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  • Articles  (120)
  • stability  (61)
  • gene expression  (59)
  • Springer  (120)
  • 2005-2009
  • 1995-1999  (120)
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  • 1999  (120)
  • 1
    Electronic Resource
    Electronic Resource
    On the stability of wavelet and Gabor frames (Riesz bases) (1999)
    Springer
    The journal of Fourier analysis and applications 5 (1999), S. 105-125 
    Details
    ISSN: 1531-5851
    Keywords: 26B05 ; 42B10 ; 42C99 ; frame ; Gabor system ; Riesz basis ; stability ; wavelet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract If the sequence of functions ϕj, k is a wavelet frame (Riesz basis) or Gabor frame (Riesz basis), we obtain its perturbation system ψj,k which is still a frame (Riesz basis) under very mild conditions. For example, we do not need to know that the support of ϕ or ψ $$(\hat \phi or\hat \psi )$$ is compact as in [14]. We also discuss the stability of irregular sampling problems. In order to arrive at some of our results, we set up a general multivariate version of Littlewood-Paley type inequality which was originally considered by Lemarié and Meyer [17], then by Chui and Shi [9], and Long [16].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01274192
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  • 2
    Electronic Resource
    Electronic Resource
    A stability criterion via fluid limits and its application to a polling system (1999)
    Springer
    Queueing systems 32 (1999), S. 131-168 
    Details
    ISSN: 1572-9443
    Keywords: stability ; positive recurrence ; fluid limit ; polling system ; exhaustive service policy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We introduce a generalized criterion for the stability of Markovian queueing systems in terms of stochastic fluid limits. We consider an example in which this criterion may be applied: a polling system with two stations and two heterogeneous servers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019187004209
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  • 3
    Electronic Resource
    Electronic Resource
    Stability of relative equilibria in arbitrary axisymmetric gravitational and magnetic fields (1999)
    Springer
    Celestial mechanics and dynamical astronomy 74 (1999), S. 19-57 
    Details
    ISSN: 1572-9478
    Keywords: stability ; Hamiltonian ; two centers ; oblate planet ; galactic disks ; dipole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Relative equilibria occur in a wide variety of physical applications, including celestial mechanics, particle accelerators, plasma physics, and atomic physics. We derive sufficient conditions for Lyapunov stability of circular orbits in arbitrary axisymmetric gravitational (electrostatic) and magnetic fields, including the effects of local mass (charge) and current density. Particularly simple stability conditions are derived for source‐free regions, where the gravitational field is harmonic (∇2U = 0) or the magnetic field irrotational (∇ × B = 0). In either case the resulting stability conditions can be expressed geometrically (coordinate‐free) in terms of dimensionless stability indices. Stability bounds are calculated for several examples, including the problem of two fixed centers, the J2 planetary model, galactic disks, and a toroidal quadrupole magnetic field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008388105585
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  • 4
    Electronic Resource
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    Unrestricted Planar Problem of a Symmetric Body and a Point Mass. Triangular Libration Points and Their Stability (1999)
    Springer
    Celestial mechanics and dynamical astronomy 75 (1999), S. 251-285 
    Details
    ISSN: 1572-9478
    Keywords: unrestricted problem ; rotational motion ; rigid body dynamics ; libration points ; stability ; resonances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present an analysis of the model introduced by Kokoriev and Kirpichnikov (1988) for the study of unrestricted planar motion of a point mass and a symmetric rigid body whose gravity field is approximated by two point masses (a dumb-bell model). To show possible generalization of the model, we give a systematic derivation of equations of motion for a more general unrestricted problem of a point and a rigid body possessing a plane of dynamical symmetry. We give a simple description of bifurcation of triangular libration points, and we perform an analysis of their linear stability. We propose to extend the model of Kokoriev and Kirpichnikov (1988) to a case when the symmetric body is oblate. In the proposed model the gravity field of moving and rotating body is approximated by two complex masses at complex distance (a complex dumb-bell model). An analysis of bifurcation of the triangular libration points in this model is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008337017789
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  • 5
    Electronic Resource
    Electronic Resource
    The Stability of Self-Organized Rule-Following Work Teams (1999)
    Springer
    Computational & mathematical organization theory 5 (1999), S. 5-30 
    Details
    ISSN: 1572-9346
    Keywords: network models ; organization theory ; rule following ; self organized ; stability ; work teams ; work routine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Self-organized rule-following systems are increasingly relevant objects of study in organization theory due to such systems&2018; capacity to maintain control while enabling decentralization of authority. This paper proposes a network model for such systems and examines the stability of the networks&2018; repetitive behavior. The networks examined are Ashby nets, a fundamental class of binary systems: connected aggregates of nodes that individually compute an interaction rule, a binary function of their three inputs. The nodes, which we interpret as workers in a work team, have two network inputs and one self-input. All workers in a given team follow the same interaction rule. We operationalize the notion of stability of the team&2018;s work routine and determine stability under small perturbations for all possible rules these teams can follow. To study the organizational concomitants of stability, we characterize the rules by their memory, fluency, homogeneity, and autonomy. We relate these measures to work routine stability, and find that stability in ten member teams is enhanced by rules that have low memory, high homogeneity, and low autonomy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009689326098
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  • 6
    Electronic Resource
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    Stability of a three‐station fluid network (1999)
    Springer
    Queueing systems 33 (1999), S. 293-325 
    Details
    ISSN: 1572-9443
    Keywords: stability ; fluid models ; multiclass queueing networks ; piecewise linear Lyapunov functions ; linear Lyapunov functions ; monotone global stability ; static buffer priority disciplines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper studies the stability of a three‐station fluid network. We show that, unlike the two‐station networks in Dai and Vande Vate [18], the global stability region of our three‐station network is not the intersection of its stability regions under static buffer priority disciplines. Thus, the “worst” or extremal disciplines are not static buffer priority disciplines. We also prove that the global stability region of our three‐station network is not monotone in the service times and so, we may move a service time vector out of the global stability region by reducing the service time for a class. We introduce the monotone global stability region and show that a linear program (LP) related to a piecewise linear Lyapunov function characterizes this largest monotone subset of the global stability region for our three‐station network. We also show that the LP proposed by Bertsimas et al. [1] does not characterize either the global stability region or even the monotone global stability region of our three‐station network. Further, we demonstrate that the LP related to the linear Lyapunov function proposed by Chen and Zhang [11] does not characterize the stability region of our three‐station network under a static buffer priority discipline.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019184331042
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  • 7
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    Electronic Resource
    Implicit Multifunction Theorems (1999)
    Springer
    Set-valued analysis 7 (1999), S. 209-238 
    Details
    ISSN: 1572-932X
    Keywords: nonsmooth analysis ; subdifferentials ; coderivatives ; implicit function theorem ; solvability ; stability ; open mapping theorem ; metric regularity ; multidirectional mean value inequality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We prove a general implicit function theorem for multifunctions with a metric estimate on the implicit multifunction and a characterization of its coderivative. Traditional open covering theorems, stability results, and sufficient conditions for a multifunction to be metrically regular or pseudo-Lipschitzian can be deduced from this implicit function theorem. We prove this implicit multifunction theorem by reducing it to an implicit function/solvability theorem for functions. This approach can also be used to prove the Robinson–Ursescu open mapping theorem. As a tool for this alternative proof of the Robinson–Ursescu theorem, we also establish a refined version of the multidirectional mean value inequality which is of independent interest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008775413250
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  • 8
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    Dynamic scheduling in multiclass queueing networks: Stability under discrete-review policies (1999)
    Springer
    Queueing systems 31 (1999), S. 171-206 
    Details
    ISSN: 1572-9443
    Keywords: scheduling ; open multiclass queueing networks ; discrete-review policies ; fluid models ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper describes a family of discrete-review policies for scheduling open multiclass queueing networks. Each of the policies in the family is derived from what we call a dynamic reward function: such a function associates with each queue length vector q and each job class k a positive value r k (q), which is treated as a reward rate for time devoted to processing class k jobs. Assuming that each station has a traffic intensity parameter less than one, all policies in the family considered are shown to be stable. In such a policy, system status is reviewed at discrete points in time, and at each such point the controller formulates a processing plan for the next review period, based on the queue length vector observed. Stability is proved by combining elementary large deviations theory with an analysis of an associated fluid control problem. These results are extended to systems with class dependent setup times as well as systems with alternate routing and admission control capabilities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019106213778
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  • 9
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    Recurrence and transience properties of some neural networks: an approach via fluid limit models (1999)
    Springer
    Queueing systems 32 (1999), S. 99-130 
    Details
    ISSN: 1572-9443
    Keywords: neural network ; inhibition ; stability ; Markov process ; fluid limit ; Harris-recurrence ; transience
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The subject of the paper is the stability analysis of some neural networks consisting of a finite number of interacting neurons. Following the approach of Dai [5] we use the fluid limit model of the network to derive a sufficient condition for positive Harris-recurrence of the associated Markov process. This improves the main result in Karpelevich et al. [11] and, at the same time, sheds some new light on it. We further derive two different conditions that are sufficient for transience of the state process and illustrate our results by classifying some examples according to positive recurrence or transience.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019135020138
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  • 10
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    Window flow control in FIFO networks with cross traffic (1999)
    Springer
    Queueing systems 32 (1999), S. 195-231 
    Details
    ISSN: 1572-9443
    Keywords: window flow control ; TCP ; stability ; multiclass networks ; stationary ergodic point processes ; (max,+)-linear system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We focus on window flow control as used in packet-switched communication networks. The approach consists in studying the stability of a system where each node on the path followed by the packets of the controlled connection is modeled by a FIFO (First-In-First-Out) queue of infinite capacity which receives in addition some cross traffic represented by an exogenous flow. Under general stochastic assumptions, namely for stationary and ergodic input processes, we show the existence of a maximum throughput allowed by the flow control. Then we establish bounds on the value of this maximum throughput. These bounds, which do not coincide in general, are reached by time-space scalings of the exogenous flows. Therefore, the performance of the window flow control depends not only on the traffic intensity of the cross flows, but also on fine statistical characteristics such as the burstiness of these flows. These results are illustrated by several examples, including the case of a nonmonotone, nonconvex and fractal stability region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019191105117
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  • 11
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    Numerical computation of stability and detection of Hopf bifurcations of steady state solutions of delay differential equations (1999)
    Springer
    Advances in computational mathematics 10 (1999), S. 271-289 
    Details
    ISSN: 1572-9044
    Keywords: delay differential equations ; steady state solutions ; stability ; 34K20 ; 65J10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The characteristic equation of a system of delay differential equations (DDEs) is a nonlinear equation with infinitely many zeros. The stability of a steady state solution of such a DDE system is determined by the number of zeros of this equation with positive real part. We present a numerical algorithm to compute the rightmost, i.e., stability determining, zeros of the characteristic equation. The algorithm is based on the application of subspace iteration on the time integration operator of the system or its variational equations. The computed zeros provide insight into the system’s behaviour, can be used for robust bifurcation detection and for efficient indirect calculation of bifurcation points.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018986817622
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  • 12
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    A New Approach to Backward Error Analysis of Lu Factorization (1999)
    Springer
    BIT 39 (1999), S. 385-402 
    Details
    ISSN: 1572-9125
    Keywords: Gaussian elimination ; stability ; backward error analysis ; growth factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A new backward error analysis of LU factorization is presented. It allows to obtain a sharper upper bound for the forward error and a new definition of the growth factor that we compare with the well known Wilkinson growth factor for some classes of matrices. Numerical experiments show that the new growth factor is often of order approximately log2 n whereas Wilkinson's growth factor is of order n or $$\sqrt n$$ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022358300517
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  • 13
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    Runge–Kutta–Nyström‐type parallel block predictor–corrector methods (1999)
    Springer
    Advances in computational mathematics 10 (1999), S. 115-133 
    Details
    ISSN: 1572-9044
    Keywords: Runge–Kutta–Nyström methods ; predictor–corrector methods ; stability ; parallelism ; 65M12 ; 65M20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper describes the construction of block predictor–corrector methods based on Runge–Kutta–Nyström correctors. Our approach is to apply the predictor–corrector method not only with stepsize h, but, in addition (and simultaneously) with stepsizes a i h, i = 1 ...,r. In this way, at each step, a whole block of approximations to the exact solution at off‐step points is computed. In the next step, these approximations are used to obtain a high‐order predictor formula using Lagrange or Hermite interpolation. Since the block approximations at the off‐step points can be computed in parallel, the sequential costs of these block predictor–corrector methods are comparable with those of a conventional predictor–corrector method. Furthermore, by using Runge–Kutta–Nyström corrector methods, the computation of the approximation at each off‐step point is also highly parallel. Numerical comparisons on a shared memory computer show the efficiency of the methods for problems with expensive function evaluations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018930732643
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  • 14
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    Exponential Integrators for Quantum-Classical Molecular Dynamics (1999)
    Springer
    BIT 39 (1999), S. 620-645 
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    ISSN: 1572-9125
    Keywords: Numerical integrator ; oscillatory solutions ; Schrödinger equation ; quantum-classical coupling ; error bounds ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We study time integration methods for equations of mixed quantum-classical molecular dynamics in which Newtonian equations of motion and Schrödinger equations are nonlinearly coupled. Such systems exhibit different time scales in the classical and the quantum evolution, and the solutions are typically highly oscillatory. The numerical methods use the exponential of the quantum Hamiltonian whose product with a state vector is approximated using Lanczos' method. This allows time steps that are much larger than the inverse of the highest frequencies. We describe various integration schemes and analyze their error behaviour, without assuming smoothness of the solution. As preparation and as a problem of independent interest, we study also integration methods for Schrödinger equations with time-dependent Hamiltonian.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022335122807
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  • 15
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    Three Dimensional Laser Simulation Code on a Desktop Personal Computer (1999)
    Springer
    Optical review 6 (1999), S. 28-36 
    Details
    ISSN: 1349-9432
    Keywords: optical propagation equation ; stability ; picosecond pulse ; 3-dimensional computation ; Fresnel’s distribution ; fast Fourier transform
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present a new simulation code able to simulate the entire propagation of laser pulse, from the amplifiers level up to the focusing stage. This algorithm has some new characteristics that we intend to present. It computes the three-dimensional optical propagation equation using no approximation other than its picosecond expression. The stability has been carefully studied so that it can be applied to any geometry. This is a great improvement since, up to now only cylindrical geometry was accessible for accuracy. In this paper we also present a method using Fast Fourier Transform able to evaluate with a high accuracy, Fresnel’s distribution of a focused laser pulse. The advantages provided by our algorithm are its rapidity and its high physical understanding of the focusing phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10043-999-0028-1
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  • 16
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    Global dynamical behavior of a three-body system with flexible connection in the gravitational field (1999)
    Springer
    Archive of applied mechanics 69 (1999), S. 47-54 
    Details
    ISSN: 1432-0681
    Keywords: Key words Bifurcation ; stability ; multibody system dynamics ; singularity theory ; Liapunov's direct method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary In this paper, the global behavior of relative equilibrium states of a three-body satellite with flexible connection under the action of the gravitational torque is studied. With geometric method, the conditions of existence of nontrivial solutions to the relative equilibrium equations are determined. By using reduction method and singularity theory, the conditions of occurrence of bifurcation from trivial solutions are derived, which agree with the existence conditions of nontrivial solutions, and the bifurcation is proved to be pitchfork-bifurcation. The Liapunov stability of each equilibrium state is considered, and a stability diagram in terms of system parameters is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004190050203
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  • 17
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    Isolation of RNA and Protein from Guard Cells of Nicotiana glauca (1999)
    Springer
    Plant molecular biology reporter 17 (1999), S. 371-383 
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    ISSN: 1572-9818
    Keywords: epidermal peel ; extraction ; gene expression ; stomata ; tree tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Stomatal guard cells are critical for maintenance of plant homeostasis and represent an interesting cell type for studies of leaf cell differentiation and patterning. Here we describe techniques for the isolation of guard cell RNA and protein from blended epidermal peels of Nicotiana glauca. The RNA isolation procedure is a modification of the hot borate method, which is particularly well-suited for recalcitrant tissues. Protein was extracted by disrupting guard cell-enriched epidermis with a French® press. This system offers the following advantages: relatively high yield, low or no contamination by other cell types, fresh tissue as a source of RNA and protein rather than protoplasts, and a plant species that is readily transformable. These techniques will allow for cloning and analysis of genes expressed in guard cells, application of traditional biochemical techniques to guard cell proteins, as well as characterization of genetic manipulation of guard cell function in transgenic plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007602017492
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  • 18
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    Sensitivity and Stability of the Classifications of Returns to Scale in Data Envelopment Analysis (1999)
    Springer
    Journal of productivity analysis 12 (1999), S. 55-75 
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    ISSN: 1573-0441
    Keywords: Data envelopment analysis (DEA) ; returns to scale (RTS) ; sensitivity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract Sensitivity of the returns to scale (RTS) classifications in data envelopment analysis is studied by means of linear programming problems. The stability region for an observation preserving its current RTS classification (constant, increasing or decreasing returns to scale) can be easily investigated by the optimal values to a set of particular DEA-type formulations. Necessary and sufficient conditions are determined for preserving the RTS classifications when input or output data perturbations are non-proportional. It is shown that the sensitivity analysis method under proportional data perturbations can also be used to estimate the RTS classifications and discover the identical RTS regions yielded by the input-based and the output-based DEA methods. Thus, our approach provides information on both the RTS classifications and the stability of the classifications. This sensitivity analysis method can easily be applied via existing DEA codes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007803207538
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  • 19
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    Can the ecosystem mimic hypotheses be applied to farms in African savannahs? (1999)
    Springer
    Agroforestry systems 45 (1999), S. 131-158 
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    ISSN: 1572-9680
    Keywords: competition ; fertility ; microclimate ; risk ; stability ; water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The first ecosystem mimic hypothesis suggests clear advantages if man-made land use systems do not deviate greatly in their resource use patterns from natural ecosystems typical of a given climatic zone. The second hypothesis claims that additional advantages will accrue if agroecosystems also maintain a substantial part of the diversity of natural systems. We test these hypotheses for the savannah zone of sub-Saharan Africa, with its low soil fertility and variable rainfall. Where annual food crops replace the natural grass understorey of savannah systems, water use will decrease and stream and groundwater flow change, unless tree density increases relative to the natural situation. Increasing tree density, however, will decrease crop yields, unless the trees meet specific criteria. Food crop production in the parkland systems may benefit from lower temperatures under tree canopies, but water use by trees providing this shade will prevent crops from benefiting. In old parkland trees that farmers have traditionally retained when opening fields for crops, water use per unit shade is less than in most fast growing trees introduced for agroforestry trials. Strong competition between plants adapted to years with different rainfall patterns may stabilise total system productivity -- but this will be appreciated by a farmer only if the components are of comparable value. The best precondition for farmers to maintain diversity in their agroecosystem hinges on the availability of a broad basket of choices, without clear winners or 'best bets'.
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    URL: http://dx.doi.org/10.1023/A:1006245605705
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  • 20
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    Classical Lattice-Gas Models of Quasicrystals (1999)
    Springer
    Journal of statistical physics 95 (1999), S. 835-850 
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    ISSN: 1572-9613
    Keywords: quasicrystals ; nonperiodic tilings ; classical lattice-gas models ; nonperiodic ground states ; nonperiodic Gibbs states ; stability ; frustration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract One of the fundamental problems of quasicrystals is to understand their occurrence in microscopic models of interacting particles. We review here recent attempts to construct stable quasicrystalline phases. In particular, we compare two recently constructed classical lattice-gas models with translation-invariant interactions and without periodic ground-state configurations. The models are based on nonperiodic tilings of the plane by square-like tiles. In the first model, all interactions can be minimized simultaneously. The second model is frustrated; its nonperiodic ground state can arise only by the minimization of the energy of competing interactions. We put forward some hypotheses concerning stabilities of nonperiodic ground states. In particular, we introduce two criteria, the so-called strict boundary conditions, and prove their equivalence to the zero-temperature stability of ground states against small perturbations of potentials of interacting particles. We discuss the relevance of these conditions for the low-temperature stability, i.e., for the existence of thermodynamically stable nonperiodic equilibrium states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004542115011
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  • 21
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    Non-Self-Similar Behavior in the LSW Theory of Ostwald Ripening (1999)
    Springer
    Journal of statistical physics 95 (1999), S. 867-902 
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    ISSN: 1572-9613
    Keywords: kinetics of phase transitions ; domain coarsening ; asymptotic behavior ; self-similarity ; stability ; chaos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The classical Lifshitz–Slyozov–Wagner theory of domain coarsening predicts asymptotically self-similar behavior for the size distribution of a dilute system of particles that evolve by diffusional mass transfer with a common mean field. Here we consider the long-time behavior of measure-valued solutions for systems in which particle size is uniformly bounded, i.e., for initial measures of compact support. We prove that the long-time behavior of the size distribution depends sensitively on the initial distribution of the largest particles in the system. Convergence to the classically predicted smooth similarity solution is impossible if the initial distribution function is comparable to any finite power of distance to the end of the support. We give a necessary criterion for convergence to other self-similar solutions, and conditional stability theorems for some such solutions. For a dense set of initial data, convergence to any self-similar solution is impossible.
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    URL: http://dx.doi.org/10.1023/A:1004546215920
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  • 22
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    Stable Neuro-Adaptive Control for Robots with the Upper Bound Estimation on the Neural Approximation Errors (1999)
    Springer
    Journal of intelligent and robotic systems 26 (1999), S. 91-100 
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    ISSN: 1573-0409
    Keywords: robots ; neural networks ; adaptiveness ; stability ; approximation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An indirect adaptive control approach is developed in this paper for robots with unknown nonlinear dynamics using neural networks (NNs). A key property of the proposed approach is that the actual joint angle values in the control law are replaced by the desired joint angles, angle velocities and accelerators, and the bound on the NN reconstruction errors is assumed to be unknown. Main theoretical results for designing such a neuro-controller are given, and the control performance of the proposed controller is verified with simulation studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008195720685
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  • 23
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    Emergence of symmetric, modular, and reciprocal connections in recurrent networks with Hebbian learning (1999)
    Springer
    Biological cybernetics 81 (1999), S. 211-225 
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    ISSN: 1432-0770
    Keywords: Key words: Hebbian learning rule ; attractor dynamics ; symmetric connections ; multiplicative normalization ; self-organization ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. While learning and development are well characterized in feedforward networks, these features are more difficult to analyze in recurrent networks due to the increased complexity of dual dynamics – the rapid dynamics arising from activation states and the slow dynamics arising from learning or developmental plasticity. We present analytical and numerical results that consider dual dynamics in a recurrent network undergoing Hebbian learning with either constant weight decay or weight normalization. Starting from initially random connections, the recurrent network develops symmetric or near-symmetric connections through Hebbian learning. Reciprocity and modularity arise naturally through correlations in the activation states. Additionally, weight normalization may be better than constant weight decay for the development of multiple attractor states that allow a diverse representation of the inputs. These results suggest a natural mechanism by which synaptic plasticity in recurrent networks such as cortical and brainstem premotor circuits could enhance neural computation and the generation of motor programs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004220050557
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    Shear band spacing in gradient-dependent thermoviscoplastic materials (1999)
    Springer
    Computational mechanics 23 (1999), S. 8-19 
    Details
    ISSN: 1432-0924
    Keywords: Keywords: Material characteristic length ; strain-rate gradient ; dominant growth rate ; viscoplastic material ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We study thermomechanical deformations of a viscoplastic body deformed in simple shear. The strain gradients are taken as independent kinematic variables and the corresponding higher order stresses are included in the balance laws, and the equation for the yield surface. Three different functional relationships, the power law, and those proposed by Wright and Batra, and Johnson and Cook are used to relate the effective strain rate to the effective stress and temperature. Effects of strain hardening of the material and elastic deformations are neglected. The homogeneous solution of the problem is perturbed and the stability of the problem linear in the perturbation variables is studied. Following Wright and Ockendon's postulate that the wavelength whose initial growth rate is maximum determines the minimum spacing between adjacent shear bands, the shear band spacing is computed. It is found that the minimum shear band spacing is very sensitive to the thermal softening coefficient/exponent, the material characteristic length and the nominal strain-rate. Approximate analytical expressions for the critical wave length for heat conducting nonpolar materials and locally adiabatic deformations of gradient dependent materials are also derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004660050381
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    Thermal Analysis, Microcalorimetry and Combined Techniques for the Study of Pharmaceuticals (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 1285-1304 
    Details
    ISSN: 1572-8943
    Keywords: amorphous state ; combined techniques ; drug design ; drug product development ; drug substance ; drug technology ; DSC ; excipients ; failure investigations ; hydrates ; MDSC ; microcalorimetry ; pharmaceuticals ; polymorphism ; polymers ; preformulation ; process optimization ; purity ; quality control ; solvates ; stability ; sub-ambient DSC ; TG ; temperature resolved X-ray diffraction ; water interactions ; thermal microscopy ; water sorption-desorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Modern thermal analysis, microcalorimetry and new emerging combined techniques which deliver calorimetric, microscopic and spectroscopic data offer a powerful analytical battery for the study of pharmaceuticals. These techniques are very useful in all steps of development of new drug products as well as methods for quality control in production. The characterization of raw materials enables to understand the relationships between polymorphs, solvates and hydrates and to choose the proper development of new drug products with very small amount of material in a very short time. Information on stability, purity is valuable for new entities as well as for marketed drug substances from different suppliers. Excipients which vary from single organic or inorganic entity to complexes matrixes or polymers need to be characterized and properly controlled. The thermodynamic phase-diagrams are the basis of the studies of drug-excipients interactions. They are very useful for the development of new delivery systems. A great number of new formulations need proper knowledge of the behaviour of the glass transition temperature of the components. Semi-liquid systems, interactions in aqueous media are also successfully studied by these techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010194020563
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    Ignitability of Polymers Related to Polymer Properties and Different Steady States of Combustion Theoretical Approach (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 727-739 
    Details
    ISSN: 1572-8943
    Keywords: ignition ; polymer combustion modelling ; stability ; steady state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A mathematical model of ignition and burning of organic polymers was used for evaluation and quantification of the tendency of polymers to ignition. The model permits investigation of the influence of one parameter of the polymer on the others. It was found that the model could be used for the verification of the ignitability method developed by Miller et al. [1]. Different steady states of combustion were found when using the model proposed. There is a characteristic steady state for normal flaming combustion, another for non-flaming combustion, and there are also unstable steady states that have no real physical meaning.
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    URL: http://dx.doi.org/10.1023/A:1010157011275
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    Thermodynamics of a 24-Mer Triple Helix Formation and Stability (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 1177-1184 
    Details
    ISSN: 1572-8943
    Keywords: differential scanning calorimetry ; DNA triple helix ; oligonucleotides ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this work we report a thermodynamic characterization of stability and melting behaviour of two 24-mer DNA triplexes. The third strand, that binds the Watson-Crick double helix with Hoogsteen hydrogen bonds, contains 3′-3′ phosphodiester junction that determines the polarity inversion. The target double helix is composed of adjacent and alternate fragments of oligopurine-oligopyrimidine tracts. The two helices differ from the substitution of the cytosine, involved in the junction, with the thymine. Calorimetric data reported here provide a quantitative measure of the influence of pH and base modification on the stability of a DNA triplex.
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    URL: http://dx.doi.org/10.1023/A:1010117431041
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    Increased peroxisomal fatty acid β-oxidation and enhanced expression of peroxisome proliferator-activated receptor-α in diabetic rat liver (1999)
    Springer
    Molecular and cellular biochemistry 194 (1999), S. 227-234 
    Details
    ISSN: 1573-4919
    Keywords: microbodies ; diabetes mellitus ; steroid hormone receptor ; β-oxidation ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract To determine whether the increased fatty acid β-oxidation in the peroxisomes of diabetic rat liver is mediated by a common peroxisome proliferation mechanism, we measured the activation of long-chain (LC) and very long chain (VLC) fatty acids catalyzed by palmitoyl CoA ligase (PAL) and lignoceryl CoA ligase and oxidation of LC (palmitic acid) and VLC (lignoceric acid) fatty acids by isotopic methods. Immunoblot analysis of acyl-CoA oxidase (ACO), and Northern blot analysis of peroxisome proliferator-activated receptor (PPAR-α), ACO, and PAL were also performed. The PAL activity increased in peroxisomes and mitochondria from the liver of diabetic rats by 2.6-fold and 2.1-fold, respectively. The lignoceroyl-CoA ligase activity increased by 2.6-fold in diabetic peroxisomes. Palmitic acid oxidation increased in the diabetic peroxisomes and mitochondria by 2.5-fold and 2.7-fold, respectively, while lignoceric acid oxidation increased by 2.0-fold in the peroxisomes. Immunoreactive ACO protein increased by 2-fold in the diabetic group. The mRNA levels for PPAR-α, ACO and PAL increased 2.9-, 2.8- and 1.6-fold, respectively, in the diabetic group. These results suggest that the increased supply of fatty acids to liver in diabetic state stimulates the expression of PPAR-α and its target genes responsible for the metabolism of fatty acids.
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    URL: http://dx.doi.org/10.1023/A:1006930513476
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    Expression of calcium-binding protein regucalcin mRNA in the cloned rat hepatoma cells (Hr-II-E) is stimulated through Ca2+ signaling factors: Involvement of protein kinase C (1999)
    Springer
    Molecular and cellular biochemistry 198 (1999), S. 101-107 
    Details
    ISSN: 1573-4919
    Keywords: regucalcin ; Ca2+-binding protein ; protein kinase C ; Ca2+signaling ; gene expression ; H4-II-E hepatoma cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The expression of hepatic Ca2+-binding protein regucalcin in the cloned rat hepatoma cells (H4-II-E) was investigated. The change in regucalcin mRNA levels was analyzed by Northern blotting using rat liver regucalcin complementary DNA (0.9 kb of open reading frame). Regucalcin mRNA was expressed in H4-II-E hepatoma cells. This expression was clearly stimulated in the presence of serum (10% fetal bovine serum). Bay K 8644 (2. 5 × 10-6 M), a Ca2+ channel agonist, significantly stimulated regucalcin mRNA expression in the absence or presence of 10% serum. Dibutyryl cyclic AMP (10-3 M) did not have a stimulatory effect on the regucalcin mRNA expression. The presence of phorbol 12-myristate 13-acetate (PMA; 10-6 M) or estrogen (10-8 M) caused a significant increase in regucalcin mRNA levels in the hepatoma cells cultured in serum-free medium, while insulin (5 × 10-9 M) or dexamethasone (10-6 M) had no effect. Bay K 8644-stimulated regucalcin mRNA expression in the hepatoma cells was completely blocked in the presence of trifluoperazine (10-5 M), an antagonist of calmodulin, or staurosporine (10-7 M), an inhibitor of protein kinase C. The stimulatory effect of PMA was clearly inhibited in the presence of stauroporine. The present study demonstrates that regucalcin mRNA is expressed in the transformed H4-II-E hepatoma cells, and that the expression is stimulated through Ca2+-dependent signaling factors.
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    URL: http://dx.doi.org/10.1023/A:1006996506238
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    Posttranscriptional regulation of urokinase receptor gene expression in human lung carcinoma and mesothelioma cells in vitro (1999)
    Springer
    Molecular and cellular biochemistry 199 (1999), S. 189-200 
    Details
    ISSN: 1573-4919
    Keywords: lung ; cancer ; urokinase ; receptor ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The urokinase-type plasminogen activator (uPA) interacts with its receptor (uPAR) to promote proteolysis as well as cell proliferation and migration. These functions contribute to the pathogenesis of neoplastic growth and invasiveness. Expression of uPAR in tumor extracts also inversely correlates with prognosis in many forms of cancer. In this study, we sought to determine if differences in uPAR expression were distinguishable between cultured human lung carcinoma and malignant mesothelioma subtypes. We also sought to determine if, as in malignant mesothelioma cells, uPAR expression is regulated at the posttranscriptional level in cultured malignant lung carcinoma cells. Using 125I-uPA binding and ligand blotting techniques, uPAR was expressed by phenotypically diverse lung carcinoma cell lines, including the H460, H157 and H1395 non-small cell lines and the H146 small cell lung carcinoma line. Increased uPAR expression was also detected in spindle-shaped (M33K) and epithelioid (M9K and MS-1) malignant mesothelioma cells. Selected mediators, including TGF-β, TNF-α, LPS and PMA, uniformly enhanced uPAR expression in each of the tumor cell lines. Steady state uPAR mRNA expression was determined by RNase protection assay and correlated directly with the changes in cell surface uPAR expression. By gel mobility shift and UV-cross linking assays, a uPAR mRNA binding protein (uPAR mRNABp) implicated in the posttranscriptional control of message stability, was identified in each of the cell lines. Expression of uPAR and its message in cultured lung carcinoma and malignant mesothelioma cells is similarly influenced by effectors present in the tumor microenvironment. Regulation of the uPAR message occurs at the posttranscriptional level in cultured small and non-small cell lung carcinoma cells as well as spindle-shaped and fibrous malignant mesothelioma cell lines. Posttranscriptional regulation of uPAR in all these cells involves the interaction of the uPAR mRNABp with uPAR mRNA, which promotes uPAR mRNA destabilization.
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    URL: http://dx.doi.org/10.1023/A:1006914800447
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    Transcriptional modulation of the human complement factor I gene in Hep G2 cells by protein kinase C activation (1999)
    Springer
    Molecular and cellular biochemistry 201 (1999), S. 111-123 
    Details
    ISSN: 1573-4919
    Keywords: complement factor I ; TPA ; protein kinase C ; gene expression ; Hep G2 cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study examined the role of the protein kinase C (PKC) signalling pathway in the regulation of expression of human complement factor I (CFI) gene. The production of CFI by Hep G2 cells was enhanced in a dose- and time-dependent fashion by 12-O-tetradecanoyl-1,2-phorbol 13-acetate (TPA), a potent PKC activator. 4α-phorbol didecanoate, an inactive phorbol ester, had no effect on CFI synthesis. The TPA-dependent increase in CFI secretion was correlated with an increase in CFI mRNA levels. Forskolin, a cAMP-inducing agent, augmented the TPA response. W7, an inhibitor of protein kinase A and genistein, an inhibitor of protein tyrosine kinase(s) both did not prevent the increase in CFI expression mediated by TPA. However, calphostin C, a specific inhibitor of PKC, abolished the TPA-induced increase in CFI mRNA levels. Down regulation of intracellular PKC levels by prior exposure of Hep G2 cells to a high concentration of TPA also blocked the increase in CFI mRNA levels induced by TPA suggesting that the TPA effects were mediated via activation of PKC. mRNA decay studies indicated that the half-life of CFI mRNA in TPA-induced cells was not significantly different from control. Nuclear run-on transcriptional assays on the other hand demonstrated that whereas the CFI gene is transcribed under basal conditions in Hep G2 cells, TPA induced a 3-4 fold increase in the transcription rate of CFI gene in 24 h. The transcription rate of GAPDH gene did not change, indicating that the effects were not general on gene transcription. Transient transfections of Hep G2 cells with chloramphenicol acetyltransferase reporter gene (CAT) constructs containing a series of sequential 5′ deletions of the CFI promoter and CAT assays showed that the sequence between -136 and -130, containing an AP-1 consensus sequence (TGAGTCA) was required for the TPA response. This observation was substantiated by the finding that mutation of this AP-1 site to TttaTCA or TtAtcCA abolished the TPA responsiveness. The enhancement of the activity of transfected chimeric CAT constructs by TPA was abrogated by calphostin C and by pyrrolidine dithiocarbamate (an inhibitor of NF-κB and AP-1 transactivation). These results indicate that TPA regulation of CFI gene requires PKC signalling and is mediated by via a TPA response element (TRE) in the CFI promoter region located at -136/-130 and involves the transactivation of AP-1 and NF-κB transcription factors. We suggest that PKC may be one of the intracellular pathways that control CFI gene expression and that cellular processes (involving growth factors, hormones, cytokines etc.) that activate PKC may upregulate the expression of the CFI gene.
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    URL: http://dx.doi.org/10.1023/A:1007064602321
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    Expression of calcium-binding protein regucalcin and microsomal Ca2+-ATPase regulation in rat brain: Attenuation with increasing age (1999)
    Springer
    Molecular and cellular biochemistry 200 (1999), S. 43-49 
    Details
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; gene expression ; Ca2+-ATPase ; brain microsomes ; aging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The expression of calcium-binding protein regucalcin and its effect on the microsomal Ca2+-ATPase activity in rat brain tissues was investigated. The expression of regucalcin mRNA was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) analysis in brain tissues using rat regucalcin-specific primers. Regucalcin concentration in the brain tissues was about 5 × 10-9 M as measured using enzyme-linked immunoadsorbent assay (ELISA), and this level was lowered with increasing age (50 weeks old). The presence of regucalcin (10-9 to 10-7 M) in the enzyme reaction mixture caused a significant decrease in Ca2+-ATPase activity in the brain microsomes of young rats (5 weeks old). Meanwhile, the enzyme activity was not significantly altered by the addition of calmodulin (1 or 50 μg/ml), calbindin (1 or 10 μg/ml), and S-100 A protein (5 or 25 μg/ml), which are other Ca2+-binding proteins in rat brain. The effect of regucalcin to inhibit microsomal Ca2+-ATPase activity was weakened in the brain of rats with increasing age (50 weeks old). The present study demonstrates that regucalcin is expressed in the brain, and that it can uniquely inhibit Ca2+-ATPase activity in the brain microsomes of rats. The findings suggest that regucalcin plays a role in the regulation of microsomal Ca2+-ATPase activity in rat brain tissues.
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    URL: http://dx.doi.org/10.1023/A:1006928402184
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    Markov Control Processes with the Expected Total Cost Criterion: Optimality, Stability, and Transient Models (1999)
    Springer
    Acta applicandae mathematicae 59 (1999), S. 229-269 
    Details
    ISSN: 1572-9036
    Keywords: (discrete-time) Markov control processes ; expected total cost ; value iteration ; policy iteration ; stability ; transient control models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper studies the expected total cost (ETC) criterion for discrete-time Markov control processes on Borel spaces, and possibly unbounded cost-per-stage functions. It presents optimality results which include conditions for a control policy to be ETC-optimal and for the ETC-value function to be a solution of the dynamic programming equation. Conditions are also given for the ETC-value function to be the limit of the α-discounted cost value function as α ↑ 1, and for the Markov control process to be `stable" in the sense of Lagrange and almost surely. In addition, transient control models are fully analized. The paper thus provides a fairly complete, up-dated, survey-like presentation of the ETC criterion for Markov control processes on Borel spaces.
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    URL: http://dx.doi.org/10.1023/A:1006368714127
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    Identification of stretch-responsive genes in pulmonary artery smooth muscle cells by a two arbitrary primer-based mRNA differential display approach (1999)
    Springer
    Molecular and cellular biochemistry 197 (1999), S. 87-96 
    Details
    ISSN: 1573-4919
    Keywords: mechanical stretch ; smooth muscle cells ; differential display ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Physical forces induce profound changes in cell phenotype, shape and behavior. These changes can occur in vascular structures as a result of pressure overload and their effects can be seen in atherosclerotic vessels in which smooth muscle cells have undergone hyperplastic and hypertrophic changes. At the molecular level, mechanical stimuli are converted into chemical ones and lead to modulation of gene expression and/or the activation of a new repertoire of genes whose encoded proteins help the cells to adapt to their microenvironment. In this study, we have used a two primer-based mRNA differential display technique to identify candidate mechano-responsive genes in pulmonary artery smooth muscle cells. As compared to the original method described by Liang and Pardee, this technique uses two arbitrary primers instead of an anchored oligo(dt) plus an arbitrary primer in the polymerase chain reaction. The chief advantages of these modifications are an increase in the efficiency of the amplification and in the identification of differentially expressed clones. Using this approach, we compared the pattern of expressed genes in cells cultured under static conditions with those in cells that were mechanically stretched (1 Hz) for 24 h in a well-defined in vitro mechanical system. Three candidate genes that showed reproducible differences were chosen for further characterization and cloning. One clone was under expressed in stretched cells and had a DNA sequence with 90% homology to the human fibronectin gene. Two other clones were highly expressed in stretched cells and had a 92% and a 83% sequence homology with human platelet-activating factor (PAF) receptor and rat insulin-like growth factor-I (IGF-I) genes respectively. Northern blot analysis confirmed low levels of fibronectin mRNA transcripts in stretched cells. In contrast, accumulation of PAF receptor mRNA occurred 30 min after mechanical stretch was initiated whereas IGF-I mRNA levels peaked at 8 h. Both mRNA levels were sustained for up to 24 h of mechanical stretching. These results demonstrate the usefulness of the two primer-based mRNA differential display that enabled us to identify and characterize alterations at the level of gene expression among matrix proteins, G-protein coupled receptors and growth factors, each of whose response to mechanical strain is different. A more complete understanding of these responses will provide further insight into the pathologic processes associated with hypertension and atherosclerosis.
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    URL: http://dx.doi.org/10.1023/A:1006966530553
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    Bicelle-based liquid crystals for NMR-measurement of dipolar couplings at acidic and basic pH values (1999)
    Springer
    Journal of biomolecular NMR 13 (1999), S. 187-191 
    Details
    ISSN: 1573-5001
    Keywords: alignment ; bicelle ; dipolar coupling ; liquid crystal ; pH ; stability ; ubiquitin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract It is demonstrated that mixtures of ditetradecyl- phosphatidylcholine or didodecyl-phoshatidylcholine and dihexyl- phosphatidylcholine in water form lyotropic liquid crystalline phases under similar conditions as previously reported for bicelles consisting of dimyristoyl-phosphatidylcholine (DMPC) and dihexanoyl- phosphatidylcholine (DHPC). The carboxy-ester bonds present in DMPC and DHPC are replaced by ether linkages in their alkyl analogs, which prevents acid- or base-catalyzed hydrolysis of these compounds. 15N-1H dipolar couplings measured for ubiquitin over the 2.3–10.4pH range indicate that this protein retains a backbone conformation which is very similar to its structure at pH 6.5 over this entire range.
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    URL: http://dx.doi.org/10.1023/A:1008395916985
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    Characterisation of genes isolated from a potato swellingstolon cDNA library (1999)
    Springer
    Potato research 42 (1999), S. 31-42 
    Details
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; tuberisation ; extensin ; acyl carrier protein thioesterase ; high mobility group protein ; gene expression ; plant development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In screening to isolate a full-length copy of a previously isolated cDNA clone, a further three cDNAs were also isolated from a library prepared from sub-apical swelling-stolon tissue of potato (Solanum tuberosum L.). Sequence analysis showed these clones to be similar to extensin-like protein genes, acyl carrier protein thioesterase genes and high mobility group protein genes, respectively. A further cDNA, isolated by subtractive hybridisation, was similar to a tomato cDNA previously isolated on the basis of its down-regulation following nematode infection. While all the newly isolated genes were expressed in swelling stolons, for most, maximal expression was seen to be in stem tissue. Possible roles for these genes in the development of potato plants are discussed, as is the significance of gene expression in stems and stolons to the process of tuberisation.
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    URL: http://dx.doi.org/10.1007/BF02358389
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    Introduction of a Proximal Stat5 Site in the Murine α-Lactalbumin Promoter Induces Prolactin Dependency In Vitro and Improves Expression Frequency In Vivo (1999)
    Springer
    Transgenic research 8 (1999), S. 23-31 
    Details
    ISSN: 1573-9368
    Keywords: transgenic mice ; prolactin ; mammary gland ; gene expression ; Stat5 ; β-globin insulator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to establish a possible correlation between in vitro prolactin induction and the transcriptional activity of mammary gene promoters in transgenic mice, a functional Stat5-binding site was created by means of site-directed mutagenesis at position −70 on a 560 bp murine α-lactalbumin promotor linked to a CAT reporter gene. Surprisingly, the wild-type promoter was constitutively active in vitro and could not be induced by prolactin. Introducing the proximal Stat5 site abolished this constitutive activity and resulted in prolactin dependence in both CHO-K1- and HC11-transfected cells. In transgenic mice, both the frequency of lines expressing the transgene and the prevalence of mid to late pregnancy expression were increased.
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    URL: http://dx.doi.org/10.1023/A:1008851802022
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    The role of competition in invertebrate community development in a recently formed stream in Glacier Bay National Park, Alaska (1999)
    Springer
    Aquatic ecology 33 (1999), S. 175-184 
    Details
    ISSN: 1573-5125
    Keywords: Chironomidae ; interspecific competition ; streams ; stability ; succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract New streams formed following ice recession in Glacier Bay National Park, southeastern Alaska allow insights into the role of abiotic and biotic interactions in the assemblage of benthic communities. Reductions in abundance of a pioneer chironomid colonizer, Diamesa alpina/lupus, in one new stream, Wolf Point Creek, is considered to be a result of competitive interactions with subsequent colonizers, as opposed to intolerance of warmer water temperature as previously suggested. Reduced densities of potential competitors (25–50 larvae per 500 cm2) in a cobble transplant experiment between streams, allowed persistence of D. alpina/lupus at low densities. In addition, significantly more D. alpina/lupus larvae emigrated from artificial stream channels containing other chironomid taxa than channels without potential competitors while there was no significant correlation of emigration with water temperature. A small number of D. alpina/lupus transplanted from a cold stream (4–6 °C) survived at water temperatures of 10–15 °C for 1 week. These results infer that interference competition is the causal mechanism in the decline of D. alpina/lupus. Complete exclusion of D. alpina/lupus from the stream has not occurred and water temperature may play a role in partitioning D. alpina/lupus from other taxa on a temporal or a spatial basis.
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    Quantitative analysis of transcription and translation in gene amplified Chinese hamster ovary cells on the basis of a kinetic model (1999)
    Springer
    Cytotechnology 29 (1999), S. 93-102 
    Details
    ISSN: 1573-0778
    Keywords: CHO cells ; gene expression ; kinetic model ; protein secretion ; transcription ; translation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The elevation of expression levels for secreted glycoproteins by gene amplification in mammalian cells shows a saturation behavior at high levels of gene amplification. At high expression levels a drop in the secretion efficiency for the recombinant protein occurs (Schröder and Friedl, 1997), coinciding with the appearance of misfolded protein in the cell. In this communication we investigated whether additional limitations exist at the levels of transcription and translation. Four Chinese hamster ovary (CHO) cell lines expressing different amounts of human antithrombin III (ATIII) were used as a model system. A tenfold increase in the ATIII cDNA copy number from the lowest to the highest producing cell line coincided with a 38-fold increase in ATIII mRNA levels, and an 80-fold increase in the amount of intracellular ATIII levels. The data was analyzed using a simple kinetic model. The following conclusions were derived: I. The transcriptional activity for the recombinant protein is not saturated. II. Translation itself is not saturated either, but may be downregulated as secretion efficiency drops. III. Two explanations for the previously reported drop in secretion efficiency for the recombinant protein with increasing expression level are possible: A. Protein degradation is an alternative fate for translated ATIII and the fraction of ATIII degraded after translation increases as expression level is increased. B. Translation is downregulated as the secretory apparatus becomes exhausted to maintain cell viability.
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    Embryonic stem cell differentiation models: cardiogenesis, myogenesis, neurogenesis, epithelial and vascular smooth muscle cell differentiation in vitro (1999)
    Springer
    Cytotechnology 30 (1999), S. 211-226 
    Details
    ISSN: 1573-0778
    Keywords: cardiogenesis ; cell differentiation ; gene expression ; mouse embryonic stem cells ; myogenesis ; neurogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Embryonic stem cells, totipotent cells of the early mouse embryo, were established as permanent cell lines of undifferentiated cells. ES cells provide an important cellular system in developmental biology for the manipulation of preselected genes in mice by using the gene targeting technology. Embryonic stem cells, when cultivated as embryo-like aggregates, so-called ‘embryoid bodies’, are able to differentiate in vitro into derivatives of all three primary germ layers, the endoderm, ectoderm and mesoderm. We established differentiation protocols for the in vitro development of undifferentiated embryonic stem cells into differentiated cardiomyocytes, skeletal muscle, neuronal, epithelial and vascular smooth muscle cells. During differentiation, tissue-specific genes, proteins, ion channels, receptors and action potentials were expressed in a developmentally controlled pattern. This pattern closely recapitulates the developmental pattern during embryogenesis in the living organism. In vitro, the controlled developmental pattern was found to be influenced by differentiation and growth factor molecules or by xenobiotics. Furthermore, the differentiation system has been used for genetic analyses by ‘gain of function’ and ‘loss of function’ approaches in vitro.
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    URL: http://dx.doi.org/10.1023/A:1008041420166
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    Transient gene expression in mammalian cells grown in serum-free suspension culture (1999)
    Springer
    Cytotechnology 30 (1999), S. 71-83 
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    ISSN: 1573-0778
    Keywords: gene expression ; HEK293(EBNA) cells ; serum-free ; transient transfection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In order to establish a simple and scaleable transfection system we have used the cationic polymer polyethylenimine (PEI) to study transient transfection in HEK293 and 293(EBNA) cells grown in serum-free suspension culture. The transfection complexes were made directly within the cell culture by consecutively adding plasmid and PEI (direct method). Alternatively, the DNA-PEI transfection complexes were prepared in fresh medium (1/10 culture volume) and then added to the cells (indirect method). The results of this study clearly show that the ratio of PEI nitrogen to DNA phosphate is very important for high expression levels. The precise ratio is dependent on the DNA concentration. For example, using 1 μg/ml DNA by the indirect method, the ratio of optimal PEI:DNA was about 10–13:1. However, the ratio increases to 33:1 for 0.1–0.2 μg/ml DNA. By testing several different molecular weights of the polycationic polymer we could show that the highest transfection efficiency was obtained with the PEI 25 kDa. Using PEI 25 kDa the indirect method is superior to the direct addition because significantly lower DNA concentrations are needed. The expression levels of the soluble human TNF receptor p55 are even higher at low DNA compared to 1 μg/ml plasmid. The EBV-based pREP vectors gave better transient gene expression when used in 293(EBNA) cells compared to HEK293 cells in suspension culture. No differences in expression levels in the two cell lines were observed when the pC1 (CMV)-TNFR was used. In conclusion, PEI is a low-toxic transfection agent which provides high levels of transient gene expression in 293(EBNA) cells grown in serum-free suspension culture. This system allows highly reproducible, cost-effective production of milligram amounts of recombinant proteins in 2–5 l spinner culture scale within 3–5 days. Fermentor scale experiments, however, are less efficient because the PEI-mediated transient tranfection is inhibited by conditioned medium.
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    URL: http://dx.doi.org/10.1023/A:1008000327766
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    Stability of a class of neural network models with delay (1999)
    Springer
    Applied mathematics and mechanics 20 (1999), S. 912-916 
    Details
    ISSN: 1573-2754
    Keywords: delay ; neural network ; stability ; TN911.23 ; O332
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract In this paper, by using Liapunov functional, some sufficient conditions are obtained for the stability of the equilibrium of a neural network model with delay of the type $$u'_i \left( t \right) = - b_i u_i \left( t \right) + \sum\limits_{j = 1}^n {T_{ij} f_j } \left( {\mu _j u_j \left( {t - \tau _j } \right)} \right) + c_i ,\tau _j \geqslant 0,i = 1,2 \cdots ,n.$$
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    URL: http://dx.doi.org/10.1007/BF02452490
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    The role of the cell cycle in determining gene expression and productivity in CHO cells (1999)
    Springer
    Cytotechnology 30 (1999), S. 49-57 
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    ISSN: 1573-0778
    Keywords: cell cycle ; CHO ; flow cytometry ; gene expression ; synchronisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Understanding the relationships between cell cycle and protein expression is critical to the optimisation of media and environmental conditions for successful commercial operation of animal cell culture processes. Using flow cytometry for the analysis of the early phases of synchronised batch cultures, the dependency of product expression on cell cycle related events has been evaluated in a recombinant CHO cell line. Although the production of recombinant protein is initially found to be cell cycle related, the maximum specific protein productivity is only achieved at a later stage of the exponential phase which also sees a maximum in the intracellular protein concentration. Subsequent work suggests that it is the batch phase/medium composition of cultures which is the major determinant of maximum specific productivity in this cell line. Furthermore the effect of the positive association between S phase and specific productivity is subordinate to the effect of batch phase/medium composition on the specific productivity of batch cultures.
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    URL: http://dx.doi.org/10.1023/A:1008093404237
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    A method for following the unstable path between two saddle-node bifurcation points in nonlinear dynamic system (1999)
    Springer
    Applied mathematics and mechanics 20 (1999), S. 1384-1388 
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    ISSN: 1573-2754
    Keywords: nonlinear dynamic system ; bifurcation ; stability ; TB123 ; O322
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract A computation algorithm based on the Poincaré Mapping in combination with Pseudo-Arc Length Continuation Method is presented for calculating the unstable response with saddle-node bifurcation, and the singularity, which occurs using the general continuation method combined with Poincaré Mapping to follow the path, is also proved. A normalization equation can be introduced to avoid the singularity in the process of iteration, and a new iteration algorithm will be presented too. There will be two directions in which the path can be continued at each point, but only one can be used. The method of determining the direction will be presented in the paper. It can be concluded that is method is effective in analysis of nonlinear dynamic system with saddle-node bifurcations.
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    URL: http://dx.doi.org/10.1007/BF02459172
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    Some dynamical properties of a viscoelastic cylindrical shell (1999)
    Springer
    Applied mathematics and mechanics 20 (1999), S. 233-240 
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    ISSN: 1573-2754
    Keywords: viscoelasticity ; cylindrical shell ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract In this paper, the dynamic stability of a viscoelastic circular cylindrical shell subject to an axial compressive force and a uniformly distributed radial compressive load is discussed. By using the Laplace transformation, stability conditions of viscoelastic shell under constant loads are yielded. By using synthetically the classical dynamic methods, the various dynamical properties for the dynamical system defined by the viscoelastic shell and the effect of parameters on the stability of structure are obtained.
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    URL: http://dx.doi.org/10.1007/BF02463847
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    Convergence of Delayed Dynamical Systems (1999)
    Springer
    Neural processing letters 10 (1999), S. 267-271 
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    ISSN: 1573-773X
    Keywords: recurrent neural networks ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper, we point out that the conditions given in [1] are sufficient but unnecessary for the global asymptotically stable equilibrium of a class of delay differential equations. Instead, we prove that under weaker conditions, it is still global asymptotically stable.
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    URL: http://dx.doi.org/10.1023/A:1018753013035
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    Stable and Real-Time Scheduling of a Class of Hybrid Dynamic Systems (1999)
    Springer
    Discrete event dynamic systems 9 (1999), S. 45-64 
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    ISSN: 1573-7594
    Keywords: hybrid dynamic systems ; event feedback ; real-time scheduling ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Based on some practical engineering problems arising from process control and space-structure control, this paper studies a class of hybrid dynamic systems in which N plants are controlled by a central controller in sharing time manner, where the plants are described by differential equations and the controller works according to the mechanism of discrete events. An event feedback strategy is suggested to be a scheduling policy such that one and only one plant among N plants is chosen to be controlled at any time. Some conditions of asymptotical and exponential stability are then given and an exponential upper bound of states norm is also estimated for the event feedback scheduling strategy. An algorithm based on event feedback strategy is presented to determine the control laws of the plants to meet the given performance. An example follows to illustrate the application and effect of the results.
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    URL: http://dx.doi.org/10.1023/A:1008320614629
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    Genetic Variation in Spiroplasma citri (1999)
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    European journal of plant pathology 105 (1999), S. 519-533 
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    ISSN: 1573-8469
    Keywords: genome ; gene expression ; mollicute ; recombination ; transposition ; virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Spiroplasmas are members of the Class Mollicutes, wall-less prokaryotes having a high adenosine–thymidine content in their small genomes. Spiroplasma citri is a plant pathogen that inhabits phloem. Like other phytopathogenic spiroplasmas and the related phytoplasmas, it is transmitted from plant to plant by phloem-feeding leafhoppers that serve as alternate hosts for the spiroplasma as well as vectors. Genetic information in spiroplasmas is carried on a circular chromosome, on plasmids and/or in virus genomes. A picture emerging from recent research on the S. citri genome is one of frequent and often extensive variation, resulting from a number of different mechanisms. Expansion and contraction events must continually be occurring in about equal proportions so that the net genome size varies within defined boundaries. Particularly impressive are large changes in genome size that can occur in only a few generations. As with most organisms, genetic variation in S. citri results from variation in extrachromosomal DNA content, changes due to DNA replication and repair processes and changes due to recombination. The implied flux of genetic information into and out of the S. citri genome should be beneficial to the bacterium, allowing it, with its small genome size, to adapt to new environments.
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    URL: http://dx.doi.org/10.1023/A:1008757716803
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    Explicit second-order accurate schemes for the nonlinear Schrödinger equations (1999)
    Springer
    Lithuanian mathematical journal 39 (1999), S. 20-32 
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    ISSN: 1573-8825
    Keywords: Schrödinger equation ; explicit finite-difference schemes ; stability ; energy conservation ; convergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We consider three-level explicit schemes for solving the nonlinear variable coefficient Schrödinger-type equation. Using spectral and energy methods we establish the stability and convergence of these schemes. The existence of discrete conservation laws is investigated. General results are applied for the DuFort-Frankel and leap-frog diffenrence schemes.
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    URL: http://dx.doi.org/10.1007/BF02465532
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    Evidence of Mucin Secretion in Human Lung Adenocarcinoma Cell Lines NCIH650 and NCIH2077 and Effect of Select Secretagogues on Mucin Secretion (1999)
    Springer
    Bioscience reports 19 (1999), S. 473-483 
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    ISSN: 1573-4935
    Keywords: Mucin ; lung cancer ; gene expression ; secretion ; lung adenocarcinoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Mucins comprise an important class of tumor-associated antigens. The objectives of the present study were (a) to establish an in vitro model system using human non-small cell lung adenocarcinoma cell lines NCIH650 and NCIH2077 (b) provide evidence that these cell lines secrete mucin in culture conditions and (c) investigate the effects of select secretagogues on mucin secretion. The cell lines were established in ACL-4 medium containing several growth factors and retinoic acid and 5% fetal calf serum. The high molecular weight glycoconjugates secreted in the culture medium were purified by ammonium sulfate precipitation and Superose 6 and Superose 12 FPLC chromatography. The purified high molecular weight glycoconjugate fraction and the carcinoma cells were shown to have mucin by dot blot, Western blot and immunohistochemical analysis, respectively, using specific antibodies to purified major mucin, HTM-1. Also, incorporation experiments with mucin precursor 3H-glucosamine demonstrated that the cells indeed synthesize high molecular weight mucins. The effects of secretagogues such as, 8-bromocyclic AMP, ionomycin, phorbol-12-myristate-13-acetate and neutrophil elastase on mucin secretion were also investigated. Only 8-bromocyclic AMP and neutrophil elastase influenced mucin secretion. These studies provided strong evidence that the lung adenocarcinoma cell lines secrete high molecular weight mucins in culture conditions and only two of the four tested secretagogues significantly increased mucin secretion. Thus, this in vitro model system may be useful in determining alterations in mucin structure, if any, in lung adenocarcinomas as well as in studying the regulation of mucin gene expression.
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    URL: http://dx.doi.org/10.1023/A:1020224625088
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    Role of the Minimal State Variable Criterion in Rational Expectations Models (1999)
    Springer
    International tax and public finance 6 (1999), S. 621-639 
    Details
    ISSN: 1573-6970
    Keywords: expectations ; bubbles ; uniqueness ; stability ; state variables ; multiplicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper concerns the minimal-state-variable (MSV) criterion for selection among solutions in rational expectationsmodels that feature a multiplicity of paths that satisfy all of the model's conditions. It compares the MSVcriterion with others, including the widely used saddle-path (dynamic stability) criterion. It is emphasized that theMSV criterion can be viewed as a scientifically useful classification scheme that delineates the unique solutionthat is free of bubble components. In the process of demonstrating uniqueness for a broad class of linear models,the paper exposits a convenient computational procedure. Applications to current issues are outlined.
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    URL: http://dx.doi.org/10.1023/A:1008746610773
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    Numerical modeling of nonlinear deformation and buckling of composite plate-shell structures under pulsed loading (1999)
    Springer
    Mechanics of composite materials 35 (1999), S. 495-506 
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    ISSN: 1573-8922
    Keywords: layered structure ; shells ; frames ; stringers ; nonlinearity ; stability ; pulsed loading ; numerical methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Nonlinear three-dimensional problems of dynamic deformation, buckling, and posteritical behavior of composite shell structures under pulsed loads are analyzed. The structure is assumed to be made of rigidly joined plates and shells of revolution along the lines coinciding with the coordinate directions of the joined elements. Individual structural elements can be made of both composite and conventional isotropic materials. The kinematic model of deformation of the structural elements is based on Timoshenko-type hypotheses. This approach is oriented to the calculation of nonstationary deformation processes in composite structures under small deformations but large displacements and rotation angles, and is implemented in the context of a simplified version of the geometrically nonlinear theory of shells. The physical relations in the composite structural elements are based on the theory of effective moduli for individual layers or for the package as a whole, whereas in the metallic elements this is done in the framework of the theory of plastic flow. The equations of motion of a composite shell structure are derived based on the principle of virtual displacements with some additional conditions allowing for the joint operation of structural elements. To solve the initial boundary-value problem formulated, an efficient numerical method is developed based on the finite-difference discretization of variational equations of motion in space variables and an explicit second-order time-integration scheme. The permissible time-integration step is determined using Neumann's spectral criterion. The above method is especially efficient in calculating thin-walled shells, as well as in the case of local loads acting on the structural element, when the discretization grid has to be condensed in the zones of rapidly changing solutions in space variables. The results of analyzing the nonstationary deformation processes and critical loads are presented for composite and isotropic cylindrical shells reinforced with a set of discrete ribs in the case of pulsed axial compression and external pressure.
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    URL: http://dx.doi.org/10.1007/BF02259471
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    On Invariant Manifolds in Singularly Perturbed Systems (1999)
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    Journal of dynamical and control systems 5 (1999), S. 501-507 
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    ISSN: 1573-8698
    Keywords: Singular perturbation ; invariant manifold ; overflowing manifold ; stability ; characteristic numbers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A singularly perturbed system with a small parameter ε at the velocity of the slow variable y and with the fast variable x is considered. The main hypothesis is that for all y from some bounded domain D, the fast subsystem has a stable invariant or overflowing manifold M 0(y) and that the motions in this system going in the directions transversal to M 0(y) are more fast than the mutual approaching of trajectories on M 0(y) (a precise statement is given in terms of appropriate Lyapunov-type characteristic numbers). It is proved that for a sufficiently small ε, the whole system has an invariant manifold close to $$\bigcup\limits_{y \in D} {M_0 (y) \times \{ y\}}$$ the degree of its smoothness is specifed.
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    Comparison of the Anticancer Effect of Free and HPMA Copolymer-Bound Adriamycin in Human Ovarian Carcinoma Cells (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 986-996 
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    ISSN: 1573-904X
    Keywords: adriamycin ; doxorubicin ; HPMA copolymer ; apoptosis, multidrug resistance ; gene expression ; signal transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To study peculiarities and the mechanism of the anticancer effect of free and HPMA copolymer-bound ADR in sensitive and resistant human ovarian carcinoma cells. Methods. Sensitive A2780 and ADR resistant A2780/AD cells were exposed to different doses of drugs during 12, 24, 36, 48, 60, and 72 hours. Cell viability, drug accumulation, apoptosis, cellular metabolism, lipid peroxidation, DNA content and gene expression were studied. Results. HPMA copolymer-bound ADR (P(GFLG)-ADR) possessed a comparable cytotoxicity to free ADR when comparison was based on intracellular concentrations. While free ADR up-regulated genes encoding ATP driven efflux pumps (MDR1, MRP), P(GFLG)-ADR overcame existing pumps and down regulated the MRP gene. Free ADR also activated cell metabolism and expression of genes responsible for detoxification and DNA repair. P(GFLG)-ADR down-regulated HSP-70, GSr-π, BUDP, Topo-IIα, β, and TK-1 genes. Apoptosis, lipid peroxidation and DNA damage were significantly higher after exposure to P(GFLG)-ADR, as reflected by simultaneous activation of p53, c-fos in A2780 cells) or c-jun (A2780/AD) signaling pathways and inhibition of the bcl-2 gene. Differences between free ADR and P(GFLG)-ADR increased with the time of incubation and drug concentration. Conclusions. P(GFLG)-ADR overcame drug efflux pumps, more significantly induced apoptosis and lipid peroxidation, inhibited DNA repair, replication, and biosynthesis when compared to free ADR.
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    Preparation and Characterization of Carmustine Loaded Polyanhydride Wafers for Treating Brain Tumors (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 762-765 
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    ISSN: 1573-904X
    Keywords: polymer implant ; brain cancer ; carmustine ; polyanhydride ; stability ; controlled release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1023/A:1011995728760
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    Formulation and Lyoprotection of Poly(Lactic Acid-Co-Ethylene Oxide) Nanoparticles: Influence on Physical Stability and In Vitro Cell Uptake (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 859-866 
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    ISSN: 1573-904X
    Keywords: nanoparticles ; poly(lactic acid) ; poly(lactic acid-co-ethylene oxide) ; freeze-drying ; stability ; flow cytometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To investigate the feasibility of producing freeze-dried poly-(ethylene oxide) (PEO)-surface modified nanoparticles and to study their ability to avoid the mononuclear phagocytic system (MPS), as a function of the PEO chain length and surface density. Methods. The nanoparticles were produced by the salting-out method using blends of poly(D,L-lactic acid) (PLA) and poly(D,L-lactic acid-co-ethylene oxide) (PLA-PEO) copolymers. The nanoparticles were purified by cross-flow filtration and freeze-dried as such or with variable amounts of trehalose as a lyoprotectant. The redispersibility of the particles was determined immediately after freeze-drying and after 12 months of storage at −25° C. The uptake of the nanoparticles by human monocytes was studied in vitro by flow cytometry. Results. PLA-PEO nanoparticles could be produced from all the polymeric blends used. Particle aggregation after freeze-drying was shown to be directly related to the presence of PEO. Whereas this problem could be circumvented by use of trehalose, subsequent aggregation was shown to occur during storage. These phenomena were possibly related to the specific thermal behaviours of PEO and trehalose. In cell studies, a clear relationship between the PEO content and the decrease of uptake was demonstrated. Conclusions. The rational design of freeze-dried PEO-surface modified nanoparticles with potential MPS avoidance ability is feasible by using the polymer blends approach combined with appropriate lyoprotection and optimal storage conditions.
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    URL: http://dx.doi.org/10.1023/A:1018826103261
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    Isolation, Characterization, and Stability of Positional Isomers of Mono-PEGylated Salmon Calcitonins (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 813-818 
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    ISSN: 1573-904X
    Keywords: calcitonin ; polyethylene glycol ; PEGylation ; peptide ; tryptic digestion ; stability ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To separate and characterize the different positional isomers of mono-PEGylated salmon calcitonins (mono-PEG-sCTs) and to evaluate the effects of the PEGylation site on the stability of different mono-PEG-sCTs in rat kidney homogenate. Methods. Mono-PEG-sCTs were prepared using succinimidyl carbonate monomethoxy polyethylene glycol (5,000 Da) and separated by gel-filtration HPLC followed by reversed-phase HPLC. To characterize PEGylated sCTs, matrix-assisted laser desorption ionization time of flight mass spectrometry (M ALDI-TOF MS) and reversed-phase HPLC of the trypsin digested samples were performed. Mono-PEG-sCTs and sCT in rat kidney homogenates were measured by column-switching reversed-phase HPLC with on-line detection of the radioiodinated samples using a flow-through radioisotope detector. Results. Three different mono-PEGylated sCTs were separated by reversed-phase gradient HPLC. From the MALDI-TOF MS analysis, the average molecular weight of mono-PEG-sCTs was confirmed as around 8650 Da. The presence of PEG moiety in the mono-PEG-sCTs was also manifested by the fact that the distance between two adjacent mass spectum lines was 44 Da which corresponds to PEG monomer unit. Tryptic digestion analysis demonstrated that these mono-PEG-sCTs are 3 positional isomers of N-terminus, Lys18- and Lys11-residue modified mono-PEGylated sCTs. The degradation half-life of these 3 positional isomers in rat kidney homogenates significantly increased in order of the N-terminus (125.5 min), Lys11- (157.3 min), and Lysl8-residue modified mono-PEGylated sCT (281.5 min) over the native sCT (4.8 min). Conclusions. Three positional isomers of mono-PEGylated sCTs were purified and characterized. Of these, the resistance to proteolytic degradation was highest for the Lysl8-residue modified mono-PEG-sCT. These studies demonstrate that the in vivo stability of PEGylated sCTs is highly dependent on the site of PEG molecule attachment.
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    Enhanced expression and differential inducibility of soybean chalcone synthase genes by supplemental UV-B in dark-grown seedlings (1999)
    Springer
    Plant molecular biology 39 (1999), S. 785-795 
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    ISSN: 1573-5028
    Keywords: UV-B ; soybean ; chalcone synthase ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract By developing gene-specific RT-PCR and using filters to allow transmission down to 290 nm (UV-B+) or blocking all radiation below 320 nm (UV-B−), the effect of UV-B+ and UV-B− light on expression of each of the presently known seven members of soybean chalcone synthase (CHS) gene family in dark-grown seedlings was analyzed. Dark expression was detectable already in 18 h dark-germinating embryos, with progressive increases on successive days, suggesting that chs belongs to a class of genes expressed very early during germination, and that the expression at this stage is either constitutive or induced by non-light-dependent factors present in the seed or made available following imbibition. Exposure of 18 h dark-germinating embryos to UV-B− or to UV-B+ light did not lead to an increase in chs signal. However, the 24 h dark-germinating embryos showed a distinct effect of UV-B+, interestingly coinciding with the stage when the head of seedlings was in the process of being pushed up above ground by stem elongation, suggesting the possibility of a developmental switch modulating the appearance of UV-B response. The response to UV-B− was most prominent in chs1 and almost silent in chs2, while the up-regulation by UV-B+ was most prominent in chs5 and chs6 and much less so in chs2. Interestingly, chs2 was noted to be the only member of the Gmchs gene family devoid of H-box, raising the possibility that the H-box may be a good indicator of the photo-inducibility of a chs gene.
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    Complexity and expression of the glutamine synthetase multigene family in the amphidiploid crop Brassica napus (1999)
    Springer
    Plant molecular biology 39 (1999), S. 395-405 
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    ISSN: 1573-5028
    Keywords: amphidiploid genome structure ; gene expression ; glutamine synthetase ; multigene family ; nitrogen assimilation ; oilseed rape
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the amphidiploid genome of oilseed rape (Brassica napus) the diploid ancestral genomes of B. campestris and B. oleracea have been merged. As a result of this crossing event, all gene loci, gene families, or multigene families of the A and C genome types encoding a certain protein are now combined in one plant genome. In the case of the multigene family for glutamine synthetase, the key enzyme of nitrogen assimilation, six different cDNA sequences were isolated from leaf and root specific libraries. One sequence pair (BnGSL1/BnGSL2) was characterized by the presence of amino- terminal transit peptides, a typical feature of all nuclear encoded chloroplast proteins. Two other cDNA pairs (BnGSR1-1/BnGSR1-2 and BnGSR2-1/BnGSR2-2) with very high homology between each other were found in a root specific cDNA library and represent protein subunits for cytosolic glutamine synthetase isoforms. Comparative PCR amplifications of genomic DNA isolated from B. napus, B. campestris and B. oleracea followed by sequence–specific restriction analyses of the PCR products permitted the assignment of the cDNA sequences to either the A genome type (BnGSL1/BnGSR1- 1/BnGSR2-1) or the C genome type (BnGSL2/BnGSR1-2/BnGSR2-2). Consequently, the ancestral GS genes of B. campestris and B. oleracea are expressed simultaneously in oilseed rape. This result was also confirmed by RFLP (restriction fragment length polymorphism) analysis of RT-PCR products. In addition, the different GS genes showed tissue specific expression patterns which are correlated with the state of development of the plant material. Especially for the GS genes encoding the cytosolic GS isoform BnGSR2, a marked increase of expression could be observed after the onset of leaf senescence.
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    URL: http://dx.doi.org/10.1023/A:1006193717093
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    Diverse range of gene activity during Arabidopsis thaliana leaf senescence includes pathogen-independent induction of defense-related genes (1999)
    Springer
    Plant molecular biology 40 (1999), S. 267-278 
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    ISSN: 1573-5028
    Keywords: defense ; gene expression ; leaf senescence ; nitrilase ; pathogen-free ; salicylic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To determine the range of gene activities associated with leaf senescence, we have identified genes that show preferential transcript accumulation during this developmental stage. The mRNA levels of a diverse array of gene products increases during leaf senescence, including a protease, a ribosomal protein, two cinnamyl alcohol dehydrogenases, a nitrilase and glyoxalase II. Two of the genes identified are known to be pathogen-induced. The senescence specificity of each gene was determined by characterization of transcript accumulation during leaf development and in different tissues. The increased expression of nitrilase in senescent leaves is paralleled by an increase in free indole-3-acetic acid (IAA) levels. Additionally, we have demonstrated that the induction of defense-related genes during leaf senescence is pathogen-independent and that salicylic acid accumulation is not essential for this induction. Our data indicate that the induction of certain genes involved in plant defense responses is a component of the leaf senescence program.
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    URL: http://dx.doi.org/10.1023/A:1006199932265
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    Isolation and molecular characterization of gibberellin-regulated H1 and H2B histone cDNAs in the leaf of the gibberellin-deficient tomato (1999)
    Springer
    Plant molecular biology 39 (1999), S. 883-890 
    Details
    ISSN: 1573-5028
    Keywords: gene expression ; gibberellin ; H1 histone ; H2B histones ; leaf ; Lycopersicon esculentum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract After differential screening we isolated cDNA clones encoding a histone H1 (leH1) and three variants of histone H2B (leH2B-1, -2 and -3) from the gibberellin (GA)-deficient mutant of tomato (gib-1). The deduced polypeptide of leH1 is 271 amino acids long and exhibits the typical tripartite structure of histones H1. The full-length cDNA clone leH2B-1 encodes for a protein of 142 amino residues and shows the tripartite organization of histones H2B. The histones leH1 and leH2B, which show no tissue specificity, are developmentally expressed in the leaf. The mRNA accumulation was higher in organs which contain meristematic tissue and/or which have a high proportion of actively cycling cells. In the leaf of the gib-1 mutant we demonstrated GA-enhanced histone leH1 and leH2B expression which was not observed in the wild type. GAs of the early-13-hydroxylated pathway (GA1 and GA3) caused most enhanced transcription compared to GAs of the early-non-hydroxylation pathway (GA4 and GA9). Application of GA to the mutant increased histone expression that could correlate with enhanced DNA replication in leaf tissue. Increased chromosome replication may indicate that there is a higher rate of cell division and/or increase of endopolyploidy which both may be dependent on cell elongation induced by GAs.
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    URL: http://dx.doi.org/10.1023/A:1006157718263
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    Differential expression of two spermidine synthase genes during early fruit development and in vegetative tissues of pea (1999)
    Springer
    Plant molecular biology 39 (1999), S. 933-943 
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    ISSN: 1573-5028
    Keywords: cloning ; fruit development ; gene expression ; pea ; polyamine ; spermidine synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two cDNAs from young pea fruits coding for functional spermidine synthases (EC 2.5.1.16) were isolated. The corresponding genes were named psSPDSYN1 and psSPDSYN2. Both cDNAs complemented spe3Δ gene when introduced into the Y480 strain of Saccharomyces cerevisiae, which is a null mutant for the spermidine synthase gene. psSPDSYN1 and psSPDSYN2 are regulated differentially. psSPDSYN1 is up-regulated early after fruit set whereas psSPDSYN2 is expressed later. Spermidine synthase activity was detected in pea ovaries, and correlates with the pattern of expression of psSPDSYN1. In the pea plant, psSPDSYN1 is highly expressed in actively growing tissues, whereas the highest level of psSPDSYN2 mRNA was detected in fully elongated stem.
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    URL: http://dx.doi.org/10.1023/A:1006158819849
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    Regulation of the chitinase gene expression in suspension-cultured rice cells by N-acetylchitooligosaccharides: differences in the signal transduction pathways leading to the activation of elicitor-responsive genes (1999)
    Springer
    Plant molecular biology 39 (1999), S. 907-914 
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    ISSN: 1573-5028
    Keywords: chitin oligomer ; chitinase ; elicitor ; gene expression ; rice ; signal transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Expression patterns of chitinase transcripts induced by N-acetylchitooligosaccharide elicitor were analyzed by northern blot hybridization in order to reveal a signal transduction pathway leading to the activation of class I chitinase genes (Cht-1 and Cht-3), which may play an important role in producing N-acetylchitooligosaccharide elicitor. The transcription level of both genes was enhanced in response to N-acetylchitooligosaccharides larger than pentaose at subnanomolar concentrations. These structure and dose dependencies were consistent not only with those for a 75 kDa high-affinity binding protein for N-acetylchitooligosaccharide elicitor in the plasma membrane, but also with other series of cellular responses including phytoalexin production and the expression of elicitor-responsive genes (EL2, EL3). Therefore, the elicitor signal to evoke these cellular responses including the activation of the chitinase genes could be common and transmitted into cells through the 75 kDa protein. However, the signal transduction pathway for the activation of the chitinase gene appeared to diverge from those for the other elicitor-responsive genes shortly after the signal perception. It was shown that the induction of chitinase expression by N-acetylchitooligosaccharide would require protein phosphorylation, but not de novo protein synthesis. The oxidative burst was demonstrated not to be necessary for transcriptional induction of the all four elicitor-responsive genes (Cht, PAL, EL2, EL3) by N-acetylchitooligosaccharide.
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    URL: http://dx.doi.org/10.1023/A:1006161802334
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    Temporal and spatial gene expression of cytochrome B5 during flower and fruit development in olives (1999)
    Springer
    Plant molecular biology 40 (1999), S. 79-90 
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    ISSN: 1573-5028
    Keywords: cytochrome b5 ; fruit and flower development ; gene expression ; in situ hybridisation ; olive
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We report the characterisation of two cytochrome b5 genes and their spatial and temporal patterns of expression during development in olive, Olea europaea. A PCR-generated probe, based on a tobacco cytochrome b5 sequence, was used to isolate two full-length cDNA clones (cytochrome b5-15 and cytochrome b5-38) from a library derived from 13 WAF olive fruits. The cDNAs encoded proteins of 17.0 and 17.7 kDa, which contained all the characteristic motifs of cytochromes b5 from other organisms and exhibited 63% identity and 85% similarity with each other. The olive cytochrome b5-15 cDNA was then used as a probe for more detailed analysis. Southern blotting revealed a gene family of at least 4–6 members while northern blotting and in situ hybridisation showed a highly specific pattern of gene expression. Very low levels of cytochrome b5 mRNA were detected in tissues characterised by high rates of lipid accumulation, such as young expanding leaves, maturing seeds and ripening mesocarp. The cytochrome b5 genes were not induced at 6 °C and their response to ABA was relatively slow compared with fatty acid desaturase genes. In contrast, high levels of cytochrome b5 gene expression were found in young fruits at the pattern formation (globular/heart) stage of embryogenesis and in vascular and transmitting tissues of male and female reproductive organs. The data are consistent with a major role for cytochrome b5 in developmental processes related to plant reproduction in addition to being an electron donor to microsomal desaturases.
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    URL: http://dx.doi.org/10.1023/A:1026417710320
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    Cloning and characterization of a trypsin inhibitor cDNA from amaranth (Amaranthus hypochondriacus) seeds (1999)
    Springer
    Plant molecular biology 41 (1999), S. 15-23 
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    ISSN: 1573-5028
    Keywords: Amaranthus hypochondriacus) ; gene expression ; trypsin inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We previously isolated and sequenced the major trypsin inhibitor from Amaranthus hypochondriacus seeds. This amaranth trypsin inhibitor (AmTI) is a 69 amino acid protein with high homology to members of the potato-1 inhibitor family. This paper describes the cloning and expression of a cDNA encoding this trypsin inhibitor in various vegetative tissues of the amaranth plant during seed development and imbibition, and investigates the possible induction of AmTI expression by wounding. We obtained a 393 bp cDNA sequence with an open reading frame corresponding to a polypeptide with 76 amino acid residues. With the exception of one residue (Ser-41), the polypeptide agrees with the amino acid sequence previously reported, plus 7 more residues at the N-terminus. These N-terminal residues are thought to be part of the signal used for intracellular sorting. The organ specificity of AmTI gene expression was investigated by northern analysis, showing that mRNA corresponding to AmTI genes was present in stems of plants growing under normal conditions. The kinetics of accumulation of the AmTI-mRNA, protein, and inhibitory activity during seed development and imbibition was determined. AmTI-mRNA accumulation reached a maximum at 14 days after anthesis (daa) and then gradually decreased, being barely detectable 36 daa. The AmTI protein accumulation followed the same profile as the inhibitory activity, both were delayed with respect to the mRNA. The maximum level was observed 22 daa, and then gradually decreased until a steady state was reached as seed maturation proceeded. Upon imbibition, a gradual decrease in AmTI protein and inhibitory activity was shown; however, an AmTI transcript was detected 24 h after imbibition. In contrast to representative members of the potato I family, this inhibitor was not inducible by wounding of leaves.
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    URL: http://dx.doi.org/10.1023/A:1006262106267
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    Localization of peroxidase mRNAs in soybean seeds by in situ hybridization (1999)
    Springer
    Plant molecular biology 41 (1999), S. 57-63 
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    ISSN: 1573-5028
    Keywords: embryo ; gene expression ; Glycine max ; oxidoreductase ; seed coat ; testa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The soybean Ep gene encodes an anionic peroxidase enzyme that accumulates in large amounts in seed coat tissues. We have isolated a second peroxidase gene, Prx2, that is also highly expressed in developing seed coat tissues. Sequence analysis of Prx2 cDNA indicates that this transcript encodes a cationic peroxidase isozyme that is far removed from Ep in peroxidase phylogeny. To determine the expression patterns for these two peroxidases in developing seeds, the abundance and localization of the Ep and Prx2 transcripts were compared by in situ hybridization. Results show the expression of Ep begins in a small number of cells flanking the vascular bundle in the seed coat, spreads to encircle the seed, and then migrates to the hourglass cells as they develop. Expression of Prx2 occurs throughout development in all cell layers of the seed coat, and is also evident in the pericarp and embryo. Nonetheless, the Ep-encoded enzyme accounts for virtually all of the peroxidase activity detected in mature seed coats. The Prx2 enzyme is either insoluble in a catalytically inactive form, or is subject to degradation during seed maturation.
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    URL: http://dx.doi.org/10.1023/A:1006244500951
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    Constitutive protein-DNA interactions on the abscisic acid-responsive element before and after developmental activation of the rab28 gene (1999)
    Springer
    Plant molecular biology 41 (1999), S. 529-536 
    Details
    ISSN: 1573-5028
    Keywords: ABRE ; embryogenesis ; G-box ; gene expression ; maize ; protein-DNA interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transcription of the rab28 gene from maize is induced in late embryo development and in response to abscisic acid. We have studied the regulation of the activity of the rab28 promoter in embryos. Two abscisic acid-responsive elements (ABREs) were necessary for expression in embryos of transgenic Arabidopsis and in transient transformation in maize embryos. In vivo footprinting showed that there was protein binding to the ABREs and to other cis elements in the promoter in young embryos before expression of rab28. This shows that the rab28 promoter is in an open chromatin structure before developmental activation. The ABREs are important for the induction and have protein binding in young embryos. Nuclear proteins extracted from embryos before activation of rab28 bound to the ABREs in band shift assays. A complex with different mobility was formed between nuclear proteins and the ABREs after induction of rab28 suggesting a modification of the ABRE-binding factor or an exchange of proteins. The footprints on the ABREs were unaltered by induction with abscisic acid or during developmental activation of rab28. These results indicate that constitutive binding of transcription factor(s) on the ABRE is central in embryonic regulation of the rab28 gene.
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    URL: http://dx.doi.org/10.1023/A:1006345113637
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    Molecular characterization of a gene for alanine aminotransferase from rice (Oryza sativa) (1999)
    Springer
    Plant molecular biology 39 (1999), S. 149-159 
    Details
    ISSN: 1573-5028
    Keywords: alanine aminotransferase ; gene expression ; GUS expression ; promoter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA clone encoding alanine aminotransferase (AlaAT) has isolated from randomly sequenced clones derived from a cDNA library of maturing rice seeds by comparison to previously identified genes. The deduced amino acid sequence was 88% and 91% homologous to those of the enzymes from barley and broomcorn millet (Panicum miliaceum), respectively. Using this cDNA as a probe, we isolated and sequenced the corresponding genomic clone. Comparison of the sequences of the cDNA and the genomic gene revealed that the coding region of the gene was interrupted by 14 introns 66 to 1547 bp long. Northern and western blotting analyses showed that the gene was expressed at high levels in developing seeds. When the 5′-flanking region between −930 and +85 from the site of initiation of transcription was fused to a reporter gene for β-glucuronidase (GUS) and then introduced into the rice genome, histochemical staining revealed strong GUS activity in the inner endosperm tissue of developing seeds and weak activity in root tips. Similar tissue-specific expression was also detected by in situ hybridization. These results suggest that AlaAT is involved in nitrogen metabolism during the maturation of rice seed.
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    URL: http://dx.doi.org/10.1023/A:1006156214716
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    Differential expression of expansin gene family members during growth and ripening of tomato fruit (1999)
    Springer
    Plant molecular biology 39 (1999), S. 161-169 
    Details
    ISSN: 1573-5028
    Keywords: expansin ; fruit growth ; fruit softening ; gene expression ; Lycopersicon esculentum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract cDNA clones encoding homologues of expansins, a class of cell wall proteins involved in cell wall modification, were isolated from various stages of growing and ripening fruit of tomato (Lycopersicon esculentum). cDNAs derived from five unique expansin genes were obtained, termed tomato Exp3 to Exp7, in addition to the previously described ripening-specific tomato Exp1 (Rose et al. (1997) Proc Natl Acad Sci USA 94: 5955–5960). Deduced amino acid sequences of tomato Exp1, Exp4 and Exp6 were highly related, whereas Exp3, Exp5 and Exp7 were more divergent. Each of the five expansin genes showed a different and characteristic pattern of mRNA expression. mRNA of Exp3 was present throughout fruit growth and ripening, with highest accumulation in green expanding and maturing fruit, and lower, declining levels during ripening. Exp4 mRNA was present only in green expanding fruit, whereas Exp5 mRNA was present in expanding fruit but had highest levels in full-size maturing green fruit and declined during the early stages of ripening. mRNAs from each of these genes were also detected in leaves, stems and flowers but not in roots. Exp6 and Exp7 mRNAs were present at much lower levels than mRNAs of the other expansin genes, and were detected only in expanding or mature green fruit. The results indicate the presence of a large and complex expansin gene family in tomato, and suggest that while the expression of several expansin genes may contribute to green fruit development, only Exp1 mRNA is present at high levels during fruit ripening.
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    URL: http://dx.doi.org/10.1023/A:1006130018931
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    Isolation and characterization of mRNAs differentially expressed during ripening of wild strawberry (Fragaria vesca L.) fruits (1999)
    Springer
    Plant molecular biology 39 (1999), S. 629-636 
    Details
    ISSN: 1573-5028
    Keywords: cDNA cloning ; fruit ripening ; gene expression ; non-climacteric fruit ; wild strawberry (Fragaria vesca L.)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wild strawberry (Fragaria vesca L.) is an attactive model system for studying ripening in non-climacteric fruit, because of its small diploid genome, its short reproductive cycle, and its capacity for transformation. We have isolated eight ripening-induced cDNAs from this species after differential screening of a cDNA library. The predicted polypeptides of seven of the clones exhibit similarity to database protein sequences, including acyl carrier protein, caffeoyl- CoA 3-O-methyltransferase, sesquiterpene cyclase, major latex protein, cystathionine γ-synthase, dehydrin and an auxin- induced gene. A ninth cDNA clone that was constitutively expressed is predicted to encode a metallothionein-like protein. None of these proteins appear to be directly related to events generally associated with ripening such as cell wall metabolism or the accumulation of sugars and pigments, rather, their putative functions are indicative of the wide range of processes upregulated during fruit ripening.
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    URL: http://dx.doi.org/10.1023/A:1006179928312
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    Enzymatic activity and gene expression under water stress of phospholipase D in two cultivars of Vigna unguiculata L.Walp. differing in drought tolerance (1999)
    Springer
    Plant molecular biology 39 (1999), S. 1257-1265 
    Details
    ISSN: 1573-5028
    Keywords: cowpea (Vigna unguiculata L.) ; drought ; gene expression ; lipid degradation ; phospholipase D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phospholipase D, a major lipid-degrading enzyme in plants, was studied in two cultivars of Vigna unguiculata L.Walp, differing in their tolerance to drought (cv. EPACE-1, drought-tolerant, and cv. 1183, drought-susceptible). Enzymatic activities, measured with 14C-PC as substrate, increased when plants were submitted to water stress, the increase being much higher in the drought-sensitive cultivar. A 2911 bp cDNA encoding a putative phospholipase D (VuPLD1) was isolated from a cDNA library prepared from V. unguiculata leaves. The deduced amino acid sequence (809 residues) shows 85.5% identity and 91.3% similarity to that of PLD from Ricinus communis. The expression of the VuPLD1 gene in the leaves is differently modulated by water deficit, depending on the intensity of stress and the tolerance or sensitivity of the plants. In the drought-susceptible V. unguiculata cv. 1183, it readily increased under water stress, reaching maximum values at mild water deficit (−1.5 MPa). In the drought-tolerant cv. EPACE-1, VuPLD1 mRNA remained low throughout the whole drought treatment. Dehydration of leaves led to a dramatic increase in transcript level in both cultivars. Changes in protein amounts semi-quantified by immunoblotting correlated well with variations in transcript steady-state level. Taken together, these results showed that phospholipase D in cowpea plants is essentially regulated at the transcriptional level, and that gene expression is strongly stimulated even by moderate water deficit in the drought-sensitive plant. On the contrary, the drought-tolerant plant presents a remarkable stability of PLD gene expression in conditions of water stress.
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    Identification of genes specifically expressed in cauliflower reproductive meristems. Molecular characterization of BoREM1 (1999)
    Springer
    Plant molecular biology 39 (1999), S. 427-436 
    Details
    ISSN: 1573-5028
    Keywords: reproductive development ; gene expression ; subtractive hybridization ; cauliflower
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using the meristems of the cauliflower curd as a source of tissue and a series of subtractive hybridizations and amplification reactions, we have constructed a cDNA library highly enriched in cDNAs expressed in reproductive meristems. The analysis of a sample of 250 clones from this library identified 22 cDNA clones corresponding to genes specifically expressed in these cauliflower meristems. Apart from two clones that corresponded to APETALA1, and two other ones showing similarity to different aminoacyl-tRNA synthetases, the remaining clones showed no similarity to any sequence in the databases and may correspond to novel genes. One of these clones, BoREM1, was further characterized and found to correspond to a gene encoding a protein with features of regulatory proteins that follows a expression pattern very similar to the LEAFY transcripts.
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    A strong constitutive positive element is essential for the ammonium-regulated expression of a soybean gene encoding cytosolic glutamine synthetase (1999)
    Springer
    Plant molecular biology 39 (1999), S. 551-564 
    Details
    ISSN: 1573-5028
    Keywords: ammonium ; gene expression ; glutamine synthetase ; nodules ; positive element ; promoter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to identify important promoter elements controlling the ammonium-regulated expression of the soybean gene GS15 encoding cytosolic glutamine synthetase, a series of 5′ promoter deletions were fused to the GUS reporter gene. To allow the detection of positive and negative regulatory elements, a series of 3′ deletions were fused to a −90 CaMV 35S promoter fragment placed upstream of the GUS gene. Both types of construct were introduced into Lotus corniculatus plants and soybean roots via Agrobacterium rhizogenes-mediated transformation. Both spectrophotometric enzymatic analysis and histochemical localization of GUS activity in roots, root nodules and shoots of transgenic plants revealed that a strong constitutive positive element (SCPE) of 400 bp, located in the promoter distal region is indispensable for the ammonium- regulated expression of GS15. Interestingly, this SCPE was able to direct constitutive expression in both a legume and non- legume background to a level similar to that driven by the CaMV 35S full-length promoter. In addition, results showed that separate proximal elements, located in the first 727 bp relative to the transcription start site, are essential for root- and root nodule-specific expression. This proximal region contains an AAAGAT and two TATTTAT consensus sequences characteristic of nodulin or nodule-enhanced gene promoters. A putative silencer region containing the same TATTTAT consensus sequence was identified between the SCPE and the organ-specific elements. The presence of positive, negative and organ-specific elements together with the three TATTTAT consensus sequences within the promoter strongly suggest that these multiple promoter fragments act in a cooperative manner, depending on the spatial conformation of the DNA for trans-acting factor accessibility.
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    Cloning and characterization of six embryogenesis-associated cDNAs from somatic embryos of Picea glauca and their comparative expression during zygotic embryogenesis (1999)
    Springer
    Plant molecular biology 39 (1999), S. 859-864 
    Details
    ISSN: 1573-5028
    Keywords: embryo-abundant cDNAs ; gene expression ; gymnosperm ; Picea glauca ; somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Six somatic embryogenesis-associated cDNAs (PgEMB2, 6, 7, 8, 24 and 34) from white spruce (Picea glauca (Moench) Voss) somatic embryos have been characterized. Transcript accumulation during somatic embryo development and subsequent germination related to these genes, indicated that they were developmentally regulated. The transcripts related to clones PgEMB2, 6, 24 and 34 were also detected during zygotic embryo development, but transcripts of clones PgEMB7 and 8 were not. PgEMB24 had a similar gene expression pattern to spruce Em-like late embryo abundant (lea) gene, but other clones had no similarities in gene expression to either spruce lea-like or storage protein genes. Abscisic acid, a stimulator for spruce somatic embryo maturation, did not obviously affect gene expression corresponding to these cDNAs. The predicted proteins are distinguishable from known LEA proteins based on analyses of hydropathy plots, amino acid compositions and deduced protein structures. The similarities of the spruce cDNAs, and protein sequences predicted from these cDNAs, to other sequence data are described.
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    URL: http://dx.doi.org/10.1023/A:1006146622614
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    Mutation of GT-1 binding sites in the Pr-1A promoter influences the level of inducible gene expression in vivo (1999)
    Springer
    Plant molecular biology 40 (1999), S. 387-396 
    Details
    ISSN: 1573-5028
    Keywords: gene expression ; GT-1 ; PR-1a ; PR proteins ; salicylic acid-induced ; transcription factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Infection of Nicotiana tabacum Samsun NN with tobacco mosaic virus (TMV) results in a hypersensitive plant response and leads to systemic acquired resistance (SAR). The induction of SAR is mediated by the plant hormone salicylic acid (SA) and is accompanied by the induced expression of a number of genes including the pathogenesis-related (PR) gene 1a. Previously, it has been found that TMV infection and SA treatment resulted in a reduction of binding of nuclear protein GT-1 to far-upstream regions (−902 to −656) of the PR-1a gene. To test if GT-1 is a negative regulator of PR-1a gene expression, the effects of mutations in the seven putative GT-1 binding sites in this region were studied in vitro using dimethyl sulfate interference footprinting and band shift assays. This showed that at least one of the seven sites is indeed a GT-1 binding site. However, when tested in transgenic plants, the mutations did not result in constitutive expression of the chimeric PR-1a/GUS transgene, while inducible expression after SA treatment was decreased. The results suggest that binding of GT-1-like proteins to far-upstream PR-1a promoter regions indeed influences gene expression. A possible model for GT-1's mode of action in PR-1a gene expression is discussed.
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    URL: http://dx.doi.org/10.1023/A:1006144505121
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    Expression of two PIP genes in rapidly growing internodes of rice is not primarily controlled by meristem activity or cell expansion (1999)
    Springer
    Plant molecular biology 40 (1999), S. 985-995 
    Details
    ISSN: 1573-5028
    Keywords: aquaporin ; gene expression ; growth ; Oryza sativa ; plasma membrane intrinsic protein (PIP) ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Membrane intrinsic proteins facilitate movement of small molecules often times functioning as water channels. We have identified two genes from rice which encode proteins with characteristic features of plasma membrane intrinsic proteins (PIP). They possess six membrane-spanning domains, an NPA repeat, overall high sequence homologies and characteristic C- and N-terminal hallmark motifs which allowed assignment of OsPIP1a to the PIP1 subfamily and of OsPIP2a to the PIP2 subfamily. OsPIP1a and OsPIP2a showed similar but not identical expression patterns. The two genes were expressed at higher levels in seedlings than in adult plants and expression in the primary root was regulated by light. In internodes of deepwater rice plants which were induced to grow rapidly by submergence, transcript levels were slightly induced in the intercalary meristem (IM) and slightly reduced in the elongation zone (EZ) after 18 h. In internodes of GA-induced excised stem sections transcript levels transiently declined in the IM and EZ after 1 h and subsequently recovered to elevated levels after 18 h. GA also induced OsPIP expression in non-growing tissue after 18 h. In the IM of submergence-induced stem sections transcript levels remained constitutive. The different growth-promoting treatments showed no direct correlation between growth rate and OsPIP gene expression in dividing or expanding cells. In fact, treatment of excised stem sections with ABA or drought stress induced similar changes in OsPIP expression in the growing zone during the first 6 h as GA did. We conclude that regulation of OsPIP1a and OsPIP2a expression is not primarily controlled by growth. GA-induced growth may however change the water status of cells which in turn results in altered PIP abundance.
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    URL: http://dx.doi.org/10.1023/A:1006265528015
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    Identification of two chilling-regulated 1-aminocyclopropane- 1-carboxylate synthase genes from citrus (Citrus sinensis Osbeck) fruit (1999)
    Springer
    Plant molecular biology 41 (1999), S. 587-600 
    Details
    ISSN: 1573-5028
    Keywords: ACC synthase ; chilling ; Citrus sinensis ; ethylene ; gene expression ; peel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Diurnal change in the temperature below or above 12.5 °C hastens the degreening of citrus peel and elicits the phytohormone ethylene production in citrus fruit. Ethylene triggers the degradation of chlorophyll and synthesis of carotenoids in citrus peel. To investigate if ethylene is required for the degreening of citrus peel elicited by low temperatures, we studied the chilling-regulated gene expression of ACC synthase, one of the key enzymes catalyzing ethylene biosynthesis. We isolated and characterized a chilling-inducible 1-aminocyclopropane-1-carboxylate synthase (ACC synthase) gene, CS-ACS1, and a chilling-repressible gene, CS-ACS2, from citrus peel. The CS-ACS1 transcript 1.7 kb in length encodes a polypeptide of 483 amino acids (M r 54 115, pI 6.63), whereas the CS-ACS2 transcript of 1.8 kb encodes a polypeptide of 477 amino acids (M r 53 291, pI 6.72). Both genes showed a rapid but transient induction (within 2.4 h) of transcripts upon rewarming after the chilling (4 °C) treatment. After 24 h of incubation at room temperature, CS-ACS1 mRNA diminished to an undetectable level, whereas the CS-ACS2 mRNA regained its basal level of expression attained prior to the chilling treatment. Chilling-induced ethylene production and ACC accumulation were also observed upon rewarming. Both genes were also induced by the wound stress (excision). The protein synthesis inhibitor cycloheximide super-enhances the accumulation of both ACS transcripts at room temperature. Molecular analysis of the 3.3 kb genomic DNA of CS-ACS1 revealed that this gene consists of three introns and four exons. The intron 3 is exceptionally large (1.2 kb) and shares significant homology with mitochondrial DNA, supporting the intron-late theory.
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    URL: http://dx.doi.org/10.1023/A:1006369016480
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    Occurrence of five different chromosomal HMG1 proteins in various maize tissues (1999)
    Springer
    Plant molecular biology 41 (1999), S. 351-361 
    Details
    ISSN: 1573-5028
    Keywords: chromatin ; gene expression ; high-mobility-group protein HMG1 ; HMGe ; protein stability ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nuclear HMG1 proteins of higher plants are small non-histone proteins that have DNA-bending activity and are considered architectural factors in chromatin. The occurrence of the chromosomal HMG1 proteins, HMGa, HMGc1/2 and HMGd, in various maize tissues was analyzed, and in the course of these studies a novel HMG1 protein, now termed HMGe, was identified. Purification and characterization of HMGe (Mr 13 655) and cloning of the corresponding cDNA revealed that it displays only moderate similarity to other members of the plant HMG1 protein family. The five maize HMG1 proteins could be detected in kernels, leaves, roots and suspension culture cells, indicating that these proteins can be expressed simultaneously and occur relatively ubiquitously. However, the various HMG1 proteins are present in significantly different quantities with HMGa and HMGc1/2 being the most abundant HMG1 proteins in all tissues tested. Furthermore, the relative amounts of the various HMG1 proteins differ among the tissues examined. The HMG1 proteins were found to be relatively stable proteins in vivo, with HMGc1/2, HMGd and HMGe having a half-life of ca. 50 h in cultured cells, while the half-life of the HMGa protein is ca. 65 h. Collectively, these findings are compatible with the concept that the different plant HMG1 proteins might act as general architectural proteins in concert with site-specific factors in the assembly of certain nucleoprotein structures involved in various biological processes.
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    URL: http://dx.doi.org/10.1023/A:1006311121717
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    Structure and expression of the gene family encoding putrescine N-methyltransferase in Nicotiana tabacum: new clues to the evolutionary origin of cultivated tobacco (1999)
    Springer
    Plant molecular biology 41 (1999), S. 387-401 
    Details
    ISSN: 1573-5028
    Keywords: alkaloids ; gene expression ; Nicotiana tabacum ; nicotine ; putrescine N-methyltransferase ; tobacco gene evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structure and nuclear genomic organization of the gene family encoding putrescine N-methyltransferase (PMT), the key enzyme in diverting polyamine metabolism towards the biosynthesis of nicotine and related alkaloids, was examined in Nicotiana tabacum. Five genes encoding PMT are present in the N. tabacum genome and all are expressed. The complete coding region and immediate 5′- and 3′- flanking regions were characterized for four members of the gene family and the Exon 1 region of the fifth member of the family was determined. Comparison of the nucleotide and deduced amino acid sequences of the N. tabacum PMT genes with those of presumed progenitor species, N. sylvestris, N. tomentosiformis and N. otophora, revealed that three members of the N. tabacum PMT gene family were most similar to the three genes present in N. sylvestris, whereas the two remaining PMT genes were similar to PMT genes present in N. tomentosiformis and N. otophora genomes, respectively. These data are consistent with an evolutionary origin of N. tabacum resulting from a cross involving N. sylvestris and an introgressed hybrid between N. tomentosiformis and N. otophora. The five PMT genes present in N. tabacum are expressed in the roots of wild-type plants, but not in other organs. The steady-state level of all five PMT transcripts is transiently increased in roots following topping (removal of the floral meristem), although the maximum level of induction for the individual transcripts varies considerably. In contrast to wild-type plants, no increase in PMT transcript levels was observed in a low-alkaloid (nic1nic2) mutant of Burley 21. These data support a role for nic1 and nic2 in the global regulation of alkaloid formation in tobacco and provide for the first time molecular confirmation of the presumed origin of cultivated tobacco.
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    URL: http://dx.doi.org/10.1023/A:1006342018991
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    Thiol redox state regulates expression of psbA genes in Synechococcus sp. PCC 7942 (1999)
    Springer
    Plant molecular biology 41 (1999), S. 425-433 
    Details
    ISSN: 1573-5028
    Keywords: D1 protein ; gene expression ; psbA genes ; redox regulation ; Synechococcus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three psbA genes encode two different forms of the photosystem II reaction centre protein D1 in Synechococcus sp. PCC 7942. The psbAI gene encoding D1 protein form I (D1:1) is mainly expressed under low growth light conditions while the psbAII and psbAIII genes, encoding D1 protein form II (D1:2), are induced under stress conditions (e.g. high light or low temperature). In this paper we show that psbAII/III genes can be rapidly induced even under low growth light conditions by adding the thiol reductant (DTTred) to Synechococcus cell culture, at a concentration that does not affect cell growth or photosynthetic activity. Similar induction of psbAII/III genes was obtained by illuminating the cells with photosystem I light. In both instances psbAI gene down-regulation coincided with the up-regulation of psbAII/III genes. DTTred-induced exchange in transcript pools was subsequently followed by an exchange of D1:1 for D1:2 at the protein level. Thiol oxidants, iodosobenzoic acid or diamide, reverted the effects of DTTred on psbA gene expression. Thiol oxidants and the thiol-modifying agent N-ethylmaleimide also totally prevented high-light induction of psbAII/III genes. These data strongly suggest that the up-regulation of psbAII/III genes that occurs under stress conditions is mediated by production of thiol reductants, whereas the expression of the psbAI gene is sustained by the more oxidizing conditions that prevail during the steady-state growth of cells.
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    URL: http://dx.doi.org/10.1023/A:1006347808475
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    Biochemical and molecular aspects of C/N interaction in ectomycorrhizal plants: an update (1999)
    Springer
    Plant and soil 215 (1999), S. 103-113 
    Details
    ISSN: 1573-5036
    Keywords: ammonium assimilation ; Amanita muscaria ; carbon allocation ; ectomycorrhiza ; gene expression ; Picea abies ; sugar transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The symbiosis (ectomycorrhiza, ECM) between roots of trees and shrubs of boreal and temperate forest ecosystems and soil fungi is essential for water and nutrient acquisition of the plants. The functionality of ECM is largely dependent on the ability of the host plant to supply photoassimilates to the fungus via the symbiotic interface. Based on sterile in vitro and non-sterile pot experiments, we review data which gives evidence that hexoses are supplied to the fungus by the host plant (mainly glucose and fructose), and that these sugars, at least in part, control development and function of ECM by interfering with fungal gene expression. We further show that any factor which reduces hexose allocation to the host–fungus interface will adversely affect ECM development. As an example, we address the impact of increased supply of nitrogen on the biochemistry of plant–fungus interaction and discuss potential consequences on host performance.
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    URL: http://dx.doi.org/10.1023/A:1004650324646
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    cDNA cloning and characterization of maize phosphoenolpyruvate carboxykinase, a bundle sheath cell-specific enzyme (1999)
    Springer
    Plant molecular biology 41 (1999), S. 301-311 
    Details
    ISSN: 1573-5028
    Keywords: bundle sheath cell ; C4 photosynthesis ; gene expression ; PEP carboxykinase ; prokaryotic expression ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We isolated a full-length cDNA that encodes ATP-dependent phosphoenolpyruvate carboxykinase (EC 4.1.1.49, PCK) from leaves of maize, an NADP-malic enzyme type C4 plant. The mRNA was specifically and rather abundantly expressed in bundle sheath cells in accordance with the recent finding of cell-type-specific localization of PCK protein in maize, which has been detected with antibodies against cucumber PCK protein. The predicted protein had an N-terminal extension, which is characteristic of plant PCKs. The transcript level was much higher in the daytime than at night in 14-day old seedlings. However, in 42-day old plants the extent of diurnal change decreased. The maize PCK was expressed in Escherichia coli with the pET32 plasmid and purified to homogeneity. Through digestion with enterokinase, two types of enzyme were prepared; one with an intact N-terminus and the other lacking its N-terminal 77 amino acid residues due to over-digestion. The truncated protein had about 2-fold higher specific activity than the intact one, and was inhibited by 3-phosphoglycerate (3-PGA) with an I0.5 of 17.5 mM. In contrast, the intact protein was almost insensitive to 3-PGA. These results strongly suggest that the intact N-terminal extension may be involved in the regulation of PCK activity in vivo through some modification such as reversible phosphorylation.
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    URL: http://dx.doi.org/10.1023/A:1006317120460
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    Rice calcium-dependent protein kinase isoforms OsCDPK2 and OsCDPK11 show different responses to light and different expression patterns during seed development (1999)
    Springer
    Plant molecular biology 41 (1999), S. 753-764 
    Details
    ISSN: 1573-5028
    Keywords: calcium-dependent protein kinase ; gene expression ; immunoassays ; light regulation ; rice ; seed development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated the spatial and temporal expression patterns of two rice calcium-dependent protein kinases (CDPKs), OsCDPK2 and OSCDPK11, using isoform-specific antisera. Bands of the expected molecular sizes for OsCDPK2 (59 kDa) and OsCDPK11 (61 kDa) were detected on western blots. OsCDPK2 and OsCDPK11 mRNA and protein levels increased in unison during flower development. However, at the onset of seed development, the protein expression profiles diverged significantly. OsCDPK2 protein was expressed at low levels during early seed development, but increased to high levels that were maintained in later stages (20 days after fertilisation, DAF). Conversely, OsCDPK11 protein levels were high at the beginning of seed development, but fell rapidly from 10 DAF onwards. This decrease in the level of OsCDPK11 protein was associated with the abundant synthesis of a truncated mRNA species. OsCDPK2 expression was also closely associated with light perception. OsCDPK2 protein was barely detectable in green leaves exposed to light, but levels increased sharply when plants were shifted to darkness. Initially, this increase reflected a rapid elevation in the levels of OsCDPK2 mRNA, which was normally located in the mesophyll. Conversely, OsCDPK11 mRNA and protein levels were unaffected by light. These data strongly indicate that two rice CDPK isoforms have different functions in seed development and in response to light in leaves.
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    URL: http://dx.doi.org/10.1023/A:1006316422400
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    Differential gene expression between wheat hybrids and their parental inbreds in seedling leaves (1999)
    Springer
    Euphytica 106 (1999), S. 117-123 
    Details
    ISSN: 1573-5060
    Keywords: differential display ; gene expression ; heterosis ; hybrid wheat ; seedling leaf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Differential display of mRNA was used to analyze the differences of gene expression in seedling leaves between heterotic hybrid/nonheterotic hybrid and their parental inbreds in order to study the molecular basis of heterosis in wheat. The results indicated that patterns of gene expression in hybrids differ significantly from their parents. Both quantitative and qualitative differences were observed. The quantitative differences include gene over-expression, gene under-expression in hybrid and dominant expression of highly-expressed parental genes in hybrids. The qualitative differences include silencing in hybrids of genes expressed either in male or female parent, and silencing in hybrids of genes expressed in both parents. Expression in hybrid of genes only expressed either in male or female parent was also observed. It was also found that some genes expressed at high level in heterotic hybrid were underexpressed or expressed at low level in nonheterotic hybrid. One differentially expressed cDNA fragment 4B was cloned and sequenced after being confirmed through Northern blot analysis. Homology search in GenBank proved that the cDNA fragment is a new sequence. The selection of primers for differential RNA display in wheat and the relationship between wheat heterosis and alteration of gene expression in hybrids as compared to their parental inbreds were also discussed.
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    URL: http://dx.doi.org/10.1023/A:1003548300088
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    Molecular analysis of acclimation to cold (1999)
    Springer
    Plant growth regulation 29 (1999), S. 47-76 
    Details
    ISSN: 1573-5087
    Keywords: cold ; chill ; freezing ; gene expression ; signal transduction pathways
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Temperature is expected to affect all plant processes. Consistent with this, expression of a large number of specific mRNAs and proteins is up-regulated during cold-acclimation. Their possible functions are outlined, encompassing a wide range of processes, some possibly related to other winter stresses besides cold. Some of the cold-responsive sequences are associated with constitutive or stress-related metabolism, others are probably protective, some may influence freezing, and many are of as yet unknown function. While many of the sequences code for intracellular proteins, a significant number code for apoplastic proteins with a variety of possible functions. Transient influx of calcium into the cytosol appears to be a key step in the response to cold, and also to many other stresses and signals. Similarly, the cold-responsive promoter element identified so far is also responsive to drought and salt. However, how cold is sensed, and any cold-specific aspects of the cold signal transduction pathway, are, so far, unknown. What is clear is that, at least in the model plant Arabidopsis thaliana, cold-, desiccation-, salt- and ABA-triggered signal transduction pathways, and possibly others, run partly in parallel and partly intersect. This may be partly explained by a need for an integrated winter-response. The total number of genes which are cold-responsive and the quantity of resources which this implies are used in this way, indicate that many must have a positive role in acclimation. Experiments which modify membrane lipid unsaturation or solute accumulation, achieved by transformation of plants to express exotic or heterologous genes or by other means, confirm that these factors affect chill- or freezing-tolerance. A transgenic test has shown that one cold-up-regulated gene of previously unknown function contributes to freezing-tolerance, but the small effect re-emphasises the probably cumulative nature of the contributions of many cold-up-regulated sequences to acclimation. On the other hand, mutant analysis indicates some genes may make a comparatively larger contribution. Transformation of alfalfa to overexpress a superoxide dismutase gene increased cold-tolerance and drought-resistance and demonstrated that improvements in field-survival of stresses is possible by transgenic means. Over-expression of a transcription factor, CBF1, conferred freezing-tolerance on Arabidopsis, showing that manipulation of the signal transduction pathway could be an important method for modifying cold-tolerance.
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    URL: http://dx.doi.org/10.1023/A:1006291330661
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    Cellular distribution of insulin-like growth factor II (IGF-II) mRNA and hormonal regulation of IGF-I and IGF-II mRNA expression in rainbow trout testis (Oncorhynchus mykiss) (1999)
    Springer
    Fish physiology and biochemistry 20 (1999), S. 219-229 
    Details
    ISSN: 1573-5168
    Keywords: fish ; gene expression ; GH ; GtH ; gonad ; growth factors ; RT-PCR ; salmonid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this study, Northern blot analysis of RNA from trout testis revealed a single transcript of insulin-like growth factor II (IGF-II) around 4.7 kb. The cellular distribution of IGF-II mRNA was studied and quantified in different testicular cells enriched populations by RT-PCR. IGF-II mRNA appears to be expressed in all cellular types tested: spermatogonia A and B, primary spermatocytes, spermatids and secondary spermatocytes and Sertoli cells. A significantly higher expression of IGF-II was found in premeiotic germ cells. The levels of IGF-II mRNA appear to be higher than those of IGF-I in immature trout testis, as judged from the semi-quantitative RT-PCR results. These data suggest that in addition to IGF-I, IGF-II may play a role in testicular physiology in fish. The hormonal regulation of IGF-I and IGF-II gene expression was investigated both in vitro and in vivo using RT-PCR approach. Gonadotropin (GtH) added to testicular explants increased IGF-II mRNA levels but had no effect on IGF-I. No statistically significant effect was observed with androgens. In vivo, GH and pituitary extracts resulted in an 8 fold and 2-3 fold increase in both IGF-I and IGF-II mRNA levels, respectively. Taken together, our study suggests that IGF-I and IGF-II may act as local mediators of GH and GtHs in fish testis. Moreover, our results imply that in fish testicular cells, IGFs are potential paracrine/autocrine regulators inside the spermatogenic compartment and can act directly on germ cells to stimulate their proliferation.
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    URL: http://dx.doi.org/10.1023/A:1007735314871
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    Uncoupling Protein 3: Its Possible Biological Role and Mode of Regulation in Rodents and Humans (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 467-473 
    Details
    ISSN: 1573-6881
    Keywords: Uncoupling proteins ; fatty acids ; skeletal muscle ; brown adipose tissue ; obesity ; thermogenesis ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The recently discovered uncoupling protein 3 (UCP3) is highly homologous to the mitochondrialinner membrane protein UCP1, which generates heat by uncoupling the respiratory chainfrom oxidative phosphorylation. The thermogenic function of UCP1 protects against cold andregulates the energy balance in rodents. We review in vitro studies investigating the uncouplingactivity of UCP3 and in vivo studies, which address UCP3 gene expression in brown adiposetissue and skeletal muscle under various metabolic conditions. The data presented are, for themost, consistent with an uncoupling role for UCP3 in regulatory thermogenesis. We alsodiscuss mediators of UCP3 regulation and propose a potential role for intracellular fatty acidsin the mechanism of UCP3 modulation. Finally, we hypothesize a role for UCP3 in themetabolic adaptation of the mitochondria to the degradation of fatty acids.
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    On the Stability of a Laminar Wall Jet with Heat Transfer (1999)
    Springer
    Flow, turbulence and combustion 62 (1999), S. 137-162 
    Details
    ISSN: 1573-1987
    Keywords: laminar wall jet ; heat transfer ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The hydrodynamic stability of a low speed, plane, non-isothermal laminar wall jet at a constant temperature boundary condition was investigated theoretically and experimentally. The mean velocity and temperature profiles used in the stability analysis were obtained by implementing the Illingworth–Stewartson transformation that allows one to extend the classical Glauert solution to a thermally non-uniform flow. The stability calculations showed that the two unstable eigenmodes coexisting at moderate Reynolds numbers are significantly affected by the heat transfer. Heating is destabilizing the flow while cooling is stabilizing it. However, the large-scale instabilities associated with the inflection point of the velocity profile still amplify in spite of the high level of the stabilizing temperature difference. The calculated stability characteristics of the wall jet with heat transfer were compared with experimental data. The comparison showed excellent agreement for small amplitudes of the imposed perturbations. The agreement is less good for the phase velocities of the sub-harmonic wave and this is attributed to experimental difficulties and to nonlinear effects.
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    Orbital Migration Of Giant Planets: Using Numerical Integration To Investigate Consequences For Other Bodies (1999)
    Springer
    Earth, moon and planets 87 (1999), S. 103-115 
    Details
    ISSN: 1573-0794
    Keywords: Accretion ; exoplanetary system ; extrasolar planets ; numerical integration ; orbital migration ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A number of extrasolar planets have been detected in close orbits around nearby stars. It is probable that these planets did not form in these orbits but migrated from their formation locations beyond the ice line. Orbital migration mechanisms involving angular momentum transfer through tidal interactions between the planets and circumstellar gas-dust disks or by gravitational interaction with a residual planetesimal disk together with several means of halting inward migration have been identified. These offer plausible schemes to explain the orbits of observed extrasolar giant planets and giant planets within the Solar System. Recent advances in numerical integration methods and in the power of computer workstations have allowed these techniques to be applied to modelling directly the mechanisms and consequences of orbital migration in the Solar System. There is now potential for these techniques also to be applied to modelling the consequences of the orbital migration of planets in the observed exoplanetary systems. In particular the detailed investigation of the stability of terrestrial planets in the habitable zone of these systems and the formation of terrestrial planets after the dissipation of the gas disk is now possible. The stability of terrestrial planets in the habitable zone of selected exoplanetary systems has been established and the possibility of the accretion of terrestrial planets in these systems is being investigated by the author in collaboration with Barrie W. Jones (Open University), and with John Chambers (NASA-Ames) and Mark Bailey of Armagh Observatory, using numerical integration. The direct simulation of orbital migration by planetesimal scattering must probably await faster hardware and/or more efficient algorithms.
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    URL: http://dx.doi.org/10.1023/A:1017996927696
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    Robust Stability of Multivariate Polynomials. Part 1: Small Coefficient Perturbations (1999)
    Springer
    Multidimensional systems and signal processing 10 (1999), S. 7-20 
    Details
    ISSN: 1573-0824
    Keywords: multivariate polynomials ; stability ; robust stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper presents a detailed analysis of some classes of stable multivariate polynomials. The main aim of the analysis is to give conditions under which polynomials preserve stability when they are subjected to small coefficient variations. The maximal class of such polynomials is introduced. Some basic properties of polynomials from this class are obtained.
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    URL: http://dx.doi.org/10.1023/A:1008456918178
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    Identification of disease response genes expressed in Gossypium hirsutum upon infection with the wilt pathogen Verticillium dahliae (1999)
    Springer
    Plant molecular biology 40 (1999), S. 289-296 
    Details
    ISSN: 1573-5028
    Keywords: gene expression ; Gossypium hirsutum ; plant defence response ; Verticillium dahliae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Verticillium wilt is a vascular disease of cotton (Gossypium spp.) caused by the fungal pathogen Verticillium dahliae. To begin to understand the molecular mechanisms of the disease response in cotton cultivars that display superior wilt tolerance, such as Gossypium hirsutum cv. Sicala V-1, a cDNA library was constructed with mRNA isolated from root tissue of Sicala V-1, 24 h after inoculation with V. dahliae. The library was screened by a differential screening technique which was successful in identifying differences in gene expression between uninfected and V. dahliae-infected G. hirsutum root tissue. Among the differentially expressed clones, 51% represented up-regulated genes which had the potential to be involved in the defence response of G. hirsutum. The temporal expression patterns of nine suspected defence response genes were examined by northern blot analysis at several time intervals after inoculation with V. dahliae. The rapid increase in mRNA transcripts corresponding to each of these clones upon infection suggests a role for these genes in the defence response of G. hirsutum. Genes not previously associated with the defence response of the cotton plant, such as those for a 14-3-3-like protein and pathogenesis-related (PR) proteins, have been identified together with presumably novel genes, for which a definite function could not be ascribed.
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    A transcript encoding translation initiation factor eIF-5A is stored in unfertilized egg cells of maize (1999)
    Springer
    Plant molecular biology 39 (1999), S. 1063-1071 
    Details
    ISSN: 1573-5028
    Keywords: cell cycle ; gene expression ; in vitro fertilization ; maize ; zygote ; embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Differential screening of cDNA libraries of unfertilized egg cells and in vitro zygotes of maize resulted in the isolation of more than 50 different genes whose expression is up- or down-regulated after in vitro fertilization (IVF). Amoung these genes, we identified a cDNA encoding the eukaryotic translation initiation factor eIF-5A. This highly conserved factor is thought to be necessary for selective mRNA stabilization and translation. It is also the only known protein that contains the unusual amino acid hypusine which is required for biological activity. High transcript amounts are stored in the egg cell, which is, in terms of metabolism, relatively inactive. Upon fertilization transcript amounts decrease, in contrast to metabolically inactive embryos in which the transcript cannot be detected and transcript levels increase upon germination. The expression pattern during the first embryonic cell cycle is also different from that observed during the somatic cell cycle: egg cells in the G0 phase contain high transcript levels, while arrested suspension cells contain few transcripts. In the somatic cell cycle, eif-5A is strongly induced during the G1 phase and transcripts are continuously degraded during the S, G2 and M phases until new induction during the G1 phase of the next cycle. eif-5A, a member of a small gene family in maize, is expressed in most maize tissues investigated. Based on our results, we suggest that the unfertilized egg cell of maize, although relatively inactive regarding its metabolism, is prepared for selective mRNA translation that is quickly triggered after fertilization. We also suggest that the regulation of eif-5A in the first embryonic cell cycle is different from the somatic cell cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006176819213
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  • 93
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    Characterization and expression of plasma and tonoplast membrane aquaporins in primed seed of Brassica napus during germination under stress conditions (1999)
    Springer
    Plant molecular biology 40 (1999), S. 635-644 
    Details
    ISSN: 1573-5028
    Keywords: aquaporin ; canola ; gene expression ; germination ; priming ; salt and osmotic stresses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two aquaporin genes were isolated from a cDNA library of canola (Brassica napus L.). The first aquaporin, BnPIP1 of 1094 bp, encoding a putative polypeptide of 287 amino acids with a predicted molecular mass of 30.4 kDa and a pI of 7.8, belongs to the family of plasma membrane intrinsic protein (PIPs) aquaporins. The B. napus aquaporin showed 85–94% identity to the Arabidopsis thaliana PIPs. ABA priming of seed induced high levels of BnPIP1 transcript which remained after subsequent re-drying of the seed. The second aquaporin, Bnγ-TIP2 of 1020 bp, encoded a putative polypeptide of 253 amino acids with a predicted molecular mass of 25.8 kDa and a pI of 5.8. Bnγ-TIP2 showed 83–90% identity to γ-TIP genes from a variety of plant species. Bnγ-TIP2 was expressed only when radicle protrusion occurred in either untreated or primed seeds. Seeds primed with PEG or ABA germinated earlier and showed a higher final percentage of germination than unprimed seed, particularly under salt and osmotic stresses at low temperature. Transcripts of both BnPIP1 and Bnγ-TIP2 genes were present earlier during germination of primed seeds than non-primed seed. From these results, we conclude that BnPIP1 is related to the water transportation required for enzymatic metabolism of storage nutrients at the early stages of canola seed germination whereas Bnγ-TIP2 expression is related to cell growth associated with radicle protrusion. Priming induced the expression of BnPIP1 but had no effect on Bnγ-TIP2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006212216876
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  • 94
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    The promoter of a Brassica napus lipid transfer protein gene is active in a range of tissues and stimulated by light and viral infection in transgenic Arabidopsis (1999)
    Springer
    Plant molecular biology 41 (1999), S. 75-87 
    Details
    ISSN: 1573-5028
    Keywords: Brassica napus ; cauliflower mosaic virus ; epidermis ; gene expression ; light induction ; lipid transfer protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract cDNA and genomic clones encoding Brassica napus non-specific lipid transfer proteins (LTP) were isolated and sequenced. The encoded amino acid sequences were very similar to those reported previously for LTPs from B. napus and other species. Sequence information indicates that B. napus contains an LTP gene family. The 5′-flanking region of one gene, designated BnLTP, was fused to GUS and the fusion introduced into Arabidopsis. LTP transcripts and BnLTP-Gus expression were present predominantly in the epidermis of leaf and stem, consistent with the hypothesised function of LTPs in the deposition of cuticular or epicuticular waxes. However, GUS activity was detected in other tissues, including lateral root initials, anthers, stigmas and vascular tissues, which may suggest additional functions. LTP transcript levels in B. napus and Arabidopsis and BnLTP-GUS expression in transgenic Arabidopsis were stimulated by blue and red light but not UV-B. BnLTP promoter activity was also stimulated upon viral infection, at a time when the virus had spread systemically. No increase in expression was observed in response to cold or wounding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006232700835
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  • 95
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    Auxin and brassinosteroid differentially regulate the expression of three members of the 1-aminocyclopropane-1-carboxylate synthase gene family in mung bean (Vigna radiata L.) (1999)
    Springer
    Plant molecular biology 41 (1999), S. 443-454 
    Details
    ISSN: 1573-5028
    Keywords: 1-aminocyclopropane-1-carboxylate synthase ; auxin ; brassinosteroid ; ethylene ; gene expression ; hypocotyl ; promoter ; transgenic tobacco ; Vigna radiata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Indole-3-acetic acid (IAA) markedly increased ethylene production by inducing the expression of three 1-aminocyclopropane-1-carboxylate (ACC) synthase cDNAs (pVR-ACS1, pVR-ACS6 and pVR-ACS7) in mung bean hypocotyls. Results from nuclear run-on transcription assay and RNA gel blot studies revealed that all three genes were transcriptionally active displaying unique patterns of induction by IAA and various hormones in etiolated hypocotyls. Particularly, 24-epibrassinolide (BR), an active brassinosteroid, specifically enhanced the expression of VR-ACS7 by a distinct temporal induction mechanism compared to that of IAA. In addition, BR synergistically increased the IAA-induced VR-ACS6 and VR-ACS7 transcript levels, while it effectively abolished both the IAA- and kinetin-induced accumulation of VR-ACS1 mRNA. In light-grown plants, VR-ACS1 was induced by IAA in roots, and VR-ACS6 in epicotyls. IAA- and BR-treatments were not able to increase the VR-ACS7 transcript in the light-grown tissues. These results indicate that the expression of ACC synthase multigene family is regulated by complex hormonal and developmental networks in a gene- and tissue-specific manner in mung bean plants. The VR-ACS7 gene was isolated, and chimeric fusion between the 2.4 kb 5′-upstream region and the β-glucuronidase (GUS) reporter gene was constructed and introduced into Nicotiana tabacum. Analysis of transgenic tobacco plants revealed the VR-ACS7 promoter-driven GUS activity at a highly localized region of the hypocotyl-root junction of control seedlings, while a marked induction of GUS activity was detected only in the hypocotyl region of the IAA-treated transgenic seedlings where rapid cell elongation occurs. Although there was a modest synergistic effect of BR on the IAA-induced GUS activity, BR alone failed to increase the GUS activity, suggesting that induction of VR-ACS7 occurs via separate signaling pathways in response to IAA and BR. A scheme of the multiple regulatory pathways for the expression of ACC synthase multigene family by auxin and BR is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006372612574
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  • 96
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    Optimisation of procedures for microprojectile bombardment of microspore-derived embryos in wheat (1999)
    Springer
    Plant cell, tissue and organ culture 57 (1999), S. 207-210 
    Details
    ISSN: 1573-5044
    Keywords: biolistics ; gene expression ; haploid ; transformation ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using the PDS-1000/He Biolistic® Particle Delivery System, the microprojectile travel distance, rupture disk pressure and DNA/gold particle concentrations were assessed in order to optimise short and longer-term β-glucuronidase reporter gene expression in microspore-derived embryos of wheat. The effects were also evaluated of using sterile filter paper to support explants and treatment with a high osmoticum medium (0.2 M mannitol/0.2 M sorbitol or 0.4 M maltose). In the optimised procedure, wheat microspore-derived embryos (MDEs), were placed on filter paper and incubated on medium containing 0.4 M maltose, for 4 h pre- and 45 h post-bombardment. Five μl pAHC25 (0.75 mg ml-1 in TE buffer) was precipitated onto 25 μl gold particles (60 mg ml-1 in sterile water), using 20 μl spermidine (0.1 M) and 50 μl CaCl2 (2.5 M). The particles were centrifuged and resuspended in 75 μl absolute ethanol prior to the preparation of 6 macrocarriers. A microprojectile travel distance of 70 mm, a rupture pressure of 1300 p.s.i., and a vacuum of 29′′ Hg were employed. Maltose at 0.4 M in the support medium was the most important factor influencing GUS activity in bombarded tissues. GUS activity, 1 day post-bombardment, reached 52 ± 17 GUS-positive foci/MDE (mean ± s.e.m, n=3), with 17 ± 4 foci/MDE at 15 days, giving a 3.0-fold increase (p〈0.05) compared to expression in MDEs bombarded on medium without a high osmoticum treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006384525513
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  • 97
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    Stability and resilience in benthic macroinvertebrate assemblages (1999)
    Springer
    Hydrobiologia 403 (1999), S. 123-133 
    Details
    ISSN: 1573-5117
    Keywords: disturbance ; stability ; resilience ; Trichoptera ; Ephemeroptera ; Psychomyia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Benthic macroinvertebrate assemblages of Bushkill Creek, Northampton County, PA were studied at the same site during the 1970s (11 dates) and 1990s (8 dates) to evaluate stability and resilience. In the 1970s, a Surber sampler was used, and in the 1990s, a Hess sampler. Assemblages appeared stable over a wide range of environmental stresses with the exception of 1994–1995 when total numbers and total Trichoptera decreased. Taxa richness and EPT indices varied little in 1994–1995 from other sampled years. By July 1996, all metrics (Trichoptera numbers, total numbers, taxa richness, EPT index, Bray-Curtis Index) resembled the 1970s exception for lower wet weight. Bray-Curtis indices and taxa composition were similar in July 1972 and July 1996, suggesting assemblage stability over 25 years. The Trichoptera, Psychomyia (Psychomiidae) and Leucotrichia (Hydroptilidae), decreased during the 1990s and never rebounded to 1970s numbers. During winter 1994, the coldest temperatures and greatest cumulative snowfall occurred in the region. These conditions probably stressed the assemblage with low temperatures, anchor/frazil ice and ice break-up. The assemblage was then exposed to four bankful floods in winter/spring 1994 and five bankful floods in winter/spring 1996. Recovery time following these multiple disturbances was 27 months. Previous recovery times from winter and flood disturbances were considerably shorter (2–5 months). The 1990s recovery time (5–9 times previusly recorded) for this assemblage was apparently extended by multiple physical disturbances, outside the predicted range. The assemblages had not been previously exposed to such severe conditions and, therefore, recovery time was extended. Despite severe weather conditions, the assemblage recovered and exhibited both stability and resilience in its return to an assemblage similar to the 1970s.
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    URL: http://dx.doi.org/10.1023/A:1003711928980
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  • 98
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    Predictivity of an in vitro model for acute and chronic skin irritation (SkinEthic) applied to the testing of topical vehicles (1999)
    Springer
    Cell biology and toxicology 15 (1999), S. 121-135 
    Details
    ISSN: 1573-6822
    Keywords: cytokines ; gene expression ; in vitro human epidermis ; acute and chronic skin irritation ; predictivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract An in vitro human reconstructed epidermis model (SkinEthic) used for screening acute and chronic skin irritation potential was validated against in vivo data from skin tolerability studies. The irritation potential of sodium lauryl sulfate (SLS), calcipotriol and trans-retinoic acid was investigated. The in vitro epidermis-like model consists of cultures of keratinocytes from human foreskin on a polycarbonate filter. The modulation of cell viability, the release and gene expression of proinflammatory cytokines, interleukins 1α and 8, and morphological changes were evaluated during 3 days as endpoints representative for an inflammatory reaction. The cumulative irritation potential of the topical products was evaluated in a human clinical study by visual scoring and biophysical measurement of inflammatory skin reaction after repeated 24 h applications over 3 weeks under Finn chamber patches. All topical products that were nonirritating in the human study were noncytotoxic and did not induce cytokine expression in the in vitro acute model (day 1 exposure). All irritating controls exhibited specific cell viability and cytokine patterns, which were predictive of the in vivo human data. The ranking of mild to moderate skin irritation potential was based on the lack of cytotoxicity and the presence of cytokine patterns including gene expression specific for each irritant, using the chronic in vitro model (up to 3 days exposure). The human reconstructed epidermis model SkinEthic was shown to be a reliable preclinical tool predicting the irritation potential of topical products. Moreover, it is a useful model in a two-step tiered strategy for screening acute and chronic irritation potential for the selection of vehicles for new topical drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007577515215
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  • 99
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    Biochemical and Molecular Characteristics of the Brain with Developing Cerebral Infarction (1999)
    Springer
    Cellular and molecular neurobiology 19 (1999), S. 93-108 
    Details
    ISSN: 1573-6830
    Keywords: focal cerebral ischemia ; cerebral infarction ; penumbra ; gene expression ; stress response ; inflammatory reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. We review the biochemical and molecular changes in brain with developing cerebral infarction, based on recent findings in experimental focal cerebral ischemia. 2. Occlusion of a cerebral artery produces focal ischemia with a gradual decline of blood flow, differentiating a severely ischemic core where infarct develops rapidly and an area peripheral to the core where the blood flow reduction is moderate (called penumbra). Neuronal injury in the penumbra is essentially reversible but only for several hours. The penumbra area tolerates a longer duration of ischemia than the core and may be salvageable by pharmacological agents such as glutamate antagonists or prompt reperfusion. 3. Upon reperfusion, brain cells alter their genomic properties so that protein synthesis becomes restricted to a small number of proteins such as stress proteins. Induction of the stress response is considered to be a rescue program to help to mitigate neuronal injury and to endow the cells with resistance to subsequent ischemic stress. The challenge now is to determine how the neuroprotection conferred by prior sublethal ischemia is achieved so that rational strategies can be developed to detect and manipulate gene expression in brain cells vulnerable to ischemia. 4. Expansion of infarction may be caused by an apoptotic mechanism. Investigation of apoptosis may also help in designing novel molecular strategies to prevent ischemic cell death. 5. Ischemia/reperfusion injury is accompanied by inflammatory reactions induced by neutrophils and monocytes/macrophages infiltrated and accumulated in ischemic areas. When the role of the inflammatory/immune systems in ischemic brain injury is revealed, new therapeutic targets and agents will emerge to complement and synergize with pharmacological intervention directed against glutamate and Ca2+ neurotoxicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006920725663
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  • 100
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    Biochemical Responses and Altered Genetic Expression Patterns in Ponderosa Pine (Pinus ponderosa Doug ex P. Laws) Grown Under Elevated CO2 (1999)
    Springer
    Water, air & soil pollution 116 (1999), S. 413-422 
    Details
    ISSN: 1573-2932
    Keywords: Ponderosa pine ; elevated CO2 ; growth ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Biochemical and gene expression changes in response to elevated atmospheric CO2 were investigated in five maternal half-sibling breeding families of Ponderosa pine. Seedlings were grown in a common garden located at Lawrence Livermore National Laboratory, in open-topped chambers (OTC) for two years. Chamber atmospheres were maintained at ambient, ambient + 175 μL L-1, CO2, or ambient + 350 μL L-1CO2. Growth measurements showed significant increases in stem volumes and volume enhancement ratios in three of the five families studied when grown under elevated CO2. Biochemical and gene expression studies were undertaken to gain a mechanistic understanding of these phenotypic responses. Biochemical studies focused on sucrose phosphate synthase (SPS) specific activities at increase CO2 levels. Kinetic evaluations of SPS showed an increase in VMax. Specific SPS probes revealed increases in the transcriptional levels of one SPS gene with exposure to increasing CO2. RT-PCR differential gene displays showed that overall only a small fraction of visualized gene transcripts responded to elevated CO2 (8-10%). There were also significant differences between the gene expression patterns of the different families, some of which correlated with alterations in growth at elevated CO2 levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005207112589
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