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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 14 (1967), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 12 (1965), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 15 (1968), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The glutamic acid decarboxylase has been purified from the lobster central nervous system. Potassium ion (0-075 m) and β-mercaptoethanol (0-025 m) were essential for enzyme activity. Enzyme had about 60 per cent of its optimal activity in the absence of added pyridoxal phosphate. Carbonyl reagents (10−4m-hydroxylamine or amino oxyacetic acid) would abolish this residual activity. The pH optimum of the enzyme was about 8-0.Standard Michaelis-Menten kinetics were applied to the decarboxylation of glutamate and a Km of 0.02 m was calculated. GABA inhibited the reaction (Ki= 1.25 × 10−3m), but the inhibition showed anomalous behaviour when graphed by the method of Lineweaver and Burk (1934). The GABA inhibition resembled competitive inhibition, but curves rather than straight lines intersecting at a common point on the velocity axis were obtained. This effect remains unexplained.Preliminary studies failed to reveal any subunit structure of the enzyme. The sedimentation coefficient (.S20.w) was 6-55 in a sucrose density gradient in an ultracentrifuge. This was unchanged by the addition of any of the agents that influence enzyme activity.The subcellular localization of the decarboxylase was explored in crude homogenates of lobster central nervous system prepared in various ways. The major proportion (about 90 per cent) of the enzyme activity was in the soluble fraction.‘Particulate’enzyme could be prepared, but gentle suspension of this material in buffer liberated most of the activity.A contaminant in the radioactive substrates led to the production of radioactive GABA without the simultaneous evolution of CO2. In this case, GABA production required active enzyme but was not an exclusive property of the glutamic decarboxylase activity.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 15 (1968), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The lack of information on the mechanism of inactivation of the crustacean neuromuscular inhibitory transmitter compound prompted a study of the disposition of radioactive γ-aminobutyric acid (GABA) in lobster nerve-muscle preparations.A specific GABA transport system was found. Radioactive GABA was concentrated by the tissues to levels several times those in the medium, and net uptake could be demonstrated. The process was dependent on sodium ions in the medium; neither lithium nor choline could substitute for sodium. Incubations with increasing GABA concentrations indicated that uptake was a saturable mechanism with an apparent Km of 5.8 × 10−5m.Of many compounds tested, only desmethylimipramine, chlopromazine (and several related compounds), and certain close structural analogues (guanidinoacetic acid, β-guani-dinopropionic acid and,β-hydroxy-GAB A) were effective inhibitors of uptake. The inhibition with all these compounds, however, was at high concentrations (5 × 10−4 to 10−3m) which limited their usefulness for physiological studies.A separate uptake mechanism for glutamate was found in the lobster nerve-muscle preparations. This process was not described in detail, but certain properties are similar to those of the GABA transport system.The cellular location of the GABA uptake system remains unknown. By analogy with noradrenaline inactivation, however, it is postulated that uptake could serve to terminate the physiological actions of GABA by rapidly removing it from its sites of action in synaptic clefts.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Acetylcholine, its precursor (choline), and the enzymes of its biosynthesis and degradation (choline acetyltransferase and acetylcholinesterase, respectively) have been studied and quantified in extracts of several regions of the nervous system of the lobster and in single, isolated axons of identified efferent excitatory, efferent inhibitory and afferent sensory neurons. The choline acetyltransferase is a soluble enzyme similar to that from other species. The predominant acetylcholine-hydrolysing enzyme is largely membrane-bound and has been characterized as a specific acetylcholinesterase. A single peak of acetylcholinesterase activity can be detected upon velocity sedimentation analysis of Triton X-100-treated extracts of all regions of the nervous system. Choline acetyltransferase distribution parallels that of sensory neural elements, and its specific activity shows nearly a 500-fold difference from the richest to the poorest neural source. Acetylcholinesterase levels span only a 23-fold range, and activity is found in all neural regions, including those free of known sensory components. A radiochemical microassay for choline and acetylcholine in the range of 20–2000 pmol is described in detail. All 3 types of axons contain comparable levels of choline (ca. 2 pmol/μg protein), but acetylcholine is asymmetrically distributed. Efferent axons contain no detectable acetylcholine, while sensory axons from abdominal muscle receptor organs have an average of 1·9 pmol/μg protein. Choline acetyltransferase is similarly distributed; sensory axons show at least 500-fold greater activity than efferent axons. Acetylcholinesterase is nearly uniformly distributed among the three types of fibres. These results are discussed in terms of a general view of transmitter accumulation in single neurons.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 14 (1967), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 22 (1957), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Archives of Biochemistry and Biophysics 59 (1955), S. 260-268 
    ISSN: 0003-9861
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Archives of Biochemistry and Biophysics 53 (1954), S. 327-332 
    ISSN: 0003-9861
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 186 (2000), S. 221-238 
    ISSN: 1432-1351
    Keywords: Key words Amine neurons ; Aggression ; Lobster ; Neurohormone ; Serotonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The amine serotonin has been suggested to play a key role in aggression in many species of animals, including man. Precisely how the amine functions, however, has remained a mystery. As with other important physiological questions, with their large uniquely identifiable neurons, invertebrate systems offer special advantages for the study of behavior. In this article we illustrate that principal with a description of our studies of the role of serotonin in aggression in a lobster model system. Aggression is a quantifiable behavior in crustaceans, the amine neuron systems believed to be important in that behavior have been completely mapped, and key physiological properties of an important subset of these neurons have been defined. These results are summarized here, including descriptions of the “gain-setter” role and “autoinhibition” shown by these neurons. Results of other investigations showing socially modulated changes in amine responsiveness at particular synaptic sites also are described. In addition, speculations are offered about how important developmental roles served by amines like serotonin, which have been well described by other investigators, may be related to the behaviors we are examining. These speculations draw heavily from the organizational/activational roles proposed for steroid hormones by Phoenix et al. (1959).
    Type of Medium: Electronic Resource
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