ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90070-T

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThis study evaluates whether the rapid transient increases in glial fibrillary acidic protein (GFAP) mRNA in the hippocampus after electrolytic lesions of the entorhinal cortex (EC) are triggered by lesion‐induced changes in hippocampal neuronal activity (either the decreases that result from loss of afferent drive or transient increases that occur during lesion production). To evaluate the role of activity, we carried out four experiments: (1) tetrodotoxin (TTX) was injected into the EC to mimic the decreases in afferent drive that occur after lesion; (2) TTX was injected into the EC or hippocampus before producing electrolytic lesions to block any abnormal activity induced during lesion production; (3) the EC was destroyed by aspiration, thus creating a lesion comparable in size to the electrolytic lesion, without passing direct current; (4) seizures were elicited by stimulating the EC of anesthetized rats, to examine whether electrographic seizures alone can induce the same type of increases in GFAP mRNA as lesions. Our results demonstrated that: (1) TTX injections into the EC did not induce the same increases in GFAP mRNA levels that occurred after EC lesions; (2) animals that received TTX injections into the EC prior to lesions exhibited increases in hippocampal GFAP mRNA that were nearly as great as following EC lesions alone; (3) aspiration lesions of the EC resulted in increases in GFAP mRNA that were comparable to those observed after electrolytic lesions (4) seizure‐inducing stimulation of the EC resulted in 2‐fold increases in GFAP mRNA in the hippocampus 24 hr after stimulation rather than the 5–13‐fold increases observed after lesions. These results suggest that lesion‐induced changes in hippocampal neuronal activity are not solely responsible for inducing the rapid transient increases in GFAP mRNA levels in the hippocampus ipsilateral to EC lesions.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90071-K

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe immunoglobulin (IgG, IgM, IgA) content of normal, reactive and migrated rat astrocytes was studied in lesioned adult rat cortex and after fetal cortex grafts. Implantation pockets were aspirated in the somatomotor cortex (under bregma) of adult Sprague‐Dawley rats. A fetal (E14) rat hemicortex incubated in the plant lectinPhaseolus vulgarisleucoagglutinin (graft premarker) was placed in the aspiration pocket or the pocket left empty (control). Sections of brain were immunohistochemically double labeled for immunoglobulins‐GFAP orPhaseolus vulgarisleucoagglutinin‐GFAP 3–60 days postoperative. Mature or fetal astrocytesin situdid not contain immunoglobulins. In pocket‐only animals, individual reactive astrocytes lining and subjacent to the pocket were positive for rat IgG, IgM and IgA (3–60 days). In grafted animals, graft derived astrocytes (Phaseolus vulgarisleucoagglutinin‐GFAP positive) were intermingled with host reactive astrocytes (Phaseolus vulgarisleucoagglutinin negative) lining and subjacent to the pocket. Both classes of astrocytes contained immunoglobulins IgG, IgM and IgA. Immunoglobulin positive graft derived astrocytes migrated into the corpus callosum, cingulum and habenula. These results demonstrate that astrocytes sequester immunoglobulins and probably other serum proteins as a critical function in restoring homeostasis to the injured or diseased nervous system.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90072-L

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractExplant cultures of glial scars generated by surgical removal of the retina in 3–60‐day‐old rats were used to determine if reactive astrocytes survivein vitroand how closely reactive astrocytes in culture resemble theirin vivocounterparts. Characterization of the composition of age matched glial scarsin vivoandin vitroshowed that reactive astrocytes survived in glial scar explants even after several weeks in culture. Reactive astrocytes in both neonatal and adult glial scars retained ultrastructural features characteristic of reactive astrocytesin vivo. However, fewer reactive astrocytes survived in culture when explants were prepared from adult rat glial scars. The results of this study demonstrate that tissue culture is a viable model for the study of reactive astrocytes. A critical factor in the survival of reactive astrocytes in culture was the complete removal of myelin debris prior to the establishment of the culture. This outcome suggests that it will be important to clarify why myelin debris persists in culture and how it affects the survival of reactive astrocytes.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90073-M

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractChanges in the distribution of proliferating astrocytes expressing glial fibrillary acidic protein (GFAP) and/or vimentin were examined in the injured cerebral hemisphere in adult mice. The injury was followed by [3H]thymidine injections at different time intervals. The brain sections were doubly immunostained for GFAP and vimentin and subjected to autoradiography. In that way three cell types were distinguished immunocytochemically: (1) astrocytes co‐expressing glial fibrillary acidic protein (GFAP) and vimentin (2) astrocytes expressing only GFAP (3) astrocyte‐like cells expressing vimentin. Thereafter, numbers of immunopositive and autoradiographically labelled cells and their locations within the region of injury were recorded at each stage of the experiment. Two hours as well as 1 day after the injury proliferation of GFAP‐positive astrocytes and of those co‐expressing GFAP and vimentin could only be seen as statistically insignificant phenomena. On day 2 the reactive proliferation of each immunocytochemically defined cell type was already maximal, then gradually decreased and its last signs were recorded on day 8. On day 2, among all the proliferating GFAP‐positive astrocytes, 67.2% were also vimentin‐positive. Later, the proportion declined to 50.7% and 38.5% on days 4 and 8, respectively. The labelled astrocyte‐like vimentin‐positive cells were located closest to the lesion margins. In comparison, the astrocytes co‐expressing GFAP and vimentin and those expressing exclusively GFAP, occupied regions progressively farther from the lesion site. At the initial stages of the response to injury, vimentin expression in cells starting their reactive proliferation did not precede the expression of GFAP. This was considered as an argument against a hypothesis that reactive astrocyte division induces a two‐stage increase in the cytoskeletal protein level in which synthesis of vimentin precedes that of GFAP.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90074-N

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractWe have examined the injury response of astrocytes in the immature hamster brain in this study, focusing on alterations in the expression of glial fibrillary acidic protein (GFAP) and vimentin. In the adult CNS these two type III intermediate filament (IF) proteins have been shown to undergo robust increases in expression in response to axonal injury. Since injury to the immature CNS reportedly elicits less glial scar formation than adult brain injury, we examined the possibility that immature astrocytes respond differently than adult astrocytes to CNS injury with respect to IF gene expression.In situhybridization using a35S‐labeled cDNA GFAP probe was done on brainstem sections obtained 2,7 and 14 days after unilateral transection of the corticospinal tract in P8 hamster pups. The results indicated that substantial increases in GFAP mRNA were associated with the degenerating portion of the corticospinal tract by 2 days after axotomy and that the levels remained elevated for at least 14 days. Double‐label immunofluorescence studies of this material suggested that GFAP as well as vimentin protein levels were also increased in many astrocytes in and around the degenerating corticospinal tract 2–14 days after axotomy. Most of the reactive astocytes in the degenerating regions exhibited increases in GFAP and vimentin immunostaining but some vimentin‐negative GFAP‐positive reactive astrocytes were also observed, particularly in regions surrounding the actual degenerative zones. The results from these experiments revealed that immature astrocytes have the potential for altering their normal developmental program of GFAP and vimentin expression after injury and mount a response that is qualitatively similar to that of astrocytes after CNS injury in the adult animal.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90075-O

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractImmunohistochemical staining for glial fibrillary acidic protein (GFAP) is standard for visualization of reactive astrocytes in tissue sections, whereas various forms of astrocytic damage remain to be described in detail. In this study we tested differences in GFAP labeling in reactive astrocytes and in glial cells damaged by ischemia and edema. Studies were performed in the anatomically well defined visual system of rat. Basic staining patterns for GFAP were established in subcortical visual nuclei and visual cortex. In the first model, deafferentation of visual centers was performed by unilateral optic nerve lesion, and characteristic changes of GFAP labeling in reactive astrocytes were studied at 0.5,1,1.5,2,4,8 and 21 days after lesion. Initial changes were seen in the deafferented superior colliculus at 1 day after deafferentation with a diffuse increase and stellate types of reactive cells formed at 2–8 days. In the second model, small ischemie infarcts were produced in the visual cortex of rats using the method of photochemically‐induced thrombosis. GFAP labeling with a polyclonal antiserum was massively enhanced in the infarct at 4 hr. Characteristic morphological changes in damaged astrocytes were seen which were also identified in experiments with simulated global ischemia. In the surround of the infarct, swelling of astrocytes also caused increased labeling. At 3–4 days infarction typical reactive astrocytes surrounded the lesioned area. In conclusion, these immunohistochemical studies on GFAP in rat visual system allow for the following classifications, (a) Normal astrocytes vary in labeling at different anatomical localizations, (b) Reactive astrocytes show enhanced labeling and larger cell‐size within an interval of 1–2 days after lesion (c) Astrocytes damaged by ischemia reveal increased labeling of disintegrating cellular elements within hours after a lesion (d) Swollen astrocytes undergo enhanced labeling in areas with vasogenic edema.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90076-P

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractPolyamines and ornithine decarboxylase, the polyamine biosynthetic enzyme, have been demonstrated to increase in the early phase of several types of brain lesion. However, their role in the pathogenesis of tissue damage is still debated. In the present paper the effects of treatments with α‐difluoromethylornithine, a suicide inhibitor of ornithine decarboxylase, have been investigated in a model of transient forebrain ischemia. Three treatment schedules were used: α‐difluoromethylornithine treatment was either started 3 hr before and repeated 1 hr after the insult, or started at the time of the insult and continued for 3 or 7 days after post‐ischemic reperfusion. The rats were sacrificed 4 hr, 7 or 40 days after reperfusion, respectively. The acute experiment demonstrated that α‐difluoromethylornithine can reduce the increase of glial fibrillary acidic protein immunoreactivity, an early marker of astroglial reaction, in ischemic striatum. Subchronic and chronic α‐difluoromethylornithine treatments induced a worsening of the morphological outcome of the ischemic lesion. In caudate‐putamen a trend for an increase of the area of neuronal loss was present after both treatments. In the hippocampal formation, a significant increase in the severity of neuronal lesion was observed in the mildly lesioned CA3 field. In addition, other alterations of lesioned tissue were observed in α‐difluoromethylornithine‐treated animals, including increases of non‐neuronal cells at 7 and especially 40 days post‐lesion in striatum and CA3 hippocampal field. In conclusion, present data indicate that ornithine decarboxylase activation after ischemic lesion is a crucial factor for survival of mildly lesioned neurons and proper tissue reaction to the ischemic lesion. The experiment on acute α‐difluoromethylornithine treatment suggests that these effects may be, at least in part, related to putrescine‐induced activation of astroglial cells in the early post‐lesion period.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90077-Q

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractAstrocytes produce factors that control the growth and differentiation of many cell types within the CNS as well as play a role in the generation of the immune response. The extent to which these two functions interact has received less attention. We now report that astrocyte cultures established from rat brain endogenously express mRNA and low levels of secreted biologically active protein for the monocyte growth and differentiation factor colony stimulating factor‐1 (CSF‐1). Exposure of astrocytes to interleukin‐1 (IL‐1) and/or tumor necrosis factor (TNF) upregulated the expression of CSF‐1 mRNA and protein. Following treatment with 100 U/ml of TNF, IL‐1, or TNF+IL‐1, maximum CSF‐1 mRNA expression was observed at 3 hr. In the presence of IL‐1 an increase in biologically active CSF‐1 was detected in the astrocyte conditioned medium at 6 hr. These data indicate that the expression of CSF‐1 by astrocytes can be modulated by exposure to the cytokines IL‐1 and TNF. To determine whether CSF‐1 provides a mitogenic signal for microglia during development, mouse spinal cord organotypic cultures were exposed to recombinant mouse CSF‐1 (rmCSF‐1), resulting in proliferation of microglia by 7 days and an increase in the number of ramified microglia over ameboid microglia by 14 days.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90078-R

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractIn order to investigate the role of neuron‐glia interactions in the response of astroglial to a non‐invasive cerebellar cortex injury, we have used two cases of the ataxic form of Creutzfeldt‐Jakob disease (CJD) with distinct neuronal loss and diffuse astrogliosis. The quantitative study showed no changes in cell density of either Purkinje or Bergmann glial cells in CJ‐1, whereas in the more affected CJ‐2 a loss of Purkinje cells and an increase of Bergmann glial cells was found. The granular layer in both CJD cases showed a similar loss of granule cells (about 60%) in parallel with the significant increase in GFAP+ reactive astrocytes. GFAP immunostaining revealed greater reactivity of Bergmann glia in CJ‐2 than in CJ‐1, as indicated by the thicker glial processes and the higher optical density. Granular layer reactive astrocytes were regularly spaced. In both CJD cases there was strict preservation of the spatial arrangement of all astroglial subtypes—Fañanas cells, Bergmann glia and granular layer astrocytes. Reactive Fañanas and Bergmann glial cells and microglia/macrophages expressed vimentin, while only a few vimentin+ reactive astrocytes were detected in the granular layer. Karyometric analysis showed that the increase in nuclear volume in reactive astrloglia was directly related with the level of glial hypertrophy. The number of nucleoli per nuclear section was constant in astroglial cells of human controls and CJD, suggesting an absence of polyploidy in reactive astroglia. Ultrastructural analysis revealed junctional complexes formed by the association of macula adherens and gap junctions. In the molecular layer numerous vacant dendritic spines were ensheathed by lamellar processes of reactive Bergmann glia. Our results suggest that quantitative (neuron/astroglia ratio) and qualitative changes in the interaction of neurons with their region‐specific astroglial partners play a central role in the astroglial response pattern to the pathogenic agent of CJD.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90079-S

出版商:Wiley    

年代:2003

数据来源: WILEY