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排序方式: 共有251条查询结果,搜索用时 15 毫秒
201.
Vlajcic Z Rado Z Stanec S Stanec Z 《Plastic and reconstructive surgery》2006,118(6):1493-5; author reply 1495-6
202.
Measurements were made of the membrane fluxes and toxicitiesof three cations with trivalent forms, Al, Ga and Sc, in internodalcells of the giant alga Chara corallina. With this species itwas possible to separate the cell wall from the cell contentsto obtain membrane fluxes which were not complicated by adsorptionof cations to the cell wall. Net uptake of Al was low, approximately1.5 pmol m2 s1, compared to the influxes of thedivalent cation 45Ca of 82 pmol m2 s1 and themonovalent cation 22Na of 1100 pmol m2 s1 at thesame external concentration. Traditional desorption methodsfor removing cell wall cations were found to be relatively ineffectivein the case of trivalent cations and, consequently, influx measuredwithout separating the cell wall component would greatly overestimatethe true membrane flux, possibly by several orders of magnitude.Al, Ga and Sc all inhibited growth at 20 mmol m3 at pH4.4. Toxicity decreased in the order Sc>Al>Ga. Sc andAl were also toxic to mature non-growing cells. Influx of 46Scincreased with increasing pH, consistent with membrane permeationby hydroxy Sc rather than Sc3+. However, Sc was more toxic atlow pH where Sc3+ was the dominant species and where influxwas low and binding to cell walls was high. These results argueagainst Sc acting intracellularly and favour a toxicity mechanismwhich is initiated extracellularly. Key words: Aluminium toxicity, trivalent cations, Chara corallina, scandium influx, gallium 相似文献
203.
Role of dynamics of intracellular calcium in aluminium-toxicity syndrome 总被引:16,自引:2,他引:14
204.
Nedić G Borovecki F Klepac N Mubrin Z Hajnsek S Nikolac M Muck-Seler D Pivac N 《Collegium antropologicum》2011,35(Z1):79-84
A functional catechol-o-methyltransferase (COMT Val158/108Met) polymorphism, a valine (Val) to methionine (Met) substitution, has been associated with cognitive processing in the normal brain, older age, mild cognitive impairment and in various dementias. COMT is involved in the breakdown of dopamine and other catecholamines, especially in the frontal cortex; hence the carriers of Met allele, with the lower enzymatic activity, are expected to perform better on particular neuro-cognitive tests. The study included 46 patients with dementia and 65 healthy older subjects. The neurological status was assessed, using the Mini Mental Status Examination (MMSE), and the batery of different neurological tests. In DNA samples COMT polymorphism was genotyped. Patients with dementia exhibited significant genotype-induced differences in scores for MMSE, Visual Association Test (VAT) duration of numbers test, VAT time of response to numbers test, VAT average response to numbers test and WPLCR/PPLR unanswered. Carriers of Met/Met genotype had significantly lower scores of MMSE, significantly longer time to respond to VAT duration of numbers test, VAT time of response to numbers test and VAT average response to numbers test, and significantly greater number of unanswered questions to WPLCR/PPLR when compared to Met/Val or Val/Val genotypes. Our preliminary data showed significantly impaired performance in several neuro-cognitive tests in carriers of Met/Met genotype in patients with dementia compared to either Met/Val or Val/Val genotype carriers. Although Met/Met genotype with more dopamine available in the frontal cortex should be associated with better neuro-cognitive test results than Met/Val or Val/Val genotype, our data on patients with dementia did not confirm this hypothesis. Further study on larger sample of patients is needed to clarify the role of COMT polymorphism in cognitive functions. 相似文献
205.
This report describes a chondromyxoid fibroma of the second metacarpal bone in a 32-year-old female patient. Chondromyxoid fibroma is a rare, benign, slow-growing bone tumor of cartilaginous origin. Tumor has a high recurrance rate. Our aim was to show successful treatment of a metacarpal chondromyxoid fibroma with wide resection and implantation of finger join endoprosthesis. 相似文献
206.
X. Huang S. Shabala L. Shabala Z. Rengel X. Wu G. Zhang M. Zhou 《Plant biology (Stuttgart, Germany)》2015,17(1):26-33
Vast agricultural areas are affected by flooding, causing up to 80% yield reduction and resulting in multibillion dollar losses. Up to now, the focus of plant breeders was predominantly on detrimental effects of anoxia, while other (potentially equally important) traits were essentially neglected; one of these is soil elemental toxicity. Excess water triggers a progressive decrease in soil redox potential, thus increasing the concentration of Mn2+ that can be toxic to plants if above a specific threshold. This work aimed to quantify the relative contribution of Mn2+ toxicity to waterlogging stress tolerance, using barley as a case study. Twenty barley (Hordeum vulgare) genotypes contrasting in waterlogging stress tolerance were studied for their ability to cope with toxic (1 mm ) amounts of Mn2+ in the root rhizosphere. Under Mn2+ toxicity, chlorophyll content of most waterlogging‐tolerant genotypes (TX9425, Yerong, CPI‐71284‐48 and CM72) remained above 60% of the control value, whereas sensitive genotypes (Franklin and Naso Nijo) had 35% less chlorophyll than 35% of controls. Manganese concentration in leaves was not related to visual Mn2+ toxicity symptoms, suggesting that various Mn2+ tolerance mechanisms might operate in different tolerant genotypes, i.e. avoidance versus tissue tolerance. The overall significant (r = 0.60) correlation between tolerance to Mn2+ toxicity and waterlogging in barley suggests that plant breeding for tolerance to waterlogging traits may be advanced by targeting mechanisms conferring tolerance to Mn2+ toxicity, at least in this species. 相似文献
207.
Breeding for better symbiosis 总被引:6,自引:0,他引:6
Z. Rengel 《Plant and Soil》2002,245(1):147-162
The present review gives a critical assessment of the literature dealing with symbiosis between rhizobia and legumes and between AM fungi and most plants. Associative N2 fixation (even though strictly speaking not a symbiotic relationship) does have some characteristics of symbiosis due to mutualistic dependence and usefulness of the relationship, and is therefore covered in this review. Nodulation in the rhizobia–legume symbiosis may be limited by an insufficient amount of the nod-gene inducers released from seed and/or roots. However, there is genotypic variation in the germplasm of legume species in all components of the signalling pathway, suggesting a prospect for improving nodulation by selecting and/or transforming legume genotypes for increased exudation of flavonoids and other signalling compounds. Deciphering chromosomal location as well as cloning nod, nif and other genes important in nodulation and N2 fixation will allow manipulation of the presence and expression of these genes to enhance the symbiotic relationship. Increased efficacy of symbiotic N2 fixation can be achieved by selecting not only the best host genotypes but by selecting the best combination of host genotype and nodule bacteria. As flavonoids exuded by legume seedlings may not only be nod-gene inducers, but also stimulants for hyphal growth of the AM fungi, selecting and/or transforming plants to increase exudation of these flavonoids may result in a double benefit for mycorrhizal legumes. Mutants unable to sustain mycorrhizal colonisation are instrumental in understanding the colonisation process, which may ultimately pay off in breeding for the more effective symbiosis. In conclusion, targeted efforts to breed genotypes for improved N2 fixation and mycorrhizal symbiosis will bring benefits in increased yields of crops under a wide range of environmental conditions and will contribute toward sustainability of agricultural ecosystems in which soil-plant-microbe interactions will be better exploited. 相似文献
208.
Physiological responses of wheat genotypes grown in chelator-buffered nutrient solutions with increasing concentrations of excess HEDTA 总被引:1,自引:0,他引:1
The chelator-buffered nutrient solutions containing excess chelator have been used frequently in the micronutrient research,
but potential toxicity of the excess chelator has not been ascertained. The present study was conducted to test effects of
four concentrations of excess HEDTA [ N-(2-hydroxyethyl)ethylenedinitrilotriacetic acid] and two levels of total Zn on growth,
root exudation, and nutrient uptake and transport by Triticum aestivum L. (cv. Aroona) and Triticum turgidum L. conv. durum
(Desf.) MacKey (cv. Durati) genotypes differing in tolerance to Zn deficiency. Excess HEDTA at 50 μM reduced root and shoot
growth and caused visual toxicity symptoms (necrotic lesions) on leaves; these effects were generally absent at lower concentrations
of excess HEDTA. Root exudation of phytosiderophores increased with increasing concentrations of excess HEDTA at deficient
and sufficient Zn levels, and was higher in Zn-deficiency-tolerant Aroona than in Zn-deficiency-sensitive Durati wheat. Shoot
and root Zn concentrations showed a saturable response to increasing Zn2+ activities in solution. Excess HEDTA at 50 μM caused an increase in shoot concentrations of Fe and a decrease in concentrations
of Mn and Cu. An average rate of Zn uptake increased with an increase in Zn2+ ionic activity in solution, with Zn-deficiency-tolerant Aroona having a higher rate of Zn uptake than Zn-deficiency-sensitive
Durati in the deficiency range of Zn2+ activities. Average uptake rates of Mn and Cu decreased with an increase in concentration of excess HEDTA. Similar observations
were noted for transport of Mn and Cu to shoots, while Zn transport to shoots was proportional to Zn2+ activities in solution. It was concluded that excess HEDTA at 50 μM adversely affects wheat growth and physiology, while
excess of 25 μM or less does not cause measurable toxicity.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
209.
Prunings of Calliandra calothyrsus, Grevillea robusta, Leucaena diversifolia and farm yard manure were applied each cropping season at 3 and 6 t dry matter ha−1 to an Oxisol in Burundi. The field plots also received basal applications of nitrogen (N), phosphorus (P) and potassium (K).
Application of the tree prunings or farm yard manure decreased the concentration of monomeric inorganic aluminium (Al) in
soil solution from 2.92 mg Al dm−3 in the control plots to 0.75 mg Al dm−3 in the plots receiving 6 t ha−1
Calliandra prunings. The other organic materials also decreased the concentration of monomeric inorganic aluminium in the soil solution.
The lowered Al concentration led to a corresponding decrease in the percentage Al saturation of the 0–10 cm soil layer from
80% to 68%. Grain yields of maize and beans were strongly inversely related to the percentage Al saturation of the soil. This
confirms that soil acidity was the main constraint to maize and beans production. The yield improvement was mainly attributed
to the ameliorating effects of the organic matter application on Al toxicity. The nutrient content had less effect presumably
because of fertilizer use. In the best treatments, the yield of maize increased from 0.9 to 2.2 t ha−1 and the corresponding beans yield increased from 0.2 to 1.2 t ha−1. A C Borstlap Section editor 相似文献
210.
Wheat genotypes differ in Zn efficiency when grown in chelate-buffered nutrient solution 总被引:11,自引:1,他引:10
Ten Triticum aestivum and two Triticum turgidum conv. durum genotypes were grown in chelate-buffered nutrient solution at Zn supplies ranging from deficient to sufficient (free Zn activities from 2 to 200 pM, pZn from 11.7 to 9.7). The critical level of Zn ion activity in solution for healthy growth of wheat plants was around 40 pM. Genotypes differed in the growth response: those classified as Zn-efficient suffered less reduction of shoot growth and did not change the rate of root growth at a Zn supply quite deficient for Zn-inefficient genotypes. Root growth of Zn-inefficient genotypes increased at deficient Zn supply. The shoot/root ratio was the most sensitive parameter of Zn efficiency; Zn-efficient genotypes showed less reduction in the ratio when grown at deficient compared to sufficient Zn supply. Classification of wheat genotypes into Zn-efficient and Zn-inefficient groups after screening in chelate-buffered nutrient solution corresponded well with classification obtained in field experiments on Zn-deficient soil. 相似文献