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91.
Summary We have worked out conditions for the study of competence development and genetic transformation in Streptococcus oralis NCTC 11427 (type strain), a species that contains choline in the cell wall. The peak of competence was found at the early exponential phase of growth and the optimal conditions for transformation were achieved with shuttle plasmids prepared from S. pneumoniae or from Escherichia coli serving as donor DNA. Transformation with dye-bouyant density gradient purified plasmid preparations followed first-order kinetics. The pneumococcal amidase can be expressed in S. oralis harbouring a plasmid carrying the lytA gene. This enzyme lysed the cell wall of the transformed cell in the presence of detergents. 相似文献
92.
NADH oxidation by plasma membrane vesicles purified from hypocotyls of etiolated soybean seedlings by two-phase partition was stimulated 2- to 3-fold by auxins, indole-3-acetic acid, 2,4-dichlorophenoxy acetic acid (2,4-D), and α-naphthaleneacetic acid. The stimulation was concentration dependent in the presence or absence of detergent with a maximum for 2,4-D at 1 micromolar. The NADH oxidation activity was solubilized with the zwitterionic detergent CHAPS and purified by ion exchange chromatography and gel filtration approximately 2000-fold over the total homogenate. Both the partially purified fraction and an active band from nondenaturing gel electrophoresis revealed the same three bands when analyzed by denaturing gel electrophoresis. When obtained from plasma membrane vesicles from the region of rapid cell elongation, the NADH oxidase complex retained auxin responsiveness throughout purification (3- to 5-fold stimulation by 1 micromolar 2,4-D). 相似文献
93.
Sequence of chicken c beta 7 tubulin. Analysis of a complete set of vertebrate beta-tubulin isotypes 总被引:6,自引:0,他引:6
In chicken, beta-tubulin is encoded by a family of seven genes. We have now isolated and sequenced overlapping cDNA clones corresponding to gene c beta 7 (previously designated c beta 4'), the only chicken beta-tubulin not previously characterized. The inferred amino acid sequence of c beta 7 tubulin is identical with the class I beta-tubulin isotype found in human, mouse and rat. Moreover, c beta 7 is highly expressed in almost all tissue and cell types in chicken, a pattern similar to those of the genes for class I beta-tubulin isotypes in other vertebrates. Comparison of the complete family of chicken beta-tubulin gene sequences reveals that the heterogeneity of beta-tubulin polypeptides encoded in a higher eukaryote is confined to six distinct beta-tubulin isotypes. Five of these are members of evolutionarily conserved isotypic classes (I to V), whereas the sixth represents a divergent erythroid-specific tubulin whose sequence has not been conserved. 相似文献
94.
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
95.
96.
José M. Facelli 《Plant Ecology》1988,78(1-2):21-25
This paper reports on changes induced by the introduction of cattle in a grassland that had remained ungrazed for 9 yr, in comparison with two adjacent grasslands: one that remained enclosed and one that has been continuously subject to grazing. Basal cover was measured on 25 interception lines, each 1 m long, three times during one year. The variables studied were: total cover, cover of grasses and dicots, cover of creeping grasses, floristic composition, and dissimilarity among sites. At the first sampling, 2 yr after cattle re-introduction, the newly grazed site was more similar to the ungrazed than to the grazed site. The newly grazed site had very low cover of dicots; the species of dicots present were different from those found in the continuously grazed area. Creeping grasses had higher cover in the newly grazed site than in the other sites, and continued to increase. At the last sampling, one year later, the newly grazed site had become more similar to the contiuously grazed site. Only after 5 yr of cattle grazing the exotic dicots that were dominant in the continuously grazed site, were recorded in the re-opened site. The absence of propagules of these species or the absence of safe sites may account for this delayed invasion. 相似文献
97.
98.
Summary Neurons containing luteinizing hormone-releasing hormone (LHRH) are first detected in newt embryos (Cynops pyrrhogaster) in the olfactory epithelium and ventromedial portion of the olfactory nerve, after which they sequentially appear in the intracerebral course of the terminal nerve at prometamorphosis, and in the septo-preoptic area at postmetamorphosis. In adults, however, LHRH-immunoreactive cells are rarely seen in the nasal region, and their distribution shifts into the brain, suggesting their migration. In order to ascertain the origin and possible migration route of these neurons in newt larvae, the effect of unilateral or bilateral olfactory placodectomy on the LHRH neuronal system has been studied. Removal of the olfactory placode results in the absence of LHRH-immunoreactive cells in the nasal and brain regions of the operated side, whereas the subsequent growth and the LHRH-immunoreactive cellular distribution in the contralateral side are identical to those of normal larvae. Following bilateral placodectomy, no LHRH immunoreactivity is detected on either side of the olfactory-brain axis. These results suggest that LHRH neurons of the newt, Cynops pyrrhogaster, originate in the olfactory placode and then migrate into the brain during embryonic development. 相似文献
99.
Glutathione reductase fromSaccharomyces cerevisiae undergoes redox interconversionin situ andin vivo
José Peinado Javier Florindo J. López-Barea 《Molecular and cellular biochemistry》1992,110(2):135-143
Redox interconversion of glutathione reductase was studiedin situ withS. cerevisiae. The enzyme was more sensitive to redox inactivation in 24 hour-starved cells than in freshly-grown ones. While 5 μM NADPH
or 100 μM NADH caused 50% inactivation in normal cells in 30 min, 0.75 μM NADPH or 50 μM NADH promoted a similar effect in
starved cells. GSSG reactivated the enzyme previously inactivated by NADPH, ascertaining that the enzyme was subjected to
redox interconversion. Low EDTA concentrations fully protected the enzyme from NADPH inactivation, thus confirming the participation
of metals in such a process. Extensive inactivation was obtained in permeabilized cells incubated with glucose-6-phosphate
or 6-phosphogluconate, in agreement with the very high specific activities of the corresponding dehydrogenases. Some inactivation
was also observed with malate, L-lactate, gluconate or isocitrate in the presence of low NADP+ concentrations.
The inactivation of yeast glutathione reductase has also been studiedin vivo. The activity decreased to 75% after 2 hours of growth with glucono-δ-lactone as carbon source, while NADPH rose to 144%
and NADP+ fell to 86% of their initial values. Greater changes were observed in the presence of 1.5 μM rotenone: enzymatic activity
descended to 23% of the control value, while the NADH/NAD+ and NADPH/NADP+ ratios rose to 171% and 262% of their initial values, respectively. Such results indicate that the lowered redox potential
of the pyridine nucleotide pool existing when glucono-δ-lactone is oxidized promotesin vivo inactivation of glutathione reductase. 相似文献
100.
We investigated the effect of phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator on insulin receptors and insulin action in freshly isolated and primary cultures of rat hepatocytes. PMA (1 x 10–7 M) did not alter insulin receptor numbers or affinity either acutely or chronically but within 60 minute inactivated insulin stimulated tyrosine kinase of the insulin receptor. PKC activation inhibitied insulin (1 x 10–7M) stimulation of glycogen and lipid synthesis with a decrease or no change in basal glycogenesis and lipogenesis respectively. However, PKC activation did not alter insulin stimulated or basal amino acid transport even though PCK activation inhibited insulin stimulation of the insulin. receptor tyrosine kinase. Thus, within one tissue, PKC activation has differential effect on insulin action depending on which pathway is examined. Furthermore, insulin stimulation of the insulin receptor tyrosine kinase may not be a necessary step for all insulin signaling pathways. 相似文献