They served to determine the levels of passive diffusion and possible spontaneous breakdown of the labeled glucose as well as the background of the radioactivity counter. At the end of incubation, the NaHCO3 fraction was collected quickly in scintillation vials containing 200 ^l of 0.1 M NaOH, which promoted the conversion of dissolved CO2 and bicarbonate into carbonate. After an overnight incubation, 10 ml of scintillation cocktail (Lumagel) was added to the vials, and the radioactivity was counted. birth control yasmin
The mean cpm of the sham preparations was subtracted from the cpm obtained for each batch of spermatozoa. The difference obtained, which was representative of the metabolism of the spermatozoa, was divided by the total cpm of labeled glucose and multiplied by the total quantity of glucose present in the 3-^l droplet. Although the metabolism of [1-14C]glucose by spermatozoa gave low cpm, they repeatedly exceeded the cpm of the sham preparations by 50-100% when the numbers of spermatozoa were sufficient. In the cases in which the cpm values obtained after sperm incubation were not different from the values of the sham preparations, the 14CO2 production was considered undetectable.