排序方式: 共有188条查询结果,搜索用时 281 毫秒
81.
Eugen Schell Ghada Nouairia Elisabeth Steiner Niclas Weber Daniel Lundin Christoph Loderer 《The Journal of biological chemistry》2021,297(2)
Ribonucleotide reductases (RNRs) catalyze the reduction of ribonucleotides to the corresponding deoxyribonucleotides, the building blocks of DNA. RNRs are specific for either ribonucleoside diphosphates or triphosphates as substrates. As far as is known, oxygen-dependent class I RNRs (NrdAB) all reduce ribonucleoside diphosphates, and oxygen-sensitive class III RNRs (NrdD) are all ribonucleoside triphosphate reducers, whereas the adenosylcobalamin-dependent class II (NrdJ) contains both ribonucleoside diphosphate and triphosphate reducers. However, it is unknown how this specificity is conveyed by the active site of the enzymes and how this feature developed in RNR evolution. By structural comparison of the active sites in different RNRs, we identified the apical loop of the phosphate-binding site as a potential structural determinant of substrate specificity. Grafting two residues from this loop from a diphosphate- to a triphosphate-specific RNR caused a change in preference from ribonucleoside triphosphate to diphosphate substrates in a class II model enzyme, confirming them as the structural determinants of phosphate specificity. The investigation of the phylogenetic distribution of this motif in class II RNRs yielded a likely monophyletic clade with the diphosphate-defining motif. This indicates a single evolutionary-split event early in NrdJ evolution in which diphosphate specificity developed from the earlier triphosphate specificity. For those interesting cases where organisms contain more than one nrdJ gene, we observed a preference for encoding enzymes with diverse phosphate specificities, suggesting that this varying phosphate specificity confers a selective advantage. 相似文献
82.
Turki S Mrabet G Jabloun Z Destain J Thonart P Kallel H 《Biotechnology and applied biochemistry》2010,57(4):139-149
Yarrowia lipolytica lipase has been assumed to be a good candidate for the treatment of fat malabsorption in patients with pancreatic insufficiency. Nevertheless, no systematic studies on its stability under physiological conditions pertaining to the human GI (gastrointestinal) tract have been published. Stability of various Y. lipolytica lipase powder formulations at various physiological pH values as well as the effect of digestive proteases and bile salts on enzyme activity were investigated. Results were compared with those obtained from another competing fungal lipase sourced from Candida rugosa. Among the studied formulations, Y. lipolytica lipase stabilized with gum arabic and skimmed milk powder was the most promising powder formulation. Under acidic conditions (pH 3-5), this formulation showed higher stability than those observed with the other Y. lipolytica lipase formulations and C. rugosa lipase. In addition, in the presence of gum arabic and skimmed milk powder as additives, Y. lipolytica lipase exhibited markedly higher resistance to pepsin, trypsin and chymotrypsin actions. Resistance to proteolytic degradation by digestive proteases was also by far higher than that observed with C. rugosa lipase. Similar behaviour was, however, observed when these two fungal lipases were incubated with increased concentrations of bile salts. Residual lipase activity of both fungal lipases showed a slight decrease in NaTDC (sodium taurodeoxycholate) concentration above 4 mM. Consequently, Y. lipolytica lipase formulated with gum arabic and milk powder seemed to have great potential for use as a therapeutic tool for patients with pancreatic insufficiency. 相似文献
83.
Ghada Allan Halima Ouadid-Ahidouch Elena M. Sanchez-Fernandez Rocío Risquez-Cuadro José M. Garcia Fernandez Carmen Ortiz-Mellet Ahmed Ahidouch 《PloS one》2013,8(10)
sp2-Iminosugar-type castanospermine analogues have been shown to exhibit anti-tumor activity. However, their effects on cell proliferation and apoptosis and the molecular mechanism at play are not fully understood. Here, we investigated the effect of two representatives, namely the pseudo-S- and C-octyl glycoside 2-oxa-3-oxocastanospermine derivatives SO-OCS and CO-OCS, on MCF-7 and MDA-MB-231 breast cancer and MCF-10A mammary normal cell lines. We found that SO-OCS and CO-OCS inhibited breast cancer cell viability in a concentration- and time-dependent manner. This effect is specific to breast cancer cells as both molecules had no impact on normal MCF-10A cell proliferation. Both drugs induced a cell cycle arrest. CO-OCS arrested cell cycle at G1 and G2/M in MCF-7 and MDA-MB-231cells respectively. In MCF-7 cells, the G1 arrest is associated with a reduction of CDK4 (cyclin-dependent kinase 4), cyclin D1 and cyclin E expression, pRb phosphorylation, and an overexpression of p21Waf1/Cip1. In MDA-MB-231 cells, CO-OCS reduced CDK1 but not cyclin B1 expression. SO-OCS accumulated cells in G2/M in both cell lines and this blockade was accompanied by a decrease of CDK1, but not cyclin B1 expression. Furthermore, both drugs induced apoptosis as demonstrated by the increased percentage of annexin V positive cells and Bax/Bcl-2 ratio. Interestingly, in normal MCF-10A cells the two drugs failed to modify cell proliferation, cell cycle progression, cyclins, or CDKs expression. These results demonstrate that the effect of CO-OCS and SO-OCS is triggered by both cell cycle arrest and apoptosis, suggesting that these castanospermine analogues may constitute potential anti-cancer agents against breast cancer. 相似文献
84.
Mohammed A. Farid Eglal A. Ghoneimy Maie A. El-Khawaga Asmaa Negm-Eldein Ghada E. A. Awad 《Annals of microbiology》2013,63(2):523-531
Response surface methodology (RSM), employing the fractional factorial design (FFD) was used to optimize the fermentation medium for the production of glucose oxidase (GOD) from a marine isolate (NRC9) of Aspergillus niger under submerged fermentation. The design was employed by selecting glucose, CaCO3, ammonium phosphate and MgSO4 concentrations as model factors by ‘one variable at a time’ experiment. A second-order quadratic model and response surface method showed that the optimum concentrations (g/l) glucose, 100; CaCO3, 25; (NH4)2HPO4, 1.8 and 0.4 of MgSO4, resulted in an improvement of GOD production (170?±?0.88 U/ml) as compared to the initial level (109.81?±?1.38 U/ml) after four days of incubation at 200 rpm and 30 °C, whereas its predicted value obtained by the quadratic model was 164.36 U/ml. Analysis of variance (ANOVA) showed a high coefficient of determination value (R 2) of 0.967, ensuring a satisfactory adjustment of the quadratic model with the experimental data. This is the first report on production of glucose oxidase from a marine fungal isolate, Aspergillus niger NRC9, using statistical experimental design and response surface methodology in optimization of its production under submerged fermentation. 相似文献
85.
Lubna A. Al-Ansary Andrea C. Tricco Yaser Adi Ghada Bawazeer Laure Perrier Mohammed Al-Ghonaim Nada AlYousefi Mariam Tashkandi Sharon E. Straus 《PloS one》2013,8(1)
Background
Despite the availability of clinical practice guidelines (CPGs), optimal hypertension control is not achieved in many parts of the world; one of the challenges is the volume of guidelines on this topic and their variable quality. To systematically review the quality, methodology, and consistency of recommendations of recently-developed national CPGs on the diagnosis, assessment and the management of hypertension.Methodology/Principal Findings
MEDLINE, EMBASE, guidelines'' websites and Google were searched for CPGs written in English on the general management of hypertension in any clinical setting published between January 2006 and September 2011. Four raters independently appraised each CPG using the AGREE-II instrument and 2 reviewers independently extracted the data. Conflicts were resolved by discussion or the involvement of an additional reviewer. Eleven CPGs were identified. The overall quality ranged from 2.5 to 6 out of 7 on the AGREE-II tool. The highest scores were for “clarity of presentation” (44.4% −88.9%) and the lowest were for “rigour of development” (8.3%–30% for 9 CGPs). None of them clearly reported being newly developed or adapted. Only one reported having a patient representative in its development team. Systematic reviews were not consistently used and only 2 up-to-date Cochrane reviews were cited. Two CPGs graded some recommendations and related that to levels (but not quality) of evidence. The CPGs'' recommendations on assessment and non-pharmacological management were fairly consistent. Guidelines varied in the selection of first-line treatment, adjustment of therapy and drug combinations. Important specific aspects of care (e.g. resistant hypertension) were ignored by 6/11 CPGs. The CPGs varied in methodological quality, suggesting that their implementation might not result in less variation of care or in better health-related outcomes.Conclusions/Significance
More efforts are needed to promote the realistic approach of localization or local adaptation of existing high-quality CPGs to the national context. 相似文献86.
Jessica Tyrrell Tamara S. Galloway Ghada Abo-Zaid David Melzer Michael H. Depledge Nicholas J. Osborne 《PloS one》2013,8(11)
Background
In recent years there has been an exponential increase in tungsten demand, potentially increasing human exposure to the metal. Currently, the toxicology of tungsten is poorly understood, but mounting evidence suggests that both the elemental metal and its alloys have cytotoxic effects. Here, we investigate the association between tungsten and cardiovascular disease (CVD) or stroke using six waves of the National Health and Nutrition Examination Survey (NHANES).Methods
We investigated associations using crude and adjusted logistic regression models in a cohort of 8614 adults (18–74 years) with 193 reported stroke diagnoses and 428 reported diagnoses of CVD. We also stratified our data to characterize associations in a subset of younger individuals (18–50 years).Results
Elevated tungsten concentrations were strongly associated with an increase in the prevalence of stroke, independent of typical risk factors (Odds Ratio (OR): 1.66, 95% Confidence Interval (95% CI): 1.17, 2.34). The association between tungsten and stroke in the young age category was still evident (OR: 2.17, 95% CI: 1.33, 3.53).Conclusion
This study represents the most comprehensive analysis of the human health effects of tungsten to date. Individuals with higher urinary tungsten concentrations have double the odds of reported stroke. We hypothesize that the pathological pathway resulting from tungsten exposure may involve oxidative stress. 相似文献87.
Ryan?P. Liegel Mark?T. Handley Adam Ronchetti Stephen Brown Lars Langemeyer Andrea Linford Bo Chang Deborah?J. Morris-Rosendahl Sarah Carpanini Renata Posmyk Verity Harthill Eamonn Sheridan Ghada?M.H. Abdel-Salam Paulien?A. Terhal Francesca Faravelli Patrizia Accorsi Lucio Giordano Lorenzo Pinelli Britta Hartmann Allison?D. Ebert Francis?A. Barr Irene?A. Aligianis Duska?J. Sidjanin 《American journal of human genetics》2013,92(6):1001-1007
Infantile myofibromatosis (IM) is a disorder of mesenchymal proliferation characterized by the development of nonmetastasizing tumors in the skin, muscle, bone, and viscera. Occurrence within families across multiple generations is suggestive of an autosomal-dominant (AD) inheritance pattern, but autosomal-recessive (AR) modes of inheritance have also been proposed. We performed whole-exome sequencing (WES) in members of nine unrelated families clinically diagnosed with AD IM to identify the genetic origin of the disorder. In eight of the families, we identified one of two disease-causing mutations, c.1978C>A (p.Pro660Thr) and c.1681C>T (p.Arg561Cys), in PDGFRB. Intriguingly, one family did not have either of these PDGFRB mutations but all affected individuals had a c.4556T>C (p.Leu1519Pro) mutation in NOTCH3. Our studies suggest that mutations in PDGFRB are a cause of IM and highlight NOTCH3 as a candidate gene. Further studies of the crosstalk between PDGFRB and NOTCH pathways may offer new opportunities to identify mutations in other genes that result in IM and is a necessary first step toward understanding the mechanisms of both tumor growth and regression and its targeted treatment. 相似文献
88.
Ghada Ben Salah Hassen Kamoun Ahmed Rebai Rafika Hajji Mohamed-Elaarbi Masmoudi Hamadi Ayadi 《人类与生态风险评估》2013,19(4):1089-1101
Gasoline constitutes a mixture of chemicals that contain well-known genotoxicants. Thus, chronic occupational exposure to gasoline may be considered to possess genotoxic risk. In this study, the frequencies of total chromosomal aberrations (TCA), aberrant cells (Ab.c.), sister chromatid exchanges (SCE), high-frequency cells (HFC), and high-frequency cell individual (HFI) were investigated in peripheral blood lymphocytes from 17 gasoline-exposed workers (10 smokers and 7 non-smokers) and 22 unexposed reference subjects (12 smokers and 10 non-smokers). The exposed subjects were gasoline truck loaders at a gasoline company from Tunis City, north of Tunisia. The results indicate multiple CA, such as dicentrics (DIC), chromatid breaks (SB), and chromosome breaks (DB). A significant difference was observed in TCA and Ab.c. frequencies between exposed and unexposed groups (p < 0.01). A significant difference was found in frequencies of SCE (p < 0.01) and HFI (p < 0.05) between exposed and unexposed groups. SCE and TCA frequencies of smokers were found to be significantly higher than those of non-smokers in both groups. There was an interaction between gasoline exposure and smoking habit for TCA (p = 0.020), but not for SCE. Our findings indicate that gasoline truck loaders were under risk of significant cytogenetic damage that was enhanced by their smoking habit. 相似文献
89.
90.
Ghada M. Ajabnoor Suhad Bahijri Anwar Borai Altaf A. Abdulkhaliq Jumana Y. Al-Aama George P. Chrousos 《PloS one》2014,9(5)