Human immunodeficiency virus type 1 efficiently binds to human fetal astrocytes and induces neuroinflammatory responses independent of infection

<p>Abstract</p> <p>Background</p> <p>HIV-1 infects human astrocytes <it>in vitro </it>and <it>in vivo </it>but the frequency of infected cells is low and its biological significance is unknown. In studies <it>in vitro</it>, recombinant gp120 alone can induce profound effects on astrocyte biology, suggesting that HIV-1 interaction with astrocytes and its functional consequences extend beyond the limited levels of infection in these cells. Here we determined the relative efficiencies of HIV-1 binding and infection in human fetal astrocytes (HFA), mainly at the single cell level, using HIV-1 tagged with green fluorescence protein (GFP)-Vpr fusion proteins, termed HIV-GFP, to detect virus binding and HIV-1 expressing Rev and NefGFP fusion proteins to detect productive infection.</p> <p>Results</p> <p>Essentially all HFA in a population bound HIV-GFP specifically and independently of CCR5 and CXCR4. The dynamics of this binding at 37°C resembled binding of an HIV fusion mutant to CD4-positive cells, indicating that most of HIV-GFP arrested infection of HFA at the stage of virus-cell fusion. Despite extensive binding, only about 1% of HFA were detectably infected by HIV-RevGFP or HIV-NefGFP, but this proportion increased to the majority of HFA when the viruses were pseudotyped with vesicular stomatitis virus envelope glycoprotein G, confirming that HFA impose a restriction upon HIV-1 entry. Exposure of HFA to HIV-1 through its native proteins rapidly induced synthesis of interleukin-6 and interleukin-8 with increased mRNA detected within 3 h and increased protein detected within 18 h of exposure.</p> <p>Conclusion</p> <p>Our results indicate that HIV-1 binding to human astrocytes, although extensive, is not generally followed by virus entry and replication. Astrocytes respond to HIV-1 binding by rapidly increased cytokine production suggesting a role of this virus-brain cell interaction in HIV-1 neuropathogenesis.</p

On vibrational stabilizability of nonlinear systems

Conditions of vibrational stabilizability for trivial solutions of nonlinear systems are derived. Several examples based on the classical equations of the theory of oscillations are given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45223/1/10957_2004_Article_BF00939147.pd

Approximate local output regulation for nonlinear distributed parameter systems

Output regulation for a class of nonlinear infinite-dimensional systems, called regular nonlinear systems (RNS), is the subject of this work. For the plants in this class, the linearization at the origin is an exponentially stable regular linear system (RLS). The plants are driven by a control input and a disturbance signal. Well-posedness of the plants for small initial states, control inputs and disturbance signals is established and it is shown that if the control input and the disturbance signal for a plant are T-periodic, then so are its state and output (asymptotically). On the basis of this characterization, an approximate local output regulator problem for multi-input multi-output (MIMO) plants in the RNS class is addressed. Given a plant, the regulation objective is to ensure that a finite number of harmonics of a T-periodic reference signal and the plant output are identical whenever the reference signal, the T-periodic disturbance signal for this plant and the initial state are small. An internal model based output feedback control scheme is proposed for an exponentially stable RLS for tracking reference signals, which are a finite sum of functions that are a product of a sinusoid and a polynomial in time. This scheme merely uses the transfer function gains of the RLS at the poles of the Laplace transform of the reference signal and practically requires no other data. Using the proposed control scheme, a linear finite-dimensional controller is designed for a MIMO nonlinear plant in the RNS class using minimal plant information. The resulting closed-loop system is rigorously analyzed to establish that the controller achieves the regulation objective. The efficacy of the control design is illustrated numerically using the model of a cable coupled to a point mass via a nonlinear spring

Models of stochastic systems in control systems robotics and automation

This entry looks at models of stochastic systems in control systems robotics and automatio

Experiment With Vibrational Control of a Laser Illuminated Thermochemical System

1 Vibrational control is an open-loop control technique which utilizes zero mean parametric excitations to modify the behavior of dynamical systems in a desired manner. A potential applicability of vibrational control to laser illuminated thermochemical systems has been recently demonstrated analytically by Bentsman and Hvostov (1988 I Introduction Vibrational control introduced by In recent years there has appeared a considerable interest in laser-induced chemical reactions due to their wide applicability to various technological systems. A distinctive feature of these reactions is an easily modulated laser beam power which can serve as a natural actuator in their control. The first experimental control study of a laser-induced reaction was reported by This reaction is known (cf. Zimmerman and Ross, 1983) to exhibit bistable behavior characterized by a significant instability region and multiple steady states. I