Exercise-induced hypoxaemia in master athletes: effects of a polyunsaturated fatty acid diet

Exercise-induced hypoxaemia (EIH) has been associated with an oxygen diffusion limitation. Because polyunsaturated fatty acids (PUFA) administration can modify cell membrane fluidity, we hypothesized that the importance of EIH could be reduced after a 6-week PUFA diet. Resting pulmonary functions and a maximal cycling test were performed before and after the diet, in eight master athletes [48 (SD 6 years)]. The partial pressure. of O₂ in arterial blood (PaO₂), alveolar ventilation ( ) and ideal alveolar-arterial oxygen partial pressure difference (P(A _i–a)O₂) were obtained at each exercise intensity. The extent of EIH at maximal exercise was significantly lower after PUFA [P_aO₂ –17.2 (SEM 1.9) vs –12.9 (SEM 2.2)]. Before PUFA, accounted for 50% of the variance in the fall inP(A _i–a) for intensities below 80% maximal oxygen uptake ( ) andP(A _i–a)O₂ for 60% between 70% and 100% . After PUFA, the reduction in EIH was highly correlated (r ² = 0.85;P < 0.001) to resulting changes inP(A_ii–a)O₂ and resting pulmonary diffusing capacity but not with changes in ideal alveolar partial pressure of oxygen. The improvement in EIH following PUFA could be related to an increase in alveolar-arterial oxygen conductance following improved pulmonary diffusion.     

Platelets and bronchospasm

The intrathoracic accumulation of radiolabelled platelets and concomitant changes in airway resistance have been recorded continuously in anaesthetised guinea pigs. Platelet-activating factor (PAF-acether) and antigen (in sensitised animals) elicited dose-related intrathoracic accumulation of platelets that could be associated with an increase in airway resistance. Maximal increases in airway resistance preceded maximal increases in platelet accumulation. Low doses of antigen could elicit substantial platelet accumulation, without detectable changes in lung function. It is concluded that physical obstruction of the pulmonary vasculature is not the sole determinant of platelet-dependent bronchoconstriction.     

A longitudinal study of gamma-interferon production by peripheral blood mononuclear cells from breast- and bottle-fed infants.

Production of gamma-interferon (gamma-IFN) in vitro by peripheral blood mononuclear cells (PBMC) from 15 breast-fed and 15 bottle-fed infants has been studied from birth to 9 months of age and compared with production by adult cells. Using a Terasaki plate microculture system with serum-free medium, PBMC were stimulated with staphylococcal enterotoxin A (SEA) and gamma-IFN production was assessed by an immunoradiometric assay. Cord blood mononuclear cells (CBMC) and PBMC from all infants secreted large quantities of gamma-IFN. The levels secreted did not change significantly with age over the 9 months of the study, nor did they differ from the levels secreted by adult cells. Cells from the bottle-fed infants secreted slightly more gamma-IFN than cells from breast-fed infants, but this difference was not significant. These results indicate that the potential for PBMC to secrete gamma-IFN in vitro is fully developed at birth in full-term infants and cannot therefore be further influenced by subsequent breast- or bottle-feeding. In addition, the greater susceptibility of infants than adults to certain bacterial and viral infections cannot be attributed to a deficiency in the potential of infant cells to secrete gamma-IFN in vitro.