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  • 1
    Electronic Resource
    Electronic Resource
    Lithium as a normal metabolite: Some implications for cyclotron resonance of ions in magnetic fields (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 9 (1988), S. 387-391 
    Details
    ISSN: 0197-8462
    Keywords: H fields ; trace elements ; nutrition ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Cyclotron resonance of ions has been proposed as a mechanism by which weak, extremely-low-frequency (ELF) electromagnetic fields can act on biological systems. Critics of a mechanism predicated on resonance of lithium have argued that this element is virtually absent from the internal milieu of mammals and otherwise plays no role in the normal physiological functioning of the organism. Sophisticated techniques of trace-element analysis have recently revealed that lithium is a normal constituent of tissues of assayed mammals, including those of rats and human beings. There is evidence, too, that lithium is an important, biologically-active element. Cyclotron resonance may or may not be a mechanism by which ELF- and static-magnetic fields at low strengths combine to affect the organism, but rejection of this mechanism on the grounds that lithium is absent or is physiologically inadequate is unwarranted. Lithium is normally present and is metabolically active in many tissues, especially those of the of the neuroendocrine system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250090409
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  • 2
    Electronic Resource
    Electronic Resource
    A Hilbert space approach to maximum entropy reconstruction (1988)
    Chichester, West Sussex : Wiley-Blackwell
    Mathematical Methods in the Applied Sciences 10 (1988), S. 397-406 
    Details
    ISSN: 0170-4214
    Keywords: Mathematics and Statistics ; Applied Mathematics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We examine here the problem of reconstructing an X-ray attenuation function from measurements of its integrals. The approach that is taken is to maximize the difference of the entropy and the residual error in meeting the measurements. The solution of this optimization problem is constrained by requiring that the solution lie in a certain weakly compact subset of L2, to be determined by physical information.We show that the constrained optimization problem is well-posed: there exists a unique solution (even when the measured data are inconsistent) and the solution depends continuously on the measurements. In the course of proving this, we show that the entropy functional is continuous on L2. We further demonstrate that the solution of the optimization problem for a special case, must be piecewise constant.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mma.1670100405
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  • 3
    Electronic Resource
    Electronic Resource
    Insulin and α2-macroglobulin-methylamine undergo endocytosis by different mechanisms in rat adipocytes: I. Comparison of cell surface events (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 133 (1987), S. 203-212 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This ultrastructural study compared the endocytosis of a peptide hormone, ferritin-labeled insulin (Fm-I) or gold-labeled insulin (Au-I), and a non-hormonal ligand, gold-labeled alpha-2-macroglobulin-methylamine (Au-α2MGMA), by rat adipocytes. Quantitative analysis of the cell surface showed that coated pits occupied 0.4% of the adipocyte surface. This was one fifth to one tenth of that which has been reported on fibroblasts and hepatocytes, cell types in which receptor-mediated endocytosis has been extensively studied. In contrast, uncoated micropinocytotic invaginations were quite numerous and occupied 13.1% of the adipocyte cell surface. The frequency of microphinocytotic invaginations, 13.8 per μm2 of plasma membrane, was 7-12 times greater than has been reported on fibroblasts. Therefore, the ultrastructure of the endocytic apparatus on rat adipocytes was different from more commonly studied cell types. At 4°C, Au-α2MGMA concentrated within coated pits to a density that was 52 times greater than that on the uncoated plasma membrane. Au-α2MGMA was excluded from micropinocytotic invaginations by more than 93%; this exclusion was unrelated to the size of the Au-α2MGMA particle. In contrast, at 4°C, Fm-I did not concentrate within coated pits and occupied micropinocytotic invaginations in a random manner. At 37°C, coated pits accounted for all of the endocytosis of Au-α2MGMA, proving that these structures were functional despite their atypically low density. In contrast, greater than 99% of the endocytosis of Fm-I or Au-I occurred through micropinocytotic invaginations. These results demonstrated for the first time by a comparative, quantitative, ultrastructural method that insulin and Au-α2MGMA undergo endocytosis by dissimilar mechanisms on rat adipocytes. Dissimilarities in the endocytosis of insulin and Au-α2MGMA may be related to the different biological roles of these two molecules.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041330202
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  • 4
    Electronic Resource
    Electronic Resource
    Insulin and α2-macroglobulin-methylamine undergo endocytosis by different mechanisms in rat adipocytes: II. Comparison of intracellular events (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 133 (1987), S. 213-218 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A previous ultrastructural study showed that gold-labeled insulin (Au-I) and the non-hormonal ligand gold-labeled alpha-2-macroglobulin-methylamine (Au-α2MGMA) underwent endocytosis by dissimilar cell surface structures on rat adipocytes. The present ultrastructural study compared the intracellular routes taken by these two ligands in adipocytes. Intracellular Au-α2MGMA was initially found within apparent coated vesicles but Au-I was not, consistent with the previous demonstration that Au-α2MGMA underwent endocytosis by coated pits whereas Au-I was internalized by uncoated micropinocytotic invaginations. Early in the endocytic pathway, the two ligands were segregated within separate small vesicles and tubulovesicles. Au-α2MGMA was concentrated in a small number of these structures whereas Au-I was sparsely distributed among a relatively large number. Subsequently, the two endocytic pathways converged as the ligands intermingled within pale multivesicular bodies and lysosome-like structures. Au-I was less efficiently transferred to lysosomes than Au-α2MGMA since a greater proportion of intracellular Au-I remained associated with small vesicles and tubulovesicles. This study indicates that early intracellular events in the endocytic pathways of insulin and α2MGMA are distinct. These findings are discussed in light of the fundamentally dissimilar biological roles of these two molecules and the possible involvement of the endocytic pathway in the insulin signaling mechanism.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041330203
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructural analysis of the organization and distribution of insulin receptors on the surface of 3T3-L1 adipocytes: Rapid microaggregation and migration of occupied receptors (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 123 (1985), S. 167-179 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Monomeric ferritin-insulin and high-resolution electron microscopic analysis were used to study the organization, distribution, and movement of insulin receptors on differentiated 3T3-L1 adipocytes. Analysis of the binding to prefixed cells showed that insulin initially occupied single and paired receptors preferentially located on microvilli. The majority of receptors (60%) were found as single molecules and 30% were pairs. In 1 min at 37%C, 50% of the receptors on nonfixed cells were found on the intervillous plasma membrane and more than 70% of the total receptors had microaggregated. By 30 min only 7% of the receptors were single or paired molecules on microvilli. The majority were on the intervillous membrane, with 95% of those receptors in groups. The receptor groups on the intervillous plasma membrane could be found in both noncoated invaginations and coated pits. The concentration of occupied receptors in the noncoated invaginations and the coated pits was similar; however, ten times more noncoated invaginations than coated pits contained occupied insulin receptors. The observations in this study contrast with those reported on rat adipocytes using identical techniques (Jarett and Smith, 1977). Insulin receptors on adipocytes were initially grouped and randomly distributed over the entire cell surface and did not microaggregate into larger groups. Insulin receptors on rat adipocytes were found in non-coated invaginations but were excluded from the coated pits. The differences in the organization and behavior of the insulin receptor between rat and 3T3-L1 adipocytes suggest that the mechanisms regulating the initial organization of insulin receptors and the aggregation of occupied receptors may be controlled by tissue-specific processes. Since both of these cell types are equally insulin sensitive, the differences in the initial organization and distribution of the insulin receptors on the cell surface may not be related to the sensitivity or biological responsiveness of these cells to insulin but may affect other processes such as receptor regulation and internalization. On the other hand, the microaggregates of occupied receptors on both cell types may relate to biological responsiveness.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041230204
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  • 6
    Electronic Resource
    Electronic Resource
    Insulin binding and processing by H4IIEC3 hepatoma cells: Ultrastructural and biochemical evidence for a unique route of internalization and processing (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 130 (1987), S. 428-435 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Biochemical and ultrastructural studies of insulin binding and cellular processing by cultured H4IIEC3 hepatoma cells were performed. Insulin binding and intracellular accumulation were rapid and after 30 min at 37°C, 65% of the total cell-associated 125I-insulin was in an acid-stable compartment. Chloroquine had no significant effect on the amount of total cell-associated insulin or the percentage of insulin in the acid-stable compartment or cell-associated insulin degradation under those conditions, but after 60-min incubations, it slightly decreased the rate of dissociation of internalized hormone. Ultrastructural analysis revealed that monomeric ferritin-insulin (Fm-I) initially bound to single or paired receptors on microvilli. Within 5 min occupied insulin receptors microaggregated and migrated to the intervillous cell surface. During the next 5-10 min occupied receptors aggregated into large clusters on the plasma membrane. Large amounts of insulin were internalized by macropinocytosis and the majority of internalized Fm-I was found in phagosomes. Less than 10% of the membrane-bound insulin was associated with pinocytotic invaginations or coated pits and less than 5% of the total cell-associated insulin was found in lysosomes. Chloroquine had no detectable effect on the amount of Fm-I or its distribution among the intracellular organelles. These studies demonstrated that, compared to previous studies with rat adipocytes or 3T3-L1 adipocytes, insulin interalization and intracellular processing in this hepatoma cell were unique. These differences provide further evidence that insulin binding and processing may be controlled by cell-specific mechanisms and that substantial heterogeneity exists in pathways previously presumed to be similar for all cell types.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041300317
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  • 7
    Electronic Resource
    Electronic Resource
    Temporally regulated expression of insulin and insulin-like growth factors and their receptors in early mammalian development (1989)
    New York, NY : Wiley-Blackwell
    BioEssays 11 (1989), S. 171-176 
    Details
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Recent studies of early development in a number of ivertebrate and vertebrate species have suggested that growth factors and their receptors may play important roles in differentiation as well as cell proliferation. In the mouse embryo, the expression of the receptors for insulin and insulin-like growth factors I and II (IGF-I and -II) are temporally regulated. The ontogeny of receptor and ligand expression within the insulin and IGF gene family suggests that the very earliest stages of mammalian embryogenesis may be subject to regulation by autocrine and paracrine factors from maternal and embryonic sources.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bies.950110604
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  • 8
    Electronic Resource
    Electronic Resource
    Capacitor-Discharge Initiation of a Detonator containing a vacuum-deposited thin-film chromium bridge (1988)
    Weinheim : Wiley-Blackwell
    Propellants, Explosives, Pyrotechnics 13 (1988), S. 129-134 
    Details
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental program is described in which the capacitor-discharge initiation characteristics of a detonator containing a vacuum-deposited thin-film chromium bridge were studied. The objective of the effort was to define the conditions that would result in overall function times of 10 μs or less. The threshold initiation energy of the detonator was in the range of 11.5 mJ-20.0 mJ. Consistent performance was obtained from a firing energy of 54 mJ, which was achieved by a 5-μF capacitor charged to 147 V. Under these conditions, the average overall function time was 4.2 μs, with a standard deviation of 0.2 μs. Other tests showed that at higher capacitances and lower voltages the function time increased substantially and became more nonreproducible, even though the stored energy was considerably above the threshold value.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prep.19880130502
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