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   23篇
  免费   1篇
  2023年   1篇
  2019年   2篇
  2018年   1篇
  2016年   1篇
  2015年   3篇
  2014年   2篇
  2013年   1篇
  2012年   2篇
  2011年   1篇
  2009年   1篇
  2007年   4篇
  2005年   1篇
  2003年   1篇
  1996年   1篇
  1993年   1篇
  1992年   1篇
排序方式: 共有24条查询结果,搜索用时 15 毫秒
1.
Diabetes in pregnancy constitutes an unfavorable environment for embryonic and fetal development, where the child has a higher risk of perinatal morbidity and mortality, with high incidence of congenital malformations and predisposition to long-term metabolic diseases that increase with a hypercaloric diet. To analyze whether hyperglycemia differentially affects proliferation, apoptosis, and mRNA expression in cells from children of normoglycemic pregnancies (NGPs) and diabetes mellitus pregnancies (DMPs), we used umbilical cord Wharton jelly cells as a research model. Proliferation assays were performed to analyze growth and determine the doubling time, and the rate of apoptosis was determined by flow cytometry-annexin-V assays. AMPK, BNIP3, HIF1α, and p53 mRNA gene expression was assessed by semi-quantitative RT-PCR. We found that hyperglycemia decreased proliferation in a statistically significant manner in NGP cells treated with 40?mM D-glucose and in DMP cells treated with 30 and 40?mM D-glucose. Apoptosis increased in hyperglycemic conditions in NGP and DMP cells. mRNA expression of BNIP3 and p53 was significantly increased in cells from DMPs but not in cells from NGPs. We found evidence that maternal irregular metabolic conditions, like diabetes with hyperglycemia in culture, affect biological properties of fetal cells. These observations could be a constituent of fetal programming.  相似文献   
2.
Roads can experience runoff problems due to the intense rain discharge associated to severe storms. Two advanced tools are combined to analyse the interaction of complex water flows with real terrains. UAV (Unmanned Aerial Vehicle) photogrammetry is employed to obtain accurate topographic information on small areas, typically on the order of a few hectares. The Smoothed Particle Hydrodynamics (SPH) technique is applied by means of the DualSPHysics model to compute the trajectory of the water flow during extreme rain events. The use of engineering solutions to palliate flood events is also analysed. The study case simulates how the collected water can flow into a close road and how precautionary measures can be effective to drain water under extreme conditions. The amount of water arriving at the road is calculated under different protection scenarios and the efficiency of a ditch is observed to decrease when sedimentation reduces its depth.  相似文献   
3.
A cementum protein 1‐derived peptide (CEMP1‐p1) consisting of 20 amino acids from the CEMP1's N‐terminus region: MGTSSTDSQQAGHRRCSTSN, and its role on the mineralization process in a cell‐free system, was characterized. CEMP1‐p1's physicochemical properties, crystal formation, and hydroxyapatite (HA) nucleation assays were performed. Crystals induced by CEMP1‐p1 were analyzed by scanning electron microscopy, Fourier‐transform infrared spectroscopy‐attenuated total reflectance (FTIR‐ATR), X‐ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and atomic force microscopy. The results indicate that CEMP1‐p1 lacks secondary structure, forms nanospheres that organize into three‐dimensional structures, possesses affinity to HA, and induces its nucleation. CEMP1‐p1 promotes the formation of spherical structures composed by densely packed prism‐like crystals, which revealed a Ca/P ratio of 1.56, corresponding to HA. FTIR‐ATR showed predominant spectrum peaks that correspond and are characteristic of HA and octacalcium phosphate (OCP). Analysis by XRD indicates that the crystals show planes with a preferential crystalline orientation for HA and for OCP. HRTEM showed interplanar distances that correspond to crystalline planes of HA and OCP. Crystals are composed by superimposed lamellae, which exhibit epitaxial growth, and each layer of the crystals is structured by nanocrystals. This study reveals that CEMP1‐p1 regulates HA crystal formation, somehow mimicking the in vivo process of mineralized tissues bioformation.  相似文献   
4.
A series of azepino[3′,4′:4,5]pyrrolo[2,1-a]isoquinolin-12-ones (3a–f), that were conformationally restricted analogs of lead compound 2, were designed as potential cytotoxic compounds and synthesized using a radical oxidative aromatic substitution reaction as the key step. Compounds 3a–f were tested on five tumor cell lines to determine the conformational requirements for biological activity of compound 2. The results show that conformational restrictions on compound 2, generating the derivatives 3af, do not appreciably reduce the cytotoxic activity of 2, although compound 3d (R = Br) showed good activity against U-251 cells. Preliminary structure–activity relationship studies with these compounds revealed the importance of halogens bonded to the isoquinoline moiety. Additionally, derivatives 3f (R = NO2) and 3b (R = F) were cytotoxic to PC-3 and K-562 cells. However, none of the azepino[3′,4′:4,5]pyrrolo[2,1-a]isoquinolinones inhibited the enzymatic activity of CDK1/cyclin B, CDK5/p25, or GSK-3.  相似文献   
5.
Floristic studies of south‐eastern Mexico have not considered the ravine component of the landscape and, in this study, we demonstrate the potential of ravines as refuges for orchids. At elevations of 1442–2358 m in the buffer zone of the Tacaná Volcano Biosphere Reserve, in the region of Soconusco, south‐eastern Mexico, where 7.68% of the landscape has slopes > 45°, we registered 86 species of orchid from 35 genera, 14 (16.25%) of which were exclusive to ravines, 47 (54.6%) were exclusive to accessible surrounding areas and 25 (29%) colonized both types of habitat. The tropical mountain cloud forest (TMCF) ecosystem was distributed in the accessible areas surrounding the ravines and in some sites extended into the ravines themselves. Evergreen mountain scrub forest (EMSF), only found in the ravines, contributed eight species of orchid exclusive to this ecosystem. The elevation, orientation and slope of the ravines influenced species richness. The instability of the ‘soils’ on steep slopes and occasional landslides were negative environmental characteristics of the ravines, which, however, were mostly dependent on the management of surrounding areas, and epiphytes inhabiting ravines and the surrounding areas shared similar risks of whole‐tree and branch fall, wind and torrential rain. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178 , 283–297.  相似文献   
6.
Economic Experimental Games have shown that individuals make decisions that deviate down from the suboptimal Nash equilibrium. However, few studies have analyzed the case when deviation is above the Nash equilibrium. Extracting from above the Nash equilibrium is inefficient not only socially but also privately and it would exacerbate the tragedy of the commons. That would be the case of a race to the fish when stocks are becoming depleted or driver behavior on a highly congested road. The objective of this study is to analyze private inefficient extraction behavior in experimental games and to associate the type of player and the type of player group with such inefficient outcomes. To do this, we carried out economic experimental games with local coastal fishermen in Colombia, using a setting where the scarcity of the resource allows for an interior Nash equilibrium and inefficient over-extraction is possible. The state of the resource, the type of player and the composition of the group explain, in part, this inefficient behavior.  相似文献   
7.
This paper presents a new method based on 3D reconstruction from images that demonstrates the utility and integration of close-range photogrammetry and computer vision as an efficient alternative to modelling complex objects and scenarios of forensic infography. The results obtained confirm the validity of the method compared to other existing alternatives as it guarantees the following: (i) flexibility, permitting work with any type of camera (calibrated and non-calibrated, smartphone or tablet) and image (visible, infrared, thermal, etc.); (ii) automation, allowing the reconstruction of three-dimensional scenarios in the absence of manual intervention, and (iii) high quality results, sometimes providing higher resolution than modern laser scanning systems. As a result, each ocular inspection of a crime scene with any camera performed by the scientific police can be transformed into a scaled 3d model.  相似文献   
8.
This paper reports an ethnobotanical investigation, performed between 1999 and 2002, to determine the wild food plants traditionally used in the province of Madrid (central Spain). One hundred and twenty-three vascular species belonging to 31 families were at one time used as vegetables, wild fruits, in the making of beverages, as seasonings, or as other preparations. Wild vegetables formed the largest group, withScolymus hispanicus, Silene vulgaris, andRumex pulcher the most frequently cooked vegetables, andRorippa nasturtium-aquaticum andMontia fontana the most commonly used in salads. Also common was the consumption of asparagus and several species of climbing plants such asBryonia dioica, Tamus communis, andHumulus lupulus. Ethnobotanical novelties includedSonchus crassifolius, the young sprouts of which were used in salads, and Inula salicina, used to make herbal tea. Some ecological and cultural aspects of the collection of wild plants for food are discussed, as well as the relationships between the food and medicinal uses of some species.  相似文献   
9.
Bone morphogenetic proteins (BMPs) and BMP receptors (BMPRs) are known to regulate the development of calcified tissues by directing mesenchymal precursor cells differentiation. However, their role in the formation of tooth-supporting tissues remains unclear. We investigated the distribution pattern of STRO-1, a marker of mesenchymal progenitor cells and several members of the BMP pathway during the development of mouse molar periodontium, from the post-natal days 6 to 23 (D6 to D23). STRO-1 was mainly localized in the dental follicle (DF) at D6 and 13 then in the periodontal ligament (PDL) at D23. BMP-2 and -7 were detected in Hertwig's epithelial root sheath (HERS) and in DF, then later in differentiated periodontal cells. BMP-3 was detected after D13 of the periodontal development. BMPRs-Ib, -II, the activin receptor-1 (ActR-1) and the phosphorylated Smad1 were detected in DF and HERS at D6 and later more diffusely in the periodontium. BMPR-Ia detection was restricted to alveolar bone. These findings were in agreement with others data obtained with mouse immortalized DF cells. These results suggest that STRO-1 positive DF cells may be target of BMPs secreted by HERS. BMP-3 might be involved in the arrest of this process by inhibiting the signaling provided by cementogenic and osteogenic BMPs.  相似文献   
10.
The effect of human anti-cementoblastoma-derived protein antibody during cementogenesis in vitro was investigated by using human cementoblastoma-derived cells. Cultures treated with 5 microg/ml of CP antibody from day 1 to day 15 revealed a significant decrease in alkaline phosphatase activity (ALP) 40% (p < 0.005), 44% (p < 0.001), 49% (p < 0.1), and 45% (p < 0.02) at 9, 11, 13, and 15 days, respectively. Immunoexpression of osteopontin revealed that in cultures treated with anti-CP antibody, the positive number of cementoblastoma cells was reduced by 87, 83, 69, and 52% at 5, 7, 9, and 11 days, respectively. Bone sialoprotein immunoexpression showed a decrease in positive cells of 82, 51, 60, 80, 83, and 87% at 5, 7, 9, 11, 13, and 15 days, respectively, as compared to controls. The Ca/P ratio of the mineral-like tissue deposited in vitro by cementoblastoma cells revealed that control cultures had a Ca/P ratio of 1.45 and 1.61 at 5 and 15 days, whereas experimental cultures revealed a Ca/P ratio of 0.50 and 0.79 at 5 and 15 days, respectively. Electron diffraction patterns showed inner double rings representing D-spacing that were consistent with those of hydroxyapatite in both control and experimental cultures. Examination of the crystallinity with high resolution transmission electron microscopy showed homogeneous and preferential spatial arrangement of hydroxyapatite crystallites in control and experimental cultures at 15 days. Atomic force microscopy images of control cultures at 5 and 15 days revealed small granular particles and grain agglomeration that favored the formation of crystalline plaques with a lamellar-like pattern of the mineral-like tissue. Experimental cultures at 5 and 15 days showed tiny and homogeneous granular morphology. The agglomerates maintained spherical morphology without organization of needle-like crystals to form plaque-like structures. Based on these findings, it is hypothesized that cementoblastoma-derived protein may be associated to crystal growth, compositional and morphological features during the mineralization process of cementum in vitro.  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