bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sprouting by intact Helisoma neurons: Role for glutamate
Authors: Bulloch A. G. M. 
Published: January 2005

AbstractWe examined the possible relationship between sprouting by intact neurons and the elevation of blood acidic amino acids that is reported to occur in Helisoma in response to osmotic stress. In the present study, buccal ganglion neurons 5 were examined following exposure of animals to conditions that induce estivation, a behavioral state exhibited by these freshwater snails in nature. Surprisingly, sprouting activity occurred in some neurons (31%) in normal animals, this being transiently elevated (to 71%) after 4 days of estivation. Blood acidic amino acids (i.e., glutamate and aspartate) were also elevated under this condition, their levels reaching a plateau on day 4. These observations give rise to two hypotheses: (1) the acidic amino acids can induce sprouting, or (2) these agents can release trophic factors, which, in turn, induce sprouting The first hypothesis was tested by exposing semi‐intact preparations in vitro to a range of concentrations of the acidic amino acids; no promotion of sprouting was observed by either glutamate or aspartate. The second hypothesis was supported, however, by the following observations. First, blood from estivated animals was tested for trophic activity. Such blood (but not that from control animals) could promote sprouting by intact neurons in vitro, a response that depended on factor(s) whose filtration behavior on Amicon membranes suggests an approximate molecular weight of 30–100 kD. Second, since medium conditioned by Helisoma ganglia is known to contain a protein(s) that is necessary for sprouting by isolated neurons, we tested the ability of such medium to promote sprouting by intact neurons. Conditioned medium promoted sprouting by intact neurons in vitro in a manner quantitatively and qualitatively similar to that observed in vivo during estivation. Additionally, sprouting by intact neurons in conditioned medium was also attributable to factor(s) that acted as 30–100 kD molecules on Amicon membranes. To test the ability of the acidic amino acids to release or activate these factors, medium was conditioned for short periods in the presence of glutamate or aspartate; glutamate, but not aspartate, was found to enhance conditioned medium. We conclude that glutamate can promote sprouting by intact neurons, but that its action is indirect and is mediated by macromolecular trophic factors.
Tyrosine phosphorylated proteins accumulate in junctional regions of the developing chick neural retina
Authors: Shores C. G. , Maness P. F. 
Published: January 2005

AbstractAntibodies specific for protein phosphotyrosyl residues were used to localize sites of action of tyrosinespecific protein kinases in developing chick neural retina by immunoperoxidase staining. Phosphotyrosine‐modified proteins became prominent in growth cone‐ and process‐rich regions of embryonic retina during neuronal differentiation. Maximal levels accumulated in the synaptic layers and limiting membranes of the adult retina, where numerous junctional complexes reside. Two major phosphotyrosine‐modified proteins in adult retina (80, 42 kDal) increased markedly during maturation. In contrast, the synaptic layers of optic tectum and other brain regions exhibited low protein phosphotyrosine levels. These results suggest a specific role for protein tyrosine phosphorylation in the retina at sites of synapses and other intercellular junctions.
Phospholipid‐derived choline intermediates and acetylcholine synthesis in mouse brain synaptosomes
Authors: Yavin E. , Tanaka Y. , Ando S. 
Published: January 2005

AbstractEndogenous free choline levels and acetylcholine (ACh) synthesis in nerve terminals were investigated using cerebral cortical synaptosomes of C57BL/6 mice. Endogenous choline was produced at a rate tenfold faster than ACh to provide levels adequate for the formation of the latter. The combined pool size of the water‐soluble intermediates derived from phosphatidylcholine (PhC), such as glycerophosphorylcholine (GpCh) and phosphorylcholine (PCh), increased significantly during the first 10–15 min of incubation and was always higher than that of free choline. These results most likely indicate an effective degradation of PhC by the combined action of phospholipase A2/lysophospholipase, as well as by phospholipase C in synaptosomes. ACh synthesis proceeded at a constant rate in the presence or absence of exogenous free choline (0–10 μM) and was almost entirely abolished in the presence of 10−6 M hemicholinium‐3. These results suggest that ACh is effectively synthesized by free choline generated in synaptosomes by a coupling mechanism involving the high‐affinity choline uptake system. No changes in the production rates of choline and ACh were observed between adult and aged mice.
Interferon‐gamma‐like immunoreactivity in certain neurons of the central and peripheral nervous system
Authors: Ljungdahl Å. , Olsson T. , Van der Meide P. H. , Holmdahl R. , Klareskog L. , Höjeberg B. 
Published: January 2005

AbstractInterferon‐gamma (IFN‐γ) has many important immunoregulatory functions. It has previously been presumed to be produced by activated lymphoid cells alone. The present study concerning the identification of IFN‐γ in neurons was initiated against the background that nerve function influences immunological events during inflammatory diseases. Furthermore, the immune system and the nervous system may have certain signal molecules as well as certain cell surface receptors in common. Neuronal IFN‐γ‐like immunoreactivity (IFN‐γ‐LI) was studied in frozen sections of rat tissues employing both rabbit polyclonal antiserum as well as seven different mouse monoclonal antibodies (mAbs) reactive with different epitopes of rat IFN‐γ. The polyclonal antiserum and three of the mAbs (DB‐1, DB‐14, and DB‐16) showed IFN‐γ‐LI in neurons. DB‐1, the most extensively studied mAb, stained distinct networks of nerve terminal‐like profiles both in the brain and spinal cord. Also, scattered brain neuronal cell bodies showed IFN‐γ‐LI as well as a subpopulation of primary sensory ganglion cells and their intra CNS terminals. In addition, IFN‐γ‐LI was also detected in nerve terminal‐like profiles in skin, gut, and lymphoid organs. Terminals were especially prominent around blood vessels. We propose that IFN‐γ has a role in cell interactions not only in the immune system but also in the nervous system as well as in interactions between the nervous and immune systems.
Cultured neurons release an inhibitor of astroglia proliferation (astrostatine)
Authors: Rogister B. , Leprince P. , Bonhomme V. , Rigo J. M. , Delree P. , Colige A. , Moonen G. 
Published: January 2005

AbstractUsing in vitro techniques, we looked for a possible downregulation of rat astroglia proliferation by neuronal cells. We demonstrate that medium conditioned by 7‐day‐old rat cerebellar granule neurons or by 16‐day‐old rat embryo hippocampal neurons strongly inhibits the proliferation of cultured astroglial cells. Two neuronal cell lines, the PC12 rat pheochromocytoma and the neuro 2A (N2A) murine neuroblastoma also release such an activity. This release in N2A‐conditioned medium (CM) occurs when the cells are at high density and show a low proliferation rate. This activity is present in media conditioned by neuronal cells, but not in media conditioned by normal astrocytes, by two glioma cell lines, or by one fibroblastic cell line. This proliferation inhibitor addresses normal astrocytes: the proliferation of two glioma cell lines, of a fibroblastic cell line, and of the two neuronal cell lines (PC12, N2A) is not inhibited by N2A CM. Moreover, this activity is directed against type 1 astrocytes, but not against type 2. Using three different assays, we demonstrate that DNA synthesis by astroglial cells is inhibited. N2A CM has no cytotoxic effect on astrocytes and does not modify their overall protein synthesis.Using affinity and gel filtration chromatography, we show that this activity is associated with a protein whose molecular weight ranges between 15 and 20 kDa. The possible relationship between this N2A cellderived astroglia proliferation inhibitor and other types of potential glial proliferation inhibitors has been investigated. A brain glycoprotein immunologically related to epidermal growth factor receptor (EGFR) was reported to inhibit astroglial cell proliferation in vitro. Using polyclonal and monoclonal antibodies against EGFR, we were unable to immunoprecipitate the astrocyte proliferation inhibitor in N2A CM or to demonstrate by immunoblotting the presence of an EGFR‐like immunoreactivity in the N2A CM or in the active chromatographic fractions of N2A CM. Transforming growth factor β (TGFβ) is a well‐known modulator of the proliferation of various cell types and was shown to be present in N2A CM. Using a polyclonal anti‐TGFβ antibody that recognizes TGFβ on Western blots of N2A CM, we were unable to immunoprecipitate the astrocyte proliferation inhibitor of N2A CM. It seems thus far that the neuronal astroglia proliferation inhibitor is a new protein for which we propose the name astrostatine.
Association of iron‐containing astrocytes with dopaminergic neurons of the arcuate nucleus
Authors: Young J. K. , McKenzie J. C. , Baker J. H. 
Published: January 2005

AbstractSpecialized astrocytes, identified by cytoplasmic granules that are electron‐dense and vividly stained by toluidine blue due to the presence in the granules of SH molecules and molecules of iron, have long been known to be present within the arcuate nucleus of the hypothalamus. Their function, however, is obscure. To determine whether or not these specialized astrocytes are in contact with dopaminergic neurons, rat brain sections were stained to detect tyrosine hydroxylase (TH) immunoreactive neurons by immunocytochemistry and were examined by both light and electron microscopy. Iron‐rich astrocytes were located in the same general portion of the arcuate nucleus as were TH+ neurons, and most appeared closely associated with TH + structures (somas, dendrites, and fibers) at the light‐microscopic level. At the ultrastructural level, close contact between TH + neurons and processes of iron‐rich glia was confirmed. This unique anatomical association suggests a functional relationship between the two cell types that may be related to unusual histochemical features of both cell types and/or to the location of these cells in an area with a highly permeable blood‐brain barrier.
The Alzheimer's amyloid precursor protein is produced by type I astrocytes in primary cultures of rat neuroglia
Authors: Berkenbosch F. , Refolo L. M. , Friedrich V. L. , Casper D. , Blum M. , Robakis Nikolaos K. 
Published: January 2005

AbstractThe production of β‐amyloid precursor protein (βAPP) by primary mixed glial cell cultures from cerebral cortex of 2–3 day postnatal rats was examined by Northern and Western blotting and by immunocytochemistry. A single 3.5 kb βAPP RNA transcript was detected using probes recognizing all forms of βAPP messenger RNA. No signal was detected with a probe specific for the alternately spliced Kuntiz protease inhibtor (KPI) region. In Western blot analysis of protein extracts, antisera specific for either the cytoplasmic or extracellular part of βAPP detected several proteins ranging from 105 to 140 kDa. None of these were recognized by an antiserum specific to the KPI insert of the βAPP. Multicolor immunofluorescence showed βAPP. immunoreactivity in type I (GFAP+A2B5−) astrocytes, distributed in a fibrillar pattern like that of glial fibrillary acidic protein (GFAP). No βAPP immunoreactivity was detected in oligodendrocytes (GC+) or in A2B5+ progenitor cells. Moreover, no cultured cells showed immunostaining with an antiserum specific for the KPI sequence of βAPP. We conclude that type I astrocytes in primary culture produce amyloid precursor, but that oligodendrocytes and their precursors do not. Moreover, type I astrocytes produce predominently the βAPP subtypes which lacks the KPI sequence.
Family of human neuronal external surface epitopes defined by torpedo monoclonal antibodies
Authors: Wright S. , Sternberg H. , Bjornskov E. K. , Stephenson D. T. , Kushner P. D. 
Published: January 2005

AbstractWe are employing a library of monoclonal antibodies (MAbs) that were made to torpedo cholinergic synaptosomes to identify conserved, physiologically vital epitopes of the neuronal surface. Our particular interest is in those epitopes that are present on some but not all neurons. In tjhe present study we screened this library on different cell lines, the neuronal cell lines PC12, NG108, MC‐IXC, and SY5Y, and the endocrine cell lines GH‐3 and HIT. Of these cell lines, only SY5Y cells bind MAbs that define neruonalo surface subsets. Utilizing its parent cell line, SK‐N‐SH, we verified that six MAbs, Tor 25, Tor 103, Tor 190, Tor 201, Tor 219, and Tor 233, bind the external neuronal surface. The cytolocalization of all six MAbs is very similar: the membrane of the cell body and its processes are finely outlined in a punctate distribution. Western blot analyses of Torpeco electric organ homogenates, a highly enriched source of antigenic mateial, revealed that each MAb identifies multiple polypeptides, two of which have the relative mobilities of 180 kD and 67 Kd. In a screen of peripheral nerves from cases of amyotrophic lateral scleroses (ALS), we found that all these MAbs revealed surface alteration; some displayed a decrease in binding, while others displayed an increase. The combined data provide evidence that these epitopes belong to an important, complex family of polypeptides of the external neuronal surface.
An in vivo model of varicella‐zoster virus latent infection of dorsal root ganglia
Authors: Sadzot‐Delvaux C. , Merville‐Louis M. P. , Delree P. , Marc P. , Piette J. , Moonen G. , Rentier B. 
Published: January 2005

AbstractWe describe here the first in vivo model of varicellazoster virus (VZV) latent infection in the adult rat peripheral nervous system. Infected Mewo cells were injected subcutaneously along the spine of healthy adult rats. No clinical sign of infection was observed even 9 months after inoculation. Humoral immune response to VZV was detected in all infected animals throughout the study (9 months). The presence of viral material in dissociated and cultured dorsal root ganglia (DRG) from inoculated animals was studied by immunoperoxidase and in situ hybridization. When DRGs from infected animals were plated in culture from 1 month and up to 9 months after inoculation, viral nucleic acids and proteins were detected in neurons. Furthermore, trypsinization and subcultivation of infected neurons in culture is needed to reactivate infectious virus at least in some of the neurons. This model provides a useful tool for studying (1) the molecular mechanisms leading to an in vivo latency, (2) the role of the immune system, in particular cellular immunity, on the establishment, maintenance, and reactivation of latency, (3) the neurotropism of mutant viruses, and (4) the effects of antiviral agents.
Prenatal alcohol exposure alters the development of sympathetic synaptic components and of nerve growth factor receptor expression selectivity in lymphoid organs
Authors: Gottesfeld Z. , Morgan B. , Perez‐Polo J. R. 
Published: January 2005

AbstractExposure to alcohol in utero has been associated with long‐term immune deficits. In addition, adult mice exposed to alcohol prenatally display altered noradrenergic synaptic transmission selectively in lymphoid organs. This is consistent with the hypothesis that sympathetic neurons play an important role in immunomodulation. The development and maintenance of sympathetic neurons are critically dependent on nerve growth factor (NGF).Furthermore, NGF has been shown to modulate immune responses and NGF receptor expression has been localized to lymphoid organs. The present work examined the effects of prenatal alcohol exposure on the development and maturation of pre‐and postsynaptic sympathetic components, including norepinephrine and β‐adrenoceptors, respectively, as well as the early expression of NGF receptors in lymphoid and other organs of the C57BL/6 mouse.Infant mice that were exposed to alcohol in utero displayed reduced levels of norepinephrine and β‐adrenoceptor density, as well as increased NGF receptor expression in the thymus and spleen, but not the heart. These selective changes may account, in part, for the persistent immune incompetence characteristic of fetal alcohol syndrome.
Cerebral energy metabolism and intracellular pH during severe hypoxia and recovery: A study using 1H, 31P, and 1H [13C] nuclear magnetic resonance spectroscopy in the guinea pig cerebral cortex in vitro
Authors: Kauppinen R. A. , Williams S. R. 
Published: January 2005

Abstract1H and 31P nuclear magnetic resonance spectroscopy was used to study intracellular pH (pH1), high‐energy phosphates, lactate, and amino acids in cortical brain slices superfused in Krebs‐Henseleit bicarbonate buffer during and after severe hypoxia at 0, 10, and 50 mM glucose. An extensive drop in phosphocreatine (PCr) and a rapid build‐up of intracellular lactate and H+ were the first signs of hypoxia. Adenosine triphosphate (ATP) was significantly more resistant to hypoxia provided that glucose was present. In the preparations that had been exposed to hypoxia in the presence of glucose, PCr became detectable within 2 min of reoxygenation, and both PCr and ATP concentrations were restored to 72–80% of normoxic levels within 30 min. Lactate was washed out, and pHi returned to normal within 4–8 min. Using 1‐[13C]glucose as a tracer, we demonstrated that the rate of lactate production in the immediate posthypoxic period was at the prehypoxic level, indicating that hte elevated lactate during this period was due solely to that produced during hypoxia. During reoxygenation of the preparations that were denied glucose during hypoxia, only 30% of total creatine + PCr and 18% of PCr were restored, and ATP was not detectable. The lactate concentration rose twofold in this period, and pHi became significantly more alkaline than before the hypoxic insult. Thus acute metabolic damage was considerably greater if glucose was absent during the insult, suggesting that either anaerobic ATP production or low pH may exert some protective effect against acute cell damage.
N‐linked glycoprotein synthesis and transport during G1 are necessary for astrocytic proliferation
Authors: Ishii S. , Volpe J. J. 
Published: January 2005

AbstractThe proliferation of astrocytes, purified by a selective detachment technique from mixed glial primary cultures derived from newborn rat cerebrum, was studied. The cells were synchronized by first inducing a quiescent state by removing fetal calf serum (FCS) from the culture medium for 2 days; reversal of the quiescent state by return of serum to the culture medium caused a marked increase in DNA synthesis 12‐24 hr later. 2‐Deoxyglucose, an inhibitor of dolichol‐linked oligosaccharide and thereby N‐linked glycoprotein biosynthesis, prevented not only an increase in glycoprotein biosynthesis in G1 phase of the cell cycle but also the burst of DNA synthesis that followed during S phase. Addition of mannose to the culture medium prevented the inhibitions by deoxyglucose of both glycoprotein and DNA synthesis. These data indicated an obligatory relationship in astrocytes between dolichol‐linked glycoprotein synthesis and DNA synthesis. To determine whether transport of the newly synthesized glycoproteins to the plasma membrane for incorporation therein or for secretion were necessary for DNA synthesis and astrocytic proliferation, we studied cells treated with monensin, an ionophore for monovalent cations, and an inhibitor of intracellular transport of glycoproteins. The presence of monensin in the first 12 hr after repletion of serum to synchronized astrocytes prevented progression to the S phase and cell proliferation; addition of monensin after the first 12 hr, at the onset of the S phase, had no effect on progression through S phase. Lectin‐staining methods combined with fluorescence microscopy demonstrated in monensin‐treated cells failure of intracellular glycoproteins to be transported to the plasma membrane. These data suggest that the glycoproteins synthesized during G1 and required for traverse of astrocytes through G1 and the S phase of the cell cycle must be transported to the cell surface. The nature of these proteins, e.g., whether plasma membrane components or secretory glycoproteins, and their specific functions remain to be elucidated.
Intracellular Na+ activity in cultured mouse oligodendrocytes
Authors: Ballanyi K. , Kettenamann H. 
Published: January 2005

AbstractNa+‐selective double‐barrelled microelectrodes were used to measure the intracellular Na+ activity (aiNa) and membrane potential (Em) in oligodendrocytes from cultures of embryonic mouse spinal cord. In Na+‐free solutions aiNa rapidly fell from its baseline of about 15 mM to values below 1 mM. Elevation of the K+ concentration in the bath ([K+]o) from 5.4 to 15 or 50 mM elicited an aiNa decrease of 4.7 or 9.0 mM, respectively. Ouabain blocked the aiNa decrease in response to 50 mM K+ by 37%. Bath application of 1 mM glutamate resulted in a membrane depolarization of 4.5 mV and a concomitant rise of aiNa by 8.6 mM. aiNa increased by approximately 11 mM after washout of a solution containing 20 mM NH4+. This aiNa increase was not blocked by amiloride, excluding a major contribution of a Na+/H+ antiporter. We conclude that, in cultured oligodendrocytes, transmembraneous Na+ movements are involved in pH regulation, glutamate causes an influx of Na+, and that the Na+/K+ pump and passive KCI uptake contribute to K+ accumulation.
Microtubule associated protein (MAP1B) is present in cultured oligodendrocytes and co‐localizes with tubulin
Authors: Fischer Itzhak , Konola J. , Cochary E. 
Published: January 2005

AbstractDifferentiation of Oligodendrocytes is accompanied by the extension of processes and the assembly of the myelin membrane. It is likely that the cytoskeleton plays an important role in this process in terms of changes in cell shape, transport of myelin components, and organization of the myelin membrane. Oligodendrocytes contain microtubules (MT) which associate with other components of the cytoskeleton, and microtubule associated proteins (MAPs) may mediate some of these interactions. In this study we haves shown the presence of MAP1B in Oligodendrocytes grown in primary glial cultures by double‐label im‐munofluorescence using antibodies to galactocerebro‐side (GC) and MAP1B. The staining of the cultures showed that GC‐positive Oligodendrocytes were also stained with MAP1B antibodies. However, MAP 1B stain was limited to ceil bodies and processes, whereas GC stain was also seen in flattened membrane sheets and punctate staining in processes. MAP1B staining was also compared with that of myelin proteolipid (PLP), myelin basic protein (MBP) and beta‐tubulin in secondary glial cultures that were enriched for Oligodendrocytes. The results showed a typical staining of cell bodies and membranous profiles using PLP antibodies, and the staining of cell bodies and flattened regions of membranous sheets by MBP antibodies. In contrast, both polyclonal and monoclonal antibodies to MAP1B showed a uniform diffuse staining of cell bodies, major processes, and fine interconnected processes. Double‐labeling of the cells showed that MAP1B was co‐localized with tubulin, but was not present in glial fibrillary acidic protein (GFAP)‐positive astrocytes. Western and Northern blot analyses of primary glial cultures showed that MAP1B had a molecular mass of 320 kDa and a mRNA of 10 kb. These values are identical to those previously reported for brain MA1MB (Safaei and Fischer, 1989) and demonstrate the presence of MAP1B in oligodendrocytes.