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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Molecular biological findings have indicated that the affinity and the density of presynaptic serotonin transporters may be subject to adaptive regulation, but the physiological conditions that may act to trigger such changes are presently unknown. By means of [3H]paroxetine binding to rat cortical membranes, we studied the influence of two physiological variables that are clearly associated with altered serotonergic activity—circadian rhythm and semistarvation—on KD and Bmax values of the serotonin transporter of the rat frontal cortex. No circadian fluctuations of both parameters were observed. Also, semistarvation (50% reduction of normal voluntary food intake) for 2 days had no effect on either KD or Bmax values of cortical [3H]paroxetine binding. Food restriction for either 7 days or 2 weeks, however, resulted in a significant, ∼30%, reduction of the density of cortical serotonin transporters with unchanged transporter affinity. These findings indicate that long-term changes in the density of cortical serotonin transporters can be induced by long-lasting alterations of certain environmental variables. Because the duration and the radius of action of presynaptically released serotonin are governed by the efficiency of the reuptake mechanism, such adaptive changes of serotonin transporter density must be expected to cause long-term alterations of the modulatory impact of the central serotonin system on certain brain functions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Serotonin (5-HT) is known to be readily oxidized and to act as a scavenger of reactive oxygen species produced, e.g., in the presence of peroxidase and H2O2 or during the respiratory burst of phagocytes. One major oxidation product formed under these conditions, the 5-HT dimer 5,5′-dihydroxy-4,4′-bitryptamine (DHBT), was suggested to have neurotoxic properties and to contribute to neuronal damage in neurodegenerative disorders. It is shown in the present study that the luminol-enhanced chemiluminescence signal measured after stimulation of the respiratory burst activity of cultivated rat microglial cells by the addition of phorbol 12-myristate 13-acetate is suppressed by 5-HT in a dose-dependent manner. During this process, 5-HT is oxidized to DHBT. Neither the intraventricular injection of DHBT nor the addition of DHBT to cultured astrocytes, neurons, or PC-12 cells was found to cause measurable cytotoxic effects. It is concluded that extracellular 5-HT locally released from platelets and 5-HT nerve endings at sites of brain damage or inflammation, through its suppressant effect on the release of reactive oxygen species during the respiratory burst of activated microglia, may contribute to attenuate secondary tissue damage in the CNS.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 19 (1995), S. 0 
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Polysomnographic sleep patterns and melatonin secretion were investigated in 10 patients (age: 41.3 ± 9.5 years) who suffered from chronic primary insomnia and complained predominantly about difficulties in maintaining sleep and in five healthy controls (age 27.2 ± 0.7 years). Nocturnal plasma melatonin concentrations were obtained hourly, measured by direct radioimmunoassay and statistically compared between insomniacs and controls with age as a covariate. Plasma melatonin levels in the patient group tended to begin increasing earlier in the evening and were significantly (P ± 0.01) lower during the middle of the night (peak value 82.5 ± 26.5 pg/ml) than in the healthy controls (peak value 116.8 ± 13.5 pg/ml). Among the patients, the most severely reduced nocturnal plasma melatonin levels were found in those patients with a history of sleep disturbance lasting for longer than five years (N = 6; age 41.8 ± 11.7 years; duration 15.3 ± 5.9 years; peak value 72.1 ± 25.0 pg/ml); whereas those chronic insomniacs affected for fewer than five years had relatively higher nocturnal levels (N = 4; age 40.6 ± 6.5 years; duration 3.8 ± 1.5 years; peak value 98.2 ± 23.9 pg/ml). These results show that the circadian rhythm of melatonin secretion is disturbed in patients with chronic primary insomnia, and that the nocturnal plasma melatonin secretion is increasingly more affected the longer the patients are unable to maintain a regular sleep pattern.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 25 (1998), S. 0 
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Rodenbeck A, Huether G, Rüther E, Hajak G. Altered circadian melatonin secretion patterns in relation to sleep in patients with chronic sleep-wake rhythm disorders. J. Pineal Res. 1998; 25:201–210. © Munksgaard, Copenhagen〈section xml:id="abs1-1"〉〈title type="main"〉AbstractHuman well-being depends on the entrainment of endogenous circadian rhythms of biological functions and the sleep-wake rhythm. Although the incidence of otherwise healthy subjects with chronically altered sleep-wake rhythms is rather low, the investigation of these patients provides new sights into circadian entrainment mechanisms. We therefore examined the circadian rhythm of circulating melatonin and the sleep-wake rhythm in five patients with chronic sleep-wake rhythm disorders and ten age-matched healthy controls. All patients showed altered circadian melatonin rhythm parameters in relation to their sleep-wake cycle compared to age-matched controls. These alterations were random, i.e., independent of the type, the duration, and the age of onset of the disorder. The melatonin onset to sleep onset interval varied between the patients and the melatonin acrophase to sleep offset interval was prolonged in four patients. These findings indicate individual phase relations between the circadian melatonin rhythm and the sleep-wake cycle in patients with chronic sleep-wake rhythm disorders. Since the prolonged melatonin acrophase to sleep offset interval was the most consistent finding independent of aetiological origins, this abnormality may be one possible maintaining factor in chronic sleep-wake rhythm disorders due to reduced phase-resetting properties of the circadian pacemaker. Furthermore, rather low circadian melatonin amplitudes and a subsensitivity to daylight may maintain the disorder in at least some patients.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 719 (1994), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 55 (1978), S. 55-62 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pattern of the multiple forms of the acetylocholinesterase (AChE, E.C. 3.1.1.7) of the rat brain is investigated using polyacrylamide gradient micro-gel electrophoresis with regard to a possible functional importance of this individual forms. The patterns of the AChE-forms of selected regions of the CNS are compared and certain differences could be shown. After increased cholinergic input (into the hippocampus by electrical stimulation of the nc. septi medialis) an aggregation of AChE subunits is detectable. Subletal intoxication with an irreversible inhibitor of AChE is followed by a faster recovery of the smaller forms. A suggestion of a possible functional role of the multiple forms of AChE is discussed.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A histochemical method for the demonstration of acetylcholinesterase using semipermeable membranes is described. This technique prevents any loss of enzyme activity caused by dissolution and/or fixation. The soluble and fixation-labile portions of acetylcholinesterase were estimated in several regions of the central nervous system of the rat and differences were found. The method improves the accuracy of the histochemical demonstration of the acetylcholinesterase on the light microscopical level.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 53 (1977), S. 317-325 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Micro-polyacrylamide gradient electrophoresis followed by active staining is applied for the demonstration of the multiple forms of acetylcholinesterase. Among other advantages the very small samples that enable the analysis of well-defined brain material as well as the almost histochemical conditions of incubation enable its successful use in topochemical investigations of the multiple form pattern of brain acetylcholinesterase. The acetylcholinesterase of bovine nc. caudatus could be separated into 4 multiple forms and the pattern was analysed microdensitometrically. These forms differ in their molecular weight as well as well as in their degree of membrane binding. Increasing ionic strength (NaCl) is followed by changes in the pattern. This result is discussed as caused by aggregation of enzyme subunits.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 49 (1976), S. 303-307 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The application of the semipermeable membrane technique in light microscopical demonstration of choline acetyltransferase is described. The method founds upon earlier developed lead salt techniques. Use of semipermeable membranes fully prevents any loss of enzyme by dissolvement or inactivation during fixation. Addition of NaCl to the incubation medium markedly increases the activity of choline acetyltransferase.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Neurochemical research 13 (1988), S. 617-620 
    ISSN: 1573-6903
    Keywords: Brain development ; free amino acids ; sensory stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Developing chicks were subjected to three different paradigmata of sensory stimulation, and the effects on the free amino acid concentrations in the blood and in various brain regions were monitored. The free amino acid pool of individual brain regions was found to be affected in a treatment-and age-specific manner. The increased neuronal activity resulting from sensory stimulation seems to affect intrinsic factors involved in the regulation of the free amino acid pool, most likely via modulations of the rate of metabolization of individual amino acids and/or of the rate of synthesis and degradation of individual proteins in certain brain regions.
    Type of Medium: Electronic Resource
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