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  • 1
    Digitale Medien
    Digitale Medien
    Sarcomeric myosin heavy chain expressed in nonmuscle cells forms thick filaments in the presence of substoichiometric amounts of light chains (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 192-204 
    Details
    ISSN: 0886-1544
    Schlagwort(e): myofibrillogenesis ; myosin heavy chain ; myosin light chains ; transfection ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Central to the function of myosin is its ability to assemble into thick filaments which interact precisely and specifically with other myofibrillar proteins. We have established a novel experimental system for studying myofibrillogenesis using transient transfections of COS cells, a monkey kidney cell line. We have expressed both full-length rat α cardiac myosin heavy chain (MHC) and a truncated heavy meromyosin-like α MHC (sHMM) and shown that immunoreactive MHC proteins of the expected sizes were detected in lysates of transfected cells. Surprisingly, the full-length MHC formed large spindle-shaped structures throughout the cytoplasm of transfected cells as determined by immunofluorescence microscopy. The structures were not found in cells expressing the sHMM construct, indicating that their formation required an MHC rod. The spindle-shaped structures ranged in length from approximately 1 μm to over 20 μm in length and were birefringent suggesting that they are ordered arrays of thick filaments. This was confirmed by electron microscopic analysis of the transfected cells which revealed arrays of filamentous structures approximately 12 nm in diameter at their widest point. In addition, the vast majority of transfected MHC did not associate with the endogenous nonmuscle myosin light chains, demonstrating that myosin thick filaments can form in the absence of stoichiometric amounts of myosin light chains. © 1993 Wiley-Liss, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cm.970260303
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  • 2
    Digitale Medien
    Digitale Medien
    The architecture of adventitial elastin in the canine infrarenal aorta (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 230 (1991), S. 86-96 
    Details
    ISSN: 0003-276X
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Although the artery wall consists of three distinct layers, only the structures of the intima and media have been well characterized. The adventitia has generally been overlooked. Our examination focused on the organization of elastin and collagen which are the major components of this tunic. Canine infrarenal aortas were excised, stretched to their in vivo length, then pressure fixed in formalin. Transverse, longitudinal, and frontal sections were prepared with specific elastin and collagen stains. Areas of adventitia in these sections were examined with LM, and interconnections between collagen and elastin were photographed at various magnifications. Subsequently, the slides were fractured for attachment to SEM stubs, and the coverslips were demounted. The identical areas were then examined with SEM using the LM micrographs as a guide to identify elastin and collagen. Whole mount aortic ring preparations were digested in formic acid for 72 and 96 h at 45°C to confirm adventitial elastin architecture. The adventitia was organized in alternating lamellae of collagen and elastin. The elastin lamellae consisted of continuous sheets of elastin with a longitudinal fibrillar substructure. Finer circumferential elastin fibers were also identified. These attached to both longitudinal elastin and adjacent collagen lamellae. Collagen lamellae were arranged in broad corrugated bands of fibrils. The unique architecture of the adventitia may explain some of the visco-elastic properties of the aorta in both normal and pathologic states.
    Zusätzliches Material: 30 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ar.1092300109
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  • 3
    Digitale Medien
    Digitale Medien
    Zona drilling enhances fertilization by mouse caput epididymal sperm (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 27 (1990), S. 332-336 
    Details
    ISSN: 1040-452X
    Schlagwort(e): Caput epididymis ; Micromanipulation ; In vitro fertilization ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Spermatozoa from the caput epididymis are known to be much less capable of fertilization when compared to sperm from more distal segments of the epididymis. The purpose of this study was to determine if two micromanipulative techniques, zona drilling (ZD) and a modification of partial zona dissection (PZD), could be used to enhance fertilization with caput epididymal sperm. A mouse in vitro fertilization model was used. Inseminating oocytes with 500-1,000 sperm/oocyte from the cauda epididymis as a control resulted in fertilization of 98 of 300 (32.6%) oocytes. Of those fertilized, 47 developed to the blastocyst stage (47.9%). Caput sperm fertilized 13 of 116 (11.2%) nonmanipulated oocytes. Only 1 of 13 developed into a blastocyst, while with oocyte ZD, caput sperm fertilized 24 of 144 (16.7%) oocytes, 50% of those fertilized developing to blastocyst (P=0.0129). When modified PZD was performed on oocytes, only one of 23 was fertilized, with no blastocyst development. These results indicate that acid Tyrode ZD enhances both fertilization and early embryonal development when caput epididymal sperm are used for insemination. These mouse studies suggest that ZD or other micromanipulation techniques may prove clinically useful in men with proximal epididymal obstruction where only caput sperm are available.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrd.1080270407
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  • 4
    Digitale Medien
    Digitale Medien
    Electron microscopic studies of magnetosomes in magnetotactic bacteria (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 389-401 
    Details
    ISSN: 1059-910X
    Schlagwort(e): Biomineralization ; Greigite ; Magnetite ; Pyrite ; Single-magnetic-domain ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Allgemeine Naturwissenschaft
    Notizen: Electron microscopic studies on magnetosomes in magnetotactic bacteria have revealed much information on their composition, structure, and even the formation of their mineral phase. The mineral phases of the magnetosomes are of two general types: iron oxides and iron sulfides. Iron oxide-type magnetosomes contain particles of the ferrimagnetic mineral magnetite (Fe3O4) while the iron sulfide-type contain ferrimagnetic greigite (Fe3S4), greigite and non-magnetic pyrite (FeS2), or possibly ferrimagnetic pyrrhotite (Fe7S8). Regardless of their composition, the crystalline particles in magnetosomes have a narrow size range: approximately 35 to 120 nm. Magnetite crystals in this size range are single-magnetic-domains and confer a permanent magnetic dipole moment to the cell. The single-domain size range for greigite is not known but is probably similar to that for magnetite.The morphology of the particles in the bacterial magnetosomes appears to be species-specific. Morphologies of magnetite crystals in different species of magnetotactic bacteria include cubooctahedra, parallelepipedal (truncated hexahedral or octahedral prisms), and tooth- or bullet-shaped (anisotropic). Morphologies of greigite particles include cubo-octahedra and rectangular prismatic. The greigite-pyrite particles are generally pleomorphic with no consistent crystalline morphology. A membrane has been shown to surround the particles in some organisms and may be involved in the formation of the crystalline phase while also providing physical constraints on the size and the shape of the crystal. These results clearly indicate that the biomineralization process involved in the bacterial magnetosome, a good example of a self-assembled structure on a nanometer scale, is highly controlled by the organism. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jemt.1070270505
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  • 5
    Digitale Medien
    Digitale Medien
    Ultrastructural and cytoarchitectural features of lymphoreticular organs in the colon and rectum of adult BALB/c mice (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 190 (1991), S. 10-18 
    Details
    ISSN: 0002-9106
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The structure and function of colonic mucosal lymphoid organs remain largely unexplored, especially in the rectum hidden within the pelvic vault. Two-month-old female BALB/c mice were anesthetized, and the entire colon was removed from cecum to anus. Distal colonic patches were then prepared for electron microscopy or were quick-frozen and sectioned for immunoperoxidase localization of B cells and T cell subsets. Aggregated lymphoid follicles were distributed irregularly along the entire colon with an average of 1.4 patches per centimeter of colon length. There were large collections of follicles opposite the ileocecal valve (cecal patches), variable numbers of patches throughout the colon, and at least one patch within 10 mm of the anus (rectal patch). Follicles were adjacent to branching crypts lined by epithelium infiltrated by lymphoid cells and containing few goblet cells. In electron micrographs, M cells were identified by their short, irregular microvilli; intraepithelial lymphoid cells; reduced lysosomal dense bodies; and an expanded tubulovesicular network. Small germinal centers were seen. Cytoarchitectural components of colonic lymphoid follicles and Peyer's patch follicles were remarkably similar, despite differences in surrounding mucosa and luminal microbial exposure. The presence of organized lymphoid tissue with M cells and germinal centers suggests that transepithelial particle transport and antigen recognition can take place in the rectum. Whether such tissue has the capacity for uptake of luminal microorganisms is of particular interest, not only because colonic follicles may be sites for local initiation of immune responses but also because they may be important entry points for systemic infection.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aja.1001900103
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  • 6
    Digitale Medien
    Digitale Medien
    Lectin and immunolabeling of microvascular endothelia (1991)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 19 (1991), S. 305-315 
    Details
    ISSN: 0741-0581
    Schlagwort(e): Endothelium ; Immunocytochemistry ; Electron microscopy ; Lectins ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Allgemeine Naturwissenschaft
    Notizen: A number of recently developed localization techniques are beginning to be applied in the study of endothelial cells and their structural components. In this article we will review a number of these cytochemical approaches as well as their advantages and disadvantages and their applications. The methods will be presented for processing tissues for either L.R. White embedding or semi-thin and thin frozen sections followed by subsequent lectin and immunolabeling for fluorescence and electron microscopic examination. These techniques are easily applied in the localization of perfused exogenous proteins and of endogenous endothelial-associated proteins. The results that can be obtained from such studies are presented and discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jemt.1060190306
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