The oxygen consumption of spermatozoa from the caudae epididymides of the mouse was measured in various media and in the presence or absence of substrates and inhibitory agents in order to investigate the relationship between oxidative metabolism and capacitation. When washed sperm were placed in a medium in which capacitation occurs, respiration increased abruptly, due to the availability of oxidizable substrates, and remained at a high, constant level throughout the period of measurement. There was no temporal change in rate during the time when capacitation was occurring, nor was the rate after capacitation had occurred higher than it was before. Capacitation does not occur in a medium in which polyvinyl alcohol is substituted for bovine serum albumin or to which ethyl alcohol is added. Prevention of capacitation by these means had no effect on the rate of oxygen consumption. The results support the conclusion that the increased respiration of sperm in a capacitating medium is due to the presence of oxidizable substrates and, as such, is an accompaniment of the process of capacitation rather than a factor in bringing it about.
SIX FIGURESAlthough tlic eggs of a number of invertebrate a i i d certaiii sub-mammalian species have been widely investigated, 110 studies have so far beeii made of the respiratory activity of the mammalian egg. The usual methods for measuring res. piratioii require a relatively large amount of material, and securing this, in tlie case of niaminaliaii cggs, is by no riieans an easy matter. The dcvclopment and improvenient of ultramicro-techniques, however, now makes it possible to determiiie tlie respiratory activity of but a few cells, so that a study of the respiratory activity of rnaiiiiiialiaii eggs becomes feasiblc. The purpose of this paper is to present the results of a stucly of the respiration, in vitm, of the cggs of tlie rat from tlic one-cell through the 16-cell stage.
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