bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microglial MHC antigen expression after ischemic and kainic acid lesions of the adult rat hippocampus
Authors: Finsen B. R. , Jørgensen M. B. , Diemer N. H. , Zimmer J. 
Published: January 2005

AbstractBy taking advantage of the specific neuronal and connective organization of the hippocampus and the different susceptibility of hippocampal neurons to transient cerebral ischemia or intraventricular injections of kainic acid (KA), we examined the microglial reactions to different types of neuronal injury. In all areas with neuronal or axonal degeneration, the microglial cells reacted by specific degeneration‐related morphological transformations and expression of class I major histocompatibility complex (MHC) antigen. Subpopulations of microglial cells also expressed class II MHC antigen and leukocyte common antigen (LCA) in relation to (1) degenerating nerve cell bodies in the dentate hilus and the CA1 and CA3 pyramidal cell layers, (2) postischemic degeneration of dendrites in the stratum radiatum of CA1, and (3) combined dendritic and axonal degeneration in the stratum radiatum of the KA‐lesioned CA3. MHC II and LCA expression was not observed in relation to degeneration of the CA3‐derived Schaffer collaterals in CA1 after KA‐induced CA3 lesions. In the case of ischemia the degeneration‐related reactions were preceded by an early, generalized microglial reaction, which also included areas without subsequent signs of neural degeneration. This reaction, which was transient and characterized by subtle morphological changes and induction of class I MHC antigen only, was presumably triggered by a general postischemic pertubation of the cerebral microenvironment, and not by actual neural degeneration. In conclusion, we found that microglial expression of class I MHC antigen was a sensitive marker of both the general pertubation after ischemia and axonal degeneration distant from the areas of actual nerve cell death. Induction of microglial LCA and class II MHC antigen expression, together with protracted expression of class I, was, characteristic of a protracted reaction, only found in areas with degeneration of nerve cell bodies and dendrites.
Heterogeneity of microglial and perivascular cell populations: Insights gained from the facial nucleus paradigm
Authors: Streit Wolfgang J. , Graeber Manuel B. 
Published: January 2005

AbstractWe reflect here on the development of a neuroimmunological concept which has been formulated over the past 5 years through studying microglial cell responses in the facial nerve system. A simple axotomy of the adult rat facial nerve which causes regeneration of facial motor neurons and little, if any, cell death can activate microglial cells just as easily as a full‐blown degeneration of the entire nucleus induced by toxic ricin. In both instances, the prompt microglial reaction is characterized by a series of structural and phenotypic changes which are in many ways similar to an immune response, e.g., there is cell proliferation and upregulation of MHC antigens. However, since white blood cells do not participate in the retrograde response of facial motor neurons, we have adopted a notion which views microglia as a CNS‐wide network of immunocompetent cells whose morphological dissimilarities from leukocytes are a result of their unique adaptation to the CNS architecture. We have continued our in vivo investigations of the phagocytic and immunophenotypic properties of microglial and perivascular cells during the retrograde reaction of facial motor neurons by using intraneural injections of fluorogold (FG) and ricin followed by lectin and immunostaining for microglia. Two new findings can be added to the microglial neuroimmune network: (1) Microglia take up FG only after motor neuron degeneration, whereas perivascular cells may take up FG under nondegenerating conditions. (2) Immunologically important molecules, such as MHC class II, CD4, and leukocyte common antigens, are expressed by different microglial subpopulations. Thus there is functional and phenotypic heterogeneity among immunocompetent cells of the CNS.
Electrophysiological behavior of microglia
Authors: Kettenmann H. , Banati R. , Walz W. 
Published: January 2005

AbstractThe present knowledge of voltage‐ and ligand‐activated ion channels of cultured microglial cells is described and its relevance is discussed. All microglial cells cultured from rat or mouse brain express an inward rectifying K+ channel but no outward currents. This expression is not changed by the length of the cultivation period, nor is it different in freshly isolated cells. It makes the microglial cells distinct from peritoneal macrophages, which possess an outward rectifying K+ channel. In bone marrow, 2 populations of cells could be distinguished electrophysiologically, one with the channel pattern of macrophages and one with that of microglial cells. This finding is interesting in light of the fact that it is presently hypothesized that the differentiation of monocytes into microglia takes place exclusively during embryonic development but not in the adult. The available data thus support the hypothesis that within the bone marrow a population of macrophage precursor cells exists with a possible lineage relationship to brain macrophages. The lack of outward currents in the microglial cells has the functional consequence that even a small inward current leads to a large membrane depolarization, since K+ outward currents are not activated with the depolarization. The microglial cell is thus very sensitive to depolarizing events. We found that ATP induced an inward current and an increase in the conductance, whereas ADP, AMP, and adenosine did not. These relative potencies indicate that microglia possess a P2 purinoceptor linked to an ion channel. The amplitude of the inward current elicited by ATP is about 80 pA and is sufficient to depolarize microglial cells close to 0 m V. Quite obviously, ATP is the agent that is activating ion channels that cause a pronounced depolarization, and as a result of the peculiar ion channel pattern of microglia, has pronounced effects on the membrane potential. Since ATP is released from cells during tissue injury, it has the potential to act as an initial trigger for the transition from one microglial functional state to another.
Reactive glia as rivals in regulating neuronal survival
Authors: Giulian Dana 
Published: January 2005

AbstractReactive gliosis is a response noted after nearly every type of CNS injury and involves both activated microglia and astroglia. Although many investigators believe that reactive glia in some way regulate the survival of injured neurons, the influence of glial elements upon damaged neural tissues remains uncertain. To examine relationships between reactive glia and neurons, secretion products from both microglia and astroglia are tested for their effects upon the survival of cultured neurons. Microglia are found to secrete neurotoxic agents, while astroglia are a source of neuronotrophic factors. Similar patterns of soluble factor production are noted for astroglia‐rich or microglia‐rich regions of rat neocortex damaged by ischemia. These observations suggest that microglia and astroglia compete for control of neuronal survival. Importantly, microglial neurotoxins might hinder the recovery of neurologic function at sites of inflammation.
Detection of lysosomal cysteine proteinases in microglia: Flow cytometric measurement and histochemical localization of cathepsin B and L
Authors: Banati R. B. , Rothe G. , Valet G. , Kreutzberg G. W. 
Published: January 2005

AbstractThe activation and differentiation of microglia is a prominent pathophysiological process in numerous inflammatory and demyelinating diseases of the central nervous system, including Alzheimer's disease and the AIDS encephalopathy. The tissue damage during these diseases has partly been attributed to lipid peroxidating reactive oxygen intermediates for which activated microglia are a major source. The destruction of tissue may also involve the release of proteolytic enzymes, such as the lysosomal cysteine proteinases cathepsin B and L, which are present notably in phagocytic cells. The cathepsins B and L are endopeptidases with a substrate specificity including important proteins, like myelin basic protein, extracellular matrix components, or the class II major histocompatibility complex. Because of this pathophysiological relevance the cathepsins B and L were chosen for histochemical demonstration in isolated and cultured rat microglia and measurement by a new flow cytometric method.Cathepsin B/L activity was measured flow cytometrically in single viable cells by the intracellular cleavage of non‐fluorescent (Z‐Phe‐Arg)2‐rhodamine 110 to the green fluorescent monoamide Z‐Phe‐Arg‐rhodamine 110 and rhodamine 110. In microglia we measured a cathepsin B/L activity that was 2.5 times higher than in thioglycolate‐elicited, i.e., inflammatory peritoneal rat macrophages. In elicited peritoneal macrophages the formation of fluorescent product was 6.2 times higher than in unstimulated resident peritoneal macrophages, demonstrating that the activation and differentiation of mononuclear phagocytes is accompanied by an increased cathepsin B/L enzyme activity.The subcellular localization of cathepsin B/L activity in plated viable microglia was demonstrated histochemically by the use of Z‐Ala‐Arg‐Arg‐4‐methoxy‐2‐naphthylamide. Its blue fluorescent cleavage product 4‐methoxy‐2‐naphthylamide was found in lysosomes.Our study shows that activated microglia are an important potential source of cathepsin B/L. This is particularly interesting as enzymatically active cathepsins have recently been found extracellularly at high levels in the senile plaques of Alzheimer's disease, which are known to contain many activated microglia. The release of proteinases by microglia may play a crucial role in the pathomechanism of tissue‐destructing diseases in the brain.
Receptor subtype involved and mechanism of norepinephrine‐induced stimulation of glutamate uptake into primary cultures of rat brain astrocytes
Authors: Fahrig Thomas 
Published: January 2005

AbstractGlutamate uptake into rat brain astrocytes is potently stimulated by addition of norepinephrine (NE). This effect is mediated by α1‐adrenergic receptors expressed by these cells (Hansson and Rönnbäck: Life Sci 44:27, 1989; Brain Res 548:215, 1991). The present study was undertaken in order to identify the adrenergic receptor subtype involved, and to determine the sequence of events following receptor activation. NE increased glutamate uptake rates in a dose‐ and time‐dependent manner (EC50 = 6 μM). Both, the selective α1‐receptor antagonist prazosine (IC50 = 2.5 μM) and the α1b‐adrenergic receptor subtype specific alkylating agent chlorethylclonidine (CEC, 100 μM) prevented NE (100 μM) evoked stimulation of glutamate uptake. Furthermore, omission of Ca2+ from the extracellular medium had no significant influence on NE‐induced increase in glutamate uptake, indicating that the stimulatory effect is mediated by α1b‐adrenergic receptors. Treatment of cells with pertussis toxin (PTX) for 24 h or with 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) for 30‐45 min prior to NE addition abolished the NE‐mediated effect on glutamate uptake. Addition of TPA alone resulted in a rapid increase of glutamate uptake, which declined to control levels when TPA was applied 30 min prior to uptake initiation by glutamate. The increase in glutamate uptake elicited by TPA and NE added at the same time showed no additivity of the stimulatory effect resulting from treatment with each agent alone. Treatment of cell cultures with 1 mM Ba2+, which has been shown to block outwardly directed K+ ‐currents in astrocytes (Barres et al.: Glia 1:10, 1988), influenced glutamate transport principally in the same manner as found for TPA and NE, respectively. Again no additivity of Ba2+ and NE effects on glutamate uptake was observed. Finally, NE; TPA; and Ba2+ ‐stimulated glutamate uptake exhibited nearly identical time‐response curves.
Appearance of GFAP‐positive cells in adult human brain cultures spontaneously decelerated in growth
Authors: Peržel'Ova Anna , Mareš Vladislav 
Published: January 2005

AbstractCell cultures were derived from adult human brain biopsies [from cortical gray (cultures 9‐HB‐G and 33‐HB‐G) and white (culture 14‐HB‐W) and stroke‐injured white matter (culture 33‐HB‐IW)]. The morphology and growth rate of cultured cells were examined and correlated with the presence of vimentin and glial fibrillary acidic protein (GFAP). The cultures from various brain matters differed in cell morphology and rate of growth but not in GFAP and vimentin staining. Cells of primary and rapidly proliferating cultures were GFAP‐negative and vimentin‐positive. Spontaneous growth deceleration occurred in culture 14‐HB‐W within passages 5 to 10 and in cultures 9‐HB‐G, 33‐HB‐G, and 33‐HB‐W within passages 17 to 20. This deceleration, as well as the successive complete growth arrest, were accompanied by an appearance of GFAP‐positive cells and an elevated intensity for vimentin staining. We propose that GFAP‐positive astrocytes originate from glial precursor cells that migrate from the explants and differentiate under prolonged subcultivation.
Inducible nitric oxide synthase activity of cloned murine microglial cells
Authors: Corradin Sally Betz , Mauël Jacques , Donini Susanne Denis , Quattrocchi Emilia , Ricciardi‐Castagnoli Paola 
Published: January 2005

AbstractNitric oxide (NO) is a short‐lived diffusable molecule now believed to participate in multiple physiologic functions in the CNS including neurotransmission and the maintenance of vascular tone. Previously, we reported that cell lines obtained by retroviral immortalization of tissue macrophages (Mϕ;) could be induced to synthesize nitrite (NO), a stable end product of the NO synthetic pathway. We have further characterized the induction and activity of this pathway in a panel of seven microglial clones derived from primary embryonic mouse brain cultures. Like Mϕ;, these clones were found to release high levels of NO‐2 in response to recombinant interferon‐γ (rIFN‐γ) as a priming signal together with either bacterial lipopolysaccharide (LPS) or exogenous recombinant tumor necrosis factor‐α (rTNF‐α). As previously demonstrated for Mϕ;, phagocytosis of zymosan particles during induction of enzyme activity enhanced subsequent NO production, which is of interest in light of the postulated phagocytic role of microglia within the CNS. Biochemical characterization of enzyme activity in intact microglial clones and in isolated cytosolic fractions indicates that the microglial NO synthase present in these murine cell clones represents the Mϕ;‐like isotype. These findings suggest that microglial cells could represent a major source of NO within the CNS.
The molecular genetics of myelination: An update
Authors: Lemke Greg 
Published: January 2005

AbstractRecent molecular genetic studies have provided new insights into the structure and function of 2 of the major integral membrane proteins of myelin—the proteolipid protein (PLP) and protein zero (Po)—and have uncovered a third such protein—PMP22/gas3. The rumpshaker mouse has been shown to carry a point mutation in the PLP gene that uncouples a deleterious effect on CNS myelin assembly, which these mice exhibit, from oligodendrocyte degeneration and cell death, which they do not. The developmental importance of the Po protein in PNS myelination has been dramatically demonstrated by the analysis of loss‐of‐function mutations engineered through the expression of antisense RNA and through the insertional inactivation of the Po gene by homologous recombination in embryonic stem cells and the generation of Po‐deficient mice. The cloned promoter of the Po gene has been shown to drive quantitative, Schwann cell‐specific expression of heterologous genes in transgenic mice. The PMP22/gas3 gene, previously cloned from fibroblast cell lines, has been found to encode an axonally regulated Schwann cell protein that is assembled into PNS myelin. Importantly, this gene appears to be the target of mutations that result in the Trembler alleles in mice, and in Charcot‐Marie‐Tooth disease Type 1a, the most common inherited peripheral neuropathy in humans.
Fish optic nerve oligodendrocytes support axonal regeneration of fish and mammalian retinal ganglion cells
Authors: Bastmeyer Martin , Bähr Mathias , Stuermer Claudia A. O. 
Published: January 2005

AbstractSegments from adult fish and rat retinae were explanted on myelin‐marker expressing oligodendrocytes derived from the regenerating goldfish optic nerve. Fish axons grew in high density and even rat retinal axons regenerated to considerable length on the surface of the fish oligodendrocytes, suggesting that this type of fish glia has axon‐growth promoting surface components that exert their influence across species boundaries. One interesting surface component of the fish oligodendrocytes as demonstrated here is the E 587 antigen, which is related to the L1 family of cell adhesion molecules.In long term cocultures of oligodendrocytes and retinal axons, the fish glial cells were found to enwrap rat axons. This suggests that the oligodendrocytes of the regenerating goldfish optic nerve/tract may, despite striking differences, represent the equivalent to mammalian optic nerve oligodendrocytes. © 1993 Wiley‐Liss, Inc.
A cell surface antigen expressed by astrocytes and their precursors
Authors: Szigeti Vilma , Miller Robert H. 
Published: January 2005

AbstractIncreasing evidence suggests that astrocytes of the mammalian CNS are a heterogeneous population of cells that express a number of common characteristics. In most cases, astrocytes or their precursors contain a class of intermediate filaments, composed in large part of glial fibrillary acidic protein (GFAP). While the expression of GFAP immunoreactivity is a specific characteristic of astrocytes in the vertebrate CNS, not all astrocytes contain detectable levels of glial filaments, particularly during early development. We have isolated a monoclonal antibody termed 7B11 which binds to the surface of astrocytes and glial precursors, but not to other major types of neural cells. The 7B11 antigen is expressed by astrocytes in the adult CNS in vivo and in cultures of developing CNS tissue, but not on cells of the peripheral nervous system. During early development, 7B11 immunoreactivity appears prior to the expression of GFAP and is retained as punctate staining on the surface of most classes of astrocytes. During CNS maturation, however, 7B11 immunoreactivity is lost from the surface of Bergmann glia in the cerebellum, suggesting that differentiative events lead to functionally and anti‐genically distinct classes of CNS glial cells. In the adult spinal cord, biochemical analysis suggests that the epitope recognized by 7B11 is associated with a group of polypeptides of apparent molecular weights 200‐160, 140, and 92 kD. The cellular distribution of 7B11 expression suggests that astrocytes and their precursors share a distinct cell surface antigenic property and that the expression of 7B11 immunoreactivity may be a useful operational marker for astrocytes in the absence of detectable GFAP expression. © 1993 Wiley‐Liss, Inc.
Differences in glycogen metabolism in astroglia‐rich primary cultures and sorbitol‐selected astroglial cultures derived from mouse brain
Authors: Dringen Ralf , Hamprecht Bernd 
Published: January 2005

AbstractRecently it has become possible by chemical selection using sorbitol instead of glucose in the culture medium to produce pure astroglial cultures from astroglia‐rich primary cultures from mouse brain. The glycogen‐degrading enzyme glycogen phosphorylase in brain is localized in astrocytes and ependymal cells. In view of this fact it appeared necessary to study the influence of glucose and other hexoses on the glycogen metabolism in these cultures lacking the influence of other cell types in comparison to the astroglia‐rich primary cultures containing several types of cells. The sorbitol‐fed selected cultures and the glucose‐deprived astroglia‐rich primary cultures contain less than 10% of the glycogen encountered in glucose‐fed primary cultures. During incubation with glucose the glycogen content of the selected cultures and the glucose‐deprived primary cultures increases by more than one order of magnitude. Nevertheless, not all cells are found to have accumulated glycogen. The time course of the replenishment of glycogen is similar in both types of culture, although maximal levels reached in the selected cultures are 3 times those in the astroglia‐rich primary cultures. This difference might be explained by the fact that the ratio of the maximal activities of glycogen synthase and glycogen phosphorylase in selected cultures was found to be twice that in the unselected cultures. During glucose deprivation the glycogen content is reduced in both culture systems with half‐maximal contents being reached at 15 min (primary culture) and 45 min (selected culture). Both types of culture can also utilize mannose for the synthesis of glycogen and the production of lactate. In contrast, fructose or galactose are poor substrates, or none at all, for the generation of glycogen. In conclusion, the absence of non‐astroglial cells and the high glycogen content after glucose feeding makes pure astroglial cultures an even better system for investigating the regulation and the function of astrocytic glycogen than astroglia‐rich primary cultures. © 1993 Wiley‐Liss, Inc.
Bergmann glia require continuous association with purkinje cells for normal phenotype expression
Authors: Fisher Marilyn , Trimmer Patricia , Ruthel Gordon 
Published: January 2005

AbstractBergmann glia (Bg) respond to the early postnatal Purkinje cell (Pc) death in Lurcher (Lc) mutant mouse cerebellum by down‐regulating expression of the enzyme glycerol‐3‐phosphate dehydrogenase (GPDH). To determine whether glial GPDH expression requires the continued presence of Pcs in adults, we used single intracerebellar injections of kainic acid to kill Pcs in wild‐type mice from 7 weeks to 11 months old. Bg at all ages tested responded to Pc loss by down‐regulating GPDH expression. To learn whether a high level of GPDH could be reinduced following down‐regulation in Lc Bg, we grafted wild‐type fetal Pcs into Lc cerebella. The influence of grafted Pcs on GPDH expression is host‐age and implant‐position dependent. Only Pcs implanted into hosts less than 6 weeks old were later found to be associated with GPDH‐positive Bg. Grafted Pcs that migrated into the anterior folia of young hosts were more likely to be associated with GPDH‐positive Bg than Pcs migrating to other positions. EM analysis showed that Bg ensheathment of grafted Pcs is thinner and more discontinuous, but qualitatively similar to normal. The results suggest that the interaction between host Bg and grafted Pcs can sustain elevated GPDH expression in Bg that have not yet down‐regulated, but is not adequate to reinduce expression in those cells that have. © 1993 Wiley‐Liss, Inc.