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   22篇
  免费   0篇
  2021年   1篇
  2020年   1篇
  2019年   1篇
  2018年   4篇
  2015年   2篇
  2013年   1篇
  2008年   1篇
  2007年   1篇
  2006年   3篇
  2005年   1篇
  1998年   1篇
  1985年   1篇
  1981年   1篇
  1979年   2篇
  1977年   1篇
排序方式: 共有22条查询结果,搜索用时 328 毫秒
1.
An experiment was conducted to study seasonal variations of thyroidal activity, serum testosterone concentration and seminal characteristics of two breeds of Iranian fat-tailed sheep. Eight 3 to 4-year-old rams of Ghezel and Mehraban breeds (4 rams/breed) were randomly selected from a flock of fertile rams. Semen was collected by using an artificial vagina, and blood samples were obtained via jugular vein. Seminal characteristics, scrotal length, width, and circumference, and blood parameters were measured at 3-week intervals. Time of the year significantly (P < 0.05) affected the volume of semen, sperm concentration, percent live sperm, percent normal sperm, total sperm number, seminal pH, seminal lactate dehydrogenase (LDH) concentration, scrotal circumference, scrotal width, and serum levels of testosterone, cholesterol, triiodothyronine (T(3)), tetraiodothyronine (T(4)), free T(4) index (FT(4)I), and TSH. Scrotal length was not affected by the time of sampling (P > 0.05). The effect of breed on the serum concentrations of hormones and cholesterol was not significant. Volume of semen, percent normal sperm, and total number of normal sperm were significantly (P < 0.05) higher in Mehraban but scrotal circumference, scrotal width and scrotal length were greater in Ghezel rams. Breedxtime interaction effect was significant for T(4), FT(4)I, sperm concentration, and total sperm number. The largest values for TSH, T(4), FT(4)I, testosterone, total sperm number, percent normal sperm, percent live sperm, sperm concentration, volume of semen and scrotal circumference were found from early summer to winter and the lowest values were recorded at the end of spring and in early summer. In both breeds, high and negative correlations (r = -0.7 to -0.8) were found between LDH levels in semen and percent live sperm, percent normal sperm and total sperm number (P < 0.01). It is unlikely that such variations in seminal quality would affect the fertility under natural mating.  相似文献   
2.

Background

Thalassemia is known as the commonest monogenic disorder with an imbalanced rate of globin chains production of adult hemoglobin. Despite the available information about the thalassemia etiology, its phenotype varies from each patient to another. This study aimed to evaluate the hematological parameters of patients with the same -α3.7 homozygote and heterozygote genotypes to amend screening programs.

Methods

In this observational study, we evaluated 1301 thalassemia suspected patients who referred to the Thalassemia and Hemoglobinopathy Research Center of Ahvaz University of Medical Sciences, Khuzestan, Iran during 2014–2016. According to the genotyping studies, patients divided into 2 groups with -α3.7/αα (n = 646) and -α3.7/-α3.7 (n = 181) genotypes. Thereafter, distribution of hematological parameters evaluated in both groups.

Results

The mean age in heterozygous and homozygous groups was 25.7±4.5 and 26±4.4 years old, respectively. The degree of anemia was considerably varied in patients with the same genotype. MCV, RBC and MCH showed a wide distribution in patients.

Conclusion

The findings presented here suggest that other molecular mechanisms along with α-globin gene mutations could be involved in determining the phenotypes of alpha thalassemia patients.
  相似文献   
3.
Dieback and canker diseases are a major problem in ornamental shrubs and trees of Ahvaz, southwestern Iran. Symptomatic stems and branches were collected from two urban parks in the downtown regions of Ahvaz to identify the dieback-causing agents of Lantana camara. Accordingly, two isolates of a new species, Allophoma hayatii sp. nov., were obtained, which are described and illustrated. This species is identified based on morphological characters and analyses of nucleotide sequences of four regions, including internal transcribed spacer 1 and 2 and 5.8S nrDNA (ITS), partial large subunit 28S nrDNA (LSU-D1/D2), a partial sequence of the β-tubulin (tub2) and part of the RNA polymerase II (rpb2). The isolates of A. hayatii generated a well-supported clade in the trees constructed from multi-locus phylogenetic analysis, distinct from other previously known species of Allophoma. Pathogenicity of both isolates was verified by the inoculation of stem fragments of L. camara. These findings confirm A. hayatii as the causal agents of dieback and canker of L. camara in Ahvaz.  相似文献   
4.

Background

An expansion of the hexanucleotide repeat (GGGGCC)n·(GGCCCC)n in the C9orf72 promoter has been shown to be the cause of Amyotrophic lateral sclerosis and frontotemporal dementia (ALS-FTD). The C9orf72 repeat can form four-stranded structures; the cationic porphyrin (TMPyP4) binds and distorts these structures.

Methods

Isothermal titration calorimetry (ITC), and circular dichroism (CD) were used to study the binding of TMPyP4 to the C-rich and G-rich DNA and RNA oligos containing the hexanucleotide repeat at pH 7.5 and 0.1?M?K+.

Results

The CD spectra of G-rich DNA and RNA TMPyP4 complexes showed features of antiparallel and parallel G-quadruplexes, respectively. The shoulder at 260?nm in the CD spectrum becomes more intense upon formation of complexes between TMPyP4 and the C-rich DNA. The peak at 290?nm becomes more intense in the c-rich RNA molecules, suggesting induction of an i-motif structure. The ITC data showed that TMPyP4 binds at two independent sites for all DNA and RNA molecules.

Conclusions

For DNA, the data are consistent with TMPyP4 stacking on the terminal tetrads and intercalation. For RNA, the thermodynamics of the two binding modes are consistent with groove binding and intercalation. In both cases, intercalation is the weaker binding mode. These findings are considered with respect to the structural differences of the folded DNA and RNA molecules and the energetics of the processes that drive site-specific recognition by TMPyP4; these data will be helpful in efforts to optimize the specificity and affinity of the binding of porphyrin-like molecules.  相似文献   
5.

Background

Expansion of the C9orf72 hexanucleotide repeat (GGGGCC)n·(GGCCCC)n is the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Both strands of the C9orf72 repeat have been shown to form unusual DNA and RNA structures that are thought to be involved in mutagenesis and/or pathogenesis. We previously showed that the C-rich DNA strands from the C9orf72 repeat can form four-stranded quadruplexes at neutral pH. The cytosine residues become protonated under slightly acidic pH (pH?4.5–6.2), facilitating the formation of intercalated i-motif structures.

Methods

Using CD spectroscopy, UV melting, and gel electrophoresis, we demonstrate a pH-induced structural transition of the C-rich DNA strand of the C9orf72 repeat at pHs reported to exist in living cells under stress, including during neurodegeneration and cancer.

Results

We show that the repeats with lengths of 4, 6, and 8?units, form intercalated quadruplex i-motifs at low pH (pH?<?5) and monomolecular hairpins and monomolecular quadruplexes under neutral-basic conditions (pH?≥?8). Furthermore, we show that the human replication protein A (RPA) binds to the G-rich and C-rich DNA strands under acidic conditions, suggesting that it can bind to i-motif structures.

Conclusions

In the proper sequence context, i-motif structures can form at pH values found in some cells in vivo.

General significance

DNA conformational plasticity exists over broad range of solution conditions.  相似文献   
6.
Molecular expression on the vascular endothelium is critical in regulating the interaction of circulating cells with the blood vessel wall. Leukocytes as well as circulating cancer cells gain entry into tissue by interacting with adhesion molecules on the endothelial cells (EC). Molecular targets on the EC are increasingly being explored for tissue-specific delivery of therapeutic and imaging agents. Here we use in vivo immunofluorescence microscopy to visualize the endothelial molecular expression in the vasculature of live animals. High-resolution images are obtained by optical sectioning through the intact skin using in vivo confocal and multiphoton microscopy after in situ labeling of EC surface markers with fluorescent antibodies. Other vascular beds such as the bone marrow and ocular blood vessels can be imaged with little or no tissue manipulation. Live imaging is particularly useful for following the dynamic expression of inducible molecules such as E-selectin during an inflammatory response.  相似文献   
7.
8.
A template-free precipitation method was used as a simple and low cost method for preparation of CeO2 nanoparticles. The structure and morphology of the prepared nanoparticle samples were studied in detail using X-ray diffraction, Raman spectroscopy and Scanning Electron Microscopy (SEM) measurements. The whole powder pattern modelling (WPPM) method was applied on XRD data to accurately measure the crystalline domain size and their size distribution. The average crystalline domain diameter was found to be 5.2 nm, with a very narrow size distribution. UV-visible absorbance spectrum was used to calculate the optical energy band gap of the prepared CeO2 nanoparticles. The FT-IR spectrum of prepared CeO2 nanoparticles showed absorption bands at 400 cm-1 to 450 cm-1 regime, which correspond to CeO2 stretching vibration. The dielectric constant (εr) and dielectric loss (tan δ) values of sintered CeO2 compact consolidated from prepared nanoparticles were measured at different temperatures in the range from 298 K (room temperature) to 623 K, and at different frequencies from 1 kHz to 1 MHz.  相似文献   
9.
Effect of butylated hydroxytoluene (BHT) on the quality of frozen-thawed Holstein bull sperm in egg yolk-citrate extender was evaluated. High quality semen samples were diluted in egg yolk-citrate extenders containing 0, 0.5, 1, 2 and 4 mM BHT and subsequently frozen in liquid nitrogen. Pre-freeze and post-thaw progressive motility, and live/dead ratio and acrosomal integrity of 200 sperm per slide, stained with Eosin-Nigrosin and Giemsa, were evaluated at 0, 2 and 4 h after thawing. There was a significant decrease in forward motility, livability and acrosomal integrity up to 4 h after thawing the frozen sperm. Upon thawing, sperm progressive motility at 1 mM BHT was significantly (P<0.001) higher (11%) than other groups, but percentages of live sperm and live sperm with intact acrosomes were higher at 0.5 mM BHT. BHT at 4 mM BHT caused a significant decrease in motility, livability and acrosomal integrity during preparatory stages of freezing sperm. It is concluded that 0.5-1.0 mM BHT can be beneficial for freezing Holstein bull spermatozoa in egg yolk-citrate diluent, when inseminated immediately after thawing.  相似文献   
10.
Enzyme histochemical techniques were applied to frozen sheep uteri from different stages of the oestrous cycle. The localization and activities of succinate, lactate, glucose-6-phosphate, and isocitrate (NADP+) dehydrogenases and acid and alkaline phosphatases were studied in the luminal and glandular epithelia, caruncle and myometrium. Enzyme activity in the sections was scored on a scale of 0--5. In general the enzyme activity in the uterine caruncles and epithelia was higher than in the myometrium. The myometrium did not show any alkaline phosphatase activity and isocitrate dehydrogenase (NADP+) activity was negligible. The low activities of acid phosphatase and lactate dehydrogenase and the moderate levels of glucose-6-phosphate and succinate dehydrogenases in the myometrium were constant. The caruncular tissue showed high levels of phosphatases and glucose-6-phosphate dehydrogenase, moderate levels of lactate and succinate dehydrogenases, and low levels of isocitrate dehydrogenase (NADP+) throughout the oestrous cycle. Much lower phosphatase and isocitrate dehydrogenase (NADP+) levels were found in the epithelium of deep glands compared with superficial glands. The high activity of acid and alkaline phosphatases in the luminal epithelium and the superficial glands was constant from mid-cycle to ovulation, but a significant decrease was observed immediately after ovulation. The level of dehydrogenases in epithelia was generally high and did not change during the oestrous cycle.  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