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  • 1
    Electronic Resource
    Electronic Resource
    A test object and criteria for high resolution electron microscopy (1968)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 1-19 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The desirability and requirements for a specimen capable of testing the resolving power and other image characteristics of an electron microscope are discussed in detail. In this discussion, the underlying diffraction phenomena are particularly utilized. A partially graphitized carbon black is shown to satisfy the requirements extremely well and constitutes an easily prepared specimen for conducting tests of image quality in the molecular size range. The structure of the test object is known in detail with the result that readily interpretable phase contrast images are obtained. Micrographs illustrating the use of the 3.4 Å (002) spacing for magnification calibration, astigmatism and asymmetry check as well as resolving power are exhibited. The second order c-spacing of 1.7 Å is occasionally found in an image. The micrographs shown herein were taken with two different electron microscopes by different operators obtaining the same structural detail in the images. It is concluded that the carbon black test object offers the best possibilities for evaluating image performance of any specimen yet suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889868004930
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  • 2
    Electronic Resource
    Electronic Resource
    The induction of taxol production in the endophytic fungus—Periconia sp from Torreya grandifolia (1998)
    Springer
    Journal of industrial microbiology and biotechnology 20 (1998), S. 259-264 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: taxol; attenuation; benzoic acid; Periconia sp; endophyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Periconia sp was isolated from Torreya grandifolia (a relative of yew that does not synthesize taxol) near Huangshan National Park in the People’s Republic of China. This fungus, not previously known as a tree endophyte, was isolated from the inner bark of a small lower limb. When freshly isolated from the tree and placed in a semi-synthetic medium, the fungus produced readily detectable quantities of the anticancer drug taxol. Other taxol-producing endophytes were also isolated from this source. The production of taxol by Periconia sp was demonstrated unequivocally via spectroscopic and immunological methods. However, successive transfers of the fungus in semi-synthetic medium resulted in gradual attenuation until low production occurred even though fungal growth was relatively unaffected. Several compounds, known previously as activators of microbial metabolism, including serinol, p-hydroxybenzoic acid, and a mixture of phenolic acids, were capable of fully or partially restoring taxol production to otherwise taxol-attenuated cultures. The compound with the most impressive ability to activate taxol production was benzoic acid at 0.01 mM. Benzoic acid was not a taxol precursor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.2900521
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  • 3
    Electronic Resource
    Electronic Resource
    Fine structure ofPenicillium megasporum conidiospores (1967)
    Springer
    Protoplasma 64 (1967), S. 75-88 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An investigation was conducted on the fine structure ofP. megasporum conidiospores using both chemical fixation and the freeze-etching techniques. The spore cell wall was shown to consist of several layers, one of which is chiefly fibrillar in nature. The surface of the spore appears to be covered by ordered arrays of “rodlets” which are embedded in or resting upon a thin layer of homogenous material. At higher magnification, these “rodlets” appear as linear arrays of particles approximately 50 Å in diameter. This layer may be of a cutaneous nature. In addition, the plasma membrane was shown to be covered by particles, some of which appear to migrate to the inner layer of the cell wall. Numerous invaginations of the plasma membrane were also seen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01257383
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  • 4
    Electronic Resource
    Electronic Resource
    Fine structure of germinatingPenicillium megasporum conidia (1967)
    Springer
    Protoplasma 64 (1967), S. 439-451 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Penicillium megasporum conidia have spore walls consisting of several layers. There is no visible change in the outer wall layers during spore germination, but the inner layers increases in thickness on only one side of the spore, resulting in a rupture of the outer wall layers and subsequently in germ tube formation. Invaginations in the plasma membrane disappear as the germ tube forms and emerges, and the nucleus migrates into the developing germ tube. Mitochondria gather at the base of the germ tube during its formation. During germination, the amount of lipid in the spore decreases and portions migrate into the germ tube. Membrane-bound, electron dense bodies are present in resting spores. These bodies decrease in size as germination proceeds, and the cytoplasm in the developing germ tube appears much more electron dense than the cytoplasm within the spore.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666542
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructure of nuclei isolated from plant protoplasts (1977)
    Springer
    Protoplasma 93 (1977), S. 267-274 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A simple method, involving selective Triton X-100 membrane solubilization, has been developed for the isolation of nuclei from barley and tobacco protoplasts which gives a high yield of essentially pure nuclei. The isolated nuclei resembled those in leaf cells and protoplasts when the isolated nuclei were fixed for short times (2 hours, Medium II), except that their chromatin appeared to be more highly condensed and barley nuclei also lacked the outer nuclear membrane. When longer times of fixation (12 hours, Medium I) were used, the isolated nuclei lacked the characteristic condensed chromatin appearance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275658
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrastructure of dormant and germinated sporangiospores ofRhizopus arrhizus (1973)
    Springer
    Protoplasma 77 (1973), S. 15-33 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ultrastructural investigations of dormant and germinated sporangiospores ofRhizopus arrhizus were conducted by the use of thin sectioning and freeze-etching procedures. Dormant spores contained deep furrows and prominent ridges with swellings along the sides of the ridges. The furrows and ridges almost disappeared as spores swelled during germination. The plasma membranes contained protuberances or depressions (approximately 50 nm diam) depending upon the nature of the fracture. Mitochondria in dormant spores were spherical and contained few cristae compared to mitochondria of germinated spores which were larger, more diverse in shape and contained abundant cristae. Treatments of spores with 20–25% glycerol prior to freeze-etching or thin sectioning resulted in the production of artifacts between the cell wall and the plasma membrane. Vesicles were rarely observed at the apices of young germ tubes, but were present in abundance in growing hyphal tips. Surface views of young germ tubes revealed the presence of microfibrils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01287290
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  • 7
    Electronic Resource
    Electronic Resource
    Surface structures of frozen-etched penicillium conidiospores (1966)
    Springer
    Naturwissenschaften 53 (1966), S. 708-708 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00602737
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  • 8
    Electronic Resource
    Electronic Resource
    Increased Susceptibility of Mg- and Mn-Deficient Pumpkin Seedlings to Fungal Attack (1977)
    Springer
    Naturwissenschaften 64 (1977), S. 437-438 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00508704
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  • 9
    Electronic Resource
    Electronic Resource
    Germ pores ofChaetomium ascospores (1967)
    Springer
    Naturwissenschaften 54 (1967), S. 521-522 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01129384
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  • 10
    Electronic Resource
    Electronic Resource
    Pseudoscopic illusions in stereo views of freeze-etch replicas (1978)
    Springer
    Protoplasma 93 (1978), S. 473-475 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The use of stereo pairs of freeze-etch replicas significantly contributes to the interpretation of spatial relationships of structures within fungal spores. However, great care must be taken to assure proper orientation of prints before publication in order to prevent pseudoscopic illusions (an optical illusion which produces an apparent reversal of surface elevations and depressions). AsHarold C. Conklin [2] pointed out in his letter to Science, this phenomenon is an ever present concern for users of vertical imagery. The sensation of seeing depth in two dimensional photographs is an illusion. The goal is to create the proper illusion. In order to convey the desired information to the reader it is essential that surface photographs be oriented as if the illumination were coming mostly from the top of the page and the shadows were projected toward the bottom of the page. Examples of neglecting this simple rule may be found in publications ranging from news magazines [5] to prestigeous scientific journals [3, 4]. Articles occasionally contain photographs which are rotated 180 degrees from the proper orientation and thus convex surfaces are displayed as concave surfaces and vice versa. In stereo pairs of electron micrographs of freeze-etch replicas pseudoscopic illusions are also caused by transposing the right hand micrograph with the left hand micrograph. When viewed in the proper orientation the various organelle spatial relationships and membrane surfaces, and other structures, are clearly discernable and easily understood. However when the same micrographs are transposed from left to right, entirely erroneous concepts are conveyed. For example protoplasmic surfaces appear as exoplasmic surfaces [1]. An organelle whose image is actually present will vanish leaving behind only its imprint.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276559
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