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  • 1975-1979  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 25 (1975), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Cyclic 3′,5′-AMP (cAMP) and cyclic 3′,5′–GMP (cGMP) phosphodiesterase activities were found in human cerebrospinal fluid (CSF) using low substrate concentration (0.4μM). More rapid hydrolysis of cGMP than that of cAMP was observed in human CSF. However, cGMP hydrolytic activity of CSF was very much lower (0.3 pmol/min/ml CSF) than that of human cerebral cortex (33.7 nmol/min/g wet cortex). The pH optimum was found to be 8.0 (cGMP phosphodiesterase) and 7.5 (cAMP phosphodiesterase). The maximum stimulation of both cAMP and cGMP phosphodiesterase was achieved at 4 mM-MgCl2. Cyclic AMP had relatively little effect on the hydrolysis of cGMP in CSF and the cortex, while cGMP inhibited hydrolysis of cAMP in both tissues. Snake venom was found to stimulate cAMP and cGMP phosphodiesterase activity of CSF, by 60% and 110% respectively. This stimulation by snake venom was also observed in the cortex phosphodiesterase, but was not observed in human plasma or thyroid phosphodiesterase. When CSF was applied to Sepharose 6B column, cGMP phosphodiesterase was separated into three different molecular forms. A plot of activity against substrate concentration using peak I (largest molecular size) revealed a high affinity (Km= 2.6μM) and a low affinity (Km= 100μM) for cAMP suggesting the existence of at least two molecular forms of the enzyme. On the other hand, using a cGMP as substrate the only one Km value (1.90 μm) was obtained. These Km values of CSF enzymes described above were close to those obtained from human cerebral cortex preparations. The enzyme under peak I corresponded to the cortex enzyme when judged from its molecular size and stimulation by snake venom. It seems likely from our results that at least a part of CSF phosphodiesterase originates from the central nervous system.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neural transmission 44 (1979), S. 287-295 
    ISSN: 1435-1463
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Dopamine (DA) sensitive adenylate cyclase activity was measured in homogenates of caudate nucleus and putamen from frozen brain of eight Parkinsonian patients and nine controls. In the control group, there was no difference in enzyme activity in respect to sex or age (21–77 years old). Caudate nucleus and putamen exhibited similar mean activity. In the Parkinsonian group, there was a significant decrease in both basal (by 50%) and DA stimulated (by 80%) activities compared with that of control group. This suggests that there may exist a functional disturbance in the postsynaptic (post-DA-nergic) region in the striatum of patients with Parkinson's disease; in addition, the decrease in basal as well as DA stimulated activity as measured in homogenates may not be the biochemical substrate for the hypothetical “denervation super-sensitivity” expected to occur in Parkinson's disease.
    Type of Medium: Electronic Resource
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