Evaluation of dynamic changes in pH and concentrations of adenosine 5'-triphosphate (ATP), phosphocreatine (PCr), and inorganic phosphate (Pi) during the transition from rest to steady-state exercise in the human has been methodologically limited. Previous work has relied on muscle biopsy of exercising subjects at different times in different exercise bouts. Chemical evaluation of metabolites has been hampered by continuing change in metabolic concentration during the biopsy procedure. Recently, Fourier-transformed 31P nuclear magnetic resonance (31P-NMR), employing surface coils, has made evaluation of phosphorus metabolites possible by noninvasive atraumatic means in human muscle. Relative concentrations of PCr, Pi, and ATP, together with pH, have been obtained with 31P-NMR from the flexor digitorum superficialis muscle on two occasions in four adult men during the transition from rest to exercise. [PCr] rapidly fell and was mirrored by a rise in [Pi]. The former temporarily exceeded the latter with the discrepancy apparently being absorbed by a transient rise in [ATP], which was itself mirrored by alteration in [H+].

In this study we investigated a possible mechanism of the human airway inflammatory response to inhaled ozone (O(3)). Cultures of human nasal epithelial (HNE) cells, initiated from excised nasal turbinates and grown on collagen-coated Transwell tissue culture inserts, were exposed to 120, 240, or 500 ppb O(3) for 3 h. An electron spin resonance (ESR) signal that changed with time suggested free radical production in HNE cells exposed to O(3). Nuclear protein extracts were analyzed for the activated transcription factor NF-kappaB by electrophoretic mobility-shift assay (EMSA), and showed a small dose-response activation of NF-kappaB that coincided with O(3)-induced free radical production. Basal media were analyzed for the presence of tumor necrosis factor-alpha (TNF-alpha) using the enzyme-linked immunosorbent assay (ELISA). In cultures exposed to 120 ppb O(3), the mean TNF-alpha concentration was not significantly different from those exposed to air. However, exposure to 240 and 500 ppb O(3) significantly increased mean TNF-alpha expression, relative to controls, 16 h after exposure. These results support the hypothesis that the human airway epithelium plays a role in directing the inflammatory response to inhaled O(3) via free radical-mediated NF-kappaB activation.

Ripening of avocado fruit is associated with a dramatic increase in respiration. In vivo 31P nuclear magnetic resonance spectroscopy revealed large increases in ATP levels accompanying the increase in respiration. Both glycolytic enzymes, phosphofructokinase, and pyrophosphate: fructose-6-phosphate phosphotransferase were present in avocado fruit with the latter activity being highly stimulated by fructose 2,6-bisphosphate. Fructose 2,6-bisphosphate levels increased approximately 90% at the onset of ripening, suggesting that the respiratory increase in ripening avocado fruit may be regulated by the activation of pyrophosphate:fructose-6-phosphate phosphotransferase by an increase in fructose 2,6-bisphosphate.

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