首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
基因枪技术发展综述   总被引:6,自引:0,他引:6  
基因枪作为一种重要的基因转移方法,随着基因工程的不断发展,在各个应用领域都显示出了其独特的优越性,因而广受重视;与此同时,基因枪技术本身也在实践中不断发展和完善。本文在回顾和总结基因枪技术产生和发展的历史的基础上,结合当前基因枪技术在基因治疗和基因免疫领域的应用情况,总结了基因枪技术下一步改进和发展的趋势:微型化、实用化和高效化。  相似文献   

2.
The field of neural transplantation has moved rapidly forward in the last decade. Initially, fetal cells were used as implants to investigate their potential to ameliorate deficits in animal models of Parkinson's disease. However, because of the moral and legal problems associated with the use of fetal tissues in humans, alternative sources of donor tissue were sought which possessed the structural and functional characteristics needed to improve motor function in Parkinsonian patients. To date, one of the most promising tissues being investigated is the adrenal medulla, whose chromaffin cells possess an inherent plasticity of form and function. Transplanted chromaffin cells currently are being studied by a variety of approaches, including electron microscopy, in mouse, rat, and primate models of Parkinson's disease. An overview of the role of the chromaffin cell in this exciting and clinically important arena is briefly reviewed, with an emphasis on the fine structure of implanted chromaffin cells.  相似文献   

3.
Novel monodisperse mesoporous iron oxide nanoparticles (m‐IONPs) were synthesized by a postsynthesis etching approach and characterized by electron microscopy. In this approach, solid iron oxide nanoparticles (s‐IONPs) were first prepared following a solvothermal method, and then etched anisotropically by polyacrylic acid to form the mesoporous nanostructures. MTT cytotoxicity assay demonstrated that the m‐IONPs have good biocompatibility with mesenchymal stem cells (MSCs). Owing to their mesoporous structure and good biocompatibility, these monodisperse m‐IONPs were used as a nonviral vector for the delivery of a gene of vascular endothelial growth factor (VEGF) tagged with a green fluorescence protein (GFP) into the hard‐to‐transfect stem cells. Successful gene delivery and transfection were verified by detecting the GFP fluorescence from MSCs using fluorescence microscopy. Our results illustrated that the m‐IONPs synthesized in this work can serve as a potential nonviral carrier in gene therapy where stem cells should be first transfected and then implanted into disease sites for disease treatment. Microsc. Res. Tech. 76:936–941, 2013. © 2013 Wiley Periodicals, Inc.  相似文献   

4.
The standard scanning electron microscope method for examining surface structure using the secondary electron mode has unexpectedly revealed the internal ladder-type medulla of some animal hairs.  相似文献   

5.
目的 探究GT-4A导乐分娩镇痛仪配合导乐陪伴分娩对自然分娩产妇的镇痛效果和舒适分娩影响.方法 选取2018年1月至2018年12月于我院进行自然分娩的124例产妇为研究对象,按照随机数表法将所有产妇平均分为两组,观察组和对照组各62例.对照组产妇采取常规镇痛进行分娩,观察组产妇在对照组的基础上进行非药物分娩镇痛仪联合...  相似文献   

6.
Cryoelectron microsopy is a widely used technique to observe biological material in an almost physiological, fully hydrated state. The sample is prepared for electron microsopy observation by quickly reducing its temperature to ?180 °C. The high‐speed cooling induces the formation of vitreous water, which preserves the sample conformation. However, the way vitrification occurs is still poorly understood. In order to better understand the phenomenon, we have used a stroboscopic device to visualize the interaction between the electron microscopy grid and the cryogen. By blocking the free fall of the plunger once the grid has penetrated the coolant by half its diameter, we have elucidated the way in which vitrification propagates. The findings were confirmed by numerical simulation. In addition, according to our observations, we now present an alternative way to prepare vitreous specimens. This new method, with the grid parallel to the liquid cryogen surface, decreases evaporation from the sample during its free fall towards the coolant and at the same time achieves a more uniform vitrification over the entire surface of the specimen.  相似文献   

7.
The aim of this work is to demonstrate that multiphoton microscopy is a preferred technique to investigate intact cornea structure without slicing and staining. At the micron resolution, multiphoton imaging can provide both large morphological features and detailed structure of epithelium, corneal collagen fibril bundles and keratocytes. A large area multiphoton cross-section across an intact eye excised from a GFP mouse was obtained by a homebuilt multiphoton microscope. The broadband multiphoton fluorescence (435-700 nm) and second harmonic generation (SHG, 360-400 nm) signals were generated by the 760 nm output of a femtosecond titanium-sapphire laser. A water immersion objective (Fluor, 40X, NA 0.8; Nikon) was used to facilitate imaging the curve ocular surface. The multiphoton image over entire cornea provides morphological information of epithelial cells, keratocytes, and global collagen orientation. Specifically, our planar, large area multiphoton image reveals a concentric pattern of the stroma collagen, indicative of the laminar collagen organization throughout the stroma. In addition, the green fluorescence protein (GFP) labeling contributed to fluorescence contrast of cellular area and facilitated visualizing of inactive keratocytes. Our results show that multiphoton imaging of GFP labeled mouse cornea manifests both morphological significance and structural details. The second harmonic generation imaging reveals the collagen orientation, while the multiphoton fluorescence imaging indicates morphology and distribution of cells in cornea. Our results support that multiphoton microscopy is an appropriate technology for further in vivo investigation and diagnosis of cornea.  相似文献   

8.
The study aimed to analyze the reporting and methodological quality of systematic reviews (SRs)/metaanalyses(MAs) of animal models to provide references for later studies and avoid the waste of medical resources.EMBASE and MEDLINE databases were searched from inception to November 2017, with no language restriction.Two reviewers selected inclusion dependently and extracted the basic characteristics. Review Manager 5.3, stata12.0, and SPSS 21 software were used to conduct analyses. A total of 46 SRs/MAs were included. The results showedthat the English databases with high retrieval frequency are PubMed/MEDLINE, EMBASE, and Web of Science.67.31% (31/46) of the articles reported the search strategy in the full text or the appendix. 65.22% (30/46) reportedthe literature screening flow diagram, and only 19.57% (9/46) reported the number of works of literature retrievedin each database. 60.87% (28/46) illustrated supplement retrieval. Through 2 subgroup analyses, it was found thatthere were no significant differences in the quality of reports of PRISMA items. But referring to the methodologicalquality or reporting of PRESS items, SCI was better than that of non-SCI, while there seemed a source of fundingto have no significant impact on the methodological quality or the items of PRESS. The results of PRESS, AMSTAR2, and PRISMA were correlated, and the correlation between PRISMA and AMSTAR 2 was strong. These resultsdemonstrated that search strategies of animal model SRs/MAs are still not enough comprehensive, report specificationand methodological quality still need to be ameliorated. To show users the scientificity and rigor of the study, futureresearch should focus on these various guidelines like PRESS, PRISMA, and AMSTAR 2 checklists that have beenissued, it can help to increase the value of research and improve the utilization of medical resources.  相似文献   

9.
10.
We used an atomic force microscope to image cell wall isolated from needles of Serbian spruce tree and that synthesized from cell wall components. We also observed the structure of lignin model polymer (DHP), as a best substitute for the natural lignin. A tendency of aggregate formation was observed in all samples. Cell wall was revealed as a laminated fibrous structure. General organization is similar in both isolated and synthesized cell wall samples, with dominating globular motifs arranged regularly as rods and forming cavities. The synthesized cell wall has a more regular structural organization than isolated cell wall. The dimensions of individual globular aggregates and pores differed between the two samples. DHP showed a similar, regular organization, with globular aggregates and holes. Globules and pores are smaller in size than the corresponding structures in both the isolated and synthesized cell walls. Such modular organization of cell walls may have a physiological role in response to the external mechanical stress caused to plant cells.  相似文献   

11.
Scanning (SEM) and transmission electron microscopy (TEM) are two fundamental microscopic techniques widely applied in biological research for the study of ultrastructural cell components. With these methods, especially TEM, it is possible to detect and quantify the morphological and ultrastructural parameters of intracellular organelles (mitochondria, Golgi apparatus, lysosomes, peroxisomes, endosomes, endoplasmic reticulum, cytoskeleton, nucleus, etc.) in normal and pathological conditions. The study of intracellular vesicle compartmentalization is raising even more interest in the light of the importance of intracellular localization of mediators of the signaling in eliciting different biological responses. The study of the morphology of some intracellular organelles can supply information on the bio‐energetic status of the cells. TEM has also a pivotal role in the determination of different types of programmed cell death. In fact, the visualization of autophagosomes and autophagolysosomes is essential to determine the occurrence of autophagy (and also to discriminate micro‐autophagy from macro‐autophagy), while the presence of fragmented nuclei and surface blebbing is characteristic of apoptosis. SEM is particularly useful for the study of the morphological features of the cells and, therefore, can shed light, for instance, on cell–cell interactions. After a brief introduction on the basic principles of the main electron microscopy methods, the article describes some cell components with the aim to demonstrate the huge role of the ultrastructural analysis played in the knowledge of the relationship between function and structure of the biological objects. Microsc. Res. Tech., 76:1057–1069, 2013. © 2013 Wiley Periodicals, Inc.  相似文献   

12.
Apoptosis is a physiologic form of cell death present in many disease conditions. When the balance of mitosis versus apoptosis is altered, tumor-like growth or degeneration of tissues may ensue. This appears to occur in several diseases, including those of the cardiovascular system, where apoptosis plays a key role in atherosclerosis and restenosis following angioplasty. Since c-myc is upregulated in the pathogenesis of these diseases, we chose to study the sequential morphologic features of programmed cell death in vascular smooth muscle cells induced by c-myc and by the adenovirus early gene E1A. Morphology and timed events in apoptotic cell cultures were analyzed by scanning electron microscopy, transmission electron microscopy, and time-lapse videomicroscopy. We observed that both c-myc-and E1A-induced apoptosis (in serum-free medium) resulted in numerous, tightly packed clusters of apoptotic blebs, as well as in one or two asymmetrically larger blebs. Transmission electron microscopy analysis revealed the larger blebs contained mostly nuclear chromatin, whereas the many smaller fragments often had little or no chromatin. Time-lapse studies showed that apoptosis was induced at a slower rate in cells stably transfected with c-myc versus those stably transfected with E1A. The early changes of apoptosis, including cell shrinkage and intense blebbing, occurred in under 5 min in both cells. Slight alterations such as cell size and further rounding occurred up to 8 h following the initial changes of apoptosis. Rather than being a part of the apoptotic response, release from the culture floor almost entirely resulted from movement of the culture flask. These studies provide a framework of timed morphologic events for future mechanistic investigation into the key aspects of myc-and E1A-induced apoptosis in vascular smooth muscle.  相似文献   

13.
A decade after the genetic link was established between mutations in the proteolipid protein gene and two leukodystrophies, Pelizaeus-Merzbacher disease and spastic paraplegia, the molecular mechanisms underlying pathogenesis are beginning to come to light. Data from animal models of these diseases suggest that the absence of proteolipid protein gene products in the central nervous system confers a relatively mild phenotype while missense mutations in and duplications of this gene give rise to mild or severe forms of disease. Previously, we have interpreted the disease process in terms of the accumulation of the mutant proteins in the secretory pathway and, herein, we review the evidence in favor of such a cellular mechanism. Furthermore, on the basis of recent data we suggest that the unfolded protein response may be involved in the pathogenesis of Pelizaeus-Merzbacher disease and spastic paraplegia through a kinase signaling cascade that links the accumulation of mutant proteins in the endoplasmic reticulum of oligodendrocytes with changes in gene regulation, protein synthesis, and possibly apoptosis.  相似文献   

14.
Ultrastructural information was obtained by imaging the block face of high-pressure-frozen cryo-sectioned biological samples in a high-resolution cryo-SEM. Cryo-sectioning leads to a well-defined flat artificial surface in contrast to cryo-fracturing. Typical artefacts of cryo-sections such as compression and crevasses were not visible on the block face. The ultrastructural features known from resin sections and from freeze-fractures could also be found on the block faces. The cytoplasms show particles of different size which most likely represent proteins. The effects of radiation damage could be reduced considerably by applying the double layer coating technique and backscattered electron imaging.
High quality cryo-sections are only obtained from vitrified material. Reasonably flat block faces were, however, also obtained from adequately frozen microcrystalline samples, thereby facilitating ultrastructural studies in the frozen hydrated state.  相似文献   

15.
The present paper proposes a cutting tool breaking and chipping detection system for continuous and interrupted cutting, based on the analysis of the cutting force componentsF x andF y. A multifactorial experimental design has been carried out, to take account of the variability of the force signal. An adaptive signal processing algorithm is proposed, which detects catastrophic failure when at least one component deviates outside an estimated oscillation band for a time duration longer than a prefixed interval. The algorithm has been implemented on a four-microprocessor transputer board. Several tests confirmed the validity of the approach for detecting breaking and chipping phenomena in a few milliseconds, both in turning and in milling operations.  相似文献   

16.
Among the proposed techniques for delivering drugs to specific sites within the human body, magnetic targeting drug delivery surpasses due to its non-invasive character and its high targeting efficiency. Although there have been some analyses theoretically for magnetic drug targeting, very few researchers have addressed the hydrodynamic models of magnetic fluids in the blood vessel of human body. This paper presents a mathematical model to describe the hydrodynamics of ferrofluids as drug carriers flowing in a blood vessel under the applied magnetic field. A 3D flow field of magnetic particles in a blood vessel model is numerically simulated in order to further understand clinical application of magnetic targeting drug delivery. Simulation results show that magnetic nanoparticles can be enriched in a target region depending on the applied magnetic field intensity. Magnetic resonance imaging conftrms the enrichment of ferrofluids in a desired body tissue of Sprague-Dawley rats. The simulation results coincide with those animal experiments. Results of the analysis provide the important information and can suggest strategies for improving delivery in favor of the clinical application.  相似文献   

17.
An algorithm for control of several servo motors by a microcontroller is presented.The limited number of programmable timers on the majority of microcontrollers presents a problem for multiple generation of timing pulses.Two software approaches are discussed in the paper and experimental results given for operation of a set of small servos using a single timer.  相似文献   

18.
19.
An outstanding example of biological pattern formation at the single cell level is the diversity of biomineral structures in the silica cell walls of the unicellular eukaryotic algae known as diatoms. We present a survey of cell wall silica structures of 16 diatom species, which included all major cell wall components (valves, girdle bands and setae), imaged across the nano-, meso- and microscales using atomic force microscopy. Because of atomic force microscopy's superior ability to image surface topology, this approach enabled visualization of the organization of possible underlying organic molecules involved in mineral structure formation. Diatom nanoscale silica structure varied greatly comparing the same feature in different species and different features within a single species, and frequently on different faces of the same object. These data indicate that there is not a strict relation between nanoscale silica morphology and the type of structure that contains it. On the mesoscale, there was a preponderance of linear structures regardless of the object imaged, suggesting that assembly or organization of linear organic molecules or subcellular assemblies that confine a linear space play an essential and conserved role in structure formation on that scale. Microscale structure imparted an overall influence over nano- and mesoscale structure, indicating that shaping of the silica deposition vesicle plays a key role in structure formation. These results provide insights into the design and assembly principles involved in diatom silica structure formation, facilitating an understanding of the native system and potentially aiding in development of biomimetic approaches.  相似文献   

20.
We have shown previously that the small square (ss) and basket weave (bw) states of the Z band lattice in cardiac and skeletal muscle are related to the contractile state of the muscle. We have used two-dimensional image processing techniques on digitized electron micrographs to enhance the structural features of each projected lattice form in cardiac and skeletal muscle. Four different processing techniques were employed to assess the effect of enhancement artifacts on the resulting Z band images. We observed only slight differences between enhanced images of a particular Z band form produced by the four different techniques. Every enhanced image showed an approximate four-fold symmetry independent of muscle type or Z band lattice form. Each enhanced image showed four cross-connecting Z-filaments which appeared to connect each axial filament to the four nearest axial filaments. In bw images from both cardiac and skeletal muscle, axial filaments had a greater apparent diameter and a greater interaxial filament spacing than in the ss images. In both muscle types, the cross-connecting Z-filaments appeared to overlap half-way between axial filaments in the ss images while the bw images showed no such overlap. These structural features are consistent with a dynamic Z band lattice that participates in muscle contraction.  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