bluuebunny/crossref_metadata_2025_split huggingface dataset:
Advantages of using microfabricated extracellular electrodes for in vitro neuronal recording
Authors: Breckenridge L. J. , Wilson R. J. A. , Connolly P. , Curtis A. S. G. , Dow J. A. T. , Blackshaw S. E. , Wilkinson C. D. W. 
Published: January 2005

AbstractWe describe fabrication methods and the characterisation and use of extracellalar microelectrode arrays for the detection of action potentials from neurons in culture. The 100 μm2 platinised gold microelectrodes in the 64 electrode array detect the external current which flows during an action potential with S:N ratios of up to 500:1, giving a maximum recorded signal of several millivolts. The performance of these electrodes is enhanced if good sealing of the cells over the electrodes is obtained and further enhanced if the electrodes and the cells lie in a deep groove in the substratum. The electrodes can be used for both recording and stimulation of activity in cultured neurons and for recording from multiple sites on a single cell. The use of such electrodes to obtain recordings from invertebrate neurons is described. The particular advantages of these electrodes, their long term stability, non‐invasive nature, high packing density, and utility in stimulation, are demonstrated. © 1995 Wiley‐Liss, Inc.
Myelin basic protein mRNA localization and polypeptide targeting
Authors: Boccaccio G. L. , Colman D. R. 
Published: January 2005

AbstractMyelin basic proteins (MBPs), the major peripheral membrane proteins of central nervous system (CNS) myelin, are encoded by mRNAs that are selectively segregated to the myelinating processes of oligodendrocy tes. In order to test whether the intracellular mechanisms responsible for MBP mRNA translocation are oligodendrocyte‐specific, or alternatively, are present in other cell types and may therefore be more general, we have studied the localization of the 14 kD MBP mRNA and its encoded polypeptide (MBP14) in transiently transfected HeLa cells (a cervical carcinoma cell line) and in the rat pheochromocytoma cell line PC12. Unlike the situation in oligodendrocytes in situ, where MBP mRNAs are translocated and become “centrifugally” distributed, in both of the non‐glial cells MBP mRNA was primarily detected in the perinuclear region. The MBP14 polypeptide was found associated with intracellular membranes, and not exclusively with the plasma membrane. Our results indicate that the inability of HeLa and PC12 cells to correctly target MBP mRNAs to the cell periphery leads to a failure to incorporate MBP polypeptides directly into the plasma membrane. Further, the data lend credence to the concept that MBP mRNA segregation appears to be a specific feature of myelin‐forming cells which is required for the precise delivery of the encoded polypeptides to the forming myelin membrane. © 1995 Wiley‐Liss, Inc.
An antineuronal monoclonal antibody that reverses neurite growth inhibition by central nervous system myelin
Authors: Lozano A. M. , Labes M. , Roder J. , Roach A. 
Published: January 2005

AbstractA component of adult mammalian central nervous system (CNS) myelin causes collapse of neuronal growth cones and inhibits axonal growth, properties that may be responsible for the lack of regrowth of injured axons in the CNS. The molecules and detailed mechanism through which the inhibitory activity acts are not known. To study the cellular molecules mediating the response to this inhibitor, we have used an in vitro neurite growth inhibition assay to screen a panel of monoclonal antibodies raised against rat neuronal membrane proteins, for clones capable of blocking the response. One monoclonal antibody (10D) neutralized the inhibition of neurite growth seen when primary sympathetic neurons, PC12 cells or NG108‐15 cells were grown on inhibitory CNS myelin substrates, but did not promote growth on noninhibitory substrates. 10D reacted with neuronal cells but not myelin substrate proteins. The antigen recognized by 10D appears to play a role in the interaction between neurons and their growth substrates, and is a novel candidate for a cellular receptor or associated signalling molecule mediating the response to myelin inhibitors. © 1995 Wiley‐Liss, Inc.
Increased production of gelatinase B (matrix metalloproteinase‐9) and interleukin‐6 by activated rat microglia in culture
Authors: Gottschall P. E. , Yu X. , Bing B. 
Published: January 2005

AbstractActivated macrophages produce several matrix metalloproteinases (MMPs), a family of extracellular matrix (ECM)‐degrading enzymes, during wound healing and in other inflammatory states. In response to brain injury, brain microglia become “activated,” in a way similar to peripheral tissue macrophages, a process which includes differentiation and probably invasion and proliferation. Little is known about the ECM‐degrading MMPs that are secreted by microglia upon activation. Thus, it was of interest to determine whether activated microglia secrete MMPs. Conditioned media samples obtained from cultured microglia that were stimulated with various activating agents were subjected to gelatin‐substrate zymography. Microglia constitutively express low levels of a 94‐kDa gelatinase (GLase) activity. Treatment with LPS, zymosan, and fixed Staphylococcus aureus for 24 hr stimulated the activity of the 94‐kDa GLase, 4‐20‐fold, in a dose‐dependent manner. Addition of INFγ inhibited the LPS‐stimulated activity of MMP‐9. LPS, zymosan, and fixed Staphylococcus aureus also stimulated the secretion of IL‐6 from microglia in a dose‐dependent manner. The 94‐kDa GLase activity was Ca++ dependent, it was inhibited by 1,10‐phenanthroline, and it was activated by organomercurial compounds. When immunoblots were performed using specific antisera against the 94‐kDa gelatinase B (MMP‐9) with untreated and LPS‐stimulated conditioned medium samples, a 94‐kDa immunopositive band was observed. Thus, it appears that the 94‐kDa GLase is gelatinase B (MMP‐9). These results indicate that activators of peripheral macrophages are potent secretagogues for the MMPs in cultured microglia. The ability of activated microglia to secrete MMPs suggests that these enzymes may play an important function in the brain parenchyma during inflammatory states. © 1995 Wiley‐Liss, Inc.
Brain injury and tumor necrosis factors induce calbindin D‐28K in astrocytes: Evidence for a cytoprotective response
Authors: Mattson M. P. , Cheng B. , Baldwin S. A. , Smith‐Swintosky V. L. , Keller J. , Geddes J. W. , Scheff S. W. , Christakos S. 
Published: January 2005

AbstractCalbindin is a 28 kDa calcium‐binding protein expressed in restricted neuronal populations in the mammalian brain where it may play a role in protecting neurons against excitotoxic insults. Recent findings indicate that electrical activity and some neurotrophic factors can induce the expression of calbindin in neurons. We now report that brain injury, effected by systemic administration of the excitotoxin kainate or mechanical trauma, induces expression of calbindin in cells of the corpus callosum and subcortical white matter. Immunohistochemical analysis using antibodies to the astrocyte‐specific proteins (glial fibrillary acidic protein and S‐100β) established the identity of calbindin immunoreactive cells as astrocytes. Because brain injury is known to induce the expression of several neurotrophic factors and cytokines, we employed cultures of hippocampal and neocortical astrocytes to test the hypothesis that such factors can induce expression of calbindin in astrocytes. Tumor necrosis factors (TNFβ and TNFβ), cytokines that are expressed in response to brain injury, induced the expression of calbindin in cultured rat hippocampal and neocortical astrocytes. Two neurotrophic factors, basic fibroblast growth factor and nerve growth factor, did not induce calbindin in astrocytes. TNF‐treated, calbindin‐expressing astrocytes were resistant to acidosis and calcium ionophore toxicity, suggesting that TNFs and calbindin may serve a cytoprotective role in astrocytes in the injured brain. © 1995 Wiley‐Liss, Inc.
Ion channels in rat microglia and their different sensitivity to lipopolysaccharide and interferon‐γ
Authors: Visentin S. , Agresti C. , Patrizio M. , Levi G. 
Published: January 2005

AbstractIn order to study the voltage‐dependent ion channels in microglia, and their possible modulation by proinflammatory substances like lipopolysaccharide (LPS) and interferon‐γ (IFN‐γ) we employed the patch‐clamp technique on purified rat microglial cell subcultures grown for 1–5 days in control condition or after a 24 hour treatment with those agents. Regardless of the culture condition, almost 100% of the cells presented inward‐rectifying (IR) K+ currents identified by the following features: (a) extracellular K+ ‐dependence of Vrev and whole‐cell conductance; (b) inward‐rectifying property; (c) channel blocking mechanism by Cs+; and (d) single channel conductance of 27 pS.A ‘n’ type outward‐rectifying (OR) K+ current was present in 30% of the cells during the first 2 days of subcultivation. Its occurrence was strongly dependent on the preparation, varying from 0% to almost 80%, and it decreased to 13% of the cells after three days in culture. It showed the following features: (i) threshold of activation close to ‐30 mV; (ii) sigmoid current onset; (iii) voltage‐% kinetics; and (iv) sensitivity to 4‐aminopyridine (4‐AP) and tetraethylammonium (TEA). Furthermore, we detected two ion currents not previously described in microglia: (i) a slowly activating outward current which appeared at potentials more positive than +20 mV and with a reversal potential close to 0 mV, tentatively identified as a proton current; and (ii) a Cl− conductance identified in ion substitution experiments as the current sensitive to the Cl− channel blocker SITS.The two agents, LPS (20–2,000 ng/ml) and IFN‐γ (10–100 u/ml), shared the following effects: (a) enhancement of membrane capacitance, and (b) increase of OR current amplitude and frequency of occurrence. Moreover, IFN‐γ was also able to increase IR current density, especially in cells with ameboid morphology, while LPS was ineffective. We conclude that the voltage‐dependent ion channel pattern of microglia is more complex than previously thought and that activating agents such as LPS and IFN‐y share some electrophysiological effects, but differ in others. © 1995 Wiley‐Liss, Inc.
Developmental changes of epidermal growth factor‐like immunoreactivity in the human fetal brain
Authors: Kato M. , Mizuguchi M. , Takashima S. 
Published: January 2005

AbstractWe investigated the immunohistochemical localization of epidermal growth factor (EGF) in the developing human brain from 6 weeks of gestation to 3 months postpartum. EGF‐like immunoreactivity varied in its localization and intensity according to the stage of development. At 10‐20 weeks of gestation, EGF‐like immunoreactivity appeared in proliferating and migrating cells in the cerebrum, disappeared thereafter, and appeared again in cortical neurons after 27 weeks of gestation. Astrocytes also showed EGF‐like immunoreactivity from 27 weeks of gestation. These results suggest developmental regulation of EGF expression in the human brain, suggesting Its physiological role in both neuronal and glial cells. © 1995 Wiley‐Liss, Inc.
Chronic opioid treatment of neuroblastoma X dorsal root ganglion neuron hybrid F11 cells results in elevated GM1 ganglioside and cyclic adenosine monophosphate levels and onset of naloxone‐evoked decreases in membrane K+ currents
Authors: Wu G. , Fan S. F. , Lu Z.‐H. , Ledeen R. W. , Crain S. M. 
Published: January 2005

AbstractProlongation of the action potential duration of dorsal root ganglion (DRG) neurons by low (nM) concentrations of opioids occurs through activation of excitatory opioid receptors that are positively coupled via Gs regulatory protein to adenylate cyclase. Previous results suggested GM1 ganglioside to have an essential role in regulating this excitatory response, but not the inhibitory (APD‐shortening) response to higher (μM) opioid concentrations. Furthermore, it was proposed that synthesis of GM1 is upregulated by prolonged activation of excitatory opioid receptor functions. To explore this possibility we have utilized cultures of hybrid F11 cells to carry out closely correlated electrophysiological and biochemical analyses of the effects of chronic opioid treatment on a homogeneous population of clonal cells which express many functions characteristic of DRG neurons. We show that chronic opioid exposure of F11 cells does, in fact, result in elevated levels of GM1 as well as cyclic adenosine monophosphate (AMP), concomitant with the onset of opioid excitatory supersensitivity as manifested by naloxone‐evoked decreases in voltage‐dependent membrane K+ currents. Such elevation of GM1 would be expected to enhance the efficacy of excitatory opioid receptor activation of the Gs/adenylate cyclase/cyclic AMP system, thereby providing a positive feedback mechanism that may account for the remarkable supersensitivity of chronic opioid‐treated neurons to the excitatory effects of opioid agonists as well as antagonists. These in vitro findings may provide novel insights into the mechanisms underlying naloxone‐precipitated withdrawal syndromes and opioid‐induced hyperalgesia after chronic opiatf addiction in vivo. © 1995 Wiley‐Liss, Inc.
Zebrafish neurons express two L1‐related molecules during early axonogenesis
Authors: Tongiorgi E. , Bernhardt R. R. , Schachner M. 
Published: January 2005

AbstractPartial clones coding for two L1‐related genes, zebrafish L1.1 and L1.2, were isolated from a zebrafish embryonic cDNA library. The homology analysis, based on the deduced amino acid sequences of L1.1 and L1.2, revealed that the two molecules are most closely related to each other and to mouse L1. Analysis by in situ hybridization revealed that during embryonic development of the nervous system the L1.1 and L1.2 messages are restricted to postmitotic neurons and that the onset of expression correlates with the initiation of axonogenesis. L1.1 is expressed by all known classes of neurons, consistent with an important general function during axonal outgrowth. Most of the neurons also express L1.2. However, L1.2 either is undetectable or is expressed at very low levels in the neurons of the olfactory placodes, anterior lateral line/acoustic ganglia complex, posterior lateral line ganglion, and in late developing hindbrain neurons. In the spinal cord, L1.2 message is detected only in a subpopulation of Rohon‐Beard cells. This suggests the possibility that different levels of L1.2 expression may serve to distinguish different populations of neurons and their axons. © 1995 Wiley‐Liss, Inc.
Regulation of the rat S100β gene expression: The role of the 2 kb 5′‐upstream sequence in glial specific expression
Authors: Hagiwara N. , Sueoka N. 
Published: January 2005

AbstractWe have studied the role of the 2047 by 5′‐upstream region and 232 by first exon sequence of the rat S100β gene in glial specific expression. S100β luciferase expression vectors carrying serial deletions of the S100β 5′; upstream sequence were constructed and transiently transfected into the peripheral nervous system (PNS) glial‐type cell line RT4‐D6, the PNS neuronal‐type cell line RT4‐E5, and the central nervous system (CNS) glial‐type cell line C6. The hepatoma cell line HTC was also transfected as a non‐neural control. From this functional analysis, we found a glial‐specific positive regulatory sequence(s) mapped between −583 and −106 relative to the transcriptional start site. This region confers a significantly higher level of luciferase expression in the glial‐type cell lines RT4‐D6 and C6 than in the neuronal cell line RT4‐E5 and the hepatoma cell line HTC. Also, a non‐cell type specific positive regulatory element was identified in the first exon sequence between + 78 and + 232. Though non‐cell type‐specific, it was found to have a predominant effect in glial cells. From these observations, we have concluded that the 2047 by 5′;‐upstream region and 232 by of the first exon sequence confers the high levels of S100β expression in glial cells through these two positive elements. © 1995 Wiley‐Liss, Inc.
Developmental changes of nitric oxide synthase in the rat superior colliculus
Authors: Tenório F. , Giraldi‐Guimarães A. , Mendez‐Otero R. 
Published: January 2005

AbstractWe used the activity of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH‐d) to detect the presence of nitric oxide synthase (NOS) in the developing rat superior colliculus. Our results showed that NOS is present in cells and nenropil in the developing and adult rat superior colliculus. The first NOS‐positive cells were detected at postnatal day 7 and were weakly stained. During the following days the number of stained cells increased markedly, reaching a peak by postnatal day 15, coinciding with the time of eye opening in the rat. By the end of the third postnatal week, both the number and intensity of stained cells showed an adult‐like pattern. We conclude that NOS expression lags behind the initial period of reorganization of the retinotectal projection. However, NOS activity could be involved in the subsequent synaptic remodeling and plasticity of the retinocollicular projection. © 1995 Wiley‐Liss, Inc.
Brain‐derived neurotrophic factor induces functional expression and phenotypic differentiation of cultured fetal neuropeptide Y‐producing neurons
Authors: Barnea A. , Cho G. , Lu G. , Mathis M. 
Published: January 2005

AbstractA series of studies from our laboratory has established an aggregate culture system of fetal rat brain cells that can serve as a model for studying regulatory processes of the developing neuropeptide Y (NPY)‐producing neurons. Using aggregate cultures derived from 17‐day‐old fetal rat cortex, we addressed these questions: (1) Does brain‐derived neurotrophic factor (BDNF) stimulate NPY production, and if so, is stimulation a function of the developmental state of the cultured NPY neuron? (2) Does BDNF induce phenotypic differentiation of NPY neurons? BDNF led to an increase in NPY production and the accumulation of NPY‐mRNA in a dose dependent manner. BDNF did not alter the stability of NPY‐mRNA, judged by the disappearance rate of NPY‐mRNA after blockade of RNA synthesis (estimated t½ was 6‐8 hr). BDNF stimulation of NPY production was dependent on length of exposure to BDNF and on culture‐age. A continuous 8‐day exposure to BDNF resulted in a significantly higher level of NPY production than a pulse of 2 days (comparing BDNF exposure on days 0‐8 vs. 6‐8, or days 8‐17 vs. 15‐17). Moreover, older neurons (age 17 days) produced twice as much NPY as younger (age 8 days) neurons in response to a 2‐day pulse of BDNF (50 ng/ml). BDNF was significantly more effective than NT‐3 in inducing NPY production, and NGF was ineffective. Immunocytochemical analysis of 8‐day NPY neurons revealed that a 2‐day pulse of BDNF induced the appearance of an abundance of morphologically well‐defined neurons bearing an elaborate network of neurites. This was in contrast to the control‐treated NPY neurons, which were morphologically undefined.In summary, the age‐dependent effect of BDNF on NPY production is consistent with induction of functional expression, rather than promotion of survival, of cultured NPY neurons. The neurotrophin specificity for stimulation of NPY production, and the lack of effect of BDNF on the stability of NPY‐mRNA, implicate the TrkB receptor in mediating transcriptional activation of the NPY gene. Thus, BDNF exerts a dual effect on developing cultured NPY neurons: induction of functional expression, and phenotypic differentiation of immature neurons into mature neurite‐bearing neurons. © 1995 Wiley‐Liss, Inc.
Hyperphosphorylation of TAU and filopodial retraction following microinjection of protein kinase C catalytic subunits
Authors: Cressman C. M. , Shea T. B. 
Published: January 2005

AbstractLimited proteolysis of protein kinase C (PKC) by calcium‐activated proteolysis cleaves the regulatory and catalytic subunits of PKC, generating a free, constitutively activated kinase (“PKM”) that, unlike the intact parent enzyme, is not calcium‐dependent, and is not restricted to the plasma membrane. These latter properties leave open the possibility that PKM may have access to, and may therefore phosphorylate, substrates normally unavailable to intact PKC. We examined the potential involvement of such aberrant phosphorylation in certain aspects of the neurodegeneration accompanying Alzheimer's disease by microinjecting PKC and PKM, along with a rhodamine‐conjugated dextran tracer, into undifferentiated NB2a/d1 mouse neuroblastoma cells. After 4 hr, cultures were fixed and processed for immunofluorescence with monoclonal antibodies (PHF‐1, ALZ‐50, Tau‐1, AT8) directed against tau in various phosphorylation states followed by fluorescein‐conjugated secondary antibodies. Microinjected cells were localized via co‐injected rhodamine‐conjugated dextran tracer under rhodamine illumination, after which antibody immunoreactivity was examined under fluorescein illumination. Microdensitometric analyses indicated that microinjection of PKC did not increase basal immunofluorescent intensities of the antibodies; by contrast, microinjection of PKM induced threeand twofold increases in PHF‐1 and ALZ‐50 levels, respectively. By contrast, no significant alteration was observed in AT8 and Tau‐1 immunofluorescence following either PKC or PKM microinjection. Whereas undifferentiated NB2a/d1 cells typically elaborate short, filopodia‐like neurites, phase‐contrast microscopy revealed the absence of fllopodia or neurites on PKM‐injected cells, while a similar percentage of PKC‐injected cells elaborated filopodialike neurites as did uninjected cells. Cell‐free analyses confirmed the ability of PKC, in the presence of necessary co‐factors, and PKM to increase PHF‐1 and ALZ‐50 immunoreactivity; no change was observed in AT8 or Tau‐1 immunoreactivity. These findings underscore the possibility that an abnormal amplification in limited PKC proteolysis to generate PKM could, under certain pathological conditions, contribute to neuronal degeneration. © 1995 Wiley‐Liss, Inc.
Acute treatment with pulsed electromagnetic fields and its effect on fast axonal transport in normal and regenerating nerve
Authors: Sisken B. F. , Jacob J. M. , Walker J. L. 
Published: January 2005

AbstractThe mechanism whereby low‐frequency electromagnetic fields accelerate axonal regrowth and regeneration of peripheral nerve after crush lesion is not known. One candidate is an alteration in axonal transport. In this study we exposed unoperated rats for 15 min/day, and rats that had undergone a crush lesion of the sciatic nerve, for 1 hr/day for 2 days, to 2‐Hz pulsed electromagnetic fields. To label fast transported proteins, [3H]‐proline was microinjected into the spinal cord, and the sciatic nerves were removed 2, 3.5, and 5 hr later. The rates of fast axonal transport were obtained for animals in all groups by counting sequential 2‐mm segments of nerves. The following transport rates were found: in unoperated normal sciatic nerve not exposed to PEMF, 373 ± 14 mm/day; in unoperated normal nerve exposed to PEMF, 383 ± 14 mm/day; in sham crush nerves not exposed to PEMF, 379 ± 19 mm/day; in sham crush nerve exposed to PEMF, 385 ± 17 mm/day; in crushed nerves not exposed to PEMF, 393 ± 16 mm/ day; and in crushed nerves exposed to PEMF, 392 ± 15 mm/day. The results of these experiments indicate that (1) a crush injury to the sciatic nerve does not alter the rate of fast axonal transport, and (2) low‐frequency pulsed electromagnetic fields do not alter fast axonal transport rates in operated (crush) or unoperated sciatic nerves. © 1995 Wiley‐Liss, Inc.