral roots using semipermeable guidance channels. Future studies involving variations in the regenerative environment may help determine the factors responsible for the different regenerative capabilities of the spi

ISSN:0092-7317    

DOI:10.1002/cne.903130305

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractTuberculoventral neurons in the deep layer of the dorsal cochlear nucleus (DCN) provide frequency‐specific inhibition to neurons in the anteroventral cochlear nucleus (AVON) of the mouse (Wickesberg and Oertel, '88, '90). The present experiments examine the projection from the deep DCN to the posteroventral cochlear nucleus (PVCN). Horseradish peroxidase (HRP) injections into the PVCN reveal that the multipolar cell area, but not the octopus cell area, is innervated by neurons in the deep layer of the DCN. Injections into the multipolar cell area, in the rostral and ventral PVCN, labeled neurons across the entire rostrocaudal extent of the deep DCN. The labeled tuberculoventral neurons generally lay within the band of labeled auditory nerve terminals in the DCN. Injections of HRP into the octopus cell area, in the dorsal caudal PVCN, labeled almost no cells within the band of auditory nerve fiber terminals that were labeled by the same injection. The inhibition from tuberculoventral neurons onto ventral cochlear nucleus (VCN) neurons is likely to be mediated by glycine (Wickesberg and Oertel, '90). Slices of the cochlear nuclear complex were immunolabeled by an antibody against glycine conjugated with glutaraldehyde to bovine serum albumin (Wenthold et al., '87). Glycine‐like immunoreactivity was found throughout the DCN, the AVCN and the multipolar cell area, but there was little labeling in the octopus cell area. This finding provides independent evidence that tuberculoventral neurons do not innervate the octopus cell area and indicates that the octopus cell area is anatomically and functionally disti

ISSN:0092-7317    

DOI:10.1002/cne.903130306

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractTo study postnatal cell generation in primary visual centres of the quokka, tritiated thymidine was injected into pouch‐young aged postnatal day (P)1–P85. Brains were examined at P100, just before eye‐opening, when primary visual projections are essentially mature. Neurons in the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) were generated at P1–P10 and P1–P18 respectively. Peak numbers of labelled cells were seen at P3 and P5 in the dLGN and SC.Cell death was assessed in the dLGN and SC of young aged P10–P150. Low numbers of dying cells were seen in the dLGN throughout this period, with a small peak at P85. A more substantial peak of cell death was seen in the SC, also at P85. In the quokka, the time interval between the peaks of cell generation and of cell death in the dLGN and SC is 70–80 days, considerably longer than the interval of 40 days between birth and death of

ISSN:0092-7317    

DOI:10.1002/cne.903130307

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe rat dentate gyrus undergoes a period of naturally occurring cell death during the first postnatal week. In the adult rat, removal of circulating adrenal steroids by adrenalectomy is followed by massive death in the granule cell layer, thus raising the possibility that developmental cell death results from low levels of these hormones. Interestingly, the first two postnatal weeks of life in the rat, termed the stress hyporesponsive period, are characterized by very low levels of adrenal steroids. In order to determine whether low levels of adrenal steroids enable developmental cell death to occur in the dentate gyrus, we examined the density of pyknotic and healthy cells in the dentate gyrus of rat pups which received one of the following treatments: (1) injections of the endogenous rat glucocorticoid corticosterone during the first postnatal week, or (2) adrenalectomy at the time when glucocorticoid levels normally rise. Quantitative analysis of the density of pyknotic cells in the granule cell layers revealed significant decreases with corticosterone treatment by the end of the first postnatal week. In these same brains, treatment with corticosterone resulted in a substantial increase in the density of pyknotic cells in the hilus. Adrenalectomy resulted in a significant increase in the density of pyknotic cells in the granule cell layer as well as in the hilus. Despite the dramatic alterations in the density of pyknotic cells with both increases and decreases in glucocorticoid levels, the density of healthy cells remained the same. These observations suggest that glucocorticoids regulate several processes, possibly including neurogenesis and migration, in addition to cell death.

ISSN:0092-7317    

DOI:10.1002/cne.903130308

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractUnlike the majority of mammalian brain regions, the rat dentate gyrus undergoes maximal cell birth and cell death during the same developmental time period. Granule cell birth and death peak at the end of the first postnatal week. We have found that manipulations of glucocorticoid levels during the stress hyporesponsive period profoundly influence the density of pyknotic cells in the dentate gyrus while apparently not affecting the density of healthy cells. This raises the possibility that glucocorticoids are regulating processes in addition to cell death, i.e., cell birth. In order to determine whether increases in circulating glucocorticoids or mineralocorticoids affect the birth of cells in the developing dentate gyrus,3H‐thymidine autoradiography was performed on brains of rat pups treated with either corticosterone or aldosterone during the first postnatal week. Quantitative analysis of3H‐thymidine‐labelled cells revealed significant decreases in the density of labelled cells in the granule cell layers with both corticosterone and aldosterone treatment. In these same brains, significant decreases in the density of pyknotic cells were also observed in the granule cell layers. However, no changes in the numbers of3H‐thymidine‐labelled pyknotic cells were observed with any treatment. Increases in circulating corticosterone or aldosterone resulted in significant increases in the density of both3H‐thymidine‐labelled and pyknotic cells in the hilus. These results suggest that dentate gyrus cell birth and cell death are related and that these processes are regulated by adr

ISSN:0092-7317    

DOI:10.1002/cne.903130309

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractWe studied the temporal and spatial localization of the low‐affinity nerve growth factor receptor (LNGF‐R) during the early postnatal period in rat brain in order to understand better the relationship between nerve growth factor (NGF)‐like responsiveness and the development of specific central neuronal populations. Four different developmental patterns of LNGF‐R mRNA hybridization were found in this study. First, some neurons contain high levels of LNGF‐R mRNA from postnatal time points into adulthood, as exemplified by neurons of the cholinergic basal forebrain and mesencephalic trigeminal nucleus. Second, several cell groups exhibit robust hybridization during the early postnatal period but contain much reduced levels of LNGF‐R mRNA in the adult brain. These include striatal neurons, Purkinje cells of the cerebellum, and several medullary nuclei. A third group of cells produces the LNGF‐R transiently during development, including cranial nerve nuclei of the brainstem, the periolivary nuclei complex, the reticular formation, and the deep cerebellar nuclei. Finally, cell populations which may exist only transiently during central nervous system (CNS) development, such as subplate neurons of the cerebral cortex, appear to express the LNGF‐R during only a brief period. These results show that the LNGF‐R gene is differentially regulated in a cell type‐specific manner during development, and suggests that diverse neuronal populations require only transient growth factor sensitivity, while others exhibit NGF‐like respons

ISSN:0092-7317    

DOI:10.1002/cne.903130310

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe correlation between birthdates of neurons and their ultimate location within the inferior olivary nucleus (ION) was investigated in the rat by the 5‐bromodeoxyuridine (BrdU) method. We performed injections every 4 hours throughout the ION generation period, and were thus able to demonstrate that (1) neurons are distributed in the adult ION following characteristic gradients that define subdivisions identical to those established by hodological studies; and (2) ION neurons born at the same time tend to be arrayed in small clusters in the adult structure. Implications of these findings for the mechanisms of olivary neuron migration, selective aggregation, and elaboration of projectional topography are discussed. This study provides direct evidence that one of the factors governing the elaboration of the cytoarchitecture of a neuronal nucleus is the temporal sequence of generation of its neuron

ISSN:0092-7317    

DOI:10.1002/cne.903130311

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY