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991.
Germinating seed ofDalbergia dolichopetala converted both [2H5]l-tryptophan and [2H5]indole-3-ethanol to [2H5]indole-3-acetic acid (IAA). Metabolism of [2-14C]IAA resulted in the production of indole-3-acetylaspartic acid (IAAsp), as well as several unidentified components, referred to as metabolites I, II, IV and V. Re-application of [14C]IAAsp to the germinating seed led to the accumulation of the polar, water-soluble compound, metabolite V, as the major metabolite, together with a small amount of IAA. Metabolites I, II and IV were not detected, nor were these compounds associated with the metabolism of [2-14C]IAA by shoots and excised cotyledons and roots from 26-d-oldD. dolichopetala seedlings. Both shoots and cotyledons converted IAA to IAAsp and metabolite V, while IAAsp was the only metabolite detected in extracts from excised roots. The available evidence indicates that inDalbergia, and other species, IAAsp may not act as a storage product that can be hydrolysed to provide the plant with a ready supply of IAA.Abbreviations HPLC-RC
high-performance liquid chromatography-radiocounting
- IAA
indole-3-acetic acid
- IAAsp
indole-3-acetylaspartic acid
- IAlnos
2-O-indole-3-acetyl-myo-inositol
- IEt
indole-3-ethanol 相似文献
992.
I. L. Sun W. Toole-Simms F. L. Crane D. J. Morré H. Löw J. Y. Chou 《Journal of bioenergetics and biomembranes》1988,20(3):383-391
Retinoic acid inhibits the reduction of diferric transferrin through the transplasma membrane electron transport system on fetal rat liver cells infected with a temperature-sensitive SV40 virus when the cells are in the nontransformed state cultured at 40°C. When the cells are in the transformed state (grown at the permissive 33°C temperature), retinoic acid does not inhibit the diferric transferrin reduction. Inhibition of activity of nontransformed cells is specific for retinoic acid with only slight inhibition by retinol and retinyl acetate at higher concentrations. Isolated rat liver plasma membrane NADH diferric transferrin reductase is also inhibited by retinoic acid. The effect of transformation with SV40 virus to decrease susceptibility to retinoic acid inhibition stands in contrast to much greater adriamycin inhibition of diferric transferrin reduction in the transformed cells than in nontransformed cells. 相似文献
993.
Aromatic l-Amino Acid Decarboxylase Activity of the Rat Retina Is Modulated In Vivo by Environmental Light Maria Hadjiconstantinou 总被引:2,自引:1,他引:2
Zvani Rossetti Christopher Silvia Dimitrij Krajnc Norton H. Neff 《Journal of neurochemistry》1988,51(5):1560-1564
Aromatic L-amino acid decarboxylase (AAAD) activity of rat retina is low in animals placed in the dark. When the room lights are turned on, activity rises for almost 3 h and reaches values that are about twice the values found in the dark. A study of the kinetics of the enzyme revealed that the apparent Km values for L-3,4-dihydroxyphenylalanine and pyridoxal-5'-phosphate were unchanged in light- and dark-exposed animals, whereas the Vmax increased in the light. Treating the animals with cycloheximide before exposure to light prevented the increase of enzyme activity. Immunotitration with antibodies to AAAD suggested that more enzyme molecules are present in the light than in the dark. When the room lights are turned off AAAD activity drops rapidly at first and then more slowly, suggesting that at least two processes are responsible for the fall of enzyme activity. Exposure to short periods of dark followed by light results in a rapid increase of AAAD activity. Mixing homogenates from light- and dark-exposed rats results in activity values that are less than expected, suggesting the presence of an endogenous inhibitor(s). These studies demonstrate that AAAD activity is modulated in vivo. 相似文献
994.
Glutamic acid decarboxylase (GAD), gamma-[3H]-aminobutyric acid [( 3H]GABA) high-affinity uptake into synaptosomes, and endogenous GABA content were measured in the rat striatum 2-3 weeks following 6-hydroxydopamine injection in the ipsilateral substantia nigra to destroy the nigrostriatal dopaminergic pathway and after kainic acid injection into the centromedial-parafascicular complex of the ipsilateral thalamus to lesion the thalamostriatal input. Both lesions resulted in apparent GAD increase concomitant with a decreased [3H]GABA uptake into striatal synaptosomes. GABA content was increased selectively following the dopaminergic lesion. Kinetic analysis of the uptake process for [3H]GABA showed selectively a decreased Vmax following the dopaminergic lesion; in animals with thalamic lesion, however, the change only concerned the Km, which showed a decreased affinity of the transport sites for [3H]GABA. Determination of Km and Vmax for GAD action on its substrate glutamic acid showed an increased affinity of GAD for glutamic acid in the case of the dopaminergic lesion without any change in Vmax, whereas the thalamic lesion resulted in GAD increase concomitant with a selective increase in Vmax. These data suggest that striatal GABA neurons are under the influence of nigrostriatal dopaminergic neurons which may reduce the GABA turnover, whereas the exact nature of the powerful control also revealed on these neurons following thalamic lesion remains to be determined. Both lesions induced adaptive neurochemical responses of striatal GABA neurons, possibly reflecting in the case of the dopaminergic deprivation an increased GABA turnover. 相似文献
995.
Vinayak N. Damle Margaret McLaughlin Arthur Karlin 《Biochemical and biophysical research communications》1978,84(4):845-851
Bromoacetyl[methyl-3H]choline is a highly specific label for the reduced acetylcholine binding site on the acetylcholine receptor from . Only one of two binding sites per receptor monomer is susceptible to labeling. The labeled site is on the α chain of the receptor. 相似文献
996.
The anion permeability of membrane vesicles prepared from the electric organ of was inhibited by the addition of 4,4′-diisothiocyano-stilbene-2,2′-disulfonic acid (DIDS). The permeability was measured by measuring changes in the scattered-light intensity caused by the osmotic volume change of vesicles; and also by the efflux measurement of ions from the vesicles using radioisotopes. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of membrane vesicles treated with dihydro analog of DIDS ([3H]H2DIDS) showed that the H2DIDS binding protein has a molecular weight of 180,000, and exists in membrane vesicles as a dimer formed by a disulfide bond between monomers of molecular weight 90,000. 相似文献
997.
Abstract: Estimates have been made of the amounts and rates of uptake of radioactive branched-chain i-amino acids, L-phenylalanine, and L-glutamine into incubated rat brain cortex slices. Estimates have also been made of the binding of these amino acids to brain cell fragments. It is shown that such binding, as well as the process of passive diffusion, is not affected by the presence of ouabain (0.2 mM), which suppresses the energy-dependent concentrative uptakes of the amino acids investigated. The maximum specific binding of L-glutamine is about three times that of the other amino acids and amounts to about 11% of the total uptake of the amino acid by rat brain cortex slices in 12 min from a medium containing 0.25 mM-glutamine. The sodium-ion concentration of the medium appears not to play a significant role in determining the rate of L-glutamine uptake in brain slices except at relatively low concentrations (<20 mequiv./l). The presence of Na+ , however, is essential for the attainment of a tissue-to-medium concentration ratio greater than 2.0 for L-glutamine. At relatively low concentrations (0.25 mM) the rapidity of uptake of L-glutamine into a suspension of nerve terminals exceeds that into brain cortex slices. The uptakes of L-glutamine (Km 's = 0.66 mM and 2.25 mM) and of the branched chain L-amino acids (Km 's approx. 0.3 mM and 2 mM) by rat brain cortex slices are characterized by a double affinity system, but that of L-phenylalanine has only one affinity system (Km = 0.23 mM). The Km 's have been calculated after subtracting the ouabain-insensitive passive uptakes of the amino acids from the total observed uptakes. 相似文献
998.
傅家瑞 《植物生理与分子生物学学报》1985,(1)
水浮莲种子是一种奇特的需光种子。在黑暗中,GA_2或BA均不能代替光照诱导萌发,可是0.1μl/l乙烯却能引起部分种子萌发,在1000μ1/1乙烯的作用下,发芽率可达80%,接近全光照处理的萌发水平(91%发芽率)。ACC也能诱导水浮莲种子的萌发,0.1 mM浓度可获30%发芽率。在较短光照下,ACC对种子萌发有增效作用。在光照前应用ACC,其诱导效应大于两者同时施用。在照光萌发中,种子的内源ACC含量及乙烯释放量均显著增加。CoCl_2和AOA均能抑制光的诱导萌发。推论光打破休眠诱导萌发的作用是与乙烯的生成密切相关。 相似文献
999.
Abstract: [3 H] γ -Aminobutyric acid ([3 H]GABA) binding to purified lipids was examined in an organic solvent-aqueous partition system. In addition, the [3 H]GABA binding capacity in the partition system was compared with the capacity of lipids to alter sodium-dependent [3 H]GABA uptake into synaptosomes isolated from rat whole brains. [3 H]GABA was found to bind to all of the lipids studied in the organic solvent-aqueous partition system [phosphatidic acid (PA), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS), gangliosides, and sulfatide], although PS exhibited the greatest binding capacity. [3 H]GABA uptake into synaptosomes was enhanced by PS (48.0%) but was not altered by any other lipid. PS enhancement of [3 H]GABA uptake required the presence of sodium and was blocked by nipecotic acid (10 μ m ). These results suggest that PS may play a role in the sodium-dependent GABA reuptake process in the presynaptic nerve end. 相似文献
1000.
Abstract: DBA/2 mice between 21 and 28 days of age are highly susceptible to sound-induced seizures. Drug studies suggest a possible deficit of γ-Aminobutyric acid (GABA)-mediated neurotransmission may be involved. We have measured the whole brain GABA concentration and glutamic acid decar-boxylase activity in DBA/2 mice at various ages before, during, and after the period of maximal susceptibility to audiogenic seizures. Corresponding determinations were carried out on age-matched TO mice, a strain much less susceptible to audiogenic seizures than DBA/2 mice at all ages. No significant differences in GABA concentration or glutamic acid decarboxylase activity were found between strains at any age. The susceptibility of DBA/2 mice to audiogenic seizures does not result from a gross inability to synthesise or store GABA. 相似文献