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  • 1
    Electronic Resource
    Electronic Resource
    Connexin43 in rat pituitary: localization at pituicyte and stellate cell gap junctions and within gonadotrophs (1993)
    Springer
    Histochemistry and cell biology 100 (1993), S. 53-64 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Immunohistochemical methods were employed to investigate the cellular and ultrastructural localization of the gap junction protein connexin43 (Cx43) in rat pituitary. Western blots of pituitary homogenates probed with anti-Cx43 antibodies showed the presence of Cx43 in both anterior and posterior pituitary lobes. By light microscopy (LM), Cx43-immunoreactive (Cx43-IR) puncta were found in all areas of the posterior lobe, but at greater concentrations in peripheral regions of this structure. By electron microscopy (EM), immunogold labelling for Cx43 was seen at gap junctions between thin cytoplasmic processes of pituicytes. No immunoreactivity was detected in the intermediate lobe. The anterior lobe contained puncta similar to but more sparsely scattered than those in the posterior lobe, and by EM analysis these were demonstrated to correspond to labelled gap junctions between stellate cells. In addition, anti-Cx43 antibodies produced intracellular labelling in a small percentage of endocrine cells, which were distributed throughout the anterior lobe and determined by double immunostaining methods to be cells containing luteinizing hormone. By EM, labelling within these cells was associated with predominantly large secretory granules and other loosely organized organelles. The results indicate that gap junctions in the pituitary are composed of Cx43 and that this or a related protein may have a novel intracellular function within gonadotrophs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00268878
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  • 2
    Electronic Resource
    Electronic Resource
    The Janusfjellet Subgroup (Bathonian to Hauterivian) on central Spitsbergen: a revised lithostratigraphy (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 9 (1991), S. 0 
    Details
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: The Janusfjellet Subgroup is a marine shelf to prodeltaic succession dominated by shales with subordinate siltstones and sandstones. The subgroup comprises a lower Agardhf jellet (Upper Bathonian - Berriasian) and an upper Rurikf jellet (Berriasian - Hauterivian) formation. Based on field work in central Spitsbergen the following subdivisions of the formations are proposed (units listed in ascending order).The Agardhf jellet Formation (up to 290 m thick) contains four members: Oppdalen - a fining upwards succession from conglomerates to shales; Lardyfjellet - black paper shales; Oppdalsata - grey shales with siltstones and sandstones; and Slottsmøya - grey shales and black paper shales. Within the Oppdalen Member three beds are recognised: Brentskardhaugen - phosphoritic conglomerate; Marhøgda - glauconitic sandstones', and Drønbreen - siltstones and shales.The Rurikfjellet Formation (thickness up to 226 m) is composed of two members: Wimanfjellet - grey and partly silty shale sequence, containing the Myklegardfjellet Bed (of plastic clays) at its base; and Ullaberget - silty and sandy shales with siltstones and sandstones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1751-8369.1991.tb00400.x
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  • 3
    Electronic Resource
    Electronic Resource
    Rat Brain Adenosine Deaminase After 2′-Deoxycoformycin Administration: Biochemical Properties and Evidence for Reduced Enzyme Levels Detected by 2′-[3H]Deoxycoformycin Ligand Binding (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 58 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Near total inhibition of brain adenosine deaminase (ADA) activity in rats injected with the potent ADA inhibitor 2′-deoxycoformycin (DCF) was previously shown to reduce enzyme activity for up to 50 days during which time the enzyme exhibited reduced sensitivity to in vivo inhibition by DCF. Here, we investigated the biochemical properties of ADA and the basis for its reduced activity after DCF treatment. It was found that much higher doses of DCF were required to inhibit ADA in DCF-treated compared with drug-naive animals. Fourteen days after DCF administration, reduced ADA activity in brain homogenates was due to a decrease in Vmax, rather than to an altered Km of ADA for adenosine. DCF treatment had no effect on Ki values for erythro-9-(2-hydroxy-3-nonyl)adenine inhibition of ADA. The IC50 value for DCF inhibition of ADA in hypothalamus was unchanged. However, the Ki for DCF inhibition of ADA in whole brain increased by fivefold. Sucrose gradient analysis of brain ADA revealed only one corresponding peak of activity and [3H]DCF-labeled ADA in DCF-treated and control rats. A radioligand filtration assay with [3H]DCF was developed to assess the effects of DCF on ADA protein levels. Over a roughly 200-fold range of ADA activities the binding of [3H]DCF was highly correlated with deaminase activity (r= 0.99). In brain tissues taken 8 and 33 days after treatment of rats with DCF, [3H]DCF binding was reduced to 27% and 48% of control levels, respectively. The results suggest that (1) although the biochemical properties of ADA are largely unchanged after treatment of rats with DCF, the enzyme in some brain regions has become less sensitive to this drug and (2) the prolonged reduction in ADA activity after DCF treatment is due to decreased levels of ADA protein possibly involving altered rates of degradation or production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb09739.x
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  • 4
    Electronic Resource
    Electronic Resource
    Phosphorylated Forms of Connexin43 Predominate in Rat Brain: Demonstration by Rapid Inactivation of Brain Metabolism (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The gap junction protein connexin43 (Cx43) has been reported to exist as several phosphorylated forms migrating at ˜43 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as well as an unphosphorylated 41-kDa form. In brain, Cx43 is expressed predominantly in astrocytes and is also expressed in several other cell types. Whereas the phosphorylated forms of Cx43 predominate in heart, several studies have indicated that high levels of the unphosphorylated form of Cx43 are present in brain. Various experiments in this report indicate that the 41-kDa molecular form in brain is a postmortem dephosphorylation product of phosphorylated Cx43. In rats killed by cranial high-energy microwave irradiation leading to rapid inactivation of brain metabolism, Cx43 in cerebral cortex was present almost exclusively as the 43-kDa phosphorylated form. Rapid dissection of brain followed by heat treatment or inclusion of phosphatase inhibitors during tissue homogenization also largely prevented the conversion of the 43-to the 41-kDa form. The 41-kDa species was generated after alkaline phosphatase digestion of the 43-kDa material obtained by immunoprecipitation from microwave-irradiated brain. Immunolabeling patterns and relative regional levels of Cx43 as seen by immunohistochemical and western blot detection were the same whether or not metabolism to the 41-kDa species was prevented. In developing rat brain, Cx43 levels in frontal cortex and brainstem increased with age, but the degree of dephosphorylation of the 43-to the 41-kDa form was greater at earlier ages in the brainstem. It appears that brain contains a phosphatase that may be involved in modulating the phosphorylation state of Cx43 and thus may regulate intercellular communication via astrocytic gap junctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.62062394.x
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  • 5
    Electronic Resource
    Electronic Resource
    Ionic Strength Dependence of Calcium, Adenine Nucleotide, Magnesium, and Caffeine Actions on Ryanodine Receptors in Rat Brain (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: [3H]Ryanodine binding studies of ryanodine receptors in brain membrane preparations typically require the presence of high salt concentrations in assay incubations to yield optimal levels of binding. Here, radioligand binding measurements on rat cerebral cortical tissues were conducted under high (1.0 M KCI) and low (200 mM KCI) salt buffer conditions to determine the effects of ionic strength on receptor binding properties as well as on modulation of ligand binding by Ca2+, Mg2+, β,γ-methylene-adenosine 5′-triphosphate (AMP-PCP), and caffeine. In 1.0 M KCI buffer, labeled titration/equilibrium analyses yielded two classes of binding sites with apparent KD (nM) and Bmax (fmol/mg of protein) values of 2.4 and 34, respectively, for the high-affinity site and 19.9 and 157, respectively, for the low-affinity site. Unlabeled titration/equilibrium measurements gave a single high-affinity site with a KD value of 1.9 nM and a Bmax value of 95 fmol/mg of protein. The apparent KD value derived from association and dissociation studies was 20 pM. Equilibrium binding was activated by Ca2+ (KD/Ca2+= 14 nM), inhibited by Mg2+ (IC60= 5.0 mM), and unaffected by AMP-PCP or caffeine. In 200 mM KCI buffer conditions, labeled titration analyses gave only a single site with a KD value similar to and a Bmax value 1.8-fold greater than those obtained for the low-affinity site in 1.0 M KCI buffer. In unlabeled titration measurements, the KD value was fivefold lower, whereas the Bmax value was unaffected. The KD value derived from association and dissociation analysis was 2.4-fold greater in 200 mM KCI compared with 1.0 M KCI buffer conditions. In 200 mM compared with 1.0 M KCI, the potency with which Mg2+ inhibited binding was increased by 3.8-fold, whereas the affinity of the activation site for Ca2+ was reduced by 13-fold. Addition of caffeine in the presence of low salt increased the affinity of Ca2+ activation by 1.7-fold. The inhibitory effect of Mg2+ on [3H]-ryanodine binding in the presence of 200 mM KCI was reversed by AMP-PCP and caffeine with apparent EC50 values of 0.25 and 7.6 mM, respectively. Taken together, these results indicate that ionic strength is an important consideration in binding studies of brain ryanodine receptors and their interactions with modulatory agents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.62062340.x
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  • 6
    Electronic Resource
    Electronic Resource
    2′-Deoxycoformycin Inhibition of Adenosine Deaminase in Rat Brain: In Vivo and In Vitro Analysis of Specificity, Potency, and Enzyme Recovery (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 54 (1990), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 2′-Deoxycoformycin (DCF), a potent inhibitor of adenosine deaminase (ADA), is increasingly used as a tool to investigate adenosine metabolism and neuromodulation. To advance further the usefulness of DCF for studies of purines in the CNS, we determined the inhibitory potency of this compound against ADA and adenylate deaminase (AMPDA) in brain, the rate of ADA recovery in various brain regions after single or repeated intraperitoneal DCF administrations, and the effect of DCF on several neurotransmitter synthetic enzymes. In vitro, the Ki values for inhibition of ADA and AMPDA were found to be 23 pM and 233 μM, respectively. In vivo, DCF inhibited ADA with ED50 values ranging from 155 to 280 μg/kg at 2 h posttreatment, and 98% inhibition was achieved with 1 mg/kg. AMPDA activity was not affected by doses up to 5.0 mg/kg. In contrast to the 〉95% inhibition of ADA seen 1 day after DCF at 5 mg/kg, the effectiveness of a second similar DCF treatment on the activity that had recovered by 14 days was dramatically reduced. Eight days after DCF treatment with doses of 5–50 mg/kg, the degree of ADA activity recovery in 10 brain regions examined was similar; it averaged 35% of control values at the low dose but showed some heterogeneity, ranging from 15 to 54% of control values, at the higher doses. Forty days after treatment with a single dose of 5 mg/kg, ADA activity recovered by 68–78% of control values in brain regions with normally high levels of activity and by 44–59% of control values in other regions. The activities of choline acetyltransferase, glutamic acid decarboxylase, and histidine decarboxylase (an enzyme colocalized with ADA in hypothalamic neurons) were unaffected by DCF treatment, a result suggesting the lack of a generalized neurotoxic effect. The very low doses of DCF required for ADA inhibition in vivo are consistent with the high potency of this drug against ADA in vitro, and any physiological effects observed at low doses might therefore be ascribed to inhibition of ADA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb01945.x
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  • 7
    Electronic Resource
    Electronic Resource
    Subsequent mapping of137Cs fallout from chernobyl in hungary using the radioactivity found in mosses (1994)
    Springer
    Naturwissenschaften 81 (1994), S. 175-177 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01134536
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  • 8
    Electronic Resource
    Electronic Resource
    Subsequent Mapping of 137Cs Fallout from Chernobyl in Hungary Using the Radioactivity Found in Mosses (1994)
    Springer
    Naturwissenschaften 81 (1994), S. 175-177 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01134536
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  • 9
    Electronic Resource
    Electronic Resource
    Possible pathogenic role of IgE in Henoch-Schönlein purpura (1994)
    Springer
    Pediatric nephrology 8 (1994), S. 169-171 
    Details
    ISSN: 1432-198X
    Keywords: Atopy ; IgA nephropathy ; Henoch-Schönlein purpura ; IgE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The incidences of clinical and biological markers of atopy were investigated in 16 children with IgA nephropathy (IgAN) (group A) and in 22 with Henoch-Schönlein purpura nephritis (HSPN) (group B). The incidence of increased plasma IgE levels according to age-matched normal values was significantly higher in group B (17/22, 77%) than in group A (7/16, 44%) (P〈0.05). Although not significant, the incidences of positive RAST tests and of a history of typical atopic symptoms were also higher in group B [10/22 (45%) and 11/22 (50%), respectively] than in group A [4/16 (25%) and 5/16 (31%), respectively]. Moreover, IgE deposits were demonstrated by a peroxidase/anti-peroxidase method on cutaneous Langerhans and mast cells in 4 of 6 patients with HSPN. Thus immunoallergy might account, in some cases, for the cutaneous, intestinal and pulmonary signs observed in HSPN, but not in IgAN. We postulate stimulation of IgE-sensitized mast cells by specific antigens in the presence of IgA circulating immune complexes (CIC), release of vasoactive substances, increased capillary permeability and perivascular deposition of IgA CIC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00865470
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal analysis of fluorine containing gels and precursors of high silica zeolites (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 693-700 
    Details
    ISSN: 1572-8943
    Keywords: fluorine containing gels ; high silica zeolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels simultaner DTA-, TG- und DTG-Techniken wurden Kieselgele und die MFI-Kristalle dieser Gele untersucht. Die Gele wurden in und ohne Gegenwart von Tetrapropylammoniumkationen (TPA+) und mit Li+-, Na+-, NH 4 − und Kaliumfluoriden hergestellt. Bei Abwesenheit von TPA+ werden für Li+- und Na+-Gele keine thermischen Effekte beobachtet. Der bei NH 4− -Gelen beobachtete Effekt ergibt sich aus der Zersetzung und Abspaltung von anorganischen Phasen: SiF4, NH4F, NH3. Die DTA/DTG-Effekte in TPA+-haltigen Gelen und in den MFI-Kristallen monodispersen Ausmaes werden der Zersetzung des TPA+-Kations zugeschrieben. Daraus kann man schlieen, da die Wechselwirkung zwischen den Gelen und dem TPA+-Kation eher schwach ist. Die Wechselwirkung zwischen TPA+ und MFI-Kristallen aus fluoridischen Medien ist strker als die Wechselwirkung mit Kristallen aus alkalischen Medien. Ähnliche thermische Effekts erhlt man, nachdem man die langen Kristalle zerkleinert und eine breite Kristallgrenverteilung erhlt.
    Notes: Abstract By means of simultaneous DTA-, TG- and DTG-technique, the silicate gels and the MFI crystals obtained from these gels have been investigated. The gels have been prepared in presence and in absence of tetrapropylammonium cation (TPA+) and with Li+, Na+, NH 4 + and K+ fluorides. In absence of TPA+ no thermal effects have been observed in Li+- and Na+-gels. The effects observed in the NH 4 + -gel stem from a decomposition and release of inorganic phases: SiF4, NH4F, NH3. The DTA/DTG effects in the TPA+ containing gels and in the MFI crystals of monodisperse size are attributed to the decomposition of TPA+ cation. It can be concluded from these effects that the interaction between the gels and the TPA+ cation is rather weak. The interaction between TPA+ and MFI crystals obtained in fluoride medium is stronger than the interaction with crystals obtained from alkaline media. Similar thermal effects are obtained after grinding the long crystals to those having a large distribution of crystal sizes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979398
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