bluuebunny/crossref_metadata_2025 huggingface dataset:
Verfahrenstechnische Auslegung von Schwingsiebzentrifugen
Authors: Molerus Otto , Brunner Karlheinz
Published: December 2004

Die Verweilzeit eines zu entwässernden Feststoffes im Fliehkraftfeld einer Schwingsiebzentrifuge bestimmt einerseits den erzielbaren Entwässerungsgrad und andererseits die Wirtschaftlichkeit des Trennverfahrens. Es sollen theoretische und experimentelle Auslegungsunterlagen bereitgestellt werden, wobei die Aussagen der Theorie mit Hilfe experimenteller Befunde zu einfach nutzbaren Anleitungen verknüpft werden können.
Verformungsgerechtes Konstruieren
Authors: Müller Herbert W.
Published: December 2004

Es wird das verformungsgerechte Konstruieren in denjenigen Fällen behandelt, bei denen die Verformung einem Bauteil aufgezwungen wird und in diesem eine erhöhte Beanspruchung hervorruft. Dabei kommt es besonders darauf an, Konstruktionsteile, insbesondere an ihren Kraftüberleitungsstellen, geometrisch so zu gestalten, daß dort erzwungene, örtliche Verformungen mit den daraus resultierenden Überhöhungen der Beanspruchung minimiert werden. Hierfür gilt die Regel, daß starke Querschnittsprünge im Kraftfluß und scharfe Kraftumlenkungen zu vermeiden sind. Eine wenig beachtete Möglichkeit zur Herabsetzung von Spannungsspitzen besteht in der Einführung elastischer Zonen. Zwangsverformungen, welche zu örtlichen Spannungsspitzen führen, können auch durch Wärmedehnungen hervorgerufen werden. Auch Fliehkräfte in den Strukturen von Zentrifugen oder Kompressoren führen zu Spannungsspitzen. Wie an einigen Beispielen gezeigt wird, können durch Untersuchungen solcher kritischen Stellen einer Konstruktion mit der Methode der finiten Elemente optimale Lösungen gefunden werden.
Plastifizierung und Belastbarkeit Berücksichtigung in verschiedenen Berechnungsverfahren
Authors: Krägeloh Egon
Published: December 2004

Im deutschen und amerikanischen Regelwerk wird für einige Spannungskategorien eine Überschreitung der Streckgrenze und damit einmalige oder Wechselplastifizierung zugelassen, um ungleichförmig beanspruchte Bauteile besser auslasten zu können. Das Prinzip ist in beiden Regelwerken gleich. Während jedoch im deutschen Regelwerk im allgemeinen die plastische Verformung direkt begrenzt wird, beurteilt der amerikanische Code die daraus resultierenden Spannungen einschließlich aller Zusatzbeanspruchungen. Die in jedem Fall erforderliche plastische Verformung muß unbedingt, auch im Gebiet der Schweißnaht, gewährleistet sein, damit Sprödbrüche vermieden werden. Eine adäquate Werkstoff‐Beurteilung ist weder durch die üblichen Verformungskennwerte und Arbeitsproben noch durch die Bruchmechanik gesichert. Der beste Weg zu einer optimalen Sprödbruch‐Beherrschung ist daher in Werkstoff‐Entwicklung und Fertigungsüberwachung zu sehen.
Einstellung des Gefüges durch Wärmebehandlung und Auswirkung auf die plastische Formänderung
Authors: Dahl Winfried
Published: December 2004

Für den Konstrukteur sind von den mechanischen Eigenschaften des Werkstoffes der Beginn der plastischen Verformung, das Verfestigungsverhalten und der Bruch von Bedeutung. Diese Größen werden bei Stählen in starkem Maße durch das Gefüge beeinflußt. Das Gefüge wiederum ergibt sich aus der Zusammensetzung, den Herstellungsverfahren einschließlich der Formgebung und der Wärmebehandlung. Die sich hieraus ergebenden Möglichkeiten zur Beeinflussung der Werkstoffeigenschaften werden eingehend diskutiert.
Entwicklung der technischen Chemie in Deutschland
Authors: Bartholomé Ernst
Published: December 2004

Schon seit der Jahrhundertwende wurden von der deutschen Industrie großtechnische Verfahren entwickelt, bei deren Ausarbeitung sehr viele Fragen, die auch heute noch von der technischen Chemie bearbeitet werden, zu lösen waren. Dennoch kann man von einer technischen Chemie als Wissenschaft in Deutschland erst seit den dreißiger Jahren sprechen. In dieser Zeit entstanden zwei Handbücher, und zwar Eucken‐Jakob: Der Chemie‐Ingenieur, und Berl: Chemische Ingenieur‐Technik. Diese Werke haben in klassischer Form und richtungweisend das ganze Gebiet dargestellt. Der Krieg verhinderte eine Auswirkung auf die Lehre. Nach dem Kriege setzten die ersten Bemühungen ein, aus der chemischen Technologie eine technische Chemie als Lehrfach für Chemiker auszuarbeiten. 1955 faßte die DECHEMA diese Aktivitäten zusammen. Durch eine Reihe von Maßnahmen ist es der DECHEMA gelungen, in kurzer Zeit eine erfolgreiche Entwicklung einzuleiten, die heute zu einem wohlfundierten Lehr‐ und Forschungsgebäude als Teilfach der Chemie und als Brücke zum Ingenieurwesen geführt hat.
Auf Schnellstraßen zur Information
Authors: Springe Wolfgang , Maurer Guillaume Marie Jacques
Published: December 2004

Die Ingenieurarbeit ist dadurch komplexer geworden, daß auch die Auswirkungen von technischen Lösungen in immer stärkerem Maße betrachtet werden müssen. Entscheidungen für „gute”︁ Lösungen können aber nur dann getroffen werden, wenn ausreichend Informationen vorliegen. Im Arbeitsbereich des Informationsbenutzers werden künftig neue Kommunikationsdienste wie Bürofernschreiben, Fernkopieren und Fernsprechkonferenz, Veränderungen in den bisherigen Gewohnheiten erzwingen, während im Bereich der Übermittlung die internationalen Netzwerke den Dialog mit vielen Informations‐speichern gegen geringe Kosten ermöglichen. Hierdurch wird einerseits dem Benutzer der schnelle Zugriff auch zu Randgebieten ermöglicht, andererseits treten durch Monopolverhalten und Datenvertraulichkeit neue Probleme auf. Das Fachinformationszentrum Chemie, Frankfurt/M., hat am 1. Januar 1977 seine Arbeit versuchsweise aufgenommen. Seine Dienstleistungen sollten von der Öffentlichkeit genutzt werden, allein schon um eine sinnvolle Ausnutzung der investierten Gelder zu gewährleisten. Betriebliche Dokumentationsstellen werden immer notwendiger, um die gebotenen neuen Informations‐möglichkeiten sinnvoll und wirtschaftlich zu nutzen.
Zur Problematik der Maßstabsvergrößerung von Wirbelschichtreaktoren
Authors: Werther Joachim
Published: December 2004

Die Maßstabsvergrößerung hat sich in der Vergangenheit oftmals als wesentliches Hindernis bei der Entwicklung neuer Wirbelschichtverfahren erwiesen, indem Reaktoren, die auf der Grundlage von Messungen an kleinen Laborapparaturen ausgelegt wurden, im Betriebsmaßstab nicht den erwarteten Umsatz brachten. Die vorliegende Arbeit führt das Maßstabsvergrößerungsproblem der Wirbelschichttechnik auf charakteristische Veränderungen der Strömungsmechanik beim Wechsel der Reaktorgeometrie zurück. Ausgehend von Gasverweilzeitverteilungs‐ und Umsatzmessungen anderer Autoren an Wirbelschichten im Durchmesserbereich zwischen 5 und 300 cm mit Höhen bis zu 10 m sowie anhand von Messungen lokaler strömungsmechanischer Eigenschaften an Wirbelschichten mit Durchmessern zwischen 10 und 100 cm wird eine Maßstabsvergrößerungsfunktion abgeleitet, die eine einheitliche Darstellung des Stoffaustausches zwischen Blasen‐ und Suspensionsphase für Wirbelschichtsysteme von extrem unterschiedlichen Abmessungen liefert und eine physikalisch begründete Interpretation der Einflüsse von Gefäßdurchmesser, Wirbelschichthöhe und Einbauten auf das Betriebsverhalten eines Wirbelschichtreaktors ermöglicht.
Starting solutions for the boundary immobilization method
Authors: Caldwell J. , Kwan Y. Y.
Published: December 2004

The boundary immobilization method (BIM) is extended to the cases of outward spherical and cylindrical solidifications, which involves the development of starting solutions. When applying the method to time‐dependent problems, good agreement is achieved when comparing the positions of the moving boundary and the temperature distribution with those obtained by the perturbation method. Copyright © 2004 John Wiley & Sons, Ltd.
Somatostatin receptors and autoimmune‐mediated diabetes
Authors: Wang Xaio‐Ping , Norman Michael A. , Charles Brunicardi F
Published: December 2004

Somatostatin (SST) peptide is produced by various SST‐secreting cells throughout the body and acts as a neurotransmitter or paracrine/autocrine regulator in response to ions, nutrients, peptides hormones and neurotransmitters. SST is also widely distributed in the periphery to regulate the inflammatory and immune cells in response to hormones, growth factors, cytokines and other secretive molecules. SST peptides are considered the most important physiologic regulator of the islet cell, gastrointestinal cell and immune cell functions, and the importance of SST production levels has been implicated in several diseases including diabetes.

The expression of SST receptors has also been found in T lymphocytes and primary immunologic organs. Interaction of SST and its receptors is also involved in T‐cell proliferation and thymocyte selection. SSTR gene‐ablated mice developed diabetes with morphologic, physiologic and immunologic alterations in the endocrine pancreas. Increased levels of mononuclear cell infiltration of the islets are associated with the increased levels of antigen‐presenting cells located in the islets and peripancreatic lymph nodes. Increased levels of SST were also found in antigen‐presenting cells and are associated with a significant increase of CD8 expression levels on CD4+/CD8+ immature thymocytes. These findings highlight the crucial role of this neuroendocrine peptide and its receptors in regulating autoimmune functions. Copyright © 2004 John Wiley & Sons, Ltd.
A 2D Thiocyanato‐Bridged Copper(II)‐Manganese(II) Bimetallic Coordination Polymer with Ferromagnetic Interactions
Authors: Shi Jing‐Min , Xu Wei , Zhao Bin , Cheng Peng , Liao Dai‐Zheng , Chen Xiao‐Yan
Published: December 2004

The first ferromagnetic coupled, thiocyanato‐bridged copper(II)‐manganese(II) bimetallic 2D polymer {[Cu(ipa)2]2Mn(NCS)6·2H2O}n (ipa = 1,2‐propanediamine) has been synthesised and characterised by a single‐crystal X‐ray structure determination and variable temperature magnetic susceptibility studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
The Nature of the Spin‐State Variation of [FeII(BPMEN)(CH3CN)2](ClO4)2 in Solution
Authors: Bryliakov Konstantin P. , Duban Eduard A. , Talsi Evgenii P.
Published: December 2004

Thermally‐induced spin variation behavior of [FeII(BPMEN)(CH3CN)2](ClO4)2 in CD3CN solution [low spin (LS)−high spin (HS)] was investigated. Variable temperature solution magnetic susceptibility measurements gave ΔH°LS−HS = 39.7 ± 2.0 kJ·mol−1 and ΔS°LS−HS = 135 ± 9 J·mol−1 K−1 values. These values are too high for a pure spin transition and reflect a significant contribution of chemical processes to the spin transition, namely, the detected dissociation of one bound acetonitrile molecule. Thus, LS−HS conversion should be regarded as a chemical equilibrium overlapped with a thermal spin crossover. The thermodynamic parameters for the overall process estimated from the variation of the NMR shifts with temperature (ΔH° = 40 ± 3 kJ·mol−1, ΔS° = 137 ± 10 J·mol−1 K−1) are in perfect agreement with those obtained by magnetic susceptibility measurements. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Two Novel Inorganic‐Organic Hybrid Frameworks Based on InIII‐BTC and InIII‐BTEC
Authors: Lin Zheng‐Zhong , Jiang Fei‐Long , Chen Lian , Yuan Da‐Qiang , Zhou You‐Fu , Hong Mao‐Chun
Published: December 2004

Hydrothermal reactions of InCl3 with 1,3,5‐benzenetricarboxylic acid (H3BTC) or pyromellitic dianhydride produced [In2(BTC)2(H2O)2]n·2nH2O (1) and [In2(H2BTEC)2(OH)2]n·2nH2O (2), respectively (H4BTEC = 1,2,4,5‐benzenetetracarboxylic acid). The structure of 1 is a 2D double‐layer network, while that of 2 is a 3D framework constructed from chains of corner‐linked octahedra. Intense greenish‐blue emissions at 494 nm (λex = 325 nm) for 1 and 489 nm (λex = 337 nm) for 2 were observed in the solid state. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Ordered Meso‐ and Macroporous Binary and Mixed Metal Oxides
Authors: Carreon Moises A. , Guliants Vadim V.
Published: December 2004

A critical review is provided of the principles guiding the synthesis of meso‐ and macroporous metal oxides on multiple length scales in the presence of surfactant mesophases and colloidal arrays of monodisperse spheres, and correlations between the synthesis conditions and the properties of the resulting meso‐ and macroporous oxides, such as thermal stability, pore structure, elemental and nanophase compositions of the inorganic wall, etc. The thermal stability of mesostructured metal‐oxide phases, in particular, is discussed in terms of charge‐matching at the organic–inorganic interface, the strength of interactions between inorganic species and surfactant headgroups, the flexibility of the M–O–M bond angles in the constituent metal oxides, the Tammann temperature of the metal oxide, and the occurrence of redox reactions in the metal‐oxide wall. The ordered meso‐ and macroporous transition‐metal‐oxide phases are highly promising for a range of potential applications in separations, chemical sensing, heterogeneous catalysis, microelectronics, and photonics as, respectively, insulating layers of low‐dielectric‐constant and photonic‐bandgap materials. Furthermore, the functionalization of the internal pore surfaces in these materials and deposition of functional nanoparticles within the pores offer numerous new possibilities for molecular engineering of catalytic and other advanced nanostructured materials displaying quantum‐confinement effects. The emerging catalytic applications of these novel metal‐oxide phases are discussed in particular detail. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Lithium Cyanocuprates: Structural Studies of a Phosphane Adduct of a “Lower‐Order” Lithium Cyanocuprate
Authors: Davies Robert P. , Hornauer Stefan
Published: December 2004

Addition of PPh3 to the “lower‐order” cyanocuprate PhCuCNLi results in a significant increase in reactivity in 1,4‐Michael addition reactions. This is explained by a marked structural change in the cyanocuprate reagent, observed in both THF solution and the solid state, to give [Ph2Cu]− cuprate anions and a [Cu2Li4(CN)4(PPh3)4(THF)10]2+ dication. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Formation of Hexagonal Coordination Complexes
Authors: Schultheiss Nate , Ellsworth Joseph M. , Bosch Eric , Barnes Charles L.
Published: December 2004

The synthesis of the ligand 1,3‐bis(3′‐pyridylethynyl)benzene and the coordination complex formed with copper(II) acetate is described. The complex is hexagonal with two ligands bridged by paddlewheel‐shaped dimeric copper(II) acetate moieties. The complexes are packed in such a way that the benzene rings from two separate complexes penetrate into the central cavity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Anion‐Induced Motion in a Ferrocene Diamide
Authors: Heinze Katja , Schlenker Manuela
Published: December 2004

An unsymmetrical diferrocene diamide has been reacted with chloride ions. The anion splits the intramolecular hydrogen bond of the receptor and is coordinated simultaneously by both amide groups of the receptor via hydrogen bonds. Chloride coordination changes the relative angular position of the cyclopentadienyl rings and the potential of the ferrocene/ferricinium redox couple. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
The composition of the leaf essential oil of Satureja punctata (Benth.) Briq. from Zimbabwe
Authors: Chagonda Lameck S. , Chalchat Jean‐Claude
Published: December 2004

Satureja punctata (Benth.) Briq., family Lamiaceae, from Mrewa, Zimbabwe, was hydrodistilled and the essential oil produced in 0.9% v/w yield was analysed by GC and GC–MS. Neral (33.4%) and geranial (52.5%) were the major components. Copyright © 2004 John Wiley & Sons, Ltd.
Chemical constituents of the essential oil of Asarum forbesii Maxim (Aristolochiaceae)
Authors: Zhang Feng , Xu Qing , Fu Shaoping , Ma Xiaoqiong , Xiao Hongbin , Liang Xinmiao
Published: December 2004

The essential oils from the leaves and roots of Asarum forbesii Maxim (Aristolochiaceae) were obtained by hydrodistillation and analysed by GC and GC–MS; 20 and 17 constituents were identiﬁed from the leaf and root oils, respectively. Methylisoeugenol (33.3%) and α‐asarone (19.2%) were the main constituents in the leaf oil, while α‐asarone (58.8%) and methyleugenol (10.3%) were the major constituents in the root oil. Copyright © 2004 John Wiley & Sons, Ltd.
BiGlobal stability analysis of steady flow in constricted channel geometries
Authors: Pitt R. E. , Sherwin S. J. , Theofilis V.
Published: December 2004

In this paper we apply a BiGlobal stability analysis technique to measure the stability of two‐dimensional constricted channel flows to three‐dimensional perturbations. Critical Reynolds numbers and spanwise perturbation wavelengths are presented for three instabilities of steady flow in constricted channels. Copyright © 2004 John Wiley & Sons, Ltd.
Novel relationships of growth factors to the G1/S transition in cultured astrocytes from rat forebrain
Authors: Langan Thomas J. , Slater Mary C. , Kelly Kindra
Published: December 2004

The cell cycle encompasses the sequential events regulating cell division. In mammalian brain, initiation of astrocyte cycling is critical during development and injury. To investigate the timing of growth factor requirements as they commit to passing through the G1 phase, primary and secondary rat astrocytes were stimulated to enter the cycle after serum or growth factor deprivation. Bromodeoxyuridine immunofluorescence was used to monitor S phase nuclei after growth factor re‐addition (at time 0). Cycle kinetics were identical whether quiescent cultures were exposed to 10% (vol/vol) calf serum, or to a defined medium containing fibroblast growth factor, insulin, and epidermal growth factor. The control point in late G1 that represents commitment to achieving the G1/S transition was identified by cycloheximide (CHX, 0.1 μg/ml) addition. Sensitivity to cycle arrest by CHX disappeared at 9–10 h. In contrast, shift‐down to growth factor‐deficient medium arrested cell cycling virtually until G1/S (12 h). With selective exposure during late G1 (9–12 h), no single agent permitted cycle progression. However, any two agents enabled cycling, and complementary or synergistic effects were apparent. These requirements were identical in astroglia from newborn and long‐term cultures.

Thus, temporal dissociation exists between the processes of escape from CHX sensitivity and from requirements for growth factors, two recognized hallmarks of commitment to cycle progression. Furthermore, simultaneous presence of at least two growth factors is necessary at or near G1/S. Both findings distinguish astrocytes from several other cell types. © 1994 Wiley‐Liss, Inc.
In vivo staining of oligodendroglia in the rabbit retina
Authors: Ehinger B. , Zucker C. L. , Bruun A. , Adolph A.
Published: December 2004

We have discovered that a strongly fluorescent dye, sulforhodamine 101, when injected intravitreally in vivo, very effectively stains a class of star‐shaped cells in the innermost layers of the rabbit retina. The cells were strictly confined to the region containing medullated fibers and emitted dichotomously branching processes that ended up running some distance along the myelinated fibers. In favorable cases they could be seen to ensheath the fibers in a tube‐like fashion. No other retinal cells were stained. Shortly (hours) after the injection, the stain appeared in the cell cytoplasm, but it later became progressively more localized to intracellular granules. Most of the dye had disappeared after 2 days.

Oligodendrocytes and astrocytes are the only cells known to be confined to the region of the medullated fibers in the rabbit retina, and hence the sulforhodamine 101‐stained cells should be one of these two types. Sulforhodamine 101‐stained cells were indistin‐guishable from oligodendrocytes identified by 2′,3′‐cyclic nucleotide phosphodiesterase (CNP) immunohistochemistry, and sequential staining showed them to be the same. Sulforhodamine 101‐stained cells were microinjected with lucifer yellow after lightly fixing rabbit retinas with formaldehyde and were found to be indistinguishable from oligodendrocytes. Glial fibrillary acidic protein staining for astrocytes showed fiber bundles that to some extent were similar to the bundles stained by sulforhodamine 101, but at the level of individual fibers, it was impossible to establish any concordance. Sulforhodamine 101 thus appears to stain oligodendrocytes rather than astrocytes in the rabbit retina.

A related dye, rhodamine 123, also stained rabbit oligodendrocytes, but with poor contrast because many other cells and structures were also stained. A number of related rhodamine dyes did not stain the rabbit oligodendrocytes.

The staining procedure is simple, has wide tolerance margins, gives robust results, and is well suited for cell microinjections and similar experiments. © 1994 Wiley‐Liss, Inc.
Gonadal hormone regulation of glial fibrillary acidic protein immunoreactivity and glial ultrastructure in the rat neuroendocrine hypothalamus
Authors: Garcia‐Segura Luis Miguel , Luqín Sonia , Párducz Arpad , Naftolin Frederjck
Published: December 2004

The influence of gonadal steroids on the ultrastructure of glial cells and on the immunoreactivity for the specific astrocytic marker glial fibrillary acidic protein (GFAP) has been assessed in the neuroendocrine hypothalamus. The following parameters were analyzed in the arcuate nucleus of adult female rats: the number and the surface density of cells immunoreactive for GFAP, the number of glial profiles showing bundles of glial filaments, the size of the bundles of glial filaments, and the proportion of neuronal perikaryal membrane apposed by glial processes. These parameters were studied during the different phases of the estrous cycle, after ovariectomy, and after the administration of estradiol or progesterone to ovariectomized rats. No significant differences were detected in the number of GFAP‐immunoreactive cells among the different experimental groups. The surface density of GFAP‐immunoreactive material, the number of glial profiles in the neuropil, and the proportion of neuronal perikaryal membrane covered by glia were increased in the afternoon of proestrus and in the morning of estrus compared with other phases of the estrous cycle or to ovariectomized rats and showed a rapid (5 h) and reversible increase in ovariectomized rats injected with 17β estradiol, with a maximal effect by 24 h after the administration of the hormone. In contrast, the size of the bundles of glial filaments was decreased in the afternoon of proestrus, in the morning of estrus, and by the administration of estradiol to ovariectomized rats. The parameters studied were not affected by the administration of progesterone. However, progesterone (300 μg/rat) blocked the effects of 17β estradiol (1, 10, and 300 μg). The results suggest that glial cells may be actively involved in the modulation of neuroendocrine events by the hypothalamus. © 1994 Wiley‐Liss, Inc.
Regulation of C6 glioma cell steroidogenesis by adenosine 3′,5′‐cyclic monophosphate
Authors: Papadopoulos Vassilios , Guarneri Patrizia
Published: December 2004

Incubation of C6 glioma cells in the presence of aminoglutethimide, an inhibitor of cholesterol metabolism, together with either adenosine 3′,5′‐cyclic monophosphate (cAMP) analogues or agents that increase cAMP synthesis, such as cholera toxin, forskolin, and isoproterenol, stimulated the rate of pregnenolone formation by their isolated mitochondria. This effect of cAMP was blocked by the antagonist (Rp)‐cAMPS. The incorporation rate of mevalonolactone into pregnenolone was also increased by the stimulation of adenylyl cyclase activity in intact C6 cells. It is concluded that cAMP stimulates glial cell steroidogenesis by increasing the movement of the substrate, cholesterol, to the mitochondria, where it will be metabolized to pregnenolone by the side chain cleavage cytochrome P450 enzyme. © 1994 Wiley‐Liss, Inc.
MAP kinase cascade in astrocytes
Authors: Tournier Cathy , Pomerance Martine , Gavaret Jean Michel , Pierre Michel
Published: December 2004

We have studied in cultured rat astroglial cells MAP kinases, known for their role in intracellular signal transduction. The MAP kinase activity was stimulated by growth factors (FGFb, FGFa, EGF, PDGF, and IGF1), by a phorbol ester (TPA) activating‐protein kinase C (PKC), by a neuropeptide (endothelin‐1), and by a neuromediator (carbachol). Astrocytes pretreated for 18 h with TPA were still stimulated by growth factors and endothelin, suggesting that down‐regulated isoforms of PKC are not involved in MAP kinase activation. In contrast, the small effect of carbachol was suppressed by TPA pretreatment. Astrocytes contained two proteins (p41 and p44) recognized by MAP kinase antibody. These proteins were phosphorylated on tyrosine residues in the cytosols of stimulated astrocytes.

The kinetics of MAP kinase activation by FGFb and IGF1 were very different. FGFb promoted a rapid activation of MAP kinase (about 10 min) plus a prolonged phase that lasted at least 12 h. IGF1 produced only a rapid transient peak of activation at about 20 min. Hence, extracellular signals might generate different effects in astrocytes by differentially modulating the MAP kinase cascade.

On a Mono Q column the growth factor‐stimulated MAP kinase activity was separated into two peaks containing p41 and p44. Stimulation of astrocytes altered the elution pattern of p44 as a result of its phosphorylation.

An ATP‐dependent MAP kinase activator (MW = 40–45 kDa) was found in fractions of FGFb‐stimulated cells which were not retained on Mono Q column, indicating the existence of a MAP kinase kinase (MEK) in astrocytes. C‐Raf, identified in other cells as a MAP kinase kinase kinase, was also present in astrocytes.

Thus astrocytes contain many components of the MAP kinase cascade activated by growth factors that may also be implicated in the action of neuropeptides and neuromediators. © 1994 Wiley‐Liss, Inc.
K+‐, hypoosmolarity‐, and NH4+‐induced taurine release from cultured rabbit Müller cells: Role of NA+ and CL− ions and relation to cell volume changes
Authors: Faff‐Michalak L. , Reichenbach A. , Dettmer D. , Kellner K. , Albrecht J.
Published: December 2004

The release of preloaded radiolabeled taurine (TAU) from cultured rabbit Müller cells [14–21 days in vitro (DIV)] was measured before and after treatment with the following stimuli: (1) isoosmotic 65 mM KCI; (2) a medium made hypoosmotic by uncompensated lowering of Na+ by 40–100 mM; and 3) NH4Cl ranging from 0.25 to 5 mM. The same stimuli were tested for their effect on the cell volume by the 3‐0‐methyl‐D‐glucose (OMG) uptake method of Kletzien et al. (Anal Biochem 68:537, 1975). Hypoosmotic media and 65 mM KCl stimulated TAU release, and the release was well correlated with the increase of cell volume. The stimulatory effect of 65 mM KCI was abolished by isotonic removal of Cl− or Na+, and omission of either ion markedly enhanced the basal release of TAU. The results are roughly consistent with the characteristics of the swelling‐induced TAU release reported for cultured astrocytes and neurons of various CNS regions, and also for freshly isolated, nondissociated retina. Taken together, the results are indicative of a significant role of TAU release from Müller cells, in the osmosensory response of the retina.

Ammonium chloride stimulated TAU release in a dose‐dependent manner, a significant stimulation being already observed at 0.5 mM, a concentration that is frequently measured in brain during acute hyperammonemia. The effect of NH4Cl was strictly chloride dependent at 0.5–2 mM, but partly Cl− independent at 5mM. The Kletzien's method did not appear to be well suited for measuring cell volume in the presence of ammonium ions. However, data from the literature on other CNS cell types plus our preliminary electron microscopic observations suggest that short‐term treatments with NH4Cl at concentrations up to 1 mM are unlikely to produce cell swelling. An alternative way in which ammonium ions might trigger the “tension sensor” for TAU release is discussed. We propose that in vivo, the outward‐driven TAU could counteract ammoniainduced neuronal disinhibition, according to a putative role for TAU as a gliotransmitter. © 1994 Wiley‐Liss, Inc.
Serum activity induces Schwann cell proliferation in vitro
Authors: Maertens Steven R.
Published: December 2004

The present series of experiments demonstrate that a polypeptide activity present in rat serum induces a proliferative response in cultured rat Schwann cells. Schwann cells in multi‐well tissue culture plates were incubated in medium containing 10% heat‐inactivated fetal bovine serum and serial dilutions of normal rat serum, and control preparations were incubated in the same culture medium without rat serum. Rates of cell proliferation were assayed by measuring DNA incorporation of tritiated thymidine using liquid scintillation counting. A prominent dose‐dependent proliferative response was observed among Schwann cells incubated with rat serum and rat plasma dilutions as compared to controls; this activity is abolished by heat inactivation and by proteolytic digestion, and was not affected by dialysis against a cellulose ester membrane that excludes molecules larger than 10,000 daltons. In contrast, no increase in DNA uptake of tritiated thymidine was observed when astrocyte and oligodendrocyte cultures were incubated with serial dilutions of rat serum. No proliferative effect was observed when rat Schwann cells were incubated with a dilution of standard adult bovine serum. These results suggest there is an intravascular plasma polypeptide with a molecular weight greater than 10,000 daltons that specifically stimulates Schwann cell proliferation, and it is proposed that this factor may be the mitogen responsible for the Schwann cell proliferative response known to occur after nerve injury. © 1994 Wiley‐Liss, Inc.
Contact with myelin evokes a release of calcium from internal stores in neonatal rat oligodendrocytes in vitro
Authors: Moorman Stephen J. , Hume Richard I.
Published: December 2004

The response of neonatal rat oligodendrocytes to contact with myelin extracts prepared from the central and peripheral nervous system was examined. Contact with either CNS myelin or PNS myelin resulted in collapse of the fine structure of the leading edge of oligodendrocytes in vitro. The collapse of the fine structure of oligodendrocyte processes was preceded by a substantial (approximately fivefold) increase in intracellular free calcium concentration. The calcium concentration increase was due, at least in part, to a release of calcium from internal stores, since it persisted when extracellular calcium was removed by chelation with EGTA. The increase in calcium concentration and the coincident morphological change suggest that oligodendrocytes might be able to recognize and react to specific molecules on the surface of other oligodendrocytes. © 1994 Wiley‐Liss, Inc.
Role of cytokines in lipopolysaccharide‐induced functional and structural abnormalities of astrocytes
Authors: Hu Shuxian , Martella Alice , Anderson W. Robert , Chao Chun C.
Published: December 2004

The mechanism underlying meningitis‐associated brain injury is unclear. This study investigated the hypothesis that lipopolysaccharide (LPS) alters astrocyte function and structure via the release of proinflammatory cytokines. In enriched murine astrocyte cultures, LPS inhibited (P < 0.05) glutamine synthetase activity, 3H‐gamma aminobutyric acid uptake, and DNA synthesis; LPS also induced ultrastructural changes. Antibodies to tumor necrosis factor‐α, interleukin‐1, and interleukin‐6 blocked (P < 0.05) in part the LPS‐induced inhibition of astrocyte function. Also, treatment of astrocyte cultures with cytokines significantly altered these astrocyte functions and ultrastructure. Taken together, the present findings support the hypothesis that LPS affects astrocyte function and structure via the release of proinflammatory cytokines, especially tumor necrosis factor‐α. © 1994 Wiley‐Liss, Inc.
Induction of nerve growth factor responsiveness in C6‐2B glioma cells by expression of trk A proto‐oncogene
Authors: Colangelo Anna Maria , Fink Donald W. , Rabin Stuart J. , Mocchetti Italo
Published: December 2004

Cells that lack the high affinity receptor component (trkA) for nerve growth factor (NGF) are unresponsive to NGF. We investigated whether C6‐2B cells, a rat glioma derived cell line, express trkA and, as a consequence, are responsive to NGF. In these cells, NGF (100 ng/ml) failed to induce the mRNA encoding for c‐fos protooncogene and the low affinity NGF receptor p75NGFR, two NGF‐responsive genes. In contrast, both mRNAs were induced in PC12 cells by NGF. Using a RNase protection assay with a cRNA probe for rat trkA RNA protected fragment was detected in PC12 but not in C6‐2B glioma cells, indicating that C6‐2B cells either do not express the gene or express it only in low amounts. Cross‐linking of 125I‐labeled NGF to PC12 cells identified two major bands with an apparent molecular weight of 158 kDa and 100 kDa corresponding to trkA and p75NGFR, respectively. In contrast, only the 100 kDa band could be detected in C6‐2B cells by cross‐linking analysis. In C6‐2B cells stably transfected with the rat trkA cDNA, NGF increased c‐fos mRNA, induced tyrosine phosphorylation of gp140trk, and SNT (suc‐associated neurotrophic factor‐induced tyrosinephosphorylated target), and caused morphological changes within 72 h. All of these effects of NGF were blocked by the protein kinase inhibitor K‐252a suggesting that NGF signal transduction was restored by trkA expression. Most important, in C6trk+ cells, NGF was a weaker (2‐fold) inducer of [3H]thymidine incorporation when compared to bFGF (5‐fold), suggesting that expression of trkA fails to confer to NGF a strong mitogenic effect. Our findings indicate that C6‐2B glioma cells do not possess high affinity NGF receptor and thus are unresponsive to NGF and that expression of trkA in neuroectoderm derived cells elicits some of the NGF responses characteristic of neuronal cells.
Characterization of C6‐10A glioma cells highly responsive to β‐adrenergic receptor agonist‐induced NGF synthesis/secretion
Authors: Fukumoto Hiroaki , Kakihana Mitsuru , Suno Masahiro
Published: December 2004

A subline of rat C6 glioma cells, C6‐10A cells, in which epinephrine can induce nerve growth factor (NGF) synthesis/secretion, was isolated. C6‐10A cells have retained their sensitivity to epinephrine for more than 2 years in a medium containing 0.5% fetal calf serum (FCS) but easily lose it in 10% FCS. C6‐10A cells are S‐100‐ and glial fibrillary acidic protein‐positive, and the doubling time is about 60 h in the medium containing 0.5% FCS and about 20 h in 10% FCS. Epinephrine induced NGF synthesis/secretion prominently in serum‐free cultures of C6‐10A cells and in cultures with a high cell density, but not in serum‐containing cultures. The induction did not occur with parent C6 cells under the appropriate conditions in C6‐10A cells. NGF secretion was induced by catecholaminergic compounds in the following order isoproterenol > epinephrine = norepinephrine » dopamine. The induction caused by epinephrine was blocked by propranolol (α‐blocker) but not by phentolamine (β‐blocker). Various compounds that activate the adenylate cyclase system also induced NGF synthesis/secretion. These results indicate that C6‐10A cells are astrocytes that are highly responsive to β‐adrenergic receptor agonists, which stimulate NGF synthesis/secretion via receptors coupled with adenylate cyclase machinery. These cells may be a useful aid in studying the mechanism of NGF synthesis/secretion.
Expression of BMP‐6, a TGF‐β related morphogenetic cytokine, in rat radial glial cells
Authors: Schluesener Hermann J. , Meyermann Richard
Published: December 2004

Bone morphogenetic protein‐6 (BMP‐6) is a member of the TGF‐β super‐family of cytokines. The bone morphogenetic proteins and homologous cytokines participate in realization of the genetic body plan by regulating homeotic gene expression, embryonic development, and neurogenesis. Here we demonstrate expression of BMP‐6 in rat radial glial cells which are involved in embryonic organisation of the central nervous system. Thus, morphogenetic cytokines like BMP‐6 might contribute to radial glial cell function in organizing the migration of immature neurons during the development of the CNS cortex.
Intracellular pH regulation in primary rat astrocytes and C6 glioma cells
Authors: Shrode Lamara D. , Putnam Robert W.
Published: December 2004

We used the pH‐sensitive fluorescent dye BCECF to study intracellular pH (pHi) regulation in primary cultures of rat astrocytes and C6 glioma cells. Both cell types contain three pH‐regulating transporters: (1) alkalinizing Na+/H+ exchange; (2) alkalinizing Na+ + HCO3 −/Cl− exchange; and (3) acidifying Cl−/HCO3 − exchange. Na+/H+ exchange was most evident in the absence of CO2; recovery from acidification was Na+ dependent and amiloride sensitive. Exposure to CO2 caused a cell alkalinization that was inhibited by DIDS, dependent on external Na+, and inhibited 75% in the absence of Cl− (thus mediated by Na+ + HCO3 −/Cl− exchange). When pHi was increased above the normal steady‐state pHi, a DIDS‐inhibitable and Na+ ‐independent acidifying recovery was evident, indicating the presence of Cl− /HCO3 − exchange. Astrocytes, but not C6 cells, contain a fourth pH‐regulating transporter, Na+ −HCO3 − cotransport; in the presence of CO2, depolarization caused an alkalinization of 0.12 +− 0.01 (n = 8) and increased the rate of CO2‐induced alkalinization from 0.23 ± 0.02 to 0.42 ± 0.03 pH unit/min. Since C6 cells lack the Na+ ‐HCO3 + cotransporter, they are an inferior model of pHi regulation in glia. Our results differ from previous observations in glia in that: (1) Na+ /H+ exchange was entirely inhibited by amiloride; (2) Na+ + HCO3 −/Cl− exchange was present and largely responsible for CO2−induced alkalinization; (3) Cl− /HCO3 − exchange was only active at pHi values above steady state; and (4) depolarization‐induced alkalinization of astrocytes was seen only in the presence of CO2.
Cytokine and insulin regulation of α2 macroglobulin, angiotensinogen, and hsp 70 in primary cultured astrocytes
Authors: Hong‐Brown Ly Q. , Brown C. Randell
Published: December 2004

Acute‐phase proteins and heat shock proteins (hsp) are upregulated following exposure to a number of conditions including bacterial infection, tissue injury, or stress. We show here that α2 macroglobulin (α2M), angiotensinogen (AOG), and hsp 70 are regulated by cytokines in primary cultures of astrocytes. In addition, we have found that insulin modulates the effect of cytokines on these proteins. In cells treated with lipopolysaccharide (LPS) conditioned Raw media, interleukin (IL)‐6, or IL‐β for 24 h, there was a significant decrease of α2M secretion below control levels. In the absence of insulin, however, similar treatments resulted in a significant increase in α2M secretion. AOG secretion increased significantly following treatment with individual cytokines either in the presence or absence of insulin, but conditioned media did not cause a response in the absence of insulin. Hsp 73 concentrations also increased following treatment with conditioned media and IL‐β in the presence or absence of insulin. Following IL‐6 treatment, however, hsp levels either decreased (‐insulin) or did not change (+ insulin). To determine whether acute‐phase proteins are regulated similarly to hsp, astrocytes were subjected to elevated environmental temperatures. Cells incubated at 43αC for 90 min showed a marked increase in AOG secretion. However, α2M and hsp 73 levels remained unchanged. In the absence of insulin, heat shock caused a significant increase of α2M and AOG secretion. Thus, in astrocytes, α2M is upregulated by cytokines and heat shock in the absence of insulin, while in the presence of insulin, cytokines function as negative regulators. On the other hand, insulin did not modulate the effects of cytokines on the production of AOG in an inverse manner.
Atrial natriuretic peptide‐like (ANP‐LIR) and ANP prohormone immunoreactive astrocytes and neurons of human cerebral cortex
Authors: McKenzie James C. , Berman Nancy E. J. , Thomas Charles R. , Young John K. , Compton Lisa Y. , Cothran Laval N. , Liu W.‐L. , Klein Robert M.
Published: December 2004

Atrial natriuretic peptide (ANP) represents a family of related peptides originally isolated from cardiac atria that have potent natriuretic, diuretic, and vasorelaxant properties. ANP has previously been localized in neurons of the rat brain in regions subserving cardiovascular functions and fluid/electrolyte balance and has been localized in astroglia of the canine brain. To determine whether ANP is present in astrocytes of the human brain and to validate the canine model for future studies, human brain tissue was obtained from autopsy cases with no brain damage or neurological or vascular disease. Human brains were obtained less than 3 h postmortem, and anterior cingulate and striate cortices were dissected following perfusion or immersion fixation. Immunohistochemical processing utilized antibodies against the processed form of ANP (ANP IV, ANP104–128) and against rat proANP (amino terminus) and the avidin‐biotin‐peroxidase technique. Isolated, strongly ANP‐immunoreactive protoplasmic astrocytes were observed in all layers of the cingulate and striate cortex gray matter. ANP‐positive fibrous astrocytes were observed in the white matter. Additionally, distinctive immunopositive astrocytes were found both within and immediately subjacent to the glia limitans. Antibody against the prohormone stained only protoplasmic astrocytes and sublimitans astrocytes and processes. In addition to the astroglia, ANP was detected in scattered multipolar neurons in the cerebral gray matter. These results provide additional evidence for diversity of peptide localization in astrocytes and suggest roles for ANP in the local regulation of cerebral blood flow, blood‐brain barrier permeability, or cerebrospinal fluid volume.
Glial development in primary cultures established from normal and X‐irradiated neonatal spinal cord
Authors: Sims Terry J. , Davies David L. , Gilmore Shirley Ann
Published: December 2004

The glial population of the lumbosacral spinal cord of the rat can be markedly depleted by exposure to ionizing radiation during the first postnatal week. Identification of specific cell populations which survive the exposure to radiation is difficult in situ; therefore, the present investigation used in vitro approaches to address issues related to specific phenotypes and maturational states of glia in cultures derived from non‐irradiated (control) and irradiated (experimental) lumbosacral spinal cords of 3‐day‐old rats. Cultures were established from the spinal cords 2 to 4 hours following irradiation and were compared to cultures from non‐irradiated, littermate controls. By 4 days in vitro (DIV) the numbers of cells in experimental cultures were profoundly reduced when compared to controls, and this reduction persisted through the termination of the study (8 DIV). In addition to reduction in numbers, astrocyte phenotypes were altered in experimental cultures, with greater proportions of the astrocyte population being constituted by the flat angular, large angular, and pancake types and a lesser proportion by stellate cells. The non‐astrocytic cell types were dramatically reduced as evidenced by the paucity of oligodendrocytes immunoreactive for galactocerebroside and of small, non‐process bearing cells binding the lectin, Griffonia (Bandeiraea) simplicifolia, a marker for microglia. Experimental cultures contained an increased incidence of binucleate astrocytes, an increase not restricted to a particular astrocyte phenotype. This study established the feasibility of utilizing this combined in vivo/in vitro approach in assessment of glial populations in immature spinal cords, and further investigations are in progress using this model.
Strongly GD3+ cells in the developing and adult rat cerebellum belong to the microglial lineage rather than to the oligodendrocyte lineage
Authors: Wolswijk Guus
Published: December 2004

A recent study has shown that ramified microglia in the adult rat optic nerve express the ganglioside GD3[Wolswijk Glia 10:244–249, 1994], thereby raising the possibility that some GD3+ in the developing rat central nervous system (CNS) belong to the microglial lineage rather than to the oligodendrocyte lineage, as previously thought. To examine this possibility, sections of postnatal and adult cerebellum were doublelabelled with markers for rat microglia [the B4 isolectin derived from Griffonia simplicifolia (GSI‐B4), the ED1 monoclonal antibody (mAb), and the OX‐42 mAb] and anti‐GD3 mAbs (the mAbs R24 and LB1). These immunolabellings showed that ramified microglia as well as amoeboid microglia are strongly GD3+ in vivo. Moreover, most, if not all, cells that express high levels of GD3 in sections of developing cerebellum appear to belong to the microglial lineage. These observations contradict previous suggestions that the strongly GD3 + cells in the putative white matter regions of the developing brain are oligodendrocyte‐type‐2 astrocyte (0–2A) progenitor cells; the cells that give rise to oligodendrocytes in the CNS. The present study did, however, confirm that some 0–2A progenitor cells in sections of postnatal cerebellum are weakly GD3+ in vivo. Amoeboid microglia are present in areas of the developing cerebellum where newly generated oligodendrocytes are found, suggesting that these cells play a role in the phagocytosis of the large numbers of oligodendrocytes that die as part of CNS development. © 1995 Wiley‐Liss, Inc.
Schwann cell ATP‐mediated calcium increases in vitro and in situ are dependent on contact with neurons
Authors: Lyons Susan A. , Morell Pierre , McCarthy Ken D.
Published: December 2004

Schwann cells freshly isolated from the sciatic nerves of neonatal rats respond to exogenously applied ATP with a rapid increase in cytosolic calcium. This increase in [Ca2+]i is mediated by a P2Y‐purinergic pathway (Lyons et al.: J. Neurochem. 63:552–560, 1994) and was measured using the calcium indicator dye, fura‐2/AM, and a video‐enhanced calcium imaging system. The ability to respond to ATP with increases in intracellular calcium is lost over a period of several days in culture; this loss can be prevented or reversed by application of cAMP analogs in a defined medium. We now demonstrate that the direct contact of Schwann cells with neurons also induces and stabilizes this ATP responsiveness. The induction of ATP responsiveness was observed among all Schwann cells contacting neurites, including those forming myelin, and regardless of whether the source of neurons was dorsal root ganglion neurons or superior cervical ganglion neurons. Approximately 85% of Schwann cells responded to ATP over the time studied (72 d in coculture). Addition of axolemma to Schwann cell cultures did not induce ATP responsiveness. We also examined the ATP responsiveness of Schwann cells in situ (excised nerves) using laser‐scanning confocal microscopy and the calcium indicator dye, fluo‐3/AM. Schwann cells in intact sciatic nerve segments isolated from neonatal and 16–day‐old rats exhibited ATP‐mediated [Ca2+]i increases. We conclude that neuronal contact is necessary for the expression of the ATP‐mediated calcium responses in Schwann cells and that these responses are independent of myelin formation or maintenance. Copy 1995 Wiley‐Liss, Inc.