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  • 1
    ISSN: 1432-0738
    Keywords: Organophosphate Intoxication ; Nitrostigmine ; Acetylcholine (ACh) ; Acetylcholinesterase (AChE) Activity ; Organophosphatvergiftung ; Nitrostigmin ; Acetylcholin (ACh) ; Acetylcholinesterase (AChE)-Aktivität
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 4 Patienten mit schwerer Nitrostigminvergiftung wurden die Konzentrationen von Acetylcholin und Nitrostigmin sowie die Aktivität der Acetylcholinesterase bestimmt. In der akuten Phase der Vergiftung wurden Acetylcholinspiegel bis zu 36 und 55 ng/ml Plasma bzw. Liquor cerebrospinalis gemessen. Zum gleichen Zeitpunkt konnte keine Acetylcholinesteraseaktivität im Plasma und Erythrocyten festgestellt werden. Die Aktivität der Acetylcholinesterase kehrte am Ende der 2. Woche wieder. Im Plasma waren Nitrostigminspiegel zwischen 409 und 86 ng/ml während der ersten 3 Tage meßbar. Nitrostigmin konnte im Plasma bis zum Ende der 3. Woche in einer Konzentration von etwa 1 ng/ml nachgewiesen werden. Als Ursache dafür werden Umverteilung aus dem Fettgewebe und Nachresorption angenommen. Die Befunde werden in Relation zum klinischen Bild besprochen.
    Notes: Abstract Concentrations of acetylcholine and nitrostigmine as well as acetylcholinesterase activity were determined in 4 patients with severe nitrostigmine intoxication. In the acute phase of the intoxication, acetylcholine levels up to 36 and 55 ng/ml were found in blood plasma and cerebrospinal fluid, respectively. At the same time no activity of acetylcholinesterase in plasma and erythrocytes was detected. Acetylcholinesterase activity gradually recovered at the end of the second week. In the first 3 days after the ingestion plasma nitrostigmine concentrations ranged from 409 to 86 ng/ml. At the end of the third week nitrostigmine was still found in a concentration of about 1 ng/ml plasma. Redistribution from fatty tissue and slow gastro-intestinal absorption may be responsible for the persistence of nitrostigmine in the blood. The findings are discussed in relation to the clinical course.
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  • 2
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Der ACh-Gehalt verschiedener höherer Pflanzen wurde mit einer gaschromatographischen Methode bestimmt. Die Identifizierung des in den Pflanzen vorkommenden ACh erfolgte durch hochspannungselektrophoretische Auftrennung des pflanzlichen Extraktes und nachfolgender Gas-Chromatographie. Der Spross enthält mehr ACh als die Wurzel. In etiolierten Pflanzen war kein ACh nachweisbar. Es wird vermutet, dass der endogene ACh-Gehalt durch Licht reguliert wird.
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Physiology-Paris 87 (1993), S. 77-81 
    ISSN: 0928-4257
    Keywords: acetylcholine release ; ileum ; muscarinic autoreceptors ; trachea
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
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  • 4
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The acetylcholine-rich myenteric plexus-longitudinal muscle preparation of the guinea-pig small intestine has been subjected to subcellular fractionation using modifications of both classical methods and that originally devised for bulk isolation of cholinergic synaptic vesicles from the electromotor nerve terminals of Torpedo marmorata by means of density gradient centrifugation in a zonal rotor. The latter method gave a vesicle fraction with the highest acetylcholine content so far recorded for a mammalian particulate fraction, 30.9 × S.E.M. 1.8 (5) nmol of acetylcholine × mg of protein−1. Electron-microscopical examination showed that it consisted of a homogeneous preparation of vesicles of mean spherical diameter 61 ×sd 4 (108) nm, with little or no contamination with other lipoprotein membrane structures, mixed how-ever with considerable amounts of actomyosin fibrils, presumably derived from the longitudinal muscle. Slab-gel electrophoresis in sodium dodecyl sulphate showed that, in addition to prominent peaks attributable to actin and myosin, there was a relatively simple pattern of (presumably) vesicle protein among which all the proteins thought to be characteristic of Torpedo synaptic vesicles were present. Dowe G. H. C. et al. Isolation of cholinergic synaptic vesicles from the myenteric plexus of guinea-pig small intestine. J. Neurochem.35, 993–1003 (1980).
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 21 (1973), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The distribution of ACh in the rabbit heart was investigated by a modified gas chromatographic estimation method. ACh was extracted with perchloric acid, precipitated as reineckate and demethylated with sodium benzenethiolate. The tertiary amines derived from ACh and other choline esters were concentrated by a microdistillation procedure. Gas chromatography was performed using a nitrogen selective detector. In the range of concentrations between 0.4 and 2.5 nmol ACh per tissue sample the coefficient of variation was 5.2 per cent. The recovery of ACh added to heart extracts was 101 per cent. Evidence for the identity of the choline ester isolated from rabbit hearts and authentic ACh was obtained by equal retention times and by correspondence of the ratio N/C of the respective tertiary amines. Parallel measurements using gas chromatography and bioassay on the rat blood pressure yielded closely corresponding values of ACh levels in the rabbit heart. The concentration of ACh was much higher in the atria than in the ventricles. In both atria, and ventricles the ACh concentration was higher in the right than in the left part of the rabbit heart. Endogenous propionylcholine or butyrylcholine were not detected.
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  • 6
    ISSN: 1432-1912
    Keywords: Isolated Perfused Rat Brain ; Acetylcholine ; Physostigmine ; Oxotremorine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ACh content of the isolated perfused rat brain as well as that of the rat brain in vivo was determined by gas chromatography. After a perfusion period of 30 min the endogenous ACh content of the isolated brain was significantly higher than that of the brain in vivo. Physostigmine caused a rise in the ACh concentration of both the isolated brain and the brain in vivo. Oxotremorine produced an increase in the ACh content in the brain in vivo, but not in the isolated brain after appropriate dosage. The concentration of the drugs in the perfusion medium of the isolated brain was so that distinct EEG changes could be observed but spontaneous electrical activity could be maintained during the whole perfusion period.
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  • 7
    ISSN: 1432-1912
    Keywords: Myenteric plexus ; Choline ; Presynaptic muscarine receptors ; Acetylcholine release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of exogenous choline on the outflow of 3H-acetylcholine evoked by field stimulation was studied on the myenteric plexus-longitudinal muscle preparation of the guinea pig. Choline at concentrations of 100 μM and higher depressed the evoked outflow of 3H-acetylcholine in a concentration-dependent manner. The EC 50 for the inhibitory action was 300 μM. Scopolamine (10 nM) antagonized the effect of choline which indicates that the inhibition of 3H-acetylcholine outflow is mediated by muscarine receptors. The findings imply that choline at high concentrations does not improve cholinergic synaptic neurotransmission in tissues that are endowed with presynaptic muscarine receptors (e.g. myenteric and central cholinergic neurones). Furthermore, it is suggested that the increase in tissue acetylcholine content that has been observed after choline administration is probably due to the depression of acetylcholine release.
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  • 8
    ISSN: 1432-1912
    Keywords: GABA ; Guinea-pig ileum ; Acetylcholine release ; Bicuculline ; Picrotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The effects of GABA on release of acetylcholine and on contractility of the smooth muscle were studied in the myenteric plexus-longitudinal muscle preparation of the guinea pig. Acetylcholine was determined as radiolabelled transmitter from strips preloaded with 3H-choline. 2. GABA (1–300 μM) caused an increase in resting tension of smooth muscle as well as an increase in release of acetylcholine that was considerably reduced by tetrodotoxin. The facilitation by GABA of acetylcholine release exhibited a marked tachyphylaxis. The increase in muscle tension was clearly related to the increase in acetylcholine release. Muscimol (0.1–10 μM) also enhanced the release of acetylcholine. The effects of GABA on acetylcholine release and on longitudinal muscle contraction were competitively antagonized by bicuculline and picrotoxin. 3. GABA (1–300 μM) inhibited both release of acetylcholine and contractions evoked by electrical stimulation. Muscimol (1, 10 μM) did not modify the evoked release. The inhibitory effects of GABA were not antagonized by bicuculline or picrotoxin. 4. It is suggested that GABA facilitates and inhibits acetylcholine release, and in turn intestinal motility via two receptors with different pharmacological properties.
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  • 9
    ISSN: 1432-1912
    Keywords: Guinea-pig myenteric plexus ; Acetylcholine release ; Frequency dependence ; Presynaptic muscarine receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The effects of scopolamine on the release of 3H-acetylcholine (ACh) from the guinea-pig myenteric plexus were studied at different stimulation frequencies (0.03–10 Hz) and train lengths (1–180 pulses). Release of 3H-ACh was measured in the absence of cholinesterase inhibitors as the outflow of tritium from myenteric plexus-longitudinal muscle preparations preloaded with 3H-choline. 2. In control experiments the volley output of 3H-ACh declined with increasing train length and increasing stimulation frequency. Stimulation by one pulse produced the highest volley output. 3. Scopolamine facilitated the evoked output of 3H-ACh via blockade of presynaptic muscarine receptors. A significant increase was already observed when the preparation was stimulated with 3 pulses at 10 Hz which indicates that the inhibitory muscarinic mechanism becomes operational within 200 ms. The facilitatory effects of scopolamine depended on both train length and frequency of stimulation. Maximal increases in 3H-ACh output were seen with brief trains (3 and 6 pulses) at a high frequency (10 Hz), or with longer trains (20 and 180 pulses) at lower frequencies (0.3 and 1 Hz). 4. Scopolamine compensated for the frequencydependent decline of 3H-ACh volley output only during brief periods of stimulation (3 and 6 pulses). It is therefore concluded that the decline in volley output during the first few pulses of a train is due to the negative feedback mechanism which is activated by the transmitter released by the preceding impulses. With longer trains of stimulation the negative feedback mechanism plays only a minor role in regulating the output per pulse.
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  • 10
    ISSN: 1432-1912
    Keywords: Guinea-pig ileum ; Release of [3H]acetylcholine ; Autoreceptors ; Heteroreceptors ; Intraneuronal availability of calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The inhibition by three modulators (oxotremorine, noradrenaline, morphine) of acetylcholine release from the myenteric plexus preincubated with [3H]choline was investigated at different stimulation frequencies and calcium concentrations. Moreover, [3H]acetylcholine release evoked by a low (0.1 Hz) or a high (10 Hz) stimulation rate was investigated at different calcium concentrations either in the absence or presence of scopolamine. A reduced calcium concentration (0.6 mmol/l) inhibited acetylcholine release more at 0.1 Hz (74% ± 3%) than at 10 Hz (44% ± 8%). Scopolamine enhanced the stimulated acetylcholine release at a calcium concentration of 1.8 mmol/l. At calcium concentrations higher than 1.8 mmol/l scopolamine failed to enhance transmitter release markedly. A reduction of the calcium concentration (〈 1.8 mmol/l) significantly enhanced the effect of scopolamine, when acetylcholine release was evoked at 0.1 Hz. Oxotremorine (10 μmol/l) completely suppressed acetylcholine release at 1 Hz (120 pulses). When 120 pulses were applied at 10 Hz the maximal effect was only a 64% inhibition and the concentration-response curve was significantly shifted to the right. However, after a reduction of both the train length or the calcium concentration oxotremorine produced a complete inhibition of acetylcholine release evoked at 10 Hz. In contrast to the effect of oxotremorine, the concentration-response curves for morphine and noradrenaline were similar at 1 Hz and 10 Hz. Following conclusions can be drawn: 1. The present findings fit into the concept that residual calcium accumulates in the nerve terminal during 10 Hz stimulation. 2. The results obtained with scopolamine and oxotremorine are consistent with the view that muscarine autoreceptor activation triggers a reduction of the intraneuronal availability of calcium for the stimulus-secretion coupling. 3. The presynaptic effect of morphine and partly that of noradrenaline might be mediated by a different mechanism, probably by a reduction of release sites.
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