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Renal ammonia production was followed in vivo in 7 dogs after the acute administration of acetazolamide. Acetazolamide at various doses decreased average renal ammoniagenesis to 55% of control and decreased ammonium excretion even more, to 18% of control. This discrepancy occurred because diffusion of ammonia into the urine was severely reduced while renal venous release was influenced little. Therefore, inhibition of ammonium excretion in dogs by acetazolamide took place because the drug both diverted ammonia from the urine and inhibited ammoniagenesis. Decreased renal ammoniagenesis could not be explained entirely by a decreased functioning mass, and it was not explicable on the basis of inhibited glutamyl transferase or stimulated glutamine synthetase in vivo or in vitro.

The process of polymeric materials production may lead to material heterogeneities. Therefore, the mechanical behavior of these materials may present unique characteristics from point to point. Nevertheless, this characteristic is rarely taken into account inasmuch as, in general, most model building strategies assumes material homogeneity when performing inverse analysis. Furthermore, the dimensions of the test specimens may not be appropriate to evaluate the levels of heterogeneity within the material. This work investigates the impact of viscoelastic material heterogeneities when these are used to build laminated structures commonly used as passive vibration components. The viscoelastic behavior is modeled by means of a fractional derivative constitutive equation. The heterogeneity of the media is modeled by means of stochastic fields. Two types of correlations are considered to model the covariance matrices. A numerical application is presented for a three-layer laminated structure with a viscoelastic core.