bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immortalization of immature and mature mouse astrocytes with SV40 T antigen
Authors: Frisa P. S. , Goodman M. N. , Smith G. M. , Silver J. , Jacobberger J. W. 
Published: January 2005

AbstractThe ability of neonatal astrocytes to promote neurite outgrowth in vitro and in vivo diminishes as astrocytes mature. This property correlates with the developmental loss of the central nervous system's ability to regenerate after injury. Cell lines representative of immature and mature astrocytes would be useful for studies to determine differences between these two populations. Previous work on immortalization of bipotential neural/glial precursors and fully differentiated glial cells suggests that immortalization of astrocytes at timed intervals of culture may yield cell lines trapped in different maturation states. To test this, neonatal mouse cortical astrocytes were immortalized by retrovirus‐mediated transfer of the SV40 T antigen (Tag) gene at 2, 6 and 17 days of culture. The clonal cell lines express Tag and are contact‐inhibited. Three phenotypes that change as a function of astrocyte maturation were examined to determine the fidelity with which the cell lines represent immature and mature astrocytes. These were: (1) cell morphology, growth pattern and size, (2) level of glial fibrillary acidic protein (GFAP) expression, and (3) neurite outgrowth promotion. First, immature and mature lines resemble mortal type 1 astrocytes of corresponding ages with respect to morphology and growth pattern, and retain a quantitative difference in cell size (mature cells are larger). Second, the pattern of GFAP expression is preserved, with immature lines expressing lower levels than mature cell lines, but the overall GFAP levels are significantly lower in immortalized cell lines compared to mortal cells. Finally, promotion of neurite outgrowth from embryonic chick retinal ganglion cells on monolayers of the cell lines was examined. While all neurite outgrowth measures are significantly greater for the immortalized lines than for control 3T3 cells, they are attenuated relative to mortal astrocytes. The age‐related pattern of stronger outgrowth support on immature astrocytes is retained for neurite initiation, but not retained for mean neurite length. Thus, SV40 Tag‐immortalized astrocytes have a complex phenotype characterized by retention of age‐related differences in morphology, growth pattern and cell size, and by a marked attenuation of some astrocyte‐specific characteristics but retention of age‐related differences in the expression level of these same characteristics, and finally, loss of the ability to support neurite extension at levels characteristic of immature astrocytes. © 1994 Wiley‐Liss, Inc.
Neuronal progenitors identified by their inability to express class I histocompatibility antigens in response to interferon‐γ
Authors: Bailey K. A. , Drago J. , Bartlett P. F. 
Published: January 2005

AbstractInterferon‐γ (IFN‐γ) can induce class I major histocompatibility complex (MHC) antigen (H‐2) expression on virtually all neuroepithelial cells isolated from embryonic day 9 (E9) mice. However, a subpopulation of cells become refractory to H‐2 induction (H‐2l−) by E10 and the percentage of H‐2 noninducible cells increases during development. Cell sorting, by flow cytometry or magnetic bead immunoselection, has shown that H‐2l− cells give rise exclusively to neuronal cells, and by E12, the majority of the neuronal progenitors are found within this population. It has also been found that 98% of the H‐2l− also express the neuron‐associated marker, A2B5. Cells of the glial cell lineage retain the ability to express class I antigens throughout development. From these studies, it is clear that the neuroepithelium contains cells committed to the neuronal cell lineage as early as E10 in the mouse. Copyright © 1994 Wiley‐Liss, Inc.
Responsiveness of cultured septal and hippocampal neurons to ethanol and neurotrophic substances
Authors: Heaton M. B. , Paiva M. , Swanson D. J. , Walker D. W. 
Published: January 2005

AbstractDissociated septal and hippocampal neurons from E18 fetal rats were cultured with varying concentrations of ethanol (0.6–2.4 g/dl) and in cultures containing ethanol plus nerve growth factor (NGF) or basic fibroblast growth factor (bFGF). These substances have been shown to provide neurotrophic support for these populations and to afford neuroprotection against certain toxic substances or conditions applied to some neuronal populations. Both the septal and hippocampal neurons responded to ethanol in a dosedependent manner. Survival of septal neurons was generally unaffected by initial ethanol concentrations of 0.6 and 1.2 g/dl but was considerably impaired by higher concentrations (1.8 and 2.4 g/dl), while neurite outgrowth was compromised by all ethanol concentrations except the lowest one applied. The hippocampal neurons survived ethanol concentrations up to 2.4 g/dl, although process extension was decreased in concentrations of 1.2 g/dl and higher. NGF or bFGF in the culture medium (in cultures without ethanol) did not affect neuronal survival or process outgrowth in either population, probably owing to the relatively high plating densities of the cultures. NGF did tend to have a moderate ameliorative effect on the ethanol neurotoxicity in the septal cultures, however, and was slightly effective in this regard in hippocampal cultures at intermediate ethanol concentrations (1.8 g/dl). High concentrations of ethanol (2.4 g/dl) reduced the proportion of cholinergic cells in the septal preparations by approximately 50%. This neuronal loss could be reversed by inclusion of high concentrations of NGF in the culture medium (100 ng/ml) but not by a lower concentration (20 ng/ml). bFGF provided some protection against ethanol cytotoxicity with respect to both populations. The implications of these results for studies of fetal alcohol effects are discussed, as well as their relation to prior reports of trophic factor neuroprotection. © 1994 Wiley‐Liss, Inc.
S100β protein expression in Alzheimer disease: Potential role in the pathogenesis of neuritic plaques
Authors: Sheng J. G. , Mrak R. E. , Griffin W. S. T. 
Published: January 2005

AbstractIncreased synthesis and release of S100β protein from activated astrocytes has been implicated in the overgrowth of dystrophic neurites in neuritic plaques in Alzheimer disease (AD). To evaluate the quantitative relationships between tissues levels of S100β and the numbers of neuritic plaques, by Tau‐2 immunoreactive (Tau‐2+) labeling, in tissue sections of hippocampus and adjacent temporal cortex and measured the levels of S100β protein, by Western immunoblot labeling, in samples of analagous regions from contralateral hemisphere of the same patients. In AD, tissue levels of S100β (two‐ to fivefold that of controls) were significantly correlated with the number of Tau‐2+ plaques (R = 0.82, P < .01). Dual‐label immunohis‐tochemical analysis showed that most S100β+ cells were activated GFAP+ astrocytes. These results were substantiated by a significant correlation between S100β and GFAP tissue levels (R = 0.81, P < .05). Many of the S100β+ astrocytes were clustered around and within Tau‐2+ plaques. Indeed, no Tau‐2+ plaques were found without associated activated S100β+ astrocytes. Our findings provide further evidence of a role for S100β protein in dysregulation of neurons that leads to apparently nonsensical growth of imperfect neurites in AD, a potential key element in early stages of neuritic plaque pathogeneis. © 1994 Wiley‐Liss, Inc.
Presence and regulation of transforming growth factor beta mRNA and protein in the normal and lesioned rat sciatic nerve
Authors: Rufer M. , Flanders K. , Unsicker K. 
Published: January 2005

AbstractThe transforming growth factors beta (TGF‐β), a family of regulatory polypeptides, are involved in numerous vital processes including inflammation and wound healing. Since repair of a peripheral nerve lesion includes a series of well‐defined steps of cellular actions possibly controlled by TGF‐βs, and since TGF‐β mRNA and immunoreactivity have been found in the normal peripheral nerve, we have examined TGF‐β mRNA regulation and protein expression in the lesioned peripheral nerve. Sciatic nerves of adult rats were either crushed (allowing axonal regenration) or transected (to prevent axonal regeneration and to induce Wallerian degeneration in the distal stump). After intervals of 6 hours, 2 and 6 days post‐lesion, the rats were sacrificed and each nerve was cut into four segments, two proximal and two distal to the lesion site. TGF‐β 1‐3 mRNA were determined for each segment. We demonstrate that TGF‐ß1 mRNA levels are higher than those of TGF‐ß3; the amplitude of mRNA regulation depends on time, type of lesion and localization relative to the lesion site. TGF‐ß2 mRNA could not be detected. For TGF‐ß1‐3 immunocytochemistry, animals were sacrificed 12, 24, 48, 72 hours and 7 and 14 days after surgery. TGF‐β immunoreactivity (IR) was observed for all isoforms in lesioned and unlesioned nerves. In the segment directly adjacent to the lesion at its proximal side, an increase of TGF‐β‐IR became apparent as soon as 12 hours after surgery; it remained elevated during the whole period observed in both models. In the segment adjoining the distal side of the lesion, an increase of TGF‐β‐IR was observed after 48 hours, which was still present after 14 days. At day 7 after crush or transection, an increase of TGF‐β‐IR was detected in the most distal segments, which reached its highest levels at the end of our observation period. Our results suggest that the presence of axonal contact might induce an enhancement of TGF‐β expression by Schwann cells in the distal stump of a lesioned and regenerating peripheral nerve. Since we demonstrate an increase of TGF‐β mRNA and protein expression also in the distal stump of transected nerves where Schwann cells are not able to contact sprouting axons from the proximal part, other regulatory pathways must exist. The acquisition of a “reactive” Schwann cell phenotype after peripheral nerve lesion might involve an upregulation of TGF‐β expression. © 1994 Wiley‐Liss, Inc.
Expression and distribution of functional intergrins in rat CNS glia
Authors: Tawil N. J. , Wilson P. , Carbonetto S. 
Published: January 2005

AbstractIn previous studies, we have reported on the expression of β1 intergrins in type 1 astrocytes and their function in cell‐substratum attachment (Tawil et al., J Cell Biol 120:261–271, 1993). Here we extend those findings by providing evidence that type 1 astrocytes express integrins of the β3 and possibly β4 subclasses and that the former (αvβ3) functions in attachment by recognizing the peptide, Arg‐Gly‐Asp, in vitronectin. In addition, we have examined immunocyto‐chemically the expression of β1 integrins on type 2 astrocytes and oligodendrocytes. The pattern of expression of integrins on these two cell types is distinct from type 1 astrocytes; most notably type 1 astrocytes but not oligodendrocytes or type 2 astrocytes express α1β1 heterodimers. Since type 2 astrocytes and oligodendrocytes originate from a common precursor (0‐2A), the α1β1 heterodimer may be a functional marker which distinguishes O‐2A‐derived cells from those of the type 1 astrocyte lineage. © 1994 Wiley‐Liss, Inc.
Formation of new sensory cells in deafferented tuberous organs of the gymnotid fish Eigenmannia virescens
Authors: Bensouilah M. , Denizot J. P. 
Published: January 2005

AbstractThe cutaneous electroreceptor “tuberous organs” of the lateral line system of Eigenmannia virescens were studied at light and electron microscopic levels with immunohistochemical and autoradiographic techniques after sectioning of the posterior branch of the lateral line nerve. After deafferentation total degeneration of the sensory cells was observed. The accessory cells of the basal platform, however, remain intact and undergo a process of differentiation. The cytoplasms and nuclei of these cells increase in volume, and the nuclei incorporate tritiated thymidine. In control tuberous organs with intact innervation, tritiated thymidine is absorbed by the nuclei of the elongated epidermal cells surrounding the sensory cavity. The newly formed sensory cells, but not those of the intact organs, are substance P immunoreactive. They have synaptic bars surrounded by vesicles and their free membrane surface is covered with microvilli. The new sensory cells are fully differentiated 35 days after the lateral line was cut. These results demonstrate that in the tuberous organs of E. virescens new sensory cells are formed in the absence of an innervation. © 1994 Wiley‐Liss, Inc.
Insertional mutagenesis inducing hypomyelination in transgenic mice
Authors: Orian J. M. , Mitchell A. W. S. , Marshman W. E. , Webb G. C. , Ayers M. M. , Grail D. , Ford J. H. , Kaye A. H. , Gonzales M. F. 
Published: January 2005

AbstractInvestigations of myelin disorders, in particular multiple sclerosis (MS), have concentrated on immunemediated damage to formed myelin, while there has been less emphasis on the molecular genetics of myelin formation. We have generated a transgenic mouse mutant (designated 2‐50) which carries an insertional mutation in a locus regulating myelination. These mice carry a transgene comprising 1.3 Kb of the mouse myelin basic protein (BMP) promoter conjugated to a fragment containing exons 2 and 3 of the human c‐myc gene. Positive mice show a significant reduction in myelin compared to controls and a shivering phenotype. Unlike other myelin mutants, all 2‐50 mice lose the shivering phenotype and breed normally. Expression of c‐myc is detectable in only 65% of transgene‐carrying mice, and when present occurs at extremely low levels. This shows that the phenotype is caused by insertional inactivation of a gene necessary for myelination rather than ectopic expression of the transgene. The transgene was found by in situ hybridization to be inserted into a single site which is very distally located on chromosome 9. The 2‐50 mice represent a unique model which will be ideal for investigating the molecular basis of myelin assembly and for developing gene therapy to promote remyelination in conditions such as MS. © 1994 Wiley‐Liss, Inc.
Methylation of the rat glial fibrillary acidic protein gene shows tissue‐specific domains
Authors: Teter B. , Osterburg H. H. , Anderson C. P. , Finch C. E. 
Published: January 2005

AbstractThe gene for glial fibrillary acidic protein (GFAP) was compared for CpG sites that are potential locations of methylated cytosine (mC). GFAP sequences in the 5′‐upstream promoter and in exon 1 of rat, mouse, and human showed extensive similarity in the locations of CpG sites in the promoter and in exon 1, implying conservation. The methylation of mC at 9 CpG sites in the promoter and 10 sites in exon 1 was analyzed in F344 male rats by a quantitative application of ligation‐mediated polymerase chain reaction (LMPCR). CpG sites with varying mC in different tissues were found in the GFAP promoter and in a CpG island in exon 1. In the brain, the promoter had about 40% less mC than in testis and liver. The degree of methylation varied strikingly between adjacent sites within and between tissues. Testis GFAP exon 1 had a gradient of mC from 5′ to 3′ across the exon that was absent in liver, brain, and cultured neurons and astrocytes. Among brain regions, the hippocampus had 10–40% less mC at 12 CpG sites than in hypothalamus; the other sites (7/19) showed smaller differences between these brain regions. In DNA from primary cultures, astrocytes has slightly less mC than neurons at all sites. Because neuron‐rich hippocampal subregions and primary neuron cultures had less methylation than nonneural tissues, we hypothesize that neuroectodermal derivatives tend to be less methylated, whether or not GFAP is expressed. Four domains of methylated CpG sites are proposed on the basis of tissue and cell‐type distribution: (I) a constitutively methylated domain in the mid‐upstream promoter; (II) a testis‐specific gradient of methylation in exon 1; (III) a hypomethylated domain found in neuroectodermal derivatives; and (IV) subsets of sites in the promoter and in exon 1 that have the least methylation in astrocytes, and therefore may be astrocytespecific domains. © 1994 Wiley‐Liss, Inc.
Domain‐specific antibodies against the B2 chain of laminin inhibit neuronal migration in the neonatal rat cerebellum
Authors: Liesi Päivi , Hager G. , Dodt H.‐U. , Seppälä I. , Zieglgänsberger W. 
Published: January 2005

AbstractAlthough the spatial and temporal patterns of neuronal migration have been analyzed in great detail, little direct evidence is available as to what extracellular matrix molecules are involved. Because there is indirect evidence implicating the extracellular matrix protein laminin in neuronal migration, we investigated the effects of antibodies against a synthetic peptide derived from a neurite outgrowth domain of the B2 chain of laminin on neuronal migration in living cerebellar slices. We show by using infrared video microscopy that divalent Fab2 fragments of these antibodies inhibit granule neuronal movement in living slices of (P8) rat cerebellum. This inhibition of neuronal movement manifests itself by cessation of both radial and horizontal translocations of nuclei inside the granule neuronal processes. Fab2 fragments of antibodies against the intact (native) laminin molecule or Fab2 fragments from the preimmune serum do not affect nuclear translocation. Immunocytochemistry shows binding of the divalent Fab2 fragments of the B2 chain‐specific antibodies to the Purkinje and Bergmann glial cell areas, and as punctate deposits in between the cells of the external granule cell layer. Native laminin antibodies bind to the basement membranes, and binding of the Fab2 fragments from the preimmune sera cannot be demonstrated. These results indicate that neuronal migration in the postnatal rat cerebellum in vivo involves nuclear translocation that can be inhibited by antibodies against a neurite outgrowth domain of the B2 chain of laminin. Thus, migration of cerebellar granule neurons may depend on the interaction between a neurite outgrowth domain of the B2 chain of laminin and neuronal cytoskeleton involved in nuclear movement. © 1995 Wiley‐Liss, Inc.
Novel forms of neuronal migration in the rat cerebellum
Authors: Hager G. , Dodt H.‐U. , Zieglgänsberger W. , Liesi P. 
Published: January 2005

AbstractInfrared video microscopy of neonatal rat cerebellum (P0‐P14) was used to directly visualize migrating granule neurons in relation to other cerebellar cells in a brain slice for up to 24 hr. Initially (P0‐P5), granule neurons move along radial migration pathways of other neuronal fibers. These pathways are probably established by the bipolar granule neurons that attach to the external basement membrane via one process and extend another process toward the Purkinje cell layer. At P5‐P8, a substantial number of granule neurons move horizontally and extend long parallel fibers. Both radially and horizontally migrating granule neurons move by nuclear translocation inside their preformed processes with a speed that varies between 6 and 120 μ/hr. In P10‐P12 animals, the horizontally oriented granule neurons start to migrate radially. They move into the internal granule cell layer either along the radial pathways of other neuronal fibers or in contact with the matured glial processes. The radial neuronal migration pathways disappear by P14 whereas the glial cell processes are maintained and reach the basal lamina. These results describe novel radial and horizontal modes of neuronal migration that proceed independently of the physical glial guidance. © 1995 Wiley‐Liss, Inc.
Microglia in colony‐stimulating factor 1‐deficient op/op mice
Authors: Blevins G. , Fedoroff S. 
Published: January 2005

AbstractMice that are homozygous for the autosomal recessive mutation osteopetrosis (op) suffer from a general skeletal sclerosis, and the numbers of macrophages in various tissues are significantly decreased. We report that microglia in op/op mice are not affected by the mutation. They have normal morphology and are present in the CNS in normal frequency.In cultures, disaggregated cells of neopallia can form microglia, but such cells from neopallia of op/op mice form microglia only when colony‐stimulating factor 1 (CSF‐1) is added to the culture medium. The addition of granulocyte/macrophage (GM)‐CSF or interleukin (IL)‐3 to the culture medium does not stimulate production of microglia. Microglia that form in op/op neopallial cell cultures, in the presence of CSF‐1, are capable of Fc‐receptor‐mediated phagocytosis.Based on our experiments, it seems that microglia are CSF‐1 dependent but in op/op mice (in which CSF‐1 is absent) microglia may use other locally produced factors. © 1995 Wiley‐Liss, Inc.
Long, interlaminar astroglial cell processes in the cortex of adult monkeys
Authors: Colombo Jorge A. , Yáñez A. , Puissant V. , Lipina S. 
Published: January 2005

AbstractAt variance with current descriptions stressing the stellate geometry of cortical astrocytes in the brain of adult mammals, GFAP‐immunoreactive astrocytes from prefrontal and rostral cingulate cortices in two adult New World monkey species, Cebus apella and Saimiri sciureus, were found to have long cellular processes traversing several cortical lamina. These unreported features of cortical astroglial cells in adult nonhuman primates pose new issues for the understanding of iso‐ and allocortical organization and processing in higher mammals. © 1995 Wiley‐Liss, Inc.
Myelinogenic potential of an immortalized oligodendrocyte cell line
Authors: Newman S. L. , Weikle A. A. , Neuberger T. J. , Bigbee J. W. 
Published: January 2005

AbstractThe myelinogenic potential of an oligodendrocyte cell line (N20.1) immortalized by transformation with a temperature‐sensitive retrovirus (Verity et al., J Neurochem 60:577–587, 1993) has been evaluated in a co‐culture system utilizing dorsal root ganglion neurons. When N20.1 cells were placed in co‐culture with dorsal root ganglion neurons at 39°C, the temperature at which TAg expression is decreased relative to that in cells maintained at 34°C, there was a dramatic decrease in the N20.1 proliferation rate compared to cells maintained in the absence of neurons at either temperature. This decrease in proliferation was observed within 3 days of co‐culture and appeared to precede a further decrease in TAg expression that occurred with time in response to the neurons. In co‐cultures the immunoreactivity of N20.1 cells for galactocerebroside increased with time, and the cells appeared to establish contact with neurites and initiate formation of membranous sheets. When the duration of co‐culture was extended to 52 days, myelin‐like figures were noted by electron microscopy. Thus, the extent of N20.1 differentiation is dependent on the presence of neurons and the duration of co‐culture. This culture system represents a potentially powerful tool for the study of neuronal‐glial interactions influencing myelinogenesis and remyelination. © 1995 Wiley‐Liss, Inc.