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  • Occupational Health and Environmental Toxicology  (4)
  • Peripheral nerves  (4)
  • Electron microscopy  (2)
  • 1
    ISSN: 1432-0878
    Keywords: Neurohypophysis ; Neurosecretion ; Neurophysin ; Neurohypophysia hormones ; Electron microscopy ; Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electron-microscope autoradiographs have been prepared from the neural lobes of the pituitary glands of rats which had received intracisternal injections of [35S] cysteine at various times before gland removal. The rate of appearance and disappearance of autoradiographically demonstrable radioactivity in the neural lobe closely paralleled that previously determined, biochemically, for radioactive hormones and neurophysins. Radioactivity was appreciably associated with the undilated parts of neurosecretory axons only during the first few hours after injection of the label. The axonal dilations were subdivided into those in which small vesicles could be seen (“endings”) and those in which no small vesicles could be seen (“swellings”). Radioactivity appeared first in “endings” and then in progressively larger and larger profiles of “swellings”. It appeared that newly arrived granules were found close to the limiting membrane of the nerve swelling and that as time progressed they moved deeper and deeper into the swelling. On the basis of the results, suggestions were made for an anatomical explanation of the readily-releasable pool of hormone which has been demonstrated pharmacologically.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 124 (1972), S. 103-130 
    ISSN: 1432-0878
    Keywords: Peripheral nerves ; Myelinated axons ; Regeneration ; Sciatic nerve, rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the first six days after division myelinated axons in the proximal stump of rat sciatic nerves produce collateral and terminal sprouts. These are present as circumscribed “groups” which are positively distinguishable from clusters of non-myelinated axons. Two types of “groups” are identifiable, and their distribution in some of the nerve segments is analysed. Their evolution was followed in sequential nerve segments, the initial ‘tight’ structure becoming looser between 7 and 10 days, and myelinated axons appeared in them during this time. At this stage a complete basal lamina was present surrounding the entire “group”. Some of the cells in the “groups” did not have the characteristics of Schwann cells. Between 7 and 10 days after division alveolate vesicles and densely staining material in the cisternae of the rough surfaced endoplasmic reticulum were prominent in Schwann cells in the distal part of the proximal stump. It is thought that both types of “group” are developed from single myelinated axons and the name “regenerating unit” is proposed for both types. Their relationship to “clusters”, seen in the distal stump of regenerating peripheral nerves, and “onion bulbs”, present in some peripheral neuropathies, is discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 124 (1972), S. 165-203 
    ISSN: 1432-0878
    Keywords: Peripheral nerves ; Regeneration ; Sciatic nerve, rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Between seven days and six weeks after division the internal architecture of rat sciatic nerves is altered, their original mono- or di-fascicular configuration being replaced by a collection of small fascicles each surrounded by perineurium. This change, called by us ‘compartmentation’, has a minimum retrograde extent of 3.5 mm and is brought about by changes in Schwann cells and endoneurial fibroblasts, which undergo circumferential elongation to surround groups of axons and so come to resemble perineurial cells. Ultrastructural changes occur in these cells during compartmentation. There is a marked rise in the number of endoneurial fibroblasts in the distal segments of the proximal stump. The stimulus to the development of compartmentation is considered to be disturbance of the endoneurial environment following rupture of the perineurium. Changes in the structure and appearance of endoneurial cells suggest that metaplasia occurs between Schwann cells, endoneurial fibroblasts and perineurial cells, and it is concluded that these cell types in the endoneurium have a common origin from embryonic ectoderm. This suggests that the surgical treatment of peripheral nerve injuries should be primarily directed to the reconstitution of the endoneurial environment.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 124 (1972), S. 103-130 
    ISSN: 1432-0878
    Keywords: Peripheral nerves ; Myelinated axons ; Regeneration ; Sciatic nerve, rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the first six days after division myelinated axons in the proximal stump of rat sciatic nerves produce collateral and terminal sprouts. These are present as circumscribed “groups” which are positively distinguishable from clusters of non-myelinated axons. Two types of “groups” are identifiable, and their distribution in some of the nerve segments is analysed. Their evolution was followed in sequential nerve segments, the initial ‘tight’ structure becoming looser between 7 and 10 days, and myelinated axons appeared in them during this time. At this stage a complete basal lamina was present surrounding the entire “group”. Some of the cells in the “groups” did not have the characteristics of Schwann cells. Between 7 and 10 days after division alveolate vesicles and densely staining material in the cisternae of the rough surfaced endoplasmic reticulum were prominent in Schwann cells in the distal part of the proximal stump. It is thought that both types of “group” are developed from single myelinated axons and the name “regenerating unit” is proposed for both types. Their relationship to “clusters”, seen in the distal stump of regenerating peripheral nerves, and “onion bulbs”, present in some peripheral neuropathies, is discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 124 (1972), S. 131-164 
    ISSN: 1432-0878
    Keywords: Peripheral nerves ; Injuries ; Axons ; Sciatic nerve, rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Changes in the proximal stump of axons of divided rat sciatic nerves in the first 6 weeks after nerve section were studied, particularly in terms of alterations in the organelle content, axoplasmic ultrastructure and the diameter of the axons. A variety of organelle types were observed; quasi-membranous structures, multivesicular bodies, dense bodies, vesicles and tubules, dense cored vesicles and alveolate vesicles: their identification and the functional implications of their presence are discussed. Alterations in the ultrastructure of the “stained” elements of the axoplasm are described. Axons containing excess organelles were divided into classes, comprising myelinated axons; and “supergiant”, “giant” and “conventional” non-myelinated axons. Temporal changes in these axons are described. The characteristics of the various classes of apparently non-myelinated axon are considered in terms of their identification as regenerating terminal sprouts of myelinated axons, segmentally demyelinated axons, sections through abnormal nodes of Ranvier or merely non-myelinated axons. The structure of axons in “regenerating units” is described. Changes in the neurofilament microtubule ratio of small axons without excess organelles are demonstrated, and “spiralling” of neurofilaments in some myelinated and non-myelinated axons with normal axoplasmic ultrastructure is illustrated and discussed.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0878
    Keywords: Gastrin cells ; Electron microscopy ; Fixation ; Granule maturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructural appearance of gastrin cell (G cell) granules was studied after different fixation procedures. When the pH of prefixation was varied there was greater preservation of the electron density of granule cores after acidic (pH 5.0 and 6.0) than after neutral or alkaline (pH 7.0 and 8.0) prefixation. Increasing duration of prefixation at pH 7.3 resulted in progressive loss of electron density of the granule core with swelling and occasional rupture of the limiting membrane. In tissues where most granules had been rendered electron lucent by fixation, those granules remaining dense cored were preferentially located close to the Golgi zone. These findings indicate that the electron density of G cell granules is profoundly affected by conditions of fixation, and that immature granules are more resistant to loss of core density than mature granules. They also suggest that the gastrin granule in vivo, like other polypeptide granules, may have a “solid”, osmotically inactive core.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 3 (1982), S. 341-347 
    ISSN: 0197-8462
    Keywords: immunology ; mice ; 60-Hz electric fields ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: We evaluated humoral and cellular functions of the immune system of Swiss-Webster mice exposed to 60-Hz electric fields at 100 kV/m. No significant differences were observed in primary antibody response to keyhole limpet hemocyanin (precipitating antibody levels) between exposed (30 or 60 days) and control mice, nor were there significant changes in mitogen-stimulation response of spleen cells from mice similarly exposed for 90 or 150 days when compared to sham-exposed animals.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 4 (1983), S. 383-396 
    ISSN: 0197-8462
    Keywords: hematology ; immunology ; mice ; pulsed microwaves ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Mice were exposed in the far field in an anechoic chamber to 2,880-MHz pulsed microwaves 3 to 7.5 h daily, 5 days/week for 60 to 360 h. Three experiments were performed at average power densities of 5 mW/cm2 and six at 10 mW/cm2, corresponding to averaged specific absorption rates (SARs) of 2.25 and 4.50 mW/g, respectively. Each experiment consisted of eight mice, with a concurrently sham-exposed group of eight. In two of three studies at 5 mW/cm2, there was a significant increase in bone marrow cellularity in the microwave-exposed groups compared to the sham-exposed groups. Significant differences were occasionally seen in erythrocyte, leukocyte, and platelet values from microwaveexposed groups, but were not consistently observed. In one of six groups exposed at 10 mW/cm2, mean bone marrow cellularity was reduced significantly in the microwaveexposed mice; in another group, the lymphocyte count was increased. In only one exposure (10 mW/cm2 for 360 h) was any significant effect noted on serum proteins: a reduction to 5.1 ± 0.3 g/dl in the exposed versus 5.6 ± 0.4 g/dl in the sham-exposed mice. This was due to a decrease in alpha and beta globulins, with no effect on albumin or gamma globulin concentrations. No effect on bone marrow granulocyte/macrophage colony-forming units (CFU) was revealed following exposure of mice to pulsed microwaves at 5 mW/cm2. In one of four exposures at 10 mW/cm2, there was a significant increase in CFU-agar colonies. No significant effects of exposures at 10 mW/cm2 were observed on in vivo and in vitro assays of cell-mediated immune functions. No exposure-related histopathologic lesions were found from examination of several tissues and organs. Results of these series of exposures of mice at SARs of 2.25 and 4.50 mW/g indicated no consistent effects on the hematologic, immunologic, or histopathologic variables examined.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0197-8462
    Keywords: alkaline elution ; human lymphocytes ; DNA damage ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: DNA damage was induced in isolated human peripheral lymphocytes by exposure at 5 Gy to 60Co radiation. Cells were permitted to repair the DNA damage while exposed to 60-Hz fields or while sham-exposed. Exposed cells were subjected to magnetic (B) or electric (E) fields, alone or in combination, throughout their allotted repair time. Repair was stopped at specific times, and the cells were immediately lysed and then analyzed for the presence of DNA single-strand breaks (SSB) by the alkaline-elution technique. Fifty to 75 percent of the induced SSB were repaired 20 min after exposure, and most of the remaining damage was repaired after 180 min. Cells were exposed to a 60-Hz ac B field of 1 mT; an E field of 1 or 20 V/m; or combined E and B fields of 0.2 V/m and 0.05 mT, 6 V/m and 0.6 mT, or 20 V/m and 1 mT. None of the exposures was observed to affect significantly the repair of DNA SSB.
    Additional Material: 1 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 12 (1991), S. 21-25 
    ISSN: 0197-8462
    Keywords: field-related movement ; electromagnetic field ; geomagnetic field ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The effect of a 16-Hz electromagnetic field on the mobility of the diatom Amphora coffeaformis was examined on agar plates that contained no added calcium and also on agar plates containing 0.25 or 2.5 mM exogenous Ca2+. Exposure conditions consisted of an ac field of 16 Hz with an amplitude of 20.9 μT parallel to the horizontal component of the dc field (BH = 20.9 μT, where Bv = 0). To assess results, the percentage of diatoms that moved a distance greater than their body length was determined. We observed the field-associated increase in diatom motion at 0.25 mM Ca++, which was previously reported in the literature. Although the magnitude of the effect at 16 Hz was significant, the percentage of cells that moved was not sufficiently reproducible to allow examination for frequency dependence.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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