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71.
72.
D. Landowne 《The Journal of membrane biology》1987,96(3):277-281
Summary In 10 K artificial seawater (ASW). D2O replacement reduced the Na efflux of squid axons by about one third. In 0 K ASW, D2O replacement had little effect. D2O reduced the K+ sensitivity of the efllux but increased the affinity for K+. A 4° decrease in temperature mimicked the effects of D2O. When axons were injected with arginine, to decrease the ATP/ADP ratio, they lost K+ sensitivity in normal ASW, as expected. Their efflux into 0 K ASW became D2O sensitive. The results are discussed in terms of conformational changes in the Na pump molecular complex. 相似文献
73.
In vitro pathogenicity tests demonstrated that Hirschmanniella caudacrena is pathogenic to Ceratophyllum demersum (coontail). Symptoms were chlorotic tissue, deformed stems, and, finally, death of the plant. Inoculum densities of 500 nematodes per 5-cm-long cutting in a test tube containing 50 ml of water resulted in death and decay of some of the cuttings within 8 weeks; 100 nematodes killed the plants in 12 weeks, and 50 and 25 nematodes killed them in 16 weeks. The lowest inoculum level of 10 nematodes did not seriously affect the plants at 16 weeks when the experiment was terminated. A second test conducted outdoors in glass jars containing 3 liters of water and two cuttings weighing a total of 15 g fresh weight showed damage, but results were not statistically significant. Hydrilla verticillata inoculated with H. caudacrena was not affected seriously. 相似文献
74.
Phosphorylation and Inactivation of Brain Glycogen Synthase by a Multifunctional Calmodulin-Dependent Protein Kinase 总被引:1,自引:1,他引:0
Nobuhiro Inoue Takafumi Iwasa Kohji Fukunaga Yasuhiko Matsukado Eishichi Miyamoto 《Journal of neurochemistry》1987,48(3):981-988
Glycogen synthase was partially purified from canine brain to about 70% purity. The purified enzyme showed differences from the properties of the skeletal muscle enzyme with respect to molecular weights of the holoenzyme and subunit and phosphopeptide mapping. The multifunctional calmodulin-dependent protein kinase from the brain phosphorylated brain glycogen synthase with concomitant inactivation of the enzyme. Although about 1.3 mol of phosphate/mol subunit was maximally incorporated into glycogen synthase, 0.4 mol of phosphate/mol subunit was sufficient for the maximal inactivation of the enzyme. The results indicate that brain glycogen synthase is regulated in a calmodulin-dependent manner similarly to the skeletal muscle enzyme, but that the brain enzyme is different from the skeletal muscle enzyme. 相似文献
75.
Tyrosine hydroxylase purified from rat pheochromocytoma was phosphorylated and activated by purified cyclic GMP-dependent protein kinase as well as by cyclic AMP-dependent protein kinase catalytic subunit. The extent of activation was correlated with the degree of phosphate incorporated into the enzyme. Comparable stoichiometric ratios (0.6 mol phosphate/mol tyrosine hydroxylase subunit) were obtained at maximal concentrations of either cyclic AMP-dependent or cyclic GMP-dependent protein kinases. The enzymes appeared to mediate the phosphorylation of the same residue based on the observation that incorporation was not increased when both enzymes were present. The major tryptic phosphopeptide obtained from tyrosine hydroxylase phosphorylated by each protein kinase exhibited an identical retention time following HPLC. The purified phosphopeptides also exhibited identical isoelectric points. These data provide support for the notion that the protein kinases are phosphorylating the same residue of tyrosine hydroxylase. 相似文献
76.
O. Carter Snead III 《Journal of neurochemistry》1987,48(1):196-201
The presence of gamma-hydroxybutyric acid (GHB) in synaptosome-enriched fractions of rat brain was ascertained using a GLC technique. The stability of GHB in synaptosomes was evaluated by addition of various gamma-aminobutyric acid (GABA) transaminase (GABA-T) inhibitors, GHB, or ethosuximide to the homogenizing medium. Furthermore, changes in whole brain GHB levels were compared with those in the synaptosomal fraction in animals treated with GABA-T inhibitors, GABA, or ethosuximide. GHB was present in synaptosome-enriched fractions in concentrations ranging from 40 to 70 pmol/mg of protein. There was no evidence for redistribution, leakage, or metabolism of GHB during the preparation of synaptosomes. The elevations of whole brain GHB level associated with GABA-T or ethosuximide treatment were reflected by a parallel increase in synaptosomal GHB content. These data add to the growing evidence that GHB may have neurotransmitter or neuromodulator function. 相似文献
77.
Stimulatory Effect of the D2 Antagonist Sulpiride on Glucose Utilization in Dopaminergic Regions of Rat Brain 总被引:1,自引:0,他引:1
Gilberto Pizzolato Timothy T. Soncrant Denise M. Larson Stanley I. Rapoport 《Journal of neurochemistry》1987,49(2):631-638
Local cerebral glucose utilization (LCGU) was measured, using the quantitative autoradiographic [14C]2-deoxy-D-glucose method, in 56 brain regions of 3-month-old, awake Fischer-344 rats, after intraperitoneal administration of sulpiride (SULP) 100 mg/kg. SULP, an "atypical" neuroleptic, is a selective antagonist of D2 dopamine receptors. LCGU was reduced in a few nondopaminergic regions at 1 h after drug administration. Thereafter, SULP progressively elevated LCGU in many other regions. At 3 h, LCGU was elevated in 23% of the regions examined, most of which are related to the CNS dopaminergic system (caudate-putamen, nucleus accumbens, olfactory tubercle, lateral habenula, median eminence, paraventricular hypothalamic nucleus). Increases of LCGU were observed also in the suprachiasmatic nucleus, lateral geniculate, and inferior olive. These effects of SULP on LCGU differ from the effects of the "typical" neuroleptic haloperidol, which produces widespread decreases in LCGU in the rat brain. Selective actions on different subpopulations of dopamine receptors may explain the different effects of the two neuroleptics on brain metabolism, which correspond to their different clinical and behavioral actions. 相似文献
78.
Heimo Haikala 《Journal of neurochemistry》1987,49(4):1033-1041
Abstract: A novel type of rotating disc electrode and a flow cell with laminar flow pattern were developed and applied to the electrochemical detection of dopamine, 3,4-dihy-droxyphenylacetic acid, homovanillic acid, 3-methoxytyra-mine (3-MT), noradrenaline, 3-methoxy-4-hydroxyphenyl-ethyleneglycol (MOPEG), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid after HPLC of these compounds. The active surface of the rotating disc working electrode was made from solid paraffin (40%; wt/wt) and graphite powder (60%; wt/wt). The sensitivity of the detector was proportional to the square root of the angular velocity and was practically independent of the flow rate of the mobile phase. The surface of the working electrode was very large (radius = 12 mm), and so the percentage of oxidation was 24–67%; (flow rate = 1.0 ml/min), depending on the compound. Electrical noise between 20 and 40 pA and background current of 20–60 nA were observed. In practice, the sensitivity for the detection of the compounds examined here was 8–16 nA/ng, and so a detection limit of 5 pg/injection could be achieved, when the detector was combined with reversed-phase HPLC. Supernatants obtained from the extracts of the tissue samples (nine brain parts of rat brain were studied) were purified by using Sephadex G-10 gel chromatography. Before this procedure, the proteins of the tissue extracts were precipitated by 0.2 M HC1O4, and the excess of HC1O4 was precipitated by KOH/HCOOH buffer. Simultaneously, the pH of the extracts was set to 2.4 by the above buffer. Adjustment of the pH was necessary so that elution of 5-HT from the Sephadex G-10 columns in the same fraction with 3-MT was avoided. If these compounds were in the same solution, their peaks would overlap on HPLC. MOPEG sulfate was purified by diethylaminoethyl-Sephadex A-25 (anion exchange resin) from the first fraction collected from the Sephadex G-10 columns. The contents of the compounds under investigation in nine brain parts agreed with those found by other investigators. 相似文献
79.
To investigate aspects of the biochemical nature of membrane-bound dopamine D1 receptors, rat striatal homogenates were pretreated with heavy metal cations and some other chemical agents, and their effects on D1 receptors were subsequently determined using a standard [3H](R)-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1-N-3- benzazepine([3H]SCH 23390) binding assay. Incubation of striatal membranes with as little as 1 microM Hg2+, 10 microM Cu2+, and 10 microM Cd2+ completely prevented specific [3H]SCH 23390 binding. The effect of Cu2+, 1.5 microM, was noncompetitive in nature, whereas 3-5 microM Cu2+ afforded mixed-type inhibition. The inhibitory effect of Cu2+ was fully reversed by dithiothreitol (0.1-1 mM). Cu2+ (2 microM) did not affect the affinity of cis-flupenthixol or clozapine for remaining [3H]SCH 23390 sites. A second series of cations, Co2+ (30 microM), Ni2+ (30 microM), Mn2+ (1 mM), Ca2+ (25 mM), and Ba2+ (20 mM), inhibited specific [3H]SCH 23390 binding by 50% at the concentrations indicated. The thiol alkylating reagent N-ethylmaleimide (NEM) (0.2 mM) reduced specific binding by 70%. The effect of NEM was completely prevented by coincubation with a D1 receptor saturating concentration of SCH 23390 (20 nM) or dopamine (10 microM). The results indicated that the dopamine D1 receptor is a thiol protein and that a thiol group is essential for the ligand binding. 相似文献
80.
Pertussis Toxin Attenuates D2 Inhibition and Enhances D1 Stimulation of Adenylate Cyclase by Dopamine in Rat Striatum 总被引:2,自引:1,他引:1
The response of adenylate cyclase to GTP and to dopamine (DA) was investigated in synaptic plasma membranes isolated from rat striatum injected with pertussis toxin, which inactivates the inhibitory guanine nucleotide-binding regulatory protein (Ni) of adenylate cyclase. Pertussis toxin treatment reverted the inhibitory effects on the enzyme activity elicited by micromolar concentrations of GTP and reduced by 50% the DA inhibition of cyclase activity via D2 receptors. The toxin treatment enhanced the net stimulation of enzyme activity by DA in the presence of micromolar concentrations of GTP. However, the stimulatory effect of the selective D1 receptor agonist SKF 38393 was not significantly affected. The data indicate that Ni mediates D2 inhibition of striatal adenylate cyclase and participates in the modulation of D1 stimulation of the enzyme activity by DA. 相似文献