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  • 1
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Die Regulationseiweisse (Tropomyo sin und Troponinkomplex), welche die Wechselwirkung der kontraktilen Eiweisse in der Myofibrille steuern, zeigen eine spezifische und unspezifische Bindung an den Actomyosinkomplex. Die spezifisch gebundene Menge der Regulationseiweisse beträgt nur etwa 1/100 derjenigen von Actomyosin, genügt aber trotzdem, um die Steuerung der Mg-ATPase und damit der Muskelkontraktion durch Ca2+ zu gewährleisten.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 10 (1954), S. 298-300 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The alkaloid muscarin was isolated from fly agaric. The analyses of crystallized salts (chloride, tetra-chloroaurate,Reinecke's salt) led to C9H20O2N+ as the simplest formula. The presence of aldehyde and tri-methyl-ammonium groups, which had been assumed hitherto, could not be proved. The quaternary nature of the nitrogen atom was shown. Pharmacological tests on frog heart, rabbit gut and cats show the purely peripheral parasympathomimetic effect of the smallest doses.
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  • 3
    ISSN: 1435-1803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung 1. In 3 verschiedenen Methoden zeigte sich, daß Mg-ADP in 2 Schritten an Myosin aus Herz- und schnell kontrahierenden Skelettmuskeln bindet. 1 Mol Mg-ADP bindet mit hoher Affinität (K∼106 M−1) und darauf ein zweites mit niederer Affinität (K∼102–104 M−1) pro Myosin. Nur 1 Mol Mg-ADP bindet mit hoher Affinität an isolierte Myosinköpfe. Dies deutet auf negative Kooperativität zwischen den beiden Bindungsstellen in intaktem Myosin. 2. In Gegenwart von Nukleotiden zeigen die beiden Köpfe eines Myosin-moleküls verschiedene Konformationen, da an jedem Kopf eine andere essentielle Thiolgruppe leicht mit N-Aethylmaleinimid reagiert. In Gegenwart von Mg-Pyrophosphat reagiert an beiden Myosinköpfen eine Thiol-1-Gruppe besonders leicht. Der Nukleosidanteil scheint für diese zweite Art von Wechselwirkung zwischen den beiden Myosinköpfen verantwortlich zu sein.
    Notes: Summary 1. Binding of Mg-ADP to both heart and fast skeletal myosin was found with 3 methods to proceed in 2 steps. One mole of Mg-ADP binds with high affinity (K∼106M−1) and subsequently a second with lower affinity (K∼102–104 M−1) per myosin. Only one mole of Mg-ADP was found to bind with the high affinity to isolated myosin heads. This implies that binding of Mg-ADP to intact myosin exhibits negative cooperativity. 2. When a nucleotide is bound, the 2 heads of a single myosin molecule adopt different conformations since on each head a different type of essential thiol group was found to be the most reactive towards N-ethylmaleimide. In the presence of Mg-pyrophosphate a thiol-1 is the most reactive essential group in both heads. Therefore, the nucleoside moiety seems to be required for this latter type of head-head interaction.
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  • 4
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A population of small unilamellar liposomes loaded with horseradish peroxidase, an electron dense marker, was prepared by passing the lipid-protein-detergent micelles through Sephadex G-50. By electron microscopy it was shown that these artificial lipid vesicles were incorporated into the cytoplasm of isolated pure cholinergic nerve endings from the electric organ ofTorpedo marmorata. This liposome carrier system may be useful in manipulating the internal parameters involved in presynaptic processes in the electric organ.
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  • 5
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The influences of various fixatives on the vesicle size of the electric organ of Torpedo marmorate were investigated. Thin section and freeze etched preparations were examined under the electron microscope. In thin section increased vesicle diameters were observed compared with the freeze etched preparations. The same experiments in different torpedo fish led to significantly different vesicle sizes observed. Variations of the molarity, the pH and osmolarities result in particularly high differences in vesicle diameters. Using Karnovsky's method (1965) and a fixative consisting of 2.5% glutaraldehyde in 0.2 M cacodylate buffer, pH 7.2, results in vesicle sizes comparable to those reported by other authors. Results obtained from freeze etched preparations are not comparable in general with results from thin section experiments with the same fixative.
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  • 6
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The light microscopic method for demonstration of choline acetyltransferase (CAT) activity based on the formation of a lead mercaptide of free SH-acetyl Coenzyme A was adapted for electron microscopy. In samples of electric organ of Torpedo marmorata CAT activity was found to be restricted to synaptic vesicles and cysternae. The precipitate formed was mostly fine grained and distributed more or less evently throughout the vesicles. Generally, the reaction product seemed not to adhere to the inner side of the vesicle membrane. CAT activity was found only in the presynaptic region of the synapse, neither the synaptic cleft nor the postsynaptic region reacted positively. CAT activity was found also within synaptic vesicles in nerve endings prepared from electric organ. Samples of Torpedo brain reacted positively too. Complete suppression of CAT activity with inhibitors, judged on the basis of lead mercaptide deposited, was rather difficult to achieve. From a group of 10 presumed enzyme inhibitors, only 2 compounds reacted satisfactorily, namely trans-1,2-dihydro-2-imino-4-(l-naphthylvinyl)-l-pyridine-ethanol hydrobromide and 5,5-dithio-bis-(2-nitrobenzoic acid) (3,3′-6). On the whole, the results obtained show the viability of the method used and furthermore it offers also some new insight into the turnover of acetylcholine, since it may be deduced from the results that under certain circunstances acetylcholine may be synthesized in synaptic vesicles.
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  • 7
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The lead pyrophosphate precipitation technique was used to visualize adenylate cyclase activity with the electron microscope in unfixed electric organ and synapto-somes ofTorpedo marmorata, with special attention to presynaptic membranes. Specificity of the deposition of reaction product was ensured by using 5′-adenylyl imidodiphosphate as substrate and 5′-guanylyl imidodiphosphate and sodium fluoride as activators. Under suitable conditions a reaction product was deposited on the Schwann cell, on presynaptic vesicles, on the inner side of membranes of cisternae and on glycogen granules of the presynaptic region of the endplate. In some cases, a precipitate was also found on postsynaptic membranes of the synaptic cleft and on mitochondria. In isolated synaptosomes localization of the reaction product was identical with that of minced tissue. However, most strikingly, on presynaptic membranes no precipitate was ever found, neither in pieces of electric organ nor in isolated synaptosomes. Furthermore, the extended membrane system of the postsynaptic region of the electroplax remained always free of leed pyrophosphate precipitate.
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  • 8
    ISSN: 1432-2072
    Keywords: Muscimol, Ibotenic Acid, LSD ; Monoamine Concentrations in Brain ; 5-Hydroxyindoleacetic Acid ; p-Chlorophenylalanine ; Probenecid ; Turnover of Serotonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The concentrations of noradrenaline, dopamine and serotonin were measured in the brain of male albino mice and rats after intraperitoneal injections of muscimol, ibotenic acid or LSD. All three drugs induced a generalized increase of serotonin. When muscimol was administered to rats after pretreatment with p-chlorophenylalanine, a serotonin synthesis inhibitor, the serotonin concentration was still increased in midbrain and hypothalamus. Muscimol also caused a reduced accumulation of 5-hydroxyindoleacetic acid in rats pretreated with probenecid. There were differences in the action of the three compounds on the catecholamine concentration. Muscimol and LSD caused a decrease of the catecholamines. Ibotenic acid increased the catecholamine concentration. Certain topographical differences were noted. The increase in the serotonin concentration in the hypothalamus and midbrain after muscimol may be due to a reduced turnover of serotonin. An increase in serotonin concentration and a decrease of 5-hydroxyindolacetic acid in the rat brain are effects observed also with other psychotomimetic drugs such as LSD or psilocybin.
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  • 9
    ISSN: 1432-2072
    Keywords: Hashish extract ; Δ 9-Tetrahydrocannabinol ; Social learning model ; Submissive behavior ; Retention deficit ; State dependency ; Analgesia ; C3H mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of hashish extract on adaptive behavior of male mice were studied in a paradigm which allows the investigation of learning mechanisms in a social context. Mice of the C3H strain, which were not submissive in a confrontation with a nonaggressive DBA mouse on day 1, were defeated on day 2 over 3 min by aggressive, isolated DBA mice, and showed conditioned submissive behavior upon mere contact with a nonaggressive DBA mouse on day 3. A hashish extract containing 38.6–39.4% Δ 9-tetrahydrocannabinol (Δ 9-THC), 11.6–12.0% cannabinol and 47.7–48.5% cannabidiol was administered orally in all experiments. Hashish extract given 90 min before defeat on day 2, in dosages corresponding to 1, 5, and 10 mg Δ 9-THC/kg, impaired retention of defensive upright, defensive sideways and immobility on day 3 (experiment 1). Experiment 2 showed that the drug (5, and 10 mg Δ 9-THC/kg) had no antinociceptive potency in mice and did not modify defeat-induced analgesia. Experiment 3, with drug (5 mg Δ 9-THC/kg) or solvent administration on day 2 and day 3, showed that the retention deficit was neither due to state-dependent learning, nor to impaired retrieval. It is suggested that hashish extract administered before learning may interfere with memory processing.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 78 (1967), S. 261-266 
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung In den verschiedenen Zellarten im Gebiet der neuro-muskulären Synapsen des mit OsO4 fixierten Maus-Diaphragmas werden Mikropinozytose-Vesikel dargestellt, die durch eine besondere Membrandifferenzierung ausgezeichnet sind. Vorkommen, Feinstruktur und Entstehung dieser “coated vesicles” werden beschrieben. Ihre mögliche Funktion sowie die Bedeutung des Saumes werden in Zusammenhang mit der bereits vorliegenden Literatur diskutiert.
    Notes: Summary Coated vesicles were demonstrated in various cell types in the region of the neuro-muscular junctions of the mouse diaphragm fixed with osmium tetroxide. These vesicles are characterized by a membrane which is specially differentiated. The occurrence, fine structure, and formation of these coated vesicles are described; their possible function and the nature of the coat are discussed in the light of existing literature.
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