摘要:

AbstractIn the following review, we address difficulties that have arisen when attempting to convert the myelin multilayers into vesicles. The emphasis is on CNS myelin of adult mammals although both central nervous system (CNS) and peripheral nervous system (PNS) myelin are considered. The ability to prepare vesicle of myelin membrane has yet not been feasible. We hope to clarify some aspect of this problem and offer some possible approaches. Special attention is paid to myelin swelling phenomena because these indicate ways in which the myelin multilayer can break down. Images of isolated myelin are reviewed with special attention to the ways in which the multilayer actually breaks down. Attempts at reproducing a procedure for vesiculating myelin are summarized, and a critique is given to account for the inability to reproduce the published results. Finally, novel approaches for vesiculating myelin are proposed, which are based on well‐characterized swelling phenomena. © 1995 Wiley‐Liss,

ISSN:0360-4012    

DOI:10.1002/jnr.490410202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the mammalian central nervous system (CNS), multipotential neural stem cells in the neuroepithelium generate the three major types of neural cells, namely, neurons, astrocytes, and oligodendrocytes. To explore the molecular mechanisms underlying proliferation and differentiation of these neural stem cells, we established a cell line named MNS‐57 from the embryonic day 12 rat neuroepithelium by introducing the mycer fusion gene, in which c‐myc can be conditionally activated by adding oestrogen to the culture medium. MNS‐57 cells expressed nestin, vimentin, and the RC1 antigen, which are potential markers for neural stem cells. We show that under particular culture conditions, MNS‐57 cells can conditionally generate neurons, astrocytes, and oligodendrocytes in vitro, indicating that they are likely to originate from multipotential neural stem cells. Incubating MNS‐57 cells with either oestrogen, which activates mycer, or growth factors such as basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) stimulated their growth, and the combination of oestrogen and bFGF (or EGF) had a synergistically stronger mitogenic effect than the single factors. Furthermore, both c‐myc activation and bFGF appeared to be necessary for the differentiation of MNS‐57 cells, and only when stimulated by both signals simultaneously, the cells committed to generating multiple neural cell types. Thus, the property of the cell line is unique in that its differentiation into neurons and glia can be conditionally manipulated invitro in an exogenous signal‐dependent manner. We propose that the cell line described here will provide an useful in vitro model to understand genetic and environmental mechanisms that control the generation of neural cell diversity in the CNS. © 1995

ISSN:0360-4012    

DOI:10.1002/jnr.490410203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe have analyzed the brain distribution of the rat cAMP‐specific phosphodiesterases (rPDEIV) which are closely related to the defective gene products of the drosophila melanogaster learning and memory mutant dunce. PCR analysis of rat brain cDNA was performed on the four known dunce‐like cAMP PDE rat isogenes (rPDE‐IV‐A, ‐B, ‐C, ‐D). High expression of three of these isogenes (rPDEIV‐A, ‐B, ‐D) highlighted their involvement in regulation of cAMP in the brain. Specific probes for all four isogenes were then used for in situ hybridization of rat brain sections. Distinct but overlapping expression patterns were observed for rPDEIV‐A, rPDEIV‐B, and rPDEIV‐D. Abundant expression of these subtypes was observed in the olfactory system, the hippocampus and the cerebellum, while no specific signals could be detected in most areas of the brain for the subtype rPDEIV

ISSN:0360-4012    

DOI:10.1002/jnr.490410204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of L‐glutamate (L‐Glu) and its structural analogs N‐methyl‐D‐aspartate (NMDA), quisqualate (QA), and kainate (KA) on the DNA binding activity of the Activator Protein 1 (AP‐(1) and the Ca2+/cAMP Responsive Element Binding Protein (CREB) families of transcription factors was examined in cultured chick retinal Müller glia cells. L‐Glu, NMDA, and KA evoked a dose and time dependent increase in AP‐1 DNA binding activity and had no effect on CREB binding. The order of potency for stimulating AP‐1 DNA binding was NMDA≥Glu>KA>>QA. L‐Glu responses were partially blocked by 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) and by 3‐[RS)‐2‐carboxypiperazin‐4‐yl)]‐propyl‐l‐phosphonate (CPP) indicating that the increase in DNA binding is mediated both by an a‐amino‐3‐hydroxy5‐methyl‐4‐isoxazolepropionate (AMPA)/low affinity KA and a NMDA subtypes of L‐Glu receptors. Since Müller glia L‐Glu receptors are probably mediators of the efficacy of the excitatory transmission in the retina, the present findings suggest that a stimulustranscription coupling triggered by L‐Glu in the glial cells might have a role in

ISSN:0360-4012    

DOI:10.1002/jnr.490410205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractNerve growth factor (NGF) stimulates expression of the low affinity neurotrophin receptor p75NGFRmRNA in primary cultures of neonatal rat cortical type I astrocytes. Nerve growth factor treatment altered glial morphology in glial fibrillary acidic protein positive (GFAP+) cell cultures derived from newborn (P0) and 3‐day‐old (P3) rat pups. When P0‐ or P3‐derived primary glial cultures were serum‐deprived, in the presence of 200 pM NGF for 5 days, the flat polygonal glia present in culture assumed a fibrous morphology, an effect not seen in the untreated serum‐deprived controls. The NGF effect on astrocytic morphology was blocked by continuous serum treatment. Nerve growth factor did not stimulate astrocytic proliferation under these culture conditions, as assayed by cell cycle analysis using3H thymidine autoradiography. P0‐derived primary glial cultures expressed the signal transducing neurotrophin receptors p145trkBand p140trkaas determined by reverse transcription‐polymerase chain reaction (RT‐PCR). RT‐PCR products were identified by sequencing or restriction enzyme analysis. Astrocytes internalized125I‐NGF at 37°C but not at 4°C, consistent with energy requirements for internalization. Also, internalization of125I‐NGF was abolished by the addition of a 300‐1,000‐fold excess of unlabeled NGF. Thus, astroglial cells in culture internalize NGF through a specific receptor‐mediated process, express trkA and full‐length trkB mRNAs at low levels, and respond to exogenous NGF by expressing a fibrous morphology under serum‐free culture

ISSN:0360-4012    

DOI:10.1002/jnr.490410206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractMesencephalic cultures contain two morphologically different tyrosine hydroxylase (TH)‐immunoreactive (IR) neurons, fusiform bipolar, and pyramidal multipolar, which project to different anatomical structures (ventral striatum and neostriatum). The possibility of functional difference of these cells in Parkinson's disease led us study the effect of 1‐methyl‐4‐phenylpyridinium (MPP+) on them. Survival and morphology of the two groups was studied in dissociated co‐cultures from mesencephalon and striatum of embryonic C57BL/6 mice. Cells were grown at first in serum containing medium and then in serum free medium supplemented with hormones. Cultures were exposed to different concentrations of MPP+on day 9 and 13 for 24 hr. They were fixed and stained, with an anti‐TH antibody. 0.1‐1.0μM MPP+caused a dramatic reduction of the total area of TH‐IR neurons. At 0.1 μM MPP+some area was reduced, at 0.5 μM it appeared similar to controls, and decreased further at 1.0 μM. The relation of soma to total area showed that the decrease of the neuronal size was mainly due to the degeneration of the neuronal processes. The length of neuronal tree as well as the number of terminal segments were reduced dose dependently when cells were treated with the toxin. Similar results were obtained for bipolar and multipolar neurons. A significant difference in the decrease in total area was observed between the two age groups when cells were treated with MPP+, as older cells appeared to be more sensitive. When other parameters were checked no apparent difference was present. ©

ISSN:0360-4012    

DOI:10.1002/jnr.490410207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe present work investigates the possible existence of molecular heterogeneity of endogenous neuropeptide Y (NPY) in the rat brain and, if existing, whether it is affected by repeated electroconvulsive stimuli (ECS). Different column chromatographic techniques (gel‐permeation chromatography, HPLC, ion‐pair reverse‐phase HPLC) were used combined with immunochemical methods based on antisera directed towards two different epitopes of NPY (antiserum N1, directed towards the midportion of NPY, and antiserum C1, directed towards the C‐terminal end of NPY). Following repeated ECS increased concentrations of NPY were seen in the occipital cortex and hippocampus (P<0.001) when analyzed by direct radioimmunoassays (RIA). Chromatographic characterization showed that the NPY mainly consisted of intact NPY (1‐36) and sulphoxidated form of NPY, no short C‐terminal homologues were found. This is of importance since it has been shown that NPY (1‐36) has different biological properties compared to C‐terminal homologues. © 1995

ISSN:0360-4012    

DOI:10.1002/jnr.490410208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPurified myelin isolated from 70‐day‐old rats was submitted to nonenzymatic peroxidative systems containing 100 μM FeC13.6H2O,100 μM ascorbic acid, and 100 μM CuSO4.6H2O 10 mM H2O2in order to investigate the extent of damage produced by reactive oxygen species (ROS). Iron and copper catalyzing systems were selected because of the known importance of these metals in producing free radical chain reactions in biological membranes (Halliwell and Gutteridge: “Free Radicals in Biology and Medicine,” Oxford: Clarendon Press, 1989). Our findings, show that (1) although after 1 hour of peroxidation, an important level of thiobarbituric acid‐reactive substances (TBARS) was detected, polyunsaturated fatty acids (20:2; 20:4; 22:4 and 22:6) were markedly affected only after 14 hours of incubation; (2) protein thiol groups were very sensitive to the attack of ROS generated by copper but resistant to iron‐generated ROS; (3) aggregation of myelin proteins produced by peroxidation could be prevented by sulfhydryl (SH)‐reducing agents, and (4) as a consequence of these modifications, compact myelin suffered disruption of its intraperiodic line. In conclusion, our results demonstrate that this unique membrane of the central nervous system (CNS) is highly vulnerable to oxidative stress and that this susceptibility to oxidative damage could be prevented, at least partially, by the use of SH‐protective molecules. © 1

ISSN:0360-4012    

DOI:10.1002/jnr.490410209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe examined the effect of bacterial wall lipopolysaccharide (LPS), a strong inflammatory agent, on the morphology, cell motility, cytoskeletal organization, and phagocytic activity of microglia in tissue cultures initiated from neopallia of newborn C3H/OuJ mice. Normally, the microglia in our cultures are non‐migratory and Mac‐1 positive, have ameboid cell morphology, no polarity, many short processes that extend into lamellipodia in opposing directions, and undulating cell membrane projections.When 1–5 μg/ml LPS is added to such cultures, some cells acquire polarity by forming a large lamellipodium and begin to migrate. Two hours later migration ceases; the membrane undulations stop; and the cells become non‐polar, assume a large, round, flat shape, and gradually develop many microspikes all over the cell body. Those cells that do not transform into large, round, flat cells enlarge and extend numerous lamellipodia in opposing directions.We found that the cytoskeleton of microglia is composed of actin, vimentin‐containing intermediate filaments (IF) and microtubules (MT). Vimentin‐containing IF and MT form dense networks that radiate into the cell periphery, whereas F‐actin is diffusely arranged throughout the cytoplasm. The LPS‐treated cells show changes in the organization of the main components of the cytoskeleton. F‐actin is reorganized by the formation of bundles‐ underneath and parallel to the cell membrane and other bundles projecting into the cores of the microspikes. The vimentin‐containing IF dense network reorganizes into two condensed rings, with fine strands of IF extended between the two rings and the MT networks become less dense and extend throughout the cytoplasm. The LPS treatment potentiates the phagocytic activity of the microglia. However, approximately 30% of microglia lose the expression of MHC class II antigens.

ISSN:0360-4012    

DOI:10.1002/jnr.490410210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractChronic brain ischemia (CBI) was induced in aging (13 month) rats by ligating the left subclavian artery and placing temporary occluders in each common carotid artery [three‐vessel occlusion (3‐VO)]. Carotid artery occluders were removed after 1, 2, or 3 weeks following brain ischemia or maintained for 9 weeks. Two rats were kept with their occluders in place for 25 weeks. On weeks 3 and 9 after CBI,31P‐/1H‐nuclear magnetic resonance (NMR) spectroscopy and high resolution diffusion weighted imaging were performed in vivo, non‐invasively for detection of hippocampal high energy phosphates, lactate, intracellular pH, N‐acetyl‐aspartate, choline, glutamate, creatine, and structural alterations of the brain following CBI. Brains were histologically processed for morphometry of glial fibrillary acidic protein (GFAP) and CA1 damaged neurons 9 weeks after CBI.31P‐/1H‐NMR spectroscopy showed that high energy substrates remained normal in ischemic animals when compared to non‐ischemic controls except for an elevation of phosphomonoesters in the hippocampal region. Rats deoccluded 1 and 2 weeks after initiation of CBI had no NMR spectroscopic or imaging changes. Rats kept ischemic for 9 weeks showed high signal intensities in the parietal cortex detected by diffusion weighted imaging as well as CAI damage and increased GFAP density but no cortical atrophy or neuronal damage could be detected histologically. Rats kept ischemic for 25 weeks showed extensive cortical atrophy which corresponded to the high, signal intensity observed with diffusion weighted imaging in the group kept ischemic for 9 weeks. These findings indicate that NMR spectroscopy and difussion weighted imaging can be used to follow the progress of neuronal injury in vivo and non‐invasively. Moreover, diffusion weighted imaging may be an excellent predictor of cerebral damage and atrophy prior to histopatholog ical detection of such damage. Our present and previous findings using our 3‐VO model indicate that this aging rat model may be useful in screening potential therapy for neurodegenerative disorders associated with abnormal aging and memory impairment.

ISSN:0360-4012    

DOI:10.1002/jnr.490410211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY