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排序方式: 共有1328条查询结果,搜索用时 203 毫秒
221.
Monier Abd El‐Ghani Abdel M. El‐Fiky Ashraf Soliman Adel Khattab 《African Journal of Ecology》2011,49(1):103-118
In generalized four sectors, 350 stands (water channels) in 50 selected and geo‐referenced sites with eighteen environmental factors were surveyed. The total number of recorded species varied from a sector to another: 21 in the northern, nineteen in the middle, seventeen in the western and sixteen in the eastern. New populations of Cyperus papyrus were explored. Vallisneria spiralis, Elodea canadensis and Najas armata were among seven extinct species that were not recorded few decades ago. The floristic composition alteration may be because of the addition of organic matter of plant and animal origin and the discharge of industrial and sewage effluents. Classification and ordination analyses (DCA) resulted in the segregation of seventeen vegetation groups (communities), three of them were repeatedly recorded; namely Phragmites australis‐Eichhornia crassipes, Phragmites australis‐Myriophyllum spicatum and Potamogeton pectinatus‐Myriophyllum spicatum. Phragmites australis‐Cyperus papyrus group was a new community spreading in the eastern sector of the Delta. Electric conductivity, Fe, Hg and chemical oxygen demand (COD) showed high significant variation (P < 0.001) among the vegetation groups. Other significant variables were Cl, Ca, NO3, pH and SO4 (P < 0.047). Redundancy analysis (RDA) was chosen as the appropriate ordination method to perform direct gradient analysis. Trace elements Cu, Fe, Hg and Pb participated in the floristic and chemical composition of each sector. 相似文献
222.
Ahmad MS Ashraf M Tabassam Q Hussain M Firdous H 《Biological trace element research》2011,144(1-3):1229-1239
The phytotoxic effects of lead (Pb) on seed germinability, seedling growth, photosynthetic performance, and nutrient accumulation (K(+) and Cu(2+)) in two maize genotypes (EV-1098 and EV-77) treated with varying levels of PbSO(4) (0.01, 0.1, and 1.0 mg L(-1)) were appraised in this study. In the seed germination experiment, lead stress significantly reduced seed germination percentage and index, plumule and radicle lengths as well as fresh and dry weights in both genotypes. In the second experiment, lengths and fresh and dry weights of shoots and roots decreased due to Pb in both genotypes with increase in plant age. Higher Pb levels also decreased photosynthetic rate (A), water use efficiency (A/E), and intrinsic water use efficiency (A/g(s)), but increased transpiration rate (E) and C(i)/C(a) ratio as a result of increase in stomatal conductance (g(s)). The concentrations of K(+) and Cu(2+) decreased in root, stem, and leaves of both genotypes, which could be a direct consequence of multifold increase in Pb concentration in these tissues. Overall, cv. EV-1098 had better Pb tolerance potential than EV-77 because the former genotype showed less reduction in seed germinability parameters, photosynthetic performance, and K(+) and Cu(2+) accumulation in shoot and root under lead stress. 相似文献
223.
The present study was conducted to examine the changes in some key metabolites in drought-stressed sunflower plants supplied
with glycine betaine externally. Imposition of drought stress at the vegetative or reproductive growth stages decreased the
plant dry matter production and increased the accumulation of organic solutes (glycine betaine, proline, soluble proteins,
free amino acids and soluble sugars) in two sunflower lines, i.e., Glushan-98 and Suncross. In general, decrease in dry matter
production and increase in the endogenous levels of organic solutes, were more pronounced when drought stress applied at the
vegetative stage than at the reproductive stage. Glycine betaine applied as a pre-sowing seed treatment was not found to be
effective in reducing the negative effects of drought stress in sunflower plants. Foliar application of GB further enhanced
the leaf endogenous levels of GB, soluble proteins and total soluble sugars in drought stressed plants without exerting any
negative effects on other osmotica. However, this GB-induced increase in endogenous levels of organic solutes was found to
be not associated with plant dry matter production under stress conditions. 相似文献
224.
Toxic Effect of Nickel (Ni) on Growth and Metabolism in Germinating Seeds of Sunflower (<Emphasis Type="Italic">Helianthus annuus</Emphasis> L.) 总被引:1,自引:0,他引:1
Ashraf MY Sadiq R Hussain M Ashraf M Ahmad MS 《Biological trace element research》2011,143(3):1695-1703
To assess the toxic effect of nickel (Ni) on the growth and some key metabolic processes in sunflower, varying levels of Ni
as Ni(NO3)2 up to 60 mg L−1 were applied once to sunflower cultivars SF-187 and Hysun-33 at sowing time in sand culture. An increase in Ni in the growth
medium adversely affected growth parameters, sugar concentration (both reducing and non-reducing), as well as the activities
of α-amylase and protease. It also slowed down mobilization of stored proteins and amino acids in the germinating seeds. However,
an increase in the activities of α-amylase and protease was observed over time from 24 to 120 h after sowing. Cultivar Hysun-33
showed better performance than SF-187 in the presence of excess Ni. Overall, Ni-induced reduction in germination of sunflower
seed appeared to be due to disturbance in biochemical metabolism as the availability of sugars for the synthesis of metabolic
energy as well as necessary amino acids for the synthesis of proteins and enzymes essential for the growing embryo are generally
reduced due to suppression in α-amylase and protease activities. 相似文献
225.
226.
Botulinum neurotoxins (BoNT) are the most potent of all toxins that cause flaccid muscle paralysis leading to death. They are also potential biothreat agents. A systematic investigation of various short peptide inhibitors of the BoNT protease domain with a 17-residue peptide substrate led to arginine-arginine-glycine-cysteine having a basic tetrapeptide structure as the most potent inhibitor. When assayed in the presence of dithiothreitol (DTT), the inhibitory effect was drastically reduced. Replacing the terminal cysteine with one hydrophobic residue eliminated the DTT effect but with two hydrophobic residues made the pentapeptide a poor inhibitor. Replacing the first arginine with cysteine or adding an additional cysteine at the N terminus did not improve inhibition. When assessed using mouse brain lysates, the tetrapeptides also inhibited BoNT/A cleavage of the endogenous SNAP-25. The peptides penetrated the neuronal cell lines, N2A and BE(2)-M17, without adversely affecting metabolic functions as measured by ATP production and P-38 phosphorylation. Biological activity of the peptides persisted within cultured chick motor neurons and rat and mouse cerebellar neurons for more than 40 h and inhibited BoNT/A protease action inside the neurons in a dose- and time-dependent fashion. Our results define a tetrapeptide as the smallest peptide inhibitor in the backdrop of a large substrate protein of 200+ amino acids having multiple interaction regions with its cognate enzyme. The inhibitors should also be valuable candidates for drug development. 相似文献
227.
Design and synthesis of broad-based mono- and bi- cyclic inhibitors of FIV and HIV proteases 总被引:2,自引:0,他引:2
Mak CC Brik A Lerner DL Elder JH Morris GM Olson AJ Wong CH 《Bioorganic & medicinal chemistry》2003,11(9):2025-2040
Based on the substrate transition state and our strategy to tackle the problem of drug resistance, a series of HIV/FIV protease (HIV /FIV PR) monocyclic inhibitors incorporating a 15- or 17-membered macrocycle with an equivalent P3 or P3' group and a unique unnatural amino acid, (2R, 3S)-3-amino-2-hydroxy-4-phenylbutyric acid, have been designed and synthesized. In addition, based on the structure of TL3 with small P3/P3' group, we have synthesized two conformationally restricted bicyclic inhibitors containing the macrocycle, which mimic the P1/P1'-P3/P3' tripeptide [Phe-Val-Ala] of TL3. We have found that the contribution of the macrocycle in our monocyclic inhibitors is important to the overall activity, but the ring size does not affect the activity to a significant extent. Several inhibitors that were developed in this work, exhibit low nanomolar inhibitory activity against the wild-type HIV/FIV PR and found to be highly effective against some drug-resistant as well as TL3-resistant mutants of HIV PRs. Compound 15, in particular, is the most effective cyclic inhibitor in hand to inhibit FIV replication in tissue culture at a concentration of 1.0 micro g/mL (1.2 microM). 相似文献
228.
Parastoo Pourali Behrooz Yahyaei Hatef Ajoudanifar Rahele Taheri Hassan Alavi Ashraf Hoseini 《Current microbiology》2014,69(6):785-793
Different wound dressings with antibacterial property have been surveyed and one among them is bacterial cellulose (BC). Since the BC does not have antibacterial property, the biologically produced silver nanoparticles (SNPs) were impregnated into the BC. For the BC production, Hestrin–Schramm broth was used. Formation of the BC was proven by enzymatic hydrolysis. For SNPs production, the bacterial supernatant was treated with AgNO3 and formation of SNPs was monitored through spectrophotometer, TEM and XRD. For impregnation of SNPs into the BC, the cleaned membrane was placed in the bacterial supernatant that contained 1 mmol of AgNO3. The antibacterial assay was done for the BC/SNPs. Enzymatic hydrolysis proved the presence of the BC. Spectrophotometer and XRD results showed the formation of SNPs. TEM analysis revealed the presence of SNPs with sizes around 5–100 nm. SEM micrographs showed the impregnation of SNPs into the BC. Antibacterial test exhibited the antibacterial activity of the BC/SNPs. 相似文献
229.
Heba M. Mahdy Mohamed R. Mohamed Manal A. Emam Amr M. Karim Ashraf B. Abdel-Naim Amani E. Khalifa 《Neurochemical research》2014,39(2):321-332
Puerarin (daidzein-8-C-glucoside), a major isoflavone glycoside purified from Pueraria lobata, is well reported to have a neuroprotective effect primarily by the antioxidant mechanisms. This investigation was designed to evaluate the efficacy of Puerarin (Pur) to offset 3-nitropropionic acid (3-NP) induced neurotoxicity. Male Wistar strain rats were given 3-NP (20 mg/kg, s.c.) over five consecutive days, whereas Pur (200 mg/kg, i.p.) was administrated 30 min before 3-NP. Rats treated with 3-NP exhibited significant weight loss, reduction of the prepulse inhibition, locomotor hypoactivity and hypothermia. The striata, hippocampi and cortices of the 3-NP treated rats showed abnormal levels of neurotransmitters, oxidative damage and characteristic histopathological lesions. Treatment with Pur ahead of 3-NP, significantly prevented weight loss, PPI deficit, locomotor hypoactivity and hypothermia. Pur treatment blocked the 3-NP-induced neurotransmitters abnormalities (GABA, DA, 5-HT and NE), and normalized the oxidative stress biomarkers (lipid peroxidation, reduced glutathione, glutathione peroxidase). Histopathological examination further affirmed Pur’s neuroprotective effect against 3-NP-induced neurotoxicity. In conclusion, Pur protected the brain tissues from 3-NP induced neurotoxicity primarily by its neuromodulation and antioxidant effect. 相似文献
230.
Mohammad Arif Ashraf Achia Khatun Tanzila Sharmin Faraid Mobin Arifur Rahman Tanu Toufique Morshed Tawkir Ahmad Fakir Rifat Ara Begum AHM Nurun Nabi 《Bioinformation》2014,10(6):384-386
The term of medicinal plants include a various types of plants used in herbalism with medicinal activities. These plants are
considered as rich resources of ingredients which can be used as complementary and alternative medicines and, also in drug
developments and synthesis. In addition, some plants regarded as valuable origin of nutrition. Thus, all these plants are
recommended as therapeutic agents. Information related to medicinal plants and herbal drugs accumulated over the ages are
scattered and unstructured which make it prudent to develop a curated database for medicinal plants. MPDB 1.0 database is
dedicated to provide the first window to find the plants around Bangladesh claimed to have medicinal and/or nutritive values by
accumulating data from the published literatures. This database contains 406 medicinal plants with their corresponding scientific,
family and local names as well as utilized parts for treatment from different districts of Bangladesh. Information regarding
ailments is available for 353 plants. In addition, we have found active compounds for 78 plants with their corresponding PubMed
ID.