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排序方式: 共有368条查询结果,搜索用时 0 毫秒
31.
Irene Popiel 《Journal of chemical ecology》1986,12(8):1745-1754
InSchistosoma mansoni and other schistosome species, pairing of the female with a male partner is necessary for the completion of reproductive morphogenesis and growth. Permanent contact with a male is also necessary for the maintenance of reproductivity in the sexually mature female. This phenomenon appears to be unique within the animal kingdom. The mechanism of male-stimulated female reproductive development in schistosomes remains unknown however. In this paper, the theories for the nature of the process are reviewed briefly, recent findings are added, and the biological and technical problems associated with its study are highlighted. 相似文献
32.
In a hypothesis derived largely from animal literature, Douglas proposed that the hippocampus in the human brain matures at about 4 to 5 years of age. In the present experiment, this was investigated with maze learning in preschool children. As predicted, younger preschoolers exhibited deficits observed in hippocampectomized adult animals, namely, perseveration, inflexibility, and invariability, in terms of several measures of errors and routes selected. Older preschoolers exhibited the flexibility and variability more characteristic of an adult animal with intact hippocampus. Thus, the base of support for the hypothesis was broadened beyond spontaneous alternation data reported by Douglas. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
33.
为研究干酪乳杆菌(Lactobacillus casei)胞外多糖(exopolysaccharide,EPS)促进体外培养的小鼠未成熟骨髓来源树突细胞(bone marrow-derived dendritic cells,BMDCs)成熟的作用,分析不同剂量的EPS对BMDCs分泌细胞因子白细胞介素(interleukin,IL)-6、转化生长因子-β(transforming growth factor-β,TGF-β)和IL-23的影响,并检测EPS对BMDCs抗原提呈能力的影响。首先从干酪乳杆菌中分离纯化出EPS,并检测EPS的纯度;把从BALB/c小鼠体内分离出的骨髓细胞分化为BMDCs,未成熟BMDCs分别与磷酸盐缓冲液、不同剂量EPS和脂多糖(lipopolysaccharide,LPS)体外培养,采用流式细胞法检测了BMDCs成熟表面标记物MHC II和CD86的表达,酶联免疫吸附检测(enzyme-linked immunosorbent assay,ELISA)法分析了IL-6、TGF-β和IL-23的表达量,CCK-8法检测了BMDCs与小鼠脾淋巴细胞的混合培养体系中淋巴细胞的增殖率。结果表明:分离出EPS的纯度约为95%;EPS能够上调BMDCs表面MHC II和CD86的表达量;EPS可以显著促进BMDCs分泌IL-6、TGF-β和IL-23(P<0.05),但促进水平低于LPS;EPS可以明显促进BMDCs刺激异基因淋巴细胞的增殖。综上所述,在体外实验中,干酪乳杆菌EPS能够促进BALB/c小鼠BMDCs的成熟,诱导BMDCs分泌与辅助性T17细胞分化和增殖相关的细胞因子IL-6、TGF-β和IL-23,并且可以增强BMDCs的抗原提呈能力。 相似文献
34.
Sylwia Judycka Joanna Nynca Piotr Hliwa Andrzej Ciereszko 《International journal of molecular sciences》2021,22(2)
Sex reversal has been used as a breeding strategy by salmonid fish to produce genetically and phenotypically single sex populations. Production of all-female fish has great importance for the creation of monosex female triploids of salmonid fish, which are valued for their sterility, lack of female maturation, and larger commercial size. Among salmonids, the majority of rainbow trout (Oncorhynchus mykiss) production is based on all-female production with a high proportion of all-female triploid production in Europe. The main aim of this review is to present the recent knowledge regarding sex-reversed females (SRFs) of salmonid fish. We discuss the methods of sex reversal as well as their effects on the morphology and histology of the reproductive tract. We focus on the characteristics of SRF semen as well as the factors determining semen quality. The lower quality of SRF sperm compared to that of normal males has resulted in the need for the artificial maturation of semen. Most importantly, methods of semen storage—both short-term and long-term (cryopreservation)—that can improve hatchery operations are presented with the special emphasis on recent progress in development of efficient cryopreservation procedures and use of cryopreserved semen in hatchery practice. Moreover, we also address the emerging knowledge concerning the proteomic investigations of salmonid sperm, focusing primarily on the proteomic comparison of normal male and SRF testicular semen and presenting changes in SRF rainbow trout sperm proteome after in vitro incubation in artificial seminal plasma. 相似文献
35.
36.
37.
Jayasheelan Vaithilingam Paola Sanjuan‐Alberte Simona Campora Graham A. Rance Long Jiang Jordan Thorpe Laurence Burroughs Christopher J. Tuck Chris Denning Ricky D. Wildman Richard J. M. Hague Morgan R. Alexander Frankie J. Rawson 《Advanced functional materials》2019,29(38)
Biological structures control cell behavior via physical, chemical, electrical, and mechanical cues. Approaches that allow us to build devices that mimic these cues in a combinatorial way are lacking due to there being no suitable instructive materials and limited manufacturing procedures. This challenge is addressed by developing a new conductive composite material, allowing for the fabrication of 3D biomimetic structures in a single manufacturing method based on two‐photon polymerization. The approach induces a combinatorial biostimulative input that can be tailored to a specific application. Development of the 3D architecture is performed with a chemically actuating photocurable acrylate previously identified for cardiomyocyte attachment. The material is made conductive by impregnation with multiwalled carbon nanotubes. The bioinstructive effect of 3D nano‐ and microtopography is combined with electrical stimulation, incorporating biochemical, and electromechanical cues to stimulate cells in serum‐free media. The manufactured architecture is combined with cardiomyocytes derived from human pluripotent stem cells. It is demonstrated that by mimicking biological occurring cues, cardiomyocyte behavior can be modulated. This represents a step change in the ability to manufacture 3D multifunctional biomimetic modulatory architectures. This platform technology has implications in areas spanning regenerative medicine, tissue engineering to biosensing, and may lead to more accurate models for predicting toxicity. 相似文献
38.
黄鸣奋 《徐州工程学院学报》2008,23(6):39-43
立克里德1968年关于网络生态的预言正在变为现实。作为新媒体的互联网不仅改变了原有的媒体格局,而且影响了人们的生产方式和生活方式,甚至转变了人们有关自身存在的观念。在考察网络生态时,必须注意到它所包含的文化与反文化的矛盾、正视互联网发展所面临的问题,并理解互联网趋“老”的必然性。趋“老”的涵义之一,是指互联网在网络生态中所占地位的变化,即从相对新的媒体转变为相对旧的媒体,表现在产业链、用户群、媒体声望、主导价值取向、管理方式、社会印象等方面。“老”不仅是积以时日,而且是日益成熟。与时光相伴的“老”不可避免,问题在于这种过程性变化是进入化境,还是导致衰朽。我们的任务不是否认互联网趋“老”的事实,而是努力使这种变化有利于网络生态、媒体生态以至于整个人文生态的建设。为此,要提倡老实诚恳地办网、上网,以增进网络公信力,老练周到地应对信息“洪水”,以增进网络净化力,老成持重地处理各种矛盾,以增进网络亲合力。 相似文献
39.
A Novel Hydrogel Surface Grafted With Dual Functional Peptides for Sustaining Long‐Term Self‐Renewal of Human Induced Pluripotent Stem Cells and Manipulating Their Osteoblastic Maturation 下载免费PDF全文
Yi Deng Shicheng Wei Lei Yang Weizhong Yang Matthew S. Dargusch Zhi‐Gang Chen 《Advanced functional materials》2018,28(11)
Realizing the clinical potential of human induced pluripotent stem cells (hiPSCs) in bone regenerative medicine requires the development of safe and chemically defined biomaterials for expansion of hiPSCs followed by directing their lineage commitment to osteoblasts. In this study, novel multipurpose peptide‐presenting hydrogel surfaces are prepared on common tissue culture plates via carboxymethyl chitosan grafting and subsequent immobilization of two functional peptides allowing for in vitro feeder‐free culture, long‐term self‐renewal, and osteogenic induction of hiPSCs. After vitronectin (VN) peptide modification, the engineered surfaces facilitate adhesion, proliferation, colony formation, and the maintenance of pluripotency of hiPSCs up to passage 10 under fully defined conditions without Matrigel or protein coating. Further, this synthetic niche exhibits an appealing regulatory effect on the osteogenic conversion of hiPSCs to osteoblastic phenotype without an embryoid body formation step by co‐decoration of different ratios of VN and bone‐forming peptide. Such a well‐defined, xeno‐free 2D engineered microenvironment not only helps to accelerate the clinical development of hiPSCs, but also provides a safe and robust platform for the generation of osteoblast‐like cells or bone‐like tissues at different maturation levels. Thus, the strategy may hold great potential for application in cell therapy and bone tissue engineering. 相似文献
40.
Classification of virgin olive oils of the two major cretan cultivars based on their fatty acid composition 总被引:2,自引:0,他引:2
E. Stefanoudaki F. Kotsifaki A. Koutsaftakis 《Journal of the American Oil Chemists' Society》1999,76(5):623-626
Fatty acid composition was determined for 105 virgin olive oil samples of the two dominant Cretan olive cultivars, Koroneiki
and Mastoides, harvested from different producing areas at different maturity stages. The oils of the Koroneiki cultivar were
characterized by lower concentrations of oleic and decaheptanoic and higher concentrations of linoleic and palmitic acids.
Oils obtained from high-altitude locations were rich in monounsaturated fatty acids, while oils obtained from low-altitude
locations had higher content of saturated fatty acids. Palmitic and palmitoleic acids increased with increasing altitude in
both cultivars examined. The statistical analysis of the compositional data showed significant potential for the classification
of the samples according to cultivar and location of origin. 相似文献