首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   42篇
  免费   0篇
  2021年   1篇
  2019年   2篇
  2018年   1篇
  2015年   6篇
  2014年   2篇
  2013年   4篇
  2012年   9篇
  2011年   4篇
  2010年   3篇
  2007年   2篇
  2006年   2篇
  2005年   3篇
  2004年   1篇
  1982年   1篇
  1981年   1篇
排序方式: 共有42条查询结果,搜索用时 343 毫秒
31.
Abstract

An objective assessment of exposure to tobacco smoke may be accomplished by means of examining particular biomarkers in body fluids. The most common biomarker of tobacco smoke exposure is urinary, or serum, cotinine. In order to distinguish non-smokers from passive smokers and passive smokers from active smokers, it is necessary to estimate cotinine cut-off points. The objective of this article was to apply statistical distribution of urinary cotinine concentration to estimate cut-off points distinguishing the three above-mentioned groups. The examined group consisted of 327 volunteers (187 women and 140 men) who were ethnically homogenous inhabitants of the same urban agglomeration (Sosnowiec, Poland). The values which enabled differentiation of the examined population into groups and subgroups were as follows: 50 µg l?1 (differentiation of non-smokers from passive smokers), 170 µg l?1 (to divide the group of passive smokers into two subgroups: minimally and highly exposed to environmental tobacco smoke), 550 µg l?1 (differentiation of passive smokers from active smokers), and 2100 µg l?1 (to divide group of active smokers into two subgroups: minimally and highly exposed to tobacco smoke). The results suggest that statistical distribution of urinary cotinine concentration is useful for estimating urinary cotinine cut-off points and for assessing the smoking status of persons exposed to tobacco smoke.  相似文献   
32.
Some sheep breeds are naturally prolific, and they are very informative for the studies of reproductive genetics and physiology. Major genes increasing litter size (LS) and ovulation rate (OR) were suspected in the French Grivette and the Polish Olkuska sheep populations, respectively. To identify genetic variants responsible for the highly prolific phenotype in these two breeds, genome-wide association studies (GWAS) followed by complementary genetic and functional analyses were performed. Highly prolific ewes (cases) and normal prolific ewes (controls) from each breed were genotyped using the Illumina OvineSNP50 Genotyping Beadchip. In both populations, an X chromosome region, close to the BMP15 gene, harbored clusters of markers with suggestive evidence of association at significance levels between 1E−05 and 1E−07. The BMP15 candidate gene was then sequenced, and two novel non-conservative mutations called FecXGr and FecXO were identified in the Grivette and Olkuska breeds, respectively. The two mutations were associated with the highly prolific phenotype (pFecXGr = 5.98E−06 and pFecXO = 2.55E−08). Homozygous ewes for the mutated allele showed a significantly increased prolificacy (FecXGr/FecXGr, LS = 2.50±0.65 versus FecX+/FecXGr, LS = 1.93±0.42, p<1E−03 and FecXO/FecXO, OR = 3.28±0.85 versus FecX+/FecXO, OR = 2.02±0.47, p<1E−03). Both mutations are located in very well conserved motifs of the protein and altered the BMP15 signaling activity in vitro using a BMP-responsive luciferase test in COV434 granulosa cells. Thus, we have identified two novel mutations in the BMP15 gene associated with increased LS and OR. Notably, homozygous FecXGr/FecXGr Grivette and homozygous FecXO/FecXO Olkuska ewes are hyperprolific in striking contrast with the sterility exhibited by all other known homozygous BMP15 mutations. Our results bring new insights into the key role played by the BMP15 protein in ovarian function and could contribute to a better understanding of the pathogenesis of women′s fertility disorders.  相似文献   
33.
Fusarium culmorum and Fusarium oxysporum are the most common fungal pathogens of flax (Linum usitatissimum L.), thus leading to the greatest losses in crop yield. A subtractive cDNA library was constructed from flax seedlings exposed for two days to F. oxysporum. This revealed a set of genes that are potentially involved in the flax defense responses. Two of those genes directly participate in cell wall sugar polymer metabolism: UDP-d-glucuronate 4-epimerase (GAE; EC 5.1.3.6) and formate dehydrogenase (FDH; EC 1.2.1.2). GAE delivers the main substrate for pectin biosynthesis, and decreases were detected in its mRNA level after Fusarium infection. FDH participates in the metabolism of formic acid, and the expression level of its gene increased after Fusarium infection. However, metabolite profiling analysis disclosed that the pectin content in the infected plants remained unchanged, but that there were reductions in both the levels of the soluble sugars that serve as pectin precursors, and in the level of formic acid. Since formic acid is the product of pectin demethylesterification, the level of mRNAs coding for pectin methylesterase (EC 3.1.1.11) in the infected flax was measured, revealing a decrease in its expression upon plant infection. Transgenic flax plants overexpressing fungal polygalacturonase (EC 3.2.1.15) and rhamnogalacturonase (EC 3.2.1.-) showed a decrease in the pectin content and an elevated level of formic acid, but the level of expression of the FDH gene remained unchanged. It is suspected that the expression of the formate dehydrogenase gene is directly controlled by the pathogen in the early stage of infection, and additionally by pectin degradation in the later stages.  相似文献   
34.
A sterically constrained non-coded amino acid, 1-aminocyclopentane-1-carboxylic acid (Apc), was introduced in position 7 or 8 of the bradykinin (BK) B(2) receptor antagonist, [D-Arg(0), Hyp(3), Thi(5, 8), D-Phe(7)]BK, previously synthesized by Stewart's group. This modification is believed to reduce the flexibility of the peptides, thereby forcing the peptide backbone and side chains to adopt specific orientations. Apc substitution was combined with acylation of the N-terminus with 1-adamantaneacetic acid (Aaa). The activity of four new analogues was assayed in isolated rat uterus and in rat blood pressure tests. The results clearly demonstrated that the Apc residue inserted in position 7 led to a reduction of antagonistic properties in the rat uterus assay or even restored the agonism in the blood pressure test, whereas Apc at position 8 enhanced antagonistic potency in both the tests. In both cases, acylation of the N-terminus led to the enhancement of the antagonistic potency. On the basis of these findings, new potent and selective B(2) blockers might be designed.  相似文献   
35.
To evaluate the synergistic effect of estrogens and progesterone on prolactin secretion, rhesus and cynomolgus monkeys in the early follicular phase received estradiol benzoate (100 μg/kg/day, sc) alone for 14 days, then in combination with progesterone (subcutaneous silastic capsule) for an additional 14 days. Blood was drawn daily by femoral venipuncture under ketamine hydrochloride anesthesia (15mg/kg). Similarly, this protocol for exogenous steroid treatment was employed in a monkey having a chronically indwelling (femoral insertion into the vena cava) cannula maintained by a vest and mobile tether apparatus; however, no anesthesia was used to obtain serum specimens. In addition, this assembly was applied to six monkeys to determine the acute effects of ketamine hydrochloride on prolactin secretion. Concentrations of prolactin, estradiol-17β, and progesterone in serum were determined by conventional radioimmunoassays. Under estrogen therapy alone, mean circulating prolactin levels declined from ~15 to < 5 ng/ml; in contrast, the addition of progesterone caused an abrupt serum prolactin elevation, ~8–12 fold. This estradiol-progesterone course led to sustained hyperprolactinemia in the chronically catheterized Monkey, whereas ketamine administration raised serum prolactin only briefly, the elevation lasting less than three hours after injection. These findings establish that an estrogen-progesterone synergy, separate from the transient effects of ketamine, Induced hyperprolactinemia in cycling monkeys having prevailing levels of estrogen and progesterone near those characteristic of late gestation, when sustained prolactin elevations are observed normally.  相似文献   
36.
Series of new ring-substituted styrylquinolines and two oxorhenium complexes were prepared and characterized. The compounds were analyzed using RP-HPLC to determine lipophilicity. Primary in vitro screening of the synthesized compounds was performed against fungal and bacterial strains. Some compounds were active against bacteria at micromolar level and against fungi at submicromolar level. Compounds 5,7-dichloro-2-[2-(2-ethoxyphenyl)vinyl]quinolin-8-ol expressed excellent antifungal activity comparable with or higher than the standard fluconazole as well as antibacterial activity against Staphylococcus strains comparable with or higher than the standards bacitracin, penicillin and ciprofloxacin. The structure–activity relationships are discussed.  相似文献   
37.
New norcantharidin analogs were designed and obtained as compounds with biological activity. As a starting material, exo‐7‐oxabicyclo[2.2.1]heptane‐2,3‐dicarboxylic acid anhydride was used. Three groups of compounds: dicarboximides, triazoles and thiazolidines were obtained in multistep reactions. The 1H‐ and 13C‐NMR spectra were used to confirm the structures of all obtained products and they were in agreement with the proposed structure of substances. All derivatives were screened for their antioxidant activity. The most promising group was dicarboximides ( 1 – 4 , 6 ). Derivatives 2–4 displayed antioxidant activity with EC50=7.75–10.89 μg/ml, which may be comparable to strong antioxidant Trolox (EC50=6.13 μg/ml). Excellent activity with EC50=10.75 μg/ml also presented norcantharidin analog with 1,2,4‐triazole system ( 12 ).  相似文献   
38.
Molecular Biology Reports - Physiological balance between pro- and antioxidative processes is crucial for placentation and further development of fetus and placenta. Parameters of pro- and...  相似文献   
39.
The solution conformation of vasopressin analogues, modified at positions 2 and 3 with N-methylphenylalanine or its enantiomer, [D-MePhe2,MePhe3]AVP and [MePhe2,D-MePhe3]AVP, were studied by 2D NMR spectroscopy in H2O/D2O and theoretical calculations (EDMC/ANALYZE). In the case of [MePhe2,D-MePhe3]AVP, the synthesis afforded two products, A and B, which had identical molecular ions and similar retention times on HPLC. This finding was explained by racemization of Cys1, which gave an additional analogue, [D-Cys1,MePhe2,D-MePhe3]AVP (B). The possibility is not excluded of racemization of Cys1 in the remaining analogues of this series. However, only in the case of [MePhe2,D-MePhe3]AVP was this process so distinct that two strong peaks in the HPLC chromatogram were observed. The NMR spectra of all the analogues showed several distinct sets of residual proton resonances. This suggests that the peptides adopt more than two groups of conformations in H2O/D2O. This fact is due to cis/trans isomerization. Two more populated isomers arise from the cis/trans isomerization across the 2-3 peptide bond in [D-MePhe2,MePhe3]AVP and [MePhe2,D-MePhe3]AVP (A) and across the 1-2 peptide bond in [D-Cys1,MePhe2,D-MePhe3]AVP (B).  相似文献   
40.
Organotellurides are newly described redox-catalyst molecules with original pro-oxidative properties. We have investigated the in vitro and in vivo antitumoral effects of the organotelluride catalyst LAB027 in a mouse model of colon cancer and determined its profile of toxicity in vivo. LAB027 induced an overproduction of H2O2 by both human HT29 and murine CT26 colon cancer cell lines in vitro. This oxidative stress was associated with a decrease in proliferation and survival rates of the two cell lines. LAB027 triggered a caspase-independent, ROS-mediated cell death by necrosis associated with mitochondrial damages and autophagy. LAB027 also synergized with the cytotoxic drug oxaliplatin to augment its cytostatic and cytotoxic effects on colon cancer cell lines but not on normal fibroblasts. The opposite effects of LAB027 on tumor and on non-transformed cells were linked to differences in the modulation of reduced glutathione metabolism between the two types of cells. In mice grafted with CT26 tumor cells, LAB027 alone decreased tumor growth compared with untreated mice, and synergized with oxaliplatin to further decrease tumor development compared with mice treated with oxaliplatin alone. LAB027 an organotelluride catalyst compound synergized with oxaliplatin to prevent both in vitro and in vivo colon cancer cell proliferation while decreasing the in vivo toxicity of oxaliplatin. No in vivo adverse effect of LAB027 was observed in this model.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号