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排序方式: 共有392条查询结果,搜索用时 15 毫秒
31.
Alberto Abbruzzese 《Journal of neurochemistry》1988,50(3):695-699
Deoxyhypusine hydroxylase catalyzes the formation of hypusine from deoxyhypusine in a precursor form of eukaryotic initiation factor 4D (eIF-4D). The enzymatic activity was examined in mammalian brain homogenates and the results were consistent with the existence of deoxyhypusine hydroxylase levels comparable to those occurring in other mammalian tissues. Interspecies differences in the enzyme distribution were quite limited, with the highest specific activity values observed in cow brain (1.82 units/ mg of protein). In the rat the enzyme was found to be unevenly distributed among various brain regions. The parietal cortex contained the highest specific activity (2.1 units/mg of protein). Rat brain deoxyhypusine hydroxylase was mainly present in the postmicrosomal supernatant (81% of the total activity). The highest specific activity (3 units/mg of protein) was observed in the rat brain during the first few days of life. Thereafter the activity started to decline, and continued to do so for 15 days, remaining throughout the rest of life at levels of less than one-half that of newborn. 相似文献
32.
Vinod Kumar Ashwani Sharma Bellur Chayapathy Narasimha Prasad Harishchandra Bhaskar Gururaj Parvatam Giridhar Gokare Aswathanarayana Ravishankar 《Acta Physiologiae Plantarum》2007,29(1):11-18
Direct shoot bud induction and plant regeneration was achieved in Capsicum frutescens var. KTOC. Aseptically grown seedling explants devoid of roots, apical meristem and cotyledons were inoculated in an inverted
position in medium comprising of Murashige and Skoog (Physiol Plant 15:472–497, 1962) basal medium supplemented with 2-(N-morpholine) ethanesulphonic acid buffer along with 2.28 μM indole-3-acetic acid, 10 μM silver nitrate and either of 13.31–89.77 μM
benzyl adenine (BA), 9.29–23.23 μM kinetin, 0.91–9.12 μM zeatin, 2.46–9.84 μM 2-isopentenyl adenine. Profuse shoot bud induction
was observed only in explants grown on a media supplemented with BA (26.63 μM) as a cytokinin source and 19.4 ± 4.2 shoot
buds per explant was obtained in inverted mode under continuous light. Incorporation of polyamine inhibitors in the culture
medium completely inhibited shoothoot bud induction. Incorporation of exogenous polyamines improved the induction of shoot
buds under 24 h photoperiod. These buds were elongated in MS medium containing 2.8 μM gibberellic acid. Transfer of these
shoots to hormone-free MS medium resulted in rooting and rooted plants were transferred to fields. This protocol can be efficiently
used for mass propagation and presumably also for regeneration of genetically transformed C. frutescens. 相似文献
33.
Tassoni A Franceschetti M Tasco G Casadio R Bagni N 《Journal of plant physiology》2007,164(9):1208-1219
In this paper we report the cloning and full sequencing of S-adenosylmethionine decarboxylase (SAMDC, EC 4.1.1.50) cDNA from Vitis vinifera L. (VV) leaves, an enzyme belonging to the polyamine biosynthetic pathway, which appears to play an important role in the regulation of plant growth and development. The presence of two overlapping ORFs (tiny ORF and small ORF) upstream of the main ORF is reported in the Vitis cDNA. When the Vitis SAMDC cDNA was expressed in yeast without the two upstream ORFs, the resulting activity was about 50 times higher than the activity obtained with the full cDNA. These results demonstrated the strong regulatory activity of the tiny and small ORFs. RT-PCR expression analysis showed evidence of a similar mRNA level in all the tissues tested, with the exception of the petioles. The VV SAMDC was also modelled using its homologues from Solanum tuberosum and Homo sapiens as template. The present work confirmed, for the first time in a woody plant of worldwide economic interest such as grapevine, the presence of a regulatory mechanism of SAMDC, enzyme that has a well-established importance in the modulation of plant growth and development. 相似文献
34.
Bjelaković G Beninati S Pavlović D Sokolović D Stojanović I Jevtović T Bjelaković GB Nikolić J Basić J 《Amino acids》2007,33(3):525-529
Summary. Our study was undertaken to elucidate the effects of selenomethionine (SeMet) on polyamine metabolism in regenerating rat
liver tissue, as useful model of rapidly growing normal tissue. We have examined the levels of spermine, spermidine and putrescine
in liver tissue. At the same time we have evaluated the activities of polyamine oxidase (PAO) and diamine oxidase (DAO), the
catabolic enzymes of polyamine metabolism.
The obtained results suggest that polyamine levels in regenerating liver tissue, at 7th day after two-thirds partial hepatectomy, were higher in comparison with control group. The administration of selenomethionine
to hepatectomized animals during seven days, in a single daily dose of 2.5 μg/100 g body weight, increases the amount of spermine
and spermidine; the level of putrescine does not change under the influence of SeMet in regenerating rat liver tissue.
PAO activity is lower in regenerating hepatic tissue than in control group. Supplementation of hepatectomized animals with
SeMet significantly decreases the activity of this enzyme. DAO activity was significantly higher in hepatectomized and in
operated animals treated with SeMet compared to the sham-operated and control ones.
The differential sensitivity observed in our model of highly proliferating normal tissue to SeMet, compared with the reported
anticancer activity of this molecule is discussed. 相似文献
35.
Summary. Gamma-aminobutyric acid (GABA) is considered to be a multifunctional molecule with various physiological effects throughout
the body. It is also evident that the liver contains GABA and its transporter. However, the functions of GABA in liver have
not been well documented. In this study, the cytoprotective effect of GABA against ethanol-induced hepatotoxicity was evaluated
in primary cultured rat hepatocytes. Addition of ethanol induced decrease of cell viability in a dose-dependent manner. However,
treatment with GABA resulted in a dose-dependent recovery from ethanol (150 mM)-induced cytotoxicity.
GABA reversed the ethanol-induced decrease in intracellular polyamine levels. Furthermore, the addition of polyamines also
reversed the ethanol-induced decrease of cell viability. These results suggest that GABA is protective against the cytotoxicity
of ethanol in isolated rat hepatocytes and this effect may be modulated by the maintenance of intracellular polyamine levels. 相似文献
36.
Summary. Trypanosomatids depend on spermidine for growth and survival. Consequently, enzymes involved in spermidine synthesis and utilization,
i.e. arginase, ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (AdoMetDC), spermidine synthase, trypanothione synthetase (TryS), and trypanothione reductase
(TryR), are promising targets for drug development. The ODC inhibitor α-difluoromethylornithine (DFMO) is about to become
a first-line drug against human late-stage gambiense sleeping sickness. Another ODC inhibitor, 3-aminooxy-1-aminopropane (APA),
is considerably more effective than DFMO against Leishmania promastigotes and amastigotes multiplying in macrophages. AdoMetDC inhibitors can cure animals infected with isolates from
patients with rhodesiense sleeping sickness and leishmaniasis, but have not been tested on humans. The antiparasitic effects
of inhibitors of polyamine and trypanothione formation, reviewed here, emphasize the relevance of these enzymes as drug targets.
By taking advantage of the differences in enzyme structure between parasite and host, it should be possible to design new
drugs that can selectively kill the parasites. 相似文献
37.
Satriano J 《Amino acids》2007,33(2):331-339
Summary. Michael Brownlee has proposed a ‘Unifying Mechanism’ of hyperglycemia-induced damage in diabetes mellitus. At the crux of
this hypothesis is the generation of reactive oxygen species (ROS), and their impact on glycolytic pathways.
Diabetes is the leading cause of chronic kidney failure. In the early phase of diabetes, prior to establishment of proteinuria
or fibrosis, comes kidney growth and hyperfiltration. This early growth phase consists of an early period of hyperplasia followed
by hypertrophy. Hypertrophy also contributes to cellular oxidative stress, and may precede the ROS perturbation of glycolytic
pathways described in the Brownlee proposal. This increase in growth promotes hyperfiltration, and along with the hypertrophic
phenotype appears required for hyperglycemia-induced cell damage and the progression of downstream diabetic complications.
Here we will evaluate this growth phenomenon in the context of diabetes mellitus. 相似文献
38.
39.
Pfaff AW Villard O Klein JP Mousli M Candolfi E 《International journal for parasitology》2005,35(14):1569-1576
Materno-foetal transmission causes one of the most severe forms of infection with the protozoan parasite Toxoplasma gondii. Several studies have shown T. gondii in placental trophoblast cells, which form the barrier between maternal blood circulation and foetal tissue. Parasite multiplication in trophoblast cells is thus a critical step leading to infection of the foetus. Here, we show that multiplication of T. gondii tachyzoites was slow in BeWo trophoblast cells, compared with MRC-5 fibroblast cells. However, unlike MRC-5 cells, even combined stimulation with interferon-γ and tumor necrosis factor- did not reduce T. gondii replication in BeWo cells. This was associated with a lack of indoleamine-2,3-dioxygenase induction by these cytokines. Neither low availability of iron salts, nor an immunosuppressive action of cyclooxygenase-2 could be attributed to the low T. gondii multiplication rate in BeWo cells. However, treatment with the nitric oxide synthesis inhibitor NG-methyl-l-arginine and addition of ornithine enhanced the proliferation rate of the intracellular pathogen. Despite detection of inducible nitric oxide synthase-II mRNA in BeWo cells, nitric oxide production could not be detected during cell culture. Thus, inhibition of arginase activity by nitric oxide synthesis may be partially responsible for the lower multiplication rate in BeWo cells. 相似文献
40.
Arabidopsis stress-inducible gene for arginine decarboxylase AtADC2 is required for accumulation of putrescine in salt tolerance 总被引:1,自引:0,他引:1
Urano K Yoshiba Y Nanjo T Ito T Yamaguchi-Shinozaki K Shinozaki K 《Biochemical and biophysical research communications》2004,313(2):369-375
Arginine decarboxylase (ADC) catalyzes the first step of polyamine (PA) biosynthesis to produce putrescine (Put) from arginine (Arg). One of the 2 Arabidopsis ADC genes, AtADC2, is induced in response to salt stress causing the accumulation of free Put. To analyze the roles of stress-inducible AtADC2 gene and endogenous Put in stress tolerance, we isolated a Ds insertion mutant of AtADC2 gene (adc2-1) and characterized its phenotypes under salt stress. In the adc2-1 mutant, free Put content was reduced to about 25% of that in the control plants and did not increase under salt stress. Furthermore, the adc2-1 mutant was more sensitive to salt stress than the control plants. The stress sensitivity of adc2-1 was recovered by the addition of exogenous Put. These results indicate that endogenous Put plays an important role in salt tolerance in Arabidopsis. AtADC2 is a key gene for the production of Put under not only salinity conditions, but also normal conditions. 相似文献