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   91篇
  免费   2篇
  2023年   1篇
  2020年   3篇
  2019年   1篇
  2018年   1篇
  2015年   3篇
  2014年   7篇
  2013年   7篇
  2012年   10篇
  2011年   8篇
  2010年   5篇
  2009年   3篇
  2008年   6篇
  2007年   7篇
  2006年   8篇
  2005年   9篇
  2004年   3篇
  2003年   6篇
  2002年   4篇
  1986年   1篇
排序方式: 共有93条查询结果,搜索用时 218 毫秒
41.
Colorectal cancer (CRC) develops as a multi-step process which results from gradual accumulation of mutations in proto-oncogenes, tumor suppressor, and DNA repair genes. Mortality rate of CRC is very high. Therefore, development of alternative diagnostic methods which can be used in the early diagnosis is crucial. ATP2B4 gene encodes one of the four isoforms of p-type ATPase PMCA enzyme and bears critical importance in maintaining the balance of intracellular calcium homeostasis by providing the export of calcium ions out of the cell. ATP5B encodes a subunit of the mitochondrial ATP synthase which is an f-type ATPase. In this study, the relationship between ATP2B4 and ATP5B genes and CRC regarding gene expression was investigated. Study groups were constructed from a number of 50 patients (25 males, 25 females) with the mean age of 55.68 ± 9.4 and the gene expression levels in the healthy and cancerous tissues of the patients were compared by using semi-quantitative PCR and Real-Time PCR methods. As a result, in patients with rectum tumors, there was a significant relationship between ATP2B4 gene expression and the tumor location and in patients younger than 45 years, ATP5B gene expressions were detected significantly higher in tumor tissues by using RT-PCR. However, no significant relationship was detected in terms of expression differences of ATP2B4 and ATP5B genes between cancerous and healthy tissues of the CRC patients. ATP2B4 and ATP5B genes might have indirect associations in CRC pathogenesis and the investigation of their interactions with DNA repair and other related genes may help in understanding of CRC formation.  相似文献   
42.
Rosularia globulariifolia (Fenzl) A. Berger and R. pallidiflora (Holmboe) Meikle were originally described as species in Umbilicus DC. in 1842 and 1914, respectively. In the present study, morphological and palynological features were examined in detail to determine the status of these taxa. The general characteristics, seed structure and micromorphology, pollen measurements and pollen characteristics were established. Morphologically, the two taxa cannot easily be distinguished. Pollen grains of both species are tricolporate, subspheroidal and eutectate, ornamentation is psilate and exine structures are similar. Based on morphological and palynological similarities, and the fact that both taxa are found in the same habitats, we propose that R. pallidiflora should be reduced to the rank of variety as Rosularia globulariifolia (Fenzl) A. Berger var. pallidiflora (Meikle) Minareci & K. Yildiz comb. et stat. nov.  相似文献   
43.
This report addresses the functional role of His residues in the proton-coupled folate transporter (PCFT; SLC46A1), which mediates intestinal folate absorption. Of ten His residues, only H247A and H281A mutations altered function. The folic acid influx Kt at pH 5.5 for H247A was ↓8.4-fold. Although wild type (WT)-PCFT Ki values varied among the folates, Ki values were much lower and comparable for H247-A, -R, -Q, or -E mutants. Homology modeling localized His247 to the large loop separating transmembrane domains 6 and 7 at the cytoplasmic entrance of the translocation pathway in hydrogen-bond distance to Ser172. The folic acid influx Kt for S172A-PCFT was decreased similar to H247A. His281 faces the extracellular region in the seventh transmembrane domain. H281A-PCFT results in loss-of-function due to ∼12-fold↑ in the folic acid influx Kt. When the pH was decreased from 5.5 to 4.5, the WT-PCFT folic acid influx Kt was unchanged, but the Kt decreased 4-fold for H281A. In electrophysiological studies in Xenopus oocytes, both WT-PCFT- and H281A-PCFT-mediated folic acid uptake produced current and acidification, and both exhibited a low level of folate-independent proton transport (slippage). Slippage was markedly increased for the H247A-PCFT mutant. The data suggest that disruption of the His247 to Ser172 interaction results in a PCFT conformational alteration causing a loss of selectivity, increased substrate access to a high affinity binding pocket, and proton transport in the absence of a folate gradient. The His281 residue is not essential for proton coupling but plays an important role in PCFT protonation, which, in turn, augments folate binding to the carrier.  相似文献   
44.
Background: A common G to A polymorphism (G870A) in the splice donor region of exon 4 of cyclin D1 (CCND1) gene generates two mRNAs (cyclin D1a and D1b) through an alternative splicing at the site of this polymorphism. Cyclin D1a and b proteins differ in their COOH-terminus, a region involved in protein degradation. We examined the association between this CCDN1 genotype and the susceptibility to hepatocellular carcinoma (HCC) in a Turkish population. Methods: The genotype frequency of this polymorphism was determined by using a polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) assay. Hospital-based case–control study was designed consisting of 160 diagnosis subjects with hepatocellular carcinoma and 160 cancer-free control subjects matched on age, gender, smoking and alcohol status. Results: The allele frequencies of case subjects (A, 0.55; G, 0.45) were significantly different from those of control subjects (A, 0.42; G, 0.58) (p = 0.002). The odds ratios (ORs) for the CCND1 870 GA and AA genotypes when compared with the GG genotypes were 1.39 (95% confidence interval [CI] 0.82–2.36, p = 0.22) and 2.52 (95% CI 1.38–4.62, p = 0.003) respectively. The presence of at least one CCND1 870A allele was associated with increased risk for HCC (OR, 1.73; 95% CI, 1.06–2.82, p = 0.03). When combining the GG and GA genotypes as a reference genotype, we found that the OR for the AA genotype was 2.06 (95% CI 1.24–3.44, p = 0.006). Conclusion: Our results suggest that the CCND1 G870A single nucleotide polymorphism is associated with an increased risk of HCC in our Turkish population.  相似文献   
45.
Defining "healthy weight" is not easy and for an adolescent with all concerns about newly developing physiognomy it is even harder. The aim of this study was to find out the frequency of obesity and the association between the body mass index (BMI), weight-control behaviors and self-perceived body weight status in high school students of a southern city of Turkey. The students from 10 schools were randomly selected among 46,271 students of 72 high schools in Adana from 1999 to 2000. The response rate was 94.8% (2352/2480). The Turkish version of Youth Risk Behavior Survey Questionnaire (YRBSQ) was completed by the students. The students' weights and heights were measured. The mean age was 16.5 +/- 1.0 years of age (range = 14-21 years). The mean BMI was 21.0 +/- 3.1, 25.5% of students were underweight, 65.7% were normal, 6.4% were overweight and 2.3% were obese (p = 0.0001). Of all students, 24.3% defined themselves as thin, 45.3% as normal, 24.9% as overweight and 5.5% as obese (p = 0.0001). The percentage of girls defining their body weight as overweight and obese was significantly higher than the boys (p = 0.0001). Of all students, 35.5% wanted to lose weight, 22.3% wanted to gain weight, 27.8% wanted to keep their current weight. Intention (p = 0.0001) and interventions to lose weight such as going on a diet (p = 0.0001), provocative vomiting (p = 0.0001) and 24-hours starving (p = 0.0001) were significantly higher in girls than boys. Of students, 26.8% (n=620) were on a diet program either to lose or to keep their body weight. There was significant relationship between being on a diet program and intention to change body weight (p = 0.047). We concluded that adolescents living in Adana have relatively higher risk of being underweight than being obese and have unhealthy weight changing plans due to their misperception of their body images. Adolescents may be unconscious on plans and attempts to change their body weights and nutrition and we suggest that education on nutrition and health is required for adolescents.  相似文献   
46.
In this study, bioaccumulation and heavy metal resistance of Cd2+, Cu2+, Co2+ and Mn2+ ions by thermophilic Geobacillus thermantarcticus and Anoxybacillus amylolyticus was investigated. The bacteria, in an order with respect to metal resistance from the most resistant to the most sensitive, was found to be Mn2+ > Co2+ > Cu2+ > Cd2+ for both G. thermantarcticus and A. amylolyticus. It was determined that the highest metal bioaccumulation was performed by A. amylolyticus in Mn2+ (28,566 μg/g dry weight), and the lowest metal bioaccumulation was performed by A. amylolyticus in Co2+ (327.3 μg/g dry weight). The highest Cd2+ capacities of dried cell membrane was found to be 36.07 and 39.55 mg/g membrane for G. thermantarticus and A. amylolyticus, respectively, and the highest Cd2+ capacities of wet cell membrane was found to be 14.36 and 12.39 mg/g membrane for G. thermantarcticus and A. amylolyticus, respectively.  相似文献   
47.
ABSTRACT

Two strains of thermophilic bacteria, Geobacillus thermantarcticus and Anoxybacillus amylolyticus, were employed to investigate the biosorption of heavy metals including Cd2+, Cu2+, Co2+, and Mn2+ ions. The effects of different biosorption parameters such as pH (2.0–10.0), initial metal concentrations (10.0–300.0 mg L?1), amount of biomass (0.25–10 g L?1), temperature (30–80°C), and contact time (15–120 min) were investigated. Concentrations of metal ions were determined by using an inductively coupled plasma optical emission spectrometry (ICP-OES). Optimum pHs for Cd2+, Cu2+, Co2+, and Mn2+ biosorption by Geobacillus thermantarcticus were found to be 4.0, 4.0, 5.0, and 6.0, respectively. For Anoxybacillus amylolyticus, the optimum pHs for Cd2+, Cu2+, Co2+, and Mn2+ biosorption were found to be 5.0, 4.0, 5.0, and 6.0, respectively. The Cd2+, Cu2+, Co2+, and Mn2+ removals at 50 mg L?1 in 60 min by 50 mg dried cells of Geobacillus thermantarcticus were 85.4%, 46.3%, 43.6%, and 65.1%, respectively, whereas 74.1%, 39.8%, 35.1%, and 36.6%, respectively, for Anoxybacillus amylolyticus. The optimum temperatures for heavy metal biosorption were near the optimum growth temperatures for both strains. Scatchard plot analysis was employed to obtain more compact information about the interaction between metal ions and biosorbents. The plot results were further studied to determine if they fit Langmuir and Freundlich models.  相似文献   
48.
Cyclooxygenase-2 (COX-2) influences carcinogenesis through immune response suppression, apoptosis inhibition, regulation of angiogenesis and tumor cell invasion, and metastasis. It is now well established that COX-2 is overexpressed in many premalignant, malignant, and metastatic cancers, including hepatocellular carcinoma (HCC). DNA sequence variations in the COX-2 gene may lead to altered COX-2 production and/or activity, and so they cause inter-individual differences in the susceptibility to HCC. Functional coding region polymorphisms -1195A>G (rs689466), -765G>C (rs20417), and +8473T>C (rs5275) in the COX-2 gene have recently been shown to be associated with several human cancers but their association with HCC has yet to be investigated. We used hospital-based case-control study to assess the hypothesis that the functional COX-2 variation may affect individual susceptibility to the HCC. COX-2 polymorphisms were investigated in 129 confirmed subjects with HCC and 129 cancer-free control subjects matched on age, gender, smoking, and alcohol consumption using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. The distribution of the COX-2 -1195A>G and +8473T>C genotypes were not significantly different between HCC cases and control. However, proportion of the COX-2 -765CC genotype which leads to a 30% reduction of the COX-2 promoter activity was significantly lower in patients with HCC (3.1%) when compared to control subjects (11.6%) (P < 0.05). Logistic regression analyses revealed that the COX-2 -765G>C variant genotype (-765CC) was associated with a significantly decreased risk of HCC compared with the -765GG wild-type homozygotes [P < 0.05, odds ratio (OR) = 0.25, 95% confidence interval (CI) = 0.08-0.79]. Our results suggest for the first time that the -765CC genotype of COX-2 -765G>C polymorphism, causing lower COX-2 gen expression, is a genetic protective factor for HCC. However, because this is the first report concerning the COX-2 -1195A>G, -765G>C, and +8473T>C polymorphisms and the risk of HCC, independent studies are needed to validate our findings.  相似文献   
49.

Introduction

Peutz-Jeghers syndrome is a rare autosomal dominant disorder characterized by hamartomatous polyps and characteristic mucocutaneous pigmentation. The hamartomatous polyps of Peutz-Jeghers syndrome can cause intestinal occlusion, especially in the small intestine. Intussusception is seen frequently in children, but rarely in adults.

Case presentation

We present the case of a 21-year-old female patient who was admitted to our emergency service with symptoms of ileus as a result of intussusception due to duodenal polyps. Radiological and endoscopic findings determined a jejunoduedonal intussusception. After an unsuccessful endoscopic attempt, a laparotomy was performed that revealed a polypoid mass originating from the fourth part of her duodenum, with intussusception of her proximal jejunum.

Conclusion

Intussusception caused by Peutz-Jeghers syndrome is a rare diagnosis and is mostly jejunojejunal or jejunoileal. Despite the fact that a few duodenojejunal cases have been reported, this is to the best of our knowledge the first case of jejunoduedonal intussusception in a patient with Peutz-Jeghers syndrome to be described in the literature.  相似文献   
50.
Lack of water resources and high water salinity levels are among the most important growth-restricting factors for plants species of the world. This research investigates the effect of irrigation levels and salinity on reflectance of Saint John’s wort leaves (Hypericum perforatum L.) under stress conditions (water and salt stress) by multiple linear regression (MLR), artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS). Empirical and heuristics modeling methods were employed in this study to relate stress conditions to leaf reflectance. It was found that the constructed ANN model exhibited a high performance than multiple regression and ANFIS in estimating leaf reflectance accurately.  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