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1.
Aloni B  Daie J  Wyse RE 《Plant physiology》1988,88(2):367-369
Leaf discs of broad bean (Vicia faba L.), peeled on the spongy mesophyll side, rapidly altered the pH of the surrounding medium (apoplast). Using pH indicator paper appressed against the leaf, immediately after peeling, initial apoplastic pH was estimated to be 4.5. Changes in the apoplastic pH were measured with a microelectrode placed into a 100-microliter drop of an unbuffered solution (2 millimolar KCl, 0.5 millimolar CaCl2, and 200 millimolar mannitol) on the peeled surface. Discs acidified the medium until the pH stabilized at about 5.0 (about 10 minutes). Acidification was inhibited by 50 micromolar sodium vanadate, an inhibitor of the plasmalemma H+-ATPase and attenuated by omitting the osmoticum or potassium ions from the medium. Fusicoccin (10 micromolar) greatly enhanced the rate of acidification. The presence of 0.1 to 1 micromolar gibberellic acid resulted in a slower rate of medium acidification. Gibberellic acid appeared to modulate the activity of the H+-translocating ATPase located at the plasma membrane of the mesophyll cells.  相似文献   
2.
ABA Uptake in Source and Sink Tissues of Sugar Beet   总被引:2,自引:2,他引:0       下载免费PDF全文
Daie J  Wyse R 《Plant physiology》1983,72(2):430-433
The mode of abscisic acid (ABA) uptake was studied in excised leaf and root tissue discs of sugar beet (Beta vulgaris L.). Discs were incubated in buffered medium that contained 1 mm CaCl2 and [14C]ABA. The sensitivity of ABA uptake to metabolic inhibitors and temperature indicated that the ABA transport system had an energy-dependent component. Energy-dependent uptake was greater in leaf than in root tissue (70% and 50%, respectively). Energy-dependent uptake by both tissues and passive uptake by root tissues were highly pH dependent. Maximal uptake was observed at pH 5.5. Leaf tissue incubated in the dark showed a 50% reduction of uptake as compared with tissue under light. The decrease was due to reduced passive uptake.  相似文献   
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7α-Hydroxylation of DHEA by Fusarium moniliforme was investigated with regard to inducibility and characterization of the responsible enzyme system. Using GC/MS, the 7-hydroxylated metabolites of DHEA produced after biotransformation by Fusarium moniliforme mycelia were identified. The strain of Fusarium moniliforme hydroxylated DHEA predominantly at the 7α-position, with minor hydroxylation occurring at the 7β-position. Constitutive 7α-hydroxylation activity was low, but DHEA induced the enzyme complex responsible for 7α-hydroxylation via an increase in protein synthesis. DHEA 7α-hydroxylase was found to be mainly microsomal, and the best production yields of 7α-hydroxy-DHEA (28.5 ± 3.51 pmol/min/mg protein) were obtained with microsomes prepared from 18-h-induced mycelia. Kinetic parameters (KM=1.18 ± 0.035 μM and Vmax=909 ± 27 pmol/min/mg protein) were determined. Carbon monoxide inhibited 7α-hydroxylation of DHEA by microsomes of Fusarium moniliforme. Also, exposure of mycelia to DHEA increased microsomal P450 content. These results demonstrated that: (i) DHEA is 7α-hydroxylated by microsomes of Fusarium moniliforme; (ii) DHEA induces Fusarium moniliforme 7α-hydroxylase; (iii) this enzyme complex contains a cytochrome P450.  相似文献   
6.

Non-albicans Candida species and other rare yeasts have emerged as major opportunistic pathogens in fungal infections. Identification of opportunistic yeasts in developing countries is mainly performed by phenotypic assay, which are time-consuming and prone to errors. The aim of the present study was to evaluate PCR-RFLP as a routinely used identification technique for the most clinically important Candida species in Iran and make a comparison with a novel multiplex PCR, called 21-plex PCR. One hundred and seventy-three yeast isolates from clinical sources were selected and identified with sequence analysis of the D1/D2 domains of rDNA (LSU rDNA) sequencing as the gold standard method. The results were compared with those obtained by PCR-RFLP using MspI restriction enzyme and the 21-plex PCR. PCR-RFLP correctly identified 93.4% of common pathogenic Candida species (C. albicans, C. glabrata, C. parapsilosis, C. tropicalis, and P. kudriavsevii (=?C. krusei)) and was able to identify 45.5% of isolates of the uncommon yeast species compared to the D1/D2 rDNA sequencing. Compared with PCR-RFLP, all common Candida species and 72.7% of uncommon yeast species were correctly identified by the 21-plex PCR. The application of the 21-plex PCR assay as a non-sequence-based molecular method for the identification of common and rare yeasts can reduce turnaround time and costs for the identification of clinically important yeasts and can be applied in resource-limited settings.

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7.
Kinetic profiles for sucrose, glucose and 3-OMG glucose were determined in leaf discs of Phaseolus coccinius L. (cv. Scarlet). All three sugars exhibited identical uptake kinetics. At sugar concentrations below 25 m M , transport was due to an active, carrier-mediated transport system. A linear component was the dominant mode of uptake at sugar concentrations above 25 m M . Sucrose and glucose carriers were specific for these sugars, since no uptake inhibition was observed from competing sugars. Sucrose was not hydrolyzed by leaf tissue because the label in asymetrically labeled sucrose was not randomized. Furthermore, no label was present in hexose fractions when tissue was incubated with [84C]-sucrose. Therefore, [14C]-sucrose uptake did not reflect hexose uptake.
Both saturable and linear components of uptake contribute significantly to total uptake rates. The former, however, is more important when apoplastic sugar concentrations are low. The molecular nature of the linear component is not well understood but accounts for most of the uptake at high sugar concentrations.  相似文献   
8.
Day respiration of illuminated C(3) leaves is not well understood and particularly, the metabolic origin of the day respiratory CO(2) production is poorly known. This issue was addressed in leaves of French bean (Phaseolus vulgaris) using (12)C/(13)C stable isotope techniques on illuminated leaves fed with (13)C-enriched glucose or pyruvate. The (13)CO(2) production in light was measured using the deviation of the photosynthetic carbon isotope discrimination induced by the decarboxylation of the (13)C-enriched compounds. Using different positional (13)C-enrichments, it is shown that the Krebs cycle is reduced by 95% in the light and that the pyruvate dehydrogenase reaction is much less reduced, by 27% or less. Glucose molecules are scarcely metabolized to liberate CO(2) in the light, simply suggesting that they can rarely enter glycolysis. Nuclear magnetic resonance analysis confirmed this view; when leaves are fed with (13)C-glucose, leaf sucrose and glucose represent nearly 90% of the leaf (13)C content, demonstrating that glucose is mainly directed to sucrose synthesis. Taken together, these data indicate that several metabolic down-regulations (glycolysis, Krebs cycle) accompany the light/dark transition and emphasize the decrease of the Krebs cycle decarboxylations as a metabolic basis of the light-dependent inhibition of mitochondrial respiration.  相似文献   
9.

Background  

The effects of ovarian drilling on the serum levels of gonadotropins and androgens have been studied previously. The aim of this study is to evaluate the effects of ovarian drilling on the serum prolactin levels and its relation to ovulation in women with polycystic ovary syndrome.  相似文献   
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