The influence of volume on gastric emptying and fluid balance during prolonged exercise.

The purpose of this study was to determine the effect of ingesting approximately 800, 1200, or 1600 ml.h-1 of a carbohydrate (CHO) solution on gastric emptying (GE), ratings of stomach fullness (RF), plasma volume changes (PVC), electrolytes, fluid loss, and blood glucose (BG) during 2 h of cycling at 70% of VO2max. Eight male cyclists completed three rides during which they ingested either 11.5 (LV), 17.1 (MV), or 23 ml.kg-1.h-1 (HV) of a 7.5% CHO solution every 15 min. Blood samples were taken at 0, 60, 90, and 120 min and 15 min after the ride for the determination of PVC, sodium (Na+), potassium (K+), and BG. Body weight was recorded before and after the rides to determine dehydration. Rates of GE were determined via stomach aspiration after the rides. A significantly (P less than 0.05) greater volume of fluid was emptied in the HV trial (2268 +/- 70.8 ml) compared with the MV and LV trials (1860 +/- 72 and 1452 +/- 24 ml, respectively). The rate of GE in the MV trial was also significantly greater than in the LV trial. RF were significantly higher in the MV and HV trials compared with the LV trial throughout the rides. There were no significant differences in PVC (0.01 +/- 2.2%, 1.05 +/- 1.62%, and 0.97 +/- 1.28% for LV, MV, and HV, respectively), Na+, K+, or BG between the three trials. There was a significantly greater decrease in body weight in the LV (-0.77 +/- 0.14 kg) compared with the MV and HV trials (-0.38 +/- 0.13 and -0.14 +/- 0.14 kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of acetate and propionate formation upon aeration of resting cells of the anaerobic Propionibacterium shermanii: evidence of the Pasteur reaction.

When resting cell suspensions of the anaerobic P. shermanii were brought to an oxygen concentration of 0.64 mumoles/ml, acid formation was completely inhibited. The cells started to respire on the propionic acid previously accumulated furing anaerobiosis. Glucose consumption was concomitantly decreased to about 60 percent of the rate during anaerobiosis. As the viability of the cells was not affected by the transition to aerobic conditions, the changes observed upon aeration were ascribed to the regulatory properties of the Pasteur reaction. Damage inflicted by oxygen was encountered in the rapid inactivation of propionate respiration. This damage outlived the time of oxygenation, and was manifested during the subsequent anaerobiosis in the decreased activity to form propionate. This indicates that oxygen may inactivate one (or more) enzyme(s) involved in the metabolism of propionate. The viability of cells in buffer, and glucose-containing buffer, was found to be only insignificantly decreased by oxygen in the range from 0 to 500 mumoles of oxygen per g of wet cells.