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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 366 (1993), S. 308-308 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Segel and Tyson in Correspondence1 tried to defend Mad-dox's assertion2 that molecular biology lacks a quantitative dimension. Maddox then went on to discuss3 an example of an attempt to redress the balance in describing a quantification of the hydration of glucose4. In ...
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  • 2
    ISSN: 1572-8471
    Keywords: teleology ; purpose ; function ; cause-effect ; natural selection ; biology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General
    Notes: Abstract For many years, biology was largely descriptive (“natural history”), but with its emergence as a scientific discipline in its own right, a reductionist approach began, which has failed to be matched by adequate understanding of function of cells, organisms and species as whole entities. Every effort was made to “explain” biological phenomena in physico-chemical terms. It is argued that there is and always has been a clear distinction between life sciences and physical sciences, explicit in the use of the word biology. If this distinction is real, it implies that biological phenomena can never be entirely satisfactorily explained in terms of extant physicochemical laws. One notable manifestation of this is that living organisms appear to -- actually do -- behave in purposeful ways, and the inanimate universe does not. While this fundamental difference continues to be suppressed, the “purposiveness” (or teleology) which pervades biology remains anathema to almost all scientists (including most biologists) even to the present day. We argue here that it can, however, become a perfectly tenable position when the Theory of Natural Selection is accepted as the main foundation, the essential tenet, of biology that distinguishes it from the realm of physical sciences. In accepting this position, it remains quite legitimate to expect that in many but not all circumstances, extant physical laws (and presumably others still to be discovered) are in no way breached by biological systems, which cannot be otherwise since all organisms are composed of physical material.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of the history of biology 33 (2000), S. 71-111 
    ISSN: 1573-0387
    Keywords: diffusion theory ; Fick ; 19th century physiology ; mechanistic materialism ; oxygen secretion ; metabolic organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , History
    Notes: Abstract Diffusion theory explains in physical terms how materials move through a medium, e.g. water or a biological fluid. There are strong and widely acknowledged grounds for doubting the applicability of this theory in biology, although it continues to be accepted almost uncritically and taught as a basis of both biology and medicine. Our principal aim is to explore how this situation arose and has been allowed to continue seemingly unchallenged for more than 150 years. The main shortcomings of diffusion theory will be briefly reviewed to show that the entrenchment of this theory in the corpus of biological knowledge needs to be explained, especially as there are equally valid historical grounds for presuming that bulk fluid movement powered by the energy of cell metabolism plays a prominent note in the transport of molecules in the living body. First, the theory's evolution, notably from its origins in connection with the mechanistic materialist philosophy of mid nineteenth century physiology, is discussed. Following this, the entrenchment of the theory in twentieth century biology is analyzed in relation to three situations: the mechanism of oxygen transport between air and mammalian tissues; the structure and function of cell membranes; and the nature of the intermediary metabolism, with its implicit presumptions about the intracellular organization and the movement of molecules within it. In our final section, we consider several historically based alternatives to diffusion theory, all of which have their precursors in nineteenth and twentieth century philosophy of science.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 140 (1980), S. 267-274 
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Uptake of amino acids into the intracellular acid-soluble pool inTetrahymena pyriformis follows similar kinetics to those seen in mammalian cells. However, after an initial faster uptake phase, most amino acids show a more prolonged accumulation in the pool inTetrahymena, this second phase being inhibited by cycloheximide. Incorporation of amino acids into protein occurs with linear kinetics except in the case of glycine where it has an initial exponential phase lasting 3–4 min. These observations are in remarkably close agreement with the uptake of the same amino acids in mammalian cell cultures, including the slow start with glycine. 2. Experiments with the phenylalanine analogue,p-fluorophenylalanine, show that the acid-soluble pood inTetrahymena cannot be the obligate precursor supply for protein synthesis. Analysis of the fate of an existing acid-soluble pool confirms that it is not ‘discharged’ into protein in pulse-chase experiments. 3. These results, in conjunction with similar studies on other organisms reported in the literature, suggest that amino acid handling mechanisms could be similar in eukaryotic cells. The significance of the acid-soluble pool inTetrahymena, as in mammalian cells, is explicable in terms of the intracellular cyclic perfusion model of Wheatley and Inglis (1980).
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  • 5
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Heat-synchronized Tetrahymena pyriformis have been subjected to 5-, 15- and 30-minute pulses of hydrostatic pressure in the range 100-300 atm, without being simultaneously subjected to significant heats of compression. The pressure-induced division delays depend on (1) the level of pressure used, (2) the length of pressure pulse and (3) the time after the synchronizing treatment at which the pressure is applied. A pressure-dependent inhibition of 3H-leucine incorporation into protein was also measured. Comparison of the effects of pressure with those of pulse treatments of cycloheximide and emetine on cell division and protein synthesis revealed that the physical agent produced characteristically different responses from those of the chemical agents. Of particular interest was the fact that the division delays induced by pressures of 200 atm and above were greater than those observed after treatments with cycloheximide and emetine which produced comparable levels of protein synthesis inhibition. Pressure also delayed cells if it was applied at a time when addition of chemical inhibitors had little effect on the first synchronous division. The results show that inhibition of protein synthesis by pressure cannot entirely account for pressure-induced effects on cell division. The possibility that pressure may also directly affect other processes, such as the assembly of proteins into structures required for division, is discussed.
    Additional Material: 10 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 101 (1979), S. 399-405 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cultures of heat-synchronized Tetrahymena pyriformis, growing in a proteose peptone medium, were subjected to short pulses of the amino acid analogue, p-flurophenylalanine, and high hydrostatic pressure. The pulses of these agents were chosen so that, when applied individually, they did not appreciably delay cell division. However, combined treatments, analogue pulse followed by pressure pulse, produced a pronounced synergism. The results are interpreted as further evidence to support the inclusion of analogue division proteins in pressure labile assemblies during the progression of Tetrahymena into division.
    Additional Material: 3 Ill.
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  • 7
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The plasma membrane of erythrocytes, as of other cells, is thought to act as the barrier responsible for maintaining intracellular gradients of most ions and small molecular species between the cell and its environment. Controlled application of the nonionic detergent Brij 58 effectively opened the erythrocyte plasma membrane, as judged by electron microscopy and lipid mobilization, but the cytoplasm maintained much of its integrity for about 30 min. Release of K+ correlated well with release of protein into the surrounding medium. The results demonstrate that permeabilization of the erythrocyte plasma membrane does not result in an instantaneous equilibration of small ions, such as K+, between the cell and its environment. A comparison was made between erythrocytes treated with Brij 58 and Triton X-100. The lipid and protein solubilizing actions of Triton X-100 were not as easily separable in time as those of Brij 58. The results of treatment of the erythrocytes with different types of nonionic detergents suggest that the membranolytic and cytoplasmic protein destabilizing actions of nonionic detergents correspond with their hydrophilic-lipophilic balance numbers (HLB values). © 1994 wiley-Liss, Inc.
    Additional Material: 6 Ill.
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  • 8
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Tetrahymena has been used as a model cell system in many studies of morphogenesis, conjugation, gene mapping, cell division and growth kinetics. In this article, we consider some advances which have resulted from the successful development of a chemically defined medium (CDM), and how subsequent work has extended the contribution that this organism has made to our understanding of different aspects of growth, nutrition, cell cycle control, cytokinesis and intercellular signalling. Finally, we discuss the considerable potential that has arisen for the biotechnological exploitation of this big and rapidly growing eukaryotic cell.
    Additional Material: 4 Ill.
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  • 9
  • 10
    Publication Date: 1982-09-01
    Print ISSN: 0022-5193
    Electronic ISSN: 1095-8541
    Topics: Biology
    Published by Elsevier
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