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  • Electron microscopy  (181)
  • Springer  (181)
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  • 1
    Electronic Resource
    Electronic Resource
    Ultrastructural morphometry of blastogenesis I: Transformation of small lymphocytes stimulated in vivo with dinitrochlorobenzene (1979)
    Springer
    Cell & tissue research 200 (1979), S. 495-509 
    Details
    ISSN: 1432-0878
    Keywords: T-lymphocytes ; Blast cells ; Lymph node ; Electron microscopy ; Stereology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Changes in the volumes and surfaces of subcellular compartments of unstimulated small lymphocytes and immunoblasts in mouse axillary lymph nodes have been established using stereological techniques. Blast transformation was induced in vivo with dinitrochlorobenzene (DNCB). Cell samples were obtained by random sampling regimes applied at light and electron microscopic levels. From electron micrographs the volume densities of euchromatin, heterochromatin, nucleoli, mitochondria, Golgi apparatus and rough endoplasmic reticulum were determined. Cell surface/volume ratios were also computed. By estimating mean nuclear volumes using light microscopy, it was possible to calculate absolute compartmental volumes and to evaluate the plasma membrane surface areas of average cells. Transformation in this model was characterized by a considerable cellular hypertrophy and a substantial increase in plasmalemma surface. Hypertrophy was the consequence of increases in the volumes of all measured intracellular compartments, notably euchromatin and “residual cytoplasm” (including ground cytoplasm and free ribosomes). These changes are discussed in the context of the altered metabolic status of cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234859
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructural morphometry of blastogenesis (1981)
    Springer
    Cell & tissue research 215 (1981), S. 643-649 
    Details
    ISSN: 1432-0878
    Keywords: T-lymphocytes ; Blast cells ; Autoradiography ; Electron microscopy ; Stereology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary As a companion to an earlier study, the morphometric attributes of stimulated (blast-derived) lymphocytes in mouse axillary lymph nodes have been established using stereological and autoradiographic methods. Blast transformation was induced in vivo with dinitrochlorobenzene (DNCB) and stimulated cells were labelled with tritiated thymidine. Random samples of cells were taken for light and electron microscopic morphometry. In comparison to the unstimulated lymphocyte, the stimulated cell increased in size and possessed a greater plasma membrane surface area. Increase in cell size was the result of increases in the volumes of all measured subcellular compartments both in the nucleus and the cytoplasm. Heterogeneity of the stimulated cell population precludes firm conclusions regarding the significance of all these ultrastructural changes, though alterations in cell surface are discussed in the context of known biochemical differences accompanying blastogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233538
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  • 3
    Electronic Resource
    Electronic Resource
    Bradyrhizobium japonicum mutants defective in root-nodule bacteroid development and nitrogen fixation (1986)
    Springer
    Archives of microbiology 144 (1986), S. 355-366 
    Details
    ISSN: 1432-072X
    Keywords: Bradyrhizobium ; Electron microscopy ; Mutants ; Nitrogen fixation ; Nodulation ; Soybean ; Symbiosis ; Transposon Tn5
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genome of the slow-growing Bradyrhizobium japonicum (strain 110) was mutagenized with transposon Tn5. A total of 1623 kanamycin/streptomycin resistant derivatives were screened in soybean infection tests for nodulation (Nod) and symbiotic nitrogen fixation (Fix). In this report we describe 14 strains possessing a stable, reproducible Nod+Fix- phenotype. These strains were also grown under microaerobic culture conditions to test them for free-living nitrogen fixation activity (Nif). In addition to strains having reduced Fix and Nif activities, there were also strains that had reduced symbiotic Fix activity but were Nif+ ex planta. Analysis of the genomic structure revealed that the majority of the strains had a single Tn5 insertion without any further apparent physical alteration. A few strains had additional insertions (by Tn5 or IS50), or a deletion, or had cointegrated part of the vector used for Tn5 mutagenesis. One of the insertions was found in a known nif gene (nifD) whereas all other mutations seem to affect different, hitherto unknown genes or operons. Several mutant strains had an altered nodulation phenotype, inducing numerous, small, widely distributed nodules. Light and electron microscopy revealed that most of these mutants were defective in different stages of bacteroid development and/or bacteroid persistence. The protein patterns of the mutants were inspected by two-dimensional gel electrophoresis after labelling microaerobic cultures with l-(35S)methionine. Of particular interest were mutants lacking a group of proteins the synthesis of which was known to be under oxygen control. Such strains can be regarded as potential regulatory mutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00409885
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  • 4
    Electronic Resource
    Electronic Resource
    Desmin filaments in the electrocytes of the electric organ of the electric eel Electrophorus electricus (1996)
    Springer
    Cell & tissue research 285 (1996), S. 387-393 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Electrocyte ; Intermediate filaments ; Desmin ; Cytoskeleton ; Electron microscopy ; Electrophorus electricus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Desmin protein is an abundant constituent of the intermediate filaments in the electrocytes of the electric organ of the electric eel Electrophorus electricus. Polyclonal antibodies were raised against purified desmin from the electric organ and used for immunolabeling of the protein in reconstituted filaments. In thick sections of the main electric organ that has been stained with fluorescein-labeled desmin-specific antibodies, light microscope revealed a diffuse meshwork of desmin filaments dispersed in the cytoplasm of electrocytes. In the region under the membrane, the immunostaining was slightly more intense than elsewhere. The meshwork of intermediate filaments composed of desmin was examined by electron microscopy of the main electric organ. Immuno-gold labeling demonstrated a widespread meshwork of desmin filaments in the cytoplasm and in close association with the plasma membrane. These observations suggest that intermediate filaments play a role in the maintenance of the morphology of electrocytes and, as an intracellular meshwork spanning the width of the cell, they may contribute to the organization of the intracellular compartments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050654
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of aflatoxin B1 on in vitro cultures ofNicotiana tabacum var. Samsun (1994)
    Springer
    Mycopathologia 125 (1994), S. 93-105 
    Details
    ISSN: 1573-0832
    Keywords: Aflatoxin B1 ; Callus ; Differentiation ; Electron microscopy ; Organogenesis ; Tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Calli ofNicotiana tabacum (tobacco) were treated with two dose ranges of aflatoxin B1 (0.1–2.0 µg ml−1 - low does; 5–25 µg ml−1 aflatoxin B1). The ability of calli to recover following 3 weeks of toxin exposure was also investigated. The I50 (50% inhibition) value for fresh mass accumulation was approximately 2 µg ml−1 AFB1. Fresh mass accumulation was significantly lower than the control value from 0.5 µg ml−1 AFB1. Following 3 weeks growth without a toxin source, the growth of calli up to and including 10 µg ml−1 AFB1, was significantly greater than control calli, indicating reversibility of the toxic effects. With increasing toxin concentration, chlorophyll content of callus was inhibited from 0.5 µg ml−1. Transfer to a toxin-free medium resulted in a degree of recovery (up to 0.5 µg ml−1). In the dose range 5–25 µg ml−1, the levels of chlorophyll were drastically reduced, with no recovery following AFB1 removal. Electron microscopy revealed a disruption of chloroplast structure as an early deteriorative event in AFB1 exposure of callus cells. Protein levels were less sensitive, with inhibition manifested only in the high dose range. Shoot development occurred at all concentrations, but was significantly inhibited from 5 µg ml−1 AFB1. Recovery following toxin removal was minimal at these higher AFB1 concentrations. The number of necrotic calli increased progressively from 5 µg ml−1 as toxin levels increased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01371098
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic properties of human liver and brain ferritin (1999)
    Springer
    European biophysics journal 28 (1999), S. 263-267 
    Details
    ISSN: 1432-1017
    Keywords: Key words Human liver ; Human brain ; Ferritin ; Electron microscopy ; Mössbauer spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Human brain (globus pallidus) and liver tissues were investigated by means of electron microscopy (EM), Mössbauer spectroscopy (MS) and SQUID magnetometry techniques. Based on MS measurements, the iron present was identified to be in the ferritin-like form (61–88%) and in the form of a low-spin iron species (the balance). Its overall concentration was estimated as 1.5(3) mg in the brain and 2.4(5) mg in the liver, per gram of lyophilized tissue. The average core diameter was determined by EM measurements to be equal to 7.5(1.3) nm for the liver and 3.3(5) nm for the brain. Magnetization measurements carried out between 5 and 300 K yielded an estimation of an average blocking temperature, KT BL, as equal to 6.7 K and 8.5 K for the liver and the brain, respectively. From the dependence of KT BL on the external magnetic field it was concluded that the ferritin-like cores in the studied samples can be regarded as non-interacting particles. Finally, the uniaxial magnetic anisotropy constant was determined to be 6×103 J/m3 for the liver and 4×104 J/m3 for the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050208
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  • 7
    Electronic Resource
    Electronic Resource
    The fine structure of Micrococcus radiophilus and Micrococcus radioproteolyticus (1976)
    Springer
    Archives of microbiology 107 (1976), S. 313-320 
    Details
    ISSN: 1432-072X
    Keywords: Micrococcus radiophilus ; Micrococcus radioproteolyticus ; Bacterial cell walls ; Fine structure ; Electron microscopy ; Taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The radiation resistant bacteria Micrococcus radiophilus and M. radioproteolyticus were studied by thin sectioning and freeze-etching techniques and the two species were found to be similar in the fine structure. The only significant difference was in the appearance of the surfaces of the cell walls in freeze-etched preparations. Since the two species, together with M. radiodurans, possess a unique cell wall structure and a cell wall peptidoglycan, which is different from that of other micrococci and Gram-positive cocci, it is recommended that they be reclassified into a new genus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425346
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  • 8
    Electronic Resource
    Electronic Resource
    X-ray diffractometry and electron microscopy of DNA from Bacillus subtilis bound on clay minerals (1998)
    Springer
    Sciences of soils 3 (1998), S. 1-10 
    Details
    ISSN: 1432-9492
    Keywords: Transformation ; Clay-DNA complexes ; Nucleases ; X-ray diffraction ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract DNA bound on clay minerals, sand, and humic acids has been shown, both in vitro and in situ, to be capable of transforming bacteria and to resist degradation by nucleases, which could result in the crypticity of genes in soil and other natural habitats. To determine where DNA is bound on clay minerals, which may help to explain how bound DNA becomes resistant to degradation by nucleases but retains the ability to transform competent cells, chromosomal DNA from Bacillus subtilis bound on montmorillonite (M) and kaolinite (K) was examined by X-ray diffractometry and transmission and scanning electron microscopy. X-ray diffraction analysis showed that the basal spacings of M and K were not altered, indicating that this DNA did not significantly intercalate the clays. Scanning and transmission electron microscopy showed that the binding of this DNA was primarily on the edges of M and K, although some binding was also apparent on the planar surfaces. Based on the results of these studies, it is postulated that: 1.extension from the edges of the clays enables the unbound end of DNA to interact with receptor sites on competent cells and result in their transformation; and 2.binding on clays alters the electron distribution and/or conformation of DNA, which reduces its hydrolysis by nucleases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10112-998-0001-3
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  • 9
    Electronic Resource
    Electronic Resource
    Evidence for stable grain boundary melt films in experimentally deformed olivine-orthopyroxene rocks (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 480-494 
    Details
    ISSN: 1432-2021
    Keywords: Key words Olivine ; Grain boundary ; Partial melt ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The microstructure of olivine-olivine grain boundaries has been studied in experimentally deformed (1200–1227 °C, 300 MPa) partially molten olivine and olivine-orthopyroxene rocks. In-situ melting produced ∼1 vol% melt in all samples studied. Grain boundary analyses were carried out using a number of transmission electron microscopy techniques. The grain boundary chemistry in undeformed olivine-orthopyroxene starting material showed evidence for the presence of an intergranular phase along some, but not all, of the olivine-olivine boundaries. In the deformed samples, ultrathin Si-rich, Al- and Ca-bearing amorphous films have been observed along all investigated olivine-olivine grain boundaries. The chemistry of the grain boundaries, which is considered to be indicative for the presence of a thin film, was measured with energy-dispersive X-ray spectroscopy (EDX) and energy-filtering imaging. The amorphous nature of the films was confirmed with diffuse dark field imaging, Fresnel fringe imaging, and high-resolution electron microscopy. The films range in thickness from 0.6 to 3.0 nm, and EDX analyses show that the presence of Al and Ca is restricted to this ultrathin film along the grain boundaries. Because thin melt films have been observed in all the samples, they are thought to be stable features of the melt microstructure in deformed partially molten rocks. The transition from the occasional presence of films in the undeformed starting material to the general occurrence of the films in deformed materials suggests that deformation promotes the formation and distribution of the films. Alternatively, hot-pressing may be too short for films to develop along all grain boundaries. A difference in creep strength between the studied samples could not be attributed to grain boundary melt films, as these have been found in all deformed samples. However, a weakening effect of grain boundary melt films on olivine rheology could not be ruled out due to the lack of confirmed melt-film free experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690000090
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  • 10
    Electronic Resource
    Electronic Resource
    Distribution of mitochondrial plasmid-like DNA in cultivated rice (Oryza sativa L.) and its relationship with varietal groups (1988)
    Springer
    Theoretical and applied genetics 76 (1988), S. 809-814 
    Details
    ISSN: 1432-2242
    Keywords: Electron microscopy ; Genetic variation ; Mitochondrial DNA ; Oryza sativa L. ; Plasmid-like DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitochondrial (mt) plasmid-like DNA was found in most of more than 100 rice cultivars (Oryza sativa L.) by the use of 0.7% agarose gel electrophoresis (AGE). The DNA varied in molecular weight and number. By electron microscopy, small circular DNAs of different sizes could be detected in addition to the DNAs of high molecular weight, even in cultivars in which mt plasmid-like DNA was not detected by AGE. The detection of the mt plasmid-like DNAs by AGE did not depend on their presence or absence, but on their high stoichiometry. The relationship between cytoplasms with mt plasmid-like DNAs and varietal (for example, Indica rice) groups was close. The geographical distribution of cytoplasms is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00273665
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