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  • 1
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A system composed of two coupled internal oscillators and an external oscillation is studied as a model of biological control systems. The type of interaction between the internal oscillators is a mutual and dissipative one. Three macroscopic states of the internal oscillators are demonstrated in the absence of the external oscillation. Strict and loose entrainment regions of the internal oscillators by the external oscillation are shown in respect to the intensity of the mutual interaction, the intrinsic frequency difference of the internal oscillations, and the magnitude and frequency of the external oscillation. On the other hand, an idea of “holonic system” is introduced and the fundamental properties of the model as a holonic system are elucidated.
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  • 2
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Insects generate walking patterns which depend upon external conditions. For example, when an insect is exposed to an additional load parallel to the direction in which it is walking, the walking pattern changes according to the magnitude of the load. Furthermore, even after some of its legs have been amputated, an insect will produce walking patterns with its remaining legs. These adaptations in insect walking could not previously be explained by a mathematical model, since the mathematical models were based upon the hypothesis that the relationship between walking velocity and walking patterns is fixed under all conditions. We have produced a mathematical model which describes self-organizing insect walking patterns in real-time by using feedback information regarding muscle load (Kimura et al. 1993). As part of this model, we introduced a new rule to coordinate leg movement, in which the information is circulated to optimize the efficiency of the energy transduction of each effector organ. We describe this mechanism as ‘the least dissatisfaction for the greatest number of elements’. In this paper, we introduce the following aspects of this model, which reflect adaptability to changing circumstances: (1) after one leg is exposed to a transient perturbation, the walking pattern recovers swiftly; (2) when the external load parallel to the walking direction is continuously increased or decreased, the pattern transition point is shifted according to the magnitude of the load increment or decrement. This model generates a walking pattern which optimizes energy consumption at a given walking velocity even under these conditions; and (3) when some of the legs are amputated, the model generates walking patterns which are consistent with experimental results. We also discuss the ability of a hierarchical self-organizing model to describe a swift and flexible information processing system.
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  • 3
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. We propose a new model for speaker-independent vowel recognition which uses the flexibility of the dynamic linking that results from the synchronization of oscillating neural units. The system consists of an input layer and three neural layers, which are referred to as the A-, B- and C-centers. The input signals are a time series of linear prediction (LPC) spectrum envelopes of auditory signals. At each time-window within the series, the A-center receives input signals and extracts local peaks of the spectrum envelope, i.e., formants, and encodes them into local groups of independent oscillations. Speaker-independent vowel characteristics are embedded as a connection matrix in the B-center according to statistical data of Japanese vowels. The associative interaction in the B-center and reciprocal interaction between the A- and B-centers selectively activate a vowel as a global synchronized pattern over two centers. The C-center evaluates the synchronized activities among the three formant regions to give the selective output of the category among the five Japanese vowels. Thus, a flexible ability of dynamical linking among features is achieved over the three centers. The capability in the present system was investigated for speaker-independent recognition of Japanese vowels. The system demonstrated a remarkable ability for the recognition of vowels very similar to that of human listeners, including misleading vowels. In addition, it showed stable recognition for unsteady input signals and robustness against background noise. The optimum condition of the frequency of oscillation is discussed in comparison with stimulus-dependent synchronizations observed in neurophysiological experiments of the cortex.
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  • 4
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. To elucidate the mechanism of the self-organizing control of heartbeats, models that include the electrical and mechanical processes of heartbeat are proposed. As the mutual interaction between the two processes, mechano-electrical feedback (MEF), mediated by stretch-activated ionic channels, is considered. Analyses of the models show that coordination of beats among myocardial cells is established by MEF even in the absence of electrical coupling. The coordination of heartbeats is found to show in-phase synchronization under normal conditions, while it is out of phase or irregular under mechanically abnormal conditions. It is concluded that coupling by MEF is important for the self-organization of heartbeats.
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  • 5
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Recent technical advances in immunoelectron microscopy (IEM), including methods of pre- and postembedding IEM and cryoultramicrotomy, have helped to elucidate the precise ultrastructural localization of various basement membrane-related molecules. Our objective was to evaluate the advantages and disadvantages of several different techniques for studying the ultrastructural organization of basement membrane components. We found that, while ”on-surface” immunolabeling of postembedding IEM and cryoultramicrotomy with anti-type IV collagen or anti-laminin-5 antibody clearly demonstrated dense labeling on the lamina densa, preembedding IEM with a 1-nm ultra-small gold probe showed labeling only on the epidermal and/or dermal surfaces of the lamina densa, with no specific gold particles being seen within the lamina densa itself. These results indicate that even ultra-small colloidal gold-labeled antibody fails to penetrate the lamina densa in preembedding IEM. However, labeling with a GB3 monoclonal antibody against laminin-5 was demonstrable with preembedding IEM and cryoultramicrotomy, but not with post-embedding IEM, probably due to a loss of antigenicity. These results confirm the advantages and limitations of these techniques of IEM and emphasize the importance of using different techniques of IEM in determining the precise ultrastructural distribution of basement membrane antigens.
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  • 6
    ISSN: 1432-069X
    Keywords: Key words Keratin ; Epidermolysis bullosa simplex ; Cornified cell envelope
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Basal keratins, suprabasal keratins, filaggrin, and cornified cell envelope (CCE) precursor proteins are expressed during the differentiation of epidermal keratinocytes. These molecules are coordinately expressed during epidermal differentiation. The present study investigated the expression patterns of keratins and CCE precursor proteins in 15 patients with epidermolysis bullosa simplex (EBS), which is caused by mutations in the genes that encode for the basal keratins, keratins 5 and 14. The patterns of expression of keratins 5, 14, 1 and 10, filaggrin, and of the three major CCE precursor proteins, involucrin, loricrin and small proline-rich proteins 1 and 2 (SPRs), were studied immunohistochemically and by electron microscopy. In 14 of the 15 patients with EBS, the distribution pattern of keratins was not altered. In one neonate with EBS, basal cell keratins were expressed in the suprabasal layers. Ultrastructurally, numerous clumped tonofilaments were observed in the basal and suprabasal cells. In all cases, findings were positive for filaggrin in the granular cells, with positivity for involucrin in the upper spinous and granular cells. The upper spinous cells and granular cells were positive for SPRs 1 and 2, and loricrin was expressed in granular cells. Ultrastructurally, no marked abnormality was observed in the suprabasal layers such as a decrease in, or agglutination of, keratin filaments, except in one neonate. A CCE about 15 nm thick was formed normally in the cell membrane of cornified cells. The patterns of distributions of basal cell keratins, suprabasal keratins, filaggrin, and CCE precursor proteins, as well as the ultrastructural findings, resembled those of normal skin. Thus, the abnormality in basal cell keratins in patients with EBS did not appear to alter the patterns of expression of the keratins and CCE precursor proteins.
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  • 7
    ISSN: 1432-069X
    Keywords: Key words Harlequin fetus ; Cornified cell envelope ; Transglutaminase ; Collodin baby ; Lamellar ichthyosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 8
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The aim of this paper is to apply a computer control scheme to a laboratory scale fermentor so that the specific growth rate in a baker's yeast fed-batch culture, which cannot be measured directly, will follow as accurately as possible the desired profile specified in advance. Using an extended Kalman filter and programmed controller/feedback compensator (PF) system proposed previously, profile control of the specific growth rate (μ) was achieved experimentally in a baker's yeast fed-batch culture. Also, bang-bang type profile control of μ minimized the proportion of budding cells, which have a strong correlation with the fermentative activity in bread-making.
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  • 9
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The constituent amino acids of the glutathione (GSH) tripeptide chain, glutamate, cysteine and glycine, were investigated for positive effects on GSH production in shake-flask cultures of Saccharomyces cerevisiae with glucose as the carbon source. Cysteine was confirmed as the key amino acid for increasing the specific GSH production rate, ϱg, but showed some growth inhibition, especially in the second growth phase (ethanol-assimilation phase). An intracellular cysteine delivery agent, thiazolidine, showed a similar pattern of increased GSH production and growth inhibition, but to a slightly lesser degree, compared with free cysteine. The initial cysteine concentration affected both the specific growth rate, µ, and ϱg, up to about 5 mm for µ and about 2–3 mm for ϱg. Results of the [35S]cysteine-labelling experiments suggest a complicated role of cysteine in increasing GSH production and further investigation may be necessary.
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  • 10
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A good cysteine addition method that could increase the specific glutathione (GSH) production rate (G9G) was investigated and utilized to maximize total GSH production in fed-batch culture of Saccharomyces cerevisiae. The single-shot addition of cysteine was a better method compared to a continuous method that maintained a constant cysteine concentration in the reactor. The shot method increased ϱG about twofold compared to a culture without cysteine. The increase in ϱG by the shot method can be achieved without growth inhibition if the cysteine dose is maintained at 0.7 mml·g-1 cell or less. The positive effect on ϱG (at every specific growth rate, µ) was saturated when the cysteine shot concentrations was 3 mM or more. A simple model was developed consisting of mass balance equations and the relationship between µ and ϱG, for the single cysteine shot addition method. From this model an optimal operating strategy was determined to maximize total GSH production in fed-batch culture. This optimal operation consisted of separating the process into phases of (1) cell growth and (2) GSH production, through a bang-bang profile control of µ, and a shot of cysteine just at the start of the GSH production phase. In other words, the cysteine shot time and the µ switching time should be the same. For a total feeding time of 10 h, both the switching time of µ and cysteine shot time were calculated to be about 6.4 h.
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