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  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 24 (1991), S. 598-602 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The tunability of synchrotron radiation was used to perform anomalous small-angle X-ray scattering (ASAXS) experiments on amorphous metal-germanium (a-MxGe100−x) alloys with the aim of detecting and characterizing composition modulation and phase separation. The combination of SAXS with the anomalous-dispersion effect allows the composition modulation to be distinguished from density fluctuations arising from voids and defects. Data gathered from a-FexGe100−x, a-WxGe100−x and a-MoxGe100−x samples in the low metal concentration regime show nanometer-scale composition modulation. In these samples the density of Ge atoms is uniform throughout. The small-angle X-ray scattering arises from fluctuations in the density of metal atoms. The position of the SAXS peak moves towards smaller values of the scattering vector with increased metal concentration indicating an increase in the correlation length of the composition fluctuations with increased metal content.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Springer seminars in immunopathology 12 (1990), S. 191-202 
    ISSN: 1432-2196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Conclusions There is good evidence for mast cell heterogeneity both in the rat model and in the human. The rat and human differ substantially in the characteristics of mast cells found in various tissues and in their functional properties. The human situation is apparently more complex than the relatively simple definitions of CTMC and IMMC available in the rat. Some of the differences between tissues may be explained by mixture of cell types within a given location and by the effects of isolation procedures. The recognition that mast cells interact with the nervous system, by whatever mechanism, allows for CNS influence on mast cell activity. The often-quoted psychological component of diseases such as “food allergy”, IBD and IBS could have a functional basis via mast cell activation. The potential role for mast cells in altering gut motility may also be important in this context. To date most of the work on mast cell-nerve interactions has considered the IMMC. Whether similar communication exists between CTMC and the nervous system remains to be elucidated. The recent observations of cytokine production by mast cells opens up an entirely new set of questions in mast cell biology. The importance of mast cells in immunoregulation and their potential for providing what have traditionally been thought of as T cell-derived factors may prove to be of great importance. This aspect of mast cell activity has not yet been examined with regard to mast cell heterogeneity. Given the differences in mast cell types with respect to other parameters, it would not be surprising if cytokine production was different in CTMC and IMMC populations. These areas and the issues still to be answered regarding the lineage and regulation of mast cells in different tissues provide major questions for future research.
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  • 4
    ISSN: 1432-0878
    Keywords: Mast cells ; Neonatal development ; Allergy ; Anaphylaxis ; Rat (Lewis SPF)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract To study why neonatal and young rats are resistant to the effects of some secretagogues, such as compound 48/80 and 2.5-S nerve growth factor, we examined peritoneal mast cells from 14–15-day-old rats (young rats) and compared them to peritoneal mast cells from adults. Peritoneal mast cells from young rats contain approximately one-tenth of the amount of histamine observed in adult peritoneal mast cells. However, both cell populations contained similar low levels of the mucosal mast cell-associated protease rat mast cell protease II. Histochemical analysis of peritoneal mast cells from young rats using safranin O and berberine sulphate suggested that only a portion of the granules of these cells contained heparin. At an ultrastructural level the young rat peritoneal mast cell contains relatively few granules. The majority of mast cells from young rats have a bilobed or indented nucleus which is only rarely observed in adult cells. Functionally, the young rat peritoneal mast cell demonstrates a significantly reduced histamine release in response to the connective tissue mast cellspecific secretagogues compound 48/80 and 2.5-S nerve growth factor. In contrast, the percent histamine release in response to the neurotransmitter substance P, which degranulates both connective tissue mast cells and intestinal mucosal mast cells, was similar in the adult cells and the young rat cells. This study demonstrates substantial differences between the young rat and adult peritoneal mast cells which may explain the ability of very young animals to withstand large doses of certain secretagogues.
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  • 5
    ISSN: 1432-0878
    Keywords: Autonomic ganglia ; Immune system ; Light microscopy ; Mast cells ; Neurons ; Tissue culture ; Mouse (CBA) ; Rat (Wistar, C. River)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Functional interactions between mast cells and peripheral nerves may occur at sites of association seen in vivo. To study the interactions, we developed a tissue culture model of murine sympathetic neurons co-cultured with rat basophilic leukaemia (RBL-2H3) cells (homologues of mucosal mast cells) or rat peritoneal mast cells. In co-cultures of up to 3 days, light microscopy identified neurite contacts with peritoneal mast cells or RBL-2H3 cells, but not with glial cells or fibroblasts. Electron microscopy confirmed membrane-membrane contact between neurites and RBL-2H3 cells. Time-lapse analysis of interactions between neurons and RBL-2H3 cells showed that 60–100% of the cells in a given field acquired neurite contact within 17 h. In matching control studies, there was no increase in the frequency of neurite contact with cells of the rat plasmacytoma line (YB2/0): these were not selected as targets, and contacts were broken if formed. Time-lapse records of the derivation of neurites from their path suggested a neurotropic effect of mast cells, with neurite contact ensuing when the intervening distance was less than 36±4 μm. Once formed, contacts were invariably maintained throughout the period of examination (up to 72 h), in contrast to YB2/0 or fibroblast contacts. We conclude that neurons selectively form and maintain connections with cells representative of rat connective tissue-type and mucosal mast cells in vitro. Similar interactions in vivo could promote nerve/mast cell contacts, which may allow bidirectional communication between the nervous and immune systems.
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  • 6
    ISSN: 1432-0878
    Keywords: Key words: Mast cells – Neonatal development – Allergy – Anaphylaxis – Rat (Lewis SPF)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. To study why neonatal and young rats are resistant to the effects of some secretagogues, such as compound 48/80 and 2.5-S nerve growth factor, we examined peritoneal mast cells from 14–15-day-old rats (young rats) and compared them to peritoneal mast cells from adults. Peritoneal mast cells from young rats contain approximately one-tenth of the amount of histamine observed in adult peritoneal mast cells. However, both cell populations contained similar low levels of the mucosal mast cell-associated protease rat mast cell protease II. Histochemical analysis of peritoneal mast cells from young rats using safranin O and berberine sulphate suggested that only a portion of the granules of these cells contained heparin. At an ultrastructural level the young rat peritoneal mast cell contains relatively few granules. The majority of mast cells from young rats have a bilobed or indented nucleus which is only rarely observed in adult cells. Functionally, the young rat peritoneal mast cell demonstrates a significantly reduced histamine release in response to the connective tissue mast cell-specific secretagogues compound 48/80 and 2.5-S nerve growth factor. In contrast, the percent histamine release in response to the neurotransmitter substance P, which degranulates both connective tissue mast cells and intestinal mucosal mast cells, was similar in the adult cells and the young rat cells. This study demonstrates substantial differences between the young rat and adult peritoneal mast cells which may explain the ability of very young animals to withstand large doses of certain secretagogues.
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