Adenosine coordinates organ metabolism and blood supply, and it modulates immune responses. In the kidney it mediates the vascular response elicited by changes in NaCl concentration in the macula densa region of the nephron, thereby serving as an important regulator of GFR. To determine whether adenosine formation depends on extracellular nucleotide hydrolysis, we studied NaCl-dependent GFR regulation (tubuloglomerular feedback) in mice with targeted deletion of ecto-5′-nucleotidase/CD73 (e-5′NT/CD73), the enzyme responsible for adenosine formation from AMP. e-5′NT/CD73–/– mice were viable and showed no gross anatomical abnormalities. Blood pressure, blood and urine chemistry, and renal blood flow were not different between e-5′NT/CD73+/+ and e-5′NT/CD73–/– mice. e-5′NT/CD73–/– mice had a significantly reduced fall in stop flow pressure and superficial nephron glomerular filtration rate in response to a saturating increase of tubular perfusion flow. Furthermore, whereas tubuloglomerular feedback responses did not change significantly during prolonged loop of Henle perfusion in e-5′NT/CD73+/+ mice, a complete disappearance of the residual feedback response was noted in e-5′NT/CD73–/– mice over 10 minutes of perfusion. The contractile response of isolated afferent arterioles to adenosine was normal in e-5′NT/CD73–/– mice. We conclude that the generation of adenosine at the glomerular pole depends to a major extent on e-5′NT/CD73–mediated dephosphorylation of 5′-AMP, presumably generated from released ATP
SUMMARYA uniÿed mathematical framework, sustained by experimental results, is presented for robust controller design taking into account the constraint on the control signal. The design procedure is exempliÿed for an active vibration suppression control problem with applications to exible structures. The considered experimental set-up is a three-storey exible structure with an active mass driver placed on the last storey. First, the considered exible structure is identiÿed and the model's parametric uncertainties are deduced. Next, control constraints are presented for the robust control design problem, taking into account the restriction imposed on the control signal. Finally, the e ectiveness of the control system is tested through experiments, when the input disturbance is assumed to be a sinusoidal one as well as a historical earthquake record (1940 El Centro record).
SUMMARYThe paper deals with gray box identiÿcation of exible structures and active vibration suppression from a robust control perspective. First, the linearized mathematical model of an N -storey exible structure is presented. Next, the generalized mathematical model is particularized for the investigated three-storey exible structure. The considered exible structure is identiÿed based on black box and gray box identiÿcation methods and the model's parametric uncertainties are deduced. Furthermore, control constraints are presented for the design problem, in case of velocity as well as acceleration feedback, from a robust control perspective. Finally, the e ectiveness of the control system is tested through experiments, when the input disturbance is assumed to be a sinusoidal one as well as a historical earthquake record (1940 El Centro record).
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