In frog sartorius muscle, after a tetanus at 20°C, during which an impulse-like increase occurs in the rate of ATP hydrolysis, the rate of 02 consumption (Qo,) reaches a peak relatively quickly and then declines monoexponentially, with a time constant not dependent on the tetanus duration (T = 2 .6 min in Rana pipiens and 2 .1 min in Rana temporaria). To a good approximation, these kinetics are those of a first-order impulse response, and the scheme of reactions that couple 02 consumption to extramitochondrial ATP hydrolysis thus behaves as a first-order system . It is first deduced and then demonstrated directly that while Qo,(t) is monoexponential, it changes in parallel with the levels of creatine and phosphorylcreatine, with proportionality constants ±1/Tp, where p is the P/02 ratio in vivo . From this, it is further deduced that the mitochondrial creatine kinase (CK) reaction is pseudo-first order in vivo . The relationship between [creatine] and Qo, predicted by published models of the control of respiration is markedly different from that actually observed . As shown here, the first-order kinetics of Qo, are consistent with the hypothesis that respiration is rate-limited by the mitochondrial CK reaction ; this has as a corollary the "creatine shuttle" hypothesis .

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Dysmetabolism in specific regions of the right prefrontal cortex may be associated with delusional thought in Alzheimer's disease. Delusions appear to reflect the pathophysiologic state of particular cortical regions. Activity across distributed neuronal networks and the specific content of delusional thoughts may modulate these relationships.

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The NRS is a useful instrument for structured assessment of a broad range of cognitive, psychiatric, and behavioral disturbances in patients with dementia.